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 FSF's Back-Cover Text is: ``You are free to copy and modify
66 this GNU Manual. Buying copies from GNU Press supports the FSF in
67 developing GNU and promoting software freedom.''
71 @title Debugging with @value{GDBN}
72 @subtitle The @sc{gnu} Source-Level Debugger
74 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
75 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
79 \hfill (Send bugs and comments on @value{GDBN} to bug-gdb\@gnu.org.)\par
80 \hfill {\it Debugging with @value{GDBN}}\par
81 \hfill \TeX{}info \texinfoversion\par
85 @vskip 0pt plus 1filll
86 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995,
87 1996, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2006
88 Free Software Foundation, Inc.
90 Published by the Free Software Foundation @*
91 51 Franklin Street, Fifth Floor,
92 Boston, MA 02110-1301, USA@*
95 Permission is granted to copy, distribute and/or modify this document
96 under the terms of the GNU Free Documentation License, Version 1.1 or
97 any later version published by the Free Software Foundation; with the
98 Invariant Sections being ``Free Software'' and ``Free Software Needs
99 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
100 and with the Back-Cover Texts as in (a) below.
102 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
103 this GNU Manual. Buying copies from GNU Press supports the FSF in
104 developing GNU and promoting software freedom.''
106 This edition of the GDB manual is dedicated to the memory of Fred
107 Fish. Fred was a long-standing contributor to GDB and to Free
108 software in general. We will miss him.
113 @node Top, Summary, (dir), (dir)
115 @top Debugging with @value{GDBN}
117 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
119 This is the @value{EDITION} Edition, for @value{GDBN} Version
122 Copyright (C) 1988-2006 Free Software Foundation, Inc.
124 This edition of the GDB manual is dedicated to the memory of Fred
125 Fish. Fred was a long-standing contributor to GDB and to Free
126 software in general. We will miss him.
129 * Summary:: Summary of @value{GDBN}
130 * Sample Session:: A sample @value{GDBN} session
132 * Invocation:: Getting in and out of @value{GDBN}
133 * Commands:: @value{GDBN} commands
134 * Running:: Running programs under @value{GDBN}
135 * Stopping:: Stopping and continuing
136 * Stack:: Examining the stack
137 * Source:: Examining source files
138 * Data:: Examining data
139 * Macros:: Preprocessor Macros
140 * Tracepoints:: Debugging remote targets non-intrusively
141 * Overlays:: Debugging programs that use overlays
143 * Languages:: Using @value{GDBN} with different languages
145 * Symbols:: Examining the symbol table
146 * Altering:: Altering execution
147 * GDB Files:: @value{GDBN} files
148 * Targets:: Specifying a debugging target
149 * Remote Debugging:: Debugging remote programs
150 * Configurations:: Configuration-specific information
151 * Controlling GDB:: Controlling @value{GDBN}
152 * Sequences:: Canned sequences of commands
153 * Interpreters:: Command Interpreters
154 * TUI:: @value{GDBN} Text User Interface
155 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
156 * GDB/MI:: @value{GDBN}'s Machine Interface.
157 * Annotations:: @value{GDBN}'s annotation interface.
159 * GDB Bugs:: Reporting bugs in @value{GDBN}
161 * Command Line Editing:: Command Line Editing
162 * Using History Interactively:: Using History Interactively
163 * Formatting Documentation:: How to format and print @value{GDBN} documentation
164 * Installing GDB:: Installing GDB
165 * Maintenance Commands:: Maintenance Commands
166 * Remote Protocol:: GDB Remote Serial Protocol
167 * Agent Expressions:: The GDB Agent Expression Mechanism
168 * Target Descriptions:: How targets can describe themselves to
170 * Copying:: GNU General Public License says
171 how you can copy and share GDB
172 * GNU Free Documentation License:: The license for this documentation
181 @unnumbered Summary of @value{GDBN}
183 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
184 going on ``inside'' another program while it executes---or what another
185 program was doing at the moment it crashed.
187 @value{GDBN} can do four main kinds of things (plus other things in support of
188 these) to help you catch bugs in the act:
192 Start your program, specifying anything that might affect its behavior.
195 Make your program stop on specified conditions.
198 Examine what has happened, when your program has stopped.
201 Change things in your program, so you can experiment with correcting the
202 effects of one bug and go on to learn about another.
205 You can use @value{GDBN} to debug programs written in C and C@t{++}.
206 For more information, see @ref{Supported Languages,,Supported Languages}.
207 For more information, see @ref{C,,C and C++}.
210 Support for Modula-2 is partial. For information on Modula-2, see
211 @ref{Modula-2,,Modula-2}.
214 Debugging Pascal programs which use sets, subranges, file variables, or
215 nested functions does not currently work. @value{GDBN} does not support
216 entering expressions, printing values, or similar features using Pascal
220 @value{GDBN} can be used to debug programs written in Fortran, although
221 it may be necessary to refer to some variables with a trailing
224 @value{GDBN} can be used to debug programs written in Objective-C,
225 using either the Apple/NeXT or the GNU Objective-C runtime.
228 * Free Software:: Freely redistributable software
229 * Contributors:: Contributors to GDB
233 @unnumberedsec Free Software
235 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
236 General Public License
237 (GPL). The GPL gives you the freedom to copy or adapt a licensed
238 program---but every person getting a copy also gets with it the
239 freedom to modify that copy (which means that they must get access to
240 the source code), and the freedom to distribute further copies.
241 Typical software companies use copyrights to limit your freedoms; the
242 Free Software Foundation uses the GPL to preserve these freedoms.
244 Fundamentally, the General Public License is a license which says that
245 you have these freedoms and that you cannot take these freedoms away
248 @unnumberedsec Free Software Needs Free Documentation
250 The biggest deficiency in the free software community today is not in
251 the software---it is the lack of good free documentation that we can
252 include with the free software. Many of our most important
253 programs do not come with free reference manuals and free introductory
254 texts. Documentation is an essential part of any software package;
255 when an important free software package does not come with a free
256 manual and a free tutorial, that is a major gap. We have many such
259 Consider Perl, for instance. The tutorial manuals that people
260 normally use are non-free. How did this come about? Because the
261 authors of those manuals published them with restrictive terms---no
262 copying, no modification, source files not available---which exclude
263 them from the free software world.
265 That wasn't the first time this sort of thing happened, and it was far
266 from the last. Many times we have heard a GNU user eagerly describe a
267 manual that he is writing, his intended contribution to the community,
268 only to learn that he had ruined everything by signing a publication
269 contract to make it non-free.
271 Free documentation, like free software, is a matter of freedom, not
272 price. The problem with the non-free manual is not that publishers
273 charge a price for printed copies---that in itself is fine. (The Free
274 Software Foundation sells printed copies of manuals, too.) The
275 problem is the restrictions on the use of the manual. Free manuals
276 are available in source code form, and give you permission to copy and
277 modify. Non-free manuals do not allow this.
279 The criteria of freedom for a free manual are roughly the same as for
280 free software. Redistribution (including the normal kinds of
281 commercial redistribution) must be permitted, so that the manual can
282 accompany every copy of the program, both on-line and on paper.
284 Permission for modification of the technical content is crucial too.
285 When people modify the software, adding or changing features, if they
286 are conscientious they will change the manual too---so they can
287 provide accurate and clear documentation for the modified program. A
288 manual that leaves you no choice but to write a new manual to document
289 a changed version of the program is not really available to our
292 Some kinds of limits on the way modification is handled are
293 acceptable. For example, requirements to preserve the original
294 author's copyright notice, the distribution terms, or the list of
295 authors, are ok. It is also no problem to require modified versions
296 to include notice that they were modified. Even entire sections that
297 may not be deleted or changed are acceptable, as long as they deal
298 with nontechnical topics (like this one). These kinds of restrictions
299 are acceptable because they don't obstruct the community's normal use
302 However, it must be possible to modify all the @emph{technical}
303 content of the manual, and then distribute the result in all the usual
304 media, through all the usual channels. Otherwise, the restrictions
305 obstruct the use of the manual, it is not free, and we need another
306 manual to replace it.
308 Please spread the word about this issue. Our community continues to
309 lose manuals to proprietary publishing. If we spread the word that
310 free software needs free reference manuals and free tutorials, perhaps
311 the next person who wants to contribute by writing documentation will
312 realize, before it is too late, that only free manuals contribute to
313 the free software community.
315 If you are writing documentation, please insist on publishing it under
316 the GNU Free Documentation License or another free documentation
317 license. Remember that this decision requires your approval---you
318 don't have to let the publisher decide. Some commercial publishers
319 will use a free license if you insist, but they will not propose the
320 option; it is up to you to raise the issue and say firmly that this is
321 what you want. If the publisher you are dealing with refuses, please
322 try other publishers. If you're not sure whether a proposed license
323 is free, write to @email{licensing@@gnu.org}.
325 You can encourage commercial publishers to sell more free, copylefted
326 manuals and tutorials by buying them, and particularly by buying
327 copies from the publishers that paid for their writing or for major
328 improvements. Meanwhile, try to avoid buying non-free documentation
329 at all. Check the distribution terms of a manual before you buy it,
330 and insist that whoever seeks your business must respect your freedom.
331 Check the history of the book, and try to reward the publishers that
332 have paid or pay the authors to work on it.
334 The Free Software Foundation maintains a list of free documentation
335 published by other publishers, at
336 @url{http://www.fsf.org/doc/other-free-books.html}.
339 @unnumberedsec Contributors to @value{GDBN}
341 Richard Stallman was the original author of @value{GDBN}, and of many
342 other @sc{gnu} programs. Many others have contributed to its
343 development. This section attempts to credit major contributors. One
344 of the virtues of free software is that everyone is free to contribute
345 to it; with regret, we cannot actually acknowledge everyone here. The
346 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
347 blow-by-blow account.
349 Changes much prior to version 2.0 are lost in the mists of time.
352 @emph{Plea:} Additions to this section are particularly welcome. If you
353 or your friends (or enemies, to be evenhanded) have been unfairly
354 omitted from this list, we would like to add your names!
357 So that they may not regard their many labors as thankless, we
358 particularly thank those who shepherded @value{GDBN} through major
360 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
361 Jim Blandy (release 4.18);
362 Jason Molenda (release 4.17);
363 Stan Shebs (release 4.14);
364 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
365 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
366 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
367 Jim Kingdon (releases 3.5, 3.4, and 3.3);
368 and Randy Smith (releases 3.2, 3.1, and 3.0).
370 Richard Stallman, assisted at various times by Peter TerMaat, Chris
371 Hanson, and Richard Mlynarik, handled releases through 2.8.
373 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
374 in @value{GDBN}, with significant additional contributions from Per
375 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
376 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
377 much general update work leading to release 3.0).
379 @value{GDBN} uses the BFD subroutine library to examine multiple
380 object-file formats; BFD was a joint project of David V.
381 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
383 David Johnson wrote the original COFF support; Pace Willison did
384 the original support for encapsulated COFF.
386 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
388 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
389 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
391 Jean-Daniel Fekete contributed Sun 386i support.
392 Chris Hanson improved the HP9000 support.
393 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
394 David Johnson contributed Encore Umax support.
395 Jyrki Kuoppala contributed Altos 3068 support.
396 Jeff Law contributed HP PA and SOM support.
397 Keith Packard contributed NS32K support.
398 Doug Rabson contributed Acorn Risc Machine support.
399 Bob Rusk contributed Harris Nighthawk CX-UX support.
400 Chris Smith contributed Convex support (and Fortran debugging).
401 Jonathan Stone contributed Pyramid support.
402 Michael Tiemann contributed SPARC support.
403 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
404 Pace Willison contributed Intel 386 support.
405 Jay Vosburgh contributed Symmetry support.
406 Marko Mlinar contributed OpenRISC 1000 support.
408 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
410 Rich Schaefer and Peter Schauer helped with support of SunOS shared
413 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
414 about several machine instruction sets.
416 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
417 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
418 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
419 and RDI targets, respectively.
421 Brian Fox is the author of the readline libraries providing
422 command-line editing and command history.
424 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
425 Modula-2 support, and contributed the Languages chapter of this manual.
427 Fred Fish wrote most of the support for Unix System Vr4.
428 He also enhanced the command-completion support to cover C@t{++} overloaded
431 Hitachi America (now Renesas America), Ltd. sponsored the support for
432 H8/300, H8/500, and Super-H processors.
434 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
436 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
439 Toshiba sponsored the support for the TX39 Mips processor.
441 Matsushita sponsored the support for the MN10200 and MN10300 processors.
443 Fujitsu sponsored the support for SPARClite and FR30 processors.
445 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
448 Michael Snyder added support for tracepoints.
450 Stu Grossman wrote gdbserver.
452 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
453 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
455 The following people at the Hewlett-Packard Company contributed
456 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
457 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
458 compiler, and the Text User Interface (nee Terminal User Interface):
459 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
460 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
461 provided HP-specific information in this manual.
463 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
464 Robert Hoehne made significant contributions to the DJGPP port.
466 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
467 development since 1991. Cygnus engineers who have worked on @value{GDBN}
468 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
469 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
470 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
471 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
472 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
473 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
474 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
475 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
476 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
477 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
478 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
479 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
480 Zuhn have made contributions both large and small.
482 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
483 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
485 Jim Blandy added support for preprocessor macros, while working for Red
488 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
489 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
490 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
491 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
492 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
493 with the migration of old architectures to this new framework.
495 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
496 unwinder framework, this consisting of a fresh new design featuring
497 frame IDs, independent frame sniffers, and the sentinel frame. Mark
498 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
499 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
500 trad unwinders. The architecture-specific changes, each involving a
501 complete rewrite of the architecture's frame code, were carried out by
502 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
503 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
504 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
505 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
508 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
509 Tensilica, Inc.@: contributed support for Xtensa processors. Others
510 who have worked on the Xtensa port of @value{GDBN} in the past include
511 Steve Tjiang, John Newlin, and Scott Foehner.
514 @chapter A Sample @value{GDBN} Session
516 You can use this manual at your leisure to read all about @value{GDBN}.
517 However, a handful of commands are enough to get started using the
518 debugger. This chapter illustrates those commands.
521 In this sample session, we emphasize user input like this: @b{input},
522 to make it easier to pick out from the surrounding output.
525 @c FIXME: this example may not be appropriate for some configs, where
526 @c FIXME...primary interest is in remote use.
528 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
529 processor) exhibits the following bug: sometimes, when we change its
530 quote strings from the default, the commands used to capture one macro
531 definition within another stop working. In the following short @code{m4}
532 session, we define a macro @code{foo} which expands to @code{0000}; we
533 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
534 same thing. However, when we change the open quote string to
535 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
536 procedure fails to define a new synonym @code{baz}:
545 @b{define(bar,defn(`foo'))}
549 @b{changequote(<QUOTE>,<UNQUOTE>)}
551 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
554 m4: End of input: 0: fatal error: EOF in string
558 Let us use @value{GDBN} to try to see what is going on.
561 $ @b{@value{GDBP} m4}
562 @c FIXME: this falsifies the exact text played out, to permit smallbook
563 @c FIXME... format to come out better.
564 @value{GDBN} is free software and you are welcome to distribute copies
565 of it under certain conditions; type "show copying" to see
567 There is absolutely no warranty for @value{GDBN}; type "show warranty"
570 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
575 @value{GDBN} reads only enough symbol data to know where to find the
576 rest when needed; as a result, the first prompt comes up very quickly.
577 We now tell @value{GDBN} to use a narrower display width than usual, so
578 that examples fit in this manual.
581 (@value{GDBP}) @b{set width 70}
585 We need to see how the @code{m4} built-in @code{changequote} works.
586 Having looked at the source, we know the relevant subroutine is
587 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
588 @code{break} command.
591 (@value{GDBP}) @b{break m4_changequote}
592 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
596 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
597 control; as long as control does not reach the @code{m4_changequote}
598 subroutine, the program runs as usual:
601 (@value{GDBP}) @b{run}
602 Starting program: /work/Editorial/gdb/gnu/m4/m4
610 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
611 suspends execution of @code{m4}, displaying information about the
612 context where it stops.
615 @b{changequote(<QUOTE>,<UNQUOTE>)}
617 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
619 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
623 Now we use the command @code{n} (@code{next}) to advance execution to
624 the next line of the current function.
628 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
633 @code{set_quotes} looks like a promising subroutine. We can go into it
634 by using the command @code{s} (@code{step}) instead of @code{next}.
635 @code{step} goes to the next line to be executed in @emph{any}
636 subroutine, so it steps into @code{set_quotes}.
640 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
642 530 if (lquote != def_lquote)
646 The display that shows the subroutine where @code{m4} is now
647 suspended (and its arguments) is called a stack frame display. It
648 shows a summary of the stack. We can use the @code{backtrace}
649 command (which can also be spelled @code{bt}), to see where we are
650 in the stack as a whole: the @code{backtrace} command displays a
651 stack frame for each active subroutine.
654 (@value{GDBP}) @b{bt}
655 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
657 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
659 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
660 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
662 #4 0x79dc in expand_input () at macro.c:40
663 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
667 We step through a few more lines to see what happens. The first two
668 times, we can use @samp{s}; the next two times we use @code{n} to avoid
669 falling into the @code{xstrdup} subroutine.
673 0x3b5c 532 if (rquote != def_rquote)
675 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
676 def_lquote : xstrdup(lq);
678 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
681 538 len_lquote = strlen(rquote);
685 The last line displayed looks a little odd; we can examine the variables
686 @code{lquote} and @code{rquote} to see if they are in fact the new left
687 and right quotes we specified. We use the command @code{p}
688 (@code{print}) to see their values.
691 (@value{GDBP}) @b{p lquote}
692 $1 = 0x35d40 "<QUOTE>"
693 (@value{GDBP}) @b{p rquote}
694 $2 = 0x35d50 "<UNQUOTE>"
698 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
699 To look at some context, we can display ten lines of source
700 surrounding the current line with the @code{l} (@code{list}) command.
706 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
708 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
711 538 len_lquote = strlen(rquote);
712 539 len_rquote = strlen(lquote);
719 Let us step past the two lines that set @code{len_lquote} and
720 @code{len_rquote}, and then examine the values of those variables.
724 539 len_rquote = strlen(lquote);
727 (@value{GDBP}) @b{p len_lquote}
729 (@value{GDBP}) @b{p len_rquote}
734 That certainly looks wrong, assuming @code{len_lquote} and
735 @code{len_rquote} are meant to be the lengths of @code{lquote} and
736 @code{rquote} respectively. We can set them to better values using
737 the @code{p} command, since it can print the value of
738 any expression---and that expression can include subroutine calls and
742 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
744 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
749 Is that enough to fix the problem of using the new quotes with the
750 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
751 executing with the @code{c} (@code{continue}) command, and then try the
752 example that caused trouble initially:
758 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
765 Success! The new quotes now work just as well as the default ones. The
766 problem seems to have been just the two typos defining the wrong
767 lengths. We allow @code{m4} exit by giving it an EOF as input:
771 Program exited normally.
775 The message @samp{Program exited normally.} is from @value{GDBN}; it
776 indicates @code{m4} has finished executing. We can end our @value{GDBN}
777 session with the @value{GDBN} @code{quit} command.
780 (@value{GDBP}) @b{quit}
784 @chapter Getting In and Out of @value{GDBN}
786 This chapter discusses how to start @value{GDBN}, and how to get out of it.
790 type @samp{@value{GDBP}} to start @value{GDBN}.
792 type @kbd{quit} or @kbd{Ctrl-d} to exit.
796 * Invoking GDB:: How to start @value{GDBN}
797 * Quitting GDB:: How to quit @value{GDBN}
798 * Shell Commands:: How to use shell commands inside @value{GDBN}
799 * Logging Output:: How to log @value{GDBN}'s output to a file
803 @section Invoking @value{GDBN}
805 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
806 @value{GDBN} reads commands from the terminal until you tell it to exit.
808 You can also run @code{@value{GDBP}} with a variety of arguments and options,
809 to specify more of your debugging environment at the outset.
811 The command-line options described here are designed
812 to cover a variety of situations; in some environments, some of these
813 options may effectively be unavailable.
815 The most usual way to start @value{GDBN} is with one argument,
816 specifying an executable program:
819 @value{GDBP} @var{program}
823 You can also start with both an executable program and a core file
827 @value{GDBP} @var{program} @var{core}
830 You can, instead, specify a process ID as a second argument, if you want
831 to debug a running process:
834 @value{GDBP} @var{program} 1234
838 would attach @value{GDBN} to process @code{1234} (unless you also have a file
839 named @file{1234}; @value{GDBN} does check for a core file first).
841 Taking advantage of the second command-line argument requires a fairly
842 complete operating system; when you use @value{GDBN} as a remote
843 debugger attached to a bare board, there may not be any notion of
844 ``process'', and there is often no way to get a core dump. @value{GDBN}
845 will warn you if it is unable to attach or to read core dumps.
847 You can optionally have @code{@value{GDBP}} pass any arguments after the
848 executable file to the inferior using @code{--args}. This option stops
851 @value{GDBP} --args gcc -O2 -c foo.c
853 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
854 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
856 You can run @code{@value{GDBP}} without printing the front material, which describes
857 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
864 You can further control how @value{GDBN} starts up by using command-line
865 options. @value{GDBN} itself can remind you of the options available.
875 to display all available options and briefly describe their use
876 (@samp{@value{GDBP} -h} is a shorter equivalent).
878 All options and command line arguments you give are processed
879 in sequential order. The order makes a difference when the
880 @samp{-x} option is used.
884 * File Options:: Choosing files
885 * Mode Options:: Choosing modes
886 * Startup:: What @value{GDBN} does during startup
890 @subsection Choosing Files
892 When @value{GDBN} starts, it reads any arguments other than options as
893 specifying an executable file and core file (or process ID). This is
894 the same as if the arguments were specified by the @samp{-se} and
895 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
896 first argument that does not have an associated option flag as
897 equivalent to the @samp{-se} option followed by that argument; and the
898 second argument that does not have an associated option flag, if any, as
899 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
900 If the second argument begins with a decimal digit, @value{GDBN} will
901 first attempt to attach to it as a process, and if that fails, attempt
902 to open it as a corefile. If you have a corefile whose name begins with
903 a digit, you can prevent @value{GDBN} from treating it as a pid by
904 prefixing it with @file{./}, e.g.@: @file{./12345}.
906 If @value{GDBN} has not been configured to included core file support,
907 such as for most embedded targets, then it will complain about a second
908 argument and ignore it.
910 Many options have both long and short forms; both are shown in the
911 following list. @value{GDBN} also recognizes the long forms if you truncate
912 them, so long as enough of the option is present to be unambiguous.
913 (If you prefer, you can flag option arguments with @samp{--} rather
914 than @samp{-}, though we illustrate the more usual convention.)
916 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
917 @c way, both those who look for -foo and --foo in the index, will find
921 @item -symbols @var{file}
923 @cindex @code{--symbols}
925 Read symbol table from file @var{file}.
927 @item -exec @var{file}
929 @cindex @code{--exec}
931 Use file @var{file} as the executable file to execute when appropriate,
932 and for examining pure data in conjunction with a core dump.
936 Read symbol table from file @var{file} and use it as the executable
939 @item -core @var{file}
941 @cindex @code{--core}
943 Use file @var{file} as a core dump to examine.
945 @item -c @var{number}
946 @item -pid @var{number}
947 @itemx -p @var{number}
950 Connect to process ID @var{number}, as with the @code{attach} command.
951 If there is no such process, @value{GDBN} will attempt to open a core
952 file named @var{number}.
954 @item -command @var{file}
956 @cindex @code{--command}
958 Execute @value{GDBN} commands from file @var{file}. @xref{Command
959 Files,, Command files}.
961 @item -eval-command @var{command}
962 @itemx -ex @var{command}
963 @cindex @code{--eval-command}
965 Execute a single @value{GDBN} command.
967 This option may be used multiple times to call multiple commands. It may
968 also be interleaved with @samp{-command} as required.
971 @value{GDBP} -ex 'target sim' -ex 'load' \
972 -x setbreakpoints -ex 'run' a.out
975 @item -directory @var{directory}
976 @itemx -d @var{directory}
977 @cindex @code{--directory}
979 Add @var{directory} to the path to search for source and script files.
983 @cindex @code{--readnow}
985 Read each symbol file's entire symbol table immediately, rather than
986 the default, which is to read it incrementally as it is needed.
987 This makes startup slower, but makes future operations faster.
992 @subsection Choosing Modes
994 You can run @value{GDBN} in various alternative modes---for example, in
995 batch mode or quiet mode.
1002 Do not execute commands found in any initialization files. Normally,
1003 @value{GDBN} executes the commands in these files after all the command
1004 options and arguments have been processed. @xref{Command Files,,Command
1010 @cindex @code{--quiet}
1011 @cindex @code{--silent}
1013 ``Quiet''. Do not print the introductory and copyright messages. These
1014 messages are also suppressed in batch mode.
1017 @cindex @code{--batch}
1018 Run in batch mode. Exit with status @code{0} after processing all the
1019 command files specified with @samp{-x} (and all commands from
1020 initialization files, if not inhibited with @samp{-n}). Exit with
1021 nonzero status if an error occurs in executing the @value{GDBN} commands
1022 in the command files.
1024 Batch mode may be useful for running @value{GDBN} as a filter, for
1025 example to download and run a program on another computer; in order to
1026 make this more useful, the message
1029 Program exited normally.
1033 (which is ordinarily issued whenever a program running under
1034 @value{GDBN} control terminates) is not issued when running in batch
1038 @cindex @code{--batch-silent}
1039 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1040 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1041 unaffected). This is much quieter than @samp{-silent} and would be useless
1042 for an interactive session.
1044 This is particularly useful when using targets that give @samp{Loading section}
1045 messages, for example.
1047 Note that targets that give their output via @value{GDBN}, as opposed to
1048 writing directly to @code{stdout}, will also be made silent.
1050 @item -return-child-result
1051 @cindex @code{--return-child-result}
1052 The return code from @value{GDBN} will be the return code from the child
1053 process (the process being debugged), with the following exceptions:
1057 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1058 internal error. In this case the exit code is the same as it would have been
1059 without @samp{-return-child-result}.
1061 The user quits with an explicit value. E.g., @samp{quit 1}.
1063 The child process never runs, or is not allowed to terminate, in which case
1064 the exit code will be -1.
1067 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1068 when @value{GDBN} is being used as a remote program loader or simulator
1073 @cindex @code{--nowindows}
1075 ``No windows''. If @value{GDBN} comes with a graphical user interface
1076 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1077 interface. If no GUI is available, this option has no effect.
1081 @cindex @code{--windows}
1083 If @value{GDBN} includes a GUI, then this option requires it to be
1086 @item -cd @var{directory}
1088 Run @value{GDBN} using @var{directory} as its working directory,
1089 instead of the current directory.
1093 @cindex @code{--fullname}
1095 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1096 subprocess. It tells @value{GDBN} to output the full file name and line
1097 number in a standard, recognizable fashion each time a stack frame is
1098 displayed (which includes each time your program stops). This
1099 recognizable format looks like two @samp{\032} characters, followed by
1100 the file name, line number and character position separated by colons,
1101 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1102 @samp{\032} characters as a signal to display the source code for the
1106 @cindex @code{--epoch}
1107 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1108 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1109 routines so as to allow Epoch to display values of expressions in a
1112 @item -annotate @var{level}
1113 @cindex @code{--annotate}
1114 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1115 effect is identical to using @samp{set annotate @var{level}}
1116 (@pxref{Annotations}). The annotation @var{level} controls how much
1117 information @value{GDBN} prints together with its prompt, values of
1118 expressions, source lines, and other types of output. Level 0 is the
1119 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1120 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1121 that control @value{GDBN}, and level 2 has been deprecated.
1123 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1127 @cindex @code{--args}
1128 Change interpretation of command line so that arguments following the
1129 executable file are passed as command line arguments to the inferior.
1130 This option stops option processing.
1132 @item -baud @var{bps}
1134 @cindex @code{--baud}
1136 Set the line speed (baud rate or bits per second) of any serial
1137 interface used by @value{GDBN} for remote debugging.
1139 @item -l @var{timeout}
1141 Set the timeout (in seconds) of any communication used by @value{GDBN}
1142 for remote debugging.
1144 @item -tty @var{device}
1145 @itemx -t @var{device}
1146 @cindex @code{--tty}
1148 Run using @var{device} for your program's standard input and output.
1149 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1151 @c resolve the situation of these eventually
1153 @cindex @code{--tui}
1154 Activate the @dfn{Text User Interface} when starting. The Text User
1155 Interface manages several text windows on the terminal, showing
1156 source, assembly, registers and @value{GDBN} command outputs
1157 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1158 Text User Interface can be enabled by invoking the program
1159 @samp{@value{GDBTUI}}. Do not use this option if you run @value{GDBN} from
1160 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1163 @c @cindex @code{--xdb}
1164 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1165 @c For information, see the file @file{xdb_trans.html}, which is usually
1166 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1169 @item -interpreter @var{interp}
1170 @cindex @code{--interpreter}
1171 Use the interpreter @var{interp} for interface with the controlling
1172 program or device. This option is meant to be set by programs which
1173 communicate with @value{GDBN} using it as a back end.
1174 @xref{Interpreters, , Command Interpreters}.
1176 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1177 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1178 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1179 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1180 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1181 @sc{gdb/mi} interfaces are no longer supported.
1184 @cindex @code{--write}
1185 Open the executable and core files for both reading and writing. This
1186 is equivalent to the @samp{set write on} command inside @value{GDBN}
1190 @cindex @code{--statistics}
1191 This option causes @value{GDBN} to print statistics about time and
1192 memory usage after it completes each command and returns to the prompt.
1195 @cindex @code{--version}
1196 This option causes @value{GDBN} to print its version number and
1197 no-warranty blurb, and exit.
1202 @subsection What @value{GDBN} Does During Startup
1203 @cindex @value{GDBN} startup
1205 Here's the description of what @value{GDBN} does during session startup:
1209 Sets up the command interpreter as specified by the command line
1210 (@pxref{Mode Options, interpreter}).
1214 Reads the @dfn{init file} (if any) in your home directory@footnote{On
1215 DOS/Windows systems, the home directory is the one pointed to by the
1216 @code{HOME} environment variable.} and executes all the commands in
1220 Processes command line options and operands.
1223 Reads and executes the commands from init file (if any) in the current
1224 working directory. This is only done if the current directory is
1225 different from your home directory. Thus, you can have more than one
1226 init file, one generic in your home directory, and another, specific
1227 to the program you are debugging, in the directory where you invoke
1231 Reads command files specified by the @samp{-x} option. @xref{Command
1232 Files}, for more details about @value{GDBN} command files.
1235 Reads the command history recorded in the @dfn{history file}.
1236 @xref{Command History}, for more details about the command history and the
1237 files where @value{GDBN} records it.
1240 Init files use the same syntax as @dfn{command files} (@pxref{Command
1241 Files}) and are processed by @value{GDBN} in the same way. The init
1242 file in your home directory can set options (such as @samp{set
1243 complaints}) that affect subsequent processing of command line options
1244 and operands. Init files are not executed if you use the @samp{-nx}
1245 option (@pxref{Mode Options, ,Choosing Modes}).
1247 @cindex init file name
1248 @cindex @file{.gdbinit}
1249 @cindex @file{gdb.ini}
1250 The @value{GDBN} init files are normally called @file{.gdbinit}.
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.
1259 @section Quitting @value{GDBN}
1260 @cindex exiting @value{GDBN}
1261 @cindex leaving @value{GDBN}
1264 @kindex quit @r{[}@var{expression}@r{]}
1265 @kindex q @r{(@code{quit})}
1266 @item quit @r{[}@var{expression}@r{]}
1268 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1269 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1270 do not supply @var{expression}, @value{GDBN} will terminate normally;
1271 otherwise it will terminate using the result of @var{expression} as the
1276 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1277 terminates the action of any @value{GDBN} command that is in progress and
1278 returns to @value{GDBN} command level. It is safe to type the interrupt
1279 character at any time because @value{GDBN} does not allow it to take effect
1280 until a time when it is safe.
1282 If you have been using @value{GDBN} to control an attached process or
1283 device, you can release it with the @code{detach} command
1284 (@pxref{Attach, ,Debugging an Already-running Process}).
1286 @node Shell Commands
1287 @section Shell Commands
1289 If you need to execute occasional shell commands during your
1290 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1291 just use the @code{shell} command.
1295 @cindex shell escape
1296 @item shell @var{command string}
1297 Invoke a standard shell to execute @var{command string}.
1298 If it exists, the environment variable @code{SHELL} determines which
1299 shell to run. Otherwise @value{GDBN} uses the default shell
1300 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1303 The utility @code{make} is often needed in development environments.
1304 You do not have to use the @code{shell} command for this purpose in
1309 @cindex calling make
1310 @item make @var{make-args}
1311 Execute the @code{make} program with the specified
1312 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1315 @node Logging Output
1316 @section Logging Output
1317 @cindex logging @value{GDBN} output
1318 @cindex save @value{GDBN} output to a file
1320 You may want to save the output of @value{GDBN} commands to a file.
1321 There are several commands to control @value{GDBN}'s logging.
1325 @item set logging on
1327 @item set logging off
1329 @cindex logging file name
1330 @item set logging file @var{file}
1331 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1332 @item set logging overwrite [on|off]
1333 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1334 you want @code{set logging on} to overwrite the logfile instead.
1335 @item set logging redirect [on|off]
1336 By default, @value{GDBN} output will go to both the terminal and the logfile.
1337 Set @code{redirect} if you want output to go only to the log file.
1338 @kindex show logging
1340 Show the current values of the logging settings.
1344 @chapter @value{GDBN} Commands
1346 You can abbreviate a @value{GDBN} command to the first few letters of the command
1347 name, if that abbreviation is unambiguous; and you can repeat certain
1348 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1349 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1350 show you the alternatives available, if there is more than one possibility).
1353 * Command Syntax:: How to give commands to @value{GDBN}
1354 * Completion:: Command completion
1355 * Help:: How to ask @value{GDBN} for help
1358 @node Command Syntax
1359 @section Command Syntax
1361 A @value{GDBN} command is a single line of input. There is no limit on
1362 how long it can be. It starts with a command name, which is followed by
1363 arguments whose meaning depends on the command name. For example, the
1364 command @code{step} accepts an argument which is the number of times to
1365 step, as in @samp{step 5}. You can also use the @code{step} command
1366 with no arguments. Some commands do not allow any arguments.
1368 @cindex abbreviation
1369 @value{GDBN} command names may always be truncated if that abbreviation is
1370 unambiguous. Other possible command abbreviations are listed in the
1371 documentation for individual commands. In some cases, even ambiguous
1372 abbreviations are allowed; for example, @code{s} is specially defined as
1373 equivalent to @code{step} even though there are other commands whose
1374 names start with @code{s}. You can test abbreviations by using them as
1375 arguments to the @code{help} command.
1377 @cindex repeating commands
1378 @kindex RET @r{(repeat last command)}
1379 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1380 repeat the previous command. Certain commands (for example, @code{run})
1381 will not repeat this way; these are commands whose unintentional
1382 repetition might cause trouble and which you are unlikely to want to
1383 repeat. User-defined commands can disable this feature; see
1384 @ref{Define, dont-repeat}.
1386 The @code{list} and @code{x} commands, when you repeat them with
1387 @key{RET}, construct new arguments rather than repeating
1388 exactly as typed. This permits easy scanning of source or memory.
1390 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1391 output, in a way similar to the common utility @code{more}
1392 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1393 @key{RET} too many in this situation, @value{GDBN} disables command
1394 repetition after any command that generates this sort of display.
1396 @kindex # @r{(a comment)}
1398 Any text from a @kbd{#} to the end of the line is a comment; it does
1399 nothing. This is useful mainly in command files (@pxref{Command
1400 Files,,Command Files}).
1402 @cindex repeating command sequences
1403 @kindex Ctrl-o @r{(operate-and-get-next)}
1404 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1405 commands. This command accepts the current line, like @key{RET}, and
1406 then fetches the next line relative to the current line from the history
1410 @section Command Completion
1413 @cindex word completion
1414 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1415 only one possibility; it can also show you what the valid possibilities
1416 are for the next word in a command, at any time. This works for @value{GDBN}
1417 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1419 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1420 of a word. If there is only one possibility, @value{GDBN} fills in the
1421 word, and waits for you to finish the command (or press @key{RET} to
1422 enter it). For example, if you type
1424 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1425 @c complete accuracy in these examples; space introduced for clarity.
1426 @c If texinfo enhancements make it unnecessary, it would be nice to
1427 @c replace " @key" by "@key" in the following...
1429 (@value{GDBP}) info bre @key{TAB}
1433 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1434 the only @code{info} subcommand beginning with @samp{bre}:
1437 (@value{GDBP}) info breakpoints
1441 You can either press @key{RET} at this point, to run the @code{info
1442 breakpoints} command, or backspace and enter something else, if
1443 @samp{breakpoints} does not look like the command you expected. (If you
1444 were sure you wanted @code{info breakpoints} in the first place, you
1445 might as well just type @key{RET} immediately after @samp{info bre},
1446 to exploit command abbreviations rather than command completion).
1448 If there is more than one possibility for the next word when you press
1449 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1450 characters and try again, or just press @key{TAB} a second time;
1451 @value{GDBN} displays all the possible completions for that word. For
1452 example, you might want to set a breakpoint on a subroutine whose name
1453 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1454 just sounds the bell. Typing @key{TAB} again displays all the
1455 function names in your program that begin with those characters, for
1459 (@value{GDBP}) b make_ @key{TAB}
1460 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1461 make_a_section_from_file make_environ
1462 make_abs_section make_function_type
1463 make_blockvector make_pointer_type
1464 make_cleanup make_reference_type
1465 make_command make_symbol_completion_list
1466 (@value{GDBP}) b make_
1470 After displaying the available possibilities, @value{GDBN} copies your
1471 partial input (@samp{b make_} in the example) so you can finish the
1474 If you just want to see the list of alternatives in the first place, you
1475 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1476 means @kbd{@key{META} ?}. You can type this either by holding down a
1477 key designated as the @key{META} shift on your keyboard (if there is
1478 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1480 @cindex quotes in commands
1481 @cindex completion of quoted strings
1482 Sometimes the string you need, while logically a ``word'', may contain
1483 parentheses or other characters that @value{GDBN} normally excludes from
1484 its notion of a word. To permit word completion to work in this
1485 situation, you may enclose words in @code{'} (single quote marks) in
1486 @value{GDBN} commands.
1488 The most likely situation where you might need this is in typing the
1489 name of a C@t{++} function. This is because C@t{++} allows function
1490 overloading (multiple definitions of the same function, distinguished
1491 by argument type). For example, when you want to set a breakpoint you
1492 may need to distinguish whether you mean the version of @code{name}
1493 that takes an @code{int} parameter, @code{name(int)}, or the version
1494 that takes a @code{float} parameter, @code{name(float)}. To use the
1495 word-completion facilities in this situation, type a single quote
1496 @code{'} at the beginning of the function name. This alerts
1497 @value{GDBN} that it may need to consider more information than usual
1498 when you press @key{TAB} or @kbd{M-?} to request word completion:
1501 (@value{GDBP}) b 'bubble( @kbd{M-?}
1502 bubble(double,double) bubble(int,int)
1503 (@value{GDBP}) b 'bubble(
1506 In some cases, @value{GDBN} can tell that completing a name requires using
1507 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1508 completing as much as it can) if you do not type the quote in the first
1512 (@value{GDBP}) b bub @key{TAB}
1513 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1514 (@value{GDBP}) b 'bubble(
1518 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1519 you have not yet started typing the argument list when you ask for
1520 completion on an overloaded symbol.
1522 For more information about overloaded functions, see @ref{C Plus Plus
1523 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1524 overload-resolution off} to disable overload resolution;
1525 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1529 @section Getting Help
1530 @cindex online documentation
1533 You can always ask @value{GDBN} itself for information on its commands,
1534 using the command @code{help}.
1537 @kindex h @r{(@code{help})}
1540 You can use @code{help} (abbreviated @code{h}) with no arguments to
1541 display a short list of named classes of commands:
1545 List of classes of commands:
1547 aliases -- Aliases of other commands
1548 breakpoints -- Making program stop at certain points
1549 data -- Examining data
1550 files -- Specifying and examining files
1551 internals -- Maintenance commands
1552 obscure -- Obscure features
1553 running -- Running the program
1554 stack -- Examining the stack
1555 status -- Status inquiries
1556 support -- Support facilities
1557 tracepoints -- Tracing of program execution without
1558 stopping the program
1559 user-defined -- User-defined commands
1561 Type "help" followed by a class name for a list of
1562 commands in that class.
1563 Type "help" followed by command name for full
1565 Command name abbreviations are allowed if unambiguous.
1568 @c the above line break eliminates huge line overfull...
1570 @item help @var{class}
1571 Using one of the general help classes as an argument, you can get a
1572 list of the individual commands in that class. For example, here is the
1573 help display for the class @code{status}:
1576 (@value{GDBP}) help status
1581 @c Line break in "show" line falsifies real output, but needed
1582 @c to fit in smallbook page size.
1583 info -- Generic command for showing things
1584 about the program being debugged
1585 show -- Generic command for showing things
1588 Type "help" followed by command name for full
1590 Command name abbreviations are allowed if unambiguous.
1594 @item help @var{command}
1595 With a command name as @code{help} argument, @value{GDBN} displays a
1596 short paragraph on how to use that command.
1599 @item apropos @var{args}
1600 The @code{apropos} command searches through all of the @value{GDBN}
1601 commands, and their documentation, for the regular expression specified in
1602 @var{args}. It prints out all matches found. For example:
1613 set symbol-reloading -- Set dynamic symbol table reloading
1614 multiple times in one run
1615 show symbol-reloading -- Show dynamic symbol table reloading
1616 multiple times in one run
1621 @item complete @var{args}
1622 The @code{complete @var{args}} command lists all the possible completions
1623 for the beginning of a command. Use @var{args} to specify the beginning of the
1624 command you want completed. For example:
1630 @noindent results in:
1641 @noindent This is intended for use by @sc{gnu} Emacs.
1644 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1645 and @code{show} to inquire about the state of your program, or the state
1646 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1647 manual introduces each of them in the appropriate context. The listings
1648 under @code{info} and under @code{show} in the Index point to
1649 all the sub-commands. @xref{Index}.
1654 @kindex i @r{(@code{info})}
1656 This command (abbreviated @code{i}) is for describing the state of your
1657 program. For example, you can list the arguments given to your program
1658 with @code{info args}, list the registers currently in use with @code{info
1659 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1660 You can get a complete list of the @code{info} sub-commands with
1661 @w{@code{help info}}.
1665 You can assign the result of an expression to an environment variable with
1666 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1667 @code{set prompt $}.
1671 In contrast to @code{info}, @code{show} is for describing the state of
1672 @value{GDBN} itself.
1673 You can change most of the things you can @code{show}, by using the
1674 related command @code{set}; for example, you can control what number
1675 system is used for displays with @code{set radix}, or simply inquire
1676 which is currently in use with @code{show radix}.
1679 To display all the settable parameters and their current
1680 values, you can use @code{show} with no arguments; you may also use
1681 @code{info set}. Both commands produce the same display.
1682 @c FIXME: "info set" violates the rule that "info" is for state of
1683 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1684 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1688 Here are three miscellaneous @code{show} subcommands, all of which are
1689 exceptional in lacking corresponding @code{set} commands:
1692 @kindex show version
1693 @cindex @value{GDBN} version number
1695 Show what version of @value{GDBN} is running. You should include this
1696 information in @value{GDBN} bug-reports. If multiple versions of
1697 @value{GDBN} are in use at your site, you may need to determine which
1698 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1699 commands are introduced, and old ones may wither away. Also, many
1700 system vendors ship variant versions of @value{GDBN}, and there are
1701 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1702 The version number is the same as the one announced when you start
1705 @kindex show copying
1706 @kindex info copying
1707 @cindex display @value{GDBN} copyright
1710 Display information about permission for copying @value{GDBN}.
1712 @kindex show warranty
1713 @kindex info warranty
1715 @itemx info warranty
1716 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1717 if your version of @value{GDBN} comes with one.
1722 @chapter Running Programs Under @value{GDBN}
1724 When you run a program under @value{GDBN}, you must first generate
1725 debugging information when you compile it.
1727 You may start @value{GDBN} with its arguments, if any, in an environment
1728 of your choice. If you are doing native debugging, you may redirect
1729 your program's input and output, debug an already running process, or
1730 kill a child process.
1733 * Compilation:: Compiling for debugging
1734 * Starting:: Starting your program
1735 * Arguments:: Your program's arguments
1736 * Environment:: Your program's environment
1738 * Working Directory:: Your program's working directory
1739 * Input/Output:: Your program's input and output
1740 * Attach:: Debugging an already-running process
1741 * Kill Process:: Killing the child process
1743 * Threads:: Debugging programs with multiple threads
1744 * Processes:: Debugging programs with multiple processes
1745 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1749 @section Compiling for Debugging
1751 In order to debug a program effectively, you need to generate
1752 debugging information when you compile it. This debugging information
1753 is stored in the object file; it describes the data type of each
1754 variable or function and the correspondence between source line numbers
1755 and addresses in the executable code.
1757 To request debugging information, specify the @samp{-g} option when you run
1760 Programs that are to be shipped to your customers are compiled with
1761 optimizations, using the @samp{-O} compiler option. However, many
1762 compilers are unable to handle the @samp{-g} and @samp{-O} options
1763 together. Using those compilers, you cannot generate optimized
1764 executables containing debugging information.
1766 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1767 without @samp{-O}, making it possible to debug optimized code. We
1768 recommend that you @emph{always} use @samp{-g} whenever you compile a
1769 program. You may think your program is correct, but there is no sense
1770 in pushing your luck.
1772 @cindex optimized code, debugging
1773 @cindex debugging optimized code
1774 When you debug a program compiled with @samp{-g -O}, remember that the
1775 optimizer is rearranging your code; the debugger shows you what is
1776 really there. Do not be too surprised when the execution path does not
1777 exactly match your source file! An extreme example: if you define a
1778 variable, but never use it, @value{GDBN} never sees that
1779 variable---because the compiler optimizes it out of existence.
1781 Some things do not work as well with @samp{-g -O} as with just
1782 @samp{-g}, particularly on machines with instruction scheduling. If in
1783 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1784 please report it to us as a bug (including a test case!).
1785 @xref{Variables}, for more information about debugging optimized code.
1787 Older versions of the @sc{gnu} C compiler permitted a variant option
1788 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1789 format; if your @sc{gnu} C compiler has this option, do not use it.
1791 @value{GDBN} knows about preprocessor macros and can show you their
1792 expansion (@pxref{Macros}). Most compilers do not include information
1793 about preprocessor macros in the debugging information if you specify
1794 the @option{-g} flag alone, because this information is rather large.
1795 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1796 provides macro information if you specify the options
1797 @option{-gdwarf-2} and @option{-g3}; the former option requests
1798 debugging information in the Dwarf 2 format, and the latter requests
1799 ``extra information''. In the future, we hope to find more compact
1800 ways to represent macro information, so that it can be included with
1805 @section Starting your Program
1811 @kindex r @r{(@code{run})}
1814 Use the @code{run} command to start your program under @value{GDBN}.
1815 You must first specify the program name (except on VxWorks) with an
1816 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1817 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1818 (@pxref{Files, ,Commands to Specify Files}).
1822 If you are running your program in an execution environment that
1823 supports processes, @code{run} creates an inferior process and makes
1824 that process run your program. (In environments without processes,
1825 @code{run} jumps to the start of your program.)
1827 The execution of a program is affected by certain information it
1828 receives from its superior. @value{GDBN} provides ways to specify this
1829 information, which you must do @emph{before} starting your program. (You
1830 can change it after starting your program, but such changes only affect
1831 your program the next time you start it.) This information may be
1832 divided into four categories:
1835 @item The @emph{arguments.}
1836 Specify the arguments to give your program as the arguments of the
1837 @code{run} command. If a shell is available on your target, the shell
1838 is used to pass the arguments, so that you may use normal conventions
1839 (such as wildcard expansion or variable substitution) in describing
1841 In Unix systems, you can control which shell is used with the
1842 @code{SHELL} environment variable.
1843 @xref{Arguments, ,Your Program's Arguments}.
1845 @item The @emph{environment.}
1846 Your program normally inherits its environment from @value{GDBN}, but you can
1847 use the @value{GDBN} commands @code{set environment} and @code{unset
1848 environment} to change parts of the environment that affect
1849 your program. @xref{Environment, ,Your Program's Environment}.
1851 @item The @emph{working directory.}
1852 Your program inherits its working directory from @value{GDBN}. You can set
1853 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1854 @xref{Working Directory, ,Your Program's Working Directory}.
1856 @item The @emph{standard input and output.}
1857 Your program normally uses the same device for standard input and
1858 standard output as @value{GDBN} is using. You can redirect input and output
1859 in the @code{run} command line, or you can use the @code{tty} command to
1860 set a different device for your program.
1861 @xref{Input/Output, ,Your Program's Input and Output}.
1864 @emph{Warning:} While input and output redirection work, you cannot use
1865 pipes to pass the output of the program you are debugging to another
1866 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1870 When you issue the @code{run} command, your program begins to execute
1871 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1872 of how to arrange for your program to stop. Once your program has
1873 stopped, you may call functions in your program, using the @code{print}
1874 or @code{call} commands. @xref{Data, ,Examining Data}.
1876 If the modification time of your symbol file has changed since the last
1877 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1878 table, and reads it again. When it does this, @value{GDBN} tries to retain
1879 your current breakpoints.
1884 @cindex run to main procedure
1885 The name of the main procedure can vary from language to language.
1886 With C or C@t{++}, the main procedure name is always @code{main}, but
1887 other languages such as Ada do not require a specific name for their
1888 main procedure. The debugger provides a convenient way to start the
1889 execution of the program and to stop at the beginning of the main
1890 procedure, depending on the language used.
1892 The @samp{start} command does the equivalent of setting a temporary
1893 breakpoint at the beginning of the main procedure and then invoking
1894 the @samp{run} command.
1896 @cindex elaboration phase
1897 Some programs contain an @dfn{elaboration} phase where some startup code is
1898 executed before the main procedure is called. This depends on the
1899 languages used to write your program. In C@t{++}, for instance,
1900 constructors for static and global objects are executed before
1901 @code{main} is called. It is therefore possible that the debugger stops
1902 before reaching the main procedure. However, the temporary breakpoint
1903 will remain to halt execution.
1905 Specify the arguments to give to your program as arguments to the
1906 @samp{start} command. These arguments will be given verbatim to the
1907 underlying @samp{run} command. Note that the same arguments will be
1908 reused if no argument is provided during subsequent calls to
1909 @samp{start} or @samp{run}.
1911 It is sometimes necessary to debug the program during elaboration. In
1912 these cases, using the @code{start} command would stop the execution of
1913 your program too late, as the program would have already completed the
1914 elaboration phase. Under these circumstances, insert breakpoints in your
1915 elaboration code before running your program.
1919 @section Your Program's Arguments
1921 @cindex arguments (to your program)
1922 The arguments to your program can be specified by the arguments of the
1924 They are passed to a shell, which expands wildcard characters and
1925 performs redirection of I/O, and thence to your program. Your
1926 @code{SHELL} environment variable (if it exists) specifies what shell
1927 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1928 the default shell (@file{/bin/sh} on Unix).
1930 On non-Unix systems, the program is usually invoked directly by
1931 @value{GDBN}, which emulates I/O redirection via the appropriate system
1932 calls, and the wildcard characters are expanded by the startup code of
1933 the program, not by the shell.
1935 @code{run} with no arguments uses the same arguments used by the previous
1936 @code{run}, or those set by the @code{set args} command.
1941 Specify the arguments to be used the next time your program is run. If
1942 @code{set args} has no arguments, @code{run} executes your program
1943 with no arguments. Once you have run your program with arguments,
1944 using @code{set args} before the next @code{run} is the only way to run
1945 it again without arguments.
1949 Show the arguments to give your program when it is started.
1953 @section Your Program's Environment
1955 @cindex environment (of your program)
1956 The @dfn{environment} consists of a set of environment variables and
1957 their values. Environment variables conventionally record such things as
1958 your user name, your home directory, your terminal type, and your search
1959 path for programs to run. Usually you set up environment variables with
1960 the shell and they are inherited by all the other programs you run. When
1961 debugging, it can be useful to try running your program with a modified
1962 environment without having to start @value{GDBN} over again.
1966 @item path @var{directory}
1967 Add @var{directory} to the front of the @code{PATH} environment variable
1968 (the search path for executables) that will be passed to your program.
1969 The value of @code{PATH} used by @value{GDBN} does not change.
1970 You may specify several directory names, separated by whitespace or by a
1971 system-dependent separator character (@samp{:} on Unix, @samp{;} on
1972 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
1973 is moved to the front, so it is searched sooner.
1975 You can use the string @samp{$cwd} to refer to whatever is the current
1976 working directory at the time @value{GDBN} searches the path. If you
1977 use @samp{.} instead, it refers to the directory where you executed the
1978 @code{path} command. @value{GDBN} replaces @samp{.} in the
1979 @var{directory} argument (with the current path) before adding
1980 @var{directory} to the search path.
1981 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
1982 @c document that, since repeating it would be a no-op.
1986 Display the list of search paths for executables (the @code{PATH}
1987 environment variable).
1989 @kindex show environment
1990 @item show environment @r{[}@var{varname}@r{]}
1991 Print the value of environment variable @var{varname} to be given to
1992 your program when it starts. If you do not supply @var{varname},
1993 print the names and values of all environment variables to be given to
1994 your program. You can abbreviate @code{environment} as @code{env}.
1996 @kindex set environment
1997 @item set environment @var{varname} @r{[}=@var{value}@r{]}
1998 Set environment variable @var{varname} to @var{value}. The value
1999 changes for your program only, not for @value{GDBN} itself. @var{value} may
2000 be any string; the values of environment variables are just strings, and
2001 any interpretation is supplied by your program itself. The @var{value}
2002 parameter is optional; if it is eliminated, the variable is set to a
2004 @c "any string" here does not include leading, trailing
2005 @c blanks. Gnu asks: does anyone care?
2007 For example, this command:
2014 tells the debugged program, when subsequently run, that its user is named
2015 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2016 are not actually required.)
2018 @kindex unset environment
2019 @item unset environment @var{varname}
2020 Remove variable @var{varname} from the environment to be passed to your
2021 program. This is different from @samp{set env @var{varname} =};
2022 @code{unset environment} removes the variable from the environment,
2023 rather than assigning it an empty value.
2026 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2028 by your @code{SHELL} environment variable if it exists (or
2029 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2030 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2031 @file{.bashrc} for BASH---any variables you set in that file affect
2032 your program. You may wish to move setting of environment variables to
2033 files that are only run when you sign on, such as @file{.login} or
2036 @node Working Directory
2037 @section Your Program's Working Directory
2039 @cindex working directory (of your program)
2040 Each time you start your program with @code{run}, it inherits its
2041 working directory from the current working directory of @value{GDBN}.
2042 The @value{GDBN} working directory is initially whatever it inherited
2043 from its parent process (typically the shell), but you can specify a new
2044 working directory in @value{GDBN} with the @code{cd} command.
2046 The @value{GDBN} working directory also serves as a default for the commands
2047 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2052 @cindex change working directory
2053 @item cd @var{directory}
2054 Set the @value{GDBN} working directory to @var{directory}.
2058 Print the @value{GDBN} working directory.
2061 It is generally impossible to find the current working directory of
2062 the process being debugged (since a program can change its directory
2063 during its run). If you work on a system where @value{GDBN} is
2064 configured with the @file{/proc} support, you can use the @code{info
2065 proc} command (@pxref{SVR4 Process Information}) to find out the
2066 current working directory of the debuggee.
2069 @section Your Program's Input and Output
2074 By default, the program you run under @value{GDBN} does input and output to
2075 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2076 to its own terminal modes to interact with you, but it records the terminal
2077 modes your program was using and switches back to them when you continue
2078 running your program.
2081 @kindex info terminal
2083 Displays information recorded by @value{GDBN} about the terminal modes your
2087 You can redirect your program's input and/or output using shell
2088 redirection with the @code{run} command. For example,
2095 starts your program, diverting its output to the file @file{outfile}.
2098 @cindex controlling terminal
2099 Another way to specify where your program should do input and output is
2100 with the @code{tty} command. This command accepts a file name as
2101 argument, and causes this file to be the default for future @code{run}
2102 commands. It also resets the controlling terminal for the child
2103 process, for future @code{run} commands. For example,
2110 directs that processes started with subsequent @code{run} commands
2111 default to do input and output on the terminal @file{/dev/ttyb} and have
2112 that as their controlling terminal.
2114 An explicit redirection in @code{run} overrides the @code{tty} command's
2115 effect on the input/output device, but not its effect on the controlling
2118 When you use the @code{tty} command or redirect input in the @code{run}
2119 command, only the input @emph{for your program} is affected. The input
2120 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2121 for @code{set inferior-tty}.
2123 @cindex inferior tty
2124 @cindex set inferior controlling terminal
2125 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2126 display the name of the terminal that will be used for future runs of your
2130 @item set inferior-tty /dev/ttyb
2131 @kindex set inferior-tty
2132 Set the tty for the program being debugged to /dev/ttyb.
2134 @item show inferior-tty
2135 @kindex show inferior-tty
2136 Show the current tty for the program being debugged.
2140 @section Debugging an Already-running Process
2145 @item attach @var{process-id}
2146 This command attaches to a running process---one that was started
2147 outside @value{GDBN}. (@code{info files} shows your active
2148 targets.) The command takes as argument a process ID. The usual way to
2149 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2150 or with the @samp{jobs -l} shell command.
2152 @code{attach} does not repeat if you press @key{RET} a second time after
2153 executing the command.
2156 To use @code{attach}, your program must be running in an environment
2157 which supports processes; for example, @code{attach} does not work for
2158 programs on bare-board targets that lack an operating system. You must
2159 also have permission to send the process a signal.
2161 When you use @code{attach}, the debugger finds the program running in
2162 the process first by looking in the current working directory, then (if
2163 the program is not found) by using the source file search path
2164 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2165 the @code{file} command to load the program. @xref{Files, ,Commands to
2168 The first thing @value{GDBN} does after arranging to debug the specified
2169 process is to stop it. You can examine and modify an attached process
2170 with all the @value{GDBN} commands that are ordinarily available when
2171 you start processes with @code{run}. You can insert breakpoints; you
2172 can step and continue; you can modify storage. If you would rather the
2173 process continue running, you may use the @code{continue} command after
2174 attaching @value{GDBN} to the process.
2179 When you have finished debugging the attached process, you can use the
2180 @code{detach} command to release it from @value{GDBN} control. Detaching
2181 the process continues its execution. After the @code{detach} command,
2182 that process and @value{GDBN} become completely independent once more, and you
2183 are ready to @code{attach} another process or start one with @code{run}.
2184 @code{detach} does not repeat if you press @key{RET} again after
2185 executing the command.
2188 If you exit @value{GDBN} while you have an attached process, you detach
2189 that process. If you use the @code{run} command, you kill that process.
2190 By default, @value{GDBN} asks for confirmation if you try to do either of these
2191 things; you can control whether or not you need to confirm by using the
2192 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2196 @section Killing the Child Process
2201 Kill the child process in which your program is running under @value{GDBN}.
2204 This command is useful if you wish to debug a core dump instead of a
2205 running process. @value{GDBN} ignores any core dump file while your program
2208 On some operating systems, a program cannot be executed outside @value{GDBN}
2209 while you have breakpoints set on it inside @value{GDBN}. You can use the
2210 @code{kill} command in this situation to permit running your program
2211 outside the debugger.
2213 The @code{kill} command is also useful if you wish to recompile and
2214 relink your program, since on many systems it is impossible to modify an
2215 executable file while it is running in a process. In this case, when you
2216 next type @code{run}, @value{GDBN} notices that the file has changed, and
2217 reads the symbol table again (while trying to preserve your current
2218 breakpoint settings).
2221 @section Debugging Programs with Multiple Threads
2223 @cindex threads of execution
2224 @cindex multiple threads
2225 @cindex switching threads
2226 In some operating systems, such as HP-UX and Solaris, a single program
2227 may have more than one @dfn{thread} of execution. The precise semantics
2228 of threads differ from one operating system to another, but in general
2229 the threads of a single program are akin to multiple processes---except
2230 that they share one address space (that is, they can all examine and
2231 modify the same variables). On the other hand, each thread has its own
2232 registers and execution stack, and perhaps private memory.
2234 @value{GDBN} provides these facilities for debugging multi-thread
2238 @item automatic notification of new threads
2239 @item @samp{thread @var{threadno}}, a command to switch among threads
2240 @item @samp{info threads}, a command to inquire about existing threads
2241 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2242 a command to apply a command to a list of threads
2243 @item thread-specific breakpoints
2247 @emph{Warning:} These facilities are not yet available on every
2248 @value{GDBN} configuration where the operating system supports threads.
2249 If your @value{GDBN} does not support threads, these commands have no
2250 effect. For example, a system without thread support shows no output
2251 from @samp{info threads}, and always rejects the @code{thread} command,
2255 (@value{GDBP}) info threads
2256 (@value{GDBP}) thread 1
2257 Thread ID 1 not known. Use the "info threads" command to
2258 see the IDs of currently known threads.
2260 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2261 @c doesn't support threads"?
2264 @cindex focus of debugging
2265 @cindex current thread
2266 The @value{GDBN} thread debugging facility allows you to observe all
2267 threads while your program runs---but whenever @value{GDBN} takes
2268 control, one thread in particular is always the focus of debugging.
2269 This thread is called the @dfn{current thread}. Debugging commands show
2270 program information from the perspective of the current thread.
2272 @cindex @code{New} @var{systag} message
2273 @cindex thread identifier (system)
2274 @c FIXME-implementors!! It would be more helpful if the [New...] message
2275 @c included GDB's numeric thread handle, so you could just go to that
2276 @c thread without first checking `info threads'.
2277 Whenever @value{GDBN} detects a new thread in your program, it displays
2278 the target system's identification for the thread with a message in the
2279 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2280 whose form varies depending on the particular system. For example, on
2281 @sc{gnu}/Linux, you might see
2284 [New Thread 46912507313328 (LWP 25582)]
2288 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2289 the @var{systag} is simply something like @samp{process 368}, with no
2292 @c FIXME!! (1) Does the [New...] message appear even for the very first
2293 @c thread of a program, or does it only appear for the
2294 @c second---i.e.@: when it becomes obvious we have a multithread
2296 @c (2) *Is* there necessarily a first thread always? Or do some
2297 @c multithread systems permit starting a program with multiple
2298 @c threads ab initio?
2300 @cindex thread number
2301 @cindex thread identifier (GDB)
2302 For debugging purposes, @value{GDBN} associates its own thread
2303 number---always a single integer---with each thread in your program.
2306 @kindex info threads
2308 Display a summary of all threads currently in your
2309 program. @value{GDBN} displays for each thread (in this order):
2313 the thread number assigned by @value{GDBN}
2316 the target system's thread identifier (@var{systag})
2319 the current stack frame summary for that thread
2323 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2324 indicates the current thread.
2328 @c end table here to get a little more width for example
2331 (@value{GDBP}) info threads
2332 3 process 35 thread 27 0x34e5 in sigpause ()
2333 2 process 35 thread 23 0x34e5 in sigpause ()
2334 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2340 @cindex debugging multithreaded programs (on HP-UX)
2341 @cindex thread identifier (GDB), on HP-UX
2342 For debugging purposes, @value{GDBN} associates its own thread
2343 number---a small integer assigned in thread-creation order---with each
2344 thread in your program.
2346 @cindex @code{New} @var{systag} message, on HP-UX
2347 @cindex thread identifier (system), on HP-UX
2348 @c FIXME-implementors!! It would be more helpful if the [New...] message
2349 @c included GDB's numeric thread handle, so you could just go to that
2350 @c thread without first checking `info threads'.
2351 Whenever @value{GDBN} detects a new thread in your program, it displays
2352 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2353 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2354 whose form varies depending on the particular system. For example, on
2358 [New thread 2 (system thread 26594)]
2362 when @value{GDBN} notices a new thread.
2365 @kindex info threads (HP-UX)
2367 Display a summary of all threads currently in your
2368 program. @value{GDBN} displays for each thread (in this order):
2371 @item the thread number assigned by @value{GDBN}
2373 @item the target system's thread identifier (@var{systag})
2375 @item the current stack frame summary for that thread
2379 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2380 indicates the current thread.
2384 @c end table here to get a little more width for example
2387 (@value{GDBP}) info threads
2388 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2390 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2391 from /usr/lib/libc.2
2392 1 system thread 27905 0x7b003498 in _brk () \@*
2393 from /usr/lib/libc.2
2396 On Solaris, you can display more information about user threads with a
2397 Solaris-specific command:
2400 @item maint info sol-threads
2401 @kindex maint info sol-threads
2402 @cindex thread info (Solaris)
2403 Display info on Solaris user threads.
2407 @kindex thread @var{threadno}
2408 @item thread @var{threadno}
2409 Make thread number @var{threadno} the current thread. The command
2410 argument @var{threadno} is the internal @value{GDBN} thread number, as
2411 shown in the first field of the @samp{info threads} display.
2412 @value{GDBN} responds by displaying the system identifier of the thread
2413 you selected, and its current stack frame summary:
2416 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2417 (@value{GDBP}) thread 2
2418 [Switching to process 35 thread 23]
2419 0x34e5 in sigpause ()
2423 As with the @samp{[New @dots{}]} message, the form of the text after
2424 @samp{Switching to} depends on your system's conventions for identifying
2427 @kindex thread apply
2428 @cindex apply command to several threads
2429 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2430 The @code{thread apply} command allows you to apply the named
2431 @var{command} to one or more threads. Specify the numbers of the
2432 threads that you want affected with the command argument
2433 @var{threadno}. It can be a single thread number, one of the numbers
2434 shown in the first field of the @samp{info threads} display; or it
2435 could be a range of thread numbers, as in @code{2-4}. To apply a
2436 command to all threads, type @kbd{thread apply all @var{command}}.
2439 @cindex automatic thread selection
2440 @cindex switching threads automatically
2441 @cindex threads, automatic switching
2442 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2443 signal, it automatically selects the thread where that breakpoint or
2444 signal happened. @value{GDBN} alerts you to the context switch with a
2445 message of the form @samp{[Switching to @var{systag}]} to identify the
2448 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2449 more information about how @value{GDBN} behaves when you stop and start
2450 programs with multiple threads.
2452 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2453 watchpoints in programs with multiple threads.
2456 @section Debugging Programs with Multiple Processes
2458 @cindex fork, debugging programs which call
2459 @cindex multiple processes
2460 @cindex processes, multiple
2461 On most systems, @value{GDBN} has no special support for debugging
2462 programs which create additional processes using the @code{fork}
2463 function. When a program forks, @value{GDBN} will continue to debug the
2464 parent process and the child process will run unimpeded. If you have
2465 set a breakpoint in any code which the child then executes, the child
2466 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2467 will cause it to terminate.
2469 However, if you want to debug the child process there is a workaround
2470 which isn't too painful. Put a call to @code{sleep} in the code which
2471 the child process executes after the fork. It may be useful to sleep
2472 only if a certain environment variable is set, or a certain file exists,
2473 so that the delay need not occur when you don't want to run @value{GDBN}
2474 on the child. While the child is sleeping, use the @code{ps} program to
2475 get its process ID. Then tell @value{GDBN} (a new invocation of
2476 @value{GDBN} if you are also debugging the parent process) to attach to
2477 the child process (@pxref{Attach}). From that point on you can debug
2478 the child process just like any other process which you attached to.
2480 On some systems, @value{GDBN} provides support for debugging programs that
2481 create additional processes using the @code{fork} or @code{vfork} functions.
2482 Currently, the only platforms with this feature are HP-UX (11.x and later
2483 only?) and GNU/Linux (kernel version 2.5.60 and later).
2485 By default, when a program forks, @value{GDBN} will continue to debug
2486 the parent process and the child process will run unimpeded.
2488 If you want to follow the child process instead of the parent process,
2489 use the command @w{@code{set follow-fork-mode}}.
2492 @kindex set follow-fork-mode
2493 @item set follow-fork-mode @var{mode}
2494 Set the debugger response to a program call of @code{fork} or
2495 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2496 process. The @var{mode} argument can be:
2500 The original process is debugged after a fork. The child process runs
2501 unimpeded. This is the default.
2504 The new process is debugged after a fork. The parent process runs
2509 @kindex show follow-fork-mode
2510 @item show follow-fork-mode
2511 Display the current debugger response to a @code{fork} or @code{vfork} call.
2514 @cindex debugging multiple processes
2515 On Linux, if you want to debug both the parent and child processes, use the
2516 command @w{@code{set detach-on-fork}}.
2519 @kindex set detach-on-fork
2520 @item set detach-on-fork @var{mode}
2521 Tells gdb whether to detach one of the processes after a fork, or
2522 retain debugger control over them both.
2526 The child process (or parent process, depending on the value of
2527 @code{follow-fork-mode}) will be detached and allowed to run
2528 independently. This is the default.
2531 Both processes will be held under the control of @value{GDBN}.
2532 One process (child or parent, depending on the value of
2533 @code{follow-fork-mode}) is debugged as usual, while the other
2538 @kindex show detach-on-follow
2539 @item show detach-on-follow
2540 Show whether detach-on-follow mode is on/off.
2543 If you choose to set @var{detach-on-follow} mode off, then
2544 @value{GDBN} will retain control of all forked processes (including
2545 nested forks). You can list the forked processes under the control of
2546 @value{GDBN} by using the @w{@code{info forks}} command, and switch
2547 from one fork to another by using the @w{@code{fork}} command.
2552 Print a list of all forked processes under the control of @value{GDBN}.
2553 The listing will include a fork id, a process id, and the current
2554 position (program counter) of the process.
2557 @kindex fork @var{fork-id}
2558 @item fork @var{fork-id}
2559 Make fork number @var{fork-id} the current process. The argument
2560 @var{fork-id} is the internal fork number assigned by @value{GDBN},
2561 as shown in the first field of the @samp{info forks} display.
2565 To quit debugging one of the forked processes, you can either detach
2566 from it by using the @w{@code{detach fork}} command (allowing it to
2567 run independently), or delete (and kill) it using the
2568 @w{@code{delete fork}} command.
2571 @kindex detach fork @var{fork-id}
2572 @item detach fork @var{fork-id}
2573 Detach from the process identified by @value{GDBN} fork number
2574 @var{fork-id}, and remove it from the fork list. The process will be
2575 allowed to run independently.
2577 @kindex delete fork @var{fork-id}
2578 @item delete fork @var{fork-id}
2579 Kill the process identified by @value{GDBN} fork number @var{fork-id},
2580 and remove it from the fork list.
2584 If you ask to debug a child process and a @code{vfork} is followed by an
2585 @code{exec}, @value{GDBN} executes the new target up to the first
2586 breakpoint in the new target. If you have a breakpoint set on
2587 @code{main} in your original program, the breakpoint will also be set on
2588 the child process's @code{main}.
2590 When a child process is spawned by @code{vfork}, you cannot debug the
2591 child or parent until an @code{exec} call completes.
2593 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2594 call executes, the new target restarts. To restart the parent process,
2595 use the @code{file} command with the parent executable name as its
2598 You can use the @code{catch} command to make @value{GDBN} stop whenever
2599 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2600 Catchpoints, ,Setting Catchpoints}.
2602 @node Checkpoint/Restart
2603 @section Setting a @emph{Bookmark} to Return to Later
2608 @cindex snapshot of a process
2609 @cindex rewind program state
2611 On certain operating systems@footnote{Currently, only
2612 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
2613 program's state, called a @dfn{checkpoint}, and come back to it
2616 Returning to a checkpoint effectively undoes everything that has
2617 happened in the program since the @code{checkpoint} was saved. This
2618 includes changes in memory, registers, and even (within some limits)
2619 system state. Effectively, it is like going back in time to the
2620 moment when the checkpoint was saved.
2622 Thus, if you're stepping thru a program and you think you're
2623 getting close to the point where things go wrong, you can save
2624 a checkpoint. Then, if you accidentally go too far and miss
2625 the critical statement, instead of having to restart your program
2626 from the beginning, you can just go back to the checkpoint and
2627 start again from there.
2629 This can be especially useful if it takes a lot of time or
2630 steps to reach the point where you think the bug occurs.
2632 To use the @code{checkpoint}/@code{restart} method of debugging:
2637 Save a snapshot of the debugged program's current execution state.
2638 The @code{checkpoint} command takes no arguments, but each checkpoint
2639 is assigned a small integer id, similar to a breakpoint id.
2641 @kindex info checkpoints
2642 @item info checkpoints
2643 List the checkpoints that have been saved in the current debugging
2644 session. For each checkpoint, the following information will be
2651 @item Source line, or label
2654 @kindex restart @var{checkpoint-id}
2655 @item restart @var{checkpoint-id}
2656 Restore the program state that was saved as checkpoint number
2657 @var{checkpoint-id}. All program variables, registers, stack frames
2658 etc.@: will be returned to the values that they had when the checkpoint
2659 was saved. In essence, gdb will ``wind back the clock'' to the point
2660 in time when the checkpoint was saved.
2662 Note that breakpoints, @value{GDBN} variables, command history etc.
2663 are not affected by restoring a checkpoint. In general, a checkpoint
2664 only restores things that reside in the program being debugged, not in
2667 @kindex delete checkpoint @var{checkpoint-id}
2668 @item delete checkpoint @var{checkpoint-id}
2669 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
2673 Returning to a previously saved checkpoint will restore the user state
2674 of the program being debugged, plus a significant subset of the system
2675 (OS) state, including file pointers. It won't ``un-write'' data from
2676 a file, but it will rewind the file pointer to the previous location,
2677 so that the previously written data can be overwritten. For files
2678 opened in read mode, the pointer will also be restored so that the
2679 previously read data can be read again.
2681 Of course, characters that have been sent to a printer (or other
2682 external device) cannot be ``snatched back'', and characters received
2683 from eg.@: a serial device can be removed from internal program buffers,
2684 but they cannot be ``pushed back'' into the serial pipeline, ready to
2685 be received again. Similarly, the actual contents of files that have
2686 been changed cannot be restored (at this time).
2688 However, within those constraints, you actually can ``rewind'' your
2689 program to a previously saved point in time, and begin debugging it
2690 again --- and you can change the course of events so as to debug a
2691 different execution path this time.
2693 @cindex checkpoints and process id
2694 Finally, there is one bit of internal program state that will be
2695 different when you return to a checkpoint --- the program's process
2696 id. Each checkpoint will have a unique process id (or @var{pid}),
2697 and each will be different from the program's original @var{pid}.
2698 If your program has saved a local copy of its process id, this could
2699 potentially pose a problem.
2701 @subsection A Non-obvious Benefit of Using Checkpoints
2703 On some systems such as @sc{gnu}/Linux, address space randomization
2704 is performed on new processes for security reasons. This makes it
2705 difficult or impossible to set a breakpoint, or watchpoint, on an
2706 absolute address if you have to restart the program, since the
2707 absolute location of a symbol will change from one execution to the
2710 A checkpoint, however, is an @emph{identical} copy of a process.
2711 Therefore if you create a checkpoint at (eg.@:) the start of main,
2712 and simply return to that checkpoint instead of restarting the
2713 process, you can avoid the effects of address randomization and
2714 your symbols will all stay in the same place.
2717 @chapter Stopping and Continuing
2719 The principal purposes of using a debugger are so that you can stop your
2720 program before it terminates; or so that, if your program runs into
2721 trouble, you can investigate and find out why.
2723 Inside @value{GDBN}, your program may stop for any of several reasons,
2724 such as a signal, a breakpoint, or reaching a new line after a
2725 @value{GDBN} command such as @code{step}. You may then examine and
2726 change variables, set new breakpoints or remove old ones, and then
2727 continue execution. Usually, the messages shown by @value{GDBN} provide
2728 ample explanation of the status of your program---but you can also
2729 explicitly request this information at any time.
2732 @kindex info program
2734 Display information about the status of your program: whether it is
2735 running or not, what process it is, and why it stopped.
2739 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2740 * Continuing and Stepping:: Resuming execution
2742 * Thread Stops:: Stopping and starting multi-thread programs
2746 @section Breakpoints, Watchpoints, and Catchpoints
2749 A @dfn{breakpoint} makes your program stop whenever a certain point in
2750 the program is reached. For each breakpoint, you can add conditions to
2751 control in finer detail whether your program stops. You can set
2752 breakpoints with the @code{break} command and its variants (@pxref{Set
2753 Breaks, ,Setting Breakpoints}), to specify the place where your program
2754 should stop by line number, function name or exact address in the
2757 On some systems, you can set breakpoints in shared libraries before
2758 the executable is run. There is a minor limitation on HP-UX systems:
2759 you must wait until the executable is run in order to set breakpoints
2760 in shared library routines that are not called directly by the program
2761 (for example, routines that are arguments in a @code{pthread_create}
2765 @cindex data breakpoints
2766 @cindex memory tracing
2767 @cindex breakpoint on memory address
2768 @cindex breakpoint on variable modification
2769 A @dfn{watchpoint} is a special breakpoint that stops your program
2770 when the value of an expression changes. The expression may be a value
2771 of a variable, or it could involve values of one or more variables
2772 combined by operators, such as @samp{a + b}. This is sometimes called
2773 @dfn{data breakpoints}. You must use a different command to set
2774 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
2775 from that, you can manage a watchpoint like any other breakpoint: you
2776 enable, disable, and delete both breakpoints and watchpoints using the
2779 You can arrange to have values from your program displayed automatically
2780 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2784 @cindex breakpoint on events
2785 A @dfn{catchpoint} is another special breakpoint that stops your program
2786 when a certain kind of event occurs, such as the throwing of a C@t{++}
2787 exception or the loading of a library. As with watchpoints, you use a
2788 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2789 Catchpoints}), but aside from that, you can manage a catchpoint like any
2790 other breakpoint. (To stop when your program receives a signal, use the
2791 @code{handle} command; see @ref{Signals, ,Signals}.)
2793 @cindex breakpoint numbers
2794 @cindex numbers for breakpoints
2795 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2796 catchpoint when you create it; these numbers are successive integers
2797 starting with one. In many of the commands for controlling various
2798 features of breakpoints you use the breakpoint number to say which
2799 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2800 @dfn{disabled}; if disabled, it has no effect on your program until you
2803 @cindex breakpoint ranges
2804 @cindex ranges of breakpoints
2805 Some @value{GDBN} commands accept a range of breakpoints on which to
2806 operate. A breakpoint range is either a single breakpoint number, like
2807 @samp{5}, or two such numbers, in increasing order, separated by a
2808 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2809 all breakpoints in that range are operated on.
2812 * Set Breaks:: Setting breakpoints
2813 * Set Watchpoints:: Setting watchpoints
2814 * Set Catchpoints:: Setting catchpoints
2815 * Delete Breaks:: Deleting breakpoints
2816 * Disabling:: Disabling breakpoints
2817 * Conditions:: Break conditions
2818 * Break Commands:: Breakpoint command lists
2819 * Breakpoint Menus:: Breakpoint menus
2820 * Error in Breakpoints:: ``Cannot insert breakpoints''
2821 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
2825 @subsection Setting Breakpoints
2827 @c FIXME LMB what does GDB do if no code on line of breakpt?
2828 @c consider in particular declaration with/without initialization.
2830 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2833 @kindex b @r{(@code{break})}
2834 @vindex $bpnum@r{, convenience variable}
2835 @cindex latest breakpoint
2836 Breakpoints are set with the @code{break} command (abbreviated
2837 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2838 number of the breakpoint you've set most recently; see @ref{Convenience
2839 Vars,, Convenience Variables}, for a discussion of what you can do with
2840 convenience variables.
2842 You have several ways to say where the breakpoint should go.
2845 @item break @var{function}
2846 Set a breakpoint at entry to function @var{function}.
2847 When using source languages that permit overloading of symbols, such as
2848 C@t{++}, @var{function} may refer to more than one possible place to break.
2849 @xref{Breakpoint Menus,,Breakpoint Menus}, for a discussion of that situation.
2851 @item break +@var{offset}
2852 @itemx break -@var{offset}
2853 Set a breakpoint some number of lines forward or back from the position
2854 at which execution stopped in the currently selected @dfn{stack frame}.
2855 (@xref{Frames, ,Frames}, for a description of stack frames.)
2857 @item break @var{linenum}
2858 Set a breakpoint at line @var{linenum} in the current source file.
2859 The current source file is the last file whose source text was printed.
2860 The breakpoint will stop your program just before it executes any of the
2863 @item break @var{filename}:@var{linenum}
2864 Set a breakpoint at line @var{linenum} in source file @var{filename}.
2866 @item break @var{filename}:@var{function}
2867 Set a breakpoint at entry to function @var{function} found in file
2868 @var{filename}. Specifying a file name as well as a function name is
2869 superfluous except when multiple files contain similarly named
2872 @item break *@var{address}
2873 Set a breakpoint at address @var{address}. You can use this to set
2874 breakpoints in parts of your program which do not have debugging
2875 information or source files.
2878 When called without any arguments, @code{break} sets a breakpoint at
2879 the next instruction to be executed in the selected stack frame
2880 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2881 innermost, this makes your program stop as soon as control
2882 returns to that frame. This is similar to the effect of a
2883 @code{finish} command in the frame inside the selected frame---except
2884 that @code{finish} does not leave an active breakpoint. If you use
2885 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2886 the next time it reaches the current location; this may be useful
2889 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2890 least one instruction has been executed. If it did not do this, you
2891 would be unable to proceed past a breakpoint without first disabling the
2892 breakpoint. This rule applies whether or not the breakpoint already
2893 existed when your program stopped.
2895 @item break @dots{} if @var{cond}
2896 Set a breakpoint with condition @var{cond}; evaluate the expression
2897 @var{cond} each time the breakpoint is reached, and stop only if the
2898 value is nonzero---that is, if @var{cond} evaluates as true.
2899 @samp{@dots{}} stands for one of the possible arguments described
2900 above (or no argument) specifying where to break. @xref{Conditions,
2901 ,Break Conditions}, for more information on breakpoint conditions.
2904 @item tbreak @var{args}
2905 Set a breakpoint enabled only for one stop. @var{args} are the
2906 same as for the @code{break} command, and the breakpoint is set in the same
2907 way, but the breakpoint is automatically deleted after the first time your
2908 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
2911 @cindex hardware breakpoints
2912 @item hbreak @var{args}
2913 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2914 @code{break} command and the breakpoint is set in the same way, but the
2915 breakpoint requires hardware support and some target hardware may not
2916 have this support. The main purpose of this is EPROM/ROM code
2917 debugging, so you can set a breakpoint at an instruction without
2918 changing the instruction. This can be used with the new trap-generation
2919 provided by SPARClite DSU and most x86-based targets. These targets
2920 will generate traps when a program accesses some data or instruction
2921 address that is assigned to the debug registers. However the hardware
2922 breakpoint registers can take a limited number of breakpoints. For
2923 example, on the DSU, only two data breakpoints can be set at a time, and
2924 @value{GDBN} will reject this command if more than two are used. Delete
2925 or disable unused hardware breakpoints before setting new ones
2926 (@pxref{Disabling, ,Disabling Breakpoints}).
2927 @xref{Conditions, ,Break Conditions}.
2928 For remote targets, you can restrict the number of hardware
2929 breakpoints @value{GDBN} will use, see @ref{set remote
2930 hardware-breakpoint-limit}.
2934 @item thbreak @var{args}
2935 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2936 are the same as for the @code{hbreak} command and the breakpoint is set in
2937 the same way. However, like the @code{tbreak} command,
2938 the breakpoint is automatically deleted after the
2939 first time your program stops there. Also, like the @code{hbreak}
2940 command, the breakpoint requires hardware support and some target hardware
2941 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
2942 See also @ref{Conditions, ,Break Conditions}.
2945 @cindex regular expression
2946 @cindex breakpoints in functions matching a regexp
2947 @cindex set breakpoints in many functions
2948 @item rbreak @var{regex}
2949 Set breakpoints on all functions matching the regular expression
2950 @var{regex}. This command sets an unconditional breakpoint on all
2951 matches, printing a list of all breakpoints it set. Once these
2952 breakpoints are set, they are treated just like the breakpoints set with
2953 the @code{break} command. You can delete them, disable them, or make
2954 them conditional the same way as any other breakpoint.
2956 The syntax of the regular expression is the standard one used with tools
2957 like @file{grep}. Note that this is different from the syntax used by
2958 shells, so for instance @code{foo*} matches all functions that include
2959 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2960 @code{.*} leading and trailing the regular expression you supply, so to
2961 match only functions that begin with @code{foo}, use @code{^foo}.
2963 @cindex non-member C@t{++} functions, set breakpoint in
2964 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2965 breakpoints on overloaded functions that are not members of any special
2968 @cindex set breakpoints on all functions
2969 The @code{rbreak} command can be used to set breakpoints in
2970 @strong{all} the functions in a program, like this:
2973 (@value{GDBP}) rbreak .
2976 @kindex info breakpoints
2977 @cindex @code{$_} and @code{info breakpoints}
2978 @item info breakpoints @r{[}@var{n}@r{]}
2979 @itemx info break @r{[}@var{n}@r{]}
2980 @itemx info watchpoints @r{[}@var{n}@r{]}
2981 Print a table of all breakpoints, watchpoints, and catchpoints set and
2982 not deleted. Optional argument @var{n} means print information only
2983 about the specified breakpoint (or watchpoint or catchpoint). For
2984 each breakpoint, following columns are printed:
2987 @item Breakpoint Numbers
2989 Breakpoint, watchpoint, or catchpoint.
2991 Whether the breakpoint is marked to be disabled or deleted when hit.
2992 @item Enabled or Disabled
2993 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
2994 that are not enabled.
2996 Where the breakpoint is in your program, as a memory address. If the
2997 breakpoint is pending (see below for details) on a future load of a shared library, the address
2998 will be listed as @samp{<PENDING>}.
3000 Where the breakpoint is in the source for your program, as a file and
3001 line number. For a pending breakpoint, the original string passed to
3002 the breakpoint command will be listed as it cannot be resolved until
3003 the appropriate shared library is loaded in the future.
3007 If a breakpoint is conditional, @code{info break} shows the condition on
3008 the line following the affected breakpoint; breakpoint commands, if any,
3009 are listed after that. A pending breakpoint is allowed to have a condition
3010 specified for it. The condition is not parsed for validity until a shared
3011 library is loaded that allows the pending breakpoint to resolve to a
3015 @code{info break} with a breakpoint
3016 number @var{n} as argument lists only that breakpoint. The
3017 convenience variable @code{$_} and the default examining-address for
3018 the @code{x} command are set to the address of the last breakpoint
3019 listed (@pxref{Memory, ,Examining Memory}).
3022 @code{info break} displays a count of the number of times the breakpoint
3023 has been hit. This is especially useful in conjunction with the
3024 @code{ignore} command. You can ignore a large number of breakpoint
3025 hits, look at the breakpoint info to see how many times the breakpoint
3026 was hit, and then run again, ignoring one less than that number. This
3027 will get you quickly to the last hit of that breakpoint.
3030 @value{GDBN} allows you to set any number of breakpoints at the same place in
3031 your program. There is nothing silly or meaningless about this. When
3032 the breakpoints are conditional, this is even useful
3033 (@pxref{Conditions, ,Break Conditions}).
3035 @cindex pending breakpoints
3036 If a specified breakpoint location cannot be found, it may be due to the fact
3037 that the location is in a shared library that is yet to be loaded. In such
3038 a case, you may want @value{GDBN} to create a special breakpoint (known as
3039 a @dfn{pending breakpoint}) that
3040 attempts to resolve itself in the future when an appropriate shared library
3043 Pending breakpoints are useful to set at the start of your
3044 @value{GDBN} session for locations that you know will be dynamically loaded
3045 later by the program being debugged. When shared libraries are loaded,
3046 a check is made to see if the load resolves any pending breakpoint locations.
3047 If a pending breakpoint location gets resolved,
3048 a regular breakpoint is created and the original pending breakpoint is removed.
3050 @value{GDBN} provides some additional commands for controlling pending
3053 @kindex set breakpoint pending
3054 @kindex show breakpoint pending
3056 @item set breakpoint pending auto
3057 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3058 location, it queries you whether a pending breakpoint should be created.
3060 @item set breakpoint pending on
3061 This indicates that an unrecognized breakpoint location should automatically
3062 result in a pending breakpoint being created.
3064 @item set breakpoint pending off
3065 This indicates that pending breakpoints are not to be created. Any
3066 unrecognized breakpoint location results in an error. This setting does
3067 not affect any pending breakpoints previously created.
3069 @item show breakpoint pending
3070 Show the current behavior setting for creating pending breakpoints.
3073 @cindex operations allowed on pending breakpoints
3074 Normal breakpoint operations apply to pending breakpoints as well. You may
3075 specify a condition for a pending breakpoint and/or commands to run when the
3076 breakpoint is reached. You can also enable or disable
3077 the pending breakpoint. When you specify a condition for a pending breakpoint,
3078 the parsing of the condition will be deferred until the point where the
3079 pending breakpoint location is resolved. Disabling a pending breakpoint
3080 tells @value{GDBN} to not attempt to resolve the breakpoint on any subsequent
3081 shared library load. When a pending breakpoint is re-enabled,
3082 @value{GDBN} checks to see if the location is already resolved.
3083 This is done because any number of shared library loads could have
3084 occurred since the time the breakpoint was disabled and one or more
3085 of these loads could resolve the location.
