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 -pid @var{number}
946 @itemx -p @var{number}
949 Connect to process ID @var{number}, as with the @code{attach} command.
951 @item -command @var{file}
953 @cindex @code{--command}
955 Execute @value{GDBN} commands from file @var{file}. @xref{Command
956 Files,, Command files}.
958 @item -eval-command @var{command}
959 @itemx -ex @var{command}
960 @cindex @code{--eval-command}
962 Execute a single @value{GDBN} command.
964 This option may be used multiple times to call multiple commands. It may
965 also be interleaved with @samp{-command} as required.
968 @value{GDBP} -ex 'target sim' -ex 'load' \
969 -x setbreakpoints -ex 'run' a.out
972 @item -directory @var{directory}
973 @itemx -d @var{directory}
974 @cindex @code{--directory}
976 Add @var{directory} to the path to search for source and script files.
980 @cindex @code{--readnow}
982 Read each symbol file's entire symbol table immediately, rather than
983 the default, which is to read it incrementally as it is needed.
984 This makes startup slower, but makes future operations faster.
989 @subsection Choosing Modes
991 You can run @value{GDBN} in various alternative modes---for example, in
992 batch mode or quiet mode.
999 Do not execute commands found in any initialization files. Normally,
1000 @value{GDBN} executes the commands in these files after all the command
1001 options and arguments have been processed. @xref{Command Files,,Command
1007 @cindex @code{--quiet}
1008 @cindex @code{--silent}
1010 ``Quiet''. Do not print the introductory and copyright messages. These
1011 messages are also suppressed in batch mode.
1014 @cindex @code{--batch}
1015 Run in batch mode. Exit with status @code{0} after processing all the
1016 command files specified with @samp{-x} (and all commands from
1017 initialization files, if not inhibited with @samp{-n}). Exit with
1018 nonzero status if an error occurs in executing the @value{GDBN} commands
1019 in the command files.
1021 Batch mode may be useful for running @value{GDBN} as a filter, for
1022 example to download and run a program on another computer; in order to
1023 make this more useful, the message
1026 Program exited normally.
1030 (which is ordinarily issued whenever a program running under
1031 @value{GDBN} control terminates) is not issued when running in batch
1035 @cindex @code{--batch-silent}
1036 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1037 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1038 unaffected). This is much quieter than @samp{-silent} and would be useless
1039 for an interactive session.
1041 This is particularly useful when using targets that give @samp{Loading section}
1042 messages, for example.
1044 Note that targets that give their output via @value{GDBN}, as opposed to
1045 writing directly to @code{stdout}, will also be made silent.
1047 @item -return-child-result
1048 @cindex @code{--return-child-result}
1049 The return code from @value{GDBN} will be the return code from the child
1050 process (the process being debugged), with the following exceptions:
1054 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1055 internal error. In this case the exit code is the same as it would have been
1056 without @samp{-return-child-result}.
1058 The user quits with an explicit value. E.g., @samp{quit 1}.
1060 The child process never runs, or is not allowed to terminate, in which case
1061 the exit code will be -1.
1064 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1065 when @value{GDBN} is being used as a remote program loader or simulator
1070 @cindex @code{--nowindows}
1072 ``No windows''. If @value{GDBN} comes with a graphical user interface
1073 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1074 interface. If no GUI is available, this option has no effect.
1078 @cindex @code{--windows}
1080 If @value{GDBN} includes a GUI, then this option requires it to be
1083 @item -cd @var{directory}
1085 Run @value{GDBN} using @var{directory} as its working directory,
1086 instead of the current directory.
1090 @cindex @code{--fullname}
1092 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1093 subprocess. It tells @value{GDBN} to output the full file name and line
1094 number in a standard, recognizable fashion each time a stack frame is
1095 displayed (which includes each time your program stops). This
1096 recognizable format looks like two @samp{\032} characters, followed by
1097 the file name, line number and character position separated by colons,
1098 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1099 @samp{\032} characters as a signal to display the source code for the
1103 @cindex @code{--epoch}
1104 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1105 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1106 routines so as to allow Epoch to display values of expressions in a
1109 @item -annotate @var{level}
1110 @cindex @code{--annotate}
1111 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1112 effect is identical to using @samp{set annotate @var{level}}
1113 (@pxref{Annotations}). The annotation @var{level} controls how much
1114 information @value{GDBN} prints together with its prompt, values of
1115 expressions, source lines, and other types of output. Level 0 is the
1116 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1117 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1118 that control @value{GDBN}, and level 2 has been deprecated.
1120 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1124 @cindex @code{--args}
1125 Change interpretation of command line so that arguments following the
1126 executable file are passed as command line arguments to the inferior.
1127 This option stops option processing.
1129 @item -baud @var{bps}
1131 @cindex @code{--baud}
1133 Set the line speed (baud rate or bits per second) of any serial
1134 interface used by @value{GDBN} for remote debugging.
1136 @item -l @var{timeout}
1138 Set the timeout (in seconds) of any communication used by @value{GDBN}
1139 for remote debugging.
1141 @item -tty @var{device}
1142 @itemx -t @var{device}
1143 @cindex @code{--tty}
1145 Run using @var{device} for your program's standard input and output.
1146 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1148 @c resolve the situation of these eventually
1150 @cindex @code{--tui}
1151 Activate the @dfn{Text User Interface} when starting. The Text User
1152 Interface manages several text windows on the terminal, showing
1153 source, assembly, registers and @value{GDBN} command outputs
1154 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1155 Text User Interface can be enabled by invoking the program
1156 @samp{@value{GDBTUI}}. Do not use this option if you run @value{GDBN} from
1157 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1160 @c @cindex @code{--xdb}
1161 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1162 @c For information, see the file @file{xdb_trans.html}, which is usually
1163 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1166 @item -interpreter @var{interp}
1167 @cindex @code{--interpreter}
1168 Use the interpreter @var{interp} for interface with the controlling
1169 program or device. This option is meant to be set by programs which
1170 communicate with @value{GDBN} using it as a back end.
1171 @xref{Interpreters, , Command Interpreters}.
1173 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1174 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1175 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1176 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1177 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1178 @sc{gdb/mi} interfaces are no longer supported.
1181 @cindex @code{--write}
1182 Open the executable and core files for both reading and writing. This
1183 is equivalent to the @samp{set write on} command inside @value{GDBN}
1187 @cindex @code{--statistics}
1188 This option causes @value{GDBN} to print statistics about time and
1189 memory usage after it completes each command and returns to the prompt.
1192 @cindex @code{--version}
1193 This option causes @value{GDBN} to print its version number and
1194 no-warranty blurb, and exit.
1199 @subsection What @value{GDBN} Does During Startup
1200 @cindex @value{GDBN} startup
1202 Here's the description of what @value{GDBN} does during session startup:
1206 Sets up the command interpreter as specified by the command line
1207 (@pxref{Mode Options, interpreter}).
1211 Reads the @dfn{init file} (if any) in your home directory@footnote{On
1212 DOS/Windows systems, the home directory is the one pointed to by the
1213 @code{HOME} environment variable.} and executes all the commands in
1217 Processes command line options and operands.
1220 Reads and executes the commands from init file (if any) in the current
1221 working directory. This is only done if the current directory is
1222 different from your home directory. Thus, you can have more than one
1223 init file, one generic in your home directory, and another, specific
1224 to the program you are debugging, in the directory where you invoke
1228 Reads command files specified by the @samp{-x} option. @xref{Command
1229 Files}, for more details about @value{GDBN} command files.
1232 Reads the command history recorded in the @dfn{history file}.
1233 @xref{Command History}, for more details about the command history and the
1234 files where @value{GDBN} records it.
1237 Init files use the same syntax as @dfn{command files} (@pxref{Command
1238 Files}) and are processed by @value{GDBN} in the same way. The init
1239 file in your home directory can set options (such as @samp{set
1240 complaints}) that affect subsequent processing of command line options
1241 and operands. Init files are not executed if you use the @samp{-nx}
1242 option (@pxref{Mode Options, ,Choosing Modes}).
1244 @cindex init file name
1245 @cindex @file{.gdbinit}
1246 @cindex @file{gdb.ini}
1247 The @value{GDBN} init files are normally called @file{.gdbinit}.
1248 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1249 the limitations of file names imposed by DOS filesystems. The Windows
1250 ports of @value{GDBN} use the standard name, but if they find a
1251 @file{gdb.ini} file, they warn you about that and suggest to rename
1252 the file to the standard name.
1256 @section Quitting @value{GDBN}
1257 @cindex exiting @value{GDBN}
1258 @cindex leaving @value{GDBN}
1261 @kindex quit @r{[}@var{expression}@r{]}
1262 @kindex q @r{(@code{quit})}
1263 @item quit @r{[}@var{expression}@r{]}
1265 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1266 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1267 do not supply @var{expression}, @value{GDBN} will terminate normally;
1268 otherwise it will terminate using the result of @var{expression} as the
1273 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1274 terminates the action of any @value{GDBN} command that is in progress and
1275 returns to @value{GDBN} command level. It is safe to type the interrupt
1276 character at any time because @value{GDBN} does not allow it to take effect
1277 until a time when it is safe.
1279 If you have been using @value{GDBN} to control an attached process or
1280 device, you can release it with the @code{detach} command
1281 (@pxref{Attach, ,Debugging an Already-running Process}).
1283 @node Shell Commands
1284 @section Shell Commands
1286 If you need to execute occasional shell commands during your
1287 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1288 just use the @code{shell} command.
1292 @cindex shell escape
1293 @item shell @var{command string}
1294 Invoke a standard shell to execute @var{command string}.
1295 If it exists, the environment variable @code{SHELL} determines which
1296 shell to run. Otherwise @value{GDBN} uses the default shell
1297 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1300 The utility @code{make} is often needed in development environments.
1301 You do not have to use the @code{shell} command for this purpose in
1306 @cindex calling make
1307 @item make @var{make-args}
1308 Execute the @code{make} program with the specified
1309 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1312 @node Logging Output
1313 @section Logging Output
1314 @cindex logging @value{GDBN} output
1315 @cindex save @value{GDBN} output to a file
1317 You may want to save the output of @value{GDBN} commands to a file.
1318 There are several commands to control @value{GDBN}'s logging.
1322 @item set logging on
1324 @item set logging off
1326 @cindex logging file name
1327 @item set logging file @var{file}
1328 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1329 @item set logging overwrite [on|off]
1330 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1331 you want @code{set logging on} to overwrite the logfile instead.
1332 @item set logging redirect [on|off]
1333 By default, @value{GDBN} output will go to both the terminal and the logfile.
1334 Set @code{redirect} if you want output to go only to the log file.
1335 @kindex show logging
1337 Show the current values of the logging settings.
1341 @chapter @value{GDBN} Commands
1343 You can abbreviate a @value{GDBN} command to the first few letters of the command
1344 name, if that abbreviation is unambiguous; and you can repeat certain
1345 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1346 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1347 show you the alternatives available, if there is more than one possibility).
1350 * Command Syntax:: How to give commands to @value{GDBN}
1351 * Completion:: Command completion
1352 * Help:: How to ask @value{GDBN} for help
1355 @node Command Syntax
1356 @section Command Syntax
1358 A @value{GDBN} command is a single line of input. There is no limit on
1359 how long it can be. It starts with a command name, which is followed by
1360 arguments whose meaning depends on the command name. For example, the
1361 command @code{step} accepts an argument which is the number of times to
1362 step, as in @samp{step 5}. You can also use the @code{step} command
1363 with no arguments. Some commands do not allow any arguments.
1365 @cindex abbreviation
1366 @value{GDBN} command names may always be truncated if that abbreviation is
1367 unambiguous. Other possible command abbreviations are listed in the
1368 documentation for individual commands. In some cases, even ambiguous
1369 abbreviations are allowed; for example, @code{s} is specially defined as
1370 equivalent to @code{step} even though there are other commands whose
1371 names start with @code{s}. You can test abbreviations by using them as
1372 arguments to the @code{help} command.
1374 @cindex repeating commands
1375 @kindex RET @r{(repeat last command)}
1376 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1377 repeat the previous command. Certain commands (for example, @code{run})
1378 will not repeat this way; these are commands whose unintentional
1379 repetition might cause trouble and which you are unlikely to want to
1380 repeat. User-defined commands can disable this feature; see
1381 @ref{Define, dont-repeat}.
1383 The @code{list} and @code{x} commands, when you repeat them with
1384 @key{RET}, construct new arguments rather than repeating
1385 exactly as typed. This permits easy scanning of source or memory.
1387 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1388 output, in a way similar to the common utility @code{more}
1389 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1390 @key{RET} too many in this situation, @value{GDBN} disables command
1391 repetition after any command that generates this sort of display.
1393 @kindex # @r{(a comment)}
1395 Any text from a @kbd{#} to the end of the line is a comment; it does
1396 nothing. This is useful mainly in command files (@pxref{Command
1397 Files,,Command Files}).
1399 @cindex repeating command sequences
1400 @kindex Ctrl-o @r{(operate-and-get-next)}
1401 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1402 commands. This command accepts the current line, like @key{RET}, and
1403 then fetches the next line relative to the current line from the history
1407 @section Command Completion
1410 @cindex word completion
1411 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1412 only one possibility; it can also show you what the valid possibilities
1413 are for the next word in a command, at any time. This works for @value{GDBN}
1414 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1416 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1417 of a word. If there is only one possibility, @value{GDBN} fills in the
1418 word, and waits for you to finish the command (or press @key{RET} to
1419 enter it). For example, if you type
1421 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1422 @c complete accuracy in these examples; space introduced for clarity.
1423 @c If texinfo enhancements make it unnecessary, it would be nice to
1424 @c replace " @key" by "@key" in the following...
1426 (@value{GDBP}) info bre @key{TAB}
1430 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1431 the only @code{info} subcommand beginning with @samp{bre}:
1434 (@value{GDBP}) info breakpoints
1438 You can either press @key{RET} at this point, to run the @code{info
1439 breakpoints} command, or backspace and enter something else, if
1440 @samp{breakpoints} does not look like the command you expected. (If you
1441 were sure you wanted @code{info breakpoints} in the first place, you
1442 might as well just type @key{RET} immediately after @samp{info bre},
1443 to exploit command abbreviations rather than command completion).
1445 If there is more than one possibility for the next word when you press
1446 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1447 characters and try again, or just press @key{TAB} a second time;
1448 @value{GDBN} displays all the possible completions for that word. For
1449 example, you might want to set a breakpoint on a subroutine whose name
1450 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1451 just sounds the bell. Typing @key{TAB} again displays all the
1452 function names in your program that begin with those characters, for
1456 (@value{GDBP}) b make_ @key{TAB}
1457 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1458 make_a_section_from_file make_environ
1459 make_abs_section make_function_type
1460 make_blockvector make_pointer_type
1461 make_cleanup make_reference_type
1462 make_command make_symbol_completion_list
1463 (@value{GDBP}) b make_
1467 After displaying the available possibilities, @value{GDBN} copies your
1468 partial input (@samp{b make_} in the example) so you can finish the
1471 If you just want to see the list of alternatives in the first place, you
1472 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1473 means @kbd{@key{META} ?}. You can type this either by holding down a
1474 key designated as the @key{META} shift on your keyboard (if there is
1475 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1477 @cindex quotes in commands
1478 @cindex completion of quoted strings
1479 Sometimes the string you need, while logically a ``word'', may contain
1480 parentheses or other characters that @value{GDBN} normally excludes from
1481 its notion of a word. To permit word completion to work in this
1482 situation, you may enclose words in @code{'} (single quote marks) in
1483 @value{GDBN} commands.
1485 The most likely situation where you might need this is in typing the
1486 name of a C@t{++} function. This is because C@t{++} allows function
1487 overloading (multiple definitions of the same function, distinguished
1488 by argument type). For example, when you want to set a breakpoint you
1489 may need to distinguish whether you mean the version of @code{name}
1490 that takes an @code{int} parameter, @code{name(int)}, or the version
1491 that takes a @code{float} parameter, @code{name(float)}. To use the
1492 word-completion facilities in this situation, type a single quote
1493 @code{'} at the beginning of the function name. This alerts
1494 @value{GDBN} that it may need to consider more information than usual
1495 when you press @key{TAB} or @kbd{M-?} to request word completion:
1498 (@value{GDBP}) b 'bubble( @kbd{M-?}
1499 bubble(double,double) bubble(int,int)
1500 (@value{GDBP}) b 'bubble(
1503 In some cases, @value{GDBN} can tell that completing a name requires using
1504 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1505 completing as much as it can) if you do not type the quote in the first
1509 (@value{GDBP}) b bub @key{TAB}
1510 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1511 (@value{GDBP}) b 'bubble(
1515 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1516 you have not yet started typing the argument list when you ask for
1517 completion on an overloaded symbol.
1519 For more information about overloaded functions, see @ref{C Plus Plus
1520 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1521 overload-resolution off} to disable overload resolution;
1522 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1526 @section Getting Help
1527 @cindex online documentation
1530 You can always ask @value{GDBN} itself for information on its commands,
1531 using the command @code{help}.
1534 @kindex h @r{(@code{help})}
1537 You can use @code{help} (abbreviated @code{h}) with no arguments to
1538 display a short list of named classes of commands:
1542 List of classes of commands:
1544 aliases -- Aliases of other commands
1545 breakpoints -- Making program stop at certain points
1546 data -- Examining data
1547 files -- Specifying and examining files
1548 internals -- Maintenance commands
1549 obscure -- Obscure features
1550 running -- Running the program
1551 stack -- Examining the stack
1552 status -- Status inquiries
1553 support -- Support facilities
1554 tracepoints -- Tracing of program execution without
1555 stopping the program
1556 user-defined -- User-defined commands
1558 Type "help" followed by a class name for a list of
1559 commands in that class.
1560 Type "help" followed by command name for full
1562 Command name abbreviations are allowed if unambiguous.
1565 @c the above line break eliminates huge line overfull...
1567 @item help @var{class}
1568 Using one of the general help classes as an argument, you can get a
1569 list of the individual commands in that class. For example, here is the
1570 help display for the class @code{status}:
1573 (@value{GDBP}) help status
1578 @c Line break in "show" line falsifies real output, but needed
1579 @c to fit in smallbook page size.
1580 info -- Generic command for showing things
1581 about the program being debugged
1582 show -- Generic command for showing things
1585 Type "help" followed by command name for full
1587 Command name abbreviations are allowed if unambiguous.
1591 @item help @var{command}
1592 With a command name as @code{help} argument, @value{GDBN} displays a
1593 short paragraph on how to use that command.
1596 @item apropos @var{args}
1597 The @code{apropos} command searches through all of the @value{GDBN}
1598 commands, and their documentation, for the regular expression specified in
1599 @var{args}. It prints out all matches found. For example:
1610 set symbol-reloading -- Set dynamic symbol table reloading
1611 multiple times in one run
1612 show symbol-reloading -- Show dynamic symbol table reloading
1613 multiple times in one run
1618 @item complete @var{args}
1619 The @code{complete @var{args}} command lists all the possible completions
1620 for the beginning of a command. Use @var{args} to specify the beginning of the
1621 command you want completed. For example:
1627 @noindent results in:
1638 @noindent This is intended for use by @sc{gnu} Emacs.
1641 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1642 and @code{show} to inquire about the state of your program, or the state
1643 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1644 manual introduces each of them in the appropriate context. The listings
1645 under @code{info} and under @code{show} in the Index point to
1646 all the sub-commands. @xref{Index}.
1651 @kindex i @r{(@code{info})}
1653 This command (abbreviated @code{i}) is for describing the state of your
1654 program. For example, you can list the arguments given to your program
1655 with @code{info args}, list the registers currently in use with @code{info
1656 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1657 You can get a complete list of the @code{info} sub-commands with
1658 @w{@code{help info}}.
1662 You can assign the result of an expression to an environment variable with
1663 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1664 @code{set prompt $}.
1668 In contrast to @code{info}, @code{show} is for describing the state of
1669 @value{GDBN} itself.
1670 You can change most of the things you can @code{show}, by using the
1671 related command @code{set}; for example, you can control what number
1672 system is used for displays with @code{set radix}, or simply inquire
1673 which is currently in use with @code{show radix}.
1676 To display all the settable parameters and their current
1677 values, you can use @code{show} with no arguments; you may also use
1678 @code{info set}. Both commands produce the same display.
1679 @c FIXME: "info set" violates the rule that "info" is for state of
1680 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1681 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1685 Here are three miscellaneous @code{show} subcommands, all of which are
1686 exceptional in lacking corresponding @code{set} commands:
1689 @kindex show version
1690 @cindex @value{GDBN} version number
1692 Show what version of @value{GDBN} is running. You should include this
1693 information in @value{GDBN} bug-reports. If multiple versions of
1694 @value{GDBN} are in use at your site, you may need to determine which
1695 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1696 commands are introduced, and old ones may wither away. Also, many
1697 system vendors ship variant versions of @value{GDBN}, and there are
1698 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1699 The version number is the same as the one announced when you start
1702 @kindex show copying
1703 @kindex info copying
1704 @cindex display @value{GDBN} copyright
1707 Display information about permission for copying @value{GDBN}.
1709 @kindex show warranty
1710 @kindex info warranty
1712 @itemx info warranty
1713 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1714 if your version of @value{GDBN} comes with one.
1719 @chapter Running Programs Under @value{GDBN}
1721 When you run a program under @value{GDBN}, you must first generate
1722 debugging information when you compile it.
1724 You may start @value{GDBN} with its arguments, if any, in an environment
1725 of your choice. If you are doing native debugging, you may redirect
1726 your program's input and output, debug an already running process, or
1727 kill a child process.
1730 * Compilation:: Compiling for debugging
1731 * Starting:: Starting your program
1732 * Arguments:: Your program's arguments
1733 * Environment:: Your program's environment
1735 * Working Directory:: Your program's working directory
1736 * Input/Output:: Your program's input and output
1737 * Attach:: Debugging an already-running process
1738 * Kill Process:: Killing the child process
1740 * Threads:: Debugging programs with multiple threads
1741 * Processes:: Debugging programs with multiple processes
1742 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1746 @section Compiling for Debugging
1748 In order to debug a program effectively, you need to generate
1749 debugging information when you compile it. This debugging information
1750 is stored in the object file; it describes the data type of each
1751 variable or function and the correspondence between source line numbers
1752 and addresses in the executable code.
1754 To request debugging information, specify the @samp{-g} option when you run
1757 Programs that are to be shipped to your customers are compiled with
1758 optimizations, using the @samp{-O} compiler option. However, many
1759 compilers are unable to handle the @samp{-g} and @samp{-O} options
1760 together. Using those compilers, you cannot generate optimized
1761 executables containing debugging information.
1763 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1764 without @samp{-O}, making it possible to debug optimized code. We
1765 recommend that you @emph{always} use @samp{-g} whenever you compile a
1766 program. You may think your program is correct, but there is no sense
1767 in pushing your luck.
1769 @cindex optimized code, debugging
1770 @cindex debugging optimized code
1771 When you debug a program compiled with @samp{-g -O}, remember that the
1772 optimizer is rearranging your code; the debugger shows you what is
1773 really there. Do not be too surprised when the execution path does not
1774 exactly match your source file! An extreme example: if you define a
1775 variable, but never use it, @value{GDBN} never sees that
1776 variable---because the compiler optimizes it out of existence.
1778 Some things do not work as well with @samp{-g -O} as with just
1779 @samp{-g}, particularly on machines with instruction scheduling. If in
1780 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1781 please report it to us as a bug (including a test case!).
1782 @xref{Variables}, for more information about debugging optimized code.
1784 Older versions of the @sc{gnu} C compiler permitted a variant option
1785 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1786 format; if your @sc{gnu} C compiler has this option, do not use it.
1788 @value{GDBN} knows about preprocessor macros and can show you their
1789 expansion (@pxref{Macros}). Most compilers do not include information
1790 about preprocessor macros in the debugging information if you specify
1791 the @option{-g} flag alone, because this information is rather large.
1792 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1793 provides macro information if you specify the options
1794 @option{-gdwarf-2} and @option{-g3}; the former option requests
1795 debugging information in the Dwarf 2 format, and the latter requests
1796 ``extra information''. In the future, we hope to find more compact
1797 ways to represent macro information, so that it can be included with
1802 @section Starting your Program
1808 @kindex r @r{(@code{run})}
1811 Use the @code{run} command to start your program under @value{GDBN}.
1812 You must first specify the program name (except on VxWorks) with an
1813 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1814 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1815 (@pxref{Files, ,Commands to Specify Files}).
1819 If you are running your program in an execution environment that
1820 supports processes, @code{run} creates an inferior process and makes
1821 that process run your program. (In environments without processes,
1822 @code{run} jumps to the start of your program.)
1824 The execution of a program is affected by certain information it
1825 receives from its superior. @value{GDBN} provides ways to specify this
1826 information, which you must do @emph{before} starting your program. (You
1827 can change it after starting your program, but such changes only affect
1828 your program the next time you start it.) This information may be
1829 divided into four categories:
1832 @item The @emph{arguments.}
1833 Specify the arguments to give your program as the arguments of the
1834 @code{run} command. If a shell is available on your target, the shell
1835 is used to pass the arguments, so that you may use normal conventions
1836 (such as wildcard expansion or variable substitution) in describing
1838 In Unix systems, you can control which shell is used with the
1839 @code{SHELL} environment variable.
1840 @xref{Arguments, ,Your Program's Arguments}.
1842 @item The @emph{environment.}
1843 Your program normally inherits its environment from @value{GDBN}, but you can
1844 use the @value{GDBN} commands @code{set environment} and @code{unset
1845 environment} to change parts of the environment that affect
1846 your program. @xref{Environment, ,Your Program's Environment}.
1848 @item The @emph{working directory.}
1849 Your program inherits its working directory from @value{GDBN}. You can set
1850 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1851 @xref{Working Directory, ,Your Program's Working Directory}.
1853 @item The @emph{standard input and output.}
1854 Your program normally uses the same device for standard input and
1855 standard output as @value{GDBN} is using. You can redirect input and output
1856 in the @code{run} command line, or you can use the @code{tty} command to
1857 set a different device for your program.
1858 @xref{Input/Output, ,Your Program's Input and Output}.
1861 @emph{Warning:} While input and output redirection work, you cannot use
1862 pipes to pass the output of the program you are debugging to another
1863 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1867 When you issue the @code{run} command, your program begins to execute
1868 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1869 of how to arrange for your program to stop. Once your program has
1870 stopped, you may call functions in your program, using the @code{print}
1871 or @code{call} commands. @xref{Data, ,Examining Data}.
1873 If the modification time of your symbol file has changed since the last
1874 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1875 table, and reads it again. When it does this, @value{GDBN} tries to retain
1876 your current breakpoints.
1881 @cindex run to main procedure
1882 The name of the main procedure can vary from language to language.
1883 With C or C@t{++}, the main procedure name is always @code{main}, but
1884 other languages such as Ada do not require a specific name for their
1885 main procedure. The debugger provides a convenient way to start the
1886 execution of the program and to stop at the beginning of the main
1887 procedure, depending on the language used.
1889 The @samp{start} command does the equivalent of setting a temporary
1890 breakpoint at the beginning of the main procedure and then invoking
1891 the @samp{run} command.
1893 @cindex elaboration phase
1894 Some programs contain an @dfn{elaboration} phase where some startup code is
1895 executed before the main procedure is called. This depends on the
1896 languages used to write your program. In C@t{++}, for instance,
1897 constructors for static and global objects are executed before
1898 @code{main} is called. It is therefore possible that the debugger stops
1899 before reaching the main procedure. However, the temporary breakpoint
1900 will remain to halt execution.
1902 Specify the arguments to give to your program as arguments to the
1903 @samp{start} command. These arguments will be given verbatim to the
1904 underlying @samp{run} command. Note that the same arguments will be
1905 reused if no argument is provided during subsequent calls to
1906 @samp{start} or @samp{run}.
1908 It is sometimes necessary to debug the program during elaboration. In
1909 these cases, using the @code{start} command would stop the execution of
1910 your program too late, as the program would have already completed the
1911 elaboration phase. Under these circumstances, insert breakpoints in your
1912 elaboration code before running your program.
1916 @section Your Program's Arguments
1918 @cindex arguments (to your program)
1919 The arguments to your program can be specified by the arguments of the
1921 They are passed to a shell, which expands wildcard characters and
1922 performs redirection of I/O, and thence to your program. Your
1923 @code{SHELL} environment variable (if it exists) specifies what shell
1924 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1925 the default shell (@file{/bin/sh} on Unix).
1927 On non-Unix systems, the program is usually invoked directly by
1928 @value{GDBN}, which emulates I/O redirection via the appropriate system
1929 calls, and the wildcard characters are expanded by the startup code of
1930 the program, not by the shell.
1932 @code{run} with no arguments uses the same arguments used by the previous
1933 @code{run}, or those set by the @code{set args} command.
1938 Specify the arguments to be used the next time your program is run. If
1939 @code{set args} has no arguments, @code{run} executes your program
1940 with no arguments. Once you have run your program with arguments,
1941 using @code{set args} before the next @code{run} is the only way to run
1942 it again without arguments.
1946 Show the arguments to give your program when it is started.
1950 @section Your Program's Environment
1952 @cindex environment (of your program)
1953 The @dfn{environment} consists of a set of environment variables and
1954 their values. Environment variables conventionally record such things as
1955 your user name, your home directory, your terminal type, and your search
1956 path for programs to run. Usually you set up environment variables with
1957 the shell and they are inherited by all the other programs you run. When
1958 debugging, it can be useful to try running your program with a modified
1959 environment without having to start @value{GDBN} over again.
1963 @item path @var{directory}
1964 Add @var{directory} to the front of the @code{PATH} environment variable
1965 (the search path for executables) that will be passed to your program.
1966 The value of @code{PATH} used by @value{GDBN} does not change.
1967 You may specify several directory names, separated by whitespace or by a
1968 system-dependent separator character (@samp{:} on Unix, @samp{;} on
1969 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
1970 is moved to the front, so it is searched sooner.
1972 You can use the string @samp{$cwd} to refer to whatever is the current
1973 working directory at the time @value{GDBN} searches the path. If you
1974 use @samp{.} instead, it refers to the directory where you executed the
1975 @code{path} command. @value{GDBN} replaces @samp{.} in the
1976 @var{directory} argument (with the current path) before adding
1977 @var{directory} to the search path.
1978 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
1979 @c document that, since repeating it would be a no-op.
1983 Display the list of search paths for executables (the @code{PATH}
1984 environment variable).
1986 @kindex show environment
1987 @item show environment @r{[}@var{varname}@r{]}
1988 Print the value of environment variable @var{varname} to be given to
1989 your program when it starts. If you do not supply @var{varname},
1990 print the names and values of all environment variables to be given to
1991 your program. You can abbreviate @code{environment} as @code{env}.
1993 @kindex set environment
1994 @item set environment @var{varname} @r{[}=@var{value}@r{]}
1995 Set environment variable @var{varname} to @var{value}. The value
1996 changes for your program only, not for @value{GDBN} itself. @var{value} may
1997 be any string; the values of environment variables are just strings, and
1998 any interpretation is supplied by your program itself. The @var{value}
1999 parameter is optional; if it is eliminated, the variable is set to a
2001 @c "any string" here does not include leading, trailing
2002 @c blanks. Gnu asks: does anyone care?
2004 For example, this command:
2011 tells the debugged program, when subsequently run, that its user is named
2012 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2013 are not actually required.)
2015 @kindex unset environment
2016 @item unset environment @var{varname}
2017 Remove variable @var{varname} from the environment to be passed to your
2018 program. This is different from @samp{set env @var{varname} =};
2019 @code{unset environment} removes the variable from the environment,
2020 rather than assigning it an empty value.
2023 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2025 by your @code{SHELL} environment variable if it exists (or
2026 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2027 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2028 @file{.bashrc} for BASH---any variables you set in that file affect
2029 your program. You may wish to move setting of environment variables to
2030 files that are only run when you sign on, such as @file{.login} or
2033 @node Working Directory
2034 @section Your Program's Working Directory
2036 @cindex working directory (of your program)
2037 Each time you start your program with @code{run}, it inherits its
2038 working directory from the current working directory of @value{GDBN}.
2039 The @value{GDBN} working directory is initially whatever it inherited
2040 from its parent process (typically the shell), but you can specify a new
2041 working directory in @value{GDBN} with the @code{cd} command.
2043 The @value{GDBN} working directory also serves as a default for the commands
2044 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2049 @cindex change working directory
2050 @item cd @var{directory}
2051 Set the @value{GDBN} working directory to @var{directory}.
2055 Print the @value{GDBN} working directory.
2058 It is generally impossible to find the current working directory of
2059 the process being debugged (since a program can change its directory
2060 during its run). If you work on a system where @value{GDBN} is
2061 configured with the @file{/proc} support, you can use the @code{info
2062 proc} command (@pxref{SVR4 Process Information}) to find out the
2063 current working directory of the debuggee.
2066 @section Your Program's Input and Output
2071 By default, the program you run under @value{GDBN} does input and output to
2072 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2073 to its own terminal modes to interact with you, but it records the terminal
2074 modes your program was using and switches back to them when you continue
2075 running your program.
2078 @kindex info terminal
2080 Displays information recorded by @value{GDBN} about the terminal modes your
2084 You can redirect your program's input and/or output using shell
2085 redirection with the @code{run} command. For example,
2092 starts your program, diverting its output to the file @file{outfile}.
2095 @cindex controlling terminal
2096 Another way to specify where your program should do input and output is
2097 with the @code{tty} command. This command accepts a file name as
2098 argument, and causes this file to be the default for future @code{run}
2099 commands. It also resets the controlling terminal for the child
2100 process, for future @code{run} commands. For example,
2107 directs that processes started with subsequent @code{run} commands
2108 default to do input and output on the terminal @file{/dev/ttyb} and have
2109 that as their controlling terminal.
2111 An explicit redirection in @code{run} overrides the @code{tty} command's
2112 effect on the input/output device, but not its effect on the controlling
2115 When you use the @code{tty} command or redirect input in the @code{run}
2116 command, only the input @emph{for your program} is affected. The input
2117 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2118 for @code{set inferior-tty}.
2120 @cindex inferior tty
2121 @cindex set inferior controlling terminal
2122 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2123 display the name of the terminal that will be used for future runs of your
2127 @item set inferior-tty /dev/ttyb
2128 @kindex set inferior-tty
2129 Set the tty for the program being debugged to /dev/ttyb.
2131 @item show inferior-tty
2132 @kindex show inferior-tty
2133 Show the current tty for the program being debugged.
2137 @section Debugging an Already-running Process
2142 @item attach @var{process-id}
2143 This command attaches to a running process---one that was started
2144 outside @value{GDBN}. (@code{info files} shows your active
2145 targets.) The command takes as argument a process ID. The usual way to
2146 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2147 or with the @samp{jobs -l} shell command.
2149 @code{attach} does not repeat if you press @key{RET} a second time after
2150 executing the command.
2153 To use @code{attach}, your program must be running in an environment
2154 which supports processes; for example, @code{attach} does not work for
2155 programs on bare-board targets that lack an operating system. You must
2156 also have permission to send the process a signal.
2158 When you use @code{attach}, the debugger finds the program running in
2159 the process first by looking in the current working directory, then (if
2160 the program is not found) by using the source file search path
2161 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2162 the @code{file} command to load the program. @xref{Files, ,Commands to
2165 The first thing @value{GDBN} does after arranging to debug the specified
2166 process is to stop it. You can examine and modify an attached process
2167 with all the @value{GDBN} commands that are ordinarily available when
2168 you start processes with @code{run}. You can insert breakpoints; you
2169 can step and continue; you can modify storage. If you would rather the
2170 process continue running, you may use the @code{continue} command after
2171 attaching @value{GDBN} to the process.
2176 When you have finished debugging the attached process, you can use the
2177 @code{detach} command to release it from @value{GDBN} control. Detaching
2178 the process continues its execution. After the @code{detach} command,
2179 that process and @value{GDBN} become completely independent once more, and you
2180 are ready to @code{attach} another process or start one with @code{run}.
2181 @code{detach} does not repeat if you press @key{RET} again after
2182 executing the command.
2185 If you exit @value{GDBN} while you have an attached process, you detach
2186 that process. If you use the @code{run} command, you kill that process.
2187 By default, @value{GDBN} asks for confirmation if you try to do either of these
2188 things; you can control whether or not you need to confirm by using the
2189 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2193 @section Killing the Child Process
2198 Kill the child process in which your program is running under @value{GDBN}.
2201 This command is useful if you wish to debug a core dump instead of a
2202 running process. @value{GDBN} ignores any core dump file while your program
2205 On some operating systems, a program cannot be executed outside @value{GDBN}
2206 while you have breakpoints set on it inside @value{GDBN}. You can use the
2207 @code{kill} command in this situation to permit running your program
2208 outside the debugger.
2210 The @code{kill} command is also useful if you wish to recompile and
2211 relink your program, since on many systems it is impossible to modify an
2212 executable file while it is running in a process. In this case, when you
2213 next type @code{run}, @value{GDBN} notices that the file has changed, and
2214 reads the symbol table again (while trying to preserve your current
2215 breakpoint settings).
2218 @section Debugging Programs with Multiple Threads
2220 @cindex threads of execution
2221 @cindex multiple threads
2222 @cindex switching threads
2223 In some operating systems, such as HP-UX and Solaris, a single program
2224 may have more than one @dfn{thread} of execution. The precise semantics
2225 of threads differ from one operating system to another, but in general
2226 the threads of a single program are akin to multiple processes---except
2227 that they share one address space (that is, they can all examine and
2228 modify the same variables). On the other hand, each thread has its own
2229 registers and execution stack, and perhaps private memory.
2231 @value{GDBN} provides these facilities for debugging multi-thread
2235 @item automatic notification of new threads
2236 @item @samp{thread @var{threadno}}, a command to switch among threads
2237 @item @samp{info threads}, a command to inquire about existing threads
2238 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2239 a command to apply a command to a list of threads
2240 @item thread-specific breakpoints
2244 @emph{Warning:} These facilities are not yet available on every
2245 @value{GDBN} configuration where the operating system supports threads.
2246 If your @value{GDBN} does not support threads, these commands have no
2247 effect. For example, a system without thread support shows no output
2248 from @samp{info threads}, and always rejects the @code{thread} command,
2252 (@value{GDBP}) info threads
2253 (@value{GDBP}) thread 1
2254 Thread ID 1 not known. Use the "info threads" command to
2255 see the IDs of currently known threads.
2257 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2258 @c doesn't support threads"?
2261 @cindex focus of debugging
2262 @cindex current thread
2263 The @value{GDBN} thread debugging facility allows you to observe all
2264 threads while your program runs---but whenever @value{GDBN} takes
2265 control, one thread in particular is always the focus of debugging.
2266 This thread is called the @dfn{current thread}. Debugging commands show
2267 program information from the perspective of the current thread.
2269 @cindex @code{New} @var{systag} message
2270 @cindex thread identifier (system)
2271 @c FIXME-implementors!! It would be more helpful if the [New...] message
2272 @c included GDB's numeric thread handle, so you could just go to that
2273 @c thread without first checking `info threads'.
2274 Whenever @value{GDBN} detects a new thread in your program, it displays
2275 the target system's identification for the thread with a message in the
2276 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2277 whose form varies depending on the particular system. For example, on
2278 @sc{gnu}/Linux, you might see
2281 [New Thread 46912507313328 (LWP 25582)]
2285 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2286 the @var{systag} is simply something like @samp{process 368}, with no
2289 @c FIXME!! (1) Does the [New...] message appear even for the very first
2290 @c thread of a program, or does it only appear for the
2291 @c second---i.e.@: when it becomes obvious we have a multithread
2293 @c (2) *Is* there necessarily a first thread always? Or do some
2294 @c multithread systems permit starting a program with multiple
2295 @c threads ab initio?
2297 @cindex thread number
2298 @cindex thread identifier (GDB)
2299 For debugging purposes, @value{GDBN} associates its own thread
2300 number---always a single integer---with each thread in your program.
2303 @kindex info threads
2305 Display a summary of all threads currently in your
2306 program. @value{GDBN} displays for each thread (in this order):
2310 the thread number assigned by @value{GDBN}
2313 the target system's thread identifier (@var{systag})
2316 the current stack frame summary for that thread
2320 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2321 indicates the current thread.
2325 @c end table here to get a little more width for example
2328 (@value{GDBP}) info threads
2329 3 process 35 thread 27 0x34e5 in sigpause ()
2330 2 process 35 thread 23 0x34e5 in sigpause ()
2331 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2337 @cindex debugging multithreaded programs (on HP-UX)
2338 @cindex thread identifier (GDB), on HP-UX
2339 For debugging purposes, @value{GDBN} associates its own thread
2340 number---a small integer assigned in thread-creation order---with each
2341 thread in your program.
2343 @cindex @code{New} @var{systag} message, on HP-UX
2344 @cindex thread identifier (system), on HP-UX
2345 @c FIXME-implementors!! It would be more helpful if the [New...] message
2346 @c included GDB's numeric thread handle, so you could just go to that
2347 @c thread without first checking `info threads'.
2348 Whenever @value{GDBN} detects a new thread in your program, it displays
2349 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2350 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2351 whose form varies depending on the particular system. For example, on
2355 [New thread 2 (system thread 26594)]
2359 when @value{GDBN} notices a new thread.
2362 @kindex info threads (HP-UX)
2364 Display a summary of all threads currently in your
2365 program. @value{GDBN} displays for each thread (in this order):
2368 @item the thread number assigned by @value{GDBN}
2370 @item the target system's thread identifier (@var{systag})
2372 @item the current stack frame summary for that thread
2376 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2377 indicates the current thread.
2381 @c end table here to get a little more width for example
2384 (@value{GDBP}) info threads
2385 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2387 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2388 from /usr/lib/libc.2
2389 1 system thread 27905 0x7b003498 in _brk () \@*
2390 from /usr/lib/libc.2
2393 On Solaris, you can display more information about user threads with a
2394 Solaris-specific command:
2397 @item maint info sol-threads
2398 @kindex maint info sol-threads
2399 @cindex thread info (Solaris)
2400 Display info on Solaris user threads.
2404 @kindex thread @var{threadno}
2405 @item thread @var{threadno}
2406 Make thread number @var{threadno} the current thread. The command
2407 argument @var{threadno} is the internal @value{GDBN} thread number, as
2408 shown in the first field of the @samp{info threads} display.
2409 @value{GDBN} responds by displaying the system identifier of the thread
2410 you selected, and its current stack frame summary:
2413 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2414 (@value{GDBP}) thread 2
2415 [Switching to process 35 thread 23]
2416 0x34e5 in sigpause ()
2420 As with the @samp{[New @dots{}]} message, the form of the text after
2421 @samp{Switching to} depends on your system's conventions for identifying
2424 @kindex thread apply
2425 @cindex apply command to several threads
2426 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2427 The @code{thread apply} command allows you to apply the named
2428 @var{command} to one or more threads. Specify the numbers of the
2429 threads that you want affected with the command argument
2430 @var{threadno}. It can be a single thread number, one of the numbers
2431 shown in the first field of the @samp{info threads} display; or it
2432 could be a range of thread numbers, as in @code{2-4}. To apply a
2433 command to all threads, type @kbd{thread apply all @var{command}}.
2436 @cindex automatic thread selection
2437 @cindex switching threads automatically
2438 @cindex threads, automatic switching
2439 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2440 signal, it automatically selects the thread where that breakpoint or
2441 signal happened. @value{GDBN} alerts you to the context switch with a
2442 message of the form @samp{[Switching to @var{systag}]} to identify the
2445 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2446 more information about how @value{GDBN} behaves when you stop and start
2447 programs with multiple threads.
2449 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2450 watchpoints in programs with multiple threads.
2453 @section Debugging Programs with Multiple Processes
2455 @cindex fork, debugging programs which call
2456 @cindex multiple processes
2457 @cindex processes, multiple
2458 On most systems, @value{GDBN} has no special support for debugging
2459 programs which create additional processes using the @code{fork}
2460 function. When a program forks, @value{GDBN} will continue to debug the
2461 parent process and the child process will run unimpeded. If you have
2462 set a breakpoint in any code which the child then executes, the child
2463 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2464 will cause it to terminate.
2466 However, if you want to debug the child process there is a workaround
2467 which isn't too painful. Put a call to @code{sleep} in the code which
2468 the child process executes after the fork. It may be useful to sleep
2469 only if a certain environment variable is set, or a certain file exists,
2470 so that the delay need not occur when you don't want to run @value{GDBN}
2471 on the child. While the child is sleeping, use the @code{ps} program to
2472 get its process ID. Then tell @value{GDBN} (a new invocation of
2473 @value{GDBN} if you are also debugging the parent process) to attach to
2474 the child process (@pxref{Attach}). From that point on you can debug
2475 the child process just like any other process which you attached to.
2477 On some systems, @value{GDBN} provides support for debugging programs that
2478 create additional processes using the @code{fork} or @code{vfork} functions.
2479 Currently, the only platforms with this feature are HP-UX (11.x and later
2480 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2482 By default, when a program forks, @value{GDBN} will continue to debug
2483 the parent process and the child process will run unimpeded.
2485 If you want to follow the child process instead of the parent process,
2486 use the command @w{@code{set follow-fork-mode}}.
2489 @kindex set follow-fork-mode
2490 @item set follow-fork-mode @var{mode}
2491 Set the debugger response to a program call of @code{fork} or
2492 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2493 process. The @var{mode} argument can be:
2497 The original process is debugged after a fork. The child process runs
2498 unimpeded. This is the default.
2501 The new process is debugged after a fork. The parent process runs
2506 @kindex show follow-fork-mode
2507 @item show follow-fork-mode
2508 Display the current debugger response to a @code{fork} or @code{vfork} call.
2511 @cindex debugging multiple processes
2512 On Linux, if you want to debug both the parent and child processes, use the
2513 command @w{@code{set detach-on-fork}}.
2516 @kindex set detach-on-fork
2517 @item set detach-on-fork @var{mode}
2518 Tells gdb whether to detach one of the processes after a fork, or
2519 retain debugger control over them both.
2523 The child process (or parent process, depending on the value of
2524 @code{follow-fork-mode}) will be detached and allowed to run
2525 independently. This is the default.
2528 Both processes will be held under the control of @value{GDBN}.
2529 One process (child or parent, depending on the value of
2530 @code{follow-fork-mode}) is debugged as usual, while the other
2535 @kindex show detach-on-follow
2536 @item show detach-on-follow
2537 Show whether detach-on-follow mode is on/off.
2540 If you choose to set @var{detach-on-follow} mode off, then
2541 @value{GDBN} will retain control of all forked processes (including
2542 nested forks). You can list the forked processes under the control of
2543 @value{GDBN} by using the @w{@code{info forks}} command, and switch
2544 from one fork to another by using the @w{@code{fork}} command.
2549 Print a list of all forked processes under the control of @value{GDBN}.
2550 The listing will include a fork id, a process id, and the current
2551 position (program counter) of the process.
2554 @kindex fork @var{fork-id}
2555 @item fork @var{fork-id}
2556 Make fork number @var{fork-id} the current process. The argument
2557 @var{fork-id} is the internal fork number assigned by @value{GDBN},
2558 as shown in the first field of the @samp{info forks} display.
2562 To quit debugging one of the forked processes, you can either detach
2563 from it by using the @w{@code{detach fork}} command (allowing it to
2564 run independently), or delete (and kill) it using the
2565 @w{@code{delete fork}} command.
2568 @kindex detach fork @var{fork-id}
2569 @item detach fork @var{fork-id}
2570 Detach from the process identified by @value{GDBN} fork number
2571 @var{fork-id}, and remove it from the fork list. The process will be
2572 allowed to run independently.
2574 @kindex delete fork @var{fork-id}
2575 @item delete fork @var{fork-id}
2576 Kill the process identified by @value{GDBN} fork number @var{fork-id},
2577 and remove it from the fork list.
2581 If you ask to debug a child process and a @code{vfork} is followed by an
2582 @code{exec}, @value{GDBN} executes the new target up to the first
2583 breakpoint in the new target. If you have a breakpoint set on
2584 @code{main} in your original program, the breakpoint will also be set on
2585 the child process's @code{main}.
2587 When a child process is spawned by @code{vfork}, you cannot debug the
2588 child or parent until an @code{exec} call completes.
2590 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2591 call executes, the new target restarts. To restart the parent process,
2592 use the @code{file} command with the parent executable name as its
2595 You can use the @code{catch} command to make @value{GDBN} stop whenever
2596 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2597 Catchpoints, ,Setting Catchpoints}.
2599 @node Checkpoint/Restart
2600 @section Setting a @emph{Bookmark} to Return to Later
2605 @cindex snapshot of a process
2606 @cindex rewind program state
2608 On certain operating systems@footnote{Currently, only
2609 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
2610 program's state, called a @dfn{checkpoint}, and come back to it
2613 Returning to a checkpoint effectively undoes everything that has
2614 happened in the program since the @code{checkpoint} was saved. This
2615 includes changes in memory, registers, and even (within some limits)
2616 system state. Effectively, it is like going back in time to the
2617 moment when the checkpoint was saved.
2619 Thus, if you're stepping thru a program and you think you're
2620 getting close to the point where things go wrong, you can save
2621 a checkpoint. Then, if you accidentally go too far and miss
2622 the critical statement, instead of having to restart your program
2623 from the beginning, you can just go back to the checkpoint and
2624 start again from there.
2626 This can be especially useful if it takes a lot of time or
2627 steps to reach the point where you think the bug occurs.
2629 To use the @code{checkpoint}/@code{restart} method of debugging:
2634 Save a snapshot of the debugged program's current execution state.
2635 The @code{checkpoint} command takes no arguments, but each checkpoint
2636 is assigned a small integer id, similar to a breakpoint id.
2638 @kindex info checkpoints
2639 @item info checkpoints
2640 List the checkpoints that have been saved in the current debugging
2641 session. For each checkpoint, the following information will be
2648 @item Source line, or label
2651 @kindex restart @var{checkpoint-id}
2652 @item restart @var{checkpoint-id}
2653 Restore the program state that was saved as checkpoint number
2654 @var{checkpoint-id}. All program variables, registers, stack frames
2655 etc.@: will be returned to the values that they had when the checkpoint
2656 was saved. In essence, gdb will ``wind back the clock'' to the point
2657 in time when the checkpoint was saved.
2659 Note that breakpoints, @value{GDBN} variables, command history etc.
2660 are not affected by restoring a checkpoint. In general, a checkpoint
2661 only restores things that reside in the program being debugged, not in
2664 @kindex delete checkpoint @var{checkpoint-id}
2665 @item delete checkpoint @var{checkpoint-id}
2666 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
2670 Returning to a previously saved checkpoint will restore the user state
2671 of the program being debugged, plus a significant subset of the system
2672 (OS) state, including file pointers. It won't ``un-write'' data from
2673 a file, but it will rewind the file pointer to the previous location,
2674 so that the previously written data can be overwritten. For files
2675 opened in read mode, the pointer will also be restored so that the
2676 previously read data can be read again.
2678 Of course, characters that have been sent to a printer (or other
2679 external device) cannot be ``snatched back'', and characters received
2680 from eg.@: a serial device can be removed from internal program buffers,
2681 but they cannot be ``pushed back'' into the serial pipeline, ready to
2682 be received again. Similarly, the actual contents of files that have
2683 been changed cannot be restored (at this time).
2685 However, within those constraints, you actually can ``rewind'' your
2686 program to a previously saved point in time, and begin debugging it
2687 again --- and you can change the course of events so as to debug a
2688 different execution path this time.
2690 @cindex checkpoints and process id
2691 Finally, there is one bit of internal program state that will be
2692 different when you return to a checkpoint --- the program's process
2693 id. Each checkpoint will have a unique process id (or @var{pid}),
2694 and each will be different from the program's original @var{pid}.
2695 If your program has saved a local copy of its process id, this could
2696 potentially pose a problem.
2698 @subsection A Non-obvious Benefit of Using Checkpoints
2700 On some systems such as @sc{gnu}/Linux, address space randomization
2701 is performed on new processes for security reasons. This makes it
2702 difficult or impossible to set a breakpoint, or watchpoint, on an
2703 absolute address if you have to restart the program, since the
2704 absolute location of a symbol will change from one execution to the
2707 A checkpoint, however, is an @emph{identical} copy of a process.
2708 Therefore if you create a checkpoint at (eg.@:) the start of main,
2709 and simply return to that checkpoint instead of restarting the
2710 process, you can avoid the effects of address randomization and
2711 your symbols will all stay in the same place.
2714 @chapter Stopping and Continuing
2716 The principal purposes of using a debugger are so that you can stop your
2717 program before it terminates; or so that, if your program runs into
2718 trouble, you can investigate and find out why.
2720 Inside @value{GDBN}, your program may stop for any of several reasons,
2721 such as a signal, a breakpoint, or reaching a new line after a
2722 @value{GDBN} command such as @code{step}. You may then examine and
2723 change variables, set new breakpoints or remove old ones, and then
2724 continue execution. Usually, the messages shown by @value{GDBN} provide
2725 ample explanation of the status of your program---but you can also
2726 explicitly request this information at any time.
2729 @kindex info program
2731 Display information about the status of your program: whether it is
2732 running or not, what process it is, and why it stopped.
2736 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2737 * Continuing and Stepping:: Resuming execution
2739 * Thread Stops:: Stopping and starting multi-thread programs
2743 @section Breakpoints, Watchpoints, and Catchpoints
2746 A @dfn{breakpoint} makes your program stop whenever a certain point in
2747 the program is reached. For each breakpoint, you can add conditions to
2748 control in finer detail whether your program stops. You can set
2749 breakpoints with the @code{break} command and its variants (@pxref{Set
2750 Breaks, ,Setting Breakpoints}), to specify the place where your program
2751 should stop by line number, function name or exact address in the
2754 On some systems, you can set breakpoints in shared libraries before
2755 the executable is run. There is a minor limitation on HP-UX systems:
2756 you must wait until the executable is run in order to set breakpoints
2757 in shared library routines that are not called directly by the program
2758 (for example, routines that are arguments in a @code{pthread_create}
2762 @cindex data breakpoints
2763 @cindex memory tracing
2764 @cindex breakpoint on memory address
2765 @cindex breakpoint on variable modification
2766 A @dfn{watchpoint} is a special breakpoint that stops your program
2767 when the value of an expression changes. The expression may be a value
2768 of a variable, or it could involve values of one or more variables
2769 combined by operators, such as @samp{a + b}. This is sometimes called
2770 @dfn{data breakpoints}. You must use a different command to set
2771 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
2772 from that, you can manage a watchpoint like any other breakpoint: you
2773 enable, disable, and delete both breakpoints and watchpoints using the
2776 You can arrange to have values from your program displayed automatically
2777 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2781 @cindex breakpoint on events
2782 A @dfn{catchpoint} is another special breakpoint that stops your program
2783 when a certain kind of event occurs, such as the throwing of a C@t{++}
2784 exception or the loading of a library. As with watchpoints, you use a
2785 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2786 Catchpoints}), but aside from that, you can manage a catchpoint like any
2787 other breakpoint. (To stop when your program receives a signal, use the
2788 @code{handle} command; see @ref{Signals, ,Signals}.)
2790 @cindex breakpoint numbers
2791 @cindex numbers for breakpoints
2792 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2793 catchpoint when you create it; these numbers are successive integers
2794 starting with one. In many of the commands for controlling various
2795 features of breakpoints you use the breakpoint number to say which
2796 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2797 @dfn{disabled}; if disabled, it has no effect on your program until you
2800 @cindex breakpoint ranges
2801 @cindex ranges of breakpoints
2802 Some @value{GDBN} commands accept a range of breakpoints on which to
2803 operate. A breakpoint range is either a single breakpoint number, like
2804 @samp{5}, or two such numbers, in increasing order, separated by a
2805 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2806 all breakpoints in that range are operated on.
2809 * Set Breaks:: Setting breakpoints
2810 * Set Watchpoints:: Setting watchpoints
2811 * Set Catchpoints:: Setting catchpoints
2812 * Delete Breaks:: Deleting breakpoints
2813 * Disabling:: Disabling breakpoints
2814 * Conditions:: Break conditions
2815 * Break Commands:: Breakpoint command lists
2816 * Breakpoint Menus:: Breakpoint menus
2817 * Error in Breakpoints:: ``Cannot insert breakpoints''
2818 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
2822 @subsection Setting Breakpoints
2824 @c FIXME LMB what does GDB do if no code on line of breakpt?
2825 @c consider in particular declaration with/without initialization.
2827 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2830 @kindex b @r{(@code{break})}
2831 @vindex $bpnum@r{, convenience variable}
2832 @cindex latest breakpoint
2833 Breakpoints are set with the @code{break} command (abbreviated
2834 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2835 number of the breakpoint you've set most recently; see @ref{Convenience
2836 Vars,, Convenience Variables}, for a discussion of what you can do with
2837 convenience variables.
2839 You have several ways to say where the breakpoint should go.
2842 @item break @var{function}
2843 Set a breakpoint at entry to function @var{function}.
2844 When using source languages that permit overloading of symbols, such as
2845 C@t{++}, @var{function} may refer to more than one possible place to break.
2846 @xref{Breakpoint Menus,,Breakpoint Menus}, for a discussion of that situation.
2848 @item break +@var{offset}
2849 @itemx break -@var{offset}
2850 Set a breakpoint some number of lines forward or back from the position
2851 at which execution stopped in the currently selected @dfn{stack frame}.
2852 (@xref{Frames, ,Frames}, for a description of stack frames.)
2854 @item break @var{linenum}
2855 Set a breakpoint at line @var{linenum} in the current source file.
2856 The current source file is the last file whose source text was printed.
2857 The breakpoint will stop your program just before it executes any of the
2860 @item break @var{filename}:@var{linenum}
2861 Set a breakpoint at line @var{linenum} in source file @var{filename}.
2863 @item break @var{filename}:@var{function}
2864 Set a breakpoint at entry to function @var{function} found in file
2865 @var{filename}. Specifying a file name as well as a function name is
2866 superfluous except when multiple files contain similarly named
2869 @item break *@var{address}
2870 Set a breakpoint at address @var{address}. You can use this to set
2871 breakpoints in parts of your program which do not have debugging
2872 information or source files.
2875 When called without any arguments, @code{break} sets a breakpoint at
2876 the next instruction to be executed in the selected stack frame
2877 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2878 innermost, this makes your program stop as soon as control
2879 returns to that frame. This is similar to the effect of a
2880 @code{finish} command in the frame inside the selected frame---except
2881 that @code{finish} does not leave an active breakpoint. If you use
2882 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2883 the next time it reaches the current location; this may be useful
2886 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2887 least one instruction has been executed. If it did not do this, you
2888 would be unable to proceed past a breakpoint without first disabling the
2889 breakpoint. This rule applies whether or not the breakpoint already
2890 existed when your program stopped.
2892 @item break @dots{} if @var{cond}
2893 Set a breakpoint with condition @var{cond}; evaluate the expression
2894 @var{cond} each time the breakpoint is reached, and stop only if the
2895 value is nonzero---that is, if @var{cond} evaluates as true.
2896 @samp{@dots{}} stands for one of the possible arguments described
2897 above (or no argument) specifying where to break. @xref{Conditions,
2898 ,Break Conditions}, for more information on breakpoint conditions.
2901 @item tbreak @var{args}
2902 Set a breakpoint enabled only for one stop. @var{args} are the
2903 same as for the @code{break} command, and the breakpoint is set in the same
2904 way, but the breakpoint is automatically deleted after the first time your
2905 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
2908 @cindex hardware breakpoints
2909 @item hbreak @var{args}
2910 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2911 @code{break} command and the breakpoint is set in the same way, but the
2912 breakpoint requires hardware support and some target hardware may not
2913 have this support. The main purpose of this is EPROM/ROM code
2914 debugging, so you can set a breakpoint at an instruction without
2915 changing the instruction. This can be used with the new trap-generation
2916 provided by SPARClite DSU and most x86-based targets. These targets
2917 will generate traps when a program accesses some data or instruction
2918 address that is assigned to the debug registers. However the hardware
2919 breakpoint registers can take a limited number of breakpoints. For
2920 example, on the DSU, only two data breakpoints can be set at a time, and
2921 @value{GDBN} will reject this command if more than two are used. Delete
2922 or disable unused hardware breakpoints before setting new ones
2923 (@pxref{Disabling, ,Disabling Breakpoints}).
2924 @xref{Conditions, ,Break Conditions}.
2925 For remote targets, you can restrict the number of hardware
2926 breakpoints @value{GDBN} will use, see @ref{set remote
2927 hardware-breakpoint-limit}.
2931 @item thbreak @var{args}
2932 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2933 are the same as for the @code{hbreak} command and the breakpoint is set in
2934 the same way. However, like the @code{tbreak} command,
2935 the breakpoint is automatically deleted after the
2936 first time your program stops there. Also, like the @code{hbreak}
2937 command, the breakpoint requires hardware support and some target hardware
2938 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
2939 See also @ref{Conditions, ,Break Conditions}.
2942 @cindex regular expression
2943 @cindex breakpoints in functions matching a regexp
2944 @cindex set breakpoints in many functions
2945 @item rbreak @var{regex}
2946 Set breakpoints on all functions matching the regular expression
2947 @var{regex}. This command sets an unconditional breakpoint on all
2948 matches, printing a list of all breakpoints it set. Once these
2949 breakpoints are set, they are treated just like the breakpoints set with
2950 the @code{break} command. You can delete them, disable them, or make
2951 them conditional the same way as any other breakpoint.
2953 The syntax of the regular expression is the standard one used with tools
2954 like @file{grep}. Note that this is different from the syntax used by
2955 shells, so for instance @code{foo*} matches all functions that include
2956 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2957 @code{.*} leading and trailing the regular expression you supply, so to
2958 match only functions that begin with @code{foo}, use @code{^foo}.
2960 @cindex non-member C@t{++} functions, set breakpoint in
2961 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2962 breakpoints on overloaded functions that are not members of any special
2965 @cindex set breakpoints on all functions
2966 The @code{rbreak} command can be used to set breakpoints in
2967 @strong{all} the functions in a program, like this:
2970 (@value{GDBP}) rbreak .
2973 @kindex info breakpoints
2974 @cindex @code{$_} and @code{info breakpoints}
2975 @item info breakpoints @r{[}@var{n}@r{]}
2976 @itemx info break @r{[}@var{n}@r{]}
2977 @itemx info watchpoints @r{[}@var{n}@r{]}
2978 Print a table of all breakpoints, watchpoints, and catchpoints set and
2979 not deleted. Optional argument @var{n} means print information only
2980 about the specified breakpoint (or watchpoint or catchpoint). For
2981 each breakpoint, following columns are printed:
2984 @item Breakpoint Numbers
2986 Breakpoint, watchpoint, or catchpoint.
2988 Whether the breakpoint is marked to be disabled or deleted when hit.
2989 @item Enabled or Disabled
2990 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
2991 that are not enabled. An optional @samp{(p)} suffix marks pending
2992 breakpoints---breakpoints for which address is either not yet
2993 resolved, pending load of a shared library, or for which address was
2994 in a shared library that was since unloaded. Such breakpoint won't
2995 fire until a shared library that has the symbol or line referred by
2996 breakpoint is loaded. See below for details.
2998 Where the breakpoint is in your program, as a memory address. For a
2999 pending breakpoint whose address is not yet known, this field will
3000 contain @samp{<PENDING>}. A breakpoint with several locations will
3001 have @samp{<MULTIPLE>} in this field---see below for details.
3003 Where the breakpoint is in the source for your program, as a file and
3004 line number. For a pending breakpoint, the original string passed to
3005 the breakpoint command will be listed as it cannot be resolved until
3006 the appropriate shared library is loaded in the future.
3010 If a breakpoint is conditional, @code{info break} shows the condition on
3011 the line following the affected breakpoint; breakpoint commands, if any,
3012 are listed after that. A pending breakpoint is allowed to have a condition
3013 specified for it. The condition is not parsed for validity until a shared
3014 library is loaded that allows the pending breakpoint to resolve to a
3018 @code{info break} with a breakpoint
3019 number @var{n} as argument lists only that breakpoint. The
3020 convenience variable @code{$_} and the default examining-address for
3021 the @code{x} command are set to the address of the last breakpoint
3022 listed (@pxref{Memory, ,Examining Memory}).
3025 @code{info break} displays a count of the number of times the breakpoint
3026 has been hit. This is especially useful in conjunction with the
3027 @code{ignore} command. You can ignore a large number of breakpoint
3028 hits, look at the breakpoint info to see how many times the breakpoint
3029 was hit, and then run again, ignoring one less than that number. This
3030 will get you quickly to the last hit of that breakpoint.
3033 @value{GDBN} allows you to set any number of breakpoints at the same place in
3034 your program. There is nothing silly or meaningless about this. When
3035 the breakpoints are conditional, this is even useful
3036 (@pxref{Conditions, ,Break Conditions}).
3038 It is possible that a breakpoint corresponds to several locations
3039 in your program. Examples of this situation are:
3044 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3045 instances of the function body, used in different cases.
3048 For a C@t{++} template function, a given line in the function can
3049 correspond to any number of instantiations.
3052 For an inlined function, a given source line can correspond to
3053 several places where that function is inlined.
3057 In all those cases, @value{GDBN} will insert a breakpoint at all
3058 the relevant locations.
3060 A breakpoint with multiple locations is displayed in the breakpoint
3061 table using several rows---one header row, followed by one row for
3062 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3063 address column. The rows for individual locations contain the actual
3064 addresses for locations, and show the functions to which those
3065 locations belong. The number column for a location is of the form
3066 @var{breakpoint-number}.@var{location-number}.
3071 Num Type Disp Enb Address What
3072 1 breakpoint keep y <MULTIPLE>
3074 breakpoint already hit 1 time
3075 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3076 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3079 Each location can be individually enabled or disabled by passing
3080 @var{breakpoint-number}.@var{location-number} as argument to the
3081 @code{enable} and @code{disable} commands. Note that you cannot
3082 delete the individual locations from the list, you can only delete the
3083 entire list of locations that belong to their parent breakpoint (with
3084 the @kbd{delete @var{num}} command, where @var{num} is the number of
3085 the parent breakpoint, 1 in the above example). Disabling or enabling
3086 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3087 that belong to that breakpoint.
3089 @cindex pending breakpoints
3090 It's quite common to have a breakpoint inside a shared library.
3091 Shared libraries can be loaded and unloaded explicitly,
3092 and possibly repeatedly, as the program is executed. To support
3093 this use case, @value{GDBN} updates breakpoint locations whenever
3094 any shared library is loaded or unloaded. Typically, you would
3095 set a breakpoint in a shared library at the beginning of your
3096 debugging session, when the library is not loaded, and when the
3097 symbols from the library are not available. When you try to set
3098 breakpoint, @value{GDBN} will ask you if you want to set
3099 a so called @dfn{pending breakpoint}---breakpoint whose address
3100 is not yet resolved.
3102 After the program is run, whenever a new shared library is loaded,
3103 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3104 shared library contains the symbol or line referred to by some
3105 pending breakpoint, that breakpoint is resolved and becomes an
3106 ordinary breakpoint. When a library is unloaded, all breakpoints
3107 that refer to its symbols or source lines become pending again.
3109 This logic works for breakpoints with multiple locations, too. For
3110 example, if you have a breakpoint in a C@t{++} template function, and
3111 a newly loaded shared library has an instantiation of that template,
3112 a new location is added to the list of locations for the breakpoint.
3114 Except for having unresolved address, pending breakpoints do not
3115 differ from regular breakpoints. You can set conditions or commands,
3116 enable and disable them and perform other breakpoint operations.
3118 @value{GDBN} provides some additional commands for controlling what
3119 happens when the @samp{break} command cannot resolve breakpoint
3120 address specification to an address:
3122 @kindex set breakpoint pending
3123 @kindex show breakpoint pending
3125 @item set breakpoint pending auto
3126 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3127 location, it queries you whether a pending breakpoint should be created.
3129 @item set breakpoint pending on
3130 This indicates that an unrecognized breakpoint location should automatically
3131 result in a pending breakpoint being created.
3133 @item set breakpoint pending off
3134 This indicates that pending breakpoints are not to be created. Any
3135 unrecognized breakpoint location results in an error. This setting does
3136 not affect any pending breakpoints previously created.
3138 @item show breakpoint pending
3139 Show the current behavior setting for creating pending breakpoints.
3142 The settings above only affect the @code{break} command and its
3143 variants. Once breakpoint is set, it will be automatically updated
3144 as shared libraries are loaded and unloaded.
3146 @cindex automatic hardware breakpoints
3147 For some targets, @value{GDBN} can automatically decide if hardware or
3148 software breakpoints should be used, depending on whether the
3149 breakpoint address is read-only or read-write. This applies to
3150 breakpoints set with the @code{break} command as well as to internal
3151 breakpoints set by commands like @code{next} and @code{finish}. For
3152 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3155 You can control this automatic behaviour with the following commands::
3157 @kindex set breakpoint auto-hw
3158 @kindex show breakpoint auto-hw
3160 @item set breakpoint auto-hw on
3161 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3162 will try to use the target memory map to decide if software or hardware
3163 breakpoint must be used.
3165 @item set breakpoint auto-hw off
3166 This indicates @value{GDBN} should not automatically select breakpoint
3167 type. If the target provides a memory map, @value{GDBN} will warn when
3168 trying to set software breakpoint at a read-only address.
3172 @cindex negative breakpoint numbers
3173 @cindex internal @value{GDBN} breakpoints
3174 @value{GDBN} itself sometimes sets breakpoints in your program for
3175 special purposes, such as proper handling of @code{longjmp} (in C
3176 programs). These internal breakpoints are assigned negative numbers,
3177 starting with @code{-1}; @samp{info breakpoints} does not display them.
3178 You can see these breakpoints with the @value{GDBN} maintenance command
3179 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3182 @node Set Watchpoints
3183 @subsection Setting Watchpoints
3185 @cindex setting watchpoints
3186 You can use a watchpoint to stop execution whenever the value of an
3187 expression changes, without having to predict a particular place where
3188 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3189 The expression may be as simple as the value of a single variable, or
3190 as complex as many variables combined by operators. Examples include:
3194 A reference to the value of a single variable.
3197 An address cast to an appropriate data type. For example,
3198 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3199 address (assuming an @code{int} occupies 4 bytes).
3202 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3203 expression can use any operators valid in the program's native
3204 language (@pxref{Languages}).
3207 @cindex software watchpoints
3208 @cindex hardware watchpoints
3209 Depending on your system, watchpoints may be implemented in software or
3210 hardware. @value{GDBN} does software watchpointing by single-stepping your
3211 program and testing the variable's value each time, which is hundreds of
3212 times slower than normal execution. (But this may still be worth it, to
3213 catch errors where you have no clue what part of your program is the
3216 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3217 x86-based targets, @value{GDBN} includes support for hardware
3218 watchpoints, which do not slow down the running of your program.
3222 @item watch @var{expr} @r{[}thread @var{threadnum}@r{]}
3223 Set a watchpoint for an expression. @value{GDBN} will break when the
3224 expression @var{expr} is written into by the program and its value
3225 changes. The simplest (and the most popular) use of this command is
3226 to watch the value of a single variable:
3229 (@value{GDBP}) watch foo
3232 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3233 clause, @value{GDBN} breaks only when the thread identified by
3234 @var{threadnum} changes the value of @var{expr}. If any other threads
3235 change the value of @var{expr}, @value{GDBN} will not break. Note
3236 that watchpoints restricted to a single thread in this way only work
3237 with Hardware Watchpoints.
3240 @item rwatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3241 Set a watchpoint that will break when the value of @var{expr} is read
3245 @item awatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3246 Set a watchpoint that will break when @var{expr} is either read from
3247 or written into by the program.
3249 @kindex info watchpoints @r{[}@var{n}@r{]}
3250 @item info watchpoints
3251 This command prints a list of watchpoints, breakpoints, and catchpoints;
3252 it is the same as @code{info break} (@pxref{Set Breaks}).
3255 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3256 watchpoints execute very quickly, and the debugger reports a change in
3257 value at the exact instruction where the change occurs. If @value{GDBN}
3258 cannot set a hardware watchpoint, it sets a software watchpoint, which
3259 executes more slowly and reports the change in value at the next
3260 @emph{statement}, not the instruction, after the change occurs.
3262 @cindex use only software watchpoints
3263 You can force @value{GDBN} to use only software watchpoints with the
3264 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3265 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3266 the underlying system supports them. (Note that hardware-assisted
3267 watchpoints that were set @emph{before} setting
3268 @code{can-use-hw-watchpoints} to zero will still use the hardware
3269 mechanism of watching expression values.)
3272 @item set can-use-hw-watchpoints
3273 @kindex set can-use-hw-watchpoints
3274 Set whether or not to use hardware watchpoints.
3276 @item show can-use-hw-watchpoints
3277 @kindex show can-use-hw-watchpoints
3278 Show the current mode of using hardware watchpoints.
3281 For remote targets, you can restrict the number of hardware
3282 watchpoints @value{GDBN} will use, see @ref{set remote
3283 hardware-breakpoint-limit}.
3285 When you issue the @code{watch} command, @value{GDBN} reports
3288 Hardware watchpoint @var{num}: @var{expr}
3292 if it was able to set a hardware watchpoint.
3294 Currently, the @code{awatch} and @code{rwatch} commands can only set
3295 hardware watchpoints, because accesses to data that don't change the
3296 value of the watched expression cannot be detected without examining
3297 every instruction as it is being executed, and @value{GDBN} does not do
3298 that currently. If @value{GDBN} finds that it is unable to set a
3299 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3300 will print a message like this:
3303 Expression cannot be implemented with read/access watchpoint.
3306 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3307 data type of the watched expression is wider than what a hardware
3308 watchpoint on the target machine can handle. For example, some systems
3309 can only watch regions that are up to 4 bytes wide; on such systems you
3310 cannot set hardware watchpoints for an expression that yields a
3311 double-precision floating-point number (which is typically 8 bytes
3312 wide). As a work-around, it might be possible to break the large region
3313 into a series of smaller ones and watch them with separate watchpoints.
3315 If you set too many hardware watchpoints, @value{GDBN} might be unable
3316 to insert all of them when you resume the execution of your program.
3317 Since the precise number of active watchpoints is unknown until such
3318 time as the program is about to be resumed, @value{GDBN} might not be
3319 able to warn you about this when you set the watchpoints, and the
3320 warning will be printed only when the program is resumed:
3323 Hardware watchpoint @var{num}: Could not insert watchpoint
3327 If this happens, delete or disable some of the watchpoints.
3329 Watching complex expressions that reference many variables can also
3330 exhaust the resources available for hardware-assisted watchpoints.
3331 That's because @value{GDBN} needs to watch every variable in the
3332 expression with separately allocated resources.
3334 The SPARClite DSU will generate traps when a program accesses some data
3335 or instruction address that is assigned to the debug registers. For the
3336 data addresses, DSU facilitates the @code{watch} command. However the
3337 hardware breakpoint registers can only take two data watchpoints, and
3338 both watchpoints must be the same kind. For example, you can set two
3339 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
3340 @strong{or} two with @code{awatch} commands, but you cannot set one
3341 watchpoint with one command and the other with a different command.
3342 @value{GDBN} will reject the command if you try to mix watchpoints.
3343 Delete or disable unused watchpoint commands before setting new ones.
3345 If you call a function interactively using @code{print} or @code{call},
3346 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3347 kind of breakpoint or the call completes.
3349 @value{GDBN} automatically deletes watchpoints that watch local
3350 (automatic) variables, or expressions that involve such variables, when
3351 they go out of scope, that is, when the execution leaves the block in
3352 which these variables were defined. In particular, when the program
3353 being debugged terminates, @emph{all} local variables go out of scope,
3354 and so only watchpoints that watch global variables remain set. If you
3355 rerun the program, you will need to set all such watchpoints again. One
3356 way of doing that would be to set a code breakpoint at the entry to the
3357 @code{main} function and when it breaks, set all the watchpoints.
3359 @cindex watchpoints and threads
3360 @cindex threads and watchpoints
3361 In multi-threaded programs, watchpoints will detect changes to the
3362 watched expression from every thread.
3365 @emph{Warning:} In multi-threaded programs, software watchpoints
3366 have only limited usefulness. If @value{GDBN} creates a software
3367 watchpoint, it can only watch the value of an expression @emph{in a
3368 single thread}. If you are confident that the expression can only
3369 change due to the current thread's activity (and if you are also
3370 confident that no other thread can become current), then you can use
3371 software watchpoints as usual. However, @value{GDBN} may not notice
3372 when a non-current thread's activity changes the expression. (Hardware
3373 watchpoints, in contrast, watch an expression in all threads.)
3376 @xref{set remote hardware-watchpoint-limit}.
3378 @node Set Catchpoints
3379 @subsection Setting Catchpoints
3380 @cindex catchpoints, setting
3381 @cindex exception handlers
3382 @cindex event handling
3384 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3385 kinds of program events, such as C@t{++} exceptions or the loading of a
3386 shared library. Use the @code{catch} command to set a catchpoint.
3390 @item catch @var{event}
3391 Stop when @var{event} occurs. @var{event} can be any of the following:
3394 @cindex stop on C@t{++} exceptions
3395 The throwing of a C@t{++} exception.
3398 The catching of a C@t{++} exception.
3401 @cindex Ada exception catching
3402 @cindex catch Ada exceptions
3403 An Ada exception being raised. If an exception name is specified
3404 at the end of the command (eg @code{catch exception Program_Error}),
3405 the debugger will stop only when this specific exception is raised.
3406 Otherwise, the debugger stops execution when any Ada exception is raised.
3408 @item exception unhandled
3409 An exception that was raised but is not handled by the program.
3412 A failed Ada assertion.
3415 @cindex break on fork/exec
3416 A call to @code{exec}. This is currently only available for HP-UX.
3419 A call to @code{fork}. This is currently only available for HP-UX.
3422 A call to @code{vfork}. This is currently only available for HP-UX.
3425 @itemx load @var{libname}
3426 @cindex break on load/unload of shared library
3427 The dynamic loading of any shared library, or the loading of the library
3428 @var{libname}. This is currently only available for HP-UX.
3431 @itemx unload @var{libname}
3432 The unloading of any dynamically loaded shared library, or the unloading
3433 of the library @var{libname}. This is currently only available for HP-UX.
3436 @item tcatch @var{event}
3437 Set a catchpoint that is enabled only for one stop. The catchpoint is
3438 automatically deleted after the first time the event is caught.
3442 Use the @code{info break} command to list the current catchpoints.
3444 There are currently some limitations to C@t{++} exception handling
3445 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
3449 If you call a function interactively, @value{GDBN} normally returns
3450 control to you when the function has finished executing. If the call
3451 raises an exception, however, the call may bypass the mechanism that
3452 returns control to you and cause your program either to abort or to
3453 simply continue running until it hits a breakpoint, catches a signal
3454 that @value{GDBN} is listening for, or exits. This is the case even if
3455 you set a catchpoint for the exception; catchpoints on exceptions are
3456 disabled within interactive calls.
3459 You cannot raise an exception interactively.
3462 You cannot install an exception handler interactively.
3465 @cindex raise exceptions
3466 Sometimes @code{catch} is not the best way to debug exception handling:
3467 if you need to know exactly where an exception is raised, it is better to
3468 stop @emph{before} the exception handler is called, since that way you
3469 can see the stack before any unwinding takes place. If you set a
3470 breakpoint in an exception handler instead, it may not be easy to find
3471 out where the exception was raised.
3473 To stop just before an exception handler is called, you need some
3474 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3475 raised by calling a library function named @code{__raise_exception}
3476 which has the following ANSI C interface:
3479 /* @var{addr} is where the exception identifier is stored.
3480 @var{id} is the exception identifier. */
3481 void __raise_exception (void **addr, void *id);
3485 To make the debugger catch all exceptions before any stack
3486 unwinding takes place, set a breakpoint on @code{__raise_exception}
3487 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
3489 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
3490 that depends on the value of @var{id}, you can stop your program when
3491 a specific exception is raised. You can use multiple conditional
3492 breakpoints to stop your program when any of a number of exceptions are
3497 @subsection Deleting Breakpoints
3499 @cindex clearing breakpoints, watchpoints, catchpoints
3500 @cindex deleting breakpoints, watchpoints, catchpoints
3501 It is often necessary to eliminate a breakpoint, watchpoint, or
3502 catchpoint once it has done its job and you no longer want your program
3503 to stop there. This is called @dfn{deleting} the breakpoint. A
3504 breakpoint that has been deleted no longer exists; it is forgotten.
3506 With the @code{clear} command you can delete breakpoints according to
3507 where they are in your program. With the @code{delete} command you can
3508 delete individual breakpoints, watchpoints, or catchpoints by specifying
3509 their breakpoint numbers.
3511 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3512 automatically ignores breakpoints on the first instruction to be executed
3513 when you continue execution without changing the execution address.
3518 Delete any breakpoints at the next instruction to be executed in the
3519 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
3520 the innermost frame is selected, this is a good way to delete a
3521 breakpoint where your program just stopped.
3523 @item clear @var{function}
3524 @itemx clear @var{filename}:@var{function}
3525 Delete any breakpoints set at entry to the named @var{function}.
3527 @item clear @var{linenum}
3528 @itemx clear @var{filename}:@var{linenum}
3529 Delete any breakpoints set at or within the code of the specified
3530 @var{linenum} of the specified @var{filename}.
3532 @cindex delete breakpoints
3534 @kindex d @r{(@code{delete})}
3535 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3536 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3537 ranges specified as arguments. If no argument is specified, delete all
3538 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3539 confirm off}). You can abbreviate this command as @code{d}.
3543 @subsection Disabling Breakpoints
3545 @cindex enable/disable a breakpoint
3546 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3547 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3548 it had been deleted, but remembers the information on the breakpoint so
3549 that you can @dfn{enable} it again later.
3551 You disable and enable breakpoints, watchpoints, and catchpoints with
3552 the @code{enable} and @code{disable} commands, optionally specifying one
3553 or more breakpoint numbers as arguments. Use @code{info break} or
3554 @code{info watch} to print a list of breakpoints, watchpoints, and
3555 catchpoints if you do not know which numbers to use.
3557 Disabling and enabling a breakpoint that has multiple locations
3558 affects all of its locations.
3560 A breakpoint, watchpoint, or catchpoint can have any of four different
3561 states of enablement:
3565 Enabled. The breakpoint stops your program. A breakpoint set
3566 with the @code{break} command starts out in this state.
3568 Disabled. The breakpoint has no effect on your program.
3570 Enabled once. The breakpoint stops your program, but then becomes
3573 Enabled for deletion. The breakpoint stops your program, but
3574 immediately after it does so it is deleted permanently. A breakpoint
3575 set with the @code{tbreak} command starts out in this state.
3578 You can use the following commands to enable or disable breakpoints,
3579 watchpoints, and catchpoints:
3583 @kindex dis @r{(@code{disable})}
3584 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3585 Disable the specified breakpoints---or all breakpoints, if none are
3586 listed. A disabled breakpoint has no effect but is not forgotten. All
3587 options such as ignore-counts, conditions and commands are remembered in
3588 case the breakpoint is enabled again later. You may abbreviate
3589 @code{disable} as @code{dis}.
3592 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3593 Enable the specified breakpoints (or all defined breakpoints). They
3594 become effective once again in stopping your program.
3596 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3597 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3598 of these breakpoints immediately after stopping your program.
3600 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3601 Enable the specified breakpoints to work once, then die. @value{GDBN}
3602 deletes any of these breakpoints as soon as your program stops there.
3603 Breakpoints set by the @code{tbreak} command start out in this state.
3606 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3607 @c confusing: tbreak is also initially enabled.
3608 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3609 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
3610 subsequently, they become disabled or enabled only when you use one of
3611 the commands above. (The command @code{until} can set and delete a
3612 breakpoint of its own, but it does not change the state of your other
3613 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3617 @subsection Break Conditions
3618 @cindex conditional breakpoints
3619 @cindex breakpoint conditions
3621 @c FIXME what is scope of break condition expr? Context where wanted?
3622 @c in particular for a watchpoint?
3623 The simplest sort of breakpoint breaks every time your program reaches a
3624 specified place. You can also specify a @dfn{condition} for a
3625 breakpoint. A condition is just a Boolean expression in your
3626 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3627 a condition evaluates the expression each time your program reaches it,
3628 and your program stops only if the condition is @emph{true}.
3630 This is the converse of using assertions for program validation; in that
3631 situation, you want to stop when the assertion is violated---that is,
3632 when the condition is false. In C, if you want to test an assertion expressed
3633 by the condition @var{assert}, you should set the condition
3634 @samp{! @var{assert}} on the appropriate breakpoint.
3636 Conditions are also accepted for watchpoints; you may not need them,
3637 since a watchpoint is inspecting the value of an expression anyhow---but
3638 it might be simpler, say, to just set a watchpoint on a variable name,
3639 and specify a condition that tests whether the new value is an interesting
3642 Break conditions can have side effects, and may even call functions in
3643 your program. This can be useful, for example, to activate functions
3644 that log program progress, or to use your own print functions to
3645 format special data structures. The effects are completely predictable
3646 unless there is another enabled breakpoint at the same address. (In
3647 that case, @value{GDBN} might see the other breakpoint first and stop your
3648 program without checking the condition of this one.) Note that
3649 breakpoint commands are usually more convenient and flexible than break
3651 purpose of performing side effects when a breakpoint is reached
3652 (@pxref{Break Commands, ,Breakpoint Command Lists}).
3654 Break conditions can be specified when a breakpoint is set, by using
3655 @samp{if} in the arguments to the @code{break} command. @xref{Set
3656 Breaks, ,Setting Breakpoints}. They can also be changed at any time
3657 with the @code{condition} command.
3659 You can also use the @code{if} keyword with the @code{watch} command.
3660 The @code{catch} command does not recognize the @code{if} keyword;
3661 @code{condition} is the only way to impose a further condition on a
3666 @item condition @var{bnum} @var{expression}
3667 Specify @var{expression} as the break condition for breakpoint,
3668 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3669 breakpoint @var{bnum} stops your program only if the value of
3670 @var{expression} is true (nonzero, in C). When you use
3671 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3672 syntactic correctness, and to determine whether symbols in it have
3673 referents in the context of your breakpoint. If @var{expression} uses
3674 symbols not referenced in the context of the breakpoint, @value{GDBN}
3675 prints an error message:
3678 No symbol "foo" in current context.
3683 not actually evaluate @var{expression} at the time the @code{condition}
3684 command (or a command that sets a breakpoint with a condition, like
3685 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3687 @item condition @var{bnum}
3688 Remove the condition from breakpoint number @var{bnum}. It becomes
3689 an ordinary unconditional breakpoint.
3692 @cindex ignore count (of breakpoint)
3693 A special case of a breakpoint condition is to stop only when the
3694 breakpoint has been reached a certain number of times. This is so
3695 useful that there is a special way to do it, using the @dfn{ignore
3696 count} of the breakpoint. Every breakpoint has an ignore count, which
3697 is an integer. Most of the time, the ignore count is zero, and
3698 therefore has no effect. But if your program reaches a breakpoint whose
3699 ignore count is positive, then instead of stopping, it just decrements
3700 the ignore count by one and continues. As a result, if the ignore count
3701 value is @var{n}, the breakpoint does not stop the next @var{n} times
3702 your program reaches it.
3706 @item ignore @var{bnum} @var{count}
3707 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3708 The next @var{count} times the breakpoint is reached, your program's
3709 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3712 To make the breakpoint stop the next time it is reached, specify
3715 When you use @code{continue} to resume execution of your program from a
3716 breakpoint, you can specify an ignore count directly as an argument to
3717 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3718 Stepping,,Continuing and Stepping}.
3720 If a breakpoint has a positive ignore count and a condition, the
3721 condition is not checked. Once the ignore count reaches zero,
3722 @value{GDBN} resumes checking the condition.
3724 You could achieve the effect of the ignore count with a condition such
3725 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3726 is decremented each time. @xref{Convenience Vars, ,Convenience
3730 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3733 @node Break Commands
3734 @subsection Breakpoint Command Lists
3736 @cindex breakpoint commands
3737 You can give any breakpoint (or watchpoint or catchpoint) a series of
3738 commands to execute when your program stops due to that breakpoint. For
3739 example, you might want to print the values of certain expressions, or
3740 enable other breakpoints.
3744 @kindex end@r{ (breakpoint commands)}
3745 @item commands @r{[}@var{bnum}@r{]}
3746 @itemx @dots{} @var{command-list} @dots{}
3748 Specify a list of commands for breakpoint number @var{bnum}. The commands
3749 themselves appear on the following lines. Type a line containing just
3750 @code{end} to terminate the commands.
3752 To remove all commands from a breakpoint, type @code{commands} and
3753 follow it immediately with @code{end}; that is, give no commands.
3755 With no @var{bnum} argument, @code{commands} refers to the last
3756 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3757 recently encountered).
3760 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3761 disabled within a @var{command-list}.
