1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,
3 @c 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006
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, 2006@*
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, 2006
89 Free Software Foundation, Inc.
91 Published by the Free Software Foundation @*
92 51 Franklin Street, Fifth Floor,
93 Boston, MA 02110-1301, 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) 1988-2006 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 6.3, 6.2, 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.
487 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
488 unwinder framework, this consisting of a fresh new design featuring
489 frame IDs, independent frame sniffers, and the sentinel frame. Mark
490 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
491 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
492 trad unwinders. The architecture specific changes, each involving a
493 complete rewrite of the architecture's frame code, were carried out by
494 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
495 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
496 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
497 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
501 @chapter A Sample @value{GDBN} Session
503 You can use this manual at your leisure to read all about @value{GDBN}.
504 However, a handful of commands are enough to get started using the
505 debugger. This chapter illustrates those commands.
508 In this sample session, we emphasize user input like this: @b{input},
509 to make it easier to pick out from the surrounding output.
512 @c FIXME: this example may not be appropriate for some configs, where
513 @c FIXME...primary interest is in remote use.
515 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
516 processor) exhibits the following bug: sometimes, when we change its
517 quote strings from the default, the commands used to capture one macro
518 definition within another stop working. In the following short @code{m4}
519 session, we define a macro @code{foo} which expands to @code{0000}; we
520 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
521 same thing. However, when we change the open quote string to
522 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
523 procedure fails to define a new synonym @code{baz}:
532 @b{define(bar,defn(`foo'))}
536 @b{changequote(<QUOTE>,<UNQUOTE>)}
538 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
541 m4: End of input: 0: fatal error: EOF in string
545 Let us use @value{GDBN} to try to see what is going on.
548 $ @b{@value{GDBP} m4}
549 @c FIXME: this falsifies the exact text played out, to permit smallbook
550 @c FIXME... format to come out better.
551 @value{GDBN} is free software and you are welcome to distribute copies
552 of it under certain conditions; type "show copying" to see
554 There is absolutely no warranty for @value{GDBN}; type "show warranty"
557 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
562 @value{GDBN} reads only enough symbol data to know where to find the
563 rest when needed; as a result, the first prompt comes up very quickly.
564 We now tell @value{GDBN} to use a narrower display width than usual, so
565 that examples fit in this manual.
568 (@value{GDBP}) @b{set width 70}
572 We need to see how the @code{m4} built-in @code{changequote} works.
573 Having looked at the source, we know the relevant subroutine is
574 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
575 @code{break} command.
578 (@value{GDBP}) @b{break m4_changequote}
579 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
583 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
584 control; as long as control does not reach the @code{m4_changequote}
585 subroutine, the program runs as usual:
588 (@value{GDBP}) @b{run}
589 Starting program: /work/Editorial/gdb/gnu/m4/m4
597 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
598 suspends execution of @code{m4}, displaying information about the
599 context where it stops.
602 @b{changequote(<QUOTE>,<UNQUOTE>)}
604 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
606 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
610 Now we use the command @code{n} (@code{next}) to advance execution to
611 the next line of the current function.
615 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
620 @code{set_quotes} looks like a promising subroutine. We can go into it
621 by using the command @code{s} (@code{step}) instead of @code{next}.
622 @code{step} goes to the next line to be executed in @emph{any}
623 subroutine, so it steps into @code{set_quotes}.
627 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
629 530 if (lquote != def_lquote)
633 The display that shows the subroutine where @code{m4} is now
634 suspended (and its arguments) is called a stack frame display. It
635 shows a summary of the stack. We can use the @code{backtrace}
636 command (which can also be spelled @code{bt}), to see where we are
637 in the stack as a whole: the @code{backtrace} command displays a
638 stack frame for each active subroutine.
641 (@value{GDBP}) @b{bt}
642 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
644 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
646 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
647 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
649 #4 0x79dc in expand_input () at macro.c:40
650 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
654 We step through a few more lines to see what happens. The first two
655 times, we can use @samp{s}; the next two times we use @code{n} to avoid
656 falling into the @code{xstrdup} subroutine.
660 0x3b5c 532 if (rquote != def_rquote)
662 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
663 def_lquote : xstrdup(lq);
665 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
668 538 len_lquote = strlen(rquote);
672 The last line displayed looks a little odd; we can examine the variables
673 @code{lquote} and @code{rquote} to see if they are in fact the new left
674 and right quotes we specified. We use the command @code{p}
675 (@code{print}) to see their values.
678 (@value{GDBP}) @b{p lquote}
679 $1 = 0x35d40 "<QUOTE>"
680 (@value{GDBP}) @b{p rquote}
681 $2 = 0x35d50 "<UNQUOTE>"
685 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
686 To look at some context, we can display ten lines of source
687 surrounding the current line with the @code{l} (@code{list}) command.
693 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
695 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
698 538 len_lquote = strlen(rquote);
699 539 len_rquote = strlen(lquote);
706 Let us step past the two lines that set @code{len_lquote} and
707 @code{len_rquote}, and then examine the values of those variables.
711 539 len_rquote = strlen(lquote);
714 (@value{GDBP}) @b{p len_lquote}
716 (@value{GDBP}) @b{p len_rquote}
721 That certainly looks wrong, assuming @code{len_lquote} and
722 @code{len_rquote} are meant to be the lengths of @code{lquote} and
723 @code{rquote} respectively. We can set them to better values using
724 the @code{p} command, since it can print the value of
725 any expression---and that expression can include subroutine calls and
729 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
731 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
736 Is that enough to fix the problem of using the new quotes with the
737 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
738 executing with the @code{c} (@code{continue}) command, and then try the
739 example that caused trouble initially:
745 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
752 Success! The new quotes now work just as well as the default ones. The
753 problem seems to have been just the two typos defining the wrong
754 lengths. We allow @code{m4} exit by giving it an EOF as input:
758 Program exited normally.
762 The message @samp{Program exited normally.} is from @value{GDBN}; it
763 indicates @code{m4} has finished executing. We can end our @value{GDBN}
764 session with the @value{GDBN} @code{quit} command.
767 (@value{GDBP}) @b{quit}
771 @chapter Getting In and Out of @value{GDBN}
773 This chapter discusses how to start @value{GDBN}, and how to get out of it.
777 type @samp{@value{GDBP}} to start @value{GDBN}.
779 type @kbd{quit} or @kbd{C-d} to exit.
783 * Invoking GDB:: How to start @value{GDBN}
784 * Quitting GDB:: How to quit @value{GDBN}
785 * Shell Commands:: How to use shell commands inside @value{GDBN}
786 * Logging output:: How to log @value{GDBN}'s output to a file
790 @section Invoking @value{GDBN}
792 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
793 @value{GDBN} reads commands from the terminal until you tell it to exit.
795 You can also run @code{@value{GDBP}} with a variety of arguments and options,
796 to specify more of your debugging environment at the outset.
798 The command-line options described here are designed
799 to cover a variety of situations; in some environments, some of these
800 options may effectively be unavailable.
802 The most usual way to start @value{GDBN} is with one argument,
803 specifying an executable program:
806 @value{GDBP} @var{program}
810 You can also start with both an executable program and a core file
814 @value{GDBP} @var{program} @var{core}
817 You can, instead, specify a process ID as a second argument, if you want
818 to debug a running process:
821 @value{GDBP} @var{program} 1234
825 would attach @value{GDBN} to process @code{1234} (unless you also have a file
826 named @file{1234}; @value{GDBN} does check for a core file first).
828 Taking advantage of the second command-line argument requires a fairly
829 complete operating system; when you use @value{GDBN} as a remote
830 debugger attached to a bare board, there may not be any notion of
831 ``process'', and there is often no way to get a core dump. @value{GDBN}
832 will warn you if it is unable to attach or to read core dumps.
834 You can optionally have @code{@value{GDBP}} pass any arguments after the
835 executable file to the inferior using @code{--args}. This option stops
838 gdb --args gcc -O2 -c foo.c
840 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
841 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
843 You can run @code{@value{GDBP}} without printing the front material, which describes
844 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
851 You can further control how @value{GDBN} starts up by using command-line
852 options. @value{GDBN} itself can remind you of the options available.
862 to display all available options and briefly describe their use
863 (@samp{@value{GDBP} -h} is a shorter equivalent).
865 All options and command line arguments you give are processed
866 in sequential order. The order makes a difference when the
867 @samp{-x} option is used.
871 * File Options:: Choosing files
872 * Mode Options:: Choosing modes
873 * Startup:: What @value{GDBN} does during startup
877 @subsection Choosing files
879 When @value{GDBN} starts, it reads any arguments other than options as
880 specifying an executable file and core file (or process ID). This is
881 the same as if the arguments were specified by the @samp{-se} and
882 @samp{-c} (or @samp{-p} options respectively. (@value{GDBN} reads the
883 first argument that does not have an associated option flag as
884 equivalent to the @samp{-se} option followed by that argument; and the
885 second argument that does not have an associated option flag, if any, as
886 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
887 If the second argument begins with a decimal digit, @value{GDBN} will
888 first attempt to attach to it as a process, and if that fails, attempt
889 to open it as a corefile. If you have a corefile whose name begins with
890 a digit, you can prevent @value{GDBN} from treating it as a pid by
891 prefixing it with @file{./}, e.g.@: @file{./12345}.
893 If @value{GDBN} has not been configured to included core file support,
894 such as for most embedded targets, then it will complain about a second
895 argument and ignore it.
897 Many options have both long and short forms; both are shown in the
898 following list. @value{GDBN} also recognizes the long forms if you truncate
899 them, so long as enough of the option is present to be unambiguous.
900 (If you prefer, you can flag option arguments with @samp{--} rather
901 than @samp{-}, though we illustrate the more usual convention.)
903 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
904 @c way, both those who look for -foo and --foo in the index, will find
908 @item -symbols @var{file}
910 @cindex @code{--symbols}
912 Read symbol table from file @var{file}.
914 @item -exec @var{file}
916 @cindex @code{--exec}
918 Use file @var{file} as the executable file to execute when appropriate,
919 and for examining pure data in conjunction with a core dump.
923 Read symbol table from file @var{file} and use it as the executable
926 @item -core @var{file}
928 @cindex @code{--core}
930 Use file @var{file} as a core dump to examine.
932 @item -c @var{number}
933 @item -pid @var{number}
934 @itemx -p @var{number}
937 Connect to process ID @var{number}, as with the @code{attach} command.
938 If there is no such process, @value{GDBN} will attempt to open a core
939 file named @var{number}.
941 @item -command @var{file}
943 @cindex @code{--command}
945 Execute @value{GDBN} commands from file @var{file}. @xref{Command
946 Files,, Command files}.
948 @item -eval-command @var{command}
949 @itemx -ex @var{command}
950 @cindex @code{--eval-command}
952 Execute a single @value{GDBN} command.
954 This option may be used multiple times to call multiple commands. It may
955 also be interleaved with @samp{-command} as required.
958 @value{GDBP} -ex 'target sim' -ex 'load' \
959 -x setbreakpoints -ex 'run' a.out
962 @item -directory @var{directory}
963 @itemx -d @var{directory}
964 @cindex @code{--directory}
966 Add @var{directory} to the path to search for source and script files.
970 @cindex @code{--readnow}
972 Read each symbol file's entire symbol table immediately, rather than
973 the default, which is to read it incrementally as it is needed.
974 This makes startup slower, but makes future operations faster.
979 @subsection Choosing modes
981 You can run @value{GDBN} in various alternative modes---for example, in
982 batch mode or quiet mode.
989 Do not execute commands found in any initialization files. Normally,
990 @value{GDBN} executes the commands in these files after all the command
991 options and arguments have been processed. @xref{Command Files,,Command
997 @cindex @code{--quiet}
998 @cindex @code{--silent}
1000 ``Quiet''. Do not print the introductory and copyright messages. These
1001 messages are also suppressed in batch mode.
1004 @cindex @code{--batch}
1005 Run in batch mode. Exit with status @code{0} after processing all the
1006 command files specified with @samp{-x} (and all commands from
1007 initialization files, if not inhibited with @samp{-n}). Exit with
1008 nonzero status if an error occurs in executing the @value{GDBN} commands
1009 in the command files.
1011 Batch mode may be useful for running @value{GDBN} as a filter, for
1012 example to download and run a program on another computer; in order to
1013 make this more useful, the message
1016 Program exited normally.
1020 (which is ordinarily issued whenever a program running under
1021 @value{GDBN} control terminates) is not issued when running in batch
1025 @cindex @code{--batch-silent}
1026 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1027 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1028 unaffected). This is much quieter than @samp{-silent} and would be useless
1029 for an interactive session.
1031 This is particularly useful when using targets that give @samp{Loading section}
1032 messages, for example.
1034 Note that targets that give their output via @value{GDBN}, as opposed to
1035 writing directly to @code{stdout}, will also be made silent.
1037 @item -return-child-result
1038 @cindex @code{--return-child-result}
1039 The return code from @value{GDBN} will be the return code from the child
1040 process (the process being debugged), with the following exceptions:
1044 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1045 internal error. In this case the exit code is the same as it would have been
1046 without @samp{-return-child-result}.
1048 The user quits with an explicit value. E.g., @samp{quit 1}.
1050 The child process never runs, or is not allowed to terminate, in which case
1051 the exit code will be -1.
1054 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1055 when @value{GDBN} is being used as a remote program loader or simulator
1060 @cindex @code{--nowindows}
1062 ``No windows''. If @value{GDBN} comes with a graphical user interface
1063 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1064 interface. If no GUI is available, this option has no effect.
1068 @cindex @code{--windows}
1070 If @value{GDBN} includes a GUI, then this option requires it to be
1073 @item -cd @var{directory}
1075 Run @value{GDBN} using @var{directory} as its working directory,
1076 instead of the current directory.
1080 @cindex @code{--fullname}
1082 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1083 subprocess. It tells @value{GDBN} to output the full file name and line
1084 number in a standard, recognizable fashion each time a stack frame is
1085 displayed (which includes each time your program stops). This
1086 recognizable format looks like two @samp{\032} characters, followed by
1087 the file name, line number and character position separated by colons,
1088 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1089 @samp{\032} characters as a signal to display the source code for the
1093 @cindex @code{--epoch}
1094 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1095 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1096 routines so as to allow Epoch to display values of expressions in a
1099 @item -annotate @var{level}
1100 @cindex @code{--annotate}
1101 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1102 effect is identical to using @samp{set annotate @var{level}}
1103 (@pxref{Annotations}). The annotation @var{level} controls how much
1104 information @value{GDBN} prints together with its prompt, values of
1105 expressions, source lines, and other types of output. Level 0 is the
1106 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1107 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1108 that control @value{GDBN}, and level 2 has been deprecated.
1110 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1114 @cindex @code{--args}
1115 Change interpretation of command line so that arguments following the
1116 executable file are passed as command line arguments to the inferior.
1117 This option stops option processing.
1119 @item -baud @var{bps}
1121 @cindex @code{--baud}
1123 Set the line speed (baud rate or bits per second) of any serial
1124 interface used by @value{GDBN} for remote debugging.
1126 @item -l @var{timeout}
1128 Set the timeout (in seconds) of any communication used by @value{GDBN}
1129 for remote debugging.
1131 @item -tty @var{device}
1132 @itemx -t @var{device}
1133 @cindex @code{--tty}
1135 Run using @var{device} for your program's standard input and output.
1136 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1138 @c resolve the situation of these eventually
1140 @cindex @code{--tui}
1141 Activate the @dfn{Text User Interface} when starting. The Text User
1142 Interface manages several text windows on the terminal, showing
1143 source, assembly, registers and @value{GDBN} command outputs
1144 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1145 Text User Interface can be enabled by invoking the program
1146 @samp{gdbtui}. Do not use this option if you run @value{GDBN} from
1147 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1150 @c @cindex @code{--xdb}
1151 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1152 @c For information, see the file @file{xdb_trans.html}, which is usually
1153 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1156 @item -interpreter @var{interp}
1157 @cindex @code{--interpreter}
1158 Use the interpreter @var{interp} for interface with the controlling
1159 program or device. This option is meant to be set by programs which
1160 communicate with @value{GDBN} using it as a back end.
1161 @xref{Interpreters, , Command Interpreters}.
1163 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1164 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1165 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1166 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1167 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1168 @sc{gdb/mi} interfaces are no longer supported.
1171 @cindex @code{--write}
1172 Open the executable and core files for both reading and writing. This
1173 is equivalent to the @samp{set write on} command inside @value{GDBN}
1177 @cindex @code{--statistics}
1178 This option causes @value{GDBN} to print statistics about time and
1179 memory usage after it completes each command and returns to the prompt.
1182 @cindex @code{--version}
1183 This option causes @value{GDBN} to print its version number and
1184 no-warranty blurb, and exit.
1189 @subsection What @value{GDBN} does during startup
1190 @cindex @value{GDBN} startup
1192 Here's the description of what @value{GDBN} does during session startup:
1196 Sets up the command interpreter as specified by the command line
1197 (@pxref{Mode Options, interpreter}).
1201 Reads the @dfn{init file} (if any) in your home directory@footnote{On
1202 DOS/Windows systems, the home directory is the one pointed to by the
1203 @code{HOME} environment variable.} and executes all the commands in
1207 Processes command line options and operands.
1210 Reads and executes the commands from init file (if any) in the current
1211 working directory. This is only done if the current directory is
1212 different from your home directory. Thus, you can have more than one
1213 init file, one generic in your home directory, and another, specific
1214 to the program you are debugging, in the directory where you invoke
1218 Reads command files specified by the @samp{-x} option. @xref{Command
1219 Files}, for more details about @value{GDBN} command files.
1222 Reads the command history recorded in the @dfn{history file}.
1223 @xref{Command History}, for more details about the command history and the
1224 files where @value{GDBN} records it.
1227 Init files use the same syntax as @dfn{command files} (@pxref{Command
1228 Files}) and are processed by @value{GDBN} in the same way. The init
1229 file in your home directory can set options (such as @samp{set
1230 complaints}) that affect subsequent processing of command line options
1231 and operands. Init files are not executed if you use the @samp{-nx}
1232 option (@pxref{Mode Options, ,Choosing modes}).
1234 @cindex init file name
1235 @cindex @file{.gdbinit}
1236 The @value{GDBN} init files are normally called @file{.gdbinit}.
1237 On some configurations of @value{GDBN}, the init file is known by a
1238 different name (these are typically environments where a specialized
1239 form of @value{GDBN} may need to coexist with other forms, hence a
1240 different name for the specialized version's init file). These are the
1241 environments with special init file names:
1244 @cindex @file{gdb.ini}
1246 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1247 the limitations of file names imposed by DOS filesystems. The Windows
1248 ports of @value{GDBN} use the standard name, but if they find a
1249 @file{gdb.ini} file, they warn you about that and suggest to rename
1250 the file to the standard name.
1252 @cindex @file{.vxgdbinit}
1254 VxWorks (Wind River Systems real-time OS): @file{.vxgdbinit}
1256 @cindex @file{.os68gdbinit}
1258 OS68K (Enea Data Systems real-time OS): @file{.os68gdbinit}
1260 @cindex @file{.esgdbinit}
1262 ES-1800 (Ericsson Telecom AB M68000 emulator): @file{.esgdbinit}
1265 CISCO 68k: @file{.cisco-gdbinit}
1270 @section Quitting @value{GDBN}
1271 @cindex exiting @value{GDBN}
1272 @cindex leaving @value{GDBN}
1275 @kindex quit @r{[}@var{expression}@r{]}
1276 @kindex q @r{(@code{quit})}
1277 @item quit @r{[}@var{expression}@r{]}
1279 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1280 @code{q}), or type an end-of-file character (usually @kbd{C-d}). If you
1281 do not supply @var{expression}, @value{GDBN} will terminate normally;
1282 otherwise it will terminate using the result of @var{expression} as the
1287 An interrupt (often @kbd{C-c}) does not exit from @value{GDBN}, but rather
1288 terminates the action of any @value{GDBN} command that is in progress and
1289 returns to @value{GDBN} command level. It is safe to type the interrupt
1290 character at any time because @value{GDBN} does not allow it to take effect
1291 until a time when it is safe.
1293 If you have been using @value{GDBN} to control an attached process or
1294 device, you can release it with the @code{detach} command
1295 (@pxref{Attach, ,Debugging an already-running process}).
1297 @node Shell Commands
1298 @section Shell commands
1300 If you need to execute occasional shell commands during your
1301 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1302 just use the @code{shell} command.
1306 @cindex shell escape
1307 @item shell @var{command string}
1308 Invoke a standard shell to execute @var{command string}.
1309 If it exists, the environment variable @code{SHELL} determines which
1310 shell to run. Otherwise @value{GDBN} uses the default shell
1311 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1314 The utility @code{make} is often needed in development environments.
1315 You do not have to use the @code{shell} command for this purpose in
1320 @cindex calling make
1321 @item make @var{make-args}
1322 Execute the @code{make} program with the specified
1323 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1326 @node Logging output
1327 @section Logging output
1328 @cindex logging @value{GDBN} output
1329 @cindex save @value{GDBN} output to a file
1331 You may want to save the output of @value{GDBN} commands to a file.
1332 There are several commands to control @value{GDBN}'s logging.
1336 @item set logging on
1338 @item set logging off
1340 @cindex logging file name
1341 @item set logging file @var{file}
1342 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1343 @item set logging overwrite [on|off]
1344 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1345 you want @code{set logging on} to overwrite the logfile instead.
1346 @item set logging redirect [on|off]
1347 By default, @value{GDBN} output will go to both the terminal and the logfile.
1348 Set @code{redirect} if you want output to go only to the log file.
1349 @kindex show logging
1351 Show the current values of the logging settings.
1355 @chapter @value{GDBN} Commands
1357 You can abbreviate a @value{GDBN} command to the first few letters of the command
1358 name, if that abbreviation is unambiguous; and you can repeat certain
1359 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1360 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1361 show you the alternatives available, if there is more than one possibility).
1364 * Command Syntax:: How to give commands to @value{GDBN}
1365 * Completion:: Command completion
1366 * Help:: How to ask @value{GDBN} for help
1369 @node Command Syntax
1370 @section Command syntax
1372 A @value{GDBN} command is a single line of input. There is no limit on
1373 how long it can be. It starts with a command name, which is followed by
1374 arguments whose meaning depends on the command name. For example, the
1375 command @code{step} accepts an argument which is the number of times to
1376 step, as in @samp{step 5}. You can also use the @code{step} command
1377 with no arguments. Some commands do not allow any arguments.
1379 @cindex abbreviation
1380 @value{GDBN} command names may always be truncated if that abbreviation is
1381 unambiguous. Other possible command abbreviations are listed in the
1382 documentation for individual commands. In some cases, even ambiguous
1383 abbreviations are allowed; for example, @code{s} is specially defined as
1384 equivalent to @code{step} even though there are other commands whose
1385 names start with @code{s}. You can test abbreviations by using them as
1386 arguments to the @code{help} command.
1388 @cindex repeating commands
1389 @kindex RET @r{(repeat last command)}
1390 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1391 repeat the previous command. Certain commands (for example, @code{run})
1392 will not repeat this way; these are commands whose unintentional
1393 repetition might cause trouble and which you are unlikely to want to
1394 repeat. User-defined commands can disable this feature; see
1395 @ref{Define, dont-repeat}.
1397 The @code{list} and @code{x} commands, when you repeat them with
1398 @key{RET}, construct new arguments rather than repeating
1399 exactly as typed. This permits easy scanning of source or memory.
1401 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1402 output, in a way similar to the common utility @code{more}
1403 (@pxref{Screen Size,,Screen size}). Since it is easy to press one
1404 @key{RET} too many in this situation, @value{GDBN} disables command
1405 repetition after any command that generates this sort of display.
1407 @kindex # @r{(a comment)}
1409 Any text from a @kbd{#} to the end of the line is a comment; it does
1410 nothing. This is useful mainly in command files (@pxref{Command
1411 Files,,Command files}).
1413 @cindex repeating command sequences
1414 @kindex C-o @r{(operate-and-get-next)}
1415 The @kbd{C-o} binding is useful for repeating a complex sequence of
1416 commands. This command accepts the current line, like @kbd{RET}, and
1417 then fetches the next line relative to the current line from the history
1421 @section Command completion
1424 @cindex word completion
1425 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1426 only one possibility; it can also show you what the valid possibilities
1427 are for the next word in a command, at any time. This works for @value{GDBN}
1428 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1430 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1431 of a word. If there is only one possibility, @value{GDBN} fills in the
1432 word, and waits for you to finish the command (or press @key{RET} to
1433 enter it). For example, if you type
1435 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1436 @c complete accuracy in these examples; space introduced for clarity.
1437 @c If texinfo enhancements make it unnecessary, it would be nice to
1438 @c replace " @key" by "@key" in the following...
1440 (@value{GDBP}) info bre @key{TAB}
1444 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1445 the only @code{info} subcommand beginning with @samp{bre}:
1448 (@value{GDBP}) info breakpoints
1452 You can either press @key{RET} at this point, to run the @code{info
1453 breakpoints} command, or backspace and enter something else, if
1454 @samp{breakpoints} does not look like the command you expected. (If you
1455 were sure you wanted @code{info breakpoints} in the first place, you
1456 might as well just type @key{RET} immediately after @samp{info bre},
1457 to exploit command abbreviations rather than command completion).
1459 If there is more than one possibility for the next word when you press
1460 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1461 characters and try again, or just press @key{TAB} a second time;
1462 @value{GDBN} displays all the possible completions for that word. For
1463 example, you might want to set a breakpoint on a subroutine whose name
1464 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1465 just sounds the bell. Typing @key{TAB} again displays all the
1466 function names in your program that begin with those characters, for
1470 (@value{GDBP}) b make_ @key{TAB}
1471 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1472 make_a_section_from_file make_environ
1473 make_abs_section make_function_type
1474 make_blockvector make_pointer_type
1475 make_cleanup make_reference_type
1476 make_command make_symbol_completion_list
1477 (@value{GDBP}) b make_
1481 After displaying the available possibilities, @value{GDBN} copies your
1482 partial input (@samp{b make_} in the example) so you can finish the
1485 If you just want to see the list of alternatives in the first place, you
1486 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1487 means @kbd{@key{META} ?}. You can type this either by holding down a
1488 key designated as the @key{META} shift on your keyboard (if there is
1489 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1491 @cindex quotes in commands
1492 @cindex completion of quoted strings
1493 Sometimes the string you need, while logically a ``word'', may contain
1494 parentheses or other characters that @value{GDBN} normally excludes from
1495 its notion of a word. To permit word completion to work in this
1496 situation, you may enclose words in @code{'} (single quote marks) in
1497 @value{GDBN} commands.
1499 The most likely situation where you might need this is in typing the
1500 name of a C@t{++} function. This is because C@t{++} allows function
1501 overloading (multiple definitions of the same function, distinguished
1502 by argument type). For example, when you want to set a breakpoint you
1503 may need to distinguish whether you mean the version of @code{name}
1504 that takes an @code{int} parameter, @code{name(int)}, or the version
1505 that takes a @code{float} parameter, @code{name(float)}. To use the
1506 word-completion facilities in this situation, type a single quote
1507 @code{'} at the beginning of the function name. This alerts
1508 @value{GDBN} that it may need to consider more information than usual
1509 when you press @key{TAB} or @kbd{M-?} to request word completion:
1512 (@value{GDBP}) b 'bubble( @kbd{M-?}
1513 bubble(double,double) bubble(int,int)
1514 (@value{GDBP}) b 'bubble(
1517 In some cases, @value{GDBN} can tell that completing a name requires using
1518 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1519 completing as much as it can) if you do not type the quote in the first
1523 (@value{GDBP}) b bub @key{TAB}
1524 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1525 (@value{GDBP}) b 'bubble(
1529 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1530 you have not yet started typing the argument list when you ask for
1531 completion on an overloaded symbol.
1533 For more information about overloaded functions, see @ref{C plus plus
1534 expressions, ,C@t{++} expressions}. You can use the command @code{set
1535 overload-resolution off} to disable overload resolution;
1536 see @ref{Debugging C plus plus, ,@value{GDBN} features for C@t{++}}.
1540 @section Getting help
1541 @cindex online documentation
1544 You can always ask @value{GDBN} itself for information on its commands,
1545 using the command @code{help}.
1548 @kindex h @r{(@code{help})}
1551 You can use @code{help} (abbreviated @code{h}) with no arguments to
1552 display a short list of named classes of commands:
1556 List of classes of commands:
1558 aliases -- Aliases of other commands
1559 breakpoints -- Making program stop at certain points
1560 data -- Examining data
1561 files -- Specifying and examining files
1562 internals -- Maintenance commands
1563 obscure -- Obscure features
1564 running -- Running the program
1565 stack -- Examining the stack
1566 status -- Status inquiries
1567 support -- Support facilities
1568 tracepoints -- Tracing of program execution without@*
1569 stopping the program
1570 user-defined -- User-defined commands
1572 Type "help" followed by a class name for a list of
1573 commands in that class.
1574 Type "help" followed by command name for full
1576 Command name abbreviations are allowed if unambiguous.
1579 @c the above line break eliminates huge line overfull...
1581 @item help @var{class}
1582 Using one of the general help classes as an argument, you can get a
1583 list of the individual commands in that class. For example, here is the
1584 help display for the class @code{status}:
1587 (@value{GDBP}) help status
1592 @c Line break in "show" line falsifies real output, but needed
1593 @c to fit in smallbook page size.
1594 info -- Generic command for showing things
1595 about the program being debugged
1596 show -- Generic command for showing things
1599 Type "help" followed by command name for full
1601 Command name abbreviations are allowed if unambiguous.
1605 @item help @var{command}
1606 With a command name as @code{help} argument, @value{GDBN} displays a
1607 short paragraph on how to use that command.
1610 @item apropos @var{args}
1611 The @code{apropos} command searches through all of the @value{GDBN}
1612 commands, and their documentation, for the regular expression specified in
1613 @var{args}. It prints out all matches found. For example:
1624 set symbol-reloading -- Set dynamic symbol table reloading
1625 multiple times in one run
1626 show symbol-reloading -- Show dynamic symbol table reloading
1627 multiple times in one run
1632 @item complete @var{args}
1633 The @code{complete @var{args}} command lists all the possible completions
1634 for the beginning of a command. Use @var{args} to specify the beginning of the
1635 command you want completed. For example:
1641 @noindent results in:
1652 @noindent This is intended for use by @sc{gnu} Emacs.
1655 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1656 and @code{show} to inquire about the state of your program, or the state
1657 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1658 manual introduces each of them in the appropriate context. The listings
1659 under @code{info} and under @code{show} in the Index point to
1660 all the sub-commands. @xref{Index}.
1665 @kindex i @r{(@code{info})}
1667 This command (abbreviated @code{i}) is for describing the state of your
1668 program. For example, you can list the arguments given to your program
1669 with @code{info args}, list the registers currently in use with @code{info
1670 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1671 You can get a complete list of the @code{info} sub-commands with
1672 @w{@code{help info}}.
1676 You can assign the result of an expression to an environment variable with
1677 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1678 @code{set prompt $}.
1682 In contrast to @code{info}, @code{show} is for describing the state of
1683 @value{GDBN} itself.
1684 You can change most of the things you can @code{show}, by using the
1685 related command @code{set}; for example, you can control what number
1686 system is used for displays with @code{set radix}, or simply inquire
1687 which is currently in use with @code{show radix}.
1690 To display all the settable parameters and their current
1691 values, you can use @code{show} with no arguments; you may also use
1692 @code{info set}. Both commands produce the same display.
1693 @c FIXME: "info set" violates the rule that "info" is for state of
1694 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1695 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1699 Here are three miscellaneous @code{show} subcommands, all of which are
1700 exceptional in lacking corresponding @code{set} commands:
1703 @kindex show version
1704 @cindex @value{GDBN} version number
1706 Show what version of @value{GDBN} is running. You should include this
1707 information in @value{GDBN} bug-reports. If multiple versions of
1708 @value{GDBN} are in use at your site, you may need to determine which
1709 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1710 commands are introduced, and old ones may wither away. Also, many
1711 system vendors ship variant versions of @value{GDBN}, and there are
1712 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1713 The version number is the same as the one announced when you start
1716 @kindex show copying
1717 @kindex info copying
1718 @cindex display @value{GDBN} copyright
1721 Display information about permission for copying @value{GDBN}.
1723 @kindex show warranty
1724 @kindex info warranty
1726 @itemx info warranty
1727 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1728 if your version of @value{GDBN} comes with one.
1733 @chapter Running Programs Under @value{GDBN}
1735 When you run a program under @value{GDBN}, you must first generate
1736 debugging information when you compile it.
1738 You may start @value{GDBN} with its arguments, if any, in an environment
1739 of your choice. If you are doing native debugging, you may redirect
1740 your program's input and output, debug an already running process, or
1741 kill a child process.
1744 * Compilation:: Compiling for debugging
1745 * Starting:: Starting your program
1746 * Arguments:: Your program's arguments
1747 * Environment:: Your program's environment
1749 * Working Directory:: Your program's working directory
1750 * Input/Output:: Your program's input and output
1751 * Attach:: Debugging an already-running process
1752 * Kill Process:: Killing the child process
1754 * Threads:: Debugging programs with multiple threads
1755 * Processes:: Debugging programs with multiple processes
1756 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1760 @section Compiling for debugging
1762 In order to debug a program effectively, you need to generate
1763 debugging information when you compile it. This debugging information
1764 is stored in the object file; it describes the data type of each
1765 variable or function and the correspondence between source line numbers
1766 and addresses in the executable code.
1768 To request debugging information, specify the @samp{-g} option when you run
1771 Programs that are to be shipped to your customers are compiled with
1772 optimizations, using the @samp{-O} compiler option. However, many
1773 compilers are unable to handle the @samp{-g} and @samp{-O} options
1774 together. Using those compilers, you cannot generate optimized
1775 executables containing debugging information.
1777 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1778 without @samp{-O}, making it possible to debug optimized code. We
1779 recommend that you @emph{always} use @samp{-g} whenever you compile a
1780 program. You may think your program is correct, but there is no sense
1781 in pushing your luck.
1783 @cindex optimized code, debugging
1784 @cindex debugging optimized code
1785 When you debug a program compiled with @samp{-g -O}, remember that the
1786 optimizer is rearranging your code; the debugger shows you what is
1787 really there. Do not be too surprised when the execution path does not
1788 exactly match your source file! An extreme example: if you define a
1789 variable, but never use it, @value{GDBN} never sees that
1790 variable---because the compiler optimizes it out of existence.
1792 Some things do not work as well with @samp{-g -O} as with just
1793 @samp{-g}, particularly on machines with instruction scheduling. If in
1794 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1795 please report it to us as a bug (including a test case!).
1796 @xref{Variables}, for more information about debugging optimized code.
1798 Older versions of the @sc{gnu} C compiler permitted a variant option
1799 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1800 format; if your @sc{gnu} C compiler has this option, do not use it.
1802 @value{GDBN} knows about preprocessor macros and can show you their
1803 expansion (@pxref{Macros}). Most compilers do not include information
1804 about preprocessor macros in the debugging information if you specify
1805 the @option{-g} flag alone, because this information is rather large.
1806 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1807 provides macro information if you specify the options
1808 @option{-gdwarf-2} and @option{-g3}; the former option requests
1809 debugging information in the Dwarf 2 format, and the latter requests
1810 ``extra information''. In the future, we hope to find more compact
1811 ways to represent macro information, so that it can be included with
1816 @section Starting your program
1822 @kindex r @r{(@code{run})}
1825 Use the @code{run} command to start your program under @value{GDBN}.
1826 You must first specify the program name (except on VxWorks) with an
1827 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1828 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1829 (@pxref{Files, ,Commands to specify files}).
1833 If you are running your program in an execution environment that
1834 supports processes, @code{run} creates an inferior process and makes
1835 that process run your program. (In environments without processes,
1836 @code{run} jumps to the start of your program.)
1838 The execution of a program is affected by certain information it
1839 receives from its superior. @value{GDBN} provides ways to specify this
1840 information, which you must do @emph{before} starting your program. (You
1841 can change it after starting your program, but such changes only affect
1842 your program the next time you start it.) This information may be
1843 divided into four categories:
1846 @item The @emph{arguments.}
1847 Specify the arguments to give your program as the arguments of the
1848 @code{run} command. If a shell is available on your target, the shell
1849 is used to pass the arguments, so that you may use normal conventions
1850 (such as wildcard expansion or variable substitution) in describing
1852 In Unix systems, you can control which shell is used with the
1853 @code{SHELL} environment variable.
1854 @xref{Arguments, ,Your program's arguments}.
1856 @item The @emph{environment.}
1857 Your program normally inherits its environment from @value{GDBN}, but you can
1858 use the @value{GDBN} commands @code{set environment} and @code{unset
1859 environment} to change parts of the environment that affect
1860 your program. @xref{Environment, ,Your program's environment}.
1862 @item The @emph{working directory.}
1863 Your program inherits its working directory from @value{GDBN}. You can set
1864 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1865 @xref{Working Directory, ,Your program's working directory}.
1867 @item The @emph{standard input and output.}
1868 Your program normally uses the same device for standard input and
1869 standard output as @value{GDBN} is using. You can redirect input and output
1870 in the @code{run} command line, or you can use the @code{tty} command to
1871 set a different device for your program.
1872 @xref{Input/Output, ,Your program's input and output}.
1875 @emph{Warning:} While input and output redirection work, you cannot use
1876 pipes to pass the output of the program you are debugging to another
1877 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1881 When you issue the @code{run} command, your program begins to execute
1882 immediately. @xref{Stopping, ,Stopping and continuing}, for discussion
1883 of how to arrange for your program to stop. Once your program has
1884 stopped, you may call functions in your program, using the @code{print}
1885 or @code{call} commands. @xref{Data, ,Examining Data}.
1887 If the modification time of your symbol file has changed since the last
1888 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1889 table, and reads it again. When it does this, @value{GDBN} tries to retain
1890 your current breakpoints.
1895 @cindex run to main procedure
1896 The name of the main procedure can vary from language to language.
1897 With C or C@t{++}, the main procedure name is always @code{main}, but
1898 other languages such as Ada do not require a specific name for their
1899 main procedure. The debugger provides a convenient way to start the
1900 execution of the program and to stop at the beginning of the main
1901 procedure, depending on the language used.
1903 The @samp{start} command does the equivalent of setting a temporary
1904 breakpoint at the beginning of the main procedure and then invoking
1905 the @samp{run} command.
1907 @cindex elaboration phase
1908 Some programs contain an @dfn{elaboration} phase where some startup code is
1909 executed before the main procedure is called. This depends on the
1910 languages used to write your program. In C@t{++}, for instance,
1911 constructors for static and global objects are executed before
1912 @code{main} is called. It is therefore possible that the debugger stops
1913 before reaching the main procedure. However, the temporary breakpoint
1914 will remain to halt execution.
1916 Specify the arguments to give to your program as arguments to the
1917 @samp{start} command. These arguments will be given verbatim to the
1918 underlying @samp{run} command. Note that the same arguments will be
1919 reused if no argument is provided during subsequent calls to
1920 @samp{start} or @samp{run}.
1922 It is sometimes necessary to debug the program during elaboration. In
1923 these cases, using the @code{start} command would stop the execution of
1924 your program too late, as the program would have already completed the
1925 elaboration phase. Under these circumstances, insert breakpoints in your
1926 elaboration code before running your program.
1930 @section Your program's arguments
1932 @cindex arguments (to your program)
1933 The arguments to your program can be specified by the arguments of the
1935 They are passed to a shell, which expands wildcard characters and
1936 performs redirection of I/O, and thence to your program. Your
1937 @code{SHELL} environment variable (if it exists) specifies what shell
1938 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1939 the default shell (@file{/bin/sh} on Unix).
1941 On non-Unix systems, the program is usually invoked directly by
1942 @value{GDBN}, which emulates I/O redirection via the appropriate system
1943 calls, and the wildcard characters are expanded by the startup code of
1944 the program, not by the shell.
1946 @code{run} with no arguments uses the same arguments used by the previous
1947 @code{run}, or those set by the @code{set args} command.
1952 Specify the arguments to be used the next time your program is run. If
1953 @code{set args} has no arguments, @code{run} executes your program
1954 with no arguments. Once you have run your program with arguments,
1955 using @code{set args} before the next @code{run} is the only way to run
1956 it again without arguments.
1960 Show the arguments to give your program when it is started.
1964 @section Your program's environment
1966 @cindex environment (of your program)
1967 The @dfn{environment} consists of a set of environment variables and
1968 their values. Environment variables conventionally record such things as
1969 your user name, your home directory, your terminal type, and your search
1970 path for programs to run. Usually you set up environment variables with
1971 the shell and they are inherited by all the other programs you run. When
1972 debugging, it can be useful to try running your program with a modified
1973 environment without having to start @value{GDBN} over again.
1977 @item path @var{directory}
1978 Add @var{directory} to the front of the @code{PATH} environment variable
1979 (the search path for executables) that will be passed to your program.
1980 The value of @code{PATH} used by @value{GDBN} does not change.
1981 You may specify several directory names, separated by whitespace or by a
1982 system-dependent separator character (@samp{:} on Unix, @samp{;} on
1983 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
1984 is moved to the front, so it is searched sooner.
1986 You can use the string @samp{$cwd} to refer to whatever is the current
1987 working directory at the time @value{GDBN} searches the path. If you
1988 use @samp{.} instead, it refers to the directory where you executed the
1989 @code{path} command. @value{GDBN} replaces @samp{.} in the
1990 @var{directory} argument (with the current path) before adding
1991 @var{directory} to the search path.
1992 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
1993 @c document that, since repeating it would be a no-op.
1997 Display the list of search paths for executables (the @code{PATH}
1998 environment variable).
2000 @kindex show environment
2001 @item show environment @r{[}@var{varname}@r{]}
2002 Print the value of environment variable @var{varname} to be given to
2003 your program when it starts. If you do not supply @var{varname},
2004 print the names and values of all environment variables to be given to
2005 your program. You can abbreviate @code{environment} as @code{env}.
2007 @kindex set environment
2008 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2009 Set environment variable @var{varname} to @var{value}. The value
2010 changes for your program only, not for @value{GDBN} itself. @var{value} may
2011 be any string; the values of environment variables are just strings, and
2012 any interpretation is supplied by your program itself. The @var{value}
2013 parameter is optional; if it is eliminated, the variable is set to a
2015 @c "any string" here does not include leading, trailing
2016 @c blanks. Gnu asks: does anyone care?
2018 For example, this command:
2025 tells the debugged program, when subsequently run, that its user is named
2026 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2027 are not actually required.)
2029 @kindex unset environment
2030 @item unset environment @var{varname}
2031 Remove variable @var{varname} from the environment to be passed to your
2032 program. This is different from @samp{set env @var{varname} =};
2033 @code{unset environment} removes the variable from the environment,
2034 rather than assigning it an empty value.
2037 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2039 by your @code{SHELL} environment variable if it exists (or
2040 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2041 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2042 @file{.bashrc} for BASH---any variables you set in that file affect
2043 your program. You may wish to move setting of environment variables to
2044 files that are only run when you sign on, such as @file{.login} or
2047 @node Working Directory
2048 @section Your program's working directory
2050 @cindex working directory (of your program)
2051 Each time you start your program with @code{run}, it inherits its
2052 working directory from the current working directory of @value{GDBN}.
2053 The @value{GDBN} working directory is initially whatever it inherited
2054 from its parent process (typically the shell), but you can specify a new
2055 working directory in @value{GDBN} with the @code{cd} command.
2057 The @value{GDBN} working directory also serves as a default for the commands
2058 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2063 @cindex change working directory
2064 @item cd @var{directory}
2065 Set the @value{GDBN} working directory to @var{directory}.
2069 Print the @value{GDBN} working directory.
2072 It is generally impossible to find the current working directory of
2073 the process being debugged (since a program can change its directory
2074 during its run). If you work on a system where @value{GDBN} is
2075 configured with the @file{/proc} support, you can use the @code{info
2076 proc} command (@pxref{SVR4 Process Information}) to find out the
2077 current working directory of the debuggee.
2080 @section Your program's input and output
2085 By default, the program you run under @value{GDBN} does input and output to
2086 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2087 to its own terminal modes to interact with you, but it records the terminal
2088 modes your program was using and switches back to them when you continue
2089 running your program.
2092 @kindex info terminal
2094 Displays information recorded by @value{GDBN} about the terminal modes your
2098 You can redirect your program's input and/or output using shell
2099 redirection with the @code{run} command. For example,
2106 starts your program, diverting its output to the file @file{outfile}.
2109 @cindex controlling terminal
2110 Another way to specify where your program should do input and output is
2111 with the @code{tty} command. This command accepts a file name as
2112 argument, and causes this file to be the default for future @code{run}
2113 commands. It also resets the controlling terminal for the child
2114 process, for future @code{run} commands. For example,
2121 directs that processes started with subsequent @code{run} commands
2122 default to do input and output on the terminal @file{/dev/ttyb} and have
2123 that as their controlling terminal.
2125 An explicit redirection in @code{run} overrides the @code{tty} command's
2126 effect on the input/output device, but not its effect on the controlling
2129 When you use the @code{tty} command or redirect input in the @code{run}
2130 command, only the input @emph{for your program} is affected. The input
2131 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2132 for @code{set inferior-tty}.
2134 @cindex inferior tty
2135 @cindex set inferior controlling terminal
2136 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2137 display the name of the terminal that will be used for future runs of your
2141 @item set inferior-tty /dev/ttyb
2142 @kindex set inferior-tty
2143 Set the tty for the program being debugged to /dev/ttyb.
2145 @item show inferior-tty
2146 @kindex show inferior-tty
2147 Show the current tty for the program being debugged.
2151 @section Debugging an already-running process
2156 @item attach @var{process-id}
2157 This command attaches to a running process---one that was started
2158 outside @value{GDBN}. (@code{info files} shows your active
2159 targets.) The command takes as argument a process ID. The usual way to
2160 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2161 or with the @samp{jobs -l} shell command.
2163 @code{attach} does not repeat if you press @key{RET} a second time after
2164 executing the command.
2167 To use @code{attach}, your program must be running in an environment
2168 which supports processes; for example, @code{attach} does not work for
2169 programs on bare-board targets that lack an operating system. You must
2170 also have permission to send the process a signal.
2172 When you use @code{attach}, the debugger finds the program running in
2173 the process first by looking in the current working directory, then (if
2174 the program is not found) by using the source file search path
2175 (@pxref{Source Path, ,Specifying source directories}). You can also use
2176 the @code{file} command to load the program. @xref{Files, ,Commands to
2179 The first thing @value{GDBN} does after arranging to debug the specified
2180 process is to stop it. You can examine and modify an attached process
2181 with all the @value{GDBN} commands that are ordinarily available when
2182 you start processes with @code{run}. You can insert breakpoints; you
2183 can step and continue; you can modify storage. If you would rather the
2184 process continue running, you may use the @code{continue} command after
2185 attaching @value{GDBN} to the process.
2190 When you have finished debugging the attached process, you can use the
2191 @code{detach} command to release it from @value{GDBN} control. Detaching
2192 the process continues its execution. After the @code{detach} command,
2193 that process and @value{GDBN} become completely independent once more, and you
2194 are ready to @code{attach} another process or start one with @code{run}.
2195 @code{detach} does not repeat if you press @key{RET} again after
2196 executing the command.
2199 If you exit @value{GDBN} or use the @code{run} command while you have an
2200 attached process, you kill that process. By default, @value{GDBN} asks
2201 for confirmation if you try to do either of these things; you can
2202 control whether or not you need to confirm by using the @code{set
2203 confirm} command (@pxref{Messages/Warnings, ,Optional warnings and
2207 @section Killing the child process
2212 Kill the child process in which your program is running under @value{GDBN}.
2215 This command is useful if you wish to debug a core dump instead of a
2216 running process. @value{GDBN} ignores any core dump file while your program
2219 On some operating systems, a program cannot be executed outside @value{GDBN}
2220 while you have breakpoints set on it inside @value{GDBN}. You can use the
2221 @code{kill} command in this situation to permit running your program
2222 outside the debugger.
2224 The @code{kill} command is also useful if you wish to recompile and
2225 relink your program, since on many systems it is impossible to modify an
2226 executable file while it is running in a process. In this case, when you
2227 next type @code{run}, @value{GDBN} notices that the file has changed, and
2228 reads the symbol table again (while trying to preserve your current
2229 breakpoint settings).
2232 @section Debugging programs with multiple threads
2234 @cindex threads of execution
2235 @cindex multiple threads
2236 @cindex switching threads
2237 In some operating systems, such as HP-UX and Solaris, a single program
2238 may have more than one @dfn{thread} of execution. The precise semantics
2239 of threads differ from one operating system to another, but in general
2240 the threads of a single program are akin to multiple processes---except
2241 that they share one address space (that is, they can all examine and
2242 modify the same variables). On the other hand, each thread has its own
2243 registers and execution stack, and perhaps private memory.
2245 @value{GDBN} provides these facilities for debugging multi-thread
2249 @item automatic notification of new threads
2250 @item @samp{thread @var{threadno}}, a command to switch among threads
2251 @item @samp{info threads}, a command to inquire about existing threads
2252 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2253 a command to apply a command to a list of threads
2254 @item thread-specific breakpoints
2258 @emph{Warning:} These facilities are not yet available on every
2259 @value{GDBN} configuration where the operating system supports threads.
2260 If your @value{GDBN} does not support threads, these commands have no
2261 effect. For example, a system without thread support shows no output
2262 from @samp{info threads}, and always rejects the @code{thread} command,
2266 (@value{GDBP}) info threads
2267 (@value{GDBP}) thread 1
2268 Thread ID 1 not known. Use the "info threads" command to
2269 see the IDs of currently known threads.
2271 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2272 @c doesn't support threads"?
2275 @cindex focus of debugging
2276 @cindex current thread
2277 The @value{GDBN} thread debugging facility allows you to observe all
2278 threads while your program runs---but whenever @value{GDBN} takes
2279 control, one thread in particular is always the focus of debugging.
2280 This thread is called the @dfn{current thread}. Debugging commands show
2281 program information from the perspective of the current thread.
2283 @cindex @code{New} @var{systag} message
2284 @cindex thread identifier (system)
2285 @c FIXME-implementors!! It would be more helpful if the [New...] message
2286 @c included GDB's numeric thread handle, so you could just go to that
2287 @c thread without first checking `info threads'.
2288 Whenever @value{GDBN} detects a new thread in your program, it displays
2289 the target system's identification for the thread with a message in the
2290 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2291 whose form varies depending on the particular system. For example, on
2292 LynxOS, you might see
2295 [New process 35 thread 27]
2299 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2300 the @var{systag} is simply something like @samp{process 368}, with no
2303 @c FIXME!! (1) Does the [New...] message appear even for the very first
2304 @c thread of a program, or does it only appear for the
2305 @c second---i.e.@: when it becomes obvious we have a multithread
2307 @c (2) *Is* there necessarily a first thread always? Or do some
2308 @c multithread systems permit starting a program with multiple
2309 @c threads ab initio?
2311 @cindex thread number
2312 @cindex thread identifier (GDB)
2313 For debugging purposes, @value{GDBN} associates its own thread
2314 number---always a single integer---with each thread in your program.
2317 @kindex info threads
2319 Display a summary of all threads currently in your
2320 program. @value{GDBN} displays for each thread (in this order):
2324 the thread number assigned by @value{GDBN}
2327 the target system's thread identifier (@var{systag})
2330 the current stack frame summary for that thread
2334 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2335 indicates the current thread.
2339 @c end table here to get a little more width for example
2342 (@value{GDBP}) info threads
2343 3 process 35 thread 27 0x34e5 in sigpause ()
2344 2 process 35 thread 23 0x34e5 in sigpause ()
2345 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2351 @cindex debugging multithreaded programs (on HP-UX)
2352 @cindex thread identifier (GDB), on HP-UX
2353 For debugging purposes, @value{GDBN} associates its own thread
2354 number---a small integer assigned in thread-creation order---with each
2355 thread in your program.
2357 @cindex @code{New} @var{systag} message, on HP-UX
2358 @cindex thread identifier (system), on HP-UX
2359 @c FIXME-implementors!! It would be more helpful if the [New...] message
2360 @c included GDB's numeric thread handle, so you could just go to that
2361 @c thread without first checking `info threads'.
2362 Whenever @value{GDBN} detects a new thread in your program, it displays
2363 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2364 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2365 whose form varies depending on the particular system. For example, on
2369 [New thread 2 (system thread 26594)]
2373 when @value{GDBN} notices a new thread.
2376 @kindex info threads (HP-UX)
2378 Display a summary of all threads currently in your
2379 program. @value{GDBN} displays for each thread (in this order):
2382 @item the thread number assigned by @value{GDBN}
2384 @item the target system's thread identifier (@var{systag})
2386 @item the current stack frame summary for that thread
2390 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2391 indicates the current thread.
2395 @c end table here to get a little more width for example
2398 (@value{GDBP}) info threads
2399 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2401 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2402 from /usr/lib/libc.2
2403 1 system thread 27905 0x7b003498 in _brk () \@*
2404 from /usr/lib/libc.2
2407 On Solaris, you can display more information about user threads with a
2408 Solaris-specific command:
2411 @item maint info sol-threads
2412 @kindex maint info sol-threads
2413 @cindex thread info (Solaris)
2414 Display info on Solaris user threads.
2418 @kindex thread @var{threadno}
2419 @item thread @var{threadno}
2420 Make thread number @var{threadno} the current thread. The command
2421 argument @var{threadno} is the internal @value{GDBN} thread number, as
2422 shown in the first field of the @samp{info threads} display.
2423 @value{GDBN} responds by displaying the system identifier of the thread
2424 you selected, and its current stack frame summary:
2427 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2428 (@value{GDBP}) thread 2
2429 [Switching to process 35 thread 23]
2430 0x34e5 in sigpause ()
2434 As with the @samp{[New @dots{}]} message, the form of the text after
2435 @samp{Switching to} depends on your system's conventions for identifying
2438 @kindex thread apply
2439 @cindex apply command to several threads
2440 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2441 The @code{thread apply} command allows you to apply the named
2442 @var{command} to one or more threads. Specify the numbers of the
2443 threads that you want affected with the command argument
2444 @var{threadno}. It can be a single thread number, one of the numbers
2445 shown in the first field of the @samp{info threads} display; or it
2446 could be a range of thread numbers, as in @code{2-4}. To apply a
2447 command to all threads, type @kbd{thread apply all @var{command}}.
2450 @cindex automatic thread selection
2451 @cindex switching threads automatically
2452 @cindex threads, automatic switching
2453 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2454 signal, it automatically selects the thread where that breakpoint or
2455 signal happened. @value{GDBN} alerts you to the context switch with a
2456 message of the form @samp{[Switching to @var{systag}]} to identify the
2459 @xref{Thread Stops,,Stopping and starting multi-thread programs}, for
2460 more information about how @value{GDBN} behaves when you stop and start
2461 programs with multiple threads.
2463 @xref{Set Watchpoints,,Setting watchpoints}, for information about
2464 watchpoints in programs with multiple threads.
2467 @section Debugging programs with multiple processes
2469 @cindex fork, debugging programs which call
2470 @cindex multiple processes
2471 @cindex processes, multiple
2472 On most systems, @value{GDBN} has no special support for debugging
2473 programs which create additional processes using the @code{fork}
2474 function. When a program forks, @value{GDBN} will continue to debug the
2475 parent process and the child process will run unimpeded. If you have
2476 set a breakpoint in any code which the child then executes, the child
2477 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2478 will cause it to terminate.
2480 However, if you want to debug the child process there is a workaround
2481 which isn't too painful. Put a call to @code{sleep} in the code which
2482 the child process executes after the fork. It may be useful to sleep
2483 only if a certain environment variable is set, or a certain file exists,
2484 so that the delay need not occur when you don't want to run @value{GDBN}
2485 on the child. While the child is sleeping, use the @code{ps} program to
2486 get its process ID. Then tell @value{GDBN} (a new invocation of
2487 @value{GDBN} if you are also debugging the parent process) to attach to
2488 the child process (@pxref{Attach}). From that point on you can debug
2489 the child process just like any other process which you attached to.
2491 On some systems, @value{GDBN} provides support for debugging programs that
2492 create additional processes using the @code{fork} or @code{vfork} functions.
2493 Currently, the only platforms with this feature are HP-UX (11.x and later
2494 only?) and GNU/Linux (kernel version 2.5.60 and later).
2496 By default, when a program forks, @value{GDBN} will continue to debug
2497 the parent process and the child process will run unimpeded.
2499 If you want to follow the child process instead of the parent process,
2500 use the command @w{@code{set follow-fork-mode}}.
2503 @kindex set follow-fork-mode
2504 @item set follow-fork-mode @var{mode}
2505 Set the debugger response to a program call of @code{fork} or
2506 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2507 process. The @var{mode} argument can be:
2511 The original process is debugged after a fork. The child process runs
2512 unimpeded. This is the default.
2515 The new process is debugged after a fork. The parent process runs
2520 @kindex show follow-fork-mode
2521 @item show follow-fork-mode
2522 Display the current debugger response to a @code{fork} or @code{vfork} call.
2525 @cindex debugging multiple processes
2526 On Linux, if you want to debug both the parent and child processes, use the
2527 command @w{@code{set detach-on-fork}}.
2530 @kindex set detach-on-fork
2531 @item set detach-on-fork @var{mode}
2532 Tells gdb whether to detach one of the processes after a fork, or
2533 retain debugger control over them both.
2537 The child process (or parent process, depending on the value of
2538 @code{follow-fork-mode}) will be detached and allowed to run
2539 independently. This is the default.
2542 Both processes will be held under the control of @value{GDBN}.
2543 One process (child or parent, depending on the value of
2544 @code{follow-fork-mode}) is debugged as usual, while the other
2549 @kindex show detach-on-follow
2550 @item show detach-on-follow
2551 Show whether detach-on-follow mode is on/off.
2554 If you choose to set @var{detach-on-follow} mode off, then
2555 @value{GDBN} will retain control of all forked processes (including
2556 nested forks). You can list the forked processes under the control of
2557 @value{GDBN} by using the @w{@code{info forks}} command, and switch
2558 from one fork to another by using the @w{@code{fork}} command.
2563 Print a list of all forked processes under the control of @value{GDBN}.
2564 The listing will include a fork id, a process id, and the current
2565 position (program counter) of the process.
2568 @kindex fork @var{fork-id}
2569 @item fork @var{fork-id}
2570 Make fork number @var{fork-id} the current process. The argument
2571 @var{fork-id} is the internal fork number assigned by @value{GDBN},
2572 as shown in the first field of the @samp{info forks} display.
2576 To quit debugging one of the forked processes, you can either detach
2577 from it by using the @w{@code{detach-fork}} command (allowing it to
2578 run independently), or delete (and kill) it using the
2579 @w{@code{delete fork}} command.
2582 @kindex detach-fork @var{fork-id}
2583 @item detach-fork @var{fork-id}
2584 Detach from the process identified by @value{GDBN} fork number
2585 @var{fork-id}, and remove it from the fork list. The process will be
2586 allowed to run independently.
2588 @kindex delete fork @var{fork-id}
2589 @item delete fork @var{fork-id}
2590 Kill the process identified by @value{GDBN} fork number @var{fork-id},
2591 and remove it from the fork list.
2595 If you ask to debug a child process and a @code{vfork} is followed by an
2596 @code{exec}, @value{GDBN} executes the new target up to the first
2597 breakpoint in the new target. If you have a breakpoint set on
2598 @code{main} in your original program, the breakpoint will also be set on
2599 the child process's @code{main}.
2601 When a child process is spawned by @code{vfork}, you cannot debug the
2602 child or parent until an @code{exec} call completes.
2604 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2605 call executes, the new target restarts. To restart the parent process,
2606 use the @code{file} command with the parent executable name as its
2609 You can use the @code{catch} command to make @value{GDBN} stop whenever
2610 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2611 Catchpoints, ,Setting catchpoints}.
2613 @node Checkpoint/Restart
2614 @section Setting a @emph{bookmark} to return to later
2619 @cindex snapshot of a process
2620 @cindex rewind program state
2622 On certain operating systems@footnote{Currently, only
2623 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
2624 program's state, called a @dfn{checkpoint}, and come back to it
2627 Returning to a checkpoint effectively undoes everything that has
2628 happened in the program since the @code{checkpoint} was saved. This
2629 includes changes in memory, registers, and even (within some limits)
2630 system state. Effectively, it is like going back in time to the
2631 moment when the checkpoint was saved.
2633 Thus, if you're stepping thru a program and you think you're
2634 getting close to the point where things go wrong, you can save
2635 a checkpoint. Then, if you accidentally go too far and miss
2636 the critical statement, instead of having to restart your program
2637 from the beginning, you can just go back to the checkpoint and
2638 start again from there.
2640 This can be especially useful if it takes a lot of time or
2641 steps to reach the point where you think the bug occurs.
2643 To use the @code{checkpoint}/@code{restart} method of debugging:
2648 Save a snapshot of the debugged program's current execution state.
2649 The @code{checkpoint} command takes no arguments, but each checkpoint
2650 is assigned a small integer id, similar to a breakpoint id.
2652 @kindex info checkpoints
2653 @item info checkpoints
2654 List the checkpoints that have been saved in the current debugging
2655 session. For each checkpoint, the following information will be
2662 @item Source line, or label
2665 @kindex restart @var{checkpoint-id}
2666 @item restart @var{checkpoint-id}
2667 Restore the program state that was saved as checkpoint number
2668 @var{checkpoint-id}. All program variables, registers, stack frames
2669 etc.@: will be returned to the values that they had when the checkpoint
2670 was saved. In essence, gdb will ``wind back the clock'' to the point
2671 in time when the checkpoint was saved.
2673 Note that breakpoints, @value{GDBN} variables, command history etc.
2674 are not affected by restoring a checkpoint. In general, a checkpoint
2675 only restores things that reside in the program being debugged, not in
2678 @kindex delete checkpoint @var{checkpoint-id}
2679 @item delete checkpoint @var{checkpoint-id}
2680 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
2684 Returning to a previously saved checkpoint will restore the user state
2685 of the program being debugged, plus a significant subset of the system
2686 (OS) state, including file pointers. It won't ``un-write'' data from
2687 a file, but it will rewind the file pointer to the previous location,
2688 so that the previously written data can be overwritten. For files
2689 opened in read mode, the pointer will also be restored so that the
2690 previously read data can be read again.
2692 Of course, characters that have been sent to a printer (or other
2693 external device) cannot be ``snatched back'', and characters received
2694 from eg.@: a serial device can be removed from internal program buffers,
2695 but they cannot be ``pushed back'' into the serial pipeline, ready to
2696 be received again. Similarly, the actual contents of files that have
2697 been changed cannot be restored (at this time).
2699 However, within those constraints, you actually can ``rewind'' your
2700 program to a previously saved point in time, and begin debugging it
2701 again --- and you can change the course of events so as to debug a
2702 different execution path this time.
2704 @cindex checkpoints and process id
2705 Finally, there is one bit of internal program state that will be
2706 different when you return to a checkpoint --- the program's process
2707 id. Each checkpoint will have a unique process id (or @var{pid}),
2708 and each will be different from the program's original @var{pid}.
2709 If your program has saved a local copy of its process id, this could
2710 potentially pose a problem.
2712 @subsection A non-obvious benefit of using checkpoints
2714 On some systems such as @sc{gnu}/Linux, address space randomization
2715 is performed on new processes for security reasons. This makes it
2716 difficult or impossible to set a breakpoint, or watchpoint, on an
2717 absolute address if you have to restart the program, since the
2718 absolute location of a symbol will change from one execution to the
2721 A checkpoint, however, is an @emph{identical} copy of a process.
2722 Therefore if you create a checkpoint at (eg.@:) the start of main,
2723 and simply return to that checkpoint instead of restarting the
2724 process, you can avoid the effects of address randomization and
2725 your symbols will all stay in the same place.
2728 @chapter Stopping and Continuing
2730 The principal purposes of using a debugger are so that you can stop your
2731 program before it terminates; or so that, if your program runs into
2732 trouble, you can investigate and find out why.
2734 Inside @value{GDBN}, your program may stop for any of several reasons,
2735 such as a signal, a breakpoint, or reaching a new line after a
2736 @value{GDBN} command such as @code{step}. You may then examine and
2737 change variables, set new breakpoints or remove old ones, and then
2738 continue execution. Usually, the messages shown by @value{GDBN} provide
2739 ample explanation of the status of your program---but you can also
2740 explicitly request this information at any time.
2743 @kindex info program
2745 Display information about the status of your program: whether it is
2746 running or not, what process it is, and why it stopped.
2750 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2751 * Continuing and Stepping:: Resuming execution
2753 * Thread Stops:: Stopping and starting multi-thread programs
2757 @section Breakpoints, watchpoints, and catchpoints
2760 A @dfn{breakpoint} makes your program stop whenever a certain point in
2761 the program is reached. For each breakpoint, you can add conditions to
2762 control in finer detail whether your program stops. You can set
2763 breakpoints with the @code{break} command and its variants (@pxref{Set
2764 Breaks, ,Setting breakpoints}), to specify the place where your program
2765 should stop by line number, function name or exact address in the
2768 On some systems, you can set breakpoints in shared libraries before
2769 the executable is run. There is a minor limitation on HP-UX systems:
2770 you must wait until the executable is run in order to set breakpoints
2771 in shared library routines that are not called directly by the program
2772 (for example, routines that are arguments in a @code{pthread_create}
2776 @cindex memory tracing
2777 @cindex breakpoint on memory address
2778 @cindex breakpoint on variable modification
2779 A @dfn{watchpoint} is a special breakpoint that stops your program
2780 when the value of an expression changes. You must use a different
2781 command to set watchpoints (@pxref{Set Watchpoints, ,Setting
2782 watchpoints}), but aside from that, you can manage a watchpoint like
2783 any other breakpoint: you enable, disable, and delete both breakpoints
2784 and watchpoints using the same commands.
2786 You can arrange to have values from your program displayed automatically
2787 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2791 @cindex breakpoint on events
2792 A @dfn{catchpoint} is another special breakpoint that stops your program
2793 when a certain kind of event occurs, such as the throwing of a C@t{++}
2794 exception or the loading of a library. As with watchpoints, you use a
2795 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2796 catchpoints}), but aside from that, you can manage a catchpoint like any
2797 other breakpoint. (To stop when your program receives a signal, use the
2798 @code{handle} command; see @ref{Signals, ,Signals}.)
2800 @cindex breakpoint numbers
2801 @cindex numbers for breakpoints
2802 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2803 catchpoint when you create it; these numbers are successive integers
2804 starting with one. In many of the commands for controlling various
2805 features of breakpoints you use the breakpoint number to say which
2806 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2807 @dfn{disabled}; if disabled, it has no effect on your program until you
2810 @cindex breakpoint ranges
2811 @cindex ranges of breakpoints
2812 Some @value{GDBN} commands accept a range of breakpoints on which to
2813 operate. A breakpoint range is either a single breakpoint number, like
2814 @samp{5}, or two such numbers, in increasing order, separated by a
2815 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2816 all breakpoint in that range are operated on.
2819 * Set Breaks:: Setting breakpoints
2820 * Set Watchpoints:: Setting watchpoints
2821 * Set Catchpoints:: Setting catchpoints
2822 * Delete Breaks:: Deleting breakpoints
2823 * Disabling:: Disabling breakpoints
2824 * Conditions:: Break conditions
2825 * Break Commands:: Breakpoint command lists
2826 * Breakpoint Menus:: Breakpoint menus
2827 * Error in Breakpoints:: ``Cannot insert breakpoints''
2828 * Breakpoint related warnings:: ``Breakpoint address adjusted...''
2832 @subsection Setting breakpoints
2834 @c FIXME LMB what does GDB do if no code on line of breakpt?
2835 @c consider in particular declaration with/without initialization.
2837 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2840 @kindex b @r{(@code{break})}
2841 @vindex $bpnum@r{, convenience variable}
2842 @cindex latest breakpoint
2843 Breakpoints are set with the @code{break} command (abbreviated
2844 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2845 number of the breakpoint you've set most recently; see @ref{Convenience
2846 Vars,, Convenience variables}, for a discussion of what you can do with
2847 convenience variables.
2849 You have several ways to say where the breakpoint should go.
2852 @item break @var{function}
2853 Set a breakpoint at entry to function @var{function}.
2854 When using source languages that permit overloading of symbols, such as
2855 C@t{++}, @var{function} may refer to more than one possible place to break.
2856 @xref{Breakpoint Menus,,Breakpoint menus}, for a discussion of that situation.
2858 @item break +@var{offset}
2859 @itemx break -@var{offset}
2860 Set a breakpoint some number of lines forward or back from the position
2861 at which execution stopped in the currently selected @dfn{stack frame}.
2862 (@xref{Frames, ,Frames}, for a description of stack frames.)
2864 @item break @var{linenum}
2865 Set a breakpoint at line @var{linenum} in the current source file.
2866 The current source file is the last file whose source text was printed.
2867 The breakpoint will stop your program just before it executes any of the
2870 @item break @var{filename}:@var{linenum}
2871 Set a breakpoint at line @var{linenum} in source file @var{filename}.
2873 @item break @var{filename}:@var{function}
2874 Set a breakpoint at entry to function @var{function} found in file
2875 @var{filename}. Specifying a file name as well as a function name is
2876 superfluous except when multiple files contain similarly named
2879 @item break *@var{address}
2880 Set a breakpoint at address @var{address}. You can use this to set
2881 breakpoints in parts of your program which do not have debugging
2882 information or source files.
2885 When called without any arguments, @code{break} sets a breakpoint at
2886 the next instruction to be executed in the selected stack frame
2887 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2888 innermost, this makes your program stop as soon as control
2889 returns to that frame. This is similar to the effect of a
2890 @code{finish} command in the frame inside the selected frame---except
2891 that @code{finish} does not leave an active breakpoint. If you use
2892 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2893 the next time it reaches the current location; this may be useful
2896 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2897 least one instruction has been executed. If it did not do this, you
2898 would be unable to proceed past a breakpoint without first disabling the
2899 breakpoint. This rule applies whether or not the breakpoint already
2900 existed when your program stopped.
2902 @item break @dots{} if @var{cond}
2903 Set a breakpoint with condition @var{cond}; evaluate the expression
2904 @var{cond} each time the breakpoint is reached, and stop only if the
2905 value is nonzero---that is, if @var{cond} evaluates as true.
2906 @samp{@dots{}} stands for one of the possible arguments described
2907 above (or no argument) specifying where to break. @xref{Conditions,
2908 ,Break conditions}, for more information on breakpoint conditions.
2911 @item tbreak @var{args}
2912 Set a breakpoint enabled only for one stop. @var{args} are the
2913 same as for the @code{break} command, and the breakpoint is set in the same
2914 way, but the breakpoint is automatically deleted after the first time your
2915 program stops there. @xref{Disabling, ,Disabling breakpoints}.
2918 @cindex hardware breakpoints
2919 @item hbreak @var{args}
2920 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2921 @code{break} command and the breakpoint is set in the same way, but the
2922 breakpoint requires hardware support and some target hardware may not
2923 have this support. The main purpose of this is EPROM/ROM code
2924 debugging, so you can set a breakpoint at an instruction without
2925 changing the instruction. This can be used with the new trap-generation
2926 provided by SPARClite DSU and most x86-based targets. These targets
2927 will generate traps when a program accesses some data or instruction
2928 address that is assigned to the debug registers. However the hardware
2929 breakpoint registers can take a limited number of breakpoints. For
2930 example, on the DSU, only two data breakpoints can be set at a time, and
2931 @value{GDBN} will reject this command if more than two are used. Delete
2932 or disable unused hardware breakpoints before setting new ones
2933 (@pxref{Disabling, ,Disabling}). @xref{Conditions, ,Break conditions}.
2934 For remote targets, you can restrict the number of hardware
2935 breakpoints @value{GDBN} will use, see @ref{set remote
2936 hardware-breakpoint-limit}.
2940 @item thbreak @var{args}
2941 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2942 are the same as for the @code{hbreak} command and the breakpoint is set in
2943 the same way. However, like the @code{tbreak} command,
2944 the breakpoint is automatically deleted after the
2945 first time your program stops there. Also, like the @code{hbreak}
2946 command, the breakpoint requires hardware support and some target hardware
2947 may not have this support. @xref{Disabling, ,Disabling breakpoints}.
2948 See also @ref{Conditions, ,Break conditions}.
2951 @cindex regular expression
2952 @cindex breakpoints in functions matching a regexp
2953 @cindex set breakpoints in many functions
2954 @item rbreak @var{regex}
2955 Set breakpoints on all functions matching the regular expression
2956 @var{regex}. This command sets an unconditional breakpoint on all
2957 matches, printing a list of all breakpoints it set. Once these
2958 breakpoints are set, they are treated just like the breakpoints set with
2959 the @code{break} command. You can delete them, disable them, or make
2960 them conditional the same way as any other breakpoint.
2962 The syntax of the regular expression is the standard one used with tools
2963 like @file{grep}. Note that this is different from the syntax used by
2964 shells, so for instance @code{foo*} matches all functions that include
2965 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2966 @code{.*} leading and trailing the regular expression you supply, so to
2967 match only functions that begin with @code{foo}, use @code{^foo}.
2969 @cindex non-member C@t{++} functions, set breakpoint in
2970 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2971 breakpoints on overloaded functions that are not members of any special
2974 @cindex set breakpoints on all functions
2975 The @code{rbreak} command can be used to set breakpoints in
2976 @strong{all} the functions in a program, like this:
2979 (@value{GDBP}) rbreak .
2982 @kindex info breakpoints
2983 @cindex @code{$_} and @code{info breakpoints}
2984 @item info breakpoints @r{[}@var{n}@r{]}
2985 @itemx info break @r{[}@var{n}@r{]}
2986 @itemx info watchpoints @r{[}@var{n}@r{]}
2987 Print a table of all breakpoints, watchpoints, and catchpoints set and
2988 not deleted, with the following columns for each breakpoint:
2991 @item Breakpoint Numbers
2993 Breakpoint, watchpoint, or catchpoint.
2995 Whether the breakpoint is marked to be disabled or deleted when hit.
2996 @item Enabled or Disabled
2997 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
2998 that are not enabled.
3000 Where the breakpoint is in your program, as a memory address. If the
3001 breakpoint is pending (see below for details) on a future load of a shared library, the address
3002 will be listed as @samp{<PENDING>}.
3004 Where the breakpoint is in the source for your program, as a file and
3005 line number. For a pending breakpoint, the original string passed to
3006 the breakpoint command will be listed as it cannot be resolved until
3007 the appropriate shared library is loaded in the future.
3011 If a breakpoint is conditional, @code{info break} shows the condition on
3012 the line following the affected breakpoint; breakpoint commands, if any,
3013 are listed after that. A pending breakpoint is allowed to have a condition
3014 specified for it. The condition is not parsed for validity until a shared
3015 library is loaded that allows the pending breakpoint to resolve to a
3019 @code{info break} with a breakpoint
3020 number @var{n} as argument lists only that breakpoint. The
3021 convenience variable @code{$_} and the default examining-address for
3022 the @code{x} command are set to the address of the last breakpoint
3023 listed (@pxref{Memory, ,Examining memory}).
3026 @code{info break} displays a count of the number of times the breakpoint
3027 has been hit. This is especially useful in conjunction with the
3028 @code{ignore} command. You can ignore a large number of breakpoint
3029 hits, look at the breakpoint info to see how many times the breakpoint
3030 was hit, and then run again, ignoring one less than that number. This
3031 will get you quickly to the last hit of that breakpoint.
3034 @value{GDBN} allows you to set any number of breakpoints at the same place in
3035 your program. There is nothing silly or meaningless about this. When
3036 the breakpoints are conditional, this is even useful
3037 (@pxref{Conditions, ,Break conditions}).
3039 @cindex pending breakpoints
3040 If a specified breakpoint location cannot be found, it may be due to the fact
3041 that the location is in a shared library that is yet to be loaded. In such
3042 a case, you may want @value{GDBN} to create a special breakpoint (known as
3043 a @dfn{pending breakpoint}) that
3044 attempts to resolve itself in the future when an appropriate shared library
3047 Pending breakpoints are useful to set at the start of your
3048 @value{GDBN} session for locations that you know will be dynamically loaded
3049 later by the program being debugged. When shared libraries are loaded,
3050 a check is made to see if the load resolves any pending breakpoint locations.
3051 If a pending breakpoint location gets resolved,
3052 a regular breakpoint is created and the original pending breakpoint is removed.
3054 @value{GDBN} provides some additional commands for controlling pending
3057 @kindex set breakpoint pending
3058 @kindex show breakpoint pending
3060 @item set breakpoint pending auto
3061 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3062 location, it queries you whether a pending breakpoint should be created.
3064 @item set breakpoint pending on
3065 This indicates that an unrecognized breakpoint location should automatically
3066 result in a pending breakpoint being created.
3068 @item set breakpoint pending off
3069 This indicates that pending breakpoints are not to be created. Any
3070 unrecognized breakpoint location results in an error. This setting does
3071 not affect any pending breakpoints previously created.
3073 @item show breakpoint pending
3074 Show the current behavior setting for creating pending breakpoints.
3077 @cindex operations allowed on pending breakpoints
3078 Normal breakpoint operations apply to pending breakpoints as well. You may
3079 specify a condition for a pending breakpoint and/or commands to run when the
3080 breakpoint is reached. You can also enable or disable
3081 the pending breakpoint. When you specify a condition for a pending breakpoint,
3082 the parsing of the condition will be deferred until the point where the
3083 pending breakpoint location is resolved. Disabling a pending breakpoint
3084 tells @value{GDBN} to not attempt to resolve the breakpoint on any subsequent
3085 shared library load. When a pending breakpoint is re-enabled,
3086 @value{GDBN} checks to see if the location is already resolved.
3087 This is done because any number of shared library loads could have
3088 occurred since the time the breakpoint was disabled and one or more
3089 of these loads could resolve the location.
3091 @cindex negative breakpoint numbers
3092 @cindex internal @value{GDBN} breakpoints
3093 @value{GDBN} itself sometimes sets breakpoints in your program for
3094 special purposes, such as proper handling of @code{longjmp} (in C
3095 programs). These internal breakpoints are assigned negative numbers,
3096 starting with @code{-1}; @samp{info breakpoints} does not display them.
3097 You can see these breakpoints with the @value{GDBN} maintenance command
3098 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3101 @node Set Watchpoints
3102 @subsection Setting watchpoints
3104 @cindex setting watchpoints
3105 You can use a watchpoint to stop execution whenever the value of an
3106 expression changes, without having to predict a particular place where
3109 @cindex software watchpoints
3110 @cindex hardware watchpoints
3111 Depending on your system, watchpoints may be implemented in software or
3112 hardware. @value{GDBN} does software watchpointing by single-stepping your
3113 program and testing the variable's value each time, which is hundreds of
3114 times slower than normal execution. (But this may still be worth it, to
3115 catch errors where you have no clue what part of your program is the
3118 On some systems, such as HP-UX, @sc{gnu}/Linux and most other
3119 x86-based targets, @value{GDBN} includes support for hardware
3120 watchpoints, which do not slow down the running of your program.
3124 @item watch @var{expr}
3125 Set a watchpoint for an expression. @value{GDBN} will break when @var{expr}
3126 is written into by the program and its value changes.
3129 @item rwatch @var{expr}
3130 Set a watchpoint that will break when the value of @var{expr} is read
3134 @item awatch @var{expr}
3135 Set a watchpoint that will break when @var{expr} is either read from
3136 or written into by the program.
3138 @kindex info watchpoints
3139 @item info watchpoints
3140 This command prints a list of watchpoints, breakpoints, and catchpoints;
3141 it is the same as @code{info break} (@pxref{Set Breaks}).
3144 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3145 watchpoints execute very quickly, and the debugger reports a change in
3146 value at the exact instruction where the change occurs. If @value{GDBN}
3147 cannot set a hardware watchpoint, it sets a software watchpoint, which
3148 executes more slowly and reports the change in value at the next
3149 @emph{statement}, not the instruction, after the change occurs.
3151 @cindex use only software watchpoints
3152 You can force @value{GDBN} to use only software watchpoints with the
3153 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3154 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3155 the underlying system supports them. (Note that hardware-assisted
3156 watchpoints that were set @emph{before} setting
3157 @code{can-use-hw-watchpoints} to zero will still use the hardware
3158 mechanism of watching expressiion values.)
3161 @item set can-use-hw-watchpoints
3162 @kindex set can-use-hw-watchpoints
3163 Set whether or not to use hardware watchpoints.
3165 @item show can-use-hw-watchpoints
3166 @kindex show can-use-hw-watchpoints
3167 Show the current mode of using hardware watchpoints.
3170 For remote targets, you can restrict the number of hardware
3171 watchpoints @value{GDBN} will use, see @ref{set remote
3172 hardware-breakpoint-limit}.
3174 When you issue the @code{watch} command, @value{GDBN} reports
3177 Hardware watchpoint @var{num}: @var{expr}
3181 if it was able to set a hardware watchpoint.
3183 Currently, the @code{awatch} and @code{rwatch} commands can only set
3184 hardware watchpoints, because accesses to data that don't change the
3185 value of the watched expression cannot be detected without examining
3186 every instruction as it is being executed, and @value{GDBN} does not do
3187 that currently. If @value{GDBN} finds that it is unable to set a
3188 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3189 will print a message like this:
3192 Expression cannot be implemented with read/access watchpoint.
3195 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3196 data type of the watched expression is wider than what a hardware
3197 watchpoint on the target machine can handle. For example, some systems
3198 can only watch regions that are up to 4 bytes wide; on such systems you
3199 cannot set hardware watchpoints for an expression that yields a
3200 double-precision floating-point number (which is typically 8 bytes
3201 wide). As a work-around, it might be possible to break the large region
3202 into a series of smaller ones and watch them with separate watchpoints.
3204 If you set too many hardware watchpoints, @value{GDBN} might be unable
3205 to insert all of them when you resume the execution of your program.
3206 Since the precise number of active watchpoints is unknown until such
3207 time as the program is about to be resumed, @value{GDBN} might not be
3208 able to warn you about this when you set the watchpoints, and the
3209 warning will be printed only when the program is resumed:
3212 Hardware watchpoint @var{num}: Could not insert watchpoint
3216 If this happens, delete or disable some of the watchpoints.
3218 The SPARClite DSU will generate traps when a program accesses some data
3219 or instruction address that is assigned to the debug registers. For the
3220 data addresses, DSU facilitates the @code{watch} command. However the
3221 hardware breakpoint registers can only take two data watchpoints, and
3222 both watchpoints must be the same kind. For example, you can set two
3223 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
3224 @strong{or} two with @code{awatch} commands, but you cannot set one
3225 watchpoint with one command and the other with a different command.
3226 @value{GDBN} will reject the command if you try to mix watchpoints.
3227 Delete or disable unused watchpoint commands before setting new ones.
3229 If you call a function interactively using @code{print} or @code{call},
3230 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3231 kind of breakpoint or the call completes.
3233 @value{GDBN} automatically deletes watchpoints that watch local
3234 (automatic) variables, or expressions that involve such variables, when
3235 they go out of scope, that is, when the execution leaves the block in
3236 which these variables were defined. In particular, when the program
3237 being debugged terminates, @emph{all} local variables go out of scope,
3238 and so only watchpoints that watch global variables remain set. If you
3239 rerun the program, you will need to set all such watchpoints again. One
3240 way of doing that would be to set a code breakpoint at the entry to the
3241 @code{main} function and when it breaks, set all the watchpoints.
3244 @cindex watchpoints and threads
3245 @cindex threads and watchpoints
3246 @emph{Warning:} In multi-thread programs, watchpoints have only limited
3247 usefulness. With the current watchpoint implementation, @value{GDBN}
3248 can only watch the value of an expression @emph{in a single thread}. If
3249 you are confident that the expression can only change due to the current
3250 thread's activity (and if you are also confident that no other thread
3251 can become current), then you can use watchpoints as usual. However,
3252 @value{GDBN} may not notice when a non-current thread's activity changes
3255 @c FIXME: this is almost identical to the previous paragraph.
3256 @emph{HP-UX Warning:} In multi-thread programs, software watchpoints
3257 have only limited usefulness. If @value{GDBN} creates a software
3258 watchpoint, it can only watch the value of an expression @emph{in a
3259 single thread}. If you are confident that the expression can only
3260 change due to the current thread's activity (and if you are also
3261 confident that no other thread can become current), then you can use
3262 software watchpoints as usual. However, @value{GDBN} may not notice
3263 when a non-current thread's activity changes the expression. (Hardware
3264 watchpoints, in contrast, watch an expression in all threads.)
3267 @xref{set remote hardware-watchpoint-limit}.
3269 @node Set Catchpoints
3270 @subsection Setting catchpoints
3271 @cindex catchpoints, setting
3272 @cindex exception handlers
3273 @cindex event handling
3275 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3276 kinds of program events, such as C@t{++} exceptions or the loading of a
3277 shared library. Use the @code{catch} command to set a catchpoint.
3281 @item catch @var{event}
3282 Stop when @var{event} occurs. @var{event} can be any of the following:
3285 @cindex stop on C@t{++} exceptions
3286 The throwing of a C@t{++} exception.
3289 The catching of a C@t{++} exception.
3292 @cindex break on fork/exec
3293 A call to @code{exec}. This is currently only available for HP-UX.
3296 A call to @code{fork}. This is currently only available for HP-UX.
3299 A call to @code{vfork}. This is currently only available for HP-UX.
3302 @itemx load @var{libname}
3303 @cindex break on load/unload of shared library
3304 The dynamic loading of any shared library, or the loading of the library
3305 @var{libname}. This is currently only available for HP-UX.
