1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,
3 @c 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006
4 @c Free Software Foundation, Inc.
7 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
8 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
25 @c readline appendices use @vindex, @findex and @ftable,
26 @c annotate.texi and gdbmi use @findex.
30 @c !!set GDB manual's edition---not the same as GDB version!
31 @c This is updated by GNU Press.
34 @c !!set GDB edit command default editor
37 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
39 @c This is a dir.info fragment to support semi-automated addition of
40 @c manuals to an info tree.
41 @dircategory Software development
43 * Gdb: (gdb). The GNU debugger.
47 This file documents the @sc{gnu} debugger @value{GDBN}.
50 This is the @value{EDITION} Edition, of @cite{Debugging with
51 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
52 Version @value{GDBVN}.
54 Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,@*
55 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006@*
56 Free Software Foundation, Inc.
58 Permission is granted to copy, distribute and/or modify this document
59 under the terms of the GNU Free Documentation License, Version 1.1 or
60 any later version published by the Free Software Foundation; with the
61 Invariant Sections being ``Free Software'' and ``Free Software Needs
62 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
63 and with the Back-Cover Texts as in (a) below.
65 (a) The Free Software Foundation's Back-Cover Text is: ``You have
66 freedom to copy and modify this GNU Manual, like GNU software. Copies
67 published by the Free Software Foundation raise funds for GNU
72 @title Debugging with @value{GDBN}
73 @subtitle The @sc{gnu} Source-Level Debugger
75 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
76 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
80 \hfill (Send bugs and comments on @value{GDBN} to bug-gdb\@gnu.org.)\par
81 \hfill {\it Debugging with @value{GDBN}}\par
82 \hfill \TeX{}info \texinfoversion\par
86 @vskip 0pt plus 1filll
87 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995,
88 1996, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2006
89 Free Software Foundation, Inc.
91 Published by the Free Software Foundation @*
92 51 Franklin Street, Fifth Floor,
93 Boston, MA 02110-1301, USA@*
96 Permission is granted to copy, distribute and/or modify this document
97 under the terms of the GNU Free Documentation License, Version 1.1 or
98 any later version published by the Free Software Foundation; with the
99 Invariant Sections being ``Free Software'' and ``Free Software Needs
100 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
101 and with the Back-Cover Texts as in (a) below.
103 (a) The Free Software Foundation's Back-Cover Text is: ``You have
104 freedom to copy and modify this GNU Manual, like GNU software. Copies
105 published by the Free Software Foundation raise funds for GNU
108 This edition of the GDB manual is dedicated to the memory of Fred
109 Fish. Fred was a long-standing contributor to GDB and to Free
110 software in general. We will miss him.
115 @node Top, Summary, (dir), (dir)
117 @top Debugging with @value{GDBN}
119 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
121 This is the @value{EDITION} Edition, for @value{GDBN} Version
124 Copyright (C) 1988-2006 Free Software Foundation, Inc.
126 This edition of the GDB manual is dedicated to the memory of Fred
127 Fish. Fred was a long-standing contributor to GDB and to Free
128 software in general. We will miss him.
131 * Summary:: Summary of @value{GDBN}
132 * Sample Session:: A sample @value{GDBN} session
134 * Invocation:: Getting in and out of @value{GDBN}
135 * Commands:: @value{GDBN} commands
136 * Running:: Running programs under @value{GDBN}
137 * Stopping:: Stopping and continuing
138 * Stack:: Examining the stack
139 * Source:: Examining source files
140 * Data:: Examining data
141 * Macros:: Preprocessor Macros
142 * Tracepoints:: Debugging remote targets non-intrusively
143 * Overlays:: Debugging programs that use overlays
145 * Languages:: Using @value{GDBN} with different languages
147 * Symbols:: Examining the symbol table
148 * Altering:: Altering execution
149 * GDB Files:: @value{GDBN} files
150 * Targets:: Specifying a debugging target
151 * Remote Debugging:: Debugging remote programs
152 * Configurations:: Configuration-specific information
153 * Controlling GDB:: Controlling @value{GDBN}
154 * Sequences:: Canned sequences of commands
155 * Interpreters:: Command Interpreters
156 * TUI:: @value{GDBN} Text User Interface
157 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
158 * GDB/MI:: @value{GDBN}'s Machine Interface.
159 * Annotations:: @value{GDBN}'s annotation interface.
161 * GDB Bugs:: Reporting bugs in @value{GDBN}
163 * Command Line Editing:: Command Line Editing
164 * Using History Interactively:: Using History Interactively
165 * Formatting Documentation:: How to format and print @value{GDBN} documentation
166 * Installing GDB:: Installing GDB
167 * Maintenance Commands:: Maintenance Commands
168 * Remote Protocol:: GDB Remote Serial Protocol
169 * Agent Expressions:: The GDB Agent Expression Mechanism
170 * Target Descriptions:: How targets can describe themselves to
172 * Copying:: GNU General Public License says
173 how you can copy and share GDB
174 * GNU Free Documentation License:: The license for this documentation
183 @unnumbered Summary of @value{GDBN}
185 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
186 going on ``inside'' another program while it executes---or what another
187 program was doing at the moment it crashed.
189 @value{GDBN} can do four main kinds of things (plus other things in support of
190 these) to help you catch bugs in the act:
194 Start your program, specifying anything that might affect its behavior.
197 Make your program stop on specified conditions.
200 Examine what has happened, when your program has stopped.
203 Change things in your program, so you can experiment with correcting the
204 effects of one bug and go on to learn about another.
207 You can use @value{GDBN} to debug programs written in C and C@t{++}.
208 For more information, see @ref{Supported Languages,,Supported Languages}.
209 For more information, see @ref{C,,C and C++}.
212 Support for Modula-2 is partial. For information on Modula-2, see
213 @ref{Modula-2,,Modula-2}.
216 Debugging Pascal programs which use sets, subranges, file variables, or
217 nested functions does not currently work. @value{GDBN} does not support
218 entering expressions, printing values, or similar features using Pascal
222 @value{GDBN} can be used to debug programs written in Fortran, although
223 it may be necessary to refer to some variables with a trailing
226 @value{GDBN} can be used to debug programs written in Objective-C,
227 using either the Apple/NeXT or the GNU Objective-C runtime.
230 * Free Software:: Freely redistributable software
231 * Contributors:: Contributors to GDB
235 @unnumberedsec Free Software
237 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
238 General Public License
239 (GPL). The GPL gives you the freedom to copy or adapt a licensed
240 program---but every person getting a copy also gets with it the
241 freedom to modify that copy (which means that they must get access to
242 the source code), and the freedom to distribute further copies.
243 Typical software companies use copyrights to limit your freedoms; the
244 Free Software Foundation uses the GPL to preserve these freedoms.
246 Fundamentally, the General Public License is a license which says that
247 you have these freedoms and that you cannot take these freedoms away
250 @unnumberedsec Free Software Needs Free Documentation
252 The biggest deficiency in the free software community today is not in
253 the software---it is the lack of good free documentation that we can
254 include with the free software. Many of our most important
255 programs do not come with free reference manuals and free introductory
256 texts. Documentation is an essential part of any software package;
257 when an important free software package does not come with a free
258 manual and a free tutorial, that is a major gap. We have many such
261 Consider Perl, for instance. The tutorial manuals that people
262 normally use are non-free. How did this come about? Because the
263 authors of those manuals published them with restrictive terms---no
264 copying, no modification, source files not available---which exclude
265 them from the free software world.
267 That wasn't the first time this sort of thing happened, and it was far
268 from the last. Many times we have heard a GNU user eagerly describe a
269 manual that he is writing, his intended contribution to the community,
270 only to learn that he had ruined everything by signing a publication
271 contract to make it non-free.
273 Free documentation, like free software, is a matter of freedom, not
274 price. The problem with the non-free manual is not that publishers
275 charge a price for printed copies---that in itself is fine. (The Free
276 Software Foundation sells printed copies of manuals, too.) The
277 problem is the restrictions on the use of the manual. Free manuals
278 are available in source code form, and give you permission to copy and
279 modify. Non-free manuals do not allow this.
281 The criteria of freedom for a free manual are roughly the same as for
282 free software. Redistribution (including the normal kinds of
283 commercial redistribution) must be permitted, so that the manual can
284 accompany every copy of the program, both on-line and on paper.
286 Permission for modification of the technical content is crucial too.
287 When people modify the software, adding or changing features, if they
288 are conscientious they will change the manual too---so they can
289 provide accurate and clear documentation for the modified program. A
290 manual that leaves you no choice but to write a new manual to document
291 a changed version of the program is not really available to our
294 Some kinds of limits on the way modification is handled are
295 acceptable. For example, requirements to preserve the original
296 author's copyright notice, the distribution terms, or the list of
297 authors, are ok. It is also no problem to require modified versions
298 to include notice that they were modified. Even entire sections that
299 may not be deleted or changed are acceptable, as long as they deal
300 with nontechnical topics (like this one). These kinds of restrictions
301 are acceptable because they don't obstruct the community's normal use
304 However, it must be possible to modify all the @emph{technical}
305 content of the manual, and then distribute the result in all the usual
306 media, through all the usual channels. Otherwise, the restrictions
307 obstruct the use of the manual, it is not free, and we need another
308 manual to replace it.
310 Please spread the word about this issue. Our community continues to
311 lose manuals to proprietary publishing. If we spread the word that
312 free software needs free reference manuals and free tutorials, perhaps
313 the next person who wants to contribute by writing documentation will
314 realize, before it is too late, that only free manuals contribute to
315 the free software community.
317 If you are writing documentation, please insist on publishing it under
318 the GNU Free Documentation License or another free documentation
319 license. Remember that this decision requires your approval---you
320 don't have to let the publisher decide. Some commercial publishers
321 will use a free license if you insist, but they will not propose the
322 option; it is up to you to raise the issue and say firmly that this is
323 what you want. If the publisher you are dealing with refuses, please
324 try other publishers. If you're not sure whether a proposed license
325 is free, write to @email{licensing@@gnu.org}.
327 You can encourage commercial publishers to sell more free, copylefted
328 manuals and tutorials by buying them, and particularly by buying
329 copies from the publishers that paid for their writing or for major
330 improvements. Meanwhile, try to avoid buying non-free documentation
331 at all. Check the distribution terms of a manual before you buy it,
332 and insist that whoever seeks your business must respect your freedom.
333 Check the history of the book, and try to reward the publishers that
334 have paid or pay the authors to work on it.
336 The Free Software Foundation maintains a list of free documentation
337 published by other publishers, at
338 @url{http://www.fsf.org/doc/other-free-books.html}.
341 @unnumberedsec Contributors to @value{GDBN}
343 Richard Stallman was the original author of @value{GDBN}, and of many
344 other @sc{gnu} programs. Many others have contributed to its
345 development. This section attempts to credit major contributors. One
346 of the virtues of free software is that everyone is free to contribute
347 to it; with regret, we cannot actually acknowledge everyone here. The
348 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
349 blow-by-blow account.
351 Changes much prior to version 2.0 are lost in the mists of time.
354 @emph{Plea:} Additions to this section are particularly welcome. If you
355 or your friends (or enemies, to be evenhanded) have been unfairly
356 omitted from this list, we would like to add your names!
359 So that they may not regard their many labors as thankless, we
360 particularly thank those who shepherded @value{GDBN} through major
362 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
363 Jim Blandy (release 4.18);
364 Jason Molenda (release 4.17);
365 Stan Shebs (release 4.14);
366 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
367 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
368 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
369 Jim Kingdon (releases 3.5, 3.4, and 3.3);
370 and Randy Smith (releases 3.2, 3.1, and 3.0).
372 Richard Stallman, assisted at various times by Peter TerMaat, Chris
373 Hanson, and Richard Mlynarik, handled releases through 2.8.
375 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
376 in @value{GDBN}, with significant additional contributions from Per
377 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
378 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
379 much general update work leading to release 3.0).
381 @value{GDBN} uses the BFD subroutine library to examine multiple
382 object-file formats; BFD was a joint project of David V.
383 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
385 David Johnson wrote the original COFF support; Pace Willison did
386 the original support for encapsulated COFF.
388 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
390 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
391 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
393 Jean-Daniel Fekete contributed Sun 386i support.
394 Chris Hanson improved the HP9000 support.
395 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
396 David Johnson contributed Encore Umax support.
397 Jyrki Kuoppala contributed Altos 3068 support.
398 Jeff Law contributed HP PA and SOM support.
399 Keith Packard contributed NS32K support.
400 Doug Rabson contributed Acorn Risc Machine support.
401 Bob Rusk contributed Harris Nighthawk CX-UX support.
402 Chris Smith contributed Convex support (and Fortran debugging).
403 Jonathan Stone contributed Pyramid support.
404 Michael Tiemann contributed SPARC support.
405 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
406 Pace Willison contributed Intel 386 support.
407 Jay Vosburgh contributed Symmetry support.
408 Marko Mlinar contributed OpenRISC 1000 support.
410 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
412 Rich Schaefer and Peter Schauer helped with support of SunOS shared
415 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
416 about several machine instruction sets.
418 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
419 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
420 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
421 and RDI targets, respectively.
423 Brian Fox is the author of the readline libraries providing
424 command-line editing and command history.
426 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
427 Modula-2 support, and contributed the Languages chapter of this manual.
429 Fred Fish wrote most of the support for Unix System Vr4.
430 He also enhanced the command-completion support to cover C@t{++} overloaded
433 Hitachi America (now Renesas America), Ltd. sponsored the support for
434 H8/300, H8/500, and Super-H processors.
436 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
438 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
441 Toshiba sponsored the support for the TX39 Mips processor.
443 Matsushita sponsored the support for the MN10200 and MN10300 processors.
445 Fujitsu sponsored the support for SPARClite and FR30 processors.
447 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
450 Michael Snyder added support for tracepoints.
452 Stu Grossman wrote gdbserver.
454 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
455 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
457 The following people at the Hewlett-Packard Company contributed
458 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
459 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
460 compiler, and the Text User Interface (nee Terminal User Interface):
461 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
462 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
463 provided HP-specific information in this manual.
465 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
466 Robert Hoehne made significant contributions to the DJGPP port.
468 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
469 development since 1991. Cygnus engineers who have worked on @value{GDBN}
470 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
471 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
472 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
473 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
474 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
475 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
476 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
477 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
478 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
479 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
480 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
481 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
482 Zuhn have made contributions both large and small.
484 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
485 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
487 Jim Blandy added support for preprocessor macros, while working for Red
490 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
491 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
492 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
493 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
494 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
495 with the migration of old architectures to this new framework.
497 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
498 unwinder framework, this consisting of a fresh new design featuring
499 frame IDs, independent frame sniffers, and the sentinel frame. Mark
500 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
501 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
502 trad unwinders. The architecture-specific changes, each involving a
503 complete rewrite of the architecture's frame code, were carried out by
504 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
505 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
506 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
507 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
510 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
511 Tensilica, Inc.@: contributed support for Xtensa processors. Others
512 who have worked on the Xtensa port of @value{GDBN} in the past include
513 Steve Tjiang, John Newlin, and Scott Foehner.
516 @chapter A Sample @value{GDBN} Session
518 You can use this manual at your leisure to read all about @value{GDBN}.
519 However, a handful of commands are enough to get started using the
520 debugger. This chapter illustrates those commands.
523 In this sample session, we emphasize user input like this: @b{input},
524 to make it easier to pick out from the surrounding output.
527 @c FIXME: this example may not be appropriate for some configs, where
528 @c FIXME...primary interest is in remote use.
530 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
531 processor) exhibits the following bug: sometimes, when we change its
532 quote strings from the default, the commands used to capture one macro
533 definition within another stop working. In the following short @code{m4}
534 session, we define a macro @code{foo} which expands to @code{0000}; we
535 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
536 same thing. However, when we change the open quote string to
537 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
538 procedure fails to define a new synonym @code{baz}:
547 @b{define(bar,defn(`foo'))}
551 @b{changequote(<QUOTE>,<UNQUOTE>)}
553 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
556 m4: End of input: 0: fatal error: EOF in string
560 Let us use @value{GDBN} to try to see what is going on.
563 $ @b{@value{GDBP} m4}
564 @c FIXME: this falsifies the exact text played out, to permit smallbook
565 @c FIXME... format to come out better.
566 @value{GDBN} is free software and you are welcome to distribute copies
567 of it under certain conditions; type "show copying" to see
569 There is absolutely no warranty for @value{GDBN}; type "show warranty"
572 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
577 @value{GDBN} reads only enough symbol data to know where to find the
578 rest when needed; as a result, the first prompt comes up very quickly.
579 We now tell @value{GDBN} to use a narrower display width than usual, so
580 that examples fit in this manual.
583 (@value{GDBP}) @b{set width 70}
587 We need to see how the @code{m4} built-in @code{changequote} works.
588 Having looked at the source, we know the relevant subroutine is
589 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
590 @code{break} command.
593 (@value{GDBP}) @b{break m4_changequote}
594 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
598 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
599 control; as long as control does not reach the @code{m4_changequote}
600 subroutine, the program runs as usual:
603 (@value{GDBP}) @b{run}
604 Starting program: /work/Editorial/gdb/gnu/m4/m4
612 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
613 suspends execution of @code{m4}, displaying information about the
614 context where it stops.
617 @b{changequote(<QUOTE>,<UNQUOTE>)}
619 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
621 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
625 Now we use the command @code{n} (@code{next}) to advance execution to
626 the next line of the current function.
630 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
635 @code{set_quotes} looks like a promising subroutine. We can go into it
636 by using the command @code{s} (@code{step}) instead of @code{next}.
637 @code{step} goes to the next line to be executed in @emph{any}
638 subroutine, so it steps into @code{set_quotes}.
642 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
644 530 if (lquote != def_lquote)
648 The display that shows the subroutine where @code{m4} is now
649 suspended (and its arguments) is called a stack frame display. It
650 shows a summary of the stack. We can use the @code{backtrace}
651 command (which can also be spelled @code{bt}), to see where we are
652 in the stack as a whole: the @code{backtrace} command displays a
653 stack frame for each active subroutine.
656 (@value{GDBP}) @b{bt}
657 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
659 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
661 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
662 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
664 #4 0x79dc in expand_input () at macro.c:40
665 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
669 We step through a few more lines to see what happens. The first two
670 times, we can use @samp{s}; the next two times we use @code{n} to avoid
671 falling into the @code{xstrdup} subroutine.
675 0x3b5c 532 if (rquote != def_rquote)
677 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
678 def_lquote : xstrdup(lq);
680 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
683 538 len_lquote = strlen(rquote);
687 The last line displayed looks a little odd; we can examine the variables
688 @code{lquote} and @code{rquote} to see if they are in fact the new left
689 and right quotes we specified. We use the command @code{p}
690 (@code{print}) to see their values.
693 (@value{GDBP}) @b{p lquote}
694 $1 = 0x35d40 "<QUOTE>"
695 (@value{GDBP}) @b{p rquote}
696 $2 = 0x35d50 "<UNQUOTE>"
700 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
701 To look at some context, we can display ten lines of source
702 surrounding the current line with the @code{l} (@code{list}) command.
708 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
710 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
713 538 len_lquote = strlen(rquote);
714 539 len_rquote = strlen(lquote);
721 Let us step past the two lines that set @code{len_lquote} and
722 @code{len_rquote}, and then examine the values of those variables.
726 539 len_rquote = strlen(lquote);
729 (@value{GDBP}) @b{p len_lquote}
731 (@value{GDBP}) @b{p len_rquote}
736 That certainly looks wrong, assuming @code{len_lquote} and
737 @code{len_rquote} are meant to be the lengths of @code{lquote} and
738 @code{rquote} respectively. We can set them to better values using
739 the @code{p} command, since it can print the value of
740 any expression---and that expression can include subroutine calls and
744 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
746 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
751 Is that enough to fix the problem of using the new quotes with the
752 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
753 executing with the @code{c} (@code{continue}) command, and then try the
754 example that caused trouble initially:
760 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
767 Success! The new quotes now work just as well as the default ones. The
768 problem seems to have been just the two typos defining the wrong
769 lengths. We allow @code{m4} exit by giving it an EOF as input:
773 Program exited normally.
777 The message @samp{Program exited normally.} is from @value{GDBN}; it
778 indicates @code{m4} has finished executing. We can end our @value{GDBN}
779 session with the @value{GDBN} @code{quit} command.
782 (@value{GDBP}) @b{quit}
786 @chapter Getting In and Out of @value{GDBN}
788 This chapter discusses how to start @value{GDBN}, and how to get out of it.
792 type @samp{@value{GDBP}} to start @value{GDBN}.
794 type @kbd{quit} or @kbd{Ctrl-d} to exit.
798 * Invoking GDB:: How to start @value{GDBN}
799 * Quitting GDB:: How to quit @value{GDBN}
800 * Shell Commands:: How to use shell commands inside @value{GDBN}
801 * Logging Output:: How to log @value{GDBN}'s output to a file
805 @section Invoking @value{GDBN}
807 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
808 @value{GDBN} reads commands from the terminal until you tell it to exit.
810 You can also run @code{@value{GDBP}} with a variety of arguments and options,
811 to specify more of your debugging environment at the outset.
813 The command-line options described here are designed
814 to cover a variety of situations; in some environments, some of these
815 options may effectively be unavailable.
817 The most usual way to start @value{GDBN} is with one argument,
818 specifying an executable program:
821 @value{GDBP} @var{program}
825 You can also start with both an executable program and a core file
829 @value{GDBP} @var{program} @var{core}
832 You can, instead, specify a process ID as a second argument, if you want
833 to debug a running process:
836 @value{GDBP} @var{program} 1234
840 would attach @value{GDBN} to process @code{1234} (unless you also have a file
841 named @file{1234}; @value{GDBN} does check for a core file first).
843 Taking advantage of the second command-line argument requires a fairly
844 complete operating system; when you use @value{GDBN} as a remote
845 debugger attached to a bare board, there may not be any notion of
846 ``process'', and there is often no way to get a core dump. @value{GDBN}
847 will warn you if it is unable to attach or to read core dumps.
849 You can optionally have @code{@value{GDBP}} pass any arguments after the
850 executable file to the inferior using @code{--args}. This option stops
853 @value{GDBP} --args gcc -O2 -c foo.c
855 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
856 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
858 You can run @code{@value{GDBP}} without printing the front material, which describes
859 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
866 You can further control how @value{GDBN} starts up by using command-line
867 options. @value{GDBN} itself can remind you of the options available.
877 to display all available options and briefly describe their use
878 (@samp{@value{GDBP} -h} is a shorter equivalent).
880 All options and command line arguments you give are processed
881 in sequential order. The order makes a difference when the
882 @samp{-x} option is used.
886 * File Options:: Choosing files
887 * Mode Options:: Choosing modes
888 * Startup:: What @value{GDBN} does during startup
892 @subsection Choosing Files
894 When @value{GDBN} starts, it reads any arguments other than options as
895 specifying an executable file and core file (or process ID). This is
896 the same as if the arguments were specified by the @samp{-se} and
897 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
898 first argument that does not have an associated option flag as
899 equivalent to the @samp{-se} option followed by that argument; and the
900 second argument that does not have an associated option flag, if any, as
901 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
902 If the second argument begins with a decimal digit, @value{GDBN} will
903 first attempt to attach to it as a process, and if that fails, attempt
904 to open it as a corefile. If you have a corefile whose name begins with
905 a digit, you can prevent @value{GDBN} from treating it as a pid by
906 prefixing it with @file{./}, e.g.@: @file{./12345}.
908 If @value{GDBN} has not been configured to included core file support,
909 such as for most embedded targets, then it will complain about a second
910 argument and ignore it.
912 Many options have both long and short forms; both are shown in the
913 following list. @value{GDBN} also recognizes the long forms if you truncate
914 them, so long as enough of the option is present to be unambiguous.
915 (If you prefer, you can flag option arguments with @samp{--} rather
916 than @samp{-}, though we illustrate the more usual convention.)
918 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
919 @c way, both those who look for -foo and --foo in the index, will find
923 @item -symbols @var{file}
925 @cindex @code{--symbols}
927 Read symbol table from file @var{file}.
929 @item -exec @var{file}
931 @cindex @code{--exec}
933 Use file @var{file} as the executable file to execute when appropriate,
934 and for examining pure data in conjunction with a core dump.
938 Read symbol table from file @var{file} and use it as the executable
941 @item -core @var{file}
943 @cindex @code{--core}
945 Use file @var{file} as a core dump to examine.
947 @item -c @var{number}
948 @item -pid @var{number}
949 @itemx -p @var{number}
952 Connect to process ID @var{number}, as with the @code{attach} command.
953 If there is no such process, @value{GDBN} will attempt to open a core
954 file named @var{number}.
956 @item -command @var{file}
958 @cindex @code{--command}
960 Execute @value{GDBN} commands from file @var{file}. @xref{Command
961 Files,, Command files}.
963 @item -eval-command @var{command}
964 @itemx -ex @var{command}
965 @cindex @code{--eval-command}
967 Execute a single @value{GDBN} command.
969 This option may be used multiple times to call multiple commands. It may
970 also be interleaved with @samp{-command} as required.
973 @value{GDBP} -ex 'target sim' -ex 'load' \
974 -x setbreakpoints -ex 'run' a.out
977 @item -directory @var{directory}
978 @itemx -d @var{directory}
979 @cindex @code{--directory}
981 Add @var{directory} to the path to search for source and script files.
985 @cindex @code{--readnow}
987 Read each symbol file's entire symbol table immediately, rather than
988 the default, which is to read it incrementally as it is needed.
989 This makes startup slower, but makes future operations faster.
994 @subsection Choosing Modes
996 You can run @value{GDBN} in various alternative modes---for example, in
997 batch mode or quiet mode.
1004 Do not execute commands found in any initialization files. Normally,
1005 @value{GDBN} executes the commands in these files after all the command
1006 options and arguments have been processed. @xref{Command Files,,Command
1012 @cindex @code{--quiet}
1013 @cindex @code{--silent}
1015 ``Quiet''. Do not print the introductory and copyright messages. These
1016 messages are also suppressed in batch mode.
1019 @cindex @code{--batch}
1020 Run in batch mode. Exit with status @code{0} after processing all the
1021 command files specified with @samp{-x} (and all commands from
1022 initialization files, if not inhibited with @samp{-n}). Exit with
1023 nonzero status if an error occurs in executing the @value{GDBN} commands
1024 in the command files.
1026 Batch mode may be useful for running @value{GDBN} as a filter, for
1027 example to download and run a program on another computer; in order to
1028 make this more useful, the message
1031 Program exited normally.
1035 (which is ordinarily issued whenever a program running under
1036 @value{GDBN} control terminates) is not issued when running in batch
1040 @cindex @code{--batch-silent}
1041 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1042 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1043 unaffected). This is much quieter than @samp{-silent} and would be useless
1044 for an interactive session.
1046 This is particularly useful when using targets that give @samp{Loading section}
1047 messages, for example.
1049 Note that targets that give their output via @value{GDBN}, as opposed to
1050 writing directly to @code{stdout}, will also be made silent.
1052 @item -return-child-result
1053 @cindex @code{--return-child-result}
1054 The return code from @value{GDBN} will be the return code from the child
1055 process (the process being debugged), with the following exceptions:
1059 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1060 internal error. In this case the exit code is the same as it would have been
1061 without @samp{-return-child-result}.
1063 The user quits with an explicit value. E.g., @samp{quit 1}.
1065 The child process never runs, or is not allowed to terminate, in which case
1066 the exit code will be -1.
1069 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1070 when @value{GDBN} is being used as a remote program loader or simulator
1075 @cindex @code{--nowindows}
1077 ``No windows''. If @value{GDBN} comes with a graphical user interface
1078 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1079 interface. If no GUI is available, this option has no effect.
1083 @cindex @code{--windows}
1085 If @value{GDBN} includes a GUI, then this option requires it to be
1088 @item -cd @var{directory}
1090 Run @value{GDBN} using @var{directory} as its working directory,
1091 instead of the current directory.
1095 @cindex @code{--fullname}
1097 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1098 subprocess. It tells @value{GDBN} to output the full file name and line
1099 number in a standard, recognizable fashion each time a stack frame is
1100 displayed (which includes each time your program stops). This
1101 recognizable format looks like two @samp{\032} characters, followed by
1102 the file name, line number and character position separated by colons,
1103 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1104 @samp{\032} characters as a signal to display the source code for the
1108 @cindex @code{--epoch}
1109 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1110 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1111 routines so as to allow Epoch to display values of expressions in a
1114 @item -annotate @var{level}
1115 @cindex @code{--annotate}
1116 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1117 effect is identical to using @samp{set annotate @var{level}}
1118 (@pxref{Annotations}). The annotation @var{level} controls how much
1119 information @value{GDBN} prints together with its prompt, values of
1120 expressions, source lines, and other types of output. Level 0 is the
1121 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1122 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1123 that control @value{GDBN}, and level 2 has been deprecated.
1125 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1129 @cindex @code{--args}
1130 Change interpretation of command line so that arguments following the
1131 executable file are passed as command line arguments to the inferior.
1132 This option stops option processing.
1134 @item -baud @var{bps}
1136 @cindex @code{--baud}
1138 Set the line speed (baud rate or bits per second) of any serial
1139 interface used by @value{GDBN} for remote debugging.
1141 @item -l @var{timeout}
1143 Set the timeout (in seconds) of any communication used by @value{GDBN}
1144 for remote debugging.
1146 @item -tty @var{device}
1147 @itemx -t @var{device}
1148 @cindex @code{--tty}
1150 Run using @var{device} for your program's standard input and output.
1151 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1153 @c resolve the situation of these eventually
1155 @cindex @code{--tui}
1156 Activate the @dfn{Text User Interface} when starting. The Text User
1157 Interface manages several text windows on the terminal, showing
1158 source, assembly, registers and @value{GDBN} command outputs
1159 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1160 Text User Interface can be enabled by invoking the program
1161 @samp{@value{GDBTUI}}. Do not use this option if you run @value{GDBN} from
1162 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1165 @c @cindex @code{--xdb}
1166 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1167 @c For information, see the file @file{xdb_trans.html}, which is usually
1168 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1171 @item -interpreter @var{interp}
1172 @cindex @code{--interpreter}
1173 Use the interpreter @var{interp} for interface with the controlling
1174 program or device. This option is meant to be set by programs which
1175 communicate with @value{GDBN} using it as a back end.
1176 @xref{Interpreters, , Command Interpreters}.
1178 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1179 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1180 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1181 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1182 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1183 @sc{gdb/mi} interfaces are no longer supported.
1186 @cindex @code{--write}
1187 Open the executable and core files for both reading and writing. This
1188 is equivalent to the @samp{set write on} command inside @value{GDBN}
1192 @cindex @code{--statistics}
1193 This option causes @value{GDBN} to print statistics about time and
1194 memory usage after it completes each command and returns to the prompt.
1197 @cindex @code{--version}
1198 This option causes @value{GDBN} to print its version number and
1199 no-warranty blurb, and exit.
1204 @subsection What @value{GDBN} Does During Startup
1205 @cindex @value{GDBN} startup
1207 Here's the description of what @value{GDBN} does during session startup:
1211 Sets up the command interpreter as specified by the command line
1212 (@pxref{Mode Options, interpreter}).
1216 Reads the @dfn{init file} (if any) in your home directory@footnote{On
1217 DOS/Windows systems, the home directory is the one pointed to by the
1218 @code{HOME} environment variable.} and executes all the commands in
1222 Processes command line options and operands.
1225 Reads and executes the commands from init file (if any) in the current
1226 working directory. This is only done if the current directory is
1227 different from your home directory. Thus, you can have more than one
1228 init file, one generic in your home directory, and another, specific
1229 to the program you are debugging, in the directory where you invoke
1233 Reads command files specified by the @samp{-x} option. @xref{Command
1234 Files}, for more details about @value{GDBN} command files.
1237 Reads the command history recorded in the @dfn{history file}.
1238 @xref{Command History}, for more details about the command history and the
1239 files where @value{GDBN} records it.
1242 Init files use the same syntax as @dfn{command files} (@pxref{Command
1243 Files}) and are processed by @value{GDBN} in the same way. The init
1244 file in your home directory can set options (such as @samp{set
1245 complaints}) that affect subsequent processing of command line options
1246 and operands. Init files are not executed if you use the @samp{-nx}
1247 option (@pxref{Mode Options, ,Choosing Modes}).
1249 @cindex init file name
1250 @cindex @file{.gdbinit}
1251 @cindex @file{gdb.ini}
1252 The @value{GDBN} init files are normally called @file{.gdbinit}.
1253 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1254 the limitations of file names imposed by DOS filesystems. The Windows
1255 ports of @value{GDBN} use the standard name, but if they find a
1256 @file{gdb.ini} file, they warn you about that and suggest to rename
1257 the file to the standard name.
1261 @section Quitting @value{GDBN}
1262 @cindex exiting @value{GDBN}
1263 @cindex leaving @value{GDBN}
1266 @kindex quit @r{[}@var{expression}@r{]}
1267 @kindex q @r{(@code{quit})}
1268 @item quit @r{[}@var{expression}@r{]}
1270 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1271 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1272 do not supply @var{expression}, @value{GDBN} will terminate normally;
1273 otherwise it will terminate using the result of @var{expression} as the
1278 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1279 terminates the action of any @value{GDBN} command that is in progress and
1280 returns to @value{GDBN} command level. It is safe to type the interrupt
1281 character at any time because @value{GDBN} does not allow it to take effect
1282 until a time when it is safe.
1284 If you have been using @value{GDBN} to control an attached process or
1285 device, you can release it with the @code{detach} command
1286 (@pxref{Attach, ,Debugging an Already-running Process}).
1288 @node Shell Commands
1289 @section Shell Commands
1291 If you need to execute occasional shell commands during your
1292 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1293 just use the @code{shell} command.
1297 @cindex shell escape
1298 @item shell @var{command string}
1299 Invoke a standard shell to execute @var{command string}.
1300 If it exists, the environment variable @code{SHELL} determines which
1301 shell to run. Otherwise @value{GDBN} uses the default shell
1302 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1305 The utility @code{make} is often needed in development environments.
1306 You do not have to use the @code{shell} command for this purpose in
1311 @cindex calling make
1312 @item make @var{make-args}
1313 Execute the @code{make} program with the specified
1314 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1317 @node Logging Output
1318 @section Logging Output
1319 @cindex logging @value{GDBN} output
1320 @cindex save @value{GDBN} output to a file
1322 You may want to save the output of @value{GDBN} commands to a file.
1323 There are several commands to control @value{GDBN}'s logging.
1327 @item set logging on
1329 @item set logging off
1331 @cindex logging file name
1332 @item set logging file @var{file}
1333 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1334 @item set logging overwrite [on|off]
1335 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1336 you want @code{set logging on} to overwrite the logfile instead.
1337 @item set logging redirect [on|off]
1338 By default, @value{GDBN} output will go to both the terminal and the logfile.
1339 Set @code{redirect} if you want output to go only to the log file.
1340 @kindex show logging
1342 Show the current values of the logging settings.
1346 @chapter @value{GDBN} Commands
1348 You can abbreviate a @value{GDBN} command to the first few letters of the command
1349 name, if that abbreviation is unambiguous; and you can repeat certain
1350 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1351 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1352 show you the alternatives available, if there is more than one possibility).
1355 * Command Syntax:: How to give commands to @value{GDBN}
1356 * Completion:: Command completion
1357 * Help:: How to ask @value{GDBN} for help
1360 @node Command Syntax
1361 @section Command Syntax
1363 A @value{GDBN} command is a single line of input. There is no limit on
1364 how long it can be. It starts with a command name, which is followed by
1365 arguments whose meaning depends on the command name. For example, the
1366 command @code{step} accepts an argument which is the number of times to
1367 step, as in @samp{step 5}. You can also use the @code{step} command
1368 with no arguments. Some commands do not allow any arguments.
1370 @cindex abbreviation
1371 @value{GDBN} command names may always be truncated if that abbreviation is
1372 unambiguous. Other possible command abbreviations are listed in the
1373 documentation for individual commands. In some cases, even ambiguous
1374 abbreviations are allowed; for example, @code{s} is specially defined as
1375 equivalent to @code{step} even though there are other commands whose
1376 names start with @code{s}. You can test abbreviations by using them as
1377 arguments to the @code{help} command.
1379 @cindex repeating commands
1380 @kindex RET @r{(repeat last command)}
1381 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1382 repeat the previous command. Certain commands (for example, @code{run})
1383 will not repeat this way; these are commands whose unintentional
1384 repetition might cause trouble and which you are unlikely to want to
1385 repeat. User-defined commands can disable this feature; see
1386 @ref{Define, dont-repeat}.
1388 The @code{list} and @code{x} commands, when you repeat them with
1389 @key{RET}, construct new arguments rather than repeating
1390 exactly as typed. This permits easy scanning of source or memory.
1392 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1393 output, in a way similar to the common utility @code{more}
1394 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1395 @key{RET} too many in this situation, @value{GDBN} disables command
1396 repetition after any command that generates this sort of display.
1398 @kindex # @r{(a comment)}
1400 Any text from a @kbd{#} to the end of the line is a comment; it does
1401 nothing. This is useful mainly in command files (@pxref{Command
1402 Files,,Command Files}).
1404 @cindex repeating command sequences
1405 @kindex Ctrl-o @r{(operate-and-get-next)}
1406 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1407 commands. This command accepts the current line, like @key{RET}, and
1408 then fetches the next line relative to the current line from the history
1412 @section Command Completion
1415 @cindex word completion
1416 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1417 only one possibility; it can also show you what the valid possibilities
1418 are for the next word in a command, at any time. This works for @value{GDBN}
1419 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1421 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1422 of a word. If there is only one possibility, @value{GDBN} fills in the
1423 word, and waits for you to finish the command (or press @key{RET} to
1424 enter it). For example, if you type
1426 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1427 @c complete accuracy in these examples; space introduced for clarity.
1428 @c If texinfo enhancements make it unnecessary, it would be nice to
1429 @c replace " @key" by "@key" in the following...
1431 (@value{GDBP}) info bre @key{TAB}
1435 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1436 the only @code{info} subcommand beginning with @samp{bre}:
1439 (@value{GDBP}) info breakpoints
1443 You can either press @key{RET} at this point, to run the @code{info
1444 breakpoints} command, or backspace and enter something else, if
1445 @samp{breakpoints} does not look like the command you expected. (If you
1446 were sure you wanted @code{info breakpoints} in the first place, you
1447 might as well just type @key{RET} immediately after @samp{info bre},
1448 to exploit command abbreviations rather than command completion).
1450 If there is more than one possibility for the next word when you press
1451 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1452 characters and try again, or just press @key{TAB} a second time;
1453 @value{GDBN} displays all the possible completions for that word. For
1454 example, you might want to set a breakpoint on a subroutine whose name
1455 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1456 just sounds the bell. Typing @key{TAB} again displays all the
1457 function names in your program that begin with those characters, for
1461 (@value{GDBP}) b make_ @key{TAB}
1462 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1463 make_a_section_from_file make_environ
1464 make_abs_section make_function_type
1465 make_blockvector make_pointer_type
1466 make_cleanup make_reference_type
1467 make_command make_symbol_completion_list
1468 (@value{GDBP}) b make_
1472 After displaying the available possibilities, @value{GDBN} copies your
1473 partial input (@samp{b make_} in the example) so you can finish the
1476 If you just want to see the list of alternatives in the first place, you
1477 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1478 means @kbd{@key{META} ?}. You can type this either by holding down a
1479 key designated as the @key{META} shift on your keyboard (if there is
1480 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1482 @cindex quotes in commands
1483 @cindex completion of quoted strings
1484 Sometimes the string you need, while logically a ``word'', may contain
1485 parentheses or other characters that @value{GDBN} normally excludes from
1486 its notion of a word. To permit word completion to work in this
1487 situation, you may enclose words in @code{'} (single quote marks) in
1488 @value{GDBN} commands.
1490 The most likely situation where you might need this is in typing the
1491 name of a C@t{++} function. This is because C@t{++} allows function
1492 overloading (multiple definitions of the same function, distinguished
1493 by argument type). For example, when you want to set a breakpoint you
1494 may need to distinguish whether you mean the version of @code{name}
1495 that takes an @code{int} parameter, @code{name(int)}, or the version
1496 that takes a @code{float} parameter, @code{name(float)}. To use the
1497 word-completion facilities in this situation, type a single quote
1498 @code{'} at the beginning of the function name. This alerts
1499 @value{GDBN} that it may need to consider more information than usual
1500 when you press @key{TAB} or @kbd{M-?} to request word completion:
1503 (@value{GDBP}) b 'bubble( @kbd{M-?}
1504 bubble(double,double) bubble(int,int)
1505 (@value{GDBP}) b 'bubble(
1508 In some cases, @value{GDBN} can tell that completing a name requires using
1509 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1510 completing as much as it can) if you do not type the quote in the first
1514 (@value{GDBP}) b bub @key{TAB}
1515 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1516 (@value{GDBP}) b 'bubble(
1520 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1521 you have not yet started typing the argument list when you ask for
1522 completion on an overloaded symbol.
1524 For more information about overloaded functions, see @ref{C Plus Plus
1525 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1526 overload-resolution off} to disable overload resolution;
1527 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1531 @section Getting Help
1532 @cindex online documentation
1535 You can always ask @value{GDBN} itself for information on its commands,
1536 using the command @code{help}.
1539 @kindex h @r{(@code{help})}
1542 You can use @code{help} (abbreviated @code{h}) with no arguments to
1543 display a short list of named classes of commands:
1547 List of classes of commands:
1549 aliases -- Aliases of other commands
1550 breakpoints -- Making program stop at certain points
1551 data -- Examining data
1552 files -- Specifying and examining files
1553 internals -- Maintenance commands
1554 obscure -- Obscure features
1555 running -- Running the program
1556 stack -- Examining the stack
1557 status -- Status inquiries
1558 support -- Support facilities
1559 tracepoints -- Tracing of program execution without
1560 stopping the program
1561 user-defined -- User-defined commands
1563 Type "help" followed by a class name for a list of
1564 commands in that class.