3763 You can use breakpoint commands to start your program up again. Simply
3764 use the @code{continue} command, or @code{step}, or any other command
3765 that resumes execution.
3767 Any other commands in the command list, after a command that resumes
3768 execution, are ignored. This is because any time you resume execution
3769 (even with a simple @code{next} or @code{step}), you may encounter
3770 another breakpoint---which could have its own command list, leading to
3771 ambiguities about which list to execute.
3774 If the first command you specify in a command list is @code{silent}, the
3775 usual message about stopping at a breakpoint is not printed. This may
3776 be desirable for breakpoints that are to print a specific message and
3777 then continue. If none of the remaining commands print anything, you
3778 see no sign that the breakpoint was reached. @code{silent} is
3779 meaningful only at the beginning of a breakpoint command list.
3781 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3782 print precisely controlled output, and are often useful in silent
3783 breakpoints. @xref{Output, ,Commands for Controlled Output}.
3785 For example, here is how you could use breakpoint commands to print the
3786 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3792 printf "x is %d\n",x
3797 One application for breakpoint commands is to compensate for one bug so
3798 you can test for another. Put a breakpoint just after the erroneous line
3799 of code, give it a condition to detect the case in which something
3800 erroneous has been done, and give it commands to assign correct values
3801 to any variables that need them. End with the @code{continue} command
3802 so that your program does not stop, and start with the @code{silent}
3803 command so that no output is produced. Here is an example:
3814 @node Breakpoint Menus
3815 @subsection Breakpoint Menus
3817 @cindex symbol overloading
3819 Some programming languages (notably C@t{++} and Objective-C) permit a
3820 single function name
3821 to be defined several times, for application in different contexts.
3822 This is called @dfn{overloading}. When a function name is overloaded,
3823 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3824 a breakpoint. You can use explicit signature of the function, as in
3825 @samp{break @var{function}(@var{types})}, to specify which
3826 particular version of the function you want. Otherwise, @value{GDBN} offers
3827 you a menu of numbered choices for different possible breakpoints, and
3828 waits for your selection with the prompt @samp{>}. The first two
3829 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3830 sets a breakpoint at each definition of @var{function}, and typing
3831 @kbd{0} aborts the @code{break} command without setting any new
3834 For example, the following session excerpt shows an attempt to set a
3835 breakpoint at the overloaded symbol @code{String::after}.
3836 We choose three particular definitions of that function name:
3838 @c FIXME! This is likely to change to show arg type lists, at least
3841 (@value{GDBP}) b String::after
3844 [2] file:String.cc; line number:867
3845 [3] file:String.cc; line number:860
3846 [4] file:String.cc; line number:875
3847 [5] file:String.cc; line number:853
3848 [6] file:String.cc; line number:846
3849 [7] file:String.cc; line number:735
3851 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3852 Breakpoint 2 at 0xb344: file String.cc, line 875.
3853 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3854 Multiple breakpoints were set.
3855 Use the "delete" command to delete unwanted
3861 @c @ifclear BARETARGET
3862 @node Error in Breakpoints
3863 @subsection ``Cannot insert breakpoints''
3865 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3867 Under some operating systems, breakpoints cannot be used in a program if
3868 any other process is running that program. In this situation,
3869 attempting to run or continue a program with a breakpoint causes
3870 @value{GDBN} to print an error message:
3873 Cannot insert breakpoints.
3874 The same program may be running in another process.
3877 When this happens, you have three ways to proceed:
3881 Remove or disable the breakpoints, then continue.
3884 Suspend @value{GDBN}, and copy the file containing your program to a new
3885 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3886 that @value{GDBN} should run your program under that name.
3887 Then start your program again.
3890 Relink your program so that the text segment is nonsharable, using the
3891 linker option @samp{-N}. The operating system limitation may not apply
3892 to nonsharable executables.
3896 A similar message can be printed if you request too many active
3897 hardware-assisted breakpoints and watchpoints:
3899 @c FIXME: the precise wording of this message may change; the relevant
3900 @c source change is not committed yet (Sep 3, 1999).
3902 Stopped; cannot insert breakpoints.
3903 You may have requested too many hardware breakpoints and watchpoints.
3907 This message is printed when you attempt to resume the program, since
3908 only then @value{GDBN} knows exactly how many hardware breakpoints and
3909 watchpoints it needs to insert.
3911 When this message is printed, you need to disable or remove some of the
3912 hardware-assisted breakpoints and watchpoints, and then continue.
3914 @node Breakpoint-related Warnings
3915 @subsection ``Breakpoint address adjusted...''
3916 @cindex breakpoint address adjusted
3918 Some processor architectures place constraints on the addresses at
3919 which breakpoints may be placed. For architectures thus constrained,
3920 @value{GDBN} will attempt to adjust the breakpoint's address to comply
3921 with the constraints dictated by the architecture.
3923 One example of such an architecture is the Fujitsu FR-V. The FR-V is
3924 a VLIW architecture in which a number of RISC-like instructions may be
3925 bundled together for parallel execution. The FR-V architecture
3926 constrains the location of a breakpoint instruction within such a
3927 bundle to the instruction with the lowest address. @value{GDBN}
3928 honors this constraint by adjusting a breakpoint's address to the
3929 first in the bundle.
3931 It is not uncommon for optimized code to have bundles which contain
3932 instructions from different source statements, thus it may happen that
3933 a breakpoint's address will be adjusted from one source statement to
3934 another. Since this adjustment may significantly alter @value{GDBN}'s
3935 breakpoint related behavior from what the user expects, a warning is
3936 printed when the breakpoint is first set and also when the breakpoint
3939 A warning like the one below is printed when setting a breakpoint
3940 that's been subject to address adjustment:
3943 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
3946 Such warnings are printed both for user settable and @value{GDBN}'s
3947 internal breakpoints. If you see one of these warnings, you should
3948 verify that a breakpoint set at the adjusted address will have the
3949 desired affect. If not, the breakpoint in question may be removed and
3950 other breakpoints may be set which will have the desired behavior.
3951 E.g., it may be sufficient to place the breakpoint at a later
3952 instruction. A conditional breakpoint may also be useful in some
3953 cases to prevent the breakpoint from triggering too often.
3955 @value{GDBN} will also issue a warning when stopping at one of these
3956 adjusted breakpoints:
3959 warning: Breakpoint 1 address previously adjusted from 0x00010414
3963 When this warning is encountered, it may be too late to take remedial
3964 action except in cases where the breakpoint is hit earlier or more
3965 frequently than expected.
3967 @node Continuing and Stepping
3968 @section Continuing and Stepping
3972 @cindex resuming execution
3973 @dfn{Continuing} means resuming program execution until your program
3974 completes normally. In contrast, @dfn{stepping} means executing just
3975 one more ``step'' of your program, where ``step'' may mean either one
3976 line of source code, or one machine instruction (depending on what
3977 particular command you use). Either when continuing or when stepping,
3978 your program may stop even sooner, due to a breakpoint or a signal. (If
3979 it stops due to a signal, you may want to use @code{handle}, or use
3980 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3984 @kindex c @r{(@code{continue})}
3985 @kindex fg @r{(resume foreground execution)}
3986 @item continue @r{[}@var{ignore-count}@r{]}
3987 @itemx c @r{[}@var{ignore-count}@r{]}
3988 @itemx fg @r{[}@var{ignore-count}@r{]}
3989 Resume program execution, at the address where your program last stopped;
3990 any breakpoints set at that address are bypassed. The optional argument
3991 @var{ignore-count} allows you to specify a further number of times to
3992 ignore a breakpoint at this location; its effect is like that of
3993 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
3995 The argument @var{ignore-count} is meaningful only when your program
3996 stopped due to a breakpoint. At other times, the argument to
3997 @code{continue} is ignored.
3999 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4000 debugged program is deemed to be the foreground program) are provided
4001 purely for convenience, and have exactly the same behavior as
4005 To resume execution at a different place, you can use @code{return}
4006 (@pxref{Returning, ,Returning from a Function}) to go back to the
4007 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4008 Different Address}) to go to an arbitrary location in your program.
4010 A typical technique for using stepping is to set a breakpoint
4011 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4012 beginning of the function or the section of your program where a problem
4013 is believed to lie, run your program until it stops at that breakpoint,
4014 and then step through the suspect area, examining the variables that are
4015 interesting, until you see the problem happen.
4019 @kindex s @r{(@code{step})}
4021 Continue running your program until control reaches a different source
4022 line, then stop it and return control to @value{GDBN}. This command is
4023 abbreviated @code{s}.
4026 @c "without debugging information" is imprecise; actually "without line
4027 @c numbers in the debugging information". (gcc -g1 has debugging info but
4028 @c not line numbers). But it seems complex to try to make that
4029 @c distinction here.
4030 @emph{Warning:} If you use the @code{step} command while control is
4031 within a function that was compiled without debugging information,
4032 execution proceeds until control reaches a function that does have
4033 debugging information. Likewise, it will not step into a function which
4034 is compiled without debugging information. To step through functions
4035 without debugging information, use the @code{stepi} command, described
4039 The @code{step} command only stops at the first instruction of a source
4040 line. This prevents the multiple stops that could otherwise occur in
4041 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4042 to stop if a function that has debugging information is called within
4043 the line. In other words, @code{step} @emph{steps inside} any functions
4044 called within the line.
4046 Also, the @code{step} command only enters a function if there is line
4047 number information for the function. Otherwise it acts like the
4048 @code{next} command. This avoids problems when using @code{cc -gl}
4049 on MIPS machines. Previously, @code{step} entered subroutines if there
4050 was any debugging information about the routine.
4052 @item step @var{count}
4053 Continue running as in @code{step}, but do so @var{count} times. If a
4054 breakpoint is reached, or a signal not related to stepping occurs before
4055 @var{count} steps, stepping stops right away.
4058 @kindex n @r{(@code{next})}
4059 @item next @r{[}@var{count}@r{]}
4060 Continue to the next source line in the current (innermost) stack frame.
4061 This is similar to @code{step}, but function calls that appear within
4062 the line of code are executed without stopping. Execution stops when
4063 control reaches a different line of code at the original stack level
4064 that was executing when you gave the @code{next} command. This command
4065 is abbreviated @code{n}.
4067 An argument @var{count} is a repeat count, as for @code{step}.
4070 @c FIX ME!! Do we delete this, or is there a way it fits in with
4071 @c the following paragraph? --- Vctoria
4073 @c @code{next} within a function that lacks debugging information acts like
4074 @c @code{step}, but any function calls appearing within the code of the
4075 @c function are executed without stopping.
4077 The @code{next} command only stops at the first instruction of a
4078 source line. This prevents multiple stops that could otherwise occur in
4079 @code{switch} statements, @code{for} loops, etc.
4081 @kindex set step-mode
4083 @cindex functions without line info, and stepping
4084 @cindex stepping into functions with no line info
4085 @itemx set step-mode on
4086 The @code{set step-mode on} command causes the @code{step} command to
4087 stop at the first instruction of a function which contains no debug line
4088 information rather than stepping over it.
4090 This is useful in cases where you may be interested in inspecting the
4091 machine instructions of a function which has no symbolic info and do not
4092 want @value{GDBN} to automatically skip over this function.
4094 @item set step-mode off
4095 Causes the @code{step} command to step over any functions which contains no
4096 debug information. This is the default.
4098 @item show step-mode
4099 Show whether @value{GDBN} will stop in or step over functions without
4100 source line debug information.
4104 Continue running until just after function in the selected stack frame
4105 returns. Print the returned value (if any).
4107 Contrast this with the @code{return} command (@pxref{Returning,
4108 ,Returning from a Function}).
4111 @kindex u @r{(@code{until})}
4112 @cindex run until specified location
4115 Continue running until a source line past the current line, in the
4116 current stack frame, is reached. This command is used to avoid single
4117 stepping through a loop more than once. It is like the @code{next}
4118 command, except that when @code{until} encounters a jump, it
4119 automatically continues execution until the program counter is greater
4120 than the address of the jump.
4122 This means that when you reach the end of a loop after single stepping
4123 though it, @code{until} makes your program continue execution until it
4124 exits the loop. In contrast, a @code{next} command at the end of a loop
4125 simply steps back to the beginning of the loop, which forces you to step
4126 through the next iteration.
4128 @code{until} always stops your program if it attempts to exit the current
4131 @code{until} may produce somewhat counterintuitive results if the order
4132 of machine code does not match the order of the source lines. For
4133 example, in the following excerpt from a debugging session, the @code{f}
4134 (@code{frame}) command shows that execution is stopped at line
4135 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4139 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4141 (@value{GDBP}) until
4142 195 for ( ; argc > 0; NEXTARG) @{
4145 This happened because, for execution efficiency, the compiler had
4146 generated code for the loop closure test at the end, rather than the
4147 start, of the loop---even though the test in a C @code{for}-loop is
4148 written before the body of the loop. The @code{until} command appeared
4149 to step back to the beginning of the loop when it advanced to this
4150 expression; however, it has not really gone to an earlier
4151 statement---not in terms of the actual machine code.
4153 @code{until} with no argument works by means of single
4154 instruction stepping, and hence is slower than @code{until} with an
4157 @item until @var{location}
4158 @itemx u @var{location}
4159 Continue running your program until either the specified location is
4160 reached, or the current stack frame returns. @var{location} is any of
4161 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
4162 ,Setting Breakpoints}). This form of the command uses breakpoints, and
4163 hence is quicker than @code{until} without an argument. The specified
4164 location is actually reached only if it is in the current frame. This
4165 implies that @code{until} can be used to skip over recursive function
4166 invocations. For instance in the code below, if the current location is
4167 line @code{96}, issuing @code{until 99} will execute the program up to
4168 line @code{99} in the same invocation of factorial, i.e., after the inner
4169 invocations have returned.
4172 94 int factorial (int value)
4174 96 if (value > 1) @{
4175 97 value *= factorial (value - 1);
4182 @kindex advance @var{location}
4183 @itemx advance @var{location}
4184 Continue running the program up to the given @var{location}. An argument is
4185 required, which should be of the same form as arguments for the @code{break}
4186 command. Execution will also stop upon exit from the current stack
4187 frame. This command is similar to @code{until}, but @code{advance} will
4188 not skip over recursive function calls, and the target location doesn't
4189 have to be in the same frame as the current one.
4193 @kindex si @r{(@code{stepi})}
4195 @itemx stepi @var{arg}
4197 Execute one machine instruction, then stop and return to the debugger.
4199 It is often useful to do @samp{display/i $pc} when stepping by machine
4200 instructions. This makes @value{GDBN} automatically display the next
4201 instruction to be executed, each time your program stops. @xref{Auto
4202 Display,, Automatic Display}.
4204 An argument is a repeat count, as in @code{step}.
4208 @kindex ni @r{(@code{nexti})}
4210 @itemx nexti @var{arg}
4212 Execute one machine instruction, but if it is a function call,
4213 proceed until the function returns.
4215 An argument is a repeat count, as in @code{next}.
4222 A signal is an asynchronous event that can happen in a program. The
4223 operating system defines the possible kinds of signals, and gives each
4224 kind a name and a number. For example, in Unix @code{SIGINT} is the
4225 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4226 @code{SIGSEGV} is the signal a program gets from referencing a place in
4227 memory far away from all the areas in use; @code{SIGALRM} occurs when
4228 the alarm clock timer goes off (which happens only if your program has
4229 requested an alarm).
4231 @cindex fatal signals
4232 Some signals, including @code{SIGALRM}, are a normal part of the
4233 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4234 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4235 program has not specified in advance some other way to handle the signal.
4236 @code{SIGINT} does not indicate an error in your program, but it is normally
4237 fatal so it can carry out the purpose of the interrupt: to kill the program.
4239 @value{GDBN} has the ability to detect any occurrence of a signal in your
4240 program. You can tell @value{GDBN} in advance what to do for each kind of
4243 @cindex handling signals
4244 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4245 @code{SIGALRM} be silently passed to your program
4246 (so as not to interfere with their role in the program's functioning)
4247 but to stop your program immediately whenever an error signal happens.
4248 You can change these settings with the @code{handle} command.
4251 @kindex info signals
4255 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4256 handle each one. You can use this to see the signal numbers of all
4257 the defined types of signals.
4259 @item info signals @var{sig}
4260 Similar, but print information only about the specified signal number.
4262 @code{info handle} is an alias for @code{info signals}.
4265 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4266 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4267 can be the number of a signal or its name (with or without the
4268 @samp{SIG} at the beginning); a list of signal numbers of the form
4269 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4270 known signals. Optional arguments @var{keywords}, described below,
4271 say what change to make.
4275 The keywords allowed by the @code{handle} command can be abbreviated.
4276 Their full names are:
4280 @value{GDBN} should not stop your program when this signal happens. It may
4281 still print a message telling you that the signal has come in.
4284 @value{GDBN} should stop your program when this signal happens. This implies
4285 the @code{print} keyword as well.
4288 @value{GDBN} should print a message when this signal happens.
4291 @value{GDBN} should not mention the occurrence of the signal at all. This
4292 implies the @code{nostop} keyword as well.
4296 @value{GDBN} should allow your program to see this signal; your program
4297 can handle the signal, or else it may terminate if the signal is fatal
4298 and not handled. @code{pass} and @code{noignore} are synonyms.
4302 @value{GDBN} should not allow your program to see this signal.
4303 @code{nopass} and @code{ignore} are synonyms.
4307 When a signal stops your program, the signal is not visible to the
4309 continue. Your program sees the signal then, if @code{pass} is in
4310 effect for the signal in question @emph{at that time}. In other words,
4311 after @value{GDBN} reports a signal, you can use the @code{handle}
4312 command with @code{pass} or @code{nopass} to control whether your
4313 program sees that signal when you continue.
4315 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4316 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4317 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4320 You can also use the @code{signal} command to prevent your program from
4321 seeing a signal, or cause it to see a signal it normally would not see,
4322 or to give it any signal at any time. For example, if your program stopped
4323 due to some sort of memory reference error, you might store correct
4324 values into the erroneous variables and continue, hoping to see more
4325 execution; but your program would probably terminate immediately as
4326 a result of the fatal signal once it saw the signal. To prevent this,
4327 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4331 @section Stopping and Starting Multi-thread Programs
4333 When your program has multiple threads (@pxref{Threads,, Debugging
4334 Programs with Multiple Threads}), you can choose whether to set
4335 breakpoints on all threads, or on a particular thread.
4338 @cindex breakpoints and threads
4339 @cindex thread breakpoints
4340 @kindex break @dots{} thread @var{threadno}
4341 @item break @var{linespec} thread @var{threadno}
4342 @itemx break @var{linespec} thread @var{threadno} if @dots{}
4343 @var{linespec} specifies source lines; there are several ways of
4344 writing them, but the effect is always to specify some source line.
4346 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
4347 to specify that you only want @value{GDBN} to stop the program when a
4348 particular thread reaches this breakpoint. @var{threadno} is one of the
4349 numeric thread identifiers assigned by @value{GDBN}, shown in the first
4350 column of the @samp{info threads} display.
4352 If you do not specify @samp{thread @var{threadno}} when you set a
4353 breakpoint, the breakpoint applies to @emph{all} threads of your
4356 You can use the @code{thread} qualifier on conditional breakpoints as
4357 well; in this case, place @samp{thread @var{threadno}} before the
4358 breakpoint condition, like this:
4361 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
4366 @cindex stopped threads
4367 @cindex threads, stopped
4368 Whenever your program stops under @value{GDBN} for any reason,
4369 @emph{all} threads of execution stop, not just the current thread. This
4370 allows you to examine the overall state of the program, including
4371 switching between threads, without worrying that things may change
4374 @cindex thread breakpoints and system calls
4375 @cindex system calls and thread breakpoints
4376 @cindex premature return from system calls
4377 There is an unfortunate side effect. If one thread stops for a
4378 breakpoint, or for some other reason, and another thread is blocked in a
4379 system call, then the system call may return prematurely. This is a
4380 consequence of the interaction between multiple threads and the signals
4381 that @value{GDBN} uses to implement breakpoints and other events that
4384 To handle this problem, your program should check the return value of
4385 each system call and react appropriately. This is good programming
4388 For example, do not write code like this:
4394 The call to @code{sleep} will return early if a different thread stops
4395 at a breakpoint or for some other reason.
4397 Instead, write this:
4402 unslept = sleep (unslept);
4405 A system call is allowed to return early, so the system is still
4406 conforming to its specification. But @value{GDBN} does cause your
4407 multi-threaded program to behave differently than it would without
4410 Also, @value{GDBN} uses internal breakpoints in the thread library to
4411 monitor certain events such as thread creation and thread destruction.
4412 When such an event happens, a system call in another thread may return
4413 prematurely, even though your program does not appear to stop.
4415 @cindex continuing threads
4416 @cindex threads, continuing
4417 Conversely, whenever you restart the program, @emph{all} threads start
4418 executing. @emph{This is true even when single-stepping} with commands
4419 like @code{step} or @code{next}.
4421 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4422 Since thread scheduling is up to your debugging target's operating
4423 system (not controlled by @value{GDBN}), other threads may
4424 execute more than one statement while the current thread completes a
4425 single step. Moreover, in general other threads stop in the middle of a
4426 statement, rather than at a clean statement boundary, when the program
4429 You might even find your program stopped in another thread after
4430 continuing or even single-stepping. This happens whenever some other
4431 thread runs into a breakpoint, a signal, or an exception before the
4432 first thread completes whatever you requested.
4434 On some OSes, you can lock the OS scheduler and thus allow only a single
4438 @item set scheduler-locking @var{mode}
4439 @cindex scheduler locking mode
4440 @cindex lock scheduler
4441 Set the scheduler locking mode. If it is @code{off}, then there is no
4442 locking and any thread may run at any time. If @code{on}, then only the
4443 current thread may run when the inferior is resumed. The @code{step}
4444 mode optimizes for single-stepping. It stops other threads from
4445 ``seizing the prompt'' by preempting the current thread while you are
4446 stepping. Other threads will only rarely (or never) get a chance to run
4447 when you step. They are more likely to run when you @samp{next} over a
4448 function call, and they are completely free to run when you use commands
4449 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4450 thread hits a breakpoint during its timeslice, they will never steal the
4451 @value{GDBN} prompt away from the thread that you are debugging.
4453 @item show scheduler-locking
4454 Display the current scheduler locking mode.
4459 @chapter Examining the Stack
4461 When your program has stopped, the first thing you need to know is where it
4462 stopped and how it got there.
4465 Each time your program performs a function call, information about the call
4467 That information includes the location of the call in your program,
4468 the arguments of the call,
4469 and the local variables of the function being called.
4470 The information is saved in a block of data called a @dfn{stack frame}.
4471 The stack frames are allocated in a region of memory called the @dfn{call
4474 When your program stops, the @value{GDBN} commands for examining the
4475 stack allow you to see all of this information.
4477 @cindex selected frame
4478 One of the stack frames is @dfn{selected} by @value{GDBN} and many
4479 @value{GDBN} commands refer implicitly to the selected frame. In
4480 particular, whenever you ask @value{GDBN} for the value of a variable in
4481 your program, the value is found in the selected frame. There are
4482 special @value{GDBN} commands to select whichever frame you are
4483 interested in. @xref{Selection, ,Selecting a Frame}.
4485 When your program stops, @value{GDBN} automatically selects the
4486 currently executing frame and describes it briefly, similar to the
4487 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
4490 * Frames:: Stack frames
4491 * Backtrace:: Backtraces
4492 * Selection:: Selecting a frame
4493 * Frame Info:: Information on a frame
4498 @section Stack Frames
4500 @cindex frame, definition
4502 The call stack is divided up into contiguous pieces called @dfn{stack
4503 frames}, or @dfn{frames} for short; each frame is the data associated
4504 with one call to one function. The frame contains the arguments given
4505 to the function, the function's local variables, and the address at
4506 which the function is executing.
4508 @cindex initial frame
4509 @cindex outermost frame
4510 @cindex innermost frame
4511 When your program is started, the stack has only one frame, that of the
4512 function @code{main}. This is called the @dfn{initial} frame or the
4513 @dfn{outermost} frame. Each time a function is called, a new frame is
4514 made. Each time a function returns, the frame for that function invocation
4515 is eliminated. If a function is recursive, there can be many frames for
4516 the same function. The frame for the function in which execution is
4517 actually occurring is called the @dfn{innermost} frame. This is the most
4518 recently created of all the stack frames that still exist.
4520 @cindex frame pointer
4521 Inside your program, stack frames are identified by their addresses. A
4522 stack frame consists of many bytes, each of which has its own address; each
4523 kind of computer has a convention for choosing one byte whose
4524 address serves as the address of the frame. Usually this address is kept
4525 in a register called the @dfn{frame pointer register}
4526 (@pxref{Registers, $fp}) while execution is going on in that frame.
4528 @cindex frame number
4529 @value{GDBN} assigns numbers to all existing stack frames, starting with
4530 zero for the innermost frame, one for the frame that called it,
4531 and so on upward. These numbers do not really exist in your program;
4532 they are assigned by @value{GDBN} to give you a way of designating stack
4533 frames in @value{GDBN} commands.
4535 @c The -fomit-frame-pointer below perennially causes hbox overflow
4536 @c underflow problems.
4537 @cindex frameless execution
4538 Some compilers provide a way to compile functions so that they operate
4539 without stack frames. (For example, the @value{NGCC} option
4541 @samp{-fomit-frame-pointer}
4543 generates functions without a frame.)
4544 This is occasionally done with heavily used library functions to save
4545 the frame setup time. @value{GDBN} has limited facilities for dealing
4546 with these function invocations. If the innermost function invocation
4547 has no stack frame, @value{GDBN} nevertheless regards it as though
4548 it had a separate frame, which is numbered zero as usual, allowing
4549 correct tracing of the function call chain. However, @value{GDBN} has
4550 no provision for frameless functions elsewhere in the stack.
4553 @kindex frame@r{, command}
4554 @cindex current stack frame
4555 @item frame @var{args}
4556 The @code{frame} command allows you to move from one stack frame to another,
4557 and to print the stack frame you select. @var{args} may be either the
4558 address of the frame or the stack frame number. Without an argument,
4559 @code{frame} prints the current stack frame.
4561 @kindex select-frame
4562 @cindex selecting frame silently
4564 The @code{select-frame} command allows you to move from one stack frame
4565 to another without printing the frame. This is the silent version of
4573 @cindex call stack traces
4574 A backtrace is a summary of how your program got where it is. It shows one
4575 line per frame, for many frames, starting with the currently executing
4576 frame (frame zero), followed by its caller (frame one), and on up the
4581 @kindex bt @r{(@code{backtrace})}
4584 Print a backtrace of the entire stack: one line per frame for all
4585 frames in the stack.
4587 You can stop the backtrace at any time by typing the system interrupt
4588 character, normally @kbd{Ctrl-c}.
4590 @item backtrace @var{n}
4592 Similar, but print only the innermost @var{n} frames.
4594 @item backtrace -@var{n}
4596 Similar, but print only the outermost @var{n} frames.
4598 @item backtrace full
4600 @itemx bt full @var{n}
4601 @itemx bt full -@var{n}
4602 Print the values of the local variables also. @var{n} specifies the
4603 number of frames to print, as described above.
4608 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4609 are additional aliases for @code{backtrace}.
4611 @cindex multiple threads, backtrace
4612 In a multi-threaded program, @value{GDBN} by default shows the
4613 backtrace only for the current thread. To display the backtrace for
4614 several or all of the threads, use the command @code{thread apply}
4615 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
4616 apply all backtrace}, @value{GDBN} will display the backtrace for all
4617 the threads; this is handy when you debug a core dump of a
4618 multi-threaded program.
4620 Each line in the backtrace shows the frame number and the function name.
4621 The program counter value is also shown---unless you use @code{set
4622 print address off}. The backtrace also shows the source file name and
4623 line number, as well as the arguments to the function. The program
4624 counter value is omitted if it is at the beginning of the code for that
4627 Here is an example of a backtrace. It was made with the command
4628 @samp{bt 3}, so it shows the innermost three frames.
4632 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4634 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4635 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4637 (More stack frames follow...)
4642 The display for frame zero does not begin with a program counter
4643 value, indicating that your program has stopped at the beginning of the
4644 code for line @code{993} of @code{builtin.c}.
4646 @cindex value optimized out, in backtrace
4647 @cindex function call arguments, optimized out
4648 If your program was compiled with optimizations, some compilers will
4649 optimize away arguments passed to functions if those arguments are
4650 never used after the call. Such optimizations generate code that
4651 passes arguments through registers, but doesn't store those arguments
4652 in the stack frame. @value{GDBN} has no way of displaying such
4653 arguments in stack frames other than the innermost one. Here's what
4654 such a backtrace might look like:
4658 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4660 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
4661 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
4663 (More stack frames follow...)
4668 The values of arguments that were not saved in their stack frames are
4669 shown as @samp{<value optimized out>}.
4671 If you need to display the values of such optimized-out arguments,
4672 either deduce that from other variables whose values depend on the one
4673 you are interested in, or recompile without optimizations.
4675 @cindex backtrace beyond @code{main} function
4676 @cindex program entry point
4677 @cindex startup code, and backtrace
4678 Most programs have a standard user entry point---a place where system
4679 libraries and startup code transition into user code. For C this is
4680 @code{main}@footnote{
4681 Note that embedded programs (the so-called ``free-standing''
4682 environment) are not required to have a @code{main} function as the
4683 entry point. They could even have multiple entry points.}.
4684 When @value{GDBN} finds the entry function in a backtrace
4685 it will terminate the backtrace, to avoid tracing into highly
4686 system-specific (and generally uninteresting) code.
4688 If you need to examine the startup code, or limit the number of levels
4689 in a backtrace, you can change this behavior:
4692 @item set backtrace past-main
4693 @itemx set backtrace past-main on
4694 @kindex set backtrace
4695 Backtraces will continue past the user entry point.
4697 @item set backtrace past-main off
4698 Backtraces will stop when they encounter the user entry point. This is the
4701 @item show backtrace past-main
4702 @kindex show backtrace
4703 Display the current user entry point backtrace policy.
4705 @item set backtrace past-entry
4706 @itemx set backtrace past-entry on
4707 Backtraces will continue past the internal entry point of an application.
4708 This entry point is encoded by the linker when the application is built,
4709 and is likely before the user entry point @code{main} (or equivalent) is called.
4711 @item set backtrace past-entry off
4712 Backtraces will stop when they encounter the internal entry point of an
4713 application. This is the default.
4715 @item show backtrace past-entry
4716 Display the current internal entry point backtrace policy.
4718 @item set backtrace limit @var{n}
4719 @itemx set backtrace limit 0
4720 @cindex backtrace limit
4721 Limit the backtrace to @var{n} levels. A value of zero means
4724 @item show backtrace limit
4725 Display the current limit on backtrace levels.
4729 @section Selecting a Frame
4731 Most commands for examining the stack and other data in your program work on
4732 whichever stack frame is selected at the moment. Here are the commands for
4733 selecting a stack frame; all of them finish by printing a brief description
4734 of the stack frame just selected.
4737 @kindex frame@r{, selecting}
4738 @kindex f @r{(@code{frame})}
4741 Select frame number @var{n}. Recall that frame zero is the innermost
4742 (currently executing) frame, frame one is the frame that called the
4743 innermost one, and so on. The highest-numbered frame is the one for
4746 @item frame @var{addr}
4748 Select the frame at address @var{addr}. This is useful mainly if the
4749 chaining of stack frames has been damaged by a bug, making it
4750 impossible for @value{GDBN} to assign numbers properly to all frames. In
4751 addition, this can be useful when your program has multiple stacks and
4752 switches between them.
4754 On the SPARC architecture, @code{frame} needs two addresses to
4755 select an arbitrary frame: a frame pointer and a stack pointer.
4757 On the MIPS and Alpha architecture, it needs two addresses: a stack
4758 pointer and a program counter.
4760 On the 29k architecture, it needs three addresses: a register stack
4761 pointer, a program counter, and a memory stack pointer.
4765 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4766 advances toward the outermost frame, to higher frame numbers, to frames
4767 that have existed longer. @var{n} defaults to one.
4770 @kindex do @r{(@code{down})}
4772 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4773 advances toward the innermost frame, to lower frame numbers, to frames
4774 that were created more recently. @var{n} defaults to one. You may
4775 abbreviate @code{down} as @code{do}.
4778 All of these commands end by printing two lines of output describing the
4779 frame. The first line shows the frame number, the function name, the
4780 arguments, and the source file and line number of execution in that
4781 frame. The second line shows the text of that source line.
4789 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4791 10 read_input_file (argv[i]);
4795 After such a printout, the @code{list} command with no arguments
4796 prints ten lines centered on the point of execution in the frame.
4797 You can also edit the program at the point of execution with your favorite
4798 editing program by typing @code{edit}.
4799 @xref{List, ,Printing Source Lines},
4803 @kindex down-silently
4805 @item up-silently @var{n}
4806 @itemx down-silently @var{n}
4807 These two commands are variants of @code{up} and @code{down},
4808 respectively; they differ in that they do their work silently, without
4809 causing display of the new frame. They are intended primarily for use
4810 in @value{GDBN} command scripts, where the output might be unnecessary and
4815 @section Information About a Frame
4817 There are several other commands to print information about the selected
4823 When used without any argument, this command does not change which
4824 frame is selected, but prints a brief description of the currently
4825 selected stack frame. It can be abbreviated @code{f}. With an
4826 argument, this command is used to select a stack frame.
4827 @xref{Selection, ,Selecting a Frame}.
4830 @kindex info f @r{(@code{info frame})}
4833 This command prints a verbose description of the selected stack frame,
4838 the address of the frame
4840 the address of the next frame down (called by this frame)
4842 the address of the next frame up (caller of this frame)
4844 the language in which the source code corresponding to this frame is written
4846 the address of the frame's arguments
4848 the address of the frame's local variables
4850 the program counter saved in it (the address of execution in the caller frame)
4852 which registers were saved in the frame
4855 @noindent The verbose description is useful when
4856 something has gone wrong that has made the stack format fail to fit
4857 the usual conventions.
4859 @item info frame @var{addr}
4860 @itemx info f @var{addr}
4861 Print a verbose description of the frame at address @var{addr}, without
4862 selecting that frame. The selected frame remains unchanged by this
4863 command. This requires the same kind of address (more than one for some
4864 architectures) that you specify in the @code{frame} command.
4865 @xref{Selection, ,Selecting a Frame}.
4869 Print the arguments of the selected frame, each on a separate line.
4873 Print the local variables of the selected frame, each on a separate
4874 line. These are all variables (declared either static or automatic)
4875 accessible at the point of execution of the selected frame.
4878 @cindex catch exceptions, list active handlers
4879 @cindex exception handlers, how to list
4881 Print a list of all the exception handlers that are active in the
4882 current stack frame at the current point of execution. To see other
4883 exception handlers, visit the associated frame (using the @code{up},
4884 @code{down}, or @code{frame} commands); then type @code{info catch}.
4885 @xref{Set Catchpoints, , Setting Catchpoints}.
4891 @chapter Examining Source Files
4893 @value{GDBN} can print parts of your program's source, since the debugging
4894 information recorded in the program tells @value{GDBN} what source files were
4895 used to build it. When your program stops, @value{GDBN} spontaneously prints
4896 the line where it stopped. Likewise, when you select a stack frame
4897 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
4898 execution in that frame has stopped. You can print other portions of
4899 source files by explicit command.
4901 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4902 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4903 @value{GDBN} under @sc{gnu} Emacs}.
4906 * List:: Printing source lines
4907 * Edit:: Editing source files
4908 * Search:: Searching source files
4909 * Source Path:: Specifying source directories
4910 * Machine Code:: Source and machine code
4914 @section Printing Source Lines
4917 @kindex l @r{(@code{list})}
4918 To print lines from a source file, use the @code{list} command
4919 (abbreviated @code{l}). By default, ten lines are printed.
4920 There are several ways to specify what part of the file you want to print.
4922 Here are the forms of the @code{list} command most commonly used:
4925 @item list @var{linenum}
4926 Print lines centered around line number @var{linenum} in the
4927 current source file.
4929 @item list @var{function}
4930 Print lines centered around the beginning of function
4934 Print more lines. If the last lines printed were printed with a
4935 @code{list} command, this prints lines following the last lines
4936 printed; however, if the last line printed was a solitary line printed
4937 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4938 Stack}), this prints lines centered around that line.
4941 Print lines just before the lines last printed.
4944 @cindex @code{list}, how many lines to display
4945 By default, @value{GDBN} prints ten source lines with any of these forms of
4946 the @code{list} command. You can change this using @code{set listsize}:
4949 @kindex set listsize
4950 @item set listsize @var{count}
4951 Make the @code{list} command display @var{count} source lines (unless
4952 the @code{list} argument explicitly specifies some other number).
4954 @kindex show listsize
4956 Display the number of lines that @code{list} prints.
4959 Repeating a @code{list} command with @key{RET} discards the argument,
4960 so it is equivalent to typing just @code{list}. This is more useful
4961 than listing the same lines again. An exception is made for an
4962 argument of @samp{-}; that argument is preserved in repetition so that
4963 each repetition moves up in the source file.
4966 In general, the @code{list} command expects you to supply zero, one or two
4967 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4968 of writing them, but the effect is always to specify some source line.
4969 Here is a complete description of the possible arguments for @code{list}:
4972 @item list @var{linespec}
4973 Print lines centered around the line specified by @var{linespec}.
4975 @item list @var{first},@var{last}
4976 Print lines from @var{first} to @var{last}. Both arguments are
4979 @item list ,@var{last}
4980 Print lines ending with @var{last}.
4982 @item list @var{first},
4983 Print lines starting with @var{first}.
4986 Print lines just after the lines last printed.
4989 Print lines just before the lines last printed.
4992 As described in the preceding table.
4995 Here are the ways of specifying a single source line---all the
5000 Specifies line @var{number} of the current source file.
5001 When a @code{list} command has two linespecs, this refers to
5002 the same source file as the first linespec.
5005 Specifies the line @var{offset} lines after the last line printed.
5006 When used as the second linespec in a @code{list} command that has
5007 two, this specifies the line @var{offset} lines down from the
5011 Specifies the line @var{offset} lines before the last line printed.
5013 @item @var{filename}:@var{number}
5014 Specifies line @var{number} in the source file @var{filename}.
5016 @item @var{function}
5017 Specifies the line that begins the body of the function @var{function}.
5018 For example: in C, this is the line with the open brace.
5020 @item @var{filename}:@var{function}
5021 Specifies the line of the open-brace that begins the body of the
5022 function @var{function} in the file @var{filename}. You only need the
5023 file name with a function name to avoid ambiguity when there are
5024 identically named functions in different source files.
5026 @item *@var{address}
5027 Specifies the line containing the program address @var{address}.
5028 @var{address} may be any expression.
5032 @section Editing Source Files
5033 @cindex editing source files
5036 @kindex e @r{(@code{edit})}
5037 To edit the lines in a source file, use the @code{edit} command.
5038 The editing program of your choice
5039 is invoked with the current line set to
5040 the active line in the program.
5041 Alternatively, there are several ways to specify what part of the file you
5042 want to print if you want to see other parts of the program.
5044 Here are the forms of the @code{edit} command most commonly used:
5048 Edit the current source file at the active line number in the program.
5050 @item edit @var{number}
5051 Edit the current source file with @var{number} as the active line number.
5053 @item edit @var{function}
5054 Edit the file containing @var{function} at the beginning of its definition.
5056 @item edit @var{filename}:@var{number}
5057 Specifies line @var{number} in the source file @var{filename}.
5059 @item edit @var{filename}:@var{function}
5060 Specifies the line that begins the body of the
5061 function @var{function} in the file @var{filename}. You only need the
5062 file name with a function name to avoid ambiguity when there are
5063 identically named functions in different source files.
5065 @item edit *@var{address}
5066 Specifies the line containing the program address @var{address}.
5067 @var{address} may be any expression.
5070 @subsection Choosing your Editor
5071 You can customize @value{GDBN} to use any editor you want
5073 The only restriction is that your editor (say @code{ex}), recognizes the
5074 following command-line syntax:
5076 ex +@var{number} file
5078 The optional numeric value +@var{number} specifies the number of the line in
5079 the file where to start editing.}.
5080 By default, it is @file{@value{EDITOR}}, but you can change this
5081 by setting the environment variable @code{EDITOR} before using
5082 @value{GDBN}. For example, to configure @value{GDBN} to use the
5083 @code{vi} editor, you could use these commands with the @code{sh} shell:
5089 or in the @code{csh} shell,
5091 setenv EDITOR /usr/bin/vi
5096 @section Searching Source Files
5097 @cindex searching source files
5099 There are two commands for searching through the current source file for a
5104 @kindex forward-search
5105 @item forward-search @var{regexp}
5106 @itemx search @var{regexp}
5107 The command @samp{forward-search @var{regexp}} checks each line,
5108 starting with the one following the last line listed, for a match for
5109 @var{regexp}. It lists the line that is found. You can use the
5110 synonym @samp{search @var{regexp}} or abbreviate the command name as
5113 @kindex reverse-search
5114 @item reverse-search @var{regexp}
5115 The command @samp{reverse-search @var{regexp}} checks each line, starting
5116 with the one before the last line listed and going backward, for a match
5117 for @var{regexp}. It lists the line that is found. You can abbreviate
5118 this command as @code{rev}.
5122 @section Specifying Source Directories
5125 @cindex directories for source files
5126 Executable programs sometimes do not record the directories of the source
5127 files from which they were compiled, just the names. Even when they do,
5128 the directories could be moved between the compilation and your debugging
5129 session. @value{GDBN} has a list of directories to search for source files;
5130 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
5131 it tries all the directories in the list, in the order they are present
5132 in the list, until it finds a file with the desired name.
5134 For example, suppose an executable references the file
5135 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
5136 @file{/mnt/cross}. The file is first looked up literally; if this
5137 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
5138 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
5139 message is printed. @value{GDBN} does not look up the parts of the
5140 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
5141 Likewise, the subdirectories of the source path are not searched: if
5142 the source path is @file{/mnt/cross}, and the binary refers to
5143 @file{foo.c}, @value{GDBN} would not find it under
5144 @file{/mnt/cross/usr/src/foo-1.0/lib}.
5146 Plain file names, relative file names with leading directories, file
5147 names containing dots, etc.@: are all treated as described above; for
5148 instance, if the source path is @file{/mnt/cross}, and the source file
5149 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
5150 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
5151 that---@file{/mnt/cross/foo.c}.
5153 Note that the executable search path is @emph{not} used to locate the
5156 Whenever you reset or rearrange the source path, @value{GDBN} clears out
5157 any information it has cached about where source files are found and where
5158 each line is in the file.
5162 When you start @value{GDBN}, its source path includes only @samp{cdir}
5163 and @samp{cwd}, in that order.
5164 To add other directories, use the @code{directory} command.
5166 The search path is used to find both program source files and @value{GDBN}
5167 script files (read using the @samp{-command} option and @samp{source} command).
5169 In addition to the source path, @value{GDBN} provides a set of commands
5170 that manage a list of source path substitution rules. A @dfn{substitution
5171 rule} specifies how to rewrite source directories stored in the program's
5172 debug information in case the sources were moved to a different
5173 directory between compilation and debugging. A rule is made of
5174 two strings, the first specifying what needs to be rewritten in
5175 the path, and the second specifying how it should be rewritten.
5176 In @ref{set substitute-path}, we name these two parts @var{from} and
5177 @var{to} respectively. @value{GDBN} does a simple string replacement
5178 of @var{from} with @var{to} at the start of the directory part of the
5179 source file name, and uses that result instead of the original file
5180 name to look up the sources.
5182 Using the previous example, suppose the @file{foo-1.0} tree has been
5183 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
5184 @value{GDBN} to replace @file{/usr/src} in all source path names with
5185 @file{/mnt/cross}. The first lookup will then be
5186 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
5187 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
5188 substitution rule, use the @code{set substitute-path} command
5189 (@pxref{set substitute-path}).
5191 To avoid unexpected substitution results, a rule is applied only if the
5192 @var{from} part of the directory name ends at a directory separator.
5193 For instance, a rule substituting @file{/usr/source} into
5194 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
5195 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
5196 is applied only at the beginning of the directory name, this rule will
5197 not be applied to @file{/root/usr/source/baz.c} either.
5199 In many cases, you can achieve the same result using the @code{directory}
5200 command. However, @code{set substitute-path} can be more efficient in
5201 the case where the sources are organized in a complex tree with multiple
5202 subdirectories. With the @code{directory} command, you need to add each
5203 subdirectory of your project. If you moved the entire tree while
5204 preserving its internal organization, then @code{set substitute-path}
5205 allows you to direct the debugger to all the sources with one single
5208 @code{set substitute-path} is also more than just a shortcut command.
5209 The source path is only used if the file at the original location no
5210 longer exists. On the other hand, @code{set substitute-path} modifies
5211 the debugger behavior to look at the rewritten location instead. So, if
5212 for any reason a source file that is not relevant to your executable is
5213 located at the original location, a substitution rule is the only
5214 method available to point @value{GDBN} at the new location.
5217 @item directory @var{dirname} @dots{}
5218 @item dir @var{dirname} @dots{}
5219 Add directory @var{dirname} to the front of the source path. Several
5220 directory names may be given to this command, separated by @samp{:}
5221 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
5222 part of absolute file names) or
5223 whitespace. You may specify a directory that is already in the source
5224 path; this moves it forward, so @value{GDBN} searches it sooner.
5228 @vindex $cdir@r{, convenience variable}
5229 @vindex $cwd@r{, convenience variable}
5230 @cindex compilation directory
5231 @cindex current directory
5232 @cindex working directory
5233 @cindex directory, current
5234 @cindex directory, compilation
5235 You can use the string @samp{$cdir} to refer to the compilation
5236 directory (if one is recorded), and @samp{$cwd} to refer to the current
5237 working directory. @samp{$cwd} is not the same as @samp{.}---the former
5238 tracks the current working directory as it changes during your @value{GDBN}
5239 session, while the latter is immediately expanded to the current
5240 directory at the time you add an entry to the source path.
5243 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
5245 @c RET-repeat for @code{directory} is explicitly disabled, but since
5246 @c repeating it would be a no-op we do not say that. (thanks to RMS)
5248 @item show directories
5249 @kindex show directories
5250 Print the source path: show which directories it contains.
5252 @anchor{set substitute-path}
5253 @item set substitute-path @var{from} @var{to}
5254 @kindex set substitute-path
5255 Define a source path substitution rule, and add it at the end of the
5256 current list of existing substitution rules. If a rule with the same
5257 @var{from} was already defined, then the old rule is also deleted.
5259 For example, if the file @file{/foo/bar/baz.c} was moved to
5260 @file{/mnt/cross/baz.c}, then the command
5263 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
5267 will tell @value{GDBN} to replace @samp{/usr/src} with
5268 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
5269 @file{baz.c} even though it was moved.
5271 In the case when more than one substitution rule have been defined,
5272 the rules are evaluated one by one in the order where they have been
5273 defined. The first one matching, if any, is selected to perform
5276 For instance, if we had entered the following commands:
5279 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
5280 (@value{GDBP}) set substitute-path /usr/src /mnt/src
5284 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
5285 @file{/mnt/include/defs.h} by using the first rule. However, it would
5286 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
5287 @file{/mnt/src/lib/foo.c}.
5290 @item unset substitute-path [path]
5291 @kindex unset substitute-path
5292 If a path is specified, search the current list of substitution rules
5293 for a rule that would rewrite that path. Delete that rule if found.
5294 A warning is emitted by the debugger if no rule could be found.
5296 If no path is specified, then all substitution rules are deleted.
5298 @item show substitute-path [path]
5299 @kindex show substitute-path
5300 If a path is specified, then print the source path substitution rule
5301 which would rewrite that path, if any.
5303 If no path is specified, then print all existing source path substitution
5308 If your source path is cluttered with directories that are no longer of
5309 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
5310 versions of source. You can correct the situation as follows:
5314 Use @code{directory} with no argument to reset the source path to its default value.
5317 Use @code{directory} with suitable arguments to reinstall the
5318 directories you want in the source path. You can add all the
5319 directories in one command.
5323 @section Source and Machine Code
5324 @cindex source line and its code address
5326 You can use the command @code{info line} to map source lines to program
5327 addresses (and vice versa), and the command @code{disassemble} to display
5328 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
5329 mode, the @code{info line} command causes the arrow to point to the
5330 line specified. Also, @code{info line} prints addresses in symbolic form as
5335 @item info line @var{linespec}
5336 Print the starting and ending addresses of the compiled code for
5337 source line @var{linespec}. You can specify source lines in any of
5338 the ways understood by the @code{list} command (@pxref{List, ,Printing
5342 For example, we can use @code{info line} to discover the location of
5343 the object code for the first line of function
5344 @code{m4_changequote}:
5346 @c FIXME: I think this example should also show the addresses in
5347 @c symbolic form, as they usually would be displayed.
5349 (@value{GDBP}) info line m4_changequote
5350 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
5354 @cindex code address and its source line
5355 We can also inquire (using @code{*@var{addr}} as the form for
5356 @var{linespec}) what source line covers a particular address:
5358 (@value{GDBP}) info line *0x63ff
5359 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
5362 @cindex @code{$_} and @code{info line}
5363 @cindex @code{x} command, default address
5364 @kindex x@r{(examine), and} info line
5365 After @code{info line}, the default address for the @code{x} command
5366 is changed to the starting address of the line, so that @samp{x/i} is
5367 sufficient to begin examining the machine code (@pxref{Memory,
5368 ,Examining Memory}). Also, this address is saved as the value of the
5369 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
5374 @cindex assembly instructions
5375 @cindex instructions, assembly
5376 @cindex machine instructions
5377 @cindex listing machine instructions
5379 This specialized command dumps a range of memory as machine
5380 instructions. The default memory range is the function surrounding the
5381 program counter of the selected frame. A single argument to this
5382 command is a program counter value; @value{GDBN} dumps the function
5383 surrounding this value. Two arguments specify a range of addresses
5384 (first inclusive, second exclusive) to dump.
5387 The following example shows the disassembly of a range of addresses of
5388 HP PA-RISC 2.0 code:
5391 (@value{GDBP}) disas 0x32c4 0x32e4
5392 Dump of assembler code from 0x32c4 to 0x32e4:
5393 0x32c4 <main+204>: addil 0,dp
5394 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
5395 0x32cc <main+212>: ldil 0x3000,r31
5396 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
5397 0x32d4 <main+220>: ldo 0(r31),rp
5398 0x32d8 <main+224>: addil -0x800,dp
5399 0x32dc <main+228>: ldo 0x588(r1),r26
5400 0x32e0 <main+232>: ldil 0x3000,r31
5401 End of assembler dump.
5404 Some architectures have more than one commonly-used set of instruction
5405 mnemonics or other syntax.
5407 For programs that were dynamically linked and use shared libraries,
5408 instructions that call functions or branch to locations in the shared
5409 libraries might show a seemingly bogus location---it's actually a
5410 location of the relocation table. On some architectures, @value{GDBN}
5411 might be able to resolve these to actual function names.
5414 @kindex set disassembly-flavor
5415 @cindex Intel disassembly flavor
5416 @cindex AT&T disassembly flavor
5417 @item set disassembly-flavor @var{instruction-set}
5418 Select the instruction set to use when disassembling the
5419 program via the @code{disassemble} or @code{x/i} commands.
5421 Currently this command is only defined for the Intel x86 family. You
5422 can set @var{instruction-set} to either @code{intel} or @code{att}.
5423 The default is @code{att}, the AT&T flavor used by default by Unix
5424 assemblers for x86-based targets.
5426 @kindex show disassembly-flavor
5427 @item show disassembly-flavor
5428 Show the current setting of the disassembly flavor.
5433 @chapter Examining Data
5435 @cindex printing data
5436 @cindex examining data
5439 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
5440 @c document because it is nonstandard... Under Epoch it displays in a
5441 @c different window or something like that.
5442 The usual way to examine data in your program is with the @code{print}
5443 command (abbreviated @code{p}), or its synonym @code{inspect}. It
5444 evaluates and prints the value of an expression of the language your
5445 program is written in (@pxref{Languages, ,Using @value{GDBN} with
5446 Different Languages}).
5449 @item print @var{expr}
5450 @itemx print /@var{f} @var{expr}
5451 @var{expr} is an expression (in the source language). By default the
5452 value of @var{expr} is printed in a format appropriate to its data type;
5453 you can choose a different format by specifying @samp{/@var{f}}, where
5454 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
5458 @itemx print /@var{f}
5459 @cindex reprint the last value
5460 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
5461 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
5462 conveniently inspect the same value in an alternative format.
5465 A more low-level way of examining data is with the @code{x} command.
5466 It examines data in memory at a specified address and prints it in a
5467 specified format. @xref{Memory, ,Examining Memory}.
5469 If you are interested in information about types, or about how the
5470 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
5471 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
5475 * Expressions:: Expressions
5476 * Variables:: Program variables
5477 * Arrays:: Artificial arrays
5478 * Output Formats:: Output formats
5479 * Memory:: Examining memory
5480 * Auto Display:: Automatic display
5481 * Print Settings:: Print settings
5482 * Value History:: Value history
5483 * Convenience Vars:: Convenience variables
5484 * Registers:: Registers
5485 * Floating Point Hardware:: Floating point hardware
5486 * Vector Unit:: Vector Unit
5487 * OS Information:: Auxiliary data provided by operating system
5488 * Memory Region Attributes:: Memory region attributes
5489 * Dump/Restore Files:: Copy between memory and a file
5490 * Core File Generation:: Cause a program dump its core
5491 * Character Sets:: Debugging programs that use a different
5492 character set than GDB does
5493 * Caching Remote Data:: Data caching for remote targets
5497 @section Expressions
5500 @code{print} and many other @value{GDBN} commands accept an expression and
5501 compute its value. Any kind of constant, variable or operator defined
5502 by the programming language you are using is valid in an expression in
5503 @value{GDBN}. This includes conditional expressions, function calls,
5504 casts, and string constants. It also includes preprocessor macros, if
5505 you compiled your program to include this information; see
5508 @cindex arrays in expressions
5509 @value{GDBN} supports array constants in expressions input by
5510 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
5511 you can use the command @code{print @{1, 2, 3@}} to build up an array in
5512 memory that is @code{malloc}ed in the target program.
5514 Because C is so widespread, most of the expressions shown in examples in
5515 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
5516 Languages}, for information on how to use expressions in other
5519 In this section, we discuss operators that you can use in @value{GDBN}
5520 expressions regardless of your programming language.
5522 @cindex casts, in expressions
5523 Casts are supported in all languages, not just in C, because it is so
5524 useful to cast a number into a pointer in order to examine a structure
5525 at that address in memory.
5526 @c FIXME: casts supported---Mod2 true?
5528 @value{GDBN} supports these operators, in addition to those common
5529 to programming languages:
5533 @samp{@@} is a binary operator for treating parts of memory as arrays.
5534 @xref{Arrays, ,Artificial Arrays}, for more information.
5537 @samp{::} allows you to specify a variable in terms of the file or
5538 function where it is defined. @xref{Variables, ,Program Variables}.
5540 @cindex @{@var{type}@}
5541 @cindex type casting memory
5542 @cindex memory, viewing as typed object
5543 @cindex casts, to view memory
5544 @item @{@var{type}@} @var{addr}
5545 Refers to an object of type @var{type} stored at address @var{addr} in
5546 memory. @var{addr} may be any expression whose value is an integer or
5547 pointer (but parentheses are required around binary operators, just as in
5548 a cast). This construct is allowed regardless of what kind of data is
5549 normally supposed to reside at @var{addr}.
5553 @section Program Variables
5555 The most common kind of expression to use is the name of a variable
5558 Variables in expressions are understood in the selected stack frame
5559 (@pxref{Selection, ,Selecting a Frame}); they must be either:
5563 global (or file-static)
5570 visible according to the scope rules of the
5571 programming language from the point of execution in that frame
5574 @noindent This means that in the function
5589 you can examine and use the variable @code{a} whenever your program is
5590 executing within the function @code{foo}, but you can only use or
5591 examine the variable @code{b} while your program is executing inside
5592 the block where @code{b} is declared.
5594 @cindex variable name conflict
5595 There is an exception: you can refer to a variable or function whose
5596 scope is a single source file even if the current execution point is not
5597 in this file. But it is possible to have more than one such variable or
5598 function with the same name (in different source files). If that
5599 happens, referring to that name has unpredictable effects. If you wish,
5600 you can specify a static variable in a particular function or file,
5601 using the colon-colon (@code{::}) notation:
5603 @cindex colon-colon, context for variables/functions
5605 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
5606 @cindex @code{::}, context for variables/functions
5609 @var{file}::@var{variable}
5610 @var{function}::@var{variable}
5614 Here @var{file} or @var{function} is the name of the context for the
5615 static @var{variable}. In the case of file names, you can use quotes to
5616 make sure @value{GDBN} parses the file name as a single word---for example,
5617 to print a global value of @code{x} defined in @file{f2.c}:
5620 (@value{GDBP}) p 'f2.c'::x
5623 @cindex C@t{++} scope resolution
5624 This use of @samp{::} is very rarely in conflict with the very similar
5625 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
5626 scope resolution operator in @value{GDBN} expressions.
5627 @c FIXME: Um, so what happens in one of those rare cases where it's in
5630 @cindex wrong values
5631 @cindex variable values, wrong
5632 @cindex function entry/exit, wrong values of variables
5633 @cindex optimized code, wrong values of variables
5635 @emph{Warning:} Occasionally, a local variable may appear to have the
5636 wrong value at certain points in a function---just after entry to a new
5637 scope, and just before exit.
5639 You may see this problem when you are stepping by machine instructions.
5640 This is because, on most machines, it takes more than one instruction to
5641 set up a stack frame (including local variable definitions); if you are
5642 stepping by machine instructions, variables may appear to have the wrong
5643 values until the stack frame is completely built. On exit, it usually
5644 also takes more than one machine instruction to destroy a stack frame;
5645 after you begin stepping through that group of instructions, local
5646 variable definitions may be gone.
5648 This may also happen when the compiler does significant optimizations.
5649 To be sure of always seeing accurate values, turn off all optimization
5652 @cindex ``No symbol "foo" in current context''
5653 Another possible effect of compiler optimizations is to optimize
5654 unused variables out of existence, or assign variables to registers (as
5655 opposed to memory addresses). Depending on the support for such cases
5656 offered by the debug info format used by the compiler, @value{GDBN}
5657 might not be able to display values for such local variables. If that
5658 happens, @value{GDBN} will print a message like this:
5661 No symbol "foo" in current context.
5664 To solve such problems, either recompile without optimizations, or use a
5665 different debug info format, if the compiler supports several such
5666 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
5667 usually supports the @option{-gstabs+} option. @option{-gstabs+}
5668 produces debug info in a format that is superior to formats such as
5669 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
5670 an effective form for debug info. @xref{Debugging Options,,Options
5671 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
5672 Compiler Collection (GCC)}.
5673 @xref{C, ,C and C@t{++}}, for more information about debug info formats
5674 that are best suited to C@t{++} programs.
5676 If you ask to print an object whose contents are unknown to
5677 @value{GDBN}, e.g., because its data type is not completely specified
5678 by the debug information, @value{GDBN} will say @samp{<incomplete
5679 type>}. @xref{Symbols, incomplete type}, for more about this.
5681 Strings are identified as arrays of @code{char} values without specified
5682 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
5683 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
5684 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
5685 defines literal string type @code{"char"} as @code{char} without a sign.
5690 signed char var1[] = "A";
5693 You get during debugging
5698 $2 = @{65 'A', 0 '\0'@}
5702 @section Artificial Arrays
5704 @cindex artificial array
5706 @kindex @@@r{, referencing memory as an array}
5707 It is often useful to print out several successive objects of the
5708 same type in memory; a section of an array, or an array of
5709 dynamically determined size for which only a pointer exists in the
5712 You can do this by referring to a contiguous span of memory as an
5713 @dfn{artificial array}, using the binary operator @samp{@@}. The left
5714 operand of @samp{@@} should be the first element of the desired array
5715 and be an individual object. The right operand should be the desired length
5716 of the array. The result is an array value whose elements are all of
5717 the type of the left argument. The first element is actually the left
5718 argument; the second element comes from bytes of memory immediately
5719 following those that hold the first element, and so on. Here is an
5720 example. If a program says
5723 int *array = (int *) malloc (len * sizeof (int));
5727 you can print the contents of @code{array} with
5733 The left operand of @samp{@@} must reside in memory. Array values made
5734 with @samp{@@} in this way behave just like other arrays in terms of
5735 subscripting, and are coerced to pointers when used in expressions.
5736 Artificial arrays most often appear in expressions via the value history
5737 (@pxref{Value History, ,Value History}), after printing one out.
5739 Another way to create an artificial array is to use a cast.
5740 This re-interprets a value as if it were an array.
5741 The value need not be in memory:
5743 (@value{GDBP}) p/x (short[2])0x12345678
5744 $1 = @{0x1234, 0x5678@}
5747 As a convenience, if you leave the array length out (as in
5748 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
5749 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
5751 (@value{GDBP}) p/x (short[])0x12345678
5752 $2 = @{0x1234, 0x5678@}
5755 Sometimes the artificial array mechanism is not quite enough; in
5756 moderately complex data structures, the elements of interest may not
5757 actually be adjacent---for example, if you are interested in the values
5758 of pointers in an array. One useful work-around in this situation is
5759 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
5760 Variables}) as a counter in an expression that prints the first
5761 interesting value, and then repeat that expression via @key{RET}. For
5762 instance, suppose you have an array @code{dtab} of pointers to
5763 structures, and you are interested in the values of a field @code{fv}
5764 in each structure. Here is an example of what you might type:
5774 @node Output Formats
5775 @section Output Formats
5777 @cindex formatted output
5778 @cindex output formats
5779 By default, @value{GDBN} prints a value according to its data type. Sometimes
5780 this is not what you want. For example, you might want to print a number
5781 in hex, or a pointer in decimal. Or you might want to view data in memory
5782 at a certain address as a character string or as an instruction. To do
5783 these things, specify an @dfn{output format} when you print a value.
5785 The simplest use of output formats is to say how to print a value
5786 already computed. This is done by starting the arguments of the
5787 @code{print} command with a slash and a format letter. The format
5788 letters supported are:
5792 Regard the bits of the value as an integer, and print the integer in
5796 Print as integer in signed decimal.
5799 Print as integer in unsigned decimal.
5802 Print as integer in octal.
5805 Print as integer in binary. The letter @samp{t} stands for ``two''.
5806 @footnote{@samp{b} cannot be used because these format letters are also
5807 used with the @code{x} command, where @samp{b} stands for ``byte'';
5808 see @ref{Memory,,Examining Memory}.}
5811 @cindex unknown address, locating
5812 @cindex locate address
5813 Print as an address, both absolute in hexadecimal and as an offset from
5814 the nearest preceding symbol. You can use this format used to discover
5815 where (in what function) an unknown address is located:
5818 (@value{GDBP}) p/a 0x54320
5819 $3 = 0x54320 <_initialize_vx+396>
5823 The command @code{info symbol 0x54320} yields similar results.
5824 @xref{Symbols, info symbol}.
5827 Regard as an integer and print it as a character constant. This
5828 prints both the numerical value and its character representation. The
5829 character representation is replaced with the octal escape @samp{\nnn}
5830 for characters outside the 7-bit @sc{ascii} range.
5832 Without this format, @value{GDBN} displays @code{char},
5833 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
5834 constants. Single-byte members of vectors are displayed as integer
5838 Regard the bits of the value as a floating point number and print
5839 using typical floating point syntax.
5842 @cindex printing strings
5843 @cindex printing byte arrays
5844 Regard as a string, if possible. With this format, pointers to single-byte
5845 data are displayed as null-terminated strings and arrays of single-byte data
5846 are displayed as fixed-length strings. Other values are displayed in their
5849 Without this format, @value{GDBN} displays pointers to and arrays of
5850 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
5851 strings. Single-byte members of a vector are displayed as an integer
5855 For example, to print the program counter in hex (@pxref{Registers}), type
5862 Note that no space is required before the slash; this is because command
5863 names in @value{GDBN} cannot contain a slash.
5865 To reprint the last value in the value history with a different format,
5866 you can use the @code{print} command with just a format and no
5867 expression. For example, @samp{p/x} reprints the last value in hex.
5870 @section Examining Memory
5872 You can use the command @code{x} (for ``examine'') to examine memory in
5873 any of several formats, independently of your program's data types.
5875 @cindex examining memory
5877 @kindex x @r{(examine memory)}
5878 @item x/@var{nfu} @var{addr}
5881 Use the @code{x} command to examine memory.
5884 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
5885 much memory to display and how to format it; @var{addr} is an
5886 expression giving the address where you want to start displaying memory.
5887 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
5888 Several commands set convenient defaults for @var{addr}.
5891 @item @var{n}, the repeat count
5892 The repeat count is a decimal integer; the default is 1. It specifies
5893 how much memory (counting by units @var{u}) to display.
5894 @c This really is **decimal**; unaffected by 'set radix' as of GDB
5897 @item @var{f}, the display format
5898 The display format is one of the formats used by @code{print}
5899 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
5900 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
5901 The default is @samp{x} (hexadecimal) initially. The default changes
5902 each time you use either @code{x} or @code{print}.
5904 @item @var{u}, the unit size
5905 The unit size is any of
5911 Halfwords (two bytes).
5913 Words (four bytes). This is the initial default.
5915 Giant words (eight bytes).
5918 Each time you specify a unit size with @code{x}, that size becomes the
5919 default unit the next time you use @code{x}. (For the @samp{s} and
5920 @samp{i} formats, the unit size is ignored and is normally not written.)
5922 @item @var{addr}, starting display address
5923 @var{addr} is the address where you want @value{GDBN} to begin displaying
5924 memory. The expression need not have a pointer value (though it may);
5925 it is always interpreted as an integer address of a byte of memory.
5926 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
5927 @var{addr} is usually just after the last address examined---but several
5928 other commands also set the default address: @code{info breakpoints} (to
5929 the address of the last breakpoint listed), @code{info line} (to the
5930 starting address of a line), and @code{print} (if you use it to display
5931 a value from memory).
5934 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
5935 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
5936 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
5937 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
5938 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
5940 Since the letters indicating unit sizes are all distinct from the
5941 letters specifying output formats, you do not have to remember whether
5942 unit size or format comes first; either order works. The output
5943 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
5944 (However, the count @var{n} must come first; @samp{wx4} does not work.)
5946 Even though the unit size @var{u} is ignored for the formats @samp{s}
5947 and @samp{i}, you might still want to use a count @var{n}; for example,
5948 @samp{3i} specifies that you want to see three machine instructions,
5949 including any operands. For convenience, especially when used with
5950 the @code{display} command, the @samp{i} format also prints branch delay
5951 slot instructions, if any, beyond the count specified, which immediately
5952 follow the last instruction that is within the count. The command
5953 @code{disassemble} gives an alternative way of inspecting machine
5954 instructions; see @ref{Machine Code,,Source and Machine Code}.
5956 All the defaults for the arguments to @code{x} are designed to make it
5957 easy to continue scanning memory with minimal specifications each time
5958 you use @code{x}. For example, after you have inspected three machine
5959 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
5960 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
5961 the repeat count @var{n} is used again; the other arguments default as
5962 for successive uses of @code{x}.
5964 @cindex @code{$_}, @code{$__}, and value history
5965 The addresses and contents printed by the @code{x} command are not saved
5966 in the value history because there is often too much of them and they
5967 would get in the way. Instead, @value{GDBN} makes these values available for
5968 subsequent use in expressions as values of the convenience variables
5969 @code{$_} and @code{$__}. After an @code{x} command, the last address
5970 examined is available for use in expressions in the convenience variable
5971 @code{$_}. The contents of that address, as examined, are available in
5972 the convenience variable @code{$__}.
5974 If the @code{x} command has a repeat count, the address and contents saved
5975 are from the last memory unit printed; this is not the same as the last
5976 address printed if several units were printed on the last line of output.
5978 @cindex remote memory comparison
5979 @cindex verify remote memory image
5980 When you are debugging a program running on a remote target machine
5981 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
5982 remote machine's memory against the executable file you downloaded to
5983 the target. The @code{compare-sections} command is provided for such
5987 @kindex compare-sections
5988 @item compare-sections @r{[}@var{section-name}@r{]}
5989 Compare the data of a loadable section @var{section-name} in the
5990 executable file of the program being debugged with the same section in
5991 the remote machine's memory, and report any mismatches. With no
5992 arguments, compares all loadable sections. This command's
5993 availability depends on the target's support for the @code{"qCRC"}
5998 @section Automatic Display
5999 @cindex automatic display
6000 @cindex display of expressions
6002 If you find that you want to print the value of an expression frequently
6003 (to see how it changes), you might want to add it to the @dfn{automatic
6004 display list} so that @value{GDBN} prints its value each time your program stops.
6005 Each expression added to the list is given a number to identify it;
6006 to remove an expression from the list, you specify that number.
6007 The automatic display looks like this:
6011 3: bar[5] = (struct hack *) 0x3804
6015 This display shows item numbers, expressions and their current values. As with
6016 displays you request manually using @code{x} or @code{print}, you can
6017 specify the output format you prefer; in fact, @code{display} decides
6018 whether to use @code{print} or @code{x} depending your format
6019 specification---it uses @code{x} if you specify either the @samp{i}
6020 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
6024 @item display @var{expr}
6025 Add the expression @var{expr} to the list of expressions to display
6026 each time your program stops. @xref{Expressions, ,Expressions}.
6028 @code{display} does not repeat if you press @key{RET} again after using it.
6030 @item display/@var{fmt} @var{expr}
6031 For @var{fmt} specifying only a display format and not a size or
6032 count, add the expression @var{expr} to the auto-display list but
6033 arrange to display it each time in the specified format @var{fmt}.
6034 @xref{Output Formats,,Output Formats}.
6036 @item display/@var{fmt} @var{addr}
6037 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
6038 number of units, add the expression @var{addr} as a memory address to
6039 be examined each time your program stops. Examining means in effect
6040 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
6043 For example, @samp{display/i $pc} can be helpful, to see the machine
6044 instruction about to be executed each time execution stops (@samp{$pc}
6045 is a common name for the program counter; @pxref{Registers, ,Registers}).
6048 @kindex delete display
6050 @item undisplay @var{dnums}@dots{}
6051 @itemx delete display @var{dnums}@dots{}
6052 Remove item numbers @var{dnums} from the list of expressions to display.
6054 @code{undisplay} does not repeat if you press @key{RET} after using it.
6055 (Otherwise you would just get the error @samp{No display number @dots{}}.)
6057 @kindex disable display
6058 @item disable display @var{dnums}@dots{}
6059 Disable the display of item numbers @var{dnums}. A disabled display
6060 item is not printed automatically, but is not forgotten. It may be
6061 enabled again later.
6063 @kindex enable display
6064 @item enable display @var{dnums}@dots{}
6065 Enable display of item numbers @var{dnums}. It becomes effective once
6066 again in auto display of its expression, until you specify otherwise.
6069 Display the current values of the expressions on the list, just as is
6070 done when your program stops.
6072 @kindex info display
6074 Print the list of expressions previously set up to display
6075 automatically, each one with its item number, but without showing the
6076 values. This includes disabled expressions, which are marked as such.
6077 It also includes expressions which would not be displayed right now
6078 because they refer to automatic variables not currently available.
6081 @cindex display disabled out of scope
6082 If a display expression refers to local variables, then it does not make
6083 sense outside the lexical context for which it was set up. Such an
6084 expression is disabled when execution enters a context where one of its
6085 variables is not defined. For example, if you give the command
6086 @code{display last_char} while inside a function with an argument
6087 @code{last_char}, @value{GDBN} displays this argument while your program
6088 continues to stop inside that function. When it stops elsewhere---where
6089 there is no variable @code{last_char}---the display is disabled
6090 automatically. The next time your program stops where @code{last_char}
6091 is meaningful, you can enable the display expression once again.
6093 @node Print Settings
6094 @section Print Settings
6096 @cindex format options
6097 @cindex print settings
6098 @value{GDBN} provides the following ways to control how arrays, structures,
6099 and symbols are printed.
6102 These settings are useful for debugging programs in any language:
6106 @item set print address
6107 @itemx set print address on
6108 @cindex print/don't print memory addresses
6109 @value{GDBN} prints memory addresses showing the location of stack
6110 traces, structure values, pointer values, breakpoints, and so forth,
6111 even when it also displays the contents of those addresses. The default
6112 is @code{on}. For example, this is what a stack frame display looks like with
6113 @code{set print address on}:
6118 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
6120 530 if (lquote != def_lquote)
6124 @item set print address off
6125 Do not print addresses when displaying their contents. For example,
6126 this is the same stack frame displayed with @code{set print address off}:
6130 (@value{GDBP}) set print addr off
6132 #0 set_quotes (lq="<<", rq=">>") at input.c:530
6133 530 if (lquote != def_lquote)
6137 You can use @samp{set print address off} to eliminate all machine
6138 dependent displays from the @value{GDBN} interface. For example, with
6139 @code{print address off}, you should get the same text for backtraces on
6140 all machines---whether or not they involve pointer arguments.
6143 @item show print address
6144 Show whether or not addresses are to be printed.
6147 When @value{GDBN} prints a symbolic address, it normally prints the
6148 closest earlier symbol plus an offset. If that symbol does not uniquely
6149 identify the address (for example, it is a name whose scope is a single
6150 source file), you may need to clarify. One way to do this is with
6151 @code{info line}, for example @samp{info line *0x4537}. Alternately,
6152 you can set @value{GDBN} to print the source file and line number when
6153 it prints a symbolic address:
6156 @item set print symbol-filename on
6157 @cindex source file and line of a symbol
6158 @cindex symbol, source file and line
6159 Tell @value{GDBN} to print the source file name and line number of a
6160 symbol in the symbolic form of an address.
6162 @item set print symbol-filename off
6163 Do not print source file name and line number of a symbol. This is the
6166 @item show print symbol-filename
6167 Show whether or not @value{GDBN} will print the source file name and
6168 line number of a symbol in the symbolic form of an address.
6171 Another situation where it is helpful to show symbol filenames and line
6172 numbers is when disassembling code; @value{GDBN} shows you the line
6173 number and source file that corresponds to each instruction.
6175 Also, you may wish to see the symbolic form only if the address being
6176 printed is reasonably close to the closest earlier symbol:
6179 @item set print max-symbolic-offset @var{max-offset}
6180 @cindex maximum value for offset of closest symbol
6181 Tell @value{GDBN} to only display the symbolic form of an address if the
6182 offset between the closest earlier symbol and the address is less than
6183 @var{max-offset}. The default is 0, which tells @value{GDBN}
6184 to always print the symbolic form of an address if any symbol precedes it.
6186 @item show print max-symbolic-offset
6187 Ask how large the maximum offset is that @value{GDBN} prints in a
6191 @cindex wild pointer, interpreting
6192 @cindex pointer, finding referent
6193 If you have a pointer and you are not sure where it points, try
6194 @samp{set print symbol-filename on}. Then you can determine the name
6195 and source file location of the variable where it points, using
6196 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
6197 For example, here @value{GDBN} shows that a variable @code{ptt} points
6198 at another variable @code{t}, defined in @file{hi2.c}:
6201 (@value{GDBP}) set print symbol-filename on
6202 (@value{GDBP}) p/a ptt
6203 $4 = 0xe008 <t in hi2.c>
6207 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
6208 does not show the symbol name and filename of the referent, even with
6209 the appropriate @code{set print} options turned on.
6212 Other settings control how different kinds of objects are printed:
6215 @item set print array
6216 @itemx set print array on
6217 @cindex pretty print arrays
6218 Pretty print arrays. This format is more convenient to read,
6219 but uses more space. The default is off.
6221 @item set print array off
6222 Return to compressed format for arrays.
6224 @item show print array
6225 Show whether compressed or pretty format is selected for displaying
6228 @cindex print array indexes
6229 @item set print array-indexes
6230 @itemx set print array-indexes on
6231 Print the index of each element when displaying arrays. May be more
6232 convenient to locate a given element in the array or quickly find the
6233 index of a given element in that printed array. The default is off.
6235 @item set print array-indexes off
6236 Stop printing element indexes when displaying arrays.
6238 @item show print array-indexes
6239 Show whether the index of each element is printed when displaying
6242 @item set print elements @var{number-of-elements}
6243 @cindex number of array elements to print
6244 @cindex limit on number of printed array elements
6245 Set a limit on how many elements of an array @value{GDBN} will print.
6246 If @value{GDBN} is printing a large array, it stops printing after it has
6247 printed the number of elements set by the @code{set print elements} command.
6248 This limit also applies to the display of strings.
6249 When @value{GDBN} starts, this limit is set to 200.
6250 Setting @var{number-of-elements} to zero means that the printing is unlimited.
6252 @item show print elements
6253 Display the number of elements of a large array that @value{GDBN} will print.
6254 If the number is 0, then the printing is unlimited.
6256 @item set print frame-arguments @var{value}
6257 @cindex printing frame argument values
6258 @cindex print all frame argument values
6259 @cindex print frame argument values for scalars only
6260 @cindex do not print frame argument values
6261 This command allows to control how the values of arguments are printed
6262 when the debugger prints a frame (@pxref{Frames}). The possible
6267 The values of all arguments are printed. This is the default.
6270 Print the value of an argument only if it is a scalar. The value of more
6271 complex arguments such as arrays, structures, unions, etc, is replaced
6272 by @code{@dots{}}. Here is an example where only scalar arguments are shown:
6275 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
6280 None of the argument values are printed. Instead, the value of each argument
6281 is replaced by @code{@dots{}}. In this case, the example above now becomes:
6284 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
6289 By default, all argument values are always printed. But this command
6290 can be useful in several cases. For instance, it can be used to reduce
6291 the amount of information printed in each frame, making the backtrace
6292 more readable. Also, this command can be used to improve performance
6293 when displaying Ada frames, because the computation of large arguments
6294 can sometimes be CPU-intensive, especiallly in large applications.
6295 Setting @code{print frame-arguments} to @code{scalars} or @code{none}
6296 avoids this computation, thus speeding up the display of each Ada frame.
6298 @item show print frame-arguments
6299 Show how the value of arguments should be displayed when printing a frame.
6301 @item set print repeats
6302 @cindex repeated array elements
6303 Set the threshold for suppressing display of repeated array
6304 elements. When the number of consecutive identical elements of an
6305 array exceeds the threshold, @value{GDBN} prints the string
6306 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
6307 identical repetitions, instead of displaying the identical elements
6308 themselves. Setting the threshold to zero will cause all elements to
6309 be individually printed. The default threshold is 10.
6311 @item show print repeats
6312 Display the current threshold for printing repeated identical
6315 @item set print null-stop
6316 @cindex @sc{null} elements in arrays
6317 Cause @value{GDBN} to stop printing the characters of an array when the first
6318 @sc{null} is encountered. This is useful when large arrays actually
6319 contain only short strings.
6322 @item show print null-stop
6323 Show whether @value{GDBN} stops printing an array on the first
6324 @sc{null} character.
6326 @item set print pretty on
6327 @cindex print structures in indented form
6328 @cindex indentation in structure display
6329 Cause @value{GDBN} to print structures in an indented format with one member
6330 per line, like this:
6345 @item set print pretty off
6346 Cause @value{GDBN} to print structures in a compact format, like this:
6350 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
6351 meat = 0x54 "Pork"@}
6356 This is the default format.
6358 @item show print pretty
6359 Show which format @value{GDBN} is using to print structures.
6361 @item set print sevenbit-strings on
6362 @cindex eight-bit characters in strings
6363 @cindex octal escapes in strings
6364 Print using only seven-bit characters; if this option is set,
6365 @value{GDBN} displays any eight-bit characters (in strings or
6366 character values) using the notation @code{\}@var{nnn}. This setting is
6367 best if you are working in English (@sc{ascii}) and you use the
6368 high-order bit of characters as a marker or ``meta'' bit.
6370 @item set print sevenbit-strings off
6371 Print full eight-bit characters. This allows the use of more
6372 international character sets, and is the default.
6374 @item show print sevenbit-strings
6375 Show whether or not @value{GDBN} is printing only seven-bit characters.
6377 @item set print union on
6378 @cindex unions in structures, printing
6379 Tell @value{GDBN} to print unions which are contained in structures
6380 and other unions. This is the default setting.
6382 @item set print union off
6383 Tell @value{GDBN} not to print unions which are contained in
6384 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
6387 @item show print union
6388 Ask @value{GDBN} whether or not it will print unions which are contained in
6389 structures and other unions.
6391 For example, given the declarations
6394 typedef enum @{Tree, Bug@} Species;
6395 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
6396 typedef enum @{Caterpillar, Cocoon, Butterfly@}
6407 struct thing foo = @{Tree, @{Acorn@}@};
6411 with @code{set print union on} in effect @samp{p foo} would print
6414 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
6418 and with @code{set print union off} in effect it would print
6421 $1 = @{it = Tree, form = @{...@}@}
6425 @code{set print union} affects programs written in C-like languages
6431 These settings are of interest when debugging C@t{++} programs:
6434 @cindex demangling C@t{++} names
6435 @item set print demangle
6436 @itemx set print demangle on
6437 Print C@t{++} names in their source form rather than in the encoded
6438 (``mangled'') form passed to the assembler and linker for type-safe
6439 linkage. The default is on.
6441 @item show print demangle
6442 Show whether C@t{++} names are printed in mangled or demangled form.
6444 @item set print asm-demangle
6445 @itemx set print asm-demangle on
6446 Print C@t{++} names in their source form rather than their mangled form, even
6447 in assembler code printouts such as instruction disassemblies.
6450 @item show print asm-demangle
6451 Show whether C@t{++} names in assembly listings are printed in mangled
6454 @cindex C@t{++} symbol decoding style
6455 @cindex symbol decoding style, C@t{++}
6456 @kindex set demangle-style
6457 @item set demangle-style @var{style}
6458 Choose among several encoding schemes used by different compilers to
6459 represent C@t{++} names. The choices for @var{style} are currently:
6463 Allow @value{GDBN} to choose a decoding style by inspecting your program.
6466 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
6467 This is the default.
6470 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
6473 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
6476 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
6477 @strong{Warning:} this setting alone is not sufficient to allow
6478 debugging @code{cfront}-generated executables. @value{GDBN} would
6479 require further enhancement to permit that.
6482 If you omit @var{style}, you will see a list of possible formats.
6484 @item show demangle-style
6485 Display the encoding style currently in use for decoding C@t{++} symbols.
6487 @item set print object
6488 @itemx set print object on
6489 @cindex derived type of an object, printing
6490 @cindex display derived types
6491 When displaying a pointer to an object, identify the @emph{actual}
6492 (derived) type of the object rather than the @emph{declared} type, using
6493 the virtual function table.
6495 @item set print object off
6496 Display only the declared type of objects, without reference to the
6497 virtual function table. This is the default setting.
6499 @item show print object
6500 Show whether actual, or declared, object types are displayed.
6502 @item set print static-members
6503 @itemx set print static-members on
6504 @cindex static members of C@t{++} objects
6505 Print static members when displaying a C@t{++} object. The default is on.
6507 @item set print static-members off
6508 Do not print static members when displaying a C@t{++} object.
6510 @item show print static-members
6511 Show whether C@t{++} static members are printed or not.
6513 @item set print pascal_static-members
6514 @itemx set print pascal_static-members on
6515 @cindex static members of Pascal objects
6516 @cindex Pascal objects, static members display
6517 Print static members when displaying a Pascal object. The default is on.
6519 @item set print pascal_static-members off
6520 Do not print static members when displaying a Pascal object.
6522 @item show print pascal_static-members
6523 Show whether Pascal static members are printed or not.
6525 @c These don't work with HP ANSI C++ yet.
6526 @item set print vtbl
6527 @itemx set print vtbl on
6528 @cindex pretty print C@t{++} virtual function tables
6529 @cindex virtual functions (C@t{++}) display
6530 @cindex VTBL display
6531 Pretty print C@t{++} virtual function tables. The default is off.
6532 (The @code{vtbl} commands do not work on programs compiled with the HP
6533 ANSI C@t{++} compiler (@code{aCC}).)
6535 @item set print vtbl off
6536 Do not pretty print C@t{++} virtual function tables.
6538 @item show print vtbl
6539 Show whether C@t{++} virtual function tables are pretty printed, or not.
6543 @section Value History
6545 @cindex value history
6546 @cindex history of values printed by @value{GDBN}
6547 Values printed by the @code{print} command are saved in the @value{GDBN}
6548 @dfn{value history}. This allows you to refer to them in other expressions.
6549 Values are kept until the symbol table is re-read or discarded
6550 (for example with the @code{file} or @code{symbol-file} commands).
6551 When the symbol table changes, the value history is discarded,
6552 since the values may contain pointers back to the types defined in the
6557 @cindex history number
6558 The values printed are given @dfn{history numbers} by which you can
6559 refer to them. These are successive integers starting with one.
6560 @code{print} shows you the history number assigned to a value by
6561 printing @samp{$@var{num} = } before the value; here @var{num} is the
6564 To refer to any previous value, use @samp{$} followed by the value's
6565 history number. The way @code{print} labels its output is designed to
6566 remind you of this. Just @code{$} refers to the most recent value in
6567 the history, and @code{$$} refers to the value before that.
6568 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
6569 is the value just prior to @code{$$}, @code{$$1} is equivalent to
6570 @code{$$}, and @code{$$0} is equivalent to @code{$}.
6572 For example, suppose you have just printed a pointer to a structure and
6573 want to see the contents of the structure. It suffices to type
6579 If you have a chain of structures where the component @code{next} points
6580 to the next one, you can print the contents of the next one with this:
6587 You can print successive links in the chain by repeating this
6588 command---which you can do by just typing @key{RET}.
6590 Note that the history records values, not expressions. If the value of
6591 @code{x} is 4 and you type these commands:
6599 then the value recorded in the value history by the @code{print} command
6600 remains 4 even though the value of @code{x} has changed.
6605 Print the last ten values in the value history, with their item numbers.
6606 This is like @samp{p@ $$9} repeated ten times, except that @code{show
6607 values} does not change the history.
6609 @item show values @var{n}
6610 Print ten history values centered on history item number @var{n}.
6613 Print ten history values just after the values last printed. If no more
6614 values are available, @code{show values +} produces no display.
6617 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
6618 same effect as @samp{show values +}.
6620 @node Convenience Vars
6621 @section Convenience Variables
6623 @cindex convenience variables
6624 @cindex user-defined variables
6625 @value{GDBN} provides @dfn{convenience variables} that you can use within
6626 @value{GDBN} to hold on to a value and refer to it later. These variables
6627 exist entirely within @value{GDBN}; they are not part of your program, and
6628 setting a convenience variable has no direct effect on further execution
6629 of your program. That is why you can use them freely.
6631 Convenience variables are prefixed with @samp{$}. Any name preceded by
6632 @samp{$} can be used for a convenience variable, unless it is one of
6633 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
6634 (Value history references, in contrast, are @emph{numbers} preceded
6635 by @samp{$}. @xref{Value History, ,Value History}.)
6637 You can save a value in a convenience variable with an assignment
6638 expression, just as you would set a variable in your program.
6642 set $foo = *object_ptr
6646 would save in @code{$foo} the value contained in the object pointed to by
6649 Using a convenience variable for the first time creates it, but its
6650 value is @code{void} until you assign a new value. You can alter the
6651 value with another assignment at any time.
6653 Convenience variables have no fixed types. You can assign a convenience
6654 variable any type of value, including structures and arrays, even if
6655 that variable already has a value of a different type. The convenience
6656 variable, when used as an expression, has the type of its current value.
6659 @kindex show convenience
6660 @cindex show all user variables
6661 @item show convenience
6662 Print a list of convenience variables used so far, and their values.
6663 Abbreviated @code{show conv}.
6665 @kindex init-if-undefined
6666 @cindex convenience variables, initializing
6667 @item init-if-undefined $@var{variable} = @var{expression}
6668 Set a convenience variable if it has not already been set. This is useful
6669 for user-defined commands that keep some state. It is similar, in concept,
6670 to using local static variables with initializers in C (except that
6671 convenience variables are global). It can also be used to allow users to
6672 override default values used in a command script.
6674 If the variable is already defined then the expression is not evaluated so
6675 any side-effects do not occur.
6678 One of the ways to use a convenience variable is as a counter to be
6679 incremented or a pointer to be advanced. For example, to print
6680 a field from successive elements of an array of structures:
6684 print bar[$i++]->contents
6688 Repeat that command by typing @key{RET}.
6690 Some convenience variables are created automatically by @value{GDBN} and given
6691 values likely to be useful.
6694 @vindex $_@r{, convenience variable}
6696 The variable @code{$_} is automatically set by the @code{x} command to
6697 the last address examined (@pxref{Memory, ,Examining Memory}). Other
6698 commands which provide a default address for @code{x} to examine also
6699 set @code{$_} to that address; these commands include @code{info line}
6700 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
6701 except when set by the @code{x} command, in which case it is a pointer
6702 to the type of @code{$__}.
