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 show the arguments passed to a function
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 some environments without processes,
1822 @code{run} jumps to the start of your program. Other targets,
1823 like @samp{remote}, are always running. If you get an error
1824 message like this one:
1827 The "remote" target does not support "run".
1828 Try "help target" or "continue".
1832 then use @code{continue} to run your program. You may need @code{load}
1833 first (@pxref{load}).
1835 The execution of a program is affected by certain information it
1836 receives from its superior. @value{GDBN} provides ways to specify this
1837 information, which you must do @emph{before} starting your program. (You
1838 can change it after starting your program, but such changes only affect
1839 your program the next time you start it.) This information may be
1840 divided into four categories:
1843 @item The @emph{arguments.}
1844 Specify the arguments to give your program as the arguments of the
1845 @code{run} command. If a shell is available on your target, the shell
1846 is used to pass the arguments, so that you may use normal conventions
1847 (such as wildcard expansion or variable substitution) in describing
1849 In Unix systems, you can control which shell is used with the
1850 @code{SHELL} environment variable.
1851 @xref{Arguments, ,Your Program's Arguments}.
1853 @item The @emph{environment.}
1854 Your program normally inherits its environment from @value{GDBN}, but you can
1855 use the @value{GDBN} commands @code{set environment} and @code{unset
1856 environment} to change parts of the environment that affect
1857 your program. @xref{Environment, ,Your Program's Environment}.
1859 @item The @emph{working directory.}
1860 Your program inherits its working directory from @value{GDBN}. You can set
1861 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1862 @xref{Working Directory, ,Your Program's Working Directory}.
1864 @item The @emph{standard input and output.}
1865 Your program normally uses the same device for standard input and
1866 standard output as @value{GDBN} is using. You can redirect input and output
1867 in the @code{run} command line, or you can use the @code{tty} command to
1868 set a different device for your program.
1869 @xref{Input/Output, ,Your Program's Input and Output}.
1872 @emph{Warning:} While input and output redirection work, you cannot use
1873 pipes to pass the output of the program you are debugging to another
1874 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1878 When you issue the @code{run} command, your program begins to execute
1879 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1880 of how to arrange for your program to stop. Once your program has
1881 stopped, you may call functions in your program, using the @code{print}
1882 or @code{call} commands. @xref{Data, ,Examining Data}.
1884 If the modification time of your symbol file has changed since the last
1885 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1886 table, and reads it again. When it does this, @value{GDBN} tries to retain
1887 your current breakpoints.
1892 @cindex run to main procedure
1893 The name of the main procedure can vary from language to language.
1894 With C or C@t{++}, the main procedure name is always @code{main}, but
1895 other languages such as Ada do not require a specific name for their
1896 main procedure. The debugger provides a convenient way to start the
1897 execution of the program and to stop at the beginning of the main
1898 procedure, depending on the language used.
1900 The @samp{start} command does the equivalent of setting a temporary
1901 breakpoint at the beginning of the main procedure and then invoking
1902 the @samp{run} command.
1904 @cindex elaboration phase
1905 Some programs contain an @dfn{elaboration} phase where some startup code is
1906 executed before the main procedure is called. This depends on the
1907 languages used to write your program. In C@t{++}, for instance,
1908 constructors for static and global objects are executed before
1909 @code{main} is called. It is therefore possible that the debugger stops
1910 before reaching the main procedure. However, the temporary breakpoint
1911 will remain to halt execution.
1913 Specify the arguments to give to your program as arguments to the
1914 @samp{start} command. These arguments will be given verbatim to the
1915 underlying @samp{run} command. Note that the same arguments will be
1916 reused if no argument is provided during subsequent calls to
1917 @samp{start} or @samp{run}.
1919 It is sometimes necessary to debug the program during elaboration. In
1920 these cases, using the @code{start} command would stop the execution of
1921 your program too late, as the program would have already completed the
1922 elaboration phase. Under these circumstances, insert breakpoints in your
1923 elaboration code before running your program.
1925 @kindex set exec-wrapper
1926 @item set exec-wrapper @var{wrapper}
1927 @itemx show exec-wrapper
1928 @itemx unset exec-wrapper
1929 When @samp{exec-wrapper} is set, the specified wrapper is used to
1930 launch programs for debugging. @value{GDBN} starts your program
1931 with a shell command of the form @kbd{exec @var{wrapper}
1932 @var{program}}. Quoting is added to @var{program} and its
1933 arguments, but not to @var{wrapper}, so you should add quotes if
1934 appropriate for your shell. The wrapper runs until it executes
1935 your program, and then @value{GDBN} takes control.
1937 You can use any program that eventually calls @code{execve} with
1938 its arguments as a wrapper. Several standard Unix utilities do
1939 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
1940 with @code{exec "$@@"} will also work.
1942 For example, you can use @code{env} to pass an environment variable to
1943 the debugged program, without setting the variable in your shell's
1947 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
1951 This command is available when debugging locally on most targets, excluding
1952 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
1957 @section Your Program's Arguments
1959 @cindex arguments (to your program)
1960 The arguments to your program can be specified by the arguments of the
1962 They are passed to a shell, which expands wildcard characters and
1963 performs redirection of I/O, and thence to your program. Your
1964 @code{SHELL} environment variable (if it exists) specifies what shell
1965 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1966 the default shell (@file{/bin/sh} on Unix).
1968 On non-Unix systems, the program is usually invoked directly by
1969 @value{GDBN}, which emulates I/O redirection via the appropriate system
1970 calls, and the wildcard characters are expanded by the startup code of
1971 the program, not by the shell.
1973 @code{run} with no arguments uses the same arguments used by the previous
1974 @code{run}, or those set by the @code{set args} command.
1979 Specify the arguments to be used the next time your program is run. If
1980 @code{set args} has no arguments, @code{run} executes your program
1981 with no arguments. Once you have run your program with arguments,
1982 using @code{set args} before the next @code{run} is the only way to run
1983 it again without arguments.
1987 Show the arguments to give your program when it is started.
1991 @section Your Program's Environment
1993 @cindex environment (of your program)
1994 The @dfn{environment} consists of a set of environment variables and
1995 their values. Environment variables conventionally record such things as
1996 your user name, your home directory, your terminal type, and your search
1997 path for programs to run. Usually you set up environment variables with
1998 the shell and they are inherited by all the other programs you run. When
1999 debugging, it can be useful to try running your program with a modified
2000 environment without having to start @value{GDBN} over again.
2004 @item path @var{directory}
2005 Add @var{directory} to the front of the @code{PATH} environment variable
2006 (the search path for executables) that will be passed to your program.
2007 The value of @code{PATH} used by @value{GDBN} does not change.
2008 You may specify several directory names, separated by whitespace or by a
2009 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2010 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2011 is moved to the front, so it is searched sooner.
2013 You can use the string @samp{$cwd} to refer to whatever is the current
2014 working directory at the time @value{GDBN} searches the path. If you
2015 use @samp{.} instead, it refers to the directory where you executed the
2016 @code{path} command. @value{GDBN} replaces @samp{.} in the
2017 @var{directory} argument (with the current path) before adding
2018 @var{directory} to the search path.
2019 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2020 @c document that, since repeating it would be a no-op.
2024 Display the list of search paths for executables (the @code{PATH}
2025 environment variable).
2027 @kindex show environment
2028 @item show environment @r{[}@var{varname}@r{]}
2029 Print the value of environment variable @var{varname} to be given to
2030 your program when it starts. If you do not supply @var{varname},
2031 print the names and values of all environment variables to be given to
2032 your program. You can abbreviate @code{environment} as @code{env}.
2034 @kindex set environment
2035 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2036 Set environment variable @var{varname} to @var{value}. The value
2037 changes for your program only, not for @value{GDBN} itself. @var{value} may
2038 be any string; the values of environment variables are just strings, and
2039 any interpretation is supplied by your program itself. The @var{value}
2040 parameter is optional; if it is eliminated, the variable is set to a
2042 @c "any string" here does not include leading, trailing
2043 @c blanks. Gnu asks: does anyone care?
2045 For example, this command:
2052 tells the debugged program, when subsequently run, that its user is named
2053 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2054 are not actually required.)
2056 @kindex unset environment
2057 @item unset environment @var{varname}
2058 Remove variable @var{varname} from the environment to be passed to your
2059 program. This is different from @samp{set env @var{varname} =};
2060 @code{unset environment} removes the variable from the environment,
2061 rather than assigning it an empty value.
2064 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2066 by your @code{SHELL} environment variable if it exists (or
2067 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2068 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2069 @file{.bashrc} for BASH---any variables you set in that file affect
2070 your program. You may wish to move setting of environment variables to
2071 files that are only run when you sign on, such as @file{.login} or
2074 @node Working Directory
2075 @section Your Program's Working Directory
2077 @cindex working directory (of your program)
2078 Each time you start your program with @code{run}, it inherits its
2079 working directory from the current working directory of @value{GDBN}.
2080 The @value{GDBN} working directory is initially whatever it inherited
2081 from its parent process (typically the shell), but you can specify a new
2082 working directory in @value{GDBN} with the @code{cd} command.
2084 The @value{GDBN} working directory also serves as a default for the commands
2085 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2090 @cindex change working directory
2091 @item cd @var{directory}
2092 Set the @value{GDBN} working directory to @var{directory}.
2096 Print the @value{GDBN} working directory.
2099 It is generally impossible to find the current working directory of
2100 the process being debugged (since a program can change its directory
2101 during its run). If you work on a system where @value{GDBN} is
2102 configured with the @file{/proc} support, you can use the @code{info
2103 proc} command (@pxref{SVR4 Process Information}) to find out the
2104 current working directory of the debuggee.
2107 @section Your Program's Input and Output
2112 By default, the program you run under @value{GDBN} does input and output to
2113 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2114 to its own terminal modes to interact with you, but it records the terminal
2115 modes your program was using and switches back to them when you continue
2116 running your program.
2119 @kindex info terminal
2121 Displays information recorded by @value{GDBN} about the terminal modes your
2125 You can redirect your program's input and/or output using shell
2126 redirection with the @code{run} command. For example,
2133 starts your program, diverting its output to the file @file{outfile}.
2136 @cindex controlling terminal
2137 Another way to specify where your program should do input and output is
2138 with the @code{tty} command. This command accepts a file name as
2139 argument, and causes this file to be the default for future @code{run}
2140 commands. It also resets the controlling terminal for the child
2141 process, for future @code{run} commands. For example,
2148 directs that processes started with subsequent @code{run} commands
2149 default to do input and output on the terminal @file{/dev/ttyb} and have
2150 that as their controlling terminal.
2152 An explicit redirection in @code{run} overrides the @code{tty} command's
2153 effect on the input/output device, but not its effect on the controlling
2156 When you use the @code{tty} command or redirect input in the @code{run}
2157 command, only the input @emph{for your program} is affected. The input
2158 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2159 for @code{set inferior-tty}.
2161 @cindex inferior tty
2162 @cindex set inferior controlling terminal
2163 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2164 display the name of the terminal that will be used for future runs of your
2168 @item set inferior-tty /dev/ttyb
2169 @kindex set inferior-tty
2170 Set the tty for the program being debugged to /dev/ttyb.
2172 @item show inferior-tty
2173 @kindex show inferior-tty
2174 Show the current tty for the program being debugged.
2178 @section Debugging an Already-running Process
2183 @item attach @var{process-id}
2184 This command attaches to a running process---one that was started
2185 outside @value{GDBN}. (@code{info files} shows your active
2186 targets.) The command takes as argument a process ID. The usual way to
2187 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2188 or with the @samp{jobs -l} shell command.
2190 @code{attach} does not repeat if you press @key{RET} a second time after
2191 executing the command.
2194 To use @code{attach}, your program must be running in an environment
2195 which supports processes; for example, @code{attach} does not work for
2196 programs on bare-board targets that lack an operating system. You must
2197 also have permission to send the process a signal.
2199 When you use @code{attach}, the debugger finds the program running in
2200 the process first by looking in the current working directory, then (if
2201 the program is not found) by using the source file search path
2202 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2203 the @code{file} command to load the program. @xref{Files, ,Commands to
2206 The first thing @value{GDBN} does after arranging to debug the specified
2207 process is to stop it. You can examine and modify an attached process
2208 with all the @value{GDBN} commands that are ordinarily available when
2209 you start processes with @code{run}. You can insert breakpoints; you
2210 can step and continue; you can modify storage. If you would rather the
2211 process continue running, you may use the @code{continue} command after
2212 attaching @value{GDBN} to the process.
2217 When you have finished debugging the attached process, you can use the
2218 @code{detach} command to release it from @value{GDBN} control. Detaching
2219 the process continues its execution. After the @code{detach} command,
2220 that process and @value{GDBN} become completely independent once more, and you
2221 are ready to @code{attach} another process or start one with @code{run}.
2222 @code{detach} does not repeat if you press @key{RET} again after
2223 executing the command.
2226 If you exit @value{GDBN} while you have an attached process, you detach
2227 that process. If you use the @code{run} command, you kill that process.
2228 By default, @value{GDBN} asks for confirmation if you try to do either of these
2229 things; you can control whether or not you need to confirm by using the
2230 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2234 @section Killing the Child Process
2239 Kill the child process in which your program is running under @value{GDBN}.
2242 This command is useful if you wish to debug a core dump instead of a
2243 running process. @value{GDBN} ignores any core dump file while your program
2246 On some operating systems, a program cannot be executed outside @value{GDBN}
2247 while you have breakpoints set on it inside @value{GDBN}. You can use the
2248 @code{kill} command in this situation to permit running your program
2249 outside the debugger.
2251 The @code{kill} command is also useful if you wish to recompile and
2252 relink your program, since on many systems it is impossible to modify an
2253 executable file while it is running in a process. In this case, when you
2254 next type @code{run}, @value{GDBN} notices that the file has changed, and
2255 reads the symbol table again (while trying to preserve your current
2256 breakpoint settings).
2259 @section Debugging Programs with Multiple Threads
2261 @cindex threads of execution
2262 @cindex multiple threads
2263 @cindex switching threads
2264 In some operating systems, such as HP-UX and Solaris, a single program
2265 may have more than one @dfn{thread} of execution. The precise semantics
2266 of threads differ from one operating system to another, but in general
2267 the threads of a single program are akin to multiple processes---except
2268 that they share one address space (that is, they can all examine and
2269 modify the same variables). On the other hand, each thread has its own
2270 registers and execution stack, and perhaps private memory.
2272 @value{GDBN} provides these facilities for debugging multi-thread
2276 @item automatic notification of new threads
2277 @item @samp{thread @var{threadno}}, a command to switch among threads
2278 @item @samp{info threads}, a command to inquire about existing threads
2279 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2280 a command to apply a command to a list of threads
2281 @item thread-specific breakpoints
2282 @item @samp{set print thread-events}, which controls printing of
2283 messages on thread start and exit.
2287 @emph{Warning:} These facilities are not yet available on every
2288 @value{GDBN} configuration where the operating system supports threads.
2289 If your @value{GDBN} does not support threads, these commands have no
2290 effect. For example, a system without thread support shows no output
2291 from @samp{info threads}, and always rejects the @code{thread} command,
2295 (@value{GDBP}) info threads
2296 (@value{GDBP}) thread 1
2297 Thread ID 1 not known. Use the "info threads" command to
2298 see the IDs of currently known threads.
2300 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2301 @c doesn't support threads"?
2304 @cindex focus of debugging
2305 @cindex current thread
2306 The @value{GDBN} thread debugging facility allows you to observe all
2307 threads while your program runs---but whenever @value{GDBN} takes
2308 control, one thread in particular is always the focus of debugging.
2309 This thread is called the @dfn{current thread}. Debugging commands show
2310 program information from the perspective of the current thread.
2312 @cindex @code{New} @var{systag} message
2313 @cindex thread identifier (system)
2314 @c FIXME-implementors!! It would be more helpful if the [New...] message
2315 @c included GDB's numeric thread handle, so you could just go to that
2316 @c thread without first checking `info threads'.
2317 Whenever @value{GDBN} detects a new thread in your program, it displays
2318 the target system's identification for the thread with a message in the
2319 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2320 whose form varies depending on the particular system. For example, on
2321 @sc{gnu}/Linux, you might see
2324 [New Thread 46912507313328 (LWP 25582)]
2328 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2329 the @var{systag} is simply something like @samp{process 368}, with no
2332 @c FIXME!! (1) Does the [New...] message appear even for the very first
2333 @c thread of a program, or does it only appear for the
2334 @c second---i.e.@: when it becomes obvious we have a multithread
2336 @c (2) *Is* there necessarily a first thread always? Or do some
2337 @c multithread systems permit starting a program with multiple
2338 @c threads ab initio?
2340 @cindex thread number
2341 @cindex thread identifier (GDB)
2342 For debugging purposes, @value{GDBN} associates its own thread
2343 number---always a single integer---with each thread in your program.
2346 @kindex info threads
2348 Display a summary of all threads currently in your
2349 program. @value{GDBN} displays for each thread (in this order):
2353 the thread number assigned by @value{GDBN}
2356 the target system's thread identifier (@var{systag})
2359 the current stack frame summary for that thread
2363 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2364 indicates the current thread.
2368 @c end table here to get a little more width for example
2371 (@value{GDBP}) info threads
2372 3 process 35 thread 27 0x34e5 in sigpause ()
2373 2 process 35 thread 23 0x34e5 in sigpause ()
2374 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2380 @cindex debugging multithreaded programs (on HP-UX)
2381 @cindex thread identifier (GDB), on HP-UX
2382 For debugging purposes, @value{GDBN} associates its own thread
2383 number---a small integer assigned in thread-creation order---with each
2384 thread in your program.
2386 @cindex @code{New} @var{systag} message, on HP-UX
2387 @cindex thread identifier (system), on HP-UX
2388 @c FIXME-implementors!! It would be more helpful if the [New...] message
2389 @c included GDB's numeric thread handle, so you could just go to that
2390 @c thread without first checking `info threads'.
2391 Whenever @value{GDBN} detects a new thread in your program, it displays
2392 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2393 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2394 whose form varies depending on the particular system. For example, on
2398 [New thread 2 (system thread 26594)]
2402 when @value{GDBN} notices a new thread.
2405 @kindex info threads (HP-UX)
2407 Display a summary of all threads currently in your
2408 program. @value{GDBN} displays for each thread (in this order):
2411 @item the thread number assigned by @value{GDBN}
2413 @item the target system's thread identifier (@var{systag})
2415 @item the current stack frame summary for that thread
2419 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2420 indicates the current thread.
2424 @c end table here to get a little more width for example
2427 (@value{GDBP}) info threads
2428 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2430 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2431 from /usr/lib/libc.2
2432 1 system thread 27905 0x7b003498 in _brk () \@*
2433 from /usr/lib/libc.2
2436 On Solaris, you can display more information about user threads with a
2437 Solaris-specific command:
2440 @item maint info sol-threads
2441 @kindex maint info sol-threads
2442 @cindex thread info (Solaris)
2443 Display info on Solaris user threads.
2447 @kindex thread @var{threadno}
2448 @item thread @var{threadno}
2449 Make thread number @var{threadno} the current thread. The command
2450 argument @var{threadno} is the internal @value{GDBN} thread number, as
2451 shown in the first field of the @samp{info threads} display.
2452 @value{GDBN} responds by displaying the system identifier of the thread
2453 you selected, and its current stack frame summary:
2456 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2457 (@value{GDBP}) thread 2
2458 [Switching to process 35 thread 23]
2459 0x34e5 in sigpause ()
2463 As with the @samp{[New @dots{}]} message, the form of the text after
2464 @samp{Switching to} depends on your system's conventions for identifying
2467 @kindex thread apply
2468 @cindex apply command to several threads
2469 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2470 The @code{thread apply} command allows you to apply the named
2471 @var{command} to one or more threads. Specify the numbers of the
2472 threads that you want affected with the command argument
2473 @var{threadno}. It can be a single thread number, one of the numbers
2474 shown in the first field of the @samp{info threads} display; or it
2475 could be a range of thread numbers, as in @code{2-4}. To apply a
2476 command to all threads, type @kbd{thread apply all @var{command}}.
2478 @kindex set print thread-events
2479 @cindex print messages on thread start and exit
2480 @item set print thread-events
2481 @itemx set print thread-events on
2482 @itemx set print thread-events off
2483 The @code{set print thread-events} command allows you to enable or
2484 disable printing of messages when @value{GDBN} notices that new threads have
2485 started or that threads have exited. By default, these messages will
2486 be printed if detection of these events is supported by the target.
2487 Note that these messages cannot be disabled on all targets.
2489 @kindex show print thread-events
2490 @item show print thread-events
2491 Show whether messages will be printed when @value{GDBN} detects that threads
2492 have started and exited.
2495 @cindex automatic thread selection
2496 @cindex switching threads automatically
2497 @cindex threads, automatic switching
2498 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2499 signal, it automatically selects the thread where that breakpoint or
2500 signal happened. @value{GDBN} alerts you to the context switch with a
2501 message of the form @samp{[Switching to @var{systag}]} to identify the
2504 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2505 more information about how @value{GDBN} behaves when you stop and start
2506 programs with multiple threads.
2508 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2509 watchpoints in programs with multiple threads.
2512 @section Debugging Programs with Multiple Processes
2514 @cindex fork, debugging programs which call
2515 @cindex multiple processes
2516 @cindex processes, multiple
2517 On most systems, @value{GDBN} has no special support for debugging
2518 programs which create additional processes using the @code{fork}
2519 function. When a program forks, @value{GDBN} will continue to debug the
2520 parent process and the child process will run unimpeded. If you have
2521 set a breakpoint in any code which the child then executes, the child
2522 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2523 will cause it to terminate.
2525 However, if you want to debug the child process there is a workaround
2526 which isn't too painful. Put a call to @code{sleep} in the code which
2527 the child process executes after the fork. It may be useful to sleep
2528 only if a certain environment variable is set, or a certain file exists,
2529 so that the delay need not occur when you don't want to run @value{GDBN}
2530 on the child. While the child is sleeping, use the @code{ps} program to
2531 get its process ID. Then tell @value{GDBN} (a new invocation of
2532 @value{GDBN} if you are also debugging the parent process) to attach to
2533 the child process (@pxref{Attach}). From that point on you can debug
2534 the child process just like any other process which you attached to.
2536 On some systems, @value{GDBN} provides support for debugging programs that
2537 create additional processes using the @code{fork} or @code{vfork} functions.
2538 Currently, the only platforms with this feature are HP-UX (11.x and later
2539 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2541 By default, when a program forks, @value{GDBN} will continue to debug
2542 the parent process and the child process will run unimpeded.
2544 If you want to follow the child process instead of the parent process,
2545 use the command @w{@code{set follow-fork-mode}}.
2548 @kindex set follow-fork-mode
2549 @item set follow-fork-mode @var{mode}
2550 Set the debugger response to a program call of @code{fork} or
2551 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2552 process. The @var{mode} argument can be:
2556 The original process is debugged after a fork. The child process runs
2557 unimpeded. This is the default.
2560 The new process is debugged after a fork. The parent process runs
2565 @kindex show follow-fork-mode
2566 @item show follow-fork-mode
2567 Display the current debugger response to a @code{fork} or @code{vfork} call.
2570 @cindex debugging multiple processes
2571 On Linux, if you want to debug both the parent and child processes, use the
2572 command @w{@code{set detach-on-fork}}.
2575 @kindex set detach-on-fork
2576 @item set detach-on-fork @var{mode}
2577 Tells gdb whether to detach one of the processes after a fork, or
2578 retain debugger control over them both.
2582 The child process (or parent process, depending on the value of
2583 @code{follow-fork-mode}) will be detached and allowed to run
2584 independently. This is the default.
2587 Both processes will be held under the control of @value{GDBN}.
2588 One process (child or parent, depending on the value of
2589 @code{follow-fork-mode}) is debugged as usual, while the other
2594 @kindex show detach-on-fork
2595 @item show detach-on-fork
2596 Show whether detach-on-fork mode is on/off.
2599 If you choose to set @samp{detach-on-fork} mode off, then
2600 @value{GDBN} will retain control of all forked processes (including
2601 nested forks). You can list the forked processes under the control of
2602 @value{GDBN} by using the @w{@code{info forks}} command, and switch
2603 from one fork to another by using the @w{@code{fork}} command.
2608 Print a list of all forked processes under the control of @value{GDBN}.
2609 The listing will include a fork id, a process id, and the current
2610 position (program counter) of the process.
2612 @kindex fork @var{fork-id}
2613 @item fork @var{fork-id}
2614 Make fork number @var{fork-id} the current process. The argument
2615 @var{fork-id} is the internal fork number assigned by @value{GDBN},
2616 as shown in the first field of the @samp{info forks} display.
2618 @kindex process @var{process-id}
2619 @item process @var{process-id}
2620 Make process number @var{process-id} the current process. The
2621 argument @var{process-id} must be one that is listed in the output of
2626 To quit debugging one of the forked processes, you can either detach
2627 from it by using the @w{@code{detach fork}} command (allowing it to
2628 run independently), or delete (and kill) it using the
2629 @w{@code{delete fork}} command.
2632 @kindex detach fork @var{fork-id}
2633 @item detach fork @var{fork-id}
2634 Detach from the process identified by @value{GDBN} fork number
2635 @var{fork-id}, and remove it from the fork list. The process will be
2636 allowed to run independently.
2638 @kindex delete fork @var{fork-id}
2639 @item delete fork @var{fork-id}
2640 Kill the process identified by @value{GDBN} fork number @var{fork-id},
2641 and remove it from the fork list.
2645 If you ask to debug a child process and a @code{vfork} is followed by an
2646 @code{exec}, @value{GDBN} executes the new target up to the first
2647 breakpoint in the new target. If you have a breakpoint set on
2648 @code{main} in your original program, the breakpoint will also be set on
2649 the child process's @code{main}.
2651 When a child process is spawned by @code{vfork}, you cannot debug the
2652 child or parent until an @code{exec} call completes.
2654 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2655 call executes, the new target restarts. To restart the parent process,
2656 use the @code{file} command with the parent executable name as its
2659 You can use the @code{catch} command to make @value{GDBN} stop whenever
2660 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2661 Catchpoints, ,Setting Catchpoints}.
2663 @node Checkpoint/Restart
2664 @section Setting a @emph{Bookmark} to Return to Later
2669 @cindex snapshot of a process
2670 @cindex rewind program state
2672 On certain operating systems@footnote{Currently, only
2673 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
2674 program's state, called a @dfn{checkpoint}, and come back to it
2677 Returning to a checkpoint effectively undoes everything that has
2678 happened in the program since the @code{checkpoint} was saved. This
2679 includes changes in memory, registers, and even (within some limits)
2680 system state. Effectively, it is like going back in time to the
2681 moment when the checkpoint was saved.
2683 Thus, if you're stepping thru a program and you think you're
2684 getting close to the point where things go wrong, you can save
2685 a checkpoint. Then, if you accidentally go too far and miss
2686 the critical statement, instead of having to restart your program
2687 from the beginning, you can just go back to the checkpoint and
2688 start again from there.
2690 This can be especially useful if it takes a lot of time or
2691 steps to reach the point where you think the bug occurs.
2693 To use the @code{checkpoint}/@code{restart} method of debugging:
2698 Save a snapshot of the debugged program's current execution state.
2699 The @code{checkpoint} command takes no arguments, but each checkpoint
2700 is assigned a small integer id, similar to a breakpoint id.
2702 @kindex info checkpoints
2703 @item info checkpoints
2704 List the checkpoints that have been saved in the current debugging
2705 session. For each checkpoint, the following information will be
2712 @item Source line, or label
2715 @kindex restart @var{checkpoint-id}
2716 @item restart @var{checkpoint-id}
2717 Restore the program state that was saved as checkpoint number
2718 @var{checkpoint-id}. All program variables, registers, stack frames
2719 etc.@: will be returned to the values that they had when the checkpoint
2720 was saved. In essence, gdb will ``wind back the clock'' to the point
2721 in time when the checkpoint was saved.
2723 Note that breakpoints, @value{GDBN} variables, command history etc.
2724 are not affected by restoring a checkpoint. In general, a checkpoint
2725 only restores things that reside in the program being debugged, not in
2728 @kindex delete checkpoint @var{checkpoint-id}
2729 @item delete checkpoint @var{checkpoint-id}
2730 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
2734 Returning to a previously saved checkpoint will restore the user state
2735 of the program being debugged, plus a significant subset of the system
2736 (OS) state, including file pointers. It won't ``un-write'' data from
2737 a file, but it will rewind the file pointer to the previous location,
2738 so that the previously written data can be overwritten. For files
2739 opened in read mode, the pointer will also be restored so that the
2740 previously read data can be read again.
2742 Of course, characters that have been sent to a printer (or other
2743 external device) cannot be ``snatched back'', and characters received
2744 from eg.@: a serial device can be removed from internal program buffers,
2745 but they cannot be ``pushed back'' into the serial pipeline, ready to
2746 be received again. Similarly, the actual contents of files that have
2747 been changed cannot be restored (at this time).
2749 However, within those constraints, you actually can ``rewind'' your
2750 program to a previously saved point in time, and begin debugging it
2751 again --- and you can change the course of events so as to debug a
2752 different execution path this time.
2754 @cindex checkpoints and process id
2755 Finally, there is one bit of internal program state that will be
2756 different when you return to a checkpoint --- the program's process
2757 id. Each checkpoint will have a unique process id (or @var{pid}),
2758 and each will be different from the program's original @var{pid}.
2759 If your program has saved a local copy of its process id, this could
2760 potentially pose a problem.
2762 @subsection A Non-obvious Benefit of Using Checkpoints
2764 On some systems such as @sc{gnu}/Linux, address space randomization
2765 is performed on new processes for security reasons. This makes it
2766 difficult or impossible to set a breakpoint, or watchpoint, on an
2767 absolute address if you have to restart the program, since the
2768 absolute location of a symbol will change from one execution to the
2771 A checkpoint, however, is an @emph{identical} copy of a process.
2772 Therefore if you create a checkpoint at (eg.@:) the start of main,
2773 and simply return to that checkpoint instead of restarting the
2774 process, you can avoid the effects of address randomization and
2775 your symbols will all stay in the same place.
2778 @chapter Stopping and Continuing
2780 The principal purposes of using a debugger are so that you can stop your
2781 program before it terminates; or so that, if your program runs into
2782 trouble, you can investigate and find out why.
2784 Inside @value{GDBN}, your program may stop for any of several reasons,
2785 such as a signal, a breakpoint, or reaching a new line after a
2786 @value{GDBN} command such as @code{step}. You may then examine and
2787 change variables, set new breakpoints or remove old ones, and then
2788 continue execution. Usually, the messages shown by @value{GDBN} provide
2789 ample explanation of the status of your program---but you can also
2790 explicitly request this information at any time.
2793 @kindex info program
2795 Display information about the status of your program: whether it is
2796 running or not, what process it is, and why it stopped.
2800 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2801 * Continuing and Stepping:: Resuming execution
2803 * Thread Stops:: Stopping and starting multi-thread programs
2807 @section Breakpoints, Watchpoints, and Catchpoints
2810 A @dfn{breakpoint} makes your program stop whenever a certain point in
2811 the program is reached. For each breakpoint, you can add conditions to
2812 control in finer detail whether your program stops. You can set
2813 breakpoints with the @code{break} command and its variants (@pxref{Set
2814 Breaks, ,Setting Breakpoints}), to specify the place where your program
2815 should stop by line number, function name or exact address in the
2818 On some systems, you can set breakpoints in shared libraries before
2819 the executable is run. There is a minor limitation on HP-UX systems:
2820 you must wait until the executable is run in order to set breakpoints
2821 in shared library routines that are not called directly by the program
2822 (for example, routines that are arguments in a @code{pthread_create}
2826 @cindex data breakpoints
2827 @cindex memory tracing
2828 @cindex breakpoint on memory address
2829 @cindex breakpoint on variable modification
2830 A @dfn{watchpoint} is a special breakpoint that stops your program
2831 when the value of an expression changes. The expression may be a value
2832 of a variable, or it could involve values of one or more variables
2833 combined by operators, such as @samp{a + b}. This is sometimes called
2834 @dfn{data breakpoints}. You must use a different command to set
2835 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
2836 from that, you can manage a watchpoint like any other breakpoint: you
2837 enable, disable, and delete both breakpoints and watchpoints using the
2840 You can arrange to have values from your program displayed automatically
2841 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2845 @cindex breakpoint on events
2846 A @dfn{catchpoint} is another special breakpoint that stops your program
2847 when a certain kind of event occurs, such as the throwing of a C@t{++}
2848 exception or the loading of a library. As with watchpoints, you use a
2849 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2850 Catchpoints}), but aside from that, you can manage a catchpoint like any
2851 other breakpoint. (To stop when your program receives a signal, use the
2852 @code{handle} command; see @ref{Signals, ,Signals}.)
2854 @cindex breakpoint numbers
2855 @cindex numbers for breakpoints
2856 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2857 catchpoint when you create it; these numbers are successive integers
2858 starting with one. In many of the commands for controlling various
2859 features of breakpoints you use the breakpoint number to say which
2860 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2861 @dfn{disabled}; if disabled, it has no effect on your program until you
2864 @cindex breakpoint ranges
2865 @cindex ranges of breakpoints
2866 Some @value{GDBN} commands accept a range of breakpoints on which to
2867 operate. A breakpoint range is either a single breakpoint number, like
2868 @samp{5}, or two such numbers, in increasing order, separated by a
2869 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2870 all breakpoints in that range are operated on.
2873 * Set Breaks:: Setting breakpoints
2874 * Set Watchpoints:: Setting watchpoints
2875 * Set Catchpoints:: Setting catchpoints
2876 * Delete Breaks:: Deleting breakpoints
2877 * Disabling:: Disabling breakpoints
2878 * Conditions:: Break conditions
2879 * Break Commands:: Breakpoint command lists
2880 * Breakpoint Menus:: Breakpoint menus
2881 * Error in Breakpoints:: ``Cannot insert breakpoints''
2882 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
2886 @subsection Setting Breakpoints
2888 @c FIXME LMB what does GDB do if no code on line of breakpt?
2889 @c consider in particular declaration with/without initialization.
2891 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2894 @kindex b @r{(@code{break})}
2895 @vindex $bpnum@r{, convenience variable}
2896 @cindex latest breakpoint
2897 Breakpoints are set with the @code{break} command (abbreviated
2898 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2899 number of the breakpoint you've set most recently; see @ref{Convenience
2900 Vars,, Convenience Variables}, for a discussion of what you can do with
2901 convenience variables.
2904 @item break @var{location}
2905 Set a breakpoint at the given @var{location}, which can specify a
2906 function name, a line number, or an address of an instruction.
2907 (@xref{Specify Location}, for a list of all the possible ways to
2908 specify a @var{location}.) The breakpoint will stop your program just
2909 before it executes any of the code in the specified @var{location}.
2911 When using source languages that permit overloading of symbols, such as
2912 C@t{++}, a function name may refer to more than one possible place to break.
2913 @xref{Breakpoint Menus,,Breakpoint Menus}, for a discussion of that situation.
2916 When called without any arguments, @code{break} sets a breakpoint at
2917 the next instruction to be executed in the selected stack frame
2918 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2919 innermost, this makes your program stop as soon as control
2920 returns to that frame. This is similar to the effect of a
2921 @code{finish} command in the frame inside the selected frame---except
2922 that @code{finish} does not leave an active breakpoint. If you use
2923 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2924 the next time it reaches the current location; this may be useful
2927 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2928 least one instruction has been executed. If it did not do this, you
2929 would be unable to proceed past a breakpoint without first disabling the
2930 breakpoint. This rule applies whether or not the breakpoint already
2931 existed when your program stopped.
2933 @item break @dots{} if @var{cond}
2934 Set a breakpoint with condition @var{cond}; evaluate the expression
2935 @var{cond} each time the breakpoint is reached, and stop only if the
2936 value is nonzero---that is, if @var{cond} evaluates as true.
2937 @samp{@dots{}} stands for one of the possible arguments described
2938 above (or no argument) specifying where to break. @xref{Conditions,
2939 ,Break Conditions}, for more information on breakpoint conditions.
2942 @item tbreak @var{args}
2943 Set a breakpoint enabled only for one stop. @var{args} are the
2944 same as for the @code{break} command, and the breakpoint is set in the same
2945 way, but the breakpoint is automatically deleted after the first time your
2946 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
2949 @cindex hardware breakpoints
2950 @item hbreak @var{args}
2951 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2952 @code{break} command and the breakpoint is set in the same way, but the
2953 breakpoint requires hardware support and some target hardware may not
2954 have this support. The main purpose of this is EPROM/ROM code
2955 debugging, so you can set a breakpoint at an instruction without
2956 changing the instruction. This can be used with the new trap-generation
2957 provided by SPARClite DSU and most x86-based targets. These targets
2958 will generate traps when a program accesses some data or instruction
2959 address that is assigned to the debug registers. However the hardware
2960 breakpoint registers can take a limited number of breakpoints. For
2961 example, on the DSU, only two data breakpoints can be set at a time, and
2962 @value{GDBN} will reject this command if more than two are used. Delete
2963 or disable unused hardware breakpoints before setting new ones
2964 (@pxref{Disabling, ,Disabling Breakpoints}).
2965 @xref{Conditions, ,Break Conditions}.
2966 For remote targets, you can restrict the number of hardware
2967 breakpoints @value{GDBN} will use, see @ref{set remote
2968 hardware-breakpoint-limit}.
2971 @item thbreak @var{args}
2972 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2973 are the same as for the @code{hbreak} command and the breakpoint is set in
2974 the same way. However, like the @code{tbreak} command,
2975 the breakpoint is automatically deleted after the
2976 first time your program stops there. Also, like the @code{hbreak}
2977 command, the breakpoint requires hardware support and some target hardware
2978 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
2979 See also @ref{Conditions, ,Break Conditions}.
2982 @cindex regular expression
2983 @cindex breakpoints in functions matching a regexp
2984 @cindex set breakpoints in many functions
2985 @item rbreak @var{regex}
2986 Set breakpoints on all functions matching the regular expression
2987 @var{regex}. This command sets an unconditional breakpoint on all
2988 matches, printing a list of all breakpoints it set. Once these
2989 breakpoints are set, they are treated just like the breakpoints set with
2990 the @code{break} command. You can delete them, disable them, or make
2991 them conditional the same way as any other breakpoint.
2993 The syntax of the regular expression is the standard one used with tools
2994 like @file{grep}. Note that this is different from the syntax used by
2995 shells, so for instance @code{foo*} matches all functions that include
2996 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2997 @code{.*} leading and trailing the regular expression you supply, so to
2998 match only functions that begin with @code{foo}, use @code{^foo}.
3000 @cindex non-member C@t{++} functions, set breakpoint in
3001 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3002 breakpoints on overloaded functions that are not members of any special
3005 @cindex set breakpoints on all functions
3006 The @code{rbreak} command can be used to set breakpoints in
3007 @strong{all} the functions in a program, like this:
3010 (@value{GDBP}) rbreak .
3013 @kindex info breakpoints
3014 @cindex @code{$_} and @code{info breakpoints}
3015 @item info breakpoints @r{[}@var{n}@r{]}
3016 @itemx info break @r{[}@var{n}@r{]}
3017 @itemx info watchpoints @r{[}@var{n}@r{]}
3018 Print a table of all breakpoints, watchpoints, and catchpoints set and
3019 not deleted. Optional argument @var{n} means print information only
3020 about the specified breakpoint (or watchpoint or catchpoint). For
3021 each breakpoint, following columns are printed:
3024 @item Breakpoint Numbers
3026 Breakpoint, watchpoint, or catchpoint.
3028 Whether the breakpoint is marked to be disabled or deleted when hit.
3029 @item Enabled or Disabled
3030 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3031 that are not enabled.
3033 Where the breakpoint is in your program, as a memory address. For a
3034 pending breakpoint whose address is not yet known, this field will
3035 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3036 library that has the symbol or line referred by breakpoint is loaded.
3037 See below for details. A breakpoint with several locations will
3038 have @samp{<MULTIPLE>} in this field---see below for details.
3040 Where the breakpoint is in the source for your program, as a file and
3041 line number. For a pending breakpoint, the original string passed to
3042 the breakpoint command will be listed as it cannot be resolved until
3043 the appropriate shared library is loaded in the future.
3047 If a breakpoint is conditional, @code{info break} shows the condition on
3048 the line following the affected breakpoint; breakpoint commands, if any,
3049 are listed after that. A pending breakpoint is allowed to have a condition
3050 specified for it. The condition is not parsed for validity until a shared
3051 library is loaded that allows the pending breakpoint to resolve to a
3055 @code{info break} with a breakpoint
3056 number @var{n} as argument lists only that breakpoint. The
3057 convenience variable @code{$_} and the default examining-address for
3058 the @code{x} command are set to the address of the last breakpoint
3059 listed (@pxref{Memory, ,Examining Memory}).
3062 @code{info break} displays a count of the number of times the breakpoint
3063 has been hit. This is especially useful in conjunction with the
3064 @code{ignore} command. You can ignore a large number of breakpoint
3065 hits, look at the breakpoint info to see how many times the breakpoint
3066 was hit, and then run again, ignoring one less than that number. This
3067 will get you quickly to the last hit of that breakpoint.
3070 @value{GDBN} allows you to set any number of breakpoints at the same place in
3071 your program. There is nothing silly or meaningless about this. When
3072 the breakpoints are conditional, this is even useful
3073 (@pxref{Conditions, ,Break Conditions}).
3075 It is possible that a breakpoint corresponds to several locations
3076 in your program. Examples of this situation are:
3081 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3082 instances of the function body, used in different cases.
3085 For a C@t{++} template function, a given line in the function can
3086 correspond to any number of instantiations.
3089 For an inlined function, a given source line can correspond to
3090 several places where that function is inlined.
3094 In all those cases, @value{GDBN} will insert a breakpoint at all
3095 the relevant locations.
3097 A breakpoint with multiple locations is displayed in the breakpoint
3098 table using several rows---one header row, followed by one row for
3099 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3100 address column. The rows for individual locations contain the actual
3101 addresses for locations, and show the functions to which those
3102 locations belong. The number column for a location is of the form
3103 @var{breakpoint-number}.@var{location-number}.
3108 Num Type Disp Enb Address What
3109 1 breakpoint keep y <MULTIPLE>
3111 breakpoint already hit 1 time
3112 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3113 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3116 Each location can be individually enabled or disabled by passing
3117 @var{breakpoint-number}.@var{location-number} as argument to the
3118 @code{enable} and @code{disable} commands. Note that you cannot
3119 delete the individual locations from the list, you can only delete the
3120 entire list of locations that belong to their parent breakpoint (with
3121 the @kbd{delete @var{num}} command, where @var{num} is the number of
3122 the parent breakpoint, 1 in the above example). Disabling or enabling
3123 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3124 that belong to that breakpoint.
3126 @cindex pending breakpoints
3127 It's quite common to have a breakpoint inside a shared library.
3128 Shared libraries can be loaded and unloaded explicitly,
3129 and possibly repeatedly, as the program is executed. To support
3130 this use case, @value{GDBN} updates breakpoint locations whenever
3131 any shared library is loaded or unloaded. Typically, you would
3132 set a breakpoint in a shared library at the beginning of your
3133 debugging session, when the library is not loaded, and when the
3134 symbols from the library are not available. When you try to set
3135 breakpoint, @value{GDBN} will ask you if you want to set
3136 a so called @dfn{pending breakpoint}---breakpoint whose address
3137 is not yet resolved.
3139 After the program is run, whenever a new shared library is loaded,
3140 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3141 shared library contains the symbol or line referred to by some
3142 pending breakpoint, that breakpoint is resolved and becomes an
3143 ordinary breakpoint. When a library is unloaded, all breakpoints
3144 that refer to its symbols or source lines become pending again.
3146 This logic works for breakpoints with multiple locations, too. For
3147 example, if you have a breakpoint in a C@t{++} template function, and
3148 a newly loaded shared library has an instantiation of that template,
3149 a new location is added to the list of locations for the breakpoint.
3151 Except for having unresolved address, pending breakpoints do not
3152 differ from regular breakpoints. You can set conditions or commands,
3153 enable and disable them and perform other breakpoint operations.
3155 @value{GDBN} provides some additional commands for controlling what
3156 happens when the @samp{break} command cannot resolve breakpoint
3157 address specification to an address:
3159 @kindex set breakpoint pending
3160 @kindex show breakpoint pending
3162 @item set breakpoint pending auto
3163 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3164 location, it queries you whether a pending breakpoint should be created.
3166 @item set breakpoint pending on
3167 This indicates that an unrecognized breakpoint location should automatically
3168 result in a pending breakpoint being created.
3170 @item set breakpoint pending off
3171 This indicates that pending breakpoints are not to be created. Any
3172 unrecognized breakpoint location results in an error. This setting does
3173 not affect any pending breakpoints previously created.
3175 @item show breakpoint pending
3176 Show the current behavior setting for creating pending breakpoints.
3179 The settings above only affect the @code{break} command and its
3180 variants. Once breakpoint is set, it will be automatically updated
3181 as shared libraries are loaded and unloaded.
3183 @cindex automatic hardware breakpoints
3184 For some targets, @value{GDBN} can automatically decide if hardware or
3185 software breakpoints should be used, depending on whether the
3186 breakpoint address is read-only or read-write. This applies to
3187 breakpoints set with the @code{break} command as well as to internal
3188 breakpoints set by commands like @code{next} and @code{finish}. For
3189 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3192 You can control this automatic behaviour with the following commands::
3194 @kindex set breakpoint auto-hw
3195 @kindex show breakpoint auto-hw
3197 @item set breakpoint auto-hw on
3198 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3199 will try to use the target memory map to decide if software or hardware
3200 breakpoint must be used.
3202 @item set breakpoint auto-hw off
3203 This indicates @value{GDBN} should not automatically select breakpoint
3204 type. If the target provides a memory map, @value{GDBN} will warn when
3205 trying to set software breakpoint at a read-only address.
3209 @cindex negative breakpoint numbers
3210 @cindex internal @value{GDBN} breakpoints
3211 @value{GDBN} itself sometimes sets breakpoints in your program for
3212 special purposes, such as proper handling of @code{longjmp} (in C
3213 programs). These internal breakpoints are assigned negative numbers,
3214 starting with @code{-1}; @samp{info breakpoints} does not display them.
3215 You can see these breakpoints with the @value{GDBN} maintenance command
3216 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3219 @node Set Watchpoints
3220 @subsection Setting Watchpoints
3222 @cindex setting watchpoints
3223 You can use a watchpoint to stop execution whenever the value of an
3224 expression changes, without having to predict a particular place where
3225 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3226 The expression may be as simple as the value of a single variable, or
3227 as complex as many variables combined by operators. Examples include:
3231 A reference to the value of a single variable.
3234 An address cast to an appropriate data type. For example,
3235 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3236 address (assuming an @code{int} occupies 4 bytes).
3239 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3240 expression can use any operators valid in the program's native
3241 language (@pxref{Languages}).
3244 You can set a watchpoint on an expression even if the expression can
3245 not be evaluated yet. For instance, you can set a watchpoint on
3246 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3247 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3248 the expression produces a valid value. If the expression becomes
3249 valid in some other way than changing a variable (e.g.@: if the memory
3250 pointed to by @samp{*global_ptr} becomes readable as the result of a
3251 @code{malloc} call), @value{GDBN} may not stop until the next time
3252 the expression changes.
3254 @cindex software watchpoints
3255 @cindex hardware watchpoints
3256 Depending on your system, watchpoints may be implemented in software or
3257 hardware. @value{GDBN} does software watchpointing by single-stepping your
3258 program and testing the variable's value each time, which is hundreds of
3259 times slower than normal execution. (But this may still be worth it, to
3260 catch errors where you have no clue what part of your program is the
3263 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3264 x86-based targets, @value{GDBN} includes support for hardware
3265 watchpoints, which do not slow down the running of your program.
3269 @item watch @var{expr} @r{[}thread @var{threadnum}@r{]}
3270 Set a watchpoint for an expression. @value{GDBN} will break when the
3271 expression @var{expr} is written into by the program and its value
3272 changes. The simplest (and the most popular) use of this command is
3273 to watch the value of a single variable:
3276 (@value{GDBP}) watch foo
3279 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3280 clause, @value{GDBN} breaks only when the thread identified by
3281 @var{threadnum} changes the value of @var{expr}. If any other threads
3282 change the value of @var{expr}, @value{GDBN} will not break. Note
3283 that watchpoints restricted to a single thread in this way only work
3284 with Hardware Watchpoints.
3287 @item rwatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3288 Set a watchpoint that will break when the value of @var{expr} is read
3292 @item awatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3293 Set a watchpoint that will break when @var{expr} is either read from
3294 or written into by the program.
3296 @kindex info watchpoints @r{[}@var{n}@r{]}
3297 @item info watchpoints
3298 This command prints a list of watchpoints, breakpoints, and catchpoints;
3299 it is the same as @code{info break} (@pxref{Set Breaks}).
3302 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3303 watchpoints execute very quickly, and the debugger reports a change in
3304 value at the exact instruction where the change occurs. If @value{GDBN}
3305 cannot set a hardware watchpoint, it sets a software watchpoint, which
3306 executes more slowly and reports the change in value at the next
3307 @emph{statement}, not the instruction, after the change occurs.
3309 @cindex use only software watchpoints
3310 You can force @value{GDBN} to use only software watchpoints with the
3311 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3312 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3313 the underlying system supports them. (Note that hardware-assisted
3314 watchpoints that were set @emph{before} setting
3315 @code{can-use-hw-watchpoints} to zero will still use the hardware
3316 mechanism of watching expression values.)
3319 @item set can-use-hw-watchpoints
3320 @kindex set can-use-hw-watchpoints
3321 Set whether or not to use hardware watchpoints.
3323 @item show can-use-hw-watchpoints
3324 @kindex show can-use-hw-watchpoints
3325 Show the current mode of using hardware watchpoints.
3328 For remote targets, you can restrict the number of hardware
3329 watchpoints @value{GDBN} will use, see @ref{set remote
3330 hardware-breakpoint-limit}.
3332 When you issue the @code{watch} command, @value{GDBN} reports
3335 Hardware watchpoint @var{num}: @var{expr}
3339 if it was able to set a hardware watchpoint.
3341 Currently, the @code{awatch} and @code{rwatch} commands can only set
3342 hardware watchpoints, because accesses to data that don't change the
3343 value of the watched expression cannot be detected without examining
3344 every instruction as it is being executed, and @value{GDBN} does not do
3345 that currently. If @value{GDBN} finds that it is unable to set a
3346 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3347 will print a message like this:
3350 Expression cannot be implemented with read/access watchpoint.
3353 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3354 data type of the watched expression is wider than what a hardware
3355 watchpoint on the target machine can handle. For example, some systems
3356 can only watch regions that are up to 4 bytes wide; on such systems you
3357 cannot set hardware watchpoints for an expression that yields a
3358 double-precision floating-point number (which is typically 8 bytes
3359 wide). As a work-around, it might be possible to break the large region
3360 into a series of smaller ones and watch them with separate watchpoints.
3362 If you set too many hardware watchpoints, @value{GDBN} might be unable
3363 to insert all of them when you resume the execution of your program.
3364 Since the precise number of active watchpoints is unknown until such
3365 time as the program is about to be resumed, @value{GDBN} might not be
3366 able to warn you about this when you set the watchpoints, and the
3367 warning will be printed only when the program is resumed:
3370 Hardware watchpoint @var{num}: Could not insert watchpoint
3374 If this happens, delete or disable some of the watchpoints.
3376 Watching complex expressions that reference many variables can also
3377 exhaust the resources available for hardware-assisted watchpoints.
3378 That's because @value{GDBN} needs to watch every variable in the
3379 expression with separately allocated resources.
3381 If you call a function interactively using @code{print} or @code{call},
3382 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3383 kind of breakpoint or the call completes.
3385 @value{GDBN} automatically deletes watchpoints that watch local
3386 (automatic) variables, or expressions that involve such variables, when
3387 they go out of scope, that is, when the execution leaves the block in
3388 which these variables were defined. In particular, when the program
3389 being debugged terminates, @emph{all} local variables go out of scope,
3390 and so only watchpoints that watch global variables remain set. If you
3391 rerun the program, you will need to set all such watchpoints again. One
3392 way of doing that would be to set a code breakpoint at the entry to the
3393 @code{main} function and when it breaks, set all the watchpoints.
3395 @cindex watchpoints and threads
3396 @cindex threads and watchpoints
3397 In multi-threaded programs, watchpoints will detect changes to the
3398 watched expression from every thread.
3401 @emph{Warning:} In multi-threaded programs, software watchpoints
3402 have only limited usefulness. If @value{GDBN} creates a software
3403 watchpoint, it can only watch the value of an expression @emph{in a
3404 single thread}. If you are confident that the expression can only
3405 change due to the current thread's activity (and if you are also
3406 confident that no other thread can become current), then you can use
3407 software watchpoints as usual. However, @value{GDBN} may not notice
3408 when a non-current thread's activity changes the expression. (Hardware
3409 watchpoints, in contrast, watch an expression in all threads.)
3412 @xref{set remote hardware-watchpoint-limit}.
3414 @node Set Catchpoints
3415 @subsection Setting Catchpoints
3416 @cindex catchpoints, setting
3417 @cindex exception handlers
3418 @cindex event handling
3420 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3421 kinds of program events, such as C@t{++} exceptions or the loading of a
3422 shared library. Use the @code{catch} command to set a catchpoint.
3426 @item catch @var{event}
3427 Stop when @var{event} occurs. @var{event} can be any of the following:
3430 @cindex stop on C@t{++} exceptions
3431 The throwing of a C@t{++} exception.
3434 The catching of a C@t{++} exception.
3437 @cindex Ada exception catching
3438 @cindex catch Ada exceptions
3439 An Ada exception being raised. If an exception name is specified
3440 at the end of the command (eg @code{catch exception Program_Error}),
3441 the debugger will stop only when this specific exception is raised.
3442 Otherwise, the debugger stops execution when any Ada exception is raised.
3444 @item exception unhandled
3445 An exception that was raised but is not handled by the program.
3448 A failed Ada assertion.
3451 @cindex break on fork/exec
3452 A call to @code{exec}. This is currently only available for HP-UX
3456 A call to @code{fork}. This is currently only available for HP-UX
3460 A call to @code{vfork}. This is currently only available for HP-UX
3464 @itemx load @var{libname}
3465 @cindex break on load/unload of shared library
3466 The dynamic loading of any shared library, or the loading of the library
3467 @var{libname}. This is currently only available for HP-UX.
3470 @itemx unload @var{libname}
3471 The unloading of any dynamically loaded shared library, or the unloading
3472 of the library @var{libname}. This is currently only available for HP-UX.
3475 @item tcatch @var{event}
3476 Set a catchpoint that is enabled only for one stop. The catchpoint is
3477 automatically deleted after the first time the event is caught.
3481 Use the @code{info break} command to list the current catchpoints.
3483 There are currently some limitations to C@t{++} exception handling
3484 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
3488 If you call a function interactively, @value{GDBN} normally returns
3489 control to you when the function has finished executing. If the call
3490 raises an exception, however, the call may bypass the mechanism that
3491 returns control to you and cause your program either to abort or to
3492 simply continue running until it hits a breakpoint, catches a signal
3493 that @value{GDBN} is listening for, or exits. This is the case even if
3494 you set a catchpoint for the exception; catchpoints on exceptions are
3495 disabled within interactive calls.
3498 You cannot raise an exception interactively.
3501 You cannot install an exception handler interactively.
3504 @cindex raise exceptions
3505 Sometimes @code{catch} is not the best way to debug exception handling:
3506 if you need to know exactly where an exception is raised, it is better to
3507 stop @emph{before} the exception handler is called, since that way you
3508 can see the stack before any unwinding takes place. If you set a
3509 breakpoint in an exception handler instead, it may not be easy to find
3510 out where the exception was raised.
3512 To stop just before an exception handler is called, you need some
3513 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3514 raised by calling a library function named @code{__raise_exception}
3515 which has the following ANSI C interface:
3518 /* @var{addr} is where the exception identifier is stored.
3519 @var{id} is the exception identifier. */
3520 void __raise_exception (void **addr, void *id);
3524 To make the debugger catch all exceptions before any stack
3525 unwinding takes place, set a breakpoint on @code{__raise_exception}
3526 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
3528 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
3529 that depends on the value of @var{id}, you can stop your program when
3530 a specific exception is raised. You can use multiple conditional
3531 breakpoints to stop your program when any of a number of exceptions are
3536 @subsection Deleting Breakpoints
3538 @cindex clearing breakpoints, watchpoints, catchpoints
3539 @cindex deleting breakpoints, watchpoints, catchpoints
3540 It is often necessary to eliminate a breakpoint, watchpoint, or
3541 catchpoint once it has done its job and you no longer want your program
3542 to stop there. This is called @dfn{deleting} the breakpoint. A
3543 breakpoint that has been deleted no longer exists; it is forgotten.
3545 With the @code{clear} command you can delete breakpoints according to
3546 where they are in your program. With the @code{delete} command you can
3547 delete individual breakpoints, watchpoints, or catchpoints by specifying
3548 their breakpoint numbers.
3550 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3551 automatically ignores breakpoints on the first instruction to be executed
3552 when you continue execution without changing the execution address.
3557 Delete any breakpoints at the next instruction to be executed in the
3558 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
3559 the innermost frame is selected, this is a good way to delete a
3560 breakpoint where your program just stopped.
3562 @item clear @var{location}
3563 Delete any breakpoints set at the specified @var{location}.
3564 @xref{Specify Location}, for the various forms of @var{location}; the
3565 most useful ones are listed below:
3568 @item clear @var{function}
3569 @itemx clear @var{filename}:@var{function}
3570 Delete any breakpoints set at entry to the named @var{function}.
3572 @item clear @var{linenum}
3573 @itemx clear @var{filename}:@var{linenum}
3574 Delete any breakpoints set at or within the code of the specified
3575 @var{linenum} of the specified @var{filename}.
3578 @cindex delete breakpoints
3580 @kindex d @r{(@code{delete})}
3581 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3582 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3583 ranges specified as arguments. If no argument is specified, delete all
3584 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3585 confirm off}). You can abbreviate this command as @code{d}.
3589 @subsection Disabling Breakpoints
3591 @cindex enable/disable a breakpoint
3592 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3593 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3594 it had been deleted, but remembers the information on the breakpoint so
3595 that you can @dfn{enable} it again later.
3597 You disable and enable breakpoints, watchpoints, and catchpoints with
3598 the @code{enable} and @code{disable} commands, optionally specifying one
3599 or more breakpoint numbers as arguments. Use @code{info break} or
3600 @code{info watch} to print a list of breakpoints, watchpoints, and
3601 catchpoints if you do not know which numbers to use.
3603 Disabling and enabling a breakpoint that has multiple locations
3604 affects all of its locations.
3606 A breakpoint, watchpoint, or catchpoint can have any of four different
3607 states of enablement:
3611 Enabled. The breakpoint stops your program. A breakpoint set
3612 with the @code{break} command starts out in this state.
3614 Disabled. The breakpoint has no effect on your program.
3616 Enabled once. The breakpoint stops your program, but then becomes
3619 Enabled for deletion. The breakpoint stops your program, but
3620 immediately after it does so it is deleted permanently. A breakpoint
3621 set with the @code{tbreak} command starts out in this state.
3624 You can use the following commands to enable or disable breakpoints,
3625 watchpoints, and catchpoints:
3629 @kindex dis @r{(@code{disable})}
3630 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3631 Disable the specified breakpoints---or all breakpoints, if none are
3632 listed. A disabled breakpoint has no effect but is not forgotten. All
3633 options such as ignore-counts, conditions and commands are remembered in
3634 case the breakpoint is enabled again later. You may abbreviate
3635 @code{disable} as @code{dis}.
3638 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3639 Enable the specified breakpoints (or all defined breakpoints). They
3640 become effective once again in stopping your program.
3642 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3643 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3644 of these breakpoints immediately after stopping your program.
3646 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3647 Enable the specified breakpoints to work once, then die. @value{GDBN}
3648 deletes any of these breakpoints as soon as your program stops there.
3649 Breakpoints set by the @code{tbreak} command start out in this state.
3652 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3653 @c confusing: tbreak is also initially enabled.
3654 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3655 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
3656 subsequently, they become disabled or enabled only when you use one of
3657 the commands above. (The command @code{until} can set and delete a
3658 breakpoint of its own, but it does not change the state of your other
3659 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3663 @subsection Break Conditions
3664 @cindex conditional breakpoints
3665 @cindex breakpoint conditions
3667 @c FIXME what is scope of break condition expr? Context where wanted?
3668 @c in particular for a watchpoint?
3669 The simplest sort of breakpoint breaks every time your program reaches a
3670 specified place. You can also specify a @dfn{condition} for a
3671 breakpoint. A condition is just a Boolean expression in your
3672 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3673 a condition evaluates the expression each time your program reaches it,
3674 and your program stops only if the condition is @emph{true}.
3676 This is the converse of using assertions for program validation; in that
3677 situation, you want to stop when the assertion is violated---that is,
3678 when the condition is false. In C, if you want to test an assertion expressed
3679 by the condition @var{assert}, you should set the condition
3680 @samp{! @var{assert}} on the appropriate breakpoint.
3682 Conditions are also accepted for watchpoints; you may not need them,
3683 since a watchpoint is inspecting the value of an expression anyhow---but
3684 it might be simpler, say, to just set a watchpoint on a variable name,
3685 and specify a condition that tests whether the new value is an interesting
3688 Break conditions can have side effects, and may even call functions in
3689 your program. This can be useful, for example, to activate functions
3690 that log program progress, or to use your own print functions to
3691 format special data structures. The effects are completely predictable
3692 unless there is another enabled breakpoint at the same address. (In
3693 that case, @value{GDBN} might see the other breakpoint first and stop your
3694 program without checking the condition of this one.) Note that
3695 breakpoint commands are usually more convenient and flexible than break
3697 purpose of performing side effects when a breakpoint is reached
3698 (@pxref{Break Commands, ,Breakpoint Command Lists}).
3700 Break conditions can be specified when a breakpoint is set, by using
3701 @samp{if} in the arguments to the @code{break} command. @xref{Set
3702 Breaks, ,Setting Breakpoints}. They can also be changed at any time
3703 with the @code{condition} command.
3705 You can also use the @code{if} keyword with the @code{watch} command.
3706 The @code{catch} command does not recognize the @code{if} keyword;
3707 @code{condition} is the only way to impose a further condition on a
3712 @item condition @var{bnum} @var{expression}
3713 Specify @var{expression} as the break condition for breakpoint,
3714 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3715 breakpoint @var{bnum} stops your program only if the value of
3716 @var{expression} is true (nonzero, in C). When you use
3717 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3718 syntactic correctness, and to determine whether symbols in it have
3719 referents in the context of your breakpoint. If @var{expression} uses
3720 symbols not referenced in the context of the breakpoint, @value{GDBN}
3721 prints an error message:
3724 No symbol "foo" in current context.
3729 not actually evaluate @var{expression} at the time the @code{condition}
3730 command (or a command that sets a breakpoint with a condition, like
3731 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3733 @item condition @var{bnum}
3734 Remove the condition from breakpoint number @var{bnum}. It becomes
3735 an ordinary unconditional breakpoint.
3738 @cindex ignore count (of breakpoint)
3739 A special case of a breakpoint condition is to stop only when the
3740 breakpoint has been reached a certain number of times. This is so
3741 useful that there is a special way to do it, using the @dfn{ignore
3742 count} of the breakpoint. Every breakpoint has an ignore count, which
3743 is an integer. Most of the time, the ignore count is zero, and
3744 therefore has no effect. But if your program reaches a breakpoint whose
3745 ignore count is positive, then instead of stopping, it just decrements
3746 the ignore count by one and continues. As a result, if the ignore count
3747 value is @var{n}, the breakpoint does not stop the next @var{n} times
3748 your program reaches it.
3752 @item ignore @var{bnum} @var{count}
3753 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3754 The next @var{count} times the breakpoint is reached, your program's
3755 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3758 To make the breakpoint stop the next time it is reached, specify
3761 When you use @code{continue} to resume execution of your program from a
3762 breakpoint, you can specify an ignore count directly as an argument to
3763 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3764 Stepping,,Continuing and Stepping}.
3766 If a breakpoint has a positive ignore count and a condition, the
3767 condition is not checked. Once the ignore count reaches zero,
3768 @value{GDBN} resumes checking the condition.
3770 You could achieve the effect of the ignore count with a condition such
3771 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3772 is decremented each time. @xref{Convenience Vars, ,Convenience
3776 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3779 @node Break Commands
3780 @subsection Breakpoint Command Lists
3782 @cindex breakpoint commands
3783 You can give any breakpoint (or watchpoint or catchpoint) a series of
3784 commands to execute when your program stops due to that breakpoint. For
3785 example, you might want to print the values of certain expressions, or
3786 enable other breakpoints.
3790 @kindex end@r{ (breakpoint commands)}
3791 @item commands @r{[}@var{bnum}@r{]}
3792 @itemx @dots{} @var{command-list} @dots{}
3794 Specify a list of commands for breakpoint number @var{bnum}. The commands
3795 themselves appear on the following lines. Type a line containing just
3796 @code{end} to terminate the commands.
3798 To remove all commands from a breakpoint, type @code{commands} and
3799 follow it immediately with @code{end}; that is, give no commands.
3801 With no @var{bnum} argument, @code{commands} refers to the last
3802 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3803 recently encountered).
3806 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3807 disabled within a @var{command-list}.
3809 You can use breakpoint commands to start your program up again. Simply
3810 use the @code{continue} command, or @code{step}, or any other command
3811 that resumes execution.
3813 Any other commands in the command list, after a command that resumes
3814 execution, are ignored. This is because any time you resume execution
3815 (even with a simple @code{next} or @code{step}), you may encounter
3816 another breakpoint---which could have its own command list, leading to
3817 ambiguities about which list to execute.
3820 If the first command you specify in a command list is @code{silent}, the
3821 usual message about stopping at a breakpoint is not printed. This may
3822 be desirable for breakpoints that are to print a specific message and
3823 then continue. If none of the remaining commands print anything, you
3824 see no sign that the breakpoint was reached. @code{silent} is
3825 meaningful only at the beginning of a breakpoint command list.
3827 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3828 print precisely controlled output, and are often useful in silent
3829 breakpoints. @xref{Output, ,Commands for Controlled Output}.
3831 For example, here is how you could use breakpoint commands to print the
3832 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3838 printf "x is %d\n",x
3843 One application for breakpoint commands is to compensate for one bug so
3844 you can test for another. Put a breakpoint just after the erroneous line
3845 of code, give it a condition to detect the case in which something
3846 erroneous has been done, and give it commands to assign correct values
3847 to any variables that need them. End with the @code{continue} command
3848 so that your program does not stop, and start with the @code{silent}
3849 command so that no output is produced. Here is an example:
3860 @node Breakpoint Menus
3861 @subsection Breakpoint Menus
3863 @cindex symbol overloading
3865 Some programming languages (notably C@t{++} and Objective-C) permit a
3866 single function name
3867 to be defined several times, for application in different contexts.
3868 This is called @dfn{overloading}. When a function name is overloaded,
3869 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3870 a breakpoint. You can use explicit signature of the function, as in
3871 @samp{break @var{function}(@var{types})}, to specify which
3872 particular version of the function you want. Otherwise, @value{GDBN} offers
3873 you a menu of numbered choices for different possible breakpoints, and
3874 waits for your selection with the prompt @samp{>}. The first two
3875 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3876 sets a breakpoint at each definition of @var{function}, and typing
3877 @kbd{0} aborts the @code{break} command without setting any new
3880 For example, the following session excerpt shows an attempt to set a
3881 breakpoint at the overloaded symbol @code{String::after}.
3882 We choose three particular definitions of that function name:
3884 @c FIXME! This is likely to change to show arg type lists, at least
3887 (@value{GDBP}) b String::after
3890 [2] file:String.cc; line number:867
3891 [3] file:String.cc; line number:860
3892 [4] file:String.cc; line number:875
3893 [5] file:String.cc; line number:853
3894 [6] file:String.cc; line number:846
3895 [7] file:String.cc; line number:735
3897 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3898 Breakpoint 2 at 0xb344: file String.cc, line 875.
3899 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3900 Multiple breakpoints were set.
3901 Use the "delete" command to delete unwanted
3907 @c @ifclear BARETARGET
3908 @node Error in Breakpoints
3909 @subsection ``Cannot insert breakpoints''
3911 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3913 Under some operating systems, breakpoints cannot be used in a program if
3914 any other process is running that program. In this situation,
3915 attempting to run or continue a program with a breakpoint causes
3916 @value{GDBN} to print an error message:
3919 Cannot insert breakpoints.
3920 The same program may be running in another process.
3923 When this happens, you have three ways to proceed:
3927 Remove or disable the breakpoints, then continue.
3930 Suspend @value{GDBN}, and copy the file containing your program to a new
3931 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3932 that @value{GDBN} should run your program under that name.
3933 Then start your program again.
3936 Relink your program so that the text segment is nonsharable, using the
3937 linker option @samp{-N}. The operating system limitation may not apply
3938 to nonsharable executables.
3942 A similar message can be printed if you request too many active
3943 hardware-assisted breakpoints and watchpoints:
3945 @c FIXME: the precise wording of this message may change; the relevant
3946 @c source change is not committed yet (Sep 3, 1999).
3948 Stopped; cannot insert breakpoints.
3949 You may have requested too many hardware breakpoints and watchpoints.
3953 This message is printed when you attempt to resume the program, since
3954 only then @value{GDBN} knows exactly how many hardware breakpoints and
3955 watchpoints it needs to insert.
3957 When this message is printed, you need to disable or remove some of the
3958 hardware-assisted breakpoints and watchpoints, and then continue.
3960 @node Breakpoint-related Warnings
3961 @subsection ``Breakpoint address adjusted...''
3962 @cindex breakpoint address adjusted
3964 Some processor architectures place constraints on the addresses at
3965 which breakpoints may be placed. For architectures thus constrained,
3966 @value{GDBN} will attempt to adjust the breakpoint's address to comply
3967 with the constraints dictated by the architecture.
3969 One example of such an architecture is the Fujitsu FR-V. The FR-V is
3970 a VLIW architecture in which a number of RISC-like instructions may be
3971 bundled together for parallel execution. The FR-V architecture
3972 constrains the location of a breakpoint instruction within such a
3973 bundle to the instruction with the lowest address. @value{GDBN}
3974 honors this constraint by adjusting a breakpoint's address to the
3975 first in the bundle.
3977 It is not uncommon for optimized code to have bundles which contain
3978 instructions from different source statements, thus it may happen that
3979 a breakpoint's address will be adjusted from one source statement to
3980 another. Since this adjustment may significantly alter @value{GDBN}'s
3981 breakpoint related behavior from what the user expects, a warning is
3982 printed when the breakpoint is first set and also when the breakpoint
3985 A warning like the one below is printed when setting a breakpoint
3986 that's been subject to address adjustment:
3989 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
3992 Such warnings are printed both for user settable and @value{GDBN}'s
3993 internal breakpoints. If you see one of these warnings, you should
3994 verify that a breakpoint set at the adjusted address will have the
3995 desired affect. If not, the breakpoint in question may be removed and
3996 other breakpoints may be set which will have the desired behavior.
3997 E.g., it may be sufficient to place the breakpoint at a later
3998 instruction. A conditional breakpoint may also be useful in some
3999 cases to prevent the breakpoint from triggering too often.
4001 @value{GDBN} will also issue a warning when stopping at one of these
4002 adjusted breakpoints:
4005 warning: Breakpoint 1 address previously adjusted from 0x00010414
4009 When this warning is encountered, it may be too late to take remedial
4010 action except in cases where the breakpoint is hit earlier or more
4011 frequently than expected.
4013 @node Continuing and Stepping
4014 @section Continuing and Stepping
4018 @cindex resuming execution
4019 @dfn{Continuing} means resuming program execution until your program
4020 completes normally. In contrast, @dfn{stepping} means executing just
4021 one more ``step'' of your program, where ``step'' may mean either one
4022 line of source code, or one machine instruction (depending on what
4023 particular command you use). Either when continuing or when stepping,
4024 your program may stop even sooner, due to a breakpoint or a signal. (If
4025 it stops due to a signal, you may want to use @code{handle}, or use
4026 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4030 @kindex c @r{(@code{continue})}
4031 @kindex fg @r{(resume foreground execution)}
4032 @item continue @r{[}@var{ignore-count}@r{]}
4033 @itemx c @r{[}@var{ignore-count}@r{]}
4034 @itemx fg @r{[}@var{ignore-count}@r{]}
4035 Resume program execution, at the address where your program last stopped;
4036 any breakpoints set at that address are bypassed. The optional argument
4037 @var{ignore-count} allows you to specify a further number of times to
4038 ignore a breakpoint at this location; its effect is like that of
4039 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4041 The argument @var{ignore-count} is meaningful only when your program
4042 stopped due to a breakpoint. At other times, the argument to
4043 @code{continue} is ignored.
4045 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4046 debugged program is deemed to be the foreground program) are provided
4047 purely for convenience, and have exactly the same behavior as
4051 To resume execution at a different place, you can use @code{return}
4052 (@pxref{Returning, ,Returning from a Function}) to go back to the
4053 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4054 Different Address}) to go to an arbitrary location in your program.
4056 A typical technique for using stepping is to set a breakpoint
4057 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4058 beginning of the function or the section of your program where a problem
4059 is believed to lie, run your program until it stops at that breakpoint,
4060 and then step through the suspect area, examining the variables that are
4061 interesting, until you see the problem happen.
4065 @kindex s @r{(@code{step})}
4067 Continue running your program until control reaches a different source
4068 line, then stop it and return control to @value{GDBN}. This command is
4069 abbreviated @code{s}.
4072 @c "without debugging information" is imprecise; actually "without line
4073 @c numbers in the debugging information". (gcc -g1 has debugging info but
4074 @c not line numbers). But it seems complex to try to make that
4075 @c distinction here.
4076 @emph{Warning:} If you use the @code{step} command while control is
4077 within a function that was compiled without debugging information,
4078 execution proceeds until control reaches a function that does have
4079 debugging information. Likewise, it will not step into a function which
4080 is compiled without debugging information. To step through functions
4081 without debugging information, use the @code{stepi} command, described
4085 The @code{step} command only stops at the first instruction of a source
4086 line. This prevents the multiple stops that could otherwise occur in
4087 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4088 to stop if a function that has debugging information is called within
4089 the line. In other words, @code{step} @emph{steps inside} any functions
4090 called within the line.
4092 Also, the @code{step} command only enters a function if there is line
4093 number information for the function. Otherwise it acts like the
4094 @code{next} command. This avoids problems when using @code{cc -gl}
4095 on MIPS machines. Previously, @code{step} entered subroutines if there
4096 was any debugging information about the routine.
4098 @item step @var{count}
4099 Continue running as in @code{step}, but do so @var{count} times. If a
4100 breakpoint is reached, or a signal not related to stepping occurs before
4101 @var{count} steps, stepping stops right away.
4104 @kindex n @r{(@code{next})}
4105 @item next @r{[}@var{count}@r{]}
4106 Continue to the next source line in the current (innermost) stack frame.
4107 This is similar to @code{step}, but function calls that appear within
4108 the line of code are executed without stopping. Execution stops when
4109 control reaches a different line of code at the original stack level
4110 that was executing when you gave the @code{next} command. This command
4111 is abbreviated @code{n}.
4113 An argument @var{count} is a repeat count, as for @code{step}.
4116 @c FIX ME!! Do we delete this, or is there a way it fits in with
4117 @c the following paragraph? --- Vctoria
4119 @c @code{next} within a function that lacks debugging information acts like
4120 @c @code{step}, but any function calls appearing within the code of the
4121 @c function are executed without stopping.
4123 The @code{next} command only stops at the first instruction of a
4124 source line. This prevents multiple stops that could otherwise occur in
4125 @code{switch} statements, @code{for} loops, etc.
4127 @kindex set step-mode
4129 @cindex functions without line info, and stepping
4130 @cindex stepping into functions with no line info
4131 @itemx set step-mode on
4132 The @code{set step-mode on} command causes the @code{step} command to
4133 stop at the first instruction of a function which contains no debug line
4134 information rather than stepping over it.
4136 This is useful in cases where you may be interested in inspecting the
4137 machine instructions of a function which has no symbolic info and do not
4138 want @value{GDBN} to automatically skip over this function.
4140 @item set step-mode off
4141 Causes the @code{step} command to step over any functions which contains no
4142 debug information. This is the default.
4144 @item show step-mode
4145 Show whether @value{GDBN} will stop in or step over functions without
4146 source line debug information.
4150 Continue running until just after function in the selected stack frame
4151 returns. Print the returned value (if any).
4153 Contrast this with the @code{return} command (@pxref{Returning,
4154 ,Returning from a Function}).
4157 @kindex u @r{(@code{until})}
4158 @cindex run until specified location
4161 Continue running until a source line past the current line, in the
4162 current stack frame, is reached. This command is used to avoid single
4163 stepping through a loop more than once. It is like the @code{next}
4164 command, except that when @code{until} encounters a jump, it
4165 automatically continues execution until the program counter is greater
4166 than the address of the jump.
4168 This means that when you reach the end of a loop after single stepping
4169 though it, @code{until} makes your program continue execution until it
4170 exits the loop. In contrast, a @code{next} command at the end of a loop
4171 simply steps back to the beginning of the loop, which forces you to step
4172 through the next iteration.
4174 @code{until} always stops your program if it attempts to exit the current
4177 @code{until} may produce somewhat counterintuitive results if the order
4178 of machine code does not match the order of the source lines. For
4179 example, in the following excerpt from a debugging session, the @code{f}
4180 (@code{frame}) command shows that execution is stopped at line
4181 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4185 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4187 (@value{GDBP}) until
4188 195 for ( ; argc > 0; NEXTARG) @{
4191 This happened because, for execution efficiency, the compiler had
4192 generated code for the loop closure test at the end, rather than the
4193 start, of the loop---even though the test in a C @code{for}-loop is
4194 written before the body of the loop. The @code{until} command appeared
4195 to step back to the beginning of the loop when it advanced to this
4196 expression; however, it has not really gone to an earlier
4197 statement---not in terms of the actual machine code.
4199 @code{until} with no argument works by means of single
4200 instruction stepping, and hence is slower than @code{until} with an
4203 @item until @var{location}
4204 @itemx u @var{location}
4205 Continue running your program until either the specified location is
4206 reached, or the current stack frame returns. @var{location} is any of
4207 the forms described in @ref{Specify Location}.
4208 This form of the command uses temporary breakpoints, and
4209 hence is quicker than @code{until} without an argument. The specified
4210 location is actually reached only if it is in the current frame. This
4211 implies that @code{until} can be used to skip over recursive function
4212 invocations. For instance in the code below, if the current location is
4213 line @code{96}, issuing @code{until 99} will execute the program up to
4214 line @code{99} in the same invocation of factorial, i.e., after the inner
4215 invocations have returned.
4218 94 int factorial (int value)
4220 96 if (value > 1) @{
4221 97 value *= factorial (value - 1);
4228 @kindex advance @var{location}
4229 @itemx advance @var{location}
4230 Continue running the program up to the given @var{location}. An argument is
4231 required, which should be of one of the forms described in
4232 @ref{Specify Location}.
4233 Execution will also stop upon exit from the current stack
4234 frame. This command is similar to @code{until}, but @code{advance} will
4235 not skip over recursive function calls, and the target location doesn't
4236 have to be in the same frame as the current one.
4240 @kindex si @r{(@code{stepi})}
4242 @itemx stepi @var{arg}
4244 Execute one machine instruction, then stop and return to the debugger.
4246 It is often useful to do @samp{display/i $pc} when stepping by machine
4247 instructions. This makes @value{GDBN} automatically display the next
4248 instruction to be executed, each time your program stops. @xref{Auto
4249 Display,, Automatic Display}.
4251 An argument is a repeat count, as in @code{step}.
4255 @kindex ni @r{(@code{nexti})}
4257 @itemx nexti @var{arg}
4259 Execute one machine instruction, but if it is a function call,
4260 proceed until the function returns.
4262 An argument is a repeat count, as in @code{next}.
4269 A signal is an asynchronous event that can happen in a program. The
4270 operating system defines the possible kinds of signals, and gives each
4271 kind a name and a number. For example, in Unix @code{SIGINT} is the
4272 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4273 @code{SIGSEGV} is the signal a program gets from referencing a place in
4274 memory far away from all the areas in use; @code{SIGALRM} occurs when
4275 the alarm clock timer goes off (which happens only if your program has
4276 requested an alarm).
4278 @cindex fatal signals
4279 Some signals, including @code{SIGALRM}, are a normal part of the
4280 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4281 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4282 program has not specified in advance some other way to handle the signal.
4283 @code{SIGINT} does not indicate an error in your program, but it is normally
4284 fatal so it can carry out the purpose of the interrupt: to kill the program.
4286 @value{GDBN} has the ability to detect any occurrence of a signal in your
4287 program. You can tell @value{GDBN} in advance what to do for each kind of
4290 @cindex handling signals
4291 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4292 @code{SIGALRM} be silently passed to your program
4293 (so as not to interfere with their role in the program's functioning)
4294 but to stop your program immediately whenever an error signal happens.
4295 You can change these settings with the @code{handle} command.
4298 @kindex info signals
4302 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4303 handle each one. You can use this to see the signal numbers of all
4304 the defined types of signals.
4306 @item info signals @var{sig}
4307 Similar, but print information only about the specified signal number.
4309 @code{info handle} is an alias for @code{info signals}.
4312 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4313 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4314 can be the number of a signal or its name (with or without the
4315 @samp{SIG} at the beginning); a list of signal numbers of the form
4316 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4317 known signals. Optional arguments @var{keywords}, described below,
4318 say what change to make.
4322 The keywords allowed by the @code{handle} command can be abbreviated.
4323 Their full names are:
4327 @value{GDBN} should not stop your program when this signal happens. It may
4328 still print a message telling you that the signal has come in.
4331 @value{GDBN} should stop your program when this signal happens. This implies
4332 the @code{print} keyword as well.
4335 @value{GDBN} should print a message when this signal happens.
4338 @value{GDBN} should not mention the occurrence of the signal at all. This
4339 implies the @code{nostop} keyword as well.
4343 @value{GDBN} should allow your program to see this signal; your program
4344 can handle the signal, or else it may terminate if the signal is fatal
4345 and not handled. @code{pass} and @code{noignore} are synonyms.
4349 @value{GDBN} should not allow your program to see this signal.
4350 @code{nopass} and @code{ignore} are synonyms.
4354 When a signal stops your program, the signal is not visible to the
4356 continue. Your program sees the signal then, if @code{pass} is in
4357 effect for the signal in question @emph{at that time}. In other words,
4358 after @value{GDBN} reports a signal, you can use the @code{handle}
4359 command with @code{pass} or @code{nopass} to control whether your
4360 program sees that signal when you continue.
4362 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4363 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4364 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4367 You can also use the @code{signal} command to prevent your program from
4368 seeing a signal, or cause it to see a signal it normally would not see,
4369 or to give it any signal at any time. For example, if your program stopped
4370 due to some sort of memory reference error, you might store correct
4371 values into the erroneous variables and continue, hoping to see more
4372 execution; but your program would probably terminate immediately as
4373 a result of the fatal signal once it saw the signal. To prevent this,
4374 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4378 @section Stopping and Starting Multi-thread Programs
4380 When your program has multiple threads (@pxref{Threads,, Debugging
4381 Programs with Multiple Threads}), you can choose whether to set
4382 breakpoints on all threads, or on a particular thread.
4385 @cindex breakpoints and threads
4386 @cindex thread breakpoints
4387 @kindex break @dots{} thread @var{threadno}
4388 @item break @var{linespec} thread @var{threadno}
4389 @itemx break @var{linespec} thread @var{threadno} if @dots{}
4390 @var{linespec} specifies source lines; there are several ways of
4391 writing them (@pxref{Specify Location}), but the effect is always to
4392 specify some source line.
4394 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
4395 to specify that you only want @value{GDBN} to stop the program when a
4396 particular thread reaches this breakpoint. @var{threadno} is one of the
4397 numeric thread identifiers assigned by @value{GDBN}, shown in the first
4398 column of the @samp{info threads} display.
4400 If you do not specify @samp{thread @var{threadno}} when you set a
4401 breakpoint, the breakpoint applies to @emph{all} threads of your
4404 You can use the @code{thread} qualifier on conditional breakpoints as
4405 well; in this case, place @samp{thread @var{threadno}} before the
4406 breakpoint condition, like this:
4409 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
4414 @cindex stopped threads
4415 @cindex threads, stopped
4416 Whenever your program stops under @value{GDBN} for any reason,
4417 @emph{all} threads of execution stop, not just the current thread. This
4418 allows you to examine the overall state of the program, including
4419 switching between threads, without worrying that things may change
4422 @cindex thread breakpoints and system calls
4423 @cindex system calls and thread breakpoints
4424 @cindex premature return from system calls
4425 There is an unfortunate side effect. If one thread stops for a
4426 breakpoint, or for some other reason, and another thread is blocked in a
4427 system call, then the system call may return prematurely. This is a
4428 consequence of the interaction between multiple threads and the signals
4429 that @value{GDBN} uses to implement breakpoints and other events that
4432 To handle this problem, your program should check the return value of
4433 each system call and react appropriately. This is good programming
4436 For example, do not write code like this:
4442 The call to @code{sleep} will return early if a different thread stops
4443 at a breakpoint or for some other reason.
4445 Instead, write this:
4450 unslept = sleep (unslept);
4453 A system call is allowed to return early, so the system is still
4454 conforming to its specification. But @value{GDBN} does cause your
4455 multi-threaded program to behave differently than it would without
4458 Also, @value{GDBN} uses internal breakpoints in the thread library to
4459 monitor certain events such as thread creation and thread destruction.
4460 When such an event happens, a system call in another thread may return
4461 prematurely, even though your program does not appear to stop.
4463 @cindex continuing threads
4464 @cindex threads, continuing
4465 Conversely, whenever you restart the program, @emph{all} threads start
4466 executing. @emph{This is true even when single-stepping} with commands
4467 like @code{step} or @code{next}.
4469 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4470 Since thread scheduling is up to your debugging target's operating
4471 system (not controlled by @value{GDBN}), other threads may
4472 execute more than one statement while the current thread completes a
4473 single step. Moreover, in general other threads stop in the middle of a
4474 statement, rather than at a clean statement boundary, when the program
4477 You might even find your program stopped in another thread after
4478 continuing or even single-stepping. This happens whenever some other
4479 thread runs into a breakpoint, a signal, or an exception before the
4480 first thread completes whatever you requested.
