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
500 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
501 Tensilica, Inc.@: contributed support for Xtensa processors. Others
502 who have worked on the Xtensa port of @value{GDBN} in the past include
503 Steve Tjiang, John Newlin, and Scott Foehner.
506 @chapter A Sample @value{GDBN} Session
508 You can use this manual at your leisure to read all about @value{GDBN}.
509 However, a handful of commands are enough to get started using the
510 debugger. This chapter illustrates those commands.
513 In this sample session, we emphasize user input like this: @b{input},
514 to make it easier to pick out from the surrounding output.
517 @c FIXME: this example may not be appropriate for some configs, where
518 @c FIXME...primary interest is in remote use.
520 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
521 processor) exhibits the following bug: sometimes, when we change its
522 quote strings from the default, the commands used to capture one macro
523 definition within another stop working. In the following short @code{m4}
524 session, we define a macro @code{foo} which expands to @code{0000}; we
525 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
526 same thing. However, when we change the open quote string to
527 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
528 procedure fails to define a new synonym @code{baz}:
537 @b{define(bar,defn(`foo'))}
541 @b{changequote(<QUOTE>,<UNQUOTE>)}
543 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
546 m4: End of input: 0: fatal error: EOF in string
550 Let us use @value{GDBN} to try to see what is going on.
553 $ @b{@value{GDBP} m4}
554 @c FIXME: this falsifies the exact text played out, to permit smallbook
555 @c FIXME... format to come out better.
556 @value{GDBN} is free software and you are welcome to distribute copies
557 of it under certain conditions; type "show copying" to see
559 There is absolutely no warranty for @value{GDBN}; type "show warranty"
562 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
567 @value{GDBN} reads only enough symbol data to know where to find the
568 rest when needed; as a result, the first prompt comes up very quickly.
569 We now tell @value{GDBN} to use a narrower display width than usual, so
570 that examples fit in this manual.
573 (@value{GDBP}) @b{set width 70}
577 We need to see how the @code{m4} built-in @code{changequote} works.
578 Having looked at the source, we know the relevant subroutine is
579 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
580 @code{break} command.
583 (@value{GDBP}) @b{break m4_changequote}
584 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
588 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
589 control; as long as control does not reach the @code{m4_changequote}
590 subroutine, the program runs as usual:
593 (@value{GDBP}) @b{run}
594 Starting program: /work/Editorial/gdb/gnu/m4/m4
602 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
603 suspends execution of @code{m4}, displaying information about the
604 context where it stops.
607 @b{changequote(<QUOTE>,<UNQUOTE>)}
609 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
611 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
615 Now we use the command @code{n} (@code{next}) to advance execution to
616 the next line of the current function.
620 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
625 @code{set_quotes} looks like a promising subroutine. We can go into it
626 by using the command @code{s} (@code{step}) instead of @code{next}.
627 @code{step} goes to the next line to be executed in @emph{any}
628 subroutine, so it steps into @code{set_quotes}.
632 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
634 530 if (lquote != def_lquote)
638 The display that shows the subroutine where @code{m4} is now
639 suspended (and its arguments) is called a stack frame display. It
640 shows a summary of the stack. We can use the @code{backtrace}
641 command (which can also be spelled @code{bt}), to see where we are
642 in the stack as a whole: the @code{backtrace} command displays a
643 stack frame for each active subroutine.
646 (@value{GDBP}) @b{bt}
647 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
649 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
651 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
652 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
654 #4 0x79dc in expand_input () at macro.c:40
655 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
659 We step through a few more lines to see what happens. The first two
660 times, we can use @samp{s}; the next two times we use @code{n} to avoid
661 falling into the @code{xstrdup} subroutine.
665 0x3b5c 532 if (rquote != def_rquote)
667 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
668 def_lquote : xstrdup(lq);
670 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
673 538 len_lquote = strlen(rquote);
677 The last line displayed looks a little odd; we can examine the variables
678 @code{lquote} and @code{rquote} to see if they are in fact the new left
679 and right quotes we specified. We use the command @code{p}
680 (@code{print}) to see their values.
683 (@value{GDBP}) @b{p lquote}
684 $1 = 0x35d40 "<QUOTE>"
685 (@value{GDBP}) @b{p rquote}
686 $2 = 0x35d50 "<UNQUOTE>"
690 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
691 To look at some context, we can display ten lines of source
692 surrounding the current line with the @code{l} (@code{list}) command.
698 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
700 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
703 538 len_lquote = strlen(rquote);
704 539 len_rquote = strlen(lquote);
711 Let us step past the two lines that set @code{len_lquote} and
712 @code{len_rquote}, and then examine the values of those variables.
716 539 len_rquote = strlen(lquote);
719 (@value{GDBP}) @b{p len_lquote}
721 (@value{GDBP}) @b{p len_rquote}
726 That certainly looks wrong, assuming @code{len_lquote} and
727 @code{len_rquote} are meant to be the lengths of @code{lquote} and
728 @code{rquote} respectively. We can set them to better values using
729 the @code{p} command, since it can print the value of
730 any expression---and that expression can include subroutine calls and
734 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
736 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
741 Is that enough to fix the problem of using the new quotes with the
742 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
743 executing with the @code{c} (@code{continue}) command, and then try the
744 example that caused trouble initially:
750 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
757 Success! The new quotes now work just as well as the default ones. The
758 problem seems to have been just the two typos defining the wrong
759 lengths. We allow @code{m4} exit by giving it an EOF as input:
763 Program exited normally.
767 The message @samp{Program exited normally.} is from @value{GDBN}; it
768 indicates @code{m4} has finished executing. We can end our @value{GDBN}
769 session with the @value{GDBN} @code{quit} command.
772 (@value{GDBP}) @b{quit}
776 @chapter Getting In and Out of @value{GDBN}
778 This chapter discusses how to start @value{GDBN}, and how to get out of it.
782 type @samp{@value{GDBP}} to start @value{GDBN}.
784 type @kbd{quit} or @kbd{Ctrl-d} to exit.
788 * Invoking GDB:: How to start @value{GDBN}
789 * Quitting GDB:: How to quit @value{GDBN}
790 * Shell Commands:: How to use shell commands inside @value{GDBN}
791 * Logging output:: How to log @value{GDBN}'s output to a file
795 @section Invoking @value{GDBN}
797 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
798 @value{GDBN} reads commands from the terminal until you tell it to exit.
800 You can also run @code{@value{GDBP}} with a variety of arguments and options,
801 to specify more of your debugging environment at the outset.
803 The command-line options described here are designed
804 to cover a variety of situations; in some environments, some of these
805 options may effectively be unavailable.
807 The most usual way to start @value{GDBN} is with one argument,
808 specifying an executable program:
811 @value{GDBP} @var{program}
815 You can also start with both an executable program and a core file
819 @value{GDBP} @var{program} @var{core}
822 You can, instead, specify a process ID as a second argument, if you want
823 to debug a running process:
826 @value{GDBP} @var{program} 1234
830 would attach @value{GDBN} to process @code{1234} (unless you also have a file
831 named @file{1234}; @value{GDBN} does check for a core file first).
833 Taking advantage of the second command-line argument requires a fairly
834 complete operating system; when you use @value{GDBN} as a remote
835 debugger attached to a bare board, there may not be any notion of
836 ``process'', and there is often no way to get a core dump. @value{GDBN}
837 will warn you if it is unable to attach or to read core dumps.
839 You can optionally have @code{@value{GDBP}} pass any arguments after the
840 executable file to the inferior using @code{--args}. This option stops
843 gdb --args gcc -O2 -c foo.c
845 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
846 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
848 You can run @code{@value{GDBP}} without printing the front material, which describes
849 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
856 You can further control how @value{GDBN} starts up by using command-line
857 options. @value{GDBN} itself can remind you of the options available.
867 to display all available options and briefly describe their use
868 (@samp{@value{GDBP} -h} is a shorter equivalent).
870 All options and command line arguments you give are processed
871 in sequential order. The order makes a difference when the
872 @samp{-x} option is used.
876 * File Options:: Choosing files
877 * Mode Options:: Choosing modes
878 * Startup:: What @value{GDBN} does during startup
882 @subsection Choosing files
884 When @value{GDBN} starts, it reads any arguments other than options as
885 specifying an executable file and core file (or process ID). This is
886 the same as if the arguments were specified by the @samp{-se} and
887 @samp{-c} (or @samp{-p} options respectively. (@value{GDBN} reads the
888 first argument that does not have an associated option flag as
889 equivalent to the @samp{-se} option followed by that argument; and the
890 second argument that does not have an associated option flag, if any, as
891 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
892 If the second argument begins with a decimal digit, @value{GDBN} will
893 first attempt to attach to it as a process, and if that fails, attempt
894 to open it as a corefile. If you have a corefile whose name begins with
895 a digit, you can prevent @value{GDBN} from treating it as a pid by
896 prefixing it with @file{./}, e.g.@: @file{./12345}.
898 If @value{GDBN} has not been configured to included core file support,
899 such as for most embedded targets, then it will complain about a second
900 argument and ignore it.
902 Many options have both long and short forms; both are shown in the
903 following list. @value{GDBN} also recognizes the long forms if you truncate
904 them, so long as enough of the option is present to be unambiguous.
905 (If you prefer, you can flag option arguments with @samp{--} rather
906 than @samp{-}, though we illustrate the more usual convention.)
908 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
909 @c way, both those who look for -foo and --foo in the index, will find
913 @item -symbols @var{file}
915 @cindex @code{--symbols}
917 Read symbol table from file @var{file}.
919 @item -exec @var{file}
921 @cindex @code{--exec}
923 Use file @var{file} as the executable file to execute when appropriate,
924 and for examining pure data in conjunction with a core dump.
928 Read symbol table from file @var{file} and use it as the executable
931 @item -core @var{file}
933 @cindex @code{--core}
935 Use file @var{file} as a core dump to examine.
937 @item -c @var{number}
938 @item -pid @var{number}
939 @itemx -p @var{number}
942 Connect to process ID @var{number}, as with the @code{attach} command.
943 If there is no such process, @value{GDBN} will attempt to open a core
944 file named @var{number}.
946 @item -command @var{file}
948 @cindex @code{--command}
950 Execute @value{GDBN} commands from file @var{file}. @xref{Command
951 Files,, Command files}.
953 @item -eval-command @var{command}
954 @itemx -ex @var{command}
955 @cindex @code{--eval-command}
957 Execute a single @value{GDBN} command.
959 This option may be used multiple times to call multiple commands. It may
960 also be interleaved with @samp{-command} as required.
963 @value{GDBP} -ex 'target sim' -ex 'load' \
964 -x setbreakpoints -ex 'run' a.out
967 @item -directory @var{directory}
968 @itemx -d @var{directory}
969 @cindex @code{--directory}
971 Add @var{directory} to the path to search for source and script files.
975 @cindex @code{--readnow}
977 Read each symbol file's entire symbol table immediately, rather than
978 the default, which is to read it incrementally as it is needed.
979 This makes startup slower, but makes future operations faster.
984 @subsection Choosing modes
986 You can run @value{GDBN} in various alternative modes---for example, in
987 batch mode or quiet mode.
994 Do not execute commands found in any initialization files. Normally,
995 @value{GDBN} executes the commands in these files after all the command
996 options and arguments have been processed. @xref{Command Files,,Command
1002 @cindex @code{--quiet}
1003 @cindex @code{--silent}
1005 ``Quiet''. Do not print the introductory and copyright messages. These
1006 messages are also suppressed in batch mode.
1009 @cindex @code{--batch}
1010 Run in batch mode. Exit with status @code{0} after processing all the
1011 command files specified with @samp{-x} (and all commands from
1012 initialization files, if not inhibited with @samp{-n}). Exit with
1013 nonzero status if an error occurs in executing the @value{GDBN} commands
1014 in the command files.
1016 Batch mode may be useful for running @value{GDBN} as a filter, for
1017 example to download and run a program on another computer; in order to
1018 make this more useful, the message
1021 Program exited normally.
1025 (which is ordinarily issued whenever a program running under
1026 @value{GDBN} control terminates) is not issued when running in batch
1030 @cindex @code{--batch-silent}
1031 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1032 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1033 unaffected). This is much quieter than @samp{-silent} and would be useless
1034 for an interactive session.
1036 This is particularly useful when using targets that give @samp{Loading section}
1037 messages, for example.
1039 Note that targets that give their output via @value{GDBN}, as opposed to
1040 writing directly to @code{stdout}, will also be made silent.
1042 @item -return-child-result
1043 @cindex @code{--return-child-result}
1044 The return code from @value{GDBN} will be the return code from the child
1045 process (the process being debugged), with the following exceptions:
1049 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1050 internal error. In this case the exit code is the same as it would have been
1051 without @samp{-return-child-result}.
1053 The user quits with an explicit value. E.g., @samp{quit 1}.
1055 The child process never runs, or is not allowed to terminate, in which case
1056 the exit code will be -1.
1059 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1060 when @value{GDBN} is being used as a remote program loader or simulator
1065 @cindex @code{--nowindows}
1067 ``No windows''. If @value{GDBN} comes with a graphical user interface
1068 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1069 interface. If no GUI is available, this option has no effect.
1073 @cindex @code{--windows}
1075 If @value{GDBN} includes a GUI, then this option requires it to be
1078 @item -cd @var{directory}
1080 Run @value{GDBN} using @var{directory} as its working directory,
1081 instead of the current directory.
1085 @cindex @code{--fullname}
1087 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1088 subprocess. It tells @value{GDBN} to output the full file name and line
1089 number in a standard, recognizable fashion each time a stack frame is
1090 displayed (which includes each time your program stops). This
1091 recognizable format looks like two @samp{\032} characters, followed by
1092 the file name, line number and character position separated by colons,
1093 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1094 @samp{\032} characters as a signal to display the source code for the
1098 @cindex @code{--epoch}
1099 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1100 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1101 routines so as to allow Epoch to display values of expressions in a
1104 @item -annotate @var{level}
1105 @cindex @code{--annotate}
1106 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1107 effect is identical to using @samp{set annotate @var{level}}
1108 (@pxref{Annotations}). The annotation @var{level} controls how much
1109 information @value{GDBN} prints together with its prompt, values of
1110 expressions, source lines, and other types of output. Level 0 is the
1111 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1112 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1113 that control @value{GDBN}, and level 2 has been deprecated.
1115 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1119 @cindex @code{--args}
1120 Change interpretation of command line so that arguments following the
1121 executable file are passed as command line arguments to the inferior.
1122 This option stops option processing.
1124 @item -baud @var{bps}
1126 @cindex @code{--baud}
1128 Set the line speed (baud rate or bits per second) of any serial
1129 interface used by @value{GDBN} for remote debugging.
1131 @item -l @var{timeout}
1133 Set the timeout (in seconds) of any communication used by @value{GDBN}
1134 for remote debugging.
1136 @item -tty @var{device}
1137 @itemx -t @var{device}
1138 @cindex @code{--tty}
1140 Run using @var{device} for your program's standard input and output.
1141 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1143 @c resolve the situation of these eventually
1145 @cindex @code{--tui}
1146 Activate the @dfn{Text User Interface} when starting. The Text User
1147 Interface manages several text windows on the terminal, showing
1148 source, assembly, registers and @value{GDBN} command outputs
1149 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1150 Text User Interface can be enabled by invoking the program
1151 @samp{gdbtui}. Do not use this option if you run @value{GDBN} from
1152 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1155 @c @cindex @code{--xdb}
1156 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1157 @c For information, see the file @file{xdb_trans.html}, which is usually
1158 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1161 @item -interpreter @var{interp}
1162 @cindex @code{--interpreter}
1163 Use the interpreter @var{interp} for interface with the controlling
1164 program or device. This option is meant to be set by programs which
1165 communicate with @value{GDBN} using it as a back end.
1166 @xref{Interpreters, , Command Interpreters}.
1168 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1169 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1170 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1171 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1172 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1173 @sc{gdb/mi} interfaces are no longer supported.
1176 @cindex @code{--write}
1177 Open the executable and core files for both reading and writing. This
1178 is equivalent to the @samp{set write on} command inside @value{GDBN}
1182 @cindex @code{--statistics}
1183 This option causes @value{GDBN} to print statistics about time and
1184 memory usage after it completes each command and returns to the prompt.
1187 @cindex @code{--version}
1188 This option causes @value{GDBN} to print its version number and
1189 no-warranty blurb, and exit.
1194 @subsection What @value{GDBN} does during startup
1195 @cindex @value{GDBN} startup
1197 Here's the description of what @value{GDBN} does during session startup:
1201 Sets up the command interpreter as specified by the command line
1202 (@pxref{Mode Options, interpreter}).
1206 Reads the @dfn{init file} (if any) in your home directory@footnote{On
1207 DOS/Windows systems, the home directory is the one pointed to by the
1208 @code{HOME} environment variable.} and executes all the commands in
1212 Processes command line options and operands.
1215 Reads and executes the commands from init file (if any) in the current
1216 working directory. This is only done if the current directory is
1217 different from your home directory. Thus, you can have more than one
1218 init file, one generic in your home directory, and another, specific
1219 to the program you are debugging, in the directory where you invoke
1223 Reads command files specified by the @samp{-x} option. @xref{Command
1224 Files}, for more details about @value{GDBN} command files.
1227 Reads the command history recorded in the @dfn{history file}.
1228 @xref{Command History}, for more details about the command history and the
1229 files where @value{GDBN} records it.
1232 Init files use the same syntax as @dfn{command files} (@pxref{Command
1233 Files}) and are processed by @value{GDBN} in the same way. The init
1234 file in your home directory can set options (such as @samp{set
1235 complaints}) that affect subsequent processing of command line options
1236 and operands. Init files are not executed if you use the @samp{-nx}
1237 option (@pxref{Mode Options, ,Choosing modes}).
1239 @cindex init file name
1240 @cindex @file{.gdbinit}
1241 The @value{GDBN} init files are normally called @file{.gdbinit}.
1242 On some configurations of @value{GDBN}, the init file is known by a
1243 different name (these are typically environments where a specialized
1244 form of @value{GDBN} may need to coexist with other forms, hence a
1245 different name for the specialized version's init file). These are the
1246 environments with special init file names:
1249 @cindex @file{gdb.ini}
1251 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1252 the limitations of file names imposed by DOS filesystems. The Windows
1253 ports of @value{GDBN} use the standard name, but if they find a
1254 @file{gdb.ini} file, they warn you about that and suggest to rename
1255 the file to the standard name.
1257 @cindex @file{.vxgdbinit}
1259 VxWorks (Wind River Systems real-time OS): @file{.vxgdbinit}
1261 @cindex @file{.os68gdbinit}
1263 OS68K (Enea Data Systems real-time OS): @file{.os68gdbinit}
1265 @cindex @file{.esgdbinit}
1267 ES-1800 (Ericsson Telecom AB M68000 emulator): @file{.esgdbinit}
1270 CISCO 68k: @file{.cisco-gdbinit}
1275 @section Quitting @value{GDBN}
1276 @cindex exiting @value{GDBN}
1277 @cindex leaving @value{GDBN}
1280 @kindex quit @r{[}@var{expression}@r{]}
1281 @kindex q @r{(@code{quit})}
1282 @item quit @r{[}@var{expression}@r{]}
1284 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1285 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1286 do not supply @var{expression}, @value{GDBN} will terminate normally;
1287 otherwise it will terminate using the result of @var{expression} as the
1292 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1293 terminates the action of any @value{GDBN} command that is in progress and
1294 returns to @value{GDBN} command level. It is safe to type the interrupt
1295 character at any time because @value{GDBN} does not allow it to take effect
1296 until a time when it is safe.
1298 If you have been using @value{GDBN} to control an attached process or
1299 device, you can release it with the @code{detach} command
1300 (@pxref{Attach, ,Debugging an already-running process}).
1302 @node Shell Commands
1303 @section Shell commands
1305 If you need to execute occasional shell commands during your
1306 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1307 just use the @code{shell} command.
1311 @cindex shell escape
1312 @item shell @var{command string}
1313 Invoke a standard shell to execute @var{command string}.
1314 If it exists, the environment variable @code{SHELL} determines which
1315 shell to run. Otherwise @value{GDBN} uses the default shell
1316 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1319 The utility @code{make} is often needed in development environments.
1320 You do not have to use the @code{shell} command for this purpose in
1325 @cindex calling make
1326 @item make @var{make-args}
1327 Execute the @code{make} program with the specified
1328 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1331 @node Logging output
1332 @section Logging output
1333 @cindex logging @value{GDBN} output
1334 @cindex save @value{GDBN} output to a file
1336 You may want to save the output of @value{GDBN} commands to a file.
1337 There are several commands to control @value{GDBN}'s logging.
1341 @item set logging on
1343 @item set logging off
1345 @cindex logging file name
1346 @item set logging file @var{file}
1347 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1348 @item set logging overwrite [on|off]
1349 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1350 you want @code{set logging on} to overwrite the logfile instead.
1351 @item set logging redirect [on|off]
1352 By default, @value{GDBN} output will go to both the terminal and the logfile.
1353 Set @code{redirect} if you want output to go only to the log file.
1354 @kindex show logging
1356 Show the current values of the logging settings.
1360 @chapter @value{GDBN} Commands
1362 You can abbreviate a @value{GDBN} command to the first few letters of the command
1363 name, if that abbreviation is unambiguous; and you can repeat certain
1364 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1365 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1366 show you the alternatives available, if there is more than one possibility).
1369 * Command Syntax:: How to give commands to @value{GDBN}
1370 * Completion:: Command completion
1371 * Help:: How to ask @value{GDBN} for help
1374 @node Command Syntax
1375 @section Command syntax
1377 A @value{GDBN} command is a single line of input. There is no limit on
1378 how long it can be. It starts with a command name, which is followed by
1379 arguments whose meaning depends on the command name. For example, the
1380 command @code{step} accepts an argument which is the number of times to
1381 step, as in @samp{step 5}. You can also use the @code{step} command
1382 with no arguments. Some commands do not allow any arguments.
1384 @cindex abbreviation
1385 @value{GDBN} command names may always be truncated if that abbreviation is
1386 unambiguous. Other possible command abbreviations are listed in the
1387 documentation for individual commands. In some cases, even ambiguous
1388 abbreviations are allowed; for example, @code{s} is specially defined as
1389 equivalent to @code{step} even though there are other commands whose
1390 names start with @code{s}. You can test abbreviations by using them as
1391 arguments to the @code{help} command.
1393 @cindex repeating commands
1394 @kindex RET @r{(repeat last command)}
1395 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1396 repeat the previous command. Certain commands (for example, @code{run})
1397 will not repeat this way; these are commands whose unintentional
1398 repetition might cause trouble and which you are unlikely to want to
1399 repeat. User-defined commands can disable this feature; see
1400 @ref{Define, dont-repeat}.
1402 The @code{list} and @code{x} commands, when you repeat them with
1403 @key{RET}, construct new arguments rather than repeating
1404 exactly as typed. This permits easy scanning of source or memory.
1406 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1407 output, in a way similar to the common utility @code{more}
1408 (@pxref{Screen Size,,Screen size}). Since it is easy to press one
1409 @key{RET} too many in this situation, @value{GDBN} disables command
1410 repetition after any command that generates this sort of display.
1412 @kindex # @r{(a comment)}
1414 Any text from a @kbd{#} to the end of the line is a comment; it does
1415 nothing. This is useful mainly in command files (@pxref{Command
1416 Files,,Command files}).
1418 @cindex repeating command sequences
1419 @kindex Ctrl-o @r{(operate-and-get-next)}
1420 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1421 commands. This command accepts the current line, like @key{RET}, and
1422 then fetches the next line relative to the current line from the history
1426 @section Command completion
1429 @cindex word completion
1430 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1431 only one possibility; it can also show you what the valid possibilities
1432 are for the next word in a command, at any time. This works for @value{GDBN}
1433 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1435 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1436 of a word. If there is only one possibility, @value{GDBN} fills in the
1437 word, and waits for you to finish the command (or press @key{RET} to
1438 enter it). For example, if you type
1440 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1441 @c complete accuracy in these examples; space introduced for clarity.
1442 @c If texinfo enhancements make it unnecessary, it would be nice to
1443 @c replace " @key" by "@key" in the following...
1445 (@value{GDBP}) info bre @key{TAB}
1449 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1450 the only @code{info} subcommand beginning with @samp{bre}:
1453 (@value{GDBP}) info breakpoints
1457 You can either press @key{RET} at this point, to run the @code{info
1458 breakpoints} command, or backspace and enter something else, if
1459 @samp{breakpoints} does not look like the command you expected. (If you
1460 were sure you wanted @code{info breakpoints} in the first place, you
1461 might as well just type @key{RET} immediately after @samp{info bre},
1462 to exploit command abbreviations rather than command completion).
1464 If there is more than one possibility for the next word when you press
1465 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1466 characters and try again, or just press @key{TAB} a second time;
1467 @value{GDBN} displays all the possible completions for that word. For
1468 example, you might want to set a breakpoint on a subroutine whose name
1469 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1470 just sounds the bell. Typing @key{TAB} again displays all the
1471 function names in your program that begin with those characters, for
1475 (@value{GDBP}) b make_ @key{TAB}
1476 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1477 make_a_section_from_file make_environ
1478 make_abs_section make_function_type
1479 make_blockvector make_pointer_type
1480 make_cleanup make_reference_type
1481 make_command make_symbol_completion_list
1482 (@value{GDBP}) b make_
1486 After displaying the available possibilities, @value{GDBN} copies your
1487 partial input (@samp{b make_} in the example) so you can finish the
1490 If you just want to see the list of alternatives in the first place, you
1491 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1492 means @kbd{@key{META} ?}. You can type this either by holding down a
1493 key designated as the @key{META} shift on your keyboard (if there is
1494 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1496 @cindex quotes in commands
1497 @cindex completion of quoted strings
1498 Sometimes the string you need, while logically a ``word'', may contain
1499 parentheses or other characters that @value{GDBN} normally excludes from
1500 its notion of a word. To permit word completion to work in this
1501 situation, you may enclose words in @code{'} (single quote marks) in
1502 @value{GDBN} commands.
1504 The most likely situation where you might need this is in typing the
1505 name of a C@t{++} function. This is because C@t{++} allows function
1506 overloading (multiple definitions of the same function, distinguished
1507 by argument type). For example, when you want to set a breakpoint you
1508 may need to distinguish whether you mean the version of @code{name}
1509 that takes an @code{int} parameter, @code{name(int)}, or the version
1510 that takes a @code{float} parameter, @code{name(float)}. To use the
1511 word-completion facilities in this situation, type a single quote
1512 @code{'} at the beginning of the function name. This alerts
1513 @value{GDBN} that it may need to consider more information than usual
1514 when you press @key{TAB} or @kbd{M-?} to request word completion:
1517 (@value{GDBP}) b 'bubble( @kbd{M-?}
1518 bubble(double,double) bubble(int,int)
1519 (@value{GDBP}) b 'bubble(
1522 In some cases, @value{GDBN} can tell that completing a name requires using
1523 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1524 completing as much as it can) if you do not type the quote in the first
1528 (@value{GDBP}) b bub @key{TAB}
1529 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1530 (@value{GDBP}) b 'bubble(
1534 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1535 you have not yet started typing the argument list when you ask for
1536 completion on an overloaded symbol.
1538 For more information about overloaded functions, see @ref{C plus plus
1539 expressions, ,C@t{++} expressions}. You can use the command @code{set
1540 overload-resolution off} to disable overload resolution;
1541 see @ref{Debugging C plus plus, ,@value{GDBN} features for C@t{++}}.
1545 @section Getting help
1546 @cindex online documentation
1549 You can always ask @value{GDBN} itself for information on its commands,
1550 using the command @code{help}.
1553 @kindex h @r{(@code{help})}
1556 You can use @code{help} (abbreviated @code{h}) with no arguments to
1557 display a short list of named classes of commands:
1561 List of classes of commands:
1563 aliases -- Aliases of other commands
1564 breakpoints -- Making program stop at certain points
1565 data -- Examining data
1566 files -- Specifying and examining files
1567 internals -- Maintenance commands
1568 obscure -- Obscure features
1569 running -- Running the program
1570 stack -- Examining the stack
1571 status -- Status inquiries
1572 support -- Support facilities
1573 tracepoints -- Tracing of program execution without@*
1574 stopping the program
1575 user-defined -- User-defined commands
1577 Type "help" followed by a class name for a list of
1578 commands in that class.
1579 Type "help" followed by command name for full
1581 Command name abbreviations are allowed if unambiguous.
1584 @c the above line break eliminates huge line overfull...
1586 @item help @var{class}
1587 Using one of the general help classes as an argument, you can get a
1588 list of the individual commands in that class. For example, here is the
1589 help display for the class @code{status}:
1592 (@value{GDBP}) help status
1597 @c Line break in "show" line falsifies real output, but needed
1598 @c to fit in smallbook page size.
1599 info -- Generic command for showing things
1600 about the program being debugged
1601 show -- Generic command for showing things
1604 Type "help" followed by command name for full
1606 Command name abbreviations are allowed if unambiguous.
1610 @item help @var{command}
1611 With a command name as @code{help} argument, @value{GDBN} displays a
1612 short paragraph on how to use that command.
1615 @item apropos @var{args}
1616 The @code{apropos} command searches through all of the @value{GDBN}
1617 commands, and their documentation, for the regular expression specified in
1618 @var{args}. It prints out all matches found. For example:
1629 set symbol-reloading -- Set dynamic symbol table reloading
1630 multiple times in one run
1631 show symbol-reloading -- Show dynamic symbol table reloading
1632 multiple times in one run
1637 @item complete @var{args}
1638 The @code{complete @var{args}} command lists all the possible completions
1639 for the beginning of a command. Use @var{args} to specify the beginning of the
1640 command you want completed. For example:
1646 @noindent results in:
1657 @noindent This is intended for use by @sc{gnu} Emacs.
1660 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1661 and @code{show} to inquire about the state of your program, or the state
1662 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1663 manual introduces each of them in the appropriate context. The listings
1664 under @code{info} and under @code{show} in the Index point to
1665 all the sub-commands. @xref{Index}.
1670 @kindex i @r{(@code{info})}
1672 This command (abbreviated @code{i}) is for describing the state of your
1673 program. For example, you can list the arguments given to your program
1674 with @code{info args}, list the registers currently in use with @code{info
1675 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1676 You can get a complete list of the @code{info} sub-commands with
1677 @w{@code{help info}}.
1681 You can assign the result of an expression to an environment variable with
1682 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1683 @code{set prompt $}.
1687 In contrast to @code{info}, @code{show} is for describing the state of
1688 @value{GDBN} itself.
1689 You can change most of the things you can @code{show}, by using the
1690 related command @code{set}; for example, you can control what number
1691 system is used for displays with @code{set radix}, or simply inquire
1692 which is currently in use with @code{show radix}.
1695 To display all the settable parameters and their current
1696 values, you can use @code{show} with no arguments; you may also use
1697 @code{info set}. Both commands produce the same display.
1698 @c FIXME: "info set" violates the rule that "info" is for state of
1699 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1700 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1704 Here are three miscellaneous @code{show} subcommands, all of which are
1705 exceptional in lacking corresponding @code{set} commands:
1708 @kindex show version
1709 @cindex @value{GDBN} version number
1711 Show what version of @value{GDBN} is running. You should include this
1712 information in @value{GDBN} bug-reports. If multiple versions of
1713 @value{GDBN} are in use at your site, you may need to determine which
1714 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1715 commands are introduced, and old ones may wither away. Also, many
1716 system vendors ship variant versions of @value{GDBN}, and there are
1717 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1718 The version number is the same as the one announced when you start
1721 @kindex show copying
1722 @kindex info copying
1723 @cindex display @value{GDBN} copyright
1726 Display information about permission for copying @value{GDBN}.
1728 @kindex show warranty
1729 @kindex info warranty
1731 @itemx info warranty
1732 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1733 if your version of @value{GDBN} comes with one.
1738 @chapter Running Programs Under @value{GDBN}
1740 When you run a program under @value{GDBN}, you must first generate
1741 debugging information when you compile it.
1743 You may start @value{GDBN} with its arguments, if any, in an environment
1744 of your choice. If you are doing native debugging, you may redirect
1745 your program's input and output, debug an already running process, or
1746 kill a child process.
1749 * Compilation:: Compiling for debugging
1750 * Starting:: Starting your program
1751 * Arguments:: Your program's arguments
1752 * Environment:: Your program's environment
1754 * Working Directory:: Your program's working directory
1755 * Input/Output:: Your program's input and output
1756 * Attach:: Debugging an already-running process
1757 * Kill Process:: Killing the child process
1759 * Threads:: Debugging programs with multiple threads
1760 * Processes:: Debugging programs with multiple processes
1761 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1765 @section Compiling for debugging
1767 In order to debug a program effectively, you need to generate
1768 debugging information when you compile it. This debugging information
1769 is stored in the object file; it describes the data type of each
1770 variable or function and the correspondence between source line numbers
1771 and addresses in the executable code.
1773 To request debugging information, specify the @samp{-g} option when you run
1776 Programs that are to be shipped to your customers are compiled with
1777 optimizations, using the @samp{-O} compiler option. However, many
1778 compilers are unable to handle the @samp{-g} and @samp{-O} options
1779 together. Using those compilers, you cannot generate optimized
1780 executables containing debugging information.
1782 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1783 without @samp{-O}, making it possible to debug optimized code. We
1784 recommend that you @emph{always} use @samp{-g} whenever you compile a
1785 program. You may think your program is correct, but there is no sense
1786 in pushing your luck.
1788 @cindex optimized code, debugging
1789 @cindex debugging optimized code
1790 When you debug a program compiled with @samp{-g -O}, remember that the
1791 optimizer is rearranging your code; the debugger shows you what is
1792 really there. Do not be too surprised when the execution path does not
1793 exactly match your source file! An extreme example: if you define a
1794 variable, but never use it, @value{GDBN} never sees that
1795 variable---because the compiler optimizes it out of existence.
1797 Some things do not work as well with @samp{-g -O} as with just
1798 @samp{-g}, particularly on machines with instruction scheduling. If in
1799 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1800 please report it to us as a bug (including a test case!).
1801 @xref{Variables}, for more information about debugging optimized code.
1803 Older versions of the @sc{gnu} C compiler permitted a variant option
1804 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1805 format; if your @sc{gnu} C compiler has this option, do not use it.
1807 @value{GDBN} knows about preprocessor macros and can show you their
1808 expansion (@pxref{Macros}). Most compilers do not include information
1809 about preprocessor macros in the debugging information if you specify
1810 the @option{-g} flag alone, because this information is rather large.
1811 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1812 provides macro information if you specify the options
1813 @option{-gdwarf-2} and @option{-g3}; the former option requests
1814 debugging information in the Dwarf 2 format, and the latter requests
1815 ``extra information''. In the future, we hope to find more compact
1816 ways to represent macro information, so that it can be included with
1821 @section Starting your program
1827 @kindex r @r{(@code{run})}
1830 Use the @code{run} command to start your program under @value{GDBN}.
1831 You must first specify the program name (except on VxWorks) with an
1832 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1833 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1834 (@pxref{Files, ,Commands to specify files}).
1838 If you are running your program in an execution environment that
1839 supports processes, @code{run} creates an inferior process and makes
1840 that process run your program. (In environments without processes,
1841 @code{run} jumps to the start of your program.)
1843 The execution of a program is affected by certain information it
1844 receives from its superior. @value{GDBN} provides ways to specify this
1845 information, which you must do @emph{before} starting your program. (You
1846 can change it after starting your program, but such changes only affect
1847 your program the next time you start it.) This information may be
1848 divided into four categories:
1851 @item The @emph{arguments.}
1852 Specify the arguments to give your program as the arguments of the
1853 @code{run} command. If a shell is available on your target, the shell
1854 is used to pass the arguments, so that you may use normal conventions
1855 (such as wildcard expansion or variable substitution) in describing
1857 In Unix systems, you can control which shell is used with the
1858 @code{SHELL} environment variable.
1859 @xref{Arguments, ,Your program's arguments}.
1861 @item The @emph{environment.}
1862 Your program normally inherits its environment from @value{GDBN}, but you can
1863 use the @value{GDBN} commands @code{set environment} and @code{unset
1864 environment} to change parts of the environment that affect
1865 your program. @xref{Environment, ,Your program's environment}.
1867 @item The @emph{working directory.}
1868 Your program inherits its working directory from @value{GDBN}. You can set
1869 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1870 @xref{Working Directory, ,Your program's working directory}.
1872 @item The @emph{standard input and output.}
1873 Your program normally uses the same device for standard input and
1874 standard output as @value{GDBN} is using. You can redirect input and output
1875 in the @code{run} command line, or you can use the @code{tty} command to
1876 set a different device for your program.
1877 @xref{Input/Output, ,Your program's input and output}.
1880 @emph{Warning:} While input and output redirection work, you cannot use
1881 pipes to pass the output of the program you are debugging to another
1882 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1886 When you issue the @code{run} command, your program begins to execute
1887 immediately. @xref{Stopping, ,Stopping and continuing}, for discussion
1888 of how to arrange for your program to stop. Once your program has
1889 stopped, you may call functions in your program, using the @code{print}
1890 or @code{call} commands. @xref{Data, ,Examining Data}.
1892 If the modification time of your symbol file has changed since the last
1893 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1894 table, and reads it again. When it does this, @value{GDBN} tries to retain
1895 your current breakpoints.
1900 @cindex run to main procedure
1901 The name of the main procedure can vary from language to language.
1902 With C or C@t{++}, the main procedure name is always @code{main}, but
1903 other languages such as Ada do not require a specific name for their
1904 main procedure. The debugger provides a convenient way to start the
1905 execution of the program and to stop at the beginning of the main
1906 procedure, depending on the language used.
1908 The @samp{start} command does the equivalent of setting a temporary
1909 breakpoint at the beginning of the main procedure and then invoking
1910 the @samp{run} command.
1912 @cindex elaboration phase
1913 Some programs contain an @dfn{elaboration} phase where some startup code is
1914 executed before the main procedure is called. This depends on the
1915 languages used to write your program. In C@t{++}, for instance,
1916 constructors for static and global objects are executed before
1917 @code{main} is called. It is therefore possible that the debugger stops
1918 before reaching the main procedure. However, the temporary breakpoint
1919 will remain to halt execution.
1921 Specify the arguments to give to your program as arguments to the
1922 @samp{start} command. These arguments will be given verbatim to the
1923 underlying @samp{run} command. Note that the same arguments will be
1924 reused if no argument is provided during subsequent calls to
1925 @samp{start} or @samp{run}.
1927 It is sometimes necessary to debug the program during elaboration. In
1928 these cases, using the @code{start} command would stop the execution of
1929 your program too late, as the program would have already completed the
1930 elaboration phase. Under these circumstances, insert breakpoints in your
1931 elaboration code before running your program.
1935 @section Your program's arguments
1937 @cindex arguments (to your program)
1938 The arguments to your program can be specified by the arguments of the
1940 They are passed to a shell, which expands wildcard characters and
1941 performs redirection of I/O, and thence to your program. Your
1942 @code{SHELL} environment variable (if it exists) specifies what shell
1943 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1944 the default shell (@file{/bin/sh} on Unix).
1946 On non-Unix systems, the program is usually invoked directly by
1947 @value{GDBN}, which emulates I/O redirection via the appropriate system
1948 calls, and the wildcard characters are expanded by the startup code of
1949 the program, not by the shell.
1951 @code{run} with no arguments uses the same arguments used by the previous
1952 @code{run}, or those set by the @code{set args} command.
1957 Specify the arguments to be used the next time your program is run. If
1958 @code{set args} has no arguments, @code{run} executes your program
1959 with no arguments. Once you have run your program with arguments,
1960 using @code{set args} before the next @code{run} is the only way to run
1961 it again without arguments.
1965 Show the arguments to give your program when it is started.
1969 @section Your program's environment
1971 @cindex environment (of your program)
1972 The @dfn{environment} consists of a set of environment variables and
1973 their values. Environment variables conventionally record such things as
1974 your user name, your home directory, your terminal type, and your search
1975 path for programs to run. Usually you set up environment variables with
1976 the shell and they are inherited by all the other programs you run. When
1977 debugging, it can be useful to try running your program with a modified
1978 environment without having to start @value{GDBN} over again.
1982 @item path @var{directory}
1983 Add @var{directory} to the front of the @code{PATH} environment variable
1984 (the search path for executables) that will be passed to your program.
1985 The value of @code{PATH} used by @value{GDBN} does not change.
1986 You may specify several directory names, separated by whitespace or by a
1987 system-dependent separator character (@samp{:} on Unix, @samp{;} on
1988 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
1989 is moved to the front, so it is searched sooner.
1991 You can use the string @samp{$cwd} to refer to whatever is the current
1992 working directory at the time @value{GDBN} searches the path. If you
1993 use @samp{.} instead, it refers to the directory where you executed the
1994 @code{path} command. @value{GDBN} replaces @samp{.} in the
1995 @var{directory} argument (with the current path) before adding
1996 @var{directory} to the search path.
1997 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
1998 @c document that, since repeating it would be a no-op.
2002 Display the list of search paths for executables (the @code{PATH}
2003 environment variable).
2005 @kindex show environment
2006 @item show environment @r{[}@var{varname}@r{]}
2007 Print the value of environment variable @var{varname} to be given to
2008 your program when it starts. If you do not supply @var{varname},
2009 print the names and values of all environment variables to be given to
2010 your program. You can abbreviate @code{environment} as @code{env}.
2012 @kindex set environment
2013 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2014 Set environment variable @var{varname} to @var{value}. The value
2015 changes for your program only, not for @value{GDBN} itself. @var{value} may
2016 be any string; the values of environment variables are just strings, and
2017 any interpretation is supplied by your program itself. The @var{value}
2018 parameter is optional; if it is eliminated, the variable is set to a
2020 @c "any string" here does not include leading, trailing
2021 @c blanks. Gnu asks: does anyone care?
2023 For example, this command:
2030 tells the debugged program, when subsequently run, that its user is named
2031 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2032 are not actually required.)
2034 @kindex unset environment
2035 @item unset environment @var{varname}
2036 Remove variable @var{varname} from the environment to be passed to your
2037 program. This is different from @samp{set env @var{varname} =};
2038 @code{unset environment} removes the variable from the environment,
2039 rather than assigning it an empty value.
2042 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2044 by your @code{SHELL} environment variable if it exists (or
2045 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2046 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2047 @file{.bashrc} for BASH---any variables you set in that file affect
2048 your program. You may wish to move setting of environment variables to
2049 files that are only run when you sign on, such as @file{.login} or
2052 @node Working Directory
2053 @section Your program's working directory
2055 @cindex working directory (of your program)
2056 Each time you start your program with @code{run}, it inherits its
2057 working directory from the current working directory of @value{GDBN}.
2058 The @value{GDBN} working directory is initially whatever it inherited
2059 from its parent process (typically the shell), but you can specify a new
2060 working directory in @value{GDBN} with the @code{cd} command.
2062 The @value{GDBN} working directory also serves as a default for the commands
2063 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2068 @cindex change working directory
2069 @item cd @var{directory}
2070 Set the @value{GDBN} working directory to @var{directory}.
2074 Print the @value{GDBN} working directory.
2077 It is generally impossible to find the current working directory of
2078 the process being debugged (since a program can change its directory
2079 during its run). If you work on a system where @value{GDBN} is
2080 configured with the @file{/proc} support, you can use the @code{info
2081 proc} command (@pxref{SVR4 Process Information}) to find out the
2082 current working directory of the debuggee.
2085 @section Your program's input and output
2090 By default, the program you run under @value{GDBN} does input and output to
2091 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2092 to its own terminal modes to interact with you, but it records the terminal
2093 modes your program was using and switches back to them when you continue
2094 running your program.
2097 @kindex info terminal
2099 Displays information recorded by @value{GDBN} about the terminal modes your
2103 You can redirect your program's input and/or output using shell
2104 redirection with the @code{run} command. For example,
2111 starts your program, diverting its output to the file @file{outfile}.
2114 @cindex controlling terminal
2115 Another way to specify where your program should do input and output is
2116 with the @code{tty} command. This command accepts a file name as
2117 argument, and causes this file to be the default for future @code{run}
2118 commands. It also resets the controlling terminal for the child
2119 process, for future @code{run} commands. For example,
2126 directs that processes started with subsequent @code{run} commands
2127 default to do input and output on the terminal @file{/dev/ttyb} and have
2128 that as their controlling terminal.
2130 An explicit redirection in @code{run} overrides the @code{tty} command's
2131 effect on the input/output device, but not its effect on the controlling
2134 When you use the @code{tty} command or redirect input in the @code{run}
2135 command, only the input @emph{for your program} is affected. The input
2136 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2137 for @code{set inferior-tty}.
2139 @cindex inferior tty
2140 @cindex set inferior controlling terminal
2141 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2142 display the name of the terminal that will be used for future runs of your
2146 @item set inferior-tty /dev/ttyb
2147 @kindex set inferior-tty
2148 Set the tty for the program being debugged to /dev/ttyb.
2150 @item show inferior-tty
2151 @kindex show inferior-tty
2152 Show the current tty for the program being debugged.
2156 @section Debugging an already-running process
2161 @item attach @var{process-id}
2162 This command attaches to a running process---one that was started
2163 outside @value{GDBN}. (@code{info files} shows your active
2164 targets.) The command takes as argument a process ID. The usual way to
2165 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2166 or with the @samp{jobs -l} shell command.
2168 @code{attach} does not repeat if you press @key{RET} a second time after
2169 executing the command.
2172 To use @code{attach}, your program must be running in an environment
2173 which supports processes; for example, @code{attach} does not work for
2174 programs on bare-board targets that lack an operating system. You must
2175 also have permission to send the process a signal.
2177 When you use @code{attach}, the debugger finds the program running in
2178 the process first by looking in the current working directory, then (if
2179 the program is not found) by using the source file search path
2180 (@pxref{Source Path, ,Specifying source directories}). You can also use
2181 the @code{file} command to load the program. @xref{Files, ,Commands to
2184 The first thing @value{GDBN} does after arranging to debug the specified
2185 process is to stop it. You can examine and modify an attached process
2186 with all the @value{GDBN} commands that are ordinarily available when
2187 you start processes with @code{run}. You can insert breakpoints; you
2188 can step and continue; you can modify storage. If you would rather the
2189 process continue running, you may use the @code{continue} command after
2190 attaching @value{GDBN} to the process.
2195 When you have finished debugging the attached process, you can use the
2196 @code{detach} command to release it from @value{GDBN} control. Detaching
2197 the process continues its execution. After the @code{detach} command,
2198 that process and @value{GDBN} become completely independent once more, and you
2199 are ready to @code{attach} another process or start one with @code{run}.
2200 @code{detach} does not repeat if you press @key{RET} again after
2201 executing the command.
2204 If you exit @value{GDBN} or use the @code{run} command while you have an
2205 attached process, you kill that process. By default, @value{GDBN} asks
2206 for confirmation if you try to do either of these things; you can
2207 control whether or not you need to confirm by using the @code{set
2208 confirm} command (@pxref{Messages/Warnings, ,Optional warnings and
2212 @section Killing the child process
2217 Kill the child process in which your program is running under @value{GDBN}.
2220 This command is useful if you wish to debug a core dump instead of a
2221 running process. @value{GDBN} ignores any core dump file while your program
2224 On some operating systems, a program cannot be executed outside @value{GDBN}
2225 while you have breakpoints set on it inside @value{GDBN}. You can use the
2226 @code{kill} command in this situation to permit running your program
2227 outside the debugger.
2229 The @code{kill} command is also useful if you wish to recompile and
2230 relink your program, since on many systems it is impossible to modify an
2231 executable file while it is running in a process. In this case, when you
2232 next type @code{run}, @value{GDBN} notices that the file has changed, and
2233 reads the symbol table again (while trying to preserve your current
2234 breakpoint settings).
2237 @section Debugging programs with multiple threads
2239 @cindex threads of execution
2240 @cindex multiple threads
2241 @cindex switching threads
2242 In some operating systems, such as HP-UX and Solaris, a single program
2243 may have more than one @dfn{thread} of execution. The precise semantics
2244 of threads differ from one operating system to another, but in general
2245 the threads of a single program are akin to multiple processes---except
2246 that they share one address space (that is, they can all examine and
2247 modify the same variables). On the other hand, each thread has its own
2248 registers and execution stack, and perhaps private memory.
2250 @value{GDBN} provides these facilities for debugging multi-thread
2254 @item automatic notification of new threads
2255 @item @samp{thread @var{threadno}}, a command to switch among threads
2256 @item @samp{info threads}, a command to inquire about existing threads
2257 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2258 a command to apply a command to a list of threads
2259 @item thread-specific breakpoints
2263 @emph{Warning:} These facilities are not yet available on every
2264 @value{GDBN} configuration where the operating system supports threads.
2265 If your @value{GDBN} does not support threads, these commands have no
2266 effect. For example, a system without thread support shows no output
2267 from @samp{info threads}, and always rejects the @code{thread} command,
2271 (@value{GDBP}) info threads
2272 (@value{GDBP}) thread 1
2273 Thread ID 1 not known. Use the "info threads" command to
2274 see the IDs of currently known threads.
2276 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2277 @c doesn't support threads"?
2280 @cindex focus of debugging
2281 @cindex current thread
2282 The @value{GDBN} thread debugging facility allows you to observe all
2283 threads while your program runs---but whenever @value{GDBN} takes
2284 control, one thread in particular is always the focus of debugging.
2285 This thread is called the @dfn{current thread}. Debugging commands show
2286 program information from the perspective of the current thread.
2288 @cindex @code{New} @var{systag} message
2289 @cindex thread identifier (system)
2290 @c FIXME-implementors!! It would be more helpful if the [New...] message
2291 @c included GDB's numeric thread handle, so you could just go to that
2292 @c thread without first checking `info threads'.
2293 Whenever @value{GDBN} detects a new thread in your program, it displays
2294 the target system's identification for the thread with a message in the
2295 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2296 whose form varies depending on the particular system. For example, on
2297 LynxOS, you might see
2300 [New process 35 thread 27]
2304 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2305 the @var{systag} is simply something like @samp{process 368}, with no
2308 @c FIXME!! (1) Does the [New...] message appear even for the very first
2309 @c thread of a program, or does it only appear for the
2310 @c second---i.e.@: when it becomes obvious we have a multithread
2312 @c (2) *Is* there necessarily a first thread always? Or do some
2313 @c multithread systems permit starting a program with multiple
2314 @c threads ab initio?
2316 @cindex thread number
2317 @cindex thread identifier (GDB)
2318 For debugging purposes, @value{GDBN} associates its own thread
2319 number---always a single integer---with each thread in your program.
2322 @kindex info threads
2324 Display a summary of all threads currently in your
2325 program. @value{GDBN} displays for each thread (in this order):
2329 the thread number assigned by @value{GDBN}
2332 the target system's thread identifier (@var{systag})
2335 the current stack frame summary for that thread
2339 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2340 indicates the current thread.
2344 @c end table here to get a little more width for example
2347 (@value{GDBP}) info threads
2348 3 process 35 thread 27 0x34e5 in sigpause ()
2349 2 process 35 thread 23 0x34e5 in sigpause ()
2350 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2356 @cindex debugging multithreaded programs (on HP-UX)
2357 @cindex thread identifier (GDB), on HP-UX
2358 For debugging purposes, @value{GDBN} associates its own thread
2359 number---a small integer assigned in thread-creation order---with each
2360 thread in your program.
2362 @cindex @code{New} @var{systag} message, on HP-UX
2363 @cindex thread identifier (system), on HP-UX
2364 @c FIXME-implementors!! It would be more helpful if the [New...] message
2365 @c included GDB's numeric thread handle, so you could just go to that
2366 @c thread without first checking `info threads'.
2367 Whenever @value{GDBN} detects a new thread in your program, it displays
2368 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2369 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2370 whose form varies depending on the particular system. For example, on
2374 [New thread 2 (system thread 26594)]
2378 when @value{GDBN} notices a new thread.
2381 @kindex info threads (HP-UX)
2383 Display a summary of all threads currently in your
2384 program. @value{GDBN} displays for each thread (in this order):
2387 @item the thread number assigned by @value{GDBN}
2389 @item the target system's thread identifier (@var{systag})
2391 @item the current stack frame summary for that thread
2395 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2396 indicates the current thread.
2400 @c end table here to get a little more width for example
2403 (@value{GDBP}) info threads
2404 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2406 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2407 from /usr/lib/libc.2
2408 1 system thread 27905 0x7b003498 in _brk () \@*
2409 from /usr/lib/libc.2
2412 On Solaris, you can display more information about user threads with a
2413 Solaris-specific command:
2416 @item maint info sol-threads
2417 @kindex maint info sol-threads
2418 @cindex thread info (Solaris)
2419 Display info on Solaris user threads.
2423 @kindex thread @var{threadno}
2424 @item thread @var{threadno}
2425 Make thread number @var{threadno} the current thread. The command
2426 argument @var{threadno} is the internal @value{GDBN} thread number, as
2427 shown in the first field of the @samp{info threads} display.
2428 @value{GDBN} responds by displaying the system identifier of the thread
2429 you selected, and its current stack frame summary:
2432 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2433 (@value{GDBP}) thread 2
2434 [Switching to process 35 thread 23]
2435 0x34e5 in sigpause ()
2439 As with the @samp{[New @dots{}]} message, the form of the text after
2440 @samp{Switching to} depends on your system's conventions for identifying
2443 @kindex thread apply
2444 @cindex apply command to several threads
2445 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2446 The @code{thread apply} command allows you to apply the named
2447 @var{command} to one or more threads. Specify the numbers of the
2448 threads that you want affected with the command argument
2449 @var{threadno}. It can be a single thread number, one of the numbers
2450 shown in the first field of the @samp{info threads} display; or it
2451 could be a range of thread numbers, as in @code{2-4}. To apply a
2452 command to all threads, type @kbd{thread apply all @var{command}}.
2455 @cindex automatic thread selection
2456 @cindex switching threads automatically
2457 @cindex threads, automatic switching
2458 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2459 signal, it automatically selects the thread where that breakpoint or
2460 signal happened. @value{GDBN} alerts you to the context switch with a
2461 message of the form @samp{[Switching to @var{systag}]} to identify the
2464 @xref{Thread Stops,,Stopping and starting multi-thread programs}, for
2465 more information about how @value{GDBN} behaves when you stop and start
2466 programs with multiple threads.
2468 @xref{Set Watchpoints,,Setting watchpoints}, for information about
2469 watchpoints in programs with multiple threads.
2472 @section Debugging programs with multiple processes
2474 @cindex fork, debugging programs which call
2475 @cindex multiple processes
2476 @cindex processes, multiple
2477 On most systems, @value{GDBN} has no special support for debugging
2478 programs which create additional processes using the @code{fork}
2479 function. When a program forks, @value{GDBN} will continue to debug the
2480 parent process and the child process will run unimpeded. If you have
2481 set a breakpoint in any code which the child then executes, the child
2482 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2483 will cause it to terminate.
2485 However, if you want to debug the child process there is a workaround
2486 which isn't too painful. Put a call to @code{sleep} in the code which
2487 the child process executes after the fork. It may be useful to sleep
2488 only if a certain environment variable is set, or a certain file exists,
2489 so that the delay need not occur when you don't want to run @value{GDBN}
2490 on the child. While the child is sleeping, use the @code{ps} program to
2491 get its process ID. Then tell @value{GDBN} (a new invocation of
2492 @value{GDBN} if you are also debugging the parent process) to attach to
2493 the child process (@pxref{Attach}). From that point on you can debug
2494 the child process just like any other process which you attached to.
2496 On some systems, @value{GDBN} provides support for debugging programs that
2497 create additional processes using the @code{fork} or @code{vfork} functions.
2498 Currently, the only platforms with this feature are HP-UX (11.x and later
2499 only?) and GNU/Linux (kernel version 2.5.60 and later).
2501 By default, when a program forks, @value{GDBN} will continue to debug
2502 the parent process and the child process will run unimpeded.
2504 If you want to follow the child process instead of the parent process,
2505 use the command @w{@code{set follow-fork-mode}}.
2508 @kindex set follow-fork-mode
2509 @item set follow-fork-mode @var{mode}
2510 Set the debugger response to a program call of @code{fork} or
2511 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2512 process. The @var{mode} argument can be:
2516 The original process is debugged after a fork. The child process runs
2517 unimpeded. This is the default.
2520 The new process is debugged after a fork. The parent process runs
2525 @kindex show follow-fork-mode
2526 @item show follow-fork-mode
2527 Display the current debugger response to a @code{fork} or @code{vfork} call.
2530 @cindex debugging multiple processes
2531 On Linux, if you want to debug both the parent and child processes, use the
2532 command @w{@code{set detach-on-fork}}.
2535 @kindex set detach-on-fork
2536 @item set detach-on-fork @var{mode}
2537 Tells gdb whether to detach one of the processes after a fork, or
2538 retain debugger control over them both.
2542 The child process (or parent process, depending on the value of
2543 @code{follow-fork-mode}) will be detached and allowed to run
2544 independently. This is the default.
2547 Both processes will be held under the control of @value{GDBN}.
2548 One process (child or parent, depending on the value of
2549 @code{follow-fork-mode}) is debugged as usual, while the other
2554 @kindex show detach-on-follow
2555 @item show detach-on-follow
2556 Show whether detach-on-follow mode is on/off.
2559 If you choose to set @var{detach-on-follow} mode off, then
2560 @value{GDBN} will retain control of all forked processes (including
2561 nested forks). You can list the forked processes under the control of
2562 @value{GDBN} by using the @w{@code{info forks}} command, and switch
2563 from one fork to another by using the @w{@code{fork}} command.
2568 Print a list of all forked processes under the control of @value{GDBN}.
2569 The listing will include a fork id, a process id, and the current
2570 position (program counter) of the process.
2573 @kindex fork @var{fork-id}
2574 @item fork @var{fork-id}
2575 Make fork number @var{fork-id} the current process. The argument
2576 @var{fork-id} is the internal fork number assigned by @value{GDBN},
2577 as shown in the first field of the @samp{info forks} display.
2581 To quit debugging one of the forked processes, you can either detach
2582 from it by using the @w{@code{detach fork}} command (allowing it to
2583 run independently), or delete (and kill) it using the
2584 @w{@code{delete fork}} command.
2587 @kindex detach fork @var{fork-id}
2588 @item detach fork @var{fork-id}
2589 Detach from the process identified by @value{GDBN} fork number
2590 @var{fork-id}, and remove it from the fork list. The process will be
2591 allowed to run independently.
2593 @kindex delete fork @var{fork-id}
2594 @item delete fork @var{fork-id}
2595 Kill the process identified by @value{GDBN} fork number @var{fork-id},
2596 and remove it from the fork list.
2600 If you ask to debug a child process and a @code{vfork} is followed by an
2601 @code{exec}, @value{GDBN} executes the new target up to the first
2602 breakpoint in the new target. If you have a breakpoint set on
2603 @code{main} in your original program, the breakpoint will also be set on
2604 the child process's @code{main}.
2606 When a child process is spawned by @code{vfork}, you cannot debug the
2607 child or parent until an @code{exec} call completes.
2609 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2610 call executes, the new target restarts. To restart the parent process,
2611 use the @code{file} command with the parent executable name as its
2614 You can use the @code{catch} command to make @value{GDBN} stop whenever
2615 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2616 Catchpoints, ,Setting catchpoints}.
2618 @node Checkpoint/Restart
2619 @section Setting a @emph{bookmark} to return to later
2624 @cindex snapshot of a process
2625 @cindex rewind program state
2627 On certain operating systems@footnote{Currently, only
2628 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
2629 program's state, called a @dfn{checkpoint}, and come back to it
2632 Returning to a checkpoint effectively undoes everything that has
2633 happened in the program since the @code{checkpoint} was saved. This
2634 includes changes in memory, registers, and even (within some limits)
2635 system state. Effectively, it is like going back in time to the
2636 moment when the checkpoint was saved.
2638 Thus, if you're stepping thru a program and you think you're
2639 getting close to the point where things go wrong, you can save
2640 a checkpoint. Then, if you accidentally go too far and miss
2641 the critical statement, instead of having to restart your program
2642 from the beginning, you can just go back to the checkpoint and
2643 start again from there.
2645 This can be especially useful if it takes a lot of time or
2646 steps to reach the point where you think the bug occurs.
2648 To use the @code{checkpoint}/@code{restart} method of debugging:
2653 Save a snapshot of the debugged program's current execution state.
2654 The @code{checkpoint} command takes no arguments, but each checkpoint
2655 is assigned a small integer id, similar to a breakpoint id.
2657 @kindex info checkpoints
2658 @item info checkpoints
2659 List the checkpoints that have been saved in the current debugging
2660 session. For each checkpoint, the following information will be
2667 @item Source line, or label
2670 @kindex restart @var{checkpoint-id}
2671 @item restart @var{checkpoint-id}
2672 Restore the program state that was saved as checkpoint number
2673 @var{checkpoint-id}. All program variables, registers, stack frames
2674 etc.@: will be returned to the values that they had when the checkpoint
2675 was saved. In essence, gdb will ``wind back the clock'' to the point
2676 in time when the checkpoint was saved.
2678 Note that breakpoints, @value{GDBN} variables, command history etc.
2679 are not affected by restoring a checkpoint. In general, a checkpoint
2680 only restores things that reside in the program being debugged, not in
2683 @kindex delete checkpoint @var{checkpoint-id}
2684 @item delete checkpoint @var{checkpoint-id}
2685 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
2689 Returning to a previously saved checkpoint will restore the user state
2690 of the program being debugged, plus a significant subset of the system
2691 (OS) state, including file pointers. It won't ``un-write'' data from
2692 a file, but it will rewind the file pointer to the previous location,
2693 so that the previously written data can be overwritten. For files
2694 opened in read mode, the pointer will also be restored so that the
2695 previously read data can be read again.
2697 Of course, characters that have been sent to a printer (or other
2698 external device) cannot be ``snatched back'', and characters received
2699 from eg.@: a serial device can be removed from internal program buffers,
2700 but they cannot be ``pushed back'' into the serial pipeline, ready to
2701 be received again. Similarly, the actual contents of files that have
2702 been changed cannot be restored (at this time).
2704 However, within those constraints, you actually can ``rewind'' your
2705 program to a previously saved point in time, and begin debugging it
2706 again --- and you can change the course of events so as to debug a
2707 different execution path this time.
2709 @cindex checkpoints and process id
2710 Finally, there is one bit of internal program state that will be
2711 different when you return to a checkpoint --- the program's process
2712 id. Each checkpoint will have a unique process id (or @var{pid}),
2713 and each will be different from the program's original @var{pid}.
2714 If your program has saved a local copy of its process id, this could
2715 potentially pose a problem.
2717 @subsection A non-obvious benefit of using checkpoints
2719 On some systems such as @sc{gnu}/Linux, address space randomization
2720 is performed on new processes for security reasons. This makes it
2721 difficult or impossible to set a breakpoint, or watchpoint, on an
2722 absolute address if you have to restart the program, since the
2723 absolute location of a symbol will change from one execution to the
2726 A checkpoint, however, is an @emph{identical} copy of a process.
2727 Therefore if you create a checkpoint at (eg.@:) the start of main,
2728 and simply return to that checkpoint instead of restarting the
2729 process, you can avoid the effects of address randomization and
2730 your symbols will all stay in the same place.
2733 @chapter Stopping and Continuing
2735 The principal purposes of using a debugger are so that you can stop your
2736 program before it terminates; or so that, if your program runs into
2737 trouble, you can investigate and find out why.
2739 Inside @value{GDBN}, your program may stop for any of several reasons,
2740 such as a signal, a breakpoint, or reaching a new line after a
2741 @value{GDBN} command such as @code{step}. You may then examine and
2742 change variables, set new breakpoints or remove old ones, and then
2743 continue execution. Usually, the messages shown by @value{GDBN} provide
2744 ample explanation of the status of your program---but you can also
2745 explicitly request this information at any time.
2748 @kindex info program
2750 Display information about the status of your program: whether it is
2751 running or not, what process it is, and why it stopped.
2755 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2756 * Continuing and Stepping:: Resuming execution
2758 * Thread Stops:: Stopping and starting multi-thread programs
2762 @section Breakpoints, watchpoints, and catchpoints
2765 A @dfn{breakpoint} makes your program stop whenever a certain point in
2766 the program is reached. For each breakpoint, you can add conditions to
2767 control in finer detail whether your program stops. You can set
2768 breakpoints with the @code{break} command and its variants (@pxref{Set
2769 Breaks, ,Setting breakpoints}), to specify the place where your program
2770 should stop by line number, function name or exact address in the
2773 On some systems, you can set breakpoints in shared libraries before
2774 the executable is run. There is a minor limitation on HP-UX systems:
2775 you must wait until the executable is run in order to set breakpoints
2776 in shared library routines that are not called directly by the program
2777 (for example, routines that are arguments in a @code{pthread_create}
2781 @cindex data breakpoints
2782 @cindex memory tracing
2783 @cindex breakpoint on memory address
2784 @cindex breakpoint on variable modification
2785 A @dfn{watchpoint} is a special breakpoint that stops your program
2786 when the value of an expression changes. The expression may be a value
2787 of a variable, or it could involve values of one or more variables
2788 combined by operators, such as @samp{a + b}. This is sometimes called
2789 @dfn{data breakpoints}. You must use a different command to set
2790 watchpoints (@pxref{Set Watchpoints, ,Setting watchpoints}), but aside
2791 from that, you can manage a watchpoint like any other breakpoint: you
2792 enable, disable, and delete both breakpoints and watchpoints using the
2795 You can arrange to have values from your program displayed automatically
2796 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2800 @cindex breakpoint on events
2801 A @dfn{catchpoint} is another special breakpoint that stops your program
2802 when a certain kind of event occurs, such as the throwing of a C@t{++}
2803 exception or the loading of a library. As with watchpoints, you use a
2804 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2805 catchpoints}), but aside from that, you can manage a catchpoint like any
2806 other breakpoint. (To stop when your program receives a signal, use the
2807 @code{handle} command; see @ref{Signals, ,Signals}.)
2809 @cindex breakpoint numbers
2810 @cindex numbers for breakpoints
2811 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2812 catchpoint when you create it; these numbers are successive integers
2813 starting with one. In many of the commands for controlling various
2814 features of breakpoints you use the breakpoint number to say which
2815 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2816 @dfn{disabled}; if disabled, it has no effect on your program until you
2819 @cindex breakpoint ranges
2820 @cindex ranges of breakpoints
2821 Some @value{GDBN} commands accept a range of breakpoints on which to
2822 operate. A breakpoint range is either a single breakpoint number, like
2823 @samp{5}, or two such numbers, in increasing order, separated by a
2824 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2825 all breakpoint in that range are operated on.
2828 * Set Breaks:: Setting breakpoints
2829 * Set Watchpoints:: Setting watchpoints
2830 * Set Catchpoints:: Setting catchpoints
2831 * Delete Breaks:: Deleting breakpoints
2832 * Disabling:: Disabling breakpoints
2833 * Conditions:: Break conditions
2834 * Break Commands:: Breakpoint command lists
2835 * Breakpoint Menus:: Breakpoint menus
2836 * Error in Breakpoints:: ``Cannot insert breakpoints''
2837 * Breakpoint related warnings:: ``Breakpoint address adjusted...''
2841 @subsection Setting breakpoints
2843 @c FIXME LMB what does GDB do if no code on line of breakpt?
2844 @c consider in particular declaration with/without initialization.
2846 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2849 @kindex b @r{(@code{break})}
2850 @vindex $bpnum@r{, convenience variable}
2851 @cindex latest breakpoint
2852 Breakpoints are set with the @code{break} command (abbreviated
2853 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2854 number of the breakpoint you've set most recently; see @ref{Convenience
2855 Vars,, Convenience variables}, for a discussion of what you can do with
2856 convenience variables.
2858 You have several ways to say where the breakpoint should go.
2861 @item break @var{function}
2862 Set a breakpoint at entry to function @var{function}.
2863 When using source languages that permit overloading of symbols, such as
2864 C@t{++}, @var{function} may refer to more than one possible place to break.
2865 @xref{Breakpoint Menus,,Breakpoint menus}, for a discussion of that situation.
2867 @item break +@var{offset}
2868 @itemx break -@var{offset}
2869 Set a breakpoint some number of lines forward or back from the position
2870 at which execution stopped in the currently selected @dfn{stack frame}.
2871 (@xref{Frames, ,Frames}, for a description of stack frames.)
2873 @item break @var{linenum}
2874 Set a breakpoint at line @var{linenum} in the current source file.
2875 The current source file is the last file whose source text was printed.
2876 The breakpoint will stop your program just before it executes any of the
2879 @item break @var{filename}:@var{linenum}
2880 Set a breakpoint at line @var{linenum} in source file @var{filename}.
2882 @item break @var{filename}:@var{function}
2883 Set a breakpoint at entry to function @var{function} found in file
2884 @var{filename}. Specifying a file name as well as a function name is
2885 superfluous except when multiple files contain similarly named
2888 @item break *@var{address}
2889 Set a breakpoint at address @var{address}. You can use this to set
2890 breakpoints in parts of your program which do not have debugging
2891 information or source files.
2894 When called without any arguments, @code{break} sets a breakpoint at
2895 the next instruction to be executed in the selected stack frame
2896 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2897 innermost, this makes your program stop as soon as control
2898 returns to that frame. This is similar to the effect of a
2899 @code{finish} command in the frame inside the selected frame---except
2900 that @code{finish} does not leave an active breakpoint. If you use
2901 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2902 the next time it reaches the current location; this may be useful
2905 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2906 least one instruction has been executed. If it did not do this, you
2907 would be unable to proceed past a breakpoint without first disabling the
2908 breakpoint. This rule applies whether or not the breakpoint already
2909 existed when your program stopped.
2911 @item break @dots{} if @var{cond}
2912 Set a breakpoint with condition @var{cond}; evaluate the expression
2913 @var{cond} each time the breakpoint is reached, and stop only if the
2914 value is nonzero---that is, if @var{cond} evaluates as true.
2915 @samp{@dots{}} stands for one of the possible arguments described
2916 above (or no argument) specifying where to break. @xref{Conditions,
2917 ,Break conditions}, for more information on breakpoint conditions.
2920 @item tbreak @var{args}
2921 Set a breakpoint enabled only for one stop. @var{args} are the
2922 same as for the @code{break} command, and the breakpoint is set in the same
2923 way, but the breakpoint is automatically deleted after the first time your
2924 program stops there. @xref{Disabling, ,Disabling breakpoints}.
2927 @cindex hardware breakpoints
2928 @item hbreak @var{args}
2929 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2930 @code{break} command and the breakpoint is set in the same way, but the
2931 breakpoint requires hardware support and some target hardware may not
2932 have this support. The main purpose of this is EPROM/ROM code
2933 debugging, so you can set a breakpoint at an instruction without
2934 changing the instruction. This can be used with the new trap-generation
2935 provided by SPARClite DSU and most x86-based targets. These targets
2936 will generate traps when a program accesses some data or instruction
2937 address that is assigned to the debug registers. However the hardware
2938 breakpoint registers can take a limited number of breakpoints. For
2939 example, on the DSU, only two data breakpoints can be set at a time, and
2940 @value{GDBN} will reject this command if more than two are used. Delete
2941 or disable unused hardware breakpoints before setting new ones
2942 (@pxref{Disabling, ,Disabling}). @xref{Conditions, ,Break conditions}.
2943 For remote targets, you can restrict the number of hardware
2944 breakpoints @value{GDBN} will use, see @ref{set remote
2945 hardware-breakpoint-limit}.
2949 @item thbreak @var{args}
2950 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2951 are the same as for the @code{hbreak} command and the breakpoint is set in
2952 the same way. However, like the @code{tbreak} command,
2953 the breakpoint is automatically deleted after the
2954 first time your program stops there. Also, like the @code{hbreak}
2955 command, the breakpoint requires hardware support and some target hardware
2956 may not have this support. @xref{Disabling, ,Disabling breakpoints}.
2957 See also @ref{Conditions, ,Break conditions}.
2960 @cindex regular expression
2961 @cindex breakpoints in functions matching a regexp
2962 @cindex set breakpoints in many functions
2963 @item rbreak @var{regex}
2964 Set breakpoints on all functions matching the regular expression
2965 @var{regex}. This command sets an unconditional breakpoint on all
2966 matches, printing a list of all breakpoints it set. Once these
2967 breakpoints are set, they are treated just like the breakpoints set with
2968 the @code{break} command. You can delete them, disable them, or make
2969 them conditional the same way as any other breakpoint.
2971 The syntax of the regular expression is the standard one used with tools
2972 like @file{grep}. Note that this is different from the syntax used by
2973 shells, so for instance @code{foo*} matches all functions that include
2974 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2975 @code{.*} leading and trailing the regular expression you supply, so to
2976 match only functions that begin with @code{foo}, use @code{^foo}.
2978 @cindex non-member C@t{++} functions, set breakpoint in
2979 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2980 breakpoints on overloaded functions that are not members of any special
2983 @cindex set breakpoints on all functions
2984 The @code{rbreak} command can be used to set breakpoints in
2985 @strong{all} the functions in a program, like this:
2988 (@value{GDBP}) rbreak .
2991 @kindex info breakpoints
2992 @cindex @code{$_} and @code{info breakpoints}
2993 @item info breakpoints @r{[}@var{n}@r{]}
2994 @itemx info break @r{[}@var{n}@r{]}
2995 @itemx info watchpoints @r{[}@var{n}@r{]}
2996 Print a table of all breakpoints, watchpoints, and catchpoints set and
2997 not deleted. Optional argument @var{n} means print information only
2998 about the specified breakpoint (or watchpoint or catchpoint). For
2999 each breakpoint, following columns are printed:
3002 @item Breakpoint Numbers
3004 Breakpoint, watchpoint, or catchpoint.
3006 Whether the breakpoint is marked to be disabled or deleted when hit.
3007 @item Enabled or Disabled
3008 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3009 that are not enabled.
3011 Where the breakpoint is in your program, as a memory address. If the
3012 breakpoint is pending (see below for details) on a future load of a shared library, the address
3013 will be listed as @samp{<PENDING>}.
3015 Where the breakpoint is in the source for your program, as a file and
3016 line number. For a pending breakpoint, the original string passed to
3017 the breakpoint command will be listed as it cannot be resolved until
3018 the appropriate shared library is loaded in the future.
3022 If a breakpoint is conditional, @code{info break} shows the condition on
3023 the line following the affected breakpoint; breakpoint commands, if any,
3024 are listed after that. A pending breakpoint is allowed to have a condition
3025 specified for it. The condition is not parsed for validity until a shared
3026 library is loaded that allows the pending breakpoint to resolve to a
3030 @code{info break} with a breakpoint
3031 number @var{n} as argument lists only that breakpoint. The
3032 convenience variable @code{$_} and the default examining-address for
3033 the @code{x} command are set to the address of the last breakpoint
3034 listed (@pxref{Memory, ,Examining memory}).
3037 @code{info break} displays a count of the number of times the breakpoint
3038 has been hit. This is especially useful in conjunction with the
3039 @code{ignore} command. You can ignore a large number of breakpoint
3040 hits, look at the breakpoint info to see how many times the breakpoint
3041 was hit, and then run again, ignoring one less than that number. This
3042 will get you quickly to the last hit of that breakpoint.
3045 @value{GDBN} allows you to set any number of breakpoints at the same place in
3046 your program. There is nothing silly or meaningless about this. When
3047 the breakpoints are conditional, this is even useful
3048 (@pxref{Conditions, ,Break conditions}).
3050 @cindex pending breakpoints
3051 If a specified breakpoint location cannot be found, it may be due to the fact
3052 that the location is in a shared library that is yet to be loaded. In such
3053 a case, you may want @value{GDBN} to create a special breakpoint (known as
3054 a @dfn{pending breakpoint}) that
3055 attempts to resolve itself in the future when an appropriate shared library
3058 Pending breakpoints are useful to set at the start of your
3059 @value{GDBN} session for locations that you know will be dynamically loaded
3060 later by the program being debugged. When shared libraries are loaded,
3061 a check is made to see if the load resolves any pending breakpoint locations.
3062 If a pending breakpoint location gets resolved,
3063 a regular breakpoint is created and the original pending breakpoint is removed.
3065 @value{GDBN} provides some additional commands for controlling pending
3068 @kindex set breakpoint pending
3069 @kindex show breakpoint pending
3071 @item set breakpoint pending auto
3072 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3073 location, it queries you whether a pending breakpoint should be created.
3075 @item set breakpoint pending on
3076 This indicates that an unrecognized breakpoint location should automatically
3077 result in a pending breakpoint being created.
3079 @item set breakpoint pending off
3080 This indicates that pending breakpoints are not to be created. Any
3081 unrecognized breakpoint location results in an error. This setting does
3082 not affect any pending breakpoints previously created.
3084 @item show breakpoint pending
3085 Show the current behavior setting for creating pending breakpoints.
3088 @cindex operations allowed on pending breakpoints
3089 Normal breakpoint operations apply to pending breakpoints as well. You may
3090 specify a condition for a pending breakpoint and/or commands to run when the
3091 breakpoint is reached. You can also enable or disable
3092 the pending breakpoint. When you specify a condition for a pending breakpoint,
3093 the parsing of the condition will be deferred until the point where the
3094 pending breakpoint location is resolved. Disabling a pending breakpoint
3095 tells @value{GDBN} to not attempt to resolve the breakpoint on any subsequent
3096 shared library load. When a pending breakpoint is re-enabled,
3097 @value{GDBN} checks to see if the location is already resolved.
3098 This is done because any number of shared library loads could have
3099 occurred since the time the breakpoint was disabled and one or more
3100 of these loads could resolve the location.
3102 @cindex automatic hardware breakpoints
3103 For some targets, @value{GDBN} can automatically decide if hardware or
3104 software breakpoints should be used, depending on whether the
3105 breakpoint address is read-only or read-write. This applies to
3106 breakpoints set with the @code{break} command as well as to internal
3107 breakpoints set by commands like @code{next} and @code{finish}. For
3108 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3111 You can control this automatic behaviour with the following commands::
3113 @kindex set breakpoint auto-hw
3114 @kindex show breakpoint auto-hw
3116 @item set breakpoint auto-hw on
3117 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3118 will try to use the target memory map to decide if software or hardware
3119 breakpoint must be used.
3121 @item set breakpoint auto-hw off
3122 This indicates @value{GDBN} should not automatically select breakpoint
3123 type. If the target provides a memory map, @value{GDBN} will warn when
3124 trying to set software breakpoint at a read-only address.
3128 @cindex negative breakpoint numbers
3129 @cindex internal @value{GDBN} breakpoints
3130 @value{GDBN} itself sometimes sets breakpoints in your program for
3131 special purposes, such as proper handling of @code{longjmp} (in C
3132 programs). These internal breakpoints are assigned negative numbers,
3133 starting with @code{-1}; @samp{info breakpoints} does not display them.
3134 You can see these breakpoints with the @value{GDBN} maintenance command
3135 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3138 @node Set Watchpoints
3139 @subsection Setting watchpoints
3141 @cindex setting watchpoints
3142 You can use a watchpoint to stop execution whenever the value of an
3143 expression changes, without having to predict a particular place where
3144 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3145 The expression may be as simple as the value of a single variable, or
3146 as complex as many variables combined by operators. Examples include:
3150 A reference to the value of a single variable.
3153 An address cast to an appropriate data type. For example,
3154 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3155 address (assuming an @code{int} occupies 4 bytes).
3158 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3159 expression can use any operators valid in the program's native
3160 language (@pxref{Languages}).
3163 @cindex software watchpoints
3164 @cindex hardware watchpoints
3165 Depending on your system, watchpoints may be implemented in software or
3166 hardware. @value{GDBN} does software watchpointing by single-stepping your
3167 program and testing the variable's value each time, which is hundreds of
3168 times slower than normal execution. (But this may still be worth it, to
3169 catch errors where you have no clue what part of your program is the
3172 On some systems, such as HP-UX, @sc{gnu}/Linux and most other
3173 x86-based targets, @value{GDBN} includes support for hardware
3174 watchpoints, which do not slow down the running of your program.
3178 @item watch @var{expr}
3179 Set a watchpoint for an expression. @value{GDBN} will break when the
3180 expression @var{expr} is written into by the program and its value
3181 changes. The simplest (and the most popular) use of this command is
3182 to watch the value of a single variable:
3185 (@value{GDBP}) watch foo
3189 @item rwatch @var{expr}
3190 Set a watchpoint that will break when the value of @var{expr} is read
3194 @item awatch @var{expr}
3195 Set a watchpoint that will break when @var{expr} is either read from
3196 or written into by the program.
3198 @kindex info watchpoints @r{[}@var{n}@r{]}
3199 @item info watchpoints
3200 This command prints a list of watchpoints, breakpoints, and catchpoints;
3201 it is the same as @code{info break} (@pxref{Set Breaks}).
3204 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3205 watchpoints execute very quickly, and the debugger reports a change in
3206 value at the exact instruction where the change occurs. If @value{GDBN}
3207 cannot set a hardware watchpoint, it sets a software watchpoint, which
3208 executes more slowly and reports the change in value at the next
3209 @emph{statement}, not the instruction, after the change occurs.
3211 @cindex use only software watchpoints
3212 You can force @value{GDBN} to use only software watchpoints with the
3213 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3214 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3215 the underlying system supports them. (Note that hardware-assisted
3216 watchpoints that were set @emph{before} setting
3217 @code{can-use-hw-watchpoints} to zero will still use the hardware
3218 mechanism of watching expressiion values.)
3221 @item set can-use-hw-watchpoints
3222 @kindex set can-use-hw-watchpoints
3223 Set whether or not to use hardware watchpoints.
3225 @item show can-use-hw-watchpoints
3226 @kindex show can-use-hw-watchpoints
3227 Show the current mode of using hardware watchpoints.
3230 For remote targets, you can restrict the number of hardware
3231 watchpoints @value{GDBN} will use, see @ref{set remote
3232 hardware-breakpoint-limit}.
3234 When you issue the @code{watch} command, @value{GDBN} reports
3237 Hardware watchpoint @var{num}: @var{expr}
3241 if it was able to set a hardware watchpoint.
3243 Currently, the @code{awatch} and @code{rwatch} commands can only set
3244 hardware watchpoints, because accesses to data that don't change the
3245 value of the watched expression cannot be detected without examining
3246 every instruction as it is being executed, and @value{GDBN} does not do
3247 that currently. If @value{GDBN} finds that it is unable to set a
3248 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3249 will print a message like this:
3252 Expression cannot be implemented with read/access watchpoint.
3255 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3256 data type of the watched expression is wider than what a hardware
3257 watchpoint on the target machine can handle. For example, some systems
3258 can only watch regions that are up to 4 bytes wide; on such systems you
3259 cannot set hardware watchpoints for an expression that yields a
3260 double-precision floating-point number (which is typically 8 bytes
3261 wide). As a work-around, it might be possible to break the large region
3262 into a series of smaller ones and watch them with separate watchpoints.
3264 If you set too many hardware watchpoints, @value{GDBN} might be unable
3265 to insert all of them when you resume the execution of your program.
3266 Since the precise number of active watchpoints is unknown until such
3267 time as the program is about to be resumed, @value{GDBN} might not be
3268 able to warn you about this when you set the watchpoints, and the
3269 warning will be printed only when the program is resumed:
3272 Hardware watchpoint @var{num}: Could not insert watchpoint
3276 If this happens, delete or disable some of the watchpoints.
3278 Watching complex expressions that reference many variables can also
3279 exhaust the resources available for hardware-assisted watchpoints.
3280 That's because @value{GDBN} needs to watch every variable in the
3281 expression with separately allocated resources.
3283 The SPARClite DSU will generate traps when a program accesses some data
3284 or instruction address that is assigned to the debug registers. For the
3285 data addresses, DSU facilitates the @code{watch} command. However the
3286 hardware breakpoint registers can only take two data watchpoints, and
3287 both watchpoints must be the same kind. For example, you can set two
3288 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
3289 @strong{or} two with @code{awatch} commands, but you cannot set one
3290 watchpoint with one command and the other with a different command.
3291 @value{GDBN} will reject the command if you try to mix watchpoints.
3292 Delete or disable unused watchpoint commands before setting new ones.
3294 If you call a function interactively using @code{print} or @code{call},
3295 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3296 kind of breakpoint or the call completes.
3298 @value{GDBN} automatically deletes watchpoints that watch local
3299 (automatic) variables, or expressions that involve such variables, when
3300 they go out of scope, that is, when the execution leaves the block in
3301 which these variables were defined. In particular, when the program
3302 being debugged terminates, @emph{all} local variables go out of scope,
3303 and so only watchpoints that watch global variables remain set. If you
3304 rerun the program, you will need to set all such watchpoints again. One
3305 way of doing that would be to set a code breakpoint at the entry to the
3306 @code{main} function and when it breaks, set all the watchpoints.
3309 @cindex watchpoints and threads
3310 @cindex threads and watchpoints
3311 @emph{Warning:} In multi-thread programs, watchpoints have only limited
3312 usefulness. With the current watchpoint implementation, @value{GDBN}
3313 can only watch the value of an expression @emph{in a single thread}. If
3314 you are confident that the expression can only change due to the current
3315 thread's activity (and if you are also confident that no other thread
3316 can become current), then you can use watchpoints as usual. However,
3317 @value{GDBN} may not notice when a non-current thread's activity changes
3320 @c FIXME: this is almost identical to the previous paragraph.
3321 @emph{HP-UX Warning:} In multi-thread programs, software watchpoints
3322 have only limited usefulness. If @value{GDBN} creates a software
3323 watchpoint, it can only watch the value of an expression @emph{in a
3324 single thread}. If you are confident that the expression can only
3325 change due to the current thread's activity (and if you are also
3326 confident that no other thread can become current), then you can use
3327 software watchpoints as usual. However, @value{GDBN} may not notice
3328 when a non-current thread's activity changes the expression. (Hardware
3329 watchpoints, in contrast, watch an expression in all threads.)
3332 @xref{set remote hardware-watchpoint-limit}.
3334 @node Set Catchpoints
3335 @subsection Setting catchpoints
3336 @cindex catchpoints, setting
3337 @cindex exception handlers
3338 @cindex event handling
3340 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3341 kinds of program events, such as C@t{++} exceptions or the loading of a
3342 shared library. Use the @code{catch} command to set a catchpoint.
3346 @item catch @var{event}
3347 Stop when @var{event} occurs. @var{event} can be any of the following:
3350 @cindex stop on C@t{++} exceptions
3351 The throwing of a C@t{++} exception.
3354 The catching of a C@t{++} exception.
3357 @cindex break on fork/exec
3358 A call to @code{exec}. This is currently only available for HP-UX.
3361 A call to @code{fork}. This is currently only available for HP-UX.
3364 A call to @code{vfork}. This is currently only available for HP-UX.
3367 @itemx load @var{libname}
3368 @cindex break on load/unload of shared library
3369 The dynamic loading of any shared library, or the loading of the library
3370 @var{libname}. This is currently only available for HP-UX.