3308 @itemx unload @var{libname}
3309 The unloading of any dynamically loaded shared library, or the unloading
3310 of the library @var{libname}. This is currently only available for HP-UX.
3313 @item tcatch @var{event}
3314 Set a catchpoint that is enabled only for one stop. The catchpoint is
3315 automatically deleted after the first time the event is caught.
3319 Use the @code{info break} command to list the current catchpoints.
3321 There are currently some limitations to C@t{++} exception handling
3322 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
3326 If you call a function interactively, @value{GDBN} normally returns
3327 control to you when the function has finished executing. If the call
3328 raises an exception, however, the call may bypass the mechanism that
3329 returns control to you and cause your program either to abort or to
3330 simply continue running until it hits a breakpoint, catches a signal
3331 that @value{GDBN} is listening for, or exits. This is the case even if
3332 you set a catchpoint for the exception; catchpoints on exceptions are
3333 disabled within interactive calls.
3336 You cannot raise an exception interactively.
3339 You cannot install an exception handler interactively.
3342 @cindex raise exceptions
3343 Sometimes @code{catch} is not the best way to debug exception handling:
3344 if you need to know exactly where an exception is raised, it is better to
3345 stop @emph{before} the exception handler is called, since that way you
3346 can see the stack before any unwinding takes place. If you set a
3347 breakpoint in an exception handler instead, it may not be easy to find
3348 out where the exception was raised.
3350 To stop just before an exception handler is called, you need some
3351 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3352 raised by calling a library function named @code{__raise_exception}
3353 which has the following ANSI C interface:
3356 /* @var{addr} is where the exception identifier is stored.
3357 @var{id} is the exception identifier. */
3358 void __raise_exception (void **addr, void *id);
3362 To make the debugger catch all exceptions before any stack
3363 unwinding takes place, set a breakpoint on @code{__raise_exception}
3364 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and exceptions}).
3366 With a conditional breakpoint (@pxref{Conditions, ,Break conditions})
3367 that depends on the value of @var{id}, you can stop your program when
3368 a specific exception is raised. You can use multiple conditional
3369 breakpoints to stop your program when any of a number of exceptions are
3374 @subsection Deleting breakpoints
3376 @cindex clearing breakpoints, watchpoints, catchpoints
3377 @cindex deleting breakpoints, watchpoints, catchpoints
3378 It is often necessary to eliminate a breakpoint, watchpoint, or
3379 catchpoint once it has done its job and you no longer want your program
3380 to stop there. This is called @dfn{deleting} the breakpoint. A
3381 breakpoint that has been deleted no longer exists; it is forgotten.
3383 With the @code{clear} command you can delete breakpoints according to
3384 where they are in your program. With the @code{delete} command you can
3385 delete individual breakpoints, watchpoints, or catchpoints by specifying
3386 their breakpoint numbers.
3388 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3389 automatically ignores breakpoints on the first instruction to be executed
3390 when you continue execution without changing the execution address.
3395 Delete any breakpoints at the next instruction to be executed in the
3396 selected stack frame (@pxref{Selection, ,Selecting a frame}). When
3397 the innermost frame is selected, this is a good way to delete a
3398 breakpoint where your program just stopped.
3400 @item clear @var{function}
3401 @itemx clear @var{filename}:@var{function}
3402 Delete any breakpoints set at entry to the named @var{function}.
3404 @item clear @var{linenum}
3405 @itemx clear @var{filename}:@var{linenum}
3406 Delete any breakpoints set at or within the code of the specified
3407 @var{linenum} of the specified @var{filename}.
3409 @cindex delete breakpoints
3411 @kindex d @r{(@code{delete})}
3412 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3413 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3414 ranges specified as arguments. If no argument is specified, delete all
3415 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3416 confirm off}). You can abbreviate this command as @code{d}.
3420 @subsection Disabling breakpoints
3422 @cindex enable/disable a breakpoint
3423 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3424 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3425 it had been deleted, but remembers the information on the breakpoint so
3426 that you can @dfn{enable} it again later.
3428 You disable and enable breakpoints, watchpoints, and catchpoints with
3429 the @code{enable} and @code{disable} commands, optionally specifying one
3430 or more breakpoint numbers as arguments. Use @code{info break} or
3431 @code{info watch} to print a list of breakpoints, watchpoints, and
3432 catchpoints if you do not know which numbers to use.
3434 A breakpoint, watchpoint, or catchpoint can have any of four different
3435 states of enablement:
3439 Enabled. The breakpoint stops your program. A breakpoint set
3440 with the @code{break} command starts out in this state.
3442 Disabled. The breakpoint has no effect on your program.
3444 Enabled once. The breakpoint stops your program, but then becomes
3447 Enabled for deletion. The breakpoint stops your program, but
3448 immediately after it does so it is deleted permanently. A breakpoint
3449 set with the @code{tbreak} command starts out in this state.
3452 You can use the following commands to enable or disable breakpoints,
3453 watchpoints, and catchpoints:
3457 @kindex dis @r{(@code{disable})}
3458 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3459 Disable the specified breakpoints---or all breakpoints, if none are
3460 listed. A disabled breakpoint has no effect but is not forgotten. All
3461 options such as ignore-counts, conditions and commands are remembered in
3462 case the breakpoint is enabled again later. You may abbreviate
3463 @code{disable} as @code{dis}.
3466 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3467 Enable the specified breakpoints (or all defined breakpoints). They
3468 become effective once again in stopping your program.
3470 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3471 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3472 of these breakpoints immediately after stopping your program.
3474 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3475 Enable the specified breakpoints to work once, then die. @value{GDBN}
3476 deletes any of these breakpoints as soon as your program stops there.
3477 Breakpoints set by the @code{tbreak} command start out in this state.
3480 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3481 @c confusing: tbreak is also initially enabled.
3482 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3483 ,Setting breakpoints}), breakpoints that you set are initially enabled;
3484 subsequently, they become disabled or enabled only when you use one of
3485 the commands above. (The command @code{until} can set and delete a
3486 breakpoint of its own, but it does not change the state of your other
3487 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3491 @subsection Break conditions
3492 @cindex conditional breakpoints
3493 @cindex breakpoint conditions
3495 @c FIXME what is scope of break condition expr? Context where wanted?
3496 @c in particular for a watchpoint?
3497 The simplest sort of breakpoint breaks every time your program reaches a
3498 specified place. You can also specify a @dfn{condition} for a
3499 breakpoint. A condition is just a Boolean expression in your
3500 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3501 a condition evaluates the expression each time your program reaches it,
3502 and your program stops only if the condition is @emph{true}.
3504 This is the converse of using assertions for program validation; in that
3505 situation, you want to stop when the assertion is violated---that is,
3506 when the condition is false. In C, if you want to test an assertion expressed
3507 by the condition @var{assert}, you should set the condition
3508 @samp{! @var{assert}} on the appropriate breakpoint.
3510 Conditions are also accepted for watchpoints; you may not need them,
3511 since a watchpoint is inspecting the value of an expression anyhow---but
3512 it might be simpler, say, to just set a watchpoint on a variable name,
3513 and specify a condition that tests whether the new value is an interesting
3516 Break conditions can have side effects, and may even call functions in
3517 your program. This can be useful, for example, to activate functions
3518 that log program progress, or to use your own print functions to
3519 format special data structures. The effects are completely predictable
3520 unless there is another enabled breakpoint at the same address. (In
3521 that case, @value{GDBN} might see the other breakpoint first and stop your
3522 program without checking the condition of this one.) Note that
3523 breakpoint commands are usually more convenient and flexible than break
3525 purpose of performing side effects when a breakpoint is reached
3526 (@pxref{Break Commands, ,Breakpoint command lists}).
3528 Break conditions can be specified when a breakpoint is set, by using
3529 @samp{if} in the arguments to the @code{break} command. @xref{Set
3530 Breaks, ,Setting breakpoints}. They can also be changed at any time
3531 with the @code{condition} command.
3533 You can also use the @code{if} keyword with the @code{watch} command.
3534 The @code{catch} command does not recognize the @code{if} keyword;
3535 @code{condition} is the only way to impose a further condition on a
3540 @item condition @var{bnum} @var{expression}
3541 Specify @var{expression} as the break condition for breakpoint,
3542 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3543 breakpoint @var{bnum} stops your program only if the value of
3544 @var{expression} is true (nonzero, in C). When you use
3545 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3546 syntactic correctness, and to determine whether symbols in it have
3547 referents in the context of your breakpoint. If @var{expression} uses
3548 symbols not referenced in the context of the breakpoint, @value{GDBN}
3549 prints an error message:
3552 No symbol "foo" in current context.
3557 not actually evaluate @var{expression} at the time the @code{condition}
3558 command (or a command that sets a breakpoint with a condition, like
3559 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3561 @item condition @var{bnum}
3562 Remove the condition from breakpoint number @var{bnum}. It becomes
3563 an ordinary unconditional breakpoint.
3566 @cindex ignore count (of breakpoint)
3567 A special case of a breakpoint condition is to stop only when the
3568 breakpoint has been reached a certain number of times. This is so
3569 useful that there is a special way to do it, using the @dfn{ignore
3570 count} of the breakpoint. Every breakpoint has an ignore count, which
3571 is an integer. Most of the time, the ignore count is zero, and
3572 therefore has no effect. But if your program reaches a breakpoint whose
3573 ignore count is positive, then instead of stopping, it just decrements
3574 the ignore count by one and continues. As a result, if the ignore count
3575 value is @var{n}, the breakpoint does not stop the next @var{n} times
3576 your program reaches it.
3580 @item ignore @var{bnum} @var{count}
3581 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3582 The next @var{count} times the breakpoint is reached, your program's
3583 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3586 To make the breakpoint stop the next time it is reached, specify
3589 When you use @code{continue} to resume execution of your program from a
3590 breakpoint, you can specify an ignore count directly as an argument to
3591 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3592 Stepping,,Continuing and stepping}.
3594 If a breakpoint has a positive ignore count and a condition, the
3595 condition is not checked. Once the ignore count reaches zero,
3596 @value{GDBN} resumes checking the condition.
3598 You could achieve the effect of the ignore count with a condition such
3599 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3600 is decremented each time. @xref{Convenience Vars, ,Convenience
3604 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3607 @node Break Commands
3608 @subsection Breakpoint command lists
3610 @cindex breakpoint commands
3611 You can give any breakpoint (or watchpoint or catchpoint) a series of
3612 commands to execute when your program stops due to that breakpoint. For
3613 example, you might want to print the values of certain expressions, or
3614 enable other breakpoints.
3618 @kindex end@r{ (breakpoint commands)}
3619 @item commands @r{[}@var{bnum}@r{]}
3620 @itemx @dots{} @var{command-list} @dots{}
3622 Specify a list of commands for breakpoint number @var{bnum}. The commands
3623 themselves appear on the following lines. Type a line containing just
3624 @code{end} to terminate the commands.
3626 To remove all commands from a breakpoint, type @code{commands} and
3627 follow it immediately with @code{end}; that is, give no commands.
3629 With no @var{bnum} argument, @code{commands} refers to the last
3630 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3631 recently encountered).
3634 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3635 disabled within a @var{command-list}.
3637 You can use breakpoint commands to start your program up again. Simply
3638 use the @code{continue} command, or @code{step}, or any other command
3639 that resumes execution.
3641 Any other commands in the command list, after a command that resumes
3642 execution, are ignored. This is because any time you resume execution
3643 (even with a simple @code{next} or @code{step}), you may encounter
3644 another breakpoint---which could have its own command list, leading to
3645 ambiguities about which list to execute.
3648 If the first command you specify in a command list is @code{silent}, the
3649 usual message about stopping at a breakpoint is not printed. This may
3650 be desirable for breakpoints that are to print a specific message and
3651 then continue. If none of the remaining commands print anything, you
3652 see no sign that the breakpoint was reached. @code{silent} is
3653 meaningful only at the beginning of a breakpoint command list.
3655 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3656 print precisely controlled output, and are often useful in silent
3657 breakpoints. @xref{Output, ,Commands for controlled output}.
3659 For example, here is how you could use breakpoint commands to print the
3660 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3666 printf "x is %d\n",x
3671 One application for breakpoint commands is to compensate for one bug so
3672 you can test for another. Put a breakpoint just after the erroneous line
3673 of code, give it a condition to detect the case in which something
3674 erroneous has been done, and give it commands to assign correct values
3675 to any variables that need them. End with the @code{continue} command
3676 so that your program does not stop, and start with the @code{silent}
3677 command so that no output is produced. Here is an example:
3688 @node Breakpoint Menus
3689 @subsection Breakpoint menus
3691 @cindex symbol overloading
3693 Some programming languages (notably C@t{++} and Objective-C) permit a
3694 single function name
3695 to be defined several times, for application in different contexts.
3696 This is called @dfn{overloading}. When a function name is overloaded,
3697 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3698 a breakpoint. If you realize this is a problem, you can use
3699 something like @samp{break @var{function}(@var{types})} to specify which
3700 particular version of the function you want. Otherwise, @value{GDBN} offers
3701 you a menu of numbered choices for different possible breakpoints, and
3702 waits for your selection with the prompt @samp{>}. The first two
3703 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3704 sets a breakpoint at each definition of @var{function}, and typing
3705 @kbd{0} aborts the @code{break} command without setting any new
3708 For example, the following session excerpt shows an attempt to set a
3709 breakpoint at the overloaded symbol @code{String::after}.
3710 We choose three particular definitions of that function name:
3712 @c FIXME! This is likely to change to show arg type lists, at least
3715 (@value{GDBP}) b String::after
3718 [2] file:String.cc; line number:867
3719 [3] file:String.cc; line number:860
3720 [4] file:String.cc; line number:875
3721 [5] file:String.cc; line number:853
3722 [6] file:String.cc; line number:846
3723 [7] file:String.cc; line number:735
3725 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3726 Breakpoint 2 at 0xb344: file String.cc, line 875.
3727 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3728 Multiple breakpoints were set.
3729 Use the "delete" command to delete unwanted
3735 @c @ifclear BARETARGET
3736 @node Error in Breakpoints
3737 @subsection ``Cannot insert breakpoints''
3739 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3741 Under some operating systems, breakpoints cannot be used in a program if
3742 any other process is running that program. In this situation,
3743 attempting to run or continue a program with a breakpoint causes
3744 @value{GDBN} to print an error message:
3747 Cannot insert breakpoints.
3748 The same program may be running in another process.
3751 When this happens, you have three ways to proceed:
3755 Remove or disable the breakpoints, then continue.
3758 Suspend @value{GDBN}, and copy the file containing your program to a new
3759 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3760 that @value{GDBN} should run your program under that name.
3761 Then start your program again.
3764 Relink your program so that the text segment is nonsharable, using the
3765 linker option @samp{-N}. The operating system limitation may not apply
3766 to nonsharable executables.
3770 A similar message can be printed if you request too many active
3771 hardware-assisted breakpoints and watchpoints:
3773 @c FIXME: the precise wording of this message may change; the relevant
3774 @c source change is not committed yet (Sep 3, 1999).
3776 Stopped; cannot insert breakpoints.
3777 You may have requested too many hardware breakpoints and watchpoints.
3781 This message is printed when you attempt to resume the program, since
3782 only then @value{GDBN} knows exactly how many hardware breakpoints and
3783 watchpoints it needs to insert.
3785 When this message is printed, you need to disable or remove some of the
3786 hardware-assisted breakpoints and watchpoints, and then continue.
3788 @node Breakpoint related warnings
3789 @subsection ``Breakpoint address adjusted...''
3790 @cindex breakpoint address adjusted
3792 Some processor architectures place constraints on the addresses at
3793 which breakpoints may be placed. For architectures thus constrained,
3794 @value{GDBN} will attempt to adjust the breakpoint's address to comply
3795 with the constraints dictated by the architecture.
3797 One example of such an architecture is the Fujitsu FR-V. The FR-V is
3798 a VLIW architecture in which a number of RISC-like instructions may be
3799 bundled together for parallel execution. The FR-V architecture
3800 constrains the location of a breakpoint instruction within such a
3801 bundle to the instruction with the lowest address. @value{GDBN}
3802 honors this constraint by adjusting a breakpoint's address to the
3803 first in the bundle.
3805 It is not uncommon for optimized code to have bundles which contain
3806 instructions from different source statements, thus it may happen that
3807 a breakpoint's address will be adjusted from one source statement to
3808 another. Since this adjustment may significantly alter @value{GDBN}'s
3809 breakpoint related behavior from what the user expects, a warning is
3810 printed when the breakpoint is first set and also when the breakpoint
3813 A warning like the one below is printed when setting a breakpoint
3814 that's been subject to address adjustment:
3817 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
3820 Such warnings are printed both for user settable and @value{GDBN}'s
3821 internal breakpoints. If you see one of these warnings, you should
3822 verify that a breakpoint set at the adjusted address will have the
3823 desired affect. If not, the breakpoint in question may be removed and
3824 other breakpoints may be set which will have the desired behavior.
3825 E.g., it may be sufficient to place the breakpoint at a later
3826 instruction. A conditional breakpoint may also be useful in some
3827 cases to prevent the breakpoint from triggering too often.
3829 @value{GDBN} will also issue a warning when stopping at one of these
3830 adjusted breakpoints:
3833 warning: Breakpoint 1 address previously adjusted from 0x00010414
3837 When this warning is encountered, it may be too late to take remedial
3838 action except in cases where the breakpoint is hit earlier or more
3839 frequently than expected.
3841 @node Continuing and Stepping
3842 @section Continuing and stepping
3846 @cindex resuming execution
3847 @dfn{Continuing} means resuming program execution until your program
3848 completes normally. In contrast, @dfn{stepping} means executing just
3849 one more ``step'' of your program, where ``step'' may mean either one
3850 line of source code, or one machine instruction (depending on what
3851 particular command you use). Either when continuing or when stepping,
3852 your program may stop even sooner, due to a breakpoint or a signal. (If
3853 it stops due to a signal, you may want to use @code{handle}, or use
3854 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3858 @kindex c @r{(@code{continue})}
3859 @kindex fg @r{(resume foreground execution)}
3860 @item continue @r{[}@var{ignore-count}@r{]}
3861 @itemx c @r{[}@var{ignore-count}@r{]}
3862 @itemx fg @r{[}@var{ignore-count}@r{]}
3863 Resume program execution, at the address where your program last stopped;
3864 any breakpoints set at that address are bypassed. The optional argument
3865 @var{ignore-count} allows you to specify a further number of times to
3866 ignore a breakpoint at this location; its effect is like that of
3867 @code{ignore} (@pxref{Conditions, ,Break conditions}).
3869 The argument @var{ignore-count} is meaningful only when your program
3870 stopped due to a breakpoint. At other times, the argument to
3871 @code{continue} is ignored.
3873 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
3874 debugged program is deemed to be the foreground program) are provided
3875 purely for convenience, and have exactly the same behavior as
3879 To resume execution at a different place, you can use @code{return}
3880 (@pxref{Returning, ,Returning from a function}) to go back to the
3881 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
3882 different address}) to go to an arbitrary location in your program.
3884 A typical technique for using stepping is to set a breakpoint
3885 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and catchpoints}) at the
3886 beginning of the function or the section of your program where a problem
3887 is believed to lie, run your program until it stops at that breakpoint,
3888 and then step through the suspect area, examining the variables that are
3889 interesting, until you see the problem happen.
3893 @kindex s @r{(@code{step})}
3895 Continue running your program until control reaches a different source
3896 line, then stop it and return control to @value{GDBN}. This command is
3897 abbreviated @code{s}.
3900 @c "without debugging information" is imprecise; actually "without line
3901 @c numbers in the debugging information". (gcc -g1 has debugging info but
3902 @c not line numbers). But it seems complex to try to make that
3903 @c distinction here.
3904 @emph{Warning:} If you use the @code{step} command while control is
3905 within a function that was compiled without debugging information,
3906 execution proceeds until control reaches a function that does have
3907 debugging information. Likewise, it will not step into a function which
3908 is compiled without debugging information. To step through functions
3909 without debugging information, use the @code{stepi} command, described
3913 The @code{step} command only stops at the first instruction of a source
3914 line. This prevents the multiple stops that could otherwise occur in
3915 @code{switch} statements, @code{for} loops, etc. @code{step} continues
3916 to stop if a function that has debugging information is called within
3917 the line. In other words, @code{step} @emph{steps inside} any functions
3918 called within the line.
3920 Also, the @code{step} command only enters a function if there is line
3921 number information for the function. Otherwise it acts like the
3922 @code{next} command. This avoids problems when using @code{cc -gl}
3923 on MIPS machines. Previously, @code{step} entered subroutines if there
3924 was any debugging information about the routine.
3926 @item step @var{count}
3927 Continue running as in @code{step}, but do so @var{count} times. If a
3928 breakpoint is reached, or a signal not related to stepping occurs before
3929 @var{count} steps, stepping stops right away.
3932 @kindex n @r{(@code{next})}
3933 @item next @r{[}@var{count}@r{]}
3934 Continue to the next source line in the current (innermost) stack frame.
3935 This is similar to @code{step}, but function calls that appear within
3936 the line of code are executed without stopping. Execution stops when
3937 control reaches a different line of code at the original stack level
3938 that was executing when you gave the @code{next} command. This command
3939 is abbreviated @code{n}.
3941 An argument @var{count} is a repeat count, as for @code{step}.
3944 @c FIX ME!! Do we delete this, or is there a way it fits in with
3945 @c the following paragraph? --- Vctoria
3947 @c @code{next} within a function that lacks debugging information acts like
3948 @c @code{step}, but any function calls appearing within the code of the
3949 @c function are executed without stopping.
3951 The @code{next} command only stops at the first instruction of a
3952 source line. This prevents multiple stops that could otherwise occur in
3953 @code{switch} statements, @code{for} loops, etc.
3955 @kindex set step-mode
3957 @cindex functions without line info, and stepping
3958 @cindex stepping into functions with no line info
3959 @itemx set step-mode on
3960 The @code{set step-mode on} command causes the @code{step} command to
3961 stop at the first instruction of a function which contains no debug line
3962 information rather than stepping over it.
3964 This is useful in cases where you may be interested in inspecting the
3965 machine instructions of a function which has no symbolic info and do not
3966 want @value{GDBN} to automatically skip over this function.
3968 @item set step-mode off
3969 Causes the @code{step} command to step over any functions which contains no
3970 debug information. This is the default.
3972 @item show step-mode
3973 Show whether @value{GDBN} will stop in or step over functions without
3974 source line debug information.
3978 Continue running until just after function in the selected stack frame
3979 returns. Print the returned value (if any).
3981 Contrast this with the @code{return} command (@pxref{Returning,
3982 ,Returning from a function}).
3985 @kindex u @r{(@code{until})}
3986 @cindex run until specified location
3989 Continue running until a source line past the current line, in the
3990 current stack frame, is reached. This command is used to avoid single
3991 stepping through a loop more than once. It is like the @code{next}
3992 command, except that when @code{until} encounters a jump, it
3993 automatically continues execution until the program counter is greater
3994 than the address of the jump.
3996 This means that when you reach the end of a loop after single stepping
3997 though it, @code{until} makes your program continue execution until it
3998 exits the loop. In contrast, a @code{next} command at the end of a loop
3999 simply steps back to the beginning of the loop, which forces you to step
4000 through the next iteration.
4002 @code{until} always stops your program if it attempts to exit the current
4005 @code{until} may produce somewhat counterintuitive results if the order
4006 of machine code does not match the order of the source lines. For
4007 example, in the following excerpt from a debugging session, the @code{f}
4008 (@code{frame}) command shows that execution is stopped at line
4009 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4013 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4015 (@value{GDBP}) until
4016 195 for ( ; argc > 0; NEXTARG) @{
4019 This happened because, for execution efficiency, the compiler had
4020 generated code for the loop closure test at the end, rather than the
4021 start, of the loop---even though the test in a C @code{for}-loop is
4022 written before the body of the loop. The @code{until} command appeared
4023 to step back to the beginning of the loop when it advanced to this
4024 expression; however, it has not really gone to an earlier
4025 statement---not in terms of the actual machine code.
4027 @code{until} with no argument works by means of single
4028 instruction stepping, and hence is slower than @code{until} with an
4031 @item until @var{location}
4032 @itemx u @var{location}
4033 Continue running your program until either the specified location is
4034 reached, or the current stack frame returns. @var{location} is any of
4035 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
4036 ,Setting breakpoints}). This form of the command uses breakpoints, and
4037 hence is quicker than @code{until} without an argument. The specified
4038 location is actually reached only if it is in the current frame. This
4039 implies that @code{until} can be used to skip over recursive function
4040 invocations. For instance in the code below, if the current location is
4041 line @code{96}, issuing @code{until 99} will execute the program up to
4042 line @code{99} in the same invocation of factorial, i.e. after the inner
4043 invocations have returned.
4046 94 int factorial (int value)
4048 96 if (value > 1) @{
4049 97 value *= factorial (value - 1);
4056 @kindex advance @var{location}
4057 @itemx advance @var{location}
4058 Continue running the program up to the given @var{location}. An argument is
4059 required, which should be of the same form as arguments for the @code{break}
4060 command. Execution will also stop upon exit from the current stack
4061 frame. This command is similar to @code{until}, but @code{advance} will
4062 not skip over recursive function calls, and the target location doesn't
4063 have to be in the same frame as the current one.
4067 @kindex si @r{(@code{stepi})}
4069 @itemx stepi @var{arg}
4071 Execute one machine instruction, then stop and return to the debugger.
4073 It is often useful to do @samp{display/i $pc} when stepping by machine
4074 instructions. This makes @value{GDBN} automatically display the next
4075 instruction to be executed, each time your program stops. @xref{Auto
4076 Display,, Automatic display}.
4078 An argument is a repeat count, as in @code{step}.
4082 @kindex ni @r{(@code{nexti})}
4084 @itemx nexti @var{arg}
4086 Execute one machine instruction, but if it is a function call,
4087 proceed until the function returns.
4089 An argument is a repeat count, as in @code{next}.
4096 A signal is an asynchronous event that can happen in a program. The
4097 operating system defines the possible kinds of signals, and gives each
4098 kind a name and a number. For example, in Unix @code{SIGINT} is the
4099 signal a program gets when you type an interrupt character (often @kbd{C-c});
4100 @code{SIGSEGV} is the signal a program gets from referencing a place in
4101 memory far away from all the areas in use; @code{SIGALRM} occurs when
4102 the alarm clock timer goes off (which happens only if your program has
4103 requested an alarm).
4105 @cindex fatal signals
4106 Some signals, including @code{SIGALRM}, are a normal part of the
4107 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4108 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4109 program has not specified in advance some other way to handle the signal.
4110 @code{SIGINT} does not indicate an error in your program, but it is normally
4111 fatal so it can carry out the purpose of the interrupt: to kill the program.
4113 @value{GDBN} has the ability to detect any occurrence of a signal in your
4114 program. You can tell @value{GDBN} in advance what to do for each kind of
4117 @cindex handling signals
4118 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4119 @code{SIGALRM} be silently passed to your program
4120 (so as not to interfere with their role in the program's functioning)
4121 but to stop your program immediately whenever an error signal happens.
4122 You can change these settings with the @code{handle} command.
4125 @kindex info signals
4129 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4130 handle each one. You can use this to see the signal numbers of all
4131 the defined types of signals.
4133 @code{info handle} is an alias for @code{info signals}.
4136 @item handle @var{signal} @var{keywords}@dots{}
4137 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4138 can be the number of a signal or its name (with or without the
4139 @samp{SIG} at the beginning); a list of signal numbers of the form
4140 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4141 known signals. The @var{keywords} say what change to make.
4145 The keywords allowed by the @code{handle} command can be abbreviated.
4146 Their full names are:
4150 @value{GDBN} should not stop your program when this signal happens. It may
4151 still print a message telling you that the signal has come in.
4154 @value{GDBN} should stop your program when this signal happens. This implies
4155 the @code{print} keyword as well.
4158 @value{GDBN} should print a message when this signal happens.
4161 @value{GDBN} should not mention the occurrence of the signal at all. This
4162 implies the @code{nostop} keyword as well.
4166 @value{GDBN} should allow your program to see this signal; your program
4167 can handle the signal, or else it may terminate if the signal is fatal
4168 and not handled. @code{pass} and @code{noignore} are synonyms.
4172 @value{GDBN} should not allow your program to see this signal.
4173 @code{nopass} and @code{ignore} are synonyms.
4177 When a signal stops your program, the signal is not visible to the
4179 continue. Your program sees the signal then, if @code{pass} is in
4180 effect for the signal in question @emph{at that time}. In other words,
4181 after @value{GDBN} reports a signal, you can use the @code{handle}
4182 command with @code{pass} or @code{nopass} to control whether your
4183 program sees that signal when you continue.
4185 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4186 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4187 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4190 You can also use the @code{signal} command to prevent your program from
4191 seeing a signal, or cause it to see a signal it normally would not see,
4192 or to give it any signal at any time. For example, if your program stopped
4193 due to some sort of memory reference error, you might store correct
4194 values into the erroneous variables and continue, hoping to see more
4195 execution; but your program would probably terminate immediately as
4196 a result of the fatal signal once it saw the signal. To prevent this,
4197 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4201 @section Stopping and starting multi-thread programs
4203 When your program has multiple threads (@pxref{Threads,, Debugging
4204 programs with multiple threads}), you can choose whether to set
4205 breakpoints on all threads, or on a particular thread.
4208 @cindex breakpoints and threads
4209 @cindex thread breakpoints
4210 @kindex break @dots{} thread @var{threadno}
4211 @item break @var{linespec} thread @var{threadno}
4212 @itemx break @var{linespec} thread @var{threadno} if @dots{}
4213 @var{linespec} specifies source lines; there are several ways of
4214 writing them, but the effect is always to specify some source line.
4216 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
4217 to specify that you only want @value{GDBN} to stop the program when a
4218 particular thread reaches this breakpoint. @var{threadno} is one of the
4219 numeric thread identifiers assigned by @value{GDBN}, shown in the first
4220 column of the @samp{info threads} display.
4222 If you do not specify @samp{thread @var{threadno}} when you set a
4223 breakpoint, the breakpoint applies to @emph{all} threads of your
4226 You can use the @code{thread} qualifier on conditional breakpoints as
4227 well; in this case, place @samp{thread @var{threadno}} before the
4228 breakpoint condition, like this:
4231 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
4236 @cindex stopped threads
4237 @cindex threads, stopped
4238 Whenever your program stops under @value{GDBN} for any reason,
4239 @emph{all} threads of execution stop, not just the current thread. This
4240 allows you to examine the overall state of the program, including
4241 switching between threads, without worrying that things may change
4244 @cindex thread breakpoints and system calls
4245 @cindex system calls and thread breakpoints
4246 @cindex premature return from system calls
4247 There is an unfortunate side effect. If one thread stops for a
4248 breakpoint, or for some other reason, and another thread is blocked in a
4249 system call, then the system call may return prematurely. This is a
4250 consequence of the interaction between multiple threads and the signals
4251 that @value{GDBN} uses to implement breakpoints and other events that
4254 To handle this problem, your program should check the return value of
4255 each system call and react appropriately. This is good programming
4258 For example, do not write code like this:
4264 The call to @code{sleep} will return early if a different thread stops
4265 at a breakpoint or for some other reason.
4267 Instead, write this:
4272 unslept = sleep (unslept);
4275 A system call is allowed to return early, so the system is still
4276 conforming to its specification. But @value{GDBN} does cause your
4277 multi-threaded program to behave differently than it would without
4280 Also, @value{GDBN} uses internal breakpoints in the thread library to
4281 monitor certain events such as thread creation and thread destruction.
4282 When such an event happens, a system call in another thread may return
4283 prematurely, even though your program does not appear to stop.
4285 @cindex continuing threads
4286 @cindex threads, continuing
4287 Conversely, whenever you restart the program, @emph{all} threads start
4288 executing. @emph{This is true even when single-stepping} with commands
4289 like @code{step} or @code{next}.
4291 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4292 Since thread scheduling is up to your debugging target's operating
4293 system (not controlled by @value{GDBN}), other threads may
4294 execute more than one statement while the current thread completes a
4295 single step. Moreover, in general other threads stop in the middle of a
4296 statement, rather than at a clean statement boundary, when the program
4299 You might even find your program stopped in another thread after
4300 continuing or even single-stepping. This happens whenever some other
4301 thread runs into a breakpoint, a signal, or an exception before the
4302 first thread completes whatever you requested.
4304 On some OSes, you can lock the OS scheduler and thus allow only a single
4308 @item set scheduler-locking @var{mode}
4309 @cindex scheduler locking mode
4310 @cindex lock scheduler
4311 Set the scheduler locking mode. If it is @code{off}, then there is no
4312 locking and any thread may run at any time. If @code{on}, then only the
4313 current thread may run when the inferior is resumed. The @code{step}
4314 mode optimizes for single-stepping. It stops other threads from
4315 ``seizing the prompt'' by preempting the current thread while you are
4316 stepping. Other threads will only rarely (or never) get a chance to run
4317 when you step. They are more likely to run when you @samp{next} over a
4318 function call, and they are completely free to run when you use commands
4319 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4320 thread hits a breakpoint during its timeslice, they will never steal the
4321 @value{GDBN} prompt away from the thread that you are debugging.
4323 @item show scheduler-locking
4324 Display the current scheduler locking mode.
4329 @chapter Examining the Stack
4331 When your program has stopped, the first thing you need to know is where it
4332 stopped and how it got there.
4335 Each time your program performs a function call, information about the call
4337 That information includes the location of the call in your program,
4338 the arguments of the call,
4339 and the local variables of the function being called.
4340 The information is saved in a block of data called a @dfn{stack frame}.
4341 The stack frames are allocated in a region of memory called the @dfn{call
4344 When your program stops, the @value{GDBN} commands for examining the
4345 stack allow you to see all of this information.
4347 @cindex selected frame
4348 One of the stack frames is @dfn{selected} by @value{GDBN} and many
4349 @value{GDBN} commands refer implicitly to the selected frame. In
4350 particular, whenever you ask @value{GDBN} for the value of a variable in
4351 your program, the value is found in the selected frame. There are
4352 special @value{GDBN} commands to select whichever frame you are
4353 interested in. @xref{Selection, ,Selecting a frame}.
4355 When your program stops, @value{GDBN} automatically selects the
4356 currently executing frame and describes it briefly, similar to the
4357 @code{frame} command (@pxref{Frame Info, ,Information about a frame}).
4360 * Frames:: Stack frames
4361 * Backtrace:: Backtraces
4362 * Selection:: Selecting a frame
4363 * Frame Info:: Information on a frame
4368 @section Stack frames
4370 @cindex frame, definition
4372 The call stack is divided up into contiguous pieces called @dfn{stack
4373 frames}, or @dfn{frames} for short; each frame is the data associated
4374 with one call to one function. The frame contains the arguments given
4375 to the function, the function's local variables, and the address at
4376 which the function is executing.
4378 @cindex initial frame
4379 @cindex outermost frame
4380 @cindex innermost frame
4381 When your program is started, the stack has only one frame, that of the
4382 function @code{main}. This is called the @dfn{initial} frame or the
4383 @dfn{outermost} frame. Each time a function is called, a new frame is
4384 made. Each time a function returns, the frame for that function invocation
4385 is eliminated. If a function is recursive, there can be many frames for
4386 the same function. The frame for the function in which execution is
4387 actually occurring is called the @dfn{innermost} frame. This is the most
4388 recently created of all the stack frames that still exist.
4390 @cindex frame pointer
4391 Inside your program, stack frames are identified by their addresses. A
4392 stack frame consists of many bytes, each of which has its own address; each
4393 kind of computer has a convention for choosing one byte whose
4394 address serves as the address of the frame. Usually this address is kept
4395 in a register called the @dfn{frame pointer register}
4396 (@pxref{Registers, $fp}) while execution is going on in that frame.
4398 @cindex frame number
4399 @value{GDBN} assigns numbers to all existing stack frames, starting with
4400 zero for the innermost frame, one for the frame that called it,
4401 and so on upward. These numbers do not really exist in your program;
4402 they are assigned by @value{GDBN} to give you a way of designating stack
4403 frames in @value{GDBN} commands.
4405 @c The -fomit-frame-pointer below perennially causes hbox overflow
4406 @c underflow problems.
4407 @cindex frameless execution
4408 Some compilers provide a way to compile functions so that they operate
4409 without stack frames. (For example, the @value{GCC} option
4411 @samp{-fomit-frame-pointer}
4413 generates functions without a frame.)
4414 This is occasionally done with heavily used library functions to save
4415 the frame setup time. @value{GDBN} has limited facilities for dealing
4416 with these function invocations. If the innermost function invocation
4417 has no stack frame, @value{GDBN} nevertheless regards it as though
4418 it had a separate frame, which is numbered zero as usual, allowing
4419 correct tracing of the function call chain. However, @value{GDBN} has
4420 no provision for frameless functions elsewhere in the stack.
4423 @kindex frame@r{, command}
4424 @cindex current stack frame
4425 @item frame @var{args}
4426 The @code{frame} command allows you to move from one stack frame to another,
4427 and to print the stack frame you select. @var{args} may be either the
4428 address of the frame or the stack frame number. Without an argument,
4429 @code{frame} prints the current stack frame.
4431 @kindex select-frame
4432 @cindex selecting frame silently
4434 The @code{select-frame} command allows you to move from one stack frame
4435 to another without printing the frame. This is the silent version of
4443 @cindex call stack traces
4444 A backtrace is a summary of how your program got where it is. It shows one
4445 line per frame, for many frames, starting with the currently executing
4446 frame (frame zero), followed by its caller (frame one), and on up the
4451 @kindex bt @r{(@code{backtrace})}
4454 Print a backtrace of the entire stack: one line per frame for all
4455 frames in the stack.
4457 You can stop the backtrace at any time by typing the system interrupt
4458 character, normally @kbd{C-c}.
4460 @item backtrace @var{n}
4462 Similar, but print only the innermost @var{n} frames.
4464 @item backtrace -@var{n}
4466 Similar, but print only the outermost @var{n} frames.
4468 @item backtrace full
4469 Print the values of the local variables also.
4475 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4476 are additional aliases for @code{backtrace}.
4478 @cindex multiple threads, backtrace
4479 In a multi-threaded program, @value{GDBN} by default shows the
4480 backtrace only for the current thread. To display the backtrace for
4481 several or all of the threads, use the command @code{thread apply}
4482 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
4483 apply all backtrace}, @value{GDBN} will display the backtrace for all
4484 the threads; this is handy when you debug a core dump of a
4485 multi-threaded program.
4487 Each line in the backtrace shows the frame number and the function name.
4488 The program counter value is also shown---unless you use @code{set
4489 print address off}. The backtrace also shows the source file name and
4490 line number, as well as the arguments to the function. The program
4491 counter value is omitted if it is at the beginning of the code for that
4494 Here is an example of a backtrace. It was made with the command
4495 @samp{bt 3}, so it shows the innermost three frames.
4499 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4501 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4502 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4504 (More stack frames follow...)
4509 The display for frame zero does not begin with a program counter
4510 value, indicating that your program has stopped at the beginning of the
4511 code for line @code{993} of @code{builtin.c}.
4513 @cindex value optimized out, in backtrace
4514 @cindex function call arguments, optimized out
4515 If your program was compiled with optimizations, some compilers will
4516 optimize away arguments passed to functions if those arguments are
4517 never used after the call. Such optimizations generate code that
4518 passes arguments through registers, but doesn't store those arguments
4519 in the stack frame. @value{GDBN} has no way of displaying such
4520 arguments in stack frames other than the innermost one. Here's what
4521 such a backtrace might look like:
4525 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4527 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
4528 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
4530 (More stack frames follow...)
4535 The values of arguments that were not saved in their stack frames are
4536 shown as @samp{<value optimized out>}.
4538 If you need to display the values of such optimized-out arguments,
4539 either deduce that from other variables whose values depend on the one
4540 you are interested in, or recompile without optimizations.
4542 @cindex backtrace beyond @code{main} function
4543 @cindex program entry point
4544 @cindex startup code, and backtrace
4545 Most programs have a standard user entry point---a place where system
4546 libraries and startup code transition into user code. For C this is
4547 @code{main}@footnote{
4548 Note that embedded programs (the so-called ``free-standing''
4549 environment) are not required to have a @code{main} function as the
4550 entry point. They could even have multiple entry points.}.
4551 When @value{GDBN} finds the entry function in a backtrace
4552 it will terminate the backtrace, to avoid tracing into highly
4553 system-specific (and generally uninteresting) code.
4555 If you need to examine the startup code, or limit the number of levels
4556 in a backtrace, you can change this behavior:
4559 @item set backtrace past-main
4560 @itemx set backtrace past-main on
4561 @kindex set backtrace
4562 Backtraces will continue past the user entry point.
4564 @item set backtrace past-main off
4565 Backtraces will stop when they encounter the user entry point. This is the
4568 @item show backtrace past-main
4569 @kindex show backtrace
4570 Display the current user entry point backtrace policy.
4572 @item set backtrace past-entry
4573 @itemx set backtrace past-entry on
4574 Backtraces will continue past the internal entry point of an application.
4575 This entry point is encoded by the linker when the application is built,
4576 and is likely before the user entry point @code{main} (or equivalent) is called.
4578 @item set backtrace past-entry off
4579 Backtraces will stop when they encouter the internal entry point of an
4580 application. This is the default.
4582 @item show backtrace past-entry
4583 Display the current internal entry point backtrace policy.
4585 @item set backtrace limit @var{n}
4586 @itemx set backtrace limit 0
4587 @cindex backtrace limit
4588 Limit the backtrace to @var{n} levels. A value of zero means
4591 @item show backtrace limit
4592 Display the current limit on backtrace levels.
4596 @section Selecting a frame
4598 Most commands for examining the stack and other data in your program work on
4599 whichever stack frame is selected at the moment. Here are the commands for
4600 selecting a stack frame; all of them finish by printing a brief description
4601 of the stack frame just selected.
4604 @kindex frame@r{, selecting}
4605 @kindex f @r{(@code{frame})}
4608 Select frame number @var{n}. Recall that frame zero is the innermost
4609 (currently executing) frame, frame one is the frame that called the
4610 innermost one, and so on. The highest-numbered frame is the one for
4613 @item frame @var{addr}
4615 Select the frame at address @var{addr}. This is useful mainly if the
4616 chaining of stack frames has been damaged by a bug, making it
4617 impossible for @value{GDBN} to assign numbers properly to all frames. In
4618 addition, this can be useful when your program has multiple stacks and
4619 switches between them.
4621 On the SPARC architecture, @code{frame} needs two addresses to
4622 select an arbitrary frame: a frame pointer and a stack pointer.
4624 On the MIPS and Alpha architecture, it needs two addresses: a stack
4625 pointer and a program counter.
4627 On the 29k architecture, it needs three addresses: a register stack
4628 pointer, a program counter, and a memory stack pointer.
4632 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4633 advances toward the outermost frame, to higher frame numbers, to frames
4634 that have existed longer. @var{n} defaults to one.
4637 @kindex do @r{(@code{down})}
4639 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4640 advances toward the innermost frame, to lower frame numbers, to frames
4641 that were created more recently. @var{n} defaults to one. You may
4642 abbreviate @code{down} as @code{do}.
4645 All of these commands end by printing two lines of output describing the
4646 frame. The first line shows the frame number, the function name, the
4647 arguments, and the source file and line number of execution in that
4648 frame. The second line shows the text of that source line.
4656 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4658 10 read_input_file (argv[i]);
4662 After such a printout, the @code{list} command with no arguments
4663 prints ten lines centered on the point of execution in the frame.
4664 You can also edit the program at the point of execution with your favorite
4665 editing program by typing @code{edit}.
4666 @xref{List, ,Printing source lines},
4670 @kindex down-silently
4672 @item up-silently @var{n}
4673 @itemx down-silently @var{n}
4674 These two commands are variants of @code{up} and @code{down},
4675 respectively; they differ in that they do their work silently, without
4676 causing display of the new frame. They are intended primarily for use
4677 in @value{GDBN} command scripts, where the output might be unnecessary and
4682 @section Information about a frame
4684 There are several other commands to print information about the selected
4690 When used without any argument, this command does not change which
4691 frame is selected, but prints a brief description of the currently
4692 selected stack frame. It can be abbreviated @code{f}. With an
4693 argument, this command is used to select a stack frame.
4694 @xref{Selection, ,Selecting a frame}.
4697 @kindex info f @r{(@code{info frame})}
4700 This command prints a verbose description of the selected stack frame,
4705 the address of the frame
4707 the address of the next frame down (called by this frame)
4709 the address of the next frame up (caller of this frame)
4711 the language in which the source code corresponding to this frame is written
4713 the address of the frame's arguments
4715 the address of the frame's local variables
4717 the program counter saved in it (the address of execution in the caller frame)
4719 which registers were saved in the frame
4722 @noindent The verbose description is useful when
4723 something has gone wrong that has made the stack format fail to fit
4724 the usual conventions.
4726 @item info frame @var{addr}
4727 @itemx info f @var{addr}
4728 Print a verbose description of the frame at address @var{addr}, without
4729 selecting that frame. The selected frame remains unchanged by this
4730 command. This requires the same kind of address (more than one for some
4731 architectures) that you specify in the @code{frame} command.
4732 @xref{Selection, ,Selecting a frame}.
4736 Print the arguments of the selected frame, each on a separate line.
4740 Print the local variables of the selected frame, each on a separate
4741 line. These are all variables (declared either static or automatic)
4742 accessible at the point of execution of the selected frame.
4745 @cindex catch exceptions, list active handlers
4746 @cindex exception handlers, how to list
4748 Print a list of all the exception handlers that are active in the
4749 current stack frame at the current point of execution. To see other
4750 exception handlers, visit the associated frame (using the @code{up},
4751 @code{down}, or @code{frame} commands); then type @code{info catch}.
4752 @xref{Set Catchpoints, , Setting catchpoints}.
4758 @chapter Examining Source Files
4760 @value{GDBN} can print parts of your program's source, since the debugging
4761 information recorded in the program tells @value{GDBN} what source files were
4762 used to build it. When your program stops, @value{GDBN} spontaneously prints
4763 the line where it stopped. Likewise, when you select a stack frame
4764 (@pxref{Selection, ,Selecting a frame}), @value{GDBN} prints the line where
4765 execution in that frame has stopped. You can print other portions of
4766 source files by explicit command.
4768 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4769 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4770 @value{GDBN} under @sc{gnu} Emacs}.
4773 * List:: Printing source lines
4774 * Edit:: Editing source files
4775 * Search:: Searching source files
4776 * Source Path:: Specifying source directories
4777 * Machine Code:: Source and machine code
4781 @section Printing source lines
4784 @kindex l @r{(@code{list})}
4785 To print lines from a source file, use the @code{list} command
4786 (abbreviated @code{l}). By default, ten lines are printed.
4787 There are several ways to specify what part of the file you want to print.
4789 Here are the forms of the @code{list} command most commonly used:
4792 @item list @var{linenum}
4793 Print lines centered around line number @var{linenum} in the
4794 current source file.
4796 @item list @var{function}
4797 Print lines centered around the beginning of function
4801 Print more lines. If the last lines printed were printed with a
4802 @code{list} command, this prints lines following the last lines
4803 printed; however, if the last line printed was a solitary line printed
4804 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4805 Stack}), this prints lines centered around that line.
4808 Print lines just before the lines last printed.
4811 @cindex @code{list}, how many lines to display
4812 By default, @value{GDBN} prints ten source lines with any of these forms of
4813 the @code{list} command. You can change this using @code{set listsize}:
4816 @kindex set listsize
4817 @item set listsize @var{count}
4818 Make the @code{list} command display @var{count} source lines (unless
4819 the @code{list} argument explicitly specifies some other number).
4821 @kindex show listsize
4823 Display the number of lines that @code{list} prints.
4826 Repeating a @code{list} command with @key{RET} discards the argument,
4827 so it is equivalent to typing just @code{list}. This is more useful
4828 than listing the same lines again. An exception is made for an
4829 argument of @samp{-}; that argument is preserved in repetition so that
4830 each repetition moves up in the source file.
4833 In general, the @code{list} command expects you to supply zero, one or two
4834 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4835 of writing them, but the effect is always to specify some source line.
4836 Here is a complete description of the possible arguments for @code{list}:
4839 @item list @var{linespec}
4840 Print lines centered around the line specified by @var{linespec}.
4842 @item list @var{first},@var{last}
4843 Print lines from @var{first} to @var{last}. Both arguments are
4846 @item list ,@var{last}
4847 Print lines ending with @var{last}.
4849 @item list @var{first},
4850 Print lines starting with @var{first}.
4853 Print lines just after the lines last printed.
4856 Print lines just before the lines last printed.
4859 As described in the preceding table.
4862 Here are the ways of specifying a single source line---all the
4867 Specifies line @var{number} of the current source file.
4868 When a @code{list} command has two linespecs, this refers to
4869 the same source file as the first linespec.
4872 Specifies the line @var{offset} lines after the last line printed.
4873 When used as the second linespec in a @code{list} command that has
4874 two, this specifies the line @var{offset} lines down from the
4878 Specifies the line @var{offset} lines before the last line printed.
4880 @item @var{filename}:@var{number}
4881 Specifies line @var{number} in the source file @var{filename}.
4883 @item @var{function}
4884 Specifies the line that begins the body of the function @var{function}.
4885 For example: in C, this is the line with the open brace.
4887 @item @var{filename}:@var{function}
4888 Specifies the line of the open-brace that begins the body of the
4889 function @var{function} in the file @var{filename}. You only need the
4890 file name with a function name to avoid ambiguity when there are
4891 identically named functions in different source files.
4893 @item *@var{address}
4894 Specifies the line containing the program address @var{address}.
4895 @var{address} may be any expression.
4899 @section Editing source files
4900 @cindex editing source files
4903 @kindex e @r{(@code{edit})}
4904 To edit the lines in a source file, use the @code{edit} command.
4905 The editing program of your choice
4906 is invoked with the current line set to
4907 the active line in the program.
4908 Alternatively, there are several ways to specify what part of the file you
4909 want to print if you want to see other parts of the program.
4911 Here are the forms of the @code{edit} command most commonly used:
4915 Edit the current source file at the active line number in the program.
4917 @item edit @var{number}
4918 Edit the current source file with @var{number} as the active line number.
4920 @item edit @var{function}
4921 Edit the file containing @var{function} at the beginning of its definition.
4923 @item edit @var{filename}:@var{number}
4924 Specifies line @var{number} in the source file @var{filename}.
4926 @item edit @var{filename}:@var{function}
4927 Specifies the line that begins the body of the
4928 function @var{function} in the file @var{filename}. You only need the
4929 file name with a function name to avoid ambiguity when there are
4930 identically named functions in different source files.
4932 @item edit *@var{address}
4933 Specifies the line containing the program address @var{address}.
4934 @var{address} may be any expression.
4937 @subsection Choosing your editor
4938 You can customize @value{GDBN} to use any editor you want
4940 The only restriction is that your editor (say @code{ex}), recognizes the
4941 following command-line syntax:
4943 ex +@var{number} file
4945 The optional numeric value +@var{number} specifies the number of the line in
4946 the file where to start editing.}.
4947 By default, it is @file{@value{EDITOR}}, but you can change this
4948 by setting the environment variable @code{EDITOR} before using
4949 @value{GDBN}. For example, to configure @value{GDBN} to use the
4950 @code{vi} editor, you could use these commands with the @code{sh} shell:
4956 or in the @code{csh} shell,
4958 setenv EDITOR /usr/bin/vi
4963 @section Searching source files
4964 @cindex searching source files
4966 There are two commands for searching through the current source file for a
4971 @kindex forward-search
4972 @item forward-search @var{regexp}
4973 @itemx search @var{regexp}
4974 The command @samp{forward-search @var{regexp}} checks each line,
4975 starting with the one following the last line listed, for a match for
4976 @var{regexp}. It lists the line that is found. You can use the
4977 synonym @samp{search @var{regexp}} or abbreviate the command name as
4980 @kindex reverse-search
4981 @item reverse-search @var{regexp}
4982 The command @samp{reverse-search @var{regexp}} checks each line, starting
4983 with the one before the last line listed and going backward, for a match
4984 for @var{regexp}. It lists the line that is found. You can abbreviate
4985 this command as @code{rev}.
4989 @section Specifying source directories
4992 @cindex directories for source files
4993 Executable programs sometimes do not record the directories of the source
4994 files from which they were compiled, just the names. Even when they do,
4995 the directories could be moved between the compilation and your debugging
4996 session. @value{GDBN} has a list of directories to search for source files;
4997 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
4998 it tries all the directories in the list, in the order they are present
4999 in the list, until it finds a file with the desired name.
5001 For example, suppose an executable references the file
5002 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
5003 @file{/mnt/cross}. The file is first looked up literally; if this
5004 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
5005 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
5006 message is printed. @value{GDBN} does not look up the parts of the
5007 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
5008 Likewise, the subdirectories of the source path are not searched: if
5009 the source path is @file{/mnt/cross}, and the binary refers to
5010 @file{foo.c}, @value{GDBN} would not find it under
5011 @file{/mnt/cross/usr/src/foo-1.0/lib}.
5013 Plain file names, relative file names with leading directories, file
5014 names containing dots, etc.@: are all treated as described above; for
5015 instance, if the source path is @file{/mnt/cross}, and the source file
5016 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
5017 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
5018 that---@file{/mnt/cross/foo.c}.
5020 Note that the executable search path is @emph{not} used to locate the
5023 Whenever you reset or rearrange the source path, @value{GDBN} clears out
5024 any information it has cached about where source files are found and where
5025 each line is in the file.
5029 When you start @value{GDBN}, its source path includes only @samp{cdir}
5030 and @samp{cwd}, in that order.
5031 To add other directories, use the @code{directory} command.
5033 The search path is used to find both program source files and @value{GDBN}
5034 script files (read using the @samp{-command} option and @samp{source} command).
5037 @item directory @var{dirname} @dots{}
5038 @item dir @var{dirname} @dots{}
5039 Add directory @var{dirname} to the front of the source path. Several
5040 directory names may be given to this command, separated by @samp{:}
5041 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
5042 part of absolute file names) or
5043 whitespace. You may specify a directory that is already in the source
5044 path; this moves it forward, so @value{GDBN} searches it sooner.
5048 @vindex $cdir@r{, convenience variable}
5049 @vindex $cwdr@r{, convenience variable}
5050 @cindex compilation directory
5051 @cindex current directory
5052 @cindex working directory
5053 @cindex directory, current
5054 @cindex directory, compilation
5055 You can use the string @samp{$cdir} to refer to the compilation
5056 directory (if one is recorded), and @samp{$cwd} to refer to the current
5057 working directory. @samp{$cwd} is not the same as @samp{.}---the former
5058 tracks the current working directory as it changes during your @value{GDBN}
5059 session, while the latter is immediately expanded to the current
5060 directory at the time you add an entry to the source path.
5063 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
5065 @c RET-repeat for @code{directory} is explicitly disabled, but since
5066 @c repeating it would be a no-op we do not say that. (thanks to RMS)
5068 @item show directories
5069 @kindex show directories
5070 Print the source path: show which directories it contains.
5073 If your source path is cluttered with directories that are no longer of
5074 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
5075 versions of source. You can correct the situation as follows:
5079 Use @code{directory} with no argument to reset the source path to its default value.
5082 Use @code{directory} with suitable arguments to reinstall the
5083 directories you want in the source path. You can add all the
5084 directories in one command.
5088 @section Source and machine code
5089 @cindex source line and its code address
5091 You can use the command @code{info line} to map source lines to program
5092 addresses (and vice versa), and the command @code{disassemble} to display
5093 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
5094 mode, the @code{info line} command causes the arrow to point to the
5095 line specified. Also, @code{info line} prints addresses in symbolic form as
5100 @item info line @var{linespec}
5101 Print the starting and ending addresses of the compiled code for
5102 source line @var{linespec}. You can specify source lines in any of
5103 the ways understood by the @code{list} command (@pxref{List, ,Printing
5107 For example, we can use @code{info line} to discover the location of
5108 the object code for the first line of function
5109 @code{m4_changequote}:
5111 @c FIXME: I think this example should also show the addresses in
5112 @c symbolic form, as they usually would be displayed.
5114 (@value{GDBP}) info line m4_changequote
5115 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
5119 @cindex code address and its source line
5120 We can also inquire (using @code{*@var{addr}} as the form for
5121 @var{linespec}) what source line covers a particular address:
5123 (@value{GDBP}) info line *0x63ff
5124 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
5127 @cindex @code{$_} and @code{info line}
5128 @cindex @code{x} command, default address
5129 @kindex x@r{(examine), and} info line
5130 After @code{info line}, the default address for the @code{x} command
5131 is changed to the starting address of the line, so that @samp{x/i} is
5132 sufficient to begin examining the machine code (@pxref{Memory,
5133 ,Examining memory}). Also, this address is saved as the value of the
5134 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
5139 @cindex assembly instructions
5140 @cindex instructions, assembly
5141 @cindex machine instructions
5142 @cindex listing machine instructions
5144 This specialized command dumps a range of memory as machine
5145 instructions. The default memory range is the function surrounding the
5146 program counter of the selected frame. A single argument to this
5147 command is a program counter value; @value{GDBN} dumps the function
5148 surrounding this value. Two arguments specify a range of addresses
5149 (first inclusive, second exclusive) to dump.
5152 The following example shows the disassembly of a range of addresses of
5153 HP PA-RISC 2.0 code:
5156 (@value{GDBP}) disas 0x32c4 0x32e4
5157 Dump of assembler code from 0x32c4 to 0x32e4:
5158 0x32c4 <main+204>: addil 0,dp
5159 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
5160 0x32cc <main+212>: ldil 0x3000,r31
5161 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
5162 0x32d4 <main+220>: ldo 0(r31),rp
5163 0x32d8 <main+224>: addil -0x800,dp
5164 0x32dc <main+228>: ldo 0x588(r1),r26
5165 0x32e0 <main+232>: ldil 0x3000,r31
5166 End of assembler dump.
5169 Some architectures have more than one commonly-used set of instruction
5170 mnemonics or other syntax.
5172 For programs that were dynamically linked and use shared libraries,
5173 instructions that call functions or branch to locations in the shared
5174 libraries might show a seemingly bogus location---it's actually a
5175 location of the relocation table. On some architectures, @value{GDBN}
5176 might be able to resolve these to actual function names.
5179 @kindex set disassembly-flavor
5180 @cindex Intel disassembly flavor
5181 @cindex AT&T disassembly flavor
5182 @item set disassembly-flavor @var{instruction-set}
5183 Select the instruction set to use when disassembling the
5184 program via the @code{disassemble} or @code{x/i} commands.
5186 Currently this command is only defined for the Intel x86 family. You
5187 can set @var{instruction-set} to either @code{intel} or @code{att}.
5188 The default is @code{att}, the AT&T flavor used by default by Unix
5189 assemblers for x86-based targets.
5191 @kindex show disassembly-flavor
5192 @item show disassembly-flavor
5193 Show the current setting of the disassembly flavor.
5198 @chapter Examining Data
5200 @cindex printing data
5201 @cindex examining data
5204 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
5205 @c document because it is nonstandard... Under Epoch it displays in a
5206 @c different window or something like that.
5207 The usual way to examine data in your program is with the @code{print}
5208 command (abbreviated @code{p}), or its synonym @code{inspect}. It
5209 evaluates and prints the value of an expression of the language your
5210 program is written in (@pxref{Languages, ,Using @value{GDBN} with
5211 Different Languages}).
5214 @item print @var{expr}
5215 @itemx print /@var{f} @var{expr}
5216 @var{expr} is an expression (in the source language). By default the
5217 value of @var{expr} is printed in a format appropriate to its data type;
5218 you can choose a different format by specifying @samp{/@var{f}}, where
5219 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
5223 @itemx print /@var{f}
5224 @cindex reprint the last value
5225 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
5226 @dfn{value history}; @pxref{Value History, ,Value history}). This allows you to
5227 conveniently inspect the same value in an alternative format.
5230 A more low-level way of examining data is with the @code{x} command.
5231 It examines data in memory at a specified address and prints it in a
5232 specified format. @xref{Memory, ,Examining memory}.
5234 If you are interested in information about types, or about how the
5235 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
5236 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
5240 * Expressions:: Expressions
5241 * Variables:: Program variables
5242 * Arrays:: Artificial arrays
5243 * Output Formats:: Output formats
5244 * Memory:: Examining memory
5245 * Auto Display:: Automatic display
5246 * Print Settings:: Print settings
5247 * Value History:: Value history
5248 * Convenience Vars:: Convenience variables
5249 * Registers:: Registers
5250 * Floating Point Hardware:: Floating point hardware
5251 * Vector Unit:: Vector Unit
5252 * OS Information:: Auxiliary data provided by operating system
5253 * Memory Region Attributes:: Memory region attributes
5254 * Dump/Restore Files:: Copy between memory and a file
5255 * Core File Generation:: Cause a program dump its core
5256 * Character Sets:: Debugging programs that use a different
5257 character set than GDB does
5258 * Caching Remote Data:: Data caching for remote targets
5262 @section Expressions
5265 @code{print} and many other @value{GDBN} commands accept an expression and
5266 compute its value. Any kind of constant, variable or operator defined
5267 by the programming language you are using is valid in an expression in
5268 @value{GDBN}. This includes conditional expressions, function calls,
5269 casts, and string constants. It also includes preprocessor macros, if
5270 you compiled your program to include this information; see
5273 @cindex arrays in expressions
5274 @value{GDBN} supports array constants in expressions input by
5275 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
5276 you can use the command @code{print @{1, 2, 3@}} to build up an array in
5277 memory that is @code{malloc}ed in the target program.
5279 Because C is so widespread, most of the expressions shown in examples in
5280 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
5281 Languages}, for information on how to use expressions in other
5284 In this section, we discuss operators that you can use in @value{GDBN}
5285 expressions regardless of your programming language.
5287 @cindex casts, in expressions
5288 Casts are supported in all languages, not just in C, because it is so
5289 useful to cast a number into a pointer in order to examine a structure
5290 at that address in memory.
5291 @c FIXME: casts supported---Mod2 true?
5293 @value{GDBN} supports these operators, in addition to those common
5294 to programming languages:
5298 @samp{@@} is a binary operator for treating parts of memory as arrays.
5299 @xref{Arrays, ,Artificial arrays}, for more information.
5302 @samp{::} allows you to specify a variable in terms of the file or
5303 function where it is defined. @xref{Variables, ,Program variables}.
5305 @cindex @{@var{type}@}
5306 @cindex type casting memory
5307 @cindex memory, viewing as typed object
5308 @cindex casts, to view memory
5309 @item @{@var{type}@} @var{addr}
5310 Refers to an object of type @var{type} stored at address @var{addr} in
5311 memory. @var{addr} may be any expression whose value is an integer or
5312 pointer (but parentheses are required around binary operators, just as in
5313 a cast). This construct is allowed regardless of what kind of data is
5314 normally supposed to reside at @var{addr}.
5318 @section Program variables
5320 The most common kind of expression to use is the name of a variable
5323 Variables in expressions are understood in the selected stack frame
5324 (@pxref{Selection, ,Selecting a frame}); they must be either:
5328 global (or file-static)
5335 visible according to the scope rules of the
5336 programming language from the point of execution in that frame
5339 @noindent This means that in the function
5354 you can examine and use the variable @code{a} whenever your program is
5355 executing within the function @code{foo}, but you can only use or
5356 examine the variable @code{b} while your program is executing inside
5357 the block where @code{b} is declared.
5359 @cindex variable name conflict
5360 There is an exception: you can refer to a variable or function whose
5361 scope is a single source file even if the current execution point is not
5362 in this file. But it is possible to have more than one such variable or
5363 function with the same name (in different source files). If that
5364 happens, referring to that name has unpredictable effects. If you wish,
5365 you can specify a static variable in a particular function or file,
5366 using the colon-colon (@code{::}) notation:
5368 @cindex colon-colon, context for variables/functions
5370 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
5371 @cindex @code{::}, context for variables/functions
5374 @var{file}::@var{variable}
5375 @var{function}::@var{variable}
5379 Here @var{file} or @var{function} is the name of the context for the
5380 static @var{variable}. In the case of file names, you can use quotes to
5381 make sure @value{GDBN} parses the file name as a single word---for example,
5382 to print a global value of @code{x} defined in @file{f2.c}:
5385 (@value{GDBP}) p 'f2.c'::x
5388 @cindex C@t{++} scope resolution
5389 This use of @samp{::} is very rarely in conflict with the very similar
5390 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
5391 scope resolution operator in @value{GDBN} expressions.
5392 @c FIXME: Um, so what happens in one of those rare cases where it's in
5395 @cindex wrong values
5396 @cindex variable values, wrong
5397 @cindex function entry/exit, wrong values of variables
5398 @cindex optimized code, wrong values of variables
5400 @emph{Warning:} Occasionally, a local variable may appear to have the
5401 wrong value at certain points in a function---just after entry to a new
5402 scope, and just before exit.
5404 You may see this problem when you are stepping by machine instructions.
5405 This is because, on most machines, it takes more than one instruction to
5406 set up a stack frame (including local variable definitions); if you are
5407 stepping by machine instructions, variables may appear to have the wrong
5408 values until the stack frame is completely built. On exit, it usually
5409 also takes more than one machine instruction to destroy a stack frame;
5410 after you begin stepping through that group of instructions, local
5411 variable definitions may be gone.
5413 This may also happen when the compiler does significant optimizations.
5414 To be sure of always seeing accurate values, turn off all optimization
5417 @cindex ``No symbol "foo" in current context''
5418 Another possible effect of compiler optimizations is to optimize
5419 unused variables out of existence, or assign variables to registers (as
5420 opposed to memory addresses). Depending on the support for such cases
5421 offered by the debug info format used by the compiler, @value{GDBN}
5422 might not be able to display values for such local variables. If that
5423 happens, @value{GDBN} will print a message like this:
5426 No symbol "foo" in current context.
5429 To solve such problems, either recompile without optimizations, or use a
5430 different debug info format, if the compiler supports several such
5431 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
5432 usually supports the @option{-gstabs+} option. @option{-gstabs+}
5433 produces debug info in a format that is superior to formats such as
5434 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
5435 an effective form for debug info. @xref{Debugging Options,,Options
5436 for Debugging Your Program or @sc{gnu} CC, gcc.info, Using @sc{gnu} CC}.
5437 @xref{C, , Debugging C++}, for more info about debug info formats
5438 that are best suited to C@t{++} programs.
5440 If you ask to print an object whose contents are unknown to
5441 @value{GDBN}, e.g., because its data type is not completely specified
5442 by the debug information, @value{GDBN} will say @samp{<incomplete
5443 type>}. @xref{Symbols, incomplete type}, for more about this.
5446 @section Artificial arrays
5448 @cindex artificial array
5450 @kindex @@@r{, referencing memory as an array}
5451 It is often useful to print out several successive objects of the
5452 same type in memory; a section of an array, or an array of
5453 dynamically determined size for which only a pointer exists in the
5456 You can do this by referring to a contiguous span of memory as an
5457 @dfn{artificial array}, using the binary operator @samp{@@}. The left
5458 operand of @samp{@@} should be the first element of the desired array
5459 and be an individual object. The right operand should be the desired length
5460 of the array. The result is an array value whose elements are all of
5461 the type of the left argument. The first element is actually the left
5462 argument; the second element comes from bytes of memory immediately
5463 following those that hold the first element, and so on. Here is an
5464 example. If a program says
5467 int *array = (int *) malloc (len * sizeof (int));
5471 you can print the contents of @code{array} with
5477 The left operand of @samp{@@} must reside in memory. Array values made
5478 with @samp{@@} in this way behave just like other arrays in terms of
5479 subscripting, and are coerced to pointers when used in expressions.
5480 Artificial arrays most often appear in expressions via the value history
5481 (@pxref{Value History, ,Value history}), after printing one out.
5483 Another way to create an artificial array is to use a cast.
5484 This re-interprets a value as if it were an array.
5485 The value need not be in memory:
5487 (@value{GDBP}) p/x (short[2])0x12345678
5488 $1 = @{0x1234, 0x5678@}
5491 As a convenience, if you leave the array length out (as in
5492 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
5493 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
5495 (@value{GDBP}) p/x (short[])0x12345678
5496 $2 = @{0x1234, 0x5678@}
5499 Sometimes the artificial array mechanism is not quite enough; in
5500 moderately complex data structures, the elements of interest may not
5501 actually be adjacent---for example, if you are interested in the values
5502 of pointers in an array. One useful work-around in this situation is
5503 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
5504 variables}) as a counter in an expression that prints the first
5505 interesting value, and then repeat that expression via @key{RET}. For
5506 instance, suppose you have an array @code{dtab} of pointers to
5507 structures, and you are interested in the values of a field @code{fv}
5508 in each structure. Here is an example of what you might type:
5518 @node Output Formats
5519 @section Output formats
5521 @cindex formatted output
5522 @cindex output formats
5523 By default, @value{GDBN} prints a value according to its data type. Sometimes
5524 this is not what you want. For example, you might want to print a number
5525 in hex, or a pointer in decimal. Or you might want to view data in memory
5526 at a certain address as a character string or as an instruction. To do
5527 these things, specify an @dfn{output format} when you print a value.
5529 The simplest use of output formats is to say how to print a value
5530 already computed. This is done by starting the arguments of the
5531 @code{print} command with a slash and a format letter. The format
5532 letters supported are:
5536 Regard the bits of the value as an integer, and print the integer in
5540 Print as integer in signed decimal.
5543 Print as integer in unsigned decimal.
5546 Print as integer in octal.
5549 Print as integer in binary. The letter @samp{t} stands for ``two''.
5550 @footnote{@samp{b} cannot be used because these format letters are also
5551 used with the @code{x} command, where @samp{b} stands for ``byte'';
5552 see @ref{Memory,,Examining memory}.}
5555 @cindex unknown address, locating
5556 @cindex locate address
5557 Print as an address, both absolute in hexadecimal and as an offset from
5558 the nearest preceding symbol. You can use this format used to discover
5559 where (in what function) an unknown address is located:
5562 (@value{GDBP}) p/a 0x54320
5563 $3 = 0x54320 <_initialize_vx+396>
5567 The command @code{info symbol 0x54320} yields similar results.
5568 @xref{Symbols, info symbol}.
5571 Regard as an integer and print it as a character constant. This
5572 prints both the numerical value and its character representation. The
5573 character representation is replaced with the octal escape @samp{\nnn}
5574 for characters outside the 7-bit @sc{ascii} range.
5577 Regard the bits of the value as a floating point number and print
5578 using typical floating point syntax.
5581 For example, to print the program counter in hex (@pxref{Registers}), type
5588 Note that no space is required before the slash; this is because command
5589 names in @value{GDBN} cannot contain a slash.
5591 To reprint the last value in the value history with a different format,
5592 you can use the @code{print} command with just a format and no
5593 expression. For example, @samp{p/x} reprints the last value in hex.
5596 @section Examining memory
5598 You can use the command @code{x} (for ``examine'') to examine memory in
5599 any of several formats, independently of your program's data types.
5601 @cindex examining memory
5603 @kindex x @r{(examine memory)}
5604 @item x/@var{nfu} @var{addr}
5607 Use the @code{x} command to examine memory.
5610 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
5611 much memory to display and how to format it; @var{addr} is an
5612 expression giving the address where you want to start displaying memory.
5613 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
5614 Several commands set convenient defaults for @var{addr}.
5617 @item @var{n}, the repeat count
5618 The repeat count is a decimal integer; the default is 1. It specifies
5619 how much memory (counting by units @var{u}) to display.
5620 @c This really is **decimal**; unaffected by 'set radix' as of GDB
5623 @item @var{f}, the display format
5624 The display format is one of the formats used by @code{print}
5625 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
5626 @samp{f}), and in addition @samp{s} (for null-terminated strings) and
5627 @samp{i} (for machine instructions). The default is @samp{x}
5628 (hexadecimal) initially. The default changes each time you use either
5629 @code{x} or @code{print}.
5631 @item @var{u}, the unit size
5632 The unit size is any of
5638 Halfwords (two bytes).
5640 Words (four bytes). This is the initial default.
5642 Giant words (eight bytes).
5645 Each time you specify a unit size with @code{x}, that size becomes the
5646 default unit the next time you use @code{x}. (For the @samp{s} and
5647 @samp{i} formats, the unit size is ignored and is normally not written.)
5649 @item @var{addr}, starting display address
5650 @var{addr} is the address where you want @value{GDBN} to begin displaying
5651 memory. The expression need not have a pointer value (though it may);
5652 it is always interpreted as an integer address of a byte of memory.
5653 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
5654 @var{addr} is usually just after the last address examined---but several
5655 other commands also set the default address: @code{info breakpoints} (to
5656 the address of the last breakpoint listed), @code{info line} (to the
5657 starting address of a line), and @code{print} (if you use it to display
5658 a value from memory).
5661 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
5662 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
5663 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
5664 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
5665 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
5667 Since the letters indicating unit sizes are all distinct from the
5668 letters specifying output formats, you do not have to remember whether
5669 unit size or format comes first; either order works. The output
5670 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
5671 (However, the count @var{n} must come first; @samp{wx4} does not work.)
5673 Even though the unit size @var{u} is ignored for the formats @samp{s}
5674 and @samp{i}, you might still want to use a count @var{n}; for example,
5675 @samp{3i} specifies that you want to see three machine instructions,
5676 including any operands. The command @code{disassemble} gives an
5677 alternative way of inspecting machine instructions; see @ref{Machine
5678 Code,,Source and machine code}.
5680 All the defaults for the arguments to @code{x} are designed to make it
5681 easy to continue scanning memory with minimal specifications each time
5682 you use @code{x}. For example, after you have inspected three machine
5683 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
5684 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
5685 the repeat count @var{n} is used again; the other arguments default as
5686 for successive uses of @code{x}.
5688 @cindex @code{$_}, @code{$__}, and value history
5689 The addresses and contents printed by the @code{x} command are not saved
5690 in the value history because there is often too much of them and they
5691 would get in the way. Instead, @value{GDBN} makes these values available for
5692 subsequent use in expressions as values of the convenience variables
5693 @code{$_} and @code{$__}. After an @code{x} command, the last address
5694 examined is available for use in expressions in the convenience variable
5695 @code{$_}. The contents of that address, as examined, are available in
5696 the convenience variable @code{$__}.
5698 If the @code{x} command has a repeat count, the address and contents saved
5699 are from the last memory unit printed; this is not the same as the last
5700 address printed if several units were printed on the last line of output.
5702 @cindex remote memory comparison
5703 @cindex verify remote memory image
5704 When you are debugging a program running on a remote target machine
5705 (@pxref{Remote}), you may wish to verify the program's image in the
5706 remote machine's memory against the executable file you downloaded to
5707 the target. The @code{compare-sections} command is provided for such
5711 @kindex compare-sections
5712 @item compare-sections @r{[}@var{section-name}@r{]}
5713 Compare the data of a loadable section @var{section-name} in the
5714 executable file of the program being debugged with the same section in
5715 the remote machine's memory, and report any mismatches. With no
5716 arguments, compares all loadable sections. This command's
5717 availability depends on the target's support for the @code{"qCRC"}
5722 @section Automatic display
5723 @cindex automatic display
5724 @cindex display of expressions
5726 If you find that you want to print the value of an expression frequently
5727 (to see how it changes), you might want to add it to the @dfn{automatic
5728 display list} so that @value{GDBN} prints its value each time your program stops.
5729 Each expression added to the list is given a number to identify it;
5730 to remove an expression from the list, you specify that number.
5731 The automatic display looks like this:
5735 3: bar[5] = (struct hack *) 0x3804
5739 This display shows item numbers, expressions and their current values. As with
5740 displays you request manually using @code{x} or @code{print}, you can
5741 specify the output format you prefer; in fact, @code{display} decides
5742 whether to use @code{print} or @code{x} depending on how elaborate your
5743 format specification is---it uses @code{x} if you specify a unit size,
5744 or one of the two formats (@samp{i} and @samp{s}) that are only
5745 supported by @code{x}; otherwise it uses @code{print}.
5749 @item display @var{expr}
5750 Add the expression @var{expr} to the list of expressions to display
5751 each time your program stops. @xref{Expressions, ,Expressions}.
5753 @code{display} does not repeat if you press @key{RET} again after using it.
5755 @item display/@var{fmt} @var{expr}
5756 For @var{fmt} specifying only a display format and not a size or
5757 count, add the expression @var{expr} to the auto-display list but
5758 arrange to display it each time in the specified format @var{fmt}.
5759 @xref{Output Formats,,Output formats}.
5761 @item display/@var{fmt} @var{addr}
5762 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
5763 number of units, add the expression @var{addr} as a memory address to
5764 be examined each time your program stops. Examining means in effect
5765 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining memory}.
5768 For example, @samp{display/i $pc} can be helpful, to see the machine
5769 instruction about to be executed each time execution stops (@samp{$pc}
5770 is a common name for the program counter; @pxref{Registers, ,Registers}).
5773 @kindex delete display
5775 @item undisplay @var{dnums}@dots{}
5776 @itemx delete display @var{dnums}@dots{}
5777 Remove item numbers @var{dnums} from the list of expressions to display.
5779 @code{undisplay} does not repeat if you press @key{RET} after using it.
5780 (Otherwise you would just get the error @samp{No display number @dots{}}.)
5782 @kindex disable display
5783 @item disable display @var{dnums}@dots{}
5784 Disable the display of item numbers @var{dnums}. A disabled display
5785 item is not printed automatically, but is not forgotten. It may be
5786 enabled again later.
5788 @kindex enable display
5789 @item enable display @var{dnums}@dots{}
5790 Enable display of item numbers @var{dnums}. It becomes effective once
5791 again in auto display of its expression, until you specify otherwise.
5794 Display the current values of the expressions on the list, just as is
5795 done when your program stops.
5797 @kindex info display
5799 Print the list of expressions previously set up to display
5800 automatically, each one with its item number, but without showing the
5801 values. This includes disabled expressions, which are marked as such.
5802 It also includes expressions which would not be displayed right now
5803 because they refer to automatic variables not currently available.
5806 @cindex display disabled out of scope
5807 If a display expression refers to local variables, then it does not make
5808 sense outside the lexical context for which it was set up. Such an
5809 expression is disabled when execution enters a context where one of its
5810 variables is not defined. For example, if you give the command
5811 @code{display last_char} while inside a function with an argument
5812 @code{last_char}, @value{GDBN} displays this argument while your program
5813 continues to stop inside that function. When it stops elsewhere---where
5814 there is no variable @code{last_char}---the display is disabled
5815 automatically. The next time your program stops where @code{last_char}
5816 is meaningful, you can enable the display expression once again.
5818 @node Print Settings
5819 @section Print settings
5821 @cindex format options
5822 @cindex print settings
5823 @value{GDBN} provides the following ways to control how arrays, structures,
5824 and symbols are printed.
5827 These settings are useful for debugging programs in any language:
5831 @item set print address
5832 @itemx set print address on
5833 @cindex print/don't print memory addresses
5834 @value{GDBN} prints memory addresses showing the location of stack
5835 traces, structure values, pointer values, breakpoints, and so forth,
5836 even when it also displays the contents of those addresses. The default
5837 is @code{on}. For example, this is what a stack frame display looks like with
5838 @code{set print address on}:
5843 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
5845 530 if (lquote != def_lquote)
5849 @item set print address off
5850 Do not print addresses when displaying their contents. For example,
5851 this is the same stack frame displayed with @code{set print address off}:
5855 (@value{GDBP}) set print addr off
5857 #0 set_quotes (lq="<<", rq=">>") at input.c:530
5858 530 if (lquote != def_lquote)
5862 You can use @samp{set print address off} to eliminate all machine
5863 dependent displays from the @value{GDBN} interface. For example, with
5864 @code{print address off}, you should get the same text for backtraces on
5865 all machines---whether or not they involve pointer arguments.
5868 @item show print address
5869 Show whether or not addresses are to be printed.
5872 When @value{GDBN} prints a symbolic address, it normally prints the
5873 closest earlier symbol plus an offset. If that symbol does not uniquely
5874 identify the address (for example, it is a name whose scope is a single
5875 source file), you may need to clarify. One way to do this is with
5876 @code{info line}, for example @samp{info line *0x4537}. Alternately,
5877 you can set @value{GDBN} to print the source file and line number when
5878 it prints a symbolic address:
5881 @item set print symbol-filename on
5882 @cindex source file and line of a symbol
5883 @cindex symbol, source file and line
5884 Tell @value{GDBN} to print the source file name and line number of a
5885 symbol in the symbolic form of an address.
5887 @item set print symbol-filename off
5888 Do not print source file name and line number of a symbol. This is the
5891 @item show print symbol-filename
5892 Show whether or not @value{GDBN} will print the source file name and
5893 line number of a symbol in the symbolic form of an address.
5896 Another situation where it is helpful to show symbol filenames and line
5897 numbers is when disassembling code; @value{GDBN} shows you the line
5898 number and source file that corresponds to each instruction.
5900 Also, you may wish to see the symbolic form only if the address being
5901 printed is reasonably close to the closest earlier symbol:
5904 @item set print max-symbolic-offset @var{max-offset}
5905 @cindex maximum value for offset of closest symbol
5906 Tell @value{GDBN} to only display the symbolic form of an address if the
5907 offset between the closest earlier symbol and the address is less than
5908 @var{max-offset}. The default is 0, which tells @value{GDBN}
5909 to always print the symbolic form of an address if any symbol precedes it.
5911 @item show print max-symbolic-offset
5912 Ask how large the maximum offset is that @value{GDBN} prints in a
5916 @cindex wild pointer, interpreting
5917 @cindex pointer, finding referent
5918 If you have a pointer and you are not sure where it points, try
5919 @samp{set print symbol-filename on}. Then you can determine the name
5920 and source file location of the variable where it points, using
5921 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
5922 For example, here @value{GDBN} shows that a variable @code{ptt} points
5923 at another variable @code{t}, defined in @file{hi2.c}:
5926 (@value{GDBP}) set print symbol-filename on
5927 (@value{GDBP}) p/a ptt
5928 $4 = 0xe008 <t in hi2.c>
5932 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
5933 does not show the symbol name and filename of the referent, even with
5934 the appropriate @code{set print} options turned on.
5937 Other settings control how different kinds of objects are printed:
5940 @item set print array
5941 @itemx set print array on
5942 @cindex pretty print arrays
5943 Pretty print arrays. This format is more convenient to read,
5944 but uses more space. The default is off.
5946 @item set print array off
5947 Return to compressed format for arrays.
5949 @item show print array
5950 Show whether compressed or pretty format is selected for displaying
5953 @cindex print array indexes
5954 @item set print array-indexes
5955 @itemx set print array-indexes on
5956 Print the index of each element when displaying arrays. May be more
5957 convenient to locate a given element in the array or quickly find the
5958 index of a given element in that printed array. The default is off.
5960 @item set print array-indexes off
5961 Stop printing element indexes when displaying arrays.
5963 @item show print array-indexes
5964 Show whether the index of each element is printed when displaying
5967 @item set print elements @var{number-of-elements}
5968 @cindex number of array elements to print
5969 @cindex limit on number of printed array elements
5970 Set a limit on how many elements of an array @value{GDBN} will print.
5971 If @value{GDBN} is printing a large array, it stops printing after it has
5972 printed the number of elements set by the @code{set print elements} command.
5973 This limit also applies to the display of strings.
5974 When @value{GDBN} starts, this limit is set to 200.
5975 Setting @var{number-of-elements} to zero means that the printing is unlimited.
5977 @item show print elements
5978 Display the number of elements of a large array that @value{GDBN} will print.
5979 If the number is 0, then the printing is unlimited.
5981 @item set print repeats
5982 @cindex repeated array elements
5983 Set the threshold for suppressing display of repeated array
5984 elelments. When the number of consecutive identical elements of an
5985 array exceeds the threshold, @value{GDBN} prints the string
5986 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
5987 identical repetitions, instead of displaying the identical elements
5988 themselves. Setting the threshold to zero will cause all elements to
5989 be individually printed. The default threshold is 10.
5991 @item show print repeats
5992 Display the current threshold for printing repeated identical
5995 @item set print null-stop
5996 @cindex @sc{null} elements in arrays
5997 Cause @value{GDBN} to stop printing the characters of an array when the first
5998 @sc{null} is encountered. This is useful when large arrays actually
5999 contain only short strings.
6002 @item show print null-stop
6003 Show whether @value{GDBN} stops printing an array on the first
6004 @sc{null} character.
6006 @item set print pretty on
6007 @cindex print structures in indented form
6008 @cindex indentation in structure display
6009 Cause @value{GDBN} to print structures in an indented format with one member
6010 per line, like this:
6025 @item set print pretty off
6026 Cause @value{GDBN} to print structures in a compact format, like this:
6030 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
6031 meat = 0x54 "Pork"@}
6036 This is the default format.
6038 @item show print pretty
6039 Show which format @value{GDBN} is using to print structures.
6041 @item set print sevenbit-strings on
6042 @cindex eight-bit characters in strings
6043 @cindex octal escapes in strings
6044 Print using only seven-bit characters; if this option is set,
6045 @value{GDBN} displays any eight-bit characters (in strings or
6046 character values) using the notation @code{\}@var{nnn}. This setting is
6047 best if you are working in English (@sc{ascii}) and you use the
6048 high-order bit of characters as a marker or ``meta'' bit.
6050 @item set print sevenbit-strings off
6051 Print full eight-bit characters. This allows the use of more
6052 international character sets, and is the default.
6054 @item show print sevenbit-strings
6055 Show whether or not @value{GDBN} is printing only seven-bit characters.
6057 @item set print union on
6058 @cindex unions in structures, printing
6059 Tell @value{GDBN} to print unions which are contained in structures
6060 and other unions. This is the default setting.