4482 On some OSes, you can lock the OS scheduler and thus allow only a single
4486 @item set scheduler-locking @var{mode}
4487 @cindex scheduler locking mode
4488 @cindex lock scheduler
4489 Set the scheduler locking mode. If it is @code{off}, then there is no
4490 locking and any thread may run at any time. If @code{on}, then only the
4491 current thread may run when the inferior is resumed. The @code{step}
4492 mode optimizes for single-stepping. It stops other threads from
4493 ``seizing the prompt'' by preempting the current thread while you are
4494 stepping. Other threads will only rarely (or never) get a chance to run
4495 when you step. They are more likely to run when you @samp{next} over a
4496 function call, and they are completely free to run when you use commands
4497 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4498 thread hits a breakpoint during its timeslice, they will never steal the
4499 @value{GDBN} prompt away from the thread that you are debugging.
4501 @item show scheduler-locking
4502 Display the current scheduler locking mode.
4507 @chapter Examining the Stack
4509 When your program has stopped, the first thing you need to know is where it
4510 stopped and how it got there.
4513 Each time your program performs a function call, information about the call
4515 That information includes the location of the call in your program,
4516 the arguments of the call,
4517 and the local variables of the function being called.
4518 The information is saved in a block of data called a @dfn{stack frame}.
4519 The stack frames are allocated in a region of memory called the @dfn{call
4522 When your program stops, the @value{GDBN} commands for examining the
4523 stack allow you to see all of this information.
4525 @cindex selected frame
4526 One of the stack frames is @dfn{selected} by @value{GDBN} and many
4527 @value{GDBN} commands refer implicitly to the selected frame. In
4528 particular, whenever you ask @value{GDBN} for the value of a variable in
4529 your program, the value is found in the selected frame. There are
4530 special @value{GDBN} commands to select whichever frame you are
4531 interested in. @xref{Selection, ,Selecting a Frame}.
4533 When your program stops, @value{GDBN} automatically selects the
4534 currently executing frame and describes it briefly, similar to the
4535 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
4538 * Frames:: Stack frames
4539 * Backtrace:: Backtraces
4540 * Selection:: Selecting a frame
4541 * Frame Info:: Information on a frame
4546 @section Stack Frames
4548 @cindex frame, definition
4550 The call stack is divided up into contiguous pieces called @dfn{stack
4551 frames}, or @dfn{frames} for short; each frame is the data associated
4552 with one call to one function. The frame contains the arguments given
4553 to the function, the function's local variables, and the address at
4554 which the function is executing.
4556 @cindex initial frame
4557 @cindex outermost frame
4558 @cindex innermost frame
4559 When your program is started, the stack has only one frame, that of the
4560 function @code{main}. This is called the @dfn{initial} frame or the
4561 @dfn{outermost} frame. Each time a function is called, a new frame is
4562 made. Each time a function returns, the frame for that function invocation
4563 is eliminated. If a function is recursive, there can be many frames for
4564 the same function. The frame for the function in which execution is
4565 actually occurring is called the @dfn{innermost} frame. This is the most
4566 recently created of all the stack frames that still exist.
4568 @cindex frame pointer
4569 Inside your program, stack frames are identified by their addresses. A
4570 stack frame consists of many bytes, each of which has its own address; each
4571 kind of computer has a convention for choosing one byte whose
4572 address serves as the address of the frame. Usually this address is kept
4573 in a register called the @dfn{frame pointer register}
4574 (@pxref{Registers, $fp}) while execution is going on in that frame.
4576 @cindex frame number
4577 @value{GDBN} assigns numbers to all existing stack frames, starting with
4578 zero for the innermost frame, one for the frame that called it,
4579 and so on upward. These numbers do not really exist in your program;
4580 they are assigned by @value{GDBN} to give you a way of designating stack
4581 frames in @value{GDBN} commands.
4583 @c The -fomit-frame-pointer below perennially causes hbox overflow
4584 @c underflow problems.
4585 @cindex frameless execution
4586 Some compilers provide a way to compile functions so that they operate
4587 without stack frames. (For example, the @value{NGCC} option
4589 @samp{-fomit-frame-pointer}
4591 generates functions without a frame.)
4592 This is occasionally done with heavily used library functions to save
4593 the frame setup time. @value{GDBN} has limited facilities for dealing
4594 with these function invocations. If the innermost function invocation
4595 has no stack frame, @value{GDBN} nevertheless regards it as though
4596 it had a separate frame, which is numbered zero as usual, allowing
4597 correct tracing of the function call chain. However, @value{GDBN} has
4598 no provision for frameless functions elsewhere in the stack.
4601 @kindex frame@r{, command}
4602 @cindex current stack frame
4603 @item frame @var{args}
4604 The @code{frame} command allows you to move from one stack frame to another,
4605 and to print the stack frame you select. @var{args} may be either the
4606 address of the frame or the stack frame number. Without an argument,
4607 @code{frame} prints the current stack frame.
4609 @kindex select-frame
4610 @cindex selecting frame silently
4612 The @code{select-frame} command allows you to move from one stack frame
4613 to another without printing the frame. This is the silent version of
4621 @cindex call stack traces
4622 A backtrace is a summary of how your program got where it is. It shows one
4623 line per frame, for many frames, starting with the currently executing
4624 frame (frame zero), followed by its caller (frame one), and on up the
4629 @kindex bt @r{(@code{backtrace})}
4632 Print a backtrace of the entire stack: one line per frame for all
4633 frames in the stack.
4635 You can stop the backtrace at any time by typing the system interrupt
4636 character, normally @kbd{Ctrl-c}.
4638 @item backtrace @var{n}
4640 Similar, but print only the innermost @var{n} frames.
4642 @item backtrace -@var{n}
4644 Similar, but print only the outermost @var{n} frames.
4646 @item backtrace full
4648 @itemx bt full @var{n}
4649 @itemx bt full -@var{n}
4650 Print the values of the local variables also. @var{n} specifies the
4651 number of frames to print, as described above.
4656 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4657 are additional aliases for @code{backtrace}.
4659 @cindex multiple threads, backtrace
4660 In a multi-threaded program, @value{GDBN} by default shows the
4661 backtrace only for the current thread. To display the backtrace for
4662 several or all of the threads, use the command @code{thread apply}
4663 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
4664 apply all backtrace}, @value{GDBN} will display the backtrace for all
4665 the threads; this is handy when you debug a core dump of a
4666 multi-threaded program.
4668 Each line in the backtrace shows the frame number and the function name.
4669 The program counter value is also shown---unless you use @code{set
4670 print address off}. The backtrace also shows the source file name and
4671 line number, as well as the arguments to the function. The program
4672 counter value is omitted if it is at the beginning of the code for that
4675 Here is an example of a backtrace. It was made with the command
4676 @samp{bt 3}, so it shows the innermost three frames.
4680 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4682 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4683 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4685 (More stack frames follow...)
4690 The display for frame zero does not begin with a program counter
4691 value, indicating that your program has stopped at the beginning of the
4692 code for line @code{993} of @code{builtin.c}.
4694 @cindex value optimized out, in backtrace
4695 @cindex function call arguments, optimized out
4696 If your program was compiled with optimizations, some compilers will
4697 optimize away arguments passed to functions if those arguments are
4698 never used after the call. Such optimizations generate code that
4699 passes arguments through registers, but doesn't store those arguments
4700 in the stack frame. @value{GDBN} has no way of displaying such
4701 arguments in stack frames other than the innermost one. Here's what
4702 such a backtrace might look like:
4706 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4708 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
4709 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
4711 (More stack frames follow...)
4716 The values of arguments that were not saved in their stack frames are
4717 shown as @samp{<value optimized out>}.
4719 If you need to display the values of such optimized-out arguments,
4720 either deduce that from other variables whose values depend on the one
4721 you are interested in, or recompile without optimizations.
4723 @cindex backtrace beyond @code{main} function
4724 @cindex program entry point
4725 @cindex startup code, and backtrace
4726 Most programs have a standard user entry point---a place where system
4727 libraries and startup code transition into user code. For C this is
4728 @code{main}@footnote{
4729 Note that embedded programs (the so-called ``free-standing''
4730 environment) are not required to have a @code{main} function as the
4731 entry point. They could even have multiple entry points.}.
4732 When @value{GDBN} finds the entry function in a backtrace
4733 it will terminate the backtrace, to avoid tracing into highly
4734 system-specific (and generally uninteresting) code.
4736 If you need to examine the startup code, or limit the number of levels
4737 in a backtrace, you can change this behavior:
4740 @item set backtrace past-main
4741 @itemx set backtrace past-main on
4742 @kindex set backtrace
4743 Backtraces will continue past the user entry point.
4745 @item set backtrace past-main off
4746 Backtraces will stop when they encounter the user entry point. This is the
4749 @item show backtrace past-main
4750 @kindex show backtrace
4751 Display the current user entry point backtrace policy.
4753 @item set backtrace past-entry
4754 @itemx set backtrace past-entry on
4755 Backtraces will continue past the internal entry point of an application.
4756 This entry point is encoded by the linker when the application is built,
4757 and is likely before the user entry point @code{main} (or equivalent) is called.
4759 @item set backtrace past-entry off
4760 Backtraces will stop when they encounter the internal entry point of an
4761 application. This is the default.
4763 @item show backtrace past-entry
4764 Display the current internal entry point backtrace policy.
4766 @item set backtrace limit @var{n}
4767 @itemx set backtrace limit 0
4768 @cindex backtrace limit
4769 Limit the backtrace to @var{n} levels. A value of zero means
4772 @item show backtrace limit
4773 Display the current limit on backtrace levels.
4777 @section Selecting a Frame
4779 Most commands for examining the stack and other data in your program work on
4780 whichever stack frame is selected at the moment. Here are the commands for
4781 selecting a stack frame; all of them finish by printing a brief description
4782 of the stack frame just selected.
4785 @kindex frame@r{, selecting}
4786 @kindex f @r{(@code{frame})}
4789 Select frame number @var{n}. Recall that frame zero is the innermost
4790 (currently executing) frame, frame one is the frame that called the
4791 innermost one, and so on. The highest-numbered frame is the one for
4794 @item frame @var{addr}
4796 Select the frame at address @var{addr}. This is useful mainly if the
4797 chaining of stack frames has been damaged by a bug, making it
4798 impossible for @value{GDBN} to assign numbers properly to all frames. In
4799 addition, this can be useful when your program has multiple stacks and
4800 switches between them.
4802 On the SPARC architecture, @code{frame} needs two addresses to
4803 select an arbitrary frame: a frame pointer and a stack pointer.
4805 On the MIPS and Alpha architecture, it needs two addresses: a stack
4806 pointer and a program counter.
4808 On the 29k architecture, it needs three addresses: a register stack
4809 pointer, a program counter, and a memory stack pointer.
4813 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4814 advances toward the outermost frame, to higher frame numbers, to frames
4815 that have existed longer. @var{n} defaults to one.
4818 @kindex do @r{(@code{down})}
4820 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4821 advances toward the innermost frame, to lower frame numbers, to frames
4822 that were created more recently. @var{n} defaults to one. You may
4823 abbreviate @code{down} as @code{do}.
4826 All of these commands end by printing two lines of output describing the
4827 frame. The first line shows the frame number, the function name, the
4828 arguments, and the source file and line number of execution in that
4829 frame. The second line shows the text of that source line.
4837 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4839 10 read_input_file (argv[i]);
4843 After such a printout, the @code{list} command with no arguments
4844 prints ten lines centered on the point of execution in the frame.
4845 You can also edit the program at the point of execution with your favorite
4846 editing program by typing @code{edit}.
4847 @xref{List, ,Printing Source Lines},
4851 @kindex down-silently
4853 @item up-silently @var{n}
4854 @itemx down-silently @var{n}
4855 These two commands are variants of @code{up} and @code{down},
4856 respectively; they differ in that they do their work silently, without
4857 causing display of the new frame. They are intended primarily for use
4858 in @value{GDBN} command scripts, where the output might be unnecessary and
4863 @section Information About a Frame
4865 There are several other commands to print information about the selected
4871 When used without any argument, this command does not change which
4872 frame is selected, but prints a brief description of the currently
4873 selected stack frame. It can be abbreviated @code{f}. With an
4874 argument, this command is used to select a stack frame.
4875 @xref{Selection, ,Selecting a Frame}.
4878 @kindex info f @r{(@code{info frame})}
4881 This command prints a verbose description of the selected stack frame,
4886 the address of the frame
4888 the address of the next frame down (called by this frame)
4890 the address of the next frame up (caller of this frame)
4892 the language in which the source code corresponding to this frame is written
4894 the address of the frame's arguments
4896 the address of the frame's local variables
4898 the program counter saved in it (the address of execution in the caller frame)
4900 which registers were saved in the frame
4903 @noindent The verbose description is useful when
4904 something has gone wrong that has made the stack format fail to fit
4905 the usual conventions.
4907 @item info frame @var{addr}
4908 @itemx info f @var{addr}
4909 Print a verbose description of the frame at address @var{addr}, without
4910 selecting that frame. The selected frame remains unchanged by this
4911 command. This requires the same kind of address (more than one for some
4912 architectures) that you specify in the @code{frame} command.
4913 @xref{Selection, ,Selecting a Frame}.
4917 Print the arguments of the selected frame, each on a separate line.
4921 Print the local variables of the selected frame, each on a separate
4922 line. These are all variables (declared either static or automatic)
4923 accessible at the point of execution of the selected frame.
4926 @cindex catch exceptions, list active handlers
4927 @cindex exception handlers, how to list
4929 Print a list of all the exception handlers that are active in the
4930 current stack frame at the current point of execution. To see other
4931 exception handlers, visit the associated frame (using the @code{up},
4932 @code{down}, or @code{frame} commands); then type @code{info catch}.
4933 @xref{Set Catchpoints, , Setting Catchpoints}.
4939 @chapter Examining Source Files
4941 @value{GDBN} can print parts of your program's source, since the debugging
4942 information recorded in the program tells @value{GDBN} what source files were
4943 used to build it. When your program stops, @value{GDBN} spontaneously prints
4944 the line where it stopped. Likewise, when you select a stack frame
4945 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
4946 execution in that frame has stopped. You can print other portions of
4947 source files by explicit command.
4949 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4950 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4951 @value{GDBN} under @sc{gnu} Emacs}.
4954 * List:: Printing source lines
4955 * Specify Location:: How to specify code locations
4956 * Edit:: Editing source files
4957 * Search:: Searching source files
4958 * Source Path:: Specifying source directories
4959 * Machine Code:: Source and machine code
4963 @section Printing Source Lines
4966 @kindex l @r{(@code{list})}
4967 To print lines from a source file, use the @code{list} command
4968 (abbreviated @code{l}). By default, ten lines are printed.
4969 There are several ways to specify what part of the file you want to
4970 print; see @ref{Specify Location}, for the full list.
4972 Here are the forms of the @code{list} command most commonly used:
4975 @item list @var{linenum}
4976 Print lines centered around line number @var{linenum} in the
4977 current source file.
4979 @item list @var{function}
4980 Print lines centered around the beginning of function
4984 Print more lines. If the last lines printed were printed with a
4985 @code{list} command, this prints lines following the last lines
4986 printed; however, if the last line printed was a solitary line printed
4987 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4988 Stack}), this prints lines centered around that line.
4991 Print lines just before the lines last printed.
4994 @cindex @code{list}, how many lines to display
4995 By default, @value{GDBN} prints ten source lines with any of these forms of
4996 the @code{list} command. You can change this using @code{set listsize}:
4999 @kindex set listsize
5000 @item set listsize @var{count}
5001 Make the @code{list} command display @var{count} source lines (unless
5002 the @code{list} argument explicitly specifies some other number).
5004 @kindex show listsize
5006 Display the number of lines that @code{list} prints.
5009 Repeating a @code{list} command with @key{RET} discards the argument,
5010 so it is equivalent to typing just @code{list}. This is more useful
5011 than listing the same lines again. An exception is made for an
5012 argument of @samp{-}; that argument is preserved in repetition so that
5013 each repetition moves up in the source file.
5015 In general, the @code{list} command expects you to supply zero, one or two
5016 @dfn{linespecs}. Linespecs specify source lines; there are several ways
5017 of writing them (@pxref{Specify Location}), but the effect is always
5018 to specify some source line.
5020 Here is a complete description of the possible arguments for @code{list}:
5023 @item list @var{linespec}
5024 Print lines centered around the line specified by @var{linespec}.
5026 @item list @var{first},@var{last}
5027 Print lines from @var{first} to @var{last}. Both arguments are
5028 linespecs. When a @code{list} command has two linespecs, and the
5029 source file of the second linespec is omitted, this refers to
5030 the same source file as the first linespec.
5032 @item list ,@var{last}
5033 Print lines ending with @var{last}.
5035 @item list @var{first},
5036 Print lines starting with @var{first}.
5039 Print lines just after the lines last printed.
5042 Print lines just before the lines last printed.
5045 As described in the preceding table.
5048 @node Specify Location
5049 @section Specifying a Location
5050 @cindex specifying location
5053 Several @value{GDBN} commands accept arguments that specify a location
5054 of your program's code. Since @value{GDBN} is a source-level
5055 debugger, a location usually specifies some line in the source code;
5056 for that reason, locations are also known as @dfn{linespecs}.
5058 Here are all the different ways of specifying a code location that
5059 @value{GDBN} understands:
5063 Specifies the line number @var{linenum} of the current source file.
5066 @itemx +@var{offset}
5067 Specifies the line @var{offset} lines before or after the @dfn{current
5068 line}. For the @code{list} command, the current line is the last one
5069 printed; for the breakpoint commands, this is the line at which
5070 execution stopped in the currently selected @dfn{stack frame}
5071 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
5072 used as the second of the two linespecs in a @code{list} command,
5073 this specifies the line @var{offset} lines up or down from the first
5076 @item @var{filename}:@var{linenum}
5077 Specifies the line @var{linenum} in the source file @var{filename}.
5079 @item @var{function}
5080 Specifies the line that begins the body of the function @var{function}.
5081 For example, in C, this is the line with the open brace.
5083 @item @var{filename}:@var{function}
5084 Specifies the line that begins the body of the function @var{function}
5085 in the file @var{filename}. You only need the file name with a
5086 function name to avoid ambiguity when there are identically named
5087 functions in different source files.
5089 @item *@var{address}
5090 Specifies the program address @var{address}. For line-oriented
5091 commands, such as @code{list} and @code{edit}, this specifies a source
5092 line that contains @var{address}. For @code{break} and other
5093 breakpoint oriented commands, this can be used to set breakpoints in
5094 parts of your program which do not have debugging information or
5097 Here @var{address} may be any expression valid in the current working
5098 language (@pxref{Languages, working language}) that specifies a code
5099 address. In addition, as a convenience, @value{GDBN} extends the
5100 semantics of expressions used in locations to cover the situations
5101 that frequently happen during debugging. Here are the various forms
5105 @item @var{expression}
5106 Any expression valid in the current working language.
5108 @item @var{funcaddr}
5109 An address of a function or procedure derived from its name. In C,
5110 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
5111 simply the function's name @var{function} (and actually a special case
5112 of a valid expression). In Pascal and Modula-2, this is
5113 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
5114 (although the Pascal form also works).
5116 This form specifies the address of the function's first instruction,
5117 before the stack frame and arguments have been set up.
5119 @item '@var{filename}'::@var{funcaddr}
5120 Like @var{funcaddr} above, but also specifies the name of the source
5121 file explicitly. This is useful if the name of the function does not
5122 specify the function unambiguously, e.g., if there are several
5123 functions with identical names in different source files.
5130 @section Editing Source Files
5131 @cindex editing source files
5134 @kindex e @r{(@code{edit})}
5135 To edit the lines in a source file, use the @code{edit} command.
5136 The editing program of your choice
5137 is invoked with the current line set to
5138 the active line in the program.
5139 Alternatively, there are several ways to specify what part of the file you
5140 want to print if you want to see other parts of the program:
5143 @item edit @var{location}
5144 Edit the source file specified by @code{location}. Editing starts at
5145 that @var{location}, e.g., at the specified source line of the
5146 specified file. @xref{Specify Location}, for all the possible forms
5147 of the @var{location} argument; here are the forms of the @code{edit}
5148 command most commonly used:
5151 @item edit @var{number}
5152 Edit the current source file with @var{number} as the active line number.
5154 @item edit @var{function}
5155 Edit the file containing @var{function} at the beginning of its definition.
5160 @subsection Choosing your Editor
5161 You can customize @value{GDBN} to use any editor you want
5163 The only restriction is that your editor (say @code{ex}), recognizes the
5164 following command-line syntax:
5166 ex +@var{number} file
5168 The optional numeric value +@var{number} specifies the number of the line in
5169 the file where to start editing.}.
5170 By default, it is @file{@value{EDITOR}}, but you can change this
5171 by setting the environment variable @code{EDITOR} before using
5172 @value{GDBN}. For example, to configure @value{GDBN} to use the
5173 @code{vi} editor, you could use these commands with the @code{sh} shell:
5179 or in the @code{csh} shell,
5181 setenv EDITOR /usr/bin/vi
5186 @section Searching Source Files
5187 @cindex searching source files
5189 There are two commands for searching through the current source file for a
5194 @kindex forward-search
5195 @item forward-search @var{regexp}
5196 @itemx search @var{regexp}
5197 The command @samp{forward-search @var{regexp}} checks each line,
5198 starting with the one following the last line listed, for a match for
5199 @var{regexp}. It lists the line that is found. You can use the
5200 synonym @samp{search @var{regexp}} or abbreviate the command name as
5203 @kindex reverse-search
5204 @item reverse-search @var{regexp}
5205 The command @samp{reverse-search @var{regexp}} checks each line, starting
5206 with the one before the last line listed and going backward, for a match
5207 for @var{regexp}. It lists the line that is found. You can abbreviate
5208 this command as @code{rev}.
5212 @section Specifying Source Directories
5215 @cindex directories for source files
5216 Executable programs sometimes do not record the directories of the source
5217 files from which they were compiled, just the names. Even when they do,
5218 the directories could be moved between the compilation and your debugging
5219 session. @value{GDBN} has a list of directories to search for source files;
5220 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
5221 it tries all the directories in the list, in the order they are present
5222 in the list, until it finds a file with the desired name.
5224 For example, suppose an executable references the file
5225 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
5226 @file{/mnt/cross}. The file is first looked up literally; if this
5227 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
5228 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
5229 message is printed. @value{GDBN} does not look up the parts of the
5230 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
5231 Likewise, the subdirectories of the source path are not searched: if
5232 the source path is @file{/mnt/cross}, and the binary refers to
5233 @file{foo.c}, @value{GDBN} would not find it under
5234 @file{/mnt/cross/usr/src/foo-1.0/lib}.
5236 Plain file names, relative file names with leading directories, file
5237 names containing dots, etc.@: are all treated as described above; for
5238 instance, if the source path is @file{/mnt/cross}, and the source file
5239 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
5240 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
5241 that---@file{/mnt/cross/foo.c}.
5243 Note that the executable search path is @emph{not} used to locate the
5246 Whenever you reset or rearrange the source path, @value{GDBN} clears out
5247 any information it has cached about where source files are found and where
5248 each line is in the file.
5252 When you start @value{GDBN}, its source path includes only @samp{cdir}
5253 and @samp{cwd}, in that order.
5254 To add other directories, use the @code{directory} command.
5256 The search path is used to find both program source files and @value{GDBN}
5257 script files (read using the @samp{-command} option and @samp{source} command).
5259 In addition to the source path, @value{GDBN} provides a set of commands
5260 that manage a list of source path substitution rules. A @dfn{substitution
5261 rule} specifies how to rewrite source directories stored in the program's
5262 debug information in case the sources were moved to a different
5263 directory between compilation and debugging. A rule is made of
5264 two strings, the first specifying what needs to be rewritten in
5265 the path, and the second specifying how it should be rewritten.
5266 In @ref{set substitute-path}, we name these two parts @var{from} and
5267 @var{to} respectively. @value{GDBN} does a simple string replacement
5268 of @var{from} with @var{to} at the start of the directory part of the
5269 source file name, and uses that result instead of the original file
5270 name to look up the sources.
5272 Using the previous example, suppose the @file{foo-1.0} tree has been
5273 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
5274 @value{GDBN} to replace @file{/usr/src} in all source path names with
5275 @file{/mnt/cross}. The first lookup will then be
5276 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
5277 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
5278 substitution rule, use the @code{set substitute-path} command
5279 (@pxref{set substitute-path}).
5281 To avoid unexpected substitution results, a rule is applied only if the
5282 @var{from} part of the directory name ends at a directory separator.
5283 For instance, a rule substituting @file{/usr/source} into
5284 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
5285 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
5286 is applied only at the beginning of the directory name, this rule will
5287 not be applied to @file{/root/usr/source/baz.c} either.
5289 In many cases, you can achieve the same result using the @code{directory}
5290 command. However, @code{set substitute-path} can be more efficient in
5291 the case where the sources are organized in a complex tree with multiple
5292 subdirectories. With the @code{directory} command, you need to add each
5293 subdirectory of your project. If you moved the entire tree while
5294 preserving its internal organization, then @code{set substitute-path}
5295 allows you to direct the debugger to all the sources with one single
5298 @code{set substitute-path} is also more than just a shortcut command.
5299 The source path is only used if the file at the original location no
5300 longer exists. On the other hand, @code{set substitute-path} modifies
5301 the debugger behavior to look at the rewritten location instead. So, if
5302 for any reason a source file that is not relevant to your executable is
5303 located at the original location, a substitution rule is the only
5304 method available to point @value{GDBN} at the new location.
5307 @item directory @var{dirname} @dots{}
5308 @item dir @var{dirname} @dots{}
5309 Add directory @var{dirname} to the front of the source path. Several
5310 directory names may be given to this command, separated by @samp{:}
5311 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
5312 part of absolute file names) or
5313 whitespace. You may specify a directory that is already in the source
5314 path; this moves it forward, so @value{GDBN} searches it sooner.
5318 @vindex $cdir@r{, convenience variable}
5319 @vindex $cwd@r{, convenience variable}
5320 @cindex compilation directory
5321 @cindex current directory
5322 @cindex working directory
5323 @cindex directory, current
5324 @cindex directory, compilation
5325 You can use the string @samp{$cdir} to refer to the compilation
5326 directory (if one is recorded), and @samp{$cwd} to refer to the current
5327 working directory. @samp{$cwd} is not the same as @samp{.}---the former
5328 tracks the current working directory as it changes during your @value{GDBN}
5329 session, while the latter is immediately expanded to the current
5330 directory at the time you add an entry to the source path.
5333 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
5335 @c RET-repeat for @code{directory} is explicitly disabled, but since
5336 @c repeating it would be a no-op we do not say that. (thanks to RMS)
5338 @item show directories
5339 @kindex show directories
5340 Print the source path: show which directories it contains.
5342 @anchor{set substitute-path}
5343 @item set substitute-path @var{from} @var{to}
5344 @kindex set substitute-path
5345 Define a source path substitution rule, and add it at the end of the
5346 current list of existing substitution rules. If a rule with the same
5347 @var{from} was already defined, then the old rule is also deleted.
5349 For example, if the file @file{/foo/bar/baz.c} was moved to
5350 @file{/mnt/cross/baz.c}, then the command
5353 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
5357 will tell @value{GDBN} to replace @samp{/usr/src} with
5358 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
5359 @file{baz.c} even though it was moved.
5361 In the case when more than one substitution rule have been defined,
5362 the rules are evaluated one by one in the order where they have been
5363 defined. The first one matching, if any, is selected to perform
5366 For instance, if we had entered the following commands:
5369 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
5370 (@value{GDBP}) set substitute-path /usr/src /mnt/src
5374 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
5375 @file{/mnt/include/defs.h} by using the first rule. However, it would
5376 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
5377 @file{/mnt/src/lib/foo.c}.
5380 @item unset substitute-path [path]
5381 @kindex unset substitute-path
5382 If a path is specified, search the current list of substitution rules
5383 for a rule that would rewrite that path. Delete that rule if found.
5384 A warning is emitted by the debugger if no rule could be found.
5386 If no path is specified, then all substitution rules are deleted.
5388 @item show substitute-path [path]
5389 @kindex show substitute-path
5390 If a path is specified, then print the source path substitution rule
5391 which would rewrite that path, if any.
5393 If no path is specified, then print all existing source path substitution
5398 If your source path is cluttered with directories that are no longer of
5399 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
5400 versions of source. You can correct the situation as follows:
5404 Use @code{directory} with no argument to reset the source path to its default value.
5407 Use @code{directory} with suitable arguments to reinstall the
5408 directories you want in the source path. You can add all the
5409 directories in one command.
5413 @section Source and Machine Code
5414 @cindex source line and its code address
5416 You can use the command @code{info line} to map source lines to program
5417 addresses (and vice versa), and the command @code{disassemble} to display
5418 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
5419 mode, the @code{info line} command causes the arrow to point to the
5420 line specified. Also, @code{info line} prints addresses in symbolic form as
5425 @item info line @var{linespec}
5426 Print the starting and ending addresses of the compiled code for
5427 source line @var{linespec}. You can specify source lines in any of
5428 the ways documented in @ref{Specify Location}.
5431 For example, we can use @code{info line} to discover the location of
5432 the object code for the first line of function
5433 @code{m4_changequote}:
5435 @c FIXME: I think this example should also show the addresses in
5436 @c symbolic form, as they usually would be displayed.
5438 (@value{GDBP}) info line m4_changequote
5439 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
5443 @cindex code address and its source line
5444 We can also inquire (using @code{*@var{addr}} as the form for
5445 @var{linespec}) what source line covers a particular address:
5447 (@value{GDBP}) info line *0x63ff
5448 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
5451 @cindex @code{$_} and @code{info line}
5452 @cindex @code{x} command, default address
5453 @kindex x@r{(examine), and} info line
5454 After @code{info line}, the default address for the @code{x} command
5455 is changed to the starting address of the line, so that @samp{x/i} is
5456 sufficient to begin examining the machine code (@pxref{Memory,
5457 ,Examining Memory}). Also, this address is saved as the value of the
5458 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
5463 @cindex assembly instructions
5464 @cindex instructions, assembly
5465 @cindex machine instructions
5466 @cindex listing machine instructions
5468 This specialized command dumps a range of memory as machine
5469 instructions. The default memory range is the function surrounding the
5470 program counter of the selected frame. A single argument to this
5471 command is a program counter value; @value{GDBN} dumps the function
5472 surrounding this value. Two arguments specify a range of addresses
5473 (first inclusive, second exclusive) to dump.
5476 The following example shows the disassembly of a range of addresses of
5477 HP PA-RISC 2.0 code:
5480 (@value{GDBP}) disas 0x32c4 0x32e4
5481 Dump of assembler code from 0x32c4 to 0x32e4:
5482 0x32c4 <main+204>: addil 0,dp
5483 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
5484 0x32cc <main+212>: ldil 0x3000,r31
5485 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
5486 0x32d4 <main+220>: ldo 0(r31),rp
5487 0x32d8 <main+224>: addil -0x800,dp
5488 0x32dc <main+228>: ldo 0x588(r1),r26
5489 0x32e0 <main+232>: ldil 0x3000,r31
5490 End of assembler dump.
5493 Some architectures have more than one commonly-used set of instruction
5494 mnemonics or other syntax.
5496 For programs that were dynamically linked and use shared libraries,
5497 instructions that call functions or branch to locations in the shared
5498 libraries might show a seemingly bogus location---it's actually a
5499 location of the relocation table. On some architectures, @value{GDBN}
5500 might be able to resolve these to actual function names.
5503 @kindex set disassembly-flavor
5504 @cindex Intel disassembly flavor
5505 @cindex AT&T disassembly flavor
5506 @item set disassembly-flavor @var{instruction-set}
5507 Select the instruction set to use when disassembling the
5508 program via the @code{disassemble} or @code{x/i} commands.
5510 Currently this command is only defined for the Intel x86 family. You
5511 can set @var{instruction-set} to either @code{intel} or @code{att}.
5512 The default is @code{att}, the AT&T flavor used by default by Unix
5513 assemblers for x86-based targets.
5515 @kindex show disassembly-flavor
5516 @item show disassembly-flavor
5517 Show the current setting of the disassembly flavor.
5522 @chapter Examining Data
5524 @cindex printing data
5525 @cindex examining data
5528 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
5529 @c document because it is nonstandard... Under Epoch it displays in a
5530 @c different window or something like that.
5531 The usual way to examine data in your program is with the @code{print}
5532 command (abbreviated @code{p}), or its synonym @code{inspect}. It
5533 evaluates and prints the value of an expression of the language your
5534 program is written in (@pxref{Languages, ,Using @value{GDBN} with
5535 Different Languages}).
5538 @item print @var{expr}
5539 @itemx print /@var{f} @var{expr}
5540 @var{expr} is an expression (in the source language). By default the
5541 value of @var{expr} is printed in a format appropriate to its data type;
5542 you can choose a different format by specifying @samp{/@var{f}}, where
5543 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
5547 @itemx print /@var{f}
5548 @cindex reprint the last value
5549 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
5550 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
5551 conveniently inspect the same value in an alternative format.
5554 A more low-level way of examining data is with the @code{x} command.
5555 It examines data in memory at a specified address and prints it in a
5556 specified format. @xref{Memory, ,Examining Memory}.
5558 If you are interested in information about types, or about how the
5559 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
5560 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
5564 * Expressions:: Expressions
5565 * Variables:: Program variables
5566 * Arrays:: Artificial arrays
5567 * Output Formats:: Output formats
5568 * Memory:: Examining memory
5569 * Auto Display:: Automatic display
5570 * Print Settings:: Print settings
5571 * Value History:: Value history
5572 * Convenience Vars:: Convenience variables
5573 * Registers:: Registers
5574 * Floating Point Hardware:: Floating point hardware
5575 * Vector Unit:: Vector Unit
5576 * OS Information:: Auxiliary data provided by operating system
5577 * Memory Region Attributes:: Memory region attributes
5578 * Dump/Restore Files:: Copy between memory and a file
5579 * Core File Generation:: Cause a program dump its core
5580 * Character Sets:: Debugging programs that use a different
5581 character set than GDB does
5582 * Caching Remote Data:: Data caching for remote targets
5586 @section Expressions
5589 @code{print} and many other @value{GDBN} commands accept an expression and
5590 compute its value. Any kind of constant, variable or operator defined
5591 by the programming language you are using is valid in an expression in
5592 @value{GDBN}. This includes conditional expressions, function calls,
5593 casts, and string constants. It also includes preprocessor macros, if
5594 you compiled your program to include this information; see
5597 @cindex arrays in expressions
5598 @value{GDBN} supports array constants in expressions input by
5599 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
5600 you can use the command @code{print @{1, 2, 3@}} to build up an array in
5601 memory that is @code{malloc}ed in the target program.
5603 Because C is so widespread, most of the expressions shown in examples in
5604 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
5605 Languages}, for information on how to use expressions in other
5608 In this section, we discuss operators that you can use in @value{GDBN}
5609 expressions regardless of your programming language.
5611 @cindex casts, in expressions
5612 Casts are supported in all languages, not just in C, because it is so
5613 useful to cast a number into a pointer in order to examine a structure
5614 at that address in memory.
5615 @c FIXME: casts supported---Mod2 true?
5617 @value{GDBN} supports these operators, in addition to those common
5618 to programming languages:
5622 @samp{@@} is a binary operator for treating parts of memory as arrays.
5623 @xref{Arrays, ,Artificial Arrays}, for more information.
5626 @samp{::} allows you to specify a variable in terms of the file or
5627 function where it is defined. @xref{Variables, ,Program Variables}.
5629 @cindex @{@var{type}@}
5630 @cindex type casting memory
5631 @cindex memory, viewing as typed object
5632 @cindex casts, to view memory
5633 @item @{@var{type}@} @var{addr}
5634 Refers to an object of type @var{type} stored at address @var{addr} in
5635 memory. @var{addr} may be any expression whose value is an integer or
5636 pointer (but parentheses are required around binary operators, just as in
5637 a cast). This construct is allowed regardless of what kind of data is
5638 normally supposed to reside at @var{addr}.
5642 @section Program Variables
5644 The most common kind of expression to use is the name of a variable
5647 Variables in expressions are understood in the selected stack frame
5648 (@pxref{Selection, ,Selecting a Frame}); they must be either:
5652 global (or file-static)
5659 visible according to the scope rules of the
5660 programming language from the point of execution in that frame
5663 @noindent This means that in the function
5678 you can examine and use the variable @code{a} whenever your program is
5679 executing within the function @code{foo}, but you can only use or
5680 examine the variable @code{b} while your program is executing inside
5681 the block where @code{b} is declared.
5683 @cindex variable name conflict
5684 There is an exception: you can refer to a variable or function whose
5685 scope is a single source file even if the current execution point is not
5686 in this file. But it is possible to have more than one such variable or
5687 function with the same name (in different source files). If that
5688 happens, referring to that name has unpredictable effects. If you wish,
5689 you can specify a static variable in a particular function or file,
5690 using the colon-colon (@code{::}) notation:
5692 @cindex colon-colon, context for variables/functions
5694 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
5695 @cindex @code{::}, context for variables/functions
5698 @var{file}::@var{variable}
5699 @var{function}::@var{variable}
5703 Here @var{file} or @var{function} is the name of the context for the
5704 static @var{variable}. In the case of file names, you can use quotes to
5705 make sure @value{GDBN} parses the file name as a single word---for example,
5706 to print a global value of @code{x} defined in @file{f2.c}:
5709 (@value{GDBP}) p 'f2.c'::x
5712 @cindex C@t{++} scope resolution
5713 This use of @samp{::} is very rarely in conflict with the very similar
5714 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
5715 scope resolution operator in @value{GDBN} expressions.
5716 @c FIXME: Um, so what happens in one of those rare cases where it's in
5719 @cindex wrong values
5720 @cindex variable values, wrong
5721 @cindex function entry/exit, wrong values of variables
5722 @cindex optimized code, wrong values of variables
5724 @emph{Warning:} Occasionally, a local variable may appear to have the
5725 wrong value at certain points in a function---just after entry to a new
5726 scope, and just before exit.
5728 You may see this problem when you are stepping by machine instructions.
5729 This is because, on most machines, it takes more than one instruction to
5730 set up a stack frame (including local variable definitions); if you are
5731 stepping by machine instructions, variables may appear to have the wrong
5732 values until the stack frame is completely built. On exit, it usually
5733 also takes more than one machine instruction to destroy a stack frame;
5734 after you begin stepping through that group of instructions, local
5735 variable definitions may be gone.
5737 This may also happen when the compiler does significant optimizations.
5738 To be sure of always seeing accurate values, turn off all optimization
5741 @cindex ``No symbol "foo" in current context''
5742 Another possible effect of compiler optimizations is to optimize
5743 unused variables out of existence, or assign variables to registers (as
5744 opposed to memory addresses). Depending on the support for such cases
5745 offered by the debug info format used by the compiler, @value{GDBN}
5746 might not be able to display values for such local variables. If that
5747 happens, @value{GDBN} will print a message like this:
5750 No symbol "foo" in current context.
5753 To solve such problems, either recompile without optimizations, or use a
5754 different debug info format, if the compiler supports several such
5755 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
5756 usually supports the @option{-gstabs+} option. @option{-gstabs+}
5757 produces debug info in a format that is superior to formats such as
5758 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
5759 an effective form for debug info. @xref{Debugging Options,,Options
5760 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
5761 Compiler Collection (GCC)}.
5762 @xref{C, ,C and C@t{++}}, for more information about debug info formats
5763 that are best suited to C@t{++} programs.
5765 If you ask to print an object whose contents are unknown to
5766 @value{GDBN}, e.g., because its data type is not completely specified
5767 by the debug information, @value{GDBN} will say @samp{<incomplete
5768 type>}. @xref{Symbols, incomplete type}, for more about this.
5770 Strings are identified as arrays of @code{char} values without specified
5771 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
5772 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
5773 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
5774 defines literal string type @code{"char"} as @code{char} without a sign.
5779 signed char var1[] = "A";
5782 You get during debugging
5787 $2 = @{65 'A', 0 '\0'@}
5791 @section Artificial Arrays
5793 @cindex artificial array
5795 @kindex @@@r{, referencing memory as an array}
5796 It is often useful to print out several successive objects of the
5797 same type in memory; a section of an array, or an array of
5798 dynamically determined size for which only a pointer exists in the
5801 You can do this by referring to a contiguous span of memory as an
5802 @dfn{artificial array}, using the binary operator @samp{@@}. The left
5803 operand of @samp{@@} should be the first element of the desired array
5804 and be an individual object. The right operand should be the desired length
5805 of the array. The result is an array value whose elements are all of
5806 the type of the left argument. The first element is actually the left
5807 argument; the second element comes from bytes of memory immediately
5808 following those that hold the first element, and so on. Here is an
5809 example. If a program says
5812 int *array = (int *) malloc (len * sizeof (int));
5816 you can print the contents of @code{array} with
5822 The left operand of @samp{@@} must reside in memory. Array values made
5823 with @samp{@@} in this way behave just like other arrays in terms of
5824 subscripting, and are coerced to pointers when used in expressions.
5825 Artificial arrays most often appear in expressions via the value history
5826 (@pxref{Value History, ,Value History}), after printing one out.
5828 Another way to create an artificial array is to use a cast.
5829 This re-interprets a value as if it were an array.
5830 The value need not be in memory:
5832 (@value{GDBP}) p/x (short[2])0x12345678
5833 $1 = @{0x1234, 0x5678@}
5836 As a convenience, if you leave the array length out (as in
5837 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
5838 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
5840 (@value{GDBP}) p/x (short[])0x12345678
5841 $2 = @{0x1234, 0x5678@}
5844 Sometimes the artificial array mechanism is not quite enough; in
5845 moderately complex data structures, the elements of interest may not
5846 actually be adjacent---for example, if you are interested in the values
5847 of pointers in an array. One useful work-around in this situation is
5848 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
5849 Variables}) as a counter in an expression that prints the first
5850 interesting value, and then repeat that expression via @key{RET}. For
5851 instance, suppose you have an array @code{dtab} of pointers to
5852 structures, and you are interested in the values of a field @code{fv}
5853 in each structure. Here is an example of what you might type:
5863 @node Output Formats
5864 @section Output Formats
5866 @cindex formatted output
5867 @cindex output formats
5868 By default, @value{GDBN} prints a value according to its data type. Sometimes
5869 this is not what you want. For example, you might want to print a number
5870 in hex, or a pointer in decimal. Or you might want to view data in memory
5871 at a certain address as a character string or as an instruction. To do
5872 these things, specify an @dfn{output format} when you print a value.
5874 The simplest use of output formats is to say how to print a value
5875 already computed. This is done by starting the arguments of the
5876 @code{print} command with a slash and a format letter. The format
5877 letters supported are:
5881 Regard the bits of the value as an integer, and print the integer in
5885 Print as integer in signed decimal.
5888 Print as integer in unsigned decimal.
5891 Print as integer in octal.
5894 Print as integer in binary. The letter @samp{t} stands for ``two''.
5895 @footnote{@samp{b} cannot be used because these format letters are also
5896 used with the @code{x} command, where @samp{b} stands for ``byte'';
5897 see @ref{Memory,,Examining Memory}.}
5900 @cindex unknown address, locating
5901 @cindex locate address
5902 Print as an address, both absolute in hexadecimal and as an offset from
5903 the nearest preceding symbol. You can use this format used to discover
5904 where (in what function) an unknown address is located:
5907 (@value{GDBP}) p/a 0x54320
5908 $3 = 0x54320 <_initialize_vx+396>
5912 The command @code{info symbol 0x54320} yields similar results.
5913 @xref{Symbols, info symbol}.
5916 Regard as an integer and print it as a character constant. This
5917 prints both the numerical value and its character representation. The
5918 character representation is replaced with the octal escape @samp{\nnn}
5919 for characters outside the 7-bit @sc{ascii} range.
5921 Without this format, @value{GDBN} displays @code{char},
5922 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
5923 constants. Single-byte members of vectors are displayed as integer
5927 Regard the bits of the value as a floating point number and print
5928 using typical floating point syntax.
5931 @cindex printing strings
5932 @cindex printing byte arrays
5933 Regard as a string, if possible. With this format, pointers to single-byte
5934 data are displayed as null-terminated strings and arrays of single-byte data
5935 are displayed as fixed-length strings. Other values are displayed in their
5938 Without this format, @value{GDBN} displays pointers to and arrays of
5939 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
5940 strings. Single-byte members of a vector are displayed as an integer
5944 For example, to print the program counter in hex (@pxref{Registers}), type
5951 Note that no space is required before the slash; this is because command
5952 names in @value{GDBN} cannot contain a slash.
5954 To reprint the last value in the value history with a different format,
5955 you can use the @code{print} command with just a format and no
5956 expression. For example, @samp{p/x} reprints the last value in hex.
5959 @section Examining Memory
5961 You can use the command @code{x} (for ``examine'') to examine memory in
5962 any of several formats, independently of your program's data types.
5964 @cindex examining memory
5966 @kindex x @r{(examine memory)}
5967 @item x/@var{nfu} @var{addr}
5970 Use the @code{x} command to examine memory.
5973 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
5974 much memory to display and how to format it; @var{addr} is an
5975 expression giving the address where you want to start displaying memory.
5976 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
5977 Several commands set convenient defaults for @var{addr}.
5980 @item @var{n}, the repeat count
5981 The repeat count is a decimal integer; the default is 1. It specifies
5982 how much memory (counting by units @var{u}) to display.
5983 @c This really is **decimal**; unaffected by 'set radix' as of GDB
5986 @item @var{f}, the display format
5987 The display format is one of the formats used by @code{print}
5988 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
5989 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
5990 The default is @samp{x} (hexadecimal) initially. The default changes
5991 each time you use either @code{x} or @code{print}.
5993 @item @var{u}, the unit size
5994 The unit size is any of
6000 Halfwords (two bytes).
6002 Words (four bytes). This is the initial default.
6004 Giant words (eight bytes).
6007 Each time you specify a unit size with @code{x}, that size becomes the
6008 default unit the next time you use @code{x}. (For the @samp{s} and
6009 @samp{i} formats, the unit size is ignored and is normally not written.)
6011 @item @var{addr}, starting display address
6012 @var{addr} is the address where you want @value{GDBN} to begin displaying
6013 memory. The expression need not have a pointer value (though it may);
6014 it is always interpreted as an integer address of a byte of memory.
6015 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
6016 @var{addr} is usually just after the last address examined---but several
6017 other commands also set the default address: @code{info breakpoints} (to
6018 the address of the last breakpoint listed), @code{info line} (to the
6019 starting address of a line), and @code{print} (if you use it to display
6020 a value from memory).
6023 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
6024 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
6025 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
6026 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
6027 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
6029 Since the letters indicating unit sizes are all distinct from the
6030 letters specifying output formats, you do not have to remember whether
6031 unit size or format comes first; either order works. The output
6032 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
6033 (However, the count @var{n} must come first; @samp{wx4} does not work.)
6035 Even though the unit size @var{u} is ignored for the formats @samp{s}
6036 and @samp{i}, you might still want to use a count @var{n}; for example,
6037 @samp{3i} specifies that you want to see three machine instructions,
6038 including any operands. For convenience, especially when used with
6039 the @code{display} command, the @samp{i} format also prints branch delay
6040 slot instructions, if any, beyond the count specified, which immediately
6041 follow the last instruction that is within the count. The command
6042 @code{disassemble} gives an alternative way of inspecting machine
6043 instructions; see @ref{Machine Code,,Source and Machine Code}.
6045 All the defaults for the arguments to @code{x} are designed to make it
6046 easy to continue scanning memory with minimal specifications each time
6047 you use @code{x}. For example, after you have inspected three machine
6048 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
6049 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
6050 the repeat count @var{n} is used again; the other arguments default as
6051 for successive uses of @code{x}.
6053 @cindex @code{$_}, @code{$__}, and value history
6054 The addresses and contents printed by the @code{x} command are not saved
6055 in the value history because there is often too much of them and they
6056 would get in the way. Instead, @value{GDBN} makes these values available for
6057 subsequent use in expressions as values of the convenience variables
6058 @code{$_} and @code{$__}. After an @code{x} command, the last address
6059 examined is available for use in expressions in the convenience variable
6060 @code{$_}. The contents of that address, as examined, are available in
6061 the convenience variable @code{$__}.
6063 If the @code{x} command has a repeat count, the address and contents saved
6064 are from the last memory unit printed; this is not the same as the last
6065 address printed if several units were printed on the last line of output.
6067 @cindex remote memory comparison
6068 @cindex verify remote memory image
6069 When you are debugging a program running on a remote target machine
6070 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
6071 remote machine's memory against the executable file you downloaded to
6072 the target. The @code{compare-sections} command is provided for such
6076 @kindex compare-sections
6077 @item compare-sections @r{[}@var{section-name}@r{]}
6078 Compare the data of a loadable section @var{section-name} in the
6079 executable file of the program being debugged with the same section in
6080 the remote machine's memory, and report any mismatches. With no
6081 arguments, compares all loadable sections. This command's
6082 availability depends on the target's support for the @code{"qCRC"}
6087 @section Automatic Display
6088 @cindex automatic display
6089 @cindex display of expressions
6091 If you find that you want to print the value of an expression frequently
6092 (to see how it changes), you might want to add it to the @dfn{automatic
6093 display list} so that @value{GDBN} prints its value each time your program stops.
6094 Each expression added to the list is given a number to identify it;
6095 to remove an expression from the list, you specify that number.
6096 The automatic display looks like this:
6100 3: bar[5] = (struct hack *) 0x3804
6104 This display shows item numbers, expressions and their current values. As with
6105 displays you request manually using @code{x} or @code{print}, you can
6106 specify the output format you prefer; in fact, @code{display} decides
6107 whether to use @code{print} or @code{x} depending your format
6108 specification---it uses @code{x} if you specify either the @samp{i}
6109 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
6113 @item display @var{expr}
6114 Add the expression @var{expr} to the list of expressions to display
6115 each time your program stops. @xref{Expressions, ,Expressions}.
6117 @code{display} does not repeat if you press @key{RET} again after using it.
6119 @item display/@var{fmt} @var{expr}
6120 For @var{fmt} specifying only a display format and not a size or
6121 count, add the expression @var{expr} to the auto-display list but
6122 arrange to display it each time in the specified format @var{fmt}.
6123 @xref{Output Formats,,Output Formats}.
6125 @item display/@var{fmt} @var{addr}
6126 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
6127 number of units, add the expression @var{addr} as a memory address to
6128 be examined each time your program stops. Examining means in effect
6129 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
6132 For example, @samp{display/i $pc} can be helpful, to see the machine
6133 instruction about to be executed each time execution stops (@samp{$pc}
6134 is a common name for the program counter; @pxref{Registers, ,Registers}).
6137 @kindex delete display
6139 @item undisplay @var{dnums}@dots{}
6140 @itemx delete display @var{dnums}@dots{}
6141 Remove item numbers @var{dnums} from the list of expressions to display.
6143 @code{undisplay} does not repeat if you press @key{RET} after using it.
6144 (Otherwise you would just get the error @samp{No display number @dots{}}.)
6146 @kindex disable display
6147 @item disable display @var{dnums}@dots{}
6148 Disable the display of item numbers @var{dnums}. A disabled display
6149 item is not printed automatically, but is not forgotten. It may be
6150 enabled again later.
6152 @kindex enable display
6153 @item enable display @var{dnums}@dots{}
6154 Enable display of item numbers @var{dnums}. It becomes effective once
6155 again in auto display of its expression, until you specify otherwise.
6158 Display the current values of the expressions on the list, just as is
6159 done when your program stops.
6161 @kindex info display
6163 Print the list of expressions previously set up to display
6164 automatically, each one with its item number, but without showing the
6165 values. This includes disabled expressions, which are marked as such.
6166 It also includes expressions which would not be displayed right now
6167 because they refer to automatic variables not currently available.
6170 @cindex display disabled out of scope
6171 If a display expression refers to local variables, then it does not make
6172 sense outside the lexical context for which it was set up. Such an
6173 expression is disabled when execution enters a context where one of its
6174 variables is not defined. For example, if you give the command
6175 @code{display last_char} while inside a function with an argument
6176 @code{last_char}, @value{GDBN} displays this argument while your program
6177 continues to stop inside that function. When it stops elsewhere---where
6178 there is no variable @code{last_char}---the display is disabled
6179 automatically. The next time your program stops where @code{last_char}
6180 is meaningful, you can enable the display expression once again.
6182 @node Print Settings
6183 @section Print Settings
6185 @cindex format options
6186 @cindex print settings
6187 @value{GDBN} provides the following ways to control how arrays, structures,
6188 and symbols are printed.
6191 These settings are useful for debugging programs in any language:
6195 @item set print address
6196 @itemx set print address on
6197 @cindex print/don't print memory addresses
6198 @value{GDBN} prints memory addresses showing the location of stack
6199 traces, structure values, pointer values, breakpoints, and so forth,
6200 even when it also displays the contents of those addresses. The default
6201 is @code{on}. For example, this is what a stack frame display looks like with
6202 @code{set print address on}:
6207 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
6209 530 if (lquote != def_lquote)
6213 @item set print address off
6214 Do not print addresses when displaying their contents. For example,
6215 this is the same stack frame displayed with @code{set print address off}:
6219 (@value{GDBP}) set print addr off
6221 #0 set_quotes (lq="<<", rq=">>") at input.c:530
6222 530 if (lquote != def_lquote)
6226 You can use @samp{set print address off} to eliminate all machine
6227 dependent displays from the @value{GDBN} interface. For example, with
6228 @code{print address off}, you should get the same text for backtraces on
6229 all machines---whether or not they involve pointer arguments.
6232 @item show print address
6233 Show whether or not addresses are to be printed.
6236 When @value{GDBN} prints a symbolic address, it normally prints the
6237 closest earlier symbol plus an offset. If that symbol does not uniquely
6238 identify the address (for example, it is a name whose scope is a single
6239 source file), you may need to clarify. One way to do this is with
6240 @code{info line}, for example @samp{info line *0x4537}. Alternately,
6241 you can set @value{GDBN} to print the source file and line number when
6242 it prints a symbolic address:
6245 @item set print symbol-filename on
6246 @cindex source file and line of a symbol
6247 @cindex symbol, source file and line
6248 Tell @value{GDBN} to print the source file name and line number of a
6249 symbol in the symbolic form of an address.
6251 @item set print symbol-filename off
6252 Do not print source file name and line number of a symbol. This is the
6255 @item show print symbol-filename
6256 Show whether or not @value{GDBN} will print the source file name and
6257 line number of a symbol in the symbolic form of an address.
6260 Another situation where it is helpful to show symbol filenames and line
6261 numbers is when disassembling code; @value{GDBN} shows you the line
6262 number and source file that corresponds to each instruction.
6264 Also, you may wish to see the symbolic form only if the address being
6265 printed is reasonably close to the closest earlier symbol:
6268 @item set print max-symbolic-offset @var{max-offset}
6269 @cindex maximum value for offset of closest symbol
6270 Tell @value{GDBN} to only display the symbolic form of an address if the
6271 offset between the closest earlier symbol and the address is less than
6272 @var{max-offset}. The default is 0, which tells @value{GDBN}
6273 to always print the symbolic form of an address if any symbol precedes it.
6275 @item show print max-symbolic-offset
6276 Ask how large the maximum offset is that @value{GDBN} prints in a
6280 @cindex wild pointer, interpreting
6281 @cindex pointer, finding referent
6282 If you have a pointer and you are not sure where it points, try
6283 @samp{set print symbol-filename on}. Then you can determine the name
6284 and source file location of the variable where it points, using
6285 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
6286 For example, here @value{GDBN} shows that a variable @code{ptt} points
6287 at another variable @code{t}, defined in @file{hi2.c}:
6290 (@value{GDBP}) set print symbol-filename on
6291 (@value{GDBP}) p/a ptt
6292 $4 = 0xe008 <t in hi2.c>
6296 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
6297 does not show the symbol name and filename of the referent, even with
6298 the appropriate @code{set print} options turned on.
6301 Other settings control how different kinds of objects are printed:
6304 @item set print array
6305 @itemx set print array on
6306 @cindex pretty print arrays
6307 Pretty print arrays. This format is more convenient to read,
6308 but uses more space. The default is off.
6310 @item set print array off
6311 Return to compressed format for arrays.
6313 @item show print array
6314 Show whether compressed or pretty format is selected for displaying
6317 @cindex print array indexes
6318 @item set print array-indexes
6319 @itemx set print array-indexes on
6320 Print the index of each element when displaying arrays. May be more
6321 convenient to locate a given element in the array or quickly find the
6322 index of a given element in that printed array. The default is off.
6324 @item set print array-indexes off
6325 Stop printing element indexes when displaying arrays.
6327 @item show print array-indexes
6328 Show whether the index of each element is printed when displaying
6331 @item set print elements @var{number-of-elements}
6332 @cindex number of array elements to print
6333 @cindex limit on number of printed array elements
6334 Set a limit on how many elements of an array @value{GDBN} will print.
6335 If @value{GDBN} is printing a large array, it stops printing after it has
6336 printed the number of elements set by the @code{set print elements} command.
6337 This limit also applies to the display of strings.
6338 When @value{GDBN} starts, this limit is set to 200.
6339 Setting @var{number-of-elements} to zero means that the printing is unlimited.
6341 @item show print elements
6342 Display the number of elements of a large array that @value{GDBN} will print.
6343 If the number is 0, then the printing is unlimited.
6345 @item set print frame-arguments @var{value}
6346 @cindex printing frame argument values
6347 @cindex print all frame argument values
6348 @cindex print frame argument values for scalars only
6349 @cindex do not print frame argument values
6350 This command allows to control how the values of arguments are printed
6351 when the debugger prints a frame (@pxref{Frames}). The possible
6356 The values of all arguments are printed. This is the default.
6359 Print the value of an argument only if it is a scalar. The value of more
6360 complex arguments such as arrays, structures, unions, etc, is replaced
6361 by @code{@dots{}}. Here is an example where only scalar arguments are shown:
6364 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
6369 None of the argument values are printed. Instead, the value of each argument
6370 is replaced by @code{@dots{}}. In this case, the example above now becomes:
6373 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
6378 By default, all argument values are always printed. But this command
6379 can be useful in several cases. For instance, it can be used to reduce
6380 the amount of information printed in each frame, making the backtrace
6381 more readable. Also, this command can be used to improve performance
6382 when displaying Ada frames, because the computation of large arguments
6383 can sometimes be CPU-intensive, especiallly in large applications.
6384 Setting @code{print frame-arguments} to @code{scalars} or @code{none}
6385 avoids this computation, thus speeding up the display of each Ada frame.
6387 @item show print frame-arguments
6388 Show how the value of arguments should be displayed when printing a frame.
6390 @item set print repeats
6391 @cindex repeated array elements
6392 Set the threshold for suppressing display of repeated array
6393 elements. When the number of consecutive identical elements of an
6394 array exceeds the threshold, @value{GDBN} prints the string
6395 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
6396 identical repetitions, instead of displaying the identical elements
6397 themselves. Setting the threshold to zero will cause all elements to
6398 be individually printed. The default threshold is 10.
6400 @item show print repeats
6401 Display the current threshold for printing repeated identical
6404 @item set print null-stop
6405 @cindex @sc{null} elements in arrays
6406 Cause @value{GDBN} to stop printing the characters of an array when the first
6407 @sc{null} is encountered. This is useful when large arrays actually
6408 contain only short strings.
6411 @item show print null-stop
6412 Show whether @value{GDBN} stops printing an array on the first
6413 @sc{null} character.
6415 @item set print pretty on
6416 @cindex print structures in indented form
6417 @cindex indentation in structure display
6418 Cause @value{GDBN} to print structures in an indented format with one member
6419 per line, like this:
6434 @item set print pretty off
6435 Cause @value{GDBN} to print structures in a compact format, like this:
6439 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
6440 meat = 0x54 "Pork"@}
6445 This is the default format.
6447 @item show print pretty
6448 Show which format @value{GDBN} is using to print structures.
6450 @item set print sevenbit-strings on
6451 @cindex eight-bit characters in strings
6452 @cindex octal escapes in strings
6453 Print using only seven-bit characters; if this option is set,
6454 @value{GDBN} displays any eight-bit characters (in strings or
6455 character values) using the notation @code{\}@var{nnn}. This setting is
6456 best if you are working in English (@sc{ascii}) and you use the
6457 high-order bit of characters as a marker or ``meta'' bit.
6459 @item set print sevenbit-strings off
6460 Print full eight-bit characters. This allows the use of more
6461 international character sets, and is the default.
6463 @item show print sevenbit-strings
6464 Show whether or not @value{GDBN} is printing only seven-bit characters.
6466 @item set print union on
6467 @cindex unions in structures, printing
6468 Tell @value{GDBN} to print unions which are contained in structures
6469 and other unions. This is the default setting.
6471 @item set print union off
6472 Tell @value{GDBN} not to print unions which are contained in
6473 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
6476 @item show print union
6477 Ask @value{GDBN} whether or not it will print unions which are contained in
6478 structures and other unions.
6480 For example, given the declarations
6483 typedef enum @{Tree, Bug@} Species;
6484 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
6485 typedef enum @{Caterpillar, Cocoon, Butterfly@}
6496 struct thing foo = @{Tree, @{Acorn@}@};
6500 with @code{set print union on} in effect @samp{p foo} would print
6503 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
6507 and with @code{set print union off} in effect it would print
6510 $1 = @{it = Tree, form = @{...@}@}
6514 @code{set print union} affects programs written in C-like languages
6520 These settings are of interest when debugging C@t{++} programs:
6523 @cindex demangling C@t{++} names
6524 @item set print demangle
6525 @itemx set print demangle on
6526 Print C@t{++} names in their source form rather than in the encoded
6527 (``mangled'') form passed to the assembler and linker for type-safe
6528 linkage. The default is on.
6530 @item show print demangle
6531 Show whether C@t{++} names are printed in mangled or demangled form.
6533 @item set print asm-demangle
6534 @itemx set print asm-demangle on
6535 Print C@t{++} names in their source form rather than their mangled form, even
6536 in assembler code printouts such as instruction disassemblies.
6539 @item show print asm-demangle
6540 Show whether C@t{++} names in assembly listings are printed in mangled
6543 @cindex C@t{++} symbol decoding style
6544 @cindex symbol decoding style, C@t{++}
6545 @kindex set demangle-style
6546 @item set demangle-style @var{style}
6547 Choose among several encoding schemes used by different compilers to
6548 represent C@t{++} names. The choices for @var{style} are currently:
6552 Allow @value{GDBN} to choose a decoding style by inspecting your program.
6555 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
6556 This is the default.
6559 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
6562 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
6565 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
6566 @strong{Warning:} this setting alone is not sufficient to allow
6567 debugging @code{cfront}-generated executables. @value{GDBN} would
6568 require further enhancement to permit that.
6571 If you omit @var{style}, you will see a list of possible formats.
6573 @item show demangle-style
6574 Display the encoding style currently in use for decoding C@t{++} symbols.
6576 @item set print object
6577 @itemx set print object on
6578 @cindex derived type of an object, printing
6579 @cindex display derived types
6580 When displaying a pointer to an object, identify the @emph{actual}
6581 (derived) type of the object rather than the @emph{declared} type, using
6582 the virtual function table.
6584 @item set print object off
6585 Display only the declared type of objects, without reference to the
6586 virtual function table. This is the default setting.
6588 @item show print object
6589 Show whether actual, or declared, object types are displayed.
6591 @item set print static-members
6592 @itemx set print static-members on
6593 @cindex static members of C@t{++} objects
6594 Print static members when displaying a C@t{++} object. The default is on.
6596 @item set print static-members off
6597 Do not print static members when displaying a C@t{++} object.
6599 @item show print static-members
6600 Show whether C@t{++} static members are printed or not.
6602 @item set print pascal_static-members
6603 @itemx set print pascal_static-members on
6604 @cindex static members of Pascal objects
6605 @cindex Pascal objects, static members display
6606 Print static members when displaying a Pascal object. The default is on.
6608 @item set print pascal_static-members off
6609 Do not print static members when displaying a Pascal object.
6611 @item show print pascal_static-members
6612 Show whether Pascal static members are printed or not.
6614 @c These don't work with HP ANSI C++ yet.
6615 @item set print vtbl
6616 @itemx set print vtbl on
6617 @cindex pretty print C@t{++} virtual function tables
6618 @cindex virtual functions (C@t{++}) display
6619 @cindex VTBL display
6620 Pretty print C@t{++} virtual function tables. The default is off.
6621 (The @code{vtbl} commands do not work on programs compiled with the HP
6622 ANSI C@t{++} compiler (@code{aCC}).)
6624 @item set print vtbl off
6625 Do not pretty print C@t{++} virtual function tables.
6627 @item show print vtbl
6628 Show whether C@t{++} virtual function tables are pretty printed, or not.
6632 @section Value History
6634 @cindex value history
6635 @cindex history of values printed by @value{GDBN}
6636 Values printed by the @code{print} command are saved in the @value{GDBN}
6637 @dfn{value history}. This allows you to refer to them in other expressions.
6638 Values are kept until the symbol table is re-read or discarded
6639 (for example with the @code{file} or @code{symbol-file} commands).
6640 When the symbol table changes, the value history is discarded,
6641 since the values may contain pointers back to the types defined in the
6646 @cindex history number
6647 The values printed are given @dfn{history numbers} by which you can
6648 refer to them. These are successive integers starting with one.
6649 @code{print} shows you the history number assigned to a value by
6650 printing @samp{$@var{num} = } before the value; here @var{num} is the
6653 To refer to any previous value, use @samp{$} followed by the value's
6654 history number. The way @code{print} labels its output is designed to
6655 remind you of this. Just @code{$} refers to the most recent value in
6656 the history, and @code{$$} refers to the value before that.
6657 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
6658 is the value just prior to @code{$$}, @code{$$1} is equivalent to
6659 @code{$$}, and @code{$$0} is equivalent to @code{$}.
6661 For example, suppose you have just printed a pointer to a structure and
6662 want to see the contents of the structure. It suffices to type
6668 If you have a chain of structures where the component @code{next} points
6669 to the next one, you can print the contents of the next one with this:
6676 You can print successive links in the chain by repeating this
6677 command---which you can do by just typing @key{RET}.
6679 Note that the history records values, not expressions. If the value of
6680 @code{x} is 4 and you type these commands:
6688 then the value recorded in the value history by the @code{print} command
6689 remains 4 even though the value of @code{x} has changed.
6694 Print the last ten values in the value history, with their item numbers.
6695 This is like @samp{p@ $$9} repeated ten times, except that @code{show
6696 values} does not change the history.
6698 @item show values @var{n}
6699 Print ten history values centered on history item number @var{n}.
6702 Print ten history values just after the values last printed. If no more
6703 values are available, @code{show values +} produces no display.
6706 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
6707 same effect as @samp{show values +}.
6709 @node Convenience Vars
6710 @section Convenience Variables
6712 @cindex convenience variables
6713 @cindex user-defined variables
6714 @value{GDBN} provides @dfn{convenience variables} that you can use within
6715 @value{GDBN} to hold on to a value and refer to it later. These variables
6716 exist entirely within @value{GDBN}; they are not part of your program, and
6717 setting a convenience variable has no direct effect on further execution
6718 of your program. That is why you can use them freely.
6720 Convenience variables are prefixed with @samp{$}. Any name preceded by
6721 @samp{$} can be used for a convenience variable, unless it is one of
6722 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
6723 (Value history references, in contrast, are @emph{numbers} preceded
6724 by @samp{$}. @xref{Value History, ,Value History}.)
6726 You can save a value in a convenience variable with an assignment
6727 expression, just as you would set a variable in your program.
6731 set $foo = *object_ptr
6735 would save in @code{$foo} the value contained in the object pointed to by
6738 Using a convenience variable for the first time creates it, but its
6739 value is @code{void} until you assign a new value. You can alter the
6740 value with another assignment at any time.
6742 Convenience variables have no fixed types. You can assign a convenience
6743 variable any type of value, including structures and arrays, even if
6744 that variable already has a value of a different type. The convenience
6745 variable, when used as an expression, has the type of its current value.
6748 @kindex show convenience
6749 @cindex show all user variables
6750 @item show convenience
6751 Print a list of convenience variables used so far, and their values.
6752 Abbreviated @code{show conv}.
6754 @kindex init-if-undefined
6755 @cindex convenience variables, initializing
6756 @item init-if-undefined $@var{variable} = @var{expression}
6757 Set a convenience variable if it has not already been set. This is useful
6758 for user-defined commands that keep some state. It is similar, in concept,
6759 to using local static variables with initializers in C (except that
6760 convenience variables are global). It can also be used to allow users to
6761 override default values used in a command script.
6763 If the variable is already defined then the expression is not evaluated so
6764 any side-effects do not occur.
6767 One of the ways to use a convenience variable is as a counter to be
6768 incremented or a pointer to be advanced. For example, to print
6769 a field from successive elements of an array of structures:
6773 print bar[$i++]->contents
6777 Repeat that command by typing @key{RET}.
6779 Some convenience variables are created automatically by @value{GDBN} and given
6780 values likely to be useful.
6783 @vindex $_@r{, convenience variable}
6785 The variable @code{$_} is automatically set by the @code{x} command to
6786 the last address examined (@pxref{Memory, ,Examining Memory}). Other
6787 commands which provide a default address for @code{x} to examine also
6788 set @code{$_} to that address; these commands include @code{info line}
6789 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
6790 except when set by the @code{x} command, in which case it is a pointer
6791 to the type of @code{$__}.
6793 @vindex $__@r{, convenience variable}
6795 The variable @code{$__} is automatically set by the @code{x} command
6796 to the value found in the last address examined. Its type is chosen
6797 to match the format in which the data was printed.
6800 @vindex $_exitcode@r{, convenience variable}
6801 The variable @code{$_exitcode} is automatically set to the exit code when
6802 the program being debugged terminates.
6805 On HP-UX systems, if you refer to a function or variable name that
6806 begins with a dollar sign, @value{GDBN} searches for a user or system
6807 name first, before it searches for a convenience variable.
6813 You can refer to machine register contents, in expressions, as variables
6814 with names starting with @samp{$}. The names of registers are different
6815 for each machine; use @code{info registers} to see the names used on
6819 @kindex info registers
6820 @item info registers
6821 Print the names and values of all registers except floating-point
6822 and vector registers (in the selected stack frame).
6824 @kindex info all-registers
6825 @cindex floating point registers
6826 @item info all-registers
6827 Print the names and values of all registers, including floating-point
6828 and vector registers (in the selected stack frame).
6830 @item info registers @var{regname} @dots{}
6831 Print the @dfn{relativized} value of each specified register @var{regname}.
6832 As discussed in detail below, register values are normally relative to
6833 the selected stack frame. @var{regname} may be any register name valid on
6834 the machine you are using, with or without the initial @samp{$}.
6837 @cindex stack pointer register
6838 @cindex program counter register
6839 @cindex process status register
6840 @cindex frame pointer register
6841 @cindex standard registers
6842 @value{GDBN} has four ``standard'' register names that are available (in
6843 expressions) on most machines---whenever they do not conflict with an
6844 architecture's canonical mnemonics for registers. The register names
6845 @code{$pc} and @code{$sp} are used for the program counter register and
6846 the stack pointer. @code{$fp} is used for a register that contains a
6847 pointer to the current stack frame, and @code{$ps} is used for a
6848 register that contains the processor status. For example,
6849 you could print the program counter in hex with
6856 or print the instruction to be executed next with
6863 or add four to the stack pointer@footnote{This is a way of removing
6864 one word from the stack, on machines where stacks grow downward in
6865 memory (most machines, nowadays). This assumes that the innermost
6866 stack frame is selected; setting @code{$sp} is not allowed when other
6867 stack frames are selected. To pop entire frames off the stack,
6868 regardless of machine architecture, use @code{return};
6869 see @ref{Returning, ,Returning from a Function}.} with
6875 Whenever possible, these four standard register names are available on
6876 your machine even though the machine has different canonical mnemonics,
6877 so long as there is no conflict. The @code{info registers} command
6878 shows the canonical names. For example, on the SPARC, @code{info
6879 registers} displays the processor status register as @code{$psr} but you
6880 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
6881 is an alias for the @sc{eflags} register.
6883 @value{GDBN} always considers the contents of an ordinary register as an
6884 integer when the register is examined in this way. Some machines have
6885 special registers which can hold nothing but floating point; these
6886 registers are considered to have floating point values. There is no way
6887 to refer to the contents of an ordinary register as floating point value
6888 (although you can @emph{print} it as a floating point value with
6889 @samp{print/f $@var{regname}}).
6891 Some registers have distinct ``raw'' and ``virtual'' data formats. This
6892 means that the data format in which the register contents are saved by
6893 the operating system is not the same one that your program normally
6894 sees. For example, the registers of the 68881 floating point
6895 coprocessor are always saved in ``extended'' (raw) format, but all C
6896 programs expect to work with ``double'' (virtual) format. In such
6897 cases, @value{GDBN} normally works with the virtual format only (the format
6898 that makes sense for your program), but the @code{info registers} command
6899 prints the data in both formats.
6901 @cindex SSE registers (x86)
6902 @cindex MMX registers (x86)
6903 Some machines have special registers whose contents can be interpreted
6904 in several different ways. For example, modern x86-based machines
6905 have SSE and MMX registers that can hold several values packed
6906 together in several different formats. @value{GDBN} refers to such
6907 registers in @code{struct} notation:
6910 (@value{GDBP}) print $xmm1
6912 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
6913 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
6914 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
6915 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
6916 v4_int32 = @{0, 20657912, 11, 13@},
6917 v2_int64 = @{88725056443645952, 55834574859@},
6918 uint128 = 0x0000000d0000000b013b36f800000000
6923 To set values of such registers, you need to tell @value{GDBN} which
6924 view of the register you wish to change, as if you were assigning
6925 value to a @code{struct} member:
6928 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
6931 Normally, register values are relative to the selected stack frame
6932 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
6933 value that the register would contain if all stack frames farther in
6934 were exited and their saved registers restored. In order to see the
6935 true contents of hardware registers, you must select the innermost
6936 frame (with @samp{frame 0}).
6938 However, @value{GDBN} must deduce where registers are saved, from the machine
6939 code generated by your compiler. If some registers are not saved, or if
6940 @value{GDBN} is unable to locate the saved registers, the selected stack
6941 frame makes no difference.
6943 @node Floating Point Hardware
6944 @section Floating Point Hardware
6945 @cindex floating point
6947 Depending on the configuration, @value{GDBN} may be able to give
6948 you more information about the status of the floating point hardware.
6953 Display hardware-dependent information about the floating
6954 point unit. The exact contents and layout vary depending on the
6955 floating point chip. Currently, @samp{info float} is supported on
6956 the ARM and x86 machines.
6960 @section Vector Unit
6963 Depending on the configuration, @value{GDBN} may be able to give you
6964 more information about the status of the vector unit.
6969 Display information about the vector unit. The exact contents and
6970 layout vary depending on the hardware.
6973 @node OS Information
6974 @section Operating System Auxiliary Information
6975 @cindex OS information
6977 @value{GDBN} provides interfaces to useful OS facilities that can help
6978 you debug your program.
6980 @cindex @code{ptrace} system call
6981 @cindex @code{struct user} contents
6982 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
6983 machines), it interfaces with the inferior via the @code{ptrace}
6984 system call. The operating system creates a special sata structure,
6985 called @code{struct user}, for this interface. You can use the
6986 command @code{info udot} to display the contents of this data
6992 Display the contents of the @code{struct user} maintained by the OS
6993 kernel for the program being debugged. @value{GDBN} displays the
6994 contents of @code{struct user} as a list of hex numbers, similar to
6995 the @code{examine} command.
6998 @cindex auxiliary vector
6999 @cindex vector, auxiliary
7000 Some operating systems supply an @dfn{auxiliary vector} to programs at
7001 startup. This is akin to the arguments and environment that you
7002 specify for a program, but contains a system-dependent variety of
7003 binary values that tell system libraries important details about the
7004 hardware, operating system, and process. Each value's purpose is
7005 identified by an integer tag; the meanings are well-known but system-specific.
7006 Depending on the configuration and operating system facilities,
7007 @value{GDBN} may be able to show you this information. For remote
7008 targets, this functionality may further depend on the remote stub's
7009 support of the @samp{qXfer:auxv:read} packet, see
7010 @ref{qXfer auxiliary vector read}.
7015 Display the auxiliary vector of the inferior, which can be either a
7016 live process or a core dump file. @value{GDBN} prints each tag value
7017 numerically, and also shows names and text descriptions for recognized
7018 tags. Some values in the vector are numbers, some bit masks, and some
7019 pointers to strings or other data. @value{GDBN} displays each value in the
7020 most appropriate form for a recognized tag, and in hexadecimal for
7021 an unrecognized tag.
7025 @node Memory Region Attributes
7026 @section Memory Region Attributes
7027 @cindex memory region attributes
7029 @dfn{Memory region attributes} allow you to describe special handling
7030 required by regions of your target's memory. @value{GDBN} uses
7031 attributes to determine whether to allow certain types of memory
7032 accesses; whether to use specific width accesses; and whether to cache
7033 target memory. By default the description of memory regions is
7034 fetched from the target (if the current target supports this), but the
7035 user can override the fetched regions.
7037 Defined memory regions can be individually enabled and disabled. When a
7038 memory region is disabled, @value{GDBN} uses the default attributes when
7039 accessing memory in that region. Similarly, if no memory regions have
7040 been defined, @value{GDBN} uses the default attributes when accessing
7043 When a memory region is defined, it is given a number to identify it;
7044 to enable, disable, or remove a memory region, you specify that number.
7048 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
7049 Define a memory region bounded by @var{lower} and @var{upper} with
7050 attributes @var{attributes}@dots{}, and add it to the list of regions
7051 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
7052 case: it is treated as the target's maximum memory address.
7053 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
7056 Discard any user changes to the memory regions and use target-supplied
7057 regions, if available, or no regions if the target does not support.
7060 @item delete mem @var{nums}@dots{}
7061 Remove memory regions @var{nums}@dots{} from the list of regions
7062 monitored by @value{GDBN}.
7065 @item disable mem @var{nums}@dots{}
7066 Disable monitoring of memory regions @var{nums}@dots{}.
7067 A disabled memory region is not forgotten.
7068 It may be enabled again later.
7071 @item enable mem @var{nums}@dots{}
7072 Enable monitoring of memory regions @var{nums}@dots{}.
7076 Print a table of all defined memory regions, with the following columns
7080 @item Memory Region Number
7081 @item Enabled or Disabled.
7082 Enabled memory regions are marked with @samp{y}.
7083 Disabled memory regions are marked with @samp{n}.
7086 The address defining the inclusive lower bound of the memory region.
7089 The address defining the exclusive upper bound of the memory region.
7092 The list of attributes set for this memory region.
7097 @subsection Attributes
7099 @subsubsection Memory Access Mode
7100 The access mode attributes set whether @value{GDBN} may make read or
7101 write accesses to a memory region.
7103 While these attributes prevent @value{GDBN} from performing invalid
7104 memory accesses, they do nothing to prevent the target system, I/O DMA,
7105 etc.@: from accessing memory.
7109 Memory is read only.
7111 Memory is write only.
7113 Memory is read/write. This is the default.
7116 @subsubsection Memory Access Size
7117 The access size attribute tells @value{GDBN} to use specific sized
7118 accesses in the memory region. Often memory mapped device registers
7119 require specific sized accesses. If no access size attribute is
7120 specified, @value{GDBN} may use accesses of any size.
7124 Use 8 bit memory accesses.
7126 Use 16 bit memory accesses.
7128 Use 32 bit memory accesses.
7130 Use 64 bit memory accesses.
7133 @c @subsubsection Hardware/Software Breakpoints
7134 @c The hardware/software breakpoint attributes set whether @value{GDBN}
7135 @c will use hardware or software breakpoints for the internal breakpoints
7136 @c used by the step, next, finish, until, etc. commands.
7140 @c Always use hardware breakpoints
7141 @c @item swbreak (default)
7144 @subsubsection Data Cache
7145 The data cache attributes set whether @value{GDBN} will cache target
7146 memory. While this generally improves performance by reducing debug
7147 protocol overhead, it can lead to incorrect results because @value{GDBN}
7148 does not know about volatile variables or memory mapped device
7153 Enable @value{GDBN} to cache target memory.
7155 Disable @value{GDBN} from caching target memory. This is the default.
7158 @subsection Memory Access Checking
7159 @value{GDBN} can be instructed to refuse accesses to memory that is
7160 not explicitly described. This can be useful if accessing such
7161 regions has undesired effects for a specific target, or to provide
7162 better error checking. The following commands control this behaviour.
7165 @kindex set mem inaccessible-by-default
7166 @item set mem inaccessible-by-default [on|off]
7167 If @code{on} is specified, make @value{GDBN} treat memory not
7168 explicitly described by the memory ranges as non-existent and refuse accesses
7169 to such memory. The checks are only performed if there's at least one
7170 memory range defined. If @code{off} is specified, make @value{GDBN}
7171 treat the memory not explicitly described by the memory ranges as RAM.
7172 The default value is @code{on}.
7173 @kindex show mem inaccessible-by-default
7174 @item show mem inaccessible-by-default
7175 Show the current handling of accesses to unknown memory.
7179 @c @subsubsection Memory Write Verification
7180 @c The memory write verification attributes set whether @value{GDBN}
7181 @c will re-reads data after each write to verify the write was successful.
7185 @c @item noverify (default)
7188 @node Dump/Restore Files
7189 @section Copy Between Memory and a File
7190 @cindex dump/restore files
7191 @cindex append data to a file
7192 @cindex dump data to a file
7193 @cindex restore data from a file
7195 You can use the commands @code{dump}, @code{append}, and
7196 @code{restore} to copy data between target memory and a file. The
7197 @code{dump} and @code{append} commands write data to a file, and the
7198 @code{restore} command reads data from a file back into the inferior's
7199 memory. Files may be in binary, Motorola S-record, Intel hex, or
7200 Tektronix Hex format; however, @value{GDBN} can only append to binary
7206 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7207 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
7208 Dump the contents of memory from @var{start_addr} to @var{end_addr},
7209 or the value of @var{expr}, to @var{filename} in the given format.
7211 The @var{format} parameter may be any one of:
7218 Motorola S-record format.
7220 Tektronix Hex format.
7223 @value{GDBN} uses the same definitions of these formats as the
7224 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
7225 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
7229 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7230 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
7231 Append the contents of memory from @var{start_addr} to @var{end_addr},
7232 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
7233 (@value{GDBN} can only append data to files in raw binary form.)
7236 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
7237 Restore the contents of file @var{filename} into memory. The
7238 @code{restore} command can automatically recognize any known @sc{bfd}
7239 file format, except for raw binary. To restore a raw binary file you
7240 must specify the optional keyword @code{binary} after the filename.
7242 If @var{bias} is non-zero, its value will be added to the addresses
7243 contained in the file. Binary files always start at address zero, so
7244 they will be restored at address @var{bias}. Other bfd files have
7245 a built-in location; they will be restored at offset @var{bias}
7248 If @var{start} and/or @var{end} are non-zero, then only data between
7249 file offset @var{start} and file offset @var{end} will be restored.
7250 These offsets are relative to the addresses in the file, before
7251 the @var{bias} argument is applied.
7255 @node Core File Generation
7256 @section How to Produce a Core File from Your Program
7257 @cindex dump core from inferior
7259 A @dfn{core file} or @dfn{core dump} is a file that records the memory
7260 image of a running process and its process status (register values
7261 etc.). Its primary use is post-mortem debugging of a program that
7262 crashed while it ran outside a debugger. A program that crashes
7263 automatically produces a core file, unless this feature is disabled by
7264 the user. @xref{Files}, for information on invoking @value{GDBN} in
7265 the post-mortem debugging mode.
7267 Occasionally, you may wish to produce a core file of the program you
7268 are debugging in order to preserve a snapshot of its state.
7269 @value{GDBN} has a special command for that.
7273 @kindex generate-core-file
7274 @item generate-core-file [@var{file}]
7275 @itemx gcore [@var{file}]
7276 Produce a core dump of the inferior process. The optional argument
7277 @var{file} specifies the file name where to put the core dump. If not
7278 specified, the file name defaults to @file{core.@var{pid}}, where
7279 @var{pid} is the inferior process ID.
7281 Note that this command is implemented only for some systems (as of
7282 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
7285 @node Character Sets
7286 @section Character Sets
7287 @cindex character sets
7289 @cindex translating between character sets
7290 @cindex host character set
7291 @cindex target character set
7293 If the program you are debugging uses a different character set to
7294 represent characters and strings than the one @value{GDBN} uses itself,
7295 @value{GDBN} can automatically translate between the character sets for
7296 you. The character set @value{GDBN} uses we call the @dfn{host
7297 character set}; the one the inferior program uses we call the
7298 @dfn{target character set}.
7300 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
7301 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
7302 remote protocol (@pxref{Remote Debugging}) to debug a program
7303 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
7304 then the host character set is Latin-1, and the target character set is
7305 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
7306 target-charset EBCDIC-US}, then @value{GDBN} translates between
7307 @sc{ebcdic} and Latin 1 as you print character or string values, or use
7308 character and string literals in expressions.
7310 @value{GDBN} has no way to automatically recognize which character set
7311 the inferior program uses; you must tell it, using the @code{set
7312 target-charset} command, described below.
7314 Here are the commands for controlling @value{GDBN}'s character set
7318 @item set target-charset @var{charset}
7319 @kindex set target-charset
7320 Set the current target character set to @var{charset}. We list the
7321 character set names @value{GDBN} recognizes below, but if you type
7322 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7323 list the target character sets it supports.
7327 @item set host-charset @var{charset}
7328 @kindex set host-charset
7329 Set the current host character set to @var{charset}.
7331 By default, @value{GDBN} uses a host character set appropriate to the
7332 system it is running on; you can override that default using the
7333 @code{set host-charset} command.
7335 @value{GDBN} can only use certain character sets as its host character
7336 set. We list the character set names @value{GDBN} recognizes below, and
7337 indicate which can be host character sets, but if you type
7338 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7339 list the host character sets it supports.
7341 @item set charset @var{charset}
7343 Set the current host and target character sets to @var{charset}. As
7344 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
7345 @value{GDBN} will list the name of the character sets that can be used
7346 for both host and target.
7350 @kindex show charset
7351 Show the names of the current host and target charsets.
7353 @itemx show host-charset
7354 @kindex show host-charset
7355 Show the name of the current host charset.
7357 @itemx show target-charset
7358 @kindex show target-charset
7359 Show the name of the current target charset.
7363 @value{GDBN} currently includes support for the following character
7369 @cindex ASCII character set
7370 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
7374 @cindex ISO 8859-1 character set
7375 @cindex ISO Latin 1 character set
7376 The ISO Latin 1 character set. This extends @sc{ascii} with accented
7377 characters needed for French, German, and Spanish. @value{GDBN} can use
7378 this as its host character set.
7382 @cindex EBCDIC character set
7383 @cindex IBM1047 character set
7384 Variants of the @sc{ebcdic} character set, used on some of IBM's
7385 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
7386 @value{GDBN} cannot use these as its host character set.