3373 @itemx unload @var{libname}
3374 The unloading of any dynamically loaded shared library, or the unloading
3375 of the library @var{libname}. This is currently only available for HP-UX.
3378 @item tcatch @var{event}
3379 Set a catchpoint that is enabled only for one stop. The catchpoint is
3380 automatically deleted after the first time the event is caught.
3384 Use the @code{info break} command to list the current catchpoints.
3386 There are currently some limitations to C@t{++} exception handling
3387 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
3391 If you call a function interactively, @value{GDBN} normally returns
3392 control to you when the function has finished executing. If the call
3393 raises an exception, however, the call may bypass the mechanism that
3394 returns control to you and cause your program either to abort or to
3395 simply continue running until it hits a breakpoint, catches a signal
3396 that @value{GDBN} is listening for, or exits. This is the case even if
3397 you set a catchpoint for the exception; catchpoints on exceptions are
3398 disabled within interactive calls.
3401 You cannot raise an exception interactively.
3404 You cannot install an exception handler interactively.
3407 @cindex raise exceptions
3408 Sometimes @code{catch} is not the best way to debug exception handling:
3409 if you need to know exactly where an exception is raised, it is better to
3410 stop @emph{before} the exception handler is called, since that way you
3411 can see the stack before any unwinding takes place. If you set a
3412 breakpoint in an exception handler instead, it may not be easy to find
3413 out where the exception was raised.
3415 To stop just before an exception handler is called, you need some
3416 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3417 raised by calling a library function named @code{__raise_exception}
3418 which has the following ANSI C interface:
3421 /* @var{addr} is where the exception identifier is stored.
3422 @var{id} is the exception identifier. */
3423 void __raise_exception (void **addr, void *id);
3427 To make the debugger catch all exceptions before any stack
3428 unwinding takes place, set a breakpoint on @code{__raise_exception}
3429 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and exceptions}).
3431 With a conditional breakpoint (@pxref{Conditions, ,Break conditions})
3432 that depends on the value of @var{id}, you can stop your program when
3433 a specific exception is raised. You can use multiple conditional
3434 breakpoints to stop your program when any of a number of exceptions are
3439 @subsection Deleting breakpoints
3441 @cindex clearing breakpoints, watchpoints, catchpoints
3442 @cindex deleting breakpoints, watchpoints, catchpoints
3443 It is often necessary to eliminate a breakpoint, watchpoint, or
3444 catchpoint once it has done its job and you no longer want your program
3445 to stop there. This is called @dfn{deleting} the breakpoint. A
3446 breakpoint that has been deleted no longer exists; it is forgotten.
3448 With the @code{clear} command you can delete breakpoints according to
3449 where they are in your program. With the @code{delete} command you can
3450 delete individual breakpoints, watchpoints, or catchpoints by specifying
3451 their breakpoint numbers.
3453 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3454 automatically ignores breakpoints on the first instruction to be executed
3455 when you continue execution without changing the execution address.
3460 Delete any breakpoints at the next instruction to be executed in the
3461 selected stack frame (@pxref{Selection, ,Selecting a frame}). When
3462 the innermost frame is selected, this is a good way to delete a
3463 breakpoint where your program just stopped.
3465 @item clear @var{function}
3466 @itemx clear @var{filename}:@var{function}
3467 Delete any breakpoints set at entry to the named @var{function}.
3469 @item clear @var{linenum}
3470 @itemx clear @var{filename}:@var{linenum}
3471 Delete any breakpoints set at or within the code of the specified
3472 @var{linenum} of the specified @var{filename}.
3474 @cindex delete breakpoints
3476 @kindex d @r{(@code{delete})}
3477 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3478 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3479 ranges specified as arguments. If no argument is specified, delete all
3480 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3481 confirm off}). You can abbreviate this command as @code{d}.
3485 @subsection Disabling breakpoints
3487 @cindex enable/disable a breakpoint
3488 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3489 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3490 it had been deleted, but remembers the information on the breakpoint so
3491 that you can @dfn{enable} it again later.
3493 You disable and enable breakpoints, watchpoints, and catchpoints with
3494 the @code{enable} and @code{disable} commands, optionally specifying one
3495 or more breakpoint numbers as arguments. Use @code{info break} or
3496 @code{info watch} to print a list of breakpoints, watchpoints, and
3497 catchpoints if you do not know which numbers to use.
3499 A breakpoint, watchpoint, or catchpoint can have any of four different
3500 states of enablement:
3504 Enabled. The breakpoint stops your program. A breakpoint set
3505 with the @code{break} command starts out in this state.
3507 Disabled. The breakpoint has no effect on your program.
3509 Enabled once. The breakpoint stops your program, but then becomes
3512 Enabled for deletion. The breakpoint stops your program, but
3513 immediately after it does so it is deleted permanently. A breakpoint
3514 set with the @code{tbreak} command starts out in this state.
3517 You can use the following commands to enable or disable breakpoints,
3518 watchpoints, and catchpoints:
3522 @kindex dis @r{(@code{disable})}
3523 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3524 Disable the specified breakpoints---or all breakpoints, if none are
3525 listed. A disabled breakpoint has no effect but is not forgotten. All
3526 options such as ignore-counts, conditions and commands are remembered in
3527 case the breakpoint is enabled again later. You may abbreviate
3528 @code{disable} as @code{dis}.
3531 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3532 Enable the specified breakpoints (or all defined breakpoints). They
3533 become effective once again in stopping your program.
3535 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3536 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3537 of these breakpoints immediately after stopping your program.
3539 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3540 Enable the specified breakpoints to work once, then die. @value{GDBN}
3541 deletes any of these breakpoints as soon as your program stops there.
3542 Breakpoints set by the @code{tbreak} command start out in this state.
3545 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3546 @c confusing: tbreak is also initially enabled.
3547 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3548 ,Setting breakpoints}), breakpoints that you set are initially enabled;
3549 subsequently, they become disabled or enabled only when you use one of
3550 the commands above. (The command @code{until} can set and delete a
3551 breakpoint of its own, but it does not change the state of your other
3552 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3556 @subsection Break conditions
3557 @cindex conditional breakpoints
3558 @cindex breakpoint conditions
3560 @c FIXME what is scope of break condition expr? Context where wanted?
3561 @c in particular for a watchpoint?
3562 The simplest sort of breakpoint breaks every time your program reaches a
3563 specified place. You can also specify a @dfn{condition} for a
3564 breakpoint. A condition is just a Boolean expression in your
3565 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3566 a condition evaluates the expression each time your program reaches it,
3567 and your program stops only if the condition is @emph{true}.
3569 This is the converse of using assertions for program validation; in that
3570 situation, you want to stop when the assertion is violated---that is,
3571 when the condition is false. In C, if you want to test an assertion expressed
3572 by the condition @var{assert}, you should set the condition
3573 @samp{! @var{assert}} on the appropriate breakpoint.
3575 Conditions are also accepted for watchpoints; you may not need them,
3576 since a watchpoint is inspecting the value of an expression anyhow---but
3577 it might be simpler, say, to just set a watchpoint on a variable name,
3578 and specify a condition that tests whether the new value is an interesting
3581 Break conditions can have side effects, and may even call functions in
3582 your program. This can be useful, for example, to activate functions
3583 that log program progress, or to use your own print functions to
3584 format special data structures. The effects are completely predictable
3585 unless there is another enabled breakpoint at the same address. (In
3586 that case, @value{GDBN} might see the other breakpoint first and stop your
3587 program without checking the condition of this one.) Note that
3588 breakpoint commands are usually more convenient and flexible than break
3590 purpose of performing side effects when a breakpoint is reached
3591 (@pxref{Break Commands, ,Breakpoint command lists}).
3593 Break conditions can be specified when a breakpoint is set, by using
3594 @samp{if} in the arguments to the @code{break} command. @xref{Set
3595 Breaks, ,Setting breakpoints}. They can also be changed at any time
3596 with the @code{condition} command.
3598 You can also use the @code{if} keyword with the @code{watch} command.
3599 The @code{catch} command does not recognize the @code{if} keyword;
3600 @code{condition} is the only way to impose a further condition on a
3605 @item condition @var{bnum} @var{expression}
3606 Specify @var{expression} as the break condition for breakpoint,
3607 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3608 breakpoint @var{bnum} stops your program only if the value of
3609 @var{expression} is true (nonzero, in C). When you use
3610 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3611 syntactic correctness, and to determine whether symbols in it have
3612 referents in the context of your breakpoint. If @var{expression} uses
3613 symbols not referenced in the context of the breakpoint, @value{GDBN}
3614 prints an error message:
3617 No symbol "foo" in current context.
3622 not actually evaluate @var{expression} at the time the @code{condition}
3623 command (or a command that sets a breakpoint with a condition, like
3624 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3626 @item condition @var{bnum}
3627 Remove the condition from breakpoint number @var{bnum}. It becomes
3628 an ordinary unconditional breakpoint.
3631 @cindex ignore count (of breakpoint)
3632 A special case of a breakpoint condition is to stop only when the
3633 breakpoint has been reached a certain number of times. This is so
3634 useful that there is a special way to do it, using the @dfn{ignore
3635 count} of the breakpoint. Every breakpoint has an ignore count, which
3636 is an integer. Most of the time, the ignore count is zero, and
3637 therefore has no effect. But if your program reaches a breakpoint whose
3638 ignore count is positive, then instead of stopping, it just decrements
3639 the ignore count by one and continues. As a result, if the ignore count
3640 value is @var{n}, the breakpoint does not stop the next @var{n} times
3641 your program reaches it.
3645 @item ignore @var{bnum} @var{count}
3646 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3647 The next @var{count} times the breakpoint is reached, your program's
3648 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3651 To make the breakpoint stop the next time it is reached, specify
3654 When you use @code{continue} to resume execution of your program from a
3655 breakpoint, you can specify an ignore count directly as an argument to
3656 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3657 Stepping,,Continuing and stepping}.
3659 If a breakpoint has a positive ignore count and a condition, the
3660 condition is not checked. Once the ignore count reaches zero,
3661 @value{GDBN} resumes checking the condition.
3663 You could achieve the effect of the ignore count with a condition such
3664 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3665 is decremented each time. @xref{Convenience Vars, ,Convenience
3669 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3672 @node Break Commands
3673 @subsection Breakpoint command lists
3675 @cindex breakpoint commands
3676 You can give any breakpoint (or watchpoint or catchpoint) a series of
3677 commands to execute when your program stops due to that breakpoint. For
3678 example, you might want to print the values of certain expressions, or
3679 enable other breakpoints.
3683 @kindex end@r{ (breakpoint commands)}
3684 @item commands @r{[}@var{bnum}@r{]}
3685 @itemx @dots{} @var{command-list} @dots{}
3687 Specify a list of commands for breakpoint number @var{bnum}. The commands
3688 themselves appear on the following lines. Type a line containing just
3689 @code{end} to terminate the commands.
3691 To remove all commands from a breakpoint, type @code{commands} and
3692 follow it immediately with @code{end}; that is, give no commands.
3694 With no @var{bnum} argument, @code{commands} refers to the last
3695 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3696 recently encountered).
3699 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3700 disabled within a @var{command-list}.
3702 You can use breakpoint commands to start your program up again. Simply
3703 use the @code{continue} command, or @code{step}, or any other command
3704 that resumes execution.
3706 Any other commands in the command list, after a command that resumes
3707 execution, are ignored. This is because any time you resume execution
3708 (even with a simple @code{next} or @code{step}), you may encounter
3709 another breakpoint---which could have its own command list, leading to
3710 ambiguities about which list to execute.
3713 If the first command you specify in a command list is @code{silent}, the
3714 usual message about stopping at a breakpoint is not printed. This may
3715 be desirable for breakpoints that are to print a specific message and
3716 then continue. If none of the remaining commands print anything, you
3717 see no sign that the breakpoint was reached. @code{silent} is
3718 meaningful only at the beginning of a breakpoint command list.
3720 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3721 print precisely controlled output, and are often useful in silent
3722 breakpoints. @xref{Output, ,Commands for controlled output}.
3724 For example, here is how you could use breakpoint commands to print the
3725 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3731 printf "x is %d\n",x
3736 One application for breakpoint commands is to compensate for one bug so
3737 you can test for another. Put a breakpoint just after the erroneous line
3738 of code, give it a condition to detect the case in which something
3739 erroneous has been done, and give it commands to assign correct values
3740 to any variables that need them. End with the @code{continue} command
3741 so that your program does not stop, and start with the @code{silent}
3742 command so that no output is produced. Here is an example:
3753 @node Breakpoint Menus
3754 @subsection Breakpoint menus
3756 @cindex symbol overloading
3758 Some programming languages (notably C@t{++} and Objective-C) permit a
3759 single function name
3760 to be defined several times, for application in different contexts.
3761 This is called @dfn{overloading}. When a function name is overloaded,
3762 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3763 a breakpoint. If you realize this is a problem, you can use
3764 something like @samp{break @var{function}(@var{types})} to specify which
3765 particular version of the function you want. Otherwise, @value{GDBN} offers
3766 you a menu of numbered choices for different possible breakpoints, and
3767 waits for your selection with the prompt @samp{>}. The first two
3768 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3769 sets a breakpoint at each definition of @var{function}, and typing
3770 @kbd{0} aborts the @code{break} command without setting any new
3773 For example, the following session excerpt shows an attempt to set a
3774 breakpoint at the overloaded symbol @code{String::after}.
3775 We choose three particular definitions of that function name:
3777 @c FIXME! This is likely to change to show arg type lists, at least
3780 (@value{GDBP}) b String::after
3783 [2] file:String.cc; line number:867
3784 [3] file:String.cc; line number:860
3785 [4] file:String.cc; line number:875
3786 [5] file:String.cc; line number:853
3787 [6] file:String.cc; line number:846
3788 [7] file:String.cc; line number:735
3790 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3791 Breakpoint 2 at 0xb344: file String.cc, line 875.
3792 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3793 Multiple breakpoints were set.
3794 Use the "delete" command to delete unwanted
3800 @c @ifclear BARETARGET
3801 @node Error in Breakpoints
3802 @subsection ``Cannot insert breakpoints''
3804 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3806 Under some operating systems, breakpoints cannot be used in a program if
3807 any other process is running that program. In this situation,
3808 attempting to run or continue a program with a breakpoint causes
3809 @value{GDBN} to print an error message:
3812 Cannot insert breakpoints.
3813 The same program may be running in another process.
3816 When this happens, you have three ways to proceed:
3820 Remove or disable the breakpoints, then continue.
3823 Suspend @value{GDBN}, and copy the file containing your program to a new
3824 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3825 that @value{GDBN} should run your program under that name.
3826 Then start your program again.
3829 Relink your program so that the text segment is nonsharable, using the
3830 linker option @samp{-N}. The operating system limitation may not apply
3831 to nonsharable executables.
3835 A similar message can be printed if you request too many active
3836 hardware-assisted breakpoints and watchpoints:
3838 @c FIXME: the precise wording of this message may change; the relevant
3839 @c source change is not committed yet (Sep 3, 1999).
3841 Stopped; cannot insert breakpoints.
3842 You may have requested too many hardware breakpoints and watchpoints.
3846 This message is printed when you attempt to resume the program, since
3847 only then @value{GDBN} knows exactly how many hardware breakpoints and
3848 watchpoints it needs to insert.
3850 When this message is printed, you need to disable or remove some of the
3851 hardware-assisted breakpoints and watchpoints, and then continue.
3853 @node Breakpoint related warnings
3854 @subsection ``Breakpoint address adjusted...''
3855 @cindex breakpoint address adjusted
3857 Some processor architectures place constraints on the addresses at
3858 which breakpoints may be placed. For architectures thus constrained,
3859 @value{GDBN} will attempt to adjust the breakpoint's address to comply
3860 with the constraints dictated by the architecture.
3862 One example of such an architecture is the Fujitsu FR-V. The FR-V is
3863 a VLIW architecture in which a number of RISC-like instructions may be
3864 bundled together for parallel execution. The FR-V architecture
3865 constrains the location of a breakpoint instruction within such a
3866 bundle to the instruction with the lowest address. @value{GDBN}
3867 honors this constraint by adjusting a breakpoint's address to the
3868 first in the bundle.
3870 It is not uncommon for optimized code to have bundles which contain
3871 instructions from different source statements, thus it may happen that
3872 a breakpoint's address will be adjusted from one source statement to
3873 another. Since this adjustment may significantly alter @value{GDBN}'s
3874 breakpoint related behavior from what the user expects, a warning is
3875 printed when the breakpoint is first set and also when the breakpoint
3878 A warning like the one below is printed when setting a breakpoint
3879 that's been subject to address adjustment:
3882 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
3885 Such warnings are printed both for user settable and @value{GDBN}'s
3886 internal breakpoints. If you see one of these warnings, you should
3887 verify that a breakpoint set at the adjusted address will have the
3888 desired affect. If not, the breakpoint in question may be removed and
3889 other breakpoints may be set which will have the desired behavior.
3890 E.g., it may be sufficient to place the breakpoint at a later
3891 instruction. A conditional breakpoint may also be useful in some
3892 cases to prevent the breakpoint from triggering too often.
3894 @value{GDBN} will also issue a warning when stopping at one of these
3895 adjusted breakpoints:
3898 warning: Breakpoint 1 address previously adjusted from 0x00010414
3902 When this warning is encountered, it may be too late to take remedial
3903 action except in cases where the breakpoint is hit earlier or more
3904 frequently than expected.
3906 @node Continuing and Stepping
3907 @section Continuing and stepping
3911 @cindex resuming execution
3912 @dfn{Continuing} means resuming program execution until your program
3913 completes normally. In contrast, @dfn{stepping} means executing just
3914 one more ``step'' of your program, where ``step'' may mean either one
3915 line of source code, or one machine instruction (depending on what
3916 particular command you use). Either when continuing or when stepping,
3917 your program may stop even sooner, due to a breakpoint or a signal. (If
3918 it stops due to a signal, you may want to use @code{handle}, or use
3919 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3923 @kindex c @r{(@code{continue})}
3924 @kindex fg @r{(resume foreground execution)}
3925 @item continue @r{[}@var{ignore-count}@r{]}
3926 @itemx c @r{[}@var{ignore-count}@r{]}
3927 @itemx fg @r{[}@var{ignore-count}@r{]}
3928 Resume program execution, at the address where your program last stopped;
3929 any breakpoints set at that address are bypassed. The optional argument
3930 @var{ignore-count} allows you to specify a further number of times to
3931 ignore a breakpoint at this location; its effect is like that of
3932 @code{ignore} (@pxref{Conditions, ,Break conditions}).
3934 The argument @var{ignore-count} is meaningful only when your program
3935 stopped due to a breakpoint. At other times, the argument to
3936 @code{continue} is ignored.
3938 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
3939 debugged program is deemed to be the foreground program) are provided
3940 purely for convenience, and have exactly the same behavior as
3944 To resume execution at a different place, you can use @code{return}
3945 (@pxref{Returning, ,Returning from a function}) to go back to the
3946 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
3947 different address}) to go to an arbitrary location in your program.
3949 A typical technique for using stepping is to set a breakpoint
3950 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and catchpoints}) at the
3951 beginning of the function or the section of your program where a problem
3952 is believed to lie, run your program until it stops at that breakpoint,
3953 and then step through the suspect area, examining the variables that are
3954 interesting, until you see the problem happen.
3958 @kindex s @r{(@code{step})}
3960 Continue running your program until control reaches a different source
3961 line, then stop it and return control to @value{GDBN}. This command is
3962 abbreviated @code{s}.
3965 @c "without debugging information" is imprecise; actually "without line
3966 @c numbers in the debugging information". (gcc -g1 has debugging info but
3967 @c not line numbers). But it seems complex to try to make that
3968 @c distinction here.
3969 @emph{Warning:} If you use the @code{step} command while control is
3970 within a function that was compiled without debugging information,
3971 execution proceeds until control reaches a function that does have
3972 debugging information. Likewise, it will not step into a function which
3973 is compiled without debugging information. To step through functions
3974 without debugging information, use the @code{stepi} command, described
3978 The @code{step} command only stops at the first instruction of a source
3979 line. This prevents the multiple stops that could otherwise occur in
3980 @code{switch} statements, @code{for} loops, etc. @code{step} continues
3981 to stop if a function that has debugging information is called within
3982 the line. In other words, @code{step} @emph{steps inside} any functions
3983 called within the line.
3985 Also, the @code{step} command only enters a function if there is line
3986 number information for the function. Otherwise it acts like the
3987 @code{next} command. This avoids problems when using @code{cc -gl}
3988 on MIPS machines. Previously, @code{step} entered subroutines if there
3989 was any debugging information about the routine.
3991 @item step @var{count}
3992 Continue running as in @code{step}, but do so @var{count} times. If a
3993 breakpoint is reached, or a signal not related to stepping occurs before
3994 @var{count} steps, stepping stops right away.
3997 @kindex n @r{(@code{next})}
3998 @item next @r{[}@var{count}@r{]}
3999 Continue to the next source line in the current (innermost) stack frame.
4000 This is similar to @code{step}, but function calls that appear within
4001 the line of code are executed without stopping. Execution stops when
4002 control reaches a different line of code at the original stack level
4003 that was executing when you gave the @code{next} command. This command
4004 is abbreviated @code{n}.
4006 An argument @var{count} is a repeat count, as for @code{step}.
4009 @c FIX ME!! Do we delete this, or is there a way it fits in with
4010 @c the following paragraph? --- Vctoria
4012 @c @code{next} within a function that lacks debugging information acts like
4013 @c @code{step}, but any function calls appearing within the code of the
4014 @c function are executed without stopping.
4016 The @code{next} command only stops at the first instruction of a
4017 source line. This prevents multiple stops that could otherwise occur in
4018 @code{switch} statements, @code{for} loops, etc.
4020 @kindex set step-mode
4022 @cindex functions without line info, and stepping
4023 @cindex stepping into functions with no line info
4024 @itemx set step-mode on
4025 The @code{set step-mode on} command causes the @code{step} command to
4026 stop at the first instruction of a function which contains no debug line
4027 information rather than stepping over it.
4029 This is useful in cases where you may be interested in inspecting the
4030 machine instructions of a function which has no symbolic info and do not
4031 want @value{GDBN} to automatically skip over this function.
4033 @item set step-mode off
4034 Causes the @code{step} command to step over any functions which contains no
4035 debug information. This is the default.
4037 @item show step-mode
4038 Show whether @value{GDBN} will stop in or step over functions without
4039 source line debug information.
4043 Continue running until just after function in the selected stack frame
4044 returns. Print the returned value (if any).
4046 Contrast this with the @code{return} command (@pxref{Returning,
4047 ,Returning from a function}).
4050 @kindex u @r{(@code{until})}
4051 @cindex run until specified location
4054 Continue running until a source line past the current line, in the
4055 current stack frame, is reached. This command is used to avoid single
4056 stepping through a loop more than once. It is like the @code{next}
4057 command, except that when @code{until} encounters a jump, it
4058 automatically continues execution until the program counter is greater
4059 than the address of the jump.
4061 This means that when you reach the end of a loop after single stepping
4062 though it, @code{until} makes your program continue execution until it
4063 exits the loop. In contrast, a @code{next} command at the end of a loop
4064 simply steps back to the beginning of the loop, which forces you to step
4065 through the next iteration.
4067 @code{until} always stops your program if it attempts to exit the current
4070 @code{until} may produce somewhat counterintuitive results if the order
4071 of machine code does not match the order of the source lines. For
4072 example, in the following excerpt from a debugging session, the @code{f}
4073 (@code{frame}) command shows that execution is stopped at line
4074 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4078 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4080 (@value{GDBP}) until
4081 195 for ( ; argc > 0; NEXTARG) @{
4084 This happened because, for execution efficiency, the compiler had
4085 generated code for the loop closure test at the end, rather than the
4086 start, of the loop---even though the test in a C @code{for}-loop is
4087 written before the body of the loop. The @code{until} command appeared
4088 to step back to the beginning of the loop when it advanced to this
4089 expression; however, it has not really gone to an earlier
4090 statement---not in terms of the actual machine code.
4092 @code{until} with no argument works by means of single
4093 instruction stepping, and hence is slower than @code{until} with an
4096 @item until @var{location}
4097 @itemx u @var{location}
4098 Continue running your program until either the specified location is
4099 reached, or the current stack frame returns. @var{location} is any of
4100 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
4101 ,Setting breakpoints}). This form of the command uses breakpoints, and
4102 hence is quicker than @code{until} without an argument. The specified
4103 location is actually reached only if it is in the current frame. This
4104 implies that @code{until} can be used to skip over recursive function
4105 invocations. For instance in the code below, if the current location is
4106 line @code{96}, issuing @code{until 99} will execute the program up to
4107 line @code{99} in the same invocation of factorial, i.e. after the inner
4108 invocations have returned.
4111 94 int factorial (int value)
4113 96 if (value > 1) @{
4114 97 value *= factorial (value - 1);
4121 @kindex advance @var{location}
4122 @itemx advance @var{location}
4123 Continue running the program up to the given @var{location}. An argument is
4124 required, which should be of the same form as arguments for the @code{break}
4125 command. Execution will also stop upon exit from the current stack
4126 frame. This command is similar to @code{until}, but @code{advance} will
4127 not skip over recursive function calls, and the target location doesn't
4128 have to be in the same frame as the current one.
4132 @kindex si @r{(@code{stepi})}
4134 @itemx stepi @var{arg}
4136 Execute one machine instruction, then stop and return to the debugger.
4138 It is often useful to do @samp{display/i $pc} when stepping by machine
4139 instructions. This makes @value{GDBN} automatically display the next
4140 instruction to be executed, each time your program stops. @xref{Auto
4141 Display,, Automatic display}.
4143 An argument is a repeat count, as in @code{step}.
4147 @kindex ni @r{(@code{nexti})}
4149 @itemx nexti @var{arg}
4151 Execute one machine instruction, but if it is a function call,
4152 proceed until the function returns.
4154 An argument is a repeat count, as in @code{next}.
4161 A signal is an asynchronous event that can happen in a program. The
4162 operating system defines the possible kinds of signals, and gives each
4163 kind a name and a number. For example, in Unix @code{SIGINT} is the
4164 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4165 @code{SIGSEGV} is the signal a program gets from referencing a place in
4166 memory far away from all the areas in use; @code{SIGALRM} occurs when
4167 the alarm clock timer goes off (which happens only if your program has
4168 requested an alarm).
4170 @cindex fatal signals
4171 Some signals, including @code{SIGALRM}, are a normal part of the
4172 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4173 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4174 program has not specified in advance some other way to handle the signal.
4175 @code{SIGINT} does not indicate an error in your program, but it is normally
4176 fatal so it can carry out the purpose of the interrupt: to kill the program.
4178 @value{GDBN} has the ability to detect any occurrence of a signal in your
4179 program. You can tell @value{GDBN} in advance what to do for each kind of
4182 @cindex handling signals
4183 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4184 @code{SIGALRM} be silently passed to your program
4185 (so as not to interfere with their role in the program's functioning)
4186 but to stop your program immediately whenever an error signal happens.
4187 You can change these settings with the @code{handle} command.
4190 @kindex info signals
4194 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4195 handle each one. You can use this to see the signal numbers of all
4196 the defined types of signals.
4198 @item info signals @var{sig}
4199 Similar, but print information only about the specified signal number.
4201 @code{info handle} is an alias for @code{info signals}.
4204 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4205 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4206 can be the number of a signal or its name (with or without the
4207 @samp{SIG} at the beginning); a list of signal numbers of the form
4208 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4209 known signals. Optional arguments @var{keywords}, described below,
4210 say what change to make.
4214 The keywords allowed by the @code{handle} command can be abbreviated.
4215 Their full names are:
4219 @value{GDBN} should not stop your program when this signal happens. It may
4220 still print a message telling you that the signal has come in.
4223 @value{GDBN} should stop your program when this signal happens. This implies
4224 the @code{print} keyword as well.
4227 @value{GDBN} should print a message when this signal happens.
4230 @value{GDBN} should not mention the occurrence of the signal at all. This
4231 implies the @code{nostop} keyword as well.
4235 @value{GDBN} should allow your program to see this signal; your program
4236 can handle the signal, or else it may terminate if the signal is fatal
4237 and not handled. @code{pass} and @code{noignore} are synonyms.
4241 @value{GDBN} should not allow your program to see this signal.
4242 @code{nopass} and @code{ignore} are synonyms.
4246 When a signal stops your program, the signal is not visible to the
4248 continue. Your program sees the signal then, if @code{pass} is in
4249 effect for the signal in question @emph{at that time}. In other words,
4250 after @value{GDBN} reports a signal, you can use the @code{handle}
4251 command with @code{pass} or @code{nopass} to control whether your
4252 program sees that signal when you continue.
4254 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4255 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4256 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4259 You can also use the @code{signal} command to prevent your program from
4260 seeing a signal, or cause it to see a signal it normally would not see,
4261 or to give it any signal at any time. For example, if your program stopped
4262 due to some sort of memory reference error, you might store correct
4263 values into the erroneous variables and continue, hoping to see more
4264 execution; but your program would probably terminate immediately as
4265 a result of the fatal signal once it saw the signal. To prevent this,
4266 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4270 @section Stopping and starting multi-thread programs
4272 When your program has multiple threads (@pxref{Threads,, Debugging
4273 programs with multiple threads}), you can choose whether to set
4274 breakpoints on all threads, or on a particular thread.
4277 @cindex breakpoints and threads
4278 @cindex thread breakpoints
4279 @kindex break @dots{} thread @var{threadno}
4280 @item break @var{linespec} thread @var{threadno}
4281 @itemx break @var{linespec} thread @var{threadno} if @dots{}
4282 @var{linespec} specifies source lines; there are several ways of
4283 writing them, but the effect is always to specify some source line.
4285 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
4286 to specify that you only want @value{GDBN} to stop the program when a
4287 particular thread reaches this breakpoint. @var{threadno} is one of the
4288 numeric thread identifiers assigned by @value{GDBN}, shown in the first
4289 column of the @samp{info threads} display.
4291 If you do not specify @samp{thread @var{threadno}} when you set a
4292 breakpoint, the breakpoint applies to @emph{all} threads of your
4295 You can use the @code{thread} qualifier on conditional breakpoints as
4296 well; in this case, place @samp{thread @var{threadno}} before the
4297 breakpoint condition, like this:
4300 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
4305 @cindex stopped threads
4306 @cindex threads, stopped
4307 Whenever your program stops under @value{GDBN} for any reason,
4308 @emph{all} threads of execution stop, not just the current thread. This
4309 allows you to examine the overall state of the program, including
4310 switching between threads, without worrying that things may change
4313 @cindex thread breakpoints and system calls
4314 @cindex system calls and thread breakpoints
4315 @cindex premature return from system calls
4316 There is an unfortunate side effect. If one thread stops for a
4317 breakpoint, or for some other reason, and another thread is blocked in a
4318 system call, then the system call may return prematurely. This is a
4319 consequence of the interaction between multiple threads and the signals
4320 that @value{GDBN} uses to implement breakpoints and other events that
4323 To handle this problem, your program should check the return value of
4324 each system call and react appropriately. This is good programming
4327 For example, do not write code like this:
4333 The call to @code{sleep} will return early if a different thread stops
4334 at a breakpoint or for some other reason.
4336 Instead, write this:
4341 unslept = sleep (unslept);
4344 A system call is allowed to return early, so the system is still
4345 conforming to its specification. But @value{GDBN} does cause your
4346 multi-threaded program to behave differently than it would without
4349 Also, @value{GDBN} uses internal breakpoints in the thread library to
4350 monitor certain events such as thread creation and thread destruction.
4351 When such an event happens, a system call in another thread may return
4352 prematurely, even though your program does not appear to stop.
4354 @cindex continuing threads
4355 @cindex threads, continuing
4356 Conversely, whenever you restart the program, @emph{all} threads start
4357 executing. @emph{This is true even when single-stepping} with commands
4358 like @code{step} or @code{next}.
4360 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4361 Since thread scheduling is up to your debugging target's operating
4362 system (not controlled by @value{GDBN}), other threads may
4363 execute more than one statement while the current thread completes a
4364 single step. Moreover, in general other threads stop in the middle of a
4365 statement, rather than at a clean statement boundary, when the program
4368 You might even find your program stopped in another thread after
4369 continuing or even single-stepping. This happens whenever some other
4370 thread runs into a breakpoint, a signal, or an exception before the
4371 first thread completes whatever you requested.
4373 On some OSes, you can lock the OS scheduler and thus allow only a single
4377 @item set scheduler-locking @var{mode}
4378 @cindex scheduler locking mode
4379 @cindex lock scheduler
4380 Set the scheduler locking mode. If it is @code{off}, then there is no
4381 locking and any thread may run at any time. If @code{on}, then only the
4382 current thread may run when the inferior is resumed. The @code{step}
4383 mode optimizes for single-stepping. It stops other threads from
4384 ``seizing the prompt'' by preempting the current thread while you are
4385 stepping. Other threads will only rarely (or never) get a chance to run
4386 when you step. They are more likely to run when you @samp{next} over a
4387 function call, and they are completely free to run when you use commands
4388 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4389 thread hits a breakpoint during its timeslice, they will never steal the
4390 @value{GDBN} prompt away from the thread that you are debugging.
4392 @item show scheduler-locking
4393 Display the current scheduler locking mode.
4398 @chapter Examining the Stack
4400 When your program has stopped, the first thing you need to know is where it
4401 stopped and how it got there.
4404 Each time your program performs a function call, information about the call
4406 That information includes the location of the call in your program,
4407 the arguments of the call,
4408 and the local variables of the function being called.
4409 The information is saved in a block of data called a @dfn{stack frame}.
4410 The stack frames are allocated in a region of memory called the @dfn{call
4413 When your program stops, the @value{GDBN} commands for examining the
4414 stack allow you to see all of this information.
4416 @cindex selected frame
4417 One of the stack frames is @dfn{selected} by @value{GDBN} and many
4418 @value{GDBN} commands refer implicitly to the selected frame. In
4419 particular, whenever you ask @value{GDBN} for the value of a variable in
4420 your program, the value is found in the selected frame. There are
4421 special @value{GDBN} commands to select whichever frame you are
4422 interested in. @xref{Selection, ,Selecting a frame}.
4424 When your program stops, @value{GDBN} automatically selects the
4425 currently executing frame and describes it briefly, similar to the
4426 @code{frame} command (@pxref{Frame Info, ,Information about a frame}).
4429 * Frames:: Stack frames
4430 * Backtrace:: Backtraces
4431 * Selection:: Selecting a frame
4432 * Frame Info:: Information on a frame
4437 @section Stack frames
4439 @cindex frame, definition
4441 The call stack is divided up into contiguous pieces called @dfn{stack
4442 frames}, or @dfn{frames} for short; each frame is the data associated
4443 with one call to one function. The frame contains the arguments given
4444 to the function, the function's local variables, and the address at
4445 which the function is executing.
4447 @cindex initial frame
4448 @cindex outermost frame
4449 @cindex innermost frame
4450 When your program is started, the stack has only one frame, that of the
4451 function @code{main}. This is called the @dfn{initial} frame or the
4452 @dfn{outermost} frame. Each time a function is called, a new frame is
4453 made. Each time a function returns, the frame for that function invocation
4454 is eliminated. If a function is recursive, there can be many frames for
4455 the same function. The frame for the function in which execution is
4456 actually occurring is called the @dfn{innermost} frame. This is the most
4457 recently created of all the stack frames that still exist.
4459 @cindex frame pointer
4460 Inside your program, stack frames are identified by their addresses. A
4461 stack frame consists of many bytes, each of which has its own address; each
4462 kind of computer has a convention for choosing one byte whose
4463 address serves as the address of the frame. Usually this address is kept
4464 in a register called the @dfn{frame pointer register}
4465 (@pxref{Registers, $fp}) while execution is going on in that frame.
4467 @cindex frame number
4468 @value{GDBN} assigns numbers to all existing stack frames, starting with
4469 zero for the innermost frame, one for the frame that called it,
4470 and so on upward. These numbers do not really exist in your program;
4471 they are assigned by @value{GDBN} to give you a way of designating stack
4472 frames in @value{GDBN} commands.
4474 @c The -fomit-frame-pointer below perennially causes hbox overflow
4475 @c underflow problems.
4476 @cindex frameless execution
4477 Some compilers provide a way to compile functions so that they operate
4478 without stack frames. (For example, the @value{GCC} option
4480 @samp{-fomit-frame-pointer}
4482 generates functions without a frame.)
4483 This is occasionally done with heavily used library functions to save
4484 the frame setup time. @value{GDBN} has limited facilities for dealing
4485 with these function invocations. If the innermost function invocation
4486 has no stack frame, @value{GDBN} nevertheless regards it as though
4487 it had a separate frame, which is numbered zero as usual, allowing
4488 correct tracing of the function call chain. However, @value{GDBN} has
4489 no provision for frameless functions elsewhere in the stack.
4492 @kindex frame@r{, command}
4493 @cindex current stack frame
4494 @item frame @var{args}
4495 The @code{frame} command allows you to move from one stack frame to another,
4496 and to print the stack frame you select. @var{args} may be either the
4497 address of the frame or the stack frame number. Without an argument,
4498 @code{frame} prints the current stack frame.
4500 @kindex select-frame
4501 @cindex selecting frame silently
4503 The @code{select-frame} command allows you to move from one stack frame
4504 to another without printing the frame. This is the silent version of
4512 @cindex call stack traces
4513 A backtrace is a summary of how your program got where it is. It shows one
4514 line per frame, for many frames, starting with the currently executing
4515 frame (frame zero), followed by its caller (frame one), and on up the
4520 @kindex bt @r{(@code{backtrace})}
4523 Print a backtrace of the entire stack: one line per frame for all
4524 frames in the stack.
4526 You can stop the backtrace at any time by typing the system interrupt
4527 character, normally @kbd{Ctrl-c}.
4529 @item backtrace @var{n}
4531 Similar, but print only the innermost @var{n} frames.
4533 @item backtrace -@var{n}
4535 Similar, but print only the outermost @var{n} frames.
4537 @item backtrace full
4539 @itemx bt full @var{n}
4540 @itemx bt full -@var{n}
4541 Print the values of the local variables also. @var{n} specifies the
4542 number of frames to print, as described above.
4547 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4548 are additional aliases for @code{backtrace}.
4550 @cindex multiple threads, backtrace
4551 In a multi-threaded program, @value{GDBN} by default shows the
4552 backtrace only for the current thread. To display the backtrace for
4553 several or all of the threads, use the command @code{thread apply}
4554 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
4555 apply all backtrace}, @value{GDBN} will display the backtrace for all
4556 the threads; this is handy when you debug a core dump of a
4557 multi-threaded program.
4559 Each line in the backtrace shows the frame number and the function name.
4560 The program counter value is also shown---unless you use @code{set
4561 print address off}. The backtrace also shows the source file name and
4562 line number, as well as the arguments to the function. The program
4563 counter value is omitted if it is at the beginning of the code for that
4566 Here is an example of a backtrace. It was made with the command
4567 @samp{bt 3}, so it shows the innermost three frames.
4571 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4573 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4574 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4576 (More stack frames follow...)
4581 The display for frame zero does not begin with a program counter
4582 value, indicating that your program has stopped at the beginning of the
4583 code for line @code{993} of @code{builtin.c}.
4585 @cindex value optimized out, in backtrace
4586 @cindex function call arguments, optimized out
4587 If your program was compiled with optimizations, some compilers will
4588 optimize away arguments passed to functions if those arguments are
4589 never used after the call. Such optimizations generate code that
4590 passes arguments through registers, but doesn't store those arguments
4591 in the stack frame. @value{GDBN} has no way of displaying such
4592 arguments in stack frames other than the innermost one. Here's what
4593 such a backtrace might look like:
4597 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4599 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
4600 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
4602 (More stack frames follow...)
4607 The values of arguments that were not saved in their stack frames are
4608 shown as @samp{<value optimized out>}.
4610 If you need to display the values of such optimized-out arguments,
4611 either deduce that from other variables whose values depend on the one
4612 you are interested in, or recompile without optimizations.
4614 @cindex backtrace beyond @code{main} function
4615 @cindex program entry point
4616 @cindex startup code, and backtrace
4617 Most programs have a standard user entry point---a place where system
4618 libraries and startup code transition into user code. For C this is
4619 @code{main}@footnote{
4620 Note that embedded programs (the so-called ``free-standing''
4621 environment) are not required to have a @code{main} function as the
4622 entry point. They could even have multiple entry points.}.
4623 When @value{GDBN} finds the entry function in a backtrace
4624 it will terminate the backtrace, to avoid tracing into highly
4625 system-specific (and generally uninteresting) code.
4627 If you need to examine the startup code, or limit the number of levels
4628 in a backtrace, you can change this behavior:
4631 @item set backtrace past-main
4632 @itemx set backtrace past-main on
4633 @kindex set backtrace
4634 Backtraces will continue past the user entry point.
4636 @item set backtrace past-main off
4637 Backtraces will stop when they encounter the user entry point. This is the
4640 @item show backtrace past-main
4641 @kindex show backtrace
4642 Display the current user entry point backtrace policy.
4644 @item set backtrace past-entry
4645 @itemx set backtrace past-entry on
4646 Backtraces will continue past the internal entry point of an application.
4647 This entry point is encoded by the linker when the application is built,
4648 and is likely before the user entry point @code{main} (or equivalent) is called.
4650 @item set backtrace past-entry off
4651 Backtraces will stop when they encouter the internal entry point of an
4652 application. This is the default.
4654 @item show backtrace past-entry
4655 Display the current internal entry point backtrace policy.
4657 @item set backtrace limit @var{n}
4658 @itemx set backtrace limit 0
4659 @cindex backtrace limit
4660 Limit the backtrace to @var{n} levels. A value of zero means
4663 @item show backtrace limit
4664 Display the current limit on backtrace levels.
4668 @section Selecting a frame
4670 Most commands for examining the stack and other data in your program work on
4671 whichever stack frame is selected at the moment. Here are the commands for
4672 selecting a stack frame; all of them finish by printing a brief description
4673 of the stack frame just selected.
4676 @kindex frame@r{, selecting}
4677 @kindex f @r{(@code{frame})}
4680 Select frame number @var{n}. Recall that frame zero is the innermost
4681 (currently executing) frame, frame one is the frame that called the
4682 innermost one, and so on. The highest-numbered frame is the one for
4685 @item frame @var{addr}
4687 Select the frame at address @var{addr}. This is useful mainly if the
4688 chaining of stack frames has been damaged by a bug, making it
4689 impossible for @value{GDBN} to assign numbers properly to all frames. In
4690 addition, this can be useful when your program has multiple stacks and
4691 switches between them.
4693 On the SPARC architecture, @code{frame} needs two addresses to
4694 select an arbitrary frame: a frame pointer and a stack pointer.
4696 On the MIPS and Alpha architecture, it needs two addresses: a stack
4697 pointer and a program counter.
4699 On the 29k architecture, it needs three addresses: a register stack
4700 pointer, a program counter, and a memory stack pointer.
4704 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4705 advances toward the outermost frame, to higher frame numbers, to frames
4706 that have existed longer. @var{n} defaults to one.
4709 @kindex do @r{(@code{down})}
4711 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4712 advances toward the innermost frame, to lower frame numbers, to frames
4713 that were created more recently. @var{n} defaults to one. You may
4714 abbreviate @code{down} as @code{do}.
4717 All of these commands end by printing two lines of output describing the
4718 frame. The first line shows the frame number, the function name, the
4719 arguments, and the source file and line number of execution in that
4720 frame. The second line shows the text of that source line.
4728 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4730 10 read_input_file (argv[i]);
4734 After such a printout, the @code{list} command with no arguments
4735 prints ten lines centered on the point of execution in the frame.
4736 You can also edit the program at the point of execution with your favorite
4737 editing program by typing @code{edit}.
4738 @xref{List, ,Printing source lines},
4742 @kindex down-silently
4744 @item up-silently @var{n}
4745 @itemx down-silently @var{n}
4746 These two commands are variants of @code{up} and @code{down},
4747 respectively; they differ in that they do their work silently, without
4748 causing display of the new frame. They are intended primarily for use
4749 in @value{GDBN} command scripts, where the output might be unnecessary and
4754 @section Information about a frame
4756 There are several other commands to print information about the selected
4762 When used without any argument, this command does not change which
4763 frame is selected, but prints a brief description of the currently
4764 selected stack frame. It can be abbreviated @code{f}. With an
4765 argument, this command is used to select a stack frame.
4766 @xref{Selection, ,Selecting a frame}.
4769 @kindex info f @r{(@code{info frame})}
4772 This command prints a verbose description of the selected stack frame,
4777 the address of the frame
4779 the address of the next frame down (called by this frame)
4781 the address of the next frame up (caller of this frame)
4783 the language in which the source code corresponding to this frame is written
4785 the address of the frame's arguments
4787 the address of the frame's local variables
4789 the program counter saved in it (the address of execution in the caller frame)
4791 which registers were saved in the frame
4794 @noindent The verbose description is useful when
4795 something has gone wrong that has made the stack format fail to fit
4796 the usual conventions.
4798 @item info frame @var{addr}
4799 @itemx info f @var{addr}
4800 Print a verbose description of the frame at address @var{addr}, without
4801 selecting that frame. The selected frame remains unchanged by this
4802 command. This requires the same kind of address (more than one for some
4803 architectures) that you specify in the @code{frame} command.
4804 @xref{Selection, ,Selecting a frame}.
4808 Print the arguments of the selected frame, each on a separate line.
4812 Print the local variables of the selected frame, each on a separate
4813 line. These are all variables (declared either static or automatic)
4814 accessible at the point of execution of the selected frame.
4817 @cindex catch exceptions, list active handlers
4818 @cindex exception handlers, how to list
4820 Print a list of all the exception handlers that are active in the
4821 current stack frame at the current point of execution. To see other
4822 exception handlers, visit the associated frame (using the @code{up},
4823 @code{down}, or @code{frame} commands); then type @code{info catch}.
4824 @xref{Set Catchpoints, , Setting catchpoints}.
4830 @chapter Examining Source Files
4832 @value{GDBN} can print parts of your program's source, since the debugging
4833 information recorded in the program tells @value{GDBN} what source files were
4834 used to build it. When your program stops, @value{GDBN} spontaneously prints
4835 the line where it stopped. Likewise, when you select a stack frame
4836 (@pxref{Selection, ,Selecting a frame}), @value{GDBN} prints the line where
4837 execution in that frame has stopped. You can print other portions of
4838 source files by explicit command.
4840 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4841 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4842 @value{GDBN} under @sc{gnu} Emacs}.
4845 * List:: Printing source lines
4846 * Edit:: Editing source files
4847 * Search:: Searching source files
4848 * Source Path:: Specifying source directories
4849 * Machine Code:: Source and machine code
4853 @section Printing source lines
4856 @kindex l @r{(@code{list})}
4857 To print lines from a source file, use the @code{list} command
4858 (abbreviated @code{l}). By default, ten lines are printed.
4859 There are several ways to specify what part of the file you want to print.
4861 Here are the forms of the @code{list} command most commonly used:
4864 @item list @var{linenum}
4865 Print lines centered around line number @var{linenum} in the
4866 current source file.
4868 @item list @var{function}
4869 Print lines centered around the beginning of function
4873 Print more lines. If the last lines printed were printed with a
4874 @code{list} command, this prints lines following the last lines
4875 printed; however, if the last line printed was a solitary line printed
4876 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4877 Stack}), this prints lines centered around that line.
4880 Print lines just before the lines last printed.
4883 @cindex @code{list}, how many lines to display
4884 By default, @value{GDBN} prints ten source lines with any of these forms of
4885 the @code{list} command. You can change this using @code{set listsize}:
4888 @kindex set listsize
4889 @item set listsize @var{count}
4890 Make the @code{list} command display @var{count} source lines (unless
4891 the @code{list} argument explicitly specifies some other number).
4893 @kindex show listsize
4895 Display the number of lines that @code{list} prints.
4898 Repeating a @code{list} command with @key{RET} discards the argument,
4899 so it is equivalent to typing just @code{list}. This is more useful
4900 than listing the same lines again. An exception is made for an
4901 argument of @samp{-}; that argument is preserved in repetition so that
4902 each repetition moves up in the source file.
4905 In general, the @code{list} command expects you to supply zero, one or two
4906 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4907 of writing them, but the effect is always to specify some source line.
4908 Here is a complete description of the possible arguments for @code{list}:
4911 @item list @var{linespec}
4912 Print lines centered around the line specified by @var{linespec}.
4914 @item list @var{first},@var{last}
4915 Print lines from @var{first} to @var{last}. Both arguments are
4918 @item list ,@var{last}
4919 Print lines ending with @var{last}.
4921 @item list @var{first},
4922 Print lines starting with @var{first}.
4925 Print lines just after the lines last printed.
4928 Print lines just before the lines last printed.
4931 As described in the preceding table.
4934 Here are the ways of specifying a single source line---all the
4939 Specifies line @var{number} of the current source file.
4940 When a @code{list} command has two linespecs, this refers to
4941 the same source file as the first linespec.
4944 Specifies the line @var{offset} lines after the last line printed.
4945 When used as the second linespec in a @code{list} command that has
4946 two, this specifies the line @var{offset} lines down from the
4950 Specifies the line @var{offset} lines before the last line printed.
4952 @item @var{filename}:@var{number}
4953 Specifies line @var{number} in the source file @var{filename}.
4955 @item @var{function}
4956 Specifies the line that begins the body of the function @var{function}.
4957 For example: in C, this is the line with the open brace.
4959 @item @var{filename}:@var{function}
4960 Specifies the line of the open-brace that begins the body of the
4961 function @var{function} in the file @var{filename}. You only need the
4962 file name with a function name to avoid ambiguity when there are
4963 identically named functions in different source files.
4965 @item *@var{address}
4966 Specifies the line containing the program address @var{address}.
4967 @var{address} may be any expression.
4971 @section Editing source files
4972 @cindex editing source files
4975 @kindex e @r{(@code{edit})}
4976 To edit the lines in a source file, use the @code{edit} command.
4977 The editing program of your choice
4978 is invoked with the current line set to
4979 the active line in the program.
4980 Alternatively, there are several ways to specify what part of the file you
4981 want to print if you want to see other parts of the program.
4983 Here are the forms of the @code{edit} command most commonly used:
4987 Edit the current source file at the active line number in the program.
4989 @item edit @var{number}
4990 Edit the current source file with @var{number} as the active line number.
4992 @item edit @var{function}
4993 Edit the file containing @var{function} at the beginning of its definition.
4995 @item edit @var{filename}:@var{number}
4996 Specifies line @var{number} in the source file @var{filename}.
4998 @item edit @var{filename}:@var{function}
4999 Specifies the line that begins the body of the
5000 function @var{function} in the file @var{filename}. You only need the
5001 file name with a function name to avoid ambiguity when there are
5002 identically named functions in different source files.
5004 @item edit *@var{address}
5005 Specifies the line containing the program address @var{address}.
5006 @var{address} may be any expression.
5009 @subsection Choosing your editor
5010 You can customize @value{GDBN} to use any editor you want
5012 The only restriction is that your editor (say @code{ex}), recognizes the
5013 following command-line syntax:
5015 ex +@var{number} file
5017 The optional numeric value +@var{number} specifies the number of the line in
5018 the file where to start editing.}.
5019 By default, it is @file{@value{EDITOR}}, but you can change this
5020 by setting the environment variable @code{EDITOR} before using
5021 @value{GDBN}. For example, to configure @value{GDBN} to use the
5022 @code{vi} editor, you could use these commands with the @code{sh} shell:
5028 or in the @code{csh} shell,
5030 setenv EDITOR /usr/bin/vi
5035 @section Searching source files
5036 @cindex searching source files
5038 There are two commands for searching through the current source file for a
5043 @kindex forward-search
5044 @item forward-search @var{regexp}
5045 @itemx search @var{regexp}
5046 The command @samp{forward-search @var{regexp}} checks each line,
5047 starting with the one following the last line listed, for a match for
5048 @var{regexp}. It lists the line that is found. You can use the
5049 synonym @samp{search @var{regexp}} or abbreviate the command name as
5052 @kindex reverse-search
5053 @item reverse-search @var{regexp}
5054 The command @samp{reverse-search @var{regexp}} checks each line, starting
5055 with the one before the last line listed and going backward, for a match
5056 for @var{regexp}. It lists the line that is found. You can abbreviate
5057 this command as @code{rev}.
5061 @section Specifying source directories
5064 @cindex directories for source files
5065 Executable programs sometimes do not record the directories of the source
5066 files from which they were compiled, just the names. Even when they do,
5067 the directories could be moved between the compilation and your debugging
5068 session. @value{GDBN} has a list of directories to search for source files;
5069 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
5070 it tries all the directories in the list, in the order they are present
5071 in the list, until it finds a file with the desired name.
5073 For example, suppose an executable references the file
5074 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
5075 @file{/mnt/cross}. The file is first looked up literally; if this
5076 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
5077 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
5078 message is printed. @value{GDBN} does not look up the parts of the
5079 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
5080 Likewise, the subdirectories of the source path are not searched: if
5081 the source path is @file{/mnt/cross}, and the binary refers to
5082 @file{foo.c}, @value{GDBN} would not find it under
5083 @file{/mnt/cross/usr/src/foo-1.0/lib}.
5085 Plain file names, relative file names with leading directories, file
5086 names containing dots, etc.@: are all treated as described above; for
5087 instance, if the source path is @file{/mnt/cross}, and the source file
5088 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
5089 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
5090 that---@file{/mnt/cross/foo.c}.
5092 Note that the executable search path is @emph{not} used to locate the
5095 Whenever you reset or rearrange the source path, @value{GDBN} clears out
5096 any information it has cached about where source files are found and where
5097 each line is in the file.
5101 When you start @value{GDBN}, its source path includes only @samp{cdir}
5102 and @samp{cwd}, in that order.
5103 To add other directories, use the @code{directory} command.
5105 The search path is used to find both program source files and @value{GDBN}
5106 script files (read using the @samp{-command} option and @samp{source} command).
5108 In addition to the source path, @value{GDBN} provides a set of commands
5109 that manage a list of source path substitution rules. A @dfn{substitution
5110 rule} specifies how to rewrite source directories stored in the program's
5111 debug information in case the sources were moved to a different
5112 directory between compilation and debugging. A rule is made of
5113 two strings, the first specifying what needs to be rewritten in
5114 the path, and the second specifying how it should be rewritten.
5115 In @ref{set substitute-path}, we name these two parts @var{from} and
5116 @var{to} respectively. @value{GDBN} does a simple string replacement
5117 of @var{from} with @var{to} at the start of the directory part of the
5118 source file name, and uses that result instead of the original file
5119 name to look up the sources.
5121 Using the previous example, suppose the @file{foo-1.0} tree has been
5122 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
5123 GDB to replace @file{/usr/src} in all source path names with
5124 @file{/mnt/cross}. The first lookup will then be
5125 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
5126 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
5127 substitution rule, use the @code{set substitute-path} command
5128 (@pxref{set substitute-path}).
5130 To avoid unexpected substitution results, a rule is applied only if the
5131 @var{from} part of the directory name ends at a directory separator.
5132 For instance, a rule substituting @file{/usr/source} into
5133 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
5134 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
5135 is applied only at the begining of the directory name, this rule will
5136 not be applied to @file{/root/usr/source/baz.c} either.
5138 In many cases, you can achieve the same result using the @code{directory}
5139 command. However, @code{set substitute-path} can be more efficient in
5140 the case where the sources are organized in a complex tree with multiple
5141 subdirectories. With the @code{directory} command, you need to add each
5142 subdirectory of your project. If you moved the entire tree while
5143 preserving its internal organization, then @code{set substitute-path}
5144 allows you to direct the debugger to all the sources with one single
5147 @code{set substitute-path} is also more than just a shortcut command.
5148 The source path is only used if the file at the original location no
5149 longer exists. On the other hand, @code{set substitute-path} modifies
5150 the debugger behavior to look at the rewritten location instead. So, if
5151 for any reason a source file that is not relevant to your executable is
5152 located at the original location, a substitution rule is the only
5153 method available to point GDB at the new location.
5156 @item directory @var{dirname} @dots{}
5157 @item dir @var{dirname} @dots{}
5158 Add directory @var{dirname} to the front of the source path. Several
5159 directory names may be given to this command, separated by @samp{:}
5160 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
5161 part of absolute file names) or
5162 whitespace. You may specify a directory that is already in the source
5163 path; this moves it forward, so @value{GDBN} searches it sooner.
5167 @vindex $cdir@r{, convenience variable}
5168 @vindex $cwdr@r{, convenience variable}
5169 @cindex compilation directory
5170 @cindex current directory
5171 @cindex working directory
5172 @cindex directory, current
5173 @cindex directory, compilation
5174 You can use the string @samp{$cdir} to refer to the compilation
5175 directory (if one is recorded), and @samp{$cwd} to refer to the current
5176 working directory. @samp{$cwd} is not the same as @samp{.}---the former
5177 tracks the current working directory as it changes during your @value{GDBN}
5178 session, while the latter is immediately expanded to the current
5179 directory at the time you add an entry to the source path.
5182 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
5184 @c RET-repeat for @code{directory} is explicitly disabled, but since
5185 @c repeating it would be a no-op we do not say that. (thanks to RMS)
5187 @item show directories
5188 @kindex show directories
5189 Print the source path: show which directories it contains.
5191 @anchor{set substitute-path}
5192 @item set substitute-path @var{from} @var{to}
5193 @kindex set substitute-path
5194 Define a source path substitution rule, and add it at the end of the
5195 current list of existing substitution rules. If a rule with the same
5196 @var{from} was already defined, then the old rule is also deleted.
5198 For example, if the file @file{/foo/bar/baz.c} was moved to
5199 @file{/mnt/cross/baz.c}, then the command
5202 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
5206 will tell @value{GDBN} to replace @samp{/usr/src} with
5207 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
5208 @file{baz.c} even though it was moved.
5210 In the case when more than one substitution rule have been defined,
5211 the rules are evaluated one by one in the order where they have been
5212 defined. The first one matching, if any, is selected to perform
5215 For instance, if we had entered the following commands:
5218 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
5219 (@value{GDBP}) set substitute-path /usr/src /mnt/src
5223 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
5224 @file{/mnt/include/defs.h} by using the first rule. However, it would
5225 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
5226 @file{/mnt/src/lib/foo.c}.
5229 @item unset substitute-path [path]
5230 @kindex unset substitute-path
5231 If a path is specified, search the current list of substitution rules
5232 for a rule that would rewrite that path. Delete that rule if found.
5233 A warning is emitted by the debugger if no rule could be found.
5235 If no path is specified, then all substitution rules are deleted.
5237 @item show substitute-path [path]
5238 @kindex show substitute-path
5239 If a path is specified, then print the source path substitution rule
5240 which would rewrite that path, if any.
5242 If no path is specified, then print all existing source path substitution
5247 If your source path is cluttered with directories that are no longer of
5248 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
5249 versions of source. You can correct the situation as follows:
5253 Use @code{directory} with no argument to reset the source path to its default value.
5256 Use @code{directory} with suitable arguments to reinstall the
5257 directories you want in the source path. You can add all the
5258 directories in one command.
5262 @section Source and machine code
5263 @cindex source line and its code address
5265 You can use the command @code{info line} to map source lines to program
5266 addresses (and vice versa), and the command @code{disassemble} to display
5267 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
5268 mode, the @code{info line} command causes the arrow to point to the
5269 line specified. Also, @code{info line} prints addresses in symbolic form as
5274 @item info line @var{linespec}
5275 Print the starting and ending addresses of the compiled code for
5276 source line @var{linespec}. You can specify source lines in any of
5277 the ways understood by the @code{list} command (@pxref{List, ,Printing
5281 For example, we can use @code{info line} to discover the location of
5282 the object code for the first line of function
5283 @code{m4_changequote}:
5285 @c FIXME: I think this example should also show the addresses in
5286 @c symbolic form, as they usually would be displayed.
5288 (@value{GDBP}) info line m4_changequote
5289 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
5293 @cindex code address and its source line
5294 We can also inquire (using @code{*@var{addr}} as the form for
5295 @var{linespec}) what source line covers a particular address:
5297 (@value{GDBP}) info line *0x63ff
5298 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
5301 @cindex @code{$_} and @code{info line}
5302 @cindex @code{x} command, default address
5303 @kindex x@r{(examine), and} info line
5304 After @code{info line}, the default address for the @code{x} command
5305 is changed to the starting address of the line, so that @samp{x/i} is
5306 sufficient to begin examining the machine code (@pxref{Memory,
5307 ,Examining memory}). Also, this address is saved as the value of the
5308 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
5313 @cindex assembly instructions
5314 @cindex instructions, assembly
5315 @cindex machine instructions
5316 @cindex listing machine instructions
5318 This specialized command dumps a range of memory as machine
5319 instructions. The default memory range is the function surrounding the
5320 program counter of the selected frame. A single argument to this
5321 command is a program counter value; @value{GDBN} dumps the function
5322 surrounding this value. Two arguments specify a range of addresses
5323 (first inclusive, second exclusive) to dump.
5326 The following example shows the disassembly of a range of addresses of
5327 HP PA-RISC 2.0 code:
5330 (@value{GDBP}) disas 0x32c4 0x32e4
5331 Dump of assembler code from 0x32c4 to 0x32e4:
5332 0x32c4 <main+204>: addil 0,dp
5333 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
5334 0x32cc <main+212>: ldil 0x3000,r31
5335 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
5336 0x32d4 <main+220>: ldo 0(r31),rp
5337 0x32d8 <main+224>: addil -0x800,dp
5338 0x32dc <main+228>: ldo 0x588(r1),r26
5339 0x32e0 <main+232>: ldil 0x3000,r31
5340 End of assembler dump.
5343 Some architectures have more than one commonly-used set of instruction
5344 mnemonics or other syntax.
5346 For programs that were dynamically linked and use shared libraries,
5347 instructions that call functions or branch to locations in the shared
5348 libraries might show a seemingly bogus location---it's actually a
5349 location of the relocation table. On some architectures, @value{GDBN}
5350 might be able to resolve these to actual function names.
5353 @kindex set disassembly-flavor
5354 @cindex Intel disassembly flavor
5355 @cindex AT&T disassembly flavor
5356 @item set disassembly-flavor @var{instruction-set}
5357 Select the instruction set to use when disassembling the
5358 program via the @code{disassemble} or @code{x/i} commands.
5360 Currently this command is only defined for the Intel x86 family. You
5361 can set @var{instruction-set} to either @code{intel} or @code{att}.
5362 The default is @code{att}, the AT&T flavor used by default by Unix
5363 assemblers for x86-based targets.
5365 @kindex show disassembly-flavor
5366 @item show disassembly-flavor
5367 Show the current setting of the disassembly flavor.
5372 @chapter Examining Data
5374 @cindex printing data
5375 @cindex examining data
5378 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
5379 @c document because it is nonstandard... Under Epoch it displays in a
5380 @c different window or something like that.
5381 The usual way to examine data in your program is with the @code{print}
5382 command (abbreviated @code{p}), or its synonym @code{inspect}. It
5383 evaluates and prints the value of an expression of the language your
5384 program is written in (@pxref{Languages, ,Using @value{GDBN} with
5385 Different Languages}).
5388 @item print @var{expr}
5389 @itemx print /@var{f} @var{expr}
5390 @var{expr} is an expression (in the source language). By default the
5391 value of @var{expr} is printed in a format appropriate to its data type;
5392 you can choose a different format by specifying @samp{/@var{f}}, where
5393 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
5397 @itemx print /@var{f}
5398 @cindex reprint the last value
5399 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
5400 @dfn{value history}; @pxref{Value History, ,Value history}). This allows you to
5401 conveniently inspect the same value in an alternative format.
5404 A more low-level way of examining data is with the @code{x} command.
5405 It examines data in memory at a specified address and prints it in a
5406 specified format. @xref{Memory, ,Examining memory}.
5408 If you are interested in information about types, or about how the
5409 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
5410 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
5414 * Expressions:: Expressions
5415 * Variables:: Program variables
5416 * Arrays:: Artificial arrays
5417 * Output Formats:: Output formats
5418 * Memory:: Examining memory
5419 * Auto Display:: Automatic display
5420 * Print Settings:: Print settings
5421 * Value History:: Value history
5422 * Convenience Vars:: Convenience variables
5423 * Registers:: Registers
5424 * Floating Point Hardware:: Floating point hardware
5425 * Vector Unit:: Vector Unit
5426 * OS Information:: Auxiliary data provided by operating system
5427 * Memory Region Attributes:: Memory region attributes
5428 * Dump/Restore Files:: Copy between memory and a file
5429 * Core File Generation:: Cause a program dump its core
5430 * Character Sets:: Debugging programs that use a different
5431 character set than GDB does
5432 * Caching Remote Data:: Data caching for remote targets
5436 @section Expressions
5439 @code{print} and many other @value{GDBN} commands accept an expression and
5440 compute its value. Any kind of constant, variable or operator defined
5441 by the programming language you are using is valid in an expression in
5442 @value{GDBN}. This includes conditional expressions, function calls,
5443 casts, and string constants. It also includes preprocessor macros, if
5444 you compiled your program to include this information; see
5447 @cindex arrays in expressions
5448 @value{GDBN} supports array constants in expressions input by
5449 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
5450 you can use the command @code{print @{1, 2, 3@}} to build up an array in
5451 memory that is @code{malloc}ed in the target program.
5453 Because C is so widespread, most of the expressions shown in examples in
5454 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
5455 Languages}, for information on how to use expressions in other
5458 In this section, we discuss operators that you can use in @value{GDBN}
5459 expressions regardless of your programming language.
5461 @cindex casts, in expressions
5462 Casts are supported in all languages, not just in C, because it is so
5463 useful to cast a number into a pointer in order to examine a structure
5464 at that address in memory.
5465 @c FIXME: casts supported---Mod2 true?
5467 @value{GDBN} supports these operators, in addition to those common
5468 to programming languages:
5472 @samp{@@} is a binary operator for treating parts of memory as arrays.
5473 @xref{Arrays, ,Artificial arrays}, for more information.
5476 @samp{::} allows you to specify a variable in terms of the file or
5477 function where it is defined. @xref{Variables, ,Program variables}.
5479 @cindex @{@var{type}@}
5480 @cindex type casting memory
5481 @cindex memory, viewing as typed object
5482 @cindex casts, to view memory
5483 @item @{@var{type}@} @var{addr}
5484 Refers to an object of type @var{type} stored at address @var{addr} in
5485 memory. @var{addr} may be any expression whose value is an integer or
5486 pointer (but parentheses are required around binary operators, just as in
5487 a cast). This construct is allowed regardless of what kind of data is
5488 normally supposed to reside at @var{addr}.
5492 @section Program variables
5494 The most common kind of expression to use is the name of a variable
5497 Variables in expressions are understood in the selected stack frame
5498 (@pxref{Selection, ,Selecting a frame}); they must be either:
5502 global (or file-static)
5509 visible according to the scope rules of the
5510 programming language from the point of execution in that frame
5513 @noindent This means that in the function
5528 you can examine and use the variable @code{a} whenever your program is
5529 executing within the function @code{foo}, but you can only use or
5530 examine the variable @code{b} while your program is executing inside
5531 the block where @code{b} is declared.
5533 @cindex variable name conflict
5534 There is an exception: you can refer to a variable or function whose
5535 scope is a single source file even if the current execution point is not
5536 in this file. But it is possible to have more than one such variable or
5537 function with the same name (in different source files). If that
5538 happens, referring to that name has unpredictable effects. If you wish,
5539 you can specify a static variable in a particular function or file,
5540 using the colon-colon (@code{::}) notation:
5542 @cindex colon-colon, context for variables/functions
5544 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
5545 @cindex @code{::}, context for variables/functions
5548 @var{file}::@var{variable}
5549 @var{function}::@var{variable}
5553 Here @var{file} or @var{function} is the name of the context for the
5554 static @var{variable}. In the case of file names, you can use quotes to
5555 make sure @value{GDBN} parses the file name as a single word---for example,
5556 to print a global value of @code{x} defined in @file{f2.c}:
5559 (@value{GDBP}) p 'f2.c'::x
5562 @cindex C@t{++} scope resolution
5563 This use of @samp{::} is very rarely in conflict with the very similar
5564 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
5565 scope resolution operator in @value{GDBN} expressions.
5566 @c FIXME: Um, so what happens in one of those rare cases where it's in
5569 @cindex wrong values
5570 @cindex variable values, wrong
5571 @cindex function entry/exit, wrong values of variables
5572 @cindex optimized code, wrong values of variables
5574 @emph{Warning:} Occasionally, a local variable may appear to have the
5575 wrong value at certain points in a function---just after entry to a new
5576 scope, and just before exit.
5578 You may see this problem when you are stepping by machine instructions.
5579 This is because, on most machines, it takes more than one instruction to
5580 set up a stack frame (including local variable definitions); if you are
5581 stepping by machine instructions, variables may appear to have the wrong
5582 values until the stack frame is completely built. On exit, it usually
5583 also takes more than one machine instruction to destroy a stack frame;
5584 after you begin stepping through that group of instructions, local
5585 variable definitions may be gone.
5587 This may also happen when the compiler does significant optimizations.
5588 To be sure of always seeing accurate values, turn off all optimization
5591 @cindex ``No symbol "foo" in current context''
5592 Another possible effect of compiler optimizations is to optimize
5593 unused variables out of existence, or assign variables to registers (as
5594 opposed to memory addresses). Depending on the support for such cases
5595 offered by the debug info format used by the compiler, @value{GDBN}
5596 might not be able to display values for such local variables. If that
5597 happens, @value{GDBN} will print a message like this:
5600 No symbol "foo" in current context.
5603 To solve such problems, either recompile without optimizations, or use a
5604 different debug info format, if the compiler supports several such
5605 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
5606 usually supports the @option{-gstabs+} option. @option{-gstabs+}
5607 produces debug info in a format that is superior to formats such as
5608 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
5609 an effective form for debug info. @xref{Debugging Options,,Options
5610 for Debugging Your Program or @sc{gnu} CC, gcc.info, Using @sc{gnu} CC}.
5611 @xref{C, , Debugging C++}, for more info about debug info formats
5612 that are best suited to C@t{++} programs.
5614 If you ask to print an object whose contents are unknown to
5615 @value{GDBN}, e.g., because its data type is not completely specified
5616 by the debug information, @value{GDBN} will say @samp{<incomplete
5617 type>}. @xref{Symbols, incomplete type}, for more about this.
5620 @section Artificial arrays
5622 @cindex artificial array
5624 @kindex @@@r{, referencing memory as an array}
5625 It is often useful to print out several successive objects of the
5626 same type in memory; a section of an array, or an array of
5627 dynamically determined size for which only a pointer exists in the
5630 You can do this by referring to a contiguous span of memory as an
5631 @dfn{artificial array}, using the binary operator @samp{@@}. The left
5632 operand of @samp{@@} should be the first element of the desired array
5633 and be an individual object. The right operand should be the desired length
5634 of the array. The result is an array value whose elements are all of
5635 the type of the left argument. The first element is actually the left
5636 argument; the second element comes from bytes of memory immediately
5637 following those that hold the first element, and so on. Here is an
5638 example. If a program says
5641 int *array = (int *) malloc (len * sizeof (int));
5645 you can print the contents of @code{array} with
5651 The left operand of @samp{@@} must reside in memory. Array values made
5652 with @samp{@@} in this way behave just like other arrays in terms of
5653 subscripting, and are coerced to pointers when used in expressions.
5654 Artificial arrays most often appear in expressions via the value history
5655 (@pxref{Value History, ,Value history}), after printing one out.
5657 Another way to create an artificial array is to use a cast.
5658 This re-interprets a value as if it were an array.
5659 The value need not be in memory:
5661 (@value{GDBP}) p/x (short[2])0x12345678
5662 $1 = @{0x1234, 0x5678@}
5665 As a convenience, if you leave the array length out (as in
5666 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
5667 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
5669 (@value{GDBP}) p/x (short[])0x12345678
5670 $2 = @{0x1234, 0x5678@}
5673 Sometimes the artificial array mechanism is not quite enough; in
5674 moderately complex data structures, the elements of interest may not
5675 actually be adjacent---for example, if you are interested in the values
5676 of pointers in an array. One useful work-around in this situation is
5677 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
5678 variables}) as a counter in an expression that prints the first
5679 interesting value, and then repeat that expression via @key{RET}. For
5680 instance, suppose you have an array @code{dtab} of pointers to
5681 structures, and you are interested in the values of a field @code{fv}
5682 in each structure. Here is an example of what you might type:
5692 @node Output Formats
5693 @section Output formats
5695 @cindex formatted output
5696 @cindex output formats
5697 By default, @value{GDBN} prints a value according to its data type. Sometimes
5698 this is not what you want. For example, you might want to print a number
5699 in hex, or a pointer in decimal. Or you might want to view data in memory
5700 at a certain address as a character string or as an instruction. To do
5701 these things, specify an @dfn{output format} when you print a value.
5703 The simplest use of output formats is to say how to print a value
5704 already computed. This is done by starting the arguments of the
5705 @code{print} command with a slash and a format letter. The format
5706 letters supported are:
5710 Regard the bits of the value as an integer, and print the integer in
5714 Print as integer in signed decimal.
5717 Print as integer in unsigned decimal.
5720 Print as integer in octal.
5723 Print as integer in binary. The letter @samp{t} stands for ``two''.
5724 @footnote{@samp{b} cannot be used because these format letters are also
5725 used with the @code{x} command, where @samp{b} stands for ``byte'';
5726 see @ref{Memory,,Examining memory}.}
5729 @cindex unknown address, locating
5730 @cindex locate address
5731 Print as an address, both absolute in hexadecimal and as an offset from
5732 the nearest preceding symbol. You can use this format used to discover
5733 where (in what function) an unknown address is located:
5736 (@value{GDBP}) p/a 0x54320
5737 $3 = 0x54320 <_initialize_vx+396>
5741 The command @code{info symbol 0x54320} yields similar results.
5742 @xref{Symbols, info symbol}.
5745 Regard as an integer and print it as a character constant. This
5746 prints both the numerical value and its character representation. The
5747 character representation is replaced with the octal escape @samp{\nnn}
5748 for characters outside the 7-bit @sc{ascii} range.
5751 Regard the bits of the value as a floating point number and print
5752 using typical floating point syntax.
5755 For example, to print the program counter in hex (@pxref{Registers}), type
5762 Note that no space is required before the slash; this is because command
5763 names in @value{GDBN} cannot contain a slash.
5765 To reprint the last value in the value history with a different format,
5766 you can use the @code{print} command with just a format and no
5767 expression. For example, @samp{p/x} reprints the last value in hex.
5770 @section Examining memory
5772 You can use the command @code{x} (for ``examine'') to examine memory in
5773 any of several formats, independently of your program's data types.
5775 @cindex examining memory
5777 @kindex x @r{(examine memory)}
5778 @item x/@var{nfu} @var{addr}
5781 Use the @code{x} command to examine memory.
5784 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
5785 much memory to display and how to format it; @var{addr} is an
5786 expression giving the address where you want to start displaying memory.
5787 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
5788 Several commands set convenient defaults for @var{addr}.
5791 @item @var{n}, the repeat count
5792 The repeat count is a decimal integer; the default is 1. It specifies
5793 how much memory (counting by units @var{u}) to display.
5794 @c This really is **decimal**; unaffected by 'set radix' as of GDB
5797 @item @var{f}, the display format
5798 The display format is one of the formats used by @code{print}
5799 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
5800 @samp{f}), and in addition @samp{s} (for null-terminated strings) and
5801 @samp{i} (for machine instructions). The default is @samp{x}
5802 (hexadecimal) initially. The default changes each time you use either
5803 @code{x} or @code{print}.
5805 @item @var{u}, the unit size
5806 The unit size is any of
5812 Halfwords (two bytes).
5814 Words (four bytes). This is the initial default.
5816 Giant words (eight bytes).
5819 Each time you specify a unit size with @code{x}, that size becomes the
5820 default unit the next time you use @code{x}. (For the @samp{s} and
5821 @samp{i} formats, the unit size is ignored and is normally not written.)
5823 @item @var{addr}, starting display address
5824 @var{addr} is the address where you want @value{GDBN} to begin displaying
5825 memory. The expression need not have a pointer value (though it may);
5826 it is always interpreted as an integer address of a byte of memory.
5827 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
5828 @var{addr} is usually just after the last address examined---but several
5829 other commands also set the default address: @code{info breakpoints} (to
5830 the address of the last breakpoint listed), @code{info line} (to the
5831 starting address of a line), and @code{print} (if you use it to display
5832 a value from memory).
5835 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
5836 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
5837 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
5838 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
5839 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
5841 Since the letters indicating unit sizes are all distinct from the
5842 letters specifying output formats, you do not have to remember whether
5843 unit size or format comes first; either order works. The output
5844 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
5845 (However, the count @var{n} must come first; @samp{wx4} does not work.)
5847 Even though the unit size @var{u} is ignored for the formats @samp{s}
5848 and @samp{i}, you might still want to use a count @var{n}; for example,
5849 @samp{3i} specifies that you want to see three machine instructions,
5850 including any operands. The command @code{disassemble} gives an
5851 alternative way of inspecting machine instructions; see @ref{Machine
5852 Code,,Source and machine code}.
5854 All the defaults for the arguments to @code{x} are designed to make it
5855 easy to continue scanning memory with minimal specifications each time
5856 you use @code{x}. For example, after you have inspected three machine
5857 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
5858 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
5859 the repeat count @var{n} is used again; the other arguments default as
5860 for successive uses of @code{x}.
5862 @cindex @code{$_}, @code{$__}, and value history
5863 The addresses and contents printed by the @code{x} command are not saved
5864 in the value history because there is often too much of them and they
5865 would get in the way. Instead, @value{GDBN} makes these values available for
5866 subsequent use in expressions as values of the convenience variables
5867 @code{$_} and @code{$__}. After an @code{x} command, the last address
5868 examined is available for use in expressions in the convenience variable
5869 @code{$_}. The contents of that address, as examined, are available in
5870 the convenience variable @code{$__}.
5872 If the @code{x} command has a repeat count, the address and contents saved
5873 are from the last memory unit printed; this is not the same as the last
5874 address printed if several units were printed on the last line of output.
5876 @cindex remote memory comparison
5877 @cindex verify remote memory image
5878 When you are debugging a program running on a remote target machine
5879 (@pxref{Remote}), you may wish to verify the program's image in the
5880 remote machine's memory against the executable file you downloaded to
5881 the target. The @code{compare-sections} command is provided for such
5885 @kindex compare-sections
5886 @item compare-sections @r{[}@var{section-name}@r{]}
5887 Compare the data of a loadable section @var{section-name} in the
5888 executable file of the program being debugged with the same section in
5889 the remote machine's memory, and report any mismatches. With no
5890 arguments, compares all loadable sections. This command's
5891 availability depends on the target's support for the @code{"qCRC"}
5896 @section Automatic display
5897 @cindex automatic display
5898 @cindex display of expressions
5900 If you find that you want to print the value of an expression frequently
5901 (to see how it changes), you might want to add it to the @dfn{automatic
5902 display list} so that @value{GDBN} prints its value each time your program stops.
5903 Each expression added to the list is given a number to identify it;
5904 to remove an expression from the list, you specify that number.
5905 The automatic display looks like this:
5909 3: bar[5] = (struct hack *) 0x3804
5913 This display shows item numbers, expressions and their current values. As with
5914 displays you request manually using @code{x} or @code{print}, you can
5915 specify the output format you prefer; in fact, @code{display} decides
5916 whether to use @code{print} or @code{x} depending on how elaborate your
5917 format specification is---it uses @code{x} if you specify a unit size,
5918 or one of the two formats (@samp{i} and @samp{s}) that are only
5919 supported by @code{x}; otherwise it uses @code{print}.
5923 @item display @var{expr}
5924 Add the expression @var{expr} to the list of expressions to display
5925 each time your program stops. @xref{Expressions, ,Expressions}.
5927 @code{display} does not repeat if you press @key{RET} again after using it.
5929 @item display/@var{fmt} @var{expr}
5930 For @var{fmt} specifying only a display format and not a size or
5931 count, add the expression @var{expr} to the auto-display list but
5932 arrange to display it each time in the specified format @var{fmt}.
5933 @xref{Output Formats,,Output formats}.
5935 @item display/@var{fmt} @var{addr}
5936 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
5937 number of units, add the expression @var{addr} as a memory address to
5938 be examined each time your program stops. Examining means in effect
5939 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining memory}.
5942 For example, @samp{display/i $pc} can be helpful, to see the machine
5943 instruction about to be executed each time execution stops (@samp{$pc}
5944 is a common name for the program counter; @pxref{Registers, ,Registers}).
5947 @kindex delete display
5949 @item undisplay @var{dnums}@dots{}
5950 @itemx delete display @var{dnums}@dots{}
5951 Remove item numbers @var{dnums} from the list of expressions to display.
5953 @code{undisplay} does not repeat if you press @key{RET} after using it.
5954 (Otherwise you would just get the error @samp{No display number @dots{}}.)
5956 @kindex disable display
5957 @item disable display @var{dnums}@dots{}
5958 Disable the display of item numbers @var{dnums}. A disabled display
5959 item is not printed automatically, but is not forgotten. It may be
5960 enabled again later.
5962 @kindex enable display
5963 @item enable display @var{dnums}@dots{}
5964 Enable display of item numbers @var{dnums}. It becomes effective once
5965 again in auto display of its expression, until you specify otherwise.
5968 Display the current values of the expressions on the list, just as is
5969 done when your program stops.
5971 @kindex info display
5973 Print the list of expressions previously set up to display
5974 automatically, each one with its item number, but without showing the
5975 values. This includes disabled expressions, which are marked as such.
5976 It also includes expressions which would not be displayed right now
5977 because they refer to automatic variables not currently available.
5980 @cindex display disabled out of scope
5981 If a display expression refers to local variables, then it does not make
5982 sense outside the lexical context for which it was set up. Such an
5983 expression is disabled when execution enters a context where one of its
5984 variables is not defined. For example, if you give the command
5985 @code{display last_char} while inside a function with an argument
5986 @code{last_char}, @value{GDBN} displays this argument while your program
5987 continues to stop inside that function. When it stops elsewhere---where
5988 there is no variable @code{last_char}---the display is disabled
5989 automatically. The next time your program stops where @code{last_char}
5990 is meaningful, you can enable the display expression once again.
5992 @node Print Settings
5993 @section Print settings
5995 @cindex format options
5996 @cindex print settings
5997 @value{GDBN} provides the following ways to control how arrays, structures,
5998 and symbols are printed.
6001 These settings are useful for debugging programs in any language:
6005 @item set print address
6006 @itemx set print address on
6007 @cindex print/don't print memory addresses
6008 @value{GDBN} prints memory addresses showing the location of stack
6009 traces, structure values, pointer values, breakpoints, and so forth,
6010 even when it also displays the contents of those addresses. The default
6011 is @code{on}. For example, this is what a stack frame display looks like with
6012 @code{set print address on}:
6017 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
6019 530 if (lquote != def_lquote)
6023 @item set print address off
6024 Do not print addresses when displaying their contents. For example,
6025 this is the same stack frame displayed with @code{set print address off}:
6029 (@value{GDBP}) set print addr off
6031 #0 set_quotes (lq="<<", rq=">>") at input.c:530
6032 530 if (lquote != def_lquote)
6036 You can use @samp{set print address off} to eliminate all machine
6037 dependent displays from the @value{GDBN} interface. For example, with
6038 @code{print address off}, you should get the same text for backtraces on
6039 all machines---whether or not they involve pointer arguments.
6042 @item show print address
6043 Show whether or not addresses are to be printed.
6046 When @value{GDBN} prints a symbolic address, it normally prints the
6047 closest earlier symbol plus an offset. If that symbol does not uniquely
6048 identify the address (for example, it is a name whose scope is a single
6049 source file), you may need to clarify. One way to do this is with
6050 @code{info line}, for example @samp{info line *0x4537}. Alternately,
6051 you can set @value{GDBN} to print the source file and line number when
6052 it prints a symbolic address:
6055 @item set print symbol-filename on
6056 @cindex source file and line of a symbol
6057 @cindex symbol, source file and line
6058 Tell @value{GDBN} to print the source file name and line number of a
6059 symbol in the symbolic form of an address.
6061 @item set print symbol-filename off
6062 Do not print source file name and line number of a symbol. This is the
6065 @item show print symbol-filename
6066 Show whether or not @value{GDBN} will print the source file name and
6067 line number of a symbol in the symbolic form of an address.
6070 Another situation where it is helpful to show symbol filenames and line
6071 numbers is when disassembling code; @value{GDBN} shows you the line
6072 number and source file that corresponds to each instruction.
6074 Also, you may wish to see the symbolic form only if the address being
6075 printed is reasonably close to the closest earlier symbol:
6078 @item set print max-symbolic-offset @var{max-offset}
6079 @cindex maximum value for offset of closest symbol
6080 Tell @value{GDBN} to only display the symbolic form of an address if the
6081 offset between the closest earlier symbol and the address is less than
6082 @var{max-offset}. The default is 0, which tells @value{GDBN}
6083 to always print the symbolic form of an address if any symbol precedes it.
6085 @item show print max-symbolic-offset
6086 Ask how large the maximum offset is that @value{GDBN} prints in a
6090 @cindex wild pointer, interpreting
6091 @cindex pointer, finding referent
6092 If you have a pointer and you are not sure where it points, try
6093 @samp{set print symbol-filename on}. Then you can determine the name
6094 and source file location of the variable where it points, using
6095 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
6096 For example, here @value{GDBN} shows that a variable @code{ptt} points
6097 at another variable @code{t}, defined in @file{hi2.c}:
6100 (@value{GDBP}) set print symbol-filename on
6101 (@value{GDBP}) p/a ptt
6102 $4 = 0xe008 <t in hi2.c>
6106 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
6107 does not show the symbol name and filename of the referent, even with
6108 the appropriate @code{set print} options turned on.
6111 Other settings control how different kinds of objects are printed:
6114 @item set print array
6115 @itemx set print array on
6116 @cindex pretty print arrays
6117 Pretty print arrays. This format is more convenient to read,
6118 but uses more space. The default is off.
6120 @item set print array off
6121 Return to compressed format for arrays.
6123 @item show print array
6124 Show whether compressed or pretty format is selected for displaying
6127 @cindex print array indexes
6128 @item set print array-indexes
6129 @itemx set print array-indexes on
6130 Print the index of each element when displaying arrays. May be more
6131 convenient to locate a given element in the array or quickly find the
6132 index of a given element in that printed array. The default is off.