6062 @item set print union off
6063 Tell @value{GDBN} not to print unions which are contained in
6064 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
6067 @item show print union
6068 Ask @value{GDBN} whether or not it will print unions which are contained in
6069 structures and other unions.
6071 For example, given the declarations
6074 typedef enum @{Tree, Bug@} Species;
6075 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
6076 typedef enum @{Caterpillar, Cocoon, Butterfly@}
6087 struct thing foo = @{Tree, @{Acorn@}@};
6091 with @code{set print union on} in effect @samp{p foo} would print
6094 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
6098 and with @code{set print union off} in effect it would print
6101 $1 = @{it = Tree, form = @{...@}@}
6105 @code{set print union} affects programs written in C-like languages
6111 These settings are of interest when debugging C@t{++} programs:
6114 @cindex demangling C@t{++} names
6115 @item set print demangle
6116 @itemx set print demangle on
6117 Print C@t{++} names in their source form rather than in the encoded
6118 (``mangled'') form passed to the assembler and linker for type-safe
6119 linkage. The default is on.
6121 @item show print demangle
6122 Show whether C@t{++} names are printed in mangled or demangled form.
6124 @item set print asm-demangle
6125 @itemx set print asm-demangle on
6126 Print C@t{++} names in their source form rather than their mangled form, even
6127 in assembler code printouts such as instruction disassemblies.
6130 @item show print asm-demangle
6131 Show whether C@t{++} names in assembly listings are printed in mangled
6134 @cindex C@t{++} symbol decoding style
6135 @cindex symbol decoding style, C@t{++}
6136 @kindex set demangle-style
6137 @item set demangle-style @var{style}
6138 Choose among several encoding schemes used by different compilers to
6139 represent C@t{++} names. The choices for @var{style} are currently:
6143 Allow @value{GDBN} to choose a decoding style by inspecting your program.
6146 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
6147 This is the default.
6150 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
6153 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
6156 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
6157 @strong{Warning:} this setting alone is not sufficient to allow
6158 debugging @code{cfront}-generated executables. @value{GDBN} would
6159 require further enhancement to permit that.
6162 If you omit @var{style}, you will see a list of possible formats.
6164 @item show demangle-style
6165 Display the encoding style currently in use for decoding C@t{++} symbols.
6167 @item set print object
6168 @itemx set print object on
6169 @cindex derived type of an object, printing
6170 @cindex display derived types
6171 When displaying a pointer to an object, identify the @emph{actual}
6172 (derived) type of the object rather than the @emph{declared} type, using
6173 the virtual function table.
6175 @item set print object off
6176 Display only the declared type of objects, without reference to the
6177 virtual function table. This is the default setting.
6179 @item show print object
6180 Show whether actual, or declared, object types are displayed.
6182 @item set print static-members
6183 @itemx set print static-members on
6184 @cindex static members of C@t{++} objects
6185 Print static members when displaying a C@t{++} object. The default is on.
6187 @item set print static-members off
6188 Do not print static members when displaying a C@t{++} object.
6190 @item show print static-members
6191 Show whether C@t{++} static members are printed or not.
6193 @item set print pascal_static-members
6194 @itemx set print pascal_static-members on
6195 @cindex static members of Pacal objects
6196 @cindex Pacal objects, static members display
6197 Print static members when displaying a Pascal object. The default is on.
6199 @item set print pascal_static-members off
6200 Do not print static members when displaying a Pascal object.
6202 @item show print pascal_static-members
6203 Show whether Pascal static members are printed or not.
6205 @c These don't work with HP ANSI C++ yet.
6206 @item set print vtbl
6207 @itemx set print vtbl on
6208 @cindex pretty print C@t{++} virtual function tables
6209 @cindex virtual functions (C@t{++}) display
6210 @cindex VTBL display
6211 Pretty print C@t{++} virtual function tables. The default is off.
6212 (The @code{vtbl} commands do not work on programs compiled with the HP
6213 ANSI C@t{++} compiler (@code{aCC}).)
6215 @item set print vtbl off
6216 Do not pretty print C@t{++} virtual function tables.
6218 @item show print vtbl
6219 Show whether C@t{++} virtual function tables are pretty printed, or not.
6223 @section Value history
6225 @cindex value history
6226 @cindex history of values printed by @value{GDBN}
6227 Values printed by the @code{print} command are saved in the @value{GDBN}
6228 @dfn{value history}. This allows you to refer to them in other expressions.
6229 Values are kept until the symbol table is re-read or discarded
6230 (for example with the @code{file} or @code{symbol-file} commands).
6231 When the symbol table changes, the value history is discarded,
6232 since the values may contain pointers back to the types defined in the
6237 @cindex history number
6238 The values printed are given @dfn{history numbers} by which you can
6239 refer to them. These are successive integers starting with one.
6240 @code{print} shows you the history number assigned to a value by
6241 printing @samp{$@var{num} = } before the value; here @var{num} is the
6244 To refer to any previous value, use @samp{$} followed by the value's
6245 history number. The way @code{print} labels its output is designed to
6246 remind you of this. Just @code{$} refers to the most recent value in
6247 the history, and @code{$$} refers to the value before that.
6248 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
6249 is the value just prior to @code{$$}, @code{$$1} is equivalent to
6250 @code{$$}, and @code{$$0} is equivalent to @code{$}.
6252 For example, suppose you have just printed a pointer to a structure and
6253 want to see the contents of the structure. It suffices to type
6259 If you have a chain of structures where the component @code{next} points
6260 to the next one, you can print the contents of the next one with this:
6267 You can print successive links in the chain by repeating this
6268 command---which you can do by just typing @key{RET}.
6270 Note that the history records values, not expressions. If the value of
6271 @code{x} is 4 and you type these commands:
6279 then the value recorded in the value history by the @code{print} command
6280 remains 4 even though the value of @code{x} has changed.
6285 Print the last ten values in the value history, with their item numbers.
6286 This is like @samp{p@ $$9} repeated ten times, except that @code{show
6287 values} does not change the history.
6289 @item show values @var{n}
6290 Print ten history values centered on history item number @var{n}.
6293 Print ten history values just after the values last printed. If no more
6294 values are available, @code{show values +} produces no display.
6297 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
6298 same effect as @samp{show values +}.
6300 @node Convenience Vars
6301 @section Convenience variables
6303 @cindex convenience variables
6304 @cindex user-defined variables
6305 @value{GDBN} provides @dfn{convenience variables} that you can use within
6306 @value{GDBN} to hold on to a value and refer to it later. These variables
6307 exist entirely within @value{GDBN}; they are not part of your program, and
6308 setting a convenience variable has no direct effect on further execution
6309 of your program. That is why you can use them freely.
6311 Convenience variables are prefixed with @samp{$}. Any name preceded by
6312 @samp{$} can be used for a convenience variable, unless it is one of
6313 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
6314 (Value history references, in contrast, are @emph{numbers} preceded
6315 by @samp{$}. @xref{Value History, ,Value history}.)
6317 You can save a value in a convenience variable with an assignment
6318 expression, just as you would set a variable in your program.
6322 set $foo = *object_ptr
6326 would save in @code{$foo} the value contained in the object pointed to by
6329 Using a convenience variable for the first time creates it, but its
6330 value is @code{void} until you assign a new value. You can alter the
6331 value with another assignment at any time.
6333 Convenience variables have no fixed types. You can assign a convenience
6334 variable any type of value, including structures and arrays, even if
6335 that variable already has a value of a different type. The convenience
6336 variable, when used as an expression, has the type of its current value.
6339 @kindex show convenience
6340 @cindex show all user variables
6341 @item show convenience
6342 Print a list of convenience variables used so far, and their values.
6343 Abbreviated @code{show conv}.
6345 @kindex init-if-undefined
6346 @cindex convenience variables, initializing
6347 @item init-if-undefined $@var{variable} = @var{expression}
6348 Set a convenience variable if it has not already been set. This is useful
6349 for user-defined commands that keep some state. It is similar, in concept,
6350 to using local static variables with initializers in C (except that
6351 convenience variables are global). It can also be used to allow users to
6352 override default values used in a command script.
6354 If the variable is already defined then the expression is not evaluated so
6355 any side-effects do not occur.
6358 One of the ways to use a convenience variable is as a counter to be
6359 incremented or a pointer to be advanced. For example, to print
6360 a field from successive elements of an array of structures:
6364 print bar[$i++]->contents
6368 Repeat that command by typing @key{RET}.
6370 Some convenience variables are created automatically by @value{GDBN} and given
6371 values likely to be useful.
6374 @vindex $_@r{, convenience variable}
6376 The variable @code{$_} is automatically set by the @code{x} command to
6377 the last address examined (@pxref{Memory, ,Examining memory}). Other
6378 commands which provide a default address for @code{x} to examine also
6379 set @code{$_} to that address; these commands include @code{info line}
6380 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
6381 except when set by the @code{x} command, in which case it is a pointer
6382 to the type of @code{$__}.
6384 @vindex $__@r{, convenience variable}
6386 The variable @code{$__} is automatically set by the @code{x} command
6387 to the value found in the last address examined. Its type is chosen
6388 to match the format in which the data was printed.
6391 @vindex $_exitcode@r{, convenience variable}
6392 The variable @code{$_exitcode} is automatically set to the exit code when
6393 the program being debugged terminates.
6396 On HP-UX systems, if you refer to a function or variable name that
6397 begins with a dollar sign, @value{GDBN} searches for a user or system
6398 name first, before it searches for a convenience variable.
6404 You can refer to machine register contents, in expressions, as variables
6405 with names starting with @samp{$}. The names of registers are different
6406 for each machine; use @code{info registers} to see the names used on
6410 @kindex info registers
6411 @item info registers
6412 Print the names and values of all registers except floating-point
6413 and vector registers (in the selected stack frame).
6415 @kindex info all-registers
6416 @cindex floating point registers
6417 @item info all-registers
6418 Print the names and values of all registers, including floating-point
6419 and vector registers (in the selected stack frame).
6421 @item info registers @var{regname} @dots{}
6422 Print the @dfn{relativized} value of each specified register @var{regname}.
6423 As discussed in detail below, register values are normally relative to
6424 the selected stack frame. @var{regname} may be any register name valid on
6425 the machine you are using, with or without the initial @samp{$}.
6428 @cindex stack pointer register
6429 @cindex program counter register
6430 @cindex process status register
6431 @cindex frame pointer register
6432 @cindex standard registers
6433 @value{GDBN} has four ``standard'' register names that are available (in
6434 expressions) on most machines---whenever they do not conflict with an
6435 architecture's canonical mnemonics for registers. The register names
6436 @code{$pc} and @code{$sp} are used for the program counter register and
6437 the stack pointer. @code{$fp} is used for a register that contains a
6438 pointer to the current stack frame, and @code{$ps} is used for a
6439 register that contains the processor status. For example,
6440 you could print the program counter in hex with
6447 or print the instruction to be executed next with
6454 or add four to the stack pointer@footnote{This is a way of removing
6455 one word from the stack, on machines where stacks grow downward in
6456 memory (most machines, nowadays). This assumes that the innermost
6457 stack frame is selected; setting @code{$sp} is not allowed when other
6458 stack frames are selected. To pop entire frames off the stack,
6459 regardless of machine architecture, use @code{return};
6460 see @ref{Returning, ,Returning from a function}.} with
6466 Whenever possible, these four standard register names are available on
6467 your machine even though the machine has different canonical mnemonics,
6468 so long as there is no conflict. The @code{info registers} command
6469 shows the canonical names. For example, on the SPARC, @code{info
6470 registers} displays the processor status register as @code{$psr} but you
6471 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
6472 is an alias for the @sc{eflags} register.
6474 @value{GDBN} always considers the contents of an ordinary register as an
6475 integer when the register is examined in this way. Some machines have
6476 special registers which can hold nothing but floating point; these
6477 registers are considered to have floating point values. There is no way
6478 to refer to the contents of an ordinary register as floating point value
6479 (although you can @emph{print} it as a floating point value with
6480 @samp{print/f $@var{regname}}).
6482 Some registers have distinct ``raw'' and ``virtual'' data formats. This
6483 means that the data format in which the register contents are saved by
6484 the operating system is not the same one that your program normally
6485 sees. For example, the registers of the 68881 floating point
6486 coprocessor are always saved in ``extended'' (raw) format, but all C
6487 programs expect to work with ``double'' (virtual) format. In such
6488 cases, @value{GDBN} normally works with the virtual format only (the format
6489 that makes sense for your program), but the @code{info registers} command
6490 prints the data in both formats.
6492 @cindex SSE registers (x86)
6493 @cindex MMX registers (x86)
6494 Some machines have special registers whose contents can be interpreted
6495 in several different ways. For example, modern x86-based machines
6496 have SSE and MMX registers that can hold several values packed
6497 together in several different formats. @value{GDBN} refers to such
6498 registers in @code{struct} notation:
6501 (@value{GDBP}) print $xmm1
6503 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
6504 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
6505 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
6506 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
6507 v4_int32 = @{0, 20657912, 11, 13@},
6508 v2_int64 = @{88725056443645952, 55834574859@},
6509 uint128 = 0x0000000d0000000b013b36f800000000
6514 To set values of such registers, you need to tell @value{GDBN} which
6515 view of the register you wish to change, as if you were assigning
6516 value to a @code{struct} member:
6519 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
6522 Normally, register values are relative to the selected stack frame
6523 (@pxref{Selection, ,Selecting a frame}). This means that you get the
6524 value that the register would contain if all stack frames farther in
6525 were exited and their saved registers restored. In order to see the
6526 true contents of hardware registers, you must select the innermost
6527 frame (with @samp{frame 0}).
6529 However, @value{GDBN} must deduce where registers are saved, from the machine
6530 code generated by your compiler. If some registers are not saved, or if
6531 @value{GDBN} is unable to locate the saved registers, the selected stack
6532 frame makes no difference.
6534 @node Floating Point Hardware
6535 @section Floating point hardware
6536 @cindex floating point
6538 Depending on the configuration, @value{GDBN} may be able to give
6539 you more information about the status of the floating point hardware.
6544 Display hardware-dependent information about the floating
6545 point unit. The exact contents and layout vary depending on the
6546 floating point chip. Currently, @samp{info float} is supported on
6547 the ARM and x86 machines.
6551 @section Vector Unit
6554 Depending on the configuration, @value{GDBN} may be able to give you
6555 more information about the status of the vector unit.
6560 Display information about the vector unit. The exact contents and
6561 layout vary depending on the hardware.
6564 @node OS Information
6565 @section Operating system auxiliary information
6566 @cindex OS information
6568 @value{GDBN} provides interfaces to useful OS facilities that can help
6569 you debug your program.
6571 @cindex @code{ptrace} system call
6572 @cindex @code{struct user} contents
6573 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
6574 machines), it interfaces with the inferior via the @code{ptrace}
6575 system call. The operating system creates a special sata structure,
6576 called @code{struct user}, for this interface. You can use the
6577 command @code{info udot} to display the contents of this data
6583 Display the contents of the @code{struct user} maintained by the OS
6584 kernel for the program being debugged. @value{GDBN} displays the
6585 contents of @code{struct user} as a list of hex numbers, similar to
6586 the @code{examine} command.
6589 @cindex auxiliary vector
6590 @cindex vector, auxiliary
6591 Some operating systems supply an @dfn{auxiliary vector} to programs at
6592 startup. This is akin to the arguments and environment that you
6593 specify for a program, but contains a system-dependent variety of
6594 binary values that tell system libraries important details about the
6595 hardware, operating system, and process. Each value's purpose is
6596 identified by an integer tag; the meanings are well-known but system-specific.
6597 Depending on the configuration and operating system facilities,
6598 @value{GDBN} may be able to show you this information. For remote
6599 targets, this functionality may further depend on the remote stub's
6600 support of the @samp{qXfer:auxv:read} packet, see @ref{Remote
6601 configuration, auxiliary vector}.
6606 Display the auxiliary vector of the inferior, which can be either a
6607 live process or a core dump file. @value{GDBN} prints each tag value
6608 numerically, and also shows names and text descriptions for recognized
6609 tags. Some values in the vector are numbers, some bit masks, and some
6610 pointers to strings or other data. @value{GDBN} displays each value in the
6611 most appropriate form for a recognized tag, and in hexadecimal for
6612 an unrecognized tag.
6616 @node Memory Region Attributes
6617 @section Memory region attributes
6618 @cindex memory region attributes
6620 @dfn{Memory region attributes} allow you to describe special handling
6621 required by regions of your target's memory. @value{GDBN} uses attributes
6622 to determine whether to allow certain types of memory accesses; whether to
6623 use specific width accesses; and whether to cache target memory.
6625 Defined memory regions can be individually enabled and disabled. When a
6626 memory region is disabled, @value{GDBN} uses the default attributes when
6627 accessing memory in that region. Similarly, if no memory regions have
6628 been defined, @value{GDBN} uses the default attributes when accessing
6631 When a memory region is defined, it is given a number to identify it;
6632 to enable, disable, or remove a memory region, you specify that number.
6636 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
6637 Define a memory region bounded by @var{lower} and @var{upper} with
6638 attributes @var{attributes}@dots{}, and add it to the list of regions
6639 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
6640 case: it is treated as the the target's maximum memory address.
6641 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
6644 @item delete mem @var{nums}@dots{}
6645 Remove memory regions @var{nums}@dots{} from the list of regions
6646 monitored by @value{GDBN}.
6649 @item disable mem @var{nums}@dots{}
6650 Disable monitoring of memory regions @var{nums}@dots{}.
6651 A disabled memory region is not forgotten.
6652 It may be enabled again later.
6655 @item enable mem @var{nums}@dots{}
6656 Enable monitoring of memory regions @var{nums}@dots{}.
6660 Print a table of all defined memory regions, with the following columns
6664 @item Memory Region Number
6665 @item Enabled or Disabled.
6666 Enabled memory regions are marked with @samp{y}.
6667 Disabled memory regions are marked with @samp{n}.
6670 The address defining the inclusive lower bound of the memory region.
6673 The address defining the exclusive upper bound of the memory region.
6676 The list of attributes set for this memory region.
6681 @subsection Attributes
6683 @subsubsection Memory Access Mode
6684 The access mode attributes set whether @value{GDBN} may make read or
6685 write accesses to a memory region.
6687 While these attributes prevent @value{GDBN} from performing invalid
6688 memory accesses, they do nothing to prevent the target system, I/O DMA,
6689 etc.@: from accessing memory.
6693 Memory is read only.
6695 Memory is write only.
6697 Memory is read/write. This is the default.
6700 @subsubsection Memory Access Size
6701 The acccess size attributes tells @value{GDBN} to use specific sized
6702 accesses in the memory region. Often memory mapped device registers
6703 require specific sized accesses. If no access size attribute is
6704 specified, @value{GDBN} may use accesses of any size.
6708 Use 8 bit memory accesses.
6710 Use 16 bit memory accesses.
6712 Use 32 bit memory accesses.
6714 Use 64 bit memory accesses.
6717 @c @subsubsection Hardware/Software Breakpoints
6718 @c The hardware/software breakpoint attributes set whether @value{GDBN}
6719 @c will use hardware or software breakpoints for the internal breakpoints
6720 @c used by the step, next, finish, until, etc. commands.
6724 @c Always use hardware breakpoints
6725 @c @item swbreak (default)
6728 @subsubsection Data Cache
6729 The data cache attributes set whether @value{GDBN} will cache target
6730 memory. While this generally improves performance by reducing debug
6731 protocol overhead, it can lead to incorrect results because @value{GDBN}
6732 does not know about volatile variables or memory mapped device
6737 Enable @value{GDBN} to cache target memory.
6739 Disable @value{GDBN} from caching target memory. This is the default.
6742 @c @subsubsection Memory Write Verification
6743 @c The memory write verification attributes set whether @value{GDBN}
6744 @c will re-reads data after each write to verify the write was successful.
6748 @c @item noverify (default)
6751 @node Dump/Restore Files
6752 @section Copy between memory and a file
6753 @cindex dump/restore files
6754 @cindex append data to a file
6755 @cindex dump data to a file
6756 @cindex restore data from a file
6758 You can use the commands @code{dump}, @code{append}, and
6759 @code{restore} to copy data between target memory and a file. The
6760 @code{dump} and @code{append} commands write data to a file, and the
6761 @code{restore} command reads data from a file back into the inferior's
6762 memory. Files may be in binary, Motorola S-record, Intel hex, or
6763 Tektronix Hex format; however, @value{GDBN} can only append to binary
6769 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6770 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
6771 Dump the contents of memory from @var{start_addr} to @var{end_addr},
6772 or the value of @var{expr}, to @var{filename} in the given format.
6774 The @var{format} parameter may be any one of:
6781 Motorola S-record format.
6783 Tektronix Hex format.
6786 @value{GDBN} uses the same definitions of these formats as the
6787 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
6788 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
6792 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6793 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
6794 Append the contents of memory from @var{start_addr} to @var{end_addr},
6795 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
6796 (@value{GDBN} can only append data to files in raw binary form.)
6799 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
6800 Restore the contents of file @var{filename} into memory. The
6801 @code{restore} command can automatically recognize any known @sc{bfd}
6802 file format, except for raw binary. To restore a raw binary file you
6803 must specify the optional keyword @code{binary} after the filename.
6805 If @var{bias} is non-zero, its value will be added to the addresses
6806 contained in the file. Binary files always start at address zero, so
6807 they will be restored at address @var{bias}. Other bfd files have
6808 a built-in location; they will be restored at offset @var{bias}
6811 If @var{start} and/or @var{end} are non-zero, then only data between
6812 file offset @var{start} and file offset @var{end} will be restored.
6813 These offsets are relative to the addresses in the file, before
6814 the @var{bias} argument is applied.
6818 @node Core File Generation
6819 @section How to Produce a Core File from Your Program
6820 @cindex dump core from inferior
6822 A @dfn{core file} or @dfn{core dump} is a file that records the memory
6823 image of a running process and its process status (register values
6824 etc.). Its primary use is post-mortem debugging of a program that
6825 crashed while it ran outside a debugger. A program that crashes
6826 automatically produces a core file, unless this feature is disabled by
6827 the user. @xref{Files}, for information on invoking @value{GDBN} in
6828 the post-mortem debugging mode.
6830 Occasionally, you may wish to produce a core file of the program you
6831 are debugging in order to preserve a snapshot of its state.
6832 @value{GDBN} has a special command for that.
6836 @kindex generate-core-file
6837 @item generate-core-file [@var{file}]
6838 @itemx gcore [@var{file}]
6839 Produce a core dump of the inferior process. The optional argument
6840 @var{file} specifies the file name where to put the core dump. If not
6841 specified, the file name defaults to @file{core.@var{pid}}, where
6842 @var{pid} is the inferior process ID.
6844 Note that this command is implemented only for some systems (as of
6845 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
6848 @node Character Sets
6849 @section Character Sets
6850 @cindex character sets
6852 @cindex translating between character sets
6853 @cindex host character set
6854 @cindex target character set
6856 If the program you are debugging uses a different character set to
6857 represent characters and strings than the one @value{GDBN} uses itself,
6858 @value{GDBN} can automatically translate between the character sets for
6859 you. The character set @value{GDBN} uses we call the @dfn{host
6860 character set}; the one the inferior program uses we call the
6861 @dfn{target character set}.
6863 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
6864 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
6865 remote protocol (@pxref{Remote,Remote Debugging}) to debug a program
6866 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
6867 then the host character set is Latin-1, and the target character set is
6868 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
6869 target-charset EBCDIC-US}, then @value{GDBN} translates between
6870 @sc{ebcdic} and Latin 1 as you print character or string values, or use
6871 character and string literals in expressions.
6873 @value{GDBN} has no way to automatically recognize which character set
6874 the inferior program uses; you must tell it, using the @code{set
6875 target-charset} command, described below.
6877 Here are the commands for controlling @value{GDBN}'s character set
6881 @item set target-charset @var{charset}
6882 @kindex set target-charset
6883 Set the current target character set to @var{charset}. We list the
6884 character set names @value{GDBN} recognizes below, but if you type
6885 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6886 list the target character sets it supports.
6890 @item set host-charset @var{charset}
6891 @kindex set host-charset
6892 Set the current host character set to @var{charset}.
6894 By default, @value{GDBN} uses a host character set appropriate to the
6895 system it is running on; you can override that default using the
6896 @code{set host-charset} command.
6898 @value{GDBN} can only use certain character sets as its host character
6899 set. We list the character set names @value{GDBN} recognizes below, and
6900 indicate which can be host character sets, but if you type
6901 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6902 list the host character sets it supports.
6904 @item set charset @var{charset}
6906 Set the current host and target character sets to @var{charset}. As
6907 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
6908 @value{GDBN} will list the name of the character sets that can be used
6909 for both host and target.
6913 @kindex show charset
6914 Show the names of the current host and target charsets.
6916 @itemx show host-charset
6917 @kindex show host-charset
6918 Show the name of the current host charset.
6920 @itemx show target-charset
6921 @kindex show target-charset
6922 Show the name of the current target charset.
6926 @value{GDBN} currently includes support for the following character
6932 @cindex ASCII character set
6933 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
6937 @cindex ISO 8859-1 character set
6938 @cindex ISO Latin 1 character set
6939 The ISO Latin 1 character set. This extends @sc{ascii} with accented
6940 characters needed for French, German, and Spanish. @value{GDBN} can use
6941 this as its host character set.
6945 @cindex EBCDIC character set
6946 @cindex IBM1047 character set
6947 Variants of the @sc{ebcdic} character set, used on some of IBM's
6948 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
6949 @value{GDBN} cannot use these as its host character set.
6953 Note that these are all single-byte character sets. More work inside
6954 GDB is needed to support multi-byte or variable-width character
6955 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
6957 Here is an example of @value{GDBN}'s character set support in action.
6958 Assume that the following source code has been placed in the file
6959 @file{charset-test.c}:
6965 = @{72, 101, 108, 108, 111, 44, 32, 119,
6966 111, 114, 108, 100, 33, 10, 0@};
6967 char ibm1047_hello[]
6968 = @{200, 133, 147, 147, 150, 107, 64, 166,
6969 150, 153, 147, 132, 90, 37, 0@};
6973 printf ("Hello, world!\n");
6977 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
6978 containing the string @samp{Hello, world!} followed by a newline,
6979 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
6981 We compile the program, and invoke the debugger on it:
6984 $ gcc -g charset-test.c -o charset-test
6985 $ gdb -nw charset-test
6986 GNU gdb 2001-12-19-cvs
6987 Copyright 2001 Free Software Foundation, Inc.
6992 We can use the @code{show charset} command to see what character sets
6993 @value{GDBN} is currently using to interpret and display characters and
6997 (@value{GDBP}) show charset
6998 The current host and target character set is `ISO-8859-1'.
7002 For the sake of printing this manual, let's use @sc{ascii} as our
7003 initial character set:
7005 (@value{GDBP}) set charset ASCII
7006 (@value{GDBP}) show charset
7007 The current host and target character set is `ASCII'.
7011 Let's assume that @sc{ascii} is indeed the correct character set for our
7012 host system --- in other words, let's assume that if @value{GDBN} prints
7013 characters using the @sc{ascii} character set, our terminal will display
7014 them properly. Since our current target character set is also
7015 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
7018 (@value{GDBP}) print ascii_hello
7019 $1 = 0x401698 "Hello, world!\n"
7020 (@value{GDBP}) print ascii_hello[0]
7025 @value{GDBN} uses the target character set for character and string
7026 literals you use in expressions:
7029 (@value{GDBP}) print '+'
7034 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
7037 @value{GDBN} relies on the user to tell it which character set the
7038 target program uses. If we print @code{ibm1047_hello} while our target
7039 character set is still @sc{ascii}, we get jibberish:
7042 (@value{GDBP}) print ibm1047_hello
7043 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
7044 (@value{GDBP}) print ibm1047_hello[0]
7049 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
7050 @value{GDBN} tells us the character sets it supports:
7053 (@value{GDBP}) set target-charset
7054 ASCII EBCDIC-US IBM1047 ISO-8859-1
7055 (@value{GDBP}) set target-charset
7058 We can select @sc{ibm1047} as our target character set, and examine the
7059 program's strings again. Now the @sc{ascii} string is wrong, but
7060 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
7061 target character set, @sc{ibm1047}, to the host character set,
7062 @sc{ascii}, and they display correctly:
7065 (@value{GDBP}) set target-charset IBM1047
7066 (@value{GDBP}) show charset
7067 The current host character set is `ASCII'.
7068 The current target character set is `IBM1047'.
7069 (@value{GDBP}) print ascii_hello
7070 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
7071 (@value{GDBP}) print ascii_hello[0]
7073 (@value{GDBP}) print ibm1047_hello
7074 $8 = 0x4016a8 "Hello, world!\n"
7075 (@value{GDBP}) print ibm1047_hello[0]
7080 As above, @value{GDBN} uses the target character set for character and
7081 string literals you use in expressions:
7084 (@value{GDBP}) print '+'
7089 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
7092 @node Caching Remote Data
7093 @section Caching Data of Remote Targets
7094 @cindex caching data of remote targets
7096 @value{GDBN} can cache data exchanged between the debugger and a
7097 remote target (@pxref{Remote}). Such caching generally improves
7098 performance, because it reduces the overhead of the remote protocol by
7099 bundling memory reads and writes into large chunks. Unfortunately,
7100 @value{GDBN} does not currently know anything about volatile
7101 registers, and thus data caching will produce incorrect results when
7102 volatile registers are in use.
7105 @kindex set remotecache
7106 @item set remotecache on
7107 @itemx set remotecache off
7108 Set caching state for remote targets. When @code{ON}, use data
7109 caching. By default, this option is @code{OFF}.
7111 @kindex show remotecache
7112 @item show remotecache
7113 Show the current state of data caching for remote targets.
7117 Print the information about the data cache performance. The
7118 information displayed includes: the dcache width and depth; and for
7119 each cache line, how many times it was referenced, and its data and
7120 state (dirty, bad, ok, etc.). This command is useful for debugging
7121 the data cache operation.
7126 @chapter C Preprocessor Macros
7128 Some languages, such as C and C@t{++}, provide a way to define and invoke
7129 ``preprocessor macros'' which expand into strings of tokens.
7130 @value{GDBN} can evaluate expressions containing macro invocations, show
7131 the result of macro expansion, and show a macro's definition, including
7132 where it was defined.
7134 You may need to compile your program specially to provide @value{GDBN}
7135 with information about preprocessor macros. Most compilers do not
7136 include macros in their debugging information, even when you compile
7137 with the @option{-g} flag. @xref{Compilation}.
7139 A program may define a macro at one point, remove that definition later,
7140 and then provide a different definition after that. Thus, at different
7141 points in the program, a macro may have different definitions, or have
7142 no definition at all. If there is a current stack frame, @value{GDBN}
7143 uses the macros in scope at that frame's source code line. Otherwise,
7144 @value{GDBN} uses the macros in scope at the current listing location;
7147 At the moment, @value{GDBN} does not support the @code{##}
7148 token-splicing operator, the @code{#} stringification operator, or
7149 variable-arity macros.
7151 Whenever @value{GDBN} evaluates an expression, it always expands any
7152 macro invocations present in the expression. @value{GDBN} also provides
7153 the following commands for working with macros explicitly.
7157 @kindex macro expand
7158 @cindex macro expansion, showing the results of preprocessor
7159 @cindex preprocessor macro expansion, showing the results of
7160 @cindex expanding preprocessor macros
7161 @item macro expand @var{expression}
7162 @itemx macro exp @var{expression}
7163 Show the results of expanding all preprocessor macro invocations in
7164 @var{expression}. Since @value{GDBN} simply expands macros, but does
7165 not parse the result, @var{expression} need not be a valid expression;
7166 it can be any string of tokens.
7169 @item macro expand-once @var{expression}
7170 @itemx macro exp1 @var{expression}
7171 @cindex expand macro once
7172 @i{(This command is not yet implemented.)} Show the results of
7173 expanding those preprocessor macro invocations that appear explicitly in
7174 @var{expression}. Macro invocations appearing in that expansion are
7175 left unchanged. This command allows you to see the effect of a
7176 particular macro more clearly, without being confused by further
7177 expansions. Since @value{GDBN} simply expands macros, but does not
7178 parse the result, @var{expression} need not be a valid expression; it
7179 can be any string of tokens.
7182 @cindex macro definition, showing
7183 @cindex definition, showing a macro's
7184 @item info macro @var{macro}
7185 Show the definition of the macro named @var{macro}, and describe the
7186 source location where that definition was established.
7188 @kindex macro define
7189 @cindex user-defined macros
7190 @cindex defining macros interactively
7191 @cindex macros, user-defined
7192 @item macro define @var{macro} @var{replacement-list}
7193 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
7194 @i{(This command is not yet implemented.)} Introduce a definition for a
7195 preprocessor macro named @var{macro}, invocations of which are replaced
7196 by the tokens given in @var{replacement-list}. The first form of this
7197 command defines an ``object-like'' macro, which takes no arguments; the
7198 second form defines a ``function-like'' macro, which takes the arguments
7199 given in @var{arglist}.
7201 A definition introduced by this command is in scope in every expression
7202 evaluated in @value{GDBN}, until it is removed with the @command{macro
7203 undef} command, described below. The definition overrides all
7204 definitions for @var{macro} present in the program being debugged, as
7205 well as any previous user-supplied definition.
7208 @item macro undef @var{macro}
7209 @i{(This command is not yet implemented.)} Remove any user-supplied
7210 definition for the macro named @var{macro}. This command only affects
7211 definitions provided with the @command{macro define} command, described
7212 above; it cannot remove definitions present in the program being
7217 @i{(This command is not yet implemented.)} List all the macros
7218 defined using the @code{macro define} command.
7221 @cindex macros, example of debugging with
7222 Here is a transcript showing the above commands in action. First, we
7223 show our source files:
7231 #define ADD(x) (M + x)
7236 printf ("Hello, world!\n");
7238 printf ("We're so creative.\n");
7240 printf ("Goodbye, world!\n");
7247 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
7248 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
7249 compiler includes information about preprocessor macros in the debugging
7253 $ gcc -gdwarf-2 -g3 sample.c -o sample
7257 Now, we start @value{GDBN} on our sample program:
7261 GNU gdb 2002-05-06-cvs
7262 Copyright 2002 Free Software Foundation, Inc.
7263 GDB is free software, @dots{}
7267 We can expand macros and examine their definitions, even when the
7268 program is not running. @value{GDBN} uses the current listing position
7269 to decide which macro definitions are in scope:
7272 (@value{GDBP}) list main
7275 5 #define ADD(x) (M + x)
7280 10 printf ("Hello, world!\n");
7282 12 printf ("We're so creative.\n");
7283 (@value{GDBP}) info macro ADD
7284 Defined at /home/jimb/gdb/macros/play/sample.c:5
7285 #define ADD(x) (M + x)
7286 (@value{GDBP}) info macro Q
7287 Defined at /home/jimb/gdb/macros/play/sample.h:1
7288 included at /home/jimb/gdb/macros/play/sample.c:2
7290 (@value{GDBP}) macro expand ADD(1)
7291 expands to: (42 + 1)
7292 (@value{GDBP}) macro expand-once ADD(1)
7293 expands to: once (M + 1)
7297 In the example above, note that @command{macro expand-once} expands only
7298 the macro invocation explicit in the original text --- the invocation of
7299 @code{ADD} --- but does not expand the invocation of the macro @code{M},
7300 which was introduced by @code{ADD}.
7302 Once the program is running, GDB uses the macro definitions in force at
7303 the source line of the current stack frame:
7306 (@value{GDBP}) break main
7307 Breakpoint 1 at 0x8048370: file sample.c, line 10.
7309 Starting program: /home/jimb/gdb/macros/play/sample
7311 Breakpoint 1, main () at sample.c:10
7312 10 printf ("Hello, world!\n");
7316 At line 10, the definition of the macro @code{N} at line 9 is in force:
7319 (@value{GDBP}) info macro N
7320 Defined at /home/jimb/gdb/macros/play/sample.c:9
7322 (@value{GDBP}) macro expand N Q M
7324 (@value{GDBP}) print N Q M
7329 As we step over directives that remove @code{N}'s definition, and then
7330 give it a new definition, @value{GDBN} finds the definition (or lack
7331 thereof) in force at each point:
7336 12 printf ("We're so creative.\n");
7337 (@value{GDBP}) info macro N
7338 The symbol `N' has no definition as a C/C++ preprocessor macro
7339 at /home/jimb/gdb/macros/play/sample.c:12
7342 14 printf ("Goodbye, world!\n");
7343 (@value{GDBP}) info macro N
7344 Defined at /home/jimb/gdb/macros/play/sample.c:13
7346 (@value{GDBP}) macro expand N Q M
7347 expands to: 1729 < 42
7348 (@value{GDBP}) print N Q M
7355 @chapter Tracepoints
7356 @c This chapter is based on the documentation written by Michael
7357 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
7360 In some applications, it is not feasible for the debugger to interrupt
7361 the program's execution long enough for the developer to learn
7362 anything helpful about its behavior. If the program's correctness
7363 depends on its real-time behavior, delays introduced by a debugger
7364 might cause the program to change its behavior drastically, or perhaps
7365 fail, even when the code itself is correct. It is useful to be able
7366 to observe the program's behavior without interrupting it.
7368 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
7369 specify locations in the program, called @dfn{tracepoints}, and
7370 arbitrary expressions to evaluate when those tracepoints are reached.
7371 Later, using the @code{tfind} command, you can examine the values
7372 those expressions had when the program hit the tracepoints. The
7373 expressions may also denote objects in memory---structures or arrays,
7374 for example---whose values @value{GDBN} should record; while visiting
7375 a particular tracepoint, you may inspect those objects as if they were
7376 in memory at that moment. However, because @value{GDBN} records these
7377 values without interacting with you, it can do so quickly and
7378 unobtrusively, hopefully not disturbing the program's behavior.
7380 The tracepoint facility is currently available only for remote
7381 targets. @xref{Targets}. In addition, your remote target must know
7382 how to collect trace data. This functionality is implemented in the
7383 remote stub; however, none of the stubs distributed with @value{GDBN}
7384 support tracepoints as of this writing. The format of the remote
7385 packets used to implement tracepoints are described in @ref{Tracepoint
7388 This chapter describes the tracepoint commands and features.
7392 * Analyze Collected Data::
7393 * Tracepoint Variables::
7396 @node Set Tracepoints
7397 @section Commands to Set Tracepoints
7399 Before running such a @dfn{trace experiment}, an arbitrary number of
7400 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
7401 tracepoint has a number assigned to it by @value{GDBN}. Like with
7402 breakpoints, tracepoint numbers are successive integers starting from
7403 one. Many of the commands associated with tracepoints take the
7404 tracepoint number as their argument, to identify which tracepoint to
7407 For each tracepoint, you can specify, in advance, some arbitrary set
7408 of data that you want the target to collect in the trace buffer when
7409 it hits that tracepoint. The collected data can include registers,
7410 local variables, or global data. Later, you can use @value{GDBN}
7411 commands to examine the values these data had at the time the
7414 This section describes commands to set tracepoints and associated
7415 conditions and actions.
7418 * Create and Delete Tracepoints::
7419 * Enable and Disable Tracepoints::
7420 * Tracepoint Passcounts::
7421 * Tracepoint Actions::
7422 * Listing Tracepoints::
7423 * Starting and Stopping Trace Experiment::
7426 @node Create and Delete Tracepoints
7427 @subsection Create and Delete Tracepoints
7430 @cindex set tracepoint
7433 The @code{trace} command is very similar to the @code{break} command.
7434 Its argument can be a source line, a function name, or an address in
7435 the target program. @xref{Set Breaks}. The @code{trace} command
7436 defines a tracepoint, which is a point in the target program where the
7437 debugger will briefly stop, collect some data, and then allow the
7438 program to continue. Setting a tracepoint or changing its commands
7439 doesn't take effect until the next @code{tstart} command; thus, you
7440 cannot change the tracepoint attributes once a trace experiment is
7443 Here are some examples of using the @code{trace} command:
7446 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
7448 (@value{GDBP}) @b{trace +2} // 2 lines forward
7450 (@value{GDBP}) @b{trace my_function} // first source line of function
7452 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
7454 (@value{GDBP}) @b{trace *0x2117c4} // an address
7458 You can abbreviate @code{trace} as @code{tr}.
7461 @cindex last tracepoint number
7462 @cindex recent tracepoint number
7463 @cindex tracepoint number
7464 The convenience variable @code{$tpnum} records the tracepoint number
7465 of the most recently set tracepoint.
7467 @kindex delete tracepoint
7468 @cindex tracepoint deletion
7469 @item delete tracepoint @r{[}@var{num}@r{]}
7470 Permanently delete one or more tracepoints. With no argument, the
7471 default is to delete all tracepoints.
7476 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
7478 (@value{GDBP}) @b{delete trace} // remove all tracepoints
7482 You can abbreviate this command as @code{del tr}.
7485 @node Enable and Disable Tracepoints
7486 @subsection Enable and Disable Tracepoints
7489 @kindex disable tracepoint
7490 @item disable tracepoint @r{[}@var{num}@r{]}
7491 Disable tracepoint @var{num}, or all tracepoints if no argument
7492 @var{num} is given. A disabled tracepoint will have no effect during
7493 the next trace experiment, but it is not forgotten. You can re-enable
7494 a disabled tracepoint using the @code{enable tracepoint} command.
7496 @kindex enable tracepoint
7497 @item enable tracepoint @r{[}@var{num}@r{]}
7498 Enable tracepoint @var{num}, or all tracepoints. The enabled
7499 tracepoints will become effective the next time a trace experiment is
7503 @node Tracepoint Passcounts
7504 @subsection Tracepoint Passcounts
7508 @cindex tracepoint pass count
7509 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
7510 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
7511 automatically stop a trace experiment. If a tracepoint's passcount is
7512 @var{n}, then the trace experiment will be automatically stopped on
7513 the @var{n}'th time that tracepoint is hit. If the tracepoint number
7514 @var{num} is not specified, the @code{passcount} command sets the
7515 passcount of the most recently defined tracepoint. If no passcount is
7516 given, the trace experiment will run until stopped explicitly by the
7522 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
7523 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
7525 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
7526 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
7527 (@value{GDBP}) @b{trace foo}
7528 (@value{GDBP}) @b{pass 3}
7529 (@value{GDBP}) @b{trace bar}
7530 (@value{GDBP}) @b{pass 2}
7531 (@value{GDBP}) @b{trace baz}
7532 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
7533 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
7534 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
7535 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
7539 @node Tracepoint Actions
7540 @subsection Tracepoint Action Lists
7544 @cindex tracepoint actions
7545 @item actions @r{[}@var{num}@r{]}
7546 This command will prompt for a list of actions to be taken when the
7547 tracepoint is hit. If the tracepoint number @var{num} is not
7548 specified, this command sets the actions for the one that was most
7549 recently defined (so that you can define a tracepoint and then say
7550 @code{actions} without bothering about its number). You specify the
7551 actions themselves on the following lines, one action at a time, and
7552 terminate the actions list with a line containing just @code{end}. So
7553 far, the only defined actions are @code{collect} and
7554 @code{while-stepping}.
7556 @cindex remove actions from a tracepoint
7557 To remove all actions from a tracepoint, type @samp{actions @var{num}}
7558 and follow it immediately with @samp{end}.
7561 (@value{GDBP}) @b{collect @var{data}} // collect some data
7563 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
7565 (@value{GDBP}) @b{end} // signals the end of actions.
7568 In the following example, the action list begins with @code{collect}
7569 commands indicating the things to be collected when the tracepoint is
7570 hit. Then, in order to single-step and collect additional data
7571 following the tracepoint, a @code{while-stepping} command is used,
7572 followed by the list of things to be collected while stepping. The
7573 @code{while-stepping} command is terminated by its own separate
7574 @code{end} command. Lastly, the action list is terminated by an
7578 (@value{GDBP}) @b{trace foo}
7579 (@value{GDBP}) @b{actions}
7580 Enter actions for tracepoint 1, one per line:
7589 @kindex collect @r{(tracepoints)}
7590 @item collect @var{expr1}, @var{expr2}, @dots{}
7591 Collect values of the given expressions when the tracepoint is hit.
7592 This command accepts a comma-separated list of any valid expressions.
7593 In addition to global, static, or local variables, the following
7594 special arguments are supported:
7598 collect all registers
7601 collect all function arguments
7604 collect all local variables.
7607 You can give several consecutive @code{collect} commands, each one
7608 with a single argument, or one @code{collect} command with several
7609 arguments separated by commas: the effect is the same.
7611 The command @code{info scope} (@pxref{Symbols, info scope}) is
7612 particularly useful for figuring out what data to collect.
7614 @kindex while-stepping @r{(tracepoints)}
7615 @item while-stepping @var{n}
7616 Perform @var{n} single-step traces after the tracepoint, collecting
7617 new data at each step. The @code{while-stepping} command is
7618 followed by the list of what to collect while stepping (followed by
7619 its own @code{end} command):
7623 > collect $regs, myglobal
7629 You may abbreviate @code{while-stepping} as @code{ws} or
7633 @node Listing Tracepoints
7634 @subsection Listing Tracepoints
7637 @kindex info tracepoints
7639 @cindex information about tracepoints
7640 @item info tracepoints @r{[}@var{num}@r{]}
7641 Display information about the tracepoint @var{num}. If you don't specify
7642 a tracepoint number, displays information about all the tracepoints
7643 defined so far. For each tracepoint, the following information is
7650 whether it is enabled or disabled
7654 its passcount as given by the @code{passcount @var{n}} command
7656 its step count as given by the @code{while-stepping @var{n}} command
7658 where in the source files is the tracepoint set
7660 its action list as given by the @code{actions} command
7664 (@value{GDBP}) @b{info trace}
7665 Num Enb Address PassC StepC What
7666 1 y 0x002117c4 0 0 <gdb_asm>
7667 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
7668 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
7673 This command can be abbreviated @code{info tp}.
7676 @node Starting and Stopping Trace Experiment
7677 @subsection Starting and Stopping Trace Experiment
7681 @cindex start a new trace experiment
7682 @cindex collected data discarded
7684 This command takes no arguments. It starts the trace experiment, and
7685 begins collecting data. This has the side effect of discarding all
7686 the data collected in the trace buffer during the previous trace
7690 @cindex stop a running trace experiment
7692 This command takes no arguments. It ends the trace experiment, and
7693 stops collecting data.
7695 @strong{Note}: a trace experiment and data collection may stop
7696 automatically if any tracepoint's passcount is reached
7697 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
7700 @cindex status of trace data collection
7701 @cindex trace experiment, status of
7703 This command displays the status of the current trace data
7707 Here is an example of the commands we described so far:
7710 (@value{GDBP}) @b{trace gdb_c_test}
7711 (@value{GDBP}) @b{actions}
7712 Enter actions for tracepoint #1, one per line.
7713 > collect $regs,$locals,$args
7718 (@value{GDBP}) @b{tstart}
7719 [time passes @dots{}]
7720 (@value{GDBP}) @b{tstop}
7724 @node Analyze Collected Data
7725 @section Using the collected data
7727 After the tracepoint experiment ends, you use @value{GDBN} commands
7728 for examining the trace data. The basic idea is that each tracepoint
7729 collects a trace @dfn{snapshot} every time it is hit and another
7730 snapshot every time it single-steps. All these snapshots are
7731 consecutively numbered from zero and go into a buffer, and you can
7732 examine them later. The way you examine them is to @dfn{focus} on a
7733 specific trace snapshot. When the remote stub is focused on a trace
7734 snapshot, it will respond to all @value{GDBN} requests for memory and
7735 registers by reading from the buffer which belongs to that snapshot,
7736 rather than from @emph{real} memory or registers of the program being
7737 debugged. This means that @strong{all} @value{GDBN} commands
7738 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
7739 behave as if we were currently debugging the program state as it was
7740 when the tracepoint occurred. Any requests for data that are not in
7741 the buffer will fail.
7744 * tfind:: How to select a trace snapshot
7745 * tdump:: How to display all data for a snapshot
7746 * save-tracepoints:: How to save tracepoints for a future run
7750 @subsection @code{tfind @var{n}}
7753 @cindex select trace snapshot
7754 @cindex find trace snapshot
7755 The basic command for selecting a trace snapshot from the buffer is
7756 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
7757 counting from zero. If no argument @var{n} is given, the next
7758 snapshot is selected.
7760 Here are the various forms of using the @code{tfind} command.
7764 Find the first snapshot in the buffer. This is a synonym for
7765 @code{tfind 0} (since 0 is the number of the first snapshot).
7768 Stop debugging trace snapshots, resume @emph{live} debugging.
7771 Same as @samp{tfind none}.
7774 No argument means find the next trace snapshot.
7777 Find the previous trace snapshot before the current one. This permits
7778 retracing earlier steps.
7780 @item tfind tracepoint @var{num}
7781 Find the next snapshot associated with tracepoint @var{num}. Search
7782 proceeds forward from the last examined trace snapshot. If no
7783 argument @var{num} is given, it means find the next snapshot collected
7784 for the same tracepoint as the current snapshot.
7786 @item tfind pc @var{addr}
7787 Find the next snapshot associated with the value @var{addr} of the
7788 program counter. Search proceeds forward from the last examined trace
7789 snapshot. If no argument @var{addr} is given, it means find the next
7790 snapshot with the same value of PC as the current snapshot.
7792 @item tfind outside @var{addr1}, @var{addr2}
7793 Find the next snapshot whose PC is outside the given range of
7796 @item tfind range @var{addr1}, @var{addr2}
7797 Find the next snapshot whose PC is between @var{addr1} and
7798 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
7800 @item tfind line @r{[}@var{file}:@r{]}@var{n}
7801 Find the next snapshot associated with the source line @var{n}. If
7802 the optional argument @var{file} is given, refer to line @var{n} in
7803 that source file. Search proceeds forward from the last examined
7804 trace snapshot. If no argument @var{n} is given, it means find the
7805 next line other than the one currently being examined; thus saying
7806 @code{tfind line} repeatedly can appear to have the same effect as
7807 stepping from line to line in a @emph{live} debugging session.
7810 The default arguments for the @code{tfind} commands are specifically
7811 designed to make it easy to scan through the trace buffer. For
7812 instance, @code{tfind} with no argument selects the next trace
7813 snapshot, and @code{tfind -} with no argument selects the previous
7814 trace snapshot. So, by giving one @code{tfind} command, and then
7815 simply hitting @key{RET} repeatedly you can examine all the trace
7816 snapshots in order. Or, by saying @code{tfind -} and then hitting
7817 @key{RET} repeatedly you can examine the snapshots in reverse order.
7818 The @code{tfind line} command with no argument selects the snapshot
7819 for the next source line executed. The @code{tfind pc} command with
7820 no argument selects the next snapshot with the same program counter
7821 (PC) as the current frame. The @code{tfind tracepoint} command with
7822 no argument selects the next trace snapshot collected by the same
7823 tracepoint as the current one.
7825 In addition to letting you scan through the trace buffer manually,
7826 these commands make it easy to construct @value{GDBN} scripts that
7827 scan through the trace buffer and print out whatever collected data
7828 you are interested in. Thus, if we want to examine the PC, FP, and SP
7829 registers from each trace frame in the buffer, we can say this:
7832 (@value{GDBP}) @b{tfind start}
7833 (@value{GDBP}) @b{while ($trace_frame != -1)}
7834 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
7835 $trace_frame, $pc, $sp, $fp
7839 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
7840 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
7841 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
7842 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
7843 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
7844 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
7845 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
7846 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
7847 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
7848 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
7849 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
7852 Or, if we want to examine the variable @code{X} at each source line in
7856 (@value{GDBP}) @b{tfind start}
7857 (@value{GDBP}) @b{while ($trace_frame != -1)}
7858 > printf "Frame %d, X == %d\n", $trace_frame, X
7868 @subsection @code{tdump}
7870 @cindex dump all data collected at tracepoint
7871 @cindex tracepoint data, display
7873 This command takes no arguments. It prints all the data collected at
7874 the current trace snapshot.
7877 (@value{GDBP}) @b{trace 444}
7878 (@value{GDBP}) @b{actions}
7879 Enter actions for tracepoint #2, one per line:
7880 > collect $regs, $locals, $args, gdb_long_test
7883 (@value{GDBP}) @b{tstart}
7885 (@value{GDBP}) @b{tfind line 444}
7886 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
7888 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
7890 (@value{GDBP}) @b{tdump}
7891 Data collected at tracepoint 2, trace frame 1:
7892 d0 0xc4aa0085 -995491707
7896 d4 0x71aea3d 119204413
7901 a1 0x3000668 50333288
7904 a4 0x3000698 50333336
7906 fp 0x30bf3c 0x30bf3c
7907 sp 0x30bf34 0x30bf34
7909 pc 0x20b2c8 0x20b2c8
7913 p = 0x20e5b4 "gdb-test"
7920 gdb_long_test = 17 '\021'
7925 @node save-tracepoints
7926 @subsection @code{save-tracepoints @var{filename}}
7927 @kindex save-tracepoints
7928 @cindex save tracepoints for future sessions
7930 This command saves all current tracepoint definitions together with
7931 their actions and passcounts, into a file @file{@var{filename}}
7932 suitable for use in a later debugging session. To read the saved
7933 tracepoint definitions, use the @code{source} command (@pxref{Command
7936 @node Tracepoint Variables
7937 @section Convenience Variables for Tracepoints
7938 @cindex tracepoint variables
7939 @cindex convenience variables for tracepoints
7942 @vindex $trace_frame
7943 @item (int) $trace_frame
7944 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
7945 snapshot is selected.
7948 @item (int) $tracepoint
7949 The tracepoint for the current trace snapshot.
7952 @item (int) $trace_line
7953 The line number for the current trace snapshot.
7956 @item (char []) $trace_file
7957 The source file for the current trace snapshot.
7960 @item (char []) $trace_func
7961 The name of the function containing @code{$tracepoint}.
7964 Note: @code{$trace_file} is not suitable for use in @code{printf},
7965 use @code{output} instead.
7967 Here's a simple example of using these convenience variables for
7968 stepping through all the trace snapshots and printing some of their
7972 (@value{GDBP}) @b{tfind start}
7974 (@value{GDBP}) @b{while $trace_frame != -1}
7975 > output $trace_file
7976 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
7982 @chapter Debugging Programs That Use Overlays
7985 If your program is too large to fit completely in your target system's
7986 memory, you can sometimes use @dfn{overlays} to work around this
7987 problem. @value{GDBN} provides some support for debugging programs that
7991 * How Overlays Work:: A general explanation of overlays.
7992 * Overlay Commands:: Managing overlays in @value{GDBN}.
7993 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
7994 mapped by asking the inferior.
7995 * Overlay Sample Program:: A sample program using overlays.
7998 @node How Overlays Work
7999 @section How Overlays Work
8000 @cindex mapped overlays
8001 @cindex unmapped overlays
8002 @cindex load address, overlay's
8003 @cindex mapped address
8004 @cindex overlay area
8006 Suppose you have a computer whose instruction address space is only 64
8007 kilobytes long, but which has much more memory which can be accessed by
8008 other means: special instructions, segment registers, or memory
8009 management hardware, for example. Suppose further that you want to
8010 adapt a program which is larger than 64 kilobytes to run on this system.
8012 One solution is to identify modules of your program which are relatively
8013 independent, and need not call each other directly; call these modules
8014 @dfn{overlays}. Separate the overlays from the main program, and place
8015 their machine code in the larger memory. Place your main program in
8016 instruction memory, but leave at least enough space there to hold the
8017 largest overlay as well.
8019 Now, to call a function located in an overlay, you must first copy that
8020 overlay's machine code from the large memory into the space set aside
8021 for it in the instruction memory, and then jump to its entry point
8024 @c NB: In the below the mapped area's size is greater or equal to the
8025 @c size of all overlays. This is intentional to remind the developer
8026 @c that overlays don't necessarily need to be the same size.
8030 Data Instruction Larger
8031 Address Space Address Space Address Space
8032 +-----------+ +-----------+ +-----------+
8034 +-----------+ +-----------+ +-----------+<-- overlay 1
8035 | program | | main | .----| overlay 1 | load address
8036 | variables | | program | | +-----------+
8037 | and heap | | | | | |
8038 +-----------+ | | | +-----------+<-- overlay 2
8039 | | +-----------+ | | | load address
8040 +-----------+ | | | .-| overlay 2 |
8042 mapped --->+-----------+ | | +-----------+
8044 | overlay | <-' | | |
8045 | area | <---' +-----------+<-- overlay 3
8046 | | <---. | | load address
8047 +-----------+ `--| overlay 3 |
8054 @anchor{A code overlay}A code overlay
8058 The diagram (@pxref{A code overlay}) shows a system with separate data
8059 and instruction address spaces. To map an overlay, the program copies
8060 its code from the larger address space to the instruction address space.
8061 Since the overlays shown here all use the same mapped address, only one
8062 may be mapped at a time. For a system with a single address space for
8063 data and instructions, the diagram would be similar, except that the
8064 program variables and heap would share an address space with the main
8065 program and the overlay area.
8067 An overlay loaded into instruction memory and ready for use is called a
8068 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
8069 instruction memory. An overlay not present (or only partially present)
8070 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
8071 is its address in the larger memory. The mapped address is also called
8072 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
8073 called the @dfn{load memory address}, or @dfn{LMA}.
8075 Unfortunately, overlays are not a completely transparent way to adapt a
8076 program to limited instruction memory. They introduce a new set of
8077 global constraints you must keep in mind as you design your program:
8082 Before calling or returning to a function in an overlay, your program
8083 must make sure that overlay is actually mapped. Otherwise, the call or
8084 return will transfer control to the right address, but in the wrong
8085 overlay, and your program will probably crash.
8088 If the process of mapping an overlay is expensive on your system, you
8089 will need to choose your overlays carefully to minimize their effect on
8090 your program's performance.
8093 The executable file you load onto your system must contain each
8094 overlay's instructions, appearing at the overlay's load address, not its
8095 mapped address. However, each overlay's instructions must be relocated
8096 and its symbols defined as if the overlay were at its mapped address.
8097 You can use GNU linker scripts to specify different load and relocation
8098 addresses for pieces of your program; see @ref{Overlay Description,,,
8099 ld.info, Using ld: the GNU linker}.
8102 The procedure for loading executable files onto your system must be able
8103 to load their contents into the larger address space as well as the
8104 instruction and data spaces.
8108 The overlay system described above is rather simple, and could be
8109 improved in many ways:
8114 If your system has suitable bank switch registers or memory management
8115 hardware, you could use those facilities to make an overlay's load area
8116 contents simply appear at their mapped address in instruction space.
8117 This would probably be faster than copying the overlay to its mapped
8118 area in the usual way.
8121 If your overlays are small enough, you could set aside more than one
8122 overlay area, and have more than one overlay mapped at a time.
8125 You can use overlays to manage data, as well as instructions. In
8126 general, data overlays are even less transparent to your design than
8127 code overlays: whereas code overlays only require care when you call or
8128 return to functions, data overlays require care every time you access
8129 the data. Also, if you change the contents of a data overlay, you
8130 must copy its contents back out to its load address before you can copy a
8131 different data overlay into the same mapped area.
8136 @node Overlay Commands
8137 @section Overlay Commands
8139 To use @value{GDBN}'s overlay support, each overlay in your program must
8140 correspond to a separate section of the executable file. The section's
8141 virtual memory address and load memory address must be the overlay's
8142 mapped and load addresses. Identifying overlays with sections allows
8143 @value{GDBN} to determine the appropriate address of a function or
8144 variable, depending on whether the overlay is mapped or not.
8146 @value{GDBN}'s overlay commands all start with the word @code{overlay};
8147 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
8152 Disable @value{GDBN}'s overlay support. When overlay support is
8153 disabled, @value{GDBN} assumes that all functions and variables are
8154 always present at their mapped addresses. By default, @value{GDBN}'s
8155 overlay support is disabled.
8157 @item overlay manual
8158 @cindex manual overlay debugging
8159 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
8160 relies on you to tell it which overlays are mapped, and which are not,
8161 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
8162 commands described below.
8164 @item overlay map-overlay @var{overlay}
8165 @itemx overlay map @var{overlay}
8166 @cindex map an overlay
8167 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
8168 be the name of the object file section containing the overlay. When an
8169 overlay is mapped, @value{GDBN} assumes it can find the overlay's
8170 functions and variables at their mapped addresses. @value{GDBN} assumes
8171 that any other overlays whose mapped ranges overlap that of
8172 @var{overlay} are now unmapped.
8174 @item overlay unmap-overlay @var{overlay}
8175 @itemx overlay unmap @var{overlay}
8176 @cindex unmap an overlay
8177 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
8178 must be the name of the object file section containing the overlay.
8179 When an overlay is unmapped, @value{GDBN} assumes it can find the
8180 overlay's functions and variables at their load addresses.
8183 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
8184 consults a data structure the overlay manager maintains in the inferior
8185 to see which overlays are mapped. For details, see @ref{Automatic
8188 @item overlay load-target
8190 @cindex reloading the overlay table
8191 Re-read the overlay table from the inferior. Normally, @value{GDBN}
8192 re-reads the table @value{GDBN} automatically each time the inferior
8193 stops, so this command should only be necessary if you have changed the
8194 overlay mapping yourself using @value{GDBN}. This command is only
8195 useful when using automatic overlay debugging.
8197 @item overlay list-overlays
8199 @cindex listing mapped overlays
8200 Display a list of the overlays currently mapped, along with their mapped
8201 addresses, load addresses, and sizes.
8205 Normally, when @value{GDBN} prints a code address, it includes the name
8206 of the function the address falls in:
8209 (@value{GDBP}) print main
8210 $3 = @{int ()@} 0x11a0 <main>
8213 When overlay debugging is enabled, @value{GDBN} recognizes code in
8214 unmapped overlays, and prints the names of unmapped functions with
8215 asterisks around them. For example, if @code{foo} is a function in an
8216 unmapped overlay, @value{GDBN} prints it this way:
8219 (@value{GDBP}) overlay list
8220 No sections are mapped.
8221 (@value{GDBP}) print foo
8222 $5 = @{int (int)@} 0x100000 <*foo*>
8225 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
8229 (@value{GDBP}) overlay list
8230 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
8231 mapped at 0x1016 - 0x104a
8232 (@value{GDBP}) print foo
8233 $6 = @{int (int)@} 0x1016 <foo>
8236 When overlay debugging is enabled, @value{GDBN} can find the correct
8237 address for functions and variables in an overlay, whether or not the
8238 overlay is mapped. This allows most @value{GDBN} commands, like
8239 @code{break} and @code{disassemble}, to work normally, even on unmapped
8240 code. However, @value{GDBN}'s breakpoint support has some limitations:
8244 @cindex breakpoints in overlays
8245 @cindex overlays, setting breakpoints in
8246 You can set breakpoints in functions in unmapped overlays, as long as
8247 @value{GDBN} can write to the overlay at its load address.
8249 @value{GDBN} can not set hardware or simulator-based breakpoints in
8250 unmapped overlays. However, if you set a breakpoint at the end of your
8251 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
8252 you are using manual overlay management), @value{GDBN} will re-set its
8253 breakpoints properly.
8257 @node Automatic Overlay Debugging
8258 @section Automatic Overlay Debugging
8259 @cindex automatic overlay debugging
8261 @value{GDBN} can automatically track which overlays are mapped and which
8262 are not, given some simple co-operation from the overlay manager in the
8263 inferior. If you enable automatic overlay debugging with the
8264 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
8265 looks in the inferior's memory for certain variables describing the
8266 current state of the overlays.
8268 Here are the variables your overlay manager must define to support
8269 @value{GDBN}'s automatic overlay debugging:
8273 @item @code{_ovly_table}:
8274 This variable must be an array of the following structures:
8279 /* The overlay's mapped address. */
8282 /* The size of the overlay, in bytes. */
8285 /* The overlay's load address. */
8288 /* Non-zero if the overlay is currently mapped;
8290 unsigned long mapped;
8294 @item @code{_novlys}:
8295 This variable must be a four-byte signed integer, holding the total
8296 number of elements in @code{_ovly_table}.
8300 To decide whether a particular overlay is mapped or not, @value{GDBN}
8301 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
8302 @code{lma} members equal the VMA and LMA of the overlay's section in the
8303 executable file. When @value{GDBN} finds a matching entry, it consults
8304 the entry's @code{mapped} member to determine whether the overlay is
8307 In addition, your overlay manager may define a function called
8308 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
8309 will silently set a breakpoint there. If the overlay manager then
8310 calls this function whenever it has changed the overlay table, this
8311 will enable @value{GDBN} to accurately keep track of which overlays
8312 are in program memory, and update any breakpoints that may be set
8313 in overlays. This will allow breakpoints to work even if the
8314 overlays are kept in ROM or other non-writable memory while they
8315 are not being executed.
8317 @node Overlay Sample Program
8318 @section Overlay Sample Program
8319 @cindex overlay example program
8321 When linking a program which uses overlays, you must place the overlays
8322 at their load addresses, while relocating them to run at their mapped
8323 addresses. To do this, you must write a linker script (@pxref{Overlay
8324 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
8325 since linker scripts are specific to a particular host system, target
8326 architecture, and target memory layout, this manual cannot provide
8327 portable sample code demonstrating @value{GDBN}'s overlay support.
8329 However, the @value{GDBN} source distribution does contain an overlaid
8330 program, with linker scripts for a few systems, as part of its test
8331 suite. The program consists of the following files from
8332 @file{gdb/testsuite/gdb.base}:
8336 The main program file.
8338 A simple overlay manager, used by @file{overlays.c}.
8343 Overlay modules, loaded and used by @file{overlays.c}.
8346 Linker scripts for linking the test program on the @code{d10v-elf}
8347 and @code{m32r-elf} targets.
8350 You can build the test program using the @code{d10v-elf} GCC
8351 cross-compiler like this:
8354 $ d10v-elf-gcc -g -c overlays.c
8355 $ d10v-elf-gcc -g -c ovlymgr.c
8356 $ d10v-elf-gcc -g -c foo.c
8357 $ d10v-elf-gcc -g -c bar.c
8358 $ d10v-elf-gcc -g -c baz.c
8359 $ d10v-elf-gcc -g -c grbx.c
8360 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
8361 baz.o grbx.o -Wl,-Td10v.ld -o overlays
8364 The build process is identical for any other architecture, except that
8365 you must substitute the appropriate compiler and linker script for the
8366 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
8370 @chapter Using @value{GDBN} with Different Languages
8373 Although programming languages generally have common aspects, they are
8374 rarely expressed in the same manner. For instance, in ANSI C,
8375 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
8376 Modula-2, it is accomplished by @code{p^}. Values can also be
8377 represented (and displayed) differently. Hex numbers in C appear as
8378 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
8380 @cindex working language
8381 Language-specific information is built into @value{GDBN} for some languages,
8382 allowing you to express operations like the above in your program's
8383 native language, and allowing @value{GDBN} to output values in a manner
8384 consistent with the syntax of your program's native language. The
8385 language you use to build expressions is called the @dfn{working
8389 * Setting:: Switching between source languages
8390 * Show:: Displaying the language
8391 * Checks:: Type and range checks
8392 * Supported languages:: Supported languages
8393 * Unsupported languages:: Unsupported languages
8397 @section Switching between source languages
8399 There are two ways to control the working language---either have @value{GDBN}
8400 set it automatically, or select it manually yourself. You can use the
8401 @code{set language} command for either purpose. On startup, @value{GDBN}
8402 defaults to setting the language automatically. The working language is
8403 used to determine how expressions you type are interpreted, how values
8406 In addition to the working language, every source file that
8407 @value{GDBN} knows about has its own working language. For some object
8408 file formats, the compiler might indicate which language a particular
8409 source file is in. However, most of the time @value{GDBN} infers the
8410 language from the name of the file. The language of a source file
8411 controls whether C@t{++} names are demangled---this way @code{backtrace} can
8412 show each frame appropriately for its own language. There is no way to
8413 set the language of a source file from within @value{GDBN}, but you can
8414 set the language associated with a filename extension. @xref{Show, ,
8415 Displaying the language}.
8417 This is most commonly a problem when you use a program, such
8418 as @code{cfront} or @code{f2c}, that generates C but is written in
8419 another language. In that case, make the
8420 program use @code{#line} directives in its C output; that way
8421 @value{GDBN} will know the correct language of the source code of the original
8422 program, and will display that source code, not the generated C code.
8425 * Filenames:: Filename extensions and languages.
8426 * Manually:: Setting the working language manually
8427 * Automatically:: Having @value{GDBN} infer the source language
8431 @subsection List of filename extensions and languages
8433 If a source file name ends in one of the following extensions, then
8434 @value{GDBN} infers that its language is the one indicated.
8455 Objective-C source file
8462 Modula-2 source file
8466 Assembler source file. This actually behaves almost like C, but
8467 @value{GDBN} does not skip over function prologues when stepping.
8470 In addition, you may set the language associated with a filename
8471 extension. @xref{Show, , Displaying the language}.
8474 @subsection Setting the working language
8476 If you allow @value{GDBN} to set the language automatically,
8477 expressions are interpreted the same way in your debugging session and
8480 @kindex set language
8481 If you wish, you may set the language manually. To do this, issue the
8482 command @samp{set language @var{lang}}, where @var{lang} is the name of
8484 @code{c} or @code{modula-2}.
8485 For a list of the supported languages, type @samp{set language}.
8487 Setting the language manually prevents @value{GDBN} from updating the working
8488 language automatically. This can lead to confusion if you try
8489 to debug a program when the working language is not the same as the
8490 source language, when an expression is acceptable to both
8491 languages---but means different things. For instance, if the current
8492 source file were written in C, and @value{GDBN} was parsing Modula-2, a
8500 might not have the effect you intended. In C, this means to add
8501 @code{b} and @code{c} and place the result in @code{a}. The result
8502 printed would be the value of @code{a}. In Modula-2, this means to compare
8503 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
8506 @subsection Having @value{GDBN} infer the source language
8508 To have @value{GDBN} set the working language automatically, use
8509 @samp{set language local} or @samp{set language auto}. @value{GDBN}
8510 then infers the working language. That is, when your program stops in a
8511 frame (usually by encountering a breakpoint), @value{GDBN} sets the
8512 working language to the language recorded for the function in that
8513 frame. If the language for a frame is unknown (that is, if the function
8514 or block corresponding to the frame was defined in a source file that
8515 does not have a recognized extension), the current working language is
8516 not changed, and @value{GDBN} issues a warning.
8518 This may not seem necessary for most programs, which are written
8519 entirely in one source language. However, program modules and libraries
8520 written in one source language can be used by a main program written in
8521 a different source language. Using @samp{set language auto} in this
8522 case frees you from having to set the working language manually.
8525 @section Displaying the language
8527 The following commands help you find out which language is the
8528 working language, and also what language source files were written in.
8532 @kindex show language
8533 Display the current working language. This is the
8534 language you can use with commands such as @code{print} to
8535 build and compute expressions that may involve variables in your program.
8538 @kindex info frame@r{, show the source language}
8539 Display the source language for this frame. This language becomes the
8540 working language if you use an identifier from this frame.
8541 @xref{Frame Info, ,Information about a frame}, to identify the other
8542 information listed here.
8545 @kindex info source@r{, show the source language}
8546 Display the source language of this source file.
8547 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
8548 information listed here.
8551 In unusual circumstances, you may have source files with extensions
8552 not in the standard list. You can then set the extension associated
8553 with a language explicitly:
8556 @item set extension-language @var{ext} @var{language}
8557 @kindex set extension-language
8558 Tell @value{GDBN} that source files with extension @var{ext} are to be
8559 assumed as written in the source language @var{language}.
8561 @item info extensions
8562 @kindex info extensions
8563 List all the filename extensions and the associated languages.
8567 @section Type and range checking
8570 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
8571 checking are included, but they do not yet have any effect. This
8572 section documents the intended facilities.
8574 @c FIXME remove warning when type/range code added
8576 Some languages are designed to guard you against making seemingly common
8577 errors through a series of compile- and run-time checks. These include
8578 checking the type of arguments to functions and operators, and making
8579 sure mathematical overflows are caught at run time. Checks such as
8580 these help to ensure a program's correctness once it has been compiled
8581 by eliminating type mismatches, and providing active checks for range
8582 errors when your program is running.
8584 @value{GDBN} can check for conditions like the above if you wish.
8585 Although @value{GDBN} does not check the statements in your program,
8586 it can check expressions entered directly into @value{GDBN} for
8587 evaluation via the @code{print} command, for example. As with the
8588 working language, @value{GDBN} can also decide whether or not to check
8589 automatically based on your program's source language.
8590 @xref{Supported languages, ,Supported languages}, for the default
8591 settings of supported languages.
8594 * Type Checking:: An overview of type checking
8595 * Range Checking:: An overview of range checking
8598 @cindex type checking
8599 @cindex checks, type
8601 @subsection An overview of type checking
8603 Some languages, such as Modula-2, are strongly typed, meaning that the
8604 arguments to operators and functions have to be of the correct type,
8605 otherwise an error occurs. These checks prevent type mismatch
8606 errors from ever causing any run-time problems. For example,
8614 The second example fails because the @code{CARDINAL} 1 is not
8615 type-compatible with the @code{REAL} 2.3.
8617 For the expressions you use in @value{GDBN} commands, you can tell the
8618 @value{GDBN} type checker to skip checking;
8619 to treat any mismatches as errors and abandon the expression;
8620 or to only issue warnings when type mismatches occur,
8621 but evaluate the expression anyway. When you choose the last of
8622 these, @value{GDBN} evaluates expressions like the second example above, but
8623 also issues a warning.
8625 Even if you turn type checking off, there may be other reasons
8626 related to type that prevent @value{GDBN} from evaluating an expression.
8627 For instance, @value{GDBN} does not know how to add an @code{int} and
8628 a @code{struct foo}. These particular type errors have nothing to do
8629 with the language in use, and usually arise from expressions, such as
8630 the one described above, which make little sense to evaluate anyway.
8632 Each language defines to what degree it is strict about type. For
8633 instance, both Modula-2 and C require the arguments to arithmetical
8634 operators to be numbers. In C, enumerated types and pointers can be
8635 represented as numbers, so that they are valid arguments to mathematical
8636 operators. @xref{Supported languages, ,Supported languages}, for further
8637 details on specific languages.
8639 @value{GDBN} provides some additional commands for controlling the type checker:
8641 @kindex set check type
8642 @kindex show check type
8644 @item set check type auto
8645 Set type checking on or off based on the current working language.
8646 @xref{Supported languages, ,Supported languages}, for the default settings for
8649 @item set check type on
8650 @itemx set check type off
8651 Set type checking on or off, overriding the default setting for the
8652 current working language. Issue a warning if the setting does not
8653 match the language default. If any type mismatches occur in
8654 evaluating an expression while type checking is on, @value{GDBN} prints a
8655 message and aborts evaluation of the expression.
8657 @item set check type warn
8658 Cause the type checker to issue warnings, but to always attempt to
8659 evaluate the expression. Evaluating the expression may still
8660 be impossible for other reasons. For example, @value{GDBN} cannot add
8661 numbers and structures.
8664 Show the current setting of the type checker, and whether or not @value{GDBN}
8665 is setting it automatically.
8668 @cindex range checking
8669 @cindex checks, range
8670 @node Range Checking
8671 @subsection An overview of range checking
8673 In some languages (such as Modula-2), it is an error to exceed the
8674 bounds of a type; this is enforced with run-time checks. Such range
8675 checking is meant to ensure program correctness by making sure
8676 computations do not overflow, or indices on an array element access do
8677 not exceed the bounds of the array.
8679 For expressions you use in @value{GDBN} commands, you can tell
8680 @value{GDBN} to treat range errors in one of three ways: ignore them,
8681 always treat them as errors and abandon the expression, or issue
8682 warnings but evaluate the expression anyway.
8684 A range error can result from numerical overflow, from exceeding an
8685 array index bound, or when you type a constant that is not a member
8686 of any type. Some languages, however, do not treat overflows as an
8687 error. In many implementations of C, mathematical overflow causes the
8688 result to ``wrap around'' to lower values---for example, if @var{m} is
8689 the largest integer value, and @var{s} is the smallest, then
8692 @var{m} + 1 @result{} @var{s}
8695 This, too, is specific to individual languages, and in some cases
8696 specific to individual compilers or machines. @xref{Supported languages, ,
8697 Supported languages}, for further details on specific languages.
8699 @value{GDBN} provides some additional commands for controlling the range checker:
8701 @kindex set check range
8702 @kindex show check range
8704 @item set check range auto
8705 Set range checking on or off based on the current working language.
8706 @xref{Supported languages, ,Supported languages}, for the default settings for
8709 @item set check range on
8710 @itemx set check range off
8711 Set range checking on or off, overriding the default setting for the
8712 current working language. A warning is issued if the setting does not
8713 match the language default. If a range error occurs and range checking is on,
8714 then a message is printed and evaluation of the expression is aborted.
8716 @item set check range warn
8717 Output messages when the @value{GDBN} range checker detects a range error,
8718 but attempt to evaluate the expression anyway. Evaluating the
8719 expression may still be impossible for other reasons, such as accessing
8720 memory that the process does not own (a typical example from many Unix
8724 Show the current setting of the range checker, and whether or not it is
8725 being set automatically by @value{GDBN}.
8728 @node Supported languages
8729 @section Supported languages
8731 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
8732 assembly, Modula-2, and Ada.
8733 @c This is false ...
8734 Some @value{GDBN} features may be used in expressions regardless of the
8735 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
8736 and the @samp{@{type@}addr} construct (@pxref{Expressions,
8737 ,Expressions}) can be used with the constructs of any supported
8740 The following sections detail to what degree each source language is
8741 supported by @value{GDBN}. These sections are not meant to be language
8742 tutorials or references, but serve only as a reference guide to what the
8743 @value{GDBN} expression parser accepts, and what input and output
8744 formats should look like for different languages. There are many good
8745 books written on each of these languages; please look to these for a
8746 language reference or tutorial.
8750 * Objective-C:: Objective-C
8753 * Modula-2:: Modula-2
8758 @subsection C and C@t{++}
8760 @cindex C and C@t{++}
8761 @cindex expressions in C or C@t{++}
8763 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
8764 to both languages. Whenever this is the case, we discuss those languages
8768 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
8769 @cindex @sc{gnu} C@t{++}
8770 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
8771 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
8772 effectively, you must compile your C@t{++} programs with a supported
8773 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
8774 compiler (@code{aCC}).
8776 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
8777 format; if it doesn't work on your system, try the stabs+ debugging
8778 format. You can select those formats explicitly with the @code{g++}
8779 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
8780 @xref{Debugging Options,,Options for Debugging Your Program or @sc{gnu}
8781 CC, gcc.info, Using @sc{gnu} CC}.
8784 * C Operators:: C and C@t{++} operators
8785 * C Constants:: C and C@t{++} constants
8786 * C plus plus expressions:: C@t{++} expressions
8787 * C Defaults:: Default settings for C and C@t{++}
8788 * C Checks:: C and C@t{++} type and range checks
8789 * Debugging C:: @value{GDBN} and C
8790 * Debugging C plus plus:: @value{GDBN} features for C@t{++}
8794 @subsubsection C and C@t{++} operators
8796 @cindex C and C@t{++} operators
8798 Operators must be defined on values of specific types. For instance,
8799 @code{+} is defined on numbers, but not on structures. Operators are
8800 often defined on groups of types.
8802 For the purposes of C and C@t{++}, the following definitions hold:
8807 @emph{Integral types} include @code{int} with any of its storage-class
8808 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
8811 @emph{Floating-point types} include @code{float}, @code{double}, and
8812 @code{long double} (if supported by the target platform).
8815 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
8818 @emph{Scalar types} include all of the above.
8823 The following operators are supported. They are listed here
8824 in order of increasing precedence:
8828 The comma or sequencing operator. Expressions in a comma-separated list
8829 are evaluated from left to right, with the result of the entire
8830 expression being the last expression evaluated.
8833 Assignment. The value of an assignment expression is the value
8834 assigned. Defined on scalar types.
8837 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
8838 and translated to @w{@code{@var{a} = @var{a op b}}}.
8839 @w{@code{@var{op}=}} and @code{=} have the same precedence.
8840 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
8841 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
8844 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
8845 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
8849 Logical @sc{or}. Defined on integral types.
8852 Logical @sc{and}. Defined on integral types.
8855 Bitwise @sc{or}. Defined on integral types.
8858 Bitwise exclusive-@sc{or}. Defined on integral types.
8861 Bitwise @sc{and}. Defined on integral types.
8864 Equality and inequality. Defined on scalar types. The value of these
8865 expressions is 0 for false and non-zero for true.
8867 @item <@r{, }>@r{, }<=@r{, }>=
8868 Less than, greater than, less than or equal, greater than or equal.
8869 Defined on scalar types. The value of these expressions is 0 for false
8870 and non-zero for true.
8873 left shift, and right shift. Defined on integral types.
8876 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8879 Addition and subtraction. Defined on integral types, floating-point types and
8882 @item *@r{, }/@r{, }%
8883 Multiplication, division, and modulus. Multiplication and division are
8884 defined on integral and floating-point types. Modulus is defined on
8888 Increment and decrement. When appearing before a variable, the
8889 operation is performed before the variable is used in an expression;
8890 when appearing after it, the variable's value is used before the
8891 operation takes place.
8894 Pointer dereferencing. Defined on pointer types. Same precedence as
8898 Address operator. Defined on variables. Same precedence as @code{++}.
8900 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
8901 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
8902 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
8903 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
8907 Negative. Defined on integral and floating-point types. Same
8908 precedence as @code{++}.
8911 Logical negation. Defined on integral types. Same precedence as
8915 Bitwise complement operator. Defined on integral types. Same precedence as
8920 Structure member, and pointer-to-structure member. For convenience,
8921 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
8922 pointer based on the stored type information.
8923 Defined on @code{struct} and @code{union} data.
8926 Dereferences of pointers to members.
8929 Array indexing. @code{@var{a}[@var{i}]} is defined as
8930 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
8933 Function parameter list. Same precedence as @code{->}.
8936 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
8937 and @code{class} types.
8940 Doubled colons also represent the @value{GDBN} scope operator
8941 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
8945 If an operator is redefined in the user code, @value{GDBN} usually
8946 attempts to invoke the redefined version instead of using the operator's
8954 @subsubsection C and C@t{++} constants
8956 @cindex C and C@t{++} constants
8958 @value{GDBN} allows you to express the constants of C and C@t{++} in the
8963 Integer constants are a sequence of digits. Octal constants are
8964 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
8965 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
8966 @samp{l}, specifying that the constant should be treated as a
8970 Floating point constants are a sequence of digits, followed by a decimal
8971 point, followed by a sequence of digits, and optionally followed by an
8972 exponent. An exponent is of the form:
8973 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
8974 sequence of digits. The @samp{+} is optional for positive exponents.
8975 A floating-point constant may also end with a letter @samp{f} or
8976 @samp{F}, specifying that the constant should be treated as being of
8977 the @code{float} (as opposed to the default @code{double}) type; or with
8978 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
8982 Enumerated constants consist of enumerated identifiers, or their
8983 integral equivalents.
8986 Character constants are a single character surrounded by single quotes
8987 (@code{'}), or a number---the ordinal value of the corresponding character
8988 (usually its @sc{ascii} value). Within quotes, the single character may
8989 be represented by a letter or by @dfn{escape sequences}, which are of
8990 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
8991 of the character's ordinal value; or of the form @samp{\@var{x}}, where
8992 @samp{@var{x}} is a predefined special character---for example,
8993 @samp{\n} for newline.
8996 String constants are a sequence of character constants surrounded by
8997 double quotes (@code{"}). Any valid character constant (as described
8998 above) may appear. Double quotes within the string must be preceded by
8999 a backslash, so for instance @samp{"a\"b'c"} is a string of five
9003 Pointer constants are an integral value. You can also write pointers
9004 to constants using the C operator @samp{&}.
9007 Array constants are comma-separated lists surrounded by braces @samp{@{}
9008 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
9009 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
9010 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
9014 * C plus plus expressions::
9021 @node C plus plus expressions
9022 @subsubsection C@t{++} expressions
9024 @cindex expressions in C@t{++}
9025 @value{GDBN} expression handling can interpret most C@t{++} expressions.
9027 @cindex debugging C@t{++} programs
9028 @cindex C@t{++} compilers
9029 @cindex debug formats and C@t{++}
9030 @cindex @value{NGCC} and C@t{++}
9032 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
9033 proper compiler and the proper debug format. Currently, @value{GDBN}
9034 works best when debugging C@t{++} code that is compiled with
9035 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
9036 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
9037 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
9038 stabs+ as their default debug format, so you usually don't need to
9039 specify a debug format explicitly. Other compilers and/or debug formats
9040 are likely to work badly or not at all when using @value{GDBN} to debug
9046 @cindex member functions
9048 Member function calls are allowed; you can use expressions like
9051 count = aml->GetOriginal(x, y)
9054 @vindex this@r{, inside C@t{++} member functions}
9055 @cindex namespace in C@t{++}
9057 While a member function is active (in the selected stack frame), your
9058 expressions have the same namespace available as the member function;
9059 that is, @value{GDBN} allows implicit references to the class instance
9060 pointer @code{this} following the same rules as C@t{++}.
9062 @cindex call overloaded functions
9063 @cindex overloaded functions, calling
9064 @cindex type conversions in C@t{++}
9066 You can call overloaded functions; @value{GDBN} resolves the function
9067 call to the right definition, with some restrictions. @value{GDBN} does not
9068 perform overload resolution involving user-defined type conversions,
9069 calls to constructors, or instantiations of templates that do not exist
9070 in the program. It also cannot handle ellipsis argument lists or
9073 It does perform integral conversions and promotions, floating-point
9074 promotions, arithmetic conversions, pointer conversions, conversions of
9075 class objects to base classes, and standard conversions such as those of
9076 functions or arrays to pointers; it requires an exact match on the
9077 number of function arguments.