1565 Type "help" followed by command name for full
1567 Command name abbreviations are allowed if unambiguous.
1570 @c the above line break eliminates huge line overfull...
1572 @item help @var{class}
1573 Using one of the general help classes as an argument, you can get a
1574 list of the individual commands in that class. For example, here is the
1575 help display for the class @code{status}:
1578 (@value{GDBP}) help status
1583 @c Line break in "show" line falsifies real output, but needed
1584 @c to fit in smallbook page size.
1585 info -- Generic command for showing things
1586 about the program being debugged
1587 show -- Generic command for showing things
1590 Type "help" followed by command name for full
1592 Command name abbreviations are allowed if unambiguous.
1596 @item help @var{command}
1597 With a command name as @code{help} argument, @value{GDBN} displays a
1598 short paragraph on how to use that command.
1601 @item apropos @var{args}
1602 The @code{apropos} command searches through all of the @value{GDBN}
1603 commands, and their documentation, for the regular expression specified in
1604 @var{args}. It prints out all matches found. For example:
1615 set symbol-reloading -- Set dynamic symbol table reloading
1616 multiple times in one run
1617 show symbol-reloading -- Show dynamic symbol table reloading
1618 multiple times in one run
1623 @item complete @var{args}
1624 The @code{complete @var{args}} command lists all the possible completions
1625 for the beginning of a command. Use @var{args} to specify the beginning of the
1626 command you want completed. For example:
1632 @noindent results in:
1643 @noindent This is intended for use by @sc{gnu} Emacs.
1646 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1647 and @code{show} to inquire about the state of your program, or the state
1648 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1649 manual introduces each of them in the appropriate context. The listings
1650 under @code{info} and under @code{show} in the Index point to
1651 all the sub-commands. @xref{Index}.
1656 @kindex i @r{(@code{info})}
1658 This command (abbreviated @code{i}) is for describing the state of your
1659 program. For example, you can list the arguments given to your program
1660 with @code{info args}, list the registers currently in use with @code{info
1661 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1662 You can get a complete list of the @code{info} sub-commands with
1663 @w{@code{help info}}.
1667 You can assign the result of an expression to an environment variable with
1668 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1669 @code{set prompt $}.
1673 In contrast to @code{info}, @code{show} is for describing the state of
1674 @value{GDBN} itself.
1675 You can change most of the things you can @code{show}, by using the
1676 related command @code{set}; for example, you can control what number
1677 system is used for displays with @code{set radix}, or simply inquire
1678 which is currently in use with @code{show radix}.
1681 To display all the settable parameters and their current
1682 values, you can use @code{show} with no arguments; you may also use
1683 @code{info set}. Both commands produce the same display.
1684 @c FIXME: "info set" violates the rule that "info" is for state of
1685 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1686 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1690 Here are three miscellaneous @code{show} subcommands, all of which are
1691 exceptional in lacking corresponding @code{set} commands:
1694 @kindex show version
1695 @cindex @value{GDBN} version number
1697 Show what version of @value{GDBN} is running. You should include this
1698 information in @value{GDBN} bug-reports. If multiple versions of
1699 @value{GDBN} are in use at your site, you may need to determine which
1700 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1701 commands are introduced, and old ones may wither away. Also, many
1702 system vendors ship variant versions of @value{GDBN}, and there are
1703 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1704 The version number is the same as the one announced when you start
1707 @kindex show copying
1708 @kindex info copying
1709 @cindex display @value{GDBN} copyright
1712 Display information about permission for copying @value{GDBN}.
1714 @kindex show warranty
1715 @kindex info warranty
1717 @itemx info warranty
1718 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1719 if your version of @value{GDBN} comes with one.
1724 @chapter Running Programs Under @value{GDBN}
1726 When you run a program under @value{GDBN}, you must first generate
1727 debugging information when you compile it.
1729 You may start @value{GDBN} with its arguments, if any, in an environment
1730 of your choice. If you are doing native debugging, you may redirect
1731 your program's input and output, debug an already running process, or
1732 kill a child process.
1735 * Compilation:: Compiling for debugging
1736 * Starting:: Starting your program
1737 * Arguments:: Your program's arguments
1738 * Environment:: Your program's environment
1740 * Working Directory:: Your program's working directory
1741 * Input/Output:: Your program's input and output
1742 * Attach:: Debugging an already-running process
1743 * Kill Process:: Killing the child process
1745 * Threads:: Debugging programs with multiple threads
1746 * Processes:: Debugging programs with multiple processes
1747 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1751 @section Compiling for Debugging
1753 In order to debug a program effectively, you need to generate
1754 debugging information when you compile it. This debugging information
1755 is stored in the object file; it describes the data type of each
1756 variable or function and the correspondence between source line numbers
1757 and addresses in the executable code.
1759 To request debugging information, specify the @samp{-g} option when you run
1762 Programs that are to be shipped to your customers are compiled with
1763 optimizations, using the @samp{-O} compiler option. However, many
1764 compilers are unable to handle the @samp{-g} and @samp{-O} options
1765 together. Using those compilers, you cannot generate optimized
1766 executables containing debugging information.
1768 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1769 without @samp{-O}, making it possible to debug optimized code. We
1770 recommend that you @emph{always} use @samp{-g} whenever you compile a
1771 program. You may think your program is correct, but there is no sense
1772 in pushing your luck.
1774 @cindex optimized code, debugging
1775 @cindex debugging optimized code
1776 When you debug a program compiled with @samp{-g -O}, remember that the
1777 optimizer is rearranging your code; the debugger shows you what is
1778 really there. Do not be too surprised when the execution path does not
1779 exactly match your source file! An extreme example: if you define a
1780 variable, but never use it, @value{GDBN} never sees that
1781 variable---because the compiler optimizes it out of existence.
1783 Some things do not work as well with @samp{-g -O} as with just
1784 @samp{-g}, particularly on machines with instruction scheduling. If in
1785 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1786 please report it to us as a bug (including a test case!).
1787 @xref{Variables}, for more information about debugging optimized code.
1789 Older versions of the @sc{gnu} C compiler permitted a variant option
1790 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1791 format; if your @sc{gnu} C compiler has this option, do not use it.
1793 @value{GDBN} knows about preprocessor macros and can show you their
1794 expansion (@pxref{Macros}). Most compilers do not include information
1795 about preprocessor macros in the debugging information if you specify
1796 the @option{-g} flag alone, because this information is rather large.
1797 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1798 provides macro information if you specify the options
1799 @option{-gdwarf-2} and @option{-g3}; the former option requests
1800 debugging information in the Dwarf 2 format, and the latter requests
1801 ``extra information''. In the future, we hope to find more compact
1802 ways to represent macro information, so that it can be included with
1807 @section Starting your Program
1813 @kindex r @r{(@code{run})}
1816 Use the @code{run} command to start your program under @value{GDBN}.
1817 You must first specify the program name (except on VxWorks) with an
1818 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1819 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1820 (@pxref{Files, ,Commands to Specify Files}).
1824 If you are running your program in an execution environment that
1825 supports processes, @code{run} creates an inferior process and makes
1826 that process run your program. (In environments without processes,
1827 @code{run} jumps to the start of your program.)
1829 The execution of a program is affected by certain information it
1830 receives from its superior. @value{GDBN} provides ways to specify this
1831 information, which you must do @emph{before} starting your program. (You
1832 can change it after starting your program, but such changes only affect
1833 your program the next time you start it.) This information may be
1834 divided into four categories:
1837 @item The @emph{arguments.}
1838 Specify the arguments to give your program as the arguments of the
1839 @code{run} command. If a shell is available on your target, the shell
1840 is used to pass the arguments, so that you may use normal conventions
1841 (such as wildcard expansion or variable substitution) in describing
1843 In Unix systems, you can control which shell is used with the
1844 @code{SHELL} environment variable.
1845 @xref{Arguments, ,Your Program's Arguments}.
1847 @item The @emph{environment.}
1848 Your program normally inherits its environment from @value{GDBN}, but you can
1849 use the @value{GDBN} commands @code{set environment} and @code{unset
1850 environment} to change parts of the environment that affect
1851 your program. @xref{Environment, ,Your Program's Environment}.
1853 @item The @emph{working directory.}
1854 Your program inherits its working directory from @value{GDBN}. You can set
1855 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1856 @xref{Working Directory, ,Your Program's Working Directory}.
1858 @item The @emph{standard input and output.}
1859 Your program normally uses the same device for standard input and
1860 standard output as @value{GDBN} is using. You can redirect input and output
1861 in the @code{run} command line, or you can use the @code{tty} command to
1862 set a different device for your program.
1863 @xref{Input/Output, ,Your Program's Input and Output}.
1866 @emph{Warning:} While input and output redirection work, you cannot use
1867 pipes to pass the output of the program you are debugging to another
1868 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1872 When you issue the @code{run} command, your program begins to execute
1873 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1874 of how to arrange for your program to stop. Once your program has
1875 stopped, you may call functions in your program, using the @code{print}
1876 or @code{call} commands. @xref{Data, ,Examining Data}.
1878 If the modification time of your symbol file has changed since the last
1879 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1880 table, and reads it again. When it does this, @value{GDBN} tries to retain
1881 your current breakpoints.
1886 @cindex run to main procedure
1887 The name of the main procedure can vary from language to language.
1888 With C or C@t{++}, the main procedure name is always @code{main}, but
1889 other languages such as Ada do not require a specific name for their
1890 main procedure. The debugger provides a convenient way to start the
1891 execution of the program and to stop at the beginning of the main
1892 procedure, depending on the language used.
1894 The @samp{start} command does the equivalent of setting a temporary
1895 breakpoint at the beginning of the main procedure and then invoking
1896 the @samp{run} command.
1898 @cindex elaboration phase
1899 Some programs contain an @dfn{elaboration} phase where some startup code is
1900 executed before the main procedure is called. This depends on the
1901 languages used to write your program. In C@t{++}, for instance,
1902 constructors for static and global objects are executed before
1903 @code{main} is called. It is therefore possible that the debugger stops
1904 before reaching the main procedure. However, the temporary breakpoint
1905 will remain to halt execution.
1907 Specify the arguments to give to your program as arguments to the
1908 @samp{start} command. These arguments will be given verbatim to the
1909 underlying @samp{run} command. Note that the same arguments will be
1910 reused if no argument is provided during subsequent calls to
1911 @samp{start} or @samp{run}.
1913 It is sometimes necessary to debug the program during elaboration. In
1914 these cases, using the @code{start} command would stop the execution of
1915 your program too late, as the program would have already completed the
1916 elaboration phase. Under these circumstances, insert breakpoints in your
1917 elaboration code before running your program.
1921 @section Your Program's Arguments
1923 @cindex arguments (to your program)
1924 The arguments to your program can be specified by the arguments of the
1926 They are passed to a shell, which expands wildcard characters and
1927 performs redirection of I/O, and thence to your program. Your
1928 @code{SHELL} environment variable (if it exists) specifies what shell
1929 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1930 the default shell (@file{/bin/sh} on Unix).
1932 On non-Unix systems, the program is usually invoked directly by
1933 @value{GDBN}, which emulates I/O redirection via the appropriate system
1934 calls, and the wildcard characters are expanded by the startup code of
1935 the program, not by the shell.
1937 @code{run} with no arguments uses the same arguments used by the previous
1938 @code{run}, or those set by the @code{set args} command.
1943 Specify the arguments to be used the next time your program is run. If
1944 @code{set args} has no arguments, @code{run} executes your program
1945 with no arguments. Once you have run your program with arguments,
1946 using @code{set args} before the next @code{run} is the only way to run
1947 it again without arguments.
1951 Show the arguments to give your program when it is started.
1955 @section Your Program's Environment
1957 @cindex environment (of your program)
1958 The @dfn{environment} consists of a set of environment variables and
1959 their values. Environment variables conventionally record such things as
1960 your user name, your home directory, your terminal type, and your search
1961 path for programs to run. Usually you set up environment variables with
1962 the shell and they are inherited by all the other programs you run. When
1963 debugging, it can be useful to try running your program with a modified
1964 environment without having to start @value{GDBN} over again.
1968 @item path @var{directory}
1969 Add @var{directory} to the front of the @code{PATH} environment variable
1970 (the search path for executables) that will be passed to your program.
1971 The value of @code{PATH} used by @value{GDBN} does not change.
1972 You may specify several directory names, separated by whitespace or by a
1973 system-dependent separator character (@samp{:} on Unix, @samp{;} on
1974 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
1975 is moved to the front, so it is searched sooner.
1977 You can use the string @samp{$cwd} to refer to whatever is the current
1978 working directory at the time @value{GDBN} searches the path. If you
1979 use @samp{.} instead, it refers to the directory where you executed the
1980 @code{path} command. @value{GDBN} replaces @samp{.} in the
1981 @var{directory} argument (with the current path) before adding
1982 @var{directory} to the search path.
1983 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
1984 @c document that, since repeating it would be a no-op.
1988 Display the list of search paths for executables (the @code{PATH}
1989 environment variable).
1991 @kindex show environment
1992 @item show environment @r{[}@var{varname}@r{]}
1993 Print the value of environment variable @var{varname} to be given to
1994 your program when it starts. If you do not supply @var{varname},
1995 print the names and values of all environment variables to be given to
1996 your program. You can abbreviate @code{environment} as @code{env}.
1998 @kindex set environment
1999 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2000 Set environment variable @var{varname} to @var{value}. The value
2001 changes for your program only, not for @value{GDBN} itself. @var{value} may
2002 be any string; the values of environment variables are just strings, and
2003 any interpretation is supplied by your program itself. The @var{value}
2004 parameter is optional; if it is eliminated, the variable is set to a
2006 @c "any string" here does not include leading, trailing
2007 @c blanks. Gnu asks: does anyone care?
2009 For example, this command:
2016 tells the debugged program, when subsequently run, that its user is named
2017 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2018 are not actually required.)
2020 @kindex unset environment
2021 @item unset environment @var{varname}
2022 Remove variable @var{varname} from the environment to be passed to your
2023 program. This is different from @samp{set env @var{varname} =};
2024 @code{unset environment} removes the variable from the environment,
2025 rather than assigning it an empty value.
2028 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2030 by your @code{SHELL} environment variable if it exists (or
2031 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2032 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2033 @file{.bashrc} for BASH---any variables you set in that file affect
2034 your program. You may wish to move setting of environment variables to
2035 files that are only run when you sign on, such as @file{.login} or
2038 @node Working Directory
2039 @section Your Program's Working Directory
2041 @cindex working directory (of your program)
2042 Each time you start your program with @code{run}, it inherits its
2043 working directory from the current working directory of @value{GDBN}.
2044 The @value{GDBN} working directory is initially whatever it inherited
2045 from its parent process (typically the shell), but you can specify a new
2046 working directory in @value{GDBN} with the @code{cd} command.
2048 The @value{GDBN} working directory also serves as a default for the commands
2049 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2054 @cindex change working directory
2055 @item cd @var{directory}
2056 Set the @value{GDBN} working directory to @var{directory}.
2060 Print the @value{GDBN} working directory.
2063 It is generally impossible to find the current working directory of
2064 the process being debugged (since a program can change its directory
2065 during its run). If you work on a system where @value{GDBN} is
2066 configured with the @file{/proc} support, you can use the @code{info
2067 proc} command (@pxref{SVR4 Process Information}) to find out the
2068 current working directory of the debuggee.
2071 @section Your Program's Input and Output
2076 By default, the program you run under @value{GDBN} does input and output to
2077 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2078 to its own terminal modes to interact with you, but it records the terminal
2079 modes your program was using and switches back to them when you continue
2080 running your program.
2083 @kindex info terminal
2085 Displays information recorded by @value{GDBN} about the terminal modes your
2089 You can redirect your program's input and/or output using shell
2090 redirection with the @code{run} command. For example,
2097 starts your program, diverting its output to the file @file{outfile}.
2100 @cindex controlling terminal
2101 Another way to specify where your program should do input and output is
2102 with the @code{tty} command. This command accepts a file name as
2103 argument, and causes this file to be the default for future @code{run}
2104 commands. It also resets the controlling terminal for the child
2105 process, for future @code{run} commands. For example,
2112 directs that processes started with subsequent @code{run} commands
2113 default to do input and output on the terminal @file{/dev/ttyb} and have
2114 that as their controlling terminal.
2116 An explicit redirection in @code{run} overrides the @code{tty} command's
2117 effect on the input/output device, but not its effect on the controlling
2120 When you use the @code{tty} command or redirect input in the @code{run}
2121 command, only the input @emph{for your program} is affected. The input
2122 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2123 for @code{set inferior-tty}.
2125 @cindex inferior tty
2126 @cindex set inferior controlling terminal
2127 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2128 display the name of the terminal that will be used for future runs of your
2132 @item set inferior-tty /dev/ttyb
2133 @kindex set inferior-tty
2134 Set the tty for the program being debugged to /dev/ttyb.
2136 @item show inferior-tty
2137 @kindex show inferior-tty
2138 Show the current tty for the program being debugged.
2142 @section Debugging an Already-running Process
2147 @item attach @var{process-id}
2148 This command attaches to a running process---one that was started
2149 outside @value{GDBN}. (@code{info files} shows your active
2150 targets.) The command takes as argument a process ID. The usual way to
2151 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2152 or with the @samp{jobs -l} shell command.
2154 @code{attach} does not repeat if you press @key{RET} a second time after
2155 executing the command.
2158 To use @code{attach}, your program must be running in an environment
2159 which supports processes; for example, @code{attach} does not work for
2160 programs on bare-board targets that lack an operating system. You must
2161 also have permission to send the process a signal.
2163 When you use @code{attach}, the debugger finds the program running in
2164 the process first by looking in the current working directory, then (if
2165 the program is not found) by using the source file search path
2166 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2167 the @code{file} command to load the program. @xref{Files, ,Commands to
2170 The first thing @value{GDBN} does after arranging to debug the specified
2171 process is to stop it. You can examine and modify an attached process
2172 with all the @value{GDBN} commands that are ordinarily available when
2173 you start processes with @code{run}. You can insert breakpoints; you
2174 can step and continue; you can modify storage. If you would rather the
2175 process continue running, you may use the @code{continue} command after
2176 attaching @value{GDBN} to the process.
2181 When you have finished debugging the attached process, you can use the
2182 @code{detach} command to release it from @value{GDBN} control. Detaching
2183 the process continues its execution. After the @code{detach} command,
2184 that process and @value{GDBN} become completely independent once more, and you
2185 are ready to @code{attach} another process or start one with @code{run}.
2186 @code{detach} does not repeat if you press @key{RET} again after
2187 executing the command.
2190 If you exit @value{GDBN} while you have an attached process, you detach
2191 that process. If you use the @code{run} command, you kill that process.
2192 By default, @value{GDBN} asks for confirmation if you try to do either of these
2193 things; you can control whether or not you need to confirm by using the
2194 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2198 @section Killing the Child Process
2203 Kill the child process in which your program is running under @value{GDBN}.
2206 This command is useful if you wish to debug a core dump instead of a
2207 running process. @value{GDBN} ignores any core dump file while your program
2210 On some operating systems, a program cannot be executed outside @value{GDBN}
2211 while you have breakpoints set on it inside @value{GDBN}. You can use the
2212 @code{kill} command in this situation to permit running your program
2213 outside the debugger.
2215 The @code{kill} command is also useful if you wish to recompile and
2216 relink your program, since on many systems it is impossible to modify an
2217 executable file while it is running in a process. In this case, when you
2218 next type @code{run}, @value{GDBN} notices that the file has changed, and
2219 reads the symbol table again (while trying to preserve your current
2220 breakpoint settings).
2223 @section Debugging Programs with Multiple Threads
2225 @cindex threads of execution
2226 @cindex multiple threads
2227 @cindex switching threads
2228 In some operating systems, such as HP-UX and Solaris, a single program
2229 may have more than one @dfn{thread} of execution. The precise semantics
2230 of threads differ from one operating system to another, but in general
2231 the threads of a single program are akin to multiple processes---except
2232 that they share one address space (that is, they can all examine and
2233 modify the same variables). On the other hand, each thread has its own
2234 registers and execution stack, and perhaps private memory.
2236 @value{GDBN} provides these facilities for debugging multi-thread
2240 @item automatic notification of new threads
2241 @item @samp{thread @var{threadno}}, a command to switch among threads
2242 @item @samp{info threads}, a command to inquire about existing threads
2243 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2244 a command to apply a command to a list of threads
2245 @item thread-specific breakpoints
2249 @emph{Warning:} These facilities are not yet available on every
2250 @value{GDBN} configuration where the operating system supports threads.
2251 If your @value{GDBN} does not support threads, these commands have no
2252 effect. For example, a system without thread support shows no output
2253 from @samp{info threads}, and always rejects the @code{thread} command,
2257 (@value{GDBP}) info threads
2258 (@value{GDBP}) thread 1
2259 Thread ID 1 not known. Use the "info threads" command to
2260 see the IDs of currently known threads.
2262 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2263 @c doesn't support threads"?
2266 @cindex focus of debugging
2267 @cindex current thread
2268 The @value{GDBN} thread debugging facility allows you to observe all
2269 threads while your program runs---but whenever @value{GDBN} takes
2270 control, one thread in particular is always the focus of debugging.
2271 This thread is called the @dfn{current thread}. Debugging commands show
2272 program information from the perspective of the current thread.
2274 @cindex @code{New} @var{systag} message
2275 @cindex thread identifier (system)
2276 @c FIXME-implementors!! It would be more helpful if the [New...] message
2277 @c included GDB's numeric thread handle, so you could just go to that
2278 @c thread without first checking `info threads'.
2279 Whenever @value{GDBN} detects a new thread in your program, it displays
2280 the target system's identification for the thread with a message in the
2281 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2282 whose form varies depending on the particular system. For example, on
2283 @sc{gnu}/Linux, you might see
2286 [New Thread 46912507313328 (LWP 25582)]
2290 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2291 the @var{systag} is simply something like @samp{process 368}, with no
2294 @c FIXME!! (1) Does the [New...] message appear even for the very first
2295 @c thread of a program, or does it only appear for the
2296 @c second---i.e.@: when it becomes obvious we have a multithread
2298 @c (2) *Is* there necessarily a first thread always? Or do some
2299 @c multithread systems permit starting a program with multiple
2300 @c threads ab initio?
2302 @cindex thread number
2303 @cindex thread identifier (GDB)
2304 For debugging purposes, @value{GDBN} associates its own thread
2305 number---always a single integer---with each thread in your program.
2308 @kindex info threads
2310 Display a summary of all threads currently in your
2311 program. @value{GDBN} displays for each thread (in this order):
2315 the thread number assigned by @value{GDBN}
2318 the target system's thread identifier (@var{systag})
2321 the current stack frame summary for that thread
2325 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2326 indicates the current thread.
2330 @c end table here to get a little more width for example
2333 (@value{GDBP}) info threads
2334 3 process 35 thread 27 0x34e5 in sigpause ()
2335 2 process 35 thread 23 0x34e5 in sigpause ()
2336 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2342 @cindex debugging multithreaded programs (on HP-UX)
2343 @cindex thread identifier (GDB), on HP-UX
2344 For debugging purposes, @value{GDBN} associates its own thread
2345 number---a small integer assigned in thread-creation order---with each
2346 thread in your program.
2348 @cindex @code{New} @var{systag} message, on HP-UX
2349 @cindex thread identifier (system), on HP-UX
2350 @c FIXME-implementors!! It would be more helpful if the [New...] message
2351 @c included GDB's numeric thread handle, so you could just go to that
2352 @c thread without first checking `info threads'.
2353 Whenever @value{GDBN} detects a new thread in your program, it displays
2354 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2355 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2356 whose form varies depending on the particular system. For example, on
2360 [New thread 2 (system thread 26594)]
2364 when @value{GDBN} notices a new thread.
2367 @kindex info threads (HP-UX)
2369 Display a summary of all threads currently in your
2370 program. @value{GDBN} displays for each thread (in this order):
2373 @item the thread number assigned by @value{GDBN}
2375 @item the target system's thread identifier (@var{systag})
2377 @item the current stack frame summary for that thread
2381 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2382 indicates the current thread.
2386 @c end table here to get a little more width for example
2389 (@value{GDBP}) info threads
2390 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2392 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2393 from /usr/lib/libc.2
2394 1 system thread 27905 0x7b003498 in _brk () \@*
2395 from /usr/lib/libc.2
2398 On Solaris, you can display more information about user threads with a
2399 Solaris-specific command:
2402 @item maint info sol-threads
2403 @kindex maint info sol-threads
2404 @cindex thread info (Solaris)
2405 Display info on Solaris user threads.
2409 @kindex thread @var{threadno}
2410 @item thread @var{threadno}
2411 Make thread number @var{threadno} the current thread. The command
2412 argument @var{threadno} is the internal @value{GDBN} thread number, as
2413 shown in the first field of the @samp{info threads} display.
2414 @value{GDBN} responds by displaying the system identifier of the thread
2415 you selected, and its current stack frame summary:
2418 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2419 (@value{GDBP}) thread 2
2420 [Switching to process 35 thread 23]
2421 0x34e5 in sigpause ()
2425 As with the @samp{[New @dots{}]} message, the form of the text after
2426 @samp{Switching to} depends on your system's conventions for identifying
2429 @kindex thread apply
2430 @cindex apply command to several threads
2431 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2432 The @code{thread apply} command allows you to apply the named
2433 @var{command} to one or more threads. Specify the numbers of the
2434 threads that you want affected with the command argument
2435 @var{threadno}. It can be a single thread number, one of the numbers
2436 shown in the first field of the @samp{info threads} display; or it
2437 could be a range of thread numbers, as in @code{2-4}. To apply a
2438 command to all threads, type @kbd{thread apply all @var{command}}.
2441 @cindex automatic thread selection
2442 @cindex switching threads automatically
2443 @cindex threads, automatic switching
2444 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2445 signal, it automatically selects the thread where that breakpoint or
2446 signal happened. @value{GDBN} alerts you to the context switch with a
2447 message of the form @samp{[Switching to @var{systag}]} to identify the
2450 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2451 more information about how @value{GDBN} behaves when you stop and start
2452 programs with multiple threads.
2454 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2455 watchpoints in programs with multiple threads.
2458 @section Debugging Programs with Multiple Processes
2460 @cindex fork, debugging programs which call
2461 @cindex multiple processes
2462 @cindex processes, multiple
2463 On most systems, @value{GDBN} has no special support for debugging
2464 programs which create additional processes using the @code{fork}
2465 function. When a program forks, @value{GDBN} will continue to debug the
2466 parent process and the child process will run unimpeded. If you have
2467 set a breakpoint in any code which the child then executes, the child
2468 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2469 will cause it to terminate.
2471 However, if you want to debug the child process there is a workaround
2472 which isn't too painful. Put a call to @code{sleep} in the code which
2473 the child process executes after the fork. It may be useful to sleep
2474 only if a certain environment variable is set, or a certain file exists,
2475 so that the delay need not occur when you don't want to run @value{GDBN}
2476 on the child. While the child is sleeping, use the @code{ps} program to
2477 get its process ID. Then tell @value{GDBN} (a new invocation of
2478 @value{GDBN} if you are also debugging the parent process) to attach to
2479 the child process (@pxref{Attach}). From that point on you can debug
2480 the child process just like any other process which you attached to.
2482 On some systems, @value{GDBN} provides support for debugging programs that
2483 create additional processes using the @code{fork} or @code{vfork} functions.
2484 Currently, the only platforms with this feature are HP-UX (11.x and later
2485 only?) and GNU/Linux (kernel version 2.5.60 and later).
2487 By default, when a program forks, @value{GDBN} will continue to debug
2488 the parent process and the child process will run unimpeded.
2490 If you want to follow the child process instead of the parent process,
2491 use the command @w{@code{set follow-fork-mode}}.
2494 @kindex set follow-fork-mode
2495 @item set follow-fork-mode @var{mode}
2496 Set the debugger response to a program call of @code{fork} or
2497 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2498 process. The @var{mode} argument can be:
2502 The original process is debugged after a fork. The child process runs
2503 unimpeded. This is the default.
2506 The new process is debugged after a fork. The parent process runs
2511 @kindex show follow-fork-mode
2512 @item show follow-fork-mode
2513 Display the current debugger response to a @code{fork} or @code{vfork} call.
2516 @cindex debugging multiple processes
2517 On Linux, if you want to debug both the parent and child processes, use the
2518 command @w{@code{set detach-on-fork}}.
2521 @kindex set detach-on-fork
2522 @item set detach-on-fork @var{mode}
2523 Tells gdb whether to detach one of the processes after a fork, or
2524 retain debugger control over them both.
2528 The child process (or parent process, depending on the value of
2529 @code{follow-fork-mode}) will be detached and allowed to run
2530 independently. This is the default.
2533 Both processes will be held under the control of @value{GDBN}.
2534 One process (child or parent, depending on the value of
2535 @code{follow-fork-mode}) is debugged as usual, while the other
2540 @kindex show detach-on-follow
2541 @item show detach-on-follow
2542 Show whether detach-on-follow mode is on/off.
2545 If you choose to set @var{detach-on-follow} mode off, then
2546 @value{GDBN} will retain control of all forked processes (including
2547 nested forks). You can list the forked processes under the control of
2548 @value{GDBN} by using the @w{@code{info forks}} command, and switch
2549 from one fork to another by using the @w{@code{fork}} command.
2554 Print a list of all forked processes under the control of @value{GDBN}.
2555 The listing will include a fork id, a process id, and the current
2556 position (program counter) of the process.
2559 @kindex fork @var{fork-id}
2560 @item fork @var{fork-id}
2561 Make fork number @var{fork-id} the current process. The argument
2562 @var{fork-id} is the internal fork number assigned by @value{GDBN},
2563 as shown in the first field of the @samp{info forks} display.
2567 To quit debugging one of the forked processes, you can either detach
2568 from it by using the @w{@code{detach fork}} command (allowing it to
2569 run independently), or delete (and kill) it using the
2570 @w{@code{delete fork}} command.
2573 @kindex detach fork @var{fork-id}
2574 @item detach fork @var{fork-id}
2575 Detach from the process identified by @value{GDBN} fork number
2576 @var{fork-id}, and remove it from the fork list. The process will be
2577 allowed to run independently.
2579 @kindex delete fork @var{fork-id}
2580 @item delete fork @var{fork-id}
2581 Kill the process identified by @value{GDBN} fork number @var{fork-id},
2582 and remove it from the fork list.
2586 If you ask to debug a child process and a @code{vfork} is followed by an
2587 @code{exec}, @value{GDBN} executes the new target up to the first
2588 breakpoint in the new target. If you have a breakpoint set on
2589 @code{main} in your original program, the breakpoint will also be set on
2590 the child process's @code{main}.
2592 When a child process is spawned by @code{vfork}, you cannot debug the
2593 child or parent until an @code{exec} call completes.
2595 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2596 call executes, the new target restarts. To restart the parent process,
2597 use the @code{file} command with the parent executable name as its
2600 You can use the @code{catch} command to make @value{GDBN} stop whenever
2601 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2602 Catchpoints, ,Setting Catchpoints}.
2604 @node Checkpoint/Restart
2605 @section Setting a @emph{Bookmark} to Return to Later
2610 @cindex snapshot of a process
2611 @cindex rewind program state
2613 On certain operating systems@footnote{Currently, only
2614 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
2615 program's state, called a @dfn{checkpoint}, and come back to it
2618 Returning to a checkpoint effectively undoes everything that has
2619 happened in the program since the @code{checkpoint} was saved. This
2620 includes changes in memory, registers, and even (within some limits)
2621 system state. Effectively, it is like going back in time to the
2622 moment when the checkpoint was saved.
2624 Thus, if you're stepping thru a program and you think you're
2625 getting close to the point where things go wrong, you can save
2626 a checkpoint. Then, if you accidentally go too far and miss
2627 the critical statement, instead of having to restart your program
2628 from the beginning, you can just go back to the checkpoint and
2629 start again from there.
2631 This can be especially useful if it takes a lot of time or
2632 steps to reach the point where you think the bug occurs.
2634 To use the @code{checkpoint}/@code{restart} method of debugging:
2639 Save a snapshot of the debugged program's current execution state.
2640 The @code{checkpoint} command takes no arguments, but each checkpoint
2641 is assigned a small integer id, similar to a breakpoint id.
2643 @kindex info checkpoints
2644 @item info checkpoints
2645 List the checkpoints that have been saved in the current debugging
2646 session. For each checkpoint, the following information will be
2653 @item Source line, or label
2656 @kindex restart @var{checkpoint-id}
2657 @item restart @var{checkpoint-id}
2658 Restore the program state that was saved as checkpoint number
2659 @var{checkpoint-id}. All program variables, registers, stack frames
2660 etc.@: will be returned to the values that they had when the checkpoint
2661 was saved. In essence, gdb will ``wind back the clock'' to the point
2662 in time when the checkpoint was saved.
2664 Note that breakpoints, @value{GDBN} variables, command history etc.
2665 are not affected by restoring a checkpoint. In general, a checkpoint
2666 only restores things that reside in the program being debugged, not in
2669 @kindex delete checkpoint @var{checkpoint-id}
2670 @item delete checkpoint @var{checkpoint-id}
2671 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
2675 Returning to a previously saved checkpoint will restore the user state
2676 of the program being debugged, plus a significant subset of the system
2677 (OS) state, including file pointers. It won't ``un-write'' data from
2678 a file, but it will rewind the file pointer to the previous location,
2679 so that the previously written data can be overwritten. For files
2680 opened in read mode, the pointer will also be restored so that the
2681 previously read data can be read again.
2683 Of course, characters that have been sent to a printer (or other
2684 external device) cannot be ``snatched back'', and characters received
2685 from eg.@: a serial device can be removed from internal program buffers,
2686 but they cannot be ``pushed back'' into the serial pipeline, ready to
2687 be received again. Similarly, the actual contents of files that have
2688 been changed cannot be restored (at this time).
2690 However, within those constraints, you actually can ``rewind'' your
2691 program to a previously saved point in time, and begin debugging it
2692 again --- and you can change the course of events so as to debug a
2693 different execution path this time.
2695 @cindex checkpoints and process id
2696 Finally, there is one bit of internal program state that will be
2697 different when you return to a checkpoint --- the program's process
2698 id. Each checkpoint will have a unique process id (or @var{pid}),
2699 and each will be different from the program's original @var{pid}.
2700 If your program has saved a local copy of its process id, this could
2701 potentially pose a problem.
2703 @subsection A Non-obvious Benefit of Using Checkpoints
2705 On some systems such as @sc{gnu}/Linux, address space randomization
2706 is performed on new processes for security reasons. This makes it
2707 difficult or impossible to set a breakpoint, or watchpoint, on an
2708 absolute address if you have to restart the program, since the
2709 absolute location of a symbol will change from one execution to the
2712 A checkpoint, however, is an @emph{identical} copy of a process.
2713 Therefore if you create a checkpoint at (eg.@:) the start of main,
2714 and simply return to that checkpoint instead of restarting the
2715 process, you can avoid the effects of address randomization and
2716 your symbols will all stay in the same place.
2719 @chapter Stopping and Continuing
2721 The principal purposes of using a debugger are so that you can stop your
2722 program before it terminates; or so that, if your program runs into
2723 trouble, you can investigate and find out why.
2725 Inside @value{GDBN}, your program may stop for any of several reasons,
2726 such as a signal, a breakpoint, or reaching a new line after a
2727 @value{GDBN} command such as @code{step}. You may then examine and
2728 change variables, set new breakpoints or remove old ones, and then
2729 continue execution. Usually, the messages shown by @value{GDBN} provide
2730 ample explanation of the status of your program---but you can also
2731 explicitly request this information at any time.
2734 @kindex info program
2736 Display information about the status of your program: whether it is
2737 running or not, what process it is, and why it stopped.
2741 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2742 * Continuing and Stepping:: Resuming execution
2744 * Thread Stops:: Stopping and starting multi-thread programs
2748 @section Breakpoints, Watchpoints, and Catchpoints
2751 A @dfn{breakpoint} makes your program stop whenever a certain point in
2752 the program is reached. For each breakpoint, you can add conditions to
2753 control in finer detail whether your program stops. You can set
2754 breakpoints with the @code{break} command and its variants (@pxref{Set
2755 Breaks, ,Setting Breakpoints}), to specify the place where your program
2756 should stop by line number, function name or exact address in the
2759 On some systems, you can set breakpoints in shared libraries before
2760 the executable is run. There is a minor limitation on HP-UX systems:
2761 you must wait until the executable is run in order to set breakpoints
2762 in shared library routines that are not called directly by the program
2763 (for example, routines that are arguments in a @code{pthread_create}
2767 @cindex data breakpoints
2768 @cindex memory tracing
2769 @cindex breakpoint on memory address
2770 @cindex breakpoint on variable modification
2771 A @dfn{watchpoint} is a special breakpoint that stops your program
2772 when the value of an expression changes. The expression may be a value
2773 of a variable, or it could involve values of one or more variables
2774 combined by operators, such as @samp{a + b}. This is sometimes called
2775 @dfn{data breakpoints}. You must use a different command to set
2776 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
2777 from that, you can manage a watchpoint like any other breakpoint: you
2778 enable, disable, and delete both breakpoints and watchpoints using the
2781 You can arrange to have values from your program displayed automatically
2782 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2786 @cindex breakpoint on events
2787 A @dfn{catchpoint} is another special breakpoint that stops your program
2788 when a certain kind of event occurs, such as the throwing of a C@t{++}
2789 exception or the loading of a library. As with watchpoints, you use a
2790 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2791 Catchpoints}), but aside from that, you can manage a catchpoint like any
2792 other breakpoint. (To stop when your program receives a signal, use the
2793 @code{handle} command; see @ref{Signals, ,Signals}.)
2795 @cindex breakpoint numbers
2796 @cindex numbers for breakpoints
2797 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2798 catchpoint when you create it; these numbers are successive integers
2799 starting with one. In many of the commands for controlling various
2800 features of breakpoints you use the breakpoint number to say which
2801 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2802 @dfn{disabled}; if disabled, it has no effect on your program until you
2805 @cindex breakpoint ranges
2806 @cindex ranges of breakpoints
2807 Some @value{GDBN} commands accept a range of breakpoints on which to
2808 operate. A breakpoint range is either a single breakpoint number, like
2809 @samp{5}, or two such numbers, in increasing order, separated by a
2810 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2811 all breakpoints in that range are operated on.
2814 * Set Breaks:: Setting breakpoints
2815 * Set Watchpoints:: Setting watchpoints
2816 * Set Catchpoints:: Setting catchpoints
2817 * Delete Breaks:: Deleting breakpoints
2818 * Disabling:: Disabling breakpoints
2819 * Conditions:: Break conditions
2820 * Break Commands:: Breakpoint command lists
2821 * Breakpoint Menus:: Breakpoint menus
2822 * Error in Breakpoints:: ``Cannot insert breakpoints''
2823 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
2827 @subsection Setting Breakpoints
2829 @c FIXME LMB what does GDB do if no code on line of breakpt?
2830 @c consider in particular declaration with/without initialization.
2832 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2835 @kindex b @r{(@code{break})}
2836 @vindex $bpnum@r{, convenience variable}
2837 @cindex latest breakpoint
2838 Breakpoints are set with the @code{break} command (abbreviated
2839 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2840 number of the breakpoint you've set most recently; see @ref{Convenience
2841 Vars,, Convenience Variables}, for a discussion of what you can do with
2842 convenience variables.
2844 You have several ways to say where the breakpoint should go.
2847 @item break @var{function}
2848 Set a breakpoint at entry to function @var{function}.
2849 When using source languages that permit overloading of symbols, such as
2850 C@t{++}, @var{function} may refer to more than one possible place to break.
2851 @xref{Breakpoint Menus,,Breakpoint Menus}, for a discussion of that situation.
2853 @item break +@var{offset}
2854 @itemx break -@var{offset}
2855 Set a breakpoint some number of lines forward or back from the position
2856 at which execution stopped in the currently selected @dfn{stack frame}.
2857 (@xref{Frames, ,Frames}, for a description of stack frames.)
2859 @item break @var{linenum}
2860 Set a breakpoint at line @var{linenum} in the current source file.
2861 The current source file is the last file whose source text was printed.
2862 The breakpoint will stop your program just before it executes any of the
2865 @item break @var{filename}:@var{linenum}
2866 Set a breakpoint at line @var{linenum} in source file @var{filename}.
2868 @item break @var{filename}:@var{function}
2869 Set a breakpoint at entry to function @var{function} found in file
2870 @var{filename}. Specifying a file name as well as a function name is
2871 superfluous except when multiple files contain similarly named
2874 @item break *@var{address}
2875 Set a breakpoint at address @var{address}. You can use this to set
2876 breakpoints in parts of your program which do not have debugging
2877 information or source files.
2880 When called without any arguments, @code{break} sets a breakpoint at
2881 the next instruction to be executed in the selected stack frame
2882 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2883 innermost, this makes your program stop as soon as control
2884 returns to that frame. This is similar to the effect of a
2885 @code{finish} command in the frame inside the selected frame---except
2886 that @code{finish} does not leave an active breakpoint. If you use
2887 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2888 the next time it reaches the current location; this may be useful
2891 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2892 least one instruction has been executed. If it did not do this, you
2893 would be unable to proceed past a breakpoint without first disabling the
2894 breakpoint. This rule applies whether or not the breakpoint already
2895 existed when your program stopped.
2897 @item break @dots{} if @var{cond}
2898 Set a breakpoint with condition @var{cond}; evaluate the expression
2899 @var{cond} each time the breakpoint is reached, and stop only if the
2900 value is nonzero---that is, if @var{cond} evaluates as true.