3087 @cindex automatic hardware breakpoints
3088 For some targets, @value{GDBN} can automatically decide if hardware or
3089 software breakpoints should be used, depending on whether the
3090 breakpoint address is read-only or read-write. This applies to
3091 breakpoints set with the @code{break} command as well as to internal
3092 breakpoints set by commands like @code{next} and @code{finish}. For
3093 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3096 You can control this automatic behaviour with the following commands::
3098 @kindex set breakpoint auto-hw
3099 @kindex show breakpoint auto-hw
3101 @item set breakpoint auto-hw on
3102 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3103 will try to use the target memory map to decide if software or hardware
3104 breakpoint must be used.
3106 @item set breakpoint auto-hw off
3107 This indicates @value{GDBN} should not automatically select breakpoint
3108 type. If the target provides a memory map, @value{GDBN} will warn when
3109 trying to set software breakpoint at a read-only address.
3113 @cindex negative breakpoint numbers
3114 @cindex internal @value{GDBN} breakpoints
3115 @value{GDBN} itself sometimes sets breakpoints in your program for
3116 special purposes, such as proper handling of @code{longjmp} (in C
3117 programs). These internal breakpoints are assigned negative numbers,
3118 starting with @code{-1}; @samp{info breakpoints} does not display them.
3119 You can see these breakpoints with the @value{GDBN} maintenance command
3120 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3123 @node Set Watchpoints
3124 @subsection Setting Watchpoints
3126 @cindex setting watchpoints
3127 You can use a watchpoint to stop execution whenever the value of an
3128 expression changes, without having to predict a particular place where
3129 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3130 The expression may be as simple as the value of a single variable, or
3131 as complex as many variables combined by operators. Examples include:
3135 A reference to the value of a single variable.
3138 An address cast to an appropriate data type. For example,
3139 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3140 address (assuming an @code{int} occupies 4 bytes).
3143 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3144 expression can use any operators valid in the program's native
3145 language (@pxref{Languages}).
3148 @cindex software watchpoints
3149 @cindex hardware watchpoints
3150 Depending on your system, watchpoints may be implemented in software or
3151 hardware. @value{GDBN} does software watchpointing by single-stepping your
3152 program and testing the variable's value each time, which is hundreds of
3153 times slower than normal execution. (But this may still be worth it, to
3154 catch errors where you have no clue what part of your program is the
3157 On some systems, such as HP-UX, @sc{gnu}/Linux and most other
3158 x86-based targets, @value{GDBN} includes support for hardware
3159 watchpoints, which do not slow down the running of your program.
3163 @item watch @var{expr}
3164 Set a watchpoint for an expression. @value{GDBN} will break when the
3165 expression @var{expr} is written into by the program and its value
3166 changes. The simplest (and the most popular) use of this command is
3167 to watch the value of a single variable:
3170 (@value{GDBP}) watch foo
3174 @item rwatch @var{expr}
3175 Set a watchpoint that will break when the value of @var{expr} is read
3179 @item awatch @var{expr}
3180 Set a watchpoint that will break when @var{expr} is either read from
3181 or written into by the program.
3183 @kindex info watchpoints @r{[}@var{n}@r{]}
3184 @item info watchpoints
3185 This command prints a list of watchpoints, breakpoints, and catchpoints;
3186 it is the same as @code{info break} (@pxref{Set Breaks}).
3189 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3190 watchpoints execute very quickly, and the debugger reports a change in
3191 value at the exact instruction where the change occurs. If @value{GDBN}
3192 cannot set a hardware watchpoint, it sets a software watchpoint, which
3193 executes more slowly and reports the change in value at the next
3194 @emph{statement}, not the instruction, after the change occurs.
3196 @cindex use only software watchpoints
3197 You can force @value{GDBN} to use only software watchpoints with the
3198 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3199 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3200 the underlying system supports them. (Note that hardware-assisted
3201 watchpoints that were set @emph{before} setting
3202 @code{can-use-hw-watchpoints} to zero will still use the hardware
3203 mechanism of watching expression values.)
3206 @item set can-use-hw-watchpoints
3207 @kindex set can-use-hw-watchpoints
3208 Set whether or not to use hardware watchpoints.
3210 @item show can-use-hw-watchpoints
3211 @kindex show can-use-hw-watchpoints
3212 Show the current mode of using hardware watchpoints.
3215 For remote targets, you can restrict the number of hardware
3216 watchpoints @value{GDBN} will use, see @ref{set remote
3217 hardware-breakpoint-limit}.
3219 When you issue the @code{watch} command, @value{GDBN} reports
3222 Hardware watchpoint @var{num}: @var{expr}
3226 if it was able to set a hardware watchpoint.
3228 Currently, the @code{awatch} and @code{rwatch} commands can only set
3229 hardware watchpoints, because accesses to data that don't change the
3230 value of the watched expression cannot be detected without examining
3231 every instruction as it is being executed, and @value{GDBN} does not do
3232 that currently. If @value{GDBN} finds that it is unable to set a
3233 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3234 will print a message like this:
3237 Expression cannot be implemented with read/access watchpoint.
3240 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3241 data type of the watched expression is wider than what a hardware
3242 watchpoint on the target machine can handle. For example, some systems
3243 can only watch regions that are up to 4 bytes wide; on such systems you
3244 cannot set hardware watchpoints for an expression that yields a
3245 double-precision floating-point number (which is typically 8 bytes
3246 wide). As a work-around, it might be possible to break the large region
3247 into a series of smaller ones and watch them with separate watchpoints.
3249 If you set too many hardware watchpoints, @value{GDBN} might be unable
3250 to insert all of them when you resume the execution of your program.
3251 Since the precise number of active watchpoints is unknown until such
3252 time as the program is about to be resumed, @value{GDBN} might not be
3253 able to warn you about this when you set the watchpoints, and the
3254 warning will be printed only when the program is resumed:
3257 Hardware watchpoint @var{num}: Could not insert watchpoint
3261 If this happens, delete or disable some of the watchpoints.
3263 Watching complex expressions that reference many variables can also
3264 exhaust the resources available for hardware-assisted watchpoints.
3265 That's because @value{GDBN} needs to watch every variable in the
3266 expression with separately allocated resources.
3268 The SPARClite DSU will generate traps when a program accesses some data
3269 or instruction address that is assigned to the debug registers. For the
3270 data addresses, DSU facilitates the @code{watch} command. However the
3271 hardware breakpoint registers can only take two data watchpoints, and
3272 both watchpoints must be the same kind. For example, you can set two
3273 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
3274 @strong{or} two with @code{awatch} commands, but you cannot set one
3275 watchpoint with one command and the other with a different command.
3276 @value{GDBN} will reject the command if you try to mix watchpoints.
3277 Delete or disable unused watchpoint commands before setting new ones.
3279 If you call a function interactively using @code{print} or @code{call},
3280 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3281 kind of breakpoint or the call completes.
3283 @value{GDBN} automatically deletes watchpoints that watch local
3284 (automatic) variables, or expressions that involve such variables, when
3285 they go out of scope, that is, when the execution leaves the block in
3286 which these variables were defined. In particular, when the program
3287 being debugged terminates, @emph{all} local variables go out of scope,
3288 and so only watchpoints that watch global variables remain set. If you
3289 rerun the program, you will need to set all such watchpoints again. One
3290 way of doing that would be to set a code breakpoint at the entry to the
3291 @code{main} function and when it breaks, set all the watchpoints.
3294 @cindex watchpoints and threads
3295 @cindex threads and watchpoints
3296 @emph{Warning:} In multi-thread programs, watchpoints have only limited
3297 usefulness. With the current watchpoint implementation, @value{GDBN}
3298 can only watch the value of an expression @emph{in a single thread}. If
3299 you are confident that the expression can only change due to the current
3300 thread's activity (and if you are also confident that no other thread
3301 can become current), then you can use watchpoints as usual. However,
3302 @value{GDBN} may not notice when a non-current thread's activity changes
3305 @c FIXME: this is almost identical to the previous paragraph.
3306 @emph{HP-UX Warning:} In multi-thread programs, software watchpoints
3307 have only limited usefulness. If @value{GDBN} creates a software
3308 watchpoint, it can only watch the value of an expression @emph{in a
3309 single thread}. If you are confident that the expression can only
3310 change due to the current thread's activity (and if you are also
3311 confident that no other thread can become current), then you can use
3312 software watchpoints as usual. However, @value{GDBN} may not notice
3313 when a non-current thread's activity changes the expression. (Hardware
3314 watchpoints, in contrast, watch an expression in all threads.)
3317 @xref{set remote hardware-watchpoint-limit}.
3319 @node Set Catchpoints
3320 @subsection Setting Catchpoints
3321 @cindex catchpoints, setting
3322 @cindex exception handlers
3323 @cindex event handling
3325 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3326 kinds of program events, such as C@t{++} exceptions or the loading of a
3327 shared library. Use the @code{catch} command to set a catchpoint.
3331 @item catch @var{event}
3332 Stop when @var{event} occurs. @var{event} can be any of the following:
3335 @cindex stop on C@t{++} exceptions
3336 The throwing of a C@t{++} exception.
3339 The catching of a C@t{++} exception.
3342 @cindex Ada exception catching
3343 @cindex catch Ada exceptions
3344 An Ada exception being raised. If an exception name is specified
3345 at the end of the command (eg @code{catch exception Program_Error}),
3346 the debugger will stop only when this specific exception is raised.
3347 Otherwise, the debugger stops execution when any Ada exception is raised.
3349 @item exception unhandled
3350 An exception that was raised but is not handled by the program.
3353 A failed Ada assertion.
3356 @cindex break on fork/exec
3357 A call to @code{exec}. This is currently only available for HP-UX.
3360 A call to @code{fork}. This is currently only available for HP-UX.
3363 A call to @code{vfork}. This is currently only available for HP-UX.
3366 @itemx load @var{libname}
3367 @cindex break on load/unload of shared library
3368 The dynamic loading of any shared library, or the loading of the library
3369 @var{libname}. This is currently only available for HP-UX.
3372 @itemx unload @var{libname}
3373 The unloading of any dynamically loaded shared library, or the unloading
3374 of the library @var{libname}. This is currently only available for HP-UX.
3377 @item tcatch @var{event}
3378 Set a catchpoint that is enabled only for one stop. The catchpoint is
3379 automatically deleted after the first time the event is caught.
3383 Use the @code{info break} command to list the current catchpoints.
3385 There are currently some limitations to C@t{++} exception handling
3386 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
3390 If you call a function interactively, @value{GDBN} normally returns
3391 control to you when the function has finished executing. If the call
3392 raises an exception, however, the call may bypass the mechanism that
3393 returns control to you and cause your program either to abort or to
3394 simply continue running until it hits a breakpoint, catches a signal
3395 that @value{GDBN} is listening for, or exits. This is the case even if
3396 you set a catchpoint for the exception; catchpoints on exceptions are
3397 disabled within interactive calls.
3400 You cannot raise an exception interactively.
3403 You cannot install an exception handler interactively.
3406 @cindex raise exceptions
3407 Sometimes @code{catch} is not the best way to debug exception handling:
3408 if you need to know exactly where an exception is raised, it is better to
3409 stop @emph{before} the exception handler is called, since that way you
3410 can see the stack before any unwinding takes place. If you set a
3411 breakpoint in an exception handler instead, it may not be easy to find
3412 out where the exception was raised.
3414 To stop just before an exception handler is called, you need some
3415 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3416 raised by calling a library function named @code{__raise_exception}
3417 which has the following ANSI C interface:
3420 /* @var{addr} is where the exception identifier is stored.
3421 @var{id} is the exception identifier. */
3422 void __raise_exception (void **addr, void *id);
3426 To make the debugger catch all exceptions before any stack
3427 unwinding takes place, set a breakpoint on @code{__raise_exception}
3428 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
3430 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
3431 that depends on the value of @var{id}, you can stop your program when
3432 a specific exception is raised. You can use multiple conditional
3433 breakpoints to stop your program when any of a number of exceptions are
3438 @subsection Deleting Breakpoints
3440 @cindex clearing breakpoints, watchpoints, catchpoints
3441 @cindex deleting breakpoints, watchpoints, catchpoints
3442 It is often necessary to eliminate a breakpoint, watchpoint, or
3443 catchpoint once it has done its job and you no longer want your program
3444 to stop there. This is called @dfn{deleting} the breakpoint. A
3445 breakpoint that has been deleted no longer exists; it is forgotten.
3447 With the @code{clear} command you can delete breakpoints according to
3448 where they are in your program. With the @code{delete} command you can
3449 delete individual breakpoints, watchpoints, or catchpoints by specifying
3450 their breakpoint numbers.
3452 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3453 automatically ignores breakpoints on the first instruction to be executed
3454 when you continue execution without changing the execution address.
3459 Delete any breakpoints at the next instruction to be executed in the
3460 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
3461 the innermost frame is selected, this is a good way to delete a
3462 breakpoint where your program just stopped.
3464 @item clear @var{function}
3465 @itemx clear @var{filename}:@var{function}
3466 Delete any breakpoints set at entry to the named @var{function}.
3468 @item clear @var{linenum}
3469 @itemx clear @var{filename}:@var{linenum}
3470 Delete any breakpoints set at or within the code of the specified
3471 @var{linenum} of the specified @var{filename}.
3473 @cindex delete breakpoints
3475 @kindex d @r{(@code{delete})}
3476 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3477 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3478 ranges specified as arguments. If no argument is specified, delete all
3479 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3480 confirm off}). You can abbreviate this command as @code{d}.
3484 @subsection Disabling Breakpoints
3486 @cindex enable/disable a breakpoint
3487 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3488 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3489 it had been deleted, but remembers the information on the breakpoint so
3490 that you can @dfn{enable} it again later.
3492 You disable and enable breakpoints, watchpoints, and catchpoints with
3493 the @code{enable} and @code{disable} commands, optionally specifying one
3494 or more breakpoint numbers as arguments. Use @code{info break} or
3495 @code{info watch} to print a list of breakpoints, watchpoints, and
3496 catchpoints if you do not know which numbers to use.
3498 A breakpoint, watchpoint, or catchpoint can have any of four different
3499 states of enablement:
3503 Enabled. The breakpoint stops your program. A breakpoint set
3504 with the @code{break} command starts out in this state.
3506 Disabled. The breakpoint has no effect on your program.
3508 Enabled once. The breakpoint stops your program, but then becomes
3511 Enabled for deletion. The breakpoint stops your program, but
3512 immediately after it does so it is deleted permanently. A breakpoint
3513 set with the @code{tbreak} command starts out in this state.
3516 You can use the following commands to enable or disable breakpoints,
3517 watchpoints, and catchpoints:
3521 @kindex dis @r{(@code{disable})}
3522 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3523 Disable the specified breakpoints---or all breakpoints, if none are
3524 listed. A disabled breakpoint has no effect but is not forgotten. All
3525 options such as ignore-counts, conditions and commands are remembered in
3526 case the breakpoint is enabled again later. You may abbreviate
3527 @code{disable} as @code{dis}.
3530 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3531 Enable the specified breakpoints (or all defined breakpoints). They
3532 become effective once again in stopping your program.
3534 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3535 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3536 of these breakpoints immediately after stopping your program.
3538 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3539 Enable the specified breakpoints to work once, then die. @value{GDBN}
3540 deletes any of these breakpoints as soon as your program stops there.
3541 Breakpoints set by the @code{tbreak} command start out in this state.
3544 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3545 @c confusing: tbreak is also initially enabled.
3546 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3547 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
3548 subsequently, they become disabled or enabled only when you use one of
3549 the commands above. (The command @code{until} can set and delete a
3550 breakpoint of its own, but it does not change the state of your other
3551 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3555 @subsection Break Conditions
3556 @cindex conditional breakpoints
3557 @cindex breakpoint conditions
3559 @c FIXME what is scope of break condition expr? Context where wanted?
3560 @c in particular for a watchpoint?
3561 The simplest sort of breakpoint breaks every time your program reaches a
3562 specified place. You can also specify a @dfn{condition} for a
3563 breakpoint. A condition is just a Boolean expression in your
3564 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3565 a condition evaluates the expression each time your program reaches it,
3566 and your program stops only if the condition is @emph{true}.
3568 This is the converse of using assertions for program validation; in that
3569 situation, you want to stop when the assertion is violated---that is,
3570 when the condition is false. In C, if you want to test an assertion expressed
3571 by the condition @var{assert}, you should set the condition
3572 @samp{! @var{assert}} on the appropriate breakpoint.
3574 Conditions are also accepted for watchpoints; you may not need them,
3575 since a watchpoint is inspecting the value of an expression anyhow---but
3576 it might be simpler, say, to just set a watchpoint on a variable name,
3577 and specify a condition that tests whether the new value is an interesting
3580 Break conditions can have side effects, and may even call functions in
3581 your program. This can be useful, for example, to activate functions
3582 that log program progress, or to use your own print functions to
3583 format special data structures. The effects are completely predictable
3584 unless there is another enabled breakpoint at the same address. (In
3585 that case, @value{GDBN} might see the other breakpoint first and stop your
3586 program without checking the condition of this one.) Note that
3587 breakpoint commands are usually more convenient and flexible than break
3589 purpose of performing side effects when a breakpoint is reached
3590 (@pxref{Break Commands, ,Breakpoint Command Lists}).
3592 Break conditions can be specified when a breakpoint is set, by using
3593 @samp{if} in the arguments to the @code{break} command. @xref{Set
3594 Breaks, ,Setting Breakpoints}. They can also be changed at any time
3595 with the @code{condition} command.
3597 You can also use the @code{if} keyword with the @code{watch} command.
3598 The @code{catch} command does not recognize the @code{if} keyword;
3599 @code{condition} is the only way to impose a further condition on a
3604 @item condition @var{bnum} @var{expression}
3605 Specify @var{expression} as the break condition for breakpoint,
3606 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3607 breakpoint @var{bnum} stops your program only if the value of
3608 @var{expression} is true (nonzero, in C). When you use
3609 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3610 syntactic correctness, and to determine whether symbols in it have
3611 referents in the context of your breakpoint. If @var{expression} uses
3612 symbols not referenced in the context of the breakpoint, @value{GDBN}
3613 prints an error message:
3616 No symbol "foo" in current context.
3621 not actually evaluate @var{expression} at the time the @code{condition}
3622 command (or a command that sets a breakpoint with a condition, like
3623 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3625 @item condition @var{bnum}
3626 Remove the condition from breakpoint number @var{bnum}. It becomes
3627 an ordinary unconditional breakpoint.
3630 @cindex ignore count (of breakpoint)
3631 A special case of a breakpoint condition is to stop only when the
3632 breakpoint has been reached a certain number of times. This is so
3633 useful that there is a special way to do it, using the @dfn{ignore
3634 count} of the breakpoint. Every breakpoint has an ignore count, which
3635 is an integer. Most of the time, the ignore count is zero, and
3636 therefore has no effect. But if your program reaches a breakpoint whose
3637 ignore count is positive, then instead of stopping, it just decrements
3638 the ignore count by one and continues. As a result, if the ignore count
3639 value is @var{n}, the breakpoint does not stop the next @var{n} times
3640 your program reaches it.
3644 @item ignore @var{bnum} @var{count}
3645 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3646 The next @var{count} times the breakpoint is reached, your program's
3647 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3650 To make the breakpoint stop the next time it is reached, specify
3653 When you use @code{continue} to resume execution of your program from a
3654 breakpoint, you can specify an ignore count directly as an argument to
3655 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3656 Stepping,,Continuing and Stepping}.
3658 If a breakpoint has a positive ignore count and a condition, the
3659 condition is not checked. Once the ignore count reaches zero,
3660 @value{GDBN} resumes checking the condition.
3662 You could achieve the effect of the ignore count with a condition such
3663 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3664 is decremented each time. @xref{Convenience Vars, ,Convenience
3668 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3671 @node Break Commands
3672 @subsection Breakpoint Command Lists
3674 @cindex breakpoint commands
3675 You can give any breakpoint (or watchpoint or catchpoint) a series of
3676 commands to execute when your program stops due to that breakpoint. For
3677 example, you might want to print the values of certain expressions, or
3678 enable other breakpoints.
3682 @kindex end@r{ (breakpoint commands)}
3683 @item commands @r{[}@var{bnum}@r{]}
3684 @itemx @dots{} @var{command-list} @dots{}
3686 Specify a list of commands for breakpoint number @var{bnum}. The commands
3687 themselves appear on the following lines. Type a line containing just
3688 @code{end} to terminate the commands.
3690 To remove all commands from a breakpoint, type @code{commands} and
3691 follow it immediately with @code{end}; that is, give no commands.
3693 With no @var{bnum} argument, @code{commands} refers to the last
3694 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3695 recently encountered).
3698 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3699 disabled within a @var{command-list}.
3701 You can use breakpoint commands to start your program up again. Simply
3702 use the @code{continue} command, or @code{step}, or any other command
3703 that resumes execution.
3705 Any other commands in the command list, after a command that resumes
3706 execution, are ignored. This is because any time you resume execution
3707 (even with a simple @code{next} or @code{step}), you may encounter
3708 another breakpoint---which could have its own command list, leading to
3709 ambiguities about which list to execute.
3712 If the first command you specify in a command list is @code{silent}, the
3713 usual message about stopping at a breakpoint is not printed. This may
3714 be desirable for breakpoints that are to print a specific message and
3715 then continue. If none of the remaining commands print anything, you
3716 see no sign that the breakpoint was reached. @code{silent} is
3717 meaningful only at the beginning of a breakpoint command list.
3719 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3720 print precisely controlled output, and are often useful in silent
3721 breakpoints. @xref{Output, ,Commands for Controlled Output}.
3723 For example, here is how you could use breakpoint commands to print the
3724 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3730 printf "x is %d\n",x
3735 One application for breakpoint commands is to compensate for one bug so
3736 you can test for another. Put a breakpoint just after the erroneous line
3737 of code, give it a condition to detect the case in which something
3738 erroneous has been done, and give it commands to assign correct values
3739 to any variables that need them. End with the @code{continue} command
3740 so that your program does not stop, and start with the @code{silent}
3741 command so that no output is produced. Here is an example:
3752 @node Breakpoint Menus
3753 @subsection Breakpoint Menus
3755 @cindex symbol overloading
3757 Some programming languages (notably C@t{++} and Objective-C) permit a
3758 single function name
3759 to be defined several times, for application in different contexts.
3760 This is called @dfn{overloading}. When a function name is overloaded,
3761 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3762 a breakpoint. If you realize this is a problem, you can use
3763 something like @samp{break @var{function}(@var{types})} to specify which
3764 particular version of the function you want. Otherwise, @value{GDBN} offers
3765 you a menu of numbered choices for different possible breakpoints, and
3766 waits for your selection with the prompt @samp{>}. The first two
3767 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3768 sets a breakpoint at each definition of @var{function}, and typing
3769 @kbd{0} aborts the @code{break} command without setting any new
3772 For example, the following session excerpt shows an attempt to set a
3773 breakpoint at the overloaded symbol @code{String::after}.
3774 We choose three particular definitions of that function name:
3776 @c FIXME! This is likely to change to show arg type lists, at least
3779 (@value{GDBP}) b String::after
3782 [2] file:String.cc; line number:867
3783 [3] file:String.cc; line number:860
3784 [4] file:String.cc; line number:875
3785 [5] file:String.cc; line number:853
3786 [6] file:String.cc; line number:846
3787 [7] file:String.cc; line number:735
3789 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3790 Breakpoint 2 at 0xb344: file String.cc, line 875.
3791 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3792 Multiple breakpoints were set.
3793 Use the "delete" command to delete unwanted
3799 @c @ifclear BARETARGET
3800 @node Error in Breakpoints
3801 @subsection ``Cannot insert breakpoints''
3803 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3805 Under some operating systems, breakpoints cannot be used in a program if
3806 any other process is running that program. In this situation,
3807 attempting to run or continue a program with a breakpoint causes
3808 @value{GDBN} to print an error message:
3811 Cannot insert breakpoints.
3812 The same program may be running in another process.
3815 When this happens, you have three ways to proceed:
3819 Remove or disable the breakpoints, then continue.
3822 Suspend @value{GDBN}, and copy the file containing your program to a new
3823 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3824 that @value{GDBN} should run your program under that name.
3825 Then start your program again.
3828 Relink your program so that the text segment is nonsharable, using the
3829 linker option @samp{-N}. The operating system limitation may not apply
3830 to nonsharable executables.
3834 A similar message can be printed if you request too many active
3835 hardware-assisted breakpoints and watchpoints:
3837 @c FIXME: the precise wording of this message may change; the relevant
3838 @c source change is not committed yet (Sep 3, 1999).
3840 Stopped; cannot insert breakpoints.
3841 You may have requested too many hardware breakpoints and watchpoints.
3845 This message is printed when you attempt to resume the program, since
3846 only then @value{GDBN} knows exactly how many hardware breakpoints and
3847 watchpoints it needs to insert.
3849 When this message is printed, you need to disable or remove some of the
3850 hardware-assisted breakpoints and watchpoints, and then continue.
3852 @node Breakpoint-related Warnings
3853 @subsection ``Breakpoint address adjusted...''
3854 @cindex breakpoint address adjusted
3856 Some processor architectures place constraints on the addresses at
3857 which breakpoints may be placed. For architectures thus constrained,
3858 @value{GDBN} will attempt to adjust the breakpoint's address to comply
3859 with the constraints dictated by the architecture.
3861 One example of such an architecture is the Fujitsu FR-V. The FR-V is
3862 a VLIW architecture in which a number of RISC-like instructions may be
3863 bundled together for parallel execution. The FR-V architecture
3864 constrains the location of a breakpoint instruction within such a
3865 bundle to the instruction with the lowest address. @value{GDBN}
3866 honors this constraint by adjusting a breakpoint's address to the
3867 first in the bundle.
3869 It is not uncommon for optimized code to have bundles which contain
3870 instructions from different source statements, thus it may happen that
3871 a breakpoint's address will be adjusted from one source statement to
3872 another. Since this adjustment may significantly alter @value{GDBN}'s
3873 breakpoint related behavior from what the user expects, a warning is
3874 printed when the breakpoint is first set and also when the breakpoint
3877 A warning like the one below is printed when setting a breakpoint
3878 that's been subject to address adjustment:
3881 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
3884 Such warnings are printed both for user settable and @value{GDBN}'s
3885 internal breakpoints. If you see one of these warnings, you should
3886 verify that a breakpoint set at the adjusted address will have the
3887 desired affect. If not, the breakpoint in question may be removed and
3888 other breakpoints may be set which will have the desired behavior.
3889 E.g., it may be sufficient to place the breakpoint at a later
3890 instruction. A conditional breakpoint may also be useful in some
3891 cases to prevent the breakpoint from triggering too often.
3893 @value{GDBN} will also issue a warning when stopping at one of these
3894 adjusted breakpoints:
3897 warning: Breakpoint 1 address previously adjusted from 0x00010414
3901 When this warning is encountered, it may be too late to take remedial
3902 action except in cases where the breakpoint is hit earlier or more
3903 frequently than expected.
3905 @node Continuing and Stepping
3906 @section Continuing and Stepping
3910 @cindex resuming execution
3911 @dfn{Continuing} means resuming program execution until your program
3912 completes normally. In contrast, @dfn{stepping} means executing just
3913 one more ``step'' of your program, where ``step'' may mean either one
3914 line of source code, or one machine instruction (depending on what
3915 particular command you use). Either when continuing or when stepping,
3916 your program may stop even sooner, due to a breakpoint or a signal. (If
3917 it stops due to a signal, you may want to use @code{handle}, or use
3918 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3922 @kindex c @r{(@code{continue})}
3923 @kindex fg @r{(resume foreground execution)}
3924 @item continue @r{[}@var{ignore-count}@r{]}
3925 @itemx c @r{[}@var{ignore-count}@r{]}
3926 @itemx fg @r{[}@var{ignore-count}@r{]}
3927 Resume program execution, at the address where your program last stopped;
3928 any breakpoints set at that address are bypassed. The optional argument
3929 @var{ignore-count} allows you to specify a further number of times to
3930 ignore a breakpoint at this location; its effect is like that of
3931 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
3933 The argument @var{ignore-count} is meaningful only when your program
3934 stopped due to a breakpoint. At other times, the argument to
3935 @code{continue} is ignored.
3937 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
3938 debugged program is deemed to be the foreground program) are provided
3939 purely for convenience, and have exactly the same behavior as
3943 To resume execution at a different place, you can use @code{return}
3944 (@pxref{Returning, ,Returning from a Function}) to go back to the
3945 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
3946 Different Address}) to go to an arbitrary location in your program.
3948 A typical technique for using stepping is to set a breakpoint
3949 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
3950 beginning of the function or the section of your program where a problem
3951 is believed to lie, run your program until it stops at that breakpoint,
3952 and then step through the suspect area, examining the variables that are
3953 interesting, until you see the problem happen.
3957 @kindex s @r{(@code{step})}
3959 Continue running your program until control reaches a different source
3960 line, then stop it and return control to @value{GDBN}. This command is
3961 abbreviated @code{s}.
3964 @c "without debugging information" is imprecise; actually "without line
3965 @c numbers in the debugging information". (gcc -g1 has debugging info but
3966 @c not line numbers). But it seems complex to try to make that
3967 @c distinction here.
3968 @emph{Warning:} If you use the @code{step} command while control is
3969 within a function that was compiled without debugging information,
3970 execution proceeds until control reaches a function that does have
3971 debugging information. Likewise, it will not step into a function which
3972 is compiled without debugging information. To step through functions
3973 without debugging information, use the @code{stepi} command, described
3977 The @code{step} command only stops at the first instruction of a source
3978 line. This prevents the multiple stops that could otherwise occur in
3979 @code{switch} statements, @code{for} loops, etc. @code{step} continues
3980 to stop if a function that has debugging information is called within
3981 the line. In other words, @code{step} @emph{steps inside} any functions
3982 called within the line.
3984 Also, the @code{step} command only enters a function if there is line
3985 number information for the function. Otherwise it acts like the
3986 @code{next} command. This avoids problems when using @code{cc -gl}
3987 on MIPS machines. Previously, @code{step} entered subroutines if there
3988 was any debugging information about the routine.
3990 @item step @var{count}
3991 Continue running as in @code{step}, but do so @var{count} times. If a
3992 breakpoint is reached, or a signal not related to stepping occurs before
3993 @var{count} steps, stepping stops right away.
3996 @kindex n @r{(@code{next})}
3997 @item next @r{[}@var{count}@r{]}
3998 Continue to the next source line in the current (innermost) stack frame.
3999 This is similar to @code{step}, but function calls that appear within
4000 the line of code are executed without stopping. Execution stops when
4001 control reaches a different line of code at the original stack level
4002 that was executing when you gave the @code{next} command. This command
4003 is abbreviated @code{n}.
4005 An argument @var{count} is a repeat count, as for @code{step}.
4008 @c FIX ME!! Do we delete this, or is there a way it fits in with
4009 @c the following paragraph? --- Vctoria
4011 @c @code{next} within a function that lacks debugging information acts like
4012 @c @code{step}, but any function calls appearing within the code of the
4013 @c function are executed without stopping.
4015 The @code{next} command only stops at the first instruction of a
4016 source line. This prevents multiple stops that could otherwise occur in
4017 @code{switch} statements, @code{for} loops, etc.
4019 @kindex set step-mode
4021 @cindex functions without line info, and stepping
4022 @cindex stepping into functions with no line info
4023 @itemx set step-mode on
4024 The @code{set step-mode on} command causes the @code{step} command to
4025 stop at the first instruction of a function which contains no debug line
4026 information rather than stepping over it.
4028 This is useful in cases where you may be interested in inspecting the
4029 machine instructions of a function which has no symbolic info and do not
4030 want @value{GDBN} to automatically skip over this function.
4032 @item set step-mode off
4033 Causes the @code{step} command to step over any functions which contains no
4034 debug information. This is the default.
4036 @item show step-mode
4037 Show whether @value{GDBN} will stop in or step over functions without
4038 source line debug information.
4042 Continue running until just after function in the selected stack frame
4043 returns. Print the returned value (if any).
4045 Contrast this with the @code{return} command (@pxref{Returning,
4046 ,Returning from a Function}).
4049 @kindex u @r{(@code{until})}
4050 @cindex run until specified location
4053 Continue running until a source line past the current line, in the
4054 current stack frame, is reached. This command is used to avoid single
4055 stepping through a loop more than once. It is like the @code{next}
4056 command, except that when @code{until} encounters a jump, it
4057 automatically continues execution until the program counter is greater
4058 than the address of the jump.
4060 This means that when you reach the end of a loop after single stepping
4061 though it, @code{until} makes your program continue execution until it
4062 exits the loop. In contrast, a @code{next} command at the end of a loop
4063 simply steps back to the beginning of the loop, which forces you to step
4064 through the next iteration.
4066 @code{until} always stops your program if it attempts to exit the current
4069 @code{until} may produce somewhat counterintuitive results if the order
4070 of machine code does not match the order of the source lines. For
4071 example, in the following excerpt from a debugging session, the @code{f}
4072 (@code{frame}) command shows that execution is stopped at line
4073 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4077 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4079 (@value{GDBP}) until
4080 195 for ( ; argc > 0; NEXTARG) @{
4083 This happened because, for execution efficiency, the compiler had
4084 generated code for the loop closure test at the end, rather than the
4085 start, of the loop---even though the test in a C @code{for}-loop is
4086 written before the body of the loop. The @code{until} command appeared
4087 to step back to the beginning of the loop when it advanced to this
4088 expression; however, it has not really gone to an earlier
4089 statement---not in terms of the actual machine code.
4091 @code{until} with no argument works by means of single
4092 instruction stepping, and hence is slower than @code{until} with an
4095 @item until @var{location}
4096 @itemx u @var{location}
4097 Continue running your program until either the specified location is
4098 reached, or the current stack frame returns. @var{location} is any of
4099 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
4100 ,Setting Breakpoints}). This form of the command uses breakpoints, and
4101 hence is quicker than @code{until} without an argument. The specified
4102 location is actually reached only if it is in the current frame. This
4103 implies that @code{until} can be used to skip over recursive function
4104 invocations. For instance in the code below, if the current location is
4105 line @code{96}, issuing @code{until 99} will execute the program up to
4106 line @code{99} in the same invocation of factorial, i.e., after the inner
4107 invocations have returned.
4110 94 int factorial (int value)
4112 96 if (value > 1) @{
4113 97 value *= factorial (value - 1);
4120 @kindex advance @var{location}
4121 @itemx advance @var{location}
4122 Continue running the program up to the given @var{location}. An argument is
4123 required, which should be of the same form as arguments for the @code{break}
4124 command. Execution will also stop upon exit from the current stack
4125 frame. This command is similar to @code{until}, but @code{advance} will
4126 not skip over recursive function calls, and the target location doesn't
4127 have to be in the same frame as the current one.
4131 @kindex si @r{(@code{stepi})}
4133 @itemx stepi @var{arg}
4135 Execute one machine instruction, then stop and return to the debugger.
4137 It is often useful to do @samp{display/i $pc} when stepping by machine
4138 instructions. This makes @value{GDBN} automatically display the next
4139 instruction to be executed, each time your program stops. @xref{Auto
4140 Display,, Automatic Display}.
4142 An argument is a repeat count, as in @code{step}.
4146 @kindex ni @r{(@code{nexti})}
4148 @itemx nexti @var{arg}
4150 Execute one machine instruction, but if it is a function call,
4151 proceed until the function returns.
4153 An argument is a repeat count, as in @code{next}.
4160 A signal is an asynchronous event that can happen in a program. The
4161 operating system defines the possible kinds of signals, and gives each
4162 kind a name and a number. For example, in Unix @code{SIGINT} is the
4163 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4164 @code{SIGSEGV} is the signal a program gets from referencing a place in
4165 memory far away from all the areas in use; @code{SIGALRM} occurs when
4166 the alarm clock timer goes off (which happens only if your program has
4167 requested an alarm).
4169 @cindex fatal signals
4170 Some signals, including @code{SIGALRM}, are a normal part of the
4171 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4172 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4173 program has not specified in advance some other way to handle the signal.
4174 @code{SIGINT} does not indicate an error in your program, but it is normally
4175 fatal so it can carry out the purpose of the interrupt: to kill the program.
4177 @value{GDBN} has the ability to detect any occurrence of a signal in your
4178 program. You can tell @value{GDBN} in advance what to do for each kind of
4181 @cindex handling signals
4182 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4183 @code{SIGALRM} be silently passed to your program
4184 (so as not to interfere with their role in the program's functioning)
4185 but to stop your program immediately whenever an error signal happens.
4186 You can change these settings with the @code{handle} command.
4189 @kindex info signals
4193 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4194 handle each one. You can use this to see the signal numbers of all
4195 the defined types of signals.
4197 @item info signals @var{sig}
4198 Similar, but print information only about the specified signal number.
4200 @code{info handle} is an alias for @code{info signals}.
4203 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4204 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4205 can be the number of a signal or its name (with or without the
4206 @samp{SIG} at the beginning); a list of signal numbers of the form
4207 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4208 known signals. Optional arguments @var{keywords}, described below,
4209 say what change to make.
4213 The keywords allowed by the @code{handle} command can be abbreviated.
4214 Their full names are:
4218 @value{GDBN} should not stop your program when this signal happens. It may
4219 still print a message telling you that the signal has come in.
4222 @value{GDBN} should stop your program when this signal happens. This implies
4223 the @code{print} keyword as well.
4226 @value{GDBN} should print a message when this signal happens.
4229 @value{GDBN} should not mention the occurrence of the signal at all. This
4230 implies the @code{nostop} keyword as well.
4234 @value{GDBN} should allow your program to see this signal; your program
4235 can handle the signal, or else it may terminate if the signal is fatal
4236 and not handled. @code{pass} and @code{noignore} are synonyms.
4240 @value{GDBN} should not allow your program to see this signal.
4241 @code{nopass} and @code{ignore} are synonyms.
4245 When a signal stops your program, the signal is not visible to the
4247 continue. Your program sees the signal then, if @code{pass} is in
4248 effect for the signal in question @emph{at that time}. In other words,
4249 after @value{GDBN} reports a signal, you can use the @code{handle}
4250 command with @code{pass} or @code{nopass} to control whether your
4251 program sees that signal when you continue.
4253 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4254 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4255 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4258 You can also use the @code{signal} command to prevent your program from
4259 seeing a signal, or cause it to see a signal it normally would not see,
4260 or to give it any signal at any time. For example, if your program stopped
4261 due to some sort of memory reference error, you might store correct
4262 values into the erroneous variables and continue, hoping to see more
4263 execution; but your program would probably terminate immediately as
4264 a result of the fatal signal once it saw the signal. To prevent this,
4265 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4269 @section Stopping and Starting Multi-thread Programs
4271 When your program has multiple threads (@pxref{Threads,, Debugging
4272 Programs with Multiple Threads}), you can choose whether to set
4273 breakpoints on all threads, or on a particular thread.
4276 @cindex breakpoints and threads
4277 @cindex thread breakpoints
4278 @kindex break @dots{} thread @var{threadno}
4279 @item break @var{linespec} thread @var{threadno}
4280 @itemx break @var{linespec} thread @var{threadno} if @dots{}
4281 @var{linespec} specifies source lines; there are several ways of
4282 writing them, but the effect is always to specify some source line.
4284 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
4285 to specify that you only want @value{GDBN} to stop the program when a
4286 particular thread reaches this breakpoint. @var{threadno} is one of the
4287 numeric thread identifiers assigned by @value{GDBN}, shown in the first
4288 column of the @samp{info threads} display.
4290 If you do not specify @samp{thread @var{threadno}} when you set a
4291 breakpoint, the breakpoint applies to @emph{all} threads of your
4294 You can use the @code{thread} qualifier on conditional breakpoints as
4295 well; in this case, place @samp{thread @var{threadno}} before the
4296 breakpoint condition, like this:
4299 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
4304 @cindex stopped threads
4305 @cindex threads, stopped
4306 Whenever your program stops under @value{GDBN} for any reason,
4307 @emph{all} threads of execution stop, not just the current thread. This
4308 allows you to examine the overall state of the program, including
4309 switching between threads, without worrying that things may change
4312 @cindex thread breakpoints and system calls
4313 @cindex system calls and thread breakpoints
4314 @cindex premature return from system calls
4315 There is an unfortunate side effect. If one thread stops for a
4316 breakpoint, or for some other reason, and another thread is blocked in a
4317 system call, then the system call may return prematurely. This is a
4318 consequence of the interaction between multiple threads and the signals
4319 that @value{GDBN} uses to implement breakpoints and other events that
4322 To handle this problem, your program should check the return value of
4323 each system call and react appropriately. This is good programming
4326 For example, do not write code like this:
4332 The call to @code{sleep} will return early if a different thread stops
4333 at a breakpoint or for some other reason.
4335 Instead, write this:
4340 unslept = sleep (unslept);
4343 A system call is allowed to return early, so the system is still
4344 conforming to its specification. But @value{GDBN} does cause your
4345 multi-threaded program to behave differently than it would without
4348 Also, @value{GDBN} uses internal breakpoints in the thread library to
4349 monitor certain events such as thread creation and thread destruction.
4350 When such an event happens, a system call in another thread may return
4351 prematurely, even though your program does not appear to stop.
4353 @cindex continuing threads
4354 @cindex threads, continuing
4355 Conversely, whenever you restart the program, @emph{all} threads start
4356 executing. @emph{This is true even when single-stepping} with commands
4357 like @code{step} or @code{next}.
4359 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4360 Since thread scheduling is up to your debugging target's operating
4361 system (not controlled by @value{GDBN}), other threads may
4362 execute more than one statement while the current thread completes a
4363 single step. Moreover, in general other threads stop in the middle of a
4364 statement, rather than at a clean statement boundary, when the program
4367 You might even find your program stopped in another thread after
4368 continuing or even single-stepping. This happens whenever some other
4369 thread runs into a breakpoint, a signal, or an exception before the
4370 first thread completes whatever you requested.
4372 On some OSes, you can lock the OS scheduler and thus allow only a single
4376 @item set scheduler-locking @var{mode}
4377 @cindex scheduler locking mode
4378 @cindex lock scheduler
4379 Set the scheduler locking mode. If it is @code{off}, then there is no
4380 locking and any thread may run at any time. If @code{on}, then only the
4381 current thread may run when the inferior is resumed. The @code{step}
4382 mode optimizes for single-stepping. It stops other threads from
4383 ``seizing the prompt'' by preempting the current thread while you are
4384 stepping. Other threads will only rarely (or never) get a chance to run
4385 when you step. They are more likely to run when you @samp{next} over a
4386 function call, and they are completely free to run when you use commands
4387 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4388 thread hits a breakpoint during its timeslice, they will never steal the
4389 @value{GDBN} prompt away from the thread that you are debugging.
4391 @item show scheduler-locking
4392 Display the current scheduler locking mode.
4397 @chapter Examining the Stack
4399 When your program has stopped, the first thing you need to know is where it
4400 stopped and how it got there.
4403 Each time your program performs a function call, information about the call
4405 That information includes the location of the call in your program,
4406 the arguments of the call,
4407 and the local variables of the function being called.
4408 The information is saved in a block of data called a @dfn{stack frame}.
4409 The stack frames are allocated in a region of memory called the @dfn{call
4412 When your program stops, the @value{GDBN} commands for examining the
4413 stack allow you to see all of this information.
4415 @cindex selected frame
4416 One of the stack frames is @dfn{selected} by @value{GDBN} and many
4417 @value{GDBN} commands refer implicitly to the selected frame. In
4418 particular, whenever you ask @value{GDBN} for the value of a variable in
4419 your program, the value is found in the selected frame. There are
4420 special @value{GDBN} commands to select whichever frame you are
4421 interested in. @xref{Selection, ,Selecting a Frame}.
4423 When your program stops, @value{GDBN} automatically selects the
4424 currently executing frame and describes it briefly, similar to the
4425 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
4428 * Frames:: Stack frames
4429 * Backtrace:: Backtraces
4430 * Selection:: Selecting a frame
4431 * Frame Info:: Information on a frame
4436 @section Stack Frames
4438 @cindex frame, definition
4440 The call stack is divided up into contiguous pieces called @dfn{stack
4441 frames}, or @dfn{frames} for short; each frame is the data associated
4442 with one call to one function. The frame contains the arguments given
4443 to the function, the function's local variables, and the address at
4444 which the function is executing.
4446 @cindex initial frame
4447 @cindex outermost frame
4448 @cindex innermost frame
4449 When your program is started, the stack has only one frame, that of the
4450 function @code{main}. This is called the @dfn{initial} frame or the
4451 @dfn{outermost} frame. Each time a function is called, a new frame is
4452 made. Each time a function returns, the frame for that function invocation
4453 is eliminated. If a function is recursive, there can be many frames for
4454 the same function. The frame for the function in which execution is
4455 actually occurring is called the @dfn{innermost} frame. This is the most
4456 recently created of all the stack frames that still exist.
4458 @cindex frame pointer
4459 Inside your program, stack frames are identified by their addresses. A
4460 stack frame consists of many bytes, each of which has its own address; each
4461 kind of computer has a convention for choosing one byte whose
4462 address serves as the address of the frame. Usually this address is kept
4463 in a register called the @dfn{frame pointer register}
4464 (@pxref{Registers, $fp}) while execution is going on in that frame.
4466 @cindex frame number
4467 @value{GDBN} assigns numbers to all existing stack frames, starting with
4468 zero for the innermost frame, one for the frame that called it,
4469 and so on upward. These numbers do not really exist in your program;
4470 they are assigned by @value{GDBN} to give you a way of designating stack
4471 frames in @value{GDBN} commands.
4473 @c The -fomit-frame-pointer below perennially causes hbox overflow
4474 @c underflow problems.
4475 @cindex frameless execution
4476 Some compilers provide a way to compile functions so that they operate
4477 without stack frames. (For example, the @value{NGCC} option
4479 @samp{-fomit-frame-pointer}
4481 generates functions without a frame.)
4482 This is occasionally done with heavily used library functions to save
4483 the frame setup time. @value{GDBN} has limited facilities for dealing
4484 with these function invocations. If the innermost function invocation
4485 has no stack frame, @value{GDBN} nevertheless regards it as though
4486 it had a separate frame, which is numbered zero as usual, allowing
4487 correct tracing of the function call chain. However, @value{GDBN} has
4488 no provision for frameless functions elsewhere in the stack.
4491 @kindex frame@r{, command}
4492 @cindex current stack frame
4493 @item frame @var{args}
4494 The @code{frame} command allows you to move from one stack frame to another,
4495 and to print the stack frame you select. @var{args} may be either the
4496 address of the frame or the stack frame number. Without an argument,
4497 @code{frame} prints the current stack frame.
4499 @kindex select-frame
4500 @cindex selecting frame silently
4502 The @code{select-frame} command allows you to move from one stack frame
4503 to another without printing the frame. This is the silent version of
4511 @cindex call stack traces
4512 A backtrace is a summary of how your program got where it is. It shows one
4513 line per frame, for many frames, starting with the currently executing
4514 frame (frame zero), followed by its caller (frame one), and on up the
4519 @kindex bt @r{(@code{backtrace})}
4522 Print a backtrace of the entire stack: one line per frame for all
4523 frames in the stack.
4525 You can stop the backtrace at any time by typing the system interrupt
4526 character, normally @kbd{Ctrl-c}.
4528 @item backtrace @var{n}
4530 Similar, but print only the innermost @var{n} frames.
4532 @item backtrace -@var{n}
4534 Similar, but print only the outermost @var{n} frames.
4536 @item backtrace full
4538 @itemx bt full @var{n}
4539 @itemx bt full -@var{n}
4540 Print the values of the local variables also. @var{n} specifies the
4541 number of frames to print, as described above.
4546 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4547 are additional aliases for @code{backtrace}.
4549 @cindex multiple threads, backtrace
4550 In a multi-threaded program, @value{GDBN} by default shows the
4551 backtrace only for the current thread. To display the backtrace for
4552 several or all of the threads, use the command @code{thread apply}
4553 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
4554 apply all backtrace}, @value{GDBN} will display the backtrace for all
4555 the threads; this is handy when you debug a core dump of a
4556 multi-threaded program.
4558 Each line in the backtrace shows the frame number and the function name.
4559 The program counter value is also shown---unless you use @code{set
4560 print address off}. The backtrace also shows the source file name and
4561 line number, as well as the arguments to the function. The program
4562 counter value is omitted if it is at the beginning of the code for that
4565 Here is an example of a backtrace. It was made with the command
4566 @samp{bt 3}, so it shows the innermost three frames.
4570 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4572 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4573 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4575 (More stack frames follow...)
4580 The display for frame zero does not begin with a program counter
4581 value, indicating that your program has stopped at the beginning of the
4582 code for line @code{993} of @code{builtin.c}.
4584 @cindex value optimized out, in backtrace
4585 @cindex function call arguments, optimized out
4586 If your program was compiled with optimizations, some compilers will
4587 optimize away arguments passed to functions if those arguments are
4588 never used after the call. Such optimizations generate code that
4589 passes arguments through registers, but doesn't store those arguments
4590 in the stack frame. @value{GDBN} has no way of displaying such
4591 arguments in stack frames other than the innermost one. Here's what
4592 such a backtrace might look like:
4596 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4598 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
4599 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
4601 (More stack frames follow...)
4606 The values of arguments that were not saved in their stack frames are
4607 shown as @samp{<value optimized out>}.
4609 If you need to display the values of such optimized-out arguments,
4610 either deduce that from other variables whose values depend on the one
4611 you are interested in, or recompile without optimizations.
4613 @cindex backtrace beyond @code{main} function
4614 @cindex program entry point
4615 @cindex startup code, and backtrace
4616 Most programs have a standard user entry point---a place where system
4617 libraries and startup code transition into user code. For C this is
4618 @code{main}@footnote{
4619 Note that embedded programs (the so-called ``free-standing''
4620 environment) are not required to have a @code{main} function as the
4621 entry point. They could even have multiple entry points.}.
4622 When @value{GDBN} finds the entry function in a backtrace
4623 it will terminate the backtrace, to avoid tracing into highly
4624 system-specific (and generally uninteresting) code.
4626 If you need to examine the startup code, or limit the number of levels
4627 in a backtrace, you can change this behavior:
4630 @item set backtrace past-main
4631 @itemx set backtrace past-main on
4632 @kindex set backtrace
4633 Backtraces will continue past the user entry point.
4635 @item set backtrace past-main off
4636 Backtraces will stop when they encounter the user entry point. This is the
4639 @item show backtrace past-main
4640 @kindex show backtrace
4641 Display the current user entry point backtrace policy.
4643 @item set backtrace past-entry
4644 @itemx set backtrace past-entry on
4645 Backtraces will continue past the internal entry point of an application.
4646 This entry point is encoded by the linker when the application is built,
4647 and is likely before the user entry point @code{main} (or equivalent) is called.
4649 @item set backtrace past-entry off
4650 Backtraces will stop when they encounter the internal entry point of an
4651 application. This is the default.
4653 @item show backtrace past-entry
4654 Display the current internal entry point backtrace policy.
4656 @item set backtrace limit @var{n}
4657 @itemx set backtrace limit 0
4658 @cindex backtrace limit
4659 Limit the backtrace to @var{n} levels. A value of zero means
4662 @item show backtrace limit
4663 Display the current limit on backtrace levels.
4667 @section Selecting a Frame
4669 Most commands for examining the stack and other data in your program work on
4670 whichever stack frame is selected at the moment. Here are the commands for
4671 selecting a stack frame; all of them finish by printing a brief description
4672 of the stack frame just selected.
4675 @kindex frame@r{, selecting}
4676 @kindex f @r{(@code{frame})}
4679 Select frame number @var{n}. Recall that frame zero is the innermost
4680 (currently executing) frame, frame one is the frame that called the
4681 innermost one, and so on. The highest-numbered frame is the one for
4684 @item frame @var{addr}
4686 Select the frame at address @var{addr}. This is useful mainly if the
4687 chaining of stack frames has been damaged by a bug, making it
4688 impossible for @value{GDBN} to assign numbers properly to all frames. In
4689 addition, this can be useful when your program has multiple stacks and
4690 switches between them.
4692 On the SPARC architecture, @code{frame} needs two addresses to
4693 select an arbitrary frame: a frame pointer and a stack pointer.
4695 On the MIPS and Alpha architecture, it needs two addresses: a stack
4696 pointer and a program counter.
4698 On the 29k architecture, it needs three addresses: a register stack
4699 pointer, a program counter, and a memory stack pointer.
4703 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4704 advances toward the outermost frame, to higher frame numbers, to frames
4705 that have existed longer. @var{n} defaults to one.
4708 @kindex do @r{(@code{down})}
4710 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4711 advances toward the innermost frame, to lower frame numbers, to frames
4712 that were created more recently. @var{n} defaults to one. You may
4713 abbreviate @code{down} as @code{do}.
4716 All of these commands end by printing two lines of output describing the
4717 frame. The first line shows the frame number, the function name, the
4718 arguments, and the source file and line number of execution in that
4719 frame. The second line shows the text of that source line.
4727 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4729 10 read_input_file (argv[i]);
4733 After such a printout, the @code{list} command with no arguments
4734 prints ten lines centered on the point of execution in the frame.
4735 You can also edit the program at the point of execution with your favorite
4736 editing program by typing @code{edit}.
4737 @xref{List, ,Printing Source Lines},
4741 @kindex down-silently
4743 @item up-silently @var{n}
4744 @itemx down-silently @var{n}
4745 These two commands are variants of @code{up} and @code{down},
4746 respectively; they differ in that they do their work silently, without
4747 causing display of the new frame. They are intended primarily for use
4748 in @value{GDBN} command scripts, where the output might be unnecessary and
4753 @section Information About a Frame
4755 There are several other commands to print information about the selected
4761 When used without any argument, this command does not change which
4762 frame is selected, but prints a brief description of the currently
4763 selected stack frame. It can be abbreviated @code{f}. With an
4764 argument, this command is used to select a stack frame.
4765 @xref{Selection, ,Selecting a Frame}.
4768 @kindex info f @r{(@code{info frame})}
4771 This command prints a verbose description of the selected stack frame,
4776 the address of the frame
4778 the address of the next frame down (called by this frame)
4780 the address of the next frame up (caller of this frame)
4782 the language in which the source code corresponding to this frame is written
4784 the address of the frame's arguments
4786 the address of the frame's local variables
4788 the program counter saved in it (the address of execution in the caller frame)
4790 which registers were saved in the frame
4793 @noindent The verbose description is useful when
4794 something has gone wrong that has made the stack format fail to fit
4795 the usual conventions.
4797 @item info frame @var{addr}
4798 @itemx info f @var{addr}
4799 Print a verbose description of the frame at address @var{addr}, without
4800 selecting that frame. The selected frame remains unchanged by this
4801 command. This requires the same kind of address (more than one for some
4802 architectures) that you specify in the @code{frame} command.
4803 @xref{Selection, ,Selecting a Frame}.
4807 Print the arguments of the selected frame, each on a separate line.
4811 Print the local variables of the selected frame, each on a separate
4812 line. These are all variables (declared either static or automatic)
4813 accessible at the point of execution of the selected frame.
4816 @cindex catch exceptions, list active handlers
4817 @cindex exception handlers, how to list
4819 Print a list of all the exception handlers that are active in the
4820 current stack frame at the current point of execution. To see other
4821 exception handlers, visit the associated frame (using the @code{up},
4822 @code{down}, or @code{frame} commands); then type @code{info catch}.
4823 @xref{Set Catchpoints, , Setting Catchpoints}.
4829 @chapter Examining Source Files
4831 @value{GDBN} can print parts of your program's source, since the debugging
4832 information recorded in the program tells @value{GDBN} what source files were
4833 used to build it. When your program stops, @value{GDBN} spontaneously prints
4834 the line where it stopped. Likewise, when you select a stack frame
4835 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
4836 execution in that frame has stopped. You can print other portions of
4837 source files by explicit command.
4839 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4840 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4841 @value{GDBN} under @sc{gnu} Emacs}.
4844 * List:: Printing source lines
4845 * Edit:: Editing source files
4846 * Search:: Searching source files
4847 * Source Path:: Specifying source directories
4848 * Machine Code:: Source and machine code
4852 @section Printing Source Lines
4855 @kindex l @r{(@code{list})}
4856 To print lines from a source file, use the @code{list} command
4857 (abbreviated @code{l}). By default, ten lines are printed.
4858 There are several ways to specify what part of the file you want to print.
4860 Here are the forms of the @code{list} command most commonly used:
4863 @item list @var{linenum}
4864 Print lines centered around line number @var{linenum} in the
4865 current source file.
4867 @item list @var{function}
4868 Print lines centered around the beginning of function
4872 Print more lines. If the last lines printed were printed with a
4873 @code{list} command, this prints lines following the last lines
4874 printed; however, if the last line printed was a solitary line printed
4875 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4876 Stack}), this prints lines centered around that line.
4879 Print lines just before the lines last printed.
4882 @cindex @code{list}, how many lines to display
4883 By default, @value{GDBN} prints ten source lines with any of these forms of
4884 the @code{list} command. You can change this using @code{set listsize}:
4887 @kindex set listsize
4888 @item set listsize @var{count}
4889 Make the @code{list} command display @var{count} source lines (unless
4890 the @code{list} argument explicitly specifies some other number).
4892 @kindex show listsize
4894 Display the number of lines that @code{list} prints.
4897 Repeating a @code{list} command with @key{RET} discards the argument,
4898 so it is equivalent to typing just @code{list}. This is more useful
4899 than listing the same lines again. An exception is made for an
4900 argument of @samp{-}; that argument is preserved in repetition so that
4901 each repetition moves up in the source file.
4904 In general, the @code{list} command expects you to supply zero, one or two
4905 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4906 of writing them, but the effect is always to specify some source line.
4907 Here is a complete description of the possible arguments for @code{list}:
4910 @item list @var{linespec}
4911 Print lines centered around the line specified by @var{linespec}.
4913 @item list @var{first},@var{last}
4914 Print lines from @var{first} to @var{last}. Both arguments are
4917 @item list ,@var{last}
4918 Print lines ending with @var{last}.
4920 @item list @var{first},
4921 Print lines starting with @var{first}.
4924 Print lines just after the lines last printed.
4927 Print lines just before the lines last printed.
4930 As described in the preceding table.
4933 Here are the ways of specifying a single source line---all the
4938 Specifies line @var{number} of the current source file.
4939 When a @code{list} command has two linespecs, this refers to
4940 the same source file as the first linespec.
4943 Specifies the line @var{offset} lines after the last line printed.
4944 When used as the second linespec in a @code{list} command that has
4945 two, this specifies the line @var{offset} lines down from the
4949 Specifies the line @var{offset} lines before the last line printed.
4951 @item @var{filename}:@var{number}
4952 Specifies line @var{number} in the source file @var{filename}.
4954 @item @var{function}
4955 Specifies the line that begins the body of the function @var{function}.
4956 For example: in C, this is the line with the open brace.
4958 @item @var{filename}:@var{function}
4959 Specifies the line of the open-brace that begins the body of the
4960 function @var{function} in the file @var{filename}. You only need the
4961 file name with a function name to avoid ambiguity when there are
4962 identically named functions in different source files.
4964 @item *@var{address}
4965 Specifies the line containing the program address @var{address}.
4966 @var{address} may be any expression.
4970 @section Editing Source Files
4971 @cindex editing source files
4974 @kindex e @r{(@code{edit})}
4975 To edit the lines in a source file, use the @code{edit} command.
4976 The editing program of your choice
4977 is invoked with the current line set to
4978 the active line in the program.
4979 Alternatively, there are several ways to specify what part of the file you
4980 want to print if you want to see other parts of the program.
4982 Here are the forms of the @code{edit} command most commonly used:
4986 Edit the current source file at the active line number in the program.
4988 @item edit @var{number}
4989 Edit the current source file with @var{number} as the active line number.
4991 @item edit @var{function}
4992 Edit the file containing @var{function} at the beginning of its definition.
4994 @item edit @var{filename}:@var{number}
4995 Specifies line @var{number} in the source file @var{filename}.
4997 @item edit @var{filename}:@var{function}
4998 Specifies the line that begins the body of the
4999 function @var{function} in the file @var{filename}. You only need the
5000 file name with a function name to avoid ambiguity when there are
5001 identically named functions in different source files.
5003 @item edit *@var{address}
5004 Specifies the line containing the program address @var{address}.
5005 @var{address} may be any expression.
5008 @subsection Choosing your Editor
5009 You can customize @value{GDBN} to use any editor you want
5011 The only restriction is that your editor (say @code{ex}), recognizes the
5012 following command-line syntax:
5014 ex +@var{number} file
5016 The optional numeric value +@var{number} specifies the number of the line in
5017 the file where to start editing.}.
5018 By default, it is @file{@value{EDITOR}}, but you can change this
5019 by setting the environment variable @code{EDITOR} before using
5020 @value{GDBN}. For example, to configure @value{GDBN} to use the
5021 @code{vi} editor, you could use these commands with the @code{sh} shell:
5027 or in the @code{csh} shell,
5029 setenv EDITOR /usr/bin/vi
5034 @section Searching Source Files
5035 @cindex searching source files
5037 There are two commands for searching through the current source file for a
5042 @kindex forward-search
5043 @item forward-search @var{regexp}
5044 @itemx search @var{regexp}
5045 The command @samp{forward-search @var{regexp}} checks each line,
5046 starting with the one following the last line listed, for a match for
5047 @var{regexp}. It lists the line that is found. You can use the
5048 synonym @samp{search @var{regexp}} or abbreviate the command name as
5051 @kindex reverse-search
5052 @item reverse-search @var{regexp}
5053 The command @samp{reverse-search @var{regexp}} checks each line, starting
5054 with the one before the last line listed and going backward, for a match
5055 for @var{regexp}. It lists the line that is found. You can abbreviate
5056 this command as @code{rev}.
5060 @section Specifying Source Directories
5063 @cindex directories for source files
5064 Executable programs sometimes do not record the directories of the source
5065 files from which they were compiled, just the names. Even when they do,
5066 the directories could be moved between the compilation and your debugging
5067 session. @value{GDBN} has a list of directories to search for source files;
5068 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
5069 it tries all the directories in the list, in the order they are present
5070 in the list, until it finds a file with the desired name.
5072 For example, suppose an executable references the file
5073 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
5074 @file{/mnt/cross}. The file is first looked up literally; if this
5075 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
5076 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
5077 message is printed. @value{GDBN} does not look up the parts of the
5078 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
5079 Likewise, the subdirectories of the source path are not searched: if
5080 the source path is @file{/mnt/cross}, and the binary refers to
5081 @file{foo.c}, @value{GDBN} would not find it under
5082 @file{/mnt/cross/usr/src/foo-1.0/lib}.
5084 Plain file names, relative file names with leading directories, file
5085 names containing dots, etc.@: are all treated as described above; for
5086 instance, if the source path is @file{/mnt/cross}, and the source file
5087 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
5088 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
5089 that---@file{/mnt/cross/foo.c}.
5091 Note that the executable search path is @emph{not} used to locate the
5094 Whenever you reset or rearrange the source path, @value{GDBN} clears out
5095 any information it has cached about where source files are found and where
5096 each line is in the file.
5100 When you start @value{GDBN}, its source path includes only @samp{cdir}
5101 and @samp{cwd}, in that order.
5102 To add other directories, use the @code{directory} command.
5104 The search path is used to find both program source files and @value{GDBN}
5105 script files (read using the @samp{-command} option and @samp{source} command).
5107 In addition to the source path, @value{GDBN} provides a set of commands
5108 that manage a list of source path substitution rules. A @dfn{substitution
5109 rule} specifies how to rewrite source directories stored in the program's
5110 debug information in case the sources were moved to a different
5111 directory between compilation and debugging. A rule is made of
5112 two strings, the first specifying what needs to be rewritten in
5113 the path, and the second specifying how it should be rewritten.
5114 In @ref{set substitute-path}, we name these two parts @var{from} and
5115 @var{to} respectively. @value{GDBN} does a simple string replacement
5116 of @var{from} with @var{to} at the start of the directory part of the
5117 source file name, and uses that result instead of the original file
5118 name to look up the sources.
5120 Using the previous example, suppose the @file{foo-1.0} tree has been
5121 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
5122 @value{GDBN} to replace @file{/usr/src} in all source path names with
5123 @file{/mnt/cross}. The first lookup will then be
5124 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
5125 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
5126 substitution rule, use the @code{set substitute-path} command
5127 (@pxref{set substitute-path}).
5129 To avoid unexpected substitution results, a rule is applied only if the
5130 @var{from} part of the directory name ends at a directory separator.
5131 For instance, a rule substituting @file{/usr/source} into
5132 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
5133 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
5134 is applied only at the beginning of the directory name, this rule will
5135 not be applied to @file{/root/usr/source/baz.c} either.
5137 In many cases, you can achieve the same result using the @code{directory}
5138 command. However, @code{set substitute-path} can be more efficient in
5139 the case where the sources are organized in a complex tree with multiple
5140 subdirectories. With the @code{directory} command, you need to add each
5141 subdirectory of your project. If you moved the entire tree while
5142 preserving its internal organization, then @code{set substitute-path}
5143 allows you to direct the debugger to all the sources with one single
5146 @code{set substitute-path} is also more than just a shortcut command.
5147 The source path is only used if the file at the original location no
5148 longer exists. On the other hand, @code{set substitute-path} modifies
5149 the debugger behavior to look at the rewritten location instead. So, if
5150 for any reason a source file that is not relevant to your executable is
5151 located at the original location, a substitution rule is the only
5152 method available to point @value{GDBN} at the new location.
5155 @item directory @var{dirname} @dots{}
5156 @item dir @var{dirname} @dots{}
5157 Add directory @var{dirname} to the front of the source path. Several
5158 directory names may be given to this command, separated by @samp{:}
5159 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
5160 part of absolute file names) or
5161 whitespace. You may specify a directory that is already in the source
5162 path; this moves it forward, so @value{GDBN} searches it sooner.
5166 @vindex $cdir@r{, convenience variable}
5167 @vindex $cwd@r{, convenience variable}
5168 @cindex compilation directory
5169 @cindex current directory
5170 @cindex working directory
5171 @cindex directory, current
5172 @cindex directory, compilation
5173 You can use the string @samp{$cdir} to refer to the compilation
5174 directory (if one is recorded), and @samp{$cwd} to refer to the current
5175 working directory. @samp{$cwd} is not the same as @samp{.}---the former
5176 tracks the current working directory as it changes during your @value{GDBN}
5177 session, while the latter is immediately expanded to the current
5178 directory at the time you add an entry to the source path.
5181 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
5183 @c RET-repeat for @code{directory} is explicitly disabled, but since
5184 @c repeating it would be a no-op we do not say that. (thanks to RMS)
5186 @item show directories
5187 @kindex show directories
5188 Print the source path: show which directories it contains.
5190 @anchor{set substitute-path}
5191 @item set substitute-path @var{from} @var{to}
5192 @kindex set substitute-path
5193 Define a source path substitution rule, and add it at the end of the
5194 current list of existing substitution rules. If a rule with the same
5195 @var{from} was already defined, then the old rule is also deleted.
5197 For example, if the file @file{/foo/bar/baz.c} was moved to
5198 @file{/mnt/cross/baz.c}, then the command
5201 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
5205 will tell @value{GDBN} to replace @samp{/usr/src} with
5206 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
5207 @file{baz.c} even though it was moved.
5209 In the case when more than one substitution rule have been defined,
5210 the rules are evaluated one by one in the order where they have been
5211 defined. The first one matching, if any, is selected to perform
5214 For instance, if we had entered the following commands:
5217 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
5218 (@value{GDBP}) set substitute-path /usr/src /mnt/src
5222 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
5223 @file{/mnt/include/defs.h} by using the first rule. However, it would
5224 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
5225 @file{/mnt/src/lib/foo.c}.
5228 @item unset substitute-path [path]
5229 @kindex unset substitute-path
5230 If a path is specified, search the current list of substitution rules
5231 for a rule that would rewrite that path. Delete that rule if found.
5232 A warning is emitted by the debugger if no rule could be found.
5234 If no path is specified, then all substitution rules are deleted.
5236 @item show substitute-path [path]
5237 @kindex show substitute-path
5238 If a path is specified, then print the source path substitution rule
5239 which would rewrite that path, if any.
5241 If no path is specified, then print all existing source path substitution
5246 If your source path is cluttered with directories that are no longer of
5247 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
5248 versions of source. You can correct the situation as follows:
5252 Use @code{directory} with no argument to reset the source path to its default value.
5255 Use @code{directory} with suitable arguments to reinstall the
5256 directories you want in the source path. You can add all the
5257 directories in one command.
5261 @section Source and Machine Code
5262 @cindex source line and its code address
5264 You can use the command @code{info line} to map source lines to program
5265 addresses (and vice versa), and the command @code{disassemble} to display
5266 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
5267 mode, the @code{info line} command causes the arrow to point to the
5268 line specified. Also, @code{info line} prints addresses in symbolic form as
5273 @item info line @var{linespec}
5274 Print the starting and ending addresses of the compiled code for
5275 source line @var{linespec}. You can specify source lines in any of
5276 the ways understood by the @code{list} command (@pxref{List, ,Printing
5280 For example, we can use @code{info line} to discover the location of
5281 the object code for the first line of function
5282 @code{m4_changequote}:
5284 @c FIXME: I think this example should also show the addresses in
5285 @c symbolic form, as they usually would be displayed.
5287 (@value{GDBP}) info line m4_changequote
5288 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
5292 @cindex code address and its source line
5293 We can also inquire (using @code{*@var{addr}} as the form for
5294 @var{linespec}) what source line covers a particular address:
5296 (@value{GDBP}) info line *0x63ff
5297 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
5300 @cindex @code{$_} and @code{info line}
5301 @cindex @code{x} command, default address
5302 @kindex x@r{(examine), and} info line
5303 After @code{info line}, the default address for the @code{x} command
5304 is changed to the starting address of the line, so that @samp{x/i} is
5305 sufficient to begin examining the machine code (@pxref{Memory,
5306 ,Examining Memory}). Also, this address is saved as the value of the
5307 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
5312 @cindex assembly instructions
5313 @cindex instructions, assembly
5314 @cindex machine instructions
5315 @cindex listing machine instructions
5317 This specialized command dumps a range of memory as machine
5318 instructions. The default memory range is the function surrounding the
5319 program counter of the selected frame. A single argument to this
5320 command is a program counter value; @value{GDBN} dumps the function
5321 surrounding this value. Two arguments specify a range of addresses
5322 (first inclusive, second exclusive) to dump.
5325 The following example shows the disassembly of a range of addresses of
5326 HP PA-RISC 2.0 code:
5329 (@value{GDBP}) disas 0x32c4 0x32e4
5330 Dump of assembler code from 0x32c4 to 0x32e4:
5331 0x32c4 <main+204>: addil 0,dp
5332 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
5333 0x32cc <main+212>: ldil 0x3000,r31
5334 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
5335 0x32d4 <main+220>: ldo 0(r31),rp
5336 0x32d8 <main+224>: addil -0x800,dp
5337 0x32dc <main+228>: ldo 0x588(r1),r26
5338 0x32e0 <main+232>: ldil 0x3000,r31
5339 End of assembler dump.
5342 Some architectures have more than one commonly-used set of instruction
5343 mnemonics or other syntax.
5345 For programs that were dynamically linked and use shared libraries,
5346 instructions that call functions or branch to locations in the shared
5347 libraries might show a seemingly bogus location---it's actually a
5348 location of the relocation table. On some architectures, @value{GDBN}
5349 might be able to resolve these to actual function names.
5352 @kindex set disassembly-flavor
5353 @cindex Intel disassembly flavor
5354 @cindex AT&T disassembly flavor
5355 @item set disassembly-flavor @var{instruction-set}
5356 Select the instruction set to use when disassembling the
5357 program via the @code{disassemble} or @code{x/i} commands.
5359 Currently this command is only defined for the Intel x86 family. You
5360 can set @var{instruction-set} to either @code{intel} or @code{att}.
5361 The default is @code{att}, the AT&T flavor used by default by Unix
5362 assemblers for x86-based targets.
5364 @kindex show disassembly-flavor
5365 @item show disassembly-flavor
5366 Show the current setting of the disassembly flavor.
5371 @chapter Examining Data
5373 @cindex printing data
5374 @cindex examining data
5377 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
5378 @c document because it is nonstandard... Under Epoch it displays in a
5379 @c different window or something like that.
5380 The usual way to examine data in your program is with the @code{print}
5381 command (abbreviated @code{p}), or its synonym @code{inspect}. It
5382 evaluates and prints the value of an expression of the language your
5383 program is written in (@pxref{Languages, ,Using @value{GDBN} with
5384 Different Languages}).
5387 @item print @var{expr}
5388 @itemx print /@var{f} @var{expr}
5389 @var{expr} is an expression (in the source language). By default the
5390 value of @var{expr} is printed in a format appropriate to its data type;
5391 you can choose a different format by specifying @samp{/@var{f}}, where
5392 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
5396 @itemx print /@var{f}
5397 @cindex reprint the last value
5398 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
5399 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
5400 conveniently inspect the same value in an alternative format.
5403 A more low-level way of examining data is with the @code{x} command.
5404 It examines data in memory at a specified address and prints it in a
5405 specified format. @xref{Memory, ,Examining Memory}.
5407 If you are interested in information about types, or about how the
5408 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
5409 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
5413 * Expressions:: Expressions
5414 * Variables:: Program variables
5415 * Arrays:: Artificial arrays
5416 * Output Formats:: Output formats
5417 * Memory:: Examining memory
5418 * Auto Display:: Automatic display
5419 * Print Settings:: Print settings
5420 * Value History:: Value history
5421 * Convenience Vars:: Convenience variables
5422 * Registers:: Registers
5423 * Floating Point Hardware:: Floating point hardware
5424 * Vector Unit:: Vector Unit
5425 * OS Information:: Auxiliary data provided by operating system
5426 * Memory Region Attributes:: Memory region attributes
5427 * Dump/Restore Files:: Copy between memory and a file
5428 * Core File Generation:: Cause a program dump its core
5429 * Character Sets:: Debugging programs that use a different
5430 character set than GDB does
5431 * Caching Remote Data:: Data caching for remote targets
5435 @section Expressions
5438 @code{print} and many other @value{GDBN} commands accept an expression and
5439 compute its value. Any kind of constant, variable or operator defined
5440 by the programming language you are using is valid in an expression in
5441 @value{GDBN}. This includes conditional expressions, function calls,
5442 casts, and string constants. It also includes preprocessor macros, if
5443 you compiled your program to include this information; see
5446 @cindex arrays in expressions
5447 @value{GDBN} supports array constants in expressions input by
5448 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
5449 you can use the command @code{print @{1, 2, 3@}} to build up an array in
5450 memory that is @code{malloc}ed in the target program.
5452 Because C is so widespread, most of the expressions shown in examples in
5453 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
5454 Languages}, for information on how to use expressions in other
5457 In this section, we discuss operators that you can use in @value{GDBN}
5458 expressions regardless of your programming language.
5460 @cindex casts, in expressions
5461 Casts are supported in all languages, not just in C, because it is so
5462 useful to cast a number into a pointer in order to examine a structure
5463 at that address in memory.
5464 @c FIXME: casts supported---Mod2 true?
5466 @value{GDBN} supports these operators, in addition to those common
5467 to programming languages:
5471 @samp{@@} is a binary operator for treating parts of memory as arrays.
5472 @xref{Arrays, ,Artificial Arrays}, for more information.
5475 @samp{::} allows you to specify a variable in terms of the file or
5476 function where it is defined. @xref{Variables, ,Program Variables}.
5478 @cindex @{@var{type}@}
5479 @cindex type casting memory
5480 @cindex memory, viewing as typed object
5481 @cindex casts, to view memory
5482 @item @{@var{type}@} @var{addr}
5483 Refers to an object of type @var{type} stored at address @var{addr} in
5484 memory. @var{addr} may be any expression whose value is an integer or
5485 pointer (but parentheses are required around binary operators, just as in
5486 a cast). This construct is allowed regardless of what kind of data is
5487 normally supposed to reside at @var{addr}.
5491 @section Program Variables
5493 The most common kind of expression to use is the name of a variable
5496 Variables in expressions are understood in the selected stack frame
5497 (@pxref{Selection, ,Selecting a Frame}); they must be either:
5501 global (or file-static)
5508 visible according to the scope rules of the
5509 programming language from the point of execution in that frame
5512 @noindent This means that in the function
5527 you can examine and use the variable @code{a} whenever your program is
5528 executing within the function @code{foo}, but you can only use or
5529 examine the variable @code{b} while your program is executing inside
5530 the block where @code{b} is declared.
5532 @cindex variable name conflict
5533 There is an exception: you can refer to a variable or function whose
5534 scope is a single source file even if the current execution point is not
5535 in this file. But it is possible to have more than one such variable or
5536 function with the same name (in different source files). If that
5537 happens, referring to that name has unpredictable effects. If you wish,
5538 you can specify a static variable in a particular function or file,
5539 using the colon-colon (@code{::}) notation:
5541 @cindex colon-colon, context for variables/functions
5543 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
5544 @cindex @code{::}, context for variables/functions
5547 @var{file}::@var{variable}
5548 @var{function}::@var{variable}
5552 Here @var{file} or @var{function} is the name of the context for the
5553 static @var{variable}. In the case of file names, you can use quotes to
5554 make sure @value{GDBN} parses the file name as a single word---for example,
5555 to print a global value of @code{x} defined in @file{f2.c}:
5558 (@value{GDBP}) p 'f2.c'::x
5561 @cindex C@t{++} scope resolution
5562 This use of @samp{::} is very rarely in conflict with the very similar
5563 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
5564 scope resolution operator in @value{GDBN} expressions.
5565 @c FIXME: Um, so what happens in one of those rare cases where it's in
5568 @cindex wrong values
5569 @cindex variable values, wrong
5570 @cindex function entry/exit, wrong values of variables
5571 @cindex optimized code, wrong values of variables
5573 @emph{Warning:} Occasionally, a local variable may appear to have the
5574 wrong value at certain points in a function---just after entry to a new
5575 scope, and just before exit.
5577 You may see this problem when you are stepping by machine instructions.
5578 This is because, on most machines, it takes more than one instruction to
5579 set up a stack frame (including local variable definitions); if you are
5580 stepping by machine instructions, variables may appear to have the wrong
5581 values until the stack frame is completely built. On exit, it usually
5582 also takes more than one machine instruction to destroy a stack frame;
5583 after you begin stepping through that group of instructions, local
5584 variable definitions may be gone.
5586 This may also happen when the compiler does significant optimizations.
5587 To be sure of always seeing accurate values, turn off all optimization
5590 @cindex ``No symbol "foo" in current context''
5591 Another possible effect of compiler optimizations is to optimize
5592 unused variables out of existence, or assign variables to registers (as
5593 opposed to memory addresses). Depending on the support for such cases
5594 offered by the debug info format used by the compiler, @value{GDBN}
5595 might not be able to display values for such local variables. If that
5596 happens, @value{GDBN} will print a message like this:
5599 No symbol "foo" in current context.
5602 To solve such problems, either recompile without optimizations, or use a
5603 different debug info format, if the compiler supports several such
5604 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
5605 usually supports the @option{-gstabs+} option. @option{-gstabs+}
5606 produces debug info in a format that is superior to formats such as
5607 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
5608 an effective form for debug info. @xref{Debugging Options,,Options
5609 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
5610 Compiler Collection (GCC)}.
5611 @xref{C, ,C and C@t{++}}, for more information 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.
5619 Strings are identified as arrays of @code{char} values without specified
5620 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
5621 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
5622 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
5623 defines literal string type @code{"char"} as @code{char} without a sign.
5628 signed char var1[] = "A";
5631 You get during debugging
5636 $2 = @{65 'A', 0 '\0'@}
5640 @section Artificial Arrays
5642 @cindex artificial array
5644 @kindex @@@r{, referencing memory as an array}
5645 It is often useful to print out several successive objects of the
5646 same type in memory; a section of an array, or an array of
5647 dynamically determined size for which only a pointer exists in the
5650 You can do this by referring to a contiguous span of memory as an
5651 @dfn{artificial array}, using the binary operator @samp{@@}. The left
5652 operand of @samp{@@} should be the first element of the desired array
5653 and be an individual object. The right operand should be the desired length
5654 of the array. The result is an array value whose elements are all of
5655 the type of the left argument. The first element is actually the left
5656 argument; the second element comes from bytes of memory immediately
5657 following those that hold the first element, and so on. Here is an
5658 example. If a program says
5661 int *array = (int *) malloc (len * sizeof (int));
5665 you can print the contents of @code{array} with
5671 The left operand of @samp{@@} must reside in memory. Array values made
5672 with @samp{@@} in this way behave just like other arrays in terms of
5673 subscripting, and are coerced to pointers when used in expressions.
5674 Artificial arrays most often appear in expressions via the value history
5675 (@pxref{Value History, ,Value History}), after printing one out.
5677 Another way to create an artificial array is to use a cast.
5678 This re-interprets a value as if it were an array.
5679 The value need not be in memory:
5681 (@value{GDBP}) p/x (short[2])0x12345678
5682 $1 = @{0x1234, 0x5678@}
5685 As a convenience, if you leave the array length out (as in
5686 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
5687 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
5689 (@value{GDBP}) p/x (short[])0x12345678
5690 $2 = @{0x1234, 0x5678@}
5693 Sometimes the artificial array mechanism is not quite enough; in
5694 moderately complex data structures, the elements of interest may not
5695 actually be adjacent---for example, if you are interested in the values
5696 of pointers in an array. One useful work-around in this situation is
5697 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
5698 Variables}) as a counter in an expression that prints the first
5699 interesting value, and then repeat that expression via @key{RET}. For
5700 instance, suppose you have an array @code{dtab} of pointers to
5701 structures, and you are interested in the values of a field @code{fv}
5702 in each structure. Here is an example of what you might type:
5712 @node Output Formats
5713 @section Output Formats
5715 @cindex formatted output
5716 @cindex output formats
5717 By default, @value{GDBN} prints a value according to its data type. Sometimes
5718 this is not what you want. For example, you might want to print a number
5719 in hex, or a pointer in decimal. Or you might want to view data in memory
5720 at a certain address as a character string or as an instruction. To do
5721 these things, specify an @dfn{output format} when you print a value.
5723 The simplest use of output formats is to say how to print a value
5724 already computed. This is done by starting the arguments of the
5725 @code{print} command with a slash and a format letter. The format
5726 letters supported are:
5730 Regard the bits of the value as an integer, and print the integer in
5734 Print as integer in signed decimal.
5737 Print as integer in unsigned decimal.
5740 Print as integer in octal.
5743 Print as integer in binary. The letter @samp{t} stands for ``two''.
5744 @footnote{@samp{b} cannot be used because these format letters are also
5745 used with the @code{x} command, where @samp{b} stands for ``byte'';
5746 see @ref{Memory,,Examining Memory}.}
5749 @cindex unknown address, locating
5750 @cindex locate address
5751 Print as an address, both absolute in hexadecimal and as an offset from
5752 the nearest preceding symbol. You can use this format used to discover
5753 where (in what function) an unknown address is located:
5756 (@value{GDBP}) p/a 0x54320
5757 $3 = 0x54320 <_initialize_vx+396>
5761 The command @code{info symbol 0x54320} yields similar results.
5762 @xref{Symbols, info symbol}.
5765 Regard as an integer and print it as a character constant. This
5766 prints both the numerical value and its character representation. The
5767 character representation is replaced with the octal escape @samp{\nnn}
5768 for characters outside the 7-bit @sc{ascii} range.
5770 Without this format, @value{GDBN} displays @code{char},
5771 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
5772 constants. Single-byte members of vectors are displayed as integer
5776 Regard the bits of the value as a floating point number and print
5777 using typical floating point syntax.
5780 @cindex printing strings
5781 @cindex printing byte arrays
5782 Regard as a string, if possible. With this format, pointers to single-byte
5783 data are displayed as null-terminated strings and arrays of single-byte data
5784 are displayed as fixed-length strings. Other values are displayed in their
5787 Without this format, @value{GDBN} displays pointers to and arrays of
5788 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
5789 strings. Single-byte members of a vector are displayed as an integer
5793 For example, to print the program counter in hex (@pxref{Registers}), type
5800 Note that no space is required before the slash; this is because command
5801 names in @value{GDBN} cannot contain a slash.
5803 To reprint the last value in the value history with a different format,
5804 you can use the @code{print} command with just a format and no
5805 expression. For example, @samp{p/x} reprints the last value in hex.
5808 @section Examining Memory
5810 You can use the command @code{x} (for ``examine'') to examine memory in
5811 any of several formats, independently of your program's data types.
5813 @cindex examining memory
5815 @kindex x @r{(examine memory)}
5816 @item x/@var{nfu} @var{addr}
5819 Use the @code{x} command to examine memory.
5822 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
5823 much memory to display and how to format it; @var{addr} is an
5824 expression giving the address where you want to start displaying memory.
5825 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
5826 Several commands set convenient defaults for @var{addr}.
5829 @item @var{n}, the repeat count
5830 The repeat count is a decimal integer; the default is 1. It specifies
5831 how much memory (counting by units @var{u}) to display.
5832 @c This really is **decimal**; unaffected by 'set radix' as of GDB
5835 @item @var{f}, the display format
5836 The display format is one of the formats used by @code{print}
5837 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
5838 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
5839 The default is @samp{x} (hexadecimal) initially. The default changes
5840 each time you use either @code{x} or @code{print}.
5842 @item @var{u}, the unit size
5843 The unit size is any of
5849 Halfwords (two bytes).
5851 Words (four bytes). This is the initial default.
5853 Giant words (eight bytes).
5856 Each time you specify a unit size with @code{x}, that size becomes the
5857 default unit the next time you use @code{x}. (For the @samp{s} and
5858 @samp{i} formats, the unit size is ignored and is normally not written.)
5860 @item @var{addr}, starting display address
5861 @var{addr} is the address where you want @value{GDBN} to begin displaying
5862 memory. The expression need not have a pointer value (though it may);
5863 it is always interpreted as an integer address of a byte of memory.
5864 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
5865 @var{addr} is usually just after the last address examined---but several
5866 other commands also set the default address: @code{info breakpoints} (to
5867 the address of the last breakpoint listed), @code{info line} (to the
5868 starting address of a line), and @code{print} (if you use it to display
5869 a value from memory).
5872 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
5873 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
5874 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
5875 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
5876 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
5878 Since the letters indicating unit sizes are all distinct from the
5879 letters specifying output formats, you do not have to remember whether
5880 unit size or format comes first; either order works. The output
5881 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
5882 (However, the count @var{n} must come first; @samp{wx4} does not work.)
5884 Even though the unit size @var{u} is ignored for the formats @samp{s}
5885 and @samp{i}, you might still want to use a count @var{n}; for example,
5886 @samp{3i} specifies that you want to see three machine instructions,
5887 including any operands. For convenience, especially when used with
5888 the @code{display} command, the @samp{i} format also prints branch delay
5889 slot instructions, if any, beyond the count specified, which immediately
5890 follow the last instruction that is within the count. The command
5891 @code{disassemble} gives an alternative way of inspecting machine
5892 instructions; see @ref{Machine Code,,Source and Machine Code}.
5894 All the defaults for the arguments to @code{x} are designed to make it
5895 easy to continue scanning memory with minimal specifications each time
5896 you use @code{x}. For example, after you have inspected three machine
5897 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
5898 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
5899 the repeat count @var{n} is used again; the other arguments default as
5900 for successive uses of @code{x}.
5902 @cindex @code{$_}, @code{$__}, and value history
5903 The addresses and contents printed by the @code{x} command are not saved
5904 in the value history because there is often too much of them and they
5905 would get in the way. Instead, @value{GDBN} makes these values available for
5906 subsequent use in expressions as values of the convenience variables
5907 @code{$_} and @code{$__}. After an @code{x} command, the last address
5908 examined is available for use in expressions in the convenience variable
5909 @code{$_}. The contents of that address, as examined, are available in
5910 the convenience variable @code{$__}.
5912 If the @code{x} command has a repeat count, the address and contents saved
5913 are from the last memory unit printed; this is not the same as the last
5914 address printed if several units were printed on the last line of output.
5916 @cindex remote memory comparison
5917 @cindex verify remote memory image
5918 When you are debugging a program running on a remote target machine
5919 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
5920 remote machine's memory against the executable file you downloaded to
5921 the target. The @code{compare-sections} command is provided for such
5925 @kindex compare-sections
5926 @item compare-sections @r{[}@var{section-name}@r{]}
5927 Compare the data of a loadable section @var{section-name} in the
5928 executable file of the program being debugged with the same section in
5929 the remote machine's memory, and report any mismatches. With no
5930 arguments, compares all loadable sections. This command's
5931 availability depends on the target's support for the @code{"qCRC"}
5936 @section Automatic Display
5937 @cindex automatic display
5938 @cindex display of expressions
5940 If you find that you want to print the value of an expression frequently
5941 (to see how it changes), you might want to add it to the @dfn{automatic
5942 display list} so that @value{GDBN} prints its value each time your program stops.
5943 Each expression added to the list is given a number to identify it;
5944 to remove an expression from the list, you specify that number.
5945 The automatic display looks like this:
5949 3: bar[5] = (struct hack *) 0x3804
5953 This display shows item numbers, expressions and their current values. As with
5954 displays you request manually using @code{x} or @code{print}, you can
5955 specify the output format you prefer; in fact, @code{display} decides
5956 whether to use @code{print} or @code{x} depending your format
5957 specification---it uses @code{x} if you specify either the @samp{i}
5958 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
5962 @item display @var{expr}
5963 Add the expression @var{expr} to the list of expressions to display
5964 each time your program stops. @xref{Expressions, ,Expressions}.
5966 @code{display} does not repeat if you press @key{RET} again after using it.
5968 @item display/@var{fmt} @var{expr}
5969 For @var{fmt} specifying only a display format and not a size or
5970 count, add the expression @var{expr} to the auto-display list but
5971 arrange to display it each time in the specified format @var{fmt}.