6134 @item set print array-indexes off
6135 Stop printing element indexes when displaying arrays.
6137 @item show print array-indexes
6138 Show whether the index of each element is printed when displaying
6141 @item set print elements @var{number-of-elements}
6142 @cindex number of array elements to print
6143 @cindex limit on number of printed array elements
6144 Set a limit on how many elements of an array @value{GDBN} will print.
6145 If @value{GDBN} is printing a large array, it stops printing after it has
6146 printed the number of elements set by the @code{set print elements} command.
6147 This limit also applies to the display of strings.
6148 When @value{GDBN} starts, this limit is set to 200.
6149 Setting @var{number-of-elements} to zero means that the printing is unlimited.
6151 @item show print elements
6152 Display the number of elements of a large array that @value{GDBN} will print.
6153 If the number is 0, then the printing is unlimited.
6155 @item set print repeats
6156 @cindex repeated array elements
6157 Set the threshold for suppressing display of repeated array
6158 elelments. When the number of consecutive identical elements of an
6159 array exceeds the threshold, @value{GDBN} prints the string
6160 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
6161 identical repetitions, instead of displaying the identical elements
6162 themselves. Setting the threshold to zero will cause all elements to
6163 be individually printed. The default threshold is 10.
6165 @item show print repeats
6166 Display the current threshold for printing repeated identical
6169 @item set print null-stop
6170 @cindex @sc{null} elements in arrays
6171 Cause @value{GDBN} to stop printing the characters of an array when the first
6172 @sc{null} is encountered. This is useful when large arrays actually
6173 contain only short strings.
6176 @item show print null-stop
6177 Show whether @value{GDBN} stops printing an array on the first
6178 @sc{null} character.
6180 @item set print pretty on
6181 @cindex print structures in indented form
6182 @cindex indentation in structure display
6183 Cause @value{GDBN} to print structures in an indented format with one member
6184 per line, like this:
6199 @item set print pretty off
6200 Cause @value{GDBN} to print structures in a compact format, like this:
6204 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
6205 meat = 0x54 "Pork"@}
6210 This is the default format.
6212 @item show print pretty
6213 Show which format @value{GDBN} is using to print structures.
6215 @item set print sevenbit-strings on
6216 @cindex eight-bit characters in strings
6217 @cindex octal escapes in strings
6218 Print using only seven-bit characters; if this option is set,
6219 @value{GDBN} displays any eight-bit characters (in strings or
6220 character values) using the notation @code{\}@var{nnn}. This setting is
6221 best if you are working in English (@sc{ascii}) and you use the
6222 high-order bit of characters as a marker or ``meta'' bit.
6224 @item set print sevenbit-strings off
6225 Print full eight-bit characters. This allows the use of more
6226 international character sets, and is the default.
6228 @item show print sevenbit-strings
6229 Show whether or not @value{GDBN} is printing only seven-bit characters.
6231 @item set print union on
6232 @cindex unions in structures, printing
6233 Tell @value{GDBN} to print unions which are contained in structures
6234 and other unions. This is the default setting.
6236 @item set print union off
6237 Tell @value{GDBN} not to print unions which are contained in
6238 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
6241 @item show print union
6242 Ask @value{GDBN} whether or not it will print unions which are contained in
6243 structures and other unions.
6245 For example, given the declarations
6248 typedef enum @{Tree, Bug@} Species;
6249 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
6250 typedef enum @{Caterpillar, Cocoon, Butterfly@}
6261 struct thing foo = @{Tree, @{Acorn@}@};
6265 with @code{set print union on} in effect @samp{p foo} would print
6268 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
6272 and with @code{set print union off} in effect it would print
6275 $1 = @{it = Tree, form = @{...@}@}
6279 @code{set print union} affects programs written in C-like languages
6285 These settings are of interest when debugging C@t{++} programs:
6288 @cindex demangling C@t{++} names
6289 @item set print demangle
6290 @itemx set print demangle on
6291 Print C@t{++} names in their source form rather than in the encoded
6292 (``mangled'') form passed to the assembler and linker for type-safe
6293 linkage. The default is on.
6295 @item show print demangle
6296 Show whether C@t{++} names are printed in mangled or demangled form.
6298 @item set print asm-demangle
6299 @itemx set print asm-demangle on
6300 Print C@t{++} names in their source form rather than their mangled form, even
6301 in assembler code printouts such as instruction disassemblies.
6304 @item show print asm-demangle
6305 Show whether C@t{++} names in assembly listings are printed in mangled
6308 @cindex C@t{++} symbol decoding style
6309 @cindex symbol decoding style, C@t{++}
6310 @kindex set demangle-style
6311 @item set demangle-style @var{style}
6312 Choose among several encoding schemes used by different compilers to
6313 represent C@t{++} names. The choices for @var{style} are currently:
6317 Allow @value{GDBN} to choose a decoding style by inspecting your program.
6320 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
6321 This is the default.
6324 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
6327 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
6330 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
6331 @strong{Warning:} this setting alone is not sufficient to allow
6332 debugging @code{cfront}-generated executables. @value{GDBN} would
6333 require further enhancement to permit that.
6336 If you omit @var{style}, you will see a list of possible formats.
6338 @item show demangle-style
6339 Display the encoding style currently in use for decoding C@t{++} symbols.
6341 @item set print object
6342 @itemx set print object on
6343 @cindex derived type of an object, printing
6344 @cindex display derived types
6345 When displaying a pointer to an object, identify the @emph{actual}
6346 (derived) type of the object rather than the @emph{declared} type, using
6347 the virtual function table.
6349 @item set print object off
6350 Display only the declared type of objects, without reference to the
6351 virtual function table. This is the default setting.
6353 @item show print object
6354 Show whether actual, or declared, object types are displayed.
6356 @item set print static-members
6357 @itemx set print static-members on
6358 @cindex static members of C@t{++} objects
6359 Print static members when displaying a C@t{++} object. The default is on.
6361 @item set print static-members off
6362 Do not print static members when displaying a C@t{++} object.
6364 @item show print static-members
6365 Show whether C@t{++} static members are printed or not.
6367 @item set print pascal_static-members
6368 @itemx set print pascal_static-members on
6369 @cindex static members of Pacal objects
6370 @cindex Pacal objects, static members display
6371 Print static members when displaying a Pascal object. The default is on.
6373 @item set print pascal_static-members off
6374 Do not print static members when displaying a Pascal object.
6376 @item show print pascal_static-members
6377 Show whether Pascal static members are printed or not.
6379 @c These don't work with HP ANSI C++ yet.
6380 @item set print vtbl
6381 @itemx set print vtbl on
6382 @cindex pretty print C@t{++} virtual function tables
6383 @cindex virtual functions (C@t{++}) display
6384 @cindex VTBL display
6385 Pretty print C@t{++} virtual function tables. The default is off.
6386 (The @code{vtbl} commands do not work on programs compiled with the HP
6387 ANSI C@t{++} compiler (@code{aCC}).)
6389 @item set print vtbl off
6390 Do not pretty print C@t{++} virtual function tables.
6392 @item show print vtbl
6393 Show whether C@t{++} virtual function tables are pretty printed, or not.
6397 @section Value history
6399 @cindex value history
6400 @cindex history of values printed by @value{GDBN}
6401 Values printed by the @code{print} command are saved in the @value{GDBN}
6402 @dfn{value history}. This allows you to refer to them in other expressions.
6403 Values are kept until the symbol table is re-read or discarded
6404 (for example with the @code{file} or @code{symbol-file} commands).
6405 When the symbol table changes, the value history is discarded,
6406 since the values may contain pointers back to the types defined in the
6411 @cindex history number
6412 The values printed are given @dfn{history numbers} by which you can
6413 refer to them. These are successive integers starting with one.
6414 @code{print} shows you the history number assigned to a value by
6415 printing @samp{$@var{num} = } before the value; here @var{num} is the
6418 To refer to any previous value, use @samp{$} followed by the value's
6419 history number. The way @code{print} labels its output is designed to
6420 remind you of this. Just @code{$} refers to the most recent value in
6421 the history, and @code{$$} refers to the value before that.
6422 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
6423 is the value just prior to @code{$$}, @code{$$1} is equivalent to
6424 @code{$$}, and @code{$$0} is equivalent to @code{$}.
6426 For example, suppose you have just printed a pointer to a structure and
6427 want to see the contents of the structure. It suffices to type
6433 If you have a chain of structures where the component @code{next} points
6434 to the next one, you can print the contents of the next one with this:
6441 You can print successive links in the chain by repeating this
6442 command---which you can do by just typing @key{RET}.
6444 Note that the history records values, not expressions. If the value of
6445 @code{x} is 4 and you type these commands:
6453 then the value recorded in the value history by the @code{print} command
6454 remains 4 even though the value of @code{x} has changed.
6459 Print the last ten values in the value history, with their item numbers.
6460 This is like @samp{p@ $$9} repeated ten times, except that @code{show
6461 values} does not change the history.
6463 @item show values @var{n}
6464 Print ten history values centered on history item number @var{n}.
6467 Print ten history values just after the values last printed. If no more
6468 values are available, @code{show values +} produces no display.
6471 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
6472 same effect as @samp{show values +}.
6474 @node Convenience Vars
6475 @section Convenience variables
6477 @cindex convenience variables
6478 @cindex user-defined variables
6479 @value{GDBN} provides @dfn{convenience variables} that you can use within
6480 @value{GDBN} to hold on to a value and refer to it later. These variables
6481 exist entirely within @value{GDBN}; they are not part of your program, and
6482 setting a convenience variable has no direct effect on further execution
6483 of your program. That is why you can use them freely.
6485 Convenience variables are prefixed with @samp{$}. Any name preceded by
6486 @samp{$} can be used for a convenience variable, unless it is one of
6487 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
6488 (Value history references, in contrast, are @emph{numbers} preceded
6489 by @samp{$}. @xref{Value History, ,Value history}.)
6491 You can save a value in a convenience variable with an assignment
6492 expression, just as you would set a variable in your program.
6496 set $foo = *object_ptr
6500 would save in @code{$foo} the value contained in the object pointed to by
6503 Using a convenience variable for the first time creates it, but its
6504 value is @code{void} until you assign a new value. You can alter the
6505 value with another assignment at any time.
6507 Convenience variables have no fixed types. You can assign a convenience
6508 variable any type of value, including structures and arrays, even if
6509 that variable already has a value of a different type. The convenience
6510 variable, when used as an expression, has the type of its current value.
6513 @kindex show convenience
6514 @cindex show all user variables
6515 @item show convenience
6516 Print a list of convenience variables used so far, and their values.
6517 Abbreviated @code{show conv}.
6519 @kindex init-if-undefined
6520 @cindex convenience variables, initializing
6521 @item init-if-undefined $@var{variable} = @var{expression}
6522 Set a convenience variable if it has not already been set. This is useful
6523 for user-defined commands that keep some state. It is similar, in concept,
6524 to using local static variables with initializers in C (except that
6525 convenience variables are global). It can also be used to allow users to
6526 override default values used in a command script.
6528 If the variable is already defined then the expression is not evaluated so
6529 any side-effects do not occur.
6532 One of the ways to use a convenience variable is as a counter to be
6533 incremented or a pointer to be advanced. For example, to print
6534 a field from successive elements of an array of structures:
6538 print bar[$i++]->contents
6542 Repeat that command by typing @key{RET}.
6544 Some convenience variables are created automatically by @value{GDBN} and given
6545 values likely to be useful.
6548 @vindex $_@r{, convenience variable}
6550 The variable @code{$_} is automatically set by the @code{x} command to
6551 the last address examined (@pxref{Memory, ,Examining memory}). Other
6552 commands which provide a default address for @code{x} to examine also
6553 set @code{$_} to that address; these commands include @code{info line}
6554 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
6555 except when set by the @code{x} command, in which case it is a pointer
6556 to the type of @code{$__}.
6558 @vindex $__@r{, convenience variable}
6560 The variable @code{$__} is automatically set by the @code{x} command
6561 to the value found in the last address examined. Its type is chosen
6562 to match the format in which the data was printed.
6565 @vindex $_exitcode@r{, convenience variable}
6566 The variable @code{$_exitcode} is automatically set to the exit code when
6567 the program being debugged terminates.
6570 On HP-UX systems, if you refer to a function or variable name that
6571 begins with a dollar sign, @value{GDBN} searches for a user or system
6572 name first, before it searches for a convenience variable.
6578 You can refer to machine register contents, in expressions, as variables
6579 with names starting with @samp{$}. The names of registers are different
6580 for each machine; use @code{info registers} to see the names used on
6584 @kindex info registers
6585 @item info registers
6586 Print the names and values of all registers except floating-point
6587 and vector registers (in the selected stack frame).
6589 @kindex info all-registers
6590 @cindex floating point registers
6591 @item info all-registers
6592 Print the names and values of all registers, including floating-point
6593 and vector registers (in the selected stack frame).
6595 @item info registers @var{regname} @dots{}
6596 Print the @dfn{relativized} value of each specified register @var{regname}.
6597 As discussed in detail below, register values are normally relative to
6598 the selected stack frame. @var{regname} may be any register name valid on
6599 the machine you are using, with or without the initial @samp{$}.
6602 @cindex stack pointer register
6603 @cindex program counter register
6604 @cindex process status register
6605 @cindex frame pointer register
6606 @cindex standard registers
6607 @value{GDBN} has four ``standard'' register names that are available (in
6608 expressions) on most machines---whenever they do not conflict with an
6609 architecture's canonical mnemonics for registers. The register names
6610 @code{$pc} and @code{$sp} are used for the program counter register and
6611 the stack pointer. @code{$fp} is used for a register that contains a
6612 pointer to the current stack frame, and @code{$ps} is used for a
6613 register that contains the processor status. For example,
6614 you could print the program counter in hex with
6621 or print the instruction to be executed next with
6628 or add four to the stack pointer@footnote{This is a way of removing
6629 one word from the stack, on machines where stacks grow downward in
6630 memory (most machines, nowadays). This assumes that the innermost
6631 stack frame is selected; setting @code{$sp} is not allowed when other
6632 stack frames are selected. To pop entire frames off the stack,
6633 regardless of machine architecture, use @code{return};
6634 see @ref{Returning, ,Returning from a function}.} with
6640 Whenever possible, these four standard register names are available on
6641 your machine even though the machine has different canonical mnemonics,
6642 so long as there is no conflict. The @code{info registers} command
6643 shows the canonical names. For example, on the SPARC, @code{info
6644 registers} displays the processor status register as @code{$psr} but you
6645 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
6646 is an alias for the @sc{eflags} register.
6648 @value{GDBN} always considers the contents of an ordinary register as an
6649 integer when the register is examined in this way. Some machines have
6650 special registers which can hold nothing but floating point; these
6651 registers are considered to have floating point values. There is no way
6652 to refer to the contents of an ordinary register as floating point value
6653 (although you can @emph{print} it as a floating point value with
6654 @samp{print/f $@var{regname}}).
6656 Some registers have distinct ``raw'' and ``virtual'' data formats. This
6657 means that the data format in which the register contents are saved by
6658 the operating system is not the same one that your program normally
6659 sees. For example, the registers of the 68881 floating point
6660 coprocessor are always saved in ``extended'' (raw) format, but all C
6661 programs expect to work with ``double'' (virtual) format. In such
6662 cases, @value{GDBN} normally works with the virtual format only (the format
6663 that makes sense for your program), but the @code{info registers} command
6664 prints the data in both formats.
6666 @cindex SSE registers (x86)
6667 @cindex MMX registers (x86)
6668 Some machines have special registers whose contents can be interpreted
6669 in several different ways. For example, modern x86-based machines
6670 have SSE and MMX registers that can hold several values packed
6671 together in several different formats. @value{GDBN} refers to such
6672 registers in @code{struct} notation:
6675 (@value{GDBP}) print $xmm1
6677 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
6678 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
6679 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
6680 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
6681 v4_int32 = @{0, 20657912, 11, 13@},
6682 v2_int64 = @{88725056443645952, 55834574859@},
6683 uint128 = 0x0000000d0000000b013b36f800000000
6688 To set values of such registers, you need to tell @value{GDBN} which
6689 view of the register you wish to change, as if you were assigning
6690 value to a @code{struct} member:
6693 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
6696 Normally, register values are relative to the selected stack frame
6697 (@pxref{Selection, ,Selecting a frame}). This means that you get the
6698 value that the register would contain if all stack frames farther in
6699 were exited and their saved registers restored. In order to see the
6700 true contents of hardware registers, you must select the innermost
6701 frame (with @samp{frame 0}).
6703 However, @value{GDBN} must deduce where registers are saved, from the machine
6704 code generated by your compiler. If some registers are not saved, or if
6705 @value{GDBN} is unable to locate the saved registers, the selected stack
6706 frame makes no difference.
6708 @node Floating Point Hardware
6709 @section Floating point hardware
6710 @cindex floating point
6712 Depending on the configuration, @value{GDBN} may be able to give
6713 you more information about the status of the floating point hardware.
6718 Display hardware-dependent information about the floating
6719 point unit. The exact contents and layout vary depending on the
6720 floating point chip. Currently, @samp{info float} is supported on
6721 the ARM and x86 machines.
6725 @section Vector Unit
6728 Depending on the configuration, @value{GDBN} may be able to give you
6729 more information about the status of the vector unit.
6734 Display information about the vector unit. The exact contents and
6735 layout vary depending on the hardware.
6738 @node OS Information
6739 @section Operating system auxiliary information
6740 @cindex OS information
6742 @value{GDBN} provides interfaces to useful OS facilities that can help
6743 you debug your program.
6745 @cindex @code{ptrace} system call
6746 @cindex @code{struct user} contents
6747 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
6748 machines), it interfaces with the inferior via the @code{ptrace}
6749 system call. The operating system creates a special sata structure,
6750 called @code{struct user}, for this interface. You can use the
6751 command @code{info udot} to display the contents of this data
6757 Display the contents of the @code{struct user} maintained by the OS
6758 kernel for the program being debugged. @value{GDBN} displays the
6759 contents of @code{struct user} as a list of hex numbers, similar to
6760 the @code{examine} command.
6763 @cindex auxiliary vector
6764 @cindex vector, auxiliary
6765 Some operating systems supply an @dfn{auxiliary vector} to programs at
6766 startup. This is akin to the arguments and environment that you
6767 specify for a program, but contains a system-dependent variety of
6768 binary values that tell system libraries important details about the
6769 hardware, operating system, and process. Each value's purpose is
6770 identified by an integer tag; the meanings are well-known but system-specific.
6771 Depending on the configuration and operating system facilities,
6772 @value{GDBN} may be able to show you this information. For remote
6773 targets, this functionality may further depend on the remote stub's
6774 support of the @samp{qXfer:auxv:read} packet, see
6775 @ref{qXfer auxiliary vector read}.
6780 Display the auxiliary vector of the inferior, which can be either a
6781 live process or a core dump file. @value{GDBN} prints each tag value
6782 numerically, and also shows names and text descriptions for recognized
6783 tags. Some values in the vector are numbers, some bit masks, and some
6784 pointers to strings or other data. @value{GDBN} displays each value in the
6785 most appropriate form for a recognized tag, and in hexadecimal for
6786 an unrecognized tag.
6790 @node Memory Region Attributes
6791 @section Memory region attributes
6792 @cindex memory region attributes
6794 @dfn{Memory region attributes} allow you to describe special handling
6795 required by regions of your target's memory. @value{GDBN} uses
6796 attributes to determine whether to allow certain types of memory
6797 accesses; whether to use specific width accesses; and whether to cache
6798 target memory. By default the description of memory regions is
6799 fetched from the target (if the current target supports this), but the
6800 user can override the fetched regions.
6802 Defined memory regions can be individually enabled and disabled. When a
6803 memory region is disabled, @value{GDBN} uses the default attributes when
6804 accessing memory in that region. Similarly, if no memory regions have
6805 been defined, @value{GDBN} uses the default attributes when accessing
6808 When a memory region is defined, it is given a number to identify it;
6809 to enable, disable, or remove a memory region, you specify that number.
6813 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
6814 Define a memory region bounded by @var{lower} and @var{upper} with
6815 attributes @var{attributes}@dots{}, and add it to the list of regions
6816 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
6817 case: it is treated as the the target's maximum memory address.
6818 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
6821 Discard any user changes to the memory regions and use target-supplied
6822 regions, if available, or no regions if the target does not support.
6825 @item delete mem @var{nums}@dots{}
6826 Remove memory regions @var{nums}@dots{} from the list of regions
6827 monitored by @value{GDBN}.
6830 @item disable mem @var{nums}@dots{}
6831 Disable monitoring of memory regions @var{nums}@dots{}.
6832 A disabled memory region is not forgotten.
6833 It may be enabled again later.
6836 @item enable mem @var{nums}@dots{}
6837 Enable monitoring of memory regions @var{nums}@dots{}.
6841 Print a table of all defined memory regions, with the following columns
6845 @item Memory Region Number
6846 @item Enabled or Disabled.
6847 Enabled memory regions are marked with @samp{y}.
6848 Disabled memory regions are marked with @samp{n}.
6851 The address defining the inclusive lower bound of the memory region.
6854 The address defining the exclusive upper bound of the memory region.
6857 The list of attributes set for this memory region.
6862 @subsection Attributes
6864 @subsubsection Memory Access Mode
6865 The access mode attributes set whether @value{GDBN} may make read or
6866 write accesses to a memory region.
6868 While these attributes prevent @value{GDBN} from performing invalid
6869 memory accesses, they do nothing to prevent the target system, I/O DMA,
6870 etc.@: from accessing memory.
6874 Memory is read only.
6876 Memory is write only.
6878 Memory is read/write. This is the default.
6881 @subsubsection Memory Access Size
6882 The acccess size attributes tells @value{GDBN} to use specific sized
6883 accesses in the memory region. Often memory mapped device registers
6884 require specific sized accesses. If no access size attribute is
6885 specified, @value{GDBN} may use accesses of any size.
6889 Use 8 bit memory accesses.
6891 Use 16 bit memory accesses.
6893 Use 32 bit memory accesses.
6895 Use 64 bit memory accesses.
6898 @c @subsubsection Hardware/Software Breakpoints
6899 @c The hardware/software breakpoint attributes set whether @value{GDBN}
6900 @c will use hardware or software breakpoints for the internal breakpoints
6901 @c used by the step, next, finish, until, etc. commands.
6905 @c Always use hardware breakpoints
6906 @c @item swbreak (default)
6909 @subsubsection Data Cache
6910 The data cache attributes set whether @value{GDBN} will cache target
6911 memory. While this generally improves performance by reducing debug
6912 protocol overhead, it can lead to incorrect results because @value{GDBN}
6913 does not know about volatile variables or memory mapped device
6918 Enable @value{GDBN} to cache target memory.
6920 Disable @value{GDBN} from caching target memory. This is the default.
6923 @subsection Memory Access Checking
6924 @value{GDBN} can be instructed to refuse accesses to memory that is
6925 not explicitly described. This can be useful if accessing such
6926 regions has undesired effects for a specific target, or to provide
6927 better error checking. The following commands control this behaviour.
6930 @kindex set mem inaccessible-by-default
6931 @item set mem inaccessible-by-default [on|off]
6932 If @code{on} is specified, make @value{GDBN} treat memory not
6933 explicitly described by the memory ranges as non-existent and refuse accesses
6934 to such memory. The checks are only performed if there's at least one
6935 memory range defined. If @code{off} is specified, make @value{GDBN}
6936 treat the memory not explicitly described by the memory ranges as RAM.
6937 The default value is @code{off}.
6938 @kindex show mem inaccessible-by-default
6939 @item show mem inaccessible-by-default
6940 Show the current handling of accesses to unknown memory.
6944 @c @subsubsection Memory Write Verification
6945 @c The memory write verification attributes set whether @value{GDBN}
6946 @c will re-reads data after each write to verify the write was successful.
6950 @c @item noverify (default)
6953 @node Dump/Restore Files
6954 @section Copy between memory and a file
6955 @cindex dump/restore files
6956 @cindex append data to a file
6957 @cindex dump data to a file
6958 @cindex restore data from a file
6960 You can use the commands @code{dump}, @code{append}, and
6961 @code{restore} to copy data between target memory and a file. The
6962 @code{dump} and @code{append} commands write data to a file, and the
6963 @code{restore} command reads data from a file back into the inferior's
6964 memory. Files may be in binary, Motorola S-record, Intel hex, or
6965 Tektronix Hex format; however, @value{GDBN} can only append to binary
6971 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6972 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
6973 Dump the contents of memory from @var{start_addr} to @var{end_addr},
6974 or the value of @var{expr}, to @var{filename} in the given format.
6976 The @var{format} parameter may be any one of:
6983 Motorola S-record format.
6985 Tektronix Hex format.
6988 @value{GDBN} uses the same definitions of these formats as the
6989 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
6990 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
6994 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6995 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
6996 Append the contents of memory from @var{start_addr} to @var{end_addr},
6997 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
6998 (@value{GDBN} can only append data to files in raw binary form.)
7001 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
7002 Restore the contents of file @var{filename} into memory. The
7003 @code{restore} command can automatically recognize any known @sc{bfd}
7004 file format, except for raw binary. To restore a raw binary file you
7005 must specify the optional keyword @code{binary} after the filename.
7007 If @var{bias} is non-zero, its value will be added to the addresses
7008 contained in the file. Binary files always start at address zero, so
7009 they will be restored at address @var{bias}. Other bfd files have
7010 a built-in location; they will be restored at offset @var{bias}
7013 If @var{start} and/or @var{end} are non-zero, then only data between
7014 file offset @var{start} and file offset @var{end} will be restored.
7015 These offsets are relative to the addresses in the file, before
7016 the @var{bias} argument is applied.
7020 @node Core File Generation
7021 @section How to Produce a Core File from Your Program
7022 @cindex dump core from inferior
7024 A @dfn{core file} or @dfn{core dump} is a file that records the memory
7025 image of a running process and its process status (register values
7026 etc.). Its primary use is post-mortem debugging of a program that
7027 crashed while it ran outside a debugger. A program that crashes
7028 automatically produces a core file, unless this feature is disabled by
7029 the user. @xref{Files}, for information on invoking @value{GDBN} in
7030 the post-mortem debugging mode.
7032 Occasionally, you may wish to produce a core file of the program you
7033 are debugging in order to preserve a snapshot of its state.
7034 @value{GDBN} has a special command for that.
7038 @kindex generate-core-file
7039 @item generate-core-file [@var{file}]
7040 @itemx gcore [@var{file}]
7041 Produce a core dump of the inferior process. The optional argument
7042 @var{file} specifies the file name where to put the core dump. If not
7043 specified, the file name defaults to @file{core.@var{pid}}, where
7044 @var{pid} is the inferior process ID.
7046 Note that this command is implemented only for some systems (as of
7047 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
7050 @node Character Sets
7051 @section Character Sets
7052 @cindex character sets
7054 @cindex translating between character sets
7055 @cindex host character set
7056 @cindex target character set
7058 If the program you are debugging uses a different character set to
7059 represent characters and strings than the one @value{GDBN} uses itself,
7060 @value{GDBN} can automatically translate between the character sets for
7061 you. The character set @value{GDBN} uses we call the @dfn{host
7062 character set}; the one the inferior program uses we call the
7063 @dfn{target character set}.
7065 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
7066 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
7067 remote protocol (@pxref{Remote,Remote Debugging}) to debug a program
7068 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
7069 then the host character set is Latin-1, and the target character set is
7070 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
7071 target-charset EBCDIC-US}, then @value{GDBN} translates between
7072 @sc{ebcdic} and Latin 1 as you print character or string values, or use
7073 character and string literals in expressions.
7075 @value{GDBN} has no way to automatically recognize which character set
7076 the inferior program uses; you must tell it, using the @code{set
7077 target-charset} command, described below.
7079 Here are the commands for controlling @value{GDBN}'s character set
7083 @item set target-charset @var{charset}
7084 @kindex set target-charset
7085 Set the current target character set to @var{charset}. We list the
7086 character set names @value{GDBN} recognizes below, but if you type
7087 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7088 list the target character sets it supports.
7092 @item set host-charset @var{charset}
7093 @kindex set host-charset
7094 Set the current host character set to @var{charset}.
7096 By default, @value{GDBN} uses a host character set appropriate to the
7097 system it is running on; you can override that default using the
7098 @code{set host-charset} command.
7100 @value{GDBN} can only use certain character sets as its host character
7101 set. We list the character set names @value{GDBN} recognizes below, and
7102 indicate which can be host character sets, but if you type
7103 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7104 list the host character sets it supports.
7106 @item set charset @var{charset}
7108 Set the current host and target character sets to @var{charset}. As
7109 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
7110 @value{GDBN} will list the name of the character sets that can be used
7111 for both host and target.
7115 @kindex show charset
7116 Show the names of the current host and target charsets.
7118 @itemx show host-charset
7119 @kindex show host-charset
7120 Show the name of the current host charset.
7122 @itemx show target-charset
7123 @kindex show target-charset
7124 Show the name of the current target charset.
7128 @value{GDBN} currently includes support for the following character
7134 @cindex ASCII character set
7135 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
7139 @cindex ISO 8859-1 character set
7140 @cindex ISO Latin 1 character set
7141 The ISO Latin 1 character set. This extends @sc{ascii} with accented
7142 characters needed for French, German, and Spanish. @value{GDBN} can use
7143 this as its host character set.
7147 @cindex EBCDIC character set
7148 @cindex IBM1047 character set
7149 Variants of the @sc{ebcdic} character set, used on some of IBM's
7150 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
7151 @value{GDBN} cannot use these as its host character set.
7155 Note that these are all single-byte character sets. More work inside
7156 GDB is needed to support multi-byte or variable-width character
7157 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
7159 Here is an example of @value{GDBN}'s character set support in action.
7160 Assume that the following source code has been placed in the file
7161 @file{charset-test.c}:
7167 = @{72, 101, 108, 108, 111, 44, 32, 119,
7168 111, 114, 108, 100, 33, 10, 0@};
7169 char ibm1047_hello[]
7170 = @{200, 133, 147, 147, 150, 107, 64, 166,
7171 150, 153, 147, 132, 90, 37, 0@};
7175 printf ("Hello, world!\n");
7179 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
7180 containing the string @samp{Hello, world!} followed by a newline,
7181 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
7183 We compile the program, and invoke the debugger on it:
7186 $ gcc -g charset-test.c -o charset-test
7187 $ gdb -nw charset-test
7188 GNU gdb 2001-12-19-cvs
7189 Copyright 2001 Free Software Foundation, Inc.
7194 We can use the @code{show charset} command to see what character sets
7195 @value{GDBN} is currently using to interpret and display characters and
7199 (@value{GDBP}) show charset
7200 The current host and target character set is `ISO-8859-1'.
7204 For the sake of printing this manual, let's use @sc{ascii} as our
7205 initial character set:
7207 (@value{GDBP}) set charset ASCII
7208 (@value{GDBP}) show charset
7209 The current host and target character set is `ASCII'.
7213 Let's assume that @sc{ascii} is indeed the correct character set for our
7214 host system --- in other words, let's assume that if @value{GDBN} prints
7215 characters using the @sc{ascii} character set, our terminal will display
7216 them properly. Since our current target character set is also
7217 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
7220 (@value{GDBP}) print ascii_hello
7221 $1 = 0x401698 "Hello, world!\n"
7222 (@value{GDBP}) print ascii_hello[0]
7227 @value{GDBN} uses the target character set for character and string
7228 literals you use in expressions:
7231 (@value{GDBP}) print '+'
7236 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
7239 @value{GDBN} relies on the user to tell it which character set the
7240 target program uses. If we print @code{ibm1047_hello} while our target
7241 character set is still @sc{ascii}, we get jibberish:
7244 (@value{GDBP}) print ibm1047_hello
7245 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
7246 (@value{GDBP}) print ibm1047_hello[0]
7251 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
7252 @value{GDBN} tells us the character sets it supports:
7255 (@value{GDBP}) set target-charset
7256 ASCII EBCDIC-US IBM1047 ISO-8859-1
7257 (@value{GDBP}) set target-charset
7260 We can select @sc{ibm1047} as our target character set, and examine the
7261 program's strings again. Now the @sc{ascii} string is wrong, but
7262 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
7263 target character set, @sc{ibm1047}, to the host character set,
7264 @sc{ascii}, and they display correctly:
7267 (@value{GDBP}) set target-charset IBM1047
7268 (@value{GDBP}) show charset
7269 The current host character set is `ASCII'.
7270 The current target character set is `IBM1047'.
7271 (@value{GDBP}) print ascii_hello
7272 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
7273 (@value{GDBP}) print ascii_hello[0]
7275 (@value{GDBP}) print ibm1047_hello
7276 $8 = 0x4016a8 "Hello, world!\n"
7277 (@value{GDBP}) print ibm1047_hello[0]
7282 As above, @value{GDBN} uses the target character set for character and
7283 string literals you use in expressions:
7286 (@value{GDBP}) print '+'
7291 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
7294 @node Caching Remote Data
7295 @section Caching Data of Remote Targets
7296 @cindex caching data of remote targets
7298 @value{GDBN} can cache data exchanged between the debugger and a
7299 remote target (@pxref{Remote}). Such caching generally improves
7300 performance, because it reduces the overhead of the remote protocol by
7301 bundling memory reads and writes into large chunks. Unfortunately,
7302 @value{GDBN} does not currently know anything about volatile
7303 registers, and thus data caching will produce incorrect results when
7304 volatile registers are in use.
7307 @kindex set remotecache
7308 @item set remotecache on
7309 @itemx set remotecache off
7310 Set caching state for remote targets. When @code{ON}, use data
7311 caching. By default, this option is @code{OFF}.
7313 @kindex show remotecache
7314 @item show remotecache
7315 Show the current state of data caching for remote targets.
7319 Print the information about the data cache performance. The
7320 information displayed includes: the dcache width and depth; and for
7321 each cache line, how many times it was referenced, and its data and
7322 state (dirty, bad, ok, etc.). This command is useful for debugging
7323 the data cache operation.
7328 @chapter C Preprocessor Macros
7330 Some languages, such as C and C@t{++}, provide a way to define and invoke
7331 ``preprocessor macros'' which expand into strings of tokens.
7332 @value{GDBN} can evaluate expressions containing macro invocations, show
7333 the result of macro expansion, and show a macro's definition, including
7334 where it was defined.
7336 You may need to compile your program specially to provide @value{GDBN}
7337 with information about preprocessor macros. Most compilers do not
7338 include macros in their debugging information, even when you compile
7339 with the @option{-g} flag. @xref{Compilation}.
7341 A program may define a macro at one point, remove that definition later,
7342 and then provide a different definition after that. Thus, at different
7343 points in the program, a macro may have different definitions, or have
7344 no definition at all. If there is a current stack frame, @value{GDBN}
7345 uses the macros in scope at that frame's source code line. Otherwise,
7346 @value{GDBN} uses the macros in scope at the current listing location;
7349 At the moment, @value{GDBN} does not support the @code{##}
7350 token-splicing operator, the @code{#} stringification operator, or
7351 variable-arity macros.
7353 Whenever @value{GDBN} evaluates an expression, it always expands any
7354 macro invocations present in the expression. @value{GDBN} also provides
7355 the following commands for working with macros explicitly.
7359 @kindex macro expand
7360 @cindex macro expansion, showing the results of preprocessor
7361 @cindex preprocessor macro expansion, showing the results of
7362 @cindex expanding preprocessor macros
7363 @item macro expand @var{expression}
7364 @itemx macro exp @var{expression}
7365 Show the results of expanding all preprocessor macro invocations in
7366 @var{expression}. Since @value{GDBN} simply expands macros, but does
7367 not parse the result, @var{expression} need not be a valid expression;
7368 it can be any string of tokens.
7371 @item macro expand-once @var{expression}
7372 @itemx macro exp1 @var{expression}
7373 @cindex expand macro once
7374 @i{(This command is not yet implemented.)} Show the results of
7375 expanding those preprocessor macro invocations that appear explicitly in
7376 @var{expression}. Macro invocations appearing in that expansion are
7377 left unchanged. This command allows you to see the effect of a
7378 particular macro more clearly, without being confused by further
7379 expansions. Since @value{GDBN} simply expands macros, but does not
7380 parse the result, @var{expression} need not be a valid expression; it
7381 can be any string of tokens.
7384 @cindex macro definition, showing
7385 @cindex definition, showing a macro's
7386 @item info macro @var{macro}
7387 Show the definition of the macro named @var{macro}, and describe the
7388 source location where that definition was established.
7390 @kindex macro define
7391 @cindex user-defined macros
7392 @cindex defining macros interactively
7393 @cindex macros, user-defined
7394 @item macro define @var{macro} @var{replacement-list}
7395 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
7396 @i{(This command is not yet implemented.)} Introduce a definition for a
7397 preprocessor macro named @var{macro}, invocations of which are replaced
7398 by the tokens given in @var{replacement-list}. The first form of this
7399 command defines an ``object-like'' macro, which takes no arguments; the
7400 second form defines a ``function-like'' macro, which takes the arguments
7401 given in @var{arglist}.
7403 A definition introduced by this command is in scope in every expression
7404 evaluated in @value{GDBN}, until it is removed with the @command{macro
7405 undef} command, described below. The definition overrides all
7406 definitions for @var{macro} present in the program being debugged, as
7407 well as any previous user-supplied definition.
7410 @item macro undef @var{macro}
7411 @i{(This command is not yet implemented.)} Remove any user-supplied
7412 definition for the macro named @var{macro}. This command only affects
7413 definitions provided with the @command{macro define} command, described
7414 above; it cannot remove definitions present in the program being
7419 @i{(This command is not yet implemented.)} List all the macros
7420 defined using the @code{macro define} command.
7423 @cindex macros, example of debugging with
7424 Here is a transcript showing the above commands in action. First, we
7425 show our source files:
7433 #define ADD(x) (M + x)
7438 printf ("Hello, world!\n");
7440 printf ("We're so creative.\n");
7442 printf ("Goodbye, world!\n");
7449 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
7450 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
7451 compiler includes information about preprocessor macros in the debugging
7455 $ gcc -gdwarf-2 -g3 sample.c -o sample
7459 Now, we start @value{GDBN} on our sample program:
7463 GNU gdb 2002-05-06-cvs
7464 Copyright 2002 Free Software Foundation, Inc.
7465 GDB is free software, @dots{}
7469 We can expand macros and examine their definitions, even when the
7470 program is not running. @value{GDBN} uses the current listing position
7471 to decide which macro definitions are in scope:
7474 (@value{GDBP}) list main
7477 5 #define ADD(x) (M + x)
7482 10 printf ("Hello, world!\n");
7484 12 printf ("We're so creative.\n");
7485 (@value{GDBP}) info macro ADD
7486 Defined at /home/jimb/gdb/macros/play/sample.c:5
7487 #define ADD(x) (M + x)
7488 (@value{GDBP}) info macro Q
7489 Defined at /home/jimb/gdb/macros/play/sample.h:1
7490 included at /home/jimb/gdb/macros/play/sample.c:2
7492 (@value{GDBP}) macro expand ADD(1)
7493 expands to: (42 + 1)
7494 (@value{GDBP}) macro expand-once ADD(1)
7495 expands to: once (M + 1)
7499 In the example above, note that @command{macro expand-once} expands only
7500 the macro invocation explicit in the original text --- the invocation of
7501 @code{ADD} --- but does not expand the invocation of the macro @code{M},
7502 which was introduced by @code{ADD}.
7504 Once the program is running, GDB uses the macro definitions in force at
7505 the source line of the current stack frame:
7508 (@value{GDBP}) break main
7509 Breakpoint 1 at 0x8048370: file sample.c, line 10.
7511 Starting program: /home/jimb/gdb/macros/play/sample
7513 Breakpoint 1, main () at sample.c:10
7514 10 printf ("Hello, world!\n");
7518 At line 10, the definition of the macro @code{N} at line 9 is in force:
7521 (@value{GDBP}) info macro N
7522 Defined at /home/jimb/gdb/macros/play/sample.c:9
7524 (@value{GDBP}) macro expand N Q M
7526 (@value{GDBP}) print N Q M
7531 As we step over directives that remove @code{N}'s definition, and then
7532 give it a new definition, @value{GDBN} finds the definition (or lack
7533 thereof) in force at each point:
7538 12 printf ("We're so creative.\n");
7539 (@value{GDBP}) info macro N
7540 The symbol `N' has no definition as a C/C++ preprocessor macro
7541 at /home/jimb/gdb/macros/play/sample.c:12
7544 14 printf ("Goodbye, world!\n");
7545 (@value{GDBP}) info macro N
7546 Defined at /home/jimb/gdb/macros/play/sample.c:13
7548 (@value{GDBP}) macro expand N Q M
7549 expands to: 1729 < 42
7550 (@value{GDBP}) print N Q M
7557 @chapter Tracepoints
7558 @c This chapter is based on the documentation written by Michael
7559 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
7562 In some applications, it is not feasible for the debugger to interrupt
7563 the program's execution long enough for the developer to learn
7564 anything helpful about its behavior. If the program's correctness
7565 depends on its real-time behavior, delays introduced by a debugger
7566 might cause the program to change its behavior drastically, or perhaps
7567 fail, even when the code itself is correct. It is useful to be able
7568 to observe the program's behavior without interrupting it.
7570 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
7571 specify locations in the program, called @dfn{tracepoints}, and
7572 arbitrary expressions to evaluate when those tracepoints are reached.
7573 Later, using the @code{tfind} command, you can examine the values
7574 those expressions had when the program hit the tracepoints. The
7575 expressions may also denote objects in memory---structures or arrays,
7576 for example---whose values @value{GDBN} should record; while visiting
7577 a particular tracepoint, you may inspect those objects as if they were
7578 in memory at that moment. However, because @value{GDBN} records these
7579 values without interacting with you, it can do so quickly and
7580 unobtrusively, hopefully not disturbing the program's behavior.
7582 The tracepoint facility is currently available only for remote
7583 targets. @xref{Targets}. In addition, your remote target must know
7584 how to collect trace data. This functionality is implemented in the
7585 remote stub; however, none of the stubs distributed with @value{GDBN}
7586 support tracepoints as of this writing. The format of the remote
7587 packets used to implement tracepoints are described in @ref{Tracepoint
7590 This chapter describes the tracepoint commands and features.
7594 * Analyze Collected Data::
7595 * Tracepoint Variables::
7598 @node Set Tracepoints
7599 @section Commands to Set Tracepoints
7601 Before running such a @dfn{trace experiment}, an arbitrary number of
7602 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
7603 tracepoint has a number assigned to it by @value{GDBN}. Like with
7604 breakpoints, tracepoint numbers are successive integers starting from
7605 one. Many of the commands associated with tracepoints take the
7606 tracepoint number as their argument, to identify which tracepoint to
7609 For each tracepoint, you can specify, in advance, some arbitrary set
7610 of data that you want the target to collect in the trace buffer when
7611 it hits that tracepoint. The collected data can include registers,
7612 local variables, or global data. Later, you can use @value{GDBN}
7613 commands to examine the values these data had at the time the
7616 This section describes commands to set tracepoints and associated
7617 conditions and actions.
7620 * Create and Delete Tracepoints::
7621 * Enable and Disable Tracepoints::
7622 * Tracepoint Passcounts::
7623 * Tracepoint Actions::
7624 * Listing Tracepoints::
7625 * Starting and Stopping Trace Experiment::
7628 @node Create and Delete Tracepoints
7629 @subsection Create and Delete Tracepoints
7632 @cindex set tracepoint
7635 The @code{trace} command is very similar to the @code{break} command.
7636 Its argument can be a source line, a function name, or an address in
7637 the target program. @xref{Set Breaks}. The @code{trace} command
7638 defines a tracepoint, which is a point in the target program where the
7639 debugger will briefly stop, collect some data, and then allow the
7640 program to continue. Setting a tracepoint or changing its commands
7641 doesn't take effect until the next @code{tstart} command; thus, you
7642 cannot change the tracepoint attributes once a trace experiment is
7645 Here are some examples of using the @code{trace} command:
7648 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
7650 (@value{GDBP}) @b{trace +2} // 2 lines forward
7652 (@value{GDBP}) @b{trace my_function} // first source line of function
7654 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
7656 (@value{GDBP}) @b{trace *0x2117c4} // an address
7660 You can abbreviate @code{trace} as @code{tr}.
7663 @cindex last tracepoint number
7664 @cindex recent tracepoint number
7665 @cindex tracepoint number
7666 The convenience variable @code{$tpnum} records the tracepoint number
7667 of the most recently set tracepoint.
7669 @kindex delete tracepoint
7670 @cindex tracepoint deletion
7671 @item delete tracepoint @r{[}@var{num}@r{]}
7672 Permanently delete one or more tracepoints. With no argument, the
7673 default is to delete all tracepoints.
7678 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
7680 (@value{GDBP}) @b{delete trace} // remove all tracepoints
7684 You can abbreviate this command as @code{del tr}.
7687 @node Enable and Disable Tracepoints
7688 @subsection Enable and Disable Tracepoints
7691 @kindex disable tracepoint
7692 @item disable tracepoint @r{[}@var{num}@r{]}
7693 Disable tracepoint @var{num}, or all tracepoints if no argument
7694 @var{num} is given. A disabled tracepoint will have no effect during
7695 the next trace experiment, but it is not forgotten. You can re-enable
7696 a disabled tracepoint using the @code{enable tracepoint} command.
7698 @kindex enable tracepoint
7699 @item enable tracepoint @r{[}@var{num}@r{]}
7700 Enable tracepoint @var{num}, or all tracepoints. The enabled
7701 tracepoints will become effective the next time a trace experiment is
7705 @node Tracepoint Passcounts
7706 @subsection Tracepoint Passcounts
7710 @cindex tracepoint pass count
7711 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
7712 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
7713 automatically stop a trace experiment. If a tracepoint's passcount is
7714 @var{n}, then the trace experiment will be automatically stopped on
7715 the @var{n}'th time that tracepoint is hit. If the tracepoint number
7716 @var{num} is not specified, the @code{passcount} command sets the
7717 passcount of the most recently defined tracepoint. If no passcount is
7718 given, the trace experiment will run until stopped explicitly by the
7724 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
7725 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
7727 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
7728 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
7729 (@value{GDBP}) @b{trace foo}
7730 (@value{GDBP}) @b{pass 3}
7731 (@value{GDBP}) @b{trace bar}
7732 (@value{GDBP}) @b{pass 2}
7733 (@value{GDBP}) @b{trace baz}
7734 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
7735 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
7736 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
7737 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
7741 @node Tracepoint Actions
7742 @subsection Tracepoint Action Lists
7746 @cindex tracepoint actions
7747 @item actions @r{[}@var{num}@r{]}
7748 This command will prompt for a list of actions to be taken when the
7749 tracepoint is hit. If the tracepoint number @var{num} is not
7750 specified, this command sets the actions for the one that was most
7751 recently defined (so that you can define a tracepoint and then say
7752 @code{actions} without bothering about its number). You specify the
7753 actions themselves on the following lines, one action at a time, and
7754 terminate the actions list with a line containing just @code{end}. So
7755 far, the only defined actions are @code{collect} and
7756 @code{while-stepping}.
7758 @cindex remove actions from a tracepoint
7759 To remove all actions from a tracepoint, type @samp{actions @var{num}}
7760 and follow it immediately with @samp{end}.
7763 (@value{GDBP}) @b{collect @var{data}} // collect some data
7765 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
7767 (@value{GDBP}) @b{end} // signals the end of actions.
7770 In the following example, the action list begins with @code{collect}
7771 commands indicating the things to be collected when the tracepoint is
7772 hit. Then, in order to single-step and collect additional data
7773 following the tracepoint, a @code{while-stepping} command is used,
7774 followed by the list of things to be collected while stepping. The
7775 @code{while-stepping} command is terminated by its own separate
7776 @code{end} command. Lastly, the action list is terminated by an
7780 (@value{GDBP}) @b{trace foo}
7781 (@value{GDBP}) @b{actions}
7782 Enter actions for tracepoint 1, one per line:
7791 @kindex collect @r{(tracepoints)}
7792 @item collect @var{expr1}, @var{expr2}, @dots{}
7793 Collect values of the given expressions when the tracepoint is hit.
7794 This command accepts a comma-separated list of any valid expressions.
7795 In addition to global, static, or local variables, the following
7796 special arguments are supported:
7800 collect all registers
7803 collect all function arguments
7806 collect all local variables.
7809 You can give several consecutive @code{collect} commands, each one
7810 with a single argument, or one @code{collect} command with several
7811 arguments separated by commas: the effect is the same.
7813 The command @code{info scope} (@pxref{Symbols, info scope}) is
7814 particularly useful for figuring out what data to collect.
7816 @kindex while-stepping @r{(tracepoints)}
7817 @item while-stepping @var{n}
7818 Perform @var{n} single-step traces after the tracepoint, collecting
7819 new data at each step. The @code{while-stepping} command is
7820 followed by the list of what to collect while stepping (followed by
7821 its own @code{end} command):
7825 > collect $regs, myglobal
7831 You may abbreviate @code{while-stepping} as @code{ws} or
7835 @node Listing Tracepoints
7836 @subsection Listing Tracepoints
7839 @kindex info tracepoints
7841 @cindex information about tracepoints
7842 @item info tracepoints @r{[}@var{num}@r{]}
7843 Display information about the tracepoint @var{num}. If you don't specify
7844 a tracepoint number, displays information about all the tracepoints
7845 defined so far. For each tracepoint, the following information is
7852 whether it is enabled or disabled
7856 its passcount as given by the @code{passcount @var{n}} command
7858 its step count as given by the @code{while-stepping @var{n}} command
7860 where in the source files is the tracepoint set
7862 its action list as given by the @code{actions} command
7866 (@value{GDBP}) @b{info trace}
7867 Num Enb Address PassC StepC What
7868 1 y 0x002117c4 0 0 <gdb_asm>
7869 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
7870 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
7875 This command can be abbreviated @code{info tp}.
7878 @node Starting and Stopping Trace Experiment
7879 @subsection Starting and Stopping Trace Experiment
7883 @cindex start a new trace experiment
7884 @cindex collected data discarded
7886 This command takes no arguments. It starts the trace experiment, and
7887 begins collecting data. This has the side effect of discarding all
7888 the data collected in the trace buffer during the previous trace
7892 @cindex stop a running trace experiment
7894 This command takes no arguments. It ends the trace experiment, and
7895 stops collecting data.
7897 @strong{Note}: a trace experiment and data collection may stop
7898 automatically if any tracepoint's passcount is reached
7899 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
7902 @cindex status of trace data collection
7903 @cindex trace experiment, status of
7905 This command displays the status of the current trace data
7909 Here is an example of the commands we described so far:
7912 (@value{GDBP}) @b{trace gdb_c_test}
7913 (@value{GDBP}) @b{actions}
7914 Enter actions for tracepoint #1, one per line.
7915 > collect $regs,$locals,$args
7920 (@value{GDBP}) @b{tstart}
7921 [time passes @dots{}]
7922 (@value{GDBP}) @b{tstop}
7926 @node Analyze Collected Data
7927 @section Using the collected data
7929 After the tracepoint experiment ends, you use @value{GDBN} commands
7930 for examining the trace data. The basic idea is that each tracepoint
7931 collects a trace @dfn{snapshot} every time it is hit and another
7932 snapshot every time it single-steps. All these snapshots are
7933 consecutively numbered from zero and go into a buffer, and you can
7934 examine them later. The way you examine them is to @dfn{focus} on a
7935 specific trace snapshot. When the remote stub is focused on a trace
7936 snapshot, it will respond to all @value{GDBN} requests for memory and
7937 registers by reading from the buffer which belongs to that snapshot,
7938 rather than from @emph{real} memory or registers of the program being
7939 debugged. This means that @strong{all} @value{GDBN} commands
7940 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
7941 behave as if we were currently debugging the program state as it was
7942 when the tracepoint occurred. Any requests for data that are not in
7943 the buffer will fail.
7946 * tfind:: How to select a trace snapshot
7947 * tdump:: How to display all data for a snapshot
7948 * save-tracepoints:: How to save tracepoints for a future run
7952 @subsection @code{tfind @var{n}}
7955 @cindex select trace snapshot
7956 @cindex find trace snapshot
7957 The basic command for selecting a trace snapshot from the buffer is
7958 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
7959 counting from zero. If no argument @var{n} is given, the next
7960 snapshot is selected.
7962 Here are the various forms of using the @code{tfind} command.
7966 Find the first snapshot in the buffer. This is a synonym for
7967 @code{tfind 0} (since 0 is the number of the first snapshot).
7970 Stop debugging trace snapshots, resume @emph{live} debugging.
7973 Same as @samp{tfind none}.
7976 No argument means find the next trace snapshot.
7979 Find the previous trace snapshot before the current one. This permits
7980 retracing earlier steps.
7982 @item tfind tracepoint @var{num}
7983 Find the next snapshot associated with tracepoint @var{num}. Search
7984 proceeds forward from the last examined trace snapshot. If no
7985 argument @var{num} is given, it means find the next snapshot collected
7986 for the same tracepoint as the current snapshot.
7988 @item tfind pc @var{addr}
7989 Find the next snapshot associated with the value @var{addr} of the
7990 program counter. Search proceeds forward from the last examined trace
7991 snapshot. If no argument @var{addr} is given, it means find the next
7992 snapshot with the same value of PC as the current snapshot.
7994 @item tfind outside @var{addr1}, @var{addr2}
7995 Find the next snapshot whose PC is outside the given range of
7998 @item tfind range @var{addr1}, @var{addr2}
7999 Find the next snapshot whose PC is between @var{addr1} and
8000 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
8002 @item tfind line @r{[}@var{file}:@r{]}@var{n}
8003 Find the next snapshot associated with the source line @var{n}. If
8004 the optional argument @var{file} is given, refer to line @var{n} in
8005 that source file. Search proceeds forward from the last examined
8006 trace snapshot. If no argument @var{n} is given, it means find the
8007 next line other than the one currently being examined; thus saying
8008 @code{tfind line} repeatedly can appear to have the same effect as
8009 stepping from line to line in a @emph{live} debugging session.
8012 The default arguments for the @code{tfind} commands are specifically
8013 designed to make it easy to scan through the trace buffer. For
8014 instance, @code{tfind} with no argument selects the next trace
8015 snapshot, and @code{tfind -} with no argument selects the previous
8016 trace snapshot. So, by giving one @code{tfind} command, and then
8017 simply hitting @key{RET} repeatedly you can examine all the trace
8018 snapshots in order. Or, by saying @code{tfind -} and then hitting
8019 @key{RET} repeatedly you can examine the snapshots in reverse order.
8020 The @code{tfind line} command with no argument selects the snapshot
8021 for the next source line executed. The @code{tfind pc} command with
8022 no argument selects the next snapshot with the same program counter
8023 (PC) as the current frame. The @code{tfind tracepoint} command with
8024 no argument selects the next trace snapshot collected by the same
8025 tracepoint as the current one.
8027 In addition to letting you scan through the trace buffer manually,
8028 these commands make it easy to construct @value{GDBN} scripts that
8029 scan through the trace buffer and print out whatever collected data
8030 you are interested in. Thus, if we want to examine the PC, FP, and SP
8031 registers from each trace frame in the buffer, we can say this:
8034 (@value{GDBP}) @b{tfind start}
8035 (@value{GDBP}) @b{while ($trace_frame != -1)}
8036 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
8037 $trace_frame, $pc, $sp, $fp
8041 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
8042 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
8043 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
8044 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
8045 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
8046 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
8047 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
8048 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
8049 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
8050 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
8051 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
8054 Or, if we want to examine the variable @code{X} at each source line in
8058 (@value{GDBP}) @b{tfind start}
8059 (@value{GDBP}) @b{while ($trace_frame != -1)}
8060 > printf "Frame %d, X == %d\n", $trace_frame, X
8070 @subsection @code{tdump}
8072 @cindex dump all data collected at tracepoint
8073 @cindex tracepoint data, display
8075 This command takes no arguments. It prints all the data collected at
8076 the current trace snapshot.
8079 (@value{GDBP}) @b{trace 444}
8080 (@value{GDBP}) @b{actions}
8081 Enter actions for tracepoint #2, one per line:
8082 > collect $regs, $locals, $args, gdb_long_test
8085 (@value{GDBP}) @b{tstart}
8087 (@value{GDBP}) @b{tfind line 444}
8088 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
8090 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
8092 (@value{GDBP}) @b{tdump}
8093 Data collected at tracepoint 2, trace frame 1:
8094 d0 0xc4aa0085 -995491707
8098 d4 0x71aea3d 119204413
8103 a1 0x3000668 50333288
8106 a4 0x3000698 50333336
8108 fp 0x30bf3c 0x30bf3c
8109 sp 0x30bf34 0x30bf34
8111 pc 0x20b2c8 0x20b2c8
8115 p = 0x20e5b4 "gdb-test"
8122 gdb_long_test = 17 '\021'
8127 @node save-tracepoints
8128 @subsection @code{save-tracepoints @var{filename}}
8129 @kindex save-tracepoints
8130 @cindex save tracepoints for future sessions
8132 This command saves all current tracepoint definitions together with
8133 their actions and passcounts, into a file @file{@var{filename}}
8134 suitable for use in a later debugging session. To read the saved
8135 tracepoint definitions, use the @code{source} command (@pxref{Command
8138 @node Tracepoint Variables
8139 @section Convenience Variables for Tracepoints
8140 @cindex tracepoint variables
8141 @cindex convenience variables for tracepoints
8144 @vindex $trace_frame
8145 @item (int) $trace_frame
8146 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
8147 snapshot is selected.
8150 @item (int) $tracepoint
8151 The tracepoint for the current trace snapshot.
8154 @item (int) $trace_line
8155 The line number for the current trace snapshot.
8158 @item (char []) $trace_file
8159 The source file for the current trace snapshot.
8162 @item (char []) $trace_func
8163 The name of the function containing @code{$tracepoint}.
8166 Note: @code{$trace_file} is not suitable for use in @code{printf},
8167 use @code{output} instead.
8169 Here's a simple example of using these convenience variables for
8170 stepping through all the trace snapshots and printing some of their
8174 (@value{GDBP}) @b{tfind start}
8176 (@value{GDBP}) @b{while $trace_frame != -1}
8177 > output $trace_file
8178 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
8184 @chapter Debugging Programs That Use Overlays
8187 If your program is too large to fit completely in your target system's
8188 memory, you can sometimes use @dfn{overlays} to work around this
8189 problem. @value{GDBN} provides some support for debugging programs that
8193 * How Overlays Work:: A general explanation of overlays.
8194 * Overlay Commands:: Managing overlays in @value{GDBN}.
8195 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
8196 mapped by asking the inferior.
8197 * Overlay Sample Program:: A sample program using overlays.
8200 @node How Overlays Work
8201 @section How Overlays Work
8202 @cindex mapped overlays
8203 @cindex unmapped overlays
8204 @cindex load address, overlay's
8205 @cindex mapped address
8206 @cindex overlay area
8208 Suppose you have a computer whose instruction address space is only 64
8209 kilobytes long, but which has much more memory which can be accessed by
8210 other means: special instructions, segment registers, or memory
8211 management hardware, for example. Suppose further that you want to
8212 adapt a program which is larger than 64 kilobytes to run on this system.
8214 One solution is to identify modules of your program which are relatively
8215 independent, and need not call each other directly; call these modules
8216 @dfn{overlays}. Separate the overlays from the main program, and place
8217 their machine code in the larger memory. Place your main program in
8218 instruction memory, but leave at least enough space there to hold the
8219 largest overlay as well.
8221 Now, to call a function located in an overlay, you must first copy that
8222 overlay's machine code from the large memory into the space set aside
8223 for it in the instruction memory, and then jump to its entry point
8226 @c NB: In the below the mapped area's size is greater or equal to the
8227 @c size of all overlays. This is intentional to remind the developer
8228 @c that overlays don't necessarily need to be the same size.
8232 Data Instruction Larger
8233 Address Space Address Space Address Space
8234 +-----------+ +-----------+ +-----------+
8236 +-----------+ +-----------+ +-----------+<-- overlay 1
8237 | program | | main | .----| overlay 1 | load address
8238 | variables | | program | | +-----------+
8239 | and heap | | | | | |
8240 +-----------+ | | | +-----------+<-- overlay 2
8241 | | +-----------+ | | | load address
8242 +-----------+ | | | .-| overlay 2 |
8244 mapped --->+-----------+ | | +-----------+
8246 | overlay | <-' | | |
8247 | area | <---' +-----------+<-- overlay 3
8248 | | <---. | | load address
8249 +-----------+ `--| overlay 3 |
8256 @anchor{A code overlay}A code overlay
8260 The diagram (@pxref{A code overlay}) shows a system with separate data
8261 and instruction address spaces. To map an overlay, the program copies
8262 its code from the larger address space to the instruction address space.
8263 Since the overlays shown here all use the same mapped address, only one
8264 may be mapped at a time. For a system with a single address space for
8265 data and instructions, the diagram would be similar, except that the
8266 program variables and heap would share an address space with the main
8267 program and the overlay area.
8269 An overlay loaded into instruction memory and ready for use is called a
8270 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
8271 instruction memory. An overlay not present (or only partially present)
8272 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
8273 is its address in the larger memory. The mapped address is also called
8274 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
8275 called the @dfn{load memory address}, or @dfn{LMA}.
8277 Unfortunately, overlays are not a completely transparent way to adapt a
8278 program to limited instruction memory. They introduce a new set of
8279 global constraints you must keep in mind as you design your program:
8284 Before calling or returning to a function in an overlay, your program
8285 must make sure that overlay is actually mapped. Otherwise, the call or
8286 return will transfer control to the right address, but in the wrong
8287 overlay, and your program will probably crash.
8290 If the process of mapping an overlay is expensive on your system, you
8291 will need to choose your overlays carefully to minimize their effect on
8292 your program's performance.
8295 The executable file you load onto your system must contain each
8296 overlay's instructions, appearing at the overlay's load address, not its
8297 mapped address. However, each overlay's instructions must be relocated
8298 and its symbols defined as if the overlay were at its mapped address.
8299 You can use GNU linker scripts to specify different load and relocation
8300 addresses for pieces of your program; see @ref{Overlay Description,,,
8301 ld.info, Using ld: the GNU linker}.
8304 The procedure for loading executable files onto your system must be able
8305 to load their contents into the larger address space as well as the
8306 instruction and data spaces.
8310 The overlay system described above is rather simple, and could be
8311 improved in many ways:
8316 If your system has suitable bank switch registers or memory management
8317 hardware, you could use those facilities to make an overlay's load area
8318 contents simply appear at their mapped address in instruction space.
8319 This would probably be faster than copying the overlay to its mapped
8320 area in the usual way.
8323 If your overlays are small enough, you could set aside more than one
8324 overlay area, and have more than one overlay mapped at a time.
8327 You can use overlays to manage data, as well as instructions. In
8328 general, data overlays are even less transparent to your design than
8329 code overlays: whereas code overlays only require care when you call or
8330 return to functions, data overlays require care every time you access
8331 the data. Also, if you change the contents of a data overlay, you
8332 must copy its contents back out to its load address before you can copy a
8333 different data overlay into the same mapped area.
8338 @node Overlay Commands
8339 @section Overlay Commands
8341 To use @value{GDBN}'s overlay support, each overlay in your program must
8342 correspond to a separate section of the executable file. The section's
8343 virtual memory address and load memory address must be the overlay's
8344 mapped and load addresses. Identifying overlays with sections allows
8345 @value{GDBN} to determine the appropriate address of a function or
8346 variable, depending on whether the overlay is mapped or not.
8348 @value{GDBN}'s overlay commands all start with the word @code{overlay};
8349 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
8354 Disable @value{GDBN}'s overlay support. When overlay support is
8355 disabled, @value{GDBN} assumes that all functions and variables are
8356 always present at their mapped addresses. By default, @value{GDBN}'s
8357 overlay support is disabled.
8359 @item overlay manual
8360 @cindex manual overlay debugging
8361 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
8362 relies on you to tell it which overlays are mapped, and which are not,
8363 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
8364 commands described below.
8366 @item overlay map-overlay @var{overlay}
8367 @itemx overlay map @var{overlay}
8368 @cindex map an overlay
8369 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
8370 be the name of the object file section containing the overlay. When an
8371 overlay is mapped, @value{GDBN} assumes it can find the overlay's
8372 functions and variables at their mapped addresses. @value{GDBN} assumes
8373 that any other overlays whose mapped ranges overlap that of
8374 @var{overlay} are now unmapped.
8376 @item overlay unmap-overlay @var{overlay}
8377 @itemx overlay unmap @var{overlay}
8378 @cindex unmap an overlay
8379 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
8380 must be the name of the object file section containing the overlay.
8381 When an overlay is unmapped, @value{GDBN} assumes it can find the
8382 overlay's functions and variables at their load addresses.
8385 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
8386 consults a data structure the overlay manager maintains in the inferior
8387 to see which overlays are mapped. For details, see @ref{Automatic
8390 @item overlay load-target
8392 @cindex reloading the overlay table
8393 Re-read the overlay table from the inferior. Normally, @value{GDBN}
8394 re-reads the table @value{GDBN} automatically each time the inferior
8395 stops, so this command should only be necessary if you have changed the
8396 overlay mapping yourself using @value{GDBN}. This command is only
8397 useful when using automatic overlay debugging.
8399 @item overlay list-overlays
8401 @cindex listing mapped overlays
8402 Display a list of the overlays currently mapped, along with their mapped
8403 addresses, load addresses, and sizes.
8407 Normally, when @value{GDBN} prints a code address, it includes the name
8408 of the function the address falls in:
8411 (@value{GDBP}) print main
8412 $3 = @{int ()@} 0x11a0 <main>
8415 When overlay debugging is enabled, @value{GDBN} recognizes code in
8416 unmapped overlays, and prints the names of unmapped functions with
8417 asterisks around them. For example, if @code{foo} is a function in an
8418 unmapped overlay, @value{GDBN} prints it this way:
8421 (@value{GDBP}) overlay list
8422 No sections are mapped.
8423 (@value{GDBP}) print foo
8424 $5 = @{int (int)@} 0x100000 <*foo*>
8427 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
8431 (@value{GDBP}) overlay list
8432 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
8433 mapped at 0x1016 - 0x104a
8434 (@value{GDBP}) print foo
8435 $6 = @{int (int)@} 0x1016 <foo>
8438 When overlay debugging is enabled, @value{GDBN} can find the correct
8439 address for functions and variables in an overlay, whether or not the
8440 overlay is mapped. This allows most @value{GDBN} commands, like
8441 @code{break} and @code{disassemble}, to work normally, even on unmapped
8442 code. However, @value{GDBN}'s breakpoint support has some limitations:
8446 @cindex breakpoints in overlays
8447 @cindex overlays, setting breakpoints in
8448 You can set breakpoints in functions in unmapped overlays, as long as
8449 @value{GDBN} can write to the overlay at its load address.
8451 @value{GDBN} can not set hardware or simulator-based breakpoints in
8452 unmapped overlays. However, if you set a breakpoint at the end of your
8453 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
8454 you are using manual overlay management), @value{GDBN} will re-set its
8455 breakpoints properly.
8459 @node Automatic Overlay Debugging
8460 @section Automatic Overlay Debugging
8461 @cindex automatic overlay debugging
8463 @value{GDBN} can automatically track which overlays are mapped and which
8464 are not, given some simple co-operation from the overlay manager in the
8465 inferior. If you enable automatic overlay debugging with the
8466 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
8467 looks in the inferior's memory for certain variables describing the
8468 current state of the overlays.
8470 Here are the variables your overlay manager must define to support
8471 @value{GDBN}'s automatic overlay debugging:
8475 @item @code{_ovly_table}:
8476 This variable must be an array of the following structures:
8481 /* The overlay's mapped address. */
8484 /* The size of the overlay, in bytes. */
8487 /* The overlay's load address. */
8490 /* Non-zero if the overlay is currently mapped;
8492 unsigned long mapped;
8496 @item @code{_novlys}:
8497 This variable must be a four-byte signed integer, holding the total
8498 number of elements in @code{_ovly_table}.
8502 To decide whether a particular overlay is mapped or not, @value{GDBN}
8503 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
8504 @code{lma} members equal the VMA and LMA of the overlay's section in the
8505 executable file. When @value{GDBN} finds a matching entry, it consults
8506 the entry's @code{mapped} member to determine whether the overlay is
8509 In addition, your overlay manager may define a function called
8510 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
8511 will silently set a breakpoint there. If the overlay manager then
8512 calls this function whenever it has changed the overlay table, this
8513 will enable @value{GDBN} to accurately keep track of which overlays
8514 are in program memory, and update any breakpoints that may be set
8515 in overlays. This will allow breakpoints to work even if the
8516 overlays are kept in ROM or other non-writable memory while they
8517 are not being executed.
8519 @node Overlay Sample Program
8520 @section Overlay Sample Program
8521 @cindex overlay example program
8523 When linking a program which uses overlays, you must place the overlays
8524 at their load addresses, while relocating them to run at their mapped
8525 addresses. To do this, you must write a linker script (@pxref{Overlay
8526 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
8527 since linker scripts are specific to a particular host system, target
8528 architecture, and target memory layout, this manual cannot provide
8529 portable sample code demonstrating @value{GDBN}'s overlay support.
8531 However, the @value{GDBN} source distribution does contain an overlaid
8532 program, with linker scripts for a few systems, as part of its test
8533 suite. The program consists of the following files from
8534 @file{gdb/testsuite/gdb.base}:
8538 The main program file.
8540 A simple overlay manager, used by @file{overlays.c}.
8545 Overlay modules, loaded and used by @file{overlays.c}.
8548 Linker scripts for linking the test program on the @code{d10v-elf}
8549 and @code{m32r-elf} targets.
8552 You can build the test program using the @code{d10v-elf} GCC
8553 cross-compiler like this:
8556 $ d10v-elf-gcc -g -c overlays.c
8557 $ d10v-elf-gcc -g -c ovlymgr.c
8558 $ d10v-elf-gcc -g -c foo.c
8559 $ d10v-elf-gcc -g -c bar.c
8560 $ d10v-elf-gcc -g -c baz.c
8561 $ d10v-elf-gcc -g -c grbx.c
8562 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
8563 baz.o grbx.o -Wl,-Td10v.ld -o overlays
8566 The build process is identical for any other architecture, except that
8567 you must substitute the appropriate compiler and linker script for the
8568 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
8572 @chapter Using @value{GDBN} with Different Languages
8575 Although programming languages generally have common aspects, they are
8576 rarely expressed in the same manner. For instance, in ANSI C,
8577 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
8578 Modula-2, it is accomplished by @code{p^}. Values can also be
8579 represented (and displayed) differently. Hex numbers in C appear as
8580 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
8582 @cindex working language
8583 Language-specific information is built into @value{GDBN} for some languages,
8584 allowing you to express operations like the above in your program's
8585 native language, and allowing @value{GDBN} to output values in a manner
8586 consistent with the syntax of your program's native language. The
8587 language you use to build expressions is called the @dfn{working
8591 * Setting:: Switching between source languages
8592 * Show:: Displaying the language
8593 * Checks:: Type and range checks
8594 * Supported languages:: Supported languages
8595 * Unsupported languages:: Unsupported languages
8599 @section Switching between source languages
8601 There are two ways to control the working language---either have @value{GDBN}
8602 set it automatically, or select it manually yourself. You can use the
8603 @code{set language} command for either purpose. On startup, @value{GDBN}
8604 defaults to setting the language automatically. The working language is
8605 used to determine how expressions you type are interpreted, how values
8608 In addition to the working language, every source file that
8609 @value{GDBN} knows about has its own working language. For some object
8610 file formats, the compiler might indicate which language a particular
8611 source file is in. However, most of the time @value{GDBN} infers the
8612 language from the name of the file. The language of a source file
8613 controls whether C@t{++} names are demangled---this way @code{backtrace} can
8614 show each frame appropriately for its own language. There is no way to
8615 set the language of a source file from within @value{GDBN}, but you can
8616 set the language associated with a filename extension. @xref{Show, ,
8617 Displaying the language}.
8619 This is most commonly a problem when you use a program, such
8620 as @code{cfront} or @code{f2c}, that generates C but is written in
8621 another language. In that case, make the
8622 program use @code{#line} directives in its C output; that way
8623 @value{GDBN} will know the correct language of the source code of the original
8624 program, and will display that source code, not the generated C code.
8627 * Filenames:: Filename extensions and languages.
8628 * Manually:: Setting the working language manually
8629 * Automatically:: Having @value{GDBN} infer the source language
8633 @subsection List of filename extensions and languages
8635 If a source file name ends in one of the following extensions, then
8636 @value{GDBN} infers that its language is the one indicated.
8657 Objective-C source file
8664 Modula-2 source file
8668 Assembler source file. This actually behaves almost like C, but
8669 @value{GDBN} does not skip over function prologues when stepping.
8672 In addition, you may set the language associated with a filename
8673 extension. @xref{Show, , Displaying the language}.
8676 @subsection Setting the working language
8678 If you allow @value{GDBN} to set the language automatically,
8679 expressions are interpreted the same way in your debugging session and
8682 @kindex set language
8683 If you wish, you may set the language manually. To do this, issue the
8684 command @samp{set language @var{lang}}, where @var{lang} is the name of
8686 @code{c} or @code{modula-2}.
8687 For a list of the supported languages, type @samp{set language}.
8689 Setting the language manually prevents @value{GDBN} from updating the working
8690 language automatically. This can lead to confusion if you try
8691 to debug a program when the working language is not the same as the
8692 source language, when an expression is acceptable to both
8693 languages---but means different things. For instance, if the current
8694 source file were written in C, and @value{GDBN} was parsing Modula-2, a
8702 might not have the effect you intended. In C, this means to add
8703 @code{b} and @code{c} and place the result in @code{a}. The result
8704 printed would be the value of @code{a}. In Modula-2, this means to compare
8705 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
8708 @subsection Having @value{GDBN} infer the source language
8710 To have @value{GDBN} set the working language automatically, use
8711 @samp{set language local} or @samp{set language auto}. @value{GDBN}
8712 then infers the working language. That is, when your program stops in a
8713 frame (usually by encountering a breakpoint), @value{GDBN} sets the
8714 working language to the language recorded for the function in that
8715 frame. If the language for a frame is unknown (that is, if the function
8716 or block corresponding to the frame was defined in a source file that
8717 does not have a recognized extension), the current working language is
8718 not changed, and @value{GDBN} issues a warning.
8720 This may not seem necessary for most programs, which are written
8721 entirely in one source language. However, program modules and libraries
8722 written in one source language can be used by a main program written in
8723 a different source language. Using @samp{set language auto} in this
8724 case frees you from having to set the working language manually.
8727 @section Displaying the language
8729 The following commands help you find out which language is the
8730 working language, and also what language source files were written in.
8734 @kindex show language
8735 Display the current working language. This is the
8736 language you can use with commands such as @code{print} to
8737 build and compute expressions that may involve variables in your program.
8740 @kindex info frame@r{, show the source language}
8741 Display the source language for this frame. This language becomes the
8742 working language if you use an identifier from this frame.
8743 @xref{Frame Info, ,Information about a frame}, to identify the other
8744 information listed here.
8747 @kindex info source@r{, show the source language}
8748 Display the source language of this source file.
8749 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
8750 information listed here.
8753 In unusual circumstances, you may have source files with extensions
8754 not in the standard list. You can then set the extension associated
8755 with a language explicitly:
8758 @item set extension-language @var{ext} @var{language}
8759 @kindex set extension-language
8760 Tell @value{GDBN} that source files with extension @var{ext} are to be
8761 assumed as written in the source language @var{language}.
8763 @item info extensions
8764 @kindex info extensions
8765 List all the filename extensions and the associated languages.
8769 @section Type and range checking
8772 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
8773 checking are included, but they do not yet have any effect. This
8774 section documents the intended facilities.
8776 @c FIXME remove warning when type/range code added
8778 Some languages are designed to guard you against making seemingly common
8779 errors through a series of compile- and run-time checks. These include
8780 checking the type of arguments to functions and operators, and making
8781 sure mathematical overflows are caught at run time. Checks such as
8782 these help to ensure a program's correctness once it has been compiled
8783 by eliminating type mismatches, and providing active checks for range
8784 errors when your program is running.
8786 @value{GDBN} can check for conditions like the above if you wish.
8787 Although @value{GDBN} does not check the statements in your program,
8788 it can check expressions entered directly into @value{GDBN} for
8789 evaluation via the @code{print} command, for example. As with the
8790 working language, @value{GDBN} can also decide whether or not to check
8791 automatically based on your program's source language.
8792 @xref{Supported languages, ,Supported languages}, for the default
8793 settings of supported languages.
8796 * Type Checking:: An overview of type checking
8797 * Range Checking:: An overview of range checking
8800 @cindex type checking
8801 @cindex checks, type
8803 @subsection An overview of type checking
8805 Some languages, such as Modula-2, are strongly typed, meaning that the
8806 arguments to operators and functions have to be of the correct type,
8807 otherwise an error occurs. These checks prevent type mismatch
8808 errors from ever causing any run-time problems. For example,
8816 The second example fails because the @code{CARDINAL} 1 is not
8817 type-compatible with the @code{REAL} 2.3.
8819 For the expressions you use in @value{GDBN} commands, you can tell the
8820 @value{GDBN} type checker to skip checking;
8821 to treat any mismatches as errors and abandon the expression;
8822 or to only issue warnings when type mismatches occur,
8823 but evaluate the expression anyway. When you choose the last of
8824 these, @value{GDBN} evaluates expressions like the second example above, but
8825 also issues a warning.
8827 Even if you turn type checking off, there may be other reasons
8828 related to type that prevent @value{GDBN} from evaluating an expression.
8829 For instance, @value{GDBN} does not know how to add an @code{int} and
8830 a @code{struct foo}. These particular type errors have nothing to do
8831 with the language in use, and usually arise from expressions, such as
8832 the one described above, which make little sense to evaluate anyway.
8834 Each language defines to what degree it is strict about type. For
8835 instance, both Modula-2 and C require the arguments to arithmetical
8836 operators to be numbers. In C, enumerated types and pointers can be
8837 represented as numbers, so that they are valid arguments to mathematical
8838 operators. @xref{Supported languages, ,Supported languages}, for further
8839 details on specific languages.
8841 @value{GDBN} provides some additional commands for controlling the type checker:
8843 @kindex set check type
8844 @kindex show check type
8846 @item set check type auto
8847 Set type checking on or off based on the current working language.
8848 @xref{Supported languages, ,Supported languages}, for the default settings for
8851 @item set check type on
8852 @itemx set check type off
8853 Set type checking on or off, overriding the default setting for the
8854 current working language. Issue a warning if the setting does not
8855 match the language default. If any type mismatches occur in
8856 evaluating an expression while type checking is on, @value{GDBN} prints a
8857 message and aborts evaluation of the expression.
8859 @item set check type warn
8860 Cause the type checker to issue warnings, but to always attempt to
8861 evaluate the expression. Evaluating the expression may still
8862 be impossible for other reasons. For example, @value{GDBN} cannot add
8863 numbers and structures.
8866 Show the current setting of the type checker, and whether or not @value{GDBN}
8867 is setting it automatically.
8870 @cindex range checking
8871 @cindex checks, range
8872 @node Range Checking
8873 @subsection An overview of range checking
8875 In some languages (such as Modula-2), it is an error to exceed the
8876 bounds of a type; this is enforced with run-time checks. Such range
8877 checking is meant to ensure program correctness by making sure
8878 computations do not overflow, or indices on an array element access do
8879 not exceed the bounds of the array.
8881 For expressions you use in @value{GDBN} commands, you can tell
8882 @value{GDBN} to treat range errors in one of three ways: ignore them,
8883 always treat them as errors and abandon the expression, or issue
8884 warnings but evaluate the expression anyway.
8886 A range error can result from numerical overflow, from exceeding an
8887 array index bound, or when you type a constant that is not a member
8888 of any type. Some languages, however, do not treat overflows as an
8889 error. In many implementations of C, mathematical overflow causes the
8890 result to ``wrap around'' to lower values---for example, if @var{m} is
8891 the largest integer value, and @var{s} is the smallest, then
8894 @var{m} + 1 @result{} @var{s}
8897 This, too, is specific to individual languages, and in some cases
8898 specific to individual compilers or machines. @xref{Supported languages, ,
8899 Supported languages}, for further details on specific languages.
8901 @value{GDBN} provides some additional commands for controlling the range checker:
8903 @kindex set check range
8904 @kindex show check range
8906 @item set check range auto
8907 Set range checking on or off based on the current working language.
8908 @xref{Supported languages, ,Supported languages}, for the default settings for
8911 @item set check range on
8912 @itemx set check range off
8913 Set range checking on or off, overriding the default setting for the
8914 current working language. A warning is issued if the setting does not
8915 match the language default. If a range error occurs and range checking is on,
8916 then a message is printed and evaluation of the expression is aborted.
8918 @item set check range warn
8919 Output messages when the @value{GDBN} range checker detects a range error,
8920 but attempt to evaluate the expression anyway. Evaluating the
8921 expression may still be impossible for other reasons, such as accessing
8922 memory that the process does not own (a typical example from many Unix
8926 Show the current setting of the range checker, and whether or not it is
8927 being set automatically by @value{GDBN}.
8930 @node Supported languages
8931 @section Supported languages
8933 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
8934 assembly, Modula-2, and Ada.
8935 @c This is false ...
8936 Some @value{GDBN} features may be used in expressions regardless of the
8937 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
8938 and the @samp{@{type@}addr} construct (@pxref{Expressions,
8939 ,Expressions}) can be used with the constructs of any supported
8942 The following sections detail to what degree each source language is
8943 supported by @value{GDBN}. These sections are not meant to be language
8944 tutorials or references, but serve only as a reference guide to what the
8945 @value{GDBN} expression parser accepts, and what input and output
8946 formats should look like for different languages. There are many good
8947 books written on each of these languages; please look to these for a
8948 language reference or tutorial.
8952 * Objective-C:: Objective-C
8955 * Modula-2:: Modula-2
8960 @subsection C and C@t{++}
8962 @cindex C and C@t{++}
8963 @cindex expressions in C or C@t{++}
8965 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
8966 to both languages. Whenever this is the case, we discuss those languages
8970 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
8971 @cindex @sc{gnu} C@t{++}
8972 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
8973 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
8974 effectively, you must compile your C@t{++} programs with a supported
8975 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
8976 compiler (@code{aCC}).
8978 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
8979 format; if it doesn't work on your system, try the stabs+ debugging
8980 format. You can select those formats explicitly with the @code{g++}
8981 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
8982 @xref{Debugging Options,,Options for Debugging Your Program or @sc{gnu}
8983 CC, gcc.info, Using @sc{gnu} CC}.
8986 * C Operators:: C and C@t{++} operators
8987 * C Constants:: C and C@t{++} constants
8988 * C plus plus expressions:: C@t{++} expressions
8989 * C Defaults:: Default settings for C and C@t{++}
8990 * C Checks:: C and C@t{++} type and range checks
8991 * Debugging C:: @value{GDBN} and C
8992 * Debugging C plus plus:: @value{GDBN} features for C@t{++}
8996 @subsubsection C and C@t{++} operators
8998 @cindex C and C@t{++} operators
9000 Operators must be defined on values of specific types. For instance,
9001 @code{+} is defined on numbers, but not on structures. Operators are
9002 often defined on groups of types.
9004 For the purposes of C and C@t{++}, the following definitions hold:
9009 @emph{Integral types} include @code{int} with any of its storage-class
9010 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
9013 @emph{Floating-point types} include @code{float}, @code{double}, and
9014 @code{long double} (if supported by the target platform).
9017 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
9020 @emph{Scalar types} include all of the above.
9025 The following operators are supported. They are listed here
9026 in order of increasing precedence:
9030 The comma or sequencing operator. Expressions in a comma-separated list
9031 are evaluated from left to right, with the result of the entire
9032 expression being the last expression evaluated.
9035 Assignment. The value of an assignment expression is the value
9036 assigned. Defined on scalar types.
9039 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
9040 and translated to @w{@code{@var{a} = @var{a op b}}}.
9041 @w{@code{@var{op}=}} and @code{=} have the same precedence.
9042 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
9043 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
9046 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
9047 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
9051 Logical @sc{or}. Defined on integral types.
9054 Logical @sc{and}. Defined on integral types.
9057 Bitwise @sc{or}. Defined on integral types.
9060 Bitwise exclusive-@sc{or}. Defined on integral types.
9063 Bitwise @sc{and}. Defined on integral types.
9066 Equality and inequality. Defined on scalar types. The value of these
9067 expressions is 0 for false and non-zero for true.
9069 @item <@r{, }>@r{, }<=@r{, }>=
9070 Less than, greater than, less than or equal, greater than or equal.
9071 Defined on scalar types. The value of these expressions is 0 for false
9072 and non-zero for true.
9075 left shift, and right shift. Defined on integral types.
9078 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9081 Addition and subtraction. Defined on integral types, floating-point types and
9084 @item *@r{, }/@r{, }%
9085 Multiplication, division, and modulus. Multiplication and division are
9086 defined on integral and floating-point types. Modulus is defined on
9090 Increment and decrement. When appearing before a variable, the
9091 operation is performed before the variable is used in an expression;
9092 when appearing after it, the variable's value is used before the
9093 operation takes place.
9096 Pointer dereferencing. Defined on pointer types. Same precedence as
9100 Address operator. Defined on variables. Same precedence as @code{++}.
9102 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
9103 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
9104 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
9105 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
9109 Negative. Defined on integral and floating-point types. Same
9110 precedence as @code{++}.
9113 Logical negation. Defined on integral types. Same precedence as
9117 Bitwise complement operator. Defined on integral types. Same precedence as
9122 Structure member, and pointer-to-structure member. For convenience,
9123 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
9124 pointer based on the stored type information.
9125 Defined on @code{struct} and @code{union} data.
9128 Dereferences of pointers to members.
9131 Array indexing. @code{@var{a}[@var{i}]} is defined as
9132 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
9135 Function parameter list. Same precedence as @code{->}.
9138 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
9139 and @code{class} types.
9142 Doubled colons also represent the @value{GDBN} scope operator
9143 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
9147 If an operator is redefined in the user code, @value{GDBN} usually
9148 attempts to invoke the redefined version instead of using the operator's
9156 @subsubsection C and C@t{++} constants
9158 @cindex C and C@t{++} constants
9160 @value{GDBN} allows you to express the constants of C and C@t{++} in the
9165 Integer constants are a sequence of digits. Octal constants are
9166 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
9167 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
9168 @samp{l}, specifying that the constant should be treated as a
9172 Floating point constants are a sequence of digits, followed by a decimal
9173 point, followed by a sequence of digits, and optionally followed by an
9174 exponent. An exponent is of the form:
9175 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
9176 sequence of digits. The @samp{+} is optional for positive exponents.
9177 A floating-point constant may also end with a letter @samp{f} or
9178 @samp{F}, specifying that the constant should be treated as being of
9179 the @code{float} (as opposed to the default @code{double}) type; or with
9180 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
9184 Enumerated constants consist of enumerated identifiers, or their
9185 integral equivalents.