2901 @samp{@dots{}} stands for one of the possible arguments described
2902 above (or no argument) specifying where to break. @xref{Conditions,
2903 ,Break Conditions}, for more information on breakpoint conditions.
2906 @item tbreak @var{args}
2907 Set a breakpoint enabled only for one stop. @var{args} are the
2908 same as for the @code{break} command, and the breakpoint is set in the same
2909 way, but the breakpoint is automatically deleted after the first time your
2910 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
2913 @cindex hardware breakpoints
2914 @item hbreak @var{args}
2915 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2916 @code{break} command and the breakpoint is set in the same way, but the
2917 breakpoint requires hardware support and some target hardware may not
2918 have this support. The main purpose of this is EPROM/ROM code
2919 debugging, so you can set a breakpoint at an instruction without
2920 changing the instruction. This can be used with the new trap-generation
2921 provided by SPARClite DSU and most x86-based targets. These targets
2922 will generate traps when a program accesses some data or instruction
2923 address that is assigned to the debug registers. However the hardware
2924 breakpoint registers can take a limited number of breakpoints. For
2925 example, on the DSU, only two data breakpoints can be set at a time, and
2926 @value{GDBN} will reject this command if more than two are used. Delete
2927 or disable unused hardware breakpoints before setting new ones
2928 (@pxref{Disabling, ,Disabling Breakpoints}).
2929 @xref{Conditions, ,Break Conditions}.
2930 For remote targets, you can restrict the number of hardware
2931 breakpoints @value{GDBN} will use, see @ref{set remote
2932 hardware-breakpoint-limit}.
2936 @item thbreak @var{args}
2937 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2938 are the same as for the @code{hbreak} command and the breakpoint is set in
2939 the same way. However, like the @code{tbreak} command,
2940 the breakpoint is automatically deleted after the
2941 first time your program stops there. Also, like the @code{hbreak}
2942 command, the breakpoint requires hardware support and some target hardware
2943 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
2944 See also @ref{Conditions, ,Break Conditions}.
2947 @cindex regular expression
2948 @cindex breakpoints in functions matching a regexp
2949 @cindex set breakpoints in many functions
2950 @item rbreak @var{regex}
2951 Set breakpoints on all functions matching the regular expression
2952 @var{regex}. This command sets an unconditional breakpoint on all
2953 matches, printing a list of all breakpoints it set. Once these
2954 breakpoints are set, they are treated just like the breakpoints set with
2955 the @code{break} command. You can delete them, disable them, or make
2956 them conditional the same way as any other breakpoint.
2958 The syntax of the regular expression is the standard one used with tools
2959 like @file{grep}. Note that this is different from the syntax used by
2960 shells, so for instance @code{foo*} matches all functions that include
2961 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2962 @code{.*} leading and trailing the regular expression you supply, so to
2963 match only functions that begin with @code{foo}, use @code{^foo}.
2965 @cindex non-member C@t{++} functions, set breakpoint in
2966 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2967 breakpoints on overloaded functions that are not members of any special
2970 @cindex set breakpoints on all functions
2971 The @code{rbreak} command can be used to set breakpoints in
2972 @strong{all} the functions in a program, like this:
2975 (@value{GDBP}) rbreak .
2978 @kindex info breakpoints
2979 @cindex @code{$_} and @code{info breakpoints}
2980 @item info breakpoints @r{[}@var{n}@r{]}
2981 @itemx info break @r{[}@var{n}@r{]}
2982 @itemx info watchpoints @r{[}@var{n}@r{]}
2983 Print a table of all breakpoints, watchpoints, and catchpoints set and
2984 not deleted. Optional argument @var{n} means print information only
2985 about the specified breakpoint (or watchpoint or catchpoint). For
2986 each breakpoint, following columns are printed:
2989 @item Breakpoint Numbers
2991 Breakpoint, watchpoint, or catchpoint.
2993 Whether the breakpoint is marked to be disabled or deleted when hit.
2994 @item Enabled or Disabled
2995 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
2996 that are not enabled.
2998 Where the breakpoint is in your program, as a memory address. If the
2999 breakpoint is pending (see below for details) on a future load of a shared library, the address
3000 will be listed as @samp{<PENDING>}.
3002 Where the breakpoint is in the source for your program, as a file and
3003 line number. For a pending breakpoint, the original string passed to
3004 the breakpoint command will be listed as it cannot be resolved until
3005 the appropriate shared library is loaded in the future.
3009 If a breakpoint is conditional, @code{info break} shows the condition on
3010 the line following the affected breakpoint; breakpoint commands, if any,
3011 are listed after that. A pending breakpoint is allowed to have a condition
3012 specified for it. The condition is not parsed for validity until a shared
3013 library is loaded that allows the pending breakpoint to resolve to a
3017 @code{info break} with a breakpoint
3018 number @var{n} as argument lists only that breakpoint. The
3019 convenience variable @code{$_} and the default examining-address for
3020 the @code{x} command are set to the address of the last breakpoint
3021 listed (@pxref{Memory, ,Examining Memory}).
3024 @code{info break} displays a count of the number of times the breakpoint
3025 has been hit. This is especially useful in conjunction with the
3026 @code{ignore} command. You can ignore a large number of breakpoint
3027 hits, look at the breakpoint info to see how many times the breakpoint
3028 was hit, and then run again, ignoring one less than that number. This
3029 will get you quickly to the last hit of that breakpoint.
3032 @value{GDBN} allows you to set any number of breakpoints at the same place in
3033 your program. There is nothing silly or meaningless about this. When
3034 the breakpoints are conditional, this is even useful
3035 (@pxref{Conditions, ,Break Conditions}).
3037 @cindex pending breakpoints
3038 If a specified breakpoint location cannot be found, it may be due to the fact
3039 that the location is in a shared library that is yet to be loaded. In such
3040 a case, you may want @value{GDBN} to create a special breakpoint (known as
3041 a @dfn{pending breakpoint}) that
3042 attempts to resolve itself in the future when an appropriate shared library
3045 Pending breakpoints are useful to set at the start of your
3046 @value{GDBN} session for locations that you know will be dynamically loaded
3047 later by the program being debugged. When shared libraries are loaded,
3048 a check is made to see if the load resolves any pending breakpoint locations.
3049 If a pending breakpoint location gets resolved,
3050 a regular breakpoint is created and the original pending breakpoint is removed.
3052 @value{GDBN} provides some additional commands for controlling pending
3055 @kindex set breakpoint pending
3056 @kindex show breakpoint pending
3058 @item set breakpoint pending auto
3059 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3060 location, it queries you whether a pending breakpoint should be created.
3062 @item set breakpoint pending on
3063 This indicates that an unrecognized breakpoint location should automatically
3064 result in a pending breakpoint being created.
3066 @item set breakpoint pending off
3067 This indicates that pending breakpoints are not to be created. Any
3068 unrecognized breakpoint location results in an error. This setting does
3069 not affect any pending breakpoints previously created.
3071 @item show breakpoint pending
3072 Show the current behavior setting for creating pending breakpoints.
3075 @cindex operations allowed on pending breakpoints
3076 Normal breakpoint operations apply to pending breakpoints as well. You may
3077 specify a condition for a pending breakpoint and/or commands to run when the
3078 breakpoint is reached. You can also enable or disable
3079 the pending breakpoint. When you specify a condition for a pending breakpoint,
3080 the parsing of the condition will be deferred until the point where the
3081 pending breakpoint location is resolved. Disabling a pending breakpoint
3082 tells @value{GDBN} to not attempt to resolve the breakpoint on any subsequent
3083 shared library load. When a pending breakpoint is re-enabled,
3084 @value{GDBN} checks to see if the location is already resolved.
3085 This is done because any number of shared library loads could have
3086 occurred since the time the breakpoint was disabled and one or more
3087 of these loads could resolve the location.
3089 @cindex automatic hardware breakpoints
3090 For some targets, @value{GDBN} can automatically decide if hardware or
3091 software breakpoints should be used, depending on whether the
3092 breakpoint address is read-only or read-write. This applies to
3093 breakpoints set with the @code{break} command as well as to internal
3094 breakpoints set by commands like @code{next} and @code{finish}. For
3095 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3098 You can control this automatic behaviour with the following commands::
3100 @kindex set breakpoint auto-hw
3101 @kindex show breakpoint auto-hw
3103 @item set breakpoint auto-hw on
3104 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3105 will try to use the target memory map to decide if software or hardware
3106 breakpoint must be used.
3108 @item set breakpoint auto-hw off
3109 This indicates @value{GDBN} should not automatically select breakpoint
3110 type. If the target provides a memory map, @value{GDBN} will warn when
3111 trying to set software breakpoint at a read-only address.
3115 @cindex negative breakpoint numbers
3116 @cindex internal @value{GDBN} breakpoints
3117 @value{GDBN} itself sometimes sets breakpoints in your program for
3118 special purposes, such as proper handling of @code{longjmp} (in C
3119 programs). These internal breakpoints are assigned negative numbers,
3120 starting with @code{-1}; @samp{info breakpoints} does not display them.
3121 You can see these breakpoints with the @value{GDBN} maintenance command
3122 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3125 @node Set Watchpoints
3126 @subsection Setting Watchpoints
3128 @cindex setting watchpoints
3129 You can use a watchpoint to stop execution whenever the value of an
3130 expression changes, without having to predict a particular place where
3131 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3132 The expression may be as simple as the value of a single variable, or
3133 as complex as many variables combined by operators. Examples include:
3137 A reference to the value of a single variable.
3140 An address cast to an appropriate data type. For example,
3141 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3142 address (assuming an @code{int} occupies 4 bytes).
3145 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3146 expression can use any operators valid in the program's native
3147 language (@pxref{Languages}).
3150 @cindex software watchpoints
3151 @cindex hardware watchpoints
3152 Depending on your system, watchpoints may be implemented in software or
3153 hardware. @value{GDBN} does software watchpointing by single-stepping your
3154 program and testing the variable's value each time, which is hundreds of
3155 times slower than normal execution. (But this may still be worth it, to
3156 catch errors where you have no clue what part of your program is the
3159 On some systems, such as HP-UX, @sc{gnu}/Linux and most other
3160 x86-based targets, @value{GDBN} includes support for hardware
3161 watchpoints, which do not slow down the running of your program.
3165 @item watch @var{expr}
3166 Set a watchpoint for an expression. @value{GDBN} will break when the
3167 expression @var{expr} is written into by the program and its value
3168 changes. The simplest (and the most popular) use of this command is
3169 to watch the value of a single variable:
3172 (@value{GDBP}) watch foo
3176 @item rwatch @var{expr}
3177 Set a watchpoint that will break when the value of @var{expr} is read
3181 @item awatch @var{expr}
3182 Set a watchpoint that will break when @var{expr} is either read from
3183 or written into by the program.
3185 @kindex info watchpoints @r{[}@var{n}@r{]}
3186 @item info watchpoints
3187 This command prints a list of watchpoints, breakpoints, and catchpoints;
3188 it is the same as @code{info break} (@pxref{Set Breaks}).
3191 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3192 watchpoints execute very quickly, and the debugger reports a change in
3193 value at the exact instruction where the change occurs. If @value{GDBN}
3194 cannot set a hardware watchpoint, it sets a software watchpoint, which
3195 executes more slowly and reports the change in value at the next
3196 @emph{statement}, not the instruction, after the change occurs.
3198 @cindex use only software watchpoints
3199 You can force @value{GDBN} to use only software watchpoints with the
3200 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3201 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3202 the underlying system supports them. (Note that hardware-assisted
3203 watchpoints that were set @emph{before} setting
3204 @code{can-use-hw-watchpoints} to zero will still use the hardware
3205 mechanism of watching expression values.)
3208 @item set can-use-hw-watchpoints
3209 @kindex set can-use-hw-watchpoints
3210 Set whether or not to use hardware watchpoints.
3212 @item show can-use-hw-watchpoints
3213 @kindex show can-use-hw-watchpoints
3214 Show the current mode of using hardware watchpoints.
3217 For remote targets, you can restrict the number of hardware
3218 watchpoints @value{GDBN} will use, see @ref{set remote
3219 hardware-breakpoint-limit}.
3221 When you issue the @code{watch} command, @value{GDBN} reports
3224 Hardware watchpoint @var{num}: @var{expr}
3228 if it was able to set a hardware watchpoint.
3230 Currently, the @code{awatch} and @code{rwatch} commands can only set
3231 hardware watchpoints, because accesses to data that don't change the
3232 value of the watched expression cannot be detected without examining
3233 every instruction as it is being executed, and @value{GDBN} does not do
3234 that currently. If @value{GDBN} finds that it is unable to set a
3235 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3236 will print a message like this:
3239 Expression cannot be implemented with read/access watchpoint.
3242 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3243 data type of the watched expression is wider than what a hardware
3244 watchpoint on the target machine can handle. For example, some systems
3245 can only watch regions that are up to 4 bytes wide; on such systems you
3246 cannot set hardware watchpoints for an expression that yields a
3247 double-precision floating-point number (which is typically 8 bytes
3248 wide). As a work-around, it might be possible to break the large region
3249 into a series of smaller ones and watch them with separate watchpoints.
3251 If you set too many hardware watchpoints, @value{GDBN} might be unable
3252 to insert all of them when you resume the execution of your program.
3253 Since the precise number of active watchpoints is unknown until such
3254 time as the program is about to be resumed, @value{GDBN} might not be
3255 able to warn you about this when you set the watchpoints, and the
3256 warning will be printed only when the program is resumed:
3259 Hardware watchpoint @var{num}: Could not insert watchpoint
3263 If this happens, delete or disable some of the watchpoints.
3265 Watching complex expressions that reference many variables can also
3266 exhaust the resources available for hardware-assisted watchpoints.
3267 That's because @value{GDBN} needs to watch every variable in the
3268 expression with separately allocated resources.
3270 The SPARClite DSU will generate traps when a program accesses some data
3271 or instruction address that is assigned to the debug registers. For the
3272 data addresses, DSU facilitates the @code{watch} command. However the
3273 hardware breakpoint registers can only take two data watchpoints, and
3274 both watchpoints must be the same kind. For example, you can set two
3275 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
3276 @strong{or} two with @code{awatch} commands, but you cannot set one
3277 watchpoint with one command and the other with a different command.
3278 @value{GDBN} will reject the command if you try to mix watchpoints.
3279 Delete or disable unused watchpoint commands before setting new ones.
3281 If you call a function interactively using @code{print} or @code{call},
3282 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3283 kind of breakpoint or the call completes.
3285 @value{GDBN} automatically deletes watchpoints that watch local
3286 (automatic) variables, or expressions that involve such variables, when
3287 they go out of scope, that is, when the execution leaves the block in
3288 which these variables were defined. In particular, when the program
3289 being debugged terminates, @emph{all} local variables go out of scope,
3290 and so only watchpoints that watch global variables remain set. If you
3291 rerun the program, you will need to set all such watchpoints again. One
3292 way of doing that would be to set a code breakpoint at the entry to the
3293 @code{main} function and when it breaks, set all the watchpoints.
3296 @cindex watchpoints and threads
3297 @cindex threads and watchpoints
3298 @emph{Warning:} In multi-thread programs, watchpoints have only limited
3299 usefulness. With the current watchpoint implementation, @value{GDBN}
3300 can only watch the value of an expression @emph{in a single thread}. If
3301 you are confident that the expression can only change due to the current
3302 thread's activity (and if you are also confident that no other thread
3303 can become current), then you can use watchpoints as usual. However,
3304 @value{GDBN} may not notice when a non-current thread's activity changes
3307 @c FIXME: this is almost identical to the previous paragraph.
3308 @emph{HP-UX Warning:} In multi-thread programs, software watchpoints
3309 have only limited usefulness. If @value{GDBN} creates a software
3310 watchpoint, it can only watch the value of an expression @emph{in a
3311 single thread}. If you are confident that the expression can only
3312 change due to the current thread's activity (and if you are also
3313 confident that no other thread can become current), then you can use
3314 software watchpoints as usual. However, @value{GDBN} may not notice
3315 when a non-current thread's activity changes the expression. (Hardware
3316 watchpoints, in contrast, watch an expression in all threads.)
3319 @xref{set remote hardware-watchpoint-limit}.
3321 @node Set Catchpoints
3322 @subsection Setting Catchpoints
3323 @cindex catchpoints, setting
3324 @cindex exception handlers
3325 @cindex event handling
3327 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3328 kinds of program events, such as C@t{++} exceptions or the loading of a
3329 shared library. Use the @code{catch} command to set a catchpoint.
3333 @item catch @var{event}
3334 Stop when @var{event} occurs. @var{event} can be any of the following:
3337 @cindex stop on C@t{++} exceptions
3338 The throwing of a C@t{++} exception.
3341 The catching of a C@t{++} exception.
3344 @cindex Ada exception catching
3345 @cindex catch Ada exceptions
3346 An Ada exception being raised. If an exception name is specified
3347 at the end of the command (eg @code{catch exception Program_Error}),
3348 the debugger will stop only when this specific exception is raised.
3349 Otherwise, the debugger stops execution when any Ada exception is raised.
3351 @item exception unhandled
3352 An exception that was raised but is not handled by the program.
3355 A failed Ada assertion.
3358 @cindex break on fork/exec
3359 A call to @code{exec}. This is currently only available for HP-UX.
3362 A call to @code{fork}. This is currently only available for HP-UX.
3365 A call to @code{vfork}. This is currently only available for HP-UX.
3368 @itemx load @var{libname}
3369 @cindex break on load/unload of shared library
3370 The dynamic loading of any shared library, or the loading of the library
3371 @var{libname}. This is currently only available for HP-UX.
3374 @itemx unload @var{libname}
3375 The unloading of any dynamically loaded shared library, or the unloading
3376 of the library @var{libname}. This is currently only available for HP-UX.
3379 @item tcatch @var{event}
3380 Set a catchpoint that is enabled only for one stop. The catchpoint is
3381 automatically deleted after the first time the event is caught.
3385 Use the @code{info break} command to list the current catchpoints.
3387 There are currently some limitations to C@t{++} exception handling
3388 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
3392 If you call a function interactively, @value{GDBN} normally returns
3393 control to you when the function has finished executing. If the call
3394 raises an exception, however, the call may bypass the mechanism that
3395 returns control to you and cause your program either to abort or to
3396 simply continue running until it hits a breakpoint, catches a signal
3397 that @value{GDBN} is listening for, or exits. This is the case even if
3398 you set a catchpoint for the exception; catchpoints on exceptions are
3399 disabled within interactive calls.
3402 You cannot raise an exception interactively.
3405 You cannot install an exception handler interactively.
3408 @cindex raise exceptions
3409 Sometimes @code{catch} is not the best way to debug exception handling:
3410 if you need to know exactly where an exception is raised, it is better to
3411 stop @emph{before} the exception handler is called, since that way you
3412 can see the stack before any unwinding takes place. If you set a
3413 breakpoint in an exception handler instead, it may not be easy to find
3414 out where the exception was raised.
3416 To stop just before an exception handler is called, you need some
3417 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3418 raised by calling a library function named @code{__raise_exception}
3419 which has the following ANSI C interface:
3422 /* @var{addr} is where the exception identifier is stored.
3423 @var{id} is the exception identifier. */
3424 void __raise_exception (void **addr, void *id);
3428 To make the debugger catch all exceptions before any stack
3429 unwinding takes place, set a breakpoint on @code{__raise_exception}
3430 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
3432 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
3433 that depends on the value of @var{id}, you can stop your program when
3434 a specific exception is raised. You can use multiple conditional
3435 breakpoints to stop your program when any of a number of exceptions are
3440 @subsection Deleting Breakpoints
3442 @cindex clearing breakpoints, watchpoints, catchpoints
3443 @cindex deleting breakpoints, watchpoints, catchpoints
3444 It is often necessary to eliminate a breakpoint, watchpoint, or
3445 catchpoint once it has done its job and you no longer want your program
3446 to stop there. This is called @dfn{deleting} the breakpoint. A
3447 breakpoint that has been deleted no longer exists; it is forgotten.
3449 With the @code{clear} command you can delete breakpoints according to
3450 where they are in your program. With the @code{delete} command you can
3451 delete individual breakpoints, watchpoints, or catchpoints by specifying
3452 their breakpoint numbers.
3454 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3455 automatically ignores breakpoints on the first instruction to be executed
3456 when you continue execution without changing the execution address.
3461 Delete any breakpoints at the next instruction to be executed in the
3462 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
3463 the innermost frame is selected, this is a good way to delete a
3464 breakpoint where your program just stopped.
3466 @item clear @var{function}
3467 @itemx clear @var{filename}:@var{function}
3468 Delete any breakpoints set at entry to the named @var{function}.
3470 @item clear @var{linenum}
3471 @itemx clear @var{filename}:@var{linenum}
3472 Delete any breakpoints set at or within the code of the specified
3473 @var{linenum} of the specified @var{filename}.
3475 @cindex delete breakpoints
3477 @kindex d @r{(@code{delete})}
3478 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3479 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3480 ranges specified as arguments. If no argument is specified, delete all
3481 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3482 confirm off}). You can abbreviate this command as @code{d}.
3486 @subsection Disabling Breakpoints
3488 @cindex enable/disable a breakpoint
3489 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3490 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3491 it had been deleted, but remembers the information on the breakpoint so
3492 that you can @dfn{enable} it again later.
3494 You disable and enable breakpoints, watchpoints, and catchpoints with
3495 the @code{enable} and @code{disable} commands, optionally specifying one
3496 or more breakpoint numbers as arguments. Use @code{info break} or
3497 @code{info watch} to print a list of breakpoints, watchpoints, and
3498 catchpoints if you do not know which numbers to use.
3500 A breakpoint, watchpoint, or catchpoint can have any of four different
3501 states of enablement:
3505 Enabled. The breakpoint stops your program. A breakpoint set
3506 with the @code{break} command starts out in this state.
3508 Disabled. The breakpoint has no effect on your program.
3510 Enabled once. The breakpoint stops your program, but then becomes
3513 Enabled for deletion. The breakpoint stops your program, but
3514 immediately after it does so it is deleted permanently. A breakpoint
3515 set with the @code{tbreak} command starts out in this state.
3518 You can use the following commands to enable or disable breakpoints,
3519 watchpoints, and catchpoints:
3523 @kindex dis @r{(@code{disable})}
3524 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3525 Disable the specified breakpoints---or all breakpoints, if none are
3526 listed. A disabled breakpoint has no effect but is not forgotten. All
3527 options such as ignore-counts, conditions and commands are remembered in
3528 case the breakpoint is enabled again later. You may abbreviate
3529 @code{disable} as @code{dis}.
3532 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3533 Enable the specified breakpoints (or all defined breakpoints). They
3534 become effective once again in stopping your program.
3536 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3537 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3538 of these breakpoints immediately after stopping your program.
3540 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3541 Enable the specified breakpoints to work once, then die. @value{GDBN}
3542 deletes any of these breakpoints as soon as your program stops there.
3543 Breakpoints set by the @code{tbreak} command start out in this state.
3546 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3547 @c confusing: tbreak is also initially enabled.
3548 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3549 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
3550 subsequently, they become disabled or enabled only when you use one of
3551 the commands above. (The command @code{until} can set and delete a
3552 breakpoint of its own, but it does not change the state of your other
3553 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3557 @subsection Break Conditions
3558 @cindex conditional breakpoints
3559 @cindex breakpoint conditions
3561 @c FIXME what is scope of break condition expr? Context where wanted?
3562 @c in particular for a watchpoint?
3563 The simplest sort of breakpoint breaks every time your program reaches a
3564 specified place. You can also specify a @dfn{condition} for a
3565 breakpoint. A condition is just a Boolean expression in your
3566 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3567 a condition evaluates the expression each time your program reaches it,
3568 and your program stops only if the condition is @emph{true}.
3570 This is the converse of using assertions for program validation; in that
3571 situation, you want to stop when the assertion is violated---that is,
3572 when the condition is false. In C, if you want to test an assertion expressed
3573 by the condition @var{assert}, you should set the condition
3574 @samp{! @var{assert}} on the appropriate breakpoint.
3576 Conditions are also accepted for watchpoints; you may not need them,
3577 since a watchpoint is inspecting the value of an expression anyhow---but
3578 it might be simpler, say, to just set a watchpoint on a variable name,
3579 and specify a condition that tests whether the new value is an interesting
3582 Break conditions can have side effects, and may even call functions in
3583 your program. This can be useful, for example, to activate functions
3584 that log program progress, or to use your own print functions to
3585 format special data structures. The effects are completely predictable
3586 unless there is another enabled breakpoint at the same address. (In
3587 that case, @value{GDBN} might see the other breakpoint first and stop your
3588 program without checking the condition of this one.) Note that
3589 breakpoint commands are usually more convenient and flexible than break
3591 purpose of performing side effects when a breakpoint is reached
3592 (@pxref{Break Commands, ,Breakpoint Command Lists}).
3594 Break conditions can be specified when a breakpoint is set, by using
3595 @samp{if} in the arguments to the @code{break} command. @xref{Set
3596 Breaks, ,Setting Breakpoints}. They can also be changed at any time
3597 with the @code{condition} command.
3599 You can also use the @code{if} keyword with the @code{watch} command.
3600 The @code{catch} command does not recognize the @code{if} keyword;
3601 @code{condition} is the only way to impose a further condition on a
3606 @item condition @var{bnum} @var{expression}
3607 Specify @var{expression} as the break condition for breakpoint,
3608 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3609 breakpoint @var{bnum} stops your program only if the value of
3610 @var{expression} is true (nonzero, in C). When you use
3611 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3612 syntactic correctness, and to determine whether symbols in it have
3613 referents in the context of your breakpoint. If @var{expression} uses
3614 symbols not referenced in the context of the breakpoint, @value{GDBN}
3615 prints an error message:
3618 No symbol "foo" in current context.
3623 not actually evaluate @var{expression} at the time the @code{condition}
3624 command (or a command that sets a breakpoint with a condition, like
3625 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3627 @item condition @var{bnum}
3628 Remove the condition from breakpoint number @var{bnum}. It becomes
3629 an ordinary unconditional breakpoint.
3632 @cindex ignore count (of breakpoint)
3633 A special case of a breakpoint condition is to stop only when the
3634 breakpoint has been reached a certain number of times. This is so
3635 useful that there is a special way to do it, using the @dfn{ignore
3636 count} of the breakpoint. Every breakpoint has an ignore count, which
3637 is an integer. Most of the time, the ignore count is zero, and
3638 therefore has no effect. But if your program reaches a breakpoint whose
3639 ignore count is positive, then instead of stopping, it just decrements
3640 the ignore count by one and continues. As a result, if the ignore count
3641 value is @var{n}, the breakpoint does not stop the next @var{n} times
3642 your program reaches it.
3646 @item ignore @var{bnum} @var{count}
3647 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3648 The next @var{count} times the breakpoint is reached, your program's
3649 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3652 To make the breakpoint stop the next time it is reached, specify
3655 When you use @code{continue} to resume execution of your program from a
3656 breakpoint, you can specify an ignore count directly as an argument to
3657 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3658 Stepping,,Continuing and Stepping}.
3660 If a breakpoint has a positive ignore count and a condition, the
3661 condition is not checked. Once the ignore count reaches zero,
3662 @value{GDBN} resumes checking the condition.
3664 You could achieve the effect of the ignore count with a condition such
3665 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3666 is decremented each time. @xref{Convenience Vars, ,Convenience
3670 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3673 @node Break Commands
3674 @subsection Breakpoint Command Lists
3676 @cindex breakpoint commands
3677 You can give any breakpoint (or watchpoint or catchpoint) a series of
3678 commands to execute when your program stops due to that breakpoint. For
3679 example, you might want to print the values of certain expressions, or
3680 enable other breakpoints.
3684 @kindex end@r{ (breakpoint commands)}
3685 @item commands @r{[}@var{bnum}@r{]}
3686 @itemx @dots{} @var{command-list} @dots{}
3688 Specify a list of commands for breakpoint number @var{bnum}. The commands
3689 themselves appear on the following lines. Type a line containing just
3690 @code{end} to terminate the commands.
3692 To remove all commands from a breakpoint, type @code{commands} and
3693 follow it immediately with @code{end}; that is, give no commands.
3695 With no @var{bnum} argument, @code{commands} refers to the last
3696 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3697 recently encountered).
3700 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3701 disabled within a @var{command-list}.
3703 You can use breakpoint commands to start your program up again. Simply
3704 use the @code{continue} command, or @code{step}, or any other command
3705 that resumes execution.
3707 Any other commands in the command list, after a command that resumes
3708 execution, are ignored. This is because any time you resume execution
3709 (even with a simple @code{next} or @code{step}), you may encounter
3710 another breakpoint---which could have its own command list, leading to
3711 ambiguities about which list to execute.
3714 If the first command you specify in a command list is @code{silent}, the
3715 usual message about stopping at a breakpoint is not printed. This may
3716 be desirable for breakpoints that are to print a specific message and
3717 then continue. If none of the remaining commands print anything, you
3718 see no sign that the breakpoint was reached. @code{silent} is
3719 meaningful only at the beginning of a breakpoint command list.
3721 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3722 print precisely controlled output, and are often useful in silent
3723 breakpoints. @xref{Output, ,Commands for Controlled Output}.
3725 For example, here is how you could use breakpoint commands to print the
3726 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3732 printf "x is %d\n",x
3737 One application for breakpoint commands is to compensate for one bug so
3738 you can test for another. Put a breakpoint just after the erroneous line
3739 of code, give it a condition to detect the case in which something
3740 erroneous has been done, and give it commands to assign correct values
3741 to any variables that need them. End with the @code{continue} command
3742 so that your program does not stop, and start with the @code{silent}
3743 command so that no output is produced. Here is an example:
3754 @node Breakpoint Menus
3755 @subsection Breakpoint Menus
3757 @cindex symbol overloading
3759 Some programming languages (notably C@t{++} and Objective-C) permit a
3760 single function name
3761 to be defined several times, for application in different contexts.
3762 This is called @dfn{overloading}. When a function name is overloaded,
3763 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3764 a breakpoint. If you realize this is a problem, you can use
3765 something like @samp{break @var{function}(@var{types})} to specify which
3766 particular version of the function you want. Otherwise, @value{GDBN} offers
3767 you a menu of numbered choices for different possible breakpoints, and
3768 waits for your selection with the prompt @samp{>}. The first two
3769 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3770 sets a breakpoint at each definition of @var{function}, and typing
3771 @kbd{0} aborts the @code{break} command without setting any new
3774 For example, the following session excerpt shows an attempt to set a
3775 breakpoint at the overloaded symbol @code{String::after}.
3776 We choose three particular definitions of that function name:
3778 @c FIXME! This is likely to change to show arg type lists, at least
3781 (@value{GDBP}) b String::after
3784 [2] file:String.cc; line number:867
3785 [3] file:String.cc; line number:860
3786 [4] file:String.cc; line number:875
3787 [5] file:String.cc; line number:853
3788 [6] file:String.cc; line number:846
3789 [7] file:String.cc; line number:735
3791 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3792 Breakpoint 2 at 0xb344: file String.cc, line 875.
3793 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3794 Multiple breakpoints were set.
3795 Use the "delete" command to delete unwanted
3801 @c @ifclear BARETARGET
3802 @node Error in Breakpoints
3803 @subsection ``Cannot insert breakpoints''
3805 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3807 Under some operating systems, breakpoints cannot be used in a program if
3808 any other process is running that program. In this situation,
3809 attempting to run or continue a program with a breakpoint causes
3810 @value{GDBN} to print an error message:
3813 Cannot insert breakpoints.
3814 The same program may be running in another process.
3817 When this happens, you have three ways to proceed:
3821 Remove or disable the breakpoints, then continue.
3824 Suspend @value{GDBN}, and copy the file containing your program to a new
3825 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3826 that @value{GDBN} should run your program under that name.
3827 Then start your program again.
3830 Relink your program so that the text segment is nonsharable, using the
3831 linker option @samp{-N}. The operating system limitation may not apply
3832 to nonsharable executables.
3836 A similar message can be printed if you request too many active
3837 hardware-assisted breakpoints and watchpoints:
3839 @c FIXME: the precise wording of this message may change; the relevant
3840 @c source change is not committed yet (Sep 3, 1999).
3842 Stopped; cannot insert breakpoints.
3843 You may have requested too many hardware breakpoints and watchpoints.
3847 This message is printed when you attempt to resume the program, since
3848 only then @value{GDBN} knows exactly how many hardware breakpoints and
3849 watchpoints it needs to insert.
3851 When this message is printed, you need to disable or remove some of the
3852 hardware-assisted breakpoints and watchpoints, and then continue.
3854 @node Breakpoint-related Warnings
3855 @subsection ``Breakpoint address adjusted...''
3856 @cindex breakpoint address adjusted
3858 Some processor architectures place constraints on the addresses at
3859 which breakpoints may be placed. For architectures thus constrained,
3860 @value{GDBN} will attempt to adjust the breakpoint's address to comply
3861 with the constraints dictated by the architecture.
3863 One example of such an architecture is the Fujitsu FR-V. The FR-V is
3864 a VLIW architecture in which a number of RISC-like instructions may be
3865 bundled together for parallel execution. The FR-V architecture
3866 constrains the location of a breakpoint instruction within such a
3867 bundle to the instruction with the lowest address. @value{GDBN}
3868 honors this constraint by adjusting a breakpoint's address to the
3869 first in the bundle.
3871 It is not uncommon for optimized code to have bundles which contain
3872 instructions from different source statements, thus it may happen that
3873 a breakpoint's address will be adjusted from one source statement to
3874 another. Since this adjustment may significantly alter @value{GDBN}'s
3875 breakpoint related behavior from what the user expects, a warning is
3876 printed when the breakpoint is first set and also when the breakpoint
3879 A warning like the one below is printed when setting a breakpoint
3880 that's been subject to address adjustment:
3883 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
3886 Such warnings are printed both for user settable and @value{GDBN}'s
3887 internal breakpoints. If you see one of these warnings, you should
3888 verify that a breakpoint set at the adjusted address will have the
3889 desired affect. If not, the breakpoint in question may be removed and
3890 other breakpoints may be set which will have the desired behavior.
3891 E.g., it may be sufficient to place the breakpoint at a later
3892 instruction. A conditional breakpoint may also be useful in some
3893 cases to prevent the breakpoint from triggering too often.
3895 @value{GDBN} will also issue a warning when stopping at one of these
3896 adjusted breakpoints:
3899 warning: Breakpoint 1 address previously adjusted from 0x00010414
3903 When this warning is encountered, it may be too late to take remedial
3904 action except in cases where the breakpoint is hit earlier or more
3905 frequently than expected.
3907 @node Continuing and Stepping
3908 @section Continuing and Stepping
3912 @cindex resuming execution
3913 @dfn{Continuing} means resuming program execution until your program
3914 completes normally. In contrast, @dfn{stepping} means executing just
3915 one more ``step'' of your program, where ``step'' may mean either one
3916 line of source code, or one machine instruction (depending on what
3917 particular command you use). Either when continuing or when stepping,
3918 your program may stop even sooner, due to a breakpoint or a signal. (If
3919 it stops due to a signal, you may want to use @code{handle}, or use
3920 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3924 @kindex c @r{(@code{continue})}
3925 @kindex fg @r{(resume foreground execution)}
3926 @item continue @r{[}@var{ignore-count}@r{]}
3927 @itemx c @r{[}@var{ignore-count}@r{]}
3928 @itemx fg @r{[}@var{ignore-count}@r{]}
3929 Resume program execution, at the address where your program last stopped;
3930 any breakpoints set at that address are bypassed. The optional argument
3931 @var{ignore-count} allows you to specify a further number of times to
3932 ignore a breakpoint at this location; its effect is like that of
3933 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
3935 The argument @var{ignore-count} is meaningful only when your program
3936 stopped due to a breakpoint. At other times, the argument to
3937 @code{continue} is ignored.
3939 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
3940 debugged program is deemed to be the foreground program) are provided
3941 purely for convenience, and have exactly the same behavior as
3945 To resume execution at a different place, you can use @code{return}
3946 (@pxref{Returning, ,Returning from a Function}) to go back to the
3947 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
3948 Different Address}) to go to an arbitrary location in your program.
3950 A typical technique for using stepping is to set a breakpoint
3951 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
3952 beginning of the function or the section of your program where a problem
3953 is believed to lie, run your program until it stops at that breakpoint,
3954 and then step through the suspect area, examining the variables that are
3955 interesting, until you see the problem happen.
3959 @kindex s @r{(@code{step})}
3961 Continue running your program until control reaches a different source
3962 line, then stop it and return control to @value{GDBN}. This command is
3963 abbreviated @code{s}.
3966 @c "without debugging information" is imprecise; actually "without line
3967 @c numbers in the debugging information". (gcc -g1 has debugging info but
3968 @c not line numbers). But it seems complex to try to make that
3969 @c distinction here.
3970 @emph{Warning:} If you use the @code{step} command while control is
3971 within a function that was compiled without debugging information,
3972 execution proceeds until control reaches a function that does have
3973 debugging information. Likewise, it will not step into a function which
3974 is compiled without debugging information. To step through functions
3975 without debugging information, use the @code{stepi} command, described
3979 The @code{step} command only stops at the first instruction of a source
3980 line. This prevents the multiple stops that could otherwise occur in
3981 @code{switch} statements, @code{for} loops, etc. @code{step} continues
3982 to stop if a function that has debugging information is called within
3983 the line. In other words, @code{step} @emph{steps inside} any functions
3984 called within the line.
3986 Also, the @code{step} command only enters a function if there is line
3987 number information for the function. Otherwise it acts like the
3988 @code{next} command. This avoids problems when using @code{cc -gl}
3989 on MIPS machines. Previously, @code{step} entered subroutines if there
3990 was any debugging information about the routine.
3992 @item step @var{count}
3993 Continue running as in @code{step}, but do so @var{count} times. If a
3994 breakpoint is reached, or a signal not related to stepping occurs before
3995 @var{count} steps, stepping stops right away.
3998 @kindex n @r{(@code{next})}
3999 @item next @r{[}@var{count}@r{]}
4000 Continue to the next source line in the current (innermost) stack frame.
4001 This is similar to @code{step}, but function calls that appear within
4002 the line of code are executed without stopping. Execution stops when
4003 control reaches a different line of code at the original stack level
4004 that was executing when you gave the @code{next} command. This command
4005 is abbreviated @code{n}.
4007 An argument @var{count} is a repeat count, as for @code{step}.
4010 @c FIX ME!! Do we delete this, or is there a way it fits in with
4011 @c the following paragraph? --- Vctoria
4013 @c @code{next} within a function that lacks debugging information acts like
4014 @c @code{step}, but any function calls appearing within the code of the
4015 @c function are executed without stopping.
4017 The @code{next} command only stops at the first instruction of a
4018 source line. This prevents multiple stops that could otherwise occur in
4019 @code{switch} statements, @code{for} loops, etc.
4021 @kindex set step-mode
4023 @cindex functions without line info, and stepping
4024 @cindex stepping into functions with no line info
4025 @itemx set step-mode on
4026 The @code{set step-mode on} command causes the @code{step} command to
4027 stop at the first instruction of a function which contains no debug line
4028 information rather than stepping over it.
4030 This is useful in cases where you may be interested in inspecting the
4031 machine instructions of a function which has no symbolic info and do not
4032 want @value{GDBN} to automatically skip over this function.
4034 @item set step-mode off
4035 Causes the @code{step} command to step over any functions which contains no
4036 debug information. This is the default.
4038 @item show step-mode
4039 Show whether @value{GDBN} will stop in or step over functions without
4040 source line debug information.
4044 Continue running until just after function in the selected stack frame
4045 returns. Print the returned value (if any).
4047 Contrast this with the @code{return} command (@pxref{Returning,
4048 ,Returning from a Function}).
4051 @kindex u @r{(@code{until})}
4052 @cindex run until specified location
4055 Continue running until a source line past the current line, in the
4056 current stack frame, is reached. This command is used to avoid single
4057 stepping through a loop more than once. It is like the @code{next}
4058 command, except that when @code{until} encounters a jump, it
4059 automatically continues execution until the program counter is greater
4060 than the address of the jump.
4062 This means that when you reach the end of a loop after single stepping
4063 though it, @code{until} makes your program continue execution until it
4064 exits the loop. In contrast, a @code{next} command at the end of a loop
4065 simply steps back to the beginning of the loop, which forces you to step
4066 through the next iteration.
4068 @code{until} always stops your program if it attempts to exit the current
4071 @code{until} may produce somewhat counterintuitive results if the order
4072 of machine code does not match the order of the source lines. For
4073 example, in the following excerpt from a debugging session, the @code{f}
4074 (@code{frame}) command shows that execution is stopped at line
4075 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4079 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4081 (@value{GDBP}) until
4082 195 for ( ; argc > 0; NEXTARG) @{
4085 This happened because, for execution efficiency, the compiler had
4086 generated code for the loop closure test at the end, rather than the
4087 start, of the loop---even though the test in a C @code{for}-loop is
4088 written before the body of the loop. The @code{until} command appeared
4089 to step back to the beginning of the loop when it advanced to this
4090 expression; however, it has not really gone to an earlier
4091 statement---not in terms of the actual machine code.
4093 @code{until} with no argument works by means of single
4094 instruction stepping, and hence is slower than @code{until} with an
4097 @item until @var{location}
4098 @itemx u @var{location}
4099 Continue running your program until either the specified location is
4100 reached, or the current stack frame returns. @var{location} is any of
4101 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
4102 ,Setting Breakpoints}). This form of the command uses breakpoints, and
4103 hence is quicker than @code{until} without an argument. The specified
4104 location is actually reached only if it is in the current frame. This
4105 implies that @code{until} can be used to skip over recursive function
4106 invocations. For instance in the code below, if the current location is
4107 line @code{96}, issuing @code{until 99} will execute the program up to
4108 line @code{99} in the same invocation of factorial, i.e., after the inner
4109 invocations have returned.