7390 Note that these are all single-byte character sets. More work inside
7391 @value{GDBN} is needed to support multi-byte or variable-width character
7392 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
7394 Here is an example of @value{GDBN}'s character set support in action.
7395 Assume that the following source code has been placed in the file
7396 @file{charset-test.c}:
7402 = @{72, 101, 108, 108, 111, 44, 32, 119,
7403 111, 114, 108, 100, 33, 10, 0@};
7404 char ibm1047_hello[]
7405 = @{200, 133, 147, 147, 150, 107, 64, 166,
7406 150, 153, 147, 132, 90, 37, 0@};
7410 printf ("Hello, world!\n");
7414 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
7415 containing the string @samp{Hello, world!} followed by a newline,
7416 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
7418 We compile the program, and invoke the debugger on it:
7421 $ gcc -g charset-test.c -o charset-test
7422 $ gdb -nw charset-test
7423 GNU gdb 2001-12-19-cvs
7424 Copyright 2001 Free Software Foundation, Inc.
7429 We can use the @code{show charset} command to see what character sets
7430 @value{GDBN} is currently using to interpret and display characters and
7434 (@value{GDBP}) show charset
7435 The current host and target character set is `ISO-8859-1'.
7439 For the sake of printing this manual, let's use @sc{ascii} as our
7440 initial character set:
7442 (@value{GDBP}) set charset ASCII
7443 (@value{GDBP}) show charset
7444 The current host and target character set is `ASCII'.
7448 Let's assume that @sc{ascii} is indeed the correct character set for our
7449 host system --- in other words, let's assume that if @value{GDBN} prints
7450 characters using the @sc{ascii} character set, our terminal will display
7451 them properly. Since our current target character set is also
7452 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
7455 (@value{GDBP}) print ascii_hello
7456 $1 = 0x401698 "Hello, world!\n"
7457 (@value{GDBP}) print ascii_hello[0]
7462 @value{GDBN} uses the target character set for character and string
7463 literals you use in expressions:
7466 (@value{GDBP}) print '+'
7471 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
7474 @value{GDBN} relies on the user to tell it which character set the
7475 target program uses. If we print @code{ibm1047_hello} while our target
7476 character set is still @sc{ascii}, we get jibberish:
7479 (@value{GDBP}) print ibm1047_hello
7480 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
7481 (@value{GDBP}) print ibm1047_hello[0]
7486 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
7487 @value{GDBN} tells us the character sets it supports:
7490 (@value{GDBP}) set target-charset
7491 ASCII EBCDIC-US IBM1047 ISO-8859-1
7492 (@value{GDBP}) set target-charset
7495 We can select @sc{ibm1047} as our target character set, and examine the
7496 program's strings again. Now the @sc{ascii} string is wrong, but
7497 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
7498 target character set, @sc{ibm1047}, to the host character set,
7499 @sc{ascii}, and they display correctly:
7502 (@value{GDBP}) set target-charset IBM1047
7503 (@value{GDBP}) show charset
7504 The current host character set is `ASCII'.
7505 The current target character set is `IBM1047'.
7506 (@value{GDBP}) print ascii_hello
7507 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
7508 (@value{GDBP}) print ascii_hello[0]
7510 (@value{GDBP}) print ibm1047_hello
7511 $8 = 0x4016a8 "Hello, world!\n"
7512 (@value{GDBP}) print ibm1047_hello[0]
7517 As above, @value{GDBN} uses the target character set for character and
7518 string literals you use in expressions:
7521 (@value{GDBP}) print '+'
7526 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
7529 @node Caching Remote Data
7530 @section Caching Data of Remote Targets
7531 @cindex caching data of remote targets
7533 @value{GDBN} can cache data exchanged between the debugger and a
7534 remote target (@pxref{Remote Debugging}). Such caching generally improves
7535 performance, because it reduces the overhead of the remote protocol by
7536 bundling memory reads and writes into large chunks. Unfortunately,
7537 @value{GDBN} does not currently know anything about volatile
7538 registers, and thus data caching will produce incorrect results when
7539 volatile registers are in use.
7542 @kindex set remotecache
7543 @item set remotecache on
7544 @itemx set remotecache off
7545 Set caching state for remote targets. When @code{ON}, use data
7546 caching. By default, this option is @code{OFF}.
7548 @kindex show remotecache
7549 @item show remotecache
7550 Show the current state of data caching for remote targets.
7554 Print the information about the data cache performance. The
7555 information displayed includes: the dcache width and depth; and for
7556 each cache line, how many times it was referenced, and its data and
7557 state (dirty, bad, ok, etc.). This command is useful for debugging
7558 the data cache operation.
7563 @chapter C Preprocessor Macros
7565 Some languages, such as C and C@t{++}, provide a way to define and invoke
7566 ``preprocessor macros'' which expand into strings of tokens.
7567 @value{GDBN} can evaluate expressions containing macro invocations, show
7568 the result of macro expansion, and show a macro's definition, including
7569 where it was defined.
7571 You may need to compile your program specially to provide @value{GDBN}
7572 with information about preprocessor macros. Most compilers do not
7573 include macros in their debugging information, even when you compile
7574 with the @option{-g} flag. @xref{Compilation}.
7576 A program may define a macro at one point, remove that definition later,
7577 and then provide a different definition after that. Thus, at different
7578 points in the program, a macro may have different definitions, or have
7579 no definition at all. If there is a current stack frame, @value{GDBN}
7580 uses the macros in scope at that frame's source code line. Otherwise,
7581 @value{GDBN} uses the macros in scope at the current listing location;
7584 At the moment, @value{GDBN} does not support the @code{##}
7585 token-splicing operator, the @code{#} stringification operator, or
7586 variable-arity macros.
7588 Whenever @value{GDBN} evaluates an expression, it always expands any
7589 macro invocations present in the expression. @value{GDBN} also provides
7590 the following commands for working with macros explicitly.
7594 @kindex macro expand
7595 @cindex macro expansion, showing the results of preprocessor
7596 @cindex preprocessor macro expansion, showing the results of
7597 @cindex expanding preprocessor macros
7598 @item macro expand @var{expression}
7599 @itemx macro exp @var{expression}
7600 Show the results of expanding all preprocessor macro invocations in
7601 @var{expression}. Since @value{GDBN} simply expands macros, but does
7602 not parse the result, @var{expression} need not be a valid expression;
7603 it can be any string of tokens.
7606 @item macro expand-once @var{expression}
7607 @itemx macro exp1 @var{expression}
7608 @cindex expand macro once
7609 @i{(This command is not yet implemented.)} Show the results of
7610 expanding those preprocessor macro invocations that appear explicitly in
7611 @var{expression}. Macro invocations appearing in that expansion are
7612 left unchanged. This command allows you to see the effect of a
7613 particular macro more clearly, without being confused by further
7614 expansions. Since @value{GDBN} simply expands macros, but does not
7615 parse the result, @var{expression} need not be a valid expression; it
7616 can be any string of tokens.
7619 @cindex macro definition, showing
7620 @cindex definition, showing a macro's
7621 @item info macro @var{macro}
7622 Show the definition of the macro named @var{macro}, and describe the
7623 source location where that definition was established.
7625 @kindex macro define
7626 @cindex user-defined macros
7627 @cindex defining macros interactively
7628 @cindex macros, user-defined
7629 @item macro define @var{macro} @var{replacement-list}
7630 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
7631 @i{(This command is not yet implemented.)} Introduce a definition for a
7632 preprocessor macro named @var{macro}, invocations of which are replaced
7633 by the tokens given in @var{replacement-list}. The first form of this
7634 command defines an ``object-like'' macro, which takes no arguments; the
7635 second form defines a ``function-like'' macro, which takes the arguments
7636 given in @var{arglist}.
7638 A definition introduced by this command is in scope in every expression
7639 evaluated in @value{GDBN}, until it is removed with the @command{macro
7640 undef} command, described below. The definition overrides all
7641 definitions for @var{macro} present in the program being debugged, as
7642 well as any previous user-supplied definition.
7645 @item macro undef @var{macro}
7646 @i{(This command is not yet implemented.)} Remove any user-supplied
7647 definition for the macro named @var{macro}. This command only affects
7648 definitions provided with the @command{macro define} command, described
7649 above; it cannot remove definitions present in the program being
7654 @i{(This command is not yet implemented.)} List all the macros
7655 defined using the @code{macro define} command.
7658 @cindex macros, example of debugging with
7659 Here is a transcript showing the above commands in action. First, we
7660 show our source files:
7668 #define ADD(x) (M + x)
7673 printf ("Hello, world!\n");
7675 printf ("We're so creative.\n");
7677 printf ("Goodbye, world!\n");
7684 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
7685 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
7686 compiler includes information about preprocessor macros in the debugging
7690 $ gcc -gdwarf-2 -g3 sample.c -o sample
7694 Now, we start @value{GDBN} on our sample program:
7698 GNU gdb 2002-05-06-cvs
7699 Copyright 2002 Free Software Foundation, Inc.
7700 GDB is free software, @dots{}
7704 We can expand macros and examine their definitions, even when the
7705 program is not running. @value{GDBN} uses the current listing position
7706 to decide which macro definitions are in scope:
7709 (@value{GDBP}) list main
7712 5 #define ADD(x) (M + x)
7717 10 printf ("Hello, world!\n");
7719 12 printf ("We're so creative.\n");
7720 (@value{GDBP}) info macro ADD
7721 Defined at /home/jimb/gdb/macros/play/sample.c:5
7722 #define ADD(x) (M + x)
7723 (@value{GDBP}) info macro Q
7724 Defined at /home/jimb/gdb/macros/play/sample.h:1
7725 included at /home/jimb/gdb/macros/play/sample.c:2
7727 (@value{GDBP}) macro expand ADD(1)
7728 expands to: (42 + 1)
7729 (@value{GDBP}) macro expand-once ADD(1)
7730 expands to: once (M + 1)
7734 In the example above, note that @command{macro expand-once} expands only
7735 the macro invocation explicit in the original text --- the invocation of
7736 @code{ADD} --- but does not expand the invocation of the macro @code{M},
7737 which was introduced by @code{ADD}.
7739 Once the program is running, @value{GDBN} uses the macro definitions in
7740 force at the source line of the current stack frame:
7743 (@value{GDBP}) break main
7744 Breakpoint 1 at 0x8048370: file sample.c, line 10.
7746 Starting program: /home/jimb/gdb/macros/play/sample
7748 Breakpoint 1, main () at sample.c:10
7749 10 printf ("Hello, world!\n");
7753 At line 10, the definition of the macro @code{N} at line 9 is in force:
7756 (@value{GDBP}) info macro N
7757 Defined at /home/jimb/gdb/macros/play/sample.c:9
7759 (@value{GDBP}) macro expand N Q M
7761 (@value{GDBP}) print N Q M
7766 As we step over directives that remove @code{N}'s definition, and then
7767 give it a new definition, @value{GDBN} finds the definition (or lack
7768 thereof) in force at each point:
7773 12 printf ("We're so creative.\n");
7774 (@value{GDBP}) info macro N
7775 The symbol `N' has no definition as a C/C++ preprocessor macro
7776 at /home/jimb/gdb/macros/play/sample.c:12
7779 14 printf ("Goodbye, world!\n");
7780 (@value{GDBP}) info macro N
7781 Defined at /home/jimb/gdb/macros/play/sample.c:13
7783 (@value{GDBP}) macro expand N Q M
7784 expands to: 1729 < 42
7785 (@value{GDBP}) print N Q M
7792 @chapter Tracepoints
7793 @c This chapter is based on the documentation written by Michael
7794 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
7797 In some applications, it is not feasible for the debugger to interrupt
7798 the program's execution long enough for the developer to learn
7799 anything helpful about its behavior. If the program's correctness
7800 depends on its real-time behavior, delays introduced by a debugger
7801 might cause the program to change its behavior drastically, or perhaps
7802 fail, even when the code itself is correct. It is useful to be able
7803 to observe the program's behavior without interrupting it.
7805 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
7806 specify locations in the program, called @dfn{tracepoints}, and
7807 arbitrary expressions to evaluate when those tracepoints are reached.
7808 Later, using the @code{tfind} command, you can examine the values
7809 those expressions had when the program hit the tracepoints. The
7810 expressions may also denote objects in memory---structures or arrays,
7811 for example---whose values @value{GDBN} should record; while visiting
7812 a particular tracepoint, you may inspect those objects as if they were
7813 in memory at that moment. However, because @value{GDBN} records these
7814 values without interacting with you, it can do so quickly and
7815 unobtrusively, hopefully not disturbing the program's behavior.
7817 The tracepoint facility is currently available only for remote
7818 targets. @xref{Targets}. In addition, your remote target must know
7819 how to collect trace data. This functionality is implemented in the
7820 remote stub; however, none of the stubs distributed with @value{GDBN}
7821 support tracepoints as of this writing. The format of the remote
7822 packets used to implement tracepoints are described in @ref{Tracepoint
7825 This chapter describes the tracepoint commands and features.
7829 * Analyze Collected Data::
7830 * Tracepoint Variables::
7833 @node Set Tracepoints
7834 @section Commands to Set Tracepoints
7836 Before running such a @dfn{trace experiment}, an arbitrary number of
7837 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
7838 tracepoint has a number assigned to it by @value{GDBN}. Like with
7839 breakpoints, tracepoint numbers are successive integers starting from
7840 one. Many of the commands associated with tracepoints take the
7841 tracepoint number as their argument, to identify which tracepoint to
7844 For each tracepoint, you can specify, in advance, some arbitrary set
7845 of data that you want the target to collect in the trace buffer when
7846 it hits that tracepoint. The collected data can include registers,
7847 local variables, or global data. Later, you can use @value{GDBN}
7848 commands to examine the values these data had at the time the
7851 This section describes commands to set tracepoints and associated
7852 conditions and actions.
7855 * Create and Delete Tracepoints::
7856 * Enable and Disable Tracepoints::
7857 * Tracepoint Passcounts::
7858 * Tracepoint Actions::
7859 * Listing Tracepoints::
7860 * Starting and Stopping Trace Experiments::
7863 @node Create and Delete Tracepoints
7864 @subsection Create and Delete Tracepoints
7867 @cindex set tracepoint
7870 The @code{trace} command is very similar to the @code{break} command.
7871 Its argument can be a source line, a function name, or an address in
7872 the target program. @xref{Set Breaks}. The @code{trace} command
7873 defines a tracepoint, which is a point in the target program where the
7874 debugger will briefly stop, collect some data, and then allow the
7875 program to continue. Setting a tracepoint or changing its commands
7876 doesn't take effect until the next @code{tstart} command; thus, you
7877 cannot change the tracepoint attributes once a trace experiment is
7880 Here are some examples of using the @code{trace} command:
7883 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
7885 (@value{GDBP}) @b{trace +2} // 2 lines forward
7887 (@value{GDBP}) @b{trace my_function} // first source line of function
7889 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
7891 (@value{GDBP}) @b{trace *0x2117c4} // an address
7895 You can abbreviate @code{trace} as @code{tr}.
7898 @cindex last tracepoint number
7899 @cindex recent tracepoint number
7900 @cindex tracepoint number
7901 The convenience variable @code{$tpnum} records the tracepoint number
7902 of the most recently set tracepoint.
7904 @kindex delete tracepoint
7905 @cindex tracepoint deletion
7906 @item delete tracepoint @r{[}@var{num}@r{]}
7907 Permanently delete one or more tracepoints. With no argument, the
7908 default is to delete all tracepoints.
7913 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
7915 (@value{GDBP}) @b{delete trace} // remove all tracepoints
7919 You can abbreviate this command as @code{del tr}.
7922 @node Enable and Disable Tracepoints
7923 @subsection Enable and Disable Tracepoints
7926 @kindex disable tracepoint
7927 @item disable tracepoint @r{[}@var{num}@r{]}
7928 Disable tracepoint @var{num}, or all tracepoints if no argument
7929 @var{num} is given. A disabled tracepoint will have no effect during
7930 the next trace experiment, but it is not forgotten. You can re-enable
7931 a disabled tracepoint using the @code{enable tracepoint} command.
7933 @kindex enable tracepoint
7934 @item enable tracepoint @r{[}@var{num}@r{]}
7935 Enable tracepoint @var{num}, or all tracepoints. The enabled
7936 tracepoints will become effective the next time a trace experiment is
7940 @node Tracepoint Passcounts
7941 @subsection Tracepoint Passcounts
7945 @cindex tracepoint pass count
7946 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
7947 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
7948 automatically stop a trace experiment. If a tracepoint's passcount is
7949 @var{n}, then the trace experiment will be automatically stopped on
7950 the @var{n}'th time that tracepoint is hit. If the tracepoint number
7951 @var{num} is not specified, the @code{passcount} command sets the
7952 passcount of the most recently defined tracepoint. If no passcount is
7953 given, the trace experiment will run until stopped explicitly by the
7959 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
7960 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
7962 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
7963 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
7964 (@value{GDBP}) @b{trace foo}
7965 (@value{GDBP}) @b{pass 3}
7966 (@value{GDBP}) @b{trace bar}
7967 (@value{GDBP}) @b{pass 2}
7968 (@value{GDBP}) @b{trace baz}
7969 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
7970 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
7971 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
7972 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
7976 @node Tracepoint Actions
7977 @subsection Tracepoint Action Lists
7981 @cindex tracepoint actions
7982 @item actions @r{[}@var{num}@r{]}
7983 This command will prompt for a list of actions to be taken when the
7984 tracepoint is hit. If the tracepoint number @var{num} is not
7985 specified, this command sets the actions for the one that was most
7986 recently defined (so that you can define a tracepoint and then say
7987 @code{actions} without bothering about its number). You specify the
7988 actions themselves on the following lines, one action at a time, and
7989 terminate the actions list with a line containing just @code{end}. So
7990 far, the only defined actions are @code{collect} and
7991 @code{while-stepping}.
7993 @cindex remove actions from a tracepoint
7994 To remove all actions from a tracepoint, type @samp{actions @var{num}}
7995 and follow it immediately with @samp{end}.
7998 (@value{GDBP}) @b{collect @var{data}} // collect some data
8000 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
8002 (@value{GDBP}) @b{end} // signals the end of actions.
8005 In the following example, the action list begins with @code{collect}
8006 commands indicating the things to be collected when the tracepoint is
8007 hit. Then, in order to single-step and collect additional data
8008 following the tracepoint, a @code{while-stepping} command is used,
8009 followed by the list of things to be collected while stepping. The
8010 @code{while-stepping} command is terminated by its own separate
8011 @code{end} command. Lastly, the action list is terminated by an
8015 (@value{GDBP}) @b{trace foo}
8016 (@value{GDBP}) @b{actions}
8017 Enter actions for tracepoint 1, one per line:
8026 @kindex collect @r{(tracepoints)}
8027 @item collect @var{expr1}, @var{expr2}, @dots{}
8028 Collect values of the given expressions when the tracepoint is hit.
8029 This command accepts a comma-separated list of any valid expressions.
8030 In addition to global, static, or local variables, the following
8031 special arguments are supported:
8035 collect all registers
8038 collect all function arguments
8041 collect all local variables.
8044 You can give several consecutive @code{collect} commands, each one
8045 with a single argument, or one @code{collect} command with several
8046 arguments separated by commas: the effect is the same.
8048 The command @code{info scope} (@pxref{Symbols, info scope}) is
8049 particularly useful for figuring out what data to collect.
8051 @kindex while-stepping @r{(tracepoints)}
8052 @item while-stepping @var{n}
8053 Perform @var{n} single-step traces after the tracepoint, collecting
8054 new data at each step. The @code{while-stepping} command is
8055 followed by the list of what to collect while stepping (followed by
8056 its own @code{end} command):
8060 > collect $regs, myglobal
8066 You may abbreviate @code{while-stepping} as @code{ws} or
8070 @node Listing Tracepoints
8071 @subsection Listing Tracepoints
8074 @kindex info tracepoints
8076 @cindex information about tracepoints
8077 @item info tracepoints @r{[}@var{num}@r{]}
8078 Display information about the tracepoint @var{num}. If you don't specify
8079 a tracepoint number, displays information about all the tracepoints
8080 defined so far. For each tracepoint, the following information is
8087 whether it is enabled or disabled
8091 its passcount as given by the @code{passcount @var{n}} command
8093 its step count as given by the @code{while-stepping @var{n}} command
8095 where in the source files is the tracepoint set
8097 its action list as given by the @code{actions} command
8101 (@value{GDBP}) @b{info trace}
8102 Num Enb Address PassC StepC What
8103 1 y 0x002117c4 0 0 <gdb_asm>
8104 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
8105 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
8110 This command can be abbreviated @code{info tp}.
8113 @node Starting and Stopping Trace Experiments
8114 @subsection Starting and Stopping Trace Experiments
8118 @cindex start a new trace experiment
8119 @cindex collected data discarded
8121 This command takes no arguments. It starts the trace experiment, and
8122 begins collecting data. This has the side effect of discarding all
8123 the data collected in the trace buffer during the previous trace
8127 @cindex stop a running trace experiment
8129 This command takes no arguments. It ends the trace experiment, and
8130 stops collecting data.
8132 @strong{Note}: a trace experiment and data collection may stop
8133 automatically if any tracepoint's passcount is reached
8134 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
8137 @cindex status of trace data collection
8138 @cindex trace experiment, status of
8140 This command displays the status of the current trace data
8144 Here is an example of the commands we described so far:
8147 (@value{GDBP}) @b{trace gdb_c_test}
8148 (@value{GDBP}) @b{actions}
8149 Enter actions for tracepoint #1, one per line.
8150 > collect $regs,$locals,$args
8155 (@value{GDBP}) @b{tstart}
8156 [time passes @dots{}]
8157 (@value{GDBP}) @b{tstop}
8161 @node Analyze Collected Data
8162 @section Using the Collected Data
8164 After the tracepoint experiment ends, you use @value{GDBN} commands
8165 for examining the trace data. The basic idea is that each tracepoint
8166 collects a trace @dfn{snapshot} every time it is hit and another
8167 snapshot every time it single-steps. All these snapshots are
8168 consecutively numbered from zero and go into a buffer, and you can
8169 examine them later. The way you examine them is to @dfn{focus} on a
8170 specific trace snapshot. When the remote stub is focused on a trace
8171 snapshot, it will respond to all @value{GDBN} requests for memory and
8172 registers by reading from the buffer which belongs to that snapshot,
8173 rather than from @emph{real} memory or registers of the program being
8174 debugged. This means that @strong{all} @value{GDBN} commands
8175 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
8176 behave as if we were currently debugging the program state as it was
8177 when the tracepoint occurred. Any requests for data that are not in
8178 the buffer will fail.
8181 * tfind:: How to select a trace snapshot
8182 * tdump:: How to display all data for a snapshot
8183 * save-tracepoints:: How to save tracepoints for a future run
8187 @subsection @code{tfind @var{n}}
8190 @cindex select trace snapshot
8191 @cindex find trace snapshot
8192 The basic command for selecting a trace snapshot from the buffer is
8193 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
8194 counting from zero. If no argument @var{n} is given, the next
8195 snapshot is selected.
8197 Here are the various forms of using the @code{tfind} command.
8201 Find the first snapshot in the buffer. This is a synonym for
8202 @code{tfind 0} (since 0 is the number of the first snapshot).
8205 Stop debugging trace snapshots, resume @emph{live} debugging.
8208 Same as @samp{tfind none}.
8211 No argument means find the next trace snapshot.
8214 Find the previous trace snapshot before the current one. This permits
8215 retracing earlier steps.
8217 @item tfind tracepoint @var{num}
8218 Find the next snapshot associated with tracepoint @var{num}. Search
8219 proceeds forward from the last examined trace snapshot. If no
8220 argument @var{num} is given, it means find the next snapshot collected
8221 for the same tracepoint as the current snapshot.
8223 @item tfind pc @var{addr}
8224 Find the next snapshot associated with the value @var{addr} of the
8225 program counter. Search proceeds forward from the last examined trace
8226 snapshot. If no argument @var{addr} is given, it means find the next
8227 snapshot with the same value of PC as the current snapshot.
8229 @item tfind outside @var{addr1}, @var{addr2}
8230 Find the next snapshot whose PC is outside the given range of
8233 @item tfind range @var{addr1}, @var{addr2}
8234 Find the next snapshot whose PC is between @var{addr1} and
8235 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
8237 @item tfind line @r{[}@var{file}:@r{]}@var{n}
8238 Find the next snapshot associated with the source line @var{n}. If
8239 the optional argument @var{file} is given, refer to line @var{n} in
8240 that source file. Search proceeds forward from the last examined
8241 trace snapshot. If no argument @var{n} is given, it means find the
8242 next line other than the one currently being examined; thus saying
8243 @code{tfind line} repeatedly can appear to have the same effect as
8244 stepping from line to line in a @emph{live} debugging session.
8247 The default arguments for the @code{tfind} commands are specifically
8248 designed to make it easy to scan through the trace buffer. For
8249 instance, @code{tfind} with no argument selects the next trace
8250 snapshot, and @code{tfind -} with no argument selects the previous
8251 trace snapshot. So, by giving one @code{tfind} command, and then
8252 simply hitting @key{RET} repeatedly you can examine all the trace
8253 snapshots in order. Or, by saying @code{tfind -} and then hitting
8254 @key{RET} repeatedly you can examine the snapshots in reverse order.
8255 The @code{tfind line} command with no argument selects the snapshot
8256 for the next source line executed. The @code{tfind pc} command with
8257 no argument selects the next snapshot with the same program counter
8258 (PC) as the current frame. The @code{tfind tracepoint} command with
8259 no argument selects the next trace snapshot collected by the same
8260 tracepoint as the current one.
8262 In addition to letting you scan through the trace buffer manually,
8263 these commands make it easy to construct @value{GDBN} scripts that
8264 scan through the trace buffer and print out whatever collected data
8265 you are interested in. Thus, if we want to examine the PC, FP, and SP
8266 registers from each trace frame in the buffer, we can say this:
8269 (@value{GDBP}) @b{tfind start}
8270 (@value{GDBP}) @b{while ($trace_frame != -1)}
8271 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
8272 $trace_frame, $pc, $sp, $fp
8276 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
8277 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
8278 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
8279 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
8280 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
8281 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
8282 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
8283 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
8284 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
8285 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
8286 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
8289 Or, if we want to examine the variable @code{X} at each source line in
8293 (@value{GDBP}) @b{tfind start}
8294 (@value{GDBP}) @b{while ($trace_frame != -1)}
8295 > printf "Frame %d, X == %d\n", $trace_frame, X
8305 @subsection @code{tdump}
8307 @cindex dump all data collected at tracepoint
8308 @cindex tracepoint data, display
8310 This command takes no arguments. It prints all the data collected at
8311 the current trace snapshot.
8314 (@value{GDBP}) @b{trace 444}
8315 (@value{GDBP}) @b{actions}
8316 Enter actions for tracepoint #2, one per line:
8317 > collect $regs, $locals, $args, gdb_long_test
8320 (@value{GDBP}) @b{tstart}
8322 (@value{GDBP}) @b{tfind line 444}
8323 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
8325 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
8327 (@value{GDBP}) @b{tdump}
8328 Data collected at tracepoint 2, trace frame 1:
8329 d0 0xc4aa0085 -995491707
8333 d4 0x71aea3d 119204413
8338 a1 0x3000668 50333288
8341 a4 0x3000698 50333336
8343 fp 0x30bf3c 0x30bf3c
8344 sp 0x30bf34 0x30bf34
8346 pc 0x20b2c8 0x20b2c8
8350 p = 0x20e5b4 "gdb-test"
8357 gdb_long_test = 17 '\021'
8362 @node save-tracepoints
8363 @subsection @code{save-tracepoints @var{filename}}
8364 @kindex save-tracepoints
8365 @cindex save tracepoints for future sessions
8367 This command saves all current tracepoint definitions together with
8368 their actions and passcounts, into a file @file{@var{filename}}
8369 suitable for use in a later debugging session. To read the saved
8370 tracepoint definitions, use the @code{source} command (@pxref{Command
8373 @node Tracepoint Variables
8374 @section Convenience Variables for Tracepoints
8375 @cindex tracepoint variables
8376 @cindex convenience variables for tracepoints
8379 @vindex $trace_frame
8380 @item (int) $trace_frame
8381 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
8382 snapshot is selected.
8385 @item (int) $tracepoint
8386 The tracepoint for the current trace snapshot.
8389 @item (int) $trace_line
8390 The line number for the current trace snapshot.
8393 @item (char []) $trace_file
8394 The source file for the current trace snapshot.
8397 @item (char []) $trace_func
8398 The name of the function containing @code{$tracepoint}.
8401 Note: @code{$trace_file} is not suitable for use in @code{printf},
8402 use @code{output} instead.
8404 Here's a simple example of using these convenience variables for
8405 stepping through all the trace snapshots and printing some of their
8409 (@value{GDBP}) @b{tfind start}
8411 (@value{GDBP}) @b{while $trace_frame != -1}
8412 > output $trace_file
8413 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
8419 @chapter Debugging Programs That Use Overlays
8422 If your program is too large to fit completely in your target system's
8423 memory, you can sometimes use @dfn{overlays} to work around this
8424 problem. @value{GDBN} provides some support for debugging programs that
8428 * How Overlays Work:: A general explanation of overlays.
8429 * Overlay Commands:: Managing overlays in @value{GDBN}.
8430 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
8431 mapped by asking the inferior.
8432 * Overlay Sample Program:: A sample program using overlays.
8435 @node How Overlays Work
8436 @section How Overlays Work
8437 @cindex mapped overlays
8438 @cindex unmapped overlays
8439 @cindex load address, overlay's
8440 @cindex mapped address
8441 @cindex overlay area
8443 Suppose you have a computer whose instruction address space is only 64
8444 kilobytes long, but which has much more memory which can be accessed by
8445 other means: special instructions, segment registers, or memory
8446 management hardware, for example. Suppose further that you want to
8447 adapt a program which is larger than 64 kilobytes to run on this system.
8449 One solution is to identify modules of your program which are relatively
8450 independent, and need not call each other directly; call these modules
8451 @dfn{overlays}. Separate the overlays from the main program, and place
8452 their machine code in the larger memory. Place your main program in
8453 instruction memory, but leave at least enough space there to hold the
8454 largest overlay as well.
8456 Now, to call a function located in an overlay, you must first copy that
8457 overlay's machine code from the large memory into the space set aside
8458 for it in the instruction memory, and then jump to its entry point
8461 @c NB: In the below the mapped area's size is greater or equal to the
8462 @c size of all overlays. This is intentional to remind the developer
8463 @c that overlays don't necessarily need to be the same size.
8467 Data Instruction Larger
8468 Address Space Address Space Address Space
8469 +-----------+ +-----------+ +-----------+
8471 +-----------+ +-----------+ +-----------+<-- overlay 1
8472 | program | | main | .----| overlay 1 | load address
8473 | variables | | program | | +-----------+
8474 | and heap | | | | | |
8475 +-----------+ | | | +-----------+<-- overlay 2
8476 | | +-----------+ | | | load address
8477 +-----------+ | | | .-| overlay 2 |
8479 mapped --->+-----------+ | | +-----------+
8481 | overlay | <-' | | |
8482 | area | <---' +-----------+<-- overlay 3
8483 | | <---. | | load address
8484 +-----------+ `--| overlay 3 |
8491 @anchor{A code overlay}A code overlay
8495 The diagram (@pxref{A code overlay}) shows a system with separate data
8496 and instruction address spaces. To map an overlay, the program copies
8497 its code from the larger address space to the instruction address space.
8498 Since the overlays shown here all use the same mapped address, only one
8499 may be mapped at a time. For a system with a single address space for
8500 data and instructions, the diagram would be similar, except that the
8501 program variables and heap would share an address space with the main
8502 program and the overlay area.
8504 An overlay loaded into instruction memory and ready for use is called a
8505 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
8506 instruction memory. An overlay not present (or only partially present)
8507 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
8508 is its address in the larger memory. The mapped address is also called
8509 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
8510 called the @dfn{load memory address}, or @dfn{LMA}.
8512 Unfortunately, overlays are not a completely transparent way to adapt a
8513 program to limited instruction memory. They introduce a new set of
8514 global constraints you must keep in mind as you design your program:
8519 Before calling or returning to a function in an overlay, your program
8520 must make sure that overlay is actually mapped. Otherwise, the call or
8521 return will transfer control to the right address, but in the wrong
8522 overlay, and your program will probably crash.
8525 If the process of mapping an overlay is expensive on your system, you
8526 will need to choose your overlays carefully to minimize their effect on
8527 your program's performance.
8530 The executable file you load onto your system must contain each
8531 overlay's instructions, appearing at the overlay's load address, not its
8532 mapped address. However, each overlay's instructions must be relocated
8533 and its symbols defined as if the overlay were at its mapped address.
8534 You can use GNU linker scripts to specify different load and relocation
8535 addresses for pieces of your program; see @ref{Overlay Description,,,
8536 ld.info, Using ld: the GNU linker}.
8539 The procedure for loading executable files onto your system must be able
8540 to load their contents into the larger address space as well as the
8541 instruction and data spaces.
8545 The overlay system described above is rather simple, and could be
8546 improved in many ways:
8551 If your system has suitable bank switch registers or memory management
8552 hardware, you could use those facilities to make an overlay's load area
8553 contents simply appear at their mapped address in instruction space.
8554 This would probably be faster than copying the overlay to its mapped
8555 area in the usual way.
8558 If your overlays are small enough, you could set aside more than one
8559 overlay area, and have more than one overlay mapped at a time.
8562 You can use overlays to manage data, as well as instructions. In
8563 general, data overlays are even less transparent to your design than
8564 code overlays: whereas code overlays only require care when you call or
8565 return to functions, data overlays require care every time you access
8566 the data. Also, if you change the contents of a data overlay, you
8567 must copy its contents back out to its load address before you can copy a
8568 different data overlay into the same mapped area.
8573 @node Overlay Commands
8574 @section Overlay Commands
8576 To use @value{GDBN}'s overlay support, each overlay in your program must
8577 correspond to a separate section of the executable file. The section's
8578 virtual memory address and load memory address must be the overlay's
8579 mapped and load addresses. Identifying overlays with sections allows
8580 @value{GDBN} to determine the appropriate address of a function or
8581 variable, depending on whether the overlay is mapped or not.
8583 @value{GDBN}'s overlay commands all start with the word @code{overlay};
8584 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
8589 Disable @value{GDBN}'s overlay support. When overlay support is
8590 disabled, @value{GDBN} assumes that all functions and variables are
8591 always present at their mapped addresses. By default, @value{GDBN}'s
8592 overlay support is disabled.
8594 @item overlay manual
8595 @cindex manual overlay debugging
8596 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
8597 relies on you to tell it which overlays are mapped, and which are not,
8598 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
8599 commands described below.
8601 @item overlay map-overlay @var{overlay}
8602 @itemx overlay map @var{overlay}
8603 @cindex map an overlay
8604 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
8605 be the name of the object file section containing the overlay. When an
8606 overlay is mapped, @value{GDBN} assumes it can find the overlay's
8607 functions and variables at their mapped addresses. @value{GDBN} assumes
8608 that any other overlays whose mapped ranges overlap that of
8609 @var{overlay} are now unmapped.
8611 @item overlay unmap-overlay @var{overlay}
8612 @itemx overlay unmap @var{overlay}
8613 @cindex unmap an overlay
8614 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
8615 must be the name of the object file section containing the overlay.
8616 When an overlay is unmapped, @value{GDBN} assumes it can find the
8617 overlay's functions and variables at their load addresses.
8620 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
8621 consults a data structure the overlay manager maintains in the inferior
8622 to see which overlays are mapped. For details, see @ref{Automatic
8625 @item overlay load-target
8627 @cindex reloading the overlay table
8628 Re-read the overlay table from the inferior. Normally, @value{GDBN}
8629 re-reads the table @value{GDBN} automatically each time the inferior
8630 stops, so this command should only be necessary if you have changed the
8631 overlay mapping yourself using @value{GDBN}. This command is only
8632 useful when using automatic overlay debugging.
8634 @item overlay list-overlays
8636 @cindex listing mapped overlays
8637 Display a list of the overlays currently mapped, along with their mapped
8638 addresses, load addresses, and sizes.
8642 Normally, when @value{GDBN} prints a code address, it includes the name
8643 of the function the address falls in:
8646 (@value{GDBP}) print main
8647 $3 = @{int ()@} 0x11a0 <main>
8650 When overlay debugging is enabled, @value{GDBN} recognizes code in
8651 unmapped overlays, and prints the names of unmapped functions with
8652 asterisks around them. For example, if @code{foo} is a function in an
8653 unmapped overlay, @value{GDBN} prints it this way:
8656 (@value{GDBP}) overlay list
8657 No sections are mapped.
8658 (@value{GDBP}) print foo
8659 $5 = @{int (int)@} 0x100000 <*foo*>
8662 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
8666 (@value{GDBP}) overlay list
8667 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
8668 mapped at 0x1016 - 0x104a
8669 (@value{GDBP}) print foo
8670 $6 = @{int (int)@} 0x1016 <foo>
8673 When overlay debugging is enabled, @value{GDBN} can find the correct
8674 address for functions and variables in an overlay, whether or not the
8675 overlay is mapped. This allows most @value{GDBN} commands, like
8676 @code{break} and @code{disassemble}, to work normally, even on unmapped
8677 code. However, @value{GDBN}'s breakpoint support has some limitations:
8681 @cindex breakpoints in overlays
8682 @cindex overlays, setting breakpoints in
8683 You can set breakpoints in functions in unmapped overlays, as long as
8684 @value{GDBN} can write to the overlay at its load address.
8686 @value{GDBN} can not set hardware or simulator-based breakpoints in
8687 unmapped overlays. However, if you set a breakpoint at the end of your
8688 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
8689 you are using manual overlay management), @value{GDBN} will re-set its
8690 breakpoints properly.
8694 @node Automatic Overlay Debugging
8695 @section Automatic Overlay Debugging
8696 @cindex automatic overlay debugging
8698 @value{GDBN} can automatically track which overlays are mapped and which
8699 are not, given some simple co-operation from the overlay manager in the
8700 inferior. If you enable automatic overlay debugging with the
8701 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
8702 looks in the inferior's memory for certain variables describing the
8703 current state of the overlays.
8705 Here are the variables your overlay manager must define to support
8706 @value{GDBN}'s automatic overlay debugging:
8710 @item @code{_ovly_table}:
8711 This variable must be an array of the following structures:
8716 /* The overlay's mapped address. */
8719 /* The size of the overlay, in bytes. */
8722 /* The overlay's load address. */
8725 /* Non-zero if the overlay is currently mapped;
8727 unsigned long mapped;
8731 @item @code{_novlys}:
8732 This variable must be a four-byte signed integer, holding the total
8733 number of elements in @code{_ovly_table}.
8737 To decide whether a particular overlay is mapped or not, @value{GDBN}
8738 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
8739 @code{lma} members equal the VMA and LMA of the overlay's section in the
8740 executable file. When @value{GDBN} finds a matching entry, it consults
8741 the entry's @code{mapped} member to determine whether the overlay is
8744 In addition, your overlay manager may define a function called
8745 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
8746 will silently set a breakpoint there. If the overlay manager then
8747 calls this function whenever it has changed the overlay table, this
8748 will enable @value{GDBN} to accurately keep track of which overlays
8749 are in program memory, and update any breakpoints that may be set
8750 in overlays. This will allow breakpoints to work even if the
8751 overlays are kept in ROM or other non-writable memory while they
8752 are not being executed.
8754 @node Overlay Sample Program
8755 @section Overlay Sample Program
8756 @cindex overlay example program
8758 When linking a program which uses overlays, you must place the overlays
8759 at their load addresses, while relocating them to run at their mapped
8760 addresses. To do this, you must write a linker script (@pxref{Overlay
8761 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
8762 since linker scripts are specific to a particular host system, target
8763 architecture, and target memory layout, this manual cannot provide
8764 portable sample code demonstrating @value{GDBN}'s overlay support.
8766 However, the @value{GDBN} source distribution does contain an overlaid
8767 program, with linker scripts for a few systems, as part of its test
8768 suite. The program consists of the following files from
8769 @file{gdb/testsuite/gdb.base}:
8773 The main program file.
8775 A simple overlay manager, used by @file{overlays.c}.
8780 Overlay modules, loaded and used by @file{overlays.c}.
8783 Linker scripts for linking the test program on the @code{d10v-elf}
8784 and @code{m32r-elf} targets.
8787 You can build the test program using the @code{d10v-elf} GCC
8788 cross-compiler like this:
8791 $ d10v-elf-gcc -g -c overlays.c
8792 $ d10v-elf-gcc -g -c ovlymgr.c
8793 $ d10v-elf-gcc -g -c foo.c
8794 $ d10v-elf-gcc -g -c bar.c
8795 $ d10v-elf-gcc -g -c baz.c
8796 $ d10v-elf-gcc -g -c grbx.c
8797 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
8798 baz.o grbx.o -Wl,-Td10v.ld -o overlays
8801 The build process is identical for any other architecture, except that
8802 you must substitute the appropriate compiler and linker script for the
8803 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
8807 @chapter Using @value{GDBN} with Different Languages
8810 Although programming languages generally have common aspects, they are
8811 rarely expressed in the same manner. For instance, in ANSI C,
8812 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
8813 Modula-2, it is accomplished by @code{p^}. Values can also be
8814 represented (and displayed) differently. Hex numbers in C appear as
8815 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
8817 @cindex working language
8818 Language-specific information is built into @value{GDBN} for some languages,
8819 allowing you to express operations like the above in your program's
8820 native language, and allowing @value{GDBN} to output values in a manner
8821 consistent with the syntax of your program's native language. The
8822 language you use to build expressions is called the @dfn{working
8826 * Setting:: Switching between source languages
8827 * Show:: Displaying the language
8828 * Checks:: Type and range checks
8829 * Supported Languages:: Supported languages
8830 * Unsupported Languages:: Unsupported languages
8834 @section Switching Between Source Languages
8836 There are two ways to control the working language---either have @value{GDBN}
8837 set it automatically, or select it manually yourself. You can use the
8838 @code{set language} command for either purpose. On startup, @value{GDBN}
8839 defaults to setting the language automatically. The working language is
8840 used to determine how expressions you type are interpreted, how values
8843 In addition to the working language, every source file that
8844 @value{GDBN} knows about has its own working language. For some object
8845 file formats, the compiler might indicate which language a particular
8846 source file is in. However, most of the time @value{GDBN} infers the
8847 language from the name of the file. The language of a source file
8848 controls whether C@t{++} names are demangled---this way @code{backtrace} can
8849 show each frame appropriately for its own language. There is no way to
8850 set the language of a source file from within @value{GDBN}, but you can
8851 set the language associated with a filename extension. @xref{Show, ,
8852 Displaying the Language}.
8854 This is most commonly a problem when you use a program, such
8855 as @code{cfront} or @code{f2c}, that generates C but is written in
8856 another language. In that case, make the
8857 program use @code{#line} directives in its C output; that way
8858 @value{GDBN} will know the correct language of the source code of the original
8859 program, and will display that source code, not the generated C code.
8862 * Filenames:: Filename extensions and languages.
8863 * Manually:: Setting the working language manually
8864 * Automatically:: Having @value{GDBN} infer the source language
8868 @subsection List of Filename Extensions and Languages
8870 If a source file name ends in one of the following extensions, then
8871 @value{GDBN} infers that its language is the one indicated.
8892 Objective-C source file
8899 Modula-2 source file
8903 Assembler source file. This actually behaves almost like C, but
8904 @value{GDBN} does not skip over function prologues when stepping.
8907 In addition, you may set the language associated with a filename
8908 extension. @xref{Show, , Displaying the Language}.
8911 @subsection Setting the Working Language
8913 If you allow @value{GDBN} to set the language automatically,
8914 expressions are interpreted the same way in your debugging session and
8917 @kindex set language
8918 If you wish, you may set the language manually. To do this, issue the
8919 command @samp{set language @var{lang}}, where @var{lang} is the name of
8921 @code{c} or @code{modula-2}.
8922 For a list of the supported languages, type @samp{set language}.
8924 Setting the language manually prevents @value{GDBN} from updating the working
8925 language automatically. This can lead to confusion if you try
8926 to debug a program when the working language is not the same as the
8927 source language, when an expression is acceptable to both
8928 languages---but means different things. For instance, if the current
8929 source file were written in C, and @value{GDBN} was parsing Modula-2, a
8937 might not have the effect you intended. In C, this means to add
8938 @code{b} and @code{c} and place the result in @code{a}. The result
8939 printed would be the value of @code{a}. In Modula-2, this means to compare
8940 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
8943 @subsection Having @value{GDBN} Infer the Source Language
8945 To have @value{GDBN} set the working language automatically, use
8946 @samp{set language local} or @samp{set language auto}. @value{GDBN}
8947 then infers the working language. That is, when your program stops in a
8948 frame (usually by encountering a breakpoint), @value{GDBN} sets the
8949 working language to the language recorded for the function in that
8950 frame. If the language for a frame is unknown (that is, if the function
8951 or block corresponding to the frame was defined in a source file that
8952 does not have a recognized extension), the current working language is
8953 not changed, and @value{GDBN} issues a warning.
8955 This may not seem necessary for most programs, which are written
8956 entirely in one source language. However, program modules and libraries
8957 written in one source language can be used by a main program written in
8958 a different source language. Using @samp{set language auto} in this
8959 case frees you from having to set the working language manually.
8962 @section Displaying the Language
8964 The following commands help you find out which language is the
8965 working language, and also what language source files were written in.
8969 @kindex show language
8970 Display the current working language. This is the
8971 language you can use with commands such as @code{print} to
8972 build and compute expressions that may involve variables in your program.
8975 @kindex info frame@r{, show the source language}
8976 Display the source language for this frame. This language becomes the
8977 working language if you use an identifier from this frame.
8978 @xref{Frame Info, ,Information about a Frame}, to identify the other
8979 information listed here.
8982 @kindex info source@r{, show the source language}
8983 Display the source language of this source file.
8984 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
8985 information listed here.
8988 In unusual circumstances, you may have source files with extensions
8989 not in the standard list. You can then set the extension associated
8990 with a language explicitly:
8993 @item set extension-language @var{ext} @var{language}
8994 @kindex set extension-language
8995 Tell @value{GDBN} that source files with extension @var{ext} are to be
8996 assumed as written in the source language @var{language}.
8998 @item info extensions
8999 @kindex info extensions
9000 List all the filename extensions and the associated languages.
9004 @section Type and Range Checking
9007 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
9008 checking are included, but they do not yet have any effect. This
9009 section documents the intended facilities.
9011 @c FIXME remove warning when type/range code added
9013 Some languages are designed to guard you against making seemingly common
9014 errors through a series of compile- and run-time checks. These include
9015 checking the type of arguments to functions and operators, and making
9016 sure mathematical overflows are caught at run time. Checks such as
9017 these help to ensure a program's correctness once it has been compiled
9018 by eliminating type mismatches, and providing active checks for range
9019 errors when your program is running.
9021 @value{GDBN} can check for conditions like the above if you wish.
9022 Although @value{GDBN} does not check the statements in your program,
9023 it can check expressions entered directly into @value{GDBN} for
9024 evaluation via the @code{print} command, for example. As with the
9025 working language, @value{GDBN} can also decide whether or not to check
9026 automatically based on your program's source language.
9027 @xref{Supported Languages, ,Supported Languages}, for the default
9028 settings of supported languages.
9031 * Type Checking:: An overview of type checking
9032 * Range Checking:: An overview of range checking
9035 @cindex type checking
9036 @cindex checks, type
9038 @subsection An Overview of Type Checking
9040 Some languages, such as Modula-2, are strongly typed, meaning that the
9041 arguments to operators and functions have to be of the correct type,
9042 otherwise an error occurs. These checks prevent type mismatch
9043 errors from ever causing any run-time problems. For example,
9051 The second example fails because the @code{CARDINAL} 1 is not
9052 type-compatible with the @code{REAL} 2.3.
9054 For the expressions you use in @value{GDBN} commands, you can tell the
9055 @value{GDBN} type checker to skip checking;
9056 to treat any mismatches as errors and abandon the expression;
9057 or to only issue warnings when type mismatches occur,
9058 but evaluate the expression anyway. When you choose the last of
9059 these, @value{GDBN} evaluates expressions like the second example above, but
9060 also issues a warning.
9062 Even if you turn type checking off, there may be other reasons
9063 related to type that prevent @value{GDBN} from evaluating an expression.
9064 For instance, @value{GDBN} does not know how to add an @code{int} and
9065 a @code{struct foo}. These particular type errors have nothing to do
9066 with the language in use, and usually arise from expressions, such as
9067 the one described above, which make little sense to evaluate anyway.
9069 Each language defines to what degree it is strict about type. For
9070 instance, both Modula-2 and C require the arguments to arithmetical
9071 operators to be numbers. In C, enumerated types and pointers can be
9072 represented as numbers, so that they are valid arguments to mathematical
9073 operators. @xref{Supported Languages, ,Supported Languages}, for further
9074 details on specific languages.
9076 @value{GDBN} provides some additional commands for controlling the type checker:
9078 @kindex set check type
9079 @kindex show check type
9081 @item set check type auto
9082 Set type checking on or off based on the current working language.
9083 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9086 @item set check type on
9087 @itemx set check type off
9088 Set type checking on or off, overriding the default setting for the
9089 current working language. Issue a warning if the setting does not
9090 match the language default. If any type mismatches occur in
9091 evaluating an expression while type checking is on, @value{GDBN} prints a
9092 message and aborts evaluation of the expression.
9094 @item set check type warn
9095 Cause the type checker to issue warnings, but to always attempt to
9096 evaluate the expression. Evaluating the expression may still
9097 be impossible for other reasons. For example, @value{GDBN} cannot add
9098 numbers and structures.
9101 Show the current setting of the type checker, and whether or not @value{GDBN}
9102 is setting it automatically.
9105 @cindex range checking
9106 @cindex checks, range
9107 @node Range Checking
9108 @subsection An Overview of Range Checking
9110 In some languages (such as Modula-2), it is an error to exceed the
9111 bounds of a type; this is enforced with run-time checks. Such range
9112 checking is meant to ensure program correctness by making sure
9113 computations do not overflow, or indices on an array element access do
9114 not exceed the bounds of the array.
9116 For expressions you use in @value{GDBN} commands, you can tell
9117 @value{GDBN} to treat range errors in one of three ways: ignore them,
9118 always treat them as errors and abandon the expression, or issue
9119 warnings but evaluate the expression anyway.
9121 A range error can result from numerical overflow, from exceeding an
9122 array index bound, or when you type a constant that is not a member
9123 of any type. Some languages, however, do not treat overflows as an
9124 error. In many implementations of C, mathematical overflow causes the
9125 result to ``wrap around'' to lower values---for example, if @var{m} is
9126 the largest integer value, and @var{s} is the smallest, then
9129 @var{m} + 1 @result{} @var{s}
9132 This, too, is specific to individual languages, and in some cases
9133 specific to individual compilers or machines. @xref{Supported Languages, ,
9134 Supported Languages}, for further details on specific languages.
9136 @value{GDBN} provides some additional commands for controlling the range checker:
9138 @kindex set check range
9139 @kindex show check range
9141 @item set check range auto
9142 Set range checking on or off based on the current working language.
9143 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9146 @item set check range on
9147 @itemx set check range off
9148 Set range checking on or off, overriding the default setting for the
9149 current working language. A warning is issued if the setting does not
9150 match the language default. If a range error occurs and range checking is on,
9151 then a message is printed and evaluation of the expression is aborted.
9153 @item set check range warn
9154 Output messages when the @value{GDBN} range checker detects a range error,
9155 but attempt to evaluate the expression anyway. Evaluating the
9156 expression may still be impossible for other reasons, such as accessing
9157 memory that the process does not own (a typical example from many Unix
9161 Show the current setting of the range checker, and whether or not it is
9162 being set automatically by @value{GDBN}.
9165 @node Supported Languages
9166 @section Supported Languages
9168 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
9169 assembly, Modula-2, and Ada.
9170 @c This is false ...
9171 Some @value{GDBN} features may be used in expressions regardless of the
9172 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
9173 and the @samp{@{type@}addr} construct (@pxref{Expressions,
9174 ,Expressions}) can be used with the constructs of any supported
9177 The following sections detail to what degree each source language is
9178 supported by @value{GDBN}. These sections are not meant to be language
9179 tutorials or references, but serve only as a reference guide to what the
9180 @value{GDBN} expression parser accepts, and what input and output
9181 formats should look like for different languages. There are many good
9182 books written on each of these languages; please look to these for a
9183 language reference or tutorial.
9187 * Objective-C:: Objective-C
9190 * Modula-2:: Modula-2
9195 @subsection C and C@t{++}
9197 @cindex C and C@t{++}
9198 @cindex expressions in C or C@t{++}
9200 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
9201 to both languages. Whenever this is the case, we discuss those languages
9205 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
9206 @cindex @sc{gnu} C@t{++}
9207 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
9208 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
9209 effectively, you must compile your C@t{++} programs with a supported
9210 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
9211 compiler (@code{aCC}).
9213 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
9214 format; if it doesn't work on your system, try the stabs+ debugging
9215 format. You can select those formats explicitly with the @code{g++}
9216 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
9217 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
9218 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
9221 * C Operators:: C and C@t{++} operators
9222 * C Constants:: C and C@t{++} constants
9223 * C Plus Plus Expressions:: C@t{++} expressions
9224 * C Defaults:: Default settings for C and C@t{++}
9225 * C Checks:: C and C@t{++} type and range checks
9226 * Debugging C:: @value{GDBN} and C
9227 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
9228 * Decimal Floating Point:: Numbers in Decimal Floating Point format
9232 @subsubsection C and C@t{++} Operators
9234 @cindex C and C@t{++} operators
9236 Operators must be defined on values of specific types. For instance,
9237 @code{+} is defined on numbers, but not on structures. Operators are
9238 often defined on groups of types.
9240 For the purposes of C and C@t{++}, the following definitions hold:
9245 @emph{Integral types} include @code{int} with any of its storage-class
9246 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
9249 @emph{Floating-point types} include @code{float}, @code{double}, and
9250 @code{long double} (if supported by the target platform).
9253 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
9256 @emph{Scalar types} include all of the above.
9261 The following operators are supported. They are listed here
9262 in order of increasing precedence:
9266 The comma or sequencing operator. Expressions in a comma-separated list
9267 are evaluated from left to right, with the result of the entire
9268 expression being the last expression evaluated.
9271 Assignment. The value of an assignment expression is the value
9272 assigned. Defined on scalar types.
9275 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
9276 and translated to @w{@code{@var{a} = @var{a op b}}}.
9277 @w{@code{@var{op}=}} and @code{=} have the same precedence.
9278 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
9279 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
9282 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
9283 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
9287 Logical @sc{or}. Defined on integral types.
9290 Logical @sc{and}. Defined on integral types.
9293 Bitwise @sc{or}. Defined on integral types.
9296 Bitwise exclusive-@sc{or}. Defined on integral types.
9299 Bitwise @sc{and}. Defined on integral types.
9302 Equality and inequality. Defined on scalar types. The value of these
9303 expressions is 0 for false and non-zero for true.
9305 @item <@r{, }>@r{, }<=@r{, }>=
9306 Less than, greater than, less than or equal, greater than or equal.
9307 Defined on scalar types. The value of these expressions is 0 for false
9308 and non-zero for true.
9311 left shift, and right shift. Defined on integral types.
9314 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9317 Addition and subtraction. Defined on integral types, floating-point types and
9320 @item *@r{, }/@r{, }%
9321 Multiplication, division, and modulus. Multiplication and division are
9322 defined on integral and floating-point types. Modulus is defined on
9326 Increment and decrement. When appearing before a variable, the
9327 operation is performed before the variable is used in an expression;
9328 when appearing after it, the variable's value is used before the
9329 operation takes place.
9332 Pointer dereferencing. Defined on pointer types. Same precedence as
9336 Address operator. Defined on variables. Same precedence as @code{++}.
9338 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
9339 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
9340 to examine the address
9341 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
9345 Negative. Defined on integral and floating-point types. Same
9346 precedence as @code{++}.
9349 Logical negation. Defined on integral types. Same precedence as
9353 Bitwise complement operator. Defined on integral types. Same precedence as
9358 Structure member, and pointer-to-structure member. For convenience,
9359 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
9360 pointer based on the stored type information.
9361 Defined on @code{struct} and @code{union} data.
9364 Dereferences of pointers to members.
9367 Array indexing. @code{@var{a}[@var{i}]} is defined as
9368 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
9371 Function parameter list. Same precedence as @code{->}.
9374 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
9375 and @code{class} types.
9378 Doubled colons also represent the @value{GDBN} scope operator
9379 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
9383 If an operator is redefined in the user code, @value{GDBN} usually
9384 attempts to invoke the redefined version instead of using the operator's
9388 @subsubsection C and C@t{++} Constants
9390 @cindex C and C@t{++} constants
9392 @value{GDBN} allows you to express the constants of C and C@t{++} in the
9397 Integer constants are a sequence of digits. Octal constants are
9398 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
9399 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
9400 @samp{l}, specifying that the constant should be treated as a
9404 Floating point constants are a sequence of digits, followed by a decimal
9405 point, followed by a sequence of digits, and optionally followed by an
9406 exponent. An exponent is of the form:
9407 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
9408 sequence of digits. The @samp{+} is optional for positive exponents.
9409 A floating-point constant may also end with a letter @samp{f} or
9410 @samp{F}, specifying that the constant should be treated as being of
9411 the @code{float} (as opposed to the default @code{double}) type; or with
9412 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
9416 Enumerated constants consist of enumerated identifiers, or their
9417 integral equivalents.
9420 Character constants are a single character surrounded by single quotes
9421 (@code{'}), or a number---the ordinal value of the corresponding character
9422 (usually its @sc{ascii} value). Within quotes, the single character may
9423 be represented by a letter or by @dfn{escape sequences}, which are of
9424 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
9425 of the character's ordinal value; or of the form @samp{\@var{x}}, where
9426 @samp{@var{x}} is a predefined special character---for example,
9427 @samp{\n} for newline.
9430 String constants are a sequence of character constants surrounded by
9431 double quotes (@code{"}). Any valid character constant (as described
9432 above) may appear. Double quotes within the string must be preceded by
9433 a backslash, so for instance @samp{"a\"b'c"} is a string of five
9437 Pointer constants are an integral value. You can also write pointers
9438 to constants using the C operator @samp{&}.
9441 Array constants are comma-separated lists surrounded by braces @samp{@{}
9442 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
9443 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
9444 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
9447 @node C Plus Plus Expressions
9448 @subsubsection C@t{++} Expressions
9450 @cindex expressions in C@t{++}
9451 @value{GDBN} expression handling can interpret most C@t{++} expressions.
9453 @cindex debugging C@t{++} programs
9454 @cindex C@t{++} compilers
9455 @cindex debug formats and C@t{++}
9456 @cindex @value{NGCC} and C@t{++}
9458 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
9459 proper compiler and the proper debug format. Currently, @value{GDBN}
9460 works best when debugging C@t{++} code that is compiled with
9461 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
9462 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
9463 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
9464 stabs+ as their default debug format, so you usually don't need to
9465 specify a debug format explicitly. Other compilers and/or debug formats
9466 are likely to work badly or not at all when using @value{GDBN} to debug
9472 @cindex member functions
9474 Member function calls are allowed; you can use expressions like
9477 count = aml->GetOriginal(x, y)
9480 @vindex this@r{, inside C@t{++} member functions}
9481 @cindex namespace in C@t{++}
9483 While a member function is active (in the selected stack frame), your
9484 expressions have the same namespace available as the member function;
9485 that is, @value{GDBN} allows implicit references to the class instance
9486 pointer @code{this} following the same rules as C@t{++}.
9488 @cindex call overloaded functions
9489 @cindex overloaded functions, calling
9490 @cindex type conversions in C@t{++}
9492 You can call overloaded functions; @value{GDBN} resolves the function
9493 call to the right definition, with some restrictions. @value{GDBN} does not
9494 perform overload resolution involving user-defined type conversions,
9495 calls to constructors, or instantiations of templates that do not exist
9496 in the program. It also cannot handle ellipsis argument lists or
9499 It does perform integral conversions and promotions, floating-point
9500 promotions, arithmetic conversions, pointer conversions, conversions of
9501 class objects to base classes, and standard conversions such as those of
9502 functions or arrays to pointers; it requires an exact match on the
9503 number of function arguments.
9505 Overload resolution is always performed, unless you have specified
9506 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
9507 ,@value{GDBN} Features for C@t{++}}.
9509 You must specify @code{set overload-resolution off} in order to use an
9510 explicit function signature to call an overloaded function, as in
9512 p 'foo(char,int)'('x', 13)
9515 The @value{GDBN} command-completion facility can simplify this;
9516 see @ref{Completion, ,Command Completion}.
9518 @cindex reference declarations
9520 @value{GDBN} understands variables declared as C@t{++} references; you can use
9521 them in expressions just as you do in C@t{++} source---they are automatically
9524 In the parameter list shown when @value{GDBN} displays a frame, the values of
9525 reference variables are not displayed (unlike other variables); this
9526 avoids clutter, since references are often used for large structures.
9527 The @emph{address} of a reference variable is always shown, unless
9528 you have specified @samp{set print address off}.
9531 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
9532 expressions can use it just as expressions in your program do. Since
9533 one scope may be defined in another, you can use @code{::} repeatedly if
9534 necessary, for example in an expression like
9535 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
9536 resolving name scope by reference to source files, in both C and C@t{++}
9537 debugging (@pxref{Variables, ,Program Variables}).
9540 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
9541 calling virtual functions correctly, printing out virtual bases of
9542 objects, calling functions in a base subobject, casting objects, and
9543 invoking user-defined operators.
9546 @subsubsection C and C@t{++} Defaults
9548 @cindex C and C@t{++} defaults
9550 If you allow @value{GDBN} to set type and range checking automatically, they
9551 both default to @code{off} whenever the working language changes to
9552 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
9553 selects the working language.
9555 If you allow @value{GDBN} to set the language automatically, it
9556 recognizes source files whose names end with @file{.c}, @file{.C}, or
9557 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
9558 these files, it sets the working language to C or C@t{++}.
9559 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
9560 for further details.
9562 @c Type checking is (a) primarily motivated by Modula-2, and (b)
9563 @c unimplemented. If (b) changes, it might make sense to let this node
9564 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
9567 @subsubsection C and C@t{++} Type and Range Checks
9569 @cindex C and C@t{++} checks
9571 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
9572 is not used. However, if you turn type checking on, @value{GDBN}
9573 considers two variables type equivalent if:
9577 The two variables are structured and have the same structure, union, or
9581 The two variables have the same type name, or types that have been
9582 declared equivalent through @code{typedef}.
9585 @c leaving this out because neither J Gilmore nor R Pesch understand it.
9588 The two @code{struct}, @code{union}, or @code{enum} variables are
9589 declared in the same declaration. (Note: this may not be true for all C
9594 Range checking, if turned on, is done on mathematical operations. Array
9595 indices are not checked, since they are often used to index a pointer
9596 that is not itself an array.
9599 @subsubsection @value{GDBN} and C
9601 The @code{set print union} and @code{show print union} commands apply to
9602 the @code{union} type. When set to @samp{on}, any @code{union} that is
9603 inside a @code{struct} or @code{class} is also printed. Otherwise, it
9604 appears as @samp{@{...@}}.
9606 The @code{@@} operator aids in the debugging of dynamic arrays, formed
9607 with pointers and a memory allocation function. @xref{Expressions,
9610 @node Debugging C Plus Plus
9611 @subsubsection @value{GDBN} Features for C@t{++}
9613 @cindex commands for C@t{++}
9615 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
9616 designed specifically for use with C@t{++}. Here is a summary:
9619 @cindex break in overloaded functions
9620 @item @r{breakpoint menus}
9621 When you want a breakpoint in a function whose name is overloaded,
9622 @value{GDBN} breakpoint menus help you specify which function definition
9623 you want. @xref{Breakpoint Menus,,Breakpoint Menus}.
9625 @cindex overloading in C@t{++}
9626 @item rbreak @var{regex}
9627 Setting breakpoints using regular expressions is helpful for setting
9628 breakpoints on overloaded functions that are not members of any special
9630 @xref{Set Breaks, ,Setting Breakpoints}.
9632 @cindex C@t{++} exception handling
9635 Debug C@t{++} exception handling using these commands. @xref{Set
9636 Catchpoints, , Setting Catchpoints}.
9639 @item ptype @var{typename}
9640 Print inheritance relationships as well as other information for type
9642 @xref{Symbols, ,Examining the Symbol Table}.
9644 @cindex C@t{++} symbol display
9645 @item set print demangle
9646 @itemx show print demangle
9647 @itemx set print asm-demangle
9648 @itemx show print asm-demangle
9649 Control whether C@t{++} symbols display in their source form, both when
9650 displaying code as C@t{++} source and when displaying disassemblies.
9651 @xref{Print Settings, ,Print Settings}.
9653 @item set print object
9654 @itemx show print object
9655 Choose whether to print derived (actual) or declared types of objects.
9656 @xref{Print Settings, ,Print Settings}.
9658 @item set print vtbl
9659 @itemx show print vtbl
9660 Control the format for printing virtual function tables.
9661 @xref{Print Settings, ,Print Settings}.
9662 (The @code{vtbl} commands do not work on programs compiled with the HP
9663 ANSI C@t{++} compiler (@code{aCC}).)
9665 @kindex set overload-resolution
9666 @cindex overloaded functions, overload resolution
9667 @item set overload-resolution on
9668 Enable overload resolution for C@t{++} expression evaluation. The default
9669 is on. For overloaded functions, @value{GDBN} evaluates the arguments
9670 and searches for a function whose signature matches the argument types,
9671 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
9672 Expressions, ,C@t{++} Expressions}, for details).
9673 If it cannot find a match, it emits a message.
9675 @item set overload-resolution off
9676 Disable overload resolution for C@t{++} expression evaluation. For
9677 overloaded functions that are not class member functions, @value{GDBN}
9678 chooses the first function of the specified name that it finds in the
9679 symbol table, whether or not its arguments are of the correct type. For
9680 overloaded functions that are class member functions, @value{GDBN}
9681 searches for a function whose signature @emph{exactly} matches the
9684 @kindex show overload-resolution
9685 @item show overload-resolution
9686 Show the current setting of overload resolution.
9688 @item @r{Overloaded symbol names}
9689 You can specify a particular definition of an overloaded symbol, using
9690 the same notation that is used to declare such symbols in C@t{++}: type
9691 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
9692 also use the @value{GDBN} command-line word completion facilities to list the
9693 available choices, or to finish the type list for you.
9694 @xref{Completion,, Command Completion}, for details on how to do this.
9697 @node Decimal Floating Point
9698 @subsubsection Decimal Floating Point format
9699 @cindex decimal floating point format
9701 @value{GDBN} can examine, set and perform computations with numbers in
9702 decimal floating point format, which in the C language correspond to the
9703 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
9704 specified by the extension to support decimal floating-point arithmetic.
9706 There are two encodings in use, depending on the architecture: BID (Binary
9707 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
9708 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
9711 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
9712 to manipulate decimal floating point numbers, it is not possible to convert
9713 (using a cast, for example) integers wider than 32-bit to decimal float.
9715 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
9716 point computations, error checking in decimal float operations ignores
9717 underflow, overflow and divide by zero exceptions.
9719 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
9720 to inspect @code{_Decimal128} values stored in floating point registers. See
9721 @ref{PowerPC,,PowerPC} for more details.
9724 @subsection Objective-C
9727 This section provides information about some commands and command
9728 options that are useful for debugging Objective-C code. See also
9729 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
9730 few more commands specific to Objective-C support.
9733 * Method Names in Commands::
9734 * The Print Command with Objective-C::
9737 @node Method Names in Commands
9738 @subsubsection Method Names in Commands
9740 The following commands have been extended to accept Objective-C method
9741 names as line specifications:
9743 @kindex clear@r{, and Objective-C}
9744 @kindex break@r{, and Objective-C}
9745 @kindex info line@r{, and Objective-C}
9746 @kindex jump@r{, and Objective-C}
9747 @kindex list@r{, and Objective-C}
9751 @item @code{info line}
9756 A fully qualified Objective-C method name is specified as
9759 -[@var{Class} @var{methodName}]
9762 where the minus sign is used to indicate an instance method and a
9763 plus sign (not shown) is used to indicate a class method. The class
9764 name @var{Class} and method name @var{methodName} are enclosed in
9765 brackets, similar to the way messages are specified in Objective-C
9766 source code. For example, to set a breakpoint at the @code{create}
9767 instance method of class @code{Fruit} in the program currently being
9771 break -[Fruit create]
9774 To list ten program lines around the @code{initialize} class method,
9778 list +[NSText initialize]
9781 In the current version of @value{GDBN}, the plus or minus sign is
9782 required. In future versions of @value{GDBN}, the plus or minus
9783 sign will be optional, but you can use it to narrow the search. It
9784 is also possible to specify just a method name:
9790 You must specify the complete method name, including any colons. If
9791 your program's source files contain more than one @code{create} method,
9792 you'll be presented with a numbered list of classes that implement that
9793 method. Indicate your choice by number, or type @samp{0} to exit if
9796 As another example, to clear a breakpoint established at the
9797 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
9800 clear -[NSWindow makeKeyAndOrderFront:]
9803 @node The Print Command with Objective-C
9804 @subsubsection The Print Command With Objective-C
9805 @cindex Objective-C, print objects
9806 @kindex print-object
9807 @kindex po @r{(@code{print-object})}
9809 The print command has also been extended to accept methods. For example:
9812 print -[@var{object} hash]
9815 @cindex print an Objective-C object description
9816 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
9818 will tell @value{GDBN} to send the @code{hash} message to @var{object}
9819 and print the result. Also, an additional command has been added,
9820 @code{print-object} or @code{po} for short, which is meant to print
9821 the description of an object. However, this command may only work
9822 with certain Objective-C libraries that have a particular hook
9823 function, @code{_NSPrintForDebugger}, defined.
9827 @cindex Fortran-specific support in @value{GDBN}
9829 @value{GDBN} can be used to debug programs written in Fortran, but it
9830 currently supports only the features of Fortran 77 language.
9832 @cindex trailing underscore, in Fortran symbols
9833 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
9834 among them) append an underscore to the names of variables and
9835 functions. When you debug programs compiled by those compilers, you
9836 will need to refer to variables and functions with a trailing
9840 * Fortran Operators:: Fortran operators and expressions
9841 * Fortran Defaults:: Default settings for Fortran
9842 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
9845 @node Fortran Operators
9846 @subsubsection Fortran Operators and Expressions
9848 @cindex Fortran operators and expressions
9850 Operators must be defined on values of specific types. For instance,
9851 @code{+} is defined on numbers, but not on characters or other non-
9852 arithmetic types. Operators are often defined on groups of types.
9856 The exponentiation operator. It raises the first operand to the power
9860 The range operator. Normally used in the form of array(low:high) to
9861 represent a section of array.
9864 @node Fortran Defaults
9865 @subsubsection Fortran Defaults
9867 @cindex Fortran Defaults
9869 Fortran symbols are usually case-insensitive, so @value{GDBN} by
9870 default uses case-insensitive matches for Fortran symbols. You can
9871 change that with the @samp{set case-insensitive} command, see
9872 @ref{Symbols}, for the details.
9874 @node Special Fortran Commands
9875 @subsubsection Special Fortran Commands
9877 @cindex Special Fortran commands
9879 @value{GDBN} has some commands to support Fortran-specific features,
9880 such as displaying common blocks.
9883 @cindex @code{COMMON} blocks, Fortran
9885 @item info common @r{[}@var{common-name}@r{]}
9886 This command prints the values contained in the Fortran @code{COMMON}
9887 block whose name is @var{common-name}. With no argument, the names of
9888 all @code{COMMON} blocks visible at the current program location are
9895 @cindex Pascal support in @value{GDBN}, limitations
9896 Debugging Pascal programs which use sets, subranges, file variables, or
9897 nested functions does not currently work. @value{GDBN} does not support
9898 entering expressions, printing values, or similar features using Pascal
9901 The Pascal-specific command @code{set print pascal_static-members}
9902 controls whether static members of Pascal objects are displayed.
9903 @xref{Print Settings, pascal_static-members}.
9906 @subsection Modula-2
9908 @cindex Modula-2, @value{GDBN} support
9910 The extensions made to @value{GDBN} to support Modula-2 only support
9911 output from the @sc{gnu} Modula-2 compiler (which is currently being
9912 developed). Other Modula-2 compilers are not currently supported, and
9913 attempting to debug executables produced by them is most likely
9914 to give an error as @value{GDBN} reads in the executable's symbol
9917 @cindex expressions in Modula-2
9919 * M2 Operators:: Built-in operators
9920 * Built-In Func/Proc:: Built-in functions and procedures
9921 * M2 Constants:: Modula-2 constants
9922 * M2 Types:: Modula-2 types
9923 * M2 Defaults:: Default settings for Modula-2
9924 * Deviations:: Deviations from standard Modula-2
9925 * M2 Checks:: Modula-2 type and range checks
9926 * M2 Scope:: The scope operators @code{::} and @code{.}
9927 * GDB/M2:: @value{GDBN} and Modula-2
9931 @subsubsection Operators
9932 @cindex Modula-2 operators
9934 Operators must be defined on values of specific types. For instance,
9935 @code{+} is defined on numbers, but not on structures. Operators are
9936 often defined on groups of types. For the purposes of Modula-2, the
9937 following definitions hold:
9942 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
9946 @emph{Character types} consist of @code{CHAR} and its subranges.
9949 @emph{Floating-point types} consist of @code{REAL}.
9952 @emph{Pointer types} consist of anything declared as @code{POINTER TO
9956 @emph{Scalar types} consist of all of the above.
9959 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
9962 @emph{Boolean types} consist of @code{BOOLEAN}.
9966 The following operators are supported, and appear in order of
9967 increasing precedence:
9971 Function argument or array index separator.
9974 Assignment. The value of @var{var} @code{:=} @var{value} is
9978 Less than, greater than on integral, floating-point, or enumerated
9982 Less than or equal to, greater than or equal to
9983 on integral, floating-point and enumerated types, or set inclusion on
9984 set types. Same precedence as @code{<}.
9986 @item =@r{, }<>@r{, }#
9987 Equality and two ways of expressing inequality, valid on scalar types.
9988 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
9989 available for inequality, since @code{#} conflicts with the script
9993 Set membership. Defined on set types and the types of their members.
9994 Same precedence as @code{<}.
9997 Boolean disjunction. Defined on boolean types.
10000 Boolean conjunction. Defined on boolean types.
10003 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
10006 Addition and subtraction on integral and floating-point types, or union
10007 and difference on set types.
10010 Multiplication on integral and floating-point types, or set intersection
10014 Division on floating-point types, or symmetric set difference on set
10015 types. Same precedence as @code{*}.
10018 Integer division and remainder. Defined on integral types. Same
10019 precedence as @code{*}.
10022 Negative. Defined on @code{INTEGER} and @code{REAL} data.
10025 Pointer dereferencing. Defined on pointer types.
10028 Boolean negation. Defined on boolean types. Same precedence as
10032 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
10033 precedence as @code{^}.
10036 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
10039 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
10043 @value{GDBN} and Modula-2 scope operators.
10047 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
10048 treats the use of the operator @code{IN}, or the use of operators
10049 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
10050 @code{<=}, and @code{>=} on sets as an error.
10054 @node Built-In Func/Proc
10055 @subsubsection Built-in Functions and Procedures
10056 @cindex Modula-2 built-ins
10058 Modula-2 also makes available several built-in procedures and functions.
10059 In describing these, the following metavariables are used:
10064 represents an @code{ARRAY} variable.
10067 represents a @code{CHAR} constant or variable.
10070 represents a variable or constant of integral type.
10073 represents an identifier that belongs to a set. Generally used in the
10074 same function with the metavariable @var{s}. The type of @var{s} should
10075 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
10078 represents a variable or constant of integral or floating-point type.
10081 represents a variable or constant of floating-point type.
10087 represents a variable.
10090 represents a variable or constant of one of many types. See the
10091 explanation of the function for details.
10094 All Modula-2 built-in procedures also return a result, described below.
10098 Returns the absolute value of @var{n}.
10101 If @var{c} is a lower case letter, it returns its upper case
10102 equivalent, otherwise it returns its argument.
10105 Returns the character whose ordinal value is @var{i}.
10108 Decrements the value in the variable @var{v} by one. Returns the new value.
10110 @item DEC(@var{v},@var{i})
10111 Decrements the value in the variable @var{v} by @var{i}. Returns the
10114 @item EXCL(@var{m},@var{s})
10115 Removes the element @var{m} from the set @var{s}. Returns the new
10118 @item FLOAT(@var{i})
10119 Returns the floating point equivalent of the integer @var{i}.
10121 @item HIGH(@var{a})
10122 Returns the index of the last member of @var{a}.
10125 Increments the value in the variable @var{v} by one. Returns the new value.
10127 @item INC(@var{v},@var{i})
10128 Increments the value in the variable @var{v} by @var{i}. Returns the
10131 @item INCL(@var{m},@var{s})
10132 Adds the element @var{m} to the set @var{s} if it is not already
10133 there. Returns the new set.
10136 Returns the maximum value of the type @var{t}.
10139 Returns the minimum value of the type @var{t}.
10142 Returns boolean TRUE if @var{i} is an odd number.
10145 Returns the ordinal value of its argument. For example, the ordinal
10146 value of a character is its @sc{ascii} value (on machines supporting the
10147 @sc{ascii} character set). @var{x} must be of an ordered type, which include
10148 integral, character and enumerated types.
10150 @item SIZE(@var{x})
10151 Returns the size of its argument. @var{x} can be a variable or a type.
10153 @item TRUNC(@var{r})
10154 Returns the integral part of @var{r}.
10156 @item TSIZE(@var{x})
10157 Returns the size of its argument. @var{x} can be a variable or a type.
10159 @item VAL(@var{t},@var{i})
10160 Returns the member of the type @var{t} whose ordinal value is @var{i}.
10164 @emph{Warning:} Sets and their operations are not yet supported, so
10165 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
10169 @cindex Modula-2 constants
10171 @subsubsection Constants
10173 @value{GDBN} allows you to express the constants of Modula-2 in the following
10179 Integer constants are simply a sequence of digits. When used in an
10180 expression, a constant is interpreted to be type-compatible with the
10181 rest of the expression. Hexadecimal integers are specified by a
10182 trailing @samp{H}, and octal integers by a trailing @samp{B}.
10185 Floating point constants appear as a sequence of digits, followed by a
10186 decimal point and another sequence of digits. An optional exponent can
10187 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
10188 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
10189 digits of the floating point constant must be valid decimal (base 10)
10193 Character constants consist of a single character enclosed by a pair of
10194 like quotes, either single (@code{'}) or double (@code{"}). They may
10195 also be expressed by their ordinal value (their @sc{ascii} value, usually)
10196 followed by a @samp{C}.
10199 String constants consist of a sequence of characters enclosed by a
10200 pair of like quotes, either single (@code{'}) or double (@code{"}).
10201 Escape sequences in the style of C are also allowed. @xref{C
10202 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
10206 Enumerated constants consist of an enumerated identifier.
10209 Boolean constants consist of the identifiers @code{TRUE} and
10213 Pointer constants consist of integral values only.
10216 Set constants are not yet supported.
10220 @subsubsection Modula-2 Types
10221 @cindex Modula-2 types
10223 Currently @value{GDBN} can print the following data types in Modula-2
10224 syntax: array types, record types, set types, pointer types, procedure
10225 types, enumerated types, subrange types and base types. You can also
10226 print the contents of variables declared using these type.
10227 This section gives a number of simple source code examples together with
10228 sample @value{GDBN} sessions.
10230 The first example contains the following section of code:
10239 and you can request @value{GDBN} to interrogate the type and value of
10240 @code{r} and @code{s}.
10243 (@value{GDBP}) print s
10245 (@value{GDBP}) ptype s
10247 (@value{GDBP}) print r
10249 (@value{GDBP}) ptype r
10254 Likewise if your source code declares @code{s} as:
10258 s: SET ['A'..'Z'] ;
10262 then you may query the type of @code{s} by:
10265 (@value{GDBP}) ptype s
10266 type = SET ['A'..'Z']
10270 Note that at present you cannot interactively manipulate set
10271 expressions using the debugger.
10273 The following example shows how you might declare an array in Modula-2
10274 and how you can interact with @value{GDBN} to print its type and contents:
10278 s: ARRAY [-10..10] OF CHAR ;
10282 (@value{GDBP}) ptype s
10283 ARRAY [-10..10] OF CHAR
10286 Note that the array handling is not yet complete and although the type
10287 is printed correctly, expression handling still assumes that all
10288 arrays have a lower bound of zero and not @code{-10} as in the example
10291 Here are some more type related Modula-2 examples:
10295 colour = (blue, red, yellow, green) ;
10296 t = [blue..yellow] ;
10304 The @value{GDBN} interaction shows how you can query the data type
10305 and value of a variable.
10308 (@value{GDBP}) print s
10310 (@value{GDBP}) ptype t
10311 type = [blue..yellow]
10315 In this example a Modula-2 array is declared and its contents
10316 displayed. Observe that the contents are written in the same way as
10317 their @code{C} counterparts.
10321 s: ARRAY [1..5] OF CARDINAL ;
10327 (@value{GDBP}) print s
10328 $1 = @{1, 0, 0, 0, 0@}
10329 (@value{GDBP}) ptype s
10330 type = ARRAY [1..5] OF CARDINAL
10333 The Modula-2 language interface to @value{GDBN} also understands
10334 pointer types as shown in this example:
10338 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
10345 and you can request that @value{GDBN} describes the type of @code{s}.
10348 (@value{GDBP}) ptype s
10349 type = POINTER TO ARRAY [1..5] OF CARDINAL
10352 @value{GDBN} handles compound types as we can see in this example.
10353 Here we combine array types, record types, pointer types and subrange
10364 myarray = ARRAY myrange OF CARDINAL ;
10365 myrange = [-2..2] ;
10367 s: POINTER TO ARRAY myrange OF foo ;
10371 and you can ask @value{GDBN} to describe the type of @code{s} as shown
10375 (@value{GDBP}) ptype s
10376 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
10379 f3 : ARRAY [-2..2] OF CARDINAL;
10384 @subsubsection Modula-2 Defaults
10385 @cindex Modula-2 defaults
10387 If type and range checking are set automatically by @value{GDBN}, they
10388 both default to @code{on} whenever the working language changes to
10389 Modula-2. This happens regardless of whether you or @value{GDBN}
10390 selected the working language.
10392 If you allow @value{GDBN} to set the language automatically, then entering
10393 code compiled from a file whose name ends with @file{.mod} sets the
10394 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
10395 Infer the Source Language}, for further details.
10398 @subsubsection Deviations from Standard Modula-2
10399 @cindex Modula-2, deviations from
10401 A few changes have been made to make Modula-2 programs easier to debug.
10402 This is done primarily via loosening its type strictness:
10406 Unlike in standard Modula-2, pointer constants can be formed by
10407 integers. This allows you to modify pointer variables during
10408 debugging. (In standard Modula-2, the actual address contained in a
10409 pointer variable is hidden from you; it can only be modified
10410 through direct assignment to another pointer variable or expression that
10411 returned a pointer.)
10414 C escape sequences can be used in strings and characters to represent
10415 non-printable characters. @value{GDBN} prints out strings with these
10416 escape sequences embedded. Single non-printable characters are
10417 printed using the @samp{CHR(@var{nnn})} format.
10420 The assignment operator (@code{:=}) returns the value of its right-hand
10424 All built-in procedures both modify @emph{and} return their argument.
10428 @subsubsection Modula-2 Type and Range Checks
10429 @cindex Modula-2 checks
10432 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
10435 @c FIXME remove warning when type/range checks added
10437 @value{GDBN} considers two Modula-2 variables type equivalent if:
10441 They are of types that have been declared equivalent via a @code{TYPE
10442 @var{t1} = @var{t2}} statement
10445 They have been declared on the same line. (Note: This is true of the
10446 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
10449 As long as type checking is enabled, any attempt to combine variables
10450 whose types are not equivalent is an error.
10452 Range checking is done on all mathematical operations, assignment, array
10453 index bounds, and all built-in functions and procedures.
10456 @subsubsection The Scope Operators @code{::} and @code{.}
10458 @cindex @code{.}, Modula-2 scope operator
10459 @cindex colon, doubled as scope operator
10461 @vindex colon-colon@r{, in Modula-2}
10462 @c Info cannot handle :: but TeX can.
10465 @vindex ::@r{, in Modula-2}
10468 There are a few subtle differences between the Modula-2 scope operator
10469 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
10474 @var{module} . @var{id}
10475 @var{scope} :: @var{id}
10479 where @var{scope} is the name of a module or a procedure,
10480 @var{module} the name of a module, and @var{id} is any declared
10481 identifier within your program, except another module.
10483 Using the @code{::} operator makes @value{GDBN} search the scope
10484 specified by @var{scope} for the identifier @var{id}. If it is not
10485 found in the specified scope, then @value{GDBN} searches all scopes
10486 enclosing the one specified by @var{scope}.
10488 Using the @code{.} operator makes @value{GDBN} search the current scope for
10489 the identifier specified by @var{id} that was imported from the
10490 definition module specified by @var{module}. With this operator, it is
10491 an error if the identifier @var{id} was not imported from definition
10492 module @var{module}, or if @var{id} is not an identifier in
10496 @subsubsection @value{GDBN} and Modula-2
10498 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
10499 Five subcommands of @code{set print} and @code{show print} apply
10500 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
10501 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
10502 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
10503 analogue in Modula-2.
10505 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
10506 with any language, is not useful with Modula-2. Its
10507 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
10508 created in Modula-2 as they can in C or C@t{++}. However, because an
10509 address can be specified by an integral constant, the construct
10510 @samp{@{@var{type}@}@var{adrexp}} is still useful.
10512 @cindex @code{#} in Modula-2
10513 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
10514 interpreted as the beginning of a comment. Use @code{<>} instead.
10520 The extensions made to @value{GDBN} for Ada only support
10521 output from the @sc{gnu} Ada (GNAT) compiler.
10522 Other Ada compilers are not currently supported, and
10523 attempting to debug executables produced by them is most likely
10527 @cindex expressions in Ada
10529 * Ada Mode Intro:: General remarks on the Ada syntax
10530 and semantics supported by Ada mode
10532 * Omissions from Ada:: Restrictions on the Ada expression syntax.
10533 * Additions to Ada:: Extensions of the Ada expression syntax.
10534 * Stopping Before Main Program:: Debugging the program during elaboration.
10535 * Ada Glitches:: Known peculiarities of Ada mode.
10538 @node Ada Mode Intro
10539 @subsubsection Introduction
10540 @cindex Ada mode, general
10542 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
10543 syntax, with some extensions.
10544 The philosophy behind the design of this subset is
10548 That @value{GDBN} should provide basic literals and access to operations for
10549 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
10550 leaving more sophisticated computations to subprograms written into the
10551 program (which therefore may be called from @value{GDBN}).
10554 That type safety and strict adherence to Ada language restrictions
10555 are not particularly important to the @value{GDBN} user.