5972 @xref{Output Formats,,Output Formats}.
5974 @item display/@var{fmt} @var{addr}
5975 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
5976 number of units, add the expression @var{addr} as a memory address to
5977 be examined each time your program stops. Examining means in effect
5978 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
5981 For example, @samp{display/i $pc} can be helpful, to see the machine
5982 instruction about to be executed each time execution stops (@samp{$pc}
5983 is a common name for the program counter; @pxref{Registers, ,Registers}).
5986 @kindex delete display
5988 @item undisplay @var{dnums}@dots{}
5989 @itemx delete display @var{dnums}@dots{}
5990 Remove item numbers @var{dnums} from the list of expressions to display.
5992 @code{undisplay} does not repeat if you press @key{RET} after using it.
5993 (Otherwise you would just get the error @samp{No display number @dots{}}.)
5995 @kindex disable display
5996 @item disable display @var{dnums}@dots{}
5997 Disable the display of item numbers @var{dnums}. A disabled display
5998 item is not printed automatically, but is not forgotten. It may be
5999 enabled again later.
6001 @kindex enable display
6002 @item enable display @var{dnums}@dots{}
6003 Enable display of item numbers @var{dnums}. It becomes effective once
6004 again in auto display of its expression, until you specify otherwise.
6007 Display the current values of the expressions on the list, just as is
6008 done when your program stops.
6010 @kindex info display
6012 Print the list of expressions previously set up to display
6013 automatically, each one with its item number, but without showing the
6014 values. This includes disabled expressions, which are marked as such.
6015 It also includes expressions which would not be displayed right now
6016 because they refer to automatic variables not currently available.
6019 @cindex display disabled out of scope
6020 If a display expression refers to local variables, then it does not make
6021 sense outside the lexical context for which it was set up. Such an
6022 expression is disabled when execution enters a context where one of its
6023 variables is not defined. For example, if you give the command
6024 @code{display last_char} while inside a function with an argument
6025 @code{last_char}, @value{GDBN} displays this argument while your program
6026 continues to stop inside that function. When it stops elsewhere---where
6027 there is no variable @code{last_char}---the display is disabled
6028 automatically. The next time your program stops where @code{last_char}
6029 is meaningful, you can enable the display expression once again.
6031 @node Print Settings
6032 @section Print Settings
6034 @cindex format options
6035 @cindex print settings
6036 @value{GDBN} provides the following ways to control how arrays, structures,
6037 and symbols are printed.
6040 These settings are useful for debugging programs in any language:
6044 @item set print address
6045 @itemx set print address on
6046 @cindex print/don't print memory addresses
6047 @value{GDBN} prints memory addresses showing the location of stack
6048 traces, structure values, pointer values, breakpoints, and so forth,
6049 even when it also displays the contents of those addresses. The default
6050 is @code{on}. For example, this is what a stack frame display looks like with
6051 @code{set print address on}:
6056 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
6058 530 if (lquote != def_lquote)
6062 @item set print address off
6063 Do not print addresses when displaying their contents. For example,
6064 this is the same stack frame displayed with @code{set print address off}:
6068 (@value{GDBP}) set print addr off
6070 #0 set_quotes (lq="<<", rq=">>") at input.c:530
6071 530 if (lquote != def_lquote)
6075 You can use @samp{set print address off} to eliminate all machine
6076 dependent displays from the @value{GDBN} interface. For example, with
6077 @code{print address off}, you should get the same text for backtraces on
6078 all machines---whether or not they involve pointer arguments.
6081 @item show print address
6082 Show whether or not addresses are to be printed.
6085 When @value{GDBN} prints a symbolic address, it normally prints the
6086 closest earlier symbol plus an offset. If that symbol does not uniquely
6087 identify the address (for example, it is a name whose scope is a single
6088 source file), you may need to clarify. One way to do this is with
6089 @code{info line}, for example @samp{info line *0x4537}. Alternately,
6090 you can set @value{GDBN} to print the source file and line number when
6091 it prints a symbolic address:
6094 @item set print symbol-filename on
6095 @cindex source file and line of a symbol
6096 @cindex symbol, source file and line
6097 Tell @value{GDBN} to print the source file name and line number of a
6098 symbol in the symbolic form of an address.
6100 @item set print symbol-filename off
6101 Do not print source file name and line number of a symbol. This is the
6104 @item show print symbol-filename
6105 Show whether or not @value{GDBN} will print the source file name and
6106 line number of a symbol in the symbolic form of an address.
6109 Another situation where it is helpful to show symbol filenames and line
6110 numbers is when disassembling code; @value{GDBN} shows you the line
6111 number and source file that corresponds to each instruction.
6113 Also, you may wish to see the symbolic form only if the address being
6114 printed is reasonably close to the closest earlier symbol:
6117 @item set print max-symbolic-offset @var{max-offset}
6118 @cindex maximum value for offset of closest symbol
6119 Tell @value{GDBN} to only display the symbolic form of an address if the
6120 offset between the closest earlier symbol and the address is less than
6121 @var{max-offset}. The default is 0, which tells @value{GDBN}
6122 to always print the symbolic form of an address if any symbol precedes it.
6124 @item show print max-symbolic-offset
6125 Ask how large the maximum offset is that @value{GDBN} prints in a
6129 @cindex wild pointer, interpreting
6130 @cindex pointer, finding referent
6131 If you have a pointer and you are not sure where it points, try
6132 @samp{set print symbol-filename on}. Then you can determine the name
6133 and source file location of the variable where it points, using
6134 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
6135 For example, here @value{GDBN} shows that a variable @code{ptt} points
6136 at another variable @code{t}, defined in @file{hi2.c}:
6139 (@value{GDBP}) set print symbol-filename on
6140 (@value{GDBP}) p/a ptt
6141 $4 = 0xe008 <t in hi2.c>
6145 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
6146 does not show the symbol name and filename of the referent, even with
6147 the appropriate @code{set print} options turned on.
6150 Other settings control how different kinds of objects are printed:
6153 @item set print array
6154 @itemx set print array on
6155 @cindex pretty print arrays
6156 Pretty print arrays. This format is more convenient to read,
6157 but uses more space. The default is off.
6159 @item set print array off
6160 Return to compressed format for arrays.
6162 @item show print array
6163 Show whether compressed or pretty format is selected for displaying
6166 @cindex print array indexes
6167 @item set print array-indexes
6168 @itemx set print array-indexes on
6169 Print the index of each element when displaying arrays. May be more
6170 convenient to locate a given element in the array or quickly find the
6171 index of a given element in that printed array. The default is off.
6173 @item set print array-indexes off
6174 Stop printing element indexes when displaying arrays.
6176 @item show print array-indexes
6177 Show whether the index of each element is printed when displaying
6180 @item set print elements @var{number-of-elements}
6181 @cindex number of array elements to print
6182 @cindex limit on number of printed array elements
6183 Set a limit on how many elements of an array @value{GDBN} will print.
6184 If @value{GDBN} is printing a large array, it stops printing after it has
6185 printed the number of elements set by the @code{set print elements} command.
6186 This limit also applies to the display of strings.
6187 When @value{GDBN} starts, this limit is set to 200.
6188 Setting @var{number-of-elements} to zero means that the printing is unlimited.
6190 @item show print elements
6191 Display the number of elements of a large array that @value{GDBN} will print.
6192 If the number is 0, then the printing is unlimited.
6194 @item set print repeats
6195 @cindex repeated array elements
6196 Set the threshold for suppressing display of repeated array
6197 elements. When the number of consecutive identical elements of an
6198 array exceeds the threshold, @value{GDBN} prints the string
6199 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
6200 identical repetitions, instead of displaying the identical elements
6201 themselves. Setting the threshold to zero will cause all elements to
6202 be individually printed. The default threshold is 10.
6204 @item show print repeats
6205 Display the current threshold for printing repeated identical
6208 @item set print null-stop
6209 @cindex @sc{null} elements in arrays
6210 Cause @value{GDBN} to stop printing the characters of an array when the first
6211 @sc{null} is encountered. This is useful when large arrays actually
6212 contain only short strings.
6215 @item show print null-stop
6216 Show whether @value{GDBN} stops printing an array on the first
6217 @sc{null} character.
6219 @item set print pretty on
6220 @cindex print structures in indented form
6221 @cindex indentation in structure display
6222 Cause @value{GDBN} to print structures in an indented format with one member
6223 per line, like this:
6238 @item set print pretty off
6239 Cause @value{GDBN} to print structures in a compact format, like this:
6243 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
6244 meat = 0x54 "Pork"@}
6249 This is the default format.
6251 @item show print pretty
6252 Show which format @value{GDBN} is using to print structures.
6254 @item set print sevenbit-strings on
6255 @cindex eight-bit characters in strings
6256 @cindex octal escapes in strings
6257 Print using only seven-bit characters; if this option is set,
6258 @value{GDBN} displays any eight-bit characters (in strings or
6259 character values) using the notation @code{\}@var{nnn}. This setting is
6260 best if you are working in English (@sc{ascii}) and you use the
6261 high-order bit of characters as a marker or ``meta'' bit.
6263 @item set print sevenbit-strings off
6264 Print full eight-bit characters. This allows the use of more
6265 international character sets, and is the default.
6267 @item show print sevenbit-strings
6268 Show whether or not @value{GDBN} is printing only seven-bit characters.
6270 @item set print union on
6271 @cindex unions in structures, printing
6272 Tell @value{GDBN} to print unions which are contained in structures
6273 and other unions. This is the default setting.
6275 @item set print union off
6276 Tell @value{GDBN} not to print unions which are contained in
6277 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
6280 @item show print union
6281 Ask @value{GDBN} whether or not it will print unions which are contained in
6282 structures and other unions.
6284 For example, given the declarations
6287 typedef enum @{Tree, Bug@} Species;
6288 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
6289 typedef enum @{Caterpillar, Cocoon, Butterfly@}
6300 struct thing foo = @{Tree, @{Acorn@}@};
6304 with @code{set print union on} in effect @samp{p foo} would print
6307 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
6311 and with @code{set print union off} in effect it would print
6314 $1 = @{it = Tree, form = @{...@}@}
6318 @code{set print union} affects programs written in C-like languages
6324 These settings are of interest when debugging C@t{++} programs:
6327 @cindex demangling C@t{++} names
6328 @item set print demangle
6329 @itemx set print demangle on
6330 Print C@t{++} names in their source form rather than in the encoded
6331 (``mangled'') form passed to the assembler and linker for type-safe
6332 linkage. The default is on.
6334 @item show print demangle
6335 Show whether C@t{++} names are printed in mangled or demangled form.
6337 @item set print asm-demangle
6338 @itemx set print asm-demangle on
6339 Print C@t{++} names in their source form rather than their mangled form, even
6340 in assembler code printouts such as instruction disassemblies.
6343 @item show print asm-demangle
6344 Show whether C@t{++} names in assembly listings are printed in mangled
6347 @cindex C@t{++} symbol decoding style
6348 @cindex symbol decoding style, C@t{++}
6349 @kindex set demangle-style
6350 @item set demangle-style @var{style}
6351 Choose among several encoding schemes used by different compilers to
6352 represent C@t{++} names. The choices for @var{style} are currently:
6356 Allow @value{GDBN} to choose a decoding style by inspecting your program.
6359 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
6360 This is the default.
6363 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
6366 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
6369 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
6370 @strong{Warning:} this setting alone is not sufficient to allow
6371 debugging @code{cfront}-generated executables. @value{GDBN} would
6372 require further enhancement to permit that.
6375 If you omit @var{style}, you will see a list of possible formats.
6377 @item show demangle-style
6378 Display the encoding style currently in use for decoding C@t{++} symbols.
6380 @item set print object
6381 @itemx set print object on
6382 @cindex derived type of an object, printing
6383 @cindex display derived types
6384 When displaying a pointer to an object, identify the @emph{actual}
6385 (derived) type of the object rather than the @emph{declared} type, using
6386 the virtual function table.
6388 @item set print object off
6389 Display only the declared type of objects, without reference to the
6390 virtual function table. This is the default setting.
6392 @item show print object
6393 Show whether actual, or declared, object types are displayed.
6395 @item set print static-members
6396 @itemx set print static-members on
6397 @cindex static members of C@t{++} objects
6398 Print static members when displaying a C@t{++} object. The default is on.
6400 @item set print static-members off
6401 Do not print static members when displaying a C@t{++} object.
6403 @item show print static-members
6404 Show whether C@t{++} static members are printed or not.
6406 @item set print pascal_static-members
6407 @itemx set print pascal_static-members on
6408 @cindex static members of Pascal objects
6409 @cindex Pascal objects, static members display
6410 Print static members when displaying a Pascal object. The default is on.
6412 @item set print pascal_static-members off
6413 Do not print static members when displaying a Pascal object.
6415 @item show print pascal_static-members
6416 Show whether Pascal static members are printed or not.
6418 @c These don't work with HP ANSI C++ yet.
6419 @item set print vtbl
6420 @itemx set print vtbl on
6421 @cindex pretty print C@t{++} virtual function tables
6422 @cindex virtual functions (C@t{++}) display
6423 @cindex VTBL display
6424 Pretty print C@t{++} virtual function tables. The default is off.
6425 (The @code{vtbl} commands do not work on programs compiled with the HP
6426 ANSI C@t{++} compiler (@code{aCC}).)
6428 @item set print vtbl off
6429 Do not pretty print C@t{++} virtual function tables.
6431 @item show print vtbl
6432 Show whether C@t{++} virtual function tables are pretty printed, or not.
6436 @section Value History
6438 @cindex value history
6439 @cindex history of values printed by @value{GDBN}
6440 Values printed by the @code{print} command are saved in the @value{GDBN}
6441 @dfn{value history}. This allows you to refer to them in other expressions.
6442 Values are kept until the symbol table is re-read or discarded
6443 (for example with the @code{file} or @code{symbol-file} commands).
6444 When the symbol table changes, the value history is discarded,
6445 since the values may contain pointers back to the types defined in the
6450 @cindex history number
6451 The values printed are given @dfn{history numbers} by which you can
6452 refer to them. These are successive integers starting with one.
6453 @code{print} shows you the history number assigned to a value by
6454 printing @samp{$@var{num} = } before the value; here @var{num} is the
6457 To refer to any previous value, use @samp{$} followed by the value's
6458 history number. The way @code{print} labels its output is designed to
6459 remind you of this. Just @code{$} refers to the most recent value in
6460 the history, and @code{$$} refers to the value before that.
6461 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
6462 is the value just prior to @code{$$}, @code{$$1} is equivalent to
6463 @code{$$}, and @code{$$0} is equivalent to @code{$}.
6465 For example, suppose you have just printed a pointer to a structure and
6466 want to see the contents of the structure. It suffices to type
6472 If you have a chain of structures where the component @code{next} points
6473 to the next one, you can print the contents of the next one with this:
6480 You can print successive links in the chain by repeating this
6481 command---which you can do by just typing @key{RET}.
6483 Note that the history records values, not expressions. If the value of
6484 @code{x} is 4 and you type these commands:
6492 then the value recorded in the value history by the @code{print} command
6493 remains 4 even though the value of @code{x} has changed.
6498 Print the last ten values in the value history, with their item numbers.
6499 This is like @samp{p@ $$9} repeated ten times, except that @code{show
6500 values} does not change the history.
6502 @item show values @var{n}
6503 Print ten history values centered on history item number @var{n}.
6506 Print ten history values just after the values last printed. If no more
6507 values are available, @code{show values +} produces no display.
6510 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
6511 same effect as @samp{show values +}.
6513 @node Convenience Vars
6514 @section Convenience Variables
6516 @cindex convenience variables
6517 @cindex user-defined variables
6518 @value{GDBN} provides @dfn{convenience variables} that you can use within
6519 @value{GDBN} to hold on to a value and refer to it later. These variables
6520 exist entirely within @value{GDBN}; they are not part of your program, and
6521 setting a convenience variable has no direct effect on further execution
6522 of your program. That is why you can use them freely.
6524 Convenience variables are prefixed with @samp{$}. Any name preceded by
6525 @samp{$} can be used for a convenience variable, unless it is one of
6526 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
6527 (Value history references, in contrast, are @emph{numbers} preceded
6528 by @samp{$}. @xref{Value History, ,Value History}.)
6530 You can save a value in a convenience variable with an assignment
6531 expression, just as you would set a variable in your program.
6535 set $foo = *object_ptr
6539 would save in @code{$foo} the value contained in the object pointed to by
6542 Using a convenience variable for the first time creates it, but its
6543 value is @code{void} until you assign a new value. You can alter the
6544 value with another assignment at any time.
6546 Convenience variables have no fixed types. You can assign a convenience
6547 variable any type of value, including structures and arrays, even if
6548 that variable already has a value of a different type. The convenience
6549 variable, when used as an expression, has the type of its current value.
6552 @kindex show convenience
6553 @cindex show all user variables
6554 @item show convenience
6555 Print a list of convenience variables used so far, and their values.
6556 Abbreviated @code{show conv}.
6558 @kindex init-if-undefined
6559 @cindex convenience variables, initializing
6560 @item init-if-undefined $@var{variable} = @var{expression}
6561 Set a convenience variable if it has not already been set. This is useful
6562 for user-defined commands that keep some state. It is similar, in concept,
6563 to using local static variables with initializers in C (except that
6564 convenience variables are global). It can also be used to allow users to
6565 override default values used in a command script.
6567 If the variable is already defined then the expression is not evaluated so
6568 any side-effects do not occur.
6571 One of the ways to use a convenience variable is as a counter to be
6572 incremented or a pointer to be advanced. For example, to print
6573 a field from successive elements of an array of structures:
6577 print bar[$i++]->contents
6581 Repeat that command by typing @key{RET}.
6583 Some convenience variables are created automatically by @value{GDBN} and given
6584 values likely to be useful.
6587 @vindex $_@r{, convenience variable}
6589 The variable @code{$_} is automatically set by the @code{x} command to
6590 the last address examined (@pxref{Memory, ,Examining Memory}). Other
6591 commands which provide a default address for @code{x} to examine also
6592 set @code{$_} to that address; these commands include @code{info line}
6593 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
6594 except when set by the @code{x} command, in which case it is a pointer
6595 to the type of @code{$__}.
6597 @vindex $__@r{, convenience variable}
6599 The variable @code{$__} is automatically set by the @code{x} command
6600 to the value found in the last address examined. Its type is chosen
6601 to match the format in which the data was printed.
6604 @vindex $_exitcode@r{, convenience variable}
6605 The variable @code{$_exitcode} is automatically set to the exit code when
6606 the program being debugged terminates.
6609 On HP-UX systems, if you refer to a function or variable name that
6610 begins with a dollar sign, @value{GDBN} searches for a user or system
6611 name first, before it searches for a convenience variable.
6617 You can refer to machine register contents, in expressions, as variables
6618 with names starting with @samp{$}. The names of registers are different
6619 for each machine; use @code{info registers} to see the names used on
6623 @kindex info registers
6624 @item info registers
6625 Print the names and values of all registers except floating-point
6626 and vector registers (in the selected stack frame).
6628 @kindex info all-registers
6629 @cindex floating point registers
6630 @item info all-registers
6631 Print the names and values of all registers, including floating-point
6632 and vector registers (in the selected stack frame).
6634 @item info registers @var{regname} @dots{}
6635 Print the @dfn{relativized} value of each specified register @var{regname}.
6636 As discussed in detail below, register values are normally relative to
6637 the selected stack frame. @var{regname} may be any register name valid on
6638 the machine you are using, with or without the initial @samp{$}.
6641 @cindex stack pointer register
6642 @cindex program counter register
6643 @cindex process status register
6644 @cindex frame pointer register
6645 @cindex standard registers
6646 @value{GDBN} has four ``standard'' register names that are available (in
6647 expressions) on most machines---whenever they do not conflict with an
6648 architecture's canonical mnemonics for registers. The register names
6649 @code{$pc} and @code{$sp} are used for the program counter register and
6650 the stack pointer. @code{$fp} is used for a register that contains a
6651 pointer to the current stack frame, and @code{$ps} is used for a
6652 register that contains the processor status. For example,
6653 you could print the program counter in hex with
6660 or print the instruction to be executed next with
6667 or add four to the stack pointer@footnote{This is a way of removing
6668 one word from the stack, on machines where stacks grow downward in
6669 memory (most machines, nowadays). This assumes that the innermost
6670 stack frame is selected; setting @code{$sp} is not allowed when other
6671 stack frames are selected. To pop entire frames off the stack,
6672 regardless of machine architecture, use @code{return};
6673 see @ref{Returning, ,Returning from a Function}.} with
6679 Whenever possible, these four standard register names are available on
6680 your machine even though the machine has different canonical mnemonics,
6681 so long as there is no conflict. The @code{info registers} command
6682 shows the canonical names. For example, on the SPARC, @code{info
6683 registers} displays the processor status register as @code{$psr} but you
6684 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
6685 is an alias for the @sc{eflags} register.
6687 @value{GDBN} always considers the contents of an ordinary register as an
6688 integer when the register is examined in this way. Some machines have
6689 special registers which can hold nothing but floating point; these
6690 registers are considered to have floating point values. There is no way
6691 to refer to the contents of an ordinary register as floating point value
6692 (although you can @emph{print} it as a floating point value with
6693 @samp{print/f $@var{regname}}).
6695 Some registers have distinct ``raw'' and ``virtual'' data formats. This
6696 means that the data format in which the register contents are saved by
6697 the operating system is not the same one that your program normally
6698 sees. For example, the registers of the 68881 floating point
6699 coprocessor are always saved in ``extended'' (raw) format, but all C
6700 programs expect to work with ``double'' (virtual) format. In such
6701 cases, @value{GDBN} normally works with the virtual format only (the format
6702 that makes sense for your program), but the @code{info registers} command
6703 prints the data in both formats.
6705 @cindex SSE registers (x86)
6706 @cindex MMX registers (x86)
6707 Some machines have special registers whose contents can be interpreted
6708 in several different ways. For example, modern x86-based machines
6709 have SSE and MMX registers that can hold several values packed
6710 together in several different formats. @value{GDBN} refers to such
6711 registers in @code{struct} notation:
6714 (@value{GDBP}) print $xmm1
6716 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
6717 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
6718 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
6719 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
6720 v4_int32 = @{0, 20657912, 11, 13@},
6721 v2_int64 = @{88725056443645952, 55834574859@},
6722 uint128 = 0x0000000d0000000b013b36f800000000
6727 To set values of such registers, you need to tell @value{GDBN} which
6728 view of the register you wish to change, as if you were assigning
6729 value to a @code{struct} member:
6732 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
6735 Normally, register values are relative to the selected stack frame
6736 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
6737 value that the register would contain if all stack frames farther in
6738 were exited and their saved registers restored. In order to see the
6739 true contents of hardware registers, you must select the innermost
6740 frame (with @samp{frame 0}).
6742 However, @value{GDBN} must deduce where registers are saved, from the machine
6743 code generated by your compiler. If some registers are not saved, or if
6744 @value{GDBN} is unable to locate the saved registers, the selected stack
6745 frame makes no difference.
6747 @node Floating Point Hardware
6748 @section Floating Point Hardware
6749 @cindex floating point
6751 Depending on the configuration, @value{GDBN} may be able to give
6752 you more information about the status of the floating point hardware.
6757 Display hardware-dependent information about the floating
6758 point unit. The exact contents and layout vary depending on the
6759 floating point chip. Currently, @samp{info float} is supported on
6760 the ARM and x86 machines.
6764 @section Vector Unit
6767 Depending on the configuration, @value{GDBN} may be able to give you
6768 more information about the status of the vector unit.
6773 Display information about the vector unit. The exact contents and
6774 layout vary depending on the hardware.
6777 @node OS Information
6778 @section Operating System Auxiliary Information
6779 @cindex OS information
6781 @value{GDBN} provides interfaces to useful OS facilities that can help
6782 you debug your program.
6784 @cindex @code{ptrace} system call
6785 @cindex @code{struct user} contents
6786 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
6787 machines), it interfaces with the inferior via the @code{ptrace}
6788 system call. The operating system creates a special sata structure,
6789 called @code{struct user}, for this interface. You can use the
6790 command @code{info udot} to display the contents of this data
6796 Display the contents of the @code{struct user} maintained by the OS
6797 kernel for the program being debugged. @value{GDBN} displays the
6798 contents of @code{struct user} as a list of hex numbers, similar to
6799 the @code{examine} command.
6802 @cindex auxiliary vector
6803 @cindex vector, auxiliary
6804 Some operating systems supply an @dfn{auxiliary vector} to programs at
6805 startup. This is akin to the arguments and environment that you
6806 specify for a program, but contains a system-dependent variety of
6807 binary values that tell system libraries important details about the
6808 hardware, operating system, and process. Each value's purpose is
6809 identified by an integer tag; the meanings are well-known but system-specific.
6810 Depending on the configuration and operating system facilities,
6811 @value{GDBN} may be able to show you this information. For remote
6812 targets, this functionality may further depend on the remote stub's
6813 support of the @samp{qXfer:auxv:read} packet, see
6814 @ref{qXfer auxiliary vector read}.
6819 Display the auxiliary vector of the inferior, which can be either a
6820 live process or a core dump file. @value{GDBN} prints each tag value
6821 numerically, and also shows names and text descriptions for recognized
6822 tags. Some values in the vector are numbers, some bit masks, and some
6823 pointers to strings or other data. @value{GDBN} displays each value in the
6824 most appropriate form for a recognized tag, and in hexadecimal for
6825 an unrecognized tag.
6829 @node Memory Region Attributes
6830 @section Memory Region Attributes
6831 @cindex memory region attributes
6833 @dfn{Memory region attributes} allow you to describe special handling
6834 required by regions of your target's memory. @value{GDBN} uses
6835 attributes to determine whether to allow certain types of memory
6836 accesses; whether to use specific width accesses; and whether to cache
6837 target memory. By default the description of memory regions is
6838 fetched from the target (if the current target supports this), but the
6839 user can override the fetched regions.
6841 Defined memory regions can be individually enabled and disabled. When a
6842 memory region is disabled, @value{GDBN} uses the default attributes when
6843 accessing memory in that region. Similarly, if no memory regions have
6844 been defined, @value{GDBN} uses the default attributes when accessing
6847 When a memory region is defined, it is given a number to identify it;
6848 to enable, disable, or remove a memory region, you specify that number.
6852 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
6853 Define a memory region bounded by @var{lower} and @var{upper} with
6854 attributes @var{attributes}@dots{}, and add it to the list of regions
6855 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
6856 case: it is treated as the target's maximum memory address.
6857 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
6860 Discard any user changes to the memory regions and use target-supplied
6861 regions, if available, or no regions if the target does not support.
6864 @item delete mem @var{nums}@dots{}
6865 Remove memory regions @var{nums}@dots{} from the list of regions
6866 monitored by @value{GDBN}.
6869 @item disable mem @var{nums}@dots{}
6870 Disable monitoring of memory regions @var{nums}@dots{}.
6871 A disabled memory region is not forgotten.
6872 It may be enabled again later.
6875 @item enable mem @var{nums}@dots{}
6876 Enable monitoring of memory regions @var{nums}@dots{}.
6880 Print a table of all defined memory regions, with the following columns
6884 @item Memory Region Number
6885 @item Enabled or Disabled.
6886 Enabled memory regions are marked with @samp{y}.
6887 Disabled memory regions are marked with @samp{n}.
6890 The address defining the inclusive lower bound of the memory region.
6893 The address defining the exclusive upper bound of the memory region.
6896 The list of attributes set for this memory region.
6901 @subsection Attributes
6903 @subsubsection Memory Access Mode
6904 The access mode attributes set whether @value{GDBN} may make read or
6905 write accesses to a memory region.
6907 While these attributes prevent @value{GDBN} from performing invalid
6908 memory accesses, they do nothing to prevent the target system, I/O DMA,
6909 etc.@: from accessing memory.
6913 Memory is read only.
6915 Memory is write only.
6917 Memory is read/write. This is the default.
6920 @subsubsection Memory Access Size
6921 The access size attribute tells @value{GDBN} to use specific sized
6922 accesses in the memory region. Often memory mapped device registers
6923 require specific sized accesses. If no access size attribute is
6924 specified, @value{GDBN} may use accesses of any size.
6928 Use 8 bit memory accesses.
6930 Use 16 bit memory accesses.
6932 Use 32 bit memory accesses.
6934 Use 64 bit memory accesses.
6937 @c @subsubsection Hardware/Software Breakpoints
6938 @c The hardware/software breakpoint attributes set whether @value{GDBN}
6939 @c will use hardware or software breakpoints for the internal breakpoints
6940 @c used by the step, next, finish, until, etc. commands.
6944 @c Always use hardware breakpoints
6945 @c @item swbreak (default)
6948 @subsubsection Data Cache
6949 The data cache attributes set whether @value{GDBN} will cache target
6950 memory. While this generally improves performance by reducing debug
6951 protocol overhead, it can lead to incorrect results because @value{GDBN}
6952 does not know about volatile variables or memory mapped device
6957 Enable @value{GDBN} to cache target memory.
6959 Disable @value{GDBN} from caching target memory. This is the default.
6962 @subsection Memory Access Checking
6963 @value{GDBN} can be instructed to refuse accesses to memory that is
6964 not explicitly described. This can be useful if accessing such
6965 regions has undesired effects for a specific target, or to provide
6966 better error checking. The following commands control this behaviour.
6969 @kindex set mem inaccessible-by-default
6970 @item set mem inaccessible-by-default [on|off]
6971 If @code{on} is specified, make @value{GDBN} treat memory not
6972 explicitly described by the memory ranges as non-existent and refuse accesses
6973 to such memory. The checks are only performed if there's at least one
6974 memory range defined. If @code{off} is specified, make @value{GDBN}
6975 treat the memory not explicitly described by the memory ranges as RAM.
6976 The default value is @code{off}.
6977 @kindex show mem inaccessible-by-default
6978 @item show mem inaccessible-by-default
6979 Show the current handling of accesses to unknown memory.
6983 @c @subsubsection Memory Write Verification
6984 @c The memory write verification attributes set whether @value{GDBN}
6985 @c will re-reads data after each write to verify the write was successful.
6989 @c @item noverify (default)
6992 @node Dump/Restore Files
6993 @section Copy Between Memory and a File
6994 @cindex dump/restore files
6995 @cindex append data to a file
6996 @cindex dump data to a file
6997 @cindex restore data from a file
6999 You can use the commands @code{dump}, @code{append}, and
7000 @code{restore} to copy data between target memory and a file. The
7001 @code{dump} and @code{append} commands write data to a file, and the
7002 @code{restore} command reads data from a file back into the inferior's
7003 memory. Files may be in binary, Motorola S-record, Intel hex, or
7004 Tektronix Hex format; however, @value{GDBN} can only append to binary
7010 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7011 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
7012 Dump the contents of memory from @var{start_addr} to @var{end_addr},
7013 or the value of @var{expr}, to @var{filename} in the given format.
7015 The @var{format} parameter may be any one of:
7022 Motorola S-record format.
7024 Tektronix Hex format.
7027 @value{GDBN} uses the same definitions of these formats as the
7028 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
7029 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
7033 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7034 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
7035 Append the contents of memory from @var{start_addr} to @var{end_addr},
7036 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
7037 (@value{GDBN} can only append data to files in raw binary form.)
7040 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
7041 Restore the contents of file @var{filename} into memory. The
7042 @code{restore} command can automatically recognize any known @sc{bfd}
7043 file format, except for raw binary. To restore a raw binary file you
7044 must specify the optional keyword @code{binary} after the filename.
7046 If @var{bias} is non-zero, its value will be added to the addresses
7047 contained in the file. Binary files always start at address zero, so
7048 they will be restored at address @var{bias}. Other bfd files have
7049 a built-in location; they will be restored at offset @var{bias}
7052 If @var{start} and/or @var{end} are non-zero, then only data between
7053 file offset @var{start} and file offset @var{end} will be restored.
7054 These offsets are relative to the addresses in the file, before
7055 the @var{bias} argument is applied.
7059 @node Core File Generation
7060 @section How to Produce a Core File from Your Program
7061 @cindex dump core from inferior
7063 A @dfn{core file} or @dfn{core dump} is a file that records the memory
7064 image of a running process and its process status (register values
7065 etc.). Its primary use is post-mortem debugging of a program that
7066 crashed while it ran outside a debugger. A program that crashes
7067 automatically produces a core file, unless this feature is disabled by
7068 the user. @xref{Files}, for information on invoking @value{GDBN} in
7069 the post-mortem debugging mode.
7071 Occasionally, you may wish to produce a core file of the program you
7072 are debugging in order to preserve a snapshot of its state.
7073 @value{GDBN} has a special command for that.
7077 @kindex generate-core-file
7078 @item generate-core-file [@var{file}]
7079 @itemx gcore [@var{file}]
7080 Produce a core dump of the inferior process. The optional argument
7081 @var{file} specifies the file name where to put the core dump. If not
7082 specified, the file name defaults to @file{core.@var{pid}}, where
7083 @var{pid} is the inferior process ID.
7085 Note that this command is implemented only for some systems (as of
7086 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
7089 @node Character Sets
7090 @section Character Sets
7091 @cindex character sets
7093 @cindex translating between character sets
7094 @cindex host character set
7095 @cindex target character set
7097 If the program you are debugging uses a different character set to
7098 represent characters and strings than the one @value{GDBN} uses itself,
7099 @value{GDBN} can automatically translate between the character sets for
7100 you. The character set @value{GDBN} uses we call the @dfn{host
7101 character set}; the one the inferior program uses we call the
7102 @dfn{target character set}.
7104 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
7105 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
7106 remote protocol (@pxref{Remote Debugging}) to debug a program
7107 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
7108 then the host character set is Latin-1, and the target character set is
7109 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
7110 target-charset EBCDIC-US}, then @value{GDBN} translates between
7111 @sc{ebcdic} and Latin 1 as you print character or string values, or use
7112 character and string literals in expressions.
7114 @value{GDBN} has no way to automatically recognize which character set
7115 the inferior program uses; you must tell it, using the @code{set
7116 target-charset} command, described below.
7118 Here are the commands for controlling @value{GDBN}'s character set
7122 @item set target-charset @var{charset}
7123 @kindex set target-charset
7124 Set the current target character set to @var{charset}. We list the
7125 character set names @value{GDBN} recognizes below, but if you type
7126 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7127 list the target character sets it supports.
7131 @item set host-charset @var{charset}
7132 @kindex set host-charset
7133 Set the current host character set to @var{charset}.
7135 By default, @value{GDBN} uses a host character set appropriate to the
7136 system it is running on; you can override that default using the
7137 @code{set host-charset} command.
7139 @value{GDBN} can only use certain character sets as its host character
7140 set. We list the character set names @value{GDBN} recognizes below, and
7141 indicate which can be host character sets, but if you type
7142 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7143 list the host character sets it supports.
7145 @item set charset @var{charset}
7147 Set the current host and target character sets to @var{charset}. As
7148 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
7149 @value{GDBN} will list the name of the character sets that can be used
7150 for both host and target.
7154 @kindex show charset
7155 Show the names of the current host and target charsets.
7157 @itemx show host-charset
7158 @kindex show host-charset
7159 Show the name of the current host charset.
7161 @itemx show target-charset
7162 @kindex show target-charset
7163 Show the name of the current target charset.
7167 @value{GDBN} currently includes support for the following character
7173 @cindex ASCII character set
7174 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
7178 @cindex ISO 8859-1 character set
7179 @cindex ISO Latin 1 character set
7180 The ISO Latin 1 character set. This extends @sc{ascii} with accented
7181 characters needed for French, German, and Spanish. @value{GDBN} can use
7182 this as its host character set.
7186 @cindex EBCDIC character set
7187 @cindex IBM1047 character set
7188 Variants of the @sc{ebcdic} character set, used on some of IBM's
7189 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
7190 @value{GDBN} cannot use these as its host character set.
7194 Note that these are all single-byte character sets. More work inside
7195 @value{GDBN} is needed to support multi-byte or variable-width character
7196 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
7198 Here is an example of @value{GDBN}'s character set support in action.
7199 Assume that the following source code has been placed in the file
7200 @file{charset-test.c}:
7206 = @{72, 101, 108, 108, 111, 44, 32, 119,
7207 111, 114, 108, 100, 33, 10, 0@};
7208 char ibm1047_hello[]
7209 = @{200, 133, 147, 147, 150, 107, 64, 166,
7210 150, 153, 147, 132, 90, 37, 0@};
7214 printf ("Hello, world!\n");
7218 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
7219 containing the string @samp{Hello, world!} followed by a newline,
7220 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
7222 We compile the program, and invoke the debugger on it:
7225 $ gcc -g charset-test.c -o charset-test
7226 $ gdb -nw charset-test
7227 GNU gdb 2001-12-19-cvs
7228 Copyright 2001 Free Software Foundation, Inc.
7233 We can use the @code{show charset} command to see what character sets
7234 @value{GDBN} is currently using to interpret and display characters and
7238 (@value{GDBP}) show charset
7239 The current host and target character set is `ISO-8859-1'.
7243 For the sake of printing this manual, let's use @sc{ascii} as our
7244 initial character set:
7246 (@value{GDBP}) set charset ASCII
7247 (@value{GDBP}) show charset
7248 The current host and target character set is `ASCII'.
7252 Let's assume that @sc{ascii} is indeed the correct character set for our
7253 host system --- in other words, let's assume that if @value{GDBN} prints
7254 characters using the @sc{ascii} character set, our terminal will display
7255 them properly. Since our current target character set is also
7256 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
7259 (@value{GDBP}) print ascii_hello
7260 $1 = 0x401698 "Hello, world!\n"
7261 (@value{GDBP}) print ascii_hello[0]
7266 @value{GDBN} uses the target character set for character and string
7267 literals you use in expressions:
7270 (@value{GDBP}) print '+'
7275 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
7278 @value{GDBN} relies on the user to tell it which character set the
7279 target program uses. If we print @code{ibm1047_hello} while our target
7280 character set is still @sc{ascii}, we get jibberish:
7283 (@value{GDBP}) print ibm1047_hello
7284 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
7285 (@value{GDBP}) print ibm1047_hello[0]
7290 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
7291 @value{GDBN} tells us the character sets it supports:
7294 (@value{GDBP}) set target-charset
7295 ASCII EBCDIC-US IBM1047 ISO-8859-1
7296 (@value{GDBP}) set target-charset
7299 We can select @sc{ibm1047} as our target character set, and examine the
7300 program's strings again. Now the @sc{ascii} string is wrong, but
7301 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
7302 target character set, @sc{ibm1047}, to the host character set,
7303 @sc{ascii}, and they display correctly:
7306 (@value{GDBP}) set target-charset IBM1047
7307 (@value{GDBP}) show charset
7308 The current host character set is `ASCII'.
7309 The current target character set is `IBM1047'.
7310 (@value{GDBP}) print ascii_hello
7311 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
7312 (@value{GDBP}) print ascii_hello[0]
7314 (@value{GDBP}) print ibm1047_hello
7315 $8 = 0x4016a8 "Hello, world!\n"
7316 (@value{GDBP}) print ibm1047_hello[0]
7321 As above, @value{GDBN} uses the target character set for character and
7322 string literals you use in expressions:
7325 (@value{GDBP}) print '+'
7330 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
7333 @node Caching Remote Data
7334 @section Caching Data of Remote Targets
7335 @cindex caching data of remote targets
7337 @value{GDBN} can cache data exchanged between the debugger and a
7338 remote target (@pxref{Remote Debugging}). Such caching generally improves
7339 performance, because it reduces the overhead of the remote protocol by
7340 bundling memory reads and writes into large chunks. Unfortunately,
7341 @value{GDBN} does not currently know anything about volatile
7342 registers, and thus data caching will produce incorrect results when
7343 volatile registers are in use.
7346 @kindex set remotecache
7347 @item set remotecache on
7348 @itemx set remotecache off
7349 Set caching state for remote targets. When @code{ON}, use data
7350 caching. By default, this option is @code{OFF}.
7352 @kindex show remotecache
7353 @item show remotecache
7354 Show the current state of data caching for remote targets.
7358 Print the information about the data cache performance. The
7359 information displayed includes: the dcache width and depth; and for
7360 each cache line, how many times it was referenced, and its data and
7361 state (dirty, bad, ok, etc.). This command is useful for debugging
7362 the data cache operation.
7367 @chapter C Preprocessor Macros
7369 Some languages, such as C and C@t{++}, provide a way to define and invoke
7370 ``preprocessor macros'' which expand into strings of tokens.
7371 @value{GDBN} can evaluate expressions containing macro invocations, show
7372 the result of macro expansion, and show a macro's definition, including
7373 where it was defined.
7375 You may need to compile your program specially to provide @value{GDBN}
7376 with information about preprocessor macros. Most compilers do not
7377 include macros in their debugging information, even when you compile
7378 with the @option{-g} flag. @xref{Compilation}.
7380 A program may define a macro at one point, remove that definition later,
7381 and then provide a different definition after that. Thus, at different
7382 points in the program, a macro may have different definitions, or have
7383 no definition at all. If there is a current stack frame, @value{GDBN}
7384 uses the macros in scope at that frame's source code line. Otherwise,
7385 @value{GDBN} uses the macros in scope at the current listing location;
7388 At the moment, @value{GDBN} does not support the @code{##}
7389 token-splicing operator, the @code{#} stringification operator, or
7390 variable-arity macros.
7392 Whenever @value{GDBN} evaluates an expression, it always expands any
7393 macro invocations present in the expression. @value{GDBN} also provides
7394 the following commands for working with macros explicitly.
7398 @kindex macro expand
7399 @cindex macro expansion, showing the results of preprocessor
7400 @cindex preprocessor macro expansion, showing the results of
7401 @cindex expanding preprocessor macros
7402 @item macro expand @var{expression}
7403 @itemx macro exp @var{expression}
7404 Show the results of expanding all preprocessor macro invocations in
7405 @var{expression}. Since @value{GDBN} simply expands macros, but does
7406 not parse the result, @var{expression} need not be a valid expression;
7407 it can be any string of tokens.
7410 @item macro expand-once @var{expression}
7411 @itemx macro exp1 @var{expression}
7412 @cindex expand macro once
7413 @i{(This command is not yet implemented.)} Show the results of
7414 expanding those preprocessor macro invocations that appear explicitly in
7415 @var{expression}. Macro invocations appearing in that expansion are
7416 left unchanged. This command allows you to see the effect of a
7417 particular macro more clearly, without being confused by further
7418 expansions. Since @value{GDBN} simply expands macros, but does not
7419 parse the result, @var{expression} need not be a valid expression; it
7420 can be any string of tokens.
7423 @cindex macro definition, showing
7424 @cindex definition, showing a macro's
7425 @item info macro @var{macro}
7426 Show the definition of the macro named @var{macro}, and describe the
7427 source location where that definition was established.
7429 @kindex macro define
7430 @cindex user-defined macros
7431 @cindex defining macros interactively
7432 @cindex macros, user-defined
7433 @item macro define @var{macro} @var{replacement-list}
7434 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
7435 @i{(This command is not yet implemented.)} Introduce a definition for a
7436 preprocessor macro named @var{macro}, invocations of which are replaced
7437 by the tokens given in @var{replacement-list}. The first form of this
7438 command defines an ``object-like'' macro, which takes no arguments; the
7439 second form defines a ``function-like'' macro, which takes the arguments
7440 given in @var{arglist}.
7442 A definition introduced by this command is in scope in every expression
7443 evaluated in @value{GDBN}, until it is removed with the @command{macro
7444 undef} command, described below. The definition overrides all
7445 definitions for @var{macro} present in the program being debugged, as
7446 well as any previous user-supplied definition.
7449 @item macro undef @var{macro}
7450 @i{(This command is not yet implemented.)} Remove any user-supplied
7451 definition for the macro named @var{macro}. This command only affects
7452 definitions provided with the @command{macro define} command, described
7453 above; it cannot remove definitions present in the program being
7458 @i{(This command is not yet implemented.)} List all the macros
7459 defined using the @code{macro define} command.
7462 @cindex macros, example of debugging with
7463 Here is a transcript showing the above commands in action. First, we
7464 show our source files:
7472 #define ADD(x) (M + x)
7477 printf ("Hello, world!\n");
7479 printf ("We're so creative.\n");
7481 printf ("Goodbye, world!\n");
7488 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
7489 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
7490 compiler includes information about preprocessor macros in the debugging
7494 $ gcc -gdwarf-2 -g3 sample.c -o sample
7498 Now, we start @value{GDBN} on our sample program:
7502 GNU gdb 2002-05-06-cvs
7503 Copyright 2002 Free Software Foundation, Inc.
7504 GDB is free software, @dots{}
7508 We can expand macros and examine their definitions, even when the
7509 program is not running. @value{GDBN} uses the current listing position
7510 to decide which macro definitions are in scope:
7513 (@value{GDBP}) list main
7516 5 #define ADD(x) (M + x)
7521 10 printf ("Hello, world!\n");
7523 12 printf ("We're so creative.\n");
7524 (@value{GDBP}) info macro ADD
7525 Defined at /home/jimb/gdb/macros/play/sample.c:5
7526 #define ADD(x) (M + x)
7527 (@value{GDBP}) info macro Q
7528 Defined at /home/jimb/gdb/macros/play/sample.h:1
7529 included at /home/jimb/gdb/macros/play/sample.c:2
7531 (@value{GDBP}) macro expand ADD(1)
7532 expands to: (42 + 1)
7533 (@value{GDBP}) macro expand-once ADD(1)
7534 expands to: once (M + 1)
7538 In the example above, note that @command{macro expand-once} expands only
7539 the macro invocation explicit in the original text --- the invocation of
7540 @code{ADD} --- but does not expand the invocation of the macro @code{M},
7541 which was introduced by @code{ADD}.
7543 Once the program is running, @value{GDBN} uses the macro definitions in
7544 force at the source line of the current stack frame:
7547 (@value{GDBP}) break main
7548 Breakpoint 1 at 0x8048370: file sample.c, line 10.
7550 Starting program: /home/jimb/gdb/macros/play/sample
7552 Breakpoint 1, main () at sample.c:10
7553 10 printf ("Hello, world!\n");
7557 At line 10, the definition of the macro @code{N} at line 9 is in force:
7560 (@value{GDBP}) info macro N
7561 Defined at /home/jimb/gdb/macros/play/sample.c:9
7563 (@value{GDBP}) macro expand N Q M
7565 (@value{GDBP}) print N Q M
7570 As we step over directives that remove @code{N}'s definition, and then
7571 give it a new definition, @value{GDBN} finds the definition (or lack
7572 thereof) in force at each point:
7577 12 printf ("We're so creative.\n");
7578 (@value{GDBP}) info macro N
7579 The symbol `N' has no definition as a C/C++ preprocessor macro
7580 at /home/jimb/gdb/macros/play/sample.c:12
7583 14 printf ("Goodbye, world!\n");
7584 (@value{GDBP}) info macro N
7585 Defined at /home/jimb/gdb/macros/play/sample.c:13
7587 (@value{GDBP}) macro expand N Q M
7588 expands to: 1729 < 42
7589 (@value{GDBP}) print N Q M
7596 @chapter Tracepoints
7597 @c This chapter is based on the documentation written by Michael
7598 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
7601 In some applications, it is not feasible for the debugger to interrupt
7602 the program's execution long enough for the developer to learn
7603 anything helpful about its behavior. If the program's correctness
7604 depends on its real-time behavior, delays introduced by a debugger
7605 might cause the program to change its behavior drastically, or perhaps
7606 fail, even when the code itself is correct. It is useful to be able
7607 to observe the program's behavior without interrupting it.
7609 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
7610 specify locations in the program, called @dfn{tracepoints}, and
7611 arbitrary expressions to evaluate when those tracepoints are reached.
7612 Later, using the @code{tfind} command, you can examine the values
7613 those expressions had when the program hit the tracepoints. The
7614 expressions may also denote objects in memory---structures or arrays,
7615 for example---whose values @value{GDBN} should record; while visiting
7616 a particular tracepoint, you may inspect those objects as if they were
7617 in memory at that moment. However, because @value{GDBN} records these
7618 values without interacting with you, it can do so quickly and
7619 unobtrusively, hopefully not disturbing the program's behavior.
7621 The tracepoint facility is currently available only for remote
7622 targets. @xref{Targets}. In addition, your remote target must know
7623 how to collect trace data. This functionality is implemented in the
7624 remote stub; however, none of the stubs distributed with @value{GDBN}
7625 support tracepoints as of this writing. The format of the remote
7626 packets used to implement tracepoints are described in @ref{Tracepoint
7629 This chapter describes the tracepoint commands and features.
7633 * Analyze Collected Data::
7634 * Tracepoint Variables::
7637 @node Set Tracepoints
7638 @section Commands to Set Tracepoints
7640 Before running such a @dfn{trace experiment}, an arbitrary number of
7641 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
7642 tracepoint has a number assigned to it by @value{GDBN}. Like with
7643 breakpoints, tracepoint numbers are successive integers starting from
7644 one. Many of the commands associated with tracepoints take the
7645 tracepoint number as their argument, to identify which tracepoint to
7648 For each tracepoint, you can specify, in advance, some arbitrary set
7649 of data that you want the target to collect in the trace buffer when
7650 it hits that tracepoint. The collected data can include registers,
7651 local variables, or global data. Later, you can use @value{GDBN}
7652 commands to examine the values these data had at the time the
7655 This section describes commands to set tracepoints and associated
7656 conditions and actions.
7659 * Create and Delete Tracepoints::
7660 * Enable and Disable Tracepoints::
7661 * Tracepoint Passcounts::
7662 * Tracepoint Actions::
7663 * Listing Tracepoints::
7664 * Starting and Stopping Trace Experiments::
7667 @node Create and Delete Tracepoints
7668 @subsection Create and Delete Tracepoints
7671 @cindex set tracepoint
7674 The @code{trace} command is very similar to the @code{break} command.
7675 Its argument can be a source line, a function name, or an address in
7676 the target program. @xref{Set Breaks}. The @code{trace} command
7677 defines a tracepoint, which is a point in the target program where the
7678 debugger will briefly stop, collect some data, and then allow the
7679 program to continue. Setting a tracepoint or changing its commands
7680 doesn't take effect until the next @code{tstart} command; thus, you
7681 cannot change the tracepoint attributes once a trace experiment is
7684 Here are some examples of using the @code{trace} command:
7687 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
7689 (@value{GDBP}) @b{trace +2} // 2 lines forward
7691 (@value{GDBP}) @b{trace my_function} // first source line of function
7693 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
7695 (@value{GDBP}) @b{trace *0x2117c4} // an address
7699 You can abbreviate @code{trace} as @code{tr}.
7702 @cindex last tracepoint number
7703 @cindex recent tracepoint number
7704 @cindex tracepoint number
7705 The convenience variable @code{$tpnum} records the tracepoint number
7706 of the most recently set tracepoint.
7708 @kindex delete tracepoint
7709 @cindex tracepoint deletion
7710 @item delete tracepoint @r{[}@var{num}@r{]}
7711 Permanently delete one or more tracepoints. With no argument, the
7712 default is to delete all tracepoints.
7717 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
7719 (@value{GDBP}) @b{delete trace} // remove all tracepoints
7723 You can abbreviate this command as @code{del tr}.
7726 @node Enable and Disable Tracepoints
7727 @subsection Enable and Disable Tracepoints
7730 @kindex disable tracepoint
7731 @item disable tracepoint @r{[}@var{num}@r{]}
7732 Disable tracepoint @var{num}, or all tracepoints if no argument
7733 @var{num} is given. A disabled tracepoint will have no effect during
7734 the next trace experiment, but it is not forgotten. You can re-enable
7735 a disabled tracepoint using the @code{enable tracepoint} command.
7737 @kindex enable tracepoint
7738 @item enable tracepoint @r{[}@var{num}@r{]}
7739 Enable tracepoint @var{num}, or all tracepoints. The enabled
7740 tracepoints will become effective the next time a trace experiment is
7744 @node Tracepoint Passcounts
7745 @subsection Tracepoint Passcounts
7749 @cindex tracepoint pass count
7750 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
7751 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
7752 automatically stop a trace experiment. If a tracepoint's passcount is
7753 @var{n}, then the trace experiment will be automatically stopped on
7754 the @var{n}'th time that tracepoint is hit. If the tracepoint number
7755 @var{num} is not specified, the @code{passcount} command sets the
7756 passcount of the most recently defined tracepoint. If no passcount is
7757 given, the trace experiment will run until stopped explicitly by the
7763 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
7764 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
7766 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
7767 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
7768 (@value{GDBP}) @b{trace foo}
7769 (@value{GDBP}) @b{pass 3}
7770 (@value{GDBP}) @b{trace bar}
7771 (@value{GDBP}) @b{pass 2}
7772 (@value{GDBP}) @b{trace baz}
7773 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
7774 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
7775 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
7776 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
7780 @node Tracepoint Actions
7781 @subsection Tracepoint Action Lists
7785 @cindex tracepoint actions
7786 @item actions @r{[}@var{num}@r{]}
7787 This command will prompt for a list of actions to be taken when the
7788 tracepoint is hit. If the tracepoint number @var{num} is not
7789 specified, this command sets the actions for the one that was most
7790 recently defined (so that you can define a tracepoint and then say
7791 @code{actions} without bothering about its number). You specify the
7792 actions themselves on the following lines, one action at a time, and
7793 terminate the actions list with a line containing just @code{end}. So
7794 far, the only defined actions are @code{collect} and
7795 @code{while-stepping}.
7797 @cindex remove actions from a tracepoint
7798 To remove all actions from a tracepoint, type @samp{actions @var{num}}
7799 and follow it immediately with @samp{end}.
7802 (@value{GDBP}) @b{collect @var{data}} // collect some data
7804 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
7806 (@value{GDBP}) @b{end} // signals the end of actions.
7809 In the following example, the action list begins with @code{collect}
7810 commands indicating the things to be collected when the tracepoint is
7811 hit. Then, in order to single-step and collect additional data
7812 following the tracepoint, a @code{while-stepping} command is used,
7813 followed by the list of things to be collected while stepping. The
7814 @code{while-stepping} command is terminated by its own separate
7815 @code{end} command. Lastly, the action list is terminated by an
7819 (@value{GDBP}) @b{trace foo}
7820 (@value{GDBP}) @b{actions}
7821 Enter actions for tracepoint 1, one per line:
7830 @kindex collect @r{(tracepoints)}
7831 @item collect @var{expr1}, @var{expr2}, @dots{}
7832 Collect values of the given expressions when the tracepoint is hit.
7833 This command accepts a comma-separated list of any valid expressions.
7834 In addition to global, static, or local variables, the following
7835 special arguments are supported:
7839 collect all registers
7842 collect all function arguments
7845 collect all local variables.
7848 You can give several consecutive @code{collect} commands, each one
7849 with a single argument, or one @code{collect} command with several
7850 arguments separated by commas: the effect is the same.
7852 The command @code{info scope} (@pxref{Symbols, info scope}) is
7853 particularly useful for figuring out what data to collect.
7855 @kindex while-stepping @r{(tracepoints)}
7856 @item while-stepping @var{n}
7857 Perform @var{n} single-step traces after the tracepoint, collecting
7858 new data at each step. The @code{while-stepping} command is
7859 followed by the list of what to collect while stepping (followed by
7860 its own @code{end} command):
7864 > collect $regs, myglobal
7870 You may abbreviate @code{while-stepping} as @code{ws} or
7874 @node Listing Tracepoints
7875 @subsection Listing Tracepoints
7878 @kindex info tracepoints
7880 @cindex information about tracepoints
7881 @item info tracepoints @r{[}@var{num}@r{]}
7882 Display information about the tracepoint @var{num}. If you don't specify
7883 a tracepoint number, displays information about all the tracepoints
7884 defined so far. For each tracepoint, the following information is
7891 whether it is enabled or disabled
7895 its passcount as given by the @code{passcount @var{n}} command
7897 its step count as given by the @code{while-stepping @var{n}} command
7899 where in the source files is the tracepoint set
7901 its action list as given by the @code{actions} command
7905 (@value{GDBP}) @b{info trace}
7906 Num Enb Address PassC StepC What
7907 1 y 0x002117c4 0 0 <gdb_asm>
7908 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
7909 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
7914 This command can be abbreviated @code{info tp}.
7917 @node Starting and Stopping Trace Experiments
7918 @subsection Starting and Stopping Trace Experiments
7922 @cindex start a new trace experiment
7923 @cindex collected data discarded
7925 This command takes no arguments. It starts the trace experiment, and
7926 begins collecting data. This has the side effect of discarding all
7927 the data collected in the trace buffer during the previous trace
7931 @cindex stop a running trace experiment
7933 This command takes no arguments. It ends the trace experiment, and
7934 stops collecting data.
7936 @strong{Note}: a trace experiment and data collection may stop
7937 automatically if any tracepoint's passcount is reached
7938 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
7941 @cindex status of trace data collection
7942 @cindex trace experiment, status of
7944 This command displays the status of the current trace data
7948 Here is an example of the commands we described so far:
7951 (@value{GDBP}) @b{trace gdb_c_test}
7952 (@value{GDBP}) @b{actions}
7953 Enter actions for tracepoint #1, one per line.
7954 > collect $regs,$locals,$args
7959 (@value{GDBP}) @b{tstart}
7960 [time passes @dots{}]
7961 (@value{GDBP}) @b{tstop}
7965 @node Analyze Collected Data
7966 @section Using the Collected Data
7968 After the tracepoint experiment ends, you use @value{GDBN} commands
7969 for examining the trace data. The basic idea is that each tracepoint
7970 collects a trace @dfn{snapshot} every time it is hit and another
7971 snapshot every time it single-steps. All these snapshots are
7972 consecutively numbered from zero and go into a buffer, and you can
7973 examine them later. The way you examine them is to @dfn{focus} on a
7974 specific trace snapshot. When the remote stub is focused on a trace
7975 snapshot, it will respond to all @value{GDBN} requests for memory and
7976 registers by reading from the buffer which belongs to that snapshot,
7977 rather than from @emph{real} memory or registers of the program being
7978 debugged. This means that @strong{all} @value{GDBN} commands
7979 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
7980 behave as if we were currently debugging the program state as it was
7981 when the tracepoint occurred. Any requests for data that are not in
7982 the buffer will fail.
7985 * tfind:: How to select a trace snapshot
7986 * tdump:: How to display all data for a snapshot
7987 * save-tracepoints:: How to save tracepoints for a future run
7991 @subsection @code{tfind @var{n}}
7994 @cindex select trace snapshot
7995 @cindex find trace snapshot
7996 The basic command for selecting a trace snapshot from the buffer is
7997 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
7998 counting from zero. If no argument @var{n} is given, the next
7999 snapshot is selected.
8001 Here are the various forms of using the @code{tfind} command.
8005 Find the first snapshot in the buffer. This is a synonym for
8006 @code{tfind 0} (since 0 is the number of the first snapshot).
8009 Stop debugging trace snapshots, resume @emph{live} debugging.
8012 Same as @samp{tfind none}.
8015 No argument means find the next trace snapshot.
8018 Find the previous trace snapshot before the current one. This permits
8019 retracing earlier steps.
8021 @item tfind tracepoint @var{num}
8022 Find the next snapshot associated with tracepoint @var{num}. Search
8023 proceeds forward from the last examined trace snapshot. If no
8024 argument @var{num} is given, it means find the next snapshot collected
8025 for the same tracepoint as the current snapshot.
8027 @item tfind pc @var{addr}
8028 Find the next snapshot associated with the value @var{addr} of the
8029 program counter. Search proceeds forward from the last examined trace
8030 snapshot. If no argument @var{addr} is given, it means find the next
8031 snapshot with the same value of PC as the current snapshot.
8033 @item tfind outside @var{addr1}, @var{addr2}
8034 Find the next snapshot whose PC is outside the given range of
8037 @item tfind range @var{addr1}, @var{addr2}
8038 Find the next snapshot whose PC is between @var{addr1} and
8039 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
8041 @item tfind line @r{[}@var{file}:@r{]}@var{n}
8042 Find the next snapshot associated with the source line @var{n}. If
8043 the optional argument @var{file} is given, refer to line @var{n} in
8044 that source file. Search proceeds forward from the last examined
8045 trace snapshot. If no argument @var{n} is given, it means find the
8046 next line other than the one currently being examined; thus saying
8047 @code{tfind line} repeatedly can appear to have the same effect as
8048 stepping from line to line in a @emph{live} debugging session.
8051 The default arguments for the @code{tfind} commands are specifically
8052 designed to make it easy to scan through the trace buffer. For
8053 instance, @code{tfind} with no argument selects the next trace
8054 snapshot, and @code{tfind -} with no argument selects the previous
8055 trace snapshot. So, by giving one @code{tfind} command, and then
8056 simply hitting @key{RET} repeatedly you can examine all the trace
8057 snapshots in order. Or, by saying @code{tfind -} and then hitting
8058 @key{RET} repeatedly you can examine the snapshots in reverse order.
8059 The @code{tfind line} command with no argument selects the snapshot
8060 for the next source line executed. The @code{tfind pc} command with
8061 no argument selects the next snapshot with the same program counter
8062 (PC) as the current frame. The @code{tfind tracepoint} command with
8063 no argument selects the next trace snapshot collected by the same
8064 tracepoint as the current one.
8066 In addition to letting you scan through the trace buffer manually,
8067 these commands make it easy to construct @value{GDBN} scripts that
8068 scan through the trace buffer and print out whatever collected data
8069 you are interested in. Thus, if we want to examine the PC, FP, and SP
8070 registers from each trace frame in the buffer, we can say this:
8073 (@value{GDBP}) @b{tfind start}
8074 (@value{GDBP}) @b{while ($trace_frame != -1)}
8075 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
8076 $trace_frame, $pc, $sp, $fp
8080 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
8081 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
8082 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
8083 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
8084 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
8085 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
8086 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
8087 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
8088 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
8089 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
8090 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
8093 Or, if we want to examine the variable @code{X} at each source line in
8097 (@value{GDBP}) @b{tfind start}
8098 (@value{GDBP}) @b{while ($trace_frame != -1)}
8099 > printf "Frame %d, X == %d\n", $trace_frame, X
8109 @subsection @code{tdump}
8111 @cindex dump all data collected at tracepoint
8112 @cindex tracepoint data, display
8114 This command takes no arguments. It prints all the data collected at
8115 the current trace snapshot.
8118 (@value{GDBP}) @b{trace 444}
8119 (@value{GDBP}) @b{actions}
8120 Enter actions for tracepoint #2, one per line:
8121 > collect $regs, $locals, $args, gdb_long_test
8124 (@value{GDBP}) @b{tstart}
8126 (@value{GDBP}) @b{tfind line 444}
8127 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
8129 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
8131 (@value{GDBP}) @b{tdump}
8132 Data collected at tracepoint 2, trace frame 1:
8133 d0 0xc4aa0085 -995491707
8137 d4 0x71aea3d 119204413
8142 a1 0x3000668 50333288
8145 a4 0x3000698 50333336
8147 fp 0x30bf3c 0x30bf3c
8148 sp 0x30bf34 0x30bf34
8150 pc 0x20b2c8 0x20b2c8
8154 p = 0x20e5b4 "gdb-test"
8161 gdb_long_test = 17 '\021'
8166 @node save-tracepoints
8167 @subsection @code{save-tracepoints @var{filename}}
8168 @kindex save-tracepoints
8169 @cindex save tracepoints for future sessions
8171 This command saves all current tracepoint definitions together with
8172 their actions and passcounts, into a file @file{@var{filename}}
8173 suitable for use in a later debugging session. To read the saved
8174 tracepoint definitions, use the @code{source} command (@pxref{Command
8177 @node Tracepoint Variables
8178 @section Convenience Variables for Tracepoints
8179 @cindex tracepoint variables
8180 @cindex convenience variables for tracepoints
8183 @vindex $trace_frame
8184 @item (int) $trace_frame
8185 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
8186 snapshot is selected.
8189 @item (int) $tracepoint
8190 The tracepoint for the current trace snapshot.
8193 @item (int) $trace_line
8194 The line number for the current trace snapshot.
8197 @item (char []) $trace_file
8198 The source file for the current trace snapshot.
8201 @item (char []) $trace_func
8202 The name of the function containing @code{$tracepoint}.
8205 Note: @code{$trace_file} is not suitable for use in @code{printf},
8206 use @code{output} instead.
8208 Here's a simple example of using these convenience variables for
8209 stepping through all the trace snapshots and printing some of their
8213 (@value{GDBP}) @b{tfind start}
8215 (@value{GDBP}) @b{while $trace_frame != -1}
8216 > output $trace_file
8217 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
8223 @chapter Debugging Programs That Use Overlays
8226 If your program is too large to fit completely in your target system's
8227 memory, you can sometimes use @dfn{overlays} to work around this
8228 problem. @value{GDBN} provides some support for debugging programs that
8232 * How Overlays Work:: A general explanation of overlays.
8233 * Overlay Commands:: Managing overlays in @value{GDBN}.
8234 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
8235 mapped by asking the inferior.
8236 * Overlay Sample Program:: A sample program using overlays.
8239 @node How Overlays Work
8240 @section How Overlays Work
8241 @cindex mapped overlays
8242 @cindex unmapped overlays
8243 @cindex load address, overlay's
8244 @cindex mapped address
8245 @cindex overlay area
8247 Suppose you have a computer whose instruction address space is only 64
8248 kilobytes long, but which has much more memory which can be accessed by
8249 other means: special instructions, segment registers, or memory
8250 management hardware, for example. Suppose further that you want to
8251 adapt a program which is larger than 64 kilobytes to run on this system.
8253 One solution is to identify modules of your program which are relatively
8254 independent, and need not call each other directly; call these modules
8255 @dfn{overlays}. Separate the overlays from the main program, and place
8256 their machine code in the larger memory. Place your main program in
8257 instruction memory, but leave at least enough space there to hold the
8258 largest overlay as well.
8260 Now, to call a function located in an overlay, you must first copy that
8261 overlay's machine code from the large memory into the space set aside
8262 for it in the instruction memory, and then jump to its entry point
8265 @c NB: In the below the mapped area's size is greater or equal to the
8266 @c size of all overlays. This is intentional to remind the developer
8267 @c that overlays don't necessarily need to be the same size.
8271 Data Instruction Larger
8272 Address Space Address Space Address Space
8273 +-----------+ +-----------+ +-----------+
8275 +-----------+ +-----------+ +-----------+<-- overlay 1
8276 | program | | main | .----| overlay 1 | load address
8277 | variables | | program | | +-----------+
8278 | and heap | | | | | |
8279 +-----------+ | | | +-----------+<-- overlay 2
8280 | | +-----------+ | | | load address
8281 +-----------+ | | | .-| overlay 2 |
8283 mapped --->+-----------+ | | +-----------+
8285 | overlay | <-' | | |
8286 | area | <---' +-----------+<-- overlay 3
8287 | | <---. | | load address
8288 +-----------+ `--| overlay 3 |
8295 @anchor{A code overlay}A code overlay
8299 The diagram (@pxref{A code overlay}) shows a system with separate data
8300 and instruction address spaces. To map an overlay, the program copies
8301 its code from the larger address space to the instruction address space.
8302 Since the overlays shown here all use the same mapped address, only one
8303 may be mapped at a time. For a system with a single address space for
8304 data and instructions, the diagram would be similar, except that the
8305 program variables and heap would share an address space with the main
8306 program and the overlay area.
8308 An overlay loaded into instruction memory and ready for use is called a
8309 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
8310 instruction memory. An overlay not present (or only partially present)
8311 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
8312 is its address in the larger memory. The mapped address is also called
8313 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
8314 called the @dfn{load memory address}, or @dfn{LMA}.
8316 Unfortunately, overlays are not a completely transparent way to adapt a
8317 program to limited instruction memory. They introduce a new set of
8318 global constraints you must keep in mind as you design your program:
8323 Before calling or returning to a function in an overlay, your program
8324 must make sure that overlay is actually mapped. Otherwise, the call or
8325 return will transfer control to the right address, but in the wrong
8326 overlay, and your program will probably crash.
8329 If the process of mapping an overlay is expensive on your system, you
8330 will need to choose your overlays carefully to minimize their effect on
8331 your program's performance.
8334 The executable file you load onto your system must contain each
8335 overlay's instructions, appearing at the overlay's load address, not its
8336 mapped address. However, each overlay's instructions must be relocated
8337 and its symbols defined as if the overlay were at its mapped address.
8338 You can use GNU linker scripts to specify different load and relocation
8339 addresses for pieces of your program; see @ref{Overlay Description,,,
8340 ld.info, Using ld: the GNU linker}.
8343 The procedure for loading executable files onto your system must be able
8344 to load their contents into the larger address space as well as the
8345 instruction and data spaces.
8349 The overlay system described above is rather simple, and could be
8350 improved in many ways:
8355 If your system has suitable bank switch registers or memory management
8356 hardware, you could use those facilities to make an overlay's load area
8357 contents simply appear at their mapped address in instruction space.
8358 This would probably be faster than copying the overlay to its mapped
8359 area in the usual way.
8362 If your overlays are small enough, you could set aside more than one
8363 overlay area, and have more than one overlay mapped at a time.
8366 You can use overlays to manage data, as well as instructions. In
8367 general, data overlays are even less transparent to your design than
8368 code overlays: whereas code overlays only require care when you call or
8369 return to functions, data overlays require care every time you access
8370 the data. Also, if you change the contents of a data overlay, you
8371 must copy its contents back out to its load address before you can copy a
8372 different data overlay into the same mapped area.
8377 @node Overlay Commands
8378 @section Overlay Commands
8380 To use @value{GDBN}'s overlay support, each overlay in your program must
8381 correspond to a separate section of the executable file. The section's
8382 virtual memory address and load memory address must be the overlay's
8383 mapped and load addresses. Identifying overlays with sections allows
8384 @value{GDBN} to determine the appropriate address of a function or
8385 variable, depending on whether the overlay is mapped or not.
8387 @value{GDBN}'s overlay commands all start with the word @code{overlay};
8388 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
8393 Disable @value{GDBN}'s overlay support. When overlay support is
8394 disabled, @value{GDBN} assumes that all functions and variables are
8395 always present at their mapped addresses. By default, @value{GDBN}'s
8396 overlay support is disabled.
8398 @item overlay manual
8399 @cindex manual overlay debugging
8400 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
8401 relies on you to tell it which overlays are mapped, and which are not,
8402 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
8403 commands described below.
8405 @item overlay map-overlay @var{overlay}
8406 @itemx overlay map @var{overlay}
8407 @cindex map an overlay
8408 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
8409 be the name of the object file section containing the overlay. When an
8410 overlay is mapped, @value{GDBN} assumes it can find the overlay's
8411 functions and variables at their mapped addresses. @value{GDBN} assumes
8412 that any other overlays whose mapped ranges overlap that of
8413 @var{overlay} are now unmapped.
8415 @item overlay unmap-overlay @var{overlay}
8416 @itemx overlay unmap @var{overlay}
8417 @cindex unmap an overlay
8418 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
8419 must be the name of the object file section containing the overlay.
8420 When an overlay is unmapped, @value{GDBN} assumes it can find the
8421 overlay's functions and variables at their load addresses.
8424 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
8425 consults a data structure the overlay manager maintains in the inferior
8426 to see which overlays are mapped. For details, see @ref{Automatic
8429 @item overlay load-target
8431 @cindex reloading the overlay table
8432 Re-read the overlay table from the inferior. Normally, @value{GDBN}
8433 re-reads the table @value{GDBN} automatically each time the inferior
8434 stops, so this command should only be necessary if you have changed the
8435 overlay mapping yourself using @value{GDBN}. This command is only
8436 useful when using automatic overlay debugging.
8438 @item overlay list-overlays
8440 @cindex listing mapped overlays
8441 Display a list of the overlays currently mapped, along with their mapped
8442 addresses, load addresses, and sizes.
8446 Normally, when @value{GDBN} prints a code address, it includes the name
8447 of the function the address falls in:
8450 (@value{GDBP}) print main
8451 $3 = @{int ()@} 0x11a0 <main>
8454 When overlay debugging is enabled, @value{GDBN} recognizes code in
8455 unmapped overlays, and prints the names of unmapped functions with
8456 asterisks around them. For example, if @code{foo} is a function in an
8457 unmapped overlay, @value{GDBN} prints it this way:
8460 (@value{GDBP}) overlay list
8461 No sections are mapped.
8462 (@value{GDBP}) print foo
8463 $5 = @{int (int)@} 0x100000 <*foo*>
8466 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
8470 (@value{GDBP}) overlay list
8471 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
8472 mapped at 0x1016 - 0x104a
8473 (@value{GDBP}) print foo
8474 $6 = @{int (int)@} 0x1016 <foo>
8477 When overlay debugging is enabled, @value{GDBN} can find the correct
8478 address for functions and variables in an overlay, whether or not the
8479 overlay is mapped. This allows most @value{GDBN} commands, like
8480 @code{break} and @code{disassemble}, to work normally, even on unmapped
8481 code. However, @value{GDBN}'s breakpoint support has some limitations:
8485 @cindex breakpoints in overlays
8486 @cindex overlays, setting breakpoints in
8487 You can set breakpoints in functions in unmapped overlays, as long as
8488 @value{GDBN} can write to the overlay at its load address.
8490 @value{GDBN} can not set hardware or simulator-based breakpoints in
8491 unmapped overlays. However, if you set a breakpoint at the end of your
8492 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
8493 you are using manual overlay management), @value{GDBN} will re-set its
8494 breakpoints properly.
8498 @node Automatic Overlay Debugging
8499 @section Automatic Overlay Debugging
8500 @cindex automatic overlay debugging
8502 @value{GDBN} can automatically track which overlays are mapped and which
8503 are not, given some simple co-operation from the overlay manager in the
8504 inferior. If you enable automatic overlay debugging with the
8505 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
8506 looks in the inferior's memory for certain variables describing the
8507 current state of the overlays.
8509 Here are the variables your overlay manager must define to support
8510 @value{GDBN}'s automatic overlay debugging:
8514 @item @code{_ovly_table}:
8515 This variable must be an array of the following structures:
8520 /* The overlay's mapped address. */
8523 /* The size of the overlay, in bytes. */
8526 /* The overlay's load address. */
8529 /* Non-zero if the overlay is currently mapped;
8531 unsigned long mapped;
8535 @item @code{_novlys}:
8536 This variable must be a four-byte signed integer, holding the total
8537 number of elements in @code{_ovly_table}.
8541 To decide whether a particular overlay is mapped or not, @value{GDBN}
8542 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
8543 @code{lma} members equal the VMA and LMA of the overlay's section in the
8544 executable file. When @value{GDBN} finds a matching entry, it consults
8545 the entry's @code{mapped} member to determine whether the overlay is
8548 In addition, your overlay manager may define a function called
8549 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
8550 will silently set a breakpoint there. If the overlay manager then
8551 calls this function whenever it has changed the overlay table, this
8552 will enable @value{GDBN} to accurately keep track of which overlays
8553 are in program memory, and update any breakpoints that may be set
8554 in overlays. This will allow breakpoints to work even if the
8555 overlays are kept in ROM or other non-writable memory while they
8556 are not being executed.
8558 @node Overlay Sample Program
8559 @section Overlay Sample Program
8560 @cindex overlay example program
8562 When linking a program which uses overlays, you must place the overlays
8563 at their load addresses, while relocating them to run at their mapped
8564 addresses. To do this, you must write a linker script (@pxref{Overlay
8565 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
8566 since linker scripts are specific to a particular host system, target
8567 architecture, and target memory layout, this manual cannot provide
8568 portable sample code demonstrating @value{GDBN}'s overlay support.
8570 However, the @value{GDBN} source distribution does contain an overlaid
8571 program, with linker scripts for a few systems, as part of its test
8572 suite. The program consists of the following files from
8573 @file{gdb/testsuite/gdb.base}:
8577 The main program file.
8579 A simple overlay manager, used by @file{overlays.c}.
8584 Overlay modules, loaded and used by @file{overlays.c}.
8587 Linker scripts for linking the test program on the @code{d10v-elf}
8588 and @code{m32r-elf} targets.
8591 You can build the test program using the @code{d10v-elf} GCC
8592 cross-compiler like this:
8595 $ d10v-elf-gcc -g -c overlays.c
8596 $ d10v-elf-gcc -g -c ovlymgr.c
8597 $ d10v-elf-gcc -g -c foo.c
8598 $ d10v-elf-gcc -g -c bar.c
8599 $ d10v-elf-gcc -g -c baz.c
8600 $ d10v-elf-gcc -g -c grbx.c
8601 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
8602 baz.o grbx.o -Wl,-Td10v.ld -o overlays
8605 The build process is identical for any other architecture, except that
8606 you must substitute the appropriate compiler and linker script for the
8607 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
8611 @chapter Using @value{GDBN} with Different Languages
8614 Although programming languages generally have common aspects, they are
8615 rarely expressed in the same manner. For instance, in ANSI C,
8616 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
8617 Modula-2, it is accomplished by @code{p^}. Values can also be
8618 represented (and displayed) differently. Hex numbers in C appear as
8619 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
8621 @cindex working language
8622 Language-specific information is built into @value{GDBN} for some languages,
8623 allowing you to express operations like the above in your program's
8624 native language, and allowing @value{GDBN} to output values in a manner
8625 consistent with the syntax of your program's native language. The
8626 language you use to build expressions is called the @dfn{working
8630 * Setting:: Switching between source languages
8631 * Show:: Displaying the language
8632 * Checks:: Type and range checks
8633 * Supported Languages:: Supported languages
8634 * Unsupported Languages:: Unsupported languages
8638 @section Switching Between Source Languages
8640 There are two ways to control the working language---either have @value{GDBN}
8641 set it automatically, or select it manually yourself. You can use the
8642 @code{set language} command for either purpose. On startup, @value{GDBN}
8643 defaults to setting the language automatically. The working language is
8644 used to determine how expressions you type are interpreted, how values
8647 In addition to the working language, every source file that
8648 @value{GDBN} knows about has its own working language. For some object
8649 file formats, the compiler might indicate which language a particular
8650 source file is in. However, most of the time @value{GDBN} infers the
8651 language from the name of the file. The language of a source file
8652 controls whether C@t{++} names are demangled---this way @code{backtrace} can
8653 show each frame appropriately for its own language. There is no way to
8654 set the language of a source file from within @value{GDBN}, but you can
8655 set the language associated with a filename extension. @xref{Show, ,
8656 Displaying the Language}.
8658 This is most commonly a problem when you use a program, such
8659 as @code{cfront} or @code{f2c}, that generates C but is written in
8660 another language. In that case, make the
8661 program use @code{#line} directives in its C output; that way
8662 @value{GDBN} will know the correct language of the source code of the original
8663 program, and will display that source code, not the generated C code.
8666 * Filenames:: Filename extensions and languages.
8667 * Manually:: Setting the working language manually
8668 * Automatically:: Having @value{GDBN} infer the source language
8672 @subsection List of Filename Extensions and Languages
8674 If a source file name ends in one of the following extensions, then
8675 @value{GDBN} infers that its language is the one indicated.
8696 Objective-C source file
8703 Modula-2 source file
8707 Assembler source file. This actually behaves almost like C, but
8708 @value{GDBN} does not skip over function prologues when stepping.
8711 In addition, you may set the language associated with a filename
8712 extension. @xref{Show, , Displaying the Language}.
8715 @subsection Setting the Working Language
8717 If you allow @value{GDBN} to set the language automatically,
8718 expressions are interpreted the same way in your debugging session and
8721 @kindex set language
8722 If you wish, you may set the language manually. To do this, issue the
8723 command @samp{set language @var{lang}}, where @var{lang} is the name of
8725 @code{c} or @code{modula-2}.
8726 For a list of the supported languages, type @samp{set language}.
8728 Setting the language manually prevents @value{GDBN} from updating the working
8729 language automatically. This can lead to confusion if you try
8730 to debug a program when the working language is not the same as the
8731 source language, when an expression is acceptable to both
8732 languages---but means different things. For instance, if the current
8733 source file were written in C, and @value{GDBN} was parsing Modula-2, a
8741 might not have the effect you intended. In C, this means to add
8742 @code{b} and @code{c} and place the result in @code{a}. The result
8743 printed would be the value of @code{a}. In Modula-2, this means to compare
8744 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
8747 @subsection Having @value{GDBN} Infer the Source Language
8749 To have @value{GDBN} set the working language automatically, use
8750 @samp{set language local} or @samp{set language auto}. @value{GDBN}
8751 then infers the working language. That is, when your program stops in a
8752 frame (usually by encountering a breakpoint), @value{GDBN} sets the
8753 working language to the language recorded for the function in that
8754 frame. If the language for a frame is unknown (that is, if the function
8755 or block corresponding to the frame was defined in a source file that
8756 does not have a recognized extension), the current working language is
8757 not changed, and @value{GDBN} issues a warning.
8759 This may not seem necessary for most programs, which are written
8760 entirely in one source language. However, program modules and libraries
8761 written in one source language can be used by a main program written in
8762 a different source language. Using @samp{set language auto} in this
8763 case frees you from having to set the working language manually.
8766 @section Displaying the Language
8768 The following commands help you find out which language is the
8769 working language, and also what language source files were written in.
8773 @kindex show language
8774 Display the current working language. This is the
8775 language you can use with commands such as @code{print} to
8776 build and compute expressions that may involve variables in your program.
8779 @kindex info frame@r{, show the source language}
8780 Display the source language for this frame. This language becomes the
8781 working language if you use an identifier from this frame.
8782 @xref{Frame Info, ,Information about a Frame}, to identify the other
8783 information listed here.
8786 @kindex info source@r{, show the source language}
8787 Display the source language of this source file.
8788 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
8789 information listed here.
8792 In unusual circumstances, you may have source files with extensions
8793 not in the standard list. You can then set the extension associated
8794 with a language explicitly:
8797 @item set extension-language @var{ext} @var{language}
8798 @kindex set extension-language
8799 Tell @value{GDBN} that source files with extension @var{ext} are to be
8800 assumed as written in the source language @var{language}.
8802 @item info extensions
8803 @kindex info extensions
8804 List all the filename extensions and the associated languages.
8808 @section Type and Range Checking
8811 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
8812 checking are included, but they do not yet have any effect. This
8813 section documents the intended facilities.
8815 @c FIXME remove warning when type/range code added
8817 Some languages are designed to guard you against making seemingly common
8818 errors through a series of compile- and run-time checks. These include
8819 checking the type of arguments to functions and operators, and making
8820 sure mathematical overflows are caught at run time. Checks such as
8821 these help to ensure a program's correctness once it has been compiled
8822 by eliminating type mismatches, and providing active checks for range
8823 errors when your program is running.
8825 @value{GDBN} can check for conditions like the above if you wish.
8826 Although @value{GDBN} does not check the statements in your program,
8827 it can check expressions entered directly into @value{GDBN} for
8828 evaluation via the @code{print} command, for example. As with the
8829 working language, @value{GDBN} can also decide whether or not to check
8830 automatically based on your program's source language.
8831 @xref{Supported Languages, ,Supported Languages}, for the default
8832 settings of supported languages.
8835 * Type Checking:: An overview of type checking
8836 * Range Checking:: An overview of range checking
8839 @cindex type checking
8840 @cindex checks, type
8842 @subsection An Overview of Type Checking
8844 Some languages, such as Modula-2, are strongly typed, meaning that the
8845 arguments to operators and functions have to be of the correct type,
8846 otherwise an error occurs. These checks prevent type mismatch
8847 errors from ever causing any run-time problems. For example,
8855 The second example fails because the @code{CARDINAL} 1 is not
8856 type-compatible with the @code{REAL} 2.3.
8858 For the expressions you use in @value{GDBN} commands, you can tell the
8859 @value{GDBN} type checker to skip checking;
8860 to treat any mismatches as errors and abandon the expression;
8861 or to only issue warnings when type mismatches occur,
8862 but evaluate the expression anyway. When you choose the last of
8863 these, @value{GDBN} evaluates expressions like the second example above, but
8864 also issues a warning.
8866 Even if you turn type checking off, there may be other reasons
8867 related to type that prevent @value{GDBN} from evaluating an expression.
8868 For instance, @value{GDBN} does not know how to add an @code{int} and
8869 a @code{struct foo}. These particular type errors have nothing to do
8870 with the language in use, and usually arise from expressions, such as
8871 the one described above, which make little sense to evaluate anyway.
8873 Each language defines to what degree it is strict about type. For
8874 instance, both Modula-2 and C require the arguments to arithmetical
8875 operators to be numbers. In C, enumerated types and pointers can be
8876 represented as numbers, so that they are valid arguments to mathematical
8877 operators. @xref{Supported Languages, ,Supported Languages}, for further
8878 details on specific languages.
8880 @value{GDBN} provides some additional commands for controlling the type checker:
8882 @kindex set check type
8883 @kindex show check type
8885 @item set check type auto
8886 Set type checking on or off based on the current working language.
8887 @xref{Supported Languages, ,Supported Languages}, for the default settings for
8890 @item set check type on
8891 @itemx set check type off
8892 Set type checking on or off, overriding the default setting for the
8893 current working language. Issue a warning if the setting does not
8894 match the language default. If any type mismatches occur in
8895 evaluating an expression while type checking is on, @value{GDBN} prints a
8896 message and aborts evaluation of the expression.
8898 @item set check type warn
8899 Cause the type checker to issue warnings, but to always attempt to
8900 evaluate the expression. Evaluating the expression may still
8901 be impossible for other reasons. For example, @value{GDBN} cannot add
8902 numbers and structures.
8905 Show the current setting of the type checker, and whether or not @value{GDBN}
8906 is setting it automatically.
8909 @cindex range checking
8910 @cindex checks, range
8911 @node Range Checking
8912 @subsection An Overview of Range Checking
8914 In some languages (such as Modula-2), it is an error to exceed the
8915 bounds of a type; this is enforced with run-time checks. Such range
8916 checking is meant to ensure program correctness by making sure
8917 computations do not overflow, or indices on an array element access do
8918 not exceed the bounds of the array.
8920 For expressions you use in @value{GDBN} commands, you can tell
8921 @value{GDBN} to treat range errors in one of three ways: ignore them,
8922 always treat them as errors and abandon the expression, or issue
8923 warnings but evaluate the expression anyway.
8925 A range error can result from numerical overflow, from exceeding an
8926 array index bound, or when you type a constant that is not a member
8927 of any type. Some languages, however, do not treat overflows as an
8928 error. In many implementations of C, mathematical overflow causes the
8929 result to ``wrap around'' to lower values---for example, if @var{m} is
8930 the largest integer value, and @var{s} is the smallest, then
8933 @var{m} + 1 @result{} @var{s}
8936 This, too, is specific to individual languages, and in some cases
8937 specific to individual compilers or machines. @xref{Supported Languages, ,
8938 Supported Languages}, for further details on specific languages.
8940 @value{GDBN} provides some additional commands for controlling the range checker:
8942 @kindex set check range
8943 @kindex show check range
8945 @item set check range auto
8946 Set range checking on or off based on the current working language.
8947 @xref{Supported Languages, ,Supported Languages}, for the default settings for
8950 @item set check range on
8951 @itemx set check range off
8952 Set range checking on or off, overriding the default setting for the
8953 current working language. A warning is issued if the setting does not
8954 match the language default. If a range error occurs and range checking is on,
8955 then a message is printed and evaluation of the expression is aborted.
8957 @item set check range warn
8958 Output messages when the @value{GDBN} range checker detects a range error,
8959 but attempt to evaluate the expression anyway. Evaluating the
8960 expression may still be impossible for other reasons, such as accessing
8961 memory that the process does not own (a typical example from many Unix
8965 Show the current setting of the range checker, and whether or not it is
8966 being set automatically by @value{GDBN}.
8969 @node Supported Languages
8970 @section Supported Languages
8972 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
8973 assembly, Modula-2, and Ada.
8974 @c This is false ...
8975 Some @value{GDBN} features may be used in expressions regardless of the
8976 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
8977 and the @samp{@{type@}addr} construct (@pxref{Expressions,
8978 ,Expressions}) can be used with the constructs of any supported
8981 The following sections detail to what degree each source language is
8982 supported by @value{GDBN}. These sections are not meant to be language
8983 tutorials or references, but serve only as a reference guide to what the
8984 @value{GDBN} expression parser accepts, and what input and output
8985 formats should look like for different languages. There are many good
8986 books written on each of these languages; please look to these for a
8987 language reference or tutorial.
8991 * Objective-C:: Objective-C
8994 * Modula-2:: Modula-2
8999 @subsection C and C@t{++}
9001 @cindex C and C@t{++}
9002 @cindex expressions in C or C@t{++}
9004 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
9005 to both languages. Whenever this is the case, we discuss those languages
9009 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
9010 @cindex @sc{gnu} C@t{++}
9011 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
9012 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
9013 effectively, you must compile your C@t{++} programs with a supported
9014 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
9015 compiler (@code{aCC}).
9017 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
9018 format; if it doesn't work on your system, try the stabs+ debugging
9019 format. You can select those formats explicitly with the @code{g++}
9020 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
9021 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
9022 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
9025 * C Operators:: C and C@t{++} operators
9026 * C Constants:: C and C@t{++} constants
9027 * C Plus Plus Expressions:: C@t{++} expressions
9028 * C Defaults:: Default settings for C and C@t{++}
9029 * C Checks:: C and C@t{++} type and range checks
9030 * Debugging C:: @value{GDBN} and C
9031 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
9035 @subsubsection C and C@t{++} Operators
9037 @cindex C and C@t{++} operators
9039 Operators must be defined on values of specific types. For instance,
9040 @code{+} is defined on numbers, but not on structures. Operators are
9041 often defined on groups of types.
9043 For the purposes of C and C@t{++}, the following definitions hold:
9048 @emph{Integral types} include @code{int} with any of its storage-class
9049 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
9052 @emph{Floating-point types} include @code{float}, @code{double}, and
9053 @code{long double} (if supported by the target platform).