9079 Overload resolution is always performed, unless you have specified
9080 @code{set overload-resolution off}. @xref{Debugging C plus plus,
9081 ,@value{GDBN} features for C@t{++}}.
9083 You must specify @code{set overload-resolution off} in order to use an
9084 explicit function signature to call an overloaded function, as in
9086 p 'foo(char,int)'('x', 13)
9089 The @value{GDBN} command-completion facility can simplify this;
9090 see @ref{Completion, ,Command completion}.
9092 @cindex reference declarations
9094 @value{GDBN} understands variables declared as C@t{++} references; you can use
9095 them in expressions just as you do in C@t{++} source---they are automatically
9098 In the parameter list shown when @value{GDBN} displays a frame, the values of
9099 reference variables are not displayed (unlike other variables); this
9100 avoids clutter, since references are often used for large structures.
9101 The @emph{address} of a reference variable is always shown, unless
9102 you have specified @samp{set print address off}.
9105 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
9106 expressions can use it just as expressions in your program do. Since
9107 one scope may be defined in another, you can use @code{::} repeatedly if
9108 necessary, for example in an expression like
9109 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
9110 resolving name scope by reference to source files, in both C and C@t{++}
9111 debugging (@pxref{Variables, ,Program variables}).
9114 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
9115 calling virtual functions correctly, printing out virtual bases of
9116 objects, calling functions in a base subobject, casting objects, and
9117 invoking user-defined operators.
9120 @subsubsection C and C@t{++} defaults
9122 @cindex C and C@t{++} defaults
9124 If you allow @value{GDBN} to set type and range checking automatically, they
9125 both default to @code{off} whenever the working language changes to
9126 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
9127 selects the working language.
9129 If you allow @value{GDBN} to set the language automatically, it
9130 recognizes source files whose names end with @file{.c}, @file{.C}, or
9131 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
9132 these files, it sets the working language to C or C@t{++}.
9133 @xref{Automatically, ,Having @value{GDBN} infer the source language},
9134 for further details.
9136 @c Type checking is (a) primarily motivated by Modula-2, and (b)
9137 @c unimplemented. If (b) changes, it might make sense to let this node
9138 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
9141 @subsubsection C and C@t{++} type and range checks
9143 @cindex C and C@t{++} checks
9145 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
9146 is not used. However, if you turn type checking on, @value{GDBN}
9147 considers two variables type equivalent if:
9151 The two variables are structured and have the same structure, union, or
9155 The two variables have the same type name, or types that have been
9156 declared equivalent through @code{typedef}.
9159 @c leaving this out because neither J Gilmore nor R Pesch understand it.
9162 The two @code{struct}, @code{union}, or @code{enum} variables are
9163 declared in the same declaration. (Note: this may not be true for all C
9168 Range checking, if turned on, is done on mathematical operations. Array
9169 indices are not checked, since they are often used to index a pointer
9170 that is not itself an array.
9173 @subsubsection @value{GDBN} and C
9175 The @code{set print union} and @code{show print union} commands apply to
9176 the @code{union} type. When set to @samp{on}, any @code{union} that is
9177 inside a @code{struct} or @code{class} is also printed. Otherwise, it
9178 appears as @samp{@{...@}}.
9180 The @code{@@} operator aids in the debugging of dynamic arrays, formed
9181 with pointers and a memory allocation function. @xref{Expressions,
9185 * Debugging C plus plus::
9188 @node Debugging C plus plus
9189 @subsubsection @value{GDBN} features for C@t{++}
9191 @cindex commands for C@t{++}
9193 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
9194 designed specifically for use with C@t{++}. Here is a summary:
9197 @cindex break in overloaded functions
9198 @item @r{breakpoint menus}
9199 When you want a breakpoint in a function whose name is overloaded,
9200 @value{GDBN} breakpoint menus help you specify which function definition
9201 you want. @xref{Breakpoint Menus,,Breakpoint menus}.
9203 @cindex overloading in C@t{++}
9204 @item rbreak @var{regex}
9205 Setting breakpoints using regular expressions is helpful for setting
9206 breakpoints on overloaded functions that are not members of any special
9208 @xref{Set Breaks, ,Setting breakpoints}.
9210 @cindex C@t{++} exception handling
9213 Debug C@t{++} exception handling using these commands. @xref{Set
9214 Catchpoints, , Setting catchpoints}.
9217 @item ptype @var{typename}
9218 Print inheritance relationships as well as other information for type
9220 @xref{Symbols, ,Examining the Symbol Table}.
9222 @cindex C@t{++} symbol display
9223 @item set print demangle
9224 @itemx show print demangle
9225 @itemx set print asm-demangle
9226 @itemx show print asm-demangle
9227 Control whether C@t{++} symbols display in their source form, both when
9228 displaying code as C@t{++} source and when displaying disassemblies.
9229 @xref{Print Settings, ,Print settings}.
9231 @item set print object
9232 @itemx show print object
9233 Choose whether to print derived (actual) or declared types of objects.
9234 @xref{Print Settings, ,Print settings}.
9236 @item set print vtbl
9237 @itemx show print vtbl
9238 Control the format for printing virtual function tables.
9239 @xref{Print Settings, ,Print settings}.
9240 (The @code{vtbl} commands do not work on programs compiled with the HP
9241 ANSI C@t{++} compiler (@code{aCC}).)
9243 @kindex set overload-resolution
9244 @cindex overloaded functions, overload resolution
9245 @item set overload-resolution on
9246 Enable overload resolution for C@t{++} expression evaluation. The default
9247 is on. For overloaded functions, @value{GDBN} evaluates the arguments
9248 and searches for a function whose signature matches the argument types,
9249 using the standard C@t{++} conversion rules (see @ref{C plus plus expressions, ,C@t{++}
9250 expressions}, for details). If it cannot find a match, it emits a
9253 @item set overload-resolution off
9254 Disable overload resolution for C@t{++} expression evaluation. For
9255 overloaded functions that are not class member functions, @value{GDBN}
9256 chooses the first function of the specified name that it finds in the
9257 symbol table, whether or not its arguments are of the correct type. For
9258 overloaded functions that are class member functions, @value{GDBN}
9259 searches for a function whose signature @emph{exactly} matches the
9262 @kindex show overload-resolution
9263 @item show overload-resolution
9264 Show the current setting of overload resolution.
9266 @item @r{Overloaded symbol names}
9267 You can specify a particular definition of an overloaded symbol, using
9268 the same notation that is used to declare such symbols in C@t{++}: type
9269 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
9270 also use the @value{GDBN} command-line word completion facilities to list the
9271 available choices, or to finish the type list for you.
9272 @xref{Completion,, Command completion}, for details on how to do this.
9276 @subsection Objective-C
9279 This section provides information about some commands and command
9280 options that are useful for debugging Objective-C code. See also
9281 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
9282 few more commands specific to Objective-C support.
9285 * Method Names in Commands::
9286 * The Print Command with Objective-C::
9289 @node Method Names in Commands, The Print Command with Objective-C, Objective-C, Objective-C
9290 @subsubsection Method Names in Commands
9292 The following commands have been extended to accept Objective-C method
9293 names as line specifications:
9295 @kindex clear@r{, and Objective-C}
9296 @kindex break@r{, and Objective-C}
9297 @kindex info line@r{, and Objective-C}
9298 @kindex jump@r{, and Objective-C}
9299 @kindex list@r{, and Objective-C}
9303 @item @code{info line}
9308 A fully qualified Objective-C method name is specified as
9311 -[@var{Class} @var{methodName}]
9314 where the minus sign is used to indicate an instance method and a
9315 plus sign (not shown) is used to indicate a class method. The class
9316 name @var{Class} and method name @var{methodName} are enclosed in
9317 brackets, similar to the way messages are specified in Objective-C
9318 source code. For example, to set a breakpoint at the @code{create}
9319 instance method of class @code{Fruit} in the program currently being
9323 break -[Fruit create]
9326 To list ten program lines around the @code{initialize} class method,
9330 list +[NSText initialize]
9333 In the current version of @value{GDBN}, the plus or minus sign is
9334 required. In future versions of @value{GDBN}, the plus or minus
9335 sign will be optional, but you can use it to narrow the search. It
9336 is also possible to specify just a method name:
9342 You must specify the complete method name, including any colons. If
9343 your program's source files contain more than one @code{create} method,
9344 you'll be presented with a numbered list of classes that implement that
9345 method. Indicate your choice by number, or type @samp{0} to exit if
9348 As another example, to clear a breakpoint established at the
9349 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
9352 clear -[NSWindow makeKeyAndOrderFront:]
9355 @node The Print Command with Objective-C
9356 @subsubsection The Print Command With Objective-C
9357 @cindex Objective-C, print objects
9358 @kindex print-object
9359 @kindex po @r{(@code{print-object})}
9361 The print command has also been extended to accept methods. For example:
9364 print -[@var{object} hash]
9367 @cindex print an Objective-C object description
9368 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
9370 will tell @value{GDBN} to send the @code{hash} message to @var{object}
9371 and print the result. Also, an additional command has been added,
9372 @code{print-object} or @code{po} for short, which is meant to print
9373 the description of an object. However, this command may only work
9374 with certain Objective-C libraries that have a particular hook
9375 function, @code{_NSPrintForDebugger}, defined.
9379 @cindex Fortran-specific support in @value{GDBN}
9381 @value{GDBN} can be used to debug programs written in Fortran, but it
9382 currently supports only the features of Fortran 77 language.
9384 @cindex trailing underscore, in Fortran symbols
9385 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
9386 among them) append an underscore to the names of variables and
9387 functions. When you debug programs compiled by those compilers, you
9388 will need to refer to variables and functions with a trailing
9392 * Fortran Operators:: Fortran operators and expressions
9393 * Fortran Defaults:: Default settings for Fortran
9394 * Special Fortran commands:: Special @value{GDBN} commands for Fortran
9397 @node Fortran Operators
9398 @subsubsection Fortran operators and expressions
9400 @cindex Fortran operators and expressions
9402 Operators must be defined on values of specific types. For instance,
9403 @code{+} is defined on numbers, but not on characters or other non-
9404 arithmetic types. Operators are often defined on groups of types.
9408 The exponentiation operator. It raises the first operand to the power
9412 The range operator. Normally used in the form of array(low:high) to
9413 represent a section of array.
9416 @node Fortran Defaults
9417 @subsubsection Fortran Defaults
9419 @cindex Fortran Defaults
9421 Fortran symbols are usually case-insensitive, so @value{GDBN} by
9422 default uses case-insensitive matches for Fortran symbols. You can
9423 change that with the @samp{set case-insensitive} command, see
9424 @ref{Symbols}, for the details.
9426 @node Special Fortran commands
9427 @subsubsection Special Fortran commands
9429 @cindex Special Fortran commands
9431 @value{GDBN} had some commands to support Fortran specific feature,
9432 such as common block displaying.
9435 @cindex @code{COMMON} blocks, Fortran
9437 @item info common @r{[}@var{common-name}@r{]}
9438 This command prints the values contained in the Fortran @code{COMMON}
9439 block whose name is @var{common-name}. With no argument, the names of
9440 all @code{COMMON} blocks visible at current program location are
9447 @cindex Pascal support in @value{GDBN}, limitations
9448 Debugging Pascal programs which use sets, subranges, file variables, or
9449 nested functions does not currently work. @value{GDBN} does not support
9450 entering expressions, printing values, or similar features using Pascal
9453 The Pascal-specific command @code{set print pascal_static-members}
9454 controls whether static members of Pascal objects are displayed.
9455 @xref{Print Settings, pascal_static-members}.
9458 @subsection Modula-2
9460 @cindex Modula-2, @value{GDBN} support
9462 The extensions made to @value{GDBN} to support Modula-2 only support
9463 output from the @sc{gnu} Modula-2 compiler (which is currently being
9464 developed). Other Modula-2 compilers are not currently supported, and
9465 attempting to debug executables produced by them is most likely
9466 to give an error as @value{GDBN} reads in the executable's symbol
9469 @cindex expressions in Modula-2
9471 * M2 Operators:: Built-in operators
9472 * Built-In Func/Proc:: Built-in functions and procedures
9473 * M2 Constants:: Modula-2 constants
9474 * M2 Types:: Modula-2 types
9475 * M2 Defaults:: Default settings for Modula-2
9476 * Deviations:: Deviations from standard Modula-2
9477 * M2 Checks:: Modula-2 type and range checks
9478 * M2 Scope:: The scope operators @code{::} and @code{.}
9479 * GDB/M2:: @value{GDBN} and Modula-2
9483 @subsubsection Operators
9484 @cindex Modula-2 operators
9486 Operators must be defined on values of specific types. For instance,
9487 @code{+} is defined on numbers, but not on structures. Operators are
9488 often defined on groups of types. For the purposes of Modula-2, the
9489 following definitions hold:
9494 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
9498 @emph{Character types} consist of @code{CHAR} and its subranges.
9501 @emph{Floating-point types} consist of @code{REAL}.
9504 @emph{Pointer types} consist of anything declared as @code{POINTER TO
9508 @emph{Scalar types} consist of all of the above.
9511 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
9514 @emph{Boolean types} consist of @code{BOOLEAN}.
9518 The following operators are supported, and appear in order of
9519 increasing precedence:
9523 Function argument or array index separator.
9526 Assignment. The value of @var{var} @code{:=} @var{value} is
9530 Less than, greater than on integral, floating-point, or enumerated
9534 Less than or equal to, greater than or equal to
9535 on integral, floating-point and enumerated types, or set inclusion on
9536 set types. Same precedence as @code{<}.
9538 @item =@r{, }<>@r{, }#
9539 Equality and two ways of expressing inequality, valid on scalar types.
9540 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
9541 available for inequality, since @code{#} conflicts with the script
9545 Set membership. Defined on set types and the types of their members.
9546 Same precedence as @code{<}.
9549 Boolean disjunction. Defined on boolean types.
9552 Boolean conjunction. Defined on boolean types.
9555 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9558 Addition and subtraction on integral and floating-point types, or union
9559 and difference on set types.
9562 Multiplication on integral and floating-point types, or set intersection
9566 Division on floating-point types, or symmetric set difference on set
9567 types. Same precedence as @code{*}.
9570 Integer division and remainder. Defined on integral types. Same
9571 precedence as @code{*}.
9574 Negative. Defined on @code{INTEGER} and @code{REAL} data.
9577 Pointer dereferencing. Defined on pointer types.
9580 Boolean negation. Defined on boolean types. Same precedence as
9584 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
9585 precedence as @code{^}.
9588 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
9591 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
9595 @value{GDBN} and Modula-2 scope operators.
9599 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
9600 treats the use of the operator @code{IN}, or the use of operators
9601 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
9602 @code{<=}, and @code{>=} on sets as an error.
9606 @node Built-In Func/Proc
9607 @subsubsection Built-in functions and procedures
9608 @cindex Modula-2 built-ins
9610 Modula-2 also makes available several built-in procedures and functions.
9611 In describing these, the following metavariables are used:
9616 represents an @code{ARRAY} variable.
9619 represents a @code{CHAR} constant or variable.
9622 represents a variable or constant of integral type.
9625 represents an identifier that belongs to a set. Generally used in the
9626 same function with the metavariable @var{s}. The type of @var{s} should
9627 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
9630 represents a variable or constant of integral or floating-point type.
9633 represents a variable or constant of floating-point type.
9639 represents a variable.
9642 represents a variable or constant of one of many types. See the
9643 explanation of the function for details.
9646 All Modula-2 built-in procedures also return a result, described below.
9650 Returns the absolute value of @var{n}.
9653 If @var{c} is a lower case letter, it returns its upper case
9654 equivalent, otherwise it returns its argument.
9657 Returns the character whose ordinal value is @var{i}.
9660 Decrements the value in the variable @var{v} by one. Returns the new value.
9662 @item DEC(@var{v},@var{i})
9663 Decrements the value in the variable @var{v} by @var{i}. Returns the
9666 @item EXCL(@var{m},@var{s})
9667 Removes the element @var{m} from the set @var{s}. Returns the new
9670 @item FLOAT(@var{i})
9671 Returns the floating point equivalent of the integer @var{i}.
9674 Returns the index of the last member of @var{a}.
9677 Increments the value in the variable @var{v} by one. Returns the new value.
9679 @item INC(@var{v},@var{i})
9680 Increments the value in the variable @var{v} by @var{i}. Returns the
9683 @item INCL(@var{m},@var{s})
9684 Adds the element @var{m} to the set @var{s} if it is not already
9685 there. Returns the new set.
9688 Returns the maximum value of the type @var{t}.
9691 Returns the minimum value of the type @var{t}.
9694 Returns boolean TRUE if @var{i} is an odd number.
9697 Returns the ordinal value of its argument. For example, the ordinal
9698 value of a character is its @sc{ascii} value (on machines supporting the
9699 @sc{ascii} character set). @var{x} must be of an ordered type, which include
9700 integral, character and enumerated types.
9703 Returns the size of its argument. @var{x} can be a variable or a type.
9705 @item TRUNC(@var{r})
9706 Returns the integral part of @var{r}.
9708 @item VAL(@var{t},@var{i})
9709 Returns the member of the type @var{t} whose ordinal value is @var{i}.
9713 @emph{Warning:} Sets and their operations are not yet supported, so
9714 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
9718 @cindex Modula-2 constants
9720 @subsubsection Constants
9722 @value{GDBN} allows you to express the constants of Modula-2 in the following
9728 Integer constants are simply a sequence of digits. When used in an
9729 expression, a constant is interpreted to be type-compatible with the
9730 rest of the expression. Hexadecimal integers are specified by a
9731 trailing @samp{H}, and octal integers by a trailing @samp{B}.
9734 Floating point constants appear as a sequence of digits, followed by a
9735 decimal point and another sequence of digits. An optional exponent can
9736 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
9737 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
9738 digits of the floating point constant must be valid decimal (base 10)
9742 Character constants consist of a single character enclosed by a pair of
9743 like quotes, either single (@code{'}) or double (@code{"}). They may
9744 also be expressed by their ordinal value (their @sc{ascii} value, usually)
9745 followed by a @samp{C}.
9748 String constants consist of a sequence of characters enclosed by a
9749 pair of like quotes, either single (@code{'}) or double (@code{"}).
9750 Escape sequences in the style of C are also allowed. @xref{C
9751 Constants, ,C and C@t{++} constants}, for a brief explanation of escape
9755 Enumerated constants consist of an enumerated identifier.
9758 Boolean constants consist of the identifiers @code{TRUE} and
9762 Pointer constants consist of integral values only.
9765 Set constants are not yet supported.
9769 @subsubsection Modula-2 Types
9770 @cindex Modula-2 types
9772 Currently @value{GDBN} can print the following data types in Modula-2
9773 syntax: array types, record types, set types, pointer types, procedure
9774 types, enumerated types, subrange types and base types. You can also
9775 print the contents of variables declared using these type.
9776 This section gives a number of simple source code examples together with
9777 sample @value{GDBN} sessions.
9779 The first example contains the following section of code:
9788 and you can request @value{GDBN} to interrogate the type and value of
9789 @code{r} and @code{s}.
9792 (@value{GDBP}) print s
9794 (@value{GDBP}) ptype s
9796 (@value{GDBP}) print r
9798 (@value{GDBP}) ptype r
9803 Likewise if your source code declares @code{s} as:
9811 then you may query the type of @code{s} by:
9814 (@value{GDBP}) ptype s
9815 type = SET ['A'..'Z']
9819 Note that at present you cannot interactively manipulate set
9820 expressions using the debugger.
9822 The following example shows how you might declare an array in Modula-2
9823 and how you can interact with @value{GDBN} to print its type and contents:
9827 s: ARRAY [-10..10] OF CHAR ;
9831 (@value{GDBP}) ptype s
9832 ARRAY [-10..10] OF CHAR
9835 Note that the array handling is not yet complete and although the type
9836 is printed correctly, expression handling still assumes that all
9837 arrays have a lower bound of zero and not @code{-10} as in the example
9838 above. Unbounded arrays are also not yet recognized in @value{GDBN}.
9840 Here are some more type related Modula-2 examples:
9844 colour = (blue, red, yellow, green) ;
9845 t = [blue..yellow] ;
9853 The @value{GDBN} interaction shows how you can query the data type
9854 and value of a variable.
9857 (@value{GDBP}) print s
9859 (@value{GDBP}) ptype t
9860 type = [blue..yellow]
9864 In this example a Modula-2 array is declared and its contents
9865 displayed. Observe that the contents are written in the same way as
9866 their @code{C} counterparts.
9870 s: ARRAY [1..5] OF CARDINAL ;
9876 (@value{GDBP}) print s
9877 $1 = @{1, 0, 0, 0, 0@}
9878 (@value{GDBP}) ptype s
9879 type = ARRAY [1..5] OF CARDINAL
9882 The Modula-2 language interface to @value{GDBN} also understands
9883 pointer types as shown in this example:
9887 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
9894 and you can request that @value{GDBN} describes the type of @code{s}.
9897 (@value{GDBP}) ptype s
9898 type = POINTER TO ARRAY [1..5] OF CARDINAL
9901 @value{GDBN} handles compound types as we can see in this example.
9902 Here we combine array types, record types, pointer types and subrange
9913 myarray = ARRAY myrange OF CARDINAL ;
9916 s: POINTER TO ARRAY myrange OF foo ;
9920 and you can ask @value{GDBN} to describe the type of @code{s} as shown
9924 (@value{GDBP}) ptype s
9925 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
9928 f3 : ARRAY [-2..2] OF CARDINAL;
9933 @subsubsection Modula-2 defaults
9934 @cindex Modula-2 defaults
9936 If type and range checking are set automatically by @value{GDBN}, they
9937 both default to @code{on} whenever the working language changes to
9938 Modula-2. This happens regardless of whether you or @value{GDBN}
9939 selected the working language.
9941 If you allow @value{GDBN} to set the language automatically, then entering
9942 code compiled from a file whose name ends with @file{.mod} sets the
9943 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} set
9944 the language automatically}, for further details.
9947 @subsubsection Deviations from standard Modula-2
9948 @cindex Modula-2, deviations from
9950 A few changes have been made to make Modula-2 programs easier to debug.
9951 This is done primarily via loosening its type strictness:
9955 Unlike in standard Modula-2, pointer constants can be formed by
9956 integers. This allows you to modify pointer variables during
9957 debugging. (In standard Modula-2, the actual address contained in a
9958 pointer variable is hidden from you; it can only be modified
9959 through direct assignment to another pointer variable or expression that
9960 returned a pointer.)
9963 C escape sequences can be used in strings and characters to represent
9964 non-printable characters. @value{GDBN} prints out strings with these
9965 escape sequences embedded. Single non-printable characters are
9966 printed using the @samp{CHR(@var{nnn})} format.
9969 The assignment operator (@code{:=}) returns the value of its right-hand
9973 All built-in procedures both modify @emph{and} return their argument.
9977 @subsubsection Modula-2 type and range checks
9978 @cindex Modula-2 checks
9981 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
9984 @c FIXME remove warning when type/range checks added
9986 @value{GDBN} considers two Modula-2 variables type equivalent if:
9990 They are of types that have been declared equivalent via a @code{TYPE
9991 @var{t1} = @var{t2}} statement
9994 They have been declared on the same line. (Note: This is true of the
9995 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
9998 As long as type checking is enabled, any attempt to combine variables
9999 whose types are not equivalent is an error.
10001 Range checking is done on all mathematical operations, assignment, array
10002 index bounds, and all built-in functions and procedures.
10005 @subsubsection The scope operators @code{::} and @code{.}
10007 @cindex @code{.}, Modula-2 scope operator
10008 @cindex colon, doubled as scope operator
10010 @vindex colon-colon@r{, in Modula-2}
10011 @c Info cannot handle :: but TeX can.
10014 @vindex ::@r{, in Modula-2}
10017 There are a few subtle differences between the Modula-2 scope operator
10018 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
10023 @var{module} . @var{id}
10024 @var{scope} :: @var{id}
10028 where @var{scope} is the name of a module or a procedure,
10029 @var{module} the name of a module, and @var{id} is any declared
10030 identifier within your program, except another module.
10032 Using the @code{::} operator makes @value{GDBN} search the scope
10033 specified by @var{scope} for the identifier @var{id}. If it is not
10034 found in the specified scope, then @value{GDBN} searches all scopes
10035 enclosing the one specified by @var{scope}.
10037 Using the @code{.} operator makes @value{GDBN} search the current scope for
10038 the identifier specified by @var{id} that was imported from the
10039 definition module specified by @var{module}. With this operator, it is
10040 an error if the identifier @var{id} was not imported from definition
10041 module @var{module}, or if @var{id} is not an identifier in
10045 @subsubsection @value{GDBN} and Modula-2
10047 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
10048 Five subcommands of @code{set print} and @code{show print} apply
10049 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
10050 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
10051 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
10052 analogue in Modula-2.
10054 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
10055 with any language, is not useful with Modula-2. Its
10056 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
10057 created in Modula-2 as they can in C or C@t{++}. However, because an
10058 address can be specified by an integral constant, the construct
10059 @samp{@{@var{type}@}@var{adrexp}} is still useful.
10061 @cindex @code{#} in Modula-2
10062 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
10063 interpreted as the beginning of a comment. Use @code{<>} instead.
10069 The extensions made to @value{GDBN} for Ada only support
10070 output from the @sc{gnu} Ada (GNAT) compiler.
10071 Other Ada compilers are not currently supported, and
10072 attempting to debug executables produced by them is most likely
10076 @cindex expressions in Ada
10078 * Ada Mode Intro:: General remarks on the Ada syntax
10079 and semantics supported by Ada mode
10081 * Omissions from Ada:: Restrictions on the Ada expression syntax.
10082 * Additions to Ada:: Extensions of the Ada expression syntax.
10083 * Stopping Before Main Program:: Debugging the program during elaboration.
10084 * Ada Glitches:: Known peculiarities of Ada mode.
10087 @node Ada Mode Intro
10088 @subsubsection Introduction
10089 @cindex Ada mode, general
10091 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
10092 syntax, with some extensions.
10093 The philosophy behind the design of this subset is
10097 That @value{GDBN} should provide basic literals and access to operations for
10098 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
10099 leaving more sophisticated computations to subprograms written into the
10100 program (which therefore may be called from @value{GDBN}).
10103 That type safety and strict adherence to Ada language restrictions
10104 are not particularly important to the @value{GDBN} user.
10107 That brevity is important to the @value{GDBN} user.
10110 Thus, for brevity, the debugger acts as if there were
10111 implicit @code{with} and @code{use} clauses in effect for all user-written
10112 packages, making it unnecessary to fully qualify most names with
10113 their packages, regardless of context. Where this causes ambiguity,
10114 @value{GDBN} asks the user's intent.
10116 The debugger will start in Ada mode if it detects an Ada main program.
10117 As for other languages, it will enter Ada mode when stopped in a program that
10118 was translated from an Ada source file.
10120 While in Ada mode, you may use `@t{--}' for comments. This is useful
10121 mostly for documenting command files. The standard @value{GDBN} comment
10122 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
10123 middle (to allow based literals).
10125 The debugger supports limited overloading. Given a subprogram call in which
10126 the function symbol has multiple definitions, it will use the number of
10127 actual parameters and some information about their types to attempt to narrow
10128 the set of definitions. It also makes very limited use of context, preferring
10129 procedures to functions in the context of the @code{call} command, and
10130 functions to procedures elsewhere.
10132 @node Omissions from Ada
10133 @subsubsection Omissions from Ada
10134 @cindex Ada, omissions from
10136 Here are the notable omissions from the subset:
10140 Only a subset of the attributes are supported:
10144 @t{'First}, @t{'Last}, and @t{'Length}
10145 on array objects (not on types and subtypes).
10148 @t{'Min} and @t{'Max}.
10151 @t{'Pos} and @t{'Val}.
10157 @t{'Range} on array objects (not subtypes), but only as the right
10158 operand of the membership (@code{in}) operator.
10161 @t{'Access}, @t{'Unchecked_Access}, and
10162 @t{'Unrestricted_Access} (a GNAT extension).
10170 @code{Characters.Latin_1} are not available and
10171 concatenation is not implemented. Thus, escape characters in strings are
10172 not currently available.
10175 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
10176 equality of representations. They will generally work correctly
10177 for strings and arrays whose elements have integer or enumeration types.
10178 They may not work correctly for arrays whose element
10179 types have user-defined equality, for arrays of real values
10180 (in particular, IEEE-conformant floating point, because of negative
10181 zeroes and NaNs), and for arrays whose elements contain unused bits with
10182 indeterminate values.
10185 The other component-by-component array operations (@code{and}, @code{or},
10186 @code{xor}, @code{not}, and relational tests other than equality)
10187 are not implemented.
10190 @cindex array aggregates (Ada)
10191 @cindex record aggregates (Ada)
10192 @cindex aggregates (Ada)
10193 There is limited support for array and record aggregates. They are
10194 permitted only on the right sides of assignments, as in these examples:
10197 set An_Array := (1, 2, 3, 4, 5, 6)
10198 set An_Array := (1, others => 0)
10199 set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
10200 set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
10201 set A_Record := (1, "Peter", True);
10202 set A_Record := (Name => "Peter", Id => 1, Alive => True)
10206 discriminant's value by assigning an aggregate has an
10207 undefined effect if that discriminant is used within the record.
10208 However, you can first modify discriminants by directly assigning to
10209 them (which normally would not be allowed in Ada), and then performing an
10210 aggregate assignment. For example, given a variable @code{A_Rec}
10211 declared to have a type such as:
10214 type Rec (Len : Small_Integer := 0) is record
10216 Vals : IntArray (1 .. Len);
10220 you can assign a value with a different size of @code{Vals} with two
10225 set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
10228 As this example also illustrates, @value{GDBN} is very loose about the usual
10229 rules concerning aggregates. You may leave out some of the
10230 components of an array or record aggregate (such as the @code{Len}
10231 component in the assignment to @code{A_Rec} above); they will retain their
10232 original values upon assignment. You may freely use dynamic values as
10233 indices in component associations. You may even use overlapping or
10234 redundant component associations, although which component values are
10235 assigned in such cases is not defined.
10238 Calls to dispatching subprograms are not implemented.
10241 The overloading algorithm is much more limited (i.e., less selective)
10242 than that of real Ada. It makes only limited use of the context in which a subexpression
10243 appears to resolve its meaning, and it is much looser in its rules for allowing
10244 type matches. As a result, some function calls will be ambiguous, and the user
10245 will be asked to choose the proper resolution.
10248 The @code{new} operator is not implemented.
10251 Entry calls are not implemented.
10254 Aside from printing, arithmetic operations on the native VAX floating-point
10255 formats are not supported.
10258 It is not possible to slice a packed array.
10261 @node Additions to Ada
10262 @subsubsection Additions to Ada
10263 @cindex Ada, deviations from
10265 As it does for other languages, @value{GDBN} makes certain generic
10266 extensions to Ada (@pxref{Expressions}):
10270 If the expression @var{E} is a variable residing in memory
10271 (typically a local variable or array element) and @var{N} is
10272 a positive integer, then @code{@var{E}@@@var{N}} displays the values of
10273 @var{E} and the @var{N}-1 adjacent variables following it in memory as an array.
10274 In Ada, this operator is generally not necessary, since its prime use
10275 is in displaying parts of an array, and slicing will usually do this in Ada.
10276 However, there are occasional uses when debugging programs
10277 in which certain debugging information has been optimized away.
10280 @code{@var{B}::@var{var}} means ``the variable named @var{var} that appears
10281 in function or file @var{B}.'' When @var{B} is a file name, you must typically
10282 surround it in single quotes.
10285 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
10286 @var{type} that appears at address @var{addr}.''
10289 A name starting with @samp{$} is a convenience variable
10290 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
10293 In addition, @value{GDBN} provides a few other shortcuts and outright additions specific
10298 The assignment statement is allowed as an expression, returning
10299 its right-hand operand as its value. Thus, you may enter
10303 print A(tmp := y + 1)
10307 The semicolon is allowed as an ``operator,'' returning as its value
10308 the value of its right-hand operand.
10309 This allows, for example,
10310 complex conditional breaks:
10314 condition 1 (report(i); k += 1; A(k) > 100)
10318 Rather than use catenation and symbolic character names to introduce special
10319 characters into strings, one may instead use a special bracket notation,
10320 which is also used to print strings. A sequence of characters of the form
10321 @samp{["@var{XX}"]} within a string or character literal denotes the
10322 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
10323 sequence of characters @samp{["""]} also denotes a single quotation mark
10324 in strings. For example,
10326 "One line.["0a"]Next line.["0a"]"
10329 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF}) after each
10333 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
10334 @t{'Max} is optional (and is ignored in any case). For example, it is valid
10342 When printing arrays, @value{GDBN} uses positional notation when the
10343 array has a lower bound of 1, and uses a modified named notation otherwise.
10344 For example, a one-dimensional array of three integers with a lower bound of 3 might print as
10351 That is, in contrast to valid Ada, only the first component has a @code{=>}
10355 You may abbreviate attributes in expressions with any unique,
10356 multi-character subsequence of
10357 their names (an exact match gets preference).
10358 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
10359 in place of @t{a'length}.
10362 @cindex quoting Ada internal identifiers
10363 Since Ada is case-insensitive, the debugger normally maps identifiers you type
10364 to lower case. The GNAT compiler uses upper-case characters for
10365 some of its internal identifiers, which are normally of no interest to users.
10366 For the rare occasions when you actually have to look at them,
10367 enclose them in angle brackets to avoid the lower-case mapping.
10370 @value{GDBP} print <JMPBUF_SAVE>[0]
10374 Printing an object of class-wide type or dereferencing an
10375 access-to-class-wide value will display all the components of the object's
10376 specific type (as indicated by its run-time tag). Likewise, component
10377 selection on such a value will operate on the specific type of the
10382 @node Stopping Before Main Program
10383 @subsubsection Stopping at the Very Beginning
10385 @cindex breakpointing Ada elaboration code
10386 It is sometimes necessary to debug the program during elaboration, and
10387 before reaching the main procedure.
10388 As defined in the Ada Reference
10389 Manual, the elaboration code is invoked from a procedure called
10390 @code{adainit}. To run your program up to the beginning of
10391 elaboration, simply use the following two commands:
10392 @code{tbreak adainit} and @code{run}.
10395 @subsubsection Known Peculiarities of Ada Mode
10396 @cindex Ada, problems
10398 Besides the omissions listed previously (@pxref{Omissions from Ada}),
10399 we know of several problems with and limitations of Ada mode in
10401 some of which will be fixed with planned future releases of the debugger
10402 and the GNU Ada compiler.
10406 Currently, the debugger
10407 has insufficient information to determine whether certain pointers represent
10408 pointers to objects or the objects themselves.
10409 Thus, the user may have to tack an extra @code{.all} after an expression
10410 to get it printed properly.
10413 Static constants that the compiler chooses not to materialize as objects in
10414 storage are invisible to the debugger.
10417 Named parameter associations in function argument lists are ignored (the
10418 argument lists are treated as positional).
10421 Many useful library packages are currently invisible to the debugger.
10424 Fixed-point arithmetic, conversions, input, and output is carried out using
10425 floating-point arithmetic, and may give results that only approximate those on
10429 The type of the @t{'Address} attribute may not be @code{System.Address}.
10432 The GNAT compiler never generates the prefix @code{Standard} for any of
10433 the standard symbols defined by the Ada language. @value{GDBN} knows about
10434 this: it will strip the prefix from names when you use it, and will never
10435 look for a name you have so qualified among local symbols, nor match against
10436 symbols in other packages or subprograms. If you have
10437 defined entities anywhere in your program other than parameters and
10438 local variables whose simple names match names in @code{Standard},
10439 GNAT's lack of qualification here can cause confusion. When this happens,
10440 you can usually resolve the confusion
10441 by qualifying the problematic names with package
10442 @code{Standard} explicitly.
10445 @node Unsupported languages
10446 @section Unsupported languages
10448 @cindex unsupported languages
10449 @cindex minimal language
10450 In addition to the other fully-supported programming languages,
10451 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
10452 It does not represent a real programming language, but provides a set
10453 of capabilities close to what the C or assembly languages provide.
10454 This should allow most simple operations to be performed while debugging
10455 an application that uses a language currently not supported by @value{GDBN}.
10457 If the language is set to @code{auto}, @value{GDBN} will automatically
10458 select this language if the current frame corresponds to an unsupported
10462 @chapter Examining the Symbol Table
10464 The commands described in this chapter allow you to inquire about the
10465 symbols (names of variables, functions and types) defined in your
10466 program. This information is inherent in the text of your program and
10467 does not change as your program executes. @value{GDBN} finds it in your
10468 program's symbol table, in the file indicated when you started @value{GDBN}
10469 (@pxref{File Options, ,Choosing files}), or by one of the
10470 file-management commands (@pxref{Files, ,Commands to specify files}).
10472 @cindex symbol names
10473 @cindex names of symbols
10474 @cindex quoting names
10475 Occasionally, you may need to refer to symbols that contain unusual
10476 characters, which @value{GDBN} ordinarily treats as word delimiters. The
10477 most frequent case is in referring to static variables in other
10478 source files (@pxref{Variables,,Program variables}). File names
10479 are recorded in object files as debugging symbols, but @value{GDBN} would
10480 ordinarily parse a typical file name, like @file{foo.c}, as the three words
10481 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
10482 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
10489 looks up the value of @code{x} in the scope of the file @file{foo.c}.
10492 @cindex case-insensitive symbol names
10493 @cindex case sensitivity in symbol names
10494 @kindex set case-sensitive
10495 @item set case-sensitive on
10496 @itemx set case-sensitive off
10497 @itemx set case-sensitive auto
10498 Normally, when @value{GDBN} looks up symbols, it matches their names
10499 with case sensitivity determined by the current source language.
10500 Occasionally, you may wish to control that. The command @code{set
10501 case-sensitive} lets you do that by specifying @code{on} for
10502 case-sensitive matches or @code{off} for case-insensitive ones. If
10503 you specify @code{auto}, case sensitivity is reset to the default
10504 suitable for the source language. The default is case-sensitive
10505 matches for all languages except for Fortran, for which the default is
10506 case-insensitive matches.
10508 @kindex show case-sensitive
10509 @item show case-sensitive
10510 This command shows the current setting of case sensitivity for symbols
10513 @kindex info address
10514 @cindex address of a symbol
10515 @item info address @var{symbol}
10516 Describe where the data for @var{symbol} is stored. For a register
10517 variable, this says which register it is kept in. For a non-register
10518 local variable, this prints the stack-frame offset at which the variable
10521 Note the contrast with @samp{print &@var{symbol}}, which does not work
10522 at all for a register variable, and for a stack local variable prints
10523 the exact address of the current instantiation of the variable.
10525 @kindex info symbol
10526 @cindex symbol from address
10527 @cindex closest symbol and offset for an address
10528 @item info symbol @var{addr}
10529 Print the name of a symbol which is stored at the address @var{addr}.
10530 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
10531 nearest symbol and an offset from it:
10534 (@value{GDBP}) info symbol 0x54320
10535 _initialize_vx + 396 in section .text
10539 This is the opposite of the @code{info address} command. You can use
10540 it to find out the name of a variable or a function given its address.
10543 @item whatis [@var{arg}]
10544 Print the data type of @var{arg}, which can be either an expression or
10545 a data type. With no argument, print the data type of @code{$}, the
10546 last value in the value history. If @var{arg} is an expression, it is
10547 not actually evaluated, and any side-effecting operations (such as
10548 assignments or function calls) inside it do not take place. If
10549 @var{arg} is a type name, it may be the name of a type or typedef, or
10550 for C code it may have the form @samp{class @var{class-name}},
10551 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
10552 @samp{enum @var{enum-tag}}.
10553 @xref{Expressions, ,Expressions}.
10556 @item ptype [@var{arg}]
10557 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
10558 detailed description of the type, instead of just the name of the type.
10559 @xref{Expressions, ,Expressions}.
10561 For example, for this variable declaration:
10564 struct complex @{double real; double imag;@} v;
10568 the two commands give this output:
10572 (@value{GDBP}) whatis v
10573 type = struct complex
10574 (@value{GDBP}) ptype v
10575 type = struct complex @{
10583 As with @code{whatis}, using @code{ptype} without an argument refers to
10584 the type of @code{$}, the last value in the value history.
10586 @cindex incomplete type
10587 Sometimes, programs use opaque data types or incomplete specifications
10588 of complex data structure. If the debug information included in the
10589 program does not allow @value{GDBN} to display a full declaration of
10590 the data type, it will say @samp{<incomplete type>}. For example,
10591 given these declarations:
10595 struct foo *fooptr;
10599 but no definition for @code{struct foo} itself, @value{GDBN} will say:
10602 (@value{GDBP}) ptype foo
10603 $1 = <incomplete type>
10607 ``Incomplete type'' is C terminology for data types that are not
10608 completely specified.
10611 @item info types @var{regexp}
10613 Print a brief description of all types whose names match the regular
10614 expression @var{regexp} (or all types in your program, if you supply
10615 no argument). Each complete typename is matched as though it were a
10616 complete line; thus, @samp{i type value} gives information on all
10617 types in your program whose names include the string @code{value}, but
10618 @samp{i type ^value$} gives information only on types whose complete
10619 name is @code{value}.
10621 This command differs from @code{ptype} in two ways: first, like
10622 @code{whatis}, it does not print a detailed description; second, it
10623 lists all source files where a type is defined.
10626 @cindex local variables
10627 @item info scope @var{location}
10628 List all the variables local to a particular scope. This command
10629 accepts a @var{location} argument---a function name, a source line, or
10630 an address preceded by a @samp{*}, and prints all the variables local
10631 to the scope defined by that location. For example:
10634 (@value{GDBP}) @b{info scope command_line_handler}
10635 Scope for command_line_handler:
10636 Symbol rl is an argument at stack/frame offset 8, length 4.
10637 Symbol linebuffer is in static storage at address 0x150a18, length 4.
10638 Symbol linelength is in static storage at address 0x150a1c, length 4.
10639 Symbol p is a local variable in register $esi, length 4.
10640 Symbol p1 is a local variable in register $ebx, length 4.
10641 Symbol nline is a local variable in register $edx, length 4.
10642 Symbol repeat is a local variable at frame offset -8, length 4.
10646 This command is especially useful for determining what data to collect
10647 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
10650 @kindex info source
10652 Show information about the current source file---that is, the source file for
10653 the function containing the current point of execution:
10656 the name of the source file, and the directory containing it,
10658 the directory it was compiled in,
10660 its length, in lines,
10662 which programming language it is written in,
10664 whether the executable includes debugging information for that file, and
10665 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
10667 whether the debugging information includes information about
10668 preprocessor macros.
10672 @kindex info sources
10674 Print the names of all source files in your program for which there is
10675 debugging information, organized into two lists: files whose symbols
10676 have already been read, and files whose symbols will be read when needed.
10678 @kindex info functions
10679 @item info functions
10680 Print the names and data types of all defined functions.
10682 @item info functions @var{regexp}
10683 Print the names and data types of all defined functions
10684 whose names contain a match for regular expression @var{regexp}.
10685 Thus, @samp{info fun step} finds all functions whose names
10686 include @code{step}; @samp{info fun ^step} finds those whose names
10687 start with @code{step}. If a function name contains characters
10688 that conflict with the regular expression language (e.g.@:
10689 @samp{operator*()}), they may be quoted with a backslash.
10691 @kindex info variables
10692 @item info variables
10693 Print the names and data types of all variables that are declared
10694 outside of functions (i.e.@: excluding local variables).
10696 @item info variables @var{regexp}
10697 Print the names and data types of all variables (except for local
10698 variables) whose names contain a match for regular expression
10701 @kindex info classes
10702 @cindex Objective-C, classes and selectors
10704 @itemx info classes @var{regexp}
10705 Display all Objective-C classes in your program, or
10706 (with the @var{regexp} argument) all those matching a particular regular
10709 @kindex info selectors
10710 @item info selectors
10711 @itemx info selectors @var{regexp}
10712 Display all Objective-C selectors in your program, or
10713 (with the @var{regexp} argument) all those matching a particular regular
10717 This was never implemented.
10718 @kindex info methods
10720 @itemx info methods @var{regexp}
10721 The @code{info methods} command permits the user to examine all defined
10722 methods within C@t{++} program, or (with the @var{regexp} argument) a
10723 specific set of methods found in the various C@t{++} classes. Many
10724 C@t{++} classes provide a large number of methods. Thus, the output
10725 from the @code{ptype} command can be overwhelming and hard to use. The
10726 @code{info-methods} command filters the methods, printing only those
10727 which match the regular-expression @var{regexp}.
10730 @cindex reloading symbols
10731 Some systems allow individual object files that make up your program to
10732 be replaced without stopping and restarting your program. For example,
10733 in VxWorks you can simply recompile a defective object file and keep on
10734 running. If you are running on one of these systems, you can allow
10735 @value{GDBN} to reload the symbols for automatically relinked modules:
10738 @kindex set symbol-reloading
10739 @item set symbol-reloading on
10740 Replace symbol definitions for the corresponding source file when an
10741 object file with a particular name is seen again.
10743 @item set symbol-reloading off
10744 Do not replace symbol definitions when encountering object files of the
10745 same name more than once. This is the default state; if you are not
10746 running on a system that permits automatic relinking of modules, you
10747 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
10748 may discard symbols when linking large programs, that may contain
10749 several modules (from different directories or libraries) with the same
10752 @kindex show symbol-reloading
10753 @item show symbol-reloading
10754 Show the current @code{on} or @code{off} setting.
10757 @cindex opaque data types
10758 @kindex set opaque-type-resolution
10759 @item set opaque-type-resolution on
10760 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
10761 declared as a pointer to a @code{struct}, @code{class}, or
10762 @code{union}---for example, @code{struct MyType *}---that is used in one
10763 source file although the full declaration of @code{struct MyType} is in
10764 another source file. The default is on.
10766 A change in the setting of this subcommand will not take effect until
10767 the next time symbols for a file are loaded.
10769 @item set opaque-type-resolution off
10770 Tell @value{GDBN} not to resolve opaque types. In this case, the type
10771 is printed as follows:
10773 @{<no data fields>@}
10776 @kindex show opaque-type-resolution
10777 @item show opaque-type-resolution
10778 Show whether opaque types are resolved or not.
10780 @kindex maint print symbols
10781 @cindex symbol dump
10782 @kindex maint print psymbols
10783 @cindex partial symbol dump
10784 @item maint print symbols @var{filename}
10785 @itemx maint print psymbols @var{filename}
10786 @itemx maint print msymbols @var{filename}
10787 Write a dump of debugging symbol data into the file @var{filename}.
10788 These commands are used to debug the @value{GDBN} symbol-reading code. Only
10789 symbols with debugging data are included. If you use @samp{maint print
10790 symbols}, @value{GDBN} includes all the symbols for which it has already
10791 collected full details: that is, @var{filename} reflects symbols for
10792 only those files whose symbols @value{GDBN} has read. You can use the
10793 command @code{info sources} to find out which files these are. If you
10794 use @samp{maint print psymbols} instead, the dump shows information about
10795 symbols that @value{GDBN} only knows partially---that is, symbols defined in
10796 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
10797 @samp{maint print msymbols} dumps just the minimal symbol information
10798 required for each object file from which @value{GDBN} has read some symbols.
10799 @xref{Files, ,Commands to specify files}, for a discussion of how
10800 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
10802 @kindex maint info symtabs
10803 @kindex maint info psymtabs
10804 @cindex listing @value{GDBN}'s internal symbol tables
10805 @cindex symbol tables, listing @value{GDBN}'s internal
10806 @cindex full symbol tables, listing @value{GDBN}'s internal
10807 @cindex partial symbol tables, listing @value{GDBN}'s internal
10808 @item maint info symtabs @r{[} @var{regexp} @r{]}
10809 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
10811 List the @code{struct symtab} or @code{struct partial_symtab}
10812 structures whose names match @var{regexp}. If @var{regexp} is not
10813 given, list them all. The output includes expressions which you can
10814 copy into a @value{GDBN} debugging this one to examine a particular
10815 structure in more detail. For example:
10818 (@value{GDBP}) maint info psymtabs dwarf2read
10819 @{ objfile /home/gnu/build/gdb/gdb
10820 ((struct objfile *) 0x82e69d0)
10821 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
10822 ((struct partial_symtab *) 0x8474b10)
10825 text addresses 0x814d3c8 -- 0x8158074
10826 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
10827 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
10828 dependencies (none)
10831 (@value{GDBP}) maint info symtabs
10835 We see that there is one partial symbol table whose filename contains
10836 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
10837 and we see that @value{GDBN} has not read in any symtabs yet at all.
10838 If we set a breakpoint on a function, that will cause @value{GDBN} to
10839 read the symtab for the compilation unit containing that function:
10842 (@value{GDBP}) break dwarf2_psymtab_to_symtab
10843 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
10845 (@value{GDBP}) maint info symtabs
10846 @{ objfile /home/gnu/build/gdb/gdb
10847 ((struct objfile *) 0x82e69d0)
10848 @{ symtab /home/gnu/src/gdb/dwarf2read.c
10849 ((struct symtab *) 0x86c1f38)
10852 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
10853 debugformat DWARF 2
10862 @chapter Altering Execution
10864 Once you think you have found an error in your program, you might want to
10865 find out for certain whether correcting the apparent error would lead to
10866 correct results in the rest of the run. You can find the answer by
10867 experiment, using the @value{GDBN} features for altering execution of the
10870 For example, you can store new values into variables or memory
10871 locations, give your program a signal, restart it at a different
10872 address, or even return prematurely from a function.
10875 * Assignment:: Assignment to variables
10876 * Jumping:: Continuing at a different address
10877 * Signaling:: Giving your program a signal
10878 * Returning:: Returning from a function
10879 * Calling:: Calling your program's functions
10880 * Patching:: Patching your program
10884 @section Assignment to variables
10887 @cindex setting variables
10888 To alter the value of a variable, evaluate an assignment expression.
10889 @xref{Expressions, ,Expressions}. For example,
10896 stores the value 4 into the variable @code{x}, and then prints the
10897 value of the assignment expression (which is 4).
10898 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
10899 information on operators in supported languages.
10901 @kindex set variable
10902 @cindex variables, setting
10903 If you are not interested in seeing the value of the assignment, use the
10904 @code{set} command instead of the @code{print} command. @code{set} is
10905 really the same as @code{print} except that the expression's value is
10906 not printed and is not put in the value history (@pxref{Value History,
10907 ,Value history}). The expression is evaluated only for its effects.
10909 If the beginning of the argument string of the @code{set} command
10910 appears identical to a @code{set} subcommand, use the @code{set
10911 variable} command instead of just @code{set}. This command is identical
10912 to @code{set} except for its lack of subcommands. For example, if your
10913 program has a variable @code{width}, you get an error if you try to set
10914 a new value with just @samp{set width=13}, because @value{GDBN} has the
10915 command @code{set width}:
10918 (@value{GDBP}) whatis width
10920 (@value{GDBP}) p width
10922 (@value{GDBP}) set width=47
10923 Invalid syntax in expression.
10927 The invalid expression, of course, is @samp{=47}. In
10928 order to actually set the program's variable @code{width}, use
10931 (@value{GDBP}) set var width=47
10934 Because the @code{set} command has many subcommands that can conflict
10935 with the names of program variables, it is a good idea to use the
10936 @code{set variable} command instead of just @code{set}. For example, if
10937 your program has a variable @code{g}, you run into problems if you try
10938 to set a new value with just @samp{set g=4}, because @value{GDBN} has
10939 the command @code{set gnutarget}, abbreviated @code{set g}:
10943 (@value{GDBP}) whatis g
10947 (@value{GDBP}) set g=4
10951 The program being debugged has been started already.
10952 Start it from the beginning? (y or n) y
10953 Starting program: /home/smith/cc_progs/a.out
10954 "/home/smith/cc_progs/a.out": can't open to read symbols:
10955 Invalid bfd target.
10956 (@value{GDBP}) show g
10957 The current BFD target is "=4".
10962 The program variable @code{g} did not change, and you silently set the
10963 @code{gnutarget} to an invalid value. In order to set the variable
10967 (@value{GDBP}) set var g=4
10970 @value{GDBN} allows more implicit conversions in assignments than C; you can
10971 freely store an integer value into a pointer variable or vice versa,
10972 and you can convert any structure to any other structure that is the
10973 same length or shorter.
10974 @comment FIXME: how do structs align/pad in these conversions?
10975 @comment /doc@cygnus.com 18dec1990
10977 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
10978 construct to generate a value of specified type at a specified address
10979 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
10980 to memory location @code{0x83040} as an integer (which implies a certain size
10981 and representation in memory), and
10984 set @{int@}0x83040 = 4
10988 stores the value 4 into that memory location.
10991 @section Continuing at a different address
10993 Ordinarily, when you continue your program, you do so at the place where
10994 it stopped, with the @code{continue} command. You can instead continue at
10995 an address of your own choosing, with the following commands:
10999 @item jump @var{linespec}
11000 Resume execution at line @var{linespec}. Execution stops again
11001 immediately if there is a breakpoint there. @xref{List, ,Printing
11002 source lines}, for a description of the different forms of
11003 @var{linespec}. It is common practice to use the @code{tbreak} command
11004 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
11007 The @code{jump} command does not change the current stack frame, or
11008 the stack pointer, or the contents of any memory location or any
11009 register other than the program counter. If line @var{linespec} is in
11010 a different function from the one currently executing, the results may
11011 be bizarre if the two functions expect different patterns of arguments or
11012 of local variables. For this reason, the @code{jump} command requests
11013 confirmation if the specified line is not in the function currently
11014 executing. However, even bizarre results are predictable if you are
11015 well acquainted with the machine-language code of your program.
11017 @item jump *@var{address}
11018 Resume execution at the instruction at address @var{address}.
11021 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
11022 On many systems, you can get much the same effect as the @code{jump}
11023 command by storing a new value into the register @code{$pc}. The
11024 difference is that this does not start your program running; it only
11025 changes the address of where it @emph{will} run when you continue. For
11033 makes the next @code{continue} command or stepping command execute at
11034 address @code{0x485}, rather than at the address where your program stopped.
11035 @xref{Continuing and Stepping, ,Continuing and stepping}.
11037 The most common occasion to use the @code{jump} command is to back
11038 up---perhaps with more breakpoints set---over a portion of a program
11039 that has already executed, in order to examine its execution in more
11044 @section Giving your program a signal
11045 @cindex deliver a signal to a program
11049 @item signal @var{signal}
11050 Resume execution where your program stopped, but immediately give it the
11051 signal @var{signal}. @var{signal} can be the name or the number of a
11052 signal. For example, on many systems @code{signal 2} and @code{signal
11053 SIGINT} are both ways of sending an interrupt signal.
11055 Alternatively, if @var{signal} is zero, continue execution without
11056 giving a signal. This is useful when your program stopped on account of
11057 a signal and would ordinary see the signal when resumed with the
11058 @code{continue} command; @samp{signal 0} causes it to resume without a
11061 @code{signal} does not repeat when you press @key{RET} a second time
11062 after executing the command.
11066 Invoking the @code{signal} command is not the same as invoking the
11067 @code{kill} utility from the shell. Sending a signal with @code{kill}
11068 causes @value{GDBN} to decide what to do with the signal depending on
11069 the signal handling tables (@pxref{Signals}). The @code{signal} command
11070 passes the signal directly to your program.
11074 @section Returning from a function
11077 @cindex returning from a function
11080 @itemx return @var{expression}
11081 You can cancel execution of a function call with the @code{return}
11082 command. If you give an
11083 @var{expression} argument, its value is used as the function's return
11087 When you use @code{return}, @value{GDBN} discards the selected stack frame
11088 (and all frames within it). You can think of this as making the
11089 discarded frame return prematurely. If you wish to specify a value to
11090 be returned, give that value as the argument to @code{return}.
11092 This pops the selected stack frame (@pxref{Selection, ,Selecting a
11093 frame}), and any other frames inside of it, leaving its caller as the
11094 innermost remaining frame. That frame becomes selected. The
11095 specified value is stored in the registers used for returning values
11098 The @code{return} command does not resume execution; it leaves the
11099 program stopped in the state that would exist if the function had just
11100 returned. In contrast, the @code{finish} command (@pxref{Continuing
11101 and Stepping, ,Continuing and stepping}) resumes execution until the
11102 selected stack frame returns naturally.
11105 @section Calling program functions
11108 @cindex calling functions
11109 @cindex inferior functions, calling
11110 @item print @var{expr}
11111 Evaluate the expression @var{expr} and display the resuling value.
11112 @var{expr} may include calls to functions in the program being
11116 @item call @var{expr}
11117 Evaluate the expression @var{expr} without displaying @code{void}
11120 You can use this variant of the @code{print} command if you want to
11121 execute a function from your program that does not return anything
11122 (a.k.a.@: @dfn{a void function}), but without cluttering the output
11123 with @code{void} returned values that @value{GDBN} will otherwise
11124 print. If the result is not void, it is printed and saved in the
11128 It is possible for the function you call via the @code{print} or
11129 @code{call} command to generate a signal (e.g., if there's a bug in
11130 the function, or if you passed it incorrect arguments). What happens
11131 in that case is controlled by the @code{set unwindonsignal} command.
11134 @item set unwindonsignal
11135 @kindex set unwindonsignal
11136 @cindex unwind stack in called functions
11137 @cindex call dummy stack unwinding
11138 Set unwinding of the stack if a signal is received while in a function
11139 that @value{GDBN} called in the program being debugged. If set to on,
11140 @value{GDBN} unwinds the stack it created for the call and restores
11141 the context to what it was before the call. If set to off (the
11142 default), @value{GDBN} stops in the frame where the signal was
11145 @item show unwindonsignal
11146 @kindex show unwindonsignal
11147 Show the current setting of stack unwinding in the functions called by
11151 @cindex weak alias functions
11152 Sometimes, a function you wish to call is actually a @dfn{weak alias}
11153 for another function. In such case, @value{GDBN} might not pick up
11154 the type information, including the types of the function arguments,
11155 which causes @value{GDBN} to call the inferior function incorrectly.
11156 As a result, the called function will function erroneously and may
11157 even crash. A solution to that is to use the name of the aliased
11161 @section Patching programs
11163 @cindex patching binaries
11164 @cindex writing into executables
11165 @cindex writing into corefiles
11167 By default, @value{GDBN} opens the file containing your program's
11168 executable code (or the corefile) read-only. This prevents accidental
11169 alterations to machine code; but it also prevents you from intentionally
11170 patching your program's binary.
11172 If you'd like to be able to patch the binary, you can specify that
11173 explicitly with the @code{set write} command. For example, you might
11174 want to turn on internal debugging flags, or even to make emergency
11180 @itemx set write off
11181 If you specify @samp{set write on}, @value{GDBN} opens executable and
11182 core files for both reading and writing; if you specify @samp{set write
11183 off} (the default), @value{GDBN} opens them read-only.
11185 If you have already loaded a file, you must load it again (using the
11186 @code{exec-file} or @code{core-file} command) after changing @code{set
11187 write}, for your new setting to take effect.
11191 Display whether executable files and core files are opened for writing
11192 as well as reading.
11196 @chapter @value{GDBN} Files
11198 @value{GDBN} needs to know the file name of the program to be debugged,
11199 both in order to read its symbol table and in order to start your
11200 program. To debug a core dump of a previous run, you must also tell
11201 @value{GDBN} the name of the core dump file.
11204 * Files:: Commands to specify files
11205 * Separate Debug Files:: Debugging information in separate files
11206 * Symbol Errors:: Errors reading symbol files
11210 @section Commands to specify files
11212 @cindex symbol table
11213 @cindex core dump file
11215 You may want to specify executable and core dump file names. The usual
11216 way to do this is at start-up time, using the arguments to
11217 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
11218 Out of @value{GDBN}}).
11220 Occasionally it is necessary to change to a different file during a
11221 @value{GDBN} session. Or you may run @value{GDBN} and forget to
11222 specify a file you want to use. Or you are debugging a remote target
11223 via @code{gdbserver} (@pxref{Server, file}). In these situations the
11224 @value{GDBN} commands to specify new files are useful.
11227 @cindex executable file
11229 @item file @var{filename}
11230 Use @var{filename} as the program to be debugged. It is read for its
11231 symbols and for the contents of pure memory. It is also the program
11232 executed when you use the @code{run} command. If you do not specify a
11233 directory and the file is not found in the @value{GDBN} working directory,
11234 @value{GDBN} uses the environment variable @code{PATH} as a list of
11235 directories to search, just as the shell does when looking for a program
11236 to run. You can change the value of this variable, for both @value{GDBN}
11237 and your program, using the @code{path} command.
11239 @cindex unlinked object files
11240 @cindex patching object files
11241 You can load unlinked object @file{.o} files into @value{GDBN} using
11242 the @code{file} command. You will not be able to ``run'' an object
11243 file, but you can disassemble functions and inspect variables. Also,
11244 if the underlying BFD functionality supports it, you could use
11245 @kbd{gdb -write} to patch object files using this technique. Note
11246 that @value{GDBN} can neither interpret nor modify relocations in this
11247 case, so branches and some initialized variables will appear to go to
11248 the wrong place. But this feature is still handy from time to time.
11251 @code{file} with no argument makes @value{GDBN} discard any information it
11252 has on both executable file and the symbol table.
11255 @item exec-file @r{[} @var{filename} @r{]}
11256 Specify that the program to be run (but not the symbol table) is found
11257 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
11258 if necessary to locate your program. Omitting @var{filename} means to
11259 discard information on the executable file.
11261 @kindex symbol-file
11262 @item symbol-file @r{[} @var{filename} @r{]}
11263 Read symbol table information from file @var{filename}. @code{PATH} is
11264 searched when necessary. Use the @code{file} command to get both symbol
11265 table and program to run from the same file.
11267 @code{symbol-file} with no argument clears out @value{GDBN} information on your
11268 program's symbol table.
11270 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
11271 some breakpoints and auto-display expressions. This is because they may
11272 contain pointers to the internal data recording symbols and data types,
11273 which are part of the old symbol table data being discarded inside
11276 @code{symbol-file} does not repeat if you press @key{RET} again after
11279 When @value{GDBN} is configured for a particular environment, it
11280 understands debugging information in whatever format is the standard
11281 generated for that environment; you may use either a @sc{gnu} compiler, or
11282 other compilers that adhere to the local conventions.
11283 Best results are usually obtained from @sc{gnu} compilers; for example,
11284 using @code{@value{GCC}} you can generate debugging information for
11287 For most kinds of object files, with the exception of old SVR3 systems
11288 using COFF, the @code{symbol-file} command does not normally read the
11289 symbol table in full right away. Instead, it scans the symbol table
11290 quickly to find which source files and which symbols are present. The
11291 details are read later, one source file at a time, as they are needed.
11293 The purpose of this two-stage reading strategy is to make @value{GDBN}
11294 start up faster. For the most part, it is invisible except for
11295 occasional pauses while the symbol table details for a particular source
11296 file are being read. (The @code{set verbose} command can turn these
11297 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
11298 warnings and messages}.)
11300 We have not implemented the two-stage strategy for COFF yet. When the
11301 symbol table is stored in COFF format, @code{symbol-file} reads the
11302 symbol table data in full right away. Note that ``stabs-in-COFF''
11303 still does the two-stage strategy, since the debug info is actually
11307 @cindex reading symbols immediately
11308 @cindex symbols, reading immediately
11309 @item symbol-file @var{filename} @r{[} -readnow @r{]}
11310 @itemx file @var{filename} @r{[} -readnow @r{]}
11311 You can override the @value{GDBN} two-stage strategy for reading symbol
11312 tables by using the @samp{-readnow} option with any of the commands that
11313 load symbol table information, if you want to be sure @value{GDBN} has the
11314 entire symbol table available.
11316 @c FIXME: for now no mention of directories, since this seems to be in
11317 @c flux. 13mar1992 status is that in theory GDB would look either in
11318 @c current dir or in same dir as myprog; but issues like competing
11319 @c GDB's, or clutter in system dirs, mean that in practice right now
11320 @c only current dir is used. FFish says maybe a special GDB hierarchy
11321 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
11325 @item core-file @r{[}@var{filename}@r{]}
11327 Specify the whereabouts of a core dump file to be used as the ``contents
11328 of memory''. Traditionally, core files contain only some parts of the
11329 address space of the process that generated them; @value{GDBN} can access the
11330 executable file itself for other parts.
11332 @code{core-file} with no argument specifies that no core file is
11335 Note that the core file is ignored when your program is actually running
11336 under @value{GDBN}. So, if you have been running your program and you
11337 wish to debug a core file instead, you must kill the subprocess in which
11338 the program is running. To do this, use the @code{kill} command
11339 (@pxref{Kill Process, ,Killing the child process}).
11341 @kindex add-symbol-file
11342 @cindex dynamic linking
11343 @item add-symbol-file @var{filename} @var{address}
11344 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
11345 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
11346 The @code{add-symbol-file} command reads additional symbol table
11347 information from the file @var{filename}. You would use this command
11348 when @var{filename} has been dynamically loaded (by some other means)
11349 into the program that is running. @var{address} should be the memory
11350 address at which the file has been loaded; @value{GDBN} cannot figure
11351 this out for itself. You can additionally specify an arbitrary number
11352 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
11353 section name and base address for that section. You can specify any
11354 @var{address} as an expression.
11356 The symbol table of the file @var{filename} is added to the symbol table
11357 originally read with the @code{symbol-file} command. You can use the
11358 @code{add-symbol-file} command any number of times; the new symbol data
11359 thus read keeps adding to the old. To discard all old symbol data
11360 instead, use the @code{symbol-file} command without any arguments.
11362 @cindex relocatable object files, reading symbols from
11363 @cindex object files, relocatable, reading symbols from
11364 @cindex reading symbols from relocatable object files
11365 @cindex symbols, reading from relocatable object files
11366 @cindex @file{.o} files, reading symbols from
11367 Although @var{filename} is typically a shared library file, an
11368 executable file, or some other object file which has been fully
11369 relocated for loading into a process, you can also load symbolic
11370 information from relocatable @file{.o} files, as long as:
11374 the file's symbolic information refers only to linker symbols defined in
11375 that file, not to symbols defined by other object files,
11377 every section the file's symbolic information refers to has actually
11378 been loaded into the inferior, as it appears in the file, and
11380 you can determine the address at which every section was loaded, and
11381 provide these to the @code{add-symbol-file} command.
11385 Some embedded operating systems, like Sun Chorus and VxWorks, can load
11386 relocatable files into an already running program; such systems
11387 typically make the requirements above easy to meet. However, it's
11388 important to recognize that many native systems use complex link
11389 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
11390 assembly, for example) that make the requirements difficult to meet. In
11391 general, one cannot assume that using @code{add-symbol-file} to read a
11392 relocatable object file's symbolic information will have the same effect
11393 as linking the relocatable object file into the program in the normal
11396 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
11398 @kindex add-symbol-file-from-memory
11399 @cindex @code{syscall DSO}
11400 @cindex load symbols from memory
11401 @item add-symbol-file-from-memory @var{address}
11402 Load symbols from the given @var{address} in a dynamically loaded
11403 object file whose image is mapped directly into the inferior's memory.
11404 For example, the Linux kernel maps a @code{syscall DSO} into each
11405 process's address space; this DSO provides kernel-specific code for
11406 some system calls. The argument can be any expression whose
11407 evaluation yields the address of the file's shared object file header.
11408 For this command to work, you must have used @code{symbol-file} or
11409 @code{exec-file} commands in advance.
11411 @kindex add-shared-symbol-files
11413 @item add-shared-symbol-files @var{library-file}
11414 @itemx assf @var{library-file}
11415 The @code{add-shared-symbol-files} command can currently be used only
11416 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
11417 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
11418 @value{GDBN} automatically looks for shared libraries, however if
11419 @value{GDBN} does not find yours, you can invoke
11420 @code{add-shared-symbol-files}. It takes one argument: the shared
11421 library's file name. @code{assf} is a shorthand alias for
11422 @code{add-shared-symbol-files}.
11425 @item section @var{section} @var{addr}
11426 The @code{section} command changes the base address of the named
11427 @var{section} of the exec file to @var{addr}. This can be used if the
11428 exec file does not contain section addresses, (such as in the
11429 @code{a.out} format), or when the addresses specified in the file
11430 itself are wrong. Each section must be changed separately. The
11431 @code{info files} command, described below, lists all the sections and
11435 @kindex info target
11438 @code{info files} and @code{info target} are synonymous; both print the
11439 current target (@pxref{Targets, ,Specifying a Debugging Target}),
11440 including the names of the executable and core dump files currently in
11441 use by @value{GDBN}, and the files from which symbols were loaded. The
11442 command @code{help target} lists all possible targets rather than
11445 @kindex maint info sections
11446 @item maint info sections
11447 Another command that can give you extra information about program sections
11448 is @code{maint info sections}. In addition to the section information
11449 displayed by @code{info files}, this command displays the flags and file
11450 offset of each section in the executable and core dump files. In addition,
11451 @code{maint info sections} provides the following command options (which
11452 may be arbitrarily combined):
11456 Display sections for all loaded object files, including shared libraries.
11457 @item @var{sections}
11458 Display info only for named @var{sections}.
11459 @item @var{section-flags}
11460 Display info only for sections for which @var{section-flags} are true.
11461 The section flags that @value{GDBN} currently knows about are:
11464 Section will have space allocated in the process when loaded.
11465 Set for all sections except those containing debug information.
11467 Section will be loaded from the file into the child process memory.
11468 Set for pre-initialized code and data, clear for @code{.bss} sections.
11470 Section needs to be relocated before loading.
11472 Section cannot be modified by the child process.
11474 Section contains executable code only.
11476 Section contains data only (no executable code).
11478 Section will reside in ROM.
11480 Section contains data for constructor/destructor lists.
11482 Section is not empty.
11484 An instruction to the linker to not output the section.
11485 @item COFF_SHARED_LIBRARY
11486 A notification to the linker that the section contains
11487 COFF shared library information.
11489 Section contains common symbols.
11492 @kindex set trust-readonly-sections
11493 @cindex read-only sections
11494 @item set trust-readonly-sections on
11495 Tell @value{GDBN} that readonly sections in your object file
11496 really are read-only (i.e.@: that their contents will not change).
11497 In that case, @value{GDBN} can fetch values from these sections
11498 out of the object file, rather than from the target program.
11499 For some targets (notably embedded ones), this can be a significant
11500 enhancement to debugging performance.
11502 The default is off.
11504 @item set trust-readonly-sections off
11505 Tell @value{GDBN} not to trust readonly sections. This means that
11506 the contents of the section might change while the program is running,
11507 and must therefore be fetched from the target when needed.
11509 @item show trust-readonly-sections
11510 Show the current setting of trusting readonly sections.
11513 All file-specifying commands allow both absolute and relative file names
11514 as arguments. @value{GDBN} always converts the file name to an absolute file
11515 name and remembers it that way.
11517 @cindex shared libraries
11518 @value{GDBN} supports GNU/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
11519 and IBM RS/6000 AIX shared libraries.
11521 @value{GDBN} automatically loads symbol definitions from shared libraries
11522 when you use the @code{run} command, or when you examine a core file.
11523 (Before you issue the @code{run} command, @value{GDBN} does not understand
11524 references to a function in a shared library, however---unless you are
11525 debugging a core file).
11527 On HP-UX, if the program loads a library explicitly, @value{GDBN}
11528 automatically loads the symbols at the time of the @code{shl_load} call.
11530 @c FIXME: some @value{GDBN} release may permit some refs to undef
11531 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
11532 @c FIXME...lib; check this from time to time when updating manual
11534 There are times, however, when you may wish to not automatically load
11535 symbol definitions from shared libraries, such as when they are
11536 particularly large or there are many of them.
11538 To control the automatic loading of shared library symbols, use the
11542 @kindex set auto-solib-add
11543 @item set auto-solib-add @var{mode}
11544 If @var{mode} is @code{on}, symbols from all shared object libraries
11545 will be loaded automatically when the inferior begins execution, you
11546 attach to an independently started inferior, or when the dynamic linker
11547 informs @value{GDBN} that a new library has been loaded. If @var{mode}
11548 is @code{off}, symbols must be loaded manually, using the
11549 @code{sharedlibrary} command. The default value is @code{on}.
11551 @cindex memory used for symbol tables
11552 If your program uses lots of shared libraries with debug info that
11553 takes large amounts of memory, you can decrease the @value{GDBN}
11554 memory footprint by preventing it from automatically loading the
11555 symbols from shared libraries. To that end, type @kbd{set
11556 auto-solib-add off} before running the inferior, then load each
11557 library whose debug symbols you do need with @kbd{sharedlibrary
11558 @var{regexp}}, where @var{regexp} is a regular expresion that matches
11559 the libraries whose symbols you want to be loaded.
11561 @kindex show auto-solib-add
11562 @item show auto-solib-add
11563 Display the current autoloading mode.
11566 @cindex load shared library
11567 To explicitly load shared library symbols, use the @code{sharedlibrary}
11571 @kindex info sharedlibrary
11574 @itemx info sharedlibrary
11575 Print the names of the shared libraries which are currently loaded.
11577 @kindex sharedlibrary
11579 @item sharedlibrary @var{regex}
11580 @itemx share @var{regex}
11581 Load shared object library symbols for files matching a
11582 Unix regular expression.
11583 As with files loaded automatically, it only loads shared libraries
11584 required by your program for a core file or after typing @code{run}. If
11585 @var{regex} is omitted all shared libraries required by your program are
11588 @item nosharedlibrary
11589 @kindex nosharedlibrary
11590 @cindex unload symbols from shared libraries
11591 Unload all shared object library symbols. This discards all symbols
11592 that have been loaded from all shared libraries. Symbols from shared
11593 libraries that were loaded by explicit user requests are not
11597 Sometimes you may wish that @value{GDBN} stops and gives you control
11598 when any of shared library events happen. Use the @code{set
11599 stop-on-solib-events} command for this:
11602 @item set stop-on-solib-events
11603 @kindex set stop-on-solib-events
11604 This command controls whether @value{GDBN} should give you control
11605 when the dynamic linker notifies it about some shared library event.
11606 The most common event of interest is loading or unloading of a new
11609 @item show stop-on-solib-events
11610 @kindex show stop-on-solib-events
11611 Show whether @value{GDBN} stops and gives you control when shared
11612 library events happen.
11615 Shared libraries are also supported in many cross or remote debugging
11616 configurations. A copy of the target's libraries need to be present on the
11617 host system; they need to be the same as the target libraries, although the
11618 copies on the target can be stripped as long as the copies on the host are
11621 @cindex where to look for shared libraries
11622 For remote debugging, you need to tell @value{GDBN} where the target
11623 libraries are, so that it can load the correct copies---otherwise, it
11624 may try to load the host's libraries. @value{GDBN} has two variables
11625 to specify the search directories for target libraries.
11628 @cindex prefix for shared library file names
11629 @kindex set solib-absolute-prefix
11630 @item set solib-absolute-prefix @var{path}
11631 If this variable is set, @var{path} will be used as a prefix for any
11632 absolute shared library paths; many runtime loaders store the absolute
11633 paths to the shared library in the target program's memory. If you use
11634 @samp{solib-absolute-prefix} to find shared libraries, they need to be laid
11635 out in the same way that they are on the target, with e.g.@: a
11636 @file{/usr/lib} hierarchy under @var{path}.
11638 @cindex default value of @samp{solib-absolute-prefix}
11639 @cindex @samp{--with-sysroot}
11640 You can set the default value of @samp{solib-absolute-prefix} by using the
11641 configure-time @samp{--with-sysroot} option.
11643 @kindex show solib-absolute-prefix
11644 @item show solib-absolute-prefix
11645 Display the current shared library prefix.
11647 @kindex set solib-search-path
11648 @item set solib-search-path @var{path}
11649 If this variable is set, @var{path} is a colon-separated list of directories
11650 to search for shared libraries. @samp{solib-search-path} is used after
11651 @samp{solib-absolute-prefix} fails to locate the library, or if the path to
11652 the library is relative instead of absolute. If you want to use
11653 @samp{solib-search-path} instead of @samp{solib-absolute-prefix}, be sure to
11654 set @samp{solib-absolute-prefix} to a nonexistant directory to prevent
11655 @value{GDBN} from finding your host's libraries.
11657 @kindex show solib-search-path
11658 @item show solib-search-path
11659 Display the current shared library search path.
11663 @node Separate Debug Files
11664 @section Debugging Information in Separate Files
11665 @cindex separate debugging information files
11666 @cindex debugging information in separate files
11667 @cindex @file{.debug} subdirectories
11668 @cindex debugging information directory, global
11669 @cindex global debugging information directory
11671 @value{GDBN} allows you to put a program's debugging information in a
11672 file separate from the executable itself, in a way that allows
11673 @value{GDBN} to find and load the debugging information automatically.
11674 Since debugging information can be very large --- sometimes larger
11675 than the executable code itself --- some systems distribute debugging
11676 information for their executables in separate files, which users can
11677 install only when they need to debug a problem.
11679 If an executable's debugging information has been extracted to a
11680 separate file, the executable should contain a @dfn{debug link} giving
11681 the name of the debugging information file (with no directory
11682 components), and a checksum of its contents. (The exact form of a
11683 debug link is described below.) If the full name of the directory
11684 containing the executable is @var{execdir}, and the executable has a
11685 debug link that specifies the name @var{debugfile}, then @value{GDBN}
11686 will automatically search for the debugging information file in three
11691 the directory containing the executable file (that is, it will look
11692 for a file named @file{@var{execdir}/@var{debugfile}},
11694 a subdirectory of that directory named @file{.debug} (that is, the
11695 file @file{@var{execdir}/.debug/@var{debugfile}}, and
11697 a subdirectory of the global debug file directory that includes the
11698 executable's full path, and the name from the link (that is, the file
11699 @file{@var{globaldebugdir}/@var{execdir}/@var{debugfile}}, where
11700 @var{globaldebugdir} is the global debug file directory, and
11701 @var{execdir} has been turned into a relative path).
11704 @value{GDBN} checks under each of these names for a debugging
11705 information file whose checksum matches that given in the link, and
11706 reads the debugging information from the first one it finds.
11708 So, for example, if you ask @value{GDBN} to debug @file{/usr/bin/ls},
11709 which has a link containing the name @file{ls.debug}, and the global
11710 debug directory is @file{/usr/lib/debug}, then @value{GDBN} will look
11711 for debug information in @file{/usr/bin/ls.debug},
11712 @file{/usr/bin/.debug/ls.debug}, and
11713 @file{/usr/lib/debug/usr/bin/ls.debug}.
11715 You can set the global debugging info directory's name, and view the
11716 name @value{GDBN} is currently using.
11720 @kindex set debug-file-directory
11721 @item set debug-file-directory @var{directory}
11722 Set the directory which @value{GDBN} searches for separate debugging
11723 information files to @var{directory}.
11725 @kindex show debug-file-directory
11726 @item show debug-file-directory
11727 Show the directory @value{GDBN} searches for separate debugging
11732 @cindex @code{.gnu_debuglink} sections
11733 @cindex debug links
11734 A debug link is a special section of the executable file named
11735 @code{.gnu_debuglink}. The section must contain:
11739 A filename, with any leading directory components removed, followed by
11742 zero to three bytes of padding, as needed to reach the next four-byte
11743 boundary within the section, and
11745 a four-byte CRC checksum, stored in the same endianness used for the
11746 executable file itself. The checksum is computed on the debugging
11747 information file's full contents by the function given below, passing
11748 zero as the @var{crc} argument.
11751 Any executable file format can carry a debug link, as long as it can
11752 contain a section named @code{.gnu_debuglink} with the contents
11755 The debugging information file itself should be an ordinary
11756 executable, containing a full set of linker symbols, sections, and
11757 debugging information. The sections of the debugging information file
11758 should have the same names, addresses and sizes as the original file,
11759 but they need not contain any data --- much like a @code{.bss} section
11760 in an ordinary executable.
11762 As of December 2002, there is no standard GNU utility to produce
11763 separated executable / debugging information file pairs. Ulrich
11764 Drepper's @file{elfutils} package, starting with version 0.53,
11765 contains a version of the @code{strip} command such that the command
11766 @kbd{strip foo -f foo.debug} removes the debugging information from
11767 the executable file @file{foo}, places it in the file
11768 @file{foo.debug}, and leaves behind a debug link in @file{foo}.
11770 Since there are many different ways to compute CRC's (different
11771 polynomials, reversals, byte ordering, etc.), the simplest way to
11772 describe the CRC used in @code{.gnu_debuglink} sections is to give the
11773 complete code for a function that computes it:
11775 @kindex gnu_debuglink_crc32
11778 gnu_debuglink_crc32 (unsigned long crc,
11779 unsigned char *buf, size_t len)
11781 static const unsigned long crc32_table[256] =
11783 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
11784 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
11785 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
11786 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
11787 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
11788 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
11789 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
11790 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
11791 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
11792 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
11793 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
11794 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
11795 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
11796 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
11797 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
11798 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
11799 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
11800 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
11801 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
11802 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
11803 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
11804 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
11805 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
11806 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
11807 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
11808 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
11809 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
11810 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
11811 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
11812 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
11813 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
11814 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
11815 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
11816 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
11817 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
11818 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
11819 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
11820 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
11821 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
11822 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
11823 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
11824 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
11825 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
11826 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
11827 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
11828 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
11829 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
11830 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
11831 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
11832 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
11833 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
11836 unsigned char *end;
11838 crc = ~crc & 0xffffffff;
11839 for (end = buf + len; buf < end; ++buf)
11840 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
11841 return ~crc & 0xffffffff;
11846 @node Symbol Errors
11847 @section Errors reading symbol files
11849 While reading a symbol file, @value{GDBN} occasionally encounters problems,
11850 such as symbol types it does not recognize, or known bugs in compiler
11851 output. By default, @value{GDBN} does not notify you of such problems, since
11852 they are relatively common and primarily of interest to people
11853 debugging compilers. If you are interested in seeing information
11854 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
11855 only one message about each such type of problem, no matter how many
11856 times the problem occurs; or you can ask @value{GDBN} to print more messages,
11857 to see how many times the problems occur, with the @code{set
11858 complaints} command (@pxref{Messages/Warnings, ,Optional warnings and
11861 The messages currently printed, and their meanings, include:
11864 @item inner block not inside outer block in @var{symbol}
11866 The symbol information shows where symbol scopes begin and end
11867 (such as at the start of a function or a block of statements). This
11868 error indicates that an inner scope block is not fully contained
11869 in its outer scope blocks.
11871 @value{GDBN} circumvents the problem by treating the inner block as if it had
11872 the same scope as the outer block. In the error message, @var{symbol}
11873 may be shown as ``@code{(don't know)}'' if the outer block is not a
11876 @item block at @var{address} out of order
11878 The symbol information for symbol scope blocks should occur in
11879 order of increasing addresses. This error indicates that it does not
11882 @value{GDBN} does not circumvent this problem, and has trouble
11883 locating symbols in the source file whose symbols it is reading. (You
11884 can often determine what source file is affected by specifying
11885 @code{set verbose on}. @xref{Messages/Warnings, ,Optional warnings and
11888 @item bad block start address patched
11890 The symbol information for a symbol scope block has a start address
11891 smaller than the address of the preceding source line. This is known
11892 to occur in the SunOS 4.1.1 (and earlier) C compiler.
11894 @value{GDBN} circumvents the problem by treating the symbol scope block as
11895 starting on the previous source line.
11897 @item bad string table offset in symbol @var{n}
11900 Symbol number @var{n} contains a pointer into the string table which is
11901 larger than the size of the string table.
11903 @value{GDBN} circumvents the problem by considering the symbol to have the
11904 name @code{foo}, which may cause other problems if many symbols end up
11907 @item unknown symbol type @code{0x@var{nn}}
11909 The symbol information contains new data types that @value{GDBN} does
11910 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
11911 uncomprehended information, in hexadecimal.
11913 @value{GDBN} circumvents the error by ignoring this symbol information.
11914 This usually allows you to debug your program, though certain symbols
11915 are not accessible. If you encounter such a problem and feel like
11916 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
11917 on @code{complain}, then go up to the function @code{read_dbx_symtab}
11918 and examine @code{*bufp} to see the symbol.
11920 @item stub type has NULL name
11922 @value{GDBN} could not find the full definition for a struct or class.
11924 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
11925 The symbol information for a C@t{++} member function is missing some
11926 information that recent versions of the compiler should have output for
11929 @item info mismatch between compiler and debugger
11931 @value{GDBN} could not parse a type specification output by the compiler.
11936 @chapter Specifying a Debugging Target
11938 @cindex debugging target
11939 A @dfn{target} is the execution environment occupied by your program.
11941 Often, @value{GDBN} runs in the same host environment as your program;
11942 in that case, the debugging target is specified as a side effect when
11943 you use the @code{file} or @code{core} commands. When you need more
11944 flexibility---for example, running @value{GDBN} on a physically separate
11945 host, or controlling a standalone system over a serial port or a
11946 realtime system over a TCP/IP connection---you can use the @code{target}
11947 command to specify one of the target types configured for @value{GDBN}
11948 (@pxref{Target Commands, ,Commands for managing targets}).
11950 @cindex target architecture
11951 It is possible to build @value{GDBN} for several different @dfn{target
11952 architectures}. When @value{GDBN} is built like that, you can choose
11953 one of the available architectures with the @kbd{set architecture}
11957 @kindex set architecture
11958 @kindex show architecture
11959 @item set architecture @var{arch}
11960 This command sets the current target architecture to @var{arch}. The
11961 value of @var{arch} can be @code{"auto"}, in addition to one of the
11962 supported architectures.
11964 @item show architecture
11965 Show the current target architecture.
11967 @item set processor
11969 @kindex set processor
11970 @kindex show processor
11971 These are alias commands for, respectively, @code{set architecture}
11972 and @code{show architecture}.