10558 That brevity is important to the @value{GDBN} user.
10561 Thus, for brevity, the debugger acts as if there were
10562 implicit @code{with} and @code{use} clauses in effect for all user-written
10563 packages, making it unnecessary to fully qualify most names with
10564 their packages, regardless of context. Where this causes ambiguity,
10565 @value{GDBN} asks the user's intent.
10567 The debugger will start in Ada mode if it detects an Ada main program.
10568 As for other languages, it will enter Ada mode when stopped in a program that
10569 was translated from an Ada source file.
10571 While in Ada mode, you may use `@t{--}' for comments. This is useful
10572 mostly for documenting command files. The standard @value{GDBN} comment
10573 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
10574 middle (to allow based literals).
10576 The debugger supports limited overloading. Given a subprogram call in which
10577 the function symbol has multiple definitions, it will use the number of
10578 actual parameters and some information about their types to attempt to narrow
10579 the set of definitions. It also makes very limited use of context, preferring
10580 procedures to functions in the context of the @code{call} command, and
10581 functions to procedures elsewhere.
10583 @node Omissions from Ada
10584 @subsubsection Omissions from Ada
10585 @cindex Ada, omissions from
10587 Here are the notable omissions from the subset:
10591 Only a subset of the attributes are supported:
10595 @t{'First}, @t{'Last}, and @t{'Length}
10596 on array objects (not on types and subtypes).
10599 @t{'Min} and @t{'Max}.
10602 @t{'Pos} and @t{'Val}.
10608 @t{'Range} on array objects (not subtypes), but only as the right
10609 operand of the membership (@code{in}) operator.
10612 @t{'Access}, @t{'Unchecked_Access}, and
10613 @t{'Unrestricted_Access} (a GNAT extension).
10621 @code{Characters.Latin_1} are not available and
10622 concatenation is not implemented. Thus, escape characters in strings are
10623 not currently available.
10626 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
10627 equality of representations. They will generally work correctly
10628 for strings and arrays whose elements have integer or enumeration types.
10629 They may not work correctly for arrays whose element
10630 types have user-defined equality, for arrays of real values
10631 (in particular, IEEE-conformant floating point, because of negative
10632 zeroes and NaNs), and for arrays whose elements contain unused bits with
10633 indeterminate values.
10636 The other component-by-component array operations (@code{and}, @code{or},
10637 @code{xor}, @code{not}, and relational tests other than equality)
10638 are not implemented.
10641 @cindex array aggregates (Ada)
10642 @cindex record aggregates (Ada)
10643 @cindex aggregates (Ada)
10644 There is limited support for array and record aggregates. They are
10645 permitted only on the right sides of assignments, as in these examples:
10648 set An_Array := (1, 2, 3, 4, 5, 6)
10649 set An_Array := (1, others => 0)
10650 set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
10651 set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
10652 set A_Record := (1, "Peter", True);
10653 set A_Record := (Name => "Peter", Id => 1, Alive => True)
10657 discriminant's value by assigning an aggregate has an
10658 undefined effect if that discriminant is used within the record.
10659 However, you can first modify discriminants by directly assigning to
10660 them (which normally would not be allowed in Ada), and then performing an
10661 aggregate assignment. For example, given a variable @code{A_Rec}
10662 declared to have a type such as:
10665 type Rec (Len : Small_Integer := 0) is record
10667 Vals : IntArray (1 .. Len);
10671 you can assign a value with a different size of @code{Vals} with two
10676 set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
10679 As this example also illustrates, @value{GDBN} is very loose about the usual
10680 rules concerning aggregates. You may leave out some of the
10681 components of an array or record aggregate (such as the @code{Len}
10682 component in the assignment to @code{A_Rec} above); they will retain their
10683 original values upon assignment. You may freely use dynamic values as
10684 indices in component associations. You may even use overlapping or
10685 redundant component associations, although which component values are
10686 assigned in such cases is not defined.
10689 Calls to dispatching subprograms are not implemented.
10692 The overloading algorithm is much more limited (i.e., less selective)
10693 than that of real Ada. It makes only limited use of the context in
10694 which a subexpression appears to resolve its meaning, and it is much
10695 looser in its rules for allowing type matches. As a result, some
10696 function calls will be ambiguous, and the user will be asked to choose
10697 the proper resolution.
10700 The @code{new} operator is not implemented.
10703 Entry calls are not implemented.
10706 Aside from printing, arithmetic operations on the native VAX floating-point
10707 formats are not supported.
10710 It is not possible to slice a packed array.
10713 @node Additions to Ada
10714 @subsubsection Additions to Ada
10715 @cindex Ada, deviations from
10717 As it does for other languages, @value{GDBN} makes certain generic
10718 extensions to Ada (@pxref{Expressions}):
10722 If the expression @var{E} is a variable residing in memory (typically
10723 a local variable or array element) and @var{N} is a positive integer,
10724 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
10725 @var{N}-1 adjacent variables following it in memory as an array. In
10726 Ada, this operator is generally not necessary, since its prime use is
10727 in displaying parts of an array, and slicing will usually do this in
10728 Ada. However, there are occasional uses when debugging programs in
10729 which certain debugging information has been optimized away.
10732 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
10733 appears in function or file @var{B}.'' When @var{B} is a file name,
10734 you must typically surround it in single quotes.
10737 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
10738 @var{type} that appears at address @var{addr}.''
10741 A name starting with @samp{$} is a convenience variable
10742 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
10745 In addition, @value{GDBN} provides a few other shortcuts and outright
10746 additions specific to Ada:
10750 The assignment statement is allowed as an expression, returning
10751 its right-hand operand as its value. Thus, you may enter
10755 print A(tmp := y + 1)
10759 The semicolon is allowed as an ``operator,'' returning as its value
10760 the value of its right-hand operand.
10761 This allows, for example,
10762 complex conditional breaks:
10766 condition 1 (report(i); k += 1; A(k) > 100)
10770 Rather than use catenation and symbolic character names to introduce special
10771 characters into strings, one may instead use a special bracket notation,
10772 which is also used to print strings. A sequence of characters of the form
10773 @samp{["@var{XX}"]} within a string or character literal denotes the
10774 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
10775 sequence of characters @samp{["""]} also denotes a single quotation mark
10776 in strings. For example,
10778 "One line.["0a"]Next line.["0a"]"
10781 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
10785 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
10786 @t{'Max} is optional (and is ignored in any case). For example, it is valid
10794 When printing arrays, @value{GDBN} uses positional notation when the
10795 array has a lower bound of 1, and uses a modified named notation otherwise.
10796 For example, a one-dimensional array of three integers with a lower bound
10797 of 3 might print as
10804 That is, in contrast to valid Ada, only the first component has a @code{=>}
10808 You may abbreviate attributes in expressions with any unique,
10809 multi-character subsequence of
10810 their names (an exact match gets preference).
10811 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
10812 in place of @t{a'length}.
10815 @cindex quoting Ada internal identifiers
10816 Since Ada is case-insensitive, the debugger normally maps identifiers you type
10817 to lower case. The GNAT compiler uses upper-case characters for
10818 some of its internal identifiers, which are normally of no interest to users.
10819 For the rare occasions when you actually have to look at them,
10820 enclose them in angle brackets to avoid the lower-case mapping.
10823 @value{GDBP} print <JMPBUF_SAVE>[0]
10827 Printing an object of class-wide type or dereferencing an
10828 access-to-class-wide value will display all the components of the object's
10829 specific type (as indicated by its run-time tag). Likewise, component
10830 selection on such a value will operate on the specific type of the
10835 @node Stopping Before Main Program
10836 @subsubsection Stopping at the Very Beginning
10838 @cindex breakpointing Ada elaboration code
10839 It is sometimes necessary to debug the program during elaboration, and
10840 before reaching the main procedure.
10841 As defined in the Ada Reference
10842 Manual, the elaboration code is invoked from a procedure called
10843 @code{adainit}. To run your program up to the beginning of
10844 elaboration, simply use the following two commands:
10845 @code{tbreak adainit} and @code{run}.
10848 @subsubsection Known Peculiarities of Ada Mode
10849 @cindex Ada, problems
10851 Besides the omissions listed previously (@pxref{Omissions from Ada}),
10852 we know of several problems with and limitations of Ada mode in
10854 some of which will be fixed with planned future releases of the debugger
10855 and the GNU Ada compiler.
10859 Currently, the debugger
10860 has insufficient information to determine whether certain pointers represent
10861 pointers to objects or the objects themselves.
10862 Thus, the user may have to tack an extra @code{.all} after an expression
10863 to get it printed properly.
10866 Static constants that the compiler chooses not to materialize as objects in
10867 storage are invisible to the debugger.
10870 Named parameter associations in function argument lists are ignored (the
10871 argument lists are treated as positional).
10874 Many useful library packages are currently invisible to the debugger.
10877 Fixed-point arithmetic, conversions, input, and output is carried out using
10878 floating-point arithmetic, and may give results that only approximate those on
10882 The type of the @t{'Address} attribute may not be @code{System.Address}.
10885 The GNAT compiler never generates the prefix @code{Standard} for any of
10886 the standard symbols defined by the Ada language. @value{GDBN} knows about
10887 this: it will strip the prefix from names when you use it, and will never
10888 look for a name you have so qualified among local symbols, nor match against
10889 symbols in other packages or subprograms. If you have
10890 defined entities anywhere in your program other than parameters and
10891 local variables whose simple names match names in @code{Standard},
10892 GNAT's lack of qualification here can cause confusion. When this happens,
10893 you can usually resolve the confusion
10894 by qualifying the problematic names with package
10895 @code{Standard} explicitly.
10898 @node Unsupported Languages
10899 @section Unsupported Languages
10901 @cindex unsupported languages
10902 @cindex minimal language
10903 In addition to the other fully-supported programming languages,
10904 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
10905 It does not represent a real programming language, but provides a set
10906 of capabilities close to what the C or assembly languages provide.
10907 This should allow most simple operations to be performed while debugging
10908 an application that uses a language currently not supported by @value{GDBN}.
10910 If the language is set to @code{auto}, @value{GDBN} will automatically
10911 select this language if the current frame corresponds to an unsupported
10915 @chapter Examining the Symbol Table
10917 The commands described in this chapter allow you to inquire about the
10918 symbols (names of variables, functions and types) defined in your
10919 program. This information is inherent in the text of your program and
10920 does not change as your program executes. @value{GDBN} finds it in your
10921 program's symbol table, in the file indicated when you started @value{GDBN}
10922 (@pxref{File Options, ,Choosing Files}), or by one of the
10923 file-management commands (@pxref{Files, ,Commands to Specify Files}).
10925 @cindex symbol names
10926 @cindex names of symbols
10927 @cindex quoting names
10928 Occasionally, you may need to refer to symbols that contain unusual
10929 characters, which @value{GDBN} ordinarily treats as word delimiters. The
10930 most frequent case is in referring to static variables in other
10931 source files (@pxref{Variables,,Program Variables}). File names
10932 are recorded in object files as debugging symbols, but @value{GDBN} would
10933 ordinarily parse a typical file name, like @file{foo.c}, as the three words
10934 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
10935 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
10942 looks up the value of @code{x} in the scope of the file @file{foo.c}.
10945 @cindex case-insensitive symbol names
10946 @cindex case sensitivity in symbol names
10947 @kindex set case-sensitive
10948 @item set case-sensitive on
10949 @itemx set case-sensitive off
10950 @itemx set case-sensitive auto
10951 Normally, when @value{GDBN} looks up symbols, it matches their names
10952 with case sensitivity determined by the current source language.
10953 Occasionally, you may wish to control that. The command @code{set
10954 case-sensitive} lets you do that by specifying @code{on} for
10955 case-sensitive matches or @code{off} for case-insensitive ones. If
10956 you specify @code{auto}, case sensitivity is reset to the default
10957 suitable for the source language. The default is case-sensitive
10958 matches for all languages except for Fortran, for which the default is
10959 case-insensitive matches.
10961 @kindex show case-sensitive
10962 @item show case-sensitive
10963 This command shows the current setting of case sensitivity for symbols
10966 @kindex info address
10967 @cindex address of a symbol
10968 @item info address @var{symbol}
10969 Describe where the data for @var{symbol} is stored. For a register
10970 variable, this says which register it is kept in. For a non-register
10971 local variable, this prints the stack-frame offset at which the variable
10974 Note the contrast with @samp{print &@var{symbol}}, which does not work
10975 at all for a register variable, and for a stack local variable prints
10976 the exact address of the current instantiation of the variable.
10978 @kindex info symbol
10979 @cindex symbol from address
10980 @cindex closest symbol and offset for an address
10981 @item info symbol @var{addr}
10982 Print the name of a symbol which is stored at the address @var{addr}.
10983 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
10984 nearest symbol and an offset from it:
10987 (@value{GDBP}) info symbol 0x54320
10988 _initialize_vx + 396 in section .text
10992 This is the opposite of the @code{info address} command. You can use
10993 it to find out the name of a variable or a function given its address.
10996 @item whatis [@var{arg}]
10997 Print the data type of @var{arg}, which can be either an expression or
10998 a data type. With no argument, print the data type of @code{$}, the
10999 last value in the value history. If @var{arg} is an expression, it is
11000 not actually evaluated, and any side-effecting operations (such as
11001 assignments or function calls) inside it do not take place. If
11002 @var{arg} is a type name, it may be the name of a type or typedef, or
11003 for C code it may have the form @samp{class @var{class-name}},
11004 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
11005 @samp{enum @var{enum-tag}}.
11006 @xref{Expressions, ,Expressions}.
11009 @item ptype [@var{arg}]
11010 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
11011 detailed description of the type, instead of just the name of the type.
11012 @xref{Expressions, ,Expressions}.
11014 For example, for this variable declaration:
11017 struct complex @{double real; double imag;@} v;
11021 the two commands give this output:
11025 (@value{GDBP}) whatis v
11026 type = struct complex
11027 (@value{GDBP}) ptype v
11028 type = struct complex @{
11036 As with @code{whatis}, using @code{ptype} without an argument refers to
11037 the type of @code{$}, the last value in the value history.
11039 @cindex incomplete type
11040 Sometimes, programs use opaque data types or incomplete specifications
11041 of complex data structure. If the debug information included in the
11042 program does not allow @value{GDBN} to display a full declaration of
11043 the data type, it will say @samp{<incomplete type>}. For example,
11044 given these declarations:
11048 struct foo *fooptr;
11052 but no definition for @code{struct foo} itself, @value{GDBN} will say:
11055 (@value{GDBP}) ptype foo
11056 $1 = <incomplete type>
11060 ``Incomplete type'' is C terminology for data types that are not
11061 completely specified.
11064 @item info types @var{regexp}
11066 Print a brief description of all types whose names match the regular
11067 expression @var{regexp} (or all types in your program, if you supply
11068 no argument). Each complete typename is matched as though it were a
11069 complete line; thus, @samp{i type value} gives information on all
11070 types in your program whose names include the string @code{value}, but
11071 @samp{i type ^value$} gives information only on types whose complete
11072 name is @code{value}.
11074 This command differs from @code{ptype} in two ways: first, like
11075 @code{whatis}, it does not print a detailed description; second, it
11076 lists all source files where a type is defined.
11079 @cindex local variables
11080 @item info scope @var{location}
11081 List all the variables local to a particular scope. This command
11082 accepts a @var{location} argument---a function name, a source line, or
11083 an address preceded by a @samp{*}, and prints all the variables local
11084 to the scope defined by that location. (@xref{Specify Location}, for
11085 details about supported forms of @var{location}.) For example:
11088 (@value{GDBP}) @b{info scope command_line_handler}
11089 Scope for command_line_handler:
11090 Symbol rl is an argument at stack/frame offset 8, length 4.
11091 Symbol linebuffer is in static storage at address 0x150a18, length 4.
11092 Symbol linelength is in static storage at address 0x150a1c, length 4.
11093 Symbol p is a local variable in register $esi, length 4.
11094 Symbol p1 is a local variable in register $ebx, length 4.
11095 Symbol nline is a local variable in register $edx, length 4.
11096 Symbol repeat is a local variable at frame offset -8, length 4.
11100 This command is especially useful for determining what data to collect
11101 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
11104 @kindex info source
11106 Show information about the current source file---that is, the source file for
11107 the function containing the current point of execution:
11110 the name of the source file, and the directory containing it,
11112 the directory it was compiled in,
11114 its length, in lines,
11116 which programming language it is written in,
11118 whether the executable includes debugging information for that file, and
11119 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
11121 whether the debugging information includes information about
11122 preprocessor macros.
11126 @kindex info sources
11128 Print the names of all source files in your program for which there is
11129 debugging information, organized into two lists: files whose symbols
11130 have already been read, and files whose symbols will be read when needed.
11132 @kindex info functions
11133 @item info functions
11134 Print the names and data types of all defined functions.
11136 @item info functions @var{regexp}
11137 Print the names and data types of all defined functions
11138 whose names contain a match for regular expression @var{regexp}.
11139 Thus, @samp{info fun step} finds all functions whose names
11140 include @code{step}; @samp{info fun ^step} finds those whose names
11141 start with @code{step}. If a function name contains characters
11142 that conflict with the regular expression language (e.g.@:
11143 @samp{operator*()}), they may be quoted with a backslash.
11145 @kindex info variables
11146 @item info variables
11147 Print the names and data types of all variables that are declared
11148 outside of functions (i.e.@: excluding local variables).
11150 @item info variables @var{regexp}
11151 Print the names and data types of all variables (except for local
11152 variables) whose names contain a match for regular expression
11155 @kindex info classes
11156 @cindex Objective-C, classes and selectors
11158 @itemx info classes @var{regexp}
11159 Display all Objective-C classes in your program, or
11160 (with the @var{regexp} argument) all those matching a particular regular
11163 @kindex info selectors
11164 @item info selectors
11165 @itemx info selectors @var{regexp}
11166 Display all Objective-C selectors in your program, or
11167 (with the @var{regexp} argument) all those matching a particular regular
11171 This was never implemented.
11172 @kindex info methods
11174 @itemx info methods @var{regexp}
11175 The @code{info methods} command permits the user to examine all defined
11176 methods within C@t{++} program, or (with the @var{regexp} argument) a
11177 specific set of methods found in the various C@t{++} classes. Many
11178 C@t{++} classes provide a large number of methods. Thus, the output
11179 from the @code{ptype} command can be overwhelming and hard to use. The
11180 @code{info-methods} command filters the methods, printing only those
11181 which match the regular-expression @var{regexp}.
11184 @cindex reloading symbols
11185 Some systems allow individual object files that make up your program to
11186 be replaced without stopping and restarting your program. For example,
11187 in VxWorks you can simply recompile a defective object file and keep on
11188 running. If you are running on one of these systems, you can allow
11189 @value{GDBN} to reload the symbols for automatically relinked modules:
11192 @kindex set symbol-reloading
11193 @item set symbol-reloading on
11194 Replace symbol definitions for the corresponding source file when an
11195 object file with a particular name is seen again.
11197 @item set symbol-reloading off
11198 Do not replace symbol definitions when encountering object files of the
11199 same name more than once. This is the default state; if you are not
11200 running on a system that permits automatic relinking of modules, you
11201 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
11202 may discard symbols when linking large programs, that may contain
11203 several modules (from different directories or libraries) with the same
11206 @kindex show symbol-reloading
11207 @item show symbol-reloading
11208 Show the current @code{on} or @code{off} setting.
11211 @cindex opaque data types
11212 @kindex set opaque-type-resolution
11213 @item set opaque-type-resolution on
11214 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
11215 declared as a pointer to a @code{struct}, @code{class}, or
11216 @code{union}---for example, @code{struct MyType *}---that is used in one
11217 source file although the full declaration of @code{struct MyType} is in
11218 another source file. The default is on.
11220 A change in the setting of this subcommand will not take effect until
11221 the next time symbols for a file are loaded.
11223 @item set opaque-type-resolution off
11224 Tell @value{GDBN} not to resolve opaque types. In this case, the type
11225 is printed as follows:
11227 @{<no data fields>@}
11230 @kindex show opaque-type-resolution
11231 @item show opaque-type-resolution
11232 Show whether opaque types are resolved or not.
11234 @kindex maint print symbols
11235 @cindex symbol dump
11236 @kindex maint print psymbols
11237 @cindex partial symbol dump
11238 @item maint print symbols @var{filename}
11239 @itemx maint print psymbols @var{filename}
11240 @itemx maint print msymbols @var{filename}
11241 Write a dump of debugging symbol data into the file @var{filename}.
11242 These commands are used to debug the @value{GDBN} symbol-reading code. Only
11243 symbols with debugging data are included. If you use @samp{maint print
11244 symbols}, @value{GDBN} includes all the symbols for which it has already
11245 collected full details: that is, @var{filename} reflects symbols for
11246 only those files whose symbols @value{GDBN} has read. You can use the
11247 command @code{info sources} to find out which files these are. If you
11248 use @samp{maint print psymbols} instead, the dump shows information about
11249 symbols that @value{GDBN} only knows partially---that is, symbols defined in
11250 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
11251 @samp{maint print msymbols} dumps just the minimal symbol information
11252 required for each object file from which @value{GDBN} has read some symbols.
11253 @xref{Files, ,Commands to Specify Files}, for a discussion of how
11254 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
11256 @kindex maint info symtabs
11257 @kindex maint info psymtabs
11258 @cindex listing @value{GDBN}'s internal symbol tables
11259 @cindex symbol tables, listing @value{GDBN}'s internal
11260 @cindex full symbol tables, listing @value{GDBN}'s internal
11261 @cindex partial symbol tables, listing @value{GDBN}'s internal
11262 @item maint info symtabs @r{[} @var{regexp} @r{]}
11263 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
11265 List the @code{struct symtab} or @code{struct partial_symtab}
11266 structures whose names match @var{regexp}. If @var{regexp} is not
11267 given, list them all. The output includes expressions which you can
11268 copy into a @value{GDBN} debugging this one to examine a particular
11269 structure in more detail. For example:
11272 (@value{GDBP}) maint info psymtabs dwarf2read
11273 @{ objfile /home/gnu/build/gdb/gdb
11274 ((struct objfile *) 0x82e69d0)
11275 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
11276 ((struct partial_symtab *) 0x8474b10)
11279 text addresses 0x814d3c8 -- 0x8158074
11280 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
11281 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
11282 dependencies (none)
11285 (@value{GDBP}) maint info symtabs
11289 We see that there is one partial symbol table whose filename contains
11290 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
11291 and we see that @value{GDBN} has not read in any symtabs yet at all.
11292 If we set a breakpoint on a function, that will cause @value{GDBN} to
11293 read the symtab for the compilation unit containing that function:
11296 (@value{GDBP}) break dwarf2_psymtab_to_symtab
11297 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
11299 (@value{GDBP}) maint info symtabs
11300 @{ objfile /home/gnu/build/gdb/gdb
11301 ((struct objfile *) 0x82e69d0)
11302 @{ symtab /home/gnu/src/gdb/dwarf2read.c
11303 ((struct symtab *) 0x86c1f38)
11306 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
11307 linetable ((struct linetable *) 0x8370fa0)
11308 debugformat DWARF 2
11317 @chapter Altering Execution
11319 Once you think you have found an error in your program, you might want to
11320 find out for certain whether correcting the apparent error would lead to
11321 correct results in the rest of the run. You can find the answer by
11322 experiment, using the @value{GDBN} features for altering execution of the
11325 For example, you can store new values into variables or memory
11326 locations, give your program a signal, restart it at a different
11327 address, or even return prematurely from a function.
11330 * Assignment:: Assignment to variables
11331 * Jumping:: Continuing at a different address
11332 * Signaling:: Giving your program a signal
11333 * Returning:: Returning from a function
11334 * Calling:: Calling your program's functions
11335 * Patching:: Patching your program
11339 @section Assignment to Variables
11342 @cindex setting variables
11343 To alter the value of a variable, evaluate an assignment expression.
11344 @xref{Expressions, ,Expressions}. For example,
11351 stores the value 4 into the variable @code{x}, and then prints the
11352 value of the assignment expression (which is 4).
11353 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
11354 information on operators in supported languages.
11356 @kindex set variable
11357 @cindex variables, setting
11358 If you are not interested in seeing the value of the assignment, use the
11359 @code{set} command instead of the @code{print} command. @code{set} is
11360 really the same as @code{print} except that the expression's value is
11361 not printed and is not put in the value history (@pxref{Value History,
11362 ,Value History}). The expression is evaluated only for its effects.
11364 If the beginning of the argument string of the @code{set} command
11365 appears identical to a @code{set} subcommand, use the @code{set
11366 variable} command instead of just @code{set}. This command is identical
11367 to @code{set} except for its lack of subcommands. For example, if your
11368 program has a variable @code{width}, you get an error if you try to set
11369 a new value with just @samp{set width=13}, because @value{GDBN} has the
11370 command @code{set width}:
11373 (@value{GDBP}) whatis width
11375 (@value{GDBP}) p width
11377 (@value{GDBP}) set width=47
11378 Invalid syntax in expression.
11382 The invalid expression, of course, is @samp{=47}. In
11383 order to actually set the program's variable @code{width}, use
11386 (@value{GDBP}) set var width=47
11389 Because the @code{set} command has many subcommands that can conflict
11390 with the names of program variables, it is a good idea to use the
11391 @code{set variable} command instead of just @code{set}. For example, if
11392 your program has a variable @code{g}, you run into problems if you try
11393 to set a new value with just @samp{set g=4}, because @value{GDBN} has
11394 the command @code{set gnutarget}, abbreviated @code{set g}:
11398 (@value{GDBP}) whatis g
11402 (@value{GDBP}) set g=4
11406 The program being debugged has been started already.
11407 Start it from the beginning? (y or n) y
11408 Starting program: /home/smith/cc_progs/a.out
11409 "/home/smith/cc_progs/a.out": can't open to read symbols:
11410 Invalid bfd target.
11411 (@value{GDBP}) show g
11412 The current BFD target is "=4".
11417 The program variable @code{g} did not change, and you silently set the
11418 @code{gnutarget} to an invalid value. In order to set the variable
11422 (@value{GDBP}) set var g=4
11425 @value{GDBN} allows more implicit conversions in assignments than C; you can
11426 freely store an integer value into a pointer variable or vice versa,
11427 and you can convert any structure to any other structure that is the
11428 same length or shorter.
11429 @comment FIXME: how do structs align/pad in these conversions?
11430 @comment /doc@cygnus.com 18dec1990
11432 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
11433 construct to generate a value of specified type at a specified address
11434 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
11435 to memory location @code{0x83040} as an integer (which implies a certain size
11436 and representation in memory), and
11439 set @{int@}0x83040 = 4
11443 stores the value 4 into that memory location.
11446 @section Continuing at a Different Address
11448 Ordinarily, when you continue your program, you do so at the place where
11449 it stopped, with the @code{continue} command. You can instead continue at
11450 an address of your own choosing, with the following commands:
11454 @item jump @var{linespec}
11455 @itemx jump @var{location}
11456 Resume execution at line @var{linespec} or at address given by
11457 @var{location}. Execution stops again immediately if there is a
11458 breakpoint there. @xref{Specify Location}, for a description of the
11459 different forms of @var{linespec} and @var{location}. It is common
11460 practice to use the @code{tbreak} command in conjunction with
11461 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
11463 The @code{jump} command does not change the current stack frame, or
11464 the stack pointer, or the contents of any memory location or any
11465 register other than the program counter. If line @var{linespec} is in
11466 a different function from the one currently executing, the results may
11467 be bizarre if the two functions expect different patterns of arguments or
11468 of local variables. For this reason, the @code{jump} command requests
11469 confirmation if the specified line is not in the function currently
11470 executing. However, even bizarre results are predictable if you are
11471 well acquainted with the machine-language code of your program.
11474 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
11475 On many systems, you can get much the same effect as the @code{jump}
11476 command by storing a new value into the register @code{$pc}. The
11477 difference is that this does not start your program running; it only
11478 changes the address of where it @emph{will} run when you continue. For
11486 makes the next @code{continue} command or stepping command execute at
11487 address @code{0x485}, rather than at the address where your program stopped.
11488 @xref{Continuing and Stepping, ,Continuing and Stepping}.
11490 The most common occasion to use the @code{jump} command is to back
11491 up---perhaps with more breakpoints set---over a portion of a program
11492 that has already executed, in order to examine its execution in more
11497 @section Giving your Program a Signal
11498 @cindex deliver a signal to a program
11502 @item signal @var{signal}
11503 Resume execution where your program stopped, but immediately give it the
11504 signal @var{signal}. @var{signal} can be the name or the number of a
11505 signal. For example, on many systems @code{signal 2} and @code{signal
11506 SIGINT} are both ways of sending an interrupt signal.
11508 Alternatively, if @var{signal} is zero, continue execution without
11509 giving a signal. This is useful when your program stopped on account of
11510 a signal and would ordinary see the signal when resumed with the
11511 @code{continue} command; @samp{signal 0} causes it to resume without a
11514 @code{signal} does not repeat when you press @key{RET} a second time
11515 after executing the command.
11519 Invoking the @code{signal} command is not the same as invoking the
11520 @code{kill} utility from the shell. Sending a signal with @code{kill}
11521 causes @value{GDBN} to decide what to do with the signal depending on
11522 the signal handling tables (@pxref{Signals}). The @code{signal} command
11523 passes the signal directly to your program.
11527 @section Returning from a Function
11530 @cindex returning from a function
11533 @itemx return @var{expression}
11534 You can cancel execution of a function call with the @code{return}
11535 command. If you give an
11536 @var{expression} argument, its value is used as the function's return
11540 When you use @code{return}, @value{GDBN} discards the selected stack frame
11541 (and all frames within it). You can think of this as making the
11542 discarded frame return prematurely. If you wish to specify a value to
11543 be returned, give that value as the argument to @code{return}.
11545 This pops the selected stack frame (@pxref{Selection, ,Selecting a
11546 Frame}), and any other frames inside of it, leaving its caller as the
11547 innermost remaining frame. That frame becomes selected. The
11548 specified value is stored in the registers used for returning values
11551 The @code{return} command does not resume execution; it leaves the
11552 program stopped in the state that would exist if the function had just
11553 returned. In contrast, the @code{finish} command (@pxref{Continuing
11554 and Stepping, ,Continuing and Stepping}) resumes execution until the
11555 selected stack frame returns naturally.
11558 @section Calling Program Functions
11561 @cindex calling functions
11562 @cindex inferior functions, calling
11563 @item print @var{expr}
11564 Evaluate the expression @var{expr} and display the resulting value.
11565 @var{expr} may include calls to functions in the program being
11569 @item call @var{expr}
11570 Evaluate the expression @var{expr} without displaying @code{void}
11573 You can use this variant of the @code{print} command if you want to
11574 execute a function from your program that does not return anything
11575 (a.k.a.@: @dfn{a void function}), but without cluttering the output
11576 with @code{void} returned values that @value{GDBN} will otherwise
11577 print. If the result is not void, it is printed and saved in the
11581 It is possible for the function you call via the @code{print} or
11582 @code{call} command to generate a signal (e.g., if there's a bug in
11583 the function, or if you passed it incorrect arguments). What happens
11584 in that case is controlled by the @code{set unwindonsignal} command.
11587 @item set unwindonsignal
11588 @kindex set unwindonsignal
11589 @cindex unwind stack in called functions
11590 @cindex call dummy stack unwinding
11591 Set unwinding of the stack if a signal is received while in a function
11592 that @value{GDBN} called in the program being debugged. If set to on,
11593 @value{GDBN} unwinds the stack it created for the call and restores
11594 the context to what it was before the call. If set to off (the
11595 default), @value{GDBN} stops in the frame where the signal was
11598 @item show unwindonsignal
11599 @kindex show unwindonsignal
11600 Show the current setting of stack unwinding in the functions called by
11604 @cindex weak alias functions
11605 Sometimes, a function you wish to call is actually a @dfn{weak alias}
11606 for another function. In such case, @value{GDBN} might not pick up
11607 the type information, including the types of the function arguments,
11608 which causes @value{GDBN} to call the inferior function incorrectly.
11609 As a result, the called function will function erroneously and may
11610 even crash. A solution to that is to use the name of the aliased
11614 @section Patching Programs
11616 @cindex patching binaries
11617 @cindex writing into executables
11618 @cindex writing into corefiles
11620 By default, @value{GDBN} opens the file containing your program's
11621 executable code (or the corefile) read-only. This prevents accidental
11622 alterations to machine code; but it also prevents you from intentionally
11623 patching your program's binary.
11625 If you'd like to be able to patch the binary, you can specify that
11626 explicitly with the @code{set write} command. For example, you might
11627 want to turn on internal debugging flags, or even to make emergency
11633 @itemx set write off
11634 If you specify @samp{set write on}, @value{GDBN} opens executable and
11635 core files for both reading and writing; if you specify @samp{set write
11636 off} (the default), @value{GDBN} opens them read-only.
11638 If you have already loaded a file, you must load it again (using the
11639 @code{exec-file} or @code{core-file} command) after changing @code{set
11640 write}, for your new setting to take effect.
11644 Display whether executable files and core files are opened for writing
11645 as well as reading.
11649 @chapter @value{GDBN} Files
11651 @value{GDBN} needs to know the file name of the program to be debugged,
11652 both in order to read its symbol table and in order to start your
11653 program. To debug a core dump of a previous run, you must also tell
11654 @value{GDBN} the name of the core dump file.
11657 * Files:: Commands to specify files
11658 * Separate Debug Files:: Debugging information in separate files
11659 * Symbol Errors:: Errors reading symbol files
11663 @section Commands to Specify Files
11665 @cindex symbol table
11666 @cindex core dump file
11668 You may want to specify executable and core dump file names. The usual
11669 way to do this is at start-up time, using the arguments to
11670 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
11671 Out of @value{GDBN}}).
11673 Occasionally it is necessary to change to a different file during a
11674 @value{GDBN} session. Or you may run @value{GDBN} and forget to
11675 specify a file you want to use. Or you are debugging a remote target
11676 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
11677 Program}). In these situations the @value{GDBN} commands to specify
11678 new files are useful.
11681 @cindex executable file
11683 @item file @var{filename}
11684 Use @var{filename} as the program to be debugged. It is read for its
11685 symbols and for the contents of pure memory. It is also the program
11686 executed when you use the @code{run} command. If you do not specify a
11687 directory and the file is not found in the @value{GDBN} working directory,
11688 @value{GDBN} uses the environment variable @code{PATH} as a list of
11689 directories to search, just as the shell does when looking for a program
11690 to run. You can change the value of this variable, for both @value{GDBN}
11691 and your program, using the @code{path} command.
11693 @cindex unlinked object files
11694 @cindex patching object files
11695 You can load unlinked object @file{.o} files into @value{GDBN} using
11696 the @code{file} command. You will not be able to ``run'' an object
11697 file, but you can disassemble functions and inspect variables. Also,
11698 if the underlying BFD functionality supports it, you could use
11699 @kbd{gdb -write} to patch object files using this technique. Note
11700 that @value{GDBN} can neither interpret nor modify relocations in this
11701 case, so branches and some initialized variables will appear to go to
11702 the wrong place. But this feature is still handy from time to time.
11705 @code{file} with no argument makes @value{GDBN} discard any information it
11706 has on both executable file and the symbol table.
11709 @item exec-file @r{[} @var{filename} @r{]}
11710 Specify that the program to be run (but not the symbol table) is found
11711 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
11712 if necessary to locate your program. Omitting @var{filename} means to
11713 discard information on the executable file.
11715 @kindex symbol-file
11716 @item symbol-file @r{[} @var{filename} @r{]}
11717 Read symbol table information from file @var{filename}. @code{PATH} is
11718 searched when necessary. Use the @code{file} command to get both symbol
11719 table and program to run from the same file.
11721 @code{symbol-file} with no argument clears out @value{GDBN} information on your
11722 program's symbol table.
11724 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
11725 some breakpoints and auto-display expressions. This is because they may
11726 contain pointers to the internal data recording symbols and data types,
11727 which are part of the old symbol table data being discarded inside
11730 @code{symbol-file} does not repeat if you press @key{RET} again after
11733 When @value{GDBN} is configured for a particular environment, it
11734 understands debugging information in whatever format is the standard
11735 generated for that environment; you may use either a @sc{gnu} compiler, or
11736 other compilers that adhere to the local conventions.
11737 Best results are usually obtained from @sc{gnu} compilers; for example,
11738 using @code{@value{NGCC}} you can generate debugging information for
11741 For most kinds of object files, with the exception of old SVR3 systems
11742 using COFF, the @code{symbol-file} command does not normally read the
11743 symbol table in full right away. Instead, it scans the symbol table
11744 quickly to find which source files and which symbols are present. The
11745 details are read later, one source file at a time, as they are needed.
11747 The purpose of this two-stage reading strategy is to make @value{GDBN}
11748 start up faster. For the most part, it is invisible except for
11749 occasional pauses while the symbol table details for a particular source
11750 file are being read. (The @code{set verbose} command can turn these
11751 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
11752 Warnings and Messages}.)
11754 We have not implemented the two-stage strategy for COFF yet. When the
11755 symbol table is stored in COFF format, @code{symbol-file} reads the
11756 symbol table data in full right away. Note that ``stabs-in-COFF''
11757 still does the two-stage strategy, since the debug info is actually
11761 @cindex reading symbols immediately
11762 @cindex symbols, reading immediately
11763 @item symbol-file @var{filename} @r{[} -readnow @r{]}
11764 @itemx file @var{filename} @r{[} -readnow @r{]}
11765 You can override the @value{GDBN} two-stage strategy for reading symbol
11766 tables by using the @samp{-readnow} option with any of the commands that
11767 load symbol table information, if you want to be sure @value{GDBN} has the
11768 entire symbol table available.
11770 @c FIXME: for now no mention of directories, since this seems to be in
11771 @c flux. 13mar1992 status is that in theory GDB would look either in
11772 @c current dir or in same dir as myprog; but issues like competing
11773 @c GDB's, or clutter in system dirs, mean that in practice right now
11774 @c only current dir is used. FFish says maybe a special GDB hierarchy
11775 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
11779 @item core-file @r{[}@var{filename}@r{]}
11781 Specify the whereabouts of a core dump file to be used as the ``contents
11782 of memory''. Traditionally, core files contain only some parts of the
11783 address space of the process that generated them; @value{GDBN} can access the
11784 executable file itself for other parts.
11786 @code{core-file} with no argument specifies that no core file is
11789 Note that the core file is ignored when your program is actually running
11790 under @value{GDBN}. So, if you have been running your program and you
11791 wish to debug a core file instead, you must kill the subprocess in which
11792 the program is running. To do this, use the @code{kill} command
11793 (@pxref{Kill Process, ,Killing the Child Process}).
11795 @kindex add-symbol-file
11796 @cindex dynamic linking
11797 @item add-symbol-file @var{filename} @var{address}
11798 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
11799 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
11800 The @code{add-symbol-file} command reads additional symbol table
11801 information from the file @var{filename}. You would use this command
11802 when @var{filename} has been dynamically loaded (by some other means)
11803 into the program that is running. @var{address} should be the memory
11804 address at which the file has been loaded; @value{GDBN} cannot figure
11805 this out for itself. You can additionally specify an arbitrary number
11806 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
11807 section name and base address for that section. You can specify any
11808 @var{address} as an expression.
11810 The symbol table of the file @var{filename} is added to the symbol table
11811 originally read with the @code{symbol-file} command. You can use the
11812 @code{add-symbol-file} command any number of times; the new symbol data
11813 thus read keeps adding to the old. To discard all old symbol data
11814 instead, use the @code{symbol-file} command without any arguments.
11816 @cindex relocatable object files, reading symbols from
11817 @cindex object files, relocatable, reading symbols from
11818 @cindex reading symbols from relocatable object files
11819 @cindex symbols, reading from relocatable object files
11820 @cindex @file{.o} files, reading symbols from
11821 Although @var{filename} is typically a shared library file, an
11822 executable file, or some other object file which has been fully
11823 relocated for loading into a process, you can also load symbolic
11824 information from relocatable @file{.o} files, as long as:
11828 the file's symbolic information refers only to linker symbols defined in
11829 that file, not to symbols defined by other object files,
11831 every section the file's symbolic information refers to has actually
11832 been loaded into the inferior, as it appears in the file, and
11834 you can determine the address at which every section was loaded, and
11835 provide these to the @code{add-symbol-file} command.
11839 Some embedded operating systems, like Sun Chorus and VxWorks, can load
11840 relocatable files into an already running program; such systems
11841 typically make the requirements above easy to meet. However, it's
11842 important to recognize that many native systems use complex link
11843 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
11844 assembly, for example) that make the requirements difficult to meet. In
11845 general, one cannot assume that using @code{add-symbol-file} to read a
11846 relocatable object file's symbolic information will have the same effect
11847 as linking the relocatable object file into the program in the normal
11850 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
11852 @kindex add-symbol-file-from-memory
11853 @cindex @code{syscall DSO}
11854 @cindex load symbols from memory
11855 @item add-symbol-file-from-memory @var{address}
11856 Load symbols from the given @var{address} in a dynamically loaded
11857 object file whose image is mapped directly into the inferior's memory.
11858 For example, the Linux kernel maps a @code{syscall DSO} into each
11859 process's address space; this DSO provides kernel-specific code for
11860 some system calls. The argument can be any expression whose
11861 evaluation yields the address of the file's shared object file header.
11862 For this command to work, you must have used @code{symbol-file} or
11863 @code{exec-file} commands in advance.
11865 @kindex add-shared-symbol-files
11867 @item add-shared-symbol-files @var{library-file}
11868 @itemx assf @var{library-file}
11869 The @code{add-shared-symbol-files} command can currently be used only
11870 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
11871 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
11872 @value{GDBN} automatically looks for shared libraries, however if
11873 @value{GDBN} does not find yours, you can invoke
11874 @code{add-shared-symbol-files}. It takes one argument: the shared
11875 library's file name. @code{assf} is a shorthand alias for
11876 @code{add-shared-symbol-files}.
11879 @item section @var{section} @var{addr}
11880 The @code{section} command changes the base address of the named
11881 @var{section} of the exec file to @var{addr}. This can be used if the
11882 exec file does not contain section addresses, (such as in the
11883 @code{a.out} format), or when the addresses specified in the file
11884 itself are wrong. Each section must be changed separately. The
11885 @code{info files} command, described below, lists all the sections and
11889 @kindex info target
11892 @code{info files} and @code{info target} are synonymous; both print the
11893 current target (@pxref{Targets, ,Specifying a Debugging Target}),
11894 including the names of the executable and core dump files currently in
11895 use by @value{GDBN}, and the files from which symbols were loaded. The
11896 command @code{help target} lists all possible targets rather than
11899 @kindex maint info sections
11900 @item maint info sections
11901 Another command that can give you extra information about program sections
11902 is @code{maint info sections}. In addition to the section information
11903 displayed by @code{info files}, this command displays the flags and file
11904 offset of each section in the executable and core dump files. In addition,
11905 @code{maint info sections} provides the following command options (which
11906 may be arbitrarily combined):
11910 Display sections for all loaded object files, including shared libraries.
11911 @item @var{sections}
11912 Display info only for named @var{sections}.
11913 @item @var{section-flags}
11914 Display info only for sections for which @var{section-flags} are true.
11915 The section flags that @value{GDBN} currently knows about are:
11918 Section will have space allocated in the process when loaded.
11919 Set for all sections except those containing debug information.
11921 Section will be loaded from the file into the child process memory.
11922 Set for pre-initialized code and data, clear for @code{.bss} sections.
11924 Section needs to be relocated before loading.
11926 Section cannot be modified by the child process.
11928 Section contains executable code only.
11930 Section contains data only (no executable code).
11932 Section will reside in ROM.
11934 Section contains data for constructor/destructor lists.
11936 Section is not empty.
11938 An instruction to the linker to not output the section.
11939 @item COFF_SHARED_LIBRARY
11940 A notification to the linker that the section contains
11941 COFF shared library information.
11943 Section contains common symbols.
11946 @kindex set trust-readonly-sections
11947 @cindex read-only sections
11948 @item set trust-readonly-sections on
11949 Tell @value{GDBN} that readonly sections in your object file
11950 really are read-only (i.e.@: that their contents will not change).
11951 In that case, @value{GDBN} can fetch values from these sections
11952 out of the object file, rather than from the target program.
11953 For some targets (notably embedded ones), this can be a significant
11954 enhancement to debugging performance.
11956 The default is off.
11958 @item set trust-readonly-sections off
11959 Tell @value{GDBN} not to trust readonly sections. This means that
11960 the contents of the section might change while the program is running,
11961 and must therefore be fetched from the target when needed.
11963 @item show trust-readonly-sections
11964 Show the current setting of trusting readonly sections.
11967 All file-specifying commands allow both absolute and relative file names
11968 as arguments. @value{GDBN} always converts the file name to an absolute file
11969 name and remembers it that way.
11971 @cindex shared libraries
11972 @anchor{Shared Libraries}
11973 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
11974 and IBM RS/6000 AIX shared libraries.
11976 On MS-Windows @value{GDBN} must be linked with the Expat library to support
11977 shared libraries. @xref{Expat}.
11979 @value{GDBN} automatically loads symbol definitions from shared libraries
11980 when you use the @code{run} command, or when you examine a core file.
11981 (Before you issue the @code{run} command, @value{GDBN} does not understand
11982 references to a function in a shared library, however---unless you are
11983 debugging a core file).
11985 On HP-UX, if the program loads a library explicitly, @value{GDBN}
11986 automatically loads the symbols at the time of the @code{shl_load} call.
11988 @c FIXME: some @value{GDBN} release may permit some refs to undef
11989 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
11990 @c FIXME...lib; check this from time to time when updating manual
11992 There are times, however, when you may wish to not automatically load
11993 symbol definitions from shared libraries, such as when they are
11994 particularly large or there are many of them.
11996 To control the automatic loading of shared library symbols, use the
12000 @kindex set auto-solib-add
12001 @item set auto-solib-add @var{mode}
12002 If @var{mode} is @code{on}, symbols from all shared object libraries
12003 will be loaded automatically when the inferior begins execution, you
12004 attach to an independently started inferior, or when the dynamic linker
12005 informs @value{GDBN} that a new library has been loaded. If @var{mode}
12006 is @code{off}, symbols must be loaded manually, using the
12007 @code{sharedlibrary} command. The default value is @code{on}.
12009 @cindex memory used for symbol tables
12010 If your program uses lots of shared libraries with debug info that
12011 takes large amounts of memory, you can decrease the @value{GDBN}
12012 memory footprint by preventing it from automatically loading the
12013 symbols from shared libraries. To that end, type @kbd{set
12014 auto-solib-add off} before running the inferior, then load each
12015 library whose debug symbols you do need with @kbd{sharedlibrary
12016 @var{regexp}}, where @var{regexp} is a regular expression that matches
12017 the libraries whose symbols you want to be loaded.
12019 @kindex show auto-solib-add
12020 @item show auto-solib-add
12021 Display the current autoloading mode.
12024 @cindex load shared library
12025 To explicitly load shared library symbols, use the @code{sharedlibrary}
12029 @kindex info sharedlibrary
12032 @itemx info sharedlibrary
12033 Print the names of the shared libraries which are currently loaded.
12035 @kindex sharedlibrary
12037 @item sharedlibrary @var{regex}
12038 @itemx share @var{regex}
12039 Load shared object library symbols for files matching a
12040 Unix regular expression.
12041 As with files loaded automatically, it only loads shared libraries
12042 required by your program for a core file or after typing @code{run}. If
12043 @var{regex} is omitted all shared libraries required by your program are
12046 @item nosharedlibrary
12047 @kindex nosharedlibrary
12048 @cindex unload symbols from shared libraries
12049 Unload all shared object library symbols. This discards all symbols
12050 that have been loaded from all shared libraries. Symbols from shared
12051 libraries that were loaded by explicit user requests are not
12055 Sometimes you may wish that @value{GDBN} stops and gives you control
12056 when any of shared library events happen. Use the @code{set
12057 stop-on-solib-events} command for this:
12060 @item set stop-on-solib-events
12061 @kindex set stop-on-solib-events
12062 This command controls whether @value{GDBN} should give you control
12063 when the dynamic linker notifies it about some shared library event.
12064 The most common event of interest is loading or unloading of a new
12067 @item show stop-on-solib-events
12068 @kindex show stop-on-solib-events
12069 Show whether @value{GDBN} stops and gives you control when shared
12070 library events happen.
12073 Shared libraries are also supported in many cross or remote debugging
12074 configurations. A copy of the target's libraries need to be present on the
12075 host system; they need to be the same as the target libraries, although the
12076 copies on the target can be stripped as long as the copies on the host are
12079 @cindex where to look for shared libraries
12080 For remote debugging, you need to tell @value{GDBN} where the target
12081 libraries are, so that it can load the correct copies---otherwise, it
12082 may try to load the host's libraries. @value{GDBN} has two variables
12083 to specify the search directories for target libraries.
12086 @cindex prefix for shared library file names
12087 @cindex system root, alternate
12088 @kindex set solib-absolute-prefix
12089 @kindex set sysroot
12090 @item set sysroot @var{path}
12091 Use @var{path} as the system root for the program being debugged. Any
12092 absolute shared library paths will be prefixed with @var{path}; many
12093 runtime loaders store the absolute paths to the shared library in the
12094 target program's memory. If you use @code{set sysroot} to find shared
12095 libraries, they need to be laid out in the same way that they are on
12096 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
12099 The @code{set solib-absolute-prefix} command is an alias for @code{set
12102 @cindex default system root
12103 @cindex @samp{--with-sysroot}
12104 You can set the default system root by using the configure-time
12105 @samp{--with-sysroot} option. If the system root is inside
12106 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
12107 @samp{--exec-prefix}), then the default system root will be updated
12108 automatically if the installed @value{GDBN} is moved to a new
12111 @kindex show sysroot
12113 Display the current shared library prefix.
12115 @kindex set solib-search-path
12116 @item set solib-search-path @var{path}
12117 If this variable is set, @var{path} is a colon-separated list of
12118 directories to search for shared libraries. @samp{solib-search-path}
12119 is used after @samp{sysroot} fails to locate the library, or if the
12120 path to the library is relative instead of absolute. If you want to
12121 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
12122 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
12123 finding your host's libraries. @samp{sysroot} is preferred; setting
12124 it to a nonexistent directory may interfere with automatic loading
12125 of shared library symbols.
12127 @kindex show solib-search-path
12128 @item show solib-search-path
12129 Display the current shared library search path.
12133 @node Separate Debug Files
12134 @section Debugging Information in Separate Files
12135 @cindex separate debugging information files
12136 @cindex debugging information in separate files
12137 @cindex @file{.debug} subdirectories
12138 @cindex debugging information directory, global
12139 @cindex global debugging information directory
12140 @cindex build ID, and separate debugging files
12141 @cindex @file{.build-id} directory
12143 @value{GDBN} allows you to put a program's debugging information in a
12144 file separate from the executable itself, in a way that allows
12145 @value{GDBN} to find and load the debugging information automatically.
12146 Since debugging information can be very large---sometimes larger
12147 than the executable code itself---some systems distribute debugging
12148 information for their executables in separate files, which users can
12149 install only when they need to debug a problem.
12151 @value{GDBN} supports two ways of specifying the separate debug info
12156 The executable contains a @dfn{debug link} that specifies the name of
12157 the separate debug info file. The separate debug file's name is
12158 usually @file{@var{executable}.debug}, where @var{executable} is the
12159 name of the corresponding executable file without leading directories
12160 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
12161 debug link specifies a CRC32 checksum for the debug file, which
12162 @value{GDBN} uses to validate that the executable and the debug file
12163 came from the same build.
12166 The executable contains a @dfn{build ID}, a unique bit string that is
12167 also present in the corresponding debug info file. (This is supported
12168 only on some operating systems, notably those which use the ELF format
12169 for binary files and the @sc{gnu} Binutils.) For more details about
12170 this feature, see the description of the @option{--build-id}
12171 command-line option in @ref{Options, , Command Line Options, ld.info,
12172 The GNU Linker}. The debug info file's name is not specified
12173 explicitly by the build ID, but can be computed from the build ID, see
12177 Depending on the way the debug info file is specified, @value{GDBN}
12178 uses two different methods of looking for the debug file:
12182 For the ``debug link'' method, @value{GDBN} looks up the named file in
12183 the directory of the executable file, then in a subdirectory of that
12184 directory named @file{.debug}, and finally under the global debug
12185 directory, in a subdirectory whose name is identical to the leading
12186 directories of the executable's absolute file name.
12189 For the ``build ID'' method, @value{GDBN} looks in the
12190 @file{.build-id} subdirectory of the global debug directory for a file
12191 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
12192 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
12193 are the rest of the bit string. (Real build ID strings are 32 or more
12194 hex characters, not 10.)
12197 So, for example, suppose you ask @value{GDBN} to debug
12198 @file{/usr/bin/ls}, which has a debug link that specifies the
12199 file @file{ls.debug}, and a build ID whose value in hex is
12200 @code{abcdef1234}. If the global debug directory is
12201 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
12202 debug information files, in the indicated order:
12206 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
12208 @file{/usr/bin/ls.debug}
12210 @file{/usr/bin/.debug/ls.debug}
12212 @file{/usr/lib/debug/usr/bin/ls.debug}.
12215 You can set the global debugging info directory's name, and view the
12216 name @value{GDBN} is currently using.
12220 @kindex set debug-file-directory
12221 @item set debug-file-directory @var{directory}
12222 Set the directory which @value{GDBN} searches for separate debugging
12223 information files to @var{directory}.
12225 @kindex show debug-file-directory
12226 @item show debug-file-directory
12227 Show the directory @value{GDBN} searches for separate debugging
12232 @cindex @code{.gnu_debuglink} sections
12233 @cindex debug link sections
12234 A debug link is a special section of the executable file named
12235 @code{.gnu_debuglink}. The section must contain:
12239 A filename, with any leading directory components removed, followed by
12242 zero to three bytes of padding, as needed to reach the next four-byte
12243 boundary within the section, and
12245 a four-byte CRC checksum, stored in the same endianness used for the
12246 executable file itself. The checksum is computed on the debugging
12247 information file's full contents by the function given below, passing
12248 zero as the @var{crc} argument.
12251 Any executable file format can carry a debug link, as long as it can
12252 contain a section named @code{.gnu_debuglink} with the contents
12255 @cindex @code{.note.gnu.build-id} sections
12256 @cindex build ID sections
12257 The build ID is a special section in the executable file (and in other
12258 ELF binary files that @value{GDBN} may consider). This section is
12259 often named @code{.note.gnu.build-id}, but that name is not mandatory.
12260 It contains unique identification for the built files---the ID remains
12261 the same across multiple builds of the same build tree. The default
12262 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
12263 content for the build ID string. The same section with an identical
12264 value is present in the original built binary with symbols, in its
12265 stripped variant, and in the separate debugging information file.
12267 The debugging information file itself should be an ordinary
12268 executable, containing a full set of linker symbols, sections, and
12269 debugging information. The sections of the debugging information file
12270 should have the same names, addresses, and sizes as the original file,
12271 but they need not contain any data---much like a @code{.bss} section
12272 in an ordinary executable.
12274 The @sc{gnu} binary utilities (Binutils) package includes the
12275 @samp{objcopy} utility that can produce
12276 the separated executable / debugging information file pairs using the
12277 following commands:
12280 @kbd{objcopy --only-keep-debug foo foo.debug}
12285 These commands remove the debugging
12286 information from the executable file @file{foo} and place it in the file
12287 @file{foo.debug}. You can use the first, second or both methods to link the
12292 The debug link method needs the following additional command to also leave
12293 behind a debug link in @file{foo}:
12296 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
12299 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
12300 a version of the @code{strip} command such that the command @kbd{strip foo -f
12301 foo.debug} has the same functionality as the two @code{objcopy} commands and
12302 the @code{ln -s} command above, together.
12305 Build ID gets embedded into the main executable using @code{ld --build-id} or
12306 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
12307 compatibility fixes for debug files separation are present in @sc{gnu} binary
12308 utilities (Binutils) package since version 2.18.
12313 Since there are many different ways to compute CRC's for the debug
12314 link (different polynomials, reversals, byte ordering, etc.), the
12315 simplest way to describe the CRC used in @code{.gnu_debuglink}
12316 sections is to give the complete code for a function that computes it:
12318 @kindex gnu_debuglink_crc32
12321 gnu_debuglink_crc32 (unsigned long crc,
12322 unsigned char *buf, size_t len)
12324 static const unsigned long crc32_table[256] =
12326 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
12327 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
12328 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
12329 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
12330 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
12331 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
12332 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
12333 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
12334 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
12335 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
12336 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
12337 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
12338 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
12339 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
12340 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
12341 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
12342 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
12343 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
12344 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
12345 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
12346 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
12347 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
12348 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
12349 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
12350 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
12351 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
12352 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
12353 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
12354 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
12355 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
12356 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
12357 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
12358 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
12359 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
12360 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
12361 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
12362 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
12363 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
12364 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
12365 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
12366 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
12367 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
12368 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
12369 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
12370 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
12371 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
12372 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
12373 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
12374 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
12375 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
12376 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
12379 unsigned char *end;
12381 crc = ~crc & 0xffffffff;
12382 for (end = buf + len; buf < end; ++buf)
12383 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
12384 return ~crc & 0xffffffff;
12389 This computation does not apply to the ``build ID'' method.
12392 @node Symbol Errors
12393 @section Errors Reading Symbol Files
12395 While reading a symbol file, @value{GDBN} occasionally encounters problems,
12396 such as symbol types it does not recognize, or known bugs in compiler
12397 output. By default, @value{GDBN} does not notify you of such problems, since
12398 they are relatively common and primarily of interest to people
12399 debugging compilers. If you are interested in seeing information
12400 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
12401 only one message about each such type of problem, no matter how many
12402 times the problem occurs; or you can ask @value{GDBN} to print more messages,
12403 to see how many times the problems occur, with the @code{set
12404 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
12407 The messages currently printed, and their meanings, include:
12410 @item inner block not inside outer block in @var{symbol}
12412 The symbol information shows where symbol scopes begin and end
12413 (such as at the start of a function or a block of statements). This
12414 error indicates that an inner scope block is not fully contained
12415 in its outer scope blocks.
12417 @value{GDBN} circumvents the problem by treating the inner block as if it had
12418 the same scope as the outer block. In the error message, @var{symbol}
12419 may be shown as ``@code{(don't know)}'' if the outer block is not a
12422 @item block at @var{address} out of order
12424 The symbol information for symbol scope blocks should occur in
12425 order of increasing addresses. This error indicates that it does not
12428 @value{GDBN} does not circumvent this problem, and has trouble
12429 locating symbols in the source file whose symbols it is reading. (You
12430 can often determine what source file is affected by specifying
12431 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
12434 @item bad block start address patched
12436 The symbol information for a symbol scope block has a start address
12437 smaller than the address of the preceding source line. This is known
12438 to occur in the SunOS 4.1.1 (and earlier) C compiler.
12440 @value{GDBN} circumvents the problem by treating the symbol scope block as
12441 starting on the previous source line.
12443 @item bad string table offset in symbol @var{n}
12446 Symbol number @var{n} contains a pointer into the string table which is
12447 larger than the size of the string table.
12449 @value{GDBN} circumvents the problem by considering the symbol to have the
12450 name @code{foo}, which may cause other problems if many symbols end up
12453 @item unknown symbol type @code{0x@var{nn}}
12455 The symbol information contains new data types that @value{GDBN} does
12456 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
12457 uncomprehended information, in hexadecimal.
12459 @value{GDBN} circumvents the error by ignoring this symbol information.
12460 This usually allows you to debug your program, though certain symbols
12461 are not accessible. If you encounter such a problem and feel like
12462 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
12463 on @code{complain}, then go up to the function @code{read_dbx_symtab}
12464 and examine @code{*bufp} to see the symbol.
12466 @item stub type has NULL name
12468 @value{GDBN} could not find the full definition for a struct or class.
12470 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
12471 The symbol information for a C@t{++} member function is missing some
12472 information that recent versions of the compiler should have output for
12475 @item info mismatch between compiler and debugger
12477 @value{GDBN} could not parse a type specification output by the compiler.
12482 @chapter Specifying a Debugging Target
12484 @cindex debugging target
12485 A @dfn{target} is the execution environment occupied by your program.
12487 Often, @value{GDBN} runs in the same host environment as your program;
12488 in that case, the debugging target is specified as a side effect when
12489 you use the @code{file} or @code{core} commands. When you need more
12490 flexibility---for example, running @value{GDBN} on a physically separate
12491 host, or controlling a standalone system over a serial port or a
12492 realtime system over a TCP/IP connection---you can use the @code{target}
12493 command to specify one of the target types configured for @value{GDBN}
12494 (@pxref{Target Commands, ,Commands for Managing Targets}).
12496 @cindex target architecture
12497 It is possible to build @value{GDBN} for several different @dfn{target
12498 architectures}. When @value{GDBN} is built like that, you can choose
12499 one of the available architectures with the @kbd{set architecture}
12503 @kindex set architecture
12504 @kindex show architecture
12505 @item set architecture @var{arch}
12506 This command sets the current target architecture to @var{arch}. The
12507 value of @var{arch} can be @code{"auto"}, in addition to one of the
12508 supported architectures.
12510 @item show architecture
12511 Show the current target architecture.
12513 @item set processor
12515 @kindex set processor
12516 @kindex show processor
12517 These are alias commands for, respectively, @code{set architecture}
12518 and @code{show architecture}.
12522 * Active Targets:: Active targets
12523 * Target Commands:: Commands for managing targets
12524 * Byte Order:: Choosing target byte order
12527 @node Active Targets
12528 @section Active Targets
12530 @cindex stacking targets
12531 @cindex active targets
12532 @cindex multiple targets
12534 There are three classes of targets: processes, core files, and
12535 executable files. @value{GDBN} can work concurrently on up to three
12536 active targets, one in each class. This allows you to (for example)
12537 start a process and inspect its activity without abandoning your work on
12540 For example, if you execute @samp{gdb a.out}, then the executable file
12541 @code{a.out} is the only active target. If you designate a core file as
12542 well---presumably from a prior run that crashed and coredumped---then
12543 @value{GDBN} has two active targets and uses them in tandem, looking
12544 first in the corefile target, then in the executable file, to satisfy
12545 requests for memory addresses. (Typically, these two classes of target
12546 are complementary, since core files contain only a program's
12547 read-write memory---variables and so on---plus machine status, while
12548 executable files contain only the program text and initialized data.)
12550 When you type @code{run}, your executable file becomes an active process
12551 target as well. When a process target is active, all @value{GDBN}
12552 commands requesting memory addresses refer to that target; addresses in
12553 an active core file or executable file target are obscured while the
12554 process target is active.
12556 Use the @code{core-file} and @code{exec-file} commands to select a new
12557 core file or executable target (@pxref{Files, ,Commands to Specify
12558 Files}). To specify as a target a process that is already running, use
12559 the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
12562 @node Target Commands
12563 @section Commands for Managing Targets
12566 @item target @var{type} @var{parameters}
12567 Connects the @value{GDBN} host environment to a target machine or
12568 process. A target is typically a protocol for talking to debugging
12569 facilities. You use the argument @var{type} to specify the type or
12570 protocol of the target machine.
12572 Further @var{parameters} are interpreted by the target protocol, but
12573 typically include things like device names or host names to connect
12574 with, process numbers, and baud rates.
12576 The @code{target} command does not repeat if you press @key{RET} again
12577 after executing the command.
12579 @kindex help target
12581 Displays the names of all targets available. To display targets
12582 currently selected, use either @code{info target} or @code{info files}
12583 (@pxref{Files, ,Commands to Specify Files}).
12585 @item help target @var{name}
12586 Describe a particular target, including any parameters necessary to
12589 @kindex set gnutarget
12590 @item set gnutarget @var{args}
12591 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
12592 knows whether it is reading an @dfn{executable},
12593 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
12594 with the @code{set gnutarget} command. Unlike most @code{target} commands,
12595 with @code{gnutarget} the @code{target} refers to a program, not a machine.
12598 @emph{Warning:} To specify a file format with @code{set gnutarget},
12599 you must know the actual BFD name.
12603 @xref{Files, , Commands to Specify Files}.
12605 @kindex show gnutarget
12606 @item show gnutarget
12607 Use the @code{show gnutarget} command to display what file format
12608 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
12609 @value{GDBN} will determine the file format for each file automatically,
12610 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
12613 @cindex common targets
12614 Here are some common targets (available, or not, depending on the GDB
12619 @item target exec @var{program}
12620 @cindex executable file target
12621 An executable file. @samp{target exec @var{program}} is the same as
12622 @samp{exec-file @var{program}}.
12624 @item target core @var{filename}
12625 @cindex core dump file target
12626 A core dump file. @samp{target core @var{filename}} is the same as
12627 @samp{core-file @var{filename}}.
12629 @item target remote @var{medium}
12630 @cindex remote target
12631 A remote system connected to @value{GDBN} via a serial line or network
12632 connection. This command tells @value{GDBN} to use its own remote
12633 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
12635 For example, if you have a board connected to @file{/dev/ttya} on the
12636 machine running @value{GDBN}, you could say:
12639 target remote /dev/ttya
12642 @code{target remote} supports the @code{load} command. This is only
12643 useful if you have some other way of getting the stub to the target
12644 system, and you can put it somewhere in memory where it won't get
12645 clobbered by the download.
12648 @cindex built-in simulator target
12649 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
12657 works; however, you cannot assume that a specific memory map, device
12658 drivers, or even basic I/O is available, although some simulators do
12659 provide these. For info about any processor-specific simulator details,
12660 see the appropriate section in @ref{Embedded Processors, ,Embedded
12665 Some configurations may include these targets as well:
12669 @item target nrom @var{dev}
12670 @cindex NetROM ROM emulator target
12671 NetROM ROM emulator. This target only supports downloading.
12675 Different targets are available on different configurations of @value{GDBN};
12676 your configuration may have more or fewer targets.
12678 Many remote targets require you to download the executable's code once
12679 you've successfully established a connection. You may wish to control
12680 various aspects of this process.
12685 @kindex set hash@r{, for remote monitors}
12686 @cindex hash mark while downloading
12687 This command controls whether a hash mark @samp{#} is displayed while
12688 downloading a file to the remote monitor. If on, a hash mark is
12689 displayed after each S-record is successfully downloaded to the
12693 @kindex show hash@r{, for remote monitors}
12694 Show the current status of displaying the hash mark.
12696 @item set debug monitor
12697 @kindex set debug monitor
12698 @cindex display remote monitor communications
12699 Enable or disable display of communications messages between
12700 @value{GDBN} and the remote monitor.
12702 @item show debug monitor
12703 @kindex show debug monitor
12704 Show the current status of displaying communications between
12705 @value{GDBN} and the remote monitor.
12710 @kindex load @var{filename}
12711 @item load @var{filename}
12713 Depending on what remote debugging facilities are configured into
12714 @value{GDBN}, the @code{load} command may be available. Where it exists, it
12715 is meant to make @var{filename} (an executable) available for debugging
12716 on the remote system---by downloading, or dynamic linking, for example.
12717 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
12718 the @code{add-symbol-file} command.
12720 If your @value{GDBN} does not have a @code{load} command, attempting to
12721 execute it gets the error message ``@code{You can't do that when your
12722 target is @dots{}}''
12724 The file is loaded at whatever address is specified in the executable.
12725 For some object file formats, you can specify the load address when you
12726 link the program; for other formats, like a.out, the object file format
12727 specifies a fixed address.
12728 @c FIXME! This would be a good place for an xref to the GNU linker doc.
12730 Depending on the remote side capabilities, @value{GDBN} may be able to
12731 load programs into flash memory.
12733 @code{load} does not repeat if you press @key{RET} again after using it.
12737 @section Choosing Target Byte Order
12739 @cindex choosing target byte order
12740 @cindex target byte order
12742 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
12743 offer the ability to run either big-endian or little-endian byte
12744 orders. Usually the executable or symbol will include a bit to
12745 designate the endian-ness, and you will not need to worry about
12746 which to use. However, you may still find it useful to adjust
12747 @value{GDBN}'s idea of processor endian-ness manually.
12751 @item set endian big
12752 Instruct @value{GDBN} to assume the target is big-endian.
12754 @item set endian little
12755 Instruct @value{GDBN} to assume the target is little-endian.
12757 @item set endian auto
12758 Instruct @value{GDBN} to use the byte order associated with the
12762 Display @value{GDBN}'s current idea of the target byte order.
12766 Note that these commands merely adjust interpretation of symbolic
12767 data on the host, and that they have absolutely no effect on the
12771 @node Remote Debugging
12772 @chapter Debugging Remote Programs
12773 @cindex remote debugging
12775 If you are trying to debug a program running on a machine that cannot run
12776 @value{GDBN} in the usual way, it is often useful to use remote debugging.
12777 For example, you might use remote debugging on an operating system kernel,
12778 or on a small system which does not have a general purpose operating system
12779 powerful enough to run a full-featured debugger.
12781 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
12782 to make this work with particular debugging targets. In addition,
12783 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
12784 but not specific to any particular target system) which you can use if you
12785 write the remote stubs---the code that runs on the remote system to
12786 communicate with @value{GDBN}.
12788 Other remote targets may be available in your
12789 configuration of @value{GDBN}; use @code{help target} to list them.
12792 * Connecting:: Connecting to a remote target
12793 * File Transfer:: Sending files to a remote system
12794 * Server:: Using the gdbserver program
12795 * Remote Configuration:: Remote configuration
12796 * Remote Stub:: Implementing a remote stub
12800 @section Connecting to a Remote Target
12802 On the @value{GDBN} host machine, you will need an unstripped copy of
12803 your program, since @value{GDBN} needs symbol and debugging information.
12804 Start up @value{GDBN} as usual, using the name of the local copy of your
12805 program as the first argument.
12807 @cindex @code{target remote}
12808 @value{GDBN} can communicate with the target over a serial line, or
12809 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
12810 each case, @value{GDBN} uses the same protocol for debugging your
12811 program; only the medium carrying the debugging packets varies. The
12812 @code{target remote} command establishes a connection to the target.
12813 Its arguments indicate which medium to use:
12817 @item target remote @var{serial-device}
12818 @cindex serial line, @code{target remote}
12819 Use @var{serial-device} to communicate with the target. For example,
12820 to use a serial line connected to the device named @file{/dev/ttyb}:
12823 target remote /dev/ttyb
12826 If you're using a serial line, you may want to give @value{GDBN} the
12827 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
12828 (@pxref{Remote Configuration, set remotebaud}) before the
12829 @code{target} command.
12831 @item target remote @code{@var{host}:@var{port}}
12832 @itemx target remote @code{tcp:@var{host}:@var{port}}
12833 @cindex @acronym{TCP} port, @code{target remote}
12834 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
12835 The @var{host} may be either a host name or a numeric @acronym{IP}
12836 address; @var{port} must be a decimal number. The @var{host} could be
12837 the target machine itself, if it is directly connected to the net, or
12838 it might be a terminal server which in turn has a serial line to the
12841 For example, to connect to port 2828 on a terminal server named
12845 target remote manyfarms:2828
12848 If your remote target is actually running on the same machine as your
12849 debugger session (e.g.@: a simulator for your target running on the
12850 same host), you can omit the hostname. For example, to connect to
12851 port 1234 on your local machine:
12854 target remote :1234
12858 Note that the colon is still required here.
12860 @item target remote @code{udp:@var{host}:@var{port}}
12861 @cindex @acronym{UDP} port, @code{target remote}
12862 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
12863 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
12866 target remote udp:manyfarms:2828
12869 When using a @acronym{UDP} connection for remote debugging, you should
12870 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
12871 can silently drop packets on busy or unreliable networks, which will
12872 cause havoc with your debugging session.
12874 @item target remote | @var{command}
12875 @cindex pipe, @code{target remote} to
12876 Run @var{command} in the background and communicate with it using a
12877 pipe. The @var{command} is a shell command, to be parsed and expanded
12878 by the system's command shell, @code{/bin/sh}; it should expect remote
12879 protocol packets on its standard input, and send replies on its
12880 standard output. You could use this to run a stand-alone simulator
12881 that speaks the remote debugging protocol, to make net connections
12882 using programs like @code{ssh}, or for other similar tricks.
12884 If @var{command} closes its standard output (perhaps by exiting),
12885 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
12886 program has already exited, this will have no effect.)
12890 Once the connection has been established, you can use all the usual
12891 commands to examine and change data. The remote program is already
12892 running; you can use @kbd{step} and @kbd{continue}, and you do not
12893 need to use @kbd{run}.
12895 @cindex interrupting remote programs
12896 @cindex remote programs, interrupting
12897 Whenever @value{GDBN} is waiting for the remote program, if you type the
12898 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
12899 program. This may or may not succeed, depending in part on the hardware
12900 and the serial drivers the remote system uses. If you type the
12901 interrupt character once again, @value{GDBN} displays this prompt:
12904 Interrupted while waiting for the program.
12905 Give up (and stop debugging it)? (y or n)
12908 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
12909 (If you decide you want to try again later, you can use @samp{target
12910 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
12911 goes back to waiting.
12914 @kindex detach (remote)
12916 When you have finished debugging the remote program, you can use the
12917 @code{detach} command to release it from @value{GDBN} control.
12918 Detaching from the target normally resumes its execution, but the results
12919 will depend on your particular remote stub. After the @code{detach}
12920 command, @value{GDBN} is free to connect to another target.
12924 The @code{disconnect} command behaves like @code{detach}, except that
12925 the target is generally not resumed. It will wait for @value{GDBN}
12926 (this instance or another one) to connect and continue debugging. After
12927 the @code{disconnect} command, @value{GDBN} is again free to connect to
12930 @cindex send command to remote monitor
12931 @cindex extend @value{GDBN} for remote targets
12932 @cindex add new commands for external monitor
12934 @item monitor @var{cmd}
12935 This command allows you to send arbitrary commands directly to the
12936 remote monitor. Since @value{GDBN} doesn't care about the commands it
12937 sends like this, this command is the way to extend @value{GDBN}---you
12938 can add new commands that only the external monitor will understand
12942 @node File Transfer
12943 @section Sending files to a remote system
12944 @cindex remote target, file transfer
12945 @cindex file transfer
12946 @cindex sending files to remote systems
12948 Some remote targets offer the ability to transfer files over the same
12949 connection used to communicate with @value{GDBN}. This is convenient
12950 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
12951 running @code{gdbserver} over a network interface. For other targets,
12952 e.g.@: embedded devices with only a single serial port, this may be
12953 the only way to upload or download files.
12955 Not all remote targets support these commands.
12959 @item remote put @var{hostfile} @var{targetfile}
12960 Copy file @var{hostfile} from the host system (the machine running
12961 @value{GDBN}) to @var{targetfile} on the target system.
12964 @item remote get @var{targetfile} @var{hostfile}
12965 Copy file @var{targetfile} from the target system to @var{hostfile}
12966 on the host system.
12968 @kindex remote delete
12969 @item remote delete @var{targetfile}
12970 Delete @var{targetfile} from the target system.
12975 @section Using the @code{gdbserver} Program
12978 @cindex remote connection without stubs
12979 @code{gdbserver} is a control program for Unix-like systems, which
12980 allows you to connect your program with a remote @value{GDBN} via
12981 @code{target remote}---but without linking in the usual debugging stub.
12983 @code{gdbserver} is not a complete replacement for the debugging stubs,
12984 because it requires essentially the same operating-system facilities
12985 that @value{GDBN} itself does. In fact, a system that can run
12986 @code{gdbserver} to connect to a remote @value{GDBN} could also run
12987 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
12988 because it is a much smaller program than @value{GDBN} itself. It is
12989 also easier to port than all of @value{GDBN}, so you may be able to get
12990 started more quickly on a new system by using @code{gdbserver}.
12991 Finally, if you develop code for real-time systems, you may find that
12992 the tradeoffs involved in real-time operation make it more convenient to
12993 do as much development work as possible on another system, for example
12994 by cross-compiling. You can use @code{gdbserver} to make a similar
12995 choice for debugging.
12997 @value{GDBN} and @code{gdbserver} communicate via either a serial line
12998 or a TCP connection, using the standard @value{GDBN} remote serial
13002 @emph{Warning:} @code{gdbserver} does not have any built-in security.
13003 Do not run @code{gdbserver} connected to any public network; a
13004 @value{GDBN} connection to @code{gdbserver} provides access to the
13005 target system with the same privileges as the user running
13009 @subsection Running @code{gdbserver}
13010 @cindex arguments, to @code{gdbserver}
13012 Run @code{gdbserver} on the target system. You need a copy of the
13013 program you want to debug, including any libraries it requires.
13014 @code{gdbserver} does not need your program's symbol table, so you can
13015 strip the program if necessary to save space. @value{GDBN} on the host
13016 system does all the symbol handling.
13018 To use the server, you must tell it how to communicate with @value{GDBN};
13019 the name of your program; and the arguments for your program. The usual
13023 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
13026 @var{comm} is either a device name (to use a serial line) or a TCP
13027 hostname and portnumber. For example, to debug Emacs with the argument
13028 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
13032 target> gdbserver /dev/com1 emacs foo.txt
13035 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
13038 To use a TCP connection instead of a serial line:
13041 target> gdbserver host:2345 emacs foo.txt
13044 The only difference from the previous example is the first argument,
13045 specifying that you are communicating with the host @value{GDBN} via
13046 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
13047 expect a TCP connection from machine @samp{host} to local TCP port 2345.
13048 (Currently, the @samp{host} part is ignored.) You can choose any number
13049 you want for the port number as long as it does not conflict with any
13050 TCP ports already in use on the target system (for example, @code{23} is
13051 reserved for @code{telnet}).@footnote{If you choose a port number that
13052 conflicts with another service, @code{gdbserver} prints an error message
13053 and exits.} You must use the same port number with the host @value{GDBN}
13054 @code{target remote} command.
13056 @subsubsection Attaching to a Running Program
13058 On some targets, @code{gdbserver} can also attach to running programs.
13059 This is accomplished via the @code{--attach} argument. The syntax is:
13062 target> gdbserver --attach @var{comm} @var{pid}
13065 @var{pid} is the process ID of a currently running process. It isn't necessary
13066 to point @code{gdbserver} at a binary for the running process.
13069 @cindex attach to a program by name
13070 You can debug processes by name instead of process ID if your target has the
13071 @code{pidof} utility:
13074 target> gdbserver --attach @var{comm} `pidof @var{program}`
13077 In case more than one copy of @var{program} is running, or @var{program}
13078 has multiple threads, most versions of @code{pidof} support the
13079 @code{-s} option to only return the first process ID.
13081 @subsubsection Multi-Process Mode for @code{gdbserver}
13082 @cindex gdbserver, multiple processes
13083 @cindex multiple processes with gdbserver
13085 When you connect to @code{gdbserver} using @code{target remote},
13086 @code{gdbserver} debugs the specified program only once. When the
13087 program exits, or you detach from it, @value{GDBN} closes the connection
13088 and @code{gdbserver} exits.
13090 If you connect using @kbd{target extended-remote}, @code{gdbserver}
13091 enters multi-process mode. When the debugged program exits, or you
13092 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
13093 though no program is running. The @code{run} and @code{attach}
13094 commands instruct @code{gdbserver} to run or attach to a new program.
13095 The @code{run} command uses @code{set remote exec-file} (@pxref{set
13096 remote exec-file}) to select the program to run. Command line
13097 arguments are supported, except for wildcard expansion and I/O
13098 redirection (@pxref{Arguments}).
13100 To start @code{gdbserver} without supplying an initial command to run
13101 or process ID to attach, use the @option{--multi} command line option.
13102 Then you can connect using @kbd{target extended-remote} and start
13103 the program you want to debug.
13105 @code{gdbserver} does not automatically exit in multi-process mode.
13106 You can terminate it by using @code{monitor exit}
13107 (@pxref{Monitor Commands for gdbserver}).
13109 @subsubsection Other Command-Line Arguments for @code{gdbserver}
13111 You can include @option{--debug} on the @code{gdbserver} command line.
13112 @code{gdbserver} will display extra status information about the debugging
13113 process. This option is intended for @code{gdbserver} development and
13114 for bug reports to the developers.
13116 The @option{--wrapper} option specifies a wrapper to launch programs
13117 for debugging. The option should be followed by the name of the
13118 wrapper, then any command-line arguments to pass to the wrapper, then
13119 @kbd{--} indicating the end of the wrapper arguments.
13121 @code{gdbserver} runs the specified wrapper program with a combined
13122 command line including the wrapper arguments, then the name of the
13123 program to debug, then any arguments to the program. The wrapper
13124 runs until it executes your program, and then @value{GDBN} gains control.
13126 You can use any program that eventually calls @code{execve} with
13127 its arguments as a wrapper. Several standard Unix utilities do
13128 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
13129 with @code{exec "$@@"} will also work.
13131 For example, you can use @code{env} to pass an environment variable to
13132 the debugged program, without setting the variable in @code{gdbserver}'s
13136 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
13139 @subsection Connecting to @code{gdbserver}
13141 Run @value{GDBN} on the host system.
13143 First make sure you have the necessary symbol files. Load symbols for
13144 your application using the @code{file} command before you connect. Use
13145 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
13146 was compiled with the correct sysroot using @code{--with-sysroot}).
13148 The symbol file and target libraries must exactly match the executable
13149 and libraries on the target, with one exception: the files on the host
13150 system should not be stripped, even if the files on the target system
13151 are. Mismatched or missing files will lead to confusing results
13152 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
13153 files may also prevent @code{gdbserver} from debugging multi-threaded
13156 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
13157 For TCP connections, you must start up @code{gdbserver} prior to using
13158 the @code{target remote} command. Otherwise you may get an error whose
13159 text depends on the host system, but which usually looks something like
13160 @samp{Connection refused}. Don't use the @code{load}
13161 command in @value{GDBN} when using @code{gdbserver}, since the program is
13162 already on the target.
13164 @subsection Monitor Commands for @code{gdbserver}
13165 @cindex monitor commands, for @code{gdbserver}
13166 @anchor{Monitor Commands for gdbserver}
13168 During a @value{GDBN} session using @code{gdbserver}, you can use the
13169 @code{monitor} command to send special requests to @code{gdbserver}.
13170 Here are the available commands.
13174 List the available monitor commands.
13176 @item monitor set debug 0
13177 @itemx monitor set debug 1
13178 Disable or enable general debugging messages.
13180 @item monitor set remote-debug 0
13181 @itemx monitor set remote-debug 1
13182 Disable or enable specific debugging messages associated with the remote
13183 protocol (@pxref{Remote Protocol}).
13186 Tell gdbserver to exit immediately. This command should be followed by
13187 @code{disconnect} to close the debugging session. @code{gdbserver} will
13188 detach from any attached processes and kill any processes it created.
13189 Use @code{monitor exit} to terminate @code{gdbserver} at the end
13190 of a multi-process mode debug session.
13194 @node Remote Configuration
13195 @section Remote Configuration
13198 @kindex show remote
13199 This section documents the configuration options available when
13200 debugging remote programs. For the options related to the File I/O
13201 extensions of the remote protocol, see @ref{system,
13202 system-call-allowed}.
13205 @item set remoteaddresssize @var{bits}
13206 @cindex address size for remote targets
13207 @cindex bits in remote address
13208 Set the maximum size of address in a memory packet to the specified
13209 number of bits. @value{GDBN} will mask off the address bits above
13210 that number, when it passes addresses to the remote target. The
13211 default value is the number of bits in the target's address.
13213 @item show remoteaddresssize
13214 Show the current value of remote address size in bits.
13216 @item set remotebaud @var{n}
13217 @cindex baud rate for remote targets
13218 Set the baud rate for the remote serial I/O to @var{n} baud. The
13219 value is used to set the speed of the serial port used for debugging
13222 @item show remotebaud
13223 Show the current speed of the remote connection.
13225 @item set remotebreak
13226 @cindex interrupt remote programs
13227 @cindex BREAK signal instead of Ctrl-C
13228 @anchor{set remotebreak}
13229 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
13230 when you type @kbd{Ctrl-c} to interrupt the program running
13231 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
13232 character instead. The default is off, since most remote systems
13233 expect to see @samp{Ctrl-C} as the interrupt signal.
13235 @item show remotebreak
13236 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
13237 interrupt the remote program.
13239 @item set remoteflow on
13240 @itemx set remoteflow off
13241 @kindex set remoteflow
13242 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
13243 on the serial port used to communicate to the remote target.
13245 @item show remoteflow
13246 @kindex show remoteflow
13247 Show the current setting of hardware flow control.
13249 @item set remotelogbase @var{base}
13250 Set the base (a.k.a.@: radix) of logging serial protocol
13251 communications to @var{base}. Supported values of @var{base} are:
13252 @code{ascii}, @code{octal}, and @code{hex}. The default is
13255 @item show remotelogbase
13256 Show the current setting of the radix for logging remote serial
13259 @item set remotelogfile @var{file}
13260 @cindex record serial communications on file
13261 Record remote serial communications on the named @var{file}. The
13262 default is not to record at all.
13264 @item show remotelogfile.
13265 Show the current setting of the file name on which to record the
13266 serial communications.
13268 @item set remotetimeout @var{num}
13269 @cindex timeout for serial communications
13270 @cindex remote timeout
13271 Set the timeout limit to wait for the remote target to respond to
13272 @var{num} seconds. The default is 2 seconds.
13274 @item show remotetimeout
13275 Show the current number of seconds to wait for the remote target
13278 @cindex limit hardware breakpoints and watchpoints
13279 @cindex remote target, limit break- and watchpoints
13280 @anchor{set remote hardware-watchpoint-limit}
13281 @anchor{set remote hardware-breakpoint-limit}
13282 @item set remote hardware-watchpoint-limit @var{limit}
13283 @itemx set remote hardware-breakpoint-limit @var{limit}
13284 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
13285 watchpoints. A limit of -1, the default, is treated as unlimited.
13287 @item set remote exec-file @var{filename}
13288 @itemx show remote exec-file
13289 @anchor{set remote exec-file}
13290 @cindex executable file, for remote target
13291 Select the file used for @code{run} with @code{target
13292 extended-remote}. This should be set to a filename valid on the
13293 target system. If it is not set, the target will use a default
13294 filename (e.g.@: the last program run).
13297 @cindex remote packets, enabling and disabling
13298 The @value{GDBN} remote protocol autodetects the packets supported by
13299 your debugging stub. If you need to override the autodetection, you
13300 can use these commands to enable or disable individual packets. Each
13301 packet can be set to @samp{on} (the remote target supports this
13302 packet), @samp{off} (the remote target does not support this packet),
13303 or @samp{auto} (detect remote target support for this packet). They
13304 all default to @samp{auto}. For more information about each packet,
13305 see @ref{Remote Protocol}.
13307 During normal use, you should not have to use any of these commands.
13308 If you do, that may be a bug in your remote debugging stub, or a bug
13309 in @value{GDBN}. You may want to report the problem to the
13310 @value{GDBN} developers.