9056 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
9059 @emph{Scalar types} include all of the above.
9064 The following operators are supported. They are listed here
9065 in order of increasing precedence:
9069 The comma or sequencing operator. Expressions in a comma-separated list
9070 are evaluated from left to right, with the result of the entire
9071 expression being the last expression evaluated.
9074 Assignment. The value of an assignment expression is the value
9075 assigned. Defined on scalar types.
9078 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
9079 and translated to @w{@code{@var{a} = @var{a op b}}}.
9080 @w{@code{@var{op}=}} and @code{=} have the same precedence.
9081 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
9082 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
9085 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
9086 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
9090 Logical @sc{or}. Defined on integral types.
9093 Logical @sc{and}. Defined on integral types.
9096 Bitwise @sc{or}. Defined on integral types.
9099 Bitwise exclusive-@sc{or}. Defined on integral types.
9102 Bitwise @sc{and}. Defined on integral types.
9105 Equality and inequality. Defined on scalar types. The value of these
9106 expressions is 0 for false and non-zero for true.
9108 @item <@r{, }>@r{, }<=@r{, }>=
9109 Less than, greater than, less than or equal, greater than or equal.
9110 Defined on scalar types. The value of these expressions is 0 for false
9111 and non-zero for true.
9114 left shift, and right shift. Defined on integral types.
9117 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9120 Addition and subtraction. Defined on integral types, floating-point types and
9123 @item *@r{, }/@r{, }%
9124 Multiplication, division, and modulus. Multiplication and division are
9125 defined on integral and floating-point types. Modulus is defined on
9129 Increment and decrement. When appearing before a variable, the
9130 operation is performed before the variable is used in an expression;
9131 when appearing after it, the variable's value is used before the
9132 operation takes place.
9135 Pointer dereferencing. Defined on pointer types. Same precedence as
9139 Address operator. Defined on variables. Same precedence as @code{++}.
9141 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
9142 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
9143 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
9144 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
9148 Negative. Defined on integral and floating-point types. Same
9149 precedence as @code{++}.
9152 Logical negation. Defined on integral types. Same precedence as
9156 Bitwise complement operator. Defined on integral types. Same precedence as
9161 Structure member, and pointer-to-structure member. For convenience,
9162 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
9163 pointer based on the stored type information.
9164 Defined on @code{struct} and @code{union} data.
9167 Dereferences of pointers to members.
9170 Array indexing. @code{@var{a}[@var{i}]} is defined as
9171 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
9174 Function parameter list. Same precedence as @code{->}.
9177 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
9178 and @code{class} types.
9181 Doubled colons also represent the @value{GDBN} scope operator
9182 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
9186 If an operator is redefined in the user code, @value{GDBN} usually
9187 attempts to invoke the redefined version instead of using the operator's
9191 @subsubsection C and C@t{++} Constants
9193 @cindex C and C@t{++} constants
9195 @value{GDBN} allows you to express the constants of C and C@t{++} in the
9200 Integer constants are a sequence of digits. Octal constants are
9201 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
9202 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
9203 @samp{l}, specifying that the constant should be treated as a
9207 Floating point constants are a sequence of digits, followed by a decimal
9208 point, followed by a sequence of digits, and optionally followed by an
9209 exponent. An exponent is of the form:
9210 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
9211 sequence of digits. The @samp{+} is optional for positive exponents.
9212 A floating-point constant may also end with a letter @samp{f} or
9213 @samp{F}, specifying that the constant should be treated as being of
9214 the @code{float} (as opposed to the default @code{double}) type; or with
9215 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
9219 Enumerated constants consist of enumerated identifiers, or their
9220 integral equivalents.
9223 Character constants are a single character surrounded by single quotes
9224 (@code{'}), or a number---the ordinal value of the corresponding character
9225 (usually its @sc{ascii} value). Within quotes, the single character may
9226 be represented by a letter or by @dfn{escape sequences}, which are of
9227 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
9228 of the character's ordinal value; or of the form @samp{\@var{x}}, where
9229 @samp{@var{x}} is a predefined special character---for example,
9230 @samp{\n} for newline.
9233 String constants are a sequence of character constants surrounded by
9234 double quotes (@code{"}). Any valid character constant (as described
9235 above) may appear. Double quotes within the string must be preceded by
9236 a backslash, so for instance @samp{"a\"b'c"} is a string of five
9240 Pointer constants are an integral value. You can also write pointers
9241 to constants using the C operator @samp{&}.
9244 Array constants are comma-separated lists surrounded by braces @samp{@{}
9245 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
9246 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
9247 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
9250 @node C Plus Plus Expressions
9251 @subsubsection C@t{++} Expressions
9253 @cindex expressions in C@t{++}
9254 @value{GDBN} expression handling can interpret most C@t{++} expressions.
9256 @cindex debugging C@t{++} programs
9257 @cindex C@t{++} compilers
9258 @cindex debug formats and C@t{++}
9259 @cindex @value{NGCC} and C@t{++}
9261 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
9262 proper compiler and the proper debug format. Currently, @value{GDBN}
9263 works best when debugging C@t{++} code that is compiled with
9264 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
9265 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
9266 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
9267 stabs+ as their default debug format, so you usually don't need to
9268 specify a debug format explicitly. Other compilers and/or debug formats
9269 are likely to work badly or not at all when using @value{GDBN} to debug
9275 @cindex member functions
9277 Member function calls are allowed; you can use expressions like
9280 count = aml->GetOriginal(x, y)
9283 @vindex this@r{, inside C@t{++} member functions}
9284 @cindex namespace in C@t{++}
9286 While a member function is active (in the selected stack frame), your
9287 expressions have the same namespace available as the member function;
9288 that is, @value{GDBN} allows implicit references to the class instance
9289 pointer @code{this} following the same rules as C@t{++}.
9291 @cindex call overloaded functions
9292 @cindex overloaded functions, calling
9293 @cindex type conversions in C@t{++}
9295 You can call overloaded functions; @value{GDBN} resolves the function
9296 call to the right definition, with some restrictions. @value{GDBN} does not
9297 perform overload resolution involving user-defined type conversions,
9298 calls to constructors, or instantiations of templates that do not exist
9299 in the program. It also cannot handle ellipsis argument lists or
9302 It does perform integral conversions and promotions, floating-point
9303 promotions, arithmetic conversions, pointer conversions, conversions of
9304 class objects to base classes, and standard conversions such as those of
9305 functions or arrays to pointers; it requires an exact match on the
9306 number of function arguments.
9308 Overload resolution is always performed, unless you have specified
9309 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
9310 ,@value{GDBN} Features for C@t{++}}.
9312 You must specify @code{set overload-resolution off} in order to use an
9313 explicit function signature to call an overloaded function, as in
9315 p 'foo(char,int)'('x', 13)
9318 The @value{GDBN} command-completion facility can simplify this;
9319 see @ref{Completion, ,Command Completion}.
9321 @cindex reference declarations
9323 @value{GDBN} understands variables declared as C@t{++} references; you can use
9324 them in expressions just as you do in C@t{++} source---they are automatically
9327 In the parameter list shown when @value{GDBN} displays a frame, the values of
9328 reference variables are not displayed (unlike other variables); this
9329 avoids clutter, since references are often used for large structures.
9330 The @emph{address} of a reference variable is always shown, unless
9331 you have specified @samp{set print address off}.
9334 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
9335 expressions can use it just as expressions in your program do. Since
9336 one scope may be defined in another, you can use @code{::} repeatedly if
9337 necessary, for example in an expression like
9338 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
9339 resolving name scope by reference to source files, in both C and C@t{++}
9340 debugging (@pxref{Variables, ,Program Variables}).
9343 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
9344 calling virtual functions correctly, printing out virtual bases of
9345 objects, calling functions in a base subobject, casting objects, and
9346 invoking user-defined operators.
9349 @subsubsection C and C@t{++} Defaults
9351 @cindex C and C@t{++} defaults
9353 If you allow @value{GDBN} to set type and range checking automatically, they
9354 both default to @code{off} whenever the working language changes to
9355 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
9356 selects the working language.
9358 If you allow @value{GDBN} to set the language automatically, it
9359 recognizes source files whose names end with @file{.c}, @file{.C}, or
9360 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
9361 these files, it sets the working language to C or C@t{++}.
9362 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
9363 for further details.
9365 @c Type checking is (a) primarily motivated by Modula-2, and (b)
9366 @c unimplemented. If (b) changes, it might make sense to let this node
9367 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
9370 @subsubsection C and C@t{++} Type and Range Checks
9372 @cindex C and C@t{++} checks
9374 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
9375 is not used. However, if you turn type checking on, @value{GDBN}
9376 considers two variables type equivalent if:
9380 The two variables are structured and have the same structure, union, or
9384 The two variables have the same type name, or types that have been
9385 declared equivalent through @code{typedef}.
9388 @c leaving this out because neither J Gilmore nor R Pesch understand it.
9391 The two @code{struct}, @code{union}, or @code{enum} variables are
9392 declared in the same declaration. (Note: this may not be true for all C
9397 Range checking, if turned on, is done on mathematical operations. Array
9398 indices are not checked, since they are often used to index a pointer
9399 that is not itself an array.
9402 @subsubsection @value{GDBN} and C
9404 The @code{set print union} and @code{show print union} commands apply to
9405 the @code{union} type. When set to @samp{on}, any @code{union} that is
9406 inside a @code{struct} or @code{class} is also printed. Otherwise, it
9407 appears as @samp{@{...@}}.
9409 The @code{@@} operator aids in the debugging of dynamic arrays, formed
9410 with pointers and a memory allocation function. @xref{Expressions,
9413 @node Debugging C Plus Plus
9414 @subsubsection @value{GDBN} Features for C@t{++}
9416 @cindex commands for C@t{++}
9418 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
9419 designed specifically for use with C@t{++}. Here is a summary:
9422 @cindex break in overloaded functions
9423 @item @r{breakpoint menus}
9424 When you want a breakpoint in a function whose name is overloaded,
9425 @value{GDBN} breakpoint menus help you specify which function definition
9426 you want. @xref{Breakpoint Menus,,Breakpoint Menus}.
9428 @cindex overloading in C@t{++}
9429 @item rbreak @var{regex}
9430 Setting breakpoints using regular expressions is helpful for setting
9431 breakpoints on overloaded functions that are not members of any special
9433 @xref{Set Breaks, ,Setting Breakpoints}.
9435 @cindex C@t{++} exception handling
9438 Debug C@t{++} exception handling using these commands. @xref{Set
9439 Catchpoints, , Setting Catchpoints}.
9442 @item ptype @var{typename}
9443 Print inheritance relationships as well as other information for type
9445 @xref{Symbols, ,Examining the Symbol Table}.
9447 @cindex C@t{++} symbol display
9448 @item set print demangle
9449 @itemx show print demangle
9450 @itemx set print asm-demangle
9451 @itemx show print asm-demangle
9452 Control whether C@t{++} symbols display in their source form, both when
9453 displaying code as C@t{++} source and when displaying disassemblies.
9454 @xref{Print Settings, ,Print Settings}.
9456 @item set print object
9457 @itemx show print object
9458 Choose whether to print derived (actual) or declared types of objects.
9459 @xref{Print Settings, ,Print Settings}.
9461 @item set print vtbl
9462 @itemx show print vtbl
9463 Control the format for printing virtual function tables.
9464 @xref{Print Settings, ,Print Settings}.
9465 (The @code{vtbl} commands do not work on programs compiled with the HP
9466 ANSI C@t{++} compiler (@code{aCC}).)
9468 @kindex set overload-resolution
9469 @cindex overloaded functions, overload resolution
9470 @item set overload-resolution on
9471 Enable overload resolution for C@t{++} expression evaluation. The default
9472 is on. For overloaded functions, @value{GDBN} evaluates the arguments
9473 and searches for a function whose signature matches the argument types,
9474 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
9475 Expressions, ,C@t{++} Expressions}, for details).
9476 If it cannot find a match, it emits a message.
9478 @item set overload-resolution off
9479 Disable overload resolution for C@t{++} expression evaluation. For
9480 overloaded functions that are not class member functions, @value{GDBN}
9481 chooses the first function of the specified name that it finds in the
9482 symbol table, whether or not its arguments are of the correct type. For
9483 overloaded functions that are class member functions, @value{GDBN}
9484 searches for a function whose signature @emph{exactly} matches the
9487 @kindex show overload-resolution
9488 @item show overload-resolution
9489 Show the current setting of overload resolution.
9491 @item @r{Overloaded symbol names}
9492 You can specify a particular definition of an overloaded symbol, using
9493 the same notation that is used to declare such symbols in C@t{++}: type
9494 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
9495 also use the @value{GDBN} command-line word completion facilities to list the
9496 available choices, or to finish the type list for you.
9497 @xref{Completion,, Command Completion}, for details on how to do this.
9501 @subsection Objective-C
9504 This section provides information about some commands and command
9505 options that are useful for debugging Objective-C code. See also
9506 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
9507 few more commands specific to Objective-C support.
9510 * Method Names in Commands::
9511 * The Print Command with Objective-C::
9514 @node Method Names in Commands
9515 @subsubsection Method Names in Commands
9517 The following commands have been extended to accept Objective-C method
9518 names as line specifications:
9520 @kindex clear@r{, and Objective-C}
9521 @kindex break@r{, and Objective-C}
9522 @kindex info line@r{, and Objective-C}
9523 @kindex jump@r{, and Objective-C}
9524 @kindex list@r{, and Objective-C}
9528 @item @code{info line}
9533 A fully qualified Objective-C method name is specified as
9536 -[@var{Class} @var{methodName}]
9539 where the minus sign is used to indicate an instance method and a
9540 plus sign (not shown) is used to indicate a class method. The class
9541 name @var{Class} and method name @var{methodName} are enclosed in
9542 brackets, similar to the way messages are specified in Objective-C
9543 source code. For example, to set a breakpoint at the @code{create}
9544 instance method of class @code{Fruit} in the program currently being
9548 break -[Fruit create]
9551 To list ten program lines around the @code{initialize} class method,
9555 list +[NSText initialize]
9558 In the current version of @value{GDBN}, the plus or minus sign is
9559 required. In future versions of @value{GDBN}, the plus or minus
9560 sign will be optional, but you can use it to narrow the search. It
9561 is also possible to specify just a method name:
9567 You must specify the complete method name, including any colons. If
9568 your program's source files contain more than one @code{create} method,
9569 you'll be presented with a numbered list of classes that implement that
9570 method. Indicate your choice by number, or type @samp{0} to exit if
9573 As another example, to clear a breakpoint established at the
9574 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
9577 clear -[NSWindow makeKeyAndOrderFront:]
9580 @node The Print Command with Objective-C
9581 @subsubsection The Print Command With Objective-C
9582 @cindex Objective-C, print objects
9583 @kindex print-object
9584 @kindex po @r{(@code{print-object})}
9586 The print command has also been extended to accept methods. For example:
9589 print -[@var{object} hash]
9592 @cindex print an Objective-C object description
9593 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
9595 will tell @value{GDBN} to send the @code{hash} message to @var{object}
9596 and print the result. Also, an additional command has been added,
9597 @code{print-object} or @code{po} for short, which is meant to print
9598 the description of an object. However, this command may only work
9599 with certain Objective-C libraries that have a particular hook
9600 function, @code{_NSPrintForDebugger}, defined.
9604 @cindex Fortran-specific support in @value{GDBN}
9606 @value{GDBN} can be used to debug programs written in Fortran, but it
9607 currently supports only the features of Fortran 77 language.
9609 @cindex trailing underscore, in Fortran symbols
9610 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
9611 among them) append an underscore to the names of variables and
9612 functions. When you debug programs compiled by those compilers, you
9613 will need to refer to variables and functions with a trailing
9617 * Fortran Operators:: Fortran operators and expressions
9618 * Fortran Defaults:: Default settings for Fortran
9619 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
9622 @node Fortran Operators
9623 @subsubsection Fortran Operators and Expressions
9625 @cindex Fortran operators and expressions
9627 Operators must be defined on values of specific types. For instance,
9628 @code{+} is defined on numbers, but not on characters or other non-
9629 arithmetic types. Operators are often defined on groups of types.
9633 The exponentiation operator. It raises the first operand to the power
9637 The range operator. Normally used in the form of array(low:high) to
9638 represent a section of array.
9641 @node Fortran Defaults
9642 @subsubsection Fortran Defaults
9644 @cindex Fortran Defaults
9646 Fortran symbols are usually case-insensitive, so @value{GDBN} by
9647 default uses case-insensitive matches for Fortran symbols. You can
9648 change that with the @samp{set case-insensitive} command, see
9649 @ref{Symbols}, for the details.
9651 @node Special Fortran Commands
9652 @subsubsection Special Fortran Commands
9654 @cindex Special Fortran commands
9656 @value{GDBN} has some commands to support Fortran-specific features,
9657 such as displaying common blocks.
9660 @cindex @code{COMMON} blocks, Fortran
9662 @item info common @r{[}@var{common-name}@r{]}
9663 This command prints the values contained in the Fortran @code{COMMON}
9664 block whose name is @var{common-name}. With no argument, the names of
9665 all @code{COMMON} blocks visible at the current program location are
9672 @cindex Pascal support in @value{GDBN}, limitations
9673 Debugging Pascal programs which use sets, subranges, file variables, or
9674 nested functions does not currently work. @value{GDBN} does not support
9675 entering expressions, printing values, or similar features using Pascal
9678 The Pascal-specific command @code{set print pascal_static-members}
9679 controls whether static members of Pascal objects are displayed.
9680 @xref{Print Settings, pascal_static-members}.
9683 @subsection Modula-2
9685 @cindex Modula-2, @value{GDBN} support
9687 The extensions made to @value{GDBN} to support Modula-2 only support
9688 output from the @sc{gnu} Modula-2 compiler (which is currently being
9689 developed). Other Modula-2 compilers are not currently supported, and
9690 attempting to debug executables produced by them is most likely
9691 to give an error as @value{GDBN} reads in the executable's symbol
9694 @cindex expressions in Modula-2
9696 * M2 Operators:: Built-in operators
9697 * Built-In Func/Proc:: Built-in functions and procedures
9698 * M2 Constants:: Modula-2 constants
9699 * M2 Types:: Modula-2 types
9700 * M2 Defaults:: Default settings for Modula-2
9701 * Deviations:: Deviations from standard Modula-2
9702 * M2 Checks:: Modula-2 type and range checks
9703 * M2 Scope:: The scope operators @code{::} and @code{.}
9704 * GDB/M2:: @value{GDBN} and Modula-2
9708 @subsubsection Operators
9709 @cindex Modula-2 operators
9711 Operators must be defined on values of specific types. For instance,
9712 @code{+} is defined on numbers, but not on structures. Operators are
9713 often defined on groups of types. For the purposes of Modula-2, the
9714 following definitions hold:
9719 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
9723 @emph{Character types} consist of @code{CHAR} and its subranges.
9726 @emph{Floating-point types} consist of @code{REAL}.
9729 @emph{Pointer types} consist of anything declared as @code{POINTER TO
9733 @emph{Scalar types} consist of all of the above.
9736 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
9739 @emph{Boolean types} consist of @code{BOOLEAN}.
9743 The following operators are supported, and appear in order of
9744 increasing precedence:
9748 Function argument or array index separator.
9751 Assignment. The value of @var{var} @code{:=} @var{value} is
9755 Less than, greater than on integral, floating-point, or enumerated
9759 Less than or equal to, greater than or equal to
9760 on integral, floating-point and enumerated types, or set inclusion on
9761 set types. Same precedence as @code{<}.
9763 @item =@r{, }<>@r{, }#
9764 Equality and two ways of expressing inequality, valid on scalar types.
9765 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
9766 available for inequality, since @code{#} conflicts with the script
9770 Set membership. Defined on set types and the types of their members.
9771 Same precedence as @code{<}.
9774 Boolean disjunction. Defined on boolean types.
9777 Boolean conjunction. Defined on boolean types.
9780 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9783 Addition and subtraction on integral and floating-point types, or union
9784 and difference on set types.
9787 Multiplication on integral and floating-point types, or set intersection
9791 Division on floating-point types, or symmetric set difference on set
9792 types. Same precedence as @code{*}.
9795 Integer division and remainder. Defined on integral types. Same
9796 precedence as @code{*}.
9799 Negative. Defined on @code{INTEGER} and @code{REAL} data.
9802 Pointer dereferencing. Defined on pointer types.
9805 Boolean negation. Defined on boolean types. Same precedence as
9809 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
9810 precedence as @code{^}.
9813 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
9816 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
9820 @value{GDBN} and Modula-2 scope operators.
9824 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
9825 treats the use of the operator @code{IN}, or the use of operators
9826 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
9827 @code{<=}, and @code{>=} on sets as an error.
9831 @node Built-In Func/Proc
9832 @subsubsection Built-in Functions and Procedures
9833 @cindex Modula-2 built-ins
9835 Modula-2 also makes available several built-in procedures and functions.
9836 In describing these, the following metavariables are used:
9841 represents an @code{ARRAY} variable.
9844 represents a @code{CHAR} constant or variable.
9847 represents a variable or constant of integral type.
9850 represents an identifier that belongs to a set. Generally used in the
9851 same function with the metavariable @var{s}. The type of @var{s} should
9852 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
9855 represents a variable or constant of integral or floating-point type.
9858 represents a variable or constant of floating-point type.
9864 represents a variable.
9867 represents a variable or constant of one of many types. See the
9868 explanation of the function for details.
9871 All Modula-2 built-in procedures also return a result, described below.
9875 Returns the absolute value of @var{n}.
9878 If @var{c} is a lower case letter, it returns its upper case
9879 equivalent, otherwise it returns its argument.
9882 Returns the character whose ordinal value is @var{i}.
9885 Decrements the value in the variable @var{v} by one. Returns the new value.
9887 @item DEC(@var{v},@var{i})
9888 Decrements the value in the variable @var{v} by @var{i}. Returns the
9891 @item EXCL(@var{m},@var{s})
9892 Removes the element @var{m} from the set @var{s}. Returns the new
9895 @item FLOAT(@var{i})
9896 Returns the floating point equivalent of the integer @var{i}.
9899 Returns the index of the last member of @var{a}.
9902 Increments the value in the variable @var{v} by one. Returns the new value.
9904 @item INC(@var{v},@var{i})
9905 Increments the value in the variable @var{v} by @var{i}. Returns the
9908 @item INCL(@var{m},@var{s})
9909 Adds the element @var{m} to the set @var{s} if it is not already
9910 there. Returns the new set.
9913 Returns the maximum value of the type @var{t}.
9916 Returns the minimum value of the type @var{t}.
9919 Returns boolean TRUE if @var{i} is an odd number.
9922 Returns the ordinal value of its argument. For example, the ordinal
9923 value of a character is its @sc{ascii} value (on machines supporting the
9924 @sc{ascii} character set). @var{x} must be of an ordered type, which include
9925 integral, character and enumerated types.
9928 Returns the size of its argument. @var{x} can be a variable or a type.
9930 @item TRUNC(@var{r})
9931 Returns the integral part of @var{r}.
9933 @item VAL(@var{t},@var{i})
9934 Returns the member of the type @var{t} whose ordinal value is @var{i}.
9938 @emph{Warning:} Sets and their operations are not yet supported, so
9939 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
9943 @cindex Modula-2 constants
9945 @subsubsection Constants
9947 @value{GDBN} allows you to express the constants of Modula-2 in the following
9953 Integer constants are simply a sequence of digits. When used in an
9954 expression, a constant is interpreted to be type-compatible with the
9955 rest of the expression. Hexadecimal integers are specified by a
9956 trailing @samp{H}, and octal integers by a trailing @samp{B}.
9959 Floating point constants appear as a sequence of digits, followed by a
9960 decimal point and another sequence of digits. An optional exponent can
9961 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
9962 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
9963 digits of the floating point constant must be valid decimal (base 10)
9967 Character constants consist of a single character enclosed by a pair of
9968 like quotes, either single (@code{'}) or double (@code{"}). They may
9969 also be expressed by their ordinal value (their @sc{ascii} value, usually)
9970 followed by a @samp{C}.
9973 String constants consist of a sequence of characters enclosed by a
9974 pair of like quotes, either single (@code{'}) or double (@code{"}).
9975 Escape sequences in the style of C are also allowed. @xref{C
9976 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
9980 Enumerated constants consist of an enumerated identifier.
9983 Boolean constants consist of the identifiers @code{TRUE} and
9987 Pointer constants consist of integral values only.
9990 Set constants are not yet supported.
9994 @subsubsection Modula-2 Types
9995 @cindex Modula-2 types
9997 Currently @value{GDBN} can print the following data types in Modula-2
9998 syntax: array types, record types, set types, pointer types, procedure
9999 types, enumerated types, subrange types and base types. You can also
10000 print the contents of variables declared using these type.
10001 This section gives a number of simple source code examples together with
10002 sample @value{GDBN} sessions.
10004 The first example contains the following section of code:
10013 and you can request @value{GDBN} to interrogate the type and value of
10014 @code{r} and @code{s}.
10017 (@value{GDBP}) print s
10019 (@value{GDBP}) ptype s
10021 (@value{GDBP}) print r
10023 (@value{GDBP}) ptype r
10028 Likewise if your source code declares @code{s} as:
10032 s: SET ['A'..'Z'] ;
10036 then you may query the type of @code{s} by:
10039 (@value{GDBP}) ptype s
10040 type = SET ['A'..'Z']
10044 Note that at present you cannot interactively manipulate set
10045 expressions using the debugger.
10047 The following example shows how you might declare an array in Modula-2
10048 and how you can interact with @value{GDBN} to print its type and contents:
10052 s: ARRAY [-10..10] OF CHAR ;
10056 (@value{GDBP}) ptype s
10057 ARRAY [-10..10] OF CHAR
10060 Note that the array handling is not yet complete and although the type
10061 is printed correctly, expression handling still assumes that all
10062 arrays have a lower bound of zero and not @code{-10} as in the example
10063 above. Unbounded arrays are also not yet recognized in @value{GDBN}.
10065 Here are some more type related Modula-2 examples:
10069 colour = (blue, red, yellow, green) ;
10070 t = [blue..yellow] ;
10078 The @value{GDBN} interaction shows how you can query the data type
10079 and value of a variable.
10082 (@value{GDBP}) print s
10084 (@value{GDBP}) ptype t
10085 type = [blue..yellow]
10089 In this example a Modula-2 array is declared and its contents
10090 displayed. Observe that the contents are written in the same way as
10091 their @code{C} counterparts.
10095 s: ARRAY [1..5] OF CARDINAL ;
10101 (@value{GDBP}) print s
10102 $1 = @{1, 0, 0, 0, 0@}
10103 (@value{GDBP}) ptype s
10104 type = ARRAY [1..5] OF CARDINAL
10107 The Modula-2 language interface to @value{GDBN} also understands
10108 pointer types as shown in this example:
10112 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
10119 and you can request that @value{GDBN} describes the type of @code{s}.
10122 (@value{GDBP}) ptype s
10123 type = POINTER TO ARRAY [1..5] OF CARDINAL
10126 @value{GDBN} handles compound types as we can see in this example.
10127 Here we combine array types, record types, pointer types and subrange
10138 myarray = ARRAY myrange OF CARDINAL ;
10139 myrange = [-2..2] ;
10141 s: POINTER TO ARRAY myrange OF foo ;
10145 and you can ask @value{GDBN} to describe the type of @code{s} as shown
10149 (@value{GDBP}) ptype s
10150 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
10153 f3 : ARRAY [-2..2] OF CARDINAL;
10158 @subsubsection Modula-2 Defaults
10159 @cindex Modula-2 defaults
10161 If type and range checking are set automatically by @value{GDBN}, they
10162 both default to @code{on} whenever the working language changes to
10163 Modula-2. This happens regardless of whether you or @value{GDBN}
10164 selected the working language.
10166 If you allow @value{GDBN} to set the language automatically, then entering
10167 code compiled from a file whose name ends with @file{.mod} sets the
10168 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
10169 Infer the Source Language}, for further details.
10172 @subsubsection Deviations from Standard Modula-2
10173 @cindex Modula-2, deviations from
10175 A few changes have been made to make Modula-2 programs easier to debug.
10176 This is done primarily via loosening its type strictness:
10180 Unlike in standard Modula-2, pointer constants can be formed by
10181 integers. This allows you to modify pointer variables during
10182 debugging. (In standard Modula-2, the actual address contained in a
10183 pointer variable is hidden from you; it can only be modified
10184 through direct assignment to another pointer variable or expression that
10185 returned a pointer.)
10188 C escape sequences can be used in strings and characters to represent
10189 non-printable characters. @value{GDBN} prints out strings with these
10190 escape sequences embedded. Single non-printable characters are
10191 printed using the @samp{CHR(@var{nnn})} format.
10194 The assignment operator (@code{:=}) returns the value of its right-hand
10198 All built-in procedures both modify @emph{and} return their argument.
10202 @subsubsection Modula-2 Type and Range Checks
10203 @cindex Modula-2 checks
10206 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
10209 @c FIXME remove warning when type/range checks added
10211 @value{GDBN} considers two Modula-2 variables type equivalent if:
10215 They are of types that have been declared equivalent via a @code{TYPE
10216 @var{t1} = @var{t2}} statement
10219 They have been declared on the same line. (Note: This is true of the
10220 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
10223 As long as type checking is enabled, any attempt to combine variables
10224 whose types are not equivalent is an error.
10226 Range checking is done on all mathematical operations, assignment, array
10227 index bounds, and all built-in functions and procedures.
10230 @subsubsection The Scope Operators @code{::} and @code{.}
10232 @cindex @code{.}, Modula-2 scope operator
10233 @cindex colon, doubled as scope operator
10235 @vindex colon-colon@r{, in Modula-2}
10236 @c Info cannot handle :: but TeX can.
10239 @vindex ::@r{, in Modula-2}
10242 There are a few subtle differences between the Modula-2 scope operator
10243 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
10248 @var{module} . @var{id}
10249 @var{scope} :: @var{id}
10253 where @var{scope} is the name of a module or a procedure,
10254 @var{module} the name of a module, and @var{id} is any declared
10255 identifier within your program, except another module.
10257 Using the @code{::} operator makes @value{GDBN} search the scope
10258 specified by @var{scope} for the identifier @var{id}. If it is not
10259 found in the specified scope, then @value{GDBN} searches all scopes
10260 enclosing the one specified by @var{scope}.
10262 Using the @code{.} operator makes @value{GDBN} search the current scope for
10263 the identifier specified by @var{id} that was imported from the
10264 definition module specified by @var{module}. With this operator, it is
10265 an error if the identifier @var{id} was not imported from definition
10266 module @var{module}, or if @var{id} is not an identifier in
10270 @subsubsection @value{GDBN} and Modula-2
10272 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
10273 Five subcommands of @code{set print} and @code{show print} apply
10274 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
10275 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
10276 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
10277 analogue in Modula-2.
10279 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
10280 with any language, is not useful with Modula-2. Its
10281 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
10282 created in Modula-2 as they can in C or C@t{++}. However, because an
10283 address can be specified by an integral constant, the construct
10284 @samp{@{@var{type}@}@var{adrexp}} is still useful.
10286 @cindex @code{#} in Modula-2
10287 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
10288 interpreted as the beginning of a comment. Use @code{<>} instead.
10294 The extensions made to @value{GDBN} for Ada only support
10295 output from the @sc{gnu} Ada (GNAT) compiler.
10296 Other Ada compilers are not currently supported, and
10297 attempting to debug executables produced by them is most likely
10301 @cindex expressions in Ada
10303 * Ada Mode Intro:: General remarks on the Ada syntax
10304 and semantics supported by Ada mode
10306 * Omissions from Ada:: Restrictions on the Ada expression syntax.
10307 * Additions to Ada:: Extensions of the Ada expression syntax.
10308 * Stopping Before Main Program:: Debugging the program during elaboration.
10309 * Ada Glitches:: Known peculiarities of Ada mode.
10312 @node Ada Mode Intro
10313 @subsubsection Introduction
10314 @cindex Ada mode, general
10316 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
10317 syntax, with some extensions.
10318 The philosophy behind the design of this subset is
10322 That @value{GDBN} should provide basic literals and access to operations for
10323 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
10324 leaving more sophisticated computations to subprograms written into the
10325 program (which therefore may be called from @value{GDBN}).
10328 That type safety and strict adherence to Ada language restrictions
10329 are not particularly important to the @value{GDBN} user.
10332 That brevity is important to the @value{GDBN} user.
10335 Thus, for brevity, the debugger acts as if there were
10336 implicit @code{with} and @code{use} clauses in effect for all user-written
10337 packages, making it unnecessary to fully qualify most names with
10338 their packages, regardless of context. Where this causes ambiguity,
10339 @value{GDBN} asks the user's intent.
10341 The debugger will start in Ada mode if it detects an Ada main program.
10342 As for other languages, it will enter Ada mode when stopped in a program that
10343 was translated from an Ada source file.
10345 While in Ada mode, you may use `@t{--}' for comments. This is useful
10346 mostly for documenting command files. The standard @value{GDBN} comment
10347 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
10348 middle (to allow based literals).
10350 The debugger supports limited overloading. Given a subprogram call in which
10351 the function symbol has multiple definitions, it will use the number of
10352 actual parameters and some information about their types to attempt to narrow
10353 the set of definitions. It also makes very limited use of context, preferring
10354 procedures to functions in the context of the @code{call} command, and
10355 functions to procedures elsewhere.
10357 @node Omissions from Ada
10358 @subsubsection Omissions from Ada
10359 @cindex Ada, omissions from
10361 Here are the notable omissions from the subset:
10365 Only a subset of the attributes are supported:
10369 @t{'First}, @t{'Last}, and @t{'Length}
10370 on array objects (not on types and subtypes).
10373 @t{'Min} and @t{'Max}.
10376 @t{'Pos} and @t{'Val}.
10382 @t{'Range} on array objects (not subtypes), but only as the right
10383 operand of the membership (@code{in}) operator.
10386 @t{'Access}, @t{'Unchecked_Access}, and
10387 @t{'Unrestricted_Access} (a GNAT extension).
10395 @code{Characters.Latin_1} are not available and
10396 concatenation is not implemented. Thus, escape characters in strings are
10397 not currently available.
10400 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
10401 equality of representations. They will generally work correctly
10402 for strings and arrays whose elements have integer or enumeration types.
10403 They may not work correctly for arrays whose element
10404 types have user-defined equality, for arrays of real values
10405 (in particular, IEEE-conformant floating point, because of negative
10406 zeroes and NaNs), and for arrays whose elements contain unused bits with
10407 indeterminate values.
10410 The other component-by-component array operations (@code{and}, @code{or},
10411 @code{xor}, @code{not}, and relational tests other than equality)
10412 are not implemented.
10415 @cindex array aggregates (Ada)
10416 @cindex record aggregates (Ada)
10417 @cindex aggregates (Ada)
10418 There is limited support for array and record aggregates. They are
10419 permitted only on the right sides of assignments, as in these examples:
10422 set An_Array := (1, 2, 3, 4, 5, 6)
10423 set An_Array := (1, others => 0)
10424 set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
10425 set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
10426 set A_Record := (1, "Peter", True);
10427 set A_Record := (Name => "Peter", Id => 1, Alive => True)
10431 discriminant's value by assigning an aggregate has an
10432 undefined effect if that discriminant is used within the record.
10433 However, you can first modify discriminants by directly assigning to
10434 them (which normally would not be allowed in Ada), and then performing an
10435 aggregate assignment. For example, given a variable @code{A_Rec}
10436 declared to have a type such as:
10439 type Rec (Len : Small_Integer := 0) is record
10441 Vals : IntArray (1 .. Len);
10445 you can assign a value with a different size of @code{Vals} with two
10450 set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
10453 As this example also illustrates, @value{GDBN} is very loose about the usual
10454 rules concerning aggregates. You may leave out some of the
10455 components of an array or record aggregate (such as the @code{Len}
10456 component in the assignment to @code{A_Rec} above); they will retain their
10457 original values upon assignment. You may freely use dynamic values as
10458 indices in component associations. You may even use overlapping or
10459 redundant component associations, although which component values are
10460 assigned in such cases is not defined.
10463 Calls to dispatching subprograms are not implemented.
10466 The overloading algorithm is much more limited (i.e., less selective)
10467 than that of real Ada. It makes only limited use of the context in
10468 which a subexpression appears to resolve its meaning, and it is much
10469 looser in its rules for allowing type matches. As a result, some
10470 function calls will be ambiguous, and the user will be asked to choose
10471 the proper resolution.
10474 The @code{new} operator is not implemented.
10477 Entry calls are not implemented.
10480 Aside from printing, arithmetic operations on the native VAX floating-point
10481 formats are not supported.
10484 It is not possible to slice a packed array.
10487 @node Additions to Ada
10488 @subsubsection Additions to Ada
10489 @cindex Ada, deviations from
10491 As it does for other languages, @value{GDBN} makes certain generic
10492 extensions to Ada (@pxref{Expressions}):
10496 If the expression @var{E} is a variable residing in memory (typically
10497 a local variable or array element) and @var{N} is a positive integer,
10498 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
10499 @var{N}-1 adjacent variables following it in memory as an array. In
10500 Ada, this operator is generally not necessary, since its prime use is
10501 in displaying parts of an array, and slicing will usually do this in
10502 Ada. However, there are occasional uses when debugging programs in
10503 which certain debugging information has been optimized away.
10506 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
10507 appears in function or file @var{B}.'' When @var{B} is a file name,
10508 you must typically surround it in single quotes.
10511 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
10512 @var{type} that appears at address @var{addr}.''
10515 A name starting with @samp{$} is a convenience variable
10516 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
10519 In addition, @value{GDBN} provides a few other shortcuts and outright
10520 additions specific to Ada:
10524 The assignment statement is allowed as an expression, returning
10525 its right-hand operand as its value. Thus, you may enter
10529 print A(tmp := y + 1)
10533 The semicolon is allowed as an ``operator,'' returning as its value
10534 the value of its right-hand operand.
10535 This allows, for example,
10536 complex conditional breaks:
10540 condition 1 (report(i); k += 1; A(k) > 100)
10544 Rather than use catenation and symbolic character names to introduce special
10545 characters into strings, one may instead use a special bracket notation,
10546 which is also used to print strings. A sequence of characters of the form
10547 @samp{["@var{XX}"]} within a string or character literal denotes the
10548 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
10549 sequence of characters @samp{["""]} also denotes a single quotation mark
10550 in strings. For example,
10552 "One line.["0a"]Next line.["0a"]"
10555 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
10559 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
10560 @t{'Max} is optional (and is ignored in any case). For example, it is valid
10568 When printing arrays, @value{GDBN} uses positional notation when the
10569 array has a lower bound of 1, and uses a modified named notation otherwise.
10570 For example, a one-dimensional array of three integers with a lower bound
10571 of 3 might print as
10578 That is, in contrast to valid Ada, only the first component has a @code{=>}
10582 You may abbreviate attributes in expressions with any unique,
10583 multi-character subsequence of
10584 their names (an exact match gets preference).
10585 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
10586 in place of @t{a'length}.
10589 @cindex quoting Ada internal identifiers
10590 Since Ada is case-insensitive, the debugger normally maps identifiers you type
10591 to lower case. The GNAT compiler uses upper-case characters for
10592 some of its internal identifiers, which are normally of no interest to users.
10593 For the rare occasions when you actually have to look at them,
10594 enclose them in angle brackets to avoid the lower-case mapping.
10597 @value{GDBP} print <JMPBUF_SAVE>[0]
10601 Printing an object of class-wide type or dereferencing an
10602 access-to-class-wide value will display all the components of the object's
10603 specific type (as indicated by its run-time tag). Likewise, component
10604 selection on such a value will operate on the specific type of the
10609 @node Stopping Before Main Program
10610 @subsubsection Stopping at the Very Beginning
10612 @cindex breakpointing Ada elaboration code
10613 It is sometimes necessary to debug the program during elaboration, and
10614 before reaching the main procedure.
10615 As defined in the Ada Reference
10616 Manual, the elaboration code is invoked from a procedure called
10617 @code{adainit}. To run your program up to the beginning of
10618 elaboration, simply use the following two commands:
10619 @code{tbreak adainit} and @code{run}.
10622 @subsubsection Known Peculiarities of Ada Mode
10623 @cindex Ada, problems
10625 Besides the omissions listed previously (@pxref{Omissions from Ada}),
10626 we know of several problems with and limitations of Ada mode in
10628 some of which will be fixed with planned future releases of the debugger
10629 and the GNU Ada compiler.
10633 Currently, the debugger
10634 has insufficient information to determine whether certain pointers represent
10635 pointers to objects or the objects themselves.
10636 Thus, the user may have to tack an extra @code{.all} after an expression
10637 to get it printed properly.
10640 Static constants that the compiler chooses not to materialize as objects in
10641 storage are invisible to the debugger.
10644 Named parameter associations in function argument lists are ignored (the
10645 argument lists are treated as positional).
10648 Many useful library packages are currently invisible to the debugger.
10651 Fixed-point arithmetic, conversions, input, and output is carried out using
10652 floating-point arithmetic, and may give results that only approximate those on
10656 The type of the @t{'Address} attribute may not be @code{System.Address}.
10659 The GNAT compiler never generates the prefix @code{Standard} for any of
10660 the standard symbols defined by the Ada language. @value{GDBN} knows about
10661 this: it will strip the prefix from names when you use it, and will never
10662 look for a name you have so qualified among local symbols, nor match against
10663 symbols in other packages or subprograms. If you have
10664 defined entities anywhere in your program other than parameters and
10665 local variables whose simple names match names in @code{Standard},
10666 GNAT's lack of qualification here can cause confusion. When this happens,
10667 you can usually resolve the confusion
10668 by qualifying the problematic names with package
10669 @code{Standard} explicitly.
10672 @node Unsupported Languages
10673 @section Unsupported Languages
10675 @cindex unsupported languages
10676 @cindex minimal language
10677 In addition to the other fully-supported programming languages,
10678 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
10679 It does not represent a real programming language, but provides a set
10680 of capabilities close to what the C or assembly languages provide.
10681 This should allow most simple operations to be performed while debugging
10682 an application that uses a language currently not supported by @value{GDBN}.
10684 If the language is set to @code{auto}, @value{GDBN} will automatically
10685 select this language if the current frame corresponds to an unsupported
10689 @chapter Examining the Symbol Table
10691 The commands described in this chapter allow you to inquire about the
10692 symbols (names of variables, functions and types) defined in your
10693 program. This information is inherent in the text of your program and
10694 does not change as your program executes. @value{GDBN} finds it in your
10695 program's symbol table, in the file indicated when you started @value{GDBN}
10696 (@pxref{File Options, ,Choosing Files}), or by one of the
10697 file-management commands (@pxref{Files, ,Commands to Specify Files}).
10699 @cindex symbol names
10700 @cindex names of symbols
10701 @cindex quoting names
10702 Occasionally, you may need to refer to symbols that contain unusual
10703 characters, which @value{GDBN} ordinarily treats as word delimiters. The
10704 most frequent case is in referring to static variables in other
10705 source files (@pxref{Variables,,Program Variables}). File names
10706 are recorded in object files as debugging symbols, but @value{GDBN} would
10707 ordinarily parse a typical file name, like @file{foo.c}, as the three words
10708 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
10709 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
10716 looks up the value of @code{x} in the scope of the file @file{foo.c}.
10719 @cindex case-insensitive symbol names
10720 @cindex case sensitivity in symbol names
10721 @kindex set case-sensitive
10722 @item set case-sensitive on
10723 @itemx set case-sensitive off
10724 @itemx set case-sensitive auto
10725 Normally, when @value{GDBN} looks up symbols, it matches their names
10726 with case sensitivity determined by the current source language.
10727 Occasionally, you may wish to control that. The command @code{set
10728 case-sensitive} lets you do that by specifying @code{on} for
10729 case-sensitive matches or @code{off} for case-insensitive ones. If
10730 you specify @code{auto}, case sensitivity is reset to the default
10731 suitable for the source language. The default is case-sensitive
10732 matches for all languages except for Fortran, for which the default is
10733 case-insensitive matches.
10735 @kindex show case-sensitive
10736 @item show case-sensitive
10737 This command shows the current setting of case sensitivity for symbols
10740 @kindex info address
10741 @cindex address of a symbol
10742 @item info address @var{symbol}
10743 Describe where the data for @var{symbol} is stored. For a register
10744 variable, this says which register it is kept in. For a non-register
10745 local variable, this prints the stack-frame offset at which the variable
10748 Note the contrast with @samp{print &@var{symbol}}, which does not work
10749 at all for a register variable, and for a stack local variable prints
10750 the exact address of the current instantiation of the variable.
10752 @kindex info symbol
10753 @cindex symbol from address
10754 @cindex closest symbol and offset for an address
10755 @item info symbol @var{addr}
10756 Print the name of a symbol which is stored at the address @var{addr}.
10757 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
10758 nearest symbol and an offset from it:
10761 (@value{GDBP}) info symbol 0x54320
10762 _initialize_vx + 396 in section .text
10766 This is the opposite of the @code{info address} command. You can use
10767 it to find out the name of a variable or a function given its address.
10770 @item whatis [@var{arg}]
10771 Print the data type of @var{arg}, which can be either an expression or
10772 a data type. With no argument, print the data type of @code{$}, the
10773 last value in the value history. If @var{arg} is an expression, it is
10774 not actually evaluated, and any side-effecting operations (such as
10775 assignments or function calls) inside it do not take place. If
10776 @var{arg} is a type name, it may be the name of a type or typedef, or
10777 for C code it may have the form @samp{class @var{class-name}},
10778 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
10779 @samp{enum @var{enum-tag}}.
10780 @xref{Expressions, ,Expressions}.
10783 @item ptype [@var{arg}]
10784 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
10785 detailed description of the type, instead of just the name of the type.
10786 @xref{Expressions, ,Expressions}.
10788 For example, for this variable declaration:
10791 struct complex @{double real; double imag;@} v;
10795 the two commands give this output:
10799 (@value{GDBP}) whatis v
10800 type = struct complex
10801 (@value{GDBP}) ptype v
10802 type = struct complex @{
10810 As with @code{whatis}, using @code{ptype} without an argument refers to
10811 the type of @code{$}, the last value in the value history.
10813 @cindex incomplete type
10814 Sometimes, programs use opaque data types or incomplete specifications
10815 of complex data structure. If the debug information included in the
10816 program does not allow @value{GDBN} to display a full declaration of
10817 the data type, it will say @samp{<incomplete type>}. For example,
10818 given these declarations:
10822 struct foo *fooptr;
10826 but no definition for @code{struct foo} itself, @value{GDBN} will say:
10829 (@value{GDBP}) ptype foo
10830 $1 = <incomplete type>
10834 ``Incomplete type'' is C terminology for data types that are not
10835 completely specified.
10838 @item info types @var{regexp}
10840 Print a brief description of all types whose names match the regular
10841 expression @var{regexp} (or all types in your program, if you supply
10842 no argument). Each complete typename is matched as though it were a
10843 complete line; thus, @samp{i type value} gives information on all
10844 types in your program whose names include the string @code{value}, but
10845 @samp{i type ^value$} gives information only on types whose complete
10846 name is @code{value}.
10848 This command differs from @code{ptype} in two ways: first, like
10849 @code{whatis}, it does not print a detailed description; second, it
10850 lists all source files where a type is defined.
10853 @cindex local variables
10854 @item info scope @var{location}
10855 List all the variables local to a particular scope. This command
10856 accepts a @var{location} argument---a function name, a source line, or
10857 an address preceded by a @samp{*}, and prints all the variables local
10858 to the scope defined by that location. For example:
10861 (@value{GDBP}) @b{info scope command_line_handler}
10862 Scope for command_line_handler:
10863 Symbol rl is an argument at stack/frame offset 8, length 4.
10864 Symbol linebuffer is in static storage at address 0x150a18, length 4.
10865 Symbol linelength is in static storage at address 0x150a1c, length 4.
10866 Symbol p is a local variable in register $esi, length 4.
10867 Symbol p1 is a local variable in register $ebx, length 4.
10868 Symbol nline is a local variable in register $edx, length 4.
10869 Symbol repeat is a local variable at frame offset -8, length 4.
10873 This command is especially useful for determining what data to collect
10874 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
10877 @kindex info source
10879 Show information about the current source file---that is, the source file for
10880 the function containing the current point of execution:
10883 the name of the source file, and the directory containing it,
10885 the directory it was compiled in,
10887 its length, in lines,
10889 which programming language it is written in,
10891 whether the executable includes debugging information for that file, and
10892 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
10894 whether the debugging information includes information about
10895 preprocessor macros.
10899 @kindex info sources
10901 Print the names of all source files in your program for which there is
10902 debugging information, organized into two lists: files whose symbols
10903 have already been read, and files whose symbols will be read when needed.
10905 @kindex info functions
10906 @item info functions
10907 Print the names and data types of all defined functions.
10909 @item info functions @var{regexp}
10910 Print the names and data types of all defined functions
10911 whose names contain a match for regular expression @var{regexp}.
10912 Thus, @samp{info fun step} finds all functions whose names
10913 include @code{step}; @samp{info fun ^step} finds those whose names
10914 start with @code{step}. If a function name contains characters
10915 that conflict with the regular expression language (e.g.@:
10916 @samp{operator*()}), they may be quoted with a backslash.
10918 @kindex info variables
10919 @item info variables
10920 Print the names and data types of all variables that are declared
10921 outside of functions (i.e.@: excluding local variables).
10923 @item info variables @var{regexp}
10924 Print the names and data types of all variables (except for local
10925 variables) whose names contain a match for regular expression
10928 @kindex info classes
10929 @cindex Objective-C, classes and selectors
10931 @itemx info classes @var{regexp}
10932 Display all Objective-C classes in your program, or
10933 (with the @var{regexp} argument) all those matching a particular regular
10936 @kindex info selectors
10937 @item info selectors
10938 @itemx info selectors @var{regexp}
10939 Display all Objective-C selectors in your program, or
10940 (with the @var{regexp} argument) all those matching a particular regular
10944 This was never implemented.
10945 @kindex info methods
10947 @itemx info methods @var{regexp}
10948 The @code{info methods} command permits the user to examine all defined
10949 methods within C@t{++} program, or (with the @var{regexp} argument) a
10950 specific set of methods found in the various C@t{++} classes. Many
10951 C@t{++} classes provide a large number of methods. Thus, the output
10952 from the @code{ptype} command can be overwhelming and hard to use. The
10953 @code{info-methods} command filters the methods, printing only those
10954 which match the regular-expression @var{regexp}.
10957 @cindex reloading symbols
10958 Some systems allow individual object files that make up your program to
10959 be replaced without stopping and restarting your program. For example,
10960 in VxWorks you can simply recompile a defective object file and keep on
10961 running. If you are running on one of these systems, you can allow
10962 @value{GDBN} to reload the symbols for automatically relinked modules:
10965 @kindex set symbol-reloading
10966 @item set symbol-reloading on
10967 Replace symbol definitions for the corresponding source file when an
10968 object file with a particular name is seen again.
10970 @item set symbol-reloading off
10971 Do not replace symbol definitions when encountering object files of the
10972 same name more than once. This is the default state; if you are not
10973 running on a system that permits automatic relinking of modules, you
10974 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
10975 may discard symbols when linking large programs, that may contain
10976 several modules (from different directories or libraries) with the same
10979 @kindex show symbol-reloading
10980 @item show symbol-reloading
10981 Show the current @code{on} or @code{off} setting.
10984 @cindex opaque data types
10985 @kindex set opaque-type-resolution
10986 @item set opaque-type-resolution on
10987 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
10988 declared as a pointer to a @code{struct}, @code{class}, or
10989 @code{union}---for example, @code{struct MyType *}---that is used in one
10990 source file although the full declaration of @code{struct MyType} is in
10991 another source file. The default is on.
10993 A change in the setting of this subcommand will not take effect until
10994 the next time symbols for a file are loaded.
10996 @item set opaque-type-resolution off
10997 Tell @value{GDBN} not to resolve opaque types. In this case, the type
10998 is printed as follows:
11000 @{<no data fields>@}
11003 @kindex show opaque-type-resolution
11004 @item show opaque-type-resolution
11005 Show whether opaque types are resolved or not.
11007 @kindex maint print symbols
11008 @cindex symbol dump
11009 @kindex maint print psymbols
11010 @cindex partial symbol dump
11011 @item maint print symbols @var{filename}
11012 @itemx maint print psymbols @var{filename}
11013 @itemx maint print msymbols @var{filename}
11014 Write a dump of debugging symbol data into the file @var{filename}.
11015 These commands are used to debug the @value{GDBN} symbol-reading code. Only
11016 symbols with debugging data are included. If you use @samp{maint print
11017 symbols}, @value{GDBN} includes all the symbols for which it has already
11018 collected full details: that is, @var{filename} reflects symbols for
11019 only those files whose symbols @value{GDBN} has read. You can use the
11020 command @code{info sources} to find out which files these are. If you
11021 use @samp{maint print psymbols} instead, the dump shows information about
11022 symbols that @value{GDBN} only knows partially---that is, symbols defined in
11023 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
11024 @samp{maint print msymbols} dumps just the minimal symbol information
11025 required for each object file from which @value{GDBN} has read some symbols.
11026 @xref{Files, ,Commands to Specify Files}, for a discussion of how
11027 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
11029 @kindex maint info symtabs
11030 @kindex maint info psymtabs
11031 @cindex listing @value{GDBN}'s internal symbol tables
11032 @cindex symbol tables, listing @value{GDBN}'s internal
11033 @cindex full symbol tables, listing @value{GDBN}'s internal
11034 @cindex partial symbol tables, listing @value{GDBN}'s internal
11035 @item maint info symtabs @r{[} @var{regexp} @r{]}
11036 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
11038 List the @code{struct symtab} or @code{struct partial_symtab}
11039 structures whose names match @var{regexp}. If @var{regexp} is not
11040 given, list them all. The output includes expressions which you can
11041 copy into a @value{GDBN} debugging this one to examine a particular
11042 structure in more detail. For example:
11045 (@value{GDBP}) maint info psymtabs dwarf2read
11046 @{ objfile /home/gnu/build/gdb/gdb
11047 ((struct objfile *) 0x82e69d0)
11048 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
11049 ((struct partial_symtab *) 0x8474b10)
11052 text addresses 0x814d3c8 -- 0x8158074
11053 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
11054 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
11055 dependencies (none)
11058 (@value{GDBP}) maint info symtabs
11062 We see that there is one partial symbol table whose filename contains
11063 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
11064 and we see that @value{GDBN} has not read in any symtabs yet at all.
11065 If we set a breakpoint on a function, that will cause @value{GDBN} to
11066 read the symtab for the compilation unit containing that function:
11069 (@value{GDBP}) break dwarf2_psymtab_to_symtab
11070 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
11072 (@value{GDBP}) maint info symtabs
11073 @{ objfile /home/gnu/build/gdb/gdb
11074 ((struct objfile *) 0x82e69d0)
11075 @{ symtab /home/gnu/src/gdb/dwarf2read.c
11076 ((struct symtab *) 0x86c1f38)
11079 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
11080 debugformat DWARF 2
11089 @chapter Altering Execution
11091 Once you think you have found an error in your program, you might want to
11092 find out for certain whether correcting the apparent error would lead to
11093 correct results in the rest of the run. You can find the answer by
11094 experiment, using the @value{GDBN} features for altering execution of the
11097 For example, you can store new values into variables or memory
11098 locations, give your program a signal, restart it at a different
11099 address, or even return prematurely from a function.
11102 * Assignment:: Assignment to variables
11103 * Jumping:: Continuing at a different address
11104 * Signaling:: Giving your program a signal
11105 * Returning:: Returning from a function
11106 * Calling:: Calling your program's functions
11107 * Patching:: Patching your program
11111 @section Assignment to Variables
11114 @cindex setting variables
11115 To alter the value of a variable, evaluate an assignment expression.
11116 @xref{Expressions, ,Expressions}. For example,
11123 stores the value 4 into the variable @code{x}, and then prints the
11124 value of the assignment expression (which is 4).
11125 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
11126 information on operators in supported languages.
11128 @kindex set variable
11129 @cindex variables, setting
11130 If you are not interested in seeing the value of the assignment, use the
11131 @code{set} command instead of the @code{print} command. @code{set} is
11132 really the same as @code{print} except that the expression's value is
11133 not printed and is not put in the value history (@pxref{Value History,
11134 ,Value History}). The expression is evaluated only for its effects.
11136 If the beginning of the argument string of the @code{set} command
11137 appears identical to a @code{set} subcommand, use the @code{set
11138 variable} command instead of just @code{set}. This command is identical
11139 to @code{set} except for its lack of subcommands. For example, if your
11140 program has a variable @code{width}, you get an error if you try to set
11141 a new value with just @samp{set width=13}, because @value{GDBN} has the
11142 command @code{set width}:
11145 (@value{GDBP}) whatis width
11147 (@value{GDBP}) p width
11149 (@value{GDBP}) set width=47
11150 Invalid syntax in expression.
11154 The invalid expression, of course, is @samp{=47}. In
11155 order to actually set the program's variable @code{width}, use
11158 (@value{GDBP}) set var width=47
11161 Because the @code{set} command has many subcommands that can conflict
11162 with the names of program variables, it is a good idea to use the
11163 @code{set variable} command instead of just @code{set}. For example, if
11164 your program has a variable @code{g}, you run into problems if you try
11165 to set a new value with just @samp{set g=4}, because @value{GDBN} has
11166 the command @code{set gnutarget}, abbreviated @code{set g}:
11170 (@value{GDBP}) whatis g
11174 (@value{GDBP}) set g=4
11178 The program being debugged has been started already.
11179 Start it from the beginning? (y or n) y
11180 Starting program: /home/smith/cc_progs/a.out
11181 "/home/smith/cc_progs/a.out": can't open to read symbols:
11182 Invalid bfd target.
11183 (@value{GDBP}) show g
11184 The current BFD target is "=4".
11189 The program variable @code{g} did not change, and you silently set the
11190 @code{gnutarget} to an invalid value. In order to set the variable
11194 (@value{GDBP}) set var g=4
11197 @value{GDBN} allows more implicit conversions in assignments than C; you can
11198 freely store an integer value into a pointer variable or vice versa,
11199 and you can convert any structure to any other structure that is the
11200 same length or shorter.
11201 @comment FIXME: how do structs align/pad in these conversions?
11202 @comment /doc@cygnus.com 18dec1990
11204 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
11205 construct to generate a value of specified type at a specified address
11206 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
11207 to memory location @code{0x83040} as an integer (which implies a certain size
11208 and representation in memory), and
11211 set @{int@}0x83040 = 4
11215 stores the value 4 into that memory location.
11218 @section Continuing at a Different Address
11220 Ordinarily, when you continue your program, you do so at the place where
11221 it stopped, with the @code{continue} command. You can instead continue at
11222 an address of your own choosing, with the following commands:
11226 @item jump @var{linespec}
11227 Resume execution at line @var{linespec}. Execution stops again
11228 immediately if there is a breakpoint there. @xref{List, ,Printing
11229 Source Lines}, for a description of the different forms of
11230 @var{linespec}. It is common practice to use the @code{tbreak} command
11231 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
11234 The @code{jump} command does not change the current stack frame, or
11235 the stack pointer, or the contents of any memory location or any
11236 register other than the program counter. If line @var{linespec} is in
11237 a different function from the one currently executing, the results may
11238 be bizarre if the two functions expect different patterns of arguments or
11239 of local variables. For this reason, the @code{jump} command requests
11240 confirmation if the specified line is not in the function currently
11241 executing. However, even bizarre results are predictable if you are
11242 well acquainted with the machine-language code of your program.
11244 @item jump *@var{address}
11245 Resume execution at the instruction at address @var{address}.
11248 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
11249 On many systems, you can get much the same effect as the @code{jump}
11250 command by storing a new value into the register @code{$pc}. The
11251 difference is that this does not start your program running; it only
11252 changes the address of where it @emph{will} run when you continue. For
11260 makes the next @code{continue} command or stepping command execute at
11261 address @code{0x485}, rather than at the address where your program stopped.
11262 @xref{Continuing and Stepping, ,Continuing and Stepping}.
11264 The most common occasion to use the @code{jump} command is to back
11265 up---perhaps with more breakpoints set---over a portion of a program
11266 that has already executed, in order to examine its execution in more
11271 @section Giving your Program a Signal
11272 @cindex deliver a signal to a program
11276 @item signal @var{signal}
11277 Resume execution where your program stopped, but immediately give it the
11278 signal @var{signal}. @var{signal} can be the name or the number of a
11279 signal. For example, on many systems @code{signal 2} and @code{signal
11280 SIGINT} are both ways of sending an interrupt signal.
11282 Alternatively, if @var{signal} is zero, continue execution without
11283 giving a signal. This is useful when your program stopped on account of
11284 a signal and would ordinary see the signal when resumed with the
11285 @code{continue} command; @samp{signal 0} causes it to resume without a
11288 @code{signal} does not repeat when you press @key{RET} a second time
11289 after executing the command.
11293 Invoking the @code{signal} command is not the same as invoking the
11294 @code{kill} utility from the shell. Sending a signal with @code{kill}
11295 causes @value{GDBN} to decide what to do with the signal depending on
11296 the signal handling tables (@pxref{Signals}). The @code{signal} command
11297 passes the signal directly to your program.
11301 @section Returning from a Function
11304 @cindex returning from a function
11307 @itemx return @var{expression}
11308 You can cancel execution of a function call with the @code{return}
11309 command. If you give an
11310 @var{expression} argument, its value is used as the function's return
11314 When you use @code{return}, @value{GDBN} discards the selected stack frame
11315 (and all frames within it). You can think of this as making the
11316 discarded frame return prematurely. If you wish to specify a value to
11317 be returned, give that value as the argument to @code{return}.
11319 This pops the selected stack frame (@pxref{Selection, ,Selecting a
11320 Frame}), and any other frames inside of it, leaving its caller as the
11321 innermost remaining frame. That frame becomes selected. The
11322 specified value is stored in the registers used for returning values
11325 The @code{return} command does not resume execution; it leaves the
11326 program stopped in the state that would exist if the function had just
11327 returned. In contrast, the @code{finish} command (@pxref{Continuing
11328 and Stepping, ,Continuing and Stepping}) resumes execution until the
11329 selected stack frame returns naturally.
11332 @section Calling Program Functions
11335 @cindex calling functions
11336 @cindex inferior functions, calling
11337 @item print @var{expr}
11338 Evaluate the expression @var{expr} and display the resulting value.
11339 @var{expr} may include calls to functions in the program being
11343 @item call @var{expr}
11344 Evaluate the expression @var{expr} without displaying @code{void}
11347 You can use this variant of the @code{print} command if you want to
11348 execute a function from your program that does not return anything
11349 (a.k.a.@: @dfn{a void function}), but without cluttering the output
11350 with @code{void} returned values that @value{GDBN} will otherwise
11351 print. If the result is not void, it is printed and saved in the
11355 It is possible for the function you call via the @code{print} or
11356 @code{call} command to generate a signal (e.g., if there's a bug in
11357 the function, or if you passed it incorrect arguments). What happens
11358 in that case is controlled by the @code{set unwindonsignal} command.
11361 @item set unwindonsignal
11362 @kindex set unwindonsignal
11363 @cindex unwind stack in called functions
11364 @cindex call dummy stack unwinding
11365 Set unwinding of the stack if a signal is received while in a function
11366 that @value{GDBN} called in the program being debugged. If set to on,
11367 @value{GDBN} unwinds the stack it created for the call and restores
11368 the context to what it was before the call. If set to off (the
11369 default), @value{GDBN} stops in the frame where the signal was
11372 @item show unwindonsignal
11373 @kindex show unwindonsignal
11374 Show the current setting of stack unwinding in the functions called by
11378 @cindex weak alias functions
11379 Sometimes, a function you wish to call is actually a @dfn{weak alias}
11380 for another function. In such case, @value{GDBN} might not pick up
11381 the type information, including the types of the function arguments,
11382 which causes @value{GDBN} to call the inferior function incorrectly.
11383 As a result, the called function will function erroneously and may
11384 even crash. A solution to that is to use the name of the aliased
11388 @section Patching Programs
11390 @cindex patching binaries
11391 @cindex writing into executables
11392 @cindex writing into corefiles
11394 By default, @value{GDBN} opens the file containing your program's
11395 executable code (or the corefile) read-only. This prevents accidental
11396 alterations to machine code; but it also prevents you from intentionally
11397 patching your program's binary.
11399 If you'd like to be able to patch the binary, you can specify that
11400 explicitly with the @code{set write} command. For example, you might
11401 want to turn on internal debugging flags, or even to make emergency
11407 @itemx set write off
11408 If you specify @samp{set write on}, @value{GDBN} opens executable and
11409 core files for both reading and writing; if you specify @samp{set write
11410 off} (the default), @value{GDBN} opens them read-only.
11412 If you have already loaded a file, you must load it again (using the
11413 @code{exec-file} or @code{core-file} command) after changing @code{set
11414 write}, for your new setting to take effect.
11418 Display whether executable files and core files are opened for writing
11419 as well as reading.
11423 @chapter @value{GDBN} Files
11425 @value{GDBN} needs to know the file name of the program to be debugged,
11426 both in order to read its symbol table and in order to start your
11427 program. To debug a core dump of a previous run, you must also tell
11428 @value{GDBN} the name of the core dump file.
11431 * Files:: Commands to specify files
11432 * Separate Debug Files:: Debugging information in separate files
11433 * Symbol Errors:: Errors reading symbol files
11437 @section Commands to Specify Files
11439 @cindex symbol table
11440 @cindex core dump file
11442 You may want to specify executable and core dump file names. The usual
11443 way to do this is at start-up time, using the arguments to
11444 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
11445 Out of @value{GDBN}}).
11447 Occasionally it is necessary to change to a different file during a
11448 @value{GDBN} session. Or you may run @value{GDBN} and forget to
11449 specify a file you want to use. Or you are debugging a remote target
11450 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
11451 Program}). In these situations the @value{GDBN} commands to specify
11452 new files are useful.
11455 @cindex executable file
11457 @item file @var{filename}
11458 Use @var{filename} as the program to be debugged. It is read for its
11459 symbols and for the contents of pure memory. It is also the program
11460 executed when you use the @code{run} command. If you do not specify a
11461 directory and the file is not found in the @value{GDBN} working directory,
11462 @value{GDBN} uses the environment variable @code{PATH} as a list of
11463 directories to search, just as the shell does when looking for a program
11464 to run. You can change the value of this variable, for both @value{GDBN}
11465 and your program, using the @code{path} command.
11467 @cindex unlinked object files
11468 @cindex patching object files
11469 You can load unlinked object @file{.o} files into @value{GDBN} using
11470 the @code{file} command. You will not be able to ``run'' an object
11471 file, but you can disassemble functions and inspect variables. Also,
11472 if the underlying BFD functionality supports it, you could use
11473 @kbd{gdb -write} to patch object files using this technique. Note
11474 that @value{GDBN} can neither interpret nor modify relocations in this
11475 case, so branches and some initialized variables will appear to go to
11476 the wrong place. But this feature is still handy from time to time.
11479 @code{file} with no argument makes @value{GDBN} discard any information it
11480 has on both executable file and the symbol table.
11483 @item exec-file @r{[} @var{filename} @r{]}
11484 Specify that the program to be run (but not the symbol table) is found
11485 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
11486 if necessary to locate your program. Omitting @var{filename} means to
11487 discard information on the executable file.
11489 @kindex symbol-file
11490 @item symbol-file @r{[} @var{filename} @r{]}
11491 Read symbol table information from file @var{filename}. @code{PATH} is
11492 searched when necessary. Use the @code{file} command to get both symbol
11493 table and program to run from the same file.
11495 @code{symbol-file} with no argument clears out @value{GDBN} information on your
11496 program's symbol table.
11498 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
11499 some breakpoints and auto-display expressions. This is because they may
11500 contain pointers to the internal data recording symbols and data types,
11501 which are part of the old symbol table data being discarded inside
11504 @code{symbol-file} does not repeat if you press @key{RET} again after
11507 When @value{GDBN} is configured for a particular environment, it
11508 understands debugging information in whatever format is the standard
11509 generated for that environment; you may use either a @sc{gnu} compiler, or
11510 other compilers that adhere to the local conventions.
11511 Best results are usually obtained from @sc{gnu} compilers; for example,
11512 using @code{@value{NGCC}} you can generate debugging information for
11515 For most kinds of object files, with the exception of old SVR3 systems
11516 using COFF, the @code{symbol-file} command does not normally read the
11517 symbol table in full right away. Instead, it scans the symbol table
11518 quickly to find which source files and which symbols are present. The
11519 details are read later, one source file at a time, as they are needed.
11521 The purpose of this two-stage reading strategy is to make @value{GDBN}
11522 start up faster. For the most part, it is invisible except for
11523 occasional pauses while the symbol table details for a particular source
11524 file are being read. (The @code{set verbose} command can turn these
11525 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
11526 Warnings and Messages}.)
11528 We have not implemented the two-stage strategy for COFF yet. When the
11529 symbol table is stored in COFF format, @code{symbol-file} reads the
11530 symbol table data in full right away. Note that ``stabs-in-COFF''
11531 still does the two-stage strategy, since the debug info is actually
11535 @cindex reading symbols immediately
11536 @cindex symbols, reading immediately
11537 @item symbol-file @var{filename} @r{[} -readnow @r{]}
11538 @itemx file @var{filename} @r{[} -readnow @r{]}
11539 You can override the @value{GDBN} two-stage strategy for reading symbol
11540 tables by using the @samp{-readnow} option with any of the commands that
11541 load symbol table information, if you want to be sure @value{GDBN} has the
11542 entire symbol table available.
11544 @c FIXME: for now no mention of directories, since this seems to be in
11545 @c flux. 13mar1992 status is that in theory GDB would look either in
11546 @c current dir or in same dir as myprog; but issues like competing
11547 @c GDB's, or clutter in system dirs, mean that in practice right now
11548 @c only current dir is used. FFish says maybe a special GDB hierarchy
11549 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
11553 @item core-file @r{[}@var{filename}@r{]}
11555 Specify the whereabouts of a core dump file to be used as the ``contents
11556 of memory''. Traditionally, core files contain only some parts of the
11557 address space of the process that generated them; @value{GDBN} can access the
11558 executable file itself for other parts.
11560 @code{core-file} with no argument specifies that no core file is
11563 Note that the core file is ignored when your program is actually running
11564 under @value{GDBN}. So, if you have been running your program and you
11565 wish to debug a core file instead, you must kill the subprocess in which
11566 the program is running. To do this, use the @code{kill} command
11567 (@pxref{Kill Process, ,Killing the Child Process}).
11569 @kindex add-symbol-file
11570 @cindex dynamic linking
11571 @item add-symbol-file @var{filename} @var{address}
11572 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
11573 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
11574 The @code{add-symbol-file} command reads additional symbol table
11575 information from the file @var{filename}. You would use this command
11576 when @var{filename} has been dynamically loaded (by some other means)
11577 into the program that is running. @var{address} should be the memory
11578 address at which the file has been loaded; @value{GDBN} cannot figure
11579 this out for itself. You can additionally specify an arbitrary number
11580 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
11581 section name and base address for that section. You can specify any
11582 @var{address} as an expression.
11584 The symbol table of the file @var{filename} is added to the symbol table
11585 originally read with the @code{symbol-file} command. You can use the
11586 @code{add-symbol-file} command any number of times; the new symbol data
11587 thus read keeps adding to the old. To discard all old symbol data
11588 instead, use the @code{symbol-file} command without any arguments.
11590 @cindex relocatable object files, reading symbols from
11591 @cindex object files, relocatable, reading symbols from
11592 @cindex reading symbols from relocatable object files
11593 @cindex symbols, reading from relocatable object files
11594 @cindex @file{.o} files, reading symbols from
11595 Although @var{filename} is typically a shared library file, an
11596 executable file, or some other object file which has been fully
11597 relocated for loading into a process, you can also load symbolic
11598 information from relocatable @file{.o} files, as long as:
11602 the file's symbolic information refers only to linker symbols defined in
11603 that file, not to symbols defined by other object files,
11605 every section the file's symbolic information refers to has actually
11606 been loaded into the inferior, as it appears in the file, and
11608 you can determine the address at which every section was loaded, and
11609 provide these to the @code{add-symbol-file} command.
11613 Some embedded operating systems, like Sun Chorus and VxWorks, can load
11614 relocatable files into an already running program; such systems
11615 typically make the requirements above easy to meet. However, it's
11616 important to recognize that many native systems use complex link
11617 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
11618 assembly, for example) that make the requirements difficult to meet. In
11619 general, one cannot assume that using @code{add-symbol-file} to read a
11620 relocatable object file's symbolic information will have the same effect
11621 as linking the relocatable object file into the program in the normal
11624 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
11626 @kindex add-symbol-file-from-memory
11627 @cindex @code{syscall DSO}
11628 @cindex load symbols from memory
11629 @item add-symbol-file-from-memory @var{address}
11630 Load symbols from the given @var{address} in a dynamically loaded
11631 object file whose image is mapped directly into the inferior's memory.
11632 For example, the Linux kernel maps a @code{syscall DSO} into each
11633 process's address space; this DSO provides kernel-specific code for
11634 some system calls. The argument can be any expression whose
11635 evaluation yields the address of the file's shared object file header.
11636 For this command to work, you must have used @code{symbol-file} or
11637 @code{exec-file} commands in advance.
11639 @kindex add-shared-symbol-files
11641 @item add-shared-symbol-files @var{library-file}
11642 @itemx assf @var{library-file}
11643 The @code{add-shared-symbol-files} command can currently be used only
11644 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
11645 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
11646 @value{GDBN} automatically looks for shared libraries, however if
11647 @value{GDBN} does not find yours, you can invoke
11648 @code{add-shared-symbol-files}. It takes one argument: the shared
11649 library's file name. @code{assf} is a shorthand alias for
11650 @code{add-shared-symbol-files}.
11653 @item section @var{section} @var{addr}
11654 The @code{section} command changes the base address of the named
11655 @var{section} of the exec file to @var{addr}. This can be used if the
11656 exec file does not contain section addresses, (such as in the
11657 @code{a.out} format), or when the addresses specified in the file
11658 itself are wrong. Each section must be changed separately. The
11659 @code{info files} command, described below, lists all the sections and
11663 @kindex info target
11666 @code{info files} and @code{info target} are synonymous; both print the
11667 current target (@pxref{Targets, ,Specifying a Debugging Target}),
11668 including the names of the executable and core dump files currently in
11669 use by @value{GDBN}, and the files from which symbols were loaded. The
11670 command @code{help target} lists all possible targets rather than
11673 @kindex maint info sections
11674 @item maint info sections
11675 Another command that can give you extra information about program sections
11676 is @code{maint info sections}. In addition to the section information
11677 displayed by @code{info files}, this command displays the flags and file
11678 offset of each section in the executable and core dump files. In addition,
11679 @code{maint info sections} provides the following command options (which
11680 may be arbitrarily combined):
11684 Display sections for all loaded object files, including shared libraries.
11685 @item @var{sections}
11686 Display info only for named @var{sections}.
11687 @item @var{section-flags}
11688 Display info only for sections for which @var{section-flags} are true.
11689 The section flags that @value{GDBN} currently knows about are:
11692 Section will have space allocated in the process when loaded.
11693 Set for all sections except those containing debug information.
11695 Section will be loaded from the file into the child process memory.
11696 Set for pre-initialized code and data, clear for @code{.bss} sections.
11698 Section needs to be relocated before loading.
11700 Section cannot be modified by the child process.
11702 Section contains executable code only.
11704 Section contains data only (no executable code).
11706 Section will reside in ROM.
11708 Section contains data for constructor/destructor lists.
11710 Section is not empty.
11712 An instruction to the linker to not output the section.
11713 @item COFF_SHARED_LIBRARY
11714 A notification to the linker that the section contains
11715 COFF shared library information.
11717 Section contains common symbols.
11720 @kindex set trust-readonly-sections
11721 @cindex read-only sections
11722 @item set trust-readonly-sections on
11723 Tell @value{GDBN} that readonly sections in your object file
11724 really are read-only (i.e.@: that their contents will not change).
11725 In that case, @value{GDBN} can fetch values from these sections
11726 out of the object file, rather than from the target program.
11727 For some targets (notably embedded ones), this can be a significant
11728 enhancement to debugging performance.
11730 The default is off.
11732 @item set trust-readonly-sections off
11733 Tell @value{GDBN} not to trust readonly sections. This means that
11734 the contents of the section might change while the program is running,
11735 and must therefore be fetched from the target when needed.
11737 @item show trust-readonly-sections
11738 Show the current setting of trusting readonly sections.
11741 All file-specifying commands allow both absolute and relative file names
11742 as arguments. @value{GDBN} always converts the file name to an absolute file
11743 name and remembers it that way.
11745 @cindex shared libraries
11746 @value{GDBN} supports GNU/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
11747 and IBM RS/6000 AIX shared libraries.
11749 @value{GDBN} automatically loads symbol definitions from shared libraries
11750 when you use the @code{run} command, or when you examine a core file.
11751 (Before you issue the @code{run} command, @value{GDBN} does not understand
11752 references to a function in a shared library, however---unless you are
11753 debugging a core file).
11755 On HP-UX, if the program loads a library explicitly, @value{GDBN}
11756 automatically loads the symbols at the time of the @code{shl_load} call.
11758 @c FIXME: some @value{GDBN} release may permit some refs to undef
11759 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
11760 @c FIXME...lib; check this from time to time when updating manual
11762 There are times, however, when you may wish to not automatically load
11763 symbol definitions from shared libraries, such as when they are
11764 particularly large or there are many of them.
11766 To control the automatic loading of shared library symbols, use the
11770 @kindex set auto-solib-add
11771 @item set auto-solib-add @var{mode}
11772 If @var{mode} is @code{on}, symbols from all shared object libraries
11773 will be loaded automatically when the inferior begins execution, you
11774 attach to an independently started inferior, or when the dynamic linker
11775 informs @value{GDBN} that a new library has been loaded. If @var{mode}
11776 is @code{off}, symbols must be loaded manually, using the
11777 @code{sharedlibrary} command. The default value is @code{on}.
11779 @cindex memory used for symbol tables
11780 If your program uses lots of shared libraries with debug info that
11781 takes large amounts of memory, you can decrease the @value{GDBN}
11782 memory footprint by preventing it from automatically loading the
11783 symbols from shared libraries. To that end, type @kbd{set
11784 auto-solib-add off} before running the inferior, then load each
11785 library whose debug symbols you do need with @kbd{sharedlibrary
11786 @var{regexp}}, where @var{regexp} is a regular expression that matches
11787 the libraries whose symbols you want to be loaded.
11789 @kindex show auto-solib-add
11790 @item show auto-solib-add
11791 Display the current autoloading mode.
11794 @cindex load shared library
11795 To explicitly load shared library symbols, use the @code{sharedlibrary}
11799 @kindex info sharedlibrary
11802 @itemx info sharedlibrary
11803 Print the names of the shared libraries which are currently loaded.
11805 @kindex sharedlibrary
11807 @item sharedlibrary @var{regex}
11808 @itemx share @var{regex}
11809 Load shared object library symbols for files matching a
11810 Unix regular expression.
11811 As with files loaded automatically, it only loads shared libraries
11812 required by your program for a core file or after typing @code{run}. If
11813 @var{regex} is omitted all shared libraries required by your program are
11816 @item nosharedlibrary
11817 @kindex nosharedlibrary
11818 @cindex unload symbols from shared libraries
11819 Unload all shared object library symbols. This discards all symbols
11820 that have been loaded from all shared libraries. Symbols from shared
11821 libraries that were loaded by explicit user requests are not
11825 Sometimes you may wish that @value{GDBN} stops and gives you control
11826 when any of shared library events happen. Use the @code{set
11827 stop-on-solib-events} command for this:
11830 @item set stop-on-solib-events
11831 @kindex set stop-on-solib-events
11832 This command controls whether @value{GDBN} should give you control
11833 when the dynamic linker notifies it about some shared library event.
11834 The most common event of interest is loading or unloading of a new
11837 @item show stop-on-solib-events
11838 @kindex show stop-on-solib-events
11839 Show whether @value{GDBN} stops and gives you control when shared
11840 library events happen.
11843 Shared libraries are also supported in many cross or remote debugging
11844 configurations. A copy of the target's libraries need to be present on the
11845 host system; they need to be the same as the target libraries, although the
11846 copies on the target can be stripped as long as the copies on the host are
11849 @cindex where to look for shared libraries
11850 For remote debugging, you need to tell @value{GDBN} where the target
11851 libraries are, so that it can load the correct copies---otherwise, it
11852 may try to load the host's libraries. @value{GDBN} has two variables
11853 to specify the search directories for target libraries.
11856 @cindex prefix for shared library file names
11857 @cindex system root, alternate
11858 @kindex set solib-absolute-prefix
11859 @kindex set sysroot
11860 @item set sysroot @var{path}
11861 Use @var{path} as the system root for the program being debugged. Any
11862 absolute shared library paths will be prefixed with @var{path}; many
11863 runtime loaders store the absolute paths to the shared library in the
11864 target program's memory. If you use @code{set sysroot} to find shared
11865 libraries, they need to be laid out in the same way that they are on
11866 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
11869 The @code{set solib-absolute-prefix} command is an alias for @code{set
11872 @cindex default system root
11873 @cindex @samp{--with-sysroot}
11874 You can set the default system root by using the configure-time
11875 @samp{--with-sysroot} option. If the system root is inside
11876 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
11877 @samp{--exec-prefix}), then the default system root will be updated
11878 automatically if the installed @value{GDBN} is moved to a new
11881 @kindex show sysroot
11883 Display the current shared library prefix.
11885 @kindex set solib-search-path
11886 @item set solib-search-path @var{path}
11887 If this variable is set, @var{path} is a colon-separated list of
11888 directories to search for shared libraries. @samp{solib-search-path}
11889 is used after @samp{sysroot} fails to locate the library, or if the
11890 path to the library is relative instead of absolute. If you want to
11891 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
11892 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
11893 finding your host's libraries. @samp{sysroot} is preferred; setting
11894 it to a nonexistent directory may interfere with automatic loading
11895 of shared library symbols.
11897 @kindex show solib-search-path
11898 @item show solib-search-path
11899 Display the current shared library search path.
11903 @node Separate Debug Files
11904 @section Debugging Information in Separate Files
11905 @cindex separate debugging information files
11906 @cindex debugging information in separate files
11907 @cindex @file{.debug} subdirectories
11908 @cindex debugging information directory, global
11909 @cindex global debugging information directory
11910 @cindex build ID, and separate debugging files
11911 @cindex @file{.build-id} directory
11913 @value{GDBN} allows you to put a program's debugging information in a
11914 file separate from the executable itself, in a way that allows
11915 @value{GDBN} to find and load the debugging information automatically.
11916 Since debugging information can be very large---sometimes larger
11917 than the executable code itself---some systems distribute debugging
11918 information for their executables in separate files, which users can
11919 install only when they need to debug a problem.
11921 @value{GDBN} supports two ways of specifying the separate debug info
11926 The executable contains a @dfn{debug link} that specifies the name of
11927 the separate debug info file. The separate debug file's name is
11928 usually @file{@var{executable}.debug}, where @var{executable} is the
11929 name of the corresponding executable file without leading directories
11930 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
11931 debug link specifies a CRC32 checksum for the debug file, which
11932 @value{GDBN} uses to validate that the executable and the debug file
11933 came from the same build.
11936 The executable contains a @dfn{build ID}, a unique signature that is
11937 also present in the corresponding debug info file. (This is supported
11938 only on some operating systems, notably on @sc{gnu}/Linux. For more
11939 details about this feature, see
11940 @uref{http://fedoraproject.org/wiki/Releases/FeatureBuildId, the
11941 Fedora Project's description of the buid ID feature}.) The debug info
11942 file's name is not specified explicitly by the build ID, but can be
11943 computed from the build ID, see below.
11946 Depending on the way the debug info file is specified, @value{GDBN}
11947 uses two different methods of looking for the debug file:
11951 For the ``debug link'' method, @value{GDBN} looks up the named file in
11952 the directory of the executable file, then in a subdirectory of that
11953 directory named @file{.debug}, and finally under the global debug
11954 directory, in a subdirectory whose name is identical to the leading
11955 directories of the executable's absolute file name.
11958 For the ``build ID'' method, @value{GDBN} looks in the
11959 @file{.build-id} subdirectory of the global debug directory for a file
11960 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
11961 first 2 hex characters of the build ID signature, and @var{nnnnnnnn}
11962 are the rest of the signature. (Real signatures are 32 or more
11963 characters, not 10.)
11966 So, for example, suppose you ask @value{GDBN} to debug
11967 @file{/usr/bin/ls}, which has a @dfn{debug link} that specifies the
11968 file @file{ls.debug}, and a @dfn{build id} whose value in hex is
11969 @code{abcdef1234}. If the global debug directory is
11970 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
11971 debug information files, in the indicated order:
11975 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
11977 @file{/usr/bin/ls.debug}
11979 @file{/usr/bin/.debug/ls.debug}
11981 @file{/usr/lib/debug/usr/bin/ls.debug}.
11984 You can set the global debugging info directory's name, and view the
11985 name @value{GDBN} is currently using.
11989 @kindex set debug-file-directory
11990 @item set debug-file-directory @var{directory}
11991 Set the directory which @value{GDBN} searches for separate debugging
11992 information files to @var{directory}.
11994 @kindex show debug-file-directory
11995 @item show debug-file-directory
11996 Show the directory @value{GDBN} searches for separate debugging
12001 @cindex @code{.gnu_debuglink} sections
12002 @cindex debug link sections
12003 A debug link is a special section of the executable file named
12004 @code{.gnu_debuglink}. The section must contain:
12008 A filename, with any leading directory components removed, followed by
12011 zero to three bytes of padding, as needed to reach the next four-byte
12012 boundary within the section, and
12014 a four-byte CRC checksum, stored in the same endianness used for the
12015 executable file itself. The checksum is computed on the debugging
12016 information file's full contents by the function given below, passing
12017 zero as the @var{crc} argument.
12020 Any executable file format can carry a debug link, as long as it can
12021 contain a section named @code{.gnu_debuglink} with the contents
12024 @cindex @code{.note.gnu.build-id} sections
12025 @cindex build ID sections
12026 A build ID is a special section of the executable file named
12027 @code{.note.gnu.build-id}. This section contains unique
12028 identification for the built files---it remains the same across
12029 multiple builds of the same build tree. The default algorithm SHA1
12030 produces 160 bits (40 hexadecimal characters) of the content. The
12031 same section with an identical value is present in the original built
12032 binary with symbols, in its stripped variant, and in the separate
12033 debugging information file.
12035 The debugging information file itself should be an ordinary
12036 executable, containing a full set of linker symbols, sections, and
12037 debugging information. The sections of the debugging information file
12038 should have the same names, addresses, and sizes as the original file,
12039 but they need not contain any data---much like a @code{.bss} section
12040 in an ordinary executable.
12042 @sc{gnu} binary utilities (Binutils) package includes the
12043 @samp{objcopy} utility that can produce
12044 the separated executable / debugging information file pairs using the
12045 following commands:
12048 @kbd{objcopy --only-keep-debug foo foo.debug}
12053 These commands remove the debugging
12054 information from the executable file @file{foo} and place it in the file
12055 @file{foo.debug}. You can use the first, second or both methods to link the
12060 The debug link method needs the following additional command to also leave
12061 behind a debug link in @file{foo}:
12064 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
12067 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
12068 a version of the @code{strip} command such that the command @kbd{strip foo -f
12069 foo.debug} has the same functionality as the two @code{objcopy} commands and
12070 the @code{ln -s} command above, together.
12073 Build ID gets embedded into the main executable using @code{ld --build-id} or
12074 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
12075 compatibility fixes for debug files separation are present in @sc{gnu} binary
12076 utilities (Binutils) since version 2.18.
12081 Since there are many different ways to compute CRC's for the debug
12082 link (different polynomials, reversals, byte ordering, etc.), the
12083 simplest way to describe the CRC used in @code{.gnu_debuglink}
12084 sections is to give the complete code for a function that computes it:
12086 @kindex gnu_debuglink_crc32
12089 gnu_debuglink_crc32 (unsigned long crc,
12090 unsigned char *buf, size_t len)
12092 static const unsigned long crc32_table[256] =
12094 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
12095 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
12096 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
12097 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
12098 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
12099 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
12100 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
12101 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
12102 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
12103 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
12104 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
12105 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
12106 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
12107 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
12108 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
12109 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
12110 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
12111 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
12112 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
12113 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
12114 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
12115 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
12116 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
12117 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
12118 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
12119 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
12120 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
12121 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
12122 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
12123 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
12124 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
12125 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
12126 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
12127 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
12128 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
12129 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
12130 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
12131 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
12132 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
12133 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
12134 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
12135 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
12136 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
12137 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
12138 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
12139 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
12140 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
12141 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
12142 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
12143 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
12144 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
12147 unsigned char *end;
12149 crc = ~crc & 0xffffffff;
12150 for (end = buf + len; buf < end; ++buf)
12151 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
12152 return ~crc & 0xffffffff;
12157 This computation does not apply to the ``build ID'' method.
12160 @node Symbol Errors
12161 @section Errors Reading Symbol Files
12163 While reading a symbol file, @value{GDBN} occasionally encounters problems,
12164 such as symbol types it does not recognize, or known bugs in compiler
12165 output. By default, @value{GDBN} does not notify you of such problems, since
12166 they are relatively common and primarily of interest to people
12167 debugging compilers. If you are interested in seeing information
12168 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
12169 only one message about each such type of problem, no matter how many
12170 times the problem occurs; or you can ask @value{GDBN} to print more messages,
12171 to see how many times the problems occur, with the @code{set
12172 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
12175 The messages currently printed, and their meanings, include:
12178 @item inner block not inside outer block in @var{symbol}
12180 The symbol information shows where symbol scopes begin and end
12181 (such as at the start of a function or a block of statements). This
12182 error indicates that an inner scope block is not fully contained
12183 in its outer scope blocks.