11976 * Active Targets:: Active targets
11977 * Target Commands:: Commands for managing targets
11978 * Byte Order:: Choosing target byte order
11979 * Remote:: Remote debugging
11983 @node Active Targets
11984 @section Active targets
11986 @cindex stacking targets
11987 @cindex active targets
11988 @cindex multiple targets
11990 There are three classes of targets: processes, core files, and
11991 executable files. @value{GDBN} can work concurrently on up to three
11992 active targets, one in each class. This allows you to (for example)
11993 start a process and inspect its activity without abandoning your work on
11996 For example, if you execute @samp{gdb a.out}, then the executable file
11997 @code{a.out} is the only active target. If you designate a core file as
11998 well---presumably from a prior run that crashed and coredumped---then
11999 @value{GDBN} has two active targets and uses them in tandem, looking
12000 first in the corefile target, then in the executable file, to satisfy
12001 requests for memory addresses. (Typically, these two classes of target
12002 are complementary, since core files contain only a program's
12003 read-write memory---variables and so on---plus machine status, while
12004 executable files contain only the program text and initialized data.)
12006 When you type @code{run}, your executable file becomes an active process
12007 target as well. When a process target is active, all @value{GDBN}
12008 commands requesting memory addresses refer to that target; addresses in
12009 an active core file or executable file target are obscured while the
12010 process target is active.
12012 Use the @code{core-file} and @code{exec-file} commands to select a new
12013 core file or executable target (@pxref{Files, ,Commands to specify
12014 files}). To specify as a target a process that is already running, use
12015 the @code{attach} command (@pxref{Attach, ,Debugging an already-running
12018 @node Target Commands
12019 @section Commands for managing targets
12022 @item target @var{type} @var{parameters}
12023 Connects the @value{GDBN} host environment to a target machine or
12024 process. A target is typically a protocol for talking to debugging
12025 facilities. You use the argument @var{type} to specify the type or
12026 protocol of the target machine.
12028 Further @var{parameters} are interpreted by the target protocol, but
12029 typically include things like device names or host names to connect
12030 with, process numbers, and baud rates.
12032 The @code{target} command does not repeat if you press @key{RET} again
12033 after executing the command.
12035 @kindex help target
12037 Displays the names of all targets available. To display targets
12038 currently selected, use either @code{info target} or @code{info files}
12039 (@pxref{Files, ,Commands to specify files}).
12041 @item help target @var{name}
12042 Describe a particular target, including any parameters necessary to
12045 @kindex set gnutarget
12046 @item set gnutarget @var{args}
12047 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
12048 knows whether it is reading an @dfn{executable},
12049 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
12050 with the @code{set gnutarget} command. Unlike most @code{target} commands,
12051 with @code{gnutarget} the @code{target} refers to a program, not a machine.
12054 @emph{Warning:} To specify a file format with @code{set gnutarget},
12055 you must know the actual BFD name.
12059 @xref{Files, , Commands to specify files}.
12061 @kindex show gnutarget
12062 @item show gnutarget
12063 Use the @code{show gnutarget} command to display what file format
12064 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
12065 @value{GDBN} will determine the file format for each file automatically,
12066 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
12069 @cindex common targets
12070 Here are some common targets (available, or not, depending on the GDB
12075 @item target exec @var{program}
12076 @cindex executable file target
12077 An executable file. @samp{target exec @var{program}} is the same as
12078 @samp{exec-file @var{program}}.
12080 @item target core @var{filename}
12081 @cindex core dump file target
12082 A core dump file. @samp{target core @var{filename}} is the same as
12083 @samp{core-file @var{filename}}.
12085 @item target remote @var{medium}
12086 @cindex remote target
12087 A remote system connected to @value{GDBN} via a serial line or network
12088 connection. This command tells @value{GDBN} to use its own remote
12089 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
12091 For example, if you have a board connected to @file{/dev/ttya} on the
12092 machine running @value{GDBN}, you could say:
12095 target remote /dev/ttya
12098 @code{target remote} supports the @code{load} command. This is only
12099 useful if you have some other way of getting the stub to the target
12100 system, and you can put it somewhere in memory where it won't get
12101 clobbered by the download.
12104 @cindex built-in simulator target
12105 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
12113 works; however, you cannot assume that a specific memory map, device
12114 drivers, or even basic I/O is available, although some simulators do
12115 provide these. For info about any processor-specific simulator details,
12116 see the appropriate section in @ref{Embedded Processors, ,Embedded
12121 Some configurations may include these targets as well:
12125 @item target nrom @var{dev}
12126 @cindex NetROM ROM emulator target
12127 NetROM ROM emulator. This target only supports downloading.
12131 Different targets are available on different configurations of @value{GDBN};
12132 your configuration may have more or fewer targets.
12134 Many remote targets require you to download the executable's code once
12135 you've successfully established a connection. You may wish to control
12136 various aspects of this process.
12141 @kindex set hash@r{, for remote monitors}
12142 @cindex hash mark while downloading
12143 This command controls whether a hash mark @samp{#} is displayed while
12144 downloading a file to the remote monitor. If on, a hash mark is
12145 displayed after each S-record is successfully downloaded to the
12149 @kindex show hash@r{, for remote monitors}
12150 Show the current status of displaying the hash mark.
12152 @item set debug monitor
12153 @kindex set debug monitor
12154 @cindex display remote monitor communications
12155 Enable or disable display of communications messages between
12156 @value{GDBN} and the remote monitor.
12158 @item show debug monitor
12159 @kindex show debug monitor
12160 Show the current status of displaying communications between
12161 @value{GDBN} and the remote monitor.
12166 @kindex load @var{filename}
12167 @item load @var{filename}
12168 Depending on what remote debugging facilities are configured into
12169 @value{GDBN}, the @code{load} command may be available. Where it exists, it
12170 is meant to make @var{filename} (an executable) available for debugging
12171 on the remote system---by downloading, or dynamic linking, for example.
12172 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
12173 the @code{add-symbol-file} command.
12175 If your @value{GDBN} does not have a @code{load} command, attempting to
12176 execute it gets the error message ``@code{You can't do that when your
12177 target is @dots{}}''
12179 The file is loaded at whatever address is specified in the executable.
12180 For some object file formats, you can specify the load address when you
12181 link the program; for other formats, like a.out, the object file format
12182 specifies a fixed address.
12183 @c FIXME! This would be a good place for an xref to the GNU linker doc.
12185 @code{load} does not repeat if you press @key{RET} again after using it.
12189 @section Choosing target byte order
12191 @cindex choosing target byte order
12192 @cindex target byte order
12194 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
12195 offer the ability to run either big-endian or little-endian byte
12196 orders. Usually the executable or symbol will include a bit to
12197 designate the endian-ness, and you will not need to worry about
12198 which to use. However, you may still find it useful to adjust
12199 @value{GDBN}'s idea of processor endian-ness manually.
12203 @item set endian big
12204 Instruct @value{GDBN} to assume the target is big-endian.
12206 @item set endian little
12207 Instruct @value{GDBN} to assume the target is little-endian.
12209 @item set endian auto
12210 Instruct @value{GDBN} to use the byte order associated with the
12214 Display @value{GDBN}'s current idea of the target byte order.
12218 Note that these commands merely adjust interpretation of symbolic
12219 data on the host, and that they have absolutely no effect on the
12223 @section Remote debugging
12224 @cindex remote debugging
12226 If you are trying to debug a program running on a machine that cannot run
12227 @value{GDBN} in the usual way, it is often useful to use remote debugging.
12228 For example, you might use remote debugging on an operating system kernel,
12229 or on a small system which does not have a general purpose operating system
12230 powerful enough to run a full-featured debugger.
12232 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
12233 to make this work with particular debugging targets. In addition,
12234 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
12235 but not specific to any particular target system) which you can use if you
12236 write the remote stubs---the code that runs on the remote system to
12237 communicate with @value{GDBN}.
12239 Other remote targets may be available in your
12240 configuration of @value{GDBN}; use @code{help target} to list them.
12242 Once you've connected to the remote target, @value{GDBN} allows you to
12243 send arbitrary commands to the remote monitor:
12246 @item remote @var{command}
12247 @kindex remote@r{, a command}
12248 @cindex send command to remote monitor
12249 Send an arbitrary @var{command} string to the remote monitor.
12253 @node Remote Debugging
12254 @chapter Debugging remote programs
12257 * Connecting:: Connecting to a remote target
12258 * Server:: Using the gdbserver program
12259 * Remote configuration:: Remote configuration
12260 * remote stub:: Implementing a remote stub
12264 @section Connecting to a remote target
12266 On the @value{GDBN} host machine, you will need an unstripped copy of
12267 your program, since @value{GDBN} needs symobl and debugging information.
12268 Start up @value{GDBN} as usual, using the name of the local copy of your
12269 program as the first argument.
12271 @cindex @code{target remote}
12272 @value{GDBN} can communicate with the target over a serial line, or
12273 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
12274 each case, @value{GDBN} uses the same protocol for debugging your
12275 program; only the medium carrying the debugging packets varies. The
12276 @code{target remote} command establishes a connection to the target.
12277 Its arguments indicate which medium to use:
12281 @item target remote @var{serial-device}
12282 @cindex serial line, @code{target remote}
12283 Use @var{serial-device} to communicate with the target. For example,
12284 to use a serial line connected to the device named @file{/dev/ttyb}:
12287 target remote /dev/ttyb
12290 If you're using a serial line, you may want to give @value{GDBN} the
12291 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
12292 (@pxref{Remote configuration, set remotebaud}) before the
12293 @code{target} command.
12295 @item target remote @code{@var{host}:@var{port}}
12296 @itemx target remote @code{tcp:@var{host}:@var{port}}
12297 @cindex @acronym{TCP} port, @code{target remote}
12298 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
12299 The @var{host} may be either a host name or a numeric @acronym{IP}
12300 address; @var{port} must be a decimal number. The @var{host} could be
12301 the target machine itself, if it is directly connected to the net, or
12302 it might be a terminal server which in turn has a serial line to the
12305 For example, to connect to port 2828 on a terminal server named
12309 target remote manyfarms:2828
12312 If your remote target is actually running on the same machine as your
12313 debugger session (e.g.@: a simulator for your target running on the
12314 same host), you can omit the hostname. For example, to connect to
12315 port 1234 on your local machine:
12318 target remote :1234
12322 Note that the colon is still required here.
12324 @item target remote @code{udp:@var{host}:@var{port}}
12325 @cindex @acronym{UDP} port, @code{target remote}
12326 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
12327 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
12330 target remote udp:manyfarms:2828
12333 When using a @acronym{UDP} connection for remote debugging, you should
12334 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
12335 can silently drop packets on busy or unreliable networks, which will
12336 cause havoc with your debugging session.
12338 @item target remote | @var{command}
12339 @cindex pipe, @code{target remote} to
12340 Run @var{command} in the background and communicate with it using a
12341 pipe. The @var{command} is a shell command, to be parsed and expanded
12342 by the system's command shell, @code{/bin/sh}; it should expect remote
12343 protocol packets on its standard input, and send replies on its
12344 standard output. You could use this to run a stand-alone simulator
12345 that speaks the remote debugging protocol, to make net connections
12346 using programs like @code{ssh}, or for other similar tricks.
12348 If @var{command} closes its standard output (perhaps by exiting),
12349 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
12350 program has already exited, this will have no effect.)
12354 Once the connection has been established, you can use all the usual
12355 commands to examine and change data and to step and continue the
12358 @cindex interrupting remote programs
12359 @cindex remote programs, interrupting
12360 Whenever @value{GDBN} is waiting for the remote program, if you type the
12361 interrupt character (often @key{C-C}), @value{GDBN} attempts to stop the
12362 program. This may or may not succeed, depending in part on the hardware
12363 and the serial drivers the remote system uses. If you type the
12364 interrupt character once again, @value{GDBN} displays this prompt:
12367 Interrupted while waiting for the program.
12368 Give up (and stop debugging it)? (y or n)
12371 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
12372 (If you decide you want to try again later, you can use @samp{target
12373 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
12374 goes back to waiting.
12377 @kindex detach (remote)
12379 When you have finished debugging the remote program, you can use the
12380 @code{detach} command to release it from @value{GDBN} control.
12381 Detaching from the target normally resumes its execution, but the results
12382 will depend on your particular remote stub. After the @code{detach}
12383 command, @value{GDBN} is free to connect to another target.
12387 The @code{disconnect} command behaves like @code{detach}, except that
12388 the target is generally not resumed. It will wait for @value{GDBN}
12389 (this instance or another one) to connect and continue debugging. After
12390 the @code{disconnect} command, @value{GDBN} is again free to connect to
12393 @cindex send command to remote monitor
12394 @cindex extend @value{GDBN} for remote targets
12395 @cindex add new commands for external monitor
12397 @item monitor @var{cmd}
12398 This command allows you to send arbitrary commands directly to the
12399 remote monitor. Since @value{GDBN} doesn't care about the commands it
12400 sends like this, this command is the way to extend @value{GDBN}---you
12401 can add new commands that only the external monitor will understand
12406 @section Using the @code{gdbserver} program
12409 @cindex remote connection without stubs
12410 @code{gdbserver} is a control program for Unix-like systems, which
12411 allows you to connect your program with a remote @value{GDBN} via
12412 @code{target remote}---but without linking in the usual debugging stub.
12414 @code{gdbserver} is not a complete replacement for the debugging stubs,
12415 because it requires essentially the same operating-system facilities
12416 that @value{GDBN} itself does. In fact, a system that can run
12417 @code{gdbserver} to connect to a remote @value{GDBN} could also run
12418 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
12419 because it is a much smaller program than @value{GDBN} itself. It is
12420 also easier to port than all of @value{GDBN}, so you may be able to get
12421 started more quickly on a new system by using @code{gdbserver}.
12422 Finally, if you develop code for real-time systems, you may find that
12423 the tradeoffs involved in real-time operation make it more convenient to
12424 do as much development work as possible on another system, for example
12425 by cross-compiling. You can use @code{gdbserver} to make a similar
12426 choice for debugging.
12428 @value{GDBN} and @code{gdbserver} communicate via either a serial line
12429 or a TCP connection, using the standard @value{GDBN} remote serial
12433 @item On the target machine,
12434 you need to have a copy of the program you want to debug.
12435 @code{gdbserver} does not need your program's symbol table, so you can
12436 strip the program if necessary to save space. @value{GDBN} on the host
12437 system does all the symbol handling.
12439 To use the server, you must tell it how to communicate with @value{GDBN};
12440 the name of your program; and the arguments for your program. The usual
12444 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
12447 @var{comm} is either a device name (to use a serial line) or a TCP
12448 hostname and portnumber. For example, to debug Emacs with the argument
12449 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
12453 target> gdbserver /dev/com1 emacs foo.txt
12456 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
12459 To use a TCP connection instead of a serial line:
12462 target> gdbserver host:2345 emacs foo.txt
12465 The only difference from the previous example is the first argument,
12466 specifying that you are communicating with the host @value{GDBN} via
12467 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
12468 expect a TCP connection from machine @samp{host} to local TCP port 2345.
12469 (Currently, the @samp{host} part is ignored.) You can choose any number
12470 you want for the port number as long as it does not conflict with any
12471 TCP ports already in use on the target system (for example, @code{23} is
12472 reserved for @code{telnet}).@footnote{If you choose a port number that
12473 conflicts with another service, @code{gdbserver} prints an error message
12474 and exits.} You must use the same port number with the host @value{GDBN}
12475 @code{target remote} command.
12477 On some targets, @code{gdbserver} can also attach to running programs.
12478 This is accomplished via the @code{--attach} argument. The syntax is:
12481 target> gdbserver @var{comm} --attach @var{pid}
12484 @var{pid} is the process ID of a currently running process. It isn't necessary
12485 to point @code{gdbserver} at a binary for the running process.
12488 @cindex attach to a program by name
12489 You can debug processes by name instead of process ID if your target has the
12490 @code{pidof} utility:
12493 target> gdbserver @var{comm} --attach `pidof @var{PROGRAM}`
12496 In case more than one copy of @var{PROGRAM} is running, or @var{PROGRAM}
12497 has multiple threads, most versions of @code{pidof} support the
12498 @code{-s} option to only return the first process ID.
12500 @item On the host machine,
12501 connect to your target (@pxref{Connecting,,Connecting to a remote target}).
12502 For TCP connections, you must start up @code{gdbserver} prior to using
12503 the @code{target remote} command. Otherwise you may get an error whose
12504 text depends on the host system, but which usually looks something like
12505 @samp{Connection refused}. You don't need to use the @code{load}
12506 command in @value{GDBN} when using @code{gdbserver}, since the program is
12507 already on the target. However, if you want to load the symbols (as
12508 you normally would), do that with the @code{file} command, and issue
12509 it @emph{before} connecting to the server; otherwise, you will get an
12510 error message saying @code{"Program is already running"}, since the
12511 program is considered running after the connection.
12515 @node Remote configuration
12516 @section Remote configuration
12519 @kindex show remote
12520 This section documents the configuration options available when
12521 debugging remote programs. For the options related to the File I/O
12522 extensions of the remote protocol, see @ref{system,
12523 system-call-allowed}.
12526 @item set remoteaddresssize @var{bits}
12527 @cindex adress size for remote targets
12528 @cindex bits in remote address
12529 Set the maximum size of address in a memory packet to the specified
12530 number of bits. @value{GDBN} will mask off the address bits above
12531 that number, when it passes addresses to the remote target. The
12532 default value is the number of bits in the target's address.
12534 @item show remoteaddresssize
12535 Show the current value of remote address size in bits.
12537 @item set remotebaud @var{n}
12538 @cindex baud rate for remote targets
12539 Set the baud rate for the remote serial I/O to @var{n} baud. The
12540 value is used to set the speed of the serial port used for debugging
12543 @item show remotebaud
12544 Show the current speed of the remote connection.
12546 @item set remotebreak
12547 @cindex interrupt remote programs
12548 @cindex BREAK signal instead of Ctrl-C
12549 @anchor{set remotebreak}
12550 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
12551 when you press the @key{Ctrl-C} key to interrupt the program running
12552 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
12553 character instead. The default is off, since most remote systems
12554 expect to see @samp{Ctrl-C} as the interrupt signal.
12556 @item show remotebreak
12557 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
12558 interrupt the remote program.
12560 @item set remotedevice @var{device}
12561 @cindex serial port name
12562 Set the name of the serial port through which to communicate to the
12563 remote target to @var{device}. This is the device used by
12564 @value{GDBN} to open the serial communications line to the remote
12565 target. There's no default, so you must set a valid port name for the
12566 remote serial communications to work. (Some varieties of the
12567 @code{target} command accept the port name as part of their
12570 @item show remotedevice
12571 Show the current name of the serial port.
12573 @item set remotelogbase @var{base}
12574 Set the base (a.k.a.@: radix) of logging serial protocol
12575 communications to @var{base}. Supported values of @var{base} are:
12576 @code{ascii}, @code{octal}, and @code{hex}. The default is
12579 @item show remotelogbase
12580 Show the current setting of the radix for logging remote serial
12583 @item set remotelogfile @var{file}
12584 @cindex record serial communications on file
12585 Record remote serial communications on the named @var{file}. The
12586 default is not to record at all.
12588 @item show remotelogfile.
12589 Show the current setting of the file name on which to record the
12590 serial communications.
12592 @item set remotetimeout @var{num}
12593 @cindex timeout for serial communications
12594 @cindex remote timeout
12595 Set the timeout limit to wait for the remote target to respond to
12596 @var{num} seconds. The default is 2 seconds.
12598 @item show remotetimeout
12599 Show the current number of seconds to wait for the remote target
12602 @cindex limit hardware breakpoints and watchpoints
12603 @cindex remote target, limit break- and watchpoints
12604 @anchor{set remote hardware-watchpoint-limit}
12605 @anchor{set remote hardware-breakpoint-limit}
12606 @item set remote hardware-watchpoint-limit @var{limit}
12607 @itemx set remote hardware-breakpoint-limit @var{limit}
12608 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
12609 watchpoints. A limit of -1, the default, is treated as unlimited.
12611 @item set remote fetch-register-packet
12612 @itemx set remote set-register-packet
12613 @itemx set remote P-packet
12614 @itemx set remote p-packet
12616 @cindex fetch registers from remote targets
12617 @cindex set registers in remote targets
12618 Determine whether @value{GDBN} can set and fetch registers from the
12619 remote target using the @samp{P} packets. The default depends on the
12620 remote stub's support of the @samp{P} packets (@value{GDBN} queries
12621 the stub when this packet is first required).
12623 @item show remote fetch-register-packet
12624 @itemx show remote set-register-packet
12625 @itemx show remote P-packet
12626 @itemx show remote p-packet
12627 Show the current setting of using the @samp{P} packets for setting and
12628 fetching registers from the remote target.
12630 @cindex binary downloads
12632 @item set remote binary-download-packet
12633 @itemx set remote X-packet
12634 Determine whether @value{GDBN} sends downloads in binary mode using
12635 the @samp{X} packets. The default is on.
12637 @item show remote binary-download-packet
12638 @itemx show remote X-packet
12639 Show the current setting of using the @samp{X} packets for binary
12642 @item set remote read-aux-vector-packet
12643 @cindex auxiliary vector of remote target
12644 @cindex @code{auxv}, and remote targets
12645 Set the use of the remote protocol's @samp{qXfer:auxv:read} (target
12646 auxiliary vector) request. This request is used to fetch the
12647 remote target's @dfn{auxiliary vector}, see @ref{OS Information,
12648 Auxiliary Vector}. The default setting depends on the remote stub's
12649 support of this request (@value{GDBN} queries the stub when this
12650 request is first required). @xref{General Query Packets, qXfer}, for
12651 more information about this request.
12653 @item show remote read-aux-vector-packet
12654 Show the current setting of use of the @samp{qXfer:auxv:read} request.
12656 @item set remote symbol-lookup-packet
12657 @cindex remote symbol lookup request
12658 Set the use of the remote protocol's @samp{qSymbol} (target symbol
12659 lookup) request. This request is used to communicate symbol
12660 information to the remote target, e.g., whenever a new shared library
12661 is loaded by the remote (@pxref{Files, shared libraries}). The
12662 default setting depends on the remote stub's support of this request
12663 (@value{GDBN} queries the stub when this request is first required).
12664 @xref{General Query Packets, qSymbol}, for more information about this
12667 @item show remote symbol-lookup-packet
12668 Show the current setting of use of the @samp{qSymbol} request.
12670 @item set remote verbose-resume-packet
12671 @cindex resume remote target
12672 @cindex signal thread, and remote targets
12673 @cindex single-step thread, and remote targets
12674 @cindex thread-specific operations on remote targets
12675 Set the use of the remote protocol's @samp{vCont} (descriptive resume)
12676 request. This request is used to resume specific threads in the
12677 remote target, and to single-step or signal them. The default setting
12678 depends on the remote stub's support of this request (@value{GDBN}
12679 queries the stub when this request is first required). This setting
12680 affects debugging of multithreaded programs: if @samp{vCont} cannot be
12681 used, @value{GDBN} might be unable to single-step a specific thread,
12682 especially under @code{set scheduler-locking off}; it is also
12683 impossible to pause a specific thread. @xref{Packets, vCont}, for
12686 @item show remote verbose-resume-packet
12687 Show the current setting of use of the @samp{vCont} request
12689 @item set remote software-breakpoint-packet
12690 @itemx set remote hardware-breakpoint-packet
12691 @itemx set remote write-watchpoint-packet
12692 @itemx set remote read-watchpoint-packet
12693 @itemx set remote access-watchpoint-packet
12694 @itemx set remote Z-packet
12696 @cindex remote hardware breakpoints and watchpoints
12697 These commands enable or disable the use of @samp{Z} packets for
12698 setting breakpoints and watchpoints in the remote target. The default
12699 depends on the remote stub's support of the @samp{Z} packets
12700 (@value{GDBN} queries the stub when each packet is first required).
12701 The command @code{set remote Z-packet}, kept for back-compatibility,
12702 turns on or off all the features that require the use of @samp{Z}
12705 @item show remote software-breakpoint-packet
12706 @itemx show remote hardware-breakpoint-packet
12707 @itemx show remote write-watchpoint-packet
12708 @itemx show remote read-watchpoint-packet
12709 @itemx show remote access-watchpoint-packet
12710 @itemx show remote Z-packet
12711 Show the current setting of @samp{Z} packets usage.
12713 @item set remote get-thread-local-storage-address
12714 @kindex set remote get-thread-local-storage-address
12715 @cindex thread local storage of remote targets
12716 This command enables or disables the use of the @samp{qGetTLSAddr}
12717 (Get Thread Local Storage Address) request packet. The default
12718 depends on whether the remote stub supports this request.
12719 @xref{General Query Packets, qGetTLSAddr}, for more details about this
12722 @item show remote get-thread-local-storage-address
12723 @kindex show remote get-thread-local-storage-address
12724 Show the current setting of @samp{qGetTLSAddr} packet usage.
12726 @item set remote supported-packets
12727 @kindex set remote supported-packets
12728 @cindex query supported packets of remote targets
12729 This command enables or disables the use of the @samp{qSupported}
12730 request packet. @xref{General Query Packets, qSupported}, for more
12731 details about this packet. The default is to use @samp{qSupported}.
12733 @item show remote supported-packets
12734 @kindex show remote supported-packets
12735 Show the current setting of @samp{qSupported} packet usage.
12739 @section Implementing a remote stub
12741 @cindex debugging stub, example
12742 @cindex remote stub, example
12743 @cindex stub example, remote debugging
12744 The stub files provided with @value{GDBN} implement the target side of the
12745 communication protocol, and the @value{GDBN} side is implemented in the
12746 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
12747 these subroutines to communicate, and ignore the details. (If you're
12748 implementing your own stub file, you can still ignore the details: start
12749 with one of the existing stub files. @file{sparc-stub.c} is the best
12750 organized, and therefore the easiest to read.)
12752 @cindex remote serial debugging, overview
12753 To debug a program running on another machine (the debugging
12754 @dfn{target} machine), you must first arrange for all the usual
12755 prerequisites for the program to run by itself. For example, for a C
12760 A startup routine to set up the C runtime environment; these usually
12761 have a name like @file{crt0}. The startup routine may be supplied by
12762 your hardware supplier, or you may have to write your own.
12765 A C subroutine library to support your program's
12766 subroutine calls, notably managing input and output.
12769 A way of getting your program to the other machine---for example, a
12770 download program. These are often supplied by the hardware
12771 manufacturer, but you may have to write your own from hardware
12775 The next step is to arrange for your program to use a serial port to
12776 communicate with the machine where @value{GDBN} is running (the @dfn{host}
12777 machine). In general terms, the scheme looks like this:
12781 @value{GDBN} already understands how to use this protocol; when everything
12782 else is set up, you can simply use the @samp{target remote} command
12783 (@pxref{Targets,,Specifying a Debugging Target}).
12785 @item On the target,
12786 you must link with your program a few special-purpose subroutines that
12787 implement the @value{GDBN} remote serial protocol. The file containing these
12788 subroutines is called a @dfn{debugging stub}.
12790 On certain remote targets, you can use an auxiliary program
12791 @code{gdbserver} instead of linking a stub into your program.
12792 @xref{Server,,Using the @code{gdbserver} program}, for details.
12795 The debugging stub is specific to the architecture of the remote
12796 machine; for example, use @file{sparc-stub.c} to debug programs on
12799 @cindex remote serial stub list
12800 These working remote stubs are distributed with @value{GDBN}:
12805 @cindex @file{i386-stub.c}
12808 For Intel 386 and compatible architectures.
12811 @cindex @file{m68k-stub.c}
12812 @cindex Motorola 680x0
12814 For Motorola 680x0 architectures.
12817 @cindex @file{sh-stub.c}
12820 For Renesas SH architectures.
12823 @cindex @file{sparc-stub.c}
12825 For @sc{sparc} architectures.
12827 @item sparcl-stub.c
12828 @cindex @file{sparcl-stub.c}
12831 For Fujitsu @sc{sparclite} architectures.
12835 The @file{README} file in the @value{GDBN} distribution may list other
12836 recently added stubs.
12839 * Stub Contents:: What the stub can do for you
12840 * Bootstrapping:: What you must do for the stub
12841 * Debug Session:: Putting it all together
12844 @node Stub Contents
12845 @subsection What the stub can do for you
12847 @cindex remote serial stub
12848 The debugging stub for your architecture supplies these three
12852 @item set_debug_traps
12853 @findex set_debug_traps
12854 @cindex remote serial stub, initialization
12855 This routine arranges for @code{handle_exception} to run when your
12856 program stops. You must call this subroutine explicitly near the
12857 beginning of your program.
12859 @item handle_exception
12860 @findex handle_exception
12861 @cindex remote serial stub, main routine
12862 This is the central workhorse, but your program never calls it
12863 explicitly---the setup code arranges for @code{handle_exception} to
12864 run when a trap is triggered.
12866 @code{handle_exception} takes control when your program stops during
12867 execution (for example, on a breakpoint), and mediates communications
12868 with @value{GDBN} on the host machine. This is where the communications
12869 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
12870 representative on the target machine. It begins by sending summary
12871 information on the state of your program, then continues to execute,
12872 retrieving and transmitting any information @value{GDBN} needs, until you
12873 execute a @value{GDBN} command that makes your program resume; at that point,
12874 @code{handle_exception} returns control to your own code on the target
12878 @cindex @code{breakpoint} subroutine, remote
12879 Use this auxiliary subroutine to make your program contain a
12880 breakpoint. Depending on the particular situation, this may be the only
12881 way for @value{GDBN} to get control. For instance, if your target
12882 machine has some sort of interrupt button, you won't need to call this;
12883 pressing the interrupt button transfers control to
12884 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
12885 simply receiving characters on the serial port may also trigger a trap;
12886 again, in that situation, you don't need to call @code{breakpoint} from
12887 your own program---simply running @samp{target remote} from the host
12888 @value{GDBN} session gets control.
12890 Call @code{breakpoint} if none of these is true, or if you simply want
12891 to make certain your program stops at a predetermined point for the
12892 start of your debugging session.
12895 @node Bootstrapping
12896 @subsection What you must do for the stub
12898 @cindex remote stub, support routines
12899 The debugging stubs that come with @value{GDBN} are set up for a particular
12900 chip architecture, but they have no information about the rest of your
12901 debugging target machine.
12903 First of all you need to tell the stub how to communicate with the
12907 @item int getDebugChar()
12908 @findex getDebugChar
12909 Write this subroutine to read a single character from the serial port.
12910 It may be identical to @code{getchar} for your target system; a
12911 different name is used to allow you to distinguish the two if you wish.
12913 @item void putDebugChar(int)
12914 @findex putDebugChar
12915 Write this subroutine to write a single character to the serial port.
12916 It may be identical to @code{putchar} for your target system; a
12917 different name is used to allow you to distinguish the two if you wish.
12920 @cindex control C, and remote debugging
12921 @cindex interrupting remote targets
12922 If you want @value{GDBN} to be able to stop your program while it is
12923 running, you need to use an interrupt-driven serial driver, and arrange
12924 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
12925 character). That is the character which @value{GDBN} uses to tell the
12926 remote system to stop.
12928 Getting the debugging target to return the proper status to @value{GDBN}
12929 probably requires changes to the standard stub; one quick and dirty way
12930 is to just execute a breakpoint instruction (the ``dirty'' part is that
12931 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
12933 Other routines you need to supply are:
12936 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
12937 @findex exceptionHandler
12938 Write this function to install @var{exception_address} in the exception
12939 handling tables. You need to do this because the stub does not have any
12940 way of knowing what the exception handling tables on your target system
12941 are like (for example, the processor's table might be in @sc{rom},
12942 containing entries which point to a table in @sc{ram}).
12943 @var{exception_number} is the exception number which should be changed;
12944 its meaning is architecture-dependent (for example, different numbers
12945 might represent divide by zero, misaligned access, etc). When this
12946 exception occurs, control should be transferred directly to
12947 @var{exception_address}, and the processor state (stack, registers,
12948 and so on) should be just as it is when a processor exception occurs. So if
12949 you want to use a jump instruction to reach @var{exception_address}, it
12950 should be a simple jump, not a jump to subroutine.
12952 For the 386, @var{exception_address} should be installed as an interrupt
12953 gate so that interrupts are masked while the handler runs. The gate
12954 should be at privilege level 0 (the most privileged level). The
12955 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
12956 help from @code{exceptionHandler}.
12958 @item void flush_i_cache()
12959 @findex flush_i_cache
12960 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
12961 instruction cache, if any, on your target machine. If there is no
12962 instruction cache, this subroutine may be a no-op.
12964 On target machines that have instruction caches, @value{GDBN} requires this
12965 function to make certain that the state of your program is stable.
12969 You must also make sure this library routine is available:
12972 @item void *memset(void *, int, int)
12974 This is the standard library function @code{memset} that sets an area of
12975 memory to a known value. If you have one of the free versions of
12976 @code{libc.a}, @code{memset} can be found there; otherwise, you must
12977 either obtain it from your hardware manufacturer, or write your own.
12980 If you do not use the GNU C compiler, you may need other standard
12981 library subroutines as well; this varies from one stub to another,
12982 but in general the stubs are likely to use any of the common library
12983 subroutines which @code{@value{GCC}} generates as inline code.
12986 @node Debug Session
12987 @subsection Putting it all together
12989 @cindex remote serial debugging summary
12990 In summary, when your program is ready to debug, you must follow these
12995 Make sure you have defined the supporting low-level routines
12996 (@pxref{Bootstrapping,,What you must do for the stub}):
12998 @code{getDebugChar}, @code{putDebugChar},
12999 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
13003 Insert these lines near the top of your program:
13011 For the 680x0 stub only, you need to provide a variable called
13012 @code{exceptionHook}. Normally you just use:
13015 void (*exceptionHook)() = 0;
13019 but if before calling @code{set_debug_traps}, you set it to point to a
13020 function in your program, that function is called when
13021 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
13022 error). The function indicated by @code{exceptionHook} is called with
13023 one parameter: an @code{int} which is the exception number.
13026 Compile and link together: your program, the @value{GDBN} debugging stub for
13027 your target architecture, and the supporting subroutines.
13030 Make sure you have a serial connection between your target machine and
13031 the @value{GDBN} host, and identify the serial port on the host.
13034 @c The "remote" target now provides a `load' command, so we should
13035 @c document that. FIXME.
13036 Download your program to your target machine (or get it there by
13037 whatever means the manufacturer provides), and start it.
13040 Start @value{GDBN} on the host, and connect to the target
13041 (@pxref{Connecting,,Connecting to a remote target}).
13045 @node Configurations
13046 @chapter Configuration-Specific Information
13048 While nearly all @value{GDBN} commands are available for all native and
13049 cross versions of the debugger, there are some exceptions. This chapter
13050 describes things that are only available in certain configurations.
13052 There are three major categories of configurations: native
13053 configurations, where the host and target are the same, embedded
13054 operating system configurations, which are usually the same for several
13055 different processor architectures, and bare embedded processors, which
13056 are quite different from each other.
13061 * Embedded Processors::
13068 This section describes details specific to particular native
13073 * BSD libkvm Interface:: Debugging BSD kernel memory images
13074 * SVR4 Process Information:: SVR4 process information
13075 * DJGPP Native:: Features specific to the DJGPP port
13076 * Cygwin Native:: Features specific to the Cygwin port
13077 * Hurd Native:: Features specific to @sc{gnu} Hurd
13078 * Neutrino:: Features specific to QNX Neutrino
13084 On HP-UX systems, if you refer to a function or variable name that
13085 begins with a dollar sign, @value{GDBN} searches for a user or system
13086 name first, before it searches for a convenience variable.
13089 @node BSD libkvm Interface
13090 @subsection BSD libkvm Interface
13093 @cindex kernel memory image
13094 @cindex kernel crash dump
13096 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
13097 interface that provides a uniform interface for accessing kernel virtual
13098 memory images, including live systems and crash dumps. @value{GDBN}
13099 uses this interface to allow you to debug live kernels and kernel crash
13100 dumps on many native BSD configurations. This is implemented as a
13101 special @code{kvm} debugging target. For debugging a live system, load
13102 the currently running kernel into @value{GDBN} and connect to the
13106 (@value{GDBP}) @b{target kvm}
13109 For debugging crash dumps, provide the file name of the crash dump as an
13113 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
13116 Once connected to the @code{kvm} target, the following commands are
13122 Set current context from the @dfn{Process Control Block} (PCB) address.
13125 Set current context from proc address. This command isn't available on
13126 modern FreeBSD systems.
13129 @node SVR4 Process Information
13130 @subsection SVR4 process information
13132 @cindex examine process image
13133 @cindex process info via @file{/proc}
13135 Many versions of SVR4 and compatible systems provide a facility called
13136 @samp{/proc} that can be used to examine the image of a running
13137 process using file-system subroutines. If @value{GDBN} is configured
13138 for an operating system with this facility, the command @code{info
13139 proc} is available to report information about the process running
13140 your program, or about any process running on your system. @code{info
13141 proc} works only on SVR4 systems that include the @code{procfs} code.
13142 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
13143 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
13149 @itemx info proc @var{process-id}
13150 Summarize available information about any running process. If a
13151 process ID is specified by @var{process-id}, display information about
13152 that process; otherwise display information about the program being
13153 debugged. The summary includes the debugged process ID, the command
13154 line used to invoke it, its current working directory, and its
13155 executable file's absolute file name.
13157 On some systems, @var{process-id} can be of the form
13158 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
13159 within a process. If the optional @var{pid} part is missing, it means
13160 a thread from the process being debugged (the leading @samp{/} still
13161 needs to be present, or else @value{GDBN} will interpret the number as
13162 a process ID rather than a thread ID).
13164 @item info proc mappings
13165 @cindex memory address space mappings
13166 Report the memory address space ranges accessible in the program, with
13167 information on whether the process has read, write, or execute access
13168 rights to each range. On @sc{gnu}/Linux systems, each memory range
13169 includes the object file which is mapped to that range, instead of the
13170 memory access rights to that range.
13172 @item info proc stat
13173 @itemx info proc status
13174 @cindex process detailed status information
13175 These subcommands are specific to @sc{gnu}/Linux systems. They show
13176 the process-related information, including the user ID and group ID;
13177 how many threads are there in the process; its virtual memory usage;
13178 the signals that are pending, blocked, and ignored; its TTY; its
13179 consumption of system and user time; its stack size; its @samp{nice}
13180 value; etc. For more information, see the @samp{proc} man page
13181 (type @kbd{man 5 proc} from your shell prompt).
13183 @item info proc all
13184 Show all the information about the process described under all of the
13185 above @code{info proc} subcommands.
13188 @comment These sub-options of 'info proc' were not included when
13189 @comment procfs.c was re-written. Keep their descriptions around
13190 @comment against the day when someone finds the time to put them back in.
13191 @kindex info proc times
13192 @item info proc times
13193 Starting time, user CPU time, and system CPU time for your program and
13196 @kindex info proc id
13198 Report on the process IDs related to your program: its own process ID,
13199 the ID of its parent, the process group ID, and the session ID.
13202 @item set procfs-trace
13203 @kindex set procfs-trace
13204 @cindex @code{procfs} API calls
13205 This command enables and disables tracing of @code{procfs} API calls.
13207 @item show procfs-trace
13208 @kindex show procfs-trace
13209 Show the current state of @code{procfs} API call tracing.
13211 @item set procfs-file @var{file}
13212 @kindex set procfs-file
13213 Tell @value{GDBN} to write @code{procfs} API trace to the named
13214 @var{file}. @value{GDBN} appends the trace info to the previous
13215 contents of the file. The default is to display the trace on the
13218 @item show procfs-file
13219 @kindex show procfs-file
13220 Show the file to which @code{procfs} API trace is written.
13222 @item proc-trace-entry
13223 @itemx proc-trace-exit
13224 @itemx proc-untrace-entry
13225 @itemx proc-untrace-exit
13226 @kindex proc-trace-entry
13227 @kindex proc-trace-exit
13228 @kindex proc-untrace-entry
13229 @kindex proc-untrace-exit
13230 These commands enable and disable tracing of entries into and exits
13231 from the @code{syscall} interface.
13234 @kindex info pidlist
13235 @cindex process list, QNX Neutrino
13236 For QNX Neutrino only, this command displays the list of all the
13237 processes and all the threads within each process.
13240 @kindex info meminfo
13241 @cindex mapinfo list, QNX Neutrino
13242 For QNX Neutrino only, this command displays the list of all mapinfos.
13246 @subsection Features for Debugging @sc{djgpp} Programs
13247 @cindex @sc{djgpp} debugging
13248 @cindex native @sc{djgpp} debugging
13249 @cindex MS-DOS-specific commands
13252 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
13253 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
13254 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
13255 top of real-mode DOS systems and their emulations.
13257 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
13258 defines a few commands specific to the @sc{djgpp} port. This
13259 subsection describes those commands.
13264 This is a prefix of @sc{djgpp}-specific commands which print
13265 information about the target system and important OS structures.
13268 @cindex MS-DOS system info
13269 @cindex free memory information (MS-DOS)
13270 @item info dos sysinfo
13271 This command displays assorted information about the underlying
13272 platform: the CPU type and features, the OS version and flavor, the
13273 DPMI version, and the available conventional and DPMI memory.
13278 @cindex segment descriptor tables
13279 @cindex descriptor tables display
13281 @itemx info dos ldt
13282 @itemx info dos idt
13283 These 3 commands display entries from, respectively, Global, Local,
13284 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
13285 tables are data structures which store a descriptor for each segment
13286 that is currently in use. The segment's selector is an index into a
13287 descriptor table; the table entry for that index holds the
13288 descriptor's base address and limit, and its attributes and access
13291 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
13292 segment (used for both data and the stack), and a DOS segment (which
13293 allows access to DOS/BIOS data structures and absolute addresses in
13294 conventional memory). However, the DPMI host will usually define
13295 additional segments in order to support the DPMI environment.
13297 @cindex garbled pointers
13298 These commands allow to display entries from the descriptor tables.
13299 Without an argument, all entries from the specified table are
13300 displayed. An argument, which should be an integer expression, means
13301 display a single entry whose index is given by the argument. For
13302 example, here's a convenient way to display information about the
13303 debugged program's data segment:
13306 @exdent @code{(@value{GDBP}) info dos ldt $ds}
13307 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
13311 This comes in handy when you want to see whether a pointer is outside
13312 the data segment's limit (i.e.@: @dfn{garbled}).
13314 @cindex page tables display (MS-DOS)
13316 @itemx info dos pte
13317 These two commands display entries from, respectively, the Page
13318 Directory and the Page Tables. Page Directories and Page Tables are
13319 data structures which control how virtual memory addresses are mapped
13320 into physical addresses. A Page Table includes an entry for every
13321 page of memory that is mapped into the program's address space; there
13322 may be several Page Tables, each one holding up to 4096 entries. A
13323 Page Directory has up to 4096 entries, one each for every Page Table
13324 that is currently in use.
13326 Without an argument, @kbd{info dos pde} displays the entire Page
13327 Directory, and @kbd{info dos pte} displays all the entries in all of
13328 the Page Tables. An argument, an integer expression, given to the
13329 @kbd{info dos pde} command means display only that entry from the Page
13330 Directory table. An argument given to the @kbd{info dos pte} command
13331 means display entries from a single Page Table, the one pointed to by
13332 the specified entry in the Page Directory.
13334 @cindex direct memory access (DMA) on MS-DOS
13335 These commands are useful when your program uses @dfn{DMA} (Direct
13336 Memory Access), which needs physical addresses to program the DMA
13339 These commands are supported only with some DPMI servers.
13341 @cindex physical address from linear address
13342 @item info dos address-pte @var{addr}
13343 This command displays the Page Table entry for a specified linear
13344 address. The argument @var{addr} is a linear address which should
13345 already have the appropriate segment's base address added to it,
13346 because this command accepts addresses which may belong to @emph{any}
13347 segment. For example, here's how to display the Page Table entry for
13348 the page where a variable @code{i} is stored:
13351 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
13352 @exdent @code{Page Table entry for address 0x11a00d30:}
13353 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
13357 This says that @code{i} is stored at offset @code{0xd30} from the page
13358 whose physical base address is @code{0x02698000}, and shows all the
13359 attributes of that page.
13361 Note that you must cast the addresses of variables to a @code{char *},
13362 since otherwise the value of @code{__djgpp_base_address}, the base
13363 address of all variables and functions in a @sc{djgpp} program, will
13364 be added using the rules of C pointer arithmetics: if @code{i} is
13365 declared an @code{int}, @value{GDBN} will add 4 times the value of
13366 @code{__djgpp_base_address} to the address of @code{i}.
13368 Here's another example, it displays the Page Table entry for the
13372 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
13373 @exdent @code{Page Table entry for address 0x29110:}
13374 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
13378 (The @code{+ 3} offset is because the transfer buffer's address is the
13379 3rd member of the @code{_go32_info_block} structure.) The output
13380 clearly shows that this DPMI server maps the addresses in conventional
13381 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
13382 linear (@code{0x29110}) addresses are identical.
13384 This command is supported only with some DPMI servers.
13387 @cindex DOS serial data link, remote debugging
13388 In addition to native debugging, the DJGPP port supports remote
13389 debugging via a serial data link. The following commands are specific
13390 to remote serial debugging in the DJGPP port of @value{GDBN}.
13393 @kindex set com1base
13394 @kindex set com1irq
13395 @kindex set com2base
13396 @kindex set com2irq
13397 @kindex set com3base
13398 @kindex set com3irq
13399 @kindex set com4base
13400 @kindex set com4irq
13401 @item set com1base @var{addr}
13402 This command sets the base I/O port address of the @file{COM1} serial
13405 @item set com1irq @var{irq}
13406 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
13407 for the @file{COM1} serial port.
13409 There are similar commands @samp{set com2base}, @samp{set com3irq},
13410 etc.@: for setting the port address and the @code{IRQ} lines for the
13413 @kindex show com1base
13414 @kindex show com1irq
13415 @kindex show com2base
13416 @kindex show com2irq
13417 @kindex show com3base
13418 @kindex show com3irq
13419 @kindex show com4base
13420 @kindex show com4irq
13421 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
13422 display the current settings of the base address and the @code{IRQ}
13423 lines used by the COM ports.
13426 @kindex info serial
13427 @cindex DOS serial port status
13428 This command prints the status of the 4 DOS serial ports. For each
13429 port, it prints whether it's active or not, its I/O base address and
13430 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
13431 counts of various errors encountered so far.
13435 @node Cygwin Native
13436 @subsection Features for Debugging MS Windows PE executables
13437 @cindex MS Windows debugging
13438 @cindex native Cygwin debugging
13439 @cindex Cygwin-specific commands
13441 @value{GDBN} supports native debugging of MS Windows programs, including
13442 DLLs with and without symbolic debugging information. There are various
13443 additional Cygwin-specific commands, described in this subsection. The
13444 subsubsection @pxref{Non-debug DLL symbols} describes working with DLLs
13445 that have no debugging symbols.
13451 This is a prefix of MS Windows specific commands which print
13452 information about the target system and important OS structures.
13454 @item info w32 selector
13455 This command displays information returned by
13456 the Win32 API @code{GetThreadSelectorEntry} function.
13457 It takes an optional argument that is evaluated to
13458 a long value to give the information about this given selector.
13459 Without argument, this command displays information
13460 about the the six segment registers.
13464 This is a Cygwin specific alias of info shared.
13466 @kindex dll-symbols
13468 This command loads symbols from a dll similarly to
13469 add-sym command but without the need to specify a base address.
13471 @kindex set cygwin-exceptions
13472 @cindex debugging the Cygwin DLL
13473 @cindex Cygwin DLL, debugging
13474 @item set cygwin-exceptions @var{mode}
13475 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
13476 happen inside the Cygwin DLL. If @var{mode} is @code{off},
13477 @value{GDBN} will delay recognition of exceptions, and may ignore some
13478 exceptions which seem to be caused by internal Cygwin DLL
13479 ``bookkeeping''. This option is meant primarily for debugging the
13480 Cygwin DLL itself; the default value is @code{off} to avoid annoying
13481 @value{GDBN} users with false @code{SIGSEGV} signals.
13483 @kindex show cygwin-exceptions
13484 @item show cygwin-exceptions
13485 Displays whether @value{GDBN} will break on exceptions that happen
13486 inside the Cygwin DLL itself.
13488 @kindex set new-console
13489 @item set new-console @var{mode}
13490 If @var{mode} is @code{on} the debuggee will
13491 be started in a new console on next start.
13492 If @var{mode} is @code{off}i, the debuggee will
13493 be started in the same console as the debugger.
13495 @kindex show new-console
13496 @item show new-console
13497 Displays whether a new console is used
13498 when the debuggee is started.
13500 @kindex set new-group
13501 @item set new-group @var{mode}
13502 This boolean value controls whether the debuggee should
13503 start a new group or stay in the same group as the debugger.
13504 This affects the way the Windows OS handles
13507 @kindex show new-group
13508 @item show new-group
13509 Displays current value of new-group boolean.
13511 @kindex set debugevents
13512 @item set debugevents
13513 This boolean value adds debug output concerning kernel events related
13514 to the debuggee seen by the debugger. This includes events that
13515 signal thread and process creation and exit, DLL loading and
13516 unloading, console interrupts, and debugging messages produced by the
13517 Windows @code{OutputDebugString} API call.
13519 @kindex set debugexec
13520 @item set debugexec
13521 This boolean value adds debug output concerning execute events
13522 (such as resume thread) seen by the debugger.
13524 @kindex set debugexceptions
13525 @item set debugexceptions
13526 This boolean value adds debug output concerning exceptions in the
13527 debuggee seen by the debugger.
13529 @kindex set debugmemory
13530 @item set debugmemory
13531 This boolean value adds debug output concerning debuggee memory reads
13532 and writes by the debugger.
13536 This boolean values specifies whether the debuggee is called
13537 via a shell or directly (default value is on).
13541 Displays if the debuggee will be started with a shell.
13546 * Non-debug DLL symbols:: Support for DLLs without debugging symbols
13549 @node Non-debug DLL symbols
13550 @subsubsection Support for DLLs without debugging symbols
13551 @cindex DLLs with no debugging symbols
13552 @cindex Minimal symbols and DLLs
13554 Very often on windows, some of the DLLs that your program relies on do
13555 not include symbolic debugging information (for example,
13556 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
13557 symbols in a DLL, it relies on the minimal amount of symbolic
13558 information contained in the DLL's export table. This subsubsection
13559 describes working with such symbols, known internally to @value{GDBN} as
13560 ``minimal symbols''.
13562 Note that before the debugged program has started execution, no DLLs
13563 will have been loaded. The easiest way around this problem is simply to
13564 start the program --- either by setting a breakpoint or letting the
13565 program run once to completion. It is also possible to force
13566 @value{GDBN} to load a particular DLL before starting the executable ---
13567 see the shared library information in @pxref{Files} or the
13568 @code{dll-symbols} command in @pxref{Cygwin Native}. Currently,
13569 explicitly loading symbols from a DLL with no debugging information will
13570 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
13571 which may adversely affect symbol lookup performance.
13573 @subsubsection DLL name prefixes
13575 In keeping with the naming conventions used by the Microsoft debugging
13576 tools, DLL export symbols are made available with a prefix based on the
13577 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
13578 also entered into the symbol table, so @code{CreateFileA} is often
13579 sufficient. In some cases there will be name clashes within a program
13580 (particularly if the executable itself includes full debugging symbols)
13581 necessitating the use of the fully qualified name when referring to the
13582 contents of the DLL. Use single-quotes around the name to avoid the
13583 exclamation mark (``!'') being interpreted as a language operator.
13585 Note that the internal name of the DLL may be all upper-case, even
13586 though the file name of the DLL is lower-case, or vice-versa. Since
13587 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
13588 some confusion. If in doubt, try the @code{info functions} and
13589 @code{info variables} commands or even @code{maint print msymbols} (see
13590 @pxref{Symbols}). Here's an example:
13593 (@value{GDBP}) info function CreateFileA
13594 All functions matching regular expression "CreateFileA":
13596 Non-debugging symbols:
13597 0x77e885f4 CreateFileA
13598 0x77e885f4 KERNEL32!CreateFileA
13602 (@value{GDBP}) info function !
13603 All functions matching regular expression "!":
13605 Non-debugging symbols:
13606 0x6100114c cygwin1!__assert
13607 0x61004034 cygwin1!_dll_crt0@@0
13608 0x61004240 cygwin1!dll_crt0(per_process *)
13612 @subsubsection Working with minimal symbols
13614 Symbols extracted from a DLL's export table do not contain very much
13615 type information. All that @value{GDBN} can do is guess whether a symbol
13616 refers to a function or variable depending on the linker section that
13617 contains the symbol. Also note that the actual contents of the memory
13618 contained in a DLL are not available unless the program is running. This
13619 means that you cannot examine the contents of a variable or disassemble
13620 a function within a DLL without a running program.
13622 Variables are generally treated as pointers and dereferenced
13623 automatically. For this reason, it is often necessary to prefix a
13624 variable name with the address-of operator (``&'') and provide explicit
13625 type information in the command. Here's an example of the type of
13629 (@value{GDBP}) print 'cygwin1!__argv'
13634 (@value{GDBP}) x 'cygwin1!__argv'
13635 0x10021610: "\230y\""
13638 And two possible solutions:
13641 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
13642 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
13646 (@value{GDBP}) x/2x &'cygwin1!__argv'
13647 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
13648 (@value{GDBP}) x/x 0x10021608
13649 0x10021608: 0x0022fd98
13650 (@value{GDBP}) x/s 0x0022fd98
13651 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
13654 Setting a break point within a DLL is possible even before the program
13655 starts execution. However, under these circumstances, @value{GDBN} can't
13656 examine the initial instructions of the function in order to skip the
13657 function's frame set-up code. You can work around this by using ``*&''
13658 to set the breakpoint at a raw memory address:
13661 (@value{GDBP}) break *&'python22!PyOS_Readline'
13662 Breakpoint 1 at 0x1e04eff0
13665 The author of these extensions is not entirely convinced that setting a
13666 break point within a shared DLL like @file{kernel32.dll} is completely
13670 @subsection Commands specific to @sc{gnu} Hurd systems
13671 @cindex @sc{gnu} Hurd debugging
13673 This subsection describes @value{GDBN} commands specific to the
13674 @sc{gnu} Hurd native debugging.
13679 @kindex set signals@r{, Hurd command}
13680 @kindex set sigs@r{, Hurd command}
13681 This command toggles the state of inferior signal interception by
13682 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
13683 affected by this command. @code{sigs} is a shorthand alias for
13688 @kindex show signals@r{, Hurd command}
13689 @kindex show sigs@r{, Hurd command}
13690 Show the current state of intercepting inferior's signals.
13692 @item set signal-thread
13693 @itemx set sigthread
13694 @kindex set signal-thread
13695 @kindex set sigthread
13696 This command tells @value{GDBN} which thread is the @code{libc} signal
13697 thread. That thread is run when a signal is delivered to a running
13698 process. @code{set sigthread} is the shorthand alias of @code{set
13701 @item show signal-thread
13702 @itemx show sigthread
13703 @kindex show signal-thread
13704 @kindex show sigthread
13705 These two commands show which thread will run when the inferior is
13706 delivered a signal.
13709 @kindex set stopped@r{, Hurd command}
13710 This commands tells @value{GDBN} that the inferior process is stopped,
13711 as with the @code{SIGSTOP} signal. The stopped process can be
13712 continued by delivering a signal to it.
13715 @kindex show stopped@r{, Hurd command}
13716 This command shows whether @value{GDBN} thinks the debuggee is
13719 @item set exceptions
13720 @kindex set exceptions@r{, Hurd command}
13721 Use this command to turn off trapping of exceptions in the inferior.
13722 When exception trapping is off, neither breakpoints nor
13723 single-stepping will work. To restore the default, set exception
13726 @item show exceptions
13727 @kindex show exceptions@r{, Hurd command}
13728 Show the current state of trapping exceptions in the inferior.
13730 @item set task pause
13731 @kindex set task@r{, Hurd commands}
13732 @cindex task attributes (@sc{gnu} Hurd)
13733 @cindex pause current task (@sc{gnu} Hurd)
13734 This command toggles task suspension when @value{GDBN} has control.
13735 Setting it to on takes effect immediately, and the task is suspended
13736 whenever @value{GDBN} gets control. Setting it to off will take
13737 effect the next time the inferior is continued. If this option is set
13738 to off, you can use @code{set thread default pause on} or @code{set
13739 thread pause on} (see below) to pause individual threads.
13741 @item show task pause
13742 @kindex show task@r{, Hurd commands}
13743 Show the current state of task suspension.
13745 @item set task detach-suspend-count
13746 @cindex task suspend count
13747 @cindex detach from task, @sc{gnu} Hurd
13748 This command sets the suspend count the task will be left with when
13749 @value{GDBN} detaches from it.
13751 @item show task detach-suspend-count
13752 Show the suspend count the task will be left with when detaching.
13754 @item set task exception-port
13755 @itemx set task excp
13756 @cindex task exception port, @sc{gnu} Hurd
13757 This command sets the task exception port to which @value{GDBN} will
13758 forward exceptions. The argument should be the value of the @dfn{send
13759 rights} of the task. @code{set task excp} is a shorthand alias.
13761 @item set noninvasive
13762 @cindex noninvasive task options
13763 This command switches @value{GDBN} to a mode that is the least
13764 invasive as far as interfering with the inferior is concerned. This
13765 is the same as using @code{set task pause}, @code{set exceptions}, and
13766 @code{set signals} to values opposite to the defaults.
13768 @item info send-rights
13769 @itemx info receive-rights
13770 @itemx info port-rights
13771 @itemx info port-sets
13772 @itemx info dead-names
13775 @cindex send rights, @sc{gnu} Hurd
13776 @cindex receive rights, @sc{gnu} Hurd
13777 @cindex port rights, @sc{gnu} Hurd
13778 @cindex port sets, @sc{gnu} Hurd
13779 @cindex dead names, @sc{gnu} Hurd
13780 These commands display information about, respectively, send rights,
13781 receive rights, port rights, port sets, and dead names of a task.
13782 There are also shorthand aliases: @code{info ports} for @code{info
13783 port-rights} and @code{info psets} for @code{info port-sets}.
13785 @item set thread pause
13786 @kindex set thread@r{, Hurd command}
13787 @cindex thread properties, @sc{gnu} Hurd
13788 @cindex pause current thread (@sc{gnu} Hurd)
13789 This command toggles current thread suspension when @value{GDBN} has
13790 control. Setting it to on takes effect immediately, and the current
13791 thread is suspended whenever @value{GDBN} gets control. Setting it to
13792 off will take effect the next time the inferior is continued.
13793 Normally, this command has no effect, since when @value{GDBN} has
13794 control, the whole task is suspended. However, if you used @code{set
13795 task pause off} (see above), this command comes in handy to suspend
13796 only the current thread.
13798 @item show thread pause
13799 @kindex show thread@r{, Hurd command}
13800 This command shows the state of current thread suspension.
13802 @item set thread run
13803 This comamnd sets whether the current thread is allowed to run.
13805 @item show thread run
13806 Show whether the current thread is allowed to run.
13808 @item set thread detach-suspend-count
13809 @cindex thread suspend count, @sc{gnu} Hurd
13810 @cindex detach from thread, @sc{gnu} Hurd
13811 This command sets the suspend count @value{GDBN} will leave on a
13812 thread when detaching. This number is relative to the suspend count
13813 found by @value{GDBN} when it notices the thread; use @code{set thread
13814 takeover-suspend-count} to force it to an absolute value.
13816 @item show thread detach-suspend-count
13817 Show the suspend count @value{GDBN} will leave on the thread when
13820 @item set thread exception-port
13821 @itemx set thread excp
13822 Set the thread exception port to which to forward exceptions. This
13823 overrides the port set by @code{set task exception-port} (see above).
13824 @code{set thread excp} is the shorthand alias.
13826 @item set thread takeover-suspend-count
13827 Normally, @value{GDBN}'s thread suspend counts are relative to the
13828 value @value{GDBN} finds when it notices each thread. This command
13829 changes the suspend counts to be absolute instead.
13831 @item set thread default
13832 @itemx show thread default
13833 @cindex thread default settings, @sc{gnu} Hurd
13834 Each of the above @code{set thread} commands has a @code{set thread
13835 default} counterpart (e.g., @code{set thread default pause}, @code{set
13836 thread default exception-port}, etc.). The @code{thread default}
13837 variety of commands sets the default thread properties for all
13838 threads; you can then change the properties of individual threads with
13839 the non-default commands.
13844 @subsection QNX Neutrino
13845 @cindex QNX Neutrino
13847 @value{GDBN} provides the following commands specific to the QNX
13851 @item set debug nto-debug
13852 @kindex set debug nto-debug
13853 When set to on, enables debugging messages specific to the QNX
13856 @item show debug nto-debug
13857 @kindex show debug nto-debug
13858 Show the current state of QNX Neutrino messages.
13863 @section Embedded Operating Systems
13865 This section describes configurations involving the debugging of
13866 embedded operating systems that are available for several different
13870 * VxWorks:: Using @value{GDBN} with VxWorks
13873 @value{GDBN} includes the ability to debug programs running on
13874 various real-time operating systems.
13877 @subsection Using @value{GDBN} with VxWorks
13883 @kindex target vxworks
13884 @item target vxworks @var{machinename}
13885 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
13886 is the target system's machine name or IP address.
13890 On VxWorks, @code{load} links @var{filename} dynamically on the
13891 current target system as well as adding its symbols in @value{GDBN}.
13893 @value{GDBN} enables developers to spawn and debug tasks running on networked
13894 VxWorks targets from a Unix host. Already-running tasks spawned from
13895 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
13896 both the Unix host and on the VxWorks target. The program
13897 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
13898 installed with the name @code{vxgdb}, to distinguish it from a
13899 @value{GDBN} for debugging programs on the host itself.)
13902 @item VxWorks-timeout @var{args}
13903 @kindex vxworks-timeout
13904 All VxWorks-based targets now support the option @code{vxworks-timeout}.
13905 This option is set by the user, and @var{args} represents the number of
13906 seconds @value{GDBN} waits for responses to rpc's. You might use this if
13907 your VxWorks target is a slow software simulator or is on the far side
13908 of a thin network line.
13911 The following information on connecting to VxWorks was current when
13912 this manual was produced; newer releases of VxWorks may use revised
13915 @findex INCLUDE_RDB
13916 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
13917 to include the remote debugging interface routines in the VxWorks
13918 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
13919 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
13920 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
13921 source debugging task @code{tRdbTask} when VxWorks is booted. For more
13922 information on configuring and remaking VxWorks, see the manufacturer's
13924 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
13926 Once you have included @file{rdb.a} in your VxWorks system image and set
13927 your Unix execution search path to find @value{GDBN}, you are ready to
13928 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
13929 @code{vxgdb}, depending on your installation).
13931 @value{GDBN} comes up showing the prompt:
13938 * VxWorks Connection:: Connecting to VxWorks
13939 * VxWorks Download:: VxWorks download
13940 * VxWorks Attach:: Running tasks
13943 @node VxWorks Connection
13944 @subsubsection Connecting to VxWorks
13946 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
13947 network. To connect to a target whose host name is ``@code{tt}'', type:
13950 (vxgdb) target vxworks tt
13954 @value{GDBN} displays messages like these:
13957 Attaching remote machine across net...
13962 @value{GDBN} then attempts to read the symbol tables of any object modules
13963 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
13964 these files by searching the directories listed in the command search
13965 path (@pxref{Environment, ,Your program's environment}); if it fails
13966 to find an object file, it displays a message such as:
13969 prog.o: No such file or directory.
13972 When this happens, add the appropriate directory to the search path with
13973 the @value{GDBN} command @code{path}, and execute the @code{target}
13976 @node VxWorks Download
13977 @subsubsection VxWorks download
13979 @cindex download to VxWorks
13980 If you have connected to the VxWorks target and you want to debug an
13981 object that has not yet been loaded, you can use the @value{GDBN}
13982 @code{load} command to download a file from Unix to VxWorks
13983 incrementally. The object file given as an argument to the @code{load}
13984 command is actually opened twice: first by the VxWorks target in order
13985 to download the code, then by @value{GDBN} in order to read the symbol
13986 table. This can lead to problems if the current working directories on
13987 the two systems differ. If both systems have NFS mounted the same
13988 filesystems, you can avoid these problems by using absolute paths.
13989 Otherwise, it is simplest to set the working directory on both systems
13990 to the directory in which the object file resides, and then to reference
13991 the file by its name, without any path. For instance, a program
13992 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
13993 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
13994 program, type this on VxWorks:
13997 -> cd "@var{vxpath}/vw/demo/rdb"
14001 Then, in @value{GDBN}, type:
14004 (vxgdb) cd @var{hostpath}/vw/demo/rdb
14005 (vxgdb) load prog.o
14008 @value{GDBN} displays a response similar to this:
14011 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
14014 You can also use the @code{load} command to reload an object module
14015 after editing and recompiling the corresponding source file. Note that
14016 this makes @value{GDBN} delete all currently-defined breakpoints,
14017 auto-displays, and convenience variables, and to clear the value
14018 history. (This is necessary in order to preserve the integrity of
14019 debugger's data structures that reference the target system's symbol
14022 @node VxWorks Attach
14023 @subsubsection Running tasks
14025 @cindex running VxWorks tasks
14026 You can also attach to an existing task using the @code{attach} command as
14030 (vxgdb) attach @var{task}
14034 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
14035 or suspended when you attach to it. Running tasks are suspended at
14036 the time of attachment.
14038 @node Embedded Processors
14039 @section Embedded Processors
14041 This section goes into details specific to particular embedded
14044 @cindex send command to simulator
14045 Whenever a specific embedded processor has a simulator, @value{GDBN}
14046 allows to send an arbitrary command to the simulator.
14049 @item sim @var{command}
14050 @kindex sim@r{, a command}
14051 Send an arbitrary @var{command} string to the simulator. Consult the
14052 documentation for the specific simulator in use for information about
14053 acceptable commands.
14059 * H8/300:: Renesas H8/300
14060 * H8/500:: Renesas H8/500
14061 * M32R/D:: Renesas M32R/D
14062 * M68K:: Motorola M68K
14063 * MIPS Embedded:: MIPS Embedded
14064 * OpenRISC 1000:: OpenRisc 1000
14065 * PA:: HP PA Embedded
14068 * Sparclet:: Tsqware Sparclet
14069 * Sparclite:: Fujitsu Sparclite
14070 * ST2000:: Tandem ST2000
14071 * Z8000:: Zilog Z8000
14074 * Super-H:: Renesas Super-H
14075 * WinCE:: Windows CE child processes
14084 @item target rdi @var{dev}
14085 ARM Angel monitor, via RDI library interface to ADP protocol. You may
14086 use this target to communicate with both boards running the Angel
14087 monitor, or with the EmbeddedICE JTAG debug device.
14090 @item target rdp @var{dev}
14095 @value{GDBN} provides the following ARM-specific commands:
14098 @item set arm disassembler
14100 This commands selects from a list of disassembly styles. The
14101 @code{"std"} style is the standard style.
14103 @item show arm disassembler
14105 Show the current disassembly style.
14107 @item set arm apcs32
14108 @cindex ARM 32-bit mode
14109 This command toggles ARM operation mode between 32-bit and 26-bit.
14111 @item show arm apcs32
14112 Display the current usage of the ARM 32-bit mode.
14114 @item set arm fpu @var{fputype}
14115 This command sets the ARM floating-point unit (FPU) type. The
14116 argument @var{fputype} can be one of these:
14120 Determine the FPU type by querying the OS ABI.
14122 Software FPU, with mixed-endian doubles on little-endian ARM
14125 GCC-compiled FPA co-processor.
14127 Software FPU with pure-endian doubles.
14133 Show the current type of the FPU.
14136 This command forces @value{GDBN} to use the specified ABI.
14139 Show the currently used ABI.
14141 @item set debug arm
14142 Toggle whether to display ARM-specific debugging messages from the ARM
14143 target support subsystem.
14145 @item show debug arm
14146 Show whether ARM-specific debugging messages are enabled.
14149 The following commands are available when an ARM target is debugged
14150 using the RDI interface:
14153 @item rdilogfile @r{[}@var{file}@r{]}
14155 @cindex ADP (Angel Debugger Protocol) logging
14156 Set the filename for the ADP (Angel Debugger Protocol) packet log.
14157 With an argument, sets the log file to the specified @var{file}. With
14158 no argument, show the current log file name. The default log file is
14161 @item rdilogenable @r{[}@var{arg}@r{]}
14162 @kindex rdilogenable
14163 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
14164 enables logging, with an argument 0 or @code{"no"} disables it. With
14165 no arguments displays the current setting. When logging is enabled,
14166 ADP packets exchanged between @value{GDBN} and the RDI target device
14167 are logged to a file.
14169 @item set rdiromatzero
14170 @kindex set rdiromatzero
14171 @cindex ROM at zero address, RDI
14172 Tell @value{GDBN} whether the target has ROM at address 0. If on,
14173 vector catching is disabled, so that zero address can be used. If off
14174 (the default), vector catching is enabled. For this command to take
14175 effect, it needs to be invoked prior to the @code{target rdi} command.
14177 @item show rdiromatzero
14178 @kindex show rdiromatzero
14179 Show the current setting of ROM at zero address.
14181 @item set rdiheartbeat
14182 @kindex set rdiheartbeat
14183 @cindex RDI heartbeat
14184 Enable or disable RDI heartbeat packets. It is not recommended to
14185 turn on this option, since it confuses ARM and EPI JTAG interface, as
14186 well as the Angel monitor.
14188 @item show rdiheartbeat
14189 @kindex show rdiheartbeat
14190 Show the setting of RDI heartbeat packets.
14195 @subsection Renesas H8/300
14199 @kindex target hms@r{, with H8/300}
14200 @item target hms @var{dev}
14201 A Renesas SH, H8/300, or H8/500 board, attached via serial line to your host.
14202 Use special commands @code{device} and @code{speed} to control the serial
14203 line and the communications speed used.
14205 @kindex target e7000@r{, with H8/300}
14206 @item target e7000 @var{dev}
14207 E7000 emulator for Renesas H8 and SH.
14209 @kindex target sh3@r{, with H8/300}
14210 @kindex target sh3e@r{, with H8/300}
14211 @item target sh3 @var{dev}
14212 @itemx target sh3e @var{dev}
14213 Renesas SH-3 and SH-3E target systems.
14217 @cindex download to H8/300 or H8/500
14218 @cindex H8/300 or H8/500 download
14219 @cindex download to Renesas SH
14220 @cindex Renesas SH download
14221 When you select remote debugging to a Renesas SH, H8/300, or H8/500
14222 board, the @code{load} command downloads your program to the Renesas
14223 board and also opens it as the current executable target for
14224 @value{GDBN} on your host (like the @code{file} command).
14226 @value{GDBN} needs to know these things to talk to your
14227 Renesas SH, H8/300, or H8/500:
14231 that you want to use @samp{target hms}, the remote debugging interface
14232 for Renesas microprocessors, or @samp{target e7000}, the in-circuit
14233 emulator for the Renesas SH and the Renesas 300H. (@samp{target hms} is
14234 the default when @value{GDBN} is configured specifically for the Renesas SH,
14235 H8/300, or H8/500.)
14238 what serial device connects your host to your Renesas board (the first
14239 serial device available on your host is the default).
14242 what speed to use over the serial device.
14246 * Renesas Boards:: Connecting to Renesas boards.
14247 * Renesas ICE:: Using the E7000 In-Circuit Emulator.
14248 * Renesas Special:: Special @value{GDBN} commands for Renesas micros.
14251 @node Renesas Boards
14252 @subsubsection Connecting to Renesas boards
14254 @c only for Unix hosts
14256 @cindex serial device, Renesas micros
14257 Use the special @code{@value{GDBN}} command @samp{device @var{port}} if you
14258 need to explicitly set the serial device. The default @var{port} is the
14259 first available port on your host. This is only necessary on Unix
14260 hosts, where it is typically something like @file{/dev/ttya}.
14263 @cindex serial line speed, Renesas micros
14264 @code{@value{GDBN}} has another special command to set the communications
14265 speed: @samp{speed @var{bps}}. This command also is only used from Unix
14266 hosts; on DOS hosts, set the line speed as usual from outside @value{GDBN} with
14267 the DOS @code{mode} command (for instance,
14268 @w{@kbd{mode com2:9600,n,8,1,p}} for a 9600@dmn{bps} connection).
14270 The @samp{device} and @samp{speed} commands are available only when you
14271 use a Unix host to debug your Renesas microprocessor programs. If you
14273 @value{GDBN} depends on an auxiliary terminate-and-stay-resident program
14274 called @code{asynctsr} to communicate with the development board
14275 through a PC serial port. You must also use the DOS @code{mode} command
14276 to set up the serial port on the DOS side.
14278 The following sample session illustrates the steps needed to start a
14279 program under @value{GDBN} control on an H8/300. The example uses a
14280 sample H8/300 program called @file{t.x}. The procedure is the same for
14281 the Renesas SH and the H8/500.
14283 First hook up your development board. In this example, we use a
14284 board attached to serial port @code{COM2}; if you use a different serial
14285 port, substitute its name in the argument of the @code{mode} command.
14286 When you call @code{asynctsr}, the auxiliary comms program used by the
14287 debugger, you give it just the numeric part of the serial port's name;
14288 for example, @samp{asyncstr 2} below runs @code{asyncstr} on
14292 C:\H8300\TEST> asynctsr 2
14293 C:\H8300\TEST> mode com2:9600,n,8,1,p
14295 Resident portion of MODE loaded
14297 COM2: 9600, n, 8, 1, p
14302 @emph{Warning:} We have noticed a bug in PC-NFS that conflicts with
14303 @code{asynctsr}. If you also run PC-NFS on your DOS host, you may need to
14304 disable it, or even boot without it, to use @code{asynctsr} to control
14305 your development board.
14308 @kindex target hms@r{, and serial protocol}
14309 Now that serial communications are set up, and the development board is
14310 connected, you can start up @value{GDBN}. Call @code{@value{GDBN}} with
14311 the name of your program as the argument. @code{@value{GDBN}} prompts
14312 you, as usual, with the prompt @samp{(@value{GDBP})}. Use two special
14313 commands to begin your debugging session: @samp{target hms} to specify
14314 cross-debugging to the Renesas board, and the @code{load} command to
14315 download your program to the board. @code{load} displays the names of
14316 the program's sections, and a @samp{*} for each 2K of data downloaded.
14317 (If you want to refresh @value{GDBN} data on symbols or on the
14318 executable file without downloading, use the @value{GDBN} commands
14319 @code{file} or @code{symbol-file}. These commands, and @code{load}
14320 itself, are described in @ref{Files,,Commands to specify files}.)
14323 (eg-C:\H8300\TEST) @value{GDBP} t.x
14324 @value{GDBN} is free software and you are welcome to distribute copies
14325 of it under certain conditions; type "show copying" to see
14327 There is absolutely no warranty for @value{GDBN}; type "show warranty"
14329 @value{GDBN} @value{GDBVN}, Copyright 1992 Free Software Foundation, Inc...
14330 (@value{GDBP}) target hms
14331 Connected to remote H8/300 HMS system.
14332 (@value{GDBP}) load t.x
14333 .text : 0x8000 .. 0xabde ***********
14334 .data : 0xabde .. 0xad30 *
14335 .stack : 0xf000 .. 0xf014 *
14338 At this point, you're ready to run or debug your program. From here on,
14339 you can use all the usual @value{GDBN} commands. The @code{break} command
14340 sets breakpoints; the @code{run} command starts your program;
14341 @code{print} or @code{x} display data; the @code{continue} command
14342 resumes execution after stopping at a breakpoint. You can use the
14343 @code{help} command at any time to find out more about @value{GDBN} commands.
14345 Remember, however, that @emph{operating system} facilities aren't
14346 available on your development board; for example, if your program hangs,
14347 you can't send an interrupt---but you can press the @sc{reset} switch!
14349 Use the @sc{reset} button on the development board
14352 to interrupt your program (don't use @kbd{ctl-C} on the DOS host---it has
14353 no way to pass an interrupt signal to the development board); and
14356 to return to the @value{GDBN} command prompt after your program finishes
14357 normally. The communications protocol provides no other way for @value{GDBN}
14358 to detect program completion.
14361 In either case, @value{GDBN} sees the effect of a @sc{reset} on the
14362 development board as a ``normal exit'' of your program.
14365 @subsubsection Using the E7000 in-circuit emulator
14367 @kindex target e7000@r{, with Renesas ICE}
14368 You can use the E7000 in-circuit emulator to develop code for either the
14369 Renesas SH or the H8/300H. Use one of these forms of the @samp{target
14370 e7000} command to connect @value{GDBN} to your E7000:
14373 @item target e7000 @var{port} @var{speed}
14374 Use this form if your E7000 is connected to a serial port. The
14375 @var{port} argument identifies what serial port to use (for example,
14376 @samp{com2}). The third argument is the line speed in bits per second
14377 (for example, @samp{9600}).
14379 @item target e7000 @var{hostname}
14380 If your E7000 is installed as a host on a TCP/IP network, you can just
14381 specify its hostname; @value{GDBN} uses @code{telnet} to connect.
14384 The following special commands are available when debugging with the
14388 @item e7000 @var{command}
14390 @cindex send command to E7000 monitor
14391 This sends the specified @var{command} to the E7000 monitor.
14393 @item ftplogin @var{machine} @var{username} @var{password} @var{dir}
14394 @kindex ftplogin@r{, E7000}
14395 This command records information for subsequent interface with the
14396 E7000 monitor via the FTP protocol: @value{GDBN} will log into the
14397 named @var{machine} using specified @var{username} and @var{password},
14398 and then chdir to the named directory @var{dir}.
14400 @item ftpload @var{file}
14401 @kindex ftpload@r{, E7000}
14402 This command uses credentials recorded by @code{ftplogin} to fetch and
14403 load the named @var{file} from the E7000 monitor.
14406 @kindex drain@r{, E7000}
14407 This command drains any pending text buffers stored on the E7000.
14409 @item set usehardbreakpoints
14410 @itemx show usehardbreakpoints
14411 @kindex set usehardbreakpoints@r{, E7000}
14412 @kindex show usehardbreakpoints@r{, E7000}
14413 @cindex hardware breakpoints, and E7000
14414 These commands set and show the use of hardware breakpoints for all
14415 breakpoints. @xref{Set Breaks, hardware-assisted breakpoint}, for
14416 more information about using hardware breakpoints selectively.
14419 @node Renesas Special
14420 @subsubsection Special @value{GDBN} commands for Renesas micros
14422 Some @value{GDBN} commands are available only for the H8/300:
14426 @kindex set machine
14427 @kindex show machine
14428 @item set machine h8300
14429 @itemx set machine h8300h
14430 Condition @value{GDBN} for one of the two variants of the H8/300
14431 architecture with @samp{set machine}. You can use @samp{show machine}
14432 to check which variant is currently in effect.
14441 @kindex set memory @var{mod}
14442 @cindex memory models, H8/500
14443 @item set memory @var{mod}
14445 Specify which H8/500 memory model (@var{mod}) you are using with
14446 @samp{set memory}; check which memory model is in effect with @samp{show
14447 memory}. The accepted values for @var{mod} are @code{small},
14448 @code{big}, @code{medium}, and @code{compact}.
14453 @subsection Renesas M32R/D and M32R/SDI
14456 @kindex target m32r
14457 @item target m32r @var{dev}
14458 Renesas M32R/D ROM monitor.
14460 @kindex target m32rsdi
14461 @item target m32rsdi @var{dev}
14462 Renesas M32R SDI server, connected via parallel port to the board.
14465 The following @value{GDBN} commands are specific to the M32R monitor:
14468 @item set download-path @var{path}
14469 @kindex set download-path
14470 @cindex find downloadable @sc{srec} files (M32R)
14471 Set the default path for finding donwloadable @sc{srec} files.
14473 @item show download-path
14474 @kindex show download-path
14475 Show the default path for downloadable @sc{srec} files.
14477 @item set board-address @var{addr}
14478 @kindex set board-address
14479 @cindex M32-EVA target board address
14480 Set the IP address for the M32R-EVA target board.
14482 @item show board-address
14483 @kindex show board-address
14484 Show the current IP address of the target board.
14486 @item set server-address @var{addr}
14487 @kindex set server-address
14488 @cindex download server address (M32R)
14489 Set the IP address for the download server, which is the @value{GDBN}'s
14492 @item show server-address
14493 @kindex show server-address
14494 Display the IP address of the download server.
14496 @item upload @r{[}@var{file}@r{]}
14497 @kindex upload@r{, M32R}
14498 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
14499 upload capability. If no @var{file} argument is given, the current
14500 executable file is uploaded.
14502 @item tload @r{[}@var{file}@r{]}
14503 @kindex tload@r{, M32R}
14504 Test the @code{upload} command.
14507 The following commands are available for M32R/SDI:
14512 @cindex reset SDI connection, M32R
14513 This command resets the SDI connection.
14517 This command shows the SDI connection status.
14520 @kindex debug_chaos
14521 @cindex M32R/Chaos debugging
14522 Instructs the remote that M32R/Chaos debugging is to be used.
14524 @item use_debug_dma
14525 @kindex use_debug_dma
14526 Instructs the remote to use the DEBUG_DMA method of accessing memory.
14529 @kindex use_mon_code
14530 Instructs the remote to use the MON_CODE method of accessing memory.
14533 @kindex use_ib_break
14534 Instructs the remote to set breakpoints by IB break.
14536 @item use_dbt_break
14537 @kindex use_dbt_break
14538 Instructs the remote to set breakpoints by DBT.
14544 The Motorola m68k configuration includes ColdFire support, and
14545 target command for the following ROM monitors.
14549 @kindex target abug
14550 @item target abug @var{dev}
14551 ABug ROM monitor for M68K.
14553 @kindex target cpu32bug
14554 @item target cpu32bug @var{dev}
14555 CPU32BUG monitor, running on a CPU32 (M68K) board.
14557 @kindex target dbug
14558 @item target dbug @var{dev}
14559 dBUG ROM monitor for Motorola ColdFire.
14562 @item target est @var{dev}
14563 EST-300 ICE monitor, running on a CPU32 (M68K) board.
14565 @kindex target rom68k
14566 @item target rom68k @var{dev}
14567 ROM 68K monitor, running on an M68K IDP board.
14573 @kindex target rombug
14574 @item target rombug @var{dev}
14575 ROMBUG ROM monitor for OS/9000.
14579 @node MIPS Embedded
14580 @subsection MIPS Embedded
14582 @cindex MIPS boards
14583 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
14584 MIPS board attached to a serial line. This is available when
14585 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
14588 Use these @value{GDBN} commands to specify the connection to your target board:
14591 @item target mips @var{port}
14592 @kindex target mips @var{port}
14593 To run a program on the board, start up @code{@value{GDBP}} with the
14594 name of your program as the argument. To connect to the board, use the
14595 command @samp{target mips @var{port}}, where @var{port} is the name of
14596 the serial port connected to the board. If the program has not already
14597 been downloaded to the board, you may use the @code{load} command to
14598 download it. You can then use all the usual @value{GDBN} commands.
14600 For example, this sequence connects to the target board through a serial
14601 port, and loads and runs a program called @var{prog} through the
14605 host$ @value{GDBP} @var{prog}
14606 @value{GDBN} is free software and @dots{}
14607 (@value{GDBP}) target mips /dev/ttyb
14608 (@value{GDBP}) load @var{prog}
14612 @item target mips @var{hostname}:@var{portnumber}
14613 On some @value{GDBN} host configurations, you can specify a TCP
14614 connection (for instance, to a serial line managed by a terminal
14615 concentrator) instead of a serial port, using the syntax
14616 @samp{@var{hostname}:@var{portnumber}}.
14618 @item target pmon @var{port}
14619 @kindex target pmon @var{port}
14622 @item target ddb @var{port}
14623 @kindex target ddb @var{port}
14624 NEC's DDB variant of PMON for Vr4300.
14626 @item target lsi @var{port}
14627 @kindex target lsi @var{port}
14628 LSI variant of PMON.
14630 @kindex target r3900
14631 @item target r3900 @var{dev}
14632 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
14634 @kindex target array
14635 @item target array @var{dev}
14636 Array Tech LSI33K RAID controller board.
14642 @value{GDBN} also supports these special commands for MIPS targets:
14645 @item set mipsfpu double
14646 @itemx set mipsfpu single
14647 @itemx set mipsfpu none
14648 @itemx set mipsfpu auto
14649 @itemx show mipsfpu
14650 @kindex set mipsfpu
14651 @kindex show mipsfpu
14652 @cindex MIPS remote floating point
14653 @cindex floating point, MIPS remote
14654 If your target board does not support the MIPS floating point
14655 coprocessor, you should use the command @samp{set mipsfpu none} (if you
14656 need this, you may wish to put the command in your @value{GDBN} init
14657 file). This tells @value{GDBN} how to find the return value of
14658 functions which return floating point values. It also allows
14659 @value{GDBN} to avoid saving the floating point registers when calling
14660 functions on the board. If you are using a floating point coprocessor
14661 with only single precision floating point support, as on the @sc{r4650}
14662 processor, use the command @samp{set mipsfpu single}. The default
14663 double precision floating point coprocessor may be selected using
14664 @samp{set mipsfpu double}.
14666 In previous versions the only choices were double precision or no
14667 floating point, so @samp{set mipsfpu on} will select double precision
14668 and @samp{set mipsfpu off} will select no floating point.
14670 As usual, you can inquire about the @code{mipsfpu} variable with
14671 @samp{show mipsfpu}.