13312 For each packet @var{name}, the command to enable or disable the
13313 packet is @code{set remote @var{name}-packet}. The available settings
13316 @multitable @columnfractions 0.28 0.32 0.25
13319 @tab Related Features
13321 @item @code{fetch-register}
13323 @tab @code{info registers}
13325 @item @code{set-register}
13329 @item @code{binary-download}
13331 @tab @code{load}, @code{set}
13333 @item @code{read-aux-vector}
13334 @tab @code{qXfer:auxv:read}
13335 @tab @code{info auxv}
13337 @item @code{symbol-lookup}
13338 @tab @code{qSymbol}
13339 @tab Detecting multiple threads
13341 @item @code{attach}
13342 @tab @code{vAttach}
13345 @item @code{verbose-resume}
13347 @tab Stepping or resuming multiple threads
13353 @item @code{software-breakpoint}
13357 @item @code{hardware-breakpoint}
13361 @item @code{write-watchpoint}
13365 @item @code{read-watchpoint}
13369 @item @code{access-watchpoint}
13373 @item @code{target-features}
13374 @tab @code{qXfer:features:read}
13375 @tab @code{set architecture}
13377 @item @code{library-info}
13378 @tab @code{qXfer:libraries:read}
13379 @tab @code{info sharedlibrary}
13381 @item @code{memory-map}
13382 @tab @code{qXfer:memory-map:read}
13383 @tab @code{info mem}
13385 @item @code{read-spu-object}
13386 @tab @code{qXfer:spu:read}
13387 @tab @code{info spu}
13389 @item @code{write-spu-object}
13390 @tab @code{qXfer:spu:write}
13391 @tab @code{info spu}
13393 @item @code{get-thread-local-@*storage-address}
13394 @tab @code{qGetTLSAddr}
13395 @tab Displaying @code{__thread} variables
13397 @item @code{supported-packets}
13398 @tab @code{qSupported}
13399 @tab Remote communications parameters
13401 @item @code{pass-signals}
13402 @tab @code{QPassSignals}
13403 @tab @code{handle @var{signal}}
13405 @item @code{hostio-close-packet}
13406 @tab @code{vFile:close}
13407 @tab @code{remote get}, @code{remote put}
13409 @item @code{hostio-open-packet}
13410 @tab @code{vFile:open}
13411 @tab @code{remote get}, @code{remote put}
13413 @item @code{hostio-pread-packet}
13414 @tab @code{vFile:pread}
13415 @tab @code{remote get}, @code{remote put}
13417 @item @code{hostio-pwrite-packet}
13418 @tab @code{vFile:pwrite}
13419 @tab @code{remote get}, @code{remote put}
13421 @item @code{hostio-unlink-packet}
13422 @tab @code{vFile:unlink}
13423 @tab @code{remote delete}
13427 @section Implementing a Remote Stub
13429 @cindex debugging stub, example
13430 @cindex remote stub, example
13431 @cindex stub example, remote debugging
13432 The stub files provided with @value{GDBN} implement the target side of the
13433 communication protocol, and the @value{GDBN} side is implemented in the
13434 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
13435 these subroutines to communicate, and ignore the details. (If you're
13436 implementing your own stub file, you can still ignore the details: start
13437 with one of the existing stub files. @file{sparc-stub.c} is the best
13438 organized, and therefore the easiest to read.)
13440 @cindex remote serial debugging, overview
13441 To debug a program running on another machine (the debugging
13442 @dfn{target} machine), you must first arrange for all the usual
13443 prerequisites for the program to run by itself. For example, for a C
13448 A startup routine to set up the C runtime environment; these usually
13449 have a name like @file{crt0}. The startup routine may be supplied by
13450 your hardware supplier, or you may have to write your own.
13453 A C subroutine library to support your program's
13454 subroutine calls, notably managing input and output.
13457 A way of getting your program to the other machine---for example, a
13458 download program. These are often supplied by the hardware
13459 manufacturer, but you may have to write your own from hardware
13463 The next step is to arrange for your program to use a serial port to
13464 communicate with the machine where @value{GDBN} is running (the @dfn{host}
13465 machine). In general terms, the scheme looks like this:
13469 @value{GDBN} already understands how to use this protocol; when everything
13470 else is set up, you can simply use the @samp{target remote} command
13471 (@pxref{Targets,,Specifying a Debugging Target}).
13473 @item On the target,
13474 you must link with your program a few special-purpose subroutines that
13475 implement the @value{GDBN} remote serial protocol. The file containing these
13476 subroutines is called a @dfn{debugging stub}.
13478 On certain remote targets, you can use an auxiliary program
13479 @code{gdbserver} instead of linking a stub into your program.
13480 @xref{Server,,Using the @code{gdbserver} Program}, for details.
13483 The debugging stub is specific to the architecture of the remote
13484 machine; for example, use @file{sparc-stub.c} to debug programs on
13487 @cindex remote serial stub list
13488 These working remote stubs are distributed with @value{GDBN}:
13493 @cindex @file{i386-stub.c}
13496 For Intel 386 and compatible architectures.
13499 @cindex @file{m68k-stub.c}
13500 @cindex Motorola 680x0
13502 For Motorola 680x0 architectures.
13505 @cindex @file{sh-stub.c}
13508 For Renesas SH architectures.
13511 @cindex @file{sparc-stub.c}
13513 For @sc{sparc} architectures.
13515 @item sparcl-stub.c
13516 @cindex @file{sparcl-stub.c}
13519 For Fujitsu @sc{sparclite} architectures.
13523 The @file{README} file in the @value{GDBN} distribution may list other
13524 recently added stubs.
13527 * Stub Contents:: What the stub can do for you
13528 * Bootstrapping:: What you must do for the stub
13529 * Debug Session:: Putting it all together
13532 @node Stub Contents
13533 @subsection What the Stub Can Do for You
13535 @cindex remote serial stub
13536 The debugging stub for your architecture supplies these three
13540 @item set_debug_traps
13541 @findex set_debug_traps
13542 @cindex remote serial stub, initialization
13543 This routine arranges for @code{handle_exception} to run when your
13544 program stops. You must call this subroutine explicitly near the
13545 beginning of your program.
13547 @item handle_exception
13548 @findex handle_exception
13549 @cindex remote serial stub, main routine
13550 This is the central workhorse, but your program never calls it
13551 explicitly---the setup code arranges for @code{handle_exception} to
13552 run when a trap is triggered.
13554 @code{handle_exception} takes control when your program stops during
13555 execution (for example, on a breakpoint), and mediates communications
13556 with @value{GDBN} on the host machine. This is where the communications
13557 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
13558 representative on the target machine. It begins by sending summary
13559 information on the state of your program, then continues to execute,
13560 retrieving and transmitting any information @value{GDBN} needs, until you
13561 execute a @value{GDBN} command that makes your program resume; at that point,
13562 @code{handle_exception} returns control to your own code on the target
13566 @cindex @code{breakpoint} subroutine, remote
13567 Use this auxiliary subroutine to make your program contain a
13568 breakpoint. Depending on the particular situation, this may be the only
13569 way for @value{GDBN} to get control. For instance, if your target
13570 machine has some sort of interrupt button, you won't need to call this;
13571 pressing the interrupt button transfers control to
13572 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
13573 simply receiving characters on the serial port may also trigger a trap;
13574 again, in that situation, you don't need to call @code{breakpoint} from
13575 your own program---simply running @samp{target remote} from the host
13576 @value{GDBN} session gets control.
13578 Call @code{breakpoint} if none of these is true, or if you simply want
13579 to make certain your program stops at a predetermined point for the
13580 start of your debugging session.
13583 @node Bootstrapping
13584 @subsection What You Must Do for the Stub
13586 @cindex remote stub, support routines
13587 The debugging stubs that come with @value{GDBN} are set up for a particular
13588 chip architecture, but they have no information about the rest of your
13589 debugging target machine.
13591 First of all you need to tell the stub how to communicate with the
13595 @item int getDebugChar()
13596 @findex getDebugChar
13597 Write this subroutine to read a single character from the serial port.
13598 It may be identical to @code{getchar} for your target system; a
13599 different name is used to allow you to distinguish the two if you wish.
13601 @item void putDebugChar(int)
13602 @findex putDebugChar
13603 Write this subroutine to write a single character to the serial port.
13604 It may be identical to @code{putchar} for your target system; a
13605 different name is used to allow you to distinguish the two if you wish.
13608 @cindex control C, and remote debugging
13609 @cindex interrupting remote targets
13610 If you want @value{GDBN} to be able to stop your program while it is
13611 running, you need to use an interrupt-driven serial driver, and arrange
13612 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
13613 character). That is the character which @value{GDBN} uses to tell the
13614 remote system to stop.
13616 Getting the debugging target to return the proper status to @value{GDBN}
13617 probably requires changes to the standard stub; one quick and dirty way
13618 is to just execute a breakpoint instruction (the ``dirty'' part is that
13619 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
13621 Other routines you need to supply are:
13624 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
13625 @findex exceptionHandler
13626 Write this function to install @var{exception_address} in the exception
13627 handling tables. You need to do this because the stub does not have any
13628 way of knowing what the exception handling tables on your target system
13629 are like (for example, the processor's table might be in @sc{rom},
13630 containing entries which point to a table in @sc{ram}).
13631 @var{exception_number} is the exception number which should be changed;
13632 its meaning is architecture-dependent (for example, different numbers
13633 might represent divide by zero, misaligned access, etc). When this
13634 exception occurs, control should be transferred directly to
13635 @var{exception_address}, and the processor state (stack, registers,
13636 and so on) should be just as it is when a processor exception occurs. So if
13637 you want to use a jump instruction to reach @var{exception_address}, it
13638 should be a simple jump, not a jump to subroutine.
13640 For the 386, @var{exception_address} should be installed as an interrupt
13641 gate so that interrupts are masked while the handler runs. The gate
13642 should be at privilege level 0 (the most privileged level). The
13643 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
13644 help from @code{exceptionHandler}.
13646 @item void flush_i_cache()
13647 @findex flush_i_cache
13648 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
13649 instruction cache, if any, on your target machine. If there is no
13650 instruction cache, this subroutine may be a no-op.
13652 On target machines that have instruction caches, @value{GDBN} requires this
13653 function to make certain that the state of your program is stable.
13657 You must also make sure this library routine is available:
13660 @item void *memset(void *, int, int)
13662 This is the standard library function @code{memset} that sets an area of
13663 memory to a known value. If you have one of the free versions of
13664 @code{libc.a}, @code{memset} can be found there; otherwise, you must
13665 either obtain it from your hardware manufacturer, or write your own.
13668 If you do not use the GNU C compiler, you may need other standard
13669 library subroutines as well; this varies from one stub to another,
13670 but in general the stubs are likely to use any of the common library
13671 subroutines which @code{@value{NGCC}} generates as inline code.
13674 @node Debug Session
13675 @subsection Putting it All Together
13677 @cindex remote serial debugging summary
13678 In summary, when your program is ready to debug, you must follow these
13683 Make sure you have defined the supporting low-level routines
13684 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
13686 @code{getDebugChar}, @code{putDebugChar},
13687 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
13691 Insert these lines near the top of your program:
13699 For the 680x0 stub only, you need to provide a variable called
13700 @code{exceptionHook}. Normally you just use:
13703 void (*exceptionHook)() = 0;
13707 but if before calling @code{set_debug_traps}, you set it to point to a
13708 function in your program, that function is called when
13709 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
13710 error). The function indicated by @code{exceptionHook} is called with
13711 one parameter: an @code{int} which is the exception number.
13714 Compile and link together: your program, the @value{GDBN} debugging stub for
13715 your target architecture, and the supporting subroutines.
13718 Make sure you have a serial connection between your target machine and
13719 the @value{GDBN} host, and identify the serial port on the host.
13722 @c The "remote" target now provides a `load' command, so we should
13723 @c document that. FIXME.
13724 Download your program to your target machine (or get it there by
13725 whatever means the manufacturer provides), and start it.
13728 Start @value{GDBN} on the host, and connect to the target
13729 (@pxref{Connecting,,Connecting to a Remote Target}).
13733 @node Configurations
13734 @chapter Configuration-Specific Information
13736 While nearly all @value{GDBN} commands are available for all native and
13737 cross versions of the debugger, there are some exceptions. This chapter
13738 describes things that are only available in certain configurations.
13740 There are three major categories of configurations: native
13741 configurations, where the host and target are the same, embedded
13742 operating system configurations, which are usually the same for several
13743 different processor architectures, and bare embedded processors, which
13744 are quite different from each other.
13749 * Embedded Processors::
13756 This section describes details specific to particular native
13761 * BSD libkvm Interface:: Debugging BSD kernel memory images
13762 * SVR4 Process Information:: SVR4 process information
13763 * DJGPP Native:: Features specific to the DJGPP port
13764 * Cygwin Native:: Features specific to the Cygwin port
13765 * Hurd Native:: Features specific to @sc{gnu} Hurd
13766 * Neutrino:: Features specific to QNX Neutrino
13772 On HP-UX systems, if you refer to a function or variable name that
13773 begins with a dollar sign, @value{GDBN} searches for a user or system
13774 name first, before it searches for a convenience variable.
13777 @node BSD libkvm Interface
13778 @subsection BSD libkvm Interface
13781 @cindex kernel memory image
13782 @cindex kernel crash dump
13784 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
13785 interface that provides a uniform interface for accessing kernel virtual
13786 memory images, including live systems and crash dumps. @value{GDBN}
13787 uses this interface to allow you to debug live kernels and kernel crash
13788 dumps on many native BSD configurations. This is implemented as a
13789 special @code{kvm} debugging target. For debugging a live system, load
13790 the currently running kernel into @value{GDBN} and connect to the
13794 (@value{GDBP}) @b{target kvm}
13797 For debugging crash dumps, provide the file name of the crash dump as an
13801 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
13804 Once connected to the @code{kvm} target, the following commands are
13810 Set current context from the @dfn{Process Control Block} (PCB) address.
13813 Set current context from proc address. This command isn't available on
13814 modern FreeBSD systems.
13817 @node SVR4 Process Information
13818 @subsection SVR4 Process Information
13820 @cindex examine process image
13821 @cindex process info via @file{/proc}
13823 Many versions of SVR4 and compatible systems provide a facility called
13824 @samp{/proc} that can be used to examine the image of a running
13825 process using file-system subroutines. If @value{GDBN} is configured
13826 for an operating system with this facility, the command @code{info
13827 proc} is available to report information about the process running
13828 your program, or about any process running on your system. @code{info
13829 proc} works only on SVR4 systems that include the @code{procfs} code.
13830 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
13831 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
13837 @itemx info proc @var{process-id}
13838 Summarize available information about any running process. If a
13839 process ID is specified by @var{process-id}, display information about
13840 that process; otherwise display information about the program being
13841 debugged. The summary includes the debugged process ID, the command
13842 line used to invoke it, its current working directory, and its
13843 executable file's absolute file name.
13845 On some systems, @var{process-id} can be of the form
13846 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
13847 within a process. If the optional @var{pid} part is missing, it means
13848 a thread from the process being debugged (the leading @samp{/} still
13849 needs to be present, or else @value{GDBN} will interpret the number as
13850 a process ID rather than a thread ID).
13852 @item info proc mappings
13853 @cindex memory address space mappings
13854 Report the memory address space ranges accessible in the program, with
13855 information on whether the process has read, write, or execute access
13856 rights to each range. On @sc{gnu}/Linux systems, each memory range
13857 includes the object file which is mapped to that range, instead of the
13858 memory access rights to that range.
13860 @item info proc stat
13861 @itemx info proc status
13862 @cindex process detailed status information
13863 These subcommands are specific to @sc{gnu}/Linux systems. They show
13864 the process-related information, including the user ID and group ID;
13865 how many threads are there in the process; its virtual memory usage;
13866 the signals that are pending, blocked, and ignored; its TTY; its
13867 consumption of system and user time; its stack size; its @samp{nice}
13868 value; etc. For more information, see the @samp{proc} man page
13869 (type @kbd{man 5 proc} from your shell prompt).
13871 @item info proc all
13872 Show all the information about the process described under all of the
13873 above @code{info proc} subcommands.
13876 @comment These sub-options of 'info proc' were not included when
13877 @comment procfs.c was re-written. Keep their descriptions around
13878 @comment against the day when someone finds the time to put them back in.
13879 @kindex info proc times
13880 @item info proc times
13881 Starting time, user CPU time, and system CPU time for your program and
13884 @kindex info proc id
13886 Report on the process IDs related to your program: its own process ID,
13887 the ID of its parent, the process group ID, and the session ID.
13890 @item set procfs-trace
13891 @kindex set procfs-trace
13892 @cindex @code{procfs} API calls
13893 This command enables and disables tracing of @code{procfs} API calls.
13895 @item show procfs-trace
13896 @kindex show procfs-trace
13897 Show the current state of @code{procfs} API call tracing.
13899 @item set procfs-file @var{file}
13900 @kindex set procfs-file
13901 Tell @value{GDBN} to write @code{procfs} API trace to the named
13902 @var{file}. @value{GDBN} appends the trace info to the previous
13903 contents of the file. The default is to display the trace on the
13906 @item show procfs-file
13907 @kindex show procfs-file
13908 Show the file to which @code{procfs} API trace is written.
13910 @item proc-trace-entry
13911 @itemx proc-trace-exit
13912 @itemx proc-untrace-entry
13913 @itemx proc-untrace-exit
13914 @kindex proc-trace-entry
13915 @kindex proc-trace-exit
13916 @kindex proc-untrace-entry
13917 @kindex proc-untrace-exit
13918 These commands enable and disable tracing of entries into and exits
13919 from the @code{syscall} interface.
13922 @kindex info pidlist
13923 @cindex process list, QNX Neutrino
13924 For QNX Neutrino only, this command displays the list of all the
13925 processes and all the threads within each process.
13928 @kindex info meminfo
13929 @cindex mapinfo list, QNX Neutrino
13930 For QNX Neutrino only, this command displays the list of all mapinfos.
13934 @subsection Features for Debugging @sc{djgpp} Programs
13935 @cindex @sc{djgpp} debugging
13936 @cindex native @sc{djgpp} debugging
13937 @cindex MS-DOS-specific commands
13940 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
13941 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
13942 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
13943 top of real-mode DOS systems and their emulations.
13945 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
13946 defines a few commands specific to the @sc{djgpp} port. This
13947 subsection describes those commands.
13952 This is a prefix of @sc{djgpp}-specific commands which print
13953 information about the target system and important OS structures.
13956 @cindex MS-DOS system info
13957 @cindex free memory information (MS-DOS)
13958 @item info dos sysinfo
13959 This command displays assorted information about the underlying
13960 platform: the CPU type and features, the OS version and flavor, the
13961 DPMI version, and the available conventional and DPMI memory.
13966 @cindex segment descriptor tables
13967 @cindex descriptor tables display
13969 @itemx info dos ldt
13970 @itemx info dos idt
13971 These 3 commands display entries from, respectively, Global, Local,
13972 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
13973 tables are data structures which store a descriptor for each segment
13974 that is currently in use. The segment's selector is an index into a
13975 descriptor table; the table entry for that index holds the
13976 descriptor's base address and limit, and its attributes and access
13979 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
13980 segment (used for both data and the stack), and a DOS segment (which
13981 allows access to DOS/BIOS data structures and absolute addresses in
13982 conventional memory). However, the DPMI host will usually define
13983 additional segments in order to support the DPMI environment.
13985 @cindex garbled pointers
13986 These commands allow to display entries from the descriptor tables.
13987 Without an argument, all entries from the specified table are
13988 displayed. An argument, which should be an integer expression, means
13989 display a single entry whose index is given by the argument. For
13990 example, here's a convenient way to display information about the
13991 debugged program's data segment:
13994 @exdent @code{(@value{GDBP}) info dos ldt $ds}
13995 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
13999 This comes in handy when you want to see whether a pointer is outside
14000 the data segment's limit (i.e.@: @dfn{garbled}).
14002 @cindex page tables display (MS-DOS)
14004 @itemx info dos pte
14005 These two commands display entries from, respectively, the Page
14006 Directory and the Page Tables. Page Directories and Page Tables are
14007 data structures which control how virtual memory addresses are mapped
14008 into physical addresses. A Page Table includes an entry for every
14009 page of memory that is mapped into the program's address space; there
14010 may be several Page Tables, each one holding up to 4096 entries. A
14011 Page Directory has up to 4096 entries, one each for every Page Table
14012 that is currently in use.
14014 Without an argument, @kbd{info dos pde} displays the entire Page
14015 Directory, and @kbd{info dos pte} displays all the entries in all of
14016 the Page Tables. An argument, an integer expression, given to the
14017 @kbd{info dos pde} command means display only that entry from the Page
14018 Directory table. An argument given to the @kbd{info dos pte} command
14019 means display entries from a single Page Table, the one pointed to by
14020 the specified entry in the Page Directory.
14022 @cindex direct memory access (DMA) on MS-DOS
14023 These commands are useful when your program uses @dfn{DMA} (Direct
14024 Memory Access), which needs physical addresses to program the DMA
14027 These commands are supported only with some DPMI servers.
14029 @cindex physical address from linear address
14030 @item info dos address-pte @var{addr}
14031 This command displays the Page Table entry for a specified linear
14032 address. The argument @var{addr} is a linear address which should
14033 already have the appropriate segment's base address added to it,
14034 because this command accepts addresses which may belong to @emph{any}
14035 segment. For example, here's how to display the Page Table entry for
14036 the page where a variable @code{i} is stored:
14039 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
14040 @exdent @code{Page Table entry for address 0x11a00d30:}
14041 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
14045 This says that @code{i} is stored at offset @code{0xd30} from the page
14046 whose physical base address is @code{0x02698000}, and shows all the
14047 attributes of that page.
14049 Note that you must cast the addresses of variables to a @code{char *},
14050 since otherwise the value of @code{__djgpp_base_address}, the base
14051 address of all variables and functions in a @sc{djgpp} program, will
14052 be added using the rules of C pointer arithmetics: if @code{i} is
14053 declared an @code{int}, @value{GDBN} will add 4 times the value of
14054 @code{__djgpp_base_address} to the address of @code{i}.
14056 Here's another example, it displays the Page Table entry for the
14060 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
14061 @exdent @code{Page Table entry for address 0x29110:}
14062 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
14066 (The @code{+ 3} offset is because the transfer buffer's address is the
14067 3rd member of the @code{_go32_info_block} structure.) The output
14068 clearly shows that this DPMI server maps the addresses in conventional
14069 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
14070 linear (@code{0x29110}) addresses are identical.
14072 This command is supported only with some DPMI servers.
14075 @cindex DOS serial data link, remote debugging
14076 In addition to native debugging, the DJGPP port supports remote
14077 debugging via a serial data link. The following commands are specific
14078 to remote serial debugging in the DJGPP port of @value{GDBN}.
14081 @kindex set com1base
14082 @kindex set com1irq
14083 @kindex set com2base
14084 @kindex set com2irq
14085 @kindex set com3base
14086 @kindex set com3irq
14087 @kindex set com4base
14088 @kindex set com4irq
14089 @item set com1base @var{addr}
14090 This command sets the base I/O port address of the @file{COM1} serial
14093 @item set com1irq @var{irq}
14094 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
14095 for the @file{COM1} serial port.
14097 There are similar commands @samp{set com2base}, @samp{set com3irq},
14098 etc.@: for setting the port address and the @code{IRQ} lines for the
14101 @kindex show com1base
14102 @kindex show com1irq
14103 @kindex show com2base
14104 @kindex show com2irq
14105 @kindex show com3base
14106 @kindex show com3irq
14107 @kindex show com4base
14108 @kindex show com4irq
14109 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
14110 display the current settings of the base address and the @code{IRQ}
14111 lines used by the COM ports.
14114 @kindex info serial
14115 @cindex DOS serial port status
14116 This command prints the status of the 4 DOS serial ports. For each
14117 port, it prints whether it's active or not, its I/O base address and
14118 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
14119 counts of various errors encountered so far.
14123 @node Cygwin Native
14124 @subsection Features for Debugging MS Windows PE Executables
14125 @cindex MS Windows debugging
14126 @cindex native Cygwin debugging
14127 @cindex Cygwin-specific commands
14129 @value{GDBN} supports native debugging of MS Windows programs, including
14130 DLLs with and without symbolic debugging information. There are various
14131 additional Cygwin-specific commands, described in this section.
14132 Working with DLLs that have no debugging symbols is described in
14133 @ref{Non-debug DLL Symbols}.
14138 This is a prefix of MS Windows-specific commands which print
14139 information about the target system and important OS structures.
14141 @item info w32 selector
14142 This command displays information returned by
14143 the Win32 API @code{GetThreadSelectorEntry} function.
14144 It takes an optional argument that is evaluated to
14145 a long value to give the information about this given selector.
14146 Without argument, this command displays information
14147 about the six segment registers.
14151 This is a Cygwin-specific alias of @code{info shared}.
14153 @kindex dll-symbols
14155 This command loads symbols from a dll similarly to
14156 add-sym command but without the need to specify a base address.
14158 @kindex set cygwin-exceptions
14159 @cindex debugging the Cygwin DLL
14160 @cindex Cygwin DLL, debugging
14161 @item set cygwin-exceptions @var{mode}
14162 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
14163 happen inside the Cygwin DLL. If @var{mode} is @code{off},
14164 @value{GDBN} will delay recognition of exceptions, and may ignore some
14165 exceptions which seem to be caused by internal Cygwin DLL
14166 ``bookkeeping''. This option is meant primarily for debugging the
14167 Cygwin DLL itself; the default value is @code{off} to avoid annoying
14168 @value{GDBN} users with false @code{SIGSEGV} signals.
14170 @kindex show cygwin-exceptions
14171 @item show cygwin-exceptions
14172 Displays whether @value{GDBN} will break on exceptions that happen
14173 inside the Cygwin DLL itself.
14175 @kindex set new-console
14176 @item set new-console @var{mode}
14177 If @var{mode} is @code{on} the debuggee will
14178 be started in a new console on next start.
14179 If @var{mode} is @code{off}i, the debuggee will
14180 be started in the same console as the debugger.
14182 @kindex show new-console
14183 @item show new-console
14184 Displays whether a new console is used
14185 when the debuggee is started.
14187 @kindex set new-group
14188 @item set new-group @var{mode}
14189 This boolean value controls whether the debuggee should
14190 start a new group or stay in the same group as the debugger.
14191 This affects the way the Windows OS handles
14194 @kindex show new-group
14195 @item show new-group
14196 Displays current value of new-group boolean.
14198 @kindex set debugevents
14199 @item set debugevents
14200 This boolean value adds debug output concerning kernel events related
14201 to the debuggee seen by the debugger. This includes events that
14202 signal thread and process creation and exit, DLL loading and
14203 unloading, console interrupts, and debugging messages produced by the
14204 Windows @code{OutputDebugString} API call.
14206 @kindex set debugexec
14207 @item set debugexec
14208 This boolean value adds debug output concerning execute events
14209 (such as resume thread) seen by the debugger.
14211 @kindex set debugexceptions
14212 @item set debugexceptions
14213 This boolean value adds debug output concerning exceptions in the
14214 debuggee seen by the debugger.
14216 @kindex set debugmemory
14217 @item set debugmemory
14218 This boolean value adds debug output concerning debuggee memory reads
14219 and writes by the debugger.
14223 This boolean values specifies whether the debuggee is called
14224 via a shell or directly (default value is on).
14228 Displays if the debuggee will be started with a shell.
14233 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
14236 @node Non-debug DLL Symbols
14237 @subsubsection Support for DLLs without Debugging Symbols
14238 @cindex DLLs with no debugging symbols
14239 @cindex Minimal symbols and DLLs
14241 Very often on windows, some of the DLLs that your program relies on do
14242 not include symbolic debugging information (for example,
14243 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
14244 symbols in a DLL, it relies on the minimal amount of symbolic
14245 information contained in the DLL's export table. This section
14246 describes working with such symbols, known internally to @value{GDBN} as
14247 ``minimal symbols''.
14249 Note that before the debugged program has started execution, no DLLs
14250 will have been loaded. The easiest way around this problem is simply to
14251 start the program --- either by setting a breakpoint or letting the
14252 program run once to completion. It is also possible to force
14253 @value{GDBN} to load a particular DLL before starting the executable ---
14254 see the shared library information in @ref{Files}, or the
14255 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
14256 explicitly loading symbols from a DLL with no debugging information will
14257 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
14258 which may adversely affect symbol lookup performance.
14260 @subsubsection DLL Name Prefixes
14262 In keeping with the naming conventions used by the Microsoft debugging
14263 tools, DLL export symbols are made available with a prefix based on the
14264 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
14265 also entered into the symbol table, so @code{CreateFileA} is often
14266 sufficient. In some cases there will be name clashes within a program
14267 (particularly if the executable itself includes full debugging symbols)
14268 necessitating the use of the fully qualified name when referring to the
14269 contents of the DLL. Use single-quotes around the name to avoid the
14270 exclamation mark (``!'') being interpreted as a language operator.
14272 Note that the internal name of the DLL may be all upper-case, even
14273 though the file name of the DLL is lower-case, or vice-versa. Since
14274 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
14275 some confusion. If in doubt, try the @code{info functions} and
14276 @code{info variables} commands or even @code{maint print msymbols}
14277 (@pxref{Symbols}). Here's an example:
14280 (@value{GDBP}) info function CreateFileA
14281 All functions matching regular expression "CreateFileA":
14283 Non-debugging symbols:
14284 0x77e885f4 CreateFileA
14285 0x77e885f4 KERNEL32!CreateFileA
14289 (@value{GDBP}) info function !
14290 All functions matching regular expression "!":
14292 Non-debugging symbols:
14293 0x6100114c cygwin1!__assert
14294 0x61004034 cygwin1!_dll_crt0@@0
14295 0x61004240 cygwin1!dll_crt0(per_process *)
14299 @subsubsection Working with Minimal Symbols
14301 Symbols extracted from a DLL's export table do not contain very much
14302 type information. All that @value{GDBN} can do is guess whether a symbol
14303 refers to a function or variable depending on the linker section that
14304 contains the symbol. Also note that the actual contents of the memory
14305 contained in a DLL are not available unless the program is running. This
14306 means that you cannot examine the contents of a variable or disassemble
14307 a function within a DLL without a running program.
14309 Variables are generally treated as pointers and dereferenced
14310 automatically. For this reason, it is often necessary to prefix a
14311 variable name with the address-of operator (``&'') and provide explicit
14312 type information in the command. Here's an example of the type of
14316 (@value{GDBP}) print 'cygwin1!__argv'
14321 (@value{GDBP}) x 'cygwin1!__argv'
14322 0x10021610: "\230y\""
14325 And two possible solutions:
14328 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
14329 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
14333 (@value{GDBP}) x/2x &'cygwin1!__argv'
14334 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
14335 (@value{GDBP}) x/x 0x10021608
14336 0x10021608: 0x0022fd98
14337 (@value{GDBP}) x/s 0x0022fd98
14338 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
14341 Setting a break point within a DLL is possible even before the program
14342 starts execution. However, under these circumstances, @value{GDBN} can't
14343 examine the initial instructions of the function in order to skip the
14344 function's frame set-up code. You can work around this by using ``*&''
14345 to set the breakpoint at a raw memory address:
14348 (@value{GDBP}) break *&'python22!PyOS_Readline'
14349 Breakpoint 1 at 0x1e04eff0
14352 The author of these extensions is not entirely convinced that setting a
14353 break point within a shared DLL like @file{kernel32.dll} is completely
14357 @subsection Commands Specific to @sc{gnu} Hurd Systems
14358 @cindex @sc{gnu} Hurd debugging
14360 This subsection describes @value{GDBN} commands specific to the
14361 @sc{gnu} Hurd native debugging.
14366 @kindex set signals@r{, Hurd command}
14367 @kindex set sigs@r{, Hurd command}
14368 This command toggles the state of inferior signal interception by
14369 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
14370 affected by this command. @code{sigs} is a shorthand alias for
14375 @kindex show signals@r{, Hurd command}
14376 @kindex show sigs@r{, Hurd command}
14377 Show the current state of intercepting inferior's signals.
14379 @item set signal-thread
14380 @itemx set sigthread
14381 @kindex set signal-thread
14382 @kindex set sigthread
14383 This command tells @value{GDBN} which thread is the @code{libc} signal
14384 thread. That thread is run when a signal is delivered to a running
14385 process. @code{set sigthread} is the shorthand alias of @code{set
14388 @item show signal-thread
14389 @itemx show sigthread
14390 @kindex show signal-thread
14391 @kindex show sigthread
14392 These two commands show which thread will run when the inferior is
14393 delivered a signal.
14396 @kindex set stopped@r{, Hurd command}
14397 This commands tells @value{GDBN} that the inferior process is stopped,
14398 as with the @code{SIGSTOP} signal. The stopped process can be
14399 continued by delivering a signal to it.
14402 @kindex show stopped@r{, Hurd command}
14403 This command shows whether @value{GDBN} thinks the debuggee is
14406 @item set exceptions
14407 @kindex set exceptions@r{, Hurd command}
14408 Use this command to turn off trapping of exceptions in the inferior.
14409 When exception trapping is off, neither breakpoints nor
14410 single-stepping will work. To restore the default, set exception
14413 @item show exceptions
14414 @kindex show exceptions@r{, Hurd command}
14415 Show the current state of trapping exceptions in the inferior.
14417 @item set task pause
14418 @kindex set task@r{, Hurd commands}
14419 @cindex task attributes (@sc{gnu} Hurd)
14420 @cindex pause current task (@sc{gnu} Hurd)
14421 This command toggles task suspension when @value{GDBN} has control.
14422 Setting it to on takes effect immediately, and the task is suspended
14423 whenever @value{GDBN} gets control. Setting it to off will take
14424 effect the next time the inferior is continued. If this option is set
14425 to off, you can use @code{set thread default pause on} or @code{set
14426 thread pause on} (see below) to pause individual threads.
14428 @item show task pause
14429 @kindex show task@r{, Hurd commands}
14430 Show the current state of task suspension.
14432 @item set task detach-suspend-count
14433 @cindex task suspend count
14434 @cindex detach from task, @sc{gnu} Hurd
14435 This command sets the suspend count the task will be left with when
14436 @value{GDBN} detaches from it.
14438 @item show task detach-suspend-count
14439 Show the suspend count the task will be left with when detaching.
14441 @item set task exception-port
14442 @itemx set task excp
14443 @cindex task exception port, @sc{gnu} Hurd
14444 This command sets the task exception port to which @value{GDBN} will
14445 forward exceptions. The argument should be the value of the @dfn{send
14446 rights} of the task. @code{set task excp} is a shorthand alias.
14448 @item set noninvasive
14449 @cindex noninvasive task options
14450 This command switches @value{GDBN} to a mode that is the least
14451 invasive as far as interfering with the inferior is concerned. This
14452 is the same as using @code{set task pause}, @code{set exceptions}, and
14453 @code{set signals} to values opposite to the defaults.
14455 @item info send-rights
14456 @itemx info receive-rights
14457 @itemx info port-rights
14458 @itemx info port-sets
14459 @itemx info dead-names
14462 @cindex send rights, @sc{gnu} Hurd
14463 @cindex receive rights, @sc{gnu} Hurd
14464 @cindex port rights, @sc{gnu} Hurd
14465 @cindex port sets, @sc{gnu} Hurd
14466 @cindex dead names, @sc{gnu} Hurd
14467 These commands display information about, respectively, send rights,
14468 receive rights, port rights, port sets, and dead names of a task.
14469 There are also shorthand aliases: @code{info ports} for @code{info
14470 port-rights} and @code{info psets} for @code{info port-sets}.
14472 @item set thread pause
14473 @kindex set thread@r{, Hurd command}
14474 @cindex thread properties, @sc{gnu} Hurd
14475 @cindex pause current thread (@sc{gnu} Hurd)
14476 This command toggles current thread suspension when @value{GDBN} has
14477 control. Setting it to on takes effect immediately, and the current
14478 thread is suspended whenever @value{GDBN} gets control. Setting it to
14479 off will take effect the next time the inferior is continued.
14480 Normally, this command has no effect, since when @value{GDBN} has
14481 control, the whole task is suspended. However, if you used @code{set
14482 task pause off} (see above), this command comes in handy to suspend
14483 only the current thread.
14485 @item show thread pause
14486 @kindex show thread@r{, Hurd command}
14487 This command shows the state of current thread suspension.
14489 @item set thread run
14490 This command sets whether the current thread is allowed to run.
14492 @item show thread run
14493 Show whether the current thread is allowed to run.
14495 @item set thread detach-suspend-count
14496 @cindex thread suspend count, @sc{gnu} Hurd
14497 @cindex detach from thread, @sc{gnu} Hurd
14498 This command sets the suspend count @value{GDBN} will leave on a
14499 thread when detaching. This number is relative to the suspend count
14500 found by @value{GDBN} when it notices the thread; use @code{set thread
14501 takeover-suspend-count} to force it to an absolute value.
14503 @item show thread detach-suspend-count
14504 Show the suspend count @value{GDBN} will leave on the thread when
14507 @item set thread exception-port
14508 @itemx set thread excp
14509 Set the thread exception port to which to forward exceptions. This
14510 overrides the port set by @code{set task exception-port} (see above).
14511 @code{set thread excp} is the shorthand alias.
14513 @item set thread takeover-suspend-count
14514 Normally, @value{GDBN}'s thread suspend counts are relative to the
14515 value @value{GDBN} finds when it notices each thread. This command
14516 changes the suspend counts to be absolute instead.
14518 @item set thread default
14519 @itemx show thread default
14520 @cindex thread default settings, @sc{gnu} Hurd
14521 Each of the above @code{set thread} commands has a @code{set thread
14522 default} counterpart (e.g., @code{set thread default pause}, @code{set
14523 thread default exception-port}, etc.). The @code{thread default}
14524 variety of commands sets the default thread properties for all
14525 threads; you can then change the properties of individual threads with
14526 the non-default commands.
14531 @subsection QNX Neutrino
14532 @cindex QNX Neutrino
14534 @value{GDBN} provides the following commands specific to the QNX
14538 @item set debug nto-debug
14539 @kindex set debug nto-debug
14540 When set to on, enables debugging messages specific to the QNX
14543 @item show debug nto-debug
14544 @kindex show debug nto-debug
14545 Show the current state of QNX Neutrino messages.
14550 @section Embedded Operating Systems
14552 This section describes configurations involving the debugging of
14553 embedded operating systems that are available for several different
14557 * VxWorks:: Using @value{GDBN} with VxWorks
14560 @value{GDBN} includes the ability to debug programs running on
14561 various real-time operating systems.
14564 @subsection Using @value{GDBN} with VxWorks
14570 @kindex target vxworks
14571 @item target vxworks @var{machinename}
14572 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
14573 is the target system's machine name or IP address.
14577 On VxWorks, @code{load} links @var{filename} dynamically on the
14578 current target system as well as adding its symbols in @value{GDBN}.
14580 @value{GDBN} enables developers to spawn and debug tasks running on networked
14581 VxWorks targets from a Unix host. Already-running tasks spawned from
14582 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
14583 both the Unix host and on the VxWorks target. The program
14584 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
14585 installed with the name @code{vxgdb}, to distinguish it from a
14586 @value{GDBN} for debugging programs on the host itself.)
14589 @item VxWorks-timeout @var{args}
14590 @kindex vxworks-timeout
14591 All VxWorks-based targets now support the option @code{vxworks-timeout}.
14592 This option is set by the user, and @var{args} represents the number of
14593 seconds @value{GDBN} waits for responses to rpc's. You might use this if
14594 your VxWorks target is a slow software simulator or is on the far side
14595 of a thin network line.
14598 The following information on connecting to VxWorks was current when
14599 this manual was produced; newer releases of VxWorks may use revised
14602 @findex INCLUDE_RDB
14603 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
14604 to include the remote debugging interface routines in the VxWorks
14605 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
14606 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
14607 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
14608 source debugging task @code{tRdbTask} when VxWorks is booted. For more
14609 information on configuring and remaking VxWorks, see the manufacturer's
14611 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
14613 Once you have included @file{rdb.a} in your VxWorks system image and set
14614 your Unix execution search path to find @value{GDBN}, you are ready to
14615 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
14616 @code{vxgdb}, depending on your installation).
14618 @value{GDBN} comes up showing the prompt:
14625 * VxWorks Connection:: Connecting to VxWorks
14626 * VxWorks Download:: VxWorks download
14627 * VxWorks Attach:: Running tasks
14630 @node VxWorks Connection
14631 @subsubsection Connecting to VxWorks
14633 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
14634 network. To connect to a target whose host name is ``@code{tt}'', type:
14637 (vxgdb) target vxworks tt
14641 @value{GDBN} displays messages like these:
14644 Attaching remote machine across net...
14649 @value{GDBN} then attempts to read the symbol tables of any object modules
14650 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
14651 these files by searching the directories listed in the command search
14652 path (@pxref{Environment, ,Your Program's Environment}); if it fails
14653 to find an object file, it displays a message such as:
14656 prog.o: No such file or directory.
14659 When this happens, add the appropriate directory to the search path with
14660 the @value{GDBN} command @code{path}, and execute the @code{target}
14663 @node VxWorks Download
14664 @subsubsection VxWorks Download
14666 @cindex download to VxWorks
14667 If you have connected to the VxWorks target and you want to debug an
14668 object that has not yet been loaded, you can use the @value{GDBN}
14669 @code{load} command to download a file from Unix to VxWorks
14670 incrementally. The object file given as an argument to the @code{load}
14671 command is actually opened twice: first by the VxWorks target in order
14672 to download the code, then by @value{GDBN} in order to read the symbol
14673 table. This can lead to problems if the current working directories on
14674 the two systems differ. If both systems have NFS mounted the same
14675 filesystems, you can avoid these problems by using absolute paths.
14676 Otherwise, it is simplest to set the working directory on both systems
14677 to the directory in which the object file resides, and then to reference
14678 the file by its name, without any path. For instance, a program
14679 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
14680 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
14681 program, type this on VxWorks:
14684 -> cd "@var{vxpath}/vw/demo/rdb"
14688 Then, in @value{GDBN}, type:
14691 (vxgdb) cd @var{hostpath}/vw/demo/rdb
14692 (vxgdb) load prog.o
14695 @value{GDBN} displays a response similar to this:
14698 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
14701 You can also use the @code{load} command to reload an object module
14702 after editing and recompiling the corresponding source file. Note that
14703 this makes @value{GDBN} delete all currently-defined breakpoints,
14704 auto-displays, and convenience variables, and to clear the value
14705 history. (This is necessary in order to preserve the integrity of
14706 debugger's data structures that reference the target system's symbol
14709 @node VxWorks Attach
14710 @subsubsection Running Tasks
14712 @cindex running VxWorks tasks
14713 You can also attach to an existing task using the @code{attach} command as
14717 (vxgdb) attach @var{task}
14721 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
14722 or suspended when you attach to it. Running tasks are suspended at
14723 the time of attachment.
14725 @node Embedded Processors
14726 @section Embedded Processors
14728 This section goes into details specific to particular embedded
14731 @cindex send command to simulator
14732 Whenever a specific embedded processor has a simulator, @value{GDBN}
14733 allows to send an arbitrary command to the simulator.
14736 @item sim @var{command}
14737 @kindex sim@r{, a command}
14738 Send an arbitrary @var{command} string to the simulator. Consult the
14739 documentation for the specific simulator in use for information about
14740 acceptable commands.
14746 * M32R/D:: Renesas M32R/D
14747 * M68K:: Motorola M68K
14748 * MIPS Embedded:: MIPS Embedded
14749 * OpenRISC 1000:: OpenRisc 1000
14750 * PA:: HP PA Embedded
14751 * PowerPC Embedded:: PowerPC Embedded
14752 * Sparclet:: Tsqware Sparclet
14753 * Sparclite:: Fujitsu Sparclite
14754 * Z8000:: Zilog Z8000
14757 * Super-H:: Renesas Super-H
14766 @item target rdi @var{dev}
14767 ARM Angel monitor, via RDI library interface to ADP protocol. You may
14768 use this target to communicate with both boards running the Angel
14769 monitor, or with the EmbeddedICE JTAG debug device.
14772 @item target rdp @var{dev}
14777 @value{GDBN} provides the following ARM-specific commands:
14780 @item set arm disassembler
14782 This commands selects from a list of disassembly styles. The
14783 @code{"std"} style is the standard style.
14785 @item show arm disassembler
14787 Show the current disassembly style.
14789 @item set arm apcs32
14790 @cindex ARM 32-bit mode
14791 This command toggles ARM operation mode between 32-bit and 26-bit.
14793 @item show arm apcs32
14794 Display the current usage of the ARM 32-bit mode.
14796 @item set arm fpu @var{fputype}
14797 This command sets the ARM floating-point unit (FPU) type. The
14798 argument @var{fputype} can be one of these:
14802 Determine the FPU type by querying the OS ABI.
14804 Software FPU, with mixed-endian doubles on little-endian ARM
14807 GCC-compiled FPA co-processor.
14809 Software FPU with pure-endian doubles.
14815 Show the current type of the FPU.
14818 This command forces @value{GDBN} to use the specified ABI.
14821 Show the currently used ABI.
14823 @item set debug arm
14824 Toggle whether to display ARM-specific debugging messages from the ARM
14825 target support subsystem.
14827 @item show debug arm
14828 Show whether ARM-specific debugging messages are enabled.
14831 The following commands are available when an ARM target is debugged
14832 using the RDI interface:
14835 @item rdilogfile @r{[}@var{file}@r{]}
14837 @cindex ADP (Angel Debugger Protocol) logging
14838 Set the filename for the ADP (Angel Debugger Protocol) packet log.
14839 With an argument, sets the log file to the specified @var{file}. With
14840 no argument, show the current log file name. The default log file is
14843 @item rdilogenable @r{[}@var{arg}@r{]}
14844 @kindex rdilogenable
14845 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
14846 enables logging, with an argument 0 or @code{"no"} disables it. With
14847 no arguments displays the current setting. When logging is enabled,
14848 ADP packets exchanged between @value{GDBN} and the RDI target device
14849 are logged to a file.
14851 @item set rdiromatzero
14852 @kindex set rdiromatzero
14853 @cindex ROM at zero address, RDI
14854 Tell @value{GDBN} whether the target has ROM at address 0. If on,
14855 vector catching is disabled, so that zero address can be used. If off
14856 (the default), vector catching is enabled. For this command to take
14857 effect, it needs to be invoked prior to the @code{target rdi} command.
14859 @item show rdiromatzero
14860 @kindex show rdiromatzero
14861 Show the current setting of ROM at zero address.
14863 @item set rdiheartbeat
14864 @kindex set rdiheartbeat
14865 @cindex RDI heartbeat
14866 Enable or disable RDI heartbeat packets. It is not recommended to
14867 turn on this option, since it confuses ARM and EPI JTAG interface, as
14868 well as the Angel monitor.
14870 @item show rdiheartbeat
14871 @kindex show rdiheartbeat
14872 Show the setting of RDI heartbeat packets.
14877 @subsection Renesas M32R/D and M32R/SDI
14880 @kindex target m32r
14881 @item target m32r @var{dev}
14882 Renesas M32R/D ROM monitor.
14884 @kindex target m32rsdi
14885 @item target m32rsdi @var{dev}
14886 Renesas M32R SDI server, connected via parallel port to the board.
14889 The following @value{GDBN} commands are specific to the M32R monitor:
14892 @item set download-path @var{path}
14893 @kindex set download-path
14894 @cindex find downloadable @sc{srec} files (M32R)
14895 Set the default path for finding downloadable @sc{srec} files.
14897 @item show download-path
14898 @kindex show download-path
14899 Show the default path for downloadable @sc{srec} files.
14901 @item set board-address @var{addr}
14902 @kindex set board-address
14903 @cindex M32-EVA target board address
14904 Set the IP address for the M32R-EVA target board.
14906 @item show board-address
14907 @kindex show board-address
14908 Show the current IP address of the target board.
14910 @item set server-address @var{addr}
14911 @kindex set server-address
14912 @cindex download server address (M32R)
14913 Set the IP address for the download server, which is the @value{GDBN}'s
14916 @item show server-address
14917 @kindex show server-address
14918 Display the IP address of the download server.
14920 @item upload @r{[}@var{file}@r{]}
14921 @kindex upload@r{, M32R}
14922 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
14923 upload capability. If no @var{file} argument is given, the current
14924 executable file is uploaded.
14926 @item tload @r{[}@var{file}@r{]}
14927 @kindex tload@r{, M32R}
14928 Test the @code{upload} command.
14931 The following commands are available for M32R/SDI:
14936 @cindex reset SDI connection, M32R
14937 This command resets the SDI connection.
14941 This command shows the SDI connection status.
14944 @kindex debug_chaos
14945 @cindex M32R/Chaos debugging
14946 Instructs the remote that M32R/Chaos debugging is to be used.
14948 @item use_debug_dma
14949 @kindex use_debug_dma
14950 Instructs the remote to use the DEBUG_DMA method of accessing memory.
14953 @kindex use_mon_code
14954 Instructs the remote to use the MON_CODE method of accessing memory.
14957 @kindex use_ib_break
14958 Instructs the remote to set breakpoints by IB break.
14960 @item use_dbt_break
14961 @kindex use_dbt_break
14962 Instructs the remote to set breakpoints by DBT.
14968 The Motorola m68k configuration includes ColdFire support, and a
14969 target command for the following ROM monitor.
14973 @kindex target dbug
14974 @item target dbug @var{dev}
14975 dBUG ROM monitor for Motorola ColdFire.
14979 @node MIPS Embedded
14980 @subsection MIPS Embedded
14982 @cindex MIPS boards
14983 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
14984 MIPS board attached to a serial line. This is available when
14985 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
14988 Use these @value{GDBN} commands to specify the connection to your target board:
14991 @item target mips @var{port}
14992 @kindex target mips @var{port}
14993 To run a program on the board, start up @code{@value{GDBP}} with the
14994 name of your program as the argument. To connect to the board, use the
14995 command @samp{target mips @var{port}}, where @var{port} is the name of
14996 the serial port connected to the board. If the program has not already
14997 been downloaded to the board, you may use the @code{load} command to
14998 download it. You can then use all the usual @value{GDBN} commands.
15000 For example, this sequence connects to the target board through a serial
15001 port, and loads and runs a program called @var{prog} through the
15005 host$ @value{GDBP} @var{prog}
15006 @value{GDBN} is free software and @dots{}
15007 (@value{GDBP}) target mips /dev/ttyb
15008 (@value{GDBP}) load @var{prog}
15012 @item target mips @var{hostname}:@var{portnumber}
15013 On some @value{GDBN} host configurations, you can specify a TCP
15014 connection (for instance, to a serial line managed by a terminal
15015 concentrator) instead of a serial port, using the syntax
15016 @samp{@var{hostname}:@var{portnumber}}.
15018 @item target pmon @var{port}
15019 @kindex target pmon @var{port}
15022 @item target ddb @var{port}
15023 @kindex target ddb @var{port}
15024 NEC's DDB variant of PMON for Vr4300.
15026 @item target lsi @var{port}
15027 @kindex target lsi @var{port}
15028 LSI variant of PMON.
15030 @kindex target r3900
15031 @item target r3900 @var{dev}
15032 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
15034 @kindex target array
15035 @item target array @var{dev}
15036 Array Tech LSI33K RAID controller board.
15042 @value{GDBN} also supports these special commands for MIPS targets:
15045 @item set mipsfpu double
15046 @itemx set mipsfpu single
15047 @itemx set mipsfpu none
15048 @itemx set mipsfpu auto
15049 @itemx show mipsfpu
15050 @kindex set mipsfpu
15051 @kindex show mipsfpu
15052 @cindex MIPS remote floating point
15053 @cindex floating point, MIPS remote
15054 If your target board does not support the MIPS floating point
15055 coprocessor, you should use the command @samp{set mipsfpu none} (if you
15056 need this, you may wish to put the command in your @value{GDBN} init
15057 file). This tells @value{GDBN} how to find the return value of
15058 functions which return floating point values. It also allows
15059 @value{GDBN} to avoid saving the floating point registers when calling
15060 functions on the board. If you are using a floating point coprocessor
15061 with only single precision floating point support, as on the @sc{r4650}
15062 processor, use the command @samp{set mipsfpu single}. The default
15063 double precision floating point coprocessor may be selected using
15064 @samp{set mipsfpu double}.
15066 In previous versions the only choices were double precision or no
15067 floating point, so @samp{set mipsfpu on} will select double precision
15068 and @samp{set mipsfpu off} will select no floating point.
15070 As usual, you can inquire about the @code{mipsfpu} variable with
15071 @samp{show mipsfpu}.
15073 @item set timeout @var{seconds}
15074 @itemx set retransmit-timeout @var{seconds}
15075 @itemx show timeout
15076 @itemx show retransmit-timeout
15077 @cindex @code{timeout}, MIPS protocol
15078 @cindex @code{retransmit-timeout}, MIPS protocol
15079 @kindex set timeout
15080 @kindex show timeout
15081 @kindex set retransmit-timeout
15082 @kindex show retransmit-timeout
15083 You can control the timeout used while waiting for a packet, in the MIPS
15084 remote protocol, with the @code{set timeout @var{seconds}} command. The
15085 default is 5 seconds. Similarly, you can control the timeout used while
15086 waiting for an acknowledgement of a packet with the @code{set
15087 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
15088 You can inspect both values with @code{show timeout} and @code{show
15089 retransmit-timeout}. (These commands are @emph{only} available when
15090 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
15092 The timeout set by @code{set timeout} does not apply when @value{GDBN}
15093 is waiting for your program to stop. In that case, @value{GDBN} waits
15094 forever because it has no way of knowing how long the program is going
15095 to run before stopping.
15097 @item set syn-garbage-limit @var{num}
15098 @kindex set syn-garbage-limit@r{, MIPS remote}
15099 @cindex synchronize with remote MIPS target
15100 Limit the maximum number of characters @value{GDBN} should ignore when
15101 it tries to synchronize with the remote target. The default is 10
15102 characters. Setting the limit to -1 means there's no limit.
15104 @item show syn-garbage-limit
15105 @kindex show syn-garbage-limit@r{, MIPS remote}
15106 Show the current limit on the number of characters to ignore when
15107 trying to synchronize with the remote system.
15109 @item set monitor-prompt @var{prompt}
15110 @kindex set monitor-prompt@r{, MIPS remote}
15111 @cindex remote monitor prompt
15112 Tell @value{GDBN} to expect the specified @var{prompt} string from the
15113 remote monitor. The default depends on the target:
15123 @item show monitor-prompt
15124 @kindex show monitor-prompt@r{, MIPS remote}
15125 Show the current strings @value{GDBN} expects as the prompt from the
15128 @item set monitor-warnings
15129 @kindex set monitor-warnings@r{, MIPS remote}
15130 Enable or disable monitor warnings about hardware breakpoints. This
15131 has effect only for the @code{lsi} target. When on, @value{GDBN} will
15132 display warning messages whose codes are returned by the @code{lsi}
15133 PMON monitor for breakpoint commands.
15135 @item show monitor-warnings
15136 @kindex show monitor-warnings@r{, MIPS remote}
15137 Show the current setting of printing monitor warnings.
15139 @item pmon @var{command}
15140 @kindex pmon@r{, MIPS remote}
15141 @cindex send PMON command
15142 This command allows sending an arbitrary @var{command} string to the
15143 monitor. The monitor must be in debug mode for this to work.
15146 @node OpenRISC 1000
15147 @subsection OpenRISC 1000
15148 @cindex OpenRISC 1000
15150 @cindex or1k boards
15151 See OR1k Architecture document (@uref{www.opencores.org}) for more information
15152 about platform and commands.
15156 @kindex target jtag
15157 @item target jtag jtag://@var{host}:@var{port}
15159 Connects to remote JTAG server.
15160 JTAG remote server can be either an or1ksim or JTAG server,
15161 connected via parallel port to the board.
15163 Example: @code{target jtag jtag://localhost:9999}
15166 @item or1ksim @var{command}
15167 If connected to @code{or1ksim} OpenRISC 1000 Architectural
15168 Simulator, proprietary commands can be executed.
15170 @kindex info or1k spr
15171 @item info or1k spr
15172 Displays spr groups.
15174 @item info or1k spr @var{group}
15175 @itemx info or1k spr @var{groupno}
15176 Displays register names in selected group.
15178 @item info or1k spr @var{group} @var{register}
15179 @itemx info or1k spr @var{register}
15180 @itemx info or1k spr @var{groupno} @var{registerno}
15181 @itemx info or1k spr @var{registerno}
15182 Shows information about specified spr register.
15185 @item spr @var{group} @var{register} @var{value}
15186 @itemx spr @var{register @var{value}}
15187 @itemx spr @var{groupno} @var{registerno @var{value}}
15188 @itemx spr @var{registerno @var{value}}
15189 Writes @var{value} to specified spr register.
15192 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
15193 It is very similar to @value{GDBN} trace, except it does not interfere with normal
15194 program execution and is thus much faster. Hardware breakpoints/watchpoint
15195 triggers can be set using:
15198 Load effective address/data
15200 Store effective address/data
15202 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
15207 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
15208 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
15210 @code{htrace} commands:
15211 @cindex OpenRISC 1000 htrace
15214 @item hwatch @var{conditional}
15215 Set hardware watchpoint on combination of Load/Store Effective Address(es)
15216 or Data. For example:
15218 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
15220 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
15224 Display information about current HW trace configuration.
15226 @item htrace trigger @var{conditional}
15227 Set starting criteria for HW trace.
15229 @item htrace qualifier @var{conditional}
15230 Set acquisition qualifier for HW trace.
15232 @item htrace stop @var{conditional}
15233 Set HW trace stopping criteria.
15235 @item htrace record [@var{data}]*
15236 Selects the data to be recorded, when qualifier is met and HW trace was
15239 @item htrace enable
15240 @itemx htrace disable
15241 Enables/disables the HW trace.
15243 @item htrace rewind [@var{filename}]
15244 Clears currently recorded trace data.
15246 If filename is specified, new trace file is made and any newly collected data
15247 will be written there.
15249 @item htrace print [@var{start} [@var{len}]]
15250 Prints trace buffer, using current record configuration.
15252 @item htrace mode continuous
15253 Set continuous trace mode.
15255 @item htrace mode suspend
15256 Set suspend trace mode.
15260 @node PowerPC Embedded
15261 @subsection PowerPC Embedded
15263 @value{GDBN} provides the following PowerPC-specific commands:
15266 @kindex set powerpc
15267 @item set powerpc soft-float
15268 @itemx show powerpc soft-float
15269 Force @value{GDBN} to use (or not use) a software floating point calling
15270 convention. By default, @value{GDBN} selects the calling convention based
15271 on the selected architecture and the provided executable file.
15273 @item set powerpc vector-abi
15274 @itemx show powerpc vector-abi
15275 Force @value{GDBN} to use the specified calling convention for vector
15276 arguments and return values. The valid options are @samp{auto};
15277 @samp{generic}, to avoid vector registers even if they are present;
15278 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
15279 registers. By default, @value{GDBN} selects the calling convention
15280 based on the selected architecture and the provided executable file.
15282 @kindex target dink32
15283 @item target dink32 @var{dev}
15284 DINK32 ROM monitor.
15286 @kindex target ppcbug
15287 @item target ppcbug @var{dev}
15288 @kindex target ppcbug1
15289 @item target ppcbug1 @var{dev}
15290 PPCBUG ROM monitor for PowerPC.
15293 @item target sds @var{dev}
15294 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
15297 @cindex SDS protocol
15298 The following commands specific to the SDS protocol are supported
15302 @item set sdstimeout @var{nsec}
15303 @kindex set sdstimeout
15304 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
15305 default is 2 seconds.
15307 @item show sdstimeout
15308 @kindex show sdstimeout
15309 Show the current value of the SDS timeout.
15311 @item sds @var{command}
15312 @kindex sds@r{, a command}
15313 Send the specified @var{command} string to the SDS monitor.
15318 @subsection HP PA Embedded
15322 @kindex target op50n
15323 @item target op50n @var{dev}
15324 OP50N monitor, running on an OKI HPPA board.
15326 @kindex target w89k
15327 @item target w89k @var{dev}
15328 W89K monitor, running on a Winbond HPPA board.
15333 @subsection Tsqware Sparclet
15337 @value{GDBN} enables developers to debug tasks running on
15338 Sparclet targets from a Unix host.
15339 @value{GDBN} uses code that runs on
15340 both the Unix host and on the Sparclet target. The program
15341 @code{@value{GDBP}} is installed and executed on the Unix host.
15344 @item remotetimeout @var{args}
15345 @kindex remotetimeout
15346 @value{GDBN} supports the option @code{remotetimeout}.
15347 This option is set by the user, and @var{args} represents the number of
15348 seconds @value{GDBN} waits for responses.
15351 @cindex compiling, on Sparclet
15352 When compiling for debugging, include the options @samp{-g} to get debug
15353 information and @samp{-Ttext} to relocate the program to where you wish to
15354 load it on the target. You may also want to add the options @samp{-n} or
15355 @samp{-N} in order to reduce the size of the sections. Example:
15358 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
15361 You can use @code{objdump} to verify that the addresses are what you intended:
15364 sparclet-aout-objdump --headers --syms prog
15367 @cindex running, on Sparclet
15369 your Unix execution search path to find @value{GDBN}, you are ready to
15370 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
15371 (or @code{sparclet-aout-gdb}, depending on your installation).
15373 @value{GDBN} comes up showing the prompt:
15380 * Sparclet File:: Setting the file to debug
15381 * Sparclet Connection:: Connecting to Sparclet
15382 * Sparclet Download:: Sparclet download
15383 * Sparclet Execution:: Running and debugging
15386 @node Sparclet File
15387 @subsubsection Setting File to Debug
15389 The @value{GDBN} command @code{file} lets you choose with program to debug.
15392 (gdbslet) file prog
15396 @value{GDBN} then attempts to read the symbol table of @file{prog}.
15397 @value{GDBN} locates
15398 the file by searching the directories listed in the command search
15400 If the file was compiled with debug information (option @samp{-g}), source
15401 files will be searched as well.
15402 @value{GDBN} locates
15403 the source files by searching the directories listed in the directory search
15404 path (@pxref{Environment, ,Your Program's Environment}).
15406 to find a file, it displays a message such as:
15409 prog: No such file or directory.
15412 When this happens, add the appropriate directories to the search paths with
15413 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
15414 @code{target} command again.
15416 @node Sparclet Connection
15417 @subsubsection Connecting to Sparclet
15419 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
15420 To connect to a target on serial port ``@code{ttya}'', type:
15423 (gdbslet) target sparclet /dev/ttya
15424 Remote target sparclet connected to /dev/ttya
15425 main () at ../prog.c:3
15429 @value{GDBN} displays messages like these:
15435 @node Sparclet Download
15436 @subsubsection Sparclet Download
15438 @cindex download to Sparclet
15439 Once connected to the Sparclet target,
15440 you can use the @value{GDBN}
15441 @code{load} command to download the file from the host to the target.
15442 The file name and load offset should be given as arguments to the @code{load}
15444 Since the file format is aout, the program must be loaded to the starting
15445 address. You can use @code{objdump} to find out what this value is. The load
15446 offset is an offset which is added to the VMA (virtual memory address)
15447 of each of the file's sections.
15448 For instance, if the program
15449 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
15450 and bss at 0x12010170, in @value{GDBN}, type:
15453 (gdbslet) load prog 0x12010000
15454 Loading section .text, size 0xdb0 vma 0x12010000
15457 If the code is loaded at a different address then what the program was linked
15458 to, you may need to use the @code{section} and @code{add-symbol-file} commands
15459 to tell @value{GDBN} where to map the symbol table.
15461 @node Sparclet Execution
15462 @subsubsection Running and Debugging
15464 @cindex running and debugging Sparclet programs
15465 You can now begin debugging the task using @value{GDBN}'s execution control
15466 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
15467 manual for the list of commands.
15471 Breakpoint 1 at 0x12010000: file prog.c, line 3.
15473 Starting program: prog
15474 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
15475 3 char *symarg = 0;
15477 4 char *execarg = "hello!";
15482 @subsection Fujitsu Sparclite
15486 @kindex target sparclite
15487 @item target sparclite @var{dev}
15488 Fujitsu sparclite boards, used only for the purpose of loading.
15489 You must use an additional command to debug the program.
15490 For example: target remote @var{dev} using @value{GDBN} standard
15496 @subsection Zilog Z8000
15499 @cindex simulator, Z8000
15500 @cindex Zilog Z8000 simulator
15502 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
15505 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
15506 unsegmented variant of the Z8000 architecture) or the Z8001 (the
15507 segmented variant). The simulator recognizes which architecture is
15508 appropriate by inspecting the object code.
15511 @item target sim @var{args}
15513 @kindex target sim@r{, with Z8000}
15514 Debug programs on a simulated CPU. If the simulator supports setup
15515 options, specify them via @var{args}.
15519 After specifying this target, you can debug programs for the simulated
15520 CPU in the same style as programs for your host computer; use the
15521 @code{file} command to load a new program image, the @code{run} command
15522 to run your program, and so on.
15524 As well as making available all the usual machine registers
15525 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
15526 additional items of information as specially named registers:
15531 Counts clock-ticks in the simulator.
15534 Counts instructions run in the simulator.
15537 Execution time in 60ths of a second.
15541 You can refer to these values in @value{GDBN} expressions with the usual
15542 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
15543 conditional breakpoint that suspends only after at least 5000
15544 simulated clock ticks.
15547 @subsection Atmel AVR
15550 When configured for debugging the Atmel AVR, @value{GDBN} supports the
15551 following AVR-specific commands:
15554 @item info io_registers
15555 @kindex info io_registers@r{, AVR}
15556 @cindex I/O registers (Atmel AVR)
15557 This command displays information about the AVR I/O registers. For
15558 each register, @value{GDBN} prints its number and value.
15565 When configured for debugging CRIS, @value{GDBN} provides the
15566 following CRIS-specific commands:
15569 @item set cris-version @var{ver}
15570 @cindex CRIS version
15571 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
15572 The CRIS version affects register names and sizes. This command is useful in
15573 case autodetection of the CRIS version fails.
15575 @item show cris-version
15576 Show the current CRIS version.
15578 @item set cris-dwarf2-cfi
15579 @cindex DWARF-2 CFI and CRIS
15580 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
15581 Change to @samp{off} when using @code{gcc-cris} whose version is below
15584 @item show cris-dwarf2-cfi
15585 Show the current state of using DWARF-2 CFI.
15587 @item set cris-mode @var{mode}
15589 Set the current CRIS mode to @var{mode}. It should only be changed when
15590 debugging in guru mode, in which case it should be set to
15591 @samp{guru} (the default is @samp{normal}).
15593 @item show cris-mode
15594 Show the current CRIS mode.
15598 @subsection Renesas Super-H
15601 For the Renesas Super-H processor, @value{GDBN} provides these
15606 @kindex regs@r{, Super-H}
15607 Show the values of all Super-H registers.
15611 @node Architectures
15612 @section Architectures
15614 This section describes characteristics of architectures that affect
15615 all uses of @value{GDBN} with the architecture, both native and cross.
15622 * HPPA:: HP PA architecture
15623 * SPU:: Cell Broadband Engine SPU architecture
15628 @subsection x86 Architecture-specific Issues
15631 @item set struct-convention @var{mode}
15632 @kindex set struct-convention
15633 @cindex struct return convention
15634 @cindex struct/union returned in registers
15635 Set the convention used by the inferior to return @code{struct}s and
15636 @code{union}s from functions to @var{mode}. Possible values of
15637 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
15638 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
15639 are returned on the stack, while @code{"reg"} means that a
15640 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
15641 be returned in a register.
15643 @item show struct-convention
15644 @kindex show struct-convention
15645 Show the current setting of the convention to return @code{struct}s
15654 @kindex set rstack_high_address
15655 @cindex AMD 29K register stack
15656 @cindex register stack, AMD29K
15657 @item set rstack_high_address @var{address}
15658 On AMD 29000 family processors, registers are saved in a separate
15659 @dfn{register stack}. There is no way for @value{GDBN} to determine the
15660 extent of this stack. Normally, @value{GDBN} just assumes that the
15661 stack is ``large enough''. This may result in @value{GDBN} referencing
15662 memory locations that do not exist. If necessary, you can get around
15663 this problem by specifying the ending address of the register stack with
15664 the @code{set rstack_high_address} command. The argument should be an
15665 address, which you probably want to precede with @samp{0x} to specify in
15668 @kindex show rstack_high_address
15669 @item show rstack_high_address
15670 Display the current limit of the register stack, on AMD 29000 family
15678 See the following section.
15683 @cindex stack on Alpha
15684 @cindex stack on MIPS
15685 @cindex Alpha stack
15687 Alpha- and MIPS-based computers use an unusual stack frame, which
15688 sometimes requires @value{GDBN} to search backward in the object code to
15689 find the beginning of a function.
15691 @cindex response time, MIPS debugging
15692 To improve response time (especially for embedded applications, where
15693 @value{GDBN} may be restricted to a slow serial line for this search)
15694 you may want to limit the size of this search, using one of these
15698 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
15699 @item set heuristic-fence-post @var{limit}
15700 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
15701 search for the beginning of a function. A value of @var{0} (the
15702 default) means there is no limit. However, except for @var{0}, the
15703 larger the limit the more bytes @code{heuristic-fence-post} must search
15704 and therefore the longer it takes to run. You should only need to use
15705 this command when debugging a stripped executable.
15707 @item show heuristic-fence-post
15708 Display the current limit.
15712 These commands are available @emph{only} when @value{GDBN} is configured
15713 for debugging programs on Alpha or MIPS processors.
15715 Several MIPS-specific commands are available when debugging MIPS
15719 @item set mips abi @var{arg}
15720 @kindex set mips abi
15721 @cindex set ABI for MIPS
15722 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
15723 values of @var{arg} are:
15727 The default ABI associated with the current binary (this is the
15738 @item show mips abi
15739 @kindex show mips abi
15740 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
15743 @itemx show mipsfpu
15744 @xref{MIPS Embedded, set mipsfpu}.
15746 @item set mips mask-address @var{arg}
15747 @kindex set mips mask-address
15748 @cindex MIPS addresses, masking
15749 This command determines whether the most-significant 32 bits of 64-bit
15750 MIPS addresses are masked off. The argument @var{arg} can be
15751 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
15752 setting, which lets @value{GDBN} determine the correct value.
15754 @item show mips mask-address
15755 @kindex show mips mask-address
15756 Show whether the upper 32 bits of MIPS addresses are masked off or
15759 @item set remote-mips64-transfers-32bit-regs
15760 @kindex set remote-mips64-transfers-32bit-regs
15761 This command controls compatibility with 64-bit MIPS targets that
15762 transfer data in 32-bit quantities. If you have an old MIPS 64 target
15763 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
15764 and 64 bits for other registers, set this option to @samp{on}.
15766 @item show remote-mips64-transfers-32bit-regs
15767 @kindex show remote-mips64-transfers-32bit-regs
15768 Show the current setting of compatibility with older MIPS 64 targets.
15770 @item set debug mips
15771 @kindex set debug mips
15772 This command turns on and off debugging messages for the MIPS-specific
15773 target code in @value{GDBN}.
15775 @item show debug mips
15776 @kindex show debug mips
15777 Show the current setting of MIPS debugging messages.
15783 @cindex HPPA support
15785 When @value{GDBN} is debugging the HP PA architecture, it provides the
15786 following special commands:
15789 @item set debug hppa
15790 @kindex set debug hppa
15791 This command determines whether HPPA architecture-specific debugging
15792 messages are to be displayed.
15794 @item show debug hppa
15795 Show whether HPPA debugging messages are displayed.
15797 @item maint print unwind @var{address}
15798 @kindex maint print unwind@r{, HPPA}
15799 This command displays the contents of the unwind table entry at the
15800 given @var{address}.
15806 @subsection Cell Broadband Engine SPU architecture
15807 @cindex Cell Broadband Engine
15810 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
15811 it provides the following special commands:
15814 @item info spu event
15816 Display SPU event facility status. Shows current event mask
15817 and pending event status.
15819 @item info spu signal
15820 Display SPU signal notification facility status. Shows pending
15821 signal-control word and signal notification mode of both signal
15822 notification channels.
15824 @item info spu mailbox
15825 Display SPU mailbox facility status. Shows all pending entries,
15826 in order of processing, in each of the SPU Write Outbound,
15827 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
15830 Display MFC DMA status. Shows all pending commands in the MFC
15831 DMA queue. For each entry, opcode, tag, class IDs, effective
15832 and local store addresses and transfer size are shown.
15834 @item info spu proxydma
15835 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
15836 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
15837 and local store addresses and transfer size are shown.
15842 @subsection PowerPC
15843 @cindex PowerPC architecture
15845 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
15846 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
15847 numbers stored in the floating point registers. These values must be stored
15848 in two consecutive registers, always starting at an even register like
15849 @code{f0} or @code{f2}.
15851 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
15852 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
15853 @code{f2} and @code{f3} for @code{$dl1} and so on.
15856 @node Controlling GDB
15857 @chapter Controlling @value{GDBN}
15859 You can alter the way @value{GDBN} interacts with you by using the
15860 @code{set} command. For commands controlling how @value{GDBN} displays
15861 data, see @ref{Print Settings, ,Print Settings}. Other settings are
15866 * Editing:: Command editing
15867 * Command History:: Command history
15868 * Screen Size:: Screen size
15869 * Numbers:: Numbers
15870 * ABI:: Configuring the current ABI
15871 * Messages/Warnings:: Optional warnings and messages
15872 * Debugging Output:: Optional messages about internal happenings
15880 @value{GDBN} indicates its readiness to read a command by printing a string
15881 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
15882 can change the prompt string with the @code{set prompt} command. For
15883 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
15884 the prompt in one of the @value{GDBN} sessions so that you can always tell
15885 which one you are talking to.
15887 @emph{Note:} @code{set prompt} does not add a space for you after the
15888 prompt you set. This allows you to set a prompt which ends in a space
15889 or a prompt that does not.
15893 @item set prompt @var{newprompt}
15894 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
15896 @kindex show prompt
15898 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
15902 @section Command Editing
15904 @cindex command line editing
15906 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
15907 @sc{gnu} library provides consistent behavior for programs which provide a
15908 command line interface to the user. Advantages are @sc{gnu} Emacs-style
15909 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
15910 substitution, and a storage and recall of command history across
15911 debugging sessions.
15913 You may control the behavior of command line editing in @value{GDBN} with the
15914 command @code{set}.
15917 @kindex set editing
15920 @itemx set editing on
15921 Enable command line editing (enabled by default).
15923 @item set editing off
15924 Disable command line editing.
15926 @kindex show editing
15928 Show whether command line editing is enabled.
15931 @xref{Command Line Editing}, for more details about the Readline
15932 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
15933 encouraged to read that chapter.
15935 @node Command History
15936 @section Command History
15937 @cindex command history
15939 @value{GDBN} can keep track of the commands you type during your
15940 debugging sessions, so that you can be certain of precisely what
15941 happened. Use these commands to manage the @value{GDBN} command
15944 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
15945 package, to provide the history facility. @xref{Using History
15946 Interactively}, for the detailed description of the History library.
15948 To issue a command to @value{GDBN} without affecting certain aspects of
15949 the state which is seen by users, prefix it with @samp{server }
15950 (@pxref{Server Prefix}). This
15951 means that this command will not affect the command history, nor will it
15952 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
15953 pressed on a line by itself.
15955 @cindex @code{server}, command prefix
15956 The server prefix does not affect the recording of values into the value
15957 history; to print a value without recording it into the value history,
15958 use the @code{output} command instead of the @code{print} command.
15960 Here is the description of @value{GDBN} commands related to command
15964 @cindex history substitution
15965 @cindex history file
15966 @kindex set history filename
15967 @cindex @env{GDBHISTFILE}, environment variable
15968 @item set history filename @var{fname}
15969 Set the name of the @value{GDBN} command history file to @var{fname}.
15970 This is the file where @value{GDBN} reads an initial command history
15971 list, and where it writes the command history from this session when it
15972 exits. You can access this list through history expansion or through
15973 the history command editing characters listed below. This file defaults
15974 to the value of the environment variable @code{GDBHISTFILE}, or to
15975 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
15978 @cindex save command history
15979 @kindex set history save
15980 @item set history save
15981 @itemx set history save on
15982 Record command history in a file, whose name may be specified with the
15983 @code{set history filename} command. By default, this option is disabled.
15985 @item set history save off
15986 Stop recording command history in a file.
15988 @cindex history size
15989 @kindex set history size
15990 @cindex @env{HISTSIZE}, environment variable
15991 @item set history size @var{size}
15992 Set the number of commands which @value{GDBN} keeps in its history list.
15993 This defaults to the value of the environment variable
15994 @code{HISTSIZE}, or to 256 if this variable is not set.
15997 History expansion assigns special meaning to the character @kbd{!}.
15998 @xref{Event Designators}, for more details.
16000 @cindex history expansion, turn on/off
16001 Since @kbd{!} is also the logical not operator in C, history expansion
16002 is off by default. If you decide to enable history expansion with the
16003 @code{set history expansion on} command, you may sometimes need to
16004 follow @kbd{!} (when it is used as logical not, in an expression) with
16005 a space or a tab to prevent it from being expanded. The readline
16006 history facilities do not attempt substitution on the strings
16007 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
16009 The commands to control history expansion are:
16012 @item set history expansion on
16013 @itemx set history expansion
16014 @kindex set history expansion
16015 Enable history expansion. History expansion is off by default.
16017 @item set history expansion off
16018 Disable history expansion.
16021 @kindex show history
16023 @itemx show history filename
16024 @itemx show history save
16025 @itemx show history size
16026 @itemx show history expansion
16027 These commands display the state of the @value{GDBN} history parameters.
16028 @code{show history} by itself displays all four states.
16033 @kindex show commands
16034 @cindex show last commands
16035 @cindex display command history
16036 @item show commands
16037 Display the last ten commands in the command history.
16039 @item show commands @var{n}
16040 Print ten commands centered on command number @var{n}.
16042 @item show commands +
16043 Print ten commands just after the commands last printed.
16047 @section Screen Size
16048 @cindex size of screen
16049 @cindex pauses in output
16051 Certain commands to @value{GDBN} may produce large amounts of
16052 information output to the screen. To help you read all of it,
16053 @value{GDBN} pauses and asks you for input at the end of each page of
16054 output. Type @key{RET} when you want to continue the output, or @kbd{q}
16055 to discard the remaining output. Also, the screen width setting
16056 determines when to wrap lines of output. Depending on what is being
16057 printed, @value{GDBN} tries to break the line at a readable place,
16058 rather than simply letting it overflow onto the following line.
16060 Normally @value{GDBN} knows the size of the screen from the terminal
16061 driver software. For example, on Unix @value{GDBN} uses the termcap data base
16062 together with the value of the @code{TERM} environment variable and the
16063 @code{stty rows} and @code{stty cols} settings. If this is not correct,
16064 you can override it with the @code{set height} and @code{set
16071 @kindex show height
16072 @item set height @var{lpp}
16074 @itemx set width @var{cpl}
16076 These @code{set} commands specify a screen height of @var{lpp} lines and
16077 a screen width of @var{cpl} characters. The associated @code{show}
16078 commands display the current settings.
16080 If you specify a height of zero lines, @value{GDBN} does not pause during
16081 output no matter how long the output is. This is useful if output is to a
16082 file or to an editor buffer.
16084 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
16085 from wrapping its output.
16087 @item set pagination on
16088 @itemx set pagination off
16089 @kindex set pagination
16090 Turn the output pagination on or off; the default is on. Turning
16091 pagination off is the alternative to @code{set height 0}.
16093 @item show pagination
16094 @kindex show pagination
16095 Show the current pagination mode.
16100 @cindex number representation
16101 @cindex entering numbers
16103 You can always enter numbers in octal, decimal, or hexadecimal in
16104 @value{GDBN} by the usual conventions: octal numbers begin with
16105 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
16106 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
16107 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
16108 10; likewise, the default display for numbers---when no particular
16109 format is specified---is base 10. You can change the default base for
16110 both input and output with the commands described below.
16113 @kindex set input-radix
16114 @item set input-radix @var{base}
16115 Set the default base for numeric input. Supported choices
16116 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
16117 specified either unambiguously or using the current input radix; for
16121 set input-radix 012
16122 set input-radix 10.
16123 set input-radix 0xa
16127 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
16128 leaves the input radix unchanged, no matter what it was, since
16129 @samp{10}, being without any leading or trailing signs of its base, is
16130 interpreted in the current radix. Thus, if the current radix is 16,
16131 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
16134 @kindex set output-radix
16135 @item set output-radix @var{base}
16136 Set the default base for numeric display. Supported choices
16137 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
16138 specified either unambiguously or using the current input radix.
16140 @kindex show input-radix
16141 @item show input-radix
16142 Display the current default base for numeric input.
16144 @kindex show output-radix
16145 @item show output-radix
16146 Display the current default base for numeric display.
16148 @item set radix @r{[}@var{base}@r{]}
16152 These commands set and show the default base for both input and output
16153 of numbers. @code{set radix} sets the radix of input and output to
16154 the same base; without an argument, it resets the radix back to its
16155 default value of 10.
16160 @section Configuring the Current ABI
16162 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
16163 application automatically. However, sometimes you need to override its
16164 conclusions. Use these commands to manage @value{GDBN}'s view of the
16171 One @value{GDBN} configuration can debug binaries for multiple operating
16172 system targets, either via remote debugging or native emulation.
16173 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
16174 but you can override its conclusion using the @code{set osabi} command.
16175 One example where this is useful is in debugging of binaries which use
16176 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
16177 not have the same identifying marks that the standard C library for your
16182 Show the OS ABI currently in use.
16185 With no argument, show the list of registered available OS ABI's.
16187 @item set osabi @var{abi}
16188 Set the current OS ABI to @var{abi}.
16191 @cindex float promotion
16193 Generally, the way that an argument of type @code{float} is passed to a
16194 function depends on whether the function is prototyped. For a prototyped
16195 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
16196 according to the architecture's convention for @code{float}. For unprototyped
16197 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
16198 @code{double} and then passed.
16200 Unfortunately, some forms of debug information do not reliably indicate whether
16201 a function is prototyped. If @value{GDBN} calls a function that is not marked
16202 as prototyped, it consults @kbd{set coerce-float-to-double}.
16205 @kindex set coerce-float-to-double
16206 @item set coerce-float-to-double
16207 @itemx set coerce-float-to-double on
16208 Arguments of type @code{float} will be promoted to @code{double} when passed
16209 to an unprototyped function. This is the default setting.
16211 @item set coerce-float-to-double off
16212 Arguments of type @code{float} will be passed directly to unprototyped
16215 @kindex show coerce-float-to-double
16216 @item show coerce-float-to-double
16217 Show the current setting of promoting @code{float} to @code{double}.
16221 @kindex show cp-abi
16222 @value{GDBN} needs to know the ABI used for your program's C@t{++}
16223 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
16224 used to build your application. @value{GDBN} only fully supports
16225 programs with a single C@t{++} ABI; if your program contains code using
16226 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
16227 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
16228 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
16229 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
16230 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
16231 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
16236 Show the C@t{++} ABI currently in use.
16239 With no argument, show the list of supported C@t{++} ABI's.
16241 @item set cp-abi @var{abi}
16242 @itemx set cp-abi auto
16243 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
16246 @node Messages/Warnings
16247 @section Optional Warnings and Messages
16249 @cindex verbose operation
16250 @cindex optional warnings
16251 By default, @value{GDBN} is silent about its inner workings. If you are
16252 running on a slow machine, you may want to use the @code{set verbose}
16253 command. This makes @value{GDBN} tell you when it does a lengthy
16254 internal operation, so you will not think it has crashed.
16256 Currently, the messages controlled by @code{set verbose} are those
16257 which announce that the symbol table for a source file is being read;
16258 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
16261 @kindex set verbose
16262 @item set verbose on
16263 Enables @value{GDBN} output of certain informational messages.
16265 @item set verbose off
16266 Disables @value{GDBN} output of certain informational messages.
16268 @kindex show verbose
16270 Displays whether @code{set verbose} is on or off.
16273 By default, if @value{GDBN} encounters bugs in the symbol table of an
16274 object file, it is silent; but if you are debugging a compiler, you may
16275 find this information useful (@pxref{Symbol Errors, ,Errors Reading
16280 @kindex set complaints
16281 @item set complaints @var{limit}
16282 Permits @value{GDBN} to output @var{limit} complaints about each type of
16283 unusual symbols before becoming silent about the problem. Set
16284 @var{limit} to zero to suppress all complaints; set it to a large number
16285 to prevent complaints from being suppressed.
16287 @kindex show complaints
16288 @item show complaints
16289 Displays how many symbol complaints @value{GDBN} is permitted to produce.
16293 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
16294 lot of stupid questions to confirm certain commands. For example, if
16295 you try to run a program which is already running:
16299 The program being debugged has been started already.
16300 Start it from the beginning? (y or n)
16303 If you are willing to unflinchingly face the consequences of your own
16304 commands, you can disable this ``feature'':
16308 @kindex set confirm
16310 @cindex confirmation
16311 @cindex stupid questions
16312 @item set confirm off
16313 Disables confirmation requests.
16315 @item set confirm on
16316 Enables confirmation requests (the default).
16318 @kindex show confirm
16320 Displays state of confirmation requests.
16324 @cindex command tracing
16325 If you need to debug user-defined commands or sourced files you may find it
16326 useful to enable @dfn{command tracing}. In this mode each command will be
16327 printed as it is executed, prefixed with one or more @samp{+} symbols, the
16328 quantity denoting the call depth of each command.
16331 @kindex set trace-commands
16332 @cindex command scripts, debugging
16333 @item set trace-commands on
16334 Enable command tracing.
16335 @item set trace-commands off
16336 Disable command tracing.
16337 @item show trace-commands
16338 Display the current state of command tracing.
16341 @node Debugging Output
16342 @section Optional Messages about Internal Happenings
16343 @cindex optional debugging messages
16345 @value{GDBN} has commands that enable optional debugging messages from
16346 various @value{GDBN} subsystems; normally these commands are of
16347 interest to @value{GDBN} maintainers, or when reporting a bug. This
16348 section documents those commands.
16351 @kindex set exec-done-display
16352 @item set exec-done-display
16353 Turns on or off the notification of asynchronous commands'
16354 completion. When on, @value{GDBN} will print a message when an
16355 asynchronous command finishes its execution. The default is off.
16356 @kindex show exec-done-display
16357 @item show exec-done-display
16358 Displays the current setting of asynchronous command completion
16361 @cindex gdbarch debugging info
16362 @cindex architecture debugging info
16363 @item set debug arch
16364 Turns on or off display of gdbarch debugging info. The default is off
16366 @item show debug arch
16367 Displays the current state of displaying gdbarch debugging info.
16368 @item set debug aix-thread
16369 @cindex AIX threads
16370 Display debugging messages about inner workings of the AIX thread
16372 @item show debug aix-thread
16373 Show the current state of AIX thread debugging info display.
16374 @item set debug event
16375 @cindex event debugging info
16376 Turns on or off display of @value{GDBN} event debugging info. The
16378 @item show debug event
16379 Displays the current state of displaying @value{GDBN} event debugging
16381 @item set debug expression
16382 @cindex expression debugging info
16383 Turns on or off display of debugging info about @value{GDBN}
16384 expression parsing. The default is off.