4112 94 int factorial (int value)
4114 96 if (value > 1) @{
4115 97 value *= factorial (value - 1);
4122 @kindex advance @var{location}
4123 @itemx advance @var{location}
4124 Continue running the program up to the given @var{location}. An argument is
4125 required, which should be of the same form as arguments for the @code{break}
4126 command. Execution will also stop upon exit from the current stack
4127 frame. This command is similar to @code{until}, but @code{advance} will
4128 not skip over recursive function calls, and the target location doesn't
4129 have to be in the same frame as the current one.
4133 @kindex si @r{(@code{stepi})}
4135 @itemx stepi @var{arg}
4137 Execute one machine instruction, then stop and return to the debugger.
4139 It is often useful to do @samp{display/i $pc} when stepping by machine
4140 instructions. This makes @value{GDBN} automatically display the next
4141 instruction to be executed, each time your program stops. @xref{Auto
4142 Display,, Automatic Display}.
4144 An argument is a repeat count, as in @code{step}.
4148 @kindex ni @r{(@code{nexti})}
4150 @itemx nexti @var{arg}
4152 Execute one machine instruction, but if it is a function call,
4153 proceed until the function returns.
4155 An argument is a repeat count, as in @code{next}.
4162 A signal is an asynchronous event that can happen in a program. The
4163 operating system defines the possible kinds of signals, and gives each
4164 kind a name and a number. For example, in Unix @code{SIGINT} is the
4165 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4166 @code{SIGSEGV} is the signal a program gets from referencing a place in
4167 memory far away from all the areas in use; @code{SIGALRM} occurs when
4168 the alarm clock timer goes off (which happens only if your program has
4169 requested an alarm).
4171 @cindex fatal signals
4172 Some signals, including @code{SIGALRM}, are a normal part of the
4173 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4174 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4175 program has not specified in advance some other way to handle the signal.
4176 @code{SIGINT} does not indicate an error in your program, but it is normally
4177 fatal so it can carry out the purpose of the interrupt: to kill the program.
4179 @value{GDBN} has the ability to detect any occurrence of a signal in your
4180 program. You can tell @value{GDBN} in advance what to do for each kind of
4183 @cindex handling signals
4184 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4185 @code{SIGALRM} be silently passed to your program
4186 (so as not to interfere with their role in the program's functioning)
4187 but to stop your program immediately whenever an error signal happens.
4188 You can change these settings with the @code{handle} command.
4191 @kindex info signals
4195 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4196 handle each one. You can use this to see the signal numbers of all
4197 the defined types of signals.
4199 @item info signals @var{sig}
4200 Similar, but print information only about the specified signal number.
4202 @code{info handle} is an alias for @code{info signals}.
4205 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4206 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4207 can be the number of a signal or its name (with or without the
4208 @samp{SIG} at the beginning); a list of signal numbers of the form
4209 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4210 known signals. Optional arguments @var{keywords}, described below,
4211 say what change to make.
4215 The keywords allowed by the @code{handle} command can be abbreviated.
4216 Their full names are:
4220 @value{GDBN} should not stop your program when this signal happens. It may
4221 still print a message telling you that the signal has come in.
4224 @value{GDBN} should stop your program when this signal happens. This implies
4225 the @code{print} keyword as well.
4228 @value{GDBN} should print a message when this signal happens.
4231 @value{GDBN} should not mention the occurrence of the signal at all. This
4232 implies the @code{nostop} keyword as well.
4236 @value{GDBN} should allow your program to see this signal; your program
4237 can handle the signal, or else it may terminate if the signal is fatal
4238 and not handled. @code{pass} and @code{noignore} are synonyms.
4242 @value{GDBN} should not allow your program to see this signal.
4243 @code{nopass} and @code{ignore} are synonyms.
4247 When a signal stops your program, the signal is not visible to the
4249 continue. Your program sees the signal then, if @code{pass} is in
4250 effect for the signal in question @emph{at that time}. In other words,
4251 after @value{GDBN} reports a signal, you can use the @code{handle}
4252 command with @code{pass} or @code{nopass} to control whether your
4253 program sees that signal when you continue.
4255 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4256 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4257 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4260 You can also use the @code{signal} command to prevent your program from
4261 seeing a signal, or cause it to see a signal it normally would not see,
4262 or to give it any signal at any time. For example, if your program stopped
4263 due to some sort of memory reference error, you might store correct
4264 values into the erroneous variables and continue, hoping to see more
4265 execution; but your program would probably terminate immediately as
4266 a result of the fatal signal once it saw the signal. To prevent this,
4267 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4271 @section Stopping and Starting Multi-thread Programs
4273 When your program has multiple threads (@pxref{Threads,, Debugging
4274 Programs with Multiple Threads}), you can choose whether to set
4275 breakpoints on all threads, or on a particular thread.
4278 @cindex breakpoints and threads
4279 @cindex thread breakpoints
4280 @kindex break @dots{} thread @var{threadno}
4281 @item break @var{linespec} thread @var{threadno}
4282 @itemx break @var{linespec} thread @var{threadno} if @dots{}
4283 @var{linespec} specifies source lines; there are several ways of
4284 writing them, but the effect is always to specify some source line.
4286 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
4287 to specify that you only want @value{GDBN} to stop the program when a
4288 particular thread reaches this breakpoint. @var{threadno} is one of the
4289 numeric thread identifiers assigned by @value{GDBN}, shown in the first
4290 column of the @samp{info threads} display.
4292 If you do not specify @samp{thread @var{threadno}} when you set a
4293 breakpoint, the breakpoint applies to @emph{all} threads of your
4296 You can use the @code{thread} qualifier on conditional breakpoints as
4297 well; in this case, place @samp{thread @var{threadno}} before the
4298 breakpoint condition, like this:
4301 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
4306 @cindex stopped threads
4307 @cindex threads, stopped
4308 Whenever your program stops under @value{GDBN} for any reason,
4309 @emph{all} threads of execution stop, not just the current thread. This
4310 allows you to examine the overall state of the program, including
4311 switching between threads, without worrying that things may change
4314 @cindex thread breakpoints and system calls
4315 @cindex system calls and thread breakpoints
4316 @cindex premature return from system calls
4317 There is an unfortunate side effect. If one thread stops for a
4318 breakpoint, or for some other reason, and another thread is blocked in a
4319 system call, then the system call may return prematurely. This is a
4320 consequence of the interaction between multiple threads and the signals
4321 that @value{GDBN} uses to implement breakpoints and other events that
4324 To handle this problem, your program should check the return value of
4325 each system call and react appropriately. This is good programming
4328 For example, do not write code like this:
4334 The call to @code{sleep} will return early if a different thread stops
4335 at a breakpoint or for some other reason.
4337 Instead, write this:
4342 unslept = sleep (unslept);
4345 A system call is allowed to return early, so the system is still
4346 conforming to its specification. But @value{GDBN} does cause your
4347 multi-threaded program to behave differently than it would without
4350 Also, @value{GDBN} uses internal breakpoints in the thread library to
4351 monitor certain events such as thread creation and thread destruction.
4352 When such an event happens, a system call in another thread may return
4353 prematurely, even though your program does not appear to stop.
4355 @cindex continuing threads
4356 @cindex threads, continuing
4357 Conversely, whenever you restart the program, @emph{all} threads start
4358 executing. @emph{This is true even when single-stepping} with commands
4359 like @code{step} or @code{next}.
4361 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4362 Since thread scheduling is up to your debugging target's operating
4363 system (not controlled by @value{GDBN}), other threads may
4364 execute more than one statement while the current thread completes a
4365 single step. Moreover, in general other threads stop in the middle of a
4366 statement, rather than at a clean statement boundary, when the program
4369 You might even find your program stopped in another thread after
4370 continuing or even single-stepping. This happens whenever some other
4371 thread runs into a breakpoint, a signal, or an exception before the
4372 first thread completes whatever you requested.
4374 On some OSes, you can lock the OS scheduler and thus allow only a single
4378 @item set scheduler-locking @var{mode}
4379 @cindex scheduler locking mode
4380 @cindex lock scheduler
4381 Set the scheduler locking mode. If it is @code{off}, then there is no
4382 locking and any thread may run at any time. If @code{on}, then only the
4383 current thread may run when the inferior is resumed. The @code{step}
4384 mode optimizes for single-stepping. It stops other threads from
4385 ``seizing the prompt'' by preempting the current thread while you are
4386 stepping. Other threads will only rarely (or never) get a chance to run
4387 when you step. They are more likely to run when you @samp{next} over a
4388 function call, and they are completely free to run when you use commands
4389 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4390 thread hits a breakpoint during its timeslice, they will never steal the
4391 @value{GDBN} prompt away from the thread that you are debugging.
4393 @item show scheduler-locking
4394 Display the current scheduler locking mode.
4399 @chapter Examining the Stack
4401 When your program has stopped, the first thing you need to know is where it
4402 stopped and how it got there.
4405 Each time your program performs a function call, information about the call
4407 That information includes the location of the call in your program,
4408 the arguments of the call,
4409 and the local variables of the function being called.
4410 The information is saved in a block of data called a @dfn{stack frame}.
4411 The stack frames are allocated in a region of memory called the @dfn{call
4414 When your program stops, the @value{GDBN} commands for examining the
4415 stack allow you to see all of this information.
4417 @cindex selected frame
4418 One of the stack frames is @dfn{selected} by @value{GDBN} and many
4419 @value{GDBN} commands refer implicitly to the selected frame. In
4420 particular, whenever you ask @value{GDBN} for the value of a variable in
4421 your program, the value is found in the selected frame. There are
4422 special @value{GDBN} commands to select whichever frame you are
4423 interested in. @xref{Selection, ,Selecting a Frame}.
4425 When your program stops, @value{GDBN} automatically selects the
4426 currently executing frame and describes it briefly, similar to the
4427 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
4430 * Frames:: Stack frames
4431 * Backtrace:: Backtraces
4432 * Selection:: Selecting a frame
4433 * Frame Info:: Information on a frame
4438 @section Stack Frames
4440 @cindex frame, definition
4442 The call stack is divided up into contiguous pieces called @dfn{stack
4443 frames}, or @dfn{frames} for short; each frame is the data associated
4444 with one call to one function. The frame contains the arguments given
4445 to the function, the function's local variables, and the address at
4446 which the function is executing.
4448 @cindex initial frame
4449 @cindex outermost frame
4450 @cindex innermost frame
4451 When your program is started, the stack has only one frame, that of the
4452 function @code{main}. This is called the @dfn{initial} frame or the
4453 @dfn{outermost} frame. Each time a function is called, a new frame is
4454 made. Each time a function returns, the frame for that function invocation
4455 is eliminated. If a function is recursive, there can be many frames for
4456 the same function. The frame for the function in which execution is
4457 actually occurring is called the @dfn{innermost} frame. This is the most
4458 recently created of all the stack frames that still exist.
4460 @cindex frame pointer
4461 Inside your program, stack frames are identified by their addresses. A
4462 stack frame consists of many bytes, each of which has its own address; each
4463 kind of computer has a convention for choosing one byte whose
4464 address serves as the address of the frame. Usually this address is kept
4465 in a register called the @dfn{frame pointer register}
4466 (@pxref{Registers, $fp}) while execution is going on in that frame.
4468 @cindex frame number
4469 @value{GDBN} assigns numbers to all existing stack frames, starting with
4470 zero for the innermost frame, one for the frame that called it,
4471 and so on upward. These numbers do not really exist in your program;
4472 they are assigned by @value{GDBN} to give you a way of designating stack
4473 frames in @value{GDBN} commands.
4475 @c The -fomit-frame-pointer below perennially causes hbox overflow
4476 @c underflow problems.
4477 @cindex frameless execution
4478 Some compilers provide a way to compile functions so that they operate
4479 without stack frames. (For example, the @value{NGCC} option
4481 @samp{-fomit-frame-pointer}
4483 generates functions without a frame.)
4484 This is occasionally done with heavily used library functions to save
4485 the frame setup time. @value{GDBN} has limited facilities for dealing
4486 with these function invocations. If the innermost function invocation
4487 has no stack frame, @value{GDBN} nevertheless regards it as though
4488 it had a separate frame, which is numbered zero as usual, allowing
4489 correct tracing of the function call chain. However, @value{GDBN} has
4490 no provision for frameless functions elsewhere in the stack.
4493 @kindex frame@r{, command}
4494 @cindex current stack frame
4495 @item frame @var{args}
4496 The @code{frame} command allows you to move from one stack frame to another,
4497 and to print the stack frame you select. @var{args} may be either the
4498 address of the frame or the stack frame number. Without an argument,
4499 @code{frame} prints the current stack frame.
4501 @kindex select-frame
4502 @cindex selecting frame silently
4504 The @code{select-frame} command allows you to move from one stack frame
4505 to another without printing the frame. This is the silent version of
4513 @cindex call stack traces
4514 A backtrace is a summary of how your program got where it is. It shows one
4515 line per frame, for many frames, starting with the currently executing
4516 frame (frame zero), followed by its caller (frame one), and on up the
4521 @kindex bt @r{(@code{backtrace})}
4524 Print a backtrace of the entire stack: one line per frame for all
4525 frames in the stack.
4527 You can stop the backtrace at any time by typing the system interrupt
4528 character, normally @kbd{Ctrl-c}.
4530 @item backtrace @var{n}
4532 Similar, but print only the innermost @var{n} frames.
4534 @item backtrace -@var{n}
4536 Similar, but print only the outermost @var{n} frames.
4538 @item backtrace full
4540 @itemx bt full @var{n}
4541 @itemx bt full -@var{n}
4542 Print the values of the local variables also. @var{n} specifies the
4543 number of frames to print, as described above.
4548 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4549 are additional aliases for @code{backtrace}.
4551 @cindex multiple threads, backtrace
4552 In a multi-threaded program, @value{GDBN} by default shows the
4553 backtrace only for the current thread. To display the backtrace for
4554 several or all of the threads, use the command @code{thread apply}
4555 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
4556 apply all backtrace}, @value{GDBN} will display the backtrace for all
4557 the threads; this is handy when you debug a core dump of a
4558 multi-threaded program.
4560 Each line in the backtrace shows the frame number and the function name.
4561 The program counter value is also shown---unless you use @code{set
4562 print address off}. The backtrace also shows the source file name and
4563 line number, as well as the arguments to the function. The program
4564 counter value is omitted if it is at the beginning of the code for that
4567 Here is an example of a backtrace. It was made with the command
4568 @samp{bt 3}, so it shows the innermost three frames.
4572 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4574 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4575 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4577 (More stack frames follow...)
4582 The display for frame zero does not begin with a program counter
4583 value, indicating that your program has stopped at the beginning of the
4584 code for line @code{993} of @code{builtin.c}.
4586 @cindex value optimized out, in backtrace
4587 @cindex function call arguments, optimized out
4588 If your program was compiled with optimizations, some compilers will
4589 optimize away arguments passed to functions if those arguments are
4590 never used after the call. Such optimizations generate code that
4591 passes arguments through registers, but doesn't store those arguments
4592 in the stack frame. @value{GDBN} has no way of displaying such
4593 arguments in stack frames other than the innermost one. Here's what
4594 such a backtrace might look like:
4598 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4600 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
4601 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
4603 (More stack frames follow...)
4608 The values of arguments that were not saved in their stack frames are
4609 shown as @samp{<value optimized out>}.
4611 If you need to display the values of such optimized-out arguments,
4612 either deduce that from other variables whose values depend on the one
4613 you are interested in, or recompile without optimizations.
4615 @cindex backtrace beyond @code{main} function
4616 @cindex program entry point
4617 @cindex startup code, and backtrace
4618 Most programs have a standard user entry point---a place where system
4619 libraries and startup code transition into user code. For C this is
4620 @code{main}@footnote{
4621 Note that embedded programs (the so-called ``free-standing''
4622 environment) are not required to have a @code{main} function as the
4623 entry point. They could even have multiple entry points.}.
4624 When @value{GDBN} finds the entry function in a backtrace
4625 it will terminate the backtrace, to avoid tracing into highly
4626 system-specific (and generally uninteresting) code.
4628 If you need to examine the startup code, or limit the number of levels
4629 in a backtrace, you can change this behavior:
4632 @item set backtrace past-main
4633 @itemx set backtrace past-main on
4634 @kindex set backtrace
4635 Backtraces will continue past the user entry point.
4637 @item set backtrace past-main off
4638 Backtraces will stop when they encounter the user entry point. This is the
4641 @item show backtrace past-main
4642 @kindex show backtrace
4643 Display the current user entry point backtrace policy.
4645 @item set backtrace past-entry
4646 @itemx set backtrace past-entry on
4647 Backtraces will continue past the internal entry point of an application.
4648 This entry point is encoded by the linker when the application is built,
4649 and is likely before the user entry point @code{main} (or equivalent) is called.
4651 @item set backtrace past-entry off
4652 Backtraces will stop when they encounter the internal entry point of an
4653 application. This is the default.
4655 @item show backtrace past-entry
4656 Display the current internal entry point backtrace policy.
4658 @item set backtrace limit @var{n}
4659 @itemx set backtrace limit 0
4660 @cindex backtrace limit
4661 Limit the backtrace to @var{n} levels. A value of zero means
4664 @item show backtrace limit
4665 Display the current limit on backtrace levels.
4669 @section Selecting a Frame
4671 Most commands for examining the stack and other data in your program work on
4672 whichever stack frame is selected at the moment. Here are the commands for
4673 selecting a stack frame; all of them finish by printing a brief description
4674 of the stack frame just selected.
4677 @kindex frame@r{, selecting}
4678 @kindex f @r{(@code{frame})}
4681 Select frame number @var{n}. Recall that frame zero is the innermost
4682 (currently executing) frame, frame one is the frame that called the
4683 innermost one, and so on. The highest-numbered frame is the one for
4686 @item frame @var{addr}
4688 Select the frame at address @var{addr}. This is useful mainly if the
4689 chaining of stack frames has been damaged by a bug, making it
4690 impossible for @value{GDBN} to assign numbers properly to all frames. In
4691 addition, this can be useful when your program has multiple stacks and
4692 switches between them.
4694 On the SPARC architecture, @code{frame} needs two addresses to
4695 select an arbitrary frame: a frame pointer and a stack pointer.
4697 On the MIPS and Alpha architecture, it needs two addresses: a stack
4698 pointer and a program counter.
4700 On the 29k architecture, it needs three addresses: a register stack
4701 pointer, a program counter, and a memory stack pointer.
4705 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4706 advances toward the outermost frame, to higher frame numbers, to frames
4707 that have existed longer. @var{n} defaults to one.
4710 @kindex do @r{(@code{down})}
4712 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4713 advances toward the innermost frame, to lower frame numbers, to frames
4714 that were created more recently. @var{n} defaults to one. You may
4715 abbreviate @code{down} as @code{do}.
4718 All of these commands end by printing two lines of output describing the
4719 frame. The first line shows the frame number, the function name, the
4720 arguments, and the source file and line number of execution in that
4721 frame. The second line shows the text of that source line.
4729 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4731 10 read_input_file (argv[i]);
4735 After such a printout, the @code{list} command with no arguments
4736 prints ten lines centered on the point of execution in the frame.
4737 You can also edit the program at the point of execution with your favorite
4738 editing program by typing @code{edit}.
4739 @xref{List, ,Printing Source Lines},
4743 @kindex down-silently
4745 @item up-silently @var{n}
4746 @itemx down-silently @var{n}
4747 These two commands are variants of @code{up} and @code{down},
4748 respectively; they differ in that they do their work silently, without
4749 causing display of the new frame. They are intended primarily for use
4750 in @value{GDBN} command scripts, where the output might be unnecessary and
4755 @section Information About a Frame
4757 There are several other commands to print information about the selected
4763 When used without any argument, this command does not change which
4764 frame is selected, but prints a brief description of the currently
4765 selected stack frame. It can be abbreviated @code{f}. With an
4766 argument, this command is used to select a stack frame.
4767 @xref{Selection, ,Selecting a Frame}.
4770 @kindex info f @r{(@code{info frame})}
4773 This command prints a verbose description of the selected stack frame,
4778 the address of the frame
4780 the address of the next frame down (called by this frame)
4782 the address of the next frame up (caller of this frame)
4784 the language in which the source code corresponding to this frame is written
4786 the address of the frame's arguments
4788 the address of the frame's local variables
4790 the program counter saved in it (the address of execution in the caller frame)
4792 which registers were saved in the frame
4795 @noindent The verbose description is useful when
4796 something has gone wrong that has made the stack format fail to fit
4797 the usual conventions.
4799 @item info frame @var{addr}
4800 @itemx info f @var{addr}
4801 Print a verbose description of the frame at address @var{addr}, without
4802 selecting that frame. The selected frame remains unchanged by this
4803 command. This requires the same kind of address (more than one for some
4804 architectures) that you specify in the @code{frame} command.
4805 @xref{Selection, ,Selecting a Frame}.
4809 Print the arguments of the selected frame, each on a separate line.
4813 Print the local variables of the selected frame, each on a separate
4814 line. These are all variables (declared either static or automatic)
4815 accessible at the point of execution of the selected frame.
4818 @cindex catch exceptions, list active handlers
4819 @cindex exception handlers, how to list
4821 Print a list of all the exception handlers that are active in the
4822 current stack frame at the current point of execution. To see other
4823 exception handlers, visit the associated frame (using the @code{up},
4824 @code{down}, or @code{frame} commands); then type @code{info catch}.
4825 @xref{Set Catchpoints, , Setting Catchpoints}.
4831 @chapter Examining Source Files
4833 @value{GDBN} can print parts of your program's source, since the debugging
4834 information recorded in the program tells @value{GDBN} what source files were
4835 used to build it. When your program stops, @value{GDBN} spontaneously prints
4836 the line where it stopped. Likewise, when you select a stack frame
4837 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
4838 execution in that frame has stopped. You can print other portions of
4839 source files by explicit command.
4841 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4842 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4843 @value{GDBN} under @sc{gnu} Emacs}.
4846 * List:: Printing source lines
4847 * Edit:: Editing source files
4848 * Search:: Searching source files
4849 * Source Path:: Specifying source directories
4850 * Machine Code:: Source and machine code
4854 @section Printing Source Lines
4857 @kindex l @r{(@code{list})}
4858 To print lines from a source file, use the @code{list} command
4859 (abbreviated @code{l}). By default, ten lines are printed.
4860 There are several ways to specify what part of the file you want to print.
4862 Here are the forms of the @code{list} command most commonly used:
4865 @item list @var{linenum}
4866 Print lines centered around line number @var{linenum} in the
4867 current source file.
4869 @item list @var{function}
4870 Print lines centered around the beginning of function
4874 Print more lines. If the last lines printed were printed with a
4875 @code{list} command, this prints lines following the last lines
4876 printed; however, if the last line printed was a solitary line printed
4877 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4878 Stack}), this prints lines centered around that line.
4881 Print lines just before the lines last printed.
4884 @cindex @code{list}, how many lines to display
4885 By default, @value{GDBN} prints ten source lines with any of these forms of
4886 the @code{list} command. You can change this using @code{set listsize}:
4889 @kindex set listsize
4890 @item set listsize @var{count}
4891 Make the @code{list} command display @var{count} source lines (unless
4892 the @code{list} argument explicitly specifies some other number).
4894 @kindex show listsize
4896 Display the number of lines that @code{list} prints.
4899 Repeating a @code{list} command with @key{RET} discards the argument,
4900 so it is equivalent to typing just @code{list}. This is more useful
4901 than listing the same lines again. An exception is made for an
4902 argument of @samp{-}; that argument is preserved in repetition so that
4903 each repetition moves up in the source file.
4906 In general, the @code{list} command expects you to supply zero, one or two
4907 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4908 of writing them, but the effect is always to specify some source line.
4909 Here is a complete description of the possible arguments for @code{list}:
4912 @item list @var{linespec}
4913 Print lines centered around the line specified by @var{linespec}.
4915 @item list @var{first},@var{last}
4916 Print lines from @var{first} to @var{last}. Both arguments are
4919 @item list ,@var{last}
4920 Print lines ending with @var{last}.
4922 @item list @var{first},
4923 Print lines starting with @var{first}.
4926 Print lines just after the lines last printed.
4929 Print lines just before the lines last printed.
4932 As described in the preceding table.
4935 Here are the ways of specifying a single source line---all the
4940 Specifies line @var{number} of the current source file.
4941 When a @code{list} command has two linespecs, this refers to
4942 the same source file as the first linespec.
4945 Specifies the line @var{offset} lines after the last line printed.
4946 When used as the second linespec in a @code{list} command that has
4947 two, this specifies the line @var{offset} lines down from the
4951 Specifies the line @var{offset} lines before the last line printed.
4953 @item @var{filename}:@var{number}
4954 Specifies line @var{number} in the source file @var{filename}.
4956 @item @var{function}
4957 Specifies the line that begins the body of the function @var{function}.
4958 For example: in C, this is the line with the open brace.
4960 @item @var{filename}:@var{function}
4961 Specifies the line of the open-brace that begins the body of the
4962 function @var{function} in the file @var{filename}. You only need the
4963 file name with a function name to avoid ambiguity when there are
4964 identically named functions in different source files.
4966 @item *@var{address}
4967 Specifies the line containing the program address @var{address}.
4968 @var{address} may be any expression.
4972 @section Editing Source Files
4973 @cindex editing source files
4976 @kindex e @r{(@code{edit})}
4977 To edit the lines in a source file, use the @code{edit} command.
4978 The editing program of your choice
4979 is invoked with the current line set to
4980 the active line in the program.
4981 Alternatively, there are several ways to specify what part of the file you
4982 want to print if you want to see other parts of the program.
4984 Here are the forms of the @code{edit} command most commonly used:
4988 Edit the current source file at the active line number in the program.
4990 @item edit @var{number}
4991 Edit the current source file with @var{number} as the active line number.
4993 @item edit @var{function}
4994 Edit the file containing @var{function} at the beginning of its definition.
4996 @item edit @var{filename}:@var{number}
4997 Specifies line @var{number} in the source file @var{filename}.
4999 @item edit @var{filename}:@var{function}
5000 Specifies the line that begins the body of the
5001 function @var{function} in the file @var{filename}. You only need the
5002 file name with a function name to avoid ambiguity when there are
5003 identically named functions in different source files.
5005 @item edit *@var{address}
5006 Specifies the line containing the program address @var{address}.
5007 @var{address} may be any expression.
5010 @subsection Choosing your Editor
5011 You can customize @value{GDBN} to use any editor you want
5013 The only restriction is that your editor (say @code{ex}), recognizes the
5014 following command-line syntax:
5016 ex +@var{number} file
5018 The optional numeric value +@var{number} specifies the number of the line in
5019 the file where to start editing.}.
5020 By default, it is @file{@value{EDITOR}}, but you can change this
5021 by setting the environment variable @code{EDITOR} before using
5022 @value{GDBN}. For example, to configure @value{GDBN} to use the
5023 @code{vi} editor, you could use these commands with the @code{sh} shell:
5029 or in the @code{csh} shell,
5031 setenv EDITOR /usr/bin/vi
5036 @section Searching Source Files
5037 @cindex searching source files
5039 There are two commands for searching through the current source file for a
5044 @kindex forward-search
5045 @item forward-search @var{regexp}
5046 @itemx search @var{regexp}
5047 The command @samp{forward-search @var{regexp}} checks each line,
5048 starting with the one following the last line listed, for a match for
5049 @var{regexp}. It lists the line that is found. You can use the
5050 synonym @samp{search @var{regexp}} or abbreviate the command name as
5053 @kindex reverse-search
5054 @item reverse-search @var{regexp}
5055 The command @samp{reverse-search @var{regexp}} checks each line, starting
5056 with the one before the last line listed and going backward, for a match
5057 for @var{regexp}. It lists the line that is found. You can abbreviate
5058 this command as @code{rev}.
5062 @section Specifying Source Directories
5065 @cindex directories for source files
5066 Executable programs sometimes do not record the directories of the source
5067 files from which they were compiled, just the names. Even when they do,
5068 the directories could be moved between the compilation and your debugging
5069 session. @value{GDBN} has a list of directories to search for source files;
5070 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
5071 it tries all the directories in the list, in the order they are present
5072 in the list, until it finds a file with the desired name.
5074 For example, suppose an executable references the file
5075 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
5076 @file{/mnt/cross}. The file is first looked up literally; if this
5077 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
5078 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
5079 message is printed. @value{GDBN} does not look up the parts of the
5080 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
5081 Likewise, the subdirectories of the source path are not searched: if
5082 the source path is @file{/mnt/cross}, and the binary refers to
5083 @file{foo.c}, @value{GDBN} would not find it under
5084 @file{/mnt/cross/usr/src/foo-1.0/lib}.
5086 Plain file names, relative file names with leading directories, file
5087 names containing dots, etc.@: are all treated as described above; for
5088 instance, if the source path is @file{/mnt/cross}, and the source file
5089 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
5090 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
5091 that---@file{/mnt/cross/foo.c}.
5093 Note that the executable search path is @emph{not} used to locate the
5096 Whenever you reset or rearrange the source path, @value{GDBN} clears out
5097 any information it has cached about where source files are found and where
5098 each line is in the file.
5102 When you start @value{GDBN}, its source path includes only @samp{cdir}
5103 and @samp{cwd}, in that order.
5104 To add other directories, use the @code{directory} command.
5106 The search path is used to find both program source files and @value{GDBN}
5107 script files (read using the @samp{-command} option and @samp{source} command).
5109 In addition to the source path, @value{GDBN} provides a set of commands
5110 that manage a list of source path substitution rules. A @dfn{substitution
5111 rule} specifies how to rewrite source directories stored in the program's
5112 debug information in case the sources were moved to a different
5113 directory between compilation and debugging. A rule is made of
5114 two strings, the first specifying what needs to be rewritten in
5115 the path, and the second specifying how it should be rewritten.
5116 In @ref{set substitute-path}, we name these two parts @var{from} and
5117 @var{to} respectively. @value{GDBN} does a simple string replacement
5118 of @var{from} with @var{to} at the start of the directory part of the
5119 source file name, and uses that result instead of the original file
5120 name to look up the sources.
5122 Using the previous example, suppose the @file{foo-1.0} tree has been
5123 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
5124 @value{GDBN} to replace @file{/usr/src} in all source path names with
5125 @file{/mnt/cross}. The first lookup will then be
5126 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
5127 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
5128 substitution rule, use the @code{set substitute-path} command
5129 (@pxref{set substitute-path}).
5131 To avoid unexpected substitution results, a rule is applied only if the
5132 @var{from} part of the directory name ends at a directory separator.
5133 For instance, a rule substituting @file{/usr/source} into
5134 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
5135 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
5136 is applied only at the beginning of the directory name, this rule will
5137 not be applied to @file{/root/usr/source/baz.c} either.
5139 In many cases, you can achieve the same result using the @code{directory}
5140 command. However, @code{set substitute-path} can be more efficient in
5141 the case where the sources are organized in a complex tree with multiple
5142 subdirectories. With the @code{directory} command, you need to add each
5143 subdirectory of your project. If you moved the entire tree while
5144 preserving its internal organization, then @code{set substitute-path}
5145 allows you to direct the debugger to all the sources with one single
5148 @code{set substitute-path} is also more than just a shortcut command.
5149 The source path is only used if the file at the original location no
5150 longer exists. On the other hand, @code{set substitute-path} modifies
5151 the debugger behavior to look at the rewritten location instead. So, if
5152 for any reason a source file that is not relevant to your executable is
5153 located at the original location, a substitution rule is the only
5154 method available to point @value{GDBN} at the new location.
5157 @item directory @var{dirname} @dots{}
5158 @item dir @var{dirname} @dots{}
5159 Add directory @var{dirname} to the front of the source path. Several
5160 directory names may be given to this command, separated by @samp{:}
5161 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
5162 part of absolute file names) or
5163 whitespace. You may specify a directory that is already in the source
5164 path; this moves it forward, so @value{GDBN} searches it sooner.
5168 @vindex $cdir@r{, convenience variable}
5169 @vindex $cwd@r{, convenience variable}
5170 @cindex compilation directory
5171 @cindex current directory
5172 @cindex working directory
5173 @cindex directory, current
5174 @cindex directory, compilation
5175 You can use the string @samp{$cdir} to refer to the compilation
5176 directory (if one is recorded), and @samp{$cwd} to refer to the current
5177 working directory. @samp{$cwd} is not the same as @samp{.}---the former
5178 tracks the current working directory as it changes during your @value{GDBN}
5179 session, while the latter is immediately expanded to the current
5180 directory at the time you add an entry to the source path.
5183 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
5185 @c RET-repeat for @code{directory} is explicitly disabled, but since
5186 @c repeating it would be a no-op we do not say that. (thanks to RMS)
5188 @item show directories
5189 @kindex show directories
5190 Print the source path: show which directories it contains.
5192 @anchor{set substitute-path}
5193 @item set substitute-path @var{from} @var{to}
5194 @kindex set substitute-path
5195 Define a source path substitution rule, and add it at the end of the
5196 current list of existing substitution rules. If a rule with the same
5197 @var{from} was already defined, then the old rule is also deleted.
5199 For example, if the file @file{/foo/bar/baz.c} was moved to
5200 @file{/mnt/cross/baz.c}, then the command
5203 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
5207 will tell @value{GDBN} to replace @samp{/usr/src} with
5208 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
5209 @file{baz.c} even though it was moved.
5211 In the case when more than one substitution rule have been defined,
5212 the rules are evaluated one by one in the order where they have been
5213 defined. The first one matching, if any, is selected to perform
5216 For instance, if we had entered the following commands:
5219 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
5220 (@value{GDBP}) set substitute-path /usr/src /mnt/src
5224 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
5225 @file{/mnt/include/defs.h} by using the first rule. However, it would
5226 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
5227 @file{/mnt/src/lib/foo.c}.
5230 @item unset substitute-path [path]
5231 @kindex unset substitute-path
5232 If a path is specified, search the current list of substitution rules
5233 for a rule that would rewrite that path. Delete that rule if found.
5234 A warning is emitted by the debugger if no rule could be found.
5236 If no path is specified, then all substitution rules are deleted.
5238 @item show substitute-path [path]
5239 @kindex show substitute-path
5240 If a path is specified, then print the source path substitution rule
5241 which would rewrite that path, if any.
5243 If no path is specified, then print all existing source path substitution
5248 If your source path is cluttered with directories that are no longer of
5249 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
5250 versions of source. You can correct the situation as follows:
5254 Use @code{directory} with no argument to reset the source path to its default value.
5257 Use @code{directory} with suitable arguments to reinstall the
5258 directories you want in the source path. You can add all the
5259 directories in one command.
5263 @section Source and Machine Code
5264 @cindex source line and its code address
5266 You can use the command @code{info line} to map source lines to program
5267 addresses (and vice versa), and the command @code{disassemble} to display
5268 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
5269 mode, the @code{info line} command causes the arrow to point to the
5270 line specified. Also, @code{info line} prints addresses in symbolic form as
5275 @item info line @var{linespec}
5276 Print the starting and ending addresses of the compiled code for
5277 source line @var{linespec}. You can specify source lines in any of
5278 the ways understood by the @code{list} command (@pxref{List, ,Printing
5282 For example, we can use @code{info line} to discover the location of
5283 the object code for the first line of function
5284 @code{m4_changequote}:
5286 @c FIXME: I think this example should also show the addresses in
5287 @c symbolic form, as they usually would be displayed.
5289 (@value{GDBP}) info line m4_changequote
5290 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
5294 @cindex code address and its source line
5295 We can also inquire (using @code{*@var{addr}} as the form for
5296 @var{linespec}) what source line covers a particular address:
5298 (@value{GDBP}) info line *0x63ff
5299 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
5302 @cindex @code{$_} and @code{info line}
5303 @cindex @code{x} command, default address
5304 @kindex x@r{(examine), and} info line
5305 After @code{info line}, the default address for the @code{x} command
5306 is changed to the starting address of the line, so that @samp{x/i} is
5307 sufficient to begin examining the machine code (@pxref{Memory,
5308 ,Examining Memory}). Also, this address is saved as the value of the
5309 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
5314 @cindex assembly instructions
5315 @cindex instructions, assembly
5316 @cindex machine instructions
5317 @cindex listing machine instructions
5319 This specialized command dumps a range of memory as machine
5320 instructions. The default memory range is the function surrounding the
5321 program counter of the selected frame. A single argument to this
5322 command is a program counter value; @value{GDBN} dumps the function
5323 surrounding this value. Two arguments specify a range of addresses
5324 (first inclusive, second exclusive) to dump.
5327 The following example shows the disassembly of a range of addresses of
5328 HP PA-RISC 2.0 code:
5331 (@value{GDBP}) disas 0x32c4 0x32e4
5332 Dump of assembler code from 0x32c4 to 0x32e4:
5333 0x32c4 <main+204>: addil 0,dp
5334 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
5335 0x32cc <main+212>: ldil 0x3000,r31
5336 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
5337 0x32d4 <main+220>: ldo 0(r31),rp
5338 0x32d8 <main+224>: addil -0x800,dp
5339 0x32dc <main+228>: ldo 0x588(r1),r26
5340 0x32e0 <main+232>: ldil 0x3000,r31
5341 End of assembler dump.
5344 Some architectures have more than one commonly-used set of instruction
5345 mnemonics or other syntax.
5347 For programs that were dynamically linked and use shared libraries,
5348 instructions that call functions or branch to locations in the shared
5349 libraries might show a seemingly bogus location---it's actually a
5350 location of the relocation table. On some architectures, @value{GDBN}
5351 might be able to resolve these to actual function names.
5354 @kindex set disassembly-flavor
5355 @cindex Intel disassembly flavor
5356 @cindex AT&T disassembly flavor
5357 @item set disassembly-flavor @var{instruction-set}
5358 Select the instruction set to use when disassembling the
5359 program via the @code{disassemble} or @code{x/i} commands.
5361 Currently this command is only defined for the Intel x86 family. You
5362 can set @var{instruction-set} to either @code{intel} or @code{att}.
5363 The default is @code{att}, the AT&T flavor used by default by Unix
5364 assemblers for x86-based targets.
5366 @kindex show disassembly-flavor
5367 @item show disassembly-flavor
5368 Show the current setting of the disassembly flavor.
5373 @chapter Examining Data
5375 @cindex printing data
5376 @cindex examining data
5379 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
5380 @c document because it is nonstandard... Under Epoch it displays in a
5381 @c different window or something like that.
5382 The usual way to examine data in your program is with the @code{print}
5383 command (abbreviated @code{p}), or its synonym @code{inspect}. It
5384 evaluates and prints the value of an expression of the language your
5385 program is written in (@pxref{Languages, ,Using @value{GDBN} with
5386 Different Languages}).
5389 @item print @var{expr}
5390 @itemx print /@var{f} @var{expr}
5391 @var{expr} is an expression (in the source language). By default the
5392 value of @var{expr} is printed in a format appropriate to its data type;
5393 you can choose a different format by specifying @samp{/@var{f}}, where
5394 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
5398 @itemx print /@var{f}
5399 @cindex reprint the last value
5400 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
5401 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
5402 conveniently inspect the same value in an alternative format.
5405 A more low-level way of examining data is with the @code{x} command.
5406 It examines data in memory at a specified address and prints it in a
5407 specified format. @xref{Memory, ,Examining Memory}.
5409 If you are interested in information about types, or about how the
5410 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
5411 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
5415 * Expressions:: Expressions
5416 * Variables:: Program variables
5417 * Arrays:: Artificial arrays
5418 * Output Formats:: Output formats
5419 * Memory:: Examining memory
5420 * Auto Display:: Automatic display
5421 * Print Settings:: Print settings
5422 * Value History:: Value history
5423 * Convenience Vars:: Convenience variables
5424 * Registers:: Registers
5425 * Floating Point Hardware:: Floating point hardware
5426 * Vector Unit:: Vector Unit
5427 * OS Information:: Auxiliary data provided by operating system
5428 * Memory Region Attributes:: Memory region attributes
5429 * Dump/Restore Files:: Copy between memory and a file
5430 * Core File Generation:: Cause a program dump its core
5431 * Character Sets:: Debugging programs that use a different
5432 character set than GDB does
5433 * Caching Remote Data:: Data caching for remote targets
5437 @section Expressions
5440 @code{print} and many other @value{GDBN} commands accept an expression and
5441 compute its value. Any kind of constant, variable or operator defined
5442 by the programming language you are using is valid in an expression in
5443 @value{GDBN}. This includes conditional expressions, function calls,
5444 casts, and string constants. It also includes preprocessor macros, if
5445 you compiled your program to include this information; see
5448 @cindex arrays in expressions
5449 @value{GDBN} supports array constants in expressions input by
5450 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
5451 you can use the command @code{print @{1, 2, 3@}} to build up an array in
5452 memory that is @code{malloc}ed in the target program.
5454 Because C is so widespread, most of the expressions shown in examples in
5455 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
5456 Languages}, for information on how to use expressions in other
5459 In this section, we discuss operators that you can use in @value{GDBN}
5460 expressions regardless of your programming language.
5462 @cindex casts, in expressions
5463 Casts are supported in all languages, not just in C, because it is so
5464 useful to cast a number into a pointer in order to examine a structure
5465 at that address in memory.
5466 @c FIXME: casts supported---Mod2 true?
5468 @value{GDBN} supports these operators, in addition to those common
5469 to programming languages:
5473 @samp{@@} is a binary operator for treating parts of memory as arrays.
5474 @xref{Arrays, ,Artificial Arrays}, for more information.
5477 @samp{::} allows you to specify a variable in terms of the file or
5478 function where it is defined. @xref{Variables, ,Program Variables}.