14673 @item set timeout @var{seconds}
14674 @itemx set retransmit-timeout @var{seconds}
14675 @itemx show timeout
14676 @itemx show retransmit-timeout
14677 @cindex @code{timeout}, MIPS protocol
14678 @cindex @code{retransmit-timeout}, MIPS protocol
14679 @kindex set timeout
14680 @kindex show timeout
14681 @kindex set retransmit-timeout
14682 @kindex show retransmit-timeout
14683 You can control the timeout used while waiting for a packet, in the MIPS
14684 remote protocol, with the @code{set timeout @var{seconds}} command. The
14685 default is 5 seconds. Similarly, you can control the timeout used while
14686 waiting for an acknowledgement of a packet with the @code{set
14687 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
14688 You can inspect both values with @code{show timeout} and @code{show
14689 retransmit-timeout}. (These commands are @emph{only} available when
14690 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
14692 The timeout set by @code{set timeout} does not apply when @value{GDBN}
14693 is waiting for your program to stop. In that case, @value{GDBN} waits
14694 forever because it has no way of knowing how long the program is going
14695 to run before stopping.
14697 @item set syn-garbage-limit @var{num}
14698 @kindex set syn-garbage-limit@r{, MIPS remote}
14699 @cindex synchronize with remote MIPS target
14700 Limit the maximum number of characters @value{GDBN} should ignore when
14701 it tries to synchronize with the remote target. The default is 10
14702 characters. Setting the limit to -1 means there's no limit.
14704 @item show syn-garbage-limit
14705 @kindex show syn-garbage-limit@r{, MIPS remote}
14706 Show the current limit on the number of characters to ignore when
14707 trying to synchronize with the remote system.
14709 @item set monitor-prompt @var{prompt}
14710 @kindex set monitor-prompt@r{, MIPS remote}
14711 @cindex remote monitor prompt
14712 Tell @value{GDBN} to expect the specified @var{prompt} string from the
14713 remote monitor. The default depends on the target:
14723 @item show monitor-prompt
14724 @kindex show monitor-prompt@r{, MIPS remote}
14725 Show the current strings @value{GDBN} expects as the prompt from the
14728 @item set monitor-warnings
14729 @kindex set monitor-warnings@r{, MIPS remote}
14730 Enable or disable monitor warnings about hardware breakpoints. This
14731 has effect only for the @code{lsi} target. When on, @value{GDBN} will
14732 display warning messages whose codes are returned by the @code{lsi}
14733 PMON monitor for breakpoint commands.
14735 @item show monitor-warnings
14736 @kindex show monitor-warnings@r{, MIPS remote}
14737 Show the current setting of printing monitor warnings.
14739 @item pmon @var{command}
14740 @kindex pmon@r{, MIPS remote}
14741 @cindex send PMON command
14742 This command allows sending an arbitrary @var{command} string to the
14743 monitor. The monitor must be in debug mode for this to work.
14746 @node OpenRISC 1000
14747 @subsection OpenRISC 1000
14748 @cindex OpenRISC 1000
14750 @cindex or1k boards
14751 See OR1k Architecture document (@uref{www.opencores.org}) for more information
14752 about platform and commands.
14756 @kindex target jtag
14757 @item target jtag jtag://@var{host}:@var{port}
14759 Connects to remote JTAG server.
14760 JTAG remote server can be either an or1ksim or JTAG server,
14761 connected via parallel port to the board.
14763 Example: @code{target jtag jtag://localhost:9999}
14766 @item or1ksim @var{command}
14767 If connected to @code{or1ksim} OpenRISC 1000 Architectural
14768 Simulator, proprietary commands can be executed.
14770 @kindex info or1k spr
14771 @item info or1k spr
14772 Displays spr groups.
14774 @item info or1k spr @var{group}
14775 @itemx info or1k spr @var{groupno}
14776 Displays register names in selected group.
14778 @item info or1k spr @var{group} @var{register}
14779 @itemx info or1k spr @var{register}
14780 @itemx info or1k spr @var{groupno} @var{registerno}
14781 @itemx info or1k spr @var{registerno}
14782 Shows information about specified spr register.
14785 @item spr @var{group} @var{register} @var{value}
14786 @itemx spr @var{register @var{value}}
14787 @itemx spr @var{groupno} @var{registerno @var{value}}
14788 @itemx spr @var{registerno @var{value}}
14789 Writes @var{value} to specified spr register.
14792 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
14793 It is very similar to @value{GDBN} trace, except it does not interfere with normal
14794 program execution and is thus much faster. Hardware breakpoints/watchpoint
14795 triggers can be set using:
14798 Load effective address/data
14800 Store effective address/data
14802 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
14807 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
14808 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
14810 @code{htrace} commands:
14811 @cindex OpenRISC 1000 htrace
14814 @item hwatch @var{conditional}
14815 Set hardware watchpoint on combination of Load/Store Effecive Address(es)
14816 or Data. For example:
14818 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
14820 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
14824 Display information about current HW trace configuration.
14826 @item htrace trigger @var{conditional}
14827 Set starting criteria for HW trace.
14829 @item htrace qualifier @var{conditional}
14830 Set acquisition qualifier for HW trace.
14832 @item htrace stop @var{conditional}
14833 Set HW trace stopping criteria.
14835 @item htrace record [@var{data}]*
14836 Selects the data to be recorded, when qualifier is met and HW trace was
14839 @item htrace enable
14840 @itemx htrace disable
14841 Enables/disables the HW trace.
14843 @item htrace rewind [@var{filename}]
14844 Clears currently recorded trace data.
14846 If filename is specified, new trace file is made and any newly collected data
14847 will be written there.
14849 @item htrace print [@var{start} [@var{len}]]
14850 Prints trace buffer, using current record configuration.
14852 @item htrace mode continuous
14853 Set continuous trace mode.
14855 @item htrace mode suspend
14856 Set suspend trace mode.
14861 @subsection PowerPC
14864 @kindex target dink32
14865 @item target dink32 @var{dev}
14866 DINK32 ROM monitor.
14868 @kindex target ppcbug
14869 @item target ppcbug @var{dev}
14870 @kindex target ppcbug1
14871 @item target ppcbug1 @var{dev}
14872 PPCBUG ROM monitor for PowerPC.
14875 @item target sds @var{dev}
14876 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
14879 @cindex SDS protocol
14880 The following commands specifi to the SDS protocol are supported
14884 @item set sdstimeout @var{nsec}
14885 @kindex set sdstimeout
14886 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
14887 default is 2 seconds.
14889 @item show sdstimeout
14890 @kindex show sdstimeout
14891 Show the current value of the SDS timeout.
14893 @item sds @var{command}
14894 @kindex sds@r{, a command}
14895 Send the specified @var{command} string to the SDS monitor.
14900 @subsection HP PA Embedded
14904 @kindex target op50n
14905 @item target op50n @var{dev}
14906 OP50N monitor, running on an OKI HPPA board.
14908 @kindex target w89k
14909 @item target w89k @var{dev}
14910 W89K monitor, running on a Winbond HPPA board.
14915 @subsection Renesas SH
14919 @kindex target hms@r{, with Renesas SH}
14920 @item target hms @var{dev}
14921 A Renesas SH board attached via serial line to your host. Use special
14922 commands @code{device} and @code{speed} to control the serial line and
14923 the communications speed used.
14925 @kindex target e7000@r{, with Renesas SH}
14926 @item target e7000 @var{dev}
14927 E7000 emulator for Renesas SH.
14929 @kindex target sh3@r{, with SH}
14930 @kindex target sh3e@r{, with SH}
14931 @item target sh3 @var{dev}
14932 @item target sh3e @var{dev}
14933 Renesas SH-3 and SH-3E target systems.
14938 @subsection Tsqware Sparclet
14942 @value{GDBN} enables developers to debug tasks running on
14943 Sparclet targets from a Unix host.
14944 @value{GDBN} uses code that runs on
14945 both the Unix host and on the Sparclet target. The program
14946 @code{@value{GDBP}} is installed and executed on the Unix host.
14949 @item remotetimeout @var{args}
14950 @kindex remotetimeout
14951 @value{GDBN} supports the option @code{remotetimeout}.
14952 This option is set by the user, and @var{args} represents the number of
14953 seconds @value{GDBN} waits for responses.
14956 @cindex compiling, on Sparclet
14957 When compiling for debugging, include the options @samp{-g} to get debug
14958 information and @samp{-Ttext} to relocate the program to where you wish to
14959 load it on the target. You may also want to add the options @samp{-n} or
14960 @samp{-N} in order to reduce the size of the sections. Example:
14963 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
14966 You can use @code{objdump} to verify that the addresses are what you intended:
14969 sparclet-aout-objdump --headers --syms prog
14972 @cindex running, on Sparclet
14974 your Unix execution search path to find @value{GDBN}, you are ready to
14975 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
14976 (or @code{sparclet-aout-gdb}, depending on your installation).
14978 @value{GDBN} comes up showing the prompt:
14985 * Sparclet File:: Setting the file to debug
14986 * Sparclet Connection:: Connecting to Sparclet
14987 * Sparclet Download:: Sparclet download
14988 * Sparclet Execution:: Running and debugging
14991 @node Sparclet File
14992 @subsubsection Setting file to debug
14994 The @value{GDBN} command @code{file} lets you choose with program to debug.
14997 (gdbslet) file prog
15001 @value{GDBN} then attempts to read the symbol table of @file{prog}.
15002 @value{GDBN} locates
15003 the file by searching the directories listed in the command search
15005 If the file was compiled with debug information (option "-g"), source
15006 files will be searched as well.
15007 @value{GDBN} locates
15008 the source files by searching the directories listed in the directory search
15009 path (@pxref{Environment, ,Your program's environment}).
15011 to find a file, it displays a message such as:
15014 prog: No such file or directory.
15017 When this happens, add the appropriate directories to the search paths with
15018 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
15019 @code{target} command again.
15021 @node Sparclet Connection
15022 @subsubsection Connecting to Sparclet
15024 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
15025 To connect to a target on serial port ``@code{ttya}'', type:
15028 (gdbslet) target sparclet /dev/ttya
15029 Remote target sparclet connected to /dev/ttya
15030 main () at ../prog.c:3
15034 @value{GDBN} displays messages like these:
15040 @node Sparclet Download
15041 @subsubsection Sparclet download
15043 @cindex download to Sparclet
15044 Once connected to the Sparclet target,
15045 you can use the @value{GDBN}
15046 @code{load} command to download the file from the host to the target.
15047 The file name and load offset should be given as arguments to the @code{load}
15049 Since the file format is aout, the program must be loaded to the starting
15050 address. You can use @code{objdump} to find out what this value is. The load
15051 offset is an offset which is added to the VMA (virtual memory address)
15052 of each of the file's sections.
15053 For instance, if the program
15054 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
15055 and bss at 0x12010170, in @value{GDBN}, type:
15058 (gdbslet) load prog 0x12010000
15059 Loading section .text, size 0xdb0 vma 0x12010000
15062 If the code is loaded at a different address then what the program was linked
15063 to, you may need to use the @code{section} and @code{add-symbol-file} commands
15064 to tell @value{GDBN} where to map the symbol table.
15066 @node Sparclet Execution
15067 @subsubsection Running and debugging
15069 @cindex running and debugging Sparclet programs
15070 You can now begin debugging the task using @value{GDBN}'s execution control
15071 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
15072 manual for the list of commands.
15076 Breakpoint 1 at 0x12010000: file prog.c, line 3.
15078 Starting program: prog
15079 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
15080 3 char *symarg = 0;
15082 4 char *execarg = "hello!";
15087 @subsection Fujitsu Sparclite
15091 @kindex target sparclite
15092 @item target sparclite @var{dev}
15093 Fujitsu sparclite boards, used only for the purpose of loading.
15094 You must use an additional command to debug the program.
15095 For example: target remote @var{dev} using @value{GDBN} standard
15101 @subsection Tandem ST2000
15103 @value{GDBN} may be used with a Tandem ST2000 phone switch, running Tandem's
15106 To connect your ST2000 to the host system, see the manufacturer's
15107 manual. Once the ST2000 is physically attached, you can run:
15110 target st2000 @var{dev} @var{speed}
15114 to establish it as your debugging environment. @var{dev} is normally
15115 the name of a serial device, such as @file{/dev/ttya}, connected to the
15116 ST2000 via a serial line. You can instead specify @var{dev} as a TCP
15117 connection (for example, to a serial line attached via a terminal
15118 concentrator) using the syntax @code{@var{hostname}:@var{portnumber}}.
15120 The @code{load} and @code{attach} commands are @emph{not} defined for
15121 this target; you must load your program into the ST2000 as you normally
15122 would for standalone operation. @value{GDBN} reads debugging information
15123 (such as symbols) from a separate, debugging version of the program
15124 available on your host computer.
15125 @c FIXME!! This is terribly vague; what little content is here is
15126 @c basically hearsay.
15128 @cindex ST2000 auxiliary commands
15129 These auxiliary @value{GDBN} commands are available to help you with the ST2000
15133 @item st2000 @var{command}
15134 @kindex st2000 @var{cmd}
15135 @cindex STDBUG commands (ST2000)
15136 @cindex commands to STDBUG (ST2000)
15137 Send a @var{command} to the STDBUG monitor. See the manufacturer's
15138 manual for available commands.
15141 @cindex connect (to STDBUG)
15142 Connect the controlling terminal to the STDBUG command monitor. When
15143 you are done interacting with STDBUG, typing either of two character
15144 sequences gets you back to the @value{GDBN} command prompt:
15145 @kbd{@key{RET}~.} (Return, followed by tilde and period) or
15146 @kbd{@key{RET}~@key{C-d}} (Return, followed by tilde and control-D).
15150 @subsection Zilog Z8000
15153 @cindex simulator, Z8000
15154 @cindex Zilog Z8000 simulator
15156 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
15159 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
15160 unsegmented variant of the Z8000 architecture) or the Z8001 (the
15161 segmented variant). The simulator recognizes which architecture is
15162 appropriate by inspecting the object code.
15165 @item target sim @var{args}
15167 @kindex target sim@r{, with Z8000}
15168 Debug programs on a simulated CPU. If the simulator supports setup
15169 options, specify them via @var{args}.
15173 After specifying this target, you can debug programs for the simulated
15174 CPU in the same style as programs for your host computer; use the
15175 @code{file} command to load a new program image, the @code{run} command
15176 to run your program, and so on.
15178 As well as making available all the usual machine registers
15179 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
15180 additional items of information as specially named registers:
15185 Counts clock-ticks in the simulator.
15188 Counts instructions run in the simulator.
15191 Execution time in 60ths of a second.
15195 You can refer to these values in @value{GDBN} expressions with the usual
15196 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
15197 conditional breakpoint that suspends only after at least 5000
15198 simulated clock ticks.
15201 @subsection Atmel AVR
15204 When configured for debugging the Atmel AVR, @value{GDBN} supports the
15205 following AVR-specific commands:
15208 @item info io_registers
15209 @kindex info io_registers@r{, AVR}
15210 @cindex I/O registers (Atmel AVR)
15211 This command displays information about the AVR I/O registers. For
15212 each register, @value{GDBN} prints its number and value.
15219 When configured for debugging CRIS, @value{GDBN} provides the
15220 following CRIS-specific commands:
15223 @item set cris-version @var{ver}
15224 @cindex CRIS version
15225 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
15226 The CRIS version affects register names and sizes. This command is useful in
15227 case autodetection of the CRIS version fails.
15229 @item show cris-version
15230 Show the current CRIS version.
15232 @item set cris-dwarf2-cfi
15233 @cindex DWARF-2 CFI and CRIS
15234 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
15235 Change to @samp{off} when using @code{gcc-cris} whose version is below
15238 @item show cris-dwarf2-cfi
15239 Show the current state of using DWARF-2 CFI.
15241 @item set cris-mode @var{mode}
15243 Set the current CRIS mode to @var{mode}. It should only be changed when
15244 debugging in guru mode, in which case it should be set to
15245 @samp{guru} (the default is @samp{normal}).
15247 @item show cris-mode
15248 Show the current CRIS mode.
15252 @subsection Renesas Super-H
15255 For the Renesas Super-H processor, @value{GDBN} provides these
15260 @kindex regs@r{, Super-H}
15261 Show the values of all Super-H registers.
15265 @subsection Windows CE
15268 The following commands are available for Windows CE:
15271 @item set remotedirectory @var{dir}
15272 @kindex set remotedirectory
15273 Tell @value{GDBN} to upload files from the named directory @var{dir}.
15274 The default is @file{/gdb}, i.e.@: the root directory on the current
15277 @item show remotedirectory
15278 @kindex show remotedirectory
15279 Show the current value of the upload directory.
15281 @item set remoteupload @var{method}
15282 @kindex set remoteupload
15283 Set the method used to upload files to remote device. Valid values
15284 for @var{method} are @samp{always}, @samp{newer}, and @samp{never}.
15285 The default is @samp{newer}.
15287 @item show remoteupload
15288 @kindex show remoteupload
15289 Show the current setting of the upload method.
15291 @item set remoteaddhost
15292 @kindex set remoteaddhost
15293 Tell @value{GDBN} whether to add this host to the remote stub's
15294 arguments when you debug over a network.
15296 @item show remoteaddhost
15297 @kindex show remoteaddhost
15298 Show whether to add this host to remote stub's arguments when
15299 debugging over a network.
15303 @node Architectures
15304 @section Architectures
15306 This section describes characteristics of architectures that affect
15307 all uses of @value{GDBN} with the architecture, both native and cross.
15314 * HPPA:: HP PA architecture
15318 @subsection x86 Architecture-specific issues.
15321 @item set struct-convention @var{mode}
15322 @kindex set struct-convention
15323 @cindex struct return convention
15324 @cindex struct/union returned in registers
15325 Set the convention used by the inferior to return @code{struct}s and
15326 @code{union}s from functions to @var{mode}. Possible values of
15327 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
15328 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
15329 are returned on the stack, while @code{"reg"} means that a
15330 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
15331 be returned in a register.
15333 @item show struct-convention
15334 @kindex show struct-convention
15335 Show the current setting of the convention to return @code{struct}s
15344 @kindex set rstack_high_address
15345 @cindex AMD 29K register stack
15346 @cindex register stack, AMD29K
15347 @item set rstack_high_address @var{address}
15348 On AMD 29000 family processors, registers are saved in a separate
15349 @dfn{register stack}. There is no way for @value{GDBN} to determine the
15350 extent of this stack. Normally, @value{GDBN} just assumes that the
15351 stack is ``large enough''. This may result in @value{GDBN} referencing
15352 memory locations that do not exist. If necessary, you can get around
15353 this problem by specifying the ending address of the register stack with
15354 the @code{set rstack_high_address} command. The argument should be an
15355 address, which you probably want to precede with @samp{0x} to specify in
15358 @kindex show rstack_high_address
15359 @item show rstack_high_address
15360 Display the current limit of the register stack, on AMD 29000 family
15368 See the following section.
15373 @cindex stack on Alpha
15374 @cindex stack on MIPS
15375 @cindex Alpha stack
15377 Alpha- and MIPS-based computers use an unusual stack frame, which
15378 sometimes requires @value{GDBN} to search backward in the object code to
15379 find the beginning of a function.
15381 @cindex response time, MIPS debugging
15382 To improve response time (especially for embedded applications, where
15383 @value{GDBN} may be restricted to a slow serial line for this search)
15384 you may want to limit the size of this search, using one of these
15388 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
15389 @item set heuristic-fence-post @var{limit}
15390 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
15391 search for the beginning of a function. A value of @var{0} (the
15392 default) means there is no limit. However, except for @var{0}, the
15393 larger the limit the more bytes @code{heuristic-fence-post} must search
15394 and therefore the longer it takes to run. You should only need to use
15395 this command when debugging a stripped executable.
15397 @item show heuristic-fence-post
15398 Display the current limit.
15402 These commands are available @emph{only} when @value{GDBN} is configured
15403 for debugging programs on Alpha or MIPS processors.
15405 Several MIPS-specific commands are available when debugging MIPS
15409 @item set mips saved-gpreg-size @var{size}
15410 @kindex set mips saved-gpreg-size
15411 @cindex MIPS GP register size on stack
15412 Set the size of MIPS general-purpose registers saved on the stack.
15413 The argument @var{size} can be one of the following:
15417 32-bit GP registers
15419 64-bit GP registers
15421 Use the target's default setting or autodetect the saved size from the
15422 information contained in the executable. This is the default
15425 @item show mips saved-gpreg-size
15426 @kindex show mips saved-gpreg-size
15427 Show the current size of MIPS GP registers on the stack.
15429 @item set mips stack-arg-size @var{size}
15430 @kindex set mips stack-arg-size
15431 @cindex MIPS stack space for arguments
15432 Set the amount of stack space reserved for arguments to functions.
15433 The argument can be one of @code{"32"}, @code{"64"} or @code{"auto"}
15436 @item set mips abi @var{arg}
15437 @kindex set mips abi
15438 @cindex set ABI for MIPS
15439 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
15440 values of @var{arg} are:
15444 The default ABI associated with the current binary (this is the
15455 @item show mips abi
15456 @kindex show mips abi
15457 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
15460 @itemx show mipsfpu
15461 @xref{MIPS Embedded, set mipsfpu}.
15463 @item set mips mask-address @var{arg}
15464 @kindex set mips mask-address
15465 @cindex MIPS addresses, masking
15466 This command determines whether the most-significant 32 bits of 64-bit
15467 MIPS addresses are masked off. The argument @var{arg} can be
15468 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
15469 setting, which lets @value{GDBN} determine the correct value.
15471 @item show mips mask-address
15472 @kindex show mips mask-address
15473 Show whether the upper 32 bits of MIPS addresses are masked off or
15476 @item set remote-mips64-transfers-32bit-regs
15477 @kindex set remote-mips64-transfers-32bit-regs
15478 This command controls compatibility with 64-bit MIPS targets that
15479 transfer data in 32-bit quantities. If you have an old MIPS 64 target
15480 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
15481 and 64 bits for other registers, set this option to @samp{on}.
15483 @item show remote-mips64-transfers-32bit-regs
15484 @kindex show remote-mips64-transfers-32bit-regs
15485 Show the current setting of compatibility with older MIPS 64 targets.
15487 @item set debug mips
15488 @kindex set debug mips
15489 This command turns on and off debugging messages for the MIPS-specific
15490 target code in @value{GDBN}.
15492 @item show debug mips
15493 @kindex show debug mips
15494 Show the current setting of MIPS debugging messages.
15500 @cindex HPPA support
15502 When @value{GDBN} is debugging te HP PA architecture, it provides the
15503 following special commands:
15506 @item set debug hppa
15507 @kindex set debug hppa
15508 THis command determines whether HPPA architecture specific debugging
15509 messages are to be displayed.
15511 @item show debug hppa
15512 Show whether HPPA debugging messages are displayed.
15514 @item maint print unwind @var{address}
15515 @kindex maint print unwind@r{, HPPA}
15516 This command displays the contents of the unwind table entry at the
15517 given @var{address}.
15522 @node Controlling GDB
15523 @chapter Controlling @value{GDBN}
15525 You can alter the way @value{GDBN} interacts with you by using the
15526 @code{set} command. For commands controlling how @value{GDBN} displays
15527 data, see @ref{Print Settings, ,Print settings}. Other settings are
15532 * Editing:: Command editing
15533 * Command History:: Command history
15534 * Screen Size:: Screen size
15535 * Numbers:: Numbers
15536 * ABI:: Configuring the current ABI
15537 * Messages/Warnings:: Optional warnings and messages
15538 * Debugging Output:: Optional messages about internal happenings
15546 @value{GDBN} indicates its readiness to read a command by printing a string
15547 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
15548 can change the prompt string with the @code{set prompt} command. For
15549 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
15550 the prompt in one of the @value{GDBN} sessions so that you can always tell
15551 which one you are talking to.
15553 @emph{Note:} @code{set prompt} does not add a space for you after the
15554 prompt you set. This allows you to set a prompt which ends in a space
15555 or a prompt that does not.
15559 @item set prompt @var{newprompt}
15560 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
15562 @kindex show prompt
15564 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
15568 @section Command editing
15570 @cindex command line editing
15572 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
15573 @sc{gnu} library provides consistent behavior for programs which provide a
15574 command line interface to the user. Advantages are @sc{gnu} Emacs-style
15575 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
15576 substitution, and a storage and recall of command history across
15577 debugging sessions.
15579 You may control the behavior of command line editing in @value{GDBN} with the
15580 command @code{set}.
15583 @kindex set editing
15586 @itemx set editing on
15587 Enable command line editing (enabled by default).
15589 @item set editing off
15590 Disable command line editing.
15592 @kindex show editing
15594 Show whether command line editing is enabled.
15597 @xref{Command Line Editing}, for more details about the Readline
15598 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
15599 encouraged to read that chapter.
15601 @node Command History
15602 @section Command history
15603 @cindex command history
15605 @value{GDBN} can keep track of the commands you type during your
15606 debugging sessions, so that you can be certain of precisely what
15607 happened. Use these commands to manage the @value{GDBN} command
15610 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
15611 package, to provide the history facility. @xref{Using History
15612 Interactively}, for the detailed description of the History library.
15614 To issue a command to @value{GDBN} without affecting certain aspects of
15615 the state which is seen by users, prefix it with @samp{server }. This
15616 means that this command will not affect the command history, nor will it
15617 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
15618 pressed on a line by itself.
15620 @cindex @code{server}, command prefix
15621 The server prefix does not affect the recording of values into the value
15622 history; to print a value without recording it into the value history,
15623 use the @code{output} command instead of the @code{print} command.
15625 Here is the description of @value{GDBN} commands related to command
15629 @cindex history substitution
15630 @cindex history file
15631 @kindex set history filename
15632 @cindex @env{GDBHISTFILE}, environment variable
15633 @item set history filename @var{fname}
15634 Set the name of the @value{GDBN} command history file to @var{fname}.
15635 This is the file where @value{GDBN} reads an initial command history
15636 list, and where it writes the command history from this session when it
15637 exits. You can access this list through history expansion or through
15638 the history command editing characters listed below. This file defaults
15639 to the value of the environment variable @code{GDBHISTFILE}, or to
15640 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
15643 @cindex save command history
15644 @kindex set history save
15645 @item set history save
15646 @itemx set history save on
15647 Record command history in a file, whose name may be specified with the
15648 @code{set history filename} command. By default, this option is disabled.
15650 @item set history save off
15651 Stop recording command history in a file.
15653 @cindex history size
15654 @kindex set history size
15655 @cindex @env{HISTSIZE}, environment variable
15656 @item set history size @var{size}
15657 Set the number of commands which @value{GDBN} keeps in its history list.
15658 This defaults to the value of the environment variable
15659 @code{HISTSIZE}, or to 256 if this variable is not set.
15662 History expansion assigns special meaning to the character @kbd{!}.
15663 @xref{Event Designators}, for more details.
15665 @cindex history expansion, turn on/off
15666 Since @kbd{!} is also the logical not operator in C, history expansion
15667 is off by default. If you decide to enable history expansion with the
15668 @code{set history expansion on} command, you may sometimes need to
15669 follow @kbd{!} (when it is used as logical not, in an expression) with
15670 a space or a tab to prevent it from being expanded. The readline
15671 history facilities do not attempt substitution on the strings
15672 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
15674 The commands to control history expansion are:
15677 @item set history expansion on
15678 @itemx set history expansion
15679 @kindex set history expansion
15680 Enable history expansion. History expansion is off by default.
15682 @item set history expansion off
15683 Disable history expansion.
15686 @kindex show history
15688 @itemx show history filename
15689 @itemx show history save
15690 @itemx show history size
15691 @itemx show history expansion
15692 These commands display the state of the @value{GDBN} history parameters.
15693 @code{show history} by itself displays all four states.
15698 @kindex show commands
15699 @cindex show last commands
15700 @cindex display command history
15701 @item show commands
15702 Display the last ten commands in the command history.
15704 @item show commands @var{n}
15705 Print ten commands centered on command number @var{n}.
15707 @item show commands +
15708 Print ten commands just after the commands last printed.
15712 @section Screen size
15713 @cindex size of screen
15714 @cindex pauses in output
15716 Certain commands to @value{GDBN} may produce large amounts of
15717 information output to the screen. To help you read all of it,
15718 @value{GDBN} pauses and asks you for input at the end of each page of
15719 output. Type @key{RET} when you want to continue the output, or @kbd{q}
15720 to discard the remaining output. Also, the screen width setting
15721 determines when to wrap lines of output. Depending on what is being
15722 printed, @value{GDBN} tries to break the line at a readable place,
15723 rather than simply letting it overflow onto the following line.
15725 Normally @value{GDBN} knows the size of the screen from the terminal
15726 driver software. For example, on Unix @value{GDBN} uses the termcap data base
15727 together with the value of the @code{TERM} environment variable and the
15728 @code{stty rows} and @code{stty cols} settings. If this is not correct,
15729 you can override it with the @code{set height} and @code{set
15736 @kindex show height
15737 @item set height @var{lpp}
15739 @itemx set width @var{cpl}
15741 These @code{set} commands specify a screen height of @var{lpp} lines and
15742 a screen width of @var{cpl} characters. The associated @code{show}
15743 commands display the current settings.
15745 If you specify a height of zero lines, @value{GDBN} does not pause during
15746 output no matter how long the output is. This is useful if output is to a
15747 file or to an editor buffer.
15749 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
15750 from wrapping its output.
15752 @item set pagination on
15753 @itemx set pagination off
15754 @kindex set pagination
15755 Turn the output pagination on or off; the default is on. Turning
15756 pagination off is the alternative to @code{set height 0}.
15758 @item show pagination
15759 @kindex show pagination
15760 Show the current pagination mode.
15765 @cindex number representation
15766 @cindex entering numbers
15768 You can always enter numbers in octal, decimal, or hexadecimal in
15769 @value{GDBN} by the usual conventions: octal numbers begin with
15770 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
15771 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
15772 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
15773 10; likewise, the default display for numbers---when no particular
15774 format is specified---is base 10. You can change the default base for
15775 both input and output with the commands described below.
15778 @kindex set input-radix
15779 @item set input-radix @var{base}
15780 Set the default base for numeric input. Supported choices
15781 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15782 specified either unambiguously or using the current input radix; for
15786 set input-radix 012
15787 set input-radix 10.
15788 set input-radix 0xa
15792 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
15793 leaves the input radix unchanged, no matter what it was, since
15794 @samp{10}, being without any leading or trailing signs of its base, is
15795 interpreted in the current radix. Thus, if the current radix is 16,
15796 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
15799 @kindex set output-radix
15800 @item set output-radix @var{base}
15801 Set the default base for numeric display. Supported choices
15802 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15803 specified either unambiguously or using the current input radix.
15805 @kindex show input-radix
15806 @item show input-radix
15807 Display the current default base for numeric input.
15809 @kindex show output-radix
15810 @item show output-radix
15811 Display the current default base for numeric display.
15813 @item set radix @r{[}@var{base}@r{]}
15817 These commands set and show the default base for both input and output
15818 of numbers. @code{set radix} sets the radix of input and output to
15819 the same base; without an argument, it resets the radix back to its
15820 default value of 10.
15825 @section Configuring the current ABI
15827 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
15828 application automatically. However, sometimes you need to override its
15829 conclusions. Use these commands to manage @value{GDBN}'s view of the
15836 One @value{GDBN} configuration can debug binaries for multiple operating
15837 system targets, either via remote debugging or native emulation.
15838 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
15839 but you can override its conclusion using the @code{set osabi} command.
15840 One example where this is useful is in debugging of binaries which use
15841 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
15842 not have the same identifying marks that the standard C library for your
15847 Show the OS ABI currently in use.
15850 With no argument, show the list of registered available OS ABI's.
15852 @item set osabi @var{abi}
15853 Set the current OS ABI to @var{abi}.
15856 @cindex float promotion
15858 Generally, the way that an argument of type @code{float} is passed to a
15859 function depends on whether the function is prototyped. For a prototyped
15860 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
15861 according to the architecture's convention for @code{float}. For unprototyped
15862 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
15863 @code{double} and then passed.
15865 Unfortunately, some forms of debug information do not reliably indicate whether
15866 a function is prototyped. If @value{GDBN} calls a function that is not marked
15867 as prototyped, it consults @kbd{set coerce-float-to-double}.
15870 @kindex set coerce-float-to-double
15871 @item set coerce-float-to-double
15872 @itemx set coerce-float-to-double on
15873 Arguments of type @code{float} will be promoted to @code{double} when passed
15874 to an unprototyped function. This is the default setting.
15876 @item set coerce-float-to-double off
15877 Arguments of type @code{float} will be passed directly to unprototyped
15880 @kindex show coerce-float-to-double
15881 @item show coerce-float-to-double
15882 Show the current setting of promoting @code{float} to @code{double}.
15886 @kindex show cp-abi
15887 @value{GDBN} needs to know the ABI used for your program's C@t{++}
15888 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
15889 used to build your application. @value{GDBN} only fully supports
15890 programs with a single C@t{++} ABI; if your program contains code using
15891 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
15892 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
15893 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
15894 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
15895 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
15896 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
15901 Show the C@t{++} ABI currently in use.
15904 With no argument, show the list of supported C@t{++} ABI's.
15906 @item set cp-abi @var{abi}
15907 @itemx set cp-abi auto
15908 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
15911 @node Messages/Warnings
15912 @section Optional warnings and messages
15914 @cindex verbose operation
15915 @cindex optional warnings
15916 By default, @value{GDBN} is silent about its inner workings. If you are
15917 running on a slow machine, you may want to use the @code{set verbose}
15918 command. This makes @value{GDBN} tell you when it does a lengthy
15919 internal operation, so you will not think it has crashed.
15921 Currently, the messages controlled by @code{set verbose} are those
15922 which announce that the symbol table for a source file is being read;
15923 see @code{symbol-file} in @ref{Files, ,Commands to specify files}.
15926 @kindex set verbose
15927 @item set verbose on
15928 Enables @value{GDBN} output of certain informational messages.
15930 @item set verbose off
15931 Disables @value{GDBN} output of certain informational messages.
15933 @kindex show verbose
15935 Displays whether @code{set verbose} is on or off.
15938 By default, if @value{GDBN} encounters bugs in the symbol table of an
15939 object file, it is silent; but if you are debugging a compiler, you may
15940 find this information useful (@pxref{Symbol Errors, ,Errors reading
15945 @kindex set complaints
15946 @item set complaints @var{limit}
15947 Permits @value{GDBN} to output @var{limit} complaints about each type of
15948 unusual symbols before becoming silent about the problem. Set
15949 @var{limit} to zero to suppress all complaints; set it to a large number
15950 to prevent complaints from being suppressed.
15952 @kindex show complaints
15953 @item show complaints
15954 Displays how many symbol complaints @value{GDBN} is permitted to produce.
15958 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
15959 lot of stupid questions to confirm certain commands. For example, if
15960 you try to run a program which is already running:
15964 The program being debugged has been started already.
15965 Start it from the beginning? (y or n)
15968 If you are willing to unflinchingly face the consequences of your own
15969 commands, you can disable this ``feature'':
15973 @kindex set confirm
15975 @cindex confirmation
15976 @cindex stupid questions
15977 @item set confirm off
15978 Disables confirmation requests.
15980 @item set confirm on
15981 Enables confirmation requests (the default).
15983 @kindex show confirm
15985 Displays state of confirmation requests.
15989 @cindex command tracing
15990 If you need to debug user-defined commands or sourced files you may find it
15991 useful to enable @dfn{command tracing}. In this mode each command will be
15992 printed as it is executed, prefixed with one or more @samp{+} symbols, the
15993 quantity denoting the call depth of each command.
15996 @kindex set trace-commands
15997 @cindex command scripts, debugging
15998 @item set trace-commands on
15999 Enable command tracing.
16000 @item set trace-commands off
16001 Disable command tracing.
16002 @item show trace-commands
16003 Display the current state of command tracing.
16006 @node Debugging Output
16007 @section Optional messages about internal happenings
16008 @cindex optional debugging messages
16010 @value{GDBN} has commands that enable optional debugging messages from
16011 various @value{GDBN} subsystems; normally these commands are of
16012 interest to @value{GDBN} maintainers, or when reporting a bug. This
16013 section documents those commands.
16016 @kindex set exec-done-display
16017 @item set exec-done-display
16018 Turns on or off the notification of asynchronous commands'
16019 completion. When on, @value{GDBN} will print a message when an
16020 asynchronous command finishes its execution. The default is off.
16021 @kindex show exec-done-display
16022 @item show exec-done-display
16023 Displays the current setting of asynchronous command completion
16026 @cindex gdbarch debugging info
16027 @cindex architecture debugging info
16028 @item set debug arch
16029 Turns on or off display of gdbarch debugging info. The default is off
16031 @item show debug arch
16032 Displays the current state of displaying gdbarch debugging info.
16033 @item set debug aix-thread
16034 @cindex AIX threads
16035 Display debugging messages about inner workings of the AIX thread
16037 @item show debug aix-thread
16038 Show the current state of AIX thread debugging info display.
16039 @item set debug event
16040 @cindex event debugging info
16041 Turns on or off display of @value{GDBN} event debugging info. The
16043 @item show debug event
16044 Displays the current state of displaying @value{GDBN} event debugging
16046 @item set debug expression
16047 @cindex expression debugging info
16048 Turns on or off display of debugging info about @value{GDBN}
16049 expression parsing. The default is off.
16050 @item show debug expression
16051 Displays the current state of displaying debugging info about
16052 @value{GDBN} expression parsing.
16053 @item set debug frame
16054 @cindex frame debugging info
16055 Turns on or off display of @value{GDBN} frame debugging info. The
16057 @item show debug frame
16058 Displays the current state of displaying @value{GDBN} frame debugging
16060 @item set debug infrun
16061 @cindex inferior debugging info
16062 Turns on or off display of @value{GDBN} debugging info for running the inferior.
16063 The default is off. @file{infrun.c} contains GDB's runtime state machine used
16064 for implementing operations such as single-stepping the inferior.
16065 @item show debug infrun
16066 Displays the current state of @value{GDBN} inferior debugging.
16067 @item set debug lin-lwp
16068 @cindex @sc{gnu}/Linux LWP debug messages
16069 @cindex Linux lightweight processes
16070 Turns on or off debugging messages from the Linux LWP debug support.
16071 @item show debug lin-lwp
16072 Show the current state of Linux LWP debugging messages.
16073 @item set debug observer
16074 @cindex observer debugging info
16075 Turns on or off display of @value{GDBN} observer debugging. This
16076 includes info such as the notification of observable events.
16077 @item show debug observer
16078 Displays the current state of observer debugging.
16079 @item set debug overload
16080 @cindex C@t{++} overload debugging info
16081 Turns on or off display of @value{GDBN} C@t{++} overload debugging
16082 info. This includes info such as ranking of functions, etc. The default
16084 @item show debug overload
16085 Displays the current state of displaying @value{GDBN} C@t{++} overload
16087 @cindex packets, reporting on stdout
16088 @cindex serial connections, debugging
16089 @cindex debug remote protocol
16090 @cindex remote protocol debugging
16091 @cindex display remote packets
16092 @item set debug remote
16093 Turns on or off display of reports on all packets sent back and forth across
16094 the serial line to the remote machine. The info is printed on the
16095 @value{GDBN} standard output stream. The default is off.
16096 @item show debug remote
16097 Displays the state of display of remote packets.
16098 @item set debug serial
16099 Turns on or off display of @value{GDBN} serial debugging info. The
16101 @item show debug serial
16102 Displays the current state of displaying @value{GDBN} serial debugging
16104 @item set debug solib-frv
16105 @cindex FR-V shared-library debugging
16106 Turns on or off debugging messages for FR-V shared-library code.
16107 @item show debug solib-frv
16108 Display the current state of FR-V shared-library code debugging
16110 @item set debug target
16111 @cindex target debugging info
16112 Turns on or off display of @value{GDBN} target debugging info. This info
16113 includes what is going on at the target level of GDB, as it happens. The
16114 default is 0. Set it to 1 to track events, and to 2 to also track the
16115 value of large memory transfers. Changes to this flag do not take effect
16116 until the next time you connect to a target or use the @code{run} command.
16117 @item show debug target
16118 Displays the current state of displaying @value{GDBN} target debugging
16120 @item set debugvarobj
16121 @cindex variable object debugging info
16122 Turns on or off display of @value{GDBN} variable object debugging
16123 info. The default is off.
16124 @item show debugvarobj
16125 Displays the current state of displaying @value{GDBN} variable object
16130 @chapter Canned Sequences of Commands
16132 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
16133 command lists}), @value{GDBN} provides two ways to store sequences of
16134 commands for execution as a unit: user-defined commands and command
16138 * Define:: How to define your own commands
16139 * Hooks:: Hooks for user-defined commands
16140 * Command Files:: How to write scripts of commands to be stored in a file
16141 * Output:: Commands for controlled output
16145 @section User-defined commands
16147 @cindex user-defined command
16148 @cindex arguments, to user-defined commands
16149 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
16150 which you assign a new name as a command. This is done with the
16151 @code{define} command. User commands may accept up to 10 arguments
16152 separated by whitespace. Arguments are accessed within the user command
16153 via @code{$arg0@dots{}$arg9}. A trivial example:
16157 print $arg0 + $arg1 + $arg2
16162 To execute the command use:
16169 This defines the command @code{adder}, which prints the sum of
16170 its three arguments. Note the arguments are text substitutions, so they may
16171 reference variables, use complex expressions, or even perform inferior
16174 @cindex argument count in user-defined commands
16175 @cindex how many arguments (user-defined commands)
16176 In addition, @code{$argc} may be used to find out how many arguments have
16177 been passed. This expands to a number in the range 0@dots{}10.
16182 print $arg0 + $arg1
16185 print $arg0 + $arg1 + $arg2
16193 @item define @var{commandname}
16194 Define a command named @var{commandname}. If there is already a command
16195 by that name, you are asked to confirm that you want to redefine it.
16197 The definition of the command is made up of other @value{GDBN} command lines,
16198 which are given following the @code{define} command. The end of these
16199 commands is marked by a line containing @code{end}.
16202 @kindex end@r{ (user-defined commands)}
16203 @item document @var{commandname}
16204 Document the user-defined command @var{commandname}, so that it can be
16205 accessed by @code{help}. The command @var{commandname} must already be
16206 defined. This command reads lines of documentation just as @code{define}
16207 reads the lines of the command definition, ending with @code{end}.
16208 After the @code{document} command is finished, @code{help} on command
16209 @var{commandname} displays the documentation you have written.
16211 You may use the @code{document} command again to change the
16212 documentation of a command. Redefining the command with @code{define}
16213 does not change the documentation.
16215 @kindex dont-repeat
16216 @cindex don't repeat command
16218 Used inside a user-defined command, this tells @value{GDBN} that this
16219 command should not be repeated when the user hits @key{RET}
16220 (@pxref{Command Syntax, repeat last command}).
16222 @kindex help user-defined
16223 @item help user-defined
16224 List all user-defined commands, with the first line of the documentation
16229 @itemx show user @var{commandname}
16230 Display the @value{GDBN} commands used to define @var{commandname} (but
16231 not its documentation). If no @var{commandname} is given, display the
16232 definitions for all user-defined commands.
16234 @cindex infinite recursion in user-defined commands
16235 @kindex show max-user-call-depth
16236 @kindex set max-user-call-depth
16237 @item show max-user-call-depth
16238 @itemx set max-user-call-depth
16239 The value of @code{max-user-call-depth} controls how many recursion
16240 levels are allowed in user-defined commands before GDB suspects an
16241 infinite recursion and aborts the command.
16244 In addition to the above commands, user-defined commands frequently
16245 use control flow commands, described in @ref{Command Files}.
16247 When user-defined commands are executed, the
16248 commands of the definition are not printed. An error in any command
16249 stops execution of the user-defined command.
16251 If used interactively, commands that would ask for confirmation proceed
16252 without asking when used inside a user-defined command. Many @value{GDBN}
16253 commands that normally print messages to say what they are doing omit the
16254 messages when used in a user-defined command.
16257 @section User-defined command hooks
16258 @cindex command hooks
16259 @cindex hooks, for commands
16260 @cindex hooks, pre-command
16263 You may define @dfn{hooks}, which are a special kind of user-defined
16264 command. Whenever you run the command @samp{foo}, if the user-defined
16265 command @samp{hook-foo} exists, it is executed (with no arguments)
16266 before that command.
16268 @cindex hooks, post-command
16270 A hook may also be defined which is run after the command you executed.
16271 Whenever you run the command @samp{foo}, if the user-defined command
16272 @samp{hookpost-foo} exists, it is executed (with no arguments) after
16273 that command. Post-execution hooks may exist simultaneously with
16274 pre-execution hooks, for the same command.
16276 It is valid for a hook to call the command which it hooks. If this
16277 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
16279 @c It would be nice if hookpost could be passed a parameter indicating
16280 @c if the command it hooks executed properly or not. FIXME!
16282 @kindex stop@r{, a pseudo-command}
16283 In addition, a pseudo-command, @samp{stop} exists. Defining
16284 (@samp{hook-stop}) makes the associated commands execute every time
16285 execution stops in your program: before breakpoint commands are run,
16286 displays are printed, or the stack frame is printed.
16288 For example, to ignore @code{SIGALRM} signals while
16289 single-stepping, but treat them normally during normal execution,
16294 handle SIGALRM nopass
16298 handle SIGALRM pass
16301 define hook-continue
16302 handle SIGLARM pass
16306 As a further example, to hook at the begining and end of the @code{echo}
16307 command, and to add extra text to the beginning and end of the message,
16315 define hookpost-echo
16319 (@value{GDBP}) echo Hello World
16320 <<<---Hello World--->>>
16325 You can define a hook for any single-word command in @value{GDBN}, but
16326 not for command aliases; you should define a hook for the basic command
16327 name, e.g.@: @code{backtrace} rather than @code{bt}.
16328 @c FIXME! So how does Joe User discover whether a command is an alias
16330 If an error occurs during the execution of your hook, execution of
16331 @value{GDBN} commands stops and @value{GDBN} issues a prompt
16332 (before the command that you actually typed had a chance to run).
16334 If you try to define a hook which does not match any known command, you
16335 get a warning from the @code{define} command.
16337 @node Command Files
16338 @section Command files
16340 @cindex command files
16341 @cindex scripting commands
16342 A command file for @value{GDBN} is a text file made of lines that are
16343 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
16344 also be included. An empty line in a command file does nothing; it
16345 does not mean to repeat the last command, as it would from the
16348 You can request the execution of a command file with the @code{source}
16353 @cindex execute commands from a file
16354 @item source [@code{-v}] @var{filename}
16355 Execute the command file @var{filename}.
16358 The lines in a command file are generally executed sequentially,
16359 unless the order of execution is changed by one of the
16360 @emph{flow-control commands} described below. The commands are not
16361 printed as they are executed. An error in any command terminates
16362 execution of the command file and control is returned to the console.
16364 @value{GDBN} searches for @var{filename} in the current directory and then
16365 on the search path (specified with the @samp{directory} command).
16367 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
16368 each command as it is executed. The option must be given before
16369 @var{filename}, and is interpreted as part of the filename anywhere else.
16371 Commands that would ask for confirmation if used interactively proceed
16372 without asking when used in a command file. Many @value{GDBN} commands that
16373 normally print messages to say what they are doing omit the messages
16374 when called from command files.
16376 @value{GDBN} also accepts command input from standard input. In this
16377 mode, normal output goes to standard output and error output goes to
16378 standard error. Errors in a command file supplied on standard input do
16379 not terminate execution of the command file---execution continues with
16383 gdb < cmds > log 2>&1
16386 (The syntax above will vary depending on the shell used.) This example
16387 will execute commands from the file @file{cmds}. All output and errors
16388 would be directed to @file{log}.
16390 Since commands stored on command files tend to be more general than
16391 commands typed interactively, they frequently need to deal with
16392 complicated situations, such as different or unexpected values of
16393 variables and symbols, changes in how the program being debugged is
16394 built, etc. @value{GDBN} provides a set of flow-control commands to
16395 deal with these complexities. Using these commands, you can write
16396 complex scripts that loop over data structures, execute commands
16397 conditionally, etc.
16404 This command allows to include in your script conditionally executed
16405 commands. The @code{if} command takes a single argument, which is an
16406 expression to evaluate. It is followed by a series of commands that
16407 are executed only if the expression is true (its value is nonzero).
16408 There can then optionally be an @code{else} line, followed by a series
16409 of commands that are only executed if the expression was false. The
16410 end of the list is marked by a line containing @code{end}.
16414 This command allows to write loops. Its syntax is similar to
16415 @code{if}: the command takes a single argument, which is an expression
16416 to evaluate, and must be followed by the commands to execute, one per
16417 line, terminated by an @code{end}. These commands are called the
16418 @dfn{body} of the loop. The commands in the body of @code{while} are
16419 executed repeatedly as long as the expression evaluates to true.
16423 This command exits the @code{while} loop in whose body it is included.
16424 Execution of the script continues after that @code{while}s @code{end}
16427 @kindex loop_continue
16428 @item loop_continue
16429 This command skips the execution of the rest of the body of commands
16430 in the @code{while} loop in whose body it is included. Execution
16431 branches to the beginning of the @code{while} loop, where it evaluates
16432 the controlling expression.
16434 @kindex end@r{ (if/else/while commands)}
16436 Terminate the block of commands that are the body of @code{if},
16437 @code{else}, or @code{while} flow-control commands.
16442 @section Commands for controlled output
16444 During the execution of a command file or a user-defined command, normal
16445 @value{GDBN} output is suppressed; the only output that appears is what is
16446 explicitly printed by the commands in the definition. This section
16447 describes three commands useful for generating exactly the output you
16452 @item echo @var{text}
16453 @c I do not consider backslash-space a standard C escape sequence
16454 @c because it is not in ANSI.
16455 Print @var{text}. Nonprinting characters can be included in
16456 @var{text} using C escape sequences, such as @samp{\n} to print a
16457 newline. @strong{No newline is printed unless you specify one.}
16458 In addition to the standard C escape sequences, a backslash followed
16459 by a space stands for a space. This is useful for displaying a
16460 string with spaces at the beginning or the end, since leading and
16461 trailing spaces are otherwise trimmed from all arguments.
16462 To print @samp{@w{ }and foo =@w{ }}, use the command
16463 @samp{echo \@w{ }and foo = \@w{ }}.
16465 A backslash at the end of @var{text} can be used, as in C, to continue
16466 the command onto subsequent lines. For example,
16469 echo This is some text\n\
16470 which is continued\n\
16471 onto several lines.\n
16474 produces the same output as
16477 echo This is some text\n
16478 echo which is continued\n
16479 echo onto several lines.\n
16483 @item output @var{expression}
16484 Print the value of @var{expression} and nothing but that value: no
16485 newlines, no @samp{$@var{nn} = }. The value is not entered in the
16486 value history either. @xref{Expressions, ,Expressions}, for more information
16489 @item output/@var{fmt} @var{expression}
16490 Print the value of @var{expression} in format @var{fmt}. You can use
16491 the same formats as for @code{print}. @xref{Output Formats,,Output
16492 formats}, for more information.
16495 @item printf @var{string}, @var{expressions}@dots{}
16496 Print the values of the @var{expressions} under the control of
16497 @var{string}. The @var{expressions} are separated by commas and may be
16498 either numbers or pointers. Their values are printed as specified by
16499 @var{string}, exactly as if your program were to execute the C
16501 @c FIXME: the above implies that at least all ANSI C formats are
16502 @c supported, but it isn't true: %E and %G don't work (or so it seems).
16503 @c Either this is a bug, or the manual should document what formats are
16507 printf (@var{string}, @var{expressions}@dots{});
16510 For example, you can print two values in hex like this:
16513 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
16516 The only backslash-escape sequences that you can use in the format
16517 string are the simple ones that consist of backslash followed by a
16522 @chapter Command Interpreters
16523 @cindex command interpreters
16525 @value{GDBN} supports multiple command interpreters, and some command
16526 infrastructure to allow users or user interface writers to switch
16527 between interpreters or run commands in other interpreters.
16529 @value{GDBN} currently supports two command interpreters, the console
16530 interpreter (sometimes called the command-line interpreter or @sc{cli})
16531 and the machine interface interpreter (or @sc{gdb/mi}). This manual
16532 describes both of these interfaces in great detail.
16534 By default, @value{GDBN} will start with the console interpreter.
16535 However, the user may choose to start @value{GDBN} with another
16536 interpreter by specifying the @option{-i} or @option{--interpreter}
16537 startup options. Defined interpreters include:
16541 @cindex console interpreter
16542 The traditional console or command-line interpreter. This is the most often
16543 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
16544 @value{GDBN} will use this interpreter.
16547 @cindex mi interpreter
16548 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
16549 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
16550 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
16554 @cindex mi2 interpreter
16555 The current @sc{gdb/mi} interface.
16558 @cindex mi1 interpreter
16559 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
16563 @cindex invoke another interpreter
16564 The interpreter being used by @value{GDBN} may not be dynamically
16565 switched at runtime. Although possible, this could lead to a very
16566 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
16567 enters the command "interpreter-set console" in a console view,
16568 @value{GDBN} would switch to using the console interpreter, rendering
16569 the IDE inoperable!
16571 @kindex interpreter-exec
16572 Although you may only choose a single interpreter at startup, you may execute
16573 commands in any interpreter from the current interpreter using the appropriate
16574 command. If you are running the console interpreter, simply use the
16575 @code{interpreter-exec} command:
16578 interpreter-exec mi "-data-list-register-names"
16581 @sc{gdb/mi} has a similar command, although it is only available in versions of
16582 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
16585 @chapter @value{GDBN} Text User Interface
16587 @cindex Text User Interface
16590 * TUI Overview:: TUI overview
16591 * TUI Keys:: TUI key bindings
16592 * TUI Single Key Mode:: TUI single key mode
16593 * TUI Commands:: TUI specific commands
16594 * TUI Configuration:: TUI configuration variables
16597 The @value{GDBN} Text User Interface, TUI in short, is a terminal
16598 interface which uses the @code{curses} library to show the source
16599 file, the assembly output, the program registers and @value{GDBN}
16600 commands in separate text windows.
16602 The TUI is enabled by invoking @value{GDBN} using either
16604 @samp{gdbtui} or @samp{gdb -tui}.
16607 @section TUI overview
16609 The TUI has two display modes that can be switched while
16614 A curses (or TUI) mode in which it displays several text
16615 windows on the terminal.
16618 A standard mode which corresponds to the @value{GDBN} configured without
16622 In the TUI mode, @value{GDBN} can display several text window
16627 This window is the @value{GDBN} command window with the @value{GDBN}
16628 prompt and the @value{GDBN} outputs. The @value{GDBN} input is still
16629 managed using readline but through the TUI. The @emph{command}
16630 window is always visible.
16633 The source window shows the source file of the program. The current
16634 line as well as active breakpoints are displayed in this window.
16637 The assembly window shows the disassembly output of the program.
16640 This window shows the processor registers. It detects when
16641 a register is changed and when this is the case, registers that have
16642 changed are highlighted.
16646 The source and assembly windows show the current program position
16647 by highlighting the current line and marking them with the @samp{>} marker.
16648 Breakpoints are also indicated with two markers. A first one
16649 indicates the breakpoint type:
16653 Breakpoint which was hit at least once.
16656 Breakpoint which was never hit.
16659 Hardware breakpoint which was hit at least once.
16662 Hardware breakpoint which was never hit.
16666 The second marker indicates whether the breakpoint is enabled or not:
16670 Breakpoint is enabled.
16673 Breakpoint is disabled.
16677 The source, assembly and register windows are attached to the thread
16678 and the frame position. They are updated when the current thread
16679 changes, when the frame changes or when the program counter changes.
16680 These three windows are arranged by the TUI according to several
16681 layouts. The layout defines which of these three windows are visible.
16682 The following layouts are available:
16692 source and assembly
16695 source and registers
16698 assembly and registers
16702 On top of the command window a status line gives various information
16703 concerning the current process begin debugged. The status line is
16704 updated when the information it shows changes. The following fields
16709 Indicates the current gdb target
16710 (@pxref{Targets, ,Specifying a Debugging Target}).
16713 Gives information about the current process or thread number.
16714 When no process is being debugged, this field is set to @code{No process}.
16717 Gives the current function name for the selected frame.
16718 The name is demangled if demangling is turned on (@pxref{Print Settings}).
16719 When there is no symbol corresponding to the current program counter
16720 the string @code{??} is displayed.
16723 Indicates the current line number for the selected frame.
16724 When the current line number is not known the string @code{??} is displayed.
16727 Indicates the current program counter address.
16732 @section TUI Key Bindings
16733 @cindex TUI key bindings
16735 The TUI installs several key bindings in the readline keymaps
16736 (@pxref{Command Line Editing}).
16737 They allow to leave or enter in the TUI mode or they operate
16738 directly on the TUI layout and windows. The TUI also provides
16739 a @emph{SingleKey} keymap which binds several keys directly to
16740 @value{GDBN} commands. The following key bindings
16741 are installed for both TUI mode and the @value{GDBN} standard mode.
16750 Enter or leave the TUI mode. When the TUI mode is left,
16751 the curses window management is left and @value{GDBN} operates using
16752 its standard mode writing on the terminal directly. When the TUI
16753 mode is entered, the control is given back to the curses windows.
16754 The screen is then refreshed.
16758 Use a TUI layout with only one window. The layout will
16759 either be @samp{source} or @samp{assembly}. When the TUI mode
16760 is not active, it will switch to the TUI mode.
16762 Think of this key binding as the Emacs @kbd{C-x 1} binding.
16766 Use a TUI layout with at least two windows. When the current
16767 layout shows already two windows, a next layout with two windows is used.
16768 When a new layout is chosen, one window will always be common to the
16769 previous layout and the new one.
16771 Think of it as the Emacs @kbd{C-x 2} binding.
16775 Change the active window. The TUI associates several key bindings
16776 (like scrolling and arrow keys) to the active window. This command
16777 gives the focus to the next TUI window.
16779 Think of it as the Emacs @kbd{C-x o} binding.
16783 Use the TUI @emph{SingleKey} keymap that binds single key to gdb commands
16784 (@pxref{TUI Single Key Mode}).
16788 The following key bindings are handled only by the TUI mode:
16793 Scroll the active window one page up.
16797 Scroll the active window one page down.
16801 Scroll the active window one line up.
16805 Scroll the active window one line down.
16809 Scroll the active window one column left.
16813 Scroll the active window one column right.
16817 Refresh the screen.
16821 In the TUI mode, the arrow keys are used by the active window
16822 for scrolling. This means they are available for readline when the
16823 active window is the command window. When the command window
16824 does not have the focus, it is necessary to use other readline
16825 key bindings such as @key{C-p}, @key{C-n}, @key{C-b} and @key{C-f}.
16827 @node TUI Single Key Mode
16828 @section TUI Single Key Mode
16829 @cindex TUI single key mode
16831 The TUI provides a @emph{SingleKey} mode in which it installs a particular
16832 key binding in the readline keymaps to connect single keys to
16836 @kindex c @r{(SingleKey TUI key)}
16840 @kindex d @r{(SingleKey TUI key)}
16844 @kindex f @r{(SingleKey TUI key)}
16848 @kindex n @r{(SingleKey TUI key)}
16852 @kindex q @r{(SingleKey TUI key)}
16854 exit the @emph{SingleKey} mode.
16856 @kindex r @r{(SingleKey TUI key)}
16860 @kindex s @r{(SingleKey TUI key)}
16864 @kindex u @r{(SingleKey TUI key)}
16868 @kindex v @r{(SingleKey TUI key)}
16872 @kindex w @r{(SingleKey TUI key)}
16878 Other keys temporarily switch to the @value{GDBN} command prompt.
16879 The key that was pressed is inserted in the editing buffer so that
16880 it is possible to type most @value{GDBN} commands without interaction
16881 with the TUI @emph{SingleKey} mode. Once the command is entered the TUI
16882 @emph{SingleKey} mode is restored. The only way to permanently leave
16883 this mode is by hitting @key{q} or @samp{@key{C-x} @key{s}}.
16887 @section TUI specific commands
16888 @cindex TUI commands
16890 The TUI has specific commands to control the text windows.
16891 These commands are always available, that is they do not depend on
16892 the current terminal mode in which @value{GDBN} runs. When @value{GDBN}
16893 is in the standard mode, using these commands will automatically switch
16899 List and give the size of all displayed windows.
16903 Display the next layout.
16906 Display the previous layout.
16909 Display the source window only.
16912 Display the assembly window only.
16915 Display the source and assembly window.
16918 Display the register window together with the source or assembly window.
16920 @item focus next | prev | src | asm | regs | split
16922 Set the focus to the named window.
16923 This command allows to change the active window so that scrolling keys
16924 can be affected to another window.
16928 Refresh the screen. This is similar to using @key{C-L} key.
16930 @item tui reg float
16932 Show the floating point registers in the register window.
16934 @item tui reg general
16935 Show the general registers in the register window.
16938 Show the next register group. The list of register groups as well as
16939 their order is target specific. The predefined register groups are the
16940 following: @code{general}, @code{float}, @code{system}, @code{vector},
16941 @code{all}, @code{save}, @code{restore}.
16943 @item tui reg system
16944 Show the system registers in the register window.
16948 Update the source window and the current execution point.
16950 @item winheight @var{name} +@var{count}
16951 @itemx winheight @var{name} -@var{count}
16953 Change the height of the window @var{name} by @var{count}
16954 lines. Positive counts increase the height, while negative counts
16958 @kindex tabset @var{nchars}
16959 Set the width of tab stops to be @var{nchars} characters.
16963 @node TUI Configuration
16964 @section TUI configuration variables
16965 @cindex TUI configuration variables
16967 The TUI has several configuration variables that control the
16968 appearance of windows on the terminal.
16971 @item set tui border-kind @var{kind}
16972 @kindex set tui border-kind
16973 Select the border appearance for the source, assembly and register windows.
16974 The possible values are the following:
16977 Use a space character to draw the border.
16980 Use ascii characters + - and | to draw the border.
16983 Use the Alternate Character Set to draw the border. The border is
16984 drawn using character line graphics if the terminal supports them.
16988 @item set tui active-border-mode @var{mode}
16989 @kindex set tui active-border-mode
16990 Select the attributes to display the border of the active window.
16991 The possible values are @code{normal}, @code{standout}, @code{reverse},
16992 @code{half}, @code{half-standout}, @code{bold} and @code{bold-standout}.
16994 @item set tui border-mode @var{mode}
16995 @kindex set tui border-mode
16996 Select the attributes to display the border of other windows.
16997 The @var{mode} can be one of the following:
17000 Use normal attributes to display the border.
17006 Use reverse video mode.
17009 Use half bright mode.
17011 @item half-standout
17012 Use half bright and standout mode.
17015 Use extra bright or bold mode.
17017 @item bold-standout
17018 Use extra bright or bold and standout mode.
17025 @chapter Using @value{GDBN} under @sc{gnu} Emacs
17028 @cindex @sc{gnu} Emacs
17029 A special interface allows you to use @sc{gnu} Emacs to view (and
17030 edit) the source files for the program you are debugging with
17033 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
17034 executable file you want to debug as an argument. This command starts
17035 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
17036 created Emacs buffer.
17037 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
17039 Using @value{GDBN} under Emacs is just like using @value{GDBN} normally except for two
17044 All ``terminal'' input and output goes through the Emacs buffer.
17047 This applies both to @value{GDBN} commands and their output, and to the input
17048 and output done by the program you are debugging.
17050 This is useful because it means that you can copy the text of previous
17051 commands and input them again; you can even use parts of the output
17054 All the facilities of Emacs' Shell mode are available for interacting
17055 with your program. In particular, you can send signals the usual
17056 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
17061 @value{GDBN} displays source code through Emacs.
17064 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
17065 source file for that frame and puts an arrow (@samp{=>}) at the
17066 left margin of the current line. Emacs uses a separate buffer for
17067 source display, and splits the screen to show both your @value{GDBN} session
17070 Explicit @value{GDBN} @code{list} or search commands still produce output as
17071 usual, but you probably have no reason to use them from Emacs.
17073 If you specify an absolute file name when prompted for the @kbd{M-x
17074 gdb} argument, then Emacs sets your current working directory to where
17075 your program resides. If you only specify the file name, then Emacs
17076 sets your current working directory to to the directory associated
17077 with the previous buffer. In this case, @value{GDBN} may find your
17078 program by searching your environment's @code{PATH} variable, but on
17079 some operating systems it might not find the source. So, although the
17080 @value{GDBN} input and output session proceeds normally, the auxiliary
17081 buffer does not display the current source and line of execution.
17083 The initial working directory of @value{GDBN} is printed on the top
17084 line of the @value{GDBN} I/O buffer and this serves as a default for
17085 the commands that specify files for @value{GDBN} to operate
17086 on. @xref{Files, ,Commands to specify files}.
17088 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
17089 need to call @value{GDBN} by a different name (for example, if you
17090 keep several configurations around, with different names) you can
17091 customize the Emacs variable @code{gud-gdb-command-name} to run the
17094 In the @value{GDBN} I/O buffer, you can use these special Emacs commands in
17095 addition to the standard Shell mode commands:
17099 Describe the features of Emacs' @value{GDBN} Mode.
17102 Execute to another source line, like the @value{GDBN} @code{step} command; also
17103 update the display window to show the current file and location.
17106 Execute to next source line in this function, skipping all function
17107 calls, like the @value{GDBN} @code{next} command. Then update the display window
17108 to show the current file and location.
17111 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
17112 display window accordingly.
17115 Execute until exit from the selected stack frame, like the @value{GDBN}
17116 @code{finish} command.
17119 Continue execution of your program, like the @value{GDBN} @code{continue}
17123 Go up the number of frames indicated by the numeric argument
17124 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
17125 like the @value{GDBN} @code{up} command.
17128 Go down the number of frames indicated by the numeric argument, like the
17129 @value{GDBN} @code{down} command.
17132 In any source file, the Emacs command @kbd{C-x SPC} (@code{gud-break})
17133 tells @value{GDBN} to set a breakpoint on the source line point is on.
17135 If you type @kbd{M-x speedbar}, then Emacs displays a separate frame which
17136 shows a backtrace when the @value{GDBN} I/O buffer is current. Move
17137 point to any frame in the stack and type @key{RET} to make it become the
17138 current frame and display the associated source in the source buffer.
17139 Alternatively, click @kbd{Mouse-2} to make the selected frame become the
17142 If you accidentally delete the source-display buffer, an easy way to get
17143 it back is to type the command @code{f} in the @value{GDBN} buffer, to
17144 request a frame display; when you run under Emacs, this recreates
17145 the source buffer if necessary to show you the context of the current
17148 The source files displayed in Emacs are in ordinary Emacs buffers
17149 which are visiting the source files in the usual way. You can edit
17150 the files with these buffers if you wish; but keep in mind that @value{GDBN}
17151 communicates with Emacs in terms of line numbers. If you add or
17152 delete lines from the text, the line numbers that @value{GDBN} knows cease
17153 to correspond properly with the code.
17155 The description given here is for GNU Emacs version 21.3 and a more
17156 detailed description of its interaction with @value{GDBN} is given in
17157 the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu} Emacs Manual}).
17159 @c The following dropped because Epoch is nonstandard. Reactivate
17160 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
17162 @kindex Emacs Epoch environment
17166 Version 18 of @sc{gnu} Emacs has a built-in window system
17167 called the @code{epoch}
17168 environment. Users of this environment can use a new command,
17169 @code{inspect} which performs identically to @code{print} except that
17170 each value is printed in its own window.
17175 @chapter The @sc{gdb/mi} Interface
17177 @unnumberedsec Function and Purpose
17179 @cindex @sc{gdb/mi}, its purpose
17180 @sc{gdb/mi} is a line based machine oriented text interface to
17181 @value{GDBN} and is activated by specifying using the
17182 @option{--interpreter} command line option (@pxref{Mode Options}). It
17183 is specifically intended to support the development of systems which
17184 use the debugger as just one small component of a larger system.
17186 This chapter is a specification of the @sc{gdb/mi} interface. It is written
17187 in the form of a reference manual.
17189 Note that @sc{gdb/mi} is still under construction, so some of the
17190 features described below are incomplete and subject to change
17191 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
17193 @unnumberedsec Notation and Terminology
17195 @cindex notational conventions, for @sc{gdb/mi}
17196 This chapter uses the following notation:
17200 @code{|} separates two alternatives.
17203 @code{[ @var{something} ]} indicates that @var{something} is optional:
17204 it may or may not be given.
17207 @code{( @var{group} )*} means that @var{group} inside the parentheses
17208 may repeat zero or more times.
17211 @code{( @var{group} )+} means that @var{group} inside the parentheses
17212 may repeat one or more times.
17215 @code{"@var{string}"} means a literal @var{string}.
17219 @heading Dependencies
17223 * GDB/MI Command Syntax::
17224 * GDB/MI Compatibility with CLI::
17225 * GDB/MI Development and Front Ends::
17226 * GDB/MI Output Records::
17227 * GDB/MI Simple Examples::
17228 * GDB/MI Command Description Format::
17229 * GDB/MI Breakpoint Commands::
17230 * GDB/MI Program Context::
17231 * GDB/MI Thread Commands::
17232 * GDB/MI Program Execution::
17233 * GDB/MI Stack Manipulation::
17234 * GDB/MI Variable Objects::
17235 * GDB/MI Data Manipulation::
17236 * GDB/MI Tracepoint Commands::
17237 * GDB/MI Symbol Query::
17238 * GDB/MI File Commands::
17240 * GDB/MI Kod Commands::
17241 * GDB/MI Memory Overlay Commands::
17242 * GDB/MI Signal Handling Commands::
17244 * GDB/MI Target Manipulation::
17245 * GDB/MI Miscellaneous Commands::
17248 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17249 @node GDB/MI Command Syntax
17250 @section @sc{gdb/mi} Command Syntax
17253 * GDB/MI Input Syntax::
17254 * GDB/MI Output Syntax::
17257 @node GDB/MI Input Syntax
17258 @subsection @sc{gdb/mi} Input Syntax
17260 @cindex input syntax for @sc{gdb/mi}
17261 @cindex @sc{gdb/mi}, input syntax
17263 @item @var{command} @expansion{}
17264 @code{@var{cli-command} | @var{mi-command}}
17266 @item @var{cli-command} @expansion{}
17267 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
17268 @var{cli-command} is any existing @value{GDBN} CLI command.
17270 @item @var{mi-command} @expansion{}
17271 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
17272 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
17274 @item @var{token} @expansion{}
17275 "any sequence of digits"
17277 @item @var{option} @expansion{}
17278 @code{"-" @var{parameter} [ " " @var{parameter} ]}
17280 @item @var{parameter} @expansion{}
17281 @code{@var{non-blank-sequence} | @var{c-string}}
17283 @item @var{operation} @expansion{}
17284 @emph{any of the operations described in this chapter}
17286 @item @var{non-blank-sequence} @expansion{}
17287 @emph{anything, provided it doesn't contain special characters such as
17288 "-", @var{nl}, """ and of course " "}
17290 @item @var{c-string} @expansion{}
17291 @code{""" @var{seven-bit-iso-c-string-content} """}
17293 @item @var{nl} @expansion{}
17302 The CLI commands are still handled by the @sc{mi} interpreter; their
17303 output is described below.
17306 The @code{@var{token}}, when present, is passed back when the command
17310 Some @sc{mi} commands accept optional arguments as part of the parameter
17311 list. Each option is identified by a leading @samp{-} (dash) and may be
17312 followed by an optional argument parameter. Options occur first in the
17313 parameter list and can be delimited from normal parameters using
17314 @samp{--} (this is useful when some parameters begin with a dash).
17321 We want easy access to the existing CLI syntax (for debugging).
17324 We want it to be easy to spot a @sc{mi} operation.
17327 @node GDB/MI Output Syntax
17328 @subsection @sc{gdb/mi} Output Syntax
17330 @cindex output syntax of @sc{gdb/mi}
17331 @cindex @sc{gdb/mi}, output syntax
17332 The output from @sc{gdb/mi} consists of zero or more out-of-band records
17333 followed, optionally, by a single result record. This result record
17334 is for the most recent command. The sequence of output records is
17335 terminated by @samp{(gdb)}.
17337 If an input command was prefixed with a @code{@var{token}} then the
17338 corresponding output for that command will also be prefixed by that same
17342 @item @var{output} @expansion{}
17343 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
17345 @item @var{result-record} @expansion{}
17346 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
17348 @item @var{out-of-band-record} @expansion{}
17349 @code{@var{async-record} | @var{stream-record}}
17351 @item @var{async-record} @expansion{}
17352 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
17354 @item @var{exec-async-output} @expansion{}
17355 @code{[ @var{token} ] "*" @var{async-output}}
17357 @item @var{status-async-output} @expansion{}
17358 @code{[ @var{token} ] "+" @var{async-output}}
17360 @item @var{notify-async-output} @expansion{}
17361 @code{[ @var{token} ] "=" @var{async-output}}
17363 @item @var{async-output} @expansion{}
17364 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
17366 @item @var{result-class} @expansion{}
17367 @code{"done" | "running" | "connected" | "error" | "exit"}
17369 @item @var{async-class} @expansion{}
17370 @code{"stopped" | @var{others}} (where @var{others} will be added
17371 depending on the needs---this is still in development).
17373 @item @var{result} @expansion{}
17374 @code{ @var{variable} "=" @var{value}}
17376 @item @var{variable} @expansion{}
17377 @code{ @var{string} }
17379 @item @var{value} @expansion{}
17380 @code{ @var{const} | @var{tuple} | @var{list} }
17382 @item @var{const} @expansion{}
17383 @code{@var{c-string}}
17385 @item @var{tuple} @expansion{}
17386 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
17388 @item @var{list} @expansion{}
17389 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
17390 @var{result} ( "," @var{result} )* "]" }
17392 @item @var{stream-record} @expansion{}
17393 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
17395 @item @var{console-stream-output} @expansion{}
17396 @code{"~" @var{c-string}}
17398 @item @var{target-stream-output} @expansion{}
17399 @code{"@@" @var{c-string}}
17401 @item @var{log-stream-output} @expansion{}
17402 @code{"&" @var{c-string}}
17404 @item @var{nl} @expansion{}
17407 @item @var{token} @expansion{}
17408 @emph{any sequence of digits}.
17416 All output sequences end in a single line containing a period.
17419 The @code{@var{token}} is from the corresponding request. If an execution
17420 command is interrupted by the @samp{-exec-interrupt} command, the
17421 @var{token} associated with the @samp{*stopped} message is the one of the
17422 original execution command, not the one of the interrupt command.
17425 @cindex status output in @sc{gdb/mi}
17426 @var{status-async-output} contains on-going status information about the
17427 progress of a slow operation. It can be discarded. All status output is
17428 prefixed by @samp{+}.
17431 @cindex async output in @sc{gdb/mi}
17432 @var{exec-async-output} contains asynchronous state change on the target
17433 (stopped, started, disappeared). All async output is prefixed by
17437 @cindex notify output in @sc{gdb/mi}
17438 @var{notify-async-output} contains supplementary information that the
17439 client should handle (e.g., a new breakpoint information). All notify
17440 output is prefixed by @samp{=}.
17443 @cindex console output in @sc{gdb/mi}
17444 @var{console-stream-output} is output that should be displayed as is in the
17445 console. It is the textual response to a CLI command. All the console
17446 output is prefixed by @samp{~}.
17449 @cindex target output in @sc{gdb/mi}
17450 @var{target-stream-output} is the output produced by the target program.
17451 All the target output is prefixed by @samp{@@}.
17454 @cindex log output in @sc{gdb/mi}
17455 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
17456 instance messages that should be displayed as part of an error log. All
17457 the log output is prefixed by @samp{&}.
17460 @cindex list output in @sc{gdb/mi}
17461 New @sc{gdb/mi} commands should only output @var{lists} containing
17467 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
17468 details about the various output records.
17470 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17471 @node GDB/MI Compatibility with CLI
17472 @section @sc{gdb/mi} Compatibility with CLI
17474 @cindex compatibility, @sc{gdb/mi} and CLI
17475 @cindex @sc{gdb/mi}, compatibility with CLI
17477 For the developers convenience CLI commands can be entered directly,
17478 but there may be some unexpected behaviour. For example, commands
17479 that query the user will behave as if the user replied yes, breakpoint
17480 command lists are not executed and some CLI commands, such as
17481 @code{if}, @code{when} and @code{define}, prompt for further input with
17482 @samp{>}, which is not valid MI output.
17484 This feature may be removed at some stage in the future and it is
17485 recommended that front ends use the @code{-interpreter-exec} command
17486 (@pxref{-interpreter-exec}).
17488 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17489 @node GDB/MI Development and Front Ends
17490 @section @sc{gdb/mi} Development and Front Ends
17491 @cindex @sc{gdb/mi} development
17493 The application which takes the MI output and presents the state of the
17494 program being debugged to the user is called a @dfn{front end}.
17496 Although @sc{gdb/mi} is still incomplete, it is currently being used
17497 by a variety of front ends to @value{GDBN}. This makes it difficult
17498 to introduce new functionality without breaking existing usage. This
17499 section tries to minimize the problems by describing how the protocol
17502 Some changes in MI need not break a carefully designed front end, and
17503 for these the MI version will remain unchanged. The following is a
17504 list of changes that may occur within one level, so front ends should
17505 parse MI output in a way that can handle them:
17509 New MI commands may be added.
17512 New fields may be added to the output of any MI command.
17514 @c The format of field's content e.g type prefix, may change so parse it
17515 @c at your own risk. Yes, in general?
17517 @c The order of fields may change? Shouldn't really matter but it might
17518 @c resolve inconsistencies.
17521 If the changes are likely to break front ends, the MI version level
17522 will be increased by one. This will allow the front end to parse the
17523 output according to the MI version. Apart from mi0, new versions of
17524 @value{GDBN} will not support old versions of MI and it will be the
17525 responsibility of the front end to work with the new one.
17527 @c Starting with mi3, add a new command -mi-version that prints the MI
17530 The best way to avoid unexpected changes in MI that might break your front
17531 end is to make your project known to @value{GDBN} developers and
17532 follow development on @email{gdb@@sourceware.org} and
17533 @email{gdb-patches@@sourceware.org}. There is also the mailing list
17534 @email{dmi-discuss@@lists.freestandards.org}, hosted by the Free Standards
17535 Group, which has the aim of creating a a more general MI protocol
17536 called Debugger Machine Interface (DMI) that will become a standard
17537 for all debuggers, not just @value{GDBN}.
17538 @cindex mailing lists
17540 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17541 @node GDB/MI Output Records
17542 @section @sc{gdb/mi} Output Records
17545 * GDB/MI Result Records::
17546 * GDB/MI Stream Records::
17547 * GDB/MI Out-of-band Records::
17550 @node GDB/MI Result Records
17551 @subsection @sc{gdb/mi} Result Records
17553 @cindex result records in @sc{gdb/mi}
17554 @cindex @sc{gdb/mi}, result records
17555 In addition to a number of out-of-band notifications, the response to a
17556 @sc{gdb/mi} command includes one of the following result indications:
17560 @item "^done" [ "," @var{results} ]
17561 The synchronous operation was successful, @code{@var{results}} are the return
17566 @c Is this one correct? Should it be an out-of-band notification?
17567 The asynchronous operation was successfully started. The target is
17572 GDB has connected to a remote target.
17574 @item "^error" "," @var{c-string}
17576 The operation failed. The @code{@var{c-string}} contains the corresponding
17581 GDB has terminated.
17585 @node GDB/MI Stream Records
17586 @subsection @sc{gdb/mi} Stream Records
17588 @cindex @sc{gdb/mi}, stream records
17589 @cindex stream records in @sc{gdb/mi}
17590 @value{GDBN} internally maintains a number of output streams: the console, the
17591 target, and the log. The output intended for each of these streams is
17592 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
17594 Each stream record begins with a unique @dfn{prefix character} which
17595 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
17596 Syntax}). In addition to the prefix, each stream record contains a
17597 @code{@var{string-output}}. This is either raw text (with an implicit new
17598 line) or a quoted C string (which does not contain an implicit newline).
17601 @item "~" @var{string-output}
17602 The console output stream contains text that should be displayed in the
17603 CLI console window. It contains the textual responses to CLI commands.
17605 @item "@@" @var{string-output}
17606 The target output stream contains any textual output from the running
17607 target. This is only present when GDB's event loop is truly
17608 asynchronous, which is currently only the case for remote targets.
17610 @item "&" @var{string-output}
17611 The log stream contains debugging messages being produced by @value{GDBN}'s
17615 @node GDB/MI Out-of-band Records
17616 @subsection @sc{gdb/mi} Out-of-band Records
17618 @cindex out-of-band records in @sc{gdb/mi}
17619 @cindex @sc{gdb/mi}, out-of-band records
17620 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
17621 additional changes that have occurred. Those changes can either be a
17622 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
17623 target activity (e.g., target stopped).
17625 The following is a preliminary list of possible out-of-band records.
17626 In particular, the @var{exec-async-output} records.
17629 @item *stopped,reason="@var{reason}"
17632 @var{reason} can be one of the following:
17635 @item breakpoint-hit
17636 A breakpoint was reached.
17637 @item watchpoint-trigger
17638 A watchpoint was triggered.
17639 @item read-watchpoint-trigger
17640 A read watchpoint was triggered.
17641 @item access-watchpoint-trigger
17642 An access watchpoint was triggered.
17643 @item function-finished
17644 An -exec-finish or similar CLI command was accomplished.
17645 @item location-reached
17646 An -exec-until or similar CLI command was accomplished.
17647 @item watchpoint-scope
17648 A watchpoint has gone out of scope.
17649 @item end-stepping-range
17650 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
17651 similar CLI command was accomplished.
17652 @item exited-signalled
17653 The inferior exited because of a signal.
17655 The inferior exited.
17656 @item exited-normally
17657 The inferior exited normally.
17658 @item signal-received
17659 A signal was received by the inferior.
17663 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17664 @node GDB/MI Simple Examples
17665 @section Simple Examples of @sc{gdb/mi} Interaction
17666 @cindex @sc{gdb/mi}, simple examples
17668 This subsection presents several simple examples of interaction using
17669 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
17670 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
17671 the output received from @sc{gdb/mi}.
17673 Note the the line breaks shown in the examples are here only for
17674 readability, they don't appear in the real output.
17676 @subheading Setting a breakpoint
17678 Setting a breakpoint generates synchronous output which contains detailed
17679 information of the breakpoint.
17682 -> -break-insert main
17683 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
17684 enabled="y",addr="0x08048564",func="main",file="myprog.c",
17685 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
17689 @subheading Program Execution
17691 Program execution generates asynchronous records and MI gives the
17692 reason that execution stopped.
17698 <- *stopped,reason="breakpoint-hit",bkptno="1",thread-id="0",
17699 frame=@{addr="0x08048564",func="main",
17700 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
17701 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
17706 <- *stopped,reason="exited-normally"
17710 @subheading Quitting GDB
17712 Quitting GDB just prints the result class @samp{^exit}.
17720 @subheading A Bad Command
17722 Here's what happens if you pass a non-existent command:
17726 <- ^error,msg="Undefined MI command: rubbish"
17731 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17732 @node GDB/MI Command Description Format
17733 @section @sc{gdb/mi} Command Description Format
17735 The remaining sections describe blocks of commands. Each block of
17736 commands is laid out in a fashion similar to this section.
17738 @subheading Motivation
17740 The motivation for this collection of commands.
17742 @subheading Introduction
17744 A brief introduction to this collection of commands as a whole.
17746 @subheading Commands
17748 For each command in the block, the following is described:
17750 @subsubheading Synopsis
17753 -command @var{args}@dots{}
17756 @subsubheading Result
17758 @subsubheading @value{GDBN} Command
17760 The corresponding @value{GDBN} CLI command(s), if any.
17762 @subsubheading Example
17764 Example(s) formatted for readability. Some of the described commands have
17765 not been implemented yet and these are labeled N.A.@: (not available).
17768 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17769 @node GDB/MI Breakpoint Commands
17770 @section @sc{gdb/mi} Breakpoint Commands
17772 @cindex breakpoint commands for @sc{gdb/mi}
17773 @cindex @sc{gdb/mi}, breakpoint commands
17774 This section documents @sc{gdb/mi} commands for manipulating
17777 @subheading The @code{-break-after} Command
17778 @findex -break-after
17780 @subsubheading Synopsis
17783 -break-after @var{number} @var{count}
17786 The breakpoint number @var{number} is not in effect until it has been
17787 hit @var{count} times. To see how this is reflected in the output of
17788 the @samp{-break-list} command, see the description of the
17789 @samp{-break-list} command below.
17791 @subsubheading @value{GDBN} Command
17793 The corresponding @value{GDBN} command is @samp{ignore}.
17795 @subsubheading Example
17800 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",
17801 fullname="/home/foo/hello.c",line="5",times="0"@}
17808 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17809 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17810 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17811 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17812 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17813 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17814 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17815 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17816 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
17817 line="5",times="0",ignore="3"@}]@}
17822 @subheading The @code{-break-catch} Command
17823 @findex -break-catch
17825 @subheading The @code{-break-commands} Command
17826 @findex -break-commands
17830 @subheading The @code{-break-condition} Command
17831 @findex -break-condition
17833 @subsubheading Synopsis
17836 -break-condition @var{number} @var{expr}
17839 Breakpoint @var{number} will stop the program only if the condition in
17840 @var{expr} is true. The condition becomes part of the
17841 @samp{-break-list} output (see the description of the @samp{-break-list}
17844 @subsubheading @value{GDBN} Command
17846 The corresponding @value{GDBN} command is @samp{condition}.
17848 @subsubheading Example
17852 -break-condition 1 1
17856 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17857 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17858 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17859 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17860 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17861 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17862 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17863 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17864 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
17865 line="5",cond="1",times="0",ignore="3"@}]@}
17869 @subheading The @code{-break-delete} Command
17870 @findex -break-delete
17872 @subsubheading Synopsis
17875 -break-delete ( @var{breakpoint} )+
17878 Delete the breakpoint(s) whose number(s) are specified in the argument
17879 list. This is obviously reflected in the breakpoint list.