12185 @value{GDBN} circumvents the problem by treating the inner block as if it had
12186 the same scope as the outer block. In the error message, @var{symbol}
12187 may be shown as ``@code{(don't know)}'' if the outer block is not a
12190 @item block at @var{address} out of order
12192 The symbol information for symbol scope blocks should occur in
12193 order of increasing addresses. This error indicates that it does not
12196 @value{GDBN} does not circumvent this problem, and has trouble
12197 locating symbols in the source file whose symbols it is reading. (You
12198 can often determine what source file is affected by specifying
12199 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
12202 @item bad block start address patched
12204 The symbol information for a symbol scope block has a start address
12205 smaller than the address of the preceding source line. This is known
12206 to occur in the SunOS 4.1.1 (and earlier) C compiler.
12208 @value{GDBN} circumvents the problem by treating the symbol scope block as
12209 starting on the previous source line.
12211 @item bad string table offset in symbol @var{n}
12214 Symbol number @var{n} contains a pointer into the string table which is
12215 larger than the size of the string table.
12217 @value{GDBN} circumvents the problem by considering the symbol to have the
12218 name @code{foo}, which may cause other problems if many symbols end up
12221 @item unknown symbol type @code{0x@var{nn}}
12223 The symbol information contains new data types that @value{GDBN} does
12224 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
12225 uncomprehended information, in hexadecimal.
12227 @value{GDBN} circumvents the error by ignoring this symbol information.
12228 This usually allows you to debug your program, though certain symbols
12229 are not accessible. If you encounter such a problem and feel like
12230 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
12231 on @code{complain}, then go up to the function @code{read_dbx_symtab}
12232 and examine @code{*bufp} to see the symbol.
12234 @item stub type has NULL name
12236 @value{GDBN} could not find the full definition for a struct or class.
12238 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
12239 The symbol information for a C@t{++} member function is missing some
12240 information that recent versions of the compiler should have output for
12243 @item info mismatch between compiler and debugger
12245 @value{GDBN} could not parse a type specification output by the compiler.
12250 @chapter Specifying a Debugging Target
12252 @cindex debugging target
12253 A @dfn{target} is the execution environment occupied by your program.
12255 Often, @value{GDBN} runs in the same host environment as your program;
12256 in that case, the debugging target is specified as a side effect when
12257 you use the @code{file} or @code{core} commands. When you need more
12258 flexibility---for example, running @value{GDBN} on a physically separate
12259 host, or controlling a standalone system over a serial port or a
12260 realtime system over a TCP/IP connection---you can use the @code{target}
12261 command to specify one of the target types configured for @value{GDBN}
12262 (@pxref{Target Commands, ,Commands for Managing Targets}).
12264 @cindex target architecture
12265 It is possible to build @value{GDBN} for several different @dfn{target
12266 architectures}. When @value{GDBN} is built like that, you can choose
12267 one of the available architectures with the @kbd{set architecture}
12271 @kindex set architecture
12272 @kindex show architecture
12273 @item set architecture @var{arch}
12274 This command sets the current target architecture to @var{arch}. The
12275 value of @var{arch} can be @code{"auto"}, in addition to one of the
12276 supported architectures.
12278 @item show architecture
12279 Show the current target architecture.
12281 @item set processor
12283 @kindex set processor
12284 @kindex show processor
12285 These are alias commands for, respectively, @code{set architecture}
12286 and @code{show architecture}.
12290 * Active Targets:: Active targets
12291 * Target Commands:: Commands for managing targets
12292 * Byte Order:: Choosing target byte order
12295 @node Active Targets
12296 @section Active Targets
12298 @cindex stacking targets
12299 @cindex active targets
12300 @cindex multiple targets
12302 There are three classes of targets: processes, core files, and
12303 executable files. @value{GDBN} can work concurrently on up to three
12304 active targets, one in each class. This allows you to (for example)
12305 start a process and inspect its activity without abandoning your work on
12308 For example, if you execute @samp{gdb a.out}, then the executable file
12309 @code{a.out} is the only active target. If you designate a core file as
12310 well---presumably from a prior run that crashed and coredumped---then
12311 @value{GDBN} has two active targets and uses them in tandem, looking
12312 first in the corefile target, then in the executable file, to satisfy
12313 requests for memory addresses. (Typically, these two classes of target
12314 are complementary, since core files contain only a program's
12315 read-write memory---variables and so on---plus machine status, while
12316 executable files contain only the program text and initialized data.)
12318 When you type @code{run}, your executable file becomes an active process
12319 target as well. When a process target is active, all @value{GDBN}
12320 commands requesting memory addresses refer to that target; addresses in
12321 an active core file or executable file target are obscured while the
12322 process target is active.
12324 Use the @code{core-file} and @code{exec-file} commands to select a new
12325 core file or executable target (@pxref{Files, ,Commands to Specify
12326 Files}). To specify as a target a process that is already running, use
12327 the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
12330 @node Target Commands
12331 @section Commands for Managing Targets
12334 @item target @var{type} @var{parameters}
12335 Connects the @value{GDBN} host environment to a target machine or
12336 process. A target is typically a protocol for talking to debugging
12337 facilities. You use the argument @var{type} to specify the type or
12338 protocol of the target machine.
12340 Further @var{parameters} are interpreted by the target protocol, but
12341 typically include things like device names or host names to connect
12342 with, process numbers, and baud rates.
12344 The @code{target} command does not repeat if you press @key{RET} again
12345 after executing the command.
12347 @kindex help target
12349 Displays the names of all targets available. To display targets
12350 currently selected, use either @code{info target} or @code{info files}
12351 (@pxref{Files, ,Commands to Specify Files}).
12353 @item help target @var{name}
12354 Describe a particular target, including any parameters necessary to
12357 @kindex set gnutarget
12358 @item set gnutarget @var{args}
12359 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
12360 knows whether it is reading an @dfn{executable},
12361 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
12362 with the @code{set gnutarget} command. Unlike most @code{target} commands,
12363 with @code{gnutarget} the @code{target} refers to a program, not a machine.
12366 @emph{Warning:} To specify a file format with @code{set gnutarget},
12367 you must know the actual BFD name.
12371 @xref{Files, , Commands to Specify Files}.
12373 @kindex show gnutarget
12374 @item show gnutarget
12375 Use the @code{show gnutarget} command to display what file format
12376 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
12377 @value{GDBN} will determine the file format for each file automatically,
12378 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
12381 @cindex common targets
12382 Here are some common targets (available, or not, depending on the GDB
12387 @item target exec @var{program}
12388 @cindex executable file target
12389 An executable file. @samp{target exec @var{program}} is the same as
12390 @samp{exec-file @var{program}}.
12392 @item target core @var{filename}
12393 @cindex core dump file target
12394 A core dump file. @samp{target core @var{filename}} is the same as
12395 @samp{core-file @var{filename}}.
12397 @item target remote @var{medium}
12398 @cindex remote target
12399 A remote system connected to @value{GDBN} via a serial line or network
12400 connection. This command tells @value{GDBN} to use its own remote
12401 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
12403 For example, if you have a board connected to @file{/dev/ttya} on the
12404 machine running @value{GDBN}, you could say:
12407 target remote /dev/ttya
12410 @code{target remote} supports the @code{load} command. This is only
12411 useful if you have some other way of getting the stub to the target
12412 system, and you can put it somewhere in memory where it won't get
12413 clobbered by the download.
12416 @cindex built-in simulator target
12417 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
12425 works; however, you cannot assume that a specific memory map, device
12426 drivers, or even basic I/O is available, although some simulators do
12427 provide these. For info about any processor-specific simulator details,
12428 see the appropriate section in @ref{Embedded Processors, ,Embedded
12433 Some configurations may include these targets as well:
12437 @item target nrom @var{dev}
12438 @cindex NetROM ROM emulator target
12439 NetROM ROM emulator. This target only supports downloading.
12443 Different targets are available on different configurations of @value{GDBN};
12444 your configuration may have more or fewer targets.
12446 Many remote targets require you to download the executable's code once
12447 you've successfully established a connection. You may wish to control
12448 various aspects of this process.
12453 @kindex set hash@r{, for remote monitors}
12454 @cindex hash mark while downloading
12455 This command controls whether a hash mark @samp{#} is displayed while
12456 downloading a file to the remote monitor. If on, a hash mark is
12457 displayed after each S-record is successfully downloaded to the
12461 @kindex show hash@r{, for remote monitors}
12462 Show the current status of displaying the hash mark.
12464 @item set debug monitor
12465 @kindex set debug monitor
12466 @cindex display remote monitor communications
12467 Enable or disable display of communications messages between
12468 @value{GDBN} and the remote monitor.
12470 @item show debug monitor
12471 @kindex show debug monitor
12472 Show the current status of displaying communications between
12473 @value{GDBN} and the remote monitor.
12478 @kindex load @var{filename}
12479 @item load @var{filename}
12480 Depending on what remote debugging facilities are configured into
12481 @value{GDBN}, the @code{load} command may be available. Where it exists, it
12482 is meant to make @var{filename} (an executable) available for debugging
12483 on the remote system---by downloading, or dynamic linking, for example.
12484 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
12485 the @code{add-symbol-file} command.
12487 If your @value{GDBN} does not have a @code{load} command, attempting to
12488 execute it gets the error message ``@code{You can't do that when your
12489 target is @dots{}}''
12491 The file is loaded at whatever address is specified in the executable.
12492 For some object file formats, you can specify the load address when you
12493 link the program; for other formats, like a.out, the object file format
12494 specifies a fixed address.
12495 @c FIXME! This would be a good place for an xref to the GNU linker doc.
12497 Depending on the remote side capabilities, @value{GDBN} may be able to
12498 load programs into flash memory.
12500 @code{load} does not repeat if you press @key{RET} again after using it.
12504 @section Choosing Target Byte Order
12506 @cindex choosing target byte order
12507 @cindex target byte order
12509 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
12510 offer the ability to run either big-endian or little-endian byte
12511 orders. Usually the executable or symbol will include a bit to
12512 designate the endian-ness, and you will not need to worry about
12513 which to use. However, you may still find it useful to adjust
12514 @value{GDBN}'s idea of processor endian-ness manually.
12518 @item set endian big
12519 Instruct @value{GDBN} to assume the target is big-endian.
12521 @item set endian little
12522 Instruct @value{GDBN} to assume the target is little-endian.
12524 @item set endian auto
12525 Instruct @value{GDBN} to use the byte order associated with the
12529 Display @value{GDBN}'s current idea of the target byte order.
12533 Note that these commands merely adjust interpretation of symbolic
12534 data on the host, and that they have absolutely no effect on the
12538 @node Remote Debugging
12539 @chapter Debugging Remote Programs
12540 @cindex remote debugging
12542 If you are trying to debug a program running on a machine that cannot run
12543 @value{GDBN} in the usual way, it is often useful to use remote debugging.
12544 For example, you might use remote debugging on an operating system kernel,
12545 or on a small system which does not have a general purpose operating system
12546 powerful enough to run a full-featured debugger.
12548 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
12549 to make this work with particular debugging targets. In addition,
12550 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
12551 but not specific to any particular target system) which you can use if you
12552 write the remote stubs---the code that runs on the remote system to
12553 communicate with @value{GDBN}.
12555 Other remote targets may be available in your
12556 configuration of @value{GDBN}; use @code{help target} to list them.
12559 * Connecting:: Connecting to a remote target
12560 * Server:: Using the gdbserver program
12561 * Remote Configuration:: Remote configuration
12562 * Remote Stub:: Implementing a remote stub
12566 @section Connecting to a Remote Target
12568 On the @value{GDBN} host machine, you will need an unstripped copy of
12569 your program, since @value{GDBN} needs symbol and debugging information.
12570 Start up @value{GDBN} as usual, using the name of the local copy of your
12571 program as the first argument.
12573 @cindex @code{target remote}
12574 @value{GDBN} can communicate with the target over a serial line, or
12575 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
12576 each case, @value{GDBN} uses the same protocol for debugging your
12577 program; only the medium carrying the debugging packets varies. The
12578 @code{target remote} command establishes a connection to the target.
12579 Its arguments indicate which medium to use:
12583 @item target remote @var{serial-device}
12584 @cindex serial line, @code{target remote}
12585 Use @var{serial-device} to communicate with the target. For example,
12586 to use a serial line connected to the device named @file{/dev/ttyb}:
12589 target remote /dev/ttyb
12592 If you're using a serial line, you may want to give @value{GDBN} the
12593 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
12594 (@pxref{Remote Configuration, set remotebaud}) before the
12595 @code{target} command.
12597 @item target remote @code{@var{host}:@var{port}}
12598 @itemx target remote @code{tcp:@var{host}:@var{port}}
12599 @cindex @acronym{TCP} port, @code{target remote}
12600 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
12601 The @var{host} may be either a host name or a numeric @acronym{IP}
12602 address; @var{port} must be a decimal number. The @var{host} could be
12603 the target machine itself, if it is directly connected to the net, or
12604 it might be a terminal server which in turn has a serial line to the
12607 For example, to connect to port 2828 on a terminal server named
12611 target remote manyfarms:2828
12614 If your remote target is actually running on the same machine as your
12615 debugger session (e.g.@: a simulator for your target running on the
12616 same host), you can omit the hostname. For example, to connect to
12617 port 1234 on your local machine:
12620 target remote :1234
12624 Note that the colon is still required here.
12626 @item target remote @code{udp:@var{host}:@var{port}}
12627 @cindex @acronym{UDP} port, @code{target remote}
12628 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
12629 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
12632 target remote udp:manyfarms:2828
12635 When using a @acronym{UDP} connection for remote debugging, you should
12636 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
12637 can silently drop packets on busy or unreliable networks, which will
12638 cause havoc with your debugging session.
12640 @item target remote | @var{command}
12641 @cindex pipe, @code{target remote} to
12642 Run @var{command} in the background and communicate with it using a
12643 pipe. The @var{command} is a shell command, to be parsed and expanded
12644 by the system's command shell, @code{/bin/sh}; it should expect remote
12645 protocol packets on its standard input, and send replies on its
12646 standard output. You could use this to run a stand-alone simulator
12647 that speaks the remote debugging protocol, to make net connections
12648 using programs like @code{ssh}, or for other similar tricks.
12650 If @var{command} closes its standard output (perhaps by exiting),
12651 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
12652 program has already exited, this will have no effect.)
12656 Once the connection has been established, you can use all the usual
12657 commands to examine and change data and to step and continue the
12660 @cindex interrupting remote programs
12661 @cindex remote programs, interrupting
12662 Whenever @value{GDBN} is waiting for the remote program, if you type the
12663 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
12664 program. This may or may not succeed, depending in part on the hardware
12665 and the serial drivers the remote system uses. If you type the
12666 interrupt character once again, @value{GDBN} displays this prompt:
12669 Interrupted while waiting for the program.
12670 Give up (and stop debugging it)? (y or n)
12673 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
12674 (If you decide you want to try again later, you can use @samp{target
12675 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
12676 goes back to waiting.
12679 @kindex detach (remote)
12681 When you have finished debugging the remote program, you can use the
12682 @code{detach} command to release it from @value{GDBN} control.
12683 Detaching from the target normally resumes its execution, but the results
12684 will depend on your particular remote stub. After the @code{detach}
12685 command, @value{GDBN} is free to connect to another target.
12689 The @code{disconnect} command behaves like @code{detach}, except that
12690 the target is generally not resumed. It will wait for @value{GDBN}
12691 (this instance or another one) to connect and continue debugging. After
12692 the @code{disconnect} command, @value{GDBN} is again free to connect to
12695 @cindex send command to remote monitor
12696 @cindex extend @value{GDBN} for remote targets
12697 @cindex add new commands for external monitor
12699 @item monitor @var{cmd}
12700 This command allows you to send arbitrary commands directly to the
12701 remote monitor. Since @value{GDBN} doesn't care about the commands it
12702 sends like this, this command is the way to extend @value{GDBN}---you
12703 can add new commands that only the external monitor will understand
12708 @section Using the @code{gdbserver} Program
12711 @cindex remote connection without stubs
12712 @code{gdbserver} is a control program for Unix-like systems, which
12713 allows you to connect your program with a remote @value{GDBN} via
12714 @code{target remote}---but without linking in the usual debugging stub.
12716 @code{gdbserver} is not a complete replacement for the debugging stubs,
12717 because it requires essentially the same operating-system facilities
12718 that @value{GDBN} itself does. In fact, a system that can run
12719 @code{gdbserver} to connect to a remote @value{GDBN} could also run
12720 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
12721 because it is a much smaller program than @value{GDBN} itself. It is
12722 also easier to port than all of @value{GDBN}, so you may be able to get
12723 started more quickly on a new system by using @code{gdbserver}.
12724 Finally, if you develop code for real-time systems, you may find that
12725 the tradeoffs involved in real-time operation make it more convenient to
12726 do as much development work as possible on another system, for example
12727 by cross-compiling. You can use @code{gdbserver} to make a similar
12728 choice for debugging.
12730 @value{GDBN} and @code{gdbserver} communicate via either a serial line
12731 or a TCP connection, using the standard @value{GDBN} remote serial
12735 @item On the target machine,
12736 you need to have a copy of the program you want to debug.
12737 @code{gdbserver} does not need your program's symbol table, so you can
12738 strip the program if necessary to save space. @value{GDBN} on the host
12739 system does all the symbol handling.
12741 To use the server, you must tell it how to communicate with @value{GDBN};
12742 the name of your program; and the arguments for your program. The usual
12746 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
12749 @var{comm} is either a device name (to use a serial line) or a TCP
12750 hostname and portnumber. For example, to debug Emacs with the argument
12751 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
12755 target> gdbserver /dev/com1 emacs foo.txt
12758 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
12761 To use a TCP connection instead of a serial line:
12764 target> gdbserver host:2345 emacs foo.txt
12767 The only difference from the previous example is the first argument,
12768 specifying that you are communicating with the host @value{GDBN} via
12769 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
12770 expect a TCP connection from machine @samp{host} to local TCP port 2345.
12771 (Currently, the @samp{host} part is ignored.) You can choose any number
12772 you want for the port number as long as it does not conflict with any
12773 TCP ports already in use on the target system (for example, @code{23} is
12774 reserved for @code{telnet}).@footnote{If you choose a port number that
12775 conflicts with another service, @code{gdbserver} prints an error message
12776 and exits.} You must use the same port number with the host @value{GDBN}
12777 @code{target remote} command.
12779 On some targets, @code{gdbserver} can also attach to running programs.
12780 This is accomplished via the @code{--attach} argument. The syntax is:
12783 target> gdbserver @var{comm} --attach @var{pid}
12786 @var{pid} is the process ID of a currently running process. It isn't necessary
12787 to point @code{gdbserver} at a binary for the running process.
12790 @cindex attach to a program by name
12791 You can debug processes by name instead of process ID if your target has the
12792 @code{pidof} utility:
12795 target> gdbserver @var{comm} --attach `pidof @var{program}`
12798 In case more than one copy of @var{program} is running, or @var{program}
12799 has multiple threads, most versions of @code{pidof} support the
12800 @code{-s} option to only return the first process ID.
12802 @item On the host machine,
12803 first make sure you have the necessary symbol files. Load symbols for
12804 your application using the @code{file} command before you connect. Use
12805 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
12806 was compiled with the correct sysroot using @code{--with-system-root}).
12808 The symbol file and target libraries must exactly match the executable
12809 and libraries on the target, with one exception: the files on the host
12810 system should not be stripped, even if the files on the target system
12811 are. Mismatched or missing files will lead to confusing results
12812 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
12813 files may also prevent @code{gdbserver} from debugging multi-threaded
12816 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
12817 For TCP connections, you must start up @code{gdbserver} prior to using
12818 the @code{target remote} command. Otherwise you may get an error whose
12819 text depends on the host system, but which usually looks something like
12820 @samp{Connection refused}. You don't need to use the @code{load}
12821 command in @value{GDBN} when using @code{gdbserver}, since the program is
12822 already on the target.
12826 @subsection Monitor Commands for @code{gdbserver}
12827 @cindex monitor commands, for @code{gdbserver}
12829 During a @value{GDBN} session using @code{gdbserver}, you can use the
12830 @code{monitor} command to send special requests to @code{gdbserver}.
12831 Here are the available commands; they are only of interest when
12832 debugging @value{GDBN} or @code{gdbserver}.
12836 List the available monitor commands.
12838 @item monitor set debug 0
12839 @itemx monitor set debug 1
12840 Disable or enable general debugging messages.
12842 @item monitor set remote-debug 0
12843 @itemx monitor set remote-debug 1
12844 Disable or enable specific debugging messages associated with the remote
12845 protocol (@pxref{Remote Protocol}).
12849 @node Remote Configuration
12850 @section Remote Configuration
12853 @kindex show remote
12854 This section documents the configuration options available when
12855 debugging remote programs. For the options related to the File I/O
12856 extensions of the remote protocol, see @ref{system,
12857 system-call-allowed}.
12860 @item set remoteaddresssize @var{bits}
12861 @cindex address size for remote targets
12862 @cindex bits in remote address
12863 Set the maximum size of address in a memory packet to the specified
12864 number of bits. @value{GDBN} will mask off the address bits above
12865 that number, when it passes addresses to the remote target. The
12866 default value is the number of bits in the target's address.
12868 @item show remoteaddresssize
12869 Show the current value of remote address size in bits.
12871 @item set remotebaud @var{n}
12872 @cindex baud rate for remote targets
12873 Set the baud rate for the remote serial I/O to @var{n} baud. The
12874 value is used to set the speed of the serial port used for debugging
12877 @item show remotebaud
12878 Show the current speed of the remote connection.
12880 @item set remotebreak
12881 @cindex interrupt remote programs
12882 @cindex BREAK signal instead of Ctrl-C
12883 @anchor{set remotebreak}
12884 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
12885 when you type @kbd{Ctrl-c} to interrupt the program running
12886 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
12887 character instead. The default is off, since most remote systems
12888 expect to see @samp{Ctrl-C} as the interrupt signal.
12890 @item show remotebreak
12891 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
12892 interrupt the remote program.
12894 @item set remoteflow on
12895 @itemx set remoteflow off
12896 @kindex set remoteflow
12897 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
12898 on the serial port used to communicate to the remote target.
12900 @item show remoteflow
12901 @kindex show remoteflow
12902 Show the current setting of hardware flow control.
12904 @item set remotelogbase @var{base}
12905 Set the base (a.k.a.@: radix) of logging serial protocol
12906 communications to @var{base}. Supported values of @var{base} are:
12907 @code{ascii}, @code{octal}, and @code{hex}. The default is
12910 @item show remotelogbase
12911 Show the current setting of the radix for logging remote serial
12914 @item set remotelogfile @var{file}
12915 @cindex record serial communications on file
12916 Record remote serial communications on the named @var{file}. The
12917 default is not to record at all.
12919 @item show remotelogfile.
12920 Show the current setting of the file name on which to record the
12921 serial communications.
12923 @item set remotetimeout @var{num}
12924 @cindex timeout for serial communications
12925 @cindex remote timeout
12926 Set the timeout limit to wait for the remote target to respond to
12927 @var{num} seconds. The default is 2 seconds.
12929 @item show remotetimeout
12930 Show the current number of seconds to wait for the remote target
12933 @cindex limit hardware breakpoints and watchpoints
12934 @cindex remote target, limit break- and watchpoints
12935 @anchor{set remote hardware-watchpoint-limit}
12936 @anchor{set remote hardware-breakpoint-limit}
12937 @item set remote hardware-watchpoint-limit @var{limit}
12938 @itemx set remote hardware-breakpoint-limit @var{limit}
12939 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
12940 watchpoints. A limit of -1, the default, is treated as unlimited.
12943 @cindex remote packets, enabling and disabling
12944 The @value{GDBN} remote protocol autodetects the packets supported by
12945 your debugging stub. If you need to override the autodetection, you
12946 can use these commands to enable or disable individual packets. Each
12947 packet can be set to @samp{on} (the remote target supports this
12948 packet), @samp{off} (the remote target does not support this packet),
12949 or @samp{auto} (detect remote target support for this packet). They
12950 all default to @samp{auto}. For more information about each packet,
12951 see @ref{Remote Protocol}.
12953 During normal use, you should not have to use any of these commands.
12954 If you do, that may be a bug in your remote debugging stub, or a bug
12955 in @value{GDBN}. You may want to report the problem to the
12956 @value{GDBN} developers.
12958 For each packet @var{name}, the command to enable or disable the
12959 packet is @code{set remote @var{name}-packet}. The available settings
12962 @multitable @columnfractions 0.28 0.32 0.25
12965 @tab Related Features
12967 @item @code{fetch-register}
12969 @tab @code{info registers}
12971 @item @code{set-register}
12975 @item @code{binary-download}
12977 @tab @code{load}, @code{set}
12979 @item @code{read-aux-vector}
12980 @tab @code{qXfer:auxv:read}
12981 @tab @code{info auxv}
12983 @item @code{symbol-lookup}
12984 @tab @code{qSymbol}
12985 @tab Detecting multiple threads
12987 @item @code{verbose-resume}
12989 @tab Stepping or resuming multiple threads
12991 @item @code{software-breakpoint}
12995 @item @code{hardware-breakpoint}
12999 @item @code{write-watchpoint}
13003 @item @code{read-watchpoint}
13007 @item @code{access-watchpoint}
13011 @item @code{target-features}
13012 @tab @code{qXfer:features:read}
13013 @tab @code{set architecture}
13015 @item @code{library-info}
13016 @tab @code{qXfer:libraries:read}
13017 @tab @code{info sharedlibrary}
13019 @item @code{memory-map}
13020 @tab @code{qXfer:memory-map:read}
13021 @tab @code{info mem}
13023 @item @code{read-spu-object}
13024 @tab @code{qXfer:spu:read}
13025 @tab @code{info spu}
13027 @item @code{write-spu-object}
13028 @tab @code{qXfer:spu:write}
13029 @tab @code{info spu}
13031 @item @code{get-thread-local-@*storage-address}
13032 @tab @code{qGetTLSAddr}
13033 @tab Displaying @code{__thread} variables
13035 @item @code{supported-packets}
13036 @tab @code{qSupported}
13037 @tab Remote communications parameters
13039 @item @code{pass-signals}
13040 @tab @code{QPassSignals}
13041 @tab @code{handle @var{signal}}
13046 @section Implementing a Remote Stub
13048 @cindex debugging stub, example
13049 @cindex remote stub, example
13050 @cindex stub example, remote debugging
13051 The stub files provided with @value{GDBN} implement the target side of the
13052 communication protocol, and the @value{GDBN} side is implemented in the
13053 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
13054 these subroutines to communicate, and ignore the details. (If you're
13055 implementing your own stub file, you can still ignore the details: start
13056 with one of the existing stub files. @file{sparc-stub.c} is the best
13057 organized, and therefore the easiest to read.)
13059 @cindex remote serial debugging, overview
13060 To debug a program running on another machine (the debugging
13061 @dfn{target} machine), you must first arrange for all the usual
13062 prerequisites for the program to run by itself. For example, for a C
13067 A startup routine to set up the C runtime environment; these usually
13068 have a name like @file{crt0}. The startup routine may be supplied by
13069 your hardware supplier, or you may have to write your own.
13072 A C subroutine library to support your program's
13073 subroutine calls, notably managing input and output.
13076 A way of getting your program to the other machine---for example, a
13077 download program. These are often supplied by the hardware
13078 manufacturer, but you may have to write your own from hardware
13082 The next step is to arrange for your program to use a serial port to
13083 communicate with the machine where @value{GDBN} is running (the @dfn{host}
13084 machine). In general terms, the scheme looks like this:
13088 @value{GDBN} already understands how to use this protocol; when everything
13089 else is set up, you can simply use the @samp{target remote} command
13090 (@pxref{Targets,,Specifying a Debugging Target}).
13092 @item On the target,
13093 you must link with your program a few special-purpose subroutines that
13094 implement the @value{GDBN} remote serial protocol. The file containing these
13095 subroutines is called a @dfn{debugging stub}.
13097 On certain remote targets, you can use an auxiliary program
13098 @code{gdbserver} instead of linking a stub into your program.
13099 @xref{Server,,Using the @code{gdbserver} Program}, for details.
13102 The debugging stub is specific to the architecture of the remote
13103 machine; for example, use @file{sparc-stub.c} to debug programs on
13106 @cindex remote serial stub list
13107 These working remote stubs are distributed with @value{GDBN}:
13112 @cindex @file{i386-stub.c}
13115 For Intel 386 and compatible architectures.
13118 @cindex @file{m68k-stub.c}
13119 @cindex Motorola 680x0
13121 For Motorola 680x0 architectures.
13124 @cindex @file{sh-stub.c}
13127 For Renesas SH architectures.
13130 @cindex @file{sparc-stub.c}
13132 For @sc{sparc} architectures.
13134 @item sparcl-stub.c
13135 @cindex @file{sparcl-stub.c}
13138 For Fujitsu @sc{sparclite} architectures.
13142 The @file{README} file in the @value{GDBN} distribution may list other
13143 recently added stubs.
13146 * Stub Contents:: What the stub can do for you
13147 * Bootstrapping:: What you must do for the stub
13148 * Debug Session:: Putting it all together
13151 @node Stub Contents
13152 @subsection What the Stub Can Do for You
13154 @cindex remote serial stub
13155 The debugging stub for your architecture supplies these three
13159 @item set_debug_traps
13160 @findex set_debug_traps
13161 @cindex remote serial stub, initialization
13162 This routine arranges for @code{handle_exception} to run when your
13163 program stops. You must call this subroutine explicitly near the
13164 beginning of your program.
13166 @item handle_exception
13167 @findex handle_exception
13168 @cindex remote serial stub, main routine
13169 This is the central workhorse, but your program never calls it
13170 explicitly---the setup code arranges for @code{handle_exception} to
13171 run when a trap is triggered.
13173 @code{handle_exception} takes control when your program stops during
13174 execution (for example, on a breakpoint), and mediates communications
13175 with @value{GDBN} on the host machine. This is where the communications
13176 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
13177 representative on the target machine. It begins by sending summary
13178 information on the state of your program, then continues to execute,
13179 retrieving and transmitting any information @value{GDBN} needs, until you
13180 execute a @value{GDBN} command that makes your program resume; at that point,
13181 @code{handle_exception} returns control to your own code on the target
13185 @cindex @code{breakpoint} subroutine, remote
13186 Use this auxiliary subroutine to make your program contain a
13187 breakpoint. Depending on the particular situation, this may be the only
13188 way for @value{GDBN} to get control. For instance, if your target
13189 machine has some sort of interrupt button, you won't need to call this;
13190 pressing the interrupt button transfers control to
13191 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
13192 simply receiving characters on the serial port may also trigger a trap;
13193 again, in that situation, you don't need to call @code{breakpoint} from
13194 your own program---simply running @samp{target remote} from the host
13195 @value{GDBN} session gets control.
13197 Call @code{breakpoint} if none of these is true, or if you simply want
13198 to make certain your program stops at a predetermined point for the
13199 start of your debugging session.
13202 @node Bootstrapping
13203 @subsection What You Must Do for the Stub
13205 @cindex remote stub, support routines
13206 The debugging stubs that come with @value{GDBN} are set up for a particular
13207 chip architecture, but they have no information about the rest of your
13208 debugging target machine.
13210 First of all you need to tell the stub how to communicate with the
13214 @item int getDebugChar()
13215 @findex getDebugChar
13216 Write this subroutine to read a single character from the serial port.
13217 It may be identical to @code{getchar} for your target system; a
13218 different name is used to allow you to distinguish the two if you wish.
13220 @item void putDebugChar(int)
13221 @findex putDebugChar
13222 Write this subroutine to write a single character to the serial port.
13223 It may be identical to @code{putchar} for your target system; a
13224 different name is used to allow you to distinguish the two if you wish.
13227 @cindex control C, and remote debugging
13228 @cindex interrupting remote targets
13229 If you want @value{GDBN} to be able to stop your program while it is
13230 running, you need to use an interrupt-driven serial driver, and arrange
13231 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
13232 character). That is the character which @value{GDBN} uses to tell the
13233 remote system to stop.
13235 Getting the debugging target to return the proper status to @value{GDBN}
13236 probably requires changes to the standard stub; one quick and dirty way
13237 is to just execute a breakpoint instruction (the ``dirty'' part is that
13238 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
13240 Other routines you need to supply are:
13243 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
13244 @findex exceptionHandler
13245 Write this function to install @var{exception_address} in the exception
13246 handling tables. You need to do this because the stub does not have any
13247 way of knowing what the exception handling tables on your target system
13248 are like (for example, the processor's table might be in @sc{rom},
13249 containing entries which point to a table in @sc{ram}).
13250 @var{exception_number} is the exception number which should be changed;
13251 its meaning is architecture-dependent (for example, different numbers
13252 might represent divide by zero, misaligned access, etc). When this
13253 exception occurs, control should be transferred directly to
13254 @var{exception_address}, and the processor state (stack, registers,
13255 and so on) should be just as it is when a processor exception occurs. So if
13256 you want to use a jump instruction to reach @var{exception_address}, it
13257 should be a simple jump, not a jump to subroutine.
13259 For the 386, @var{exception_address} should be installed as an interrupt
13260 gate so that interrupts are masked while the handler runs. The gate
13261 should be at privilege level 0 (the most privileged level). The
13262 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
13263 help from @code{exceptionHandler}.
13265 @item void flush_i_cache()
13266 @findex flush_i_cache
13267 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
13268 instruction cache, if any, on your target machine. If there is no
13269 instruction cache, this subroutine may be a no-op.
13271 On target machines that have instruction caches, @value{GDBN} requires this
13272 function to make certain that the state of your program is stable.
13276 You must also make sure this library routine is available:
13279 @item void *memset(void *, int, int)
13281 This is the standard library function @code{memset} that sets an area of
13282 memory to a known value. If you have one of the free versions of
13283 @code{libc.a}, @code{memset} can be found there; otherwise, you must
13284 either obtain it from your hardware manufacturer, or write your own.
13287 If you do not use the GNU C compiler, you may need other standard
13288 library subroutines as well; this varies from one stub to another,
13289 but in general the stubs are likely to use any of the common library
13290 subroutines which @code{@value{NGCC}} generates as inline code.
13293 @node Debug Session
13294 @subsection Putting it All Together
13296 @cindex remote serial debugging summary
13297 In summary, when your program is ready to debug, you must follow these
13302 Make sure you have defined the supporting low-level routines
13303 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
13305 @code{getDebugChar}, @code{putDebugChar},
13306 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
13310 Insert these lines near the top of your program:
13318 For the 680x0 stub only, you need to provide a variable called
13319 @code{exceptionHook}. Normally you just use:
13322 void (*exceptionHook)() = 0;
13326 but if before calling @code{set_debug_traps}, you set it to point to a
13327 function in your program, that function is called when
13328 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
13329 error). The function indicated by @code{exceptionHook} is called with
13330 one parameter: an @code{int} which is the exception number.
13333 Compile and link together: your program, the @value{GDBN} debugging stub for
13334 your target architecture, and the supporting subroutines.
13337 Make sure you have a serial connection between your target machine and
13338 the @value{GDBN} host, and identify the serial port on the host.
13341 @c The "remote" target now provides a `load' command, so we should
13342 @c document that. FIXME.
13343 Download your program to your target machine (or get it there by
13344 whatever means the manufacturer provides), and start it.
13347 Start @value{GDBN} on the host, and connect to the target
13348 (@pxref{Connecting,,Connecting to a Remote Target}).
13352 @node Configurations
13353 @chapter Configuration-Specific Information
13355 While nearly all @value{GDBN} commands are available for all native and
13356 cross versions of the debugger, there are some exceptions. This chapter
13357 describes things that are only available in certain configurations.
13359 There are three major categories of configurations: native
13360 configurations, where the host and target are the same, embedded
13361 operating system configurations, which are usually the same for several
13362 different processor architectures, and bare embedded processors, which
13363 are quite different from each other.
13368 * Embedded Processors::
13375 This section describes details specific to particular native
13380 * BSD libkvm Interface:: Debugging BSD kernel memory images
13381 * SVR4 Process Information:: SVR4 process information
13382 * DJGPP Native:: Features specific to the DJGPP port
13383 * Cygwin Native:: Features specific to the Cygwin port
13384 * Hurd Native:: Features specific to @sc{gnu} Hurd
13385 * Neutrino:: Features specific to QNX Neutrino
13391 On HP-UX systems, if you refer to a function or variable name that
13392 begins with a dollar sign, @value{GDBN} searches for a user or system
13393 name first, before it searches for a convenience variable.
13396 @node BSD libkvm Interface
13397 @subsection BSD libkvm Interface
13400 @cindex kernel memory image
13401 @cindex kernel crash dump
13403 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
13404 interface that provides a uniform interface for accessing kernel virtual
13405 memory images, including live systems and crash dumps. @value{GDBN}
13406 uses this interface to allow you to debug live kernels and kernel crash
13407 dumps on many native BSD configurations. This is implemented as a
13408 special @code{kvm} debugging target. For debugging a live system, load
13409 the currently running kernel into @value{GDBN} and connect to the
13413 (@value{GDBP}) @b{target kvm}
13416 For debugging crash dumps, provide the file name of the crash dump as an
13420 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
13423 Once connected to the @code{kvm} target, the following commands are
13429 Set current context from the @dfn{Process Control Block} (PCB) address.
13432 Set current context from proc address. This command isn't available on
13433 modern FreeBSD systems.
13436 @node SVR4 Process Information
13437 @subsection SVR4 Process Information
13439 @cindex examine process image
13440 @cindex process info via @file{/proc}
13442 Many versions of SVR4 and compatible systems provide a facility called
13443 @samp{/proc} that can be used to examine the image of a running
13444 process using file-system subroutines. If @value{GDBN} is configured
13445 for an operating system with this facility, the command @code{info
13446 proc} is available to report information about the process running
13447 your program, or about any process running on your system. @code{info
13448 proc} works only on SVR4 systems that include the @code{procfs} code.
13449 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
13450 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
13456 @itemx info proc @var{process-id}
13457 Summarize available information about any running process. If a
13458 process ID is specified by @var{process-id}, display information about
13459 that process; otherwise display information about the program being
13460 debugged. The summary includes the debugged process ID, the command
13461 line used to invoke it, its current working directory, and its
13462 executable file's absolute file name.
13464 On some systems, @var{process-id} can be of the form
13465 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
13466 within a process. If the optional @var{pid} part is missing, it means
13467 a thread from the process being debugged (the leading @samp{/} still
13468 needs to be present, or else @value{GDBN} will interpret the number as
13469 a process ID rather than a thread ID).
13471 @item info proc mappings
13472 @cindex memory address space mappings
13473 Report the memory address space ranges accessible in the program, with
13474 information on whether the process has read, write, or execute access
13475 rights to each range. On @sc{gnu}/Linux systems, each memory range
13476 includes the object file which is mapped to that range, instead of the
13477 memory access rights to that range.
13479 @item info proc stat
13480 @itemx info proc status
13481 @cindex process detailed status information
13482 These subcommands are specific to @sc{gnu}/Linux systems. They show
13483 the process-related information, including the user ID and group ID;
13484 how many threads are there in the process; its virtual memory usage;
13485 the signals that are pending, blocked, and ignored; its TTY; its
13486 consumption of system and user time; its stack size; its @samp{nice}
13487 value; etc. For more information, see the @samp{proc} man page
13488 (type @kbd{man 5 proc} from your shell prompt).
13490 @item info proc all
13491 Show all the information about the process described under all of the
13492 above @code{info proc} subcommands.
13495 @comment These sub-options of 'info proc' were not included when
13496 @comment procfs.c was re-written. Keep their descriptions around
13497 @comment against the day when someone finds the time to put them back in.
13498 @kindex info proc times
13499 @item info proc times
13500 Starting time, user CPU time, and system CPU time for your program and
13503 @kindex info proc id
13505 Report on the process IDs related to your program: its own process ID,
13506 the ID of its parent, the process group ID, and the session ID.
13509 @item set procfs-trace
13510 @kindex set procfs-trace
13511 @cindex @code{procfs} API calls
13512 This command enables and disables tracing of @code{procfs} API calls.
13514 @item show procfs-trace
13515 @kindex show procfs-trace
13516 Show the current state of @code{procfs} API call tracing.
13518 @item set procfs-file @var{file}
13519 @kindex set procfs-file
13520 Tell @value{GDBN} to write @code{procfs} API trace to the named
13521 @var{file}. @value{GDBN} appends the trace info to the previous
13522 contents of the file. The default is to display the trace on the
13525 @item show procfs-file
13526 @kindex show procfs-file
13527 Show the file to which @code{procfs} API trace is written.
13529 @item proc-trace-entry
13530 @itemx proc-trace-exit
13531 @itemx proc-untrace-entry
13532 @itemx proc-untrace-exit
13533 @kindex proc-trace-entry
13534 @kindex proc-trace-exit
13535 @kindex proc-untrace-entry
13536 @kindex proc-untrace-exit
13537 These commands enable and disable tracing of entries into and exits
13538 from the @code{syscall} interface.
13541 @kindex info pidlist
13542 @cindex process list, QNX Neutrino
13543 For QNX Neutrino only, this command displays the list of all the
13544 processes and all the threads within each process.
13547 @kindex info meminfo
13548 @cindex mapinfo list, QNX Neutrino
13549 For QNX Neutrino only, this command displays the list of all mapinfos.
13553 @subsection Features for Debugging @sc{djgpp} Programs
13554 @cindex @sc{djgpp} debugging
13555 @cindex native @sc{djgpp} debugging
13556 @cindex MS-DOS-specific commands
13559 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
13560 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
13561 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
13562 top of real-mode DOS systems and their emulations.
13564 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
13565 defines a few commands specific to the @sc{djgpp} port. This
13566 subsection describes those commands.
13571 This is a prefix of @sc{djgpp}-specific commands which print
13572 information about the target system and important OS structures.
13575 @cindex MS-DOS system info
13576 @cindex free memory information (MS-DOS)
13577 @item info dos sysinfo
13578 This command displays assorted information about the underlying
13579 platform: the CPU type and features, the OS version and flavor, the
13580 DPMI version, and the available conventional and DPMI memory.
13585 @cindex segment descriptor tables
13586 @cindex descriptor tables display
13588 @itemx info dos ldt
13589 @itemx info dos idt
13590 These 3 commands display entries from, respectively, Global, Local,
13591 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
13592 tables are data structures which store a descriptor for each segment
13593 that is currently in use. The segment's selector is an index into a
13594 descriptor table; the table entry for that index holds the
13595 descriptor's base address and limit, and its attributes and access
13598 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
13599 segment (used for both data and the stack), and a DOS segment (which
13600 allows access to DOS/BIOS data structures and absolute addresses in
13601 conventional memory). However, the DPMI host will usually define
13602 additional segments in order to support the DPMI environment.
13604 @cindex garbled pointers
13605 These commands allow to display entries from the descriptor tables.
13606 Without an argument, all entries from the specified table are
13607 displayed. An argument, which should be an integer expression, means
13608 display a single entry whose index is given by the argument. For
13609 example, here's a convenient way to display information about the
13610 debugged program's data segment:
13613 @exdent @code{(@value{GDBP}) info dos ldt $ds}
13614 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
13618 This comes in handy when you want to see whether a pointer is outside
13619 the data segment's limit (i.e.@: @dfn{garbled}).
13621 @cindex page tables display (MS-DOS)
13623 @itemx info dos pte
13624 These two commands display entries from, respectively, the Page
13625 Directory and the Page Tables. Page Directories and Page Tables are
13626 data structures which control how virtual memory addresses are mapped
13627 into physical addresses. A Page Table includes an entry for every
13628 page of memory that is mapped into the program's address space; there
13629 may be several Page Tables, each one holding up to 4096 entries. A
13630 Page Directory has up to 4096 entries, one each for every Page Table
13631 that is currently in use.
13633 Without an argument, @kbd{info dos pde} displays the entire Page
13634 Directory, and @kbd{info dos pte} displays all the entries in all of
13635 the Page Tables. An argument, an integer expression, given to the
13636 @kbd{info dos pde} command means display only that entry from the Page
13637 Directory table. An argument given to the @kbd{info dos pte} command
13638 means display entries from a single Page Table, the one pointed to by
13639 the specified entry in the Page Directory.
13641 @cindex direct memory access (DMA) on MS-DOS
13642 These commands are useful when your program uses @dfn{DMA} (Direct
13643 Memory Access), which needs physical addresses to program the DMA
13646 These commands are supported only with some DPMI servers.
13648 @cindex physical address from linear address
13649 @item info dos address-pte @var{addr}
13650 This command displays the Page Table entry for a specified linear
13651 address. The argument @var{addr} is a linear address which should
13652 already have the appropriate segment's base address added to it,
13653 because this command accepts addresses which may belong to @emph{any}
13654 segment. For example, here's how to display the Page Table entry for
13655 the page where a variable @code{i} is stored:
13658 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
13659 @exdent @code{Page Table entry for address 0x11a00d30:}
13660 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
13664 This says that @code{i} is stored at offset @code{0xd30} from the page
13665 whose physical base address is @code{0x02698000}, and shows all the
13666 attributes of that page.
13668 Note that you must cast the addresses of variables to a @code{char *},
13669 since otherwise the value of @code{__djgpp_base_address}, the base
13670 address of all variables and functions in a @sc{djgpp} program, will
13671 be added using the rules of C pointer arithmetics: if @code{i} is
13672 declared an @code{int}, @value{GDBN} will add 4 times the value of
13673 @code{__djgpp_base_address} to the address of @code{i}.
13675 Here's another example, it displays the Page Table entry for the
13679 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
13680 @exdent @code{Page Table entry for address 0x29110:}
13681 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
13685 (The @code{+ 3} offset is because the transfer buffer's address is the
13686 3rd member of the @code{_go32_info_block} structure.) The output
13687 clearly shows that this DPMI server maps the addresses in conventional
13688 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
13689 linear (@code{0x29110}) addresses are identical.
13691 This command is supported only with some DPMI servers.
13694 @cindex DOS serial data link, remote debugging
13695 In addition to native debugging, the DJGPP port supports remote
13696 debugging via a serial data link. The following commands are specific
13697 to remote serial debugging in the DJGPP port of @value{GDBN}.
13700 @kindex set com1base
13701 @kindex set com1irq
13702 @kindex set com2base
13703 @kindex set com2irq
13704 @kindex set com3base
13705 @kindex set com3irq
13706 @kindex set com4base
13707 @kindex set com4irq
13708 @item set com1base @var{addr}
13709 This command sets the base I/O port address of the @file{COM1} serial
13712 @item set com1irq @var{irq}
13713 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
13714 for the @file{COM1} serial port.
13716 There are similar commands @samp{set com2base}, @samp{set com3irq},
13717 etc.@: for setting the port address and the @code{IRQ} lines for the
13720 @kindex show com1base
13721 @kindex show com1irq
13722 @kindex show com2base
13723 @kindex show com2irq
13724 @kindex show com3base
13725 @kindex show com3irq
13726 @kindex show com4base
13727 @kindex show com4irq
13728 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
13729 display the current settings of the base address and the @code{IRQ}
13730 lines used by the COM ports.
13733 @kindex info serial
13734 @cindex DOS serial port status
13735 This command prints the status of the 4 DOS serial ports. For each
13736 port, it prints whether it's active or not, its I/O base address and
13737 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
13738 counts of various errors encountered so far.
13742 @node Cygwin Native
13743 @subsection Features for Debugging MS Windows PE Executables
13744 @cindex MS Windows debugging
13745 @cindex native Cygwin debugging
13746 @cindex Cygwin-specific commands
13748 @value{GDBN} supports native debugging of MS Windows programs, including
13749 DLLs with and without symbolic debugging information. There are various
13750 additional Cygwin-specific commands, described in this section.
13751 Working with DLLs that have no debugging symbols is described in
13752 @ref{Non-debug DLL Symbols}.
13757 This is a prefix of MS Windows-specific commands which print
13758 information about the target system and important OS structures.
13760 @item info w32 selector
13761 This command displays information returned by
13762 the Win32 API @code{GetThreadSelectorEntry} function.
13763 It takes an optional argument that is evaluated to
13764 a long value to give the information about this given selector.
13765 Without argument, this command displays information
13766 about the six segment registers.
13770 This is a Cygwin-specific alias of @code{info shared}.
13772 @kindex dll-symbols
13774 This command loads symbols from a dll similarly to
13775 add-sym command but without the need to specify a base address.
13777 @kindex set cygwin-exceptions
13778 @cindex debugging the Cygwin DLL
13779 @cindex Cygwin DLL, debugging
13780 @item set cygwin-exceptions @var{mode}
13781 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
13782 happen inside the Cygwin DLL. If @var{mode} is @code{off},
13783 @value{GDBN} will delay recognition of exceptions, and may ignore some
13784 exceptions which seem to be caused by internal Cygwin DLL
13785 ``bookkeeping''. This option is meant primarily for debugging the
13786 Cygwin DLL itself; the default value is @code{off} to avoid annoying
13787 @value{GDBN} users with false @code{SIGSEGV} signals.
13789 @kindex show cygwin-exceptions
13790 @item show cygwin-exceptions
13791 Displays whether @value{GDBN} will break on exceptions that happen
13792 inside the Cygwin DLL itself.
13794 @kindex set new-console
13795 @item set new-console @var{mode}
13796 If @var{mode} is @code{on} the debuggee will
13797 be started in a new console on next start.
13798 If @var{mode} is @code{off}i, the debuggee will
13799 be started in the same console as the debugger.
13801 @kindex show new-console
13802 @item show new-console
13803 Displays whether a new console is used
13804 when the debuggee is started.
13806 @kindex set new-group
13807 @item set new-group @var{mode}
13808 This boolean value controls whether the debuggee should
13809 start a new group or stay in the same group as the debugger.
13810 This affects the way the Windows OS handles
13813 @kindex show new-group
13814 @item show new-group
13815 Displays current value of new-group boolean.
13817 @kindex set debugevents
13818 @item set debugevents
13819 This boolean value adds debug output concerning kernel events related
13820 to the debuggee seen by the debugger. This includes events that
13821 signal thread and process creation and exit, DLL loading and
13822 unloading, console interrupts, and debugging messages produced by the
13823 Windows @code{OutputDebugString} API call.
13825 @kindex set debugexec
13826 @item set debugexec
13827 This boolean value adds debug output concerning execute events
13828 (such as resume thread) seen by the debugger.
13830 @kindex set debugexceptions
13831 @item set debugexceptions
13832 This boolean value adds debug output concerning exceptions in the
13833 debuggee seen by the debugger.
13835 @kindex set debugmemory
13836 @item set debugmemory
13837 This boolean value adds debug output concerning debuggee memory reads
13838 and writes by the debugger.
13842 This boolean values specifies whether the debuggee is called
13843 via a shell or directly (default value is on).
13847 Displays if the debuggee will be started with a shell.
13852 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
13855 @node Non-debug DLL Symbols
13856 @subsubsection Support for DLLs without Debugging Symbols
13857 @cindex DLLs with no debugging symbols
13858 @cindex Minimal symbols and DLLs
13860 Very often on windows, some of the DLLs that your program relies on do
13861 not include symbolic debugging information (for example,
13862 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
13863 symbols in a DLL, it relies on the minimal amount of symbolic
13864 information contained in the DLL's export table. This section
13865 describes working with such symbols, known internally to @value{GDBN} as
13866 ``minimal symbols''.
13868 Note that before the debugged program has started execution, no DLLs
13869 will have been loaded. The easiest way around this problem is simply to
13870 start the program --- either by setting a breakpoint or letting the
13871 program run once to completion. It is also possible to force
13872 @value{GDBN} to load a particular DLL before starting the executable ---
13873 see the shared library information in @ref{Files}, or the
13874 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
13875 explicitly loading symbols from a DLL with no debugging information will
13876 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
13877 which may adversely affect symbol lookup performance.
13879 @subsubsection DLL Name Prefixes
13881 In keeping with the naming conventions used by the Microsoft debugging
13882 tools, DLL export symbols are made available with a prefix based on the
13883 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
13884 also entered into the symbol table, so @code{CreateFileA} is often
13885 sufficient. In some cases there will be name clashes within a program
13886 (particularly if the executable itself includes full debugging symbols)
13887 necessitating the use of the fully qualified name when referring to the
13888 contents of the DLL. Use single-quotes around the name to avoid the
13889 exclamation mark (``!'') being interpreted as a language operator.
13891 Note that the internal name of the DLL may be all upper-case, even
13892 though the file name of the DLL is lower-case, or vice-versa. Since
13893 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
13894 some confusion. If in doubt, try the @code{info functions} and
13895 @code{info variables} commands or even @code{maint print msymbols}
13896 (@pxref{Symbols}). Here's an example:
13899 (@value{GDBP}) info function CreateFileA
13900 All functions matching regular expression "CreateFileA":
13902 Non-debugging symbols:
13903 0x77e885f4 CreateFileA
13904 0x77e885f4 KERNEL32!CreateFileA
13908 (@value{GDBP}) info function !
13909 All functions matching regular expression "!":
13911 Non-debugging symbols:
13912 0x6100114c cygwin1!__assert
13913 0x61004034 cygwin1!_dll_crt0@@0
13914 0x61004240 cygwin1!dll_crt0(per_process *)
13918 @subsubsection Working with Minimal Symbols
13920 Symbols extracted from a DLL's export table do not contain very much
13921 type information. All that @value{GDBN} can do is guess whether a symbol
13922 refers to a function or variable depending on the linker section that
13923 contains the symbol. Also note that the actual contents of the memory
13924 contained in a DLL are not available unless the program is running. This
13925 means that you cannot examine the contents of a variable or disassemble
13926 a function within a DLL without a running program.
13928 Variables are generally treated as pointers and dereferenced
13929 automatically. For this reason, it is often necessary to prefix a
13930 variable name with the address-of operator (``&'') and provide explicit
13931 type information in the command. Here's an example of the type of
13935 (@value{GDBP}) print 'cygwin1!__argv'
13940 (@value{GDBP}) x 'cygwin1!__argv'
13941 0x10021610: "\230y\""
13944 And two possible solutions:
13947 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
13948 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
13952 (@value{GDBP}) x/2x &'cygwin1!__argv'
13953 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
13954 (@value{GDBP}) x/x 0x10021608
13955 0x10021608: 0x0022fd98
13956 (@value{GDBP}) x/s 0x0022fd98
13957 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
13960 Setting a break point within a DLL is possible even before the program
13961 starts execution. However, under these circumstances, @value{GDBN} can't
13962 examine the initial instructions of the function in order to skip the
13963 function's frame set-up code. You can work around this by using ``*&''
13964 to set the breakpoint at a raw memory address:
13967 (@value{GDBP}) break *&'python22!PyOS_Readline'
13968 Breakpoint 1 at 0x1e04eff0
13971 The author of these extensions is not entirely convinced that setting a
13972 break point within a shared DLL like @file{kernel32.dll} is completely
13976 @subsection Commands Specific to @sc{gnu} Hurd Systems
13977 @cindex @sc{gnu} Hurd debugging
13979 This subsection describes @value{GDBN} commands specific to the
13980 @sc{gnu} Hurd native debugging.
13985 @kindex set signals@r{, Hurd command}
13986 @kindex set sigs@r{, Hurd command}
13987 This command toggles the state of inferior signal interception by
13988 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
13989 affected by this command. @code{sigs} is a shorthand alias for
13994 @kindex show signals@r{, Hurd command}
13995 @kindex show sigs@r{, Hurd command}
13996 Show the current state of intercepting inferior's signals.
13998 @item set signal-thread
13999 @itemx set sigthread
14000 @kindex set signal-thread
14001 @kindex set sigthread
14002 This command tells @value{GDBN} which thread is the @code{libc} signal
14003 thread. That thread is run when a signal is delivered to a running
14004 process. @code{set sigthread} is the shorthand alias of @code{set
14007 @item show signal-thread
14008 @itemx show sigthread
14009 @kindex show signal-thread
14010 @kindex show sigthread
14011 These two commands show which thread will run when the inferior is
14012 delivered a signal.
14015 @kindex set stopped@r{, Hurd command}
14016 This commands tells @value{GDBN} that the inferior process is stopped,
14017 as with the @code{SIGSTOP} signal. The stopped process can be
14018 continued by delivering a signal to it.
14021 @kindex show stopped@r{, Hurd command}
14022 This command shows whether @value{GDBN} thinks the debuggee is
14025 @item set exceptions
14026 @kindex set exceptions@r{, Hurd command}
14027 Use this command to turn off trapping of exceptions in the inferior.
14028 When exception trapping is off, neither breakpoints nor
14029 single-stepping will work. To restore the default, set exception
14032 @item show exceptions
14033 @kindex show exceptions@r{, Hurd command}
14034 Show the current state of trapping exceptions in the inferior.
14036 @item set task pause
14037 @kindex set task@r{, Hurd commands}
14038 @cindex task attributes (@sc{gnu} Hurd)
14039 @cindex pause current task (@sc{gnu} Hurd)
14040 This command toggles task suspension when @value{GDBN} has control.
14041 Setting it to on takes effect immediately, and the task is suspended
14042 whenever @value{GDBN} gets control. Setting it to off will take
14043 effect the next time the inferior is continued. If this option is set
14044 to off, you can use @code{set thread default pause on} or @code{set
14045 thread pause on} (see below) to pause individual threads.
14047 @item show task pause
14048 @kindex show task@r{, Hurd commands}
14049 Show the current state of task suspension.
14051 @item set task detach-suspend-count
14052 @cindex task suspend count
14053 @cindex detach from task, @sc{gnu} Hurd
14054 This command sets the suspend count the task will be left with when
14055 @value{GDBN} detaches from it.
14057 @item show task detach-suspend-count
14058 Show the suspend count the task will be left with when detaching.
14060 @item set task exception-port
14061 @itemx set task excp
14062 @cindex task exception port, @sc{gnu} Hurd
14063 This command sets the task exception port to which @value{GDBN} will
14064 forward exceptions. The argument should be the value of the @dfn{send
14065 rights} of the task. @code{set task excp} is a shorthand alias.
14067 @item set noninvasive
14068 @cindex noninvasive task options
14069 This command switches @value{GDBN} to a mode that is the least
14070 invasive as far as interfering with the inferior is concerned. This
14071 is the same as using @code{set task pause}, @code{set exceptions}, and
14072 @code{set signals} to values opposite to the defaults.
14074 @item info send-rights
14075 @itemx info receive-rights
14076 @itemx info port-rights
14077 @itemx info port-sets
14078 @itemx info dead-names
14081 @cindex send rights, @sc{gnu} Hurd
14082 @cindex receive rights, @sc{gnu} Hurd
14083 @cindex port rights, @sc{gnu} Hurd
14084 @cindex port sets, @sc{gnu} Hurd
14085 @cindex dead names, @sc{gnu} Hurd
14086 These commands display information about, respectively, send rights,
14087 receive rights, port rights, port sets, and dead names of a task.
14088 There are also shorthand aliases: @code{info ports} for @code{info
14089 port-rights} and @code{info psets} for @code{info port-sets}.
14091 @item set thread pause
14092 @kindex set thread@r{, Hurd command}
14093 @cindex thread properties, @sc{gnu} Hurd
14094 @cindex pause current thread (@sc{gnu} Hurd)
14095 This command toggles current thread suspension when @value{GDBN} has
14096 control. Setting it to on takes effect immediately, and the current
14097 thread is suspended whenever @value{GDBN} gets control. Setting it to
14098 off will take effect the next time the inferior is continued.
14099 Normally, this command has no effect, since when @value{GDBN} has
14100 control, the whole task is suspended. However, if you used @code{set
14101 task pause off} (see above), this command comes in handy to suspend
14102 only the current thread.
14104 @item show thread pause
14105 @kindex show thread@r{, Hurd command}
14106 This command shows the state of current thread suspension.
14108 @item set thread run
14109 This command sets whether the current thread is allowed to run.
14111 @item show thread run
14112 Show whether the current thread is allowed to run.
14114 @item set thread detach-suspend-count
14115 @cindex thread suspend count, @sc{gnu} Hurd
14116 @cindex detach from thread, @sc{gnu} Hurd
14117 This command sets the suspend count @value{GDBN} will leave on a
14118 thread when detaching. This number is relative to the suspend count
14119 found by @value{GDBN} when it notices the thread; use @code{set thread
14120 takeover-suspend-count} to force it to an absolute value.
14122 @item show thread detach-suspend-count
14123 Show the suspend count @value{GDBN} will leave on the thread when
14126 @item set thread exception-port
14127 @itemx set thread excp
14128 Set the thread exception port to which to forward exceptions. This
14129 overrides the port set by @code{set task exception-port} (see above).
14130 @code{set thread excp} is the shorthand alias.
14132 @item set thread takeover-suspend-count
14133 Normally, @value{GDBN}'s thread suspend counts are relative to the
14134 value @value{GDBN} finds when it notices each thread. This command
14135 changes the suspend counts to be absolute instead.
14137 @item set thread default
14138 @itemx show thread default
14139 @cindex thread default settings, @sc{gnu} Hurd
14140 Each of the above @code{set thread} commands has a @code{set thread
14141 default} counterpart (e.g., @code{set thread default pause}, @code{set
14142 thread default exception-port}, etc.). The @code{thread default}
14143 variety of commands sets the default thread properties for all
14144 threads; you can then change the properties of individual threads with
14145 the non-default commands.
14150 @subsection QNX Neutrino
14151 @cindex QNX Neutrino
14153 @value{GDBN} provides the following commands specific to the QNX
14157 @item set debug nto-debug
14158 @kindex set debug nto-debug
14159 When set to on, enables debugging messages specific to the QNX
14162 @item show debug nto-debug
14163 @kindex show debug nto-debug
14164 Show the current state of QNX Neutrino messages.
14169 @section Embedded Operating Systems
14171 This section describes configurations involving the debugging of
14172 embedded operating systems that are available for several different
14176 * VxWorks:: Using @value{GDBN} with VxWorks
14179 @value{GDBN} includes the ability to debug programs running on
14180 various real-time operating systems.
14183 @subsection Using @value{GDBN} with VxWorks
14189 @kindex target vxworks
14190 @item target vxworks @var{machinename}
14191 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
14192 is the target system's machine name or IP address.
14196 On VxWorks, @code{load} links @var{filename} dynamically on the
14197 current target system as well as adding its symbols in @value{GDBN}.
14199 @value{GDBN} enables developers to spawn and debug tasks running on networked
14200 VxWorks targets from a Unix host. Already-running tasks spawned from
14201 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
14202 both the Unix host and on the VxWorks target. The program
14203 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
14204 installed with the name @code{vxgdb}, to distinguish it from a
14205 @value{GDBN} for debugging programs on the host itself.)
14208 @item VxWorks-timeout @var{args}
14209 @kindex vxworks-timeout
14210 All VxWorks-based targets now support the option @code{vxworks-timeout}.
14211 This option is set by the user, and @var{args} represents the number of
14212 seconds @value{GDBN} waits for responses to rpc's. You might use this if
14213 your VxWorks target is a slow software simulator or is on the far side
14214 of a thin network line.
14217 The following information on connecting to VxWorks was current when
14218 this manual was produced; newer releases of VxWorks may use revised
14221 @findex INCLUDE_RDB
14222 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
14223 to include the remote debugging interface routines in the VxWorks
14224 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
14225 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
14226 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
14227 source debugging task @code{tRdbTask} when VxWorks is booted. For more
14228 information on configuring and remaking VxWorks, see the manufacturer's
14230 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
14232 Once you have included @file{rdb.a} in your VxWorks system image and set
14233 your Unix execution search path to find @value{GDBN}, you are ready to
14234 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
14235 @code{vxgdb}, depending on your installation).
14237 @value{GDBN} comes up showing the prompt:
14244 * VxWorks Connection:: Connecting to VxWorks
14245 * VxWorks Download:: VxWorks download
14246 * VxWorks Attach:: Running tasks
14249 @node VxWorks Connection
14250 @subsubsection Connecting to VxWorks
14252 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
14253 network. To connect to a target whose host name is ``@code{tt}'', type:
14256 (vxgdb) target vxworks tt
14260 @value{GDBN} displays messages like these:
14263 Attaching remote machine across net...
14268 @value{GDBN} then attempts to read the symbol tables of any object modules
14269 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
14270 these files by searching the directories listed in the command search
14271 path (@pxref{Environment, ,Your Program's Environment}); if it fails
14272 to find an object file, it displays a message such as:
14275 prog.o: No such file or directory.
14278 When this happens, add the appropriate directory to the search path with
14279 the @value{GDBN} command @code{path}, and execute the @code{target}
14282 @node VxWorks Download
14283 @subsubsection VxWorks Download
14285 @cindex download to VxWorks
14286 If you have connected to the VxWorks target and you want to debug an
14287 object that has not yet been loaded, you can use the @value{GDBN}
14288 @code{load} command to download a file from Unix to VxWorks
14289 incrementally. The object file given as an argument to the @code{load}
14290 command is actually opened twice: first by the VxWorks target in order
14291 to download the code, then by @value{GDBN} in order to read the symbol
14292 table. This can lead to problems if the current working directories on
14293 the two systems differ. If both systems have NFS mounted the same
14294 filesystems, you can avoid these problems by using absolute paths.
14295 Otherwise, it is simplest to set the working directory on both systems
14296 to the directory in which the object file resides, and then to reference
14297 the file by its name, without any path. For instance, a program
14298 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
14299 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
14300 program, type this on VxWorks:
14303 -> cd "@var{vxpath}/vw/demo/rdb"
14307 Then, in @value{GDBN}, type:
14310 (vxgdb) cd @var{hostpath}/vw/demo/rdb
14311 (vxgdb) load prog.o
14314 @value{GDBN} displays a response similar to this:
14317 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
14320 You can also use the @code{load} command to reload an object module
14321 after editing and recompiling the corresponding source file. Note that
14322 this makes @value{GDBN} delete all currently-defined breakpoints,
14323 auto-displays, and convenience variables, and to clear the value
14324 history. (This is necessary in order to preserve the integrity of
14325 debugger's data structures that reference the target system's symbol
14328 @node VxWorks Attach
14329 @subsubsection Running Tasks
14331 @cindex running VxWorks tasks
14332 You can also attach to an existing task using the @code{attach} command as
14336 (vxgdb) attach @var{task}
14340 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
14341 or suspended when you attach to it. Running tasks are suspended at
14342 the time of attachment.
14344 @node Embedded Processors
14345 @section Embedded Processors
14347 This section goes into details specific to particular embedded
14350 @cindex send command to simulator
14351 Whenever a specific embedded processor has a simulator, @value{GDBN}
14352 allows to send an arbitrary command to the simulator.
14355 @item sim @var{command}
14356 @kindex sim@r{, a command}
14357 Send an arbitrary @var{command} string to the simulator. Consult the
14358 documentation for the specific simulator in use for information about
14359 acceptable commands.
14365 * M32R/D:: Renesas M32R/D
14366 * M68K:: Motorola M68K
14367 * MIPS Embedded:: MIPS Embedded
14368 * OpenRISC 1000:: OpenRisc 1000
14369 * PA:: HP PA Embedded
14370 * PowerPC:: PowerPC
14371 * Sparclet:: Tsqware Sparclet
14372 * Sparclite:: Fujitsu Sparclite
14373 * Z8000:: Zilog Z8000
14376 * Super-H:: Renesas Super-H
14385 @item target rdi @var{dev}
14386 ARM Angel monitor, via RDI library interface to ADP protocol. You may
14387 use this target to communicate with both boards running the Angel
14388 monitor, or with the EmbeddedICE JTAG debug device.
14391 @item target rdp @var{dev}
14396 @value{GDBN} provides the following ARM-specific commands:
14399 @item set arm disassembler
14401 This commands selects from a list of disassembly styles. The
14402 @code{"std"} style is the standard style.
14404 @item show arm disassembler
14406 Show the current disassembly style.
14408 @item set arm apcs32
14409 @cindex ARM 32-bit mode
14410 This command toggles ARM operation mode between 32-bit and 26-bit.
14412 @item show arm apcs32
14413 Display the current usage of the ARM 32-bit mode.
14415 @item set arm fpu @var{fputype}
14416 This command sets the ARM floating-point unit (FPU) type. The
14417 argument @var{fputype} can be one of these:
14421 Determine the FPU type by querying the OS ABI.
14423 Software FPU, with mixed-endian doubles on little-endian ARM
14426 GCC-compiled FPA co-processor.
14428 Software FPU with pure-endian doubles.
14434 Show the current type of the FPU.
14437 This command forces @value{GDBN} to use the specified ABI.
14440 Show the currently used ABI.
14442 @item set debug arm
14443 Toggle whether to display ARM-specific debugging messages from the ARM
14444 target support subsystem.
14446 @item show debug arm
14447 Show whether ARM-specific debugging messages are enabled.
14450 The following commands are available when an ARM target is debugged
14451 using the RDI interface:
14454 @item rdilogfile @r{[}@var{file}@r{]}
14456 @cindex ADP (Angel Debugger Protocol) logging
14457 Set the filename for the ADP (Angel Debugger Protocol) packet log.
14458 With an argument, sets the log file to the specified @var{file}. With
14459 no argument, show the current log file name. The default log file is
14462 @item rdilogenable @r{[}@var{arg}@r{]}
14463 @kindex rdilogenable
14464 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
14465 enables logging, with an argument 0 or @code{"no"} disables it. With
14466 no arguments displays the current setting. When logging is enabled,
14467 ADP packets exchanged between @value{GDBN} and the RDI target device
14468 are logged to a file.
14470 @item set rdiromatzero
14471 @kindex set rdiromatzero
14472 @cindex ROM at zero address, RDI
14473 Tell @value{GDBN} whether the target has ROM at address 0. If on,
14474 vector catching is disabled, so that zero address can be used. If off
14475 (the default), vector catching is enabled. For this command to take
14476 effect, it needs to be invoked prior to the @code{target rdi} command.
14478 @item show rdiromatzero
14479 @kindex show rdiromatzero
14480 Show the current setting of ROM at zero address.
14482 @item set rdiheartbeat
14483 @kindex set rdiheartbeat
14484 @cindex RDI heartbeat
14485 Enable or disable RDI heartbeat packets. It is not recommended to
14486 turn on this option, since it confuses ARM and EPI JTAG interface, as
14487 well as the Angel monitor.
14489 @item show rdiheartbeat
14490 @kindex show rdiheartbeat
14491 Show the setting of RDI heartbeat packets.
14496 @subsection Renesas M32R/D and M32R/SDI
14499 @kindex target m32r
14500 @item target m32r @var{dev}
14501 Renesas M32R/D ROM monitor.
14503 @kindex target m32rsdi
14504 @item target m32rsdi @var{dev}
14505 Renesas M32R SDI server, connected via parallel port to the board.
14508 The following @value{GDBN} commands are specific to the M32R monitor:
14511 @item set download-path @var{path}
14512 @kindex set download-path
14513 @cindex find downloadable @sc{srec} files (M32R)
14514 Set the default path for finding downloadable @sc{srec} files.
14516 @item show download-path
14517 @kindex show download-path
14518 Show the default path for downloadable @sc{srec} files.
14520 @item set board-address @var{addr}
14521 @kindex set board-address
14522 @cindex M32-EVA target board address
14523 Set the IP address for the M32R-EVA target board.
14525 @item show board-address
14526 @kindex show board-address
14527 Show the current IP address of the target board.
14529 @item set server-address @var{addr}
14530 @kindex set server-address
14531 @cindex download server address (M32R)
14532 Set the IP address for the download server, which is the @value{GDBN}'s
14535 @item show server-address
14536 @kindex show server-address
14537 Display the IP address of the download server.
14539 @item upload @r{[}@var{file}@r{]}
14540 @kindex upload@r{, M32R}
14541 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
14542 upload capability. If no @var{file} argument is given, the current
14543 executable file is uploaded.
14545 @item tload @r{[}@var{file}@r{]}
14546 @kindex tload@r{, M32R}
14547 Test the @code{upload} command.
14550 The following commands are available for M32R/SDI:
14555 @cindex reset SDI connection, M32R
14556 This command resets the SDI connection.
14560 This command shows the SDI connection status.
14563 @kindex debug_chaos
14564 @cindex M32R/Chaos debugging
14565 Instructs the remote that M32R/Chaos debugging is to be used.
14567 @item use_debug_dma
14568 @kindex use_debug_dma
14569 Instructs the remote to use the DEBUG_DMA method of accessing memory.
14572 @kindex use_mon_code
14573 Instructs the remote to use the MON_CODE method of accessing memory.
14576 @kindex use_ib_break
14577 Instructs the remote to set breakpoints by IB break.
14579 @item use_dbt_break
14580 @kindex use_dbt_break
14581 Instructs the remote to set breakpoints by DBT.
14587 The Motorola m68k configuration includes ColdFire support, and a
14588 target command for the following ROM monitor.
14592 @kindex target dbug
14593 @item target dbug @var{dev}
14594 dBUG ROM monitor for Motorola ColdFire.
14598 @node MIPS Embedded
14599 @subsection MIPS Embedded
14601 @cindex MIPS boards
14602 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
14603 MIPS board attached to a serial line. This is available when
14604 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
14607 Use these @value{GDBN} commands to specify the connection to your target board:
14610 @item target mips @var{port}
14611 @kindex target mips @var{port}
14612 To run a program on the board, start up @code{@value{GDBP}} with the
14613 name of your program as the argument. To connect to the board, use the
14614 command @samp{target mips @var{port}}, where @var{port} is the name of
14615 the serial port connected to the board. If the program has not already
14616 been downloaded to the board, you may use the @code{load} command to
14617 download it. You can then use all the usual @value{GDBN} commands.
14619 For example, this sequence connects to the target board through a serial
14620 port, and loads and runs a program called @var{prog} through the
14624 host$ @value{GDBP} @var{prog}
14625 @value{GDBN} is free software and @dots{}
14626 (@value{GDBP}) target mips /dev/ttyb
14627 (@value{GDBP}) load @var{prog}
14631 @item target mips @var{hostname}:@var{portnumber}
14632 On some @value{GDBN} host configurations, you can specify a TCP
14633 connection (for instance, to a serial line managed by a terminal
14634 concentrator) instead of a serial port, using the syntax
14635 @samp{@var{hostname}:@var{portnumber}}.
14637 @item target pmon @var{port}
14638 @kindex target pmon @var{port}
14641 @item target ddb @var{port}
14642 @kindex target ddb @var{port}
14643 NEC's DDB variant of PMON for Vr4300.
14645 @item target lsi @var{port}
14646 @kindex target lsi @var{port}
14647 LSI variant of PMON.
14649 @kindex target r3900
14650 @item target r3900 @var{dev}
14651 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
14653 @kindex target array
14654 @item target array @var{dev}
14655 Array Tech LSI33K RAID controller board.
14661 @value{GDBN} also supports these special commands for MIPS targets:
14664 @item set mipsfpu double
14665 @itemx set mipsfpu single
14666 @itemx set mipsfpu none
14667 @itemx set mipsfpu auto
14668 @itemx show mipsfpu
14669 @kindex set mipsfpu
14670 @kindex show mipsfpu
14671 @cindex MIPS remote floating point
14672 @cindex floating point, MIPS remote
14673 If your target board does not support the MIPS floating point
14674 coprocessor, you should use the command @samp{set mipsfpu none} (if you
14675 need this, you may wish to put the command in your @value{GDBN} init
14676 file). This tells @value{GDBN} how to find the return value of
14677 functions which return floating point values. It also allows
14678 @value{GDBN} to avoid saving the floating point registers when calling
14679 functions on the board. If you are using a floating point coprocessor
14680 with only single precision floating point support, as on the @sc{r4650}
14681 processor, use the command @samp{set mipsfpu single}. The default
14682 double precision floating point coprocessor may be selected using
14683 @samp{set mipsfpu double}.
14685 In previous versions the only choices were double precision or no
14686 floating point, so @samp{set mipsfpu on} will select double precision
14687 and @samp{set mipsfpu off} will select no floating point.
14689 As usual, you can inquire about the @code{mipsfpu} variable with
14690 @samp{show mipsfpu}.
14692 @item set timeout @var{seconds}
14693 @itemx set retransmit-timeout @var{seconds}
14694 @itemx show timeout
14695 @itemx show retransmit-timeout
14696 @cindex @code{timeout}, MIPS protocol
14697 @cindex @code{retransmit-timeout}, MIPS protocol
14698 @kindex set timeout
14699 @kindex show timeout
14700 @kindex set retransmit-timeout
14701 @kindex show retransmit-timeout
14702 You can control the timeout used while waiting for a packet, in the MIPS
14703 remote protocol, with the @code{set timeout @var{seconds}} command. The
14704 default is 5 seconds. Similarly, you can control the timeout used while
14705 waiting for an acknowledgement of a packet with the @code{set
14706 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
14707 You can inspect both values with @code{show timeout} and @code{show
14708 retransmit-timeout}. (These commands are @emph{only} available when
14709 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
14711 The timeout set by @code{set timeout} does not apply when @value{GDBN}
14712 is waiting for your program to stop. In that case, @value{GDBN} waits
14713 forever because it has no way of knowing how long the program is going
14714 to run before stopping.
14716 @item set syn-garbage-limit @var{num}
14717 @kindex set syn-garbage-limit@r{, MIPS remote}
14718 @cindex synchronize with remote MIPS target
14719 Limit the maximum number of characters @value{GDBN} should ignore when
14720 it tries to synchronize with the remote target. The default is 10
14721 characters. Setting the limit to -1 means there's no limit.
14723 @item show syn-garbage-limit
14724 @kindex show syn-garbage-limit@r{, MIPS remote}
14725 Show the current limit on the number of characters to ignore when
14726 trying to synchronize with the remote system.
14728 @item set monitor-prompt @var{prompt}
14729 @kindex set monitor-prompt@r{, MIPS remote}
14730 @cindex remote monitor prompt
14731 Tell @value{GDBN} to expect the specified @var{prompt} string from the
14732 remote monitor. The default depends on the target:
14742 @item show monitor-prompt
14743 @kindex show monitor-prompt@r{, MIPS remote}
14744 Show the current strings @value{GDBN} expects as the prompt from the
14747 @item set monitor-warnings
14748 @kindex set monitor-warnings@r{, MIPS remote}
14749 Enable or disable monitor warnings about hardware breakpoints. This
14750 has effect only for the @code{lsi} target. When on, @value{GDBN} will
14751 display warning messages whose codes are returned by the @code{lsi}
14752 PMON monitor for breakpoint commands.
14754 @item show monitor-warnings
14755 @kindex show monitor-warnings@r{, MIPS remote}
14756 Show the current setting of printing monitor warnings.
14758 @item pmon @var{command}
14759 @kindex pmon@r{, MIPS remote}
14760 @cindex send PMON command
14761 This command allows sending an arbitrary @var{command} string to the
14762 monitor. The monitor must be in debug mode for this to work.
14765 @node OpenRISC 1000
14766 @subsection OpenRISC 1000
14767 @cindex OpenRISC 1000
14769 @cindex or1k boards
14770 See OR1k Architecture document (@uref{www.opencores.org}) for more information
14771 about platform and commands.
14775 @kindex target jtag
14776 @item target jtag jtag://@var{host}:@var{port}
14778 Connects to remote JTAG server.
14779 JTAG remote server can be either an or1ksim or JTAG server,
14780 connected via parallel port to the board.
14782 Example: @code{target jtag jtag://localhost:9999}
14785 @item or1ksim @var{command}
14786 If connected to @code{or1ksim} OpenRISC 1000 Architectural
14787 Simulator, proprietary commands can be executed.
14789 @kindex info or1k spr
14790 @item info or1k spr
14791 Displays spr groups.
14793 @item info or1k spr @var{group}
14794 @itemx info or1k spr @var{groupno}
14795 Displays register names in selected group.
14797 @item info or1k spr @var{group} @var{register}
14798 @itemx info or1k spr @var{register}
14799 @itemx info or1k spr @var{groupno} @var{registerno}
14800 @itemx info or1k spr @var{registerno}
14801 Shows information about specified spr register.
14804 @item spr @var{group} @var{register} @var{value}
14805 @itemx spr @var{register @var{value}}
14806 @itemx spr @var{groupno} @var{registerno @var{value}}
14807 @itemx spr @var{registerno @var{value}}
14808 Writes @var{value} to specified spr register.
14811 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
14812 It is very similar to @value{GDBN} trace, except it does not interfere with normal
14813 program execution and is thus much faster. Hardware breakpoints/watchpoint
14814 triggers can be set using:
14817 Load effective address/data
14819 Store effective address/data
14821 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
14826 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
14827 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
14829 @code{htrace} commands:
14830 @cindex OpenRISC 1000 htrace
14833 @item hwatch @var{conditional}
14834 Set hardware watchpoint on combination of Load/Store Effective Address(es)
14835 or Data. For example:
14837 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
14839 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
14843 Display information about current HW trace configuration.
14845 @item htrace trigger @var{conditional}
14846 Set starting criteria for HW trace.
14848 @item htrace qualifier @var{conditional}
14849 Set acquisition qualifier for HW trace.
14851 @item htrace stop @var{conditional}
14852 Set HW trace stopping criteria.
14854 @item htrace record [@var{data}]*
14855 Selects the data to be recorded, when qualifier is met and HW trace was
14858 @item htrace enable
14859 @itemx htrace disable
14860 Enables/disables the HW trace.
14862 @item htrace rewind [@var{filename}]
14863 Clears currently recorded trace data.
14865 If filename is specified, new trace file is made and any newly collected data
14866 will be written there.
14868 @item htrace print [@var{start} [@var{len}]]
14869 Prints trace buffer, using current record configuration.
14871 @item htrace mode continuous
14872 Set continuous trace mode.
14874 @item htrace mode suspend
14875 Set suspend trace mode.
14880 @subsection PowerPC
14883 @kindex target dink32
14884 @item target dink32 @var{dev}
14885 DINK32 ROM monitor.
14887 @kindex target ppcbug
14888 @item target ppcbug @var{dev}
14889 @kindex target ppcbug1
14890 @item target ppcbug1 @var{dev}
14891 PPCBUG ROM monitor for PowerPC.
14894 @item target sds @var{dev}
14895 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
14898 @cindex SDS protocol
14899 The following commands specific to the SDS protocol are supported
14903 @item set sdstimeout @var{nsec}
14904 @kindex set sdstimeout
14905 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
14906 default is 2 seconds.
14908 @item show sdstimeout
14909 @kindex show sdstimeout
14910 Show the current value of the SDS timeout.
14912 @item sds @var{command}
14913 @kindex sds@r{, a command}
14914 Send the specified @var{command} string to the SDS monitor.
14919 @subsection HP PA Embedded
14923 @kindex target op50n
14924 @item target op50n @var{dev}
14925 OP50N monitor, running on an OKI HPPA board.
14927 @kindex target w89k
14928 @item target w89k @var{dev}
14929 W89K monitor, running on a Winbond HPPA board.
14934 @subsection Tsqware Sparclet
14938 @value{GDBN} enables developers to debug tasks running on
14939 Sparclet targets from a Unix host.
14940 @value{GDBN} uses code that runs on
14941 both the Unix host and on the Sparclet target. The program
14942 @code{@value{GDBP}} is installed and executed on the Unix host.
14945 @item remotetimeout @var{args}
14946 @kindex remotetimeout
14947 @value{GDBN} supports the option @code{remotetimeout}.
14948 This option is set by the user, and @var{args} represents the number of
14949 seconds @value{GDBN} waits for responses.
14952 @cindex compiling, on Sparclet
14953 When compiling for debugging, include the options @samp{-g} to get debug
14954 information and @samp{-Ttext} to relocate the program to where you wish to
14955 load it on the target. You may also want to add the options @samp{-n} or
14956 @samp{-N} in order to reduce the size of the sections. Example:
14959 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
14962 You can use @code{objdump} to verify that the addresses are what you intended:
14965 sparclet-aout-objdump --headers --syms prog
14968 @cindex running, on Sparclet
14970 your Unix execution search path to find @value{GDBN}, you are ready to
14971 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
14972 (or @code{sparclet-aout-gdb}, depending on your installation).
14974 @value{GDBN} comes up showing the prompt:
14981 * Sparclet File:: Setting the file to debug
14982 * Sparclet Connection:: Connecting to Sparclet
14983 * Sparclet Download:: Sparclet download
14984 * Sparclet Execution:: Running and debugging
14987 @node Sparclet File
14988 @subsubsection Setting File to Debug
14990 The @value{GDBN} command @code{file} lets you choose with program to debug.
14993 (gdbslet) file prog
14997 @value{GDBN} then attempts to read the symbol table of @file{prog}.
14998 @value{GDBN} locates
14999 the file by searching the directories listed in the command search
15001 If the file was compiled with debug information (option @samp{-g}), source
15002 files will be searched as well.
15003 @value{GDBN} locates
15004 the source files by searching the directories listed in the directory search
15005 path (@pxref{Environment, ,Your Program's Environment}).
15007 to find a file, it displays a message such as:
15010 prog: No such file or directory.
15013 When this happens, add the appropriate directories to the search paths with
15014 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
15015 @code{target} command again.
15017 @node Sparclet Connection
15018 @subsubsection Connecting to Sparclet
15020 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
15021 To connect to a target on serial port ``@code{ttya}'', type:
15024 (gdbslet) target sparclet /dev/ttya
15025 Remote target sparclet connected to /dev/ttya
15026 main () at ../prog.c:3
15030 @value{GDBN} displays messages like these:
15036 @node Sparclet Download
15037 @subsubsection Sparclet Download
15039 @cindex download to Sparclet
15040 Once connected to the Sparclet target,
15041 you can use the @value{GDBN}
15042 @code{load} command to download the file from the host to the target.
15043 The file name and load offset should be given as arguments to the @code{load}
15045 Since the file format is aout, the program must be loaded to the starting
15046 address. You can use @code{objdump} to find out what this value is. The load
15047 offset is an offset which is added to the VMA (virtual memory address)
15048 of each of the file's sections.
15049 For instance, if the program
15050 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
15051 and bss at 0x12010170, in @value{GDBN}, type:
15054 (gdbslet) load prog 0x12010000
15055 Loading section .text, size 0xdb0 vma 0x12010000
15058 If the code is loaded at a different address then what the program was linked
15059 to, you may need to use the @code{section} and @code{add-symbol-file} commands
15060 to tell @value{GDBN} where to map the symbol table.
15062 @node Sparclet Execution
15063 @subsubsection Running and Debugging
15065 @cindex running and debugging Sparclet programs
15066 You can now begin debugging the task using @value{GDBN}'s execution control
15067 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
15068 manual for the list of commands.
15072 Breakpoint 1 at 0x12010000: file prog.c, line 3.
15074 Starting program: prog
15075 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
15076 3 char *symarg = 0;
15078 4 char *execarg = "hello!";
15083 @subsection Fujitsu Sparclite
15087 @kindex target sparclite
15088 @item target sparclite @var{dev}
15089 Fujitsu sparclite boards, used only for the purpose of loading.
15090 You must use an additional command to debug the program.
15091 For example: target remote @var{dev} using @value{GDBN} standard
15097 @subsection Zilog Z8000
15100 @cindex simulator, Z8000
15101 @cindex Zilog Z8000 simulator
15103 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
15106 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
15107 unsegmented variant of the Z8000 architecture) or the Z8001 (the
15108 segmented variant). The simulator recognizes which architecture is
15109 appropriate by inspecting the object code.
15112 @item target sim @var{args}
15114 @kindex target sim@r{, with Z8000}
15115 Debug programs on a simulated CPU. If the simulator supports setup
15116 options, specify them via @var{args}.
15120 After specifying this target, you can debug programs for the simulated
15121 CPU in the same style as programs for your host computer; use the
15122 @code{file} command to load a new program image, the @code{run} command
15123 to run your program, and so on.
15125 As well as making available all the usual machine registers
15126 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
15127 additional items of information as specially named registers:
15132 Counts clock-ticks in the simulator.
15135 Counts instructions run in the simulator.
15138 Execution time in 60ths of a second.
15142 You can refer to these values in @value{GDBN} expressions with the usual
15143 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
15144 conditional breakpoint that suspends only after at least 5000
15145 simulated clock ticks.
15148 @subsection Atmel AVR
15151 When configured for debugging the Atmel AVR, @value{GDBN} supports the
15152 following AVR-specific commands:
15155 @item info io_registers
15156 @kindex info io_registers@r{, AVR}
15157 @cindex I/O registers (Atmel AVR)
15158 This command displays information about the AVR I/O registers. For
15159 each register, @value{GDBN} prints its number and value.
15166 When configured for debugging CRIS, @value{GDBN} provides the
15167 following CRIS-specific commands:
15170 @item set cris-version @var{ver}
15171 @cindex CRIS version
15172 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
15173 The CRIS version affects register names and sizes. This command is useful in
15174 case autodetection of the CRIS version fails.
15176 @item show cris-version
15177 Show the current CRIS version.
15179 @item set cris-dwarf2-cfi
15180 @cindex DWARF-2 CFI and CRIS
15181 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
15182 Change to @samp{off} when using @code{gcc-cris} whose version is below
15185 @item show cris-dwarf2-cfi
15186 Show the current state of using DWARF-2 CFI.
15188 @item set cris-mode @var{mode}
15190 Set the current CRIS mode to @var{mode}. It should only be changed when
15191 debugging in guru mode, in which case it should be set to
15192 @samp{guru} (the default is @samp{normal}).
15194 @item show cris-mode
15195 Show the current CRIS mode.
15199 @subsection Renesas Super-H
15202 For the Renesas Super-H processor, @value{GDBN} provides these
15207 @kindex regs@r{, Super-H}
15208 Show the values of all Super-H registers.
15212 @node Architectures
15213 @section Architectures
15215 This section describes characteristics of architectures that affect
15216 all uses of @value{GDBN} with the architecture, both native and cross.