5480 @cindex @{@var{type}@}
5481 @cindex type casting memory
5482 @cindex memory, viewing as typed object
5483 @cindex casts, to view memory
5484 @item @{@var{type}@} @var{addr}
5485 Refers to an object of type @var{type} stored at address @var{addr} in
5486 memory. @var{addr} may be any expression whose value is an integer or
5487 pointer (but parentheses are required around binary operators, just as in
5488 a cast). This construct is allowed regardless of what kind of data is
5489 normally supposed to reside at @var{addr}.
5493 @section Program Variables
5495 The most common kind of expression to use is the name of a variable
5498 Variables in expressions are understood in the selected stack frame
5499 (@pxref{Selection, ,Selecting a Frame}); they must be either:
5503 global (or file-static)
5510 visible according to the scope rules of the
5511 programming language from the point of execution in that frame
5514 @noindent This means that in the function
5529 you can examine and use the variable @code{a} whenever your program is
5530 executing within the function @code{foo}, but you can only use or
5531 examine the variable @code{b} while your program is executing inside
5532 the block where @code{b} is declared.
5534 @cindex variable name conflict
5535 There is an exception: you can refer to a variable or function whose
5536 scope is a single source file even if the current execution point is not
5537 in this file. But it is possible to have more than one such variable or
5538 function with the same name (in different source files). If that
5539 happens, referring to that name has unpredictable effects. If you wish,
5540 you can specify a static variable in a particular function or file,
5541 using the colon-colon (@code{::}) notation:
5543 @cindex colon-colon, context for variables/functions
5545 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
5546 @cindex @code{::}, context for variables/functions
5549 @var{file}::@var{variable}
5550 @var{function}::@var{variable}
5554 Here @var{file} or @var{function} is the name of the context for the
5555 static @var{variable}. In the case of file names, you can use quotes to
5556 make sure @value{GDBN} parses the file name as a single word---for example,
5557 to print a global value of @code{x} defined in @file{f2.c}:
5560 (@value{GDBP}) p 'f2.c'::x
5563 @cindex C@t{++} scope resolution
5564 This use of @samp{::} is very rarely in conflict with the very similar
5565 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
5566 scope resolution operator in @value{GDBN} expressions.
5567 @c FIXME: Um, so what happens in one of those rare cases where it's in
5570 @cindex wrong values
5571 @cindex variable values, wrong
5572 @cindex function entry/exit, wrong values of variables
5573 @cindex optimized code, wrong values of variables
5575 @emph{Warning:} Occasionally, a local variable may appear to have the
5576 wrong value at certain points in a function---just after entry to a new
5577 scope, and just before exit.
5579 You may see this problem when you are stepping by machine instructions.
5580 This is because, on most machines, it takes more than one instruction to
5581 set up a stack frame (including local variable definitions); if you are
5582 stepping by machine instructions, variables may appear to have the wrong
5583 values until the stack frame is completely built. On exit, it usually
5584 also takes more than one machine instruction to destroy a stack frame;
5585 after you begin stepping through that group of instructions, local
5586 variable definitions may be gone.
5588 This may also happen when the compiler does significant optimizations.
5589 To be sure of always seeing accurate values, turn off all optimization
5592 @cindex ``No symbol "foo" in current context''
5593 Another possible effect of compiler optimizations is to optimize
5594 unused variables out of existence, or assign variables to registers (as
5595 opposed to memory addresses). Depending on the support for such cases
5596 offered by the debug info format used by the compiler, @value{GDBN}
5597 might not be able to display values for such local variables. If that
5598 happens, @value{GDBN} will print a message like this:
5601 No symbol "foo" in current context.
5604 To solve such problems, either recompile without optimizations, or use a
5605 different debug info format, if the compiler supports several such
5606 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
5607 usually supports the @option{-gstabs+} option. @option{-gstabs+}
5608 produces debug info in a format that is superior to formats such as
5609 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
5610 an effective form for debug info. @xref{Debugging Options,,Options
5611 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
5612 Compiler Collection (GCC)}.
5613 @xref{C, ,C and C@t{++}}, for more information about debug info formats
5614 that are best suited to C@t{++} programs.
5616 If you ask to print an object whose contents are unknown to
5617 @value{GDBN}, e.g., because its data type is not completely specified
5618 by the debug information, @value{GDBN} will say @samp{<incomplete
5619 type>}. @xref{Symbols, incomplete type}, for more about this.
5621 Strings are identified as arrays of @code{char} values without specified
5622 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
5623 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
5624 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
5625 defines literal string type @code{"char"} as @code{char} without a sign.
5630 signed char var1[] = "A";
5633 You get during debugging
5638 $2 = @{65 'A', 0 '\0'@}
5642 @section Artificial Arrays
5644 @cindex artificial array
5646 @kindex @@@r{, referencing memory as an array}
5647 It is often useful to print out several successive objects of the
5648 same type in memory; a section of an array, or an array of
5649 dynamically determined size for which only a pointer exists in the
5652 You can do this by referring to a contiguous span of memory as an
5653 @dfn{artificial array}, using the binary operator @samp{@@}. The left
5654 operand of @samp{@@} should be the first element of the desired array
5655 and be an individual object. The right operand should be the desired length
5656 of the array. The result is an array value whose elements are all of
5657 the type of the left argument. The first element is actually the left
5658 argument; the second element comes from bytes of memory immediately
5659 following those that hold the first element, and so on. Here is an
5660 example. If a program says
5663 int *array = (int *) malloc (len * sizeof (int));
5667 you can print the contents of @code{array} with
5673 The left operand of @samp{@@} must reside in memory. Array values made
5674 with @samp{@@} in this way behave just like other arrays in terms of
5675 subscripting, and are coerced to pointers when used in expressions.
5676 Artificial arrays most often appear in expressions via the value history
5677 (@pxref{Value History, ,Value History}), after printing one out.
5679 Another way to create an artificial array is to use a cast.
5680 This re-interprets a value as if it were an array.
5681 The value need not be in memory:
5683 (@value{GDBP}) p/x (short[2])0x12345678
5684 $1 = @{0x1234, 0x5678@}
5687 As a convenience, if you leave the array length out (as in
5688 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
5689 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
5691 (@value{GDBP}) p/x (short[])0x12345678
5692 $2 = @{0x1234, 0x5678@}
5695 Sometimes the artificial array mechanism is not quite enough; in
5696 moderately complex data structures, the elements of interest may not
5697 actually be adjacent---for example, if you are interested in the values
5698 of pointers in an array. One useful work-around in this situation is
5699 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
5700 Variables}) as a counter in an expression that prints the first
5701 interesting value, and then repeat that expression via @key{RET}. For
5702 instance, suppose you have an array @code{dtab} of pointers to
5703 structures, and you are interested in the values of a field @code{fv}
5704 in each structure. Here is an example of what you might type:
5714 @node Output Formats
5715 @section Output Formats
5717 @cindex formatted output
5718 @cindex output formats
5719 By default, @value{GDBN} prints a value according to its data type. Sometimes
5720 this is not what you want. For example, you might want to print a number
5721 in hex, or a pointer in decimal. Or you might want to view data in memory
5722 at a certain address as a character string or as an instruction. To do
5723 these things, specify an @dfn{output format} when you print a value.
5725 The simplest use of output formats is to say how to print a value
5726 already computed. This is done by starting the arguments of the
5727 @code{print} command with a slash and a format letter. The format
5728 letters supported are:
5732 Regard the bits of the value as an integer, and print the integer in
5736 Print as integer in signed decimal.
5739 Print as integer in unsigned decimal.
5742 Print as integer in octal.
5745 Print as integer in binary. The letter @samp{t} stands for ``two''.
5746 @footnote{@samp{b} cannot be used because these format letters are also
5747 used with the @code{x} command, where @samp{b} stands for ``byte'';
5748 see @ref{Memory,,Examining Memory}.}
5751 @cindex unknown address, locating
5752 @cindex locate address
5753 Print as an address, both absolute in hexadecimal and as an offset from
5754 the nearest preceding symbol. You can use this format used to discover
5755 where (in what function) an unknown address is located:
5758 (@value{GDBP}) p/a 0x54320
5759 $3 = 0x54320 <_initialize_vx+396>
5763 The command @code{info symbol 0x54320} yields similar results.
5764 @xref{Symbols, info symbol}.
5767 Regard as an integer and print it as a character constant. This
5768 prints both the numerical value and its character representation. The
5769 character representation is replaced with the octal escape @samp{\nnn}
5770 for characters outside the 7-bit @sc{ascii} range.
5773 Regard the bits of the value as a floating point number and print
5774 using typical floating point syntax.
5777 For example, to print the program counter in hex (@pxref{Registers}), type
5784 Note that no space is required before the slash; this is because command
5785 names in @value{GDBN} cannot contain a slash.
5787 To reprint the last value in the value history with a different format,
5788 you can use the @code{print} command with just a format and no
5789 expression. For example, @samp{p/x} reprints the last value in hex.
5792 @section Examining Memory
5794 You can use the command @code{x} (for ``examine'') to examine memory in
5795 any of several formats, independently of your program's data types.
5797 @cindex examining memory
5799 @kindex x @r{(examine memory)}
5800 @item x/@var{nfu} @var{addr}
5803 Use the @code{x} command to examine memory.
5806 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
5807 much memory to display and how to format it; @var{addr} is an
5808 expression giving the address where you want to start displaying memory.
5809 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
5810 Several commands set convenient defaults for @var{addr}.
5813 @item @var{n}, the repeat count
5814 The repeat count is a decimal integer; the default is 1. It specifies
5815 how much memory (counting by units @var{u}) to display.
5816 @c This really is **decimal**; unaffected by 'set radix' as of GDB
5819 @item @var{f}, the display format
5820 The display format is one of the formats used by @code{print}
5821 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
5822 @samp{f}), and in addition @samp{s} (for null-terminated strings) and
5823 @samp{i} (for machine instructions). The default is @samp{x}
5824 (hexadecimal) initially. The default changes each time you use either
5825 @code{x} or @code{print}.
5827 @item @var{u}, the unit size
5828 The unit size is any of
5834 Halfwords (two bytes).
5836 Words (four bytes). This is the initial default.
5838 Giant words (eight bytes).
5841 Each time you specify a unit size with @code{x}, that size becomes the
5842 default unit the next time you use @code{x}. (For the @samp{s} and
5843 @samp{i} formats, the unit size is ignored and is normally not written.)
5845 @item @var{addr}, starting display address
5846 @var{addr} is the address where you want @value{GDBN} to begin displaying
5847 memory. The expression need not have a pointer value (though it may);
5848 it is always interpreted as an integer address of a byte of memory.
5849 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
5850 @var{addr} is usually just after the last address examined---but several
5851 other commands also set the default address: @code{info breakpoints} (to
5852 the address of the last breakpoint listed), @code{info line} (to the
5853 starting address of a line), and @code{print} (if you use it to display
5854 a value from memory).
5857 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
5858 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
5859 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
5860 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
5861 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
5863 Since the letters indicating unit sizes are all distinct from the
5864 letters specifying output formats, you do not have to remember whether
5865 unit size or format comes first; either order works. The output
5866 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
5867 (However, the count @var{n} must come first; @samp{wx4} does not work.)
5869 Even though the unit size @var{u} is ignored for the formats @samp{s}
5870 and @samp{i}, you might still want to use a count @var{n}; for example,
5871 @samp{3i} specifies that you want to see three machine instructions,
5872 including any operands. For convenience, especially when used with
5873 the @code{display} command, the @samp{i} format also prints branch delay
5874 slot instructions, if any, beyond the count specified, which immediately
5875 follow the last instruction that is within the count. The command
5876 @code{disassemble} gives an alternative way of inspecting machine
5877 instructions; see @ref{Machine Code,,Source and Machine Code}.
5879 All the defaults for the arguments to @code{x} are designed to make it
5880 easy to continue scanning memory with minimal specifications each time
5881 you use @code{x}. For example, after you have inspected three machine
5882 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
5883 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
5884 the repeat count @var{n} is used again; the other arguments default as
5885 for successive uses of @code{x}.
5887 @cindex @code{$_}, @code{$__}, and value history
5888 The addresses and contents printed by the @code{x} command are not saved
5889 in the value history because there is often too much of them and they
5890 would get in the way. Instead, @value{GDBN} makes these values available for
5891 subsequent use in expressions as values of the convenience variables
5892 @code{$_} and @code{$__}. After an @code{x} command, the last address
5893 examined is available for use in expressions in the convenience variable
5894 @code{$_}. The contents of that address, as examined, are available in
5895 the convenience variable @code{$__}.
5897 If the @code{x} command has a repeat count, the address and contents saved
5898 are from the last memory unit printed; this is not the same as the last
5899 address printed if several units were printed on the last line of output.
5901 @cindex remote memory comparison
5902 @cindex verify remote memory image
5903 When you are debugging a program running on a remote target machine
5904 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
5905 remote machine's memory against the executable file you downloaded to
5906 the target. The @code{compare-sections} command is provided for such
5910 @kindex compare-sections
5911 @item compare-sections @r{[}@var{section-name}@r{]}
5912 Compare the data of a loadable section @var{section-name} in the
5913 executable file of the program being debugged with the same section in
5914 the remote machine's memory, and report any mismatches. With no
5915 arguments, compares all loadable sections. This command's
5916 availability depends on the target's support for the @code{"qCRC"}
5921 @section Automatic Display
5922 @cindex automatic display
5923 @cindex display of expressions
5925 If you find that you want to print the value of an expression frequently
5926 (to see how it changes), you might want to add it to the @dfn{automatic
5927 display list} so that @value{GDBN} prints its value each time your program stops.
5928 Each expression added to the list is given a number to identify it;
5929 to remove an expression from the list, you specify that number.
5930 The automatic display looks like this:
5934 3: bar[5] = (struct hack *) 0x3804
5938 This display shows item numbers, expressions and their current values. As with
5939 displays you request manually using @code{x} or @code{print}, you can
5940 specify the output format you prefer; in fact, @code{display} decides
5941 whether to use @code{print} or @code{x} depending on how elaborate your
5942 format specification is---it uses @code{x} if you specify a unit size,
5943 or one of the two formats (@samp{i} and @samp{s}) that are only
5944 supported by @code{x}; otherwise it uses @code{print}.
5948 @item display @var{expr}
5949 Add the expression @var{expr} to the list of expressions to display
5950 each time your program stops. @xref{Expressions, ,Expressions}.
5952 @code{display} does not repeat if you press @key{RET} again after using it.
5954 @item display/@var{fmt} @var{expr}
5955 For @var{fmt} specifying only a display format and not a size or
5956 count, add the expression @var{expr} to the auto-display list but
5957 arrange to display it each time in the specified format @var{fmt}.
5958 @xref{Output Formats,,Output Formats}.
5960 @item display/@var{fmt} @var{addr}
5961 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
5962 number of units, add the expression @var{addr} as a memory address to
5963 be examined each time your program stops. Examining means in effect
5964 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
5967 For example, @samp{display/i $pc} can be helpful, to see the machine
5968 instruction about to be executed each time execution stops (@samp{$pc}
5969 is a common name for the program counter; @pxref{Registers, ,Registers}).
5972 @kindex delete display
5974 @item undisplay @var{dnums}@dots{}
5975 @itemx delete display @var{dnums}@dots{}
5976 Remove item numbers @var{dnums} from the list of expressions to display.
5978 @code{undisplay} does not repeat if you press @key{RET} after using it.
5979 (Otherwise you would just get the error @samp{No display number @dots{}}.)
5981 @kindex disable display
5982 @item disable display @var{dnums}@dots{}
5983 Disable the display of item numbers @var{dnums}. A disabled display
5984 item is not printed automatically, but is not forgotten. It may be
5985 enabled again later.
5987 @kindex enable display
5988 @item enable display @var{dnums}@dots{}
5989 Enable display of item numbers @var{dnums}. It becomes effective once
5990 again in auto display of its expression, until you specify otherwise.
5993 Display the current values of the expressions on the list, just as is
5994 done when your program stops.
5996 @kindex info display
5998 Print the list of expressions previously set up to display
5999 automatically, each one with its item number, but without showing the
6000 values. This includes disabled expressions, which are marked as such.
6001 It also includes expressions which would not be displayed right now
6002 because they refer to automatic variables not currently available.
6005 @cindex display disabled out of scope
6006 If a display expression refers to local variables, then it does not make
6007 sense outside the lexical context for which it was set up. Such an
6008 expression is disabled when execution enters a context where one of its
6009 variables is not defined. For example, if you give the command
6010 @code{display last_char} while inside a function with an argument
6011 @code{last_char}, @value{GDBN} displays this argument while your program
6012 continues to stop inside that function. When it stops elsewhere---where
6013 there is no variable @code{last_char}---the display is disabled
6014 automatically. The next time your program stops where @code{last_char}
6015 is meaningful, you can enable the display expression once again.
6017 @node Print Settings
6018 @section Print Settings
6020 @cindex format options
6021 @cindex print settings
6022 @value{GDBN} provides the following ways to control how arrays, structures,
6023 and symbols are printed.
6026 These settings are useful for debugging programs in any language:
6030 @item set print address
6031 @itemx set print address on
6032 @cindex print/don't print memory addresses
6033 @value{GDBN} prints memory addresses showing the location of stack
6034 traces, structure values, pointer values, breakpoints, and so forth,
6035 even when it also displays the contents of those addresses. The default
6036 is @code{on}. For example, this is what a stack frame display looks like with
6037 @code{set print address on}:
6042 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
6044 530 if (lquote != def_lquote)
6048 @item set print address off
6049 Do not print addresses when displaying their contents. For example,
6050 this is the same stack frame displayed with @code{set print address off}:
6054 (@value{GDBP}) set print addr off
6056 #0 set_quotes (lq="<<", rq=">>") at input.c:530
6057 530 if (lquote != def_lquote)
6061 You can use @samp{set print address off} to eliminate all machine
6062 dependent displays from the @value{GDBN} interface. For example, with
6063 @code{print address off}, you should get the same text for backtraces on
6064 all machines---whether or not they involve pointer arguments.
6067 @item show print address
6068 Show whether or not addresses are to be printed.
6071 When @value{GDBN} prints a symbolic address, it normally prints the
6072 closest earlier symbol plus an offset. If that symbol does not uniquely
6073 identify the address (for example, it is a name whose scope is a single
6074 source file), you may need to clarify. One way to do this is with
6075 @code{info line}, for example @samp{info line *0x4537}. Alternately,
6076 you can set @value{GDBN} to print the source file and line number when
6077 it prints a symbolic address:
6080 @item set print symbol-filename on
6081 @cindex source file and line of a symbol
6082 @cindex symbol, source file and line
6083 Tell @value{GDBN} to print the source file name and line number of a
6084 symbol in the symbolic form of an address.
6086 @item set print symbol-filename off
6087 Do not print source file name and line number of a symbol. This is the
6090 @item show print symbol-filename
6091 Show whether or not @value{GDBN} will print the source file name and
6092 line number of a symbol in the symbolic form of an address.
6095 Another situation where it is helpful to show symbol filenames and line
6096 numbers is when disassembling code; @value{GDBN} shows you the line
6097 number and source file that corresponds to each instruction.
6099 Also, you may wish to see the symbolic form only if the address being
6100 printed is reasonably close to the closest earlier symbol:
6103 @item set print max-symbolic-offset @var{max-offset}
6104 @cindex maximum value for offset of closest symbol
6105 Tell @value{GDBN} to only display the symbolic form of an address if the
6106 offset between the closest earlier symbol and the address is less than
6107 @var{max-offset}. The default is 0, which tells @value{GDBN}
6108 to always print the symbolic form of an address if any symbol precedes it.
6110 @item show print max-symbolic-offset
6111 Ask how large the maximum offset is that @value{GDBN} prints in a
6115 @cindex wild pointer, interpreting
6116 @cindex pointer, finding referent
6117 If you have a pointer and you are not sure where it points, try
6118 @samp{set print symbol-filename on}. Then you can determine the name
6119 and source file location of the variable where it points, using
6120 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
6121 For example, here @value{GDBN} shows that a variable @code{ptt} points
6122 at another variable @code{t}, defined in @file{hi2.c}:
6125 (@value{GDBP}) set print symbol-filename on
6126 (@value{GDBP}) p/a ptt
6127 $4 = 0xe008 <t in hi2.c>
6131 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
6132 does not show the symbol name and filename of the referent, even with
6133 the appropriate @code{set print} options turned on.
6136 Other settings control how different kinds of objects are printed:
6139 @item set print array
6140 @itemx set print array on
6141 @cindex pretty print arrays
6142 Pretty print arrays. This format is more convenient to read,
6143 but uses more space. The default is off.
6145 @item set print array off
6146 Return to compressed format for arrays.
6148 @item show print array
6149 Show whether compressed or pretty format is selected for displaying
6152 @cindex print array indexes
6153 @item set print array-indexes
6154 @itemx set print array-indexes on
6155 Print the index of each element when displaying arrays. May be more
6156 convenient to locate a given element in the array or quickly find the
6157 index of a given element in that printed array. The default is off.
6159 @item set print array-indexes off
6160 Stop printing element indexes when displaying arrays.
6162 @item show print array-indexes
6163 Show whether the index of each element is printed when displaying
6166 @item set print elements @var{number-of-elements}
6167 @cindex number of array elements to print
6168 @cindex limit on number of printed array elements
6169 Set a limit on how many elements of an array @value{GDBN} will print.
6170 If @value{GDBN} is printing a large array, it stops printing after it has
6171 printed the number of elements set by the @code{set print elements} command.
6172 This limit also applies to the display of strings.
6173 When @value{GDBN} starts, this limit is set to 200.
6174 Setting @var{number-of-elements} to zero means that the printing is unlimited.
6176 @item show print elements
6177 Display the number of elements of a large array that @value{GDBN} will print.
6178 If the number is 0, then the printing is unlimited.
6180 @item set print repeats
6181 @cindex repeated array elements
6182 Set the threshold for suppressing display of repeated array
6183 elements. When the number of consecutive identical elements of an
6184 array exceeds the threshold, @value{GDBN} prints the string
6185 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
6186 identical repetitions, instead of displaying the identical elements
6187 themselves. Setting the threshold to zero will cause all elements to
6188 be individually printed. The default threshold is 10.
6190 @item show print repeats
6191 Display the current threshold for printing repeated identical
6194 @item set print null-stop
6195 @cindex @sc{null} elements in arrays
6196 Cause @value{GDBN} to stop printing the characters of an array when the first
6197 @sc{null} is encountered. This is useful when large arrays actually
6198 contain only short strings.
6201 @item show print null-stop
6202 Show whether @value{GDBN} stops printing an array on the first
6203 @sc{null} character.
6205 @item set print pretty on
6206 @cindex print structures in indented form
6207 @cindex indentation in structure display
6208 Cause @value{GDBN} to print structures in an indented format with one member
6209 per line, like this:
6224 @item set print pretty off
6225 Cause @value{GDBN} to print structures in a compact format, like this:
6229 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
6230 meat = 0x54 "Pork"@}
6235 This is the default format.
6237 @item show print pretty
6238 Show which format @value{GDBN} is using to print structures.
6240 @item set print sevenbit-strings on
6241 @cindex eight-bit characters in strings
6242 @cindex octal escapes in strings
6243 Print using only seven-bit characters; if this option is set,
6244 @value{GDBN} displays any eight-bit characters (in strings or
6245 character values) using the notation @code{\}@var{nnn}. This setting is
6246 best if you are working in English (@sc{ascii}) and you use the
6247 high-order bit of characters as a marker or ``meta'' bit.
6249 @item set print sevenbit-strings off
6250 Print full eight-bit characters. This allows the use of more
6251 international character sets, and is the default.
6253 @item show print sevenbit-strings
6254 Show whether or not @value{GDBN} is printing only seven-bit characters.
6256 @item set print union on
6257 @cindex unions in structures, printing
6258 Tell @value{GDBN} to print unions which are contained in structures
6259 and other unions. This is the default setting.
6261 @item set print union off
6262 Tell @value{GDBN} not to print unions which are contained in
6263 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
6266 @item show print union
6267 Ask @value{GDBN} whether or not it will print unions which are contained in
6268 structures and other unions.
6270 For example, given the declarations
6273 typedef enum @{Tree, Bug@} Species;
6274 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
6275 typedef enum @{Caterpillar, Cocoon, Butterfly@}
6286 struct thing foo = @{Tree, @{Acorn@}@};
6290 with @code{set print union on} in effect @samp{p foo} would print
6293 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
6297 and with @code{set print union off} in effect it would print
6300 $1 = @{it = Tree, form = @{...@}@}
6304 @code{set print union} affects programs written in C-like languages
6310 These settings are of interest when debugging C@t{++} programs:
6313 @cindex demangling C@t{++} names
6314 @item set print demangle
6315 @itemx set print demangle on
6316 Print C@t{++} names in their source form rather than in the encoded
6317 (``mangled'') form passed to the assembler and linker for type-safe
6318 linkage. The default is on.
6320 @item show print demangle
6321 Show whether C@t{++} names are printed in mangled or demangled form.
6323 @item set print asm-demangle
6324 @itemx set print asm-demangle on
6325 Print C@t{++} names in their source form rather than their mangled form, even
6326 in assembler code printouts such as instruction disassemblies.
6329 @item show print asm-demangle
6330 Show whether C@t{++} names in assembly listings are printed in mangled
6333 @cindex C@t{++} symbol decoding style
6334 @cindex symbol decoding style, C@t{++}
6335 @kindex set demangle-style
6336 @item set demangle-style @var{style}
6337 Choose among several encoding schemes used by different compilers to
6338 represent C@t{++} names. The choices for @var{style} are currently:
6342 Allow @value{GDBN} to choose a decoding style by inspecting your program.
6345 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
6346 This is the default.
6349 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
6352 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
6355 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
6356 @strong{Warning:} this setting alone is not sufficient to allow
6357 debugging @code{cfront}-generated executables. @value{GDBN} would
6358 require further enhancement to permit that.
6361 If you omit @var{style}, you will see a list of possible formats.
6363 @item show demangle-style
6364 Display the encoding style currently in use for decoding C@t{++} symbols.
6366 @item set print object
6367 @itemx set print object on
6368 @cindex derived type of an object, printing
6369 @cindex display derived types
6370 When displaying a pointer to an object, identify the @emph{actual}
6371 (derived) type of the object rather than the @emph{declared} type, using
6372 the virtual function table.
6374 @item set print object off
6375 Display only the declared type of objects, without reference to the
6376 virtual function table. This is the default setting.
6378 @item show print object
6379 Show whether actual, or declared, object types are displayed.
6381 @item set print static-members
6382 @itemx set print static-members on
6383 @cindex static members of C@t{++} objects
6384 Print static members when displaying a C@t{++} object. The default is on.
6386 @item set print static-members off
6387 Do not print static members when displaying a C@t{++} object.
6389 @item show print static-members
6390 Show whether C@t{++} static members are printed or not.
6392 @item set print pascal_static-members
6393 @itemx set print pascal_static-members on
6394 @cindex static members of Pascal objects
6395 @cindex Pascal objects, static members display
6396 Print static members when displaying a Pascal object. The default is on.
6398 @item set print pascal_static-members off
6399 Do not print static members when displaying a Pascal object.
6401 @item show print pascal_static-members
6402 Show whether Pascal static members are printed or not.
6404 @c These don't work with HP ANSI C++ yet.
6405 @item set print vtbl
6406 @itemx set print vtbl on
6407 @cindex pretty print C@t{++} virtual function tables
6408 @cindex virtual functions (C@t{++}) display
6409 @cindex VTBL display
6410 Pretty print C@t{++} virtual function tables. The default is off.
6411 (The @code{vtbl} commands do not work on programs compiled with the HP
6412 ANSI C@t{++} compiler (@code{aCC}).)
6414 @item set print vtbl off
6415 Do not pretty print C@t{++} virtual function tables.
6417 @item show print vtbl
6418 Show whether C@t{++} virtual function tables are pretty printed, or not.
6422 @section Value History
6424 @cindex value history
6425 @cindex history of values printed by @value{GDBN}
6426 Values printed by the @code{print} command are saved in the @value{GDBN}
6427 @dfn{value history}. This allows you to refer to them in other expressions.
6428 Values are kept until the symbol table is re-read or discarded
6429 (for example with the @code{file} or @code{symbol-file} commands).
6430 When the symbol table changes, the value history is discarded,
6431 since the values may contain pointers back to the types defined in the
6436 @cindex history number
6437 The values printed are given @dfn{history numbers} by which you can
6438 refer to them. These are successive integers starting with one.
6439 @code{print} shows you the history number assigned to a value by
6440 printing @samp{$@var{num} = } before the value; here @var{num} is the
6443 To refer to any previous value, use @samp{$} followed by the value's
6444 history number. The way @code{print} labels its output is designed to
6445 remind you of this. Just @code{$} refers to the most recent value in
6446 the history, and @code{$$} refers to the value before that.
6447 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
6448 is the value just prior to @code{$$}, @code{$$1} is equivalent to
6449 @code{$$}, and @code{$$0} is equivalent to @code{$}.
6451 For example, suppose you have just printed a pointer to a structure and
6452 want to see the contents of the structure. It suffices to type
6458 If you have a chain of structures where the component @code{next} points
6459 to the next one, you can print the contents of the next one with this:
6466 You can print successive links in the chain by repeating this
6467 command---which you can do by just typing @key{RET}.
6469 Note that the history records values, not expressions. If the value of
6470 @code{x} is 4 and you type these commands:
6478 then the value recorded in the value history by the @code{print} command
6479 remains 4 even though the value of @code{x} has changed.
6484 Print the last ten values in the value history, with their item numbers.
6485 This is like @samp{p@ $$9} repeated ten times, except that @code{show
6486 values} does not change the history.
6488 @item show values @var{n}
6489 Print ten history values centered on history item number @var{n}.
6492 Print ten history values just after the values last printed. If no more
6493 values are available, @code{show values +} produces no display.
6496 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
6497 same effect as @samp{show values +}.
6499 @node Convenience Vars
6500 @section Convenience Variables
6502 @cindex convenience variables
6503 @cindex user-defined variables
6504 @value{GDBN} provides @dfn{convenience variables} that you can use within
6505 @value{GDBN} to hold on to a value and refer to it later. These variables
6506 exist entirely within @value{GDBN}; they are not part of your program, and
6507 setting a convenience variable has no direct effect on further execution
6508 of your program. That is why you can use them freely.
6510 Convenience variables are prefixed with @samp{$}. Any name preceded by
6511 @samp{$} can be used for a convenience variable, unless it is one of
6512 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
6513 (Value history references, in contrast, are @emph{numbers} preceded
6514 by @samp{$}. @xref{Value History, ,Value History}.)
6516 You can save a value in a convenience variable with an assignment
6517 expression, just as you would set a variable in your program.
6521 set $foo = *object_ptr
6525 would save in @code{$foo} the value contained in the object pointed to by
6528 Using a convenience variable for the first time creates it, but its
6529 value is @code{void} until you assign a new value. You can alter the
6530 value with another assignment at any time.
6532 Convenience variables have no fixed types. You can assign a convenience
6533 variable any type of value, including structures and arrays, even if
6534 that variable already has a value of a different type. The convenience
6535 variable, when used as an expression, has the type of its current value.
6538 @kindex show convenience
6539 @cindex show all user variables
6540 @item show convenience
6541 Print a list of convenience variables used so far, and their values.
6542 Abbreviated @code{show conv}.
6544 @kindex init-if-undefined
6545 @cindex convenience variables, initializing
6546 @item init-if-undefined $@var{variable} = @var{expression}
6547 Set a convenience variable if it has not already been set. This is useful
6548 for user-defined commands that keep some state. It is similar, in concept,
6549 to using local static variables with initializers in C (except that
6550 convenience variables are global). It can also be used to allow users to
6551 override default values used in a command script.
6553 If the variable is already defined then the expression is not evaluated so
6554 any side-effects do not occur.
6557 One of the ways to use a convenience variable is as a counter to be
6558 incremented or a pointer to be advanced. For example, to print
6559 a field from successive elements of an array of structures:
6563 print bar[$i++]->contents
6567 Repeat that command by typing @key{RET}.
6569 Some convenience variables are created automatically by @value{GDBN} and given
6570 values likely to be useful.
6573 @vindex $_@r{, convenience variable}
6575 The variable @code{$_} is automatically set by the @code{x} command to
6576 the last address examined (@pxref{Memory, ,Examining Memory}). Other
6577 commands which provide a default address for @code{x} to examine also
6578 set @code{$_} to that address; these commands include @code{info line}
6579 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
6580 except when set by the @code{x} command, in which case it is a pointer
6581 to the type of @code{$__}.
6583 @vindex $__@r{, convenience variable}
6585 The variable @code{$__} is automatically set by the @code{x} command
6586 to the value found in the last address examined. Its type is chosen
6587 to match the format in which the data was printed.
6590 @vindex $_exitcode@r{, convenience variable}
6591 The variable @code{$_exitcode} is automatically set to the exit code when
6592 the program being debugged terminates.
6595 On HP-UX systems, if you refer to a function or variable name that
6596 begins with a dollar sign, @value{GDBN} searches for a user or system
6597 name first, before it searches for a convenience variable.
6603 You can refer to machine register contents, in expressions, as variables
6604 with names starting with @samp{$}. The names of registers are different
6605 for each machine; use @code{info registers} to see the names used on
6609 @kindex info registers
6610 @item info registers
6611 Print the names and values of all registers except floating-point
6612 and vector registers (in the selected stack frame).
6614 @kindex info all-registers
6615 @cindex floating point registers
6616 @item info all-registers
6617 Print the names and values of all registers, including floating-point
6618 and vector registers (in the selected stack frame).
6620 @item info registers @var{regname} @dots{}
6621 Print the @dfn{relativized} value of each specified register @var{regname}.
6622 As discussed in detail below, register values are normally relative to
6623 the selected stack frame. @var{regname} may be any register name valid on
6624 the machine you are using, with or without the initial @samp{$}.
6627 @cindex stack pointer register
6628 @cindex program counter register
6629 @cindex process status register
6630 @cindex frame pointer register
6631 @cindex standard registers
6632 @value{GDBN} has four ``standard'' register names that are available (in
6633 expressions) on most machines---whenever they do not conflict with an
6634 architecture's canonical mnemonics for registers. The register names
6635 @code{$pc} and @code{$sp} are used for the program counter register and
6636 the stack pointer. @code{$fp} is used for a register that contains a
6637 pointer to the current stack frame, and @code{$ps} is used for a
6638 register that contains the processor status. For example,
6639 you could print the program counter in hex with
6646 or print the instruction to be executed next with
6653 or add four to the stack pointer@footnote{This is a way of removing
6654 one word from the stack, on machines where stacks grow downward in
6655 memory (most machines, nowadays). This assumes that the innermost
6656 stack frame is selected; setting @code{$sp} is not allowed when other
6657 stack frames are selected. To pop entire frames off the stack,
6658 regardless of machine architecture, use @code{return};
6659 see @ref{Returning, ,Returning from a Function}.} with
6665 Whenever possible, these four standard register names are available on
6666 your machine even though the machine has different canonical mnemonics,
6667 so long as there is no conflict. The @code{info registers} command
6668 shows the canonical names. For example, on the SPARC, @code{info
6669 registers} displays the processor status register as @code{$psr} but you
6670 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
6671 is an alias for the @sc{eflags} register.
6673 @value{GDBN} always considers the contents of an ordinary register as an
6674 integer when the register is examined in this way. Some machines have
6675 special registers which can hold nothing but floating point; these
6676 registers are considered to have floating point values. There is no way
6677 to refer to the contents of an ordinary register as floating point value
6678 (although you can @emph{print} it as a floating point value with
6679 @samp{print/f $@var{regname}}).
6681 Some registers have distinct ``raw'' and ``virtual'' data formats. This
6682 means that the data format in which the register contents are saved by
6683 the operating system is not the same one that your program normally
6684 sees. For example, the registers of the 68881 floating point
6685 coprocessor are always saved in ``extended'' (raw) format, but all C
6686 programs expect to work with ``double'' (virtual) format. In such
6687 cases, @value{GDBN} normally works with the virtual format only (the format
6688 that makes sense for your program), but the @code{info registers} command
6689 prints the data in both formats.
6691 @cindex SSE registers (x86)
6692 @cindex MMX registers (x86)
6693 Some machines have special registers whose contents can be interpreted
6694 in several different ways. For example, modern x86-based machines
6695 have SSE and MMX registers that can hold several values packed
6696 together in several different formats. @value{GDBN} refers to such
6697 registers in @code{struct} notation:
6700 (@value{GDBP}) print $xmm1
6702 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
6703 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
6704 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
6705 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
6706 v4_int32 = @{0, 20657912, 11, 13@},
6707 v2_int64 = @{88725056443645952, 55834574859@},
6708 uint128 = 0x0000000d0000000b013b36f800000000
6713 To set values of such registers, you need to tell @value{GDBN} which
6714 view of the register you wish to change, as if you were assigning
6715 value to a @code{struct} member:
6718 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
6721 Normally, register values are relative to the selected stack frame
6722 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
6723 value that the register would contain if all stack frames farther in
6724 were exited and their saved registers restored. In order to see the
6725 true contents of hardware registers, you must select the innermost
6726 frame (with @samp{frame 0}).
6728 However, @value{GDBN} must deduce where registers are saved, from the machine
6729 code generated by your compiler. If some registers are not saved, or if
6730 @value{GDBN} is unable to locate the saved registers, the selected stack
6731 frame makes no difference.
6733 @node Floating Point Hardware
6734 @section Floating Point Hardware
6735 @cindex floating point
6737 Depending on the configuration, @value{GDBN} may be able to give
6738 you more information about the status of the floating point hardware.
6743 Display hardware-dependent information about the floating
6744 point unit. The exact contents and layout vary depending on the
6745 floating point chip. Currently, @samp{info float} is supported on
6746 the ARM and x86 machines.
6750 @section Vector Unit
6753 Depending on the configuration, @value{GDBN} may be able to give you
6754 more information about the status of the vector unit.
6759 Display information about the vector unit. The exact contents and
6760 layout vary depending on the hardware.
6763 @node OS Information
6764 @section Operating System Auxiliary Information
6765 @cindex OS information
6767 @value{GDBN} provides interfaces to useful OS facilities that can help
6768 you debug your program.
6770 @cindex @code{ptrace} system call
6771 @cindex @code{struct user} contents
6772 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
6773 machines), it interfaces with the inferior via the @code{ptrace}
6774 system call. The operating system creates a special sata structure,
6775 called @code{struct user}, for this interface. You can use the
6776 command @code{info udot} to display the contents of this data
6782 Display the contents of the @code{struct user} maintained by the OS
6783 kernel for the program being debugged. @value{GDBN} displays the
6784 contents of @code{struct user} as a list of hex numbers, similar to
6785 the @code{examine} command.
6788 @cindex auxiliary vector
6789 @cindex vector, auxiliary
6790 Some operating systems supply an @dfn{auxiliary vector} to programs at
6791 startup. This is akin to the arguments and environment that you
6792 specify for a program, but contains a system-dependent variety of
6793 binary values that tell system libraries important details about the
6794 hardware, operating system, and process. Each value's purpose is
6795 identified by an integer tag; the meanings are well-known but system-specific.
6796 Depending on the configuration and operating system facilities,
6797 @value{GDBN} may be able to show you this information. For remote
6798 targets, this functionality may further depend on the remote stub's
6799 support of the @samp{qXfer:auxv:read} packet, see
6800 @ref{qXfer auxiliary vector read}.
6805 Display the auxiliary vector of the inferior, which can be either a
6806 live process or a core dump file. @value{GDBN} prints each tag value
6807 numerically, and also shows names and text descriptions for recognized
6808 tags. Some values in the vector are numbers, some bit masks, and some
6809 pointers to strings or other data. @value{GDBN} displays each value in the
6810 most appropriate form for a recognized tag, and in hexadecimal for
6811 an unrecognized tag.
6815 @node Memory Region Attributes
6816 @section Memory Region Attributes
6817 @cindex memory region attributes
6819 @dfn{Memory region attributes} allow you to describe special handling
6820 required by regions of your target's memory. @value{GDBN} uses
6821 attributes to determine whether to allow certain types of memory
6822 accesses; whether to use specific width accesses; and whether to cache
6823 target memory. By default the description of memory regions is
6824 fetched from the target (if the current target supports this), but the
6825 user can override the fetched regions.
6827 Defined memory regions can be individually enabled and disabled. When a
6828 memory region is disabled, @value{GDBN} uses the default attributes when
6829 accessing memory in that region. Similarly, if no memory regions have
6830 been defined, @value{GDBN} uses the default attributes when accessing
6833 When a memory region is defined, it is given a number to identify it;
6834 to enable, disable, or remove a memory region, you specify that number.
6838 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
6839 Define a memory region bounded by @var{lower} and @var{upper} with
6840 attributes @var{attributes}@dots{}, and add it to the list of regions
6841 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
6842 case: it is treated as the target's maximum memory address.
6843 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
6846 Discard any user changes to the memory regions and use target-supplied
6847 regions, if available, or no regions if the target does not support.
6850 @item delete mem @var{nums}@dots{}
6851 Remove memory regions @var{nums}@dots{} from the list of regions
6852 monitored by @value{GDBN}.
6855 @item disable mem @var{nums}@dots{}
6856 Disable monitoring of memory regions @var{nums}@dots{}.
6857 A disabled memory region is not forgotten.
6858 It may be enabled again later.
6861 @item enable mem @var{nums}@dots{}
6862 Enable monitoring of memory regions @var{nums}@dots{}.
6866 Print a table of all defined memory regions, with the following columns
6870 @item Memory Region Number
6871 @item Enabled or Disabled.
6872 Enabled memory regions are marked with @samp{y}.
6873 Disabled memory regions are marked with @samp{n}.
6876 The address defining the inclusive lower bound of the memory region.
6879 The address defining the exclusive upper bound of the memory region.
6882 The list of attributes set for this memory region.
6887 @subsection Attributes
6889 @subsubsection Memory Access Mode
6890 The access mode attributes set whether @value{GDBN} may make read or
6891 write accesses to a memory region.