16385 @item show debug expression
16386 Displays the current state of displaying debugging info about
16387 @value{GDBN} expression parsing.
16388 @item set debug frame
16389 @cindex frame debugging info
16390 Turns on or off display of @value{GDBN} frame debugging info. The
16392 @item show debug frame
16393 Displays the current state of displaying @value{GDBN} frame debugging
16395 @item set debug infrun
16396 @cindex inferior debugging info
16397 Turns on or off display of @value{GDBN} debugging info for running the inferior.
16398 The default is off. @file{infrun.c} contains GDB's runtime state machine used
16399 for implementing operations such as single-stepping the inferior.
16400 @item show debug infrun
16401 Displays the current state of @value{GDBN} inferior debugging.
16402 @item set debug lin-lwp
16403 @cindex @sc{gnu}/Linux LWP debug messages
16404 @cindex Linux lightweight processes
16405 Turns on or off debugging messages from the Linux LWP debug support.
16406 @item show debug lin-lwp
16407 Show the current state of Linux LWP debugging messages.
16408 @item set debug observer
16409 @cindex observer debugging info
16410 Turns on or off display of @value{GDBN} observer debugging. This
16411 includes info such as the notification of observable events.
16412 @item show debug observer
16413 Displays the current state of observer debugging.
16414 @item set debug overload
16415 @cindex C@t{++} overload debugging info
16416 Turns on or off display of @value{GDBN} C@t{++} overload debugging
16417 info. This includes info such as ranking of functions, etc. The default
16419 @item show debug overload
16420 Displays the current state of displaying @value{GDBN} C@t{++} overload
16422 @cindex packets, reporting on stdout
16423 @cindex serial connections, debugging
16424 @cindex debug remote protocol
16425 @cindex remote protocol debugging
16426 @cindex display remote packets
16427 @item set debug remote
16428 Turns on or off display of reports on all packets sent back and forth across
16429 the serial line to the remote machine. The info is printed on the
16430 @value{GDBN} standard output stream. The default is off.
16431 @item show debug remote
16432 Displays the state of display of remote packets.
16433 @item set debug serial
16434 Turns on or off display of @value{GDBN} serial debugging info. The
16436 @item show debug serial
16437 Displays the current state of displaying @value{GDBN} serial debugging
16439 @item set debug solib-frv
16440 @cindex FR-V shared-library debugging
16441 Turns on or off debugging messages for FR-V shared-library code.
16442 @item show debug solib-frv
16443 Display the current state of FR-V shared-library code debugging
16445 @item set debug target
16446 @cindex target debugging info
16447 Turns on or off display of @value{GDBN} target debugging info. This info
16448 includes what is going on at the target level of GDB, as it happens. The
16449 default is 0. Set it to 1 to track events, and to 2 to also track the
16450 value of large memory transfers. Changes to this flag do not take effect
16451 until the next time you connect to a target or use the @code{run} command.
16452 @item show debug target
16453 Displays the current state of displaying @value{GDBN} target debugging
16455 @item set debug timestamp
16456 @cindex timestampping debugging info
16457 Turns on or off display of timestamps with @value{GDBN} debugging info.
16458 When enabled, seconds and microseconds are displayed before each debugging
16460 @item show debug timestamp
16461 Displays the current state of displaying timestamps with @value{GDBN}
16463 @item set debugvarobj
16464 @cindex variable object debugging info
16465 Turns on or off display of @value{GDBN} variable object debugging
16466 info. The default is off.
16467 @item show debugvarobj
16468 Displays the current state of displaying @value{GDBN} variable object
16470 @item set debug xml
16471 @cindex XML parser debugging
16472 Turns on or off debugging messages for built-in XML parsers.
16473 @item show debug xml
16474 Displays the current state of XML debugging messages.
16478 @chapter Canned Sequences of Commands
16480 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
16481 Command Lists}), @value{GDBN} provides two ways to store sequences of
16482 commands for execution as a unit: user-defined commands and command
16486 * Define:: How to define your own commands
16487 * Hooks:: Hooks for user-defined commands
16488 * Command Files:: How to write scripts of commands to be stored in a file
16489 * Output:: Commands for controlled output
16493 @section User-defined Commands
16495 @cindex user-defined command
16496 @cindex arguments, to user-defined commands
16497 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
16498 which you assign a new name as a command. This is done with the
16499 @code{define} command. User commands may accept up to 10 arguments
16500 separated by whitespace. Arguments are accessed within the user command
16501 via @code{$arg0@dots{}$arg9}. A trivial example:
16505 print $arg0 + $arg1 + $arg2
16510 To execute the command use:
16517 This defines the command @code{adder}, which prints the sum of
16518 its three arguments. Note the arguments are text substitutions, so they may
16519 reference variables, use complex expressions, or even perform inferior
16522 @cindex argument count in user-defined commands
16523 @cindex how many arguments (user-defined commands)
16524 In addition, @code{$argc} may be used to find out how many arguments have
16525 been passed. This expands to a number in the range 0@dots{}10.
16530 print $arg0 + $arg1
16533 print $arg0 + $arg1 + $arg2
16541 @item define @var{commandname}
16542 Define a command named @var{commandname}. If there is already a command
16543 by that name, you are asked to confirm that you want to redefine it.
16545 The definition of the command is made up of other @value{GDBN} command lines,
16546 which are given following the @code{define} command. The end of these
16547 commands is marked by a line containing @code{end}.
16550 @kindex end@r{ (user-defined commands)}
16551 @item document @var{commandname}
16552 Document the user-defined command @var{commandname}, so that it can be
16553 accessed by @code{help}. The command @var{commandname} must already be
16554 defined. This command reads lines of documentation just as @code{define}
16555 reads the lines of the command definition, ending with @code{end}.
16556 After the @code{document} command is finished, @code{help} on command
16557 @var{commandname} displays the documentation you have written.
16559 You may use the @code{document} command again to change the
16560 documentation of a command. Redefining the command with @code{define}
16561 does not change the documentation.
16563 @kindex dont-repeat
16564 @cindex don't repeat command
16566 Used inside a user-defined command, this tells @value{GDBN} that this
16567 command should not be repeated when the user hits @key{RET}
16568 (@pxref{Command Syntax, repeat last command}).
16570 @kindex help user-defined
16571 @item help user-defined
16572 List all user-defined commands, with the first line of the documentation
16577 @itemx show user @var{commandname}
16578 Display the @value{GDBN} commands used to define @var{commandname} (but
16579 not its documentation). If no @var{commandname} is given, display the
16580 definitions for all user-defined commands.
16582 @cindex infinite recursion in user-defined commands
16583 @kindex show max-user-call-depth
16584 @kindex set max-user-call-depth
16585 @item show max-user-call-depth
16586 @itemx set max-user-call-depth
16587 The value of @code{max-user-call-depth} controls how many recursion
16588 levels are allowed in user-defined commands before @value{GDBN} suspects an
16589 infinite recursion and aborts the command.
16592 In addition to the above commands, user-defined commands frequently
16593 use control flow commands, described in @ref{Command Files}.
16595 When user-defined commands are executed, the
16596 commands of the definition are not printed. An error in any command
16597 stops execution of the user-defined command.
16599 If used interactively, commands that would ask for confirmation proceed
16600 without asking when used inside a user-defined command. Many @value{GDBN}
16601 commands that normally print messages to say what they are doing omit the
16602 messages when used in a user-defined command.
16605 @section User-defined Command Hooks
16606 @cindex command hooks
16607 @cindex hooks, for commands
16608 @cindex hooks, pre-command
16611 You may define @dfn{hooks}, which are a special kind of user-defined
16612 command. Whenever you run the command @samp{foo}, if the user-defined
16613 command @samp{hook-foo} exists, it is executed (with no arguments)
16614 before that command.
16616 @cindex hooks, post-command
16618 A hook may also be defined which is run after the command you executed.
16619 Whenever you run the command @samp{foo}, if the user-defined command
16620 @samp{hookpost-foo} exists, it is executed (with no arguments) after
16621 that command. Post-execution hooks may exist simultaneously with
16622 pre-execution hooks, for the same command.
16624 It is valid for a hook to call the command which it hooks. If this
16625 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
16627 @c It would be nice if hookpost could be passed a parameter indicating
16628 @c if the command it hooks executed properly or not. FIXME!
16630 @kindex stop@r{, a pseudo-command}
16631 In addition, a pseudo-command, @samp{stop} exists. Defining
16632 (@samp{hook-stop}) makes the associated commands execute every time
16633 execution stops in your program: before breakpoint commands are run,
16634 displays are printed, or the stack frame is printed.
16636 For example, to ignore @code{SIGALRM} signals while
16637 single-stepping, but treat them normally during normal execution,
16642 handle SIGALRM nopass
16646 handle SIGALRM pass
16649 define hook-continue
16650 handle SIGALRM pass
16654 As a further example, to hook at the beginning and end of the @code{echo}
16655 command, and to add extra text to the beginning and end of the message,
16663 define hookpost-echo
16667 (@value{GDBP}) echo Hello World
16668 <<<---Hello World--->>>
16673 You can define a hook for any single-word command in @value{GDBN}, but
16674 not for command aliases; you should define a hook for the basic command
16675 name, e.g.@: @code{backtrace} rather than @code{bt}.
16676 @c FIXME! So how does Joe User discover whether a command is an alias
16678 If an error occurs during the execution of your hook, execution of
16679 @value{GDBN} commands stops and @value{GDBN} issues a prompt
16680 (before the command that you actually typed had a chance to run).
16682 If you try to define a hook which does not match any known command, you
16683 get a warning from the @code{define} command.
16685 @node Command Files
16686 @section Command Files
16688 @cindex command files
16689 @cindex scripting commands
16690 A command file for @value{GDBN} is a text file made of lines that are
16691 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
16692 also be included. An empty line in a command file does nothing; it
16693 does not mean to repeat the last command, as it would from the
16696 You can request the execution of a command file with the @code{source}
16701 @cindex execute commands from a file
16702 @item source [@code{-v}] @var{filename}
16703 Execute the command file @var{filename}.
16706 The lines in a command file are generally executed sequentially,
16707 unless the order of execution is changed by one of the
16708 @emph{flow-control commands} described below. The commands are not
16709 printed as they are executed. An error in any command terminates
16710 execution of the command file and control is returned to the console.
16712 @value{GDBN} searches for @var{filename} in the current directory and then
16713 on the search path (specified with the @samp{directory} command).
16715 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
16716 each command as it is executed. The option must be given before
16717 @var{filename}, and is interpreted as part of the filename anywhere else.
16719 Commands that would ask for confirmation if used interactively proceed
16720 without asking when used in a command file. Many @value{GDBN} commands that
16721 normally print messages to say what they are doing omit the messages
16722 when called from command files.
16724 @value{GDBN} also accepts command input from standard input. In this
16725 mode, normal output goes to standard output and error output goes to
16726 standard error. Errors in a command file supplied on standard input do
16727 not terminate execution of the command file---execution continues with
16731 gdb < cmds > log 2>&1
16734 (The syntax above will vary depending on the shell used.) This example
16735 will execute commands from the file @file{cmds}. All output and errors
16736 would be directed to @file{log}.
16738 Since commands stored on command files tend to be more general than
16739 commands typed interactively, they frequently need to deal with
16740 complicated situations, such as different or unexpected values of
16741 variables and symbols, changes in how the program being debugged is
16742 built, etc. @value{GDBN} provides a set of flow-control commands to
16743 deal with these complexities. Using these commands, you can write
16744 complex scripts that loop over data structures, execute commands
16745 conditionally, etc.
16752 This command allows to include in your script conditionally executed
16753 commands. The @code{if} command takes a single argument, which is an
16754 expression to evaluate. It is followed by a series of commands that
16755 are executed only if the expression is true (its value is nonzero).
16756 There can then optionally be an @code{else} line, followed by a series
16757 of commands that are only executed if the expression was false. The
16758 end of the list is marked by a line containing @code{end}.
16762 This command allows to write loops. Its syntax is similar to
16763 @code{if}: the command takes a single argument, which is an expression
16764 to evaluate, and must be followed by the commands to execute, one per
16765 line, terminated by an @code{end}. These commands are called the
16766 @dfn{body} of the loop. The commands in the body of @code{while} are
16767 executed repeatedly as long as the expression evaluates to true.
16771 This command exits the @code{while} loop in whose body it is included.
16772 Execution of the script continues after that @code{while}s @code{end}
16775 @kindex loop_continue
16776 @item loop_continue
16777 This command skips the execution of the rest of the body of commands
16778 in the @code{while} loop in whose body it is included. Execution
16779 branches to the beginning of the @code{while} loop, where it evaluates
16780 the controlling expression.
16782 @kindex end@r{ (if/else/while commands)}
16784 Terminate the block of commands that are the body of @code{if},
16785 @code{else}, or @code{while} flow-control commands.
16790 @section Commands for Controlled Output
16792 During the execution of a command file or a user-defined command, normal
16793 @value{GDBN} output is suppressed; the only output that appears is what is
16794 explicitly printed by the commands in the definition. This section
16795 describes three commands useful for generating exactly the output you
16800 @item echo @var{text}
16801 @c I do not consider backslash-space a standard C escape sequence
16802 @c because it is not in ANSI.
16803 Print @var{text}. Nonprinting characters can be included in
16804 @var{text} using C escape sequences, such as @samp{\n} to print a
16805 newline. @strong{No newline is printed unless you specify one.}
16806 In addition to the standard C escape sequences, a backslash followed
16807 by a space stands for a space. This is useful for displaying a
16808 string with spaces at the beginning or the end, since leading and
16809 trailing spaces are otherwise trimmed from all arguments.
16810 To print @samp{@w{ }and foo =@w{ }}, use the command
16811 @samp{echo \@w{ }and foo = \@w{ }}.
16813 A backslash at the end of @var{text} can be used, as in C, to continue
16814 the command onto subsequent lines. For example,
16817 echo This is some text\n\
16818 which is continued\n\
16819 onto several lines.\n
16822 produces the same output as
16825 echo This is some text\n
16826 echo which is continued\n
16827 echo onto several lines.\n
16831 @item output @var{expression}
16832 Print the value of @var{expression} and nothing but that value: no
16833 newlines, no @samp{$@var{nn} = }. The value is not entered in the
16834 value history either. @xref{Expressions, ,Expressions}, for more information
16837 @item output/@var{fmt} @var{expression}
16838 Print the value of @var{expression} in format @var{fmt}. You can use
16839 the same formats as for @code{print}. @xref{Output Formats,,Output
16840 Formats}, for more information.
16843 @item printf @var{template}, @var{expressions}@dots{}
16844 Print the values of one or more @var{expressions} under the control of
16845 the string @var{template}. To print several values, make
16846 @var{expressions} be a comma-separated list of individual expressions,
16847 which may be either numbers or pointers. Their values are printed as
16848 specified by @var{template}, exactly as a C program would do by
16849 executing the code below:
16852 printf (@var{template}, @var{expressions}@dots{});
16855 As in @code{C} @code{printf}, ordinary characters in @var{template}
16856 are printed verbatim, while @dfn{conversion specification} introduced
16857 by the @samp{%} character cause subsequent @var{expressions} to be
16858 evaluated, their values converted and formatted according to type and
16859 style information encoded in the conversion specifications, and then
16862 For example, you can print two values in hex like this:
16865 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
16868 @code{printf} supports all the standard @code{C} conversion
16869 specifications, including the flags and modifiers between the @samp{%}
16870 character and the conversion letter, with the following exceptions:
16874 The argument-ordering modifiers, such as @samp{2$}, are not supported.
16877 The modifier @samp{*} is not supported for specifying precision or
16881 The @samp{'} flag (for separation of digits into groups according to
16882 @code{LC_NUMERIC'}) is not supported.
16885 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
16889 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
16892 The conversion letters @samp{a} and @samp{A} are not supported.
16896 Note that the @samp{ll} type modifier is supported only if the
16897 underlying @code{C} implementation used to build @value{GDBN} supports
16898 the @code{long long int} type, and the @samp{L} type modifier is
16899 supported only if @code{long double} type is available.
16901 As in @code{C}, @code{printf} supports simple backslash-escape
16902 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
16903 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
16904 single character. Octal and hexadecimal escape sequences are not
16907 Additionally, @code{printf} supports conversion specifications for DFP
16908 (@dfn{Decimal Floating Point}) types using the following length modifiers
16909 together with a floating point specifier.
16914 @samp{H} for printing @code{Decimal32} types.
16917 @samp{D} for printing @code{Decimal64} types.
16920 @samp{DD} for printing @code{Decimal128} types.
16923 If the underlying @code{C} implementation used to build @value{GDBN} has
16924 support for the three length modifiers for DFP types, other modifiers
16925 such as width and precision will also be available for @value{GDBN} to use.
16927 In case there is no such @code{C} support, no additional modifiers will be
16928 available and the value will be printed in the standard way.
16930 Here's an example of printing DFP types using the above conversion letters:
16932 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
16938 @chapter Command Interpreters
16939 @cindex command interpreters
16941 @value{GDBN} supports multiple command interpreters, and some command
16942 infrastructure to allow users or user interface writers to switch
16943 between interpreters or run commands in other interpreters.
16945 @value{GDBN} currently supports two command interpreters, the console
16946 interpreter (sometimes called the command-line interpreter or @sc{cli})
16947 and the machine interface interpreter (or @sc{gdb/mi}). This manual
16948 describes both of these interfaces in great detail.
16950 By default, @value{GDBN} will start with the console interpreter.
16951 However, the user may choose to start @value{GDBN} with another
16952 interpreter by specifying the @option{-i} or @option{--interpreter}
16953 startup options. Defined interpreters include:
16957 @cindex console interpreter
16958 The traditional console or command-line interpreter. This is the most often
16959 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
16960 @value{GDBN} will use this interpreter.
16963 @cindex mi interpreter
16964 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
16965 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
16966 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
16970 @cindex mi2 interpreter
16971 The current @sc{gdb/mi} interface.
16974 @cindex mi1 interpreter
16975 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
16979 @cindex invoke another interpreter
16980 The interpreter being used by @value{GDBN} may not be dynamically
16981 switched at runtime. Although possible, this could lead to a very
16982 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
16983 enters the command "interpreter-set console" in a console view,
16984 @value{GDBN} would switch to using the console interpreter, rendering
16985 the IDE inoperable!
16987 @kindex interpreter-exec
16988 Although you may only choose a single interpreter at startup, you may execute
16989 commands in any interpreter from the current interpreter using the appropriate
16990 command. If you are running the console interpreter, simply use the
16991 @code{interpreter-exec} command:
16994 interpreter-exec mi "-data-list-register-names"
16997 @sc{gdb/mi} has a similar command, although it is only available in versions of
16998 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
17001 @chapter @value{GDBN} Text User Interface
17003 @cindex Text User Interface
17006 * TUI Overview:: TUI overview
17007 * TUI Keys:: TUI key bindings
17008 * TUI Single Key Mode:: TUI single key mode
17009 * TUI Commands:: TUI-specific commands
17010 * TUI Configuration:: TUI configuration variables
17013 The @value{GDBN} Text User Interface (TUI) is a terminal
17014 interface which uses the @code{curses} library to show the source
17015 file, the assembly output, the program registers and @value{GDBN}
17016 commands in separate text windows. The TUI mode is supported only
17017 on platforms where a suitable version of the @code{curses} library
17020 @pindex @value{GDBTUI}
17021 The TUI mode is enabled by default when you invoke @value{GDBN} as
17022 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
17023 You can also switch in and out of TUI mode while @value{GDBN} runs by
17024 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
17025 @xref{TUI Keys, ,TUI Key Bindings}.
17028 @section TUI Overview
17030 In TUI mode, @value{GDBN} can display several text windows:
17034 This window is the @value{GDBN} command window with the @value{GDBN}
17035 prompt and the @value{GDBN} output. The @value{GDBN} input is still
17036 managed using readline.
17039 The source window shows the source file of the program. The current
17040 line and active breakpoints are displayed in this window.
17043 The assembly window shows the disassembly output of the program.
17046 This window shows the processor registers. Registers are highlighted
17047 when their values change.
17050 The source and assembly windows show the current program position
17051 by highlighting the current line and marking it with a @samp{>} marker.
17052 Breakpoints are indicated with two markers. The first marker
17053 indicates the breakpoint type:
17057 Breakpoint which was hit at least once.
17060 Breakpoint which was never hit.
17063 Hardware breakpoint which was hit at least once.
17066 Hardware breakpoint which was never hit.
17069 The second marker indicates whether the breakpoint is enabled or not:
17073 Breakpoint is enabled.
17076 Breakpoint is disabled.
17079 The source, assembly and register windows are updated when the current
17080 thread changes, when the frame changes, or when the program counter
17083 These windows are not all visible at the same time. The command
17084 window is always visible. The others can be arranged in several
17095 source and assembly,
17098 source and registers, or
17101 assembly and registers.
17104 A status line above the command window shows the following information:
17108 Indicates the current @value{GDBN} target.
17109 (@pxref{Targets, ,Specifying a Debugging Target}).
17112 Gives the current process or thread number.
17113 When no process is being debugged, this field is set to @code{No process}.
17116 Gives the current function name for the selected frame.
17117 The name is demangled if demangling is turned on (@pxref{Print Settings}).
17118 When there is no symbol corresponding to the current program counter,
17119 the string @code{??} is displayed.
17122 Indicates the current line number for the selected frame.
17123 When the current line number is not known, the string @code{??} is displayed.
17126 Indicates the current program counter address.
17130 @section TUI Key Bindings
17131 @cindex TUI key bindings
17133 The TUI installs several key bindings in the readline keymaps
17134 (@pxref{Command Line Editing}). The following key bindings
17135 are installed for both TUI mode and the @value{GDBN} standard mode.
17144 Enter or leave the TUI mode. When leaving the TUI mode,
17145 the curses window management stops and @value{GDBN} operates using
17146 its standard mode, writing on the terminal directly. When reentering
17147 the TUI mode, control is given back to the curses windows.
17148 The screen is then refreshed.
17152 Use a TUI layout with only one window. The layout will
17153 either be @samp{source} or @samp{assembly}. When the TUI mode
17154 is not active, it will switch to the TUI mode.
17156 Think of this key binding as the Emacs @kbd{C-x 1} binding.
17160 Use a TUI layout with at least two windows. When the current
17161 layout already has two windows, the next layout with two windows is used.
17162 When a new layout is chosen, one window will always be common to the
17163 previous layout and the new one.
17165 Think of it as the Emacs @kbd{C-x 2} binding.
17169 Change the active window. The TUI associates several key bindings
17170 (like scrolling and arrow keys) with the active window. This command
17171 gives the focus to the next TUI window.
17173 Think of it as the Emacs @kbd{C-x o} binding.
17177 Switch in and out of the TUI SingleKey mode that binds single
17178 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
17181 The following key bindings only work in the TUI mode:
17186 Scroll the active window one page up.
17190 Scroll the active window one page down.
17194 Scroll the active window one line up.
17198 Scroll the active window one line down.
17202 Scroll the active window one column left.
17206 Scroll the active window one column right.
17210 Refresh the screen.
17213 Because the arrow keys scroll the active window in the TUI mode, they
17214 are not available for their normal use by readline unless the command
17215 window has the focus. When another window is active, you must use
17216 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
17217 and @kbd{C-f} to control the command window.
17219 @node TUI Single Key Mode
17220 @section TUI Single Key Mode
17221 @cindex TUI single key mode
17223 The TUI also provides a @dfn{SingleKey} mode, which binds several
17224 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
17225 switch into this mode, where the following key bindings are used:
17228 @kindex c @r{(SingleKey TUI key)}
17232 @kindex d @r{(SingleKey TUI key)}
17236 @kindex f @r{(SingleKey TUI key)}
17240 @kindex n @r{(SingleKey TUI key)}
17244 @kindex q @r{(SingleKey TUI key)}
17246 exit the SingleKey mode.
17248 @kindex r @r{(SingleKey TUI key)}
17252 @kindex s @r{(SingleKey TUI key)}
17256 @kindex u @r{(SingleKey TUI key)}
17260 @kindex v @r{(SingleKey TUI key)}
17264 @kindex w @r{(SingleKey TUI key)}
17269 Other keys temporarily switch to the @value{GDBN} command prompt.
17270 The key that was pressed is inserted in the editing buffer so that
17271 it is possible to type most @value{GDBN} commands without interaction
17272 with the TUI SingleKey mode. Once the command is entered the TUI
17273 SingleKey mode is restored. The only way to permanently leave
17274 this mode is by typing @kbd{q} or @kbd{C-x s}.
17278 @section TUI-specific Commands
17279 @cindex TUI commands
17281 The TUI has specific commands to control the text windows.
17282 These commands are always available, even when @value{GDBN} is not in
17283 the TUI mode. When @value{GDBN} is in the standard mode, most
17284 of these commands will automatically switch to the TUI mode.
17289 List and give the size of all displayed windows.
17293 Display the next layout.
17296 Display the previous layout.
17299 Display the source window only.
17302 Display the assembly window only.
17305 Display the source and assembly window.
17308 Display the register window together with the source or assembly window.
17312 Make the next window active for scrolling.
17315 Make the previous window active for scrolling.
17318 Make the source window active for scrolling.
17321 Make the assembly window active for scrolling.
17324 Make the register window active for scrolling.
17327 Make the command window active for scrolling.
17331 Refresh the screen. This is similar to typing @kbd{C-L}.
17333 @item tui reg float
17335 Show the floating point registers in the register window.
17337 @item tui reg general
17338 Show the general registers in the register window.
17341 Show the next register group. The list of register groups as well as
17342 their order is target specific. The predefined register groups are the
17343 following: @code{general}, @code{float}, @code{system}, @code{vector},
17344 @code{all}, @code{save}, @code{restore}.
17346 @item tui reg system
17347 Show the system registers in the register window.
17351 Update the source window and the current execution point.
17353 @item winheight @var{name} +@var{count}
17354 @itemx winheight @var{name} -@var{count}
17356 Change the height of the window @var{name} by @var{count}
17357 lines. Positive counts increase the height, while negative counts
17360 @item tabset @var{nchars}
17362 Set the width of tab stops to be @var{nchars} characters.
17365 @node TUI Configuration
17366 @section TUI Configuration Variables
17367 @cindex TUI configuration variables
17369 Several configuration variables control the appearance of TUI windows.
17372 @item set tui border-kind @var{kind}
17373 @kindex set tui border-kind
17374 Select the border appearance for the source, assembly and register windows.
17375 The possible values are the following:
17378 Use a space character to draw the border.
17381 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
17384 Use the Alternate Character Set to draw the border. The border is
17385 drawn using character line graphics if the terminal supports them.
17388 @item set tui border-mode @var{mode}
17389 @kindex set tui border-mode
17390 @itemx set tui active-border-mode @var{mode}
17391 @kindex set tui active-border-mode
17392 Select the display attributes for the borders of the inactive windows
17393 or the active window. The @var{mode} can be one of the following:
17396 Use normal attributes to display the border.
17402 Use reverse video mode.
17405 Use half bright mode.
17407 @item half-standout
17408 Use half bright and standout mode.
17411 Use extra bright or bold mode.
17413 @item bold-standout
17414 Use extra bright or bold and standout mode.
17419 @chapter Using @value{GDBN} under @sc{gnu} Emacs
17422 @cindex @sc{gnu} Emacs
17423 A special interface allows you to use @sc{gnu} Emacs to view (and
17424 edit) the source files for the program you are debugging with
17427 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
17428 executable file you want to debug as an argument. This command starts
17429 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
17430 created Emacs buffer.
17431 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
17433 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
17438 All ``terminal'' input and output goes through an Emacs buffer, called
17441 This applies both to @value{GDBN} commands and their output, and to the input
17442 and output done by the program you are debugging.
17444 This is useful because it means that you can copy the text of previous
17445 commands and input them again; you can even use parts of the output
17448 All the facilities of Emacs' Shell mode are available for interacting
17449 with your program. In particular, you can send signals the usual
17450 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
17454 @value{GDBN} displays source code through Emacs.
17456 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
17457 source file for that frame and puts an arrow (@samp{=>}) at the
17458 left margin of the current line. Emacs uses a separate buffer for
17459 source display, and splits the screen to show both your @value{GDBN} session
17462 Explicit @value{GDBN} @code{list} or search commands still produce output as
17463 usual, but you probably have no reason to use them from Emacs.
17466 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
17467 a graphical mode, enabled by default, which provides further buffers
17468 that can control the execution and describe the state of your program.
17469 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
17471 If you specify an absolute file name when prompted for the @kbd{M-x
17472 gdb} argument, then Emacs sets your current working directory to where
17473 your program resides. If you only specify the file name, then Emacs
17474 sets your current working directory to to the directory associated
17475 with the previous buffer. In this case, @value{GDBN} may find your
17476 program by searching your environment's @code{PATH} variable, but on
17477 some operating systems it might not find the source. So, although the
17478 @value{GDBN} input and output session proceeds normally, the auxiliary
17479 buffer does not display the current source and line of execution.
17481 The initial working directory of @value{GDBN} is printed on the top
17482 line of the GUD buffer and this serves as a default for the commands
17483 that specify files for @value{GDBN} to operate on. @xref{Files,
17484 ,Commands to Specify Files}.
17486 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
17487 need to call @value{GDBN} by a different name (for example, if you
17488 keep several configurations around, with different names) you can
17489 customize the Emacs variable @code{gud-gdb-command-name} to run the
17492 In the GUD buffer, you can use these special Emacs commands in
17493 addition to the standard Shell mode commands:
17497 Describe the features of Emacs' GUD Mode.
17500 Execute to another source line, like the @value{GDBN} @code{step} command; also
17501 update the display window to show the current file and location.
17504 Execute to next source line in this function, skipping all function
17505 calls, like the @value{GDBN} @code{next} command. Then update the display window
17506 to show the current file and location.
17509 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
17510 display window accordingly.
17513 Execute until exit from the selected stack frame, like the @value{GDBN}
17514 @code{finish} command.
17517 Continue execution of your program, like the @value{GDBN} @code{continue}
17521 Go up the number of frames indicated by the numeric argument
17522 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
17523 like the @value{GDBN} @code{up} command.
17526 Go down the number of frames indicated by the numeric argument, like the
17527 @value{GDBN} @code{down} command.
17530 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
17531 tells @value{GDBN} to set a breakpoint on the source line point is on.
17533 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
17534 separate frame which shows a backtrace when the GUD buffer is current.
17535 Move point to any frame in the stack and type @key{RET} to make it
17536 become the current frame and display the associated source in the
17537 source buffer. Alternatively, click @kbd{Mouse-2} to make the
17538 selected frame become the current one. In graphical mode, the
17539 speedbar displays watch expressions.
17541 If you accidentally delete the source-display buffer, an easy way to get
17542 it back is to type the command @code{f} in the @value{GDBN} buffer, to
17543 request a frame display; when you run under Emacs, this recreates
17544 the source buffer if necessary to show you the context of the current
17547 The source files displayed in Emacs are in ordinary Emacs buffers
17548 which are visiting the source files in the usual way. You can edit
17549 the files with these buffers if you wish; but keep in mind that @value{GDBN}
17550 communicates with Emacs in terms of line numbers. If you add or
17551 delete lines from the text, the line numbers that @value{GDBN} knows cease
17552 to correspond properly with the code.
17554 A more detailed description of Emacs' interaction with @value{GDBN} is
17555 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
17558 @c The following dropped because Epoch is nonstandard. Reactivate
17559 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
17561 @kindex Emacs Epoch environment
17565 Version 18 of @sc{gnu} Emacs has a built-in window system
17566 called the @code{epoch}
17567 environment. Users of this environment can use a new command,
17568 @code{inspect} which performs identically to @code{print} except that
17569 each value is printed in its own window.
17574 @chapter The @sc{gdb/mi} Interface
17576 @unnumberedsec Function and Purpose
17578 @cindex @sc{gdb/mi}, its purpose
17579 @sc{gdb/mi} is a line based machine oriented text interface to
17580 @value{GDBN} and is activated by specifying using the
17581 @option{--interpreter} command line option (@pxref{Mode Options}). It
17582 is specifically intended to support the development of systems which
17583 use the debugger as just one small component of a larger system.
17585 This chapter is a specification of the @sc{gdb/mi} interface. It is written
17586 in the form of a reference manual.
17588 Note that @sc{gdb/mi} is still under construction, so some of the
17589 features described below are incomplete and subject to change
17590 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
17592 @unnumberedsec Notation and Terminology
17594 @cindex notational conventions, for @sc{gdb/mi}
17595 This chapter uses the following notation:
17599 @code{|} separates two alternatives.
17602 @code{[ @var{something} ]} indicates that @var{something} is optional:
17603 it may or may not be given.
17606 @code{( @var{group} )*} means that @var{group} inside the parentheses
17607 may repeat zero or more times.
17610 @code{( @var{group} )+} means that @var{group} inside the parentheses
17611 may repeat one or more times.
17614 @code{"@var{string}"} means a literal @var{string}.
17618 @heading Dependencies
17622 * GDB/MI Command Syntax::
17623 * GDB/MI Compatibility with CLI::
17624 * GDB/MI Development and Front Ends::
17625 * GDB/MI Output Records::
17626 * GDB/MI Simple Examples::
17627 * GDB/MI Command Description Format::
17628 * GDB/MI Breakpoint Commands::
17629 * GDB/MI Program Context::
17630 * GDB/MI Thread Commands::
17631 * GDB/MI Program Execution::
17632 * GDB/MI Stack Manipulation::
17633 * GDB/MI Variable Objects::
17634 * GDB/MI Data Manipulation::
17635 * GDB/MI Tracepoint Commands::
17636 * GDB/MI Symbol Query::
17637 * GDB/MI File Commands::
17639 * GDB/MI Kod Commands::
17640 * GDB/MI Memory Overlay Commands::
17641 * GDB/MI Signal Handling Commands::
17643 * GDB/MI Target Manipulation::
17644 * GDB/MI File Transfer Commands::
17645 * GDB/MI Miscellaneous Commands::
17648 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17649 @node GDB/MI Command Syntax
17650 @section @sc{gdb/mi} Command Syntax
17653 * GDB/MI Input Syntax::
17654 * GDB/MI Output Syntax::
17657 @node GDB/MI Input Syntax
17658 @subsection @sc{gdb/mi} Input Syntax
17660 @cindex input syntax for @sc{gdb/mi}
17661 @cindex @sc{gdb/mi}, input syntax
17663 @item @var{command} @expansion{}
17664 @code{@var{cli-command} | @var{mi-command}}
17666 @item @var{cli-command} @expansion{}
17667 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
17668 @var{cli-command} is any existing @value{GDBN} CLI command.
17670 @item @var{mi-command} @expansion{}
17671 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
17672 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
17674 @item @var{token} @expansion{}
17675 "any sequence of digits"
17677 @item @var{option} @expansion{}
17678 @code{"-" @var{parameter} [ " " @var{parameter} ]}
17680 @item @var{parameter} @expansion{}
17681 @code{@var{non-blank-sequence} | @var{c-string}}
17683 @item @var{operation} @expansion{}
17684 @emph{any of the operations described in this chapter}
17686 @item @var{non-blank-sequence} @expansion{}
17687 @emph{anything, provided it doesn't contain special characters such as
17688 "-", @var{nl}, """ and of course " "}
17690 @item @var{c-string} @expansion{}
17691 @code{""" @var{seven-bit-iso-c-string-content} """}
17693 @item @var{nl} @expansion{}
17702 The CLI commands are still handled by the @sc{mi} interpreter; their
17703 output is described below.
17706 The @code{@var{token}}, when present, is passed back when the command
17710 Some @sc{mi} commands accept optional arguments as part of the parameter
17711 list. Each option is identified by a leading @samp{-} (dash) and may be
17712 followed by an optional argument parameter. Options occur first in the
17713 parameter list and can be delimited from normal parameters using
17714 @samp{--} (this is useful when some parameters begin with a dash).
17721 We want easy access to the existing CLI syntax (for debugging).
17724 We want it to be easy to spot a @sc{mi} operation.
17727 @node GDB/MI Output Syntax
17728 @subsection @sc{gdb/mi} Output Syntax
17730 @cindex output syntax of @sc{gdb/mi}
17731 @cindex @sc{gdb/mi}, output syntax
17732 The output from @sc{gdb/mi} consists of zero or more out-of-band records
17733 followed, optionally, by a single result record. This result record
17734 is for the most recent command. The sequence of output records is
17735 terminated by @samp{(gdb)}.
17737 If an input command was prefixed with a @code{@var{token}} then the
17738 corresponding output for that command will also be prefixed by that same
17742 @item @var{output} @expansion{}
17743 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
17745 @item @var{result-record} @expansion{}
17746 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
17748 @item @var{out-of-band-record} @expansion{}
17749 @code{@var{async-record} | @var{stream-record}}
17751 @item @var{async-record} @expansion{}
17752 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
17754 @item @var{exec-async-output} @expansion{}
17755 @code{[ @var{token} ] "*" @var{async-output}}
17757 @item @var{status-async-output} @expansion{}
17758 @code{[ @var{token} ] "+" @var{async-output}}
17760 @item @var{notify-async-output} @expansion{}
17761 @code{[ @var{token} ] "=" @var{async-output}}
17763 @item @var{async-output} @expansion{}
17764 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
17766 @item @var{result-class} @expansion{}
17767 @code{"done" | "running" | "connected" | "error" | "exit"}
17769 @item @var{async-class} @expansion{}
17770 @code{"stopped" | @var{others}} (where @var{others} will be added
17771 depending on the needs---this is still in development).
17773 @item @var{result} @expansion{}
17774 @code{ @var{variable} "=" @var{value}}
17776 @item @var{variable} @expansion{}
17777 @code{ @var{string} }
17779 @item @var{value} @expansion{}
17780 @code{ @var{const} | @var{tuple} | @var{list} }
17782 @item @var{const} @expansion{}
17783 @code{@var{c-string}}
17785 @item @var{tuple} @expansion{}
17786 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
17788 @item @var{list} @expansion{}
17789 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
17790 @var{result} ( "," @var{result} )* "]" }
17792 @item @var{stream-record} @expansion{}
17793 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
17795 @item @var{console-stream-output} @expansion{}
17796 @code{"~" @var{c-string}}
17798 @item @var{target-stream-output} @expansion{}
17799 @code{"@@" @var{c-string}}
17801 @item @var{log-stream-output} @expansion{}
17802 @code{"&" @var{c-string}}
17804 @item @var{nl} @expansion{}
17807 @item @var{token} @expansion{}
17808 @emph{any sequence of digits}.
17816 All output sequences end in a single line containing a period.
17819 The @code{@var{token}} is from the corresponding request. If an execution
17820 command is interrupted by the @samp{-exec-interrupt} command, the
17821 @var{token} associated with the @samp{*stopped} message is the one of the
17822 original execution command, not the one of the interrupt command.
17825 @cindex status output in @sc{gdb/mi}
17826 @var{status-async-output} contains on-going status information about the
17827 progress of a slow operation. It can be discarded. All status output is
17828 prefixed by @samp{+}.
17831 @cindex async output in @sc{gdb/mi}
17832 @var{exec-async-output} contains asynchronous state change on the target
17833 (stopped, started, disappeared). All async output is prefixed by
17837 @cindex notify output in @sc{gdb/mi}
17838 @var{notify-async-output} contains supplementary information that the
17839 client should handle (e.g., a new breakpoint information). All notify
17840 output is prefixed by @samp{=}.
17843 @cindex console output in @sc{gdb/mi}
17844 @var{console-stream-output} is output that should be displayed as is in the
17845 console. It is the textual response to a CLI command. All the console
17846 output is prefixed by @samp{~}.
17849 @cindex target output in @sc{gdb/mi}
17850 @var{target-stream-output} is the output produced by the target program.
17851 All the target output is prefixed by @samp{@@}.
17854 @cindex log output in @sc{gdb/mi}
17855 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
17856 instance messages that should be displayed as part of an error log. All
17857 the log output is prefixed by @samp{&}.
17860 @cindex list output in @sc{gdb/mi}
17861 New @sc{gdb/mi} commands should only output @var{lists} containing
17867 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
17868 details about the various output records.
17870 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17871 @node GDB/MI Compatibility with CLI
17872 @section @sc{gdb/mi} Compatibility with CLI
17874 @cindex compatibility, @sc{gdb/mi} and CLI
17875 @cindex @sc{gdb/mi}, compatibility with CLI
17877 For the developers convenience CLI commands can be entered directly,
17878 but there may be some unexpected behaviour. For example, commands
17879 that query the user will behave as if the user replied yes, breakpoint
17880 command lists are not executed and some CLI commands, such as
17881 @code{if}, @code{when} and @code{define}, prompt for further input with
17882 @samp{>}, which is not valid MI output.
17884 This feature may be removed at some stage in the future and it is
17885 recommended that front ends use the @code{-interpreter-exec} command
17886 (@pxref{-interpreter-exec}).
17888 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17889 @node GDB/MI Development and Front Ends
17890 @section @sc{gdb/mi} Development and Front Ends
17891 @cindex @sc{gdb/mi} development
17893 The application which takes the MI output and presents the state of the
17894 program being debugged to the user is called a @dfn{front end}.
17896 Although @sc{gdb/mi} is still incomplete, it is currently being used
17897 by a variety of front ends to @value{GDBN}. This makes it difficult
17898 to introduce new functionality without breaking existing usage. This
17899 section tries to minimize the problems by describing how the protocol
17902 Some changes in MI need not break a carefully designed front end, and
17903 for these the MI version will remain unchanged. The following is a
17904 list of changes that may occur within one level, so front ends should
17905 parse MI output in a way that can handle them:
17909 New MI commands may be added.
17912 New fields may be added to the output of any MI command.
17915 The range of values for fields with specified values, e.g.,
17916 @code{in_scope} (@pxref{-var-update}) may be extended.
17918 @c The format of field's content e.g type prefix, may change so parse it
17919 @c at your own risk. Yes, in general?
17921 @c The order of fields may change? Shouldn't really matter but it might
17922 @c resolve inconsistencies.
17925 If the changes are likely to break front ends, the MI version level
17926 will be increased by one. This will allow the front end to parse the
17927 output according to the MI version. Apart from mi0, new versions of
17928 @value{GDBN} will not support old versions of MI and it will be the
17929 responsibility of the front end to work with the new one.
17931 @c Starting with mi3, add a new command -mi-version that prints the MI
17934 The best way to avoid unexpected changes in MI that might break your front
17935 end is to make your project known to @value{GDBN} developers and
17936 follow development on @email{gdb@@sourceware.org} and
17937 @email{gdb-patches@@sourceware.org}. There is also the mailing list
17938 @email{dmi-discuss@@lists.freestandards.org}, hosted by the Free Standards
17939 Group, which has the aim of creating a more general MI protocol
17940 called Debugger Machine Interface (DMI) that will become a standard
17941 for all debuggers, not just @value{GDBN}.
17942 @cindex mailing lists
17944 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17945 @node GDB/MI Output Records
17946 @section @sc{gdb/mi} Output Records
17949 * GDB/MI Result Records::
17950 * GDB/MI Stream Records::
17951 * GDB/MI Out-of-band Records::
17954 @node GDB/MI Result Records
17955 @subsection @sc{gdb/mi} Result Records
17957 @cindex result records in @sc{gdb/mi}
17958 @cindex @sc{gdb/mi}, result records
17959 In addition to a number of out-of-band notifications, the response to a
17960 @sc{gdb/mi} command includes one of the following result indications:
17964 @item "^done" [ "," @var{results} ]
17965 The synchronous operation was successful, @code{@var{results}} are the return
17970 @c Is this one correct? Should it be an out-of-band notification?
17971 The asynchronous operation was successfully started. The target is
17976 @value{GDBN} has connected to a remote target.
17978 @item "^error" "," @var{c-string}
17980 The operation failed. The @code{@var{c-string}} contains the corresponding
17985 @value{GDBN} has terminated.
17989 @node GDB/MI Stream Records
17990 @subsection @sc{gdb/mi} Stream Records
17992 @cindex @sc{gdb/mi}, stream records
17993 @cindex stream records in @sc{gdb/mi}
17994 @value{GDBN} internally maintains a number of output streams: the console, the
17995 target, and the log. The output intended for each of these streams is
17996 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
17998 Each stream record begins with a unique @dfn{prefix character} which
17999 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
18000 Syntax}). In addition to the prefix, each stream record contains a
18001 @code{@var{string-output}}. This is either raw text (with an implicit new
18002 line) or a quoted C string (which does not contain an implicit newline).
18005 @item "~" @var{string-output}
18006 The console output stream contains text that should be displayed in the
18007 CLI console window. It contains the textual responses to CLI commands.
18009 @item "@@" @var{string-output}
18010 The target output stream contains any textual output from the running
18011 target. This is only present when GDB's event loop is truly
18012 asynchronous, which is currently only the case for remote targets.
18014 @item "&" @var{string-output}
18015 The log stream contains debugging messages being produced by @value{GDBN}'s
18019 @node GDB/MI Out-of-band Records
18020 @subsection @sc{gdb/mi} Out-of-band Records
18022 @cindex out-of-band records in @sc{gdb/mi}
18023 @cindex @sc{gdb/mi}, out-of-band records
18024 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
18025 additional changes that have occurred. Those changes can either be a
18026 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
18027 target activity (e.g., target stopped).
18029 The following is a preliminary list of possible out-of-band records.
18030 In particular, the @var{exec-async-output} records.
18033 @item *stopped,reason="@var{reason}"
18036 @var{reason} can be one of the following:
18039 @item breakpoint-hit
18040 A breakpoint was reached.
18041 @item watchpoint-trigger
18042 A watchpoint was triggered.
18043 @item read-watchpoint-trigger
18044 A read watchpoint was triggered.
18045 @item access-watchpoint-trigger
18046 An access watchpoint was triggered.
18047 @item function-finished
18048 An -exec-finish or similar CLI command was accomplished.
18049 @item location-reached
18050 An -exec-until or similar CLI command was accomplished.
18051 @item watchpoint-scope
18052 A watchpoint has gone out of scope.
18053 @item end-stepping-range
18054 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
18055 similar CLI command was accomplished.
18056 @item exited-signalled
18057 The inferior exited because of a signal.
18059 The inferior exited.
18060 @item exited-normally
18061 The inferior exited normally.
18062 @item signal-received
18063 A signal was received by the inferior.
18067 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18068 @node GDB/MI Simple Examples
18069 @section Simple Examples of @sc{gdb/mi} Interaction
18070 @cindex @sc{gdb/mi}, simple examples
18072 This subsection presents several simple examples of interaction using
18073 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
18074 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
18075 the output received from @sc{gdb/mi}.
18077 Note the line breaks shown in the examples are here only for
18078 readability, they don't appear in the real output.
18080 @subheading Setting a Breakpoint
18082 Setting a breakpoint generates synchronous output which contains detailed
18083 information of the breakpoint.
18086 -> -break-insert main
18087 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
18088 enabled="y",addr="0x08048564",func="main",file="myprog.c",
18089 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
18093 @subheading Program Execution
18095 Program execution generates asynchronous records and MI gives the
18096 reason that execution stopped.
18102 <- *stopped,reason="breakpoint-hit",bkptno="1",thread-id="0",
18103 frame=@{addr="0x08048564",func="main",
18104 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
18105 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
18110 <- *stopped,reason="exited-normally"
18114 @subheading Quitting @value{GDBN}
18116 Quitting @value{GDBN} just prints the result class @samp{^exit}.
18124 @subheading A Bad Command
18126 Here's what happens if you pass a non-existent command:
18130 <- ^error,msg="Undefined MI command: rubbish"
18135 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18136 @node GDB/MI Command Description Format
18137 @section @sc{gdb/mi} Command Description Format
18139 The remaining sections describe blocks of commands. Each block of
18140 commands is laid out in a fashion similar to this section.
18142 @subheading Motivation
18144 The motivation for this collection of commands.
18146 @subheading Introduction
18148 A brief introduction to this collection of commands as a whole.
18150 @subheading Commands
18152 For each command in the block, the following is described:
18154 @subsubheading Synopsis
18157 -command @var{args}@dots{}
18160 @subsubheading Result
18162 @subsubheading @value{GDBN} Command
18164 The corresponding @value{GDBN} CLI command(s), if any.
18166 @subsubheading Example
18168 Example(s) formatted for readability. Some of the described commands have
18169 not been implemented yet and these are labeled N.A.@: (not available).
18172 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18173 @node GDB/MI Breakpoint Commands
18174 @section @sc{gdb/mi} Breakpoint Commands
18176 @cindex breakpoint commands for @sc{gdb/mi}
18177 @cindex @sc{gdb/mi}, breakpoint commands
18178 This section documents @sc{gdb/mi} commands for manipulating
18181 @subheading The @code{-break-after} Command
18182 @findex -break-after
18184 @subsubheading Synopsis
18187 -break-after @var{number} @var{count}
18190 The breakpoint number @var{number} is not in effect until it has been
18191 hit @var{count} times. To see how this is reflected in the output of
18192 the @samp{-break-list} command, see the description of the
18193 @samp{-break-list} command below.
18195 @subsubheading @value{GDBN} Command
18197 The corresponding @value{GDBN} command is @samp{ignore}.
18199 @subsubheading Example
18204 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",
18205 fullname="/home/foo/hello.c",line="5",times="0"@}
18212 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18213 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18214 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18215 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18216 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18217 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18218 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18219 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18220 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18221 line="5",times="0",ignore="3"@}]@}
18226 @subheading The @code{-break-catch} Command
18227 @findex -break-catch
18229 @subheading The @code{-break-commands} Command
18230 @findex -break-commands
18234 @subheading The @code{-break-condition} Command
18235 @findex -break-condition
18237 @subsubheading Synopsis
18240 -break-condition @var{number} @var{expr}
18243 Breakpoint @var{number} will stop the program only if the condition in
18244 @var{expr} is true. The condition becomes part of the
18245 @samp{-break-list} output (see the description of the @samp{-break-list}
18248 @subsubheading @value{GDBN} Command
18250 The corresponding @value{GDBN} command is @samp{condition}.
18252 @subsubheading Example
18256 -break-condition 1 1
18260 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18261 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18262 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18263 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18264 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18265 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18266 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18267 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18268 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18269 line="5",cond="1",times="0",ignore="3"@}]@}
18273 @subheading The @code{-break-delete} Command
18274 @findex -break-delete
18276 @subsubheading Synopsis
18279 -break-delete ( @var{breakpoint} )+
18282 Delete the breakpoint(s) whose number(s) are specified in the argument
18283 list. This is obviously reflected in the breakpoint list.
18285 @subsubheading @value{GDBN} Command
18287 The corresponding @value{GDBN} command is @samp{delete}.
18289 @subsubheading Example
18297 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
18298 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18299 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18300 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18301 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18302 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18303 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18308 @subheading The @code{-break-disable} Command
18309 @findex -break-disable
18311 @subsubheading Synopsis
18314 -break-disable ( @var{breakpoint} )+
18317 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
18318 break list is now set to @samp{n} for the named @var{breakpoint}(s).
18320 @subsubheading @value{GDBN} Command
18322 The corresponding @value{GDBN} command is @samp{disable}.
18324 @subsubheading Example
18332 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18333 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18334 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18335 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18336 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18337 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18338 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18339 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
18340 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18341 line="5",times="0"@}]@}
18345 @subheading The @code{-break-enable} Command
18346 @findex -break-enable
18348 @subsubheading Synopsis
18351 -break-enable ( @var{breakpoint} )+
18354 Enable (previously disabled) @var{breakpoint}(s).
18356 @subsubheading @value{GDBN} Command
18358 The corresponding @value{GDBN} command is @samp{enable}.
18360 @subsubheading Example
18368 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18369 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18370 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18371 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18372 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18373 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18374 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18375 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
18376 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18377 line="5",times="0"@}]@}
18381 @subheading The @code{-break-info} Command
18382 @findex -break-info
18384 @subsubheading Synopsis
18387 -break-info @var{breakpoint}
18391 Get information about a single breakpoint.
18393 @subsubheading @value{GDBN} Command
18395 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
18397 @subsubheading Example
18400 @subheading The @code{-break-insert} Command
18401 @findex -break-insert
18403 @subsubheading Synopsis
18406 -break-insert [ -t ] [ -h ] [ -f ]
18407 [ -c @var{condition} ] [ -i @var{ignore-count} ]
18408 [ -p @var{thread} ] [ @var{location} ]
18412 If specified, @var{location}, can be one of:
18419 @item filename:linenum
18420 @item filename:function
18424 The possible optional parameters of this command are:
18428 Insert a temporary breakpoint.
18430 Insert a hardware breakpoint.
18431 @item -c @var{condition}
18432 Make the breakpoint conditional on @var{condition}.
18433 @item -i @var{ignore-count}
18434 Initialize the @var{ignore-count}.
18436 If @var{location} cannot be parsed (for example if it
18437 refers to unknown files or functions), create a pending
18438 breakpoint. Without this flag, @value{GDBN} will report
18439 an error, and won't create a breakpoint, if @var{location}
18443 @subsubheading Result
18445 The result is in the form:
18448 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
18449 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
18450 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
18451 times="@var{times}"@}
18455 where @var{number} is the @value{GDBN} number for this breakpoint,
18456 @var{funcname} is the name of the function where the breakpoint was
18457 inserted, @var{filename} is the name of the source file which contains
18458 this function, @var{lineno} is the source line number within that file
18459 and @var{times} the number of times that the breakpoint has been hit
18460 (always 0 for -break-insert but may be greater for -break-info or -break-list
18461 which use the same output).
18463 Note: this format is open to change.
18464 @c An out-of-band breakpoint instead of part of the result?
18466 @subsubheading @value{GDBN} Command
18468 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
18469 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
18471 @subsubheading Example
18476 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
18477 fullname="/home/foo/recursive2.c,line="4",times="0"@}
18479 -break-insert -t foo
18480 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
18481 fullname="/home/foo/recursive2.c,line="11",times="0"@}
18484 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18485 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18486 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18487 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18488 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18489 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18490 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18491 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18492 addr="0x0001072c", func="main",file="recursive2.c",
18493 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
18494 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
18495 addr="0x00010774",func="foo",file="recursive2.c",
18496 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
18498 -break-insert -r foo.*
18499 ~int foo(int, int);
18500 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
18501 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
18505 @subheading The @code{-break-list} Command
18506 @findex -break-list
18508 @subsubheading Synopsis
18514 Displays the list of inserted breakpoints, showing the following fields:
18518 number of the breakpoint
18520 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
18522 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
18525 is the breakpoint enabled or no: @samp{y} or @samp{n}
18527 memory location at which the breakpoint is set
18529 logical location of the breakpoint, expressed by function name, file
18532 number of times the breakpoint has been hit
18535 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
18536 @code{body} field is an empty list.
18538 @subsubheading @value{GDBN} Command
18540 The corresponding @value{GDBN} command is @samp{info break}.
18542 @subsubheading Example
18547 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18548 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18549 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18550 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18551 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18552 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18553 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18554 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18555 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
18556 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
18557 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
18558 line="13",times="0"@}]@}
18562 Here's an example of the result when there are no breakpoints:
18567 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
18568 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18569 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18570 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18571 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18572 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18573 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18578 @subheading The @code{-break-watch} Command
18579 @findex -break-watch
18581 @subsubheading Synopsis
18584 -break-watch [ -a | -r ]
18587 Create a watchpoint. With the @samp{-a} option it will create an
18588 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
18589 read from or on a write to the memory location. With the @samp{-r}
18590 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
18591 trigger only when the memory location is accessed for reading. Without
18592 either of the options, the watchpoint created is a regular watchpoint,
18593 i.e., it will trigger when the memory location is accessed for writing.
18594 @xref{Set Watchpoints, , Setting Watchpoints}.
18596 Note that @samp{-break-list} will report a single list of watchpoints and
18597 breakpoints inserted.
18599 @subsubheading @value{GDBN} Command
18601 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
18604 @subsubheading Example
18606 Setting a watchpoint on a variable in the @code{main} function:
18611 ^done,wpt=@{number="2",exp="x"@}
18616 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
18617 value=@{old="-268439212",new="55"@},
18618 frame=@{func="main",args=[],file="recursive2.c",
18619 fullname="/home/foo/bar/recursive2.c",line="5"@}
18623 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
18624 the program execution twice: first for the variable changing value, then
18625 for the watchpoint going out of scope.
18630 ^done,wpt=@{number="5",exp="C"@}
18635 *stopped,reason="watchpoint-trigger",
18636 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
18637 frame=@{func="callee4",args=[],
18638 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18639 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
18644 *stopped,reason="watchpoint-scope",wpnum="5",
18645 frame=@{func="callee3",args=[@{name="strarg",
18646 value="0x11940 \"A string argument.\""@}],
18647 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18648 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18652 Listing breakpoints and watchpoints, at different points in the program
18653 execution. Note that once the watchpoint goes out of scope, it is
18659 ^done,wpt=@{number="2",exp="C"@}
18662 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18663 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18664 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18665 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18666 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18667 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18668 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18669 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18670 addr="0x00010734",func="callee4",
18671 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18672 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
18673 bkpt=@{number="2",type="watchpoint",disp="keep",
18674 enabled="y",addr="",what="C",times="0"@}]@}
18679 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
18680 value=@{old="-276895068",new="3"@},
18681 frame=@{func="callee4",args=[],
18682 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18683 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
18686 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18687 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18688 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18689 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18690 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18691 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18692 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18693 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18694 addr="0x00010734",func="callee4",
18695 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18696 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
18697 bkpt=@{number="2",type="watchpoint",disp="keep",
18698 enabled="y",addr="",what="C",times="-5"@}]@}
18702 ^done,reason="watchpoint-scope",wpnum="2",
18703 frame=@{func="callee3",args=[@{name="strarg",
18704 value="0x11940 \"A string argument.\""@}],
18705 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18706 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18709 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18710 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18711 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18712 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18713 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18714 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18715 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18716 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18717 addr="0x00010734",func="callee4",
18718 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18719 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
18724 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18725 @node GDB/MI Program Context
18726 @section @sc{gdb/mi} Program Context
18728 @subheading The @code{-exec-arguments} Command
18729 @findex -exec-arguments
18732 @subsubheading Synopsis
18735 -exec-arguments @var{args}
18738 Set the inferior program arguments, to be used in the next
18741 @subsubheading @value{GDBN} Command
18743 The corresponding @value{GDBN} command is @samp{set args}.
18745 @subsubheading Example
18748 Don't have one around.
18751 @subheading The @code{-exec-show-arguments} Command
18752 @findex -exec-show-arguments
18754 @subsubheading Synopsis
18757 -exec-show-arguments
18760 Print the arguments of the program.
18762 @subsubheading @value{GDBN} Command
18764 The corresponding @value{GDBN} command is @samp{show args}.
18766 @subsubheading Example
18770 @subheading The @code{-environment-cd} Command
18771 @findex -environment-cd
18773 @subsubheading Synopsis
18776 -environment-cd @var{pathdir}
18779 Set @value{GDBN}'s working directory.
18781 @subsubheading @value{GDBN} Command
18783 The corresponding @value{GDBN} command is @samp{cd}.
18785 @subsubheading Example
18789 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18795 @subheading The @code{-environment-directory} Command
18796 @findex -environment-directory
18798 @subsubheading Synopsis
18801 -environment-directory [ -r ] [ @var{pathdir} ]+
18804 Add directories @var{pathdir} to beginning of search path for source files.
18805 If the @samp{-r} option is used, the search path is reset to the default
18806 search path. If directories @var{pathdir} are supplied in addition to the
18807 @samp{-r} option, the search path is first reset and then addition
18809 Multiple directories may be specified, separated by blanks. Specifying
18810 multiple directories in a single command
18811 results in the directories added to the beginning of the
18812 search path in the same order they were presented in the command.
18813 If blanks are needed as
18814 part of a directory name, double-quotes should be used around
18815 the name. In the command output, the path will show up separated
18816 by the system directory-separator character. The directory-separator
18817 character must not be used
18818 in any directory name.
18819 If no directories are specified, the current search path is displayed.
18821 @subsubheading @value{GDBN} Command
18823 The corresponding @value{GDBN} command is @samp{dir}.
18825 @subsubheading Example
18829 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18830 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18832 -environment-directory ""
18833 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18835 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
18836 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
18838 -environment-directory -r
18839 ^done,source-path="$cdir:$cwd"
18844 @subheading The @code{-environment-path} Command
18845 @findex -environment-path
18847 @subsubheading Synopsis
18850 -environment-path [ -r ] [ @var{pathdir} ]+
18853 Add directories @var{pathdir} to beginning of search path for object files.
18854 If the @samp{-r} option is used, the search path is reset to the original
18855 search path that existed at gdb start-up. If directories @var{pathdir} are
18856 supplied in addition to the
18857 @samp{-r} option, the search path is first reset and then addition
18859 Multiple directories may be specified, separated by blanks. Specifying
18860 multiple directories in a single command
18861 results in the directories added to the beginning of the
18862 search path in the same order they were presented in the command.
18863 If blanks are needed as
18864 part of a directory name, double-quotes should be used around
18865 the name. In the command output, the path will show up separated
18866 by the system directory-separator character. The directory-separator
18867 character must not be used
18868 in any directory name.
18869 If no directories are specified, the current path is displayed.
18872 @subsubheading @value{GDBN} Command
18874 The corresponding @value{GDBN} command is @samp{path}.
18876 @subsubheading Example
18881 ^done,path="/usr/bin"
18883 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
18884 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
18886 -environment-path -r /usr/local/bin
18887 ^done,path="/usr/local/bin:/usr/bin"
18892 @subheading The @code{-environment-pwd} Command
18893 @findex -environment-pwd
18895 @subsubheading Synopsis
18901 Show the current working directory.
18903 @subsubheading @value{GDBN} Command
18905 The corresponding @value{GDBN} command is @samp{pwd}.
18907 @subsubheading Example
18912 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
18916 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18917 @node GDB/MI Thread Commands
18918 @section @sc{gdb/mi} Thread Commands
18921 @subheading The @code{-thread-info} Command
18922 @findex -thread-info
18924 @subsubheading Synopsis
18927 -thread-info [ @var{thread-id} ]
18930 Reports information about either a specific thread, if
18931 the @var{thread-id} parameter is present, or about all
18932 threads. When printing information about all threads,
18933 also reports the current thread.
18935 @subsubheading @value{GDBN} Command
18937 The @samp{info thread} command prints the same information
18940 @subsubheading Example
18945 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
18946 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},
18947 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
18948 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
18949 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@}@}],
18950 current-thread-id="1"
18954 @subheading The @code{-thread-list-ids} Command
18955 @findex -thread-list-ids
18957 @subsubheading Synopsis
18963 Produces a list of the currently known @value{GDBN} thread ids. At the
18964 end of the list it also prints the total number of such threads.
18966 @subsubheading @value{GDBN} Command
18968 Part of @samp{info threads} supplies the same information.
18970 @subsubheading Example
18972 No threads present, besides the main process:
18977 ^done,thread-ids=@{@},number-of-threads="0"
18987 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
18988 number-of-threads="3"
18993 @subheading The @code{-thread-select} Command
18994 @findex -thread-select
18996 @subsubheading Synopsis
18999 -thread-select @var{threadnum}
19002 Make @var{threadnum} the current thread. It prints the number of the new
19003 current thread, and the topmost frame for that thread.
19005 @subsubheading @value{GDBN} Command
19007 The corresponding @value{GDBN} command is @samp{thread}.
19009 @subsubheading Example
19016 *stopped,reason="end-stepping-range",thread-id="2",line="187",
19017 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
19021 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
19022 number-of-threads="3"
19025 ^done,new-thread-id="3",
19026 frame=@{level="0",func="vprintf",
19027 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
19028 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
19032 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19033 @node GDB/MI Program Execution
19034 @section @sc{gdb/mi} Program Execution
19036 These are the asynchronous commands which generate the out-of-band
19037 record @samp{*stopped}. Currently @value{GDBN} only really executes
19038 asynchronously with remote targets and this interaction is mimicked in
19041 @subheading The @code{-exec-continue} Command
19042 @findex -exec-continue
19044 @subsubheading Synopsis
19050 Resumes the execution of the inferior program until a breakpoint is
19051 encountered, or until the inferior exits.
19053 @subsubheading @value{GDBN} Command
19055 The corresponding @value{GDBN} corresponding is @samp{continue}.
19057 @subsubheading Example
19064 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
19065 file="hello.c",fullname="/home/foo/bar/hello.c",line="13"@}
19070 @subheading The @code{-exec-finish} Command
19071 @findex -exec-finish
19073 @subsubheading Synopsis
19079 Resumes the execution of the inferior program until the current
19080 function is exited. Displays the results returned by the function.
19082 @subsubheading @value{GDBN} Command
19084 The corresponding @value{GDBN} command is @samp{finish}.
19086 @subsubheading Example
19088 Function returning @code{void}.
19095 *stopped,reason="function-finished",frame=@{func="main",args=[],
19096 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
19100 Function returning other than @code{void}. The name of the internal
19101 @value{GDBN} variable storing the result is printed, together with the
19108 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
19109 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
19110 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19111 gdb-result-var="$1",return-value="0"
19116 @subheading The @code{-exec-interrupt} Command
19117 @findex -exec-interrupt
19119 @subsubheading Synopsis
19125 Interrupts the background execution of the target. Note how the token
19126 associated with the stop message is the one for the execution command
19127 that has been interrupted. The token for the interrupt itself only
19128 appears in the @samp{^done} output. If the user is trying to
19129 interrupt a non-running program, an error message will be printed.
19131 @subsubheading @value{GDBN} Command
19133 The corresponding @value{GDBN} command is @samp{interrupt}.
19135 @subsubheading Example
19146 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
19147 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
19148 fullname="/home/foo/bar/try.c",line="13"@}
19153 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
19158 @subheading The @code{-exec-next} Command
19161 @subsubheading Synopsis
19167 Resumes execution of the inferior program, stopping when the beginning
19168 of the next source line is reached.
19170 @subsubheading @value{GDBN} Command
19172 The corresponding @value{GDBN} command is @samp{next}.
19174 @subsubheading Example
19180 *stopped,reason="end-stepping-range",line="8",file="hello.c"
19185 @subheading The @code{-exec-next-instruction} Command
19186 @findex -exec-next-instruction
19188 @subsubheading Synopsis
19191 -exec-next-instruction
19194 Executes one machine instruction. If the instruction is a function
19195 call, continues until the function returns. If the program stops at an
19196 instruction in the middle of a source line, the address will be
19199 @subsubheading @value{GDBN} Command
19201 The corresponding @value{GDBN} command is @samp{nexti}.
19203 @subsubheading Example
19207 -exec-next-instruction
19211 *stopped,reason="end-stepping-range",
19212 addr="0x000100d4",line="5",file="hello.c"
19217 @subheading The @code{-exec-return} Command
19218 @findex -exec-return
19220 @subsubheading Synopsis
19226 Makes current function return immediately. Doesn't execute the inferior.
19227 Displays the new current frame.
19229 @subsubheading @value{GDBN} Command
19231 The corresponding @value{GDBN} command is @samp{return}.
19233 @subsubheading Example
19237 200-break-insert callee4
19238 200^done,bkpt=@{number="1",addr="0x00010734",
19239 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
19244 000*stopped,reason="breakpoint-hit",bkptno="1",
19245 frame=@{func="callee4",args=[],
19246 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19247 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
19253 111^done,frame=@{level="0",func="callee3",
19254 args=[@{name="strarg",
19255 value="0x11940 \"A string argument.\""@}],
19256 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19257 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
19262 @subheading The @code{-exec-run} Command
19265 @subsubheading Synopsis
19271 Starts execution of the inferior from the beginning. The inferior
19272 executes until either a breakpoint is encountered or the program
19273 exits. In the latter case the output will include an exit code, if
19274 the program has exited exceptionally.
19276 @subsubheading @value{GDBN} Command
19278 The corresponding @value{GDBN} command is @samp{run}.
19280 @subsubheading Examples
19285 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
19290 *stopped,reason="breakpoint-hit",bkptno="1",
19291 frame=@{func="main",args=[],file="recursive2.c",
19292 fullname="/home/foo/bar/recursive2.c",line="4"@}
19297 Program exited normally:
19305 *stopped,reason="exited-normally"
19310 Program exited exceptionally:
19318 *stopped,reason="exited",exit-code="01"
19322 Another way the program can terminate is if it receives a signal such as
19323 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
19327 *stopped,reason="exited-signalled",signal-name="SIGINT",
19328 signal-meaning="Interrupt"
19332 @c @subheading -exec-signal
19335 @subheading The @code{-exec-step} Command
19338 @subsubheading Synopsis
19344 Resumes execution of the inferior program, stopping when the beginning
19345 of the next source line is reached, if the next source line is not a
19346 function call. If it is, stop at the first instruction of the called
19349 @subsubheading @value{GDBN} Command
19351 The corresponding @value{GDBN} command is @samp{step}.
19353 @subsubheading Example
19355 Stepping into a function:
19361 *stopped,reason="end-stepping-range",
19362 frame=@{func="foo",args=[@{name="a",value="10"@},
19363 @{name="b",value="0"@}],file="recursive2.c",
19364 fullname="/home/foo/bar/recursive2.c",line="11"@}
19374 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
19379 @subheading The @code{-exec-step-instruction} Command
19380 @findex -exec-step-instruction
19382 @subsubheading Synopsis
19385 -exec-step-instruction
19388 Resumes the inferior which executes one machine instruction. The
19389 output, once @value{GDBN} has stopped, will vary depending on whether
19390 we have stopped in the middle of a source line or not. In the former
19391 case, the address at which the program stopped will be printed as
19394 @subsubheading @value{GDBN} Command
19396 The corresponding @value{GDBN} command is @samp{stepi}.
19398 @subsubheading Example
19402 -exec-step-instruction
19406 *stopped,reason="end-stepping-range",
19407 frame=@{func="foo",args=[],file="try.c",
19408 fullname="/home/foo/bar/try.c",line="10"@}
19410 -exec-step-instruction
19414 *stopped,reason="end-stepping-range",
19415 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
19416 fullname="/home/foo/bar/try.c",line="10"@}
19421 @subheading The @code{-exec-until} Command
19422 @findex -exec-until
19424 @subsubheading Synopsis
19427 -exec-until [ @var{location} ]
19430 Executes the inferior until the @var{location} specified in the
19431 argument is reached. If there is no argument, the inferior executes
19432 until a source line greater than the current one is reached. The
19433 reason for stopping in this case will be @samp{location-reached}.
19435 @subsubheading @value{GDBN} Command
19437 The corresponding @value{GDBN} command is @samp{until}.
19439 @subsubheading Example
19443 -exec-until recursive2.c:6
19447 *stopped,reason="location-reached",frame=@{func="main",args=[],
19448 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
19453 @subheading -file-clear
19454 Is this going away????
19457 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19458 @node GDB/MI Stack Manipulation
19459 @section @sc{gdb/mi} Stack Manipulation Commands
19462 @subheading The @code{-stack-info-frame} Command
19463 @findex -stack-info-frame
19465 @subsubheading Synopsis
19471 Get info on the selected frame.
19473 @subsubheading @value{GDBN} Command
19475 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
19476 (without arguments).
19478 @subsubheading Example
19483 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
19484 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19485 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
19489 @subheading The @code{-stack-info-depth} Command
19490 @findex -stack-info-depth
19492 @subsubheading Synopsis
19495 -stack-info-depth [ @var{max-depth} ]
19498 Return the depth of the stack. If the integer argument @var{max-depth}
19499 is specified, do not count beyond @var{max-depth} frames.
19501 @subsubheading @value{GDBN} Command
19503 There's no equivalent @value{GDBN} command.
19505 @subsubheading Example
19507 For a stack with frame levels 0 through 11:
19514 -stack-info-depth 4
19517 -stack-info-depth 12
19520 -stack-info-depth 11
19523 -stack-info-depth 13
19528 @subheading The @code{-stack-list-arguments} Command
19529 @findex -stack-list-arguments
19531 @subsubheading Synopsis
19534 -stack-list-arguments @var{show-values}
19535 [ @var{low-frame} @var{high-frame} ]
19538 Display a list of the arguments for the frames between @var{low-frame}
19539 and @var{high-frame} (inclusive). If @var{low-frame} and
19540 @var{high-frame} are not provided, list the arguments for the whole
19541 call stack. If the two arguments are equal, show the single frame
19542 at the corresponding level. It is an error if @var{low-frame} is
19543 larger than the actual number of frames. On the other hand,
19544 @var{high-frame} may be larger than the actual number of frames, in
19545 which case only existing frames will be returned.
19547 The @var{show-values} argument must have a value of 0 or 1. A value of
19548 0 means that only the names of the arguments are listed, a value of 1
19549 means that both names and values of the arguments are printed.
19551 @subsubheading @value{GDBN} Command
19553 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
19554 @samp{gdb_get_args} command which partially overlaps with the
19555 functionality of @samp{-stack-list-arguments}.
19557 @subsubheading Example
19564 frame=@{level="0",addr="0x00010734",func="callee4",
19565 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19566 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
19567 frame=@{level="1",addr="0x0001076c",func="callee3",
19568 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19569 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
19570 frame=@{level="2",addr="0x0001078c",func="callee2",
19571 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19572 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
19573 frame=@{level="3",addr="0x000107b4",func="callee1",
19574 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19575 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
19576 frame=@{level="4",addr="0x000107e0",func="main",
19577 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19578 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
19580 -stack-list-arguments 0
19583 frame=@{level="0",args=[]@},
19584 frame=@{level="1",args=[name="strarg"]@},
19585 frame=@{level="2",args=[name="intarg",name="strarg"]@},
19586 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
19587 frame=@{level="4",args=[]@}]
19589 -stack-list-arguments 1
19592 frame=@{level="0",args=[]@},
19594 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19595 frame=@{level="2",args=[
19596 @{name="intarg",value="2"@},
19597 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19598 @{frame=@{level="3",args=[
19599 @{name="intarg",value="2"@},
19600 @{name="strarg",value="0x11940 \"A string argument.\""@},
19601 @{name="fltarg",value="3.5"@}]@},
19602 frame=@{level="4",args=[]@}]
19604 -stack-list-arguments 0 2 2
19605 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
19607 -stack-list-arguments 1 2 2
19608 ^done,stack-args=[frame=@{level="2",
19609 args=[@{name="intarg",value="2"@},
19610 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
19614 @c @subheading -stack-list-exception-handlers
19617 @subheading The @code{-stack-list-frames} Command
19618 @findex -stack-list-frames
19620 @subsubheading Synopsis
19623 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
19626 List the frames currently on the stack. For each frame it displays the
19631 The frame number, 0 being the topmost frame, i.e., the innermost function.
19633 The @code{$pc} value for that frame.
19637 File name of the source file where the function lives.
19639 Line number corresponding to the @code{$pc}.
19642 If invoked without arguments, this command prints a backtrace for the
19643 whole stack. If given two integer arguments, it shows the frames whose
19644 levels are between the two arguments (inclusive). If the two arguments
19645 are equal, it shows the single frame at the corresponding level. It is
19646 an error if @var{low-frame} is larger than the actual number of
19647 frames. On the other hand, @var{high-frame} may be larger than the
19648 actual number of frames, in which case only existing frames will be returned.
19650 @subsubheading @value{GDBN} Command
19652 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
19654 @subsubheading Example
19656 Full stack backtrace:
19662 [frame=@{level="0",addr="0x0001076c",func="foo",
19663 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
19664 frame=@{level="1",addr="0x000107a4",func="foo",
19665 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19666 frame=@{level="2",addr="0x000107a4",func="foo",
19667 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19668 frame=@{level="3",addr="0x000107a4",func="foo",
19669 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19670 frame=@{level="4",addr="0x000107a4",func="foo",
19671 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19672 frame=@{level="5",addr="0x000107a4",func="foo",
19673 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19674 frame=@{level="6",addr="0x000107a4",func="foo",
19675 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19676 frame=@{level="7",addr="0x000107a4",func="foo",
19677 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19678 frame=@{level="8",addr="0x000107a4",func="foo",
19679 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19680 frame=@{level="9",addr="0x000107a4",func="foo",
19681 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19682 frame=@{level="10",addr="0x000107a4",func="foo",
19683 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19684 frame=@{level="11",addr="0x00010738",func="main",
19685 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
19689 Show frames between @var{low_frame} and @var{high_frame}:
19693 -stack-list-frames 3 5
19695 [frame=@{level="3",addr="0x000107a4",func="foo",
19696 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19697 frame=@{level="4",addr="0x000107a4",func="foo",
19698 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19699 frame=@{level="5",addr="0x000107a4",func="foo",
19700 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
19704 Show a single frame:
19708 -stack-list-frames 3 3
19710 [frame=@{level="3",addr="0x000107a4",func="foo",
19711 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
19716 @subheading The @code{-stack-list-locals} Command
19717 @findex -stack-list-locals
19719 @subsubheading Synopsis
19722 -stack-list-locals @var{print-values}
19725 Display the local variable names for the selected frame. If
19726 @var{print-values} is 0 or @code{--no-values}, print only the names of
19727 the variables; if it is 1 or @code{--all-values}, print also their
19728 values; and if it is 2 or @code{--simple-values}, print the name,
19729 type and value for simple data types and the name and type for arrays,
19730 structures and unions. In this last case, a frontend can immediately
19731 display the value of simple data types and create variable objects for
19732 other data types when the user wishes to explore their values in
19735 @subsubheading @value{GDBN} Command
19737 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
19739 @subsubheading Example
19743 -stack-list-locals 0
19744 ^done,locals=[name="A",name="B",name="C"]
19746 -stack-list-locals --all-values
19747 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
19748 @{name="C",value="@{1, 2, 3@}"@}]
19749 -stack-list-locals --simple-values
19750 ^done,locals=[@{name="A",type="int",value="1"@},
19751 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
19756 @subheading The @code{-stack-select-frame} Command
19757 @findex -stack-select-frame
19759 @subsubheading Synopsis
19762 -stack-select-frame @var{framenum}
19765 Change the selected frame. Select a different frame @var{framenum} on
19768 @subsubheading @value{GDBN} Command
19770 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
19771 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
19773 @subsubheading Example
19777 -stack-select-frame 2
19782 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19783 @node GDB/MI Variable Objects
19784 @section @sc{gdb/mi} Variable Objects
19788 @subheading Motivation for Variable Objects in @sc{gdb/mi}
19790 For the implementation of a variable debugger window (locals, watched
19791 expressions, etc.), we are proposing the adaptation of the existing code
19792 used by @code{Insight}.
19794 The two main reasons for that are:
19798 It has been proven in practice (it is already on its second generation).
19801 It will shorten development time (needless to say how important it is
19805 The original interface was designed to be used by Tcl code, so it was
19806 slightly changed so it could be used through @sc{gdb/mi}. This section
19807 describes the @sc{gdb/mi} operations that will be available and gives some
19808 hints about their use.
19810 @emph{Note}: In addition to the set of operations described here, we
19811 expect the @sc{gui} implementation of a variable window to require, at
19812 least, the following operations:
19815 @item @code{-gdb-show} @code{output-radix}
19816 @item @code{-stack-list-arguments}
19817 @item @code{-stack-list-locals}
19818 @item @code{-stack-select-frame}
19823 @subheading Introduction to Variable Objects
19825 @cindex variable objects in @sc{gdb/mi}
19827 Variable objects are "object-oriented" MI interface for examining and
19828 changing values of expressions. Unlike some other MI interfaces that
19829 work with expressions, variable objects are specifically designed for
19830 simple and efficient presentation in the frontend. A variable object
19831 is identified by string name. When a variable object is created, the
19832 frontend specifies the expression for that variable object. The
19833 expression can be a simple variable, or it can be an arbitrary complex
19834 expression, and can even involve CPU registers. After creating a
19835 variable object, the frontend can invoke other variable object
19836 operations---for example to obtain or change the value of a variable
19837 object, or to change display format.
19839 Variable objects have hierarchical tree structure. Any variable object
19840 that corresponds to a composite type, such as structure in C, has
19841 a number of child variable objects, for example corresponding to each
19842 element of a structure. A child variable object can itself have
19843 children, recursively. Recursion ends when we reach
19844 leaf variable objects, which always have built-in types. Child variable
19845 objects are created only by explicit request, so if a frontend
19846 is not interested in the children of a particular variable object, no
19847 child will be created.
19849 For a leaf variable object it is possible to obtain its value as a
19850 string, or set the value from a string. String value can be also
19851 obtained for a non-leaf variable object, but it's generally a string
19852 that only indicates the type of the object, and does not list its
19853 contents. Assignment to a non-leaf variable object is not allowed.
19855 A frontend does not need to read the values of all variable objects each time
19856 the program stops. Instead, MI provides an update command that lists all
19857 variable objects whose values has changed since the last update
19858 operation. This considerably reduces the amount of data that must
19859 be transferred to the frontend. As noted above, children variable
19860 objects are created on demand, and only leaf variable objects have a
19861 real value. As result, gdb will read target memory only for leaf
19862 variables that frontend has created.
19864 The automatic update is not always desirable. For example, a frontend
19865 might want to keep a value of some expression for future reference,
19866 and never update it. For another example, fetching memory is
19867 relatively slow for embedded targets, so a frontend might want
19868 to disable automatic update for the variables that are either not
19869 visible on the screen, or ``closed''. This is possible using so
19870 called ``frozen variable objects''. Such variable objects are never
19871 implicitly updated.
19873 The following is the complete set of @sc{gdb/mi} operations defined to
19874 access this functionality:
19876 @multitable @columnfractions .4 .6
19877 @item @strong{Operation}
19878 @tab @strong{Description}
19880 @item @code{-var-create}
19881 @tab create a variable object
19882 @item @code{-var-delete}
19883 @tab delete the variable object and/or its children
19884 @item @code{-var-set-format}
19885 @tab set the display format of this variable
19886 @item @code{-var-show-format}
19887 @tab show the display format of this variable
19888 @item @code{-var-info-num-children}
19889 @tab tells how many children this object has
19890 @item @code{-var-list-children}
19891 @tab return a list of the object's children
19892 @item @code{-var-info-type}
19893 @tab show the type of this variable object
19894 @item @code{-var-info-expression}
19895 @tab print parent-relative expression that this variable object represents
19896 @item @code{-var-info-path-expression}
19897 @tab print full expression that this variable object represents
19898 @item @code{-var-show-attributes}
19899 @tab is this variable editable? does it exist here?
19900 @item @code{-var-evaluate-expression}
19901 @tab get the value of this variable
19902 @item @code{-var-assign}
19903 @tab set the value of this variable
19904 @item @code{-var-update}
19905 @tab update the variable and its children
19906 @item @code{-var-set-frozen}
19907 @tab set frozeness attribute
19910 In the next subsection we describe each operation in detail and suggest
19911 how it can be used.
19913 @subheading Description And Use of Operations on Variable Objects
19915 @subheading The @code{-var-create} Command
19916 @findex -var-create
19918 @subsubheading Synopsis
19921 -var-create @{@var{name} | "-"@}
19922 @{@var{frame-addr} | "*"@} @var{expression}
19925 This operation creates a variable object, which allows the monitoring of
19926 a variable, the result of an expression, a memory cell or a CPU
19929 The @var{name} parameter is the string by which the object can be
19930 referenced. It must be unique. If @samp{-} is specified, the varobj
19931 system will generate a string ``varNNNNNN'' automatically. It will be
19932 unique provided that one does not specify @var{name} on that format.
19933 The command fails if a duplicate name is found.
19935 The frame under which the expression should be evaluated can be
19936 specified by @var{frame-addr}. A @samp{*} indicates that the current
19937 frame should be used.
19939 @var{expression} is any expression valid on the current language set (must not
19940 begin with a @samp{*}), or one of the following:
19944 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
19947 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
19950 @samp{$@var{regname}} --- a CPU register name
19953 @subsubheading Result
19955 This operation returns the name, number of children and the type of the
19956 object created. Type is returned as a string as the ones generated by
19957 the @value{GDBN} CLI:
19960 name="@var{name}",numchild="N",type="@var{type}"
19964 @subheading The @code{-var-delete} Command
19965 @findex -var-delete
19967 @subsubheading Synopsis
19970 -var-delete [ -c ] @var{name}
19973 Deletes a previously created variable object and all of its children.
19974 With the @samp{-c} option, just deletes the children.
19976 Returns an error if the object @var{name} is not found.
19979 @subheading The @code{-var-set-format} Command
19980 @findex -var-set-format
19982 @subsubheading Synopsis
19985 -var-set-format @var{name} @var{format-spec}
19988 Sets the output format for the value of the object @var{name} to be
19991 The syntax for the @var{format-spec} is as follows:
19994 @var{format-spec} @expansion{}
19995 @{binary | decimal | hexadecimal | octal | natural@}
19998 The natural format is the default format choosen automatically
19999 based on the variable type (like decimal for an @code{int}, hex
20000 for pointers, etc.).
20002 For a variable with children, the format is set only on the
20003 variable itself, and the children are not affected.
20005 @subheading The @code{-var-show-format} Command
20006 @findex -var-show-format
20008 @subsubheading Synopsis
20011 -var-show-format @var{name}
20014 Returns the format used to display the value of the object @var{name}.
20017 @var{format} @expansion{}
20022 @subheading The @code{-var-info-num-children} Command
20023 @findex -var-info-num-children
20025 @subsubheading Synopsis
20028 -var-info-num-children @var{name}
20031 Returns the number of children of a variable object @var{name}:
20038 @subheading The @code{-var-list-children} Command
20039 @findex -var-list-children
20041 @subsubheading Synopsis
20044 -var-list-children [@var{print-values}] @var{name}
20046 @anchor{-var-list-children}
20048 Return a list of the children of the specified variable object and
20049 create variable objects for them, if they do not already exist. With
20050 a single argument or if @var{print-values} has a value for of 0 or
20051 @code{--no-values}, print only the names of the variables; if
20052 @var{print-values} is 1 or @code{--all-values}, also print their
20053 values; and if it is 2 or @code{--simple-values} print the name and
20054 value for simple data types and just the name for arrays, structures
20057 @subsubheading Example
20061 -var-list-children n
20062 ^done,numchild=@var{n},children=[@{name=@var{name},
20063 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
20065 -var-list-children --all-values n
20066 ^done,numchild=@var{n},children=[@{name=@var{name},
20067 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
20071 @subheading The @code{-var-info-type} Command
20072 @findex -var-info-type
20074 @subsubheading Synopsis
20077 -var-info-type @var{name}
20080 Returns the type of the specified variable @var{name}. The type is
20081 returned as a string in the same format as it is output by the
20085 type=@var{typename}
20089 @subheading The @code{-var-info-expression} Command
20090 @findex -var-info-expression
20092 @subsubheading Synopsis
20095 -var-info-expression @var{name}
20098 Returns a string that is suitable for presenting this
20099 variable object in user interface. The string is generally
20100 not valid expression in the current language, and cannot be evaluated.