9188 Character constants are a single character surrounded by single quotes
9189 (@code{'}), or a number---the ordinal value of the corresponding character
9190 (usually its @sc{ascii} value). Within quotes, the single character may
9191 be represented by a letter or by @dfn{escape sequences}, which are of
9192 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
9193 of the character's ordinal value; or of the form @samp{\@var{x}}, where
9194 @samp{@var{x}} is a predefined special character---for example,
9195 @samp{\n} for newline.
9198 String constants are a sequence of character constants surrounded by
9199 double quotes (@code{"}). Any valid character constant (as described
9200 above) may appear. Double quotes within the string must be preceded by
9201 a backslash, so for instance @samp{"a\"b'c"} is a string of five
9205 Pointer constants are an integral value. You can also write pointers
9206 to constants using the C operator @samp{&}.
9209 Array constants are comma-separated lists surrounded by braces @samp{@{}
9210 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
9211 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
9212 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
9216 * C plus plus expressions::
9223 @node C plus plus expressions
9224 @subsubsection C@t{++} expressions
9226 @cindex expressions in C@t{++}
9227 @value{GDBN} expression handling can interpret most C@t{++} expressions.
9229 @cindex debugging C@t{++} programs
9230 @cindex C@t{++} compilers
9231 @cindex debug formats and C@t{++}
9232 @cindex @value{NGCC} and C@t{++}
9234 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
9235 proper compiler and the proper debug format. Currently, @value{GDBN}
9236 works best when debugging C@t{++} code that is compiled with
9237 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
9238 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
9239 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
9240 stabs+ as their default debug format, so you usually don't need to
9241 specify a debug format explicitly. Other compilers and/or debug formats
9242 are likely to work badly or not at all when using @value{GDBN} to debug
9248 @cindex member functions
9250 Member function calls are allowed; you can use expressions like
9253 count = aml->GetOriginal(x, y)
9256 @vindex this@r{, inside C@t{++} member functions}
9257 @cindex namespace in C@t{++}
9259 While a member function is active (in the selected stack frame), your
9260 expressions have the same namespace available as the member function;
9261 that is, @value{GDBN} allows implicit references to the class instance
9262 pointer @code{this} following the same rules as C@t{++}.
9264 @cindex call overloaded functions
9265 @cindex overloaded functions, calling
9266 @cindex type conversions in C@t{++}
9268 You can call overloaded functions; @value{GDBN} resolves the function
9269 call to the right definition, with some restrictions. @value{GDBN} does not
9270 perform overload resolution involving user-defined type conversions,
9271 calls to constructors, or instantiations of templates that do not exist
9272 in the program. It also cannot handle ellipsis argument lists or
9275 It does perform integral conversions and promotions, floating-point
9276 promotions, arithmetic conversions, pointer conversions, conversions of
9277 class objects to base classes, and standard conversions such as those of
9278 functions or arrays to pointers; it requires an exact match on the
9279 number of function arguments.
9281 Overload resolution is always performed, unless you have specified
9282 @code{set overload-resolution off}. @xref{Debugging C plus plus,
9283 ,@value{GDBN} features for C@t{++}}.
9285 You must specify @code{set overload-resolution off} in order to use an
9286 explicit function signature to call an overloaded function, as in
9288 p 'foo(char,int)'('x', 13)
9291 The @value{GDBN} command-completion facility can simplify this;
9292 see @ref{Completion, ,Command completion}.
9294 @cindex reference declarations
9296 @value{GDBN} understands variables declared as C@t{++} references; you can use
9297 them in expressions just as you do in C@t{++} source---they are automatically
9300 In the parameter list shown when @value{GDBN} displays a frame, the values of
9301 reference variables are not displayed (unlike other variables); this
9302 avoids clutter, since references are often used for large structures.
9303 The @emph{address} of a reference variable is always shown, unless
9304 you have specified @samp{set print address off}.
9307 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
9308 expressions can use it just as expressions in your program do. Since
9309 one scope may be defined in another, you can use @code{::} repeatedly if
9310 necessary, for example in an expression like
9311 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
9312 resolving name scope by reference to source files, in both C and C@t{++}
9313 debugging (@pxref{Variables, ,Program variables}).
9316 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
9317 calling virtual functions correctly, printing out virtual bases of
9318 objects, calling functions in a base subobject, casting objects, and
9319 invoking user-defined operators.
9322 @subsubsection C and C@t{++} defaults
9324 @cindex C and C@t{++} defaults
9326 If you allow @value{GDBN} to set type and range checking automatically, they
9327 both default to @code{off} whenever the working language changes to
9328 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
9329 selects the working language.
9331 If you allow @value{GDBN} to set the language automatically, it
9332 recognizes source files whose names end with @file{.c}, @file{.C}, or
9333 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
9334 these files, it sets the working language to C or C@t{++}.
9335 @xref{Automatically, ,Having @value{GDBN} infer the source language},
9336 for further details.
9338 @c Type checking is (a) primarily motivated by Modula-2, and (b)
9339 @c unimplemented. If (b) changes, it might make sense to let this node
9340 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
9343 @subsubsection C and C@t{++} type and range checks
9345 @cindex C and C@t{++} checks
9347 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
9348 is not used. However, if you turn type checking on, @value{GDBN}
9349 considers two variables type equivalent if:
9353 The two variables are structured and have the same structure, union, or
9357 The two variables have the same type name, or types that have been
9358 declared equivalent through @code{typedef}.
9361 @c leaving this out because neither J Gilmore nor R Pesch understand it.
9364 The two @code{struct}, @code{union}, or @code{enum} variables are
9365 declared in the same declaration. (Note: this may not be true for all C
9370 Range checking, if turned on, is done on mathematical operations. Array
9371 indices are not checked, since they are often used to index a pointer
9372 that is not itself an array.
9375 @subsubsection @value{GDBN} and C
9377 The @code{set print union} and @code{show print union} commands apply to
9378 the @code{union} type. When set to @samp{on}, any @code{union} that is
9379 inside a @code{struct} or @code{class} is also printed. Otherwise, it
9380 appears as @samp{@{...@}}.
9382 The @code{@@} operator aids in the debugging of dynamic arrays, formed
9383 with pointers and a memory allocation function. @xref{Expressions,
9387 * Debugging C plus plus::
9390 @node Debugging C plus plus
9391 @subsubsection @value{GDBN} features for C@t{++}
9393 @cindex commands for C@t{++}
9395 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
9396 designed specifically for use with C@t{++}. Here is a summary:
9399 @cindex break in overloaded functions
9400 @item @r{breakpoint menus}
9401 When you want a breakpoint in a function whose name is overloaded,
9402 @value{GDBN} breakpoint menus help you specify which function definition
9403 you want. @xref{Breakpoint Menus,,Breakpoint menus}.
9405 @cindex overloading in C@t{++}
9406 @item rbreak @var{regex}
9407 Setting breakpoints using regular expressions is helpful for setting
9408 breakpoints on overloaded functions that are not members of any special
9410 @xref{Set Breaks, ,Setting breakpoints}.
9412 @cindex C@t{++} exception handling
9415 Debug C@t{++} exception handling using these commands. @xref{Set
9416 Catchpoints, , Setting catchpoints}.
9419 @item ptype @var{typename}
9420 Print inheritance relationships as well as other information for type
9422 @xref{Symbols, ,Examining the Symbol Table}.
9424 @cindex C@t{++} symbol display
9425 @item set print demangle
9426 @itemx show print demangle
9427 @itemx set print asm-demangle
9428 @itemx show print asm-demangle
9429 Control whether C@t{++} symbols display in their source form, both when
9430 displaying code as C@t{++} source and when displaying disassemblies.
9431 @xref{Print Settings, ,Print settings}.
9433 @item set print object
9434 @itemx show print object
9435 Choose whether to print derived (actual) or declared types of objects.
9436 @xref{Print Settings, ,Print settings}.
9438 @item set print vtbl
9439 @itemx show print vtbl
9440 Control the format for printing virtual function tables.
9441 @xref{Print Settings, ,Print settings}.
9442 (The @code{vtbl} commands do not work on programs compiled with the HP
9443 ANSI C@t{++} compiler (@code{aCC}).)
9445 @kindex set overload-resolution
9446 @cindex overloaded functions, overload resolution
9447 @item set overload-resolution on
9448 Enable overload resolution for C@t{++} expression evaluation. The default
9449 is on. For overloaded functions, @value{GDBN} evaluates the arguments
9450 and searches for a function whose signature matches the argument types,
9451 using the standard C@t{++} conversion rules (see @ref{C plus plus expressions, ,C@t{++}
9452 expressions}, for details). If it cannot find a match, it emits a
9455 @item set overload-resolution off
9456 Disable overload resolution for C@t{++} expression evaluation. For
9457 overloaded functions that are not class member functions, @value{GDBN}
9458 chooses the first function of the specified name that it finds in the
9459 symbol table, whether or not its arguments are of the correct type. For
9460 overloaded functions that are class member functions, @value{GDBN}
9461 searches for a function whose signature @emph{exactly} matches the
9464 @kindex show overload-resolution
9465 @item show overload-resolution
9466 Show the current setting of overload resolution.
9468 @item @r{Overloaded symbol names}
9469 You can specify a particular definition of an overloaded symbol, using
9470 the same notation that is used to declare such symbols in C@t{++}: type
9471 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
9472 also use the @value{GDBN} command-line word completion facilities to list the
9473 available choices, or to finish the type list for you.
9474 @xref{Completion,, Command completion}, for details on how to do this.
9478 @subsection Objective-C
9481 This section provides information about some commands and command
9482 options that are useful for debugging Objective-C code. See also
9483 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
9484 few more commands specific to Objective-C support.
9487 * Method Names in Commands::
9488 * The Print Command with Objective-C::
9491 @node Method Names in Commands, The Print Command with Objective-C, Objective-C, Objective-C
9492 @subsubsection Method Names in Commands
9494 The following commands have been extended to accept Objective-C method
9495 names as line specifications:
9497 @kindex clear@r{, and Objective-C}
9498 @kindex break@r{, and Objective-C}
9499 @kindex info line@r{, and Objective-C}
9500 @kindex jump@r{, and Objective-C}
9501 @kindex list@r{, and Objective-C}
9505 @item @code{info line}
9510 A fully qualified Objective-C method name is specified as
9513 -[@var{Class} @var{methodName}]
9516 where the minus sign is used to indicate an instance method and a
9517 plus sign (not shown) is used to indicate a class method. The class
9518 name @var{Class} and method name @var{methodName} are enclosed in
9519 brackets, similar to the way messages are specified in Objective-C
9520 source code. For example, to set a breakpoint at the @code{create}
9521 instance method of class @code{Fruit} in the program currently being
9525 break -[Fruit create]
9528 To list ten program lines around the @code{initialize} class method,
9532 list +[NSText initialize]
9535 In the current version of @value{GDBN}, the plus or minus sign is
9536 required. In future versions of @value{GDBN}, the plus or minus
9537 sign will be optional, but you can use it to narrow the search. It
9538 is also possible to specify just a method name:
9544 You must specify the complete method name, including any colons. If
9545 your program's source files contain more than one @code{create} method,
9546 you'll be presented with a numbered list of classes that implement that
9547 method. Indicate your choice by number, or type @samp{0} to exit if
9550 As another example, to clear a breakpoint established at the
9551 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
9554 clear -[NSWindow makeKeyAndOrderFront:]
9557 @node The Print Command with Objective-C
9558 @subsubsection The Print Command With Objective-C
9559 @cindex Objective-C, print objects
9560 @kindex print-object
9561 @kindex po @r{(@code{print-object})}
9563 The print command has also been extended to accept methods. For example:
9566 print -[@var{object} hash]
9569 @cindex print an Objective-C object description
9570 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
9572 will tell @value{GDBN} to send the @code{hash} message to @var{object}
9573 and print the result. Also, an additional command has been added,
9574 @code{print-object} or @code{po} for short, which is meant to print
9575 the description of an object. However, this command may only work
9576 with certain Objective-C libraries that have a particular hook
9577 function, @code{_NSPrintForDebugger}, defined.
9581 @cindex Fortran-specific support in @value{GDBN}
9583 @value{GDBN} can be used to debug programs written in Fortran, but it
9584 currently supports only the features of Fortran 77 language.
9586 @cindex trailing underscore, in Fortran symbols
9587 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
9588 among them) append an underscore to the names of variables and
9589 functions. When you debug programs compiled by those compilers, you
9590 will need to refer to variables and functions with a trailing
9594 * Fortran Operators:: Fortran operators and expressions
9595 * Fortran Defaults:: Default settings for Fortran
9596 * Special Fortran commands:: Special @value{GDBN} commands for Fortran
9599 @node Fortran Operators
9600 @subsubsection Fortran operators and expressions
9602 @cindex Fortran operators and expressions
9604 Operators must be defined on values of specific types. For instance,
9605 @code{+} is defined on numbers, but not on characters or other non-
9606 arithmetic types. Operators are often defined on groups of types.
9610 The exponentiation operator. It raises the first operand to the power
9614 The range operator. Normally used in the form of array(low:high) to
9615 represent a section of array.
9618 @node Fortran Defaults
9619 @subsubsection Fortran Defaults
9621 @cindex Fortran Defaults
9623 Fortran symbols are usually case-insensitive, so @value{GDBN} by
9624 default uses case-insensitive matches for Fortran symbols. You can
9625 change that with the @samp{set case-insensitive} command, see
9626 @ref{Symbols}, for the details.
9628 @node Special Fortran commands
9629 @subsubsection Special Fortran commands
9631 @cindex Special Fortran commands
9633 @value{GDBN} had some commands to support Fortran specific feature,
9634 such as common block displaying.
9637 @cindex @code{COMMON} blocks, Fortran
9639 @item info common @r{[}@var{common-name}@r{]}
9640 This command prints the values contained in the Fortran @code{COMMON}
9641 block whose name is @var{common-name}. With no argument, the names of
9642 all @code{COMMON} blocks visible at current program location are
9649 @cindex Pascal support in @value{GDBN}, limitations
9650 Debugging Pascal programs which use sets, subranges, file variables, or
9651 nested functions does not currently work. @value{GDBN} does not support
9652 entering expressions, printing values, or similar features using Pascal
9655 The Pascal-specific command @code{set print pascal_static-members}
9656 controls whether static members of Pascal objects are displayed.
9657 @xref{Print Settings, pascal_static-members}.
9660 @subsection Modula-2
9662 @cindex Modula-2, @value{GDBN} support
9664 The extensions made to @value{GDBN} to support Modula-2 only support
9665 output from the @sc{gnu} Modula-2 compiler (which is currently being
9666 developed). Other Modula-2 compilers are not currently supported, and
9667 attempting to debug executables produced by them is most likely
9668 to give an error as @value{GDBN} reads in the executable's symbol
9671 @cindex expressions in Modula-2
9673 * M2 Operators:: Built-in operators
9674 * Built-In Func/Proc:: Built-in functions and procedures
9675 * M2 Constants:: Modula-2 constants
9676 * M2 Types:: Modula-2 types
9677 * M2 Defaults:: Default settings for Modula-2
9678 * Deviations:: Deviations from standard Modula-2
9679 * M2 Checks:: Modula-2 type and range checks
9680 * M2 Scope:: The scope operators @code{::} and @code{.}
9681 * GDB/M2:: @value{GDBN} and Modula-2
9685 @subsubsection Operators
9686 @cindex Modula-2 operators
9688 Operators must be defined on values of specific types. For instance,
9689 @code{+} is defined on numbers, but not on structures. Operators are
9690 often defined on groups of types. For the purposes of Modula-2, the
9691 following definitions hold:
9696 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
9700 @emph{Character types} consist of @code{CHAR} and its subranges.
9703 @emph{Floating-point types} consist of @code{REAL}.
9706 @emph{Pointer types} consist of anything declared as @code{POINTER TO
9710 @emph{Scalar types} consist of all of the above.
9713 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
9716 @emph{Boolean types} consist of @code{BOOLEAN}.
9720 The following operators are supported, and appear in order of
9721 increasing precedence:
9725 Function argument or array index separator.
9728 Assignment. The value of @var{var} @code{:=} @var{value} is
9732 Less than, greater than on integral, floating-point, or enumerated
9736 Less than or equal to, greater than or equal to
9737 on integral, floating-point and enumerated types, or set inclusion on
9738 set types. Same precedence as @code{<}.
9740 @item =@r{, }<>@r{, }#
9741 Equality and two ways of expressing inequality, valid on scalar types.
9742 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
9743 available for inequality, since @code{#} conflicts with the script
9747 Set membership. Defined on set types and the types of their members.
9748 Same precedence as @code{<}.
9751 Boolean disjunction. Defined on boolean types.
9754 Boolean conjunction. Defined on boolean types.
9757 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9760 Addition and subtraction on integral and floating-point types, or union
9761 and difference on set types.
9764 Multiplication on integral and floating-point types, or set intersection
9768 Division on floating-point types, or symmetric set difference on set
9769 types. Same precedence as @code{*}.
9772 Integer division and remainder. Defined on integral types. Same
9773 precedence as @code{*}.
9776 Negative. Defined on @code{INTEGER} and @code{REAL} data.
9779 Pointer dereferencing. Defined on pointer types.
9782 Boolean negation. Defined on boolean types. Same precedence as
9786 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
9787 precedence as @code{^}.
9790 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
9793 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
9797 @value{GDBN} and Modula-2 scope operators.
9801 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
9802 treats the use of the operator @code{IN}, or the use of operators
9803 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
9804 @code{<=}, and @code{>=} on sets as an error.
9808 @node Built-In Func/Proc
9809 @subsubsection Built-in functions and procedures
9810 @cindex Modula-2 built-ins
9812 Modula-2 also makes available several built-in procedures and functions.
9813 In describing these, the following metavariables are used:
9818 represents an @code{ARRAY} variable.
9821 represents a @code{CHAR} constant or variable.
9824 represents a variable or constant of integral type.
9827 represents an identifier that belongs to a set. Generally used in the
9828 same function with the metavariable @var{s}. The type of @var{s} should
9829 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
9832 represents a variable or constant of integral or floating-point type.
9835 represents a variable or constant of floating-point type.
9841 represents a variable.
9844 represents a variable or constant of one of many types. See the
9845 explanation of the function for details.
9848 All Modula-2 built-in procedures also return a result, described below.
9852 Returns the absolute value of @var{n}.
9855 If @var{c} is a lower case letter, it returns its upper case
9856 equivalent, otherwise it returns its argument.
9859 Returns the character whose ordinal value is @var{i}.
9862 Decrements the value in the variable @var{v} by one. Returns the new value.
9864 @item DEC(@var{v},@var{i})
9865 Decrements the value in the variable @var{v} by @var{i}. Returns the
9868 @item EXCL(@var{m},@var{s})
9869 Removes the element @var{m} from the set @var{s}. Returns the new
9872 @item FLOAT(@var{i})
9873 Returns the floating point equivalent of the integer @var{i}.
9876 Returns the index of the last member of @var{a}.
9879 Increments the value in the variable @var{v} by one. Returns the new value.
9881 @item INC(@var{v},@var{i})
9882 Increments the value in the variable @var{v} by @var{i}. Returns the
9885 @item INCL(@var{m},@var{s})
9886 Adds the element @var{m} to the set @var{s} if it is not already
9887 there. Returns the new set.
9890 Returns the maximum value of the type @var{t}.
9893 Returns the minimum value of the type @var{t}.
9896 Returns boolean TRUE if @var{i} is an odd number.
9899 Returns the ordinal value of its argument. For example, the ordinal
9900 value of a character is its @sc{ascii} value (on machines supporting the
9901 @sc{ascii} character set). @var{x} must be of an ordered type, which include
9902 integral, character and enumerated types.
9905 Returns the size of its argument. @var{x} can be a variable or a type.
9907 @item TRUNC(@var{r})
9908 Returns the integral part of @var{r}.
9910 @item VAL(@var{t},@var{i})
9911 Returns the member of the type @var{t} whose ordinal value is @var{i}.
9915 @emph{Warning:} Sets and their operations are not yet supported, so
9916 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
9920 @cindex Modula-2 constants
9922 @subsubsection Constants
9924 @value{GDBN} allows you to express the constants of Modula-2 in the following
9930 Integer constants are simply a sequence of digits. When used in an
9931 expression, a constant is interpreted to be type-compatible with the
9932 rest of the expression. Hexadecimal integers are specified by a
9933 trailing @samp{H}, and octal integers by a trailing @samp{B}.
9936 Floating point constants appear as a sequence of digits, followed by a
9937 decimal point and another sequence of digits. An optional exponent can
9938 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
9939 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
9940 digits of the floating point constant must be valid decimal (base 10)
9944 Character constants consist of a single character enclosed by a pair of
9945 like quotes, either single (@code{'}) or double (@code{"}). They may
9946 also be expressed by their ordinal value (their @sc{ascii} value, usually)
9947 followed by a @samp{C}.
9950 String constants consist of a sequence of characters enclosed by a
9951 pair of like quotes, either single (@code{'}) or double (@code{"}).
9952 Escape sequences in the style of C are also allowed. @xref{C
9953 Constants, ,C and C@t{++} constants}, for a brief explanation of escape
9957 Enumerated constants consist of an enumerated identifier.
9960 Boolean constants consist of the identifiers @code{TRUE} and
9964 Pointer constants consist of integral values only.
9967 Set constants are not yet supported.
9971 @subsubsection Modula-2 Types
9972 @cindex Modula-2 types
9974 Currently @value{GDBN} can print the following data types in Modula-2
9975 syntax: array types, record types, set types, pointer types, procedure
9976 types, enumerated types, subrange types and base types. You can also
9977 print the contents of variables declared using these type.
9978 This section gives a number of simple source code examples together with
9979 sample @value{GDBN} sessions.
9981 The first example contains the following section of code:
9990 and you can request @value{GDBN} to interrogate the type and value of
9991 @code{r} and @code{s}.
9994 (@value{GDBP}) print s
9996 (@value{GDBP}) ptype s
9998 (@value{GDBP}) print r
10000 (@value{GDBP}) ptype r
10005 Likewise if your source code declares @code{s} as:
10009 s: SET ['A'..'Z'] ;
10013 then you may query the type of @code{s} by:
10016 (@value{GDBP}) ptype s
10017 type = SET ['A'..'Z']
10021 Note that at present you cannot interactively manipulate set
10022 expressions using the debugger.
10024 The following example shows how you might declare an array in Modula-2
10025 and how you can interact with @value{GDBN} to print its type and contents:
10029 s: ARRAY [-10..10] OF CHAR ;
10033 (@value{GDBP}) ptype s
10034 ARRAY [-10..10] OF CHAR
10037 Note that the array handling is not yet complete and although the type
10038 is printed correctly, expression handling still assumes that all
10039 arrays have a lower bound of zero and not @code{-10} as in the example
10040 above. Unbounded arrays are also not yet recognized in @value{GDBN}.
10042 Here are some more type related Modula-2 examples:
10046 colour = (blue, red, yellow, green) ;
10047 t = [blue..yellow] ;
10055 The @value{GDBN} interaction shows how you can query the data type
10056 and value of a variable.
10059 (@value{GDBP}) print s
10061 (@value{GDBP}) ptype t
10062 type = [blue..yellow]
10066 In this example a Modula-2 array is declared and its contents
10067 displayed. Observe that the contents are written in the same way as
10068 their @code{C} counterparts.
10072 s: ARRAY [1..5] OF CARDINAL ;
10078 (@value{GDBP}) print s
10079 $1 = @{1, 0, 0, 0, 0@}
10080 (@value{GDBP}) ptype s
10081 type = ARRAY [1..5] OF CARDINAL
10084 The Modula-2 language interface to @value{GDBN} also understands
10085 pointer types as shown in this example:
10089 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
10096 and you can request that @value{GDBN} describes the type of @code{s}.
10099 (@value{GDBP}) ptype s
10100 type = POINTER TO ARRAY [1..5] OF CARDINAL
10103 @value{GDBN} handles compound types as we can see in this example.
10104 Here we combine array types, record types, pointer types and subrange
10115 myarray = ARRAY myrange OF CARDINAL ;
10116 myrange = [-2..2] ;
10118 s: POINTER TO ARRAY myrange OF foo ;
10122 and you can ask @value{GDBN} to describe the type of @code{s} as shown
10126 (@value{GDBP}) ptype s
10127 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
10130 f3 : ARRAY [-2..2] OF CARDINAL;
10135 @subsubsection Modula-2 defaults
10136 @cindex Modula-2 defaults
10138 If type and range checking are set automatically by @value{GDBN}, they
10139 both default to @code{on} whenever the working language changes to
10140 Modula-2. This happens regardless of whether you or @value{GDBN}
10141 selected the working language.
10143 If you allow @value{GDBN} to set the language automatically, then entering
10144 code compiled from a file whose name ends with @file{.mod} sets the
10145 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} set
10146 the language automatically}, for further details.
10149 @subsubsection Deviations from standard Modula-2
10150 @cindex Modula-2, deviations from
10152 A few changes have been made to make Modula-2 programs easier to debug.
10153 This is done primarily via loosening its type strictness:
10157 Unlike in standard Modula-2, pointer constants can be formed by
10158 integers. This allows you to modify pointer variables during
10159 debugging. (In standard Modula-2, the actual address contained in a
10160 pointer variable is hidden from you; it can only be modified
10161 through direct assignment to another pointer variable or expression that
10162 returned a pointer.)
10165 C escape sequences can be used in strings and characters to represent
10166 non-printable characters. @value{GDBN} prints out strings with these
10167 escape sequences embedded. Single non-printable characters are
10168 printed using the @samp{CHR(@var{nnn})} format.
10171 The assignment operator (@code{:=}) returns the value of its right-hand
10175 All built-in procedures both modify @emph{and} return their argument.
10179 @subsubsection Modula-2 type and range checks
10180 @cindex Modula-2 checks
10183 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
10186 @c FIXME remove warning when type/range checks added
10188 @value{GDBN} considers two Modula-2 variables type equivalent if:
10192 They are of types that have been declared equivalent via a @code{TYPE
10193 @var{t1} = @var{t2}} statement
10196 They have been declared on the same line. (Note: This is true of the
10197 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
10200 As long as type checking is enabled, any attempt to combine variables
10201 whose types are not equivalent is an error.
10203 Range checking is done on all mathematical operations, assignment, array
10204 index bounds, and all built-in functions and procedures.
10207 @subsubsection The scope operators @code{::} and @code{.}
10209 @cindex @code{.}, Modula-2 scope operator
10210 @cindex colon, doubled as scope operator
10212 @vindex colon-colon@r{, in Modula-2}
10213 @c Info cannot handle :: but TeX can.
10216 @vindex ::@r{, in Modula-2}
10219 There are a few subtle differences between the Modula-2 scope operator
10220 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
10225 @var{module} . @var{id}
10226 @var{scope} :: @var{id}
10230 where @var{scope} is the name of a module or a procedure,
10231 @var{module} the name of a module, and @var{id} is any declared
10232 identifier within your program, except another module.
10234 Using the @code{::} operator makes @value{GDBN} search the scope
10235 specified by @var{scope} for the identifier @var{id}. If it is not
10236 found in the specified scope, then @value{GDBN} searches all scopes
10237 enclosing the one specified by @var{scope}.
10239 Using the @code{.} operator makes @value{GDBN} search the current scope for
10240 the identifier specified by @var{id} that was imported from the
10241 definition module specified by @var{module}. With this operator, it is
10242 an error if the identifier @var{id} was not imported from definition
10243 module @var{module}, or if @var{id} is not an identifier in
10247 @subsubsection @value{GDBN} and Modula-2
10249 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
10250 Five subcommands of @code{set print} and @code{show print} apply
10251 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
10252 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
10253 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
10254 analogue in Modula-2.
10256 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
10257 with any language, is not useful with Modula-2. Its
10258 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
10259 created in Modula-2 as they can in C or C@t{++}. However, because an
10260 address can be specified by an integral constant, the construct
10261 @samp{@{@var{type}@}@var{adrexp}} is still useful.
10263 @cindex @code{#} in Modula-2
10264 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
10265 interpreted as the beginning of a comment. Use @code{<>} instead.
10271 The extensions made to @value{GDBN} for Ada only support
10272 output from the @sc{gnu} Ada (GNAT) compiler.
10273 Other Ada compilers are not currently supported, and
10274 attempting to debug executables produced by them is most likely
10278 @cindex expressions in Ada
10280 * Ada Mode Intro:: General remarks on the Ada syntax
10281 and semantics supported by Ada mode
10283 * Omissions from Ada:: Restrictions on the Ada expression syntax.
10284 * Additions to Ada:: Extensions of the Ada expression syntax.
10285 * Stopping Before Main Program:: Debugging the program during elaboration.
10286 * Ada Glitches:: Known peculiarities of Ada mode.
10289 @node Ada Mode Intro
10290 @subsubsection Introduction
10291 @cindex Ada mode, general
10293 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
10294 syntax, with some extensions.
10295 The philosophy behind the design of this subset is
10299 That @value{GDBN} should provide basic literals and access to operations for
10300 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
10301 leaving more sophisticated computations to subprograms written into the
10302 program (which therefore may be called from @value{GDBN}).
10305 That type safety and strict adherence to Ada language restrictions
10306 are not particularly important to the @value{GDBN} user.
10309 That brevity is important to the @value{GDBN} user.
10312 Thus, for brevity, the debugger acts as if there were
10313 implicit @code{with} and @code{use} clauses in effect for all user-written
10314 packages, making it unnecessary to fully qualify most names with
10315 their packages, regardless of context. Where this causes ambiguity,
10316 @value{GDBN} asks the user's intent.
10318 The debugger will start in Ada mode if it detects an Ada main program.
10319 As for other languages, it will enter Ada mode when stopped in a program that
10320 was translated from an Ada source file.
10322 While in Ada mode, you may use `@t{--}' for comments. This is useful
10323 mostly for documenting command files. The standard @value{GDBN} comment
10324 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
10325 middle (to allow based literals).
10327 The debugger supports limited overloading. Given a subprogram call in which
10328 the function symbol has multiple definitions, it will use the number of
10329 actual parameters and some information about their types to attempt to narrow
10330 the set of definitions. It also makes very limited use of context, preferring
10331 procedures to functions in the context of the @code{call} command, and
10332 functions to procedures elsewhere.
10334 @node Omissions from Ada
10335 @subsubsection Omissions from Ada
10336 @cindex Ada, omissions from
10338 Here are the notable omissions from the subset:
10342 Only a subset of the attributes are supported:
10346 @t{'First}, @t{'Last}, and @t{'Length}
10347 on array objects (not on types and subtypes).
10350 @t{'Min} and @t{'Max}.
10353 @t{'Pos} and @t{'Val}.
10359 @t{'Range} on array objects (not subtypes), but only as the right
10360 operand of the membership (@code{in}) operator.
10363 @t{'Access}, @t{'Unchecked_Access}, and
10364 @t{'Unrestricted_Access} (a GNAT extension).
10372 @code{Characters.Latin_1} are not available and
10373 concatenation is not implemented. Thus, escape characters in strings are
10374 not currently available.
10377 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
10378 equality of representations. They will generally work correctly
10379 for strings and arrays whose elements have integer or enumeration types.
10380 They may not work correctly for arrays whose element
10381 types have user-defined equality, for arrays of real values
10382 (in particular, IEEE-conformant floating point, because of negative
10383 zeroes and NaNs), and for arrays whose elements contain unused bits with
10384 indeterminate values.
10387 The other component-by-component array operations (@code{and}, @code{or},
10388 @code{xor}, @code{not}, and relational tests other than equality)
10389 are not implemented.
10392 @cindex array aggregates (Ada)
10393 @cindex record aggregates (Ada)
10394 @cindex aggregates (Ada)
10395 There is limited support for array and record aggregates. They are
10396 permitted only on the right sides of assignments, as in these examples:
10399 set An_Array := (1, 2, 3, 4, 5, 6)
10400 set An_Array := (1, others => 0)
10401 set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
10402 set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
10403 set A_Record := (1, "Peter", True);
10404 set A_Record := (Name => "Peter", Id => 1, Alive => True)
10408 discriminant's value by assigning an aggregate has an
10409 undefined effect if that discriminant is used within the record.
10410 However, you can first modify discriminants by directly assigning to
10411 them (which normally would not be allowed in Ada), and then performing an
10412 aggregate assignment. For example, given a variable @code{A_Rec}
10413 declared to have a type such as:
10416 type Rec (Len : Small_Integer := 0) is record
10418 Vals : IntArray (1 .. Len);
10422 you can assign a value with a different size of @code{Vals} with two
10427 set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
10430 As this example also illustrates, @value{GDBN} is very loose about the usual
10431 rules concerning aggregates. You may leave out some of the
10432 components of an array or record aggregate (such as the @code{Len}
10433 component in the assignment to @code{A_Rec} above); they will retain their
10434 original values upon assignment. You may freely use dynamic values as
10435 indices in component associations. You may even use overlapping or
10436 redundant component associations, although which component values are
10437 assigned in such cases is not defined.
10440 Calls to dispatching subprograms are not implemented.
10443 The overloading algorithm is much more limited (i.e., less selective)
10444 than that of real Ada. It makes only limited use of the context in which a subexpression
10445 appears to resolve its meaning, and it is much looser in its rules for allowing
10446 type matches. As a result, some function calls will be ambiguous, and the user
10447 will be asked to choose the proper resolution.
10450 The @code{new} operator is not implemented.
10453 Entry calls are not implemented.
10456 Aside from printing, arithmetic operations on the native VAX floating-point
10457 formats are not supported.
10460 It is not possible to slice a packed array.
10463 @node Additions to Ada
10464 @subsubsection Additions to Ada
10465 @cindex Ada, deviations from
10467 As it does for other languages, @value{GDBN} makes certain generic
10468 extensions to Ada (@pxref{Expressions}):
10472 If the expression @var{E} is a variable residing in memory
10473 (typically a local variable or array element) and @var{N} is
10474 a positive integer, then @code{@var{E}@@@var{N}} displays the values of
10475 @var{E} and the @var{N}-1 adjacent variables following it in memory as an array.
10476 In Ada, this operator is generally not necessary, since its prime use
10477 is in displaying parts of an array, and slicing will usually do this in Ada.
10478 However, there are occasional uses when debugging programs
10479 in which certain debugging information has been optimized away.
10482 @code{@var{B}::@var{var}} means ``the variable named @var{var} that appears
10483 in function or file @var{B}.'' When @var{B} is a file name, you must typically
10484 surround it in single quotes.
10487 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
10488 @var{type} that appears at address @var{addr}.''
10491 A name starting with @samp{$} is a convenience variable
10492 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
10495 In addition, @value{GDBN} provides a few other shortcuts and outright additions specific
10500 The assignment statement is allowed as an expression, returning
10501 its right-hand operand as its value. Thus, you may enter
10505 print A(tmp := y + 1)
10509 The semicolon is allowed as an ``operator,'' returning as its value
10510 the value of its right-hand operand.
10511 This allows, for example,
10512 complex conditional breaks:
10516 condition 1 (report(i); k += 1; A(k) > 100)
10520 Rather than use catenation and symbolic character names to introduce special
10521 characters into strings, one may instead use a special bracket notation,
10522 which is also used to print strings. A sequence of characters of the form
10523 @samp{["@var{XX}"]} within a string or character literal denotes the
10524 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
10525 sequence of characters @samp{["""]} also denotes a single quotation mark
10526 in strings. For example,
10528 "One line.["0a"]Next line.["0a"]"
10531 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF}) after each
10535 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
10536 @t{'Max} is optional (and is ignored in any case). For example, it is valid
10544 When printing arrays, @value{GDBN} uses positional notation when the
10545 array has a lower bound of 1, and uses a modified named notation otherwise.
10546 For example, a one-dimensional array of three integers with a lower bound of 3 might print as
10553 That is, in contrast to valid Ada, only the first component has a @code{=>}
10557 You may abbreviate attributes in expressions with any unique,
10558 multi-character subsequence of
10559 their names (an exact match gets preference).
10560 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
10561 in place of @t{a'length}.
10564 @cindex quoting Ada internal identifiers
10565 Since Ada is case-insensitive, the debugger normally maps identifiers you type
10566 to lower case. The GNAT compiler uses upper-case characters for
10567 some of its internal identifiers, which are normally of no interest to users.
10568 For the rare occasions when you actually have to look at them,
10569 enclose them in angle brackets to avoid the lower-case mapping.
10572 @value{GDBP} print <JMPBUF_SAVE>[0]
10576 Printing an object of class-wide type or dereferencing an
10577 access-to-class-wide value will display all the components of the object's
10578 specific type (as indicated by its run-time tag). Likewise, component
10579 selection on such a value will operate on the specific type of the
10584 @node Stopping Before Main Program
10585 @subsubsection Stopping at the Very Beginning
10587 @cindex breakpointing Ada elaboration code
10588 It is sometimes necessary to debug the program during elaboration, and
10589 before reaching the main procedure.
10590 As defined in the Ada Reference
10591 Manual, the elaboration code is invoked from a procedure called
10592 @code{adainit}. To run your program up to the beginning of
10593 elaboration, simply use the following two commands:
10594 @code{tbreak adainit} and @code{run}.
10597 @subsubsection Known Peculiarities of Ada Mode
10598 @cindex Ada, problems
10600 Besides the omissions listed previously (@pxref{Omissions from Ada}),
10601 we know of several problems with and limitations of Ada mode in
10603 some of which will be fixed with planned future releases of the debugger
10604 and the GNU Ada compiler.
10608 Currently, the debugger
10609 has insufficient information to determine whether certain pointers represent
10610 pointers to objects or the objects themselves.
10611 Thus, the user may have to tack an extra @code{.all} after an expression
10612 to get it printed properly.
10615 Static constants that the compiler chooses not to materialize as objects in
10616 storage are invisible to the debugger.
10619 Named parameter associations in function argument lists are ignored (the
10620 argument lists are treated as positional).
10623 Many useful library packages are currently invisible to the debugger.
10626 Fixed-point arithmetic, conversions, input, and output is carried out using
10627 floating-point arithmetic, and may give results that only approximate those on
10631 The type of the @t{'Address} attribute may not be @code{System.Address}.
10634 The GNAT compiler never generates the prefix @code{Standard} for any of
10635 the standard symbols defined by the Ada language. @value{GDBN} knows about
10636 this: it will strip the prefix from names when you use it, and will never
10637 look for a name you have so qualified among local symbols, nor match against
10638 symbols in other packages or subprograms. If you have
10639 defined entities anywhere in your program other than parameters and
10640 local variables whose simple names match names in @code{Standard},
10641 GNAT's lack of qualification here can cause confusion. When this happens,
10642 you can usually resolve the confusion
10643 by qualifying the problematic names with package
10644 @code{Standard} explicitly.
10647 @node Unsupported languages
10648 @section Unsupported languages
10650 @cindex unsupported languages
10651 @cindex minimal language
10652 In addition to the other fully-supported programming languages,
10653 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
10654 It does not represent a real programming language, but provides a set
10655 of capabilities close to what the C or assembly languages provide.
10656 This should allow most simple operations to be performed while debugging
10657 an application that uses a language currently not supported by @value{GDBN}.
10659 If the language is set to @code{auto}, @value{GDBN} will automatically
10660 select this language if the current frame corresponds to an unsupported
10664 @chapter Examining the Symbol Table
10666 The commands described in this chapter allow you to inquire about the
10667 symbols (names of variables, functions and types) defined in your
10668 program. This information is inherent in the text of your program and
10669 does not change as your program executes. @value{GDBN} finds it in your
10670 program's symbol table, in the file indicated when you started @value{GDBN}
10671 (@pxref{File Options, ,Choosing files}), or by one of the
10672 file-management commands (@pxref{Files, ,Commands to specify files}).
10674 @cindex symbol names
10675 @cindex names of symbols
10676 @cindex quoting names
10677 Occasionally, you may need to refer to symbols that contain unusual
10678 characters, which @value{GDBN} ordinarily treats as word delimiters. The
10679 most frequent case is in referring to static variables in other
10680 source files (@pxref{Variables,,Program variables}). File names
10681 are recorded in object files as debugging symbols, but @value{GDBN} would
10682 ordinarily parse a typical file name, like @file{foo.c}, as the three words
10683 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
10684 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
10691 looks up the value of @code{x} in the scope of the file @file{foo.c}.
10694 @cindex case-insensitive symbol names
10695 @cindex case sensitivity in symbol names
10696 @kindex set case-sensitive
10697 @item set case-sensitive on
10698 @itemx set case-sensitive off
10699 @itemx set case-sensitive auto
10700 Normally, when @value{GDBN} looks up symbols, it matches their names
10701 with case sensitivity determined by the current source language.
10702 Occasionally, you may wish to control that. The command @code{set
10703 case-sensitive} lets you do that by specifying @code{on} for
10704 case-sensitive matches or @code{off} for case-insensitive ones. If
10705 you specify @code{auto}, case sensitivity is reset to the default
10706 suitable for the source language. The default is case-sensitive
10707 matches for all languages except for Fortran, for which the default is
10708 case-insensitive matches.
10710 @kindex show case-sensitive
10711 @item show case-sensitive
10712 This command shows the current setting of case sensitivity for symbols
10715 @kindex info address
10716 @cindex address of a symbol
10717 @item info address @var{symbol}
10718 Describe where the data for @var{symbol} is stored. For a register
10719 variable, this says which register it is kept in. For a non-register
10720 local variable, this prints the stack-frame offset at which the variable
10723 Note the contrast with @samp{print &@var{symbol}}, which does not work
10724 at all for a register variable, and for a stack local variable prints
10725 the exact address of the current instantiation of the variable.
10727 @kindex info symbol
10728 @cindex symbol from address
10729 @cindex closest symbol and offset for an address
10730 @item info symbol @var{addr}
10731 Print the name of a symbol which is stored at the address @var{addr}.
10732 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
10733 nearest symbol and an offset from it:
10736 (@value{GDBP}) info symbol 0x54320
10737 _initialize_vx + 396 in section .text
10741 This is the opposite of the @code{info address} command. You can use
10742 it to find out the name of a variable or a function given its address.
10745 @item whatis [@var{arg}]
10746 Print the data type of @var{arg}, which can be either an expression or
10747 a data type. With no argument, print the data type of @code{$}, the
10748 last value in the value history. If @var{arg} is an expression, it is
10749 not actually evaluated, and any side-effecting operations (such as
10750 assignments or function calls) inside it do not take place. If
10751 @var{arg} is a type name, it may be the name of a type or typedef, or
10752 for C code it may have the form @samp{class @var{class-name}},
10753 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
10754 @samp{enum @var{enum-tag}}.
10755 @xref{Expressions, ,Expressions}.
10758 @item ptype [@var{arg}]
10759 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
10760 detailed description of the type, instead of just the name of the type.
10761 @xref{Expressions, ,Expressions}.
10763 For example, for this variable declaration:
10766 struct complex @{double real; double imag;@} v;
10770 the two commands give this output:
10774 (@value{GDBP}) whatis v
10775 type = struct complex
10776 (@value{GDBP}) ptype v
10777 type = struct complex @{
10785 As with @code{whatis}, using @code{ptype} without an argument refers to
10786 the type of @code{$}, the last value in the value history.
10788 @cindex incomplete type
10789 Sometimes, programs use opaque data types or incomplete specifications
10790 of complex data structure. If the debug information included in the
10791 program does not allow @value{GDBN} to display a full declaration of
10792 the data type, it will say @samp{<incomplete type>}. For example,
10793 given these declarations:
10797 struct foo *fooptr;
10801 but no definition for @code{struct foo} itself, @value{GDBN} will say:
10804 (@value{GDBP}) ptype foo
10805 $1 = <incomplete type>
10809 ``Incomplete type'' is C terminology for data types that are not
10810 completely specified.
10813 @item info types @var{regexp}
10815 Print a brief description of all types whose names match the regular
10816 expression @var{regexp} (or all types in your program, if you supply
10817 no argument). Each complete typename is matched as though it were a
10818 complete line; thus, @samp{i type value} gives information on all
10819 types in your program whose names include the string @code{value}, but
10820 @samp{i type ^value$} gives information only on types whose complete
10821 name is @code{value}.
10823 This command differs from @code{ptype} in two ways: first, like
10824 @code{whatis}, it does not print a detailed description; second, it
10825 lists all source files where a type is defined.
10828 @cindex local variables
10829 @item info scope @var{location}
10830 List all the variables local to a particular scope. This command
10831 accepts a @var{location} argument---a function name, a source line, or
10832 an address preceded by a @samp{*}, and prints all the variables local
10833 to the scope defined by that location. For example:
10836 (@value{GDBP}) @b{info scope command_line_handler}
10837 Scope for command_line_handler:
10838 Symbol rl is an argument at stack/frame offset 8, length 4.
10839 Symbol linebuffer is in static storage at address 0x150a18, length 4.
10840 Symbol linelength is in static storage at address 0x150a1c, length 4.
10841 Symbol p is a local variable in register $esi, length 4.
10842 Symbol p1 is a local variable in register $ebx, length 4.
10843 Symbol nline is a local variable in register $edx, length 4.
10844 Symbol repeat is a local variable at frame offset -8, length 4.
10848 This command is especially useful for determining what data to collect
10849 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
10852 @kindex info source
10854 Show information about the current source file---that is, the source file for
10855 the function containing the current point of execution:
10858 the name of the source file, and the directory containing it,
10860 the directory it was compiled in,
10862 its length, in lines,
10864 which programming language it is written in,
10866 whether the executable includes debugging information for that file, and
10867 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
10869 whether the debugging information includes information about
10870 preprocessor macros.
10874 @kindex info sources
10876 Print the names of all source files in your program for which there is
10877 debugging information, organized into two lists: files whose symbols
10878 have already been read, and files whose symbols will be read when needed.
10880 @kindex info functions
10881 @item info functions
10882 Print the names and data types of all defined functions.
10884 @item info functions @var{regexp}
10885 Print the names and data types of all defined functions
10886 whose names contain a match for regular expression @var{regexp}.
10887 Thus, @samp{info fun step} finds all functions whose names
10888 include @code{step}; @samp{info fun ^step} finds those whose names
10889 start with @code{step}. If a function name contains characters
10890 that conflict with the regular expression language (e.g.@:
10891 @samp{operator*()}), they may be quoted with a backslash.
10893 @kindex info variables
10894 @item info variables
10895 Print the names and data types of all variables that are declared
10896 outside of functions (i.e.@: excluding local variables).
10898 @item info variables @var{regexp}
10899 Print the names and data types of all variables (except for local
10900 variables) whose names contain a match for regular expression
10903 @kindex info classes
10904 @cindex Objective-C, classes and selectors
10906 @itemx info classes @var{regexp}
10907 Display all Objective-C classes in your program, or
10908 (with the @var{regexp} argument) all those matching a particular regular
10911 @kindex info selectors
10912 @item info selectors
10913 @itemx info selectors @var{regexp}
10914 Display all Objective-C selectors in your program, or
10915 (with the @var{regexp} argument) all those matching a particular regular
10919 This was never implemented.
10920 @kindex info methods
10922 @itemx info methods @var{regexp}
10923 The @code{info methods} command permits the user to examine all defined
10924 methods within C@t{++} program, or (with the @var{regexp} argument) a
10925 specific set of methods found in the various C@t{++} classes. Many
10926 C@t{++} classes provide a large number of methods. Thus, the output
10927 from the @code{ptype} command can be overwhelming and hard to use. The
10928 @code{info-methods} command filters the methods, printing only those
10929 which match the regular-expression @var{regexp}.
10932 @cindex reloading symbols
10933 Some systems allow individual object files that make up your program to
10934 be replaced without stopping and restarting your program. For example,
10935 in VxWorks you can simply recompile a defective object file and keep on
10936 running. If you are running on one of these systems, you can allow
10937 @value{GDBN} to reload the symbols for automatically relinked modules:
10940 @kindex set symbol-reloading
10941 @item set symbol-reloading on
10942 Replace symbol definitions for the corresponding source file when an
10943 object file with a particular name is seen again.
10945 @item set symbol-reloading off
10946 Do not replace symbol definitions when encountering object files of the
10947 same name more than once. This is the default state; if you are not
10948 running on a system that permits automatic relinking of modules, you
10949 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
10950 may discard symbols when linking large programs, that may contain
10951 several modules (from different directories or libraries) with the same
10954 @kindex show symbol-reloading
10955 @item show symbol-reloading
10956 Show the current @code{on} or @code{off} setting.
10959 @cindex opaque data types
10960 @kindex set opaque-type-resolution
10961 @item set opaque-type-resolution on
10962 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
10963 declared as a pointer to a @code{struct}, @code{class}, or
10964 @code{union}---for example, @code{struct MyType *}---that is used in one
10965 source file although the full declaration of @code{struct MyType} is in
10966 another source file. The default is on.
10968 A change in the setting of this subcommand will not take effect until
10969 the next time symbols for a file are loaded.
10971 @item set opaque-type-resolution off
10972 Tell @value{GDBN} not to resolve opaque types. In this case, the type
10973 is printed as follows:
10975 @{<no data fields>@}
10978 @kindex show opaque-type-resolution
10979 @item show opaque-type-resolution
10980 Show whether opaque types are resolved or not.
10982 @kindex maint print symbols
10983 @cindex symbol dump
10984 @kindex maint print psymbols
10985 @cindex partial symbol dump
10986 @item maint print symbols @var{filename}
10987 @itemx maint print psymbols @var{filename}
10988 @itemx maint print msymbols @var{filename}
10989 Write a dump of debugging symbol data into the file @var{filename}.
10990 These commands are used to debug the @value{GDBN} symbol-reading code. Only
10991 symbols with debugging data are included. If you use @samp{maint print
10992 symbols}, @value{GDBN} includes all the symbols for which it has already
10993 collected full details: that is, @var{filename} reflects symbols for
10994 only those files whose symbols @value{GDBN} has read. You can use the
10995 command @code{info sources} to find out which files these are. If you
10996 use @samp{maint print psymbols} instead, the dump shows information about
10997 symbols that @value{GDBN} only knows partially---that is, symbols defined in
10998 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
10999 @samp{maint print msymbols} dumps just the minimal symbol information
11000 required for each object file from which @value{GDBN} has read some symbols.
11001 @xref{Files, ,Commands to specify files}, for a discussion of how
11002 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
11004 @kindex maint info symtabs
11005 @kindex maint info psymtabs
11006 @cindex listing @value{GDBN}'s internal symbol tables
11007 @cindex symbol tables, listing @value{GDBN}'s internal
11008 @cindex full symbol tables, listing @value{GDBN}'s internal
11009 @cindex partial symbol tables, listing @value{GDBN}'s internal
11010 @item maint info symtabs @r{[} @var{regexp} @r{]}
11011 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
11013 List the @code{struct symtab} or @code{struct partial_symtab}
11014 structures whose names match @var{regexp}. If @var{regexp} is not
11015 given, list them all. The output includes expressions which you can
11016 copy into a @value{GDBN} debugging this one to examine a particular
11017 structure in more detail. For example:
11020 (@value{GDBP}) maint info psymtabs dwarf2read
11021 @{ objfile /home/gnu/build/gdb/gdb
11022 ((struct objfile *) 0x82e69d0)
11023 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
11024 ((struct partial_symtab *) 0x8474b10)
11027 text addresses 0x814d3c8 -- 0x8158074
11028 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
11029 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
11030 dependencies (none)
11033 (@value{GDBP}) maint info symtabs
11037 We see that there is one partial symbol table whose filename contains
11038 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
11039 and we see that @value{GDBN} has not read in any symtabs yet at all.
11040 If we set a breakpoint on a function, that will cause @value{GDBN} to
11041 read the symtab for the compilation unit containing that function:
11044 (@value{GDBP}) break dwarf2_psymtab_to_symtab
11045 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
11047 (@value{GDBP}) maint info symtabs
11048 @{ objfile /home/gnu/build/gdb/gdb
11049 ((struct objfile *) 0x82e69d0)
11050 @{ symtab /home/gnu/src/gdb/dwarf2read.c
11051 ((struct symtab *) 0x86c1f38)
11054 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
11055 debugformat DWARF 2
11064 @chapter Altering Execution
11066 Once you think you have found an error in your program, you might want to
11067 find out for certain whether correcting the apparent error would lead to
11068 correct results in the rest of the run. You can find the answer by
11069 experiment, using the @value{GDBN} features for altering execution of the
11072 For example, you can store new values into variables or memory
11073 locations, give your program a signal, restart it at a different
11074 address, or even return prematurely from a function.
11077 * Assignment:: Assignment to variables
11078 * Jumping:: Continuing at a different address
11079 * Signaling:: Giving your program a signal
11080 * Returning:: Returning from a function
11081 * Calling:: Calling your program's functions
11082 * Patching:: Patching your program
11086 @section Assignment to variables
11089 @cindex setting variables
11090 To alter the value of a variable, evaluate an assignment expression.
11091 @xref{Expressions, ,Expressions}. For example,
11098 stores the value 4 into the variable @code{x}, and then prints the
11099 value of the assignment expression (which is 4).
11100 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
11101 information on operators in supported languages.
11103 @kindex set variable
11104 @cindex variables, setting
11105 If you are not interested in seeing the value of the assignment, use the
11106 @code{set} command instead of the @code{print} command. @code{set} is
11107 really the same as @code{print} except that the expression's value is
11108 not printed and is not put in the value history (@pxref{Value History,
11109 ,Value history}). The expression is evaluated only for its effects.
11111 If the beginning of the argument string of the @code{set} command
11112 appears identical to a @code{set} subcommand, use the @code{set
11113 variable} command instead of just @code{set}. This command is identical
11114 to @code{set} except for its lack of subcommands. For example, if your
11115 program has a variable @code{width}, you get an error if you try to set
11116 a new value with just @samp{set width=13}, because @value{GDBN} has the
11117 command @code{set width}:
11120 (@value{GDBP}) whatis width
11122 (@value{GDBP}) p width
11124 (@value{GDBP}) set width=47
11125 Invalid syntax in expression.
11129 The invalid expression, of course, is @samp{=47}. In
11130 order to actually set the program's variable @code{width}, use
11133 (@value{GDBP}) set var width=47
11136 Because the @code{set} command has many subcommands that can conflict
11137 with the names of program variables, it is a good idea to use the
11138 @code{set variable} command instead of just @code{set}. For example, if
11139 your program has a variable @code{g}, you run into problems if you try
11140 to set a new value with just @samp{set g=4}, because @value{GDBN} has
11141 the command @code{set gnutarget}, abbreviated @code{set g}:
11145 (@value{GDBP}) whatis g
11149 (@value{GDBP}) set g=4
11153 The program being debugged has been started already.
11154 Start it from the beginning? (y or n) y
11155 Starting program: /home/smith/cc_progs/a.out
11156 "/home/smith/cc_progs/a.out": can't open to read symbols:
11157 Invalid bfd target.
11158 (@value{GDBP}) show g
11159 The current BFD target is "=4".
11164 The program variable @code{g} did not change, and you silently set the
11165 @code{gnutarget} to an invalid value. In order to set the variable
11169 (@value{GDBP}) set var g=4
11172 @value{GDBN} allows more implicit conversions in assignments than C; you can
11173 freely store an integer value into a pointer variable or vice versa,
11174 and you can convert any structure to any other structure that is the
11175 same length or shorter.
11176 @comment FIXME: how do structs align/pad in these conversions?
11177 @comment /doc@cygnus.com 18dec1990
11179 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
11180 construct to generate a value of specified type at a specified address
11181 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
11182 to memory location @code{0x83040} as an integer (which implies a certain size
11183 and representation in memory), and
11186 set @{int@}0x83040 = 4
11190 stores the value 4 into that memory location.
11193 @section Continuing at a different address
11195 Ordinarily, when you continue your program, you do so at the place where
11196 it stopped, with the @code{continue} command. You can instead continue at
11197 an address of your own choosing, with the following commands:
11201 @item jump @var{linespec}
11202 Resume execution at line @var{linespec}. Execution stops again
11203 immediately if there is a breakpoint there. @xref{List, ,Printing
11204 source lines}, for a description of the different forms of
11205 @var{linespec}. It is common practice to use the @code{tbreak} command
11206 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
11209 The @code{jump} command does not change the current stack frame, or
11210 the stack pointer, or the contents of any memory location or any
11211 register other than the program counter. If line @var{linespec} is in
11212 a different function from the one currently executing, the results may
11213 be bizarre if the two functions expect different patterns of arguments or
11214 of local variables. For this reason, the @code{jump} command requests
11215 confirmation if the specified line is not in the function currently
11216 executing. However, even bizarre results are predictable if you are
11217 well acquainted with the machine-language code of your program.
11219 @item jump *@var{address}
11220 Resume execution at the instruction at address @var{address}.
11223 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
11224 On many systems, you can get much the same effect as the @code{jump}
11225 command by storing a new value into the register @code{$pc}. The
11226 difference is that this does not start your program running; it only
11227 changes the address of where it @emph{will} run when you continue. For
11235 makes the next @code{continue} command or stepping command execute at
11236 address @code{0x485}, rather than at the address where your program stopped.
11237 @xref{Continuing and Stepping, ,Continuing and stepping}.
11239 The most common occasion to use the @code{jump} command is to back
11240 up---perhaps with more breakpoints set---over a portion of a program
11241 that has already executed, in order to examine its execution in more
11246 @section Giving your program a signal
11247 @cindex deliver a signal to a program
11251 @item signal @var{signal}
11252 Resume execution where your program stopped, but immediately give it the
11253 signal @var{signal}. @var{signal} can be the name or the number of a
11254 signal. For example, on many systems @code{signal 2} and @code{signal
11255 SIGINT} are both ways of sending an interrupt signal.
11257 Alternatively, if @var{signal} is zero, continue execution without
11258 giving a signal. This is useful when your program stopped on account of
11259 a signal and would ordinary see the signal when resumed with the
11260 @code{continue} command; @samp{signal 0} causes it to resume without a
11263 @code{signal} does not repeat when you press @key{RET} a second time
11264 after executing the command.
11268 Invoking the @code{signal} command is not the same as invoking the
11269 @code{kill} utility from the shell. Sending a signal with @code{kill}
11270 causes @value{GDBN} to decide what to do with the signal depending on
11271 the signal handling tables (@pxref{Signals}). The @code{signal} command
11272 passes the signal directly to your program.
11276 @section Returning from a function
11279 @cindex returning from a function
11282 @itemx return @var{expression}
11283 You can cancel execution of a function call with the @code{return}
11284 command. If you give an
11285 @var{expression} argument, its value is used as the function's return
11289 When you use @code{return}, @value{GDBN} discards the selected stack frame
11290 (and all frames within it). You can think of this as making the
11291 discarded frame return prematurely. If you wish to specify a value to
11292 be returned, give that value as the argument to @code{return}.
11294 This pops the selected stack frame (@pxref{Selection, ,Selecting a
11295 frame}), and any other frames inside of it, leaving its caller as the
11296 innermost remaining frame. That frame becomes selected. The
11297 specified value is stored in the registers used for returning values
11300 The @code{return} command does not resume execution; it leaves the
11301 program stopped in the state that would exist if the function had just
11302 returned. In contrast, the @code{finish} command (@pxref{Continuing
11303 and Stepping, ,Continuing and stepping}) resumes execution until the
11304 selected stack frame returns naturally.
11307 @section Calling program functions
11310 @cindex calling functions
11311 @cindex inferior functions, calling
11312 @item print @var{expr}
11313 Evaluate the expression @var{expr} and display the resuling value.
11314 @var{expr} may include calls to functions in the program being
11318 @item call @var{expr}
11319 Evaluate the expression @var{expr} without displaying @code{void}
11322 You can use this variant of the @code{print} command if you want to
11323 execute a function from your program that does not return anything
11324 (a.k.a.@: @dfn{a void function}), but without cluttering the output
11325 with @code{void} returned values that @value{GDBN} will otherwise
11326 print. If the result is not void, it is printed and saved in the
11330 It is possible for the function you call via the @code{print} or
11331 @code{call} command to generate a signal (e.g., if there's a bug in
11332 the function, or if you passed it incorrect arguments). What happens
11333 in that case is controlled by the @code{set unwindonsignal} command.
11336 @item set unwindonsignal
11337 @kindex set unwindonsignal
11338 @cindex unwind stack in called functions
11339 @cindex call dummy stack unwinding
11340 Set unwinding of the stack if a signal is received while in a function
11341 that @value{GDBN} called in the program being debugged. If set to on,
11342 @value{GDBN} unwinds the stack it created for the call and restores
11343 the context to what it was before the call. If set to off (the
11344 default), @value{GDBN} stops in the frame where the signal was
11347 @item show unwindonsignal
11348 @kindex show unwindonsignal
11349 Show the current setting of stack unwinding in the functions called by
11353 @cindex weak alias functions
11354 Sometimes, a function you wish to call is actually a @dfn{weak alias}
11355 for another function. In such case, @value{GDBN} might not pick up
11356 the type information, including the types of the function arguments,
11357 which causes @value{GDBN} to call the inferior function incorrectly.
11358 As a result, the called function will function erroneously and may
11359 even crash. A solution to that is to use the name of the aliased
11363 @section Patching programs
11365 @cindex patching binaries
11366 @cindex writing into executables
11367 @cindex writing into corefiles
11369 By default, @value{GDBN} opens the file containing your program's
11370 executable code (or the corefile) read-only. This prevents accidental
11371 alterations to machine code; but it also prevents you from intentionally
11372 patching your program's binary.
11374 If you'd like to be able to patch the binary, you can specify that
11375 explicitly with the @code{set write} command. For example, you might
11376 want to turn on internal debugging flags, or even to make emergency
11382 @itemx set write off
11383 If you specify @samp{set write on}, @value{GDBN} opens executable and
11384 core files for both reading and writing; if you specify @samp{set write
11385 off} (the default), @value{GDBN} opens them read-only.
11387 If you have already loaded a file, you must load it again (using the
11388 @code{exec-file} or @code{core-file} command) after changing @code{set
11389 write}, for your new setting to take effect.
11393 Display whether executable files and core files are opened for writing
11394 as well as reading.
11398 @chapter @value{GDBN} Files
11400 @value{GDBN} needs to know the file name of the program to be debugged,
11401 both in order to read its symbol table and in order to start your
11402 program. To debug a core dump of a previous run, you must also tell
11403 @value{GDBN} the name of the core dump file.
11406 * Files:: Commands to specify files
11407 * Separate Debug Files:: Debugging information in separate files
11408 * Symbol Errors:: Errors reading symbol files
11412 @section Commands to specify files
11414 @cindex symbol table
11415 @cindex core dump file
11417 You may want to specify executable and core dump file names. The usual
11418 way to do this is at start-up time, using the arguments to
11419 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
11420 Out of @value{GDBN}}).
11422 Occasionally it is necessary to change to a different file during a
11423 @value{GDBN} session. Or you may run @value{GDBN} and forget to
11424 specify a file you want to use. Or you are debugging a remote target
11425 via @code{gdbserver} (@pxref{Server, file}). In these situations the
11426 @value{GDBN} commands to specify new files are useful.
11429 @cindex executable file
11431 @item file @var{filename}
11432 Use @var{filename} as the program to be debugged. It is read for its
11433 symbols and for the contents of pure memory. It is also the program
11434 executed when you use the @code{run} command. If you do not specify a
11435 directory and the file is not found in the @value{GDBN} working directory,
11436 @value{GDBN} uses the environment variable @code{PATH} as a list of
11437 directories to search, just as the shell does when looking for a program
11438 to run. You can change the value of this variable, for both @value{GDBN}
11439 and your program, using the @code{path} command.
11441 @cindex unlinked object files
11442 @cindex patching object files
11443 You can load unlinked object @file{.o} files into @value{GDBN} using
11444 the @code{file} command. You will not be able to ``run'' an object
11445 file, but you can disassemble functions and inspect variables. Also,
11446 if the underlying BFD functionality supports it, you could use
11447 @kbd{gdb -write} to patch object files using this technique. Note
11448 that @value{GDBN} can neither interpret nor modify relocations in this
11449 case, so branches and some initialized variables will appear to go to
11450 the wrong place. But this feature is still handy from time to time.
11453 @code{file} with no argument makes @value{GDBN} discard any information it
11454 has on both executable file and the symbol table.
11457 @item exec-file @r{[} @var{filename} @r{]}
11458 Specify that the program to be run (but not the symbol table) is found
11459 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
11460 if necessary to locate your program. Omitting @var{filename} means to
11461 discard information on the executable file.
11463 @kindex symbol-file
11464 @item symbol-file @r{[} @var{filename} @r{]}
11465 Read symbol table information from file @var{filename}. @code{PATH} is
11466 searched when necessary. Use the @code{file} command to get both symbol
11467 table and program to run from the same file.
11469 @code{symbol-file} with no argument clears out @value{GDBN} information on your
11470 program's symbol table.
11472 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
11473 some breakpoints and auto-display expressions. This is because they may
11474 contain pointers to the internal data recording symbols and data types,
11475 which are part of the old symbol table data being discarded inside
11478 @code{symbol-file} does not repeat if you press @key{RET} again after
11481 When @value{GDBN} is configured for a particular environment, it
11482 understands debugging information in whatever format is the standard
11483 generated for that environment; you may use either a @sc{gnu} compiler, or
11484 other compilers that adhere to the local conventions.
11485 Best results are usually obtained from @sc{gnu} compilers; for example,
11486 using @code{@value{GCC}} you can generate debugging information for
11489 For most kinds of object files, with the exception of old SVR3 systems
11490 using COFF, the @code{symbol-file} command does not normally read the
11491 symbol table in full right away. Instead, it scans the symbol table
11492 quickly to find which source files and which symbols are present. The
11493 details are read later, one source file at a time, as they are needed.
11495 The purpose of this two-stage reading strategy is to make @value{GDBN}
11496 start up faster. For the most part, it is invisible except for
11497 occasional pauses while the symbol table details for a particular source
11498 file are being read. (The @code{set verbose} command can turn these
11499 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
11500 warnings and messages}.)
11502 We have not implemented the two-stage strategy for COFF yet. When the
11503 symbol table is stored in COFF format, @code{symbol-file} reads the
11504 symbol table data in full right away. Note that ``stabs-in-COFF''
11505 still does the two-stage strategy, since the debug info is actually
11509 @cindex reading symbols immediately
11510 @cindex symbols, reading immediately
11511 @item symbol-file @var{filename} @r{[} -readnow @r{]}
11512 @itemx file @var{filename} @r{[} -readnow @r{]}
11513 You can override the @value{GDBN} two-stage strategy for reading symbol
11514 tables by using the @samp{-readnow} option with any of the commands that
11515 load symbol table information, if you want to be sure @value{GDBN} has the
11516 entire symbol table available.
11518 @c FIXME: for now no mention of directories, since this seems to be in
11519 @c flux. 13mar1992 status is that in theory GDB would look either in
11520 @c current dir or in same dir as myprog; but issues like competing
11521 @c GDB's, or clutter in system dirs, mean that in practice right now
11522 @c only current dir is used. FFish says maybe a special GDB hierarchy
11523 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
11527 @item core-file @r{[}@var{filename}@r{]}
11529 Specify the whereabouts of a core dump file to be used as the ``contents
11530 of memory''. Traditionally, core files contain only some parts of the
11531 address space of the process that generated them; @value{GDBN} can access the
11532 executable file itself for other parts.
11534 @code{core-file} with no argument specifies that no core file is
11537 Note that the core file is ignored when your program is actually running
11538 under @value{GDBN}. So, if you have been running your program and you
11539 wish to debug a core file instead, you must kill the subprocess in which
11540 the program is running. To do this, use the @code{kill} command
11541 (@pxref{Kill Process, ,Killing the child process}).
11543 @kindex add-symbol-file
11544 @cindex dynamic linking
11545 @item add-symbol-file @var{filename} @var{address}
11546 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
11547 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
11548 The @code{add-symbol-file} command reads additional symbol table
11549 information from the file @var{filename}. You would use this command
11550 when @var{filename} has been dynamically loaded (by some other means)
11551 into the program that is running. @var{address} should be the memory
11552 address at which the file has been loaded; @value{GDBN} cannot figure
11553 this out for itself. You can additionally specify an arbitrary number
11554 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
11555 section name and base address for that section. You can specify any
11556 @var{address} as an expression.
11558 The symbol table of the file @var{filename} is added to the symbol table
11559 originally read with the @code{symbol-file} command. You can use the
11560 @code{add-symbol-file} command any number of times; the new symbol data
11561 thus read keeps adding to the old. To discard all old symbol data
11562 instead, use the @code{symbol-file} command without any arguments.
11564 @cindex relocatable object files, reading symbols from
11565 @cindex object files, relocatable, reading symbols from
11566 @cindex reading symbols from relocatable object files
11567 @cindex symbols, reading from relocatable object files
11568 @cindex @file{.o} files, reading symbols from
11569 Although @var{filename} is typically a shared library file, an
11570 executable file, or some other object file which has been fully
11571 relocated for loading into a process, you can also load symbolic
11572 information from relocatable @file{.o} files, as long as:
11576 the file's symbolic information refers only to linker symbols defined in
11577 that file, not to symbols defined by other object files,
11579 every section the file's symbolic information refers to has actually
11580 been loaded into the inferior, as it appears in the file, and
11582 you can determine the address at which every section was loaded, and
11583 provide these to the @code{add-symbol-file} command.
11587 Some embedded operating systems, like Sun Chorus and VxWorks, can load
11588 relocatable files into an already running program; such systems
11589 typically make the requirements above easy to meet. However, it's
11590 important to recognize that many native systems use complex link
11591 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
11592 assembly, for example) that make the requirements difficult to meet. In
11593 general, one cannot assume that using @code{add-symbol-file} to read a
11594 relocatable object file's symbolic information will have the same effect
11595 as linking the relocatable object file into the program in the normal
11598 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
11600 @kindex add-symbol-file-from-memory
11601 @cindex @code{syscall DSO}
11602 @cindex load symbols from memory
11603 @item add-symbol-file-from-memory @var{address}
11604 Load symbols from the given @var{address} in a dynamically loaded
11605 object file whose image is mapped directly into the inferior's memory.
11606 For example, the Linux kernel maps a @code{syscall DSO} into each
11607 process's address space; this DSO provides kernel-specific code for
11608 some system calls. The argument can be any expression whose
11609 evaluation yields the address of the file's shared object file header.
11610 For this command to work, you must have used @code{symbol-file} or
11611 @code{exec-file} commands in advance.
11613 @kindex add-shared-symbol-files
11615 @item add-shared-symbol-files @var{library-file}
11616 @itemx assf @var{library-file}
11617 The @code{add-shared-symbol-files} command can currently be used only
11618 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
11619 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
11620 @value{GDBN} automatically looks for shared libraries, however if
11621 @value{GDBN} does not find yours, you can invoke
11622 @code{add-shared-symbol-files}. It takes one argument: the shared
11623 library's file name. @code{assf} is a shorthand alias for
11624 @code{add-shared-symbol-files}.
11627 @item section @var{section} @var{addr}
11628 The @code{section} command changes the base address of the named
11629 @var{section} of the exec file to @var{addr}. This can be used if the
11630 exec file does not contain section addresses, (such as in the
11631 @code{a.out} format), or when the addresses specified in the file
11632 itself are wrong. Each section must be changed separately. The
11633 @code{info files} command, described below, lists all the sections and
11637 @kindex info target
11640 @code{info files} and @code{info target} are synonymous; both print the
11641 current target (@pxref{Targets, ,Specifying a Debugging Target}),
11642 including the names of the executable and core dump files currently in
11643 use by @value{GDBN}, and the files from which symbols were loaded. The
11644 command @code{help target} lists all possible targets rather than
11647 @kindex maint info sections
11648 @item maint info sections
11649 Another command that can give you extra information about program sections
11650 is @code{maint info sections}. In addition to the section information
11651 displayed by @code{info files}, this command displays the flags and file
11652 offset of each section in the executable and core dump files. In addition,
11653 @code{maint info sections} provides the following command options (which
11654 may be arbitrarily combined):
11658 Display sections for all loaded object files, including shared libraries.
11659 @item @var{sections}
11660 Display info only for named @var{sections}.
11661 @item @var{section-flags}
11662 Display info only for sections for which @var{section-flags} are true.
11663 The section flags that @value{GDBN} currently knows about are:
11666 Section will have space allocated in the process when loaded.
11667 Set for all sections except those containing debug information.
11669 Section will be loaded from the file into the child process memory.
11670 Set for pre-initialized code and data, clear for @code{.bss} sections.
11672 Section needs to be relocated before loading.
11674 Section cannot be modified by the child process.
11676 Section contains executable code only.
11678 Section contains data only (no executable code).
11680 Section will reside in ROM.
11682 Section contains data for constructor/destructor lists.
11684 Section is not empty.
11686 An instruction to the linker to not output the section.
11687 @item COFF_SHARED_LIBRARY
11688 A notification to the linker that the section contains
11689 COFF shared library information.
11691 Section contains common symbols.
11694 @kindex set trust-readonly-sections
11695 @cindex read-only sections
11696 @item set trust-readonly-sections on
11697 Tell @value{GDBN} that readonly sections in your object file
11698 really are read-only (i.e.@: that their contents will not change).
11699 In that case, @value{GDBN} can fetch values from these sections
11700 out of the object file, rather than from the target program.
11701 For some targets (notably embedded ones), this can be a significant
11702 enhancement to debugging performance.
11704 The default is off.
11706 @item set trust-readonly-sections off
11707 Tell @value{GDBN} not to trust readonly sections. This means that
11708 the contents of the section might change while the program is running,
11709 and must therefore be fetched from the target when needed.
11711 @item show trust-readonly-sections
11712 Show the current setting of trusting readonly sections.
11715 All file-specifying commands allow both absolute and relative file names
11716 as arguments. @value{GDBN} always converts the file name to an absolute file
11717 name and remembers it that way.
11719 @cindex shared libraries
11720 @value{GDBN} supports GNU/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
11721 and IBM RS/6000 AIX shared libraries.
11723 @value{GDBN} automatically loads symbol definitions from shared libraries
11724 when you use the @code{run} command, or when you examine a core file.
11725 (Before you issue the @code{run} command, @value{GDBN} does not understand
11726 references to a function in a shared library, however---unless you are
11727 debugging a core file).
11729 On HP-UX, if the program loads a library explicitly, @value{GDBN}
11730 automatically loads the symbols at the time of the @code{shl_load} call.
11732 @c FIXME: some @value{GDBN} release may permit some refs to undef
11733 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
11734 @c FIXME...lib; check this from time to time when updating manual
11736 There are times, however, when you may wish to not automatically load
11737 symbol definitions from shared libraries, such as when they are
11738 particularly large or there are many of them.
11740 To control the automatic loading of shared library symbols, use the
11744 @kindex set auto-solib-add
11745 @item set auto-solib-add @var{mode}
11746 If @var{mode} is @code{on}, symbols from all shared object libraries
11747 will be loaded automatically when the inferior begins execution, you
11748 attach to an independently started inferior, or when the dynamic linker
11749 informs @value{GDBN} that a new library has been loaded. If @var{mode}
11750 is @code{off}, symbols must be loaded manually, using the
11751 @code{sharedlibrary} command. The default value is @code{on}.
11753 @cindex memory used for symbol tables
11754 If your program uses lots of shared libraries with debug info that
11755 takes large amounts of memory, you can decrease the @value{GDBN}
11756 memory footprint by preventing it from automatically loading the
11757 symbols from shared libraries. To that end, type @kbd{set
11758 auto-solib-add off} before running the inferior, then load each
11759 library whose debug symbols you do need with @kbd{sharedlibrary
11760 @var{regexp}}, where @var{regexp} is a regular expresion that matches
11761 the libraries whose symbols you want to be loaded.
11763 @kindex show auto-solib-add
11764 @item show auto-solib-add
11765 Display the current autoloading mode.
11768 @cindex load shared library
11769 To explicitly load shared library symbols, use the @code{sharedlibrary}
11773 @kindex info sharedlibrary
11776 @itemx info sharedlibrary
11777 Print the names of the shared libraries which are currently loaded.
11779 @kindex sharedlibrary
11781 @item sharedlibrary @var{regex}
11782 @itemx share @var{regex}
11783 Load shared object library symbols for files matching a
11784 Unix regular expression.
11785 As with files loaded automatically, it only loads shared libraries
11786 required by your program for a core file or after typing @code{run}. If
11787 @var{regex} is omitted all shared libraries required by your program are
11790 @item nosharedlibrary
11791 @kindex nosharedlibrary
11792 @cindex unload symbols from shared libraries
11793 Unload all shared object library symbols. This discards all symbols
11794 that have been loaded from all shared libraries. Symbols from shared
11795 libraries that were loaded by explicit user requests are not
11799 Sometimes you may wish that @value{GDBN} stops and gives you control
11800 when any of shared library events happen. Use the @code{set
11801 stop-on-solib-events} command for this:
11804 @item set stop-on-solib-events
11805 @kindex set stop-on-solib-events
11806 This command controls whether @value{GDBN} should give you control
11807 when the dynamic linker notifies it about some shared library event.
11808 The most common event of interest is loading or unloading of a new
11811 @item show stop-on-solib-events
11812 @kindex show stop-on-solib-events
11813 Show whether @value{GDBN} stops and gives you control when shared
11814 library events happen.
11817 Shared libraries are also supported in many cross or remote debugging
11818 configurations. A copy of the target's libraries need to be present on the
11819 host system; they need to be the same as the target libraries, although the
11820 copies on the target can be stripped as long as the copies on the host are
11823 @cindex where to look for shared libraries
11824 For remote debugging, you need to tell @value{GDBN} where the target
11825 libraries are, so that it can load the correct copies---otherwise, it
11826 may try to load the host's libraries. @value{GDBN} has two variables
11827 to specify the search directories for target libraries.
11830 @cindex prefix for shared library file names
11831 @kindex set solib-absolute-prefix
11832 @item set solib-absolute-prefix @var{path}
11833 If this variable is set, @var{path} will be used as a prefix for any
11834 absolute shared library paths; many runtime loaders store the absolute
11835 paths to the shared library in the target program's memory. If you use
11836 @samp{solib-absolute-prefix} to find shared libraries, they need to be laid
11837 out in the same way that they are on the target, with e.g.@: a
11838 @file{/usr/lib} hierarchy under @var{path}.
11840 @cindex default value of @samp{solib-absolute-prefix}
11841 @cindex @samp{--with-sysroot}
11842 You can set the default value of @samp{solib-absolute-prefix} by using the
11843 configure-time @samp{--with-sysroot} option.
11845 @kindex show solib-absolute-prefix
11846 @item show solib-absolute-prefix
11847 Display the current shared library prefix.
11849 @kindex set solib-search-path
11850 @item set solib-search-path @var{path}
11851 If this variable is set, @var{path} is a colon-separated list of directories
11852 to search for shared libraries. @samp{solib-search-path} is used after
11853 @samp{solib-absolute-prefix} fails to locate the library, or if the path to
11854 the library is relative instead of absolute. If you want to use
11855 @samp{solib-search-path} instead of @samp{solib-absolute-prefix}, be sure to
11856 set @samp{solib-absolute-prefix} to a nonexistant directory to prevent
11857 @value{GDBN} from finding your host's libraries.
11859 @kindex show solib-search-path
11860 @item show solib-search-path
11861 Display the current shared library search path.
11865 @node Separate Debug Files
11866 @section Debugging Information in Separate Files
11867 @cindex separate debugging information files
11868 @cindex debugging information in separate files
11869 @cindex @file{.debug} subdirectories
11870 @cindex debugging information directory, global
11871 @cindex global debugging information directory
11873 @value{GDBN} allows you to put a program's debugging information in a
11874 file separate from the executable itself, in a way that allows
11875 @value{GDBN} to find and load the debugging information automatically.
11876 Since debugging information can be very large --- sometimes larger
11877 than the executable code itself --- some systems distribute debugging
11878 information for their executables in separate files, which users can
11879 install only when they need to debug a problem.
11881 If an executable's debugging information has been extracted to a
11882 separate file, the executable should contain a @dfn{debug link} giving
11883 the name of the debugging information file (with no directory
11884 components), and a checksum of its contents. (The exact form of a
11885 debug link is described below.) If the full name of the directory
11886 containing the executable is @var{execdir}, and the executable has a
11887 debug link that specifies the name @var{debugfile}, then @value{GDBN}
11888 will automatically search for the debugging information file in three
11893 the directory containing the executable file (that is, it will look
11894 for a file named @file{@var{execdir}/@var{debugfile}},
11896 a subdirectory of that directory named @file{.debug} (that is, the
11897 file @file{@var{execdir}/.debug/@var{debugfile}}, and
11899 a subdirectory of the global debug file directory that includes the
11900 executable's full path, and the name from the link (that is, the file
11901 @file{@var{globaldebugdir}/@var{execdir}/@var{debugfile}}, where
11902 @var{globaldebugdir} is the global debug file directory, and
11903 @var{execdir} has been turned into a relative path).
11906 @value{GDBN} checks under each of these names for a debugging
11907 information file whose checksum matches that given in the link, and
11908 reads the debugging information from the first one it finds.
11910 So, for example, if you ask @value{GDBN} to debug @file{/usr/bin/ls},
11911 which has a link containing the name @file{ls.debug}, and the global
11912 debug directory is @file{/usr/lib/debug}, then @value{GDBN} will look
11913 for debug information in @file{/usr/bin/ls.debug},
11914 @file{/usr/bin/.debug/ls.debug}, and
11915 @file{/usr/lib/debug/usr/bin/ls.debug}.
11917 You can set the global debugging info directory's name, and view the
11918 name @value{GDBN} is currently using.
11922 @kindex set debug-file-directory
11923 @item set debug-file-directory @var{directory}
11924 Set the directory which @value{GDBN} searches for separate debugging
11925 information files to @var{directory}.
11927 @kindex show debug-file-directory
11928 @item show debug-file-directory
11929 Show the directory @value{GDBN} searches for separate debugging
11934 @cindex @code{.gnu_debuglink} sections
11935 @cindex debug links
11936 A debug link is a special section of the executable file named
11937 @code{.gnu_debuglink}. The section must contain:
11941 A filename, with any leading directory components removed, followed by
11944 zero to three bytes of padding, as needed to reach the next four-byte
11945 boundary within the section, and
11947 a four-byte CRC checksum, stored in the same endianness used for the
11948 executable file itself. The checksum is computed on the debugging
11949 information file's full contents by the function given below, passing
11950 zero as the @var{crc} argument.
11953 Any executable file format can carry a debug link, as long as it can
11954 contain a section named @code{.gnu_debuglink} with the contents
11957 The debugging information file itself should be an ordinary
11958 executable, containing a full set of linker symbols, sections, and
11959 debugging information. The sections of the debugging information file
11960 should have the same names, addresses and sizes as the original file,
11961 but they need not contain any data --- much like a @code{.bss} section
11962 in an ordinary executable.
11964 As of December 2002, there is no standard GNU utility to produce
11965 separated executable / debugging information file pairs. Ulrich
11966 Drepper's @file{elfutils} package, starting with version 0.53,
11967 contains a version of the @code{strip} command such that the command
11968 @kbd{strip foo -f foo.debug} removes the debugging information from
11969 the executable file @file{foo}, places it in the file
11970 @file{foo.debug}, and leaves behind a debug link in @file{foo}.
11972 Since there are many different ways to compute CRC's (different
11973 polynomials, reversals, byte ordering, etc.), the simplest way to
11974 describe the CRC used in @code{.gnu_debuglink} sections is to give the
11975 complete code for a function that computes it:
11977 @kindex gnu_debuglink_crc32
11980 gnu_debuglink_crc32 (unsigned long crc,
11981 unsigned char *buf, size_t len)
11983 static const unsigned long crc32_table[256] =
11985 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
11986 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
11987 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
11988 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
11989 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
11990 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
11991 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
11992 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
11993 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
11994 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
11995 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
11996 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
11997 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
11998 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
11999 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
12000 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
12001 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
12002 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
12003 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
12004 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
12005 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
12006 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
12007 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
12008 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
12009 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
12010 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
12011 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
12012 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
12013 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
12014 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
12015 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
12016 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
12017 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
12018 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
12019 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
12020 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
12021 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
12022 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
12023 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
12024 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
12025 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
12026 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
12027 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
12028 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
12029 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
12030 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
12031 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
12032 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
12033 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
12034 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
12035 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
12038 unsigned char *end;
12040 crc = ~crc & 0xffffffff;
12041 for (end = buf + len; buf < end; ++buf)
12042 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
12043 return ~crc & 0xffffffff;
12048 @node Symbol Errors
12049 @section Errors reading symbol files
12051 While reading a symbol file, @value{GDBN} occasionally encounters problems,
12052 such as symbol types it does not recognize, or known bugs in compiler
12053 output. By default, @value{GDBN} does not notify you of such problems, since
12054 they are relatively common and primarily of interest to people
12055 debugging compilers. If you are interested in seeing information
12056 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
12057 only one message about each such type of problem, no matter how many
12058 times the problem occurs; or you can ask @value{GDBN} to print more messages,
12059 to see how many times the problems occur, with the @code{set
12060 complaints} command (@pxref{Messages/Warnings, ,Optional warnings and
12063 The messages currently printed, and their meanings, include:
12066 @item inner block not inside outer block in @var{symbol}
12068 The symbol information shows where symbol scopes begin and end
12069 (such as at the start of a function or a block of statements). This
12070 error indicates that an inner scope block is not fully contained
12071 in its outer scope blocks.
12073 @value{GDBN} circumvents the problem by treating the inner block as if it had
12074 the same scope as the outer block. In the error message, @var{symbol}
12075 may be shown as ``@code{(don't know)}'' if the outer block is not a
12078 @item block at @var{address} out of order
12080 The symbol information for symbol scope blocks should occur in
12081 order of increasing addresses. This error indicates that it does not
12084 @value{GDBN} does not circumvent this problem, and has trouble
12085 locating symbols in the source file whose symbols it is reading. (You
12086 can often determine what source file is affected by specifying
12087 @code{set verbose on}. @xref{Messages/Warnings, ,Optional warnings and
12090 @item bad block start address patched
12092 The symbol information for a symbol scope block has a start address
12093 smaller than the address of the preceding source line. This is known
12094 to occur in the SunOS 4.1.1 (and earlier) C compiler.
12096 @value{GDBN} circumvents the problem by treating the symbol scope block as
12097 starting on the previous source line.
12099 @item bad string table offset in symbol @var{n}
12102 Symbol number @var{n} contains a pointer into the string table which is
12103 larger than the size of the string table.
12105 @value{GDBN} circumvents the problem by considering the symbol to have the
12106 name @code{foo}, which may cause other problems if many symbols end up
12109 @item unknown symbol type @code{0x@var{nn}}
12111 The symbol information contains new data types that @value{GDBN} does
12112 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
12113 uncomprehended information, in hexadecimal.
12115 @value{GDBN} circumvents the error by ignoring this symbol information.
12116 This usually allows you to debug your program, though certain symbols
12117 are not accessible. If you encounter such a problem and feel like
12118 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
12119 on @code{complain}, then go up to the function @code{read_dbx_symtab}
12120 and examine @code{*bufp} to see the symbol.