6893 While these attributes prevent @value{GDBN} from performing invalid
6894 memory accesses, they do nothing to prevent the target system, I/O DMA,
6895 etc.@: from accessing memory.
6899 Memory is read only.
6901 Memory is write only.
6903 Memory is read/write. This is the default.
6906 @subsubsection Memory Access Size
6907 The access size attribute tells @value{GDBN} to use specific sized
6908 accesses in the memory region. Often memory mapped device registers
6909 require specific sized accesses. If no access size attribute is
6910 specified, @value{GDBN} may use accesses of any size.
6914 Use 8 bit memory accesses.
6916 Use 16 bit memory accesses.
6918 Use 32 bit memory accesses.
6920 Use 64 bit memory accesses.
6923 @c @subsubsection Hardware/Software Breakpoints
6924 @c The hardware/software breakpoint attributes set whether @value{GDBN}
6925 @c will use hardware or software breakpoints for the internal breakpoints
6926 @c used by the step, next, finish, until, etc. commands.
6930 @c Always use hardware breakpoints
6931 @c @item swbreak (default)
6934 @subsubsection Data Cache
6935 The data cache attributes set whether @value{GDBN} will cache target
6936 memory. While this generally improves performance by reducing debug
6937 protocol overhead, it can lead to incorrect results because @value{GDBN}
6938 does not know about volatile variables or memory mapped device
6943 Enable @value{GDBN} to cache target memory.
6945 Disable @value{GDBN} from caching target memory. This is the default.
6948 @subsection Memory Access Checking
6949 @value{GDBN} can be instructed to refuse accesses to memory that is
6950 not explicitly described. This can be useful if accessing such
6951 regions has undesired effects for a specific target, or to provide
6952 better error checking. The following commands control this behaviour.
6955 @kindex set mem inaccessible-by-default
6956 @item set mem inaccessible-by-default [on|off]
6957 If @code{on} is specified, make @value{GDBN} treat memory not
6958 explicitly described by the memory ranges as non-existent and refuse accesses
6959 to such memory. The checks are only performed if there's at least one
6960 memory range defined. If @code{off} is specified, make @value{GDBN}
6961 treat the memory not explicitly described by the memory ranges as RAM.
6962 The default value is @code{off}.
6963 @kindex show mem inaccessible-by-default
6964 @item show mem inaccessible-by-default
6965 Show the current handling of accesses to unknown memory.
6969 @c @subsubsection Memory Write Verification
6970 @c The memory write verification attributes set whether @value{GDBN}
6971 @c will re-reads data after each write to verify the write was successful.
6975 @c @item noverify (default)
6978 @node Dump/Restore Files
6979 @section Copy Between Memory and a File
6980 @cindex dump/restore files
6981 @cindex append data to a file
6982 @cindex dump data to a file
6983 @cindex restore data from a file
6985 You can use the commands @code{dump}, @code{append}, and
6986 @code{restore} to copy data between target memory and a file. The
6987 @code{dump} and @code{append} commands write data to a file, and the
6988 @code{restore} command reads data from a file back into the inferior's
6989 memory. Files may be in binary, Motorola S-record, Intel hex, or
6990 Tektronix Hex format; however, @value{GDBN} can only append to binary
6996 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6997 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
6998 Dump the contents of memory from @var{start_addr} to @var{end_addr},
6999 or the value of @var{expr}, to @var{filename} in the given format.
7001 The @var{format} parameter may be any one of:
7008 Motorola S-record format.
7010 Tektronix Hex format.
7013 @value{GDBN} uses the same definitions of these formats as the
7014 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
7015 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
7019 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7020 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
7021 Append the contents of memory from @var{start_addr} to @var{end_addr},
7022 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
7023 (@value{GDBN} can only append data to files in raw binary form.)
7026 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
7027 Restore the contents of file @var{filename} into memory. The
7028 @code{restore} command can automatically recognize any known @sc{bfd}
7029 file format, except for raw binary. To restore a raw binary file you
7030 must specify the optional keyword @code{binary} after the filename.
7032 If @var{bias} is non-zero, its value will be added to the addresses
7033 contained in the file. Binary files always start at address zero, so
7034 they will be restored at address @var{bias}. Other bfd files have
7035 a built-in location; they will be restored at offset @var{bias}
7038 If @var{start} and/or @var{end} are non-zero, then only data between
7039 file offset @var{start} and file offset @var{end} will be restored.
7040 These offsets are relative to the addresses in the file, before
7041 the @var{bias} argument is applied.
7045 @node Core File Generation
7046 @section How to Produce a Core File from Your Program
7047 @cindex dump core from inferior
7049 A @dfn{core file} or @dfn{core dump} is a file that records the memory
7050 image of a running process and its process status (register values
7051 etc.). Its primary use is post-mortem debugging of a program that
7052 crashed while it ran outside a debugger. A program that crashes
7053 automatically produces a core file, unless this feature is disabled by
7054 the user. @xref{Files}, for information on invoking @value{GDBN} in
7055 the post-mortem debugging mode.
7057 Occasionally, you may wish to produce a core file of the program you
7058 are debugging in order to preserve a snapshot of its state.
7059 @value{GDBN} has a special command for that.
7063 @kindex generate-core-file
7064 @item generate-core-file [@var{file}]
7065 @itemx gcore [@var{file}]
7066 Produce a core dump of the inferior process. The optional argument
7067 @var{file} specifies the file name where to put the core dump. If not
7068 specified, the file name defaults to @file{core.@var{pid}}, where
7069 @var{pid} is the inferior process ID.
7071 Note that this command is implemented only for some systems (as of
7072 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
7075 @node Character Sets
7076 @section Character Sets
7077 @cindex character sets
7079 @cindex translating between character sets
7080 @cindex host character set
7081 @cindex target character set
7083 If the program you are debugging uses a different character set to
7084 represent characters and strings than the one @value{GDBN} uses itself,
7085 @value{GDBN} can automatically translate between the character sets for
7086 you. The character set @value{GDBN} uses we call the @dfn{host
7087 character set}; the one the inferior program uses we call the
7088 @dfn{target character set}.
7090 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
7091 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
7092 remote protocol (@pxref{Remote Debugging}) to debug a program
7093 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
7094 then the host character set is Latin-1, and the target character set is
7095 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
7096 target-charset EBCDIC-US}, then @value{GDBN} translates between
7097 @sc{ebcdic} and Latin 1 as you print character or string values, or use
7098 character and string literals in expressions.
7100 @value{GDBN} has no way to automatically recognize which character set
7101 the inferior program uses; you must tell it, using the @code{set
7102 target-charset} command, described below.
7104 Here are the commands for controlling @value{GDBN}'s character set
7108 @item set target-charset @var{charset}
7109 @kindex set target-charset
7110 Set the current target character set to @var{charset}. We list the
7111 character set names @value{GDBN} recognizes below, but if you type
7112 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7113 list the target character sets it supports.
7117 @item set host-charset @var{charset}
7118 @kindex set host-charset
7119 Set the current host character set to @var{charset}.
7121 By default, @value{GDBN} uses a host character set appropriate to the
7122 system it is running on; you can override that default using the
7123 @code{set host-charset} command.
7125 @value{GDBN} can only use certain character sets as its host character
7126 set. We list the character set names @value{GDBN} recognizes below, and
7127 indicate which can be host character sets, but if you type
7128 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7129 list the host character sets it supports.
7131 @item set charset @var{charset}
7133 Set the current host and target character sets to @var{charset}. As
7134 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
7135 @value{GDBN} will list the name of the character sets that can be used
7136 for both host and target.
7140 @kindex show charset
7141 Show the names of the current host and target charsets.
7143 @itemx show host-charset
7144 @kindex show host-charset
7145 Show the name of the current host charset.
7147 @itemx show target-charset
7148 @kindex show target-charset
7149 Show the name of the current target charset.
7153 @value{GDBN} currently includes support for the following character
7159 @cindex ASCII character set
7160 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
7164 @cindex ISO 8859-1 character set
7165 @cindex ISO Latin 1 character set
7166 The ISO Latin 1 character set. This extends @sc{ascii} with accented
7167 characters needed for French, German, and Spanish. @value{GDBN} can use
7168 this as its host character set.
7172 @cindex EBCDIC character set
7173 @cindex IBM1047 character set
7174 Variants of the @sc{ebcdic} character set, used on some of IBM's
7175 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
7176 @value{GDBN} cannot use these as its host character set.
7180 Note that these are all single-byte character sets. More work inside
7181 @value{GDBN} is needed to support multi-byte or variable-width character
7182 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
7184 Here is an example of @value{GDBN}'s character set support in action.
7185 Assume that the following source code has been placed in the file
7186 @file{charset-test.c}:
7192 = @{72, 101, 108, 108, 111, 44, 32, 119,
7193 111, 114, 108, 100, 33, 10, 0@};
7194 char ibm1047_hello[]
7195 = @{200, 133, 147, 147, 150, 107, 64, 166,
7196 150, 153, 147, 132, 90, 37, 0@};
7200 printf ("Hello, world!\n");
7204 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
7205 containing the string @samp{Hello, world!} followed by a newline,
7206 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
7208 We compile the program, and invoke the debugger on it:
7211 $ gcc -g charset-test.c -o charset-test
7212 $ gdb -nw charset-test
7213 GNU gdb 2001-12-19-cvs
7214 Copyright 2001 Free Software Foundation, Inc.
7219 We can use the @code{show charset} command to see what character sets
7220 @value{GDBN} is currently using to interpret and display characters and
7224 (@value{GDBP}) show charset
7225 The current host and target character set is `ISO-8859-1'.
7229 For the sake of printing this manual, let's use @sc{ascii} as our
7230 initial character set:
7232 (@value{GDBP}) set charset ASCII
7233 (@value{GDBP}) show charset
7234 The current host and target character set is `ASCII'.
7238 Let's assume that @sc{ascii} is indeed the correct character set for our
7239 host system --- in other words, let's assume that if @value{GDBN} prints
7240 characters using the @sc{ascii} character set, our terminal will display
7241 them properly. Since our current target character set is also
7242 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
7245 (@value{GDBP}) print ascii_hello
7246 $1 = 0x401698 "Hello, world!\n"
7247 (@value{GDBP}) print ascii_hello[0]
7252 @value{GDBN} uses the target character set for character and string
7253 literals you use in expressions:
7256 (@value{GDBP}) print '+'
7261 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
7264 @value{GDBN} relies on the user to tell it which character set the
7265 target program uses. If we print @code{ibm1047_hello} while our target
7266 character set is still @sc{ascii}, we get jibberish:
7269 (@value{GDBP}) print ibm1047_hello
7270 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
7271 (@value{GDBP}) print ibm1047_hello[0]
7276 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
7277 @value{GDBN} tells us the character sets it supports:
7280 (@value{GDBP}) set target-charset
7281 ASCII EBCDIC-US IBM1047 ISO-8859-1
7282 (@value{GDBP}) set target-charset
7285 We can select @sc{ibm1047} as our target character set, and examine the
7286 program's strings again. Now the @sc{ascii} string is wrong, but
7287 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
7288 target character set, @sc{ibm1047}, to the host character set,
7289 @sc{ascii}, and they display correctly:
7292 (@value{GDBP}) set target-charset IBM1047
7293 (@value{GDBP}) show charset
7294 The current host character set is `ASCII'.
7295 The current target character set is `IBM1047'.
7296 (@value{GDBP}) print ascii_hello
7297 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
7298 (@value{GDBP}) print ascii_hello[0]
7300 (@value{GDBP}) print ibm1047_hello
7301 $8 = 0x4016a8 "Hello, world!\n"
7302 (@value{GDBP}) print ibm1047_hello[0]
7307 As above, @value{GDBN} uses the target character set for character and
7308 string literals you use in expressions:
7311 (@value{GDBP}) print '+'
7316 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
7319 @node Caching Remote Data
7320 @section Caching Data of Remote Targets
7321 @cindex caching data of remote targets
7323 @value{GDBN} can cache data exchanged between the debugger and a
7324 remote target (@pxref{Remote Debugging}). Such caching generally improves
7325 performance, because it reduces the overhead of the remote protocol by
7326 bundling memory reads and writes into large chunks. Unfortunately,
7327 @value{GDBN} does not currently know anything about volatile
7328 registers, and thus data caching will produce incorrect results when
7329 volatile registers are in use.
7332 @kindex set remotecache
7333 @item set remotecache on
7334 @itemx set remotecache off
7335 Set caching state for remote targets. When @code{ON}, use data
7336 caching. By default, this option is @code{OFF}.
7338 @kindex show remotecache
7339 @item show remotecache
7340 Show the current state of data caching for remote targets.
7344 Print the information about the data cache performance. The
7345 information displayed includes: the dcache width and depth; and for
7346 each cache line, how many times it was referenced, and its data and
7347 state (dirty, bad, ok, etc.). This command is useful for debugging
7348 the data cache operation.
7353 @chapter C Preprocessor Macros
7355 Some languages, such as C and C@t{++}, provide a way to define and invoke
7356 ``preprocessor macros'' which expand into strings of tokens.
7357 @value{GDBN} can evaluate expressions containing macro invocations, show
7358 the result of macro expansion, and show a macro's definition, including
7359 where it was defined.
7361 You may need to compile your program specially to provide @value{GDBN}
7362 with information about preprocessor macros. Most compilers do not
7363 include macros in their debugging information, even when you compile
7364 with the @option{-g} flag. @xref{Compilation}.
7366 A program may define a macro at one point, remove that definition later,
7367 and then provide a different definition after that. Thus, at different
7368 points in the program, a macro may have different definitions, or have
7369 no definition at all. If there is a current stack frame, @value{GDBN}
7370 uses the macros in scope at that frame's source code line. Otherwise,
7371 @value{GDBN} uses the macros in scope at the current listing location;
7374 At the moment, @value{GDBN} does not support the @code{##}
7375 token-splicing operator, the @code{#} stringification operator, or
7376 variable-arity macros.
7378 Whenever @value{GDBN} evaluates an expression, it always expands any
7379 macro invocations present in the expression. @value{GDBN} also provides
7380 the following commands for working with macros explicitly.
7384 @kindex macro expand
7385 @cindex macro expansion, showing the results of preprocessor
7386 @cindex preprocessor macro expansion, showing the results of
7387 @cindex expanding preprocessor macros
7388 @item macro expand @var{expression}
7389 @itemx macro exp @var{expression}
7390 Show the results of expanding all preprocessor macro invocations in
7391 @var{expression}. Since @value{GDBN} simply expands macros, but does
7392 not parse the result, @var{expression} need not be a valid expression;
7393 it can be any string of tokens.
7396 @item macro expand-once @var{expression}
7397 @itemx macro exp1 @var{expression}
7398 @cindex expand macro once
7399 @i{(This command is not yet implemented.)} Show the results of
7400 expanding those preprocessor macro invocations that appear explicitly in
7401 @var{expression}. Macro invocations appearing in that expansion are
7402 left unchanged. This command allows you to see the effect of a
7403 particular macro more clearly, without being confused by further
7404 expansions. Since @value{GDBN} simply expands macros, but does not
7405 parse the result, @var{expression} need not be a valid expression; it
7406 can be any string of tokens.
7409 @cindex macro definition, showing
7410 @cindex definition, showing a macro's
7411 @item info macro @var{macro}
7412 Show the definition of the macro named @var{macro}, and describe the
7413 source location where that definition was established.
7415 @kindex macro define
7416 @cindex user-defined macros
7417 @cindex defining macros interactively
7418 @cindex macros, user-defined
7419 @item macro define @var{macro} @var{replacement-list}
7420 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
7421 @i{(This command is not yet implemented.)} Introduce a definition for a
7422 preprocessor macro named @var{macro}, invocations of which are replaced
7423 by the tokens given in @var{replacement-list}. The first form of this
7424 command defines an ``object-like'' macro, which takes no arguments; the
7425 second form defines a ``function-like'' macro, which takes the arguments
7426 given in @var{arglist}.
7428 A definition introduced by this command is in scope in every expression
7429 evaluated in @value{GDBN}, until it is removed with the @command{macro
7430 undef} command, described below. The definition overrides all
7431 definitions for @var{macro} present in the program being debugged, as
7432 well as any previous user-supplied definition.
7435 @item macro undef @var{macro}
7436 @i{(This command is not yet implemented.)} Remove any user-supplied
7437 definition for the macro named @var{macro}. This command only affects
7438 definitions provided with the @command{macro define} command, described
7439 above; it cannot remove definitions present in the program being
7444 @i{(This command is not yet implemented.)} List all the macros
7445 defined using the @code{macro define} command.
7448 @cindex macros, example of debugging with
7449 Here is a transcript showing the above commands in action. First, we
7450 show our source files:
7458 #define ADD(x) (M + x)
7463 printf ("Hello, world!\n");
7465 printf ("We're so creative.\n");
7467 printf ("Goodbye, world!\n");
7474 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
7475 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
7476 compiler includes information about preprocessor macros in the debugging
7480 $ gcc -gdwarf-2 -g3 sample.c -o sample
7484 Now, we start @value{GDBN} on our sample program:
7488 GNU gdb 2002-05-06-cvs
7489 Copyright 2002 Free Software Foundation, Inc.
7490 GDB is free software, @dots{}
7494 We can expand macros and examine their definitions, even when the
7495 program is not running. @value{GDBN} uses the current listing position
7496 to decide which macro definitions are in scope:
7499 (@value{GDBP}) list main
7502 5 #define ADD(x) (M + x)
7507 10 printf ("Hello, world!\n");
7509 12 printf ("We're so creative.\n");
7510 (@value{GDBP}) info macro ADD
7511 Defined at /home/jimb/gdb/macros/play/sample.c:5
7512 #define ADD(x) (M + x)
7513 (@value{GDBP}) info macro Q
7514 Defined at /home/jimb/gdb/macros/play/sample.h:1
7515 included at /home/jimb/gdb/macros/play/sample.c:2
7517 (@value{GDBP}) macro expand ADD(1)
7518 expands to: (42 + 1)
7519 (@value{GDBP}) macro expand-once ADD(1)
7520 expands to: once (M + 1)
7524 In the example above, note that @command{macro expand-once} expands only
7525 the macro invocation explicit in the original text --- the invocation of
7526 @code{ADD} --- but does not expand the invocation of the macro @code{M},
7527 which was introduced by @code{ADD}.
7529 Once the program is running, @value{GDBN} uses the macro definitions in
7530 force at the source line of the current stack frame:
7533 (@value{GDBP}) break main
7534 Breakpoint 1 at 0x8048370: file sample.c, line 10.
7536 Starting program: /home/jimb/gdb/macros/play/sample
7538 Breakpoint 1, main () at sample.c:10
7539 10 printf ("Hello, world!\n");
7543 At line 10, the definition of the macro @code{N} at line 9 is in force:
7546 (@value{GDBP}) info macro N
7547 Defined at /home/jimb/gdb/macros/play/sample.c:9
7549 (@value{GDBP}) macro expand N Q M
7551 (@value{GDBP}) print N Q M
7556 As we step over directives that remove @code{N}'s definition, and then
7557 give it a new definition, @value{GDBN} finds the definition (or lack
7558 thereof) in force at each point:
7563 12 printf ("We're so creative.\n");
7564 (@value{GDBP}) info macro N
7565 The symbol `N' has no definition as a C/C++ preprocessor macro
7566 at /home/jimb/gdb/macros/play/sample.c:12
7569 14 printf ("Goodbye, world!\n");
7570 (@value{GDBP}) info macro N
7571 Defined at /home/jimb/gdb/macros/play/sample.c:13
7573 (@value{GDBP}) macro expand N Q M
7574 expands to: 1729 < 42
7575 (@value{GDBP}) print N Q M
7582 @chapter Tracepoints
7583 @c This chapter is based on the documentation written by Michael
7584 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
7587 In some applications, it is not feasible for the debugger to interrupt
7588 the program's execution long enough for the developer to learn
7589 anything helpful about its behavior. If the program's correctness
7590 depends on its real-time behavior, delays introduced by a debugger
7591 might cause the program to change its behavior drastically, or perhaps
7592 fail, even when the code itself is correct. It is useful to be able
7593 to observe the program's behavior without interrupting it.
7595 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
7596 specify locations in the program, called @dfn{tracepoints}, and
7597 arbitrary expressions to evaluate when those tracepoints are reached.
7598 Later, using the @code{tfind} command, you can examine the values
7599 those expressions had when the program hit the tracepoints. The
7600 expressions may also denote objects in memory---structures or arrays,
7601 for example---whose values @value{GDBN} should record; while visiting
7602 a particular tracepoint, you may inspect those objects as if they were
7603 in memory at that moment. However, because @value{GDBN} records these
7604 values without interacting with you, it can do so quickly and
7605 unobtrusively, hopefully not disturbing the program's behavior.
7607 The tracepoint facility is currently available only for remote
7608 targets. @xref{Targets}. In addition, your remote target must know
7609 how to collect trace data. This functionality is implemented in the
7610 remote stub; however, none of the stubs distributed with @value{GDBN}
7611 support tracepoints as of this writing. The format of the remote
7612 packets used to implement tracepoints are described in @ref{Tracepoint
7615 This chapter describes the tracepoint commands and features.
7619 * Analyze Collected Data::
7620 * Tracepoint Variables::
7623 @node Set Tracepoints
7624 @section Commands to Set Tracepoints
7626 Before running such a @dfn{trace experiment}, an arbitrary number of
7627 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
7628 tracepoint has a number assigned to it by @value{GDBN}. Like with
7629 breakpoints, tracepoint numbers are successive integers starting from
7630 one. Many of the commands associated with tracepoints take the
7631 tracepoint number as their argument, to identify which tracepoint to
7634 For each tracepoint, you can specify, in advance, some arbitrary set
7635 of data that you want the target to collect in the trace buffer when
7636 it hits that tracepoint. The collected data can include registers,
7637 local variables, or global data. Later, you can use @value{GDBN}
7638 commands to examine the values these data had at the time the
7641 This section describes commands to set tracepoints and associated
7642 conditions and actions.
7645 * Create and Delete Tracepoints::
7646 * Enable and Disable Tracepoints::
7647 * Tracepoint Passcounts::
7648 * Tracepoint Actions::
7649 * Listing Tracepoints::
7650 * Starting and Stopping Trace Experiments::
7653 @node Create and Delete Tracepoints
7654 @subsection Create and Delete Tracepoints
7657 @cindex set tracepoint
7660 The @code{trace} command is very similar to the @code{break} command.
7661 Its argument can be a source line, a function name, or an address in
7662 the target program. @xref{Set Breaks}. The @code{trace} command
7663 defines a tracepoint, which is a point in the target program where the
7664 debugger will briefly stop, collect some data, and then allow the
7665 program to continue. Setting a tracepoint or changing its commands
7666 doesn't take effect until the next @code{tstart} command; thus, you
7667 cannot change the tracepoint attributes once a trace experiment is
7670 Here are some examples of using the @code{trace} command:
7673 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
7675 (@value{GDBP}) @b{trace +2} // 2 lines forward
7677 (@value{GDBP}) @b{trace my_function} // first source line of function
7679 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
7681 (@value{GDBP}) @b{trace *0x2117c4} // an address
7685 You can abbreviate @code{trace} as @code{tr}.
7688 @cindex last tracepoint number
7689 @cindex recent tracepoint number
7690 @cindex tracepoint number
7691 The convenience variable @code{$tpnum} records the tracepoint number
7692 of the most recently set tracepoint.
7694 @kindex delete tracepoint
7695 @cindex tracepoint deletion
7696 @item delete tracepoint @r{[}@var{num}@r{]}
7697 Permanently delete one or more tracepoints. With no argument, the
7698 default is to delete all tracepoints.
7703 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
7705 (@value{GDBP}) @b{delete trace} // remove all tracepoints
7709 You can abbreviate this command as @code{del tr}.
7712 @node Enable and Disable Tracepoints
7713 @subsection Enable and Disable Tracepoints
7716 @kindex disable tracepoint
7717 @item disable tracepoint @r{[}@var{num}@r{]}
7718 Disable tracepoint @var{num}, or all tracepoints if no argument
7719 @var{num} is given. A disabled tracepoint will have no effect during
7720 the next trace experiment, but it is not forgotten. You can re-enable
7721 a disabled tracepoint using the @code{enable tracepoint} command.
7723 @kindex enable tracepoint
7724 @item enable tracepoint @r{[}@var{num}@r{]}
7725 Enable tracepoint @var{num}, or all tracepoints. The enabled
7726 tracepoints will become effective the next time a trace experiment is
7730 @node Tracepoint Passcounts
7731 @subsection Tracepoint Passcounts
7735 @cindex tracepoint pass count
7736 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
7737 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
7738 automatically stop a trace experiment. If a tracepoint's passcount is
7739 @var{n}, then the trace experiment will be automatically stopped on
7740 the @var{n}'th time that tracepoint is hit. If the tracepoint number
7741 @var{num} is not specified, the @code{passcount} command sets the
7742 passcount of the most recently defined tracepoint. If no passcount is
7743 given, the trace experiment will run until stopped explicitly by the
7749 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
7750 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
7752 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
7753 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
7754 (@value{GDBP}) @b{trace foo}
7755 (@value{GDBP}) @b{pass 3}
7756 (@value{GDBP}) @b{trace bar}
7757 (@value{GDBP}) @b{pass 2}
7758 (@value{GDBP}) @b{trace baz}
7759 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
7760 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
7761 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
7762 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
7766 @node Tracepoint Actions
7767 @subsection Tracepoint Action Lists
7771 @cindex tracepoint actions
7772 @item actions @r{[}@var{num}@r{]}
7773 This command will prompt for a list of actions to be taken when the
7774 tracepoint is hit. If the tracepoint number @var{num} is not
7775 specified, this command sets the actions for the one that was most
7776 recently defined (so that you can define a tracepoint and then say
7777 @code{actions} without bothering about its number). You specify the
7778 actions themselves on the following lines, one action at a time, and
7779 terminate the actions list with a line containing just @code{end}. So
7780 far, the only defined actions are @code{collect} and
7781 @code{while-stepping}.
7783 @cindex remove actions from a tracepoint
7784 To remove all actions from a tracepoint, type @samp{actions @var{num}}
7785 and follow it immediately with @samp{end}.
7788 (@value{GDBP}) @b{collect @var{data}} // collect some data
7790 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
7792 (@value{GDBP}) @b{end} // signals the end of actions.
7795 In the following example, the action list begins with @code{collect}
7796 commands indicating the things to be collected when the tracepoint is
7797 hit. Then, in order to single-step and collect additional data
7798 following the tracepoint, a @code{while-stepping} command is used,
7799 followed by the list of things to be collected while stepping. The
7800 @code{while-stepping} command is terminated by its own separate
7801 @code{end} command. Lastly, the action list is terminated by an
7805 (@value{GDBP}) @b{trace foo}
7806 (@value{GDBP}) @b{actions}
7807 Enter actions for tracepoint 1, one per line:
7816 @kindex collect @r{(tracepoints)}
7817 @item collect @var{expr1}, @var{expr2}, @dots{}
7818 Collect values of the given expressions when the tracepoint is hit.
7819 This command accepts a comma-separated list of any valid expressions.
7820 In addition to global, static, or local variables, the following
7821 special arguments are supported:
7825 collect all registers
7828 collect all function arguments
7831 collect all local variables.
7834 You can give several consecutive @code{collect} commands, each one
7835 with a single argument, or one @code{collect} command with several
7836 arguments separated by commas: the effect is the same.
7838 The command @code{info scope} (@pxref{Symbols, info scope}) is
7839 particularly useful for figuring out what data to collect.
7841 @kindex while-stepping @r{(tracepoints)}
7842 @item while-stepping @var{n}
7843 Perform @var{n} single-step traces after the tracepoint, collecting
7844 new data at each step. The @code{while-stepping} command is
7845 followed by the list of what to collect while stepping (followed by
7846 its own @code{end} command):
7850 > collect $regs, myglobal
7856 You may abbreviate @code{while-stepping} as @code{ws} or
7860 @node Listing Tracepoints
7861 @subsection Listing Tracepoints
7864 @kindex info tracepoints
7866 @cindex information about tracepoints
7867 @item info tracepoints @r{[}@var{num}@r{]}
7868 Display information about the tracepoint @var{num}. If you don't specify
7869 a tracepoint number, displays information about all the tracepoints
7870 defined so far. For each tracepoint, the following information is
7877 whether it is enabled or disabled
7881 its passcount as given by the @code{passcount @var{n}} command
7883 its step count as given by the @code{while-stepping @var{n}} command
7885 where in the source files is the tracepoint set
7887 its action list as given by the @code{actions} command
7891 (@value{GDBP}) @b{info trace}
7892 Num Enb Address PassC StepC What
7893 1 y 0x002117c4 0 0 <gdb_asm>
7894 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
7895 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
7900 This command can be abbreviated @code{info tp}.
7903 @node Starting and Stopping Trace Experiments
7904 @subsection Starting and Stopping Trace Experiments
7908 @cindex start a new trace experiment
7909 @cindex collected data discarded
7911 This command takes no arguments. It starts the trace experiment, and
7912 begins collecting data. This has the side effect of discarding all
7913 the data collected in the trace buffer during the previous trace
7917 @cindex stop a running trace experiment
7919 This command takes no arguments. It ends the trace experiment, and
7920 stops collecting data.
7922 @strong{Note}: a trace experiment and data collection may stop
7923 automatically if any tracepoint's passcount is reached
7924 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
7927 @cindex status of trace data collection
7928 @cindex trace experiment, status of
7930 This command displays the status of the current trace data
7934 Here is an example of the commands we described so far:
7937 (@value{GDBP}) @b{trace gdb_c_test}
7938 (@value{GDBP}) @b{actions}
7939 Enter actions for tracepoint #1, one per line.
7940 > collect $regs,$locals,$args
7945 (@value{GDBP}) @b{tstart}
7946 [time passes @dots{}]
7947 (@value{GDBP}) @b{tstop}
7951 @node Analyze Collected Data
7952 @section Using the Collected Data
7954 After the tracepoint experiment ends, you use @value{GDBN} commands
7955 for examining the trace data. The basic idea is that each tracepoint
7956 collects a trace @dfn{snapshot} every time it is hit and another
7957 snapshot every time it single-steps. All these snapshots are
7958 consecutively numbered from zero and go into a buffer, and you can
7959 examine them later. The way you examine them is to @dfn{focus} on a
7960 specific trace snapshot. When the remote stub is focused on a trace
7961 snapshot, it will respond to all @value{GDBN} requests for memory and
7962 registers by reading from the buffer which belongs to that snapshot,
7963 rather than from @emph{real} memory or registers of the program being
7964 debugged. This means that @strong{all} @value{GDBN} commands
7965 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
7966 behave as if we were currently debugging the program state as it was
7967 when the tracepoint occurred. Any requests for data that are not in
7968 the buffer will fail.
7971 * tfind:: How to select a trace snapshot
7972 * tdump:: How to display all data for a snapshot
7973 * save-tracepoints:: How to save tracepoints for a future run
7977 @subsection @code{tfind @var{n}}
7980 @cindex select trace snapshot
7981 @cindex find trace snapshot
7982 The basic command for selecting a trace snapshot from the buffer is
7983 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
7984 counting from zero. If no argument @var{n} is given, the next
7985 snapshot is selected.
7987 Here are the various forms of using the @code{tfind} command.
7991 Find the first snapshot in the buffer. This is a synonym for
7992 @code{tfind 0} (since 0 is the number of the first snapshot).
7995 Stop debugging trace snapshots, resume @emph{live} debugging.
7998 Same as @samp{tfind none}.
8001 No argument means find the next trace snapshot.
8004 Find the previous trace snapshot before the current one. This permits
8005 retracing earlier steps.
8007 @item tfind tracepoint @var{num}
8008 Find the next snapshot associated with tracepoint @var{num}. Search
8009 proceeds forward from the last examined trace snapshot. If no
8010 argument @var{num} is given, it means find the next snapshot collected
8011 for the same tracepoint as the current snapshot.
8013 @item tfind pc @var{addr}
8014 Find the next snapshot associated with the value @var{addr} of the
8015 program counter. Search proceeds forward from the last examined trace
8016 snapshot. If no argument @var{addr} is given, it means find the next
8017 snapshot with the same value of PC as the current snapshot.
8019 @item tfind outside @var{addr1}, @var{addr2}
8020 Find the next snapshot whose PC is outside the given range of
8023 @item tfind range @var{addr1}, @var{addr2}
8024 Find the next snapshot whose PC is between @var{addr1} and
8025 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
8027 @item tfind line @r{[}@var{file}:@r{]}@var{n}
8028 Find the next snapshot associated with the source line @var{n}. If
8029 the optional argument @var{file} is given, refer to line @var{n} in
8030 that source file. Search proceeds forward from the last examined
8031 trace snapshot. If no argument @var{n} is given, it means find the
8032 next line other than the one currently being examined; thus saying
8033 @code{tfind line} repeatedly can appear to have the same effect as
8034 stepping from line to line in a @emph{live} debugging session.
8037 The default arguments for the @code{tfind} commands are specifically
8038 designed to make it easy to scan through the trace buffer. For
8039 instance, @code{tfind} with no argument selects the next trace
8040 snapshot, and @code{tfind -} with no argument selects the previous
8041 trace snapshot. So, by giving one @code{tfind} command, and then
8042 simply hitting @key{RET} repeatedly you can examine all the trace
8043 snapshots in order. Or, by saying @code{tfind -} and then hitting
8044 @key{RET} repeatedly you can examine the snapshots in reverse order.
8045 The @code{tfind line} command with no argument selects the snapshot
8046 for the next source line executed. The @code{tfind pc} command with
8047 no argument selects the next snapshot with the same program counter
8048 (PC) as the current frame. The @code{tfind tracepoint} command with
8049 no argument selects the next trace snapshot collected by the same
8050 tracepoint as the current one.
8052 In addition to letting you scan through the trace buffer manually,
8053 these commands make it easy to construct @value{GDBN} scripts that
8054 scan through the trace buffer and print out whatever collected data
8055 you are interested in. Thus, if we want to examine the PC, FP, and SP
8056 registers from each trace frame in the buffer, we can say this:
8059 (@value{GDBP}) @b{tfind start}
8060 (@value{GDBP}) @b{while ($trace_frame != -1)}
8061 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
8062 $trace_frame, $pc, $sp, $fp
8066 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
8067 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
8068 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
8069 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
8070 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
8071 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
8072 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
8073 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
8074 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
8075 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
8076 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
8079 Or, if we want to examine the variable @code{X} at each source line in
8083 (@value{GDBP}) @b{tfind start}
8084 (@value{GDBP}) @b{while ($trace_frame != -1)}
8085 > printf "Frame %d, X == %d\n", $trace_frame, X
8095 @subsection @code{tdump}
8097 @cindex dump all data collected at tracepoint
8098 @cindex tracepoint data, display
8100 This command takes no arguments. It prints all the data collected at
8101 the current trace snapshot.
8104 (@value{GDBP}) @b{trace 444}
8105 (@value{GDBP}) @b{actions}
8106 Enter actions for tracepoint #2, one per line:
8107 > collect $regs, $locals, $args, gdb_long_test
8110 (@value{GDBP}) @b{tstart}
8112 (@value{GDBP}) @b{tfind line 444}
8113 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
8115 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
8117 (@value{GDBP}) @b{tdump}
8118 Data collected at tracepoint 2, trace frame 1:
8119 d0 0xc4aa0085 -995491707
8123 d4 0x71aea3d 119204413
8128 a1 0x3000668 50333288
8131 a4 0x3000698 50333336
8133 fp 0x30bf3c 0x30bf3c
8134 sp 0x30bf34 0x30bf34
8136 pc 0x20b2c8 0x20b2c8
8140 p = 0x20e5b4 "gdb-test"
8147 gdb_long_test = 17 '\021'
8152 @node save-tracepoints
8153 @subsection @code{save-tracepoints @var{filename}}
8154 @kindex save-tracepoints
8155 @cindex save tracepoints for future sessions
8157 This command saves all current tracepoint definitions together with
8158 their actions and passcounts, into a file @file{@var{filename}}
8159 suitable for use in a later debugging session. To read the saved
8160 tracepoint definitions, use the @code{source} command (@pxref{Command
8163 @node Tracepoint Variables
8164 @section Convenience Variables for Tracepoints
8165 @cindex tracepoint variables
8166 @cindex convenience variables for tracepoints
8169 @vindex $trace_frame
8170 @item (int) $trace_frame
8171 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
8172 snapshot is selected.
8175 @item (int) $tracepoint
8176 The tracepoint for the current trace snapshot.
8179 @item (int) $trace_line
8180 The line number for the current trace snapshot.
8183 @item (char []) $trace_file
8184 The source file for the current trace snapshot.
8187 @item (char []) $trace_func
8188 The name of the function containing @code{$tracepoint}.
8191 Note: @code{$trace_file} is not suitable for use in @code{printf},
8192 use @code{output} instead.
8194 Here's a simple example of using these convenience variables for
8195 stepping through all the trace snapshots and printing some of their
8199 (@value{GDBP}) @b{tfind start}
8201 (@value{GDBP}) @b{while $trace_frame != -1}
8202 > output $trace_file
8203 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
8209 @chapter Debugging Programs That Use Overlays
8212 If your program is too large to fit completely in your target system's
8213 memory, you can sometimes use @dfn{overlays} to work around this
8214 problem. @value{GDBN} provides some support for debugging programs that
8218 * How Overlays Work:: A general explanation of overlays.
8219 * Overlay Commands:: Managing overlays in @value{GDBN}.
8220 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
8221 mapped by asking the inferior.
8222 * Overlay Sample Program:: A sample program using overlays.
8225 @node How Overlays Work
8226 @section How Overlays Work
8227 @cindex mapped overlays
8228 @cindex unmapped overlays
8229 @cindex load address, overlay's
8230 @cindex mapped address
8231 @cindex overlay area
8233 Suppose you have a computer whose instruction address space is only 64
8234 kilobytes long, but which has much more memory which can be accessed by
8235 other means: special instructions, segment registers, or memory
8236 management hardware, for example. Suppose further that you want to
8237 adapt a program which is larger than 64 kilobytes to run on this system.
8239 One solution is to identify modules of your program which are relatively
8240 independent, and need not call each other directly; call these modules
8241 @dfn{overlays}. Separate the overlays from the main program, and place
8242 their machine code in the larger memory. Place your main program in
8243 instruction memory, but leave at least enough space there to hold the
8244 largest overlay as well.
8246 Now, to call a function located in an overlay, you must first copy that
8247 overlay's machine code from the large memory into the space set aside
8248 for it in the instruction memory, and then jump to its entry point
8251 @c NB: In the below the mapped area's size is greater or equal to the
8252 @c size of all overlays. This is intentional to remind the developer
8253 @c that overlays don't necessarily need to be the same size.
8257 Data Instruction Larger
8258 Address Space Address Space Address Space
8259 +-----------+ +-----------+ +-----------+
8261 +-----------+ +-----------+ +-----------+<-- overlay 1
8262 | program | | main | .----| overlay 1 | load address
8263 | variables | | program | | +-----------+
8264 | and heap | | | | | |
8265 +-----------+ | | | +-----------+<-- overlay 2
8266 | | +-----------+ | | | load address
8267 +-----------+ | | | .-| overlay 2 |
8269 mapped --->+-----------+ | | +-----------+
8271 | overlay | <-' | | |
8272 | area | <---' +-----------+<-- overlay 3
8273 | | <---. | | load address
8274 +-----------+ `--| overlay 3 |
8281 @anchor{A code overlay}A code overlay
8285 The diagram (@pxref{A code overlay}) shows a system with separate data
8286 and instruction address spaces. To map an overlay, the program copies
8287 its code from the larger address space to the instruction address space.
8288 Since the overlays shown here all use the same mapped address, only one
8289 may be mapped at a time. For a system with a single address space for
8290 data and instructions, the diagram would be similar, except that the
8291 program variables and heap would share an address space with the main
8292 program and the overlay area.
8294 An overlay loaded into instruction memory and ready for use is called a
8295 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
8296 instruction memory. An overlay not present (or only partially present)
8297 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
8298 is its address in the larger memory. The mapped address is also called
8299 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
8300 called the @dfn{load memory address}, or @dfn{LMA}.
8302 Unfortunately, overlays are not a completely transparent way to adapt a
8303 program to limited instruction memory. They introduce a new set of
8304 global constraints you must keep in mind as you design your program:
8309 Before calling or returning to a function in an overlay, your program
8310 must make sure that overlay is actually mapped. Otherwise, the call or
8311 return will transfer control to the right address, but in the wrong
8312 overlay, and your program will probably crash.
8315 If the process of mapping an overlay is expensive on your system, you
8316 will need to choose your overlays carefully to minimize their effect on
8317 your program's performance.
8320 The executable file you load onto your system must contain each
8321 overlay's instructions, appearing at the overlay's load address, not its
8322 mapped address. However, each overlay's instructions must be relocated
8323 and its symbols defined as if the overlay were at its mapped address.
8324 You can use GNU linker scripts to specify different load and relocation
8325 addresses for pieces of your program; see @ref{Overlay Description,,,
8326 ld.info, Using ld: the GNU linker}.
8329 The procedure for loading executable files onto your system must be able
8330 to load their contents into the larger address space as well as the
8331 instruction and data spaces.
8335 The overlay system described above is rather simple, and could be
8336 improved in many ways:
8341 If your system has suitable bank switch registers or memory management
8342 hardware, you could use those facilities to make an overlay's load area
8343 contents simply appear at their mapped address in instruction space.
8344 This would probably be faster than copying the overlay to its mapped
8345 area in the usual way.
8348 If your overlays are small enough, you could set aside more than one
8349 overlay area, and have more than one overlay mapped at a time.