15223 * HPPA:: HP PA architecture
15224 * SPU:: Cell Broadband Engine SPU architecture
15228 @subsection x86 Architecture-specific Issues
15231 @item set struct-convention @var{mode}
15232 @kindex set struct-convention
15233 @cindex struct return convention
15234 @cindex struct/union returned in registers
15235 Set the convention used by the inferior to return @code{struct}s and
15236 @code{union}s from functions to @var{mode}. Possible values of
15237 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
15238 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
15239 are returned on the stack, while @code{"reg"} means that a
15240 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
15241 be returned in a register.
15243 @item show struct-convention
15244 @kindex show struct-convention
15245 Show the current setting of the convention to return @code{struct}s
15254 @kindex set rstack_high_address
15255 @cindex AMD 29K register stack
15256 @cindex register stack, AMD29K
15257 @item set rstack_high_address @var{address}
15258 On AMD 29000 family processors, registers are saved in a separate
15259 @dfn{register stack}. There is no way for @value{GDBN} to determine the
15260 extent of this stack. Normally, @value{GDBN} just assumes that the
15261 stack is ``large enough''. This may result in @value{GDBN} referencing
15262 memory locations that do not exist. If necessary, you can get around
15263 this problem by specifying the ending address of the register stack with
15264 the @code{set rstack_high_address} command. The argument should be an
15265 address, which you probably want to precede with @samp{0x} to specify in
15268 @kindex show rstack_high_address
15269 @item show rstack_high_address
15270 Display the current limit of the register stack, on AMD 29000 family
15278 See the following section.
15283 @cindex stack on Alpha
15284 @cindex stack on MIPS
15285 @cindex Alpha stack
15287 Alpha- and MIPS-based computers use an unusual stack frame, which
15288 sometimes requires @value{GDBN} to search backward in the object code to
15289 find the beginning of a function.
15291 @cindex response time, MIPS debugging
15292 To improve response time (especially for embedded applications, where
15293 @value{GDBN} may be restricted to a slow serial line for this search)
15294 you may want to limit the size of this search, using one of these
15298 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
15299 @item set heuristic-fence-post @var{limit}
15300 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
15301 search for the beginning of a function. A value of @var{0} (the
15302 default) means there is no limit. However, except for @var{0}, the
15303 larger the limit the more bytes @code{heuristic-fence-post} must search
15304 and therefore the longer it takes to run. You should only need to use
15305 this command when debugging a stripped executable.
15307 @item show heuristic-fence-post
15308 Display the current limit.
15312 These commands are available @emph{only} when @value{GDBN} is configured
15313 for debugging programs on Alpha or MIPS processors.
15315 Several MIPS-specific commands are available when debugging MIPS
15319 @item set mips abi @var{arg}
15320 @kindex set mips abi
15321 @cindex set ABI for MIPS
15322 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
15323 values of @var{arg} are:
15327 The default ABI associated with the current binary (this is the
15338 @item show mips abi
15339 @kindex show mips abi
15340 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
15343 @itemx show mipsfpu
15344 @xref{MIPS Embedded, set mipsfpu}.
15346 @item set mips mask-address @var{arg}
15347 @kindex set mips mask-address
15348 @cindex MIPS addresses, masking
15349 This command determines whether the most-significant 32 bits of 64-bit
15350 MIPS addresses are masked off. The argument @var{arg} can be
15351 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
15352 setting, which lets @value{GDBN} determine the correct value.
15354 @item show mips mask-address
15355 @kindex show mips mask-address
15356 Show whether the upper 32 bits of MIPS addresses are masked off or
15359 @item set remote-mips64-transfers-32bit-regs
15360 @kindex set remote-mips64-transfers-32bit-regs
15361 This command controls compatibility with 64-bit MIPS targets that
15362 transfer data in 32-bit quantities. If you have an old MIPS 64 target
15363 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
15364 and 64 bits for other registers, set this option to @samp{on}.
15366 @item show remote-mips64-transfers-32bit-regs
15367 @kindex show remote-mips64-transfers-32bit-regs
15368 Show the current setting of compatibility with older MIPS 64 targets.
15370 @item set debug mips
15371 @kindex set debug mips
15372 This command turns on and off debugging messages for the MIPS-specific
15373 target code in @value{GDBN}.
15375 @item show debug mips
15376 @kindex show debug mips
15377 Show the current setting of MIPS debugging messages.
15383 @cindex HPPA support
15385 When @value{GDBN} is debugging the HP PA architecture, it provides the
15386 following special commands:
15389 @item set debug hppa
15390 @kindex set debug hppa
15391 This command determines whether HPPA architecture-specific debugging
15392 messages are to be displayed.
15394 @item show debug hppa
15395 Show whether HPPA debugging messages are displayed.
15397 @item maint print unwind @var{address}
15398 @kindex maint print unwind@r{, HPPA}
15399 This command displays the contents of the unwind table entry at the
15400 given @var{address}.
15406 @subsection Cell Broadband Engine SPU architecture
15407 @cindex Cell Broadband Engine
15410 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
15411 it provides the following special commands:
15414 @item info spu event
15416 Display SPU event facility status. Shows current event mask
15417 and pending event status.
15419 @item info spu signal
15420 Display SPU signal notification facility status. Shows pending
15421 signal-control word and signal notification mode of both signal
15422 notification channels.
15424 @item info spu mailbox
15425 Display SPU mailbox facility status. Shows all pending entries,
15426 in order of processing, in each of the SPU Write Outbound,
15427 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
15430 Display MFC DMA status. Shows all pending commands in the MFC
15431 DMA queue. For each entry, opcode, tag, class IDs, effective
15432 and local store addresses and transfer size are shown.
15434 @item info spu proxydma
15435 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
15436 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
15437 and local store addresses and transfer size are shown.
15442 @node Controlling GDB
15443 @chapter Controlling @value{GDBN}
15445 You can alter the way @value{GDBN} interacts with you by using the
15446 @code{set} command. For commands controlling how @value{GDBN} displays
15447 data, see @ref{Print Settings, ,Print Settings}. Other settings are
15452 * Editing:: Command editing
15453 * Command History:: Command history
15454 * Screen Size:: Screen size
15455 * Numbers:: Numbers
15456 * ABI:: Configuring the current ABI
15457 * Messages/Warnings:: Optional warnings and messages
15458 * Debugging Output:: Optional messages about internal happenings
15466 @value{GDBN} indicates its readiness to read a command by printing a string
15467 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
15468 can change the prompt string with the @code{set prompt} command. For
15469 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
15470 the prompt in one of the @value{GDBN} sessions so that you can always tell
15471 which one you are talking to.
15473 @emph{Note:} @code{set prompt} does not add a space for you after the
15474 prompt you set. This allows you to set a prompt which ends in a space
15475 or a prompt that does not.
15479 @item set prompt @var{newprompt}
15480 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
15482 @kindex show prompt
15484 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
15488 @section Command Editing
15490 @cindex command line editing
15492 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
15493 @sc{gnu} library provides consistent behavior for programs which provide a
15494 command line interface to the user. Advantages are @sc{gnu} Emacs-style
15495 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
15496 substitution, and a storage and recall of command history across
15497 debugging sessions.
15499 You may control the behavior of command line editing in @value{GDBN} with the
15500 command @code{set}.
15503 @kindex set editing
15506 @itemx set editing on
15507 Enable command line editing (enabled by default).
15509 @item set editing off
15510 Disable command line editing.
15512 @kindex show editing
15514 Show whether command line editing is enabled.
15517 @xref{Command Line Editing}, for more details about the Readline
15518 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
15519 encouraged to read that chapter.
15521 @node Command History
15522 @section Command History
15523 @cindex command history
15525 @value{GDBN} can keep track of the commands you type during your
15526 debugging sessions, so that you can be certain of precisely what
15527 happened. Use these commands to manage the @value{GDBN} command
15530 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
15531 package, to provide the history facility. @xref{Using History
15532 Interactively}, for the detailed description of the History library.
15534 To issue a command to @value{GDBN} without affecting certain aspects of
15535 the state which is seen by users, prefix it with @samp{server }
15536 (@pxref{Server Prefix}). This
15537 means that this command will not affect the command history, nor will it
15538 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
15539 pressed on a line by itself.
15541 @cindex @code{server}, command prefix
15542 The server prefix does not affect the recording of values into the value
15543 history; to print a value without recording it into the value history,
15544 use the @code{output} command instead of the @code{print} command.
15546 Here is the description of @value{GDBN} commands related to command
15550 @cindex history substitution
15551 @cindex history file
15552 @kindex set history filename
15553 @cindex @env{GDBHISTFILE}, environment variable
15554 @item set history filename @var{fname}
15555 Set the name of the @value{GDBN} command history file to @var{fname}.
15556 This is the file where @value{GDBN} reads an initial command history
15557 list, and where it writes the command history from this session when it
15558 exits. You can access this list through history expansion or through
15559 the history command editing characters listed below. This file defaults
15560 to the value of the environment variable @code{GDBHISTFILE}, or to
15561 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
15564 @cindex save command history
15565 @kindex set history save
15566 @item set history save
15567 @itemx set history save on
15568 Record command history in a file, whose name may be specified with the
15569 @code{set history filename} command. By default, this option is disabled.
15571 @item set history save off
15572 Stop recording command history in a file.
15574 @cindex history size
15575 @kindex set history size
15576 @cindex @env{HISTSIZE}, environment variable
15577 @item set history size @var{size}
15578 Set the number of commands which @value{GDBN} keeps in its history list.
15579 This defaults to the value of the environment variable
15580 @code{HISTSIZE}, or to 256 if this variable is not set.
15583 History expansion assigns special meaning to the character @kbd{!}.
15584 @xref{Event Designators}, for more details.
15586 @cindex history expansion, turn on/off
15587 Since @kbd{!} is also the logical not operator in C, history expansion
15588 is off by default. If you decide to enable history expansion with the
15589 @code{set history expansion on} command, you may sometimes need to
15590 follow @kbd{!} (when it is used as logical not, in an expression) with
15591 a space or a tab to prevent it from being expanded. The readline
15592 history facilities do not attempt substitution on the strings
15593 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
15595 The commands to control history expansion are:
15598 @item set history expansion on
15599 @itemx set history expansion
15600 @kindex set history expansion
15601 Enable history expansion. History expansion is off by default.
15603 @item set history expansion off
15604 Disable history expansion.
15607 @kindex show history
15609 @itemx show history filename
15610 @itemx show history save
15611 @itemx show history size
15612 @itemx show history expansion
15613 These commands display the state of the @value{GDBN} history parameters.
15614 @code{show history} by itself displays all four states.
15619 @kindex show commands
15620 @cindex show last commands
15621 @cindex display command history
15622 @item show commands
15623 Display the last ten commands in the command history.
15625 @item show commands @var{n}
15626 Print ten commands centered on command number @var{n}.
15628 @item show commands +
15629 Print ten commands just after the commands last printed.
15633 @section Screen Size
15634 @cindex size of screen
15635 @cindex pauses in output
15637 Certain commands to @value{GDBN} may produce large amounts of
15638 information output to the screen. To help you read all of it,
15639 @value{GDBN} pauses and asks you for input at the end of each page of
15640 output. Type @key{RET} when you want to continue the output, or @kbd{q}
15641 to discard the remaining output. Also, the screen width setting
15642 determines when to wrap lines of output. Depending on what is being
15643 printed, @value{GDBN} tries to break the line at a readable place,
15644 rather than simply letting it overflow onto the following line.
15646 Normally @value{GDBN} knows the size of the screen from the terminal
15647 driver software. For example, on Unix @value{GDBN} uses the termcap data base
15648 together with the value of the @code{TERM} environment variable and the
15649 @code{stty rows} and @code{stty cols} settings. If this is not correct,
15650 you can override it with the @code{set height} and @code{set
15657 @kindex show height
15658 @item set height @var{lpp}
15660 @itemx set width @var{cpl}
15662 These @code{set} commands specify a screen height of @var{lpp} lines and
15663 a screen width of @var{cpl} characters. The associated @code{show}
15664 commands display the current settings.
15666 If you specify a height of zero lines, @value{GDBN} does not pause during
15667 output no matter how long the output is. This is useful if output is to a
15668 file or to an editor buffer.
15670 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
15671 from wrapping its output.
15673 @item set pagination on
15674 @itemx set pagination off
15675 @kindex set pagination
15676 Turn the output pagination on or off; the default is on. Turning
15677 pagination off is the alternative to @code{set height 0}.
15679 @item show pagination
15680 @kindex show pagination
15681 Show the current pagination mode.
15686 @cindex number representation
15687 @cindex entering numbers
15689 You can always enter numbers in octal, decimal, or hexadecimal in
15690 @value{GDBN} by the usual conventions: octal numbers begin with
15691 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
15692 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
15693 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
15694 10; likewise, the default display for numbers---when no particular
15695 format is specified---is base 10. You can change the default base for
15696 both input and output with the commands described below.
15699 @kindex set input-radix
15700 @item set input-radix @var{base}
15701 Set the default base for numeric input. Supported choices
15702 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15703 specified either unambiguously or using the current input radix; for
15707 set input-radix 012
15708 set input-radix 10.
15709 set input-radix 0xa
15713 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
15714 leaves the input radix unchanged, no matter what it was, since
15715 @samp{10}, being without any leading or trailing signs of its base, is
15716 interpreted in the current radix. Thus, if the current radix is 16,
15717 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
15720 @kindex set output-radix
15721 @item set output-radix @var{base}
15722 Set the default base for numeric display. Supported choices
15723 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15724 specified either unambiguously or using the current input radix.
15726 @kindex show input-radix
15727 @item show input-radix
15728 Display the current default base for numeric input.
15730 @kindex show output-radix
15731 @item show output-radix
15732 Display the current default base for numeric display.
15734 @item set radix @r{[}@var{base}@r{]}
15738 These commands set and show the default base for both input and output
15739 of numbers. @code{set radix} sets the radix of input and output to
15740 the same base; without an argument, it resets the radix back to its
15741 default value of 10.
15746 @section Configuring the Current ABI
15748 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
15749 application automatically. However, sometimes you need to override its
15750 conclusions. Use these commands to manage @value{GDBN}'s view of the
15757 One @value{GDBN} configuration can debug binaries for multiple operating
15758 system targets, either via remote debugging or native emulation.
15759 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
15760 but you can override its conclusion using the @code{set osabi} command.
15761 One example where this is useful is in debugging of binaries which use
15762 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
15763 not have the same identifying marks that the standard C library for your
15768 Show the OS ABI currently in use.
15771 With no argument, show the list of registered available OS ABI's.
15773 @item set osabi @var{abi}
15774 Set the current OS ABI to @var{abi}.
15777 @cindex float promotion
15779 Generally, the way that an argument of type @code{float} is passed to a
15780 function depends on whether the function is prototyped. For a prototyped
15781 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
15782 according to the architecture's convention for @code{float}. For unprototyped
15783 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
15784 @code{double} and then passed.
15786 Unfortunately, some forms of debug information do not reliably indicate whether
15787 a function is prototyped. If @value{GDBN} calls a function that is not marked
15788 as prototyped, it consults @kbd{set coerce-float-to-double}.
15791 @kindex set coerce-float-to-double
15792 @item set coerce-float-to-double
15793 @itemx set coerce-float-to-double on
15794 Arguments of type @code{float} will be promoted to @code{double} when passed
15795 to an unprototyped function. This is the default setting.
15797 @item set coerce-float-to-double off
15798 Arguments of type @code{float} will be passed directly to unprototyped
15801 @kindex show coerce-float-to-double
15802 @item show coerce-float-to-double
15803 Show the current setting of promoting @code{float} to @code{double}.
15807 @kindex show cp-abi
15808 @value{GDBN} needs to know the ABI used for your program's C@t{++}
15809 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
15810 used to build your application. @value{GDBN} only fully supports
15811 programs with a single C@t{++} ABI; if your program contains code using
15812 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
15813 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
15814 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
15815 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
15816 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
15817 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
15822 Show the C@t{++} ABI currently in use.
15825 With no argument, show the list of supported C@t{++} ABI's.
15827 @item set cp-abi @var{abi}
15828 @itemx set cp-abi auto
15829 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
15832 @node Messages/Warnings
15833 @section Optional Warnings and Messages
15835 @cindex verbose operation
15836 @cindex optional warnings
15837 By default, @value{GDBN} is silent about its inner workings. If you are
15838 running on a slow machine, you may want to use the @code{set verbose}
15839 command. This makes @value{GDBN} tell you when it does a lengthy
15840 internal operation, so you will not think it has crashed.
15842 Currently, the messages controlled by @code{set verbose} are those
15843 which announce that the symbol table for a source file is being read;
15844 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
15847 @kindex set verbose
15848 @item set verbose on
15849 Enables @value{GDBN} output of certain informational messages.
15851 @item set verbose off
15852 Disables @value{GDBN} output of certain informational messages.
15854 @kindex show verbose
15856 Displays whether @code{set verbose} is on or off.
15859 By default, if @value{GDBN} encounters bugs in the symbol table of an
15860 object file, it is silent; but if you are debugging a compiler, you may
15861 find this information useful (@pxref{Symbol Errors, ,Errors Reading
15866 @kindex set complaints
15867 @item set complaints @var{limit}
15868 Permits @value{GDBN} to output @var{limit} complaints about each type of
15869 unusual symbols before becoming silent about the problem. Set
15870 @var{limit} to zero to suppress all complaints; set it to a large number
15871 to prevent complaints from being suppressed.
15873 @kindex show complaints
15874 @item show complaints
15875 Displays how many symbol complaints @value{GDBN} is permitted to produce.
15879 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
15880 lot of stupid questions to confirm certain commands. For example, if
15881 you try to run a program which is already running:
15885 The program being debugged has been started already.
15886 Start it from the beginning? (y or n)
15889 If you are willing to unflinchingly face the consequences of your own
15890 commands, you can disable this ``feature'':
15894 @kindex set confirm
15896 @cindex confirmation
15897 @cindex stupid questions
15898 @item set confirm off
15899 Disables confirmation requests.
15901 @item set confirm on
15902 Enables confirmation requests (the default).
15904 @kindex show confirm
15906 Displays state of confirmation requests.
15910 @cindex command tracing
15911 If you need to debug user-defined commands or sourced files you may find it
15912 useful to enable @dfn{command tracing}. In this mode each command will be
15913 printed as it is executed, prefixed with one or more @samp{+} symbols, the
15914 quantity denoting the call depth of each command.
15917 @kindex set trace-commands
15918 @cindex command scripts, debugging
15919 @item set trace-commands on
15920 Enable command tracing.
15921 @item set trace-commands off
15922 Disable command tracing.
15923 @item show trace-commands
15924 Display the current state of command tracing.
15927 @node Debugging Output
15928 @section Optional Messages about Internal Happenings
15929 @cindex optional debugging messages
15931 @value{GDBN} has commands that enable optional debugging messages from
15932 various @value{GDBN} subsystems; normally these commands are of
15933 interest to @value{GDBN} maintainers, or when reporting a bug. This
15934 section documents those commands.
15937 @kindex set exec-done-display
15938 @item set exec-done-display
15939 Turns on or off the notification of asynchronous commands'
15940 completion. When on, @value{GDBN} will print a message when an
15941 asynchronous command finishes its execution. The default is off.
15942 @kindex show exec-done-display
15943 @item show exec-done-display
15944 Displays the current setting of asynchronous command completion
15947 @cindex gdbarch debugging info
15948 @cindex architecture debugging info
15949 @item set debug arch
15950 Turns on or off display of gdbarch debugging info. The default is off
15952 @item show debug arch
15953 Displays the current state of displaying gdbarch debugging info.
15954 @item set debug aix-thread
15955 @cindex AIX threads
15956 Display debugging messages about inner workings of the AIX thread
15958 @item show debug aix-thread
15959 Show the current state of AIX thread debugging info display.
15960 @item set debug event
15961 @cindex event debugging info
15962 Turns on or off display of @value{GDBN} event debugging info. The
15964 @item show debug event
15965 Displays the current state of displaying @value{GDBN} event debugging
15967 @item set debug expression
15968 @cindex expression debugging info
15969 Turns on or off display of debugging info about @value{GDBN}
15970 expression parsing. The default is off.
15971 @item show debug expression
15972 Displays the current state of displaying debugging info about
15973 @value{GDBN} expression parsing.
15974 @item set debug frame
15975 @cindex frame debugging info
15976 Turns on or off display of @value{GDBN} frame debugging info. The
15978 @item show debug frame
15979 Displays the current state of displaying @value{GDBN} frame debugging
15981 @item set debug infrun
15982 @cindex inferior debugging info
15983 Turns on or off display of @value{GDBN} debugging info for running the inferior.
15984 The default is off. @file{infrun.c} contains GDB's runtime state machine used
15985 for implementing operations such as single-stepping the inferior.
15986 @item show debug infrun
15987 Displays the current state of @value{GDBN} inferior debugging.
15988 @item set debug lin-lwp
15989 @cindex @sc{gnu}/Linux LWP debug messages
15990 @cindex Linux lightweight processes
15991 Turns on or off debugging messages from the Linux LWP debug support.
15992 @item show debug lin-lwp
15993 Show the current state of Linux LWP debugging messages.
15994 @item set debug observer
15995 @cindex observer debugging info
15996 Turns on or off display of @value{GDBN} observer debugging. This
15997 includes info such as the notification of observable events.
15998 @item show debug observer
15999 Displays the current state of observer debugging.
16000 @item set debug overload
16001 @cindex C@t{++} overload debugging info
16002 Turns on or off display of @value{GDBN} C@t{++} overload debugging
16003 info. This includes info such as ranking of functions, etc. The default
16005 @item show debug overload
16006 Displays the current state of displaying @value{GDBN} C@t{++} overload
16008 @cindex packets, reporting on stdout
16009 @cindex serial connections, debugging
16010 @cindex debug remote protocol
16011 @cindex remote protocol debugging
16012 @cindex display remote packets
16013 @item set debug remote
16014 Turns on or off display of reports on all packets sent back and forth across
16015 the serial line to the remote machine. The info is printed on the
16016 @value{GDBN} standard output stream. The default is off.
16017 @item show debug remote
16018 Displays the state of display of remote packets.
16019 @item set debug serial
16020 Turns on or off display of @value{GDBN} serial debugging info. The
16022 @item show debug serial
16023 Displays the current state of displaying @value{GDBN} serial debugging
16025 @item set debug solib-frv
16026 @cindex FR-V shared-library debugging
16027 Turns on or off debugging messages for FR-V shared-library code.
16028 @item show debug solib-frv
16029 Display the current state of FR-V shared-library code debugging
16031 @item set debug target
16032 @cindex target debugging info
16033 Turns on or off display of @value{GDBN} target debugging info. This info
16034 includes what is going on at the target level of GDB, as it happens. The
16035 default is 0. Set it to 1 to track events, and to 2 to also track the
16036 value of large memory transfers. Changes to this flag do not take effect
16037 until the next time you connect to a target or use the @code{run} command.
16038 @item show debug target
16039 Displays the current state of displaying @value{GDBN} target debugging
16041 @item set debugvarobj
16042 @cindex variable object debugging info
16043 Turns on or off display of @value{GDBN} variable object debugging
16044 info. The default is off.
16045 @item show debugvarobj
16046 Displays the current state of displaying @value{GDBN} variable object
16048 @item set debug xml
16049 @cindex XML parser debugging
16050 Turns on or off debugging messages for built-in XML parsers.
16051 @item show debug xml
16052 Displays the current state of XML debugging messages.
16056 @chapter Canned Sequences of Commands
16058 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
16059 Command Lists}), @value{GDBN} provides two ways to store sequences of
16060 commands for execution as a unit: user-defined commands and command
16064 * Define:: How to define your own commands
16065 * Hooks:: Hooks for user-defined commands
16066 * Command Files:: How to write scripts of commands to be stored in a file
16067 * Output:: Commands for controlled output
16071 @section User-defined Commands
16073 @cindex user-defined command
16074 @cindex arguments, to user-defined commands
16075 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
16076 which you assign a new name as a command. This is done with the
16077 @code{define} command. User commands may accept up to 10 arguments
16078 separated by whitespace. Arguments are accessed within the user command
16079 via @code{$arg0@dots{}$arg9}. A trivial example:
16083 print $arg0 + $arg1 + $arg2
16088 To execute the command use:
16095 This defines the command @code{adder}, which prints the sum of
16096 its three arguments. Note the arguments are text substitutions, so they may
16097 reference variables, use complex expressions, or even perform inferior
16100 @cindex argument count in user-defined commands
16101 @cindex how many arguments (user-defined commands)
16102 In addition, @code{$argc} may be used to find out how many arguments have
16103 been passed. This expands to a number in the range 0@dots{}10.
16108 print $arg0 + $arg1
16111 print $arg0 + $arg1 + $arg2
16119 @item define @var{commandname}
16120 Define a command named @var{commandname}. If there is already a command
16121 by that name, you are asked to confirm that you want to redefine it.
16123 The definition of the command is made up of other @value{GDBN} command lines,
16124 which are given following the @code{define} command. The end of these
16125 commands is marked by a line containing @code{end}.
16128 @kindex end@r{ (user-defined commands)}
16129 @item document @var{commandname}
16130 Document the user-defined command @var{commandname}, so that it can be
16131 accessed by @code{help}. The command @var{commandname} must already be
16132 defined. This command reads lines of documentation just as @code{define}
16133 reads the lines of the command definition, ending with @code{end}.
16134 After the @code{document} command is finished, @code{help} on command
16135 @var{commandname} displays the documentation you have written.
16137 You may use the @code{document} command again to change the
16138 documentation of a command. Redefining the command with @code{define}
16139 does not change the documentation.
16141 @kindex dont-repeat
16142 @cindex don't repeat command
16144 Used inside a user-defined command, this tells @value{GDBN} that this
16145 command should not be repeated when the user hits @key{RET}
16146 (@pxref{Command Syntax, repeat last command}).
16148 @kindex help user-defined
16149 @item help user-defined
16150 List all user-defined commands, with the first line of the documentation
16155 @itemx show user @var{commandname}
16156 Display the @value{GDBN} commands used to define @var{commandname} (but
16157 not its documentation). If no @var{commandname} is given, display the
16158 definitions for all user-defined commands.
16160 @cindex infinite recursion in user-defined commands
16161 @kindex show max-user-call-depth
16162 @kindex set max-user-call-depth
16163 @item show max-user-call-depth
16164 @itemx set max-user-call-depth
16165 The value of @code{max-user-call-depth} controls how many recursion
16166 levels are allowed in user-defined commands before @value{GDBN} suspects an
16167 infinite recursion and aborts the command.
16170 In addition to the above commands, user-defined commands frequently
16171 use control flow commands, described in @ref{Command Files}.
16173 When user-defined commands are executed, the
16174 commands of the definition are not printed. An error in any command
16175 stops execution of the user-defined command.
16177 If used interactively, commands that would ask for confirmation proceed
16178 without asking when used inside a user-defined command. Many @value{GDBN}
16179 commands that normally print messages to say what they are doing omit the
16180 messages when used in a user-defined command.
16183 @section User-defined Command Hooks
16184 @cindex command hooks
16185 @cindex hooks, for commands
16186 @cindex hooks, pre-command
16189 You may define @dfn{hooks}, which are a special kind of user-defined
16190 command. Whenever you run the command @samp{foo}, if the user-defined
16191 command @samp{hook-foo} exists, it is executed (with no arguments)
16192 before that command.
16194 @cindex hooks, post-command
16196 A hook may also be defined which is run after the command you executed.
16197 Whenever you run the command @samp{foo}, if the user-defined command
16198 @samp{hookpost-foo} exists, it is executed (with no arguments) after
16199 that command. Post-execution hooks may exist simultaneously with
16200 pre-execution hooks, for the same command.
16202 It is valid for a hook to call the command which it hooks. If this
16203 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
16205 @c It would be nice if hookpost could be passed a parameter indicating
16206 @c if the command it hooks executed properly or not. FIXME!
16208 @kindex stop@r{, a pseudo-command}
16209 In addition, a pseudo-command, @samp{stop} exists. Defining
16210 (@samp{hook-stop}) makes the associated commands execute every time
16211 execution stops in your program: before breakpoint commands are run,
16212 displays are printed, or the stack frame is printed.
16214 For example, to ignore @code{SIGALRM} signals while
16215 single-stepping, but treat them normally during normal execution,
16220 handle SIGALRM nopass
16224 handle SIGALRM pass
16227 define hook-continue
16228 handle SIGALRM pass
16232 As a further example, to hook at the beginning and end of the @code{echo}
16233 command, and to add extra text to the beginning and end of the message,
16241 define hookpost-echo
16245 (@value{GDBP}) echo Hello World
16246 <<<---Hello World--->>>
16251 You can define a hook for any single-word command in @value{GDBN}, but
16252 not for command aliases; you should define a hook for the basic command
16253 name, e.g.@: @code{backtrace} rather than @code{bt}.
16254 @c FIXME! So how does Joe User discover whether a command is an alias
16256 If an error occurs during the execution of your hook, execution of
16257 @value{GDBN} commands stops and @value{GDBN} issues a prompt
16258 (before the command that you actually typed had a chance to run).
16260 If you try to define a hook which does not match any known command, you
16261 get a warning from the @code{define} command.
16263 @node Command Files
16264 @section Command Files
16266 @cindex command files
16267 @cindex scripting commands
16268 A command file for @value{GDBN} is a text file made of lines that are
16269 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
16270 also be included. An empty line in a command file does nothing; it
16271 does not mean to repeat the last command, as it would from the
16274 You can request the execution of a command file with the @code{source}
16279 @cindex execute commands from a file
16280 @item source [@code{-v}] @var{filename}
16281 Execute the command file @var{filename}.
16284 The lines in a command file are generally executed sequentially,
16285 unless the order of execution is changed by one of the
16286 @emph{flow-control commands} described below. The commands are not
16287 printed as they are executed. An error in any command terminates
16288 execution of the command file and control is returned to the console.
16290 @value{GDBN} searches for @var{filename} in the current directory and then
16291 on the search path (specified with the @samp{directory} command).
16293 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
16294 each command as it is executed. The option must be given before
16295 @var{filename}, and is interpreted as part of the filename anywhere else.
16297 Commands that would ask for confirmation if used interactively proceed
16298 without asking when used in a command file. Many @value{GDBN} commands that
16299 normally print messages to say what they are doing omit the messages
16300 when called from command files.
16302 @value{GDBN} also accepts command input from standard input. In this
16303 mode, normal output goes to standard output and error output goes to
16304 standard error. Errors in a command file supplied on standard input do
16305 not terminate execution of the command file---execution continues with
16309 gdb < cmds > log 2>&1
16312 (The syntax above will vary depending on the shell used.) This example
16313 will execute commands from the file @file{cmds}. All output and errors
16314 would be directed to @file{log}.
16316 Since commands stored on command files tend to be more general than
16317 commands typed interactively, they frequently need to deal with
16318 complicated situations, such as different or unexpected values of
16319 variables and symbols, changes in how the program being debugged is
16320 built, etc. @value{GDBN} provides a set of flow-control commands to
16321 deal with these complexities. Using these commands, you can write
16322 complex scripts that loop over data structures, execute commands
16323 conditionally, etc.
16330 This command allows to include in your script conditionally executed
16331 commands. The @code{if} command takes a single argument, which is an
16332 expression to evaluate. It is followed by a series of commands that
16333 are executed only if the expression is true (its value is nonzero).
16334 There can then optionally be an @code{else} line, followed by a series
16335 of commands that are only executed if the expression was false. The
16336 end of the list is marked by a line containing @code{end}.
16340 This command allows to write loops. Its syntax is similar to
16341 @code{if}: the command takes a single argument, which is an expression
16342 to evaluate, and must be followed by the commands to execute, one per
16343 line, terminated by an @code{end}. These commands are called the
16344 @dfn{body} of the loop. The commands in the body of @code{while} are
16345 executed repeatedly as long as the expression evaluates to true.
16349 This command exits the @code{while} loop in whose body it is included.
16350 Execution of the script continues after that @code{while}s @code{end}
16353 @kindex loop_continue
16354 @item loop_continue
16355 This command skips the execution of the rest of the body of commands
16356 in the @code{while} loop in whose body it is included. Execution
16357 branches to the beginning of the @code{while} loop, where it evaluates
16358 the controlling expression.
16360 @kindex end@r{ (if/else/while commands)}
16362 Terminate the block of commands that are the body of @code{if},
16363 @code{else}, or @code{while} flow-control commands.
16368 @section Commands for Controlled Output
16370 During the execution of a command file or a user-defined command, normal
16371 @value{GDBN} output is suppressed; the only output that appears is what is
16372 explicitly printed by the commands in the definition. This section
16373 describes three commands useful for generating exactly the output you
16378 @item echo @var{text}
16379 @c I do not consider backslash-space a standard C escape sequence
16380 @c because it is not in ANSI.
16381 Print @var{text}. Nonprinting characters can be included in
16382 @var{text} using C escape sequences, such as @samp{\n} to print a
16383 newline. @strong{No newline is printed unless you specify one.}
16384 In addition to the standard C escape sequences, a backslash followed
16385 by a space stands for a space. This is useful for displaying a
16386 string with spaces at the beginning or the end, since leading and
16387 trailing spaces are otherwise trimmed from all arguments.
16388 To print @samp{@w{ }and foo =@w{ }}, use the command
16389 @samp{echo \@w{ }and foo = \@w{ }}.
16391 A backslash at the end of @var{text} can be used, as in C, to continue
16392 the command onto subsequent lines. For example,
16395 echo This is some text\n\
16396 which is continued\n\
16397 onto several lines.\n
16400 produces the same output as
16403 echo This is some text\n
16404 echo which is continued\n
16405 echo onto several lines.\n
16409 @item output @var{expression}
16410 Print the value of @var{expression} and nothing but that value: no
16411 newlines, no @samp{$@var{nn} = }. The value is not entered in the
16412 value history either. @xref{Expressions, ,Expressions}, for more information
16415 @item output/@var{fmt} @var{expression}
16416 Print the value of @var{expression} in format @var{fmt}. You can use
16417 the same formats as for @code{print}. @xref{Output Formats,,Output
16418 Formats}, for more information.
16421 @item printf @var{string}, @var{expressions}@dots{}
16422 Print the values of the @var{expressions} under the control of
16423 @var{string}. The @var{expressions} are separated by commas and may be
16424 either numbers or pointers. Their values are printed as specified by
16425 @var{string}, exactly as if your program were to execute the C
16427 @c FIXME: the above implies that at least all ANSI C formats are
16428 @c supported, but it isn't true: %E and %G don't work (or so it seems).
16429 @c Either this is a bug, or the manual should document what formats are
16433 printf (@var{string}, @var{expressions}@dots{});
16436 For example, you can print two values in hex like this:
16439 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
16442 The only backslash-escape sequences that you can use in the format
16443 string are the simple ones that consist of backslash followed by a
16448 @chapter Command Interpreters
16449 @cindex command interpreters
16451 @value{GDBN} supports multiple command interpreters, and some command
16452 infrastructure to allow users or user interface writers to switch
16453 between interpreters or run commands in other interpreters.
16455 @value{GDBN} currently supports two command interpreters, the console
16456 interpreter (sometimes called the command-line interpreter or @sc{cli})
16457 and the machine interface interpreter (or @sc{gdb/mi}). This manual
16458 describes both of these interfaces in great detail.
16460 By default, @value{GDBN} will start with the console interpreter.
16461 However, the user may choose to start @value{GDBN} with another
16462 interpreter by specifying the @option{-i} or @option{--interpreter}
16463 startup options. Defined interpreters include:
16467 @cindex console interpreter
16468 The traditional console or command-line interpreter. This is the most often
16469 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
16470 @value{GDBN} will use this interpreter.
16473 @cindex mi interpreter
16474 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
16475 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
16476 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
16480 @cindex mi2 interpreter
16481 The current @sc{gdb/mi} interface.
16484 @cindex mi1 interpreter
16485 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
16489 @cindex invoke another interpreter
16490 The interpreter being used by @value{GDBN} may not be dynamically
16491 switched at runtime. Although possible, this could lead to a very
16492 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
16493 enters the command "interpreter-set console" in a console view,
16494 @value{GDBN} would switch to using the console interpreter, rendering
16495 the IDE inoperable!
16497 @kindex interpreter-exec
16498 Although you may only choose a single interpreter at startup, you may execute
16499 commands in any interpreter from the current interpreter using the appropriate
16500 command. If you are running the console interpreter, simply use the
16501 @code{interpreter-exec} command:
16504 interpreter-exec mi "-data-list-register-names"
16507 @sc{gdb/mi} has a similar command, although it is only available in versions of
16508 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
16511 @chapter @value{GDBN} Text User Interface
16513 @cindex Text User Interface
16516 * TUI Overview:: TUI overview
16517 * TUI Keys:: TUI key bindings
16518 * TUI Single Key Mode:: TUI single key mode
16519 * TUI Commands:: TUI-specific commands
16520 * TUI Configuration:: TUI configuration variables
16523 The @value{GDBN} Text User Interface (TUI) is a terminal
16524 interface which uses the @code{curses} library to show the source
16525 file, the assembly output, the program registers and @value{GDBN}
16526 commands in separate text windows. The TUI mode is supported only
16527 on platforms where a suitable version of the @code{curses} library
16530 @pindex @value{GDBTUI}
16531 The TUI mode is enabled by default when you invoke @value{GDBN} as
16532 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
16533 You can also switch in and out of TUI mode while @value{GDBN} runs by
16534 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
16535 @xref{TUI Keys, ,TUI Key Bindings}.
16538 @section TUI Overview
16540 In TUI mode, @value{GDBN} can display several text windows:
16544 This window is the @value{GDBN} command window with the @value{GDBN}
16545 prompt and the @value{GDBN} output. The @value{GDBN} input is still
16546 managed using readline.
16549 The source window shows the source file of the program. The current
16550 line and active breakpoints are displayed in this window.
16553 The assembly window shows the disassembly output of the program.
16556 This window shows the processor registers. Registers are highlighted
16557 when their values change.
16560 The source and assembly windows show the current program position
16561 by highlighting the current line and marking it with a @samp{>} marker.
16562 Breakpoints are indicated with two markers. The first marker
16563 indicates the breakpoint type:
16567 Breakpoint which was hit at least once.
16570 Breakpoint which was never hit.
16573 Hardware breakpoint which was hit at least once.
16576 Hardware breakpoint which was never hit.
16579 The second marker indicates whether the breakpoint is enabled or not:
16583 Breakpoint is enabled.
16586 Breakpoint is disabled.
16589 The source, assembly and register windows are updated when the current
16590 thread changes, when the frame changes, or when the program counter
16593 These windows are not all visible at the same time. The command
16594 window is always visible. The others can be arranged in several
16605 source and assembly,
16608 source and registers, or
16611 assembly and registers.
16614 A status line above the command window shows the following information:
16618 Indicates the current @value{GDBN} target.
16619 (@pxref{Targets, ,Specifying a Debugging Target}).
16622 Gives the current process or thread number.
16623 When no process is being debugged, this field is set to @code{No process}.
16626 Gives the current function name for the selected frame.
16627 The name is demangled if demangling is turned on (@pxref{Print Settings}).
16628 When there is no symbol corresponding to the current program counter,
16629 the string @code{??} is displayed.
16632 Indicates the current line number for the selected frame.
16633 When the current line number is not known, the string @code{??} is displayed.
16636 Indicates the current program counter address.
16640 @section TUI Key Bindings
16641 @cindex TUI key bindings
16643 The TUI installs several key bindings in the readline keymaps
16644 (@pxref{Command Line Editing}). The following key bindings
16645 are installed for both TUI mode and the @value{GDBN} standard mode.
16654 Enter or leave the TUI mode. When leaving the TUI mode,
16655 the curses window management stops and @value{GDBN} operates using
16656 its standard mode, writing on the terminal directly. When reentering
16657 the TUI mode, control is given back to the curses windows.
16658 The screen is then refreshed.
16662 Use a TUI layout with only one window. The layout will
16663 either be @samp{source} or @samp{assembly}. When the TUI mode
16664 is not active, it will switch to the TUI mode.
16666 Think of this key binding as the Emacs @kbd{C-x 1} binding.
16670 Use a TUI layout with at least two windows. When the current
16671 layout already has two windows, the next layout with two windows is used.
16672 When a new layout is chosen, one window will always be common to the
16673 previous layout and the new one.
16675 Think of it as the Emacs @kbd{C-x 2} binding.
16679 Change the active window. The TUI associates several key bindings
16680 (like scrolling and arrow keys) with the active window. This command
16681 gives the focus to the next TUI window.
16683 Think of it as the Emacs @kbd{C-x o} binding.
16687 Switch in and out of the TUI SingleKey mode that binds single
16688 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
16691 The following key bindings only work in the TUI mode:
16696 Scroll the active window one page up.
16700 Scroll the active window one page down.
16704 Scroll the active window one line up.
16708 Scroll the active window one line down.
16712 Scroll the active window one column left.
16716 Scroll the active window one column right.
16720 Refresh the screen.
16723 Because the arrow keys scroll the active window in the TUI mode, they
16724 are not available for their normal use by readline unless the command
16725 window has the focus. When another window is active, you must use
16726 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
16727 and @kbd{C-f} to control the command window.
16729 @node TUI Single Key Mode
16730 @section TUI Single Key Mode
16731 @cindex TUI single key mode
16733 The TUI also provides a @dfn{SingleKey} mode, which binds several
16734 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
16735 switch into this mode, where the following key bindings are used:
16738 @kindex c @r{(SingleKey TUI key)}
16742 @kindex d @r{(SingleKey TUI key)}
16746 @kindex f @r{(SingleKey TUI key)}
16750 @kindex n @r{(SingleKey TUI key)}
16754 @kindex q @r{(SingleKey TUI key)}
16756 exit the SingleKey mode.
16758 @kindex r @r{(SingleKey TUI key)}
16762 @kindex s @r{(SingleKey TUI key)}
16766 @kindex u @r{(SingleKey TUI key)}
16770 @kindex v @r{(SingleKey TUI key)}
16774 @kindex w @r{(SingleKey TUI key)}
16779 Other keys temporarily switch to the @value{GDBN} command prompt.
16780 The key that was pressed is inserted in the editing buffer so that
16781 it is possible to type most @value{GDBN} commands without interaction
16782 with the TUI SingleKey mode. Once the command is entered the TUI
16783 SingleKey mode is restored. The only way to permanently leave
16784 this mode is by typing @kbd{q} or @kbd{C-x s}.
16788 @section TUI-specific Commands
16789 @cindex TUI commands
16791 The TUI has specific commands to control the text windows.
16792 These commands are always available, even when @value{GDBN} is not in
16793 the TUI mode. When @value{GDBN} is in the standard mode, most
16794 of these commands will automatically switch to the TUI mode.
16799 List and give the size of all displayed windows.
16803 Display the next layout.
16806 Display the previous layout.
16809 Display the source window only.
16812 Display the assembly window only.
16815 Display the source and assembly window.
16818 Display the register window together with the source or assembly window.
16822 Make the next window active for scrolling.
16825 Make the previous window active for scrolling.
16828 Make the source window active for scrolling.
16831 Make the assembly window active for scrolling.
16834 Make the register window active for scrolling.
16837 Make the command window active for scrolling.
16841 Refresh the screen. This is similar to typing @kbd{C-L}.
16843 @item tui reg float
16845 Show the floating point registers in the register window.
16847 @item tui reg general
16848 Show the general registers in the register window.
16851 Show the next register group. The list of register groups as well as
16852 their order is target specific. The predefined register groups are the
16853 following: @code{general}, @code{float}, @code{system}, @code{vector},
16854 @code{all}, @code{save}, @code{restore}.
16856 @item tui reg system
16857 Show the system registers in the register window.
16861 Update the source window and the current execution point.
16863 @item winheight @var{name} +@var{count}
16864 @itemx winheight @var{name} -@var{count}
16866 Change the height of the window @var{name} by @var{count}
16867 lines. Positive counts increase the height, while negative counts
16870 @item tabset @var{nchars}
16872 Set the width of tab stops to be @var{nchars} characters.
16875 @node TUI Configuration
16876 @section TUI Configuration Variables
16877 @cindex TUI configuration variables
16879 Several configuration variables control the appearance of TUI windows.
16882 @item set tui border-kind @var{kind}
16883 @kindex set tui border-kind
16884 Select the border appearance for the source, assembly and register windows.
16885 The possible values are the following:
16888 Use a space character to draw the border.
16891 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
16894 Use the Alternate Character Set to draw the border. The border is
16895 drawn using character line graphics if the terminal supports them.
16898 @item set tui border-mode @var{mode}
16899 @kindex set tui border-mode
16900 @itemx set tui active-border-mode @var{mode}
16901 @kindex set tui active-border-mode
16902 Select the display attributes for the borders of the inactive windows
16903 or the active window. The @var{mode} can be one of the following:
16906 Use normal attributes to display the border.
16912 Use reverse video mode.
16915 Use half bright mode.
16917 @item half-standout
16918 Use half bright and standout mode.
16921 Use extra bright or bold mode.
16923 @item bold-standout
16924 Use extra bright or bold and standout mode.
16929 @chapter Using @value{GDBN} under @sc{gnu} Emacs
16932 @cindex @sc{gnu} Emacs
16933 A special interface allows you to use @sc{gnu} Emacs to view (and
16934 edit) the source files for the program you are debugging with
16937 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
16938 executable file you want to debug as an argument. This command starts
16939 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
16940 created Emacs buffer.
16941 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
16943 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
16948 All ``terminal'' input and output goes through an Emacs buffer, called
16951 This applies both to @value{GDBN} commands and their output, and to the input
16952 and output done by the program you are debugging.
16954 This is useful because it means that you can copy the text of previous
16955 commands and input them again; you can even use parts of the output
16958 All the facilities of Emacs' Shell mode are available for interacting
16959 with your program. In particular, you can send signals the usual
16960 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
16964 @value{GDBN} displays source code through Emacs.
16966 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
16967 source file for that frame and puts an arrow (@samp{=>}) at the
16968 left margin of the current line. Emacs uses a separate buffer for
16969 source display, and splits the screen to show both your @value{GDBN} session
16972 Explicit @value{GDBN} @code{list} or search commands still produce output as
16973 usual, but you probably have no reason to use them from Emacs.
16976 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
16977 a graphical mode, enabled by default, which provides further buffers
16978 that can control the execution and describe the state of your program.
16979 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
16981 If you specify an absolute file name when prompted for the @kbd{M-x
16982 gdb} argument, then Emacs sets your current working directory to where
16983 your program resides. If you only specify the file name, then Emacs
16984 sets your current working directory to to the directory associated
16985 with the previous buffer. In this case, @value{GDBN} may find your
16986 program by searching your environment's @code{PATH} variable, but on
16987 some operating systems it might not find the source. So, although the
16988 @value{GDBN} input and output session proceeds normally, the auxiliary
16989 buffer does not display the current source and line of execution.
16991 The initial working directory of @value{GDBN} is printed on the top
16992 line of the GUD buffer and this serves as a default for the commands
16993 that specify files for @value{GDBN} to operate on. @xref{Files,
16994 ,Commands to Specify Files}.
16996 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
16997 need to call @value{GDBN} by a different name (for example, if you
16998 keep several configurations around, with different names) you can
16999 customize the Emacs variable @code{gud-gdb-command-name} to run the
17002 In the GUD buffer, you can use these special Emacs commands in
17003 addition to the standard Shell mode commands:
17007 Describe the features of Emacs' GUD Mode.
17010 Execute to another source line, like the @value{GDBN} @code{step} command; also
17011 update the display window to show the current file and location.
17014 Execute to next source line in this function, skipping all function
17015 calls, like the @value{GDBN} @code{next} command. Then update the display window
17016 to show the current file and location.
17019 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
17020 display window accordingly.
17023 Execute until exit from the selected stack frame, like the @value{GDBN}
17024 @code{finish} command.
17027 Continue execution of your program, like the @value{GDBN} @code{continue}
17031 Go up the number of frames indicated by the numeric argument
17032 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
17033 like the @value{GDBN} @code{up} command.
17036 Go down the number of frames indicated by the numeric argument, like the
17037 @value{GDBN} @code{down} command.
17040 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
17041 tells @value{GDBN} to set a breakpoint on the source line point is on.
17043 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
17044 separate frame which shows a backtrace when the GUD buffer is current.
17045 Move point to any frame in the stack and type @key{RET} to make it
17046 become the current frame and display the associated source in the
17047 source buffer. Alternatively, click @kbd{Mouse-2} to make the
17048 selected frame become the current one. In graphical mode, the
17049 speedbar displays watch expressions.
17051 If you accidentally delete the source-display buffer, an easy way to get
17052 it back is to type the command @code{f} in the @value{GDBN} buffer, to
17053 request a frame display; when you run under Emacs, this recreates
17054 the source buffer if necessary to show you the context of the current
17057 The source files displayed in Emacs are in ordinary Emacs buffers
17058 which are visiting the source files in the usual way. You can edit
17059 the files with these buffers if you wish; but keep in mind that @value{GDBN}
17060 communicates with Emacs in terms of line numbers. If you add or
17061 delete lines from the text, the line numbers that @value{GDBN} knows cease
17062 to correspond properly with the code.
17064 A more detailed description of Emacs' interaction with @value{GDBN} is
17065 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
17068 @c The following dropped because Epoch is nonstandard. Reactivate
17069 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
17071 @kindex Emacs Epoch environment
17075 Version 18 of @sc{gnu} Emacs has a built-in window system
17076 called the @code{epoch}
17077 environment. Users of this environment can use a new command,
17078 @code{inspect} which performs identically to @code{print} except that
17079 each value is printed in its own window.
17084 @chapter The @sc{gdb/mi} Interface
17086 @unnumberedsec Function and Purpose
17088 @cindex @sc{gdb/mi}, its purpose
17089 @sc{gdb/mi} is a line based machine oriented text interface to
17090 @value{GDBN} and is activated by specifying using the
17091 @option{--interpreter} command line option (@pxref{Mode Options}). It
17092 is specifically intended to support the development of systems which
17093 use the debugger as just one small component of a larger system.
17095 This chapter is a specification of the @sc{gdb/mi} interface. It is written
17096 in the form of a reference manual.
17098 Note that @sc{gdb/mi} is still under construction, so some of the
17099 features described below are incomplete and subject to change
17100 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
17102 @unnumberedsec Notation and Terminology
17104 @cindex notational conventions, for @sc{gdb/mi}
17105 This chapter uses the following notation:
17109 @code{|} separates two alternatives.
17112 @code{[ @var{something} ]} indicates that @var{something} is optional:
17113 it may or may not be given.
17116 @code{( @var{group} )*} means that @var{group} inside the parentheses
17117 may repeat zero or more times.
17120 @code{( @var{group} )+} means that @var{group} inside the parentheses
17121 may repeat one or more times.
17124 @code{"@var{string}"} means a literal @var{string}.
17128 @heading Dependencies
17132 * GDB/MI Command Syntax::
17133 * GDB/MI Compatibility with CLI::
17134 * GDB/MI Development and Front Ends::
17135 * GDB/MI Output Records::
17136 * GDB/MI Simple Examples::
17137 * GDB/MI Command Description Format::
17138 * GDB/MI Breakpoint Commands::
17139 * GDB/MI Program Context::
17140 * GDB/MI Thread Commands::
17141 * GDB/MI Program Execution::
17142 * GDB/MI Stack Manipulation::
17143 * GDB/MI Variable Objects::
17144 * GDB/MI Data Manipulation::
17145 * GDB/MI Tracepoint Commands::
17146 * GDB/MI Symbol Query::
17147 * GDB/MI File Commands::
17149 * GDB/MI Kod Commands::
17150 * GDB/MI Memory Overlay Commands::
17151 * GDB/MI Signal Handling Commands::
17153 * GDB/MI Target Manipulation::
17154 * GDB/MI Miscellaneous Commands::
17157 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17158 @node GDB/MI Command Syntax
17159 @section @sc{gdb/mi} Command Syntax
17162 * GDB/MI Input Syntax::
17163 * GDB/MI Output Syntax::
17166 @node GDB/MI Input Syntax
17167 @subsection @sc{gdb/mi} Input Syntax
17169 @cindex input syntax for @sc{gdb/mi}
17170 @cindex @sc{gdb/mi}, input syntax
17172 @item @var{command} @expansion{}
17173 @code{@var{cli-command} | @var{mi-command}}
17175 @item @var{cli-command} @expansion{}
17176 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
17177 @var{cli-command} is any existing @value{GDBN} CLI command.
17179 @item @var{mi-command} @expansion{}
17180 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
17181 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
17183 @item @var{token} @expansion{}
17184 "any sequence of digits"
17186 @item @var{option} @expansion{}
17187 @code{"-" @var{parameter} [ " " @var{parameter} ]}
17189 @item @var{parameter} @expansion{}
17190 @code{@var{non-blank-sequence} | @var{c-string}}
17192 @item @var{operation} @expansion{}
17193 @emph{any of the operations described in this chapter}
17195 @item @var{non-blank-sequence} @expansion{}
17196 @emph{anything, provided it doesn't contain special characters such as
17197 "-", @var{nl}, """ and of course " "}
17199 @item @var{c-string} @expansion{}
17200 @code{""" @var{seven-bit-iso-c-string-content} """}
17202 @item @var{nl} @expansion{}
17211 The CLI commands are still handled by the @sc{mi} interpreter; their
17212 output is described below.
17215 The @code{@var{token}}, when present, is passed back when the command
17219 Some @sc{mi} commands accept optional arguments as part of the parameter
17220 list. Each option is identified by a leading @samp{-} (dash) and may be
17221 followed by an optional argument parameter. Options occur first in the
17222 parameter list and can be delimited from normal parameters using
17223 @samp{--} (this is useful when some parameters begin with a dash).
17230 We want easy access to the existing CLI syntax (for debugging).
17233 We want it to be easy to spot a @sc{mi} operation.
17236 @node GDB/MI Output Syntax
17237 @subsection @sc{gdb/mi} Output Syntax
17239 @cindex output syntax of @sc{gdb/mi}
17240 @cindex @sc{gdb/mi}, output syntax
17241 The output from @sc{gdb/mi} consists of zero or more out-of-band records
17242 followed, optionally, by a single result record. This result record
17243 is for the most recent command. The sequence of output records is
17244 terminated by @samp{(gdb)}.
17246 If an input command was prefixed with a @code{@var{token}} then the
17247 corresponding output for that command will also be prefixed by that same
17251 @item @var{output} @expansion{}
17252 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
17254 @item @var{result-record} @expansion{}
17255 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
17257 @item @var{out-of-band-record} @expansion{}
17258 @code{@var{async-record} | @var{stream-record}}
17260 @item @var{async-record} @expansion{}
17261 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
17263 @item @var{exec-async-output} @expansion{}
17264 @code{[ @var{token} ] "*" @var{async-output}}
17266 @item @var{status-async-output} @expansion{}
17267 @code{[ @var{token} ] "+" @var{async-output}}
17269 @item @var{notify-async-output} @expansion{}
17270 @code{[ @var{token} ] "=" @var{async-output}}
17272 @item @var{async-output} @expansion{}
17273 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
17275 @item @var{result-class} @expansion{}
17276 @code{"done" | "running" | "connected" | "error" | "exit"}
17278 @item @var{async-class} @expansion{}
17279 @code{"stopped" | @var{others}} (where @var{others} will be added
17280 depending on the needs---this is still in development).
17282 @item @var{result} @expansion{}
17283 @code{ @var{variable} "=" @var{value}}
17285 @item @var{variable} @expansion{}
17286 @code{ @var{string} }
17288 @item @var{value} @expansion{}
17289 @code{ @var{const} | @var{tuple} | @var{list} }
17291 @item @var{const} @expansion{}
17292 @code{@var{c-string}}
17294 @item @var{tuple} @expansion{}
17295 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
17297 @item @var{list} @expansion{}
17298 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
17299 @var{result} ( "," @var{result} )* "]" }
17301 @item @var{stream-record} @expansion{}
17302 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
17304 @item @var{console-stream-output} @expansion{}
17305 @code{"~" @var{c-string}}
17307 @item @var{target-stream-output} @expansion{}
17308 @code{"@@" @var{c-string}}
17310 @item @var{log-stream-output} @expansion{}
17311 @code{"&" @var{c-string}}
17313 @item @var{nl} @expansion{}
17316 @item @var{token} @expansion{}
17317 @emph{any sequence of digits}.
17325 All output sequences end in a single line containing a period.
17328 The @code{@var{token}} is from the corresponding request. If an execution
17329 command is interrupted by the @samp{-exec-interrupt} command, the
17330 @var{token} associated with the @samp{*stopped} message is the one of the
17331 original execution command, not the one of the interrupt command.
17334 @cindex status output in @sc{gdb/mi}
17335 @var{status-async-output} contains on-going status information about the
17336 progress of a slow operation. It can be discarded. All status output is
17337 prefixed by @samp{+}.
17340 @cindex async output in @sc{gdb/mi}
17341 @var{exec-async-output} contains asynchronous state change on the target
17342 (stopped, started, disappeared). All async output is prefixed by
17346 @cindex notify output in @sc{gdb/mi}
17347 @var{notify-async-output} contains supplementary information that the
17348 client should handle (e.g., a new breakpoint information). All notify
17349 output is prefixed by @samp{=}.
17352 @cindex console output in @sc{gdb/mi}
17353 @var{console-stream-output} is output that should be displayed as is in the
17354 console. It is the textual response to a CLI command. All the console
17355 output is prefixed by @samp{~}.
17358 @cindex target output in @sc{gdb/mi}
17359 @var{target-stream-output} is the output produced by the target program.
17360 All the target output is prefixed by @samp{@@}.
17363 @cindex log output in @sc{gdb/mi}
17364 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
17365 instance messages that should be displayed as part of an error log. All
17366 the log output is prefixed by @samp{&}.
17369 @cindex list output in @sc{gdb/mi}
17370 New @sc{gdb/mi} commands should only output @var{lists} containing
17376 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
17377 details about the various output records.
17379 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17380 @node GDB/MI Compatibility with CLI
17381 @section @sc{gdb/mi} Compatibility with CLI
17383 @cindex compatibility, @sc{gdb/mi} and CLI
17384 @cindex @sc{gdb/mi}, compatibility with CLI
17386 For the developers convenience CLI commands can be entered directly,
17387 but there may be some unexpected behaviour. For example, commands
17388 that query the user will behave as if the user replied yes, breakpoint
17389 command lists are not executed and some CLI commands, such as
17390 @code{if}, @code{when} and @code{define}, prompt for further input with
17391 @samp{>}, which is not valid MI output.
17393 This feature may be removed at some stage in the future and it is
17394 recommended that front ends use the @code{-interpreter-exec} command
17395 (@pxref{-interpreter-exec}).
17397 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17398 @node GDB/MI Development and Front Ends
17399 @section @sc{gdb/mi} Development and Front Ends
17400 @cindex @sc{gdb/mi} development
17402 The application which takes the MI output and presents the state of the
17403 program being debugged to the user is called a @dfn{front end}.
17405 Although @sc{gdb/mi} is still incomplete, it is currently being used
17406 by a variety of front ends to @value{GDBN}. This makes it difficult
17407 to introduce new functionality without breaking existing usage. This
17408 section tries to minimize the problems by describing how the protocol
17411 Some changes in MI need not break a carefully designed front end, and
17412 for these the MI version will remain unchanged. The following is a
17413 list of changes that may occur within one level, so front ends should
17414 parse MI output in a way that can handle them:
17418 New MI commands may be added.
17421 New fields may be added to the output of any MI command.
17424 The range of values for fields with specified values, e.g.,
17425 @code{in_scope} (@pxref{-var-update}) may be extended.
17427 @c The format of field's content e.g type prefix, may change so parse it
17428 @c at your own risk. Yes, in general?
17430 @c The order of fields may change? Shouldn't really matter but it might
17431 @c resolve inconsistencies.
17434 If the changes are likely to break front ends, the MI version level
17435 will be increased by one. This will allow the front end to parse the
17436 output according to the MI version. Apart from mi0, new versions of
17437 @value{GDBN} will not support old versions of MI and it will be the
17438 responsibility of the front end to work with the new one.
17440 @c Starting with mi3, add a new command -mi-version that prints the MI
17443 The best way to avoid unexpected changes in MI that might break your front
17444 end is to make your project known to @value{GDBN} developers and
17445 follow development on @email{gdb@@sourceware.org} and
17446 @email{gdb-patches@@sourceware.org}. There is also the mailing list
17447 @email{dmi-discuss@@lists.freestandards.org}, hosted by the Free Standards
17448 Group, which has the aim of creating a more general MI protocol
17449 called Debugger Machine Interface (DMI) that will become a standard
17450 for all debuggers, not just @value{GDBN}.
17451 @cindex mailing lists
17453 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17454 @node GDB/MI Output Records
17455 @section @sc{gdb/mi} Output Records
17458 * GDB/MI Result Records::
17459 * GDB/MI Stream Records::
17460 * GDB/MI Out-of-band Records::
17463 @node GDB/MI Result Records
17464 @subsection @sc{gdb/mi} Result Records
17466 @cindex result records in @sc{gdb/mi}
17467 @cindex @sc{gdb/mi}, result records
17468 In addition to a number of out-of-band notifications, the response to a
17469 @sc{gdb/mi} command includes one of the following result indications:
17473 @item "^done" [ "," @var{results} ]
17474 The synchronous operation was successful, @code{@var{results}} are the return
17479 @c Is this one correct? Should it be an out-of-band notification?
17480 The asynchronous operation was successfully started. The target is
17485 @value{GDBN} has connected to a remote target.
17487 @item "^error" "," @var{c-string}
17489 The operation failed. The @code{@var{c-string}} contains the corresponding
17494 @value{GDBN} has terminated.
17498 @node GDB/MI Stream Records
17499 @subsection @sc{gdb/mi} Stream Records
17501 @cindex @sc{gdb/mi}, stream records
17502 @cindex stream records in @sc{gdb/mi}
17503 @value{GDBN} internally maintains a number of output streams: the console, the
17504 target, and the log. The output intended for each of these streams is
17505 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
17507 Each stream record begins with a unique @dfn{prefix character} which
17508 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
17509 Syntax}). In addition to the prefix, each stream record contains a
17510 @code{@var{string-output}}. This is either raw text (with an implicit new
17511 line) or a quoted C string (which does not contain an implicit newline).
17514 @item "~" @var{string-output}
17515 The console output stream contains text that should be displayed in the
17516 CLI console window. It contains the textual responses to CLI commands.
17518 @item "@@" @var{string-output}
17519 The target output stream contains any textual output from the running
17520 target. This is only present when GDB's event loop is truly
17521 asynchronous, which is currently only the case for remote targets.
17523 @item "&" @var{string-output}
17524 The log stream contains debugging messages being produced by @value{GDBN}'s
17528 @node GDB/MI Out-of-band Records
17529 @subsection @sc{gdb/mi} Out-of-band Records
17531 @cindex out-of-band records in @sc{gdb/mi}
17532 @cindex @sc{gdb/mi}, out-of-band records
17533 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
17534 additional changes that have occurred. Those changes can either be a
17535 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
17536 target activity (e.g., target stopped).
17538 The following is a preliminary list of possible out-of-band records.
17539 In particular, the @var{exec-async-output} records.
17542 @item *stopped,reason="@var{reason}"
17545 @var{reason} can be one of the following:
17548 @item breakpoint-hit
17549 A breakpoint was reached.
17550 @item watchpoint-trigger
17551 A watchpoint was triggered.
17552 @item read-watchpoint-trigger
17553 A read watchpoint was triggered.
17554 @item access-watchpoint-trigger
17555 An access watchpoint was triggered.
17556 @item function-finished
17557 An -exec-finish or similar CLI command was accomplished.
17558 @item location-reached
17559 An -exec-until or similar CLI command was accomplished.
17560 @item watchpoint-scope
17561 A watchpoint has gone out of scope.
17562 @item end-stepping-range
17563 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
17564 similar CLI command was accomplished.
17565 @item exited-signalled
17566 The inferior exited because of a signal.
17568 The inferior exited.
17569 @item exited-normally
17570 The inferior exited normally.
17571 @item signal-received
17572 A signal was received by the inferior.
17576 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17577 @node GDB/MI Simple Examples
17578 @section Simple Examples of @sc{gdb/mi} Interaction
17579 @cindex @sc{gdb/mi}, simple examples
17581 This subsection presents several simple examples of interaction using
17582 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
17583 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
17584 the output received from @sc{gdb/mi}.
17586 Note the line breaks shown in the examples are here only for
17587 readability, they don't appear in the real output.
17589 @subheading Setting a Breakpoint
17591 Setting a breakpoint generates synchronous output which contains detailed
17592 information of the breakpoint.
17595 -> -break-insert main
17596 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
17597 enabled="y",addr="0x08048564",func="main",file="myprog.c",
17598 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
17602 @subheading Program Execution
17604 Program execution generates asynchronous records and MI gives the
17605 reason that execution stopped.
17611 <- *stopped,reason="breakpoint-hit",bkptno="1",thread-id="0",
17612 frame=@{addr="0x08048564",func="main",
17613 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
17614 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
17619 <- *stopped,reason="exited-normally"
17623 @subheading Quitting @value{GDBN}
17625 Quitting @value{GDBN} just prints the result class @samp{^exit}.
17633 @subheading A Bad Command
17635 Here's what happens if you pass a non-existent command:
17639 <- ^error,msg="Undefined MI command: rubbish"
17644 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17645 @node GDB/MI Command Description Format
17646 @section @sc{gdb/mi} Command Description Format
17648 The remaining sections describe blocks of commands. Each block of
17649 commands is laid out in a fashion similar to this section.
17651 @subheading Motivation
17653 The motivation for this collection of commands.
17655 @subheading Introduction
17657 A brief introduction to this collection of commands as a whole.
17659 @subheading Commands
17661 For each command in the block, the following is described:
17663 @subsubheading Synopsis
17666 -command @var{args}@dots{}
17669 @subsubheading Result
17671 @subsubheading @value{GDBN} Command
17673 The corresponding @value{GDBN} CLI command(s), if any.
17675 @subsubheading Example
17677 Example(s) formatted for readability. Some of the described commands have
17678 not been implemented yet and these are labeled N.A.@: (not available).
17681 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17682 @node GDB/MI Breakpoint Commands
17683 @section @sc{gdb/mi} Breakpoint Commands
17685 @cindex breakpoint commands for @sc{gdb/mi}
17686 @cindex @sc{gdb/mi}, breakpoint commands
17687 This section documents @sc{gdb/mi} commands for manipulating
17690 @subheading The @code{-break-after} Command
17691 @findex -break-after
17693 @subsubheading Synopsis
17696 -break-after @var{number} @var{count}
17699 The breakpoint number @var{number} is not in effect until it has been
17700 hit @var{count} times. To see how this is reflected in the output of
17701 the @samp{-break-list} command, see the description of the
17702 @samp{-break-list} command below.
17704 @subsubheading @value{GDBN} Command
17706 The corresponding @value{GDBN} command is @samp{ignore}.
17708 @subsubheading Example
17713 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",
17714 fullname="/home/foo/hello.c",line="5",times="0"@}
17721 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17722 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17723 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17724 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17725 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17726 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17727 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17728 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17729 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
17730 line="5",times="0",ignore="3"@}]@}
17735 @subheading The @code{-break-catch} Command
17736 @findex -break-catch
17738 @subheading The @code{-break-commands} Command
17739 @findex -break-commands
17743 @subheading The @code{-break-condition} Command
17744 @findex -break-condition
17746 @subsubheading Synopsis
17749 -break-condition @var{number} @var{expr}
17752 Breakpoint @var{number} will stop the program only if the condition in
17753 @var{expr} is true. The condition becomes part of the
17754 @samp{-break-list} output (see the description of the @samp{-break-list}
17757 @subsubheading @value{GDBN} Command
17759 The corresponding @value{GDBN} command is @samp{condition}.
17761 @subsubheading Example
17765 -break-condition 1 1
17769 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17770 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17771 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17772 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17773 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17774 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17775 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17776 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17777 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
17778 line="5",cond="1",times="0",ignore="3"@}]@}
17782 @subheading The @code{-break-delete} Command
17783 @findex -break-delete
17785 @subsubheading Synopsis
17788 -break-delete ( @var{breakpoint} )+
17791 Delete the breakpoint(s) whose number(s) are specified in the argument
17792 list. This is obviously reflected in the breakpoint list.
17794 @subsubheading @value{GDBN} Command
17796 The corresponding @value{GDBN} command is @samp{delete}.
17798 @subsubheading Example
17806 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
17807 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17808 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17809 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17810 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17811 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17812 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17817 @subheading The @code{-break-disable} Command
17818 @findex -break-disable
17820 @subsubheading Synopsis
17823 -break-disable ( @var{breakpoint} )+
17826 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
17827 break list is now set to @samp{n} for the named @var{breakpoint}(s).
17829 @subsubheading @value{GDBN} Command
17831 The corresponding @value{GDBN} command is @samp{disable}.
17833 @subsubheading Example
17841 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17842 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17843 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17844 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17845 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17846 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17847 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17848 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
17849 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
17850 line="5",times="0"@}]@}
17854 @subheading The @code{-break-enable} Command
17855 @findex -break-enable
17857 @subsubheading Synopsis
17860 -break-enable ( @var{breakpoint} )+
17863 Enable (previously disabled) @var{breakpoint}(s).
17865 @subsubheading @value{GDBN} Command
17867 The corresponding @value{GDBN} command is @samp{enable}.
17869 @subsubheading Example
17877 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17878 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17879 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17880 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17881 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17882 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17883 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17884 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
17885 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
17886 line="5",times="0"@}]@}
17890 @subheading The @code{-break-info} Command
17891 @findex -break-info
17893 @subsubheading Synopsis
17896 -break-info @var{breakpoint}
17900 Get information about a single breakpoint.
17902 @subsubheading @value{GDBN} Command
17904 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
17906 @subsubheading Example
17909 @subheading The @code{-break-insert} Command
17910 @findex -break-insert
17912 @subsubheading Synopsis
17915 -break-insert [ -t ] [ -h ] [ -r ]
17916 [ -c @var{condition} ] [ -i @var{ignore-count} ]
17917 [ -p @var{thread} ] [ @var{line} | @var{addr} ]
17921 If specified, @var{line}, can be one of:
17928 @item filename:linenum
17929 @item filename:function
17933 The possible optional parameters of this command are:
17937 Insert a temporary breakpoint.
17939 Insert a hardware breakpoint.
17940 @item -c @var{condition}
17941 Make the breakpoint conditional on @var{condition}.
17942 @item -i @var{ignore-count}
17943 Initialize the @var{ignore-count}.
17945 Insert a regular breakpoint in all the functions whose names match the
17946 given regular expression. Other flags are not applicable to regular
17950 @subsubheading Result
17952 The result is in the form:
17955 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
17956 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
17957 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
17958 times="@var{times}"@}
17962 where @var{number} is the @value{GDBN} number for this breakpoint,
17963 @var{funcname} is the name of the function where the breakpoint was
17964 inserted, @var{filename} is the name of the source file which contains
17965 this function, @var{lineno} is the source line number within that file
17966 and @var{times} the number of times that the breakpoint has been hit
17967 (always 0 for -break-insert but may be greater for -break-info or -break-list
17968 which use the same output).
17970 Note: this format is open to change.
17971 @c An out-of-band breakpoint instead of part of the result?
17973 @subsubheading @value{GDBN} Command
17975 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
17976 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
17978 @subsubheading Example
17983 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
17984 fullname="/home/foo/recursive2.c,line="4",times="0"@}
17986 -break-insert -t foo
17987 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
17988 fullname="/home/foo/recursive2.c,line="11",times="0"@}
17991 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17992 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17993 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17994 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17995 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17996 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17997 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17998 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17999 addr="0x0001072c", func="main",file="recursive2.c",
18000 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
18001 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
18002 addr="0x00010774",func="foo",file="recursive2.c",
18003 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
18005 -break-insert -r foo.*
18006 ~int foo(int, int);
18007 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
18008 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
18012 @subheading The @code{-break-list} Command
18013 @findex -break-list
18015 @subsubheading Synopsis
18021 Displays the list of inserted breakpoints, showing the following fields:
18025 number of the breakpoint
18027 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
18029 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
18032 is the breakpoint enabled or no: @samp{y} or @samp{n}
18034 memory location at which the breakpoint is set
18036 logical location of the breakpoint, expressed by function name, file
18039 number of times the breakpoint has been hit
18042 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
18043 @code{body} field is an empty list.
18045 @subsubheading @value{GDBN} Command
18047 The corresponding @value{GDBN} command is @samp{info break}.
18049 @subsubheading Example
18054 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18055 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18056 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18057 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18058 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18059 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18060 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18061 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18062 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
18063 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
18064 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
18065 line="13",times="0"@}]@}
18069 Here's an example of the result when there are no breakpoints:
18074 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
18075 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18076 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18077 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18078 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18079 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18080 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18085 @subheading The @code{-break-watch} Command
18086 @findex -break-watch
18088 @subsubheading Synopsis
18091 -break-watch [ -a | -r ]
18094 Create a watchpoint. With the @samp{-a} option it will create an
18095 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
18096 read from or on a write to the memory location. With the @samp{-r}
18097 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
18098 trigger only when the memory location is accessed for reading. Without
18099 either of the options, the watchpoint created is a regular watchpoint,
18100 i.e., it will trigger when the memory location is accessed for writing.
18101 @xref{Set Watchpoints, , Setting Watchpoints}.
18103 Note that @samp{-break-list} will report a single list of watchpoints and
18104 breakpoints inserted.
18106 @subsubheading @value{GDBN} Command
18108 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
18111 @subsubheading Example
18113 Setting a watchpoint on a variable in the @code{main} function:
18118 ^done,wpt=@{number="2",exp="x"@}
18123 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
18124 value=@{old="-268439212",new="55"@},
18125 frame=@{func="main",args=[],file="recursive2.c",
18126 fullname="/home/foo/bar/recursive2.c",line="5"@}
18130 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
18131 the program execution twice: first for the variable changing value, then
18132 for the watchpoint going out of scope.
18137 ^done,wpt=@{number="5",exp="C"@}
18142 *stopped,reason="watchpoint-trigger",
18143 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
18144 frame=@{func="callee4",args=[],
18145 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18146 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
18151 *stopped,reason="watchpoint-scope",wpnum="5",
18152 frame=@{func="callee3",args=[@{name="strarg",
18153 value="0x11940 \"A string argument.\""@}],
18154 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18155 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18159 Listing breakpoints and watchpoints, at different points in the program
18160 execution. Note that once the watchpoint goes out of scope, it is
18166 ^done,wpt=@{number="2",exp="C"@}
18169 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18170 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18171 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18172 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18173 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18174 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18175 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18176 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18177 addr="0x00010734",func="callee4",
18178 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18179 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
18180 bkpt=@{number="2",type="watchpoint",disp="keep",
18181 enabled="y",addr="",what="C",times="0"@}]@}
18186 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
18187 value=@{old="-276895068",new="3"@},
18188 frame=@{func="callee4",args=[],
18189 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18190 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
18193 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18194 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18195 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18196 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18197 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18198 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18199 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18200 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18201 addr="0x00010734",func="callee4",
18202 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18203 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
18204 bkpt=@{number="2",type="watchpoint",disp="keep",
18205 enabled="y",addr="",what="C",times="-5"@}]@}
18209 ^done,reason="watchpoint-scope",wpnum="2",
18210 frame=@{func="callee3",args=[@{name="strarg",
18211 value="0x11940 \"A string argument.\""@}],
18212 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18213 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18216 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18217 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18218 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18219 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18220 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18221 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18222 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18223 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18224 addr="0x00010734",func="callee4",
18225 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18226 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
18231 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18232 @node GDB/MI Program Context
18233 @section @sc{gdb/mi} Program Context
18235 @subheading The @code{-exec-arguments} Command
18236 @findex -exec-arguments
18239 @subsubheading Synopsis
18242 -exec-arguments @var{args}
18245 Set the inferior program arguments, to be used in the next
18248 @subsubheading @value{GDBN} Command
18250 The corresponding @value{GDBN} command is @samp{set args}.
18252 @subsubheading Example
18255 Don't have one around.
18258 @subheading The @code{-exec-show-arguments} Command
18259 @findex -exec-show-arguments
18261 @subsubheading Synopsis
18264 -exec-show-arguments
18267 Print the arguments of the program.
18269 @subsubheading @value{GDBN} Command
18271 The corresponding @value{GDBN} command is @samp{show args}.
18273 @subsubheading Example
18277 @subheading The @code{-environment-cd} Command
18278 @findex -environment-cd
18280 @subsubheading Synopsis
18283 -environment-cd @var{pathdir}
18286 Set @value{GDBN}'s working directory.
18288 @subsubheading @value{GDBN} Command
18290 The corresponding @value{GDBN} command is @samp{cd}.
18292 @subsubheading Example
18296 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18302 @subheading The @code{-environment-directory} Command
18303 @findex -environment-directory
18305 @subsubheading Synopsis
18308 -environment-directory [ -r ] [ @var{pathdir} ]+
18311 Add directories @var{pathdir} to beginning of search path for source files.
18312 If the @samp{-r} option is used, the search path is reset to the default
18313 search path. If directories @var{pathdir} are supplied in addition to the
18314 @samp{-r} option, the search path is first reset and then addition
18316 Multiple directories may be specified, separated by blanks. Specifying
18317 multiple directories in a single command
18318 results in the directories added to the beginning of the
18319 search path in the same order they were presented in the command.
18320 If blanks are needed as
18321 part of a directory name, double-quotes should be used around
18322 the name. In the command output, the path will show up separated
18323 by the system directory-separator character. The directory-separator
18324 character must not be used
18325 in any directory name.
18326 If no directories are specified, the current search path is displayed.
18328 @subsubheading @value{GDBN} Command
18330 The corresponding @value{GDBN} command is @samp{dir}.
18332 @subsubheading Example
18336 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18337 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18339 -environment-directory ""
18340 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18342 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
18343 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
18345 -environment-directory -r
18346 ^done,source-path="$cdir:$cwd"
18351 @subheading The @code{-environment-path} Command
18352 @findex -environment-path
18354 @subsubheading Synopsis
18357 -environment-path [ -r ] [ @var{pathdir} ]+
18360 Add directories @var{pathdir} to beginning of search path for object files.
18361 If the @samp{-r} option is used, the search path is reset to the original
18362 search path that existed at gdb start-up. If directories @var{pathdir} are
18363 supplied in addition to the
18364 @samp{-r} option, the search path is first reset and then addition
18366 Multiple directories may be specified, separated by blanks. Specifying
18367 multiple directories in a single command
18368 results in the directories added to the beginning of the
18369 search path in the same order they were presented in the command.
18370 If blanks are needed as
18371 part of a directory name, double-quotes should be used around
18372 the name. In the command output, the path will show up separated
18373 by the system directory-separator character. The directory-separator
18374 character must not be used
18375 in any directory name.
18376 If no directories are specified, the current path is displayed.
18379 @subsubheading @value{GDBN} Command
18381 The corresponding @value{GDBN} command is @samp{path}.
18383 @subsubheading Example
18388 ^done,path="/usr/bin"
18390 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
18391 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
18393 -environment-path -r /usr/local/bin
18394 ^done,path="/usr/local/bin:/usr/bin"
18399 @subheading The @code{-environment-pwd} Command
18400 @findex -environment-pwd
18402 @subsubheading Synopsis
18408 Show the current working directory.
18410 @subsubheading @value{GDBN} Command
18412 The corresponding @value{GDBN} command is @samp{pwd}.
18414 @subsubheading Example
18419 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
18423 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18424 @node GDB/MI Thread Commands
18425 @section @sc{gdb/mi} Thread Commands
18428 @subheading The @code{-thread-info} Command
18429 @findex -thread-info
18431 @subsubheading Synopsis
18437 @subsubheading @value{GDBN} Command
18441 @subsubheading Example
18445 @subheading The @code{-thread-list-all-threads} Command
18446 @findex -thread-list-all-threads
18448 @subsubheading Synopsis
18451 -thread-list-all-threads
18454 @subsubheading @value{GDBN} Command
18456 The equivalent @value{GDBN} command is @samp{info threads}.
18458 @subsubheading Example
18462 @subheading The @code{-thread-list-ids} Command
18463 @findex -thread-list-ids
18465 @subsubheading Synopsis
18471 Produces a list of the currently known @value{GDBN} thread ids. At the
18472 end of the list it also prints the total number of such threads.
18474 @subsubheading @value{GDBN} Command
18476 Part of @samp{info threads} supplies the same information.
18478 @subsubheading Example
18480 No threads present, besides the main process:
18485 ^done,thread-ids=@{@},number-of-threads="0"
18495 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
18496 number-of-threads="3"
18501 @subheading The @code{-thread-select} Command
18502 @findex -thread-select
18504 @subsubheading Synopsis
18507 -thread-select @var{threadnum}
18510 Make @var{threadnum} the current thread. It prints the number of the new
18511 current thread, and the topmost frame for that thread.
18513 @subsubheading @value{GDBN} Command
18515 The corresponding @value{GDBN} command is @samp{thread}.
18517 @subsubheading Example
18524 *stopped,reason="end-stepping-range",thread-id="2",line="187",
18525 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
18529 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
18530 number-of-threads="3"
18533 ^done,new-thread-id="3",
18534 frame=@{level="0",func="vprintf",
18535 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
18536 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
18540 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18541 @node GDB/MI Program Execution
18542 @section @sc{gdb/mi} Program Execution
18544 These are the asynchronous commands which generate the out-of-band
18545 record @samp{*stopped}. Currently @value{GDBN} only really executes
18546 asynchronously with remote targets and this interaction is mimicked in
18549 @subheading The @code{-exec-continue} Command
18550 @findex -exec-continue
18552 @subsubheading Synopsis
18558 Resumes the execution of the inferior program until a breakpoint is
18559 encountered, or until the inferior exits.
18561 @subsubheading @value{GDBN} Command
18563 The corresponding @value{GDBN} corresponding is @samp{continue}.
18565 @subsubheading Example
18572 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
18573 file="hello.c",fullname="/home/foo/bar/hello.c",line="13"@}
18578 @subheading The @code{-exec-finish} Command
18579 @findex -exec-finish
18581 @subsubheading Synopsis
18587 Resumes the execution of the inferior program until the current
18588 function is exited. Displays the results returned by the function.
18590 @subsubheading @value{GDBN} Command
18592 The corresponding @value{GDBN} command is @samp{finish}.
18594 @subsubheading Example
18596 Function returning @code{void}.
18603 *stopped,reason="function-finished",frame=@{func="main",args=[],
18604 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
18608 Function returning other than @code{void}. The name of the internal
18609 @value{GDBN} variable storing the result is printed, together with the
18616 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
18617 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
18618 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
18619 gdb-result-var="$1",return-value="0"
18624 @subheading The @code{-exec-interrupt} Command
18625 @findex -exec-interrupt
18627 @subsubheading Synopsis
18633 Interrupts the background execution of the target. Note how the token
18634 associated with the stop message is the one for the execution command
18635 that has been interrupted. The token for the interrupt itself only
18636 appears in the @samp{^done} output. If the user is trying to
18637 interrupt a non-running program, an error message will be printed.
18639 @subsubheading @value{GDBN} Command
18641 The corresponding @value{GDBN} command is @samp{interrupt}.
18643 @subsubheading Example
18654 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
18655 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
18656 fullname="/home/foo/bar/try.c",line="13"@}
18661 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
18666 @subheading The @code{-exec-next} Command
18669 @subsubheading Synopsis
18675 Resumes execution of the inferior program, stopping when the beginning
18676 of the next source line is reached.
18678 @subsubheading @value{GDBN} Command
18680 The corresponding @value{GDBN} command is @samp{next}.
18682 @subsubheading Example
18688 *stopped,reason="end-stepping-range",line="8",file="hello.c"
18693 @subheading The @code{-exec-next-instruction} Command
18694 @findex -exec-next-instruction
18696 @subsubheading Synopsis
18699 -exec-next-instruction
18702 Executes one machine instruction. If the instruction is a function
18703 call, continues until the function returns. If the program stops at an
18704 instruction in the middle of a source line, the address will be
18707 @subsubheading @value{GDBN} Command
18709 The corresponding @value{GDBN} command is @samp{nexti}.
18711 @subsubheading Example
18715 -exec-next-instruction
18719 *stopped,reason="end-stepping-range",
18720 addr="0x000100d4",line="5",file="hello.c"
18725 @subheading The @code{-exec-return} Command
18726 @findex -exec-return
18728 @subsubheading Synopsis
18734 Makes current function return immediately. Doesn't execute the inferior.
18735 Displays the new current frame.
18737 @subsubheading @value{GDBN} Command
18739 The corresponding @value{GDBN} command is @samp{return}.
18741 @subsubheading Example
18745 200-break-insert callee4
18746 200^done,bkpt=@{number="1",addr="0x00010734",
18747 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
18752 000*stopped,reason="breakpoint-hit",bkptno="1",
18753 frame=@{func="callee4",args=[],
18754 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18755 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
18761 111^done,frame=@{level="0",func="callee3",
18762 args=[@{name="strarg",
18763 value="0x11940 \"A string argument.\""@}],
18764 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18765 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18770 @subheading The @code{-exec-run} Command
18773 @subsubheading Synopsis
18779 Starts execution of the inferior from the beginning. The inferior
18780 executes until either a breakpoint is encountered or the program
18781 exits. In the latter case the output will include an exit code, if
18782 the program has exited exceptionally.
18784 @subsubheading @value{GDBN} Command
18786 The corresponding @value{GDBN} command is @samp{run}.
18788 @subsubheading Examples
18793 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
18798 *stopped,reason="breakpoint-hit",bkptno="1",
18799 frame=@{func="main",args=[],file="recursive2.c",
18800 fullname="/home/foo/bar/recursive2.c",line="4"@}
18805 Program exited normally:
18813 *stopped,reason="exited-normally"
18818 Program exited exceptionally:
18826 *stopped,reason="exited",exit-code="01"
18830 Another way the program can terminate is if it receives a signal such as
18831 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
18835 *stopped,reason="exited-signalled",signal-name="SIGINT",
18836 signal-meaning="Interrupt"
18840 @c @subheading -exec-signal
18843 @subheading The @code{-exec-step} Command
18846 @subsubheading Synopsis
18852 Resumes execution of the inferior program, stopping when the beginning
18853 of the next source line is reached, if the next source line is not a
18854 function call. If it is, stop at the first instruction of the called
18857 @subsubheading @value{GDBN} Command
18859 The corresponding @value{GDBN} command is @samp{step}.
18861 @subsubheading Example
18863 Stepping into a function:
18869 *stopped,reason="end-stepping-range",
18870 frame=@{func="foo",args=[@{name="a",value="10"@},
18871 @{name="b",value="0"@}],file="recursive2.c",
18872 fullname="/home/foo/bar/recursive2.c",line="11"@}
18882 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
18887 @subheading The @code{-exec-step-instruction} Command
18888 @findex -exec-step-instruction
18890 @subsubheading Synopsis
18893 -exec-step-instruction
18896 Resumes the inferior which executes one machine instruction. The
18897 output, once @value{GDBN} has stopped, will vary depending on whether
18898 we have stopped in the middle of a source line or not. In the former
18899 case, the address at which the program stopped will be printed as
18902 @subsubheading @value{GDBN} Command
18904 The corresponding @value{GDBN} command is @samp{stepi}.
18906 @subsubheading Example
18910 -exec-step-instruction
18914 *stopped,reason="end-stepping-range",
18915 frame=@{func="foo",args=[],file="try.c",
18916 fullname="/home/foo/bar/try.c",line="10"@}
18918 -exec-step-instruction
18922 *stopped,reason="end-stepping-range",
18923 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
18924 fullname="/home/foo/bar/try.c",line="10"@}
18929 @subheading The @code{-exec-until} Command
18930 @findex -exec-until
18932 @subsubheading Synopsis
18935 -exec-until [ @var{location} ]
18938 Executes the inferior until the @var{location} specified in the
18939 argument is reached. If there is no argument, the inferior executes
18940 until a source line greater than the current one is reached. The
18941 reason for stopping in this case will be @samp{location-reached}.
18943 @subsubheading @value{GDBN} Command
18945 The corresponding @value{GDBN} command is @samp{until}.
18947 @subsubheading Example
18951 -exec-until recursive2.c:6
18955 *stopped,reason="location-reached",frame=@{func="main",args=[],
18956 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
18961 @subheading -file-clear
18962 Is this going away????
18965 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18966 @node GDB/MI Stack Manipulation
18967 @section @sc{gdb/mi} Stack Manipulation Commands
18970 @subheading The @code{-stack-info-frame} Command
18971 @findex -stack-info-frame
18973 @subsubheading Synopsis
18979 Get info on the selected frame.
18981 @subsubheading @value{GDBN} Command
18983 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
18984 (without arguments).
18986 @subsubheading Example
18991 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
18992 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18993 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
18997 @subheading The @code{-stack-info-depth} Command
18998 @findex -stack-info-depth
19000 @subsubheading Synopsis
19003 -stack-info-depth [ @var{max-depth} ]
19006 Return the depth of the stack. If the integer argument @var{max-depth}
19007 is specified, do not count beyond @var{max-depth} frames.