20102 For example, if @code{a} is an array, and variable object
20103 @code{A} was created for @code{a}, then we'll get this output:
20106 (gdb) -var-info-expression A.1
20107 ^done,lang="C",exp="1"
20111 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
20113 Note that the output of the @code{-var-list-children} command also
20114 includes those expressions, so the @code{-var-info-expression} command
20117 @subheading The @code{-var-info-path-expression} Command
20118 @findex -var-info-path-expression
20120 @subsubheading Synopsis
20123 -var-info-path-expression @var{name}
20126 Returns an expression that can be evaluated in the current
20127 context and will yield the same value that a variable object has.
20128 Compare this with the @code{-var-info-expression} command, which
20129 result can be used only for UI presentation. Typical use of
20130 the @code{-var-info-path-expression} command is creating a
20131 watchpoint from a variable object.
20133 For example, suppose @code{C} is a C@t{++} class, derived from class
20134 @code{Base}, and that the @code{Base} class has a member called
20135 @code{m_size}. Assume a variable @code{c} is has the type of
20136 @code{C} and a variable object @code{C} was created for variable
20137 @code{c}. Then, we'll get this output:
20139 (gdb) -var-info-path-expression C.Base.public.m_size
20140 ^done,path_expr=((Base)c).m_size)
20143 @subheading The @code{-var-show-attributes} Command
20144 @findex -var-show-attributes
20146 @subsubheading Synopsis
20149 -var-show-attributes @var{name}
20152 List attributes of the specified variable object @var{name}:
20155 status=@var{attr} [ ( ,@var{attr} )* ]
20159 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
20161 @subheading The @code{-var-evaluate-expression} Command
20162 @findex -var-evaluate-expression
20164 @subsubheading Synopsis
20167 -var-evaluate-expression @var{name}
20170 Evaluates the expression that is represented by the specified variable
20171 object and returns its value as a string. The format of the
20172 string can be changed using the @code{-var-set-format} command.
20178 Note that one must invoke @code{-var-list-children} for a variable
20179 before the value of a child variable can be evaluated.
20181 @subheading The @code{-var-assign} Command
20182 @findex -var-assign
20184 @subsubheading Synopsis
20187 -var-assign @var{name} @var{expression}
20190 Assigns the value of @var{expression} to the variable object specified
20191 by @var{name}. The object must be @samp{editable}. If the variable's
20192 value is altered by the assign, the variable will show up in any
20193 subsequent @code{-var-update} list.
20195 @subsubheading Example
20203 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
20207 @subheading The @code{-var-update} Command
20208 @findex -var-update
20210 @subsubheading Synopsis
20213 -var-update [@var{print-values}] @{@var{name} | "*"@}
20216 Reevaluate the expressions corresponding to the variable object
20217 @var{name} and all its direct and indirect children, and return the
20218 list of variable objects whose values have changed; @var{name} must
20219 be a root variable object. Here, ``changed'' means that the result of
20220 @code{-var-evaluate-expression} before and after the
20221 @code{-var-update} is different. If @samp{*} is used as the variable
20222 object names, all existing variable objects are updated, except
20223 for frozen ones (@pxref{-var-set-frozen}). The option
20224 @var{print-values} determines whether both names and values, or just
20225 names are printed. The possible values of this options are the same
20226 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
20227 recommended to use the @samp{--all-values} option, to reduce the
20228 number of MI commands needed on each program stop.
20231 @subsubheading Example
20238 -var-update --all-values var1
20239 ^done,changelist=[@{name="var1",value="3",in_scope="true",
20240 type_changed="false"@}]
20244 @anchor{-var-update}
20245 The field in_scope may take three values:
20249 The variable object's current value is valid.
20252 The variable object does not currently hold a valid value but it may
20253 hold one in the future if its associated expression comes back into
20257 The variable object no longer holds a valid value.
20258 This can occur when the executable file being debugged has changed,
20259 either through recompilation or by using the @value{GDBN} @code{file}
20260 command. The front end should normally choose to delete these variable
20264 In the future new values may be added to this list so the front should
20265 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
20267 @subheading The @code{-var-set-frozen} Command
20268 @findex -var-set-frozen
20269 @anchor{-var-set-frozen}
20271 @subsubheading Synopsis
20274 -var-set-frozen @var{name} @var{flag}
20277 Set the frozenness flag on the variable object @var{name}. The
20278 @var{flag} parameter should be either @samp{1} to make the variable
20279 frozen or @samp{0} to make it unfrozen. If a variable object is
20280 frozen, then neither itself, nor any of its children, are
20281 implicitly updated by @code{-var-update} of
20282 a parent variable or by @code{-var-update *}. Only
20283 @code{-var-update} of the variable itself will update its value and
20284 values of its children. After a variable object is unfrozen, it is
20285 implicitly updated by all subsequent @code{-var-update} operations.
20286 Unfreezing a variable does not update it, only subsequent
20287 @code{-var-update} does.
20289 @subsubheading Example
20293 -var-set-frozen V 1
20299 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20300 @node GDB/MI Data Manipulation
20301 @section @sc{gdb/mi} Data Manipulation
20303 @cindex data manipulation, in @sc{gdb/mi}
20304 @cindex @sc{gdb/mi}, data manipulation
20305 This section describes the @sc{gdb/mi} commands that manipulate data:
20306 examine memory and registers, evaluate expressions, etc.
20308 @c REMOVED FROM THE INTERFACE.
20309 @c @subheading -data-assign
20310 @c Change the value of a program variable. Plenty of side effects.
20311 @c @subsubheading GDB Command
20313 @c @subsubheading Example
20316 @subheading The @code{-data-disassemble} Command
20317 @findex -data-disassemble
20319 @subsubheading Synopsis
20323 [ -s @var{start-addr} -e @var{end-addr} ]
20324 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
20332 @item @var{start-addr}
20333 is the beginning address (or @code{$pc})
20334 @item @var{end-addr}
20336 @item @var{filename}
20337 is the name of the file to disassemble
20338 @item @var{linenum}
20339 is the line number to disassemble around
20341 is the number of disassembly lines to be produced. If it is -1,
20342 the whole function will be disassembled, in case no @var{end-addr} is
20343 specified. If @var{end-addr} is specified as a non-zero value, and
20344 @var{lines} is lower than the number of disassembly lines between
20345 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
20346 displayed; if @var{lines} is higher than the number of lines between
20347 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
20350 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
20354 @subsubheading Result
20356 The output for each instruction is composed of four fields:
20365 Note that whatever included in the instruction field, is not manipulated
20366 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
20368 @subsubheading @value{GDBN} Command
20370 There's no direct mapping from this command to the CLI.
20372 @subsubheading Example
20374 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
20378 -data-disassemble -s $pc -e "$pc + 20" -- 0
20381 @{address="0x000107c0",func-name="main",offset="4",
20382 inst="mov 2, %o0"@},
20383 @{address="0x000107c4",func-name="main",offset="8",
20384 inst="sethi %hi(0x11800), %o2"@},
20385 @{address="0x000107c8",func-name="main",offset="12",
20386 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
20387 @{address="0x000107cc",func-name="main",offset="16",
20388 inst="sethi %hi(0x11800), %o2"@},
20389 @{address="0x000107d0",func-name="main",offset="20",
20390 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
20394 Disassemble the whole @code{main} function. Line 32 is part of
20398 -data-disassemble -f basics.c -l 32 -- 0
20400 @{address="0x000107bc",func-name="main",offset="0",
20401 inst="save %sp, -112, %sp"@},
20402 @{address="0x000107c0",func-name="main",offset="4",
20403 inst="mov 2, %o0"@},
20404 @{address="0x000107c4",func-name="main",offset="8",
20405 inst="sethi %hi(0x11800), %o2"@},
20407 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
20408 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
20412 Disassemble 3 instructions from the start of @code{main}:
20416 -data-disassemble -f basics.c -l 32 -n 3 -- 0
20418 @{address="0x000107bc",func-name="main",offset="0",
20419 inst="save %sp, -112, %sp"@},
20420 @{address="0x000107c0",func-name="main",offset="4",
20421 inst="mov 2, %o0"@},
20422 @{address="0x000107c4",func-name="main",offset="8",
20423 inst="sethi %hi(0x11800), %o2"@}]
20427 Disassemble 3 instructions from the start of @code{main} in mixed mode:
20431 -data-disassemble -f basics.c -l 32 -n 3 -- 1
20433 src_and_asm_line=@{line="31",
20434 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
20435 testsuite/gdb.mi/basics.c",line_asm_insn=[
20436 @{address="0x000107bc",func-name="main",offset="0",
20437 inst="save %sp, -112, %sp"@}]@},
20438 src_and_asm_line=@{line="32",
20439 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
20440 testsuite/gdb.mi/basics.c",line_asm_insn=[
20441 @{address="0x000107c0",func-name="main",offset="4",
20442 inst="mov 2, %o0"@},
20443 @{address="0x000107c4",func-name="main",offset="8",
20444 inst="sethi %hi(0x11800), %o2"@}]@}]
20449 @subheading The @code{-data-evaluate-expression} Command
20450 @findex -data-evaluate-expression
20452 @subsubheading Synopsis
20455 -data-evaluate-expression @var{expr}
20458 Evaluate @var{expr} as an expression. The expression could contain an
20459 inferior function call. The function call will execute synchronously.
20460 If the expression contains spaces, it must be enclosed in double quotes.
20462 @subsubheading @value{GDBN} Command
20464 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
20465 @samp{call}. In @code{gdbtk} only, there's a corresponding
20466 @samp{gdb_eval} command.
20468 @subsubheading Example
20470 In the following example, the numbers that precede the commands are the
20471 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
20472 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
20476 211-data-evaluate-expression A
20479 311-data-evaluate-expression &A
20480 311^done,value="0xefffeb7c"
20482 411-data-evaluate-expression A+3
20485 511-data-evaluate-expression "A + 3"
20491 @subheading The @code{-data-list-changed-registers} Command
20492 @findex -data-list-changed-registers
20494 @subsubheading Synopsis
20497 -data-list-changed-registers
20500 Display a list of the registers that have changed.
20502 @subsubheading @value{GDBN} Command
20504 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
20505 has the corresponding command @samp{gdb_changed_register_list}.
20507 @subsubheading Example
20509 On a PPC MBX board:
20517 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
20518 args=[],file="try.c",fullname="/home/foo/bar/try.c",line="5"@}
20520 -data-list-changed-registers
20521 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
20522 "10","11","13","14","15","16","17","18","19","20","21","22","23",
20523 "24","25","26","27","28","30","31","64","65","66","67","69"]
20528 @subheading The @code{-data-list-register-names} Command
20529 @findex -data-list-register-names
20531 @subsubheading Synopsis
20534 -data-list-register-names [ ( @var{regno} )+ ]
20537 Show a list of register names for the current target. If no arguments
20538 are given, it shows a list of the names of all the registers. If
20539 integer numbers are given as arguments, it will print a list of the
20540 names of the registers corresponding to the arguments. To ensure
20541 consistency between a register name and its number, the output list may
20542 include empty register names.
20544 @subsubheading @value{GDBN} Command
20546 @value{GDBN} does not have a command which corresponds to
20547 @samp{-data-list-register-names}. In @code{gdbtk} there is a
20548 corresponding command @samp{gdb_regnames}.
20550 @subsubheading Example
20552 For the PPC MBX board:
20555 -data-list-register-names
20556 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
20557 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
20558 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
20559 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
20560 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
20561 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
20562 "", "pc","ps","cr","lr","ctr","xer"]
20564 -data-list-register-names 1 2 3
20565 ^done,register-names=["r1","r2","r3"]
20569 @subheading The @code{-data-list-register-values} Command
20570 @findex -data-list-register-values
20572 @subsubheading Synopsis
20575 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
20578 Display the registers' contents. @var{fmt} is the format according to
20579 which the registers' contents are to be returned, followed by an optional
20580 list of numbers specifying the registers to display. A missing list of
20581 numbers indicates that the contents of all the registers must be returned.
20583 Allowed formats for @var{fmt} are:
20600 @subsubheading @value{GDBN} Command
20602 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
20603 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
20605 @subsubheading Example
20607 For a PPC MBX board (note: line breaks are for readability only, they
20608 don't appear in the actual output):
20612 -data-list-register-values r 64 65
20613 ^done,register-values=[@{number="64",value="0xfe00a300"@},
20614 @{number="65",value="0x00029002"@}]
20616 -data-list-register-values x
20617 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
20618 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
20619 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
20620 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
20621 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
20622 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
20623 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
20624 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
20625 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
20626 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
20627 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
20628 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
20629 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
20630 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
20631 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
20632 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
20633 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
20634 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
20635 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
20636 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
20637 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
20638 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
20639 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
20640 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
20641 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
20642 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
20643 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
20644 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
20645 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
20646 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
20647 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
20648 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
20649 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
20650 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
20651 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
20652 @{number="69",value="0x20002b03"@}]
20657 @subheading The @code{-data-read-memory} Command
20658 @findex -data-read-memory
20660 @subsubheading Synopsis
20663 -data-read-memory [ -o @var{byte-offset} ]
20664 @var{address} @var{word-format} @var{word-size}
20665 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
20672 @item @var{address}
20673 An expression specifying the address of the first memory word to be
20674 read. Complex expressions containing embedded white space should be
20675 quoted using the C convention.
20677 @item @var{word-format}
20678 The format to be used to print the memory words. The notation is the
20679 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
20682 @item @var{word-size}
20683 The size of each memory word in bytes.
20685 @item @var{nr-rows}
20686 The number of rows in the output table.
20688 @item @var{nr-cols}
20689 The number of columns in the output table.
20692 If present, indicates that each row should include an @sc{ascii} dump. The
20693 value of @var{aschar} is used as a padding character when a byte is not a
20694 member of the printable @sc{ascii} character set (printable @sc{ascii}
20695 characters are those whose code is between 32 and 126, inclusively).
20697 @item @var{byte-offset}
20698 An offset to add to the @var{address} before fetching memory.
20701 This command displays memory contents as a table of @var{nr-rows} by
20702 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
20703 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
20704 (returned as @samp{total-bytes}). Should less than the requested number
20705 of bytes be returned by the target, the missing words are identified
20706 using @samp{N/A}. The number of bytes read from the target is returned
20707 in @samp{nr-bytes} and the starting address used to read memory in
20710 The address of the next/previous row or page is available in
20711 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
20714 @subsubheading @value{GDBN} Command
20716 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
20717 @samp{gdb_get_mem} memory read command.
20719 @subsubheading Example
20721 Read six bytes of memory starting at @code{bytes+6} but then offset by
20722 @code{-6} bytes. Format as three rows of two columns. One byte per
20723 word. Display each word in hex.
20727 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
20728 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
20729 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
20730 prev-page="0x0000138a",memory=[
20731 @{addr="0x00001390",data=["0x00","0x01"]@},
20732 @{addr="0x00001392",data=["0x02","0x03"]@},
20733 @{addr="0x00001394",data=["0x04","0x05"]@}]
20737 Read two bytes of memory starting at address @code{shorts + 64} and
20738 display as a single word formatted in decimal.
20742 5-data-read-memory shorts+64 d 2 1 1
20743 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
20744 next-row="0x00001512",prev-row="0x0000150e",
20745 next-page="0x00001512",prev-page="0x0000150e",memory=[
20746 @{addr="0x00001510",data=["128"]@}]
20750 Read thirty two bytes of memory starting at @code{bytes+16} and format
20751 as eight rows of four columns. Include a string encoding with @samp{x}
20752 used as the non-printable character.
20756 4-data-read-memory bytes+16 x 1 8 4 x
20757 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
20758 next-row="0x000013c0",prev-row="0x0000139c",
20759 next-page="0x000013c0",prev-page="0x00001380",memory=[
20760 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
20761 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
20762 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
20763 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
20764 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
20765 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
20766 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
20767 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
20771 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20772 @node GDB/MI Tracepoint Commands
20773 @section @sc{gdb/mi} Tracepoint Commands
20775 The tracepoint commands are not yet implemented.
20777 @c @subheading -trace-actions
20779 @c @subheading -trace-delete
20781 @c @subheading -trace-disable
20783 @c @subheading -trace-dump
20785 @c @subheading -trace-enable
20787 @c @subheading -trace-exists
20789 @c @subheading -trace-find
20791 @c @subheading -trace-frame-number
20793 @c @subheading -trace-info
20795 @c @subheading -trace-insert
20797 @c @subheading -trace-list
20799 @c @subheading -trace-pass-count
20801 @c @subheading -trace-save
20803 @c @subheading -trace-start
20805 @c @subheading -trace-stop
20808 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20809 @node GDB/MI Symbol Query
20810 @section @sc{gdb/mi} Symbol Query Commands
20813 @subheading The @code{-symbol-info-address} Command
20814 @findex -symbol-info-address
20816 @subsubheading Synopsis
20819 -symbol-info-address @var{symbol}
20822 Describe where @var{symbol} is stored.
20824 @subsubheading @value{GDBN} Command
20826 The corresponding @value{GDBN} command is @samp{info address}.
20828 @subsubheading Example
20832 @subheading The @code{-symbol-info-file} Command
20833 @findex -symbol-info-file
20835 @subsubheading Synopsis
20841 Show the file for the symbol.
20843 @subsubheading @value{GDBN} Command
20845 There's no equivalent @value{GDBN} command. @code{gdbtk} has
20846 @samp{gdb_find_file}.
20848 @subsubheading Example
20852 @subheading The @code{-symbol-info-function} Command
20853 @findex -symbol-info-function
20855 @subsubheading Synopsis
20858 -symbol-info-function
20861 Show which function the symbol lives in.
20863 @subsubheading @value{GDBN} Command
20865 @samp{gdb_get_function} in @code{gdbtk}.
20867 @subsubheading Example
20871 @subheading The @code{-symbol-info-line} Command
20872 @findex -symbol-info-line
20874 @subsubheading Synopsis
20880 Show the core addresses of the code for a source line.
20882 @subsubheading @value{GDBN} Command
20884 The corresponding @value{GDBN} command is @samp{info line}.
20885 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
20887 @subsubheading Example
20891 @subheading The @code{-symbol-info-symbol} Command
20892 @findex -symbol-info-symbol
20894 @subsubheading Synopsis
20897 -symbol-info-symbol @var{addr}
20900 Describe what symbol is at location @var{addr}.
20902 @subsubheading @value{GDBN} Command
20904 The corresponding @value{GDBN} command is @samp{info symbol}.
20906 @subsubheading Example
20910 @subheading The @code{-symbol-list-functions} Command
20911 @findex -symbol-list-functions
20913 @subsubheading Synopsis
20916 -symbol-list-functions
20919 List the functions in the executable.
20921 @subsubheading @value{GDBN} Command
20923 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
20924 @samp{gdb_search} in @code{gdbtk}.
20926 @subsubheading Example
20930 @subheading The @code{-symbol-list-lines} Command
20931 @findex -symbol-list-lines
20933 @subsubheading Synopsis
20936 -symbol-list-lines @var{filename}
20939 Print the list of lines that contain code and their associated program
20940 addresses for the given source filename. The entries are sorted in
20941 ascending PC order.
20943 @subsubheading @value{GDBN} Command
20945 There is no corresponding @value{GDBN} command.
20947 @subsubheading Example
20950 -symbol-list-lines basics.c
20951 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
20956 @subheading The @code{-symbol-list-types} Command
20957 @findex -symbol-list-types
20959 @subsubheading Synopsis
20965 List all the type names.
20967 @subsubheading @value{GDBN} Command
20969 The corresponding commands are @samp{info types} in @value{GDBN},
20970 @samp{gdb_search} in @code{gdbtk}.
20972 @subsubheading Example
20976 @subheading The @code{-symbol-list-variables} Command
20977 @findex -symbol-list-variables
20979 @subsubheading Synopsis
20982 -symbol-list-variables
20985 List all the global and static variable names.
20987 @subsubheading @value{GDBN} Command
20989 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
20991 @subsubheading Example
20995 @subheading The @code{-symbol-locate} Command
20996 @findex -symbol-locate
20998 @subsubheading Synopsis
21004 @subsubheading @value{GDBN} Command
21006 @samp{gdb_loc} in @code{gdbtk}.
21008 @subsubheading Example
21012 @subheading The @code{-symbol-type} Command
21013 @findex -symbol-type
21015 @subsubheading Synopsis
21018 -symbol-type @var{variable}
21021 Show type of @var{variable}.
21023 @subsubheading @value{GDBN} Command
21025 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
21026 @samp{gdb_obj_variable}.
21028 @subsubheading Example
21032 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21033 @node GDB/MI File Commands
21034 @section @sc{gdb/mi} File Commands
21036 This section describes the GDB/MI commands to specify executable file names
21037 and to read in and obtain symbol table information.
21039 @subheading The @code{-file-exec-and-symbols} Command
21040 @findex -file-exec-and-symbols
21042 @subsubheading Synopsis
21045 -file-exec-and-symbols @var{file}
21048 Specify the executable file to be debugged. This file is the one from
21049 which the symbol table is also read. If no file is specified, the
21050 command clears the executable and symbol information. If breakpoints
21051 are set when using this command with no arguments, @value{GDBN} will produce
21052 error messages. Otherwise, no output is produced, except a completion
21055 @subsubheading @value{GDBN} Command
21057 The corresponding @value{GDBN} command is @samp{file}.
21059 @subsubheading Example
21063 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
21069 @subheading The @code{-file-exec-file} Command
21070 @findex -file-exec-file
21072 @subsubheading Synopsis
21075 -file-exec-file @var{file}
21078 Specify the executable file to be debugged. Unlike
21079 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
21080 from this file. If used without argument, @value{GDBN} clears the information
21081 about the executable file. No output is produced, except a completion
21084 @subsubheading @value{GDBN} Command
21086 The corresponding @value{GDBN} command is @samp{exec-file}.
21088 @subsubheading Example
21092 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
21098 @subheading The @code{-file-list-exec-sections} Command
21099 @findex -file-list-exec-sections
21101 @subsubheading Synopsis
21104 -file-list-exec-sections
21107 List the sections of the current executable file.
21109 @subsubheading @value{GDBN} Command
21111 The @value{GDBN} command @samp{info file} shows, among the rest, the same
21112 information as this command. @code{gdbtk} has a corresponding command
21113 @samp{gdb_load_info}.
21115 @subsubheading Example
21119 @subheading The @code{-file-list-exec-source-file} Command
21120 @findex -file-list-exec-source-file
21122 @subsubheading Synopsis
21125 -file-list-exec-source-file
21128 List the line number, the current source file, and the absolute path
21129 to the current source file for the current executable. The macro
21130 information field has a value of @samp{1} or @samp{0} depending on
21131 whether or not the file includes preprocessor macro information.
21133 @subsubheading @value{GDBN} Command
21135 The @value{GDBN} equivalent is @samp{info source}
21137 @subsubheading Example
21141 123-file-list-exec-source-file
21142 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
21147 @subheading The @code{-file-list-exec-source-files} Command
21148 @findex -file-list-exec-source-files
21150 @subsubheading Synopsis
21153 -file-list-exec-source-files
21156 List the source files for the current executable.
21158 It will always output the filename, but only when @value{GDBN} can find
21159 the absolute file name of a source file, will it output the fullname.
21161 @subsubheading @value{GDBN} Command
21163 The @value{GDBN} equivalent is @samp{info sources}.
21164 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
21166 @subsubheading Example
21169 -file-list-exec-source-files
21171 @{file=foo.c,fullname=/home/foo.c@},
21172 @{file=/home/bar.c,fullname=/home/bar.c@},
21173 @{file=gdb_could_not_find_fullpath.c@}]
21177 @subheading The @code{-file-list-shared-libraries} Command
21178 @findex -file-list-shared-libraries
21180 @subsubheading Synopsis
21183 -file-list-shared-libraries
21186 List the shared libraries in the program.
21188 @subsubheading @value{GDBN} Command
21190 The corresponding @value{GDBN} command is @samp{info shared}.
21192 @subsubheading Example
21196 @subheading The @code{-file-list-symbol-files} Command
21197 @findex -file-list-symbol-files
21199 @subsubheading Synopsis
21202 -file-list-symbol-files
21207 @subsubheading @value{GDBN} Command
21209 The corresponding @value{GDBN} command is @samp{info file} (part of it).
21211 @subsubheading Example
21215 @subheading The @code{-file-symbol-file} Command
21216 @findex -file-symbol-file
21218 @subsubheading Synopsis
21221 -file-symbol-file @var{file}
21224 Read symbol table info from the specified @var{file} argument. When
21225 used without arguments, clears @value{GDBN}'s symbol table info. No output is
21226 produced, except for a completion notification.
21228 @subsubheading @value{GDBN} Command
21230 The corresponding @value{GDBN} command is @samp{symbol-file}.
21232 @subsubheading Example
21236 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
21242 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21243 @node GDB/MI Memory Overlay Commands
21244 @section @sc{gdb/mi} Memory Overlay Commands
21246 The memory overlay commands are not implemented.
21248 @c @subheading -overlay-auto
21250 @c @subheading -overlay-list-mapping-state
21252 @c @subheading -overlay-list-overlays
21254 @c @subheading -overlay-map
21256 @c @subheading -overlay-off
21258 @c @subheading -overlay-on
21260 @c @subheading -overlay-unmap
21262 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21263 @node GDB/MI Signal Handling Commands
21264 @section @sc{gdb/mi} Signal Handling Commands
21266 Signal handling commands are not implemented.
21268 @c @subheading -signal-handle
21270 @c @subheading -signal-list-handle-actions
21272 @c @subheading -signal-list-signal-types
21276 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21277 @node GDB/MI Target Manipulation
21278 @section @sc{gdb/mi} Target Manipulation Commands
21281 @subheading The @code{-target-attach} Command
21282 @findex -target-attach
21284 @subsubheading Synopsis
21287 -target-attach @var{pid} | @var{file}
21290 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
21292 @subsubheading @value{GDBN} Command
21294 The corresponding @value{GDBN} command is @samp{attach}.
21296 @subsubheading Example
21300 @subheading The @code{-target-compare-sections} Command
21301 @findex -target-compare-sections
21303 @subsubheading Synopsis
21306 -target-compare-sections [ @var{section} ]
21309 Compare data of section @var{section} on target to the exec file.
21310 Without the argument, all sections are compared.
21312 @subsubheading @value{GDBN} Command
21314 The @value{GDBN} equivalent is @samp{compare-sections}.
21316 @subsubheading Example
21320 @subheading The @code{-target-detach} Command
21321 @findex -target-detach
21323 @subsubheading Synopsis
21329 Detach from the remote target which normally resumes its execution.
21332 @subsubheading @value{GDBN} Command
21334 The corresponding @value{GDBN} command is @samp{detach}.
21336 @subsubheading Example
21346 @subheading The @code{-target-disconnect} Command
21347 @findex -target-disconnect
21349 @subsubheading Synopsis
21355 Disconnect from the remote target. There's no output and the target is
21356 generally not resumed.
21358 @subsubheading @value{GDBN} Command
21360 The corresponding @value{GDBN} command is @samp{disconnect}.
21362 @subsubheading Example
21372 @subheading The @code{-target-download} Command
21373 @findex -target-download
21375 @subsubheading Synopsis
21381 Loads the executable onto the remote target.
21382 It prints out an update message every half second, which includes the fields:
21386 The name of the section.
21388 The size of what has been sent so far for that section.
21390 The size of the section.
21392 The total size of what was sent so far (the current and the previous sections).
21394 The size of the overall executable to download.
21398 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
21399 @sc{gdb/mi} Output Syntax}).
21401 In addition, it prints the name and size of the sections, as they are
21402 downloaded. These messages include the following fields:
21406 The name of the section.
21408 The size of the section.
21410 The size of the overall executable to download.
21414 At the end, a summary is printed.
21416 @subsubheading @value{GDBN} Command
21418 The corresponding @value{GDBN} command is @samp{load}.
21420 @subsubheading Example
21422 Note: each status message appears on a single line. Here the messages
21423 have been broken down so that they can fit onto a page.
21428 +download,@{section=".text",section-size="6668",total-size="9880"@}
21429 +download,@{section=".text",section-sent="512",section-size="6668",
21430 total-sent="512",total-size="9880"@}
21431 +download,@{section=".text",section-sent="1024",section-size="6668",
21432 total-sent="1024",total-size="9880"@}
21433 +download,@{section=".text",section-sent="1536",section-size="6668",
21434 total-sent="1536",total-size="9880"@}
21435 +download,@{section=".text",section-sent="2048",section-size="6668",
21436 total-sent="2048",total-size="9880"@}
21437 +download,@{section=".text",section-sent="2560",section-size="6668",
21438 total-sent="2560",total-size="9880"@}
21439 +download,@{section=".text",section-sent="3072",section-size="6668",
21440 total-sent="3072",total-size="9880"@}
21441 +download,@{section=".text",section-sent="3584",section-size="6668",
21442 total-sent="3584",total-size="9880"@}
21443 +download,@{section=".text",section-sent="4096",section-size="6668",
21444 total-sent="4096",total-size="9880"@}
21445 +download,@{section=".text",section-sent="4608",section-size="6668",
21446 total-sent="4608",total-size="9880"@}
21447 +download,@{section=".text",section-sent="5120",section-size="6668",
21448 total-sent="5120",total-size="9880"@}
21449 +download,@{section=".text",section-sent="5632",section-size="6668",
21450 total-sent="5632",total-size="9880"@}
21451 +download,@{section=".text",section-sent="6144",section-size="6668",
21452 total-sent="6144",total-size="9880"@}
21453 +download,@{section=".text",section-sent="6656",section-size="6668",
21454 total-sent="6656",total-size="9880"@}
21455 +download,@{section=".init",section-size="28",total-size="9880"@}
21456 +download,@{section=".fini",section-size="28",total-size="9880"@}
21457 +download,@{section=".data",section-size="3156",total-size="9880"@}
21458 +download,@{section=".data",section-sent="512",section-size="3156",
21459 total-sent="7236",total-size="9880"@}
21460 +download,@{section=".data",section-sent="1024",section-size="3156",
21461 total-sent="7748",total-size="9880"@}
21462 +download,@{section=".data",section-sent="1536",section-size="3156",
21463 total-sent="8260",total-size="9880"@}
21464 +download,@{section=".data",section-sent="2048",section-size="3156",
21465 total-sent="8772",total-size="9880"@}
21466 +download,@{section=".data",section-sent="2560",section-size="3156",
21467 total-sent="9284",total-size="9880"@}
21468 +download,@{section=".data",section-sent="3072",section-size="3156",
21469 total-sent="9796",total-size="9880"@}
21470 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
21476 @subheading The @code{-target-exec-status} Command
21477 @findex -target-exec-status
21479 @subsubheading Synopsis
21482 -target-exec-status
21485 Provide information on the state of the target (whether it is running or
21486 not, for instance).
21488 @subsubheading @value{GDBN} Command
21490 There's no equivalent @value{GDBN} command.
21492 @subsubheading Example
21496 @subheading The @code{-target-list-available-targets} Command
21497 @findex -target-list-available-targets
21499 @subsubheading Synopsis
21502 -target-list-available-targets
21505 List the possible targets to connect to.
21507 @subsubheading @value{GDBN} Command
21509 The corresponding @value{GDBN} command is @samp{help target}.
21511 @subsubheading Example
21515 @subheading The @code{-target-list-current-targets} Command
21516 @findex -target-list-current-targets
21518 @subsubheading Synopsis
21521 -target-list-current-targets
21524 Describe the current target.
21526 @subsubheading @value{GDBN} Command
21528 The corresponding information is printed by @samp{info file} (among
21531 @subsubheading Example
21535 @subheading The @code{-target-list-parameters} Command
21536 @findex -target-list-parameters
21538 @subsubheading Synopsis
21541 -target-list-parameters
21546 @subsubheading @value{GDBN} Command
21550 @subsubheading Example
21554 @subheading The @code{-target-select} Command
21555 @findex -target-select
21557 @subsubheading Synopsis
21560 -target-select @var{type} @var{parameters @dots{}}
21563 Connect @value{GDBN} to the remote target. This command takes two args:
21567 The type of target, for instance @samp{async}, @samp{remote}, etc.
21568 @item @var{parameters}
21569 Device names, host names and the like. @xref{Target Commands, ,
21570 Commands for Managing Targets}, for more details.
21573 The output is a connection notification, followed by the address at
21574 which the target program is, in the following form:
21577 ^connected,addr="@var{address}",func="@var{function name}",
21578 args=[@var{arg list}]
21581 @subsubheading @value{GDBN} Command
21583 The corresponding @value{GDBN} command is @samp{target}.
21585 @subsubheading Example
21589 -target-select async /dev/ttya
21590 ^connected,addr="0xfe00a300",func="??",args=[]
21594 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21595 @node GDB/MI File Transfer Commands
21596 @section @sc{gdb/mi} File Transfer Commands
21599 @subheading The @code{-target-file-put} Command
21600 @findex -target-file-put
21602 @subsubheading Synopsis
21605 -target-file-put @var{hostfile} @var{targetfile}
21608 Copy file @var{hostfile} from the host system (the machine running
21609 @value{GDBN}) to @var{targetfile} on the target system.
21611 @subsubheading @value{GDBN} Command
21613 The corresponding @value{GDBN} command is @samp{remote put}.
21615 @subsubheading Example
21619 -target-file-put localfile remotefile
21625 @subheading The @code{-target-file-put} Command
21626 @findex -target-file-get
21628 @subsubheading Synopsis
21631 -target-file-get @var{targetfile} @var{hostfile}
21634 Copy file @var{targetfile} from the target system to @var{hostfile}
21635 on the host system.
21637 @subsubheading @value{GDBN} Command
21639 The corresponding @value{GDBN} command is @samp{remote get}.
21641 @subsubheading Example
21645 -target-file-get remotefile localfile
21651 @subheading The @code{-target-file-delete} Command
21652 @findex -target-file-delete
21654 @subsubheading Synopsis
21657 -target-file-delete @var{targetfile}
21660 Delete @var{targetfile} from the target system.
21662 @subsubheading @value{GDBN} Command
21664 The corresponding @value{GDBN} command is @samp{remote delete}.
21666 @subsubheading Example
21670 -target-file-delete remotefile
21676 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21677 @node GDB/MI Miscellaneous Commands
21678 @section Miscellaneous @sc{gdb/mi} Commands
21680 @c @subheading -gdb-complete
21682 @subheading The @code{-gdb-exit} Command
21685 @subsubheading Synopsis
21691 Exit @value{GDBN} immediately.
21693 @subsubheading @value{GDBN} Command
21695 Approximately corresponds to @samp{quit}.
21697 @subsubheading Example
21706 @subheading The @code{-exec-abort} Command
21707 @findex -exec-abort
21709 @subsubheading Synopsis
21715 Kill the inferior running program.
21717 @subsubheading @value{GDBN} Command
21719 The corresponding @value{GDBN} command is @samp{kill}.
21721 @subsubheading Example
21725 @subheading The @code{-gdb-set} Command
21728 @subsubheading Synopsis
21734 Set an internal @value{GDBN} variable.
21735 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
21737 @subsubheading @value{GDBN} Command
21739 The corresponding @value{GDBN} command is @samp{set}.
21741 @subsubheading Example
21751 @subheading The @code{-gdb-show} Command
21754 @subsubheading Synopsis
21760 Show the current value of a @value{GDBN} variable.
21762 @subsubheading @value{GDBN} Command
21764 The corresponding @value{GDBN} command is @samp{show}.
21766 @subsubheading Example
21775 @c @subheading -gdb-source
21778 @subheading The @code{-gdb-version} Command
21779 @findex -gdb-version
21781 @subsubheading Synopsis
21787 Show version information for @value{GDBN}. Used mostly in testing.
21789 @subsubheading @value{GDBN} Command
21791 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
21792 default shows this information when you start an interactive session.
21794 @subsubheading Example
21796 @c This example modifies the actual output from GDB to avoid overfull
21802 ~Copyright 2000 Free Software Foundation, Inc.
21803 ~GDB is free software, covered by the GNU General Public License, and
21804 ~you are welcome to change it and/or distribute copies of it under
21805 ~ certain conditions.
21806 ~Type "show copying" to see the conditions.
21807 ~There is absolutely no warranty for GDB. Type "show warranty" for
21809 ~This GDB was configured as
21810 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
21815 @subheading The @code{-list-features} Command
21816 @findex -list-features
21818 Returns a list of particular features of the MI protocol that
21819 this version of gdb implements. A feature can be a command,
21820 or a new field in an output of some command, or even an
21821 important bugfix. While a frontend can sometimes detect presence
21822 of a feature at runtime, it is easier to perform detection at debugger
21825 The command returns a list of strings, with each string naming an
21826 available feature. Each returned string is just a name, it does not
21827 have any internal structure. The list of possible feature names
21833 (gdb) -list-features
21834 ^done,result=["feature1","feature2"]
21837 The current list of features is:
21841 @samp{frozen-varobjs}---indicates presence of the
21842 @code{-var-set-frozen} command, as well as possible presense of the
21843 @code{frozen} field in the output of @code{-varobj-create}.
21845 @samp{pending-breakpoints}---indicates presence of the @code{-f}
21846 option to the @code{-break-insert} command.
21848 @samp{thread-info}---indicates presence of the @code{-thread-info} command.
21852 @subheading The @code{-interpreter-exec} Command
21853 @findex -interpreter-exec
21855 @subheading Synopsis
21858 -interpreter-exec @var{interpreter} @var{command}
21860 @anchor{-interpreter-exec}
21862 Execute the specified @var{command} in the given @var{interpreter}.
21864 @subheading @value{GDBN} Command
21866 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
21868 @subheading Example
21872 -interpreter-exec console "break main"
21873 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
21874 &"During symbol reading, bad structure-type format.\n"
21875 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
21880 @subheading The @code{-inferior-tty-set} Command
21881 @findex -inferior-tty-set
21883 @subheading Synopsis
21886 -inferior-tty-set /dev/pts/1
21889 Set terminal for future runs of the program being debugged.
21891 @subheading @value{GDBN} Command
21893 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
21895 @subheading Example
21899 -inferior-tty-set /dev/pts/1
21904 @subheading The @code{-inferior-tty-show} Command
21905 @findex -inferior-tty-show
21907 @subheading Synopsis
21913 Show terminal for future runs of program being debugged.
21915 @subheading @value{GDBN} Command
21917 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
21919 @subheading Example
21923 -inferior-tty-set /dev/pts/1
21927 ^done,inferior_tty_terminal="/dev/pts/1"
21931 @subheading The @code{-enable-timings} Command
21932 @findex -enable-timings
21934 @subheading Synopsis
21937 -enable-timings [yes | no]
21940 Toggle the printing of the wallclock, user and system times for an MI
21941 command as a field in its output. This command is to help frontend
21942 developers optimize the performance of their code. No argument is
21943 equivalent to @samp{yes}.
21945 @subheading @value{GDBN} Command
21949 @subheading Example
21957 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
21958 addr="0x080484ed",func="main",file="myprog.c",
21959 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
21960 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
21968 *stopped,reason="breakpoint-hit",bkptno="1",thread-id="0",
21969 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
21970 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
21971 fullname="/home/nickrob/myprog.c",line="73"@}
21976 @chapter @value{GDBN} Annotations
21978 This chapter describes annotations in @value{GDBN}. Annotations were
21979 designed to interface @value{GDBN} to graphical user interfaces or other
21980 similar programs which want to interact with @value{GDBN} at a
21981 relatively high level.
21983 The annotation mechanism has largely been superseded by @sc{gdb/mi}
21987 This is Edition @value{EDITION}, @value{DATE}.
21991 * Annotations Overview:: What annotations are; the general syntax.
21992 * Server Prefix:: Issuing a command without affecting user state.
21993 * Prompting:: Annotations marking @value{GDBN}'s need for input.
21994 * Errors:: Annotations for error messages.
21995 * Invalidation:: Some annotations describe things now invalid.
21996 * Annotations for Running::
21997 Whether the program is running, how it stopped, etc.
21998 * Source Annotations:: Annotations describing source code.
22001 @node Annotations Overview
22002 @section What is an Annotation?
22003 @cindex annotations
22005 Annotations start with a newline character, two @samp{control-z}
22006 characters, and the name of the annotation. If there is no additional
22007 information associated with this annotation, the name of the annotation
22008 is followed immediately by a newline. If there is additional
22009 information, the name of the annotation is followed by a space, the
22010 additional information, and a newline. The additional information
22011 cannot contain newline characters.
22013 Any output not beginning with a newline and two @samp{control-z}
22014 characters denotes literal output from @value{GDBN}. Currently there is
22015 no need for @value{GDBN} to output a newline followed by two
22016 @samp{control-z} characters, but if there was such a need, the
22017 annotations could be extended with an @samp{escape} annotation which
22018 means those three characters as output.
22020 The annotation @var{level}, which is specified using the
22021 @option{--annotate} command line option (@pxref{Mode Options}), controls
22022 how much information @value{GDBN} prints together with its prompt,
22023 values of expressions, source lines, and other types of output. Level 0
22024 is for no annotations, level 1 is for use when @value{GDBN} is run as a
22025 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
22026 for programs that control @value{GDBN}, and level 2 annotations have
22027 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
22028 Interface, annotate, GDB's Obsolete Annotations}).
22031 @kindex set annotate
22032 @item set annotate @var{level}
22033 The @value{GDBN} command @code{set annotate} sets the level of
22034 annotations to the specified @var{level}.
22036 @item show annotate
22037 @kindex show annotate
22038 Show the current annotation level.
22041 This chapter describes level 3 annotations.
22043 A simple example of starting up @value{GDBN} with annotations is:
22046 $ @kbd{gdb --annotate=3}
22048 Copyright 2003 Free Software Foundation, Inc.
22049 GDB is free software, covered by the GNU General Public License,
22050 and you are welcome to change it and/or distribute copies of it
22051 under certain conditions.
22052 Type "show copying" to see the conditions.
22053 There is absolutely no warranty for GDB. Type "show warranty"
22055 This GDB was configured as "i386-pc-linux-gnu"
22066 Here @samp{quit} is input to @value{GDBN}; the rest is output from
22067 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
22068 denotes a @samp{control-z} character) are annotations; the rest is
22069 output from @value{GDBN}.
22071 @node Server Prefix
22072 @section The Server Prefix
22073 @cindex server prefix
22075 If you prefix a command with @samp{server } then it will not affect
22076 the command history, nor will it affect @value{GDBN}'s notion of which
22077 command to repeat if @key{RET} is pressed on a line by itself. This
22078 means that commands can be run behind a user's back by a front-end in
22079 a transparent manner.
22081 The server prefix does not affect the recording of values into the value
22082 history; to print a value without recording it into the value history,
22083 use the @code{output} command instead of the @code{print} command.
22086 @section Annotation for @value{GDBN} Input
22088 @cindex annotations for prompts
22089 When @value{GDBN} prompts for input, it annotates this fact so it is possible
22090 to know when to send output, when the output from a given command is
22093 Different kinds of input each have a different @dfn{input type}. Each
22094 input type has three annotations: a @code{pre-} annotation, which
22095 denotes the beginning of any prompt which is being output, a plain
22096 annotation, which denotes the end of the prompt, and then a @code{post-}
22097 annotation which denotes the end of any echo which may (or may not) be
22098 associated with the input. For example, the @code{prompt} input type
22099 features the following annotations:
22107 The input types are
22110 @findex pre-prompt annotation
22111 @findex prompt annotation
22112 @findex post-prompt annotation
22114 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
22116 @findex pre-commands annotation
22117 @findex commands annotation
22118 @findex post-commands annotation
22120 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
22121 command. The annotations are repeated for each command which is input.
22123 @findex pre-overload-choice annotation
22124 @findex overload-choice annotation
22125 @findex post-overload-choice annotation
22126 @item overload-choice
22127 When @value{GDBN} wants the user to select between various overloaded functions.
22129 @findex pre-query annotation
22130 @findex query annotation
22131 @findex post-query annotation
22133 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
22135 @findex pre-prompt-for-continue annotation
22136 @findex prompt-for-continue annotation
22137 @findex post-prompt-for-continue annotation
22138 @item prompt-for-continue
22139 When @value{GDBN} is asking the user to press return to continue. Note: Don't
22140 expect this to work well; instead use @code{set height 0} to disable
22141 prompting. This is because the counting of lines is buggy in the
22142 presence of annotations.
22147 @cindex annotations for errors, warnings and interrupts
22149 @findex quit annotation
22154 This annotation occurs right before @value{GDBN} responds to an interrupt.
22156 @findex error annotation
22161 This annotation occurs right before @value{GDBN} responds to an error.
22163 Quit and error annotations indicate that any annotations which @value{GDBN} was
22164 in the middle of may end abruptly. For example, if a
22165 @code{value-history-begin} annotation is followed by a @code{error}, one
22166 cannot expect to receive the matching @code{value-history-end}. One
22167 cannot expect not to receive it either, however; an error annotation
22168 does not necessarily mean that @value{GDBN} is immediately returning all the way
22171 @findex error-begin annotation
22172 A quit or error annotation may be preceded by
22178 Any output between that and the quit or error annotation is the error
22181 Warning messages are not yet annotated.
22182 @c If we want to change that, need to fix warning(), type_error(),
22183 @c range_error(), and possibly other places.
22186 @section Invalidation Notices
22188 @cindex annotations for invalidation messages
22189 The following annotations say that certain pieces of state may have
22193 @findex frames-invalid annotation
22194 @item ^Z^Zframes-invalid
22196 The frames (for example, output from the @code{backtrace} command) may
22199 @findex breakpoints-invalid annotation
22200 @item ^Z^Zbreakpoints-invalid
22202 The breakpoints may have changed. For example, the user just added or
22203 deleted a breakpoint.
22206 @node Annotations for Running
22207 @section Running the Program
22208 @cindex annotations for running programs
22210 @findex starting annotation
22211 @findex stopping annotation
22212 When the program starts executing due to a @value{GDBN} command such as
22213 @code{step} or @code{continue},
22219 is output. When the program stops,
22225 is output. Before the @code{stopped} annotation, a variety of
22226 annotations describe how the program stopped.
22229 @findex exited annotation
22230 @item ^Z^Zexited @var{exit-status}
22231 The program exited, and @var{exit-status} is the exit status (zero for
22232 successful exit, otherwise nonzero).
22234 @findex signalled annotation
22235 @findex signal-name annotation
22236 @findex signal-name-end annotation
22237 @findex signal-string annotation
22238 @findex signal-string-end annotation
22239 @item ^Z^Zsignalled
22240 The program exited with a signal. After the @code{^Z^Zsignalled}, the
22241 annotation continues:
22247 ^Z^Zsignal-name-end
22251 ^Z^Zsignal-string-end
22256 where @var{name} is the name of the signal, such as @code{SIGILL} or
22257 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
22258 as @code{Illegal Instruction} or @code{Segmentation fault}.
22259 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
22260 user's benefit and have no particular format.
22262 @findex signal annotation
22264 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
22265 just saying that the program received the signal, not that it was
22266 terminated with it.
22268 @findex breakpoint annotation
22269 @item ^Z^Zbreakpoint @var{number}
22270 The program hit breakpoint number @var{number}.
22272 @findex watchpoint annotation
22273 @item ^Z^Zwatchpoint @var{number}
22274 The program hit watchpoint number @var{number}.
22277 @node Source Annotations
22278 @section Displaying Source
22279 @cindex annotations for source display
22281 @findex source annotation
22282 The following annotation is used instead of displaying source code:
22285 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
22288 where @var{filename} is an absolute file name indicating which source
22289 file, @var{line} is the line number within that file (where 1 is the
22290 first line in the file), @var{character} is the character position
22291 within the file (where 0 is the first character in the file) (for most
22292 debug formats this will necessarily point to the beginning of a line),
22293 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
22294 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
22295 @var{addr} is the address in the target program associated with the
22296 source which is being displayed. @var{addr} is in the form @samp{0x}
22297 followed by one or more lowercase hex digits (note that this does not
22298 depend on the language).
22301 @chapter Reporting Bugs in @value{GDBN}
22302 @cindex bugs in @value{GDBN}
22303 @cindex reporting bugs in @value{GDBN}
22305 Your bug reports play an essential role in making @value{GDBN} reliable.
22307 Reporting a bug may help you by bringing a solution to your problem, or it
22308 may not. But in any case the principal function of a bug report is to help
22309 the entire community by making the next version of @value{GDBN} work better. Bug
22310 reports are your contribution to the maintenance of @value{GDBN}.
22312 In order for a bug report to serve its purpose, you must include the
22313 information that enables us to fix the bug.
22316 * Bug Criteria:: Have you found a bug?
22317 * Bug Reporting:: How to report bugs
22321 @section Have You Found a Bug?
22322 @cindex bug criteria
22324 If you are not sure whether you have found a bug, here are some guidelines:
22327 @cindex fatal signal
22328 @cindex debugger crash
22329 @cindex crash of debugger
22331 If the debugger gets a fatal signal, for any input whatever, that is a
22332 @value{GDBN} bug. Reliable debuggers never crash.
22334 @cindex error on valid input
22336 If @value{GDBN} produces an error message for valid input, that is a
22337 bug. (Note that if you're cross debugging, the problem may also be
22338 somewhere in the connection to the target.)
22340 @cindex invalid input
22342 If @value{GDBN} does not produce an error message for invalid input,
22343 that is a bug. However, you should note that your idea of
22344 ``invalid input'' might be our idea of ``an extension'' or ``support
22345 for traditional practice''.
22348 If you are an experienced user of debugging tools, your suggestions
22349 for improvement of @value{GDBN} are welcome in any case.
22352 @node Bug Reporting
22353 @section How to Report Bugs
22354 @cindex bug reports
22355 @cindex @value{GDBN} bugs, reporting
22357 A number of companies and individuals offer support for @sc{gnu} products.
22358 If you obtained @value{GDBN} from a support organization, we recommend you
22359 contact that organization first.
22361 You can find contact information for many support companies and
22362 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
22364 @c should add a web page ref...
22366 In any event, we also recommend that you submit bug reports for
22367 @value{GDBN}. The preferred method is to submit them directly using
22368 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
22369 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
22372 @strong{Do not send bug reports to @samp{info-gdb}, or to
22373 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
22374 not want to receive bug reports. Those that do have arranged to receive
22377 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
22378 serves as a repeater. The mailing list and the newsgroup carry exactly
22379 the same messages. Often people think of posting bug reports to the
22380 newsgroup instead of mailing them. This appears to work, but it has one
22381 problem which can be crucial: a newsgroup posting often lacks a mail
22382 path back to the sender. Thus, if we need to ask for more information,
22383 we may be unable to reach you. For this reason, it is better to send
22384 bug reports to the mailing list.
22386 The fundamental principle of reporting bugs usefully is this:
22387 @strong{report all the facts}. If you are not sure whether to state a
22388 fact or leave it out, state it!
22390 Often people omit facts because they think they know what causes the
22391 problem and assume that some details do not matter. Thus, you might
22392 assume that the name of the variable you use in an example does not matter.
22393 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
22394 stray memory reference which happens to fetch from the location where that
22395 name is stored in memory; perhaps, if the name were different, the contents
22396 of that location would fool the debugger into doing the right thing despite
22397 the bug. Play it safe and give a specific, complete example. That is the
22398 easiest thing for you to do, and the most helpful.
22400 Keep in mind that the purpose of a bug report is to enable us to fix the
22401 bug. It may be that the bug has been reported previously, but neither
22402 you nor we can know that unless your bug report is complete and
22405 Sometimes people give a few sketchy facts and ask, ``Does this ring a
22406 bell?'' Those bug reports are useless, and we urge everyone to
22407 @emph{refuse to respond to them} except to chide the sender to report
22410 To enable us to fix the bug, you should include all these things:
22414 The version of @value{GDBN}. @value{GDBN} announces it if you start
22415 with no arguments; you can also print it at any time using @code{show
22418 Without this, we will not know whether there is any point in looking for
22419 the bug in the current version of @value{GDBN}.
22422 The type of machine you are using, and the operating system name and
22426 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
22427 ``@value{GCC}--2.8.1''.
22430 What compiler (and its version) was used to compile the program you are
22431 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
22432 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
22433 to get this information; for other compilers, see the documentation for
22437 The command arguments you gave the compiler to compile your example and
22438 observe the bug. For example, did you use @samp{-O}? To guarantee
22439 you will not omit something important, list them all. A copy of the
22440 Makefile (or the output from make) is sufficient.
22442 If we were to try to guess the arguments, we would probably guess wrong
22443 and then we might not encounter the bug.
22446 A complete input script, and all necessary source files, that will
22450 A description of what behavior you observe that you believe is
22451 incorrect. For example, ``It gets a fatal signal.''
22453 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
22454 will certainly notice it. But if the bug is incorrect output, we might
22455 not notice unless it is glaringly wrong. You might as well not give us
22456 a chance to make a mistake.
22458 Even if the problem you experience is a fatal signal, you should still
22459 say so explicitly. Suppose something strange is going on, such as, your
22460 copy of @value{GDBN} is out of synch, or you have encountered a bug in
22461 the C library on your system. (This has happened!) Your copy might
22462 crash and ours would not. If you told us to expect a crash, then when
22463 ours fails to crash, we would know that the bug was not happening for
22464 us. If you had not told us to expect a crash, then we would not be able
22465 to draw any conclusion from our observations.
22468 @cindex recording a session script
22469 To collect all this information, you can use a session recording program
22470 such as @command{script}, which is available on many Unix systems.
22471 Just run your @value{GDBN} session inside @command{script} and then
22472 include the @file{typescript} file with your bug report.
22474 Another way to record a @value{GDBN} session is to run @value{GDBN}
22475 inside Emacs and then save the entire buffer to a file.
22478 If you wish to suggest changes to the @value{GDBN} source, send us context
22479 diffs. If you even discuss something in the @value{GDBN} source, refer to
22480 it by context, not by line number.
22482 The line numbers in our development sources will not match those in your
22483 sources. Your line numbers would convey no useful information to us.
22487 Here are some things that are not necessary:
22491 A description of the envelope of the bug.
22493 Often people who encounter a bug spend a lot of time investigating
22494 which changes to the input file will make the bug go away and which
22495 changes will not affect it.
22497 This is often time consuming and not very useful, because the way we
22498 will find the bug is by running a single example under the debugger
22499 with breakpoints, not by pure deduction from a series of examples.
22500 We recommend that you save your time for something else.
22502 Of course, if you can find a simpler example to report @emph{instead}
22503 of the original one, that is a convenience for us. Errors in the
22504 output will be easier to spot, running under the debugger will take
22505 less time, and so on.
22507 However, simplification is not vital; if you do not want to do this,
22508 report the bug anyway and send us the entire test case you used.
22511 A patch for the bug.
22513 A patch for the bug does help us if it is a good one. But do not omit
22514 the necessary information, such as the test case, on the assumption that
22515 a patch is all we need. We might see problems with your patch and decide
22516 to fix the problem another way, or we might not understand it at all.
22518 Sometimes with a program as complicated as @value{GDBN} it is very hard to
22519 construct an example that will make the program follow a certain path
22520 through the code. If you do not send us the example, we will not be able
22521 to construct one, so we will not be able to verify that the bug is fixed.
22523 And if we cannot understand what bug you are trying to fix, or why your
22524 patch should be an improvement, we will not install it. A test case will
22525 help us to understand.
22528 A guess about what the bug is or what it depends on.
22530 Such guesses are usually wrong. Even we cannot guess right about such
22531 things without first using the debugger to find the facts.
22534 @c The readline documentation is distributed with the readline code
22535 @c and consists of the two following files:
22537 @c inc-hist.texinfo
22538 @c Use -I with makeinfo to point to the appropriate directory,
22539 @c environment var TEXINPUTS with TeX.
22540 @include rluser.texi
22541 @include inc-hist.texinfo
22544 @node Formatting Documentation
22545 @appendix Formatting Documentation
22547 @cindex @value{GDBN} reference card
22548 @cindex reference card
22549 The @value{GDBN} 4 release includes an already-formatted reference card, ready
22550 for printing with PostScript or Ghostscript, in the @file{gdb}
22551 subdirectory of the main source directory@footnote{In
22552 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
22553 release.}. If you can use PostScript or Ghostscript with your printer,
22554 you can print the reference card immediately with @file{refcard.ps}.
22556 The release also includes the source for the reference card. You
22557 can format it, using @TeX{}, by typing:
22563 The @value{GDBN} reference card is designed to print in @dfn{landscape}
22564 mode on US ``letter'' size paper;
22565 that is, on a sheet 11 inches wide by 8.5 inches
22566 high. You will need to specify this form of printing as an option to
22567 your @sc{dvi} output program.
22569 @cindex documentation
22571 All the documentation for @value{GDBN} comes as part of the machine-readable
22572 distribution. The documentation is written in Texinfo format, which is
22573 a documentation system that uses a single source file to produce both
22574 on-line information and a printed manual. You can use one of the Info
22575 formatting commands to create the on-line version of the documentation
22576 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
22578 @value{GDBN} includes an already formatted copy of the on-line Info
22579 version of this manual in the @file{gdb} subdirectory. The main Info
22580 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
22581 subordinate files matching @samp{gdb.info*} in the same directory. If
22582 necessary, you can print out these files, or read them with any editor;
22583 but they are easier to read using the @code{info} subsystem in @sc{gnu}
22584 Emacs or the standalone @code{info} program, available as part of the
22585 @sc{gnu} Texinfo distribution.
22587 If you want to format these Info files yourself, you need one of the
22588 Info formatting programs, such as @code{texinfo-format-buffer} or
22591 If you have @code{makeinfo} installed, and are in the top level
22592 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
22593 version @value{GDBVN}), you can make the Info file by typing:
22600 If you want to typeset and print copies of this manual, you need @TeX{},
22601 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
22602 Texinfo definitions file.
22604 @TeX{} is a typesetting program; it does not print files directly, but
22605 produces output files called @sc{dvi} files. To print a typeset
22606 document, you need a program to print @sc{dvi} files. If your system
22607 has @TeX{} installed, chances are it has such a program. The precise
22608 command to use depends on your system; @kbd{lpr -d} is common; another
22609 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
22610 require a file name without any extension or a @samp{.dvi} extension.
22612 @TeX{} also requires a macro definitions file called
22613 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
22614 written in Texinfo format. On its own, @TeX{} cannot either read or
22615 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
22616 and is located in the @file{gdb-@var{version-number}/texinfo}
22619 If you have @TeX{} and a @sc{dvi} printer program installed, you can
22620 typeset and print this manual. First switch to the @file{gdb}
22621 subdirectory of the main source directory (for example, to
22622 @file{gdb-@value{GDBVN}/gdb}) and type:
22628 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
22630 @node Installing GDB
22631 @appendix Installing @value{GDBN}
22632 @cindex installation
22635 * Requirements:: Requirements for building @value{GDBN}
22636 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
22637 * Separate Objdir:: Compiling @value{GDBN} in another directory
22638 * Config Names:: Specifying names for hosts and targets
22639 * Configure Options:: Summary of options for configure
22643 @section Requirements for Building @value{GDBN}
22644 @cindex building @value{GDBN}, requirements for
22646 Building @value{GDBN} requires various tools and packages to be available.
22647 Other packages will be used only if they are found.
22649 @heading Tools/Packages Necessary for Building @value{GDBN}
22651 @item ISO C90 compiler
22652 @value{GDBN} is written in ISO C90. It should be buildable with any
22653 working C90 compiler, e.g.@: GCC.
22657 @heading Tools/Packages Optional for Building @value{GDBN}
22661 @value{GDBN} can use the Expat XML parsing library. This library may be
22662 included with your operating system distribution; if it is not, you
22663 can get the latest version from @url{http://expat.sourceforge.net}.
22664 The @file{configure} script will search for this library in several
22665 standard locations; if it is installed in an unusual path, you can
22666 use the @option{--with-libexpat-prefix} option to specify its location.
22672 Remote protocol memory maps (@pxref{Memory Map Format})
22674 Target descriptions (@pxref{Target Descriptions})
22676 Remote shared library lists (@pxref{Library List Format})
22678 MS-Windows shared libraries (@pxref{Shared Libraries})
22683 @node Running Configure
22684 @section Invoking the @value{GDBN} @file{configure} Script
22685 @cindex configuring @value{GDBN}
22686 @value{GDBN} comes with a @file{configure} script that automates the process
22687 of preparing @value{GDBN} for installation; you can then use @code{make} to
22688 build the @code{gdb} program.
22690 @c irrelevant in info file; it's as current as the code it lives with.
22691 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
22692 look at the @file{README} file in the sources; we may have improved the
22693 installation procedures since publishing this manual.}
22696 The @value{GDBN} distribution includes all the source code you need for
22697 @value{GDBN} in a single directory, whose name is usually composed by
22698 appending the version number to @samp{gdb}.
22700 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
22701 @file{gdb-@value{GDBVN}} directory. That directory contains:
22704 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
22705 script for configuring @value{GDBN} and all its supporting libraries
22707 @item gdb-@value{GDBVN}/gdb
22708 the source specific to @value{GDBN} itself
22710 @item gdb-@value{GDBVN}/bfd
22711 source for the Binary File Descriptor library
22713 @item gdb-@value{GDBVN}/include
22714 @sc{gnu} include files
22716 @item gdb-@value{GDBVN}/libiberty
22717 source for the @samp{-liberty} free software library
22719 @item gdb-@value{GDBVN}/opcodes
22720 source for the library of opcode tables and disassemblers
22722 @item gdb-@value{GDBVN}/readline
22723 source for the @sc{gnu} command-line interface
22725 @item gdb-@value{GDBVN}/glob
22726 source for the @sc{gnu} filename pattern-matching subroutine
22728 @item gdb-@value{GDBVN}/mmalloc
22729 source for the @sc{gnu} memory-mapped malloc package
22732 The simplest way to configure and build @value{GDBN} is to run @file{configure}
22733 from the @file{gdb-@var{version-number}} source directory, which in
22734 this example is the @file{gdb-@value{GDBVN}} directory.
22736 First switch to the @file{gdb-@var{version-number}} source directory
22737 if you are not already in it; then run @file{configure}. Pass the
22738 identifier for the platform on which @value{GDBN} will run as an
22744 cd gdb-@value{GDBVN}
22745 ./configure @var{host}
22750 where @var{host} is an identifier such as @samp{sun4} or
22751 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
22752 (You can often leave off @var{host}; @file{configure} tries to guess the
22753 correct value by examining your system.)
22755 Running @samp{configure @var{host}} and then running @code{make} builds the
22756 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
22757 libraries, then @code{gdb} itself. The configured source files, and the
22758 binaries, are left in the corresponding source directories.
22761 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
22762 system does not recognize this automatically when you run a different
22763 shell, you may need to run @code{sh} on it explicitly:
22766 sh configure @var{host}
22769 If you run @file{configure} from a directory that contains source
22770 directories for multiple libraries or programs, such as the
22771 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
22773 creates configuration files for every directory level underneath (unless
22774 you tell it not to, with the @samp{--norecursion} option).
22776 You should run the @file{configure} script from the top directory in the
22777 source tree, the @file{gdb-@var{version-number}} directory. If you run
22778 @file{configure} from one of the subdirectories, you will configure only
22779 that subdirectory. That is usually not what you want. In particular,
22780 if you run the first @file{configure} from the @file{gdb} subdirectory
22781 of the @file{gdb-@var{version-number}} directory, you will omit the
22782 configuration of @file{bfd}, @file{readline}, and other sibling
22783 directories of the @file{gdb} subdirectory. This leads to build errors
22784 about missing include files such as @file{bfd/bfd.h}.
22786 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
22787 However, you should make sure that the shell on your path (named by
22788 the @samp{SHELL} environment variable) is publicly readable. Remember
22789 that @value{GDBN} uses the shell to start your program---some systems refuse to
22790 let @value{GDBN} debug child processes whose programs are not readable.
22792 @node Separate Objdir
22793 @section Compiling @value{GDBN} in Another Directory
22795 If you want to run @value{GDBN} versions for several host or target machines,
22796 you need a different @code{gdb} compiled for each combination of
22797 host and target. @file{configure} is designed to make this easy by
22798 allowing you to generate each configuration in a separate subdirectory,
22799 rather than in the source directory. If your @code{make} program
22800 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
22801 @code{make} in each of these directories builds the @code{gdb}
22802 program specified there.
22804 To build @code{gdb} in a separate directory, run @file{configure}
22805 with the @samp{--srcdir} option to specify where to find the source.
22806 (You also need to specify a path to find @file{configure}
22807 itself from your working directory. If the path to @file{configure}
22808 would be the same as the argument to @samp{--srcdir}, you can leave out
22809 the @samp{--srcdir} option; it is assumed.)
22811 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
22812 separate directory for a Sun 4 like this:
22816 cd gdb-@value{GDBVN}
22819 ../gdb-@value{GDBVN}/configure sun4
22824 When @file{configure} builds a configuration using a remote source
22825 directory, it creates a tree for the binaries with the same structure
22826 (and using the same names) as the tree under the source directory. In
22827 the example, you'd find the Sun 4 library @file{libiberty.a} in the
22828 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
22829 @file{gdb-sun4/gdb}.
22831 Make sure that your path to the @file{configure} script has just one
22832 instance of @file{gdb} in it. If your path to @file{configure} looks
22833 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
22834 one subdirectory of @value{GDBN}, not the whole package. This leads to
22835 build errors about missing include files such as @file{bfd/bfd.h}.
22837 One popular reason to build several @value{GDBN} configurations in separate
22838 directories is to configure @value{GDBN} for cross-compiling (where
22839 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
22840 programs that run on another machine---the @dfn{target}).
22841 You specify a cross-debugging target by
22842 giving the @samp{--target=@var{target}} option to @file{configure}.
22844 When you run @code{make} to build a program or library, you must run
22845 it in a configured directory---whatever directory you were in when you
22846 called @file{configure} (or one of its subdirectories).
22848 The @code{Makefile} that @file{configure} generates in each source
22849 directory also runs recursively. If you type @code{make} in a source
22850 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
22851 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
22852 will build all the required libraries, and then build GDB.
22854 When you have multiple hosts or targets configured in separate
22855 directories, you can run @code{make} on them in parallel (for example,
22856 if they are NFS-mounted on each of the hosts); they will not interfere
22860 @section Specifying Names for Hosts and Targets
22862 The specifications used for hosts and targets in the @file{configure}
22863 script are based on a three-part naming scheme, but some short predefined
22864 aliases are also supported. The full naming scheme encodes three pieces
22865 of information in the following pattern:
22868 @var{architecture}-@var{vendor}-@var{os}
22871 For example, you can use the alias @code{sun4} as a @var{host} argument,
22872 or as the value for @var{target} in a @code{--target=@var{target}}
22873 option. The equivalent full name is @samp{sparc-sun-sunos4}.
22875 The @file{configure} script accompanying @value{GDBN} does not provide
22876 any query facility to list all supported host and target names or
22877 aliases. @file{configure} calls the Bourne shell script
22878 @code{config.sub} to map abbreviations to full names; you can read the
22879 script, if you wish, or you can use it to test your guesses on
22880 abbreviations---for example:
22883 % sh config.sub i386-linux
22885 % sh config.sub alpha-linux
22886 alpha-unknown-linux-gnu
22887 % sh config.sub hp9k700
22889 % sh config.sub sun4
22890 sparc-sun-sunos4.1.1
22891 % sh config.sub sun3
22892 m68k-sun-sunos4.1.1
22893 % sh config.sub i986v
22894 Invalid configuration `i986v': machine `i986v' not recognized
22898 @code{config.sub} is also distributed in the @value{GDBN} source
22899 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
22901 @node Configure Options
22902 @section @file{configure} Options
22904 Here is a summary of the @file{configure} options and arguments that
22905 are most often useful for building @value{GDBN}. @file{configure} also has
22906 several other options not listed here. @inforef{What Configure
22907 Does,,configure.info}, for a full explanation of @file{configure}.
22910 configure @r{[}--help@r{]}
22911 @r{[}--prefix=@var{dir}@r{]}
22912 @r{[}--exec-prefix=@var{dir}@r{]}
22913 @r{[}--srcdir=@var{dirname}@r{]}
22914 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
22915 @r{[}--target=@var{target}@r{]}
22920 You may introduce options with a single @samp{-} rather than
22921 @samp{--} if you prefer; but you may abbreviate option names if you use
22926 Display a quick summary of how to invoke @file{configure}.
22928 @item --prefix=@var{dir}
22929 Configure the source to install programs and files under directory
22932 @item --exec-prefix=@var{dir}
22933 Configure the source to install programs under directory
22936 @c avoid splitting the warning from the explanation:
22938 @item --srcdir=@var{dirname}
22939 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
22940 @code{make} that implements the @code{VPATH} feature.}@*
22941 Use this option to make configurations in directories separate from the
22942 @value{GDBN} source directories. Among other things, you can use this to
22943 build (or maintain) several configurations simultaneously, in separate
22944 directories. @file{configure} writes configuration-specific files in
22945 the current directory, but arranges for them to use the source in the
22946 directory @var{dirname}. @file{configure} creates directories under
22947 the working directory in parallel to the source directories below
22950 @item --norecursion
22951 Configure only the directory level where @file{configure} is executed; do not
22952 propagate configuration to subdirectories.
22954 @item --target=@var{target}
22955 Configure @value{GDBN} for cross-debugging programs running on the specified
22956 @var{target}. Without this option, @value{GDBN} is configured to debug
22957 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
22959 There is no convenient way to generate a list of all available targets.
22961 @item @var{host} @dots{}
22962 Configure @value{GDBN} to run on the specified @var{host}.
22964 There is no convenient way to generate a list of all available hosts.
22967 There are many other options available as well, but they are generally
22968 needed for special purposes only.
22970 @node Maintenance Commands
22971 @appendix Maintenance Commands
22972 @cindex maintenance commands
22973 @cindex internal commands
22975 In addition to commands intended for @value{GDBN} users, @value{GDBN}
22976 includes a number of commands intended for @value{GDBN} developers,
22977 that are not documented elsewhere in this manual. These commands are
22978 provided here for reference. (For commands that turn on debugging
22979 messages, see @ref{Debugging Output}.)
22982 @kindex maint agent
22983 @item maint agent @var{expression}
22984 Translate the given @var{expression} into remote agent bytecodes.
22985 This command is useful for debugging the Agent Expression mechanism
22986 (@pxref{Agent Expressions}).
22988 @kindex maint info breakpoints
22989 @item @anchor{maint info breakpoints}maint info breakpoints
22990 Using the same format as @samp{info breakpoints}, display both the
22991 breakpoints you've set explicitly, and those @value{GDBN} is using for
22992 internal purposes. Internal breakpoints are shown with negative
22993 breakpoint numbers. The type column identifies what kind of breakpoint
22998 Normal, explicitly set breakpoint.
23001 Normal, explicitly set watchpoint.
23004 Internal breakpoint, used to handle correctly stepping through
23005 @code{longjmp} calls.
23007 @item longjmp resume
23008 Internal breakpoint at the target of a @code{longjmp}.
23011 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
23014 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
23017 Shared library events.
23021 @kindex maint check-symtabs
23022 @item maint check-symtabs
23023 Check the consistency of psymtabs and symtabs.
23025 @kindex maint cplus first_component
23026 @item maint cplus first_component @var{name}
23027 Print the first C@t{++} class/namespace component of @var{name}.
23029 @kindex maint cplus namespace
23030 @item maint cplus namespace
23031 Print the list of possible C@t{++} namespaces.
23033 @kindex maint demangle
23034 @item maint demangle @var{name}
23035 Demangle a C@t{++} or Objective-C mangled @var{name}.
23037 @kindex maint deprecate
23038 @kindex maint undeprecate
23039 @cindex deprecated commands
23040 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
23041 @itemx maint undeprecate @var{command}
23042 Deprecate or undeprecate the named @var{command}. Deprecated commands
23043 cause @value{GDBN} to issue a warning when you use them. The optional
23044 argument @var{replacement} says which newer command should be used in
23045 favor of the deprecated one; if it is given, @value{GDBN} will mention
23046 the replacement as part of the warning.
23048 @kindex maint dump-me
23049 @item maint dump-me
23050 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
23051 Cause a fatal signal in the debugger and force it to dump its core.
23052 This is supported only on systems which support aborting a program
23053 with the @code{SIGQUIT} signal.
23055 @kindex maint internal-error
23056 @kindex maint internal-warning
23057 @item maint internal-error @r{[}@var{message-text}@r{]}
23058 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
23059 Cause @value{GDBN} to call the internal function @code{internal_error}
23060 or @code{internal_warning} and hence behave as though an internal error
23061 or internal warning has been detected. In addition to reporting the
23062 internal problem, these functions give the user the opportunity to
23063 either quit @value{GDBN} or create a core file of the current
23064 @value{GDBN} session.
23066 These commands take an optional parameter @var{message-text} that is
23067 used as the text of the error or warning message.
23069 Here's an example of using @code{internal-error}:
23072 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
23073 @dots{}/maint.c:121: internal-error: testing, 1, 2
23074 A problem internal to GDB has been detected. Further
23075 debugging may prove unreliable.
23076 Quit this debugging session? (y or n) @kbd{n}
23077 Create a core file? (y or n) @kbd{n}
23081 @kindex maint packet
23082 @item maint packet @var{text}
23083 If @value{GDBN} is talking to an inferior via the serial protocol,
23084 then this command sends the string @var{text} to the inferior, and
23085 displays the response packet. @value{GDBN} supplies the initial
23086 @samp{$} character, the terminating @samp{#} character, and the
23089 @kindex maint print architecture
23090 @item maint print architecture @r{[}@var{file}@r{]}
23091 Print the entire architecture configuration. The optional argument
23092 @var{file} names the file where the output goes.
23094 @kindex maint print c-tdesc
23095 @item maint print c-tdesc
23096 Print the current target description (@pxref{Target Descriptions}) as
23097 a C source file. The created source file can be used in @value{GDBN}
23098 when an XML parser is not available to parse the description.
23100 @kindex maint print dummy-frames
23101 @item maint print dummy-frames
23102 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
23105 (@value{GDBP}) @kbd{b add}
23107 (@value{GDBP}) @kbd{print add(2,3)}
23108 Breakpoint 2, add (a=2, b=3) at @dots{}
23110 The program being debugged stopped while in a function called from GDB.
23112 (@value{GDBP}) @kbd{maint print dummy-frames}
23113 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
23114 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
23115 call_lo=0x01014000 call_hi=0x01014001
23119 Takes an optional file parameter.
23121 @kindex maint print registers
23122 @kindex maint print raw-registers
23123 @kindex maint print cooked-registers
23124 @kindex maint print register-groups
23125 @item maint print registers @r{[}@var{file}@r{]}
23126 @itemx maint print raw-registers @r{[}@var{file}@r{]}
23127 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
23128 @itemx maint print register-groups @r{[}@var{file}@r{]}
23129 Print @value{GDBN}'s internal register data structures.
23131 The command @code{maint print raw-registers} includes the contents of
23132 the raw register cache; the command @code{maint print cooked-registers}
23133 includes the (cooked) value of all registers; and the command
23134 @code{maint print register-groups} includes the groups that each
23135 register is a member of. @xref{Registers,, Registers, gdbint,
23136 @value{GDBN} Internals}.
23138 These commands take an optional parameter, a file name to which to
23139 write the information.
23141 @kindex maint print reggroups
23142 @item maint print reggroups @r{[}@var{file}@r{]}
23143 Print @value{GDBN}'s internal register group data structures. The
23144 optional argument @var{file} tells to what file to write the
23147 The register groups info looks like this:
23150 (@value{GDBP}) @kbd{maint print reggroups}
23163 This command forces @value{GDBN} to flush its internal register cache.
23165 @kindex maint print objfiles
23166 @cindex info for known object files
23167 @item maint print objfiles
23168 Print a dump of all known object files. For each object file, this
23169 command prints its name, address in memory, and all of its psymtabs
23172 @kindex maint print statistics
23173 @cindex bcache statistics
23174 @item maint print statistics
23175 This command prints, for each object file in the program, various data
23176 about that object file followed by the byte cache (@dfn{bcache})
23177 statistics for the object file. The objfile data includes the number
23178 of minimal, partial, full, and stabs symbols, the number of types
23179 defined by the objfile, the number of as yet unexpanded psym tables,
23180 the number of line tables and string tables, and the amount of memory
23181 used by the various tables. The bcache statistics include the counts,
23182 sizes, and counts of duplicates of all and unique objects, max,
23183 average, and median entry size, total memory used and its overhead and
23184 savings, and various measures of the hash table size and chain
23187 @kindex maint print target-stack
23188 @cindex target stack description
23189 @item maint print target-stack
23190 A @dfn{target} is an interface between the debugger and a particular
23191 kind of file or process. Targets can be stacked in @dfn{strata},
23192 so that more than one target can potentially respond to a request.
23193 In particular, memory accesses will walk down the stack of targets
23194 until they find a target that is interested in handling that particular
23197 This command prints a short description of each layer that was pushed on
23198 the @dfn{target stack}, starting from the top layer down to the bottom one.
23200 @kindex maint print type
23201 @cindex type chain of a data type
23202 @item maint print type @var{expr}
23203 Print the type chain for a type specified by @var{expr}. The argument
23204 can be either a type name or a symbol. If it is a symbol, the type of
23205 that symbol is described. The type chain produced by this command is
23206 a recursive definition of the data type as stored in @value{GDBN}'s
23207 data structures, including its flags and contained types.
23209 @kindex maint set dwarf2 max-cache-age
23210 @kindex maint show dwarf2 max-cache-age
23211 @item maint set dwarf2 max-cache-age
23212 @itemx maint show dwarf2 max-cache-age
23213 Control the DWARF 2 compilation unit cache.
23215 @cindex DWARF 2 compilation units cache
23216 In object files with inter-compilation-unit references, such as those
23217 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
23218 reader needs to frequently refer to previously read compilation units.
23219 This setting controls how long a compilation unit will remain in the
23220 cache if it is not referenced. A higher limit means that cached
23221 compilation units will be stored in memory longer, and more total
23222 memory will be used. Setting it to zero disables caching, which will
23223 slow down @value{GDBN} startup, but reduce memory consumption.
23225 @kindex maint set profile
23226 @kindex maint show profile
23227 @cindex profiling GDB
23228 @item maint set profile
23229 @itemx maint show profile
23230 Control profiling of @value{GDBN}.
23232 Profiling will be disabled until you use the @samp{maint set profile}
23233 command to enable it. When you enable profiling, the system will begin
23234 collecting timing and execution count data; when you disable profiling or
23235 exit @value{GDBN}, the results will be written to a log file. Remember that
23236 if you use profiling, @value{GDBN} will overwrite the profiling log file
23237 (often called @file{gmon.out}). If you have a record of important profiling
23238 data in a @file{gmon.out} file, be sure to move it to a safe location.
23240 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
23241 compiled with the @samp{-pg} compiler option.
23243 @kindex maint show-debug-regs
23244 @cindex x86 hardware debug registers
23245 @item maint show-debug-regs
23246 Control whether to show variables that mirror the x86 hardware debug
23247 registers. Use @code{ON} to enable, @code{OFF} to disable. If
23248 enabled, the debug registers values are shown when @value{GDBN} inserts or
23249 removes a hardware breakpoint or watchpoint, and when the inferior
23250 triggers a hardware-assisted breakpoint or watchpoint.
23252 @kindex maint space
23253 @cindex memory used by commands
23255 Control whether to display memory usage for each command. If set to a
23256 nonzero value, @value{GDBN} will display how much memory each command
23257 took, following the command's own output. This can also be requested
23258 by invoking @value{GDBN} with the @option{--statistics} command-line
23259 switch (@pxref{Mode Options}).
23262 @cindex time of command execution
23264 Control whether to display the execution time for each command. If
23265 set to a nonzero value, @value{GDBN} will display how much time it
23266 took to execute each command, following the command's own output.
23267 This can also be requested by invoking @value{GDBN} with the
23268 @option{--statistics} command-line switch (@pxref{Mode Options}).
23270 @kindex maint translate-address
23271 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
23272 Find the symbol stored at the location specified by the address
23273 @var{addr} and an optional section name @var{section}. If found,
23274 @value{GDBN} prints the name of the closest symbol and an offset from
23275 the symbol's location to the specified address. This is similar to
23276 the @code{info address} command (@pxref{Symbols}), except that this
23277 command also allows to find symbols in other sections.
23281 The following command is useful for non-interactive invocations of
23282 @value{GDBN}, such as in the test suite.
23285 @item set watchdog @var{nsec}
23286 @kindex set watchdog
23287 @cindex watchdog timer
23288 @cindex timeout for commands
23289 Set the maximum number of seconds @value{GDBN} will wait for the
23290 target operation to finish. If this time expires, @value{GDBN}
23291 reports and error and the command is aborted.
23293 @item show watchdog
23294 Show the current setting of the target wait timeout.
23297 @node Remote Protocol
23298 @appendix @value{GDBN} Remote Serial Protocol
23303 * Stop Reply Packets::
23304 * General Query Packets::
23305 * Register Packet Format::
23306 * Tracepoint Packets::
23307 * Host I/O Packets::
23310 * File-I/O Remote Protocol Extension::
23311 * Library List Format::
23312 * Memory Map Format::
23318 There may be occasions when you need to know something about the
23319 protocol---for example, if there is only one serial port to your target
23320 machine, you might want your program to do something special if it
23321 recognizes a packet meant for @value{GDBN}.
23323 In the examples below, @samp{->} and @samp{<-} are used to indicate
23324 transmitted and received data, respectively.
23326 @cindex protocol, @value{GDBN} remote serial
23327 @cindex serial protocol, @value{GDBN} remote
23328 @cindex remote serial protocol
23329 All @value{GDBN} commands and responses (other than acknowledgments) are
23330 sent as a @var{packet}. A @var{packet} is introduced with the character
23331 @samp{$}, the actual @var{packet-data}, and the terminating character
23332 @samp{#} followed by a two-digit @var{checksum}:
23335 @code{$}@var{packet-data}@code{#}@var{checksum}
23339 @cindex checksum, for @value{GDBN} remote
23341 The two-digit @var{checksum} is computed as the modulo 256 sum of all
23342 characters between the leading @samp{$} and the trailing @samp{#} (an
23343 eight bit unsigned checksum).
23345 Implementors should note that prior to @value{GDBN} 5.0 the protocol
23346 specification also included an optional two-digit @var{sequence-id}:
23349 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
23352 @cindex sequence-id, for @value{GDBN} remote
23354 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
23355 has never output @var{sequence-id}s. Stubs that handle packets added
23356 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
23358 @cindex acknowledgment, for @value{GDBN} remote
23359 When either the host or the target machine receives a packet, the first
23360 response expected is an acknowledgment: either @samp{+} (to indicate
23361 the package was received correctly) or @samp{-} (to request
23365 -> @code{$}@var{packet-data}@code{#}@var{checksum}
23370 The host (@value{GDBN}) sends @var{command}s, and the target (the
23371 debugging stub incorporated in your program) sends a @var{response}. In
23372 the case of step and continue @var{command}s, the response is only sent
23373 when the operation has completed (the target has again stopped).
23375 @var{packet-data} consists of a sequence of characters with the
23376 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
23379 @cindex remote protocol, field separator
23380 Fields within the packet should be separated using @samp{,} @samp{;} or
23381 @samp{:}. Except where otherwise noted all numbers are represented in
23382 @sc{hex} with leading zeros suppressed.
23384 Implementors should note that prior to @value{GDBN} 5.0, the character
23385 @samp{:} could not appear as the third character in a packet (as it
23386 would potentially conflict with the @var{sequence-id}).
23388 @cindex remote protocol, binary data
23389 @anchor{Binary Data}
23390 Binary data in most packets is encoded either as two hexadecimal
23391 digits per byte of binary data. This allowed the traditional remote
23392 protocol to work over connections which were only seven-bit clean.
23393 Some packets designed more recently assume an eight-bit clean
23394 connection, and use a more efficient encoding to send and receive
23397 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
23398 as an escape character. Any escaped byte is transmitted as the escape
23399 character followed by the original character XORed with @code{0x20}.
23400 For example, the byte @code{0x7d} would be transmitted as the two
23401 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
23402 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
23403 @samp{@}}) must always be escaped. Responses sent by the stub
23404 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
23405 is not interpreted as the start of a run-length encoded sequence
23408 Response @var{data} can be run-length encoded to save space.
23409 Run-length encoding replaces runs of identical characters with one
23410 instance of the repeated character, followed by a @samp{*} and a
23411 repeat count. The repeat count is itself sent encoded, to avoid
23412 binary characters in @var{data}: a value of @var{n} is sent as
23413 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
23414 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
23415 code 32) for a repeat count of 3. (This is because run-length
23416 encoding starts to win for counts 3 or more.) Thus, for example,
23417 @samp{0* } is a run-length encoding of ``0000'': the space character
23418 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
23421 The printable characters @samp{#} and @samp{$} or with a numeric value
23422 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
23423 seven repeats (@samp{$}) can be expanded using a repeat count of only
23424 five (@samp{"}). For example, @samp{00000000} can be encoded as
23427 The error response returned for some packets includes a two character
23428 error number. That number is not well defined.
23430 @cindex empty response, for unsupported packets
23431 For any @var{command} not supported by the stub, an empty response
23432 (@samp{$#00}) should be returned. That way it is possible to extend the
23433 protocol. A newer @value{GDBN} can tell if a packet is supported based
23436 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
23437 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
23443 The following table provides a complete list of all currently defined
23444 @var{command}s and their corresponding response @var{data}.
23445 @xref{File-I/O Remote Protocol Extension}, for details about the File
23446 I/O extension of the remote protocol.
23448 Each packet's description has a template showing the packet's overall
23449 syntax, followed by an explanation of the packet's meaning. We
23450 include spaces in some of the templates for clarity; these are not
23451 part of the packet's syntax. No @value{GDBN} packet uses spaces to
23452 separate its components. For example, a template like @samp{foo
23453 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
23454 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
23455 @var{baz}. @value{GDBN} does not transmit a space character between the
23456 @samp{foo} and the @var{bar}, or between the @var{bar} and the
23459 Note that all packet forms beginning with an upper- or lower-case
23460 letter, other than those described here, are reserved for future use.
23462 Here are the packet descriptions.
23467 @cindex @samp{!} packet
23468 @anchor{extended mode}
23469 Enable extended mode. In extended mode, the remote server is made
23470 persistent. The @samp{R} packet is used to restart the program being
23476 The remote target both supports and has enabled extended mode.
23480 @cindex @samp{?} packet
23481 Indicate the reason the target halted. The reply is the same as for
23485 @xref{Stop Reply Packets}, for the reply specifications.
23487 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
23488 @cindex @samp{A} packet
23489 Initialized @code{argv[]} array passed into program. @var{arglen}
23490 specifies the number of bytes in the hex encoded byte stream
23491 @var{arg}. See @code{gdbserver} for more details.
23496 The arguments were set.
23502 @cindex @samp{b} packet
23503 (Don't use this packet; its behavior is not well-defined.)
23504 Change the serial line speed to @var{baud}.
23506 JTC: @emph{When does the transport layer state change? When it's
23507 received, or after the ACK is transmitted. In either case, there are
23508 problems if the command or the acknowledgment packet is dropped.}
23510 Stan: @emph{If people really wanted to add something like this, and get
23511 it working for the first time, they ought to modify ser-unix.c to send
23512 some kind of out-of-band message to a specially-setup stub and have the
23513 switch happen "in between" packets, so that from remote protocol's point
23514 of view, nothing actually happened.}
23516 @item B @var{addr},@var{mode}
23517 @cindex @samp{B} packet
23518 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
23519 breakpoint at @var{addr}.