6704 @vindex $__@r{, convenience variable}
6706 The variable @code{$__} is automatically set by the @code{x} command
6707 to the value found in the last address examined. Its type is chosen
6708 to match the format in which the data was printed.
6711 @vindex $_exitcode@r{, convenience variable}
6712 The variable @code{$_exitcode} is automatically set to the exit code when
6713 the program being debugged terminates.
6716 On HP-UX systems, if you refer to a function or variable name that
6717 begins with a dollar sign, @value{GDBN} searches for a user or system
6718 name first, before it searches for a convenience variable.
6724 You can refer to machine register contents, in expressions, as variables
6725 with names starting with @samp{$}. The names of registers are different
6726 for each machine; use @code{info registers} to see the names used on
6730 @kindex info registers
6731 @item info registers
6732 Print the names and values of all registers except floating-point
6733 and vector registers (in the selected stack frame).
6735 @kindex info all-registers
6736 @cindex floating point registers
6737 @item info all-registers
6738 Print the names and values of all registers, including floating-point
6739 and vector registers (in the selected stack frame).
6741 @item info registers @var{regname} @dots{}
6742 Print the @dfn{relativized} value of each specified register @var{regname}.
6743 As discussed in detail below, register values are normally relative to
6744 the selected stack frame. @var{regname} may be any register name valid on
6745 the machine you are using, with or without the initial @samp{$}.
6748 @cindex stack pointer register
6749 @cindex program counter register
6750 @cindex process status register
6751 @cindex frame pointer register
6752 @cindex standard registers
6753 @value{GDBN} has four ``standard'' register names that are available (in
6754 expressions) on most machines---whenever they do not conflict with an
6755 architecture's canonical mnemonics for registers. The register names
6756 @code{$pc} and @code{$sp} are used for the program counter register and
6757 the stack pointer. @code{$fp} is used for a register that contains a
6758 pointer to the current stack frame, and @code{$ps} is used for a
6759 register that contains the processor status. For example,
6760 you could print the program counter in hex with
6767 or print the instruction to be executed next with
6774 or add four to the stack pointer@footnote{This is a way of removing
6775 one word from the stack, on machines where stacks grow downward in
6776 memory (most machines, nowadays). This assumes that the innermost
6777 stack frame is selected; setting @code{$sp} is not allowed when other
6778 stack frames are selected. To pop entire frames off the stack,
6779 regardless of machine architecture, use @code{return};
6780 see @ref{Returning, ,Returning from a Function}.} with
6786 Whenever possible, these four standard register names are available on
6787 your machine even though the machine has different canonical mnemonics,
6788 so long as there is no conflict. The @code{info registers} command
6789 shows the canonical names. For example, on the SPARC, @code{info
6790 registers} displays the processor status register as @code{$psr} but you
6791 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
6792 is an alias for the @sc{eflags} register.
6794 @value{GDBN} always considers the contents of an ordinary register as an
6795 integer when the register is examined in this way. Some machines have
6796 special registers which can hold nothing but floating point; these
6797 registers are considered to have floating point values. There is no way
6798 to refer to the contents of an ordinary register as floating point value
6799 (although you can @emph{print} it as a floating point value with
6800 @samp{print/f $@var{regname}}).
6802 Some registers have distinct ``raw'' and ``virtual'' data formats. This
6803 means that the data format in which the register contents are saved by
6804 the operating system is not the same one that your program normally
6805 sees. For example, the registers of the 68881 floating point
6806 coprocessor are always saved in ``extended'' (raw) format, but all C
6807 programs expect to work with ``double'' (virtual) format. In such
6808 cases, @value{GDBN} normally works with the virtual format only (the format
6809 that makes sense for your program), but the @code{info registers} command
6810 prints the data in both formats.
6812 @cindex SSE registers (x86)
6813 @cindex MMX registers (x86)
6814 Some machines have special registers whose contents can be interpreted
6815 in several different ways. For example, modern x86-based machines
6816 have SSE and MMX registers that can hold several values packed
6817 together in several different formats. @value{GDBN} refers to such
6818 registers in @code{struct} notation:
6821 (@value{GDBP}) print $xmm1
6823 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
6824 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
6825 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
6826 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
6827 v4_int32 = @{0, 20657912, 11, 13@},
6828 v2_int64 = @{88725056443645952, 55834574859@},
6829 uint128 = 0x0000000d0000000b013b36f800000000
6834 To set values of such registers, you need to tell @value{GDBN} which
6835 view of the register you wish to change, as if you were assigning
6836 value to a @code{struct} member:
6839 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
6842 Normally, register values are relative to the selected stack frame
6843 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
6844 value that the register would contain if all stack frames farther in
6845 were exited and their saved registers restored. In order to see the
6846 true contents of hardware registers, you must select the innermost
6847 frame (with @samp{frame 0}).
6849 However, @value{GDBN} must deduce where registers are saved, from the machine
6850 code generated by your compiler. If some registers are not saved, or if
6851 @value{GDBN} is unable to locate the saved registers, the selected stack
6852 frame makes no difference.
6854 @node Floating Point Hardware
6855 @section Floating Point Hardware
6856 @cindex floating point
6858 Depending on the configuration, @value{GDBN} may be able to give
6859 you more information about the status of the floating point hardware.
6864 Display hardware-dependent information about the floating
6865 point unit. The exact contents and layout vary depending on the
6866 floating point chip. Currently, @samp{info float} is supported on
6867 the ARM and x86 machines.
6871 @section Vector Unit
6874 Depending on the configuration, @value{GDBN} may be able to give you
6875 more information about the status of the vector unit.
6880 Display information about the vector unit. The exact contents and
6881 layout vary depending on the hardware.
6884 @node OS Information
6885 @section Operating System Auxiliary Information
6886 @cindex OS information
6888 @value{GDBN} provides interfaces to useful OS facilities that can help
6889 you debug your program.
6891 @cindex @code{ptrace} system call
6892 @cindex @code{struct user} contents
6893 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
6894 machines), it interfaces with the inferior via the @code{ptrace}
6895 system call. The operating system creates a special sata structure,
6896 called @code{struct user}, for this interface. You can use the
6897 command @code{info udot} to display the contents of this data
6903 Display the contents of the @code{struct user} maintained by the OS
6904 kernel for the program being debugged. @value{GDBN} displays the
6905 contents of @code{struct user} as a list of hex numbers, similar to
6906 the @code{examine} command.
6909 @cindex auxiliary vector
6910 @cindex vector, auxiliary
6911 Some operating systems supply an @dfn{auxiliary vector} to programs at
6912 startup. This is akin to the arguments and environment that you
6913 specify for a program, but contains a system-dependent variety of
6914 binary values that tell system libraries important details about the
6915 hardware, operating system, and process. Each value's purpose is
6916 identified by an integer tag; the meanings are well-known but system-specific.
6917 Depending on the configuration and operating system facilities,
6918 @value{GDBN} may be able to show you this information. For remote
6919 targets, this functionality may further depend on the remote stub's
6920 support of the @samp{qXfer:auxv:read} packet, see
6921 @ref{qXfer auxiliary vector read}.
6926 Display the auxiliary vector of the inferior, which can be either a
6927 live process or a core dump file. @value{GDBN} prints each tag value
6928 numerically, and also shows names and text descriptions for recognized
6929 tags. Some values in the vector are numbers, some bit masks, and some
6930 pointers to strings or other data. @value{GDBN} displays each value in the
6931 most appropriate form for a recognized tag, and in hexadecimal for
6932 an unrecognized tag.
6936 @node Memory Region Attributes
6937 @section Memory Region Attributes
6938 @cindex memory region attributes
6940 @dfn{Memory region attributes} allow you to describe special handling
6941 required by regions of your target's memory. @value{GDBN} uses
6942 attributes to determine whether to allow certain types of memory
6943 accesses; whether to use specific width accesses; and whether to cache
6944 target memory. By default the description of memory regions is
6945 fetched from the target (if the current target supports this), but the
6946 user can override the fetched regions.
6948 Defined memory regions can be individually enabled and disabled. When a
6949 memory region is disabled, @value{GDBN} uses the default attributes when
6950 accessing memory in that region. Similarly, if no memory regions have
6951 been defined, @value{GDBN} uses the default attributes when accessing
6954 When a memory region is defined, it is given a number to identify it;
6955 to enable, disable, or remove a memory region, you specify that number.
6959 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
6960 Define a memory region bounded by @var{lower} and @var{upper} with
6961 attributes @var{attributes}@dots{}, and add it to the list of regions
6962 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
6963 case: it is treated as the target's maximum memory address.
6964 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
6967 Discard any user changes to the memory regions and use target-supplied
6968 regions, if available, or no regions if the target does not support.
6971 @item delete mem @var{nums}@dots{}
6972 Remove memory regions @var{nums}@dots{} from the list of regions
6973 monitored by @value{GDBN}.
6976 @item disable mem @var{nums}@dots{}
6977 Disable monitoring of memory regions @var{nums}@dots{}.
6978 A disabled memory region is not forgotten.
6979 It may be enabled again later.
6982 @item enable mem @var{nums}@dots{}
6983 Enable monitoring of memory regions @var{nums}@dots{}.
6987 Print a table of all defined memory regions, with the following columns
6991 @item Memory Region Number
6992 @item Enabled or Disabled.
6993 Enabled memory regions are marked with @samp{y}.
6994 Disabled memory regions are marked with @samp{n}.
6997 The address defining the inclusive lower bound of the memory region.
7000 The address defining the exclusive upper bound of the memory region.
7003 The list of attributes set for this memory region.
7008 @subsection Attributes
7010 @subsubsection Memory Access Mode
7011 The access mode attributes set whether @value{GDBN} may make read or
7012 write accesses to a memory region.
7014 While these attributes prevent @value{GDBN} from performing invalid
7015 memory accesses, they do nothing to prevent the target system, I/O DMA,
7016 etc.@: from accessing memory.
7020 Memory is read only.
7022 Memory is write only.
7024 Memory is read/write. This is the default.
7027 @subsubsection Memory Access Size
7028 The access size attribute tells @value{GDBN} to use specific sized
7029 accesses in the memory region. Often memory mapped device registers
7030 require specific sized accesses. If no access size attribute is
7031 specified, @value{GDBN} may use accesses of any size.
7035 Use 8 bit memory accesses.
7037 Use 16 bit memory accesses.
7039 Use 32 bit memory accesses.
7041 Use 64 bit memory accesses.
7044 @c @subsubsection Hardware/Software Breakpoints
7045 @c The hardware/software breakpoint attributes set whether @value{GDBN}
7046 @c will use hardware or software breakpoints for the internal breakpoints
7047 @c used by the step, next, finish, until, etc. commands.
7051 @c Always use hardware breakpoints
7052 @c @item swbreak (default)
7055 @subsubsection Data Cache
7056 The data cache attributes set whether @value{GDBN} will cache target
7057 memory. While this generally improves performance by reducing debug
7058 protocol overhead, it can lead to incorrect results because @value{GDBN}
7059 does not know about volatile variables or memory mapped device
7064 Enable @value{GDBN} to cache target memory.
7066 Disable @value{GDBN} from caching target memory. This is the default.
7069 @subsection Memory Access Checking
7070 @value{GDBN} can be instructed to refuse accesses to memory that is
7071 not explicitly described. This can be useful if accessing such
7072 regions has undesired effects for a specific target, or to provide
7073 better error checking. The following commands control this behaviour.
7076 @kindex set mem inaccessible-by-default
7077 @item set mem inaccessible-by-default [on|off]
7078 If @code{on} is specified, make @value{GDBN} treat memory not
7079 explicitly described by the memory ranges as non-existent and refuse accesses
7080 to such memory. The checks are only performed if there's at least one
7081 memory range defined. If @code{off} is specified, make @value{GDBN}
7082 treat the memory not explicitly described by the memory ranges as RAM.
7083 The default value is @code{on}.
7084 @kindex show mem inaccessible-by-default
7085 @item show mem inaccessible-by-default
7086 Show the current handling of accesses to unknown memory.
7090 @c @subsubsection Memory Write Verification
7091 @c The memory write verification attributes set whether @value{GDBN}
7092 @c will re-reads data after each write to verify the write was successful.
7096 @c @item noverify (default)
7099 @node Dump/Restore Files
7100 @section Copy Between Memory and a File
7101 @cindex dump/restore files
7102 @cindex append data to a file
7103 @cindex dump data to a file
7104 @cindex restore data from a file
7106 You can use the commands @code{dump}, @code{append}, and
7107 @code{restore} to copy data between target memory and a file. The
7108 @code{dump} and @code{append} commands write data to a file, and the
7109 @code{restore} command reads data from a file back into the inferior's
7110 memory. Files may be in binary, Motorola S-record, Intel hex, or
7111 Tektronix Hex format; however, @value{GDBN} can only append to binary
7117 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7118 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
7119 Dump the contents of memory from @var{start_addr} to @var{end_addr},
7120 or the value of @var{expr}, to @var{filename} in the given format.
7122 The @var{format} parameter may be any one of:
7129 Motorola S-record format.
7131 Tektronix Hex format.
7134 @value{GDBN} uses the same definitions of these formats as the
7135 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
7136 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
7140 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7141 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
7142 Append the contents of memory from @var{start_addr} to @var{end_addr},
7143 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
7144 (@value{GDBN} can only append data to files in raw binary form.)
7147 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
7148 Restore the contents of file @var{filename} into memory. The
7149 @code{restore} command can automatically recognize any known @sc{bfd}
7150 file format, except for raw binary. To restore a raw binary file you
7151 must specify the optional keyword @code{binary} after the filename.
7153 If @var{bias} is non-zero, its value will be added to the addresses
7154 contained in the file. Binary files always start at address zero, so
7155 they will be restored at address @var{bias}. Other bfd files have
7156 a built-in location; they will be restored at offset @var{bias}
7159 If @var{start} and/or @var{end} are non-zero, then only data between
7160 file offset @var{start} and file offset @var{end} will be restored.
7161 These offsets are relative to the addresses in the file, before
7162 the @var{bias} argument is applied.
7166 @node Core File Generation
7167 @section How to Produce a Core File from Your Program
7168 @cindex dump core from inferior
7170 A @dfn{core file} or @dfn{core dump} is a file that records the memory
7171 image of a running process and its process status (register values
7172 etc.). Its primary use is post-mortem debugging of a program that
7173 crashed while it ran outside a debugger. A program that crashes
7174 automatically produces a core file, unless this feature is disabled by
7175 the user. @xref{Files}, for information on invoking @value{GDBN} in
7176 the post-mortem debugging mode.
7178 Occasionally, you may wish to produce a core file of the program you
7179 are debugging in order to preserve a snapshot of its state.
7180 @value{GDBN} has a special command for that.
7184 @kindex generate-core-file
7185 @item generate-core-file [@var{file}]
7186 @itemx gcore [@var{file}]
7187 Produce a core dump of the inferior process. The optional argument
7188 @var{file} specifies the file name where to put the core dump. If not
7189 specified, the file name defaults to @file{core.@var{pid}}, where
7190 @var{pid} is the inferior process ID.
7192 Note that this command is implemented only for some systems (as of
7193 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
7196 @node Character Sets
7197 @section Character Sets
7198 @cindex character sets
7200 @cindex translating between character sets
7201 @cindex host character set
7202 @cindex target character set
7204 If the program you are debugging uses a different character set to
7205 represent characters and strings than the one @value{GDBN} uses itself,
7206 @value{GDBN} can automatically translate between the character sets for
7207 you. The character set @value{GDBN} uses we call the @dfn{host
7208 character set}; the one the inferior program uses we call the
7209 @dfn{target character set}.
7211 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
7212 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
7213 remote protocol (@pxref{Remote Debugging}) to debug a program
7214 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
7215 then the host character set is Latin-1, and the target character set is
7216 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
7217 target-charset EBCDIC-US}, then @value{GDBN} translates between
7218 @sc{ebcdic} and Latin 1 as you print character or string values, or use
7219 character and string literals in expressions.
7221 @value{GDBN} has no way to automatically recognize which character set
7222 the inferior program uses; you must tell it, using the @code{set
7223 target-charset} command, described below.
7225 Here are the commands for controlling @value{GDBN}'s character set
7229 @item set target-charset @var{charset}
7230 @kindex set target-charset
7231 Set the current target character set to @var{charset}. We list the
7232 character set names @value{GDBN} recognizes below, but if you type
7233 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7234 list the target character sets it supports.
7238 @item set host-charset @var{charset}
7239 @kindex set host-charset
7240 Set the current host character set to @var{charset}.
7242 By default, @value{GDBN} uses a host character set appropriate to the
7243 system it is running on; you can override that default using the
7244 @code{set host-charset} command.
7246 @value{GDBN} can only use certain character sets as its host character
7247 set. We list the character set names @value{GDBN} recognizes below, and
7248 indicate which can be host character sets, but if you type
7249 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7250 list the host character sets it supports.
7252 @item set charset @var{charset}
7254 Set the current host and target character sets to @var{charset}. As
7255 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
7256 @value{GDBN} will list the name of the character sets that can be used
7257 for both host and target.
7261 @kindex show charset
7262 Show the names of the current host and target charsets.
7264 @itemx show host-charset
7265 @kindex show host-charset
7266 Show the name of the current host charset.
7268 @itemx show target-charset
7269 @kindex show target-charset
7270 Show the name of the current target charset.
7274 @value{GDBN} currently includes support for the following character
7280 @cindex ASCII character set
7281 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
7285 @cindex ISO 8859-1 character set
7286 @cindex ISO Latin 1 character set
7287 The ISO Latin 1 character set. This extends @sc{ascii} with accented
7288 characters needed for French, German, and Spanish. @value{GDBN} can use
7289 this as its host character set.
7293 @cindex EBCDIC character set
7294 @cindex IBM1047 character set
7295 Variants of the @sc{ebcdic} character set, used on some of IBM's
7296 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
7297 @value{GDBN} cannot use these as its host character set.
7301 Note that these are all single-byte character sets. More work inside
7302 @value{GDBN} is needed to support multi-byte or variable-width character
7303 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
7305 Here is an example of @value{GDBN}'s character set support in action.
7306 Assume that the following source code has been placed in the file
7307 @file{charset-test.c}:
7313 = @{72, 101, 108, 108, 111, 44, 32, 119,
7314 111, 114, 108, 100, 33, 10, 0@};
7315 char ibm1047_hello[]
7316 = @{200, 133, 147, 147, 150, 107, 64, 166,
7317 150, 153, 147, 132, 90, 37, 0@};
7321 printf ("Hello, world!\n");
7325 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
7326 containing the string @samp{Hello, world!} followed by a newline,
7327 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
7329 We compile the program, and invoke the debugger on it:
7332 $ gcc -g charset-test.c -o charset-test
7333 $ gdb -nw charset-test
7334 GNU gdb 2001-12-19-cvs
7335 Copyright 2001 Free Software Foundation, Inc.
7340 We can use the @code{show charset} command to see what character sets
7341 @value{GDBN} is currently using to interpret and display characters and
7345 (@value{GDBP}) show charset
7346 The current host and target character set is `ISO-8859-1'.
7350 For the sake of printing this manual, let's use @sc{ascii} as our
7351 initial character set:
7353 (@value{GDBP}) set charset ASCII
7354 (@value{GDBP}) show charset
7355 The current host and target character set is `ASCII'.
7359 Let's assume that @sc{ascii} is indeed the correct character set for our
7360 host system --- in other words, let's assume that if @value{GDBN} prints
7361 characters using the @sc{ascii} character set, our terminal will display
7362 them properly. Since our current target character set is also
7363 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
7366 (@value{GDBP}) print ascii_hello
7367 $1 = 0x401698 "Hello, world!\n"
7368 (@value{GDBP}) print ascii_hello[0]
7373 @value{GDBN} uses the target character set for character and string
7374 literals you use in expressions:
7377 (@value{GDBP}) print '+'
7382 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
7385 @value{GDBN} relies on the user to tell it which character set the
7386 target program uses. If we print @code{ibm1047_hello} while our target
7387 character set is still @sc{ascii}, we get jibberish:
7390 (@value{GDBP}) print ibm1047_hello
7391 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
7392 (@value{GDBP}) print ibm1047_hello[0]
7397 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
7398 @value{GDBN} tells us the character sets it supports:
7401 (@value{GDBP}) set target-charset
7402 ASCII EBCDIC-US IBM1047 ISO-8859-1
7403 (@value{GDBP}) set target-charset
7406 We can select @sc{ibm1047} as our target character set, and examine the
7407 program's strings again. Now the @sc{ascii} string is wrong, but
7408 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
7409 target character set, @sc{ibm1047}, to the host character set,
7410 @sc{ascii}, and they display correctly:
7413 (@value{GDBP}) set target-charset IBM1047
7414 (@value{GDBP}) show charset
7415 The current host character set is `ASCII'.
7416 The current target character set is `IBM1047'.
7417 (@value{GDBP}) print ascii_hello
7418 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
7419 (@value{GDBP}) print ascii_hello[0]
7421 (@value{GDBP}) print ibm1047_hello
7422 $8 = 0x4016a8 "Hello, world!\n"
7423 (@value{GDBP}) print ibm1047_hello[0]
7428 As above, @value{GDBN} uses the target character set for character and
7429 string literals you use in expressions:
7432 (@value{GDBP}) print '+'
7437 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
7440 @node Caching Remote Data
7441 @section Caching Data of Remote Targets
7442 @cindex caching data of remote targets
7444 @value{GDBN} can cache data exchanged between the debugger and a
7445 remote target (@pxref{Remote Debugging}). Such caching generally improves
7446 performance, because it reduces the overhead of the remote protocol by
7447 bundling memory reads and writes into large chunks. Unfortunately,
7448 @value{GDBN} does not currently know anything about volatile
7449 registers, and thus data caching will produce incorrect results when
7450 volatile registers are in use.
7453 @kindex set remotecache
7454 @item set remotecache on
7455 @itemx set remotecache off
7456 Set caching state for remote targets. When @code{ON}, use data
7457 caching. By default, this option is @code{OFF}.
7459 @kindex show remotecache
7460 @item show remotecache
7461 Show the current state of data caching for remote targets.
7465 Print the information about the data cache performance. The
7466 information displayed includes: the dcache width and depth; and for
7467 each cache line, how many times it was referenced, and its data and
7468 state (dirty, bad, ok, etc.). This command is useful for debugging
7469 the data cache operation.
7474 @chapter C Preprocessor Macros
7476 Some languages, such as C and C@t{++}, provide a way to define and invoke
7477 ``preprocessor macros'' which expand into strings of tokens.
7478 @value{GDBN} can evaluate expressions containing macro invocations, show
7479 the result of macro expansion, and show a macro's definition, including
7480 where it was defined.
7482 You may need to compile your program specially to provide @value{GDBN}
7483 with information about preprocessor macros. Most compilers do not
7484 include macros in their debugging information, even when you compile
7485 with the @option{-g} flag. @xref{Compilation}.
7487 A program may define a macro at one point, remove that definition later,
7488 and then provide a different definition after that. Thus, at different
7489 points in the program, a macro may have different definitions, or have
7490 no definition at all. If there is a current stack frame, @value{GDBN}
7491 uses the macros in scope at that frame's source code line. Otherwise,
7492 @value{GDBN} uses the macros in scope at the current listing location;
7495 At the moment, @value{GDBN} does not support the @code{##}
7496 token-splicing operator, the @code{#} stringification operator, or
7497 variable-arity macros.
7499 Whenever @value{GDBN} evaluates an expression, it always expands any
7500 macro invocations present in the expression. @value{GDBN} also provides
7501 the following commands for working with macros explicitly.
7505 @kindex macro expand
7506 @cindex macro expansion, showing the results of preprocessor
7507 @cindex preprocessor macro expansion, showing the results of
7508 @cindex expanding preprocessor macros
7509 @item macro expand @var{expression}
7510 @itemx macro exp @var{expression}
7511 Show the results of expanding all preprocessor macro invocations in
7512 @var{expression}. Since @value{GDBN} simply expands macros, but does
7513 not parse the result, @var{expression} need not be a valid expression;
7514 it can be any string of tokens.
7517 @item macro expand-once @var{expression}
7518 @itemx macro exp1 @var{expression}
7519 @cindex expand macro once
7520 @i{(This command is not yet implemented.)} Show the results of
7521 expanding those preprocessor macro invocations that appear explicitly in
7522 @var{expression}. Macro invocations appearing in that expansion are
7523 left unchanged. This command allows you to see the effect of a
7524 particular macro more clearly, without being confused by further
7525 expansions. Since @value{GDBN} simply expands macros, but does not
7526 parse the result, @var{expression} need not be a valid expression; it
7527 can be any string of tokens.
7530 @cindex macro definition, showing
7531 @cindex definition, showing a macro's
7532 @item info macro @var{macro}
7533 Show the definition of the macro named @var{macro}, and describe the
7534 source location where that definition was established.
7536 @kindex macro define
7537 @cindex user-defined macros
7538 @cindex defining macros interactively
7539 @cindex macros, user-defined
7540 @item macro define @var{macro} @var{replacement-list}
7541 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
7542 @i{(This command is not yet implemented.)} Introduce a definition for a
7543 preprocessor macro named @var{macro}, invocations of which are replaced
7544 by the tokens given in @var{replacement-list}. The first form of this
7545 command defines an ``object-like'' macro, which takes no arguments; the
7546 second form defines a ``function-like'' macro, which takes the arguments
7547 given in @var{arglist}.
7549 A definition introduced by this command is in scope in every expression
7550 evaluated in @value{GDBN}, until it is removed with the @command{macro
7551 undef} command, described below. The definition overrides all
7552 definitions for @var{macro} present in the program being debugged, as
7553 well as any previous user-supplied definition.
7556 @item macro undef @var{macro}
7557 @i{(This command is not yet implemented.)} Remove any user-supplied
7558 definition for the macro named @var{macro}. This command only affects
7559 definitions provided with the @command{macro define} command, described
7560 above; it cannot remove definitions present in the program being
7565 @i{(This command is not yet implemented.)} List all the macros
7566 defined using the @code{macro define} command.
7569 @cindex macros, example of debugging with
7570 Here is a transcript showing the above commands in action. First, we
7571 show our source files:
7579 #define ADD(x) (M + x)
7584 printf ("Hello, world!\n");
7586 printf ("We're so creative.\n");
7588 printf ("Goodbye, world!\n");
7595 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
7596 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
7597 compiler includes information about preprocessor macros in the debugging
7601 $ gcc -gdwarf-2 -g3 sample.c -o sample
7605 Now, we start @value{GDBN} on our sample program:
7609 GNU gdb 2002-05-06-cvs
7610 Copyright 2002 Free Software Foundation, Inc.
7611 GDB is free software, @dots{}
7615 We can expand macros and examine their definitions, even when the
7616 program is not running. @value{GDBN} uses the current listing position
7617 to decide which macro definitions are in scope:
7620 (@value{GDBP}) list main
7623 5 #define ADD(x) (M + x)
7628 10 printf ("Hello, world!\n");
7630 12 printf ("We're so creative.\n");
7631 (@value{GDBP}) info macro ADD
7632 Defined at /home/jimb/gdb/macros/play/sample.c:5
7633 #define ADD(x) (M + x)
7634 (@value{GDBP}) info macro Q
7635 Defined at /home/jimb/gdb/macros/play/sample.h:1
7636 included at /home/jimb/gdb/macros/play/sample.c:2
7638 (@value{GDBP}) macro expand ADD(1)
7639 expands to: (42 + 1)
7640 (@value{GDBP}) macro expand-once ADD(1)
7641 expands to: once (M + 1)
7645 In the example above, note that @command{macro expand-once} expands only
7646 the macro invocation explicit in the original text --- the invocation of
7647 @code{ADD} --- but does not expand the invocation of the macro @code{M},
7648 which was introduced by @code{ADD}.
7650 Once the program is running, @value{GDBN} uses the macro definitions in
7651 force at the source line of the current stack frame:
7654 (@value{GDBP}) break main
7655 Breakpoint 1 at 0x8048370: file sample.c, line 10.
7657 Starting program: /home/jimb/gdb/macros/play/sample
7659 Breakpoint 1, main () at sample.c:10
7660 10 printf ("Hello, world!\n");
7664 At line 10, the definition of the macro @code{N} at line 9 is in force:
7667 (@value{GDBP}) info macro N
7668 Defined at /home/jimb/gdb/macros/play/sample.c:9
7670 (@value{GDBP}) macro expand N Q M
7672 (@value{GDBP}) print N Q M
7677 As we step over directives that remove @code{N}'s definition, and then
7678 give it a new definition, @value{GDBN} finds the definition (or lack
7679 thereof) in force at each point:
7684 12 printf ("We're so creative.\n");
7685 (@value{GDBP}) info macro N
7686 The symbol `N' has no definition as a C/C++ preprocessor macro
7687 at /home/jimb/gdb/macros/play/sample.c:12
7690 14 printf ("Goodbye, world!\n");
7691 (@value{GDBP}) info macro N
7692 Defined at /home/jimb/gdb/macros/play/sample.c:13
7694 (@value{GDBP}) macro expand N Q M
7695 expands to: 1729 < 42
7696 (@value{GDBP}) print N Q M
7703 @chapter Tracepoints
7704 @c This chapter is based on the documentation written by Michael
7705 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
7708 In some applications, it is not feasible for the debugger to interrupt
7709 the program's execution long enough for the developer to learn
7710 anything helpful about its behavior. If the program's correctness
7711 depends on its real-time behavior, delays introduced by a debugger
7712 might cause the program to change its behavior drastically, or perhaps
7713 fail, even when the code itself is correct. It is useful to be able
7714 to observe the program's behavior without interrupting it.
7716 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
7717 specify locations in the program, called @dfn{tracepoints}, and
7718 arbitrary expressions to evaluate when those tracepoints are reached.
7719 Later, using the @code{tfind} command, you can examine the values
7720 those expressions had when the program hit the tracepoints. The
7721 expressions may also denote objects in memory---structures or arrays,
7722 for example---whose values @value{GDBN} should record; while visiting
7723 a particular tracepoint, you may inspect those objects as if they were
7724 in memory at that moment. However, because @value{GDBN} records these
7725 values without interacting with you, it can do so quickly and
7726 unobtrusively, hopefully not disturbing the program's behavior.
7728 The tracepoint facility is currently available only for remote
7729 targets. @xref{Targets}. In addition, your remote target must know
7730 how to collect trace data. This functionality is implemented in the
7731 remote stub; however, none of the stubs distributed with @value{GDBN}
7732 support tracepoints as of this writing. The format of the remote
7733 packets used to implement tracepoints are described in @ref{Tracepoint
7736 This chapter describes the tracepoint commands and features.
7740 * Analyze Collected Data::
7741 * Tracepoint Variables::
7744 @node Set Tracepoints
7745 @section Commands to Set Tracepoints
7747 Before running such a @dfn{trace experiment}, an arbitrary number of
7748 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
7749 tracepoint has a number assigned to it by @value{GDBN}. Like with
7750 breakpoints, tracepoint numbers are successive integers starting from
7751 one. Many of the commands associated with tracepoints take the
7752 tracepoint number as their argument, to identify which tracepoint to
7755 For each tracepoint, you can specify, in advance, some arbitrary set
7756 of data that you want the target to collect in the trace buffer when
7757 it hits that tracepoint. The collected data can include registers,
7758 local variables, or global data. Later, you can use @value{GDBN}
7759 commands to examine the values these data had at the time the
7762 This section describes commands to set tracepoints and associated
7763 conditions and actions.
7766 * Create and Delete Tracepoints::
7767 * Enable and Disable Tracepoints::
7768 * Tracepoint Passcounts::
7769 * Tracepoint Actions::
7770 * Listing Tracepoints::
7771 * Starting and Stopping Trace Experiments::
7774 @node Create and Delete Tracepoints
7775 @subsection Create and Delete Tracepoints
7778 @cindex set tracepoint
7781 The @code{trace} command is very similar to the @code{break} command.
7782 Its argument can be a source line, a function name, or an address in
7783 the target program. @xref{Set Breaks}. The @code{trace} command
7784 defines a tracepoint, which is a point in the target program where the
7785 debugger will briefly stop, collect some data, and then allow the
7786 program to continue. Setting a tracepoint or changing its commands
7787 doesn't take effect until the next @code{tstart} command; thus, you
7788 cannot change the tracepoint attributes once a trace experiment is
7791 Here are some examples of using the @code{trace} command:
7794 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
7796 (@value{GDBP}) @b{trace +2} // 2 lines forward
7798 (@value{GDBP}) @b{trace my_function} // first source line of function
7800 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
7802 (@value{GDBP}) @b{trace *0x2117c4} // an address
7806 You can abbreviate @code{trace} as @code{tr}.
7809 @cindex last tracepoint number
7810 @cindex recent tracepoint number
7811 @cindex tracepoint number
7812 The convenience variable @code{$tpnum} records the tracepoint number
7813 of the most recently set tracepoint.
7815 @kindex delete tracepoint
7816 @cindex tracepoint deletion
7817 @item delete tracepoint @r{[}@var{num}@r{]}
7818 Permanently delete one or more tracepoints. With no argument, the
7819 default is to delete all tracepoints.
7824 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
7826 (@value{GDBP}) @b{delete trace} // remove all tracepoints
7830 You can abbreviate this command as @code{del tr}.
7833 @node Enable and Disable Tracepoints
7834 @subsection Enable and Disable Tracepoints
7837 @kindex disable tracepoint
7838 @item disable tracepoint @r{[}@var{num}@r{]}
7839 Disable tracepoint @var{num}, or all tracepoints if no argument
7840 @var{num} is given. A disabled tracepoint will have no effect during
7841 the next trace experiment, but it is not forgotten. You can re-enable
7842 a disabled tracepoint using the @code{enable tracepoint} command.
7844 @kindex enable tracepoint
7845 @item enable tracepoint @r{[}@var{num}@r{]}
7846 Enable tracepoint @var{num}, or all tracepoints. The enabled
7847 tracepoints will become effective the next time a trace experiment is
7851 @node Tracepoint Passcounts
7852 @subsection Tracepoint Passcounts
7856 @cindex tracepoint pass count
7857 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
7858 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
7859 automatically stop a trace experiment. If a tracepoint's passcount is
7860 @var{n}, then the trace experiment will be automatically stopped on
7861 the @var{n}'th time that tracepoint is hit. If the tracepoint number
7862 @var{num} is not specified, the @code{passcount} command sets the
7863 passcount of the most recently defined tracepoint. If no passcount is
7864 given, the trace experiment will run until stopped explicitly by the
7870 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
7871 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
7873 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
7874 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
7875 (@value{GDBP}) @b{trace foo}
7876 (@value{GDBP}) @b{pass 3}
7877 (@value{GDBP}) @b{trace bar}
7878 (@value{GDBP}) @b{pass 2}
7879 (@value{GDBP}) @b{trace baz}
7880 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
7881 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
7882 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
7883 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
7887 @node Tracepoint Actions
7888 @subsection Tracepoint Action Lists
7892 @cindex tracepoint actions
7893 @item actions @r{[}@var{num}@r{]}
7894 This command will prompt for a list of actions to be taken when the
7895 tracepoint is hit. If the tracepoint number @var{num} is not
7896 specified, this command sets the actions for the one that was most
7897 recently defined (so that you can define a tracepoint and then say
7898 @code{actions} without bothering about its number). You specify the
7899 actions themselves on the following lines, one action at a time, and
7900 terminate the actions list with a line containing just @code{end}. So
7901 far, the only defined actions are @code{collect} and
7902 @code{while-stepping}.
7904 @cindex remove actions from a tracepoint
7905 To remove all actions from a tracepoint, type @samp{actions @var{num}}
7906 and follow it immediately with @samp{end}.
7909 (@value{GDBP}) @b{collect @var{data}} // collect some data
7911 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
7913 (@value{GDBP}) @b{end} // signals the end of actions.
7916 In the following example, the action list begins with @code{collect}
7917 commands indicating the things to be collected when the tracepoint is
7918 hit. Then, in order to single-step and collect additional data
7919 following the tracepoint, a @code{while-stepping} command is used,
7920 followed by the list of things to be collected while stepping. The
7921 @code{while-stepping} command is terminated by its own separate
7922 @code{end} command. Lastly, the action list is terminated by an
7926 (@value{GDBP}) @b{trace foo}
7927 (@value{GDBP}) @b{actions}
7928 Enter actions for tracepoint 1, one per line:
7937 @kindex collect @r{(tracepoints)}
7938 @item collect @var{expr1}, @var{expr2}, @dots{}
7939 Collect values of the given expressions when the tracepoint is hit.
7940 This command accepts a comma-separated list of any valid expressions.
7941 In addition to global, static, or local variables, the following
7942 special arguments are supported:
7946 collect all registers
7949 collect all function arguments
7952 collect all local variables.
7955 You can give several consecutive @code{collect} commands, each one
7956 with a single argument, or one @code{collect} command with several
7957 arguments separated by commas: the effect is the same.
7959 The command @code{info scope} (@pxref{Symbols, info scope}) is
7960 particularly useful for figuring out what data to collect.
7962 @kindex while-stepping @r{(tracepoints)}
7963 @item while-stepping @var{n}
7964 Perform @var{n} single-step traces after the tracepoint, collecting
7965 new data at each step. The @code{while-stepping} command is
7966 followed by the list of what to collect while stepping (followed by
7967 its own @code{end} command):
7971 > collect $regs, myglobal
7977 You may abbreviate @code{while-stepping} as @code{ws} or
7981 @node Listing Tracepoints
7982 @subsection Listing Tracepoints
7985 @kindex info tracepoints
7987 @cindex information about tracepoints
7988 @item info tracepoints @r{[}@var{num}@r{]}
7989 Display information about the tracepoint @var{num}. If you don't specify
7990 a tracepoint number, displays information about all the tracepoints
7991 defined so far. For each tracepoint, the following information is
7998 whether it is enabled or disabled
8002 its passcount as given by the @code{passcount @var{n}} command
8004 its step count as given by the @code{while-stepping @var{n}} command
8006 where in the source files is the tracepoint set
8008 its action list as given by the @code{actions} command
8012 (@value{GDBP}) @b{info trace}
8013 Num Enb Address PassC StepC What
8014 1 y 0x002117c4 0 0 <gdb_asm>
8015 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
8016 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
8021 This command can be abbreviated @code{info tp}.
8024 @node Starting and Stopping Trace Experiments
8025 @subsection Starting and Stopping Trace Experiments
8029 @cindex start a new trace experiment
8030 @cindex collected data discarded
8032 This command takes no arguments. It starts the trace experiment, and
8033 begins collecting data. This has the side effect of discarding all
8034 the data collected in the trace buffer during the previous trace
8038 @cindex stop a running trace experiment
8040 This command takes no arguments. It ends the trace experiment, and
8041 stops collecting data.
8043 @strong{Note}: a trace experiment and data collection may stop
8044 automatically if any tracepoint's passcount is reached
8045 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
8048 @cindex status of trace data collection
8049 @cindex trace experiment, status of
8051 This command displays the status of the current trace data
8055 Here is an example of the commands we described so far:
8058 (@value{GDBP}) @b{trace gdb_c_test}
8059 (@value{GDBP}) @b{actions}
8060 Enter actions for tracepoint #1, one per line.
8061 > collect $regs,$locals,$args
8066 (@value{GDBP}) @b{tstart}
8067 [time passes @dots{}]
8068 (@value{GDBP}) @b{tstop}
8072 @node Analyze Collected Data
8073 @section Using the Collected Data
8075 After the tracepoint experiment ends, you use @value{GDBN} commands
8076 for examining the trace data. The basic idea is that each tracepoint
8077 collects a trace @dfn{snapshot} every time it is hit and another
8078 snapshot every time it single-steps. All these snapshots are
8079 consecutively numbered from zero and go into a buffer, and you can
8080 examine them later. The way you examine them is to @dfn{focus} on a
8081 specific trace snapshot. When the remote stub is focused on a trace
8082 snapshot, it will respond to all @value{GDBN} requests for memory and
8083 registers by reading from the buffer which belongs to that snapshot,
8084 rather than from @emph{real} memory or registers of the program being
8085 debugged. This means that @strong{all} @value{GDBN} commands
8086 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
8087 behave as if we were currently debugging the program state as it was
8088 when the tracepoint occurred. Any requests for data that are not in
8089 the buffer will fail.
8092 * tfind:: How to select a trace snapshot
8093 * tdump:: How to display all data for a snapshot
8094 * save-tracepoints:: How to save tracepoints for a future run
8098 @subsection @code{tfind @var{n}}
8101 @cindex select trace snapshot
8102 @cindex find trace snapshot
8103 The basic command for selecting a trace snapshot from the buffer is
8104 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
8105 counting from zero. If no argument @var{n} is given, the next
8106 snapshot is selected.
8108 Here are the various forms of using the @code{tfind} command.
8112 Find the first snapshot in the buffer. This is a synonym for
8113 @code{tfind 0} (since 0 is the number of the first snapshot).
8116 Stop debugging trace snapshots, resume @emph{live} debugging.
8119 Same as @samp{tfind none}.
8122 No argument means find the next trace snapshot.
8125 Find the previous trace snapshot before the current one. This permits
8126 retracing earlier steps.
8128 @item tfind tracepoint @var{num}
8129 Find the next snapshot associated with tracepoint @var{num}. Search
8130 proceeds forward from the last examined trace snapshot. If no
8131 argument @var{num} is given, it means find the next snapshot collected
8132 for the same tracepoint as the current snapshot.
8134 @item tfind pc @var{addr}
8135 Find the next snapshot associated with the value @var{addr} of the
8136 program counter. Search proceeds forward from the last examined trace
8137 snapshot. If no argument @var{addr} is given, it means find the next
8138 snapshot with the same value of PC as the current snapshot.
8140 @item tfind outside @var{addr1}, @var{addr2}
8141 Find the next snapshot whose PC is outside the given range of
8144 @item tfind range @var{addr1}, @var{addr2}
8145 Find the next snapshot whose PC is between @var{addr1} and
8146 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
8148 @item tfind line @r{[}@var{file}:@r{]}@var{n}
8149 Find the next snapshot associated with the source line @var{n}. If
8150 the optional argument @var{file} is given, refer to line @var{n} in
8151 that source file. Search proceeds forward from the last examined
8152 trace snapshot. If no argument @var{n} is given, it means find the
8153 next line other than the one currently being examined; thus saying
8154 @code{tfind line} repeatedly can appear to have the same effect as
8155 stepping from line to line in a @emph{live} debugging session.
8158 The default arguments for the @code{tfind} commands are specifically
8159 designed to make it easy to scan through the trace buffer. For
8160 instance, @code{tfind} with no argument selects the next trace
8161 snapshot, and @code{tfind -} with no argument selects the previous
8162 trace snapshot. So, by giving one @code{tfind} command, and then
8163 simply hitting @key{RET} repeatedly you can examine all the trace
8164 snapshots in order. Or, by saying @code{tfind -} and then hitting
8165 @key{RET} repeatedly you can examine the snapshots in reverse order.
8166 The @code{tfind line} command with no argument selects the snapshot
8167 for the next source line executed. The @code{tfind pc} command with
8168 no argument selects the next snapshot with the same program counter
8169 (PC) as the current frame. The @code{tfind tracepoint} command with
8170 no argument selects the next trace snapshot collected by the same
8171 tracepoint as the current one.
8173 In addition to letting you scan through the trace buffer manually,
8174 these commands make it easy to construct @value{GDBN} scripts that
8175 scan through the trace buffer and print out whatever collected data
8176 you are interested in. Thus, if we want to examine the PC, FP, and SP
8177 registers from each trace frame in the buffer, we can say this:
8180 (@value{GDBP}) @b{tfind start}
8181 (@value{GDBP}) @b{while ($trace_frame != -1)}
8182 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
8183 $trace_frame, $pc, $sp, $fp
8187 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
8188 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
8189 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
8190 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
8191 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
8192 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
8193 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
8194 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
8195 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
8196 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
8197 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
8200 Or, if we want to examine the variable @code{X} at each source line in
8204 (@value{GDBP}) @b{tfind start}
8205 (@value{GDBP}) @b{while ($trace_frame != -1)}
8206 > printf "Frame %d, X == %d\n", $trace_frame, X
8216 @subsection @code{tdump}
8218 @cindex dump all data collected at tracepoint
8219 @cindex tracepoint data, display
8221 This command takes no arguments. It prints all the data collected at
8222 the current trace snapshot.
8225 (@value{GDBP}) @b{trace 444}
8226 (@value{GDBP}) @b{actions}
8227 Enter actions for tracepoint #2, one per line:
8228 > collect $regs, $locals, $args, gdb_long_test
8231 (@value{GDBP}) @b{tstart}
8233 (@value{GDBP}) @b{tfind line 444}
8234 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
8236 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
8238 (@value{GDBP}) @b{tdump}
8239 Data collected at tracepoint 2, trace frame 1:
8240 d0 0xc4aa0085 -995491707
8244 d4 0x71aea3d 119204413
8249 a1 0x3000668 50333288
8252 a4 0x3000698 50333336
8254 fp 0x30bf3c 0x30bf3c
8255 sp 0x30bf34 0x30bf34
8257 pc 0x20b2c8 0x20b2c8
8261 p = 0x20e5b4 "gdb-test"
8268 gdb_long_test = 17 '\021'
8273 @node save-tracepoints
8274 @subsection @code{save-tracepoints @var{filename}}
8275 @kindex save-tracepoints
8276 @cindex save tracepoints for future sessions
8278 This command saves all current tracepoint definitions together with
8279 their actions and passcounts, into a file @file{@var{filename}}
8280 suitable for use in a later debugging session. To read the saved
8281 tracepoint definitions, use the @code{source} command (@pxref{Command
8284 @node Tracepoint Variables
8285 @section Convenience Variables for Tracepoints
8286 @cindex tracepoint variables
8287 @cindex convenience variables for tracepoints
8290 @vindex $trace_frame
8291 @item (int) $trace_frame
8292 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
8293 snapshot is selected.
8296 @item (int) $tracepoint
8297 The tracepoint for the current trace snapshot.
8300 @item (int) $trace_line
8301 The line number for the current trace snapshot.
8304 @item (char []) $trace_file
8305 The source file for the current trace snapshot.
8308 @item (char []) $trace_func
8309 The name of the function containing @code{$tracepoint}.
8312 Note: @code{$trace_file} is not suitable for use in @code{printf},
8313 use @code{output} instead.
8315 Here's a simple example of using these convenience variables for
8316 stepping through all the trace snapshots and printing some of their
8320 (@value{GDBP}) @b{tfind start}
8322 (@value{GDBP}) @b{while $trace_frame != -1}
8323 > output $trace_file
8324 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
8330 @chapter Debugging Programs That Use Overlays
8333 If your program is too large to fit completely in your target system's
8334 memory, you can sometimes use @dfn{overlays} to work around this
8335 problem. @value{GDBN} provides some support for debugging programs that
8339 * How Overlays Work:: A general explanation of overlays.
8340 * Overlay Commands:: Managing overlays in @value{GDBN}.
8341 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
8342 mapped by asking the inferior.
8343 * Overlay Sample Program:: A sample program using overlays.
8346 @node How Overlays Work
8347 @section How Overlays Work
8348 @cindex mapped overlays
8349 @cindex unmapped overlays
8350 @cindex load address, overlay's
8351 @cindex mapped address
8352 @cindex overlay area
8354 Suppose you have a computer whose instruction address space is only 64
8355 kilobytes long, but which has much more memory which can be accessed by
8356 other means: special instructions, segment registers, or memory
8357 management hardware, for example. Suppose further that you want to
8358 adapt a program which is larger than 64 kilobytes to run on this system.
8360 One solution is to identify modules of your program which are relatively
8361 independent, and need not call each other directly; call these modules
8362 @dfn{overlays}. Separate the overlays from the main program, and place
8363 their machine code in the larger memory. Place your main program in
8364 instruction memory, but leave at least enough space there to hold the
8365 largest overlay as well.
8367 Now, to call a function located in an overlay, you must first copy that
8368 overlay's machine code from the large memory into the space set aside
8369 for it in the instruction memory, and then jump to its entry point
8372 @c NB: In the below the mapped area's size is greater or equal to the
8373 @c size of all overlays. This is intentional to remind the developer
8374 @c that overlays don't necessarily need to be the same size.
8378 Data Instruction Larger
8379 Address Space Address Space Address Space
8380 +-----------+ +-----------+ +-----------+
8382 +-----------+ +-----------+ +-----------+<-- overlay 1
8383 | program | | main | .----| overlay 1 | load address
8384 | variables | | program | | +-----------+
8385 | and heap | | | | | |
8386 +-----------+ | | | +-----------+<-- overlay 2
8387 | | +-----------+ | | | load address
8388 +-----------+ | | | .-| overlay 2 |
8390 mapped --->+-----------+ | | +-----------+
8392 | overlay | <-' | | |
8393 | area | <---' +-----------+<-- overlay 3
8394 | | <---. | | load address
8395 +-----------+ `--| overlay 3 |
8402 @anchor{A code overlay}A code overlay
8406 The diagram (@pxref{A code overlay}) shows a system with separate data
8407 and instruction address spaces. To map an overlay, the program copies
8408 its code from the larger address space to the instruction address space.
8409 Since the overlays shown here all use the same mapped address, only one
8410 may be mapped at a time. For a system with a single address space for
8411 data and instructions, the diagram would be similar, except that the
8412 program variables and heap would share an address space with the main
8413 program and the overlay area.
8415 An overlay loaded into instruction memory and ready for use is called a
8416 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
8417 instruction memory. An overlay not present (or only partially present)
8418 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
8419 is its address in the larger memory. The mapped address is also called
8420 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
8421 called the @dfn{load memory address}, or @dfn{LMA}.
8423 Unfortunately, overlays are not a completely transparent way to adapt a
8424 program to limited instruction memory. They introduce a new set of
8425 global constraints you must keep in mind as you design your program:
8430 Before calling or returning to a function in an overlay, your program
8431 must make sure that overlay is actually mapped. Otherwise, the call or
8432 return will transfer control to the right address, but in the wrong
8433 overlay, and your program will probably crash.
8436 If the process of mapping an overlay is expensive on your system, you
8437 will need to choose your overlays carefully to minimize their effect on
8438 your program's performance.
8441 The executable file you load onto your system must contain each
8442 overlay's instructions, appearing at the overlay's load address, not its
8443 mapped address. However, each overlay's instructions must be relocated
8444 and its symbols defined as if the overlay were at its mapped address.
8445 You can use GNU linker scripts to specify different load and relocation
8446 addresses for pieces of your program; see @ref{Overlay Description,,,
8447 ld.info, Using ld: the GNU linker}.
8450 The procedure for loading executable files onto your system must be able
8451 to load their contents into the larger address space as well as the
8452 instruction and data spaces.
8456 The overlay system described above is rather simple, and could be
8457 improved in many ways:
8462 If your system has suitable bank switch registers or memory management
8463 hardware, you could use those facilities to make an overlay's load area
8464 contents simply appear at their mapped address in instruction space.
8465 This would probably be faster than copying the overlay to its mapped
8466 area in the usual way.
8469 If your overlays are small enough, you could set aside more than one
8470 overlay area, and have more than one overlay mapped at a time.
8473 You can use overlays to manage data, as well as instructions. In
8474 general, data overlays are even less transparent to your design than
8475 code overlays: whereas code overlays only require care when you call or
8476 return to functions, data overlays require care every time you access
8477 the data. Also, if you change the contents of a data overlay, you
8478 must copy its contents back out to its load address before you can copy a
8479 different data overlay into the same mapped area.
8484 @node Overlay Commands
8485 @section Overlay Commands
8487 To use @value{GDBN}'s overlay support, each overlay in your program must
8488 correspond to a separate section of the executable file. The section's
8489 virtual memory address and load memory address must be the overlay's
8490 mapped and load addresses. Identifying overlays with sections allows
8491 @value{GDBN} to determine the appropriate address of a function or
8492 variable, depending on whether the overlay is mapped or not.
8494 @value{GDBN}'s overlay commands all start with the word @code{overlay};
8495 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
8500 Disable @value{GDBN}'s overlay support. When overlay support is
8501 disabled, @value{GDBN} assumes that all functions and variables are
8502 always present at their mapped addresses. By default, @value{GDBN}'s
8503 overlay support is disabled.
8505 @item overlay manual
8506 @cindex manual overlay debugging
8507 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
8508 relies on you to tell it which overlays are mapped, and which are not,
8509 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
8510 commands described below.
8512 @item overlay map-overlay @var{overlay}
8513 @itemx overlay map @var{overlay}
8514 @cindex map an overlay
8515 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
8516 be the name of the object file section containing the overlay. When an
8517 overlay is mapped, @value{GDBN} assumes it can find the overlay's
8518 functions and variables at their mapped addresses. @value{GDBN} assumes
8519 that any other overlays whose mapped ranges overlap that of
8520 @var{overlay} are now unmapped.
8522 @item overlay unmap-overlay @var{overlay}
8523 @itemx overlay unmap @var{overlay}
8524 @cindex unmap an overlay
8525 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
8526 must be the name of the object file section containing the overlay.
8527 When an overlay is unmapped, @value{GDBN} assumes it can find the
8528 overlay's functions and variables at their load addresses.
8531 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
8532 consults a data structure the overlay manager maintains in the inferior
8533 to see which overlays are mapped. For details, see @ref{Automatic
8536 @item overlay load-target
8538 @cindex reloading the overlay table
8539 Re-read the overlay table from the inferior. Normally, @value{GDBN}
8540 re-reads the table @value{GDBN} automatically each time the inferior
8541 stops, so this command should only be necessary if you have changed the
8542 overlay mapping yourself using @value{GDBN}. This command is only
8543 useful when using automatic overlay debugging.
8545 @item overlay list-overlays
8547 @cindex listing mapped overlays
8548 Display a list of the overlays currently mapped, along with their mapped
8549 addresses, load addresses, and sizes.
8553 Normally, when @value{GDBN} prints a code address, it includes the name
8554 of the function the address falls in:
8557 (@value{GDBP}) print main
8558 $3 = @{int ()@} 0x11a0 <main>
8561 When overlay debugging is enabled, @value{GDBN} recognizes code in
8562 unmapped overlays, and prints the names of unmapped functions with
8563 asterisks around them. For example, if @code{foo} is a function in an
8564 unmapped overlay, @value{GDBN} prints it this way:
8567 (@value{GDBP}) overlay list
8568 No sections are mapped.
8569 (@value{GDBP}) print foo
8570 $5 = @{int (int)@} 0x100000 <*foo*>
8573 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
8577 (@value{GDBP}) overlay list
8578 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
8579 mapped at 0x1016 - 0x104a
8580 (@value{GDBP}) print foo
8581 $6 = @{int (int)@} 0x1016 <foo>
8584 When overlay debugging is enabled, @value{GDBN} can find the correct
8585 address for functions and variables in an overlay, whether or not the
8586 overlay is mapped. This allows most @value{GDBN} commands, like
8587 @code{break} and @code{disassemble}, to work normally, even on unmapped
8588 code. However, @value{GDBN}'s breakpoint support has some limitations:
8592 @cindex breakpoints in overlays
8593 @cindex overlays, setting breakpoints in
8594 You can set breakpoints in functions in unmapped overlays, as long as
8595 @value{GDBN} can write to the overlay at its load address.
8597 @value{GDBN} can not set hardware or simulator-based breakpoints in
8598 unmapped overlays. However, if you set a breakpoint at the end of your
8599 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
8600 you are using manual overlay management), @value{GDBN} will re-set its
8601 breakpoints properly.
8605 @node Automatic Overlay Debugging
8606 @section Automatic Overlay Debugging
8607 @cindex automatic overlay debugging
8609 @value{GDBN} can automatically track which overlays are mapped and which
8610 are not, given some simple co-operation from the overlay manager in the
8611 inferior. If you enable automatic overlay debugging with the
8612 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
8613 looks in the inferior's memory for certain variables describing the
8614 current state of the overlays.
8616 Here are the variables your overlay manager must define to support
8617 @value{GDBN}'s automatic overlay debugging:
8621 @item @code{_ovly_table}:
8622 This variable must be an array of the following structures:
8627 /* The overlay's mapped address. */
8630 /* The size of the overlay, in bytes. */
8633 /* The overlay's load address. */
8636 /* Non-zero if the overlay is currently mapped;
8638 unsigned long mapped;
8642 @item @code{_novlys}:
8643 This variable must be a four-byte signed integer, holding the total
8644 number of elements in @code{_ovly_table}.
8648 To decide whether a particular overlay is mapped or not, @value{GDBN}
8649 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
8650 @code{lma} members equal the VMA and LMA of the overlay's section in the
8651 executable file. When @value{GDBN} finds a matching entry, it consults
8652 the entry's @code{mapped} member to determine whether the overlay is
8655 In addition, your overlay manager may define a function called
8656 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
8657 will silently set a breakpoint there. If the overlay manager then
8658 calls this function whenever it has changed the overlay table, this
8659 will enable @value{GDBN} to accurately keep track of which overlays
8660 are in program memory, and update any breakpoints that may be set
8661 in overlays. This will allow breakpoints to work even if the
8662 overlays are kept in ROM or other non-writable memory while they
8663 are not being executed.
8665 @node Overlay Sample Program
8666 @section Overlay Sample Program
8667 @cindex overlay example program
8669 When linking a program which uses overlays, you must place the overlays
8670 at their load addresses, while relocating them to run at their mapped
8671 addresses. To do this, you must write a linker script (@pxref{Overlay
8672 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
8673 since linker scripts are specific to a particular host system, target
8674 architecture, and target memory layout, this manual cannot provide
8675 portable sample code demonstrating @value{GDBN}'s overlay support.
8677 However, the @value{GDBN} source distribution does contain an overlaid
8678 program, with linker scripts for a few systems, as part of its test
8679 suite. The program consists of the following files from
8680 @file{gdb/testsuite/gdb.base}:
8684 The main program file.
8686 A simple overlay manager, used by @file{overlays.c}.
8691 Overlay modules, loaded and used by @file{overlays.c}.
8694 Linker scripts for linking the test program on the @code{d10v-elf}
8695 and @code{m32r-elf} targets.
8698 You can build the test program using the @code{d10v-elf} GCC
8699 cross-compiler like this:
8702 $ d10v-elf-gcc -g -c overlays.c
8703 $ d10v-elf-gcc -g -c ovlymgr.c
8704 $ d10v-elf-gcc -g -c foo.c
8705 $ d10v-elf-gcc -g -c bar.c
8706 $ d10v-elf-gcc -g -c baz.c
8707 $ d10v-elf-gcc -g -c grbx.c
8708 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
8709 baz.o grbx.o -Wl,-Td10v.ld -o overlays
8712 The build process is identical for any other architecture, except that
8713 you must substitute the appropriate compiler and linker script for the
8714 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
8718 @chapter Using @value{GDBN} with Different Languages
8721 Although programming languages generally have common aspects, they are
8722 rarely expressed in the same manner. For instance, in ANSI C,
8723 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
8724 Modula-2, it is accomplished by @code{p^}. Values can also be
8725 represented (and displayed) differently. Hex numbers in C appear as
8726 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
8728 @cindex working language
8729 Language-specific information is built into @value{GDBN} for some languages,
8730 allowing you to express operations like the above in your program's
8731 native language, and allowing @value{GDBN} to output values in a manner
8732 consistent with the syntax of your program's native language. The
8733 language you use to build expressions is called the @dfn{working
8737 * Setting:: Switching between source languages
8738 * Show:: Displaying the language
8739 * Checks:: Type and range checks
8740 * Supported Languages:: Supported languages
8741 * Unsupported Languages:: Unsupported languages
8745 @section Switching Between Source Languages
8747 There are two ways to control the working language---either have @value{GDBN}
8748 set it automatically, or select it manually yourself. You can use the
8749 @code{set language} command for either purpose. On startup, @value{GDBN}
8750 defaults to setting the language automatically. The working language is
8751 used to determine how expressions you type are interpreted, how values
8754 In addition to the working language, every source file that
8755 @value{GDBN} knows about has its own working language. For some object
8756 file formats, the compiler might indicate which language a particular
8757 source file is in. However, most of the time @value{GDBN} infers the
8758 language from the name of the file. The language of a source file
8759 controls whether C@t{++} names are demangled---this way @code{backtrace} can
8760 show each frame appropriately for its own language. There is no way to
8761 set the language of a source file from within @value{GDBN}, but you can
8762 set the language associated with a filename extension. @xref{Show, ,
8763 Displaying the Language}.
8765 This is most commonly a problem when you use a program, such
8766 as @code{cfront} or @code{f2c}, that generates C but is written in
8767 another language. In that case, make the
8768 program use @code{#line} directives in its C output; that way
8769 @value{GDBN} will know the correct language of the source code of the original
8770 program, and will display that source code, not the generated C code.
8773 * Filenames:: Filename extensions and languages.
8774 * Manually:: Setting the working language manually
8775 * Automatically:: Having @value{GDBN} infer the source language
8779 @subsection List of Filename Extensions and Languages
8781 If a source file name ends in one of the following extensions, then
8782 @value{GDBN} infers that its language is the one indicated.
8803 Objective-C source file
8810 Modula-2 source file
8814 Assembler source file. This actually behaves almost like C, but
8815 @value{GDBN} does not skip over function prologues when stepping.
8818 In addition, you may set the language associated with a filename
8819 extension. @xref{Show, , Displaying the Language}.
8822 @subsection Setting the Working Language
8824 If you allow @value{GDBN} to set the language automatically,
8825 expressions are interpreted the same way in your debugging session and
8828 @kindex set language
8829 If you wish, you may set the language manually. To do this, issue the
8830 command @samp{set language @var{lang}}, where @var{lang} is the name of
8832 @code{c} or @code{modula-2}.
8833 For a list of the supported languages, type @samp{set language}.
8835 Setting the language manually prevents @value{GDBN} from updating the working
8836 language automatically. This can lead to confusion if you try
8837 to debug a program when the working language is not the same as the
8838 source language, when an expression is acceptable to both
8839 languages---but means different things. For instance, if the current
8840 source file were written in C, and @value{GDBN} was parsing Modula-2, a
8848 might not have the effect you intended. In C, this means to add
8849 @code{b} and @code{c} and place the result in @code{a}. The result
8850 printed would be the value of @code{a}. In Modula-2, this means to compare
8851 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
8854 @subsection Having @value{GDBN} Infer the Source Language
8856 To have @value{GDBN} set the working language automatically, use
8857 @samp{set language local} or @samp{set language auto}. @value{GDBN}
8858 then infers the working language. That is, when your program stops in a
8859 frame (usually by encountering a breakpoint), @value{GDBN} sets the
8860 working language to the language recorded for the function in that
8861 frame. If the language for a frame is unknown (that is, if the function
8862 or block corresponding to the frame was defined in a source file that
8863 does not have a recognized extension), the current working language is
8864 not changed, and @value{GDBN} issues a warning.
8866 This may not seem necessary for most programs, which are written
8867 entirely in one source language. However, program modules and libraries
8868 written in one source language can be used by a main program written in
8869 a different source language. Using @samp{set language auto} in this
8870 case frees you from having to set the working language manually.
8873 @section Displaying the Language
8875 The following commands help you find out which language is the
8876 working language, and also what language source files were written in.
8880 @kindex show language
8881 Display the current working language. This is the
8882 language you can use with commands such as @code{print} to
8883 build and compute expressions that may involve variables in your program.
8886 @kindex info frame@r{, show the source language}
8887 Display the source language for this frame. This language becomes the
8888 working language if you use an identifier from this frame.
8889 @xref{Frame Info, ,Information about a Frame}, to identify the other
8890 information listed here.
8893 @kindex info source@r{, show the source language}
8894 Display the source language of this source file.
8895 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
8896 information listed here.
8899 In unusual circumstances, you may have source files with extensions
8900 not in the standard list. You can then set the extension associated
8901 with a language explicitly:
8904 @item set extension-language @var{ext} @var{language}
8905 @kindex set extension-language
8906 Tell @value{GDBN} that source files with extension @var{ext} are to be
8907 assumed as written in the source language @var{language}.
8909 @item info extensions
8910 @kindex info extensions
8911 List all the filename extensions and the associated languages.
8915 @section Type and Range Checking
8918 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
8919 checking are included, but they do not yet have any effect. This
8920 section documents the intended facilities.
8922 @c FIXME remove warning when type/range code added
8924 Some languages are designed to guard you against making seemingly common
8925 errors through a series of compile- and run-time checks. These include
8926 checking the type of arguments to functions and operators, and making
8927 sure mathematical overflows are caught at run time. Checks such as
8928 these help to ensure a program's correctness once it has been compiled
8929 by eliminating type mismatches, and providing active checks for range
8930 errors when your program is running.
8932 @value{GDBN} can check for conditions like the above if you wish.
8933 Although @value{GDBN} does not check the statements in your program,
8934 it can check expressions entered directly into @value{GDBN} for
8935 evaluation via the @code{print} command, for example. As with the
8936 working language, @value{GDBN} can also decide whether or not to check
8937 automatically based on your program's source language.
8938 @xref{Supported Languages, ,Supported Languages}, for the default
8939 settings of supported languages.
8942 * Type Checking:: An overview of type checking
8943 * Range Checking:: An overview of range checking
8946 @cindex type checking
8947 @cindex checks, type
8949 @subsection An Overview of Type Checking
8951 Some languages, such as Modula-2, are strongly typed, meaning that the
8952 arguments to operators and functions have to be of the correct type,
8953 otherwise an error occurs. These checks prevent type mismatch
8954 errors from ever causing any run-time problems. For example,
8962 The second example fails because the @code{CARDINAL} 1 is not
8963 type-compatible with the @code{REAL} 2.3.
8965 For the expressions you use in @value{GDBN} commands, you can tell the
8966 @value{GDBN} type checker to skip checking;
8967 to treat any mismatches as errors and abandon the expression;
8968 or to only issue warnings when type mismatches occur,
8969 but evaluate the expression anyway. When you choose the last of
8970 these, @value{GDBN} evaluates expressions like the second example above, but
8971 also issues a warning.
8973 Even if you turn type checking off, there may be other reasons
8974 related to type that prevent @value{GDBN} from evaluating an expression.
8975 For instance, @value{GDBN} does not know how to add an @code{int} and
8976 a @code{struct foo}. These particular type errors have nothing to do
8977 with the language in use, and usually arise from expressions, such as
8978 the one described above, which make little sense to evaluate anyway.
8980 Each language defines to what degree it is strict about type. For
8981 instance, both Modula-2 and C require the arguments to arithmetical
8982 operators to be numbers. In C, enumerated types and pointers can be
8983 represented as numbers, so that they are valid arguments to mathematical
8984 operators. @xref{Supported Languages, ,Supported Languages}, for further
8985 details on specific languages.
8987 @value{GDBN} provides some additional commands for controlling the type checker:
8989 @kindex set check type
8990 @kindex show check type
8992 @item set check type auto
8993 Set type checking on or off based on the current working language.
8994 @xref{Supported Languages, ,Supported Languages}, for the default settings for
8997 @item set check type on
8998 @itemx set check type off
8999 Set type checking on or off, overriding the default setting for the
9000 current working language. Issue a warning if the setting does not
9001 match the language default. If any type mismatches occur in
9002 evaluating an expression while type checking is on, @value{GDBN} prints a
9003 message and aborts evaluation of the expression.
9005 @item set check type warn
9006 Cause the type checker to issue warnings, but to always attempt to
9007 evaluate the expression. Evaluating the expression may still
9008 be impossible for other reasons. For example, @value{GDBN} cannot add
9009 numbers and structures.
9012 Show the current setting of the type checker, and whether or not @value{GDBN}
9013 is setting it automatically.
9016 @cindex range checking
9017 @cindex checks, range
9018 @node Range Checking
9019 @subsection An Overview of Range Checking
9021 In some languages (such as Modula-2), it is an error to exceed the
9022 bounds of a type; this is enforced with run-time checks. Such range
9023 checking is meant to ensure program correctness by making sure
9024 computations do not overflow, or indices on an array element access do
9025 not exceed the bounds of the array.
9027 For expressions you use in @value{GDBN} commands, you can tell
9028 @value{GDBN} to treat range errors in one of three ways: ignore them,
9029 always treat them as errors and abandon the expression, or issue
9030 warnings but evaluate the expression anyway.
9032 A range error can result from numerical overflow, from exceeding an
9033 array index bound, or when you type a constant that is not a member
9034 of any type. Some languages, however, do not treat overflows as an
9035 error. In many implementations of C, mathematical overflow causes the
9036 result to ``wrap around'' to lower values---for example, if @var{m} is
9037 the largest integer value, and @var{s} is the smallest, then
9040 @var{m} + 1 @result{} @var{s}
9043 This, too, is specific to individual languages, and in some cases
9044 specific to individual compilers or machines. @xref{Supported Languages, ,
9045 Supported Languages}, for further details on specific languages.
9047 @value{GDBN} provides some additional commands for controlling the range checker:
9049 @kindex set check range
9050 @kindex show check range
9052 @item set check range auto
9053 Set range checking on or off based on the current working language.
9054 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9057 @item set check range on
9058 @itemx set check range off
9059 Set range checking on or off, overriding the default setting for the
9060 current working language. A warning is issued if the setting does not
9061 match the language default. If a range error occurs and range checking is on,
9062 then a message is printed and evaluation of the expression is aborted.
9064 @item set check range warn
9065 Output messages when the @value{GDBN} range checker detects a range error,
9066 but attempt to evaluate the expression anyway. Evaluating the
9067 expression may still be impossible for other reasons, such as accessing
9068 memory that the process does not own (a typical example from many Unix
9072 Show the current setting of the range checker, and whether or not it is
9073 being set automatically by @value{GDBN}.
9076 @node Supported Languages
9077 @section Supported Languages
9079 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
9080 assembly, Modula-2, and Ada.
9081 @c This is false ...
9082 Some @value{GDBN} features may be used in expressions regardless of the
9083 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
9084 and the @samp{@{type@}addr} construct (@pxref{Expressions,
9085 ,Expressions}) can be used with the constructs of any supported
9088 The following sections detail to what degree each source language is
9089 supported by @value{GDBN}. These sections are not meant to be language
9090 tutorials or references, but serve only as a reference guide to what the
9091 @value{GDBN} expression parser accepts, and what input and output
9092 formats should look like for different languages. There are many good
9093 books written on each of these languages; please look to these for a
9094 language reference or tutorial.
9098 * Objective-C:: Objective-C
9101 * Modula-2:: Modula-2
9106 @subsection C and C@t{++}
9108 @cindex C and C@t{++}
9109 @cindex expressions in C or C@t{++}
9111 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
9112 to both languages. Whenever this is the case, we discuss those languages
9116 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
9117 @cindex @sc{gnu} C@t{++}
9118 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
9119 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
9120 effectively, you must compile your C@t{++} programs with a supported
9121 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
9122 compiler (@code{aCC}).
9124 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
9125 format; if it doesn't work on your system, try the stabs+ debugging
9126 format. You can select those formats explicitly with the @code{g++}
9127 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
9128 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
9129 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
9132 * C Operators:: C and C@t{++} operators
9133 * C Constants:: C and C@t{++} constants
9134 * C Plus Plus Expressions:: C@t{++} expressions
9135 * C Defaults:: Default settings for C and C@t{++}
9136 * C Checks:: C and C@t{++} type and range checks
9137 * Debugging C:: @value{GDBN} and C
9138 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
9139 * Decimal Floating Point:: Numbers in Decimal Floating Point format
9143 @subsubsection C and C@t{++} Operators
9145 @cindex C and C@t{++} operators
9147 Operators must be defined on values of specific types. For instance,
9148 @code{+} is defined on numbers, but not on structures. Operators are
9149 often defined on groups of types.
9151 For the purposes of C and C@t{++}, the following definitions hold:
9156 @emph{Integral types} include @code{int} with any of its storage-class
9157 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
9160 @emph{Floating-point types} include @code{float}, @code{double}, and
9161 @code{long double} (if supported by the target platform).
9164 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
9167 @emph{Scalar types} include all of the above.
9172 The following operators are supported. They are listed here
9173 in order of increasing precedence:
9177 The comma or sequencing operator. Expressions in a comma-separated list
9178 are evaluated from left to right, with the result of the entire
9179 expression being the last expression evaluated.
9182 Assignment. The value of an assignment expression is the value
9183 assigned. Defined on scalar types.
9186 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
9187 and translated to @w{@code{@var{a} = @var{a op b}}}.
9188 @w{@code{@var{op}=}} and @code{=} have the same precedence.
9189 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
9190 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
9193 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
9194 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
9198 Logical @sc{or}. Defined on integral types.
9201 Logical @sc{and}. Defined on integral types.
9204 Bitwise @sc{or}. Defined on integral types.
9207 Bitwise exclusive-@sc{or}. Defined on integral types.
9210 Bitwise @sc{and}. Defined on integral types.
9213 Equality and inequality. Defined on scalar types. The value of these
9214 expressions is 0 for false and non-zero for true.
9216 @item <@r{, }>@r{, }<=@r{, }>=
9217 Less than, greater than, less than or equal, greater than or equal.
9218 Defined on scalar types. The value of these expressions is 0 for false
9219 and non-zero for true.
9222 left shift, and right shift. Defined on integral types.
9225 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9228 Addition and subtraction. Defined on integral types, floating-point types and
9231 @item *@r{, }/@r{, }%
9232 Multiplication, division, and modulus. Multiplication and division are
9233 defined on integral and floating-point types. Modulus is defined on
9237 Increment and decrement. When appearing before a variable, the
9238 operation is performed before the variable is used in an expression;
9239 when appearing after it, the variable's value is used before the
9240 operation takes place.
9243 Pointer dereferencing. Defined on pointer types. Same precedence as
9247 Address operator. Defined on variables. Same precedence as @code{++}.
9249 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
9250 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
9251 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
9252 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
9256 Negative. Defined on integral and floating-point types. Same
9257 precedence as @code{++}.
9260 Logical negation. Defined on integral types. Same precedence as
9264 Bitwise complement operator. Defined on integral types. Same precedence as
9269 Structure member, and pointer-to-structure member. For convenience,
9270 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
9271 pointer based on the stored type information.
9272 Defined on @code{struct} and @code{union} data.
9275 Dereferences of pointers to members.
9278 Array indexing. @code{@var{a}[@var{i}]} is defined as
9279 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
9282 Function parameter list. Same precedence as @code{->}.
9285 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
9286 and @code{class} types.
9289 Doubled colons also represent the @value{GDBN} scope operator
9290 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
9294 If an operator is redefined in the user code, @value{GDBN} usually
9295 attempts to invoke the redefined version instead of using the operator's
9299 @subsubsection C and C@t{++} Constants
9301 @cindex C and C@t{++} constants
9303 @value{GDBN} allows you to express the constants of C and C@t{++} in the
9308 Integer constants are a sequence of digits. Octal constants are
9309 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
9310 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
9311 @samp{l}, specifying that the constant should be treated as a
9315 Floating point constants are a sequence of digits, followed by a decimal
9316 point, followed by a sequence of digits, and optionally followed by an
9317 exponent. An exponent is of the form:
9318 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
9319 sequence of digits. The @samp{+} is optional for positive exponents.
9320 A floating-point constant may also end with a letter @samp{f} or
9321 @samp{F}, specifying that the constant should be treated as being of
9322 the @code{float} (as opposed to the default @code{double}) type; or with
9323 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
9327 Enumerated constants consist of enumerated identifiers, or their
9328 integral equivalents.
9331 Character constants are a single character surrounded by single quotes
9332 (@code{'}), or a number---the ordinal value of the corresponding character
9333 (usually its @sc{ascii} value). Within quotes, the single character may
9334 be represented by a letter or by @dfn{escape sequences}, which are of
9335 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
9336 of the character's ordinal value; or of the form @samp{\@var{x}}, where
9337 @samp{@var{x}} is a predefined special character---for example,
9338 @samp{\n} for newline.
9341 String constants are a sequence of character constants surrounded by
9342 double quotes (@code{"}). Any valid character constant (as described
9343 above) may appear. Double quotes within the string must be preceded by
9344 a backslash, so for instance @samp{"a\"b'c"} is a string of five
9348 Pointer constants are an integral value. You can also write pointers
9349 to constants using the C operator @samp{&}.
9352 Array constants are comma-separated lists surrounded by braces @samp{@{}
9353 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
9354 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
9355 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
9358 @node C Plus Plus Expressions
9359 @subsubsection C@t{++} Expressions
9361 @cindex expressions in C@t{++}
9362 @value{GDBN} expression handling can interpret most C@t{++} expressions.
9364 @cindex debugging C@t{++} programs
9365 @cindex C@t{++} compilers
9366 @cindex debug formats and C@t{++}
9367 @cindex @value{NGCC} and C@t{++}
9369 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
9370 proper compiler and the proper debug format. Currently, @value{GDBN}
9371 works best when debugging C@t{++} code that is compiled with
9372 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
9373 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
9374 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
9375 stabs+ as their default debug format, so you usually don't need to
9376 specify a debug format explicitly. Other compilers and/or debug formats
9377 are likely to work badly or not at all when using @value{GDBN} to debug
9383 @cindex member functions
9385 Member function calls are allowed; you can use expressions like
9388 count = aml->GetOriginal(x, y)
9391 @vindex this@r{, inside C@t{++} member functions}
9392 @cindex namespace in C@t{++}
9394 While a member function is active (in the selected stack frame), your
9395 expressions have the same namespace available as the member function;
9396 that is, @value{GDBN} allows implicit references to the class instance
9397 pointer @code{this} following the same rules as C@t{++}.
9399 @cindex call overloaded functions
9400 @cindex overloaded functions, calling
9401 @cindex type conversions in C@t{++}
9403 You can call overloaded functions; @value{GDBN} resolves the function
9404 call to the right definition, with some restrictions. @value{GDBN} does not
9405 perform overload resolution involving user-defined type conversions,
9406 calls to constructors, or instantiations of templates that do not exist
9407 in the program. It also cannot handle ellipsis argument lists or
9410 It does perform integral conversions and promotions, floating-point
9411 promotions, arithmetic conversions, pointer conversions, conversions of
9412 class objects to base classes, and standard conversions such as those of
9413 functions or arrays to pointers; it requires an exact match on the
9414 number of function arguments.
9416 Overload resolution is always performed, unless you have specified
9417 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
9418 ,@value{GDBN} Features for C@t{++}}.
9420 You must specify @code{set overload-resolution off} in order to use an
9421 explicit function signature to call an overloaded function, as in
9423 p 'foo(char,int)'('x', 13)
9426 The @value{GDBN} command-completion facility can simplify this;
9427 see @ref{Completion, ,Command Completion}.
9429 @cindex reference declarations
9431 @value{GDBN} understands variables declared as C@t{++} references; you can use
9432 them in expressions just as you do in C@t{++} source---they are automatically
9435 In the parameter list shown when @value{GDBN} displays a frame, the values of
9436 reference variables are not displayed (unlike other variables); this
9437 avoids clutter, since references are often used for large structures.
9438 The @emph{address} of a reference variable is always shown, unless
9439 you have specified @samp{set print address off}.
9442 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
9443 expressions can use it just as expressions in your program do. Since
9444 one scope may be defined in another, you can use @code{::} repeatedly if
9445 necessary, for example in an expression like
9446 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
9447 resolving name scope by reference to source files, in both C and C@t{++}
9448 debugging (@pxref{Variables, ,Program Variables}).
9451 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
9452 calling virtual functions correctly, printing out virtual bases of
9453 objects, calling functions in a base subobject, casting objects, and
9454 invoking user-defined operators.
9457 @subsubsection C and C@t{++} Defaults
9459 @cindex C and C@t{++} defaults
9461 If you allow @value{GDBN} to set type and range checking automatically, they
9462 both default to @code{off} whenever the working language changes to
9463 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
9464 selects the working language.
9466 If you allow @value{GDBN} to set the language automatically, it
9467 recognizes source files whose names end with @file{.c}, @file{.C}, or
9468 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
9469 these files, it sets the working language to C or C@t{++}.
9470 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
9471 for further details.
9473 @c Type checking is (a) primarily motivated by Modula-2, and (b)
9474 @c unimplemented. If (b) changes, it might make sense to let this node
9475 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
9478 @subsubsection C and C@t{++} Type and Range Checks
9480 @cindex C and C@t{++} checks
9482 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
9483 is not used. However, if you turn type checking on, @value{GDBN}
9484 considers two variables type equivalent if:
9488 The two variables are structured and have the same structure, union, or
9492 The two variables have the same type name, or types that have been
9493 declared equivalent through @code{typedef}.
9496 @c leaving this out because neither J Gilmore nor R Pesch understand it.
9499 The two @code{struct}, @code{union}, or @code{enum} variables are
9500 declared in the same declaration. (Note: this may not be true for all C
9505 Range checking, if turned on, is done on mathematical operations. Array
9506 indices are not checked, since they are often used to index a pointer
9507 that is not itself an array.
9510 @subsubsection @value{GDBN} and C
9512 The @code{set print union} and @code{show print union} commands apply to
9513 the @code{union} type. When set to @samp{on}, any @code{union} that is
9514 inside a @code{struct} or @code{class} is also printed. Otherwise, it
9515 appears as @samp{@{...@}}.
9517 The @code{@@} operator aids in the debugging of dynamic arrays, formed
9518 with pointers and a memory allocation function. @xref{Expressions,
9521 @node Debugging C Plus Plus
9522 @subsubsection @value{GDBN} Features for C@t{++}
9524 @cindex commands for C@t{++}
9526 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
9527 designed specifically for use with C@t{++}. Here is a summary:
9530 @cindex break in overloaded functions
9531 @item @r{breakpoint menus}
9532 When you want a breakpoint in a function whose name is overloaded,
9533 @value{GDBN} breakpoint menus help you specify which function definition
9534 you want. @xref{Breakpoint Menus,,Breakpoint Menus}.
9536 @cindex overloading in C@t{++}
9537 @item rbreak @var{regex}
9538 Setting breakpoints using regular expressions is helpful for setting
9539 breakpoints on overloaded functions that are not members of any special
9541 @xref{Set Breaks, ,Setting Breakpoints}.
9543 @cindex C@t{++} exception handling
9546 Debug C@t{++} exception handling using these commands. @xref{Set
9547 Catchpoints, , Setting Catchpoints}.
9550 @item ptype @var{typename}
9551 Print inheritance relationships as well as other information for type
9553 @xref{Symbols, ,Examining the Symbol Table}.
9555 @cindex C@t{++} symbol display
9556 @item set print demangle
9557 @itemx show print demangle
9558 @itemx set print asm-demangle
9559 @itemx show print asm-demangle
9560 Control whether C@t{++} symbols display in their source form, both when
9561 displaying code as C@t{++} source and when displaying disassemblies.
9562 @xref{Print Settings, ,Print Settings}.
9564 @item set print object
9565 @itemx show print object
9566 Choose whether to print derived (actual) or declared types of objects.
9567 @xref{Print Settings, ,Print Settings}.
9569 @item set print vtbl
9570 @itemx show print vtbl
9571 Control the format for printing virtual function tables.
9572 @xref{Print Settings, ,Print Settings}.
9573 (The @code{vtbl} commands do not work on programs compiled with the HP
9574 ANSI C@t{++} compiler (@code{aCC}).)
9576 @kindex set overload-resolution
9577 @cindex overloaded functions, overload resolution
9578 @item set overload-resolution on
9579 Enable overload resolution for C@t{++} expression evaluation. The default
9580 is on. For overloaded functions, @value{GDBN} evaluates the arguments
9581 and searches for a function whose signature matches the argument types,
9582 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
9583 Expressions, ,C@t{++} Expressions}, for details).
9584 If it cannot find a match, it emits a message.
9586 @item set overload-resolution off
9587 Disable overload resolution for C@t{++} expression evaluation. For
9588 overloaded functions that are not class member functions, @value{GDBN}
9589 chooses the first function of the specified name that it finds in the
9590 symbol table, whether or not its arguments are of the correct type. For
9591 overloaded functions that are class member functions, @value{GDBN}
9592 searches for a function whose signature @emph{exactly} matches the
9595 @kindex show overload-resolution
9596 @item show overload-resolution
9597 Show the current setting of overload resolution.
9599 @item @r{Overloaded symbol names}
9600 You can specify a particular definition of an overloaded symbol, using
9601 the same notation that is used to declare such symbols in C@t{++}: type
9602 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
9603 also use the @value{GDBN} command-line word completion facilities to list the
9604 available choices, or to finish the type list for you.
9605 @xref{Completion,, Command Completion}, for details on how to do this.
9608 @node Decimal Floating Point
9609 @subsubsection Decimal Floating Point format
9610 @cindex decimal floating point format
9612 @value{GDBN} can examine, set and perform computations with numbers in
9613 decimal floating point format, which in the C language correspond to the
9614 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
9615 specified by the extension to support decimal floating-point arithmetic.
9617 There are two encodings in use, depending on the architecture: BID (Binary
9618 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
9619 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
9622 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
9623 to manipulate decimal floating point numbers, it is not possible to convert
9624 (using a cast, for example) integers wider than 32-bit to decimal float.
9626 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
9627 point computations, error checking in decimal float operations ignores
9628 underflow, overflow and divide by zero exceptions.
9631 @subsection Objective-C
9634 This section provides information about some commands and command
9635 options that are useful for debugging Objective-C code. See also
9636 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
9637 few more commands specific to Objective-C support.
9640 * Method Names in Commands::
9641 * The Print Command with Objective-C::
9644 @node Method Names in Commands
9645 @subsubsection Method Names in Commands
9647 The following commands have been extended to accept Objective-C method
9648 names as line specifications:
9650 @kindex clear@r{, and Objective-C}
9651 @kindex break@r{, and Objective-C}
9652 @kindex info line@r{, and Objective-C}
9653 @kindex jump@r{, and Objective-C}
9654 @kindex list@r{, and Objective-C}
9658 @item @code{info line}
9663 A fully qualified Objective-C method name is specified as
9666 -[@var{Class} @var{methodName}]
9669 where the minus sign is used to indicate an instance method and a
9670 plus sign (not shown) is used to indicate a class method. The class
9671 name @var{Class} and method name @var{methodName} are enclosed in
9672 brackets, similar to the way messages are specified in Objective-C
9673 source code. For example, to set a breakpoint at the @code{create}
9674 instance method of class @code{Fruit} in the program currently being
9678 break -[Fruit create]
9681 To list ten program lines around the @code{initialize} class method,
9685 list +[NSText initialize]
9688 In the current version of @value{GDBN}, the plus or minus sign is
9689 required. In future versions of @value{GDBN}, the plus or minus
9690 sign will be optional, but you can use it to narrow the search. It
9691 is also possible to specify just a method name:
9697 You must specify the complete method name, including any colons. If
9698 your program's source files contain more than one @code{create} method,
9699 you'll be presented with a numbered list of classes that implement that
9700 method. Indicate your choice by number, or type @samp{0} to exit if
9703 As another example, to clear a breakpoint established at the
9704 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
9707 clear -[NSWindow makeKeyAndOrderFront:]
9710 @node The Print Command with Objective-C
9711 @subsubsection The Print Command With Objective-C
9712 @cindex Objective-C, print objects
9713 @kindex print-object
9714 @kindex po @r{(@code{print-object})}
9716 The print command has also been extended to accept methods. For example:
9719 print -[@var{object} hash]
9722 @cindex print an Objective-C object description
9723 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
9725 will tell @value{GDBN} to send the @code{hash} message to @var{object}
9726 and print the result. Also, an additional command has been added,
9727 @code{print-object} or @code{po} for short, which is meant to print
9728 the description of an object. However, this command may only work
9729 with certain Objective-C libraries that have a particular hook
9730 function, @code{_NSPrintForDebugger}, defined.
9734 @cindex Fortran-specific support in @value{GDBN}
9736 @value{GDBN} can be used to debug programs written in Fortran, but it
9737 currently supports only the features of Fortran 77 language.
9739 @cindex trailing underscore, in Fortran symbols
9740 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
9741 among them) append an underscore to the names of variables and
9742 functions. When you debug programs compiled by those compilers, you
9743 will need to refer to variables and functions with a trailing
9747 * Fortran Operators:: Fortran operators and expressions
9748 * Fortran Defaults:: Default settings for Fortran
9749 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
9752 @node Fortran Operators
9753 @subsubsection Fortran Operators and Expressions
9755 @cindex Fortran operators and expressions
9757 Operators must be defined on values of specific types. For instance,
9758 @code{+} is defined on numbers, but not on characters or other non-
9759 arithmetic types. Operators are often defined on groups of types.
9763 The exponentiation operator. It raises the first operand to the power
9767 The range operator. Normally used in the form of array(low:high) to
9768 represent a section of array.
9771 @node Fortran Defaults
9772 @subsubsection Fortran Defaults
9774 @cindex Fortran Defaults
9776 Fortran symbols are usually case-insensitive, so @value{GDBN} by
9777 default uses case-insensitive matches for Fortran symbols. You can
9778 change that with the @samp{set case-insensitive} command, see
9779 @ref{Symbols}, for the details.