8352 You can use overlays to manage data, as well as instructions. In
8353 general, data overlays are even less transparent to your design than
8354 code overlays: whereas code overlays only require care when you call or
8355 return to functions, data overlays require care every time you access
8356 the data. Also, if you change the contents of a data overlay, you
8357 must copy its contents back out to its load address before you can copy a
8358 different data overlay into the same mapped area.
8363 @node Overlay Commands
8364 @section Overlay Commands
8366 To use @value{GDBN}'s overlay support, each overlay in your program must
8367 correspond to a separate section of the executable file. The section's
8368 virtual memory address and load memory address must be the overlay's
8369 mapped and load addresses. Identifying overlays with sections allows
8370 @value{GDBN} to determine the appropriate address of a function or
8371 variable, depending on whether the overlay is mapped or not.
8373 @value{GDBN}'s overlay commands all start with the word @code{overlay};
8374 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
8379 Disable @value{GDBN}'s overlay support. When overlay support is
8380 disabled, @value{GDBN} assumes that all functions and variables are
8381 always present at their mapped addresses. By default, @value{GDBN}'s
8382 overlay support is disabled.
8384 @item overlay manual
8385 @cindex manual overlay debugging
8386 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
8387 relies on you to tell it which overlays are mapped, and which are not,
8388 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
8389 commands described below.
8391 @item overlay map-overlay @var{overlay}
8392 @itemx overlay map @var{overlay}
8393 @cindex map an overlay
8394 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
8395 be the name of the object file section containing the overlay. When an
8396 overlay is mapped, @value{GDBN} assumes it can find the overlay's
8397 functions and variables at their mapped addresses. @value{GDBN} assumes
8398 that any other overlays whose mapped ranges overlap that of
8399 @var{overlay} are now unmapped.
8401 @item overlay unmap-overlay @var{overlay}
8402 @itemx overlay unmap @var{overlay}
8403 @cindex unmap an overlay
8404 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
8405 must be the name of the object file section containing the overlay.
8406 When an overlay is unmapped, @value{GDBN} assumes it can find the
8407 overlay's functions and variables at their load addresses.
8410 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
8411 consults a data structure the overlay manager maintains in the inferior
8412 to see which overlays are mapped. For details, see @ref{Automatic
8415 @item overlay load-target
8417 @cindex reloading the overlay table
8418 Re-read the overlay table from the inferior. Normally, @value{GDBN}
8419 re-reads the table @value{GDBN} automatically each time the inferior
8420 stops, so this command should only be necessary if you have changed the
8421 overlay mapping yourself using @value{GDBN}. This command is only
8422 useful when using automatic overlay debugging.
8424 @item overlay list-overlays
8426 @cindex listing mapped overlays
8427 Display a list of the overlays currently mapped, along with their mapped
8428 addresses, load addresses, and sizes.
8432 Normally, when @value{GDBN} prints a code address, it includes the name
8433 of the function the address falls in:
8436 (@value{GDBP}) print main
8437 $3 = @{int ()@} 0x11a0 <main>
8440 When overlay debugging is enabled, @value{GDBN} recognizes code in
8441 unmapped overlays, and prints the names of unmapped functions with
8442 asterisks around them. For example, if @code{foo} is a function in an
8443 unmapped overlay, @value{GDBN} prints it this way:
8446 (@value{GDBP}) overlay list
8447 No sections are mapped.
8448 (@value{GDBP}) print foo
8449 $5 = @{int (int)@} 0x100000 <*foo*>
8452 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
8456 (@value{GDBP}) overlay list
8457 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
8458 mapped at 0x1016 - 0x104a
8459 (@value{GDBP}) print foo
8460 $6 = @{int (int)@} 0x1016 <foo>
8463 When overlay debugging is enabled, @value{GDBN} can find the correct
8464 address for functions and variables in an overlay, whether or not the
8465 overlay is mapped. This allows most @value{GDBN} commands, like
8466 @code{break} and @code{disassemble}, to work normally, even on unmapped
8467 code. However, @value{GDBN}'s breakpoint support has some limitations:
8471 @cindex breakpoints in overlays
8472 @cindex overlays, setting breakpoints in
8473 You can set breakpoints in functions in unmapped overlays, as long as
8474 @value{GDBN} can write to the overlay at its load address.
8476 @value{GDBN} can not set hardware or simulator-based breakpoints in
8477 unmapped overlays. However, if you set a breakpoint at the end of your
8478 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
8479 you are using manual overlay management), @value{GDBN} will re-set its
8480 breakpoints properly.
8484 @node Automatic Overlay Debugging
8485 @section Automatic Overlay Debugging
8486 @cindex automatic overlay debugging
8488 @value{GDBN} can automatically track which overlays are mapped and which
8489 are not, given some simple co-operation from the overlay manager in the
8490 inferior. If you enable automatic overlay debugging with the
8491 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
8492 looks in the inferior's memory for certain variables describing the
8493 current state of the overlays.
8495 Here are the variables your overlay manager must define to support
8496 @value{GDBN}'s automatic overlay debugging:
8500 @item @code{_ovly_table}:
8501 This variable must be an array of the following structures:
8506 /* The overlay's mapped address. */
8509 /* The size of the overlay, in bytes. */
8512 /* The overlay's load address. */
8515 /* Non-zero if the overlay is currently mapped;
8517 unsigned long mapped;
8521 @item @code{_novlys}:
8522 This variable must be a four-byte signed integer, holding the total
8523 number of elements in @code{_ovly_table}.
8527 To decide whether a particular overlay is mapped or not, @value{GDBN}
8528 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
8529 @code{lma} members equal the VMA and LMA of the overlay's section in the
8530 executable file. When @value{GDBN} finds a matching entry, it consults
8531 the entry's @code{mapped} member to determine whether the overlay is
8534 In addition, your overlay manager may define a function called
8535 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
8536 will silently set a breakpoint there. If the overlay manager then
8537 calls this function whenever it has changed the overlay table, this
8538 will enable @value{GDBN} to accurately keep track of which overlays
8539 are in program memory, and update any breakpoints that may be set
8540 in overlays. This will allow breakpoints to work even if the
8541 overlays are kept in ROM or other non-writable memory while they
8542 are not being executed.
8544 @node Overlay Sample Program
8545 @section Overlay Sample Program
8546 @cindex overlay example program
8548 When linking a program which uses overlays, you must place the overlays
8549 at their load addresses, while relocating them to run at their mapped
8550 addresses. To do this, you must write a linker script (@pxref{Overlay
8551 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
8552 since linker scripts are specific to a particular host system, target
8553 architecture, and target memory layout, this manual cannot provide
8554 portable sample code demonstrating @value{GDBN}'s overlay support.
8556 However, the @value{GDBN} source distribution does contain an overlaid
8557 program, with linker scripts for a few systems, as part of its test
8558 suite. The program consists of the following files from
8559 @file{gdb/testsuite/gdb.base}:
8563 The main program file.
8565 A simple overlay manager, used by @file{overlays.c}.
8570 Overlay modules, loaded and used by @file{overlays.c}.
8573 Linker scripts for linking the test program on the @code{d10v-elf}
8574 and @code{m32r-elf} targets.
8577 You can build the test program using the @code{d10v-elf} GCC
8578 cross-compiler like this:
8581 $ d10v-elf-gcc -g -c overlays.c
8582 $ d10v-elf-gcc -g -c ovlymgr.c
8583 $ d10v-elf-gcc -g -c foo.c
8584 $ d10v-elf-gcc -g -c bar.c
8585 $ d10v-elf-gcc -g -c baz.c
8586 $ d10v-elf-gcc -g -c grbx.c
8587 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
8588 baz.o grbx.o -Wl,-Td10v.ld -o overlays
8591 The build process is identical for any other architecture, except that
8592 you must substitute the appropriate compiler and linker script for the
8593 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
8597 @chapter Using @value{GDBN} with Different Languages
8600 Although programming languages generally have common aspects, they are
8601 rarely expressed in the same manner. For instance, in ANSI C,
8602 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
8603 Modula-2, it is accomplished by @code{p^}. Values can also be
8604 represented (and displayed) differently. Hex numbers in C appear as
8605 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
8607 @cindex working language
8608 Language-specific information is built into @value{GDBN} for some languages,
8609 allowing you to express operations like the above in your program's
8610 native language, and allowing @value{GDBN} to output values in a manner
8611 consistent with the syntax of your program's native language. The
8612 language you use to build expressions is called the @dfn{working
8616 * Setting:: Switching between source languages
8617 * Show:: Displaying the language
8618 * Checks:: Type and range checks
8619 * Supported Languages:: Supported languages
8620 * Unsupported Languages:: Unsupported languages
8624 @section Switching Between Source Languages
8626 There are two ways to control the working language---either have @value{GDBN}
8627 set it automatically, or select it manually yourself. You can use the
8628 @code{set language} command for either purpose. On startup, @value{GDBN}
8629 defaults to setting the language automatically. The working language is
8630 used to determine how expressions you type are interpreted, how values
8633 In addition to the working language, every source file that
8634 @value{GDBN} knows about has its own working language. For some object
8635 file formats, the compiler might indicate which language a particular
8636 source file is in. However, most of the time @value{GDBN} infers the
8637 language from the name of the file. The language of a source file
8638 controls whether C@t{++} names are demangled---this way @code{backtrace} can
8639 show each frame appropriately for its own language. There is no way to
8640 set the language of a source file from within @value{GDBN}, but you can
8641 set the language associated with a filename extension. @xref{Show, ,
8642 Displaying the Language}.
8644 This is most commonly a problem when you use a program, such
8645 as @code{cfront} or @code{f2c}, that generates C but is written in
8646 another language. In that case, make the
8647 program use @code{#line} directives in its C output; that way
8648 @value{GDBN} will know the correct language of the source code of the original
8649 program, and will display that source code, not the generated C code.
8652 * Filenames:: Filename extensions and languages.
8653 * Manually:: Setting the working language manually
8654 * Automatically:: Having @value{GDBN} infer the source language
8658 @subsection List of Filename Extensions and Languages
8660 If a source file name ends in one of the following extensions, then
8661 @value{GDBN} infers that its language is the one indicated.
8682 Objective-C source file
8689 Modula-2 source file
8693 Assembler source file. This actually behaves almost like C, but
8694 @value{GDBN} does not skip over function prologues when stepping.
8697 In addition, you may set the language associated with a filename
8698 extension. @xref{Show, , Displaying the Language}.
8701 @subsection Setting the Working Language
8703 If you allow @value{GDBN} to set the language automatically,
8704 expressions are interpreted the same way in your debugging session and
8707 @kindex set language
8708 If you wish, you may set the language manually. To do this, issue the
8709 command @samp{set language @var{lang}}, where @var{lang} is the name of
8711 @code{c} or @code{modula-2}.
8712 For a list of the supported languages, type @samp{set language}.
8714 Setting the language manually prevents @value{GDBN} from updating the working
8715 language automatically. This can lead to confusion if you try
8716 to debug a program when the working language is not the same as the
8717 source language, when an expression is acceptable to both
8718 languages---but means different things. For instance, if the current
8719 source file were written in C, and @value{GDBN} was parsing Modula-2, a
8727 might not have the effect you intended. In C, this means to add
8728 @code{b} and @code{c} and place the result in @code{a}. The result
8729 printed would be the value of @code{a}. In Modula-2, this means to compare
8730 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
8733 @subsection Having @value{GDBN} Infer the Source Language
8735 To have @value{GDBN} set the working language automatically, use
8736 @samp{set language local} or @samp{set language auto}. @value{GDBN}
8737 then infers the working language. That is, when your program stops in a
8738 frame (usually by encountering a breakpoint), @value{GDBN} sets the
8739 working language to the language recorded for the function in that
8740 frame. If the language for a frame is unknown (that is, if the function
8741 or block corresponding to the frame was defined in a source file that
8742 does not have a recognized extension), the current working language is
8743 not changed, and @value{GDBN} issues a warning.
8745 This may not seem necessary for most programs, which are written
8746 entirely in one source language. However, program modules and libraries
8747 written in one source language can be used by a main program written in
8748 a different source language. Using @samp{set language auto} in this
8749 case frees you from having to set the working language manually.
8752 @section Displaying the Language
8754 The following commands help you find out which language is the
8755 working language, and also what language source files were written in.
8759 @kindex show language
8760 Display the current working language. This is the
8761 language you can use with commands such as @code{print} to
8762 build and compute expressions that may involve variables in your program.
8765 @kindex info frame@r{, show the source language}
8766 Display the source language for this frame. This language becomes the
8767 working language if you use an identifier from this frame.
8768 @xref{Frame Info, ,Information about a Frame}, to identify the other
8769 information listed here.
8772 @kindex info source@r{, show the source language}
8773 Display the source language of this source file.
8774 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
8775 information listed here.
8778 In unusual circumstances, you may have source files with extensions
8779 not in the standard list. You can then set the extension associated
8780 with a language explicitly:
8783 @item set extension-language @var{ext} @var{language}
8784 @kindex set extension-language
8785 Tell @value{GDBN} that source files with extension @var{ext} are to be
8786 assumed as written in the source language @var{language}.
8788 @item info extensions
8789 @kindex info extensions
8790 List all the filename extensions and the associated languages.
8794 @section Type and Range Checking
8797 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
8798 checking are included, but they do not yet have any effect. This
8799 section documents the intended facilities.
8801 @c FIXME remove warning when type/range code added
8803 Some languages are designed to guard you against making seemingly common
8804 errors through a series of compile- and run-time checks. These include
8805 checking the type of arguments to functions and operators, and making
8806 sure mathematical overflows are caught at run time. Checks such as
8807 these help to ensure a program's correctness once it has been compiled
8808 by eliminating type mismatches, and providing active checks for range
8809 errors when your program is running.
8811 @value{GDBN} can check for conditions like the above if you wish.
8812 Although @value{GDBN} does not check the statements in your program,
8813 it can check expressions entered directly into @value{GDBN} for
8814 evaluation via the @code{print} command, for example. As with the
8815 working language, @value{GDBN} can also decide whether or not to check
8816 automatically based on your program's source language.
8817 @xref{Supported Languages, ,Supported Languages}, for the default
8818 settings of supported languages.
8821 * Type Checking:: An overview of type checking
8822 * Range Checking:: An overview of range checking
8825 @cindex type checking
8826 @cindex checks, type
8828 @subsection An Overview of Type Checking
8830 Some languages, such as Modula-2, are strongly typed, meaning that the
8831 arguments to operators and functions have to be of the correct type,
8832 otherwise an error occurs. These checks prevent type mismatch
8833 errors from ever causing any run-time problems. For example,
8841 The second example fails because the @code{CARDINAL} 1 is not
8842 type-compatible with the @code{REAL} 2.3.
8844 For the expressions you use in @value{GDBN} commands, you can tell the
8845 @value{GDBN} type checker to skip checking;
8846 to treat any mismatches as errors and abandon the expression;
8847 or to only issue warnings when type mismatches occur,
8848 but evaluate the expression anyway. When you choose the last of
8849 these, @value{GDBN} evaluates expressions like the second example above, but
8850 also issues a warning.
8852 Even if you turn type checking off, there may be other reasons
8853 related to type that prevent @value{GDBN} from evaluating an expression.
8854 For instance, @value{GDBN} does not know how to add an @code{int} and
8855 a @code{struct foo}. These particular type errors have nothing to do
8856 with the language in use, and usually arise from expressions, such as
8857 the one described above, which make little sense to evaluate anyway.
8859 Each language defines to what degree it is strict about type. For
8860 instance, both Modula-2 and C require the arguments to arithmetical
8861 operators to be numbers. In C, enumerated types and pointers can be
8862 represented as numbers, so that they are valid arguments to mathematical
8863 operators. @xref{Supported Languages, ,Supported Languages}, for further
8864 details on specific languages.
8866 @value{GDBN} provides some additional commands for controlling the type checker:
8868 @kindex set check type
8869 @kindex show check type
8871 @item set check type auto
8872 Set type checking on or off based on the current working language.
8873 @xref{Supported Languages, ,Supported Languages}, for the default settings for
8876 @item set check type on
8877 @itemx set check type off
8878 Set type checking on or off, overriding the default setting for the
8879 current working language. Issue a warning if the setting does not
8880 match the language default. If any type mismatches occur in
8881 evaluating an expression while type checking is on, @value{GDBN} prints a
8882 message and aborts evaluation of the expression.
8884 @item set check type warn
8885 Cause the type checker to issue warnings, but to always attempt to
8886 evaluate the expression. Evaluating the expression may still
8887 be impossible for other reasons. For example, @value{GDBN} cannot add
8888 numbers and structures.
8891 Show the current setting of the type checker, and whether or not @value{GDBN}
8892 is setting it automatically.
8895 @cindex range checking
8896 @cindex checks, range
8897 @node Range Checking
8898 @subsection An Overview of Range Checking
8900 In some languages (such as Modula-2), it is an error to exceed the
8901 bounds of a type; this is enforced with run-time checks. Such range
8902 checking is meant to ensure program correctness by making sure
8903 computations do not overflow, or indices on an array element access do
8904 not exceed the bounds of the array.
8906 For expressions you use in @value{GDBN} commands, you can tell
8907 @value{GDBN} to treat range errors in one of three ways: ignore them,
8908 always treat them as errors and abandon the expression, or issue
8909 warnings but evaluate the expression anyway.
8911 A range error can result from numerical overflow, from exceeding an
8912 array index bound, or when you type a constant that is not a member
8913 of any type. Some languages, however, do not treat overflows as an
8914 error. In many implementations of C, mathematical overflow causes the
8915 result to ``wrap around'' to lower values---for example, if @var{m} is
8916 the largest integer value, and @var{s} is the smallest, then
8919 @var{m} + 1 @result{} @var{s}
8922 This, too, is specific to individual languages, and in some cases
8923 specific to individual compilers or machines. @xref{Supported Languages, ,
8924 Supported Languages}, for further details on specific languages.
8926 @value{GDBN} provides some additional commands for controlling the range checker:
8928 @kindex set check range
8929 @kindex show check range
8931 @item set check range auto
8932 Set range checking on or off based on the current working language.
8933 @xref{Supported Languages, ,Supported Languages}, for the default settings for
8936 @item set check range on
8937 @itemx set check range off
8938 Set range checking on or off, overriding the default setting for the
8939 current working language. A warning is issued if the setting does not
8940 match the language default. If a range error occurs and range checking is on,
8941 then a message is printed and evaluation of the expression is aborted.
8943 @item set check range warn
8944 Output messages when the @value{GDBN} range checker detects a range error,
8945 but attempt to evaluate the expression anyway. Evaluating the
8946 expression may still be impossible for other reasons, such as accessing
8947 memory that the process does not own (a typical example from many Unix
8951 Show the current setting of the range checker, and whether or not it is
8952 being set automatically by @value{GDBN}.
8955 @node Supported Languages
8956 @section Supported Languages
8958 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
8959 assembly, Modula-2, and Ada.
8960 @c This is false ...
8961 Some @value{GDBN} features may be used in expressions regardless of the
8962 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
8963 and the @samp{@{type@}addr} construct (@pxref{Expressions,
8964 ,Expressions}) can be used with the constructs of any supported
8967 The following sections detail to what degree each source language is
8968 supported by @value{GDBN}. These sections are not meant to be language
8969 tutorials or references, but serve only as a reference guide to what the
8970 @value{GDBN} expression parser accepts, and what input and output
8971 formats should look like for different languages. There are many good
8972 books written on each of these languages; please look to these for a
8973 language reference or tutorial.
8977 * Objective-C:: Objective-C
8980 * Modula-2:: Modula-2
8985 @subsection C and C@t{++}
8987 @cindex C and C@t{++}
8988 @cindex expressions in C or C@t{++}
8990 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
8991 to both languages. Whenever this is the case, we discuss those languages
8995 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
8996 @cindex @sc{gnu} C@t{++}
8997 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
8998 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
8999 effectively, you must compile your C@t{++} programs with a supported
9000 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
9001 compiler (@code{aCC}).
9003 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
9004 format; if it doesn't work on your system, try the stabs+ debugging
9005 format. You can select those formats explicitly with the @code{g++}
9006 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
9007 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
9008 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
9011 * C Operators:: C and C@t{++} operators
9012 * C Constants:: C and C@t{++} constants
9013 * C Plus Plus Expressions:: C@t{++} expressions
9014 * C Defaults:: Default settings for C and C@t{++}
9015 * C Checks:: C and C@t{++} type and range checks
9016 * Debugging C:: @value{GDBN} and C
9017 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
9021 @subsubsection C and C@t{++} Operators
9023 @cindex C and C@t{++} operators
9025 Operators must be defined on values of specific types. For instance,
9026 @code{+} is defined on numbers, but not on structures. Operators are
9027 often defined on groups of types.
9029 For the purposes of C and C@t{++}, the following definitions hold:
9034 @emph{Integral types} include @code{int} with any of its storage-class
9035 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
9038 @emph{Floating-point types} include @code{float}, @code{double}, and
9039 @code{long double} (if supported by the target platform).
9042 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
9045 @emph{Scalar types} include all of the above.
9050 The following operators are supported. They are listed here
9051 in order of increasing precedence:
9055 The comma or sequencing operator. Expressions in a comma-separated list
9056 are evaluated from left to right, with the result of the entire
9057 expression being the last expression evaluated.
9060 Assignment. The value of an assignment expression is the value
9061 assigned. Defined on scalar types.
9064 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
9065 and translated to @w{@code{@var{a} = @var{a op b}}}.
9066 @w{@code{@var{op}=}} and @code{=} have the same precedence.
9067 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
9068 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
9071 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
9072 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
9076 Logical @sc{or}. Defined on integral types.
9079 Logical @sc{and}. Defined on integral types.
9082 Bitwise @sc{or}. Defined on integral types.
9085 Bitwise exclusive-@sc{or}. Defined on integral types.
9088 Bitwise @sc{and}. Defined on integral types.
9091 Equality and inequality. Defined on scalar types. The value of these
9092 expressions is 0 for false and non-zero for true.
9094 @item <@r{, }>@r{, }<=@r{, }>=
9095 Less than, greater than, less than or equal, greater than or equal.
9096 Defined on scalar types. The value of these expressions is 0 for false
9097 and non-zero for true.
9100 left shift, and right shift. Defined on integral types.
9103 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9106 Addition and subtraction. Defined on integral types, floating-point types and
9109 @item *@r{, }/@r{, }%
9110 Multiplication, division, and modulus. Multiplication and division are
9111 defined on integral and floating-point types. Modulus is defined on
9115 Increment and decrement. When appearing before a variable, the
9116 operation is performed before the variable is used in an expression;
9117 when appearing after it, the variable's value is used before the
9118 operation takes place.
9121 Pointer dereferencing. Defined on pointer types. Same precedence as
9125 Address operator. Defined on variables. Same precedence as @code{++}.
9127 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
9128 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
9129 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
9130 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
9134 Negative. Defined on integral and floating-point types. Same
9135 precedence as @code{++}.
9138 Logical negation. Defined on integral types. Same precedence as
9142 Bitwise complement operator. Defined on integral types. Same precedence as
9147 Structure member, and pointer-to-structure member. For convenience,
9148 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
9149 pointer based on the stored type information.
9150 Defined on @code{struct} and @code{union} data.
9153 Dereferences of pointers to members.
9156 Array indexing. @code{@var{a}[@var{i}]} is defined as
9157 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
9160 Function parameter list. Same precedence as @code{->}.
9163 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
9164 and @code{class} types.
9167 Doubled colons also represent the @value{GDBN} scope operator
9168 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
9172 If an operator is redefined in the user code, @value{GDBN} usually
9173 attempts to invoke the redefined version instead of using the operator's
9177 @subsubsection C and C@t{++} Constants
9179 @cindex C and C@t{++} constants
9181 @value{GDBN} allows you to express the constants of C and C@t{++} in the
9186 Integer constants are a sequence of digits. Octal constants are
9187 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
9188 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
9189 @samp{l}, specifying that the constant should be treated as a
9193 Floating point constants are a sequence of digits, followed by a decimal
9194 point, followed by a sequence of digits, and optionally followed by an
9195 exponent. An exponent is of the form:
9196 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
9197 sequence of digits. The @samp{+} is optional for positive exponents.
9198 A floating-point constant may also end with a letter @samp{f} or
9199 @samp{F}, specifying that the constant should be treated as being of
9200 the @code{float} (as opposed to the default @code{double}) type; or with
9201 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
9205 Enumerated constants consist of enumerated identifiers, or their
9206 integral equivalents.
9209 Character constants are a single character surrounded by single quotes
9210 (@code{'}), or a number---the ordinal value of the corresponding character
9211 (usually its @sc{ascii} value). Within quotes, the single character may
9212 be represented by a letter or by @dfn{escape sequences}, which are of
9213 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
9214 of the character's ordinal value; or of the form @samp{\@var{x}}, where
9215 @samp{@var{x}} is a predefined special character---for example,
9216 @samp{\n} for newline.
9219 String constants are a sequence of character constants surrounded by
9220 double quotes (@code{"}). Any valid character constant (as described
9221 above) may appear. Double quotes within the string must be preceded by
9222 a backslash, so for instance @samp{"a\"b'c"} is a string of five
9226 Pointer constants are an integral value. You can also write pointers
9227 to constants using the C operator @samp{&}.
9230 Array constants are comma-separated lists surrounded by braces @samp{@{}
9231 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
9232 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
9233 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
9236 @node C Plus Plus Expressions
9237 @subsubsection C@t{++} Expressions
9239 @cindex expressions in C@t{++}
9240 @value{GDBN} expression handling can interpret most C@t{++} expressions.
9242 @cindex debugging C@t{++} programs
9243 @cindex C@t{++} compilers
9244 @cindex debug formats and C@t{++}
9245 @cindex @value{NGCC} and C@t{++}
9247 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
9248 proper compiler and the proper debug format. Currently, @value{GDBN}
9249 works best when debugging C@t{++} code that is compiled with
9250 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
9251 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
9252 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
9253 stabs+ as their default debug format, so you usually don't need to
9254 specify a debug format explicitly. Other compilers and/or debug formats
9255 are likely to work badly or not at all when using @value{GDBN} to debug
9261 @cindex member functions
9263 Member function calls are allowed; you can use expressions like
9266 count = aml->GetOriginal(x, y)
9269 @vindex this@r{, inside C@t{++} member functions}
9270 @cindex namespace in C@t{++}
9272 While a member function is active (in the selected stack frame), your
9273 expressions have the same namespace available as the member function;
9274 that is, @value{GDBN} allows implicit references to the class instance
9275 pointer @code{this} following the same rules as C@t{++}.
9277 @cindex call overloaded functions
9278 @cindex overloaded functions, calling
9279 @cindex type conversions in C@t{++}
9281 You can call overloaded functions; @value{GDBN} resolves the function
9282 call to the right definition, with some restrictions. @value{GDBN} does not
9283 perform overload resolution involving user-defined type conversions,
9284 calls to constructors, or instantiations of templates that do not exist
9285 in the program. It also cannot handle ellipsis argument lists or
9288 It does perform integral conversions and promotions, floating-point
9289 promotions, arithmetic conversions, pointer conversions, conversions of
9290 class objects to base classes, and standard conversions such as those of
9291 functions or arrays to pointers; it requires an exact match on the
9292 number of function arguments.
9294 Overload resolution is always performed, unless you have specified
9295 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
9296 ,@value{GDBN} Features for C@t{++}}.
9298 You must specify @code{set overload-resolution off} in order to use an
9299 explicit function signature to call an overloaded function, as in
9301 p 'foo(char,int)'('x', 13)
9304 The @value{GDBN} command-completion facility can simplify this;
9305 see @ref{Completion, ,Command Completion}.
9307 @cindex reference declarations
9309 @value{GDBN} understands variables declared as C@t{++} references; you can use
9310 them in expressions just as you do in C@t{++} source---they are automatically
9313 In the parameter list shown when @value{GDBN} displays a frame, the values of
9314 reference variables are not displayed (unlike other variables); this
9315 avoids clutter, since references are often used for large structures.
9316 The @emph{address} of a reference variable is always shown, unless
9317 you have specified @samp{set print address off}.
9320 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
9321 expressions can use it just as expressions in your program do. Since
9322 one scope may be defined in another, you can use @code{::} repeatedly if
9323 necessary, for example in an expression like
9324 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
9325 resolving name scope by reference to source files, in both C and C@t{++}
9326 debugging (@pxref{Variables, ,Program Variables}).
9329 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
9330 calling virtual functions correctly, printing out virtual bases of
9331 objects, calling functions in a base subobject, casting objects, and
9332 invoking user-defined operators.
9335 @subsubsection C and C@t{++} Defaults
9337 @cindex C and C@t{++} defaults
9339 If you allow @value{GDBN} to set type and range checking automatically, they
9340 both default to @code{off} whenever the working language changes to
9341 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
9342 selects the working language.
9344 If you allow @value{GDBN} to set the language automatically, it
9345 recognizes source files whose names end with @file{.c}, @file{.C}, or
9346 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
9347 these files, it sets the working language to C or C@t{++}.
9348 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
9349 for further details.
9351 @c Type checking is (a) primarily motivated by Modula-2, and (b)
9352 @c unimplemented. If (b) changes, it might make sense to let this node
9353 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
9356 @subsubsection C and C@t{++} Type and Range Checks
9358 @cindex C and C@t{++} checks
9360 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
9361 is not used. However, if you turn type checking on, @value{GDBN}
9362 considers two variables type equivalent if:
9366 The two variables are structured and have the same structure, union, or
9370 The two variables have the same type name, or types that have been
9371 declared equivalent through @code{typedef}.
9374 @c leaving this out because neither J Gilmore nor R Pesch understand it.
9377 The two @code{struct}, @code{union}, or @code{enum} variables are
9378 declared in the same declaration. (Note: this may not be true for all C
9383 Range checking, if turned on, is done on mathematical operations. Array
9384 indices are not checked, since they are often used to index a pointer
9385 that is not itself an array.
9388 @subsubsection @value{GDBN} and C
9390 The @code{set print union} and @code{show print union} commands apply to
9391 the @code{union} type. When set to @samp{on}, any @code{union} that is
9392 inside a @code{struct} or @code{class} is also printed. Otherwise, it
9393 appears as @samp{@{...@}}.
9395 The @code{@@} operator aids in the debugging of dynamic arrays, formed
9396 with pointers and a memory allocation function. @xref{Expressions,
9399 @node Debugging C Plus Plus
9400 @subsubsection @value{GDBN} Features for C@t{++}
9402 @cindex commands for C@t{++}
9404 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
9405 designed specifically for use with C@t{++}. Here is a summary:
9408 @cindex break in overloaded functions
9409 @item @r{breakpoint menus}
9410 When you want a breakpoint in a function whose name is overloaded,
9411 @value{GDBN} breakpoint menus help you specify which function definition
9412 you want. @xref{Breakpoint Menus,,Breakpoint Menus}.
9414 @cindex overloading in C@t{++}
9415 @item rbreak @var{regex}
9416 Setting breakpoints using regular expressions is helpful for setting
9417 breakpoints on overloaded functions that are not members of any special
9419 @xref{Set Breaks, ,Setting Breakpoints}.
9421 @cindex C@t{++} exception handling
9424 Debug C@t{++} exception handling using these commands. @xref{Set
9425 Catchpoints, , Setting Catchpoints}.
9428 @item ptype @var{typename}
9429 Print inheritance relationships as well as other information for type
9431 @xref{Symbols, ,Examining the Symbol Table}.
9433 @cindex C@t{++} symbol display
9434 @item set print demangle
9435 @itemx show print demangle
9436 @itemx set print asm-demangle
9437 @itemx show print asm-demangle
9438 Control whether C@t{++} symbols display in their source form, both when
9439 displaying code as C@t{++} source and when displaying disassemblies.
9440 @xref{Print Settings, ,Print Settings}.
9442 @item set print object
9443 @itemx show print object
9444 Choose whether to print derived (actual) or declared types of objects.
9445 @xref{Print Settings, ,Print Settings}.
9447 @item set print vtbl
9448 @itemx show print vtbl
9449 Control the format for printing virtual function tables.
9450 @xref{Print Settings, ,Print Settings}.
9451 (The @code{vtbl} commands do not work on programs compiled with the HP
9452 ANSI C@t{++} compiler (@code{aCC}).)
9454 @kindex set overload-resolution
9455 @cindex overloaded functions, overload resolution
9456 @item set overload-resolution on
9457 Enable overload resolution for C@t{++} expression evaluation. The default
9458 is on. For overloaded functions, @value{GDBN} evaluates the arguments
9459 and searches for a function whose signature matches the argument types,
9460 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
9461 Expressions, ,C@t{++} Expressions}, for details).
9462 If it cannot find a match, it emits a message.
9464 @item set overload-resolution off
9465 Disable overload resolution for C@t{++} expression evaluation. For
9466 overloaded functions that are not class member functions, @value{GDBN}
9467 chooses the first function of the specified name that it finds in the
9468 symbol table, whether or not its arguments are of the correct type. For
9469 overloaded functions that are class member functions, @value{GDBN}
9470 searches for a function whose signature @emph{exactly} matches the
9473 @kindex show overload-resolution
9474 @item show overload-resolution
9475 Show the current setting of overload resolution.
9477 @item @r{Overloaded symbol names}
9478 You can specify a particular definition of an overloaded symbol, using
9479 the same notation that is used to declare such symbols in C@t{++}: type
9480 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
9481 also use the @value{GDBN} command-line word completion facilities to list the
9482 available choices, or to finish the type list for you.
9483 @xref{Completion,, Command Completion}, for details on how to do this.
9487 @subsection Objective-C
9490 This section provides information about some commands and command
9491 options that are useful for debugging Objective-C code. See also
9492 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
9493 few more commands specific to Objective-C support.
9496 * Method Names in Commands::
9497 * The Print Command with Objective-C::
9500 @node Method Names in Commands
9501 @subsubsection Method Names in Commands
9503 The following commands have been extended to accept Objective-C method
9504 names as line specifications:
9506 @kindex clear@r{, and Objective-C}
9507 @kindex break@r{, and Objective-C}
9508 @kindex info line@r{, and Objective-C}
9509 @kindex jump@r{, and Objective-C}
9510 @kindex list@r{, and Objective-C}
9514 @item @code{info line}
9519 A fully qualified Objective-C method name is specified as
9522 -[@var{Class} @var{methodName}]
9525 where the minus sign is used to indicate an instance method and a
9526 plus sign (not shown) is used to indicate a class method. The class
9527 name @var{Class} and method name @var{methodName} are enclosed in
9528 brackets, similar to the way messages are specified in Objective-C
9529 source code. For example, to set a breakpoint at the @code{create}
9530 instance method of class @code{Fruit} in the program currently being
9534 break -[Fruit create]
9537 To list ten program lines around the @code{initialize} class method,
9541 list +[NSText initialize]
9544 In the current version of @value{GDBN}, the plus or minus sign is
9545 required. In future versions of @value{GDBN}, the plus or minus
9546 sign will be optional, but you can use it to narrow the search. It
9547 is also possible to specify just a method name:
9553 You must specify the complete method name, including any colons. If
9554 your program's source files contain more than one @code{create} method,
9555 you'll be presented with a numbered list of classes that implement that
9556 method. Indicate your choice by number, or type @samp{0} to exit if
9559 As another example, to clear a breakpoint established at the
9560 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
9563 clear -[NSWindow makeKeyAndOrderFront:]
9566 @node The Print Command with Objective-C
9567 @subsubsection The Print Command With Objective-C
9568 @cindex Objective-C, print objects
9569 @kindex print-object
9570 @kindex po @r{(@code{print-object})}
9572 The print command has also been extended to accept methods. For example:
9575 print -[@var{object} hash]
9578 @cindex print an Objective-C object description
9579 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
9581 will tell @value{GDBN} to send the @code{hash} message to @var{object}
9582 and print the result. Also, an additional command has been added,
9583 @code{print-object} or @code{po} for short, which is meant to print
9584 the description of an object. However, this command may only work
9585 with certain Objective-C libraries that have a particular hook
9586 function, @code{_NSPrintForDebugger}, defined.
9590 @cindex Fortran-specific support in @value{GDBN}
9592 @value{GDBN} can be used to debug programs written in Fortran, but it
9593 currently supports only the features of Fortran 77 language.
9595 @cindex trailing underscore, in Fortran symbols
9596 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
9597 among them) append an underscore to the names of variables and
9598 functions. When you debug programs compiled by those compilers, you
9599 will need to refer to variables and functions with a trailing
9603 * Fortran Operators:: Fortran operators and expressions
9604 * Fortran Defaults:: Default settings for Fortran
9605 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
9608 @node Fortran Operators
9609 @subsubsection Fortran Operators and Expressions
9611 @cindex Fortran operators and expressions
9613 Operators must be defined on values of specific types. For instance,
9614 @code{+} is defined on numbers, but not on characters or other non-
9615 arithmetic types. Operators are often defined on groups of types.
9619 The exponentiation operator. It raises the first operand to the power
9623 The range operator. Normally used in the form of array(low:high) to
9624 represent a section of array.
9627 @node Fortran Defaults
9628 @subsubsection Fortran Defaults
9630 @cindex Fortran Defaults
9632 Fortran symbols are usually case-insensitive, so @value{GDBN} by
9633 default uses case-insensitive matches for Fortran symbols. You can
9634 change that with the @samp{set case-insensitive} command, see
9635 @ref{Symbols}, for the details.
9637 @node Special Fortran Commands
9638 @subsubsection Special Fortran Commands
9640 @cindex Special Fortran commands
9642 @value{GDBN} has some commands to support Fortran-specific features,
9643 such as displaying common blocks.
9646 @cindex @code{COMMON} blocks, Fortran
9648 @item info common @r{[}@var{common-name}@r{]}
9649 This command prints the values contained in the Fortran @code{COMMON}
9650 block whose name is @var{common-name}. With no argument, the names of
9651 all @code{COMMON} blocks visible at the current program location are
9658 @cindex Pascal support in @value{GDBN}, limitations
9659 Debugging Pascal programs which use sets, subranges, file variables, or
9660 nested functions does not currently work. @value{GDBN} does not support
9661 entering expressions, printing values, or similar features using Pascal
9664 The Pascal-specific command @code{set print pascal_static-members}
9665 controls whether static members of Pascal objects are displayed.
9666 @xref{Print Settings, pascal_static-members}.
9669 @subsection Modula-2
9671 @cindex Modula-2, @value{GDBN} support
9673 The extensions made to @value{GDBN} to support Modula-2 only support
9674 output from the @sc{gnu} Modula-2 compiler (which is currently being
9675 developed). Other Modula-2 compilers are not currently supported, and
9676 attempting to debug executables produced by them is most likely
9677 to give an error as @value{GDBN} reads in the executable's symbol
9680 @cindex expressions in Modula-2
9682 * M2 Operators:: Built-in operators
9683 * Built-In Func/Proc:: Built-in functions and procedures
9684 * M2 Constants:: Modula-2 constants
9685 * M2 Types:: Modula-2 types
9686 * M2 Defaults:: Default settings for Modula-2
9687 * Deviations:: Deviations from standard Modula-2
9688 * M2 Checks:: Modula-2 type and range checks
9689 * M2 Scope:: The scope operators @code{::} and @code{.}
9690 * GDB/M2:: @value{GDBN} and Modula-2
9694 @subsubsection Operators
9695 @cindex Modula-2 operators
9697 Operators must be defined on values of specific types. For instance,
9698 @code{+} is defined on numbers, but not on structures. Operators are
9699 often defined on groups of types. For the purposes of Modula-2, the
9700 following definitions hold:
9705 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
9709 @emph{Character types} consist of @code{CHAR} and its subranges.
9712 @emph{Floating-point types} consist of @code{REAL}.
9715 @emph{Pointer types} consist of anything declared as @code{POINTER TO
9719 @emph{Scalar types} consist of all of the above.
9722 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
9725 @emph{Boolean types} consist of @code{BOOLEAN}.
9729 The following operators are supported, and appear in order of
9730 increasing precedence:
9734 Function argument or array index separator.
9737 Assignment. The value of @var{var} @code{:=} @var{value} is
9741 Less than, greater than on integral, floating-point, or enumerated
9745 Less than or equal to, greater than or equal to
9746 on integral, floating-point and enumerated types, or set inclusion on
9747 set types. Same precedence as @code{<}.
9749 @item =@r{, }<>@r{, }#
9750 Equality and two ways of expressing inequality, valid on scalar types.
9751 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
9752 available for inequality, since @code{#} conflicts with the script
9756 Set membership. Defined on set types and the types of their members.
9757 Same precedence as @code{<}.
9760 Boolean disjunction. Defined on boolean types.
9763 Boolean conjunction. Defined on boolean types.
9766 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9769 Addition and subtraction on integral and floating-point types, or union
9770 and difference on set types.
9773 Multiplication on integral and floating-point types, or set intersection
9777 Division on floating-point types, or symmetric set difference on set
9778 types. Same precedence as @code{*}.
9781 Integer division and remainder. Defined on integral types. Same
9782 precedence as @code{*}.
9785 Negative. Defined on @code{INTEGER} and @code{REAL} data.
9788 Pointer dereferencing. Defined on pointer types.
9791 Boolean negation. Defined on boolean types. Same precedence as
9795 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
9796 precedence as @code{^}.
9799 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
9802 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
9806 @value{GDBN} and Modula-2 scope operators.
9810 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
9811 treats the use of the operator @code{IN}, or the use of operators
9812 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
9813 @code{<=}, and @code{>=} on sets as an error.
9817 @node Built-In Func/Proc
9818 @subsubsection Built-in Functions and Procedures
9819 @cindex Modula-2 built-ins
9821 Modula-2 also makes available several built-in procedures and functions.
9822 In describing these, the following metavariables are used:
9827 represents an @code{ARRAY} variable.
9830 represents a @code{CHAR} constant or variable.
9833 represents a variable or constant of integral type.