12122 @item stub type has NULL name
12124 @value{GDBN} could not find the full definition for a struct or class.
12126 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
12127 The symbol information for a C@t{++} member function is missing some
12128 information that recent versions of the compiler should have output for
12131 @item info mismatch between compiler and debugger
12133 @value{GDBN} could not parse a type specification output by the compiler.
12138 @chapter Specifying a Debugging Target
12140 @cindex debugging target
12141 A @dfn{target} is the execution environment occupied by your program.
12143 Often, @value{GDBN} runs in the same host environment as your program;
12144 in that case, the debugging target is specified as a side effect when
12145 you use the @code{file} or @code{core} commands. When you need more
12146 flexibility---for example, running @value{GDBN} on a physically separate
12147 host, or controlling a standalone system over a serial port or a
12148 realtime system over a TCP/IP connection---you can use the @code{target}
12149 command to specify one of the target types configured for @value{GDBN}
12150 (@pxref{Target Commands, ,Commands for managing targets}).
12152 @cindex target architecture
12153 It is possible to build @value{GDBN} for several different @dfn{target
12154 architectures}. When @value{GDBN} is built like that, you can choose
12155 one of the available architectures with the @kbd{set architecture}
12159 @kindex set architecture
12160 @kindex show architecture
12161 @item set architecture @var{arch}
12162 This command sets the current target architecture to @var{arch}. The
12163 value of @var{arch} can be @code{"auto"}, in addition to one of the
12164 supported architectures.
12166 @item show architecture
12167 Show the current target architecture.
12169 @item set processor
12171 @kindex set processor
12172 @kindex show processor
12173 These are alias commands for, respectively, @code{set architecture}
12174 and @code{show architecture}.
12178 * Active Targets:: Active targets
12179 * Target Commands:: Commands for managing targets
12180 * Byte Order:: Choosing target byte order
12181 * Remote:: Remote debugging
12185 @node Active Targets
12186 @section Active targets
12188 @cindex stacking targets
12189 @cindex active targets
12190 @cindex multiple targets
12192 There are three classes of targets: processes, core files, and
12193 executable files. @value{GDBN} can work concurrently on up to three
12194 active targets, one in each class. This allows you to (for example)
12195 start a process and inspect its activity without abandoning your work on
12198 For example, if you execute @samp{gdb a.out}, then the executable file
12199 @code{a.out} is the only active target. If you designate a core file as
12200 well---presumably from a prior run that crashed and coredumped---then
12201 @value{GDBN} has two active targets and uses them in tandem, looking
12202 first in the corefile target, then in the executable file, to satisfy
12203 requests for memory addresses. (Typically, these two classes of target
12204 are complementary, since core files contain only a program's
12205 read-write memory---variables and so on---plus machine status, while
12206 executable files contain only the program text and initialized data.)
12208 When you type @code{run}, your executable file becomes an active process
12209 target as well. When a process target is active, all @value{GDBN}
12210 commands requesting memory addresses refer to that target; addresses in
12211 an active core file or executable file target are obscured while the
12212 process target is active.
12214 Use the @code{core-file} and @code{exec-file} commands to select a new
12215 core file or executable target (@pxref{Files, ,Commands to specify
12216 files}). To specify as a target a process that is already running, use
12217 the @code{attach} command (@pxref{Attach, ,Debugging an already-running
12220 @node Target Commands
12221 @section Commands for managing targets
12224 @item target @var{type} @var{parameters}
12225 Connects the @value{GDBN} host environment to a target machine or
12226 process. A target is typically a protocol for talking to debugging
12227 facilities. You use the argument @var{type} to specify the type or
12228 protocol of the target machine.
12230 Further @var{parameters} are interpreted by the target protocol, but
12231 typically include things like device names or host names to connect
12232 with, process numbers, and baud rates.
12234 The @code{target} command does not repeat if you press @key{RET} again
12235 after executing the command.
12237 @kindex help target
12239 Displays the names of all targets available. To display targets
12240 currently selected, use either @code{info target} or @code{info files}
12241 (@pxref{Files, ,Commands to specify files}).
12243 @item help target @var{name}
12244 Describe a particular target, including any parameters necessary to
12247 @kindex set gnutarget
12248 @item set gnutarget @var{args}
12249 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
12250 knows whether it is reading an @dfn{executable},
12251 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
12252 with the @code{set gnutarget} command. Unlike most @code{target} commands,
12253 with @code{gnutarget} the @code{target} refers to a program, not a machine.
12256 @emph{Warning:} To specify a file format with @code{set gnutarget},
12257 you must know the actual BFD name.
12261 @xref{Files, , Commands to specify files}.
12263 @kindex show gnutarget
12264 @item show gnutarget
12265 Use the @code{show gnutarget} command to display what file format
12266 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
12267 @value{GDBN} will determine the file format for each file automatically,
12268 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
12271 @cindex common targets
12272 Here are some common targets (available, or not, depending on the GDB
12277 @item target exec @var{program}
12278 @cindex executable file target
12279 An executable file. @samp{target exec @var{program}} is the same as
12280 @samp{exec-file @var{program}}.
12282 @item target core @var{filename}
12283 @cindex core dump file target
12284 A core dump file. @samp{target core @var{filename}} is the same as
12285 @samp{core-file @var{filename}}.
12287 @item target remote @var{medium}
12288 @cindex remote target
12289 A remote system connected to @value{GDBN} via a serial line or network
12290 connection. This command tells @value{GDBN} to use its own remote
12291 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
12293 For example, if you have a board connected to @file{/dev/ttya} on the
12294 machine running @value{GDBN}, you could say:
12297 target remote /dev/ttya
12300 @code{target remote} supports the @code{load} command. This is only
12301 useful if you have some other way of getting the stub to the target
12302 system, and you can put it somewhere in memory where it won't get
12303 clobbered by the download.
12306 @cindex built-in simulator target
12307 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
12315 works; however, you cannot assume that a specific memory map, device
12316 drivers, or even basic I/O is available, although some simulators do
12317 provide these. For info about any processor-specific simulator details,
12318 see the appropriate section in @ref{Embedded Processors, ,Embedded
12323 Some configurations may include these targets as well:
12327 @item target nrom @var{dev}
12328 @cindex NetROM ROM emulator target
12329 NetROM ROM emulator. This target only supports downloading.
12333 Different targets are available on different configurations of @value{GDBN};
12334 your configuration may have more or fewer targets.
12336 Many remote targets require you to download the executable's code once
12337 you've successfully established a connection. You may wish to control
12338 various aspects of this process.
12343 @kindex set hash@r{, for remote monitors}
12344 @cindex hash mark while downloading
12345 This command controls whether a hash mark @samp{#} is displayed while
12346 downloading a file to the remote monitor. If on, a hash mark is
12347 displayed after each S-record is successfully downloaded to the
12351 @kindex show hash@r{, for remote monitors}
12352 Show the current status of displaying the hash mark.
12354 @item set debug monitor
12355 @kindex set debug monitor
12356 @cindex display remote monitor communications
12357 Enable or disable display of communications messages between
12358 @value{GDBN} and the remote monitor.
12360 @item show debug monitor
12361 @kindex show debug monitor
12362 Show the current status of displaying communications between
12363 @value{GDBN} and the remote monitor.
12368 @kindex load @var{filename}
12369 @item load @var{filename}
12370 Depending on what remote debugging facilities are configured into
12371 @value{GDBN}, the @code{load} command may be available. Where it exists, it
12372 is meant to make @var{filename} (an executable) available for debugging
12373 on the remote system---by downloading, or dynamic linking, for example.
12374 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
12375 the @code{add-symbol-file} command.
12377 If your @value{GDBN} does not have a @code{load} command, attempting to
12378 execute it gets the error message ``@code{You can't do that when your
12379 target is @dots{}}''
12381 The file is loaded at whatever address is specified in the executable.
12382 For some object file formats, you can specify the load address when you
12383 link the program; for other formats, like a.out, the object file format
12384 specifies a fixed address.
12385 @c FIXME! This would be a good place for an xref to the GNU linker doc.
12387 Depending on the remote side capabilities, @value{GDBN} may be able to
12388 load programs into flash memory.
12390 @code{load} does not repeat if you press @key{RET} again after using it.
12394 @section Choosing target byte order
12396 @cindex choosing target byte order
12397 @cindex target byte order
12399 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
12400 offer the ability to run either big-endian or little-endian byte
12401 orders. Usually the executable or symbol will include a bit to
12402 designate the endian-ness, and you will not need to worry about
12403 which to use. However, you may still find it useful to adjust
12404 @value{GDBN}'s idea of processor endian-ness manually.
12408 @item set endian big
12409 Instruct @value{GDBN} to assume the target is big-endian.
12411 @item set endian little
12412 Instruct @value{GDBN} to assume the target is little-endian.
12414 @item set endian auto
12415 Instruct @value{GDBN} to use the byte order associated with the
12419 Display @value{GDBN}'s current idea of the target byte order.
12423 Note that these commands merely adjust interpretation of symbolic
12424 data on the host, and that they have absolutely no effect on the
12428 @section Remote debugging
12429 @cindex remote debugging
12431 If you are trying to debug a program running on a machine that cannot run
12432 @value{GDBN} in the usual way, it is often useful to use remote debugging.
12433 For example, you might use remote debugging on an operating system kernel,
12434 or on a small system which does not have a general purpose operating system
12435 powerful enough to run a full-featured debugger.
12437 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
12438 to make this work with particular debugging targets. In addition,
12439 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
12440 but not specific to any particular target system) which you can use if you
12441 write the remote stubs---the code that runs on the remote system to
12442 communicate with @value{GDBN}.
12444 Other remote targets may be available in your
12445 configuration of @value{GDBN}; use @code{help target} to list them.
12447 Once you've connected to the remote target, @value{GDBN} allows you to
12448 send arbitrary commands to the remote monitor:
12451 @item remote @var{command}
12452 @kindex remote@r{, a command}
12453 @cindex send command to remote monitor
12454 Send an arbitrary @var{command} string to the remote monitor.
12458 @node Remote Debugging
12459 @chapter Debugging remote programs
12462 * Connecting:: Connecting to a remote target
12463 * Server:: Using the gdbserver program
12464 * Remote configuration:: Remote configuration
12465 * remote stub:: Implementing a remote stub
12469 @section Connecting to a remote target
12471 On the @value{GDBN} host machine, you will need an unstripped copy of
12472 your program, since @value{GDBN} needs symobl and debugging information.
12473 Start up @value{GDBN} as usual, using the name of the local copy of your
12474 program as the first argument.
12476 @cindex @code{target remote}
12477 @value{GDBN} can communicate with the target over a serial line, or
12478 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
12479 each case, @value{GDBN} uses the same protocol for debugging your
12480 program; only the medium carrying the debugging packets varies. The
12481 @code{target remote} command establishes a connection to the target.
12482 Its arguments indicate which medium to use:
12486 @item target remote @var{serial-device}
12487 @cindex serial line, @code{target remote}
12488 Use @var{serial-device} to communicate with the target. For example,
12489 to use a serial line connected to the device named @file{/dev/ttyb}:
12492 target remote /dev/ttyb
12495 If you're using a serial line, you may want to give @value{GDBN} the
12496 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
12497 (@pxref{Remote configuration, set remotebaud}) before the
12498 @code{target} command.
12500 @item target remote @code{@var{host}:@var{port}}
12501 @itemx target remote @code{tcp:@var{host}:@var{port}}
12502 @cindex @acronym{TCP} port, @code{target remote}
12503 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
12504 The @var{host} may be either a host name or a numeric @acronym{IP}
12505 address; @var{port} must be a decimal number. The @var{host} could be
12506 the target machine itself, if it is directly connected to the net, or
12507 it might be a terminal server which in turn has a serial line to the
12510 For example, to connect to port 2828 on a terminal server named
12514 target remote manyfarms:2828
12517 If your remote target is actually running on the same machine as your
12518 debugger session (e.g.@: a simulator for your target running on the
12519 same host), you can omit the hostname. For example, to connect to
12520 port 1234 on your local machine:
12523 target remote :1234
12527 Note that the colon is still required here.
12529 @item target remote @code{udp:@var{host}:@var{port}}
12530 @cindex @acronym{UDP} port, @code{target remote}
12531 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
12532 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
12535 target remote udp:manyfarms:2828
12538 When using a @acronym{UDP} connection for remote debugging, you should
12539 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
12540 can silently drop packets on busy or unreliable networks, which will
12541 cause havoc with your debugging session.
12543 @item target remote | @var{command}
12544 @cindex pipe, @code{target remote} to
12545 Run @var{command} in the background and communicate with it using a
12546 pipe. The @var{command} is a shell command, to be parsed and expanded
12547 by the system's command shell, @code{/bin/sh}; it should expect remote
12548 protocol packets on its standard input, and send replies on its
12549 standard output. You could use this to run a stand-alone simulator
12550 that speaks the remote debugging protocol, to make net connections
12551 using programs like @code{ssh}, or for other similar tricks.
12553 If @var{command} closes its standard output (perhaps by exiting),
12554 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
12555 program has already exited, this will have no effect.)
12559 Once the connection has been established, you can use all the usual
12560 commands to examine and change data and to step and continue the
12563 @cindex interrupting remote programs
12564 @cindex remote programs, interrupting
12565 Whenever @value{GDBN} is waiting for the remote program, if you type the
12566 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
12567 program. This may or may not succeed, depending in part on the hardware
12568 and the serial drivers the remote system uses. If you type the
12569 interrupt character once again, @value{GDBN} displays this prompt:
12572 Interrupted while waiting for the program.
12573 Give up (and stop debugging it)? (y or n)
12576 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
12577 (If you decide you want to try again later, you can use @samp{target
12578 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
12579 goes back to waiting.
12582 @kindex detach (remote)
12584 When you have finished debugging the remote program, you can use the
12585 @code{detach} command to release it from @value{GDBN} control.
12586 Detaching from the target normally resumes its execution, but the results
12587 will depend on your particular remote stub. After the @code{detach}
12588 command, @value{GDBN} is free to connect to another target.
12592 The @code{disconnect} command behaves like @code{detach}, except that
12593 the target is generally not resumed. It will wait for @value{GDBN}
12594 (this instance or another one) to connect and continue debugging. After
12595 the @code{disconnect} command, @value{GDBN} is again free to connect to
12598 @cindex send command to remote monitor
12599 @cindex extend @value{GDBN} for remote targets
12600 @cindex add new commands for external monitor
12602 @item monitor @var{cmd}
12603 This command allows you to send arbitrary commands directly to the
12604 remote monitor. Since @value{GDBN} doesn't care about the commands it
12605 sends like this, this command is the way to extend @value{GDBN}---you
12606 can add new commands that only the external monitor will understand
12611 @section Using the @code{gdbserver} program
12614 @cindex remote connection without stubs
12615 @code{gdbserver} is a control program for Unix-like systems, which
12616 allows you to connect your program with a remote @value{GDBN} via
12617 @code{target remote}---but without linking in the usual debugging stub.
12619 @code{gdbserver} is not a complete replacement for the debugging stubs,
12620 because it requires essentially the same operating-system facilities
12621 that @value{GDBN} itself does. In fact, a system that can run
12622 @code{gdbserver} to connect to a remote @value{GDBN} could also run
12623 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
12624 because it is a much smaller program than @value{GDBN} itself. It is
12625 also easier to port than all of @value{GDBN}, so you may be able to get
12626 started more quickly on a new system by using @code{gdbserver}.
12627 Finally, if you develop code for real-time systems, you may find that
12628 the tradeoffs involved in real-time operation make it more convenient to
12629 do as much development work as possible on another system, for example
12630 by cross-compiling. You can use @code{gdbserver} to make a similar
12631 choice for debugging.
12633 @value{GDBN} and @code{gdbserver} communicate via either a serial line
12634 or a TCP connection, using the standard @value{GDBN} remote serial
12638 @item On the target machine,
12639 you need to have a copy of the program you want to debug.
12640 @code{gdbserver} does not need your program's symbol table, so you can
12641 strip the program if necessary to save space. @value{GDBN} on the host
12642 system does all the symbol handling.
12644 To use the server, you must tell it how to communicate with @value{GDBN};
12645 the name of your program; and the arguments for your program. The usual
12649 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
12652 @var{comm} is either a device name (to use a serial line) or a TCP
12653 hostname and portnumber. For example, to debug Emacs with the argument
12654 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
12658 target> gdbserver /dev/com1 emacs foo.txt
12661 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
12664 To use a TCP connection instead of a serial line:
12667 target> gdbserver host:2345 emacs foo.txt
12670 The only difference from the previous example is the first argument,
12671 specifying that you are communicating with the host @value{GDBN} via
12672 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
12673 expect a TCP connection from machine @samp{host} to local TCP port 2345.
12674 (Currently, the @samp{host} part is ignored.) You can choose any number
12675 you want for the port number as long as it does not conflict with any
12676 TCP ports already in use on the target system (for example, @code{23} is
12677 reserved for @code{telnet}).@footnote{If you choose a port number that
12678 conflicts with another service, @code{gdbserver} prints an error message
12679 and exits.} You must use the same port number with the host @value{GDBN}
12680 @code{target remote} command.
12682 On some targets, @code{gdbserver} can also attach to running programs.
12683 This is accomplished via the @code{--attach} argument. The syntax is:
12686 target> gdbserver @var{comm} --attach @var{pid}
12689 @var{pid} is the process ID of a currently running process. It isn't necessary
12690 to point @code{gdbserver} at a binary for the running process.
12693 @cindex attach to a program by name
12694 You can debug processes by name instead of process ID if your target has the
12695 @code{pidof} utility:
12698 target> gdbserver @var{comm} --attach `pidof @var{PROGRAM}`
12701 In case more than one copy of @var{PROGRAM} is running, or @var{PROGRAM}
12702 has multiple threads, most versions of @code{pidof} support the
12703 @code{-s} option to only return the first process ID.
12705 @item On the host machine,
12706 connect to your target (@pxref{Connecting,,Connecting to a remote target}).
12707 For TCP connections, you must start up @code{gdbserver} prior to using
12708 the @code{target remote} command. Otherwise you may get an error whose
12709 text depends on the host system, but which usually looks something like
12710 @samp{Connection refused}. You don't need to use the @code{load}
12711 command in @value{GDBN} when using @code{gdbserver}, since the program is
12712 already on the target. However, if you want to load the symbols (as
12713 you normally would), do that with the @code{file} command, and issue
12714 it @emph{before} connecting to the server; otherwise, you will get an
12715 error message saying @code{"Program is already running"}, since the
12716 program is considered running after the connection.
12720 @node Remote configuration
12721 @section Remote configuration
12724 @kindex show remote
12725 This section documents the configuration options available when
12726 debugging remote programs. For the options related to the File I/O
12727 extensions of the remote protocol, see @ref{system,
12728 system-call-allowed}.
12731 @item set remoteaddresssize @var{bits}
12732 @cindex adress size for remote targets
12733 @cindex bits in remote address
12734 Set the maximum size of address in a memory packet to the specified
12735 number of bits. @value{GDBN} will mask off the address bits above
12736 that number, when it passes addresses to the remote target. The
12737 default value is the number of bits in the target's address.
12739 @item show remoteaddresssize
12740 Show the current value of remote address size in bits.
12742 @item set remotebaud @var{n}
12743 @cindex baud rate for remote targets
12744 Set the baud rate for the remote serial I/O to @var{n} baud. The
12745 value is used to set the speed of the serial port used for debugging
12748 @item show remotebaud
12749 Show the current speed of the remote connection.
12751 @item set remotebreak
12752 @cindex interrupt remote programs
12753 @cindex BREAK signal instead of Ctrl-C
12754 @anchor{set remotebreak}
12755 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
12756 when you type @kbd{Ctrl-c} to interrupt the program running
12757 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
12758 character instead. The default is off, since most remote systems
12759 expect to see @samp{Ctrl-C} as the interrupt signal.
12761 @item show remotebreak
12762 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
12763 interrupt the remote program.
12765 @item set remotedevice @var{device}
12766 @cindex serial port name
12767 Set the name of the serial port through which to communicate to the
12768 remote target to @var{device}. This is the device used by
12769 @value{GDBN} to open the serial communications line to the remote
12770 target. There's no default, so you must set a valid port name for the
12771 remote serial communications to work. (Some varieties of the
12772 @code{target} command accept the port name as part of their
12775 @item show remotedevice
12776 Show the current name of the serial port.
12778 @item set remotelogbase @var{base}
12779 Set the base (a.k.a.@: radix) of logging serial protocol
12780 communications to @var{base}. Supported values of @var{base} are:
12781 @code{ascii}, @code{octal}, and @code{hex}. The default is
12784 @item show remotelogbase
12785 Show the current setting of the radix for logging remote serial
12788 @item set remotelogfile @var{file}
12789 @cindex record serial communications on file
12790 Record remote serial communications on the named @var{file}. The
12791 default is not to record at all.
12793 @item show remotelogfile.
12794 Show the current setting of the file name on which to record the
12795 serial communications.
12797 @item set remotetimeout @var{num}
12798 @cindex timeout for serial communications
12799 @cindex remote timeout
12800 Set the timeout limit to wait for the remote target to respond to
12801 @var{num} seconds. The default is 2 seconds.
12803 @item show remotetimeout
12804 Show the current number of seconds to wait for the remote target
12807 @cindex limit hardware breakpoints and watchpoints
12808 @cindex remote target, limit break- and watchpoints
12809 @anchor{set remote hardware-watchpoint-limit}
12810 @anchor{set remote hardware-breakpoint-limit}
12811 @item set remote hardware-watchpoint-limit @var{limit}
12812 @itemx set remote hardware-breakpoint-limit @var{limit}
12813 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
12814 watchpoints. A limit of -1, the default, is treated as unlimited.
12817 @cindex remote packets, enabling and disabling
12818 The @value{GDBN} remote protocol autodetects the packets supported by
12819 your debugging stub. If you need to override the autodetection, you
12820 can use these commands to enable or disable individual packets. Each
12821 packet can be set to @samp{on} (the remote target supports this
12822 packet), @samp{off} (the remote target does not support this packet),
12823 or @samp{auto} (detect remote target support for this packet). They
12824 all default to @samp{auto}. For more information about each packet,
12825 see @ref{Remote Protocol}.
12827 During normal use, you should not have to use any of these commands.
12828 If you do, that may be a bug in your remote debugging stub, or a bug
12829 in @value{GDBN}. You may want to report the problem to the
12830 @value{GDBN} developers.
12832 The available settings are:
12834 @multitable @columnfractions 0.3 0.2 0.35
12837 @tab Related Features
12839 @item @code{fetch-register-packet}
12841 @tab @code{info registers}
12843 @item @code{set-register-packet}
12847 @item @code{binary-download-packet}
12849 @tab @code{load}, @code{set}
12851 @item @code{read-aux-vector-packet}
12852 @tab @code{qXfer:auxv:read}
12853 @tab @code{info auxv}
12855 @item @code{symbol-lookup-packet}
12856 @tab @code{qSymbol}
12857 @tab Detecting multiple threads
12859 @item @code{verbose-resume-packet}
12861 @tab Stepping or resuming multiple threads
12863 @item @code{software-breakpoint-packet}
12867 @item @code{hardware-breakpoint-packet}
12871 @item @code{write-watchpoint-packet}
12875 @item @code{read-watchpoint-packet}
12879 @item @code{access-watchpoint-packet}
12883 @item @code{get-thread-local-storage-address-packet}
12884 @tab @code{qGetTLSAddr}
12885 @tab Displaying @code{__thread} variables
12887 @item @code{supported-packets}
12888 @tab @code{qSupported}
12889 @tab Remote communications parameters
12891 @item @code{pass-signals-packet}
12892 @tab @code{QPassSignals}
12893 @tab @code{handle @var{signal}}
12898 @section Implementing a remote stub
12900 @cindex debugging stub, example
12901 @cindex remote stub, example
12902 @cindex stub example, remote debugging
12903 The stub files provided with @value{GDBN} implement the target side of the
12904 communication protocol, and the @value{GDBN} side is implemented in the
12905 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
12906 these subroutines to communicate, and ignore the details. (If you're
12907 implementing your own stub file, you can still ignore the details: start
12908 with one of the existing stub files. @file{sparc-stub.c} is the best
12909 organized, and therefore the easiest to read.)
12911 @cindex remote serial debugging, overview
12912 To debug a program running on another machine (the debugging
12913 @dfn{target} machine), you must first arrange for all the usual
12914 prerequisites for the program to run by itself. For example, for a C
12919 A startup routine to set up the C runtime environment; these usually
12920 have a name like @file{crt0}. The startup routine may be supplied by
12921 your hardware supplier, or you may have to write your own.
12924 A C subroutine library to support your program's
12925 subroutine calls, notably managing input and output.
12928 A way of getting your program to the other machine---for example, a
12929 download program. These are often supplied by the hardware
12930 manufacturer, but you may have to write your own from hardware
12934 The next step is to arrange for your program to use a serial port to
12935 communicate with the machine where @value{GDBN} is running (the @dfn{host}
12936 machine). In general terms, the scheme looks like this:
12940 @value{GDBN} already understands how to use this protocol; when everything
12941 else is set up, you can simply use the @samp{target remote} command
12942 (@pxref{Targets,,Specifying a Debugging Target}).
12944 @item On the target,
12945 you must link with your program a few special-purpose subroutines that
12946 implement the @value{GDBN} remote serial protocol. The file containing these
12947 subroutines is called a @dfn{debugging stub}.
12949 On certain remote targets, you can use an auxiliary program
12950 @code{gdbserver} instead of linking a stub into your program.
12951 @xref{Server,,Using the @code{gdbserver} program}, for details.
12954 The debugging stub is specific to the architecture of the remote
12955 machine; for example, use @file{sparc-stub.c} to debug programs on
12958 @cindex remote serial stub list
12959 These working remote stubs are distributed with @value{GDBN}:
12964 @cindex @file{i386-stub.c}
12967 For Intel 386 and compatible architectures.
12970 @cindex @file{m68k-stub.c}
12971 @cindex Motorola 680x0
12973 For Motorola 680x0 architectures.
12976 @cindex @file{sh-stub.c}
12979 For Renesas SH architectures.
12982 @cindex @file{sparc-stub.c}
12984 For @sc{sparc} architectures.
12986 @item sparcl-stub.c
12987 @cindex @file{sparcl-stub.c}
12990 For Fujitsu @sc{sparclite} architectures.
12994 The @file{README} file in the @value{GDBN} distribution may list other
12995 recently added stubs.
12998 * Stub Contents:: What the stub can do for you
12999 * Bootstrapping:: What you must do for the stub
13000 * Debug Session:: Putting it all together
13003 @node Stub Contents
13004 @subsection What the stub can do for you
13006 @cindex remote serial stub
13007 The debugging stub for your architecture supplies these three
13011 @item set_debug_traps
13012 @findex set_debug_traps
13013 @cindex remote serial stub, initialization
13014 This routine arranges for @code{handle_exception} to run when your
13015 program stops. You must call this subroutine explicitly near the
13016 beginning of your program.
13018 @item handle_exception
13019 @findex handle_exception
13020 @cindex remote serial stub, main routine
13021 This is the central workhorse, but your program never calls it
13022 explicitly---the setup code arranges for @code{handle_exception} to
13023 run when a trap is triggered.
13025 @code{handle_exception} takes control when your program stops during
13026 execution (for example, on a breakpoint), and mediates communications
13027 with @value{GDBN} on the host machine. This is where the communications
13028 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
13029 representative on the target machine. It begins by sending summary
13030 information on the state of your program, then continues to execute,
13031 retrieving and transmitting any information @value{GDBN} needs, until you
13032 execute a @value{GDBN} command that makes your program resume; at that point,
13033 @code{handle_exception} returns control to your own code on the target
13037 @cindex @code{breakpoint} subroutine, remote
13038 Use this auxiliary subroutine to make your program contain a
13039 breakpoint. Depending on the particular situation, this may be the only
13040 way for @value{GDBN} to get control. For instance, if your target
13041 machine has some sort of interrupt button, you won't need to call this;
13042 pressing the interrupt button transfers control to
13043 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
13044 simply receiving characters on the serial port may also trigger a trap;
13045 again, in that situation, you don't need to call @code{breakpoint} from
13046 your own program---simply running @samp{target remote} from the host
13047 @value{GDBN} session gets control.
13049 Call @code{breakpoint} if none of these is true, or if you simply want
13050 to make certain your program stops at a predetermined point for the
13051 start of your debugging session.
13054 @node Bootstrapping
13055 @subsection What you must do for the stub
13057 @cindex remote stub, support routines
13058 The debugging stubs that come with @value{GDBN} are set up for a particular
13059 chip architecture, but they have no information about the rest of your
13060 debugging target machine.
13062 First of all you need to tell the stub how to communicate with the
13066 @item int getDebugChar()
13067 @findex getDebugChar
13068 Write this subroutine to read a single character from the serial port.
13069 It may be identical to @code{getchar} for your target system; a
13070 different name is used to allow you to distinguish the two if you wish.
13072 @item void putDebugChar(int)
13073 @findex putDebugChar
13074 Write this subroutine to write a single character to the serial port.
13075 It may be identical to @code{putchar} for your target system; a
13076 different name is used to allow you to distinguish the two if you wish.
13079 @cindex control C, and remote debugging
13080 @cindex interrupting remote targets
13081 If you want @value{GDBN} to be able to stop your program while it is
13082 running, you need to use an interrupt-driven serial driver, and arrange
13083 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
13084 character). That is the character which @value{GDBN} uses to tell the
13085 remote system to stop.
13087 Getting the debugging target to return the proper status to @value{GDBN}
13088 probably requires changes to the standard stub; one quick and dirty way
13089 is to just execute a breakpoint instruction (the ``dirty'' part is that
13090 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
13092 Other routines you need to supply are:
13095 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
13096 @findex exceptionHandler
13097 Write this function to install @var{exception_address} in the exception
13098 handling tables. You need to do this because the stub does not have any
13099 way of knowing what the exception handling tables on your target system
13100 are like (for example, the processor's table might be in @sc{rom},
13101 containing entries which point to a table in @sc{ram}).
13102 @var{exception_number} is the exception number which should be changed;
13103 its meaning is architecture-dependent (for example, different numbers
13104 might represent divide by zero, misaligned access, etc). When this
13105 exception occurs, control should be transferred directly to
13106 @var{exception_address}, and the processor state (stack, registers,
13107 and so on) should be just as it is when a processor exception occurs. So if
13108 you want to use a jump instruction to reach @var{exception_address}, it
13109 should be a simple jump, not a jump to subroutine.
13111 For the 386, @var{exception_address} should be installed as an interrupt
13112 gate so that interrupts are masked while the handler runs. The gate
13113 should be at privilege level 0 (the most privileged level). The
13114 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
13115 help from @code{exceptionHandler}.
13117 @item void flush_i_cache()
13118 @findex flush_i_cache
13119 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
13120 instruction cache, if any, on your target machine. If there is no
13121 instruction cache, this subroutine may be a no-op.
13123 On target machines that have instruction caches, @value{GDBN} requires this
13124 function to make certain that the state of your program is stable.
13128 You must also make sure this library routine is available:
13131 @item void *memset(void *, int, int)
13133 This is the standard library function @code{memset} that sets an area of
13134 memory to a known value. If you have one of the free versions of
13135 @code{libc.a}, @code{memset} can be found there; otherwise, you must
13136 either obtain it from your hardware manufacturer, or write your own.
13139 If you do not use the GNU C compiler, you may need other standard
13140 library subroutines as well; this varies from one stub to another,
13141 but in general the stubs are likely to use any of the common library
13142 subroutines which @code{@value{GCC}} generates as inline code.
13145 @node Debug Session
13146 @subsection Putting it all together
13148 @cindex remote serial debugging summary
13149 In summary, when your program is ready to debug, you must follow these
13154 Make sure you have defined the supporting low-level routines
13155 (@pxref{Bootstrapping,,What you must do for the stub}):
13157 @code{getDebugChar}, @code{putDebugChar},
13158 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
13162 Insert these lines near the top of your program:
13170 For the 680x0 stub only, you need to provide a variable called
13171 @code{exceptionHook}. Normally you just use:
13174 void (*exceptionHook)() = 0;
13178 but if before calling @code{set_debug_traps}, you set it to point to a
13179 function in your program, that function is called when
13180 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
13181 error). The function indicated by @code{exceptionHook} is called with
13182 one parameter: an @code{int} which is the exception number.
13185 Compile and link together: your program, the @value{GDBN} debugging stub for
13186 your target architecture, and the supporting subroutines.
13189 Make sure you have a serial connection between your target machine and
13190 the @value{GDBN} host, and identify the serial port on the host.
13193 @c The "remote" target now provides a `load' command, so we should
13194 @c document that. FIXME.
13195 Download your program to your target machine (or get it there by
13196 whatever means the manufacturer provides), and start it.
13199 Start @value{GDBN} on the host, and connect to the target
13200 (@pxref{Connecting,,Connecting to a remote target}).
13204 @node Configurations
13205 @chapter Configuration-Specific Information
13207 While nearly all @value{GDBN} commands are available for all native and
13208 cross versions of the debugger, there are some exceptions. This chapter
13209 describes things that are only available in certain configurations.
13211 There are three major categories of configurations: native
13212 configurations, where the host and target are the same, embedded
13213 operating system configurations, which are usually the same for several
13214 different processor architectures, and bare embedded processors, which
13215 are quite different from each other.
13220 * Embedded Processors::
13227 This section describes details specific to particular native
13232 * BSD libkvm Interface:: Debugging BSD kernel memory images
13233 * SVR4 Process Information:: SVR4 process information
13234 * DJGPP Native:: Features specific to the DJGPP port
13235 * Cygwin Native:: Features specific to the Cygwin port
13236 * Hurd Native:: Features specific to @sc{gnu} Hurd
13237 * Neutrino:: Features specific to QNX Neutrino
13243 On HP-UX systems, if you refer to a function or variable name that
13244 begins with a dollar sign, @value{GDBN} searches for a user or system
13245 name first, before it searches for a convenience variable.
13248 @node BSD libkvm Interface
13249 @subsection BSD libkvm Interface
13252 @cindex kernel memory image
13253 @cindex kernel crash dump
13255 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
13256 interface that provides a uniform interface for accessing kernel virtual
13257 memory images, including live systems and crash dumps. @value{GDBN}
13258 uses this interface to allow you to debug live kernels and kernel crash
13259 dumps on many native BSD configurations. This is implemented as a
13260 special @code{kvm} debugging target. For debugging a live system, load
13261 the currently running kernel into @value{GDBN} and connect to the
13265 (@value{GDBP}) @b{target kvm}
13268 For debugging crash dumps, provide the file name of the crash dump as an
13272 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
13275 Once connected to the @code{kvm} target, the following commands are
13281 Set current context from the @dfn{Process Control Block} (PCB) address.
13284 Set current context from proc address. This command isn't available on
13285 modern FreeBSD systems.
13288 @node SVR4 Process Information
13289 @subsection SVR4 process information
13291 @cindex examine process image
13292 @cindex process info via @file{/proc}
13294 Many versions of SVR4 and compatible systems provide a facility called
13295 @samp{/proc} that can be used to examine the image of a running
13296 process using file-system subroutines. If @value{GDBN} is configured
13297 for an operating system with this facility, the command @code{info
13298 proc} is available to report information about the process running
13299 your program, or about any process running on your system. @code{info
13300 proc} works only on SVR4 systems that include the @code{procfs} code.
13301 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
13302 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
13308 @itemx info proc @var{process-id}
13309 Summarize available information about any running process. If a
13310 process ID is specified by @var{process-id}, display information about
13311 that process; otherwise display information about the program being
13312 debugged. The summary includes the debugged process ID, the command
13313 line used to invoke it, its current working directory, and its
13314 executable file's absolute file name.
13316 On some systems, @var{process-id} can be of the form
13317 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
13318 within a process. If the optional @var{pid} part is missing, it means
13319 a thread from the process being debugged (the leading @samp{/} still
13320 needs to be present, or else @value{GDBN} will interpret the number as
13321 a process ID rather than a thread ID).
13323 @item info proc mappings
13324 @cindex memory address space mappings
13325 Report the memory address space ranges accessible in the program, with
13326 information on whether the process has read, write, or execute access
13327 rights to each range. On @sc{gnu}/Linux systems, each memory range
13328 includes the object file which is mapped to that range, instead of the
13329 memory access rights to that range.
13331 @item info proc stat
13332 @itemx info proc status
13333 @cindex process detailed status information
13334 These subcommands are specific to @sc{gnu}/Linux systems. They show
13335 the process-related information, including the user ID and group ID;
13336 how many threads are there in the process; its virtual memory usage;
13337 the signals that are pending, blocked, and ignored; its TTY; its
13338 consumption of system and user time; its stack size; its @samp{nice}
13339 value; etc. For more information, see the @samp{proc} man page
13340 (type @kbd{man 5 proc} from your shell prompt).
13342 @item info proc all
13343 Show all the information about the process described under all of the
13344 above @code{info proc} subcommands.
13347 @comment These sub-options of 'info proc' were not included when
13348 @comment procfs.c was re-written. Keep their descriptions around
13349 @comment against the day when someone finds the time to put them back in.
13350 @kindex info proc times
13351 @item info proc times
13352 Starting time, user CPU time, and system CPU time for your program and
13355 @kindex info proc id
13357 Report on the process IDs related to your program: its own process ID,
13358 the ID of its parent, the process group ID, and the session ID.
13361 @item set procfs-trace
13362 @kindex set procfs-trace
13363 @cindex @code{procfs} API calls
13364 This command enables and disables tracing of @code{procfs} API calls.
13366 @item show procfs-trace
13367 @kindex show procfs-trace
13368 Show the current state of @code{procfs} API call tracing.
13370 @item set procfs-file @var{file}
13371 @kindex set procfs-file
13372 Tell @value{GDBN} to write @code{procfs} API trace to the named
13373 @var{file}. @value{GDBN} appends the trace info to the previous
13374 contents of the file. The default is to display the trace on the
13377 @item show procfs-file
13378 @kindex show procfs-file
13379 Show the file to which @code{procfs} API trace is written.
13381 @item proc-trace-entry
13382 @itemx proc-trace-exit
13383 @itemx proc-untrace-entry
13384 @itemx proc-untrace-exit
13385 @kindex proc-trace-entry
13386 @kindex proc-trace-exit
13387 @kindex proc-untrace-entry
13388 @kindex proc-untrace-exit
13389 These commands enable and disable tracing of entries into and exits
13390 from the @code{syscall} interface.
13393 @kindex info pidlist
13394 @cindex process list, QNX Neutrino
13395 For QNX Neutrino only, this command displays the list of all the
13396 processes and all the threads within each process.
13399 @kindex info meminfo
13400 @cindex mapinfo list, QNX Neutrino
13401 For QNX Neutrino only, this command displays the list of all mapinfos.
13405 @subsection Features for Debugging @sc{djgpp} Programs
13406 @cindex @sc{djgpp} debugging
13407 @cindex native @sc{djgpp} debugging
13408 @cindex MS-DOS-specific commands
13411 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
13412 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
13413 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
13414 top of real-mode DOS systems and their emulations.
13416 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
13417 defines a few commands specific to the @sc{djgpp} port. This
13418 subsection describes those commands.
13423 This is a prefix of @sc{djgpp}-specific commands which print
13424 information about the target system and important OS structures.
13427 @cindex MS-DOS system info
13428 @cindex free memory information (MS-DOS)
13429 @item info dos sysinfo
13430 This command displays assorted information about the underlying
13431 platform: the CPU type and features, the OS version and flavor, the
13432 DPMI version, and the available conventional and DPMI memory.
13437 @cindex segment descriptor tables
13438 @cindex descriptor tables display
13440 @itemx info dos ldt
13441 @itemx info dos idt
13442 These 3 commands display entries from, respectively, Global, Local,
13443 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
13444 tables are data structures which store a descriptor for each segment
13445 that is currently in use. The segment's selector is an index into a
13446 descriptor table; the table entry for that index holds the
13447 descriptor's base address and limit, and its attributes and access
13450 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
13451 segment (used for both data and the stack), and a DOS segment (which
13452 allows access to DOS/BIOS data structures and absolute addresses in
13453 conventional memory). However, the DPMI host will usually define
13454 additional segments in order to support the DPMI environment.
13456 @cindex garbled pointers
13457 These commands allow to display entries from the descriptor tables.
13458 Without an argument, all entries from the specified table are
13459 displayed. An argument, which should be an integer expression, means
13460 display a single entry whose index is given by the argument. For
13461 example, here's a convenient way to display information about the
13462 debugged program's data segment:
13465 @exdent @code{(@value{GDBP}) info dos ldt $ds}
13466 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
13470 This comes in handy when you want to see whether a pointer is outside
13471 the data segment's limit (i.e.@: @dfn{garbled}).
13473 @cindex page tables display (MS-DOS)
13475 @itemx info dos pte
13476 These two commands display entries from, respectively, the Page
13477 Directory and the Page Tables. Page Directories and Page Tables are
13478 data structures which control how virtual memory addresses are mapped
13479 into physical addresses. A Page Table includes an entry for every
13480 page of memory that is mapped into the program's address space; there
13481 may be several Page Tables, each one holding up to 4096 entries. A
13482 Page Directory has up to 4096 entries, one each for every Page Table
13483 that is currently in use.
13485 Without an argument, @kbd{info dos pde} displays the entire Page
13486 Directory, and @kbd{info dos pte} displays all the entries in all of
13487 the Page Tables. An argument, an integer expression, given to the
13488 @kbd{info dos pde} command means display only that entry from the Page
13489 Directory table. An argument given to the @kbd{info dos pte} command
13490 means display entries from a single Page Table, the one pointed to by
13491 the specified entry in the Page Directory.
13493 @cindex direct memory access (DMA) on MS-DOS
13494 These commands are useful when your program uses @dfn{DMA} (Direct
13495 Memory Access), which needs physical addresses to program the DMA
13498 These commands are supported only with some DPMI servers.
13500 @cindex physical address from linear address
13501 @item info dos address-pte @var{addr}
13502 This command displays the Page Table entry for a specified linear
13503 address. The argument @var{addr} is a linear address which should
13504 already have the appropriate segment's base address added to it,
13505 because this command accepts addresses which may belong to @emph{any}
13506 segment. For example, here's how to display the Page Table entry for
13507 the page where a variable @code{i} is stored:
13510 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
13511 @exdent @code{Page Table entry for address 0x11a00d30:}
13512 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
13516 This says that @code{i} is stored at offset @code{0xd30} from the page
13517 whose physical base address is @code{0x02698000}, and shows all the
13518 attributes of that page.
13520 Note that you must cast the addresses of variables to a @code{char *},
13521 since otherwise the value of @code{__djgpp_base_address}, the base
13522 address of all variables and functions in a @sc{djgpp} program, will
13523 be added using the rules of C pointer arithmetics: if @code{i} is
13524 declared an @code{int}, @value{GDBN} will add 4 times the value of
13525 @code{__djgpp_base_address} to the address of @code{i}.
13527 Here's another example, it displays the Page Table entry for the
13531 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
13532 @exdent @code{Page Table entry for address 0x29110:}
13533 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
13537 (The @code{+ 3} offset is because the transfer buffer's address is the
13538 3rd member of the @code{_go32_info_block} structure.) The output
13539 clearly shows that this DPMI server maps the addresses in conventional
13540 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
13541 linear (@code{0x29110}) addresses are identical.
13543 This command is supported only with some DPMI servers.
13546 @cindex DOS serial data link, remote debugging
13547 In addition to native debugging, the DJGPP port supports remote
13548 debugging via a serial data link. The following commands are specific
13549 to remote serial debugging in the DJGPP port of @value{GDBN}.
13552 @kindex set com1base
13553 @kindex set com1irq
13554 @kindex set com2base
13555 @kindex set com2irq
13556 @kindex set com3base
13557 @kindex set com3irq
13558 @kindex set com4base
13559 @kindex set com4irq
13560 @item set com1base @var{addr}
13561 This command sets the base I/O port address of the @file{COM1} serial
13564 @item set com1irq @var{irq}
13565 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
13566 for the @file{COM1} serial port.
13568 There are similar commands @samp{set com2base}, @samp{set com3irq},
13569 etc.@: for setting the port address and the @code{IRQ} lines for the
13572 @kindex show com1base
13573 @kindex show com1irq
13574 @kindex show com2base
13575 @kindex show com2irq
13576 @kindex show com3base
13577 @kindex show com3irq
13578 @kindex show com4base
13579 @kindex show com4irq
13580 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
13581 display the current settings of the base address and the @code{IRQ}
13582 lines used by the COM ports.
13585 @kindex info serial
13586 @cindex DOS serial port status
13587 This command prints the status of the 4 DOS serial ports. For each
13588 port, it prints whether it's active or not, its I/O base address and
13589 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
13590 counts of various errors encountered so far.
13594 @node Cygwin Native
13595 @subsection Features for Debugging MS Windows PE executables
13596 @cindex MS Windows debugging
13597 @cindex native Cygwin debugging
13598 @cindex Cygwin-specific commands
13600 @value{GDBN} supports native debugging of MS Windows programs, including
13601 DLLs with and without symbolic debugging information. There are various
13602 additional Cygwin-specific commands, described in this subsection. The
13603 subsubsection @pxref{Non-debug DLL symbols} describes working with DLLs
13604 that have no debugging symbols.
13610 This is a prefix of MS Windows specific commands which print
13611 information about the target system and important OS structures.
13613 @item info w32 selector
13614 This command displays information returned by
13615 the Win32 API @code{GetThreadSelectorEntry} function.
13616 It takes an optional argument that is evaluated to
13617 a long value to give the information about this given selector.
13618 Without argument, this command displays information
13619 about the the six segment registers.
13623 This is a Cygwin specific alias of info shared.
13625 @kindex dll-symbols
13627 This command loads symbols from a dll similarly to
13628 add-sym command but without the need to specify a base address.
13630 @kindex set cygwin-exceptions
13631 @cindex debugging the Cygwin DLL
13632 @cindex Cygwin DLL, debugging
13633 @item set cygwin-exceptions @var{mode}
13634 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
13635 happen inside the Cygwin DLL. If @var{mode} is @code{off},
13636 @value{GDBN} will delay recognition of exceptions, and may ignore some
13637 exceptions which seem to be caused by internal Cygwin DLL
13638 ``bookkeeping''. This option is meant primarily for debugging the
13639 Cygwin DLL itself; the default value is @code{off} to avoid annoying
13640 @value{GDBN} users with false @code{SIGSEGV} signals.
13642 @kindex show cygwin-exceptions
13643 @item show cygwin-exceptions
13644 Displays whether @value{GDBN} will break on exceptions that happen
13645 inside the Cygwin DLL itself.
13647 @kindex set new-console
13648 @item set new-console @var{mode}
13649 If @var{mode} is @code{on} the debuggee will
13650 be started in a new console on next start.
13651 If @var{mode} is @code{off}i, the debuggee will
13652 be started in the same console as the debugger.
13654 @kindex show new-console
13655 @item show new-console
13656 Displays whether a new console is used
13657 when the debuggee is started.
13659 @kindex set new-group
13660 @item set new-group @var{mode}
13661 This boolean value controls whether the debuggee should
13662 start a new group or stay in the same group as the debugger.
13663 This affects the way the Windows OS handles
13666 @kindex show new-group
13667 @item show new-group
13668 Displays current value of new-group boolean.
13670 @kindex set debugevents
13671 @item set debugevents
13672 This boolean value adds debug output concerning kernel events related
13673 to the debuggee seen by the debugger. This includes events that
13674 signal thread and process creation and exit, DLL loading and
13675 unloading, console interrupts, and debugging messages produced by the
13676 Windows @code{OutputDebugString} API call.
13678 @kindex set debugexec
13679 @item set debugexec
13680 This boolean value adds debug output concerning execute events
13681 (such as resume thread) seen by the debugger.
13683 @kindex set debugexceptions
13684 @item set debugexceptions
13685 This boolean value adds debug output concerning exceptions in the
13686 debuggee seen by the debugger.
13688 @kindex set debugmemory
13689 @item set debugmemory
13690 This boolean value adds debug output concerning debuggee memory reads
13691 and writes by the debugger.
13695 This boolean values specifies whether the debuggee is called
13696 via a shell or directly (default value is on).
13700 Displays if the debuggee will be started with a shell.
13705 * Non-debug DLL symbols:: Support for DLLs without debugging symbols
13708 @node Non-debug DLL symbols
13709 @subsubsection Support for DLLs without debugging symbols
13710 @cindex DLLs with no debugging symbols
13711 @cindex Minimal symbols and DLLs
13713 Very often on windows, some of the DLLs that your program relies on do
13714 not include symbolic debugging information (for example,
13715 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
13716 symbols in a DLL, it relies on the minimal amount of symbolic
13717 information contained in the DLL's export table. This subsubsection
13718 describes working with such symbols, known internally to @value{GDBN} as
13719 ``minimal symbols''.
13721 Note that before the debugged program has started execution, no DLLs
13722 will have been loaded. The easiest way around this problem is simply to
13723 start the program --- either by setting a breakpoint or letting the
13724 program run once to completion. It is also possible to force
13725 @value{GDBN} to load a particular DLL before starting the executable ---
13726 see the shared library information in @pxref{Files} or the
13727 @code{dll-symbols} command in @pxref{Cygwin Native}. Currently,
13728 explicitly loading symbols from a DLL with no debugging information will
13729 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
13730 which may adversely affect symbol lookup performance.
13732 @subsubsection DLL name prefixes
13734 In keeping with the naming conventions used by the Microsoft debugging
13735 tools, DLL export symbols are made available with a prefix based on the
13736 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
13737 also entered into the symbol table, so @code{CreateFileA} is often
13738 sufficient. In some cases there will be name clashes within a program
13739 (particularly if the executable itself includes full debugging symbols)
13740 necessitating the use of the fully qualified name when referring to the
13741 contents of the DLL. Use single-quotes around the name to avoid the
13742 exclamation mark (``!'') being interpreted as a language operator.
13744 Note that the internal name of the DLL may be all upper-case, even
13745 though the file name of the DLL is lower-case, or vice-versa. Since
13746 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
13747 some confusion. If in doubt, try the @code{info functions} and
13748 @code{info variables} commands or even @code{maint print msymbols} (see
13749 @pxref{Symbols}). Here's an example:
13752 (@value{GDBP}) info function CreateFileA
13753 All functions matching regular expression "CreateFileA":
13755 Non-debugging symbols:
13756 0x77e885f4 CreateFileA
13757 0x77e885f4 KERNEL32!CreateFileA
13761 (@value{GDBP}) info function !
13762 All functions matching regular expression "!":
13764 Non-debugging symbols:
13765 0x6100114c cygwin1!__assert
13766 0x61004034 cygwin1!_dll_crt0@@0
13767 0x61004240 cygwin1!dll_crt0(per_process *)
13771 @subsubsection Working with minimal symbols
13773 Symbols extracted from a DLL's export table do not contain very much
13774 type information. All that @value{GDBN} can do is guess whether a symbol
13775 refers to a function or variable depending on the linker section that
13776 contains the symbol. Also note that the actual contents of the memory
13777 contained in a DLL are not available unless the program is running. This
13778 means that you cannot examine the contents of a variable or disassemble
13779 a function within a DLL without a running program.
13781 Variables are generally treated as pointers and dereferenced
13782 automatically. For this reason, it is often necessary to prefix a
13783 variable name with the address-of operator (``&'') and provide explicit
13784 type information in the command. Here's an example of the type of
13788 (@value{GDBP}) print 'cygwin1!__argv'
13793 (@value{GDBP}) x 'cygwin1!__argv'
13794 0x10021610: "\230y\""
13797 And two possible solutions:
13800 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
13801 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
13805 (@value{GDBP}) x/2x &'cygwin1!__argv'
13806 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
13807 (@value{GDBP}) x/x 0x10021608
13808 0x10021608: 0x0022fd98
13809 (@value{GDBP}) x/s 0x0022fd98
13810 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
13813 Setting a break point within a DLL is possible even before the program
13814 starts execution. However, under these circumstances, @value{GDBN} can't
13815 examine the initial instructions of the function in order to skip the
13816 function's frame set-up code. You can work around this by using ``*&''
13817 to set the breakpoint at a raw memory address:
13820 (@value{GDBP}) break *&'python22!PyOS_Readline'
13821 Breakpoint 1 at 0x1e04eff0
13824 The author of these extensions is not entirely convinced that setting a
13825 break point within a shared DLL like @file{kernel32.dll} is completely
13829 @subsection Commands specific to @sc{gnu} Hurd systems
13830 @cindex @sc{gnu} Hurd debugging
13832 This subsection describes @value{GDBN} commands specific to the
13833 @sc{gnu} Hurd native debugging.
13838 @kindex set signals@r{, Hurd command}
13839 @kindex set sigs@r{, Hurd command}
13840 This command toggles the state of inferior signal interception by
13841 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
13842 affected by this command. @code{sigs} is a shorthand alias for
13847 @kindex show signals@r{, Hurd command}
13848 @kindex show sigs@r{, Hurd command}
13849 Show the current state of intercepting inferior's signals.
13851 @item set signal-thread
13852 @itemx set sigthread
13853 @kindex set signal-thread
13854 @kindex set sigthread
13855 This command tells @value{GDBN} which thread is the @code{libc} signal
13856 thread. That thread is run when a signal is delivered to a running
13857 process. @code{set sigthread} is the shorthand alias of @code{set
13860 @item show signal-thread
13861 @itemx show sigthread
13862 @kindex show signal-thread
13863 @kindex show sigthread
13864 These two commands show which thread will run when the inferior is
13865 delivered a signal.
13868 @kindex set stopped@r{, Hurd command}
13869 This commands tells @value{GDBN} that the inferior process is stopped,
13870 as with the @code{SIGSTOP} signal. The stopped process can be
13871 continued by delivering a signal to it.
13874 @kindex show stopped@r{, Hurd command}
13875 This command shows whether @value{GDBN} thinks the debuggee is
13878 @item set exceptions
13879 @kindex set exceptions@r{, Hurd command}
13880 Use this command to turn off trapping of exceptions in the inferior.
13881 When exception trapping is off, neither breakpoints nor
13882 single-stepping will work. To restore the default, set exception
13885 @item show exceptions
13886 @kindex show exceptions@r{, Hurd command}
13887 Show the current state of trapping exceptions in the inferior.
13889 @item set task pause
13890 @kindex set task@r{, Hurd commands}
13891 @cindex task attributes (@sc{gnu} Hurd)
13892 @cindex pause current task (@sc{gnu} Hurd)
13893 This command toggles task suspension when @value{GDBN} has control.
13894 Setting it to on takes effect immediately, and the task is suspended
13895 whenever @value{GDBN} gets control. Setting it to off will take
13896 effect the next time the inferior is continued. If this option is set
13897 to off, you can use @code{set thread default pause on} or @code{set
13898 thread pause on} (see below) to pause individual threads.
13900 @item show task pause
13901 @kindex show task@r{, Hurd commands}
13902 Show the current state of task suspension.
13904 @item set task detach-suspend-count
13905 @cindex task suspend count
13906 @cindex detach from task, @sc{gnu} Hurd
13907 This command sets the suspend count the task will be left with when
13908 @value{GDBN} detaches from it.
13910 @item show task detach-suspend-count
13911 Show the suspend count the task will be left with when detaching.
13913 @item set task exception-port
13914 @itemx set task excp
13915 @cindex task exception port, @sc{gnu} Hurd
13916 This command sets the task exception port to which @value{GDBN} will
13917 forward exceptions. The argument should be the value of the @dfn{send
13918 rights} of the task. @code{set task excp} is a shorthand alias.
13920 @item set noninvasive
13921 @cindex noninvasive task options
13922 This command switches @value{GDBN} to a mode that is the least
13923 invasive as far as interfering with the inferior is concerned. This
13924 is the same as using @code{set task pause}, @code{set exceptions}, and
13925 @code{set signals} to values opposite to the defaults.
13927 @item info send-rights
13928 @itemx info receive-rights
13929 @itemx info port-rights
13930 @itemx info port-sets
13931 @itemx info dead-names
13934 @cindex send rights, @sc{gnu} Hurd
13935 @cindex receive rights, @sc{gnu} Hurd
13936 @cindex port rights, @sc{gnu} Hurd
13937 @cindex port sets, @sc{gnu} Hurd
13938 @cindex dead names, @sc{gnu} Hurd
13939 These commands display information about, respectively, send rights,
13940 receive rights, port rights, port sets, and dead names of a task.
13941 There are also shorthand aliases: @code{info ports} for @code{info
13942 port-rights} and @code{info psets} for @code{info port-sets}.
13944 @item set thread pause
13945 @kindex set thread@r{, Hurd command}
13946 @cindex thread properties, @sc{gnu} Hurd
13947 @cindex pause current thread (@sc{gnu} Hurd)
13948 This command toggles current thread suspension when @value{GDBN} has
13949 control. Setting it to on takes effect immediately, and the current
13950 thread is suspended whenever @value{GDBN} gets control. Setting it to
13951 off will take effect the next time the inferior is continued.
13952 Normally, this command has no effect, since when @value{GDBN} has
13953 control, the whole task is suspended. However, if you used @code{set
13954 task pause off} (see above), this command comes in handy to suspend
13955 only the current thread.
13957 @item show thread pause
13958 @kindex show thread@r{, Hurd command}
13959 This command shows the state of current thread suspension.
13961 @item set thread run
13962 This comamnd sets whether the current thread is allowed to run.
13964 @item show thread run
13965 Show whether the current thread is allowed to run.
13967 @item set thread detach-suspend-count
13968 @cindex thread suspend count, @sc{gnu} Hurd
13969 @cindex detach from thread, @sc{gnu} Hurd
13970 This command sets the suspend count @value{GDBN} will leave on a
13971 thread when detaching. This number is relative to the suspend count
13972 found by @value{GDBN} when it notices the thread; use @code{set thread
13973 takeover-suspend-count} to force it to an absolute value.
13975 @item show thread detach-suspend-count
13976 Show the suspend count @value{GDBN} will leave on the thread when
13979 @item set thread exception-port
13980 @itemx set thread excp
13981 Set the thread exception port to which to forward exceptions. This
13982 overrides the port set by @code{set task exception-port} (see above).
13983 @code{set thread excp} is the shorthand alias.
13985 @item set thread takeover-suspend-count
13986 Normally, @value{GDBN}'s thread suspend counts are relative to the
13987 value @value{GDBN} finds when it notices each thread. This command
13988 changes the suspend counts to be absolute instead.
13990 @item set thread default
13991 @itemx show thread default
13992 @cindex thread default settings, @sc{gnu} Hurd
13993 Each of the above @code{set thread} commands has a @code{set thread
13994 default} counterpart (e.g., @code{set thread default pause}, @code{set
13995 thread default exception-port}, etc.). The @code{thread default}
13996 variety of commands sets the default thread properties for all
13997 threads; you can then change the properties of individual threads with
13998 the non-default commands.
14003 @subsection QNX Neutrino
14004 @cindex QNX Neutrino
14006 @value{GDBN} provides the following commands specific to the QNX
14010 @item set debug nto-debug
14011 @kindex set debug nto-debug
14012 When set to on, enables debugging messages specific to the QNX
14015 @item show debug nto-debug
14016 @kindex show debug nto-debug
14017 Show the current state of QNX Neutrino messages.
14022 @section Embedded Operating Systems
14024 This section describes configurations involving the debugging of
14025 embedded operating systems that are available for several different
14029 * VxWorks:: Using @value{GDBN} with VxWorks
14032 @value{GDBN} includes the ability to debug programs running on
14033 various real-time operating systems.
14036 @subsection Using @value{GDBN} with VxWorks
14042 @kindex target vxworks
14043 @item target vxworks @var{machinename}
14044 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
14045 is the target system's machine name or IP address.
14049 On VxWorks, @code{load} links @var{filename} dynamically on the
14050 current target system as well as adding its symbols in @value{GDBN}.
14052 @value{GDBN} enables developers to spawn and debug tasks running on networked
14053 VxWorks targets from a Unix host. Already-running tasks spawned from
14054 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
14055 both the Unix host and on the VxWorks target. The program
14056 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
14057 installed with the name @code{vxgdb}, to distinguish it from a
14058 @value{GDBN} for debugging programs on the host itself.)
14061 @item VxWorks-timeout @var{args}
14062 @kindex vxworks-timeout
14063 All VxWorks-based targets now support the option @code{vxworks-timeout}.
14064 This option is set by the user, and @var{args} represents the number of
14065 seconds @value{GDBN} waits for responses to rpc's. You might use this if
14066 your VxWorks target is a slow software simulator or is on the far side
14067 of a thin network line.
14070 The following information on connecting to VxWorks was current when
14071 this manual was produced; newer releases of VxWorks may use revised
14074 @findex INCLUDE_RDB
14075 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
14076 to include the remote debugging interface routines in the VxWorks
14077 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
14078 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
14079 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
14080 source debugging task @code{tRdbTask} when VxWorks is booted. For more
14081 information on configuring and remaking VxWorks, see the manufacturer's
14083 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
14085 Once you have included @file{rdb.a} in your VxWorks system image and set
14086 your Unix execution search path to find @value{GDBN}, you are ready to
14087 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
14088 @code{vxgdb}, depending on your installation).
14090 @value{GDBN} comes up showing the prompt:
14097 * VxWorks Connection:: Connecting to VxWorks
14098 * VxWorks Download:: VxWorks download
14099 * VxWorks Attach:: Running tasks
14102 @node VxWorks Connection
14103 @subsubsection Connecting to VxWorks
14105 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
14106 network. To connect to a target whose host name is ``@code{tt}'', type:
14109 (vxgdb) target vxworks tt
14113 @value{GDBN} displays messages like these:
14116 Attaching remote machine across net...
14121 @value{GDBN} then attempts to read the symbol tables of any object modules
14122 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
14123 these files by searching the directories listed in the command search
14124 path (@pxref{Environment, ,Your program's environment}); if it fails
14125 to find an object file, it displays a message such as:
14128 prog.o: No such file or directory.
14131 When this happens, add the appropriate directory to the search path with
14132 the @value{GDBN} command @code{path}, and execute the @code{target}
14135 @node VxWorks Download
14136 @subsubsection VxWorks download
14138 @cindex download to VxWorks
14139 If you have connected to the VxWorks target and you want to debug an
14140 object that has not yet been loaded, you can use the @value{GDBN}
14141 @code{load} command to download a file from Unix to VxWorks
14142 incrementally. The object file given as an argument to the @code{load}
14143 command is actually opened twice: first by the VxWorks target in order
14144 to download the code, then by @value{GDBN} in order to read the symbol
14145 table. This can lead to problems if the current working directories on
14146 the two systems differ. If both systems have NFS mounted the same
14147 filesystems, you can avoid these problems by using absolute paths.
14148 Otherwise, it is simplest to set the working directory on both systems
14149 to the directory in which the object file resides, and then to reference
14150 the file by its name, without any path. For instance, a program
14151 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
14152 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
14153 program, type this on VxWorks:
14156 -> cd "@var{vxpath}/vw/demo/rdb"
14160 Then, in @value{GDBN}, type:
14163 (vxgdb) cd @var{hostpath}/vw/demo/rdb
14164 (vxgdb) load prog.o
14167 @value{GDBN} displays a response similar to this:
14170 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
14173 You can also use the @code{load} command to reload an object module
14174 after editing and recompiling the corresponding source file. Note that
14175 this makes @value{GDBN} delete all currently-defined breakpoints,
14176 auto-displays, and convenience variables, and to clear the value
14177 history. (This is necessary in order to preserve the integrity of
14178 debugger's data structures that reference the target system's symbol
14181 @node VxWorks Attach
14182 @subsubsection Running tasks
14184 @cindex running VxWorks tasks
14185 You can also attach to an existing task using the @code{attach} command as
14189 (vxgdb) attach @var{task}
14193 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
14194 or suspended when you attach to it. Running tasks are suspended at
14195 the time of attachment.
14197 @node Embedded Processors
14198 @section Embedded Processors
14200 This section goes into details specific to particular embedded
14203 @cindex send command to simulator
14204 Whenever a specific embedded processor has a simulator, @value{GDBN}
14205 allows to send an arbitrary command to the simulator.
14208 @item sim @var{command}
14209 @kindex sim@r{, a command}
14210 Send an arbitrary @var{command} string to the simulator. Consult the
14211 documentation for the specific simulator in use for information about
14212 acceptable commands.
14218 * H8/300:: Renesas H8/300
14219 * H8/500:: Renesas H8/500
14220 * M32R/D:: Renesas M32R/D
14221 * M68K:: Motorola M68K
14222 * MIPS Embedded:: MIPS Embedded
14223 * OpenRISC 1000:: OpenRisc 1000
14224 * PA:: HP PA Embedded
14227 * Sparclet:: Tsqware Sparclet
14228 * Sparclite:: Fujitsu Sparclite
14229 * ST2000:: Tandem ST2000
14230 * Z8000:: Zilog Z8000
14233 * Super-H:: Renesas Super-H
14234 * WinCE:: Windows CE child processes
14243 @item target rdi @var{dev}
14244 ARM Angel monitor, via RDI library interface to ADP protocol. You may
14245 use this target to communicate with both boards running the Angel
14246 monitor, or with the EmbeddedICE JTAG debug device.
14249 @item target rdp @var{dev}
14254 @value{GDBN} provides the following ARM-specific commands:
14257 @item set arm disassembler
14259 This commands selects from a list of disassembly styles. The
14260 @code{"std"} style is the standard style.
14262 @item show arm disassembler
14264 Show the current disassembly style.
14266 @item set arm apcs32
14267 @cindex ARM 32-bit mode
14268 This command toggles ARM operation mode between 32-bit and 26-bit.
14270 @item show arm apcs32
14271 Display the current usage of the ARM 32-bit mode.
14273 @item set arm fpu @var{fputype}
14274 This command sets the ARM floating-point unit (FPU) type. The
14275 argument @var{fputype} can be one of these:
14279 Determine the FPU type by querying the OS ABI.
14281 Software FPU, with mixed-endian doubles on little-endian ARM
14284 GCC-compiled FPA co-processor.
14286 Software FPU with pure-endian doubles.
14292 Show the current type of the FPU.
14295 This command forces @value{GDBN} to use the specified ABI.
14298 Show the currently used ABI.
14300 @item set debug arm
14301 Toggle whether to display ARM-specific debugging messages from the ARM
14302 target support subsystem.
14304 @item show debug arm
14305 Show whether ARM-specific debugging messages are enabled.
14308 The following commands are available when an ARM target is debugged
14309 using the RDI interface:
14312 @item rdilogfile @r{[}@var{file}@r{]}
14314 @cindex ADP (Angel Debugger Protocol) logging
14315 Set the filename for the ADP (Angel Debugger Protocol) packet log.
14316 With an argument, sets the log file to the specified @var{file}. With
14317 no argument, show the current log file name. The default log file is
14320 @item rdilogenable @r{[}@var{arg}@r{]}
14321 @kindex rdilogenable
14322 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
14323 enables logging, with an argument 0 or @code{"no"} disables it. With
14324 no arguments displays the current setting. When logging is enabled,
14325 ADP packets exchanged between @value{GDBN} and the RDI target device
14326 are logged to a file.
14328 @item set rdiromatzero
14329 @kindex set rdiromatzero
14330 @cindex ROM at zero address, RDI
14331 Tell @value{GDBN} whether the target has ROM at address 0. If on,
14332 vector catching is disabled, so that zero address can be used. If off
14333 (the default), vector catching is enabled. For this command to take
14334 effect, it needs to be invoked prior to the @code{target rdi} command.
14336 @item show rdiromatzero
14337 @kindex show rdiromatzero
14338 Show the current setting of ROM at zero address.
14340 @item set rdiheartbeat
14341 @kindex set rdiheartbeat
14342 @cindex RDI heartbeat
14343 Enable or disable RDI heartbeat packets. It is not recommended to
14344 turn on this option, since it confuses ARM and EPI JTAG interface, as
14345 well as the Angel monitor.
14347 @item show rdiheartbeat
14348 @kindex show rdiheartbeat
14349 Show the setting of RDI heartbeat packets.
14354 @subsection Renesas H8/300
14358 @kindex target hms@r{, with H8/300}
14359 @item target hms @var{dev}
14360 A Renesas SH, H8/300, or H8/500 board, attached via serial line to your host.
14361 Use special commands @code{device} and @code{speed} to control the serial
14362 line and the communications speed used.
14364 @kindex target e7000@r{, with H8/300}
14365 @item target e7000 @var{dev}
14366 E7000 emulator for Renesas H8 and SH.
14368 @kindex target sh3@r{, with H8/300}
14369 @kindex target sh3e@r{, with H8/300}
14370 @item target sh3 @var{dev}
14371 @itemx target sh3e @var{dev}
14372 Renesas SH-3 and SH-3E target systems.
14376 @cindex download to H8/300 or H8/500
14377 @cindex H8/300 or H8/500 download
14378 @cindex download to Renesas SH
14379 @cindex Renesas SH download
14380 When you select remote debugging to a Renesas SH, H8/300, or H8/500
14381 board, the @code{load} command downloads your program to the Renesas
14382 board and also opens it as the current executable target for
14383 @value{GDBN} on your host (like the @code{file} command).
14385 @value{GDBN} needs to know these things to talk to your
14386 Renesas SH, H8/300, or H8/500:
14390 that you want to use @samp{target hms}, the remote debugging interface
14391 for Renesas microprocessors, or @samp{target e7000}, the in-circuit
14392 emulator for the Renesas SH and the Renesas 300H. (@samp{target hms} is
14393 the default when @value{GDBN} is configured specifically for the Renesas SH,
14394 H8/300, or H8/500.)
14397 what serial device connects your host to your Renesas board (the first
14398 serial device available on your host is the default).
14401 what speed to use over the serial device.
14405 * Renesas Boards:: Connecting to Renesas boards.
14406 * Renesas ICE:: Using the E7000 In-Circuit Emulator.
14407 * Renesas Special:: Special @value{GDBN} commands for Renesas micros.
14410 @node Renesas Boards
14411 @subsubsection Connecting to Renesas boards
14413 @c only for Unix hosts
14415 @cindex serial device, Renesas micros
14416 Use the special @code{@value{GDBN}} command @samp{device @var{port}} if you
14417 need to explicitly set the serial device. The default @var{port} is the
14418 first available port on your host. This is only necessary on Unix
14419 hosts, where it is typically something like @file{/dev/ttya}.
14422 @cindex serial line speed, Renesas micros
14423 @code{@value{GDBN}} has another special command to set the communications
14424 speed: @samp{speed @var{bps}}. This command also is only used from Unix
14425 hosts; on DOS hosts, set the line speed as usual from outside @value{GDBN} with
14426 the DOS @code{mode} command (for instance,
14427 @w{@kbd{mode com2:9600,n,8,1,p}} for a 9600@dmn{bps} connection).
14429 The @samp{device} and @samp{speed} commands are available only when you
14430 use a Unix host to debug your Renesas microprocessor programs. If you
14432 @value{GDBN} depends on an auxiliary terminate-and-stay-resident program
14433 called @code{asynctsr} to communicate with the development board
14434 through a PC serial port. You must also use the DOS @code{mode} command
14435 to set up the serial port on the DOS side.
14437 The following sample session illustrates the steps needed to start a
14438 program under @value{GDBN} control on an H8/300. The example uses a
14439 sample H8/300 program called @file{t.x}. The procedure is the same for
14440 the Renesas SH and the H8/500.
14442 First hook up your development board. In this example, we use a
14443 board attached to serial port @code{COM2}; if you use a different serial
14444 port, substitute its name in the argument of the @code{mode} command.
14445 When you call @code{asynctsr}, the auxiliary comms program used by the
14446 debugger, you give it just the numeric part of the serial port's name;
14447 for example, @samp{asyncstr 2} below runs @code{asyncstr} on
14451 C:\H8300\TEST> asynctsr 2
14452 C:\H8300\TEST> mode com2:9600,n,8,1,p
14454 Resident portion of MODE loaded
14456 COM2: 9600, n, 8, 1, p
14461 @emph{Warning:} We have noticed a bug in PC-NFS that conflicts with
14462 @code{asynctsr}. If you also run PC-NFS on your DOS host, you may need to
14463 disable it, or even boot without it, to use @code{asynctsr} to control
14464 your development board.
14467 @kindex target hms@r{, and serial protocol}
14468 Now that serial communications are set up, and the development board is
14469 connected, you can start up @value{GDBN}. Call @code{@value{GDBN}} with
14470 the name of your program as the argument. @code{@value{GDBN}} prompts
14471 you, as usual, with the prompt @samp{(@value{GDBP})}. Use two special
14472 commands to begin your debugging session: @samp{target hms} to specify
14473 cross-debugging to the Renesas board, and the @code{load} command to
14474 download your program to the board. @code{load} displays the names of
14475 the program's sections, and a @samp{*} for each 2K of data downloaded.
14476 (If you want to refresh @value{GDBN} data on symbols or on the
14477 executable file without downloading, use the @value{GDBN} commands
14478 @code{file} or @code{symbol-file}. These commands, and @code{load}
14479 itself, are described in @ref{Files,,Commands to specify files}.)
14482 (eg-C:\H8300\TEST) @value{GDBP} t.x
14483 @value{GDBN} is free software and you are welcome to distribute copies
14484 of it under certain conditions; type "show copying" to see
14486 There is absolutely no warranty for @value{GDBN}; type "show warranty"
14488 @value{GDBN} @value{GDBVN}, Copyright 1992 Free Software Foundation, Inc...
14489 (@value{GDBP}) target hms
14490 Connected to remote H8/300 HMS system.
14491 (@value{GDBP}) load t.x
14492 .text : 0x8000 .. 0xabde ***********
14493 .data : 0xabde .. 0xad30 *
14494 .stack : 0xf000 .. 0xf014 *
14497 At this point, you're ready to run or debug your program. From here on,
14498 you can use all the usual @value{GDBN} commands. The @code{break} command
14499 sets breakpoints; the @code{run} command starts your program;
14500 @code{print} or @code{x} display data; the @code{continue} command
14501 resumes execution after stopping at a breakpoint. You can use the
14502 @code{help} command at any time to find out more about @value{GDBN} commands.
14504 Remember, however, that @emph{operating system} facilities aren't
14505 available on your development board; for example, if your program hangs,
14506 you can't send an interrupt---but you can press the @sc{reset} switch!
14508 Use the @sc{reset} button on the development board
14511 to interrupt your program (don't use @kbd{Ctrl-c} on the DOS host---it has
14512 no way to pass an interrupt signal to the development board); and
14515 to return to the @value{GDBN} command prompt after your program finishes
14516 normally. The communications protocol provides no other way for @value{GDBN}
14517 to detect program completion.
14520 In either case, @value{GDBN} sees the effect of a @sc{reset} on the
14521 development board as a ``normal exit'' of your program.
14524 @subsubsection Using the E7000 in-circuit emulator
14526 @kindex target e7000@r{, with Renesas ICE}
14527 You can use the E7000 in-circuit emulator to develop code for either the
14528 Renesas SH or the H8/300H. Use one of these forms of the @samp{target
14529 e7000} command to connect @value{GDBN} to your E7000:
14532 @item target e7000 @var{port} @var{speed}
14533 Use this form if your E7000 is connected to a serial port. The
14534 @var{port} argument identifies what serial port to use (for example,
14535 @samp{com2}). The third argument is the line speed in bits per second
14536 (for example, @samp{9600}).
14538 @item target e7000 @var{hostname}
14539 If your E7000 is installed as a host on a TCP/IP network, you can just
14540 specify its hostname; @value{GDBN} uses @code{telnet} to connect.
14543 The following special commands are available when debugging with the
14547 @item e7000 @var{command}
14549 @cindex send command to E7000 monitor
14550 This sends the specified @var{command} to the E7000 monitor.
14552 @item ftplogin @var{machine} @var{username} @var{password} @var{dir}
14553 @kindex ftplogin@r{, E7000}
14554 This command records information for subsequent interface with the
14555 E7000 monitor via the FTP protocol: @value{GDBN} will log into the
14556 named @var{machine} using specified @var{username} and @var{password},
14557 and then chdir to the named directory @var{dir}.
14559 @item ftpload @var{file}
14560 @kindex ftpload@r{, E7000}
14561 This command uses credentials recorded by @code{ftplogin} to fetch and
14562 load the named @var{file} from the E7000 monitor.
14565 @kindex drain@r{, E7000}
14566 This command drains any pending text buffers stored on the E7000.
14568 @item set usehardbreakpoints
14569 @itemx show usehardbreakpoints
14570 @kindex set usehardbreakpoints@r{, E7000}
14571 @kindex show usehardbreakpoints@r{, E7000}
14572 @cindex hardware breakpoints, and E7000
14573 These commands set and show the use of hardware breakpoints for all
14574 breakpoints. @xref{Set Breaks, hardware-assisted breakpoint}, for
14575 more information about using hardware breakpoints selectively.
14578 @node Renesas Special
14579 @subsubsection Special @value{GDBN} commands for Renesas micros
14581 Some @value{GDBN} commands are available only for the H8/300:
14585 @kindex set machine
14586 @kindex show machine
14587 @item set machine h8300
14588 @itemx set machine h8300h
14589 Condition @value{GDBN} for one of the two variants of the H8/300
14590 architecture with @samp{set machine}. You can use @samp{show machine}
14591 to check which variant is currently in effect.
14600 @kindex set memory @var{mod}
14601 @cindex memory models, H8/500
14602 @item set memory @var{mod}
14604 Specify which H8/500 memory model (@var{mod}) you are using with
14605 @samp{set memory}; check which memory model is in effect with @samp{show
14606 memory}. The accepted values for @var{mod} are @code{small},
14607 @code{big}, @code{medium}, and @code{compact}.
14612 @subsection Renesas M32R/D and M32R/SDI
14615 @kindex target m32r
14616 @item target m32r @var{dev}
14617 Renesas M32R/D ROM monitor.
14619 @kindex target m32rsdi
14620 @item target m32rsdi @var{dev}
14621 Renesas M32R SDI server, connected via parallel port to the board.
14624 The following @value{GDBN} commands are specific to the M32R monitor:
14627 @item set download-path @var{path}
14628 @kindex set download-path
14629 @cindex find downloadable @sc{srec} files (M32R)
14630 Set the default path for finding donwloadable @sc{srec} files.
14632 @item show download-path
14633 @kindex show download-path
14634 Show the default path for downloadable @sc{srec} files.
14636 @item set board-address @var{addr}
14637 @kindex set board-address
14638 @cindex M32-EVA target board address
14639 Set the IP address for the M32R-EVA target board.
14641 @item show board-address
14642 @kindex show board-address
14643 Show the current IP address of the target board.
14645 @item set server-address @var{addr}
14646 @kindex set server-address
14647 @cindex download server address (M32R)
14648 Set the IP address for the download server, which is the @value{GDBN}'s
14651 @item show server-address
14652 @kindex show server-address
14653 Display the IP address of the download server.
14655 @item upload @r{[}@var{file}@r{]}
14656 @kindex upload@r{, M32R}
14657 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
14658 upload capability. If no @var{file} argument is given, the current
14659 executable file is uploaded.
14661 @item tload @r{[}@var{file}@r{]}
14662 @kindex tload@r{, M32R}
14663 Test the @code{upload} command.
14666 The following commands are available for M32R/SDI:
14671 @cindex reset SDI connection, M32R
14672 This command resets the SDI connection.
14676 This command shows the SDI connection status.
14679 @kindex debug_chaos
14680 @cindex M32R/Chaos debugging
14681 Instructs the remote that M32R/Chaos debugging is to be used.
14683 @item use_debug_dma
14684 @kindex use_debug_dma
14685 Instructs the remote to use the DEBUG_DMA method of accessing memory.
14688 @kindex use_mon_code
14689 Instructs the remote to use the MON_CODE method of accessing memory.
14692 @kindex use_ib_break
14693 Instructs the remote to set breakpoints by IB break.
14695 @item use_dbt_break
14696 @kindex use_dbt_break
14697 Instructs the remote to set breakpoints by DBT.
14703 The Motorola m68k configuration includes ColdFire support, and
14704 target command for the following ROM monitors.
14708 @kindex target abug
14709 @item target abug @var{dev}
14710 ABug ROM monitor for M68K.
14712 @kindex target cpu32bug
14713 @item target cpu32bug @var{dev}
14714 CPU32BUG monitor, running on a CPU32 (M68K) board.
14716 @kindex target dbug
14717 @item target dbug @var{dev}
14718 dBUG ROM monitor for Motorola ColdFire.
14721 @item target est @var{dev}
14722 EST-300 ICE monitor, running on a CPU32 (M68K) board.
14724 @kindex target rom68k
14725 @item target rom68k @var{dev}
14726 ROM 68K monitor, running on an M68K IDP board.
14732 @kindex target rombug
14733 @item target rombug @var{dev}
14734 ROMBUG ROM monitor for OS/9000.
14738 @node MIPS Embedded
14739 @subsection MIPS Embedded
14741 @cindex MIPS boards
14742 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
14743 MIPS board attached to a serial line. This is available when
14744 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
14747 Use these @value{GDBN} commands to specify the connection to your target board:
14750 @item target mips @var{port}
14751 @kindex target mips @var{port}
14752 To run a program on the board, start up @code{@value{GDBP}} with the
14753 name of your program as the argument. To connect to the board, use the
14754 command @samp{target mips @var{port}}, where @var{port} is the name of
14755 the serial port connected to the board. If the program has not already
14756 been downloaded to the board, you may use the @code{load} command to
14757 download it. You can then use all the usual @value{GDBN} commands.
14759 For example, this sequence connects to the target board through a serial
14760 port, and loads and runs a program called @var{prog} through the
14764 host$ @value{GDBP} @var{prog}
14765 @value{GDBN} is free software and @dots{}
14766 (@value{GDBP}) target mips /dev/ttyb
14767 (@value{GDBP}) load @var{prog}
14771 @item target mips @var{hostname}:@var{portnumber}
14772 On some @value{GDBN} host configurations, you can specify a TCP
14773 connection (for instance, to a serial line managed by a terminal
14774 concentrator) instead of a serial port, using the syntax
14775 @samp{@var{hostname}:@var{portnumber}}.
14777 @item target pmon @var{port}
14778 @kindex target pmon @var{port}
14781 @item target ddb @var{port}
14782 @kindex target ddb @var{port}
14783 NEC's DDB variant of PMON for Vr4300.
14785 @item target lsi @var{port}
14786 @kindex target lsi @var{port}
14787 LSI variant of PMON.
14789 @kindex target r3900
14790 @item target r3900 @var{dev}
14791 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
14793 @kindex target array
14794 @item target array @var{dev}
14795 Array Tech LSI33K RAID controller board.
14801 @value{GDBN} also supports these special commands for MIPS targets:
14804 @item set mipsfpu double
14805 @itemx set mipsfpu single
14806 @itemx set mipsfpu none
14807 @itemx set mipsfpu auto
14808 @itemx show mipsfpu
14809 @kindex set mipsfpu
14810 @kindex show mipsfpu
14811 @cindex MIPS remote floating point
14812 @cindex floating point, MIPS remote
14813 If your target board does not support the MIPS floating point
14814 coprocessor, you should use the command @samp{set mipsfpu none} (if you
14815 need this, you may wish to put the command in your @value{GDBN} init
14816 file). This tells @value{GDBN} how to find the return value of
14817 functions which return floating point values. It also allows
14818 @value{GDBN} to avoid saving the floating point registers when calling
14819 functions on the board. If you are using a floating point coprocessor
14820 with only single precision floating point support, as on the @sc{r4650}
14821 processor, use the command @samp{set mipsfpu single}. The default
14822 double precision floating point coprocessor may be selected using
14823 @samp{set mipsfpu double}.
14825 In previous versions the only choices were double precision or no
14826 floating point, so @samp{set mipsfpu on} will select double precision
14827 and @samp{set mipsfpu off} will select no floating point.
14829 As usual, you can inquire about the @code{mipsfpu} variable with
14830 @samp{show mipsfpu}.
14832 @item set timeout @var{seconds}
14833 @itemx set retransmit-timeout @var{seconds}
14834 @itemx show timeout
14835 @itemx show retransmit-timeout
14836 @cindex @code{timeout}, MIPS protocol
14837 @cindex @code{retransmit-timeout}, MIPS protocol
14838 @kindex set timeout
14839 @kindex show timeout
14840 @kindex set retransmit-timeout
14841 @kindex show retransmit-timeout
14842 You can control the timeout used while waiting for a packet, in the MIPS
14843 remote protocol, with the @code{set timeout @var{seconds}} command. The
14844 default is 5 seconds. Similarly, you can control the timeout used while
14845 waiting for an acknowledgement of a packet with the @code{set
14846 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
14847 You can inspect both values with @code{show timeout} and @code{show
14848 retransmit-timeout}. (These commands are @emph{only} available when
14849 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
14851 The timeout set by @code{set timeout} does not apply when @value{GDBN}
14852 is waiting for your program to stop. In that case, @value{GDBN} waits
14853 forever because it has no way of knowing how long the program is going
14854 to run before stopping.
14856 @item set syn-garbage-limit @var{num}
14857 @kindex set syn-garbage-limit@r{, MIPS remote}
14858 @cindex synchronize with remote MIPS target
14859 Limit the maximum number of characters @value{GDBN} should ignore when
14860 it tries to synchronize with the remote target. The default is 10
14861 characters. Setting the limit to -1 means there's no limit.
14863 @item show syn-garbage-limit
14864 @kindex show syn-garbage-limit@r{, MIPS remote}
14865 Show the current limit on the number of characters to ignore when
14866 trying to synchronize with the remote system.
14868 @item set monitor-prompt @var{prompt}
14869 @kindex set monitor-prompt@r{, MIPS remote}
14870 @cindex remote monitor prompt
14871 Tell @value{GDBN} to expect the specified @var{prompt} string from the
14872 remote monitor. The default depends on the target:
14882 @item show monitor-prompt
14883 @kindex show monitor-prompt@r{, MIPS remote}
14884 Show the current strings @value{GDBN} expects as the prompt from the
14887 @item set monitor-warnings
14888 @kindex set monitor-warnings@r{, MIPS remote}
14889 Enable or disable monitor warnings about hardware breakpoints. This
14890 has effect only for the @code{lsi} target. When on, @value{GDBN} will
14891 display warning messages whose codes are returned by the @code{lsi}
14892 PMON monitor for breakpoint commands.
14894 @item show monitor-warnings
14895 @kindex show monitor-warnings@r{, MIPS remote}
14896 Show the current setting of printing monitor warnings.
14898 @item pmon @var{command}
14899 @kindex pmon@r{, MIPS remote}
14900 @cindex send PMON command
14901 This command allows sending an arbitrary @var{command} string to the
14902 monitor. The monitor must be in debug mode for this to work.