9781 @node Special Fortran Commands
9782 @subsubsection Special Fortran Commands
9784 @cindex Special Fortran commands
9786 @value{GDBN} has some commands to support Fortran-specific features,
9787 such as displaying common blocks.
9790 @cindex @code{COMMON} blocks, Fortran
9792 @item info common @r{[}@var{common-name}@r{]}
9793 This command prints the values contained in the Fortran @code{COMMON}
9794 block whose name is @var{common-name}. With no argument, the names of
9795 all @code{COMMON} blocks visible at the current program location are
9802 @cindex Pascal support in @value{GDBN}, limitations
9803 Debugging Pascal programs which use sets, subranges, file variables, or
9804 nested functions does not currently work. @value{GDBN} does not support
9805 entering expressions, printing values, or similar features using Pascal
9808 The Pascal-specific command @code{set print pascal_static-members}
9809 controls whether static members of Pascal objects are displayed.
9810 @xref{Print Settings, pascal_static-members}.
9813 @subsection Modula-2
9815 @cindex Modula-2, @value{GDBN} support
9817 The extensions made to @value{GDBN} to support Modula-2 only support
9818 output from the @sc{gnu} Modula-2 compiler (which is currently being
9819 developed). Other Modula-2 compilers are not currently supported, and
9820 attempting to debug executables produced by them is most likely
9821 to give an error as @value{GDBN} reads in the executable's symbol
9824 @cindex expressions in Modula-2
9826 * M2 Operators:: Built-in operators
9827 * Built-In Func/Proc:: Built-in functions and procedures
9828 * M2 Constants:: Modula-2 constants
9829 * M2 Types:: Modula-2 types
9830 * M2 Defaults:: Default settings for Modula-2
9831 * Deviations:: Deviations from standard Modula-2
9832 * M2 Checks:: Modula-2 type and range checks
9833 * M2 Scope:: The scope operators @code{::} and @code{.}
9834 * GDB/M2:: @value{GDBN} and Modula-2
9838 @subsubsection Operators
9839 @cindex Modula-2 operators
9841 Operators must be defined on values of specific types. For instance,
9842 @code{+} is defined on numbers, but not on structures. Operators are
9843 often defined on groups of types. For the purposes of Modula-2, the
9844 following definitions hold:
9849 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
9853 @emph{Character types} consist of @code{CHAR} and its subranges.
9856 @emph{Floating-point types} consist of @code{REAL}.
9859 @emph{Pointer types} consist of anything declared as @code{POINTER TO
9863 @emph{Scalar types} consist of all of the above.
9866 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
9869 @emph{Boolean types} consist of @code{BOOLEAN}.
9873 The following operators are supported, and appear in order of
9874 increasing precedence:
9878 Function argument or array index separator.
9881 Assignment. The value of @var{var} @code{:=} @var{value} is
9885 Less than, greater than on integral, floating-point, or enumerated
9889 Less than or equal to, greater than or equal to
9890 on integral, floating-point and enumerated types, or set inclusion on
9891 set types. Same precedence as @code{<}.
9893 @item =@r{, }<>@r{, }#
9894 Equality and two ways of expressing inequality, valid on scalar types.
9895 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
9896 available for inequality, since @code{#} conflicts with the script
9900 Set membership. Defined on set types and the types of their members.
9901 Same precedence as @code{<}.
9904 Boolean disjunction. Defined on boolean types.
9907 Boolean conjunction. Defined on boolean types.
9910 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9913 Addition and subtraction on integral and floating-point types, or union
9914 and difference on set types.
9917 Multiplication on integral and floating-point types, or set intersection
9921 Division on floating-point types, or symmetric set difference on set
9922 types. Same precedence as @code{*}.
9925 Integer division and remainder. Defined on integral types. Same
9926 precedence as @code{*}.
9929 Negative. Defined on @code{INTEGER} and @code{REAL} data.
9932 Pointer dereferencing. Defined on pointer types.
9935 Boolean negation. Defined on boolean types. Same precedence as
9939 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
9940 precedence as @code{^}.
9943 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
9946 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
9950 @value{GDBN} and Modula-2 scope operators.
9954 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
9955 treats the use of the operator @code{IN}, or the use of operators
9956 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
9957 @code{<=}, and @code{>=} on sets as an error.
9961 @node Built-In Func/Proc
9962 @subsubsection Built-in Functions and Procedures
9963 @cindex Modula-2 built-ins
9965 Modula-2 also makes available several built-in procedures and functions.
9966 In describing these, the following metavariables are used:
9971 represents an @code{ARRAY} variable.
9974 represents a @code{CHAR} constant or variable.
9977 represents a variable or constant of integral type.
9980 represents an identifier that belongs to a set. Generally used in the
9981 same function with the metavariable @var{s}. The type of @var{s} should
9982 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
9985 represents a variable or constant of integral or floating-point type.
9988 represents a variable or constant of floating-point type.
9994 represents a variable.
9997 represents a variable or constant of one of many types. See the
9998 explanation of the function for details.
10001 All Modula-2 built-in procedures also return a result, described below.
10005 Returns the absolute value of @var{n}.
10008 If @var{c} is a lower case letter, it returns its upper case
10009 equivalent, otherwise it returns its argument.
10012 Returns the character whose ordinal value is @var{i}.
10015 Decrements the value in the variable @var{v} by one. Returns the new value.
10017 @item DEC(@var{v},@var{i})
10018 Decrements the value in the variable @var{v} by @var{i}. Returns the
10021 @item EXCL(@var{m},@var{s})
10022 Removes the element @var{m} from the set @var{s}. Returns the new
10025 @item FLOAT(@var{i})
10026 Returns the floating point equivalent of the integer @var{i}.
10028 @item HIGH(@var{a})
10029 Returns the index of the last member of @var{a}.
10032 Increments the value in the variable @var{v} by one. Returns the new value.
10034 @item INC(@var{v},@var{i})
10035 Increments the value in the variable @var{v} by @var{i}. Returns the
10038 @item INCL(@var{m},@var{s})
10039 Adds the element @var{m} to the set @var{s} if it is not already
10040 there. Returns the new set.
10043 Returns the maximum value of the type @var{t}.
10046 Returns the minimum value of the type @var{t}.
10049 Returns boolean TRUE if @var{i} is an odd number.
10052 Returns the ordinal value of its argument. For example, the ordinal
10053 value of a character is its @sc{ascii} value (on machines supporting the
10054 @sc{ascii} character set). @var{x} must be of an ordered type, which include
10055 integral, character and enumerated types.
10057 @item SIZE(@var{x})
10058 Returns the size of its argument. @var{x} can be a variable or a type.
10060 @item TRUNC(@var{r})
10061 Returns the integral part of @var{r}.
10063 @item TSIZE(@var{x})
10064 Returns the size of its argument. @var{x} can be a variable or a type.
10066 @item VAL(@var{t},@var{i})
10067 Returns the member of the type @var{t} whose ordinal value is @var{i}.
10071 @emph{Warning:} Sets and their operations are not yet supported, so
10072 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
10076 @cindex Modula-2 constants
10078 @subsubsection Constants
10080 @value{GDBN} allows you to express the constants of Modula-2 in the following
10086 Integer constants are simply a sequence of digits. When used in an
10087 expression, a constant is interpreted to be type-compatible with the
10088 rest of the expression. Hexadecimal integers are specified by a
10089 trailing @samp{H}, and octal integers by a trailing @samp{B}.
10092 Floating point constants appear as a sequence of digits, followed by a
10093 decimal point and another sequence of digits. An optional exponent can
10094 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
10095 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
10096 digits of the floating point constant must be valid decimal (base 10)
10100 Character constants consist of a single character enclosed by a pair of
10101 like quotes, either single (@code{'}) or double (@code{"}). They may
10102 also be expressed by their ordinal value (their @sc{ascii} value, usually)
10103 followed by a @samp{C}.
10106 String constants consist of a sequence of characters enclosed by a
10107 pair of like quotes, either single (@code{'}) or double (@code{"}).
10108 Escape sequences in the style of C are also allowed. @xref{C
10109 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
10113 Enumerated constants consist of an enumerated identifier.
10116 Boolean constants consist of the identifiers @code{TRUE} and
10120 Pointer constants consist of integral values only.
10123 Set constants are not yet supported.
10127 @subsubsection Modula-2 Types
10128 @cindex Modula-2 types
10130 Currently @value{GDBN} can print the following data types in Modula-2
10131 syntax: array types, record types, set types, pointer types, procedure
10132 types, enumerated types, subrange types and base types. You can also
10133 print the contents of variables declared using these type.
10134 This section gives a number of simple source code examples together with
10135 sample @value{GDBN} sessions.
10137 The first example contains the following section of code:
10146 and you can request @value{GDBN} to interrogate the type and value of
10147 @code{r} and @code{s}.
10150 (@value{GDBP}) print s
10152 (@value{GDBP}) ptype s
10154 (@value{GDBP}) print r
10156 (@value{GDBP}) ptype r
10161 Likewise if your source code declares @code{s} as:
10165 s: SET ['A'..'Z'] ;
10169 then you may query the type of @code{s} by:
10172 (@value{GDBP}) ptype s
10173 type = SET ['A'..'Z']
10177 Note that at present you cannot interactively manipulate set
10178 expressions using the debugger.
10180 The following example shows how you might declare an array in Modula-2
10181 and how you can interact with @value{GDBN} to print its type and contents:
10185 s: ARRAY [-10..10] OF CHAR ;
10189 (@value{GDBP}) ptype s
10190 ARRAY [-10..10] OF CHAR
10193 Note that the array handling is not yet complete and although the type
10194 is printed correctly, expression handling still assumes that all
10195 arrays have a lower bound of zero and not @code{-10} as in the example
10198 Here are some more type related Modula-2 examples:
10202 colour = (blue, red, yellow, green) ;
10203 t = [blue..yellow] ;
10211 The @value{GDBN} interaction shows how you can query the data type
10212 and value of a variable.
10215 (@value{GDBP}) print s
10217 (@value{GDBP}) ptype t
10218 type = [blue..yellow]
10222 In this example a Modula-2 array is declared and its contents
10223 displayed. Observe that the contents are written in the same way as
10224 their @code{C} counterparts.
10228 s: ARRAY [1..5] OF CARDINAL ;
10234 (@value{GDBP}) print s
10235 $1 = @{1, 0, 0, 0, 0@}
10236 (@value{GDBP}) ptype s
10237 type = ARRAY [1..5] OF CARDINAL
10240 The Modula-2 language interface to @value{GDBN} also understands
10241 pointer types as shown in this example:
10245 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
10252 and you can request that @value{GDBN} describes the type of @code{s}.
10255 (@value{GDBP}) ptype s
10256 type = POINTER TO ARRAY [1..5] OF CARDINAL
10259 @value{GDBN} handles compound types as we can see in this example.
10260 Here we combine array types, record types, pointer types and subrange
10271 myarray = ARRAY myrange OF CARDINAL ;
10272 myrange = [-2..2] ;
10274 s: POINTER TO ARRAY myrange OF foo ;
10278 and you can ask @value{GDBN} to describe the type of @code{s} as shown
10282 (@value{GDBP}) ptype s
10283 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
10286 f3 : ARRAY [-2..2] OF CARDINAL;
10291 @subsubsection Modula-2 Defaults
10292 @cindex Modula-2 defaults
10294 If type and range checking are set automatically by @value{GDBN}, they
10295 both default to @code{on} whenever the working language changes to
10296 Modula-2. This happens regardless of whether you or @value{GDBN}
10297 selected the working language.
10299 If you allow @value{GDBN} to set the language automatically, then entering
10300 code compiled from a file whose name ends with @file{.mod} sets the
10301 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
10302 Infer the Source Language}, for further details.
10305 @subsubsection Deviations from Standard Modula-2
10306 @cindex Modula-2, deviations from
10308 A few changes have been made to make Modula-2 programs easier to debug.
10309 This is done primarily via loosening its type strictness:
10313 Unlike in standard Modula-2, pointer constants can be formed by
10314 integers. This allows you to modify pointer variables during
10315 debugging. (In standard Modula-2, the actual address contained in a
10316 pointer variable is hidden from you; it can only be modified
10317 through direct assignment to another pointer variable or expression that
10318 returned a pointer.)
10321 C escape sequences can be used in strings and characters to represent
10322 non-printable characters. @value{GDBN} prints out strings with these
10323 escape sequences embedded. Single non-printable characters are
10324 printed using the @samp{CHR(@var{nnn})} format.
10327 The assignment operator (@code{:=}) returns the value of its right-hand
10331 All built-in procedures both modify @emph{and} return their argument.
10335 @subsubsection Modula-2 Type and Range Checks
10336 @cindex Modula-2 checks
10339 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
10342 @c FIXME remove warning when type/range checks added
10344 @value{GDBN} considers two Modula-2 variables type equivalent if:
10348 They are of types that have been declared equivalent via a @code{TYPE
10349 @var{t1} = @var{t2}} statement
10352 They have been declared on the same line. (Note: This is true of the
10353 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
10356 As long as type checking is enabled, any attempt to combine variables
10357 whose types are not equivalent is an error.
10359 Range checking is done on all mathematical operations, assignment, array
10360 index bounds, and all built-in functions and procedures.
10363 @subsubsection The Scope Operators @code{::} and @code{.}
10365 @cindex @code{.}, Modula-2 scope operator
10366 @cindex colon, doubled as scope operator
10368 @vindex colon-colon@r{, in Modula-2}
10369 @c Info cannot handle :: but TeX can.
10372 @vindex ::@r{, in Modula-2}
10375 There are a few subtle differences between the Modula-2 scope operator
10376 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
10381 @var{module} . @var{id}
10382 @var{scope} :: @var{id}
10386 where @var{scope} is the name of a module or a procedure,
10387 @var{module} the name of a module, and @var{id} is any declared
10388 identifier within your program, except another module.
10390 Using the @code{::} operator makes @value{GDBN} search the scope
10391 specified by @var{scope} for the identifier @var{id}. If it is not
10392 found in the specified scope, then @value{GDBN} searches all scopes
10393 enclosing the one specified by @var{scope}.
10395 Using the @code{.} operator makes @value{GDBN} search the current scope for
10396 the identifier specified by @var{id} that was imported from the
10397 definition module specified by @var{module}. With this operator, it is
10398 an error if the identifier @var{id} was not imported from definition
10399 module @var{module}, or if @var{id} is not an identifier in
10403 @subsubsection @value{GDBN} and Modula-2
10405 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
10406 Five subcommands of @code{set print} and @code{show print} apply
10407 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
10408 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
10409 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
10410 analogue in Modula-2.
10412 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
10413 with any language, is not useful with Modula-2. Its
10414 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
10415 created in Modula-2 as they can in C or C@t{++}. However, because an
10416 address can be specified by an integral constant, the construct
10417 @samp{@{@var{type}@}@var{adrexp}} is still useful.
10419 @cindex @code{#} in Modula-2
10420 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
10421 interpreted as the beginning of a comment. Use @code{<>} instead.
10427 The extensions made to @value{GDBN} for Ada only support
10428 output from the @sc{gnu} Ada (GNAT) compiler.
10429 Other Ada compilers are not currently supported, and
10430 attempting to debug executables produced by them is most likely
10434 @cindex expressions in Ada
10436 * Ada Mode Intro:: General remarks on the Ada syntax
10437 and semantics supported by Ada mode
10439 * Omissions from Ada:: Restrictions on the Ada expression syntax.
10440 * Additions to Ada:: Extensions of the Ada expression syntax.
10441 * Stopping Before Main Program:: Debugging the program during elaboration.
10442 * Ada Glitches:: Known peculiarities of Ada mode.
10445 @node Ada Mode Intro
10446 @subsubsection Introduction
10447 @cindex Ada mode, general
10449 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
10450 syntax, with some extensions.
10451 The philosophy behind the design of this subset is
10455 That @value{GDBN} should provide basic literals and access to operations for
10456 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
10457 leaving more sophisticated computations to subprograms written into the
10458 program (which therefore may be called from @value{GDBN}).
10461 That type safety and strict adherence to Ada language restrictions
10462 are not particularly important to the @value{GDBN} user.
10465 That brevity is important to the @value{GDBN} user.
10468 Thus, for brevity, the debugger acts as if there were
10469 implicit @code{with} and @code{use} clauses in effect for all user-written
10470 packages, making it unnecessary to fully qualify most names with
10471 their packages, regardless of context. Where this causes ambiguity,
10472 @value{GDBN} asks the user's intent.
10474 The debugger will start in Ada mode if it detects an Ada main program.
10475 As for other languages, it will enter Ada mode when stopped in a program that
10476 was translated from an Ada source file.
10478 While in Ada mode, you may use `@t{--}' for comments. This is useful
10479 mostly for documenting command files. The standard @value{GDBN} comment
10480 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
10481 middle (to allow based literals).
10483 The debugger supports limited overloading. Given a subprogram call in which
10484 the function symbol has multiple definitions, it will use the number of
10485 actual parameters and some information about their types to attempt to narrow
10486 the set of definitions. It also makes very limited use of context, preferring
10487 procedures to functions in the context of the @code{call} command, and
10488 functions to procedures elsewhere.
10490 @node Omissions from Ada
10491 @subsubsection Omissions from Ada
10492 @cindex Ada, omissions from
10494 Here are the notable omissions from the subset:
10498 Only a subset of the attributes are supported:
10502 @t{'First}, @t{'Last}, and @t{'Length}
10503 on array objects (not on types and subtypes).
10506 @t{'Min} and @t{'Max}.
10509 @t{'Pos} and @t{'Val}.
10515 @t{'Range} on array objects (not subtypes), but only as the right
10516 operand of the membership (@code{in}) operator.
10519 @t{'Access}, @t{'Unchecked_Access}, and
10520 @t{'Unrestricted_Access} (a GNAT extension).
10528 @code{Characters.Latin_1} are not available and
10529 concatenation is not implemented. Thus, escape characters in strings are
10530 not currently available.
10533 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
10534 equality of representations. They will generally work correctly
10535 for strings and arrays whose elements have integer or enumeration types.
10536 They may not work correctly for arrays whose element
10537 types have user-defined equality, for arrays of real values
10538 (in particular, IEEE-conformant floating point, because of negative
10539 zeroes and NaNs), and for arrays whose elements contain unused bits with
10540 indeterminate values.
10543 The other component-by-component array operations (@code{and}, @code{or},
10544 @code{xor}, @code{not}, and relational tests other than equality)
10545 are not implemented.
10548 @cindex array aggregates (Ada)
10549 @cindex record aggregates (Ada)
10550 @cindex aggregates (Ada)
10551 There is limited support for array and record aggregates. They are
10552 permitted only on the right sides of assignments, as in these examples:
10555 set An_Array := (1, 2, 3, 4, 5, 6)
10556 set An_Array := (1, others => 0)
10557 set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
10558 set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
10559 set A_Record := (1, "Peter", True);
10560 set A_Record := (Name => "Peter", Id => 1, Alive => True)
10564 discriminant's value by assigning an aggregate has an
10565 undefined effect if that discriminant is used within the record.
10566 However, you can first modify discriminants by directly assigning to
10567 them (which normally would not be allowed in Ada), and then performing an
10568 aggregate assignment. For example, given a variable @code{A_Rec}
10569 declared to have a type such as:
10572 type Rec (Len : Small_Integer := 0) is record
10574 Vals : IntArray (1 .. Len);
10578 you can assign a value with a different size of @code{Vals} with two
10583 set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
10586 As this example also illustrates, @value{GDBN} is very loose about the usual
10587 rules concerning aggregates. You may leave out some of the
10588 components of an array or record aggregate (such as the @code{Len}
10589 component in the assignment to @code{A_Rec} above); they will retain their
10590 original values upon assignment. You may freely use dynamic values as
10591 indices in component associations. You may even use overlapping or
10592 redundant component associations, although which component values are
10593 assigned in such cases is not defined.
10596 Calls to dispatching subprograms are not implemented.
10599 The overloading algorithm is much more limited (i.e., less selective)
10600 than that of real Ada. It makes only limited use of the context in
10601 which a subexpression appears to resolve its meaning, and it is much
10602 looser in its rules for allowing type matches. As a result, some
10603 function calls will be ambiguous, and the user will be asked to choose
10604 the proper resolution.
10607 The @code{new} operator is not implemented.
10610 Entry calls are not implemented.
10613 Aside from printing, arithmetic operations on the native VAX floating-point
10614 formats are not supported.
10617 It is not possible to slice a packed array.
10620 @node Additions to Ada
10621 @subsubsection Additions to Ada
10622 @cindex Ada, deviations from
10624 As it does for other languages, @value{GDBN} makes certain generic
10625 extensions to Ada (@pxref{Expressions}):
10629 If the expression @var{E} is a variable residing in memory (typically
10630 a local variable or array element) and @var{N} is a positive integer,
10631 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
10632 @var{N}-1 adjacent variables following it in memory as an array. In
10633 Ada, this operator is generally not necessary, since its prime use is
10634 in displaying parts of an array, and slicing will usually do this in
10635 Ada. However, there are occasional uses when debugging programs in
10636 which certain debugging information has been optimized away.
10639 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
10640 appears in function or file @var{B}.'' When @var{B} is a file name,
10641 you must typically surround it in single quotes.
10644 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
10645 @var{type} that appears at address @var{addr}.''
10648 A name starting with @samp{$} is a convenience variable
10649 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
10652 In addition, @value{GDBN} provides a few other shortcuts and outright
10653 additions specific to Ada:
10657 The assignment statement is allowed as an expression, returning
10658 its right-hand operand as its value. Thus, you may enter
10662 print A(tmp := y + 1)
10666 The semicolon is allowed as an ``operator,'' returning as its value
10667 the value of its right-hand operand.
10668 This allows, for example,
10669 complex conditional breaks:
10673 condition 1 (report(i); k += 1; A(k) > 100)
10677 Rather than use catenation and symbolic character names to introduce special
10678 characters into strings, one may instead use a special bracket notation,
10679 which is also used to print strings. A sequence of characters of the form
10680 @samp{["@var{XX}"]} within a string or character literal denotes the
10681 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
10682 sequence of characters @samp{["""]} also denotes a single quotation mark
10683 in strings. For example,
10685 "One line.["0a"]Next line.["0a"]"
10688 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
10692 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
10693 @t{'Max} is optional (and is ignored in any case). For example, it is valid
10701 When printing arrays, @value{GDBN} uses positional notation when the
10702 array has a lower bound of 1, and uses a modified named notation otherwise.
10703 For example, a one-dimensional array of three integers with a lower bound
10704 of 3 might print as
10711 That is, in contrast to valid Ada, only the first component has a @code{=>}
10715 You may abbreviate attributes in expressions with any unique,
10716 multi-character subsequence of
10717 their names (an exact match gets preference).
10718 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
10719 in place of @t{a'length}.
10722 @cindex quoting Ada internal identifiers
10723 Since Ada is case-insensitive, the debugger normally maps identifiers you type
10724 to lower case. The GNAT compiler uses upper-case characters for
10725 some of its internal identifiers, which are normally of no interest to users.
10726 For the rare occasions when you actually have to look at them,
10727 enclose them in angle brackets to avoid the lower-case mapping.
10730 @value{GDBP} print <JMPBUF_SAVE>[0]
10734 Printing an object of class-wide type or dereferencing an
10735 access-to-class-wide value will display all the components of the object's
10736 specific type (as indicated by its run-time tag). Likewise, component
10737 selection on such a value will operate on the specific type of the
10742 @node Stopping Before Main Program
10743 @subsubsection Stopping at the Very Beginning
10745 @cindex breakpointing Ada elaboration code
10746 It is sometimes necessary to debug the program during elaboration, and
10747 before reaching the main procedure.
10748 As defined in the Ada Reference
10749 Manual, the elaboration code is invoked from a procedure called
10750 @code{adainit}. To run your program up to the beginning of
10751 elaboration, simply use the following two commands:
10752 @code{tbreak adainit} and @code{run}.
10755 @subsubsection Known Peculiarities of Ada Mode
10756 @cindex Ada, problems
10758 Besides the omissions listed previously (@pxref{Omissions from Ada}),
10759 we know of several problems with and limitations of Ada mode in
10761 some of which will be fixed with planned future releases of the debugger
10762 and the GNU Ada compiler.
10766 Currently, the debugger
10767 has insufficient information to determine whether certain pointers represent
10768 pointers to objects or the objects themselves.
10769 Thus, the user may have to tack an extra @code{.all} after an expression
10770 to get it printed properly.
10773 Static constants that the compiler chooses not to materialize as objects in
10774 storage are invisible to the debugger.
10777 Named parameter associations in function argument lists are ignored (the
10778 argument lists are treated as positional).
10781 Many useful library packages are currently invisible to the debugger.
10784 Fixed-point arithmetic, conversions, input, and output is carried out using
10785 floating-point arithmetic, and may give results that only approximate those on
10789 The type of the @t{'Address} attribute may not be @code{System.Address}.
10792 The GNAT compiler never generates the prefix @code{Standard} for any of
10793 the standard symbols defined by the Ada language. @value{GDBN} knows about
10794 this: it will strip the prefix from names when you use it, and will never
10795 look for a name you have so qualified among local symbols, nor match against
10796 symbols in other packages or subprograms. If you have
10797 defined entities anywhere in your program other than parameters and
10798 local variables whose simple names match names in @code{Standard},
10799 GNAT's lack of qualification here can cause confusion. When this happens,
10800 you can usually resolve the confusion
10801 by qualifying the problematic names with package
10802 @code{Standard} explicitly.
10805 @node Unsupported Languages
10806 @section Unsupported Languages
10808 @cindex unsupported languages
10809 @cindex minimal language
10810 In addition to the other fully-supported programming languages,
10811 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
10812 It does not represent a real programming language, but provides a set
10813 of capabilities close to what the C or assembly languages provide.
10814 This should allow most simple operations to be performed while debugging
10815 an application that uses a language currently not supported by @value{GDBN}.
10817 If the language is set to @code{auto}, @value{GDBN} will automatically
10818 select this language if the current frame corresponds to an unsupported
10822 @chapter Examining the Symbol Table
10824 The commands described in this chapter allow you to inquire about the
10825 symbols (names of variables, functions and types) defined in your
10826 program. This information is inherent in the text of your program and
10827 does not change as your program executes. @value{GDBN} finds it in your
10828 program's symbol table, in the file indicated when you started @value{GDBN}
10829 (@pxref{File Options, ,Choosing Files}), or by one of the
10830 file-management commands (@pxref{Files, ,Commands to Specify Files}).
10832 @cindex symbol names
10833 @cindex names of symbols
10834 @cindex quoting names
10835 Occasionally, you may need to refer to symbols that contain unusual
10836 characters, which @value{GDBN} ordinarily treats as word delimiters. The
10837 most frequent case is in referring to static variables in other
10838 source files (@pxref{Variables,,Program Variables}). File names
10839 are recorded in object files as debugging symbols, but @value{GDBN} would
10840 ordinarily parse a typical file name, like @file{foo.c}, as the three words
10841 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
10842 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
10849 looks up the value of @code{x} in the scope of the file @file{foo.c}.
10852 @cindex case-insensitive symbol names
10853 @cindex case sensitivity in symbol names
10854 @kindex set case-sensitive
10855 @item set case-sensitive on
10856 @itemx set case-sensitive off
10857 @itemx set case-sensitive auto
10858 Normally, when @value{GDBN} looks up symbols, it matches their names
10859 with case sensitivity determined by the current source language.
10860 Occasionally, you may wish to control that. The command @code{set
10861 case-sensitive} lets you do that by specifying @code{on} for
10862 case-sensitive matches or @code{off} for case-insensitive ones. If
10863 you specify @code{auto}, case sensitivity is reset to the default
10864 suitable for the source language. The default is case-sensitive
10865 matches for all languages except for Fortran, for which the default is
10866 case-insensitive matches.
10868 @kindex show case-sensitive
10869 @item show case-sensitive
10870 This command shows the current setting of case sensitivity for symbols
10873 @kindex info address
10874 @cindex address of a symbol
10875 @item info address @var{symbol}
10876 Describe where the data for @var{symbol} is stored. For a register
10877 variable, this says which register it is kept in. For a non-register
10878 local variable, this prints the stack-frame offset at which the variable
10881 Note the contrast with @samp{print &@var{symbol}}, which does not work
10882 at all for a register variable, and for a stack local variable prints
10883 the exact address of the current instantiation of the variable.
10885 @kindex info symbol
10886 @cindex symbol from address
10887 @cindex closest symbol and offset for an address
10888 @item info symbol @var{addr}
10889 Print the name of a symbol which is stored at the address @var{addr}.
10890 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
10891 nearest symbol and an offset from it:
10894 (@value{GDBP}) info symbol 0x54320
10895 _initialize_vx + 396 in section .text
10899 This is the opposite of the @code{info address} command. You can use
10900 it to find out the name of a variable or a function given its address.
10903 @item whatis [@var{arg}]
10904 Print the data type of @var{arg}, which can be either an expression or
10905 a data type. With no argument, print the data type of @code{$}, the
10906 last value in the value history. If @var{arg} is an expression, it is
10907 not actually evaluated, and any side-effecting operations (such as
10908 assignments or function calls) inside it do not take place. If
10909 @var{arg} is a type name, it may be the name of a type or typedef, or
10910 for C code it may have the form @samp{class @var{class-name}},
10911 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
10912 @samp{enum @var{enum-tag}}.
10913 @xref{Expressions, ,Expressions}.
10916 @item ptype [@var{arg}]
10917 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
10918 detailed description of the type, instead of just the name of the type.
10919 @xref{Expressions, ,Expressions}.
10921 For example, for this variable declaration:
10924 struct complex @{double real; double imag;@} v;
10928 the two commands give this output:
10932 (@value{GDBP}) whatis v
10933 type = struct complex
10934 (@value{GDBP}) ptype v
10935 type = struct complex @{
10943 As with @code{whatis}, using @code{ptype} without an argument refers to
10944 the type of @code{$}, the last value in the value history.
10946 @cindex incomplete type
10947 Sometimes, programs use opaque data types or incomplete specifications
10948 of complex data structure. If the debug information included in the
10949 program does not allow @value{GDBN} to display a full declaration of
10950 the data type, it will say @samp{<incomplete type>}. For example,
10951 given these declarations:
10955 struct foo *fooptr;
10959 but no definition for @code{struct foo} itself, @value{GDBN} will say:
10962 (@value{GDBP}) ptype foo
10963 $1 = <incomplete type>
10967 ``Incomplete type'' is C terminology for data types that are not
10968 completely specified.
10971 @item info types @var{regexp}
10973 Print a brief description of all types whose names match the regular
10974 expression @var{regexp} (or all types in your program, if you supply
10975 no argument). Each complete typename is matched as though it were a
10976 complete line; thus, @samp{i type value} gives information on all
10977 types in your program whose names include the string @code{value}, but
10978 @samp{i type ^value$} gives information only on types whose complete
10979 name is @code{value}.
10981 This command differs from @code{ptype} in two ways: first, like
10982 @code{whatis}, it does not print a detailed description; second, it
10983 lists all source files where a type is defined.
10986 @cindex local variables
10987 @item info scope @var{location}
10988 List all the variables local to a particular scope. This command
10989 accepts a @var{location} argument---a function name, a source line, or
10990 an address preceded by a @samp{*}, and prints all the variables local
10991 to the scope defined by that location. For example:
10994 (@value{GDBP}) @b{info scope command_line_handler}
10995 Scope for command_line_handler:
10996 Symbol rl is an argument at stack/frame offset 8, length 4.
10997 Symbol linebuffer is in static storage at address 0x150a18, length 4.
10998 Symbol linelength is in static storage at address 0x150a1c, length 4.
10999 Symbol p is a local variable in register $esi, length 4.
11000 Symbol p1 is a local variable in register $ebx, length 4.
11001 Symbol nline is a local variable in register $edx, length 4.
11002 Symbol repeat is a local variable at frame offset -8, length 4.
11006 This command is especially useful for determining what data to collect
11007 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
11010 @kindex info source
11012 Show information about the current source file---that is, the source file for
11013 the function containing the current point of execution:
11016 the name of the source file, and the directory containing it,
11018 the directory it was compiled in,
11020 its length, in lines,
11022 which programming language it is written in,
11024 whether the executable includes debugging information for that file, and
11025 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
11027 whether the debugging information includes information about
11028 preprocessor macros.
11032 @kindex info sources
11034 Print the names of all source files in your program for which there is
11035 debugging information, organized into two lists: files whose symbols
11036 have already been read, and files whose symbols will be read when needed.
11038 @kindex info functions
11039 @item info functions
11040 Print the names and data types of all defined functions.
11042 @item info functions @var{regexp}
11043 Print the names and data types of all defined functions
11044 whose names contain a match for regular expression @var{regexp}.
11045 Thus, @samp{info fun step} finds all functions whose names
11046 include @code{step}; @samp{info fun ^step} finds those whose names
11047 start with @code{step}. If a function name contains characters
11048 that conflict with the regular expression language (e.g.@:
11049 @samp{operator*()}), they may be quoted with a backslash.
11051 @kindex info variables
11052 @item info variables
11053 Print the names and data types of all variables that are declared
11054 outside of functions (i.e.@: excluding local variables).
11056 @item info variables @var{regexp}
11057 Print the names and data types of all variables (except for local
11058 variables) whose names contain a match for regular expression
11061 @kindex info classes
11062 @cindex Objective-C, classes and selectors
11064 @itemx info classes @var{regexp}
11065 Display all Objective-C classes in your program, or
11066 (with the @var{regexp} argument) all those matching a particular regular
11069 @kindex info selectors
11070 @item info selectors
11071 @itemx info selectors @var{regexp}
11072 Display all Objective-C selectors in your program, or
11073 (with the @var{regexp} argument) all those matching a particular regular
11077 This was never implemented.
11078 @kindex info methods
11080 @itemx info methods @var{regexp}
11081 The @code{info methods} command permits the user to examine all defined
11082 methods within C@t{++} program, or (with the @var{regexp} argument) a
11083 specific set of methods found in the various C@t{++} classes. Many
11084 C@t{++} classes provide a large number of methods. Thus, the output
11085 from the @code{ptype} command can be overwhelming and hard to use. The
11086 @code{info-methods} command filters the methods, printing only those
11087 which match the regular-expression @var{regexp}.
11090 @cindex reloading symbols
11091 Some systems allow individual object files that make up your program to
11092 be replaced without stopping and restarting your program. For example,
11093 in VxWorks you can simply recompile a defective object file and keep on
11094 running. If you are running on one of these systems, you can allow
11095 @value{GDBN} to reload the symbols for automatically relinked modules:
11098 @kindex set symbol-reloading
11099 @item set symbol-reloading on
11100 Replace symbol definitions for the corresponding source file when an
11101 object file with a particular name is seen again.
11103 @item set symbol-reloading off
11104 Do not replace symbol definitions when encountering object files of the
11105 same name more than once. This is the default state; if you are not
11106 running on a system that permits automatic relinking of modules, you
11107 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
11108 may discard symbols when linking large programs, that may contain
11109 several modules (from different directories or libraries) with the same
11112 @kindex show symbol-reloading
11113 @item show symbol-reloading
11114 Show the current @code{on} or @code{off} setting.
11117 @cindex opaque data types
11118 @kindex set opaque-type-resolution
11119 @item set opaque-type-resolution on
11120 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
11121 declared as a pointer to a @code{struct}, @code{class}, or
11122 @code{union}---for example, @code{struct MyType *}---that is used in one
11123 source file although the full declaration of @code{struct MyType} is in
11124 another source file. The default is on.
11126 A change in the setting of this subcommand will not take effect until
11127 the next time symbols for a file are loaded.
11129 @item set opaque-type-resolution off
11130 Tell @value{GDBN} not to resolve opaque types. In this case, the type
11131 is printed as follows:
11133 @{<no data fields>@}
11136 @kindex show opaque-type-resolution
11137 @item show opaque-type-resolution
11138 Show whether opaque types are resolved or not.
11140 @kindex maint print symbols
11141 @cindex symbol dump
11142 @kindex maint print psymbols
11143 @cindex partial symbol dump
11144 @item maint print symbols @var{filename}
11145 @itemx maint print psymbols @var{filename}
11146 @itemx maint print msymbols @var{filename}
11147 Write a dump of debugging symbol data into the file @var{filename}.
11148 These commands are used to debug the @value{GDBN} symbol-reading code. Only
11149 symbols with debugging data are included. If you use @samp{maint print
11150 symbols}, @value{GDBN} includes all the symbols for which it has already
11151 collected full details: that is, @var{filename} reflects symbols for
11152 only those files whose symbols @value{GDBN} has read. You can use the
11153 command @code{info sources} to find out which files these are. If you
11154 use @samp{maint print psymbols} instead, the dump shows information about
11155 symbols that @value{GDBN} only knows partially---that is, symbols defined in
11156 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
11157 @samp{maint print msymbols} dumps just the minimal symbol information
11158 required for each object file from which @value{GDBN} has read some symbols.
11159 @xref{Files, ,Commands to Specify Files}, for a discussion of how
11160 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
11162 @kindex maint info symtabs
11163 @kindex maint info psymtabs
11164 @cindex listing @value{GDBN}'s internal symbol tables
11165 @cindex symbol tables, listing @value{GDBN}'s internal
11166 @cindex full symbol tables, listing @value{GDBN}'s internal
11167 @cindex partial symbol tables, listing @value{GDBN}'s internal
11168 @item maint info symtabs @r{[} @var{regexp} @r{]}
11169 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
11171 List the @code{struct symtab} or @code{struct partial_symtab}
11172 structures whose names match @var{regexp}. If @var{regexp} is not
11173 given, list them all. The output includes expressions which you can
11174 copy into a @value{GDBN} debugging this one to examine a particular
11175 structure in more detail. For example:
11178 (@value{GDBP}) maint info psymtabs dwarf2read
11179 @{ objfile /home/gnu/build/gdb/gdb
11180 ((struct objfile *) 0x82e69d0)
11181 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
11182 ((struct partial_symtab *) 0x8474b10)
11185 text addresses 0x814d3c8 -- 0x8158074
11186 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
11187 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
11188 dependencies (none)
11191 (@value{GDBP}) maint info symtabs
11195 We see that there is one partial symbol table whose filename contains
11196 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
11197 and we see that @value{GDBN} has not read in any symtabs yet at all.
11198 If we set a breakpoint on a function, that will cause @value{GDBN} to
11199 read the symtab for the compilation unit containing that function:
11202 (@value{GDBP}) break dwarf2_psymtab_to_symtab
11203 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
11205 (@value{GDBP}) maint info symtabs
11206 @{ objfile /home/gnu/build/gdb/gdb
11207 ((struct objfile *) 0x82e69d0)
11208 @{ symtab /home/gnu/src/gdb/dwarf2read.c
11209 ((struct symtab *) 0x86c1f38)
11212 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
11213 linetable ((struct linetable *) 0x8370fa0)
11214 debugformat DWARF 2
11223 @chapter Altering Execution
11225 Once you think you have found an error in your program, you might want to
11226 find out for certain whether correcting the apparent error would lead to
11227 correct results in the rest of the run. You can find the answer by
11228 experiment, using the @value{GDBN} features for altering execution of the
11231 For example, you can store new values into variables or memory
11232 locations, give your program a signal, restart it at a different
11233 address, or even return prematurely from a function.
11236 * Assignment:: Assignment to variables
11237 * Jumping:: Continuing at a different address
11238 * Signaling:: Giving your program a signal
11239 * Returning:: Returning from a function
11240 * Calling:: Calling your program's functions
11241 * Patching:: Patching your program
11245 @section Assignment to Variables
11248 @cindex setting variables
11249 To alter the value of a variable, evaluate an assignment expression.
11250 @xref{Expressions, ,Expressions}. For example,
11257 stores the value 4 into the variable @code{x}, and then prints the
11258 value of the assignment expression (which is 4).
11259 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
11260 information on operators in supported languages.
11262 @kindex set variable
11263 @cindex variables, setting
11264 If you are not interested in seeing the value of the assignment, use the
11265 @code{set} command instead of the @code{print} command. @code{set} is
11266 really the same as @code{print} except that the expression's value is
11267 not printed and is not put in the value history (@pxref{Value History,
11268 ,Value History}). The expression is evaluated only for its effects.
11270 If the beginning of the argument string of the @code{set} command
11271 appears identical to a @code{set} subcommand, use the @code{set
11272 variable} command instead of just @code{set}. This command is identical
11273 to @code{set} except for its lack of subcommands. For example, if your
11274 program has a variable @code{width}, you get an error if you try to set
11275 a new value with just @samp{set width=13}, because @value{GDBN} has the
11276 command @code{set width}:
11279 (@value{GDBP}) whatis width
11281 (@value{GDBP}) p width
11283 (@value{GDBP}) set width=47
11284 Invalid syntax in expression.
11288 The invalid expression, of course, is @samp{=47}. In
11289 order to actually set the program's variable @code{width}, use
11292 (@value{GDBP}) set var width=47
11295 Because the @code{set} command has many subcommands that can conflict
11296 with the names of program variables, it is a good idea to use the
11297 @code{set variable} command instead of just @code{set}. For example, if
11298 your program has a variable @code{g}, you run into problems if you try
11299 to set a new value with just @samp{set g=4}, because @value{GDBN} has
11300 the command @code{set gnutarget}, abbreviated @code{set g}:
11304 (@value{GDBP}) whatis g
11308 (@value{GDBP}) set g=4
11312 The program being debugged has been started already.
11313 Start it from the beginning? (y or n) y
11314 Starting program: /home/smith/cc_progs/a.out
11315 "/home/smith/cc_progs/a.out": can't open to read symbols:
11316 Invalid bfd target.
11317 (@value{GDBP}) show g
11318 The current BFD target is "=4".
11323 The program variable @code{g} did not change, and you silently set the
11324 @code{gnutarget} to an invalid value. In order to set the variable
11328 (@value{GDBP}) set var g=4
11331 @value{GDBN} allows more implicit conversions in assignments than C; you can
11332 freely store an integer value into a pointer variable or vice versa,
11333 and you can convert any structure to any other structure that is the
11334 same length or shorter.
11335 @comment FIXME: how do structs align/pad in these conversions?
11336 @comment /doc@cygnus.com 18dec1990
11338 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
11339 construct to generate a value of specified type at a specified address
11340 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
11341 to memory location @code{0x83040} as an integer (which implies a certain size
11342 and representation in memory), and
11345 set @{int@}0x83040 = 4
11349 stores the value 4 into that memory location.
11352 @section Continuing at a Different Address
11354 Ordinarily, when you continue your program, you do so at the place where
11355 it stopped, with the @code{continue} command. You can instead continue at
11356 an address of your own choosing, with the following commands:
11360 @item jump @var{linespec}
11361 Resume execution at line @var{linespec}. Execution stops again
11362 immediately if there is a breakpoint there. @xref{List, ,Printing
11363 Source Lines}, for a description of the different forms of
11364 @var{linespec}. It is common practice to use the @code{tbreak} command
11365 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
11368 The @code{jump} command does not change the current stack frame, or
11369 the stack pointer, or the contents of any memory location or any
11370 register other than the program counter. If line @var{linespec} is in
11371 a different function from the one currently executing, the results may
11372 be bizarre if the two functions expect different patterns of arguments or
11373 of local variables. For this reason, the @code{jump} command requests
11374 confirmation if the specified line is not in the function currently
11375 executing. However, even bizarre results are predictable if you are
11376 well acquainted with the machine-language code of your program.
11378 @item jump *@var{address}
11379 Resume execution at the instruction at address @var{address}.
11382 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
11383 On many systems, you can get much the same effect as the @code{jump}
11384 command by storing a new value into the register @code{$pc}. The
11385 difference is that this does not start your program running; it only
11386 changes the address of where it @emph{will} run when you continue. For
11394 makes the next @code{continue} command or stepping command execute at
11395 address @code{0x485}, rather than at the address where your program stopped.
11396 @xref{Continuing and Stepping, ,Continuing and Stepping}.
11398 The most common occasion to use the @code{jump} command is to back
11399 up---perhaps with more breakpoints set---over a portion of a program
11400 that has already executed, in order to examine its execution in more
11405 @section Giving your Program a Signal
11406 @cindex deliver a signal to a program
11410 @item signal @var{signal}
11411 Resume execution where your program stopped, but immediately give it the
11412 signal @var{signal}. @var{signal} can be the name or the number of a
11413 signal. For example, on many systems @code{signal 2} and @code{signal
11414 SIGINT} are both ways of sending an interrupt signal.
11416 Alternatively, if @var{signal} is zero, continue execution without
11417 giving a signal. This is useful when your program stopped on account of
11418 a signal and would ordinary see the signal when resumed with the
11419 @code{continue} command; @samp{signal 0} causes it to resume without a
11422 @code{signal} does not repeat when you press @key{RET} a second time
11423 after executing the command.
11427 Invoking the @code{signal} command is not the same as invoking the
11428 @code{kill} utility from the shell. Sending a signal with @code{kill}
11429 causes @value{GDBN} to decide what to do with the signal depending on
11430 the signal handling tables (@pxref{Signals}). The @code{signal} command
11431 passes the signal directly to your program.
11435 @section Returning from a Function
11438 @cindex returning from a function
11441 @itemx return @var{expression}
11442 You can cancel execution of a function call with the @code{return}
11443 command. If you give an
11444 @var{expression} argument, its value is used as the function's return
11448 When you use @code{return}, @value{GDBN} discards the selected stack frame
11449 (and all frames within it). You can think of this as making the
11450 discarded frame return prematurely. If you wish to specify a value to
11451 be returned, give that value as the argument to @code{return}.
11453 This pops the selected stack frame (@pxref{Selection, ,Selecting a
11454 Frame}), and any other frames inside of it, leaving its caller as the
11455 innermost remaining frame. That frame becomes selected. The
11456 specified value is stored in the registers used for returning values
11459 The @code{return} command does not resume execution; it leaves the
11460 program stopped in the state that would exist if the function had just
11461 returned. In contrast, the @code{finish} command (@pxref{Continuing
11462 and Stepping, ,Continuing and Stepping}) resumes execution until the
11463 selected stack frame returns naturally.
11466 @section Calling Program Functions
11469 @cindex calling functions
11470 @cindex inferior functions, calling
11471 @item print @var{expr}
11472 Evaluate the expression @var{expr} and display the resulting value.
11473 @var{expr} may include calls to functions in the program being
11477 @item call @var{expr}
11478 Evaluate the expression @var{expr} without displaying @code{void}
11481 You can use this variant of the @code{print} command if you want to
11482 execute a function from your program that does not return anything
11483 (a.k.a.@: @dfn{a void function}), but without cluttering the output
11484 with @code{void} returned values that @value{GDBN} will otherwise
11485 print. If the result is not void, it is printed and saved in the
11489 It is possible for the function you call via the @code{print} or
11490 @code{call} command to generate a signal (e.g., if there's a bug in
11491 the function, or if you passed it incorrect arguments). What happens
11492 in that case is controlled by the @code{set unwindonsignal} command.
11495 @item set unwindonsignal
11496 @kindex set unwindonsignal
11497 @cindex unwind stack in called functions
11498 @cindex call dummy stack unwinding
11499 Set unwinding of the stack if a signal is received while in a function
11500 that @value{GDBN} called in the program being debugged. If set to on,
11501 @value{GDBN} unwinds the stack it created for the call and restores
11502 the context to what it was before the call. If set to off (the
11503 default), @value{GDBN} stops in the frame where the signal was
11506 @item show unwindonsignal
11507 @kindex show unwindonsignal
11508 Show the current setting of stack unwinding in the functions called by
11512 @cindex weak alias functions
11513 Sometimes, a function you wish to call is actually a @dfn{weak alias}
11514 for another function. In such case, @value{GDBN} might not pick up
11515 the type information, including the types of the function arguments,
11516 which causes @value{GDBN} to call the inferior function incorrectly.
11517 As a result, the called function will function erroneously and may
11518 even crash. A solution to that is to use the name of the aliased
11522 @section Patching Programs
11524 @cindex patching binaries
11525 @cindex writing into executables
11526 @cindex writing into corefiles
11528 By default, @value{GDBN} opens the file containing your program's
11529 executable code (or the corefile) read-only. This prevents accidental
11530 alterations to machine code; but it also prevents you from intentionally
11531 patching your program's binary.
11533 If you'd like to be able to patch the binary, you can specify that
11534 explicitly with the @code{set write} command. For example, you might
11535 want to turn on internal debugging flags, or even to make emergency
11541 @itemx set write off
11542 If you specify @samp{set write on}, @value{GDBN} opens executable and
11543 core files for both reading and writing; if you specify @samp{set write
11544 off} (the default), @value{GDBN} opens them read-only.
11546 If you have already loaded a file, you must load it again (using the
11547 @code{exec-file} or @code{core-file} command) after changing @code{set
11548 write}, for your new setting to take effect.
11552 Display whether executable files and core files are opened for writing
11553 as well as reading.
11557 @chapter @value{GDBN} Files
11559 @value{GDBN} needs to know the file name of the program to be debugged,
11560 both in order to read its symbol table and in order to start your
11561 program. To debug a core dump of a previous run, you must also tell
11562 @value{GDBN} the name of the core dump file.
11565 * Files:: Commands to specify files
11566 * Separate Debug Files:: Debugging information in separate files
11567 * Symbol Errors:: Errors reading symbol files
11571 @section Commands to Specify Files
11573 @cindex symbol table
11574 @cindex core dump file
11576 You may want to specify executable and core dump file names. The usual
11577 way to do this is at start-up time, using the arguments to
11578 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
11579 Out of @value{GDBN}}).
11581 Occasionally it is necessary to change to a different file during a
11582 @value{GDBN} session. Or you may run @value{GDBN} and forget to
11583 specify a file you want to use. Or you are debugging a remote target
11584 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
11585 Program}). In these situations the @value{GDBN} commands to specify
11586 new files are useful.
11589 @cindex executable file
11591 @item file @var{filename}
11592 Use @var{filename} as the program to be debugged. It is read for its
11593 symbols and for the contents of pure memory. It is also the program
11594 executed when you use the @code{run} command. If you do not specify a
11595 directory and the file is not found in the @value{GDBN} working directory,
11596 @value{GDBN} uses the environment variable @code{PATH} as a list of
11597 directories to search, just as the shell does when looking for a program
11598 to run. You can change the value of this variable, for both @value{GDBN}
11599 and your program, using the @code{path} command.
11601 @cindex unlinked object files
11602 @cindex patching object files
11603 You can load unlinked object @file{.o} files into @value{GDBN} using
11604 the @code{file} command. You will not be able to ``run'' an object
11605 file, but you can disassemble functions and inspect variables. Also,
11606 if the underlying BFD functionality supports it, you could use
11607 @kbd{gdb -write} to patch object files using this technique. Note
11608 that @value{GDBN} can neither interpret nor modify relocations in this
11609 case, so branches and some initialized variables will appear to go to
11610 the wrong place. But this feature is still handy from time to time.
11613 @code{file} with no argument makes @value{GDBN} discard any information it
11614 has on both executable file and the symbol table.
11617 @item exec-file @r{[} @var{filename} @r{]}
11618 Specify that the program to be run (but not the symbol table) is found
11619 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
11620 if necessary to locate your program. Omitting @var{filename} means to
11621 discard information on the executable file.
11623 @kindex symbol-file
11624 @item symbol-file @r{[} @var{filename} @r{]}
11625 Read symbol table information from file @var{filename}. @code{PATH} is
11626 searched when necessary. Use the @code{file} command to get both symbol
11627 table and program to run from the same file.
11629 @code{symbol-file} with no argument clears out @value{GDBN} information on your
11630 program's symbol table.
11632 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
11633 some breakpoints and auto-display expressions. This is because they may
11634 contain pointers to the internal data recording symbols and data types,
11635 which are part of the old symbol table data being discarded inside
11638 @code{symbol-file} does not repeat if you press @key{RET} again after
11641 When @value{GDBN} is configured for a particular environment, it
11642 understands debugging information in whatever format is the standard
11643 generated for that environment; you may use either a @sc{gnu} compiler, or
11644 other compilers that adhere to the local conventions.
11645 Best results are usually obtained from @sc{gnu} compilers; for example,
11646 using @code{@value{NGCC}} you can generate debugging information for
11649 For most kinds of object files, with the exception of old SVR3 systems
11650 using COFF, the @code{symbol-file} command does not normally read the
11651 symbol table in full right away. Instead, it scans the symbol table
11652 quickly to find which source files and which symbols are present. The
11653 details are read later, one source file at a time, as they are needed.
11655 The purpose of this two-stage reading strategy is to make @value{GDBN}
11656 start up faster. For the most part, it is invisible except for
11657 occasional pauses while the symbol table details for a particular source
11658 file are being read. (The @code{set verbose} command can turn these
11659 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
11660 Warnings and Messages}.)
11662 We have not implemented the two-stage strategy for COFF yet. When the
11663 symbol table is stored in COFF format, @code{symbol-file} reads the
11664 symbol table data in full right away. Note that ``stabs-in-COFF''
11665 still does the two-stage strategy, since the debug info is actually
11669 @cindex reading symbols immediately
11670 @cindex symbols, reading immediately
11671 @item symbol-file @var{filename} @r{[} -readnow @r{]}
11672 @itemx file @var{filename} @r{[} -readnow @r{]}
11673 You can override the @value{GDBN} two-stage strategy for reading symbol
11674 tables by using the @samp{-readnow} option with any of the commands that
11675 load symbol table information, if you want to be sure @value{GDBN} has the
11676 entire symbol table available.
11678 @c FIXME: for now no mention of directories, since this seems to be in
11679 @c flux. 13mar1992 status is that in theory GDB would look either in
11680 @c current dir or in same dir as myprog; but issues like competing
11681 @c GDB's, or clutter in system dirs, mean that in practice right now
11682 @c only current dir is used. FFish says maybe a special GDB hierarchy
11683 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
11687 @item core-file @r{[}@var{filename}@r{]}
11689 Specify the whereabouts of a core dump file to be used as the ``contents
11690 of memory''. Traditionally, core files contain only some parts of the
11691 address space of the process that generated them; @value{GDBN} can access the
11692 executable file itself for other parts.
11694 @code{core-file} with no argument specifies that no core file is
11697 Note that the core file is ignored when your program is actually running
11698 under @value{GDBN}. So, if you have been running your program and you
11699 wish to debug a core file instead, you must kill the subprocess in which
11700 the program is running. To do this, use the @code{kill} command
11701 (@pxref{Kill Process, ,Killing the Child Process}).
11703 @kindex add-symbol-file
11704 @cindex dynamic linking
11705 @item add-symbol-file @var{filename} @var{address}
11706 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
11707 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
11708 The @code{add-symbol-file} command reads additional symbol table
11709 information from the file @var{filename}. You would use this command
11710 when @var{filename} has been dynamically loaded (by some other means)
11711 into the program that is running. @var{address} should be the memory
11712 address at which the file has been loaded; @value{GDBN} cannot figure
11713 this out for itself. You can additionally specify an arbitrary number
11714 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
11715 section name and base address for that section. You can specify any
11716 @var{address} as an expression.
11718 The symbol table of the file @var{filename} is added to the symbol table
11719 originally read with the @code{symbol-file} command. You can use the
11720 @code{add-symbol-file} command any number of times; the new symbol data
11721 thus read keeps adding to the old. To discard all old symbol data
11722 instead, use the @code{symbol-file} command without any arguments.
11724 @cindex relocatable object files, reading symbols from
11725 @cindex object files, relocatable, reading symbols from
11726 @cindex reading symbols from relocatable object files
11727 @cindex symbols, reading from relocatable object files
11728 @cindex @file{.o} files, reading symbols from
11729 Although @var{filename} is typically a shared library file, an
11730 executable file, or some other object file which has been fully
11731 relocated for loading into a process, you can also load symbolic
11732 information from relocatable @file{.o} files, as long as:
11736 the file's symbolic information refers only to linker symbols defined in
11737 that file, not to symbols defined by other object files,
11739 every section the file's symbolic information refers to has actually
11740 been loaded into the inferior, as it appears in the file, and
11742 you can determine the address at which every section was loaded, and
11743 provide these to the @code{add-symbol-file} command.
11747 Some embedded operating systems, like Sun Chorus and VxWorks, can load
11748 relocatable files into an already running program; such systems
11749 typically make the requirements above easy to meet. However, it's
11750 important to recognize that many native systems use complex link
11751 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
11752 assembly, for example) that make the requirements difficult to meet. In
11753 general, one cannot assume that using @code{add-symbol-file} to read a
11754 relocatable object file's symbolic information will have the same effect
11755 as linking the relocatable object file into the program in the normal
11758 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
11760 @kindex add-symbol-file-from-memory
11761 @cindex @code{syscall DSO}
11762 @cindex load symbols from memory
11763 @item add-symbol-file-from-memory @var{address}
11764 Load symbols from the given @var{address} in a dynamically loaded
11765 object file whose image is mapped directly into the inferior's memory.
11766 For example, the Linux kernel maps a @code{syscall DSO} into each
11767 process's address space; this DSO provides kernel-specific code for
11768 some system calls. The argument can be any expression whose
11769 evaluation yields the address of the file's shared object file header.
11770 For this command to work, you must have used @code{symbol-file} or
11771 @code{exec-file} commands in advance.
11773 @kindex add-shared-symbol-files
11775 @item add-shared-symbol-files @var{library-file}
11776 @itemx assf @var{library-file}
11777 The @code{add-shared-symbol-files} command can currently be used only
11778 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
11779 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
11780 @value{GDBN} automatically looks for shared libraries, however if
11781 @value{GDBN} does not find yours, you can invoke
11782 @code{add-shared-symbol-files}. It takes one argument: the shared
11783 library's file name. @code{assf} is a shorthand alias for
11784 @code{add-shared-symbol-files}.
11787 @item section @var{section} @var{addr}
11788 The @code{section} command changes the base address of the named
11789 @var{section} of the exec file to @var{addr}. This can be used if the
11790 exec file does not contain section addresses, (such as in the
11791 @code{a.out} format), or when the addresses specified in the file
11792 itself are wrong. Each section must be changed separately. The
11793 @code{info files} command, described below, lists all the sections and
11797 @kindex info target
11800 @code{info files} and @code{info target} are synonymous; both print the
11801 current target (@pxref{Targets, ,Specifying a Debugging Target}),
11802 including the names of the executable and core dump files currently in
11803 use by @value{GDBN}, and the files from which symbols were loaded. The
11804 command @code{help target} lists all possible targets rather than
11807 @kindex maint info sections
11808 @item maint info sections
11809 Another command that can give you extra information about program sections
11810 is @code{maint info sections}. In addition to the section information
11811 displayed by @code{info files}, this command displays the flags and file
11812 offset of each section in the executable and core dump files. In addition,
11813 @code{maint info sections} provides the following command options (which
11814 may be arbitrarily combined):
11818 Display sections for all loaded object files, including shared libraries.
11819 @item @var{sections}
11820 Display info only for named @var{sections}.
11821 @item @var{section-flags}
11822 Display info only for sections for which @var{section-flags} are true.
11823 The section flags that @value{GDBN} currently knows about are:
11826 Section will have space allocated in the process when loaded.
11827 Set for all sections except those containing debug information.
11829 Section will be loaded from the file into the child process memory.
11830 Set for pre-initialized code and data, clear for @code{.bss} sections.
11832 Section needs to be relocated before loading.
11834 Section cannot be modified by the child process.
11836 Section contains executable code only.
11838 Section contains data only (no executable code).
11840 Section will reside in ROM.
11842 Section contains data for constructor/destructor lists.
11844 Section is not empty.
11846 An instruction to the linker to not output the section.
11847 @item COFF_SHARED_LIBRARY
11848 A notification to the linker that the section contains
11849 COFF shared library information.
11851 Section contains common symbols.
11854 @kindex set trust-readonly-sections
11855 @cindex read-only sections
11856 @item set trust-readonly-sections on
11857 Tell @value{GDBN} that readonly sections in your object file
11858 really are read-only (i.e.@: that their contents will not change).
11859 In that case, @value{GDBN} can fetch values from these sections
11860 out of the object file, rather than from the target program.
11861 For some targets (notably embedded ones), this can be a significant
11862 enhancement to debugging performance.
11864 The default is off.
11866 @item set trust-readonly-sections off
11867 Tell @value{GDBN} not to trust readonly sections. This means that
11868 the contents of the section might change while the program is running,
11869 and must therefore be fetched from the target when needed.
11871 @item show trust-readonly-sections
11872 Show the current setting of trusting readonly sections.
11875 All file-specifying commands allow both absolute and relative file names
11876 as arguments. @value{GDBN} always converts the file name to an absolute file
11877 name and remembers it that way.
11879 @cindex shared libraries
11880 @anchor{Shared Libraries}
11881 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
11882 and IBM RS/6000 AIX shared libraries.
11884 On MS-Windows @value{GDBN} must be linked with the Expat library to support
11885 shared libraries. @xref{Expat}.
11887 @value{GDBN} automatically loads symbol definitions from shared libraries
11888 when you use the @code{run} command, or when you examine a core file.
11889 (Before you issue the @code{run} command, @value{GDBN} does not understand
11890 references to a function in a shared library, however---unless you are
11891 debugging a core file).
11893 On HP-UX, if the program loads a library explicitly, @value{GDBN}
11894 automatically loads the symbols at the time of the @code{shl_load} call.
11896 @c FIXME: some @value{GDBN} release may permit some refs to undef
11897 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
11898 @c FIXME...lib; check this from time to time when updating manual
11900 There are times, however, when you may wish to not automatically load
11901 symbol definitions from shared libraries, such as when they are
11902 particularly large or there are many of them.
11904 To control the automatic loading of shared library symbols, use the
11908 @kindex set auto-solib-add
11909 @item set auto-solib-add @var{mode}
11910 If @var{mode} is @code{on}, symbols from all shared object libraries
11911 will be loaded automatically when the inferior begins execution, you
11912 attach to an independently started inferior, or when the dynamic linker
11913 informs @value{GDBN} that a new library has been loaded. If @var{mode}
11914 is @code{off}, symbols must be loaded manually, using the
11915 @code{sharedlibrary} command. The default value is @code{on}.
11917 @cindex memory used for symbol tables
11918 If your program uses lots of shared libraries with debug info that
11919 takes large amounts of memory, you can decrease the @value{GDBN}
11920 memory footprint by preventing it from automatically loading the
11921 symbols from shared libraries. To that end, type @kbd{set
11922 auto-solib-add off} before running the inferior, then load each
11923 library whose debug symbols you do need with @kbd{sharedlibrary
11924 @var{regexp}}, where @var{regexp} is a regular expression that matches
11925 the libraries whose symbols you want to be loaded.
11927 @kindex show auto-solib-add
11928 @item show auto-solib-add
11929 Display the current autoloading mode.
11932 @cindex load shared library
11933 To explicitly load shared library symbols, use the @code{sharedlibrary}
11937 @kindex info sharedlibrary
11940 @itemx info sharedlibrary
11941 Print the names of the shared libraries which are currently loaded.
11943 @kindex sharedlibrary
11945 @item sharedlibrary @var{regex}
11946 @itemx share @var{regex}
11947 Load shared object library symbols for files matching a
11948 Unix regular expression.
11949 As with files loaded automatically, it only loads shared libraries
11950 required by your program for a core file or after typing @code{run}. If
11951 @var{regex} is omitted all shared libraries required by your program are
11954 @item nosharedlibrary
11955 @kindex nosharedlibrary
11956 @cindex unload symbols from shared libraries
11957 Unload all shared object library symbols. This discards all symbols
11958 that have been loaded from all shared libraries. Symbols from shared
11959 libraries that were loaded by explicit user requests are not
11963 Sometimes you may wish that @value{GDBN} stops and gives you control
11964 when any of shared library events happen. Use the @code{set
11965 stop-on-solib-events} command for this:
11968 @item set stop-on-solib-events
11969 @kindex set stop-on-solib-events
11970 This command controls whether @value{GDBN} should give you control
11971 when the dynamic linker notifies it about some shared library event.
11972 The most common event of interest is loading or unloading of a new
11975 @item show stop-on-solib-events
11976 @kindex show stop-on-solib-events
11977 Show whether @value{GDBN} stops and gives you control when shared
11978 library events happen.
11981 Shared libraries are also supported in many cross or remote debugging
11982 configurations. A copy of the target's libraries need to be present on the
11983 host system; they need to be the same as the target libraries, although the
11984 copies on the target can be stripped as long as the copies on the host are
11987 @cindex where to look for shared libraries
11988 For remote debugging, you need to tell @value{GDBN} where the target
11989 libraries are, so that it can load the correct copies---otherwise, it
11990 may try to load the host's libraries. @value{GDBN} has two variables
11991 to specify the search directories for target libraries.
11994 @cindex prefix for shared library file names
11995 @cindex system root, alternate
11996 @kindex set solib-absolute-prefix
11997 @kindex set sysroot
11998 @item set sysroot @var{path}
11999 Use @var{path} as the system root for the program being debugged. Any
12000 absolute shared library paths will be prefixed with @var{path}; many
12001 runtime loaders store the absolute paths to the shared library in the
12002 target program's memory. If you use @code{set sysroot} to find shared
12003 libraries, they need to be laid out in the same way that they are on
12004 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
12007 The @code{set solib-absolute-prefix} command is an alias for @code{set
12010 @cindex default system root
12011 @cindex @samp{--with-sysroot}
12012 You can set the default system root by using the configure-time
12013 @samp{--with-sysroot} option. If the system root is inside
12014 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
12015 @samp{--exec-prefix}), then the default system root will be updated
12016 automatically if the installed @value{GDBN} is moved to a new
12019 @kindex show sysroot
12021 Display the current shared library prefix.
12023 @kindex set solib-search-path
12024 @item set solib-search-path @var{path}
12025 If this variable is set, @var{path} is a colon-separated list of
12026 directories to search for shared libraries. @samp{solib-search-path}
12027 is used after @samp{sysroot} fails to locate the library, or if the
12028 path to the library is relative instead of absolute. If you want to
12029 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
12030 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
12031 finding your host's libraries. @samp{sysroot} is preferred; setting
12032 it to a nonexistent directory may interfere with automatic loading
12033 of shared library symbols.
12035 @kindex show solib-search-path
12036 @item show solib-search-path
12037 Display the current shared library search path.
12041 @node Separate Debug Files
12042 @section Debugging Information in Separate Files
12043 @cindex separate debugging information files
12044 @cindex debugging information in separate files
12045 @cindex @file{.debug} subdirectories
12046 @cindex debugging information directory, global
12047 @cindex global debugging information directory
12048 @cindex build ID, and separate debugging files
12049 @cindex @file{.build-id} directory
12051 @value{GDBN} allows you to put a program's debugging information in a
12052 file separate from the executable itself, in a way that allows
12053 @value{GDBN} to find and load the debugging information automatically.
12054 Since debugging information can be very large---sometimes larger
12055 than the executable code itself---some systems distribute debugging
12056 information for their executables in separate files, which users can
12057 install only when they need to debug a problem.
12059 @value{GDBN} supports two ways of specifying the separate debug info
12064 The executable contains a @dfn{debug link} that specifies the name of
12065 the separate debug info file. The separate debug file's name is
12066 usually @file{@var{executable}.debug}, where @var{executable} is the
12067 name of the corresponding executable file without leading directories
12068 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
12069 debug link specifies a CRC32 checksum for the debug file, which
12070 @value{GDBN} uses to validate that the executable and the debug file
12071 came from the same build.
12074 The executable contains a @dfn{build ID}, a unique bit string that is
12075 also present in the corresponding debug info file. (This is supported
12076 only on some operating systems, notably those which use the ELF format
12077 for binary files and the @sc{gnu} Binutils.) For more details about
12078 this feature, see the description of the @option{--build-id}
12079 command-line option in @ref{Options, , Command Line Options, ld.info,
12080 The GNU Linker}. The debug info file's name is not specified
12081 explicitly by the build ID, but can be computed from the build ID, see
12085 Depending on the way the debug info file is specified, @value{GDBN}
12086 uses two different methods of looking for the debug file:
12090 For the ``debug link'' method, @value{GDBN} looks up the named file in
12091 the directory of the executable file, then in a subdirectory of that
12092 directory named @file{.debug}, and finally under the global debug
12093 directory, in a subdirectory whose name is identical to the leading
12094 directories of the executable's absolute file name.
12097 For the ``build ID'' method, @value{GDBN} looks in the
12098 @file{.build-id} subdirectory of the global debug directory for a file
12099 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
12100 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
12101 are the rest of the bit string. (Real build ID strings are 32 or more
12102 hex characters, not 10.)
12105 So, for example, suppose you ask @value{GDBN} to debug
12106 @file{/usr/bin/ls}, which has a debug link that specifies the
12107 file @file{ls.debug}, and a build ID whose value in hex is
12108 @code{abcdef1234}. If the global debug directory is
12109 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
12110 debug information files, in the indicated order:
12114 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
12116 @file{/usr/bin/ls.debug}
12118 @file{/usr/bin/.debug/ls.debug}
12120 @file{/usr/lib/debug/usr/bin/ls.debug}.
12123 You can set the global debugging info directory's name, and view the
12124 name @value{GDBN} is currently using.
12128 @kindex set debug-file-directory
12129 @item set debug-file-directory @var{directory}
12130 Set the directory which @value{GDBN} searches for separate debugging
12131 information files to @var{directory}.
12133 @kindex show debug-file-directory
12134 @item show debug-file-directory
12135 Show the directory @value{GDBN} searches for separate debugging
12140 @cindex @code{.gnu_debuglink} sections
12141 @cindex debug link sections
12142 A debug link is a special section of the executable file named
12143 @code{.gnu_debuglink}. The section must contain:
12147 A filename, with any leading directory components removed, followed by
12150 zero to three bytes of padding, as needed to reach the next four-byte
12151 boundary within the section, and
12153 a four-byte CRC checksum, stored in the same endianness used for the
12154 executable file itself. The checksum is computed on the debugging
12155 information file's full contents by the function given below, passing
12156 zero as the @var{crc} argument.
12159 Any executable file format can carry a debug link, as long as it can
12160 contain a section named @code{.gnu_debuglink} with the contents
12163 @cindex @code{.note.gnu.build-id} sections
12164 @cindex build ID sections
12165 The build ID is a special section in the executable file (and in other
12166 ELF binary files that @value{GDBN} may consider). This section is
12167 often named @code{.note.gnu.build-id}, but that name is not mandatory.
12168 It contains unique identification for the built files---the ID remains
12169 the same across multiple builds of the same build tree. The default
12170 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
12171 content for the build ID string. The same section with an identical
12172 value is present in the original built binary with symbols, in its
12173 stripped variant, and in the separate debugging information file.
12175 The debugging information file itself should be an ordinary
12176 executable, containing a full set of linker symbols, sections, and
12177 debugging information. The sections of the debugging information file
12178 should have the same names, addresses, and sizes as the original file,
12179 but they need not contain any data---much like a @code{.bss} section
12180 in an ordinary executable.
12182 The @sc{gnu} binary utilities (Binutils) package includes the
12183 @samp{objcopy} utility that can produce
12184 the separated executable / debugging information file pairs using the
12185 following commands:
12188 @kbd{objcopy --only-keep-debug foo foo.debug}
12193 These commands remove the debugging
12194 information from the executable file @file{foo} and place it in the file
12195 @file{foo.debug}. You can use the first, second or both methods to link the
12200 The debug link method needs the following additional command to also leave
12201 behind a debug link in @file{foo}:
12204 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
12207 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
12208 a version of the @code{strip} command such that the command @kbd{strip foo -f
12209 foo.debug} has the same functionality as the two @code{objcopy} commands and
12210 the @code{ln -s} command above, together.
12213 Build ID gets embedded into the main executable using @code{ld --build-id} or
12214 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
12215 compatibility fixes for debug files separation are present in @sc{gnu} binary
12216 utilities (Binutils) package since version 2.18.
12221 Since there are many different ways to compute CRC's for the debug
12222 link (different polynomials, reversals, byte ordering, etc.), the
12223 simplest way to describe the CRC used in @code{.gnu_debuglink}
12224 sections is to give the complete code for a function that computes it:
12226 @kindex gnu_debuglink_crc32
12229 gnu_debuglink_crc32 (unsigned long crc,
12230 unsigned char *buf, size_t len)
12232 static const unsigned long crc32_table[256] =
12234 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
12235 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
12236 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
12237 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
12238 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
12239 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
12240 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
12241 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
12242 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
12243 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
12244 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
12245 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
12246 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
12247 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
12248 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
12249 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
12250 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
12251 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
12252 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
12253 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
12254 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
12255 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
12256 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
12257 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
12258 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
12259 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
12260 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
12261 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
12262 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
12263 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
12264 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
12265 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
12266 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
12267 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
12268 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
12269 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
12270 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
12271 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
12272 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
12273 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
12274 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
12275 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
12276 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
12277 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
12278 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
12279 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
12280 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
12281 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
12282 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
12283 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
12284 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
12287 unsigned char *end;
12289 crc = ~crc & 0xffffffff;
12290 for (end = buf + len; buf < end; ++buf)
12291 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
12292 return ~crc & 0xffffffff;
12297 This computation does not apply to the ``build ID'' method.
12300 @node Symbol Errors
12301 @section Errors Reading Symbol Files
12303 While reading a symbol file, @value{GDBN} occasionally encounters problems,
12304 such as symbol types it does not recognize, or known bugs in compiler
12305 output. By default, @value{GDBN} does not notify you of such problems, since
12306 they are relatively common and primarily of interest to people
12307 debugging compilers. If you are interested in seeing information
12308 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
12309 only one message about each such type of problem, no matter how many
12310 times the problem occurs; or you can ask @value{GDBN} to print more messages,
12311 to see how many times the problems occur, with the @code{set
12312 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
12315 The messages currently printed, and their meanings, include:
12318 @item inner block not inside outer block in @var{symbol}
12320 The symbol information shows where symbol scopes begin and end
12321 (such as at the start of a function or a block of statements). This
12322 error indicates that an inner scope block is not fully contained
12323 in its outer scope blocks.
12325 @value{GDBN} circumvents the problem by treating the inner block as if it had
12326 the same scope as the outer block. In the error message, @var{symbol}
12327 may be shown as ``@code{(don't know)}'' if the outer block is not a
12330 @item block at @var{address} out of order
12332 The symbol information for symbol scope blocks should occur in
12333 order of increasing addresses. This error indicates that it does not
12336 @value{GDBN} does not circumvent this problem, and has trouble
12337 locating symbols in the source file whose symbols it is reading. (You
12338 can often determine what source file is affected by specifying
12339 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
12342 @item bad block start address patched
12344 The symbol information for a symbol scope block has a start address
12345 smaller than the address of the preceding source line. This is known
12346 to occur in the SunOS 4.1.1 (and earlier) C compiler.
12348 @value{GDBN} circumvents the problem by treating the symbol scope block as
12349 starting on the previous source line.
12351 @item bad string table offset in symbol @var{n}
12354 Symbol number @var{n} contains a pointer into the string table which is
12355 larger than the size of the string table.
12357 @value{GDBN} circumvents the problem by considering the symbol to have the
12358 name @code{foo}, which may cause other problems if many symbols end up
12361 @item unknown symbol type @code{0x@var{nn}}
12363 The symbol information contains new data types that @value{GDBN} does
12364 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
12365 uncomprehended information, in hexadecimal.
12367 @value{GDBN} circumvents the error by ignoring this symbol information.
12368 This usually allows you to debug your program, though certain symbols
12369 are not accessible. If you encounter such a problem and feel like
12370 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
12371 on @code{complain}, then go up to the function @code{read_dbx_symtab}
12372 and examine @code{*bufp} to see the symbol.
12374 @item stub type has NULL name
12376 @value{GDBN} could not find the full definition for a struct or class.
12378 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
12379 The symbol information for a C@t{++} member function is missing some
12380 information that recent versions of the compiler should have output for
12383 @item info mismatch between compiler and debugger
12385 @value{GDBN} could not parse a type specification output by the compiler.
12390 @chapter Specifying a Debugging Target
12392 @cindex debugging target
12393 A @dfn{target} is the execution environment occupied by your program.
12395 Often, @value{GDBN} runs in the same host environment as your program;
12396 in that case, the debugging target is specified as a side effect when
12397 you use the @code{file} or @code{core} commands. When you need more
12398 flexibility---for example, running @value{GDBN} on a physically separate
12399 host, or controlling a standalone system over a serial port or a
12400 realtime system over a TCP/IP connection---you can use the @code{target}
12401 command to specify one of the target types configured for @value{GDBN}
12402 (@pxref{Target Commands, ,Commands for Managing Targets}).
12404 @cindex target architecture
12405 It is possible to build @value{GDBN} for several different @dfn{target
12406 architectures}. When @value{GDBN} is built like that, you can choose
12407 one of the available architectures with the @kbd{set architecture}
12411 @kindex set architecture
12412 @kindex show architecture
12413 @item set architecture @var{arch}
12414 This command sets the current target architecture to @var{arch}. The
12415 value of @var{arch} can be @code{"auto"}, in addition to one of the
12416 supported architectures.
12418 @item show architecture
12419 Show the current target architecture.
12421 @item set processor
12423 @kindex set processor
12424 @kindex show processor
12425 These are alias commands for, respectively, @code{set architecture}
12426 and @code{show architecture}.
12430 * Active Targets:: Active targets
12431 * Target Commands:: Commands for managing targets
12432 * Byte Order:: Choosing target byte order
12435 @node Active Targets
12436 @section Active Targets
12438 @cindex stacking targets
12439 @cindex active targets
12440 @cindex multiple targets
12442 There are three classes of targets: processes, core files, and
12443 executable files. @value{GDBN} can work concurrently on up to three
12444 active targets, one in each class. This allows you to (for example)
12445 start a process and inspect its activity without abandoning your work on
12448 For example, if you execute @samp{gdb a.out}, then the executable file
12449 @code{a.out} is the only active target. If you designate a core file as
12450 well---presumably from a prior run that crashed and coredumped---then
12451 @value{GDBN} has two active targets and uses them in tandem, looking
12452 first in the corefile target, then in the executable file, to satisfy
12453 requests for memory addresses. (Typically, these two classes of target
12454 are complementary, since core files contain only a program's
12455 read-write memory---variables and so on---plus machine status, while
12456 executable files contain only the program text and initialized data.)
12458 When you type @code{run}, your executable file becomes an active process
12459 target as well. When a process target is active, all @value{GDBN}
12460 commands requesting memory addresses refer to that target; addresses in
12461 an active core file or executable file target are obscured while the
12462 process target is active.
12464 Use the @code{core-file} and @code{exec-file} commands to select a new
12465 core file or executable target (@pxref{Files, ,Commands to Specify
12466 Files}). To specify as a target a process that is already running, use
12467 the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
12470 @node Target Commands
12471 @section Commands for Managing Targets
12474 @item target @var{type} @var{parameters}
12475 Connects the @value{GDBN} host environment to a target machine or
12476 process. A target is typically a protocol for talking to debugging
12477 facilities. You use the argument @var{type} to specify the type or
12478 protocol of the target machine.
12480 Further @var{parameters} are interpreted by the target protocol, but
12481 typically include things like device names or host names to connect
12482 with, process numbers, and baud rates.
12484 The @code{target} command does not repeat if you press @key{RET} again
12485 after executing the command.
12487 @kindex help target
12489 Displays the names of all targets available. To display targets
12490 currently selected, use either @code{info target} or @code{info files}
12491 (@pxref{Files, ,Commands to Specify Files}).
12493 @item help target @var{name}
12494 Describe a particular target, including any parameters necessary to
12497 @kindex set gnutarget
12498 @item set gnutarget @var{args}
12499 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
12500 knows whether it is reading an @dfn{executable},
12501 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
12502 with the @code{set gnutarget} command. Unlike most @code{target} commands,
12503 with @code{gnutarget} the @code{target} refers to a program, not a machine.
12506 @emph{Warning:} To specify a file format with @code{set gnutarget},
12507 you must know the actual BFD name.
12511 @xref{Files, , Commands to Specify Files}.
12513 @kindex show gnutarget
12514 @item show gnutarget
12515 Use the @code{show gnutarget} command to display what file format
12516 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
12517 @value{GDBN} will determine the file format for each file automatically,
12518 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
12521 @cindex common targets
12522 Here are some common targets (available, or not, depending on the GDB
12527 @item target exec @var{program}
12528 @cindex executable file target
12529 An executable file. @samp{target exec @var{program}} is the same as
12530 @samp{exec-file @var{program}}.
12532 @item target core @var{filename}
12533 @cindex core dump file target
12534 A core dump file. @samp{target core @var{filename}} is the same as
12535 @samp{core-file @var{filename}}.
12537 @item target remote @var{medium}
12538 @cindex remote target
12539 A remote system connected to @value{GDBN} via a serial line or network
12540 connection. This command tells @value{GDBN} to use its own remote
12541 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
12543 For example, if you have a board connected to @file{/dev/ttya} on the
12544 machine running @value{GDBN}, you could say:
12547 target remote /dev/ttya
12550 @code{target remote} supports the @code{load} command. This is only
12551 useful if you have some other way of getting the stub to the target
12552 system, and you can put it somewhere in memory where it won't get
12553 clobbered by the download.
12556 @cindex built-in simulator target
12557 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
12565 works; however, you cannot assume that a specific memory map, device
12566 drivers, or even basic I/O is available, although some simulators do
12567 provide these. For info about any processor-specific simulator details,
12568 see the appropriate section in @ref{Embedded Processors, ,Embedded
12573 Some configurations may include these targets as well:
12577 @item target nrom @var{dev}
12578 @cindex NetROM ROM emulator target
12579 NetROM ROM emulator. This target only supports downloading.
12583 Different targets are available on different configurations of @value{GDBN};
12584 your configuration may have more or fewer targets.
12586 Many remote targets require you to download the executable's code once
12587 you've successfully established a connection. You may wish to control
12588 various aspects of this process.
12593 @kindex set hash@r{, for remote monitors}
12594 @cindex hash mark while downloading
12595 This command controls whether a hash mark @samp{#} is displayed while
12596 downloading a file to the remote monitor. If on, a hash mark is
12597 displayed after each S-record is successfully downloaded to the
12601 @kindex show hash@r{, for remote monitors}
12602 Show the current status of displaying the hash mark.
12604 @item set debug monitor
12605 @kindex set debug monitor
12606 @cindex display remote monitor communications
12607 Enable or disable display of communications messages between
12608 @value{GDBN} and the remote monitor.
12610 @item show debug monitor
12611 @kindex show debug monitor
12612 Show the current status of displaying communications between
12613 @value{GDBN} and the remote monitor.
12618 @kindex load @var{filename}
12619 @item load @var{filename}
12620 Depending on what remote debugging facilities are configured into
12621 @value{GDBN}, the @code{load} command may be available. Where it exists, it
12622 is meant to make @var{filename} (an executable) available for debugging
12623 on the remote system---by downloading, or dynamic linking, for example.
12624 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
12625 the @code{add-symbol-file} command.
12627 If your @value{GDBN} does not have a @code{load} command, attempting to
12628 execute it gets the error message ``@code{You can't do that when your
12629 target is @dots{}}''
12631 The file is loaded at whatever address is specified in the executable.
12632 For some object file formats, you can specify the load address when you
12633 link the program; for other formats, like a.out, the object file format
12634 specifies a fixed address.
12635 @c FIXME! This would be a good place for an xref to the GNU linker doc.
12637 Depending on the remote side capabilities, @value{GDBN} may be able to
12638 load programs into flash memory.
12640 @code{load} does not repeat if you press @key{RET} again after using it.
12644 @section Choosing Target Byte Order
12646 @cindex choosing target byte order
12647 @cindex target byte order
12649 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
12650 offer the ability to run either big-endian or little-endian byte
12651 orders. Usually the executable or symbol will include a bit to
12652 designate the endian-ness, and you will not need to worry about
12653 which to use. However, you may still find it useful to adjust
12654 @value{GDBN}'s idea of processor endian-ness manually.
12658 @item set endian big
12659 Instruct @value{GDBN} to assume the target is big-endian.
12661 @item set endian little
12662 Instruct @value{GDBN} to assume the target is little-endian.
12664 @item set endian auto
12665 Instruct @value{GDBN} to use the byte order associated with the
12669 Display @value{GDBN}'s current idea of the target byte order.
12673 Note that these commands merely adjust interpretation of symbolic
12674 data on the host, and that they have absolutely no effect on the
12678 @node Remote Debugging
12679 @chapter Debugging Remote Programs
12680 @cindex remote debugging
12682 If you are trying to debug a program running on a machine that cannot run
12683 @value{GDBN} in the usual way, it is often useful to use remote debugging.
12684 For example, you might use remote debugging on an operating system kernel,
12685 or on a small system which does not have a general purpose operating system
12686 powerful enough to run a full-featured debugger.
12688 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
12689 to make this work with particular debugging targets. In addition,
12690 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
12691 but not specific to any particular target system) which you can use if you
12692 write the remote stubs---the code that runs on the remote system to
12693 communicate with @value{GDBN}.
12695 Other remote targets may be available in your
12696 configuration of @value{GDBN}; use @code{help target} to list them.
12699 * Connecting:: Connecting to a remote target
12700 * File Transfer:: Sending files to a remote system
12701 * Server:: Using the gdbserver program
12702 * Remote Configuration:: Remote configuration
12703 * Remote Stub:: Implementing a remote stub
12707 @section Connecting to a Remote Target
12709 On the @value{GDBN} host machine, you will need an unstripped copy of
12710 your program, since @value{GDBN} needs symbol and debugging information.
12711 Start up @value{GDBN} as usual, using the name of the local copy of your
12712 program as the first argument.
12714 @cindex @code{target remote}
12715 @value{GDBN} can communicate with the target over a serial line, or
12716 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
12717 each case, @value{GDBN} uses the same protocol for debugging your
12718 program; only the medium carrying the debugging packets varies. The
12719 @code{target remote} command establishes a connection to the target.
12720 Its arguments indicate which medium to use:
12724 @item target remote @var{serial-device}
12725 @cindex serial line, @code{target remote}
12726 Use @var{serial-device} to communicate with the target. For example,
12727 to use a serial line connected to the device named @file{/dev/ttyb}:
12730 target remote /dev/ttyb
12733 If you're using a serial line, you may want to give @value{GDBN} the
12734 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
12735 (@pxref{Remote Configuration, set remotebaud}) before the
12736 @code{target} command.
12738 @item target remote @code{@var{host}:@var{port}}
12739 @itemx target remote @code{tcp:@var{host}:@var{port}}
12740 @cindex @acronym{TCP} port, @code{target remote}
12741 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
12742 The @var{host} may be either a host name or a numeric @acronym{IP}
12743 address; @var{port} must be a decimal number. The @var{host} could be
12744 the target machine itself, if it is directly connected to the net, or
12745 it might be a terminal server which in turn has a serial line to the
12748 For example, to connect to port 2828 on a terminal server named
12752 target remote manyfarms:2828
12755 If your remote target is actually running on the same machine as your
12756 debugger session (e.g.@: a simulator for your target running on the
12757 same host), you can omit the hostname. For example, to connect to
12758 port 1234 on your local machine:
12761 target remote :1234
12765 Note that the colon is still required here.
12767 @item target remote @code{udp:@var{host}:@var{port}}
12768 @cindex @acronym{UDP} port, @code{target remote}
12769 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
12770 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
12773 target remote udp:manyfarms:2828
12776 When using a @acronym{UDP} connection for remote debugging, you should
12777 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
12778 can silently drop packets on busy or unreliable networks, which will
12779 cause havoc with your debugging session.
12781 @item target remote | @var{command}
12782 @cindex pipe, @code{target remote} to
12783 Run @var{command} in the background and communicate with it using a
12784 pipe. The @var{command} is a shell command, to be parsed and expanded
12785 by the system's command shell, @code{/bin/sh}; it should expect remote
12786 protocol packets on its standard input, and send replies on its
12787 standard output. You could use this to run a stand-alone simulator
12788 that speaks the remote debugging protocol, to make net connections
12789 using programs like @code{ssh}, or for other similar tricks.
12791 If @var{command} closes its standard output (perhaps by exiting),
12792 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
12793 program has already exited, this will have no effect.)
12797 Once the connection has been established, you can use all the usual
12798 commands to examine and change data and to step and continue the
12801 @cindex interrupting remote programs
12802 @cindex remote programs, interrupting
12803 Whenever @value{GDBN} is waiting for the remote program, if you type the
12804 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
12805 program. This may or may not succeed, depending in part on the hardware
12806 and the serial drivers the remote system uses. If you type the
12807 interrupt character once again, @value{GDBN} displays this prompt:
12810 Interrupted while waiting for the program.
12811 Give up (and stop debugging it)? (y or n)
12814 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
12815 (If you decide you want to try again later, you can use @samp{target
12816 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
12817 goes back to waiting.
12820 @kindex detach (remote)
12822 When you have finished debugging the remote program, you can use the
12823 @code{detach} command to release it from @value{GDBN} control.
12824 Detaching from the target normally resumes its execution, but the results
12825 will depend on your particular remote stub. After the @code{detach}
12826 command, @value{GDBN} is free to connect to another target.