23521 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
23522 (@pxref{insert breakpoint or watchpoint packet}).
23524 @item c @r{[}@var{addr}@r{]}
23525 @cindex @samp{c} packet
23526 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
23527 resume at current address.
23530 @xref{Stop Reply Packets}, for the reply specifications.
23532 @item C @var{sig}@r{[};@var{addr}@r{]}
23533 @cindex @samp{C} packet
23534 Continue with signal @var{sig} (hex signal number). If
23535 @samp{;@var{addr}} is omitted, resume at same address.
23538 @xref{Stop Reply Packets}, for the reply specifications.
23541 @cindex @samp{d} packet
23544 Don't use this packet; instead, define a general set packet
23545 (@pxref{General Query Packets}).
23548 @cindex @samp{D} packet
23549 Detach @value{GDBN} from the remote system. Sent to the remote target
23550 before @value{GDBN} disconnects via the @code{detach} command.
23560 @item F @var{RC},@var{EE},@var{CF};@var{XX}
23561 @cindex @samp{F} packet
23562 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
23563 This is part of the File-I/O protocol extension. @xref{File-I/O
23564 Remote Protocol Extension}, for the specification.
23567 @anchor{read registers packet}
23568 @cindex @samp{g} packet
23569 Read general registers.
23573 @item @var{XX@dots{}}
23574 Each byte of register data is described by two hex digits. The bytes
23575 with the register are transmitted in target byte order. The size of
23576 each register and their position within the @samp{g} packet are
23577 determined by the @value{GDBN} internal gdbarch functions
23578 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
23579 specification of several standard @samp{g} packets is specified below.
23584 @item G @var{XX@dots{}}
23585 @cindex @samp{G} packet
23586 Write general registers. @xref{read registers packet}, for a
23587 description of the @var{XX@dots{}} data.
23597 @item H @var{c} @var{t}
23598 @cindex @samp{H} packet
23599 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
23600 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
23601 should be @samp{c} for step and continue operations, @samp{g} for other
23602 operations. The thread designator @var{t} may be @samp{-1}, meaning all
23603 the threads, a thread number, or @samp{0} which means pick any thread.
23614 @c 'H': How restrictive (or permissive) is the thread model. If a
23615 @c thread is selected and stopped, are other threads allowed
23616 @c to continue to execute? As I mentioned above, I think the
23617 @c semantics of each command when a thread is selected must be
23618 @c described. For example:
23620 @c 'g': If the stub supports threads and a specific thread is
23621 @c selected, returns the register block from that thread;
23622 @c otherwise returns current registers.
23624 @c 'G' If the stub supports threads and a specific thread is
23625 @c selected, sets the registers of the register block of
23626 @c that thread; otherwise sets current registers.
23628 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
23629 @anchor{cycle step packet}
23630 @cindex @samp{i} packet
23631 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
23632 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
23633 step starting at that address.
23636 @cindex @samp{I} packet
23637 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
23641 @cindex @samp{k} packet
23644 FIXME: @emph{There is no description of how to operate when a specific
23645 thread context has been selected (i.e.@: does 'k' kill only that
23648 @item m @var{addr},@var{length}
23649 @cindex @samp{m} packet
23650 Read @var{length} bytes of memory starting at address @var{addr}.
23651 Note that @var{addr} may not be aligned to any particular boundary.
23653 The stub need not use any particular size or alignment when gathering
23654 data from memory for the response; even if @var{addr} is word-aligned
23655 and @var{length} is a multiple of the word size, the stub is free to
23656 use byte accesses, or not. For this reason, this packet may not be
23657 suitable for accessing memory-mapped I/O devices.
23658 @cindex alignment of remote memory accesses
23659 @cindex size of remote memory accesses
23660 @cindex memory, alignment and size of remote accesses
23664 @item @var{XX@dots{}}
23665 Memory contents; each byte is transmitted as a two-digit hexadecimal
23666 number. The reply may contain fewer bytes than requested if the
23667 server was able to read only part of the region of memory.
23672 @item M @var{addr},@var{length}:@var{XX@dots{}}
23673 @cindex @samp{M} packet
23674 Write @var{length} bytes of memory starting at address @var{addr}.
23675 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
23676 hexadecimal number.
23683 for an error (this includes the case where only part of the data was
23688 @cindex @samp{p} packet
23689 Read the value of register @var{n}; @var{n} is in hex.
23690 @xref{read registers packet}, for a description of how the returned
23691 register value is encoded.
23695 @item @var{XX@dots{}}
23696 the register's value
23700 Indicating an unrecognized @var{query}.
23703 @item P @var{n@dots{}}=@var{r@dots{}}
23704 @anchor{write register packet}
23705 @cindex @samp{P} packet
23706 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
23707 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
23708 digits for each byte in the register (target byte order).
23718 @item q @var{name} @var{params}@dots{}
23719 @itemx Q @var{name} @var{params}@dots{}
23720 @cindex @samp{q} packet
23721 @cindex @samp{Q} packet
23722 General query (@samp{q}) and set (@samp{Q}). These packets are
23723 described fully in @ref{General Query Packets}.
23726 @cindex @samp{r} packet
23727 Reset the entire system.
23729 Don't use this packet; use the @samp{R} packet instead.
23732 @cindex @samp{R} packet
23733 Restart the program being debugged. @var{XX}, while needed, is ignored.
23734 This packet is only available in extended mode (@pxref{extended mode}).
23736 The @samp{R} packet has no reply.
23738 @item s @r{[}@var{addr}@r{]}
23739 @cindex @samp{s} packet
23740 Single step. @var{addr} is the address at which to resume. If
23741 @var{addr} is omitted, resume at same address.
23744 @xref{Stop Reply Packets}, for the reply specifications.
23746 @item S @var{sig}@r{[};@var{addr}@r{]}
23747 @anchor{step with signal packet}
23748 @cindex @samp{S} packet
23749 Step with signal. This is analogous to the @samp{C} packet, but
23750 requests a single-step, rather than a normal resumption of execution.
23753 @xref{Stop Reply Packets}, for the reply specifications.
23755 @item t @var{addr}:@var{PP},@var{MM}
23756 @cindex @samp{t} packet
23757 Search backwards starting at address @var{addr} for a match with pattern
23758 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
23759 @var{addr} must be at least 3 digits.
23762 @cindex @samp{T} packet
23763 Find out if the thread XX is alive.
23768 thread is still alive
23774 Packets starting with @samp{v} are identified by a multi-letter name,
23775 up to the first @samp{;} or @samp{?} (or the end of the packet).
23777 @item vAttach;@var{pid}
23778 @cindex @samp{vAttach} packet
23779 Attach to a new process with the specified process ID. @var{pid} is a
23780 hexadecimal integer identifying the process. If the stub is currently
23781 controlling a process, it is killed. The attached process is stopped.
23783 This packet is only available in extended mode (@pxref{extended mode}).
23789 @item @r{Any stop packet}
23790 for success (@pxref{Stop Reply Packets})
23793 @item vCont@r{[};@var{action}@r{[}:@var{tid}@r{]]}@dots{}
23794 @cindex @samp{vCont} packet
23795 Resume the inferior, specifying different actions for each thread.
23796 If an action is specified with no @var{tid}, then it is applied to any
23797 threads that don't have a specific action specified; if no default action is
23798 specified then other threads should remain stopped. Specifying multiple
23799 default actions is an error; specifying no actions is also an error.
23800 Thread IDs are specified in hexadecimal. Currently supported actions are:
23806 Continue with signal @var{sig}. @var{sig} should be two hex digits.
23810 Step with signal @var{sig}. @var{sig} should be two hex digits.
23813 The optional @var{addr} argument normally associated with these packets is
23814 not supported in @samp{vCont}.
23817 @xref{Stop Reply Packets}, for the reply specifications.
23820 @cindex @samp{vCont?} packet
23821 Request a list of actions supported by the @samp{vCont} packet.
23825 @item vCont@r{[};@var{action}@dots{}@r{]}
23826 The @samp{vCont} packet is supported. Each @var{action} is a supported
23827 command in the @samp{vCont} packet.
23829 The @samp{vCont} packet is not supported.
23832 @item vFile:@var{operation}:@var{parameter}@dots{}
23833 @cindex @samp{vFile} packet
23834 Perform a file operation on the target system. For details,
23835 see @ref{Host I/O Packets}.
23837 @item vFlashErase:@var{addr},@var{length}
23838 @cindex @samp{vFlashErase} packet
23839 Direct the stub to erase @var{length} bytes of flash starting at
23840 @var{addr}. The region may enclose any number of flash blocks, but
23841 its start and end must fall on block boundaries, as indicated by the
23842 flash block size appearing in the memory map (@pxref{Memory Map
23843 Format}). @value{GDBN} groups flash memory programming operations
23844 together, and sends a @samp{vFlashDone} request after each group; the
23845 stub is allowed to delay erase operation until the @samp{vFlashDone}
23846 packet is received.
23856 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
23857 @cindex @samp{vFlashWrite} packet
23858 Direct the stub to write data to flash address @var{addr}. The data
23859 is passed in binary form using the same encoding as for the @samp{X}
23860 packet (@pxref{Binary Data}). The memory ranges specified by
23861 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
23862 not overlap, and must appear in order of increasing addresses
23863 (although @samp{vFlashErase} packets for higher addresses may already
23864 have been received; the ordering is guaranteed only between
23865 @samp{vFlashWrite} packets). If a packet writes to an address that was
23866 neither erased by a preceding @samp{vFlashErase} packet nor by some other
23867 target-specific method, the results are unpredictable.
23875 for vFlashWrite addressing non-flash memory
23881 @cindex @samp{vFlashDone} packet
23882 Indicate to the stub that flash programming operation is finished.
23883 The stub is permitted to delay or batch the effects of a group of
23884 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
23885 @samp{vFlashDone} packet is received. The contents of the affected
23886 regions of flash memory are unpredictable until the @samp{vFlashDone}
23887 request is completed.
23889 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
23890 @cindex @samp{vRun} packet
23891 Run the program @var{filename}, passing it each @var{argument} on its
23892 command line. The file and arguments are hex-encoded strings. If
23893 @var{filename} is an empty string, the stub may use a default program
23894 (e.g.@: the last program run). The program is created in the stopped
23895 state. If the stub is currently controlling a process, it is killed.
23897 This packet is only available in extended mode (@pxref{extended mode}).
23903 @item @r{Any stop packet}
23904 for success (@pxref{Stop Reply Packets})
23907 @item X @var{addr},@var{length}:@var{XX@dots{}}
23909 @cindex @samp{X} packet
23910 Write data to memory, where the data is transmitted in binary.
23911 @var{addr} is address, @var{length} is number of bytes,
23912 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
23922 @item z @var{type},@var{addr},@var{length}
23923 @itemx Z @var{type},@var{addr},@var{length}
23924 @anchor{insert breakpoint or watchpoint packet}
23925 @cindex @samp{z} packet
23926 @cindex @samp{Z} packets
23927 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
23928 watchpoint starting at address @var{address} and covering the next
23929 @var{length} bytes.
23931 Each breakpoint and watchpoint packet @var{type} is documented
23934 @emph{Implementation notes: A remote target shall return an empty string
23935 for an unrecognized breakpoint or watchpoint packet @var{type}. A
23936 remote target shall support either both or neither of a given
23937 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
23938 avoid potential problems with duplicate packets, the operations should
23939 be implemented in an idempotent way.}
23941 @item z0,@var{addr},@var{length}
23942 @itemx Z0,@var{addr},@var{length}
23943 @cindex @samp{z0} packet
23944 @cindex @samp{Z0} packet
23945 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
23946 @var{addr} of size @var{length}.
23948 A memory breakpoint is implemented by replacing the instruction at
23949 @var{addr} with a software breakpoint or trap instruction. The
23950 @var{length} is used by targets that indicates the size of the
23951 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
23952 @sc{mips} can insert either a 2 or 4 byte breakpoint).
23954 @emph{Implementation note: It is possible for a target to copy or move
23955 code that contains memory breakpoints (e.g., when implementing
23956 overlays). The behavior of this packet, in the presence of such a
23957 target, is not defined.}
23969 @item z1,@var{addr},@var{length}
23970 @itemx Z1,@var{addr},@var{length}
23971 @cindex @samp{z1} packet
23972 @cindex @samp{Z1} packet
23973 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
23974 address @var{addr} of size @var{length}.
23976 A hardware breakpoint is implemented using a mechanism that is not
23977 dependant on being able to modify the target's memory.
23979 @emph{Implementation note: A hardware breakpoint is not affected by code
23992 @item z2,@var{addr},@var{length}
23993 @itemx Z2,@var{addr},@var{length}
23994 @cindex @samp{z2} packet
23995 @cindex @samp{Z2} packet
23996 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint.
24008 @item z3,@var{addr},@var{length}
24009 @itemx Z3,@var{addr},@var{length}
24010 @cindex @samp{z3} packet
24011 @cindex @samp{Z3} packet
24012 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint.
24024 @item z4,@var{addr},@var{length}
24025 @itemx Z4,@var{addr},@var{length}
24026 @cindex @samp{z4} packet
24027 @cindex @samp{Z4} packet
24028 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint.
24042 @node Stop Reply Packets
24043 @section Stop Reply Packets
24044 @cindex stop reply packets
24046 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
24047 receive any of the below as a reply. In the case of the @samp{C},
24048 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
24049 when the target halts. In the below the exact meaning of @dfn{signal
24050 number} is defined by the header @file{include/gdb/signals.h} in the
24051 @value{GDBN} source code.
24053 As in the description of request packets, we include spaces in the
24054 reply templates for clarity; these are not part of the reply packet's
24055 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
24061 The program received signal number @var{AA} (a two-digit hexadecimal
24062 number). This is equivalent to a @samp{T} response with no
24063 @var{n}:@var{r} pairs.
24065 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
24066 @cindex @samp{T} packet reply
24067 The program received signal number @var{AA} (a two-digit hexadecimal
24068 number). This is equivalent to an @samp{S} response, except that the
24069 @samp{@var{n}:@var{r}} pairs can carry values of important registers
24070 and other information directly in the stop reply packet, reducing
24071 round-trip latency. Single-step and breakpoint traps are reported
24072 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
24076 If @var{n} is a hexadecimal number, it is a register number, and the
24077 corresponding @var{r} gives that register's value. @var{r} is a
24078 series of bytes in target byte order, with each byte given by a
24079 two-digit hex number.
24082 If @var{n} is @samp{thread}, then @var{r} is the thread process ID, in
24086 If @var{n} is a recognized @dfn{stop reason}, it describes a more
24087 specific event that stopped the target. The currently defined stop
24088 reasons are listed below. @var{aa} should be @samp{05}, the trap
24089 signal. At most one stop reason should be present.
24092 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
24093 and go on to the next; this allows us to extend the protocol in the
24097 The currently defined stop reasons are:
24103 The packet indicates a watchpoint hit, and @var{r} is the data address, in
24106 @cindex shared library events, remote reply
24108 The packet indicates that the loaded libraries have changed.
24109 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
24110 list of loaded libraries. @var{r} is ignored.
24114 The process exited, and @var{AA} is the exit status. This is only
24115 applicable to certain targets.
24118 The process terminated with signal @var{AA}.
24120 @item O @var{XX}@dots{}
24121 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
24122 written as the program's console output. This can happen at any time
24123 while the program is running and the debugger should continue to wait
24124 for @samp{W}, @samp{T}, etc.
24126 @item F @var{call-id},@var{parameter}@dots{}
24127 @var{call-id} is the identifier which says which host system call should
24128 be called. This is just the name of the function. Translation into the
24129 correct system call is only applicable as it's defined in @value{GDBN}.
24130 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
24133 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
24134 this very system call.
24136 The target replies with this packet when it expects @value{GDBN} to
24137 call a host system call on behalf of the target. @value{GDBN} replies
24138 with an appropriate @samp{F} packet and keeps up waiting for the next
24139 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
24140 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
24141 Protocol Extension}, for more details.
24145 @node General Query Packets
24146 @section General Query Packets
24147 @cindex remote query requests
24149 Packets starting with @samp{q} are @dfn{general query packets};
24150 packets starting with @samp{Q} are @dfn{general set packets}. General
24151 query and set packets are a semi-unified form for retrieving and
24152 sending information to and from the stub.
24154 The initial letter of a query or set packet is followed by a name
24155 indicating what sort of thing the packet applies to. For example,
24156 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
24157 definitions with the stub. These packet names follow some
24162 The name must not contain commas, colons or semicolons.
24164 Most @value{GDBN} query and set packets have a leading upper case
24167 The names of custom vendor packets should use a company prefix, in
24168 lower case, followed by a period. For example, packets designed at
24169 the Acme Corporation might begin with @samp{qacme.foo} (for querying
24170 foos) or @samp{Qacme.bar} (for setting bars).
24173 The name of a query or set packet should be separated from any
24174 parameters by a @samp{:}; the parameters themselves should be
24175 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
24176 full packet name, and check for a separator or the end of the packet,
24177 in case two packet names share a common prefix. New packets should not begin
24178 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
24179 packets predate these conventions, and have arguments without any terminator
24180 for the packet name; we suspect they are in widespread use in places that
24181 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
24182 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
24185 Like the descriptions of the other packets, each description here
24186 has a template showing the packet's overall syntax, followed by an
24187 explanation of the packet's meaning. We include spaces in some of the
24188 templates for clarity; these are not part of the packet's syntax. No
24189 @value{GDBN} packet uses spaces to separate its components.
24191 Here are the currently defined query and set packets:
24196 @cindex current thread, remote request
24197 @cindex @samp{qC} packet
24198 Return the current thread id.
24203 Where @var{pid} is an unsigned hexadecimal process id.
24204 @item @r{(anything else)}
24205 Any other reply implies the old pid.
24208 @item qCRC:@var{addr},@var{length}
24209 @cindex CRC of memory block, remote request
24210 @cindex @samp{qCRC} packet
24211 Compute the CRC checksum of a block of memory.
24215 An error (such as memory fault)
24216 @item C @var{crc32}
24217 The specified memory region's checksum is @var{crc32}.
24221 @itemx qsThreadInfo
24222 @cindex list active threads, remote request
24223 @cindex @samp{qfThreadInfo} packet
24224 @cindex @samp{qsThreadInfo} packet
24225 Obtain a list of all active thread ids from the target (OS). Since there
24226 may be too many active threads to fit into one reply packet, this query
24227 works iteratively: it may require more than one query/reply sequence to
24228 obtain the entire list of threads. The first query of the sequence will
24229 be the @samp{qfThreadInfo} query; subsequent queries in the
24230 sequence will be the @samp{qsThreadInfo} query.
24232 NOTE: This packet replaces the @samp{qL} query (see below).
24238 @item m @var{id},@var{id}@dots{}
24239 a comma-separated list of thread ids
24241 (lower case letter @samp{L}) denotes end of list.
24244 In response to each query, the target will reply with a list of one or
24245 more thread ids, in big-endian unsigned hex, separated by commas.
24246 @value{GDBN} will respond to each reply with a request for more thread
24247 ids (using the @samp{qs} form of the query), until the target responds
24248 with @samp{l} (lower-case el, for @dfn{last}).
24250 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
24251 @cindex get thread-local storage address, remote request
24252 @cindex @samp{qGetTLSAddr} packet
24253 Fetch the address associated with thread local storage specified
24254 by @var{thread-id}, @var{offset}, and @var{lm}.
24256 @var{thread-id} is the (big endian, hex encoded) thread id associated with the
24257 thread for which to fetch the TLS address.
24259 @var{offset} is the (big endian, hex encoded) offset associated with the
24260 thread local variable. (This offset is obtained from the debug
24261 information associated with the variable.)
24263 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
24264 the load module associated with the thread local storage. For example,
24265 a @sc{gnu}/Linux system will pass the link map address of the shared
24266 object associated with the thread local storage under consideration.
24267 Other operating environments may choose to represent the load module
24268 differently, so the precise meaning of this parameter will vary.
24272 @item @var{XX}@dots{}
24273 Hex encoded (big endian) bytes representing the address of the thread
24274 local storage requested.
24277 An error occurred. @var{nn} are hex digits.
24280 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
24283 @item qL @var{startflag} @var{threadcount} @var{nextthread}
24284 Obtain thread information from RTOS. Where: @var{startflag} (one hex
24285 digit) is one to indicate the first query and zero to indicate a
24286 subsequent query; @var{threadcount} (two hex digits) is the maximum
24287 number of threads the response packet can contain; and @var{nextthread}
24288 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
24289 returned in the response as @var{argthread}.
24291 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
24295 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
24296 Where: @var{count} (two hex digits) is the number of threads being
24297 returned; @var{done} (one hex digit) is zero to indicate more threads
24298 and one indicates no further threads; @var{argthreadid} (eight hex
24299 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
24300 is a sequence of thread IDs from the target. @var{threadid} (eight hex
24301 digits). See @code{remote.c:parse_threadlist_response()}.
24305 @cindex section offsets, remote request
24306 @cindex @samp{qOffsets} packet
24307 Get section offsets that the target used when relocating the downloaded
24312 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
24313 Relocate the @code{Text} section by @var{xxx} from its original address.
24314 Relocate the @code{Data} section by @var{yyy} from its original address.
24315 If the object file format provides segment information (e.g.@: @sc{elf}
24316 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
24317 segments by the supplied offsets.
24319 @emph{Note: while a @code{Bss} offset may be included in the response,
24320 @value{GDBN} ignores this and instead applies the @code{Data} offset
24321 to the @code{Bss} section.}
24323 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
24324 Relocate the first segment of the object file, which conventionally
24325 contains program code, to a starting address of @var{xxx}. If
24326 @samp{DataSeg} is specified, relocate the second segment, which
24327 conventionally contains modifiable data, to a starting address of
24328 @var{yyy}. @value{GDBN} will report an error if the object file
24329 does not contain segment information, or does not contain at least
24330 as many segments as mentioned in the reply. Extra segments are
24331 kept at fixed offsets relative to the last relocated segment.
24334 @item qP @var{mode} @var{threadid}
24335 @cindex thread information, remote request
24336 @cindex @samp{qP} packet
24337 Returns information on @var{threadid}. Where: @var{mode} is a hex
24338 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
24340 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
24343 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
24345 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
24346 @cindex pass signals to inferior, remote request
24347 @cindex @samp{QPassSignals} packet
24348 @anchor{QPassSignals}
24349 Each listed @var{signal} should be passed directly to the inferior process.
24350 Signals are numbered identically to continue packets and stop replies
24351 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
24352 strictly greater than the previous item. These signals do not need to stop
24353 the inferior, or be reported to @value{GDBN}. All other signals should be
24354 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
24355 combine; any earlier @samp{QPassSignals} list is completely replaced by the
24356 new list. This packet improves performance when using @samp{handle
24357 @var{signal} nostop noprint pass}.
24362 The request succeeded.
24365 An error occurred. @var{nn} are hex digits.
24368 An empty reply indicates that @samp{QPassSignals} is not supported by
24372 Use of this packet is controlled by the @code{set remote pass-signals}
24373 command (@pxref{Remote Configuration, set remote pass-signals}).
24374 This packet is not probed by default; the remote stub must request it,
24375 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24377 @item qRcmd,@var{command}
24378 @cindex execute remote command, remote request
24379 @cindex @samp{qRcmd} packet
24380 @var{command} (hex encoded) is passed to the local interpreter for
24381 execution. Invalid commands should be reported using the output
24382 string. Before the final result packet, the target may also respond
24383 with a number of intermediate @samp{O@var{output}} console output
24384 packets. @emph{Implementors should note that providing access to a
24385 stubs's interpreter may have security implications}.
24390 A command response with no output.
24392 A command response with the hex encoded output string @var{OUTPUT}.
24394 Indicate a badly formed request.
24396 An empty reply indicates that @samp{qRcmd} is not recognized.
24399 (Note that the @code{qRcmd} packet's name is separated from the
24400 command by a @samp{,}, not a @samp{:}, contrary to the naming
24401 conventions above. Please don't use this packet as a model for new
24404 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
24405 @cindex supported packets, remote query
24406 @cindex features of the remote protocol
24407 @cindex @samp{qSupported} packet
24408 @anchor{qSupported}
24409 Tell the remote stub about features supported by @value{GDBN}, and
24410 query the stub for features it supports. This packet allows
24411 @value{GDBN} and the remote stub to take advantage of each others'
24412 features. @samp{qSupported} also consolidates multiple feature probes
24413 at startup, to improve @value{GDBN} performance---a single larger
24414 packet performs better than multiple smaller probe packets on
24415 high-latency links. Some features may enable behavior which must not
24416 be on by default, e.g.@: because it would confuse older clients or
24417 stubs. Other features may describe packets which could be
24418 automatically probed for, but are not. These features must be
24419 reported before @value{GDBN} will use them. This ``default
24420 unsupported'' behavior is not appropriate for all packets, but it
24421 helps to keep the initial connection time under control with new
24422 versions of @value{GDBN} which support increasing numbers of packets.
24426 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
24427 The stub supports or does not support each returned @var{stubfeature},
24428 depending on the form of each @var{stubfeature} (see below for the
24431 An empty reply indicates that @samp{qSupported} is not recognized,
24432 or that no features needed to be reported to @value{GDBN}.
24435 The allowed forms for each feature (either a @var{gdbfeature} in the
24436 @samp{qSupported} packet, or a @var{stubfeature} in the response)
24440 @item @var{name}=@var{value}
24441 The remote protocol feature @var{name} is supported, and associated
24442 with the specified @var{value}. The format of @var{value} depends
24443 on the feature, but it must not include a semicolon.
24445 The remote protocol feature @var{name} is supported, and does not
24446 need an associated value.
24448 The remote protocol feature @var{name} is not supported.
24450 The remote protocol feature @var{name} may be supported, and
24451 @value{GDBN} should auto-detect support in some other way when it is
24452 needed. This form will not be used for @var{gdbfeature} notifications,
24453 but may be used for @var{stubfeature} responses.
24456 Whenever the stub receives a @samp{qSupported} request, the
24457 supplied set of @value{GDBN} features should override any previous
24458 request. This allows @value{GDBN} to put the stub in a known
24459 state, even if the stub had previously been communicating with
24460 a different version of @value{GDBN}.
24462 No values of @var{gdbfeature} (for the packet sent by @value{GDBN})
24463 are defined yet. Stubs should ignore any unknown values for
24464 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
24465 packet supports receiving packets of unlimited length (earlier
24466 versions of @value{GDBN} may reject overly long responses). Values
24467 for @var{gdbfeature} may be defined in the future to let the stub take
24468 advantage of new features in @value{GDBN}, e.g.@: incompatible
24469 improvements in the remote protocol---support for unlimited length
24470 responses would be a @var{gdbfeature} example, if it were not implied by
24471 the @samp{qSupported} query. The stub's reply should be independent
24472 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
24473 describes all the features it supports, and then the stub replies with
24474 all the features it supports.
24476 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
24477 responses, as long as each response uses one of the standard forms.
24479 Some features are flags. A stub which supports a flag feature
24480 should respond with a @samp{+} form response. Other features
24481 require values, and the stub should respond with an @samp{=}
24484 Each feature has a default value, which @value{GDBN} will use if
24485 @samp{qSupported} is not available or if the feature is not mentioned
24486 in the @samp{qSupported} response. The default values are fixed; a
24487 stub is free to omit any feature responses that match the defaults.
24489 Not all features can be probed, but for those which can, the probing
24490 mechanism is useful: in some cases, a stub's internal
24491 architecture may not allow the protocol layer to know some information
24492 about the underlying target in advance. This is especially common in
24493 stubs which may be configured for multiple targets.
24495 These are the currently defined stub features and their properties:
24497 @multitable @columnfractions 0.35 0.2 0.12 0.2
24498 @c NOTE: The first row should be @headitem, but we do not yet require
24499 @c a new enough version of Texinfo (4.7) to use @headitem.
24501 @tab Value Required
24505 @item @samp{PacketSize}
24510 @item @samp{qXfer:auxv:read}
24515 @item @samp{qXfer:features:read}
24520 @item @samp{qXfer:libraries:read}
24525 @item @samp{qXfer:memory-map:read}
24530 @item @samp{qXfer:spu:read}
24535 @item @samp{qXfer:spu:write}
24540 @item @samp{QPassSignals}
24547 These are the currently defined stub features, in more detail:
24550 @cindex packet size, remote protocol
24551 @item PacketSize=@var{bytes}
24552 The remote stub can accept packets up to at least @var{bytes} in
24553 length. @value{GDBN} will send packets up to this size for bulk
24554 transfers, and will never send larger packets. This is a limit on the
24555 data characters in the packet, including the frame and checksum.
24556 There is no trailing NUL byte in a remote protocol packet; if the stub
24557 stores packets in a NUL-terminated format, it should allow an extra
24558 byte in its buffer for the NUL. If this stub feature is not supported,
24559 @value{GDBN} guesses based on the size of the @samp{g} packet response.
24561 @item qXfer:auxv:read
24562 The remote stub understands the @samp{qXfer:auxv:read} packet
24563 (@pxref{qXfer auxiliary vector read}).
24565 @item qXfer:features:read
24566 The remote stub understands the @samp{qXfer:features:read} packet
24567 (@pxref{qXfer target description read}).
24569 @item qXfer:libraries:read
24570 The remote stub understands the @samp{qXfer:libraries:read} packet
24571 (@pxref{qXfer library list read}).
24573 @item qXfer:memory-map:read
24574 The remote stub understands the @samp{qXfer:memory-map:read} packet
24575 (@pxref{qXfer memory map read}).
24577 @item qXfer:spu:read
24578 The remote stub understands the @samp{qXfer:spu:read} packet
24579 (@pxref{qXfer spu read}).
24581 @item qXfer:spu:write
24582 The remote stub understands the @samp{qXfer:spu:write} packet
24583 (@pxref{qXfer spu write}).
24586 The remote stub understands the @samp{QPassSignals} packet
24587 (@pxref{QPassSignals}).
24592 @cindex symbol lookup, remote request
24593 @cindex @samp{qSymbol} packet
24594 Notify the target that @value{GDBN} is prepared to serve symbol lookup
24595 requests. Accept requests from the target for the values of symbols.
24600 The target does not need to look up any (more) symbols.
24601 @item qSymbol:@var{sym_name}
24602 The target requests the value of symbol @var{sym_name} (hex encoded).
24603 @value{GDBN} may provide the value by using the
24604 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
24608 @item qSymbol:@var{sym_value}:@var{sym_name}
24609 Set the value of @var{sym_name} to @var{sym_value}.
24611 @var{sym_name} (hex encoded) is the name of a symbol whose value the
24612 target has previously requested.
24614 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
24615 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
24621 The target does not need to look up any (more) symbols.
24622 @item qSymbol:@var{sym_name}
24623 The target requests the value of a new symbol @var{sym_name} (hex
24624 encoded). @value{GDBN} will continue to supply the values of symbols
24625 (if available), until the target ceases to request them.
24630 @xref{Tracepoint Packets}.
24632 @item qThreadExtraInfo,@var{id}
24633 @cindex thread attributes info, remote request
24634 @cindex @samp{qThreadExtraInfo} packet
24635 Obtain a printable string description of a thread's attributes from
24636 the target OS. @var{id} is a thread-id in big-endian hex. This
24637 string may contain anything that the target OS thinks is interesting
24638 for @value{GDBN} to tell the user about the thread. The string is
24639 displayed in @value{GDBN}'s @code{info threads} display. Some
24640 examples of possible thread extra info strings are @samp{Runnable}, or
24641 @samp{Blocked on Mutex}.
24645 @item @var{XX}@dots{}
24646 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
24647 comprising the printable string containing the extra information about
24648 the thread's attributes.
24651 (Note that the @code{qThreadExtraInfo} packet's name is separated from
24652 the command by a @samp{,}, not a @samp{:}, contrary to the naming
24653 conventions above. Please don't use this packet as a model for new
24661 @xref{Tracepoint Packets}.
24663 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
24664 @cindex read special object, remote request
24665 @cindex @samp{qXfer} packet
24666 @anchor{qXfer read}
24667 Read uninterpreted bytes from the target's special data area
24668 identified by the keyword @var{object}. Request @var{length} bytes
24669 starting at @var{offset} bytes into the data. The content and
24670 encoding of @var{annex} is specific to @var{object}; it can supply
24671 additional details about what data to access.
24673 Here are the specific requests of this form defined so far. All
24674 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
24675 formats, listed below.
24678 @item qXfer:auxv:read::@var{offset},@var{length}
24679 @anchor{qXfer auxiliary vector read}
24680 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
24681 auxiliary vector}. Note @var{annex} must be empty.
24683 This packet is not probed by default; the remote stub must request it,
24684 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24686 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
24687 @anchor{qXfer target description read}
24688 Access the @dfn{target description}. @xref{Target Descriptions}. The
24689 annex specifies which XML document to access. The main description is
24690 always loaded from the @samp{target.xml} annex.
24692 This packet is not probed by default; the remote stub must request it,
24693 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24695 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
24696 @anchor{qXfer library list read}
24697 Access the target's list of loaded libraries. @xref{Library List Format}.
24698 The annex part of the generic @samp{qXfer} packet must be empty
24699 (@pxref{qXfer read}).
24701 Targets which maintain a list of libraries in the program's memory do
24702 not need to implement this packet; it is designed for platforms where
24703 the operating system manages the list of loaded libraries.
24705 This packet is not probed by default; the remote stub must request it,
24706 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24708 @item qXfer:memory-map:read::@var{offset},@var{length}
24709 @anchor{qXfer memory map read}
24710 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
24711 annex part of the generic @samp{qXfer} packet must be empty
24712 (@pxref{qXfer read}).
24714 This packet is not probed by default; the remote stub must request it,
24715 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24717 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
24718 @anchor{qXfer spu read}
24719 Read contents of an @code{spufs} file on the target system. The
24720 annex specifies which file to read; it must be of the form
24721 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
24722 in the target process, and @var{name} identifes the @code{spufs} file
24723 in that context to be accessed.
24725 This packet is not probed by default; the remote stub must request it,
24726 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24732 Data @var{data} (@pxref{Binary Data}) has been read from the
24733 target. There may be more data at a higher address (although
24734 it is permitted to return @samp{m} even for the last valid
24735 block of data, as long as at least one byte of data was read).
24736 @var{data} may have fewer bytes than the @var{length} in the
24740 Data @var{data} (@pxref{Binary Data}) has been read from the target.
24741 There is no more data to be read. @var{data} may have fewer bytes
24742 than the @var{length} in the request.
24745 The @var{offset} in the request is at the end of the data.
24746 There is no more data to be read.
24749 The request was malformed, or @var{annex} was invalid.
24752 The offset was invalid, or there was an error encountered reading the data.
24753 @var{nn} is a hex-encoded @code{errno} value.
24756 An empty reply indicates the @var{object} string was not recognized by
24757 the stub, or that the object does not support reading.
24760 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
24761 @cindex write data into object, remote request
24762 Write uninterpreted bytes into the target's special data area
24763 identified by the keyword @var{object}, starting at @var{offset} bytes
24764 into the data. @var{data}@dots{} is the binary-encoded data
24765 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
24766 is specific to @var{object}; it can supply additional details about what data
24769 Here are the specific requests of this form defined so far. All
24770 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
24771 formats, listed below.
24774 @item qXfer:@var{spu}:write:@var{annex}:@var{offset}:@var{data}@dots{}
24775 @anchor{qXfer spu write}
24776 Write @var{data} to an @code{spufs} file on the target system. The
24777 annex specifies which file to write; it must be of the form
24778 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
24779 in the target process, and @var{name} identifes the @code{spufs} file
24780 in that context to be accessed.
24782 This packet is not probed by default; the remote stub must request it,
24783 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24789 @var{nn} (hex encoded) is the number of bytes written.
24790 This may be fewer bytes than supplied in the request.
24793 The request was malformed, or @var{annex} was invalid.
24796 The offset was invalid, or there was an error encountered writing the data.
24797 @var{nn} is a hex-encoded @code{errno} value.
24800 An empty reply indicates the @var{object} string was not
24801 recognized by the stub, or that the object does not support writing.
24804 @item qXfer:@var{object}:@var{operation}:@dots{}
24805 Requests of this form may be added in the future. When a stub does
24806 not recognize the @var{object} keyword, or its support for
24807 @var{object} does not recognize the @var{operation} keyword, the stub
24808 must respond with an empty packet.
24812 @node Register Packet Format
24813 @section Register Packet Format
24815 The following @code{g}/@code{G} packets have previously been defined.
24816 In the below, some thirty-two bit registers are transferred as
24817 sixty-four bits. Those registers should be zero/sign extended (which?)
24818 to fill the space allocated. Register bytes are transferred in target
24819 byte order. The two nibbles within a register byte are transferred
24820 most-significant - least-significant.
24826 All registers are transferred as thirty-two bit quantities in the order:
24827 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
24828 registers; fsr; fir; fp.
24832 All registers are transferred as sixty-four bit quantities (including
24833 thirty-two bit registers such as @code{sr}). The ordering is the same
24838 @node Tracepoint Packets
24839 @section Tracepoint Packets
24840 @cindex tracepoint packets
24841 @cindex packets, tracepoint
24843 Here we describe the packets @value{GDBN} uses to implement
24844 tracepoints (@pxref{Tracepoints}).
24848 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}@r{[}-@r{]}
24849 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
24850 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
24851 the tracepoint is disabled. @var{step} is the tracepoint's step
24852 count, and @var{pass} is its pass count. If the trailing @samp{-} is
24853 present, further @samp{QTDP} packets will follow to specify this
24854 tracepoint's actions.
24859 The packet was understood and carried out.
24861 The packet was not recognized.
24864 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
24865 Define actions to be taken when a tracepoint is hit. @var{n} and
24866 @var{addr} must be the same as in the initial @samp{QTDP} packet for
24867 this tracepoint. This packet may only be sent immediately after
24868 another @samp{QTDP} packet that ended with a @samp{-}. If the
24869 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
24870 specifying more actions for this tracepoint.
24872 In the series of action packets for a given tracepoint, at most one
24873 can have an @samp{S} before its first @var{action}. If such a packet
24874 is sent, it and the following packets define ``while-stepping''
24875 actions. Any prior packets define ordinary actions --- that is, those
24876 taken when the tracepoint is first hit. If no action packet has an
24877 @samp{S}, then all the packets in the series specify ordinary
24878 tracepoint actions.
24880 The @samp{@var{action}@dots{}} portion of the packet is a series of
24881 actions, concatenated without separators. Each action has one of the
24887 Collect the registers whose bits are set in @var{mask}. @var{mask} is
24888 a hexadecimal number whose @var{i}'th bit is set if register number
24889 @var{i} should be collected. (The least significant bit is numbered
24890 zero.) Note that @var{mask} may be any number of digits long; it may
24891 not fit in a 32-bit word.
24893 @item M @var{basereg},@var{offset},@var{len}
24894 Collect @var{len} bytes of memory starting at the address in register
24895 number @var{basereg}, plus @var{offset}. If @var{basereg} is
24896 @samp{-1}, then the range has a fixed address: @var{offset} is the
24897 address of the lowest byte to collect. The @var{basereg},
24898 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
24899 values (the @samp{-1} value for @var{basereg} is a special case).
24901 @item X @var{len},@var{expr}
24902 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
24903 it directs. @var{expr} is an agent expression, as described in
24904 @ref{Agent Expressions}. Each byte of the expression is encoded as a
24905 two-digit hex number in the packet; @var{len} is the number of bytes
24906 in the expression (and thus one-half the number of hex digits in the
24911 Any number of actions may be packed together in a single @samp{QTDP}
24912 packet, as long as the packet does not exceed the maximum packet
24913 length (400 bytes, for many stubs). There may be only one @samp{R}
24914 action per tracepoint, and it must precede any @samp{M} or @samp{X}
24915 actions. Any registers referred to by @samp{M} and @samp{X} actions
24916 must be collected by a preceding @samp{R} action. (The
24917 ``while-stepping'' actions are treated as if they were attached to a
24918 separate tracepoint, as far as these restrictions are concerned.)
24923 The packet was understood and carried out.
24925 The packet was not recognized.
24928 @item QTFrame:@var{n}
24929 Select the @var{n}'th tracepoint frame from the buffer, and use the
24930 register and memory contents recorded there to answer subsequent
24931 request packets from @value{GDBN}.
24933 A successful reply from the stub indicates that the stub has found the
24934 requested frame. The response is a series of parts, concatenated
24935 without separators, describing the frame we selected. Each part has
24936 one of the following forms:
24940 The selected frame is number @var{n} in the trace frame buffer;
24941 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
24942 was no frame matching the criteria in the request packet.
24945 The selected trace frame records a hit of tracepoint number @var{t};
24946 @var{t} is a hexadecimal number.
24950 @item QTFrame:pc:@var{addr}
24951 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
24952 currently selected frame whose PC is @var{addr};
24953 @var{addr} is a hexadecimal number.
24955 @item QTFrame:tdp:@var{t}
24956 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
24957 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
24958 is a hexadecimal number.
24960 @item QTFrame:range:@var{start}:@var{end}
24961 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
24962 currently selected frame whose PC is between @var{start} (inclusive)
24963 and @var{end} (exclusive); @var{start} and @var{end} are hexadecimal
24966 @item QTFrame:outside:@var{start}:@var{end}
24967 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
24968 frame @emph{outside} the given range of addresses.
24971 Begin the tracepoint experiment. Begin collecting data from tracepoint
24972 hits in the trace frame buffer.
24975 End the tracepoint experiment. Stop collecting trace frames.
24978 Clear the table of tracepoints, and empty the trace frame buffer.
24980 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
24981 Establish the given ranges of memory as ``transparent''. The stub
24982 will answer requests for these ranges from memory's current contents,
24983 if they were not collected as part of the tracepoint hit.
24985 @value{GDBN} uses this to mark read-only regions of memory, like those
24986 containing program code. Since these areas never change, they should
24987 still have the same contents they did when the tracepoint was hit, so
24988 there's no reason for the stub to refuse to provide their contents.
24991 Ask the stub if there is a trace experiment running right now.
24996 There is no trace experiment running.
24998 There is a trace experiment running.
25004 @node Host I/O Packets
25005 @section Host I/O Packets
25006 @cindex Host I/O, remote protocol
25007 @cindex file transfer, remote protocol
25009 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
25010 operations on the far side of a remote link. For example, Host I/O is
25011 used to upload and download files to a remote target with its own
25012 filesystem. Host I/O uses the same constant values and data structure
25013 layout as the target-initiated File-I/O protocol. However, the
25014 Host I/O packets are structured differently. The target-initiated
25015 protocol relies on target memory to store parameters and buffers.
25016 Host I/O requests are initiated by @value{GDBN}, and the
25017 target's memory is not involved. @xref{File-I/O Remote Protocol
25018 Extension}, for more details on the target-initiated protocol.
25020 The Host I/O request packets all encode a single operation along with
25021 its arguments. They have this format:
25025 @item vFile:@var{operation}: @var{parameter}@dots{}
25026 @var{operation} is the name of the particular request; the target
25027 should compare the entire packet name up to the second colon when checking
25028 for a supported operation. The format of @var{parameter} depends on
25029 the operation. Numbers are always passed in hexadecimal. Negative
25030 numbers have an explicit minus sign (i.e.@: two's complement is not
25031 used). Strings (e.g.@: filenames) are encoded as a series of
25032 hexadecimal bytes. The last argument to a system call may be a
25033 buffer of escaped binary data (@pxref{Binary Data}).
25037 The valid responses to Host I/O packets are:
25041 @item F @var{result} [, @var{errno}] [; @var{attachment}]
25042 @var{result} is the integer value returned by this operation, usually
25043 non-negative for success and -1 for errors. If an error has occured,
25044 @var{errno} will be included in the result. @var{errno} will have a
25045 value defined by the File-I/O protocol (@pxref{Errno Values}). For
25046 operations which return data, @var{attachment} supplies the data as a
25047 binary buffer. Binary buffers in response packets are escaped in the
25048 normal way (@pxref{Binary Data}). See the individual packet
25049 documentation for the interpretation of @var{result} and
25053 An empty response indicates that this operation is not recognized.
25057 These are the supported Host I/O operations:
25060 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
25061 Open a file at @var{pathname} and return a file descriptor for it, or
25062 return -1 if an error occurs. @var{pathname} is a string,
25063 @var{flags} is an integer indicating a mask of open flags
25064 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
25065 of mode bits to use if the file is created (@pxref{mode_t Values}).
25066 @xref{open}, for details of the open flags and mode values.
25068 @item vFile:close: @var{fd}
25069 Close the open file corresponding to @var{fd} and return 0, or
25070 -1 if an error occurs.
25072 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
25073 Read data from the open file corresponding to @var{fd}. Up to
25074 @var{count} bytes will be read from the file, starting at @var{offset}
25075 relative to the start of the file. The target may read fewer bytes;
25076 common reasons include packet size limits and an end-of-file
25077 condition. The number of bytes read is returned. Zero should only be
25078 returned for a successful read at the end of the file, or if
25079 @var{count} was zero.
25081 The data read should be returned as a binary attachment on success.
25082 If zero bytes were read, the response should include an empty binary
25083 attachment (i.e.@: a trailing semicolon). The return value is the
25084 number of target bytes read; the binary attachment may be longer if
25085 some characters were escaped.
25087 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
25088 Write @var{data} (a binary buffer) to the open file corresponding
25089 to @var{fd}. Start the write at @var{offset} from the start of the
25090 file. Unlike many @code{write} system calls, there is no
25091 separate @var{count} argument; the length of @var{data} in the
25092 packet is used. @samp{vFile:write} returns the number of bytes written,
25093 which may be shorter than the length of @var{data}, or -1 if an
25096 @item vFile:unlink: @var{pathname}
25097 Delete the file at @var{pathname} on the target. Return 0,
25098 or -1 if an error occurs. @var{pathname} is a string.
25103 @section Interrupts
25104 @cindex interrupts (remote protocol)
25106 When a program on the remote target is running, @value{GDBN} may
25107 attempt to interrupt it by sending a @samp{Ctrl-C} or a @code{BREAK},
25108 control of which is specified via @value{GDBN}'s @samp{remotebreak}
25109 setting (@pxref{set remotebreak}).
25111 The precise meaning of @code{BREAK} is defined by the transport
25112 mechanism and may, in fact, be undefined. @value{GDBN} does
25113 not currently define a @code{BREAK} mechanism for any of the network
25116 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
25117 transport mechanisms. It is represented by sending the single byte
25118 @code{0x03} without any of the usual packet overhead described in
25119 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
25120 transmitted as part of a packet, it is considered to be packet data
25121 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
25122 (@pxref{X packet}), used for binary downloads, may include an unescaped
25123 @code{0x03} as part of its packet.
25125 Stubs are not required to recognize these interrupt mechanisms and the
25126 precise meaning associated with receipt of the interrupt is
25127 implementation defined. If the stub is successful at interrupting the
25128 running program, it is expected that it will send one of the Stop
25129 Reply Packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
25130 of successfully stopping the program. Interrupts received while the
25131 program is stopped will be discarded.
25136 Example sequence of a target being re-started. Notice how the restart
25137 does not get any direct output:
25142 @emph{target restarts}
25145 <- @code{T001:1234123412341234}
25149 Example sequence of a target being stepped by a single instruction:
25152 -> @code{G1445@dots{}}
25157 <- @code{T001:1234123412341234}
25161 <- @code{1455@dots{}}
25165 @node File-I/O Remote Protocol Extension
25166 @section File-I/O Remote Protocol Extension
25167 @cindex File-I/O remote protocol extension
25170 * File-I/O Overview::
25171 * Protocol Basics::
25172 * The F Request Packet::
25173 * The F Reply Packet::
25174 * The Ctrl-C Message::
25176 * List of Supported Calls::
25177 * Protocol-specific Representation of Datatypes::
25179 * File-I/O Examples::
25182 @node File-I/O Overview
25183 @subsection File-I/O Overview
25184 @cindex file-i/o overview
25186 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
25187 target to use the host's file system and console I/O to perform various
25188 system calls. System calls on the target system are translated into a
25189 remote protocol packet to the host system, which then performs the needed
25190 actions and returns a response packet to the target system.
25191 This simulates file system operations even on targets that lack file systems.
25193 The protocol is defined to be independent of both the host and target systems.
25194 It uses its own internal representation of datatypes and values. Both
25195 @value{GDBN} and the target's @value{GDBN} stub are responsible for
25196 translating the system-dependent value representations into the internal
25197 protocol representations when data is transmitted.
25199 The communication is synchronous. A system call is possible only when
25200 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
25201 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
25202 the target is stopped to allow deterministic access to the target's
25203 memory. Therefore File-I/O is not interruptible by target signals. On
25204 the other hand, it is possible to interrupt File-I/O by a user interrupt
25205 (@samp{Ctrl-C}) within @value{GDBN}.
25207 The target's request to perform a host system call does not finish
25208 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
25209 after finishing the system call, the target returns to continuing the
25210 previous activity (continue, step). No additional continue or step
25211 request from @value{GDBN} is required.
25214 (@value{GDBP}) continue
25215 <- target requests 'system call X'
25216 target is stopped, @value{GDBN} executes system call
25217 -> @value{GDBN} returns result
25218 ... target continues, @value{GDBN} returns to wait for the target
25219 <- target hits breakpoint and sends a Txx packet
25222 The protocol only supports I/O on the console and to regular files on
25223 the host file system. Character or block special devices, pipes,
25224 named pipes, sockets or any other communication method on the host
25225 system are not supported by this protocol.
25227 @node Protocol Basics
25228 @subsection Protocol Basics
25229 @cindex protocol basics, file-i/o
25231 The File-I/O protocol uses the @code{F} packet as the request as well
25232 as reply packet. Since a File-I/O system call can only occur when
25233 @value{GDBN} is waiting for a response from the continuing or stepping target,
25234 the File-I/O request is a reply that @value{GDBN} has to expect as a result
25235 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
25236 This @code{F} packet contains all information needed to allow @value{GDBN}
25237 to call the appropriate host system call:
25241 A unique identifier for the requested system call.
25244 All parameters to the system call. Pointers are given as addresses
25245 in the target memory address space. Pointers to strings are given as
25246 pointer/length pair. Numerical values are given as they are.
25247 Numerical control flags are given in a protocol-specific representation.
25251 At this point, @value{GDBN} has to perform the following actions.
25255 If the parameters include pointer values to data needed as input to a
25256 system call, @value{GDBN} requests this data from the target with a
25257 standard @code{m} packet request. This additional communication has to be
25258 expected by the target implementation and is handled as any other @code{m}
25262 @value{GDBN} translates all value from protocol representation to host
25263 representation as needed. Datatypes are coerced into the host types.
25266 @value{GDBN} calls the system call.
25269 It then coerces datatypes back to protocol representation.
25272 If the system call is expected to return data in buffer space specified
25273 by pointer parameters to the call, the data is transmitted to the
25274 target using a @code{M} or @code{X} packet. This packet has to be expected
25275 by the target implementation and is handled as any other @code{M} or @code{X}
25280 Eventually @value{GDBN} replies with another @code{F} packet which contains all
25281 necessary information for the target to continue. This at least contains
25288 @code{errno}, if has been changed by the system call.
25295 After having done the needed type and value coercion, the target continues
25296 the latest continue or step action.
25298 @node The F Request Packet
25299 @subsection The @code{F} Request Packet
25300 @cindex file-i/o request packet
25301 @cindex @code{F} request packet
25303 The @code{F} request packet has the following format:
25306 @item F@var{call-id},@var{parameter@dots{}}
25308 @var{call-id} is the identifier to indicate the host system call to be called.
25309 This is just the name of the function.
25311 @var{parameter@dots{}} are the parameters to the system call.
25312 Parameters are hexadecimal integer values, either the actual values in case
25313 of scalar datatypes, pointers to target buffer space in case of compound
25314 datatypes and unspecified memory areas, or pointer/length pairs in case
25315 of string parameters. These are appended to the @var{call-id} as a
25316 comma-delimited list. All values are transmitted in ASCII
25317 string representation, pointer/length pairs separated by a slash.
25323 @node The F Reply Packet
25324 @subsection The @code{F} Reply Packet
25325 @cindex file-i/o reply packet
25326 @cindex @code{F} reply packet
25328 The @code{F} reply packet has the following format:
25332 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
25334 @var{retcode} is the return code of the system call as hexadecimal value.
25336 @var{errno} is the @code{errno} set by the call, in protocol-specific
25338 This parameter can be omitted if the call was successful.
25340 @var{Ctrl-C flag} is only sent if the user requested a break. In this
25341 case, @var{errno} must be sent as well, even if the call was successful.
25342 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
25349 or, if the call was interrupted before the host call has been performed:
25356 assuming 4 is the protocol-specific representation of @code{EINTR}.
25361 @node The Ctrl-C Message
25362 @subsection The @samp{Ctrl-C} Message
25363 @cindex ctrl-c message, in file-i/o protocol
25365 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
25366 reply packet (@pxref{The F Reply Packet}),
25367 the target should behave as if it had
25368 gotten a break message. The meaning for the target is ``system call
25369 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
25370 (as with a break message) and return to @value{GDBN} with a @code{T02}
25373 It's important for the target to know in which
25374 state the system call was interrupted. There are two possible cases:
25378 The system call hasn't been performed on the host yet.
25381 The system call on the host has been finished.
25385 These two states can be distinguished by the target by the value of the
25386 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
25387 call hasn't been performed. This is equivalent to the @code{EINTR} handling
25388 on POSIX systems. In any other case, the target may presume that the
25389 system call has been finished --- successfully or not --- and should behave
25390 as if the break message arrived right after the system call.
25392 @value{GDBN} must behave reliably. If the system call has not been called
25393 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
25394 @code{errno} in the packet. If the system call on the host has been finished
25395 before the user requests a break, the full action must be finished by
25396 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
25397 The @code{F} packet may only be sent when either nothing has happened
25398 or the full action has been completed.
25401 @subsection Console I/O
25402 @cindex console i/o as part of file-i/o
25404 By default and if not explicitly closed by the target system, the file
25405 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
25406 on the @value{GDBN} console is handled as any other file output operation
25407 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
25408 by @value{GDBN} so that after the target read request from file descriptor
25409 0 all following typing is buffered until either one of the following
25414 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
25416 system call is treated as finished.
25419 The user presses @key{RET}. This is treated as end of input with a trailing
25423 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
25424 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
25428 If the user has typed more characters than fit in the buffer given to
25429 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
25430 either another @code{read(0, @dots{})} is requested by the target, or debugging
25431 is stopped at the user's request.
25434 @node List of Supported Calls
25435 @subsection List of Supported Calls
25436 @cindex list of supported file-i/o calls
25453 @unnumberedsubsubsec open
25454 @cindex open, file-i/o system call
25459 int open(const char *pathname, int flags);
25460 int open(const char *pathname, int flags, mode_t mode);
25464 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
25467 @var{flags} is the bitwise @code{OR} of the following values:
25471 If the file does not exist it will be created. The host
25472 rules apply as far as file ownership and time stamps
25476 When used with @code{O_CREAT}, if the file already exists it is
25477 an error and open() fails.
25480 If the file already exists and the open mode allows
25481 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
25482 truncated to zero length.
25485 The file is opened in append mode.
25488 The file is opened for reading only.
25491 The file is opened for writing only.
25494 The file is opened for reading and writing.
25498 Other bits are silently ignored.
25502 @var{mode} is the bitwise @code{OR} of the following values:
25506 User has read permission.
25509 User has write permission.
25512 Group has read permission.
25515 Group has write permission.
25518 Others have read permission.
25521 Others have write permission.
25525 Other bits are silently ignored.
25528 @item Return value:
25529 @code{open} returns the new file descriptor or -1 if an error
25536 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
25539 @var{pathname} refers to a directory.
25542 The requested access is not allowed.
25545 @var{pathname} was too long.
25548 A directory component in @var{pathname} does not exist.
25551 @var{pathname} refers to a device, pipe, named pipe or socket.
25554 @var{pathname} refers to a file on a read-only filesystem and
25555 write access was requested.
25558 @var{pathname} is an invalid pointer value.
25561 No space on device to create the file.
25564 The process already has the maximum number of files open.
25567 The limit on the total number of files open on the system
25571 The call was interrupted by the user.
25577 @unnumberedsubsubsec close
25578 @cindex close, file-i/o system call
25587 @samp{Fclose,@var{fd}}
25589 @item Return value:
25590 @code{close} returns zero on success, or -1 if an error occurred.
25596 @var{fd} isn't a valid open file descriptor.
25599 The call was interrupted by the user.
25605 @unnumberedsubsubsec read
25606 @cindex read, file-i/o system call
25611 int read(int fd, void *buf, unsigned int count);
25615 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
25617 @item Return value:
25618 On success, the number of bytes read is returned.
25619 Zero indicates end of file. If count is zero, read
25620 returns zero as well. On error, -1 is returned.
25626 @var{fd} is not a valid file descriptor or is not open for
25630 @var{bufptr} is an invalid pointer value.
25633 The call was interrupted by the user.
25639 @unnumberedsubsubsec write
25640 @cindex write, file-i/o system call
25645 int write(int fd, const void *buf, unsigned int count);
25649 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
25651 @item Return value:
25652 On success, the number of bytes written are returned.
25653 Zero indicates nothing was written. On error, -1
25660 @var{fd} is not a valid file descriptor or is not open for
25664 @var{bufptr} is an invalid pointer value.
25667 An attempt was made to write a file that exceeds the
25668 host-specific maximum file size allowed.
25671 No space on device to write the data.
25674 The call was interrupted by the user.
25680 @unnumberedsubsubsec lseek
25681 @cindex lseek, file-i/o system call
25686 long lseek (int fd, long offset, int flag);
25690 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
25692 @var{flag} is one of:
25696 The offset is set to @var{offset} bytes.
25699 The offset is set to its current location plus @var{offset}
25703 The offset is set to the size of the file plus @var{offset}
25707 @item Return value:
25708 On success, the resulting unsigned offset in bytes from
25709 the beginning of the file is returned. Otherwise, a
25710 value of -1 is returned.
25716 @var{fd} is not a valid open file descriptor.
25719 @var{fd} is associated with the @value{GDBN} console.
25722 @var{flag} is not a proper value.
25725 The call was interrupted by the user.
25731 @unnumberedsubsubsec rename
25732 @cindex rename, file-i/o system call
25737 int rename(const char *oldpath, const char *newpath);
25741 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
25743 @item Return value:
25744 On success, zero is returned. On error, -1 is returned.
25750 @var{newpath} is an existing directory, but @var{oldpath} is not a
25754 @var{newpath} is a non-empty directory.
25757 @var{oldpath} or @var{newpath} is a directory that is in use by some
25761 An attempt was made to make a directory a subdirectory
25765 A component used as a directory in @var{oldpath} or new
25766 path is not a directory. Or @var{oldpath} is a directory
25767 and @var{newpath} exists but is not a directory.
25770 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
25773 No access to the file or the path of the file.
25777 @var{oldpath} or @var{newpath} was too long.
25780 A directory component in @var{oldpath} or @var{newpath} does not exist.
25783 The file is on a read-only filesystem.
25786 The device containing the file has no room for the new
25790 The call was interrupted by the user.
25796 @unnumberedsubsubsec unlink
25797 @cindex unlink, file-i/o system call
25802 int unlink(const char *pathname);
25806 @samp{Funlink,@var{pathnameptr}/@var{len}}
25808 @item Return value:
25809 On success, zero is returned. On error, -1 is returned.
25815 No access to the file or the path of the file.
25818 The system does not allow unlinking of directories.
25821 The file @var{pathname} cannot be unlinked because it's
25822 being used by another process.
25825 @var{pathnameptr} is an invalid pointer value.
25828 @var{pathname} was too long.
25831 A directory component in @var{pathname} does not exist.
25834 A component of the path is not a directory.
25837 The file is on a read-only filesystem.
25840 The call was interrupted by the user.
25846 @unnumberedsubsubsec stat/fstat
25847 @cindex fstat, file-i/o system call
25848 @cindex stat, file-i/o system call
25853 int stat(const char *pathname, struct stat *buf);
25854 int fstat(int fd, struct stat *buf);
25858 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
25859 @samp{Ffstat,@var{fd},@var{bufptr}}
25861 @item Return value:
25862 On success, zero is returned. On error, -1 is returned.
25868 @var{fd} is not a valid open file.
25871 A directory component in @var{pathname} does not exist or the
25872 path is an empty string.
25875 A component of the path is not a directory.
25878 @var{pathnameptr} is an invalid pointer value.
25881 No access to the file or the path of the file.
25884 @var{pathname} was too long.
25887 The call was interrupted by the user.
25893 @unnumberedsubsubsec gettimeofday
25894 @cindex gettimeofday, file-i/o system call
25899 int gettimeofday(struct timeval *tv, void *tz);
25903 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
25905 @item Return value:
25906 On success, 0 is returned, -1 otherwise.
25912 @var{tz} is a non-NULL pointer.
25915 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
25921 @unnumberedsubsubsec isatty
25922 @cindex isatty, file-i/o system call
25927 int isatty(int fd);
25931 @samp{Fisatty,@var{fd}}
25933 @item Return value:
25934 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
25940 The call was interrupted by the user.
25945 Note that the @code{isatty} call is treated as a special case: it returns
25946 1 to the target if the file descriptor is attached
25947 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
25948 would require implementing @code{ioctl} and would be more complex than
25953 @unnumberedsubsubsec system
25954 @cindex system, file-i/o system call
25959 int system(const char *command);
25963 @samp{Fsystem,@var{commandptr}/@var{len}}
25965 @item Return value:
25966 If @var{len} is zero, the return value indicates whether a shell is
25967 available. A zero return value indicates a shell is not available.
25968 For non-zero @var{len}, the value returned is -1 on error and the
25969 return status of the command otherwise. Only the exit status of the
25970 command is returned, which is extracted from the host's @code{system}
25971 return value by calling @code{WEXITSTATUS(retval)}. In case
25972 @file{/bin/sh} could not be executed, 127 is returned.
25978 The call was interrupted by the user.
25983 @value{GDBN} takes over the full task of calling the necessary host calls
25984 to perform the @code{system} call. The return value of @code{system} on
25985 the host is simplified before it's returned
25986 to the target. Any termination signal information from the child process
25987 is discarded, and the return value consists
25988 entirely of the exit status of the called command.
25990 Due to security concerns, the @code{system} call is by default refused
25991 by @value{GDBN}. The user has to allow this call explicitly with the
25992 @code{set remote system-call-allowed 1} command.
25995 @item set remote system-call-allowed
25996 @kindex set remote system-call-allowed
25997 Control whether to allow the @code{system} calls in the File I/O
25998 protocol for the remote target. The default is zero (disabled).
26000 @item show remote system-call-allowed
26001 @kindex show remote system-call-allowed
26002 Show whether the @code{system} calls are allowed in the File I/O
26006 @node Protocol-specific Representation of Datatypes
26007 @subsection Protocol-specific Representation of Datatypes
26008 @cindex protocol-specific representation of datatypes, in file-i/o protocol
26011 * Integral Datatypes::
26013 * Memory Transfer::
26018 @node Integral Datatypes
26019 @unnumberedsubsubsec Integral Datatypes
26020 @cindex integral datatypes, in file-i/o protocol
26022 The integral datatypes used in the system calls are @code{int},
26023 @code{unsigned int}, @code{long}, @code{unsigned long},
26024 @code{mode_t}, and @code{time_t}.
26026 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
26027 implemented as 32 bit values in this protocol.
26029 @code{long} and @code{unsigned long} are implemented as 64 bit types.
26031 @xref{Limits}, for corresponding MIN and MAX values (similar to those
26032 in @file{limits.h}) to allow range checking on host and target.
26034 @code{time_t} datatypes are defined as seconds since the Epoch.
26036 All integral datatypes transferred as part of a memory read or write of a
26037 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
26040 @node Pointer Values
26041 @unnumberedsubsubsec Pointer Values
26042 @cindex pointer values, in file-i/o protocol
26044 Pointers to target data are transmitted as they are. An exception
26045 is made for pointers to buffers for which the length isn't
26046 transmitted as part of the function call, namely strings. Strings
26047 are transmitted as a pointer/length pair, both as hex values, e.g.@:
26054 which is a pointer to data of length 18 bytes at position 0x1aaf.
26055 The length is defined as the full string length in bytes, including
26056 the trailing null byte. For example, the string @code{"hello world"}
26057 at address 0x123456 is transmitted as
26063 @node Memory Transfer
26064 @unnumberedsubsubsec Memory Transfer
26065 @cindex memory transfer, in file-i/o protocol
26067 Structured data which is transferred using a memory read or write (for
26068 example, a @code{struct stat}) is expected to be in a protocol-specific format
26069 with all scalar multibyte datatypes being big endian. Translation to
26070 this representation needs to be done both by the target before the @code{F}
26071 packet is sent, and by @value{GDBN} before
26072 it transfers memory to the target. Transferred pointers to structured
26073 data should point to the already-coerced data at any time.
26077 @unnumberedsubsubsec struct stat
26078 @cindex struct stat, in file-i/o protocol
26080 The buffer of type @code{struct stat} used by the target and @value{GDBN}
26081 is defined as follows:
26085 unsigned int st_dev; /* device */
26086 unsigned int st_ino; /* inode */
26087 mode_t st_mode; /* protection */
26088 unsigned int st_nlink; /* number of hard links */
26089 unsigned int st_uid; /* user ID of owner */
26090 unsigned int st_gid; /* group ID of owner */
26091 unsigned int st_rdev; /* device type (if inode device) */
26092 unsigned long st_size; /* total size, in bytes */
26093 unsigned long st_blksize; /* blocksize for filesystem I/O */
26094 unsigned long st_blocks; /* number of blocks allocated */
26095 time_t st_atime; /* time of last access */
26096 time_t st_mtime; /* time of last modification */
26097 time_t st_ctime; /* time of last change */
26101 The integral datatypes conform to the definitions given in the
26102 appropriate section (see @ref{Integral Datatypes}, for details) so this
26103 structure is of size 64 bytes.
26105 The values of several fields have a restricted meaning and/or
26111 A value of 0 represents a file, 1 the console.
26114 No valid meaning for the target. Transmitted unchanged.
26117 Valid mode bits are described in @ref{Constants}. Any other
26118 bits have currently no meaning for the target.
26123 No valid meaning for the target. Transmitted unchanged.
26128 These values have a host and file system dependent
26129 accuracy. Especially on Windows hosts, the file system may not
26130 support exact timing values.
26133 The target gets a @code{struct stat} of the above representation and is
26134 responsible for coercing it to the target representation before
26137 Note that due to size differences between the host, target, and protocol
26138 representations of @code{struct stat} members, these members could eventually
26139 get truncated on the target.
26141 @node struct timeval
26142 @unnumberedsubsubsec struct timeval
26143 @cindex struct timeval, in file-i/o protocol
26145 The buffer of type @code{struct timeval} used by the File-I/O protocol
26146 is defined as follows:
26150 time_t tv_sec; /* second */
26151 long tv_usec; /* microsecond */
26155 The integral datatypes conform to the definitions given in the
26156 appropriate section (see @ref{Integral Datatypes}, for details) so this
26157 structure is of size 8 bytes.
26160 @subsection Constants
26161 @cindex constants, in file-i/o protocol
26163 The following values are used for the constants inside of the
26164 protocol. @value{GDBN} and target are responsible for translating these
26165 values before and after the call as needed.
26176 @unnumberedsubsubsec Open Flags
26177 @cindex open flags, in file-i/o protocol
26179 All values are given in hexadecimal representation.
26191 @node mode_t Values
26192 @unnumberedsubsubsec mode_t Values
26193 @cindex mode_t values, in file-i/o protocol
26195 All values are given in octal representation.
26212 @unnumberedsubsubsec Errno Values
26213 @cindex errno values, in file-i/o protocol
26215 All values are given in decimal representation.
26240 @code{EUNKNOWN} is used as a fallback error value if a host system returns
26241 any error value not in the list of supported error numbers.
26244 @unnumberedsubsubsec Lseek Flags
26245 @cindex lseek flags, in file-i/o protocol
26254 @unnumberedsubsubsec Limits
26255 @cindex limits, in file-i/o protocol
26257 All values are given in decimal representation.
26260 INT_MIN -2147483648
26262 UINT_MAX 4294967295
26263 LONG_MIN -9223372036854775808
26264 LONG_MAX 9223372036854775807
26265 ULONG_MAX 18446744073709551615
26268 @node File-I/O Examples
26269 @subsection File-I/O Examples
26270 @cindex file-i/o examples
26272 Example sequence of a write call, file descriptor 3, buffer is at target
26273 address 0x1234, 6 bytes should be written:
26276 <- @code{Fwrite,3,1234,6}
26277 @emph{request memory read from target}
26280 @emph{return "6 bytes written"}
26284 Example sequence of a read call, file descriptor 3, buffer is at target
26285 address 0x1234, 6 bytes should be read:
26288 <- @code{Fread,3,1234,6}
26289 @emph{request memory write to target}
26290 -> @code{X1234,6:XXXXXX}
26291 @emph{return "6 bytes read"}
26295 Example sequence of a read call, call fails on the host due to invalid
26296 file descriptor (@code{EBADF}):
26299 <- @code{Fread,3,1234,6}
26303 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
26307 <- @code{Fread,3,1234,6}
26312 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
26316 <- @code{Fread,3,1234,6}
26317 -> @code{X1234,6:XXXXXX}
26321 @node Library List Format
26322 @section Library List Format
26323 @cindex library list format, remote protocol
26325 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
26326 same process as your application to manage libraries. In this case,
26327 @value{GDBN} can use the loader's symbol table and normal memory
26328 operations to maintain a list of shared libraries. On other
26329 platforms, the operating system manages loaded libraries.
26330 @value{GDBN} can not retrieve the list of currently loaded libraries
26331 through memory operations, so it uses the @samp{qXfer:libraries:read}
26332 packet (@pxref{qXfer library list read}) instead. The remote stub
26333 queries the target's operating system and reports which libraries
26336 The @samp{qXfer:libraries:read} packet returns an XML document which
26337 lists loaded libraries and their offsets. Each library has an
26338 associated name and one or more segment or section base addresses,
26339 which report where the library was loaded in memory.
26341 For the common case of libraries that are fully linked binaries, the
26342 library should have a list of segments. If the target supports
26343 dynamic linking of a relocatable object file, its library XML element
26344 should instead include a list of allocated sections. The segment or
26345 section bases are start addresses, not relocation offsets; they do not
26346 depend on the library's link-time base addresses.
26348 @value{GDBN} must be linked with the Expat library to support XML
26349 library lists. @xref{Expat}.
26351 A simple memory map, with one loaded library relocated by a single
26352 offset, looks like this:
26356 <library name="/lib/libc.so.6">
26357 <segment address="0x10000000"/>
26362 Another simple memory map, with one loaded library with three
26363 allocated sections (.text, .data, .bss), looks like this:
26367 <library name="sharedlib.o">
26368 <section address="0x10000000"/>
26369 <section address="0x20000000"/>
26370 <section address="0x30000000"/>
26375 The format of a library list is described by this DTD:
26378 <!-- library-list: Root element with versioning -->
26379 <!ELEMENT library-list (library)*>
26380 <!ATTLIST library-list version CDATA #FIXED "1.0">
26381 <!ELEMENT library (segment*, section*)>
26382 <!ATTLIST library name CDATA #REQUIRED>
26383 <!ELEMENT segment EMPTY>
26384 <!ATTLIST segment address CDATA #REQUIRED>
26385 <!ELEMENT section EMPTY>
26386 <!ATTLIST section address CDATA #REQUIRED>
26389 In addition, segments and section descriptors cannot be mixed within a
26390 single library element, and you must supply at least one segment or
26391 section for each library.
26393 @node Memory Map Format
26394 @section Memory Map Format
26395 @cindex memory map format
26397 To be able to write into flash memory, @value{GDBN} needs to obtain a
26398 memory map from the target. This section describes the format of the
26401 The memory map is obtained using the @samp{qXfer:memory-map:read}
26402 (@pxref{qXfer memory map read}) packet and is an XML document that
26403 lists memory regions.
26405 @value{GDBN} must be linked with the Expat library to support XML
26406 memory maps. @xref{Expat}.
26408 The top-level structure of the document is shown below:
26411 <?xml version="1.0"?>
26412 <!DOCTYPE memory-map
26413 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
26414 "http://sourceware.org/gdb/gdb-memory-map.dtd">
26420 Each region can be either:
26425 A region of RAM starting at @var{addr} and extending for @var{length}
26429 <memory type="ram" start="@var{addr}" length="@var{length}"/>
26434 A region of read-only memory:
26437 <memory type="rom" start="@var{addr}" length="@var{length}"/>
26442 A region of flash memory, with erasure blocks @var{blocksize}
26446 <memory type="flash" start="@var{addr}" length="@var{length}">
26447 <property name="blocksize">@var{blocksize}</property>
26453 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
26454 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
26455 packets to write to addresses in such ranges.
26457 The formal DTD for memory map format is given below:
26460 <!-- ................................................... -->
26461 <!-- Memory Map XML DTD ................................ -->
26462 <!-- File: memory-map.dtd .............................. -->
26463 <!-- .................................... .............. -->
26464 <!-- memory-map.dtd -->
26465 <!-- memory-map: Root element with versioning -->
26466 <!ELEMENT memory-map (memory | property)>
26467 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
26468 <!ELEMENT memory (property)>
26469 <!-- memory: Specifies a memory region,
26470 and its type, or device. -->
26471 <!ATTLIST memory type CDATA #REQUIRED
26472 start CDATA #REQUIRED
26473 length CDATA #REQUIRED
26474 device CDATA #IMPLIED>
26475 <!-- property: Generic attribute tag -->
26476 <!ELEMENT property (#PCDATA | property)*>
26477 <!ATTLIST property name CDATA #REQUIRED>
26480 @include agentexpr.texi
26482 @node Target Descriptions
26483 @appendix Target Descriptions
26484 @cindex target descriptions
26486 @strong{Warning:} target descriptions are still under active development,
26487 and the contents and format may change between @value{GDBN} releases.
26488 The format is expected to stabilize in the future.
26490 One of the challenges of using @value{GDBN} to debug embedded systems
26491 is that there are so many minor variants of each processor
26492 architecture in use. It is common practice for vendors to start with
26493 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
26494 and then make changes to adapt it to a particular market niche. Some
26495 architectures have hundreds of variants, available from dozens of
26496 vendors. This leads to a number of problems:
26500 With so many different customized processors, it is difficult for
26501 the @value{GDBN} maintainers to keep up with the changes.
26503 Since individual variants may have short lifetimes or limited
26504 audiences, it may not be worthwhile to carry information about every
26505 variant in the @value{GDBN} source tree.
26507 When @value{GDBN} does support the architecture of the embedded system
26508 at hand, the task of finding the correct architecture name to give the
26509 @command{set architecture} command can be error-prone.
26512 To address these problems, the @value{GDBN} remote protocol allows a
26513 target system to not only identify itself to @value{GDBN}, but to
26514 actually describe its own features. This lets @value{GDBN} support
26515 processor variants it has never seen before --- to the extent that the
26516 descriptions are accurate, and that @value{GDBN} understands them.
26518 @value{GDBN} must be linked with the Expat library to support XML
26519 target descriptions. @xref{Expat}.
26522 * Retrieving Descriptions:: How descriptions are fetched from a target.
26523 * Target Description Format:: The contents of a target description.
26524 * Predefined Target Types:: Standard types available for target
26526 * Standard Target Features:: Features @value{GDBN} knows about.
26529 @node Retrieving Descriptions
26530 @section Retrieving Descriptions
26532 Target descriptions can be read from the target automatically, or
26533 specified by the user manually. The default behavior is to read the
26534 description from the target. @value{GDBN} retrieves it via the remote
26535 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
26536 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
26537 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
26538 XML document, of the form described in @ref{Target Description
26541 Alternatively, you can specify a file to read for the target description.
26542 If a file is set, the target will not be queried. The commands to
26543 specify a file are:
26546 @cindex set tdesc filename
26547 @item set tdesc filename @var{path}
26548 Read the target description from @var{path}.
26550 @cindex unset tdesc filename
26551 @item unset tdesc filename
26552 Do not read the XML target description from a file. @value{GDBN}
26553 will use the description supplied by the current target.
26555 @cindex show tdesc filename
26556 @item show tdesc filename
26557 Show the filename to read for a target description, if any.
26561 @node Target Description Format
26562 @section Target Description Format
26563 @cindex target descriptions, XML format
26565 A target description annex is an @uref{http://www.w3.org/XML/, XML}
26566 document which complies with the Document Type Definition provided in
26567 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
26568 means you can use generally available tools like @command{xmllint} to
26569 check that your feature descriptions are well-formed and valid.
26570 However, to help people unfamiliar with XML write descriptions for
26571 their targets, we also describe the grammar here.
26573 Target descriptions can identify the architecture of the remote target
26574 and (for some architectures) provide information about custom register
26575 sets. @value{GDBN} can use this information to autoconfigure for your
26576 target, or to warn you if you connect to an unsupported target.
26578 Here is a simple target description:
26581 <target version="1.0">
26582 <architecture>i386:x86-64</architecture>
26587 This minimal description only says that the target uses
26588 the x86-64 architecture.
26590 A target description has the following overall form, with [ ] marking
26591 optional elements and @dots{} marking repeatable elements. The elements
26592 are explained further below.
26595 <?xml version="1.0"?>
26596 <!DOCTYPE target SYSTEM "gdb-target.dtd">
26597 <target version="1.0">
26598 @r{[}@var{architecture}@r{]}
26599 @r{[}@var{feature}@dots{}@r{]}
26604 The description is generally insensitive to whitespace and line
26605 breaks, under the usual common-sense rules. The XML version
26606 declaration and document type declaration can generally be omitted
26607 (@value{GDBN} does not require them), but specifying them may be
26608 useful for XML validation tools. The @samp{version} attribute for
26609 @samp{<target>} may also be omitted, but we recommend
26610 including it; if future versions of @value{GDBN} use an incompatible
26611 revision of @file{gdb-target.dtd}, they will detect and report
26612 the version mismatch.
26614 @subsection Inclusion
26615 @cindex target descriptions, inclusion
26618 @cindex <xi:include>
26621 It can sometimes be valuable to split a target description up into
26622 several different annexes, either for organizational purposes, or to
26623 share files between different possible target descriptions. You can
26624 divide a description into multiple files by replacing any element of
26625 the target description with an inclusion directive of the form:
26628 <xi:include href="@var{document}"/>
26632 When @value{GDBN} encounters an element of this form, it will retrieve
26633 the named XML @var{document}, and replace the inclusion directive with
26634 the contents of that document. If the current description was read
26635 using @samp{qXfer}, then so will be the included document;
26636 @var{document} will be interpreted as the name of an annex. If the
26637 current description was read from a file, @value{GDBN} will look for
26638 @var{document} as a file in the same directory where it found the
26639 original description.
26641 @subsection Architecture
26642 @cindex <architecture>
26644 An @samp{<architecture>} element has this form:
26647 <architecture>@var{arch}</architecture>
26650 @var{arch} is an architecture name from the same selection
26651 accepted by @code{set architecture} (@pxref{Targets, ,Specifying a
26652 Debugging Target}).
26654 @subsection Features
26657 Each @samp{<feature>} describes some logical portion of the target
26658 system. Features are currently used to describe available CPU
26659 registers and the types of their contents. A @samp{<feature>} element
26663 <feature name="@var{name}">
26664 @r{[}@var{type}@dots{}@r{]}
26670 Each feature's name should be unique within the description. The name
26671 of a feature does not matter unless @value{GDBN} has some special
26672 knowledge of the contents of that feature; if it does, the feature
26673 should have its standard name. @xref{Standard Target Features}.
26677 Any register's value is a collection of bits which @value{GDBN} must
26678 interpret. The default interpretation is a two's complement integer,
26679 but other types can be requested by name in the register description.
26680 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
26681 Target Types}), and the description can define additional composite types.
26683 Each type element must have an @samp{id} attribute, which gives
26684 a unique (within the containing @samp{<feature>}) name to the type.
26685 Types must be defined before they are used.
26688 Some targets offer vector registers, which can be treated as arrays
26689 of scalar elements. These types are written as @samp{<vector>} elements,
26690 specifying the array element type, @var{type}, and the number of elements,
26694 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
26698 If a register's value is usefully viewed in multiple ways, define it
26699 with a union type containing the useful representations. The
26700 @samp{<union>} element contains one or more @samp{<field>} elements,
26701 each of which has a @var{name} and a @var{type}:
26704 <union id="@var{id}">
26705 <field name="@var{name}" type="@var{type}"/>
26710 @subsection Registers
26713 Each register is represented as an element with this form:
26716 <reg name="@var{name}"
26717 bitsize="@var{size}"
26718 @r{[}regnum="@var{num}"@r{]}
26719 @r{[}save-restore="@var{save-restore}"@r{]}
26720 @r{[}type="@var{type}"@r{]}
26721 @r{[}group="@var{group}"@r{]}/>
26725 The components are as follows:
26730 The register's name; it must be unique within the target description.
26733 The register's size, in bits.
26736 The register's number. If omitted, a register's number is one greater
26737 than that of the previous register (either in the current feature or in
26738 a preceeding feature); the first register in the target description
26739 defaults to zero. This register number is used to read or write
26740 the register; e.g.@: it is used in the remote @code{p} and @code{P}
26741 packets, and registers appear in the @code{g} and @code{G} packets
26742 in order of increasing register number.
26745 Whether the register should be preserved across inferior function
26746 calls; this must be either @code{yes} or @code{no}. The default is
26747 @code{yes}, which is appropriate for most registers except for
26748 some system control registers; this is not related to the target's
26752 The type of the register. @var{type} may be a predefined type, a type
26753 defined in the current feature, or one of the special types @code{int}
26754 and @code{float}. @code{int} is an integer type of the correct size
26755 for @var{bitsize}, and @code{float} is a floating point type (in the
26756 architecture's normal floating point format) of the correct size for
26757 @var{bitsize}. The default is @code{int}.
26760 The register group to which this register belongs. @var{group} must
26761 be either @code{general}, @code{float}, or @code{vector}. If no
26762 @var{group} is specified, @value{GDBN} will not display the register
26763 in @code{info registers}.
26767 @node Predefined Target Types
26768 @section Predefined Target Types
26769 @cindex target descriptions, predefined types
26771 Type definitions in the self-description can build up composite types
26772 from basic building blocks, but can not define fundamental types. Instead,
26773 standard identifiers are provided by @value{GDBN} for the fundamental
26774 types. The currently supported types are:
26783 Signed integer types holding the specified number of bits.
26790 Unsigned integer types holding the specified number of bits.
26794 Pointers to unspecified code and data. The program counter and
26795 any dedicated return address register may be marked as code
26796 pointers; printing a code pointer converts it into a symbolic
26797 address. The stack pointer and any dedicated address registers
26798 may be marked as data pointers.
26801 Single precision IEEE floating point.
26804 Double precision IEEE floating point.
26807 The 12-byte extended precision format used by ARM FPA registers.
26811 @node Standard Target Features
26812 @section Standard Target Features
26813 @cindex target descriptions, standard features
26815 A target description must contain either no registers or all the
26816 target's registers. If the description contains no registers, then
26817 @value{GDBN} will assume a default register layout, selected based on
26818 the architecture. If the description contains any registers, the
26819 default layout will not be used; the standard registers must be
26820 described in the target description, in such a way that @value{GDBN}
26821 can recognize them.
26823 This is accomplished by giving specific names to feature elements
26824 which contain standard registers. @value{GDBN} will look for features
26825 with those names and verify that they contain the expected registers;
26826 if any known feature is missing required registers, or if any required
26827 feature is missing, @value{GDBN} will reject the target
26828 description. You can add additional registers to any of the
26829 standard features --- @value{GDBN} will display them just as if
26830 they were added to an unrecognized feature.
26832 This section lists the known features and their expected contents.
26833 Sample XML documents for these features are included in the
26834 @value{GDBN} source tree, in the directory @file{gdb/features}.
26836 Names recognized by @value{GDBN} should include the name of the
26837 company or organization which selected the name, and the overall
26838 architecture to which the feature applies; so e.g.@: the feature
26839 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
26841 The names of registers are not case sensitive for the purpose
26842 of recognizing standard features, but @value{GDBN} will only display
26843 registers using the capitalization used in the description.
26852 @subsection ARM Features
26853 @cindex target descriptions, ARM features
26855 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
26856 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
26857 @samp{lr}, @samp{pc}, and @samp{cpsr}.
26859 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
26860 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
26862 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
26863 it should contain at least registers @samp{wR0} through @samp{wR15} and
26864 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
26865 @samp{wCSSF}, and @samp{wCASF} registers are optional.
26867 @subsection MIPS Features
26868 @cindex target descriptions, MIPS features
26870 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
26871 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
26872 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
26875 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
26876 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
26877 registers. They may be 32-bit or 64-bit depending on the target.
26879 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
26880 it may be optional in a future version of @value{GDBN}. It should
26881 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
26882 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
26884 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
26885 contain a single register, @samp{restart}, which is used by the
26886 Linux kernel to control restartable syscalls.
26888 @node M68K Features
26889 @subsection M68K Features
26890 @cindex target descriptions, M68K features
26893 @item @samp{org.gnu.gdb.m68k.core}
26894 @itemx @samp{org.gnu.gdb.coldfire.core}
26895 @itemx @samp{org.gnu.gdb.fido.core}
26896 One of those features must be always present.
26897 The feature that is present determines which flavor of m86k is
26898 used. The feature that is present should contain registers
26899 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
26900 @samp{sp}, @samp{ps} and @samp{pc}.
26902 @item @samp{org.gnu.gdb.coldfire.fp}
26903 This feature is optional. If present, it should contain registers
26904 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
26908 @subsection PowerPC Features
26909 @cindex target descriptions, PowerPC features
26911 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
26912 targets. It should contain registers @samp{r0} through @samp{r31},
26913 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
26914 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
26916 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
26917 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
26919 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
26920 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
26923 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
26924 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
26925 @samp{spefscr}. SPE targets should provide 32-bit registers in
26926 @samp{org.gnu.gdb.power.core} and provide the upper halves in
26927 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
26928 these to present registers @samp{ev0} through @samp{ev31} to the
26943 % I think something like @colophon should be in texinfo. In the
26945 \long\def\colophon{\hbox to0pt{}\vfill
26946 \centerline{The body of this manual is set in}
26947 \centerline{\fontname\tenrm,}
26948 \centerline{with headings in {\bf\fontname\tenbf}}
26949 \centerline{and examples in {\tt\fontname\tentt}.}
26950 \centerline{{\it\fontname\tenit\/},}
26951 \centerline{{\bf\fontname\tenbf}, and}
26952 \centerline{{\sl\fontname\tensl\/}}
26953 \centerline{are used for emphasis.}\vfill}
26955 % Blame: doc@cygnus.com, 1991.