14905 @node OpenRISC 1000
14906 @subsection OpenRISC 1000
14907 @cindex OpenRISC 1000
14909 @cindex or1k boards
14910 See OR1k Architecture document (@uref{www.opencores.org}) for more information
14911 about platform and commands.
14915 @kindex target jtag
14916 @item target jtag jtag://@var{host}:@var{port}
14918 Connects to remote JTAG server.
14919 JTAG remote server can be either an or1ksim or JTAG server,
14920 connected via parallel port to the board.
14922 Example: @code{target jtag jtag://localhost:9999}
14925 @item or1ksim @var{command}
14926 If connected to @code{or1ksim} OpenRISC 1000 Architectural
14927 Simulator, proprietary commands can be executed.
14929 @kindex info or1k spr
14930 @item info or1k spr
14931 Displays spr groups.
14933 @item info or1k spr @var{group}
14934 @itemx info or1k spr @var{groupno}
14935 Displays register names in selected group.
14937 @item info or1k spr @var{group} @var{register}
14938 @itemx info or1k spr @var{register}
14939 @itemx info or1k spr @var{groupno} @var{registerno}
14940 @itemx info or1k spr @var{registerno}
14941 Shows information about specified spr register.
14944 @item spr @var{group} @var{register} @var{value}
14945 @itemx spr @var{register @var{value}}
14946 @itemx spr @var{groupno} @var{registerno @var{value}}
14947 @itemx spr @var{registerno @var{value}}
14948 Writes @var{value} to specified spr register.
14951 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
14952 It is very similar to @value{GDBN} trace, except it does not interfere with normal
14953 program execution and is thus much faster. Hardware breakpoints/watchpoint
14954 triggers can be set using:
14957 Load effective address/data
14959 Store effective address/data
14961 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
14966 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
14967 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
14969 @code{htrace} commands:
14970 @cindex OpenRISC 1000 htrace
14973 @item hwatch @var{conditional}
14974 Set hardware watchpoint on combination of Load/Store Effecive Address(es)
14975 or Data. For example:
14977 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
14979 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
14983 Display information about current HW trace configuration.
14985 @item htrace trigger @var{conditional}
14986 Set starting criteria for HW trace.
14988 @item htrace qualifier @var{conditional}
14989 Set acquisition qualifier for HW trace.
14991 @item htrace stop @var{conditional}
14992 Set HW trace stopping criteria.
14994 @item htrace record [@var{data}]*
14995 Selects the data to be recorded, when qualifier is met and HW trace was
14998 @item htrace enable
14999 @itemx htrace disable
15000 Enables/disables the HW trace.
15002 @item htrace rewind [@var{filename}]
15003 Clears currently recorded trace data.
15005 If filename is specified, new trace file is made and any newly collected data
15006 will be written there.
15008 @item htrace print [@var{start} [@var{len}]]
15009 Prints trace buffer, using current record configuration.
15011 @item htrace mode continuous
15012 Set continuous trace mode.
15014 @item htrace mode suspend
15015 Set suspend trace mode.
15020 @subsection PowerPC
15023 @kindex target dink32
15024 @item target dink32 @var{dev}
15025 DINK32 ROM monitor.
15027 @kindex target ppcbug
15028 @item target ppcbug @var{dev}
15029 @kindex target ppcbug1
15030 @item target ppcbug1 @var{dev}
15031 PPCBUG ROM monitor for PowerPC.
15034 @item target sds @var{dev}
15035 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
15038 @cindex SDS protocol
15039 The following commands specifi to the SDS protocol are supported
15043 @item set sdstimeout @var{nsec}
15044 @kindex set sdstimeout
15045 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
15046 default is 2 seconds.
15048 @item show sdstimeout
15049 @kindex show sdstimeout
15050 Show the current value of the SDS timeout.
15052 @item sds @var{command}
15053 @kindex sds@r{, a command}
15054 Send the specified @var{command} string to the SDS monitor.
15059 @subsection HP PA Embedded
15063 @kindex target op50n
15064 @item target op50n @var{dev}
15065 OP50N monitor, running on an OKI HPPA board.
15067 @kindex target w89k
15068 @item target w89k @var{dev}
15069 W89K monitor, running on a Winbond HPPA board.
15074 @subsection Renesas SH
15078 @kindex target hms@r{, with Renesas SH}
15079 @item target hms @var{dev}
15080 A Renesas SH board attached via serial line to your host. Use special
15081 commands @code{device} and @code{speed} to control the serial line and
15082 the communications speed used.
15084 @kindex target e7000@r{, with Renesas SH}
15085 @item target e7000 @var{dev}
15086 E7000 emulator for Renesas SH.
15088 @kindex target sh3@r{, with SH}
15089 @kindex target sh3e@r{, with SH}
15090 @item target sh3 @var{dev}
15091 @item target sh3e @var{dev}
15092 Renesas SH-3 and SH-3E target systems.
15097 @subsection Tsqware Sparclet
15101 @value{GDBN} enables developers to debug tasks running on
15102 Sparclet targets from a Unix host.
15103 @value{GDBN} uses code that runs on
15104 both the Unix host and on the Sparclet target. The program
15105 @code{@value{GDBP}} is installed and executed on the Unix host.
15108 @item remotetimeout @var{args}
15109 @kindex remotetimeout
15110 @value{GDBN} supports the option @code{remotetimeout}.
15111 This option is set by the user, and @var{args} represents the number of
15112 seconds @value{GDBN} waits for responses.
15115 @cindex compiling, on Sparclet
15116 When compiling for debugging, include the options @samp{-g} to get debug
15117 information and @samp{-Ttext} to relocate the program to where you wish to
15118 load it on the target. You may also want to add the options @samp{-n} or
15119 @samp{-N} in order to reduce the size of the sections. Example:
15122 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
15125 You can use @code{objdump} to verify that the addresses are what you intended:
15128 sparclet-aout-objdump --headers --syms prog
15131 @cindex running, on Sparclet
15133 your Unix execution search path to find @value{GDBN}, you are ready to
15134 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
15135 (or @code{sparclet-aout-gdb}, depending on your installation).
15137 @value{GDBN} comes up showing the prompt:
15144 * Sparclet File:: Setting the file to debug
15145 * Sparclet Connection:: Connecting to Sparclet
15146 * Sparclet Download:: Sparclet download
15147 * Sparclet Execution:: Running and debugging
15150 @node Sparclet File
15151 @subsubsection Setting file to debug
15153 The @value{GDBN} command @code{file} lets you choose with program to debug.
15156 (gdbslet) file prog
15160 @value{GDBN} then attempts to read the symbol table of @file{prog}.
15161 @value{GDBN} locates
15162 the file by searching the directories listed in the command search
15164 If the file was compiled with debug information (option "-g"), source
15165 files will be searched as well.
15166 @value{GDBN} locates
15167 the source files by searching the directories listed in the directory search
15168 path (@pxref{Environment, ,Your program's environment}).
15170 to find a file, it displays a message such as:
15173 prog: No such file or directory.
15176 When this happens, add the appropriate directories to the search paths with
15177 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
15178 @code{target} command again.
15180 @node Sparclet Connection
15181 @subsubsection Connecting to Sparclet
15183 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
15184 To connect to a target on serial port ``@code{ttya}'', type:
15187 (gdbslet) target sparclet /dev/ttya
15188 Remote target sparclet connected to /dev/ttya
15189 main () at ../prog.c:3
15193 @value{GDBN} displays messages like these:
15199 @node Sparclet Download
15200 @subsubsection Sparclet download
15202 @cindex download to Sparclet
15203 Once connected to the Sparclet target,
15204 you can use the @value{GDBN}
15205 @code{load} command to download the file from the host to the target.
15206 The file name and load offset should be given as arguments to the @code{load}
15208 Since the file format is aout, the program must be loaded to the starting
15209 address. You can use @code{objdump} to find out what this value is. The load
15210 offset is an offset which is added to the VMA (virtual memory address)
15211 of each of the file's sections.
15212 For instance, if the program
15213 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
15214 and bss at 0x12010170, in @value{GDBN}, type:
15217 (gdbslet) load prog 0x12010000
15218 Loading section .text, size 0xdb0 vma 0x12010000
15221 If the code is loaded at a different address then what the program was linked
15222 to, you may need to use the @code{section} and @code{add-symbol-file} commands
15223 to tell @value{GDBN} where to map the symbol table.
15225 @node Sparclet Execution
15226 @subsubsection Running and debugging
15228 @cindex running and debugging Sparclet programs
15229 You can now begin debugging the task using @value{GDBN}'s execution control
15230 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
15231 manual for the list of commands.
15235 Breakpoint 1 at 0x12010000: file prog.c, line 3.
15237 Starting program: prog
15238 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
15239 3 char *symarg = 0;
15241 4 char *execarg = "hello!";
15246 @subsection Fujitsu Sparclite
15250 @kindex target sparclite
15251 @item target sparclite @var{dev}
15252 Fujitsu sparclite boards, used only for the purpose of loading.
15253 You must use an additional command to debug the program.
15254 For example: target remote @var{dev} using @value{GDBN} standard
15260 @subsection Tandem ST2000
15262 @value{GDBN} may be used with a Tandem ST2000 phone switch, running Tandem's
15265 To connect your ST2000 to the host system, see the manufacturer's
15266 manual. Once the ST2000 is physically attached, you can run:
15269 target st2000 @var{dev} @var{speed}
15273 to establish it as your debugging environment. @var{dev} is normally
15274 the name of a serial device, such as @file{/dev/ttya}, connected to the
15275 ST2000 via a serial line. You can instead specify @var{dev} as a TCP
15276 connection (for example, to a serial line attached via a terminal
15277 concentrator) using the syntax @code{@var{hostname}:@var{portnumber}}.
15279 The @code{load} and @code{attach} commands are @emph{not} defined for
15280 this target; you must load your program into the ST2000 as you normally
15281 would for standalone operation. @value{GDBN} reads debugging information
15282 (such as symbols) from a separate, debugging version of the program
15283 available on your host computer.
15284 @c FIXME!! This is terribly vague; what little content is here is
15285 @c basically hearsay.
15287 @cindex ST2000 auxiliary commands
15288 These auxiliary @value{GDBN} commands are available to help you with the ST2000
15292 @item st2000 @var{command}
15293 @kindex st2000 @var{cmd}
15294 @cindex STDBUG commands (ST2000)
15295 @cindex commands to STDBUG (ST2000)
15296 Send a @var{command} to the STDBUG monitor. See the manufacturer's
15297 manual for available commands.
15300 @cindex connect (to STDBUG)
15301 Connect the controlling terminal to the STDBUG command monitor. When
15302 you are done interacting with STDBUG, typing either of two character
15303 sequences gets you back to the @value{GDBN} command prompt:
15304 @kbd{@key{RET} ~ .} (Return, followed by tilde and period) or
15305 @kbd{@key{RET} ~ Ctrl-d} (Return, followed by tilde and control-D).
15309 @subsection Zilog Z8000
15312 @cindex simulator, Z8000
15313 @cindex Zilog Z8000 simulator
15315 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
15318 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
15319 unsegmented variant of the Z8000 architecture) or the Z8001 (the
15320 segmented variant). The simulator recognizes which architecture is
15321 appropriate by inspecting the object code.
15324 @item target sim @var{args}
15326 @kindex target sim@r{, with Z8000}
15327 Debug programs on a simulated CPU. If the simulator supports setup
15328 options, specify them via @var{args}.
15332 After specifying this target, you can debug programs for the simulated
15333 CPU in the same style as programs for your host computer; use the
15334 @code{file} command to load a new program image, the @code{run} command
15335 to run your program, and so on.
15337 As well as making available all the usual machine registers
15338 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
15339 additional items of information as specially named registers:
15344 Counts clock-ticks in the simulator.
15347 Counts instructions run in the simulator.
15350 Execution time in 60ths of a second.
15354 You can refer to these values in @value{GDBN} expressions with the usual
15355 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
15356 conditional breakpoint that suspends only after at least 5000
15357 simulated clock ticks.
15360 @subsection Atmel AVR
15363 When configured for debugging the Atmel AVR, @value{GDBN} supports the
15364 following AVR-specific commands:
15367 @item info io_registers
15368 @kindex info io_registers@r{, AVR}
15369 @cindex I/O registers (Atmel AVR)
15370 This command displays information about the AVR I/O registers. For
15371 each register, @value{GDBN} prints its number and value.
15378 When configured for debugging CRIS, @value{GDBN} provides the
15379 following CRIS-specific commands:
15382 @item set cris-version @var{ver}
15383 @cindex CRIS version
15384 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
15385 The CRIS version affects register names and sizes. This command is useful in
15386 case autodetection of the CRIS version fails.
15388 @item show cris-version
15389 Show the current CRIS version.
15391 @item set cris-dwarf2-cfi
15392 @cindex DWARF-2 CFI and CRIS
15393 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
15394 Change to @samp{off} when using @code{gcc-cris} whose version is below
15397 @item show cris-dwarf2-cfi
15398 Show the current state of using DWARF-2 CFI.
15400 @item set cris-mode @var{mode}
15402 Set the current CRIS mode to @var{mode}. It should only be changed when
15403 debugging in guru mode, in which case it should be set to
15404 @samp{guru} (the default is @samp{normal}).
15406 @item show cris-mode
15407 Show the current CRIS mode.
15411 @subsection Renesas Super-H
15414 For the Renesas Super-H processor, @value{GDBN} provides these
15419 @kindex regs@r{, Super-H}
15420 Show the values of all Super-H registers.
15424 @subsection Windows CE
15427 The following commands are available for Windows CE:
15430 @item set remotedirectory @var{dir}
15431 @kindex set remotedirectory
15432 Tell @value{GDBN} to upload files from the named directory @var{dir}.
15433 The default is @file{/gdb}, i.e.@: the root directory on the current
15436 @item show remotedirectory
15437 @kindex show remotedirectory
15438 Show the current value of the upload directory.
15440 @item set remoteupload @var{method}
15441 @kindex set remoteupload
15442 Set the method used to upload files to remote device. Valid values
15443 for @var{method} are @samp{always}, @samp{newer}, and @samp{never}.
15444 The default is @samp{newer}.
15446 @item show remoteupload
15447 @kindex show remoteupload
15448 Show the current setting of the upload method.
15450 @item set remoteaddhost
15451 @kindex set remoteaddhost
15452 Tell @value{GDBN} whether to add this host to the remote stub's
15453 arguments when you debug over a network.
15455 @item show remoteaddhost
15456 @kindex show remoteaddhost
15457 Show whether to add this host to remote stub's arguments when
15458 debugging over a network.
15462 @node Architectures
15463 @section Architectures
15465 This section describes characteristics of architectures that affect
15466 all uses of @value{GDBN} with the architecture, both native and cross.
15473 * HPPA:: HP PA architecture
15477 @subsection x86 Architecture-specific issues.
15480 @item set struct-convention @var{mode}
15481 @kindex set struct-convention
15482 @cindex struct return convention
15483 @cindex struct/union returned in registers
15484 Set the convention used by the inferior to return @code{struct}s and
15485 @code{union}s from functions to @var{mode}. Possible values of
15486 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
15487 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
15488 are returned on the stack, while @code{"reg"} means that a
15489 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
15490 be returned in a register.
15492 @item show struct-convention
15493 @kindex show struct-convention
15494 Show the current setting of the convention to return @code{struct}s
15503 @kindex set rstack_high_address
15504 @cindex AMD 29K register stack
15505 @cindex register stack, AMD29K
15506 @item set rstack_high_address @var{address}
15507 On AMD 29000 family processors, registers are saved in a separate
15508 @dfn{register stack}. There is no way for @value{GDBN} to determine the
15509 extent of this stack. Normally, @value{GDBN} just assumes that the
15510 stack is ``large enough''. This may result in @value{GDBN} referencing
15511 memory locations that do not exist. If necessary, you can get around
15512 this problem by specifying the ending address of the register stack with
15513 the @code{set rstack_high_address} command. The argument should be an
15514 address, which you probably want to precede with @samp{0x} to specify in
15517 @kindex show rstack_high_address
15518 @item show rstack_high_address
15519 Display the current limit of the register stack, on AMD 29000 family
15527 See the following section.
15532 @cindex stack on Alpha
15533 @cindex stack on MIPS
15534 @cindex Alpha stack
15536 Alpha- and MIPS-based computers use an unusual stack frame, which
15537 sometimes requires @value{GDBN} to search backward in the object code to
15538 find the beginning of a function.
15540 @cindex response time, MIPS debugging
15541 To improve response time (especially for embedded applications, where
15542 @value{GDBN} may be restricted to a slow serial line for this search)
15543 you may want to limit the size of this search, using one of these
15547 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
15548 @item set heuristic-fence-post @var{limit}
15549 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
15550 search for the beginning of a function. A value of @var{0} (the
15551 default) means there is no limit. However, except for @var{0}, the
15552 larger the limit the more bytes @code{heuristic-fence-post} must search
15553 and therefore the longer it takes to run. You should only need to use
15554 this command when debugging a stripped executable.
15556 @item show heuristic-fence-post
15557 Display the current limit.
15561 These commands are available @emph{only} when @value{GDBN} is configured
15562 for debugging programs on Alpha or MIPS processors.
15564 Several MIPS-specific commands are available when debugging MIPS
15568 @item set mips saved-gpreg-size @var{size}
15569 @kindex set mips saved-gpreg-size
15570 @cindex MIPS GP register size on stack
15571 Set the size of MIPS general-purpose registers saved on the stack.
15572 The argument @var{size} can be one of the following:
15576 32-bit GP registers
15578 64-bit GP registers
15580 Use the target's default setting or autodetect the saved size from the
15581 information contained in the executable. This is the default
15584 @item show mips saved-gpreg-size
15585 @kindex show mips saved-gpreg-size
15586 Show the current size of MIPS GP registers on the stack.
15588 @item set mips stack-arg-size @var{size}
15589 @kindex set mips stack-arg-size
15590 @cindex MIPS stack space for arguments
15591 Set the amount of stack space reserved for arguments to functions.
15592 The argument can be one of @code{"32"}, @code{"64"} or @code{"auto"}
15595 @item set mips abi @var{arg}
15596 @kindex set mips abi
15597 @cindex set ABI for MIPS
15598 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
15599 values of @var{arg} are:
15603 The default ABI associated with the current binary (this is the
15614 @item show mips abi
15615 @kindex show mips abi
15616 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
15619 @itemx show mipsfpu
15620 @xref{MIPS Embedded, set mipsfpu}.
15622 @item set mips mask-address @var{arg}
15623 @kindex set mips mask-address
15624 @cindex MIPS addresses, masking
15625 This command determines whether the most-significant 32 bits of 64-bit
15626 MIPS addresses are masked off. The argument @var{arg} can be
15627 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
15628 setting, which lets @value{GDBN} determine the correct value.
15630 @item show mips mask-address
15631 @kindex show mips mask-address
15632 Show whether the upper 32 bits of MIPS addresses are masked off or
15635 @item set remote-mips64-transfers-32bit-regs
15636 @kindex set remote-mips64-transfers-32bit-regs
15637 This command controls compatibility with 64-bit MIPS targets that
15638 transfer data in 32-bit quantities. If you have an old MIPS 64 target
15639 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
15640 and 64 bits for other registers, set this option to @samp{on}.
15642 @item show remote-mips64-transfers-32bit-regs
15643 @kindex show remote-mips64-transfers-32bit-regs
15644 Show the current setting of compatibility with older MIPS 64 targets.
15646 @item set debug mips
15647 @kindex set debug mips
15648 This command turns on and off debugging messages for the MIPS-specific
15649 target code in @value{GDBN}.
15651 @item show debug mips
15652 @kindex show debug mips
15653 Show the current setting of MIPS debugging messages.
15659 @cindex HPPA support
15661 When @value{GDBN} is debugging te HP PA architecture, it provides the
15662 following special commands:
15665 @item set debug hppa
15666 @kindex set debug hppa
15667 THis command determines whether HPPA architecture specific debugging
15668 messages are to be displayed.
15670 @item show debug hppa
15671 Show whether HPPA debugging messages are displayed.
15673 @item maint print unwind @var{address}
15674 @kindex maint print unwind@r{, HPPA}
15675 This command displays the contents of the unwind table entry at the
15676 given @var{address}.
15681 @node Controlling GDB
15682 @chapter Controlling @value{GDBN}
15684 You can alter the way @value{GDBN} interacts with you by using the
15685 @code{set} command. For commands controlling how @value{GDBN} displays
15686 data, see @ref{Print Settings, ,Print settings}. Other settings are
15691 * Editing:: Command editing
15692 * Command History:: Command history
15693 * Screen Size:: Screen size
15694 * Numbers:: Numbers
15695 * ABI:: Configuring the current ABI
15696 * Messages/Warnings:: Optional warnings and messages
15697 * Debugging Output:: Optional messages about internal happenings
15705 @value{GDBN} indicates its readiness to read a command by printing a string
15706 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
15707 can change the prompt string with the @code{set prompt} command. For
15708 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
15709 the prompt in one of the @value{GDBN} sessions so that you can always tell
15710 which one you are talking to.
15712 @emph{Note:} @code{set prompt} does not add a space for you after the
15713 prompt you set. This allows you to set a prompt which ends in a space
15714 or a prompt that does not.
15718 @item set prompt @var{newprompt}
15719 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
15721 @kindex show prompt
15723 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
15727 @section Command editing
15729 @cindex command line editing
15731 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
15732 @sc{gnu} library provides consistent behavior for programs which provide a
15733 command line interface to the user. Advantages are @sc{gnu} Emacs-style
15734 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
15735 substitution, and a storage and recall of command history across
15736 debugging sessions.
15738 You may control the behavior of command line editing in @value{GDBN} with the
15739 command @code{set}.
15742 @kindex set editing
15745 @itemx set editing on
15746 Enable command line editing (enabled by default).
15748 @item set editing off
15749 Disable command line editing.
15751 @kindex show editing
15753 Show whether command line editing is enabled.
15756 @xref{Command Line Editing}, for more details about the Readline
15757 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
15758 encouraged to read that chapter.
15760 @node Command History
15761 @section Command history
15762 @cindex command history
15764 @value{GDBN} can keep track of the commands you type during your
15765 debugging sessions, so that you can be certain of precisely what
15766 happened. Use these commands to manage the @value{GDBN} command
15769 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
15770 package, to provide the history facility. @xref{Using History
15771 Interactively}, for the detailed description of the History library.
15773 To issue a command to @value{GDBN} without affecting certain aspects of
15774 the state which is seen by users, prefix it with @samp{server }. This
15775 means that this command will not affect the command history, nor will it
15776 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
15777 pressed on a line by itself.
15779 @cindex @code{server}, command prefix
15780 The server prefix does not affect the recording of values into the value
15781 history; to print a value without recording it into the value history,
15782 use the @code{output} command instead of the @code{print} command.
15784 Here is the description of @value{GDBN} commands related to command
15788 @cindex history substitution
15789 @cindex history file
15790 @kindex set history filename
15791 @cindex @env{GDBHISTFILE}, environment variable
15792 @item set history filename @var{fname}
15793 Set the name of the @value{GDBN} command history file to @var{fname}.
15794 This is the file where @value{GDBN} reads an initial command history
15795 list, and where it writes the command history from this session when it
15796 exits. You can access this list through history expansion or through
15797 the history command editing characters listed below. This file defaults
15798 to the value of the environment variable @code{GDBHISTFILE}, or to
15799 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
15802 @cindex save command history
15803 @kindex set history save
15804 @item set history save
15805 @itemx set history save on
15806 Record command history in a file, whose name may be specified with the
15807 @code{set history filename} command. By default, this option is disabled.
15809 @item set history save off
15810 Stop recording command history in a file.
15812 @cindex history size
15813 @kindex set history size
15814 @cindex @env{HISTSIZE}, environment variable
15815 @item set history size @var{size}
15816 Set the number of commands which @value{GDBN} keeps in its history list.
15817 This defaults to the value of the environment variable
15818 @code{HISTSIZE}, or to 256 if this variable is not set.
15821 History expansion assigns special meaning to the character @kbd{!}.
15822 @xref{Event Designators}, for more details.
15824 @cindex history expansion, turn on/off
15825 Since @kbd{!} is also the logical not operator in C, history expansion
15826 is off by default. If you decide to enable history expansion with the
15827 @code{set history expansion on} command, you may sometimes need to
15828 follow @kbd{!} (when it is used as logical not, in an expression) with
15829 a space or a tab to prevent it from being expanded. The readline
15830 history facilities do not attempt substitution on the strings
15831 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
15833 The commands to control history expansion are:
15836 @item set history expansion on
15837 @itemx set history expansion
15838 @kindex set history expansion
15839 Enable history expansion. History expansion is off by default.
15841 @item set history expansion off
15842 Disable history expansion.
15845 @kindex show history
15847 @itemx show history filename
15848 @itemx show history save
15849 @itemx show history size
15850 @itemx show history expansion
15851 These commands display the state of the @value{GDBN} history parameters.
15852 @code{show history} by itself displays all four states.
15857 @kindex show commands
15858 @cindex show last commands
15859 @cindex display command history
15860 @item show commands
15861 Display the last ten commands in the command history.
15863 @item show commands @var{n}
15864 Print ten commands centered on command number @var{n}.
15866 @item show commands +
15867 Print ten commands just after the commands last printed.
15871 @section Screen size
15872 @cindex size of screen
15873 @cindex pauses in output
15875 Certain commands to @value{GDBN} may produce large amounts of
15876 information output to the screen. To help you read all of it,
15877 @value{GDBN} pauses and asks you for input at the end of each page of
15878 output. Type @key{RET} when you want to continue the output, or @kbd{q}
15879 to discard the remaining output. Also, the screen width setting
15880 determines when to wrap lines of output. Depending on what is being
15881 printed, @value{GDBN} tries to break the line at a readable place,
15882 rather than simply letting it overflow onto the following line.
15884 Normally @value{GDBN} knows the size of the screen from the terminal
15885 driver software. For example, on Unix @value{GDBN} uses the termcap data base
15886 together with the value of the @code{TERM} environment variable and the
15887 @code{stty rows} and @code{stty cols} settings. If this is not correct,
15888 you can override it with the @code{set height} and @code{set
15895 @kindex show height
15896 @item set height @var{lpp}
15898 @itemx set width @var{cpl}
15900 These @code{set} commands specify a screen height of @var{lpp} lines and
15901 a screen width of @var{cpl} characters. The associated @code{show}
15902 commands display the current settings.
15904 If you specify a height of zero lines, @value{GDBN} does not pause during
15905 output no matter how long the output is. This is useful if output is to a
15906 file or to an editor buffer.
15908 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
15909 from wrapping its output.
15911 @item set pagination on
15912 @itemx set pagination off
15913 @kindex set pagination
15914 Turn the output pagination on or off; the default is on. Turning
15915 pagination off is the alternative to @code{set height 0}.
15917 @item show pagination
15918 @kindex show pagination
15919 Show the current pagination mode.
15924 @cindex number representation
15925 @cindex entering numbers
15927 You can always enter numbers in octal, decimal, or hexadecimal in
15928 @value{GDBN} by the usual conventions: octal numbers begin with
15929 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
15930 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
15931 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
15932 10; likewise, the default display for numbers---when no particular
15933 format is specified---is base 10. You can change the default base for
15934 both input and output with the commands described below.
15937 @kindex set input-radix
15938 @item set input-radix @var{base}
15939 Set the default base for numeric input. Supported choices
15940 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15941 specified either unambiguously or using the current input radix; for
15945 set input-radix 012
15946 set input-radix 10.
15947 set input-radix 0xa
15951 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
15952 leaves the input radix unchanged, no matter what it was, since
15953 @samp{10}, being without any leading or trailing signs of its base, is
15954 interpreted in the current radix. Thus, if the current radix is 16,
15955 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
15958 @kindex set output-radix
15959 @item set output-radix @var{base}
15960 Set the default base for numeric display. Supported choices
15961 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15962 specified either unambiguously or using the current input radix.
15964 @kindex show input-radix
15965 @item show input-radix
15966 Display the current default base for numeric input.
15968 @kindex show output-radix
15969 @item show output-radix
15970 Display the current default base for numeric display.
15972 @item set radix @r{[}@var{base}@r{]}
15976 These commands set and show the default base for both input and output
15977 of numbers. @code{set radix} sets the radix of input and output to
15978 the same base; without an argument, it resets the radix back to its
15979 default value of 10.
15984 @section Configuring the current ABI
15986 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
15987 application automatically. However, sometimes you need to override its
15988 conclusions. Use these commands to manage @value{GDBN}'s view of the
15995 One @value{GDBN} configuration can debug binaries for multiple operating
15996 system targets, either via remote debugging or native emulation.
15997 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
15998 but you can override its conclusion using the @code{set osabi} command.
15999 One example where this is useful is in debugging of binaries which use
16000 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
16001 not have the same identifying marks that the standard C library for your
16006 Show the OS ABI currently in use.
16009 With no argument, show the list of registered available OS ABI's.
16011 @item set osabi @var{abi}
16012 Set the current OS ABI to @var{abi}.
16015 @cindex float promotion
16017 Generally, the way that an argument of type @code{float} is passed to a
16018 function depends on whether the function is prototyped. For a prototyped
16019 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
16020 according to the architecture's convention for @code{float}. For unprototyped
16021 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
16022 @code{double} and then passed.
16024 Unfortunately, some forms of debug information do not reliably indicate whether
16025 a function is prototyped. If @value{GDBN} calls a function that is not marked
16026 as prototyped, it consults @kbd{set coerce-float-to-double}.
16029 @kindex set coerce-float-to-double
16030 @item set coerce-float-to-double
16031 @itemx set coerce-float-to-double on
16032 Arguments of type @code{float} will be promoted to @code{double} when passed
16033 to an unprototyped function. This is the default setting.
16035 @item set coerce-float-to-double off
16036 Arguments of type @code{float} will be passed directly to unprototyped
16039 @kindex show coerce-float-to-double
16040 @item show coerce-float-to-double
16041 Show the current setting of promoting @code{float} to @code{double}.
16045 @kindex show cp-abi
16046 @value{GDBN} needs to know the ABI used for your program's C@t{++}
16047 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
16048 used to build your application. @value{GDBN} only fully supports
16049 programs with a single C@t{++} ABI; if your program contains code using
16050 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
16051 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
16052 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
16053 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
16054 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
16055 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
16060 Show the C@t{++} ABI currently in use.
16063 With no argument, show the list of supported C@t{++} ABI's.
16065 @item set cp-abi @var{abi}
16066 @itemx set cp-abi auto
16067 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
16070 @node Messages/Warnings
16071 @section Optional warnings and messages
16073 @cindex verbose operation
16074 @cindex optional warnings
16075 By default, @value{GDBN} is silent about its inner workings. If you are
16076 running on a slow machine, you may want to use the @code{set verbose}
16077 command. This makes @value{GDBN} tell you when it does a lengthy
16078 internal operation, so you will not think it has crashed.
16080 Currently, the messages controlled by @code{set verbose} are those
16081 which announce that the symbol table for a source file is being read;
16082 see @code{symbol-file} in @ref{Files, ,Commands to specify files}.
16085 @kindex set verbose
16086 @item set verbose on
16087 Enables @value{GDBN} output of certain informational messages.
16089 @item set verbose off
16090 Disables @value{GDBN} output of certain informational messages.
16092 @kindex show verbose
16094 Displays whether @code{set verbose} is on or off.
16097 By default, if @value{GDBN} encounters bugs in the symbol table of an
16098 object file, it is silent; but if you are debugging a compiler, you may
16099 find this information useful (@pxref{Symbol Errors, ,Errors reading
16104 @kindex set complaints
16105 @item set complaints @var{limit}
16106 Permits @value{GDBN} to output @var{limit} complaints about each type of
16107 unusual symbols before becoming silent about the problem. Set
16108 @var{limit} to zero to suppress all complaints; set it to a large number
16109 to prevent complaints from being suppressed.
16111 @kindex show complaints
16112 @item show complaints
16113 Displays how many symbol complaints @value{GDBN} is permitted to produce.
16117 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
16118 lot of stupid questions to confirm certain commands. For example, if
16119 you try to run a program which is already running:
16123 The program being debugged has been started already.
16124 Start it from the beginning? (y or n)
16127 If you are willing to unflinchingly face the consequences of your own
16128 commands, you can disable this ``feature'':
16132 @kindex set confirm
16134 @cindex confirmation
16135 @cindex stupid questions
16136 @item set confirm off
16137 Disables confirmation requests.
16139 @item set confirm on
16140 Enables confirmation requests (the default).
16142 @kindex show confirm
16144 Displays state of confirmation requests.
16148 @cindex command tracing
16149 If you need to debug user-defined commands or sourced files you may find it
16150 useful to enable @dfn{command tracing}. In this mode each command will be
16151 printed as it is executed, prefixed with one or more @samp{+} symbols, the
16152 quantity denoting the call depth of each command.
16155 @kindex set trace-commands
16156 @cindex command scripts, debugging
16157 @item set trace-commands on
16158 Enable command tracing.
16159 @item set trace-commands off
16160 Disable command tracing.
16161 @item show trace-commands
16162 Display the current state of command tracing.
16165 @node Debugging Output
16166 @section Optional messages about internal happenings
16167 @cindex optional debugging messages
16169 @value{GDBN} has commands that enable optional debugging messages from
16170 various @value{GDBN} subsystems; normally these commands are of
16171 interest to @value{GDBN} maintainers, or when reporting a bug. This
16172 section documents those commands.
16175 @kindex set exec-done-display
16176 @item set exec-done-display
16177 Turns on or off the notification of asynchronous commands'
16178 completion. When on, @value{GDBN} will print a message when an
16179 asynchronous command finishes its execution. The default is off.
16180 @kindex show exec-done-display
16181 @item show exec-done-display
16182 Displays the current setting of asynchronous command completion
16185 @cindex gdbarch debugging info
16186 @cindex architecture debugging info
16187 @item set debug arch
16188 Turns on or off display of gdbarch debugging info. The default is off
16190 @item show debug arch
16191 Displays the current state of displaying gdbarch debugging info.
16192 @item set debug aix-thread
16193 @cindex AIX threads
16194 Display debugging messages about inner workings of the AIX thread
16196 @item show debug aix-thread
16197 Show the current state of AIX thread debugging info display.
16198 @item set debug event
16199 @cindex event debugging info
16200 Turns on or off display of @value{GDBN} event debugging info. The
16202 @item show debug event
16203 Displays the current state of displaying @value{GDBN} event debugging
16205 @item set debug expression
16206 @cindex expression debugging info
16207 Turns on or off display of debugging info about @value{GDBN}
16208 expression parsing. The default is off.
16209 @item show debug expression
16210 Displays the current state of displaying debugging info about
16211 @value{GDBN} expression parsing.
16212 @item set debug frame
16213 @cindex frame debugging info
16214 Turns on or off display of @value{GDBN} frame debugging info. The
16216 @item show debug frame
16217 Displays the current state of displaying @value{GDBN} frame debugging
16219 @item set debug infrun
16220 @cindex inferior debugging info
16221 Turns on or off display of @value{GDBN} debugging info for running the inferior.
16222 The default is off. @file{infrun.c} contains GDB's runtime state machine used
16223 for implementing operations such as single-stepping the inferior.
16224 @item show debug infrun
16225 Displays the current state of @value{GDBN} inferior debugging.
16226 @item set debug lin-lwp
16227 @cindex @sc{gnu}/Linux LWP debug messages
16228 @cindex Linux lightweight processes
16229 Turns on or off debugging messages from the Linux LWP debug support.
16230 @item show debug lin-lwp
16231 Show the current state of Linux LWP debugging messages.
16232 @item set debug observer
16233 @cindex observer debugging info
16234 Turns on or off display of @value{GDBN} observer debugging. This
16235 includes info such as the notification of observable events.
16236 @item show debug observer
16237 Displays the current state of observer debugging.
16238 @item set debug overload
16239 @cindex C@t{++} overload debugging info
16240 Turns on or off display of @value{GDBN} C@t{++} overload debugging
16241 info. This includes info such as ranking of functions, etc. The default
16243 @item show debug overload
16244 Displays the current state of displaying @value{GDBN} C@t{++} overload
16246 @cindex packets, reporting on stdout
16247 @cindex serial connections, debugging
16248 @cindex debug remote protocol
16249 @cindex remote protocol debugging
16250 @cindex display remote packets
16251 @item set debug remote
16252 Turns on or off display of reports on all packets sent back and forth across
16253 the serial line to the remote machine. The info is printed on the
16254 @value{GDBN} standard output stream. The default is off.
16255 @item show debug remote
16256 Displays the state of display of remote packets.
16257 @item set debug serial
16258 Turns on or off display of @value{GDBN} serial debugging info. The
16260 @item show debug serial
16261 Displays the current state of displaying @value{GDBN} serial debugging
16263 @item set debug solib-frv
16264 @cindex FR-V shared-library debugging
16265 Turns on or off debugging messages for FR-V shared-library code.
16266 @item show debug solib-frv
16267 Display the current state of FR-V shared-library code debugging
16269 @item set debug target
16270 @cindex target debugging info
16271 Turns on or off display of @value{GDBN} target debugging info. This info
16272 includes what is going on at the target level of GDB, as it happens. The
16273 default is 0. Set it to 1 to track events, and to 2 to also track the
16274 value of large memory transfers. Changes to this flag do not take effect
16275 until the next time you connect to a target or use the @code{run} command.
16276 @item show debug target
16277 Displays the current state of displaying @value{GDBN} target debugging
16279 @item set debugvarobj
16280 @cindex variable object debugging info
16281 Turns on or off display of @value{GDBN} variable object debugging
16282 info. The default is off.
16283 @item show debugvarobj
16284 Displays the current state of displaying @value{GDBN} variable object
16289 @chapter Canned Sequences of Commands
16291 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
16292 command lists}), @value{GDBN} provides two ways to store sequences of
16293 commands for execution as a unit: user-defined commands and command
16297 * Define:: How to define your own commands
16298 * Hooks:: Hooks for user-defined commands
16299 * Command Files:: How to write scripts of commands to be stored in a file
16300 * Output:: Commands for controlled output
16304 @section User-defined commands
16306 @cindex user-defined command
16307 @cindex arguments, to user-defined commands
16308 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
16309 which you assign a new name as a command. This is done with the
16310 @code{define} command. User commands may accept up to 10 arguments
16311 separated by whitespace. Arguments are accessed within the user command
16312 via @code{$arg0@dots{}$arg9}. A trivial example:
16316 print $arg0 + $arg1 + $arg2
16321 To execute the command use:
16328 This defines the command @code{adder}, which prints the sum of
16329 its three arguments. Note the arguments are text substitutions, so they may
16330 reference variables, use complex expressions, or even perform inferior
16333 @cindex argument count in user-defined commands
16334 @cindex how many arguments (user-defined commands)
16335 In addition, @code{$argc} may be used to find out how many arguments have
16336 been passed. This expands to a number in the range 0@dots{}10.
16341 print $arg0 + $arg1
16344 print $arg0 + $arg1 + $arg2
16352 @item define @var{commandname}
16353 Define a command named @var{commandname}. If there is already a command
16354 by that name, you are asked to confirm that you want to redefine it.
16356 The definition of the command is made up of other @value{GDBN} command lines,
16357 which are given following the @code{define} command. The end of these
16358 commands is marked by a line containing @code{end}.
16361 @kindex end@r{ (user-defined commands)}
16362 @item document @var{commandname}
16363 Document the user-defined command @var{commandname}, so that it can be
16364 accessed by @code{help}. The command @var{commandname} must already be
16365 defined. This command reads lines of documentation just as @code{define}
16366 reads the lines of the command definition, ending with @code{end}.
16367 After the @code{document} command is finished, @code{help} on command
16368 @var{commandname} displays the documentation you have written.
16370 You may use the @code{document} command again to change the
16371 documentation of a command. Redefining the command with @code{define}
16372 does not change the documentation.
16374 @kindex dont-repeat
16375 @cindex don't repeat command
16377 Used inside a user-defined command, this tells @value{GDBN} that this
16378 command should not be repeated when the user hits @key{RET}
16379 (@pxref{Command Syntax, repeat last command}).
16381 @kindex help user-defined
16382 @item help user-defined
16383 List all user-defined commands, with the first line of the documentation
16388 @itemx show user @var{commandname}
16389 Display the @value{GDBN} commands used to define @var{commandname} (but
16390 not its documentation). If no @var{commandname} is given, display the
16391 definitions for all user-defined commands.
16393 @cindex infinite recursion in user-defined commands
16394 @kindex show max-user-call-depth
16395 @kindex set max-user-call-depth
16396 @item show max-user-call-depth
16397 @itemx set max-user-call-depth
16398 The value of @code{max-user-call-depth} controls how many recursion
16399 levels are allowed in user-defined commands before GDB suspects an
16400 infinite recursion and aborts the command.
16403 In addition to the above commands, user-defined commands frequently
16404 use control flow commands, described in @ref{Command Files}.
16406 When user-defined commands are executed, the
16407 commands of the definition are not printed. An error in any command
16408 stops execution of the user-defined command.
16410 If used interactively, commands that would ask for confirmation proceed
16411 without asking when used inside a user-defined command. Many @value{GDBN}
16412 commands that normally print messages to say what they are doing omit the
16413 messages when used in a user-defined command.
16416 @section User-defined command hooks
16417 @cindex command hooks
16418 @cindex hooks, for commands
16419 @cindex hooks, pre-command
16422 You may define @dfn{hooks}, which are a special kind of user-defined
16423 command. Whenever you run the command @samp{foo}, if the user-defined
16424 command @samp{hook-foo} exists, it is executed (with no arguments)
16425 before that command.
16427 @cindex hooks, post-command
16429 A hook may also be defined which is run after the command you executed.
16430 Whenever you run the command @samp{foo}, if the user-defined command
16431 @samp{hookpost-foo} exists, it is executed (with no arguments) after
16432 that command. Post-execution hooks may exist simultaneously with
16433 pre-execution hooks, for the same command.
16435 It is valid for a hook to call the command which it hooks. If this
16436 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
16438 @c It would be nice if hookpost could be passed a parameter indicating
16439 @c if the command it hooks executed properly or not. FIXME!
16441 @kindex stop@r{, a pseudo-command}
16442 In addition, a pseudo-command, @samp{stop} exists. Defining
16443 (@samp{hook-stop}) makes the associated commands execute every time
16444 execution stops in your program: before breakpoint commands are run,
16445 displays are printed, or the stack frame is printed.
16447 For example, to ignore @code{SIGALRM} signals while
16448 single-stepping, but treat them normally during normal execution,
16453 handle SIGALRM nopass
16457 handle SIGALRM pass
16460 define hook-continue
16461 handle SIGLARM pass
16465 As a further example, to hook at the begining and end of the @code{echo}
16466 command, and to add extra text to the beginning and end of the message,
16474 define hookpost-echo
16478 (@value{GDBP}) echo Hello World
16479 <<<---Hello World--->>>
16484 You can define a hook for any single-word command in @value{GDBN}, but
16485 not for command aliases; you should define a hook for the basic command
16486 name, e.g.@: @code{backtrace} rather than @code{bt}.
16487 @c FIXME! So how does Joe User discover whether a command is an alias
16489 If an error occurs during the execution of your hook, execution of
16490 @value{GDBN} commands stops and @value{GDBN} issues a prompt
16491 (before the command that you actually typed had a chance to run).
16493 If you try to define a hook which does not match any known command, you
16494 get a warning from the @code{define} command.
16496 @node Command Files
16497 @section Command files
16499 @cindex command files
16500 @cindex scripting commands
16501 A command file for @value{GDBN} is a text file made of lines that are
16502 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
16503 also be included. An empty line in a command file does nothing; it
16504 does not mean to repeat the last command, as it would from the
16507 You can request the execution of a command file with the @code{source}
16512 @cindex execute commands from a file
16513 @item source [@code{-v}] @var{filename}
16514 Execute the command file @var{filename}.
16517 The lines in a command file are generally executed sequentially,
16518 unless the order of execution is changed by one of the
16519 @emph{flow-control commands} described below. The commands are not
16520 printed as they are executed. An error in any command terminates
16521 execution of the command file and control is returned to the console.
16523 @value{GDBN} searches for @var{filename} in the current directory and then
16524 on the search path (specified with the @samp{directory} command).
16526 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
16527 each command as it is executed. The option must be given before
16528 @var{filename}, and is interpreted as part of the filename anywhere else.
16530 Commands that would ask for confirmation if used interactively proceed
16531 without asking when used in a command file. Many @value{GDBN} commands that
16532 normally print messages to say what they are doing omit the messages
16533 when called from command files.
16535 @value{GDBN} also accepts command input from standard input. In this
16536 mode, normal output goes to standard output and error output goes to
16537 standard error. Errors in a command file supplied on standard input do
16538 not terminate execution of the command file---execution continues with
16542 gdb < cmds > log 2>&1
16545 (The syntax above will vary depending on the shell used.) This example
16546 will execute commands from the file @file{cmds}. All output and errors
16547 would be directed to @file{log}.
16549 Since commands stored on command files tend to be more general than
16550 commands typed interactively, they frequently need to deal with
16551 complicated situations, such as different or unexpected values of
16552 variables and symbols, changes in how the program being debugged is
16553 built, etc. @value{GDBN} provides a set of flow-control commands to
16554 deal with these complexities. Using these commands, you can write
16555 complex scripts that loop over data structures, execute commands
16556 conditionally, etc.
16563 This command allows to include in your script conditionally executed
16564 commands. The @code{if} command takes a single argument, which is an
16565 expression to evaluate. It is followed by a series of commands that
16566 are executed only if the expression is true (its value is nonzero).
16567 There can then optionally be an @code{else} line, followed by a series
16568 of commands that are only executed if the expression was false. The
16569 end of the list is marked by a line containing @code{end}.
16573 This command allows to write loops. Its syntax is similar to
16574 @code{if}: the command takes a single argument, which is an expression
16575 to evaluate, and must be followed by the commands to execute, one per
16576 line, terminated by an @code{end}. These commands are called the
16577 @dfn{body} of the loop. The commands in the body of @code{while} are
16578 executed repeatedly as long as the expression evaluates to true.
16582 This command exits the @code{while} loop in whose body it is included.
16583 Execution of the script continues after that @code{while}s @code{end}
16586 @kindex loop_continue
16587 @item loop_continue
16588 This command skips the execution of the rest of the body of commands
16589 in the @code{while} loop in whose body it is included. Execution
16590 branches to the beginning of the @code{while} loop, where it evaluates
16591 the controlling expression.
16593 @kindex end@r{ (if/else/while commands)}
16595 Terminate the block of commands that are the body of @code{if},
16596 @code{else}, or @code{while} flow-control commands.
16601 @section Commands for controlled output
16603 During the execution of a command file or a user-defined command, normal
16604 @value{GDBN} output is suppressed; the only output that appears is what is
16605 explicitly printed by the commands in the definition. This section
16606 describes three commands useful for generating exactly the output you
16611 @item echo @var{text}
16612 @c I do not consider backslash-space a standard C escape sequence
16613 @c because it is not in ANSI.
16614 Print @var{text}. Nonprinting characters can be included in
16615 @var{text} using C escape sequences, such as @samp{\n} to print a
16616 newline. @strong{No newline is printed unless you specify one.}
16617 In addition to the standard C escape sequences, a backslash followed
16618 by a space stands for a space. This is useful for displaying a
16619 string with spaces at the beginning or the end, since leading and
16620 trailing spaces are otherwise trimmed from all arguments.
16621 To print @samp{@w{ }and foo =@w{ }}, use the command
16622 @samp{echo \@w{ }and foo = \@w{ }}.
16624 A backslash at the end of @var{text} can be used, as in C, to continue
16625 the command onto subsequent lines. For example,
16628 echo This is some text\n\
16629 which is continued\n\
16630 onto several lines.\n
16633 produces the same output as
16636 echo This is some text\n
16637 echo which is continued\n
16638 echo onto several lines.\n
16642 @item output @var{expression}
16643 Print the value of @var{expression} and nothing but that value: no
16644 newlines, no @samp{$@var{nn} = }. The value is not entered in the
16645 value history either. @xref{Expressions, ,Expressions}, for more information
16648 @item output/@var{fmt} @var{expression}
16649 Print the value of @var{expression} in format @var{fmt}. You can use
16650 the same formats as for @code{print}. @xref{Output Formats,,Output
16651 formats}, for more information.
16654 @item printf @var{string}, @var{expressions}@dots{}
16655 Print the values of the @var{expressions} under the control of
16656 @var{string}. The @var{expressions} are separated by commas and may be
16657 either numbers or pointers. Their values are printed as specified by
16658 @var{string}, exactly as if your program were to execute the C
16660 @c FIXME: the above implies that at least all ANSI C formats are
16661 @c supported, but it isn't true: %E and %G don't work (or so it seems).
16662 @c Either this is a bug, or the manual should document what formats are
16666 printf (@var{string}, @var{expressions}@dots{});
16669 For example, you can print two values in hex like this:
16672 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
16675 The only backslash-escape sequences that you can use in the format
16676 string are the simple ones that consist of backslash followed by a
16681 @chapter Command Interpreters
16682 @cindex command interpreters
16684 @value{GDBN} supports multiple command interpreters, and some command
16685 infrastructure to allow users or user interface writers to switch
16686 between interpreters or run commands in other interpreters.
16688 @value{GDBN} currently supports two command interpreters, the console
16689 interpreter (sometimes called the command-line interpreter or @sc{cli})
16690 and the machine interface interpreter (or @sc{gdb/mi}). This manual
16691 describes both of these interfaces in great detail.
16693 By default, @value{GDBN} will start with the console interpreter.
16694 However, the user may choose to start @value{GDBN} with another
16695 interpreter by specifying the @option{-i} or @option{--interpreter}
16696 startup options. Defined interpreters include:
16700 @cindex console interpreter
16701 The traditional console or command-line interpreter. This is the most often
16702 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
16703 @value{GDBN} will use this interpreter.
16706 @cindex mi interpreter
16707 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
16708 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
16709 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
16713 @cindex mi2 interpreter
16714 The current @sc{gdb/mi} interface.
16717 @cindex mi1 interpreter
16718 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
16722 @cindex invoke another interpreter
16723 The interpreter being used by @value{GDBN} may not be dynamically
16724 switched at runtime. Although possible, this could lead to a very
16725 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
16726 enters the command "interpreter-set console" in a console view,
16727 @value{GDBN} would switch to using the console interpreter, rendering
16728 the IDE inoperable!
16730 @kindex interpreter-exec
16731 Although you may only choose a single interpreter at startup, you may execute
16732 commands in any interpreter from the current interpreter using the appropriate
16733 command. If you are running the console interpreter, simply use the
16734 @code{interpreter-exec} command:
16737 interpreter-exec mi "-data-list-register-names"
16740 @sc{gdb/mi} has a similar command, although it is only available in versions of
16741 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
16744 @chapter @value{GDBN} Text User Interface
16746 @cindex Text User Interface
16749 * TUI Overview:: TUI overview
16750 * TUI Keys:: TUI key bindings
16751 * TUI Single Key Mode:: TUI single key mode
16752 * TUI Commands:: TUI specific commands
16753 * TUI Configuration:: TUI configuration variables
16756 The @value{GDBN} Text User Interface, TUI in short, is a terminal
16757 interface which uses the @code{curses} library to show the source
16758 file, the assembly output, the program registers and @value{GDBN}
16759 commands in separate text windows.
16761 The TUI is enabled by invoking @value{GDBN} using either
16763 @samp{gdbtui} or @samp{gdb -tui}.
16766 @section TUI overview
16768 The TUI has two display modes that can be switched while
16773 A curses (or TUI) mode in which it displays several text
16774 windows on the terminal.
16777 A standard mode which corresponds to the @value{GDBN} configured without
16781 In the TUI mode, @value{GDBN} can display several text window
16786 This window is the @value{GDBN} command window with the @value{GDBN}
16787 prompt and the @value{GDBN} outputs. The @value{GDBN} input is still
16788 managed using readline but through the TUI. The @emph{command}
16789 window is always visible.
16792 The source window shows the source file of the program. The current
16793 line as well as active breakpoints are displayed in this window.
16796 The assembly window shows the disassembly output of the program.
16799 This window shows the processor registers. It detects when
16800 a register is changed and when this is the case, registers that have
16801 changed are highlighted.
16805 The source and assembly windows show the current program position
16806 by highlighting the current line and marking them with the @samp{>} marker.
16807 Breakpoints are also indicated with two markers. A first one
16808 indicates the breakpoint type:
16812 Breakpoint which was hit at least once.
16815 Breakpoint which was never hit.
16818 Hardware breakpoint which was hit at least once.
16821 Hardware breakpoint which was never hit.
16825 The second marker indicates whether the breakpoint is enabled or not:
16829 Breakpoint is enabled.
16832 Breakpoint is disabled.
16836 The source, assembly and register windows are attached to the thread
16837 and the frame position. They are updated when the current thread
16838 changes, when the frame changes or when the program counter changes.
16839 These three windows are arranged by the TUI according to several
16840 layouts. The layout defines which of these three windows are visible.
16841 The following layouts are available:
16851 source and assembly
16854 source and registers
16857 assembly and registers
16861 On top of the command window a status line gives various information
16862 concerning the current process begin debugged. The status line is
16863 updated when the information it shows changes. The following fields
16868 Indicates the current gdb target
16869 (@pxref{Targets, ,Specifying a Debugging Target}).
16872 Gives information about the current process or thread number.
16873 When no process is being debugged, this field is set to @code{No process}.
16876 Gives the current function name for the selected frame.
16877 The name is demangled if demangling is turned on (@pxref{Print Settings}).
16878 When there is no symbol corresponding to the current program counter
16879 the string @code{??} is displayed.
16882 Indicates the current line number for the selected frame.
16883 When the current line number is not known the string @code{??} is displayed.
16886 Indicates the current program counter address.
16891 @section TUI Key Bindings
16892 @cindex TUI key bindings
16894 The TUI installs several key bindings in the readline keymaps
16895 (@pxref{Command Line Editing}).
16896 They allow to leave or enter in the TUI mode or they operate
16897 directly on the TUI layout and windows. The TUI also provides
16898 a @emph{SingleKey} keymap which binds several keys directly to
16899 @value{GDBN} commands. The following key bindings
16900 are installed for both TUI mode and the @value{GDBN} standard mode.
16909 Enter or leave the TUI mode. When the TUI mode is left,
16910 the curses window management is left and @value{GDBN} operates using
16911 its standard mode writing on the terminal directly. When the TUI
16912 mode is entered, the control is given back to the curses windows.
16913 The screen is then refreshed.
16917 Use a TUI layout with only one window. The layout will
16918 either be @samp{source} or @samp{assembly}. When the TUI mode
16919 is not active, it will switch to the TUI mode.
16921 Think of this key binding as the Emacs @kbd{C-x 1} binding.
16925 Use a TUI layout with at least two windows. When the current
16926 layout shows already two windows, a next layout with two windows is used.
16927 When a new layout is chosen, one window will always be common to the
16928 previous layout and the new one.
16930 Think of it as the Emacs @kbd{C-x 2} binding.
16934 Change the active window. The TUI associates several key bindings
16935 (like scrolling and arrow keys) to the active window. This command
16936 gives the focus to the next TUI window.
16938 Think of it as the Emacs @kbd{C-x o} binding.
16942 Use the TUI @emph{SingleKey} keymap that binds single key to gdb commands
16943 (@pxref{TUI Single Key Mode}).
16947 The following key bindings are handled only by the TUI mode:
16952 Scroll the active window one page up.
16956 Scroll the active window one page down.
16960 Scroll the active window one line up.
16964 Scroll the active window one line down.
16968 Scroll the active window one column left.
16972 Scroll the active window one column right.
16976 Refresh the screen.
16980 In the TUI mode, the arrow keys are used by the active window
16981 for scrolling. This means they are available for readline when the
16982 active window is the command window. When the command window
16983 does not have the focus, it is necessary to use other readline
16984 key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b} and @kbd{C-f}.
16986 @node TUI Single Key Mode
16987 @section TUI Single Key Mode
16988 @cindex TUI single key mode
16990 The TUI provides a @emph{SingleKey} mode in which it installs a particular
16991 key binding in the readline keymaps to connect single keys to
16995 @kindex c @r{(SingleKey TUI key)}
16999 @kindex d @r{(SingleKey TUI key)}
17003 @kindex f @r{(SingleKey TUI key)}
17007 @kindex n @r{(SingleKey TUI key)}
17011 @kindex q @r{(SingleKey TUI key)}
17013 exit the @emph{SingleKey} mode.
17015 @kindex r @r{(SingleKey TUI key)}
17019 @kindex s @r{(SingleKey TUI key)}
17023 @kindex u @r{(SingleKey TUI key)}
17027 @kindex v @r{(SingleKey TUI key)}
17031 @kindex w @r{(SingleKey TUI key)}
17037 Other keys temporarily switch to the @value{GDBN} command prompt.
17038 The key that was pressed is inserted in the editing buffer so that
17039 it is possible to type most @value{GDBN} commands without interaction
17040 with the TUI @emph{SingleKey} mode. Once the command is entered the TUI
17041 @emph{SingleKey} mode is restored. The only way to permanently leave
17042 this mode is by typing @kbd{q} or @kbd{C-x s}.
17046 @section TUI specific commands
17047 @cindex TUI commands
17049 The TUI has specific commands to control the text windows.
17050 These commands are always available, that is they do not depend on
17051 the current terminal mode in which @value{GDBN} runs. When @value{GDBN}
17052 is in the standard mode, using these commands will automatically switch
17058 List and give the size of all displayed windows.
17062 Display the next layout.
17065 Display the previous layout.
17068 Display the source window only.
17071 Display the assembly window only.
17074 Display the source and assembly window.
17077 Display the register window together with the source or assembly window.
17079 @item focus next | prev | src | asm | regs | split
17081 Set the focus to the named window.
17082 This command allows to change the active window so that scrolling keys
17083 can be affected to another window.
17087 Refresh the screen. This is similar to typing @kbd{C-L}.
17089 @item tui reg float
17091 Show the floating point registers in the register window.
17093 @item tui reg general
17094 Show the general registers in the register window.
17097 Show the next register group. The list of register groups as well as
17098 their order is target specific. The predefined register groups are the
17099 following: @code{general}, @code{float}, @code{system}, @code{vector},
17100 @code{all}, @code{save}, @code{restore}.
17102 @item tui reg system
17103 Show the system registers in the register window.
17107 Update the source window and the current execution point.
17109 @item winheight @var{name} +@var{count}
17110 @itemx winheight @var{name} -@var{count}
17112 Change the height of the window @var{name} by @var{count}
17113 lines. Positive counts increase the height, while negative counts
17117 @kindex tabset @var{nchars}
17118 Set the width of tab stops to be @var{nchars} characters.
17122 @node TUI Configuration
17123 @section TUI configuration variables
17124 @cindex TUI configuration variables
17126 The TUI has several configuration variables that control the
17127 appearance of windows on the terminal.
17130 @item set tui border-kind @var{kind}
17131 @kindex set tui border-kind
17132 Select the border appearance for the source, assembly and register windows.
17133 The possible values are the following:
17136 Use a space character to draw the border.
17139 Use ascii characters + - and | to draw the border.
17142 Use the Alternate Character Set to draw the border. The border is
17143 drawn using character line graphics if the terminal supports them.
17147 @item set tui active-border-mode @var{mode}
17148 @kindex set tui active-border-mode
17149 Select the attributes to display the border of the active window.
17150 The possible values are @code{normal}, @code{standout}, @code{reverse},
17151 @code{half}, @code{half-standout}, @code{bold} and @code{bold-standout}.
17153 @item set tui border-mode @var{mode}
17154 @kindex set tui border-mode
17155 Select the attributes to display the border of other windows.
17156 The @var{mode} can be one of the following:
17159 Use normal attributes to display the border.
17165 Use reverse video mode.
17168 Use half bright mode.
17170 @item half-standout
17171 Use half bright and standout mode.
17174 Use extra bright or bold mode.
17176 @item bold-standout
17177 Use extra bright or bold and standout mode.
17184 @chapter Using @value{GDBN} under @sc{gnu} Emacs
17187 @cindex @sc{gnu} Emacs
17188 A special interface allows you to use @sc{gnu} Emacs to view (and
17189 edit) the source files for the program you are debugging with
17192 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
17193 executable file you want to debug as an argument. This command starts
17194 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
17195 created Emacs buffer.
17196 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
17198 Using @value{GDBN} under Emacs is just like using @value{GDBN} normally except for two
17203 All ``terminal'' input and output goes through the Emacs buffer.
17206 This applies both to @value{GDBN} commands and their output, and to the input
17207 and output done by the program you are debugging.
17209 This is useful because it means that you can copy the text of previous
17210 commands and input them again; you can even use parts of the output
17213 All the facilities of Emacs' Shell mode are available for interacting
17214 with your program. In particular, you can send signals the usual
17215 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
17220 @value{GDBN} displays source code through Emacs.
17223 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
17224 source file for that frame and puts an arrow (@samp{=>}) at the
17225 left margin of the current line. Emacs uses a separate buffer for
17226 source display, and splits the screen to show both your @value{GDBN} session
17229 Explicit @value{GDBN} @code{list} or search commands still produce output as
17230 usual, but you probably have no reason to use them from Emacs.
17232 If you specify an absolute file name when prompted for the @kbd{M-x
17233 gdb} argument, then Emacs sets your current working directory to where
17234 your program resides. If you only specify the file name, then Emacs
17235 sets your current working directory to to the directory associated
17236 with the previous buffer. In this case, @value{GDBN} may find your
17237 program by searching your environment's @code{PATH} variable, but on
17238 some operating systems it might not find the source. So, although the
17239 @value{GDBN} input and output session proceeds normally, the auxiliary
17240 buffer does not display the current source and line of execution.
17242 The initial working directory of @value{GDBN} is printed on the top
17243 line of the @value{GDBN} I/O buffer and this serves as a default for
17244 the commands that specify files for @value{GDBN} to operate
17245 on. @xref{Files, ,Commands to specify files}.
17247 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
17248 need to call @value{GDBN} by a different name (for example, if you
17249 keep several configurations around, with different names) you can
17250 customize the Emacs variable @code{gud-gdb-command-name} to run the
17253 In the @value{GDBN} I/O buffer, you can use these special Emacs commands in
17254 addition to the standard Shell mode commands:
17258 Describe the features of Emacs' @value{GDBN} Mode.
17261 Execute to another source line, like the @value{GDBN} @code{step} command; also
17262 update the display window to show the current file and location.
17265 Execute to next source line in this function, skipping all function
17266 calls, like the @value{GDBN} @code{next} command. Then update the display window
17267 to show the current file and location.
17270 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
17271 display window accordingly.
17274 Execute until exit from the selected stack frame, like the @value{GDBN}
17275 @code{finish} command.
17278 Continue execution of your program, like the @value{GDBN} @code{continue}
17282 Go up the number of frames indicated by the numeric argument
17283 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
17284 like the @value{GDBN} @code{up} command.
17287 Go down the number of frames indicated by the numeric argument, like the
17288 @value{GDBN} @code{down} command.
17291 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
17292 tells @value{GDBN} to set a breakpoint on the source line point is on.
17294 If you type @kbd{M-x speedbar}, then Emacs displays a separate frame which
17295 shows a backtrace when the @value{GDBN} I/O buffer is current. Move
17296 point to any frame in the stack and type @key{RET} to make it become the
17297 current frame and display the associated source in the source buffer.
17298 Alternatively, click @kbd{Mouse-2} to make the selected frame become the
17301 If you accidentally delete the source-display buffer, an easy way to get
17302 it back is to type the command @code{f} in the @value{GDBN} buffer, to
17303 request a frame display; when you run under Emacs, this recreates
17304 the source buffer if necessary to show you the context of the current
17307 The source files displayed in Emacs are in ordinary Emacs buffers
17308 which are visiting the source files in the usual way. You can edit
17309 the files with these buffers if you wish; but keep in mind that @value{GDBN}
17310 communicates with Emacs in terms of line numbers. If you add or
17311 delete lines from the text, the line numbers that @value{GDBN} knows cease
17312 to correspond properly with the code.
17314 The description given here is for GNU Emacs version 21.3 and a more
17315 detailed description of its interaction with @value{GDBN} is given in
17316 the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu} Emacs Manual}).
17318 @c The following dropped because Epoch is nonstandard. Reactivate
17319 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
17321 @kindex Emacs Epoch environment
17325 Version 18 of @sc{gnu} Emacs has a built-in window system
17326 called the @code{epoch}
17327 environment. Users of this environment can use a new command,
17328 @code{inspect} which performs identically to @code{print} except that
17329 each value is printed in its own window.
17334 @chapter The @sc{gdb/mi} Interface
17336 @unnumberedsec Function and Purpose
17338 @cindex @sc{gdb/mi}, its purpose
17339 @sc{gdb/mi} is a line based machine oriented text interface to
17340 @value{GDBN} and is activated by specifying using the
17341 @option{--interpreter} command line option (@pxref{Mode Options}). It
17342 is specifically intended to support the development of systems which
17343 use the debugger as just one small component of a larger system.
17345 This chapter is a specification of the @sc{gdb/mi} interface. It is written
17346 in the form of a reference manual.
17348 Note that @sc{gdb/mi} is still under construction, so some of the
17349 features described below are incomplete and subject to change
17350 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
17352 @unnumberedsec Notation and Terminology
17354 @cindex notational conventions, for @sc{gdb/mi}
17355 This chapter uses the following notation:
17359 @code{|} separates two alternatives.
17362 @code{[ @var{something} ]} indicates that @var{something} is optional:
17363 it may or may not be given.
17366 @code{( @var{group} )*} means that @var{group} inside the parentheses
17367 may repeat zero or more times.
17370 @code{( @var{group} )+} means that @var{group} inside the parentheses
17371 may repeat one or more times.
17374 @code{"@var{string}"} means a literal @var{string}.
17378 @heading Dependencies
17382 * GDB/MI Command Syntax::
17383 * GDB/MI Compatibility with CLI::
17384 * GDB/MI Development and Front Ends::
17385 * GDB/MI Output Records::
17386 * GDB/MI Simple Examples::
17387 * GDB/MI Command Description Format::
17388 * GDB/MI Breakpoint Commands::
17389 * GDB/MI Program Context::
17390 * GDB/MI Thread Commands::
17391 * GDB/MI Program Execution::
17392 * GDB/MI Stack Manipulation::
17393 * GDB/MI Variable Objects::
17394 * GDB/MI Data Manipulation::
17395 * GDB/MI Tracepoint Commands::
17396 * GDB/MI Symbol Query::
17397 * GDB/MI File Commands::
17399 * GDB/MI Kod Commands::
17400 * GDB/MI Memory Overlay Commands::
17401 * GDB/MI Signal Handling Commands::
17403 * GDB/MI Target Manipulation::
17404 * GDB/MI Miscellaneous Commands::
17407 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17408 @node GDB/MI Command Syntax
17409 @section @sc{gdb/mi} Command Syntax
17412 * GDB/MI Input Syntax::
17413 * GDB/MI Output Syntax::
17416 @node GDB/MI Input Syntax
17417 @subsection @sc{gdb/mi} Input Syntax
17419 @cindex input syntax for @sc{gdb/mi}
17420 @cindex @sc{gdb/mi}, input syntax
17422 @item @var{command} @expansion{}
17423 @code{@var{cli-command} | @var{mi-command}}
17425 @item @var{cli-command} @expansion{}
17426 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
17427 @var{cli-command} is any existing @value{GDBN} CLI command.
17429 @item @var{mi-command} @expansion{}
17430 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
17431 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
17433 @item @var{token} @expansion{}
17434 "any sequence of digits"
17436 @item @var{option} @expansion{}
17437 @code{"-" @var{parameter} [ " " @var{parameter} ]}
17439 @item @var{parameter} @expansion{}
17440 @code{@var{non-blank-sequence} | @var{c-string}}
17442 @item @var{operation} @expansion{}
17443 @emph{any of the operations described in this chapter}
17445 @item @var{non-blank-sequence} @expansion{}
17446 @emph{anything, provided it doesn't contain special characters such as
17447 "-", @var{nl}, """ and of course " "}
17449 @item @var{c-string} @expansion{}
17450 @code{""" @var{seven-bit-iso-c-string-content} """}
17452 @item @var{nl} @expansion{}
17461 The CLI commands are still handled by the @sc{mi} interpreter; their
17462 output is described below.
17465 The @code{@var{token}}, when present, is passed back when the command
17469 Some @sc{mi} commands accept optional arguments as part of the parameter
17470 list. Each option is identified by a leading @samp{-} (dash) and may be
17471 followed by an optional argument parameter. Options occur first in the
17472 parameter list and can be delimited from normal parameters using
17473 @samp{--} (this is useful when some parameters begin with a dash).
17480 We want easy access to the existing CLI syntax (for debugging).
17483 We want it to be easy to spot a @sc{mi} operation.
17486 @node GDB/MI Output Syntax
17487 @subsection @sc{gdb/mi} Output Syntax
17489 @cindex output syntax of @sc{gdb/mi}
17490 @cindex @sc{gdb/mi}, output syntax
17491 The output from @sc{gdb/mi} consists of zero or more out-of-band records
17492 followed, optionally, by a single result record. This result record
17493 is for the most recent command. The sequence of output records is
17494 terminated by @samp{(gdb)}.
17496 If an input command was prefixed with a @code{@var{token}} then the
17497 corresponding output for that command will also be prefixed by that same
17501 @item @var{output} @expansion{}
17502 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
17504 @item @var{result-record} @expansion{}
17505 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
17507 @item @var{out-of-band-record} @expansion{}
17508 @code{@var{async-record} | @var{stream-record}}
17510 @item @var{async-record} @expansion{}
17511 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
17513 @item @var{exec-async-output} @expansion{}
17514 @code{[ @var{token} ] "*" @var{async-output}}
17516 @item @var{status-async-output} @expansion{}
17517 @code{[ @var{token} ] "+" @var{async-output}}
17519 @item @var{notify-async-output} @expansion{}
17520 @code{[ @var{token} ] "=" @var{async-output}}
17522 @item @var{async-output} @expansion{}
17523 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
17525 @item @var{result-class} @expansion{}
17526 @code{"done" | "running" | "connected" | "error" | "exit"}
17528 @item @var{async-class} @expansion{}
17529 @code{"stopped" | @var{others}} (where @var{others} will be added
17530 depending on the needs---this is still in development).
17532 @item @var{result} @expansion{}
17533 @code{ @var{variable} "=" @var{value}}
17535 @item @var{variable} @expansion{}
17536 @code{ @var{string} }
17538 @item @var{value} @expansion{}
17539 @code{ @var{const} | @var{tuple} | @var{list} }
17541 @item @var{const} @expansion{}
17542 @code{@var{c-string}}
17544 @item @var{tuple} @expansion{}
17545 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
17547 @item @var{list} @expansion{}
17548 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
17549 @var{result} ( "," @var{result} )* "]" }
17551 @item @var{stream-record} @expansion{}
17552 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
17554 @item @var{console-stream-output} @expansion{}
17555 @code{"~" @var{c-string}}
17557 @item @var{target-stream-output} @expansion{}
17558 @code{"@@" @var{c-string}}
17560 @item @var{log-stream-output} @expansion{}
17561 @code{"&" @var{c-string}}
17563 @item @var{nl} @expansion{}
17566 @item @var{token} @expansion{}
17567 @emph{any sequence of digits}.
17575 All output sequences end in a single line containing a period.
17578 The @code{@var{token}} is from the corresponding request. If an execution
17579 command is interrupted by the @samp{-exec-interrupt} command, the
17580 @var{token} associated with the @samp{*stopped} message is the one of the
17581 original execution command, not the one of the interrupt command.
17584 @cindex status output in @sc{gdb/mi}
17585 @var{status-async-output} contains on-going status information about the
17586 progress of a slow operation. It can be discarded. All status output is
17587 prefixed by @samp{+}.
17590 @cindex async output in @sc{gdb/mi}
17591 @var{exec-async-output} contains asynchronous state change on the target
17592 (stopped, started, disappeared). All async output is prefixed by
17596 @cindex notify output in @sc{gdb/mi}
17597 @var{notify-async-output} contains supplementary information that the
17598 client should handle (e.g., a new breakpoint information). All notify
17599 output is prefixed by @samp{=}.
17602 @cindex console output in @sc{gdb/mi}
17603 @var{console-stream-output} is output that should be displayed as is in the
17604 console. It is the textual response to a CLI command. All the console
17605 output is prefixed by @samp{~}.
17608 @cindex target output in @sc{gdb/mi}
17609 @var{target-stream-output} is the output produced by the target program.
17610 All the target output is prefixed by @samp{@@}.
17613 @cindex log output in @sc{gdb/mi}
17614 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
17615 instance messages that should be displayed as part of an error log. All
17616 the log output is prefixed by @samp{&}.
17619 @cindex list output in @sc{gdb/mi}
17620 New @sc{gdb/mi} commands should only output @var{lists} containing
17626 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
17627 details about the various output records.
17629 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17630 @node GDB/MI Compatibility with CLI
17631 @section @sc{gdb/mi} Compatibility with CLI
17633 @cindex compatibility, @sc{gdb/mi} and CLI
17634 @cindex @sc{gdb/mi}, compatibility with CLI
17636 For the developers convenience CLI commands can be entered directly,
17637 but there may be some unexpected behaviour. For example, commands
17638 that query the user will behave as if the user replied yes, breakpoint
17639 command lists are not executed and some CLI commands, such as
17640 @code{if}, @code{when} and @code{define}, prompt for further input with
17641 @samp{>}, which is not valid MI output.
17643 This feature may be removed at some stage in the future and it is
17644 recommended that front ends use the @code{-interpreter-exec} command
17645 (@pxref{-interpreter-exec}).
17647 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17648 @node GDB/MI Development and Front Ends
17649 @section @sc{gdb/mi} Development and Front Ends
17650 @cindex @sc{gdb/mi} development
17652 The application which takes the MI output and presents the state of the
17653 program being debugged to the user is called a @dfn{front end}.
17655 Although @sc{gdb/mi} is still incomplete, it is currently being used
17656 by a variety of front ends to @value{GDBN}. This makes it difficult
17657 to introduce new functionality without breaking existing usage. This
17658 section tries to minimize the problems by describing how the protocol
17661 Some changes in MI need not break a carefully designed front end, and
17662 for these the MI version will remain unchanged. The following is a
17663 list of changes that may occur within one level, so front ends should
17664 parse MI output in a way that can handle them:
17668 New MI commands may be added.
17671 New fields may be added to the output of any MI command.
17673 @c The format of field's content e.g type prefix, may change so parse it
17674 @c at your own risk. Yes, in general?
17676 @c The order of fields may change? Shouldn't really matter but it might
17677 @c resolve inconsistencies.
17680 If the changes are likely to break front ends, the MI version level
17681 will be increased by one. This will allow the front end to parse the
17682 output according to the MI version. Apart from mi0, new versions of
17683 @value{GDBN} will not support old versions of MI and it will be the
17684 responsibility of the front end to work with the new one.
17686 @c Starting with mi3, add a new command -mi-version that prints the MI
17689 The best way to avoid unexpected changes in MI that might break your front
17690 end is to make your project known to @value{GDBN} developers and
17691 follow development on @email{gdb@@sourceware.org} and
17692 @email{gdb-patches@@sourceware.org}. There is also the mailing list
17693 @email{dmi-discuss@@lists.freestandards.org}, hosted by the Free Standards
17694 Group, which has the aim of creating a a more general MI protocol
17695 called Debugger Machine Interface (DMI) that will become a standard
17696 for all debuggers, not just @value{GDBN}.
17697 @cindex mailing lists
17699 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17700 @node GDB/MI Output Records
17701 @section @sc{gdb/mi} Output Records
17704 * GDB/MI Result Records::
17705 * GDB/MI Stream Records::
17706 * GDB/MI Out-of-band Records::
17709 @node GDB/MI Result Records
17710 @subsection @sc{gdb/mi} Result Records
17712 @cindex result records in @sc{gdb/mi}
17713 @cindex @sc{gdb/mi}, result records
17714 In addition to a number of out-of-band notifications, the response to a
17715 @sc{gdb/mi} command includes one of the following result indications:
17719 @item "^done" [ "," @var{results} ]
17720 The synchronous operation was successful, @code{@var{results}} are the return
17725 @c Is this one correct? Should it be an out-of-band notification?
17726 The asynchronous operation was successfully started. The target is
17731 GDB has connected to a remote target.
17733 @item "^error" "," @var{c-string}
17735 The operation failed. The @code{@var{c-string}} contains the corresponding
17740 GDB has terminated.
17744 @node GDB/MI Stream Records
17745 @subsection @sc{gdb/mi} Stream Records
17747 @cindex @sc{gdb/mi}, stream records
17748 @cindex stream records in @sc{gdb/mi}
17749 @value{GDBN} internally maintains a number of output streams: the console, the
17750 target, and the log. The output intended for each of these streams is
17751 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
17753 Each stream record begins with a unique @dfn{prefix character} which
17754 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
17755 Syntax}). In addition to the prefix, each stream record contains a
17756 @code{@var{string-output}}. This is either raw text (with an implicit new
17757 line) or a quoted C string (which does not contain an implicit newline).
17760 @item "~" @var{string-output}
17761 The console output stream contains text that should be displayed in the
17762 CLI console window. It contains the textual responses to CLI commands.
17764 @item "@@" @var{string-output}
17765 The target output stream contains any textual output from the running
17766 target. This is only present when GDB's event loop is truly
17767 asynchronous, which is currently only the case for remote targets.
17769 @item "&" @var{string-output}
17770 The log stream contains debugging messages being produced by @value{GDBN}'s
17774 @node GDB/MI Out-of-band Records
17775 @subsection @sc{gdb/mi} Out-of-band Records
17777 @cindex out-of-band records in @sc{gdb/mi}
17778 @cindex @sc{gdb/mi}, out-of-band records
17779 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
17780 additional changes that have occurred. Those changes can either be a
17781 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
17782 target activity (e.g., target stopped).
17784 The following is a preliminary list of possible out-of-band records.
17785 In particular, the @var{exec-async-output} records.
17788 @item *stopped,reason="@var{reason}"
17791 @var{reason} can be one of the following:
17794 @item breakpoint-hit
17795 A breakpoint was reached.
17796 @item watchpoint-trigger
17797 A watchpoint was triggered.
17798 @item read-watchpoint-trigger
17799 A read watchpoint was triggered.
17800 @item access-watchpoint-trigger
17801 An access watchpoint was triggered.
17802 @item function-finished
17803 An -exec-finish or similar CLI command was accomplished.
17804 @item location-reached
17805 An -exec-until or similar CLI command was accomplished.
17806 @item watchpoint-scope
17807 A watchpoint has gone out of scope.
17808 @item end-stepping-range
17809 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
17810 similar CLI command was accomplished.
17811 @item exited-signalled
17812 The inferior exited because of a signal.
17814 The inferior exited.
17815 @item exited-normally
17816 The inferior exited normally.
17817 @item signal-received
17818 A signal was received by the inferior.
17822 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17823 @node GDB/MI Simple Examples
17824 @section Simple Examples of @sc{gdb/mi} Interaction
17825 @cindex @sc{gdb/mi}, simple examples
17827 This subsection presents several simple examples of interaction using
17828 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
17829 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
17830 the output received from @sc{gdb/mi}.
17832 Note the the line breaks shown in the examples are here only for
17833 readability, they don't appear in the real output.
17835 @subheading Setting a breakpoint
17837 Setting a breakpoint generates synchronous output which contains detailed
17838 information of the breakpoint.
17841 -> -break-insert main
17842 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
17843 enabled="y",addr="0x08048564",func="main",file="myprog.c",
17844 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
17848 @subheading Program Execution
17850 Program execution generates asynchronous records and MI gives the
17851 reason that execution stopped.
17857 <- *stopped,reason="breakpoint-hit",bkptno="1",thread-id="0",
17858 frame=@{addr="0x08048564",func="main",
17859 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
17860 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
17865 <- *stopped,reason="exited-normally"
17869 @subheading Quitting GDB
17871 Quitting GDB just prints the result class @samp{^exit}.
17879 @subheading A Bad Command
17881 Here's what happens if you pass a non-existent command:
17885 <- ^error,msg="Undefined MI command: rubbish"
17890 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17891 @node GDB/MI Command Description Format
17892 @section @sc{gdb/mi} Command Description Format
17894 The remaining sections describe blocks of commands. Each block of
17895 commands is laid out in a fashion similar to this section.
17897 @subheading Motivation
17899 The motivation for this collection of commands.
17901 @subheading Introduction
17903 A brief introduction to this collection of commands as a whole.
17905 @subheading Commands
17907 For each command in the block, the following is described:
17909 @subsubheading Synopsis
17912 -command @var{args}@dots{}
17915 @subsubheading Result
17917 @subsubheading @value{GDBN} Command
17919 The corresponding @value{GDBN} CLI command(s), if any.
17921 @subsubheading Example
17923 Example(s) formatted for readability. Some of the described commands have
17924 not been implemented yet and these are labeled N.A.@: (not available).
17927 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17928 @node GDB/MI Breakpoint Commands
17929 @section @sc{gdb/mi} Breakpoint Commands
17931 @cindex breakpoint commands for @sc{gdb/mi}
17932 @cindex @sc{gdb/mi}, breakpoint commands
17933 This section documents @sc{gdb/mi} commands for manipulating
17936 @subheading The @code{-break-after} Command
17937 @findex -break-after
17939 @subsubheading Synopsis
17942 -break-after @var{number} @var{count}
17945 The breakpoint number @var{number} is not in effect until it has been
17946 hit @var{count} times. To see how this is reflected in the output of
17947 the @samp{-break-list} command, see the description of the
17948 @samp{-break-list} command below.
17950 @subsubheading @value{GDBN} Command
17952 The corresponding @value{GDBN} command is @samp{ignore}.
17954 @subsubheading Example
17959 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",
17960 fullname="/home/foo/hello.c",line="5",times="0"@}
17967 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17968 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17969 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17970 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17971 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17972 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17973 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17974 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17975 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
17976 line="5",times="0",ignore="3"@}]@}
17981 @subheading The @code{-break-catch} Command
17982 @findex -break-catch
17984 @subheading The @code{-break-commands} Command
17985 @findex -break-commands
17989 @subheading The @code{-break-condition} Command
17990 @findex -break-condition
17992 @subsubheading Synopsis
17995 -break-condition @var{number} @var{expr}
17998 Breakpoint @var{number} will stop the program only if the condition in
17999 @var{expr} is true. The condition becomes part of the
18000 @samp{-break-list} output (see the description of the @samp{-break-list}
18003 @subsubheading @value{GDBN} Command
18005 The corresponding @value{GDBN} command is @samp{condition}.
18007 @subsubheading Example
18011 -break-condition 1 1
18015 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18016 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18017 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18018 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18019 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18020 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18021 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18022 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18023 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18024 line="5",cond="1",times="0",ignore="3"@}]@}
18028 @subheading The @code{-break-delete} Command
18029 @findex -break-delete
18031 @subsubheading Synopsis
18034 -break-delete ( @var{breakpoint} )+
18037 Delete the breakpoint(s) whose number(s) are specified in the argument
18038 list. This is obviously reflected in the breakpoint list.
18040 @subsubheading @value{GDBN} command
18042 The corresponding @value{GDBN} command is @samp{delete}.
18044 @subsubheading Example
18052 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
18053 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18054 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18055 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18056 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18057 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18058 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18063 @subheading The @code{-break-disable} Command
18064 @findex -break-disable
18066 @subsubheading Synopsis
18069 -break-disable ( @var{breakpoint} )+
18072 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
18073 break list is now set to @samp{n} for the named @var{breakpoint}(s).
18075 @subsubheading @value{GDBN} Command
18077 The corresponding @value{GDBN} command is @samp{disable}.
18079 @subsubheading Example
18087 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18088 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18089 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18090 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18091 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18092 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18093 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18094 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
18095 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18096 line="5",times="0"@}]@}
18100 @subheading The @code{-break-enable} Command
18101 @findex -break-enable
18103 @subsubheading Synopsis
18106 -break-enable ( @var{breakpoint} )+
18109 Enable (previously disabled) @var{breakpoint}(s).
18111 @subsubheading @value{GDBN} Command
18113 The corresponding @value{GDBN} command is @samp{enable}.
18115 @subsubheading Example
18123 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18124 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18125 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18126 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18127 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18128 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18129 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18130 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
18131 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18132 line="5",times="0"@}]@}
18136 @subheading The @code{-break-info} Command
18137 @findex -break-info
18139 @subsubheading Synopsis
18142 -break-info @var{breakpoint}
18146 Get information about a single breakpoint.
18148 @subsubheading @value{GDBN} command
18150 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
18152 @subsubheading Example
18155 @subheading The @code{-break-insert} Command
18156 @findex -break-insert
18158 @subsubheading Synopsis
18161 -break-insert [ -t ] [ -h ] [ -r ]
18162 [ -c @var{condition} ] [ -i @var{ignore-count} ]
18163 [ -p @var{thread} ] [ @var{line} | @var{addr} ]
18167 If specified, @var{line}, can be one of:
18174 @item filename:linenum
18175 @item filename:function
18179 The possible optional parameters of this command are:
18183 Insert a temporary breakpoint.
18185 Insert a hardware breakpoint.
18186 @item -c @var{condition}
18187 Make the breakpoint conditional on @var{condition}.
18188 @item -i @var{ignore-count}
18189 Initialize the @var{ignore-count}.
18191 Insert a regular breakpoint in all the functions whose names match the
18192 given regular expression. Other flags are not applicable to regular
18196 @subsubheading Result
18198 The result is in the form:
18201 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
18202 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
18203 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
18204 times="@var{times}"@}
18208 where @var{number} is the @value{GDBN} number for this breakpoint,
18209 @var{funcname} is the name of the function where the breakpoint was
18210 inserted, @var{filename} is the name of the source file which contains
18211 this function, @var{lineno} is the source line number within that file
18212 and @var{times} the number of times that the breakpoint has been hit
18213 (always 0 for -break-insert but may be greater for -break-info or -break-list
18214 which use the same output).
18216 Note: this format is open to change.
18217 @c An out-of-band breakpoint instead of part of the result?
18219 @subsubheading @value{GDBN} Command
18221 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
18222 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
18224 @subsubheading Example
18229 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
18230 fullname="/home/foo/recursive2.c,line="4",times="0"@}
18232 -break-insert -t foo
18233 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
18234 fullname="/home/foo/recursive2.c,line="11",times="0"@}
18237 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18238 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18239 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18240 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18241 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18242 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18243 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18244 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18245 addr="0x0001072c", func="main",file="recursive2.c",
18246 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
18247 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
18248 addr="0x00010774",func="foo",file="recursive2.c",
18249 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
18251 -break-insert -r foo.*
18252 ~int foo(int, int);
18253 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
18254 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
18258 @subheading The @code{-break-list} Command
18259 @findex -break-list
18261 @subsubheading Synopsis
18267 Displays the list of inserted breakpoints, showing the following fields:
18271 number of the breakpoint
18273 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
18275 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
18278 is the breakpoint enabled or no: @samp{y} or @samp{n}
18280 memory location at which the breakpoint is set
18282 logical location of the breakpoint, expressed by function name, file
18285 number of times the breakpoint has been hit
18288 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
18289 @code{body} field is an empty list.