12830 The @code{disconnect} command behaves like @code{detach}, except that
12831 the target is generally not resumed. It will wait for @value{GDBN}
12832 (this instance or another one) to connect and continue debugging. After
12833 the @code{disconnect} command, @value{GDBN} is again free to connect to
12836 @cindex send command to remote monitor
12837 @cindex extend @value{GDBN} for remote targets
12838 @cindex add new commands for external monitor
12840 @item monitor @var{cmd}
12841 This command allows you to send arbitrary commands directly to the
12842 remote monitor. Since @value{GDBN} doesn't care about the commands it
12843 sends like this, this command is the way to extend @value{GDBN}---you
12844 can add new commands that only the external monitor will understand
12848 @node File Transfer
12849 @section Sending files to a remote system
12850 @cindex remote target, file transfer
12851 @cindex file transfer
12852 @cindex sending files to remote systems
12854 Some remote targets offer the ability to transfer files over the same
12855 connection used to communicate with @value{GDBN}. This is convenient
12856 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
12857 running @code{gdbserver} over a network interface. For other targets,
12858 e.g.@: embedded devices with only a single serial port, this may be
12859 the only way to upload or download files.
12861 Not all remote targets support these commands.
12865 @item remote put @var{hostfile} @var{targetfile}
12866 Copy file @var{hostfile} from the host system (the machine running
12867 @value{GDBN}) to @var{targetfile} on the target system.
12870 @item remote get @var{targetfile} @var{hostfile}
12871 Copy file @var{targetfile} from the target system to @var{hostfile}
12872 on the host system.
12874 @kindex remote delete
12875 @item remote delete @var{targetfile}
12876 Delete @var{targetfile} from the target system.
12881 @section Using the @code{gdbserver} Program
12884 @cindex remote connection without stubs
12885 @code{gdbserver} is a control program for Unix-like systems, which
12886 allows you to connect your program with a remote @value{GDBN} via
12887 @code{target remote}---but without linking in the usual debugging stub.
12889 @code{gdbserver} is not a complete replacement for the debugging stubs,
12890 because it requires essentially the same operating-system facilities
12891 that @value{GDBN} itself does. In fact, a system that can run
12892 @code{gdbserver} to connect to a remote @value{GDBN} could also run
12893 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
12894 because it is a much smaller program than @value{GDBN} itself. It is
12895 also easier to port than all of @value{GDBN}, so you may be able to get
12896 started more quickly on a new system by using @code{gdbserver}.
12897 Finally, if you develop code for real-time systems, you may find that
12898 the tradeoffs involved in real-time operation make it more convenient to
12899 do as much development work as possible on another system, for example
12900 by cross-compiling. You can use @code{gdbserver} to make a similar
12901 choice for debugging.
12903 @value{GDBN} and @code{gdbserver} communicate via either a serial line
12904 or a TCP connection, using the standard @value{GDBN} remote serial
12908 @item On the target machine,
12909 you need to have a copy of the program you want to debug.
12910 @code{gdbserver} does not need your program's symbol table, so you can
12911 strip the program if necessary to save space. @value{GDBN} on the host
12912 system does all the symbol handling.
12914 To use the server, you must tell it how to communicate with @value{GDBN};
12915 the name of your program; and the arguments for your program. The usual
12919 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
12922 @var{comm} is either a device name (to use a serial line) or a TCP
12923 hostname and portnumber. For example, to debug Emacs with the argument
12924 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
12928 target> gdbserver /dev/com1 emacs foo.txt
12931 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
12934 To use a TCP connection instead of a serial line:
12937 target> gdbserver host:2345 emacs foo.txt
12940 The only difference from the previous example is the first argument,
12941 specifying that you are communicating with the host @value{GDBN} via
12942 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
12943 expect a TCP connection from machine @samp{host} to local TCP port 2345.
12944 (Currently, the @samp{host} part is ignored.) You can choose any number
12945 you want for the port number as long as it does not conflict with any
12946 TCP ports already in use on the target system (for example, @code{23} is
12947 reserved for @code{telnet}).@footnote{If you choose a port number that
12948 conflicts with another service, @code{gdbserver} prints an error message
12949 and exits.} You must use the same port number with the host @value{GDBN}
12950 @code{target remote} command.
12952 On some targets, @code{gdbserver} can also attach to running programs.
12953 This is accomplished via the @code{--attach} argument. The syntax is:
12956 target> gdbserver @var{comm} --attach @var{pid}
12959 @var{pid} is the process ID of a currently running process. It isn't necessary
12960 to point @code{gdbserver} at a binary for the running process.
12963 @cindex attach to a program by name
12964 You can debug processes by name instead of process ID if your target has the
12965 @code{pidof} utility:
12968 target> gdbserver @var{comm} --attach `pidof @var{program}`
12971 In case more than one copy of @var{program} is running, or @var{program}
12972 has multiple threads, most versions of @code{pidof} support the
12973 @code{-s} option to only return the first process ID.
12975 @item On the host machine,
12976 first make sure you have the necessary symbol files. Load symbols for
12977 your application using the @code{file} command before you connect. Use
12978 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
12979 was compiled with the correct sysroot using @code{--with-system-root}).
12981 The symbol file and target libraries must exactly match the executable
12982 and libraries on the target, with one exception: the files on the host
12983 system should not be stripped, even if the files on the target system
12984 are. Mismatched or missing files will lead to confusing results
12985 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
12986 files may also prevent @code{gdbserver} from debugging multi-threaded
12989 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
12990 For TCP connections, you must start up @code{gdbserver} prior to using
12991 the @code{target remote} command. Otherwise you may get an error whose
12992 text depends on the host system, but which usually looks something like
12993 @samp{Connection refused}. You don't need to use the @code{load}
12994 command in @value{GDBN} when using @code{gdbserver}, since the program is
12995 already on the target.
12999 @subsection Monitor Commands for @code{gdbserver}
13000 @cindex monitor commands, for @code{gdbserver}
13002 During a @value{GDBN} session using @code{gdbserver}, you can use the
13003 @code{monitor} command to send special requests to @code{gdbserver}.
13004 Here are the available commands; they are only of interest when
13005 debugging @value{GDBN} or @code{gdbserver}.
13009 List the available monitor commands.
13011 @item monitor set debug 0
13012 @itemx monitor set debug 1
13013 Disable or enable general debugging messages.
13015 @item monitor set remote-debug 0
13016 @itemx monitor set remote-debug 1
13017 Disable or enable specific debugging messages associated with the remote
13018 protocol (@pxref{Remote Protocol}).
13022 @node Remote Configuration
13023 @section Remote Configuration
13026 @kindex show remote
13027 This section documents the configuration options available when
13028 debugging remote programs. For the options related to the File I/O
13029 extensions of the remote protocol, see @ref{system,
13030 system-call-allowed}.
13033 @item set remoteaddresssize @var{bits}
13034 @cindex address size for remote targets
13035 @cindex bits in remote address
13036 Set the maximum size of address in a memory packet to the specified
13037 number of bits. @value{GDBN} will mask off the address bits above
13038 that number, when it passes addresses to the remote target. The
13039 default value is the number of bits in the target's address.
13041 @item show remoteaddresssize
13042 Show the current value of remote address size in bits.
13044 @item set remotebaud @var{n}
13045 @cindex baud rate for remote targets
13046 Set the baud rate for the remote serial I/O to @var{n} baud. The
13047 value is used to set the speed of the serial port used for debugging
13050 @item show remotebaud
13051 Show the current speed of the remote connection.
13053 @item set remotebreak
13054 @cindex interrupt remote programs
13055 @cindex BREAK signal instead of Ctrl-C
13056 @anchor{set remotebreak}
13057 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
13058 when you type @kbd{Ctrl-c} to interrupt the program running
13059 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
13060 character instead. The default is off, since most remote systems
13061 expect to see @samp{Ctrl-C} as the interrupt signal.
13063 @item show remotebreak
13064 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
13065 interrupt the remote program.
13067 @item set remoteflow on
13068 @itemx set remoteflow off
13069 @kindex set remoteflow
13070 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
13071 on the serial port used to communicate to the remote target.
13073 @item show remoteflow
13074 @kindex show remoteflow
13075 Show the current setting of hardware flow control.
13077 @item set remotelogbase @var{base}
13078 Set the base (a.k.a.@: radix) of logging serial protocol
13079 communications to @var{base}. Supported values of @var{base} are:
13080 @code{ascii}, @code{octal}, and @code{hex}. The default is
13083 @item show remotelogbase
13084 Show the current setting of the radix for logging remote serial
13087 @item set remotelogfile @var{file}
13088 @cindex record serial communications on file
13089 Record remote serial communications on the named @var{file}. The
13090 default is not to record at all.
13092 @item show remotelogfile.
13093 Show the current setting of the file name on which to record the
13094 serial communications.
13096 @item set remotetimeout @var{num}
13097 @cindex timeout for serial communications
13098 @cindex remote timeout
13099 Set the timeout limit to wait for the remote target to respond to
13100 @var{num} seconds. The default is 2 seconds.
13102 @item show remotetimeout
13103 Show the current number of seconds to wait for the remote target
13106 @cindex limit hardware breakpoints and watchpoints
13107 @cindex remote target, limit break- and watchpoints
13108 @anchor{set remote hardware-watchpoint-limit}
13109 @anchor{set remote hardware-breakpoint-limit}
13110 @item set remote hardware-watchpoint-limit @var{limit}
13111 @itemx set remote hardware-breakpoint-limit @var{limit}
13112 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
13113 watchpoints. A limit of -1, the default, is treated as unlimited.
13116 @cindex remote packets, enabling and disabling
13117 The @value{GDBN} remote protocol autodetects the packets supported by
13118 your debugging stub. If you need to override the autodetection, you
13119 can use these commands to enable or disable individual packets. Each
13120 packet can be set to @samp{on} (the remote target supports this
13121 packet), @samp{off} (the remote target does not support this packet),
13122 or @samp{auto} (detect remote target support for this packet). They
13123 all default to @samp{auto}. For more information about each packet,
13124 see @ref{Remote Protocol}.
13126 During normal use, you should not have to use any of these commands.
13127 If you do, that may be a bug in your remote debugging stub, or a bug
13128 in @value{GDBN}. You may want to report the problem to the
13129 @value{GDBN} developers.
13131 For each packet @var{name}, the command to enable or disable the
13132 packet is @code{set remote @var{name}-packet}. The available settings
13135 @multitable @columnfractions 0.28 0.32 0.25
13138 @tab Related Features
13140 @item @code{fetch-register}
13142 @tab @code{info registers}
13144 @item @code{set-register}
13148 @item @code{binary-download}
13150 @tab @code{load}, @code{set}
13152 @item @code{read-aux-vector}
13153 @tab @code{qXfer:auxv:read}
13154 @tab @code{info auxv}
13156 @item @code{symbol-lookup}
13157 @tab @code{qSymbol}
13158 @tab Detecting multiple threads
13160 @item @code{verbose-resume}
13162 @tab Stepping or resuming multiple threads
13164 @item @code{software-breakpoint}
13168 @item @code{hardware-breakpoint}
13172 @item @code{write-watchpoint}
13176 @item @code{read-watchpoint}
13180 @item @code{access-watchpoint}
13184 @item @code{target-features}
13185 @tab @code{qXfer:features:read}
13186 @tab @code{set architecture}
13188 @item @code{library-info}
13189 @tab @code{qXfer:libraries:read}
13190 @tab @code{info sharedlibrary}
13192 @item @code{memory-map}
13193 @tab @code{qXfer:memory-map:read}
13194 @tab @code{info mem}
13196 @item @code{read-spu-object}
13197 @tab @code{qXfer:spu:read}
13198 @tab @code{info spu}
13200 @item @code{write-spu-object}
13201 @tab @code{qXfer:spu:write}
13202 @tab @code{info spu}
13204 @item @code{get-thread-local-@*storage-address}
13205 @tab @code{qGetTLSAddr}
13206 @tab Displaying @code{__thread} variables
13208 @item @code{supported-packets}
13209 @tab @code{qSupported}
13210 @tab Remote communications parameters
13212 @item @code{pass-signals}
13213 @tab @code{QPassSignals}
13214 @tab @code{handle @var{signal}}
13216 @item @code{hostio-close-packet}
13217 @tab @code{vFile:close}
13218 @tab @code{remote get}, @code{remote put}
13220 @item @code{hostio-open-packet}
13221 @tab @code{vFile:open}
13222 @tab @code{remote get}, @code{remote put}
13224 @item @code{hostio-pread-packet}
13225 @tab @code{vFile:pread}
13226 @tab @code{remote get}, @code{remote put}
13228 @item @code{hostio-pwrite-packet}
13229 @tab @code{vFile:pwrite}
13230 @tab @code{remote get}, @code{remote put}
13232 @item @code{hostio-unlink-packet}
13233 @tab @code{vFile:unlink}
13234 @tab @code{remote delete}
13238 @section Implementing a Remote Stub
13240 @cindex debugging stub, example
13241 @cindex remote stub, example
13242 @cindex stub example, remote debugging
13243 The stub files provided with @value{GDBN} implement the target side of the
13244 communication protocol, and the @value{GDBN} side is implemented in the
13245 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
13246 these subroutines to communicate, and ignore the details. (If you're
13247 implementing your own stub file, you can still ignore the details: start
13248 with one of the existing stub files. @file{sparc-stub.c} is the best
13249 organized, and therefore the easiest to read.)
13251 @cindex remote serial debugging, overview
13252 To debug a program running on another machine (the debugging
13253 @dfn{target} machine), you must first arrange for all the usual
13254 prerequisites for the program to run by itself. For example, for a C
13259 A startup routine to set up the C runtime environment; these usually
13260 have a name like @file{crt0}. The startup routine may be supplied by
13261 your hardware supplier, or you may have to write your own.
13264 A C subroutine library to support your program's
13265 subroutine calls, notably managing input and output.
13268 A way of getting your program to the other machine---for example, a
13269 download program. These are often supplied by the hardware
13270 manufacturer, but you may have to write your own from hardware
13274 The next step is to arrange for your program to use a serial port to
13275 communicate with the machine where @value{GDBN} is running (the @dfn{host}
13276 machine). In general terms, the scheme looks like this:
13280 @value{GDBN} already understands how to use this protocol; when everything
13281 else is set up, you can simply use the @samp{target remote} command
13282 (@pxref{Targets,,Specifying a Debugging Target}).
13284 @item On the target,
13285 you must link with your program a few special-purpose subroutines that
13286 implement the @value{GDBN} remote serial protocol. The file containing these
13287 subroutines is called a @dfn{debugging stub}.
13289 On certain remote targets, you can use an auxiliary program
13290 @code{gdbserver} instead of linking a stub into your program.
13291 @xref{Server,,Using the @code{gdbserver} Program}, for details.
13294 The debugging stub is specific to the architecture of the remote
13295 machine; for example, use @file{sparc-stub.c} to debug programs on
13298 @cindex remote serial stub list
13299 These working remote stubs are distributed with @value{GDBN}:
13304 @cindex @file{i386-stub.c}
13307 For Intel 386 and compatible architectures.
13310 @cindex @file{m68k-stub.c}
13311 @cindex Motorola 680x0
13313 For Motorola 680x0 architectures.
13316 @cindex @file{sh-stub.c}
13319 For Renesas SH architectures.
13322 @cindex @file{sparc-stub.c}
13324 For @sc{sparc} architectures.
13326 @item sparcl-stub.c
13327 @cindex @file{sparcl-stub.c}
13330 For Fujitsu @sc{sparclite} architectures.
13334 The @file{README} file in the @value{GDBN} distribution may list other
13335 recently added stubs.
13338 * Stub Contents:: What the stub can do for you
13339 * Bootstrapping:: What you must do for the stub
13340 * Debug Session:: Putting it all together
13343 @node Stub Contents
13344 @subsection What the Stub Can Do for You
13346 @cindex remote serial stub
13347 The debugging stub for your architecture supplies these three
13351 @item set_debug_traps
13352 @findex set_debug_traps
13353 @cindex remote serial stub, initialization
13354 This routine arranges for @code{handle_exception} to run when your
13355 program stops. You must call this subroutine explicitly near the
13356 beginning of your program.
13358 @item handle_exception
13359 @findex handle_exception
13360 @cindex remote serial stub, main routine
13361 This is the central workhorse, but your program never calls it
13362 explicitly---the setup code arranges for @code{handle_exception} to
13363 run when a trap is triggered.
13365 @code{handle_exception} takes control when your program stops during
13366 execution (for example, on a breakpoint), and mediates communications
13367 with @value{GDBN} on the host machine. This is where the communications
13368 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
13369 representative on the target machine. It begins by sending summary
13370 information on the state of your program, then continues to execute,
13371 retrieving and transmitting any information @value{GDBN} needs, until you
13372 execute a @value{GDBN} command that makes your program resume; at that point,
13373 @code{handle_exception} returns control to your own code on the target
13377 @cindex @code{breakpoint} subroutine, remote
13378 Use this auxiliary subroutine to make your program contain a
13379 breakpoint. Depending on the particular situation, this may be the only
13380 way for @value{GDBN} to get control. For instance, if your target
13381 machine has some sort of interrupt button, you won't need to call this;
13382 pressing the interrupt button transfers control to
13383 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
13384 simply receiving characters on the serial port may also trigger a trap;
13385 again, in that situation, you don't need to call @code{breakpoint} from
13386 your own program---simply running @samp{target remote} from the host
13387 @value{GDBN} session gets control.
13389 Call @code{breakpoint} if none of these is true, or if you simply want
13390 to make certain your program stops at a predetermined point for the
13391 start of your debugging session.
13394 @node Bootstrapping
13395 @subsection What You Must Do for the Stub
13397 @cindex remote stub, support routines
13398 The debugging stubs that come with @value{GDBN} are set up for a particular
13399 chip architecture, but they have no information about the rest of your
13400 debugging target machine.
13402 First of all you need to tell the stub how to communicate with the
13406 @item int getDebugChar()
13407 @findex getDebugChar
13408 Write this subroutine to read a single character from the serial port.
13409 It may be identical to @code{getchar} for your target system; a
13410 different name is used to allow you to distinguish the two if you wish.
13412 @item void putDebugChar(int)
13413 @findex putDebugChar
13414 Write this subroutine to write a single character to the serial port.
13415 It may be identical to @code{putchar} for your target system; a
13416 different name is used to allow you to distinguish the two if you wish.
13419 @cindex control C, and remote debugging
13420 @cindex interrupting remote targets
13421 If you want @value{GDBN} to be able to stop your program while it is
13422 running, you need to use an interrupt-driven serial driver, and arrange
13423 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
13424 character). That is the character which @value{GDBN} uses to tell the
13425 remote system to stop.
13427 Getting the debugging target to return the proper status to @value{GDBN}
13428 probably requires changes to the standard stub; one quick and dirty way
13429 is to just execute a breakpoint instruction (the ``dirty'' part is that
13430 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
13432 Other routines you need to supply are:
13435 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
13436 @findex exceptionHandler
13437 Write this function to install @var{exception_address} in the exception
13438 handling tables. You need to do this because the stub does not have any
13439 way of knowing what the exception handling tables on your target system
13440 are like (for example, the processor's table might be in @sc{rom},
13441 containing entries which point to a table in @sc{ram}).
13442 @var{exception_number} is the exception number which should be changed;
13443 its meaning is architecture-dependent (for example, different numbers
13444 might represent divide by zero, misaligned access, etc). When this
13445 exception occurs, control should be transferred directly to
13446 @var{exception_address}, and the processor state (stack, registers,
13447 and so on) should be just as it is when a processor exception occurs. So if
13448 you want to use a jump instruction to reach @var{exception_address}, it
13449 should be a simple jump, not a jump to subroutine.
13451 For the 386, @var{exception_address} should be installed as an interrupt
13452 gate so that interrupts are masked while the handler runs. The gate
13453 should be at privilege level 0 (the most privileged level). The
13454 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
13455 help from @code{exceptionHandler}.
13457 @item void flush_i_cache()
13458 @findex flush_i_cache
13459 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
13460 instruction cache, if any, on your target machine. If there is no
13461 instruction cache, this subroutine may be a no-op.
13463 On target machines that have instruction caches, @value{GDBN} requires this
13464 function to make certain that the state of your program is stable.
13468 You must also make sure this library routine is available:
13471 @item void *memset(void *, int, int)
13473 This is the standard library function @code{memset} that sets an area of
13474 memory to a known value. If you have one of the free versions of
13475 @code{libc.a}, @code{memset} can be found there; otherwise, you must
13476 either obtain it from your hardware manufacturer, or write your own.
13479 If you do not use the GNU C compiler, you may need other standard
13480 library subroutines as well; this varies from one stub to another,
13481 but in general the stubs are likely to use any of the common library
13482 subroutines which @code{@value{NGCC}} generates as inline code.
13485 @node Debug Session
13486 @subsection Putting it All Together
13488 @cindex remote serial debugging summary
13489 In summary, when your program is ready to debug, you must follow these
13494 Make sure you have defined the supporting low-level routines
13495 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
13497 @code{getDebugChar}, @code{putDebugChar},
13498 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
13502 Insert these lines near the top of your program:
13510 For the 680x0 stub only, you need to provide a variable called
13511 @code{exceptionHook}. Normally you just use:
13514 void (*exceptionHook)() = 0;
13518 but if before calling @code{set_debug_traps}, you set it to point to a
13519 function in your program, that function is called when
13520 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
13521 error). The function indicated by @code{exceptionHook} is called with
13522 one parameter: an @code{int} which is the exception number.
13525 Compile and link together: your program, the @value{GDBN} debugging stub for
13526 your target architecture, and the supporting subroutines.
13529 Make sure you have a serial connection between your target machine and
13530 the @value{GDBN} host, and identify the serial port on the host.
13533 @c The "remote" target now provides a `load' command, so we should
13534 @c document that. FIXME.
13535 Download your program to your target machine (or get it there by
13536 whatever means the manufacturer provides), and start it.
13539 Start @value{GDBN} on the host, and connect to the target
13540 (@pxref{Connecting,,Connecting to a Remote Target}).
13544 @node Configurations
13545 @chapter Configuration-Specific Information
13547 While nearly all @value{GDBN} commands are available for all native and
13548 cross versions of the debugger, there are some exceptions. This chapter
13549 describes things that are only available in certain configurations.
13551 There are three major categories of configurations: native
13552 configurations, where the host and target are the same, embedded
13553 operating system configurations, which are usually the same for several
13554 different processor architectures, and bare embedded processors, which
13555 are quite different from each other.
13560 * Embedded Processors::
13567 This section describes details specific to particular native
13572 * BSD libkvm Interface:: Debugging BSD kernel memory images
13573 * SVR4 Process Information:: SVR4 process information
13574 * DJGPP Native:: Features specific to the DJGPP port
13575 * Cygwin Native:: Features specific to the Cygwin port
13576 * Hurd Native:: Features specific to @sc{gnu} Hurd
13577 * Neutrino:: Features specific to QNX Neutrino
13583 On HP-UX systems, if you refer to a function or variable name that
13584 begins with a dollar sign, @value{GDBN} searches for a user or system
13585 name first, before it searches for a convenience variable.
13588 @node BSD libkvm Interface
13589 @subsection BSD libkvm Interface
13592 @cindex kernel memory image
13593 @cindex kernel crash dump
13595 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
13596 interface that provides a uniform interface for accessing kernel virtual
13597 memory images, including live systems and crash dumps. @value{GDBN}
13598 uses this interface to allow you to debug live kernels and kernel crash
13599 dumps on many native BSD configurations. This is implemented as a
13600 special @code{kvm} debugging target. For debugging a live system, load
13601 the currently running kernel into @value{GDBN} and connect to the
13605 (@value{GDBP}) @b{target kvm}
13608 For debugging crash dumps, provide the file name of the crash dump as an
13612 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
13615 Once connected to the @code{kvm} target, the following commands are
13621 Set current context from the @dfn{Process Control Block} (PCB) address.
13624 Set current context from proc address. This command isn't available on
13625 modern FreeBSD systems.
13628 @node SVR4 Process Information
13629 @subsection SVR4 Process Information
13631 @cindex examine process image
13632 @cindex process info via @file{/proc}
13634 Many versions of SVR4 and compatible systems provide a facility called
13635 @samp{/proc} that can be used to examine the image of a running
13636 process using file-system subroutines. If @value{GDBN} is configured
13637 for an operating system with this facility, the command @code{info
13638 proc} is available to report information about the process running
13639 your program, or about any process running on your system. @code{info
13640 proc} works only on SVR4 systems that include the @code{procfs} code.
13641 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
13642 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
13648 @itemx info proc @var{process-id}
13649 Summarize available information about any running process. If a
13650 process ID is specified by @var{process-id}, display information about
13651 that process; otherwise display information about the program being
13652 debugged. The summary includes the debugged process ID, the command
13653 line used to invoke it, its current working directory, and its
13654 executable file's absolute file name.
13656 On some systems, @var{process-id} can be of the form
13657 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
13658 within a process. If the optional @var{pid} part is missing, it means
13659 a thread from the process being debugged (the leading @samp{/} still
13660 needs to be present, or else @value{GDBN} will interpret the number as
13661 a process ID rather than a thread ID).
13663 @item info proc mappings
13664 @cindex memory address space mappings
13665 Report the memory address space ranges accessible in the program, with
13666 information on whether the process has read, write, or execute access
13667 rights to each range. On @sc{gnu}/Linux systems, each memory range
13668 includes the object file which is mapped to that range, instead of the
13669 memory access rights to that range.
13671 @item info proc stat
13672 @itemx info proc status
13673 @cindex process detailed status information
13674 These subcommands are specific to @sc{gnu}/Linux systems. They show
13675 the process-related information, including the user ID and group ID;
13676 how many threads are there in the process; its virtual memory usage;
13677 the signals that are pending, blocked, and ignored; its TTY; its
13678 consumption of system and user time; its stack size; its @samp{nice}
13679 value; etc. For more information, see the @samp{proc} man page
13680 (type @kbd{man 5 proc} from your shell prompt).
13682 @item info proc all
13683 Show all the information about the process described under all of the
13684 above @code{info proc} subcommands.
13687 @comment These sub-options of 'info proc' were not included when
13688 @comment procfs.c was re-written. Keep their descriptions around
13689 @comment against the day when someone finds the time to put them back in.
13690 @kindex info proc times
13691 @item info proc times
13692 Starting time, user CPU time, and system CPU time for your program and
13695 @kindex info proc id
13697 Report on the process IDs related to your program: its own process ID,
13698 the ID of its parent, the process group ID, and the session ID.
13701 @item set procfs-trace
13702 @kindex set procfs-trace
13703 @cindex @code{procfs} API calls
13704 This command enables and disables tracing of @code{procfs} API calls.
13706 @item show procfs-trace
13707 @kindex show procfs-trace
13708 Show the current state of @code{procfs} API call tracing.
13710 @item set procfs-file @var{file}
13711 @kindex set procfs-file
13712 Tell @value{GDBN} to write @code{procfs} API trace to the named
13713 @var{file}. @value{GDBN} appends the trace info to the previous
13714 contents of the file. The default is to display the trace on the
13717 @item show procfs-file
13718 @kindex show procfs-file
13719 Show the file to which @code{procfs} API trace is written.
13721 @item proc-trace-entry
13722 @itemx proc-trace-exit
13723 @itemx proc-untrace-entry
13724 @itemx proc-untrace-exit
13725 @kindex proc-trace-entry
13726 @kindex proc-trace-exit
13727 @kindex proc-untrace-entry
13728 @kindex proc-untrace-exit
13729 These commands enable and disable tracing of entries into and exits
13730 from the @code{syscall} interface.
13733 @kindex info pidlist
13734 @cindex process list, QNX Neutrino
13735 For QNX Neutrino only, this command displays the list of all the
13736 processes and all the threads within each process.
13739 @kindex info meminfo
13740 @cindex mapinfo list, QNX Neutrino
13741 For QNX Neutrino only, this command displays the list of all mapinfos.
13745 @subsection Features for Debugging @sc{djgpp} Programs
13746 @cindex @sc{djgpp} debugging
13747 @cindex native @sc{djgpp} debugging
13748 @cindex MS-DOS-specific commands
13751 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
13752 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
13753 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
13754 top of real-mode DOS systems and their emulations.
13756 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
13757 defines a few commands specific to the @sc{djgpp} port. This
13758 subsection describes those commands.
13763 This is a prefix of @sc{djgpp}-specific commands which print
13764 information about the target system and important OS structures.
13767 @cindex MS-DOS system info
13768 @cindex free memory information (MS-DOS)
13769 @item info dos sysinfo
13770 This command displays assorted information about the underlying
13771 platform: the CPU type and features, the OS version and flavor, the
13772 DPMI version, and the available conventional and DPMI memory.
13777 @cindex segment descriptor tables
13778 @cindex descriptor tables display
13780 @itemx info dos ldt
13781 @itemx info dos idt
13782 These 3 commands display entries from, respectively, Global, Local,
13783 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
13784 tables are data structures which store a descriptor for each segment
13785 that is currently in use. The segment's selector is an index into a
13786 descriptor table; the table entry for that index holds the
13787 descriptor's base address and limit, and its attributes and access
13790 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
13791 segment (used for both data and the stack), and a DOS segment (which
13792 allows access to DOS/BIOS data structures and absolute addresses in
13793 conventional memory). However, the DPMI host will usually define
13794 additional segments in order to support the DPMI environment.
13796 @cindex garbled pointers
13797 These commands allow to display entries from the descriptor tables.
13798 Without an argument, all entries from the specified table are
13799 displayed. An argument, which should be an integer expression, means
13800 display a single entry whose index is given by the argument. For
13801 example, here's a convenient way to display information about the
13802 debugged program's data segment:
13805 @exdent @code{(@value{GDBP}) info dos ldt $ds}
13806 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
13810 This comes in handy when you want to see whether a pointer is outside
13811 the data segment's limit (i.e.@: @dfn{garbled}).
13813 @cindex page tables display (MS-DOS)
13815 @itemx info dos pte
13816 These two commands display entries from, respectively, the Page
13817 Directory and the Page Tables. Page Directories and Page Tables are
13818 data structures which control how virtual memory addresses are mapped
13819 into physical addresses. A Page Table includes an entry for every
13820 page of memory that is mapped into the program's address space; there
13821 may be several Page Tables, each one holding up to 4096 entries. A
13822 Page Directory has up to 4096 entries, one each for every Page Table
13823 that is currently in use.
13825 Without an argument, @kbd{info dos pde} displays the entire Page
13826 Directory, and @kbd{info dos pte} displays all the entries in all of
13827 the Page Tables. An argument, an integer expression, given to the
13828 @kbd{info dos pde} command means display only that entry from the Page
13829 Directory table. An argument given to the @kbd{info dos pte} command
13830 means display entries from a single Page Table, the one pointed to by
13831 the specified entry in the Page Directory.
13833 @cindex direct memory access (DMA) on MS-DOS
13834 These commands are useful when your program uses @dfn{DMA} (Direct
13835 Memory Access), which needs physical addresses to program the DMA
13838 These commands are supported only with some DPMI servers.
13840 @cindex physical address from linear address
13841 @item info dos address-pte @var{addr}
13842 This command displays the Page Table entry for a specified linear
13843 address. The argument @var{addr} is a linear address which should
13844 already have the appropriate segment's base address added to it,
13845 because this command accepts addresses which may belong to @emph{any}
13846 segment. For example, here's how to display the Page Table entry for
13847 the page where a variable @code{i} is stored:
13850 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
13851 @exdent @code{Page Table entry for address 0x11a00d30:}
13852 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
13856 This says that @code{i} is stored at offset @code{0xd30} from the page
13857 whose physical base address is @code{0x02698000}, and shows all the
13858 attributes of that page.
13860 Note that you must cast the addresses of variables to a @code{char *},
13861 since otherwise the value of @code{__djgpp_base_address}, the base
13862 address of all variables and functions in a @sc{djgpp} program, will
13863 be added using the rules of C pointer arithmetics: if @code{i} is
13864 declared an @code{int}, @value{GDBN} will add 4 times the value of
13865 @code{__djgpp_base_address} to the address of @code{i}.
13867 Here's another example, it displays the Page Table entry for the
13871 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
13872 @exdent @code{Page Table entry for address 0x29110:}
13873 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
13877 (The @code{+ 3} offset is because the transfer buffer's address is the
13878 3rd member of the @code{_go32_info_block} structure.) The output
13879 clearly shows that this DPMI server maps the addresses in conventional
13880 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
13881 linear (@code{0x29110}) addresses are identical.
13883 This command is supported only with some DPMI servers.
13886 @cindex DOS serial data link, remote debugging
13887 In addition to native debugging, the DJGPP port supports remote
13888 debugging via a serial data link. The following commands are specific
13889 to remote serial debugging in the DJGPP port of @value{GDBN}.
13892 @kindex set com1base
13893 @kindex set com1irq
13894 @kindex set com2base
13895 @kindex set com2irq
13896 @kindex set com3base
13897 @kindex set com3irq
13898 @kindex set com4base
13899 @kindex set com4irq
13900 @item set com1base @var{addr}
13901 This command sets the base I/O port address of the @file{COM1} serial
13904 @item set com1irq @var{irq}
13905 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
13906 for the @file{COM1} serial port.
13908 There are similar commands @samp{set com2base}, @samp{set com3irq},
13909 etc.@: for setting the port address and the @code{IRQ} lines for the
13912 @kindex show com1base
13913 @kindex show com1irq
13914 @kindex show com2base
13915 @kindex show com2irq
13916 @kindex show com3base
13917 @kindex show com3irq
13918 @kindex show com4base
13919 @kindex show com4irq
13920 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
13921 display the current settings of the base address and the @code{IRQ}
13922 lines used by the COM ports.
13925 @kindex info serial
13926 @cindex DOS serial port status
13927 This command prints the status of the 4 DOS serial ports. For each
13928 port, it prints whether it's active or not, its I/O base address and
13929 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
13930 counts of various errors encountered so far.
13934 @node Cygwin Native
13935 @subsection Features for Debugging MS Windows PE Executables
13936 @cindex MS Windows debugging
13937 @cindex native Cygwin debugging
13938 @cindex Cygwin-specific commands
13940 @value{GDBN} supports native debugging of MS Windows programs, including
13941 DLLs with and without symbolic debugging information. There are various
13942 additional Cygwin-specific commands, described in this section.
13943 Working with DLLs that have no debugging symbols is described in
13944 @ref{Non-debug DLL Symbols}.
13949 This is a prefix of MS Windows-specific commands which print
13950 information about the target system and important OS structures.
13952 @item info w32 selector
13953 This command displays information returned by
13954 the Win32 API @code{GetThreadSelectorEntry} function.
13955 It takes an optional argument that is evaluated to
13956 a long value to give the information about this given selector.
13957 Without argument, this command displays information
13958 about the six segment registers.
13962 This is a Cygwin-specific alias of @code{info shared}.
13964 @kindex dll-symbols
13966 This command loads symbols from a dll similarly to
13967 add-sym command but without the need to specify a base address.
13969 @kindex set cygwin-exceptions
13970 @cindex debugging the Cygwin DLL
13971 @cindex Cygwin DLL, debugging
13972 @item set cygwin-exceptions @var{mode}
13973 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
13974 happen inside the Cygwin DLL. If @var{mode} is @code{off},
13975 @value{GDBN} will delay recognition of exceptions, and may ignore some
13976 exceptions which seem to be caused by internal Cygwin DLL
13977 ``bookkeeping''. This option is meant primarily for debugging the
13978 Cygwin DLL itself; the default value is @code{off} to avoid annoying
13979 @value{GDBN} users with false @code{SIGSEGV} signals.
13981 @kindex show cygwin-exceptions
13982 @item show cygwin-exceptions
13983 Displays whether @value{GDBN} will break on exceptions that happen
13984 inside the Cygwin DLL itself.
13986 @kindex set new-console
13987 @item set new-console @var{mode}
13988 If @var{mode} is @code{on} the debuggee will
13989 be started in a new console on next start.
13990 If @var{mode} is @code{off}i, the debuggee will
13991 be started in the same console as the debugger.
13993 @kindex show new-console
13994 @item show new-console
13995 Displays whether a new console is used
13996 when the debuggee is started.
13998 @kindex set new-group
13999 @item set new-group @var{mode}
14000 This boolean value controls whether the debuggee should
14001 start a new group or stay in the same group as the debugger.
14002 This affects the way the Windows OS handles
14005 @kindex show new-group
14006 @item show new-group
14007 Displays current value of new-group boolean.
14009 @kindex set debugevents
14010 @item set debugevents
14011 This boolean value adds debug output concerning kernel events related
14012 to the debuggee seen by the debugger. This includes events that
14013 signal thread and process creation and exit, DLL loading and
14014 unloading, console interrupts, and debugging messages produced by the
14015 Windows @code{OutputDebugString} API call.
14017 @kindex set debugexec
14018 @item set debugexec
14019 This boolean value adds debug output concerning execute events
14020 (such as resume thread) seen by the debugger.
14022 @kindex set debugexceptions
14023 @item set debugexceptions
14024 This boolean value adds debug output concerning exceptions in the
14025 debuggee seen by the debugger.
14027 @kindex set debugmemory
14028 @item set debugmemory
14029 This boolean value adds debug output concerning debuggee memory reads
14030 and writes by the debugger.
14034 This boolean values specifies whether the debuggee is called
14035 via a shell or directly (default value is on).
14039 Displays if the debuggee will be started with a shell.
14044 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
14047 @node Non-debug DLL Symbols
14048 @subsubsection Support for DLLs without Debugging Symbols
14049 @cindex DLLs with no debugging symbols
14050 @cindex Minimal symbols and DLLs
14052 Very often on windows, some of the DLLs that your program relies on do
14053 not include symbolic debugging information (for example,
14054 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
14055 symbols in a DLL, it relies on the minimal amount of symbolic
14056 information contained in the DLL's export table. This section
14057 describes working with such symbols, known internally to @value{GDBN} as
14058 ``minimal symbols''.
14060 Note that before the debugged program has started execution, no DLLs
14061 will have been loaded. The easiest way around this problem is simply to
14062 start the program --- either by setting a breakpoint or letting the
14063 program run once to completion. It is also possible to force
14064 @value{GDBN} to load a particular DLL before starting the executable ---
14065 see the shared library information in @ref{Files}, or the
14066 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
14067 explicitly loading symbols from a DLL with no debugging information will
14068 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
14069 which may adversely affect symbol lookup performance.
14071 @subsubsection DLL Name Prefixes
14073 In keeping with the naming conventions used by the Microsoft debugging
14074 tools, DLL export symbols are made available with a prefix based on the
14075 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
14076 also entered into the symbol table, so @code{CreateFileA} is often
14077 sufficient. In some cases there will be name clashes within a program
14078 (particularly if the executable itself includes full debugging symbols)
14079 necessitating the use of the fully qualified name when referring to the
14080 contents of the DLL. Use single-quotes around the name to avoid the
14081 exclamation mark (``!'') being interpreted as a language operator.
14083 Note that the internal name of the DLL may be all upper-case, even
14084 though the file name of the DLL is lower-case, or vice-versa. Since
14085 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
14086 some confusion. If in doubt, try the @code{info functions} and
14087 @code{info variables} commands or even @code{maint print msymbols}
14088 (@pxref{Symbols}). Here's an example:
14091 (@value{GDBP}) info function CreateFileA
14092 All functions matching regular expression "CreateFileA":
14094 Non-debugging symbols:
14095 0x77e885f4 CreateFileA
14096 0x77e885f4 KERNEL32!CreateFileA
14100 (@value{GDBP}) info function !
14101 All functions matching regular expression "!":
14103 Non-debugging symbols:
14104 0x6100114c cygwin1!__assert
14105 0x61004034 cygwin1!_dll_crt0@@0
14106 0x61004240 cygwin1!dll_crt0(per_process *)
14110 @subsubsection Working with Minimal Symbols
14112 Symbols extracted from a DLL's export table do not contain very much
14113 type information. All that @value{GDBN} can do is guess whether a symbol
14114 refers to a function or variable depending on the linker section that
14115 contains the symbol. Also note that the actual contents of the memory
14116 contained in a DLL are not available unless the program is running. This
14117 means that you cannot examine the contents of a variable or disassemble
14118 a function within a DLL without a running program.
14120 Variables are generally treated as pointers and dereferenced
14121 automatically. For this reason, it is often necessary to prefix a
14122 variable name with the address-of operator (``&'') and provide explicit
14123 type information in the command. Here's an example of the type of
14127 (@value{GDBP}) print 'cygwin1!__argv'
14132 (@value{GDBP}) x 'cygwin1!__argv'
14133 0x10021610: "\230y\""
14136 And two possible solutions:
14139 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
14140 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
14144 (@value{GDBP}) x/2x &'cygwin1!__argv'
14145 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
14146 (@value{GDBP}) x/x 0x10021608
14147 0x10021608: 0x0022fd98
14148 (@value{GDBP}) x/s 0x0022fd98
14149 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
14152 Setting a break point within a DLL is possible even before the program
14153 starts execution. However, under these circumstances, @value{GDBN} can't
14154 examine the initial instructions of the function in order to skip the
14155 function's frame set-up code. You can work around this by using ``*&''
14156 to set the breakpoint at a raw memory address:
14159 (@value{GDBP}) break *&'python22!PyOS_Readline'
14160 Breakpoint 1 at 0x1e04eff0
14163 The author of these extensions is not entirely convinced that setting a
14164 break point within a shared DLL like @file{kernel32.dll} is completely
14168 @subsection Commands Specific to @sc{gnu} Hurd Systems
14169 @cindex @sc{gnu} Hurd debugging
14171 This subsection describes @value{GDBN} commands specific to the
14172 @sc{gnu} Hurd native debugging.
14177 @kindex set signals@r{, Hurd command}
14178 @kindex set sigs@r{, Hurd command}
14179 This command toggles the state of inferior signal interception by
14180 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
14181 affected by this command. @code{sigs} is a shorthand alias for
14186 @kindex show signals@r{, Hurd command}
14187 @kindex show sigs@r{, Hurd command}
14188 Show the current state of intercepting inferior's signals.
14190 @item set signal-thread
14191 @itemx set sigthread
14192 @kindex set signal-thread
14193 @kindex set sigthread
14194 This command tells @value{GDBN} which thread is the @code{libc} signal
14195 thread. That thread is run when a signal is delivered to a running
14196 process. @code{set sigthread} is the shorthand alias of @code{set
14199 @item show signal-thread
14200 @itemx show sigthread
14201 @kindex show signal-thread
14202 @kindex show sigthread
14203 These two commands show which thread will run when the inferior is
14204 delivered a signal.
14207 @kindex set stopped@r{, Hurd command}
14208 This commands tells @value{GDBN} that the inferior process is stopped,
14209 as with the @code{SIGSTOP} signal. The stopped process can be
14210 continued by delivering a signal to it.
14213 @kindex show stopped@r{, Hurd command}
14214 This command shows whether @value{GDBN} thinks the debuggee is
14217 @item set exceptions
14218 @kindex set exceptions@r{, Hurd command}
14219 Use this command to turn off trapping of exceptions in the inferior.
14220 When exception trapping is off, neither breakpoints nor
14221 single-stepping will work. To restore the default, set exception
14224 @item show exceptions
14225 @kindex show exceptions@r{, Hurd command}
14226 Show the current state of trapping exceptions in the inferior.
14228 @item set task pause
14229 @kindex set task@r{, Hurd commands}
14230 @cindex task attributes (@sc{gnu} Hurd)
14231 @cindex pause current task (@sc{gnu} Hurd)
14232 This command toggles task suspension when @value{GDBN} has control.
14233 Setting it to on takes effect immediately, and the task is suspended
14234 whenever @value{GDBN} gets control. Setting it to off will take
14235 effect the next time the inferior is continued. If this option is set
14236 to off, you can use @code{set thread default pause on} or @code{set
14237 thread pause on} (see below) to pause individual threads.
14239 @item show task pause
14240 @kindex show task@r{, Hurd commands}
14241 Show the current state of task suspension.
14243 @item set task detach-suspend-count
14244 @cindex task suspend count
14245 @cindex detach from task, @sc{gnu} Hurd
14246 This command sets the suspend count the task will be left with when
14247 @value{GDBN} detaches from it.
14249 @item show task detach-suspend-count
14250 Show the suspend count the task will be left with when detaching.
14252 @item set task exception-port
14253 @itemx set task excp
14254 @cindex task exception port, @sc{gnu} Hurd
14255 This command sets the task exception port to which @value{GDBN} will
14256 forward exceptions. The argument should be the value of the @dfn{send
14257 rights} of the task. @code{set task excp} is a shorthand alias.
14259 @item set noninvasive
14260 @cindex noninvasive task options
14261 This command switches @value{GDBN} to a mode that is the least
14262 invasive as far as interfering with the inferior is concerned. This
14263 is the same as using @code{set task pause}, @code{set exceptions}, and
14264 @code{set signals} to values opposite to the defaults.
14266 @item info send-rights
14267 @itemx info receive-rights
14268 @itemx info port-rights
14269 @itemx info port-sets
14270 @itemx info dead-names
14273 @cindex send rights, @sc{gnu} Hurd
14274 @cindex receive rights, @sc{gnu} Hurd
14275 @cindex port rights, @sc{gnu} Hurd
14276 @cindex port sets, @sc{gnu} Hurd
14277 @cindex dead names, @sc{gnu} Hurd
14278 These commands display information about, respectively, send rights,
14279 receive rights, port rights, port sets, and dead names of a task.
14280 There are also shorthand aliases: @code{info ports} for @code{info
14281 port-rights} and @code{info psets} for @code{info port-sets}.
14283 @item set thread pause
14284 @kindex set thread@r{, Hurd command}
14285 @cindex thread properties, @sc{gnu} Hurd
14286 @cindex pause current thread (@sc{gnu} Hurd)
14287 This command toggles current thread suspension when @value{GDBN} has
14288 control. Setting it to on takes effect immediately, and the current
14289 thread is suspended whenever @value{GDBN} gets control. Setting it to
14290 off will take effect the next time the inferior is continued.
14291 Normally, this command has no effect, since when @value{GDBN} has
14292 control, the whole task is suspended. However, if you used @code{set
14293 task pause off} (see above), this command comes in handy to suspend
14294 only the current thread.
14296 @item show thread pause
14297 @kindex show thread@r{, Hurd command}
14298 This command shows the state of current thread suspension.
14300 @item set thread run
14301 This command sets whether the current thread is allowed to run.
14303 @item show thread run
14304 Show whether the current thread is allowed to run.
14306 @item set thread detach-suspend-count
14307 @cindex thread suspend count, @sc{gnu} Hurd
14308 @cindex detach from thread, @sc{gnu} Hurd
14309 This command sets the suspend count @value{GDBN} will leave on a
14310 thread when detaching. This number is relative to the suspend count
14311 found by @value{GDBN} when it notices the thread; use @code{set thread
14312 takeover-suspend-count} to force it to an absolute value.
14314 @item show thread detach-suspend-count
14315 Show the suspend count @value{GDBN} will leave on the thread when
14318 @item set thread exception-port
14319 @itemx set thread excp
14320 Set the thread exception port to which to forward exceptions. This
14321 overrides the port set by @code{set task exception-port} (see above).
14322 @code{set thread excp} is the shorthand alias.
14324 @item set thread takeover-suspend-count
14325 Normally, @value{GDBN}'s thread suspend counts are relative to the
14326 value @value{GDBN} finds when it notices each thread. This command
14327 changes the suspend counts to be absolute instead.
14329 @item set thread default
14330 @itemx show thread default
14331 @cindex thread default settings, @sc{gnu} Hurd
14332 Each of the above @code{set thread} commands has a @code{set thread
14333 default} counterpart (e.g., @code{set thread default pause}, @code{set
14334 thread default exception-port}, etc.). The @code{thread default}
14335 variety of commands sets the default thread properties for all
14336 threads; you can then change the properties of individual threads with
14337 the non-default commands.
14342 @subsection QNX Neutrino
14343 @cindex QNX Neutrino
14345 @value{GDBN} provides the following commands specific to the QNX
14349 @item set debug nto-debug
14350 @kindex set debug nto-debug
14351 When set to on, enables debugging messages specific to the QNX
14354 @item show debug nto-debug
14355 @kindex show debug nto-debug
14356 Show the current state of QNX Neutrino messages.
14361 @section Embedded Operating Systems
14363 This section describes configurations involving the debugging of
14364 embedded operating systems that are available for several different
14368 * VxWorks:: Using @value{GDBN} with VxWorks
14371 @value{GDBN} includes the ability to debug programs running on
14372 various real-time operating systems.
14375 @subsection Using @value{GDBN} with VxWorks
14381 @kindex target vxworks
14382 @item target vxworks @var{machinename}
14383 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
14384 is the target system's machine name or IP address.
14388 On VxWorks, @code{load} links @var{filename} dynamically on the
14389 current target system as well as adding its symbols in @value{GDBN}.
14391 @value{GDBN} enables developers to spawn and debug tasks running on networked
14392 VxWorks targets from a Unix host. Already-running tasks spawned from
14393 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
14394 both the Unix host and on the VxWorks target. The program
14395 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
14396 installed with the name @code{vxgdb}, to distinguish it from a
14397 @value{GDBN} for debugging programs on the host itself.)
14400 @item VxWorks-timeout @var{args}
14401 @kindex vxworks-timeout
14402 All VxWorks-based targets now support the option @code{vxworks-timeout}.
14403 This option is set by the user, and @var{args} represents the number of
14404 seconds @value{GDBN} waits for responses to rpc's. You might use this if
14405 your VxWorks target is a slow software simulator or is on the far side
14406 of a thin network line.
14409 The following information on connecting to VxWorks was current when
14410 this manual was produced; newer releases of VxWorks may use revised
14413 @findex INCLUDE_RDB
14414 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
14415 to include the remote debugging interface routines in the VxWorks
14416 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
14417 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
14418 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
14419 source debugging task @code{tRdbTask} when VxWorks is booted. For more
14420 information on configuring and remaking VxWorks, see the manufacturer's
14422 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
14424 Once you have included @file{rdb.a} in your VxWorks system image and set
14425 your Unix execution search path to find @value{GDBN}, you are ready to
14426 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
14427 @code{vxgdb}, depending on your installation).
14429 @value{GDBN} comes up showing the prompt:
14436 * VxWorks Connection:: Connecting to VxWorks
14437 * VxWorks Download:: VxWorks download
14438 * VxWorks Attach:: Running tasks
14441 @node VxWorks Connection
14442 @subsubsection Connecting to VxWorks
14444 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
14445 network. To connect to a target whose host name is ``@code{tt}'', type:
14448 (vxgdb) target vxworks tt
14452 @value{GDBN} displays messages like these:
14455 Attaching remote machine across net...
14460 @value{GDBN} then attempts to read the symbol tables of any object modules
14461 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
14462 these files by searching the directories listed in the command search
14463 path (@pxref{Environment, ,Your Program's Environment}); if it fails
14464 to find an object file, it displays a message such as:
14467 prog.o: No such file or directory.
14470 When this happens, add the appropriate directory to the search path with
14471 the @value{GDBN} command @code{path}, and execute the @code{target}
14474 @node VxWorks Download
14475 @subsubsection VxWorks Download
14477 @cindex download to VxWorks
14478 If you have connected to the VxWorks target and you want to debug an
14479 object that has not yet been loaded, you can use the @value{GDBN}
14480 @code{load} command to download a file from Unix to VxWorks
14481 incrementally. The object file given as an argument to the @code{load}
14482 command is actually opened twice: first by the VxWorks target in order
14483 to download the code, then by @value{GDBN} in order to read the symbol
14484 table. This can lead to problems if the current working directories on
14485 the two systems differ. If both systems have NFS mounted the same
14486 filesystems, you can avoid these problems by using absolute paths.
14487 Otherwise, it is simplest to set the working directory on both systems
14488 to the directory in which the object file resides, and then to reference
14489 the file by its name, without any path. For instance, a program
14490 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
14491 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
14492 program, type this on VxWorks:
14495 -> cd "@var{vxpath}/vw/demo/rdb"
14499 Then, in @value{GDBN}, type:
14502 (vxgdb) cd @var{hostpath}/vw/demo/rdb
14503 (vxgdb) load prog.o
14506 @value{GDBN} displays a response similar to this:
14509 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
14512 You can also use the @code{load} command to reload an object module
14513 after editing and recompiling the corresponding source file. Note that
14514 this makes @value{GDBN} delete all currently-defined breakpoints,
14515 auto-displays, and convenience variables, and to clear the value
14516 history. (This is necessary in order to preserve the integrity of
14517 debugger's data structures that reference the target system's symbol
14520 @node VxWorks Attach
14521 @subsubsection Running Tasks
14523 @cindex running VxWorks tasks
14524 You can also attach to an existing task using the @code{attach} command as
14528 (vxgdb) attach @var{task}
14532 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
14533 or suspended when you attach to it. Running tasks are suspended at
14534 the time of attachment.
14536 @node Embedded Processors
14537 @section Embedded Processors
14539 This section goes into details specific to particular embedded
14542 @cindex send command to simulator
14543 Whenever a specific embedded processor has a simulator, @value{GDBN}
14544 allows to send an arbitrary command to the simulator.
14547 @item sim @var{command}
14548 @kindex sim@r{, a command}
14549 Send an arbitrary @var{command} string to the simulator. Consult the
14550 documentation for the specific simulator in use for information about
14551 acceptable commands.
14557 * M32R/D:: Renesas M32R/D
14558 * M68K:: Motorola M68K
14559 * MIPS Embedded:: MIPS Embedded
14560 * OpenRISC 1000:: OpenRisc 1000
14561 * PA:: HP PA Embedded
14562 * PowerPC:: PowerPC
14563 * Sparclet:: Tsqware Sparclet
14564 * Sparclite:: Fujitsu Sparclite
14565 * Z8000:: Zilog Z8000
14568 * Super-H:: Renesas Super-H
14577 @item target rdi @var{dev}
14578 ARM Angel monitor, via RDI library interface to ADP protocol. You may
14579 use this target to communicate with both boards running the Angel
14580 monitor, or with the EmbeddedICE JTAG debug device.
14583 @item target rdp @var{dev}
14588 @value{GDBN} provides the following ARM-specific commands:
14591 @item set arm disassembler
14593 This commands selects from a list of disassembly styles. The
14594 @code{"std"} style is the standard style.
14596 @item show arm disassembler
14598 Show the current disassembly style.
14600 @item set arm apcs32
14601 @cindex ARM 32-bit mode
14602 This command toggles ARM operation mode between 32-bit and 26-bit.
14604 @item show arm apcs32
14605 Display the current usage of the ARM 32-bit mode.
14607 @item set arm fpu @var{fputype}
14608 This command sets the ARM floating-point unit (FPU) type. The
14609 argument @var{fputype} can be one of these:
14613 Determine the FPU type by querying the OS ABI.
14615 Software FPU, with mixed-endian doubles on little-endian ARM
14618 GCC-compiled FPA co-processor.
14620 Software FPU with pure-endian doubles.
14626 Show the current type of the FPU.
14629 This command forces @value{GDBN} to use the specified ABI.
14632 Show the currently used ABI.
14634 @item set debug arm
14635 Toggle whether to display ARM-specific debugging messages from the ARM
14636 target support subsystem.
14638 @item show debug arm
14639 Show whether ARM-specific debugging messages are enabled.
14642 The following commands are available when an ARM target is debugged
14643 using the RDI interface:
14646 @item rdilogfile @r{[}@var{file}@r{]}
14648 @cindex ADP (Angel Debugger Protocol) logging
14649 Set the filename for the ADP (Angel Debugger Protocol) packet log.
14650 With an argument, sets the log file to the specified @var{file}. With
14651 no argument, show the current log file name. The default log file is
14654 @item rdilogenable @r{[}@var{arg}@r{]}
14655 @kindex rdilogenable
14656 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
14657 enables logging, with an argument 0 or @code{"no"} disables it. With
14658 no arguments displays the current setting. When logging is enabled,
14659 ADP packets exchanged between @value{GDBN} and the RDI target device
14660 are logged to a file.
14662 @item set rdiromatzero
14663 @kindex set rdiromatzero
14664 @cindex ROM at zero address, RDI
14665 Tell @value{GDBN} whether the target has ROM at address 0. If on,
14666 vector catching is disabled, so that zero address can be used. If off
14667 (the default), vector catching is enabled. For this command to take
14668 effect, it needs to be invoked prior to the @code{target rdi} command.
14670 @item show rdiromatzero
14671 @kindex show rdiromatzero
14672 Show the current setting of ROM at zero address.
14674 @item set rdiheartbeat
14675 @kindex set rdiheartbeat
14676 @cindex RDI heartbeat
14677 Enable or disable RDI heartbeat packets. It is not recommended to
14678 turn on this option, since it confuses ARM and EPI JTAG interface, as
14679 well as the Angel monitor.
14681 @item show rdiheartbeat
14682 @kindex show rdiheartbeat
14683 Show the setting of RDI heartbeat packets.
14688 @subsection Renesas M32R/D and M32R/SDI
14691 @kindex target m32r
14692 @item target m32r @var{dev}
14693 Renesas M32R/D ROM monitor.
14695 @kindex target m32rsdi
14696 @item target m32rsdi @var{dev}
14697 Renesas M32R SDI server, connected via parallel port to the board.
14700 The following @value{GDBN} commands are specific to the M32R monitor:
14703 @item set download-path @var{path}
14704 @kindex set download-path
14705 @cindex find downloadable @sc{srec} files (M32R)
14706 Set the default path for finding downloadable @sc{srec} files.
14708 @item show download-path
14709 @kindex show download-path
14710 Show the default path for downloadable @sc{srec} files.
14712 @item set board-address @var{addr}
14713 @kindex set board-address
14714 @cindex M32-EVA target board address
14715 Set the IP address for the M32R-EVA target board.
14717 @item show board-address
14718 @kindex show board-address
14719 Show the current IP address of the target board.
14721 @item set server-address @var{addr}
14722 @kindex set server-address
14723 @cindex download server address (M32R)
14724 Set the IP address for the download server, which is the @value{GDBN}'s
14727 @item show server-address
14728 @kindex show server-address
14729 Display the IP address of the download server.
14731 @item upload @r{[}@var{file}@r{]}
14732 @kindex upload@r{, M32R}
14733 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
14734 upload capability. If no @var{file} argument is given, the current
14735 executable file is uploaded.
14737 @item tload @r{[}@var{file}@r{]}
14738 @kindex tload@r{, M32R}
14739 Test the @code{upload} command.
14742 The following commands are available for M32R/SDI:
14747 @cindex reset SDI connection, M32R
14748 This command resets the SDI connection.
14752 This command shows the SDI connection status.
14755 @kindex debug_chaos
14756 @cindex M32R/Chaos debugging
14757 Instructs the remote that M32R/Chaos debugging is to be used.
14759 @item use_debug_dma
14760 @kindex use_debug_dma
14761 Instructs the remote to use the DEBUG_DMA method of accessing memory.
14764 @kindex use_mon_code
14765 Instructs the remote to use the MON_CODE method of accessing memory.
14768 @kindex use_ib_break
14769 Instructs the remote to set breakpoints by IB break.
14771 @item use_dbt_break
14772 @kindex use_dbt_break
14773 Instructs the remote to set breakpoints by DBT.
14779 The Motorola m68k configuration includes ColdFire support, and a
14780 target command for the following ROM monitor.
14784 @kindex target dbug
14785 @item target dbug @var{dev}
14786 dBUG ROM monitor for Motorola ColdFire.
14790 @node MIPS Embedded
14791 @subsection MIPS Embedded
14793 @cindex MIPS boards
14794 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
14795 MIPS board attached to a serial line. This is available when
14796 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
14799 Use these @value{GDBN} commands to specify the connection to your target board:
14802 @item target mips @var{port}
14803 @kindex target mips @var{port}
14804 To run a program on the board, start up @code{@value{GDBP}} with the
14805 name of your program as the argument. To connect to the board, use the
14806 command @samp{target mips @var{port}}, where @var{port} is the name of
14807 the serial port connected to the board. If the program has not already
14808 been downloaded to the board, you may use the @code{load} command to
14809 download it. You can then use all the usual @value{GDBN} commands.
14811 For example, this sequence connects to the target board through a serial
14812 port, and loads and runs a program called @var{prog} through the
14816 host$ @value{GDBP} @var{prog}
14817 @value{GDBN} is free software and @dots{}
14818 (@value{GDBP}) target mips /dev/ttyb
14819 (@value{GDBP}) load @var{prog}
14823 @item target mips @var{hostname}:@var{portnumber}
14824 On some @value{GDBN} host configurations, you can specify a TCP
14825 connection (for instance, to a serial line managed by a terminal
14826 concentrator) instead of a serial port, using the syntax
14827 @samp{@var{hostname}:@var{portnumber}}.
14829 @item target pmon @var{port}
14830 @kindex target pmon @var{port}
14833 @item target ddb @var{port}
14834 @kindex target ddb @var{port}
14835 NEC's DDB variant of PMON for Vr4300.
14837 @item target lsi @var{port}
14838 @kindex target lsi @var{port}
14839 LSI variant of PMON.
14841 @kindex target r3900
14842 @item target r3900 @var{dev}
14843 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
14845 @kindex target array
14846 @item target array @var{dev}
14847 Array Tech LSI33K RAID controller board.
14853 @value{GDBN} also supports these special commands for MIPS targets:
14856 @item set mipsfpu double
14857 @itemx set mipsfpu single
14858 @itemx set mipsfpu none
14859 @itemx set mipsfpu auto
14860 @itemx show mipsfpu
14861 @kindex set mipsfpu
14862 @kindex show mipsfpu
14863 @cindex MIPS remote floating point
14864 @cindex floating point, MIPS remote
14865 If your target board does not support the MIPS floating point
14866 coprocessor, you should use the command @samp{set mipsfpu none} (if you
14867 need this, you may wish to put the command in your @value{GDBN} init
14868 file). This tells @value{GDBN} how to find the return value of
14869 functions which return floating point values. It also allows
14870 @value{GDBN} to avoid saving the floating point registers when calling
14871 functions on the board. If you are using a floating point coprocessor
14872 with only single precision floating point support, as on the @sc{r4650}
14873 processor, use the command @samp{set mipsfpu single}. The default
14874 double precision floating point coprocessor may be selected using
14875 @samp{set mipsfpu double}.
14877 In previous versions the only choices were double precision or no
14878 floating point, so @samp{set mipsfpu on} will select double precision
14879 and @samp{set mipsfpu off} will select no floating point.
14881 As usual, you can inquire about the @code{mipsfpu} variable with
14882 @samp{show mipsfpu}.
14884 @item set timeout @var{seconds}
14885 @itemx set retransmit-timeout @var{seconds}
14886 @itemx show timeout
14887 @itemx show retransmit-timeout
14888 @cindex @code{timeout}, MIPS protocol
14889 @cindex @code{retransmit-timeout}, MIPS protocol
14890 @kindex set timeout
14891 @kindex show timeout
14892 @kindex set retransmit-timeout
14893 @kindex show retransmit-timeout
14894 You can control the timeout used while waiting for a packet, in the MIPS
14895 remote protocol, with the @code{set timeout @var{seconds}} command. The
14896 default is 5 seconds. Similarly, you can control the timeout used while
14897 waiting for an acknowledgement of a packet with the @code{set
14898 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
14899 You can inspect both values with @code{show timeout} and @code{show
14900 retransmit-timeout}. (These commands are @emph{only} available when
14901 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
14903 The timeout set by @code{set timeout} does not apply when @value{GDBN}
14904 is waiting for your program to stop. In that case, @value{GDBN} waits
14905 forever because it has no way of knowing how long the program is going
14906 to run before stopping.
14908 @item set syn-garbage-limit @var{num}
14909 @kindex set syn-garbage-limit@r{, MIPS remote}
14910 @cindex synchronize with remote MIPS target
14911 Limit the maximum number of characters @value{GDBN} should ignore when
14912 it tries to synchronize with the remote target. The default is 10
14913 characters. Setting the limit to -1 means there's no limit.
14915 @item show syn-garbage-limit
14916 @kindex show syn-garbage-limit@r{, MIPS remote}
14917 Show the current limit on the number of characters to ignore when
14918 trying to synchronize with the remote system.
14920 @item set monitor-prompt @var{prompt}
14921 @kindex set monitor-prompt@r{, MIPS remote}
14922 @cindex remote monitor prompt
14923 Tell @value{GDBN} to expect the specified @var{prompt} string from the
14924 remote monitor. The default depends on the target:
14934 @item show monitor-prompt
14935 @kindex show monitor-prompt@r{, MIPS remote}
14936 Show the current strings @value{GDBN} expects as the prompt from the
14939 @item set monitor-warnings
14940 @kindex set monitor-warnings@r{, MIPS remote}
14941 Enable or disable monitor warnings about hardware breakpoints. This
14942 has effect only for the @code{lsi} target. When on, @value{GDBN} will
14943 display warning messages whose codes are returned by the @code{lsi}
14944 PMON monitor for breakpoint commands.
14946 @item show monitor-warnings
14947 @kindex show monitor-warnings@r{, MIPS remote}
14948 Show the current setting of printing monitor warnings.
14950 @item pmon @var{command}
14951 @kindex pmon@r{, MIPS remote}
14952 @cindex send PMON command
14953 This command allows sending an arbitrary @var{command} string to the
14954 monitor. The monitor must be in debug mode for this to work.
14957 @node OpenRISC 1000
14958 @subsection OpenRISC 1000
14959 @cindex OpenRISC 1000
14961 @cindex or1k boards
14962 See OR1k Architecture document (@uref{www.opencores.org}) for more information
14963 about platform and commands.
14967 @kindex target jtag
14968 @item target jtag jtag://@var{host}:@var{port}
14970 Connects to remote JTAG server.
14971 JTAG remote server can be either an or1ksim or JTAG server,
14972 connected via parallel port to the board.
14974 Example: @code{target jtag jtag://localhost:9999}
14977 @item or1ksim @var{command}
14978 If connected to @code{or1ksim} OpenRISC 1000 Architectural
14979 Simulator, proprietary commands can be executed.
14981 @kindex info or1k spr
14982 @item info or1k spr
14983 Displays spr groups.
14985 @item info or1k spr @var{group}
14986 @itemx info or1k spr @var{groupno}
14987 Displays register names in selected group.
14989 @item info or1k spr @var{group} @var{register}
14990 @itemx info or1k spr @var{register}
14991 @itemx info or1k spr @var{groupno} @var{registerno}
14992 @itemx info or1k spr @var{registerno}
14993 Shows information about specified spr register.
14996 @item spr @var{group} @var{register} @var{value}
14997 @itemx spr @var{register @var{value}}
14998 @itemx spr @var{groupno} @var{registerno @var{value}}
14999 @itemx spr @var{registerno @var{value}}
15000 Writes @var{value} to specified spr register.
15003 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
15004 It is very similar to @value{GDBN} trace, except it does not interfere with normal
15005 program execution and is thus much faster. Hardware breakpoints/watchpoint
15006 triggers can be set using:
15009 Load effective address/data
15011 Store effective address/data
15013 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
15018 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
15019 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
15021 @code{htrace} commands:
15022 @cindex OpenRISC 1000 htrace
15025 @item hwatch @var{conditional}
15026 Set hardware watchpoint on combination of Load/Store Effective Address(es)
15027 or Data. For example:
15029 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
15031 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
15035 Display information about current HW trace configuration.
15037 @item htrace trigger @var{conditional}
15038 Set starting criteria for HW trace.
15040 @item htrace qualifier @var{conditional}
15041 Set acquisition qualifier for HW trace.
15043 @item htrace stop @var{conditional}
15044 Set HW trace stopping criteria.
15046 @item htrace record [@var{data}]*
15047 Selects the data to be recorded, when qualifier is met and HW trace was
15050 @item htrace enable
15051 @itemx htrace disable
15052 Enables/disables the HW trace.
15054 @item htrace rewind [@var{filename}]
15055 Clears currently recorded trace data.
15057 If filename is specified, new trace file is made and any newly collected data
15058 will be written there.
15060 @item htrace print [@var{start} [@var{len}]]
15061 Prints trace buffer, using current record configuration.
15063 @item htrace mode continuous
15064 Set continuous trace mode.
15066 @item htrace mode suspend
15067 Set suspend trace mode.
15072 @subsection PowerPC
15074 @value{GDBN} provides the following PowerPC-specific commands:
15077 @kindex set powerpc
15078 @item set powerpc soft-float
15079 @itemx show powerpc soft-float
15080 Force @value{GDBN} to use (or not use) a software floating point calling
15081 convention. By default, @value{GDBN} selects the calling convention based
15082 on the selected architecture and the provided executable file.
15084 @item set powerpc vector-abi
15085 @itemx show powerpc vector-abi
15086 Force @value{GDBN} to use the specified calling convention for vector
15087 arguments and return values. The valid options are @samp{auto};
15088 @samp{generic}, to avoid vector registers even if they are present;
15089 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
15090 registers. By default, @value{GDBN} selects the calling convention
15091 based on the selected architecture and the provided executable file.
15093 @kindex target dink32
15094 @item target dink32 @var{dev}
15095 DINK32 ROM monitor.
15097 @kindex target ppcbug
15098 @item target ppcbug @var{dev}
15099 @kindex target ppcbug1
15100 @item target ppcbug1 @var{dev}
15101 PPCBUG ROM monitor for PowerPC.
15104 @item target sds @var{dev}
15105 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
15108 @cindex SDS protocol
15109 The following commands specific to the SDS protocol are supported
15113 @item set sdstimeout @var{nsec}
15114 @kindex set sdstimeout
15115 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
15116 default is 2 seconds.
15118 @item show sdstimeout
15119 @kindex show sdstimeout
15120 Show the current value of the SDS timeout.
15122 @item sds @var{command}
15123 @kindex sds@r{, a command}
15124 Send the specified @var{command} string to the SDS monitor.
15129 @subsection HP PA Embedded
15133 @kindex target op50n
15134 @item target op50n @var{dev}
15135 OP50N monitor, running on an OKI HPPA board.
15137 @kindex target w89k
15138 @item target w89k @var{dev}
15139 W89K monitor, running on a Winbond HPPA board.
15144 @subsection Tsqware Sparclet
15148 @value{GDBN} enables developers to debug tasks running on
15149 Sparclet targets from a Unix host.
15150 @value{GDBN} uses code that runs on
15151 both the Unix host and on the Sparclet target. The program
15152 @code{@value{GDBP}} is installed and executed on the Unix host.
15155 @item remotetimeout @var{args}
15156 @kindex remotetimeout
15157 @value{GDBN} supports the option @code{remotetimeout}.
15158 This option is set by the user, and @var{args} represents the number of
15159 seconds @value{GDBN} waits for responses.
15162 @cindex compiling, on Sparclet
15163 When compiling for debugging, include the options @samp{-g} to get debug
15164 information and @samp{-Ttext} to relocate the program to where you wish to
15165 load it on the target. You may also want to add the options @samp{-n} or
15166 @samp{-N} in order to reduce the size of the sections. Example:
15169 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
15172 You can use @code{objdump} to verify that the addresses are what you intended:
15175 sparclet-aout-objdump --headers --syms prog
15178 @cindex running, on Sparclet
15180 your Unix execution search path to find @value{GDBN}, you are ready to
15181 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
15182 (or @code{sparclet-aout-gdb}, depending on your installation).
15184 @value{GDBN} comes up showing the prompt:
15191 * Sparclet File:: Setting the file to debug
15192 * Sparclet Connection:: Connecting to Sparclet
15193 * Sparclet Download:: Sparclet download
15194 * Sparclet Execution:: Running and debugging
15197 @node Sparclet File
15198 @subsubsection Setting File to Debug
15200 The @value{GDBN} command @code{file} lets you choose with program to debug.
15203 (gdbslet) file prog
15207 @value{GDBN} then attempts to read the symbol table of @file{prog}.
15208 @value{GDBN} locates
15209 the file by searching the directories listed in the command search
15211 If the file was compiled with debug information (option @samp{-g}), source
15212 files will be searched as well.
15213 @value{GDBN} locates
15214 the source files by searching the directories listed in the directory search
15215 path (@pxref{Environment, ,Your Program's Environment}).
15217 to find a file, it displays a message such as:
15220 prog: No such file or directory.
15223 When this happens, add the appropriate directories to the search paths with
15224 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
15225 @code{target} command again.
15227 @node Sparclet Connection
15228 @subsubsection Connecting to Sparclet
15230 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
15231 To connect to a target on serial port ``@code{ttya}'', type:
15234 (gdbslet) target sparclet /dev/ttya
15235 Remote target sparclet connected to /dev/ttya
15236 main () at ../prog.c:3
15240 @value{GDBN} displays messages like these:
15246 @node Sparclet Download
15247 @subsubsection Sparclet Download
15249 @cindex download to Sparclet
15250 Once connected to the Sparclet target,
15251 you can use the @value{GDBN}
15252 @code{load} command to download the file from the host to the target.
15253 The file name and load offset should be given as arguments to the @code{load}
15255 Since the file format is aout, the program must be loaded to the starting
15256 address. You can use @code{objdump} to find out what this value is. The load
15257 offset is an offset which is added to the VMA (virtual memory address)
15258 of each of the file's sections.
15259 For instance, if the program
15260 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
15261 and bss at 0x12010170, in @value{GDBN}, type:
15264 (gdbslet) load prog 0x12010000
15265 Loading section .text, size 0xdb0 vma 0x12010000
15268 If the code is loaded at a different address then what the program was linked
15269 to, you may need to use the @code{section} and @code{add-symbol-file} commands
15270 to tell @value{GDBN} where to map the symbol table.
15272 @node Sparclet Execution
15273 @subsubsection Running and Debugging
15275 @cindex running and debugging Sparclet programs
15276 You can now begin debugging the task using @value{GDBN}'s execution control
15277 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
15278 manual for the list of commands.
15282 Breakpoint 1 at 0x12010000: file prog.c, line 3.
15284 Starting program: prog
15285 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
15286 3 char *symarg = 0;
15288 4 char *execarg = "hello!";
15293 @subsection Fujitsu Sparclite
15297 @kindex target sparclite
15298 @item target sparclite @var{dev}
15299 Fujitsu sparclite boards, used only for the purpose of loading.
15300 You must use an additional command to debug the program.
15301 For example: target remote @var{dev} using @value{GDBN} standard
15307 @subsection Zilog Z8000
15310 @cindex simulator, Z8000
15311 @cindex Zilog Z8000 simulator
15313 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
15316 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
15317 unsegmented variant of the Z8000 architecture) or the Z8001 (the
15318 segmented variant). The simulator recognizes which architecture is
15319 appropriate by inspecting the object code.
15322 @item target sim @var{args}
15324 @kindex target sim@r{, with Z8000}
15325 Debug programs on a simulated CPU. If the simulator supports setup
15326 options, specify them via @var{args}.
15330 After specifying this target, you can debug programs for the simulated
15331 CPU in the same style as programs for your host computer; use the
15332 @code{file} command to load a new program image, the @code{run} command
15333 to run your program, and so on.
15335 As well as making available all the usual machine registers
15336 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
15337 additional items of information as specially named registers:
15342 Counts clock-ticks in the simulator.
15345 Counts instructions run in the simulator.
15348 Execution time in 60ths of a second.
15352 You can refer to these values in @value{GDBN} expressions with the usual
15353 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
15354 conditional breakpoint that suspends only after at least 5000
15355 simulated clock ticks.
15358 @subsection Atmel AVR
15361 When configured for debugging the Atmel AVR, @value{GDBN} supports the
15362 following AVR-specific commands:
15365 @item info io_registers
15366 @kindex info io_registers@r{, AVR}
15367 @cindex I/O registers (Atmel AVR)
15368 This command displays information about the AVR I/O registers. For
15369 each register, @value{GDBN} prints its number and value.
15376 When configured for debugging CRIS, @value{GDBN} provides the
15377 following CRIS-specific commands:
15380 @item set cris-version @var{ver}
15381 @cindex CRIS version
15382 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
15383 The CRIS version affects register names and sizes. This command is useful in
15384 case autodetection of the CRIS version fails.
15386 @item show cris-version
15387 Show the current CRIS version.
15389 @item set cris-dwarf2-cfi
15390 @cindex DWARF-2 CFI and CRIS
15391 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
15392 Change to @samp{off} when using @code{gcc-cris} whose version is below
15395 @item show cris-dwarf2-cfi
15396 Show the current state of using DWARF-2 CFI.
15398 @item set cris-mode @var{mode}
15400 Set the current CRIS mode to @var{mode}. It should only be changed when
15401 debugging in guru mode, in which case it should be set to
15402 @samp{guru} (the default is @samp{normal}).
15404 @item show cris-mode
15405 Show the current CRIS mode.
15409 @subsection Renesas Super-H
15412 For the Renesas Super-H processor, @value{GDBN} provides these
15417 @kindex regs@r{, Super-H}
15418 Show the values of all Super-H registers.
15422 @node Architectures
15423 @section Architectures
15425 This section describes characteristics of architectures that affect
15426 all uses of @value{GDBN} with the architecture, both native and cross.
15433 * HPPA:: HP PA architecture
15434 * SPU:: Cell Broadband Engine SPU architecture
15438 @subsection x86 Architecture-specific Issues
15441 @item set struct-convention @var{mode}
15442 @kindex set struct-convention
15443 @cindex struct return convention
15444 @cindex struct/union returned in registers
15445 Set the convention used by the inferior to return @code{struct}s and
15446 @code{union}s from functions to @var{mode}. Possible values of
15447 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
15448 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
15449 are returned on the stack, while @code{"reg"} means that a
15450 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
15451 be returned in a register.
15453 @item show struct-convention
15454 @kindex show struct-convention
15455 Show the current setting of the convention to return @code{struct}s
15464 @kindex set rstack_high_address
15465 @cindex AMD 29K register stack
15466 @cindex register stack, AMD29K
15467 @item set rstack_high_address @var{address}
15468 On AMD 29000 family processors, registers are saved in a separate
15469 @dfn{register stack}. There is no way for @value{GDBN} to determine the
15470 extent of this stack. Normally, @value{GDBN} just assumes that the
15471 stack is ``large enough''. This may result in @value{GDBN} referencing
15472 memory locations that do not exist. If necessary, you can get around
15473 this problem by specifying the ending address of the register stack with
15474 the @code{set rstack_high_address} command. The argument should be an
15475 address, which you probably want to precede with @samp{0x} to specify in
15478 @kindex show rstack_high_address
15479 @item show rstack_high_address
15480 Display the current limit of the register stack, on AMD 29000 family
15488 See the following section.
15493 @cindex stack on Alpha
15494 @cindex stack on MIPS
15495 @cindex Alpha stack
15497 Alpha- and MIPS-based computers use an unusual stack frame, which
15498 sometimes requires @value{GDBN} to search backward in the object code to
15499 find the beginning of a function.
15501 @cindex response time, MIPS debugging
15502 To improve response time (especially for embedded applications, where
15503 @value{GDBN} may be restricted to a slow serial line for this search)
15504 you may want to limit the size of this search, using one of these
15508 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
15509 @item set heuristic-fence-post @var{limit}
15510 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
15511 search for the beginning of a function. A value of @var{0} (the
15512 default) means there is no limit. However, except for @var{0}, the
15513 larger the limit the more bytes @code{heuristic-fence-post} must search
15514 and therefore the longer it takes to run. You should only need to use
15515 this command when debugging a stripped executable.
15517 @item show heuristic-fence-post
15518 Display the current limit.
15522 These commands are available @emph{only} when @value{GDBN} is configured
15523 for debugging programs on Alpha or MIPS processors.
15525 Several MIPS-specific commands are available when debugging MIPS
15529 @item set mips abi @var{arg}
15530 @kindex set mips abi
15531 @cindex set ABI for MIPS
15532 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
15533 values of @var{arg} are:
15537 The default ABI associated with the current binary (this is the
15548 @item show mips abi
15549 @kindex show mips abi
15550 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
15553 @itemx show mipsfpu
15554 @xref{MIPS Embedded, set mipsfpu}.
15556 @item set mips mask-address @var{arg}
15557 @kindex set mips mask-address
15558 @cindex MIPS addresses, masking
15559 This command determines whether the most-significant 32 bits of 64-bit
15560 MIPS addresses are masked off. The argument @var{arg} can be
15561 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
15562 setting, which lets @value{GDBN} determine the correct value.
15564 @item show mips mask-address
15565 @kindex show mips mask-address
15566 Show whether the upper 32 bits of MIPS addresses are masked off or
15569 @item set remote-mips64-transfers-32bit-regs
15570 @kindex set remote-mips64-transfers-32bit-regs
15571 This command controls compatibility with 64-bit MIPS targets that
15572 transfer data in 32-bit quantities. If you have an old MIPS 64 target
15573 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
15574 and 64 bits for other registers, set this option to @samp{on}.
15576 @item show remote-mips64-transfers-32bit-regs
15577 @kindex show remote-mips64-transfers-32bit-regs
15578 Show the current setting of compatibility with older MIPS 64 targets.
15580 @item set debug mips
15581 @kindex set debug mips
15582 This command turns on and off debugging messages for the MIPS-specific
15583 target code in @value{GDBN}.
15585 @item show debug mips
15586 @kindex show debug mips
15587 Show the current setting of MIPS debugging messages.
15593 @cindex HPPA support
15595 When @value{GDBN} is debugging the HP PA architecture, it provides the
15596 following special commands:
15599 @item set debug hppa
15600 @kindex set debug hppa
15601 This command determines whether HPPA architecture-specific debugging
15602 messages are to be displayed.
15604 @item show debug hppa
15605 Show whether HPPA debugging messages are displayed.
15607 @item maint print unwind @var{address}
15608 @kindex maint print unwind@r{, HPPA}
15609 This command displays the contents of the unwind table entry at the
15610 given @var{address}.
15616 @subsection Cell Broadband Engine SPU architecture
15617 @cindex Cell Broadband Engine
15620 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
15621 it provides the following special commands:
15624 @item info spu event
15626 Display SPU event facility status. Shows current event mask
15627 and pending event status.
15629 @item info spu signal
15630 Display SPU signal notification facility status. Shows pending
15631 signal-control word and signal notification mode of both signal
15632 notification channels.
15634 @item info spu mailbox
15635 Display SPU mailbox facility status. Shows all pending entries,
15636 in order of processing, in each of the SPU Write Outbound,
15637 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
15640 Display MFC DMA status. Shows all pending commands in the MFC
15641 DMA queue. For each entry, opcode, tag, class IDs, effective
15642 and local store addresses and transfer size are shown.
15644 @item info spu proxydma
15645 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
15646 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
15647 and local store addresses and transfer size are shown.
15652 @node Controlling GDB
15653 @chapter Controlling @value{GDBN}
15655 You can alter the way @value{GDBN} interacts with you by using the
15656 @code{set} command. For commands controlling how @value{GDBN} displays
15657 data, see @ref{Print Settings, ,Print Settings}. Other settings are
15662 * Editing:: Command editing
15663 * Command History:: Command history
15664 * Screen Size:: Screen size
15665 * Numbers:: Numbers
15666 * ABI:: Configuring the current ABI
15667 * Messages/Warnings:: Optional warnings and messages
15668 * Debugging Output:: Optional messages about internal happenings
15676 @value{GDBN} indicates its readiness to read a command by printing a string
15677 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
15678 can change the prompt string with the @code{set prompt} command. For
15679 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
15680 the prompt in one of the @value{GDBN} sessions so that you can always tell
15681 which one you are talking to.
15683 @emph{Note:} @code{set prompt} does not add a space for you after the
15684 prompt you set. This allows you to set a prompt which ends in a space
15685 or a prompt that does not.
15689 @item set prompt @var{newprompt}
15690 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
15692 @kindex show prompt
15694 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
15698 @section Command Editing
15700 @cindex command line editing
15702 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
15703 @sc{gnu} library provides consistent behavior for programs which provide a
15704 command line interface to the user. Advantages are @sc{gnu} Emacs-style
15705 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
15706 substitution, and a storage and recall of command history across
15707 debugging sessions.
15709 You may control the behavior of command line editing in @value{GDBN} with the
15710 command @code{set}.
15713 @kindex set editing
15716 @itemx set editing on
15717 Enable command line editing (enabled by default).
15719 @item set editing off
15720 Disable command line editing.
15722 @kindex show editing
15724 Show whether command line editing is enabled.
15727 @xref{Command Line Editing}, for more details about the Readline
15728 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
15729 encouraged to read that chapter.
15731 @node Command History
15732 @section Command History
15733 @cindex command history
15735 @value{GDBN} can keep track of the commands you type during your
15736 debugging sessions, so that you can be certain of precisely what
15737 happened. Use these commands to manage the @value{GDBN} command
15740 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
15741 package, to provide the history facility. @xref{Using History
15742 Interactively}, for the detailed description of the History library.
15744 To issue a command to @value{GDBN} without affecting certain aspects of
15745 the state which is seen by users, prefix it with @samp{server }
15746 (@pxref{Server Prefix}). This
15747 means that this command will not affect the command history, nor will it
15748 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
15749 pressed on a line by itself.
15751 @cindex @code{server}, command prefix
15752 The server prefix does not affect the recording of values into the value
15753 history; to print a value without recording it into the value history,
15754 use the @code{output} command instead of the @code{print} command.
15756 Here is the description of @value{GDBN} commands related to command
15760 @cindex history substitution
15761 @cindex history file
15762 @kindex set history filename
15763 @cindex @env{GDBHISTFILE}, environment variable
15764 @item set history filename @var{fname}
15765 Set the name of the @value{GDBN} command history file to @var{fname}.
15766 This is the file where @value{GDBN} reads an initial command history
15767 list, and where it writes the command history from this session when it
15768 exits. You can access this list through history expansion or through
15769 the history command editing characters listed below. This file defaults
15770 to the value of the environment variable @code{GDBHISTFILE}, or to
15771 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
15774 @cindex save command history
15775 @kindex set history save
15776 @item set history save
15777 @itemx set history save on
15778 Record command history in a file, whose name may be specified with the
15779 @code{set history filename} command. By default, this option is disabled.
15781 @item set history save off
15782 Stop recording command history in a file.
15784 @cindex history size
15785 @kindex set history size
15786 @cindex @env{HISTSIZE}, environment variable
15787 @item set history size @var{size}
15788 Set the number of commands which @value{GDBN} keeps in its history list.
15789 This defaults to the value of the environment variable
15790 @code{HISTSIZE}, or to 256 if this variable is not set.
15793 History expansion assigns special meaning to the character @kbd{!}.
15794 @xref{Event Designators}, for more details.
15796 @cindex history expansion, turn on/off
15797 Since @kbd{!} is also the logical not operator in C, history expansion
15798 is off by default. If you decide to enable history expansion with the
15799 @code{set history expansion on} command, you may sometimes need to
15800 follow @kbd{!} (when it is used as logical not, in an expression) with
15801 a space or a tab to prevent it from being expanded. The readline
15802 history facilities do not attempt substitution on the strings
15803 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
15805 The commands to control history expansion are:
15808 @item set history expansion on
15809 @itemx set history expansion
15810 @kindex set history expansion
15811 Enable history expansion. History expansion is off by default.
15813 @item set history expansion off
15814 Disable history expansion.
15817 @kindex show history
15819 @itemx show history filename
15820 @itemx show history save
15821 @itemx show history size
15822 @itemx show history expansion
15823 These commands display the state of the @value{GDBN} history parameters.
15824 @code{show history} by itself displays all four states.
15829 @kindex show commands
15830 @cindex show last commands
15831 @cindex display command history
15832 @item show commands
15833 Display the last ten commands in the command history.
15835 @item show commands @var{n}
15836 Print ten commands centered on command number @var{n}.
15838 @item show commands +
15839 Print ten commands just after the commands last printed.
15843 @section Screen Size
15844 @cindex size of screen
15845 @cindex pauses in output
15847 Certain commands to @value{GDBN} may produce large amounts of
15848 information output to the screen. To help you read all of it,
15849 @value{GDBN} pauses and asks you for input at the end of each page of
15850 output. Type @key{RET} when you want to continue the output, or @kbd{q}
15851 to discard the remaining output. Also, the screen width setting
15852 determines when to wrap lines of output. Depending on what is being
15853 printed, @value{GDBN} tries to break the line at a readable place,
15854 rather than simply letting it overflow onto the following line.
15856 Normally @value{GDBN} knows the size of the screen from the terminal
15857 driver software. For example, on Unix @value{GDBN} uses the termcap data base
15858 together with the value of the @code{TERM} environment variable and the
15859 @code{stty rows} and @code{stty cols} settings. If this is not correct,
15860 you can override it with the @code{set height} and @code{set
15867 @kindex show height
15868 @item set height @var{lpp}
15870 @itemx set width @var{cpl}
15872 These @code{set} commands specify a screen height of @var{lpp} lines and
15873 a screen width of @var{cpl} characters. The associated @code{show}
15874 commands display the current settings.