19009 @subsubheading @value{GDBN} Command
19011 There's no equivalent @value{GDBN} command.
19013 @subsubheading Example
19015 For a stack with frame levels 0 through 11:
19022 -stack-info-depth 4
19025 -stack-info-depth 12
19028 -stack-info-depth 11
19031 -stack-info-depth 13
19036 @subheading The @code{-stack-list-arguments} Command
19037 @findex -stack-list-arguments
19039 @subsubheading Synopsis
19042 -stack-list-arguments @var{show-values}
19043 [ @var{low-frame} @var{high-frame} ]
19046 Display a list of the arguments for the frames between @var{low-frame}
19047 and @var{high-frame} (inclusive). If @var{low-frame} and
19048 @var{high-frame} are not provided, list the arguments for the whole
19049 call stack. If the two arguments are equal, show the single frame
19050 at the corresponding level. It is an error if @var{low-frame} is
19051 larger than the actual number of frames. On the other hand,
19052 @var{high-frame} may be larger than the actual number of frames, in
19053 which case only existing frames will be returned.
19055 The @var{show-values} argument must have a value of 0 or 1. A value of
19056 0 means that only the names of the arguments are listed, a value of 1
19057 means that both names and values of the arguments are printed.
19059 @subsubheading @value{GDBN} Command
19061 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
19062 @samp{gdb_get_args} command which partially overlaps with the
19063 functionality of @samp{-stack-list-arguments}.
19065 @subsubheading Example
19072 frame=@{level="0",addr="0x00010734",func="callee4",
19073 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19074 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
19075 frame=@{level="1",addr="0x0001076c",func="callee3",
19076 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19077 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
19078 frame=@{level="2",addr="0x0001078c",func="callee2",
19079 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19080 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
19081 frame=@{level="3",addr="0x000107b4",func="callee1",
19082 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19083 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
19084 frame=@{level="4",addr="0x000107e0",func="main",
19085 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19086 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
19088 -stack-list-arguments 0
19091 frame=@{level="0",args=[]@},
19092 frame=@{level="1",args=[name="strarg"]@},
19093 frame=@{level="2",args=[name="intarg",name="strarg"]@},
19094 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
19095 frame=@{level="4",args=[]@}]
19097 -stack-list-arguments 1
19100 frame=@{level="0",args=[]@},
19102 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19103 frame=@{level="2",args=[
19104 @{name="intarg",value="2"@},
19105 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19106 @{frame=@{level="3",args=[
19107 @{name="intarg",value="2"@},
19108 @{name="strarg",value="0x11940 \"A string argument.\""@},
19109 @{name="fltarg",value="3.5"@}]@},
19110 frame=@{level="4",args=[]@}]
19112 -stack-list-arguments 0 2 2
19113 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
19115 -stack-list-arguments 1 2 2
19116 ^done,stack-args=[frame=@{level="2",
19117 args=[@{name="intarg",value="2"@},
19118 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
19122 @c @subheading -stack-list-exception-handlers
19125 @subheading The @code{-stack-list-frames} Command
19126 @findex -stack-list-frames
19128 @subsubheading Synopsis
19131 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
19134 List the frames currently on the stack. For each frame it displays the
19139 The frame number, 0 being the topmost frame, i.e., the innermost function.
19141 The @code{$pc} value for that frame.
19145 File name of the source file where the function lives.
19147 Line number corresponding to the @code{$pc}.
19150 If invoked without arguments, this command prints a backtrace for the
19151 whole stack. If given two integer arguments, it shows the frames whose
19152 levels are between the two arguments (inclusive). If the two arguments
19153 are equal, it shows the single frame at the corresponding level. It is
19154 an error if @var{low-frame} is larger than the actual number of
19155 frames. On the other hand, @var{high-frame} may be larger than the
19156 actual number of frames, in which case only existing frames will be returned.
19158 @subsubheading @value{GDBN} Command
19160 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
19162 @subsubheading Example
19164 Full stack backtrace:
19170 [frame=@{level="0",addr="0x0001076c",func="foo",
19171 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
19172 frame=@{level="1",addr="0x000107a4",func="foo",
19173 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19174 frame=@{level="2",addr="0x000107a4",func="foo",
19175 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19176 frame=@{level="3",addr="0x000107a4",func="foo",
19177 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19178 frame=@{level="4",addr="0x000107a4",func="foo",
19179 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19180 frame=@{level="5",addr="0x000107a4",func="foo",
19181 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19182 frame=@{level="6",addr="0x000107a4",func="foo",
19183 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19184 frame=@{level="7",addr="0x000107a4",func="foo",
19185 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19186 frame=@{level="8",addr="0x000107a4",func="foo",
19187 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19188 frame=@{level="9",addr="0x000107a4",func="foo",
19189 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19190 frame=@{level="10",addr="0x000107a4",func="foo",
19191 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19192 frame=@{level="11",addr="0x00010738",func="main",
19193 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
19197 Show frames between @var{low_frame} and @var{high_frame}:
19201 -stack-list-frames 3 5
19203 [frame=@{level="3",addr="0x000107a4",func="foo",
19204 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19205 frame=@{level="4",addr="0x000107a4",func="foo",
19206 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19207 frame=@{level="5",addr="0x000107a4",func="foo",
19208 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
19212 Show a single frame:
19216 -stack-list-frames 3 3
19218 [frame=@{level="3",addr="0x000107a4",func="foo",
19219 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
19224 @subheading The @code{-stack-list-locals} Command
19225 @findex -stack-list-locals
19227 @subsubheading Synopsis
19230 -stack-list-locals @var{print-values}
19233 Display the local variable names for the selected frame. If
19234 @var{print-values} is 0 or @code{--no-values}, print only the names of
19235 the variables; if it is 1 or @code{--all-values}, print also their
19236 values; and if it is 2 or @code{--simple-values}, print the name,
19237 type and value for simple data types and the name and type for arrays,
19238 structures and unions. In this last case, a frontend can immediately
19239 display the value of simple data types and create variable objects for
19240 other data types when the user wishes to explore their values in
19243 @subsubheading @value{GDBN} Command
19245 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
19247 @subsubheading Example
19251 -stack-list-locals 0
19252 ^done,locals=[name="A",name="B",name="C"]
19254 -stack-list-locals --all-values
19255 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
19256 @{name="C",value="@{1, 2, 3@}"@}]
19257 -stack-list-locals --simple-values
19258 ^done,locals=[@{name="A",type="int",value="1"@},
19259 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
19264 @subheading The @code{-stack-select-frame} Command
19265 @findex -stack-select-frame
19267 @subsubheading Synopsis
19270 -stack-select-frame @var{framenum}
19273 Change the selected frame. Select a different frame @var{framenum} on
19276 @subsubheading @value{GDBN} Command
19278 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
19279 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
19281 @subsubheading Example
19285 -stack-select-frame 2
19290 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19291 @node GDB/MI Variable Objects
19292 @section @sc{gdb/mi} Variable Objects
19296 @subheading Motivation for Variable Objects in @sc{gdb/mi}
19298 For the implementation of a variable debugger window (locals, watched
19299 expressions, etc.), we are proposing the adaptation of the existing code
19300 used by @code{Insight}.
19302 The two main reasons for that are:
19306 It has been proven in practice (it is already on its second generation).
19309 It will shorten development time (needless to say how important it is
19313 The original interface was designed to be used by Tcl code, so it was
19314 slightly changed so it could be used through @sc{gdb/mi}. This section
19315 describes the @sc{gdb/mi} operations that will be available and gives some
19316 hints about their use.
19318 @emph{Note}: In addition to the set of operations described here, we
19319 expect the @sc{gui} implementation of a variable window to require, at
19320 least, the following operations:
19323 @item @code{-gdb-show} @code{output-radix}
19324 @item @code{-stack-list-arguments}
19325 @item @code{-stack-list-locals}
19326 @item @code{-stack-select-frame}
19331 @subheading Introduction to Variable Objects
19333 @cindex variable objects in @sc{gdb/mi}
19335 Variable objects are "object-oriented" MI interface for examining and
19336 changing values of expressions. Unlike some other MI interfaces that
19337 work with expressions, variable objects are specifically designed for
19338 simple and efficient presentation in the frontend. A variable object
19339 is identified by string name. When a variable object is created, the
19340 frontend specifies the expression for that variable object. The
19341 expression can be a simple variable, or it can be an arbitrary complex
19342 expression, and can even involve CPU registers. After creating a
19343 variable object, the frontend can invoke other variable object
19344 operations---for example to obtain or change the value of a variable
19345 object, or to change display format.
19347 Variable objects have hierarchical tree structure. Any variable object
19348 that corresponds to a composite type, such as structure in C, has
19349 a number of child variable objects, for example corresponding to each
19350 element of a structure. A child variable object can itself have
19351 children, recursively. Recursion ends when we reach
19352 leaf variable objects, which always have built-in types. Child variable
19353 objects are created only by explicit request, so if a frontend
19354 is not interested in the children of a particular variable object, no
19355 child will be created.
19357 For a leaf variable object it is possible to obtain its value as a
19358 string, or set the value from a string. String value can be also
19359 obtained for a non-leaf variable object, but it's generally a string
19360 that only indicates the type of the object, and does not list its
19361 contents. Assignment to a non-leaf variable object is not allowed.
19363 A frontend does not need to read the values of all variable objects each time
19364 the program stops. Instead, MI provides an update command that lists all
19365 variable objects whose values has changed since the last update
19366 operation. This considerably reduces the amount of data that must
19367 be transferred to the frontend. As noted above, children variable
19368 objects are created on demand, and only leaf variable objects have a
19369 real value. As result, gdb will read target memory only for leaf
19370 variables that frontend has created.
19372 The automatic update is not always desirable. For example, a frontend
19373 might want to keep a value of some expression for future reference,
19374 and never update it. For another example, fetching memory is
19375 relatively slow for embedded targets, so a frontend might want
19376 to disable automatic update for the variables that are either not
19377 visible on the screen, or ``closed''. This is possible using so
19378 called ``frozen variable objects''. Such variable objects are never
19379 implicitly updated.
19381 The following is the complete set of @sc{gdb/mi} operations defined to
19382 access this functionality:
19384 @multitable @columnfractions .4 .6
19385 @item @strong{Operation}
19386 @tab @strong{Description}
19388 @item @code{-var-create}
19389 @tab create a variable object
19390 @item @code{-var-delete}
19391 @tab delete the variable object and/or its children
19392 @item @code{-var-set-format}
19393 @tab set the display format of this variable
19394 @item @code{-var-show-format}
19395 @tab show the display format of this variable
19396 @item @code{-var-info-num-children}
19397 @tab tells how many children this object has
19398 @item @code{-var-list-children}
19399 @tab return a list of the object's children
19400 @item @code{-var-info-type}
19401 @tab show the type of this variable object
19402 @item @code{-var-info-expression}
19403 @tab print parent-relative expression that this variable object represents
19404 @item @code{-var-info-path-expression}
19405 @tab print full expression that this variable object represents
19406 @item @code{-var-show-attributes}
19407 @tab is this variable editable? does it exist here?
19408 @item @code{-var-evaluate-expression}
19409 @tab get the value of this variable
19410 @item @code{-var-assign}
19411 @tab set the value of this variable
19412 @item @code{-var-update}
19413 @tab update the variable and its children
19414 @item @code{-var-set-frozen}
19415 @tab set frozeness attribute
19418 In the next subsection we describe each operation in detail and suggest
19419 how it can be used.
19421 @subheading Description And Use of Operations on Variable Objects
19423 @subheading The @code{-var-create} Command
19424 @findex -var-create
19426 @subsubheading Synopsis
19429 -var-create @{@var{name} | "-"@}
19430 @{@var{frame-addr} | "*"@} @var{expression}
19433 This operation creates a variable object, which allows the monitoring of
19434 a variable, the result of an expression, a memory cell or a CPU
19437 The @var{name} parameter is the string by which the object can be
19438 referenced. It must be unique. If @samp{-} is specified, the varobj
19439 system will generate a string ``varNNNNNN'' automatically. It will be
19440 unique provided that one does not specify @var{name} on that format.
19441 The command fails if a duplicate name is found.
19443 The frame under which the expression should be evaluated can be
19444 specified by @var{frame-addr}. A @samp{*} indicates that the current
19445 frame should be used.
19447 @var{expression} is any expression valid on the current language set (must not
19448 begin with a @samp{*}), or one of the following:
19452 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
19455 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
19458 @samp{$@var{regname}} --- a CPU register name
19461 @subsubheading Result
19463 This operation returns the name, number of children and the type of the
19464 object created. Type is returned as a string as the ones generated by
19465 the @value{GDBN} CLI:
19468 name="@var{name}",numchild="N",type="@var{type}"
19472 @subheading The @code{-var-delete} Command
19473 @findex -var-delete
19475 @subsubheading Synopsis
19478 -var-delete [ -c ] @var{name}
19481 Deletes a previously created variable object and all of its children.
19482 With the @samp{-c} option, just deletes the children.
19484 Returns an error if the object @var{name} is not found.
19487 @subheading The @code{-var-set-format} Command
19488 @findex -var-set-format
19490 @subsubheading Synopsis
19493 -var-set-format @var{name} @var{format-spec}
19496 Sets the output format for the value of the object @var{name} to be
19499 The syntax for the @var{format-spec} is as follows:
19502 @var{format-spec} @expansion{}
19503 @{binary | decimal | hexadecimal | octal | natural@}
19506 The natural format is the default format choosen automatically
19507 based on the variable type (like decimal for an @code{int}, hex
19508 for pointers, etc.).
19510 For a variable with children, the format is set only on the
19511 variable itself, and the children are not affected.
19513 @subheading The @code{-var-show-format} Command
19514 @findex -var-show-format
19516 @subsubheading Synopsis
19519 -var-show-format @var{name}
19522 Returns the format used to display the value of the object @var{name}.
19525 @var{format} @expansion{}
19530 @subheading The @code{-var-info-num-children} Command
19531 @findex -var-info-num-children
19533 @subsubheading Synopsis
19536 -var-info-num-children @var{name}
19539 Returns the number of children of a variable object @var{name}:
19546 @subheading The @code{-var-list-children} Command
19547 @findex -var-list-children
19549 @subsubheading Synopsis
19552 -var-list-children [@var{print-values}] @var{name}
19554 @anchor{-var-list-children}
19556 Return a list of the children of the specified variable object and
19557 create variable objects for them, if they do not already exist. With
19558 a single argument or if @var{print-values} has a value for of 0 or
19559 @code{--no-values}, print only the names of the variables; if
19560 @var{print-values} is 1 or @code{--all-values}, also print their
19561 values; and if it is 2 or @code{--simple-values} print the name and
19562 value for simple data types and just the name for arrays, structures
19565 @subsubheading Example
19569 -var-list-children n
19570 ^done,numchild=@var{n},children=[@{name=@var{name},
19571 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
19573 -var-list-children --all-values n
19574 ^done,numchild=@var{n},children=[@{name=@var{name},
19575 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
19579 @subheading The @code{-var-info-type} Command
19580 @findex -var-info-type
19582 @subsubheading Synopsis
19585 -var-info-type @var{name}
19588 Returns the type of the specified variable @var{name}. The type is
19589 returned as a string in the same format as it is output by the
19593 type=@var{typename}
19597 @subheading The @code{-var-info-expression} Command
19598 @findex -var-info-expression
19600 @subsubheading Synopsis
19603 -var-info-expression @var{name}
19606 Returns a string that is suitable for presenting this
19607 variable object in user interface. The string is generally
19608 not valid expression in the current language, and cannot be evaluated.
19610 For example, if @code{a} is an array, and variable object
19611 @code{A} was created for @code{a}, then we'll get this output:
19614 (gdb) -var-info-expression A.1
19615 ^done,lang="C",exp="1"
19619 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
19621 Note that the output of the @code{-var-list-children} command also
19622 includes those expressions, so the @code{-var-info-expression} command
19625 @subheading The @code{-var-info-path-expression} Command
19626 @findex -var-info-path-expression
19628 @subsubheading Synopsis
19631 -var-info-path-expression @var{name}
19634 Returns an expression that can be evaluated in the current
19635 context and will yield the same value that a variable object has.
19636 Compare this with the @code{-var-info-expression} command, which
19637 result can be used only for UI presentation. Typical use of
19638 the @code{-var-info-path-expression} command is creating a
19639 watchpoint from a variable object.
19641 For example, suppose @code{C} is a C@t{++} class, derived from class
19642 @code{Base}, and that the @code{Base} class has a member called
19643 @code{m_size}. Assume a variable @code{c} is has the type of
19644 @code{C} and a variable object @code{C} was created for variable
19645 @code{c}. Then, we'll get this output:
19647 (gdb) -var-info-path-expression C.Base.public.m_size
19648 ^done,path_expr=((Base)c).m_size)
19651 @subheading The @code{-var-show-attributes} Command
19652 @findex -var-show-attributes
19654 @subsubheading Synopsis
19657 -var-show-attributes @var{name}
19660 List attributes of the specified variable object @var{name}:
19663 status=@var{attr} [ ( ,@var{attr} )* ]
19667 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
19669 @subheading The @code{-var-evaluate-expression} Command
19670 @findex -var-evaluate-expression
19672 @subsubheading Synopsis
19675 -var-evaluate-expression @var{name}
19678 Evaluates the expression that is represented by the specified variable
19679 object and returns its value as a string. The format of the
19680 string can be changed using the @code{-var-set-format} command.
19686 Note that one must invoke @code{-var-list-children} for a variable
19687 before the value of a child variable can be evaluated.
19689 @subheading The @code{-var-assign} Command
19690 @findex -var-assign
19692 @subsubheading Synopsis
19695 -var-assign @var{name} @var{expression}
19698 Assigns the value of @var{expression} to the variable object specified
19699 by @var{name}. The object must be @samp{editable}. If the variable's
19700 value is altered by the assign, the variable will show up in any
19701 subsequent @code{-var-update} list.
19703 @subsubheading Example
19711 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
19715 @subheading The @code{-var-update} Command
19716 @findex -var-update
19718 @subsubheading Synopsis
19721 -var-update [@var{print-values}] @{@var{name} | "*"@}
19724 Reevaluate the expressions corresponding to the variable object
19725 @var{name} and all its direct and indirect children, and return the
19726 list of variable objects whose values have changed; @var{name} must
19727 be a root variable object. Here, ``changed'' means that the result of
19728 @code{-var-evaluate-expression} before and after the
19729 @code{-var-update} is different. If @samp{*} is used as the variable
19730 object names, all existing variable objects are updated, except
19731 for frozen ones (@pxref{-var-set-frozen}). The option
19732 @var{print-values} determines whether both names and values, or just
19733 names are printed. The possible values of this options are the same
19734 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
19735 recommended to use the @samp{--all-values} option, to reduce the
19736 number of MI commands needed on each program stop.
19739 @subsubheading Example
19746 -var-update --all-values var1
19747 ^done,changelist=[@{name="var1",value="3",in_scope="true",
19748 type_changed="false"@}]
19752 @anchor{-var-update}
19753 The field in_scope may take three values:
19757 The variable object's current value is valid.
19760 The variable object does not currently hold a valid value but it may
19761 hold one in the future if its associated expression comes back into
19765 The variable object no longer holds a valid value.
19766 This can occur when the executable file being debugged has changed,
19767 either through recompilation or by using the @value{GDBN} @code{file}
19768 command. The front end should normally choose to delete these variable
19772 In the future new values may be added to this list so the front should
19773 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
19775 @subheading The @code{-var-set-frozen} Command
19776 @findex -var-set-frozen
19777 @anchor{-var-set-frozen}
19779 @subsubheading Synopsis
19782 -var-set-frozen @var{name} @var{flag}
19785 Set the frozenness flag on the variable object @var{name}. The
19786 @var{flag} parameter should be either @samp{1} to make the variable
19787 frozen or @samp{0} to make it unfrozen. If a variable object is
19788 frozen, then neither itself, nor any of its children, are
19789 implicitly updated by @code{-var-update} of
19790 a parent variable or by @code{-var-update *}. Only
19791 @code{-var-update} of the variable itself will update its value and
19792 values of its children. After a variable object is unfrozen, it is
19793 implicitly updated by all subsequent @code{-var-update} operations.
19794 Unfreezing a variable does not update it, only subsequent
19795 @code{-var-update} does.
19797 @subsubheading Example
19801 -var-set-frozen V 1
19807 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19808 @node GDB/MI Data Manipulation
19809 @section @sc{gdb/mi} Data Manipulation
19811 @cindex data manipulation, in @sc{gdb/mi}
19812 @cindex @sc{gdb/mi}, data manipulation
19813 This section describes the @sc{gdb/mi} commands that manipulate data:
19814 examine memory and registers, evaluate expressions, etc.
19816 @c REMOVED FROM THE INTERFACE.
19817 @c @subheading -data-assign
19818 @c Change the value of a program variable. Plenty of side effects.
19819 @c @subsubheading GDB Command
19821 @c @subsubheading Example
19824 @subheading The @code{-data-disassemble} Command
19825 @findex -data-disassemble
19827 @subsubheading Synopsis
19831 [ -s @var{start-addr} -e @var{end-addr} ]
19832 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
19840 @item @var{start-addr}
19841 is the beginning address (or @code{$pc})
19842 @item @var{end-addr}
19844 @item @var{filename}
19845 is the name of the file to disassemble
19846 @item @var{linenum}
19847 is the line number to disassemble around
19849 is the number of disassembly lines to be produced. If it is -1,
19850 the whole function will be disassembled, in case no @var{end-addr} is
19851 specified. If @var{end-addr} is specified as a non-zero value, and
19852 @var{lines} is lower than the number of disassembly lines between
19853 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
19854 displayed; if @var{lines} is higher than the number of lines between
19855 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
19858 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
19862 @subsubheading Result
19864 The output for each instruction is composed of four fields:
19873 Note that whatever included in the instruction field, is not manipulated
19874 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
19876 @subsubheading @value{GDBN} Command
19878 There's no direct mapping from this command to the CLI.
19880 @subsubheading Example
19882 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
19886 -data-disassemble -s $pc -e "$pc + 20" -- 0
19889 @{address="0x000107c0",func-name="main",offset="4",
19890 inst="mov 2, %o0"@},
19891 @{address="0x000107c4",func-name="main",offset="8",
19892 inst="sethi %hi(0x11800), %o2"@},
19893 @{address="0x000107c8",func-name="main",offset="12",
19894 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
19895 @{address="0x000107cc",func-name="main",offset="16",
19896 inst="sethi %hi(0x11800), %o2"@},
19897 @{address="0x000107d0",func-name="main",offset="20",
19898 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
19902 Disassemble the whole @code{main} function. Line 32 is part of
19906 -data-disassemble -f basics.c -l 32 -- 0
19908 @{address="0x000107bc",func-name="main",offset="0",
19909 inst="save %sp, -112, %sp"@},
19910 @{address="0x000107c0",func-name="main",offset="4",
19911 inst="mov 2, %o0"@},
19912 @{address="0x000107c4",func-name="main",offset="8",
19913 inst="sethi %hi(0x11800), %o2"@},
19915 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
19916 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
19920 Disassemble 3 instructions from the start of @code{main}:
19924 -data-disassemble -f basics.c -l 32 -n 3 -- 0
19926 @{address="0x000107bc",func-name="main",offset="0",
19927 inst="save %sp, -112, %sp"@},
19928 @{address="0x000107c0",func-name="main",offset="4",
19929 inst="mov 2, %o0"@},
19930 @{address="0x000107c4",func-name="main",offset="8",
19931 inst="sethi %hi(0x11800), %o2"@}]
19935 Disassemble 3 instructions from the start of @code{main} in mixed mode:
19939 -data-disassemble -f basics.c -l 32 -n 3 -- 1
19941 src_and_asm_line=@{line="31",
19942 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
19943 testsuite/gdb.mi/basics.c",line_asm_insn=[
19944 @{address="0x000107bc",func-name="main",offset="0",
19945 inst="save %sp, -112, %sp"@}]@},
19946 src_and_asm_line=@{line="32",
19947 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
19948 testsuite/gdb.mi/basics.c",line_asm_insn=[
19949 @{address="0x000107c0",func-name="main",offset="4",
19950 inst="mov 2, %o0"@},
19951 @{address="0x000107c4",func-name="main",offset="8",
19952 inst="sethi %hi(0x11800), %o2"@}]@}]
19957 @subheading The @code{-data-evaluate-expression} Command
19958 @findex -data-evaluate-expression
19960 @subsubheading Synopsis
19963 -data-evaluate-expression @var{expr}
19966 Evaluate @var{expr} as an expression. The expression could contain an
19967 inferior function call. The function call will execute synchronously.
19968 If the expression contains spaces, it must be enclosed in double quotes.
19970 @subsubheading @value{GDBN} Command
19972 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
19973 @samp{call}. In @code{gdbtk} only, there's a corresponding
19974 @samp{gdb_eval} command.
19976 @subsubheading Example
19978 In the following example, the numbers that precede the commands are the
19979 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
19980 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
19984 211-data-evaluate-expression A
19987 311-data-evaluate-expression &A
19988 311^done,value="0xefffeb7c"
19990 411-data-evaluate-expression A+3
19993 511-data-evaluate-expression "A + 3"
19999 @subheading The @code{-data-list-changed-registers} Command
20000 @findex -data-list-changed-registers
20002 @subsubheading Synopsis
20005 -data-list-changed-registers
20008 Display a list of the registers that have changed.
20010 @subsubheading @value{GDBN} Command
20012 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
20013 has the corresponding command @samp{gdb_changed_register_list}.
20015 @subsubheading Example
20017 On a PPC MBX board:
20025 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
20026 args=[],file="try.c",fullname="/home/foo/bar/try.c",line="5"@}
20028 -data-list-changed-registers
20029 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
20030 "10","11","13","14","15","16","17","18","19","20","21","22","23",
20031 "24","25","26","27","28","30","31","64","65","66","67","69"]
20036 @subheading The @code{-data-list-register-names} Command
20037 @findex -data-list-register-names
20039 @subsubheading Synopsis
20042 -data-list-register-names [ ( @var{regno} )+ ]
20045 Show a list of register names for the current target. If no arguments
20046 are given, it shows a list of the names of all the registers. If
20047 integer numbers are given as arguments, it will print a list of the
20048 names of the registers corresponding to the arguments. To ensure
20049 consistency between a register name and its number, the output list may
20050 include empty register names.
20052 @subsubheading @value{GDBN} Command
20054 @value{GDBN} does not have a command which corresponds to
20055 @samp{-data-list-register-names}. In @code{gdbtk} there is a
20056 corresponding command @samp{gdb_regnames}.
20058 @subsubheading Example
20060 For the PPC MBX board:
20063 -data-list-register-names
20064 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
20065 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
20066 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
20067 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
20068 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
20069 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
20070 "", "pc","ps","cr","lr","ctr","xer"]
20072 -data-list-register-names 1 2 3
20073 ^done,register-names=["r1","r2","r3"]
20077 @subheading The @code{-data-list-register-values} Command
20078 @findex -data-list-register-values
20080 @subsubheading Synopsis
20083 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
20086 Display the registers' contents. @var{fmt} is the format according to
20087 which the registers' contents are to be returned, followed by an optional
20088 list of numbers specifying the registers to display. A missing list of
20089 numbers indicates that the contents of all the registers must be returned.
20091 Allowed formats for @var{fmt} are:
20108 @subsubheading @value{GDBN} Command
20110 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
20111 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
20113 @subsubheading Example
20115 For a PPC MBX board (note: line breaks are for readability only, they
20116 don't appear in the actual output):
20120 -data-list-register-values r 64 65
20121 ^done,register-values=[@{number="64",value="0xfe00a300"@},
20122 @{number="65",value="0x00029002"@}]
20124 -data-list-register-values x
20125 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
20126 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
20127 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
20128 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
20129 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
20130 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
20131 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
20132 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
20133 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
20134 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
20135 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
20136 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
20137 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
20138 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
20139 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
20140 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
20141 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
20142 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
20143 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
20144 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
20145 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
20146 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
20147 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
20148 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
20149 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
20150 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
20151 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
20152 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
20153 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
20154 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
20155 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
20156 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
20157 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
20158 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
20159 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
20160 @{number="69",value="0x20002b03"@}]
20165 @subheading The @code{-data-read-memory} Command
20166 @findex -data-read-memory
20168 @subsubheading Synopsis
20171 -data-read-memory [ -o @var{byte-offset} ]
20172 @var{address} @var{word-format} @var{word-size}
20173 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
20180 @item @var{address}
20181 An expression specifying the address of the first memory word to be
20182 read. Complex expressions containing embedded white space should be
20183 quoted using the C convention.
20185 @item @var{word-format}
20186 The format to be used to print the memory words. The notation is the
20187 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
20190 @item @var{word-size}
20191 The size of each memory word in bytes.
20193 @item @var{nr-rows}
20194 The number of rows in the output table.
20196 @item @var{nr-cols}
20197 The number of columns in the output table.
20200 If present, indicates that each row should include an @sc{ascii} dump. The
20201 value of @var{aschar} is used as a padding character when a byte is not a
20202 member of the printable @sc{ascii} character set (printable @sc{ascii}
20203 characters are those whose code is between 32 and 126, inclusively).
20205 @item @var{byte-offset}
20206 An offset to add to the @var{address} before fetching memory.
20209 This command displays memory contents as a table of @var{nr-rows} by
20210 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
20211 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
20212 (returned as @samp{total-bytes}). Should less than the requested number
20213 of bytes be returned by the target, the missing words are identified
20214 using @samp{N/A}. The number of bytes read from the target is returned
20215 in @samp{nr-bytes} and the starting address used to read memory in
20218 The address of the next/previous row or page is available in
20219 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
20222 @subsubheading @value{GDBN} Command
20224 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
20225 @samp{gdb_get_mem} memory read command.
20227 @subsubheading Example
20229 Read six bytes of memory starting at @code{bytes+6} but then offset by
20230 @code{-6} bytes. Format as three rows of two columns. One byte per
20231 word. Display each word in hex.
20235 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
20236 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
20237 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
20238 prev-page="0x0000138a",memory=[
20239 @{addr="0x00001390",data=["0x00","0x01"]@},
20240 @{addr="0x00001392",data=["0x02","0x03"]@},
20241 @{addr="0x00001394",data=["0x04","0x05"]@}]
20245 Read two bytes of memory starting at address @code{shorts + 64} and
20246 display as a single word formatted in decimal.
20250 5-data-read-memory shorts+64 d 2 1 1
20251 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
20252 next-row="0x00001512",prev-row="0x0000150e",
20253 next-page="0x00001512",prev-page="0x0000150e",memory=[
20254 @{addr="0x00001510",data=["128"]@}]
20258 Read thirty two bytes of memory starting at @code{bytes+16} and format
20259 as eight rows of four columns. Include a string encoding with @samp{x}
20260 used as the non-printable character.
20264 4-data-read-memory bytes+16 x 1 8 4 x
20265 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
20266 next-row="0x000013c0",prev-row="0x0000139c",
20267 next-page="0x000013c0",prev-page="0x00001380",memory=[
20268 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
20269 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
20270 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
20271 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
20272 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
20273 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
20274 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
20275 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
20279 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20280 @node GDB/MI Tracepoint Commands
20281 @section @sc{gdb/mi} Tracepoint Commands
20283 The tracepoint commands are not yet implemented.
20285 @c @subheading -trace-actions
20287 @c @subheading -trace-delete
20289 @c @subheading -trace-disable
20291 @c @subheading -trace-dump
20293 @c @subheading -trace-enable
20295 @c @subheading -trace-exists
20297 @c @subheading -trace-find
20299 @c @subheading -trace-frame-number
20301 @c @subheading -trace-info
20303 @c @subheading -trace-insert
20305 @c @subheading -trace-list
20307 @c @subheading -trace-pass-count
20309 @c @subheading -trace-save
20311 @c @subheading -trace-start
20313 @c @subheading -trace-stop
20316 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20317 @node GDB/MI Symbol Query
20318 @section @sc{gdb/mi} Symbol Query Commands
20321 @subheading The @code{-symbol-info-address} Command
20322 @findex -symbol-info-address
20324 @subsubheading Synopsis
20327 -symbol-info-address @var{symbol}
20330 Describe where @var{symbol} is stored.
20332 @subsubheading @value{GDBN} Command
20334 The corresponding @value{GDBN} command is @samp{info address}.
20336 @subsubheading Example
20340 @subheading The @code{-symbol-info-file} Command
20341 @findex -symbol-info-file
20343 @subsubheading Synopsis
20349 Show the file for the symbol.
20351 @subsubheading @value{GDBN} Command
20353 There's no equivalent @value{GDBN} command. @code{gdbtk} has
20354 @samp{gdb_find_file}.
20356 @subsubheading Example
20360 @subheading The @code{-symbol-info-function} Command
20361 @findex -symbol-info-function
20363 @subsubheading Synopsis
20366 -symbol-info-function
20369 Show which function the symbol lives in.
20371 @subsubheading @value{GDBN} Command
20373 @samp{gdb_get_function} in @code{gdbtk}.
20375 @subsubheading Example
20379 @subheading The @code{-symbol-info-line} Command
20380 @findex -symbol-info-line
20382 @subsubheading Synopsis
20388 Show the core addresses of the code for a source line.
20390 @subsubheading @value{GDBN} Command
20392 The corresponding @value{GDBN} command is @samp{info line}.
20393 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
20395 @subsubheading Example
20399 @subheading The @code{-symbol-info-symbol} Command
20400 @findex -symbol-info-symbol
20402 @subsubheading Synopsis
20405 -symbol-info-symbol @var{addr}
20408 Describe what symbol is at location @var{addr}.
20410 @subsubheading @value{GDBN} Command
20412 The corresponding @value{GDBN} command is @samp{info symbol}.
20414 @subsubheading Example
20418 @subheading The @code{-symbol-list-functions} Command
20419 @findex -symbol-list-functions
20421 @subsubheading Synopsis
20424 -symbol-list-functions
20427 List the functions in the executable.
20429 @subsubheading @value{GDBN} Command
20431 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
20432 @samp{gdb_search} in @code{gdbtk}.
20434 @subsubheading Example
20438 @subheading The @code{-symbol-list-lines} Command
20439 @findex -symbol-list-lines
20441 @subsubheading Synopsis
20444 -symbol-list-lines @var{filename}
20447 Print the list of lines that contain code and their associated program
20448 addresses for the given source filename. The entries are sorted in
20449 ascending PC order.
20451 @subsubheading @value{GDBN} Command
20453 There is no corresponding @value{GDBN} command.
20455 @subsubheading Example
20458 -symbol-list-lines basics.c
20459 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
20464 @subheading The @code{-symbol-list-types} Command
20465 @findex -symbol-list-types
20467 @subsubheading Synopsis
20473 List all the type names.
20475 @subsubheading @value{GDBN} Command
20477 The corresponding commands are @samp{info types} in @value{GDBN},
20478 @samp{gdb_search} in @code{gdbtk}.
20480 @subsubheading Example
20484 @subheading The @code{-symbol-list-variables} Command
20485 @findex -symbol-list-variables
20487 @subsubheading Synopsis
20490 -symbol-list-variables
20493 List all the global and static variable names.
20495 @subsubheading @value{GDBN} Command
20497 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
20499 @subsubheading Example
20503 @subheading The @code{-symbol-locate} Command
20504 @findex -symbol-locate
20506 @subsubheading Synopsis
20512 @subsubheading @value{GDBN} Command
20514 @samp{gdb_loc} in @code{gdbtk}.
20516 @subsubheading Example
20520 @subheading The @code{-symbol-type} Command
20521 @findex -symbol-type
20523 @subsubheading Synopsis
20526 -symbol-type @var{variable}
20529 Show type of @var{variable}.
20531 @subsubheading @value{GDBN} Command
20533 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
20534 @samp{gdb_obj_variable}.
20536 @subsubheading Example
20540 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20541 @node GDB/MI File Commands
20542 @section @sc{gdb/mi} File Commands
20544 This section describes the GDB/MI commands to specify executable file names
20545 and to read in and obtain symbol table information.
20547 @subheading The @code{-file-exec-and-symbols} Command
20548 @findex -file-exec-and-symbols
20550 @subsubheading Synopsis
20553 -file-exec-and-symbols @var{file}
20556 Specify the executable file to be debugged. This file is the one from
20557 which the symbol table is also read. If no file is specified, the
20558 command clears the executable and symbol information. If breakpoints
20559 are set when using this command with no arguments, @value{GDBN} will produce
20560 error messages. Otherwise, no output is produced, except a completion
20563 @subsubheading @value{GDBN} Command
20565 The corresponding @value{GDBN} command is @samp{file}.
20567 @subsubheading Example
20571 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
20577 @subheading The @code{-file-exec-file} Command
20578 @findex -file-exec-file
20580 @subsubheading Synopsis
20583 -file-exec-file @var{file}
20586 Specify the executable file to be debugged. Unlike
20587 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
20588 from this file. If used without argument, @value{GDBN} clears the information
20589 about the executable file. No output is produced, except a completion
20592 @subsubheading @value{GDBN} Command
20594 The corresponding @value{GDBN} command is @samp{exec-file}.
20596 @subsubheading Example
20600 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
20606 @subheading The @code{-file-list-exec-sections} Command
20607 @findex -file-list-exec-sections
20609 @subsubheading Synopsis
20612 -file-list-exec-sections
20615 List the sections of the current executable file.
20617 @subsubheading @value{GDBN} Command
20619 The @value{GDBN} command @samp{info file} shows, among the rest, the same
20620 information as this command. @code{gdbtk} has a corresponding command
20621 @samp{gdb_load_info}.
20623 @subsubheading Example
20627 @subheading The @code{-file-list-exec-source-file} Command
20628 @findex -file-list-exec-source-file
20630 @subsubheading Synopsis
20633 -file-list-exec-source-file
20636 List the line number, the current source file, and the absolute path
20637 to the current source file for the current executable.
20639 @subsubheading @value{GDBN} Command
20641 The @value{GDBN} equivalent is @samp{info source}
20643 @subsubheading Example
20647 123-file-list-exec-source-file
20648 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c"
20653 @subheading The @code{-file-list-exec-source-files} Command
20654 @findex -file-list-exec-source-files
20656 @subsubheading Synopsis
20659 -file-list-exec-source-files
20662 List the source files for the current executable.
20664 It will always output the filename, but only when @value{GDBN} can find
20665 the absolute file name of a source file, will it output the fullname.
20667 @subsubheading @value{GDBN} Command
20669 The @value{GDBN} equivalent is @samp{info sources}.
20670 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
20672 @subsubheading Example
20675 -file-list-exec-source-files
20677 @{file=foo.c,fullname=/home/foo.c@},
20678 @{file=/home/bar.c,fullname=/home/bar.c@},
20679 @{file=gdb_could_not_find_fullpath.c@}]
20683 @subheading The @code{-file-list-shared-libraries} Command
20684 @findex -file-list-shared-libraries
20686 @subsubheading Synopsis
20689 -file-list-shared-libraries
20692 List the shared libraries in the program.
20694 @subsubheading @value{GDBN} Command
20696 The corresponding @value{GDBN} command is @samp{info shared}.
20698 @subsubheading Example
20702 @subheading The @code{-file-list-symbol-files} Command
20703 @findex -file-list-symbol-files
20705 @subsubheading Synopsis
20708 -file-list-symbol-files
20713 @subsubheading @value{GDBN} Command
20715 The corresponding @value{GDBN} command is @samp{info file} (part of it).
20717 @subsubheading Example
20721 @subheading The @code{-file-symbol-file} Command
20722 @findex -file-symbol-file
20724 @subsubheading Synopsis
20727 -file-symbol-file @var{file}
20730 Read symbol table info from the specified @var{file} argument. When
20731 used without arguments, clears @value{GDBN}'s symbol table info. No output is
20732 produced, except for a completion notification.
20734 @subsubheading @value{GDBN} Command
20736 The corresponding @value{GDBN} command is @samp{symbol-file}.
20738 @subsubheading Example
20742 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
20748 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20749 @node GDB/MI Memory Overlay Commands
20750 @section @sc{gdb/mi} Memory Overlay Commands
20752 The memory overlay commands are not implemented.
20754 @c @subheading -overlay-auto
20756 @c @subheading -overlay-list-mapping-state
20758 @c @subheading -overlay-list-overlays
20760 @c @subheading -overlay-map
20762 @c @subheading -overlay-off
20764 @c @subheading -overlay-on
20766 @c @subheading -overlay-unmap
20768 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20769 @node GDB/MI Signal Handling Commands
20770 @section @sc{gdb/mi} Signal Handling Commands
20772 Signal handling commands are not implemented.
20774 @c @subheading -signal-handle
20776 @c @subheading -signal-list-handle-actions
20778 @c @subheading -signal-list-signal-types
20782 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20783 @node GDB/MI Target Manipulation
20784 @section @sc{gdb/mi} Target Manipulation Commands
20787 @subheading The @code{-target-attach} Command
20788 @findex -target-attach
20790 @subsubheading Synopsis
20793 -target-attach @var{pid} | @var{file}
20796 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
20798 @subsubheading @value{GDBN} Command
20800 The corresponding @value{GDBN} command is @samp{attach}.
20802 @subsubheading Example
20806 @subheading The @code{-target-compare-sections} Command
20807 @findex -target-compare-sections
20809 @subsubheading Synopsis
20812 -target-compare-sections [ @var{section} ]
20815 Compare data of section @var{section} on target to the exec file.
20816 Without the argument, all sections are compared.
20818 @subsubheading @value{GDBN} Command
20820 The @value{GDBN} equivalent is @samp{compare-sections}.
20822 @subsubheading Example
20826 @subheading The @code{-target-detach} Command
20827 @findex -target-detach
20829 @subsubheading Synopsis
20835 Detach from the remote target which normally resumes its execution.
20838 @subsubheading @value{GDBN} Command
20840 The corresponding @value{GDBN} command is @samp{detach}.
20842 @subsubheading Example
20852 @subheading The @code{-target-disconnect} Command
20853 @findex -target-disconnect
20855 @subsubheading Synopsis
20861 Disconnect from the remote target. There's no output and the target is
20862 generally not resumed.
20864 @subsubheading @value{GDBN} Command
20866 The corresponding @value{GDBN} command is @samp{disconnect}.
20868 @subsubheading Example
20878 @subheading The @code{-target-download} Command
20879 @findex -target-download
20881 @subsubheading Synopsis
20887 Loads the executable onto the remote target.
20888 It prints out an update message every half second, which includes the fields:
20892 The name of the section.
20894 The size of what has been sent so far for that section.
20896 The size of the section.
20898 The total size of what was sent so far (the current and the previous sections).
20900 The size of the overall executable to download.
20904 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
20905 @sc{gdb/mi} Output Syntax}).
20907 In addition, it prints the name and size of the sections, as they are
20908 downloaded. These messages include the following fields:
20912 The name of the section.
20914 The size of the section.
20916 The size of the overall executable to download.
20920 At the end, a summary is printed.
20922 @subsubheading @value{GDBN} Command
20924 The corresponding @value{GDBN} command is @samp{load}.
20926 @subsubheading Example
20928 Note: each status message appears on a single line. Here the messages
20929 have been broken down so that they can fit onto a page.
20934 +download,@{section=".text",section-size="6668",total-size="9880"@}
20935 +download,@{section=".text",section-sent="512",section-size="6668",
20936 total-sent="512",total-size="9880"@}
20937 +download,@{section=".text",section-sent="1024",section-size="6668",
20938 total-sent="1024",total-size="9880"@}
20939 +download,@{section=".text",section-sent="1536",section-size="6668",
20940 total-sent="1536",total-size="9880"@}
20941 +download,@{section=".text",section-sent="2048",section-size="6668",
20942 total-sent="2048",total-size="9880"@}
20943 +download,@{section=".text",section-sent="2560",section-size="6668",
20944 total-sent="2560",total-size="9880"@}
20945 +download,@{section=".text",section-sent="3072",section-size="6668",
20946 total-sent="3072",total-size="9880"@}
20947 +download,@{section=".text",section-sent="3584",section-size="6668",
20948 total-sent="3584",total-size="9880"@}
20949 +download,@{section=".text",section-sent="4096",section-size="6668",
20950 total-sent="4096",total-size="9880"@}
20951 +download,@{section=".text",section-sent="4608",section-size="6668",
20952 total-sent="4608",total-size="9880"@}
20953 +download,@{section=".text",section-sent="5120",section-size="6668",
20954 total-sent="5120",total-size="9880"@}
20955 +download,@{section=".text",section-sent="5632",section-size="6668",
20956 total-sent="5632",total-size="9880"@}
20957 +download,@{section=".text",section-sent="6144",section-size="6668",
20958 total-sent="6144",total-size="9880"@}
20959 +download,@{section=".text",section-sent="6656",section-size="6668",
20960 total-sent="6656",total-size="9880"@}
20961 +download,@{section=".init",section-size="28",total-size="9880"@}
20962 +download,@{section=".fini",section-size="28",total-size="9880"@}
20963 +download,@{section=".data",section-size="3156",total-size="9880"@}
20964 +download,@{section=".data",section-sent="512",section-size="3156",
20965 total-sent="7236",total-size="9880"@}
20966 +download,@{section=".data",section-sent="1024",section-size="3156",
20967 total-sent="7748",total-size="9880"@}
20968 +download,@{section=".data",section-sent="1536",section-size="3156",
20969 total-sent="8260",total-size="9880"@}
20970 +download,@{section=".data",section-sent="2048",section-size="3156",
20971 total-sent="8772",total-size="9880"@}
20972 +download,@{section=".data",section-sent="2560",section-size="3156",
20973 total-sent="9284",total-size="9880"@}
20974 +download,@{section=".data",section-sent="3072",section-size="3156",
20975 total-sent="9796",total-size="9880"@}
20976 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
20982 @subheading The @code{-target-exec-status} Command
20983 @findex -target-exec-status
20985 @subsubheading Synopsis
20988 -target-exec-status
20991 Provide information on the state of the target (whether it is running or
20992 not, for instance).
20994 @subsubheading @value{GDBN} Command
20996 There's no equivalent @value{GDBN} command.
20998 @subsubheading Example
21002 @subheading The @code{-target-list-available-targets} Command
21003 @findex -target-list-available-targets
21005 @subsubheading Synopsis
21008 -target-list-available-targets
21011 List the possible targets to connect to.
21013 @subsubheading @value{GDBN} Command
21015 The corresponding @value{GDBN} command is @samp{help target}.
21017 @subsubheading Example
21021 @subheading The @code{-target-list-current-targets} Command
21022 @findex -target-list-current-targets
21024 @subsubheading Synopsis
21027 -target-list-current-targets
21030 Describe the current target.
21032 @subsubheading @value{GDBN} Command
21034 The corresponding information is printed by @samp{info file} (among
21037 @subsubheading Example
21041 @subheading The @code{-target-list-parameters} Command
21042 @findex -target-list-parameters
21044 @subsubheading Synopsis
21047 -target-list-parameters
21052 @subsubheading @value{GDBN} Command
21056 @subsubheading Example
21060 @subheading The @code{-target-select} Command
21061 @findex -target-select
21063 @subsubheading Synopsis
21066 -target-select @var{type} @var{parameters @dots{}}
21069 Connect @value{GDBN} to the remote target. This command takes two args:
21073 The type of target, for instance @samp{async}, @samp{remote}, etc.
21074 @item @var{parameters}
21075 Device names, host names and the like. @xref{Target Commands, ,
21076 Commands for Managing Targets}, for more details.
21079 The output is a connection notification, followed by the address at
21080 which the target program is, in the following form:
21083 ^connected,addr="@var{address}",func="@var{function name}",
21084 args=[@var{arg list}]
21087 @subsubheading @value{GDBN} Command
21089 The corresponding @value{GDBN} command is @samp{target}.
21091 @subsubheading Example
21095 -target-select async /dev/ttya
21096 ^connected,addr="0xfe00a300",func="??",args=[]
21100 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21101 @node GDB/MI Miscellaneous Commands
21102 @section Miscellaneous @sc{gdb/mi} Commands
21104 @c @subheading -gdb-complete
21106 @subheading The @code{-gdb-exit} Command
21109 @subsubheading Synopsis
21115 Exit @value{GDBN} immediately.
21117 @subsubheading @value{GDBN} Command
21119 Approximately corresponds to @samp{quit}.
21121 @subsubheading Example
21130 @subheading The @code{-exec-abort} Command
21131 @findex -exec-abort
21133 @subsubheading Synopsis
21139 Kill the inferior running program.
21141 @subsubheading @value{GDBN} Command
21143 The corresponding @value{GDBN} command is @samp{kill}.
21145 @subsubheading Example
21149 @subheading The @code{-gdb-set} Command
21152 @subsubheading Synopsis
21158 Set an internal @value{GDBN} variable.
21159 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
21161 @subsubheading @value{GDBN} Command
21163 The corresponding @value{GDBN} command is @samp{set}.
21165 @subsubheading Example
21175 @subheading The @code{-gdb-show} Command
21178 @subsubheading Synopsis
21184 Show the current value of a @value{GDBN} variable.
21186 @subsubheading @value{GDBN} Command
21188 The corresponding @value{GDBN} command is @samp{show}.
21190 @subsubheading Example
21199 @c @subheading -gdb-source
21202 @subheading The @code{-gdb-version} Command
21203 @findex -gdb-version
21205 @subsubheading Synopsis
21211 Show version information for @value{GDBN}. Used mostly in testing.
21213 @subsubheading @value{GDBN} Command
21215 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
21216 default shows this information when you start an interactive session.
21218 @subsubheading Example
21220 @c This example modifies the actual output from GDB to avoid overfull
21226 ~Copyright 2000 Free Software Foundation, Inc.
21227 ~GDB is free software, covered by the GNU General Public License, and
21228 ~you are welcome to change it and/or distribute copies of it under
21229 ~ certain conditions.
21230 ~Type "show copying" to see the conditions.
21231 ~There is absolutely no warranty for GDB. Type "show warranty" for
21233 ~This GDB was configured as
21234 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
21239 @subheading The @code{-interpreter-exec} Command
21240 @findex -interpreter-exec
21242 @subheading Synopsis
21245 -interpreter-exec @var{interpreter} @var{command}
21247 @anchor{-interpreter-exec}
21249 Execute the specified @var{command} in the given @var{interpreter}.
21251 @subheading @value{GDBN} Command
21253 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
21255 @subheading Example
21259 -interpreter-exec console "break main"
21260 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
21261 &"During symbol reading, bad structure-type format.\n"
21262 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
21267 @subheading The @code{-inferior-tty-set} Command
21268 @findex -inferior-tty-set
21270 @subheading Synopsis
21273 -inferior-tty-set /dev/pts/1
21276 Set terminal for future runs of the program being debugged.
21278 @subheading @value{GDBN} Command
21280 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
21282 @subheading Example
21286 -inferior-tty-set /dev/pts/1
21291 @subheading The @code{-inferior-tty-show} Command
21292 @findex -inferior-tty-show
21294 @subheading Synopsis
21300 Show terminal for future runs of program being debugged.
21302 @subheading @value{GDBN} Command
21304 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
21306 @subheading Example
21310 -inferior-tty-set /dev/pts/1
21314 ^done,inferior_tty_terminal="/dev/pts/1"
21318 @subheading The @code{-enable-timings} Command
21319 @findex -enable-timings
21321 @subheading Synopsis
21324 -enable-timings [yes | no]
21327 Toggle the printing of the wallclock, user and system times for an MI
21328 command as a field in its output. This command is to help frontend
21329 developers optimize the performance of their code. No argument is
21330 equivalent to @samp{yes}.
21332 @subheading @value{GDBN} Command
21336 @subheading Example
21344 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
21345 addr="0x080484ed",func="main",file="myprog.c",
21346 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
21347 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
21355 *stopped,reason="breakpoint-hit",bkptno="1",thread-id="0",
21356 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
21357 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
21358 fullname="/home/nickrob/myprog.c",line="73"@}
21363 @chapter @value{GDBN} Annotations
21365 This chapter describes annotations in @value{GDBN}. Annotations were
21366 designed to interface @value{GDBN} to graphical user interfaces or other
21367 similar programs which want to interact with @value{GDBN} at a
21368 relatively high level.
21370 The annotation mechanism has largely been superseded by @sc{gdb/mi}
21374 This is Edition @value{EDITION}, @value{DATE}.
21378 * Annotations Overview:: What annotations are; the general syntax.
21379 * Server Prefix:: Issuing a command without affecting user state.
21380 * Prompting:: Annotations marking @value{GDBN}'s need for input.
21381 * Errors:: Annotations for error messages.
21382 * Invalidation:: Some annotations describe things now invalid.
21383 * Annotations for Running::
21384 Whether the program is running, how it stopped, etc.
21385 * Source Annotations:: Annotations describing source code.
21388 @node Annotations Overview
21389 @section What is an Annotation?
21390 @cindex annotations
21392 Annotations start with a newline character, two @samp{control-z}
21393 characters, and the name of the annotation. If there is no additional
21394 information associated with this annotation, the name of the annotation
21395 is followed immediately by a newline. If there is additional
21396 information, the name of the annotation is followed by a space, the
21397 additional information, and a newline. The additional information
21398 cannot contain newline characters.
21400 Any output not beginning with a newline and two @samp{control-z}
21401 characters denotes literal output from @value{GDBN}. Currently there is
21402 no need for @value{GDBN} to output a newline followed by two
21403 @samp{control-z} characters, but if there was such a need, the
21404 annotations could be extended with an @samp{escape} annotation which
21405 means those three characters as output.
21407 The annotation @var{level}, which is specified using the
21408 @option{--annotate} command line option (@pxref{Mode Options}), controls
21409 how much information @value{GDBN} prints together with its prompt,
21410 values of expressions, source lines, and other types of output. Level 0
21411 is for no annotations, level 1 is for use when @value{GDBN} is run as a
21412 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
21413 for programs that control @value{GDBN}, and level 2 annotations have
21414 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
21415 Interface, annotate, GDB's Obsolete Annotations}).
21418 @kindex set annotate
21419 @item set annotate @var{level}
21420 The @value{GDBN} command @code{set annotate} sets the level of
21421 annotations to the specified @var{level}.
21423 @item show annotate
21424 @kindex show annotate
21425 Show the current annotation level.
21428 This chapter describes level 3 annotations.
21430 A simple example of starting up @value{GDBN} with annotations is:
21433 $ @kbd{gdb --annotate=3}
21435 Copyright 2003 Free Software Foundation, Inc.
21436 GDB is free software, covered by the GNU General Public License,
21437 and you are welcome to change it and/or distribute copies of it
21438 under certain conditions.
21439 Type "show copying" to see the conditions.
21440 There is absolutely no warranty for GDB. Type "show warranty"
21442 This GDB was configured as "i386-pc-linux-gnu"
21453 Here @samp{quit} is input to @value{GDBN}; the rest is output from
21454 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
21455 denotes a @samp{control-z} character) are annotations; the rest is
21456 output from @value{GDBN}.
21458 @node Server Prefix
21459 @section The Server Prefix
21460 @cindex server prefix
21462 If you prefix a command with @samp{server } then it will not affect
21463 the command history, nor will it affect @value{GDBN}'s notion of which
21464 command to repeat if @key{RET} is pressed on a line by itself. This
21465 means that commands can be run behind a user's back by a front-end in
21466 a transparent manner.
21468 The server prefix does not affect the recording of values into the value
21469 history; to print a value without recording it into the value history,
21470 use the @code{output} command instead of the @code{print} command.
21473 @section Annotation for @value{GDBN} Input
21475 @cindex annotations for prompts
21476 When @value{GDBN} prompts for input, it annotates this fact so it is possible
21477 to know when to send output, when the output from a given command is
21480 Different kinds of input each have a different @dfn{input type}. Each
21481 input type has three annotations: a @code{pre-} annotation, which
21482 denotes the beginning of any prompt which is being output, a plain
21483 annotation, which denotes the end of the prompt, and then a @code{post-}
21484 annotation which denotes the end of any echo which may (or may not) be
21485 associated with the input. For example, the @code{prompt} input type
21486 features the following annotations:
21494 The input types are
21497 @findex pre-prompt annotation
21498 @findex prompt annotation
21499 @findex post-prompt annotation
21501 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
21503 @findex pre-commands annotation
21504 @findex commands annotation
21505 @findex post-commands annotation
21507 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
21508 command. The annotations are repeated for each command which is input.
21510 @findex pre-overload-choice annotation
21511 @findex overload-choice annotation
21512 @findex post-overload-choice annotation
21513 @item overload-choice
21514 When @value{GDBN} wants the user to select between various overloaded functions.
21516 @findex pre-query annotation
21517 @findex query annotation
21518 @findex post-query annotation
21520 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
21522 @findex pre-prompt-for-continue annotation
21523 @findex prompt-for-continue annotation
21524 @findex post-prompt-for-continue annotation
21525 @item prompt-for-continue
21526 When @value{GDBN} is asking the user to press return to continue. Note: Don't
21527 expect this to work well; instead use @code{set height 0} to disable
21528 prompting. This is because the counting of lines is buggy in the
21529 presence of annotations.
21534 @cindex annotations for errors, warnings and interrupts
21536 @findex quit annotation
21541 This annotation occurs right before @value{GDBN} responds to an interrupt.
21543 @findex error annotation
21548 This annotation occurs right before @value{GDBN} responds to an error.
21550 Quit and error annotations indicate that any annotations which @value{GDBN} was
21551 in the middle of may end abruptly. For example, if a
21552 @code{value-history-begin} annotation is followed by a @code{error}, one
21553 cannot expect to receive the matching @code{value-history-end}. One
21554 cannot expect not to receive it either, however; an error annotation
21555 does not necessarily mean that @value{GDBN} is immediately returning all the way
21558 @findex error-begin annotation
21559 A quit or error annotation may be preceded by
21565 Any output between that and the quit or error annotation is the error
21568 Warning messages are not yet annotated.
21569 @c If we want to change that, need to fix warning(), type_error(),
21570 @c range_error(), and possibly other places.
21573 @section Invalidation Notices
21575 @cindex annotations for invalidation messages
21576 The following annotations say that certain pieces of state may have
21580 @findex frames-invalid annotation
21581 @item ^Z^Zframes-invalid
21583 The frames (for example, output from the @code{backtrace} command) may
21586 @findex breakpoints-invalid annotation
21587 @item ^Z^Zbreakpoints-invalid
21589 The breakpoints may have changed. For example, the user just added or
21590 deleted a breakpoint.
21593 @node Annotations for Running
21594 @section Running the Program
21595 @cindex annotations for running programs
21597 @findex starting annotation
21598 @findex stopping annotation
21599 When the program starts executing due to a @value{GDBN} command such as
21600 @code{step} or @code{continue},
21606 is output. When the program stops,
21612 is output. Before the @code{stopped} annotation, a variety of
21613 annotations describe how the program stopped.
21616 @findex exited annotation
21617 @item ^Z^Zexited @var{exit-status}
21618 The program exited, and @var{exit-status} is the exit status (zero for
21619 successful exit, otherwise nonzero).
21621 @findex signalled annotation
21622 @findex signal-name annotation
21623 @findex signal-name-end annotation
21624 @findex signal-string annotation
21625 @findex signal-string-end annotation
21626 @item ^Z^Zsignalled
21627 The program exited with a signal. After the @code{^Z^Zsignalled}, the
21628 annotation continues:
21634 ^Z^Zsignal-name-end
21638 ^Z^Zsignal-string-end
21643 where @var{name} is the name of the signal, such as @code{SIGILL} or
21644 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
21645 as @code{Illegal Instruction} or @code{Segmentation fault}.
21646 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
21647 user's benefit and have no particular format.
21649 @findex signal annotation
21651 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
21652 just saying that the program received the signal, not that it was
21653 terminated with it.
21655 @findex breakpoint annotation
21656 @item ^Z^Zbreakpoint @var{number}
21657 The program hit breakpoint number @var{number}.
21659 @findex watchpoint annotation
21660 @item ^Z^Zwatchpoint @var{number}
21661 The program hit watchpoint number @var{number}.
21664 @node Source Annotations
21665 @section Displaying Source
21666 @cindex annotations for source display
21668 @findex source annotation
21669 The following annotation is used instead of displaying source code:
21672 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
21675 where @var{filename} is an absolute file name indicating which source
21676 file, @var{line} is the line number within that file (where 1 is the
21677 first line in the file), @var{character} is the character position
21678 within the file (where 0 is the first character in the file) (for most
21679 debug formats this will necessarily point to the beginning of a line),
21680 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
21681 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
21682 @var{addr} is the address in the target program associated with the
21683 source which is being displayed. @var{addr} is in the form @samp{0x}
21684 followed by one or more lowercase hex digits (note that this does not
21685 depend on the language).
21688 @chapter Reporting Bugs in @value{GDBN}
21689 @cindex bugs in @value{GDBN}
21690 @cindex reporting bugs in @value{GDBN}
21692 Your bug reports play an essential role in making @value{GDBN} reliable.
21694 Reporting a bug may help you by bringing a solution to your problem, or it
21695 may not. But in any case the principal function of a bug report is to help
21696 the entire community by making the next version of @value{GDBN} work better. Bug
21697 reports are your contribution to the maintenance of @value{GDBN}.
21699 In order for a bug report to serve its purpose, you must include the
21700 information that enables us to fix the bug.
21703 * Bug Criteria:: Have you found a bug?
21704 * Bug Reporting:: How to report bugs
21708 @section Have You Found a Bug?
21709 @cindex bug criteria
21711 If you are not sure whether you have found a bug, here are some guidelines:
21714 @cindex fatal signal
21715 @cindex debugger crash
21716 @cindex crash of debugger
21718 If the debugger gets a fatal signal, for any input whatever, that is a
21719 @value{GDBN} bug. Reliable debuggers never crash.
21721 @cindex error on valid input
21723 If @value{GDBN} produces an error message for valid input, that is a
21724 bug. (Note that if you're cross debugging, the problem may also be
21725 somewhere in the connection to the target.)
21727 @cindex invalid input
21729 If @value{GDBN} does not produce an error message for invalid input,
21730 that is a bug. However, you should note that your idea of
21731 ``invalid input'' might be our idea of ``an extension'' or ``support
21732 for traditional practice''.
21735 If you are an experienced user of debugging tools, your suggestions
21736 for improvement of @value{GDBN} are welcome in any case.
21739 @node Bug Reporting
21740 @section How to Report Bugs
21741 @cindex bug reports
21742 @cindex @value{GDBN} bugs, reporting
21744 A number of companies and individuals offer support for @sc{gnu} products.
21745 If you obtained @value{GDBN} from a support organization, we recommend you
21746 contact that organization first.
21748 You can find contact information for many support companies and
21749 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
21751 @c should add a web page ref...
21753 In any event, we also recommend that you submit bug reports for
21754 @value{GDBN}. The preferred method is to submit them directly using
21755 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
21756 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
21759 @strong{Do not send bug reports to @samp{info-gdb}, or to
21760 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
21761 not want to receive bug reports. Those that do have arranged to receive
21764 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
21765 serves as a repeater. The mailing list and the newsgroup carry exactly
21766 the same messages. Often people think of posting bug reports to the
21767 newsgroup instead of mailing them. This appears to work, but it has one
21768 problem which can be crucial: a newsgroup posting often lacks a mail
21769 path back to the sender. Thus, if we need to ask for more information,
21770 we may be unable to reach you. For this reason, it is better to send
21771 bug reports to the mailing list.
21773 The fundamental principle of reporting bugs usefully is this:
21774 @strong{report all the facts}. If you are not sure whether to state a
21775 fact or leave it out, state it!
21777 Often people omit facts because they think they know what causes the
21778 problem and assume that some details do not matter. Thus, you might
21779 assume that the name of the variable you use in an example does not matter.
21780 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
21781 stray memory reference which happens to fetch from the location where that
21782 name is stored in memory; perhaps, if the name were different, the contents
21783 of that location would fool the debugger into doing the right thing despite
21784 the bug. Play it safe and give a specific, complete example. That is the
21785 easiest thing for you to do, and the most helpful.
21787 Keep in mind that the purpose of a bug report is to enable us to fix the
21788 bug. It may be that the bug has been reported previously, but neither
21789 you nor we can know that unless your bug report is complete and
21792 Sometimes people give a few sketchy facts and ask, ``Does this ring a
21793 bell?'' Those bug reports are useless, and we urge everyone to
21794 @emph{refuse to respond to them} except to chide the sender to report
21797 To enable us to fix the bug, you should include all these things:
21801 The version of @value{GDBN}. @value{GDBN} announces it if you start
21802 with no arguments; you can also print it at any time using @code{show
21805 Without this, we will not know whether there is any point in looking for
21806 the bug in the current version of @value{GDBN}.
21809 The type of machine you are using, and the operating system name and
21813 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
21814 ``@value{GCC}--2.8.1''.
21817 What compiler (and its version) was used to compile the program you are
21818 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
21819 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
21820 to get this information; for other compilers, see the documentation for
21824 The command arguments you gave the compiler to compile your example and
21825 observe the bug. For example, did you use @samp{-O}? To guarantee
21826 you will not omit something important, list them all. A copy of the
21827 Makefile (or the output from make) is sufficient.
21829 If we were to try to guess the arguments, we would probably guess wrong
21830 and then we might not encounter the bug.
21833 A complete input script, and all necessary source files, that will
21837 A description of what behavior you observe that you believe is
21838 incorrect. For example, ``It gets a fatal signal.''
21840 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
21841 will certainly notice it. But if the bug is incorrect output, we might
21842 not notice unless it is glaringly wrong. You might as well not give us
21843 a chance to make a mistake.
21845 Even if the problem you experience is a fatal signal, you should still
21846 say so explicitly. Suppose something strange is going on, such as, your
21847 copy of @value{GDBN} is out of synch, or you have encountered a bug in
21848 the C library on your system. (This has happened!) Your copy might
21849 crash and ours would not. If you told us to expect a crash, then when
21850 ours fails to crash, we would know that the bug was not happening for
21851 us. If you had not told us to expect a crash, then we would not be able
21852 to draw any conclusion from our observations.
21855 @cindex recording a session script
21856 To collect all this information, you can use a session recording program
21857 such as @command{script}, which is available on many Unix systems.
21858 Just run your @value{GDBN} session inside @command{script} and then
21859 include the @file{typescript} file with your bug report.
21861 Another way to record a @value{GDBN} session is to run @value{GDBN}
21862 inside Emacs and then save the entire buffer to a file.
21865 If you wish to suggest changes to the @value{GDBN} source, send us context
21866 diffs. If you even discuss something in the @value{GDBN} source, refer to
21867 it by context, not by line number.
21869 The line numbers in our development sources will not match those in your
21870 sources. Your line numbers would convey no useful information to us.
21874 Here are some things that are not necessary:
21878 A description of the envelope of the bug.
21880 Often people who encounter a bug spend a lot of time investigating
21881 which changes to the input file will make the bug go away and which
21882 changes will not affect it.
21884 This is often time consuming and not very useful, because the way we
21885 will find the bug is by running a single example under the debugger
21886 with breakpoints, not by pure deduction from a series of examples.
21887 We recommend that you save your time for something else.
21889 Of course, if you can find a simpler example to report @emph{instead}
21890 of the original one, that is a convenience for us. Errors in the
21891 output will be easier to spot, running under the debugger will take
21892 less time, and so on.
21894 However, simplification is not vital; if you do not want to do this,
21895 report the bug anyway and send us the entire test case you used.
21898 A patch for the bug.
21900 A patch for the bug does help us if it is a good one. But do not omit
21901 the necessary information, such as the test case, on the assumption that
21902 a patch is all we need. We might see problems with your patch and decide
21903 to fix the problem another way, or we might not understand it at all.
21905 Sometimes with a program as complicated as @value{GDBN} it is very hard to
21906 construct an example that will make the program follow a certain path
21907 through the code. If you do not send us the example, we will not be able
21908 to construct one, so we will not be able to verify that the bug is fixed.
21910 And if we cannot understand what bug you are trying to fix, or why your
21911 patch should be an improvement, we will not install it. A test case will
21912 help us to understand.
21915 A guess about what the bug is or what it depends on.
21917 Such guesses are usually wrong. Even we cannot guess right about such
21918 things without first using the debugger to find the facts.
21921 @c The readline documentation is distributed with the readline code
21922 @c and consists of the two following files:
21924 @c inc-hist.texinfo
21925 @c Use -I with makeinfo to point to the appropriate directory,
21926 @c environment var TEXINPUTS with TeX.
21927 @include rluser.texi
21928 @include inc-hist.texinfo
21931 @node Formatting Documentation
21932 @appendix Formatting Documentation
21934 @cindex @value{GDBN} reference card
21935 @cindex reference card
21936 The @value{GDBN} 4 release includes an already-formatted reference card, ready
21937 for printing with PostScript or Ghostscript, in the @file{gdb}
21938 subdirectory of the main source directory@footnote{In
21939 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
21940 release.}. If you can use PostScript or Ghostscript with your printer,
21941 you can print the reference card immediately with @file{refcard.ps}.
21943 The release also includes the source for the reference card. You
21944 can format it, using @TeX{}, by typing:
21950 The @value{GDBN} reference card is designed to print in @dfn{landscape}
21951 mode on US ``letter'' size paper;
21952 that is, on a sheet 11 inches wide by 8.5 inches
21953 high. You will need to specify this form of printing as an option to
21954 your @sc{dvi} output program.
21956 @cindex documentation
21958 All the documentation for @value{GDBN} comes as part of the machine-readable
21959 distribution. The documentation is written in Texinfo format, which is
21960 a documentation system that uses a single source file to produce both
21961 on-line information and a printed manual. You can use one of the Info
21962 formatting commands to create the on-line version of the documentation
21963 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
21965 @value{GDBN} includes an already formatted copy of the on-line Info
21966 version of this manual in the @file{gdb} subdirectory. The main Info
21967 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
21968 subordinate files matching @samp{gdb.info*} in the same directory. If
21969 necessary, you can print out these files, or read them with any editor;
21970 but they are easier to read using the @code{info} subsystem in @sc{gnu}
21971 Emacs or the standalone @code{info} program, available as part of the
21972 @sc{gnu} Texinfo distribution.
21974 If you want to format these Info files yourself, you need one of the
21975 Info formatting programs, such as @code{texinfo-format-buffer} or
21978 If you have @code{makeinfo} installed, and are in the top level
21979 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
21980 version @value{GDBVN}), you can make the Info file by typing:
21987 If you want to typeset and print copies of this manual, you need @TeX{},
21988 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
21989 Texinfo definitions file.
21991 @TeX{} is a typesetting program; it does not print files directly, but
21992 produces output files called @sc{dvi} files. To print a typeset
21993 document, you need a program to print @sc{dvi} files. If your system
21994 has @TeX{} installed, chances are it has such a program. The precise
21995 command to use depends on your system; @kbd{lpr -d} is common; another
21996 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
21997 require a file name without any extension or a @samp{.dvi} extension.
21999 @TeX{} also requires a macro definitions file called
22000 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
22001 written in Texinfo format. On its own, @TeX{} cannot either read or
22002 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
22003 and is located in the @file{gdb-@var{version-number}/texinfo}
22006 If you have @TeX{} and a @sc{dvi} printer program installed, you can
22007 typeset and print this manual. First switch to the @file{gdb}
22008 subdirectory of the main source directory (for example, to
22009 @file{gdb-@value{GDBVN}/gdb}) and type:
22015 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
22017 @node Installing GDB
22018 @appendix Installing @value{GDBN}
22019 @cindex installation
22022 * Requirements:: Requirements for building @value{GDBN}
22023 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
22024 * Separate Objdir:: Compiling @value{GDBN} in another directory
22025 * Config Names:: Specifying names for hosts and targets
22026 * Configure Options:: Summary of options for configure
22030 @section Requirements for Building @value{GDBN}
22031 @cindex building @value{GDBN}, requirements for
22033 Building @value{GDBN} requires various tools and packages to be available.
22034 Other packages will be used only if they are found.
22036 @heading Tools/Packages Necessary for Building @value{GDBN}
22038 @item ISO C90 compiler
22039 @value{GDBN} is written in ISO C90. It should be buildable with any
22040 working C90 compiler, e.g.@: GCC.
22044 @heading Tools/Packages Optional for Building @value{GDBN}
22048 @value{GDBN} can use the Expat XML parsing library. This library may be
22049 included with your operating system distribution; if it is not, you
22050 can get the latest version from @url{http://expat.sourceforge.net}.
22051 The @file{configure} script will search for this library in several
22052 standard locations; if it is installed in an unusual path, you can
22053 use the @option{--with-libexpat-prefix} option to specify its location.
22055 Expat is used for remote protocol memory maps (@pxref{Memory Map Format})
22056 and for target descriptions (@pxref{Target Descriptions}).
22060 @node Running Configure
22061 @section Invoking the @value{GDBN} @file{configure} Script
22062 @cindex configuring @value{GDBN}
22063 @value{GDBN} comes with a @file{configure} script that automates the process
22064 of preparing @value{GDBN} for installation; you can then use @code{make} to
22065 build the @code{gdb} program.
22067 @c irrelevant in info file; it's as current as the code it lives with.
22068 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
22069 look at the @file{README} file in the sources; we may have improved the
22070 installation procedures since publishing this manual.}
22073 The @value{GDBN} distribution includes all the source code you need for
22074 @value{GDBN} in a single directory, whose name is usually composed by
22075 appending the version number to @samp{gdb}.
22077 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
22078 @file{gdb-@value{GDBVN}} directory. That directory contains:
22081 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
22082 script for configuring @value{GDBN} and all its supporting libraries
22084 @item gdb-@value{GDBVN}/gdb
22085 the source specific to @value{GDBN} itself
22087 @item gdb-@value{GDBVN}/bfd
22088 source for the Binary File Descriptor library
22090 @item gdb-@value{GDBVN}/include
22091 @sc{gnu} include files
22093 @item gdb-@value{GDBVN}/libiberty
22094 source for the @samp{-liberty} free software library
22096 @item gdb-@value{GDBVN}/opcodes
22097 source for the library of opcode tables and disassemblers
22099 @item gdb-@value{GDBVN}/readline
22100 source for the @sc{gnu} command-line interface
22102 @item gdb-@value{GDBVN}/glob
22103 source for the @sc{gnu} filename pattern-matching subroutine
22105 @item gdb-@value{GDBVN}/mmalloc
22106 source for the @sc{gnu} memory-mapped malloc package
22109 The simplest way to configure and build @value{GDBN} is to run @file{configure}
22110 from the @file{gdb-@var{version-number}} source directory, which in
22111 this example is the @file{gdb-@value{GDBVN}} directory.
22113 First switch to the @file{gdb-@var{version-number}} source directory
22114 if you are not already in it; then run @file{configure}. Pass the
22115 identifier for the platform on which @value{GDBN} will run as an
22121 cd gdb-@value{GDBVN}
22122 ./configure @var{host}
22127 where @var{host} is an identifier such as @samp{sun4} or
22128 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
22129 (You can often leave off @var{host}; @file{configure} tries to guess the
22130 correct value by examining your system.)
22132 Running @samp{configure @var{host}} and then running @code{make} builds the
22133 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
22134 libraries, then @code{gdb} itself. The configured source files, and the
22135 binaries, are left in the corresponding source directories.
22138 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
22139 system does not recognize this automatically when you run a different
22140 shell, you may need to run @code{sh} on it explicitly:
22143 sh configure @var{host}
22146 If you run @file{configure} from a directory that contains source
22147 directories for multiple libraries or programs, such as the
22148 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
22150 creates configuration files for every directory level underneath (unless
22151 you tell it not to, with the @samp{--norecursion} option).
22153 You should run the @file{configure} script from the top directory in the
22154 source tree, the @file{gdb-@var{version-number}} directory. If you run
22155 @file{configure} from one of the subdirectories, you will configure only
22156 that subdirectory. That is usually not what you want. In particular,
22157 if you run the first @file{configure} from the @file{gdb} subdirectory
22158 of the @file{gdb-@var{version-number}} directory, you will omit the
22159 configuration of @file{bfd}, @file{readline}, and other sibling
22160 directories of the @file{gdb} subdirectory. This leads to build errors
22161 about missing include files such as @file{bfd/bfd.h}.
22163 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
22164 However, you should make sure that the shell on your path (named by
22165 the @samp{SHELL} environment variable) is publicly readable. Remember
22166 that @value{GDBN} uses the shell to start your program---some systems refuse to
22167 let @value{GDBN} debug child processes whose programs are not readable.
22169 @node Separate Objdir
22170 @section Compiling @value{GDBN} in Another Directory
22172 If you want to run @value{GDBN} versions for several host or target machines,
22173 you need a different @code{gdb} compiled for each combination of
22174 host and target. @file{configure} is designed to make this easy by
22175 allowing you to generate each configuration in a separate subdirectory,
22176 rather than in the source directory. If your @code{make} program
22177 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
22178 @code{make} in each of these directories builds the @code{gdb}
22179 program specified there.
22181 To build @code{gdb} in a separate directory, run @file{configure}
22182 with the @samp{--srcdir} option to specify where to find the source.
22183 (You also need to specify a path to find @file{configure}
22184 itself from your working directory. If the path to @file{configure}
22185 would be the same as the argument to @samp{--srcdir}, you can leave out
22186 the @samp{--srcdir} option; it is assumed.)
22188 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
22189 separate directory for a Sun 4 like this:
22193 cd gdb-@value{GDBVN}
22196 ../gdb-@value{GDBVN}/configure sun4
22201 When @file{configure} builds a configuration using a remote source
22202 directory, it creates a tree for the binaries with the same structure
22203 (and using the same names) as the tree under the source directory. In
22204 the example, you'd find the Sun 4 library @file{libiberty.a} in the
22205 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
22206 @file{gdb-sun4/gdb}.
22208 Make sure that your path to the @file{configure} script has just one
22209 instance of @file{gdb} in it. If your path to @file{configure} looks
22210 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
22211 one subdirectory of @value{GDBN}, not the whole package. This leads to
22212 build errors about missing include files such as @file{bfd/bfd.h}.
22214 One popular reason to build several @value{GDBN} configurations in separate
22215 directories is to configure @value{GDBN} for cross-compiling (where
22216 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
22217 programs that run on another machine---the @dfn{target}).
22218 You specify a cross-debugging target by
22219 giving the @samp{--target=@var{target}} option to @file{configure}.
22221 When you run @code{make} to build a program or library, you must run
22222 it in a configured directory---whatever directory you were in when you
22223 called @file{configure} (or one of its subdirectories).
22225 The @code{Makefile} that @file{configure} generates in each source
22226 directory also runs recursively. If you type @code{make} in a source
22227 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
22228 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
22229 will build all the required libraries, and then build GDB.
22231 When you have multiple hosts or targets configured in separate
22232 directories, you can run @code{make} on them in parallel (for example,
22233 if they are NFS-mounted on each of the hosts); they will not interfere
22237 @section Specifying Names for Hosts and Targets
22239 The specifications used for hosts and targets in the @file{configure}
22240 script are based on a three-part naming scheme, but some short predefined
22241 aliases are also supported. The full naming scheme encodes three pieces
22242 of information in the following pattern:
22245 @var{architecture}-@var{vendor}-@var{os}
22248 For example, you can use the alias @code{sun4} as a @var{host} argument,
22249 or as the value for @var{target} in a @code{--target=@var{target}}
22250 option. The equivalent full name is @samp{sparc-sun-sunos4}.
22252 The @file{configure} script accompanying @value{GDBN} does not provide
22253 any query facility to list all supported host and target names or
22254 aliases. @file{configure} calls the Bourne shell script
22255 @code{config.sub} to map abbreviations to full names; you can read the
22256 script, if you wish, or you can use it to test your guesses on
22257 abbreviations---for example:
22260 % sh config.sub i386-linux
22262 % sh config.sub alpha-linux
22263 alpha-unknown-linux-gnu
22264 % sh config.sub hp9k700
22266 % sh config.sub sun4
22267 sparc-sun-sunos4.1.1
22268 % sh config.sub sun3
22269 m68k-sun-sunos4.1.1
22270 % sh config.sub i986v
22271 Invalid configuration `i986v': machine `i986v' not recognized
22275 @code{config.sub} is also distributed in the @value{GDBN} source
22276 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
22278 @node Configure Options
22279 @section @file{configure} Options
22281 Here is a summary of the @file{configure} options and arguments that
22282 are most often useful for building @value{GDBN}. @file{configure} also has
22283 several other options not listed here. @inforef{What Configure
22284 Does,,configure.info}, for a full explanation of @file{configure}.
22287 configure @r{[}--help@r{]}
22288 @r{[}--prefix=@var{dir}@r{]}
22289 @r{[}--exec-prefix=@var{dir}@r{]}
22290 @r{[}--srcdir=@var{dirname}@r{]}
22291 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
22292 @r{[}--target=@var{target}@r{]}
22297 You may introduce options with a single @samp{-} rather than
22298 @samp{--} if you prefer; but you may abbreviate option names if you use
22303 Display a quick summary of how to invoke @file{configure}.
22305 @item --prefix=@var{dir}
22306 Configure the source to install programs and files under directory
22309 @item --exec-prefix=@var{dir}
22310 Configure the source to install programs under directory
22313 @c avoid splitting the warning from the explanation:
22315 @item --srcdir=@var{dirname}
22316 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
22317 @code{make} that implements the @code{VPATH} feature.}@*
22318 Use this option to make configurations in directories separate from the
22319 @value{GDBN} source directories. Among other things, you can use this to
22320 build (or maintain) several configurations simultaneously, in separate
22321 directories. @file{configure} writes configuration-specific files in
22322 the current directory, but arranges for them to use the source in the
22323 directory @var{dirname}. @file{configure} creates directories under
22324 the working directory in parallel to the source directories below
22327 @item --norecursion
22328 Configure only the directory level where @file{configure} is executed; do not
22329 propagate configuration to subdirectories.
22331 @item --target=@var{target}
22332 Configure @value{GDBN} for cross-debugging programs running on the specified
22333 @var{target}. Without this option, @value{GDBN} is configured to debug
22334 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
22336 There is no convenient way to generate a list of all available targets.
22338 @item @var{host} @dots{}
22339 Configure @value{GDBN} to run on the specified @var{host}.
22341 There is no convenient way to generate a list of all available hosts.
22344 There are many other options available as well, but they are generally
22345 needed for special purposes only.
22347 @node Maintenance Commands
22348 @appendix Maintenance Commands
22349 @cindex maintenance commands
22350 @cindex internal commands
22352 In addition to commands intended for @value{GDBN} users, @value{GDBN}
22353 includes a number of commands intended for @value{GDBN} developers,
22354 that are not documented elsewhere in this manual. These commands are
22355 provided here for reference. (For commands that turn on debugging
22356 messages, see @ref{Debugging Output}.)
22359 @kindex maint agent
22360 @item maint agent @var{expression}
22361 Translate the given @var{expression} into remote agent bytecodes.
22362 This command is useful for debugging the Agent Expression mechanism
22363 (@pxref{Agent Expressions}).
22365 @kindex maint info breakpoints
22366 @item @anchor{maint info breakpoints}maint info breakpoints
22367 Using the same format as @samp{info breakpoints}, display both the
22368 breakpoints you've set explicitly, and those @value{GDBN} is using for
22369 internal purposes. Internal breakpoints are shown with negative
22370 breakpoint numbers. The type column identifies what kind of breakpoint
22375 Normal, explicitly set breakpoint.
22378 Normal, explicitly set watchpoint.
22381 Internal breakpoint, used to handle correctly stepping through
22382 @code{longjmp} calls.
22384 @item longjmp resume
22385 Internal breakpoint at the target of a @code{longjmp}.
22388 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
22391 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
22394 Shared library events.
22398 @kindex maint check-symtabs
22399 @item maint check-symtabs
22400 Check the consistency of psymtabs and symtabs.
22402 @kindex maint cplus first_component
22403 @item maint cplus first_component @var{name}
22404 Print the first C@t{++} class/namespace component of @var{name}.
22406 @kindex maint cplus namespace
22407 @item maint cplus namespace
22408 Print the list of possible C@t{++} namespaces.
22410 @kindex maint demangle
22411 @item maint demangle @var{name}
22412 Demangle a C@t{++} or Objective-C mangled @var{name}.
22414 @kindex maint deprecate
22415 @kindex maint undeprecate
22416 @cindex deprecated commands
22417 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
22418 @itemx maint undeprecate @var{command}
22419 Deprecate or undeprecate the named @var{command}. Deprecated commands
22420 cause @value{GDBN} to issue a warning when you use them. The optional
22421 argument @var{replacement} says which newer command should be used in
22422 favor of the deprecated one; if it is given, @value{GDBN} will mention
22423 the replacement as part of the warning.
22425 @kindex maint dump-me
22426 @item maint dump-me
22427 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
22428 Cause a fatal signal in the debugger and force it to dump its core.
22429 This is supported only on systems which support aborting a program
22430 with the @code{SIGQUIT} signal.
22432 @kindex maint internal-error
22433 @kindex maint internal-warning
22434 @item maint internal-error @r{[}@var{message-text}@r{]}
22435 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
22436 Cause @value{GDBN} to call the internal function @code{internal_error}
22437 or @code{internal_warning} and hence behave as though an internal error
22438 or internal warning has been detected. In addition to reporting the
22439 internal problem, these functions give the user the opportunity to
22440 either quit @value{GDBN} or create a core file of the current
22441 @value{GDBN} session.
22443 These commands take an optional parameter @var{message-text} that is
22444 used as the text of the error or warning message.
22446 Here's an example of using @code{internal-error}:
22449 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
22450 @dots{}/maint.c:121: internal-error: testing, 1, 2
22451 A problem internal to GDB has been detected. Further
22452 debugging may prove unreliable.
22453 Quit this debugging session? (y or n) @kbd{n}
22454 Create a core file? (y or n) @kbd{n}
22458 @kindex maint packet
22459 @item maint packet @var{text}
22460 If @value{GDBN} is talking to an inferior via the serial protocol,
22461 then this command sends the string @var{text} to the inferior, and
22462 displays the response packet. @value{GDBN} supplies the initial
22463 @samp{$} character, the terminating @samp{#} character, and the
22466 @kindex maint print architecture
22467 @item maint print architecture @r{[}@var{file}@r{]}
22468 Print the entire architecture configuration. The optional argument
22469 @var{file} names the file where the output goes.
22471 @kindex maint print dummy-frames
22472 @item maint print dummy-frames
22473 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
22476 (@value{GDBP}) @kbd{b add}
22478 (@value{GDBP}) @kbd{print add(2,3)}
22479 Breakpoint 2, add (a=2, b=3) at @dots{}
22481 The program being debugged stopped while in a function called from GDB.
22483 (@value{GDBP}) @kbd{maint print dummy-frames}
22484 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
22485 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
22486 call_lo=0x01014000 call_hi=0x01014001
22490 Takes an optional file parameter.
22492 @kindex maint print registers
22493 @kindex maint print raw-registers
22494 @kindex maint print cooked-registers
22495 @kindex maint print register-groups
22496 @item maint print registers @r{[}@var{file}@r{]}
22497 @itemx maint print raw-registers @r{[}@var{file}@r{]}
22498 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
22499 @itemx maint print register-groups @r{[}@var{file}@r{]}
22500 Print @value{GDBN}'s internal register data structures.
22502 The command @code{maint print raw-registers} includes the contents of
22503 the raw register cache; the command @code{maint print cooked-registers}
22504 includes the (cooked) value of all registers; and the command
22505 @code{maint print register-groups} includes the groups that each
22506 register is a member of. @xref{Registers,, Registers, gdbint,
22507 @value{GDBN} Internals}.
22509 These commands take an optional parameter, a file name to which to
22510 write the information.
22512 @kindex maint print reggroups
22513 @item maint print reggroups @r{[}@var{file}@r{]}
22514 Print @value{GDBN}'s internal register group data structures. The
22515 optional argument @var{file} tells to what file to write the
22518 The register groups info looks like this:
22521 (@value{GDBP}) @kbd{maint print reggroups}
22534 This command forces @value{GDBN} to flush its internal register cache.
22536 @kindex maint print objfiles
22537 @cindex info for known object files
22538 @item maint print objfiles
22539 Print a dump of all known object files. For each object file, this
22540 command prints its name, address in memory, and all of its psymtabs
22543 @kindex maint print statistics
22544 @cindex bcache statistics
22545 @item maint print statistics
22546 This command prints, for each object file in the program, various data
22547 about that object file followed by the byte cache (@dfn{bcache})
22548 statistics for the object file. The objfile data includes the number
22549 of minimal, partial, full, and stabs symbols, the number of types
22550 defined by the objfile, the number of as yet unexpanded psym tables,
22551 the number of line tables and string tables, and the amount of memory
22552 used by the various tables. The bcache statistics include the counts,
22553 sizes, and counts of duplicates of all and unique objects, max,
22554 average, and median entry size, total memory used and its overhead and
22555 savings, and various measures of the hash table size and chain
22558 @kindex maint print target-stack
22559 @cindex target stack description
22560 @item maint print target-stack
22561 A @dfn{target} is an interface between the debugger and a particular
22562 kind of file or process. Targets can be stacked in @dfn{strata},
22563 so that more than one target can potentially respond to a request.
22564 In particular, memory accesses will walk down the stack of targets
22565 until they find a target that is interested in handling that particular
22568 This command prints a short description of each layer that was pushed on
22569 the @dfn{target stack}, starting from the top layer down to the bottom one.
22571 @kindex maint print type
22572 @cindex type chain of a data type
22573 @item maint print type @var{expr}
22574 Print the type chain for a type specified by @var{expr}. The argument
22575 can be either a type name or a symbol. If it is a symbol, the type of
22576 that symbol is described. The type chain produced by this command is
22577 a recursive definition of the data type as stored in @value{GDBN}'s
22578 data structures, including its flags and contained types.
22580 @kindex maint set dwarf2 max-cache-age
22581 @kindex maint show dwarf2 max-cache-age
22582 @item maint set dwarf2 max-cache-age
22583 @itemx maint show dwarf2 max-cache-age
22584 Control the DWARF 2 compilation unit cache.
22586 @cindex DWARF 2 compilation units cache
22587 In object files with inter-compilation-unit references, such as those
22588 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
22589 reader needs to frequently refer to previously read compilation units.