18291 @subsubheading @value{GDBN} Command
18293 The corresponding @value{GDBN} command is @samp{info break}.
18295 @subsubheading Example
18300 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18301 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18302 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18303 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18304 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18305 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18306 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18307 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18308 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
18309 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
18310 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
18311 line="13",times="0"@}]@}
18315 Here's an example of the result when there are no breakpoints:
18320 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
18321 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18322 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18323 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18324 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18325 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18326 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18331 @subheading The @code{-break-watch} Command
18332 @findex -break-watch
18334 @subsubheading Synopsis
18337 -break-watch [ -a | -r ]
18340 Create a watchpoint. With the @samp{-a} option it will create an
18341 @dfn{access} watchpoint, i.e. a watchpoint that triggers either on a
18342 read from or on a write to the memory location. With the @samp{-r}
18343 option, the watchpoint created is a @dfn{read} watchpoint, i.e. it will
18344 trigger only when the memory location is accessed for reading. Without
18345 either of the options, the watchpoint created is a regular watchpoint,
18346 i.e. it will trigger when the memory location is accessed for writing.
18347 @xref{Set Watchpoints, , Setting watchpoints}.
18349 Note that @samp{-break-list} will report a single list of watchpoints and
18350 breakpoints inserted.
18352 @subsubheading @value{GDBN} Command
18354 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
18357 @subsubheading Example
18359 Setting a watchpoint on a variable in the @code{main} function:
18364 ^done,wpt=@{number="2",exp="x"@}
18368 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
18369 value=@{old="-268439212",new="55"@},
18370 frame=@{func="main",args=[],file="recursive2.c",
18371 fullname="/home/foo/bar/recursive2.c",line="5"@}
18375 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
18376 the program execution twice: first for the variable changing value, then
18377 for the watchpoint going out of scope.
18382 ^done,wpt=@{number="5",exp="C"@}
18386 ^done,reason="watchpoint-trigger",
18387 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
18388 frame=@{func="callee4",args=[],
18389 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18390 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
18394 ^done,reason="watchpoint-scope",wpnum="5",
18395 frame=@{func="callee3",args=[@{name="strarg",
18396 value="0x11940 \"A string argument.\""@}],
18397 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18398 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18402 Listing breakpoints and watchpoints, at different points in the program
18403 execution. Note that once the watchpoint goes out of scope, it is
18409 ^done,wpt=@{number="2",exp="C"@}
18412 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18413 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18414 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18415 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18416 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18417 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18418 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18419 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18420 addr="0x00010734",func="callee4",
18421 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18422 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
18423 bkpt=@{number="2",type="watchpoint",disp="keep",
18424 enabled="y",addr="",what="C",times="0"@}]@}
18428 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
18429 value=@{old="-276895068",new="3"@},
18430 frame=@{func="callee4",args=[],
18431 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18432 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
18435 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18436 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18437 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18438 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18439 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18440 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18441 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18442 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18443 addr="0x00010734",func="callee4",
18444 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18445 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
18446 bkpt=@{number="2",type="watchpoint",disp="keep",
18447 enabled="y",addr="",what="C",times="-5"@}]@}
18451 ^done,reason="watchpoint-scope",wpnum="2",
18452 frame=@{func="callee3",args=[@{name="strarg",
18453 value="0x11940 \"A string argument.\""@}],
18454 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18455 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18458 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18459 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18460 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18461 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18462 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18463 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18464 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18465 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18466 addr="0x00010734",func="callee4",
18467 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18468 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
18473 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18474 @node GDB/MI Program Context
18475 @section @sc{gdb/mi} Program Context
18477 @subheading The @code{-exec-arguments} Command
18478 @findex -exec-arguments
18481 @subsubheading Synopsis
18484 -exec-arguments @var{args}
18487 Set the inferior program arguments, to be used in the next
18490 @subsubheading @value{GDBN} Command
18492 The corresponding @value{GDBN} command is @samp{set args}.
18494 @subsubheading Example
18497 Don't have one around.
18500 @subheading The @code{-exec-show-arguments} Command
18501 @findex -exec-show-arguments
18503 @subsubheading Synopsis
18506 -exec-show-arguments
18509 Print the arguments of the program.
18511 @subsubheading @value{GDBN} Command
18513 The corresponding @value{GDBN} command is @samp{show args}.
18515 @subsubheading Example
18519 @subheading The @code{-environment-cd} Command
18520 @findex -environment-cd
18522 @subsubheading Synopsis
18525 -environment-cd @var{pathdir}
18528 Set @value{GDBN}'s working directory.
18530 @subsubheading @value{GDBN} Command
18532 The corresponding @value{GDBN} command is @samp{cd}.
18534 @subsubheading Example
18538 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18544 @subheading The @code{-environment-directory} Command
18545 @findex -environment-directory
18547 @subsubheading Synopsis
18550 -environment-directory [ -r ] [ @var{pathdir} ]+
18553 Add directories @var{pathdir} to beginning of search path for source files.
18554 If the @samp{-r} option is used, the search path is reset to the default
18555 search path. If directories @var{pathdir} are supplied in addition to the
18556 @samp{-r} option, the search path is first reset and then addition
18558 Multiple directories may be specified, separated by blanks. Specifying
18559 multiple directories in a single command
18560 results in the directories added to the beginning of the
18561 search path in the same order they were presented in the command.
18562 If blanks are needed as
18563 part of a directory name, double-quotes should be used around
18564 the name. In the command output, the path will show up separated
18565 by the system directory-separator character. The directory-seperator
18566 character must not be used
18567 in any directory name.
18568 If no directories are specified, the current search path is displayed.
18570 @subsubheading @value{GDBN} Command
18572 The corresponding @value{GDBN} command is @samp{dir}.
18574 @subsubheading Example
18578 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18579 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18581 -environment-directory ""
18582 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18584 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
18585 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
18587 -environment-directory -r
18588 ^done,source-path="$cdir:$cwd"
18593 @subheading The @code{-environment-path} Command
18594 @findex -environment-path
18596 @subsubheading Synopsis
18599 -environment-path [ -r ] [ @var{pathdir} ]+
18602 Add directories @var{pathdir} to beginning of search path for object files.
18603 If the @samp{-r} option is used, the search path is reset to the original
18604 search path that existed at gdb start-up. If directories @var{pathdir} are
18605 supplied in addition to the
18606 @samp{-r} option, the search path is first reset and then addition
18608 Multiple directories may be specified, separated by blanks. Specifying
18609 multiple directories in a single command
18610 results in the directories added to the beginning of the
18611 search path in the same order they were presented in the command.
18612 If blanks are needed as
18613 part of a directory name, double-quotes should be used around
18614 the name. In the command output, the path will show up separated
18615 by the system directory-separator character. The directory-seperator
18616 character must not be used
18617 in any directory name.
18618 If no directories are specified, the current path is displayed.
18621 @subsubheading @value{GDBN} Command
18623 The corresponding @value{GDBN} command is @samp{path}.
18625 @subsubheading Example
18630 ^done,path="/usr/bin"
18632 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
18633 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
18635 -environment-path -r /usr/local/bin
18636 ^done,path="/usr/local/bin:/usr/bin"
18641 @subheading The @code{-environment-pwd} Command
18642 @findex -environment-pwd
18644 @subsubheading Synopsis
18650 Show the current working directory.
18652 @subsubheading @value{GDBN} command
18654 The corresponding @value{GDBN} command is @samp{pwd}.
18656 @subsubheading Example
18661 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
18665 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18666 @node GDB/MI Thread Commands
18667 @section @sc{gdb/mi} Thread Commands
18670 @subheading The @code{-thread-info} Command
18671 @findex -thread-info
18673 @subsubheading Synopsis
18679 @subsubheading @value{GDBN} command
18683 @subsubheading Example
18687 @subheading The @code{-thread-list-all-threads} Command
18688 @findex -thread-list-all-threads
18690 @subsubheading Synopsis
18693 -thread-list-all-threads
18696 @subsubheading @value{GDBN} Command
18698 The equivalent @value{GDBN} command is @samp{info threads}.
18700 @subsubheading Example
18704 @subheading The @code{-thread-list-ids} Command
18705 @findex -thread-list-ids
18707 @subsubheading Synopsis
18713 Produces a list of the currently known @value{GDBN} thread ids. At the
18714 end of the list it also prints the total number of such threads.
18716 @subsubheading @value{GDBN} Command
18718 Part of @samp{info threads} supplies the same information.
18720 @subsubheading Example
18722 No threads present, besides the main process:
18727 ^done,thread-ids=@{@},number-of-threads="0"
18737 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
18738 number-of-threads="3"
18743 @subheading The @code{-thread-select} Command
18744 @findex -thread-select
18746 @subsubheading Synopsis
18749 -thread-select @var{threadnum}
18752 Make @var{threadnum} the current thread. It prints the number of the new
18753 current thread, and the topmost frame for that thread.
18755 @subsubheading @value{GDBN} Command
18757 The corresponding @value{GDBN} command is @samp{thread}.
18759 @subsubheading Example
18766 *stopped,reason="end-stepping-range",thread-id="2",line="187",
18767 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
18771 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
18772 number-of-threads="3"
18775 ^done,new-thread-id="3",
18776 frame=@{level="0",func="vprintf",
18777 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
18778 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
18782 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18783 @node GDB/MI Program Execution
18784 @section @sc{gdb/mi} Program Execution
18786 These are the asynchronous commands which generate the out-of-band
18787 record @samp{*stopped}. Currently GDB only really executes
18788 asynchronously with remote targets and this interaction is mimicked in
18791 @subheading The @code{-exec-continue} Command
18792 @findex -exec-continue
18794 @subsubheading Synopsis
18800 Resumes the execution of the inferior program until a breakpoint is
18801 encountered, or until the inferior exits.
18803 @subsubheading @value{GDBN} Command
18805 The corresponding @value{GDBN} corresponding is @samp{continue}.
18807 @subsubheading Example
18814 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
18815 file="hello.c",fullname="/home/foo/bar/hello.c",line="13"@}
18820 @subheading The @code{-exec-finish} Command
18821 @findex -exec-finish
18823 @subsubheading Synopsis
18829 Resumes the execution of the inferior program until the current
18830 function is exited. Displays the results returned by the function.
18832 @subsubheading @value{GDBN} Command
18834 The corresponding @value{GDBN} command is @samp{finish}.
18836 @subsubheading Example
18838 Function returning @code{void}.
18845 *stopped,reason="function-finished",frame=@{func="main",args=[],
18846 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
18850 Function returning other than @code{void}. The name of the internal
18851 @value{GDBN} variable storing the result is printed, together with the
18858 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
18859 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
18860 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
18861 gdb-result-var="$1",return-value="0"
18866 @subheading The @code{-exec-interrupt} Command
18867 @findex -exec-interrupt
18869 @subsubheading Synopsis
18875 Interrupts the background execution of the target. Note how the token
18876 associated with the stop message is the one for the execution command
18877 that has been interrupted. The token for the interrupt itself only
18878 appears in the @samp{^done} output. If the user is trying to
18879 interrupt a non-running program, an error message will be printed.
18881 @subsubheading @value{GDBN} Command
18883 The corresponding @value{GDBN} command is @samp{interrupt}.
18885 @subsubheading Example
18896 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
18897 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
18898 fullname="/home/foo/bar/try.c",line="13"@}
18903 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
18908 @subheading The @code{-exec-next} Command
18911 @subsubheading Synopsis
18917 Resumes execution of the inferior program, stopping when the beginning
18918 of the next source line is reached.
18920 @subsubheading @value{GDBN} Command
18922 The corresponding @value{GDBN} command is @samp{next}.
18924 @subsubheading Example
18930 *stopped,reason="end-stepping-range",line="8",file="hello.c"
18935 @subheading The @code{-exec-next-instruction} Command
18936 @findex -exec-next-instruction
18938 @subsubheading Synopsis
18941 -exec-next-instruction
18944 Executes one machine instruction. If the instruction is a function
18945 call, continues until the function returns. If the program stops at an
18946 instruction in the middle of a source line, the address will be
18949 @subsubheading @value{GDBN} Command
18951 The corresponding @value{GDBN} command is @samp{nexti}.
18953 @subsubheading Example
18957 -exec-next-instruction
18961 *stopped,reason="end-stepping-range",
18962 addr="0x000100d4",line="5",file="hello.c"
18967 @subheading The @code{-exec-return} Command
18968 @findex -exec-return
18970 @subsubheading Synopsis
18976 Makes current function return immediately. Doesn't execute the inferior.
18977 Displays the new current frame.
18979 @subsubheading @value{GDBN} Command
18981 The corresponding @value{GDBN} command is @samp{return}.
18983 @subsubheading Example
18987 200-break-insert callee4
18988 200^done,bkpt=@{number="1",addr="0x00010734",
18989 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
18994 000*stopped,reason="breakpoint-hit",bkptno="1",
18995 frame=@{func="callee4",args=[],
18996 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18997 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
19003 111^done,frame=@{level="0",func="callee3",
19004 args=[@{name="strarg",
19005 value="0x11940 \"A string argument.\""@}],
19006 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19007 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
19012 @subheading The @code{-exec-run} Command
19015 @subsubheading Synopsis
19021 Starts execution of the inferior from the beginning. The inferior
19022 executes until either a breakpoint is encountered or the program
19023 exits. In the latter case the output will include an exit code, if
19024 the program has exited exceptionally.
19026 @subsubheading @value{GDBN} Command
19028 The corresponding @value{GDBN} command is @samp{run}.
19030 @subsubheading Examples
19035 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
19040 *stopped,reason="breakpoint-hit",bkptno="1",
19041 frame=@{func="main",args=[],file="recursive2.c",
19042 fullname="/home/foo/bar/recursive2.c",line="4"@}
19047 Program exited normally:
19055 *stopped,reason="exited-normally"
19060 Program exited exceptionally:
19068 *stopped,reason="exited",exit-code="01"
19072 Another way the program can terminate is if it receives a signal such as
19073 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
19077 *stopped,reason="exited-signalled",signal-name="SIGINT",
19078 signal-meaning="Interrupt"
19082 @c @subheading -exec-signal
19085 @subheading The @code{-exec-step} Command
19088 @subsubheading Synopsis
19094 Resumes execution of the inferior program, stopping when the beginning
19095 of the next source line is reached, if the next source line is not a
19096 function call. If it is, stop at the first instruction of the called
19099 @subsubheading @value{GDBN} Command
19101 The corresponding @value{GDBN} command is @samp{step}.
19103 @subsubheading Example
19105 Stepping into a function:
19111 *stopped,reason="end-stepping-range",
19112 frame=@{func="foo",args=[@{name="a",value="10"@},
19113 @{name="b",value="0"@}],file="recursive2.c",
19114 fullname="/home/foo/bar/recursive2.c",line="11"@}
19124 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
19129 @subheading The @code{-exec-step-instruction} Command
19130 @findex -exec-step-instruction
19132 @subsubheading Synopsis
19135 -exec-step-instruction
19138 Resumes the inferior which executes one machine instruction. The
19139 output, once @value{GDBN} has stopped, will vary depending on whether
19140 we have stopped in the middle of a source line or not. In the former
19141 case, the address at which the program stopped will be printed as
19144 @subsubheading @value{GDBN} Command
19146 The corresponding @value{GDBN} command is @samp{stepi}.
19148 @subsubheading Example
19152 -exec-step-instruction
19156 *stopped,reason="end-stepping-range",
19157 frame=@{func="foo",args=[],file="try.c",
19158 fullname="/home/foo/bar/try.c",line="10"@}
19160 -exec-step-instruction
19164 *stopped,reason="end-stepping-range",
19165 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
19166 fullname="/home/foo/bar/try.c",line="10"@}
19171 @subheading The @code{-exec-until} Command
19172 @findex -exec-until
19174 @subsubheading Synopsis
19177 -exec-until [ @var{location} ]
19180 Executes the inferior until the @var{location} specified in the
19181 argument is reached. If there is no argument, the inferior executes
19182 until a source line greater than the current one is reached. The
19183 reason for stopping in this case will be @samp{location-reached}.
19185 @subsubheading @value{GDBN} Command
19187 The corresponding @value{GDBN} command is @samp{until}.
19189 @subsubheading Example
19193 -exec-until recursive2.c:6
19197 *stopped,reason="location-reached",frame=@{func="main",args=[],
19198 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
19203 @subheading -file-clear
19204 Is this going away????
19207 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19208 @node GDB/MI Stack Manipulation
19209 @section @sc{gdb/mi} Stack Manipulation Commands
19212 @subheading The @code{-stack-info-frame} Command
19213 @findex -stack-info-frame
19215 @subsubheading Synopsis
19221 Get info on the selected frame.
19223 @subsubheading @value{GDBN} Command
19225 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
19226 (without arguments).
19228 @subsubheading Example
19233 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
19234 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19235 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
19239 @subheading The @code{-stack-info-depth} Command
19240 @findex -stack-info-depth
19242 @subsubheading Synopsis
19245 -stack-info-depth [ @var{max-depth} ]
19248 Return the depth of the stack. If the integer argument @var{max-depth}
19249 is specified, do not count beyond @var{max-depth} frames.
19251 @subsubheading @value{GDBN} Command
19253 There's no equivalent @value{GDBN} command.
19255 @subsubheading Example
19257 For a stack with frame levels 0 through 11:
19264 -stack-info-depth 4
19267 -stack-info-depth 12
19270 -stack-info-depth 11
19273 -stack-info-depth 13
19278 @subheading The @code{-stack-list-arguments} Command
19279 @findex -stack-list-arguments
19281 @subsubheading Synopsis
19284 -stack-list-arguments @var{show-values}
19285 [ @var{low-frame} @var{high-frame} ]
19288 Display a list of the arguments for the frames between @var{low-frame}
19289 and @var{high-frame} (inclusive). If @var{low-frame} and
19290 @var{high-frame} are not provided, list the arguments for the whole
19291 call stack. If the two arguments are equal, show the single frame
19292 at the corresponding level. It is an error if @var{low-frame} is
19293 larger than the actual number of frames. On the other hand,
19294 @var{high-frame} may be larger than the actual number of frames, in
19295 which case only existing frames will be returned.
19297 The @var{show-values} argument must have a value of 0 or 1. A value of
19298 0 means that only the names of the arguments are listed, a value of 1
19299 means that both names and values of the arguments are printed.
19301 @subsubheading @value{GDBN} Command
19303 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
19304 @samp{gdb_get_args} command which partially overlaps with the
19305 functionality of @samp{-stack-list-arguments}.
19307 @subsubheading Example
19314 frame=@{level="0",addr="0x00010734",func="callee4",
19315 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19316 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
19317 frame=@{level="1",addr="0x0001076c",func="callee3",
19318 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19319 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
19320 frame=@{level="2",addr="0x0001078c",func="callee2",
19321 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19322 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
19323 frame=@{level="3",addr="0x000107b4",func="callee1",
19324 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19325 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
19326 frame=@{level="4",addr="0x000107e0",func="main",
19327 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19328 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
19330 -stack-list-arguments 0
19333 frame=@{level="0",args=[]@},
19334 frame=@{level="1",args=[name="strarg"]@},
19335 frame=@{level="2",args=[name="intarg",name="strarg"]@},
19336 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
19337 frame=@{level="4",args=[]@}]
19339 -stack-list-arguments 1
19342 frame=@{level="0",args=[]@},
19344 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19345 frame=@{level="2",args=[
19346 @{name="intarg",value="2"@},
19347 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19348 @{frame=@{level="3",args=[
19349 @{name="intarg",value="2"@},
19350 @{name="strarg",value="0x11940 \"A string argument.\""@},
19351 @{name="fltarg",value="3.5"@}]@},
19352 frame=@{level="4",args=[]@}]
19354 -stack-list-arguments 0 2 2
19355 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
19357 -stack-list-arguments 1 2 2
19358 ^done,stack-args=[frame=@{level="2",
19359 args=[@{name="intarg",value="2"@},
19360 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
19364 @c @subheading -stack-list-exception-handlers
19367 @subheading The @code{-stack-list-frames} Command
19368 @findex -stack-list-frames
19370 @subsubheading Synopsis
19373 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
19376 List the frames currently on the stack. For each frame it displays the
19381 The frame number, 0 being the topmost frame, i.e. the innermost function.
19383 The @code{$pc} value for that frame.
19387 File name of the source file where the function lives.
19389 Line number corresponding to the @code{$pc}.
19392 If invoked without arguments, this command prints a backtrace for the
19393 whole stack. If given two integer arguments, it shows the frames whose
19394 levels are between the two arguments (inclusive). If the two arguments
19395 are equal, it shows the single frame at the corresponding level. It is
19396 an error if @var{low-frame} is larger than the actual number of
19397 frames. On the other hand, @var{high-frame} may be larger than the
19398 actual number of frames, in which case only existing frames will be returned.
19400 @subsubheading @value{GDBN} Command
19402 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
19404 @subsubheading Example
19406 Full stack backtrace:
19412 [frame=@{level="0",addr="0x0001076c",func="foo",
19413 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
19414 frame=@{level="1",addr="0x000107a4",func="foo",
19415 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19416 frame=@{level="2",addr="0x000107a4",func="foo",
19417 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19418 frame=@{level="3",addr="0x000107a4",func="foo",
19419 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19420 frame=@{level="4",addr="0x000107a4",func="foo",
19421 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19422 frame=@{level="5",addr="0x000107a4",func="foo",
19423 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19424 frame=@{level="6",addr="0x000107a4",func="foo",
19425 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19426 frame=@{level="7",addr="0x000107a4",func="foo",
19427 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19428 frame=@{level="8",addr="0x000107a4",func="foo",
19429 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19430 frame=@{level="9",addr="0x000107a4",func="foo",
19431 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19432 frame=@{level="10",addr="0x000107a4",func="foo",
19433 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19434 frame=@{level="11",addr="0x00010738",func="main",
19435 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
19439 Show frames between @var{low_frame} and @var{high_frame}:
19443 -stack-list-frames 3 5
19445 [frame=@{level="3",addr="0x000107a4",func="foo",
19446 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19447 frame=@{level="4",addr="0x000107a4",func="foo",
19448 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19449 frame=@{level="5",addr="0x000107a4",func="foo",
19450 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
19454 Show a single frame:
19458 -stack-list-frames 3 3
19460 [frame=@{level="3",addr="0x000107a4",func="foo",
19461 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
19466 @subheading The @code{-stack-list-locals} Command
19467 @findex -stack-list-locals
19469 @subsubheading Synopsis
19472 -stack-list-locals @var{print-values}
19475 Display the local variable names for the selected frame. If
19476 @var{print-values} is 0 or @code{--no-values}, print only the names of
19477 the variables; if it is 1 or @code{--all-values}, print also their
19478 values; and if it is 2 or @code{--simple-values}, print the name,
19479 type and value for simple data types and the name and type for arrays,
19480 structures and unions. In this last case, a frontend can immediately
19481 display the value of simple data types and create variable objects for
19482 other data types when the the user wishes to explore their values in
19485 @subsubheading @value{GDBN} Command
19487 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
19489 @subsubheading Example
19493 -stack-list-locals 0
19494 ^done,locals=[name="A",name="B",name="C"]
19496 -stack-list-locals --all-values
19497 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
19498 @{name="C",value="@{1, 2, 3@}"@}]
19499 -stack-list-locals --simple-values
19500 ^done,locals=[@{name="A",type="int",value="1"@},
19501 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
19506 @subheading The @code{-stack-select-frame} Command
19507 @findex -stack-select-frame
19509 @subsubheading Synopsis
19512 -stack-select-frame @var{framenum}
19515 Change the selected frame. Select a different frame @var{framenum} on
19518 @subsubheading @value{GDBN} Command
19520 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
19521 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
19523 @subsubheading Example
19527 -stack-select-frame 2
19532 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19533 @node GDB/MI Variable Objects
19534 @section @sc{gdb/mi} Variable Objects
19537 @subheading Motivation for Variable Objects in @sc{gdb/mi}
19539 For the implementation of a variable debugger window (locals, watched
19540 expressions, etc.), we are proposing the adaptation of the existing code
19541 used by @code{Insight}.
19543 The two main reasons for that are:
19547 It has been proven in practice (it is already on its second generation).
19550 It will shorten development time (needless to say how important it is
19554 The original interface was designed to be used by Tcl code, so it was
19555 slightly changed so it could be used through @sc{gdb/mi}. This section
19556 describes the @sc{gdb/mi} operations that will be available and gives some
19557 hints about their use.
19559 @emph{Note}: In addition to the set of operations described here, we
19560 expect the @sc{gui} implementation of a variable window to require, at
19561 least, the following operations:
19564 @item @code{-gdb-show} @code{output-radix}
19565 @item @code{-stack-list-arguments}
19566 @item @code{-stack-list-locals}
19567 @item @code{-stack-select-frame}
19570 @subheading Introduction to Variable Objects in @sc{gdb/mi}
19572 @cindex variable objects in @sc{gdb/mi}
19573 The basic idea behind variable objects is the creation of a named object
19574 to represent a variable, an expression, a memory location or even a CPU
19575 register. For each object created, a set of operations is available for
19576 examining or changing its properties.
19578 Furthermore, complex data types, such as C structures, are represented
19579 in a tree format. For instance, the @code{struct} type variable is the
19580 root and the children will represent the struct members. If a child
19581 is itself of a complex type, it will also have children of its own.
19582 Appropriate language differences are handled for C, C@t{++} and Java.
19584 When returning the actual values of the objects, this facility allows
19585 for the individual selection of the display format used in the result
19586 creation. It can be chosen among: binary, decimal, hexadecimal, octal
19587 and natural. Natural refers to a default format automatically
19588 chosen based on the variable type (like decimal for an @code{int}, hex
19589 for pointers, etc.).
19591 The following is the complete set of @sc{gdb/mi} operations defined to
19592 access this functionality:
19594 @multitable @columnfractions .4 .6
19595 @item @strong{Operation}
19596 @tab @strong{Description}
19598 @item @code{-var-create}
19599 @tab create a variable object
19600 @item @code{-var-delete}
19601 @tab delete the variable object and its children
19602 @item @code{-var-set-format}
19603 @tab set the display format of this variable
19604 @item @code{-var-show-format}
19605 @tab show the display format of this variable
19606 @item @code{-var-info-num-children}
19607 @tab tells how many children this object has
19608 @item @code{-var-list-children}
19609 @tab return a list of the object's children
19610 @item @code{-var-info-type}
19611 @tab show the type of this variable object
19612 @item @code{-var-info-expression}
19613 @tab print what this variable object represents
19614 @item @code{-var-show-attributes}
19615 @tab is this variable editable? does it exist here?
19616 @item @code{-var-evaluate-expression}
19617 @tab get the value of this variable
19618 @item @code{-var-assign}
19619 @tab set the value of this variable
19620 @item @code{-var-update}
19621 @tab update the variable and its children
19624 In the next subsection we describe each operation in detail and suggest
19625 how it can be used.
19627 @subheading Description And Use of Operations on Variable Objects
19629 @subheading The @code{-var-create} Command
19630 @findex -var-create
19632 @subsubheading Synopsis
19635 -var-create @{@var{name} | "-"@}
19636 @{@var{frame-addr} | "*"@} @var{expression}
19639 This operation creates a variable object, which allows the monitoring of
19640 a variable, the result of an expression, a memory cell or a CPU
19643 The @var{name} parameter is the string by which the object can be
19644 referenced. It must be unique. If @samp{-} is specified, the varobj
19645 system will generate a string ``varNNNNNN'' automatically. It will be
19646 unique provided that one does not specify @var{name} on that format.
19647 The command fails if a duplicate name is found.
19649 The frame under which the expression should be evaluated can be
19650 specified by @var{frame-addr}. A @samp{*} indicates that the current
19651 frame should be used.
19653 @var{expression} is any expression valid on the current language set (must not
19654 begin with a @samp{*}), or one of the following:
19658 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
19661 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
19664 @samp{$@var{regname}} --- a CPU register name
19667 @subsubheading Result
19669 This operation returns the name, number of children and the type of the
19670 object created. Type is returned as a string as the ones generated by
19671 the @value{GDBN} CLI:
19674 name="@var{name}",numchild="N",type="@var{type}"
19678 @subheading The @code{-var-delete} Command
19679 @findex -var-delete
19681 @subsubheading Synopsis
19684 -var-delete @var{name}
19687 Deletes a previously created variable object and all of its children.
19689 Returns an error if the object @var{name} is not found.
19692 @subheading The @code{-var-set-format} Command
19693 @findex -var-set-format
19695 @subsubheading Synopsis
19698 -var-set-format @var{name} @var{format-spec}
19701 Sets the output format for the value of the object @var{name} to be
19704 The syntax for the @var{format-spec} is as follows:
19707 @var{format-spec} @expansion{}
19708 @{binary | decimal | hexadecimal | octal | natural@}
19712 @subheading The @code{-var-show-format} Command
19713 @findex -var-show-format
19715 @subsubheading Synopsis
19718 -var-show-format @var{name}
19721 Returns the format used to display the value of the object @var{name}.
19724 @var{format} @expansion{}
19729 @subheading The @code{-var-info-num-children} Command
19730 @findex -var-info-num-children
19732 @subsubheading Synopsis
19735 -var-info-num-children @var{name}
19738 Returns the number of children of a variable object @var{name}:
19745 @subheading The @code{-var-list-children} Command
19746 @findex -var-list-children
19748 @subsubheading Synopsis
19751 -var-list-children [@var{print-values}] @var{name}
19753 @anchor{-var-list-children}
19755 Return a list of the children of the specified variable object and
19756 create variable objects for them, if they do not already exist. With
19757 a single argument or if @var{print-values} has a value for of 0 or
19758 @code{--no-values}, print only the names of the variables; if
19759 @var{print-values} is 1 or @code{--all-values}, also print their
19760 values; and if it is 2 or @code{--simple-values} print the name and
19761 value for simple data types and just the name for arrays, structures
19764 @subsubheading Example
19768 -var-list-children n
19769 ^done,numchild=@var{n},children=[@{name=@var{name},
19770 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
19772 -var-list-children --all-values n
19773 ^done,numchild=@var{n},children=[@{name=@var{name},
19774 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
19778 @subheading The @code{-var-info-type} Command
19779 @findex -var-info-type
19781 @subsubheading Synopsis
19784 -var-info-type @var{name}
19787 Returns the type of the specified variable @var{name}. The type is
19788 returned as a string in the same format as it is output by the
19792 type=@var{typename}
19796 @subheading The @code{-var-info-expression} Command
19797 @findex -var-info-expression
19799 @subsubheading Synopsis
19802 -var-info-expression @var{name}
19805 Returns what is represented by the variable object @var{name}:
19808 lang=@var{lang-spec},exp=@var{expression}
19812 where @var{lang-spec} is @code{@{"C" | "C++" | "Java"@}}.
19814 @subheading The @code{-var-show-attributes} Command
19815 @findex -var-show-attributes
19817 @subsubheading Synopsis
19820 -var-show-attributes @var{name}
19823 List attributes of the specified variable object @var{name}:
19826 status=@var{attr} [ ( ,@var{attr} )* ]
19830 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
19832 @subheading The @code{-var-evaluate-expression} Command
19833 @findex -var-evaluate-expression
19835 @subsubheading Synopsis
19838 -var-evaluate-expression @var{name}
19841 Evaluates the expression that is represented by the specified variable
19842 object and returns its value as a string in the current format specified
19849 Note that one must invoke @code{-var-list-children} for a variable
19850 before the value of a child variable can be evaluated.
19852 @subheading The @code{-var-assign} Command
19853 @findex -var-assign
19855 @subsubheading Synopsis
19858 -var-assign @var{name} @var{expression}
19861 Assigns the value of @var{expression} to the variable object specified
19862 by @var{name}. The object must be @samp{editable}. If the variable's
19863 value is altered by the assign, the variable will show up in any
19864 subsequent @code{-var-update} list.
19866 @subsubheading Example
19874 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
19878 @subheading The @code{-var-update} Command
19879 @findex -var-update
19881 @subsubheading Synopsis
19884 -var-update [@var{print-values}] @{@var{name} | "*"@}
19887 Update the value of the variable object @var{name} by evaluating its
19888 expression after fetching all the new values from memory or registers.
19889 A @samp{*} causes all existing variable objects to be updated. The
19890 option @var{print-values} determines whether names both and values, or
19891 just names are printed in the manner described for
19892 @code{-var-list-children} (@pxref{-var-list-children}).
19894 @subsubheading Example
19901 -var-update --all-values var1
19902 ^done,changelist=[@{name="var1",value="3",in_scope="true",
19903 type_changed="false"@}]
19907 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19908 @node GDB/MI Data Manipulation
19909 @section @sc{gdb/mi} Data Manipulation
19911 @cindex data manipulation, in @sc{gdb/mi}
19912 @cindex @sc{gdb/mi}, data manipulation
19913 This section describes the @sc{gdb/mi} commands that manipulate data:
19914 examine memory and registers, evaluate expressions, etc.
19916 @c REMOVED FROM THE INTERFACE.
19917 @c @subheading -data-assign
19918 @c Change the value of a program variable. Plenty of side effects.
19919 @c @subsubheading GDB command
19921 @c @subsubheading Example
19924 @subheading The @code{-data-disassemble} Command
19925 @findex -data-disassemble
19927 @subsubheading Synopsis
19931 [ -s @var{start-addr} -e @var{end-addr} ]
19932 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
19940 @item @var{start-addr}
19941 is the beginning address (or @code{$pc})
19942 @item @var{end-addr}
19944 @item @var{filename}
19945 is the name of the file to disassemble
19946 @item @var{linenum}
19947 is the line number to disassemble around
19949 is the the number of disassembly lines to be produced. If it is -1,
19950 the whole function will be disassembled, in case no @var{end-addr} is
19951 specified. If @var{end-addr} is specified as a non-zero value, and
19952 @var{lines} is lower than the number of disassembly lines between
19953 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
19954 displayed; if @var{lines} is higher than the number of lines between
19955 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
19958 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
19962 @subsubheading Result
19964 The output for each instruction is composed of four fields:
19973 Note that whatever included in the instruction field, is not manipulated
19974 directely by @sc{gdb/mi}, i.e. it is not possible to adjust its format.
19976 @subsubheading @value{GDBN} Command
19978 There's no direct mapping from this command to the CLI.
19980 @subsubheading Example
19982 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
19986 -data-disassemble -s $pc -e "$pc + 20" -- 0
19989 @{address="0x000107c0",func-name="main",offset="4",
19990 inst="mov 2, %o0"@},
19991 @{address="0x000107c4",func-name="main",offset="8",
19992 inst="sethi %hi(0x11800), %o2"@},
19993 @{address="0x000107c8",func-name="main",offset="12",
19994 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
19995 @{address="0x000107cc",func-name="main",offset="16",
19996 inst="sethi %hi(0x11800), %o2"@},
19997 @{address="0x000107d0",func-name="main",offset="20",
19998 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
20002 Disassemble the whole @code{main} function. Line 32 is part of
20006 -data-disassemble -f basics.c -l 32 -- 0
20008 @{address="0x000107bc",func-name="main",offset="0",
20009 inst="save %sp, -112, %sp"@},
20010 @{address="0x000107c0",func-name="main",offset="4",
20011 inst="mov 2, %o0"@},
20012 @{address="0x000107c4",func-name="main",offset="8",
20013 inst="sethi %hi(0x11800), %o2"@},
20015 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
20016 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
20020 Disassemble 3 instructions from the start of @code{main}:
20024 -data-disassemble -f basics.c -l 32 -n 3 -- 0
20026 @{address="0x000107bc",func-name="main",offset="0",
20027 inst="save %sp, -112, %sp"@},
20028 @{address="0x000107c0",func-name="main",offset="4",
20029 inst="mov 2, %o0"@},
20030 @{address="0x000107c4",func-name="main",offset="8",
20031 inst="sethi %hi(0x11800), %o2"@}]
20035 Disassemble 3 instructions from the start of @code{main} in mixed mode:
20039 -data-disassemble -f basics.c -l 32 -n 3 -- 1
20041 src_and_asm_line=@{line="31",
20042 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
20043 testsuite/gdb.mi/basics.c",line_asm_insn=[
20044 @{address="0x000107bc",func-name="main",offset="0",
20045 inst="save %sp, -112, %sp"@}]@},
20046 src_and_asm_line=@{line="32",
20047 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
20048 testsuite/gdb.mi/basics.c",line_asm_insn=[
20049 @{address="0x000107c0",func-name="main",offset="4",
20050 inst="mov 2, %o0"@},
20051 @{address="0x000107c4",func-name="main",offset="8",
20052 inst="sethi %hi(0x11800), %o2"@}]@}]
20057 @subheading The @code{-data-evaluate-expression} Command
20058 @findex -data-evaluate-expression
20060 @subsubheading Synopsis
20063 -data-evaluate-expression @var{expr}
20066 Evaluate @var{expr} as an expression. The expression could contain an
20067 inferior function call. The function call will execute synchronously.
20068 If the expression contains spaces, it must be enclosed in double quotes.
20070 @subsubheading @value{GDBN} Command
20072 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
20073 @samp{call}. In @code{gdbtk} only, there's a corresponding
20074 @samp{gdb_eval} command.
20076 @subsubheading Example
20078 In the following example, the numbers that precede the commands are the
20079 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
20080 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
20084 211-data-evaluate-expression A
20087 311-data-evaluate-expression &A
20088 311^done,value="0xefffeb7c"
20090 411-data-evaluate-expression A+3
20093 511-data-evaluate-expression "A + 3"
20099 @subheading The @code{-data-list-changed-registers} Command
20100 @findex -data-list-changed-registers
20102 @subsubheading Synopsis
20105 -data-list-changed-registers
20108 Display a list of the registers that have changed.
20110 @subsubheading @value{GDBN} Command
20112 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
20113 has the corresponding command @samp{gdb_changed_register_list}.
20115 @subsubheading Example
20117 On a PPC MBX board:
20125 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
20126 args=[],file="try.c",fullname="/home/foo/bar/try.c",line="5"@}
20128 -data-list-changed-registers
20129 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
20130 "10","11","13","14","15","16","17","18","19","20","21","22","23",
20131 "24","25","26","27","28","30","31","64","65","66","67","69"]
20136 @subheading The @code{-data-list-register-names} Command
20137 @findex -data-list-register-names
20139 @subsubheading Synopsis
20142 -data-list-register-names [ ( @var{regno} )+ ]
20145 Show a list of register names for the current target. If no arguments
20146 are given, it shows a list of the names of all the registers. If
20147 integer numbers are given as arguments, it will print a list of the
20148 names of the registers corresponding to the arguments. To ensure
20149 consistency between a register name and its number, the output list may
20150 include empty register names.
20152 @subsubheading @value{GDBN} Command
20154 @value{GDBN} does not have a command which corresponds to
20155 @samp{-data-list-register-names}. In @code{gdbtk} there is a
20156 corresponding command @samp{gdb_regnames}.
20158 @subsubheading Example
20160 For the PPC MBX board:
20163 -data-list-register-names
20164 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
20165 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
20166 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
20167 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
20168 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
20169 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
20170 "", "pc","ps","cr","lr","ctr","xer"]
20172 -data-list-register-names 1 2 3
20173 ^done,register-names=["r1","r2","r3"]
20177 @subheading The @code{-data-list-register-values} Command
20178 @findex -data-list-register-values
20180 @subsubheading Synopsis
20183 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
20186 Display the registers' contents. @var{fmt} is the format according to
20187 which the registers' contents are to be returned, followed by an optional
20188 list of numbers specifying the registers to display. A missing list of
20189 numbers indicates that the contents of all the registers must be returned.
20191 Allowed formats for @var{fmt} are:
20208 @subsubheading @value{GDBN} Command
20210 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
20211 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
20213 @subsubheading Example
20215 For a PPC MBX board (note: line breaks are for readability only, they
20216 don't appear in the actual output):
20220 -data-list-register-values r 64 65
20221 ^done,register-values=[@{number="64",value="0xfe00a300"@},
20222 @{number="65",value="0x00029002"@}]
20224 -data-list-register-values x
20225 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
20226 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
20227 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
20228 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
20229 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
20230 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
20231 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
20232 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
20233 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
20234 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
20235 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
20236 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
20237 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
20238 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
20239 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
20240 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
20241 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
20242 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
20243 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
20244 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
20245 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
20246 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
20247 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
20248 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
20249 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
20250 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
20251 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
20252 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
20253 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
20254 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
20255 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
20256 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
20257 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
20258 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
20259 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
20260 @{number="69",value="0x20002b03"@}]
20265 @subheading The @code{-data-read-memory} Command
20266 @findex -data-read-memory
20268 @subsubheading Synopsis
20271 -data-read-memory [ -o @var{byte-offset} ]
20272 @var{address} @var{word-format} @var{word-size}
20273 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
20280 @item @var{address}
20281 An expression specifying the address of the first memory word to be
20282 read. Complex expressions containing embedded white space should be
20283 quoted using the C convention.
20285 @item @var{word-format}
20286 The format to be used to print the memory words. The notation is the
20287 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
20290 @item @var{word-size}
20291 The size of each memory word in bytes.
20293 @item @var{nr-rows}
20294 The number of rows in the output table.
20296 @item @var{nr-cols}
20297 The number of columns in the output table.
20300 If present, indicates that each row should include an @sc{ascii} dump. The
20301 value of @var{aschar} is used as a padding character when a byte is not a
20302 member of the printable @sc{ascii} character set (printable @sc{ascii}
20303 characters are those whose code is between 32 and 126, inclusively).
20305 @item @var{byte-offset}
20306 An offset to add to the @var{address} before fetching memory.
20309 This command displays memory contents as a table of @var{nr-rows} by
20310 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
20311 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
20312 (returned as @samp{total-bytes}). Should less than the requested number
20313 of bytes be returned by the target, the missing words are identified
20314 using @samp{N/A}. The number of bytes read from the target is returned
20315 in @samp{nr-bytes} and the starting address used to read memory in
20318 The address of the next/previous row or page is available in
20319 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
20322 @subsubheading @value{GDBN} Command
20324 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
20325 @samp{gdb_get_mem} memory read command.
20327 @subsubheading Example
20329 Read six bytes of memory starting at @code{bytes+6} but then offset by
20330 @code{-6} bytes. Format as three rows of two columns. One byte per
20331 word. Display each word in hex.
20335 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
20336 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
20337 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
20338 prev-page="0x0000138a",memory=[
20339 @{addr="0x00001390",data=["0x00","0x01"]@},
20340 @{addr="0x00001392",data=["0x02","0x03"]@},
20341 @{addr="0x00001394",data=["0x04","0x05"]@}]
20345 Read two bytes of memory starting at address @code{shorts + 64} and
20346 display as a single word formatted in decimal.
20350 5-data-read-memory shorts+64 d 2 1 1
20351 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
20352 next-row="0x00001512",prev-row="0x0000150e",
20353 next-page="0x00001512",prev-page="0x0000150e",memory=[
20354 @{addr="0x00001510",data=["128"]@}]
20358 Read thirty two bytes of memory starting at @code{bytes+16} and format
20359 as eight rows of four columns. Include a string encoding with @samp{x}
20360 used as the non-printable character.
20364 4-data-read-memory bytes+16 x 1 8 4 x
20365 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
20366 next-row="0x000013c0",prev-row="0x0000139c",
20367 next-page="0x000013c0",prev-page="0x00001380",memory=[
20368 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
20369 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
20370 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
20371 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
20372 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
20373 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
20374 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
20375 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
20379 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20380 @node GDB/MI Tracepoint Commands
20381 @section @sc{gdb/mi} Tracepoint Commands
20383 The tracepoint commands are not yet implemented.
20385 @c @subheading -trace-actions
20387 @c @subheading -trace-delete
20389 @c @subheading -trace-disable
20391 @c @subheading -trace-dump
20393 @c @subheading -trace-enable
20395 @c @subheading -trace-exists
20397 @c @subheading -trace-find
20399 @c @subheading -trace-frame-number
20401 @c @subheading -trace-info
20403 @c @subheading -trace-insert
20405 @c @subheading -trace-list
20407 @c @subheading -trace-pass-count
20409 @c @subheading -trace-save
20411 @c @subheading -trace-start
20413 @c @subheading -trace-stop
20416 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20417 @node GDB/MI Symbol Query
20418 @section @sc{gdb/mi} Symbol Query Commands
20421 @subheading The @code{-symbol-info-address} Command
20422 @findex -symbol-info-address
20424 @subsubheading Synopsis
20427 -symbol-info-address @var{symbol}
20430 Describe where @var{symbol} is stored.
20432 @subsubheading @value{GDBN} Command
20434 The corresponding @value{GDBN} command is @samp{info address}.
20436 @subsubheading Example
20440 @subheading The @code{-symbol-info-file} Command
20441 @findex -symbol-info-file
20443 @subsubheading Synopsis
20449 Show the file for the symbol.
20451 @subsubheading @value{GDBN} Command
20453 There's no equivalent @value{GDBN} command. @code{gdbtk} has
20454 @samp{gdb_find_file}.
20456 @subsubheading Example
20460 @subheading The @code{-symbol-info-function} Command
20461 @findex -symbol-info-function
20463 @subsubheading Synopsis
20466 -symbol-info-function
20469 Show which function the symbol lives in.
20471 @subsubheading @value{GDBN} Command
20473 @samp{gdb_get_function} in @code{gdbtk}.
20475 @subsubheading Example
20479 @subheading The @code{-symbol-info-line} Command
20480 @findex -symbol-info-line
20482 @subsubheading Synopsis
20488 Show the core addresses of the code for a source line.
20490 @subsubheading @value{GDBN} Command
20492 The corresponding @value{GDBN} command is @samp{info line}.
20493 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
20495 @subsubheading Example
20499 @subheading The @code{-symbol-info-symbol} Command
20500 @findex -symbol-info-symbol
20502 @subsubheading Synopsis
20505 -symbol-info-symbol @var{addr}
20508 Describe what symbol is at location @var{addr}.
20510 @subsubheading @value{GDBN} Command
20512 The corresponding @value{GDBN} command is @samp{info symbol}.
20514 @subsubheading Example
20518 @subheading The @code{-symbol-list-functions} Command
20519 @findex -symbol-list-functions
20521 @subsubheading Synopsis
20524 -symbol-list-functions
20527 List the functions in the executable.
20529 @subsubheading @value{GDBN} Command
20531 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
20532 @samp{gdb_search} in @code{gdbtk}.
20534 @subsubheading Example
20538 @subheading The @code{-symbol-list-lines} Command
20539 @findex -symbol-list-lines
20541 @subsubheading Synopsis
20544 -symbol-list-lines @var{filename}
20547 Print the list of lines that contain code and their associated program
20548 addresses for the given source filename. The entries are sorted in
20549 ascending PC order.
20551 @subsubheading @value{GDBN} Command
20553 There is no corresponding @value{GDBN} command.
20555 @subsubheading Example
20558 -symbol-list-lines basics.c
20559 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
20564 @subheading The @code{-symbol-list-types} Command
20565 @findex -symbol-list-types
20567 @subsubheading Synopsis
20573 List all the type names.
20575 @subsubheading @value{GDBN} Command
20577 The corresponding commands are @samp{info types} in @value{GDBN},
20578 @samp{gdb_search} in @code{gdbtk}.
20580 @subsubheading Example
20584 @subheading The @code{-symbol-list-variables} Command
20585 @findex -symbol-list-variables
20587 @subsubheading Synopsis
20590 -symbol-list-variables
20593 List all the global and static variable names.
20595 @subsubheading @value{GDBN} Command
20597 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
20599 @subsubheading Example
20603 @subheading The @code{-symbol-locate} Command
20604 @findex -symbol-locate
20606 @subsubheading Synopsis
20612 @subsubheading @value{GDBN} Command
20614 @samp{gdb_loc} in @code{gdbtk}.
20616 @subsubheading Example
20620 @subheading The @code{-symbol-type} Command
20621 @findex -symbol-type
20623 @subsubheading Synopsis
20626 -symbol-type @var{variable}
20629 Show type of @var{variable}.
20631 @subsubheading @value{GDBN} Command
20633 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
20634 @samp{gdb_obj_variable}.
20636 @subsubheading Example
20640 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20641 @node GDB/MI File Commands
20642 @section @sc{gdb/mi} File Commands
20644 This section describes the GDB/MI commands to specify executable file names
20645 and to read in and obtain symbol table information.
20647 @subheading The @code{-file-exec-and-symbols} Command
20648 @findex -file-exec-and-symbols
20650 @subsubheading Synopsis
20653 -file-exec-and-symbols @var{file}
20656 Specify the executable file to be debugged. This file is the one from
20657 which the symbol table is also read. If no file is specified, the
20658 command clears the executable and symbol information. If breakpoints
20659 are set when using this command with no arguments, @value{GDBN} will produce
20660 error messages. Otherwise, no output is produced, except a completion
20663 @subsubheading @value{GDBN} Command
20665 The corresponding @value{GDBN} command is @samp{file}.
20667 @subsubheading Example
20671 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
20677 @subheading The @code{-file-exec-file} Command
20678 @findex -file-exec-file
20680 @subsubheading Synopsis
20683 -file-exec-file @var{file}
20686 Specify the executable file to be debugged. Unlike
20687 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
20688 from this file. If used without argument, @value{GDBN} clears the information
20689 about the executable file. No output is produced, except a completion
20692 @subsubheading @value{GDBN} Command
20694 The corresponding @value{GDBN} command is @samp{exec-file}.
20696 @subsubheading Example
20700 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
20706 @subheading The @code{-file-list-exec-sections} Command
20707 @findex -file-list-exec-sections
20709 @subsubheading Synopsis
20712 -file-list-exec-sections
20715 List the sections of the current executable file.
20717 @subsubheading @value{GDBN} Command
20719 The @value{GDBN} command @samp{info file} shows, among the rest, the same
20720 information as this command. @code{gdbtk} has a corresponding command
20721 @samp{gdb_load_info}.
20723 @subsubheading Example
20727 @subheading The @code{-file-list-exec-source-file} Command
20728 @findex -file-list-exec-source-file
20730 @subsubheading Synopsis
20733 -file-list-exec-source-file
20736 List the line number, the current source file, and the absolute path
20737 to the current source file for the current executable.
20739 @subsubheading @value{GDBN} Command
20741 The @value{GDBN} equivalent is @samp{info source}
20743 @subsubheading Example
20747 123-file-list-exec-source-file
20748 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c"
20753 @subheading The @code{-file-list-exec-source-files} Command
20754 @findex -file-list-exec-source-files
20756 @subsubheading Synopsis
20759 -file-list-exec-source-files
20762 List the source files for the current executable.
20764 It will always output the filename, but only when GDB can find the absolute
20765 file name of a source file, will it output the fullname.
20767 @subsubheading @value{GDBN} Command
20769 The @value{GDBN} equivalent is @samp{info sources}.
20770 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
20772 @subsubheading Example
20775 -file-list-exec-source-files
20777 @{file=foo.c,fullname=/home/foo.c@},
20778 @{file=/home/bar.c,fullname=/home/bar.c@},
20779 @{file=gdb_could_not_find_fullpath.c@}]
20783 @subheading The @code{-file-list-shared-libraries} Command
20784 @findex -file-list-shared-libraries
20786 @subsubheading Synopsis
20789 -file-list-shared-libraries
20792 List the shared libraries in the program.
20794 @subsubheading @value{GDBN} Command
20796 The corresponding @value{GDBN} command is @samp{info shared}.
20798 @subsubheading Example
20802 @subheading The @code{-file-list-symbol-files} Command
20803 @findex -file-list-symbol-files
20805 @subsubheading Synopsis
20808 -file-list-symbol-files
20813 @subsubheading @value{GDBN} Command
20815 The corresponding @value{GDBN} command is @samp{info file} (part of it).
20817 @subsubheading Example
20821 @subheading The @code{-file-symbol-file} Command
20822 @findex -file-symbol-file
20824 @subsubheading Synopsis
20827 -file-symbol-file @var{file}
20830 Read symbol table info from the specified @var{file} argument. When
20831 used without arguments, clears @value{GDBN}'s symbol table info. No output is
20832 produced, except for a completion notification.
20834 @subsubheading @value{GDBN} Command
20836 The corresponding @value{GDBN} command is @samp{symbol-file}.
20838 @subsubheading Example
20842 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
20848 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20849 @node GDB/MI Memory Overlay Commands
20850 @section @sc{gdb/mi} Memory Overlay Commands
20852 The memory overlay commands are not implemented.
20854 @c @subheading -overlay-auto
20856 @c @subheading -overlay-list-mapping-state
20858 @c @subheading -overlay-list-overlays
20860 @c @subheading -overlay-map
20862 @c @subheading -overlay-off
20864 @c @subheading -overlay-on
20866 @c @subheading -overlay-unmap
20868 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20869 @node GDB/MI Signal Handling Commands
20870 @section @sc{gdb/mi} Signal Handling Commands
20872 Signal handling commands are not implemented.
20874 @c @subheading -signal-handle
20876 @c @subheading -signal-list-handle-actions
20878 @c @subheading -signal-list-signal-types
20882 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20883 @node GDB/MI Target Manipulation
20884 @section @sc{gdb/mi} Target Manipulation Commands
20887 @subheading The @code{-target-attach} Command
20888 @findex -target-attach
20890 @subsubheading Synopsis
20893 -target-attach @var{pid} | @var{file}
20896 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
20898 @subsubheading @value{GDBN} command
20900 The corresponding @value{GDBN} command is @samp{attach}.
20902 @subsubheading Example
20906 @subheading The @code{-target-compare-sections} Command
20907 @findex -target-compare-sections
20909 @subsubheading Synopsis
20912 -target-compare-sections [ @var{section} ]
20915 Compare data of section @var{section} on target to the exec file.
20916 Without the argument, all sections are compared.
20918 @subsubheading @value{GDBN} Command
20920 The @value{GDBN} equivalent is @samp{compare-sections}.
20922 @subsubheading Example
20926 @subheading The @code{-target-detach} Command
20927 @findex -target-detach
20929 @subsubheading Synopsis
20935 Detach from the remote target which normally resumes its execution.
20938 @subsubheading @value{GDBN} command
20940 The corresponding @value{GDBN} command is @samp{detach}.
20942 @subsubheading Example
20952 @subheading The @code{-target-disconnect} Command
20953 @findex -target-disconnect
20955 @subsubheading Synopsis
20961 Disconnect from the remote target. There's no output and the target is
20962 generally not resumed.
20964 @subsubheading @value{GDBN} command
20966 The corresponding @value{GDBN} command is @samp{disconnect}.
20968 @subsubheading Example
20978 @subheading The @code{-target-download} Command
20979 @findex -target-download
20981 @subsubheading Synopsis
20987 Loads the executable onto the remote target.
20988 It prints out an update message every half second, which includes the fields:
20992 The name of the section.
20994 The size of what has been sent so far for that section.
20996 The size of the section.
20998 The total size of what was sent so far (the current and the previous sections).
21000 The size of the overall executable to download.
21004 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
21005 @sc{gdb/mi} Output Syntax}).
21007 In addition, it prints the name and size of the sections, as they are
21008 downloaded. These messages include the following fields:
21012 The name of the section.
21014 The size of the section.
21016 The size of the overall executable to download.
21020 At the end, a summary is printed.
21022 @subsubheading @value{GDBN} Command
21024 The corresponding @value{GDBN} command is @samp{load}.
21026 @subsubheading Example
21028 Note: each status message appears on a single line. Here the messages
21029 have been broken down so that they can fit onto a page.
21034 +download,@{section=".text",section-size="6668",total-size="9880"@}
21035 +download,@{section=".text",section-sent="512",section-size="6668",
21036 total-sent="512",total-size="9880"@}
21037 +download,@{section=".text",section-sent="1024",section-size="6668",
21038 total-sent="1024",total-size="9880"@}
21039 +download,@{section=".text",section-sent="1536",section-size="6668",
21040 total-sent="1536",total-size="9880"@}
21041 +download,@{section=".text",section-sent="2048",section-size="6668",
21042 total-sent="2048",total-size="9880"@}
21043 +download,@{section=".text",section-sent="2560",section-size="6668",
21044 total-sent="2560",total-size="9880"@}
21045 +download,@{section=".text",section-sent="3072",section-size="6668",
21046 total-sent="3072",total-size="9880"@}
21047 +download,@{section=".text",section-sent="3584",section-size="6668",
21048 total-sent="3584",total-size="9880"@}
21049 +download,@{section=".text",section-sent="4096",section-size="6668",
21050 total-sent="4096",total-size="9880"@}
21051 +download,@{section=".text",section-sent="4608",section-size="6668",
21052 total-sent="4608",total-size="9880"@}
21053 +download,@{section=".text",section-sent="5120",section-size="6668",
21054 total-sent="5120",total-size="9880"@}
21055 +download,@{section=".text",section-sent="5632",section-size="6668",
21056 total-sent="5632",total-size="9880"@}
21057 +download,@{section=".text",section-sent="6144",section-size="6668",
21058 total-sent="6144",total-size="9880"@}
21059 +download,@{section=".text",section-sent="6656",section-size="6668",
21060 total-sent="6656",total-size="9880"@}
21061 +download,@{section=".init",section-size="28",total-size="9880"@}
21062 +download,@{section=".fini",section-size="28",total-size="9880"@}
21063 +download,@{section=".data",section-size="3156",total-size="9880"@}
21064 +download,@{section=".data",section-sent="512",section-size="3156",
21065 total-sent="7236",total-size="9880"@}
21066 +download,@{section=".data",section-sent="1024",section-size="3156",
21067 total-sent="7748",total-size="9880"@}
21068 +download,@{section=".data",section-sent="1536",section-size="3156",
21069 total-sent="8260",total-size="9880"@}
21070 +download,@{section=".data",section-sent="2048",section-size="3156",
21071 total-sent="8772",total-size="9880"@}
21072 +download,@{section=".data",section-sent="2560",section-size="3156",
21073 total-sent="9284",total-size="9880"@}
21074 +download,@{section=".data",section-sent="3072",section-size="3156",
21075 total-sent="9796",total-size="9880"@}
21076 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
21082 @subheading The @code{-target-exec-status} Command
21083 @findex -target-exec-status
21085 @subsubheading Synopsis
21088 -target-exec-status
21091 Provide information on the state of the target (whether it is running or
21092 not, for instance).
21094 @subsubheading @value{GDBN} Command
21096 There's no equivalent @value{GDBN} command.
21098 @subsubheading Example
21102 @subheading The @code{-target-list-available-targets} Command
21103 @findex -target-list-available-targets
21105 @subsubheading Synopsis
21108 -target-list-available-targets
21111 List the possible targets to connect to.
21113 @subsubheading @value{GDBN} Command
21115 The corresponding @value{GDBN} command is @samp{help target}.
21117 @subsubheading Example
21121 @subheading The @code{-target-list-current-targets} Command
21122 @findex -target-list-current-targets
21124 @subsubheading Synopsis
21127 -target-list-current-targets
21130 Describe the current target.
21132 @subsubheading @value{GDBN} Command
21134 The corresponding information is printed by @samp{info file} (among
21137 @subsubheading Example
21141 @subheading The @code{-target-list-parameters} Command
21142 @findex -target-list-parameters
21144 @subsubheading Synopsis
21147 -target-list-parameters
21152 @subsubheading @value{GDBN} Command
21156 @subsubheading Example
21160 @subheading The @code{-target-select} Command
21161 @findex -target-select
21163 @subsubheading Synopsis
21166 -target-select @var{type} @var{parameters @dots{}}
21169 Connect @value{GDBN} to the remote target. This command takes two args:
21173 The type of target, for instance @samp{async}, @samp{remote}, etc.
21174 @item @var{parameters}
21175 Device names, host names and the like. @xref{Target Commands, ,
21176 Commands for managing targets}, for more details.
21179 The output is a connection notification, followed by the address at
21180 which the target program is, in the following form:
21183 ^connected,addr="@var{address}",func="@var{function name}",
21184 args=[@var{arg list}]
21187 @subsubheading @value{GDBN} Command
21189 The corresponding @value{GDBN} command is @samp{target}.
21191 @subsubheading Example
21195 -target-select async /dev/ttya
21196 ^connected,addr="0xfe00a300",func="??",args=[]
21200 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21201 @node GDB/MI Miscellaneous Commands
21202 @section Miscellaneous @sc{gdb/mi} Commands
21204 @c @subheading -gdb-complete
21206 @subheading The @code{-gdb-exit} Command
21209 @subsubheading Synopsis
21215 Exit @value{GDBN} immediately.
21217 @subsubheading @value{GDBN} Command
21219 Approximately corresponds to @samp{quit}.
21221 @subsubheading Example
21230 @subheading The @code{-exec-abort} Command
21231 @findex -exec-abort
21233 @subsubheading Synopsis
21239 Kill the inferior running program.
21241 @subsubheading @value{GDBN} Command
21243 The corresponding @value{GDBN} command is @samp{kill}.
21245 @subsubheading Example
21249 @subheading The @code{-gdb-set} Command
21252 @subsubheading Synopsis
21258 Set an internal @value{GDBN} variable.
21259 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
21261 @subsubheading @value{GDBN} Command
21263 The corresponding @value{GDBN} command is @samp{set}.
21265 @subsubheading Example
21275 @subheading The @code{-gdb-show} Command
21278 @subsubheading Synopsis
21284 Show the current value of a @value{GDBN} variable.
21286 @subsubheading @value{GDBN} command
21288 The corresponding @value{GDBN} command is @samp{show}.
21290 @subsubheading Example
21299 @c @subheading -gdb-source
21302 @subheading The @code{-gdb-version} Command
21303 @findex -gdb-version
21305 @subsubheading Synopsis
21311 Show version information for @value{GDBN}. Used mostly in testing.
21313 @subsubheading @value{GDBN} Command
21315 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
21316 default shows this information when you start an interactive session.
21318 @subsubheading Example
21320 @c This example modifies the actual output from GDB to avoid overfull
21326 ~Copyright 2000 Free Software Foundation, Inc.
21327 ~GDB is free software, covered by the GNU General Public License, and
21328 ~you are welcome to change it and/or distribute copies of it under
21329 ~ certain conditions.
21330 ~Type "show copying" to see the conditions.
21331 ~There is absolutely no warranty for GDB. Type "show warranty" for
21333 ~This GDB was configured as
21334 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
21339 @subheading The @code{-interpreter-exec} Command
21340 @findex -interpreter-exec
21342 @subheading Synopsis
21345 -interpreter-exec @var{interpreter} @var{command}
21347 @anchor{-interpreter-exec}
21349 Execute the specified @var{command} in the given @var{interpreter}.
21351 @subheading @value{GDBN} Command
21353 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
21355 @subheading Example
21359 -interpreter-exec console "break main"
21360 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
21361 &"During symbol reading, bad structure-type format.\n"
21362 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
21367 @subheading The @code{-inferior-tty-set} Command
21368 @findex -inferior-tty-set
21370 @subheading Synopsis
21373 -inferior-tty-set /dev/pts/1
21376 Set terminal for future runs of the program being debugged.
21378 @subheading @value{GDBN} Command
21380 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
21382 @subheading Example
21386 -inferior-tty-set /dev/pts/1
21391 @subheading The @code{-inferior-tty-show} Command
21392 @findex -inferior-tty-show
21394 @subheading Synopsis
21400 Show terminal for future runs of program being debugged.
21402 @subheading @value{GDBN} Command
21404 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
21406 @subheading Example
21410 -inferior-tty-set /dev/pts/1
21414 ^done,inferior_tty_terminal="/dev/pts/1"
21419 @chapter @value{GDBN} Annotations
21421 This chapter describes annotations in @value{GDBN}. Annotations were
21422 designed to interface @value{GDBN} to graphical user interfaces or other
21423 similar programs which want to interact with @value{GDBN} at a
21424 relatively high level.
21426 The annotation mechanism has largely been superseeded by @sc{gdb/mi}
21430 This is Edition @value{EDITION}, @value{DATE}.
21434 * Annotations Overview:: What annotations are; the general syntax.
21435 * Prompting:: Annotations marking @value{GDBN}'s need for input.
21436 * Errors:: Annotations for error messages.
21437 * Invalidation:: Some annotations describe things now invalid.
21438 * Annotations for Running::
21439 Whether the program is running, how it stopped, etc.
21440 * Source Annotations:: Annotations describing source code.
21443 @node Annotations Overview
21444 @section What is an Annotation?
21445 @cindex annotations
21447 Annotations start with a newline character, two @samp{control-z}
21448 characters, and the name of the annotation. If there is no additional
21449 information associated with this annotation, the name of the annotation
21450 is followed immediately by a newline. If there is additional
21451 information, the name of the annotation is followed by a space, the
21452 additional information, and a newline. The additional information
21453 cannot contain newline characters.
21455 Any output not beginning with a newline and two @samp{control-z}
21456 characters denotes literal output from @value{GDBN}. Currently there is
21457 no need for @value{GDBN} to output a newline followed by two
21458 @samp{control-z} characters, but if there was such a need, the
21459 annotations could be extended with an @samp{escape} annotation which
21460 means those three characters as output.
21462 The annotation @var{level}, which is specified using the
21463 @option{--annotate} command line option (@pxref{Mode Options}), controls
21464 how much information @value{GDBN} prints together with its prompt,
21465 values of expressions, source lines, and other types of output. Level 0
21466 is for no anntations, level 1 is for use when @value{GDBN} is run as a
21467 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
21468 for programs that control @value{GDBN}, and level 2 annotations have
21469 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
21470 Interface, annotate, GDB's Obsolete Annotations}).
21473 @kindex set annotate
21474 @item set annotate @var{level}
21475 The @value{GDBN} command @code{set annotate} sets the level of
21476 annotations to the specified @var{level}.
21478 @item show annotate
21479 @kindex show annotate
21480 Show the current annotation level.
21483 This chapter describes level 3 annotations.
21485 A simple example of starting up @value{GDBN} with annotations is:
21488 $ @kbd{gdb --annotate=3}
21490 Copyright 2003 Free Software Foundation, Inc.
21491 GDB is free software, covered by the GNU General Public License,
21492 and you are welcome to change it and/or distribute copies of it
21493 under certain conditions.
21494 Type "show copying" to see the conditions.
21495 There is absolutely no warranty for GDB. Type "show warranty"
21497 This GDB was configured as "i386-pc-linux-gnu"
21508 Here @samp{quit} is input to @value{GDBN}; the rest is output from
21509 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
21510 denotes a @samp{control-z} character) are annotations; the rest is
21511 output from @value{GDBN}.
21514 @section Annotation for @value{GDBN} Input
21516 @cindex annotations for prompts
21517 When @value{GDBN} prompts for input, it annotates this fact so it is possible
21518 to know when to send output, when the output from a given command is
21521 Different kinds of input each have a different @dfn{input type}. Each
21522 input type has three annotations: a @code{pre-} annotation, which
21523 denotes the beginning of any prompt which is being output, a plain
21524 annotation, which denotes the end of the prompt, and then a @code{post-}
21525 annotation which denotes the end of any echo which may (or may not) be
21526 associated with the input. For example, the @code{prompt} input type
21527 features the following annotations:
21535 The input types are
21538 @findex pre-prompt annotation
21539 @findex prompt annotation
21540 @findex post-prompt annotation
21542 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
21544 @findex pre-commands annotation
21545 @findex commands annotation
21546 @findex post-commands annotation
21548 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
21549 command. The annotations are repeated for each command which is input.
21551 @findex pre-overload-choice annotation
21552 @findex overload-choice annotation
21553 @findex post-overload-choice annotation
21554 @item overload-choice
21555 When @value{GDBN} wants the user to select between various overloaded functions.
21557 @findex pre-query annotation
21558 @findex query annotation
21559 @findex post-query annotation
21561 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
21563 @findex pre-prompt-for-continue annotation
21564 @findex prompt-for-continue annotation
21565 @findex post-prompt-for-continue annotation
21566 @item prompt-for-continue
21567 When @value{GDBN} is asking the user to press return to continue. Note: Don't
21568 expect this to work well; instead use @code{set height 0} to disable
21569 prompting. This is because the counting of lines is buggy in the
21570 presence of annotations.
21575 @cindex annotations for errors, warnings and interrupts
21577 @findex quit annotation
21582 This annotation occurs right before @value{GDBN} responds to an interrupt.
21584 @findex error annotation
21589 This annotation occurs right before @value{GDBN} responds to an error.
21591 Quit and error annotations indicate that any annotations which @value{GDBN} was
21592 in the middle of may end abruptly. For example, if a
21593 @code{value-history-begin} annotation is followed by a @code{error}, one
21594 cannot expect to receive the matching @code{value-history-end}. One
21595 cannot expect not to receive it either, however; an error annotation
21596 does not necessarily mean that @value{GDBN} is immediately returning all the way
21599 @findex error-begin annotation
21600 A quit or error annotation may be preceded by
21606 Any output between that and the quit or error annotation is the error
21609 Warning messages are not yet annotated.
21610 @c If we want to change that, need to fix warning(), type_error(),
21611 @c range_error(), and possibly other places.
21614 @section Invalidation Notices
21616 @cindex annotations for invalidation messages
21617 The following annotations say that certain pieces of state may have
21621 @findex frames-invalid annotation
21622 @item ^Z^Zframes-invalid
21624 The frames (for example, output from the @code{backtrace} command) may
21627 @findex breakpoints-invalid annotation
21628 @item ^Z^Zbreakpoints-invalid
21630 The breakpoints may have changed. For example, the user just added or
21631 deleted a breakpoint.
21634 @node Annotations for Running
21635 @section Running the Program
21636 @cindex annotations for running programs
21638 @findex starting annotation
21639 @findex stopping annotation
21640 When the program starts executing due to a @value{GDBN} command such as
21641 @code{step} or @code{continue},
21647 is output. When the program stops,
21653 is output. Before the @code{stopped} annotation, a variety of
21654 annotations describe how the program stopped.
21657 @findex exited annotation
21658 @item ^Z^Zexited @var{exit-status}
21659 The program exited, and @var{exit-status} is the exit status (zero for
21660 successful exit, otherwise nonzero).
21662 @findex signalled annotation
21663 @findex signal-name annotation
21664 @findex signal-name-end annotation
21665 @findex signal-string annotation
21666 @findex signal-string-end annotation
21667 @item ^Z^Zsignalled
21668 The program exited with a signal. After the @code{^Z^Zsignalled}, the
21669 annotation continues:
21675 ^Z^Zsignal-name-end
21679 ^Z^Zsignal-string-end
21684 where @var{name} is the name of the signal, such as @code{SIGILL} or
21685 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
21686 as @code{Illegal Instruction} or @code{Segmentation fault}.
21687 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
21688 user's benefit and have no particular format.
21690 @findex signal annotation
21692 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
21693 just saying that the program received the signal, not that it was
21694 terminated with it.
21696 @findex breakpoint annotation
21697 @item ^Z^Zbreakpoint @var{number}
21698 The program hit breakpoint number @var{number}.
21700 @findex watchpoint annotation
21701 @item ^Z^Zwatchpoint @var{number}
21702 The program hit watchpoint number @var{number}.
21705 @node Source Annotations
21706 @section Displaying Source
21707 @cindex annotations for source display
21709 @findex source annotation
21710 The following annotation is used instead of displaying source code:
21713 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
21716 where @var{filename} is an absolute file name indicating which source
21717 file, @var{line} is the line number within that file (where 1 is the
21718 first line in the file), @var{character} is the character position
21719 within the file (where 0 is the first character in the file) (for most
21720 debug formats this will necessarily point to the beginning of a line),
21721 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
21722 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
21723 @var{addr} is the address in the target program associated with the
21724 source which is being displayed. @var{addr} is in the form @samp{0x}
21725 followed by one or more lowercase hex digits (note that this does not
21726 depend on the language).
21729 @chapter Reporting Bugs in @value{GDBN}
21730 @cindex bugs in @value{GDBN}
21731 @cindex reporting bugs in @value{GDBN}
21733 Your bug reports play an essential role in making @value{GDBN} reliable.
21735 Reporting a bug may help you by bringing a solution to your problem, or it
21736 may not. But in any case the principal function of a bug report is to help
21737 the entire community by making the next version of @value{GDBN} work better. Bug
21738 reports are your contribution to the maintenance of @value{GDBN}.
21740 In order for a bug report to serve its purpose, you must include the
21741 information that enables us to fix the bug.
21744 * Bug Criteria:: Have you found a bug?
21745 * Bug Reporting:: How to report bugs
21749 @section Have you found a bug?
21750 @cindex bug criteria
21752 If you are not sure whether you have found a bug, here are some guidelines:
21755 @cindex fatal signal
21756 @cindex debugger crash
21757 @cindex crash of debugger
21759 If the debugger gets a fatal signal, for any input whatever, that is a
21760 @value{GDBN} bug. Reliable debuggers never crash.
21762 @cindex error on valid input
21764 If @value{GDBN} produces an error message for valid input, that is a
21765 bug. (Note that if you're cross debugging, the problem may also be
21766 somewhere in the connection to the target.)
21768 @cindex invalid input
21770 If @value{GDBN} does not produce an error message for invalid input,
21771 that is a bug. However, you should note that your idea of
21772 ``invalid input'' might be our idea of ``an extension'' or ``support
21773 for traditional practice''.
21776 If you are an experienced user of debugging tools, your suggestions
21777 for improvement of @value{GDBN} are welcome in any case.
21780 @node Bug Reporting
21781 @section How to report bugs
21782 @cindex bug reports
21783 @cindex @value{GDBN} bugs, reporting
21785 A number of companies and individuals offer support for @sc{gnu} products.
21786 If you obtained @value{GDBN} from a support organization, we recommend you
21787 contact that organization first.
21789 You can find contact information for many support companies and
21790 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
21792 @c should add a web page ref...
21794 In any event, we also recommend that you submit bug reports for
21795 @value{GDBN}. The prefered method is to submit them directly using
21796 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
21797 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
21800 @strong{Do not send bug reports to @samp{info-gdb}, or to
21801 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
21802 not want to receive bug reports. Those that do have arranged to receive
21805 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
21806 serves as a repeater. The mailing list and the newsgroup carry exactly
21807 the same messages. Often people think of posting bug reports to the
21808 newsgroup instead of mailing them. This appears to work, but it has one
21809 problem which can be crucial: a newsgroup posting often lacks a mail
21810 path back to the sender. Thus, if we need to ask for more information,
21811 we may be unable to reach you. For this reason, it is better to send
21812 bug reports to the mailing list.
21814 The fundamental principle of reporting bugs usefully is this:
21815 @strong{report all the facts}. If you are not sure whether to state a
21816 fact or leave it out, state it!
21818 Often people omit facts because they think they know what causes the
21819 problem and assume that some details do not matter. Thus, you might
21820 assume that the name of the variable you use in an example does not matter.
21821 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
21822 stray memory reference which happens to fetch from the location where that
21823 name is stored in memory; perhaps, if the name were different, the contents
21824 of that location would fool the debugger into doing the right thing despite
21825 the bug. Play it safe and give a specific, complete example. That is the
21826 easiest thing for you to do, and the most helpful.
21828 Keep in mind that the purpose of a bug report is to enable us to fix the
21829 bug. It may be that the bug has been reported previously, but neither
21830 you nor we can know that unless your bug report is complete and
21833 Sometimes people give a few sketchy facts and ask, ``Does this ring a
21834 bell?'' Those bug reports are useless, and we urge everyone to
21835 @emph{refuse to respond to them} except to chide the sender to report
21838 To enable us to fix the bug, you should include all these things:
21842 The version of @value{GDBN}. @value{GDBN} announces it if you start
21843 with no arguments; you can also print it at any time using @code{show
21846 Without this, we will not know whether there is any point in looking for
21847 the bug in the current version of @value{GDBN}.
21850 The type of machine you are using, and the operating system name and
21854 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
21855 ``@value{GCC}--2.8.1''.
21858 What compiler (and its version) was used to compile the program you are
21859 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
21860 C Compiler''. For GCC, you can say @code{gcc --version} to get this
21861 information; for other compilers, see the documentation for those
21865 The command arguments you gave the compiler to compile your example and
21866 observe the bug. For example, did you use @samp{-O}? To guarantee
21867 you will not omit something important, list them all. A copy of the
21868 Makefile (or the output from make) is sufficient.
21870 If we were to try to guess the arguments, we would probably guess wrong
21871 and then we might not encounter the bug.
21874 A complete input script, and all necessary source files, that will
21878 A description of what behavior you observe that you believe is
21879 incorrect. For example, ``It gets a fatal signal.''
21881 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
21882 will certainly notice it. But if the bug is incorrect output, we might
21883 not notice unless it is glaringly wrong. You might as well not give us
21884 a chance to make a mistake.
21886 Even if the problem you experience is a fatal signal, you should still
21887 say so explicitly. Suppose something strange is going on, such as, your
21888 copy of @value{GDBN} is out of synch, or you have encountered a bug in
21889 the C library on your system. (This has happened!) Your copy might
21890 crash and ours would not. If you told us to expect a crash, then when
21891 ours fails to crash, we would know that the bug was not happening for
21892 us. If you had not told us to expect a crash, then we would not be able
21893 to draw any conclusion from our observations.
21896 @cindex recording a session script
21897 To collect all this information, you can use a session recording program
21898 such as @command{script}, which is available on many Unix systems.
21899 Just run your @value{GDBN} session inside @command{script} and then
21900 include the @file{typescript} file with your bug report.
21902 Another way to record a @value{GDBN} session is to run @value{GDBN}
21903 inside Emacs and then save the entire buffer to a file.
21906 If you wish to suggest changes to the @value{GDBN} source, send us context
21907 diffs. If you even discuss something in the @value{GDBN} source, refer to
21908 it by context, not by line number.
21910 The line numbers in our development sources will not match those in your
21911 sources. Your line numbers would convey no useful information to us.
21915 Here are some things that are not necessary:
21919 A description of the envelope of the bug.
21921 Often people who encounter a bug spend a lot of time investigating
21922 which changes to the input file will make the bug go away and which
21923 changes will not affect it.
21925 This is often time consuming and not very useful, because the way we
21926 will find the bug is by running a single example under the debugger
21927 with breakpoints, not by pure deduction from a series of examples.
21928 We recommend that you save your time for something else.
21930 Of course, if you can find a simpler example to report @emph{instead}
21931 of the original one, that is a convenience for us. Errors in the
21932 output will be easier to spot, running under the debugger will take
21933 less time, and so on.
21935 However, simplification is not vital; if you do not want to do this,
21936 report the bug anyway and send us the entire test case you used.
21939 A patch for the bug.
21941 A patch for the bug does help us if it is a good one. But do not omit
21942 the necessary information, such as the test case, on the assumption that
21943 a patch is all we need. We might see problems with your patch and decide
21944 to fix the problem another way, or we might not understand it at all.
21946 Sometimes with a program as complicated as @value{GDBN} it is very hard to
21947 construct an example that will make the program follow a certain path
21948 through the code. If you do not send us the example, we will not be able
21949 to construct one, so we will not be able to verify that the bug is fixed.
21951 And if we cannot understand what bug you are trying to fix, or why your
21952 patch should be an improvement, we will not install it. A test case will
21953 help us to understand.
21956 A guess about what the bug is or what it depends on.
21958 Such guesses are usually wrong. Even we cannot guess right about such
21959 things without first using the debugger to find the facts.
21962 @c The readline documentation is distributed with the readline code
21963 @c and consists of the two following files:
21965 @c inc-hist.texinfo
21966 @c Use -I with makeinfo to point to the appropriate directory,
21967 @c environment var TEXINPUTS with TeX.
21968 @include rluser.texi
21969 @include inc-hist.texinfo
21972 @node Formatting Documentation
21973 @appendix Formatting Documentation
21975 @cindex @value{GDBN} reference card
21976 @cindex reference card
21977 The @value{GDBN} 4 release includes an already-formatted reference card, ready
21978 for printing with PostScript or Ghostscript, in the @file{gdb}
21979 subdirectory of the main source directory@footnote{In
21980 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
21981 release.}. If you can use PostScript or Ghostscript with your printer,
21982 you can print the reference card immediately with @file{refcard.ps}.
21984 The release also includes the source for the reference card. You
21985 can format it, using @TeX{}, by typing:
21991 The @value{GDBN} reference card is designed to print in @dfn{landscape}
21992 mode on US ``letter'' size paper;
21993 that is, on a sheet 11 inches wide by 8.5 inches
21994 high. You will need to specify this form of printing as an option to
21995 your @sc{dvi} output program.
21997 @cindex documentation
21999 All the documentation for @value{GDBN} comes as part of the machine-readable
22000 distribution. The documentation is written in Texinfo format, which is
22001 a documentation system that uses a single source file to produce both
22002 on-line information and a printed manual. You can use one of the Info
22003 formatting commands to create the on-line version of the documentation
22004 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
22006 @value{GDBN} includes an already formatted copy of the on-line Info
22007 version of this manual in the @file{gdb} subdirectory. The main Info
22008 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
22009 subordinate files matching @samp{gdb.info*} in the same directory. If
22010 necessary, you can print out these files, or read them with any editor;
22011 but they are easier to read using the @code{info} subsystem in @sc{gnu}
22012 Emacs or the standalone @code{info} program, available as part of the
22013 @sc{gnu} Texinfo distribution.
22015 If you want to format these Info files yourself, you need one of the
22016 Info formatting programs, such as @code{texinfo-format-buffer} or
22019 If you have @code{makeinfo} installed, and are in the top level
22020 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
22021 version @value{GDBVN}), you can make the Info file by typing:
22028 If you want to typeset and print copies of this manual, you need @TeX{},
22029 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
22030 Texinfo definitions file.
22032 @TeX{} is a typesetting program; it does not print files directly, but
22033 produces output files called @sc{dvi} files. To print a typeset
22034 document, you need a program to print @sc{dvi} files. If your system
22035 has @TeX{} installed, chances are it has such a program. The precise
22036 command to use depends on your system; @kbd{lpr -d} is common; another
22037 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
22038 require a file name without any extension or a @samp{.dvi} extension.
22040 @TeX{} also requires a macro definitions file called
22041 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
22042 written in Texinfo format. On its own, @TeX{} cannot either read or
22043 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
22044 and is located in the @file{gdb-@var{version-number}/texinfo}
22047 If you have @TeX{} and a @sc{dvi} printer program installed, you can
22048 typeset and print this manual. First switch to the the @file{gdb}
22049 subdirectory of the main source directory (for example, to
22050 @file{gdb-@value{GDBVN}/gdb}) and type:
22056 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
22058 @node Installing GDB
22059 @appendix Installing @value{GDBN}
22060 @cindex installation
22063 * Requirements:: Requirements for building @value{GDBN}
22064 * Running Configure:: Invoking the @value{GDBN} @code{configure} script
22065 * Separate Objdir:: Compiling @value{GDBN} in another directory
22066 * Config Names:: Specifying names for hosts and targets
22067 * Configure Options:: Summary of options for configure
22071 @section Requirements for building @value{GDBN}
22072 @cindex building @value{GDBN}, requirements for
22074 Building @value{GDBN} requires various tools and packages to be available.
22075 Other packages will be used only if they are found.
22077 @heading Tools/packages necessary for building @value{GDBN}
22079 @item ISO C90 compiler
22080 @value{GDBN} is written in ISO C90. It should be buildable with any
22081 working C90 compiler, e.g.@: GCC.
22085 @heading Tools/packages optional for building @value{GDBN}
22088 @value{GDBN} can use the Expat XML parsing library. This library may be
22089 included with your operating system distribution; if it is not, you
22090 can get the latest version from @url{http://expat.sourceforge.net}.
22091 The @code{configure} script will search for this library in several
22092 standard locations; if it is installed in an unusual path, you can
22093 use the @option{--with-libexpat-prefix} option to specify its location.
22095 Expat is used currently only used to implement some remote-specific
22100 @node Running Configure
22101 @section Invoking the @value{GDBN} @code{configure} script
22102 @cindex configuring @value{GDBN}
22103 @value{GDBN} comes with a @code{configure} script that automates the process
22104 of preparing @value{GDBN} for installation; you can then use @code{make} to
22105 build the @code{gdb} program.
22107 @c irrelevant in info file; it's as current as the code it lives with.
22108 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
22109 look at the @file{README} file in the sources; we may have improved the
22110 installation procedures since publishing this manual.}
22113 The @value{GDBN} distribution includes all the source code you need for
22114 @value{GDBN} in a single directory, whose name is usually composed by
22115 appending the version number to @samp{gdb}.
22117 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
22118 @file{gdb-@value{GDBVN}} directory. That directory contains:
22121 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
22122 script for configuring @value{GDBN} and all its supporting libraries
22124 @item gdb-@value{GDBVN}/gdb
22125 the source specific to @value{GDBN} itself
22127 @item gdb-@value{GDBVN}/bfd
22128 source for the Binary File Descriptor library
22130 @item gdb-@value{GDBVN}/include
22131 @sc{gnu} include files
22133 @item gdb-@value{GDBVN}/libiberty
22134 source for the @samp{-liberty} free software library
22136 @item gdb-@value{GDBVN}/opcodes
22137 source for the library of opcode tables and disassemblers
22139 @item gdb-@value{GDBVN}/readline
22140 source for the @sc{gnu} command-line interface
22142 @item gdb-@value{GDBVN}/glob
22143 source for the @sc{gnu} filename pattern-matching subroutine
22145 @item gdb-@value{GDBVN}/mmalloc
22146 source for the @sc{gnu} memory-mapped malloc package
22149 The simplest way to configure and build @value{GDBN} is to run @code{configure}
22150 from the @file{gdb-@var{version-number}} source directory, which in
22151 this example is the @file{gdb-@value{GDBVN}} directory.
22153 First switch to the @file{gdb-@var{version-number}} source directory
22154 if you are not already in it; then run @code{configure}. Pass the
22155 identifier for the platform on which @value{GDBN} will run as an
22161 cd gdb-@value{GDBVN}
22162 ./configure @var{host}
22167 where @var{host} is an identifier such as @samp{sun4} or
22168 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
22169 (You can often leave off @var{host}; @code{configure} tries to guess the
22170 correct value by examining your system.)
22172 Running @samp{configure @var{host}} and then running @code{make} builds the
22173 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
22174 libraries, then @code{gdb} itself. The configured source files, and the
22175 binaries, are left in the corresponding source directories.
22178 @code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
22179 system does not recognize this automatically when you run a different
22180 shell, you may need to run @code{sh} on it explicitly:
22183 sh configure @var{host}
22186 If you run @code{configure} from a directory that contains source
22187 directories for multiple libraries or programs, such as the
22188 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, @code{configure}
22189 creates configuration files for every directory level underneath (unless
22190 you tell it not to, with the @samp{--norecursion} option).