15876 If you specify a height of zero lines, @value{GDBN} does not pause during
15877 output no matter how long the output is. This is useful if output is to a
15878 file or to an editor buffer.
15880 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
15881 from wrapping its output.
15883 @item set pagination on
15884 @itemx set pagination off
15885 @kindex set pagination
15886 Turn the output pagination on or off; the default is on. Turning
15887 pagination off is the alternative to @code{set height 0}.
15889 @item show pagination
15890 @kindex show pagination
15891 Show the current pagination mode.
15896 @cindex number representation
15897 @cindex entering numbers
15899 You can always enter numbers in octal, decimal, or hexadecimal in
15900 @value{GDBN} by the usual conventions: octal numbers begin with
15901 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
15902 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
15903 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
15904 10; likewise, the default display for numbers---when no particular
15905 format is specified---is base 10. You can change the default base for
15906 both input and output with the commands described below.
15909 @kindex set input-radix
15910 @item set input-radix @var{base}
15911 Set the default base for numeric input. Supported choices
15912 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15913 specified either unambiguously or using the current input radix; for
15917 set input-radix 012
15918 set input-radix 10.
15919 set input-radix 0xa
15923 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
15924 leaves the input radix unchanged, no matter what it was, since
15925 @samp{10}, being without any leading or trailing signs of its base, is
15926 interpreted in the current radix. Thus, if the current radix is 16,
15927 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
15930 @kindex set output-radix
15931 @item set output-radix @var{base}
15932 Set the default base for numeric display. Supported choices
15933 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15934 specified either unambiguously or using the current input radix.
15936 @kindex show input-radix
15937 @item show input-radix
15938 Display the current default base for numeric input.
15940 @kindex show output-radix
15941 @item show output-radix
15942 Display the current default base for numeric display.
15944 @item set radix @r{[}@var{base}@r{]}
15948 These commands set and show the default base for both input and output
15949 of numbers. @code{set radix} sets the radix of input and output to
15950 the same base; without an argument, it resets the radix back to its
15951 default value of 10.
15956 @section Configuring the Current ABI
15958 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
15959 application automatically. However, sometimes you need to override its
15960 conclusions. Use these commands to manage @value{GDBN}'s view of the
15967 One @value{GDBN} configuration can debug binaries for multiple operating
15968 system targets, either via remote debugging or native emulation.
15969 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
15970 but you can override its conclusion using the @code{set osabi} command.
15971 One example where this is useful is in debugging of binaries which use
15972 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
15973 not have the same identifying marks that the standard C library for your
15978 Show the OS ABI currently in use.
15981 With no argument, show the list of registered available OS ABI's.
15983 @item set osabi @var{abi}
15984 Set the current OS ABI to @var{abi}.
15987 @cindex float promotion
15989 Generally, the way that an argument of type @code{float} is passed to a
15990 function depends on whether the function is prototyped. For a prototyped
15991 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
15992 according to the architecture's convention for @code{float}. For unprototyped
15993 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
15994 @code{double} and then passed.
15996 Unfortunately, some forms of debug information do not reliably indicate whether
15997 a function is prototyped. If @value{GDBN} calls a function that is not marked
15998 as prototyped, it consults @kbd{set coerce-float-to-double}.
16001 @kindex set coerce-float-to-double
16002 @item set coerce-float-to-double
16003 @itemx set coerce-float-to-double on
16004 Arguments of type @code{float} will be promoted to @code{double} when passed
16005 to an unprototyped function. This is the default setting.
16007 @item set coerce-float-to-double off
16008 Arguments of type @code{float} will be passed directly to unprototyped
16011 @kindex show coerce-float-to-double
16012 @item show coerce-float-to-double
16013 Show the current setting of promoting @code{float} to @code{double}.
16017 @kindex show cp-abi
16018 @value{GDBN} needs to know the ABI used for your program's C@t{++}
16019 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
16020 used to build your application. @value{GDBN} only fully supports
16021 programs with a single C@t{++} ABI; if your program contains code using
16022 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
16023 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
16024 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
16025 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
16026 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
16027 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
16032 Show the C@t{++} ABI currently in use.
16035 With no argument, show the list of supported C@t{++} ABI's.
16037 @item set cp-abi @var{abi}
16038 @itemx set cp-abi auto
16039 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
16042 @node Messages/Warnings
16043 @section Optional Warnings and Messages
16045 @cindex verbose operation
16046 @cindex optional warnings
16047 By default, @value{GDBN} is silent about its inner workings. If you are
16048 running on a slow machine, you may want to use the @code{set verbose}
16049 command. This makes @value{GDBN} tell you when it does a lengthy
16050 internal operation, so you will not think it has crashed.
16052 Currently, the messages controlled by @code{set verbose} are those
16053 which announce that the symbol table for a source file is being read;
16054 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
16057 @kindex set verbose
16058 @item set verbose on
16059 Enables @value{GDBN} output of certain informational messages.
16061 @item set verbose off
16062 Disables @value{GDBN} output of certain informational messages.
16064 @kindex show verbose
16066 Displays whether @code{set verbose} is on or off.
16069 By default, if @value{GDBN} encounters bugs in the symbol table of an
16070 object file, it is silent; but if you are debugging a compiler, you may
16071 find this information useful (@pxref{Symbol Errors, ,Errors Reading
16076 @kindex set complaints
16077 @item set complaints @var{limit}
16078 Permits @value{GDBN} to output @var{limit} complaints about each type of
16079 unusual symbols before becoming silent about the problem. Set
16080 @var{limit} to zero to suppress all complaints; set it to a large number
16081 to prevent complaints from being suppressed.
16083 @kindex show complaints
16084 @item show complaints
16085 Displays how many symbol complaints @value{GDBN} is permitted to produce.
16089 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
16090 lot of stupid questions to confirm certain commands. For example, if
16091 you try to run a program which is already running:
16095 The program being debugged has been started already.
16096 Start it from the beginning? (y or n)
16099 If you are willing to unflinchingly face the consequences of your own
16100 commands, you can disable this ``feature'':
16104 @kindex set confirm
16106 @cindex confirmation
16107 @cindex stupid questions
16108 @item set confirm off
16109 Disables confirmation requests.
16111 @item set confirm on
16112 Enables confirmation requests (the default).
16114 @kindex show confirm
16116 Displays state of confirmation requests.
16120 @cindex command tracing
16121 If you need to debug user-defined commands or sourced files you may find it
16122 useful to enable @dfn{command tracing}. In this mode each command will be
16123 printed as it is executed, prefixed with one or more @samp{+} symbols, the
16124 quantity denoting the call depth of each command.
16127 @kindex set trace-commands
16128 @cindex command scripts, debugging
16129 @item set trace-commands on
16130 Enable command tracing.
16131 @item set trace-commands off
16132 Disable command tracing.
16133 @item show trace-commands
16134 Display the current state of command tracing.
16137 @node Debugging Output
16138 @section Optional Messages about Internal Happenings
16139 @cindex optional debugging messages
16141 @value{GDBN} has commands that enable optional debugging messages from
16142 various @value{GDBN} subsystems; normally these commands are of
16143 interest to @value{GDBN} maintainers, or when reporting a bug. This
16144 section documents those commands.
16147 @kindex set exec-done-display
16148 @item set exec-done-display
16149 Turns on or off the notification of asynchronous commands'
16150 completion. When on, @value{GDBN} will print a message when an
16151 asynchronous command finishes its execution. The default is off.
16152 @kindex show exec-done-display
16153 @item show exec-done-display
16154 Displays the current setting of asynchronous command completion
16157 @cindex gdbarch debugging info
16158 @cindex architecture debugging info
16159 @item set debug arch
16160 Turns on or off display of gdbarch debugging info. The default is off
16162 @item show debug arch
16163 Displays the current state of displaying gdbarch debugging info.
16164 @item set debug aix-thread
16165 @cindex AIX threads
16166 Display debugging messages about inner workings of the AIX thread
16168 @item show debug aix-thread
16169 Show the current state of AIX thread debugging info display.
16170 @item set debug event
16171 @cindex event debugging info
16172 Turns on or off display of @value{GDBN} event debugging info. The
16174 @item show debug event
16175 Displays the current state of displaying @value{GDBN} event debugging
16177 @item set debug expression
16178 @cindex expression debugging info
16179 Turns on or off display of debugging info about @value{GDBN}
16180 expression parsing. The default is off.
16181 @item show debug expression
16182 Displays the current state of displaying debugging info about
16183 @value{GDBN} expression parsing.
16184 @item set debug frame
16185 @cindex frame debugging info
16186 Turns on or off display of @value{GDBN} frame debugging info. The
16188 @item show debug frame
16189 Displays the current state of displaying @value{GDBN} frame debugging
16191 @item set debug infrun
16192 @cindex inferior debugging info
16193 Turns on or off display of @value{GDBN} debugging info for running the inferior.
16194 The default is off. @file{infrun.c} contains GDB's runtime state machine used
16195 for implementing operations such as single-stepping the inferior.
16196 @item show debug infrun
16197 Displays the current state of @value{GDBN} inferior debugging.
16198 @item set debug lin-lwp
16199 @cindex @sc{gnu}/Linux LWP debug messages
16200 @cindex Linux lightweight processes
16201 Turns on or off debugging messages from the Linux LWP debug support.
16202 @item show debug lin-lwp
16203 Show the current state of Linux LWP debugging messages.
16204 @item set debug observer
16205 @cindex observer debugging info
16206 Turns on or off display of @value{GDBN} observer debugging. This
16207 includes info such as the notification of observable events.
16208 @item show debug observer
16209 Displays the current state of observer debugging.
16210 @item set debug overload
16211 @cindex C@t{++} overload debugging info
16212 Turns on or off display of @value{GDBN} C@t{++} overload debugging
16213 info. This includes info such as ranking of functions, etc. The default
16215 @item show debug overload
16216 Displays the current state of displaying @value{GDBN} C@t{++} overload
16218 @cindex packets, reporting on stdout
16219 @cindex serial connections, debugging
16220 @cindex debug remote protocol
16221 @cindex remote protocol debugging
16222 @cindex display remote packets
16223 @item set debug remote
16224 Turns on or off display of reports on all packets sent back and forth across
16225 the serial line to the remote machine. The info is printed on the
16226 @value{GDBN} standard output stream. The default is off.
16227 @item show debug remote
16228 Displays the state of display of remote packets.
16229 @item set debug serial
16230 Turns on or off display of @value{GDBN} serial debugging info. The
16232 @item show debug serial
16233 Displays the current state of displaying @value{GDBN} serial debugging
16235 @item set debug solib-frv
16236 @cindex FR-V shared-library debugging
16237 Turns on or off debugging messages for FR-V shared-library code.
16238 @item show debug solib-frv
16239 Display the current state of FR-V shared-library code debugging
16241 @item set debug target
16242 @cindex target debugging info
16243 Turns on or off display of @value{GDBN} target debugging info. This info
16244 includes what is going on at the target level of GDB, as it happens. The
16245 default is 0. Set it to 1 to track events, and to 2 to also track the
16246 value of large memory transfers. Changes to this flag do not take effect
16247 until the next time you connect to a target or use the @code{run} command.
16248 @item show debug target
16249 Displays the current state of displaying @value{GDBN} target debugging
16251 @item set debugvarobj
16252 @cindex variable object debugging info
16253 Turns on or off display of @value{GDBN} variable object debugging
16254 info. The default is off.
16255 @item show debugvarobj
16256 Displays the current state of displaying @value{GDBN} variable object
16258 @item set debug xml
16259 @cindex XML parser debugging
16260 Turns on or off debugging messages for built-in XML parsers.
16261 @item show debug xml
16262 Displays the current state of XML debugging messages.
16266 @chapter Canned Sequences of Commands
16268 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
16269 Command Lists}), @value{GDBN} provides two ways to store sequences of
16270 commands for execution as a unit: user-defined commands and command
16274 * Define:: How to define your own commands
16275 * Hooks:: Hooks for user-defined commands
16276 * Command Files:: How to write scripts of commands to be stored in a file
16277 * Output:: Commands for controlled output
16281 @section User-defined Commands
16283 @cindex user-defined command
16284 @cindex arguments, to user-defined commands
16285 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
16286 which you assign a new name as a command. This is done with the
16287 @code{define} command. User commands may accept up to 10 arguments
16288 separated by whitespace. Arguments are accessed within the user command
16289 via @code{$arg0@dots{}$arg9}. A trivial example:
16293 print $arg0 + $arg1 + $arg2
16298 To execute the command use:
16305 This defines the command @code{adder}, which prints the sum of
16306 its three arguments. Note the arguments are text substitutions, so they may
16307 reference variables, use complex expressions, or even perform inferior
16310 @cindex argument count in user-defined commands
16311 @cindex how many arguments (user-defined commands)
16312 In addition, @code{$argc} may be used to find out how many arguments have
16313 been passed. This expands to a number in the range 0@dots{}10.
16318 print $arg0 + $arg1
16321 print $arg0 + $arg1 + $arg2
16329 @item define @var{commandname}
16330 Define a command named @var{commandname}. If there is already a command
16331 by that name, you are asked to confirm that you want to redefine it.
16333 The definition of the command is made up of other @value{GDBN} command lines,
16334 which are given following the @code{define} command. The end of these
16335 commands is marked by a line containing @code{end}.
16338 @kindex end@r{ (user-defined commands)}
16339 @item document @var{commandname}
16340 Document the user-defined command @var{commandname}, so that it can be
16341 accessed by @code{help}. The command @var{commandname} must already be
16342 defined. This command reads lines of documentation just as @code{define}
16343 reads the lines of the command definition, ending with @code{end}.
16344 After the @code{document} command is finished, @code{help} on command
16345 @var{commandname} displays the documentation you have written.
16347 You may use the @code{document} command again to change the
16348 documentation of a command. Redefining the command with @code{define}
16349 does not change the documentation.
16351 @kindex dont-repeat
16352 @cindex don't repeat command
16354 Used inside a user-defined command, this tells @value{GDBN} that this
16355 command should not be repeated when the user hits @key{RET}
16356 (@pxref{Command Syntax, repeat last command}).
16358 @kindex help user-defined
16359 @item help user-defined
16360 List all user-defined commands, with the first line of the documentation
16365 @itemx show user @var{commandname}
16366 Display the @value{GDBN} commands used to define @var{commandname} (but
16367 not its documentation). If no @var{commandname} is given, display the
16368 definitions for all user-defined commands.
16370 @cindex infinite recursion in user-defined commands
16371 @kindex show max-user-call-depth
16372 @kindex set max-user-call-depth
16373 @item show max-user-call-depth
16374 @itemx set max-user-call-depth
16375 The value of @code{max-user-call-depth} controls how many recursion
16376 levels are allowed in user-defined commands before @value{GDBN} suspects an
16377 infinite recursion and aborts the command.
16380 In addition to the above commands, user-defined commands frequently
16381 use control flow commands, described in @ref{Command Files}.
16383 When user-defined commands are executed, the
16384 commands of the definition are not printed. An error in any command
16385 stops execution of the user-defined command.
16387 If used interactively, commands that would ask for confirmation proceed
16388 without asking when used inside a user-defined command. Many @value{GDBN}
16389 commands that normally print messages to say what they are doing omit the
16390 messages when used in a user-defined command.
16393 @section User-defined Command Hooks
16394 @cindex command hooks
16395 @cindex hooks, for commands
16396 @cindex hooks, pre-command
16399 You may define @dfn{hooks}, which are a special kind of user-defined
16400 command. Whenever you run the command @samp{foo}, if the user-defined
16401 command @samp{hook-foo} exists, it is executed (with no arguments)
16402 before that command.
16404 @cindex hooks, post-command
16406 A hook may also be defined which is run after the command you executed.
16407 Whenever you run the command @samp{foo}, if the user-defined command
16408 @samp{hookpost-foo} exists, it is executed (with no arguments) after
16409 that command. Post-execution hooks may exist simultaneously with
16410 pre-execution hooks, for the same command.
16412 It is valid for a hook to call the command which it hooks. If this
16413 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
16415 @c It would be nice if hookpost could be passed a parameter indicating
16416 @c if the command it hooks executed properly or not. FIXME!
16418 @kindex stop@r{, a pseudo-command}
16419 In addition, a pseudo-command, @samp{stop} exists. Defining
16420 (@samp{hook-stop}) makes the associated commands execute every time
16421 execution stops in your program: before breakpoint commands are run,
16422 displays are printed, or the stack frame is printed.
16424 For example, to ignore @code{SIGALRM} signals while
16425 single-stepping, but treat them normally during normal execution,
16430 handle SIGALRM nopass
16434 handle SIGALRM pass
16437 define hook-continue
16438 handle SIGALRM pass
16442 As a further example, to hook at the beginning and end of the @code{echo}
16443 command, and to add extra text to the beginning and end of the message,
16451 define hookpost-echo
16455 (@value{GDBP}) echo Hello World
16456 <<<---Hello World--->>>
16461 You can define a hook for any single-word command in @value{GDBN}, but
16462 not for command aliases; you should define a hook for the basic command
16463 name, e.g.@: @code{backtrace} rather than @code{bt}.
16464 @c FIXME! So how does Joe User discover whether a command is an alias
16466 If an error occurs during the execution of your hook, execution of
16467 @value{GDBN} commands stops and @value{GDBN} issues a prompt
16468 (before the command that you actually typed had a chance to run).
16470 If you try to define a hook which does not match any known command, you
16471 get a warning from the @code{define} command.
16473 @node Command Files
16474 @section Command Files
16476 @cindex command files
16477 @cindex scripting commands
16478 A command file for @value{GDBN} is a text file made of lines that are
16479 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
16480 also be included. An empty line in a command file does nothing; it
16481 does not mean to repeat the last command, as it would from the
16484 You can request the execution of a command file with the @code{source}
16489 @cindex execute commands from a file
16490 @item source [@code{-v}] @var{filename}
16491 Execute the command file @var{filename}.
16494 The lines in a command file are generally executed sequentially,
16495 unless the order of execution is changed by one of the
16496 @emph{flow-control commands} described below. The commands are not
16497 printed as they are executed. An error in any command terminates
16498 execution of the command file and control is returned to the console.
16500 @value{GDBN} searches for @var{filename} in the current directory and then
16501 on the search path (specified with the @samp{directory} command).
16503 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
16504 each command as it is executed. The option must be given before
16505 @var{filename}, and is interpreted as part of the filename anywhere else.
16507 Commands that would ask for confirmation if used interactively proceed
16508 without asking when used in a command file. Many @value{GDBN} commands that
16509 normally print messages to say what they are doing omit the messages
16510 when called from command files.
16512 @value{GDBN} also accepts command input from standard input. In this
16513 mode, normal output goes to standard output and error output goes to
16514 standard error. Errors in a command file supplied on standard input do
16515 not terminate execution of the command file---execution continues with
16519 gdb < cmds > log 2>&1
16522 (The syntax above will vary depending on the shell used.) This example
16523 will execute commands from the file @file{cmds}. All output and errors
16524 would be directed to @file{log}.
16526 Since commands stored on command files tend to be more general than
16527 commands typed interactively, they frequently need to deal with
16528 complicated situations, such as different or unexpected values of
16529 variables and symbols, changes in how the program being debugged is
16530 built, etc. @value{GDBN} provides a set of flow-control commands to
16531 deal with these complexities. Using these commands, you can write
16532 complex scripts that loop over data structures, execute commands
16533 conditionally, etc.
16540 This command allows to include in your script conditionally executed
16541 commands. The @code{if} command takes a single argument, which is an
16542 expression to evaluate. It is followed by a series of commands that
16543 are executed only if the expression is true (its value is nonzero).
16544 There can then optionally be an @code{else} line, followed by a series
16545 of commands that are only executed if the expression was false. The
16546 end of the list is marked by a line containing @code{end}.
16550 This command allows to write loops. Its syntax is similar to
16551 @code{if}: the command takes a single argument, which is an expression
16552 to evaluate, and must be followed by the commands to execute, one per
16553 line, terminated by an @code{end}. These commands are called the
16554 @dfn{body} of the loop. The commands in the body of @code{while} are
16555 executed repeatedly as long as the expression evaluates to true.
16559 This command exits the @code{while} loop in whose body it is included.
16560 Execution of the script continues after that @code{while}s @code{end}
16563 @kindex loop_continue
16564 @item loop_continue
16565 This command skips the execution of the rest of the body of commands
16566 in the @code{while} loop in whose body it is included. Execution
16567 branches to the beginning of the @code{while} loop, where it evaluates
16568 the controlling expression.
16570 @kindex end@r{ (if/else/while commands)}
16572 Terminate the block of commands that are the body of @code{if},
16573 @code{else}, or @code{while} flow-control commands.
16578 @section Commands for Controlled Output
16580 During the execution of a command file or a user-defined command, normal
16581 @value{GDBN} output is suppressed; the only output that appears is what is
16582 explicitly printed by the commands in the definition. This section
16583 describes three commands useful for generating exactly the output you
16588 @item echo @var{text}
16589 @c I do not consider backslash-space a standard C escape sequence
16590 @c because it is not in ANSI.
16591 Print @var{text}. Nonprinting characters can be included in
16592 @var{text} using C escape sequences, such as @samp{\n} to print a
16593 newline. @strong{No newline is printed unless you specify one.}
16594 In addition to the standard C escape sequences, a backslash followed
16595 by a space stands for a space. This is useful for displaying a
16596 string with spaces at the beginning or the end, since leading and
16597 trailing spaces are otherwise trimmed from all arguments.
16598 To print @samp{@w{ }and foo =@w{ }}, use the command
16599 @samp{echo \@w{ }and foo = \@w{ }}.
16601 A backslash at the end of @var{text} can be used, as in C, to continue
16602 the command onto subsequent lines. For example,
16605 echo This is some text\n\
16606 which is continued\n\
16607 onto several lines.\n
16610 produces the same output as
16613 echo This is some text\n
16614 echo which is continued\n
16615 echo onto several lines.\n
16619 @item output @var{expression}
16620 Print the value of @var{expression} and nothing but that value: no
16621 newlines, no @samp{$@var{nn} = }. The value is not entered in the
16622 value history either. @xref{Expressions, ,Expressions}, for more information
16625 @item output/@var{fmt} @var{expression}
16626 Print the value of @var{expression} in format @var{fmt}. You can use
16627 the same formats as for @code{print}. @xref{Output Formats,,Output
16628 Formats}, for more information.
16631 @item printf @var{template}, @var{expressions}@dots{}
16632 Print the values of one or more @var{expressions} under the control of
16633 the string @var{template}. To print several values, make
16634 @var{expressions} be a comma-separated list of individual expressions,
16635 which may be either numbers or pointers. Their values are printed as
16636 specified by @var{template}, exactly as a C program would do by
16637 executing the code below:
16640 printf (@var{template}, @var{expressions}@dots{});
16643 As in @code{C} @code{printf}, ordinary characters in @var{template}
16644 are printed verbatim, while @dfn{conversion specification} introduced
16645 by the @samp{%} character cause subsequent @var{expressions} to be
16646 evaluated, their values converted and formatted according to type and
16647 style information encoded in the conversion specifications, and then
16650 For example, you can print two values in hex like this:
16653 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
16656 @code{printf} supports all the standard @code{C} conversion
16657 specifications, including the flags and modifiers between the @samp{%}
16658 character and the conversion letter, with the following exceptions:
16662 The argument-ordering modifiers, such as @samp{2$}, are not supported.
16665 The modifier @samp{*} is not supported for specifying precision or
16669 The @samp{'} flag (for separation of digits into groups according to
16670 @code{LC_NUMERIC'}) is not supported.
16673 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
16677 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
16680 The conversion letters @samp{a} and @samp{A} are not supported.
16684 Note that the @samp{ll} type modifier is supported only if the
16685 underlying @code{C} implementation used to build @value{GDBN} supports
16686 the @code{long long int} type, and the @samp{L} type modifier is
16687 supported only if @code{long double} type is available.
16689 As in @code{C}, @code{printf} supports simple backslash-escape
16690 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
16691 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
16692 single character. Octal and hexadecimal escape sequences are not
16695 Additionally, @code{printf} supports conversion specifications for DFP
16696 (@dfn{Decimal Floating Point}) types using the following length modifiers
16697 together with a floating point specifier.
16702 @samp{H} for printing @code{Decimal32} types.
16705 @samp{D} for printing @code{Decimal64} types.
16708 @samp{DD} for printing @code{Decimal128} types.
16711 If the underlying @code{C} implementation used to build @value{GDBN} has
16712 support for the three length modifiers for DFP types, other modifiers
16713 such as width and precision will also be available for @value{GDBN} to use.
16715 In case there is no such @code{C} support, no additional modifiers will be
16716 available and the value will be printed in the standard way.
16718 Here's an example of printing DFP types using the above conversion letters:
16720 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
16726 @chapter Command Interpreters
16727 @cindex command interpreters
16729 @value{GDBN} supports multiple command interpreters, and some command
16730 infrastructure to allow users or user interface writers to switch
16731 between interpreters or run commands in other interpreters.
16733 @value{GDBN} currently supports two command interpreters, the console
16734 interpreter (sometimes called the command-line interpreter or @sc{cli})
16735 and the machine interface interpreter (or @sc{gdb/mi}). This manual
16736 describes both of these interfaces in great detail.
16738 By default, @value{GDBN} will start with the console interpreter.
16739 However, the user may choose to start @value{GDBN} with another
16740 interpreter by specifying the @option{-i} or @option{--interpreter}
16741 startup options. Defined interpreters include:
16745 @cindex console interpreter
16746 The traditional console or command-line interpreter. This is the most often
16747 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
16748 @value{GDBN} will use this interpreter.
16751 @cindex mi interpreter
16752 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
16753 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
16754 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
16758 @cindex mi2 interpreter
16759 The current @sc{gdb/mi} interface.
16762 @cindex mi1 interpreter
16763 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
16767 @cindex invoke another interpreter
16768 The interpreter being used by @value{GDBN} may not be dynamically
16769 switched at runtime. Although possible, this could lead to a very
16770 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
16771 enters the command "interpreter-set console" in a console view,
16772 @value{GDBN} would switch to using the console interpreter, rendering
16773 the IDE inoperable!
16775 @kindex interpreter-exec
16776 Although you may only choose a single interpreter at startup, you may execute
16777 commands in any interpreter from the current interpreter using the appropriate
16778 command. If you are running the console interpreter, simply use the
16779 @code{interpreter-exec} command:
16782 interpreter-exec mi "-data-list-register-names"
16785 @sc{gdb/mi} has a similar command, although it is only available in versions of
16786 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
16789 @chapter @value{GDBN} Text User Interface
16791 @cindex Text User Interface
16794 * TUI Overview:: TUI overview
16795 * TUI Keys:: TUI key bindings
16796 * TUI Single Key Mode:: TUI single key mode
16797 * TUI Commands:: TUI-specific commands
16798 * TUI Configuration:: TUI configuration variables
16801 The @value{GDBN} Text User Interface (TUI) is a terminal
16802 interface which uses the @code{curses} library to show the source
16803 file, the assembly output, the program registers and @value{GDBN}
16804 commands in separate text windows. The TUI mode is supported only
16805 on platforms where a suitable version of the @code{curses} library
16808 @pindex @value{GDBTUI}
16809 The TUI mode is enabled by default when you invoke @value{GDBN} as
16810 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
16811 You can also switch in and out of TUI mode while @value{GDBN} runs by
16812 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
16813 @xref{TUI Keys, ,TUI Key Bindings}.
16816 @section TUI Overview
16818 In TUI mode, @value{GDBN} can display several text windows:
16822 This window is the @value{GDBN} command window with the @value{GDBN}
16823 prompt and the @value{GDBN} output. The @value{GDBN} input is still
16824 managed using readline.
16827 The source window shows the source file of the program. The current
16828 line and active breakpoints are displayed in this window.
16831 The assembly window shows the disassembly output of the program.
16834 This window shows the processor registers. Registers are highlighted
16835 when their values change.
16838 The source and assembly windows show the current program position
16839 by highlighting the current line and marking it with a @samp{>} marker.
16840 Breakpoints are indicated with two markers. The first marker
16841 indicates the breakpoint type:
16845 Breakpoint which was hit at least once.
16848 Breakpoint which was never hit.
16851 Hardware breakpoint which was hit at least once.
16854 Hardware breakpoint which was never hit.
16857 The second marker indicates whether the breakpoint is enabled or not:
16861 Breakpoint is enabled.
16864 Breakpoint is disabled.
16867 The source, assembly and register windows are updated when the current
16868 thread changes, when the frame changes, or when the program counter
16871 These windows are not all visible at the same time. The command
16872 window is always visible. The others can be arranged in several
16883 source and assembly,
16886 source and registers, or
16889 assembly and registers.
16892 A status line above the command window shows the following information:
16896 Indicates the current @value{GDBN} target.
16897 (@pxref{Targets, ,Specifying a Debugging Target}).
16900 Gives the current process or thread number.
16901 When no process is being debugged, this field is set to @code{No process}.
16904 Gives the current function name for the selected frame.
16905 The name is demangled if demangling is turned on (@pxref{Print Settings}).
16906 When there is no symbol corresponding to the current program counter,
16907 the string @code{??} is displayed.
16910 Indicates the current line number for the selected frame.
16911 When the current line number is not known, the string @code{??} is displayed.
16914 Indicates the current program counter address.
16918 @section TUI Key Bindings
16919 @cindex TUI key bindings
16921 The TUI installs several key bindings in the readline keymaps
16922 (@pxref{Command Line Editing}). The following key bindings
16923 are installed for both TUI mode and the @value{GDBN} standard mode.
16932 Enter or leave the TUI mode. When leaving the TUI mode,
16933 the curses window management stops and @value{GDBN} operates using
16934 its standard mode, writing on the terminal directly. When reentering
16935 the TUI mode, control is given back to the curses windows.
16936 The screen is then refreshed.
16940 Use a TUI layout with only one window. The layout will
16941 either be @samp{source} or @samp{assembly}. When the TUI mode
16942 is not active, it will switch to the TUI mode.
16944 Think of this key binding as the Emacs @kbd{C-x 1} binding.
16948 Use a TUI layout with at least two windows. When the current
16949 layout already has two windows, the next layout with two windows is used.
16950 When a new layout is chosen, one window will always be common to the
16951 previous layout and the new one.
16953 Think of it as the Emacs @kbd{C-x 2} binding.
16957 Change the active window. The TUI associates several key bindings
16958 (like scrolling and arrow keys) with the active window. This command
16959 gives the focus to the next TUI window.
16961 Think of it as the Emacs @kbd{C-x o} binding.
16965 Switch in and out of the TUI SingleKey mode that binds single
16966 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
16969 The following key bindings only work in the TUI mode:
16974 Scroll the active window one page up.
16978 Scroll the active window one page down.
16982 Scroll the active window one line up.
16986 Scroll the active window one line down.
16990 Scroll the active window one column left.
16994 Scroll the active window one column right.
16998 Refresh the screen.
17001 Because the arrow keys scroll the active window in the TUI mode, they
17002 are not available for their normal use by readline unless the command
17003 window has the focus. When another window is active, you must use
17004 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
17005 and @kbd{C-f} to control the command window.
17007 @node TUI Single Key Mode
17008 @section TUI Single Key Mode
17009 @cindex TUI single key mode
17011 The TUI also provides a @dfn{SingleKey} mode, which binds several
17012 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
17013 switch into this mode, where the following key bindings are used:
17016 @kindex c @r{(SingleKey TUI key)}
17020 @kindex d @r{(SingleKey TUI key)}
17024 @kindex f @r{(SingleKey TUI key)}
17028 @kindex n @r{(SingleKey TUI key)}
17032 @kindex q @r{(SingleKey TUI key)}
17034 exit the SingleKey mode.
17036 @kindex r @r{(SingleKey TUI key)}
17040 @kindex s @r{(SingleKey TUI key)}
17044 @kindex u @r{(SingleKey TUI key)}
17048 @kindex v @r{(SingleKey TUI key)}
17052 @kindex w @r{(SingleKey TUI key)}
17057 Other keys temporarily switch to the @value{GDBN} command prompt.
17058 The key that was pressed is inserted in the editing buffer so that
17059 it is possible to type most @value{GDBN} commands without interaction
17060 with the TUI SingleKey mode. Once the command is entered the TUI
17061 SingleKey mode is restored. The only way to permanently leave
17062 this mode is by typing @kbd{q} or @kbd{C-x s}.
17066 @section TUI-specific Commands
17067 @cindex TUI commands
17069 The TUI has specific commands to control the text windows.
17070 These commands are always available, even when @value{GDBN} is not in
17071 the TUI mode. When @value{GDBN} is in the standard mode, most
17072 of these commands will automatically switch to the TUI mode.
17077 List and give the size of all displayed windows.
17081 Display the next layout.
17084 Display the previous layout.
17087 Display the source window only.
17090 Display the assembly window only.
17093 Display the source and assembly window.
17096 Display the register window together with the source or assembly window.
17100 Make the next window active for scrolling.
17103 Make the previous window active for scrolling.
17106 Make the source window active for scrolling.
17109 Make the assembly window active for scrolling.
17112 Make the register window active for scrolling.
17115 Make the command window active for scrolling.
17119 Refresh the screen. This is similar to typing @kbd{C-L}.
17121 @item tui reg float
17123 Show the floating point registers in the register window.
17125 @item tui reg general
17126 Show the general registers in the register window.
17129 Show the next register group. The list of register groups as well as
17130 their order is target specific. The predefined register groups are the
17131 following: @code{general}, @code{float}, @code{system}, @code{vector},
17132 @code{all}, @code{save}, @code{restore}.
17134 @item tui reg system
17135 Show the system registers in the register window.
17139 Update the source window and the current execution point.
17141 @item winheight @var{name} +@var{count}
17142 @itemx winheight @var{name} -@var{count}
17144 Change the height of the window @var{name} by @var{count}
17145 lines. Positive counts increase the height, while negative counts
17148 @item tabset @var{nchars}
17150 Set the width of tab stops to be @var{nchars} characters.
17153 @node TUI Configuration
17154 @section TUI Configuration Variables
17155 @cindex TUI configuration variables
17157 Several configuration variables control the appearance of TUI windows.
17160 @item set tui border-kind @var{kind}
17161 @kindex set tui border-kind
17162 Select the border appearance for the source, assembly and register windows.
17163 The possible values are the following:
17166 Use a space character to draw the border.
17169 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
17172 Use the Alternate Character Set to draw the border. The border is
17173 drawn using character line graphics if the terminal supports them.
17176 @item set tui border-mode @var{mode}
17177 @kindex set tui border-mode
17178 @itemx set tui active-border-mode @var{mode}
17179 @kindex set tui active-border-mode
17180 Select the display attributes for the borders of the inactive windows
17181 or the active window. The @var{mode} can be one of the following:
17184 Use normal attributes to display the border.
17190 Use reverse video mode.
17193 Use half bright mode.
17195 @item half-standout
17196 Use half bright and standout mode.
17199 Use extra bright or bold mode.
17201 @item bold-standout
17202 Use extra bright or bold and standout mode.
17207 @chapter Using @value{GDBN} under @sc{gnu} Emacs
17210 @cindex @sc{gnu} Emacs
17211 A special interface allows you to use @sc{gnu} Emacs to view (and
17212 edit) the source files for the program you are debugging with
17215 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
17216 executable file you want to debug as an argument. This command starts
17217 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
17218 created Emacs buffer.
17219 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
17221 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
17226 All ``terminal'' input and output goes through an Emacs buffer, called
17229 This applies both to @value{GDBN} commands and their output, and to the input
17230 and output done by the program you are debugging.
17232 This is useful because it means that you can copy the text of previous
17233 commands and input them again; you can even use parts of the output
17236 All the facilities of Emacs' Shell mode are available for interacting
17237 with your program. In particular, you can send signals the usual
17238 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
17242 @value{GDBN} displays source code through Emacs.
17244 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
17245 source file for that frame and puts an arrow (@samp{=>}) at the
17246 left margin of the current line. Emacs uses a separate buffer for
17247 source display, and splits the screen to show both your @value{GDBN} session
17250 Explicit @value{GDBN} @code{list} or search commands still produce output as
17251 usual, but you probably have no reason to use them from Emacs.
17254 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
17255 a graphical mode, enabled by default, which provides further buffers
17256 that can control the execution and describe the state of your program.
17257 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
17259 If you specify an absolute file name when prompted for the @kbd{M-x
17260 gdb} argument, then Emacs sets your current working directory to where
17261 your program resides. If you only specify the file name, then Emacs
17262 sets your current working directory to to the directory associated
17263 with the previous buffer. In this case, @value{GDBN} may find your
17264 program by searching your environment's @code{PATH} variable, but on
17265 some operating systems it might not find the source. So, although the
17266 @value{GDBN} input and output session proceeds normally, the auxiliary
17267 buffer does not display the current source and line of execution.
17269 The initial working directory of @value{GDBN} is printed on the top
17270 line of the GUD buffer and this serves as a default for the commands
17271 that specify files for @value{GDBN} to operate on. @xref{Files,
17272 ,Commands to Specify Files}.
17274 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
17275 need to call @value{GDBN} by a different name (for example, if you
17276 keep several configurations around, with different names) you can
17277 customize the Emacs variable @code{gud-gdb-command-name} to run the
17280 In the GUD buffer, you can use these special Emacs commands in
17281 addition to the standard Shell mode commands:
17285 Describe the features of Emacs' GUD Mode.
17288 Execute to another source line, like the @value{GDBN} @code{step} command; also
17289 update the display window to show the current file and location.
17292 Execute to next source line in this function, skipping all function
17293 calls, like the @value{GDBN} @code{next} command. Then update the display window
17294 to show the current file and location.
17297 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
17298 display window accordingly.
17301 Execute until exit from the selected stack frame, like the @value{GDBN}
17302 @code{finish} command.
17305 Continue execution of your program, like the @value{GDBN} @code{continue}
17309 Go up the number of frames indicated by the numeric argument
17310 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
17311 like the @value{GDBN} @code{up} command.
17314 Go down the number of frames indicated by the numeric argument, like the
17315 @value{GDBN} @code{down} command.
17318 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
17319 tells @value{GDBN} to set a breakpoint on the source line point is on.
17321 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
17322 separate frame which shows a backtrace when the GUD buffer is current.
17323 Move point to any frame in the stack and type @key{RET} to make it
17324 become the current frame and display the associated source in the
17325 source buffer. Alternatively, click @kbd{Mouse-2} to make the
17326 selected frame become the current one. In graphical mode, the
17327 speedbar displays watch expressions.
17329 If you accidentally delete the source-display buffer, an easy way to get
17330 it back is to type the command @code{f} in the @value{GDBN} buffer, to
17331 request a frame display; when you run under Emacs, this recreates
17332 the source buffer if necessary to show you the context of the current
17335 The source files displayed in Emacs are in ordinary Emacs buffers
17336 which are visiting the source files in the usual way. You can edit
17337 the files with these buffers if you wish; but keep in mind that @value{GDBN}
17338 communicates with Emacs in terms of line numbers. If you add or
17339 delete lines from the text, the line numbers that @value{GDBN} knows cease
17340 to correspond properly with the code.
17342 A more detailed description of Emacs' interaction with @value{GDBN} is
17343 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
17346 @c The following dropped because Epoch is nonstandard. Reactivate
17347 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
17349 @kindex Emacs Epoch environment
17353 Version 18 of @sc{gnu} Emacs has a built-in window system
17354 called the @code{epoch}
17355 environment. Users of this environment can use a new command,
17356 @code{inspect} which performs identically to @code{print} except that
17357 each value is printed in its own window.
17362 @chapter The @sc{gdb/mi} Interface
17364 @unnumberedsec Function and Purpose
17366 @cindex @sc{gdb/mi}, its purpose
17367 @sc{gdb/mi} is a line based machine oriented text interface to
17368 @value{GDBN} and is activated by specifying using the
17369 @option{--interpreter} command line option (@pxref{Mode Options}). It
17370 is specifically intended to support the development of systems which
17371 use the debugger as just one small component of a larger system.
17373 This chapter is a specification of the @sc{gdb/mi} interface. It is written
17374 in the form of a reference manual.
17376 Note that @sc{gdb/mi} is still under construction, so some of the
17377 features described below are incomplete and subject to change
17378 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
17380 @unnumberedsec Notation and Terminology
17382 @cindex notational conventions, for @sc{gdb/mi}
17383 This chapter uses the following notation:
17387 @code{|} separates two alternatives.
17390 @code{[ @var{something} ]} indicates that @var{something} is optional:
17391 it may or may not be given.
17394 @code{( @var{group} )*} means that @var{group} inside the parentheses
17395 may repeat zero or more times.
17398 @code{( @var{group} )+} means that @var{group} inside the parentheses
17399 may repeat one or more times.
17402 @code{"@var{string}"} means a literal @var{string}.
17406 @heading Dependencies
17410 * GDB/MI Command Syntax::
17411 * GDB/MI Compatibility with CLI::
17412 * GDB/MI Development and Front Ends::
17413 * GDB/MI Output Records::
17414 * GDB/MI Simple Examples::
17415 * GDB/MI Command Description Format::
17416 * GDB/MI Breakpoint Commands::
17417 * GDB/MI Program Context::
17418 * GDB/MI Thread Commands::
17419 * GDB/MI Program Execution::
17420 * GDB/MI Stack Manipulation::
17421 * GDB/MI Variable Objects::
17422 * GDB/MI Data Manipulation::
17423 * GDB/MI Tracepoint Commands::
17424 * GDB/MI Symbol Query::
17425 * GDB/MI File Commands::
17427 * GDB/MI Kod Commands::
17428 * GDB/MI Memory Overlay Commands::
17429 * GDB/MI Signal Handling Commands::
17431 * GDB/MI Target Manipulation::
17432 * GDB/MI File Transfer Commands::
17433 * GDB/MI Miscellaneous Commands::
17436 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17437 @node GDB/MI Command Syntax
17438 @section @sc{gdb/mi} Command Syntax
17441 * GDB/MI Input Syntax::
17442 * GDB/MI Output Syntax::
17445 @node GDB/MI Input Syntax
17446 @subsection @sc{gdb/mi} Input Syntax
17448 @cindex input syntax for @sc{gdb/mi}
17449 @cindex @sc{gdb/mi}, input syntax
17451 @item @var{command} @expansion{}
17452 @code{@var{cli-command} | @var{mi-command}}
17454 @item @var{cli-command} @expansion{}
17455 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
17456 @var{cli-command} is any existing @value{GDBN} CLI command.
17458 @item @var{mi-command} @expansion{}
17459 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
17460 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
17462 @item @var{token} @expansion{}
17463 "any sequence of digits"
17465 @item @var{option} @expansion{}
17466 @code{"-" @var{parameter} [ " " @var{parameter} ]}
17468 @item @var{parameter} @expansion{}
17469 @code{@var{non-blank-sequence} | @var{c-string}}
17471 @item @var{operation} @expansion{}
17472 @emph{any of the operations described in this chapter}
17474 @item @var{non-blank-sequence} @expansion{}
17475 @emph{anything, provided it doesn't contain special characters such as
17476 "-", @var{nl}, """ and of course " "}
17478 @item @var{c-string} @expansion{}
17479 @code{""" @var{seven-bit-iso-c-string-content} """}
17481 @item @var{nl} @expansion{}
17490 The CLI commands are still handled by the @sc{mi} interpreter; their
17491 output is described below.
17494 The @code{@var{token}}, when present, is passed back when the command
17498 Some @sc{mi} commands accept optional arguments as part of the parameter
17499 list. Each option is identified by a leading @samp{-} (dash) and may be
17500 followed by an optional argument parameter. Options occur first in the
17501 parameter list and can be delimited from normal parameters using
17502 @samp{--} (this is useful when some parameters begin with a dash).
17509 We want easy access to the existing CLI syntax (for debugging).
17512 We want it to be easy to spot a @sc{mi} operation.
17515 @node GDB/MI Output Syntax
17516 @subsection @sc{gdb/mi} Output Syntax
17518 @cindex output syntax of @sc{gdb/mi}
17519 @cindex @sc{gdb/mi}, output syntax
17520 The output from @sc{gdb/mi} consists of zero or more out-of-band records
17521 followed, optionally, by a single result record. This result record
17522 is for the most recent command. The sequence of output records is
17523 terminated by @samp{(gdb)}.
17525 If an input command was prefixed with a @code{@var{token}} then the
17526 corresponding output for that command will also be prefixed by that same
17530 @item @var{output} @expansion{}
17531 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
17533 @item @var{result-record} @expansion{}
17534 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
17536 @item @var{out-of-band-record} @expansion{}
17537 @code{@var{async-record} | @var{stream-record}}
17539 @item @var{async-record} @expansion{}
17540 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
17542 @item @var{exec-async-output} @expansion{}
17543 @code{[ @var{token} ] "*" @var{async-output}}
17545 @item @var{status-async-output} @expansion{}
17546 @code{[ @var{token} ] "+" @var{async-output}}
17548 @item @var{notify-async-output} @expansion{}
17549 @code{[ @var{token} ] "=" @var{async-output}}
17551 @item @var{async-output} @expansion{}
17552 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
17554 @item @var{result-class} @expansion{}
17555 @code{"done" | "running" | "connected" | "error" | "exit"}
17557 @item @var{async-class} @expansion{}
17558 @code{"stopped" | @var{others}} (where @var{others} will be added
17559 depending on the needs---this is still in development).
17561 @item @var{result} @expansion{}
17562 @code{ @var{variable} "=" @var{value}}
17564 @item @var{variable} @expansion{}
17565 @code{ @var{string} }
17567 @item @var{value} @expansion{}
17568 @code{ @var{const} | @var{tuple} | @var{list} }
17570 @item @var{const} @expansion{}
17571 @code{@var{c-string}}
17573 @item @var{tuple} @expansion{}
17574 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
17576 @item @var{list} @expansion{}
17577 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
17578 @var{result} ( "," @var{result} )* "]" }
17580 @item @var{stream-record} @expansion{}
17581 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
17583 @item @var{console-stream-output} @expansion{}
17584 @code{"~" @var{c-string}}
17586 @item @var{target-stream-output} @expansion{}
17587 @code{"@@" @var{c-string}}
17589 @item @var{log-stream-output} @expansion{}
17590 @code{"&" @var{c-string}}
17592 @item @var{nl} @expansion{}
17595 @item @var{token} @expansion{}
17596 @emph{any sequence of digits}.
17604 All output sequences end in a single line containing a period.
17607 The @code{@var{token}} is from the corresponding request. If an execution
17608 command is interrupted by the @samp{-exec-interrupt} command, the
17609 @var{token} associated with the @samp{*stopped} message is the one of the
17610 original execution command, not the one of the interrupt command.
17613 @cindex status output in @sc{gdb/mi}
17614 @var{status-async-output} contains on-going status information about the
17615 progress of a slow operation. It can be discarded. All status output is
17616 prefixed by @samp{+}.
17619 @cindex async output in @sc{gdb/mi}
17620 @var{exec-async-output} contains asynchronous state change on the target
17621 (stopped, started, disappeared). All async output is prefixed by
17625 @cindex notify output in @sc{gdb/mi}
17626 @var{notify-async-output} contains supplementary information that the
17627 client should handle (e.g., a new breakpoint information). All notify
17628 output is prefixed by @samp{=}.
17631 @cindex console output in @sc{gdb/mi}
17632 @var{console-stream-output} is output that should be displayed as is in the
17633 console. It is the textual response to a CLI command. All the console
17634 output is prefixed by @samp{~}.
17637 @cindex target output in @sc{gdb/mi}
17638 @var{target-stream-output} is the output produced by the target program.
17639 All the target output is prefixed by @samp{@@}.
17642 @cindex log output in @sc{gdb/mi}
17643 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
17644 instance messages that should be displayed as part of an error log. All
17645 the log output is prefixed by @samp{&}.
17648 @cindex list output in @sc{gdb/mi}
17649 New @sc{gdb/mi} commands should only output @var{lists} containing
17655 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
17656 details about the various output records.
17658 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17659 @node GDB/MI Compatibility with CLI
17660 @section @sc{gdb/mi} Compatibility with CLI
17662 @cindex compatibility, @sc{gdb/mi} and CLI
17663 @cindex @sc{gdb/mi}, compatibility with CLI
17665 For the developers convenience CLI commands can be entered directly,
17666 but there may be some unexpected behaviour. For example, commands
17667 that query the user will behave as if the user replied yes, breakpoint
17668 command lists are not executed and some CLI commands, such as
17669 @code{if}, @code{when} and @code{define}, prompt for further input with
17670 @samp{>}, which is not valid MI output.
17672 This feature may be removed at some stage in the future and it is
17673 recommended that front ends use the @code{-interpreter-exec} command
17674 (@pxref{-interpreter-exec}).
17676 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17677 @node GDB/MI Development and Front Ends
17678 @section @sc{gdb/mi} Development and Front Ends
17679 @cindex @sc{gdb/mi} development
17681 The application which takes the MI output and presents the state of the
17682 program being debugged to the user is called a @dfn{front end}.
17684 Although @sc{gdb/mi} is still incomplete, it is currently being used
17685 by a variety of front ends to @value{GDBN}. This makes it difficult
17686 to introduce new functionality without breaking existing usage. This
17687 section tries to minimize the problems by describing how the protocol
17690 Some changes in MI need not break a carefully designed front end, and
17691 for these the MI version will remain unchanged. The following is a
17692 list of changes that may occur within one level, so front ends should
17693 parse MI output in a way that can handle them:
17697 New MI commands may be added.
17700 New fields may be added to the output of any MI command.
17703 The range of values for fields with specified values, e.g.,
17704 @code{in_scope} (@pxref{-var-update}) may be extended.
17706 @c The format of field's content e.g type prefix, may change so parse it
17707 @c at your own risk. Yes, in general?
17709 @c The order of fields may change? Shouldn't really matter but it might
17710 @c resolve inconsistencies.
17713 If the changes are likely to break front ends, the MI version level
17714 will be increased by one. This will allow the front end to parse the
17715 output according to the MI version. Apart from mi0, new versions of
17716 @value{GDBN} will not support old versions of MI and it will be the
17717 responsibility of the front end to work with the new one.
17719 @c Starting with mi3, add a new command -mi-version that prints the MI
17722 The best way to avoid unexpected changes in MI that might break your front
17723 end is to make your project known to @value{GDBN} developers and
17724 follow development on @email{gdb@@sourceware.org} and
17725 @email{gdb-patches@@sourceware.org}. There is also the mailing list
17726 @email{dmi-discuss@@lists.freestandards.org}, hosted by the Free Standards
17727 Group, which has the aim of creating a more general MI protocol
17728 called Debugger Machine Interface (DMI) that will become a standard
17729 for all debuggers, not just @value{GDBN}.
17730 @cindex mailing lists
17732 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17733 @node GDB/MI Output Records
17734 @section @sc{gdb/mi} Output Records
17737 * GDB/MI Result Records::
17738 * GDB/MI Stream Records::
17739 * GDB/MI Out-of-band Records::
17742 @node GDB/MI Result Records
17743 @subsection @sc{gdb/mi} Result Records
17745 @cindex result records in @sc{gdb/mi}
17746 @cindex @sc{gdb/mi}, result records
17747 In addition to a number of out-of-band notifications, the response to a
17748 @sc{gdb/mi} command includes one of the following result indications:
17752 @item "^done" [ "," @var{results} ]
17753 The synchronous operation was successful, @code{@var{results}} are the return
17758 @c Is this one correct? Should it be an out-of-band notification?
17759 The asynchronous operation was successfully started. The target is
17764 @value{GDBN} has connected to a remote target.
17766 @item "^error" "," @var{c-string}
17768 The operation failed. The @code{@var{c-string}} contains the corresponding
17773 @value{GDBN} has terminated.
17777 @node GDB/MI Stream Records
17778 @subsection @sc{gdb/mi} Stream Records
17780 @cindex @sc{gdb/mi}, stream records
17781 @cindex stream records in @sc{gdb/mi}
17782 @value{GDBN} internally maintains a number of output streams: the console, the
17783 target, and the log. The output intended for each of these streams is
17784 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
17786 Each stream record begins with a unique @dfn{prefix character} which
17787 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
17788 Syntax}). In addition to the prefix, each stream record contains a
17789 @code{@var{string-output}}. This is either raw text (with an implicit new
17790 line) or a quoted C string (which does not contain an implicit newline).
17793 @item "~" @var{string-output}
17794 The console output stream contains text that should be displayed in the
17795 CLI console window. It contains the textual responses to CLI commands.
17797 @item "@@" @var{string-output}
17798 The target output stream contains any textual output from the running
17799 target. This is only present when GDB's event loop is truly
17800 asynchronous, which is currently only the case for remote targets.
17802 @item "&" @var{string-output}
17803 The log stream contains debugging messages being produced by @value{GDBN}'s
17807 @node GDB/MI Out-of-band Records
17808 @subsection @sc{gdb/mi} Out-of-band Records
17810 @cindex out-of-band records in @sc{gdb/mi}
17811 @cindex @sc{gdb/mi}, out-of-band records
17812 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
17813 additional changes that have occurred. Those changes can either be a
17814 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
17815 target activity (e.g., target stopped).
17817 The following is a preliminary list of possible out-of-band records.
17818 In particular, the @var{exec-async-output} records.
17821 @item *stopped,reason="@var{reason}"
17824 @var{reason} can be one of the following:
17827 @item breakpoint-hit
17828 A breakpoint was reached.
17829 @item watchpoint-trigger
17830 A watchpoint was triggered.
17831 @item read-watchpoint-trigger
17832 A read watchpoint was triggered.
17833 @item access-watchpoint-trigger
17834 An access watchpoint was triggered.
17835 @item function-finished
17836 An -exec-finish or similar CLI command was accomplished.
17837 @item location-reached
17838 An -exec-until or similar CLI command was accomplished.
17839 @item watchpoint-scope
17840 A watchpoint has gone out of scope.
17841 @item end-stepping-range
17842 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
17843 similar CLI command was accomplished.
17844 @item exited-signalled
17845 The inferior exited because of a signal.
17847 The inferior exited.
17848 @item exited-normally
17849 The inferior exited normally.
17850 @item signal-received
17851 A signal was received by the inferior.
17855 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17856 @node GDB/MI Simple Examples
17857 @section Simple Examples of @sc{gdb/mi} Interaction
17858 @cindex @sc{gdb/mi}, simple examples
17860 This subsection presents several simple examples of interaction using
17861 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
17862 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
17863 the output received from @sc{gdb/mi}.
17865 Note the line breaks shown in the examples are here only for
17866 readability, they don't appear in the real output.
17868 @subheading Setting a Breakpoint
17870 Setting a breakpoint generates synchronous output which contains detailed
17871 information of the breakpoint.
17874 -> -break-insert main
17875 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
17876 enabled="y",addr="0x08048564",func="main",file="myprog.c",
17877 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
17881 @subheading Program Execution
17883 Program execution generates asynchronous records and MI gives the
17884 reason that execution stopped.
17890 <- *stopped,reason="breakpoint-hit",bkptno="1",thread-id="0",
17891 frame=@{addr="0x08048564",func="main",
17892 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
17893 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
17898 <- *stopped,reason="exited-normally"
17902 @subheading Quitting @value{GDBN}
17904 Quitting @value{GDBN} just prints the result class @samp{^exit}.
17912 @subheading A Bad Command
17914 Here's what happens if you pass a non-existent command:
17918 <- ^error,msg="Undefined MI command: rubbish"
17923 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17924 @node GDB/MI Command Description Format
17925 @section @sc{gdb/mi} Command Description Format
17927 The remaining sections describe blocks of commands. Each block of
17928 commands is laid out in a fashion similar to this section.
17930 @subheading Motivation
17932 The motivation for this collection of commands.
17934 @subheading Introduction
17936 A brief introduction to this collection of commands as a whole.
17938 @subheading Commands
17940 For each command in the block, the following is described:
17942 @subsubheading Synopsis
17945 -command @var{args}@dots{}
17948 @subsubheading Result
17950 @subsubheading @value{GDBN} Command
17952 The corresponding @value{GDBN} CLI command(s), if any.
17954 @subsubheading Example
17956 Example(s) formatted for readability. Some of the described commands have
17957 not been implemented yet and these are labeled N.A.@: (not available).
17960 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17961 @node GDB/MI Breakpoint Commands
17962 @section @sc{gdb/mi} Breakpoint Commands
17964 @cindex breakpoint commands for @sc{gdb/mi}
17965 @cindex @sc{gdb/mi}, breakpoint commands
17966 This section documents @sc{gdb/mi} commands for manipulating
17969 @subheading The @code{-break-after} Command
17970 @findex -break-after
17972 @subsubheading Synopsis
17975 -break-after @var{number} @var{count}
17978 The breakpoint number @var{number} is not in effect until it has been
17979 hit @var{count} times. To see how this is reflected in the output of
17980 the @samp{-break-list} command, see the description of the
17981 @samp{-break-list} command below.
17983 @subsubheading @value{GDBN} Command
17985 The corresponding @value{GDBN} command is @samp{ignore}.
17987 @subsubheading Example
17992 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",
17993 fullname="/home/foo/hello.c",line="5",times="0"@}
18000 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18001 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18002 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18003 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18004 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18005 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18006 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18007 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18008 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18009 line="5",times="0",ignore="3"@}]@}
18014 @subheading The @code{-break-catch} Command
18015 @findex -break-catch
18017 @subheading The @code{-break-commands} Command
18018 @findex -break-commands
18022 @subheading The @code{-break-condition} Command
18023 @findex -break-condition
18025 @subsubheading Synopsis
18028 -break-condition @var{number} @var{expr}
18031 Breakpoint @var{number} will stop the program only if the condition in
18032 @var{expr} is true. The condition becomes part of the
18033 @samp{-break-list} output (see the description of the @samp{-break-list}
18036 @subsubheading @value{GDBN} Command
18038 The corresponding @value{GDBN} command is @samp{condition}.
18040 @subsubheading Example
18044 -break-condition 1 1
18048 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18049 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18050 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18051 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18052 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18053 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18054 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18055 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18056 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18057 line="5",cond="1",times="0",ignore="3"@}]@}
18061 @subheading The @code{-break-delete} Command
18062 @findex -break-delete
18064 @subsubheading Synopsis
18067 -break-delete ( @var{breakpoint} )+
18070 Delete the breakpoint(s) whose number(s) are specified in the argument
18071 list. This is obviously reflected in the breakpoint list.
18073 @subsubheading @value{GDBN} Command
18075 The corresponding @value{GDBN} command is @samp{delete}.
18077 @subsubheading Example
18085 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
18086 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18087 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18088 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18089 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18090 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18091 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18096 @subheading The @code{-break-disable} Command
18097 @findex -break-disable
18099 @subsubheading Synopsis
18102 -break-disable ( @var{breakpoint} )+
18105 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
18106 break list is now set to @samp{n} for the named @var{breakpoint}(s).
18108 @subsubheading @value{GDBN} Command
18110 The corresponding @value{GDBN} command is @samp{disable}.
18112 @subsubheading Example
18120 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18121 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18122 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18123 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18124 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18125 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18126 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18127 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
18128 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18129 line="5",times="0"@}]@}
18133 @subheading The @code{-break-enable} Command
18134 @findex -break-enable
18136 @subsubheading Synopsis
18139 -break-enable ( @var{breakpoint} )+
18142 Enable (previously disabled) @var{breakpoint}(s).
18144 @subsubheading @value{GDBN} Command
18146 The corresponding @value{GDBN} command is @samp{enable}.
18148 @subsubheading Example
18156 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18157 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18158 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18159 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18160 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18161 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18162 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18163 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
18164 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18165 line="5",times="0"@}]@}
18169 @subheading The @code{-break-info} Command
18170 @findex -break-info
18172 @subsubheading Synopsis
18175 -break-info @var{breakpoint}
18179 Get information about a single breakpoint.
18181 @subsubheading @value{GDBN} Command
18183 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
18185 @subsubheading Example
18188 @subheading The @code{-break-insert} Command
18189 @findex -break-insert
18191 @subsubheading Synopsis
18194 -break-insert [ -t ] [ -h ] [ -f ]
18195 [ -c @var{condition} ] [ -i @var{ignore-count} ]
18196 [ -p @var{thread} ] [ @var{location} ]
18200 If specified, @var{location}, can be one of:
18207 @item filename:linenum
18208 @item filename:function
18212 The possible optional parameters of this command are:
18216 Insert a temporary breakpoint.
18218 Insert a hardware breakpoint.
18219 @item -c @var{condition}
18220 Make the breakpoint conditional on @var{condition}.
18221 @item -i @var{ignore-count}
18222 Initialize the @var{ignore-count}.
18224 If @var{location} cannot be parsed (for example if it
18225 refers to unknown files or functions), create a pending
18226 breakpoint. Without this flag, @value{GDBN} will report
18227 an error, and won't create a breakpoint, if @var{location}
18231 @subsubheading Result
18233 The result is in the form:
18236 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
18237 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
18238 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
18239 times="@var{times}"@}
18243 where @var{number} is the @value{GDBN} number for this breakpoint,
18244 @var{funcname} is the name of the function where the breakpoint was
18245 inserted, @var{filename} is the name of the source file which contains
18246 this function, @var{lineno} is the source line number within that file
18247 and @var{times} the number of times that the breakpoint has been hit
18248 (always 0 for -break-insert but may be greater for -break-info or -break-list
18249 which use the same output).
18251 Note: this format is open to change.
18252 @c An out-of-band breakpoint instead of part of the result?
18254 @subsubheading @value{GDBN} Command
18256 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
18257 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
18259 @subsubheading Example
18264 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
18265 fullname="/home/foo/recursive2.c,line="4",times="0"@}
18267 -break-insert -t foo
18268 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
18269 fullname="/home/foo/recursive2.c,line="11",times="0"@}
18272 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18273 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18274 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18275 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18276 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18277 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18278 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18279 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18280 addr="0x0001072c", func="main",file="recursive2.c",
18281 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
18282 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
18283 addr="0x00010774",func="foo",file="recursive2.c",
18284 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
18286 -break-insert -r foo.*
18287 ~int foo(int, int);
18288 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
18289 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
18293 @subheading The @code{-break-list} Command
18294 @findex -break-list
18296 @subsubheading Synopsis
18302 Displays the list of inserted breakpoints, showing the following fields:
18306 number of the breakpoint
18308 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
18310 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
18313 is the breakpoint enabled or no: @samp{y} or @samp{n}
18315 memory location at which the breakpoint is set
18317 logical location of the breakpoint, expressed by function name, file
18320 number of times the breakpoint has been hit
18323 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
18324 @code{body} field is an empty list.
18326 @subsubheading @value{GDBN} Command
18328 The corresponding @value{GDBN} command is @samp{info break}.
18330 @subsubheading Example
18335 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18336 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18337 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18338 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18339 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18340 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18341 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18342 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18343 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
18344 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
18345 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
18346 line="13",times="0"@}]@}
18350 Here's an example of the result when there are no breakpoints:
18355 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
18356 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18357 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18358 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18359 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18360 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18361 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18366 @subheading The @code{-break-watch} Command
18367 @findex -break-watch
18369 @subsubheading Synopsis
18372 -break-watch [ -a | -r ]
18375 Create a watchpoint. With the @samp{-a} option it will create an
18376 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
18377 read from or on a write to the memory location. With the @samp{-r}
18378 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
18379 trigger only when the memory location is accessed for reading. Without
18380 either of the options, the watchpoint created is a regular watchpoint,
18381 i.e., it will trigger when the memory location is accessed for writing.
18382 @xref{Set Watchpoints, , Setting Watchpoints}.
18384 Note that @samp{-break-list} will report a single list of watchpoints and
18385 breakpoints inserted.
18387 @subsubheading @value{GDBN} Command
18389 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
18392 @subsubheading Example
18394 Setting a watchpoint on a variable in the @code{main} function:
18399 ^done,wpt=@{number="2",exp="x"@}
18404 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
18405 value=@{old="-268439212",new="55"@},
18406 frame=@{func="main",args=[],file="recursive2.c",
18407 fullname="/home/foo/bar/recursive2.c",line="5"@}
18411 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
18412 the program execution twice: first for the variable changing value, then
18413 for the watchpoint going out of scope.
18418 ^done,wpt=@{number="5",exp="C"@}
18423 *stopped,reason="watchpoint-trigger",
18424 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
18425 frame=@{func="callee4",args=[],
18426 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18427 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
18432 *stopped,reason="watchpoint-scope",wpnum="5",
18433 frame=@{func="callee3",args=[@{name="strarg",
18434 value="0x11940 \"A string argument.\""@}],
18435 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18436 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18440 Listing breakpoints and watchpoints, at different points in the program
18441 execution. Note that once the watchpoint goes out of scope, it is
18447 ^done,wpt=@{number="2",exp="C"@}
18450 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18451 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18452 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18453 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18454 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18455 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18456 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18457 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18458 addr="0x00010734",func="callee4",
18459 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18460 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
18461 bkpt=@{number="2",type="watchpoint",disp="keep",
18462 enabled="y",addr="",what="C",times="0"@}]@}
18467 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
18468 value=@{old="-276895068",new="3"@},
18469 frame=@{func="callee4",args=[],
18470 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18471 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
18474 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18475 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18476 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18477 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18478 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18479 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18480 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18481 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18482 addr="0x00010734",func="callee4",
18483 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18484 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
18485 bkpt=@{number="2",type="watchpoint",disp="keep",
18486 enabled="y",addr="",what="C",times="-5"@}]@}
18490 ^done,reason="watchpoint-scope",wpnum="2",
18491 frame=@{func="callee3",args=[@{name="strarg",
18492 value="0x11940 \"A string argument.\""@}],
18493 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18494 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18497 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18498 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18499 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18500 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18501 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18502 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18503 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18504 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18505 addr="0x00010734",func="callee4",
18506 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18507 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
18512 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18513 @node GDB/MI Program Context
18514 @section @sc{gdb/mi} Program Context
18516 @subheading The @code{-exec-arguments} Command
18517 @findex -exec-arguments
18520 @subsubheading Synopsis
18523 -exec-arguments @var{args}
18526 Set the inferior program arguments, to be used in the next
18529 @subsubheading @value{GDBN} Command
18531 The corresponding @value{GDBN} command is @samp{set args}.
18533 @subsubheading Example
18536 Don't have one around.
18539 @subheading The @code{-exec-show-arguments} Command
18540 @findex -exec-show-arguments
18542 @subsubheading Synopsis
18545 -exec-show-arguments
18548 Print the arguments of the program.
18550 @subsubheading @value{GDBN} Command
18552 The corresponding @value{GDBN} command is @samp{show args}.
18554 @subsubheading Example
18558 @subheading The @code{-environment-cd} Command
18559 @findex -environment-cd
18561 @subsubheading Synopsis
18564 -environment-cd @var{pathdir}
18567 Set @value{GDBN}'s working directory.
18569 @subsubheading @value{GDBN} Command
18571 The corresponding @value{GDBN} command is @samp{cd}.
18573 @subsubheading Example
18577 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18583 @subheading The @code{-environment-directory} Command
18584 @findex -environment-directory
18586 @subsubheading Synopsis
18589 -environment-directory [ -r ] [ @var{pathdir} ]+
18592 Add directories @var{pathdir} to beginning of search path for source files.
18593 If the @samp{-r} option is used, the search path is reset to the default
18594 search path. If directories @var{pathdir} are supplied in addition to the
18595 @samp{-r} option, the search path is first reset and then addition
18597 Multiple directories may be specified, separated by blanks. Specifying
18598 multiple directories in a single command
18599 results in the directories added to the beginning of the
18600 search path in the same order they were presented in the command.
18601 If blanks are needed as
18602 part of a directory name, double-quotes should be used around
18603 the name. In the command output, the path will show up separated
18604 by the system directory-separator character. The directory-separator
18605 character must not be used
18606 in any directory name.
18607 If no directories are specified, the current search path is displayed.
18609 @subsubheading @value{GDBN} Command
18611 The corresponding @value{GDBN} command is @samp{dir}.
18613 @subsubheading Example
18617 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18618 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18620 -environment-directory ""
18621 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18623 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
18624 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
18626 -environment-directory -r
18627 ^done,source-path="$cdir:$cwd"
18632 @subheading The @code{-environment-path} Command
18633 @findex -environment-path
18635 @subsubheading Synopsis
18638 -environment-path [ -r ] [ @var{pathdir} ]+
18641 Add directories @var{pathdir} to beginning of search path for object files.
18642 If the @samp{-r} option is used, the search path is reset to the original
18643 search path that existed at gdb start-up. If directories @var{pathdir} are
18644 supplied in addition to the
18645 @samp{-r} option, the search path is first reset and then addition
18647 Multiple directories may be specified, separated by blanks. Specifying
18648 multiple directories in a single command
18649 results in the directories added to the beginning of the
18650 search path in the same order they were presented in the command.
18651 If blanks are needed as
18652 part of a directory name, double-quotes should be used around
18653 the name. In the command output, the path will show up separated
18654 by the system directory-separator character. The directory-separator
18655 character must not be used
18656 in any directory name.
18657 If no directories are specified, the current path is displayed.
18660 @subsubheading @value{GDBN} Command
18662 The corresponding @value{GDBN} command is @samp{path}.
18664 @subsubheading Example
18669 ^done,path="/usr/bin"
18671 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
18672 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
18674 -environment-path -r /usr/local/bin
18675 ^done,path="/usr/local/bin:/usr/bin"
18680 @subheading The @code{-environment-pwd} Command
18681 @findex -environment-pwd
18683 @subsubheading Synopsis
18689 Show the current working directory.
18691 @subsubheading @value{GDBN} Command
18693 The corresponding @value{GDBN} command is @samp{pwd}.
18695 @subsubheading Example
18700 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
18704 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18705 @node GDB/MI Thread Commands
18706 @section @sc{gdb/mi} Thread Commands
18709 @subheading The @code{-thread-info} Command
18710 @findex -thread-info
18712 @subsubheading Synopsis
18718 @subsubheading @value{GDBN} Command
18722 @subsubheading Example
18726 @subheading The @code{-thread-list-all-threads} Command
18727 @findex -thread-list-all-threads
18729 @subsubheading Synopsis
18732 -thread-list-all-threads
18735 @subsubheading @value{GDBN} Command
18737 The equivalent @value{GDBN} command is @samp{info threads}.
18739 @subsubheading Example
18743 @subheading The @code{-thread-list-ids} Command
18744 @findex -thread-list-ids
18746 @subsubheading Synopsis
18752 Produces a list of the currently known @value{GDBN} thread ids. At the
18753 end of the list it also prints the total number of such threads.
18755 @subsubheading @value{GDBN} Command
18757 Part of @samp{info threads} supplies the same information.
18759 @subsubheading Example
18761 No threads present, besides the main process:
18766 ^done,thread-ids=@{@},number-of-threads="0"
18776 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
18777 number-of-threads="3"
18782 @subheading The @code{-thread-select} Command
18783 @findex -thread-select
18785 @subsubheading Synopsis
18788 -thread-select @var{threadnum}
18791 Make @var{threadnum} the current thread. It prints the number of the new
18792 current thread, and the topmost frame for that thread.
18794 @subsubheading @value{GDBN} Command
18796 The corresponding @value{GDBN} command is @samp{thread}.
18798 @subsubheading Example
18805 *stopped,reason="end-stepping-range",thread-id="2",line="187",
18806 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
18810 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
18811 number-of-threads="3"
18814 ^done,new-thread-id="3",
18815 frame=@{level="0",func="vprintf",
18816 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
18817 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
18821 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18822 @node GDB/MI Program Execution
18823 @section @sc{gdb/mi} Program Execution
18825 These are the asynchronous commands which generate the out-of-band
18826 record @samp{*stopped}. Currently @value{GDBN} only really executes
18827 asynchronously with remote targets and this interaction is mimicked in
18830 @subheading The @code{-exec-continue} Command
18831 @findex -exec-continue
18833 @subsubheading Synopsis
18839 Resumes the execution of the inferior program until a breakpoint is
18840 encountered, or until the inferior exits.
18842 @subsubheading @value{GDBN} Command
18844 The corresponding @value{GDBN} corresponding is @samp{continue}.
18846 @subsubheading Example
18853 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
18854 file="hello.c",fullname="/home/foo/bar/hello.c",line="13"@}
18859 @subheading The @code{-exec-finish} Command
18860 @findex -exec-finish
18862 @subsubheading Synopsis
18868 Resumes the execution of the inferior program until the current
18869 function is exited. Displays the results returned by the function.
18871 @subsubheading @value{GDBN} Command
18873 The corresponding @value{GDBN} command is @samp{finish}.
18875 @subsubheading Example
18877 Function returning @code{void}.
18884 *stopped,reason="function-finished",frame=@{func="main",args=[],
18885 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
18889 Function returning other than @code{void}. The name of the internal
18890 @value{GDBN} variable storing the result is printed, together with the
18897 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
18898 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
18899 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
18900 gdb-result-var="$1",return-value="0"
18905 @subheading The @code{-exec-interrupt} Command
18906 @findex -exec-interrupt
18908 @subsubheading Synopsis
18914 Interrupts the background execution of the target. Note how the token
18915 associated with the stop message is the one for the execution command
18916 that has been interrupted. The token for the interrupt itself only
18917 appears in the @samp{^done} output. If the user is trying to
18918 interrupt a non-running program, an error message will be printed.
18920 @subsubheading @value{GDBN} Command
18922 The corresponding @value{GDBN} command is @samp{interrupt}.
18924 @subsubheading Example
18935 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
18936 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
18937 fullname="/home/foo/bar/try.c",line="13"@}
18942 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
18947 @subheading The @code{-exec-next} Command
18950 @subsubheading Synopsis
18956 Resumes execution of the inferior program, stopping when the beginning
18957 of the next source line is reached.
18959 @subsubheading @value{GDBN} Command
18961 The corresponding @value{GDBN} command is @samp{next}.
18963 @subsubheading Example
18969 *stopped,reason="end-stepping-range",line="8",file="hello.c"
18974 @subheading The @code{-exec-next-instruction} Command
18975 @findex -exec-next-instruction
18977 @subsubheading Synopsis
18980 -exec-next-instruction
18983 Executes one machine instruction. If the instruction is a function
18984 call, continues until the function returns. If the program stops at an
18985 instruction in the middle of a source line, the address will be
18988 @subsubheading @value{GDBN} Command
18990 The corresponding @value{GDBN} command is @samp{nexti}.
18992 @subsubheading Example
18996 -exec-next-instruction
19000 *stopped,reason="end-stepping-range",
19001 addr="0x000100d4",line="5",file="hello.c"
19006 @subheading The @code{-exec-return} Command
19007 @findex -exec-return
19009 @subsubheading Synopsis
19015 Makes current function return immediately. Doesn't execute the inferior.
19016 Displays the new current frame.
19018 @subsubheading @value{GDBN} Command
19020 The corresponding @value{GDBN} command is @samp{return}.
19022 @subsubheading Example
19026 200-break-insert callee4
19027 200^done,bkpt=@{number="1",addr="0x00010734",
19028 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
19033 000*stopped,reason="breakpoint-hit",bkptno="1",
19034 frame=@{func="callee4",args=[],
19035 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19036 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
19042 111^done,frame=@{level="0",func="callee3",
19043 args=[@{name="strarg",
19044 value="0x11940 \"A string argument.\""@}],
19045 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19046 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
19051 @subheading The @code{-exec-run} Command
19054 @subsubheading Synopsis
19060 Starts execution of the inferior from the beginning. The inferior
19061 executes until either a breakpoint is encountered or the program
19062 exits. In the latter case the output will include an exit code, if
19063 the program has exited exceptionally.
19065 @subsubheading @value{GDBN} Command
19067 The corresponding @value{GDBN} command is @samp{run}.
19069 @subsubheading Examples
19074 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
19079 *stopped,reason="breakpoint-hit",bkptno="1",
19080 frame=@{func="main",args=[],file="recursive2.c",
19081 fullname="/home/foo/bar/recursive2.c",line="4"@}
19086 Program exited normally:
19094 *stopped,reason="exited-normally"
19099 Program exited exceptionally:
19107 *stopped,reason="exited",exit-code="01"
19111 Another way the program can terminate is if it receives a signal such as
19112 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
19116 *stopped,reason="exited-signalled",signal-name="SIGINT",
19117 signal-meaning="Interrupt"
19121 @c @subheading -exec-signal
19124 @subheading The @code{-exec-step} Command
19127 @subsubheading Synopsis
19133 Resumes execution of the inferior program, stopping when the beginning
19134 of the next source line is reached, if the next source line is not a
19135 function call. If it is, stop at the first instruction of the called
19138 @subsubheading @value{GDBN} Command
19140 The corresponding @value{GDBN} command is @samp{step}.
19142 @subsubheading Example
19144 Stepping into a function:
19150 *stopped,reason="end-stepping-range",
19151 frame=@{func="foo",args=[@{name="a",value="10"@},
19152 @{name="b",value="0"@}],file="recursive2.c",
19153 fullname="/home/foo/bar/recursive2.c",line="11"@}
19163 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
19168 @subheading The @code{-exec-step-instruction} Command
19169 @findex -exec-step-instruction
19171 @subsubheading Synopsis
19174 -exec-step-instruction
19177 Resumes the inferior which executes one machine instruction. The
19178 output, once @value{GDBN} has stopped, will vary depending on whether
19179 we have stopped in the middle of a source line or not. In the former
19180 case, the address at which the program stopped will be printed as
19183 @subsubheading @value{GDBN} Command
19185 The corresponding @value{GDBN} command is @samp{stepi}.
19187 @subsubheading Example
19191 -exec-step-instruction
19195 *stopped,reason="end-stepping-range",
19196 frame=@{func="foo",args=[],file="try.c",
19197 fullname="/home/foo/bar/try.c",line="10"@}
19199 -exec-step-instruction
19203 *stopped,reason="end-stepping-range",
19204 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
19205 fullname="/home/foo/bar/try.c",line="10"@}
19210 @subheading The @code{-exec-until} Command
19211 @findex -exec-until
19213 @subsubheading Synopsis
19216 -exec-until [ @var{location} ]
19219 Executes the inferior until the @var{location} specified in the
19220 argument is reached. If there is no argument, the inferior executes
19221 until a source line greater than the current one is reached. The
19222 reason for stopping in this case will be @samp{location-reached}.
19224 @subsubheading @value{GDBN} Command
19226 The corresponding @value{GDBN} command is @samp{until}.
19228 @subsubheading Example
19232 -exec-until recursive2.c:6
19236 *stopped,reason="location-reached",frame=@{func="main",args=[],
19237 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
19242 @subheading -file-clear
19243 Is this going away????
19246 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19247 @node GDB/MI Stack Manipulation
19248 @section @sc{gdb/mi} Stack Manipulation Commands
19251 @subheading The @code{-stack-info-frame} Command
19252 @findex -stack-info-frame
19254 @subsubheading Synopsis
19260 Get info on the selected frame.
19262 @subsubheading @value{GDBN} Command
19264 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
19265 (without arguments).
19267 @subsubheading Example
19272 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
19273 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19274 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
19278 @subheading The @code{-stack-info-depth} Command
19279 @findex -stack-info-depth
19281 @subsubheading Synopsis
19284 -stack-info-depth [ @var{max-depth} ]
19287 Return the depth of the stack. If the integer argument @var{max-depth}
19288 is specified, do not count beyond @var{max-depth} frames.
19290 @subsubheading @value{GDBN} Command
19292 There's no equivalent @value{GDBN} command.
19294 @subsubheading Example
19296 For a stack with frame levels 0 through 11:
19303 -stack-info-depth 4
19306 -stack-info-depth 12
19309 -stack-info-depth 11
19312 -stack-info-depth 13
19317 @subheading The @code{-stack-list-arguments} Command
19318 @findex -stack-list-arguments
19320 @subsubheading Synopsis
19323 -stack-list-arguments @var{show-values}
19324 [ @var{low-frame} @var{high-frame} ]
19327 Display a list of the arguments for the frames between @var{low-frame}
19328 and @var{high-frame} (inclusive). If @var{low-frame} and
19329 @var{high-frame} are not provided, list the arguments for the whole
19330 call stack. If the two arguments are equal, show the single frame
19331 at the corresponding level. It is an error if @var{low-frame} is
19332 larger than the actual number of frames. On the other hand,
19333 @var{high-frame} may be larger than the actual number of frames, in
19334 which case only existing frames will be returned.
19336 The @var{show-values} argument must have a value of 0 or 1. A value of
19337 0 means that only the names of the arguments are listed, a value of 1
19338 means that both names and values of the arguments are printed.
19340 @subsubheading @value{GDBN} Command
19342 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
19343 @samp{gdb_get_args} command which partially overlaps with the
19344 functionality of @samp{-stack-list-arguments}.
19346 @subsubheading Example
19353 frame=@{level="0",addr="0x00010734",func="callee4",
19354 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19355 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
19356 frame=@{level="1",addr="0x0001076c",func="callee3",
19357 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19358 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
19359 frame=@{level="2",addr="0x0001078c",func="callee2",
19360 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19361 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
19362 frame=@{level="3",addr="0x000107b4",func="callee1",
19363 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19364 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
19365 frame=@{level="4",addr="0x000107e0",func="main",
19366 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19367 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
19369 -stack-list-arguments 0
19372 frame=@{level="0",args=[]@},
19373 frame=@{level="1",args=[name="strarg"]@},
19374 frame=@{level="2",args=[name="intarg",name="strarg"]@},
19375 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
19376 frame=@{level="4",args=[]@}]
19378 -stack-list-arguments 1
19381 frame=@{level="0",args=[]@},
19383 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19384 frame=@{level="2",args=[
19385 @{name="intarg",value="2"@},
19386 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19387 @{frame=@{level="3",args=[
19388 @{name="intarg",value="2"@},
19389 @{name="strarg",value="0x11940 \"A string argument.\""@},
19390 @{name="fltarg",value="3.5"@}]@},
19391 frame=@{level="4",args=[]@}]
19393 -stack-list-arguments 0 2 2
19394 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
19396 -stack-list-arguments 1 2 2
19397 ^done,stack-args=[frame=@{level="2",
19398 args=[@{name="intarg",value="2"@},
19399 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
19403 @c @subheading -stack-list-exception-handlers
19406 @subheading The @code{-stack-list-frames} Command
19407 @findex -stack-list-frames
19409 @subsubheading Synopsis
19412 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
19415 List the frames currently on the stack. For each frame it displays the
19420 The frame number, 0 being the topmost frame, i.e., the innermost function.
19422 The @code{$pc} value for that frame.
19426 File name of the source file where the function lives.
19428 Line number corresponding to the @code{$pc}.
19431 If invoked without arguments, this command prints a backtrace for the
19432 whole stack. If given two integer arguments, it shows the frames whose
19433 levels are between the two arguments (inclusive). If the two arguments
19434 are equal, it shows the single frame at the corresponding level. It is
19435 an error if @var{low-frame} is larger than the actual number of
19436 frames. On the other hand, @var{high-frame} may be larger than the
19437 actual number of frames, in which case only existing frames will be returned.
19439 @subsubheading @value{GDBN} Command
19441 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
19443 @subsubheading Example
19445 Full stack backtrace:
19451 [frame=@{level="0",addr="0x0001076c",func="foo",
19452 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
19453 frame=@{level="1",addr="0x000107a4",func="foo",
19454 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19455 frame=@{level="2",addr="0x000107a4",func="foo",
19456 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19457 frame=@{level="3",addr="0x000107a4",func="foo",
19458 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19459 frame=@{level="4",addr="0x000107a4",func="foo",
19460 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19461 frame=@{level="5",addr="0x000107a4",func="foo",
19462 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19463 frame=@{level="6",addr="0x000107a4",func="foo",
19464 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19465 frame=@{level="7",addr="0x000107a4",func="foo",
19466 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19467 frame=@{level="8",addr="0x000107a4",func="foo",
19468 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19469 frame=@{level="9",addr="0x000107a4",func="foo",
19470 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19471 frame=@{level="10",addr="0x000107a4",func="foo",
19472 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19473 frame=@{level="11",addr="0x00010738",func="main",
19474 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
19478 Show frames between @var{low_frame} and @var{high_frame}:
19482 -stack-list-frames 3 5
19484 [frame=@{level="3",addr="0x000107a4",func="foo",
19485 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19486 frame=@{level="4",addr="0x000107a4",func="foo",
19487 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19488 frame=@{level="5",addr="0x000107a4",func="foo",
19489 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
19493 Show a single frame:
19497 -stack-list-frames 3 3
19499 [frame=@{level="3",addr="0x000107a4",func="foo",
19500 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
19505 @subheading The @code{-stack-list-locals} Command
19506 @findex -stack-list-locals
19508 @subsubheading Synopsis
19511 -stack-list-locals @var{print-values}
19514 Display the local variable names for the selected frame. If
19515 @var{print-values} is 0 or @code{--no-values}, print only the names of
19516 the variables; if it is 1 or @code{--all-values}, print also their
19517 values; and if it is 2 or @code{--simple-values}, print the name,
19518 type and value for simple data types and the name and type for arrays,
19519 structures and unions. In this last case, a frontend can immediately
19520 display the value of simple data types and create variable objects for
19521 other data types when the user wishes to explore their values in
19524 @subsubheading @value{GDBN} Command
19526 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
19528 @subsubheading Example
19532 -stack-list-locals 0
19533 ^done,locals=[name="A",name="B",name="C"]
19535 -stack-list-locals --all-values
19536 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
19537 @{name="C",value="@{1, 2, 3@}"@}]
19538 -stack-list-locals --simple-values
19539 ^done,locals=[@{name="A",type="int",value="1"@},
19540 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
19545 @subheading The @code{-stack-select-frame} Command
19546 @findex -stack-select-frame
19548 @subsubheading Synopsis
19551 -stack-select-frame @var{framenum}
19554 Change the selected frame. Select a different frame @var{framenum} on
19557 @subsubheading @value{GDBN} Command
19559 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
19560 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
19562 @subsubheading Example
19566 -stack-select-frame 2
19571 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19572 @node GDB/MI Variable Objects
19573 @section @sc{gdb/mi} Variable Objects
19577 @subheading Motivation for Variable Objects in @sc{gdb/mi}
19579 For the implementation of a variable debugger window (locals, watched
19580 expressions, etc.), we are proposing the adaptation of the existing code
19581 used by @code{Insight}.
19583 The two main reasons for that are:
19587 It has been proven in practice (it is already on its second generation).
19590 It will shorten development time (needless to say how important it is
19594 The original interface was designed to be used by Tcl code, so it was
19595 slightly changed so it could be used through @sc{gdb/mi}. This section
19596 describes the @sc{gdb/mi} operations that will be available and gives some
19597 hints about their use.
19599 @emph{Note}: In addition to the set of operations described here, we
19600 expect the @sc{gui} implementation of a variable window to require, at
19601 least, the following operations:
19604 @item @code{-gdb-show} @code{output-radix}
19605 @item @code{-stack-list-arguments}
19606 @item @code{-stack-list-locals}
19607 @item @code{-stack-select-frame}
19612 @subheading Introduction to Variable Objects
19614 @cindex variable objects in @sc{gdb/mi}
19616 Variable objects are "object-oriented" MI interface for examining and
19617 changing values of expressions. Unlike some other MI interfaces that
19618 work with expressions, variable objects are specifically designed for
19619 simple and efficient presentation in the frontend. A variable object
19620 is identified by string name. When a variable object is created, the
19621 frontend specifies the expression for that variable object. The
19622 expression can be a simple variable, or it can be an arbitrary complex
19623 expression, and can even involve CPU registers. After creating a
19624 variable object, the frontend can invoke other variable object
19625 operations---for example to obtain or change the value of a variable
19626 object, or to change display format.
19628 Variable objects have hierarchical tree structure. Any variable object
19629 that corresponds to a composite type, such as structure in C, has
19630 a number of child variable objects, for example corresponding to each
19631 element of a structure. A child variable object can itself have
19632 children, recursively. Recursion ends when we reach
19633 leaf variable objects, which always have built-in types. Child variable
19634 objects are created only by explicit request, so if a frontend
19635 is not interested in the children of a particular variable object, no
19636 child will be created.
19638 For a leaf variable object it is possible to obtain its value as a
19639 string, or set the value from a string. String value can be also
19640 obtained for a non-leaf variable object, but it's generally a string
19641 that only indicates the type of the object, and does not list its
19642 contents. Assignment to a non-leaf variable object is not allowed.
19644 A frontend does not need to read the values of all variable objects each time
19645 the program stops. Instead, MI provides an update command that lists all
19646 variable objects whose values has changed since the last update
19647 operation. This considerably reduces the amount of data that must
19648 be transferred to the frontend. As noted above, children variable
19649 objects are created on demand, and only leaf variable objects have a
19650 real value. As result, gdb will read target memory only for leaf
19651 variables that frontend has created.
19653 The automatic update is not always desirable. For example, a frontend
19654 might want to keep a value of some expression for future reference,
19655 and never update it. For another example, fetching memory is
19656 relatively slow for embedded targets, so a frontend might want
19657 to disable automatic update for the variables that are either not
19658 visible on the screen, or ``closed''. This is possible using so
19659 called ``frozen variable objects''. Such variable objects are never
19660 implicitly updated.