17881 @subsubheading @value{GDBN} command
17883 The corresponding @value{GDBN} command is @samp{delete}.
17885 @subsubheading Example
17893 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
17894 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17895 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17896 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17897 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17898 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17899 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17904 @subheading The @code{-break-disable} Command
17905 @findex -break-disable
17907 @subsubheading Synopsis
17910 -break-disable ( @var{breakpoint} )+
17913 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
17914 break list is now set to @samp{n} for the named @var{breakpoint}(s).
17916 @subsubheading @value{GDBN} Command
17918 The corresponding @value{GDBN} command is @samp{disable}.
17920 @subsubheading Example
17928 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17929 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17930 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17931 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17932 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17933 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17934 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17935 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
17936 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
17937 line="5",times="0"@}]@}
17941 @subheading The @code{-break-enable} Command
17942 @findex -break-enable
17944 @subsubheading Synopsis
17947 -break-enable ( @var{breakpoint} )+
17950 Enable (previously disabled) @var{breakpoint}(s).
17952 @subsubheading @value{GDBN} Command
17954 The corresponding @value{GDBN} command is @samp{enable}.
17956 @subsubheading Example
17964 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17965 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17966 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17967 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17968 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17969 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17970 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17971 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
17972 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
17973 line="5",times="0"@}]@}
17977 @subheading The @code{-break-info} Command
17978 @findex -break-info
17980 @subsubheading Synopsis
17983 -break-info @var{breakpoint}
17987 Get information about a single breakpoint.
17989 @subsubheading @value{GDBN} command
17991 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
17993 @subsubheading Example
17996 @subheading The @code{-break-insert} Command
17997 @findex -break-insert
17999 @subsubheading Synopsis
18002 -break-insert [ -t ] [ -h ] [ -r ]
18003 [ -c @var{condition} ] [ -i @var{ignore-count} ]
18004 [ -p @var{thread} ] [ @var{line} | @var{addr} ]
18008 If specified, @var{line}, can be one of:
18015 @item filename:linenum
18016 @item filename:function
18020 The possible optional parameters of this command are:
18024 Insert a temporary breakpoint.
18026 Insert a hardware breakpoint.
18027 @item -c @var{condition}
18028 Make the breakpoint conditional on @var{condition}.
18029 @item -i @var{ignore-count}
18030 Initialize the @var{ignore-count}.
18032 Insert a regular breakpoint in all the functions whose names match the
18033 given regular expression. Other flags are not applicable to regular
18037 @subsubheading Result
18039 The result is in the form:
18042 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
18043 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
18044 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
18045 times="@var{times}"@}
18049 where @var{number} is the @value{GDBN} number for this breakpoint,
18050 @var{funcname} is the name of the function where the breakpoint was
18051 inserted, @var{filename} is the name of the source file which contains
18052 this function, @var{lineno} is the source line number within that file
18053 and @var{times} the number of times that the breakpoint has been hit
18054 (always 0 for -break-insert but may be greater for -break-info or -break-list
18055 which use the same output).
18057 Note: this format is open to change.
18058 @c An out-of-band breakpoint instead of part of the result?
18060 @subsubheading @value{GDBN} Command
18062 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
18063 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
18065 @subsubheading Example
18070 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
18071 fullname="/home/foo/recursive2.c,line="4",times="0"@}
18073 -break-insert -t foo
18074 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
18075 fullname="/home/foo/recursive2.c,line="11",times="0"@}
18078 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18079 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18080 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18081 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18082 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18083 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18084 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18085 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18086 addr="0x0001072c", func="main",file="recursive2.c",
18087 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
18088 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
18089 addr="0x00010774",func="foo",file="recursive2.c",
18090 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
18092 -break-insert -r foo.*
18093 ~int foo(int, int);
18094 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
18095 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
18099 @subheading The @code{-break-list} Command
18100 @findex -break-list
18102 @subsubheading Synopsis
18108 Displays the list of inserted breakpoints, showing the following fields:
18112 number of the breakpoint
18114 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
18116 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
18119 is the breakpoint enabled or no: @samp{y} or @samp{n}
18121 memory location at which the breakpoint is set
18123 logical location of the breakpoint, expressed by function name, file
18126 number of times the breakpoint has been hit
18129 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
18130 @code{body} field is an empty list.
18132 @subsubheading @value{GDBN} Command
18134 The corresponding @value{GDBN} command is @samp{info break}.
18136 @subsubheading Example
18141 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18142 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18143 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18144 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18145 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18146 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18147 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18148 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18149 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
18150 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
18151 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
18152 line="13",times="0"@}]@}
18156 Here's an example of the result when there are no breakpoints:
18161 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
18162 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18163 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18164 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18165 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18166 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18167 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18172 @subheading The @code{-break-watch} Command
18173 @findex -break-watch
18175 @subsubheading Synopsis
18178 -break-watch [ -a | -r ]
18181 Create a watchpoint. With the @samp{-a} option it will create an
18182 @dfn{access} watchpoint, i.e. a watchpoint that triggers either on a
18183 read from or on a write to the memory location. With the @samp{-r}
18184 option, the watchpoint created is a @dfn{read} watchpoint, i.e. it will
18185 trigger only when the memory location is accessed for reading. Without
18186 either of the options, the watchpoint created is a regular watchpoint,
18187 i.e. it will trigger when the memory location is accessed for writing.
18188 @xref{Set Watchpoints, , Setting watchpoints}.
18190 Note that @samp{-break-list} will report a single list of watchpoints and
18191 breakpoints inserted.
18193 @subsubheading @value{GDBN} Command
18195 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
18198 @subsubheading Example
18200 Setting a watchpoint on a variable in the @code{main} function:
18205 ^done,wpt=@{number="2",exp="x"@}
18209 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
18210 value=@{old="-268439212",new="55"@},
18211 frame=@{func="main",args=[],file="recursive2.c",
18212 fullname="/home/foo/bar/recursive2.c",line="5"@}
18216 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
18217 the program execution twice: first for the variable changing value, then
18218 for the watchpoint going out of scope.
18223 ^done,wpt=@{number="5",exp="C"@}
18227 ^done,reason="watchpoint-trigger",
18228 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
18229 frame=@{func="callee4",args=[],
18230 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18231 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
18235 ^done,reason="watchpoint-scope",wpnum="5",
18236 frame=@{func="callee3",args=[@{name="strarg",
18237 value="0x11940 \"A string argument.\""@}],
18238 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18239 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18243 Listing breakpoints and watchpoints, at different points in the program
18244 execution. Note that once the watchpoint goes out of scope, it is
18250 ^done,wpt=@{number="2",exp="C"@}
18253 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18254 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18255 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18256 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18257 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18258 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18259 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18260 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18261 addr="0x00010734",func="callee4",
18262 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18263 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
18264 bkpt=@{number="2",type="watchpoint",disp="keep",
18265 enabled="y",addr="",what="C",times="0"@}]@}
18269 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
18270 value=@{old="-276895068",new="3"@},
18271 frame=@{func="callee4",args=[],
18272 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18273 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
18276 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18277 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18278 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18279 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18280 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18281 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18282 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18283 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18284 addr="0x00010734",func="callee4",
18285 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18286 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
18287 bkpt=@{number="2",type="watchpoint",disp="keep",
18288 enabled="y",addr="",what="C",times="-5"@}]@}
18292 ^done,reason="watchpoint-scope",wpnum="2",
18293 frame=@{func="callee3",args=[@{name="strarg",
18294 value="0x11940 \"A string argument.\""@}],
18295 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18296 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18299 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18300 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18301 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18302 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18303 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18304 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18305 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18306 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18307 addr="0x00010734",func="callee4",
18308 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18309 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
18314 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18315 @node GDB/MI Program Context
18316 @section @sc{gdb/mi} Program Context
18318 @subheading The @code{-exec-arguments} Command
18319 @findex -exec-arguments
18322 @subsubheading Synopsis
18325 -exec-arguments @var{args}
18328 Set the inferior program arguments, to be used in the next
18331 @subsubheading @value{GDBN} Command
18333 The corresponding @value{GDBN} command is @samp{set args}.
18335 @subsubheading Example
18338 Don't have one around.
18341 @subheading The @code{-exec-show-arguments} Command
18342 @findex -exec-show-arguments
18344 @subsubheading Synopsis
18347 -exec-show-arguments
18350 Print the arguments of the program.
18352 @subsubheading @value{GDBN} Command
18354 The corresponding @value{GDBN} command is @samp{show args}.
18356 @subsubheading Example
18360 @subheading The @code{-environment-cd} Command
18361 @findex -environment-cd
18363 @subsubheading Synopsis
18366 -environment-cd @var{pathdir}
18369 Set @value{GDBN}'s working directory.
18371 @subsubheading @value{GDBN} Command
18373 The corresponding @value{GDBN} command is @samp{cd}.
18375 @subsubheading Example
18379 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18385 @subheading The @code{-environment-directory} Command
18386 @findex -environment-directory
18388 @subsubheading Synopsis
18391 -environment-directory [ -r ] [ @var{pathdir} ]+
18394 Add directories @var{pathdir} to beginning of search path for source files.
18395 If the @samp{-r} option is used, the search path is reset to the default
18396 search path. If directories @var{pathdir} are supplied in addition to the
18397 @samp{-r} option, the search path is first reset and then addition
18399 Multiple directories may be specified, separated by blanks. Specifying
18400 multiple directories in a single command
18401 results in the directories added to the beginning of the
18402 search path in the same order they were presented in the command.
18403 If blanks are needed as
18404 part of a directory name, double-quotes should be used around
18405 the name. In the command output, the path will show up separated
18406 by the system directory-separator character. The directory-seperator
18407 character must not be used
18408 in any directory name.
18409 If no directories are specified, the current search path is displayed.
18411 @subsubheading @value{GDBN} Command
18413 The corresponding @value{GDBN} command is @samp{dir}.
18415 @subsubheading Example
18419 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18420 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18422 -environment-directory ""
18423 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18425 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
18426 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
18428 -environment-directory -r
18429 ^done,source-path="$cdir:$cwd"
18434 @subheading The @code{-environment-path} Command
18435 @findex -environment-path
18437 @subsubheading Synopsis
18440 -environment-path [ -r ] [ @var{pathdir} ]+
18443 Add directories @var{pathdir} to beginning of search path for object files.
18444 If the @samp{-r} option is used, the search path is reset to the original
18445 search path that existed at gdb start-up. If directories @var{pathdir} are
18446 supplied in addition to the
18447 @samp{-r} option, the search path is first reset and then addition
18449 Multiple directories may be specified, separated by blanks. Specifying
18450 multiple directories in a single command
18451 results in the directories added to the beginning of the
18452 search path in the same order they were presented in the command.
18453 If blanks are needed as
18454 part of a directory name, double-quotes should be used around
18455 the name. In the command output, the path will show up separated
18456 by the system directory-separator character. The directory-seperator
18457 character must not be used
18458 in any directory name.
18459 If no directories are specified, the current path is displayed.
18462 @subsubheading @value{GDBN} Command
18464 The corresponding @value{GDBN} command is @samp{path}.
18466 @subsubheading Example
18471 ^done,path="/usr/bin"
18473 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
18474 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
18476 -environment-path -r /usr/local/bin
18477 ^done,path="/usr/local/bin:/usr/bin"
18482 @subheading The @code{-environment-pwd} Command
18483 @findex -environment-pwd
18485 @subsubheading Synopsis
18491 Show the current working directory.
18493 @subsubheading @value{GDBN} command
18495 The corresponding @value{GDBN} command is @samp{pwd}.
18497 @subsubheading Example
18502 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
18506 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18507 @node GDB/MI Thread Commands
18508 @section @sc{gdb/mi} Thread Commands
18511 @subheading The @code{-thread-info} Command
18512 @findex -thread-info
18514 @subsubheading Synopsis
18520 @subsubheading @value{GDBN} command
18524 @subsubheading Example
18528 @subheading The @code{-thread-list-all-threads} Command
18529 @findex -thread-list-all-threads
18531 @subsubheading Synopsis
18534 -thread-list-all-threads
18537 @subsubheading @value{GDBN} Command
18539 The equivalent @value{GDBN} command is @samp{info threads}.
18541 @subsubheading Example
18545 @subheading The @code{-thread-list-ids} Command
18546 @findex -thread-list-ids
18548 @subsubheading Synopsis
18554 Produces a list of the currently known @value{GDBN} thread ids. At the
18555 end of the list it also prints the total number of such threads.
18557 @subsubheading @value{GDBN} Command
18559 Part of @samp{info threads} supplies the same information.
18561 @subsubheading Example
18563 No threads present, besides the main process:
18568 ^done,thread-ids=@{@},number-of-threads="0"
18578 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
18579 number-of-threads="3"
18584 @subheading The @code{-thread-select} Command
18585 @findex -thread-select
18587 @subsubheading Synopsis
18590 -thread-select @var{threadnum}
18593 Make @var{threadnum} the current thread. It prints the number of the new
18594 current thread, and the topmost frame for that thread.
18596 @subsubheading @value{GDBN} Command
18598 The corresponding @value{GDBN} command is @samp{thread}.
18600 @subsubheading Example
18607 *stopped,reason="end-stepping-range",thread-id="2",line="187",
18608 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
18612 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
18613 number-of-threads="3"
18616 ^done,new-thread-id="3",
18617 frame=@{level="0",func="vprintf",
18618 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
18619 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
18623 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18624 @node GDB/MI Program Execution
18625 @section @sc{gdb/mi} Program Execution
18627 These are the asynchronous commands which generate the out-of-band
18628 record @samp{*stopped}. Currently GDB only really executes
18629 asynchronously with remote targets and this interaction is mimicked in
18632 @subheading The @code{-exec-continue} Command
18633 @findex -exec-continue
18635 @subsubheading Synopsis
18641 Resumes the execution of the inferior program until a breakpoint is
18642 encountered, or until the inferior exits.
18644 @subsubheading @value{GDBN} Command
18646 The corresponding @value{GDBN} corresponding is @samp{continue}.
18648 @subsubheading Example
18655 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
18656 file="hello.c",fullname="/home/foo/bar/hello.c",line="13"@}
18661 @subheading The @code{-exec-finish} Command
18662 @findex -exec-finish
18664 @subsubheading Synopsis
18670 Resumes the execution of the inferior program until the current
18671 function is exited. Displays the results returned by the function.
18673 @subsubheading @value{GDBN} Command
18675 The corresponding @value{GDBN} command is @samp{finish}.
18677 @subsubheading Example
18679 Function returning @code{void}.
18686 *stopped,reason="function-finished",frame=@{func="main",args=[],
18687 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
18691 Function returning other than @code{void}. The name of the internal
18692 @value{GDBN} variable storing the result is printed, together with the
18699 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
18700 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
18701 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
18702 gdb-result-var="$1",return-value="0"
18707 @subheading The @code{-exec-interrupt} Command
18708 @findex -exec-interrupt
18710 @subsubheading Synopsis
18716 Interrupts the background execution of the target. Note how the token
18717 associated with the stop message is the one for the execution command
18718 that has been interrupted. The token for the interrupt itself only
18719 appears in the @samp{^done} output. If the user is trying to
18720 interrupt a non-running program, an error message will be printed.
18722 @subsubheading @value{GDBN} Command
18724 The corresponding @value{GDBN} command is @samp{interrupt}.
18726 @subsubheading Example
18737 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
18738 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
18739 fullname="/home/foo/bar/try.c",line="13"@}
18744 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
18749 @subheading The @code{-exec-next} Command
18752 @subsubheading Synopsis
18758 Resumes execution of the inferior program, stopping when the beginning
18759 of the next source line is reached.
18761 @subsubheading @value{GDBN} Command
18763 The corresponding @value{GDBN} command is @samp{next}.
18765 @subsubheading Example
18771 *stopped,reason="end-stepping-range",line="8",file="hello.c"
18776 @subheading The @code{-exec-next-instruction} Command
18777 @findex -exec-next-instruction
18779 @subsubheading Synopsis
18782 -exec-next-instruction
18785 Executes one machine instruction. If the instruction is a function
18786 call, continues until the function returns. If the program stops at an
18787 instruction in the middle of a source line, the address will be
18790 @subsubheading @value{GDBN} Command
18792 The corresponding @value{GDBN} command is @samp{nexti}.
18794 @subsubheading Example
18798 -exec-next-instruction
18802 *stopped,reason="end-stepping-range",
18803 addr="0x000100d4",line="5",file="hello.c"
18808 @subheading The @code{-exec-return} Command
18809 @findex -exec-return
18811 @subsubheading Synopsis
18817 Makes current function return immediately. Doesn't execute the inferior.
18818 Displays the new current frame.
18820 @subsubheading @value{GDBN} Command
18822 The corresponding @value{GDBN} command is @samp{return}.
18824 @subsubheading Example
18828 200-break-insert callee4
18829 200^done,bkpt=@{number="1",addr="0x00010734",
18830 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
18835 000*stopped,reason="breakpoint-hit",bkptno="1",
18836 frame=@{func="callee4",args=[],
18837 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18838 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
18844 111^done,frame=@{level="0",func="callee3",
18845 args=[@{name="strarg",
18846 value="0x11940 \"A string argument.\""@}],
18847 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18848 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18853 @subheading The @code{-exec-run} Command
18856 @subsubheading Synopsis
18862 Starts execution of the inferior from the beginning. The inferior
18863 executes until either a breakpoint is encountered or the program
18864 exits. In the latter case the output will include an exit code, if
18865 the program has exited exceptionally.
18867 @subsubheading @value{GDBN} Command
18869 The corresponding @value{GDBN} command is @samp{run}.
18871 @subsubheading Examples
18876 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
18881 *stopped,reason="breakpoint-hit",bkptno="1",
18882 frame=@{func="main",args=[],file="recursive2.c",
18883 fullname="/home/foo/bar/recursive2.c",line="4"@}
18888 Program exited normally:
18896 *stopped,reason="exited-normally"
18901 Program exited exceptionally:
18909 *stopped,reason="exited",exit-code="01"
18913 Another way the program can terminate is if it receives a signal such as
18914 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
18918 *stopped,reason="exited-signalled",signal-name="SIGINT",
18919 signal-meaning="Interrupt"
18923 @c @subheading -exec-signal
18926 @subheading The @code{-exec-step} Command
18929 @subsubheading Synopsis
18935 Resumes execution of the inferior program, stopping when the beginning
18936 of the next source line is reached, if the next source line is not a
18937 function call. If it is, stop at the first instruction of the called
18940 @subsubheading @value{GDBN} Command
18942 The corresponding @value{GDBN} command is @samp{step}.
18944 @subsubheading Example
18946 Stepping into a function:
18952 *stopped,reason="end-stepping-range",
18953 frame=@{func="foo",args=[@{name="a",value="10"@},
18954 @{name="b",value="0"@}],file="recursive2.c",
18955 fullname="/home/foo/bar/recursive2.c",line="11"@}
18965 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
18970 @subheading The @code{-exec-step-instruction} Command
18971 @findex -exec-step-instruction
18973 @subsubheading Synopsis
18976 -exec-step-instruction
18979 Resumes the inferior which executes one machine instruction. The
18980 output, once @value{GDBN} has stopped, will vary depending on whether
18981 we have stopped in the middle of a source line or not. In the former
18982 case, the address at which the program stopped will be printed as
18985 @subsubheading @value{GDBN} Command
18987 The corresponding @value{GDBN} command is @samp{stepi}.
18989 @subsubheading Example
18993 -exec-step-instruction
18997 *stopped,reason="end-stepping-range",
18998 frame=@{func="foo",args=[],file="try.c",
18999 fullname="/home/foo/bar/try.c",line="10"@}
19001 -exec-step-instruction
19005 *stopped,reason="end-stepping-range",
19006 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
19007 fullname="/home/foo/bar/try.c",line="10"@}
19012 @subheading The @code{-exec-until} Command
19013 @findex -exec-until
19015 @subsubheading Synopsis
19018 -exec-until [ @var{location} ]
19021 Executes the inferior until the @var{location} specified in the
19022 argument is reached. If there is no argument, the inferior executes
19023 until a source line greater than the current one is reached. The
19024 reason for stopping in this case will be @samp{location-reached}.
19026 @subsubheading @value{GDBN} Command
19028 The corresponding @value{GDBN} command is @samp{until}.
19030 @subsubheading Example
19034 -exec-until recursive2.c:6
19038 *stopped,reason="location-reached",frame=@{func="main",args=[],
19039 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
19044 @subheading -file-clear
19045 Is this going away????
19048 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19049 @node GDB/MI Stack Manipulation
19050 @section @sc{gdb/mi} Stack Manipulation Commands
19053 @subheading The @code{-stack-info-frame} Command
19054 @findex -stack-info-frame
19056 @subsubheading Synopsis
19062 Get info on the selected frame.
19064 @subsubheading @value{GDBN} Command
19066 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
19067 (without arguments).
19069 @subsubheading Example
19074 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
19075 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19076 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
19080 @subheading The @code{-stack-info-depth} Command
19081 @findex -stack-info-depth
19083 @subsubheading Synopsis
19086 -stack-info-depth [ @var{max-depth} ]
19089 Return the depth of the stack. If the integer argument @var{max-depth}
19090 is specified, do not count beyond @var{max-depth} frames.
19092 @subsubheading @value{GDBN} Command
19094 There's no equivalent @value{GDBN} command.
19096 @subsubheading Example
19098 For a stack with frame levels 0 through 11:
19105 -stack-info-depth 4
19108 -stack-info-depth 12
19111 -stack-info-depth 11
19114 -stack-info-depth 13
19119 @subheading The @code{-stack-list-arguments} Command
19120 @findex -stack-list-arguments
19122 @subsubheading Synopsis
19125 -stack-list-arguments @var{show-values}
19126 [ @var{low-frame} @var{high-frame} ]
19129 Display a list of the arguments for the frames between @var{low-frame}
19130 and @var{high-frame} (inclusive). If @var{low-frame} and
19131 @var{high-frame} are not provided, list the arguments for the whole call
19134 The @var{show-values} argument must have a value of 0 or 1. A value of
19135 0 means that only the names of the arguments are listed, a value of 1
19136 means that both names and values of the arguments are printed.
19138 @subsubheading @value{GDBN} Command
19140 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
19141 @samp{gdb_get_args} command which partially overlaps with the
19142 functionality of @samp{-stack-list-arguments}.
19144 @subsubheading Example
19151 frame=@{level="0",addr="0x00010734",func="callee4",
19152 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19153 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
19154 frame=@{level="1",addr="0x0001076c",func="callee3",
19155 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19156 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
19157 frame=@{level="2",addr="0x0001078c",func="callee2",
19158 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19159 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
19160 frame=@{level="3",addr="0x000107b4",func="callee1",
19161 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19162 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
19163 frame=@{level="4",addr="0x000107e0",func="main",
19164 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19165 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
19167 -stack-list-arguments 0
19170 frame=@{level="0",args=[]@},
19171 frame=@{level="1",args=[name="strarg"]@},
19172 frame=@{level="2",args=[name="intarg",name="strarg"]@},
19173 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
19174 frame=@{level="4",args=[]@}]
19176 -stack-list-arguments 1
19179 frame=@{level="0",args=[]@},
19181 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19182 frame=@{level="2",args=[
19183 @{name="intarg",value="2"@},
19184 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19185 @{frame=@{level="3",args=[
19186 @{name="intarg",value="2"@},
19187 @{name="strarg",value="0x11940 \"A string argument.\""@},
19188 @{name="fltarg",value="3.5"@}]@},
19189 frame=@{level="4",args=[]@}]
19191 -stack-list-arguments 0 2 2
19192 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
19194 -stack-list-arguments 1 2 2
19195 ^done,stack-args=[frame=@{level="2",
19196 args=[@{name="intarg",value="2"@},
19197 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
19201 @c @subheading -stack-list-exception-handlers
19204 @subheading The @code{-stack-list-frames} Command
19205 @findex -stack-list-frames
19207 @subsubheading Synopsis
19210 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
19213 List the frames currently on the stack. For each frame it displays the
19218 The frame number, 0 being the topmost frame, i.e. the innermost function.
19220 The @code{$pc} value for that frame.
19224 File name of the source file where the function lives.
19226 Line number corresponding to the @code{$pc}.
19229 If invoked without arguments, this command prints a backtrace for the
19230 whole stack. If given two integer arguments, it shows the frames whose
19231 levels are between the two arguments (inclusive). If the two arguments
19232 are equal, it shows the single frame at the corresponding level.
19234 @subsubheading @value{GDBN} Command
19236 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
19238 @subsubheading Example
19240 Full stack backtrace:
19246 [frame=@{level="0",addr="0x0001076c",func="foo",
19247 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
19248 frame=@{level="1",addr="0x000107a4",func="foo",
19249 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19250 frame=@{level="2",addr="0x000107a4",func="foo",
19251 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19252 frame=@{level="3",addr="0x000107a4",func="foo",
19253 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19254 frame=@{level="4",addr="0x000107a4",func="foo",
19255 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19256 frame=@{level="5",addr="0x000107a4",func="foo",
19257 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19258 frame=@{level="6",addr="0x000107a4",func="foo",
19259 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19260 frame=@{level="7",addr="0x000107a4",func="foo",
19261 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19262 frame=@{level="8",addr="0x000107a4",func="foo",
19263 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19264 frame=@{level="9",addr="0x000107a4",func="foo",
19265 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19266 frame=@{level="10",addr="0x000107a4",func="foo",
19267 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19268 frame=@{level="11",addr="0x00010738",func="main",
19269 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
19273 Show frames between @var{low_frame} and @var{high_frame}:
19277 -stack-list-frames 3 5
19279 [frame=@{level="3",addr="0x000107a4",func="foo",
19280 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19281 frame=@{level="4",addr="0x000107a4",func="foo",
19282 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19283 frame=@{level="5",addr="0x000107a4",func="foo",
19284 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
19288 Show a single frame:
19292 -stack-list-frames 3 3
19294 [frame=@{level="3",addr="0x000107a4",func="foo",
19295 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
19300 @subheading The @code{-stack-list-locals} Command
19301 @findex -stack-list-locals
19303 @subsubheading Synopsis
19306 -stack-list-locals @var{print-values}
19309 Display the local variable names for the selected frame. If
19310 @var{print-values} is 0 or @code{--no-values}, print only the names of
19311 the variables; if it is 1 or @code{--all-values}, print also their
19312 values; and if it is 2 or @code{--simple-values}, print the name,
19313 type and value for simple data types and the name and type for arrays,
19314 structures and unions. In this last case, a frontend can immediately
19315 display the value of simple data types and create variable objects for
19316 other data types when the the user wishes to explore their values in
19319 @subsubheading @value{GDBN} Command
19321 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
19323 @subsubheading Example
19327 -stack-list-locals 0
19328 ^done,locals=[name="A",name="B",name="C"]
19330 -stack-list-locals --all-values
19331 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
19332 @{name="C",value="@{1, 2, 3@}"@}]
19333 -stack-list-locals --simple-values
19334 ^done,locals=[@{name="A",type="int",value="1"@},
19335 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
19340 @subheading The @code{-stack-select-frame} Command
19341 @findex -stack-select-frame
19343 @subsubheading Synopsis
19346 -stack-select-frame @var{framenum}
19349 Change the selected frame. Select a different frame @var{framenum} on
19352 @subsubheading @value{GDBN} Command
19354 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
19355 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
19357 @subsubheading Example
19361 -stack-select-frame 2
19366 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19367 @node GDB/MI Variable Objects
19368 @section @sc{gdb/mi} Variable Objects
19371 @subheading Motivation for Variable Objects in @sc{gdb/mi}
19373 For the implementation of a variable debugger window (locals, watched
19374 expressions, etc.), we are proposing the adaptation of the existing code
19375 used by @code{Insight}.
19377 The two main reasons for that are:
19381 It has been proven in practice (it is already on its second generation).
19384 It will shorten development time (needless to say how important it is
19388 The original interface was designed to be used by Tcl code, so it was
19389 slightly changed so it could be used through @sc{gdb/mi}. This section
19390 describes the @sc{gdb/mi} operations that will be available and gives some
19391 hints about their use.
19393 @emph{Note}: In addition to the set of operations described here, we
19394 expect the @sc{gui} implementation of a variable window to require, at
19395 least, the following operations:
19398 @item @code{-gdb-show} @code{output-radix}
19399 @item @code{-stack-list-arguments}
19400 @item @code{-stack-list-locals}
19401 @item @code{-stack-select-frame}
19404 @subheading Introduction to Variable Objects in @sc{gdb/mi}
19406 @cindex variable objects in @sc{gdb/mi}
19407 The basic idea behind variable objects is the creation of a named object
19408 to represent a variable, an expression, a memory location or even a CPU
19409 register. For each object created, a set of operations is available for
19410 examining or changing its properties.
19412 Furthermore, complex data types, such as C structures, are represented
19413 in a tree format. For instance, the @code{struct} type variable is the
19414 root and the children will represent the struct members. If a child
19415 is itself of a complex type, it will also have children of its own.
19416 Appropriate language differences are handled for C, C@t{++} and Java.
19418 When returning the actual values of the objects, this facility allows
19419 for the individual selection of the display format used in the result
19420 creation. It can be chosen among: binary, decimal, hexadecimal, octal
19421 and natural. Natural refers to a default format automatically
19422 chosen based on the variable type (like decimal for an @code{int}, hex
19423 for pointers, etc.).
19425 The following is the complete set of @sc{gdb/mi} operations defined to
19426 access this functionality:
19428 @multitable @columnfractions .4 .6
19429 @item @strong{Operation}
19430 @tab @strong{Description}
19432 @item @code{-var-create}
19433 @tab create a variable object
19434 @item @code{-var-delete}
19435 @tab delete the variable object and its children
19436 @item @code{-var-set-format}
19437 @tab set the display format of this variable
19438 @item @code{-var-show-format}
19439 @tab show the display format of this variable
19440 @item @code{-var-info-num-children}
19441 @tab tells how many children this object has
19442 @item @code{-var-list-children}
19443 @tab return a list of the object's children
19444 @item @code{-var-info-type}
19445 @tab show the type of this variable object
19446 @item @code{-var-info-expression}
19447 @tab print what this variable object represents
19448 @item @code{-var-show-attributes}
19449 @tab is this variable editable? does it exist here?
19450 @item @code{-var-evaluate-expression}
19451 @tab get the value of this variable
19452 @item @code{-var-assign}
19453 @tab set the value of this variable
19454 @item @code{-var-update}
19455 @tab update the variable and its children
19458 In the next subsection we describe each operation in detail and suggest
19459 how it can be used.
19461 @subheading Description And Use of Operations on Variable Objects
19463 @subheading The @code{-var-create} Command
19464 @findex -var-create
19466 @subsubheading Synopsis
19469 -var-create @{@var{name} | "-"@}
19470 @{@var{frame-addr} | "*"@} @var{expression}
19473 This operation creates a variable object, which allows the monitoring of
19474 a variable, the result of an expression, a memory cell or a CPU
19477 The @var{name} parameter is the string by which the object can be
19478 referenced. It must be unique. If @samp{-} is specified, the varobj
19479 system will generate a string ``varNNNNNN'' automatically. It will be
19480 unique provided that one does not specify @var{name} on that format.
19481 The command fails if a duplicate name is found.
19483 The frame under which the expression should be evaluated can be
19484 specified by @var{frame-addr}. A @samp{*} indicates that the current
19485 frame should be used.
19487 @var{expression} is any expression valid on the current language set (must not
19488 begin with a @samp{*}), or one of the following:
19492 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
19495 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
19498 @samp{$@var{regname}} --- a CPU register name
19501 @subsubheading Result
19503 This operation returns the name, number of children and the type of the
19504 object created. Type is returned as a string as the ones generated by
19505 the @value{GDBN} CLI:
19508 name="@var{name}",numchild="N",type="@var{type}"
19512 @subheading The @code{-var-delete} Command
19513 @findex -var-delete
19515 @subsubheading Synopsis
19518 -var-delete @var{name}
19521 Deletes a previously created variable object and all of its children.
19523 Returns an error if the object @var{name} is not found.
19526 @subheading The @code{-var-set-format} Command
19527 @findex -var-set-format
19529 @subsubheading Synopsis
19532 -var-set-format @var{name} @var{format-spec}
19535 Sets the output format for the value of the object @var{name} to be
19538 The syntax for the @var{format-spec} is as follows:
19541 @var{format-spec} @expansion{}
19542 @{binary | decimal | hexadecimal | octal | natural@}
19546 @subheading The @code{-var-show-format} Command
19547 @findex -var-show-format
19549 @subsubheading Synopsis
19552 -var-show-format @var{name}
19555 Returns the format used to display the value of the object @var{name}.
19558 @var{format} @expansion{}
19563 @subheading The @code{-var-info-num-children} Command
19564 @findex -var-info-num-children
19566 @subsubheading Synopsis
19569 -var-info-num-children @var{name}
19572 Returns the number of children of a variable object @var{name}:
19579 @subheading The @code{-var-list-children} Command
19580 @findex -var-list-children
19582 @subsubheading Synopsis
19585 -var-list-children [@var{print-values}] @var{name}
19587 @anchor{-var-list-children}
19589 Return a list of the children of the specified variable object and
19590 create variable objects for them, if they do not already exist. With
19591 a single argument or if @var{print-values} has a value for of 0 or
19592 @code{--no-values}, print only the names of the variables; if
19593 @var{print-values} is 1 or @code{--all-values}, also print their
19594 values; and if it is 2 or @code{--simple-values} print the name and
19595 value for simple data types and just the name for arrays, structures
19598 @subsubheading Example
19602 -var-list-children n
19603 ^done,numchild=@var{n},children=[@{name=@var{name},
19604 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
19606 -var-list-children --all-values n
19607 ^done,numchild=@var{n},children=[@{name=@var{name},
19608 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
19612 @subheading The @code{-var-info-type} Command
19613 @findex -var-info-type
19615 @subsubheading Synopsis
19618 -var-info-type @var{name}
19621 Returns the type of the specified variable @var{name}. The type is
19622 returned as a string in the same format as it is output by the
19626 type=@var{typename}
19630 @subheading The @code{-var-info-expression} Command
19631 @findex -var-info-expression
19633 @subsubheading Synopsis
19636 -var-info-expression @var{name}
19639 Returns what is represented by the variable object @var{name}:
19642 lang=@var{lang-spec},exp=@var{expression}
19646 where @var{lang-spec} is @code{@{"C" | "C++" | "Java"@}}.
19648 @subheading The @code{-var-show-attributes} Command
19649 @findex -var-show-attributes
19651 @subsubheading Synopsis
19654 -var-show-attributes @var{name}
19657 List attributes of the specified variable object @var{name}:
19660 status=@var{attr} [ ( ,@var{attr} )* ]
19664 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
19666 @subheading The @code{-var-evaluate-expression} Command
19667 @findex -var-evaluate-expression
19669 @subsubheading Synopsis
19672 -var-evaluate-expression @var{name}
19675 Evaluates the expression that is represented by the specified variable
19676 object and returns its value as a string in the current format specified
19683 Note that one must invoke @code{-var-list-children} for a variable
19684 before the value of a child variable can be evaluated.
19686 @subheading The @code{-var-assign} Command
19687 @findex -var-assign
19689 @subsubheading Synopsis
19692 -var-assign @var{name} @var{expression}
19695 Assigns the value of @var{expression} to the variable object specified
19696 by @var{name}. The object must be @samp{editable}. If the variable's
19697 value is altered by the assign, the variable will show up in any
19698 subsequent @code{-var-update} list.
19700 @subsubheading Example
19708 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
19712 @subheading The @code{-var-update} Command
19713 @findex -var-update
19715 @subsubheading Synopsis
19718 -var-update [@var{print-values}] @{@var{name} | "*"@}
19721 Update the value of the variable object @var{name} by evaluating its
19722 expression after fetching all the new values from memory or registers.
19723 A @samp{*} causes all existing variable objects to be updated. The
19724 option @var{print-values} determines whether names both and values, or
19725 just names are printed in the manner described for
19726 @code{-var-list-children} (@pxref{-var-list-children}).
19728 @subsubheading Example
19735 -var-update --all-values var1
19736 ^done,changelist=[@{name="var1",value="3",in_scope="true",
19737 type_changed="false"@}]
19741 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19742 @node GDB/MI Data Manipulation
19743 @section @sc{gdb/mi} Data Manipulation
19745 @cindex data manipulation, in @sc{gdb/mi}
19746 @cindex @sc{gdb/mi}, data manipulation
19747 This section describes the @sc{gdb/mi} commands that manipulate data:
19748 examine memory and registers, evaluate expressions, etc.
19750 @c REMOVED FROM THE INTERFACE.
19751 @c @subheading -data-assign
19752 @c Change the value of a program variable. Plenty of side effects.
19753 @c @subsubheading GDB command
19755 @c @subsubheading Example
19758 @subheading The @code{-data-disassemble} Command
19759 @findex -data-disassemble
19761 @subsubheading Synopsis
19765 [ -s @var{start-addr} -e @var{end-addr} ]
19766 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
19774 @item @var{start-addr}
19775 is the beginning address (or @code{$pc})
19776 @item @var{end-addr}
19778 @item @var{filename}
19779 is the name of the file to disassemble
19780 @item @var{linenum}
19781 is the line number to disassemble around
19783 is the the number of disassembly lines to be produced. If it is -1,
19784 the whole function will be disassembled, in case no @var{end-addr} is
19785 specified. If @var{end-addr} is specified as a non-zero value, and
19786 @var{lines} is lower than the number of disassembly lines between
19787 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
19788 displayed; if @var{lines} is higher than the number of lines between
19789 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
19792 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
19796 @subsubheading Result
19798 The output for each instruction is composed of four fields:
19807 Note that whatever included in the instruction field, is not manipulated
19808 directely by @sc{gdb/mi}, i.e. it is not possible to adjust its format.
19810 @subsubheading @value{GDBN} Command
19812 There's no direct mapping from this command to the CLI.
19814 @subsubheading Example
19816 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
19820 -data-disassemble -s $pc -e "$pc + 20" -- 0
19823 @{address="0x000107c0",func-name="main",offset="4",
19824 inst="mov 2, %o0"@},
19825 @{address="0x000107c4",func-name="main",offset="8",
19826 inst="sethi %hi(0x11800), %o2"@},
19827 @{address="0x000107c8",func-name="main",offset="12",
19828 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
19829 @{address="0x000107cc",func-name="main",offset="16",
19830 inst="sethi %hi(0x11800), %o2"@},
19831 @{address="0x000107d0",func-name="main",offset="20",
19832 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
19836 Disassemble the whole @code{main} function. Line 32 is part of
19840 -data-disassemble -f basics.c -l 32 -- 0
19842 @{address="0x000107bc",func-name="main",offset="0",
19843 inst="save %sp, -112, %sp"@},
19844 @{address="0x000107c0",func-name="main",offset="4",
19845 inst="mov 2, %o0"@},
19846 @{address="0x000107c4",func-name="main",offset="8",
19847 inst="sethi %hi(0x11800), %o2"@},
19849 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
19850 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
19854 Disassemble 3 instructions from the start of @code{main}:
19858 -data-disassemble -f basics.c -l 32 -n 3 -- 0
19860 @{address="0x000107bc",func-name="main",offset="0",
19861 inst="save %sp, -112, %sp"@},
19862 @{address="0x000107c0",func-name="main",offset="4",
19863 inst="mov 2, %o0"@},
19864 @{address="0x000107c4",func-name="main",offset="8",
19865 inst="sethi %hi(0x11800), %o2"@}]
19869 Disassemble 3 instructions from the start of @code{main} in mixed mode:
19873 -data-disassemble -f basics.c -l 32 -n 3 -- 1
19875 src_and_asm_line=@{line="31",
19876 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
19877 testsuite/gdb.mi/basics.c",line_asm_insn=[
19878 @{address="0x000107bc",func-name="main",offset="0",
19879 inst="save %sp, -112, %sp"@}]@},
19880 src_and_asm_line=@{line="32",
19881 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
19882 testsuite/gdb.mi/basics.c",line_asm_insn=[
19883 @{address="0x000107c0",func-name="main",offset="4",
19884 inst="mov 2, %o0"@},
19885 @{address="0x000107c4",func-name="main",offset="8",
19886 inst="sethi %hi(0x11800), %o2"@}]@}]
19891 @subheading The @code{-data-evaluate-expression} Command
19892 @findex -data-evaluate-expression
19894 @subsubheading Synopsis
19897 -data-evaluate-expression @var{expr}
19900 Evaluate @var{expr} as an expression. The expression could contain an
19901 inferior function call. The function call will execute synchronously.
19902 If the expression contains spaces, it must be enclosed in double quotes.
19904 @subsubheading @value{GDBN} Command
19906 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
19907 @samp{call}. In @code{gdbtk} only, there's a corresponding
19908 @samp{gdb_eval} command.
19910 @subsubheading Example
19912 In the following example, the numbers that precede the commands are the
19913 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
19914 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
19918 211-data-evaluate-expression A
19921 311-data-evaluate-expression &A
19922 311^done,value="0xefffeb7c"
19924 411-data-evaluate-expression A+3
19927 511-data-evaluate-expression "A + 3"
19933 @subheading The @code{-data-list-changed-registers} Command
19934 @findex -data-list-changed-registers
19936 @subsubheading Synopsis
19939 -data-list-changed-registers
19942 Display a list of the registers that have changed.
19944 @subsubheading @value{GDBN} Command
19946 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
19947 has the corresponding command @samp{gdb_changed_register_list}.
19949 @subsubheading Example
19951 On a PPC MBX board:
19959 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
19960 args=[],file="try.c",fullname="/home/foo/bar/try.c",line="5"@}
19962 -data-list-changed-registers
19963 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
19964 "10","11","13","14","15","16","17","18","19","20","21","22","23",
19965 "24","25","26","27","28","30","31","64","65","66","67","69"]
19970 @subheading The @code{-data-list-register-names} Command
19971 @findex -data-list-register-names
19973 @subsubheading Synopsis
19976 -data-list-register-names [ ( @var{regno} )+ ]
19979 Show a list of register names for the current target. If no arguments
19980 are given, it shows a list of the names of all the registers. If
19981 integer numbers are given as arguments, it will print a list of the
19982 names of the registers corresponding to the arguments. To ensure
19983 consistency between a register name and its number, the output list may
19984 include empty register names.
19986 @subsubheading @value{GDBN} Command
19988 @value{GDBN} does not have a command which corresponds to
19989 @samp{-data-list-register-names}. In @code{gdbtk} there is a
19990 corresponding command @samp{gdb_regnames}.
19992 @subsubheading Example
19994 For the PPC MBX board:
19997 -data-list-register-names
19998 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
19999 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
20000 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
20001 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
20002 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
20003 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
20004 "", "pc","ps","cr","lr","ctr","xer"]
20006 -data-list-register-names 1 2 3
20007 ^done,register-names=["r1","r2","r3"]
20011 @subheading The @code{-data-list-register-values} Command
20012 @findex -data-list-register-values
20014 @subsubheading Synopsis
20017 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
20020 Display the registers' contents. @var{fmt} is the format according to
20021 which the registers' contents are to be returned, followed by an optional
20022 list of numbers specifying the registers to display. A missing list of
20023 numbers indicates that the contents of all the registers must be returned.
20025 Allowed formats for @var{fmt} are:
20042 @subsubheading @value{GDBN} Command
20044 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
20045 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
20047 @subsubheading Example
20049 For a PPC MBX board (note: line breaks are for readability only, they
20050 don't appear in the actual output):
20054 -data-list-register-values r 64 65
20055 ^done,register-values=[@{number="64",value="0xfe00a300"@},
20056 @{number="65",value="0x00029002"@}]
20058 -data-list-register-values x
20059 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
20060 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
20061 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
20062 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
20063 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
20064 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
20065 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
20066 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
20067 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
20068 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
20069 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
20070 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
20071 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
20072 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
20073 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
20074 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
20075 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
20076 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
20077 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
20078 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
20079 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
20080 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
20081 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
20082 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
20083 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
20084 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
20085 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
20086 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
20087 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
20088 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
20089 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
20090 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
20091 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
20092 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
20093 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
20094 @{number="69",value="0x20002b03"@}]
20099 @subheading The @code{-data-read-memory} Command
20100 @findex -data-read-memory
20102 @subsubheading Synopsis
20105 -data-read-memory [ -o @var{byte-offset} ]
20106 @var{address} @var{word-format} @var{word-size}
20107 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
20114 @item @var{address}
20115 An expression specifying the address of the first memory word to be
20116 read. Complex expressions containing embedded white space should be
20117 quoted using the C convention.
20119 @item @var{word-format}
20120 The format to be used to print the memory words. The notation is the
20121 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
20124 @item @var{word-size}
20125 The size of each memory word in bytes.
20127 @item @var{nr-rows}
20128 The number of rows in the output table.
20130 @item @var{nr-cols}
20131 The number of columns in the output table.
20134 If present, indicates that each row should include an @sc{ascii} dump. The
20135 value of @var{aschar} is used as a padding character when a byte is not a
20136 member of the printable @sc{ascii} character set (printable @sc{ascii}
20137 characters are those whose code is between 32 and 126, inclusively).
20139 @item @var{byte-offset}
20140 An offset to add to the @var{address} before fetching memory.
20143 This command displays memory contents as a table of @var{nr-rows} by
20144 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
20145 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
20146 (returned as @samp{total-bytes}). Should less than the requested number
20147 of bytes be returned by the target, the missing words are identified
20148 using @samp{N/A}. The number of bytes read from the target is returned
20149 in @samp{nr-bytes} and the starting address used to read memory in
20152 The address of the next/previous row or page is available in
20153 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
20156 @subsubheading @value{GDBN} Command
20158 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
20159 @samp{gdb_get_mem} memory read command.
20161 @subsubheading Example
20163 Read six bytes of memory starting at @code{bytes+6} but then offset by
20164 @code{-6} bytes. Format as three rows of two columns. One byte per
20165 word. Display each word in hex.
20169 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
20170 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
20171 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
20172 prev-page="0x0000138a",memory=[
20173 @{addr="0x00001390",data=["0x00","0x01"]@},
20174 @{addr="0x00001392",data=["0x02","0x03"]@},
20175 @{addr="0x00001394",data=["0x04","0x05"]@}]
20179 Read two bytes of memory starting at address @code{shorts + 64} and
20180 display as a single word formatted in decimal.
20184 5-data-read-memory shorts+64 d 2 1 1
20185 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
20186 next-row="0x00001512",prev-row="0x0000150e",
20187 next-page="0x00001512",prev-page="0x0000150e",memory=[
20188 @{addr="0x00001510",data=["128"]@}]
20192 Read thirty two bytes of memory starting at @code{bytes+16} and format
20193 as eight rows of four columns. Include a string encoding with @samp{x}
20194 used as the non-printable character.
20198 4-data-read-memory bytes+16 x 1 8 4 x
20199 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
20200 next-row="0x000013c0",prev-row="0x0000139c",
20201 next-page="0x000013c0",prev-page="0x00001380",memory=[
20202 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
20203 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
20204 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
20205 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
20206 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
20207 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
20208 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
20209 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
20213 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20214 @node GDB/MI Tracepoint Commands
20215 @section @sc{gdb/mi} Tracepoint Commands
20217 The tracepoint commands are not yet implemented.
20219 @c @subheading -trace-actions
20221 @c @subheading -trace-delete
20223 @c @subheading -trace-disable
20225 @c @subheading -trace-dump
20227 @c @subheading -trace-enable
20229 @c @subheading -trace-exists
20231 @c @subheading -trace-find
20233 @c @subheading -trace-frame-number
20235 @c @subheading -trace-info
20237 @c @subheading -trace-insert
20239 @c @subheading -trace-list
20241 @c @subheading -trace-pass-count
20243 @c @subheading -trace-save
20245 @c @subheading -trace-start
20247 @c @subheading -trace-stop
20250 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20251 @node GDB/MI Symbol Query
20252 @section @sc{gdb/mi} Symbol Query Commands
20255 @subheading The @code{-symbol-info-address} Command
20256 @findex -symbol-info-address
20258 @subsubheading Synopsis
20261 -symbol-info-address @var{symbol}
20264 Describe where @var{symbol} is stored.
20266 @subsubheading @value{GDBN} Command
20268 The corresponding @value{GDBN} command is @samp{info address}.
20270 @subsubheading Example
20274 @subheading The @code{-symbol-info-file} Command
20275 @findex -symbol-info-file
20277 @subsubheading Synopsis
20283 Show the file for the symbol.
20285 @subsubheading @value{GDBN} Command
20287 There's no equivalent @value{GDBN} command. @code{gdbtk} has
20288 @samp{gdb_find_file}.
20290 @subsubheading Example
20294 @subheading The @code{-symbol-info-function} Command
20295 @findex -symbol-info-function
20297 @subsubheading Synopsis
20300 -symbol-info-function
20303 Show which function the symbol lives in.
20305 @subsubheading @value{GDBN} Command
20307 @samp{gdb_get_function} in @code{gdbtk}.
20309 @subsubheading Example
20313 @subheading The @code{-symbol-info-line} Command
20314 @findex -symbol-info-line
20316 @subsubheading Synopsis
20322 Show the core addresses of the code for a source line.
20324 @subsubheading @value{GDBN} Command
20326 The corresponding @value{GDBN} command is @samp{info line}.
20327 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
20329 @subsubheading Example
20333 @subheading The @code{-symbol-info-symbol} Command
20334 @findex -symbol-info-symbol
20336 @subsubheading Synopsis
20339 -symbol-info-symbol @var{addr}
20342 Describe what symbol is at location @var{addr}.
20344 @subsubheading @value{GDBN} Command
20346 The corresponding @value{GDBN} command is @samp{info symbol}.
20348 @subsubheading Example
20352 @subheading The @code{-symbol-list-functions} Command
20353 @findex -symbol-list-functions
20355 @subsubheading Synopsis
20358 -symbol-list-functions
20361 List the functions in the executable.
20363 @subsubheading @value{GDBN} Command
20365 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
20366 @samp{gdb_search} in @code{gdbtk}.
20368 @subsubheading Example
20372 @subheading The @code{-symbol-list-lines} Command
20373 @findex -symbol-list-lines
20375 @subsubheading Synopsis
20378 -symbol-list-lines @var{filename}
20381 Print the list of lines that contain code and their associated program
20382 addresses for the given source filename. The entries are sorted in
20383 ascending PC order.
20385 @subsubheading @value{GDBN} Command
20387 There is no corresponding @value{GDBN} command.
20389 @subsubheading Example
20392 -symbol-list-lines basics.c
20393 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
20398 @subheading The @code{-symbol-list-types} Command
20399 @findex -symbol-list-types
20401 @subsubheading Synopsis
20407 List all the type names.
20409 @subsubheading @value{GDBN} Command
20411 The corresponding commands are @samp{info types} in @value{GDBN},
20412 @samp{gdb_search} in @code{gdbtk}.
20414 @subsubheading Example
20418 @subheading The @code{-symbol-list-variables} Command
20419 @findex -symbol-list-variables
20421 @subsubheading Synopsis
20424 -symbol-list-variables
20427 List all the global and static variable names.
20429 @subsubheading @value{GDBN} Command
20431 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
20433 @subsubheading Example
20437 @subheading The @code{-symbol-locate} Command
20438 @findex -symbol-locate
20440 @subsubheading Synopsis
20446 @subsubheading @value{GDBN} Command
20448 @samp{gdb_loc} in @code{gdbtk}.
20450 @subsubheading Example
20454 @subheading The @code{-symbol-type} Command
20455 @findex -symbol-type
20457 @subsubheading Synopsis
20460 -symbol-type @var{variable}
20463 Show type of @var{variable}.
20465 @subsubheading @value{GDBN} Command
20467 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
20468 @samp{gdb_obj_variable}.
20470 @subsubheading Example
20474 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20475 @node GDB/MI File Commands
20476 @section @sc{gdb/mi} File Commands
20478 This section describes the GDB/MI commands to specify executable file names
20479 and to read in and obtain symbol table information.
20481 @subheading The @code{-file-exec-and-symbols} Command
20482 @findex -file-exec-and-symbols
20484 @subsubheading Synopsis
20487 -file-exec-and-symbols @var{file}
20490 Specify the executable file to be debugged. This file is the one from
20491 which the symbol table is also read. If no file is specified, the
20492 command clears the executable and symbol information. If breakpoints
20493 are set when using this command with no arguments, @value{GDBN} will produce
20494 error messages. Otherwise, no output is produced, except a completion
20497 @subsubheading @value{GDBN} Command
20499 The corresponding @value{GDBN} command is @samp{file}.
20501 @subsubheading Example
20505 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
20511 @subheading The @code{-file-exec-file} Command
20512 @findex -file-exec-file
20514 @subsubheading Synopsis
20517 -file-exec-file @var{file}
20520 Specify the executable file to be debugged. Unlike
20521 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
20522 from this file. If used without argument, @value{GDBN} clears the information
20523 about the executable file. No output is produced, except a completion
20526 @subsubheading @value{GDBN} Command
20528 The corresponding @value{GDBN} command is @samp{exec-file}.
20530 @subsubheading Example
20534 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
20540 @subheading The @code{-file-list-exec-sections} Command
20541 @findex -file-list-exec-sections
20543 @subsubheading Synopsis
20546 -file-list-exec-sections
20549 List the sections of the current executable file.
20551 @subsubheading @value{GDBN} Command
20553 The @value{GDBN} command @samp{info file} shows, among the rest, the same
20554 information as this command. @code{gdbtk} has a corresponding command
20555 @samp{gdb_load_info}.
20557 @subsubheading Example
20561 @subheading The @code{-file-list-exec-source-file} Command
20562 @findex -file-list-exec-source-file
20564 @subsubheading Synopsis
20567 -file-list-exec-source-file
20570 List the line number, the current source file, and the absolute path
20571 to the current source file for the current executable.
20573 @subsubheading @value{GDBN} Command
20575 The @value{GDBN} equivalent is @samp{info source}
20577 @subsubheading Example
20581 123-file-list-exec-source-file
20582 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c"
20587 @subheading The @code{-file-list-exec-source-files} Command
20588 @findex -file-list-exec-source-files
20590 @subsubheading Synopsis
20593 -file-list-exec-source-files
20596 List the source files for the current executable.
20598 It will always output the filename, but only when GDB can find the absolute
20599 file name of a source file, will it output the fullname.
20601 @subsubheading @value{GDBN} Command
20603 The @value{GDBN} equivalent is @samp{info sources}.
20604 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
20606 @subsubheading Example
20609 -file-list-exec-source-files
20611 @{file=foo.c,fullname=/home/foo.c@},
20612 @{file=/home/bar.c,fullname=/home/bar.c@},
20613 @{file=gdb_could_not_find_fullpath.c@}]
20617 @subheading The @code{-file-list-shared-libraries} Command
20618 @findex -file-list-shared-libraries
20620 @subsubheading Synopsis
20623 -file-list-shared-libraries
20626 List the shared libraries in the program.
20628 @subsubheading @value{GDBN} Command
20630 The corresponding @value{GDBN} command is @samp{info shared}.
20632 @subsubheading Example
20636 @subheading The @code{-file-list-symbol-files} Command
20637 @findex -file-list-symbol-files
20639 @subsubheading Synopsis
20642 -file-list-symbol-files
20647 @subsubheading @value{GDBN} Command
20649 The corresponding @value{GDBN} command is @samp{info file} (part of it).
20651 @subsubheading Example
20655 @subheading The @code{-file-symbol-file} Command
20656 @findex -file-symbol-file
20658 @subsubheading Synopsis
20661 -file-symbol-file @var{file}
20664 Read symbol table info from the specified @var{file} argument. When
20665 used without arguments, clears @value{GDBN}'s symbol table info. No output is
20666 produced, except for a completion notification.
20668 @subsubheading @value{GDBN} Command
20670 The corresponding @value{GDBN} command is @samp{symbol-file}.
20672 @subsubheading Example
20676 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
20682 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20683 @node GDB/MI Memory Overlay Commands
20684 @section @sc{gdb/mi} Memory Overlay Commands
20686 The memory overlay commands are not implemented.
20688 @c @subheading -overlay-auto
20690 @c @subheading -overlay-list-mapping-state
20692 @c @subheading -overlay-list-overlays
20694 @c @subheading -overlay-map
20696 @c @subheading -overlay-off
20698 @c @subheading -overlay-on
20700 @c @subheading -overlay-unmap
20702 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20703 @node GDB/MI Signal Handling Commands
20704 @section @sc{gdb/mi} Signal Handling Commands
20706 Signal handling commands are not implemented.
20708 @c @subheading -signal-handle
20710 @c @subheading -signal-list-handle-actions
20712 @c @subheading -signal-list-signal-types
20716 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20717 @node GDB/MI Target Manipulation
20718 @section @sc{gdb/mi} Target Manipulation Commands
20721 @subheading The @code{-target-attach} Command
20722 @findex -target-attach
20724 @subsubheading Synopsis
20727 -target-attach @var{pid} | @var{file}
20730 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
20732 @subsubheading @value{GDBN} command
20734 The corresponding @value{GDBN} command is @samp{attach}.
20736 @subsubheading Example
20740 @subheading The @code{-target-compare-sections} Command
20741 @findex -target-compare-sections
20743 @subsubheading Synopsis
20746 -target-compare-sections [ @var{section} ]
20749 Compare data of section @var{section} on target to the exec file.
20750 Without the argument, all sections are compared.
20752 @subsubheading @value{GDBN} Command
20754 The @value{GDBN} equivalent is @samp{compare-sections}.
20756 @subsubheading Example
20760 @subheading The @code{-target-detach} Command
20761 @findex -target-detach
20763 @subsubheading Synopsis
20769 Detach from the remote target which normally resumes its execution.
20772 @subsubheading @value{GDBN} command
20774 The corresponding @value{GDBN} command is @samp{detach}.
20776 @subsubheading Example
20786 @subheading The @code{-target-disconnect} Command
20787 @findex -target-disconnect
20789 @subsubheading Synopsis
20795 Disconnect from the remote target. There's no output and the target is
20796 generally not resumed.
20798 @subsubheading @value{GDBN} command
20800 The corresponding @value{GDBN} command is @samp{disconnect}.
20802 @subsubheading Example
20812 @subheading The @code{-target-download} Command
20813 @findex -target-download
20815 @subsubheading Synopsis
20821 Loads the executable onto the remote target.
20822 It prints out an update message every half second, which includes the fields:
20826 The name of the section.
20828 The size of what has been sent so far for that section.
20830 The size of the section.
20832 The total size of what was sent so far (the current and the previous sections).
20834 The size of the overall executable to download.
20838 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
20839 @sc{gdb/mi} Output Syntax}).
20841 In addition, it prints the name and size of the sections, as they are
20842 downloaded. These messages include the following fields:
20846 The name of the section.
20848 The size of the section.
20850 The size of the overall executable to download.
20854 At the end, a summary is printed.
20856 @subsubheading @value{GDBN} Command
20858 The corresponding @value{GDBN} command is @samp{load}.
20860 @subsubheading Example
20862 Note: each status message appears on a single line. Here the messages
20863 have been broken down so that they can fit onto a page.
20868 +download,@{section=".text",section-size="6668",total-size="9880"@}
20869 +download,@{section=".text",section-sent="512",section-size="6668",
20870 total-sent="512",total-size="9880"@}
20871 +download,@{section=".text",section-sent="1024",section-size="6668",
20872 total-sent="1024",total-size="9880"@}
20873 +download,@{section=".text",section-sent="1536",section-size="6668",
20874 total-sent="1536",total-size="9880"@}
20875 +download,@{section=".text",section-sent="2048",section-size="6668",
20876 total-sent="2048",total-size="9880"@}
20877 +download,@{section=".text",section-sent="2560",section-size="6668",
20878 total-sent="2560",total-size="9880"@}
20879 +download,@{section=".text",section-sent="3072",section-size="6668",
20880 total-sent="3072",total-size="9880"@}
20881 +download,@{section=".text",section-sent="3584",section-size="6668",
20882 total-sent="3584",total-size="9880"@}
20883 +download,@{section=".text",section-sent="4096",section-size="6668",
20884 total-sent="4096",total-size="9880"@}
20885 +download,@{section=".text",section-sent="4608",section-size="6668",
20886 total-sent="4608",total-size="9880"@}
20887 +download,@{section=".text",section-sent="5120",section-size="6668",
20888 total-sent="5120",total-size="9880"@}
20889 +download,@{section=".text",section-sent="5632",section-size="6668",
20890 total-sent="5632",total-size="9880"@}
20891 +download,@{section=".text",section-sent="6144",section-size="6668",
20892 total-sent="6144",total-size="9880"@}
20893 +download,@{section=".text",section-sent="6656",section-size="6668",
20894 total-sent="6656",total-size="9880"@}
20895 +download,@{section=".init",section-size="28",total-size="9880"@}
20896 +download,@{section=".fini",section-size="28",total-size="9880"@}
20897 +download,@{section=".data",section-size="3156",total-size="9880"@}
20898 +download,@{section=".data",section-sent="512",section-size="3156",
20899 total-sent="7236",total-size="9880"@}
20900 +download,@{section=".data",section-sent="1024",section-size="3156",
20901 total-sent="7748",total-size="9880"@}
20902 +download,@{section=".data",section-sent="1536",section-size="3156",
20903 total-sent="8260",total-size="9880"@}
20904 +download,@{section=".data",section-sent="2048",section-size="3156",
20905 total-sent="8772",total-size="9880"@}
20906 +download,@{section=".data",section-sent="2560",section-size="3156",
20907 total-sent="9284",total-size="9880"@}
20908 +download,@{section=".data",section-sent="3072",section-size="3156",
20909 total-sent="9796",total-size="9880"@}
20910 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
20916 @subheading The @code{-target-exec-status} Command
20917 @findex -target-exec-status
20919 @subsubheading Synopsis
20922 -target-exec-status
20925 Provide information on the state of the target (whether it is running or
20926 not, for instance).
20928 @subsubheading @value{GDBN} Command
20930 There's no equivalent @value{GDBN} command.
20932 @subsubheading Example
20936 @subheading The @code{-target-list-available-targets} Command
20937 @findex -target-list-available-targets
20939 @subsubheading Synopsis
20942 -target-list-available-targets
20945 List the possible targets to connect to.
20947 @subsubheading @value{GDBN} Command
20949 The corresponding @value{GDBN} command is @samp{help target}.
20951 @subsubheading Example
20955 @subheading The @code{-target-list-current-targets} Command
20956 @findex -target-list-current-targets
20958 @subsubheading Synopsis
20961 -target-list-current-targets
20964 Describe the current target.
20966 @subsubheading @value{GDBN} Command
20968 The corresponding information is printed by @samp{info file} (among
20971 @subsubheading Example
20975 @subheading The @code{-target-list-parameters} Command
20976 @findex -target-list-parameters
20978 @subsubheading Synopsis
20981 -target-list-parameters
20986 @subsubheading @value{GDBN} Command
20990 @subsubheading Example
20994 @subheading The @code{-target-select} Command
20995 @findex -target-select
20997 @subsubheading Synopsis
21000 -target-select @var{type} @var{parameters @dots{}}
21003 Connect @value{GDBN} to the remote target. This command takes two args:
21007 The type of target, for instance @samp{async}, @samp{remote}, etc.
21008 @item @var{parameters}
21009 Device names, host names and the like. @xref{Target Commands, ,
21010 Commands for managing targets}, for more details.
21013 The output is a connection notification, followed by the address at
21014 which the target program is, in the following form:
21017 ^connected,addr="@var{address}",func="@var{function name}",
21018 args=[@var{arg list}]
21021 @subsubheading @value{GDBN} Command
21023 The corresponding @value{GDBN} command is @samp{target}.
21025 @subsubheading Example
21029 -target-select async /dev/ttya
21030 ^connected,addr="0xfe00a300",func="??",args=[]
21034 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21035 @node GDB/MI Miscellaneous Commands
21036 @section Miscellaneous @sc{gdb/mi} Commands
21038 @c @subheading -gdb-complete
21040 @subheading The @code{-gdb-exit} Command
21043 @subsubheading Synopsis
21049 Exit @value{GDBN} immediately.
21051 @subsubheading @value{GDBN} Command
21053 Approximately corresponds to @samp{quit}.
21055 @subsubheading Example
21064 @subheading The @code{-exec-abort} Command
21065 @findex -exec-abort
21067 @subsubheading Synopsis
21073 Kill the inferior running program.
21075 @subsubheading @value{GDBN} Command
21077 The corresponding @value{GDBN} command is @samp{kill}.
21079 @subsubheading Example
21083 @subheading The @code{-gdb-set} Command
21086 @subsubheading Synopsis
21092 Set an internal @value{GDBN} variable.
21093 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
21095 @subsubheading @value{GDBN} Command
21097 The corresponding @value{GDBN} command is @samp{set}.
21099 @subsubheading Example
21109 @subheading The @code{-gdb-show} Command
21112 @subsubheading Synopsis
21118 Show the current value of a @value{GDBN} variable.
21120 @subsubheading @value{GDBN} command
21122 The corresponding @value{GDBN} command is @samp{show}.
21124 @subsubheading Example
21133 @c @subheading -gdb-source
21136 @subheading The @code{-gdb-version} Command
21137 @findex -gdb-version
21139 @subsubheading Synopsis
21145 Show version information for @value{GDBN}. Used mostly in testing.
21147 @subsubheading @value{GDBN} Command
21149 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
21150 default shows this information when you start an interactive session.
21152 @subsubheading Example
21154 @c This example modifies the actual output from GDB to avoid overfull
21160 ~Copyright 2000 Free Software Foundation, Inc.
21161 ~GDB is free software, covered by the GNU General Public License, and
21162 ~you are welcome to change it and/or distribute copies of it under
21163 ~ certain conditions.
21164 ~Type "show copying" to see the conditions.
21165 ~There is absolutely no warranty for GDB. Type "show warranty" for
21167 ~This GDB was configured as
21168 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
21173 @subheading The @code{-interpreter-exec} Command
21174 @findex -interpreter-exec
21176 @subheading Synopsis
21179 -interpreter-exec @var{interpreter} @var{command}
21181 @anchor{-interpreter-exec}
21183 Execute the specified @var{command} in the given @var{interpreter}.
21185 @subheading @value{GDBN} Command
21187 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
21189 @subheading Example
21193 -interpreter-exec console "break main"
21194 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
21195 &"During symbol reading, bad structure-type format.\n"
21196 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
21201 @subheading The @code{-inferior-tty-set} Command
21202 @findex -inferior-tty-set
21204 @subheading Synopsis
21207 -inferior-tty-set /dev/pts/1
21210 Set terminal for future runs of the program being debugged.
21212 @subheading @value{GDBN} Command
21214 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
21216 @subheading Example
21220 -inferior-tty-set /dev/pts/1
21225 @subheading The @code{-inferior-tty-show} Command
21226 @findex -inferior-tty-show
21228 @subheading Synopsis
21234 Show terminal for future runs of program being debugged.
21236 @subheading @value{GDBN} Command
21238 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
21240 @subheading Example
21244 -inferior-tty-set /dev/pts/1
21248 ^done,inferior_tty_terminal="/dev/pts/1"
21253 @chapter @value{GDBN} Annotations
21255 This chapter describes annotations in @value{GDBN}. Annotations were
21256 designed to interface @value{GDBN} to graphical user interfaces or other
21257 similar programs which want to interact with @value{GDBN} at a
21258 relatively high level.
21260 The annotation mechanism has largely been superseeded by @sc{gdb/mi}
21264 This is Edition @value{EDITION}, @value{DATE}.
21268 * Annotations Overview:: What annotations are; the general syntax.
21269 * Prompting:: Annotations marking @value{GDBN}'s need for input.
21270 * Errors:: Annotations for error messages.
21271 * Invalidation:: Some annotations describe things now invalid.
21272 * Annotations for Running::
21273 Whether the program is running, how it stopped, etc.
21274 * Source Annotations:: Annotations describing source code.
21277 @node Annotations Overview
21278 @section What is an Annotation?
21279 @cindex annotations
21281 Annotations start with a newline character, two @samp{control-z}
21282 characters, and the name of the annotation. If there is no additional
21283 information associated with this annotation, the name of the annotation
21284 is followed immediately by a newline. If there is additional
21285 information, the name of the annotation is followed by a space, the
21286 additional information, and a newline. The additional information
21287 cannot contain newline characters.
21289 Any output not beginning with a newline and two @samp{control-z}
21290 characters denotes literal output from @value{GDBN}. Currently there is
21291 no need for @value{GDBN} to output a newline followed by two
21292 @samp{control-z} characters, but if there was such a need, the
21293 annotations could be extended with an @samp{escape} annotation which
21294 means those three characters as output.
21296 The annotation @var{level}, which is specified using the
21297 @option{--annotate} command line option (@pxref{Mode Options}), controls
21298 how much information @value{GDBN} prints together with its prompt,
21299 values of expressions, source lines, and other types of output. Level 0
21300 is for no anntations, level 1 is for use when @value{GDBN} is run as a
21301 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
21302 for programs that control @value{GDBN}, and level 2 annotations have
21303 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
21304 Interface, annotate, GDB's Obsolete Annotations}).
21307 @kindex set annotate
21308 @item set annotate @var{level}
21309 The @value{GDBN} command @code{set annotate} sets the level of
21310 annotations to the specified @var{level}.
21312 @item show annotate
21313 @kindex show annotate
21314 Show the current annotation level.
21317 This chapter describes level 3 annotations.
21319 A simple example of starting up @value{GDBN} with annotations is:
21322 $ @kbd{gdb --annotate=3}
21324 Copyright 2003 Free Software Foundation, Inc.
21325 GDB is free software, covered by the GNU General Public License,
21326 and you are welcome to change it and/or distribute copies of it
21327 under certain conditions.
21328 Type "show copying" to see the conditions.
21329 There is absolutely no warranty for GDB. Type "show warranty"
21331 This GDB was configured as "i386-pc-linux-gnu"
21342 Here @samp{quit} is input to @value{GDBN}; the rest is output from
21343 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
21344 denotes a @samp{control-z} character) are annotations; the rest is
21345 output from @value{GDBN}.
21348 @section Annotation for @value{GDBN} Input
21350 @cindex annotations for prompts
21351 When @value{GDBN} prompts for input, it annotates this fact so it is possible
21352 to know when to send output, when the output from a given command is
21355 Different kinds of input each have a different @dfn{input type}. Each
21356 input type has three annotations: a @code{pre-} annotation, which
21357 denotes the beginning of any prompt which is being output, a plain
21358 annotation, which denotes the end of the prompt, and then a @code{post-}
21359 annotation which denotes the end of any echo which may (or may not) be
21360 associated with the input. For example, the @code{prompt} input type
21361 features the following annotations:
21369 The input types are
21374 @findex post-prompt
21376 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
21378 @findex pre-commands
21380 @findex post-commands
21382 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
21383 command. The annotations are repeated for each command which is input.
21385 @findex pre-overload-choice
21386 @findex overload-choice
21387 @findex post-overload-choice
21388 @item overload-choice
21389 When @value{GDBN} wants the user to select between various overloaded functions.
21395 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
21397 @findex pre-prompt-for-continue
21398 @findex prompt-for-continue
21399 @findex post-prompt-for-continue
21400 @item prompt-for-continue
21401 When @value{GDBN} is asking the user to press return to continue. Note: Don't
21402 expect this to work well; instead use @code{set height 0} to disable
21403 prompting. This is because the counting of lines is buggy in the
21404 presence of annotations.
21409 @cindex annotations for errors, warnings and interrupts
21416 This annotation occurs right before @value{GDBN} responds to an interrupt.
21423 This annotation occurs right before @value{GDBN} responds to an error.
21425 Quit and error annotations indicate that any annotations which @value{GDBN} was
21426 in the middle of may end abruptly. For example, if a
21427 @code{value-history-begin} annotation is followed by a @code{error}, one
21428 cannot expect to receive the matching @code{value-history-end}. One
21429 cannot expect not to receive it either, however; an error annotation
21430 does not necessarily mean that @value{GDBN} is immediately returning all the way
21433 @findex error-begin
21434 A quit or error annotation may be preceded by
21440 Any output between that and the quit or error annotation is the error
21443 Warning messages are not yet annotated.
21444 @c If we want to change that, need to fix warning(), type_error(),
21445 @c range_error(), and possibly other places.
21448 @section Invalidation Notices
21450 @cindex annotations for invalidation messages
21451 The following annotations say that certain pieces of state may have
21455 @findex frames-invalid
21456 @item ^Z^Zframes-invalid
21458 The frames (for example, output from the @code{backtrace} command) may
21461 @findex breakpoints-invalid
21462 @item ^Z^Zbreakpoints-invalid
21464 The breakpoints may have changed. For example, the user just added or
21465 deleted a breakpoint.
21468 @node Annotations for Running
21469 @section Running the Program
21470 @cindex annotations for running programs
21474 When the program starts executing due to a @value{GDBN} command such as
21475 @code{step} or @code{continue},
21481 is output. When the program stops,
21487 is output. Before the @code{stopped} annotation, a variety of
21488 annotations describe how the program stopped.
21492 @item ^Z^Zexited @var{exit-status}
21493 The program exited, and @var{exit-status} is the exit status (zero for
21494 successful exit, otherwise nonzero).
21497 @findex signal-name
21498 @findex signal-name-end
21499 @findex signal-string
21500 @findex signal-string-end
21501 @item ^Z^Zsignalled
21502 The program exited with a signal. After the @code{^Z^Zsignalled}, the
21503 annotation continues:
21509 ^Z^Zsignal-name-end
21513 ^Z^Zsignal-string-end
21518 where @var{name} is the name of the signal, such as @code{SIGILL} or
21519 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
21520 as @code{Illegal Instruction} or @code{Segmentation fault}.
21521 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
21522 user's benefit and have no particular format.
21526 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
21527 just saying that the program received the signal, not that it was
21528 terminated with it.
21531 @item ^Z^Zbreakpoint @var{number}
21532 The program hit breakpoint number @var{number}.
21535 @item ^Z^Zwatchpoint @var{number}
21536 The program hit watchpoint number @var{number}.
21539 @node Source Annotations
21540 @section Displaying Source
21541 @cindex annotations for source display
21544 The following annotation is used instead of displaying source code:
21547 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
21550 where @var{filename} is an absolute file name indicating which source
21551 file, @var{line} is the line number within that file (where 1 is the
21552 first line in the file), @var{character} is the character position
21553 within the file (where 0 is the first character in the file) (for most
21554 debug formats this will necessarily point to the beginning of a line),
21555 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
21556 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
21557 @var{addr} is the address in the target program associated with the
21558 source which is being displayed. @var{addr} is in the form @samp{0x}
21559 followed by one or more lowercase hex digits (note that this does not
21560 depend on the language).
21563 @chapter Reporting Bugs in @value{GDBN}
21564 @cindex bugs in @value{GDBN}
21565 @cindex reporting bugs in @value{GDBN}
21567 Your bug reports play an essential role in making @value{GDBN} reliable.
21569 Reporting a bug may help you by bringing a solution to your problem, or it
21570 may not. But in any case the principal function of a bug report is to help
21571 the entire community by making the next version of @value{GDBN} work better. Bug
21572 reports are your contribution to the maintenance of @value{GDBN}.
21574 In order for a bug report to serve its purpose, you must include the
21575 information that enables us to fix the bug.
21578 * Bug Criteria:: Have you found a bug?
21579 * Bug Reporting:: How to report bugs
21583 @section Have you found a bug?
21584 @cindex bug criteria
21586 If you are not sure whether you have found a bug, here are some guidelines:
21589 @cindex fatal signal
21590 @cindex debugger crash
21591 @cindex crash of debugger
21593 If the debugger gets a fatal signal, for any input whatever, that is a
21594 @value{GDBN} bug. Reliable debuggers never crash.
21596 @cindex error on valid input
21598 If @value{GDBN} produces an error message for valid input, that is a
21599 bug. (Note that if you're cross debugging, the problem may also be
21600 somewhere in the connection to the target.)
21602 @cindex invalid input
21604 If @value{GDBN} does not produce an error message for invalid input,
21605 that is a bug. However, you should note that your idea of
21606 ``invalid input'' might be our idea of ``an extension'' or ``support
21607 for traditional practice''.
21610 If you are an experienced user of debugging tools, your suggestions
21611 for improvement of @value{GDBN} are welcome in any case.
21614 @node Bug Reporting
21615 @section How to report bugs
21616 @cindex bug reports
21617 @cindex @value{GDBN} bugs, reporting
21619 A number of companies and individuals offer support for @sc{gnu} products.
21620 If you obtained @value{GDBN} from a support organization, we recommend you
21621 contact that organization first.
21623 You can find contact information for many support companies and
21624 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
21626 @c should add a web page ref...
21628 In any event, we also recommend that you submit bug reports for
21629 @value{GDBN}. The prefered method is to submit them directly using
21630 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
21631 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
21634 @strong{Do not send bug reports to @samp{info-gdb}, or to
21635 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
21636 not want to receive bug reports. Those that do have arranged to receive
21639 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
21640 serves as a repeater. The mailing list and the newsgroup carry exactly
21641 the same messages. Often people think of posting bug reports to the
21642 newsgroup instead of mailing them. This appears to work, but it has one
21643 problem which can be crucial: a newsgroup posting often lacks a mail
21644 path back to the sender. Thus, if we need to ask for more information,
21645 we may be unable to reach you. For this reason, it is better to send
21646 bug reports to the mailing list.
21648 The fundamental principle of reporting bugs usefully is this:
21649 @strong{report all the facts}. If you are not sure whether to state a
21650 fact or leave it out, state it!
21652 Often people omit facts because they think they know what causes the
21653 problem and assume that some details do not matter. Thus, you might
21654 assume that the name of the variable you use in an example does not matter.
21655 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
21656 stray memory reference which happens to fetch from the location where that
21657 name is stored in memory; perhaps, if the name were different, the contents
21658 of that location would fool the debugger into doing the right thing despite
21659 the bug. Play it safe and give a specific, complete example. That is the
21660 easiest thing for you to do, and the most helpful.
21662 Keep in mind that the purpose of a bug report is to enable us to fix the
21663 bug. It may be that the bug has been reported previously, but neither
21664 you nor we can know that unless your bug report is complete and
21667 Sometimes people give a few sketchy facts and ask, ``Does this ring a
21668 bell?'' Those bug reports are useless, and we urge everyone to
21669 @emph{refuse to respond to them} except to chide the sender to report
21672 To enable us to fix the bug, you should include all these things:
21676 The version of @value{GDBN}. @value{GDBN} announces it if you start
21677 with no arguments; you can also print it at any time using @code{show
21680 Without this, we will not know whether there is any point in looking for
21681 the bug in the current version of @value{GDBN}.
21684 The type of machine you are using, and the operating system name and
21688 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
21689 ``@value{GCC}--2.8.1''.
21692 What compiler (and its version) was used to compile the program you are
21693 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
21694 C Compiler''. For GCC, you can say @code{gcc --version} to get this
21695 information; for other compilers, see the documentation for those
21699 The command arguments you gave the compiler to compile your example and
21700 observe the bug. For example, did you use @samp{-O}? To guarantee
21701 you will not omit something important, list them all. A copy of the
21702 Makefile (or the output from make) is sufficient.
21704 If we were to try to guess the arguments, we would probably guess wrong
21705 and then we might not encounter the bug.
21708 A complete input script, and all necessary source files, that will
21712 A description of what behavior you observe that you believe is
21713 incorrect. For example, ``It gets a fatal signal.''
21715 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
21716 will certainly notice it. But if the bug is incorrect output, we might
21717 not notice unless it is glaringly wrong. You might as well not give us
21718 a chance to make a mistake.
21720 Even if the problem you experience is a fatal signal, you should still
21721 say so explicitly. Suppose something strange is going on, such as, your
21722 copy of @value{GDBN} is out of synch, or you have encountered a bug in
21723 the C library on your system. (This has happened!) Your copy might
21724 crash and ours would not. If you told us to expect a crash, then when
21725 ours fails to crash, we would know that the bug was not happening for
21726 us. If you had not told us to expect a crash, then we would not be able
21727 to draw any conclusion from our observations.
21730 @cindex recording a session script
21731 To collect all this information, you can use a session recording program
21732 such as @command{script}, which is available on many Unix systems.
21733 Just run your @value{GDBN} session inside @command{script} and then
21734 include the @file{typescript} file with your bug report.
21736 Another way to record a @value{GDBN} session is to run @value{GDBN}
21737 inside Emacs and then save the entire buffer to a file.
21740 If you wish to suggest changes to the @value{GDBN} source, send us context
21741 diffs. If you even discuss something in the @value{GDBN} source, refer to
21742 it by context, not by line number.
21744 The line numbers in our development sources will not match those in your
21745 sources. Your line numbers would convey no useful information to us.
21749 Here are some things that are not necessary:
21753 A description of the envelope of the bug.
21755 Often people who encounter a bug spend a lot of time investigating
21756 which changes to the input file will make the bug go away and which
21757 changes will not affect it.
21759 This is often time consuming and not very useful, because the way we
21760 will find the bug is by running a single example under the debugger
21761 with breakpoints, not by pure deduction from a series of examples.
21762 We recommend that you save your time for something else.
21764 Of course, if you can find a simpler example to report @emph{instead}
21765 of the original one, that is a convenience for us. Errors in the
21766 output will be easier to spot, running under the debugger will take
21767 less time, and so on.
21769 However, simplification is not vital; if you do not want to do this,
21770 report the bug anyway and send us the entire test case you used.
21773 A patch for the bug.
21775 A patch for the bug does help us if it is a good one. But do not omit
21776 the necessary information, such as the test case, on the assumption that
21777 a patch is all we need. We might see problems with your patch and decide
21778 to fix the problem another way, or we might not understand it at all.
21780 Sometimes with a program as complicated as @value{GDBN} it is very hard to
21781 construct an example that will make the program follow a certain path
21782 through the code. If you do not send us the example, we will not be able
21783 to construct one, so we will not be able to verify that the bug is fixed.
21785 And if we cannot understand what bug you are trying to fix, or why your
21786 patch should be an improvement, we will not install it. A test case will
21787 help us to understand.
21790 A guess about what the bug is or what it depends on.
21792 Such guesses are usually wrong. Even we cannot guess right about such
21793 things without first using the debugger to find the facts.
21796 @c The readline documentation is distributed with the readline code
21797 @c and consists of the two following files:
21799 @c inc-hist.texinfo
21800 @c Use -I with makeinfo to point to the appropriate directory,
21801 @c environment var TEXINPUTS with TeX.
21802 @include rluser.texi
21803 @include inc-hist.texinfo
21806 @node Formatting Documentation
21807 @appendix Formatting Documentation
21809 @cindex @value{GDBN} reference card
21810 @cindex reference card
21811 The @value{GDBN} 4 release includes an already-formatted reference card, ready
21812 for printing with PostScript or Ghostscript, in the @file{gdb}
21813 subdirectory of the main source directory@footnote{In
21814 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
21815 release.}. If you can use PostScript or Ghostscript with your printer,
21816 you can print the reference card immediately with @file{refcard.ps}.
21818 The release also includes the source for the reference card. You
21819 can format it, using @TeX{}, by typing:
21825 The @value{GDBN} reference card is designed to print in @dfn{landscape}
21826 mode on US ``letter'' size paper;
21827 that is, on a sheet 11 inches wide by 8.5 inches
21828 high. You will need to specify this form of printing as an option to
21829 your @sc{dvi} output program.
21831 @cindex documentation
21833 All the documentation for @value{GDBN} comes as part of the machine-readable
21834 distribution. The documentation is written in Texinfo format, which is
21835 a documentation system that uses a single source file to produce both
21836 on-line information and a printed manual. You can use one of the Info
21837 formatting commands to create the on-line version of the documentation
21838 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
21840 @value{GDBN} includes an already formatted copy of the on-line Info
21841 version of this manual in the @file{gdb} subdirectory. The main Info
21842 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
21843 subordinate files matching @samp{gdb.info*} in the same directory. If
21844 necessary, you can print out these files, or read them with any editor;
21845 but they are easier to read using the @code{info} subsystem in @sc{gnu}
21846 Emacs or the standalone @code{info} program, available as part of the
21847 @sc{gnu} Texinfo distribution.
21849 If you want to format these Info files yourself, you need one of the
21850 Info formatting programs, such as @code{texinfo-format-buffer} or
21853 If you have @code{makeinfo} installed, and are in the top level
21854 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
21855 version @value{GDBVN}), you can make the Info file by typing:
21862 If you want to typeset and print copies of this manual, you need @TeX{},
21863 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
21864 Texinfo definitions file.
21866 @TeX{} is a typesetting program; it does not print files directly, but
21867 produces output files called @sc{dvi} files. To print a typeset
21868 document, you need a program to print @sc{dvi} files. If your system
21869 has @TeX{} installed, chances are it has such a program. The precise
21870 command to use depends on your system; @kbd{lpr -d} is common; another
21871 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
21872 require a file name without any extension or a @samp{.dvi} extension.
21874 @TeX{} also requires a macro definitions file called
21875 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
21876 written in Texinfo format. On its own, @TeX{} cannot either read or
21877 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
21878 and is located in the @file{gdb-@var{version-number}/texinfo}
21881 If you have @TeX{} and a @sc{dvi} printer program installed, you can
21882 typeset and print this manual. First switch to the the @file{gdb}
21883 subdirectory of the main source directory (for example, to
21884 @file{gdb-@value{GDBVN}/gdb}) and type:
21890 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
21892 @node Installing GDB
21893 @appendix Installing @value{GDBN}
21894 @cindex configuring @value{GDBN}
21895 @cindex installation
21896 @cindex configuring @value{GDBN}, and source tree subdirectories
21898 @value{GDBN} comes with a @code{configure} script that automates the process
21899 of preparing @value{GDBN} for installation; you can then use @code{make} to
21900 build the @code{gdb} program.