22192 You should run the @code{configure} script from the top directory in the
22193 source tree, the @file{gdb-@var{version-number}} directory. If you run
22194 @code{configure} from one of the subdirectories, you will configure only
22195 that subdirectory. That is usually not what you want. In particular,
22196 if you run the first @code{configure} from the @file{gdb} subdirectory
22197 of the @file{gdb-@var{version-number}} directory, you will omit the
22198 configuration of @file{bfd}, @file{readline}, and other sibling
22199 directories of the @file{gdb} subdirectory. This leads to build errors
22200 about missing include files such as @file{bfd/bfd.h}.
22202 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
22203 However, you should make sure that the shell on your path (named by
22204 the @samp{SHELL} environment variable) is publicly readable. Remember
22205 that @value{GDBN} uses the shell to start your program---some systems refuse to
22206 let @value{GDBN} debug child processes whose programs are not readable.
22208 @node Separate Objdir
22209 @section Compiling @value{GDBN} in another directory
22211 If you want to run @value{GDBN} versions for several host or target machines,
22212 you need a different @code{gdb} compiled for each combination of
22213 host and target. @code{configure} is designed to make this easy by
22214 allowing you to generate each configuration in a separate subdirectory,
22215 rather than in the source directory. If your @code{make} program
22216 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
22217 @code{make} in each of these directories builds the @code{gdb}
22218 program specified there.
22220 To build @code{gdb} in a separate directory, run @code{configure}
22221 with the @samp{--srcdir} option to specify where to find the source.
22222 (You also need to specify a path to find @code{configure}
22223 itself from your working directory. If the path to @code{configure}
22224 would be the same as the argument to @samp{--srcdir}, you can leave out
22225 the @samp{--srcdir} option; it is assumed.)
22227 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
22228 separate directory for a Sun 4 like this:
22232 cd gdb-@value{GDBVN}
22235 ../gdb-@value{GDBVN}/configure sun4
22240 When @code{configure} builds a configuration using a remote source
22241 directory, it creates a tree for the binaries with the same structure
22242 (and using the same names) as the tree under the source directory. In
22243 the example, you'd find the Sun 4 library @file{libiberty.a} in the
22244 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
22245 @file{gdb-sun4/gdb}.
22247 Make sure that your path to the @file{configure} script has just one
22248 instance of @file{gdb} in it. If your path to @file{configure} looks
22249 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
22250 one subdirectory of @value{GDBN}, not the whole package. This leads to
22251 build errors about missing include files such as @file{bfd/bfd.h}.
22253 One popular reason to build several @value{GDBN} configurations in separate
22254 directories is to configure @value{GDBN} for cross-compiling (where
22255 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
22256 programs that run on another machine---the @dfn{target}).
22257 You specify a cross-debugging target by
22258 giving the @samp{--target=@var{target}} option to @code{configure}.
22260 When you run @code{make} to build a program or library, you must run
22261 it in a configured directory---whatever directory you were in when you
22262 called @code{configure} (or one of its subdirectories).
22264 The @code{Makefile} that @code{configure} generates in each source
22265 directory also runs recursively. If you type @code{make} in a source
22266 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
22267 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
22268 will build all the required libraries, and then build GDB.
22270 When you have multiple hosts or targets configured in separate
22271 directories, you can run @code{make} on them in parallel (for example,
22272 if they are NFS-mounted on each of the hosts); they will not interfere
22276 @section Specifying names for hosts and targets
22278 The specifications used for hosts and targets in the @code{configure}
22279 script are based on a three-part naming scheme, but some short predefined
22280 aliases are also supported. The full naming scheme encodes three pieces
22281 of information in the following pattern:
22284 @var{architecture}-@var{vendor}-@var{os}
22287 For example, you can use the alias @code{sun4} as a @var{host} argument,
22288 or as the value for @var{target} in a @code{--target=@var{target}}
22289 option. The equivalent full name is @samp{sparc-sun-sunos4}.
22291 The @code{configure} script accompanying @value{GDBN} does not provide
22292 any query facility to list all supported host and target names or
22293 aliases. @code{configure} calls the Bourne shell script
22294 @code{config.sub} to map abbreviations to full names; you can read the
22295 script, if you wish, or you can use it to test your guesses on
22296 abbreviations---for example:
22299 % sh config.sub i386-linux
22301 % sh config.sub alpha-linux
22302 alpha-unknown-linux-gnu
22303 % sh config.sub hp9k700
22305 % sh config.sub sun4
22306 sparc-sun-sunos4.1.1
22307 % sh config.sub sun3
22308 m68k-sun-sunos4.1.1
22309 % sh config.sub i986v
22310 Invalid configuration `i986v': machine `i986v' not recognized
22314 @code{config.sub} is also distributed in the @value{GDBN} source
22315 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
22317 @node Configure Options
22318 @section @code{configure} options
22320 Here is a summary of the @code{configure} options and arguments that
22321 are most often useful for building @value{GDBN}. @code{configure} also has
22322 several other options not listed here. @inforef{What Configure
22323 Does,,configure.info}, for a full explanation of @code{configure}.
22326 configure @r{[}--help@r{]}
22327 @r{[}--prefix=@var{dir}@r{]}
22328 @r{[}--exec-prefix=@var{dir}@r{]}
22329 @r{[}--srcdir=@var{dirname}@r{]}
22330 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
22331 @r{[}--target=@var{target}@r{]}
22336 You may introduce options with a single @samp{-} rather than
22337 @samp{--} if you prefer; but you may abbreviate option names if you use
22342 Display a quick summary of how to invoke @code{configure}.
22344 @item --prefix=@var{dir}
22345 Configure the source to install programs and files under directory
22348 @item --exec-prefix=@var{dir}
22349 Configure the source to install programs under directory
22352 @c avoid splitting the warning from the explanation:
22354 @item --srcdir=@var{dirname}
22355 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
22356 @code{make} that implements the @code{VPATH} feature.}@*
22357 Use this option to make configurations in directories separate from the
22358 @value{GDBN} source directories. Among other things, you can use this to
22359 build (or maintain) several configurations simultaneously, in separate
22360 directories. @code{configure} writes configuration specific files in
22361 the current directory, but arranges for them to use the source in the
22362 directory @var{dirname}. @code{configure} creates directories under
22363 the working directory in parallel to the source directories below
22366 @item --norecursion
22367 Configure only the directory level where @code{configure} is executed; do not
22368 propagate configuration to subdirectories.
22370 @item --target=@var{target}
22371 Configure @value{GDBN} for cross-debugging programs running on the specified
22372 @var{target}. Without this option, @value{GDBN} is configured to debug
22373 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
22375 There is no convenient way to generate a list of all available targets.
22377 @item @var{host} @dots{}
22378 Configure @value{GDBN} to run on the specified @var{host}.
22380 There is no convenient way to generate a list of all available hosts.
22383 There are many other options available as well, but they are generally
22384 needed for special purposes only.
22386 @node Maintenance Commands
22387 @appendix Maintenance Commands
22388 @cindex maintenance commands
22389 @cindex internal commands
22391 In addition to commands intended for @value{GDBN} users, @value{GDBN}
22392 includes a number of commands intended for @value{GDBN} developers,
22393 that are not documented elsewhere in this manual. These commands are
22394 provided here for reference. (For commands that turn on debugging
22395 messages, see @ref{Debugging Output}.)
22398 @kindex maint agent
22399 @item maint agent @var{expression}
22400 Translate the given @var{expression} into remote agent bytecodes.
22401 This command is useful for debugging the Agent Expression mechanism
22402 (@pxref{Agent Expressions}).
22404 @kindex maint info breakpoints
22405 @item @anchor{maint info breakpoints}maint info breakpoints
22406 Using the same format as @samp{info breakpoints}, display both the
22407 breakpoints you've set explicitly, and those @value{GDBN} is using for
22408 internal purposes. Internal breakpoints are shown with negative
22409 breakpoint numbers. The type column identifies what kind of breakpoint
22414 Normal, explicitly set breakpoint.
22417 Normal, explicitly set watchpoint.
22420 Internal breakpoint, used to handle correctly stepping through
22421 @code{longjmp} calls.
22423 @item longjmp resume
22424 Internal breakpoint at the target of a @code{longjmp}.
22427 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
22430 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
22433 Shared library events.
22437 @kindex maint check-symtabs
22438 @item maint check-symtabs
22439 Check the consistency of psymtabs and symtabs.
22441 @kindex maint cplus first_component
22442 @item maint cplus first_component @var{name}
22443 Print the first C@t{++} class/namespace component of @var{name}.
22445 @kindex maint cplus namespace
22446 @item maint cplus namespace
22447 Print the list of possible C@t{++} namespaces.
22449 @kindex maint demangle
22450 @item maint demangle @var{name}
22451 Demangle a C@t{++} or Objective-C manled @var{name}.
22453 @kindex maint deprecate
22454 @kindex maint undeprecate
22455 @cindex deprecated commands
22456 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
22457 @itemx maint undeprecate @var{command}
22458 Deprecate or undeprecate the named @var{command}. Deprecated commands
22459 cause @value{GDBN} to issue a warning when you use them. The optional
22460 argument @var{replacement} says which newer command should be used in
22461 favor of the deprecated one; if it is given, @value{GDBN} will mention
22462 the replacement as part of the warning.
22464 @kindex maint dump-me
22465 @item maint dump-me
22466 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
22467 Cause a fatal signal in the debugger and force it to dump its core.
22468 This is supported only on systems which support aborting a program
22469 with the @code{SIGQUIT} signal.
22471 @kindex maint internal-error
22472 @kindex maint internal-warning
22473 @item maint internal-error @r{[}@var{message-text}@r{]}
22474 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
22475 Cause @value{GDBN} to call the internal function @code{internal_error}
22476 or @code{internal_warning} and hence behave as though an internal error
22477 or internal warning has been detected. In addition to reporting the
22478 internal problem, these functions give the user the opportunity to
22479 either quit @value{GDBN} or create a core file of the current
22480 @value{GDBN} session.
22482 These commands take an optional parameter @var{message-text} that is
22483 used as the text of the error or warning message.
22485 Here's an example of using @code{indernal-error}:
22488 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
22489 @dots{}/maint.c:121: internal-error: testing, 1, 2
22490 A problem internal to GDB has been detected. Further
22491 debugging may prove unreliable.
22492 Quit this debugging session? (y or n) @kbd{n}
22493 Create a core file? (y or n) @kbd{n}
22497 @kindex maint packet
22498 @item maint packet @var{text}
22499 If @value{GDBN} is talking to an inferior via the serial protocol,
22500 then this command sends the string @var{text} to the inferior, and
22501 displays the response packet. @value{GDBN} supplies the initial
22502 @samp{$} character, the terminating @samp{#} character, and the
22505 @kindex maint print architecture
22506 @item maint print architecture @r{[}@var{file}@r{]}
22507 Print the entire architecture configuration. The optional argument
22508 @var{file} names the file where the output goes.
22510 @kindex maint print dummy-frames
22511 @item maint print dummy-frames
22512 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
22515 (@value{GDBP}) @kbd{b add}
22517 (@value{GDBP}) @kbd{print add(2,3)}
22518 Breakpoint 2, add (a=2, b=3) at @dots{}
22520 The program being debugged stopped while in a function called from GDB.
22522 (@value{GDBP}) @kbd{maint print dummy-frames}
22523 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
22524 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
22525 call_lo=0x01014000 call_hi=0x01014001
22529 Takes an optional file parameter.
22531 @kindex maint print registers
22532 @kindex maint print raw-registers
22533 @kindex maint print cooked-registers
22534 @kindex maint print register-groups
22535 @item maint print registers @r{[}@var{file}@r{]}
22536 @itemx maint print raw-registers @r{[}@var{file}@r{]}
22537 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
22538 @itemx maint print register-groups @r{[}@var{file}@r{]}
22539 Print @value{GDBN}'s internal register data structures.
22541 The command @code{maint print raw-registers} includes the contents of
22542 the raw register cache; the command @code{maint print cooked-registers}
22543 includes the (cooked) value of all registers; and the command
22544 @code{maint print register-groups} includes the groups that each
22545 register is a member of. @xref{Registers,, Registers, gdbint,
22546 @value{GDBN} Internals}.
22548 These commands take an optional parameter, a file name to which to
22549 write the information.
22551 @kindex maint print reggroups
22552 @item maint print reggroups @r{[}@var{file}@r{]}
22553 Print @value{GDBN}'s internal register group data structures. The
22554 optional argument @var{file} tells to what file to write the
22557 The register groups info looks like this:
22560 (@value{GDBP}) @kbd{maint print reggroups}
22573 This command forces @value{GDBN} to flush its internal register cache.
22575 @kindex maint print objfiles
22576 @cindex info for known object files
22577 @item maint print objfiles
22578 Print a dump of all known object files. For each object file, this
22579 command prints its name, address in memory, and all of its psymtabs
22582 @kindex maint print statistics
22583 @cindex bcache statistics
22584 @item maint print statistics
22585 This command prints, for each object file in the program, various data
22586 about that object file followed by the byte cache (@dfn{bcache})
22587 statistics for the object file. The objfile data includes the number
22588 of minimal, partical, full, and stabs symbols, the number of types
22589 defined by the objfile, the number of as yet unexpanded psym tables,
22590 the number of line tables and string tables, and the amount of memory
22591 used by the various tables. The bcache statistics include the counts,
22592 sizes, and counts of duplicates of all and unique objects, max,
22593 average, and median entry size, total memory used and its overhead and
22594 savings, and various measures of the hash table size and chain
22597 @kindex maint print type
22598 @cindex type chain of a data type
22599 @item maint print type @var{expr}
22600 Print the type chain for a type specified by @var{expr}. The argument
22601 can be either a type name or a symbol. If it is a symbol, the type of
22602 that symbol is described. The type chain produced by this command is
22603 a recursive definition of the data type as stored in @value{GDBN}'s
22604 data structures, including its flags and contained types.
22606 @kindex maint set dwarf2 max-cache-age
22607 @kindex maint show dwarf2 max-cache-age
22608 @item maint set dwarf2 max-cache-age
22609 @itemx maint show dwarf2 max-cache-age
22610 Control the DWARF 2 compilation unit cache.
22612 @cindex DWARF 2 compilation units cache
22613 In object files with inter-compilation-unit references, such as those
22614 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
22615 reader needs to frequently refer to previously read compilation units.
22616 This setting controls how long a compilation unit will remain in the
22617 cache if it is not referenced. A higher limit means that cached
22618 compilation units will be stored in memory longer, and more total
22619 memory will be used. Setting it to zero disables caching, which will
22620 slow down @value{GDBN} startup, but reduce memory consumption.
22622 @kindex maint set profile
22623 @kindex maint show profile
22624 @cindex profiling GDB
22625 @item maint set profile
22626 @itemx maint show profile
22627 Control profiling of @value{GDBN}.
22629 Profiling will be disabled until you use the @samp{maint set profile}
22630 command to enable it. When you enable profiling, the system will begin
22631 collecting timing and execution count data; when you disable profiling or
22632 exit @value{GDBN}, the results will be written to a log file. Remember that
22633 if you use profiling, @value{GDBN} will overwrite the profiling log file
22634 (often called @file{gmon.out}). If you have a record of important profiling
22635 data in a @file{gmon.out} file, be sure to move it to a safe location.
22637 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
22638 compiled with the @samp{-pg} compiler option.
22640 @kindex maint show-debug-regs
22641 @cindex x86 hardware debug registers
22642 @item maint show-debug-regs
22643 Control whether to show variables that mirror the x86 hardware debug
22644 registers. Use @code{ON} to enable, @code{OFF} to disable. If
22645 enabled, the debug registers values are shown when GDB inserts or
22646 removes a hardware breakpoint or watchpoint, and when the inferior
22647 triggers a hardware-assisted breakpoint or watchpoint.
22649 @kindex maint space
22650 @cindex memory used by commands
22652 Control whether to display memory usage for each command. If set to a
22653 nonzero value, @value{GDBN} will display how much memory each command
22654 took, following the command's own output. This can also be requested
22655 by invoking @value{GDBN} with the @option{--statistics} command-line
22656 switch (@pxref{Mode Options}).
22659 @cindex time of command execution
22661 Control whether to display the execution time for each command. If
22662 set to a nonzero value, @value{GDBN} will display how much time it
22663 took to execute each command, following the command's own output.
22664 This can also be requested by invoking @value{GDBN} with the
22665 @option{--statistics} command-line switch (@pxref{Mode Options}).
22667 @kindex maint translate-address
22668 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
22669 Find the symbol stored at the location specified by the address
22670 @var{addr} and an optional section name @var{section}. If found,
22671 @value{GDBN} prints the name of the closest symbol and an offset from
22672 the symbol's location to the specified address. This is similar to
22673 the @code{info address} command (@pxref{Symbols}), except that this
22674 command also allows to find symbols in other sections.
22678 The following command is useful for non-interactive invocations of
22679 @value{GDBN}, such as in the test suite.
22682 @item set watchdog @var{nsec}
22683 @kindex set watchdog
22684 @cindex watchdog timer
22685 @cindex timeout for commands
22686 Set the maximum number of seconds @value{GDBN} will wait for the
22687 target operation to finish. If this time expires, @value{GDBN}
22688 reports and error and the command is aborted.
22690 @item show watchdog
22691 Show the current setting of the target wait timeout.
22694 @node Remote Protocol
22695 @appendix @value{GDBN} Remote Serial Protocol
22700 * Stop Reply Packets::
22701 * General Query Packets::
22702 * Register Packet Format::
22703 * Tracepoint Packets::
22706 * File-I/O remote protocol extension::
22707 * Memory map format::
22713 There may be occasions when you need to know something about the
22714 protocol---for example, if there is only one serial port to your target
22715 machine, you might want your program to do something special if it
22716 recognizes a packet meant for @value{GDBN}.
22718 In the examples below, @samp{->} and @samp{<-} are used to indicate
22719 transmitted and received data respectfully.
22721 @cindex protocol, @value{GDBN} remote serial
22722 @cindex serial protocol, @value{GDBN} remote
22723 @cindex remote serial protocol
22724 All @value{GDBN} commands and responses (other than acknowledgments) are
22725 sent as a @var{packet}. A @var{packet} is introduced with the character
22726 @samp{$}, the actual @var{packet-data}, and the terminating character
22727 @samp{#} followed by a two-digit @var{checksum}:
22730 @code{$}@var{packet-data}@code{#}@var{checksum}
22734 @cindex checksum, for @value{GDBN} remote
22736 The two-digit @var{checksum} is computed as the modulo 256 sum of all
22737 characters between the leading @samp{$} and the trailing @samp{#} (an
22738 eight bit unsigned checksum).
22740 Implementors should note that prior to @value{GDBN} 5.0 the protocol
22741 specification also included an optional two-digit @var{sequence-id}:
22744 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
22747 @cindex sequence-id, for @value{GDBN} remote
22749 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
22750 has never output @var{sequence-id}s. Stubs that handle packets added
22751 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
22753 @cindex acknowledgment, for @value{GDBN} remote
22754 When either the host or the target machine receives a packet, the first
22755 response expected is an acknowledgment: either @samp{+} (to indicate
22756 the package was received correctly) or @samp{-} (to request
22760 -> @code{$}@var{packet-data}@code{#}@var{checksum}
22765 The host (@value{GDBN}) sends @var{command}s, and the target (the
22766 debugging stub incorporated in your program) sends a @var{response}. In
22767 the case of step and continue @var{command}s, the response is only sent
22768 when the operation has completed (the target has again stopped).
22770 @var{packet-data} consists of a sequence of characters with the
22771 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
22774 @cindex remote protocol, field separator
22775 Fields within the packet should be separated using @samp{,} @samp{;} or
22776 @samp{:}. Except where otherwise noted all numbers are represented in
22777 @sc{hex} with leading zeros suppressed.
22779 Implementors should note that prior to @value{GDBN} 5.0, the character
22780 @samp{:} could not appear as the third character in a packet (as it
22781 would potentially conflict with the @var{sequence-id}).
22783 @cindex remote protocol, binary data
22784 @anchor{Binary Data}
22785 Binary data in most packets is encoded either as two hexadecimal
22786 digits per byte of binary data. This allowed the traditional remote
22787 protocol to work over connections which were only seven-bit clean.
22788 Some packets designed more recently assume an eight-bit clean
22789 connection, and use a more efficient encoding to send and receive
22792 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
22793 as an escape character. Any escaped byte is transmitted as the escape
22794 character followed by the original character XORed with @code{0x20}.
22795 For example, the byte @code{0x7d} would be transmitted as the two
22796 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
22797 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
22798 @samp{@}}) must always be escaped. Responses sent by the stub
22799 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
22800 is not interpreted as the start of a run-length encoded sequence
22803 Response @var{data} can be run-length encoded to save space. A @samp{*}
22804 means that the next character is an @sc{ascii} encoding giving a repeat count
22805 which stands for that many repetitions of the character preceding the
22806 @samp{*}. The encoding is @code{n+29}, yielding a printable character
22807 where @code{n >=3} (which is where rle starts to win). The printable
22808 characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric
22809 value greater than 126 should not be used.
22816 means the same as "0000".
22818 The error response returned for some packets includes a two character
22819 error number. That number is not well defined.
22821 @cindex empty response, for unsupported packets
22822 For any @var{command} not supported by the stub, an empty response
22823 (@samp{$#00}) should be returned. That way it is possible to extend the
22824 protocol. A newer @value{GDBN} can tell if a packet is supported based
22827 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
22828 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
22834 The following table provides a complete list of all currently defined
22835 @var{command}s and their corresponding response @var{data}.
22836 @xref{File-I/O remote protocol extension}, for details about the File
22837 I/O extension of the remote protocol.
22839 Each packet's description has a template showing the packet's overall
22840 syntax, followed by an explanation of the packet's meaning. We
22841 include spaces in some of the templates for clarity; these are not
22842 part of the packet's syntax. No @value{GDBN} packet uses spaces to
22843 separate its components. For example, a template like @samp{foo
22844 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
22845 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
22846 @var{baz}. GDB does not transmit a space character between the
22847 @samp{foo} and the @var{bar}, or between the @var{bar} and the
22850 Note that all packet forms beginning with an upper- or lower-case
22851 letter, other than those described here, are reserved for future use.
22853 Here are the packet descriptions.
22858 @cindex @samp{!} packet
22859 Enable extended mode. In extended mode, the remote server is made
22860 persistent. The @samp{R} packet is used to restart the program being
22866 The remote target both supports and has enabled extended mode.
22870 @cindex @samp{?} packet
22871 Indicate the reason the target halted. The reply is the same as for
22875 @xref{Stop Reply Packets}, for the reply specifications.
22877 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
22878 @cindex @samp{A} packet
22879 Initialized @code{argv[]} array passed into program. @var{arglen}
22880 specifies the number of bytes in the hex encoded byte stream
22881 @var{arg}. See @code{gdbserver} for more details.
22886 The arguments were set.
22892 @cindex @samp{b} packet
22893 (Don't use this packet; its behavior is not well-defined.)
22894 Change the serial line speed to @var{baud}.
22896 JTC: @emph{When does the transport layer state change? When it's
22897 received, or after the ACK is transmitted. In either case, there are
22898 problems if the command or the acknowledgment packet is dropped.}
22900 Stan: @emph{If people really wanted to add something like this, and get
22901 it working for the first time, they ought to modify ser-unix.c to send
22902 some kind of out-of-band message to a specially-setup stub and have the
22903 switch happen "in between" packets, so that from remote protocol's point
22904 of view, nothing actually happened.}
22906 @item B @var{addr},@var{mode}
22907 @cindex @samp{B} packet
22908 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
22909 breakpoint at @var{addr}.
22911 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
22912 (@pxref{insert breakpoint or watchpoint packet}).
22914 @item c @r{[}@var{addr}@r{]}
22915 @cindex @samp{c} packet
22916 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
22917 resume at current address.
22920 @xref{Stop Reply Packets}, for the reply specifications.
22922 @item C @var{sig}@r{[};@var{addr}@r{]}
22923 @cindex @samp{C} packet
22924 Continue with signal @var{sig} (hex signal number). If
22925 @samp{;@var{addr}} is omitted, resume at same address.
22928 @xref{Stop Reply Packets}, for the reply specifications.
22931 @cindex @samp{d} packet
22934 Don't use this packet; instead, define a general set packet
22935 (@pxref{General Query Packets}).
22938 @cindex @samp{D} packet
22939 Detach @value{GDBN} from the remote system. Sent to the remote target
22940 before @value{GDBN} disconnects via the @code{detach} command.
22950 @item F @var{RC},@var{EE},@var{CF};@var{XX}
22951 @cindex @samp{F} packet
22952 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
22953 This is part of the File-I/O protocol extension. @xref{File-I/O
22954 remote protocol extension}, for the specification.
22957 @anchor{read registers packet}
22958 @cindex @samp{g} packet
22959 Read general registers.
22963 @item @var{XX@dots{}}
22964 Each byte of register data is described by two hex digits. The bytes
22965 with the register are transmitted in target byte order. The size of
22966 each register and their position within the @samp{g} packet are
22967 determined by the @value{GDBN} internal macros
22968 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{REGISTER_NAME} macros. The
22969 specification of several standard @samp{g} packets is specified below.
22974 @item G @var{XX@dots{}}
22975 @cindex @samp{G} packet
22976 Write general registers. @xref{read registers packet}, for a
22977 description of the @var{XX@dots{}} data.
22987 @item H @var{c} @var{t}
22988 @cindex @samp{H} packet
22989 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
22990 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
22991 should be @samp{c} for step and continue operations, @samp{g} for other
22992 operations. The thread designator @var{t} may be @samp{-1}, meaning all
22993 the threads, a thread number, or @samp{0} which means pick any thread.
23004 @c 'H': How restrictive (or permissive) is the thread model. If a
23005 @c thread is selected and stopped, are other threads allowed
23006 @c to continue to execute? As I mentioned above, I think the
23007 @c semantics of each command when a thread is selected must be
23008 @c described. For example:
23010 @c 'g': If the stub supports threads and a specific thread is
23011 @c selected, returns the register block from that thread;
23012 @c otherwise returns current registers.
23014 @c 'G' If the stub supports threads and a specific thread is
23015 @c selected, sets the registers of the register block of
23016 @c that thread; otherwise sets current registers.
23018 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
23019 @anchor{cycle step packet}
23020 @cindex @samp{i} packet
23021 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
23022 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
23023 step starting at that address.
23026 @cindex @samp{I} packet
23027 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
23031 @cindex @samp{k} packet
23034 FIXME: @emph{There is no description of how to operate when a specific
23035 thread context has been selected (i.e.@: does 'k' kill only that
23038 @item m @var{addr},@var{length}
23039 @cindex @samp{m} packet
23040 Read @var{length} bytes of memory starting at address @var{addr}.
23041 Note that @var{addr} may not be aligned to any particular boundary.
23043 The stub need not use any particular size or alignment when gathering
23044 data from memory for the response; even if @var{addr} is word-aligned
23045 and @var{length} is a multiple of the word size, the stub is free to
23046 use byte accesses, or not. For this reason, this packet may not be
23047 suitable for accessing memory-mapped I/O devices.
23048 @cindex alignment of remote memory accesses
23049 @cindex size of remote memory accesses
23050 @cindex memory, alignment and size of remote accesses
23054 @item @var{XX@dots{}}
23055 Memory contents; each byte is transmitted as a two-digit hexadecimal
23056 number. The reply may contain fewer bytes than requested if the
23057 server was able to read only part of the region of memory.
23062 @item M @var{addr},@var{length}:@var{XX@dots{}}
23063 @cindex @samp{M} packet
23064 Write @var{length} bytes of memory starting at address @var{addr}.
23065 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
23066 hexadecimal number.
23073 for an error (this includes the case where only part of the data was
23078 @cindex @samp{p} packet
23079 Read the value of register @var{n}; @var{n} is in hex.
23080 @xref{read registers packet}, for a description of how the returned
23081 register value is encoded.
23085 @item @var{XX@dots{}}
23086 the register's value
23090 Indicating an unrecognized @var{query}.
23093 @item P @var{n@dots{}}=@var{r@dots{}}
23094 @anchor{write register packet}
23095 @cindex @samp{P} packet
23096 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
23097 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
23098 digits for each byte in the register (target byte order).
23108 @item q @var{name} @var{params}@dots{}
23109 @itemx Q @var{name} @var{params}@dots{}
23110 @cindex @samp{q} packet
23111 @cindex @samp{Q} packet
23112 General query (@samp{q}) and set (@samp{Q}). These packets are
23113 described fully in @ref{General Query Packets}.
23116 @cindex @samp{r} packet
23117 Reset the entire system.
23119 Don't use this packet; use the @samp{R} packet instead.
23122 @cindex @samp{R} packet
23123 Restart the program being debugged. @var{XX}, while needed, is ignored.
23124 This packet is only available in extended mode.
23126 The @samp{R} packet has no reply.
23128 @item s @r{[}@var{addr}@r{]}
23129 @cindex @samp{s} packet
23130 Single step. @var{addr} is the address at which to resume. If
23131 @var{addr} is omitted, resume at same address.
23134 @xref{Stop Reply Packets}, for the reply specifications.
23136 @item S @var{sig}@r{[};@var{addr}@r{]}
23137 @anchor{step with signal packet}
23138 @cindex @samp{S} packet
23139 Step with signal. This is analogous to the @samp{C} packet, but
23140 requests a single-step, rather than a normal resumption of execution.
23143 @xref{Stop Reply Packets}, for the reply specifications.
23145 @item t @var{addr}:@var{PP},@var{MM}
23146 @cindex @samp{t} packet
23147 Search backwards starting at address @var{addr} for a match with pattern
23148 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
23149 @var{addr} must be at least 3 digits.
23152 @cindex @samp{T} packet
23153 Find out if the thread XX is alive.
23158 thread is still alive
23164 Packets starting with @samp{v} are identified by a multi-letter name,
23165 up to the first @samp{;} or @samp{?} (or the end of the packet).
23167 @item vCont@r{[};@var{action}@r{[}:@var{tid}@r{]]}@dots{}
23168 @cindex @samp{vCont} packet
23169 Resume the inferior, specifying different actions for each thread.
23170 If an action is specified with no @var{tid}, then it is applied to any
23171 threads that don't have a specific action specified; if no default action is
23172 specified then other threads should remain stopped. Specifying multiple
23173 default actions is an error; specifying no actions is also an error.
23174 Thread IDs are specified in hexadecimal. Currently supported actions are:
23180 Continue with signal @var{sig}. @var{sig} should be two hex digits.
23184 Step with signal @var{sig}. @var{sig} should be two hex digits.
23187 The optional @var{addr} argument normally associated with these packets is
23188 not supported in @samp{vCont}.
23191 @xref{Stop Reply Packets}, for the reply specifications.
23194 @cindex @samp{vCont?} packet
23195 Request a list of actions supporetd by the @samp{vCont} packet.
23199 @item vCont@r{[};@var{action}@dots{}@r{]}
23200 The @samp{vCont} packet is supported. Each @var{action} is a supported
23201 command in the @samp{vCont} packet.
23203 The @samp{vCont} packet is not supported.
23206 @item vFlashErase:@var{addr},@var{length}
23207 @cindex @samp{vFlashErase} packet
23208 Direct the stub to erase @var{length} bytes of flash starting at
23209 @var{addr}. The region may enclose any number of flash blocks, but
23210 its start and end must fall on block boundaries, as indicated by the
23211 flash block size appearing in the memory map (@pxref{Memory map
23212 format}). @value{GDBN} groups flash memory programming operations
23213 together, and sends a @samp{vFlashDone} request after each group; the
23214 stub is allowed to delay erase operation until the @samp{vFlashDone}
23215 packet is received.
23225 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
23226 @cindex @samp{vFlashWrite} packet
23227 Direct the stub to write data to flash address @var{addr}. The data
23228 is passed in binary form using the same encoding as for the @samp{X}
23229 packet (@pxref{Binary Data}). The memory ranges specified by
23230 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
23231 not overlap, and must appear in order of increasing addresses
23232 (although @samp{vFlashErase} packets for higher addresses may already
23233 have been received; the ordering is guaranteed only between
23234 @samp{vFlashWrite} packets). If a packet writes to an address that was
23235 neither erased by a preceding @samp{vFlashErase} packet nor by some other
23236 target-specific method, the results are unpredictable.
23244 for vFlashWrite addressing non-flash memory
23250 @cindex @samp{vFlashDone} packet
23251 Indicate to the stub that flash programming operation is finished.
23252 The stub is permitted to delay or batch the effects of a group of
23253 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
23254 @samp{vFlashDone} packet is received. The contents of the affected
23255 regions of flash memory are unpredictable until the @samp{vFlashDone}
23256 request is completed.
23258 @item X @var{addr},@var{length}:@var{XX@dots{}}
23260 @cindex @samp{X} packet
23261 Write data to memory, where the data is transmitted in binary.
23262 @var{addr} is address, @var{length} is number of bytes,
23263 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
23273 @item z @var{type},@var{addr},@var{length}
23274 @itemx Z @var{type},@var{addr},@var{length}
23275 @anchor{insert breakpoint or watchpoint packet}
23276 @cindex @samp{z} packet
23277 @cindex @samp{Z} packets
23278 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
23279 watchpoint starting at address @var{address} and covering the next
23280 @var{length} bytes.
23282 Each breakpoint and watchpoint packet @var{type} is documented
23285 @emph{Implementation notes: A remote target shall return an empty string
23286 for an unrecognized breakpoint or watchpoint packet @var{type}. A
23287 remote target shall support either both or neither of a given
23288 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
23289 avoid potential problems with duplicate packets, the operations should
23290 be implemented in an idempotent way.}
23292 @item z0,@var{addr},@var{length}
23293 @itemx Z0,@var{addr},@var{length}
23294 @cindex @samp{z0} packet
23295 @cindex @samp{Z0} packet
23296 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
23297 @var{addr} of size @var{length}.
23299 A memory breakpoint is implemented by replacing the instruction at
23300 @var{addr} with a software breakpoint or trap instruction. The
23301 @var{length} is used by targets that indicates the size of the
23302 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
23303 @sc{mips} can insert either a 2 or 4 byte breakpoint).
23305 @emph{Implementation note: It is possible for a target to copy or move
23306 code that contains memory breakpoints (e.g., when implementing
23307 overlays). The behavior of this packet, in the presence of such a
23308 target, is not defined.}
23320 @item z1,@var{addr},@var{length}
23321 @itemx Z1,@var{addr},@var{length}
23322 @cindex @samp{z1} packet
23323 @cindex @samp{Z1} packet
23324 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
23325 address @var{addr} of size @var{length}.
23327 A hardware breakpoint is implemented using a mechanism that is not
23328 dependant on being able to modify the target's memory.
23330 @emph{Implementation note: A hardware breakpoint is not affected by code
23343 @item z2,@var{addr},@var{length}
23344 @itemx Z2,@var{addr},@var{length}
23345 @cindex @samp{z2} packet
23346 @cindex @samp{Z2} packet
23347 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint.
23359 @item z3,@var{addr},@var{length}
23360 @itemx Z3,@var{addr},@var{length}
23361 @cindex @samp{z3} packet
23362 @cindex @samp{Z3} packet
23363 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint.
23375 @item z4,@var{addr},@var{length}
23376 @itemx Z4,@var{addr},@var{length}
23377 @cindex @samp{z4} packet
23378 @cindex @samp{Z4} packet
23379 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint.
23393 @node Stop Reply Packets
23394 @section Stop Reply Packets
23395 @cindex stop reply packets
23397 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
23398 receive any of the below as a reply. In the case of the @samp{C},
23399 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
23400 when the target halts. In the below the exact meaning of @dfn{signal
23401 number} is defined by the header @file{include/gdb/signals.h} in the
23402 @value{GDBN} source code.
23404 As in the description of request packets, we include spaces in the
23405 reply templates for clarity; these are not part of the reply packet's
23406 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
23412 The program received signal number @var{AA} (a two-digit hexadecimal
23413 number). This is equivalent to a @samp{T} response with no
23414 @var{n}:@var{r} pairs.
23416 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
23417 @cindex @samp{T} packet reply
23418 The program received signal number @var{AA} (a two-digit hexadecimal
23419 number). This is equivalent to an @samp{S} response, except that the
23420 @samp{@var{n}:@var{r}} pairs can carry values of important registers
23421 and other information directly in the stop reply packet, reducing
23422 round-trip latency. Single-step and breakpoint traps are reported
23423 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
23426 If @var{n} is a hexadecimal number, it is a register number, and the
23427 corresponding @var{r} gives that register's value. @var{r} is a
23428 series of bytes in target byte order, with each byte given by a
23429 two-digit hex number.
23431 If @var{n} is @samp{thread}, then @var{r} is the thread process ID, in
23434 If @var{n} is @samp{watch}, @samp{rwatch}, or @samp{awatch}, then the
23435 packet indicates a watchpoint hit, and @var{r} is the data address, in
23438 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
23439 and go on to the next; this allows us to extend the protocol in the
23444 The process exited, and @var{AA} is the exit status. This is only
23445 applicable to certain targets.
23448 The process terminated with signal @var{AA}.
23450 @item O @var{XX}@dots{}
23451 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
23452 written as the program's console output. This can happen at any time
23453 while the program is running and the debugger should continue to wait
23454 for @samp{W}, @samp{T}, etc.
23456 @item F @var{call-id},@var{parameter}@dots{}
23457 @var{call-id} is the identifier which says which host system call should
23458 be called. This is just the name of the function. Translation into the
23459 correct system call is only applicable as it's defined in @value{GDBN}.
23460 @xref{File-I/O remote protocol extension}, for a list of implemented
23463 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
23464 this very system call.
23466 The target replies with this packet when it expects @value{GDBN} to
23467 call a host system call on behalf of the target. @value{GDBN} replies
23468 with an appropriate @samp{F} packet and keeps up waiting for the next
23469 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
23470 or @samp{s} action is expected to be continued. @xref{File-I/O remote
23471 protocol extension}, for more details.
23475 @node General Query Packets
23476 @section General Query Packets
23477 @cindex remote query requests
23479 Packets starting with @samp{q} are @dfn{general query packets};
23480 packets starting with @samp{Q} are @dfn{general set packets}. General
23481 query and set packets are a semi-unified form for retrieving and
23482 sending information to and from the stub.
23484 The initial letter of a query or set packet is followed by a name
23485 indicating what sort of thing the packet applies to. For example,
23486 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
23487 definitions with the stub. These packet names follow some
23492 The name must not contain commas, colons or semicolons.
23494 Most @value{GDBN} query and set packets have a leading upper case
23497 The names of custom vendor packets should use a company prefix, in
23498 lower case, followed by a period. For example, packets designed at
23499 the Acme Corporation might begin with @samp{qacme.foo} (for querying
23500 foos) or @samp{Qacme.bar} (for setting bars).
23503 The name of a query or set packet should be separated from any
23504 parameters by a @samp{:}; the parameters themselves should be
23505 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
23506 full packet name, and check for a separator or the end of the packet,
23507 in case two packet names share a common prefix. New packets should not begin
23508 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
23509 packets predate these conventions, and have arguments without any terminator
23510 for the packet name; we suspect they are in widespread use in places that
23511 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
23512 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
23515 Like the descriptions of the other packets, each description here
23516 has a template showing the packet's overall syntax, followed by an
23517 explanation of the packet's meaning. We include spaces in some of the
23518 templates for clarity; these are not part of the packet's syntax. No
23519 @value{GDBN} packet uses spaces to separate its components.
23521 Here are the currently defined query and set packets:
23526 @cindex current thread, remote request
23527 @cindex @samp{qC} packet
23528 Return the current thread id.
23533 Where @var{pid} is an unsigned hexadecimal process id.
23534 @item @r{(anything else)}
23535 Any other reply implies the old pid.
23538 @item qCRC:@var{addr},@var{length}
23539 @cindex CRC of memory block, remote request
23540 @cindex @samp{qCRC} packet
23541 Compute the CRC checksum of a block of memory.
23545 An error (such as memory fault)
23546 @item C @var{crc32}
23547 The specified memory region's checksum is @var{crc32}.
23551 @itemx qsThreadInfo
23552 @cindex list active threads, remote request
23553 @cindex @samp{qfThreadInfo} packet
23554 @cindex @samp{qsThreadInfo} packet
23555 Obtain a list of all active thread ids from the target (OS). Since there
23556 may be too many active threads to fit into one reply packet, this query
23557 works iteratively: it may require more than one query/reply sequence to
23558 obtain the entire list of threads. The first query of the sequence will
23559 be the @samp{qfThreadInfo} query; subsequent queries in the
23560 sequence will be the @samp{qsThreadInfo} query.
23562 NOTE: This packet replaces the @samp{qL} query (see below).
23568 @item m @var{id},@var{id}@dots{}
23569 a comma-separated list of thread ids
23571 (lower case letter @samp{L}) denotes end of list.
23574 In response to each query, the target will reply with a list of one or
23575 more thread ids, in big-endian unsigned hex, separated by commas.
23576 @value{GDBN} will respond to each reply with a request for more thread
23577 ids (using the @samp{qs} form of the query), until the target responds
23578 with @samp{l} (lower-case el, for @dfn{last}).
23580 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
23581 @cindex get thread-local storage address, remote request
23582 @cindex @samp{qGetTLSAddr} packet
23583 Fetch the address associated with thread local storage specified
23584 by @var{thread-id}, @var{offset}, and @var{lm}.
23586 @var{thread-id} is the (big endian, hex encoded) thread id associated with the
23587 thread for which to fetch the TLS address.
23589 @var{offset} is the (big endian, hex encoded) offset associated with the
23590 thread local variable. (This offset is obtained from the debug
23591 information associated with the variable.)
23593 @var{lm} is the (big endian, hex encoded) OS/ABI specific encoding of the
23594 the load module associated with the thread local storage. For example,
23595 a @sc{gnu}/Linux system will pass the link map address of the shared
23596 object associated with the thread local storage under consideration.
23597 Other operating environments may choose to represent the load module
23598 differently, so the precise meaning of this parameter will vary.
23602 @item @var{XX}@dots{}
23603 Hex encoded (big endian) bytes representing the address of the thread
23604 local storage requested.
23607 An error occurred. @var{nn} are hex digits.
23610 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
23613 @item qL @var{startflag} @var{threadcount} @var{nextthread}
23614 Obtain thread information from RTOS. Where: @var{startflag} (one hex
23615 digit) is one to indicate the first query and zero to indicate a
23616 subsequent query; @var{threadcount} (two hex digits) is the maximum
23617 number of threads the response packet can contain; and @var{nextthread}
23618 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
23619 returned in the response as @var{argthread}.
23621 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
23625 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
23626 Where: @var{count} (two hex digits) is the number of threads being
23627 returned; @var{done} (one hex digit) is zero to indicate more threads
23628 and one indicates no further threads; @var{argthreadid} (eight hex
23629 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
23630 is a sequence of thread IDs from the target. @var{threadid} (eight hex
23631 digits). See @code{remote.c:parse_threadlist_response()}.
23635 @cindex section offsets, remote request
23636 @cindex @samp{qOffsets} packet
23637 Get section offsets that the target used when re-locating the downloaded
23638 image. @emph{Note: while a @code{Bss} offset is included in the
23639 response, @value{GDBN} ignores this and instead applies the @code{Data}
23640 offset to the @code{Bss} section.}
23644 @item Text=@var{xxx};Data=@var{yyy};Bss=@var{zzz}
23647 @item qP @var{mode} @var{threadid}
23648 @cindex thread information, remote request
23649 @cindex @samp{qP} packet
23650 Returns information on @var{threadid}. Where: @var{mode} is a hex
23651 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
23653 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
23656 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
23658 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
23659 @cindex pass signals to inferior, remote request
23660 @cindex @samp{QPassSignals} packet
23661 Each listed @var{signal} should be passed directly to the inferior process.
23662 Signals are numbered identically to continue packets and stop replies
23663 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
23664 strictly greater than the previous item. These signals do not need to stop
23665 the inferior, or be reported to @value{GDBN}. All other signals should be
23666 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
23667 combine; any earlier @samp{QPassSignals} list is completely replaced by the
23668 new list. This packet improves performance when using @samp{handle
23669 @var{signal} nostop noprint pass}.
23674 The request succeeded.
23677 An error occurred. @var{nn} are hex digits.
23680 An empty reply indicates that @samp{QPassSignals} is not supported by
23684 Use of this packet is controlled by the @code{set remote pass-signals}
23685 command (@pxref{Remote configuration, set remote pass-signals}).
23686 This packet is not probed by default; the remote stub must request it,
23687 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
23689 @item qRcmd,@var{command}
23690 @cindex execute remote command, remote request
23691 @cindex @samp{qRcmd} packet
23692 @var{command} (hex encoded) is passed to the local interpreter for
23693 execution. Invalid commands should be reported using the output
23694 string. Before the final result packet, the target may also respond
23695 with a number of intermediate @samp{O@var{output}} console output
23696 packets. @emph{Implementors should note that providing access to a
23697 stubs's interpreter may have security implications}.
23702 A command response with no output.
23704 A command response with the hex encoded output string @var{OUTPUT}.
23706 Indicate a badly formed request.
23708 An empty reply indicates that @samp{qRcmd} is not recognized.
23711 (Note that the @code{qRcmd} packet's name is separated from the
23712 command by a @samp{,}, not a @samp{:}, contrary to the naming
23713 conventions above. Please don't use this packet as a model for new
23716 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
23717 @cindex supported packets, remote query
23718 @cindex features of the remote protocol
23719 @cindex @samp{qSupported} packet
23720 @anchor{qSupported}
23721 Tell the remote stub about features supported by @value{GDBN}, and
23722 query the stub for features it supports. This packet allows
23723 @value{GDBN} and the remote stub to take advantage of each others'
23724 features. @samp{qSupported} also consolidates multiple feature probes
23725 at startup, to improve @value{GDBN} performance---a single larger
23726 packet performs better than multiple smaller probe packets on
23727 high-latency links. Some features may enable behavior which must not
23728 be on by default, e.g.@: because it would confuse older clients or
23729 stubs. Other features may describe packets which could be
23730 automatically probed for, but are not. These features must be
23731 reported before @value{GDBN} will use them. This ``default
23732 unsupported'' behavior is not appropriate for all packets, but it
23733 helps to keep the initial connection time under control with new
23734 versions of @value{GDBN} which support increasing numbers of packets.
23738 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
23739 The stub supports or does not support each returned @var{stubfeature},
23740 depending on the form of each @var{stubfeature} (see below for the
23743 An empty reply indicates that @samp{qSupported} is not recognized,
23744 or that no features needed to be reported to @value{GDBN}.
23747 The allowed forms for each feature (either a @var{gdbfeature} in the
23748 @samp{qSupported} packet, or a @var{stubfeature} in the response)
23752 @item @var{name}=@var{value}
23753 The remote protocol feature @var{name} is supported, and associated
23754 with the specified @var{value}. The format of @var{value} depends
23755 on the feature, but it must not include a semicolon.
23757 The remote protocol feature @var{name} is supported, and does not
23758 need an associated value.
23760 The remote protocol feature @var{name} is not supported.
23762 The remote protocol feature @var{name} may be supported, and
23763 @value{GDBN} should auto-detect support in some other way when it is
23764 needed. This form will not be used for @var{gdbfeature} notifications,
23765 but may be used for @var{stubfeature} responses.
23768 Whenever the stub receives a @samp{qSupported} request, the
23769 supplied set of @value{GDBN} features should override any previous
23770 request. This allows @value{GDBN} to put the stub in a known
23771 state, even if the stub had previously been communicating with
23772 a different version of @value{GDBN}.
23774 No values of @var{gdbfeature} (for the packet sent by @value{GDBN})
23775 are defined yet. Stubs should ignore any unknown values for
23776 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
23777 packet supports receiving packets of unlimited length (earlier
23778 versions of @value{GDBN} may reject overly long responses). Values
23779 for @var{gdbfeature} may be defined in the future to let the stub take
23780 advantage of new features in @value{GDBN}, e.g.@: incompatible
23781 improvements in the remote protocol---support for unlimited length
23782 responses would be a @var{gdbfeature} example, if it were not implied by
23783 the @samp{qSupported} query. The stub's reply should be independent
23784 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
23785 describes all the features it supports, and then the stub replies with
23786 all the features it supports.
23788 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
23789 responses, as long as each response uses one of the standard forms.
23791 Some features are flags. A stub which supports a flag feature
23792 should respond with a @samp{+} form response. Other features
23793 require values, and the stub should respond with an @samp{=}
23796 Each feature has a default value, which @value{GDBN} will use if
23797 @samp{qSupported} is not available or if the feature is not mentioned
23798 in the @samp{qSupported} response. The default values are fixed; a
23799 stub is free to omit any feature responses that match the defaults.
23801 Not all features can be probed, but for those which can, the probing
23802 mechanism is useful: in some cases, a stub's internal
23803 architecture may not allow the protocol layer to know some information
23804 about the underlying target in advance. This is especially common in
23805 stubs which may be configured for multiple targets.
23807 These are the currently defined stub features and their properties:
23809 @multitable @columnfractions 0.25 0.2 0.2 0.2
23810 @c NOTE: The first row should be @headitem, but we do not yet require
23811 @c a new enough version of Texinfo (4.7) to use @headitem.
23813 @tab Value Required
23817 @item @samp{PacketSize}
23822 @item @samp{qXfer:auxv:read}
23827 @item @samp{qXfer:memory-map:read}
23832 @item @samp{QPassSignals}
23839 These are the currently defined stub features, in more detail:
23842 @cindex packet size, remote protocol
23843 @item PacketSize=@var{bytes}
23844 The remote stub can accept packets up to at least @var{bytes} in
23845 length. @value{GDBN} will send packets up to this size for bulk
23846 transfers, and will never send larger packets. This is a limit on the
23847 data characters in the packet, including the frame and checksum.
23848 There is no trailing NUL byte in a remote protocol packet; if the stub
23849 stores packets in a NUL-terminated format, it should allow an extra
23850 byte in its buffer for the NUL. If this stub feature is not supported,
23851 @value{GDBN} guesses based on the size of the @samp{g} packet response.
23853 @item qXfer:auxv:read
23854 The remote stub understands the @samp{qXfer:auxv:read} packet
23855 (@pxref{qXfer auxiliary vector read}).
23860 @cindex symbol lookup, remote request
23861 @cindex @samp{qSymbol} packet
23862 Notify the target that @value{GDBN} is prepared to serve symbol lookup
23863 requests. Accept requests from the target for the values of symbols.
23868 The target does not need to look up any (more) symbols.
23869 @item qSymbol:@var{sym_name}
23870 The target requests the value of symbol @var{sym_name} (hex encoded).
23871 @value{GDBN} may provide the value by using the
23872 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
23876 @item qSymbol:@var{sym_value}:@var{sym_name}
23877 Set the value of @var{sym_name} to @var{sym_value}.
23879 @var{sym_name} (hex encoded) is the name of a symbol whose value the
23880 target has previously requested.
23882 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
23883 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
23889 The target does not need to look up any (more) symbols.
23890 @item qSymbol:@var{sym_name}
23891 The target requests the value of a new symbol @var{sym_name} (hex
23892 encoded). @value{GDBN} will continue to supply the values of symbols
23893 (if available), until the target ceases to request them.
23898 @xref{Tracepoint Packets}.
23900 @item qThreadExtraInfo,@var{id}
23901 @cindex thread attributes info, remote request
23902 @cindex @samp{qThreadExtraInfo} packet
23903 Obtain a printable string description of a thread's attributes from
23904 the target OS. @var{id} is a thread-id in big-endian hex. This
23905 string may contain anything that the target OS thinks is interesting
23906 for @value{GDBN} to tell the user about the thread. The string is
23907 displayed in @value{GDBN}'s @code{info threads} display. Some
23908 examples of possible thread extra info strings are @samp{Runnable}, or
23909 @samp{Blocked on Mutex}.
23913 @item @var{XX}@dots{}
23914 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
23915 comprising the printable string containing the extra information about
23916 the thread's attributes.
23919 (Note that the @code{qThreadExtraInfo} packet's name is separated from
23920 the command by a @samp{,}, not a @samp{:}, contrary to the naming
23921 conventions above. Please don't use this packet as a model for new
23929 @xref{Tracepoint Packets}.
23931 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
23932 @cindex read special object, remote request
23933 @cindex @samp{qXfer} packet
23934 @anchor{qXfer read}
23935 Read uninterpreted bytes from the target's special data area
23936 identified by the keyword @var{object}. Request @var{length} bytes
23937 starting at @var{offset} bytes into the data. The content and
23938 encoding of @var{annex} is specific to the object; it can supply
23939 additional details about what data to access.
23941 Here are the specific requests of this form defined so far. All
23942 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
23943 formats, listed below.
23946 @item qXfer:auxv:read::@var{offset},@var{length}
23947 @anchor{qXfer auxiliary vector read}
23948 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
23949 auxiliary vector}. Note @var{annex} must be empty.
23951 This packet is not probed by default; the remote stub must request it,
23952 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
23956 @item qXfer:memory-map:read::@var{offset},@var{length}
23957 @anchor{qXfer memory map read}
23958 Access the target's @dfn{memory-map}. @xref{Memory map format}. The
23959 annex part of the generic @samp{qXfer} packet must be empty
23960 (@pxref{qXfer read}).
23962 This packet is not probed by default; the remote stub must request it,
23963 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
23969 Data @var{data} (@pxref{Binary Data}) has been read from the
23970 target. There may be more data at a higher address (although
23971 it is permitted to return @samp{m} even for the last valid
23972 block of data, as long as at least one byte of data was read).
23973 @var{data} may have fewer bytes than the @var{length} in the
23977 Data @var{data} (@pxref{Binary Data}) has been read from the target.
23978 There is no more data to be read. @var{data} may have fewer bytes
23979 than the @var{length} in the request.
23982 The @var{offset} in the request is at the end of the data.
23983 There is no more data to be read.
23986 The request was malformed, or @var{annex} was invalid.
23989 The offset was invalid, or there was an error encountered reading the data.
23990 @var{nn} is a hex-encoded @code{errno} value.
23993 An empty reply indicates the @var{object} string was not recognized by
23994 the stub, or that the object does not support reading.
23997 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
23998 @cindex write data into object, remote request
23999 Write uninterpreted bytes into the target's special data area
24000 identified by the keyword @var{object}, starting at @var{offset} bytes
24001 into the data. @samp{@var{data}@dots{}} is the binary-encoded data
24002 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
24003 is specific to the object; it can supply additional details about what data
24006 No requests of this form are presently in use. This specification
24007 serves as a placeholder to document the common format that new
24008 specific request specifications ought to use.
24013 @var{nn} (hex encoded) is the number of bytes written.
24014 This may be fewer bytes than supplied in the request.
24017 The request was malformed, or @var{annex} was invalid.
24020 The offset was invalid, or there was an error encountered writing the data.
24021 @var{nn} is a hex-encoded @code{errno} value.
24024 An empty reply indicates the @var{object} string was not
24025 recognized by the stub, or that the object does not support writing.
24028 @item qXfer:@var{object}:@var{operation}:@dots{}
24029 Requests of this form may be added in the future. When a stub does
24030 not recognize the @var{object} keyword, or its support for
24031 @var{object} does not recognize the @var{operation} keyword, the stub
24032 must respond with an empty packet.
24036 @node Register Packet Format
24037 @section Register Packet Format
24039 The following @code{g}/@code{G} packets have previously been defined.
24040 In the below, some thirty-two bit registers are transferred as
24041 sixty-four bits. Those registers should be zero/sign extended (which?)
24042 to fill the space allocated. Register bytes are transferred in target
24043 byte order. The two nibbles within a register byte are transferred
24044 most-significant - least-significant.
24050 All registers are transferred as thirty-two bit quantities in the order:
24051 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
24052 registers; fsr; fir; fp.
24056 All registers are transferred as sixty-four bit quantities (including
24057 thirty-two bit registers such as @code{sr}). The ordering is the same
24062 @node Tracepoint Packets
24063 @section Tracepoint Packets
24064 @cindex tracepoint packets
24065 @cindex packets, tracepoint
24067 Here we describe the packets @value{GDBN} uses to implement
24068 tracepoints (@pxref{Tracepoints}).
24072 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}@r{[}-@r{]}
24073 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
24074 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
24075 the tracepoint is disabled. @var{step} is the tracepoint's step
24076 count, and @var{pass} is its pass count. If the trailing @samp{-} is
24077 present, further @samp{QTDP} packets will follow to specify this
24078 tracepoint's actions.
24083 The packet was understood and carried out.
24085 The packet was not recognized.
24088 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
24089 Define actions to be taken when a tracepoint is hit. @var{n} and
24090 @var{addr} must be the same as in the initial @samp{QTDP} packet for
24091 this tracepoint. This packet may only be sent immediately after
24092 another @samp{QTDP} packet that ended with a @samp{-}. If the
24093 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
24094 specifying more actions for this tracepoint.
24096 In the series of action packets for a given tracepoint, at most one
24097 can have an @samp{S} before its first @var{action}. If such a packet
24098 is sent, it and the following packets define ``while-stepping''
24099 actions. Any prior packets define ordinary actions --- that is, those
24100 taken when the tracepoint is first hit. If no action packet has an
24101 @samp{S}, then all the packets in the series specify ordinary
24102 tracepoint actions.
24104 The @samp{@var{action}@dots{}} portion of the packet is a series of
24105 actions, concatenated without separators. Each action has one of the
24111 Collect the registers whose bits are set in @var{mask}. @var{mask} is
24112 a hexadecimal number whose @var{i}'th bit is set if register number
24113 @var{i} should be collected. (The least significant bit is numbered
24114 zero.) Note that @var{mask} may be any number of digits long; it may
24115 not fit in a 32-bit word.
24117 @item M @var{basereg},@var{offset},@var{len}
24118 Collect @var{len} bytes of memory starting at the address in register
24119 number @var{basereg}, plus @var{offset}. If @var{basereg} is
24120 @samp{-1}, then the range has a fixed address: @var{offset} is the
24121 address of the lowest byte to collect. The @var{basereg},
24122 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
24123 values (the @samp{-1} value for @var{basereg} is a special case).
24125 @item X @var{len},@var{expr}
24126 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
24127 it directs. @var{expr} is an agent expression, as described in
24128 @ref{Agent Expressions}. Each byte of the expression is encoded as a
24129 two-digit hex number in the packet; @var{len} is the number of bytes
24130 in the expression (and thus one-half the number of hex digits in the
24135 Any number of actions may be packed together in a single @samp{QTDP}
24136 packet, as long as the packet does not exceed the maximum packet
24137 length (400 bytes, for many stubs). There may be only one @samp{R}
24138 action per tracepoint, and it must precede any @samp{M} or @samp{X}
24139 actions. Any registers referred to by @samp{M} and @samp{X} actions
24140 must be collected by a preceding @samp{R} action. (The
24141 ``while-stepping'' actions are treated as if they were attached to a
24142 separate tracepoint, as far as these restrictions are concerned.)
24147 The packet was understood and carried out.
24149 The packet was not recognized.
24152 @item QTFrame:@var{n}
24153 Select the @var{n}'th tracepoint frame from the buffer, and use the
24154 register and memory contents recorded there to answer subsequent
24155 request packets from @value{GDBN}.
24157 A successful reply from the stub indicates that the stub has found the
24158 requested frame. The response is a series of parts, concatenated
24159 without separators, describing the frame we selected. Each part has
24160 one of the following forms:
24164 The selected frame is number @var{n} in the trace frame buffer;
24165 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
24166 was no frame matching the criteria in the request packet.
24169 The selected trace frame records a hit of tracepoint number @var{t};
24170 @var{t} is a hexadecimal number.
24174 @item QTFrame:pc:@var{addr}
24175 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
24176 currently selected frame whose PC is @var{addr};
24177 @var{addr} is a hexadecimal number.
24179 @item QTFrame:tdp:@var{t}
24180 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
24181 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
24182 is a hexadecimal number.
24184 @item QTFrame:range:@var{start}:@var{end}
24185 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
24186 currently selected frame whose PC is between @var{start} (inclusive)
24187 and @var{end} (exclusive); @var{start} and @var{end} are hexadecimal
24190 @item QTFrame:outside:@var{start}:@var{end}
24191 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
24192 frame @emph{outside} the given range of addresses.
24195 Begin the tracepoint experiment. Begin collecting data from tracepoint
24196 hits in the trace frame buffer.
24199 End the tracepoint experiment. Stop collecting trace frames.
24202 Clear the table of tracepoints, and empty the trace frame buffer.
24204 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
24205 Establish the given ranges of memory as ``transparent''. The stub
24206 will answer requests for these ranges from memory's current contents,
24207 if they were not collected as part of the tracepoint hit.
24209 @value{GDBN} uses this to mark read-only regions of memory, like those
24210 containing program code. Since these areas never change, they should
24211 still have the same contents they did when the tracepoint was hit, so
24212 there's no reason for the stub to refuse to provide their contents.
24215 Ask the stub if there is a trace experiment running right now.
24220 There is no trace experiment running.
24222 There is a trace experiment running.
24229 @section Interrupts
24230 @cindex interrupts (remote protocol)
24232 When a program on the remote target is running, @value{GDBN} may
24233 attempt to interrupt it by sending a @samp{Ctrl-C} or a @code{BREAK},
24234 control of which is specified via @value{GDBN}'s @samp{remotebreak}
24235 setting (@pxref{set remotebreak}).
24237 The precise meaning of @code{BREAK} is defined by the transport
24238 mechanism and may, in fact, be undefined. @value{GDBN} does
24239 not currently define a @code{BREAK} mechanism for any of the network
24242 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
24243 transport mechanisms. It is represented by sending the single byte
24244 @code{0x03} without any of the usual packet overhead described in
24245 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
24246 transmitted as part of a packet, it is considered to be packet data
24247 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
24248 (@pxref{X packet}), used for binary downloads, may include an unescaped
24249 @code{0x03} as part of its packet.
24251 Stubs are not required to recognize these interrupt mechanisms and the
24252 precise meaning associated with receipt of the interrupt is
24253 implementation defined. If the stub is successful at interrupting the
24254 running program, it is expected that it will send one of the Stop
24255 Reply Packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
24256 of successfully stopping the program. Interrupts received while the
24257 program is stopped will be discarded.
24262 Example sequence of a target being re-started. Notice how the restart
24263 does not get any direct output:
24268 @emph{target restarts}
24271 <- @code{T001:1234123412341234}
24275 Example sequence of a target being stepped by a single instruction:
24278 -> @code{G1445@dots{}}
24283 <- @code{T001:1234123412341234}
24287 <- @code{1455@dots{}}
24291 @node File-I/O remote protocol extension
24292 @section File-I/O remote protocol extension
24293 @cindex File-I/O remote protocol extension
24296 * File-I/O Overview::
24297 * Protocol basics::
24298 * The F request packet::
24299 * The F reply packet::
24300 * The Ctrl-C message::
24302 * List of supported calls::
24303 * Protocol specific representation of datatypes::
24305 * File-I/O Examples::
24308 @node File-I/O Overview
24309 @subsection File-I/O Overview
24310 @cindex file-i/o overview
24312 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
24313 target to use the host's file system and console I/O to perform various
24314 system calls. System calls on the target system are translated into a
24315 remote protocol packet to the host system, which then performs the needed
24316 actions and returns a response packet to the target system.
24317 This simulates file system operations even on targets that lack file systems.
24319 The protocol is defined to be independent of both the host and target systems.
24320 It uses its own internal representation of datatypes and values. Both
24321 @value{GDBN} and the target's @value{GDBN} stub are responsible for
24322 translating the system-dependent value representations into the internal
24323 protocol representations when data is transmitted.
24325 The communication is synchronous. A system call is possible only when
24326 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
24327 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
24328 the target is stopped to allow deterministic access to the target's
24329 memory. Therefore File-I/O is not interruptible by target signals. On
24330 the other hand, it is possible to interrupt File-I/O by a user interrupt
24331 (@samp{Ctrl-C}) within @value{GDBN}.
24333 The target's request to perform a host system call does not finish
24334 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
24335 after finishing the system call, the target returns to continuing the
24336 previous activity (continue, step). No additional continue or step
24337 request from @value{GDBN} is required.
24340 (@value{GDBP}) continue
24341 <- target requests 'system call X'
24342 target is stopped, @value{GDBN} executes system call
24343 -> GDB returns result
24344 ... target continues, GDB returns to wait for the target
24345 <- target hits breakpoint and sends a Txx packet
24348 The protocol only supports I/O on the console and to regular files on
24349 the host file system. Character or block special devices, pipes,
24350 named pipes, sockets or any other communication method on the host
24351 system are not supported by this protocol.
24353 @node Protocol basics
24354 @subsection Protocol basics
24355 @cindex protocol basics, file-i/o
24357 The File-I/O protocol uses the @code{F} packet as the request as well
24358 as reply packet. Since a File-I/O system call can only occur when
24359 @value{GDBN} is waiting for a response from the continuing or stepping target,
24360 the File-I/O request is a reply that @value{GDBN} has to expect as a result
24361 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
24362 This @code{F} packet contains all information needed to allow @value{GDBN}
24363 to call the appropriate host system call:
24367 A unique identifier for the requested system call.
24370 All parameters to the system call. Pointers are given as addresses
24371 in the target memory address space. Pointers to strings are given as
24372 pointer/length pair. Numerical values are given as they are.
24373 Numerical control flags are given in a protocol specific representation.
24377 At this point, @value{GDBN} has to perform the following actions.
24381 If the parameters include pointer values to data needed as input to a
24382 system call, @value{GDBN} requests this data from the target with a
24383 standard @code{m} packet request. This additional communication has to be
24384 expected by the target implementation and is handled as any other @code{m}
24388 @value{GDBN} translates all value from protocol representation to host
24389 representation as needed. Datatypes are coerced into the host types.
24392 @value{GDBN} calls the system call.
24395 It then coerces datatypes back to protocol representation.
24398 If the system call is expected to return data in buffer space specified
24399 by pointer parameters to the call, the data is transmitted to the
24400 target using a @code{M} or @code{X} packet. This packet has to be expected
24401 by the target implementation and is handled as any other @code{M} or @code{X}
24406 Eventually @value{GDBN} replies with another @code{F} packet which contains all
24407 necessary information for the target to continue. This at least contains
24414 @code{errno}, if has been changed by the system call.
24421 After having done the needed type and value coercion, the target continues
24422 the latest continue or step action.
24424 @node The F request packet
24425 @subsection The @code{F} request packet
24426 @cindex file-i/o request packet
24427 @cindex @code{F} request packet
24429 The @code{F} request packet has the following format:
24432 @item F@var{call-id},@var{parameter@dots{}}
24434 @var{call-id} is the identifier to indicate the host system call to be called.
24435 This is just the name of the function.
24437 @var{parameter@dots{}} are the parameters to the system call.
24438 Parameters are hexadecimal integer values, either the actual values in case
24439 of scalar datatypes, pointers to target buffer space in case of compound
24440 datatypes and unspecified memory areas, or pointer/length pairs in case
24441 of string parameters. These are appended to the @var{call-id} as a
24442 comma-delimited list. All values are transmitted in ASCII
24443 string representation, pointer/length pairs separated by a slash.
24449 @node The F reply packet
24450 @subsection The @code{F} reply packet
24451 @cindex file-i/o reply packet
24452 @cindex @code{F} reply packet
24454 The @code{F} reply packet has the following format:
24458 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call specific attachment}
24460 @var{retcode} is the return code of the system call as hexadecimal value.
24462 @var{errno} is the @code{errno} set by the call, in protocol specific representation.
24463 This parameter can be omitted if the call was successful.
24465 @var{Ctrl-C flag} is only sent if the user requested a break. In this
24466 case, @var{errno} must be sent as well, even if the call was successful.
24467 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
24474 or, if the call was interrupted before the host call has been performed:
24481 assuming 4 is the protocol specific representation of @code{EINTR}.
24486 @node The Ctrl-C message
24487 @subsection The @samp{Ctrl-C} message
24488 @cindex ctrl-c message, in file-i/o protocol
24490 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
24491 reply packet (@pxref{The F reply packet}),
24492 the target should behave as if it had
24493 gotten a break message. The meaning for the target is ``system call
24494 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
24495 (as with a break message) and return to @value{GDBN} with a @code{T02}
24498 It's important for the target to know in which
24499 state the system call was interrupted. There are two possible cases:
24503 The system call hasn't been performed on the host yet.
24506 The system call on the host has been finished.
24510 These two states can be distinguished by the target by the value of the
24511 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
24512 call hasn't been performed. This is equivalent to the @code{EINTR} handling
24513 on POSIX systems. In any other case, the target may presume that the
24514 system call has been finished --- successfully or not --- and should behave
24515 as if the break message arrived right after the system call.
24517 @value{GDBN} must behave reliably. If the system call has not been called
24518 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
24519 @code{errno} in the packet. If the system call on the host has been finished
24520 before the user requests a break, the full action must be finished by
24521 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
24522 The @code{F} packet may only be sent when either nothing has happened
24523 or the full action has been completed.
24526 @subsection Console I/O
24527 @cindex console i/o as part of file-i/o
24529 By default and if not explicitely closed by the target system, the file
24530 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
24531 on the @value{GDBN} console is handled as any other file output operation
24532 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
24533 by @value{GDBN} so that after the target read request from file descriptor
24534 0 all following typing is buffered until either one of the following
24539 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
24541 system call is treated as finished.
24544 The user presses @key{RET}. This is treated as end of input with a trailing
24548 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
24549 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
24553 If the user has typed more characters than fit in the buffer given to
24554 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
24555 either another @code{read(0, @dots{})} is requested by the target, or debugging
24556 is stopped at the user's request.
24559 @node List of supported calls
24560 @subsection List of supported calls
24561 @cindex list of supported file-i/o calls
24578 @unnumberedsubsubsec open
24579 @cindex open, file-i/o system call
24584 int open(const char *pathname, int flags);
24585 int open(const char *pathname, int flags, mode_t mode);
24589 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
24592 @var{flags} is the bitwise @code{OR} of the following values:
24596 If the file does not exist it will be created. The host
24597 rules apply as far as file ownership and time stamps
24601 When used with @code{O_CREAT}, if the file already exists it is
24602 an error and open() fails.
24605 If the file already exists and the open mode allows
24606 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
24607 truncated to zero length.
24610 The file is opened in append mode.
24613 The file is opened for reading only.
24616 The file is opened for writing only.
24619 The file is opened for reading and writing.
24623 Other bits are silently ignored.
24627 @var{mode} is the bitwise @code{OR} of the following values:
24631 User has read permission.
24634 User has write permission.
24637 Group has read permission.
24640 Group has write permission.
24643 Others have read permission.
24646 Others have write permission.
24650 Other bits are silently ignored.
24653 @item Return value:
24654 @code{open} returns the new file descriptor or -1 if an error
24661 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
24664 @var{pathname} refers to a directory.
24667 The requested access is not allowed.
24670 @var{pathname} was too long.
24673 A directory component in @var{pathname} does not exist.
24676 @var{pathname} refers to a device, pipe, named pipe or socket.
24679 @var{pathname} refers to a file on a read-only filesystem and
24680 write access was requested.
24683 @var{pathname} is an invalid pointer value.
24686 No space on device to create the file.
24689 The process already has the maximum number of files open.
24692 The limit on the total number of files open on the system
24696 The call was interrupted by the user.
24702 @unnumberedsubsubsec close
24703 @cindex close, file-i/o system call
24712 @samp{Fclose,@var{fd}}
24714 @item Return value:
24715 @code{close} returns zero on success, or -1 if an error occurred.
24721 @var{fd} isn't a valid open file descriptor.
24724 The call was interrupted by the user.
24730 @unnumberedsubsubsec read
24731 @cindex read, file-i/o system call
24736 int read(int fd, void *buf, unsigned int count);
24740 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
24742 @item Return value:
24743 On success, the number of bytes read is returned.
24744 Zero indicates end of file. If count is zero, read
24745 returns zero as well. On error, -1 is returned.
24751 @var{fd} is not a valid file descriptor or is not open for
24755 @var{bufptr} is an invalid pointer value.
24758 The call was interrupted by the user.
24764 @unnumberedsubsubsec write
24765 @cindex write, file-i/o system call
24770 int write(int fd, const void *buf, unsigned int count);
24774 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
24776 @item Return value:
24777 On success, the number of bytes written are returned.
24778 Zero indicates nothing was written. On error, -1
24785 @var{fd} is not a valid file descriptor or is not open for
24789 @var{bufptr} is an invalid pointer value.
24792 An attempt was made to write a file that exceeds the
24793 host specific maximum file size allowed.
24796 No space on device to write the data.
24799 The call was interrupted by the user.
24805 @unnumberedsubsubsec lseek
24806 @cindex lseek, file-i/o system call
24811 long lseek (int fd, long offset, int flag);
24815 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
24817 @var{flag} is one of:
24821 The offset is set to @var{offset} bytes.
24824 The offset is set to its current location plus @var{offset}
24828 The offset is set to the size of the file plus @var{offset}
24832 @item Return value:
24833 On success, the resulting unsigned offset in bytes from
24834 the beginning of the file is returned. Otherwise, a
24835 value of -1 is returned.
24841 @var{fd} is not a valid open file descriptor.
24844 @var{fd} is associated with the @value{GDBN} console.
24847 @var{flag} is not a proper value.
24850 The call was interrupted by the user.
24856 @unnumberedsubsubsec rename
24857 @cindex rename, file-i/o system call
24862 int rename(const char *oldpath, const char *newpath);
24866 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
24868 @item Return value:
24869 On success, zero is returned. On error, -1 is returned.
24875 @var{newpath} is an existing directory, but @var{oldpath} is not a
24879 @var{newpath} is a non-empty directory.
24882 @var{oldpath} or @var{newpath} is a directory that is in use by some
24886 An attempt was made to make a directory a subdirectory
24890 A component used as a directory in @var{oldpath} or new
24891 path is not a directory. Or @var{oldpath} is a directory
24892 and @var{newpath} exists but is not a directory.
24895 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
24898 No access to the file or the path of the file.
24902 @var{oldpath} or @var{newpath} was too long.
24905 A directory component in @var{oldpath} or @var{newpath} does not exist.
24908 The file is on a read-only filesystem.
24911 The device containing the file has no room for the new
24915 The call was interrupted by the user.
24921 @unnumberedsubsubsec unlink
24922 @cindex unlink, file-i/o system call
24927 int unlink(const char *pathname);
24931 @samp{Funlink,@var{pathnameptr}/@var{len}}
24933 @item Return value:
24934 On success, zero is returned. On error, -1 is returned.
24940 No access to the file or the path of the file.
24943 The system does not allow unlinking of directories.
24946 The file @var{pathname} cannot be unlinked because it's
24947 being used by another process.
24950 @var{pathnameptr} is an invalid pointer value.
24953 @var{pathname} was too long.
24956 A directory component in @var{pathname} does not exist.
24959 A component of the path is not a directory.
24962 The file is on a read-only filesystem.
24965 The call was interrupted by the user.
24971 @unnumberedsubsubsec stat/fstat
24972 @cindex fstat, file-i/o system call
24973 @cindex stat, file-i/o system call
24978 int stat(const char *pathname, struct stat *buf);
24979 int fstat(int fd, struct stat *buf);
24983 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
24984 @samp{Ffstat,@var{fd},@var{bufptr}}
24986 @item Return value:
24987 On success, zero is returned. On error, -1 is returned.
24993 @var{fd} is not a valid open file.
24996 A directory component in @var{pathname} does not exist or the
24997 path is an empty string.
25000 A component of the path is not a directory.
25003 @var{pathnameptr} is an invalid pointer value.
25006 No access to the file or the path of the file.
25009 @var{pathname} was too long.
25012 The call was interrupted by the user.
25018 @unnumberedsubsubsec gettimeofday
25019 @cindex gettimeofday, file-i/o system call
25024 int gettimeofday(struct timeval *tv, void *tz);
25028 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
25030 @item Return value:
25031 On success, 0 is returned, -1 otherwise.
25037 @var{tz} is a non-NULL pointer.
25040 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
25046 @unnumberedsubsubsec isatty
25047 @cindex isatty, file-i/o system call
25052 int isatty(int fd);
25056 @samp{Fisatty,@var{fd}}
25058 @item Return value:
25059 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
25065 The call was interrupted by the user.
25070 Note that the @code{isatty} call is treated as a special case: it returns
25071 1 to the target if the file descriptor is attached
25072 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
25073 would require implementing @code{ioctl} and would be more complex than
25078 @unnumberedsubsubsec system
25079 @cindex system, file-i/o system call
25084 int system(const char *command);
25088 @samp{Fsystem,@var{commandptr}/@var{len}}
25090 @item Return value:
25091 If @var{len} is zero, the return value indicates whether a shell is
25092 available. A zero return value indicates a shell is not available.
25093 For non-zero @var{len}, the value returned is -1 on error and the
25094 return status of the command otherwise. Only the exit status of the
25095 command is returned, which is extracted from the host's @code{system}
25096 return value by calling @code{WEXITSTATUS(retval)}. In case
25097 @file{/bin/sh} could not be executed, 127 is returned.
25103 The call was interrupted by the user.
25108 @value{GDBN} takes over the full task of calling the necessary host calls
25109 to perform the @code{system} call. The return value of @code{system} on
25110 the host is simplified before it's returned
25111 to the target. Any termination signal information from the child process
25112 is discarded, and the return value consists
25113 entirely of the exit status of the called command.
25115 Due to security concerns, the @code{system} call is by default refused
25116 by @value{GDBN}. The user has to allow this call explicitly with the
25117 @code{set remote system-call-allowed 1} command.
25120 @item set remote system-call-allowed
25121 @kindex set remote system-call-allowed
25122 Control whether to allow the @code{system} calls in the File I/O
25123 protocol for the remote target. The default is zero (disabled).
25125 @item show remote system-call-allowed
25126 @kindex show remote system-call-allowed
25127 Show whether the @code{system} calls are allowed in the File I/O
25131 @node Protocol specific representation of datatypes
25132 @subsection Protocol specific representation of datatypes
25133 @cindex protocol specific representation of datatypes, in file-i/o protocol
25136 * Integral datatypes::
25138 * Memory transfer::
25143 @node Integral datatypes
25144 @unnumberedsubsubsec Integral datatypes
25145 @cindex integral datatypes, in file-i/o protocol
25147 The integral datatypes used in the system calls are @code{int},
25148 @code{unsigned int}, @code{long}, @code{unsigned long},
25149 @code{mode_t}, and @code{time_t}.
25151 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
25152 implemented as 32 bit values in this protocol.
25154 @code{long} and @code{unsigned long} are implemented as 64 bit types.
25156 @xref{Limits}, for corresponding MIN and MAX values (similar to those
25157 in @file{limits.h}) to allow range checking on host and target.
25159 @code{time_t} datatypes are defined as seconds since the Epoch.
25161 All integral datatypes transferred as part of a memory read or write of a
25162 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
25165 @node Pointer values
25166 @unnumberedsubsubsec Pointer values
25167 @cindex pointer values, in file-i/o protocol
25169 Pointers to target data are transmitted as they are. An exception
25170 is made for pointers to buffers for which the length isn't
25171 transmitted as part of the function call, namely strings. Strings
25172 are transmitted as a pointer/length pair, both as hex values, e.g.@:
25179 which is a pointer to data of length 18 bytes at position 0x1aaf.
25180 The length is defined as the full string length in bytes, including
25181 the trailing null byte. For example, the string @code{"hello world"}
25182 at address 0x123456 is transmitted as
25188 @node Memory transfer
25189 @unnumberedsubsubsec Memory transfer
25190 @cindex memory transfer, in file-i/o protocol
25192 Structured data which is transferred using a memory read or write (for
25193 example, a @code{struct stat}) is expected to be in a protocol specific format
25194 with all scalar multibyte datatypes being big endian. Translation to
25195 this representation needs to be done both by the target before the @code{F}
25196 packet is sent, and by @value{GDBN} before
25197 it transfers memory to the target. Transferred pointers to structured
25198 data should point to the already-coerced data at any time.
25202 @unnumberedsubsubsec struct stat
25203 @cindex struct stat, in file-i/o protocol
25205 The buffer of type @code{struct stat} used by the target and @value{GDBN}
25206 is defined as follows:
25210 unsigned int st_dev; /* device */
25211 unsigned int st_ino; /* inode */
25212 mode_t st_mode; /* protection */
25213 unsigned int st_nlink; /* number of hard links */
25214 unsigned int st_uid; /* user ID of owner */
25215 unsigned int st_gid; /* group ID of owner */
25216 unsigned int st_rdev; /* device type (if inode device) */
25217 unsigned long st_size; /* total size, in bytes */
25218 unsigned long st_blksize; /* blocksize for filesystem I/O */
25219 unsigned long st_blocks; /* number of blocks allocated */
25220 time_t st_atime; /* time of last access */
25221 time_t st_mtime; /* time of last modification */
25222 time_t st_ctime; /* time of last change */
25226 The integral datatypes conform to the definitions given in the
25227 appropriate section (see @ref{Integral datatypes}, for details) so this
25228 structure is of size 64 bytes.
25230 The values of several fields have a restricted meaning and/or
25236 A value of 0 represents a file, 1 the console.
25239 No valid meaning for the target. Transmitted unchanged.
25242 Valid mode bits are described in @ref{Constants}. Any other
25243 bits have currently no meaning for the target.
25248 No valid meaning for the target. Transmitted unchanged.
25253 These values have a host and file system dependent
25254 accuracy. Especially on Windows hosts, the file system may not
25255 support exact timing values.
25258 The target gets a @code{struct stat} of the above representation and is
25259 responsible for coercing it to the target representation before
25262 Note that due to size differences between the host, target, and protocol
25263 representations of @code{struct stat} members, these members could eventually
25264 get truncated on the target.
25266 @node struct timeval
25267 @unnumberedsubsubsec struct timeval
25268 @cindex struct timeval, in file-i/o protocol
25270 The buffer of type @code{struct timeval} used by the File-I/O protocol
25271 is defined as follows:
25275 time_t tv_sec; /* second */
25276 long tv_usec; /* microsecond */
25280 The integral datatypes conform to the definitions given in the
25281 appropriate section (see @ref{Integral datatypes}, for details) so this
25282 structure is of size 8 bytes.
25285 @subsection Constants
25286 @cindex constants, in file-i/o protocol
25288 The following values are used for the constants inside of the
25289 protocol. @value{GDBN} and target are responsible for translating these
25290 values before and after the call as needed.
25301 @unnumberedsubsubsec Open flags
25302 @cindex open flags, in file-i/o protocol
25304 All values are given in hexadecimal representation.
25316 @node mode_t values
25317 @unnumberedsubsubsec mode_t values
25318 @cindex mode_t values, in file-i/o protocol
25320 All values are given in octal representation.
25337 @unnumberedsubsubsec Errno values
25338 @cindex errno values, in file-i/o protocol
25340 All values are given in decimal representation.
25365 @code{EUNKNOWN} is used as a fallback error value if a host system returns
25366 any error value not in the list of supported error numbers.
25369 @unnumberedsubsubsec Lseek flags
25370 @cindex lseek flags, in file-i/o protocol
25379 @unnumberedsubsubsec Limits
25380 @cindex limits, in file-i/o protocol
25382 All values are given in decimal representation.
25385 INT_MIN -2147483648
25387 UINT_MAX 4294967295
25388 LONG_MIN -9223372036854775808
25389 LONG_MAX 9223372036854775807
25390 ULONG_MAX 18446744073709551615
25393 @node File-I/O Examples
25394 @subsection File-I/O Examples
25395 @cindex file-i/o examples
25397 Example sequence of a write call, file descriptor 3, buffer is at target
25398 address 0x1234, 6 bytes should be written:
25401 <- @code{Fwrite,3,1234,6}
25402 @emph{request memory read from target}
25405 @emph{return "6 bytes written"}
25409 Example sequence of a read call, file descriptor 3, buffer is at target
25410 address 0x1234, 6 bytes should be read:
25413 <- @code{Fread,3,1234,6}
25414 @emph{request memory write to target}
25415 -> @code{X1234,6:XXXXXX}
25416 @emph{return "6 bytes read"}
25420 Example sequence of a read call, call fails on the host due to invalid
25421 file descriptor (@code{EBADF}):
25424 <- @code{Fread,3,1234,6}
25428 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
25432 <- @code{Fread,3,1234,6}
25437 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
25441 <- @code{Fread,3,1234,6}
25442 -> @code{X1234,6:XXXXXX}
25446 @node Memory map format
25447 @section Memory map format
25448 @cindex memory map format
25450 To be able to write into flash memory, @value{GDBN} needs to obtain a
25451 memory map from the target. This section describes the format of the
25454 The memory map is obtained using the @samp{qXfer:memory-map:read}
25455 (@pxref{qXfer memory map read}) packet and is an XML document that
25456 lists memory regions. The top-level structure of the document is shown below:
25459 <?xml version="1.0"?>
25460 <!DOCTYPE memory-map
25461 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
25462 "http://sourceware.org/gdb/gdb-memory-map.dtd">
25468 Each region can be either:
25473 A region of RAM starting at @var{addr} and extending for @var{length}
25477 <memory type="ram" start="@var{addr}" length="@var{length}"/>
25482 A region of read-only memory:
25485 <memory type="rom" start="@var{addr}" length="@var{length}"/>
25490 A region of flash memory, with erasure blocks @var{blocksize}
25494 <memory type="flash" start="@var{addr}" length="@var{length}">
25495 <property name="blocksize">@var{blocksize}</property>
25501 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
25502 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
25503 packets to write to addresses in such ranges.
25505 The formal DTD for memory map format is given below:
25508 <!-- ................................................... -->
25509 <!-- Memory Map XML DTD ................................ -->
25510 <!-- File: memory-map.dtd .............................. -->
25511 <!-- .................................... .............. -->
25512 <!-- memory-map.dtd -->
25513 <!-- memory-map: Root element with versioning -->
25514 <!ELEMENT memory-map (memory | property)>
25515 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
25516 <!ELEMENT memory (property)>
25517 <!-- memory: Specifies a memory region,
25518 and its type, or device. -->
25519 <!ATTLIST memory type CDATA #REQUIRED
25520 start CDATA #REQUIRED
25521 length CDATA #REQUIRED
25522 device CDATA #IMPLIED>
25523 <!-- property: Generic attribute tag -->
25524 <!ELEMENT property (#PCDATA | property)*>
25525 <!ATTLIST property name CDATA #REQUIRED>
25528 @include agentexpr.texi
25542 % I think something like @colophon should be in texinfo. In the
25544 \long\def\colophon{\hbox to0pt{}\vfill
25545 \centerline{The body of this manual is set in}
25546 \centerline{\fontname\tenrm,}
25547 \centerline{with headings in {\bf\fontname\tenbf}}
25548 \centerline{and examples in {\tt\fontname\tentt}.}
25549 \centerline{{\it\fontname\tenit\/},}
25550 \centerline{{\bf\fontname\tenbf}, and}
25551 \centerline{{\sl\fontname\tensl\/}}
25552 \centerline{are used for emphasis.}\vfill}
25554 % Blame: doc@cygnus.com, 1991.