19662 The following is the complete set of @sc{gdb/mi} operations defined to
19663 access this functionality:
19665 @multitable @columnfractions .4 .6
19666 @item @strong{Operation}
19667 @tab @strong{Description}
19669 @item @code{-var-create}
19670 @tab create a variable object
19671 @item @code{-var-delete}
19672 @tab delete the variable object and/or its children
19673 @item @code{-var-set-format}
19674 @tab set the display format of this variable
19675 @item @code{-var-show-format}
19676 @tab show the display format of this variable
19677 @item @code{-var-info-num-children}
19678 @tab tells how many children this object has
19679 @item @code{-var-list-children}
19680 @tab return a list of the object's children
19681 @item @code{-var-info-type}
19682 @tab show the type of this variable object
19683 @item @code{-var-info-expression}
19684 @tab print parent-relative expression that this variable object represents
19685 @item @code{-var-info-path-expression}
19686 @tab print full expression that this variable object represents
19687 @item @code{-var-show-attributes}
19688 @tab is this variable editable? does it exist here?
19689 @item @code{-var-evaluate-expression}
19690 @tab get the value of this variable
19691 @item @code{-var-assign}
19692 @tab set the value of this variable
19693 @item @code{-var-update}
19694 @tab update the variable and its children
19695 @item @code{-var-set-frozen}
19696 @tab set frozeness attribute
19699 In the next subsection we describe each operation in detail and suggest
19700 how it can be used.
19702 @subheading Description And Use of Operations on Variable Objects
19704 @subheading The @code{-var-create} Command
19705 @findex -var-create
19707 @subsubheading Synopsis
19710 -var-create @{@var{name} | "-"@}
19711 @{@var{frame-addr} | "*"@} @var{expression}
19714 This operation creates a variable object, which allows the monitoring of
19715 a variable, the result of an expression, a memory cell or a CPU
19718 The @var{name} parameter is the string by which the object can be
19719 referenced. It must be unique. If @samp{-} is specified, the varobj
19720 system will generate a string ``varNNNNNN'' automatically. It will be
19721 unique provided that one does not specify @var{name} on that format.
19722 The command fails if a duplicate name is found.
19724 The frame under which the expression should be evaluated can be
19725 specified by @var{frame-addr}. A @samp{*} indicates that the current
19726 frame should be used.
19728 @var{expression} is any expression valid on the current language set (must not
19729 begin with a @samp{*}), or one of the following:
19733 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
19736 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
19739 @samp{$@var{regname}} --- a CPU register name
19742 @subsubheading Result
19744 This operation returns the name, number of children and the type of the
19745 object created. Type is returned as a string as the ones generated by
19746 the @value{GDBN} CLI:
19749 name="@var{name}",numchild="N",type="@var{type}"
19753 @subheading The @code{-var-delete} Command
19754 @findex -var-delete
19756 @subsubheading Synopsis
19759 -var-delete [ -c ] @var{name}
19762 Deletes a previously created variable object and all of its children.
19763 With the @samp{-c} option, just deletes the children.
19765 Returns an error if the object @var{name} is not found.
19768 @subheading The @code{-var-set-format} Command
19769 @findex -var-set-format
19771 @subsubheading Synopsis
19774 -var-set-format @var{name} @var{format-spec}
19777 Sets the output format for the value of the object @var{name} to be
19780 The syntax for the @var{format-spec} is as follows:
19783 @var{format-spec} @expansion{}
19784 @{binary | decimal | hexadecimal | octal | natural@}
19787 The natural format is the default format choosen automatically
19788 based on the variable type (like decimal for an @code{int}, hex
19789 for pointers, etc.).
19791 For a variable with children, the format is set only on the
19792 variable itself, and the children are not affected.
19794 @subheading The @code{-var-show-format} Command
19795 @findex -var-show-format
19797 @subsubheading Synopsis
19800 -var-show-format @var{name}
19803 Returns the format used to display the value of the object @var{name}.
19806 @var{format} @expansion{}
19811 @subheading The @code{-var-info-num-children} Command
19812 @findex -var-info-num-children
19814 @subsubheading Synopsis
19817 -var-info-num-children @var{name}
19820 Returns the number of children of a variable object @var{name}:
19827 @subheading The @code{-var-list-children} Command
19828 @findex -var-list-children
19830 @subsubheading Synopsis
19833 -var-list-children [@var{print-values}] @var{name}
19835 @anchor{-var-list-children}
19837 Return a list of the children of the specified variable object and
19838 create variable objects for them, if they do not already exist. With
19839 a single argument or if @var{print-values} has a value for of 0 or
19840 @code{--no-values}, print only the names of the variables; if
19841 @var{print-values} is 1 or @code{--all-values}, also print their
19842 values; and if it is 2 or @code{--simple-values} print the name and
19843 value for simple data types and just the name for arrays, structures
19846 @subsubheading Example
19850 -var-list-children n
19851 ^done,numchild=@var{n},children=[@{name=@var{name},
19852 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
19854 -var-list-children --all-values n
19855 ^done,numchild=@var{n},children=[@{name=@var{name},
19856 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
19860 @subheading The @code{-var-info-type} Command
19861 @findex -var-info-type
19863 @subsubheading Synopsis
19866 -var-info-type @var{name}
19869 Returns the type of the specified variable @var{name}. The type is
19870 returned as a string in the same format as it is output by the
19874 type=@var{typename}
19878 @subheading The @code{-var-info-expression} Command
19879 @findex -var-info-expression
19881 @subsubheading Synopsis
19884 -var-info-expression @var{name}
19887 Returns a string that is suitable for presenting this
19888 variable object in user interface. The string is generally
19889 not valid expression in the current language, and cannot be evaluated.
19891 For example, if @code{a} is an array, and variable object
19892 @code{A} was created for @code{a}, then we'll get this output:
19895 (gdb) -var-info-expression A.1
19896 ^done,lang="C",exp="1"
19900 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
19902 Note that the output of the @code{-var-list-children} command also
19903 includes those expressions, so the @code{-var-info-expression} command
19906 @subheading The @code{-var-info-path-expression} Command
19907 @findex -var-info-path-expression
19909 @subsubheading Synopsis
19912 -var-info-path-expression @var{name}
19915 Returns an expression that can be evaluated in the current
19916 context and will yield the same value that a variable object has.
19917 Compare this with the @code{-var-info-expression} command, which
19918 result can be used only for UI presentation. Typical use of
19919 the @code{-var-info-path-expression} command is creating a
19920 watchpoint from a variable object.
19922 For example, suppose @code{C} is a C@t{++} class, derived from class
19923 @code{Base}, and that the @code{Base} class has a member called
19924 @code{m_size}. Assume a variable @code{c} is has the type of
19925 @code{C} and a variable object @code{C} was created for variable
19926 @code{c}. Then, we'll get this output:
19928 (gdb) -var-info-path-expression C.Base.public.m_size
19929 ^done,path_expr=((Base)c).m_size)
19932 @subheading The @code{-var-show-attributes} Command
19933 @findex -var-show-attributes
19935 @subsubheading Synopsis
19938 -var-show-attributes @var{name}
19941 List attributes of the specified variable object @var{name}:
19944 status=@var{attr} [ ( ,@var{attr} )* ]
19948 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
19950 @subheading The @code{-var-evaluate-expression} Command
19951 @findex -var-evaluate-expression
19953 @subsubheading Synopsis
19956 -var-evaluate-expression @var{name}
19959 Evaluates the expression that is represented by the specified variable
19960 object and returns its value as a string. The format of the
19961 string can be changed using the @code{-var-set-format} command.
19967 Note that one must invoke @code{-var-list-children} for a variable
19968 before the value of a child variable can be evaluated.
19970 @subheading The @code{-var-assign} Command
19971 @findex -var-assign
19973 @subsubheading Synopsis
19976 -var-assign @var{name} @var{expression}
19979 Assigns the value of @var{expression} to the variable object specified
19980 by @var{name}. The object must be @samp{editable}. If the variable's
19981 value is altered by the assign, the variable will show up in any
19982 subsequent @code{-var-update} list.
19984 @subsubheading Example
19992 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
19996 @subheading The @code{-var-update} Command
19997 @findex -var-update
19999 @subsubheading Synopsis
20002 -var-update [@var{print-values}] @{@var{name} | "*"@}
20005 Reevaluate the expressions corresponding to the variable object
20006 @var{name} and all its direct and indirect children, and return the
20007 list of variable objects whose values have changed; @var{name} must
20008 be a root variable object. Here, ``changed'' means that the result of
20009 @code{-var-evaluate-expression} before and after the
20010 @code{-var-update} is different. If @samp{*} is used as the variable
20011 object names, all existing variable objects are updated, except
20012 for frozen ones (@pxref{-var-set-frozen}). The option
20013 @var{print-values} determines whether both names and values, or just
20014 names are printed. The possible values of this options are the same
20015 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
20016 recommended to use the @samp{--all-values} option, to reduce the
20017 number of MI commands needed on each program stop.
20020 @subsubheading Example
20027 -var-update --all-values var1
20028 ^done,changelist=[@{name="var1",value="3",in_scope="true",
20029 type_changed="false"@}]
20033 @anchor{-var-update}
20034 The field in_scope may take three values:
20038 The variable object's current value is valid.
20041 The variable object does not currently hold a valid value but it may
20042 hold one in the future if its associated expression comes back into
20046 The variable object no longer holds a valid value.
20047 This can occur when the executable file being debugged has changed,
20048 either through recompilation or by using the @value{GDBN} @code{file}
20049 command. The front end should normally choose to delete these variable
20053 In the future new values may be added to this list so the front should
20054 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
20056 @subheading The @code{-var-set-frozen} Command
20057 @findex -var-set-frozen
20058 @anchor{-var-set-frozen}
20060 @subsubheading Synopsis
20063 -var-set-frozen @var{name} @var{flag}
20066 Set the frozenness flag on the variable object @var{name}. The
20067 @var{flag} parameter should be either @samp{1} to make the variable
20068 frozen or @samp{0} to make it unfrozen. If a variable object is
20069 frozen, then neither itself, nor any of its children, are
20070 implicitly updated by @code{-var-update} of
20071 a parent variable or by @code{-var-update *}. Only
20072 @code{-var-update} of the variable itself will update its value and
20073 values of its children. After a variable object is unfrozen, it is
20074 implicitly updated by all subsequent @code{-var-update} operations.
20075 Unfreezing a variable does not update it, only subsequent
20076 @code{-var-update} does.
20078 @subsubheading Example
20082 -var-set-frozen V 1
20088 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20089 @node GDB/MI Data Manipulation
20090 @section @sc{gdb/mi} Data Manipulation
20092 @cindex data manipulation, in @sc{gdb/mi}
20093 @cindex @sc{gdb/mi}, data manipulation
20094 This section describes the @sc{gdb/mi} commands that manipulate data:
20095 examine memory and registers, evaluate expressions, etc.
20097 @c REMOVED FROM THE INTERFACE.
20098 @c @subheading -data-assign
20099 @c Change the value of a program variable. Plenty of side effects.
20100 @c @subsubheading GDB Command
20102 @c @subsubheading Example
20105 @subheading The @code{-data-disassemble} Command
20106 @findex -data-disassemble
20108 @subsubheading Synopsis
20112 [ -s @var{start-addr} -e @var{end-addr} ]
20113 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
20121 @item @var{start-addr}
20122 is the beginning address (or @code{$pc})
20123 @item @var{end-addr}
20125 @item @var{filename}
20126 is the name of the file to disassemble
20127 @item @var{linenum}
20128 is the line number to disassemble around
20130 is the number of disassembly lines to be produced. If it is -1,
20131 the whole function will be disassembled, in case no @var{end-addr} is
20132 specified. If @var{end-addr} is specified as a non-zero value, and
20133 @var{lines} is lower than the number of disassembly lines between
20134 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
20135 displayed; if @var{lines} is higher than the number of lines between
20136 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
20139 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
20143 @subsubheading Result
20145 The output for each instruction is composed of four fields:
20154 Note that whatever included in the instruction field, is not manipulated
20155 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
20157 @subsubheading @value{GDBN} Command
20159 There's no direct mapping from this command to the CLI.
20161 @subsubheading Example
20163 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
20167 -data-disassemble -s $pc -e "$pc + 20" -- 0
20170 @{address="0x000107c0",func-name="main",offset="4",
20171 inst="mov 2, %o0"@},
20172 @{address="0x000107c4",func-name="main",offset="8",
20173 inst="sethi %hi(0x11800), %o2"@},
20174 @{address="0x000107c8",func-name="main",offset="12",
20175 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
20176 @{address="0x000107cc",func-name="main",offset="16",
20177 inst="sethi %hi(0x11800), %o2"@},
20178 @{address="0x000107d0",func-name="main",offset="20",
20179 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
20183 Disassemble the whole @code{main} function. Line 32 is part of
20187 -data-disassemble -f basics.c -l 32 -- 0
20189 @{address="0x000107bc",func-name="main",offset="0",
20190 inst="save %sp, -112, %sp"@},
20191 @{address="0x000107c0",func-name="main",offset="4",
20192 inst="mov 2, %o0"@},
20193 @{address="0x000107c4",func-name="main",offset="8",
20194 inst="sethi %hi(0x11800), %o2"@},
20196 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
20197 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
20201 Disassemble 3 instructions from the start of @code{main}:
20205 -data-disassemble -f basics.c -l 32 -n 3 -- 0
20207 @{address="0x000107bc",func-name="main",offset="0",
20208 inst="save %sp, -112, %sp"@},
20209 @{address="0x000107c0",func-name="main",offset="4",
20210 inst="mov 2, %o0"@},
20211 @{address="0x000107c4",func-name="main",offset="8",
20212 inst="sethi %hi(0x11800), %o2"@}]
20216 Disassemble 3 instructions from the start of @code{main} in mixed mode:
20220 -data-disassemble -f basics.c -l 32 -n 3 -- 1
20222 src_and_asm_line=@{line="31",
20223 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
20224 testsuite/gdb.mi/basics.c",line_asm_insn=[
20225 @{address="0x000107bc",func-name="main",offset="0",
20226 inst="save %sp, -112, %sp"@}]@},
20227 src_and_asm_line=@{line="32",
20228 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
20229 testsuite/gdb.mi/basics.c",line_asm_insn=[
20230 @{address="0x000107c0",func-name="main",offset="4",
20231 inst="mov 2, %o0"@},
20232 @{address="0x000107c4",func-name="main",offset="8",
20233 inst="sethi %hi(0x11800), %o2"@}]@}]
20238 @subheading The @code{-data-evaluate-expression} Command
20239 @findex -data-evaluate-expression
20241 @subsubheading Synopsis
20244 -data-evaluate-expression @var{expr}
20247 Evaluate @var{expr} as an expression. The expression could contain an
20248 inferior function call. The function call will execute synchronously.
20249 If the expression contains spaces, it must be enclosed in double quotes.
20251 @subsubheading @value{GDBN} Command
20253 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
20254 @samp{call}. In @code{gdbtk} only, there's a corresponding
20255 @samp{gdb_eval} command.
20257 @subsubheading Example
20259 In the following example, the numbers that precede the commands are the
20260 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
20261 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
20265 211-data-evaluate-expression A
20268 311-data-evaluate-expression &A
20269 311^done,value="0xefffeb7c"
20271 411-data-evaluate-expression A+3
20274 511-data-evaluate-expression "A + 3"
20280 @subheading The @code{-data-list-changed-registers} Command
20281 @findex -data-list-changed-registers
20283 @subsubheading Synopsis
20286 -data-list-changed-registers
20289 Display a list of the registers that have changed.
20291 @subsubheading @value{GDBN} Command
20293 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
20294 has the corresponding command @samp{gdb_changed_register_list}.
20296 @subsubheading Example
20298 On a PPC MBX board:
20306 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
20307 args=[],file="try.c",fullname="/home/foo/bar/try.c",line="5"@}
20309 -data-list-changed-registers
20310 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
20311 "10","11","13","14","15","16","17","18","19","20","21","22","23",
20312 "24","25","26","27","28","30","31","64","65","66","67","69"]
20317 @subheading The @code{-data-list-register-names} Command
20318 @findex -data-list-register-names
20320 @subsubheading Synopsis
20323 -data-list-register-names [ ( @var{regno} )+ ]
20326 Show a list of register names for the current target. If no arguments
20327 are given, it shows a list of the names of all the registers. If
20328 integer numbers are given as arguments, it will print a list of the
20329 names of the registers corresponding to the arguments. To ensure
20330 consistency between a register name and its number, the output list may
20331 include empty register names.
20333 @subsubheading @value{GDBN} Command
20335 @value{GDBN} does not have a command which corresponds to
20336 @samp{-data-list-register-names}. In @code{gdbtk} there is a
20337 corresponding command @samp{gdb_regnames}.
20339 @subsubheading Example
20341 For the PPC MBX board:
20344 -data-list-register-names
20345 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
20346 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
20347 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
20348 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
20349 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
20350 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
20351 "", "pc","ps","cr","lr","ctr","xer"]
20353 -data-list-register-names 1 2 3
20354 ^done,register-names=["r1","r2","r3"]
20358 @subheading The @code{-data-list-register-values} Command
20359 @findex -data-list-register-values
20361 @subsubheading Synopsis
20364 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
20367 Display the registers' contents. @var{fmt} is the format according to
20368 which the registers' contents are to be returned, followed by an optional
20369 list of numbers specifying the registers to display. A missing list of
20370 numbers indicates that the contents of all the registers must be returned.
20372 Allowed formats for @var{fmt} are:
20389 @subsubheading @value{GDBN} Command
20391 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
20392 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
20394 @subsubheading Example
20396 For a PPC MBX board (note: line breaks are for readability only, they
20397 don't appear in the actual output):
20401 -data-list-register-values r 64 65
20402 ^done,register-values=[@{number="64",value="0xfe00a300"@},
20403 @{number="65",value="0x00029002"@}]
20405 -data-list-register-values x
20406 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
20407 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
20408 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
20409 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
20410 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
20411 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
20412 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
20413 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
20414 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
20415 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
20416 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
20417 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
20418 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
20419 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
20420 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
20421 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
20422 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
20423 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
20424 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
20425 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
20426 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
20427 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
20428 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
20429 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
20430 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
20431 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
20432 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
20433 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
20434 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
20435 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
20436 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
20437 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
20438 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
20439 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
20440 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
20441 @{number="69",value="0x20002b03"@}]
20446 @subheading The @code{-data-read-memory} Command
20447 @findex -data-read-memory
20449 @subsubheading Synopsis
20452 -data-read-memory [ -o @var{byte-offset} ]
20453 @var{address} @var{word-format} @var{word-size}
20454 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
20461 @item @var{address}
20462 An expression specifying the address of the first memory word to be
20463 read. Complex expressions containing embedded white space should be
20464 quoted using the C convention.
20466 @item @var{word-format}
20467 The format to be used to print the memory words. The notation is the
20468 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
20471 @item @var{word-size}
20472 The size of each memory word in bytes.
20474 @item @var{nr-rows}
20475 The number of rows in the output table.
20477 @item @var{nr-cols}
20478 The number of columns in the output table.
20481 If present, indicates that each row should include an @sc{ascii} dump. The
20482 value of @var{aschar} is used as a padding character when a byte is not a
20483 member of the printable @sc{ascii} character set (printable @sc{ascii}
20484 characters are those whose code is between 32 and 126, inclusively).
20486 @item @var{byte-offset}
20487 An offset to add to the @var{address} before fetching memory.
20490 This command displays memory contents as a table of @var{nr-rows} by
20491 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
20492 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
20493 (returned as @samp{total-bytes}). Should less than the requested number
20494 of bytes be returned by the target, the missing words are identified
20495 using @samp{N/A}. The number of bytes read from the target is returned
20496 in @samp{nr-bytes} and the starting address used to read memory in
20499 The address of the next/previous row or page is available in
20500 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
20503 @subsubheading @value{GDBN} Command
20505 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
20506 @samp{gdb_get_mem} memory read command.
20508 @subsubheading Example
20510 Read six bytes of memory starting at @code{bytes+6} but then offset by
20511 @code{-6} bytes. Format as three rows of two columns. One byte per
20512 word. Display each word in hex.
20516 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
20517 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
20518 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
20519 prev-page="0x0000138a",memory=[
20520 @{addr="0x00001390",data=["0x00","0x01"]@},
20521 @{addr="0x00001392",data=["0x02","0x03"]@},
20522 @{addr="0x00001394",data=["0x04","0x05"]@}]
20526 Read two bytes of memory starting at address @code{shorts + 64} and
20527 display as a single word formatted in decimal.
20531 5-data-read-memory shorts+64 d 2 1 1
20532 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
20533 next-row="0x00001512",prev-row="0x0000150e",
20534 next-page="0x00001512",prev-page="0x0000150e",memory=[
20535 @{addr="0x00001510",data=["128"]@}]
20539 Read thirty two bytes of memory starting at @code{bytes+16} and format
20540 as eight rows of four columns. Include a string encoding with @samp{x}
20541 used as the non-printable character.
20545 4-data-read-memory bytes+16 x 1 8 4 x
20546 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
20547 next-row="0x000013c0",prev-row="0x0000139c",
20548 next-page="0x000013c0",prev-page="0x00001380",memory=[
20549 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
20550 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
20551 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
20552 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
20553 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
20554 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
20555 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
20556 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
20560 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20561 @node GDB/MI Tracepoint Commands
20562 @section @sc{gdb/mi} Tracepoint Commands
20564 The tracepoint commands are not yet implemented.
20566 @c @subheading -trace-actions
20568 @c @subheading -trace-delete
20570 @c @subheading -trace-disable
20572 @c @subheading -trace-dump
20574 @c @subheading -trace-enable
20576 @c @subheading -trace-exists
20578 @c @subheading -trace-find
20580 @c @subheading -trace-frame-number
20582 @c @subheading -trace-info
20584 @c @subheading -trace-insert
20586 @c @subheading -trace-list
20588 @c @subheading -trace-pass-count
20590 @c @subheading -trace-save
20592 @c @subheading -trace-start
20594 @c @subheading -trace-stop
20597 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20598 @node GDB/MI Symbol Query
20599 @section @sc{gdb/mi} Symbol Query Commands
20602 @subheading The @code{-symbol-info-address} Command
20603 @findex -symbol-info-address
20605 @subsubheading Synopsis
20608 -symbol-info-address @var{symbol}
20611 Describe where @var{symbol} is stored.
20613 @subsubheading @value{GDBN} Command
20615 The corresponding @value{GDBN} command is @samp{info address}.
20617 @subsubheading Example
20621 @subheading The @code{-symbol-info-file} Command
20622 @findex -symbol-info-file
20624 @subsubheading Synopsis
20630 Show the file for the symbol.
20632 @subsubheading @value{GDBN} Command
20634 There's no equivalent @value{GDBN} command. @code{gdbtk} has
20635 @samp{gdb_find_file}.
20637 @subsubheading Example
20641 @subheading The @code{-symbol-info-function} Command
20642 @findex -symbol-info-function
20644 @subsubheading Synopsis
20647 -symbol-info-function
20650 Show which function the symbol lives in.
20652 @subsubheading @value{GDBN} Command
20654 @samp{gdb_get_function} in @code{gdbtk}.
20656 @subsubheading Example
20660 @subheading The @code{-symbol-info-line} Command
20661 @findex -symbol-info-line
20663 @subsubheading Synopsis
20669 Show the core addresses of the code for a source line.
20671 @subsubheading @value{GDBN} Command
20673 The corresponding @value{GDBN} command is @samp{info line}.
20674 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
20676 @subsubheading Example
20680 @subheading The @code{-symbol-info-symbol} Command
20681 @findex -symbol-info-symbol
20683 @subsubheading Synopsis
20686 -symbol-info-symbol @var{addr}
20689 Describe what symbol is at location @var{addr}.
20691 @subsubheading @value{GDBN} Command
20693 The corresponding @value{GDBN} command is @samp{info symbol}.
20695 @subsubheading Example
20699 @subheading The @code{-symbol-list-functions} Command
20700 @findex -symbol-list-functions
20702 @subsubheading Synopsis
20705 -symbol-list-functions
20708 List the functions in the executable.
20710 @subsubheading @value{GDBN} Command
20712 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
20713 @samp{gdb_search} in @code{gdbtk}.
20715 @subsubheading Example
20719 @subheading The @code{-symbol-list-lines} Command
20720 @findex -symbol-list-lines
20722 @subsubheading Synopsis
20725 -symbol-list-lines @var{filename}
20728 Print the list of lines that contain code and their associated program
20729 addresses for the given source filename. The entries are sorted in
20730 ascending PC order.
20732 @subsubheading @value{GDBN} Command
20734 There is no corresponding @value{GDBN} command.
20736 @subsubheading Example
20739 -symbol-list-lines basics.c
20740 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
20745 @subheading The @code{-symbol-list-types} Command
20746 @findex -symbol-list-types
20748 @subsubheading Synopsis
20754 List all the type names.
20756 @subsubheading @value{GDBN} Command
20758 The corresponding commands are @samp{info types} in @value{GDBN},
20759 @samp{gdb_search} in @code{gdbtk}.
20761 @subsubheading Example
20765 @subheading The @code{-symbol-list-variables} Command
20766 @findex -symbol-list-variables
20768 @subsubheading Synopsis
20771 -symbol-list-variables
20774 List all the global and static variable names.
20776 @subsubheading @value{GDBN} Command
20778 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
20780 @subsubheading Example
20784 @subheading The @code{-symbol-locate} Command
20785 @findex -symbol-locate
20787 @subsubheading Synopsis
20793 @subsubheading @value{GDBN} Command
20795 @samp{gdb_loc} in @code{gdbtk}.
20797 @subsubheading Example
20801 @subheading The @code{-symbol-type} Command
20802 @findex -symbol-type
20804 @subsubheading Synopsis
20807 -symbol-type @var{variable}
20810 Show type of @var{variable}.
20812 @subsubheading @value{GDBN} Command
20814 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
20815 @samp{gdb_obj_variable}.
20817 @subsubheading Example
20821 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20822 @node GDB/MI File Commands
20823 @section @sc{gdb/mi} File Commands
20825 This section describes the GDB/MI commands to specify executable file names
20826 and to read in and obtain symbol table information.
20828 @subheading The @code{-file-exec-and-symbols} Command
20829 @findex -file-exec-and-symbols
20831 @subsubheading Synopsis
20834 -file-exec-and-symbols @var{file}
20837 Specify the executable file to be debugged. This file is the one from
20838 which the symbol table is also read. If no file is specified, the
20839 command clears the executable and symbol information. If breakpoints
20840 are set when using this command with no arguments, @value{GDBN} will produce
20841 error messages. Otherwise, no output is produced, except a completion
20844 @subsubheading @value{GDBN} Command
20846 The corresponding @value{GDBN} command is @samp{file}.
20848 @subsubheading Example
20852 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
20858 @subheading The @code{-file-exec-file} Command
20859 @findex -file-exec-file
20861 @subsubheading Synopsis
20864 -file-exec-file @var{file}
20867 Specify the executable file to be debugged. Unlike
20868 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
20869 from this file. If used without argument, @value{GDBN} clears the information
20870 about the executable file. No output is produced, except a completion
20873 @subsubheading @value{GDBN} Command
20875 The corresponding @value{GDBN} command is @samp{exec-file}.
20877 @subsubheading Example
20881 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
20887 @subheading The @code{-file-list-exec-sections} Command
20888 @findex -file-list-exec-sections
20890 @subsubheading Synopsis
20893 -file-list-exec-sections
20896 List the sections of the current executable file.
20898 @subsubheading @value{GDBN} Command
20900 The @value{GDBN} command @samp{info file} shows, among the rest, the same
20901 information as this command. @code{gdbtk} has a corresponding command
20902 @samp{gdb_load_info}.
20904 @subsubheading Example
20908 @subheading The @code{-file-list-exec-source-file} Command
20909 @findex -file-list-exec-source-file
20911 @subsubheading Synopsis
20914 -file-list-exec-source-file
20917 List the line number, the current source file, and the absolute path
20918 to the current source file for the current executable.
20920 @subsubheading @value{GDBN} Command
20922 The @value{GDBN} equivalent is @samp{info source}
20924 @subsubheading Example
20928 123-file-list-exec-source-file
20929 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c"
20934 @subheading The @code{-file-list-exec-source-files} Command
20935 @findex -file-list-exec-source-files
20937 @subsubheading Synopsis
20940 -file-list-exec-source-files
20943 List the source files for the current executable.
20945 It will always output the filename, but only when @value{GDBN} can find
20946 the absolute file name of a source file, will it output the fullname.
20948 @subsubheading @value{GDBN} Command
20950 The @value{GDBN} equivalent is @samp{info sources}.
20951 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
20953 @subsubheading Example
20956 -file-list-exec-source-files
20958 @{file=foo.c,fullname=/home/foo.c@},
20959 @{file=/home/bar.c,fullname=/home/bar.c@},
20960 @{file=gdb_could_not_find_fullpath.c@}]
20964 @subheading The @code{-file-list-shared-libraries} Command
20965 @findex -file-list-shared-libraries
20967 @subsubheading Synopsis
20970 -file-list-shared-libraries
20973 List the shared libraries in the program.
20975 @subsubheading @value{GDBN} Command
20977 The corresponding @value{GDBN} command is @samp{info shared}.
20979 @subsubheading Example
20983 @subheading The @code{-file-list-symbol-files} Command
20984 @findex -file-list-symbol-files
20986 @subsubheading Synopsis
20989 -file-list-symbol-files
20994 @subsubheading @value{GDBN} Command
20996 The corresponding @value{GDBN} command is @samp{info file} (part of it).
20998 @subsubheading Example
21002 @subheading The @code{-file-symbol-file} Command
21003 @findex -file-symbol-file
21005 @subsubheading Synopsis
21008 -file-symbol-file @var{file}
21011 Read symbol table info from the specified @var{file} argument. When
21012 used without arguments, clears @value{GDBN}'s symbol table info. No output is
21013 produced, except for a completion notification.
21015 @subsubheading @value{GDBN} Command
21017 The corresponding @value{GDBN} command is @samp{symbol-file}.
21019 @subsubheading Example
21023 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
21029 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21030 @node GDB/MI Memory Overlay Commands
21031 @section @sc{gdb/mi} Memory Overlay Commands
21033 The memory overlay commands are not implemented.
21035 @c @subheading -overlay-auto
21037 @c @subheading -overlay-list-mapping-state
21039 @c @subheading -overlay-list-overlays
21041 @c @subheading -overlay-map
21043 @c @subheading -overlay-off
21045 @c @subheading -overlay-on
21047 @c @subheading -overlay-unmap
21049 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21050 @node GDB/MI Signal Handling Commands
21051 @section @sc{gdb/mi} Signal Handling Commands
21053 Signal handling commands are not implemented.
21055 @c @subheading -signal-handle
21057 @c @subheading -signal-list-handle-actions
21059 @c @subheading -signal-list-signal-types
21063 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21064 @node GDB/MI Target Manipulation
21065 @section @sc{gdb/mi} Target Manipulation Commands
21068 @subheading The @code{-target-attach} Command
21069 @findex -target-attach
21071 @subsubheading Synopsis
21074 -target-attach @var{pid} | @var{file}
21077 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
21079 @subsubheading @value{GDBN} Command
21081 The corresponding @value{GDBN} command is @samp{attach}.
21083 @subsubheading Example
21087 @subheading The @code{-target-compare-sections} Command
21088 @findex -target-compare-sections
21090 @subsubheading Synopsis
21093 -target-compare-sections [ @var{section} ]
21096 Compare data of section @var{section} on target to the exec file.
21097 Without the argument, all sections are compared.
21099 @subsubheading @value{GDBN} Command
21101 The @value{GDBN} equivalent is @samp{compare-sections}.
21103 @subsubheading Example
21107 @subheading The @code{-target-detach} Command
21108 @findex -target-detach
21110 @subsubheading Synopsis
21116 Detach from the remote target which normally resumes its execution.
21119 @subsubheading @value{GDBN} Command
21121 The corresponding @value{GDBN} command is @samp{detach}.
21123 @subsubheading Example
21133 @subheading The @code{-target-disconnect} Command
21134 @findex -target-disconnect
21136 @subsubheading Synopsis
21142 Disconnect from the remote target. There's no output and the target is
21143 generally not resumed.
21145 @subsubheading @value{GDBN} Command
21147 The corresponding @value{GDBN} command is @samp{disconnect}.
21149 @subsubheading Example
21159 @subheading The @code{-target-download} Command
21160 @findex -target-download
21162 @subsubheading Synopsis
21168 Loads the executable onto the remote target.
21169 It prints out an update message every half second, which includes the fields:
21173 The name of the section.
21175 The size of what has been sent so far for that section.
21177 The size of the section.
21179 The total size of what was sent so far (the current and the previous sections).
21181 The size of the overall executable to download.
21185 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
21186 @sc{gdb/mi} Output Syntax}).
21188 In addition, it prints the name and size of the sections, as they are
21189 downloaded. These messages include the following fields:
21193 The name of the section.
21195 The size of the section.
21197 The size of the overall executable to download.
21201 At the end, a summary is printed.
21203 @subsubheading @value{GDBN} Command
21205 The corresponding @value{GDBN} command is @samp{load}.
21207 @subsubheading Example
21209 Note: each status message appears on a single line. Here the messages
21210 have been broken down so that they can fit onto a page.
21215 +download,@{section=".text",section-size="6668",total-size="9880"@}
21216 +download,@{section=".text",section-sent="512",section-size="6668",
21217 total-sent="512",total-size="9880"@}
21218 +download,@{section=".text",section-sent="1024",section-size="6668",
21219 total-sent="1024",total-size="9880"@}
21220 +download,@{section=".text",section-sent="1536",section-size="6668",
21221 total-sent="1536",total-size="9880"@}
21222 +download,@{section=".text",section-sent="2048",section-size="6668",
21223 total-sent="2048",total-size="9880"@}
21224 +download,@{section=".text",section-sent="2560",section-size="6668",
21225 total-sent="2560",total-size="9880"@}
21226 +download,@{section=".text",section-sent="3072",section-size="6668",
21227 total-sent="3072",total-size="9880"@}
21228 +download,@{section=".text",section-sent="3584",section-size="6668",
21229 total-sent="3584",total-size="9880"@}
21230 +download,@{section=".text",section-sent="4096",section-size="6668",
21231 total-sent="4096",total-size="9880"@}
21232 +download,@{section=".text",section-sent="4608",section-size="6668",
21233 total-sent="4608",total-size="9880"@}
21234 +download,@{section=".text",section-sent="5120",section-size="6668",
21235 total-sent="5120",total-size="9880"@}
21236 +download,@{section=".text",section-sent="5632",section-size="6668",
21237 total-sent="5632",total-size="9880"@}
21238 +download,@{section=".text",section-sent="6144",section-size="6668",
21239 total-sent="6144",total-size="9880"@}
21240 +download,@{section=".text",section-sent="6656",section-size="6668",
21241 total-sent="6656",total-size="9880"@}
21242 +download,@{section=".init",section-size="28",total-size="9880"@}
21243 +download,@{section=".fini",section-size="28",total-size="9880"@}
21244 +download,@{section=".data",section-size="3156",total-size="9880"@}
21245 +download,@{section=".data",section-sent="512",section-size="3156",
21246 total-sent="7236",total-size="9880"@}
21247 +download,@{section=".data",section-sent="1024",section-size="3156",
21248 total-sent="7748",total-size="9880"@}
21249 +download,@{section=".data",section-sent="1536",section-size="3156",
21250 total-sent="8260",total-size="9880"@}
21251 +download,@{section=".data",section-sent="2048",section-size="3156",
21252 total-sent="8772",total-size="9880"@}
21253 +download,@{section=".data",section-sent="2560",section-size="3156",
21254 total-sent="9284",total-size="9880"@}
21255 +download,@{section=".data",section-sent="3072",section-size="3156",
21256 total-sent="9796",total-size="9880"@}
21257 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
21263 @subheading The @code{-target-exec-status} Command
21264 @findex -target-exec-status
21266 @subsubheading Synopsis
21269 -target-exec-status
21272 Provide information on the state of the target (whether it is running or
21273 not, for instance).
21275 @subsubheading @value{GDBN} Command
21277 There's no equivalent @value{GDBN} command.
21279 @subsubheading Example
21283 @subheading The @code{-target-list-available-targets} Command
21284 @findex -target-list-available-targets
21286 @subsubheading Synopsis
21289 -target-list-available-targets
21292 List the possible targets to connect to.
21294 @subsubheading @value{GDBN} Command
21296 The corresponding @value{GDBN} command is @samp{help target}.
21298 @subsubheading Example
21302 @subheading The @code{-target-list-current-targets} Command
21303 @findex -target-list-current-targets
21305 @subsubheading Synopsis
21308 -target-list-current-targets
21311 Describe the current target.
21313 @subsubheading @value{GDBN} Command
21315 The corresponding information is printed by @samp{info file} (among
21318 @subsubheading Example
21322 @subheading The @code{-target-list-parameters} Command
21323 @findex -target-list-parameters
21325 @subsubheading Synopsis
21328 -target-list-parameters
21333 @subsubheading @value{GDBN} Command
21337 @subsubheading Example
21341 @subheading The @code{-target-select} Command
21342 @findex -target-select
21344 @subsubheading Synopsis
21347 -target-select @var{type} @var{parameters @dots{}}
21350 Connect @value{GDBN} to the remote target. This command takes two args:
21354 The type of target, for instance @samp{async}, @samp{remote}, etc.
21355 @item @var{parameters}
21356 Device names, host names and the like. @xref{Target Commands, ,
21357 Commands for Managing Targets}, for more details.
21360 The output is a connection notification, followed by the address at
21361 which the target program is, in the following form:
21364 ^connected,addr="@var{address}",func="@var{function name}",
21365 args=[@var{arg list}]
21368 @subsubheading @value{GDBN} Command
21370 The corresponding @value{GDBN} command is @samp{target}.
21372 @subsubheading Example
21376 -target-select async /dev/ttya
21377 ^connected,addr="0xfe00a300",func="??",args=[]
21381 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21382 @node GDB/MI File Transfer Commands
21383 @section @sc{gdb/mi} File Transfer Commands
21386 @subheading The @code{-target-file-put} Command
21387 @findex -target-file-put
21389 @subsubheading Synopsis
21392 -target-file-put @var{hostfile} @var{targetfile}
21395 Copy file @var{hostfile} from the host system (the machine running
21396 @value{GDBN}) to @var{targetfile} on the target system.
21398 @subsubheading @value{GDBN} Command
21400 The corresponding @value{GDBN} command is @samp{remote put}.
21402 @subsubheading Example
21406 -target-file-put localfile remotefile
21412 @subheading The @code{-target-file-put} Command
21413 @findex -target-file-get
21415 @subsubheading Synopsis
21418 -target-file-get @var{targetfile} @var{hostfile}
21421 Copy file @var{targetfile} from the target system to @var{hostfile}
21422 on the host system.
21424 @subsubheading @value{GDBN} Command
21426 The corresponding @value{GDBN} command is @samp{remote get}.
21428 @subsubheading Example
21432 -target-file-get remotefile localfile
21438 @subheading The @code{-target-file-delete} Command
21439 @findex -target-file-delete
21441 @subsubheading Synopsis
21444 -target-file-delete @var{targetfile}
21447 Delete @var{targetfile} from the target system.
21449 @subsubheading @value{GDBN} Command
21451 The corresponding @value{GDBN} command is @samp{remote delete}.
21453 @subsubheading Example
21457 -target-file-delete remotefile
21463 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21464 @node GDB/MI Miscellaneous Commands
21465 @section Miscellaneous @sc{gdb/mi} Commands
21467 @c @subheading -gdb-complete
21469 @subheading The @code{-gdb-exit} Command
21472 @subsubheading Synopsis
21478 Exit @value{GDBN} immediately.
21480 @subsubheading @value{GDBN} Command
21482 Approximately corresponds to @samp{quit}.
21484 @subsubheading Example
21493 @subheading The @code{-exec-abort} Command
21494 @findex -exec-abort
21496 @subsubheading Synopsis
21502 Kill the inferior running program.
21504 @subsubheading @value{GDBN} Command
21506 The corresponding @value{GDBN} command is @samp{kill}.
21508 @subsubheading Example
21512 @subheading The @code{-gdb-set} Command
21515 @subsubheading Synopsis
21521 Set an internal @value{GDBN} variable.
21522 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
21524 @subsubheading @value{GDBN} Command
21526 The corresponding @value{GDBN} command is @samp{set}.
21528 @subsubheading Example
21538 @subheading The @code{-gdb-show} Command
21541 @subsubheading Synopsis
21547 Show the current value of a @value{GDBN} variable.
21549 @subsubheading @value{GDBN} Command
21551 The corresponding @value{GDBN} command is @samp{show}.
21553 @subsubheading Example
21562 @c @subheading -gdb-source
21565 @subheading The @code{-gdb-version} Command
21566 @findex -gdb-version
21568 @subsubheading Synopsis
21574 Show version information for @value{GDBN}. Used mostly in testing.
21576 @subsubheading @value{GDBN} Command
21578 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
21579 default shows this information when you start an interactive session.
21581 @subsubheading Example
21583 @c This example modifies the actual output from GDB to avoid overfull
21589 ~Copyright 2000 Free Software Foundation, Inc.
21590 ~GDB is free software, covered by the GNU General Public License, and
21591 ~you are welcome to change it and/or distribute copies of it under
21592 ~ certain conditions.
21593 ~Type "show copying" to see the conditions.
21594 ~There is absolutely no warranty for GDB. Type "show warranty" for
21596 ~This GDB was configured as
21597 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
21602 @subheading The @code{-list-features} Command
21603 @findex -list-features
21605 Returns a list of particular features of the MI protocol that
21606 this version of gdb implements. A feature can be a command,
21607 or a new field in an output of some command, or even an
21608 important bugfix. While a frontend can sometimes detect presence
21609 of a feature at runtime, it is easier to perform detection at debugger
21612 The command returns a list of strings, with each string naming an
21613 available feature. Each returned string is just a name, it does not
21614 have any internal structure. The list of possible feature names
21620 (gdb) -list-features
21621 ^done,result=["feature1","feature2"]
21624 The current list of features is:
21628 @samp{frozen-varobjs}---indicates presence of the
21629 @code{-var-set-frozen} command, as well as possible presense of the
21630 @code{frozen} field in the output of @code{-varobj-create}.
21632 @samp{pending-breakpoints}---indicates presence of the @code{-f}
21633 option to the @code{-break-insert} command.
21637 @subheading The @code{-interpreter-exec} Command
21638 @findex -interpreter-exec
21640 @subheading Synopsis
21643 -interpreter-exec @var{interpreter} @var{command}
21645 @anchor{-interpreter-exec}
21647 Execute the specified @var{command} in the given @var{interpreter}.
21649 @subheading @value{GDBN} Command
21651 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
21653 @subheading Example
21657 -interpreter-exec console "break main"
21658 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
21659 &"During symbol reading, bad structure-type format.\n"
21660 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
21665 @subheading The @code{-inferior-tty-set} Command
21666 @findex -inferior-tty-set
21668 @subheading Synopsis
21671 -inferior-tty-set /dev/pts/1
21674 Set terminal for future runs of the program being debugged.
21676 @subheading @value{GDBN} Command
21678 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
21680 @subheading Example
21684 -inferior-tty-set /dev/pts/1
21689 @subheading The @code{-inferior-tty-show} Command
21690 @findex -inferior-tty-show
21692 @subheading Synopsis
21698 Show terminal for future runs of program being debugged.
21700 @subheading @value{GDBN} Command
21702 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
21704 @subheading Example
21708 -inferior-tty-set /dev/pts/1
21712 ^done,inferior_tty_terminal="/dev/pts/1"
21716 @subheading The @code{-enable-timings} Command
21717 @findex -enable-timings
21719 @subheading Synopsis
21722 -enable-timings [yes | no]
21725 Toggle the printing of the wallclock, user and system times for an MI
21726 command as a field in its output. This command is to help frontend
21727 developers optimize the performance of their code. No argument is
21728 equivalent to @samp{yes}.
21730 @subheading @value{GDBN} Command
21734 @subheading Example
21742 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
21743 addr="0x080484ed",func="main",file="myprog.c",
21744 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
21745 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
21753 *stopped,reason="breakpoint-hit",bkptno="1",thread-id="0",
21754 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
21755 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
21756 fullname="/home/nickrob/myprog.c",line="73"@}
21761 @chapter @value{GDBN} Annotations
21763 This chapter describes annotations in @value{GDBN}. Annotations were
21764 designed to interface @value{GDBN} to graphical user interfaces or other
21765 similar programs which want to interact with @value{GDBN} at a
21766 relatively high level.
21768 The annotation mechanism has largely been superseded by @sc{gdb/mi}
21772 This is Edition @value{EDITION}, @value{DATE}.
21776 * Annotations Overview:: What annotations are; the general syntax.
21777 * Server Prefix:: Issuing a command without affecting user state.
21778 * Prompting:: Annotations marking @value{GDBN}'s need for input.
21779 * Errors:: Annotations for error messages.
21780 * Invalidation:: Some annotations describe things now invalid.
21781 * Annotations for Running::
21782 Whether the program is running, how it stopped, etc.
21783 * Source Annotations:: Annotations describing source code.
21786 @node Annotations Overview
21787 @section What is an Annotation?
21788 @cindex annotations
21790 Annotations start with a newline character, two @samp{control-z}
21791 characters, and the name of the annotation. If there is no additional
21792 information associated with this annotation, the name of the annotation
21793 is followed immediately by a newline. If there is additional
21794 information, the name of the annotation is followed by a space, the
21795 additional information, and a newline. The additional information
21796 cannot contain newline characters.
21798 Any output not beginning with a newline and two @samp{control-z}
21799 characters denotes literal output from @value{GDBN}. Currently there is
21800 no need for @value{GDBN} to output a newline followed by two
21801 @samp{control-z} characters, but if there was such a need, the
21802 annotations could be extended with an @samp{escape} annotation which
21803 means those three characters as output.
21805 The annotation @var{level}, which is specified using the
21806 @option{--annotate} command line option (@pxref{Mode Options}), controls
21807 how much information @value{GDBN} prints together with its prompt,
21808 values of expressions, source lines, and other types of output. Level 0
21809 is for no annotations, level 1 is for use when @value{GDBN} is run as a
21810 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
21811 for programs that control @value{GDBN}, and level 2 annotations have
21812 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
21813 Interface, annotate, GDB's Obsolete Annotations}).
21816 @kindex set annotate
21817 @item set annotate @var{level}
21818 The @value{GDBN} command @code{set annotate} sets the level of
21819 annotations to the specified @var{level}.
21821 @item show annotate
21822 @kindex show annotate
21823 Show the current annotation level.
21826 This chapter describes level 3 annotations.
21828 A simple example of starting up @value{GDBN} with annotations is:
21831 $ @kbd{gdb --annotate=3}
21833 Copyright 2003 Free Software Foundation, Inc.
21834 GDB is free software, covered by the GNU General Public License,
21835 and you are welcome to change it and/or distribute copies of it
21836 under certain conditions.
21837 Type "show copying" to see the conditions.
21838 There is absolutely no warranty for GDB. Type "show warranty"
21840 This GDB was configured as "i386-pc-linux-gnu"
21851 Here @samp{quit} is input to @value{GDBN}; the rest is output from
21852 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
21853 denotes a @samp{control-z} character) are annotations; the rest is
21854 output from @value{GDBN}.
21856 @node Server Prefix
21857 @section The Server Prefix
21858 @cindex server prefix
21860 If you prefix a command with @samp{server } then it will not affect
21861 the command history, nor will it affect @value{GDBN}'s notion of which
21862 command to repeat if @key{RET} is pressed on a line by itself. This
21863 means that commands can be run behind a user's back by a front-end in
21864 a transparent manner.
21866 The server prefix does not affect the recording of values into the value
21867 history; to print a value without recording it into the value history,
21868 use the @code{output} command instead of the @code{print} command.
21871 @section Annotation for @value{GDBN} Input
21873 @cindex annotations for prompts
21874 When @value{GDBN} prompts for input, it annotates this fact so it is possible
21875 to know when to send output, when the output from a given command is
21878 Different kinds of input each have a different @dfn{input type}. Each
21879 input type has three annotations: a @code{pre-} annotation, which
21880 denotes the beginning of any prompt which is being output, a plain
21881 annotation, which denotes the end of the prompt, and then a @code{post-}
21882 annotation which denotes the end of any echo which may (or may not) be
21883 associated with the input. For example, the @code{prompt} input type
21884 features the following annotations:
21892 The input types are
21895 @findex pre-prompt annotation
21896 @findex prompt annotation
21897 @findex post-prompt annotation
21899 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
21901 @findex pre-commands annotation
21902 @findex commands annotation
21903 @findex post-commands annotation
21905 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
21906 command. The annotations are repeated for each command which is input.
21908 @findex pre-overload-choice annotation
21909 @findex overload-choice annotation
21910 @findex post-overload-choice annotation
21911 @item overload-choice
21912 When @value{GDBN} wants the user to select between various overloaded functions.
21914 @findex pre-query annotation
21915 @findex query annotation
21916 @findex post-query annotation
21918 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
21920 @findex pre-prompt-for-continue annotation
21921 @findex prompt-for-continue annotation
21922 @findex post-prompt-for-continue annotation
21923 @item prompt-for-continue
21924 When @value{GDBN} is asking the user to press return to continue. Note: Don't
21925 expect this to work well; instead use @code{set height 0} to disable
21926 prompting. This is because the counting of lines is buggy in the
21927 presence of annotations.
21932 @cindex annotations for errors, warnings and interrupts
21934 @findex quit annotation
21939 This annotation occurs right before @value{GDBN} responds to an interrupt.
21941 @findex error annotation
21946 This annotation occurs right before @value{GDBN} responds to an error.
21948 Quit and error annotations indicate that any annotations which @value{GDBN} was
21949 in the middle of may end abruptly. For example, if a
21950 @code{value-history-begin} annotation is followed by a @code{error}, one
21951 cannot expect to receive the matching @code{value-history-end}. One
21952 cannot expect not to receive it either, however; an error annotation
21953 does not necessarily mean that @value{GDBN} is immediately returning all the way
21956 @findex error-begin annotation
21957 A quit or error annotation may be preceded by
21963 Any output between that and the quit or error annotation is the error
21966 Warning messages are not yet annotated.
21967 @c If we want to change that, need to fix warning(), type_error(),
21968 @c range_error(), and possibly other places.
21971 @section Invalidation Notices
21973 @cindex annotations for invalidation messages
21974 The following annotations say that certain pieces of state may have
21978 @findex frames-invalid annotation
21979 @item ^Z^Zframes-invalid
21981 The frames (for example, output from the @code{backtrace} command) may
21984 @findex breakpoints-invalid annotation
21985 @item ^Z^Zbreakpoints-invalid
21987 The breakpoints may have changed. For example, the user just added or
21988 deleted a breakpoint.
21991 @node Annotations for Running
21992 @section Running the Program
21993 @cindex annotations for running programs
21995 @findex starting annotation
21996 @findex stopping annotation
21997 When the program starts executing due to a @value{GDBN} command such as
21998 @code{step} or @code{continue},
22004 is output. When the program stops,
22010 is output. Before the @code{stopped} annotation, a variety of
22011 annotations describe how the program stopped.
22014 @findex exited annotation
22015 @item ^Z^Zexited @var{exit-status}
22016 The program exited, and @var{exit-status} is the exit status (zero for
22017 successful exit, otherwise nonzero).
22019 @findex signalled annotation
22020 @findex signal-name annotation
22021 @findex signal-name-end annotation
22022 @findex signal-string annotation
22023 @findex signal-string-end annotation
22024 @item ^Z^Zsignalled
22025 The program exited with a signal. After the @code{^Z^Zsignalled}, the
22026 annotation continues:
22032 ^Z^Zsignal-name-end
22036 ^Z^Zsignal-string-end
22041 where @var{name} is the name of the signal, such as @code{SIGILL} or
22042 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
22043 as @code{Illegal Instruction} or @code{Segmentation fault}.
22044 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
22045 user's benefit and have no particular format.
22047 @findex signal annotation
22049 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
22050 just saying that the program received the signal, not that it was
22051 terminated with it.
22053 @findex breakpoint annotation
22054 @item ^Z^Zbreakpoint @var{number}
22055 The program hit breakpoint number @var{number}.
22057 @findex watchpoint annotation
22058 @item ^Z^Zwatchpoint @var{number}
22059 The program hit watchpoint number @var{number}.
22062 @node Source Annotations
22063 @section Displaying Source
22064 @cindex annotations for source display
22066 @findex source annotation
22067 The following annotation is used instead of displaying source code:
22070 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
22073 where @var{filename} is an absolute file name indicating which source
22074 file, @var{line} is the line number within that file (where 1 is the
22075 first line in the file), @var{character} is the character position
22076 within the file (where 0 is the first character in the file) (for most
22077 debug formats this will necessarily point to the beginning of a line),
22078 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
22079 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
22080 @var{addr} is the address in the target program associated with the
22081 source which is being displayed. @var{addr} is in the form @samp{0x}
22082 followed by one or more lowercase hex digits (note that this does not
22083 depend on the language).
22086 @chapter Reporting Bugs in @value{GDBN}
22087 @cindex bugs in @value{GDBN}
22088 @cindex reporting bugs in @value{GDBN}
22090 Your bug reports play an essential role in making @value{GDBN} reliable.
22092 Reporting a bug may help you by bringing a solution to your problem, or it
22093 may not. But in any case the principal function of a bug report is to help
22094 the entire community by making the next version of @value{GDBN} work better. Bug
22095 reports are your contribution to the maintenance of @value{GDBN}.
22097 In order for a bug report to serve its purpose, you must include the
22098 information that enables us to fix the bug.
22101 * Bug Criteria:: Have you found a bug?
22102 * Bug Reporting:: How to report bugs
22106 @section Have You Found a Bug?
22107 @cindex bug criteria
22109 If you are not sure whether you have found a bug, here are some guidelines:
22112 @cindex fatal signal
22113 @cindex debugger crash
22114 @cindex crash of debugger
22116 If the debugger gets a fatal signal, for any input whatever, that is a
22117 @value{GDBN} bug. Reliable debuggers never crash.
22119 @cindex error on valid input
22121 If @value{GDBN} produces an error message for valid input, that is a
22122 bug. (Note that if you're cross debugging, the problem may also be
22123 somewhere in the connection to the target.)
22125 @cindex invalid input
22127 If @value{GDBN} does not produce an error message for invalid input,
22128 that is a bug. However, you should note that your idea of
22129 ``invalid input'' might be our idea of ``an extension'' or ``support
22130 for traditional practice''.
22133 If you are an experienced user of debugging tools, your suggestions
22134 for improvement of @value{GDBN} are welcome in any case.
22137 @node Bug Reporting
22138 @section How to Report Bugs
22139 @cindex bug reports
22140 @cindex @value{GDBN} bugs, reporting
22142 A number of companies and individuals offer support for @sc{gnu} products.
22143 If you obtained @value{GDBN} from a support organization, we recommend you
22144 contact that organization first.
22146 You can find contact information for many support companies and
22147 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
22149 @c should add a web page ref...
22151 In any event, we also recommend that you submit bug reports for
22152 @value{GDBN}. The preferred method is to submit them directly using
22153 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
22154 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
22157 @strong{Do not send bug reports to @samp{info-gdb}, or to
22158 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
22159 not want to receive bug reports. Those that do have arranged to receive
22162 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
22163 serves as a repeater. The mailing list and the newsgroup carry exactly
22164 the same messages. Often people think of posting bug reports to the
22165 newsgroup instead of mailing them. This appears to work, but it has one
22166 problem which can be crucial: a newsgroup posting often lacks a mail
22167 path back to the sender. Thus, if we need to ask for more information,
22168 we may be unable to reach you. For this reason, it is better to send
22169 bug reports to the mailing list.
22171 The fundamental principle of reporting bugs usefully is this:
22172 @strong{report all the facts}. If you are not sure whether to state a
22173 fact or leave it out, state it!
22175 Often people omit facts because they think they know what causes the
22176 problem and assume that some details do not matter. Thus, you might
22177 assume that the name of the variable you use in an example does not matter.
22178 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
22179 stray memory reference which happens to fetch from the location where that
22180 name is stored in memory; perhaps, if the name were different, the contents
22181 of that location would fool the debugger into doing the right thing despite
22182 the bug. Play it safe and give a specific, complete example. That is the
22183 easiest thing for you to do, and the most helpful.
22185 Keep in mind that the purpose of a bug report is to enable us to fix the
22186 bug. It may be that the bug has been reported previously, but neither
22187 you nor we can know that unless your bug report is complete and
22190 Sometimes people give a few sketchy facts and ask, ``Does this ring a
22191 bell?'' Those bug reports are useless, and we urge everyone to
22192 @emph{refuse to respond to them} except to chide the sender to report
22195 To enable us to fix the bug, you should include all these things:
22199 The version of @value{GDBN}. @value{GDBN} announces it if you start
22200 with no arguments; you can also print it at any time using @code{show
22203 Without this, we will not know whether there is any point in looking for
22204 the bug in the current version of @value{GDBN}.
22207 The type of machine you are using, and the operating system name and
22211 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
22212 ``@value{GCC}--2.8.1''.
22215 What compiler (and its version) was used to compile the program you are
22216 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
22217 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
22218 to get this information; for other compilers, see the documentation for
22222 The command arguments you gave the compiler to compile your example and
22223 observe the bug. For example, did you use @samp{-O}? To guarantee
22224 you will not omit something important, list them all. A copy of the
22225 Makefile (or the output from make) is sufficient.
22227 If we were to try to guess the arguments, we would probably guess wrong
22228 and then we might not encounter the bug.
22231 A complete input script, and all necessary source files, that will
22235 A description of what behavior you observe that you believe is
22236 incorrect. For example, ``It gets a fatal signal.''
22238 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
22239 will certainly notice it. But if the bug is incorrect output, we might
22240 not notice unless it is glaringly wrong. You might as well not give us
22241 a chance to make a mistake.
22243 Even if the problem you experience is a fatal signal, you should still
22244 say so explicitly. Suppose something strange is going on, such as, your
22245 copy of @value{GDBN} is out of synch, or you have encountered a bug in
22246 the C library on your system. (This has happened!) Your copy might
22247 crash and ours would not. If you told us to expect a crash, then when
22248 ours fails to crash, we would know that the bug was not happening for
22249 us. If you had not told us to expect a crash, then we would not be able
22250 to draw any conclusion from our observations.
22253 @cindex recording a session script
22254 To collect all this information, you can use a session recording program
22255 such as @command{script}, which is available on many Unix systems.
22256 Just run your @value{GDBN} session inside @command{script} and then
22257 include the @file{typescript} file with your bug report.
22259 Another way to record a @value{GDBN} session is to run @value{GDBN}
22260 inside Emacs and then save the entire buffer to a file.
22263 If you wish to suggest changes to the @value{GDBN} source, send us context
22264 diffs. If you even discuss something in the @value{GDBN} source, refer to
22265 it by context, not by line number.
22267 The line numbers in our development sources will not match those in your
22268 sources. Your line numbers would convey no useful information to us.
22272 Here are some things that are not necessary:
22276 A description of the envelope of the bug.
22278 Often people who encounter a bug spend a lot of time investigating
22279 which changes to the input file will make the bug go away and which
22280 changes will not affect it.
22282 This is often time consuming and not very useful, because the way we
22283 will find the bug is by running a single example under the debugger
22284 with breakpoints, not by pure deduction from a series of examples.
22285 We recommend that you save your time for something else.
22287 Of course, if you can find a simpler example to report @emph{instead}
22288 of the original one, that is a convenience for us. Errors in the
22289 output will be easier to spot, running under the debugger will take
22290 less time, and so on.
22292 However, simplification is not vital; if you do not want to do this,
22293 report the bug anyway and send us the entire test case you used.
22296 A patch for the bug.
22298 A patch for the bug does help us if it is a good one. But do not omit
22299 the necessary information, such as the test case, on the assumption that
22300 a patch is all we need. We might see problems with your patch and decide
22301 to fix the problem another way, or we might not understand it at all.
22303 Sometimes with a program as complicated as @value{GDBN} it is very hard to
22304 construct an example that will make the program follow a certain path
22305 through the code. If you do not send us the example, we will not be able
22306 to construct one, so we will not be able to verify that the bug is fixed.
22308 And if we cannot understand what bug you are trying to fix, or why your
22309 patch should be an improvement, we will not install it. A test case will
22310 help us to understand.
22313 A guess about what the bug is or what it depends on.
22315 Such guesses are usually wrong. Even we cannot guess right about such
22316 things without first using the debugger to find the facts.
22319 @c The readline documentation is distributed with the readline code
22320 @c and consists of the two following files:
22322 @c inc-hist.texinfo
22323 @c Use -I with makeinfo to point to the appropriate directory,
22324 @c environment var TEXINPUTS with TeX.
22325 @include rluser.texi
22326 @include inc-hist.texinfo
22329 @node Formatting Documentation
22330 @appendix Formatting Documentation
22332 @cindex @value{GDBN} reference card
22333 @cindex reference card
22334 The @value{GDBN} 4 release includes an already-formatted reference card, ready
22335 for printing with PostScript or Ghostscript, in the @file{gdb}
22336 subdirectory of the main source directory@footnote{In
22337 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
22338 release.}. If you can use PostScript or Ghostscript with your printer,
22339 you can print the reference card immediately with @file{refcard.ps}.
22341 The release also includes the source for the reference card. You
22342 can format it, using @TeX{}, by typing:
22348 The @value{GDBN} reference card is designed to print in @dfn{landscape}
22349 mode on US ``letter'' size paper;
22350 that is, on a sheet 11 inches wide by 8.5 inches
22351 high. You will need to specify this form of printing as an option to
22352 your @sc{dvi} output program.
22354 @cindex documentation
22356 All the documentation for @value{GDBN} comes as part of the machine-readable
22357 distribution. The documentation is written in Texinfo format, which is
22358 a documentation system that uses a single source file to produce both
22359 on-line information and a printed manual. You can use one of the Info
22360 formatting commands to create the on-line version of the documentation
22361 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
22363 @value{GDBN} includes an already formatted copy of the on-line Info
22364 version of this manual in the @file{gdb} subdirectory. The main Info
22365 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
22366 subordinate files matching @samp{gdb.info*} in the same directory. If
22367 necessary, you can print out these files, or read them with any editor;
22368 but they are easier to read using the @code{info} subsystem in @sc{gnu}
22369 Emacs or the standalone @code{info} program, available as part of the
22370 @sc{gnu} Texinfo distribution.
22372 If you want to format these Info files yourself, you need one of the
22373 Info formatting programs, such as @code{texinfo-format-buffer} or
22376 If you have @code{makeinfo} installed, and are in the top level
22377 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
22378 version @value{GDBVN}), you can make the Info file by typing:
22385 If you want to typeset and print copies of this manual, you need @TeX{},
22386 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
22387 Texinfo definitions file.
22389 @TeX{} is a typesetting program; it does not print files directly, but
22390 produces output files called @sc{dvi} files. To print a typeset
22391 document, you need a program to print @sc{dvi} files. If your system
22392 has @TeX{} installed, chances are it has such a program. The precise
22393 command to use depends on your system; @kbd{lpr -d} is common; another
22394 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
22395 require a file name without any extension or a @samp{.dvi} extension.
22397 @TeX{} also requires a macro definitions file called
22398 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
22399 written in Texinfo format. On its own, @TeX{} cannot either read or
22400 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
22401 and is located in the @file{gdb-@var{version-number}/texinfo}
22404 If you have @TeX{} and a @sc{dvi} printer program installed, you can
22405 typeset and print this manual. First switch to the @file{gdb}
22406 subdirectory of the main source directory (for example, to
22407 @file{gdb-@value{GDBVN}/gdb}) and type:
22413 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
22415 @node Installing GDB
22416 @appendix Installing @value{GDBN}
22417 @cindex installation
22420 * Requirements:: Requirements for building @value{GDBN}
22421 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
22422 * Separate Objdir:: Compiling @value{GDBN} in another directory
22423 * Config Names:: Specifying names for hosts and targets
22424 * Configure Options:: Summary of options for configure
22428 @section Requirements for Building @value{GDBN}
22429 @cindex building @value{GDBN}, requirements for
22431 Building @value{GDBN} requires various tools and packages to be available.
22432 Other packages will be used only if they are found.
22434 @heading Tools/Packages Necessary for Building @value{GDBN}
22436 @item ISO C90 compiler
22437 @value{GDBN} is written in ISO C90. It should be buildable with any
22438 working C90 compiler, e.g.@: GCC.
22442 @heading Tools/Packages Optional for Building @value{GDBN}
22446 @value{GDBN} can use the Expat XML parsing library. This library may be
22447 included with your operating system distribution; if it is not, you
22448 can get the latest version from @url{http://expat.sourceforge.net}.
22449 The @file{configure} script will search for this library in several
22450 standard locations; if it is installed in an unusual path, you can
22451 use the @option{--with-libexpat-prefix} option to specify its location.
22457 Remote protocol memory maps (@pxref{Memory Map Format})
22459 Target descriptions (@pxref{Target Descriptions})
22461 Remote shared library lists (@pxref{Library List Format})
22463 MS-Windows shared libraries (@pxref{Shared Libraries})
22468 @node Running Configure
22469 @section Invoking the @value{GDBN} @file{configure} Script
22470 @cindex configuring @value{GDBN}
22471 @value{GDBN} comes with a @file{configure} script that automates the process
22472 of preparing @value{GDBN} for installation; you can then use @code{make} to
22473 build the @code{gdb} program.
22475 @c irrelevant in info file; it's as current as the code it lives with.
22476 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
22477 look at the @file{README} file in the sources; we may have improved the
22478 installation procedures since publishing this manual.}
22481 The @value{GDBN} distribution includes all the source code you need for
22482 @value{GDBN} in a single directory, whose name is usually composed by
22483 appending the version number to @samp{gdb}.
22485 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
22486 @file{gdb-@value{GDBVN}} directory. That directory contains:
22489 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
22490 script for configuring @value{GDBN} and all its supporting libraries
22492 @item gdb-@value{GDBVN}/gdb
22493 the source specific to @value{GDBN} itself
22495 @item gdb-@value{GDBVN}/bfd
22496 source for the Binary File Descriptor library
22498 @item gdb-@value{GDBVN}/include
22499 @sc{gnu} include files
22501 @item gdb-@value{GDBVN}/libiberty
22502 source for the @samp{-liberty} free software library
22504 @item gdb-@value{GDBVN}/opcodes
22505 source for the library of opcode tables and disassemblers
22507 @item gdb-@value{GDBVN}/readline
22508 source for the @sc{gnu} command-line interface
22510 @item gdb-@value{GDBVN}/glob
22511 source for the @sc{gnu} filename pattern-matching subroutine
22513 @item gdb-@value{GDBVN}/mmalloc
22514 source for the @sc{gnu} memory-mapped malloc package
22517 The simplest way to configure and build @value{GDBN} is to run @file{configure}
22518 from the @file{gdb-@var{version-number}} source directory, which in
22519 this example is the @file{gdb-@value{GDBVN}} directory.
22521 First switch to the @file{gdb-@var{version-number}} source directory
22522 if you are not already in it; then run @file{configure}. Pass the
22523 identifier for the platform on which @value{GDBN} will run as an
22529 cd gdb-@value{GDBVN}
22530 ./configure @var{host}
22535 where @var{host} is an identifier such as @samp{sun4} or
22536 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
22537 (You can often leave off @var{host}; @file{configure} tries to guess the
22538 correct value by examining your system.)
22540 Running @samp{configure @var{host}} and then running @code{make} builds the
22541 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
22542 libraries, then @code{gdb} itself. The configured source files, and the
22543 binaries, are left in the corresponding source directories.
22546 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
22547 system does not recognize this automatically when you run a different
22548 shell, you may need to run @code{sh} on it explicitly:
22551 sh configure @var{host}
22554 If you run @file{configure} from a directory that contains source
22555 directories for multiple libraries or programs, such as the
22556 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
22558 creates configuration files for every directory level underneath (unless
22559 you tell it not to, with the @samp{--norecursion} option).
22561 You should run the @file{configure} script from the top directory in the
22562 source tree, the @file{gdb-@var{version-number}} directory. If you run
22563 @file{configure} from one of the subdirectories, you will configure only
22564 that subdirectory. That is usually not what you want. In particular,
22565 if you run the first @file{configure} from the @file{gdb} subdirectory
22566 of the @file{gdb-@var{version-number}} directory, you will omit the
22567 configuration of @file{bfd}, @file{readline}, and other sibling
22568 directories of the @file{gdb} subdirectory. This leads to build errors
22569 about missing include files such as @file{bfd/bfd.h}.
22571 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
22572 However, you should make sure that the shell on your path (named by
22573 the @samp{SHELL} environment variable) is publicly readable. Remember
22574 that @value{GDBN} uses the shell to start your program---some systems refuse to
22575 let @value{GDBN} debug child processes whose programs are not readable.
22577 @node Separate Objdir
22578 @section Compiling @value{GDBN} in Another Directory
22580 If you want to run @value{GDBN} versions for several host or target machines,
22581 you need a different @code{gdb} compiled for each combination of
22582 host and target. @file{configure} is designed to make this easy by
22583 allowing you to generate each configuration in a separate subdirectory,
22584 rather than in the source directory. If your @code{make} program
22585 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
22586 @code{make} in each of these directories builds the @code{gdb}
22587 program specified there.
22589 To build @code{gdb} in a separate directory, run @file{configure}
22590 with the @samp{--srcdir} option to specify where to find the source.
22591 (You also need to specify a path to find @file{configure}
22592 itself from your working directory. If the path to @file{configure}
22593 would be the same as the argument to @samp{--srcdir}, you can leave out
22594 the @samp{--srcdir} option; it is assumed.)
22596 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
22597 separate directory for a Sun 4 like this:
22601 cd gdb-@value{GDBVN}
22604 ../gdb-@value{GDBVN}/configure sun4
22609 When @file{configure} builds a configuration using a remote source
22610 directory, it creates a tree for the binaries with the same structure
22611 (and using the same names) as the tree under the source directory. In
22612 the example, you'd find the Sun 4 library @file{libiberty.a} in the
22613 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
22614 @file{gdb-sun4/gdb}.
22616 Make sure that your path to the @file{configure} script has just one
22617 instance of @file{gdb} in it. If your path to @file{configure} looks
22618 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
22619 one subdirectory of @value{GDBN}, not the whole package. This leads to
22620 build errors about missing include files such as @file{bfd/bfd.h}.
22622 One popular reason to build several @value{GDBN} configurations in separate
22623 directories is to configure @value{GDBN} for cross-compiling (where
22624 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
22625 programs that run on another machine---the @dfn{target}).
22626 You specify a cross-debugging target by
22627 giving the @samp{--target=@var{target}} option to @file{configure}.
22629 When you run @code{make} to build a program or library, you must run
22630 it in a configured directory---whatever directory you were in when you
22631 called @file{configure} (or one of its subdirectories).
22633 The @code{Makefile} that @file{configure} generates in each source
22634 directory also runs recursively. If you type @code{make} in a source
22635 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
22636 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
22637 will build all the required libraries, and then build GDB.
22639 When you have multiple hosts or targets configured in separate
22640 directories, you can run @code{make} on them in parallel (for example,
22641 if they are NFS-mounted on each of the hosts); they will not interfere
22645 @section Specifying Names for Hosts and Targets
22647 The specifications used for hosts and targets in the @file{configure}
22648 script are based on a three-part naming scheme, but some short predefined
22649 aliases are also supported. The full naming scheme encodes three pieces
22650 of information in the following pattern:
22653 @var{architecture}-@var{vendor}-@var{os}
22656 For example, you can use the alias @code{sun4} as a @var{host} argument,
22657 or as the value for @var{target} in a @code{--target=@var{target}}
22658 option. The equivalent full name is @samp{sparc-sun-sunos4}.
22660 The @file{configure} script accompanying @value{GDBN} does not provide
22661 any query facility to list all supported host and target names or
22662 aliases. @file{configure} calls the Bourne shell script
22663 @code{config.sub} to map abbreviations to full names; you can read the
22664 script, if you wish, or you can use it to test your guesses on
22665 abbreviations---for example:
22668 % sh config.sub i386-linux
22670 % sh config.sub alpha-linux
22671 alpha-unknown-linux-gnu
22672 % sh config.sub hp9k700
22674 % sh config.sub sun4
22675 sparc-sun-sunos4.1.1
22676 % sh config.sub sun3
22677 m68k-sun-sunos4.1.1
22678 % sh config.sub i986v
22679 Invalid configuration `i986v': machine `i986v' not recognized
22683 @code{config.sub} is also distributed in the @value{GDBN} source
22684 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
22686 @node Configure Options
22687 @section @file{configure} Options
22689 Here is a summary of the @file{configure} options and arguments that
22690 are most often useful for building @value{GDBN}. @file{configure} also has
22691 several other options not listed here. @inforef{What Configure
22692 Does,,configure.info}, for a full explanation of @file{configure}.
22695 configure @r{[}--help@r{]}
22696 @r{[}--prefix=@var{dir}@r{]}
22697 @r{[}--exec-prefix=@var{dir}@r{]}
22698 @r{[}--srcdir=@var{dirname}@r{]}
22699 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
22700 @r{[}--target=@var{target}@r{]}
22705 You may introduce options with a single @samp{-} rather than
22706 @samp{--} if you prefer; but you may abbreviate option names if you use
22711 Display a quick summary of how to invoke @file{configure}.
22713 @item --prefix=@var{dir}
22714 Configure the source to install programs and files under directory
22717 @item --exec-prefix=@var{dir}
22718 Configure the source to install programs under directory
22721 @c avoid splitting the warning from the explanation:
22723 @item --srcdir=@var{dirname}
22724 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
22725 @code{make} that implements the @code{VPATH} feature.}@*
22726 Use this option to make configurations in directories separate from the
22727 @value{GDBN} source directories. Among other things, you can use this to
22728 build (or maintain) several configurations simultaneously, in separate
22729 directories. @file{configure} writes configuration-specific files in
22730 the current directory, but arranges for them to use the source in the
22731 directory @var{dirname}. @file{configure} creates directories under
22732 the working directory in parallel to the source directories below
22735 @item --norecursion
22736 Configure only the directory level where @file{configure} is executed; do not
22737 propagate configuration to subdirectories.
22739 @item --target=@var{target}
22740 Configure @value{GDBN} for cross-debugging programs running on the specified
22741 @var{target}. Without this option, @value{GDBN} is configured to debug
22742 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
22744 There is no convenient way to generate a list of all available targets.
22746 @item @var{host} @dots{}
22747 Configure @value{GDBN} to run on the specified @var{host}.
22749 There is no convenient way to generate a list of all available hosts.
22752 There are many other options available as well, but they are generally
22753 needed for special purposes only.
22755 @node Maintenance Commands
22756 @appendix Maintenance Commands
22757 @cindex maintenance commands
22758 @cindex internal commands
22760 In addition to commands intended for @value{GDBN} users, @value{GDBN}
22761 includes a number of commands intended for @value{GDBN} developers,
22762 that are not documented elsewhere in this manual. These commands are
22763 provided here for reference. (For commands that turn on debugging
22764 messages, see @ref{Debugging Output}.)
22767 @kindex maint agent
22768 @item maint agent @var{expression}
22769 Translate the given @var{expression} into remote agent bytecodes.
22770 This command is useful for debugging the Agent Expression mechanism
22771 (@pxref{Agent Expressions}).
22773 @kindex maint info breakpoints
22774 @item @anchor{maint info breakpoints}maint info breakpoints
22775 Using the same format as @samp{info breakpoints}, display both the
22776 breakpoints you've set explicitly, and those @value{GDBN} is using for
22777 internal purposes. Internal breakpoints are shown with negative
22778 breakpoint numbers. The type column identifies what kind of breakpoint
22783 Normal, explicitly set breakpoint.
22786 Normal, explicitly set watchpoint.
22789 Internal breakpoint, used to handle correctly stepping through
22790 @code{longjmp} calls.
22792 @item longjmp resume
22793 Internal breakpoint at the target of a @code{longjmp}.
22796 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
22799 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
22802 Shared library events.
22806 @kindex maint check-symtabs
22807 @item maint check-symtabs
22808 Check the consistency of psymtabs and symtabs.
22810 @kindex maint cplus first_component
22811 @item maint cplus first_component @var{name}
22812 Print the first C@t{++} class/namespace component of @var{name}.
22814 @kindex maint cplus namespace
22815 @item maint cplus namespace
22816 Print the list of possible C@t{++} namespaces.
22818 @kindex maint demangle
22819 @item maint demangle @var{name}
22820 Demangle a C@t{++} or Objective-C mangled @var{name}.
22822 @kindex maint deprecate
22823 @kindex maint undeprecate
22824 @cindex deprecated commands
22825 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
22826 @itemx maint undeprecate @var{command}
22827 Deprecate or undeprecate the named @var{command}. Deprecated commands
22828 cause @value{GDBN} to issue a warning when you use them. The optional
22829 argument @var{replacement} says which newer command should be used in
22830 favor of the deprecated one; if it is given, @value{GDBN} will mention
22831 the replacement as part of the warning.
22833 @kindex maint dump-me
22834 @item maint dump-me
22835 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
22836 Cause a fatal signal in the debugger and force it to dump its core.
22837 This is supported only on systems which support aborting a program
22838 with the @code{SIGQUIT} signal.
22840 @kindex maint internal-error
22841 @kindex maint internal-warning
22842 @item maint internal-error @r{[}@var{message-text}@r{]}
22843 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
22844 Cause @value{GDBN} to call the internal function @code{internal_error}
22845 or @code{internal_warning} and hence behave as though an internal error
22846 or internal warning has been detected. In addition to reporting the
22847 internal problem, these functions give the user the opportunity to
22848 either quit @value{GDBN} or create a core file of the current
22849 @value{GDBN} session.
22851 These commands take an optional parameter @var{message-text} that is
22852 used as the text of the error or warning message.
22854 Here's an example of using @code{internal-error}:
22857 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
22858 @dots{}/maint.c:121: internal-error: testing, 1, 2
22859 A problem internal to GDB has been detected. Further
22860 debugging may prove unreliable.
22861 Quit this debugging session? (y or n) @kbd{n}
22862 Create a core file? (y or n) @kbd{n}
22866 @kindex maint packet
22867 @item maint packet @var{text}
22868 If @value{GDBN} is talking to an inferior via the serial protocol,
22869 then this command sends the string @var{text} to the inferior, and
22870 displays the response packet. @value{GDBN} supplies the initial
22871 @samp{$} character, the terminating @samp{#} character, and the
22874 @kindex maint print architecture
22875 @item maint print architecture @r{[}@var{file}@r{]}
22876 Print the entire architecture configuration. The optional argument
22877 @var{file} names the file where the output goes.
22879 @kindex maint print c-tdesc
22880 @item maint print c-tdesc
22881 Print the current target description (@pxref{Target Descriptions}) as
22882 a C source file. The created source file can be used in @value{GDBN}
22883 when an XML parser is not available to parse the description.
22885 @kindex maint print dummy-frames
22886 @item maint print dummy-frames
22887 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
22890 (@value{GDBP}) @kbd{b add}
22892 (@value{GDBP}) @kbd{print add(2,3)}
22893 Breakpoint 2, add (a=2, b=3) at @dots{}
22895 The program being debugged stopped while in a function called from GDB.
22897 (@value{GDBP}) @kbd{maint print dummy-frames}
22898 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
22899 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
22900 call_lo=0x01014000 call_hi=0x01014001
22904 Takes an optional file parameter.
22906 @kindex maint print registers
22907 @kindex maint print raw-registers
22908 @kindex maint print cooked-registers
22909 @kindex maint print register-groups
22910 @item maint print registers @r{[}@var{file}@r{]}
22911 @itemx maint print raw-registers @r{[}@var{file}@r{]}
22912 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
22913 @itemx maint print register-groups @r{[}@var{file}@r{]}
22914 Print @value{GDBN}'s internal register data structures.
22916 The command @code{maint print raw-registers} includes the contents of
22917 the raw register cache; the command @code{maint print cooked-registers}
22918 includes the (cooked) value of all registers; and the command
22919 @code{maint print register-groups} includes the groups that each
22920 register is a member of. @xref{Registers,, Registers, gdbint,
22921 @value{GDBN} Internals}.
22923 These commands take an optional parameter, a file name to which to
22924 write the information.
22926 @kindex maint print reggroups
22927 @item maint print reggroups @r{[}@var{file}@r{]}
22928 Print @value{GDBN}'s internal register group data structures. The
22929 optional argument @var{file} tells to what file to write the
22932 The register groups info looks like this:
22935 (@value{GDBP}) @kbd{maint print reggroups}
22948 This command forces @value{GDBN} to flush its internal register cache.
22950 @kindex maint print objfiles
22951 @cindex info for known object files
22952 @item maint print objfiles
22953 Print a dump of all known object files. For each object file, this
22954 command prints its name, address in memory, and all of its psymtabs
22957 @kindex maint print statistics
22958 @cindex bcache statistics
22959 @item maint print statistics
22960 This command prints, for each object file in the program, various data
22961 about that object file followed by the byte cache (@dfn{bcache})
22962 statistics for the object file. The objfile data includes the number
22963 of minimal, partial, full, and stabs symbols, the number of types
22964 defined by the objfile, the number of as yet unexpanded psym tables,
22965 the number of line tables and string tables, and the amount of memory
22966 used by the various tables. The bcache statistics include the counts,
22967 sizes, and counts of duplicates of all and unique objects, max,
22968 average, and median entry size, total memory used and its overhead and
22969 savings, and various measures of the hash table size and chain
22972 @kindex maint print target-stack
22973 @cindex target stack description
22974 @item maint print target-stack
22975 A @dfn{target} is an interface between the debugger and a particular
22976 kind of file or process. Targets can be stacked in @dfn{strata},
22977 so that more than one target can potentially respond to a request.
22978 In particular, memory accesses will walk down the stack of targets
22979 until they find a target that is interested in handling that particular
22982 This command prints a short description of each layer that was pushed on
22983 the @dfn{target stack}, starting from the top layer down to the bottom one.
22985 @kindex maint print type
22986 @cindex type chain of a data type
22987 @item maint print type @var{expr}
22988 Print the type chain for a type specified by @var{expr}. The argument
22989 can be either a type name or a symbol. If it is a symbol, the type of
22990 that symbol is described. The type chain produced by this command is
22991 a recursive definition of the data type as stored in @value{GDBN}'s
22992 data structures, including its flags and contained types.
22994 @kindex maint set dwarf2 max-cache-age
22995 @kindex maint show dwarf2 max-cache-age
22996 @item maint set dwarf2 max-cache-age
22997 @itemx maint show dwarf2 max-cache-age
22998 Control the DWARF 2 compilation unit cache.
23000 @cindex DWARF 2 compilation units cache
23001 In object files with inter-compilation-unit references, such as those
23002 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
23003 reader needs to frequently refer to previously read compilation units.
23004 This setting controls how long a compilation unit will remain in the
23005 cache if it is not referenced. A higher limit means that cached
23006 compilation units will be stored in memory longer, and more total
23007 memory will be used. Setting it to zero disables caching, which will
23008 slow down @value{GDBN} startup, but reduce memory consumption.
23010 @kindex maint set profile
23011 @kindex maint show profile
23012 @cindex profiling GDB
23013 @item maint set profile
23014 @itemx maint show profile
23015 Control profiling of @value{GDBN}.
23017 Profiling will be disabled until you use the @samp{maint set profile}
23018 command to enable it. When you enable profiling, the system will begin
23019 collecting timing and execution count data; when you disable profiling or
23020 exit @value{GDBN}, the results will be written to a log file. Remember that
23021 if you use profiling, @value{GDBN} will overwrite the profiling log file
23022 (often called @file{gmon.out}). If you have a record of important profiling
23023 data in a @file{gmon.out} file, be sure to move it to a safe location.
23025 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
23026 compiled with the @samp{-pg} compiler option.
23028 @kindex maint show-debug-regs
23029 @cindex x86 hardware debug registers
23030 @item maint show-debug-regs
23031 Control whether to show variables that mirror the x86 hardware debug
23032 registers. Use @code{ON} to enable, @code{OFF} to disable. If
23033 enabled, the debug registers values are shown when @value{GDBN} inserts or
23034 removes a hardware breakpoint or watchpoint, and when the inferior
23035 triggers a hardware-assisted breakpoint or watchpoint.
23037 @kindex maint space
23038 @cindex memory used by commands
23040 Control whether to display memory usage for each command. If set to a
23041 nonzero value, @value{GDBN} will display how much memory each command
23042 took, following the command's own output. This can also be requested
23043 by invoking @value{GDBN} with the @option{--statistics} command-line
23044 switch (@pxref{Mode Options}).
23047 @cindex time of command execution
23049 Control whether to display the execution time for each command. If
23050 set to a nonzero value, @value{GDBN} will display how much time it
23051 took to execute each command, following the command's own output.
23052 This can also be requested by invoking @value{GDBN} with the
23053 @option{--statistics} command-line switch (@pxref{Mode Options}).
23055 @kindex maint translate-address
23056 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
23057 Find the symbol stored at the location specified by the address
23058 @var{addr} and an optional section name @var{section}. If found,
23059 @value{GDBN} prints the name of the closest symbol and an offset from
23060 the symbol's location to the specified address. This is similar to
23061 the @code{info address} command (@pxref{Symbols}), except that this
23062 command also allows to find symbols in other sections.
23066 The following command is useful for non-interactive invocations of
23067 @value{GDBN}, such as in the test suite.
23070 @item set watchdog @var{nsec}
23071 @kindex set watchdog
23072 @cindex watchdog timer
23073 @cindex timeout for commands
23074 Set the maximum number of seconds @value{GDBN} will wait for the
23075 target operation to finish. If this time expires, @value{GDBN}
23076 reports and error and the command is aborted.
23078 @item show watchdog
23079 Show the current setting of the target wait timeout.
23082 @node Remote Protocol
23083 @appendix @value{GDBN} Remote Serial Protocol
23088 * Stop Reply Packets::
23089 * General Query Packets::
23090 * Register Packet Format::
23091 * Tracepoint Packets::
23092 * Host I/O Packets::
23095 * File-I/O Remote Protocol Extension::
23096 * Library List Format::
23097 * Memory Map Format::
23103 There may be occasions when you need to know something about the
23104 protocol---for example, if there is only one serial port to your target
23105 machine, you might want your program to do something special if it
23106 recognizes a packet meant for @value{GDBN}.
23108 In the examples below, @samp{->} and @samp{<-} are used to indicate
23109 transmitted and received data, respectively.
23111 @cindex protocol, @value{GDBN} remote serial
23112 @cindex serial protocol, @value{GDBN} remote
23113 @cindex remote serial protocol
23114 All @value{GDBN} commands and responses (other than acknowledgments) are
23115 sent as a @var{packet}. A @var{packet} is introduced with the character
23116 @samp{$}, the actual @var{packet-data}, and the terminating character
23117 @samp{#} followed by a two-digit @var{checksum}:
23120 @code{$}@var{packet-data}@code{#}@var{checksum}
23124 @cindex checksum, for @value{GDBN} remote
23126 The two-digit @var{checksum} is computed as the modulo 256 sum of all
23127 characters between the leading @samp{$} and the trailing @samp{#} (an
23128 eight bit unsigned checksum).
23130 Implementors should note that prior to @value{GDBN} 5.0 the protocol
23131 specification also included an optional two-digit @var{sequence-id}:
23134 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
23137 @cindex sequence-id, for @value{GDBN} remote
23139 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
23140 has never output @var{sequence-id}s. Stubs that handle packets added
23141 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
23143 @cindex acknowledgment, for @value{GDBN} remote
23144 When either the host or the target machine receives a packet, the first
23145 response expected is an acknowledgment: either @samp{+} (to indicate
23146 the package was received correctly) or @samp{-} (to request
23150 -> @code{$}@var{packet-data}@code{#}@var{checksum}
23155 The host (@value{GDBN}) sends @var{command}s, and the target (the
23156 debugging stub incorporated in your program) sends a @var{response}. In
23157 the case of step and continue @var{command}s, the response is only sent
23158 when the operation has completed (the target has again stopped).
23160 @var{packet-data} consists of a sequence of characters with the
23161 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
23164 @cindex remote protocol, field separator
23165 Fields within the packet should be separated using @samp{,} @samp{;} or
23166 @samp{:}. Except where otherwise noted all numbers are represented in
23167 @sc{hex} with leading zeros suppressed.
23169 Implementors should note that prior to @value{GDBN} 5.0, the character
23170 @samp{:} could not appear as the third character in a packet (as it
23171 would potentially conflict with the @var{sequence-id}).
23173 @cindex remote protocol, binary data
23174 @anchor{Binary Data}
23175 Binary data in most packets is encoded either as two hexadecimal
23176 digits per byte of binary data. This allowed the traditional remote
23177 protocol to work over connections which were only seven-bit clean.