21902 @c irrelevant in info file; it's as current as the code it lives with.
21903 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
21904 look at the @file{README} file in the sources; we may have improved the
21905 installation procedures since publishing this manual.}
21908 The @value{GDBN} distribution includes all the source code you need for
21909 @value{GDBN} in a single directory, whose name is usually composed by
21910 appending the version number to @samp{gdb}.
21912 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
21913 @file{gdb-@value{GDBVN}} directory. That directory contains:
21916 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
21917 script for configuring @value{GDBN} and all its supporting libraries
21919 @item gdb-@value{GDBVN}/gdb
21920 the source specific to @value{GDBN} itself
21922 @item gdb-@value{GDBVN}/bfd
21923 source for the Binary File Descriptor library
21925 @item gdb-@value{GDBVN}/include
21926 @sc{gnu} include files
21928 @item gdb-@value{GDBVN}/libiberty
21929 source for the @samp{-liberty} free software library
21931 @item gdb-@value{GDBVN}/opcodes
21932 source for the library of opcode tables and disassemblers
21934 @item gdb-@value{GDBVN}/readline
21935 source for the @sc{gnu} command-line interface
21937 @item gdb-@value{GDBVN}/glob
21938 source for the @sc{gnu} filename pattern-matching subroutine
21940 @item gdb-@value{GDBVN}/mmalloc
21941 source for the @sc{gnu} memory-mapped malloc package
21944 The simplest way to configure and build @value{GDBN} is to run @code{configure}
21945 from the @file{gdb-@var{version-number}} source directory, which in
21946 this example is the @file{gdb-@value{GDBVN}} directory.
21948 First switch to the @file{gdb-@var{version-number}} source directory
21949 if you are not already in it; then run @code{configure}. Pass the
21950 identifier for the platform on which @value{GDBN} will run as an
21956 cd gdb-@value{GDBVN}
21957 ./configure @var{host}
21962 where @var{host} is an identifier such as @samp{sun4} or
21963 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
21964 (You can often leave off @var{host}; @code{configure} tries to guess the
21965 correct value by examining your system.)
21967 Running @samp{configure @var{host}} and then running @code{make} builds the
21968 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
21969 libraries, then @code{gdb} itself. The configured source files, and the
21970 binaries, are left in the corresponding source directories.
21973 @code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
21974 system does not recognize this automatically when you run a different
21975 shell, you may need to run @code{sh} on it explicitly:
21978 sh configure @var{host}
21981 If you run @code{configure} from a directory that contains source
21982 directories for multiple libraries or programs, such as the
21983 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, @code{configure}
21984 creates configuration files for every directory level underneath (unless
21985 you tell it not to, with the @samp{--norecursion} option).
21987 You should run the @code{configure} script from the top directory in the
21988 source tree, the @file{gdb-@var{version-number}} directory. If you run
21989 @code{configure} from one of the subdirectories, you will configure only
21990 that subdirectory. That is usually not what you want. In particular,
21991 if you run the first @code{configure} from the @file{gdb} subdirectory
21992 of the @file{gdb-@var{version-number}} directory, you will omit the
21993 configuration of @file{bfd}, @file{readline}, and other sibling
21994 directories of the @file{gdb} subdirectory. This leads to build errors
21995 about missing include files such as @file{bfd/bfd.h}.
21997 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
21998 However, you should make sure that the shell on your path (named by
21999 the @samp{SHELL} environment variable) is publicly readable. Remember
22000 that @value{GDBN} uses the shell to start your program---some systems refuse to
22001 let @value{GDBN} debug child processes whose programs are not readable.
22004 * Separate Objdir:: Compiling @value{GDBN} in another directory
22005 * Config Names:: Specifying names for hosts and targets
22006 * Configure Options:: Summary of options for configure
22009 @node Separate Objdir
22010 @section Compiling @value{GDBN} in another directory
22012 If you want to run @value{GDBN} versions for several host or target machines,
22013 you need a different @code{gdb} compiled for each combination of
22014 host and target. @code{configure} is designed to make this easy by
22015 allowing you to generate each configuration in a separate subdirectory,
22016 rather than in the source directory. If your @code{make} program
22017 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
22018 @code{make} in each of these directories builds the @code{gdb}
22019 program specified there.
22021 To build @code{gdb} in a separate directory, run @code{configure}
22022 with the @samp{--srcdir} option to specify where to find the source.
22023 (You also need to specify a path to find @code{configure}
22024 itself from your working directory. If the path to @code{configure}
22025 would be the same as the argument to @samp{--srcdir}, you can leave out
22026 the @samp{--srcdir} option; it is assumed.)
22028 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
22029 separate directory for a Sun 4 like this:
22033 cd gdb-@value{GDBVN}
22036 ../gdb-@value{GDBVN}/configure sun4
22041 When @code{configure} builds a configuration using a remote source
22042 directory, it creates a tree for the binaries with the same structure
22043 (and using the same names) as the tree under the source directory. In
22044 the example, you'd find the Sun 4 library @file{libiberty.a} in the
22045 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
22046 @file{gdb-sun4/gdb}.
22048 Make sure that your path to the @file{configure} script has just one
22049 instance of @file{gdb} in it. If your path to @file{configure} looks
22050 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
22051 one subdirectory of @value{GDBN}, not the whole package. This leads to
22052 build errors about missing include files such as @file{bfd/bfd.h}.
22054 One popular reason to build several @value{GDBN} configurations in separate
22055 directories is to configure @value{GDBN} for cross-compiling (where
22056 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
22057 programs that run on another machine---the @dfn{target}).
22058 You specify a cross-debugging target by
22059 giving the @samp{--target=@var{target}} option to @code{configure}.
22061 When you run @code{make} to build a program or library, you must run
22062 it in a configured directory---whatever directory you were in when you
22063 called @code{configure} (or one of its subdirectories).
22065 The @code{Makefile} that @code{configure} generates in each source
22066 directory also runs recursively. If you type @code{make} in a source
22067 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
22068 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
22069 will build all the required libraries, and then build GDB.
22071 When you have multiple hosts or targets configured in separate
22072 directories, you can run @code{make} on them in parallel (for example,
22073 if they are NFS-mounted on each of the hosts); they will not interfere
22077 @section Specifying names for hosts and targets
22079 The specifications used for hosts and targets in the @code{configure}
22080 script are based on a three-part naming scheme, but some short predefined
22081 aliases are also supported. The full naming scheme encodes three pieces
22082 of information in the following pattern:
22085 @var{architecture}-@var{vendor}-@var{os}
22088 For example, you can use the alias @code{sun4} as a @var{host} argument,
22089 or as the value for @var{target} in a @code{--target=@var{target}}
22090 option. The equivalent full name is @samp{sparc-sun-sunos4}.
22092 The @code{configure} script accompanying @value{GDBN} does not provide
22093 any query facility to list all supported host and target names or
22094 aliases. @code{configure} calls the Bourne shell script
22095 @code{config.sub} to map abbreviations to full names; you can read the
22096 script, if you wish, or you can use it to test your guesses on
22097 abbreviations---for example:
22100 % sh config.sub i386-linux
22102 % sh config.sub alpha-linux
22103 alpha-unknown-linux-gnu
22104 % sh config.sub hp9k700
22106 % sh config.sub sun4
22107 sparc-sun-sunos4.1.1
22108 % sh config.sub sun3
22109 m68k-sun-sunos4.1.1
22110 % sh config.sub i986v
22111 Invalid configuration `i986v': machine `i986v' not recognized
22115 @code{config.sub} is also distributed in the @value{GDBN} source
22116 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
22118 @node Configure Options
22119 @section @code{configure} options
22121 Here is a summary of the @code{configure} options and arguments that
22122 are most often useful for building @value{GDBN}. @code{configure} also has
22123 several other options not listed here. @inforef{What Configure
22124 Does,,configure.info}, for a full explanation of @code{configure}.
22127 configure @r{[}--help@r{]}
22128 @r{[}--prefix=@var{dir}@r{]}
22129 @r{[}--exec-prefix=@var{dir}@r{]}
22130 @r{[}--srcdir=@var{dirname}@r{]}
22131 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
22132 @r{[}--target=@var{target}@r{]}
22137 You may introduce options with a single @samp{-} rather than
22138 @samp{--} if you prefer; but you may abbreviate option names if you use
22143 Display a quick summary of how to invoke @code{configure}.
22145 @item --prefix=@var{dir}
22146 Configure the source to install programs and files under directory
22149 @item --exec-prefix=@var{dir}
22150 Configure the source to install programs under directory
22153 @c avoid splitting the warning from the explanation:
22155 @item --srcdir=@var{dirname}
22156 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
22157 @code{make} that implements the @code{VPATH} feature.}@*
22158 Use this option to make configurations in directories separate from the
22159 @value{GDBN} source directories. Among other things, you can use this to
22160 build (or maintain) several configurations simultaneously, in separate
22161 directories. @code{configure} writes configuration specific files in
22162 the current directory, but arranges for them to use the source in the
22163 directory @var{dirname}. @code{configure} creates directories under
22164 the working directory in parallel to the source directories below
22167 @item --norecursion
22168 Configure only the directory level where @code{configure} is executed; do not
22169 propagate configuration to subdirectories.
22171 @item --target=@var{target}
22172 Configure @value{GDBN} for cross-debugging programs running on the specified
22173 @var{target}. Without this option, @value{GDBN} is configured to debug
22174 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
22176 There is no convenient way to generate a list of all available targets.
22178 @item @var{host} @dots{}
22179 Configure @value{GDBN} to run on the specified @var{host}.
22181 There is no convenient way to generate a list of all available hosts.
22184 There are many other options available as well, but they are generally
22185 needed for special purposes only.
22187 @node Maintenance Commands
22188 @appendix Maintenance Commands
22189 @cindex maintenance commands
22190 @cindex internal commands
22192 In addition to commands intended for @value{GDBN} users, @value{GDBN}
22193 includes a number of commands intended for @value{GDBN} developers,
22194 that are not documented elsewhere in this manual. These commands are
22195 provided here for reference. (For commands that turn on debugging
22196 messages, see @ref{Debugging Output}.)
22199 @kindex maint agent
22200 @item maint agent @var{expression}
22201 Translate the given @var{expression} into remote agent bytecodes.
22202 This command is useful for debugging the Agent Expression mechanism
22203 (@pxref{Agent Expressions}).
22205 @kindex maint info breakpoints
22206 @item @anchor{maint info breakpoints}maint info breakpoints
22207 Using the same format as @samp{info breakpoints}, display both the
22208 breakpoints you've set explicitly, and those @value{GDBN} is using for
22209 internal purposes. Internal breakpoints are shown with negative
22210 breakpoint numbers. The type column identifies what kind of breakpoint
22215 Normal, explicitly set breakpoint.
22218 Normal, explicitly set watchpoint.
22221 Internal breakpoint, used to handle correctly stepping through
22222 @code{longjmp} calls.
22224 @item longjmp resume
22225 Internal breakpoint at the target of a @code{longjmp}.
22228 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
22231 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
22234 Shared library events.
22238 @kindex maint check-symtabs
22239 @item maint check-symtabs
22240 Check the consistency of psymtabs and symtabs.
22242 @kindex maint cplus first_component
22243 @item maint cplus first_component @var{name}
22244 Print the first C@t{++} class/namespace component of @var{name}.
22246 @kindex maint cplus namespace
22247 @item maint cplus namespace
22248 Print the list of possible C@t{++} namespaces.
22250 @kindex maint demangle
22251 @item maint demangle @var{name}
22252 Demangle a C@t{++} or Objective-C manled @var{name}.
22254 @kindex maint deprecate
22255 @kindex maint undeprecate
22256 @cindex deprecated commands
22257 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
22258 @itemx maint undeprecate @var{command}
22259 Deprecate or undeprecate the named @var{command}. Deprecated commands
22260 cause @value{GDBN} to issue a warning when you use them. The optional
22261 argument @var{replacement} says which newer command should be used in
22262 favor of the deprecated one; if it is given, @value{GDBN} will mention
22263 the replacement as part of the warning.
22265 @kindex maint dump-me
22266 @item maint dump-me
22267 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
22268 Cause a fatal signal in the debugger and force it to dump its core.
22269 This is supported only on systems which support aborting a program
22270 with the @code{SIGQUIT} signal.
22272 @kindex maint internal-error
22273 @kindex maint internal-warning
22274 @item maint internal-error @r{[}@var{message-text}@r{]}
22275 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
22276 Cause @value{GDBN} to call the internal function @code{internal_error}
22277 or @code{internal_warning} and hence behave as though an internal error
22278 or internal warning has been detected. In addition to reporting the
22279 internal problem, these functions give the user the opportunity to
22280 either quit @value{GDBN} or create a core file of the current
22281 @value{GDBN} session.
22283 These commands take an optional parameter @var{message-text} that is
22284 used as the text of the error or warning message.
22286 Here's an example of using @code{indernal-error}:
22289 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
22290 @dots{}/maint.c:121: internal-error: testing, 1, 2
22291 A problem internal to GDB has been detected. Further
22292 debugging may prove unreliable.
22293 Quit this debugging session? (y or n) @kbd{n}
22294 Create a core file? (y or n) @kbd{n}
22298 @kindex maint packet
22299 @item maint packet @var{text}
22300 If @value{GDBN} is talking to an inferior via the serial protocol,
22301 then this command sends the string @var{text} to the inferior, and
22302 displays the response packet. @value{GDBN} supplies the initial
22303 @samp{$} character, the terminating @samp{#} character, and the
22306 @kindex maint print architecture
22307 @item maint print architecture @r{[}@var{file}@r{]}
22308 Print the entire architecture configuration. The optional argument
22309 @var{file} names the file where the output goes.
22311 @kindex maint print dummy-frames
22312 @item maint print dummy-frames
22313 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
22316 (@value{GDBP}) @kbd{b add}
22318 (@value{GDBP}) @kbd{print add(2,3)}
22319 Breakpoint 2, add (a=2, b=3) at @dots{}
22321 The program being debugged stopped while in a function called from GDB.
22323 (@value{GDBP}) @kbd{maint print dummy-frames}
22324 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
22325 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
22326 call_lo=0x01014000 call_hi=0x01014001
22330 Takes an optional file parameter.
22332 @kindex maint print registers
22333 @kindex maint print raw-registers
22334 @kindex maint print cooked-registers
22335 @kindex maint print register-groups
22336 @item maint print registers @r{[}@var{file}@r{]}
22337 @itemx maint print raw-registers @r{[}@var{file}@r{]}
22338 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
22339 @itemx maint print register-groups @r{[}@var{file}@r{]}
22340 Print @value{GDBN}'s internal register data structures.
22342 The command @code{maint print raw-registers} includes the contents of
22343 the raw register cache; the command @code{maint print cooked-registers}
22344 includes the (cooked) value of all registers; and the command
22345 @code{maint print register-groups} includes the groups that each
22346 register is a member of. @xref{Registers,, Registers, gdbint,
22347 @value{GDBN} Internals}.
22349 These commands take an optional parameter, a file name to which to
22350 write the information.
22352 @kindex maint print reggroups
22353 @item maint print reggroups @r{[}@var{file}@r{]}
22354 Print @value{GDBN}'s internal register group data structures. The
22355 optional argument @var{file} tells to what file to write the
22358 The register groups info looks like this:
22361 (@value{GDBP}) @kbd{maint print reggroups}
22374 This command forces @value{GDBN} to flush its internal register cache.
22376 @kindex maint print objfiles
22377 @cindex info for known object files
22378 @item maint print objfiles
22379 Print a dump of all known object files. For each object file, this
22380 command prints its name, address in memory, and all of its psymtabs
22383 @kindex maint print statistics
22384 @cindex bcache statistics
22385 @item maint print statistics
22386 This command prints, for each object file in the program, various data
22387 about that object file followed by the byte cache (@dfn{bcache})
22388 statistics for the object file. The objfile data includes the number
22389 of minimal, partical, full, and stabs symbols, the number of types
22390 defined by the objfile, the number of as yet unexpanded psym tables,
22391 the number of line tables and string tables, and the amount of memory
22392 used by the various tables. The bcache statistics include the counts,
22393 sizes, and counts of duplicates of all and unique objects, max,
22394 average, and median entry size, total memory used and its overhead and
22395 savings, and various measures of the hash table size and chain
22398 @kindex maint print type
22399 @cindex type chain of a data type
22400 @item maint print type @var{expr}
22401 Print the type chain for a type specified by @var{expr}. The argument
22402 can be either a type name or a symbol. If it is a symbol, the type of
22403 that symbol is described. The type chain produced by this command is
22404 a recursive definition of the data type as stored in @value{GDBN}'s
22405 data structures, including its flags and contained types.
22407 @kindex maint set dwarf2 max-cache-age
22408 @kindex maint show dwarf2 max-cache-age
22409 @item maint set dwarf2 max-cache-age
22410 @itemx maint show dwarf2 max-cache-age
22411 Control the DWARF 2 compilation unit cache.
22413 @cindex DWARF 2 compilation units cache
22414 In object files with inter-compilation-unit references, such as those
22415 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
22416 reader needs to frequently refer to previously read compilation units.
22417 This setting controls how long a compilation unit will remain in the
22418 cache if it is not referenced. A higher limit means that cached
22419 compilation units will be stored in memory longer, and more total
22420 memory will be used. Setting it to zero disables caching, which will
22421 slow down @value{GDBN} startup, but reduce memory consumption.
22423 @kindex maint set profile
22424 @kindex maint show profile
22425 @cindex profiling GDB
22426 @item maint set profile
22427 @itemx maint show profile
22428 Control profiling of @value{GDBN}.
22430 Profiling will be disabled until you use the @samp{maint set profile}
22431 command to enable it. When you enable profiling, the system will begin
22432 collecting timing and execution count data; when you disable profiling or
22433 exit @value{GDBN}, the results will be written to a log file. Remember that
22434 if you use profiling, @value{GDBN} will overwrite the profiling log file
22435 (often called @file{gmon.out}). If you have a record of important profiling
22436 data in a @file{gmon.out} file, be sure to move it to a safe location.
22438 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
22439 compiled with the @samp{-pg} compiler option.
22441 @kindex maint show-debug-regs
22442 @cindex x86 hardware debug registers
22443 @item maint show-debug-regs
22444 Control whether to show variables that mirror the x86 hardware debug
22445 registers. Use @code{ON} to enable, @code{OFF} to disable. If
22446 enabled, the debug registers values are shown when GDB inserts or
22447 removes a hardware breakpoint or watchpoint, and when the inferior
22448 triggers a hardware-assisted breakpoint or watchpoint.
22450 @kindex maint space
22451 @cindex memory used by commands
22453 Control whether to display memory usage for each command. If set to a
22454 nonzero value, @value{GDBN} will display how much memory each command
22455 took, following the command's own output. This can also be requested
22456 by invoking @value{GDBN} with the @option{--statistics} command-line
22457 switch (@pxref{Mode Options}).
22460 @cindex time of command execution
22462 Control whether to display the execution time for each command. If
22463 set to a nonzero value, @value{GDBN} will display how much time it
22464 took to execute each command, following the command's own output.
22465 This can also be requested by invoking @value{GDBN} with the
22466 @option{--statistics} command-line switch (@pxref{Mode Options}).
22468 @kindex maint translate-address
22469 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
22470 Find the symbol stored at the location specified by the address
22471 @var{addr} and an optional section name @var{section}. If found,
22472 @value{GDBN} prints the name of the closest symbol and an offset from
22473 the symbol's location to the specified address. This is similar to
22474 the @code{info address} command (@pxref{Symbols}), except that this
22475 command also allows to find symbols in other sections.
22479 The following command is useful for non-interactive invocations of
22480 @value{GDBN}, such as in the test suite.
22483 @item set watchdog @var{nsec}
22484 @kindex set watchdog
22485 @cindex watchdog timer
22486 @cindex timeout for commands
22487 Set the maximum number of seconds @value{GDBN} will wait for the
22488 target operation to finish. If this time expires, @value{GDBN}
22489 reports and error and the command is aborted.
22491 @item show watchdog
22492 Show the current setting of the target wait timeout.
22495 @node Remote Protocol
22496 @appendix @value{GDBN} Remote Serial Protocol
22501 * Stop Reply Packets::
22502 * General Query Packets::
22503 * Register Packet Format::
22504 * Tracepoint Packets::
22507 * File-I/O remote protocol extension::
22513 There may be occasions when you need to know something about the
22514 protocol---for example, if there is only one serial port to your target
22515 machine, you might want your program to do something special if it
22516 recognizes a packet meant for @value{GDBN}.
22518 In the examples below, @samp{->} and @samp{<-} are used to indicate
22519 transmitted and received data respectfully.
22521 @cindex protocol, @value{GDBN} remote serial
22522 @cindex serial protocol, @value{GDBN} remote
22523 @cindex remote serial protocol
22524 All @value{GDBN} commands and responses (other than acknowledgments) are
22525 sent as a @var{packet}. A @var{packet} is introduced with the character
22526 @samp{$}, the actual @var{packet-data}, and the terminating character
22527 @samp{#} followed by a two-digit @var{checksum}:
22530 @code{$}@var{packet-data}@code{#}@var{checksum}
22534 @cindex checksum, for @value{GDBN} remote
22536 The two-digit @var{checksum} is computed as the modulo 256 sum of all
22537 characters between the leading @samp{$} and the trailing @samp{#} (an
22538 eight bit unsigned checksum).
22540 Implementors should note that prior to @value{GDBN} 5.0 the protocol
22541 specification also included an optional two-digit @var{sequence-id}:
22544 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
22547 @cindex sequence-id, for @value{GDBN} remote
22549 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
22550 has never output @var{sequence-id}s. Stubs that handle packets added
22551 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
22553 @cindex acknowledgment, for @value{GDBN} remote
22554 When either the host or the target machine receives a packet, the first
22555 response expected is an acknowledgment: either @samp{+} (to indicate
22556 the package was received correctly) or @samp{-} (to request
22560 -> @code{$}@var{packet-data}@code{#}@var{checksum}
22565 The host (@value{GDBN}) sends @var{command}s, and the target (the
22566 debugging stub incorporated in your program) sends a @var{response}. In
22567 the case of step and continue @var{command}s, the response is only sent
22568 when the operation has completed (the target has again stopped).
22570 @var{packet-data} consists of a sequence of characters with the
22571 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
22574 @cindex remote protocol, field separator
22575 Fields within the packet should be separated using @samp{,} @samp{;} or
22576 @samp{:}. Except where otherwise noted all numbers are represented in
22577 @sc{hex} with leading zeros suppressed.
22579 Implementors should note that prior to @value{GDBN} 5.0, the character
22580 @samp{:} could not appear as the third character in a packet (as it
22581 would potentially conflict with the @var{sequence-id}).
22583 @cindex remote protocol, binary data
22584 @anchor{Binary Data}
22585 Binary data in most packets is encoded either as two hexadecimal
22586 digits per byte of binary data. This allowed the traditional remote
22587 protocol to work over connections which were only seven-bit clean.
22588 Some packets designed more recently assume an eight-bit clean
22589 connection, and use a more efficient encoding to send and receive
22592 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
22593 as an escape character. Any escaped byte is transmitted as the escape
22594 character followed by the original character XORed with @code{0x20}.
22595 For example, the byte @code{0x7d} would be transmitted as the two
22596 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
22597 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
22598 @samp{@}}) must always be escaped. Responses sent by the stub
22599 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
22600 is not interpreted as the start of a run-length encoded sequence
22603 Response @var{data} can be run-length encoded to save space. A @samp{*}
22604 means that the next character is an @sc{ascii} encoding giving a repeat count
22605 which stands for that many repetitions of the character preceding the
22606 @samp{*}. The encoding is @code{n+29}, yielding a printable character
22607 where @code{n >=3} (which is where rle starts to win). The printable
22608 characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric
22609 value greater than 126 should not be used.
22616 means the same as "0000".
22618 The error response returned for some packets includes a two character
22619 error number. That number is not well defined.
22621 @cindex empty response, for unsupported packets
22622 For any @var{command} not supported by the stub, an empty response
22623 (@samp{$#00}) should be returned. That way it is possible to extend the
22624 protocol. A newer @value{GDBN} can tell if a packet is supported based
22627 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
22628 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
22634 The following table provides a complete list of all currently defined
22635 @var{command}s and their corresponding response @var{data}.
22636 @xref{File-I/O remote protocol extension}, for details about the File
22637 I/O extension of the remote protocol.
22639 Each packet's description has a template showing the packet's overall
22640 syntax, followed by an explanation of the packet's meaning. We
22641 include spaces in some of the templates for clarity; these are not
22642 part of the packet's syntax. No @value{GDBN} packet uses spaces to
22643 separate its components. For example, a template like @samp{foo
22644 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
22645 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
22646 @var{baz}. GDB does not transmit a space character between the
22647 @samp{foo} and the @var{bar}, or between the @var{bar} and the
22650 Note that all packet forms beginning with an upper- or lower-case
22651 letter, other than those described here, are reserved for future use.
22653 Here are the packet descriptions.
22658 @cindex @samp{!} packet
22659 Enable extended mode. In extended mode, the remote server is made
22660 persistent. The @samp{R} packet is used to restart the program being
22666 The remote target both supports and has enabled extended mode.
22670 @cindex @samp{?} packet
22671 Indicate the reason the target halted. The reply is the same as for
22675 @xref{Stop Reply Packets}, for the reply specifications.
22677 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
22678 @cindex @samp{A} packet
22679 Initialized @code{argv[]} array passed into program. @var{arglen}
22680 specifies the number of bytes in the hex encoded byte stream
22681 @var{arg}. See @code{gdbserver} for more details.
22686 The arguments were set.
22692 @cindex @samp{b} packet
22693 (Don't use this packet; its behavior is not well-defined.)
22694 Change the serial line speed to @var{baud}.
22696 JTC: @emph{When does the transport layer state change? When it's
22697 received, or after the ACK is transmitted. In either case, there are
22698 problems if the command or the acknowledgment packet is dropped.}
22700 Stan: @emph{If people really wanted to add something like this, and get
22701 it working for the first time, they ought to modify ser-unix.c to send
22702 some kind of out-of-band message to a specially-setup stub and have the
22703 switch happen "in between" packets, so that from remote protocol's point
22704 of view, nothing actually happened.}
22706 @item B @var{addr},@var{mode}
22707 @cindex @samp{B} packet
22708 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
22709 breakpoint at @var{addr}.
22711 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
22712 (@pxref{insert breakpoint or watchpoint packet}).
22714 @item c @r{[}@var{addr}@r{]}
22715 @cindex @samp{c} packet
22716 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
22717 resume at current address.
22720 @xref{Stop Reply Packets}, for the reply specifications.
22722 @item C @var{sig}@r{[};@var{addr}@r{]}
22723 @cindex @samp{C} packet
22724 Continue with signal @var{sig} (hex signal number). If
22725 @samp{;@var{addr}} is omitted, resume at same address.
22728 @xref{Stop Reply Packets}, for the reply specifications.
22731 @cindex @samp{d} packet
22734 Don't use this packet; instead, define a general set packet
22735 (@pxref{General Query Packets}).
22738 @cindex @samp{D} packet
22739 Detach @value{GDBN} from the remote system. Sent to the remote target
22740 before @value{GDBN} disconnects via the @code{detach} command.
22750 @item F @var{RC},@var{EE},@var{CF};@var{XX}
22751 @cindex @samp{F} packet
22752 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
22753 This is part of the File-I/O protocol extension. @xref{File-I/O
22754 remote protocol extension}, for the specification.
22757 @anchor{read registers packet}
22758 @cindex @samp{g} packet
22759 Read general registers.
22763 @item @var{XX@dots{}}
22764 Each byte of register data is described by two hex digits. The bytes
22765 with the register are transmitted in target byte order. The size of
22766 each register and their position within the @samp{g} packet are
22767 determined by the @value{GDBN} internal macros
22768 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{REGISTER_NAME} macros. The
22769 specification of several standard @samp{g} packets is specified below.
22774 @item G @var{XX@dots{}}
22775 @cindex @samp{G} packet
22776 Write general registers. @xref{read registers packet}, for a
22777 description of the @var{XX@dots{}} data.
22787 @item H @var{c} @var{t}
22788 @cindex @samp{H} packet
22789 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
22790 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
22791 should be @samp{c} for step and continue operations, @samp{g} for other
22792 operations. The thread designator @var{t} may be @samp{-1}, meaning all
22793 the threads, a thread number, or @samp{0} which means pick any thread.
22804 @c 'H': How restrictive (or permissive) is the thread model. If a
22805 @c thread is selected and stopped, are other threads allowed
22806 @c to continue to execute? As I mentioned above, I think the
22807 @c semantics of each command when a thread is selected must be
22808 @c described. For example:
22810 @c 'g': If the stub supports threads and a specific thread is
22811 @c selected, returns the register block from that thread;
22812 @c otherwise returns current registers.
22814 @c 'G' If the stub supports threads and a specific thread is
22815 @c selected, sets the registers of the register block of
22816 @c that thread; otherwise sets current registers.
22818 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
22819 @anchor{cycle step packet}
22820 @cindex @samp{i} packet
22821 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
22822 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
22823 step starting at that address.
22826 @cindex @samp{I} packet
22827 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
22831 @cindex @samp{k} packet
22834 FIXME: @emph{There is no description of how to operate when a specific
22835 thread context has been selected (i.e.@: does 'k' kill only that
22838 @item m @var{addr},@var{length}
22839 @cindex @samp{m} packet
22840 Read @var{length} bytes of memory starting at address @var{addr}.
22841 Note that @var{addr} may not be aligned to any particular boundary.
22843 The stub need not use any particular size or alignment when gathering
22844 data from memory for the response; even if @var{addr} is word-aligned
22845 and @var{length} is a multiple of the word size, the stub is free to
22846 use byte accesses, or not. For this reason, this packet may not be
22847 suitable for accessing memory-mapped I/O devices.
22848 @cindex alignment of remote memory accesses
22849 @cindex size of remote memory accesses
22850 @cindex memory, alignment and size of remote accesses
22854 @item @var{XX@dots{}}
22855 Memory contents; each byte is transmitted as a two-digit hexidecimal
22856 number. The reply may contain fewer bytes than requested if the
22857 server was able to read only part of the region of memory.
22862 @item M @var{addr},@var{length}:@var{XX@dots{}}
22863 @cindex @samp{M} packet
22864 Write @var{length} bytes of memory starting at address @var{addr}.
22865 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
22866 hexidecimal number.
22873 for an error (this includes the case where only part of the data was
22878 @cindex @samp{p} packet
22879 Read the value of register @var{n}; @var{n} is in hex.
22880 @xref{read registers packet}, for a description of how the returned
22881 register value is encoded.
22885 @item @var{XX@dots{}}
22886 the register's value
22890 Indicating an unrecognized @var{query}.
22893 @item P @var{n@dots{}}=@var{r@dots{}}
22894 @anchor{write register packet}
22895 @cindex @samp{P} packet
22896 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
22897 number @var{n} is in hexidecimal, and @var{r@dots{}} contains two hex
22898 digits for each byte in the register (target byte order).
22908 @item q @var{name} @var{params}@dots{}
22909 @itemx Q @var{name} @var{params}@dots{}
22910 @cindex @samp{q} packet
22911 @cindex @samp{Q} packet
22912 General query (@samp{q}) and set (@samp{Q}). These packets are
22913 described fully in @ref{General Query Packets}.
22916 @cindex @samp{r} packet
22917 Reset the entire system.
22919 Don't use this packet; use the @samp{R} packet instead.
22922 @cindex @samp{R} packet
22923 Restart the program being debugged. @var{XX}, while needed, is ignored.
22924 This packet is only available in extended mode.
22926 The @samp{R} packet has no reply.
22928 @item s @r{[}@var{addr}@r{]}
22929 @cindex @samp{s} packet
22930 Single step. @var{addr} is the address at which to resume. If
22931 @var{addr} is omitted, resume at same address.
22934 @xref{Stop Reply Packets}, for the reply specifications.
22936 @item S @var{sig}@r{[};@var{addr}@r{]}
22937 @anchor{step with signal packet}
22938 @cindex @samp{S} packet
22939 Step with signal. This is analogous to the @samp{C} packet, but
22940 requests a single-step, rather than a normal resumption of execution.
22943 @xref{Stop Reply Packets}, for the reply specifications.
22945 @item t @var{addr}:@var{PP},@var{MM}
22946 @cindex @samp{t} packet
22947 Search backwards starting at address @var{addr} for a match with pattern
22948 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
22949 @var{addr} must be at least 3 digits.
22952 @cindex @samp{T} packet
22953 Find out if the thread XX is alive.
22958 thread is still alive
22964 Packets starting with @samp{v} are identified by a multi-letter name,
22965 up to the first @samp{;} or @samp{?} (or the end of the packet).
22967 @item vCont@r{[};@var{action}@r{[}:@var{tid}@r{]]}@dots{}
22968 @cindex @samp{vCont} packet
22969 Resume the inferior, specifying different actions for each thread.
22970 If an action is specified with no @var{tid}, then it is applied to any
22971 threads that don't have a specific action specified; if no default action is
22972 specified then other threads should remain stopped. Specifying multiple
22973 default actions is an error; specifying no actions is also an error.
22974 Thread IDs are specified in hexadecimal. Currently supported actions are:
22980 Continue with signal @var{sig}. @var{sig} should be two hex digits.
22984 Step with signal @var{sig}. @var{sig} should be two hex digits.
22987 The optional @var{addr} argument normally associated with these packets is
22988 not supported in @samp{vCont}.
22991 @xref{Stop Reply Packets}, for the reply specifications.
22994 @cindex @samp{vCont?} packet
22995 Request a list of actions supporetd by the @samp{vCont} packet.
22999 @item vCont@r{[};@var{action}@dots{}@r{]}
23000 The @samp{vCont} packet is supported. Each @var{action} is a supported
23001 command in the @samp{vCont} packet.
23003 The @samp{vCont} packet is not supported.
23006 @item X @var{addr},@var{length}:@var{XX@dots{}}
23008 @cindex @samp{X} packet
23009 Write data to memory, where the data is transmitted in binary.
23010 @var{addr} is address, @var{length} is number of bytes,
23011 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
23021 @item z @var{type},@var{addr},@var{length}
23022 @itemx Z @var{type},@var{addr},@var{length}
23023 @anchor{insert breakpoint or watchpoint packet}
23024 @cindex @samp{z} packet
23025 @cindex @samp{Z} packets
23026 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
23027 watchpoint starting at address @var{address} and covering the next
23028 @var{length} bytes.
23030 Each breakpoint and watchpoint packet @var{type} is documented
23033 @emph{Implementation notes: A remote target shall return an empty string
23034 for an unrecognized breakpoint or watchpoint packet @var{type}. A
23035 remote target shall support either both or neither of a given
23036 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
23037 avoid potential problems with duplicate packets, the operations should
23038 be implemented in an idempotent way.}
23040 @item z0,@var{addr},@var{length}
23041 @itemx Z0,@var{addr},@var{length}
23042 @cindex @samp{z0} packet
23043 @cindex @samp{Z0} packet
23044 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
23045 @var{addr} of size @var{length}.
23047 A memory breakpoint is implemented by replacing the instruction at
23048 @var{addr} with a software breakpoint or trap instruction. The
23049 @var{length} is used by targets that indicates the size of the
23050 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
23051 @sc{mips} can insert either a 2 or 4 byte breakpoint).
23053 @emph{Implementation note: It is possible for a target to copy or move
23054 code that contains memory breakpoints (e.g., when implementing
23055 overlays). The behavior of this packet, in the presence of such a
23056 target, is not defined.}
23068 @item z1,@var{addr},@var{length}
23069 @itemx Z1,@var{addr},@var{length}
23070 @cindex @samp{z1} packet
23071 @cindex @samp{Z1} packet
23072 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
23073 address @var{addr} of size @var{length}.
23075 A hardware breakpoint is implemented using a mechanism that is not
23076 dependant on being able to modify the target's memory.
23078 @emph{Implementation note: A hardware breakpoint is not affected by code
23091 @item z2,@var{addr},@var{length}
23092 @itemx Z2,@var{addr},@var{length}
23093 @cindex @samp{z2} packet
23094 @cindex @samp{Z2} packet
23095 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint.
23107 @item z3,@var{addr},@var{length}
23108 @itemx Z3,@var{addr},@var{length}
23109 @cindex @samp{z3} packet
23110 @cindex @samp{Z3} packet
23111 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint.
23123 @item z4,@var{addr},@var{length}
23124 @itemx Z4,@var{addr},@var{length}
23125 @cindex @samp{z4} packet
23126 @cindex @samp{Z4} packet
23127 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint.
23141 @node Stop Reply Packets
23142 @section Stop Reply Packets
23143 @cindex stop reply packets
23145 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
23146 receive any of the below as a reply. In the case of the @samp{C},
23147 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
23148 when the target halts. In the below the exact meaning of @dfn{signal
23149 number} is poorly defined. In general one of the UNIX signal
23150 numbering conventions is used.
23152 As in the description of request packets, we include spaces in the
23153 reply templates for clarity; these are not part of the reply packet's
23154 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
23160 The program received signal number @var{AA} (a two-digit hexidecimal
23163 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
23164 @cindex @samp{T} packet reply
23165 The program received signal number @var{AA} (a two-digit hexidecimal
23166 number). Single-step and breakpoint traps are reported this way. The
23167 @samp{@var{n}:@var{r}} pairs give the values of important registers or
23171 If @var{n} is a hexidecimal number, it is a register number, and the
23172 corresponding @var{r} gives that register's value. @var{r} is a
23173 series of bytes in target byte order, with each byte given by a
23174 two-digit hex number.
23176 If @var{n} is @samp{thread}, then @var{r} is the thread process ID, in
23179 If @var{n} is @samp{watch}, @samp{rwatch}, or @samp{awatch}, then the
23180 packet indicates a watchpoint hit, and @var{r} is the data address, in
23183 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
23184 and go on to the next; this allows us to extend the protocol in the
23189 The process exited, and @var{AA} is the exit status. This is only
23190 applicable to certain targets.
23193 The process terminated with signal @var{AA}.
23195 @item O @var{XX}@dots{}
23196 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
23197 written as the program's console output. This can happen at any time
23198 while the program is running and the debugger should continue to wait
23199 for @samp{W}, @samp{T}, etc.
23201 @item F @var{call-id},@var{parameter}@dots{}
23202 @var{call-id} is the identifier which says which host system call should
23203 be called. This is just the name of the function. Translation into the
23204 correct system call is only applicable as it's defined in @value{GDBN}.
23205 @xref{File-I/O remote protocol extension}, for a list of implemented
23208 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
23209 this very system call.
23211 The target replies with this packet when it expects @value{GDBN} to
23212 call a host system call on behalf of the target. @value{GDBN} replies
23213 with an appropriate @samp{F} packet and keeps up waiting for the next
23214 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
23215 or @samp{s} action is expected to be continued. @xref{File-I/O remote
23216 protocol extension}, for more details.
23220 @node General Query Packets
23221 @section General Query Packets
23222 @cindex remote query requests
23224 Packets starting with @samp{q} are @dfn{general query packets};
23225 packets starting with @samp{Q} are @dfn{general set packets}. General
23226 query and set packets are a semi-unified form for retrieving and
23227 sending information to and from the stub.
23229 The initial letter of a query or set packet is followed by a name
23230 indicating what sort of thing the packet applies to. For example,
23231 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
23232 definitions with the stub. These packet names follow some
23237 The name must not contain commas, colons or semicolons.
23239 Most @value{GDBN} query and set packets have a leading upper case
23242 The names of custom vendor packets should use a company prefix, in
23243 lower case, followed by a period. For example, packets designed at
23244 the Acme Corporation might begin with @samp{qacme.foo} (for querying
23245 foos) or @samp{Qacme.bar} (for setting bars).
23248 The name of a query or set packet should be separated from any
23249 parameters by a @samp{:}; the parameters themselves should be
23250 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
23251 full packet name, and check for a separator or the end of the packet,
23252 in case two packet names share a common prefix. New packets should not begin
23253 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
23254 packets predate these conventions, and have arguments without any terminator
23255 for the packet name; we suspect they are in widespread use in places that
23256 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
23257 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
23260 Like the descriptions of the other packets, each description here
23261 has a template showing the packet's overall syntax, followed by an
23262 explanation of the packet's meaning. We include spaces in some of the
23263 templates for clarity; these are not part of the packet's syntax. No
23264 @value{GDBN} packet uses spaces to separate its components.
23266 Here are the currently defined query and set packets:
23271 @cindex current thread, remote request
23272 @cindex @samp{qC} packet
23273 Return the current thread id.
23278 Where @var{pid} is an unsigned hexidecimal process id.
23279 @item @r{(anything else)}
23280 Any other reply implies the old pid.
23283 @item qCRC:@var{addr},@var{length}
23284 @cindex CRC of memory block, remote request
23285 @cindex @samp{qCRC} packet
23286 Compute the CRC checksum of a block of memory.
23290 An error (such as memory fault)
23291 @item C @var{crc32}
23292 The specified memory region's checksum is @var{crc32}.
23296 @itemx qsThreadInfo
23297 @cindex list active threads, remote request
23298 @cindex @samp{qfThreadInfo} packet
23299 @cindex @samp{qsThreadInfo} packet
23300 Obtain a list of all active thread ids from the target (OS). Since there
23301 may be too many active threads to fit into one reply packet, this query
23302 works iteratively: it may require more than one query/reply sequence to
23303 obtain the entire list of threads. The first query of the sequence will
23304 be the @samp{qfThreadInfo} query; subsequent queries in the
23305 sequence will be the @samp{qsThreadInfo} query.
23307 NOTE: This packet replaces the @samp{qL} query (see below).
23313 @item m @var{id},@var{id}@dots{}
23314 a comma-separated list of thread ids
23316 (lower case letter @samp{L}) denotes end of list.
23319 In response to each query, the target will reply with a list of one or
23320 more thread ids, in big-endian unsigned hex, separated by commas.
23321 @value{GDBN} will respond to each reply with a request for more thread
23322 ids (using the @samp{qs} form of the query), until the target responds
23323 with @samp{l} (lower-case el, for @dfn{last}).
23325 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
23326 @cindex get thread-local storage address, remote request
23327 @cindex @samp{qGetTLSAddr} packet
23328 Fetch the address associated with thread local storage specified
23329 by @var{thread-id}, @var{offset}, and @var{lm}.
23331 @var{thread-id} is the (big endian, hex encoded) thread id associated with the
23332 thread for which to fetch the TLS address.
23334 @var{offset} is the (big endian, hex encoded) offset associated with the
23335 thread local variable. (This offset is obtained from the debug
23336 information associated with the variable.)
23338 @var{lm} is the (big endian, hex encoded) OS/ABI specific encoding of the
23339 the load module associated with the thread local storage. For example,
23340 a @sc{gnu}/Linux system will pass the link map address of the shared
23341 object associated with the thread local storage under consideration.
23342 Other operating environments may choose to represent the load module
23343 differently, so the precise meaning of this parameter will vary.
23347 @item @var{XX}@dots{}
23348 Hex encoded (big endian) bytes representing the address of the thread
23349 local storage requested.
23352 An error occurred. @var{nn} are hex digits.
23355 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
23358 Use of this request packet is controlled by the @code{set remote
23359 get-thread-local-storage-address} command (@pxref{Remote
23360 configuration, set remote get-thread-local-storage-address}).
23362 @item qL @var{startflag} @var{threadcount} @var{nextthread}
23363 Obtain thread information from RTOS. Where: @var{startflag} (one hex
23364 digit) is one to indicate the first query and zero to indicate a
23365 subsequent query; @var{threadcount} (two hex digits) is the maximum
23366 number of threads the response packet can contain; and @var{nextthread}
23367 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
23368 returned in the response as @var{argthread}.
23370 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
23374 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
23375 Where: @var{count} (two hex digits) is the number of threads being
23376 returned; @var{done} (one hex digit) is zero to indicate more threads
23377 and one indicates no further threads; @var{argthreadid} (eight hex
23378 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
23379 is a sequence of thread IDs from the target. @var{threadid} (eight hex
23380 digits). See @code{remote.c:parse_threadlist_response()}.
23384 @cindex section offsets, remote request
23385 @cindex @samp{qOffsets} packet
23386 Get section offsets that the target used when re-locating the downloaded
23387 image. @emph{Note: while a @code{Bss} offset is included in the
23388 response, @value{GDBN} ignores this and instead applies the @code{Data}
23389 offset to the @code{Bss} section.}
23393 @item Text=@var{xxx};Data=@var{yyy};Bss=@var{zzz}
23396 @item qP @var{mode} @var{threadid}
23397 @cindex thread information, remote request
23398 @cindex @samp{qP} packet
23399 Returns information on @var{threadid}. Where: @var{mode} is a hex
23400 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
23402 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
23405 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
23407 @item qRcmd,@var{command}
23408 @cindex execute remote command, remote request
23409 @cindex @samp{qRcmd} packet
23410 @var{command} (hex encoded) is passed to the local interpreter for
23411 execution. Invalid commands should be reported using the output
23412 string. Before the final result packet, the target may also respond
23413 with a number of intermediate @samp{O@var{output}} console output
23414 packets. @emph{Implementors should note that providing access to a
23415 stubs's interpreter may have security implications}.
23420 A command response with no output.
23422 A command response with the hex encoded output string @var{OUTPUT}.
23424 Indicate a badly formed request.
23426 An empty reply indicates that @samp{qRcmd} is not recognized.
23429 (Note that the @code{qRcmd} packet's name is separated from the
23430 command by a @samp{,}, not a @samp{:}, contrary to the naming
23431 conventions above. Please don't use this packet as a model for new
23434 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
23435 @cindex supported packets, remote query
23436 @cindex features of the remote protocol
23437 @cindex @samp{qSupported} packet
23438 @anchor{qSupported}
23439 Tell the remote stub about features supported by @value{GDBN}, and
23440 query the stub for features it supports. This packet allows
23441 @value{GDBN} and the remote stub to take advantage of each others'
23442 features. @samp{qSupported} also consolidates multiple feature probes
23443 at startup, to improve @value{GDBN} performance---a single larger
23444 packet performs better than multiple smaller probe packets on
23445 high-latency links. Some features may enable behavior which must not
23446 be on by default, e.g.@: because it would confuse older clients or
23447 stubs. Other features may describe packets which could be
23448 automatically probed for, but are not. These features must be
23449 reported before @value{GDBN} will use them. This ``default
23450 unsupported'' behavior is not appropriate for all packets, but it
23451 helps to keep the initial connection time under control with new
23452 versions of @value{GDBN} which support increasing numbers of packets.
23456 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
23457 The stub supports or does not support each returned @var{stubfeature},
23458 depending on the form of each @var{stubfeature} (see below for the
23461 An empty reply indicates that @samp{qSupported} is not recognized,
23462 or that no features needed to be reported to @value{GDBN}.
23465 The allowed forms for each feature (either a @var{gdbfeature} in the
23466 @samp{qSupported} packet, or a @var{stubfeature} in the response)
23470 @item @var{name}=@var{value}
23471 The remote protocol feature @var{name} is supported, and associated
23472 with the specified @var{value}. The format of @var{value} depends
23473 on the feature, but it must not include a semicolon.
23475 The remote protocol feature @var{name} is supported, and does not
23476 need an associated value.
23478 The remote protocol feature @var{name} is not supported.
23480 The remote protocol feature @var{name} may be supported, and
23481 @value{GDBN} should auto-detect support in some other way when it is
23482 needed. This form will not be used for @var{gdbfeature} notifications,
23483 but may be used for @var{stubfeature} responses.
23486 Whenever the stub receives a @samp{qSupported} request, the
23487 supplied set of @value{GDBN} features should override any previous
23488 request. This allows @value{GDBN} to put the stub in a known
23489 state, even if the stub had previously been communicating with
23490 a different version of @value{GDBN}.
23492 No values of @var{gdbfeature} (for the packet sent by @value{GDBN})
23493 are defined yet. Stubs should ignore any unknown values for
23494 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
23495 packet supports receiving packets of unlimited length (earlier
23496 versions of @value{GDBN} may reject overly long responses). Values
23497 for @var{gdbfeature} may be defined in the future to let the stub take
23498 advantage of new features in @value{GDBN}, e.g.@: incompatible
23499 improvements in the remote protocol---support for unlimited length
23500 responses would be a @var{gdbfeature} example, if it were not implied by
23501 the @samp{qSupported} query. The stub's reply should be independent
23502 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
23503 describes all the features it supports, and then the stub replies with
23504 all the features it supports.
23506 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
23507 responses, as long as each response uses one of the standard forms.
23509 Some features are flags. A stub which supports a flag feature
23510 should respond with a @samp{+} form response. Other features
23511 require values, and the stub should respond with an @samp{=}
23514 Each feature has a default value, which @value{GDBN} will use if
23515 @samp{qSupported} is not available or if the feature is not mentioned
23516 in the @samp{qSupported} response. The default values are fixed; a
23517 stub is free to omit any feature responses that match the defaults.
23519 Not all features can be probed, but for those which can, the probing
23520 mechanism is useful: in some cases, a stub's internal
23521 architecture may not allow the protocol layer to know some information
23522 about the underlying target in advance. This is especially common in
23523 stubs which may be configured for multiple targets.
23525 These are the currently defined stub features and their properties:
23527 @multitable @columnfractions 0.25 0.2 0.2 0.2
23528 @c NOTE: The first row should be @headitem, but we do not yet require
23529 @c a new enough version of Texinfo (4.7) to use @headitem.
23531 @tab Value Required
23535 @item @samp{PacketSize}
23540 @item @samp{qXfer:auxv:read}
23547 These are the currently defined stub features, in more detail:
23550 @cindex packet size, remote protocol
23551 @item PacketSize=@var{bytes}
23552 The remote stub can accept packets up to at least @var{bytes} in
23553 length. @value{GDBN} will send packets up to this size for bulk
23554 transfers, and will never send larger packets. This is a limit on the
23555 data characters in the packet, including the frame and checksum.
23556 There is no trailing NUL byte in a remote protocol packet; if the stub
23557 stores packets in a NUL-terminated format, it should allow an extra
23558 byte in its buffer for the NUL. If this stub feature is not supported,
23559 @value{GDBN} guesses based on the size of the @samp{g} packet response.
23561 @item qXfer:auxv:read
23562 The remote stub understands the @samp{qXfer:auxv:read} packet
23563 (@pxref{qXfer auxiliary vector read}).
23568 @cindex symbol lookup, remote request
23569 @cindex @samp{qSymbol} packet
23570 Notify the target that @value{GDBN} is prepared to serve symbol lookup
23571 requests. Accept requests from the target for the values of symbols.
23576 The target does not need to look up any (more) symbols.
23577 @item qSymbol:@var{sym_name}
23578 The target requests the value of symbol @var{sym_name} (hex encoded).
23579 @value{GDBN} may provide the value by using the
23580 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
23584 @item qSymbol:@var{sym_value}:@var{sym_name}
23585 Set the value of @var{sym_name} to @var{sym_value}.
23587 @var{sym_name} (hex encoded) is the name of a symbol whose value the
23588 target has previously requested.
23590 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
23591 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
23597 The target does not need to look up any (more) symbols.
23598 @item qSymbol:@var{sym_name}
23599 The target requests the value of a new symbol @var{sym_name} (hex
23600 encoded). @value{GDBN} will continue to supply the values of symbols
23601 (if available), until the target ceases to request them.
23606 @xref{Tracepoint Packets}.
23608 @item qThreadExtraInfo,@var{id}
23609 @cindex thread attributes info, remote request
23610 @cindex @samp{qThreadExtraInfo} packet
23611 Obtain a printable string description of a thread's attributes from
23612 the target OS. @var{id} is a thread-id in big-endian hex. This
23613 string may contain anything that the target OS thinks is interesting
23614 for @value{GDBN} to tell the user about the thread. The string is
23615 displayed in @value{GDBN}'s @code{info threads} display. Some
23616 examples of possible thread extra info strings are @samp{Runnable}, or
23617 @samp{Blocked on Mutex}.
23621 @item @var{XX}@dots{}
23622 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
23623 comprising the printable string containing the extra information about
23624 the thread's attributes.
23627 (Note that the @code{qThreadExtraInfo} packet's name is separated from
23628 the command by a @samp{,}, not a @samp{:}, contrary to the naming
23629 conventions above. Please don't use this packet as a model for new
23637 @xref{Tracepoint Packets}.
23639 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
23640 @cindex read special object, remote request
23641 @cindex @samp{qXfer} packet
23642 Read uninterpreted bytes from the target's special data area
23643 identified by the keyword @var{object}. Request @var{length} bytes
23644 starting at @var{offset} bytes into the data. The content and
23645 encoding of @var{annex} is specific to the object; it can supply
23646 additional details about what data to access.
23648 Here are the specific requests of this form defined so far. All
23649 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
23650 formats, listed below.
23653 @item qXfer:auxv:read::@var{offset},@var{length}
23654 @anchor{qXfer auxiliary vector read}
23655 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
23656 auxiliary vector}, and @ref{Remote configuration,
23657 read-aux-vector-packet}. Note @var{annex} must be empty.
23659 This packet is not probed by default; the remote stub must request it,
23660 by suppling an appropriate @samp{qSupported} response (@pxref{qSupported}).
23666 Data @var{data} (@pxref{Binary Data}) has been read from the
23667 target. There may be more data at a higher address (although
23668 it is permitted to return @samp{m} even for the last valid
23669 block of data, as long as at least one byte of data was read).
23670 @var{data} may have fewer bytes than the @var{length} in the
23674 Data @var{data} (@pxref{Binary Data}) has been read from the target.
23675 There is no more data to be read. @var{data} may have fewer bytes
23676 than the @var{length} in the request.
23679 The @var{offset} in the request is at the end of the data.
23680 There is no more data to be read.
23683 The request was malformed, or @var{annex} was invalid.
23686 The offset was invalid, or there was an error encountered reading the data.
23687 @var{nn} is a hex-encoded @code{errno} value.
23690 An empty reply indicates the @var{object} string was not recognized by
23691 the stub, or that the object does not support reading.
23694 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
23695 @cindex write data into object, remote request
23696 Write uninterpreted bytes into the target's special data area
23697 identified by the keyword @var{object}, starting at @var{offset} bytes
23698 into the data. @samp{@var{data}@dots{}} is the binary-encoded data
23699 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
23700 is specific to the object; it can supply additional details about what data
23703 No requests of this form are presently in use. This specification
23704 serves as a placeholder to document the common format that new
23705 specific request specifications ought to use.
23710 @var{nn} (hex encoded) is the number of bytes written.
23711 This may be fewer bytes than supplied in the request.
23714 The request was malformed, or @var{annex} was invalid.
23717 The offset was invalid, or there was an error encountered writing the data.
23718 @var{nn} is a hex-encoded @code{errno} value.
23721 An empty reply indicates the @var{object} string was not
23722 recognized by the stub, or that the object does not support writing.
23725 @item qXfer:@var{object}:@var{operation}:@dots{}
23726 Requests of this form may be added in the future. When a stub does
23727 not recognize the @var{object} keyword, or its support for
23728 @var{object} does not recognize the @var{operation} keyword, the stub
23729 must respond with an empty packet.
23733 @node Register Packet Format
23734 @section Register Packet Format
23736 The following @code{g}/@code{G} packets have previously been defined.
23737 In the below, some thirty-two bit registers are transferred as
23738 sixty-four bits. Those registers should be zero/sign extended (which?)
23739 to fill the space allocated. Register bytes are transfered in target
23740 byte order. The two nibbles within a register byte are transfered
23741 most-significant - least-significant.
23747 All registers are transfered as thirty-two bit quantities in the order:
23748 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
23749 registers; fsr; fir; fp.
23753 All registers are transfered as sixty-four bit quantities (including
23754 thirty-two bit registers such as @code{sr}). The ordering is the same
23759 @node Tracepoint Packets
23760 @section Tracepoint Packets
23761 @cindex tracepoint packets
23762 @cindex packets, tracepoint
23764 Here we describe the packets @value{GDBN} uses to implement
23765 tracepoints (@pxref{Tracepoints}).
23769 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}@r{[}-@r{]}
23770 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
23771 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
23772 the tracepoint is disabled. @var{step} is the tracepoint's step
23773 count, and @var{pass} is its pass count. If the trailing @samp{-} is
23774 present, further @samp{QTDP} packets will follow to specify this
23775 tracepoint's actions.
23780 The packet was understood and carried out.
23782 The packet was not recognized.
23785 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
23786 Define actions to be taken when a tracepoint is hit. @var{n} and
23787 @var{addr} must be the same as in the initial @samp{QTDP} packet for
23788 this tracepoint. This packet may only be sent immediately after
23789 another @samp{QTDP} packet that ended with a @samp{-}. If the
23790 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
23791 specifying more actions for this tracepoint.
23793 In the series of action packets for a given tracepoint, at most one
23794 can have an @samp{S} before its first @var{action}. If such a packet
23795 is sent, it and the following packets define ``while-stepping''
23796 actions. Any prior packets define ordinary actions --- that is, those
23797 taken when the tracepoint is first hit. If no action packet has an
23798 @samp{S}, then all the packets in the series specify ordinary
23799 tracepoint actions.
23801 The @samp{@var{action}@dots{}} portion of the packet is a series of
23802 actions, concatenated without separators. Each action has one of the
23808 Collect the registers whose bits are set in @var{mask}. @var{mask} is
23809 a hexidecimal number whose @var{i}'th bit is set if register number
23810 @var{i} should be collected. (The least significant bit is numbered
23811 zero.) Note that @var{mask} may be any number of digits long; it may
23812 not fit in a 32-bit word.
23814 @item M @var{basereg},@var{offset},@var{len}
23815 Collect @var{len} bytes of memory starting at the address in register
23816 number @var{basereg}, plus @var{offset}. If @var{basereg} is
23817 @samp{-1}, then the range has a fixed address: @var{offset} is the
23818 address of the lowest byte to collect. The @var{basereg},
23819 @var{offset}, and @var{len} parameters are all unsigned hexidecimal
23820 values (the @samp{-1} value for @var{basereg} is a special case).
23822 @item X @var{len},@var{expr}
23823 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
23824 it directs. @var{expr} is an agent expression, as described in
23825 @ref{Agent Expressions}. Each byte of the expression is encoded as a
23826 two-digit hex number in the packet; @var{len} is the number of bytes
23827 in the expression (and thus one-half the number of hex digits in the
23832 Any number of actions may be packed together in a single @samp{QTDP}
23833 packet, as long as the packet does not exceed the maximum packet
23834 length (400 bytes, for many stubs). There may be only one @samp{R}
23835 action per tracepoint, and it must precede any @samp{M} or @samp{X}
23836 actions. Any registers referred to by @samp{M} and @samp{X} actions
23837 must be collected by a preceding @samp{R} action. (The
23838 ``while-stepping'' actions are treated as if they were attached to a
23839 separate tracepoint, as far as these restrictions are concerned.)
23844 The packet was understood and carried out.
23846 The packet was not recognized.
23849 @item QTFrame:@var{n}
23850 Select the @var{n}'th tracepoint frame from the buffer, and use the
23851 register and memory contents recorded there to answer subsequent
23852 request packets from @value{GDBN}.
23854 A successful reply from the stub indicates that the stub has found the
23855 requested frame. The response is a series of parts, concatenated
23856 without separators, describing the frame we selected. Each part has
23857 one of the following forms:
23861 The selected frame is number @var{n} in the trace frame buffer;
23862 @var{f} is a hexidecimal number. If @var{f} is @samp{-1}, then there
23863 was no frame matching the criteria in the request packet.
23866 The selected trace frame records a hit of tracepoint number @var{t};
23867 @var{t} is a hexidecimal number.
23871 @item QTFrame:pc:@var{addr}
23872 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
23873 currently selected frame whose PC is @var{addr};
23874 @var{addr} is a hexidecimal number.
23876 @item QTFrame:tdp:@var{t}
23877 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
23878 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
23879 is a hexidecimal number.
23881 @item QTFrame:range:@var{start}:@var{end}
23882 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
23883 currently selected frame whose PC is between @var{start} (inclusive)
23884 and @var{end} (exclusive); @var{start} and @var{end} are hexidecimal
23887 @item QTFrame:outside:@var{start}:@var{end}
23888 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
23889 frame @emph{outside} the given range of addresses.
23892 Begin the tracepoint experiment. Begin collecting data from tracepoint
23893 hits in the trace frame buffer.
23896 End the tracepoint experiment. Stop collecting trace frames.
23899 Clear the table of tracepoints, and empty the trace frame buffer.
23901 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
23902 Establish the given ranges of memory as ``transparent''. The stub
23903 will answer requests for these ranges from memory's current contents,
23904 if they were not collected as part of the tracepoint hit.
23906 @value{GDBN} uses this to mark read-only regions of memory, like those
23907 containing program code. Since these areas never change, they should
23908 still have the same contents they did when the tracepoint was hit, so
23909 there's no reason for the stub to refuse to provide their contents.
23912 Ask the stub if there is a trace experiment running right now.
23917 There is no trace experiment running.
23919 There is a trace experiment running.
23926 @section Interrupts
23927 @cindex interrupts (remote protocol)
23929 When a program on the remote target is running, @value{GDBN} may
23930 attempt to interrupt it by sending a @samp{Ctrl-C} or a @code{BREAK},
23931 control of which is specified via @value{GDBN}'s @samp{remotebreak}
23932 setting (@pxref{set remotebreak}).
23934 The precise meaning of @code{BREAK} is defined by the transport
23935 mechanism and may, in fact, be undefined. @value{GDBN} does
23936 not currently define a @code{BREAK} mechanism for any of the network
23939 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
23940 transport mechanisms. It is represented by sending the single byte
23941 @code{0x03} without any of the usual packet overhead described in
23942 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
23943 transmitted as part of a packet, it is considered to be packet data
23944 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
23945 (@pxref{X packet}), used for binary downloads, may include an unescaped
23946 @code{0x03} as part of its packet.
23948 Stubs are not required to recognize these interrupt mechanisms and the
23949 precise meaning associated with receipt of the interrupt is
23950 implementation defined. If the stub is successful at interrupting the
23951 running program, it is expected that it will send one of the Stop
23952 Reply Packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
23953 of successfully stopping the program. Interrupts received while the
23954 program is stopped will be discarded.
23959 Example sequence of a target being re-started. Notice how the restart
23960 does not get any direct output:
23965 @emph{target restarts}
23968 <- @code{T001:1234123412341234}
23972 Example sequence of a target being stepped by a single instruction:
23975 -> @code{G1445@dots{}}
23980 <- @code{T001:1234123412341234}
23984 <- @code{1455@dots{}}
23988 @node File-I/O remote protocol extension
23989 @section File-I/O remote protocol extension
23990 @cindex File-I/O remote protocol extension
23993 * File-I/O Overview::
23994 * Protocol basics::
23995 * The F request packet::
23996 * The F reply packet::
23997 * The Ctrl-C message::
23999 * List of supported calls::
24000 * Protocol specific representation of datatypes::
24002 * File-I/O Examples::
24005 @node File-I/O Overview
24006 @subsection File-I/O Overview
24007 @cindex file-i/o overview
24009 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
24010 target to use the host's file system and console I/O to perform various
24011 system calls. System calls on the target system are translated into a
24012 remote protocol packet to the host system, which then performs the needed
24013 actions and returns a response packet to the target system.
24014 This simulates file system operations even on targets that lack file systems.
24016 The protocol is defined to be independent of both the host and target systems.
24017 It uses its own internal representation of datatypes and values. Both
24018 @value{GDBN} and the target's @value{GDBN} stub are responsible for
24019 translating the system-dependent value representations into the internal
24020 protocol representations when data is transmitted.
24022 The communication is synchronous. A system call is possible only when
24023 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
24024 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
24025 the target is stopped to allow deterministic access to the target's
24026 memory. Therefore File-I/O is not interruptible by target signals. On
24027 the other hand, it is possible to interrupt File-I/O by a user interrupt
24028 (Ctrl-C) within @value{GDBN}.
24030 The target's request to perform a host system call does not finish
24031 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
24032 after finishing the system call, the target returns to continuing the
24033 previous activity (continue, step). No additional continue or step
24034 request from @value{GDBN} is required.
24037 (@value{GDBP}) continue
24038 <- target requests 'system call X'
24039 target is stopped, @value{GDBN} executes system call
24040 -> GDB returns result
24041 ... target continues, GDB returns to wait for the target
24042 <- target hits breakpoint and sends a Txx packet
24045 The protocol only supports I/O on the console and to regular files on
24046 the host file system. Character or block special devices, pipes,
24047 named pipes, sockets or any other communication method on the host
24048 system are not supported by this protocol.
24050 @node Protocol basics
24051 @subsection Protocol basics
24052 @cindex protocol basics, file-i/o
24054 The File-I/O protocol uses the @code{F} packet as the request as well
24055 as reply packet. Since a File-I/O system call can only occur when
24056 @value{GDBN} is waiting for a response from the continuing or stepping target,
24057 the File-I/O request is a reply that @value{GDBN} has to expect as a result
24058 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
24059 This @code{F} packet contains all information needed to allow @value{GDBN}
24060 to call the appropriate host system call:
24064 A unique identifier for the requested system call.
24067 All parameters to the system call. Pointers are given as addresses
24068 in the target memory address space. Pointers to strings are given as
24069 pointer/length pair. Numerical values are given as they are.
24070 Numerical control flags are given in a protocol specific representation.
24074 At this point, @value{GDBN} has to perform the following actions.
24078 If the parameters include pointer values to data needed as input to a
24079 system call, @value{GDBN} requests this data from the target with a
24080 standard @code{m} packet request. This additional communication has to be
24081 expected by the target implementation and is handled as any other @code{m}
24085 @value{GDBN} translates all value from protocol representation to host
24086 representation as needed. Datatypes are coerced into the host types.
24089 @value{GDBN} calls the system call.
24092 It then coerces datatypes back to protocol representation.
24095 If the system call is expected to return data in buffer space specified
24096 by pointer parameters to the call, the data is transmitted to the
24097 target using a @code{M} or @code{X} packet. This packet has to be expected
24098 by the target implementation and is handled as any other @code{M} or @code{X}
24103 Eventually @value{GDBN} replies with another @code{F} packet which contains all
24104 necessary information for the target to continue. This at least contains
24111 @code{errno}, if has been changed by the system call.
24118 After having done the needed type and value coercion, the target continues
24119 the latest continue or step action.
24121 @node The F request packet
24122 @subsection The @code{F} request packet
24123 @cindex file-i/o request packet
24124 @cindex @code{F} request packet
24126 The @code{F} request packet has the following format:
24129 @item F@var{call-id},@var{parameter@dots{}}
24131 @var{call-id} is the identifier to indicate the host system call to be called.
24132 This is just the name of the function.
24134 @var{parameter@dots{}} are the parameters to the system call.
24135 Parameters are hexadecimal integer values, either the actual values in case
24136 of scalar datatypes, pointers to target buffer space in case of compound
24137 datatypes and unspecified memory areas, or pointer/length pairs in case
24138 of string parameters. These are appended to the @var{call-id} as a
24139 comma-delimited list. All values are transmitted in ASCII
24140 string representation, pointer/length pairs separated by a slash.
24146 @node The F reply packet
24147 @subsection The @code{F} reply packet
24148 @cindex file-i/o reply packet
24149 @cindex @code{F} reply packet
24151 The @code{F} reply packet has the following format:
24155 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call specific attachment}
24157 @var{retcode} is the return code of the system call as hexadecimal value.
24159 @var{errno} is the @code{errno} set by the call, in protocol specific representation.
24160 This parameter can be omitted if the call was successful.
24162 @var{Ctrl-C flag} is only sent if the user requested a break. In this
24163 case, @var{errno} must be sent as well, even if the call was successful.
24164 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
24171 or, if the call was interrupted before the host call has been performed:
24178 assuming 4 is the protocol specific representation of @code{EINTR}.
24183 @node The Ctrl-C message
24184 @subsection The Ctrl-C message
24185 @cindex ctrl-c message, in file-i/o protocol
24187 If the Ctrl-C flag is set in the @value{GDBN}
24188 reply packet (@pxref{The F reply packet}),
24189 the target should behave as if it had
24190 gotten a break message. The meaning for the target is ``system call
24191 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
24192 (as with a break message) and return to @value{GDBN} with a @code{T02}
24195 It's important for the target to know in which
24196 state the system call was interrupted. There are two possible cases:
24200 The system call hasn't been performed on the host yet.
24203 The system call on the host has been finished.
24207 These two states can be distinguished by the target by the value of the
24208 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
24209 call hasn't been performed. This is equivalent to the @code{EINTR} handling
24210 on POSIX systems. In any other case, the target may presume that the
24211 system call has been finished --- successfully or not --- and should behave
24212 as if the break message arrived right after the system call.
24214 @value{GDBN} must behave reliably. If the system call has not been called
24215 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
24216 @code{errno} in the packet. If the system call on the host has been finished
24217 before the user requests a break, the full action must be finished by
24218 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
24219 The @code{F} packet may only be sent when either nothing has happened
24220 or the full action has been completed.
24223 @subsection Console I/O
24224 @cindex console i/o as part of file-i/o
24226 By default and if not explicitely closed by the target system, the file
24227 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
24228 on the @value{GDBN} console is handled as any other file output operation
24229 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
24230 by @value{GDBN} so that after the target read request from file descriptor
24231 0 all following typing is buffered until either one of the following
24236 The user presses @kbd{Ctrl-C}. The behaviour is as explained above, and the
24238 system call is treated as finished.
24241 The user presses @kbd{Enter}. This is treated as end of input with a trailing
24245 The user presses @kbd{Ctrl-D}. This is treated as end of input. No trailing
24246 character (neither newline nor Ctrl-D) is appended to the input.
24250 If the user has typed more characters than fit in the buffer given to
24251 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
24252 either another @code{read(0, @dots{})} is requested by the target, or debugging
24253 is stopped at the user's request.
24256 @node List of supported calls
24257 @subsection List of supported calls
24258 @cindex list of supported file-i/o calls
24275 @unnumberedsubsubsec open
24276 @cindex open, file-i/o system call
24281 int open(const char *pathname, int flags);
24282 int open(const char *pathname, int flags, mode_t mode);
24286 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
24289 @var{flags} is the bitwise @code{OR} of the following values:
24293 If the file does not exist it will be created. The host
24294 rules apply as far as file ownership and time stamps
24298 When used with @code{O_CREAT}, if the file already exists it is
24299 an error and open() fails.
24302 If the file already exists and the open mode allows
24303 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
24304 truncated to zero length.
24307 The file is opened in append mode.
24310 The file is opened for reading only.
24313 The file is opened for writing only.
24316 The file is opened for reading and writing.
24320 Other bits are silently ignored.
24324 @var{mode} is the bitwise @code{OR} of the following values:
24328 User has read permission.
24331 User has write permission.
24334 Group has read permission.
24337 Group has write permission.
24340 Others have read permission.
24343 Others have write permission.
24347 Other bits are silently ignored.
24350 @item Return value:
24351 @code{open} returns the new file descriptor or -1 if an error
24358 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
24361 @var{pathname} refers to a directory.
24364 The requested access is not allowed.
24367 @var{pathname} was too long.
24370 A directory component in @var{pathname} does not exist.
24373 @var{pathname} refers to a device, pipe, named pipe or socket.
24376 @var{pathname} refers to a file on a read-only filesystem and
24377 write access was requested.
24380 @var{pathname} is an invalid pointer value.
24383 No space on device to create the file.
24386 The process already has the maximum number of files open.
24389 The limit on the total number of files open on the system
24393 The call was interrupted by the user.
24399 @unnumberedsubsubsec close
24400 @cindex close, file-i/o system call
24409 @samp{Fclose,@var{fd}}
24411 @item Return value:
24412 @code{close} returns zero on success, or -1 if an error occurred.
24418 @var{fd} isn't a valid open file descriptor.
24421 The call was interrupted by the user.
24427 @unnumberedsubsubsec read
24428 @cindex read, file-i/o system call
24433 int read(int fd, void *buf, unsigned int count);
24437 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
24439 @item Return value:
24440 On success, the number of bytes read is returned.
24441 Zero indicates end of file. If count is zero, read
24442 returns zero as well. On error, -1 is returned.
24448 @var{fd} is not a valid file descriptor or is not open for
24452 @var{bufptr} is an invalid pointer value.
24455 The call was interrupted by the user.
24461 @unnumberedsubsubsec write
24462 @cindex write, file-i/o system call
24467 int write(int fd, const void *buf, unsigned int count);
24471 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
24473 @item Return value:
24474 On success, the number of bytes written are returned.
24475 Zero indicates nothing was written. On error, -1
24482 @var{fd} is not a valid file descriptor or is not open for
24486 @var{bufptr} is an invalid pointer value.
24489 An attempt was made to write a file that exceeds the
24490 host specific maximum file size allowed.
24493 No space on device to write the data.
24496 The call was interrupted by the user.
24502 @unnumberedsubsubsec lseek
24503 @cindex lseek, file-i/o system call
24508 long lseek (int fd, long offset, int flag);
24512 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
24514 @var{flag} is one of:
24518 The offset is set to @var{offset} bytes.
24521 The offset is set to its current location plus @var{offset}
24525 The offset is set to the size of the file plus @var{offset}
24529 @item Return value:
24530 On success, the resulting unsigned offset in bytes from
24531 the beginning of the file is returned. Otherwise, a
24532 value of -1 is returned.
24538 @var{fd} is not a valid open file descriptor.
24541 @var{fd} is associated with the @value{GDBN} console.
24544 @var{flag} is not a proper value.
24547 The call was interrupted by the user.
24553 @unnumberedsubsubsec rename
24554 @cindex rename, file-i/o system call
24559 int rename(const char *oldpath, const char *newpath);
24563 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
24565 @item Return value:
24566 On success, zero is returned. On error, -1 is returned.
24572 @var{newpath} is an existing directory, but @var{oldpath} is not a
24576 @var{newpath} is a non-empty directory.
24579 @var{oldpath} or @var{newpath} is a directory that is in use by some
24583 An attempt was made to make a directory a subdirectory
24587 A component used as a directory in @var{oldpath} or new
24588 path is not a directory. Or @var{oldpath} is a directory
24589 and @var{newpath} exists but is not a directory.
24592 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
24595 No access to the file or the path of the file.
24599 @var{oldpath} or @var{newpath} was too long.
24602 A directory component in @var{oldpath} or @var{newpath} does not exist.
24605 The file is on a read-only filesystem.
24608 The device containing the file has no room for the new
24612 The call was interrupted by the user.
24618 @unnumberedsubsubsec unlink
24619 @cindex unlink, file-i/o system call
24624 int unlink(const char *pathname);
24628 @samp{Funlink,@var{pathnameptr}/@var{len}}
24630 @item Return value:
24631 On success, zero is returned. On error, -1 is returned.
24637 No access to the file or the path of the file.
24640 The system does not allow unlinking of directories.
24643 The file @var{pathname} cannot be unlinked because it's
24644 being used by another process.
24647 @var{pathnameptr} is an invalid pointer value.
24650 @var{pathname} was too long.
24653 A directory component in @var{pathname} does not exist.
24656 A component of the path is not a directory.
24659 The file is on a read-only filesystem.
24662 The call was interrupted by the user.
24668 @unnumberedsubsubsec stat/fstat
24669 @cindex fstat, file-i/o system call
24670 @cindex stat, file-i/o system call
24675 int stat(const char *pathname, struct stat *buf);
24676 int fstat(int fd, struct stat *buf);
24680 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
24681 @samp{Ffstat,@var{fd},@var{bufptr}}
24683 @item Return value:
24684 On success, zero is returned. On error, -1 is returned.
24690 @var{fd} is not a valid open file.
24693 A directory component in @var{pathname} does not exist or the
24694 path is an empty string.
24697 A component of the path is not a directory.
24700 @var{pathnameptr} is an invalid pointer value.
24703 No access to the file or the path of the file.
24706 @var{pathname} was too long.
24709 The call was interrupted by the user.
24715 @unnumberedsubsubsec gettimeofday
24716 @cindex gettimeofday, file-i/o system call
24721 int gettimeofday(struct timeval *tv, void *tz);
24725 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
24727 @item Return value:
24728 On success, 0 is returned, -1 otherwise.
24734 @var{tz} is a non-NULL pointer.
24737 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
24743 @unnumberedsubsubsec isatty
24744 @cindex isatty, file-i/o system call
24749 int isatty(int fd);
24753 @samp{Fisatty,@var{fd}}
24755 @item Return value:
24756 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
24762 The call was interrupted by the user.
24767 Note that the @code{isatty} call is treated as a special case: it returns
24768 1 to the target if the file descriptor is attached
24769 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
24770 would require implementing @code{ioctl} and would be more complex than
24775 @unnumberedsubsubsec system
24776 @cindex system, file-i/o system call
24781 int system(const char *command);
24785 @samp{Fsystem,@var{commandptr}/@var{len}}
24787 @item Return value:
24788 If @var{len} is zero, the return value indicates whether a shell is
24789 available. A zero return value indicates a shell is not available.
24790 For non-zero @var{len}, the value returned is -1 on error and the
24791 return status of the command otherwise. Only the exit status of the
24792 command is returned, which is extracted from the host's @code{system}
24793 return value by calling @code{WEXITSTATUS(retval)}. In case
24794 @file{/bin/sh} could not be executed, 127 is returned.
24800 The call was interrupted by the user.
24805 @value{GDBN} takes over the full task of calling the necessary host calls
24806 to perform the @code{system} call. The return value of @code{system} on
24807 the host is simplified before it's returned
24808 to the target. Any termination signal information from the child process
24809 is discarded, and the return value consists
24810 entirely of the exit status of the called command.
24812 Due to security concerns, the @code{system} call is by default refused
24813 by @value{GDBN}. The user has to allow this call explicitly with the
24814 @code{set remote system-call-allowed 1} command.
24817 @item set remote system-call-allowed
24818 @kindex set remote system-call-allowed
24819 Control whether to allow the @code{system} calls in the File I/O
24820 protocol for the remote target. The default is zero (disabled).
24822 @item show remote system-call-allowed
24823 @kindex show remote system-call-allowed
24824 Show whether the @code{system} calls are allowed in the File I/O
24828 @node Protocol specific representation of datatypes
24829 @subsection Protocol specific representation of datatypes
24830 @cindex protocol specific representation of datatypes, in file-i/o protocol
24833 * Integral datatypes::
24835 * Memory transfer::
24840 @node Integral datatypes
24841 @unnumberedsubsubsec Integral datatypes
24842 @cindex integral datatypes, in file-i/o protocol
24844 The integral datatypes used in the system calls are @code{int},
24845 @code{unsigned int}, @code{long}, @code{unsigned long},
24846 @code{mode_t}, and @code{time_t}.
24848 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
24849 implemented as 32 bit values in this protocol.
24851 @code{long} and @code{unsigned long} are implemented as 64 bit types.
24853 @xref{Limits}, for corresponding MIN and MAX values (similar to those
24854 in @file{limits.h}) to allow range checking on host and target.
24856 @code{time_t} datatypes are defined as seconds since the Epoch.
24858 All integral datatypes transferred as part of a memory read or write of a
24859 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
24862 @node Pointer values
24863 @unnumberedsubsubsec Pointer values
24864 @cindex pointer values, in file-i/o protocol
24866 Pointers to target data are transmitted as they are. An exception
24867 is made for pointers to buffers for which the length isn't
24868 transmitted as part of the function call, namely strings. Strings
24869 are transmitted as a pointer/length pair, both as hex values, e.g.@:
24876 which is a pointer to data of length 18 bytes at position 0x1aaf.
24877 The length is defined as the full string length in bytes, including
24878 the trailing null byte. For example, the string @code{"hello world"}
24879 at address 0x123456 is transmitted as
24885 @node Memory transfer
24886 @unnumberedsubsubsec Memory transfer
24887 @cindex memory transfer, in file-i/o protocol
24889 Structured data which is transferred using a memory read or write (for
24890 example, a @code{struct stat}) is expected to be in a protocol specific format
24891 with all scalar multibyte datatypes being big endian. Translation to
24892 this representation needs to be done both by the target before the @code{F}
24893 packet is sent, and by @value{GDBN} before
24894 it transfers memory to the target. Transferred pointers to structured
24895 data should point to the already-coerced data at any time.
24899 @unnumberedsubsubsec struct stat
24900 @cindex struct stat, in file-i/o protocol
24902 The buffer of type @code{struct stat} used by the target and @value{GDBN}
24903 is defined as follows:
24907 unsigned int st_dev; /* device */
24908 unsigned int st_ino; /* inode */
24909 mode_t st_mode; /* protection */
24910 unsigned int st_nlink; /* number of hard links */
24911 unsigned int st_uid; /* user ID of owner */
24912 unsigned int st_gid; /* group ID of owner */
24913 unsigned int st_rdev; /* device type (if inode device) */
24914 unsigned long st_size; /* total size, in bytes */
24915 unsigned long st_blksize; /* blocksize for filesystem I/O */
24916 unsigned long st_blocks; /* number of blocks allocated */
24917 time_t st_atime; /* time of last access */
24918 time_t st_mtime; /* time of last modification */
24919 time_t st_ctime; /* time of last change */
24923 The integral datatypes conform to the definitions given in the
24924 appropriate section (see @ref{Integral datatypes}, for details) so this
24925 structure is of size 64 bytes.
24927 The values of several fields have a restricted meaning and/or
24933 A value of 0 represents a file, 1 the console.
24936 No valid meaning for the target. Transmitted unchanged.
24939 Valid mode bits are described in @ref{Constants}. Any other
24940 bits have currently no meaning for the target.
24945 No valid meaning for the target. Transmitted unchanged.
24950 These values have a host and file system dependent
24951 accuracy. Especially on Windows hosts, the file system may not
24952 support exact timing values.
24955 The target gets a @code{struct stat} of the above representation and is
24956 responsible for coercing it to the target representation before
24959 Note that due to size differences between the host, target, and protocol
24960 representations of @code{struct stat} members, these members could eventually
24961 get truncated on the target.
24963 @node struct timeval
24964 @unnumberedsubsubsec struct timeval
24965 @cindex struct timeval, in file-i/o protocol
24967 The buffer of type @code{struct timeval} used by the File-I/O protocol
24968 is defined as follows:
24972 time_t tv_sec; /* second */
24973 long tv_usec; /* microsecond */
24977 The integral datatypes conform to the definitions given in the
24978 appropriate section (see @ref{Integral datatypes}, for details) so this
24979 structure is of size 8 bytes.
24982 @subsection Constants
24983 @cindex constants, in file-i/o protocol
24985 The following values are used for the constants inside of the
24986 protocol. @value{GDBN} and target are responsible for translating these
24987 values before and after the call as needed.
24998 @unnumberedsubsubsec Open flags
24999 @cindex open flags, in file-i/o protocol
25001 All values are given in hexadecimal representation.
25013 @node mode_t values
25014 @unnumberedsubsubsec mode_t values
25015 @cindex mode_t values, in file-i/o protocol
25017 All values are given in octal representation.
25034 @unnumberedsubsubsec Errno values
25035 @cindex errno values, in file-i/o protocol
25037 All values are given in decimal representation.
25062 @code{EUNKNOWN} is used as a fallback error value if a host system returns
25063 any error value not in the list of supported error numbers.
25066 @unnumberedsubsubsec Lseek flags
25067 @cindex lseek flags, in file-i/o protocol
25076 @unnumberedsubsubsec Limits
25077 @cindex limits, in file-i/o protocol
25079 All values are given in decimal representation.
25082 INT_MIN -2147483648
25084 UINT_MAX 4294967295
25085 LONG_MIN -9223372036854775808
25086 LONG_MAX 9223372036854775807
25087 ULONG_MAX 18446744073709551615
25090 @node File-I/O Examples
25091 @subsection File-I/O Examples
25092 @cindex file-i/o examples
25094 Example sequence of a write call, file descriptor 3, buffer is at target
25095 address 0x1234, 6 bytes should be written:
25098 <- @code{Fwrite,3,1234,6}
25099 @emph{request memory read from target}
25102 @emph{return "6 bytes written"}
25106 Example sequence of a read call, file descriptor 3, buffer is at target
25107 address 0x1234, 6 bytes should be read:
25110 <- @code{Fread,3,1234,6}
25111 @emph{request memory write to target}
25112 -> @code{X1234,6:XXXXXX}
25113 @emph{return "6 bytes read"}
25117 Example sequence of a read call, call fails on the host due to invalid
25118 file descriptor (@code{EBADF}):
25121 <- @code{Fread,3,1234,6}
25125 Example sequence of a read call, user presses Ctrl-C before syscall on
25129 <- @code{Fread,3,1234,6}
25134 Example sequence of a read call, user presses Ctrl-C after syscall on
25138 <- @code{Fread,3,1234,6}
25139 -> @code{X1234,6:XXXXXX}
25143 @include agentexpr.texi
25157 % I think something like @colophon should be in texinfo. In the
25159 \long\def\colophon{\hbox to0pt{}\vfill
25160 \centerline{The body of this manual is set in}
25161 \centerline{\fontname\tenrm,}
25162 \centerline{with headings in {\bf\fontname\tenbf}}
25163 \centerline{and examples in {\tt\fontname\tentt}.}
25164 \centerline{{\it\fontname\tenit\/},}
25165 \centerline{{\bf\fontname\tenbf}, and}
25166 \centerline{{\sl\fontname\tensl\/}}
25167 \centerline{are used for emphasis.}\vfill}
25169 % Blame: doc@cygnus.com, 1991.