22590 This setting controls how long a compilation unit will remain in the
22591 cache if it is not referenced. A higher limit means that cached
22592 compilation units will be stored in memory longer, and more total
22593 memory will be used. Setting it to zero disables caching, which will
22594 slow down @value{GDBN} startup, but reduce memory consumption.
22596 @kindex maint set profile
22597 @kindex maint show profile
22598 @cindex profiling GDB
22599 @item maint set profile
22600 @itemx maint show profile
22601 Control profiling of @value{GDBN}.
22603 Profiling will be disabled until you use the @samp{maint set profile}
22604 command to enable it. When you enable profiling, the system will begin
22605 collecting timing and execution count data; when you disable profiling or
22606 exit @value{GDBN}, the results will be written to a log file. Remember that
22607 if you use profiling, @value{GDBN} will overwrite the profiling log file
22608 (often called @file{gmon.out}). If you have a record of important profiling
22609 data in a @file{gmon.out} file, be sure to move it to a safe location.
22611 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
22612 compiled with the @samp{-pg} compiler option.
22614 @kindex maint show-debug-regs
22615 @cindex x86 hardware debug registers
22616 @item maint show-debug-regs
22617 Control whether to show variables that mirror the x86 hardware debug
22618 registers. Use @code{ON} to enable, @code{OFF} to disable. If
22619 enabled, the debug registers values are shown when @value{GDBN} inserts or
22620 removes a hardware breakpoint or watchpoint, and when the inferior
22621 triggers a hardware-assisted breakpoint or watchpoint.
22623 @kindex maint space
22624 @cindex memory used by commands
22626 Control whether to display memory usage for each command. If set to a
22627 nonzero value, @value{GDBN} will display how much memory each command
22628 took, following the command's own output. This can also be requested
22629 by invoking @value{GDBN} with the @option{--statistics} command-line
22630 switch (@pxref{Mode Options}).
22633 @cindex time of command execution
22635 Control whether to display the execution time for each command. If
22636 set to a nonzero value, @value{GDBN} will display how much time it
22637 took to execute each command, following the command's own output.
22638 This can also be requested by invoking @value{GDBN} with the
22639 @option{--statistics} command-line switch (@pxref{Mode Options}).
22641 @kindex maint translate-address
22642 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
22643 Find the symbol stored at the location specified by the address
22644 @var{addr} and an optional section name @var{section}. If found,
22645 @value{GDBN} prints the name of the closest symbol and an offset from
22646 the symbol's location to the specified address. This is similar to
22647 the @code{info address} command (@pxref{Symbols}), except that this
22648 command also allows to find symbols in other sections.
22652 The following command is useful for non-interactive invocations of
22653 @value{GDBN}, such as in the test suite.
22656 @item set watchdog @var{nsec}
22657 @kindex set watchdog
22658 @cindex watchdog timer
22659 @cindex timeout for commands
22660 Set the maximum number of seconds @value{GDBN} will wait for the
22661 target operation to finish. If this time expires, @value{GDBN}
22662 reports and error and the command is aborted.
22664 @item show watchdog
22665 Show the current setting of the target wait timeout.
22668 @node Remote Protocol
22669 @appendix @value{GDBN} Remote Serial Protocol
22674 * Stop Reply Packets::
22675 * General Query Packets::
22676 * Register Packet Format::
22677 * Tracepoint Packets::
22680 * File-I/O Remote Protocol Extension::
22681 * Library List Format::
22682 * Memory Map Format::
22688 There may be occasions when you need to know something about the
22689 protocol---for example, if there is only one serial port to your target
22690 machine, you might want your program to do something special if it
22691 recognizes a packet meant for @value{GDBN}.
22693 In the examples below, @samp{->} and @samp{<-} are used to indicate
22694 transmitted and received data, respectively.
22696 @cindex protocol, @value{GDBN} remote serial
22697 @cindex serial protocol, @value{GDBN} remote
22698 @cindex remote serial protocol
22699 All @value{GDBN} commands and responses (other than acknowledgments) are
22700 sent as a @var{packet}. A @var{packet} is introduced with the character
22701 @samp{$}, the actual @var{packet-data}, and the terminating character
22702 @samp{#} followed by a two-digit @var{checksum}:
22705 @code{$}@var{packet-data}@code{#}@var{checksum}
22709 @cindex checksum, for @value{GDBN} remote
22711 The two-digit @var{checksum} is computed as the modulo 256 sum of all
22712 characters between the leading @samp{$} and the trailing @samp{#} (an
22713 eight bit unsigned checksum).
22715 Implementors should note that prior to @value{GDBN} 5.0 the protocol
22716 specification also included an optional two-digit @var{sequence-id}:
22719 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
22722 @cindex sequence-id, for @value{GDBN} remote
22724 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
22725 has never output @var{sequence-id}s. Stubs that handle packets added
22726 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
22728 @cindex acknowledgment, for @value{GDBN} remote
22729 When either the host or the target machine receives a packet, the first
22730 response expected is an acknowledgment: either @samp{+} (to indicate
22731 the package was received correctly) or @samp{-} (to request
22735 -> @code{$}@var{packet-data}@code{#}@var{checksum}
22740 The host (@value{GDBN}) sends @var{command}s, and the target (the
22741 debugging stub incorporated in your program) sends a @var{response}. In
22742 the case of step and continue @var{command}s, the response is only sent
22743 when the operation has completed (the target has again stopped).
22745 @var{packet-data} consists of a sequence of characters with the
22746 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
22749 @cindex remote protocol, field separator
22750 Fields within the packet should be separated using @samp{,} @samp{;} or
22751 @samp{:}. Except where otherwise noted all numbers are represented in
22752 @sc{hex} with leading zeros suppressed.
22754 Implementors should note that prior to @value{GDBN} 5.0, the character
22755 @samp{:} could not appear as the third character in a packet (as it
22756 would potentially conflict with the @var{sequence-id}).
22758 @cindex remote protocol, binary data
22759 @anchor{Binary Data}
22760 Binary data in most packets is encoded either as two hexadecimal
22761 digits per byte of binary data. This allowed the traditional remote
22762 protocol to work over connections which were only seven-bit clean.
22763 Some packets designed more recently assume an eight-bit clean
22764 connection, and use a more efficient encoding to send and receive
22767 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
22768 as an escape character. Any escaped byte is transmitted as the escape
22769 character followed by the original character XORed with @code{0x20}.
22770 For example, the byte @code{0x7d} would be transmitted as the two
22771 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
22772 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
22773 @samp{@}}) must always be escaped. Responses sent by the stub
22774 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
22775 is not interpreted as the start of a run-length encoded sequence
22778 Response @var{data} can be run-length encoded to save space. A @samp{*}
22779 means that the next character is an @sc{ascii} encoding giving a repeat count
22780 which stands for that many repetitions of the character preceding the
22781 @samp{*}. The encoding is @code{n+29}, yielding a printable character
22782 where @code{n >=3} (which is where rle starts to win). The printable
22783 characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric
22784 value greater than 126 should not be used.
22791 means the same as "0000".
22793 The error response returned for some packets includes a two character
22794 error number. That number is not well defined.
22796 @cindex empty response, for unsupported packets
22797 For any @var{command} not supported by the stub, an empty response
22798 (@samp{$#00}) should be returned. That way it is possible to extend the
22799 protocol. A newer @value{GDBN} can tell if a packet is supported based
22802 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
22803 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
22809 The following table provides a complete list of all currently defined
22810 @var{command}s and their corresponding response @var{data}.
22811 @xref{File-I/O Remote Protocol Extension}, for details about the File
22812 I/O extension of the remote protocol.
22814 Each packet's description has a template showing the packet's overall
22815 syntax, followed by an explanation of the packet's meaning. We
22816 include spaces in some of the templates for clarity; these are not
22817 part of the packet's syntax. No @value{GDBN} packet uses spaces to
22818 separate its components. For example, a template like @samp{foo
22819 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
22820 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
22821 @var{baz}. @value{GDBN} does not transmit a space character between the
22822 @samp{foo} and the @var{bar}, or between the @var{bar} and the
22825 Note that all packet forms beginning with an upper- or lower-case
22826 letter, other than those described here, are reserved for future use.
22828 Here are the packet descriptions.
22833 @cindex @samp{!} packet
22834 Enable extended mode. In extended mode, the remote server is made
22835 persistent. The @samp{R} packet is used to restart the program being
22841 The remote target both supports and has enabled extended mode.
22845 @cindex @samp{?} packet
22846 Indicate the reason the target halted. The reply is the same as for
22850 @xref{Stop Reply Packets}, for the reply specifications.
22852 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
22853 @cindex @samp{A} packet
22854 Initialized @code{argv[]} array passed into program. @var{arglen}
22855 specifies the number of bytes in the hex encoded byte stream
22856 @var{arg}. See @code{gdbserver} for more details.
22861 The arguments were set.
22867 @cindex @samp{b} packet
22868 (Don't use this packet; its behavior is not well-defined.)
22869 Change the serial line speed to @var{baud}.
22871 JTC: @emph{When does the transport layer state change? When it's
22872 received, or after the ACK is transmitted. In either case, there are
22873 problems if the command or the acknowledgment packet is dropped.}
22875 Stan: @emph{If people really wanted to add something like this, and get
22876 it working for the first time, they ought to modify ser-unix.c to send
22877 some kind of out-of-band message to a specially-setup stub and have the
22878 switch happen "in between" packets, so that from remote protocol's point
22879 of view, nothing actually happened.}
22881 @item B @var{addr},@var{mode}
22882 @cindex @samp{B} packet
22883 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
22884 breakpoint at @var{addr}.
22886 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
22887 (@pxref{insert breakpoint or watchpoint packet}).
22889 @item c @r{[}@var{addr}@r{]}
22890 @cindex @samp{c} packet
22891 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
22892 resume at current address.
22895 @xref{Stop Reply Packets}, for the reply specifications.
22897 @item C @var{sig}@r{[};@var{addr}@r{]}
22898 @cindex @samp{C} packet
22899 Continue with signal @var{sig} (hex signal number). If
22900 @samp{;@var{addr}} is omitted, resume at same address.
22903 @xref{Stop Reply Packets}, for the reply specifications.
22906 @cindex @samp{d} packet
22909 Don't use this packet; instead, define a general set packet
22910 (@pxref{General Query Packets}).
22913 @cindex @samp{D} packet
22914 Detach @value{GDBN} from the remote system. Sent to the remote target
22915 before @value{GDBN} disconnects via the @code{detach} command.
22925 @item F @var{RC},@var{EE},@var{CF};@var{XX}
22926 @cindex @samp{F} packet
22927 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
22928 This is part of the File-I/O protocol extension. @xref{File-I/O
22929 Remote Protocol Extension}, for the specification.
22932 @anchor{read registers packet}
22933 @cindex @samp{g} packet
22934 Read general registers.
22938 @item @var{XX@dots{}}
22939 Each byte of register data is described by two hex digits. The bytes
22940 with the register are transmitted in target byte order. The size of
22941 each register and their position within the @samp{g} packet are
22942 determined by the @value{GDBN} internal gdbarch functions
22943 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
22944 specification of several standard @samp{g} packets is specified below.
22949 @item G @var{XX@dots{}}
22950 @cindex @samp{G} packet
22951 Write general registers. @xref{read registers packet}, for a
22952 description of the @var{XX@dots{}} data.
22962 @item H @var{c} @var{t}
22963 @cindex @samp{H} packet
22964 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
22965 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
22966 should be @samp{c} for step and continue operations, @samp{g} for other
22967 operations. The thread designator @var{t} may be @samp{-1}, meaning all
22968 the threads, a thread number, or @samp{0} which means pick any thread.
22979 @c 'H': How restrictive (or permissive) is the thread model. If a
22980 @c thread is selected and stopped, are other threads allowed
22981 @c to continue to execute? As I mentioned above, I think the
22982 @c semantics of each command when a thread is selected must be
22983 @c described. For example:
22985 @c 'g': If the stub supports threads and a specific thread is
22986 @c selected, returns the register block from that thread;
22987 @c otherwise returns current registers.
22989 @c 'G' If the stub supports threads and a specific thread is
22990 @c selected, sets the registers of the register block of
22991 @c that thread; otherwise sets current registers.
22993 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
22994 @anchor{cycle step packet}
22995 @cindex @samp{i} packet
22996 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
22997 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
22998 step starting at that address.
23001 @cindex @samp{I} packet
23002 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
23006 @cindex @samp{k} packet
23009 FIXME: @emph{There is no description of how to operate when a specific
23010 thread context has been selected (i.e.@: does 'k' kill only that
23013 @item m @var{addr},@var{length}
23014 @cindex @samp{m} packet
23015 Read @var{length} bytes of memory starting at address @var{addr}.
23016 Note that @var{addr} may not be aligned to any particular boundary.
23018 The stub need not use any particular size or alignment when gathering
23019 data from memory for the response; even if @var{addr} is word-aligned
23020 and @var{length} is a multiple of the word size, the stub is free to
23021 use byte accesses, or not. For this reason, this packet may not be
23022 suitable for accessing memory-mapped I/O devices.
23023 @cindex alignment of remote memory accesses
23024 @cindex size of remote memory accesses
23025 @cindex memory, alignment and size of remote accesses
23029 @item @var{XX@dots{}}
23030 Memory contents; each byte is transmitted as a two-digit hexadecimal
23031 number. The reply may contain fewer bytes than requested if the
23032 server was able to read only part of the region of memory.
23037 @item M @var{addr},@var{length}:@var{XX@dots{}}
23038 @cindex @samp{M} packet
23039 Write @var{length} bytes of memory starting at address @var{addr}.
23040 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
23041 hexadecimal number.
23048 for an error (this includes the case where only part of the data was
23053 @cindex @samp{p} packet
23054 Read the value of register @var{n}; @var{n} is in hex.
23055 @xref{read registers packet}, for a description of how the returned
23056 register value is encoded.
23060 @item @var{XX@dots{}}
23061 the register's value
23065 Indicating an unrecognized @var{query}.
23068 @item P @var{n@dots{}}=@var{r@dots{}}
23069 @anchor{write register packet}
23070 @cindex @samp{P} packet
23071 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
23072 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
23073 digits for each byte in the register (target byte order).
23083 @item q @var{name} @var{params}@dots{}
23084 @itemx Q @var{name} @var{params}@dots{}
23085 @cindex @samp{q} packet
23086 @cindex @samp{Q} packet
23087 General query (@samp{q}) and set (@samp{Q}). These packets are
23088 described fully in @ref{General Query Packets}.
23091 @cindex @samp{r} packet
23092 Reset the entire system.
23094 Don't use this packet; use the @samp{R} packet instead.
23097 @cindex @samp{R} packet
23098 Restart the program being debugged. @var{XX}, while needed, is ignored.
23099 This packet is only available in extended mode.
23101 The @samp{R} packet has no reply.
23103 @item s @r{[}@var{addr}@r{]}
23104 @cindex @samp{s} packet
23105 Single step. @var{addr} is the address at which to resume. If
23106 @var{addr} is omitted, resume at same address.
23109 @xref{Stop Reply Packets}, for the reply specifications.
23111 @item S @var{sig}@r{[};@var{addr}@r{]}
23112 @anchor{step with signal packet}
23113 @cindex @samp{S} packet
23114 Step with signal. This is analogous to the @samp{C} packet, but
23115 requests a single-step, rather than a normal resumption of execution.
23118 @xref{Stop Reply Packets}, for the reply specifications.
23120 @item t @var{addr}:@var{PP},@var{MM}
23121 @cindex @samp{t} packet
23122 Search backwards starting at address @var{addr} for a match with pattern
23123 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
23124 @var{addr} must be at least 3 digits.
23127 @cindex @samp{T} packet
23128 Find out if the thread XX is alive.
23133 thread is still alive
23139 Packets starting with @samp{v} are identified by a multi-letter name,
23140 up to the first @samp{;} or @samp{?} (or the end of the packet).
23142 @item vCont@r{[};@var{action}@r{[}:@var{tid}@r{]]}@dots{}
23143 @cindex @samp{vCont} packet
23144 Resume the inferior, specifying different actions for each thread.
23145 If an action is specified with no @var{tid}, then it is applied to any
23146 threads that don't have a specific action specified; if no default action is
23147 specified then other threads should remain stopped. Specifying multiple
23148 default actions is an error; specifying no actions is also an error.
23149 Thread IDs are specified in hexadecimal. Currently supported actions are:
23155 Continue with signal @var{sig}. @var{sig} should be two hex digits.
23159 Step with signal @var{sig}. @var{sig} should be two hex digits.
23162 The optional @var{addr} argument normally associated with these packets is
23163 not supported in @samp{vCont}.
23166 @xref{Stop Reply Packets}, for the reply specifications.
23169 @cindex @samp{vCont?} packet
23170 Request a list of actions supported by the @samp{vCont} packet.
23174 @item vCont@r{[};@var{action}@dots{}@r{]}
23175 The @samp{vCont} packet is supported. Each @var{action} is a supported
23176 command in the @samp{vCont} packet.
23178 The @samp{vCont} packet is not supported.
23181 @item vFlashErase:@var{addr},@var{length}
23182 @cindex @samp{vFlashErase} packet
23183 Direct the stub to erase @var{length} bytes of flash starting at
23184 @var{addr}. The region may enclose any number of flash blocks, but
23185 its start and end must fall on block boundaries, as indicated by the
23186 flash block size appearing in the memory map (@pxref{Memory Map
23187 Format}). @value{GDBN} groups flash memory programming operations
23188 together, and sends a @samp{vFlashDone} request after each group; the
23189 stub is allowed to delay erase operation until the @samp{vFlashDone}
23190 packet is received.
23200 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
23201 @cindex @samp{vFlashWrite} packet
23202 Direct the stub to write data to flash address @var{addr}. The data
23203 is passed in binary form using the same encoding as for the @samp{X}
23204 packet (@pxref{Binary Data}). The memory ranges specified by
23205 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
23206 not overlap, and must appear in order of increasing addresses
23207 (although @samp{vFlashErase} packets for higher addresses may already
23208 have been received; the ordering is guaranteed only between
23209 @samp{vFlashWrite} packets). If a packet writes to an address that was
23210 neither erased by a preceding @samp{vFlashErase} packet nor by some other
23211 target-specific method, the results are unpredictable.
23219 for vFlashWrite addressing non-flash memory
23225 @cindex @samp{vFlashDone} packet
23226 Indicate to the stub that flash programming operation is finished.
23227 The stub is permitted to delay or batch the effects of a group of
23228 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
23229 @samp{vFlashDone} packet is received. The contents of the affected
23230 regions of flash memory are unpredictable until the @samp{vFlashDone}
23231 request is completed.
23233 @item X @var{addr},@var{length}:@var{XX@dots{}}
23235 @cindex @samp{X} packet
23236 Write data to memory, where the data is transmitted in binary.
23237 @var{addr} is address, @var{length} is number of bytes,
23238 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
23248 @item z @var{type},@var{addr},@var{length}
23249 @itemx Z @var{type},@var{addr},@var{length}
23250 @anchor{insert breakpoint or watchpoint packet}
23251 @cindex @samp{z} packet
23252 @cindex @samp{Z} packets
23253 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
23254 watchpoint starting at address @var{address} and covering the next
23255 @var{length} bytes.
23257 Each breakpoint and watchpoint packet @var{type} is documented
23260 @emph{Implementation notes: A remote target shall return an empty string
23261 for an unrecognized breakpoint or watchpoint packet @var{type}. A
23262 remote target shall support either both or neither of a given
23263 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
23264 avoid potential problems with duplicate packets, the operations should
23265 be implemented in an idempotent way.}
23267 @item z0,@var{addr},@var{length}
23268 @itemx Z0,@var{addr},@var{length}
23269 @cindex @samp{z0} packet
23270 @cindex @samp{Z0} packet
23271 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
23272 @var{addr} of size @var{length}.
23274 A memory breakpoint is implemented by replacing the instruction at
23275 @var{addr} with a software breakpoint or trap instruction. The
23276 @var{length} is used by targets that indicates the size of the
23277 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
23278 @sc{mips} can insert either a 2 or 4 byte breakpoint).
23280 @emph{Implementation note: It is possible for a target to copy or move
23281 code that contains memory breakpoints (e.g., when implementing
23282 overlays). The behavior of this packet, in the presence of such a
23283 target, is not defined.}
23295 @item z1,@var{addr},@var{length}
23296 @itemx Z1,@var{addr},@var{length}
23297 @cindex @samp{z1} packet
23298 @cindex @samp{Z1} packet
23299 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
23300 address @var{addr} of size @var{length}.
23302 A hardware breakpoint is implemented using a mechanism that is not
23303 dependant on being able to modify the target's memory.
23305 @emph{Implementation note: A hardware breakpoint is not affected by code
23318 @item z2,@var{addr},@var{length}
23319 @itemx Z2,@var{addr},@var{length}
23320 @cindex @samp{z2} packet
23321 @cindex @samp{Z2} packet
23322 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint.
23334 @item z3,@var{addr},@var{length}
23335 @itemx Z3,@var{addr},@var{length}
23336 @cindex @samp{z3} packet
23337 @cindex @samp{Z3} packet
23338 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint.
23350 @item z4,@var{addr},@var{length}
23351 @itemx Z4,@var{addr},@var{length}
23352 @cindex @samp{z4} packet
23353 @cindex @samp{Z4} packet
23354 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint.
23368 @node Stop Reply Packets
23369 @section Stop Reply Packets
23370 @cindex stop reply packets
23372 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
23373 receive any of the below as a reply. In the case of the @samp{C},
23374 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
23375 when the target halts. In the below the exact meaning of @dfn{signal
23376 number} is defined by the header @file{include/gdb/signals.h} in the
23377 @value{GDBN} source code.
23379 As in the description of request packets, we include spaces in the
23380 reply templates for clarity; these are not part of the reply packet's
23381 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
23387 The program received signal number @var{AA} (a two-digit hexadecimal
23388 number). This is equivalent to a @samp{T} response with no
23389 @var{n}:@var{r} pairs.
23391 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
23392 @cindex @samp{T} packet reply
23393 The program received signal number @var{AA} (a two-digit hexadecimal
23394 number). This is equivalent to an @samp{S} response, except that the
23395 @samp{@var{n}:@var{r}} pairs can carry values of important registers
23396 and other information directly in the stop reply packet, reducing
23397 round-trip latency. Single-step and breakpoint traps are reported
23398 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
23402 If @var{n} is a hexadecimal number, it is a register number, and the
23403 corresponding @var{r} gives that register's value. @var{r} is a
23404 series of bytes in target byte order, with each byte given by a
23405 two-digit hex number.
23408 If @var{n} is @samp{thread}, then @var{r} is the thread process ID, in
23412 If @var{n} is a recognized @dfn{stop reason}, it describes a more
23413 specific event that stopped the target. The currently defined stop
23414 reasons are listed below. @var{aa} should be @samp{05}, the trap
23415 signal. At most one stop reason should be present.
23418 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
23419 and go on to the next; this allows us to extend the protocol in the
23423 The currently defined stop reasons are:
23429 The packet indicates a watchpoint hit, and @var{r} is the data address, in
23432 @cindex shared library events, remote reply
23434 The packet indicates that the loaded libraries have changed.
23435 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
23436 list of loaded libraries. @var{r} is ignored.
23440 The process exited, and @var{AA} is the exit status. This is only
23441 applicable to certain targets.
23444 The process terminated with signal @var{AA}.
23446 @item O @var{XX}@dots{}
23447 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
23448 written as the program's console output. This can happen at any time
23449 while the program is running and the debugger should continue to wait
23450 for @samp{W}, @samp{T}, etc.
23452 @item F @var{call-id},@var{parameter}@dots{}
23453 @var{call-id} is the identifier which says which host system call should
23454 be called. This is just the name of the function. Translation into the
23455 correct system call is only applicable as it's defined in @value{GDBN}.
23456 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
23459 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
23460 this very system call.
23462 The target replies with this packet when it expects @value{GDBN} to
23463 call a host system call on behalf of the target. @value{GDBN} replies
23464 with an appropriate @samp{F} packet and keeps up waiting for the next
23465 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
23466 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
23467 Protocol Extension}, for more details.
23471 @node General Query Packets
23472 @section General Query Packets
23473 @cindex remote query requests
23475 Packets starting with @samp{q} are @dfn{general query packets};
23476 packets starting with @samp{Q} are @dfn{general set packets}. General
23477 query and set packets are a semi-unified form for retrieving and
23478 sending information to and from the stub.
23480 The initial letter of a query or set packet is followed by a name
23481 indicating what sort of thing the packet applies to. For example,
23482 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
23483 definitions with the stub. These packet names follow some
23488 The name must not contain commas, colons or semicolons.
23490 Most @value{GDBN} query and set packets have a leading upper case
23493 The names of custom vendor packets should use a company prefix, in
23494 lower case, followed by a period. For example, packets designed at
23495 the Acme Corporation might begin with @samp{qacme.foo} (for querying
23496 foos) or @samp{Qacme.bar} (for setting bars).
23499 The name of a query or set packet should be separated from any
23500 parameters by a @samp{:}; the parameters themselves should be
23501 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
23502 full packet name, and check for a separator or the end of the packet,
23503 in case two packet names share a common prefix. New packets should not begin
23504 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
23505 packets predate these conventions, and have arguments without any terminator
23506 for the packet name; we suspect they are in widespread use in places that
23507 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
23508 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
23511 Like the descriptions of the other packets, each description here
23512 has a template showing the packet's overall syntax, followed by an
23513 explanation of the packet's meaning. We include spaces in some of the
23514 templates for clarity; these are not part of the packet's syntax. No
23515 @value{GDBN} packet uses spaces to separate its components.
23517 Here are the currently defined query and set packets:
23522 @cindex current thread, remote request
23523 @cindex @samp{qC} packet
23524 Return the current thread id.
23529 Where @var{pid} is an unsigned hexadecimal process id.
23530 @item @r{(anything else)}
23531 Any other reply implies the old pid.
23534 @item qCRC:@var{addr},@var{length}
23535 @cindex CRC of memory block, remote request
23536 @cindex @samp{qCRC} packet
23537 Compute the CRC checksum of a block of memory.
23541 An error (such as memory fault)
23542 @item C @var{crc32}
23543 The specified memory region's checksum is @var{crc32}.
23547 @itemx qsThreadInfo
23548 @cindex list active threads, remote request
23549 @cindex @samp{qfThreadInfo} packet
23550 @cindex @samp{qsThreadInfo} packet
23551 Obtain a list of all active thread ids from the target (OS). Since there
23552 may be too many active threads to fit into one reply packet, this query
23553 works iteratively: it may require more than one query/reply sequence to
23554 obtain the entire list of threads. The first query of the sequence will
23555 be the @samp{qfThreadInfo} query; subsequent queries in the
23556 sequence will be the @samp{qsThreadInfo} query.
23558 NOTE: This packet replaces the @samp{qL} query (see below).
23564 @item m @var{id},@var{id}@dots{}
23565 a comma-separated list of thread ids
23567 (lower case letter @samp{L}) denotes end of list.
23570 In response to each query, the target will reply with a list of one or
23571 more thread ids, in big-endian unsigned hex, separated by commas.
23572 @value{GDBN} will respond to each reply with a request for more thread
23573 ids (using the @samp{qs} form of the query), until the target responds
23574 with @samp{l} (lower-case el, for @dfn{last}).
23576 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
23577 @cindex get thread-local storage address, remote request
23578 @cindex @samp{qGetTLSAddr} packet
23579 Fetch the address associated with thread local storage specified
23580 by @var{thread-id}, @var{offset}, and @var{lm}.
23582 @var{thread-id} is the (big endian, hex encoded) thread id associated with the
23583 thread for which to fetch the TLS address.
23585 @var{offset} is the (big endian, hex encoded) offset associated with the
23586 thread local variable. (This offset is obtained from the debug
23587 information associated with the variable.)
23589 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
23590 the load module associated with the thread local storage. For example,
23591 a @sc{gnu}/Linux system will pass the link map address of the shared
23592 object associated with the thread local storage under consideration.
23593 Other operating environments may choose to represent the load module
23594 differently, so the precise meaning of this parameter will vary.
23598 @item @var{XX}@dots{}
23599 Hex encoded (big endian) bytes representing the address of the thread
23600 local storage requested.
23603 An error occurred. @var{nn} are hex digits.
23606 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
23609 @item qL @var{startflag} @var{threadcount} @var{nextthread}
23610 Obtain thread information from RTOS. Where: @var{startflag} (one hex
23611 digit) is one to indicate the first query and zero to indicate a
23612 subsequent query; @var{threadcount} (two hex digits) is the maximum
23613 number of threads the response packet can contain; and @var{nextthread}
23614 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
23615 returned in the response as @var{argthread}.
23617 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
23621 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
23622 Where: @var{count} (two hex digits) is the number of threads being
23623 returned; @var{done} (one hex digit) is zero to indicate more threads
23624 and one indicates no further threads; @var{argthreadid} (eight hex
23625 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
23626 is a sequence of thread IDs from the target. @var{threadid} (eight hex
23627 digits). See @code{remote.c:parse_threadlist_response()}.
23631 @cindex section offsets, remote request
23632 @cindex @samp{qOffsets} packet
23633 Get section offsets that the target used when relocating the downloaded
23638 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
23639 Relocate the @code{Text} section by @var{xxx} from its original address.
23640 Relocate the @code{Data} section by @var{yyy} from its original address.
23641 If the object file format provides segment information (e.g.@: @sc{elf}
23642 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
23643 segments by the supplied offsets.
23645 @emph{Note: while a @code{Bss} offset may be included in the response,
23646 @value{GDBN} ignores this and instead applies the @code{Data} offset
23647 to the @code{Bss} section.}
23649 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
23650 Relocate the first segment of the object file, which conventionally
23651 contains program code, to a starting address of @var{xxx}. If
23652 @samp{DataSeg} is specified, relocate the second segment, which
23653 conventionally contains modifiable data, to a starting address of
23654 @var{yyy}. @value{GDBN} will report an error if the object file
23655 does not contain segment information, or does not contain at least
23656 as many segments as mentioned in the reply. Extra segments are
23657 kept at fixed offsets relative to the last relocated segment.
23660 @item qP @var{mode} @var{threadid}
23661 @cindex thread information, remote request
23662 @cindex @samp{qP} packet
23663 Returns information on @var{threadid}. Where: @var{mode} is a hex
23664 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
23666 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
23669 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
23671 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
23672 @cindex pass signals to inferior, remote request
23673 @cindex @samp{QPassSignals} packet
23674 @anchor{QPassSignals}
23675 Each listed @var{signal} should be passed directly to the inferior process.
23676 Signals are numbered identically to continue packets and stop replies
23677 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
23678 strictly greater than the previous item. These signals do not need to stop
23679 the inferior, or be reported to @value{GDBN}. All other signals should be
23680 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
23681 combine; any earlier @samp{QPassSignals} list is completely replaced by the
23682 new list. This packet improves performance when using @samp{handle
23683 @var{signal} nostop noprint pass}.
23688 The request succeeded.
23691 An error occurred. @var{nn} are hex digits.
23694 An empty reply indicates that @samp{QPassSignals} is not supported by
23698 Use of this packet is controlled by the @code{set remote pass-signals}
23699 command (@pxref{Remote Configuration, set remote pass-signals}).
23700 This packet is not probed by default; the remote stub must request it,
23701 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
23703 @item qRcmd,@var{command}
23704 @cindex execute remote command, remote request
23705 @cindex @samp{qRcmd} packet
23706 @var{command} (hex encoded) is passed to the local interpreter for
23707 execution. Invalid commands should be reported using the output
23708 string. Before the final result packet, the target may also respond
23709 with a number of intermediate @samp{O@var{output}} console output
23710 packets. @emph{Implementors should note that providing access to a
23711 stubs's interpreter may have security implications}.
23716 A command response with no output.
23718 A command response with the hex encoded output string @var{OUTPUT}.
23720 Indicate a badly formed request.
23722 An empty reply indicates that @samp{qRcmd} is not recognized.
23725 (Note that the @code{qRcmd} packet's name is separated from the
23726 command by a @samp{,}, not a @samp{:}, contrary to the naming
23727 conventions above. Please don't use this packet as a model for new
23730 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
23731 @cindex supported packets, remote query
23732 @cindex features of the remote protocol
23733 @cindex @samp{qSupported} packet
23734 @anchor{qSupported}
23735 Tell the remote stub about features supported by @value{GDBN}, and
23736 query the stub for features it supports. This packet allows
23737 @value{GDBN} and the remote stub to take advantage of each others'
23738 features. @samp{qSupported} also consolidates multiple feature probes
23739 at startup, to improve @value{GDBN} performance---a single larger
23740 packet performs better than multiple smaller probe packets on
23741 high-latency links. Some features may enable behavior which must not
23742 be on by default, e.g.@: because it would confuse older clients or
23743 stubs. Other features may describe packets which could be
23744 automatically probed for, but are not. These features must be
23745 reported before @value{GDBN} will use them. This ``default
23746 unsupported'' behavior is not appropriate for all packets, but it
23747 helps to keep the initial connection time under control with new
23748 versions of @value{GDBN} which support increasing numbers of packets.
23752 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
23753 The stub supports or does not support each returned @var{stubfeature},
23754 depending on the form of each @var{stubfeature} (see below for the
23757 An empty reply indicates that @samp{qSupported} is not recognized,
23758 or that no features needed to be reported to @value{GDBN}.
23761 The allowed forms for each feature (either a @var{gdbfeature} in the
23762 @samp{qSupported} packet, or a @var{stubfeature} in the response)
23766 @item @var{name}=@var{value}
23767 The remote protocol feature @var{name} is supported, and associated
23768 with the specified @var{value}. The format of @var{value} depends
23769 on the feature, but it must not include a semicolon.
23771 The remote protocol feature @var{name} is supported, and does not
23772 need an associated value.
23774 The remote protocol feature @var{name} is not supported.
23776 The remote protocol feature @var{name} may be supported, and
23777 @value{GDBN} should auto-detect support in some other way when it is
23778 needed. This form will not be used for @var{gdbfeature} notifications,
23779 but may be used for @var{stubfeature} responses.
23782 Whenever the stub receives a @samp{qSupported} request, the
23783 supplied set of @value{GDBN} features should override any previous
23784 request. This allows @value{GDBN} to put the stub in a known
23785 state, even if the stub had previously been communicating with
23786 a different version of @value{GDBN}.
23788 No values of @var{gdbfeature} (for the packet sent by @value{GDBN})
23789 are defined yet. Stubs should ignore any unknown values for
23790 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
23791 packet supports receiving packets of unlimited length (earlier
23792 versions of @value{GDBN} may reject overly long responses). Values
23793 for @var{gdbfeature} may be defined in the future to let the stub take
23794 advantage of new features in @value{GDBN}, e.g.@: incompatible
23795 improvements in the remote protocol---support for unlimited length
23796 responses would be a @var{gdbfeature} example, if it were not implied by
23797 the @samp{qSupported} query. The stub's reply should be independent
23798 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
23799 describes all the features it supports, and then the stub replies with
23800 all the features it supports.
23802 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
23803 responses, as long as each response uses one of the standard forms.
23805 Some features are flags. A stub which supports a flag feature
23806 should respond with a @samp{+} form response. Other features
23807 require values, and the stub should respond with an @samp{=}
23810 Each feature has a default value, which @value{GDBN} will use if
23811 @samp{qSupported} is not available or if the feature is not mentioned
23812 in the @samp{qSupported} response. The default values are fixed; a
23813 stub is free to omit any feature responses that match the defaults.
23815 Not all features can be probed, but for those which can, the probing
23816 mechanism is useful: in some cases, a stub's internal
23817 architecture may not allow the protocol layer to know some information
23818 about the underlying target in advance. This is especially common in
23819 stubs which may be configured for multiple targets.
23821 These are the currently defined stub features and their properties:
23823 @multitable @columnfractions 0.35 0.2 0.12 0.2
23824 @c NOTE: The first row should be @headitem, but we do not yet require
23825 @c a new enough version of Texinfo (4.7) to use @headitem.
23827 @tab Value Required
23831 @item @samp{PacketSize}
23836 @item @samp{qXfer:auxv:read}
23841 @item @samp{qXfer:features:read}
23846 @item @samp{qXfer:libraries:read}
23851 @item @samp{qXfer:memory-map:read}
23856 @item @samp{qXfer:spu:read}
23861 @item @samp{qXfer:spu:write}
23866 @item @samp{QPassSignals}
23873 These are the currently defined stub features, in more detail:
23876 @cindex packet size, remote protocol
23877 @item PacketSize=@var{bytes}
23878 The remote stub can accept packets up to at least @var{bytes} in
23879 length. @value{GDBN} will send packets up to this size for bulk
23880 transfers, and will never send larger packets. This is a limit on the
23881 data characters in the packet, including the frame and checksum.
23882 There is no trailing NUL byte in a remote protocol packet; if the stub
23883 stores packets in a NUL-terminated format, it should allow an extra
23884 byte in its buffer for the NUL. If this stub feature is not supported,
23885 @value{GDBN} guesses based on the size of the @samp{g} packet response.
23887 @item qXfer:auxv:read
23888 The remote stub understands the @samp{qXfer:auxv:read} packet
23889 (@pxref{qXfer auxiliary vector read}).
23891 @item qXfer:features:read
23892 The remote stub understands the @samp{qXfer:features:read} packet
23893 (@pxref{qXfer target description read}).
23895 @item qXfer:libraries:read
23896 The remote stub understands the @samp{qXfer:libraries:read} packet
23897 (@pxref{qXfer library list read}).
23899 @item qXfer:memory-map:read
23900 The remote stub understands the @samp{qXfer:memory-map:read} packet
23901 (@pxref{qXfer memory map read}).
23903 @item qXfer:spu:read
23904 The remote stub understands the @samp{qXfer:spu:read} packet
23905 (@pxref{qXfer spu read}).
23907 @item qXfer:spu:write
23908 The remote stub understands the @samp{qXfer:spu:write} packet
23909 (@pxref{qXfer spu write}).
23912 The remote stub understands the @samp{QPassSignals} packet
23913 (@pxref{QPassSignals}).
23918 @cindex symbol lookup, remote request
23919 @cindex @samp{qSymbol} packet
23920 Notify the target that @value{GDBN} is prepared to serve symbol lookup
23921 requests. Accept requests from the target for the values of symbols.
23926 The target does not need to look up any (more) symbols.
23927 @item qSymbol:@var{sym_name}
23928 The target requests the value of symbol @var{sym_name} (hex encoded).
23929 @value{GDBN} may provide the value by using the
23930 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
23934 @item qSymbol:@var{sym_value}:@var{sym_name}
23935 Set the value of @var{sym_name} to @var{sym_value}.
23937 @var{sym_name} (hex encoded) is the name of a symbol whose value the
23938 target has previously requested.
23940 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
23941 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
23947 The target does not need to look up any (more) symbols.
23948 @item qSymbol:@var{sym_name}
23949 The target requests the value of a new symbol @var{sym_name} (hex
23950 encoded). @value{GDBN} will continue to supply the values of symbols
23951 (if available), until the target ceases to request them.
23956 @xref{Tracepoint Packets}.
23958 @item qThreadExtraInfo,@var{id}
23959 @cindex thread attributes info, remote request
23960 @cindex @samp{qThreadExtraInfo} packet
23961 Obtain a printable string description of a thread's attributes from
23962 the target OS. @var{id} is a thread-id in big-endian hex. This
23963 string may contain anything that the target OS thinks is interesting
23964 for @value{GDBN} to tell the user about the thread. The string is
23965 displayed in @value{GDBN}'s @code{info threads} display. Some
23966 examples of possible thread extra info strings are @samp{Runnable}, or
23967 @samp{Blocked on Mutex}.
23971 @item @var{XX}@dots{}
23972 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
23973 comprising the printable string containing the extra information about
23974 the thread's attributes.
23977 (Note that the @code{qThreadExtraInfo} packet's name is separated from
23978 the command by a @samp{,}, not a @samp{:}, contrary to the naming
23979 conventions above. Please don't use this packet as a model for new
23987 @xref{Tracepoint Packets}.
23989 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
23990 @cindex read special object, remote request
23991 @cindex @samp{qXfer} packet
23992 @anchor{qXfer read}
23993 Read uninterpreted bytes from the target's special data area
23994 identified by the keyword @var{object}. Request @var{length} bytes
23995 starting at @var{offset} bytes into the data. The content and
23996 encoding of @var{annex} is specific to @var{object}; it can supply
23997 additional details about what data to access.
23999 Here are the specific requests of this form defined so far. All
24000 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
24001 formats, listed below.
24004 @item qXfer:auxv:read::@var{offset},@var{length}
24005 @anchor{qXfer auxiliary vector read}
24006 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
24007 auxiliary vector}. Note @var{annex} must be empty.
24009 This packet is not probed by default; the remote stub must request it,
24010 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24012 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
24013 @anchor{qXfer target description read}
24014 Access the @dfn{target description}. @xref{Target Descriptions}. The
24015 annex specifies which XML document to access. The main description is
24016 always loaded from the @samp{target.xml} annex.
24018 This packet is not probed by default; the remote stub must request it,
24019 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24021 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
24022 @anchor{qXfer library list read}
24023 Access the target's list of loaded libraries. @xref{Library List Format}.
24024 The annex part of the generic @samp{qXfer} packet must be empty
24025 (@pxref{qXfer read}).
24027 Targets which maintain a list of libraries in the program's memory do
24028 not need to implement this packet; it is designed for platforms where
24029 the operating system manages the list of loaded libraries.
24031 This packet is not probed by default; the remote stub must request it,
24032 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24034 @item qXfer:memory-map:read::@var{offset},@var{length}
24035 @anchor{qXfer memory map read}
24036 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
24037 annex part of the generic @samp{qXfer} packet must be empty
24038 (@pxref{qXfer read}).
24040 This packet is not probed by default; the remote stub must request it,
24041 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24043 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
24044 @anchor{qXfer spu read}
24045 Read contents of an @code{spufs} file on the target system. The
24046 annex specifies which file to read; it must be of the form
24047 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
24048 in the target process, and @var{name} identifes the @code{spufs} file
24049 in that context to be accessed.
24051 This packet is not probed by default; the remote stub must request it,
24052 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24058 Data @var{data} (@pxref{Binary Data}) has been read from the
24059 target. There may be more data at a higher address (although
24060 it is permitted to return @samp{m} even for the last valid
24061 block of data, as long as at least one byte of data was read).
24062 @var{data} may have fewer bytes than the @var{length} in the
24066 Data @var{data} (@pxref{Binary Data}) has been read from the target.
24067 There is no more data to be read. @var{data} may have fewer bytes
24068 than the @var{length} in the request.
24071 The @var{offset} in the request is at the end of the data.
24072 There is no more data to be read.
24075 The request was malformed, or @var{annex} was invalid.
24078 The offset was invalid, or there was an error encountered reading the data.
24079 @var{nn} is a hex-encoded @code{errno} value.
24082 An empty reply indicates the @var{object} string was not recognized by
24083 the stub, or that the object does not support reading.
24086 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
24087 @cindex write data into object, remote request
24088 Write uninterpreted bytes into the target's special data area
24089 identified by the keyword @var{object}, starting at @var{offset} bytes
24090 into the data. @var{data}@dots{} is the binary-encoded data
24091 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
24092 is specific to @var{object}; it can supply additional details about what data
24095 Here are the specific requests of this form defined so far. All
24096 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
24097 formats, listed below.
24100 @item qXfer:@var{spu}:write:@var{annex}:@var{offset}:@var{data}@dots{}
24101 @anchor{qXfer spu write}
24102 Write @var{data} to an @code{spufs} file on the target system. The
24103 annex specifies which file to write; it must be of the form
24104 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
24105 in the target process, and @var{name} identifes the @code{spufs} file
24106 in that context to be accessed.
24108 This packet is not probed by default; the remote stub must request it,
24109 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24115 @var{nn} (hex encoded) is the number of bytes written.
24116 This may be fewer bytes than supplied in the request.
24119 The request was malformed, or @var{annex} was invalid.
24122 The offset was invalid, or there was an error encountered writing the data.
24123 @var{nn} is a hex-encoded @code{errno} value.
24126 An empty reply indicates the @var{object} string was not
24127 recognized by the stub, or that the object does not support writing.
24130 @item qXfer:@var{object}:@var{operation}:@dots{}
24131 Requests of this form may be added in the future. When a stub does
24132 not recognize the @var{object} keyword, or its support for
24133 @var{object} does not recognize the @var{operation} keyword, the stub
24134 must respond with an empty packet.
24138 @node Register Packet Format
24139 @section Register Packet Format
24141 The following @code{g}/@code{G} packets have previously been defined.
24142 In the below, some thirty-two bit registers are transferred as
24143 sixty-four bits. Those registers should be zero/sign extended (which?)
24144 to fill the space allocated. Register bytes are transferred in target
24145 byte order. The two nibbles within a register byte are transferred
24146 most-significant - least-significant.
24152 All registers are transferred as thirty-two bit quantities in the order:
24153 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
24154 registers; fsr; fir; fp.
24158 All registers are transferred as sixty-four bit quantities (including
24159 thirty-two bit registers such as @code{sr}). The ordering is the same
24164 @node Tracepoint Packets
24165 @section Tracepoint Packets
24166 @cindex tracepoint packets
24167 @cindex packets, tracepoint
24169 Here we describe the packets @value{GDBN} uses to implement
24170 tracepoints (@pxref{Tracepoints}).
24174 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}@r{[}-@r{]}
24175 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
24176 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
24177 the tracepoint is disabled. @var{step} is the tracepoint's step
24178 count, and @var{pass} is its pass count. If the trailing @samp{-} is
24179 present, further @samp{QTDP} packets will follow to specify this
24180 tracepoint's actions.
24185 The packet was understood and carried out.
24187 The packet was not recognized.
24190 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
24191 Define actions to be taken when a tracepoint is hit. @var{n} and
24192 @var{addr} must be the same as in the initial @samp{QTDP} packet for
24193 this tracepoint. This packet may only be sent immediately after
24194 another @samp{QTDP} packet that ended with a @samp{-}. If the
24195 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
24196 specifying more actions for this tracepoint.
24198 In the series of action packets for a given tracepoint, at most one
24199 can have an @samp{S} before its first @var{action}. If such a packet
24200 is sent, it and the following packets define ``while-stepping''
24201 actions. Any prior packets define ordinary actions --- that is, those
24202 taken when the tracepoint is first hit. If no action packet has an
24203 @samp{S}, then all the packets in the series specify ordinary
24204 tracepoint actions.
24206 The @samp{@var{action}@dots{}} portion of the packet is a series of
24207 actions, concatenated without separators. Each action has one of the
24213 Collect the registers whose bits are set in @var{mask}. @var{mask} is
24214 a hexadecimal number whose @var{i}'th bit is set if register number
24215 @var{i} should be collected. (The least significant bit is numbered
24216 zero.) Note that @var{mask} may be any number of digits long; it may
24217 not fit in a 32-bit word.
24219 @item M @var{basereg},@var{offset},@var{len}
24220 Collect @var{len} bytes of memory starting at the address in register
24221 number @var{basereg}, plus @var{offset}. If @var{basereg} is
24222 @samp{-1}, then the range has a fixed address: @var{offset} is the
24223 address of the lowest byte to collect. The @var{basereg},
24224 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
24225 values (the @samp{-1} value for @var{basereg} is a special case).
24227 @item X @var{len},@var{expr}
24228 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
24229 it directs. @var{expr} is an agent expression, as described in
24230 @ref{Agent Expressions}. Each byte of the expression is encoded as a
24231 two-digit hex number in the packet; @var{len} is the number of bytes
24232 in the expression (and thus one-half the number of hex digits in the
24237 Any number of actions may be packed together in a single @samp{QTDP}
24238 packet, as long as the packet does not exceed the maximum packet
24239 length (400 bytes, for many stubs). There may be only one @samp{R}
24240 action per tracepoint, and it must precede any @samp{M} or @samp{X}
24241 actions. Any registers referred to by @samp{M} and @samp{X} actions
24242 must be collected by a preceding @samp{R} action. (The
24243 ``while-stepping'' actions are treated as if they were attached to a
24244 separate tracepoint, as far as these restrictions are concerned.)
24249 The packet was understood and carried out.
24251 The packet was not recognized.
24254 @item QTFrame:@var{n}
24255 Select the @var{n}'th tracepoint frame from the buffer, and use the
24256 register and memory contents recorded there to answer subsequent
24257 request packets from @value{GDBN}.
24259 A successful reply from the stub indicates that the stub has found the
24260 requested frame. The response is a series of parts, concatenated
24261 without separators, describing the frame we selected. Each part has
24262 one of the following forms:
24266 The selected frame is number @var{n} in the trace frame buffer;
24267 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
24268 was no frame matching the criteria in the request packet.
24271 The selected trace frame records a hit of tracepoint number @var{t};
24272 @var{t} is a hexadecimal number.
24276 @item QTFrame:pc:@var{addr}
24277 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
24278 currently selected frame whose PC is @var{addr};
24279 @var{addr} is a hexadecimal number.
24281 @item QTFrame:tdp:@var{t}
24282 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
24283 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
24284 is a hexadecimal number.
24286 @item QTFrame:range:@var{start}:@var{end}
24287 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
24288 currently selected frame whose PC is between @var{start} (inclusive)
24289 and @var{end} (exclusive); @var{start} and @var{end} are hexadecimal
24292 @item QTFrame:outside:@var{start}:@var{end}
24293 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
24294 frame @emph{outside} the given range of addresses.
24297 Begin the tracepoint experiment. Begin collecting data from tracepoint
24298 hits in the trace frame buffer.
24301 End the tracepoint experiment. Stop collecting trace frames.
24304 Clear the table of tracepoints, and empty the trace frame buffer.
24306 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
24307 Establish the given ranges of memory as ``transparent''. The stub
24308 will answer requests for these ranges from memory's current contents,
24309 if they were not collected as part of the tracepoint hit.
24311 @value{GDBN} uses this to mark read-only regions of memory, like those
24312 containing program code. Since these areas never change, they should
24313 still have the same contents they did when the tracepoint was hit, so
24314 there's no reason for the stub to refuse to provide their contents.
24317 Ask the stub if there is a trace experiment running right now.
24322 There is no trace experiment running.
24324 There is a trace experiment running.
24331 @section Interrupts
24332 @cindex interrupts (remote protocol)
24334 When a program on the remote target is running, @value{GDBN} may
24335 attempt to interrupt it by sending a @samp{Ctrl-C} or a @code{BREAK},
24336 control of which is specified via @value{GDBN}'s @samp{remotebreak}
24337 setting (@pxref{set remotebreak}).
24339 The precise meaning of @code{BREAK} is defined by the transport
24340 mechanism and may, in fact, be undefined. @value{GDBN} does
24341 not currently define a @code{BREAK} mechanism for any of the network
24344 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
24345 transport mechanisms. It is represented by sending the single byte
24346 @code{0x03} without any of the usual packet overhead described in
24347 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
24348 transmitted as part of a packet, it is considered to be packet data
24349 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
24350 (@pxref{X packet}), used for binary downloads, may include an unescaped
24351 @code{0x03} as part of its packet.
24353 Stubs are not required to recognize these interrupt mechanisms and the
24354 precise meaning associated with receipt of the interrupt is
24355 implementation defined. If the stub is successful at interrupting the
24356 running program, it is expected that it will send one of the Stop
24357 Reply Packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
24358 of successfully stopping the program. Interrupts received while the
24359 program is stopped will be discarded.
24364 Example sequence of a target being re-started. Notice how the restart
24365 does not get any direct output:
24370 @emph{target restarts}
24373 <- @code{T001:1234123412341234}
24377 Example sequence of a target being stepped by a single instruction:
24380 -> @code{G1445@dots{}}
24385 <- @code{T001:1234123412341234}
24389 <- @code{1455@dots{}}
24393 @node File-I/O Remote Protocol Extension
24394 @section File-I/O Remote Protocol Extension
24395 @cindex File-I/O remote protocol extension
24398 * File-I/O Overview::
24399 * Protocol Basics::
24400 * The F Request Packet::
24401 * The F Reply Packet::
24402 * The Ctrl-C Message::
24404 * List of Supported Calls::
24405 * Protocol-specific Representation of Datatypes::
24407 * File-I/O Examples::
24410 @node File-I/O Overview
24411 @subsection File-I/O Overview
24412 @cindex file-i/o overview
24414 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
24415 target to use the host's file system and console I/O to perform various
24416 system calls. System calls on the target system are translated into a
24417 remote protocol packet to the host system, which then performs the needed
24418 actions and returns a response packet to the target system.
24419 This simulates file system operations even on targets that lack file systems.
24421 The protocol is defined to be independent of both the host and target systems.
24422 It uses its own internal representation of datatypes and values. Both
24423 @value{GDBN} and the target's @value{GDBN} stub are responsible for
24424 translating the system-dependent value representations into the internal
24425 protocol representations when data is transmitted.
24427 The communication is synchronous. A system call is possible only when
24428 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
24429 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
24430 the target is stopped to allow deterministic access to the target's
24431 memory. Therefore File-I/O is not interruptible by target signals. On
24432 the other hand, it is possible to interrupt File-I/O by a user interrupt
24433 (@samp{Ctrl-C}) within @value{GDBN}.
24435 The target's request to perform a host system call does not finish
24436 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
24437 after finishing the system call, the target returns to continuing the
24438 previous activity (continue, step). No additional continue or step
24439 request from @value{GDBN} is required.
24442 (@value{GDBP}) continue
24443 <- target requests 'system call X'
24444 target is stopped, @value{GDBN} executes system call
24445 -> @value{GDBN} returns result
24446 ... target continues, @value{GDBN} returns to wait for the target
24447 <- target hits breakpoint and sends a Txx packet
24450 The protocol only supports I/O on the console and to regular files on
24451 the host file system. Character or block special devices, pipes,
24452 named pipes, sockets or any other communication method on the host
24453 system are not supported by this protocol.
24455 @node Protocol Basics
24456 @subsection Protocol Basics
24457 @cindex protocol basics, file-i/o
24459 The File-I/O protocol uses the @code{F} packet as the request as well
24460 as reply packet. Since a File-I/O system call can only occur when
24461 @value{GDBN} is waiting for a response from the continuing or stepping target,
24462 the File-I/O request is a reply that @value{GDBN} has to expect as a result
24463 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
24464 This @code{F} packet contains all information needed to allow @value{GDBN}
24465 to call the appropriate host system call:
24469 A unique identifier for the requested system call.
24472 All parameters to the system call. Pointers are given as addresses
24473 in the target memory address space. Pointers to strings are given as
24474 pointer/length pair. Numerical values are given as they are.
24475 Numerical control flags are given in a protocol-specific representation.
24479 At this point, @value{GDBN} has to perform the following actions.
24483 If the parameters include pointer values to data needed as input to a
24484 system call, @value{GDBN} requests this data from the target with a
24485 standard @code{m} packet request. This additional communication has to be
24486 expected by the target implementation and is handled as any other @code{m}
24490 @value{GDBN} translates all value from protocol representation to host
24491 representation as needed. Datatypes are coerced into the host types.
24494 @value{GDBN} calls the system call.
24497 It then coerces datatypes back to protocol representation.
24500 If the system call is expected to return data in buffer space specified
24501 by pointer parameters to the call, the data is transmitted to the
24502 target using a @code{M} or @code{X} packet. This packet has to be expected
24503 by the target implementation and is handled as any other @code{M} or @code{X}
24508 Eventually @value{GDBN} replies with another @code{F} packet which contains all
24509 necessary information for the target to continue. This at least contains
24516 @code{errno}, if has been changed by the system call.
24523 After having done the needed type and value coercion, the target continues
24524 the latest continue or step action.
24526 @node The F Request Packet
24527 @subsection The @code{F} Request Packet
24528 @cindex file-i/o request packet
24529 @cindex @code{F} request packet
24531 The @code{F} request packet has the following format:
24534 @item F@var{call-id},@var{parameter@dots{}}
24536 @var{call-id} is the identifier to indicate the host system call to be called.
24537 This is just the name of the function.
24539 @var{parameter@dots{}} are the parameters to the system call.
24540 Parameters are hexadecimal integer values, either the actual values in case
24541 of scalar datatypes, pointers to target buffer space in case of compound
24542 datatypes and unspecified memory areas, or pointer/length pairs in case
24543 of string parameters. These are appended to the @var{call-id} as a
24544 comma-delimited list. All values are transmitted in ASCII
24545 string representation, pointer/length pairs separated by a slash.
24551 @node The F Reply Packet
24552 @subsection The @code{F} Reply Packet
24553 @cindex file-i/o reply packet
24554 @cindex @code{F} reply packet
24556 The @code{F} reply packet has the following format:
24560 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
24562 @var{retcode} is the return code of the system call as hexadecimal value.
24564 @var{errno} is the @code{errno} set by the call, in protocol-specific
24566 This parameter can be omitted if the call was successful.
24568 @var{Ctrl-C flag} is only sent if the user requested a break. In this
24569 case, @var{errno} must be sent as well, even if the call was successful.
24570 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
24577 or, if the call was interrupted before the host call has been performed:
24584 assuming 4 is the protocol-specific representation of @code{EINTR}.
24589 @node The Ctrl-C Message
24590 @subsection The @samp{Ctrl-C} Message
24591 @cindex ctrl-c message, in file-i/o protocol
24593 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
24594 reply packet (@pxref{The F Reply Packet}),
24595 the target should behave as if it had
24596 gotten a break message. The meaning for the target is ``system call
24597 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
24598 (as with a break message) and return to @value{GDBN} with a @code{T02}
24601 It's important for the target to know in which
24602 state the system call was interrupted. There are two possible cases:
24606 The system call hasn't been performed on the host yet.
24609 The system call on the host has been finished.
24613 These two states can be distinguished by the target by the value of the
24614 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
24615 call hasn't been performed. This is equivalent to the @code{EINTR} handling
24616 on POSIX systems. In any other case, the target may presume that the
24617 system call has been finished --- successfully or not --- and should behave
24618 as if the break message arrived right after the system call.
24620 @value{GDBN} must behave reliably. If the system call has not been called
24621 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
24622 @code{errno} in the packet. If the system call on the host has been finished
24623 before the user requests a break, the full action must be finished by
24624 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
24625 The @code{F} packet may only be sent when either nothing has happened
24626 or the full action has been completed.
24629 @subsection Console I/O
24630 @cindex console i/o as part of file-i/o
24632 By default and if not explicitly closed by the target system, the file
24633 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
24634 on the @value{GDBN} console is handled as any other file output operation
24635 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
24636 by @value{GDBN} so that after the target read request from file descriptor
24637 0 all following typing is buffered until either one of the following
24642 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
24644 system call is treated as finished.
24647 The user presses @key{RET}. This is treated as end of input with a trailing
24651 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
24652 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
24656 If the user has typed more characters than fit in the buffer given to
24657 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
24658 either another @code{read(0, @dots{})} is requested by the target, or debugging
24659 is stopped at the user's request.
24662 @node List of Supported Calls
24663 @subsection List of Supported Calls
24664 @cindex list of supported file-i/o calls
24681 @unnumberedsubsubsec open
24682 @cindex open, file-i/o system call
24687 int open(const char *pathname, int flags);
24688 int open(const char *pathname, int flags, mode_t mode);
24692 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
24695 @var{flags} is the bitwise @code{OR} of the following values:
24699 If the file does not exist it will be created. The host
24700 rules apply as far as file ownership and time stamps
24704 When used with @code{O_CREAT}, if the file already exists it is
24705 an error and open() fails.
24708 If the file already exists and the open mode allows
24709 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
24710 truncated to zero length.
24713 The file is opened in append mode.
24716 The file is opened for reading only.
24719 The file is opened for writing only.
24722 The file is opened for reading and writing.
24726 Other bits are silently ignored.
24730 @var{mode} is the bitwise @code{OR} of the following values:
24734 User has read permission.
24737 User has write permission.
24740 Group has read permission.
24743 Group has write permission.
24746 Others have read permission.
24749 Others have write permission.
24753 Other bits are silently ignored.
24756 @item Return value:
24757 @code{open} returns the new file descriptor or -1 if an error
24764 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
24767 @var{pathname} refers to a directory.
24770 The requested access is not allowed.
24773 @var{pathname} was too long.
24776 A directory component in @var{pathname} does not exist.
24779 @var{pathname} refers to a device, pipe, named pipe or socket.
24782 @var{pathname} refers to a file on a read-only filesystem and
24783 write access was requested.
24786 @var{pathname} is an invalid pointer value.
24789 No space on device to create the file.
24792 The process already has the maximum number of files open.
24795 The limit on the total number of files open on the system
24799 The call was interrupted by the user.
24805 @unnumberedsubsubsec close
24806 @cindex close, file-i/o system call
24815 @samp{Fclose,@var{fd}}
24817 @item Return value:
24818 @code{close} returns zero on success, or -1 if an error occurred.
24824 @var{fd} isn't a valid open file descriptor.
24827 The call was interrupted by the user.
24833 @unnumberedsubsubsec read
24834 @cindex read, file-i/o system call
24839 int read(int fd, void *buf, unsigned int count);
24843 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
24845 @item Return value:
24846 On success, the number of bytes read is returned.
24847 Zero indicates end of file. If count is zero, read
24848 returns zero as well. On error, -1 is returned.
24854 @var{fd} is not a valid file descriptor or is not open for
24858 @var{bufptr} is an invalid pointer value.
24861 The call was interrupted by the user.
24867 @unnumberedsubsubsec write
24868 @cindex write, file-i/o system call
24873 int write(int fd, const void *buf, unsigned int count);
24877 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
24879 @item Return value:
24880 On success, the number of bytes written are returned.
24881 Zero indicates nothing was written. On error, -1
24888 @var{fd} is not a valid file descriptor or is not open for
24892 @var{bufptr} is an invalid pointer value.
24895 An attempt was made to write a file that exceeds the
24896 host-specific maximum file size allowed.
24899 No space on device to write the data.
24902 The call was interrupted by the user.
24908 @unnumberedsubsubsec lseek
24909 @cindex lseek, file-i/o system call
24914 long lseek (int fd, long offset, int flag);
24918 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
24920 @var{flag} is one of:
24924 The offset is set to @var{offset} bytes.
24927 The offset is set to its current location plus @var{offset}
24931 The offset is set to the size of the file plus @var{offset}
24935 @item Return value:
24936 On success, the resulting unsigned offset in bytes from
24937 the beginning of the file is returned. Otherwise, a
24938 value of -1 is returned.
24944 @var{fd} is not a valid open file descriptor.
24947 @var{fd} is associated with the @value{GDBN} console.
24950 @var{flag} is not a proper value.
24953 The call was interrupted by the user.
24959 @unnumberedsubsubsec rename
24960 @cindex rename, file-i/o system call
24965 int rename(const char *oldpath, const char *newpath);
24969 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
24971 @item Return value:
24972 On success, zero is returned. On error, -1 is returned.
24978 @var{newpath} is an existing directory, but @var{oldpath} is not a
24982 @var{newpath} is a non-empty directory.
24985 @var{oldpath} or @var{newpath} is a directory that is in use by some
24989 An attempt was made to make a directory a subdirectory
24993 A component used as a directory in @var{oldpath} or new
24994 path is not a directory. Or @var{oldpath} is a directory
24995 and @var{newpath} exists but is not a directory.
24998 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
25001 No access to the file or the path of the file.
25005 @var{oldpath} or @var{newpath} was too long.
25008 A directory component in @var{oldpath} or @var{newpath} does not exist.
25011 The file is on a read-only filesystem.
25014 The device containing the file has no room for the new
25018 The call was interrupted by the user.
25024 @unnumberedsubsubsec unlink
25025 @cindex unlink, file-i/o system call
25030 int unlink(const char *pathname);
25034 @samp{Funlink,@var{pathnameptr}/@var{len}}
25036 @item Return value:
25037 On success, zero is returned. On error, -1 is returned.
25043 No access to the file or the path of the file.
25046 The system does not allow unlinking of directories.
25049 The file @var{pathname} cannot be unlinked because it's
25050 being used by another process.
25053 @var{pathnameptr} is an invalid pointer value.
25056 @var{pathname} was too long.
25059 A directory component in @var{pathname} does not exist.
25062 A component of the path is not a directory.
25065 The file is on a read-only filesystem.
25068 The call was interrupted by the user.
25074 @unnumberedsubsubsec stat/fstat
25075 @cindex fstat, file-i/o system call
25076 @cindex stat, file-i/o system call
25081 int stat(const char *pathname, struct stat *buf);
25082 int fstat(int fd, struct stat *buf);
25086 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
25087 @samp{Ffstat,@var{fd},@var{bufptr}}
25089 @item Return value:
25090 On success, zero is returned. On error, -1 is returned.
25096 @var{fd} is not a valid open file.
25099 A directory component in @var{pathname} does not exist or the
25100 path is an empty string.
25103 A component of the path is not a directory.
25106 @var{pathnameptr} is an invalid pointer value.
25109 No access to the file or the path of the file.
25112 @var{pathname} was too long.
25115 The call was interrupted by the user.
25121 @unnumberedsubsubsec gettimeofday
25122 @cindex gettimeofday, file-i/o system call
25127 int gettimeofday(struct timeval *tv, void *tz);
25131 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
25133 @item Return value:
25134 On success, 0 is returned, -1 otherwise.
25140 @var{tz} is a non-NULL pointer.
25143 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
25149 @unnumberedsubsubsec isatty
25150 @cindex isatty, file-i/o system call
25155 int isatty(int fd);
25159 @samp{Fisatty,@var{fd}}
25161 @item Return value:
25162 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
25168 The call was interrupted by the user.
25173 Note that the @code{isatty} call is treated as a special case: it returns
25174 1 to the target if the file descriptor is attached
25175 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
25176 would require implementing @code{ioctl} and would be more complex than
25181 @unnumberedsubsubsec system
25182 @cindex system, file-i/o system call
25187 int system(const char *command);
25191 @samp{Fsystem,@var{commandptr}/@var{len}}
25193 @item Return value:
25194 If @var{len} is zero, the return value indicates whether a shell is
25195 available. A zero return value indicates a shell is not available.
25196 For non-zero @var{len}, the value returned is -1 on error and the
25197 return status of the command otherwise. Only the exit status of the
25198 command is returned, which is extracted from the host's @code{system}
25199 return value by calling @code{WEXITSTATUS(retval)}. In case
25200 @file{/bin/sh} could not be executed, 127 is returned.
25206 The call was interrupted by the user.
25211 @value{GDBN} takes over the full task of calling the necessary host calls
25212 to perform the @code{system} call. The return value of @code{system} on
25213 the host is simplified before it's returned
25214 to the target. Any termination signal information from the child process
25215 is discarded, and the return value consists
25216 entirely of the exit status of the called command.
25218 Due to security concerns, the @code{system} call is by default refused
25219 by @value{GDBN}. The user has to allow this call explicitly with the
25220 @code{set remote system-call-allowed 1} command.
25223 @item set remote system-call-allowed
25224 @kindex set remote system-call-allowed
25225 Control whether to allow the @code{system} calls in the File I/O
25226 protocol for the remote target. The default is zero (disabled).
25228 @item show remote system-call-allowed
25229 @kindex show remote system-call-allowed
25230 Show whether the @code{system} calls are allowed in the File I/O
25234 @node Protocol-specific Representation of Datatypes
25235 @subsection Protocol-specific Representation of Datatypes
25236 @cindex protocol-specific representation of datatypes, in file-i/o protocol
25239 * Integral Datatypes::
25241 * Memory Transfer::
25246 @node Integral Datatypes
25247 @unnumberedsubsubsec Integral Datatypes
25248 @cindex integral datatypes, in file-i/o protocol
25250 The integral datatypes used in the system calls are @code{int},
25251 @code{unsigned int}, @code{long}, @code{unsigned long},
25252 @code{mode_t}, and @code{time_t}.
25254 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
25255 implemented as 32 bit values in this protocol.
25257 @code{long} and @code{unsigned long} are implemented as 64 bit types.
25259 @xref{Limits}, for corresponding MIN and MAX values (similar to those
25260 in @file{limits.h}) to allow range checking on host and target.
25262 @code{time_t} datatypes are defined as seconds since the Epoch.
25264 All integral datatypes transferred as part of a memory read or write of a
25265 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
25268 @node Pointer Values
25269 @unnumberedsubsubsec Pointer Values
25270 @cindex pointer values, in file-i/o protocol
25272 Pointers to target data are transmitted as they are. An exception
25273 is made for pointers to buffers for which the length isn't
25274 transmitted as part of the function call, namely strings. Strings
25275 are transmitted as a pointer/length pair, both as hex values, e.g.@:
25282 which is a pointer to data of length 18 bytes at position 0x1aaf.
25283 The length is defined as the full string length in bytes, including
25284 the trailing null byte. For example, the string @code{"hello world"}
25285 at address 0x123456 is transmitted as
25291 @node Memory Transfer
25292 @unnumberedsubsubsec Memory Transfer
25293 @cindex memory transfer, in file-i/o protocol
25295 Structured data which is transferred using a memory read or write (for
25296 example, a @code{struct stat}) is expected to be in a protocol-specific format
25297 with all scalar multibyte datatypes being big endian. Translation to
25298 this representation needs to be done both by the target before the @code{F}
25299 packet is sent, and by @value{GDBN} before
25300 it transfers memory to the target. Transferred pointers to structured
25301 data should point to the already-coerced data at any time.
25305 @unnumberedsubsubsec struct stat
25306 @cindex struct stat, in file-i/o protocol
25308 The buffer of type @code{struct stat} used by the target and @value{GDBN}
25309 is defined as follows:
25313 unsigned int st_dev; /* device */
25314 unsigned int st_ino; /* inode */
25315 mode_t st_mode; /* protection */
25316 unsigned int st_nlink; /* number of hard links */
25317 unsigned int st_uid; /* user ID of owner */
25318 unsigned int st_gid; /* group ID of owner */
25319 unsigned int st_rdev; /* device type (if inode device) */
25320 unsigned long st_size; /* total size, in bytes */
25321 unsigned long st_blksize; /* blocksize for filesystem I/O */
25322 unsigned long st_blocks; /* number of blocks allocated */
25323 time_t st_atime; /* time of last access */
25324 time_t st_mtime; /* time of last modification */
25325 time_t st_ctime; /* time of last change */
25329 The integral datatypes conform to the definitions given in the
25330 appropriate section (see @ref{Integral Datatypes}, for details) so this
25331 structure is of size 64 bytes.
25333 The values of several fields have a restricted meaning and/or
25339 A value of 0 represents a file, 1 the console.
25342 No valid meaning for the target. Transmitted unchanged.
25345 Valid mode bits are described in @ref{Constants}. Any other
25346 bits have currently no meaning for the target.
25351 No valid meaning for the target. Transmitted unchanged.
25356 These values have a host and file system dependent
25357 accuracy. Especially on Windows hosts, the file system may not
25358 support exact timing values.
25361 The target gets a @code{struct stat} of the above representation and is
25362 responsible for coercing it to the target representation before
25365 Note that due to size differences between the host, target, and protocol
25366 representations of @code{struct stat} members, these members could eventually
25367 get truncated on the target.
25369 @node struct timeval
25370 @unnumberedsubsubsec struct timeval
25371 @cindex struct timeval, in file-i/o protocol
25373 The buffer of type @code{struct timeval} used by the File-I/O protocol
25374 is defined as follows:
25378 time_t tv_sec; /* second */
25379 long tv_usec; /* microsecond */
25383 The integral datatypes conform to the definitions given in the
25384 appropriate section (see @ref{Integral Datatypes}, for details) so this
25385 structure is of size 8 bytes.
25388 @subsection Constants
25389 @cindex constants, in file-i/o protocol
25391 The following values are used for the constants inside of the
25392 protocol. @value{GDBN} and target are responsible for translating these
25393 values before and after the call as needed.
25404 @unnumberedsubsubsec Open Flags
25405 @cindex open flags, in file-i/o protocol
25407 All values are given in hexadecimal representation.
25419 @node mode_t Values
25420 @unnumberedsubsubsec mode_t Values
25421 @cindex mode_t values, in file-i/o protocol
25423 All values are given in octal representation.
25440 @unnumberedsubsubsec Errno Values
25441 @cindex errno values, in file-i/o protocol
25443 All values are given in decimal representation.
25468 @code{EUNKNOWN} is used as a fallback error value if a host system returns
25469 any error value not in the list of supported error numbers.
25472 @unnumberedsubsubsec Lseek Flags
25473 @cindex lseek flags, in file-i/o protocol
25482 @unnumberedsubsubsec Limits
25483 @cindex limits, in file-i/o protocol
25485 All values are given in decimal representation.
25488 INT_MIN -2147483648
25490 UINT_MAX 4294967295
25491 LONG_MIN -9223372036854775808
25492 LONG_MAX 9223372036854775807
25493 ULONG_MAX 18446744073709551615
25496 @node File-I/O Examples
25497 @subsection File-I/O Examples
25498 @cindex file-i/o examples
25500 Example sequence of a write call, file descriptor 3, buffer is at target
25501 address 0x1234, 6 bytes should be written:
25504 <- @code{Fwrite,3,1234,6}
25505 @emph{request memory read from target}
25508 @emph{return "6 bytes written"}
25512 Example sequence of a read call, file descriptor 3, buffer is at target
25513 address 0x1234, 6 bytes should be read:
25516 <- @code{Fread,3,1234,6}
25517 @emph{request memory write to target}
25518 -> @code{X1234,6:XXXXXX}
25519 @emph{return "6 bytes read"}
25523 Example sequence of a read call, call fails on the host due to invalid
25524 file descriptor (@code{EBADF}):
25527 <- @code{Fread,3,1234,6}
25531 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
25535 <- @code{Fread,3,1234,6}
25540 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
25544 <- @code{Fread,3,1234,6}
25545 -> @code{X1234,6:XXXXXX}
25549 @node Library List Format
25550 @section Library List Format
25551 @cindex library list format, remote protocol
25553 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
25554 same process as your application to manage libraries. In this case,
25555 @value{GDBN} can use the loader's symbol table and normal memory
25556 operations to maintain a list of shared libraries. On other
25557 platforms, the operating system manages loaded libraries.
25558 @value{GDBN} can not retrieve the list of currently loaded libraries
25559 through memory operations, so it uses the @samp{qXfer:libraries:read}
25560 packet (@pxref{qXfer library list read}) instead. The remote stub
25561 queries the target's operating system and reports which libraries
25564 The @samp{qXfer:libraries:read} packet returns an XML document which
25565 lists loaded libraries and their offsets. Each library has an
25566 associated name and one or more segment base addresses, which report
25567 where the library was loaded in memory. The segment bases are start
25568 addresses, not relocation offsets; they do not depend on the library's
25569 link-time base addresses.
25571 A simple memory map, with one loaded library relocated by a single
25572 offset, looks like this:
25576 <library name="/lib/libc.so.6">
25577 <segment address="0x10000000"/>
25582 The format of a library list is described by this DTD:
25585 <!-- library-list: Root element with versioning -->
25586 <!ELEMENT library-list (library)*>
25587 <!ATTLIST library-list version CDATA #FIXED "1.0">
25588 <!ELEMENT library (segment)*>
25589 <!ATTLIST library name CDATA #REQUIRED>
25590 <!ELEMENT segment EMPTY>
25591 <!ATTLIST segment address CDATA #REQUIRED>
25594 @node Memory Map Format
25595 @section Memory Map Format
25596 @cindex memory map format
25598 To be able to write into flash memory, @value{GDBN} needs to obtain a
25599 memory map from the target. This section describes the format of the
25602 The memory map is obtained using the @samp{qXfer:memory-map:read}
25603 (@pxref{qXfer memory map read}) packet and is an XML document that
25604 lists memory regions. The top-level structure of the document is shown below:
25607 <?xml version="1.0"?>
25608 <!DOCTYPE memory-map
25609 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
25610 "http://sourceware.org/gdb/gdb-memory-map.dtd">
25616 Each region can be either:
25621 A region of RAM starting at @var{addr} and extending for @var{length}
25625 <memory type="ram" start="@var{addr}" length="@var{length}"/>
25630 A region of read-only memory:
25633 <memory type="rom" start="@var{addr}" length="@var{length}"/>
25638 A region of flash memory, with erasure blocks @var{blocksize}
25642 <memory type="flash" start="@var{addr}" length="@var{length}">
25643 <property name="blocksize">@var{blocksize}</property>
25649 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
25650 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
25651 packets to write to addresses in such ranges.
25653 The formal DTD for memory map format is given below:
25656 <!-- ................................................... -->
25657 <!-- Memory Map XML DTD ................................ -->
25658 <!-- File: memory-map.dtd .............................. -->
25659 <!-- .................................... .............. -->
25660 <!-- memory-map.dtd -->
25661 <!-- memory-map: Root element with versioning -->
25662 <!ELEMENT memory-map (memory | property)>
25663 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
25664 <!ELEMENT memory (property)>
25665 <!-- memory: Specifies a memory region,
25666 and its type, or device. -->
25667 <!ATTLIST memory type CDATA #REQUIRED
25668 start CDATA #REQUIRED
25669 length CDATA #REQUIRED
25670 device CDATA #IMPLIED>
25671 <!-- property: Generic attribute tag -->
25672 <!ELEMENT property (#PCDATA | property)*>
25673 <!ATTLIST property name CDATA #REQUIRED>
25676 @include agentexpr.texi
25678 @node Target Descriptions
25679 @appendix Target Descriptions
25680 @cindex target descriptions
25682 @strong{Warning:} target descriptions are still under active development,
25683 and the contents and format may change between @value{GDBN} releases.
25684 The format is expected to stabilize in the future.
25686 One of the challenges of using @value{GDBN} to debug embedded systems
25687 is that there are so many minor variants of each processor
25688 architecture in use. It is common practice for vendors to start with
25689 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
25690 and then make changes to adapt it to a particular market niche. Some
25691 architectures have hundreds of variants, available from dozens of
25692 vendors. This leads to a number of problems:
25696 With so many different customized processors, it is difficult for
25697 the @value{GDBN} maintainers to keep up with the changes.
25699 Since individual variants may have short lifetimes or limited
25700 audiences, it may not be worthwhile to carry information about every
25701 variant in the @value{GDBN} source tree.
25703 When @value{GDBN} does support the architecture of the embedded system
25704 at hand, the task of finding the correct architecture name to give the
25705 @command{set architecture} command can be error-prone.
25708 To address these problems, the @value{GDBN} remote protocol allows a
25709 target system to not only identify itself to @value{GDBN}, but to
25710 actually describe its own features. This lets @value{GDBN} support
25711 processor variants it has never seen before --- to the extent that the
25712 descriptions are accurate, and that @value{GDBN} understands them.
25714 @value{GDBN} must be compiled with Expat support to support XML target
25715 descriptions. @xref{Expat}.
25718 * Retrieving Descriptions:: How descriptions are fetched from a target.
25719 * Target Description Format:: The contents of a target description.
25720 * Predefined Target Types:: Standard types available for target
25722 * Standard Target Features:: Features @value{GDBN} knows about.
25725 @node Retrieving Descriptions
25726 @section Retrieving Descriptions
25728 Target descriptions can be read from the target automatically, or
25729 specified by the user manually. The default behavior is to read the
25730 description from the target. @value{GDBN} retrieves it via the remote
25731 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
25732 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
25733 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
25734 XML document, of the form described in @ref{Target Description
25737 Alternatively, you can specify a file to read for the target description.
25738 If a file is set, the target will not be queried. The commands to
25739 specify a file are:
25742 @cindex set tdesc filename
25743 @item set tdesc filename @var{path}
25744 Read the target description from @var{path}.
25746 @cindex unset tdesc filename
25747 @item unset tdesc filename
25748 Do not read the XML target description from a file. @value{GDBN}
25749 will use the description supplied by the current target.
25751 @cindex show tdesc filename
25752 @item show tdesc filename
25753 Show the filename to read for a target description, if any.
25757 @node Target Description Format
25758 @section Target Description Format
25759 @cindex target descriptions, XML format
25761 A target description annex is an @uref{http://www.w3.org/XML/, XML}
25762 document which complies with the Document Type Definition provided in
25763 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
25764 means you can use generally available tools like @command{xmllint} to
25765 check that your feature descriptions are well-formed and valid.
25766 However, to help people unfamiliar with XML write descriptions for
25767 their targets, we also describe the grammar here.
25769 Target descriptions can identify the architecture of the remote target
25770 and (for some architectures) provide information about custom register
25771 sets. @value{GDBN} can use this information to autoconfigure for your
25772 target, or to warn you if you connect to an unsupported target.
25774 Here is a simple target description:
25777 <target version="1.0">
25778 <architecture>i386:x86-64</architecture>
25783 This minimal description only says that the target uses
25784 the x86-64 architecture.
25786 A target description has the following overall form, with [ ] marking
25787 optional elements and @dots{} marking repeatable elements. The elements
25788 are explained further below.
25791 <?xml version="1.0"?>
25792 <!DOCTYPE target SYSTEM "gdb-target.dtd">
25793 <target version="1.0">
25794 @r{[}@var{architecture}@r{]}
25795 @r{[}@var{feature}@dots{}@r{]}
25800 The description is generally insensitive to whitespace and line
25801 breaks, under the usual common-sense rules. The XML version
25802 declaration and document type declaration can generally be omitted
25803 (@value{GDBN} does not require them), but specifying them may be
25804 useful for XML validation tools. The @samp{version} attribute for
25805 @samp{<target>} may also be omitted, but we recommend
25806 including it; if future versions of @value{GDBN} use an incompatible
25807 revision of @file{gdb-target.dtd}, they will detect and report
25808 the version mismatch.
25810 @subsection Inclusion
25811 @cindex target descriptions, inclusion
25814 @cindex <xi:include>
25817 It can sometimes be valuable to split a target description up into
25818 several different annexes, either for organizational purposes, or to
25819 share files between different possible target descriptions. You can
25820 divide a description into multiple files by replacing any element of
25821 the target description with an inclusion directive of the form:
25824 <xi:include href="@var{document}"/>
25828 When @value{GDBN} encounters an element of this form, it will retrieve
25829 the named XML @var{document}, and replace the inclusion directive with
25830 the contents of that document. If the current description was read
25831 using @samp{qXfer}, then so will be the included document;
25832 @var{document} will be interpreted as the name of an annex. If the
25833 current description was read from a file, @value{GDBN} will look for
25834 @var{document} as a file in the same directory where it found the
25835 original description.
25837 @subsection Architecture
25838 @cindex <architecture>
25840 An @samp{<architecture>} element has this form:
25843 <architecture>@var{arch}</architecture>
25846 @var{arch} is an architecture name from the same selection
25847 accepted by @code{set architecture} (@pxref{Targets, ,Specifying a
25848 Debugging Target}).
25850 @subsection Features
25853 Each @samp{<feature>} describes some logical portion of the target
25854 system. Features are currently used to describe available CPU
25855 registers and the types of their contents. A @samp{<feature>} element
25859 <feature name="@var{name}">
25860 @r{[}@var{type}@dots{}@r{]}
25866 Each feature's name should be unique within the description. The name
25867 of a feature does not matter unless @value{GDBN} has some special
25868 knowledge of the contents of that feature; if it does, the feature
25869 should have its standard name. @xref{Standard Target Features}.
25873 Any register's value is a collection of bits which @value{GDBN} must
25874 interpret. The default interpretation is a two's complement integer,
25875 but other types can be requested by name in the register description.
25876 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
25877 Target Types}), and the description can define additional composite types.
25879 Each type element must have an @samp{id} attribute, which gives
25880 a unique (within the containing @samp{<feature>}) name to the type.
25881 Types must be defined before they are used.
25884 Some targets offer vector registers, which can be treated as arrays
25885 of scalar elements. These types are written as @samp{<vector>} elements,
25886 specifying the array element type, @var{type}, and the number of elements,
25890 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
25894 If a register's value is usefully viewed in multiple ways, define it
25895 with a union type containing the useful representations. The
25896 @samp{<union>} element contains one or more @samp{<field>} elements,
25897 each of which has a @var{name} and a @var{type}:
25900 <union id="@var{id}">
25901 <field name="@var{name}" type="@var{type}"/>
25906 @subsection Registers
25909 Each register is represented as an element with this form:
25912 <reg name="@var{name}"
25913 bitsize="@var{size}"
25914 @r{[}regnum="@var{num}"@r{]}
25915 @r{[}save-restore="@var{save-restore}"@r{]}
25916 @r{[}type="@var{type}"@r{]}
25917 @r{[}group="@var{group}"@r{]}/>
25921 The components are as follows:
25926 The register's name; it must be unique within the target description.
25929 The register's size, in bits.
25932 The register's number. If omitted, a register's number is one greater
25933 than that of the previous register (either in the current feature or in
25934 a preceeding feature); the first register in the target description
25935 defaults to zero. This register number is used to read or write
25936 the register; e.g.@: it is used in the remote @code{p} and @code{P}
25937 packets, and registers appear in the @code{g} and @code{G} packets
25938 in order of increasing register number.
25941 Whether the register should be preserved across inferior function
25942 calls; this must be either @code{yes} or @code{no}. The default is
25943 @code{yes}, which is appropriate for most registers except for
25944 some system control registers; this is not related to the target's
25948 The type of the register. @var{type} may be a predefined type, a type
25949 defined in the current feature, or one of the special types @code{int}
25950 and @code{float}. @code{int} is an integer type of the correct size
25951 for @var{bitsize}, and @code{float} is a floating point type (in the
25952 architecture's normal floating point format) of the correct size for
25953 @var{bitsize}. The default is @code{int}.
25956 The register group to which this register belongs. @var{group} must
25957 be either @code{general}, @code{float}, or @code{vector}. If no
25958 @var{group} is specified, @value{GDBN} will not display the register
25959 in @code{info registers}.
25963 @node Predefined Target Types
25964 @section Predefined Target Types
25965 @cindex target descriptions, predefined types
25967 Type definitions in the self-description can build up composite types
25968 from basic building blocks, but can not define fundamental types. Instead,
25969 standard identifiers are provided by @value{GDBN} for the fundamental
25970 types. The currently supported types are:
25978 Signed integer types holding the specified number of bits.
25984 Unsigned integer types holding the specified number of bits.
25988 Pointers to unspecified code and data. The program counter and
25989 any dedicated return address register may be marked as code
25990 pointers; printing a code pointer converts it into a symbolic
25991 address. The stack pointer and any dedicated address registers
25992 may be marked as data pointers.
25995 Single precision IEEE floating point.
25998 Double precision IEEE floating point.
26001 The 12-byte extended precision format used by ARM FPA registers.
26005 @node Standard Target Features
26006 @section Standard Target Features
26007 @cindex target descriptions, standard features
26009 A target description must contain either no registers or all the
26010 target's registers. If the description contains no registers, then
26011 @value{GDBN} will assume a default register layout, selected based on
26012 the architecture. If the description contains any registers, the
26013 default layout will not be used; the standard registers must be
26014 described in the target description, in such a way that @value{GDBN}
26015 can recognize them.
26017 This is accomplished by giving specific names to feature elements
26018 which contain standard registers. @value{GDBN} will look for features
26019 with those names and verify that they contain the expected registers;
26020 if any known feature is missing required registers, or if any required
26021 feature is missing, @value{GDBN} will reject the target
26022 description. You can add additional registers to any of the
26023 standard features --- @value{GDBN} will display them just as if
26024 they were added to an unrecognized feature.
26026 This section lists the known features and their expected contents.
26027 Sample XML documents for these features are included in the
26028 @value{GDBN} source tree, in the directory @file{gdb/features}.
26030 Names recognized by @value{GDBN} should include the name of the
26031 company or organization which selected the name, and the overall
26032 architecture to which the feature applies; so e.g.@: the feature
26033 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
26035 The names of registers are not case sensitive for the purpose
26036 of recognizing standard features, but @value{GDBN} will only display
26037 registers using the capitalization used in the description.
26046 @subsection ARM Features
26047 @cindex target descriptions, ARM features
26049 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
26050 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
26051 @samp{lr}, @samp{pc}, and @samp{cpsr}.
26053 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
26054 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
26056 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
26057 it should contain at least registers @samp{wR0} through @samp{wR15} and
26058 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
26059 @samp{wCSSF}, and @samp{wCASF} registers are optional.
26061 @subsection MIPS Features
26062 @cindex target descriptions, MIPS features
26064 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
26065 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
26066 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
26069 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
26070 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
26071 registers. They may be 32-bit or 64-bit depending on the target.
26073 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
26074 it may be optional in a future version of @value{GDBN}. It should
26075 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
26076 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
26078 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
26079 contain a single register, @samp{restart}, which is used by the
26080 Linux kernel to control restartable syscalls.
26082 @node M68K Features
26083 @subsection M68K Features
26084 @cindex target descriptions, M68K features
26087 @item @samp{org.gnu.gdb.m68k.core}
26088 @itemx @samp{org.gnu.gdb.coldfire.core}
26089 @itemx @samp{org.gnu.gdb.fido.core}
26090 One of those features must be always present.
26091 The feature that is present determines which flavor of m86k is
26092 used. The feature that is present should contain registers
26093 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
26094 @samp{sp}, @samp{ps} and @samp{pc}.
26096 @item @samp{org.gnu.gdb.coldfire.fp}
26097 This feature is optional. If present, it should contain registers
26098 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
26114 % I think something like @colophon should be in texinfo. In the
26116 \long\def\colophon{\hbox to0pt{}\vfill
26117 \centerline{The body of this manual is set in}
26118 \centerline{\fontname\tenrm,}
26119 \centerline{with headings in {\bf\fontname\tenbf}}
26120 \centerline{and examples in {\tt\fontname\tentt}.}
26121 \centerline{{\it\fontname\tenit\/},}
26122 \centerline{{\bf\fontname\tenbf}, and}
26123 \centerline{{\sl\fontname\tensl\/}}
26124 \centerline{are used for emphasis.}\vfill}
26126 % Blame: doc@cygnus.com, 1991.