23178 Some packets designed more recently assume an eight-bit clean
23179 connection, and use a more efficient encoding to send and receive
23182 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
23183 as an escape character. Any escaped byte is transmitted as the escape
23184 character followed by the original character XORed with @code{0x20}.
23185 For example, the byte @code{0x7d} would be transmitted as the two
23186 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
23187 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
23188 @samp{@}}) must always be escaped. Responses sent by the stub
23189 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
23190 is not interpreted as the start of a run-length encoded sequence
23193 Response @var{data} can be run-length encoded to save space.
23194 Run-length encoding replaces runs of identical characters with one
23195 instance of the repeated character, followed by a @samp{*} and a
23196 repeat count. The repeat count is itself sent encoded, to avoid
23197 binary characters in @var{data}: a value of @var{n} is sent as
23198 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
23199 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
23200 code 32) for a repeat count of 3. (This is because run-length
23201 encoding starts to win for counts 3 or more.) Thus, for example,
23202 @samp{0* } is a run-length encoding of ``0000'': the space character
23203 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
23206 The printable characters @samp{#} and @samp{$} or with a numeric value
23207 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
23208 seven repeats (@samp{$}) can be expanded using a repeat count of only
23209 five (@samp{"}). For example, @samp{00000000} can be encoded as
23212 The error response returned for some packets includes a two character
23213 error number. That number is not well defined.
23215 @cindex empty response, for unsupported packets
23216 For any @var{command} not supported by the stub, an empty response
23217 (@samp{$#00}) should be returned. That way it is possible to extend the
23218 protocol. A newer @value{GDBN} can tell if a packet is supported based
23221 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
23222 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
23228 The following table provides a complete list of all currently defined
23229 @var{command}s and their corresponding response @var{data}.
23230 @xref{File-I/O Remote Protocol Extension}, for details about the File
23231 I/O extension of the remote protocol.
23233 Each packet's description has a template showing the packet's overall
23234 syntax, followed by an explanation of the packet's meaning. We
23235 include spaces in some of the templates for clarity; these are not
23236 part of the packet's syntax. No @value{GDBN} packet uses spaces to
23237 separate its components. For example, a template like @samp{foo
23238 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
23239 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
23240 @var{baz}. @value{GDBN} does not transmit a space character between the
23241 @samp{foo} and the @var{bar}, or between the @var{bar} and the
23244 Note that all packet forms beginning with an upper- or lower-case
23245 letter, other than those described here, are reserved for future use.
23247 Here are the packet descriptions.
23252 @cindex @samp{!} packet
23253 Enable extended mode. In extended mode, the remote server is made
23254 persistent. The @samp{R} packet is used to restart the program being
23260 The remote target both supports and has enabled extended mode.
23264 @cindex @samp{?} packet
23265 Indicate the reason the target halted. The reply is the same as for
23269 @xref{Stop Reply Packets}, for the reply specifications.
23271 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
23272 @cindex @samp{A} packet
23273 Initialized @code{argv[]} array passed into program. @var{arglen}
23274 specifies the number of bytes in the hex encoded byte stream
23275 @var{arg}. See @code{gdbserver} for more details.
23280 The arguments were set.
23286 @cindex @samp{b} packet
23287 (Don't use this packet; its behavior is not well-defined.)
23288 Change the serial line speed to @var{baud}.
23290 JTC: @emph{When does the transport layer state change? When it's
23291 received, or after the ACK is transmitted. In either case, there are
23292 problems if the command or the acknowledgment packet is dropped.}
23294 Stan: @emph{If people really wanted to add something like this, and get
23295 it working for the first time, they ought to modify ser-unix.c to send
23296 some kind of out-of-band message to a specially-setup stub and have the
23297 switch happen "in between" packets, so that from remote protocol's point
23298 of view, nothing actually happened.}
23300 @item B @var{addr},@var{mode}
23301 @cindex @samp{B} packet
23302 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
23303 breakpoint at @var{addr}.
23305 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
23306 (@pxref{insert breakpoint or watchpoint packet}).
23308 @item c @r{[}@var{addr}@r{]}
23309 @cindex @samp{c} packet
23310 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
23311 resume at current address.
23314 @xref{Stop Reply Packets}, for the reply specifications.
23316 @item C @var{sig}@r{[};@var{addr}@r{]}
23317 @cindex @samp{C} packet
23318 Continue with signal @var{sig} (hex signal number). If
23319 @samp{;@var{addr}} is omitted, resume at same address.
23322 @xref{Stop Reply Packets}, for the reply specifications.
23325 @cindex @samp{d} packet
23328 Don't use this packet; instead, define a general set packet
23329 (@pxref{General Query Packets}).
23332 @cindex @samp{D} packet
23333 Detach @value{GDBN} from the remote system. Sent to the remote target
23334 before @value{GDBN} disconnects via the @code{detach} command.
23344 @item F @var{RC},@var{EE},@var{CF};@var{XX}
23345 @cindex @samp{F} packet
23346 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
23347 This is part of the File-I/O protocol extension. @xref{File-I/O
23348 Remote Protocol Extension}, for the specification.
23351 @anchor{read registers packet}
23352 @cindex @samp{g} packet
23353 Read general registers.
23357 @item @var{XX@dots{}}
23358 Each byte of register data is described by two hex digits. The bytes
23359 with the register are transmitted in target byte order. The size of
23360 each register and their position within the @samp{g} packet are
23361 determined by the @value{GDBN} internal gdbarch functions
23362 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
23363 specification of several standard @samp{g} packets is specified below.
23368 @item G @var{XX@dots{}}
23369 @cindex @samp{G} packet
23370 Write general registers. @xref{read registers packet}, for a
23371 description of the @var{XX@dots{}} data.
23381 @item H @var{c} @var{t}
23382 @cindex @samp{H} packet
23383 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
23384 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
23385 should be @samp{c} for step and continue operations, @samp{g} for other
23386 operations. The thread designator @var{t} may be @samp{-1}, meaning all
23387 the threads, a thread number, or @samp{0} which means pick any thread.
23398 @c 'H': How restrictive (or permissive) is the thread model. If a
23399 @c thread is selected and stopped, are other threads allowed
23400 @c to continue to execute? As I mentioned above, I think the
23401 @c semantics of each command when a thread is selected must be
23402 @c described. For example:
23404 @c 'g': If the stub supports threads and a specific thread is
23405 @c selected, returns the register block from that thread;
23406 @c otherwise returns current registers.
23408 @c 'G' If the stub supports threads and a specific thread is
23409 @c selected, sets the registers of the register block of
23410 @c that thread; otherwise sets current registers.
23412 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
23413 @anchor{cycle step packet}
23414 @cindex @samp{i} packet
23415 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
23416 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
23417 step starting at that address.
23420 @cindex @samp{I} packet
23421 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
23425 @cindex @samp{k} packet
23428 FIXME: @emph{There is no description of how to operate when a specific
23429 thread context has been selected (i.e.@: does 'k' kill only that
23432 @item m @var{addr},@var{length}
23433 @cindex @samp{m} packet
23434 Read @var{length} bytes of memory starting at address @var{addr}.
23435 Note that @var{addr} may not be aligned to any particular boundary.
23437 The stub need not use any particular size or alignment when gathering
23438 data from memory for the response; even if @var{addr} is word-aligned
23439 and @var{length} is a multiple of the word size, the stub is free to
23440 use byte accesses, or not. For this reason, this packet may not be
23441 suitable for accessing memory-mapped I/O devices.
23442 @cindex alignment of remote memory accesses
23443 @cindex size of remote memory accesses
23444 @cindex memory, alignment and size of remote accesses
23448 @item @var{XX@dots{}}
23449 Memory contents; each byte is transmitted as a two-digit hexadecimal
23450 number. The reply may contain fewer bytes than requested if the
23451 server was able to read only part of the region of memory.
23456 @item M @var{addr},@var{length}:@var{XX@dots{}}
23457 @cindex @samp{M} packet
23458 Write @var{length} bytes of memory starting at address @var{addr}.
23459 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
23460 hexadecimal number.
23467 for an error (this includes the case where only part of the data was
23472 @cindex @samp{p} packet
23473 Read the value of register @var{n}; @var{n} is in hex.
23474 @xref{read registers packet}, for a description of how the returned
23475 register value is encoded.
23479 @item @var{XX@dots{}}
23480 the register's value
23484 Indicating an unrecognized @var{query}.
23487 @item P @var{n@dots{}}=@var{r@dots{}}
23488 @anchor{write register packet}
23489 @cindex @samp{P} packet
23490 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
23491 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
23492 digits for each byte in the register (target byte order).
23502 @item q @var{name} @var{params}@dots{}
23503 @itemx Q @var{name} @var{params}@dots{}
23504 @cindex @samp{q} packet
23505 @cindex @samp{Q} packet
23506 General query (@samp{q}) and set (@samp{Q}). These packets are
23507 described fully in @ref{General Query Packets}.
23510 @cindex @samp{r} packet
23511 Reset the entire system.
23513 Don't use this packet; use the @samp{R} packet instead.
23516 @cindex @samp{R} packet
23517 Restart the program being debugged. @var{XX}, while needed, is ignored.
23518 This packet is only available in extended mode.
23520 The @samp{R} packet has no reply.
23522 @item s @r{[}@var{addr}@r{]}
23523 @cindex @samp{s} packet
23524 Single step. @var{addr} is the address at which to resume. If
23525 @var{addr} is omitted, resume at same address.
23528 @xref{Stop Reply Packets}, for the reply specifications.
23530 @item S @var{sig}@r{[};@var{addr}@r{]}
23531 @anchor{step with signal packet}
23532 @cindex @samp{S} packet
23533 Step with signal. This is analogous to the @samp{C} packet, but
23534 requests a single-step, rather than a normal resumption of execution.
23537 @xref{Stop Reply Packets}, for the reply specifications.
23539 @item t @var{addr}:@var{PP},@var{MM}
23540 @cindex @samp{t} packet
23541 Search backwards starting at address @var{addr} for a match with pattern
23542 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
23543 @var{addr} must be at least 3 digits.
23546 @cindex @samp{T} packet
23547 Find out if the thread XX is alive.
23552 thread is still alive
23558 Packets starting with @samp{v} are identified by a multi-letter name,
23559 up to the first @samp{;} or @samp{?} (or the end of the packet).
23561 @item vCont@r{[};@var{action}@r{[}:@var{tid}@r{]]}@dots{}
23562 @cindex @samp{vCont} packet
23563 Resume the inferior, specifying different actions for each thread.
23564 If an action is specified with no @var{tid}, then it is applied to any
23565 threads that don't have a specific action specified; if no default action is
23566 specified then other threads should remain stopped. Specifying multiple
23567 default actions is an error; specifying no actions is also an error.
23568 Thread IDs are specified in hexadecimal. Currently supported actions are:
23574 Continue with signal @var{sig}. @var{sig} should be two hex digits.
23578 Step with signal @var{sig}. @var{sig} should be two hex digits.
23581 The optional @var{addr} argument normally associated with these packets is
23582 not supported in @samp{vCont}.
23585 @xref{Stop Reply Packets}, for the reply specifications.
23588 @cindex @samp{vCont?} packet
23589 Request a list of actions supported by the @samp{vCont} packet.
23593 @item vCont@r{[};@var{action}@dots{}@r{]}
23594 The @samp{vCont} packet is supported. Each @var{action} is a supported
23595 command in the @samp{vCont} packet.
23597 The @samp{vCont} packet is not supported.
23600 @item vFile:@var{operation}:@var{parameter}@dots{}
23601 @cindex @samp{vFile} packet
23602 Perform a file operation on the target system. For details,
23603 see @ref{Host I/O Packets}.
23605 @item vFlashErase:@var{addr},@var{length}
23606 @cindex @samp{vFlashErase} packet
23607 Direct the stub to erase @var{length} bytes of flash starting at
23608 @var{addr}. The region may enclose any number of flash blocks, but
23609 its start and end must fall on block boundaries, as indicated by the
23610 flash block size appearing in the memory map (@pxref{Memory Map
23611 Format}). @value{GDBN} groups flash memory programming operations
23612 together, and sends a @samp{vFlashDone} request after each group; the
23613 stub is allowed to delay erase operation until the @samp{vFlashDone}
23614 packet is received.
23624 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
23625 @cindex @samp{vFlashWrite} packet
23626 Direct the stub to write data to flash address @var{addr}. The data
23627 is passed in binary form using the same encoding as for the @samp{X}
23628 packet (@pxref{Binary Data}). The memory ranges specified by
23629 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
23630 not overlap, and must appear in order of increasing addresses
23631 (although @samp{vFlashErase} packets for higher addresses may already
23632 have been received; the ordering is guaranteed only between
23633 @samp{vFlashWrite} packets). If a packet writes to an address that was
23634 neither erased by a preceding @samp{vFlashErase} packet nor by some other
23635 target-specific method, the results are unpredictable.
23643 for vFlashWrite addressing non-flash memory
23649 @cindex @samp{vFlashDone} packet
23650 Indicate to the stub that flash programming operation is finished.
23651 The stub is permitted to delay or batch the effects of a group of
23652 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
23653 @samp{vFlashDone} packet is received. The contents of the affected
23654 regions of flash memory are unpredictable until the @samp{vFlashDone}
23655 request is completed.
23657 @item X @var{addr},@var{length}:@var{XX@dots{}}
23659 @cindex @samp{X} packet
23660 Write data to memory, where the data is transmitted in binary.
23661 @var{addr} is address, @var{length} is number of bytes,
23662 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
23672 @item z @var{type},@var{addr},@var{length}
23673 @itemx Z @var{type},@var{addr},@var{length}
23674 @anchor{insert breakpoint or watchpoint packet}
23675 @cindex @samp{z} packet
23676 @cindex @samp{Z} packets
23677 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
23678 watchpoint starting at address @var{address} and covering the next
23679 @var{length} bytes.
23681 Each breakpoint and watchpoint packet @var{type} is documented
23684 @emph{Implementation notes: A remote target shall return an empty string
23685 for an unrecognized breakpoint or watchpoint packet @var{type}. A
23686 remote target shall support either both or neither of a given
23687 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
23688 avoid potential problems with duplicate packets, the operations should
23689 be implemented in an idempotent way.}
23691 @item z0,@var{addr},@var{length}
23692 @itemx Z0,@var{addr},@var{length}
23693 @cindex @samp{z0} packet
23694 @cindex @samp{Z0} packet
23695 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
23696 @var{addr} of size @var{length}.
23698 A memory breakpoint is implemented by replacing the instruction at
23699 @var{addr} with a software breakpoint or trap instruction. The
23700 @var{length} is used by targets that indicates the size of the
23701 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
23702 @sc{mips} can insert either a 2 or 4 byte breakpoint).
23704 @emph{Implementation note: It is possible for a target to copy or move
23705 code that contains memory breakpoints (e.g., when implementing
23706 overlays). The behavior of this packet, in the presence of such a
23707 target, is not defined.}
23719 @item z1,@var{addr},@var{length}
23720 @itemx Z1,@var{addr},@var{length}
23721 @cindex @samp{z1} packet
23722 @cindex @samp{Z1} packet
23723 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
23724 address @var{addr} of size @var{length}.
23726 A hardware breakpoint is implemented using a mechanism that is not
23727 dependant on being able to modify the target's memory.
23729 @emph{Implementation note: A hardware breakpoint is not affected by code
23742 @item z2,@var{addr},@var{length}
23743 @itemx Z2,@var{addr},@var{length}
23744 @cindex @samp{z2} packet
23745 @cindex @samp{Z2} packet
23746 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint.
23758 @item z3,@var{addr},@var{length}
23759 @itemx Z3,@var{addr},@var{length}
23760 @cindex @samp{z3} packet
23761 @cindex @samp{Z3} packet
23762 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint.
23774 @item z4,@var{addr},@var{length}
23775 @itemx Z4,@var{addr},@var{length}
23776 @cindex @samp{z4} packet
23777 @cindex @samp{Z4} packet
23778 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint.
23792 @node Stop Reply Packets
23793 @section Stop Reply Packets
23794 @cindex stop reply packets
23796 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
23797 receive any of the below as a reply. In the case of the @samp{C},
23798 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
23799 when the target halts. In the below the exact meaning of @dfn{signal
23800 number} is defined by the header @file{include/gdb/signals.h} in the
23801 @value{GDBN} source code.
23803 As in the description of request packets, we include spaces in the
23804 reply templates for clarity; these are not part of the reply packet's
23805 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
23811 The program received signal number @var{AA} (a two-digit hexadecimal
23812 number). This is equivalent to a @samp{T} response with no
23813 @var{n}:@var{r} pairs.
23815 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
23816 @cindex @samp{T} packet reply
23817 The program received signal number @var{AA} (a two-digit hexadecimal
23818 number). This is equivalent to an @samp{S} response, except that the
23819 @samp{@var{n}:@var{r}} pairs can carry values of important registers
23820 and other information directly in the stop reply packet, reducing
23821 round-trip latency. Single-step and breakpoint traps are reported
23822 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
23826 If @var{n} is a hexadecimal number, it is a register number, and the
23827 corresponding @var{r} gives that register's value. @var{r} is a
23828 series of bytes in target byte order, with each byte given by a
23829 two-digit hex number.
23832 If @var{n} is @samp{thread}, then @var{r} is the thread process ID, in
23836 If @var{n} is a recognized @dfn{stop reason}, it describes a more
23837 specific event that stopped the target. The currently defined stop
23838 reasons are listed below. @var{aa} should be @samp{05}, the trap
23839 signal. At most one stop reason should be present.
23842 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
23843 and go on to the next; this allows us to extend the protocol in the
23847 The currently defined stop reasons are:
23853 The packet indicates a watchpoint hit, and @var{r} is the data address, in
23856 @cindex shared library events, remote reply
23858 The packet indicates that the loaded libraries have changed.
23859 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
23860 list of loaded libraries. @var{r} is ignored.
23864 The process exited, and @var{AA} is the exit status. This is only
23865 applicable to certain targets.
23868 The process terminated with signal @var{AA}.
23870 @item O @var{XX}@dots{}
23871 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
23872 written as the program's console output. This can happen at any time
23873 while the program is running and the debugger should continue to wait
23874 for @samp{W}, @samp{T}, etc.
23876 @item F @var{call-id},@var{parameter}@dots{}
23877 @var{call-id} is the identifier which says which host system call should
23878 be called. This is just the name of the function. Translation into the
23879 correct system call is only applicable as it's defined in @value{GDBN}.
23880 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
23883 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
23884 this very system call.
23886 The target replies with this packet when it expects @value{GDBN} to
23887 call a host system call on behalf of the target. @value{GDBN} replies
23888 with an appropriate @samp{F} packet and keeps up waiting for the next
23889 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
23890 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
23891 Protocol Extension}, for more details.
23895 @node General Query Packets
23896 @section General Query Packets
23897 @cindex remote query requests
23899 Packets starting with @samp{q} are @dfn{general query packets};
23900 packets starting with @samp{Q} are @dfn{general set packets}. General
23901 query and set packets are a semi-unified form for retrieving and
23902 sending information to and from the stub.
23904 The initial letter of a query or set packet is followed by a name
23905 indicating what sort of thing the packet applies to. For example,
23906 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
23907 definitions with the stub. These packet names follow some
23912 The name must not contain commas, colons or semicolons.
23914 Most @value{GDBN} query and set packets have a leading upper case
23917 The names of custom vendor packets should use a company prefix, in
23918 lower case, followed by a period. For example, packets designed at
23919 the Acme Corporation might begin with @samp{qacme.foo} (for querying
23920 foos) or @samp{Qacme.bar} (for setting bars).
23923 The name of a query or set packet should be separated from any
23924 parameters by a @samp{:}; the parameters themselves should be
23925 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
23926 full packet name, and check for a separator or the end of the packet,
23927 in case two packet names share a common prefix. New packets should not begin
23928 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
23929 packets predate these conventions, and have arguments without any terminator
23930 for the packet name; we suspect they are in widespread use in places that
23931 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
23932 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
23935 Like the descriptions of the other packets, each description here
23936 has a template showing the packet's overall syntax, followed by an
23937 explanation of the packet's meaning. We include spaces in some of the
23938 templates for clarity; these are not part of the packet's syntax. No
23939 @value{GDBN} packet uses spaces to separate its components.
23941 Here are the currently defined query and set packets:
23946 @cindex current thread, remote request
23947 @cindex @samp{qC} packet
23948 Return the current thread id.
23953 Where @var{pid} is an unsigned hexadecimal process id.
23954 @item @r{(anything else)}
23955 Any other reply implies the old pid.
23958 @item qCRC:@var{addr},@var{length}
23959 @cindex CRC of memory block, remote request
23960 @cindex @samp{qCRC} packet
23961 Compute the CRC checksum of a block of memory.
23965 An error (such as memory fault)
23966 @item C @var{crc32}
23967 The specified memory region's checksum is @var{crc32}.
23971 @itemx qsThreadInfo
23972 @cindex list active threads, remote request
23973 @cindex @samp{qfThreadInfo} packet
23974 @cindex @samp{qsThreadInfo} packet
23975 Obtain a list of all active thread ids from the target (OS). Since there
23976 may be too many active threads to fit into one reply packet, this query
23977 works iteratively: it may require more than one query/reply sequence to
23978 obtain the entire list of threads. The first query of the sequence will
23979 be the @samp{qfThreadInfo} query; subsequent queries in the
23980 sequence will be the @samp{qsThreadInfo} query.
23982 NOTE: This packet replaces the @samp{qL} query (see below).
23988 @item m @var{id},@var{id}@dots{}
23989 a comma-separated list of thread ids
23991 (lower case letter @samp{L}) denotes end of list.
23994 In response to each query, the target will reply with a list of one or
23995 more thread ids, in big-endian unsigned hex, separated by commas.
23996 @value{GDBN} will respond to each reply with a request for more thread
23997 ids (using the @samp{qs} form of the query), until the target responds
23998 with @samp{l} (lower-case el, for @dfn{last}).
24000 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
24001 @cindex get thread-local storage address, remote request
24002 @cindex @samp{qGetTLSAddr} packet
24003 Fetch the address associated with thread local storage specified
24004 by @var{thread-id}, @var{offset}, and @var{lm}.
24006 @var{thread-id} is the (big endian, hex encoded) thread id associated with the
24007 thread for which to fetch the TLS address.
24009 @var{offset} is the (big endian, hex encoded) offset associated with the
24010 thread local variable. (This offset is obtained from the debug
24011 information associated with the variable.)
24013 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
24014 the load module associated with the thread local storage. For example,
24015 a @sc{gnu}/Linux system will pass the link map address of the shared
24016 object associated with the thread local storage under consideration.
24017 Other operating environments may choose to represent the load module
24018 differently, so the precise meaning of this parameter will vary.
24022 @item @var{XX}@dots{}
24023 Hex encoded (big endian) bytes representing the address of the thread
24024 local storage requested.
24027 An error occurred. @var{nn} are hex digits.
24030 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
24033 @item qL @var{startflag} @var{threadcount} @var{nextthread}
24034 Obtain thread information from RTOS. Where: @var{startflag} (one hex
24035 digit) is one to indicate the first query and zero to indicate a
24036 subsequent query; @var{threadcount} (two hex digits) is the maximum
24037 number of threads the response packet can contain; and @var{nextthread}
24038 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
24039 returned in the response as @var{argthread}.
24041 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
24045 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
24046 Where: @var{count} (two hex digits) is the number of threads being
24047 returned; @var{done} (one hex digit) is zero to indicate more threads
24048 and one indicates no further threads; @var{argthreadid} (eight hex
24049 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
24050 is a sequence of thread IDs from the target. @var{threadid} (eight hex
24051 digits). See @code{remote.c:parse_threadlist_response()}.
24055 @cindex section offsets, remote request
24056 @cindex @samp{qOffsets} packet
24057 Get section offsets that the target used when relocating the downloaded
24062 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
24063 Relocate the @code{Text} section by @var{xxx} from its original address.
24064 Relocate the @code{Data} section by @var{yyy} from its original address.
24065 If the object file format provides segment information (e.g.@: @sc{elf}
24066 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
24067 segments by the supplied offsets.
24069 @emph{Note: while a @code{Bss} offset may be included in the response,
24070 @value{GDBN} ignores this and instead applies the @code{Data} offset
24071 to the @code{Bss} section.}
24073 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
24074 Relocate the first segment of the object file, which conventionally
24075 contains program code, to a starting address of @var{xxx}. If
24076 @samp{DataSeg} is specified, relocate the second segment, which
24077 conventionally contains modifiable data, to a starting address of
24078 @var{yyy}. @value{GDBN} will report an error if the object file
24079 does not contain segment information, or does not contain at least
24080 as many segments as mentioned in the reply. Extra segments are
24081 kept at fixed offsets relative to the last relocated segment.
24084 @item qP @var{mode} @var{threadid}
24085 @cindex thread information, remote request
24086 @cindex @samp{qP} packet
24087 Returns information on @var{threadid}. Where: @var{mode} is a hex
24088 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
24090 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
24093 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
24095 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
24096 @cindex pass signals to inferior, remote request
24097 @cindex @samp{QPassSignals} packet
24098 @anchor{QPassSignals}
24099 Each listed @var{signal} should be passed directly to the inferior process.
24100 Signals are numbered identically to continue packets and stop replies
24101 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
24102 strictly greater than the previous item. These signals do not need to stop
24103 the inferior, or be reported to @value{GDBN}. All other signals should be
24104 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
24105 combine; any earlier @samp{QPassSignals} list is completely replaced by the
24106 new list. This packet improves performance when using @samp{handle
24107 @var{signal} nostop noprint pass}.
24112 The request succeeded.
24115 An error occurred. @var{nn} are hex digits.
24118 An empty reply indicates that @samp{QPassSignals} is not supported by
24122 Use of this packet is controlled by the @code{set remote pass-signals}
24123 command (@pxref{Remote Configuration, set remote pass-signals}).
24124 This packet is not probed by default; the remote stub must request it,
24125 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24127 @item qRcmd,@var{command}
24128 @cindex execute remote command, remote request
24129 @cindex @samp{qRcmd} packet
24130 @var{command} (hex encoded) is passed to the local interpreter for
24131 execution. Invalid commands should be reported using the output
24132 string. Before the final result packet, the target may also respond
24133 with a number of intermediate @samp{O@var{output}} console output
24134 packets. @emph{Implementors should note that providing access to a
24135 stubs's interpreter may have security implications}.
24140 A command response with no output.
24142 A command response with the hex encoded output string @var{OUTPUT}.
24144 Indicate a badly formed request.
24146 An empty reply indicates that @samp{qRcmd} is not recognized.
24149 (Note that the @code{qRcmd} packet's name is separated from the
24150 command by a @samp{,}, not a @samp{:}, contrary to the naming
24151 conventions above. Please don't use this packet as a model for new
24154 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
24155 @cindex supported packets, remote query
24156 @cindex features of the remote protocol
24157 @cindex @samp{qSupported} packet
24158 @anchor{qSupported}
24159 Tell the remote stub about features supported by @value{GDBN}, and
24160 query the stub for features it supports. This packet allows
24161 @value{GDBN} and the remote stub to take advantage of each others'
24162 features. @samp{qSupported} also consolidates multiple feature probes
24163 at startup, to improve @value{GDBN} performance---a single larger
24164 packet performs better than multiple smaller probe packets on
24165 high-latency links. Some features may enable behavior which must not
24166 be on by default, e.g.@: because it would confuse older clients or
24167 stubs. Other features may describe packets which could be
24168 automatically probed for, but are not. These features must be
24169 reported before @value{GDBN} will use them. This ``default
24170 unsupported'' behavior is not appropriate for all packets, but it
24171 helps to keep the initial connection time under control with new
24172 versions of @value{GDBN} which support increasing numbers of packets.
24176 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
24177 The stub supports or does not support each returned @var{stubfeature},
24178 depending on the form of each @var{stubfeature} (see below for the
24181 An empty reply indicates that @samp{qSupported} is not recognized,
24182 or that no features needed to be reported to @value{GDBN}.
24185 The allowed forms for each feature (either a @var{gdbfeature} in the
24186 @samp{qSupported} packet, or a @var{stubfeature} in the response)
24190 @item @var{name}=@var{value}
24191 The remote protocol feature @var{name} is supported, and associated
24192 with the specified @var{value}. The format of @var{value} depends
24193 on the feature, but it must not include a semicolon.
24195 The remote protocol feature @var{name} is supported, and does not
24196 need an associated value.
24198 The remote protocol feature @var{name} is not supported.
24200 The remote protocol feature @var{name} may be supported, and
24201 @value{GDBN} should auto-detect support in some other way when it is
24202 needed. This form will not be used for @var{gdbfeature} notifications,
24203 but may be used for @var{stubfeature} responses.
24206 Whenever the stub receives a @samp{qSupported} request, the
24207 supplied set of @value{GDBN} features should override any previous
24208 request. This allows @value{GDBN} to put the stub in a known
24209 state, even if the stub had previously been communicating with
24210 a different version of @value{GDBN}.
24212 No values of @var{gdbfeature} (for the packet sent by @value{GDBN})
24213 are defined yet. Stubs should ignore any unknown values for
24214 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
24215 packet supports receiving packets of unlimited length (earlier
24216 versions of @value{GDBN} may reject overly long responses). Values
24217 for @var{gdbfeature} may be defined in the future to let the stub take
24218 advantage of new features in @value{GDBN}, e.g.@: incompatible
24219 improvements in the remote protocol---support for unlimited length
24220 responses would be a @var{gdbfeature} example, if it were not implied by
24221 the @samp{qSupported} query. The stub's reply should be independent
24222 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
24223 describes all the features it supports, and then the stub replies with
24224 all the features it supports.
24226 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
24227 responses, as long as each response uses one of the standard forms.
24229 Some features are flags. A stub which supports a flag feature
24230 should respond with a @samp{+} form response. Other features
24231 require values, and the stub should respond with an @samp{=}
24234 Each feature has a default value, which @value{GDBN} will use if
24235 @samp{qSupported} is not available or if the feature is not mentioned
24236 in the @samp{qSupported} response. The default values are fixed; a
24237 stub is free to omit any feature responses that match the defaults.
24239 Not all features can be probed, but for those which can, the probing
24240 mechanism is useful: in some cases, a stub's internal
24241 architecture may not allow the protocol layer to know some information
24242 about the underlying target in advance. This is especially common in
24243 stubs which may be configured for multiple targets.
24245 These are the currently defined stub features and their properties:
24247 @multitable @columnfractions 0.35 0.2 0.12 0.2
24248 @c NOTE: The first row should be @headitem, but we do not yet require
24249 @c a new enough version of Texinfo (4.7) to use @headitem.
24251 @tab Value Required
24255 @item @samp{PacketSize}
24260 @item @samp{qXfer:auxv:read}
24265 @item @samp{qXfer:features:read}
24270 @item @samp{qXfer:libraries:read}
24275 @item @samp{qXfer:memory-map:read}
24280 @item @samp{qXfer:spu:read}
24285 @item @samp{qXfer:spu:write}
24290 @item @samp{QPassSignals}
24297 These are the currently defined stub features, in more detail:
24300 @cindex packet size, remote protocol
24301 @item PacketSize=@var{bytes}
24302 The remote stub can accept packets up to at least @var{bytes} in
24303 length. @value{GDBN} will send packets up to this size for bulk
24304 transfers, and will never send larger packets. This is a limit on the
24305 data characters in the packet, including the frame and checksum.
24306 There is no trailing NUL byte in a remote protocol packet; if the stub
24307 stores packets in a NUL-terminated format, it should allow an extra
24308 byte in its buffer for the NUL. If this stub feature is not supported,
24309 @value{GDBN} guesses based on the size of the @samp{g} packet response.
24311 @item qXfer:auxv:read
24312 The remote stub understands the @samp{qXfer:auxv:read} packet
24313 (@pxref{qXfer auxiliary vector read}).
24315 @item qXfer:features:read
24316 The remote stub understands the @samp{qXfer:features:read} packet
24317 (@pxref{qXfer target description read}).
24319 @item qXfer:libraries:read
24320 The remote stub understands the @samp{qXfer:libraries:read} packet
24321 (@pxref{qXfer library list read}).
24323 @item qXfer:memory-map:read
24324 The remote stub understands the @samp{qXfer:memory-map:read} packet
24325 (@pxref{qXfer memory map read}).
24327 @item qXfer:spu:read
24328 The remote stub understands the @samp{qXfer:spu:read} packet
24329 (@pxref{qXfer spu read}).
24331 @item qXfer:spu:write
24332 The remote stub understands the @samp{qXfer:spu:write} packet
24333 (@pxref{qXfer spu write}).
24336 The remote stub understands the @samp{QPassSignals} packet
24337 (@pxref{QPassSignals}).
24342 @cindex symbol lookup, remote request
24343 @cindex @samp{qSymbol} packet
24344 Notify the target that @value{GDBN} is prepared to serve symbol lookup
24345 requests. Accept requests from the target for the values of symbols.
24350 The target does not need to look up any (more) symbols.
24351 @item qSymbol:@var{sym_name}
24352 The target requests the value of symbol @var{sym_name} (hex encoded).
24353 @value{GDBN} may provide the value by using the
24354 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
24358 @item qSymbol:@var{sym_value}:@var{sym_name}
24359 Set the value of @var{sym_name} to @var{sym_value}.
24361 @var{sym_name} (hex encoded) is the name of a symbol whose value the
24362 target has previously requested.
24364 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
24365 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
24371 The target does not need to look up any (more) symbols.
24372 @item qSymbol:@var{sym_name}
24373 The target requests the value of a new symbol @var{sym_name} (hex
24374 encoded). @value{GDBN} will continue to supply the values of symbols
24375 (if available), until the target ceases to request them.
24380 @xref{Tracepoint Packets}.
24382 @item qThreadExtraInfo,@var{id}
24383 @cindex thread attributes info, remote request
24384 @cindex @samp{qThreadExtraInfo} packet
24385 Obtain a printable string description of a thread's attributes from
24386 the target OS. @var{id} is a thread-id in big-endian hex. This
24387 string may contain anything that the target OS thinks is interesting
24388 for @value{GDBN} to tell the user about the thread. The string is
24389 displayed in @value{GDBN}'s @code{info threads} display. Some
24390 examples of possible thread extra info strings are @samp{Runnable}, or
24391 @samp{Blocked on Mutex}.
24395 @item @var{XX}@dots{}
24396 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
24397 comprising the printable string containing the extra information about
24398 the thread's attributes.
24401 (Note that the @code{qThreadExtraInfo} packet's name is separated from
24402 the command by a @samp{,}, not a @samp{:}, contrary to the naming
24403 conventions above. Please don't use this packet as a model for new
24411 @xref{Tracepoint Packets}.
24413 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
24414 @cindex read special object, remote request
24415 @cindex @samp{qXfer} packet
24416 @anchor{qXfer read}
24417 Read uninterpreted bytes from the target's special data area
24418 identified by the keyword @var{object}. Request @var{length} bytes
24419 starting at @var{offset} bytes into the data. The content and
24420 encoding of @var{annex} is specific to @var{object}; it can supply
24421 additional details about what data to access.
24423 Here are the specific requests of this form defined so far. All
24424 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
24425 formats, listed below.
24428 @item qXfer:auxv:read::@var{offset},@var{length}
24429 @anchor{qXfer auxiliary vector read}
24430 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
24431 auxiliary vector}. Note @var{annex} must be empty.
24433 This packet is not probed by default; the remote stub must request it,
24434 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24436 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
24437 @anchor{qXfer target description read}
24438 Access the @dfn{target description}. @xref{Target Descriptions}. The
24439 annex specifies which XML document to access. The main description is
24440 always loaded from the @samp{target.xml} annex.
24442 This packet is not probed by default; the remote stub must request it,
24443 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24445 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
24446 @anchor{qXfer library list read}
24447 Access the target's list of loaded libraries. @xref{Library List Format}.
24448 The annex part of the generic @samp{qXfer} packet must be empty
24449 (@pxref{qXfer read}).
24451 Targets which maintain a list of libraries in the program's memory do
24452 not need to implement this packet; it is designed for platforms where
24453 the operating system manages the list of loaded libraries.
24455 This packet is not probed by default; the remote stub must request it,
24456 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24458 @item qXfer:memory-map:read::@var{offset},@var{length}
24459 @anchor{qXfer memory map read}
24460 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
24461 annex part of the generic @samp{qXfer} packet must be empty
24462 (@pxref{qXfer read}).
24464 This packet is not probed by default; the remote stub must request it,
24465 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24467 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
24468 @anchor{qXfer spu read}
24469 Read contents of an @code{spufs} file on the target system. The
24470 annex specifies which file to read; it must be of the form
24471 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
24472 in the target process, and @var{name} identifes the @code{spufs} file
24473 in that context to be accessed.
24475 This packet is not probed by default; the remote stub must request it,
24476 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24482 Data @var{data} (@pxref{Binary Data}) has been read from the
24483 target. There may be more data at a higher address (although
24484 it is permitted to return @samp{m} even for the last valid
24485 block of data, as long as at least one byte of data was read).
24486 @var{data} may have fewer bytes than the @var{length} in the
24490 Data @var{data} (@pxref{Binary Data}) has been read from the target.
24491 There is no more data to be read. @var{data} may have fewer bytes
24492 than the @var{length} in the request.
24495 The @var{offset} in the request is at the end of the data.
24496 There is no more data to be read.
24499 The request was malformed, or @var{annex} was invalid.
24502 The offset was invalid, or there was an error encountered reading the data.
24503 @var{nn} is a hex-encoded @code{errno} value.
24506 An empty reply indicates the @var{object} string was not recognized by
24507 the stub, or that the object does not support reading.
24510 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
24511 @cindex write data into object, remote request
24512 Write uninterpreted bytes into the target's special data area
24513 identified by the keyword @var{object}, starting at @var{offset} bytes
24514 into the data. @var{data}@dots{} is the binary-encoded data
24515 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
24516 is specific to @var{object}; it can supply additional details about what data
24519 Here are the specific requests of this form defined so far. All
24520 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
24521 formats, listed below.
24524 @item qXfer:@var{spu}:write:@var{annex}:@var{offset}:@var{data}@dots{}
24525 @anchor{qXfer spu write}
24526 Write @var{data} to an @code{spufs} file on the target system. The
24527 annex specifies which file to write; it must be of the form
24528 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
24529 in the target process, and @var{name} identifes the @code{spufs} file
24530 in that context to be accessed.
24532 This packet is not probed by default; the remote stub must request it,
24533 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24539 @var{nn} (hex encoded) is the number of bytes written.
24540 This may be fewer bytes than supplied in the request.
24543 The request was malformed, or @var{annex} was invalid.
24546 The offset was invalid, or there was an error encountered writing the data.
24547 @var{nn} is a hex-encoded @code{errno} value.
24550 An empty reply indicates the @var{object} string was not
24551 recognized by the stub, or that the object does not support writing.
24554 @item qXfer:@var{object}:@var{operation}:@dots{}
24555 Requests of this form may be added in the future. When a stub does
24556 not recognize the @var{object} keyword, or its support for
24557 @var{object} does not recognize the @var{operation} keyword, the stub
24558 must respond with an empty packet.
24562 @node Register Packet Format
24563 @section Register Packet Format
24565 The following @code{g}/@code{G} packets have previously been defined.
24566 In the below, some thirty-two bit registers are transferred as
24567 sixty-four bits. Those registers should be zero/sign extended (which?)
24568 to fill the space allocated. Register bytes are transferred in target
24569 byte order. The two nibbles within a register byte are transferred
24570 most-significant - least-significant.
24576 All registers are transferred as thirty-two bit quantities in the order:
24577 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
24578 registers; fsr; fir; fp.
24582 All registers are transferred as sixty-four bit quantities (including
24583 thirty-two bit registers such as @code{sr}). The ordering is the same
24588 @node Tracepoint Packets
24589 @section Tracepoint Packets
24590 @cindex tracepoint packets
24591 @cindex packets, tracepoint
24593 Here we describe the packets @value{GDBN} uses to implement
24594 tracepoints (@pxref{Tracepoints}).
24598 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}@r{[}-@r{]}
24599 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
24600 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
24601 the tracepoint is disabled. @var{step} is the tracepoint's step
24602 count, and @var{pass} is its pass count. If the trailing @samp{-} is
24603 present, further @samp{QTDP} packets will follow to specify this
24604 tracepoint's actions.
24609 The packet was understood and carried out.
24611 The packet was not recognized.
24614 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
24615 Define actions to be taken when a tracepoint is hit. @var{n} and
24616 @var{addr} must be the same as in the initial @samp{QTDP} packet for
24617 this tracepoint. This packet may only be sent immediately after
24618 another @samp{QTDP} packet that ended with a @samp{-}. If the
24619 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
24620 specifying more actions for this tracepoint.
24622 In the series of action packets for a given tracepoint, at most one
24623 can have an @samp{S} before its first @var{action}. If such a packet
24624 is sent, it and the following packets define ``while-stepping''
24625 actions. Any prior packets define ordinary actions --- that is, those
24626 taken when the tracepoint is first hit. If no action packet has an
24627 @samp{S}, then all the packets in the series specify ordinary
24628 tracepoint actions.
24630 The @samp{@var{action}@dots{}} portion of the packet is a series of
24631 actions, concatenated without separators. Each action has one of the
24637 Collect the registers whose bits are set in @var{mask}. @var{mask} is
24638 a hexadecimal number whose @var{i}'th bit is set if register number
24639 @var{i} should be collected. (The least significant bit is numbered
24640 zero.) Note that @var{mask} may be any number of digits long; it may
24641 not fit in a 32-bit word.
24643 @item M @var{basereg},@var{offset},@var{len}
24644 Collect @var{len} bytes of memory starting at the address in register
24645 number @var{basereg}, plus @var{offset}. If @var{basereg} is
24646 @samp{-1}, then the range has a fixed address: @var{offset} is the
24647 address of the lowest byte to collect. The @var{basereg},
24648 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
24649 values (the @samp{-1} value for @var{basereg} is a special case).
24651 @item X @var{len},@var{expr}
24652 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
24653 it directs. @var{expr} is an agent expression, as described in
24654 @ref{Agent Expressions}. Each byte of the expression is encoded as a
24655 two-digit hex number in the packet; @var{len} is the number of bytes
24656 in the expression (and thus one-half the number of hex digits in the
24661 Any number of actions may be packed together in a single @samp{QTDP}
24662 packet, as long as the packet does not exceed the maximum packet
24663 length (400 bytes, for many stubs). There may be only one @samp{R}
24664 action per tracepoint, and it must precede any @samp{M} or @samp{X}
24665 actions. Any registers referred to by @samp{M} and @samp{X} actions
24666 must be collected by a preceding @samp{R} action. (The
24667 ``while-stepping'' actions are treated as if they were attached to a
24668 separate tracepoint, as far as these restrictions are concerned.)
24673 The packet was understood and carried out.
24675 The packet was not recognized.
24678 @item QTFrame:@var{n}
24679 Select the @var{n}'th tracepoint frame from the buffer, and use the
24680 register and memory contents recorded there to answer subsequent
24681 request packets from @value{GDBN}.
24683 A successful reply from the stub indicates that the stub has found the
24684 requested frame. The response is a series of parts, concatenated
24685 without separators, describing the frame we selected. Each part has
24686 one of the following forms:
24690 The selected frame is number @var{n} in the trace frame buffer;
24691 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
24692 was no frame matching the criteria in the request packet.
24695 The selected trace frame records a hit of tracepoint number @var{t};
24696 @var{t} is a hexadecimal number.
24700 @item QTFrame:pc:@var{addr}
24701 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
24702 currently selected frame whose PC is @var{addr};
24703 @var{addr} is a hexadecimal number.
24705 @item QTFrame:tdp:@var{t}
24706 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
24707 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
24708 is a hexadecimal number.
24710 @item QTFrame:range:@var{start}:@var{end}
24711 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
24712 currently selected frame whose PC is between @var{start} (inclusive)
24713 and @var{end} (exclusive); @var{start} and @var{end} are hexadecimal
24716 @item QTFrame:outside:@var{start}:@var{end}
24717 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
24718 frame @emph{outside} the given range of addresses.
24721 Begin the tracepoint experiment. Begin collecting data from tracepoint
24722 hits in the trace frame buffer.
24725 End the tracepoint experiment. Stop collecting trace frames.
24728 Clear the table of tracepoints, and empty the trace frame buffer.
24730 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
24731 Establish the given ranges of memory as ``transparent''. The stub
24732 will answer requests for these ranges from memory's current contents,
24733 if they were not collected as part of the tracepoint hit.
24735 @value{GDBN} uses this to mark read-only regions of memory, like those
24736 containing program code. Since these areas never change, they should
24737 still have the same contents they did when the tracepoint was hit, so
24738 there's no reason for the stub to refuse to provide their contents.
24741 Ask the stub if there is a trace experiment running right now.
24746 There is no trace experiment running.
24748 There is a trace experiment running.
24754 @node Host I/O Packets
24755 @section Host I/O Packets
24756 @cindex Host I/O, remote protocol
24757 @cindex file transfer, remote protocol
24759 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
24760 operations on the far side of a remote link. For example, Host I/O is
24761 used to upload and download files to a remote target with its own
24762 filesystem. Host I/O uses the same constant values and data structure
24763 layout as the target-initiated File-I/O protocol. However, the
24764 Host I/O packets are structured differently. The target-initiated
24765 protocol relies on target memory to store parameters and buffers.
24766 Host I/O requests are initiated by @value{GDBN}, and the
24767 target's memory is not involved. @xref{File-I/O Remote Protocol
24768 Extension}, for more details on the target-initiated protocol.
24770 The Host I/O request packets all encode a single operation along with
24771 its arguments. They have this format:
24775 @item vFile:@var{operation}: @var{parameter}@dots{}
24776 @var{operation} is the name of the particular request; the target
24777 should compare the entire packet name up to the second colon when checking
24778 for a supported operation. The format of @var{parameter} depends on
24779 the operation. Numbers are always passed in hexadecimal. Negative
24780 numbers have an explicit minus sign (i.e.@: two's complement is not
24781 used). Strings (e.g.@: filenames) are encoded as a series of
24782 hexadecimal bytes. The last argument to a system call may be a
24783 buffer of escaped binary data (@pxref{Binary Data}).
24787 The valid responses to Host I/O packets are:
24791 @item F @var{result} [, @var{errno}] [; @var{attachment}]
24792 @var{result} is the integer value returned by this operation, usually
24793 non-negative for success and -1 for errors. If an error has occured,
24794 @var{errno} will be included in the result. @var{errno} will have a
24795 value defined by the File-I/O protocol (@pxref{Errno Values}). For
24796 operations which return data, @var{attachment} supplies the data as a
24797 binary buffer. Binary buffers in response packets are escaped in the
24798 normal way (@pxref{Binary Data}). See the individual packet
24799 documentation for the interpretation of @var{result} and
24803 An empty response indicates that this operation is not recognized.
24807 These are the supported Host I/O operations:
24810 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
24811 Open a file at @var{pathname} and return a file descriptor for it, or
24812 return -1 if an error occurs. @var{pathname} is a string,
24813 @var{flags} is an integer indicating a mask of open flags
24814 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
24815 of mode bits to use if the file is created (@pxref{mode_t Values}).
24816 @xref{open}, for details of the open flags and mode values.
24818 @item vFile:close: @var{fd}
24819 Close the open file corresponding to @var{fd} and return 0, or
24820 -1 if an error occurs.
24822 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
24823 Read data from the open file corresponding to @var{fd}. Up to
24824 @var{count} bytes will be read from the file, starting at @var{offset}
24825 relative to the start of the file. The target may read fewer bytes;
24826 common reasons include packet size limits and an end-of-file
24827 condition. The number of bytes read is returned. Zero should only be
24828 returned for a successful read at the end of the file, or if
24829 @var{count} was zero.
24831 The data read should be returned as a binary attachment on success.
24832 If zero bytes were read, the response should include an empty binary
24833 attachment (i.e.@: a trailing semicolon). The return value is the
24834 number of target bytes read; the binary attachment may be longer if
24835 some characters were escaped.
24837 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
24838 Write @var{data} (a binary buffer) to the open file corresponding
24839 to @var{fd}. Start the write at @var{offset} from the start of the
24840 file. Unlike many @code{write} system calls, there is no
24841 separate @var{count} argument; the length of @var{data} in the
24842 packet is used. @samp{vFile:write} returns the number of bytes written,
24843 which may be shorter than the length of @var{data}, or -1 if an
24846 @item vFile:unlink: @var{pathname}
24847 Delete the file at @var{pathname} on the target. Return 0,
24848 or -1 if an error occurs. @var{pathname} is a string.
24853 @section Interrupts
24854 @cindex interrupts (remote protocol)
24856 When a program on the remote target is running, @value{GDBN} may
24857 attempt to interrupt it by sending a @samp{Ctrl-C} or a @code{BREAK},
24858 control of which is specified via @value{GDBN}'s @samp{remotebreak}
24859 setting (@pxref{set remotebreak}).
24861 The precise meaning of @code{BREAK} is defined by the transport
24862 mechanism and may, in fact, be undefined. @value{GDBN} does
24863 not currently define a @code{BREAK} mechanism for any of the network
24866 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
24867 transport mechanisms. It is represented by sending the single byte
24868 @code{0x03} without any of the usual packet overhead described in
24869 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
24870 transmitted as part of a packet, it is considered to be packet data
24871 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
24872 (@pxref{X packet}), used for binary downloads, may include an unescaped
24873 @code{0x03} as part of its packet.
24875 Stubs are not required to recognize these interrupt mechanisms and the
24876 precise meaning associated with receipt of the interrupt is
24877 implementation defined. If the stub is successful at interrupting the
24878 running program, it is expected that it will send one of the Stop
24879 Reply Packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
24880 of successfully stopping the program. Interrupts received while the
24881 program is stopped will be discarded.
24886 Example sequence of a target being re-started. Notice how the restart
24887 does not get any direct output:
24892 @emph{target restarts}
24895 <- @code{T001:1234123412341234}
24899 Example sequence of a target being stepped by a single instruction:
24902 -> @code{G1445@dots{}}
24907 <- @code{T001:1234123412341234}
24911 <- @code{1455@dots{}}
24915 @node File-I/O Remote Protocol Extension
24916 @section File-I/O Remote Protocol Extension
24917 @cindex File-I/O remote protocol extension
24920 * File-I/O Overview::
24921 * Protocol Basics::
24922 * The F Request Packet::
24923 * The F Reply Packet::
24924 * The Ctrl-C Message::
24926 * List of Supported Calls::
24927 * Protocol-specific Representation of Datatypes::
24929 * File-I/O Examples::
24932 @node File-I/O Overview
24933 @subsection File-I/O Overview
24934 @cindex file-i/o overview
24936 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
24937 target to use the host's file system and console I/O to perform various
24938 system calls. System calls on the target system are translated into a
24939 remote protocol packet to the host system, which then performs the needed
24940 actions and returns a response packet to the target system.
24941 This simulates file system operations even on targets that lack file systems.
24943 The protocol is defined to be independent of both the host and target systems.
24944 It uses its own internal representation of datatypes and values. Both
24945 @value{GDBN} and the target's @value{GDBN} stub are responsible for
24946 translating the system-dependent value representations into the internal
24947 protocol representations when data is transmitted.
24949 The communication is synchronous. A system call is possible only when
24950 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
24951 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
24952 the target is stopped to allow deterministic access to the target's
24953 memory. Therefore File-I/O is not interruptible by target signals. On
24954 the other hand, it is possible to interrupt File-I/O by a user interrupt
24955 (@samp{Ctrl-C}) within @value{GDBN}.
24957 The target's request to perform a host system call does not finish
24958 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
24959 after finishing the system call, the target returns to continuing the
24960 previous activity (continue, step). No additional continue or step
24961 request from @value{GDBN} is required.
24964 (@value{GDBP}) continue
24965 <- target requests 'system call X'
24966 target is stopped, @value{GDBN} executes system call
24967 -> @value{GDBN} returns result
24968 ... target continues, @value{GDBN} returns to wait for the target
24969 <- target hits breakpoint and sends a Txx packet
24972 The protocol only supports I/O on the console and to regular files on
24973 the host file system. Character or block special devices, pipes,
24974 named pipes, sockets or any other communication method on the host
24975 system are not supported by this protocol.
24977 @node Protocol Basics
24978 @subsection Protocol Basics
24979 @cindex protocol basics, file-i/o
24981 The File-I/O protocol uses the @code{F} packet as the request as well
24982 as reply packet. Since a File-I/O system call can only occur when
24983 @value{GDBN} is waiting for a response from the continuing or stepping target,
24984 the File-I/O request is a reply that @value{GDBN} has to expect as a result
24985 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
24986 This @code{F} packet contains all information needed to allow @value{GDBN}
24987 to call the appropriate host system call:
24991 A unique identifier for the requested system call.
24994 All parameters to the system call. Pointers are given as addresses
24995 in the target memory address space. Pointers to strings are given as
24996 pointer/length pair. Numerical values are given as they are.
24997 Numerical control flags are given in a protocol-specific representation.
25001 At this point, @value{GDBN} has to perform the following actions.
25005 If the parameters include pointer values to data needed as input to a
25006 system call, @value{GDBN} requests this data from the target with a
25007 standard @code{m} packet request. This additional communication has to be
25008 expected by the target implementation and is handled as any other @code{m}
25012 @value{GDBN} translates all value from protocol representation to host
25013 representation as needed. Datatypes are coerced into the host types.
25016 @value{GDBN} calls the system call.
25019 It then coerces datatypes back to protocol representation.
25022 If the system call is expected to return data in buffer space specified
25023 by pointer parameters to the call, the data is transmitted to the
25024 target using a @code{M} or @code{X} packet. This packet has to be expected
25025 by the target implementation and is handled as any other @code{M} or @code{X}
25030 Eventually @value{GDBN} replies with another @code{F} packet which contains all
25031 necessary information for the target to continue. This at least contains
25038 @code{errno}, if has been changed by the system call.
25045 After having done the needed type and value coercion, the target continues
25046 the latest continue or step action.
25048 @node The F Request Packet
25049 @subsection The @code{F} Request Packet
25050 @cindex file-i/o request packet
25051 @cindex @code{F} request packet
25053 The @code{F} request packet has the following format:
25056 @item F@var{call-id},@var{parameter@dots{}}
25058 @var{call-id} is the identifier to indicate the host system call to be called.
25059 This is just the name of the function.
25061 @var{parameter@dots{}} are the parameters to the system call.
25062 Parameters are hexadecimal integer values, either the actual values in case
25063 of scalar datatypes, pointers to target buffer space in case of compound
25064 datatypes and unspecified memory areas, or pointer/length pairs in case
25065 of string parameters. These are appended to the @var{call-id} as a
25066 comma-delimited list. All values are transmitted in ASCII
25067 string representation, pointer/length pairs separated by a slash.
25073 @node The F Reply Packet
25074 @subsection The @code{F} Reply Packet
25075 @cindex file-i/o reply packet
25076 @cindex @code{F} reply packet
25078 The @code{F} reply packet has the following format:
25082 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
25084 @var{retcode} is the return code of the system call as hexadecimal value.
25086 @var{errno} is the @code{errno} set by the call, in protocol-specific
25088 This parameter can be omitted if the call was successful.
25090 @var{Ctrl-C flag} is only sent if the user requested a break. In this
25091 case, @var{errno} must be sent as well, even if the call was successful.
25092 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
25099 or, if the call was interrupted before the host call has been performed:
25106 assuming 4 is the protocol-specific representation of @code{EINTR}.
25111 @node The Ctrl-C Message
25112 @subsection The @samp{Ctrl-C} Message
25113 @cindex ctrl-c message, in file-i/o protocol
25115 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
25116 reply packet (@pxref{The F Reply Packet}),
25117 the target should behave as if it had
25118 gotten a break message. The meaning for the target is ``system call
25119 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
25120 (as with a break message) and return to @value{GDBN} with a @code{T02}
25123 It's important for the target to know in which
25124 state the system call was interrupted. There are two possible cases:
25128 The system call hasn't been performed on the host yet.
25131 The system call on the host has been finished.
25135 These two states can be distinguished by the target by the value of the
25136 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
25137 call hasn't been performed. This is equivalent to the @code{EINTR} handling
25138 on POSIX systems. In any other case, the target may presume that the
25139 system call has been finished --- successfully or not --- and should behave
25140 as if the break message arrived right after the system call.
25142 @value{GDBN} must behave reliably. If the system call has not been called
25143 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
25144 @code{errno} in the packet. If the system call on the host has been finished
25145 before the user requests a break, the full action must be finished by
25146 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
25147 The @code{F} packet may only be sent when either nothing has happened
25148 or the full action has been completed.
25151 @subsection Console I/O
25152 @cindex console i/o as part of file-i/o
25154 By default and if not explicitly closed by the target system, the file
25155 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
25156 on the @value{GDBN} console is handled as any other file output operation
25157 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
25158 by @value{GDBN} so that after the target read request from file descriptor
25159 0 all following typing is buffered until either one of the following
25164 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
25166 system call is treated as finished.
25169 The user presses @key{RET}. This is treated as end of input with a trailing
25173 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
25174 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
25178 If the user has typed more characters than fit in the buffer given to
25179 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
25180 either another @code{read(0, @dots{})} is requested by the target, or debugging
25181 is stopped at the user's request.
25184 @node List of Supported Calls
25185 @subsection List of Supported Calls
25186 @cindex list of supported file-i/o calls
25203 @unnumberedsubsubsec open
25204 @cindex open, file-i/o system call
25209 int open(const char *pathname, int flags);
25210 int open(const char *pathname, int flags, mode_t mode);
25214 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
25217 @var{flags} is the bitwise @code{OR} of the following values:
25221 If the file does not exist it will be created. The host
25222 rules apply as far as file ownership and time stamps
25226 When used with @code{O_CREAT}, if the file already exists it is
25227 an error and open() fails.
25230 If the file already exists and the open mode allows
25231 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
25232 truncated to zero length.
25235 The file is opened in append mode.
25238 The file is opened for reading only.
25241 The file is opened for writing only.
25244 The file is opened for reading and writing.
25248 Other bits are silently ignored.
25252 @var{mode} is the bitwise @code{OR} of the following values:
25256 User has read permission.
25259 User has write permission.
25262 Group has read permission.
25265 Group has write permission.
25268 Others have read permission.
25271 Others have write permission.
25275 Other bits are silently ignored.
25278 @item Return value:
25279 @code{open} returns the new file descriptor or -1 if an error
25286 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
25289 @var{pathname} refers to a directory.
25292 The requested access is not allowed.
25295 @var{pathname} was too long.
25298 A directory component in @var{pathname} does not exist.
25301 @var{pathname} refers to a device, pipe, named pipe or socket.
25304 @var{pathname} refers to a file on a read-only filesystem and
25305 write access was requested.
25308 @var{pathname} is an invalid pointer value.
25311 No space on device to create the file.
25314 The process already has the maximum number of files open.
25317 The limit on the total number of files open on the system
25321 The call was interrupted by the user.
25327 @unnumberedsubsubsec close
25328 @cindex close, file-i/o system call
25337 @samp{Fclose,@var{fd}}
25339 @item Return value:
25340 @code{close} returns zero on success, or -1 if an error occurred.
25346 @var{fd} isn't a valid open file descriptor.
25349 The call was interrupted by the user.
25355 @unnumberedsubsubsec read
25356 @cindex read, file-i/o system call
25361 int read(int fd, void *buf, unsigned int count);
25365 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
25367 @item Return value:
25368 On success, the number of bytes read is returned.
25369 Zero indicates end of file. If count is zero, read
25370 returns zero as well. On error, -1 is returned.
25376 @var{fd} is not a valid file descriptor or is not open for
25380 @var{bufptr} is an invalid pointer value.
25383 The call was interrupted by the user.
25389 @unnumberedsubsubsec write
25390 @cindex write, file-i/o system call
25395 int write(int fd, const void *buf, unsigned int count);
25399 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
25401 @item Return value:
25402 On success, the number of bytes written are returned.
25403 Zero indicates nothing was written. On error, -1
25410 @var{fd} is not a valid file descriptor or is not open for
25414 @var{bufptr} is an invalid pointer value.
25417 An attempt was made to write a file that exceeds the
25418 host-specific maximum file size allowed.
25421 No space on device to write the data.
25424 The call was interrupted by the user.
25430 @unnumberedsubsubsec lseek
25431 @cindex lseek, file-i/o system call
25436 long lseek (int fd, long offset, int flag);
25440 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
25442 @var{flag} is one of:
25446 The offset is set to @var{offset} bytes.
25449 The offset is set to its current location plus @var{offset}
25453 The offset is set to the size of the file plus @var{offset}
25457 @item Return value:
25458 On success, the resulting unsigned offset in bytes from
25459 the beginning of the file is returned. Otherwise, a
25460 value of -1 is returned.
25466 @var{fd} is not a valid open file descriptor.
25469 @var{fd} is associated with the @value{GDBN} console.
25472 @var{flag} is not a proper value.
25475 The call was interrupted by the user.
25481 @unnumberedsubsubsec rename
25482 @cindex rename, file-i/o system call
25487 int rename(const char *oldpath, const char *newpath);
25491 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
25493 @item Return value:
25494 On success, zero is returned. On error, -1 is returned.
25500 @var{newpath} is an existing directory, but @var{oldpath} is not a
25504 @var{newpath} is a non-empty directory.
25507 @var{oldpath} or @var{newpath} is a directory that is in use by some
25511 An attempt was made to make a directory a subdirectory
25515 A component used as a directory in @var{oldpath} or new
25516 path is not a directory. Or @var{oldpath} is a directory
25517 and @var{newpath} exists but is not a directory.
25520 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
25523 No access to the file or the path of the file.
25527 @var{oldpath} or @var{newpath} was too long.
25530 A directory component in @var{oldpath} or @var{newpath} does not exist.
25533 The file is on a read-only filesystem.
25536 The device containing the file has no room for the new
25540 The call was interrupted by the user.
25546 @unnumberedsubsubsec unlink
25547 @cindex unlink, file-i/o system call
25552 int unlink(const char *pathname);
25556 @samp{Funlink,@var{pathnameptr}/@var{len}}
25558 @item Return value:
25559 On success, zero is returned. On error, -1 is returned.
25565 No access to the file or the path of the file.
25568 The system does not allow unlinking of directories.
25571 The file @var{pathname} cannot be unlinked because it's
25572 being used by another process.
25575 @var{pathnameptr} is an invalid pointer value.
25578 @var{pathname} was too long.
25581 A directory component in @var{pathname} does not exist.
25584 A component of the path is not a directory.
25587 The file is on a read-only filesystem.
25590 The call was interrupted by the user.
25596 @unnumberedsubsubsec stat/fstat
25597 @cindex fstat, file-i/o system call
25598 @cindex stat, file-i/o system call
25603 int stat(const char *pathname, struct stat *buf);
25604 int fstat(int fd, struct stat *buf);
25608 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
25609 @samp{Ffstat,@var{fd},@var{bufptr}}
25611 @item Return value:
25612 On success, zero is returned. On error, -1 is returned.
25618 @var{fd} is not a valid open file.
25621 A directory component in @var{pathname} does not exist or the
25622 path is an empty string.
25625 A component of the path is not a directory.
25628 @var{pathnameptr} is an invalid pointer value.
25631 No access to the file or the path of the file.
25634 @var{pathname} was too long.
25637 The call was interrupted by the user.
25643 @unnumberedsubsubsec gettimeofday
25644 @cindex gettimeofday, file-i/o system call
25649 int gettimeofday(struct timeval *tv, void *tz);
25653 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
25655 @item Return value:
25656 On success, 0 is returned, -1 otherwise.
25662 @var{tz} is a non-NULL pointer.
25665 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
25671 @unnumberedsubsubsec isatty
25672 @cindex isatty, file-i/o system call
25677 int isatty(int fd);
25681 @samp{Fisatty,@var{fd}}
25683 @item Return value:
25684 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
25690 The call was interrupted by the user.
25695 Note that the @code{isatty} call is treated as a special case: it returns
25696 1 to the target if the file descriptor is attached
25697 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
25698 would require implementing @code{ioctl} and would be more complex than
25703 @unnumberedsubsubsec system
25704 @cindex system, file-i/o system call
25709 int system(const char *command);
25713 @samp{Fsystem,@var{commandptr}/@var{len}}
25715 @item Return value:
25716 If @var{len} is zero, the return value indicates whether a shell is
25717 available. A zero return value indicates a shell is not available.
25718 For non-zero @var{len}, the value returned is -1 on error and the
25719 return status of the command otherwise. Only the exit status of the
25720 command is returned, which is extracted from the host's @code{system}
25721 return value by calling @code{WEXITSTATUS(retval)}. In case
25722 @file{/bin/sh} could not be executed, 127 is returned.
25728 The call was interrupted by the user.
25733 @value{GDBN} takes over the full task of calling the necessary host calls
25734 to perform the @code{system} call. The return value of @code{system} on
25735 the host is simplified before it's returned
25736 to the target. Any termination signal information from the child process
25737 is discarded, and the return value consists
25738 entirely of the exit status of the called command.
25740 Due to security concerns, the @code{system} call is by default refused
25741 by @value{GDBN}. The user has to allow this call explicitly with the
25742 @code{set remote system-call-allowed 1} command.
25745 @item set remote system-call-allowed
25746 @kindex set remote system-call-allowed
25747 Control whether to allow the @code{system} calls in the File I/O
25748 protocol for the remote target. The default is zero (disabled).
25750 @item show remote system-call-allowed
25751 @kindex show remote system-call-allowed
25752 Show whether the @code{system} calls are allowed in the File I/O
25756 @node Protocol-specific Representation of Datatypes
25757 @subsection Protocol-specific Representation of Datatypes
25758 @cindex protocol-specific representation of datatypes, in file-i/o protocol
25761 * Integral Datatypes::
25763 * Memory Transfer::
25768 @node Integral Datatypes
25769 @unnumberedsubsubsec Integral Datatypes
25770 @cindex integral datatypes, in file-i/o protocol
25772 The integral datatypes used in the system calls are @code{int},
25773 @code{unsigned int}, @code{long}, @code{unsigned long},
25774 @code{mode_t}, and @code{time_t}.
25776 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
25777 implemented as 32 bit values in this protocol.
25779 @code{long} and @code{unsigned long} are implemented as 64 bit types.
25781 @xref{Limits}, for corresponding MIN and MAX values (similar to those
25782 in @file{limits.h}) to allow range checking on host and target.
25784 @code{time_t} datatypes are defined as seconds since the Epoch.
25786 All integral datatypes transferred as part of a memory read or write of a
25787 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
25790 @node Pointer Values
25791 @unnumberedsubsubsec Pointer Values
25792 @cindex pointer values, in file-i/o protocol
25794 Pointers to target data are transmitted as they are. An exception
25795 is made for pointers to buffers for which the length isn't
25796 transmitted as part of the function call, namely strings. Strings
25797 are transmitted as a pointer/length pair, both as hex values, e.g.@:
25804 which is a pointer to data of length 18 bytes at position 0x1aaf.
25805 The length is defined as the full string length in bytes, including
25806 the trailing null byte. For example, the string @code{"hello world"}
25807 at address 0x123456 is transmitted as
25813 @node Memory Transfer
25814 @unnumberedsubsubsec Memory Transfer
25815 @cindex memory transfer, in file-i/o protocol
25817 Structured data which is transferred using a memory read or write (for
25818 example, a @code{struct stat}) is expected to be in a protocol-specific format
25819 with all scalar multibyte datatypes being big endian. Translation to
25820 this representation needs to be done both by the target before the @code{F}
25821 packet is sent, and by @value{GDBN} before
25822 it transfers memory to the target. Transferred pointers to structured
25823 data should point to the already-coerced data at any time.
25827 @unnumberedsubsubsec struct stat
25828 @cindex struct stat, in file-i/o protocol
25830 The buffer of type @code{struct stat} used by the target and @value{GDBN}
25831 is defined as follows:
25835 unsigned int st_dev; /* device */
25836 unsigned int st_ino; /* inode */
25837 mode_t st_mode; /* protection */
25838 unsigned int st_nlink; /* number of hard links */
25839 unsigned int st_uid; /* user ID of owner */
25840 unsigned int st_gid; /* group ID of owner */
25841 unsigned int st_rdev; /* device type (if inode device) */
25842 unsigned long st_size; /* total size, in bytes */
25843 unsigned long st_blksize; /* blocksize for filesystem I/O */
25844 unsigned long st_blocks; /* number of blocks allocated */
25845 time_t st_atime; /* time of last access */
25846 time_t st_mtime; /* time of last modification */
25847 time_t st_ctime; /* time of last change */
25851 The integral datatypes conform to the definitions given in the
25852 appropriate section (see @ref{Integral Datatypes}, for details) so this
25853 structure is of size 64 bytes.
25855 The values of several fields have a restricted meaning and/or
25861 A value of 0 represents a file, 1 the console.
25864 No valid meaning for the target. Transmitted unchanged.
25867 Valid mode bits are described in @ref{Constants}. Any other
25868 bits have currently no meaning for the target.
25873 No valid meaning for the target. Transmitted unchanged.
25878 These values have a host and file system dependent
25879 accuracy. Especially on Windows hosts, the file system may not
25880 support exact timing values.
25883 The target gets a @code{struct stat} of the above representation and is
25884 responsible for coercing it to the target representation before
25887 Note that due to size differences between the host, target, and protocol
25888 representations of @code{struct stat} members, these members could eventually
25889 get truncated on the target.
25891 @node struct timeval
25892 @unnumberedsubsubsec struct timeval
25893 @cindex struct timeval, in file-i/o protocol
25895 The buffer of type @code{struct timeval} used by the File-I/O protocol
25896 is defined as follows:
25900 time_t tv_sec; /* second */
25901 long tv_usec; /* microsecond */
25905 The integral datatypes conform to the definitions given in the
25906 appropriate section (see @ref{Integral Datatypes}, for details) so this
25907 structure is of size 8 bytes.
25910 @subsection Constants
25911 @cindex constants, in file-i/o protocol
25913 The following values are used for the constants inside of the
25914 protocol. @value{GDBN} and target are responsible for translating these
25915 values before and after the call as needed.
25926 @unnumberedsubsubsec Open Flags
25927 @cindex open flags, in file-i/o protocol
25929 All values are given in hexadecimal representation.
25941 @node mode_t Values
25942 @unnumberedsubsubsec mode_t Values
25943 @cindex mode_t values, in file-i/o protocol
25945 All values are given in octal representation.
25962 @unnumberedsubsubsec Errno Values
25963 @cindex errno values, in file-i/o protocol
25965 All values are given in decimal representation.
25990 @code{EUNKNOWN} is used as a fallback error value if a host system returns
25991 any error value not in the list of supported error numbers.
25994 @unnumberedsubsubsec Lseek Flags
25995 @cindex lseek flags, in file-i/o protocol
26004 @unnumberedsubsubsec Limits
26005 @cindex limits, in file-i/o protocol
26007 All values are given in decimal representation.
26010 INT_MIN -2147483648
26012 UINT_MAX 4294967295
26013 LONG_MIN -9223372036854775808
26014 LONG_MAX 9223372036854775807
26015 ULONG_MAX 18446744073709551615
26018 @node File-I/O Examples
26019 @subsection File-I/O Examples
26020 @cindex file-i/o examples
26022 Example sequence of a write call, file descriptor 3, buffer is at target
26023 address 0x1234, 6 bytes should be written:
26026 <- @code{Fwrite,3,1234,6}
26027 @emph{request memory read from target}
26030 @emph{return "6 bytes written"}
26034 Example sequence of a read call, file descriptor 3, buffer is at target
26035 address 0x1234, 6 bytes should be read:
26038 <- @code{Fread,3,1234,6}
26039 @emph{request memory write to target}
26040 -> @code{X1234,6:XXXXXX}
26041 @emph{return "6 bytes read"}
26045 Example sequence of a read call, call fails on the host due to invalid
26046 file descriptor (@code{EBADF}):
26049 <- @code{Fread,3,1234,6}
26053 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
26057 <- @code{Fread,3,1234,6}
26062 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
26066 <- @code{Fread,3,1234,6}
26067 -> @code{X1234,6:XXXXXX}
26071 @node Library List Format
26072 @section Library List Format
26073 @cindex library list format, remote protocol
26075 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
26076 same process as your application to manage libraries. In this case,
26077 @value{GDBN} can use the loader's symbol table and normal memory
26078 operations to maintain a list of shared libraries. On other
26079 platforms, the operating system manages loaded libraries.
26080 @value{GDBN} can not retrieve the list of currently loaded libraries
26081 through memory operations, so it uses the @samp{qXfer:libraries:read}
26082 packet (@pxref{qXfer library list read}) instead. The remote stub
26083 queries the target's operating system and reports which libraries
26086 The @samp{qXfer:libraries:read} packet returns an XML document which
26087 lists loaded libraries and their offsets. Each library has an
26088 associated name and one or more segment base addresses, which report
26089 where the library was loaded in memory. The segment bases are start
26090 addresses, not relocation offsets; they do not depend on the library's
26091 link-time base addresses.
26093 @value{GDBN} must be linked with the Expat library to support XML
26094 library lists. @xref{Expat}.
26096 A simple memory map, with one loaded library relocated by a single
26097 offset, looks like this:
26101 <library name="/lib/libc.so.6">
26102 <segment address="0x10000000"/>
26107 The format of a library list is described by this DTD:
26110 <!-- library-list: Root element with versioning -->
26111 <!ELEMENT library-list (library)*>
26112 <!ATTLIST library-list version CDATA #FIXED "1.0">
26113 <!ELEMENT library (segment)*>
26114 <!ATTLIST library name CDATA #REQUIRED>
26115 <!ELEMENT segment EMPTY>
26116 <!ATTLIST segment address CDATA #REQUIRED>
26119 @node Memory Map Format
26120 @section Memory Map Format
26121 @cindex memory map format
26123 To be able to write into flash memory, @value{GDBN} needs to obtain a
26124 memory map from the target. This section describes the format of the
26127 The memory map is obtained using the @samp{qXfer:memory-map:read}
26128 (@pxref{qXfer memory map read}) packet and is an XML document that
26129 lists memory regions.
26131 @value{GDBN} must be linked with the Expat library to support XML
26132 memory maps. @xref{Expat}.
26134 The top-level structure of the document is shown below:
26137 <?xml version="1.0"?>
26138 <!DOCTYPE memory-map
26139 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
26140 "http://sourceware.org/gdb/gdb-memory-map.dtd">
26146 Each region can be either:
26151 A region of RAM starting at @var{addr} and extending for @var{length}
26155 <memory type="ram" start="@var{addr}" length="@var{length}"/>
26160 A region of read-only memory:
26163 <memory type="rom" start="@var{addr}" length="@var{length}"/>
26168 A region of flash memory, with erasure blocks @var{blocksize}
26172 <memory type="flash" start="@var{addr}" length="@var{length}">
26173 <property name="blocksize">@var{blocksize}</property>
26179 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
26180 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
26181 packets to write to addresses in such ranges.
26183 The formal DTD for memory map format is given below:
26186 <!-- ................................................... -->
26187 <!-- Memory Map XML DTD ................................ -->
26188 <!-- File: memory-map.dtd .............................. -->
26189 <!-- .................................... .............. -->
26190 <!-- memory-map.dtd -->
26191 <!-- memory-map: Root element with versioning -->
26192 <!ELEMENT memory-map (memory | property)>
26193 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
26194 <!ELEMENT memory (property)>
26195 <!-- memory: Specifies a memory region,
26196 and its type, or device. -->
26197 <!ATTLIST memory type CDATA #REQUIRED
26198 start CDATA #REQUIRED
26199 length CDATA #REQUIRED
26200 device CDATA #IMPLIED>
26201 <!-- property: Generic attribute tag -->
26202 <!ELEMENT property (#PCDATA | property)*>
26203 <!ATTLIST property name CDATA #REQUIRED>
26206 @include agentexpr.texi
26208 @node Target Descriptions
26209 @appendix Target Descriptions
26210 @cindex target descriptions
26212 @strong{Warning:} target descriptions are still under active development,
26213 and the contents and format may change between @value{GDBN} releases.
26214 The format is expected to stabilize in the future.
26216 One of the challenges of using @value{GDBN} to debug embedded systems
26217 is that there are so many minor variants of each processor
26218 architecture in use. It is common practice for vendors to start with
26219 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
26220 and then make changes to adapt it to a particular market niche. Some
26221 architectures have hundreds of variants, available from dozens of
26222 vendors. This leads to a number of problems:
26226 With so many different customized processors, it is difficult for
26227 the @value{GDBN} maintainers to keep up with the changes.
26229 Since individual variants may have short lifetimes or limited
26230 audiences, it may not be worthwhile to carry information about every
26231 variant in the @value{GDBN} source tree.
26233 When @value{GDBN} does support the architecture of the embedded system
26234 at hand, the task of finding the correct architecture name to give the
26235 @command{set architecture} command can be error-prone.
26238 To address these problems, the @value{GDBN} remote protocol allows a
26239 target system to not only identify itself to @value{GDBN}, but to
26240 actually describe its own features. This lets @value{GDBN} support
26241 processor variants it has never seen before --- to the extent that the
26242 descriptions are accurate, and that @value{GDBN} understands them.
26244 @value{GDBN} must be linked with the Expat library to support XML
26245 target descriptions. @xref{Expat}.
26248 * Retrieving Descriptions:: How descriptions are fetched from a target.
26249 * Target Description Format:: The contents of a target description.
26250 * Predefined Target Types:: Standard types available for target
26252 * Standard Target Features:: Features @value{GDBN} knows about.
26255 @node Retrieving Descriptions
26256 @section Retrieving Descriptions
26258 Target descriptions can be read from the target automatically, or
26259 specified by the user manually. The default behavior is to read the
26260 description from the target. @value{GDBN} retrieves it via the remote
26261 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
26262 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
26263 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
26264 XML document, of the form described in @ref{Target Description
26267 Alternatively, you can specify a file to read for the target description.
26268 If a file is set, the target will not be queried. The commands to
26269 specify a file are:
26272 @cindex set tdesc filename
26273 @item set tdesc filename @var{path}
26274 Read the target description from @var{path}.
26276 @cindex unset tdesc filename
26277 @item unset tdesc filename
26278 Do not read the XML target description from a file. @value{GDBN}
26279 will use the description supplied by the current target.
26281 @cindex show tdesc filename
26282 @item show tdesc filename
26283 Show the filename to read for a target description, if any.
26287 @node Target Description Format
26288 @section Target Description Format
26289 @cindex target descriptions, XML format
26291 A target description annex is an @uref{http://www.w3.org/XML/, XML}
26292 document which complies with the Document Type Definition provided in
26293 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
26294 means you can use generally available tools like @command{xmllint} to
26295 check that your feature descriptions are well-formed and valid.
26296 However, to help people unfamiliar with XML write descriptions for
26297 their targets, we also describe the grammar here.
26299 Target descriptions can identify the architecture of the remote target
26300 and (for some architectures) provide information about custom register
26301 sets. @value{GDBN} can use this information to autoconfigure for your
26302 target, or to warn you if you connect to an unsupported target.
26304 Here is a simple target description:
26307 <target version="1.0">
26308 <architecture>i386:x86-64</architecture>
26313 This minimal description only says that the target uses
26314 the x86-64 architecture.
26316 A target description has the following overall form, with [ ] marking
26317 optional elements and @dots{} marking repeatable elements. The elements
26318 are explained further below.
26321 <?xml version="1.0"?>
26322 <!DOCTYPE target SYSTEM "gdb-target.dtd">
26323 <target version="1.0">
26324 @r{[}@var{architecture}@r{]}
26325 @r{[}@var{feature}@dots{}@r{]}
26330 The description is generally insensitive to whitespace and line
26331 breaks, under the usual common-sense rules. The XML version
26332 declaration and document type declaration can generally be omitted
26333 (@value{GDBN} does not require them), but specifying them may be
26334 useful for XML validation tools. The @samp{version} attribute for
26335 @samp{<target>} may also be omitted, but we recommend
26336 including it; if future versions of @value{GDBN} use an incompatible
26337 revision of @file{gdb-target.dtd}, they will detect and report
26338 the version mismatch.
26340 @subsection Inclusion
26341 @cindex target descriptions, inclusion
26344 @cindex <xi:include>
26347 It can sometimes be valuable to split a target description up into
26348 several different annexes, either for organizational purposes, or to
26349 share files between different possible target descriptions. You can
26350 divide a description into multiple files by replacing any element of
26351 the target description with an inclusion directive of the form:
26354 <xi:include href="@var{document}"/>
26358 When @value{GDBN} encounters an element of this form, it will retrieve
26359 the named XML @var{document}, and replace the inclusion directive with
26360 the contents of that document. If the current description was read
26361 using @samp{qXfer}, then so will be the included document;
26362 @var{document} will be interpreted as the name of an annex. If the
26363 current description was read from a file, @value{GDBN} will look for
26364 @var{document} as a file in the same directory where it found the
26365 original description.
26367 @subsection Architecture
26368 @cindex <architecture>
26370 An @samp{<architecture>} element has this form:
26373 <architecture>@var{arch}</architecture>
26376 @var{arch} is an architecture name from the same selection
26377 accepted by @code{set architecture} (@pxref{Targets, ,Specifying a
26378 Debugging Target}).
26380 @subsection Features
26383 Each @samp{<feature>} describes some logical portion of the target
26384 system. Features are currently used to describe available CPU
26385 registers and the types of their contents. A @samp{<feature>} element
26389 <feature name="@var{name}">
26390 @r{[}@var{type}@dots{}@r{]}
26396 Each feature's name should be unique within the description. The name
26397 of a feature does not matter unless @value{GDBN} has some special
26398 knowledge of the contents of that feature; if it does, the feature
26399 should have its standard name. @xref{Standard Target Features}.
26403 Any register's value is a collection of bits which @value{GDBN} must
26404 interpret. The default interpretation is a two's complement integer,
26405 but other types can be requested by name in the register description.
26406 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
26407 Target Types}), and the description can define additional composite types.
26409 Each type element must have an @samp{id} attribute, which gives
26410 a unique (within the containing @samp{<feature>}) name to the type.
26411 Types must be defined before they are used.
26414 Some targets offer vector registers, which can be treated as arrays
26415 of scalar elements. These types are written as @samp{<vector>} elements,
26416 specifying the array element type, @var{type}, and the number of elements,
26420 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
26424 If a register's value is usefully viewed in multiple ways, define it
26425 with a union type containing the useful representations. The
26426 @samp{<union>} element contains one or more @samp{<field>} elements,
26427 each of which has a @var{name} and a @var{type}:
26430 <union id="@var{id}">
26431 <field name="@var{name}" type="@var{type}"/>
26436 @subsection Registers
26439 Each register is represented as an element with this form:
26442 <reg name="@var{name}"
26443 bitsize="@var{size}"
26444 @r{[}regnum="@var{num}"@r{]}
26445 @r{[}save-restore="@var{save-restore}"@r{]}
26446 @r{[}type="@var{type}"@r{]}
26447 @r{[}group="@var{group}"@r{]}/>
26451 The components are as follows:
26456 The register's name; it must be unique within the target description.
26459 The register's size, in bits.
26462 The register's number. If omitted, a register's number is one greater
26463 than that of the previous register (either in the current feature or in
26464 a preceeding feature); the first register in the target description
26465 defaults to zero. This register number is used to read or write
26466 the register; e.g.@: it is used in the remote @code{p} and @code{P}
26467 packets, and registers appear in the @code{g} and @code{G} packets
26468 in order of increasing register number.
26471 Whether the register should be preserved across inferior function
26472 calls; this must be either @code{yes} or @code{no}. The default is
26473 @code{yes}, which is appropriate for most registers except for
26474 some system control registers; this is not related to the target's
26478 The type of the register. @var{type} may be a predefined type, a type
26479 defined in the current feature, or one of the special types @code{int}
26480 and @code{float}. @code{int} is an integer type of the correct size
26481 for @var{bitsize}, and @code{float} is a floating point type (in the
26482 architecture's normal floating point format) of the correct size for
26483 @var{bitsize}. The default is @code{int}.
26486 The register group to which this register belongs. @var{group} must
26487 be either @code{general}, @code{float}, or @code{vector}. If no
26488 @var{group} is specified, @value{GDBN} will not display the register
26489 in @code{info registers}.
26493 @node Predefined Target Types
26494 @section Predefined Target Types
26495 @cindex target descriptions, predefined types
26497 Type definitions in the self-description can build up composite types
26498 from basic building blocks, but can not define fundamental types. Instead,
26499 standard identifiers are provided by @value{GDBN} for the fundamental
26500 types. The currently supported types are:
26509 Signed integer types holding the specified number of bits.
26516 Unsigned integer types holding the specified number of bits.
26520 Pointers to unspecified code and data. The program counter and
26521 any dedicated return address register may be marked as code
26522 pointers; printing a code pointer converts it into a symbolic
26523 address. The stack pointer and any dedicated address registers
26524 may be marked as data pointers.
26527 Single precision IEEE floating point.
26530 Double precision IEEE floating point.
26533 The 12-byte extended precision format used by ARM FPA registers.
26537 @node Standard Target Features
26538 @section Standard Target Features
26539 @cindex target descriptions, standard features
26541 A target description must contain either no registers or all the
26542 target's registers. If the description contains no registers, then
26543 @value{GDBN} will assume a default register layout, selected based on
26544 the architecture. If the description contains any registers, the
26545 default layout will not be used; the standard registers must be
26546 described in the target description, in such a way that @value{GDBN}
26547 can recognize them.
26549 This is accomplished by giving specific names to feature elements
26550 which contain standard registers. @value{GDBN} will look for features
26551 with those names and verify that they contain the expected registers;
26552 if any known feature is missing required registers, or if any required
26553 feature is missing, @value{GDBN} will reject the target
26554 description. You can add additional registers to any of the
26555 standard features --- @value{GDBN} will display them just as if
26556 they were added to an unrecognized feature.
26558 This section lists the known features and their expected contents.
26559 Sample XML documents for these features are included in the
26560 @value{GDBN} source tree, in the directory @file{gdb/features}.
26562 Names recognized by @value{GDBN} should include the name of the
26563 company or organization which selected the name, and the overall
26564 architecture to which the feature applies; so e.g.@: the feature
26565 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
26567 The names of registers are not case sensitive for the purpose
26568 of recognizing standard features, but @value{GDBN} will only display
26569 registers using the capitalization used in the description.
26578 @subsection ARM Features
26579 @cindex target descriptions, ARM features
26581 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
26582 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
26583 @samp{lr}, @samp{pc}, and @samp{cpsr}.
26585 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
26586 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
26588 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
26589 it should contain at least registers @samp{wR0} through @samp{wR15} and
26590 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
26591 @samp{wCSSF}, and @samp{wCASF} registers are optional.
26593 @subsection MIPS Features
26594 @cindex target descriptions, MIPS features
26596 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
26597 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
26598 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
26601 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
26602 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
26603 registers. They may be 32-bit or 64-bit depending on the target.
26605 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
26606 it may be optional in a future version of @value{GDBN}. It should
26607 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
26608 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
26610 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
26611 contain a single register, @samp{restart}, which is used by the
26612 Linux kernel to control restartable syscalls.
26614 @node M68K Features
26615 @subsection M68K Features
26616 @cindex target descriptions, M68K features
26619 @item @samp{org.gnu.gdb.m68k.core}
26620 @itemx @samp{org.gnu.gdb.coldfire.core}
26621 @itemx @samp{org.gnu.gdb.fido.core}
26622 One of those features must be always present.
26623 The feature that is present determines which flavor of m86k is
26624 used. The feature that is present should contain registers
26625 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
26626 @samp{sp}, @samp{ps} and @samp{pc}.
26628 @item @samp{org.gnu.gdb.coldfire.fp}
26629 This feature is optional. If present, it should contain registers
26630 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
26634 @subsection PowerPC Features
26635 @cindex target descriptions, PowerPC features
26637 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
26638 targets. It should contain registers @samp{r0} through @samp{r31},
26639 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
26640 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
26642 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
26643 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
26645 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
26646 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
26649 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
26650 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
26651 @samp{spefscr}. SPE targets should provide 32-bit registers in
26652 @samp{org.gnu.gdb.power.core} and provide the upper halves in
26653 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
26654 these to present registers @samp{ev0} through @samp{ev31} to the
26669 % I think something like @colophon should be in texinfo. In the
26671 \long\def\colophon{\hbox to0pt{}\vfill
26672 \centerline{The body of this manual is set in}
26673 \centerline{\fontname\tenrm,}
26674 \centerline{with headings in {\bf\fontname\tenbf}}
26675 \centerline{and examples in {\tt\fontname\tentt}.}
26676 \centerline{{\it\fontname\tenit\/},}
26677 \centerline{{\bf\fontname\tenbf}, and}
26678 \centerline{{\sl\fontname\tensl\/}}
26679 \centerline{are used for emphasis.}\vfill}
26681 % Blame: doc@cygnus.com, 1991.