9836 represents an identifier that belongs to a set. Generally used in the
9837 same function with the metavariable @var{s}. The type of @var{s} should
9838 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
9841 represents a variable or constant of integral or floating-point type.
9844 represents a variable or constant of floating-point type.
9850 represents a variable.
9853 represents a variable or constant of one of many types. See the
9854 explanation of the function for details.
9857 All Modula-2 built-in procedures also return a result, described below.
9861 Returns the absolute value of @var{n}.
9864 If @var{c} is a lower case letter, it returns its upper case
9865 equivalent, otherwise it returns its argument.
9868 Returns the character whose ordinal value is @var{i}.
9871 Decrements the value in the variable @var{v} by one. Returns the new value.
9873 @item DEC(@var{v},@var{i})
9874 Decrements the value in the variable @var{v} by @var{i}. Returns the
9877 @item EXCL(@var{m},@var{s})
9878 Removes the element @var{m} from the set @var{s}. Returns the new
9881 @item FLOAT(@var{i})
9882 Returns the floating point equivalent of the integer @var{i}.
9885 Returns the index of the last member of @var{a}.
9888 Increments the value in the variable @var{v} by one. Returns the new value.
9890 @item INC(@var{v},@var{i})
9891 Increments the value in the variable @var{v} by @var{i}. Returns the
9894 @item INCL(@var{m},@var{s})
9895 Adds the element @var{m} to the set @var{s} if it is not already
9896 there. Returns the new set.
9899 Returns the maximum value of the type @var{t}.
9902 Returns the minimum value of the type @var{t}.
9905 Returns boolean TRUE if @var{i} is an odd number.
9908 Returns the ordinal value of its argument. For example, the ordinal
9909 value of a character is its @sc{ascii} value (on machines supporting the
9910 @sc{ascii} character set). @var{x} must be of an ordered type, which include
9911 integral, character and enumerated types.
9914 Returns the size of its argument. @var{x} can be a variable or a type.
9916 @item TRUNC(@var{r})
9917 Returns the integral part of @var{r}.
9919 @item VAL(@var{t},@var{i})
9920 Returns the member of the type @var{t} whose ordinal value is @var{i}.
9924 @emph{Warning:} Sets and their operations are not yet supported, so
9925 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
9929 @cindex Modula-2 constants
9931 @subsubsection Constants
9933 @value{GDBN} allows you to express the constants of Modula-2 in the following
9939 Integer constants are simply a sequence of digits. When used in an
9940 expression, a constant is interpreted to be type-compatible with the
9941 rest of the expression. Hexadecimal integers are specified by a
9942 trailing @samp{H}, and octal integers by a trailing @samp{B}.
9945 Floating point constants appear as a sequence of digits, followed by a
9946 decimal point and another sequence of digits. An optional exponent can
9947 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
9948 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
9949 digits of the floating point constant must be valid decimal (base 10)
9953 Character constants consist of a single character enclosed by a pair of
9954 like quotes, either single (@code{'}) or double (@code{"}). They may
9955 also be expressed by their ordinal value (their @sc{ascii} value, usually)
9956 followed by a @samp{C}.
9959 String constants consist of a sequence of characters enclosed by a
9960 pair of like quotes, either single (@code{'}) or double (@code{"}).
9961 Escape sequences in the style of C are also allowed. @xref{C
9962 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
9966 Enumerated constants consist of an enumerated identifier.
9969 Boolean constants consist of the identifiers @code{TRUE} and
9973 Pointer constants consist of integral values only.
9976 Set constants are not yet supported.
9980 @subsubsection Modula-2 Types
9981 @cindex Modula-2 types
9983 Currently @value{GDBN} can print the following data types in Modula-2
9984 syntax: array types, record types, set types, pointer types, procedure
9985 types, enumerated types, subrange types and base types. You can also
9986 print the contents of variables declared using these type.
9987 This section gives a number of simple source code examples together with
9988 sample @value{GDBN} sessions.
9990 The first example contains the following section of code:
9999 and you can request @value{GDBN} to interrogate the type and value of
10000 @code{r} and @code{s}.
10003 (@value{GDBP}) print s
10005 (@value{GDBP}) ptype s
10007 (@value{GDBP}) print r
10009 (@value{GDBP}) ptype r
10014 Likewise if your source code declares @code{s} as:
10018 s: SET ['A'..'Z'] ;
10022 then you may query the type of @code{s} by:
10025 (@value{GDBP}) ptype s
10026 type = SET ['A'..'Z']
10030 Note that at present you cannot interactively manipulate set
10031 expressions using the debugger.
10033 The following example shows how you might declare an array in Modula-2
10034 and how you can interact with @value{GDBN} to print its type and contents:
10038 s: ARRAY [-10..10] OF CHAR ;
10042 (@value{GDBP}) ptype s
10043 ARRAY [-10..10] OF CHAR
10046 Note that the array handling is not yet complete and although the type
10047 is printed correctly, expression handling still assumes that all
10048 arrays have a lower bound of zero and not @code{-10} as in the example
10049 above. Unbounded arrays are also not yet recognized in @value{GDBN}.
10051 Here are some more type related Modula-2 examples:
10055 colour = (blue, red, yellow, green) ;
10056 t = [blue..yellow] ;
10064 The @value{GDBN} interaction shows how you can query the data type
10065 and value of a variable.
10068 (@value{GDBP}) print s
10070 (@value{GDBP}) ptype t
10071 type = [blue..yellow]
10075 In this example a Modula-2 array is declared and its contents
10076 displayed. Observe that the contents are written in the same way as
10077 their @code{C} counterparts.
10081 s: ARRAY [1..5] OF CARDINAL ;
10087 (@value{GDBP}) print s
10088 $1 = @{1, 0, 0, 0, 0@}
10089 (@value{GDBP}) ptype s
10090 type = ARRAY [1..5] OF CARDINAL
10093 The Modula-2 language interface to @value{GDBN} also understands
10094 pointer types as shown in this example:
10098 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
10105 and you can request that @value{GDBN} describes the type of @code{s}.
10108 (@value{GDBP}) ptype s
10109 type = POINTER TO ARRAY [1..5] OF CARDINAL
10112 @value{GDBN} handles compound types as we can see in this example.
10113 Here we combine array types, record types, pointer types and subrange
10124 myarray = ARRAY myrange OF CARDINAL ;
10125 myrange = [-2..2] ;
10127 s: POINTER TO ARRAY myrange OF foo ;
10131 and you can ask @value{GDBN} to describe the type of @code{s} as shown
10135 (@value{GDBP}) ptype s
10136 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
10139 f3 : ARRAY [-2..2] OF CARDINAL;
10144 @subsubsection Modula-2 Defaults
10145 @cindex Modula-2 defaults
10147 If type and range checking are set automatically by @value{GDBN}, they
10148 both default to @code{on} whenever the working language changes to
10149 Modula-2. This happens regardless of whether you or @value{GDBN}
10150 selected the working language.
10152 If you allow @value{GDBN} to set the language automatically, then entering
10153 code compiled from a file whose name ends with @file{.mod} sets the
10154 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
10155 Infer the Source Language}, for further details.
10158 @subsubsection Deviations from Standard Modula-2
10159 @cindex Modula-2, deviations from
10161 A few changes have been made to make Modula-2 programs easier to debug.
10162 This is done primarily via loosening its type strictness:
10166 Unlike in standard Modula-2, pointer constants can be formed by
10167 integers. This allows you to modify pointer variables during
10168 debugging. (In standard Modula-2, the actual address contained in a
10169 pointer variable is hidden from you; it can only be modified
10170 through direct assignment to another pointer variable or expression that
10171 returned a pointer.)
10174 C escape sequences can be used in strings and characters to represent
10175 non-printable characters. @value{GDBN} prints out strings with these
10176 escape sequences embedded. Single non-printable characters are
10177 printed using the @samp{CHR(@var{nnn})} format.
10180 The assignment operator (@code{:=}) returns the value of its right-hand
10184 All built-in procedures both modify @emph{and} return their argument.
10188 @subsubsection Modula-2 Type and Range Checks
10189 @cindex Modula-2 checks
10192 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
10195 @c FIXME remove warning when type/range checks added
10197 @value{GDBN} considers two Modula-2 variables type equivalent if:
10201 They are of types that have been declared equivalent via a @code{TYPE
10202 @var{t1} = @var{t2}} statement
10205 They have been declared on the same line. (Note: This is true of the
10206 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
10209 As long as type checking is enabled, any attempt to combine variables
10210 whose types are not equivalent is an error.
10212 Range checking is done on all mathematical operations, assignment, array
10213 index bounds, and all built-in functions and procedures.
10216 @subsubsection The Scope Operators @code{::} and @code{.}
10218 @cindex @code{.}, Modula-2 scope operator
10219 @cindex colon, doubled as scope operator
10221 @vindex colon-colon@r{, in Modula-2}
10222 @c Info cannot handle :: but TeX can.
10225 @vindex ::@r{, in Modula-2}
10228 There are a few subtle differences between the Modula-2 scope operator
10229 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
10234 @var{module} . @var{id}
10235 @var{scope} :: @var{id}
10239 where @var{scope} is the name of a module or a procedure,
10240 @var{module} the name of a module, and @var{id} is any declared
10241 identifier within your program, except another module.
10243 Using the @code{::} operator makes @value{GDBN} search the scope
10244 specified by @var{scope} for the identifier @var{id}. If it is not
10245 found in the specified scope, then @value{GDBN} searches all scopes
10246 enclosing the one specified by @var{scope}.
10248 Using the @code{.} operator makes @value{GDBN} search the current scope for
10249 the identifier specified by @var{id} that was imported from the
10250 definition module specified by @var{module}. With this operator, it is
10251 an error if the identifier @var{id} was not imported from definition
10252 module @var{module}, or if @var{id} is not an identifier in
10256 @subsubsection @value{GDBN} and Modula-2
10258 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
10259 Five subcommands of @code{set print} and @code{show print} apply
10260 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
10261 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
10262 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
10263 analogue in Modula-2.
10265 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
10266 with any language, is not useful with Modula-2. Its
10267 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
10268 created in Modula-2 as they can in C or C@t{++}. However, because an
10269 address can be specified by an integral constant, the construct
10270 @samp{@{@var{type}@}@var{adrexp}} is still useful.
10272 @cindex @code{#} in Modula-2
10273 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
10274 interpreted as the beginning of a comment. Use @code{<>} instead.
10280 The extensions made to @value{GDBN} for Ada only support
10281 output from the @sc{gnu} Ada (GNAT) compiler.
10282 Other Ada compilers are not currently supported, and
10283 attempting to debug executables produced by them is most likely
10287 @cindex expressions in Ada
10289 * Ada Mode Intro:: General remarks on the Ada syntax
10290 and semantics supported by Ada mode
10292 * Omissions from Ada:: Restrictions on the Ada expression syntax.
10293 * Additions to Ada:: Extensions of the Ada expression syntax.
10294 * Stopping Before Main Program:: Debugging the program during elaboration.
10295 * Ada Glitches:: Known peculiarities of Ada mode.
10298 @node Ada Mode Intro
10299 @subsubsection Introduction
10300 @cindex Ada mode, general
10302 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
10303 syntax, with some extensions.
10304 The philosophy behind the design of this subset is
10308 That @value{GDBN} should provide basic literals and access to operations for
10309 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
10310 leaving more sophisticated computations to subprograms written into the
10311 program (which therefore may be called from @value{GDBN}).
10314 That type safety and strict adherence to Ada language restrictions
10315 are not particularly important to the @value{GDBN} user.
10318 That brevity is important to the @value{GDBN} user.
10321 Thus, for brevity, the debugger acts as if there were
10322 implicit @code{with} and @code{use} clauses in effect for all user-written
10323 packages, making it unnecessary to fully qualify most names with
10324 their packages, regardless of context. Where this causes ambiguity,
10325 @value{GDBN} asks the user's intent.
10327 The debugger will start in Ada mode if it detects an Ada main program.
10328 As for other languages, it will enter Ada mode when stopped in a program that
10329 was translated from an Ada source file.
10331 While in Ada mode, you may use `@t{--}' for comments. This is useful
10332 mostly for documenting command files. The standard @value{GDBN} comment
10333 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
10334 middle (to allow based literals).
10336 The debugger supports limited overloading. Given a subprogram call in which
10337 the function symbol has multiple definitions, it will use the number of
10338 actual parameters and some information about their types to attempt to narrow
10339 the set of definitions. It also makes very limited use of context, preferring
10340 procedures to functions in the context of the @code{call} command, and
10341 functions to procedures elsewhere.
10343 @node Omissions from Ada
10344 @subsubsection Omissions from Ada
10345 @cindex Ada, omissions from
10347 Here are the notable omissions from the subset:
10351 Only a subset of the attributes are supported:
10355 @t{'First}, @t{'Last}, and @t{'Length}
10356 on array objects (not on types and subtypes).
10359 @t{'Min} and @t{'Max}.
10362 @t{'Pos} and @t{'Val}.
10368 @t{'Range} on array objects (not subtypes), but only as the right
10369 operand of the membership (@code{in}) operator.
10372 @t{'Access}, @t{'Unchecked_Access}, and
10373 @t{'Unrestricted_Access} (a GNAT extension).
10381 @code{Characters.Latin_1} are not available and
10382 concatenation is not implemented. Thus, escape characters in strings are
10383 not currently available.
10386 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
10387 equality of representations. They will generally work correctly
10388 for strings and arrays whose elements have integer or enumeration types.
10389 They may not work correctly for arrays whose element
10390 types have user-defined equality, for arrays of real values
10391 (in particular, IEEE-conformant floating point, because of negative
10392 zeroes and NaNs), and for arrays whose elements contain unused bits with
10393 indeterminate values.
10396 The other component-by-component array operations (@code{and}, @code{or},
10397 @code{xor}, @code{not}, and relational tests other than equality)
10398 are not implemented.
10401 @cindex array aggregates (Ada)
10402 @cindex record aggregates (Ada)
10403 @cindex aggregates (Ada)
10404 There is limited support for array and record aggregates. They are
10405 permitted only on the right sides of assignments, as in these examples:
10408 set An_Array := (1, 2, 3, 4, 5, 6)
10409 set An_Array := (1, others => 0)
10410 set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
10411 set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
10412 set A_Record := (1, "Peter", True);
10413 set A_Record := (Name => "Peter", Id => 1, Alive => True)
10417 discriminant's value by assigning an aggregate has an
10418 undefined effect if that discriminant is used within the record.
10419 However, you can first modify discriminants by directly assigning to
10420 them (which normally would not be allowed in Ada), and then performing an
10421 aggregate assignment. For example, given a variable @code{A_Rec}
10422 declared to have a type such as:
10425 type Rec (Len : Small_Integer := 0) is record
10427 Vals : IntArray (1 .. Len);
10431 you can assign a value with a different size of @code{Vals} with two
10436 set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
10439 As this example also illustrates, @value{GDBN} is very loose about the usual
10440 rules concerning aggregates. You may leave out some of the
10441 components of an array or record aggregate (such as the @code{Len}
10442 component in the assignment to @code{A_Rec} above); they will retain their
10443 original values upon assignment. You may freely use dynamic values as
10444 indices in component associations. You may even use overlapping or
10445 redundant component associations, although which component values are
10446 assigned in such cases is not defined.
10449 Calls to dispatching subprograms are not implemented.
10452 The overloading algorithm is much more limited (i.e., less selective)
10453 than that of real Ada. It makes only limited use of the context in
10454 which a subexpression appears to resolve its meaning, and it is much
10455 looser in its rules for allowing type matches. As a result, some
10456 function calls will be ambiguous, and the user will be asked to choose
10457 the proper resolution.
10460 The @code{new} operator is not implemented.
10463 Entry calls are not implemented.
10466 Aside from printing, arithmetic operations on the native VAX floating-point
10467 formats are not supported.
10470 It is not possible to slice a packed array.
10473 @node Additions to Ada
10474 @subsubsection Additions to Ada
10475 @cindex Ada, deviations from
10477 As it does for other languages, @value{GDBN} makes certain generic
10478 extensions to Ada (@pxref{Expressions}):
10482 If the expression @var{E} is a variable residing in memory (typically
10483 a local variable or array element) and @var{N} is a positive integer,
10484 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
10485 @var{N}-1 adjacent variables following it in memory as an array. In
10486 Ada, this operator is generally not necessary, since its prime use is
10487 in displaying parts of an array, and slicing will usually do this in
10488 Ada. However, there are occasional uses when debugging programs in
10489 which certain debugging information has been optimized away.
10492 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
10493 appears in function or file @var{B}.'' When @var{B} is a file name,
10494 you must typically surround it in single quotes.
10497 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
10498 @var{type} that appears at address @var{addr}.''
10501 A name starting with @samp{$} is a convenience variable
10502 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
10505 In addition, @value{GDBN} provides a few other shortcuts and outright
10506 additions specific to Ada:
10510 The assignment statement is allowed as an expression, returning
10511 its right-hand operand as its value. Thus, you may enter
10515 print A(tmp := y + 1)
10519 The semicolon is allowed as an ``operator,'' returning as its value
10520 the value of its right-hand operand.
10521 This allows, for example,
10522 complex conditional breaks:
10526 condition 1 (report(i); k += 1; A(k) > 100)
10530 Rather than use catenation and symbolic character names to introduce special
10531 characters into strings, one may instead use a special bracket notation,
10532 which is also used to print strings. A sequence of characters of the form
10533 @samp{["@var{XX}"]} within a string or character literal denotes the
10534 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
10535 sequence of characters @samp{["""]} also denotes a single quotation mark
10536 in strings. For example,
10538 "One line.["0a"]Next line.["0a"]"
10541 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
10545 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
10546 @t{'Max} is optional (and is ignored in any case). For example, it is valid
10554 When printing arrays, @value{GDBN} uses positional notation when the
10555 array has a lower bound of 1, and uses a modified named notation otherwise.
10556 For example, a one-dimensional array of three integers with a lower bound
10557 of 3 might print as
10564 That is, in contrast to valid Ada, only the first component has a @code{=>}
10568 You may abbreviate attributes in expressions with any unique,
10569 multi-character subsequence of
10570 their names (an exact match gets preference).
10571 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
10572 in place of @t{a'length}.
10575 @cindex quoting Ada internal identifiers
10576 Since Ada is case-insensitive, the debugger normally maps identifiers you type
10577 to lower case. The GNAT compiler uses upper-case characters for
10578 some of its internal identifiers, which are normally of no interest to users.
10579 For the rare occasions when you actually have to look at them,
10580 enclose them in angle brackets to avoid the lower-case mapping.
10583 @value{GDBP} print <JMPBUF_SAVE>[0]
10587 Printing an object of class-wide type or dereferencing an
10588 access-to-class-wide value will display all the components of the object's
10589 specific type (as indicated by its run-time tag). Likewise, component
10590 selection on such a value will operate on the specific type of the
10595 @node Stopping Before Main Program
10596 @subsubsection Stopping at the Very Beginning
10598 @cindex breakpointing Ada elaboration code
10599 It is sometimes necessary to debug the program during elaboration, and
10600 before reaching the main procedure.
10601 As defined in the Ada Reference
10602 Manual, the elaboration code is invoked from a procedure called
10603 @code{adainit}. To run your program up to the beginning of
10604 elaboration, simply use the following two commands:
10605 @code{tbreak adainit} and @code{run}.
10608 @subsubsection Known Peculiarities of Ada Mode
10609 @cindex Ada, problems
10611 Besides the omissions listed previously (@pxref{Omissions from Ada}),
10612 we know of several problems with and limitations of Ada mode in
10614 some of which will be fixed with planned future releases of the debugger
10615 and the GNU Ada compiler.
10619 Currently, the debugger
10620 has insufficient information to determine whether certain pointers represent
10621 pointers to objects or the objects themselves.
10622 Thus, the user may have to tack an extra @code{.all} after an expression
10623 to get it printed properly.
10626 Static constants that the compiler chooses not to materialize as objects in
10627 storage are invisible to the debugger.
10630 Named parameter associations in function argument lists are ignored (the
10631 argument lists are treated as positional).
10634 Many useful library packages are currently invisible to the debugger.
10637 Fixed-point arithmetic, conversions, input, and output is carried out using
10638 floating-point arithmetic, and may give results that only approximate those on
10642 The type of the @t{'Address} attribute may not be @code{System.Address}.
10645 The GNAT compiler never generates the prefix @code{Standard} for any of
10646 the standard symbols defined by the Ada language. @value{GDBN} knows about
10647 this: it will strip the prefix from names when you use it, and will never
10648 look for a name you have so qualified among local symbols, nor match against
10649 symbols in other packages or subprograms. If you have
10650 defined entities anywhere in your program other than parameters and
10651 local variables whose simple names match names in @code{Standard},
10652 GNAT's lack of qualification here can cause confusion. When this happens,
10653 you can usually resolve the confusion
10654 by qualifying the problematic names with package
10655 @code{Standard} explicitly.
10658 @node Unsupported Languages
10659 @section Unsupported Languages
10661 @cindex unsupported languages
10662 @cindex minimal language
10663 In addition to the other fully-supported programming languages,
10664 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
10665 It does not represent a real programming language, but provides a set
10666 of capabilities close to what the C or assembly languages provide.
10667 This should allow most simple operations to be performed while debugging
10668 an application that uses a language currently not supported by @value{GDBN}.
10670 If the language is set to @code{auto}, @value{GDBN} will automatically
10671 select this language if the current frame corresponds to an unsupported
10675 @chapter Examining the Symbol Table
10677 The commands described in this chapter allow you to inquire about the
10678 symbols (names of variables, functions and types) defined in your
10679 program. This information is inherent in the text of your program and
10680 does not change as your program executes. @value{GDBN} finds it in your
10681 program's symbol table, in the file indicated when you started @value{GDBN}
10682 (@pxref{File Options, ,Choosing Files}), or by one of the
10683 file-management commands (@pxref{Files, ,Commands to Specify Files}).
10685 @cindex symbol names
10686 @cindex names of symbols
10687 @cindex quoting names
10688 Occasionally, you may need to refer to symbols that contain unusual
10689 characters, which @value{GDBN} ordinarily treats as word delimiters. The
10690 most frequent case is in referring to static variables in other
10691 source files (@pxref{Variables,,Program Variables}). File names
10692 are recorded in object files as debugging symbols, but @value{GDBN} would
10693 ordinarily parse a typical file name, like @file{foo.c}, as the three words
10694 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
10695 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
10702 looks up the value of @code{x} in the scope of the file @file{foo.c}.
10705 @cindex case-insensitive symbol names
10706 @cindex case sensitivity in symbol names
10707 @kindex set case-sensitive
10708 @item set case-sensitive on
10709 @itemx set case-sensitive off
10710 @itemx set case-sensitive auto
10711 Normally, when @value{GDBN} looks up symbols, it matches their names
10712 with case sensitivity determined by the current source language.
10713 Occasionally, you may wish to control that. The command @code{set
10714 case-sensitive} lets you do that by specifying @code{on} for
10715 case-sensitive matches or @code{off} for case-insensitive ones. If
10716 you specify @code{auto}, case sensitivity is reset to the default
10717 suitable for the source language. The default is case-sensitive
10718 matches for all languages except for Fortran, for which the default is
10719 case-insensitive matches.
10721 @kindex show case-sensitive
10722 @item show case-sensitive
10723 This command shows the current setting of case sensitivity for symbols
10726 @kindex info address
10727 @cindex address of a symbol
10728 @item info address @var{symbol}
10729 Describe where the data for @var{symbol} is stored. For a register
10730 variable, this says which register it is kept in. For a non-register
10731 local variable, this prints the stack-frame offset at which the variable
10734 Note the contrast with @samp{print &@var{symbol}}, which does not work
10735 at all for a register variable, and for a stack local variable prints
10736 the exact address of the current instantiation of the variable.
10738 @kindex info symbol
10739 @cindex symbol from address
10740 @cindex closest symbol and offset for an address
10741 @item info symbol @var{addr}
10742 Print the name of a symbol which is stored at the address @var{addr}.
10743 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
10744 nearest symbol and an offset from it:
10747 (@value{GDBP}) info symbol 0x54320
10748 _initialize_vx + 396 in section .text
10752 This is the opposite of the @code{info address} command. You can use
10753 it to find out the name of a variable or a function given its address.
10756 @item whatis [@var{arg}]
10757 Print the data type of @var{arg}, which can be either an expression or
10758 a data type. With no argument, print the data type of @code{$}, the
10759 last value in the value history. If @var{arg} is an expression, it is
10760 not actually evaluated, and any side-effecting operations (such as
10761 assignments or function calls) inside it do not take place. If
10762 @var{arg} is a type name, it may be the name of a type or typedef, or
10763 for C code it may have the form @samp{class @var{class-name}},
10764 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
10765 @samp{enum @var{enum-tag}}.
10766 @xref{Expressions, ,Expressions}.
10769 @item ptype [@var{arg}]
10770 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
10771 detailed description of the type, instead of just the name of the type.
10772 @xref{Expressions, ,Expressions}.
10774 For example, for this variable declaration:
10777 struct complex @{double real; double imag;@} v;
10781 the two commands give this output:
10785 (@value{GDBP}) whatis v
10786 type = struct complex
10787 (@value{GDBP}) ptype v
10788 type = struct complex @{
10796 As with @code{whatis}, using @code{ptype} without an argument refers to
10797 the type of @code{$}, the last value in the value history.
10799 @cindex incomplete type
10800 Sometimes, programs use opaque data types or incomplete specifications
10801 of complex data structure. If the debug information included in the
10802 program does not allow @value{GDBN} to display a full declaration of
10803 the data type, it will say @samp{<incomplete type>}. For example,
10804 given these declarations:
10808 struct foo *fooptr;
10812 but no definition for @code{struct foo} itself, @value{GDBN} will say:
10815 (@value{GDBP}) ptype foo
10816 $1 = <incomplete type>
10820 ``Incomplete type'' is C terminology for data types that are not
10821 completely specified.
10824 @item info types @var{regexp}
10826 Print a brief description of all types whose names match the regular
10827 expression @var{regexp} (or all types in your program, if you supply
10828 no argument). Each complete typename is matched as though it were a
10829 complete line; thus, @samp{i type value} gives information on all
10830 types in your program whose names include the string @code{value}, but
10831 @samp{i type ^value$} gives information only on types whose complete
10832 name is @code{value}.
10834 This command differs from @code{ptype} in two ways: first, like
10835 @code{whatis}, it does not print a detailed description; second, it
10836 lists all source files where a type is defined.
10839 @cindex local variables
10840 @item info scope @var{location}
10841 List all the variables local to a particular scope. This command
10842 accepts a @var{location} argument---a function name, a source line, or
10843 an address preceded by a @samp{*}, and prints all the variables local
10844 to the scope defined by that location. For example:
10847 (@value{GDBP}) @b{info scope command_line_handler}
10848 Scope for command_line_handler:
10849 Symbol rl is an argument at stack/frame offset 8, length 4.
10850 Symbol linebuffer is in static storage at address 0x150a18, length 4.
10851 Symbol linelength is in static storage at address 0x150a1c, length 4.
10852 Symbol p is a local variable in register $esi, length 4.
10853 Symbol p1 is a local variable in register $ebx, length 4.
10854 Symbol nline is a local variable in register $edx, length 4.
10855 Symbol repeat is a local variable at frame offset -8, length 4.
10859 This command is especially useful for determining what data to collect
10860 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
10863 @kindex info source
10865 Show information about the current source file---that is, the source file for
10866 the function containing the current point of execution:
10869 the name of the source file, and the directory containing it,
10871 the directory it was compiled in,
10873 its length, in lines,
10875 which programming language it is written in,
10877 whether the executable includes debugging information for that file, and
10878 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
10880 whether the debugging information includes information about
10881 preprocessor macros.
10885 @kindex info sources
10887 Print the names of all source files in your program for which there is
10888 debugging information, organized into two lists: files whose symbols
10889 have already been read, and files whose symbols will be read when needed.
10891 @kindex info functions
10892 @item info functions
10893 Print the names and data types of all defined functions.
10895 @item info functions @var{regexp}
10896 Print the names and data types of all defined functions
10897 whose names contain a match for regular expression @var{regexp}.
10898 Thus, @samp{info fun step} finds all functions whose names
10899 include @code{step}; @samp{info fun ^step} finds those whose names
10900 start with @code{step}. If a function name contains characters
10901 that conflict with the regular expression language (e.g.@:
10902 @samp{operator*()}), they may be quoted with a backslash.
10904 @kindex info variables
10905 @item info variables
10906 Print the names and data types of all variables that are declared
10907 outside of functions (i.e.@: excluding local variables).
10909 @item info variables @var{regexp}
10910 Print the names and data types of all variables (except for local
10911 variables) whose names contain a match for regular expression
10914 @kindex info classes
10915 @cindex Objective-C, classes and selectors
10917 @itemx info classes @var{regexp}
10918 Display all Objective-C classes in your program, or
10919 (with the @var{regexp} argument) all those matching a particular regular
10922 @kindex info selectors
10923 @item info selectors
10924 @itemx info selectors @var{regexp}
10925 Display all Objective-C selectors in your program, or
10926 (with the @var{regexp} argument) all those matching a particular regular
10930 This was never implemented.
10931 @kindex info methods
10933 @itemx info methods @var{regexp}
10934 The @code{info methods} command permits the user to examine all defined
10935 methods within C@t{++} program, or (with the @var{regexp} argument) a
10936 specific set of methods found in the various C@t{++} classes. Many
10937 C@t{++} classes provide a large number of methods. Thus, the output
10938 from the @code{ptype} command can be overwhelming and hard to use. The
10939 @code{info-methods} command filters the methods, printing only those
10940 which match the regular-expression @var{regexp}.
10943 @cindex reloading symbols
10944 Some systems allow individual object files that make up your program to
10945 be replaced without stopping and restarting your program. For example,
10946 in VxWorks you can simply recompile a defective object file and keep on
10947 running. If you are running on one of these systems, you can allow
10948 @value{GDBN} to reload the symbols for automatically relinked modules:
10951 @kindex set symbol-reloading
10952 @item set symbol-reloading on
10953 Replace symbol definitions for the corresponding source file when an
10954 object file with a particular name is seen again.
10956 @item set symbol-reloading off
10957 Do not replace symbol definitions when encountering object files of the
10958 same name more than once. This is the default state; if you are not
10959 running on a system that permits automatic relinking of modules, you
10960 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
10961 may discard symbols when linking large programs, that may contain
10962 several modules (from different directories or libraries) with the same
10965 @kindex show symbol-reloading
10966 @item show symbol-reloading
10967 Show the current @code{on} or @code{off} setting.
10970 @cindex opaque data types
10971 @kindex set opaque-type-resolution
10972 @item set opaque-type-resolution on
10973 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
10974 declared as a pointer to a @code{struct}, @code{class}, or
10975 @code{union}---for example, @code{struct MyType *}---that is used in one
10976 source file although the full declaration of @code{struct MyType} is in
10977 another source file. The default is on.
10979 A change in the setting of this subcommand will not take effect until
10980 the next time symbols for a file are loaded.
10982 @item set opaque-type-resolution off
10983 Tell @value{GDBN} not to resolve opaque types. In this case, the type
10984 is printed as follows:
10986 @{<no data fields>@}
10989 @kindex show opaque-type-resolution
10990 @item show opaque-type-resolution
10991 Show whether opaque types are resolved or not.
10993 @kindex maint print symbols
10994 @cindex symbol dump
10995 @kindex maint print psymbols
10996 @cindex partial symbol dump
10997 @item maint print symbols @var{filename}
10998 @itemx maint print psymbols @var{filename}
10999 @itemx maint print msymbols @var{filename}
11000 Write a dump of debugging symbol data into the file @var{filename}.
11001 These commands are used to debug the @value{GDBN} symbol-reading code. Only
11002 symbols with debugging data are included. If you use @samp{maint print
11003 symbols}, @value{GDBN} includes all the symbols for which it has already
11004 collected full details: that is, @var{filename} reflects symbols for
11005 only those files whose symbols @value{GDBN} has read. You can use the
11006 command @code{info sources} to find out which files these are. If you
11007 use @samp{maint print psymbols} instead, the dump shows information about
11008 symbols that @value{GDBN} only knows partially---that is, symbols defined in
11009 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
11010 @samp{maint print msymbols} dumps just the minimal symbol information
11011 required for each object file from which @value{GDBN} has read some symbols.
11012 @xref{Files, ,Commands to Specify Files}, for a discussion of how
11013 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
11015 @kindex maint info symtabs
11016 @kindex maint info psymtabs
11017 @cindex listing @value{GDBN}'s internal symbol tables
11018 @cindex symbol tables, listing @value{GDBN}'s internal
11019 @cindex full symbol tables, listing @value{GDBN}'s internal
11020 @cindex partial symbol tables, listing @value{GDBN}'s internal
11021 @item maint info symtabs @r{[} @var{regexp} @r{]}
11022 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
11024 List the @code{struct symtab} or @code{struct partial_symtab}
11025 structures whose names match @var{regexp}. If @var{regexp} is not
11026 given, list them all. The output includes expressions which you can
11027 copy into a @value{GDBN} debugging this one to examine a particular
11028 structure in more detail. For example:
11031 (@value{GDBP}) maint info psymtabs dwarf2read
11032 @{ objfile /home/gnu/build/gdb/gdb
11033 ((struct objfile *) 0x82e69d0)
11034 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
11035 ((struct partial_symtab *) 0x8474b10)
11038 text addresses 0x814d3c8 -- 0x8158074
11039 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
11040 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
11041 dependencies (none)
11044 (@value{GDBP}) maint info symtabs
11048 We see that there is one partial symbol table whose filename contains
11049 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
11050 and we see that @value{GDBN} has not read in any symtabs yet at all.
11051 If we set a breakpoint on a function, that will cause @value{GDBN} to
11052 read the symtab for the compilation unit containing that function:
11055 (@value{GDBP}) break dwarf2_psymtab_to_symtab
11056 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
11058 (@value{GDBP}) maint info symtabs
11059 @{ objfile /home/gnu/build/gdb/gdb
11060 ((struct objfile *) 0x82e69d0)
11061 @{ symtab /home/gnu/src/gdb/dwarf2read.c
11062 ((struct symtab *) 0x86c1f38)
11065 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
11066 debugformat DWARF 2
11075 @chapter Altering Execution
11077 Once you think you have found an error in your program, you might want to
11078 find out for certain whether correcting the apparent error would lead to
11079 correct results in the rest of the run. You can find the answer by
11080 experiment, using the @value{GDBN} features for altering execution of the
11083 For example, you can store new values into variables or memory
11084 locations, give your program a signal, restart it at a different
11085 address, or even return prematurely from a function.
11088 * Assignment:: Assignment to variables
11089 * Jumping:: Continuing at a different address
11090 * Signaling:: Giving your program a signal
11091 * Returning:: Returning from a function
11092 * Calling:: Calling your program's functions
11093 * Patching:: Patching your program
11097 @section Assignment to Variables
11100 @cindex setting variables
11101 To alter the value of a variable, evaluate an assignment expression.
11102 @xref{Expressions, ,Expressions}. For example,
11109 stores the value 4 into the variable @code{x}, and then prints the
11110 value of the assignment expression (which is 4).
11111 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
11112 information on operators in supported languages.
11114 @kindex set variable
11115 @cindex variables, setting
11116 If you are not interested in seeing the value of the assignment, use the
11117 @code{set} command instead of the @code{print} command. @code{set} is
11118 really the same as @code{print} except that the expression's value is
11119 not printed and is not put in the value history (@pxref{Value History,
11120 ,Value History}). The expression is evaluated only for its effects.
11122 If the beginning of the argument string of the @code{set} command
11123 appears identical to a @code{set} subcommand, use the @code{set
11124 variable} command instead of just @code{set}. This command is identical
11125 to @code{set} except for its lack of subcommands. For example, if your
11126 program has a variable @code{width}, you get an error if you try to set
11127 a new value with just @samp{set width=13}, because @value{GDBN} has the
11128 command @code{set width}:
11131 (@value{GDBP}) whatis width
11133 (@value{GDBP}) p width
11135 (@value{GDBP}) set width=47
11136 Invalid syntax in expression.
11140 The invalid expression, of course, is @samp{=47}. In
11141 order to actually set the program's variable @code{width}, use
11144 (@value{GDBP}) set var width=47
11147 Because the @code{set} command has many subcommands that can conflict
11148 with the names of program variables, it is a good idea to use the
11149 @code{set variable} command instead of just @code{set}. For example, if
11150 your program has a variable @code{g}, you run into problems if you try
11151 to set a new value with just @samp{set g=4}, because @value{GDBN} has
11152 the command @code{set gnutarget}, abbreviated @code{set g}:
11156 (@value{GDBP}) whatis g
11160 (@value{GDBP}) set g=4
11164 The program being debugged has been started already.
11165 Start it from the beginning? (y or n) y
11166 Starting program: /home/smith/cc_progs/a.out
11167 "/home/smith/cc_progs/a.out": can't open to read symbols:
11168 Invalid bfd target.
11169 (@value{GDBP}) show g
11170 The current BFD target is "=4".
11175 The program variable @code{g} did not change, and you silently set the
11176 @code{gnutarget} to an invalid value. In order to set the variable
11180 (@value{GDBP}) set var g=4
11183 @value{GDBN} allows more implicit conversions in assignments than C; you can
11184 freely store an integer value into a pointer variable or vice versa,
11185 and you can convert any structure to any other structure that is the
11186 same length or shorter.
11187 @comment FIXME: how do structs align/pad in these conversions?
11188 @comment /doc@cygnus.com 18dec1990
11190 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
11191 construct to generate a value of specified type at a specified address
11192 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
11193 to memory location @code{0x83040} as an integer (which implies a certain size
11194 and representation in memory), and
11197 set @{int@}0x83040 = 4
11201 stores the value 4 into that memory location.
11204 @section Continuing at a Different Address
11206 Ordinarily, when you continue your program, you do so at the place where
11207 it stopped, with the @code{continue} command. You can instead continue at
11208 an address of your own choosing, with the following commands:
11212 @item jump @var{linespec}
11213 Resume execution at line @var{linespec}. Execution stops again
11214 immediately if there is a breakpoint there. @xref{List, ,Printing
11215 Source Lines}, for a description of the different forms of
11216 @var{linespec}. It is common practice to use the @code{tbreak} command
11217 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
11220 The @code{jump} command does not change the current stack frame, or
11221 the stack pointer, or the contents of any memory location or any
11222 register other than the program counter. If line @var{linespec} is in
11223 a different function from the one currently executing, the results may
11224 be bizarre if the two functions expect different patterns of arguments or
11225 of local variables. For this reason, the @code{jump} command requests
11226 confirmation if the specified line is not in the function currently
11227 executing. However, even bizarre results are predictable if you are
11228 well acquainted with the machine-language code of your program.
11230 @item jump *@var{address}
11231 Resume execution at the instruction at address @var{address}.
11234 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
11235 On many systems, you can get much the same effect as the @code{jump}
11236 command by storing a new value into the register @code{$pc}. The
11237 difference is that this does not start your program running; it only
11238 changes the address of where it @emph{will} run when you continue. For
11246 makes the next @code{continue} command or stepping command execute at
11247 address @code{0x485}, rather than at the address where your program stopped.
11248 @xref{Continuing and Stepping, ,Continuing and Stepping}.
11250 The most common occasion to use the @code{jump} command is to back
11251 up---perhaps with more breakpoints set---over a portion of a program
11252 that has already executed, in order to examine its execution in more
11257 @section Giving your Program a Signal
11258 @cindex deliver a signal to a program
11262 @item signal @var{signal}
11263 Resume execution where your program stopped, but immediately give it the
11264 signal @var{signal}. @var{signal} can be the name or the number of a
11265 signal. For example, on many systems @code{signal 2} and @code{signal
11266 SIGINT} are both ways of sending an interrupt signal.
11268 Alternatively, if @var{signal} is zero, continue execution without
11269 giving a signal. This is useful when your program stopped on account of
11270 a signal and would ordinary see the signal when resumed with the
11271 @code{continue} command; @samp{signal 0} causes it to resume without a
11274 @code{signal} does not repeat when you press @key{RET} a second time
11275 after executing the command.
11279 Invoking the @code{signal} command is not the same as invoking the
11280 @code{kill} utility from the shell. Sending a signal with @code{kill}
11281 causes @value{GDBN} to decide what to do with the signal depending on
11282 the signal handling tables (@pxref{Signals}). The @code{signal} command
11283 passes the signal directly to your program.
11287 @section Returning from a Function
11290 @cindex returning from a function
11293 @itemx return @var{expression}
11294 You can cancel execution of a function call with the @code{return}
11295 command. If you give an
11296 @var{expression} argument, its value is used as the function's return
11300 When you use @code{return}, @value{GDBN} discards the selected stack frame
11301 (and all frames within it). You can think of this as making the
11302 discarded frame return prematurely. If you wish to specify a value to
11303 be returned, give that value as the argument to @code{return}.
11305 This pops the selected stack frame (@pxref{Selection, ,Selecting a
11306 Frame}), and any other frames inside of it, leaving its caller as the
11307 innermost remaining frame. That frame becomes selected. The
11308 specified value is stored in the registers used for returning values
11311 The @code{return} command does not resume execution; it leaves the
11312 program stopped in the state that would exist if the function had just
11313 returned. In contrast, the @code{finish} command (@pxref{Continuing
11314 and Stepping, ,Continuing and Stepping}) resumes execution until the
11315 selected stack frame returns naturally.
11318 @section Calling Program Functions
11321 @cindex calling functions
11322 @cindex inferior functions, calling
11323 @item print @var{expr}
11324 Evaluate the expression @var{expr} and display the resulting value.
11325 @var{expr} may include calls to functions in the program being
11329 @item call @var{expr}
11330 Evaluate the expression @var{expr} without displaying @code{void}
11333 You can use this variant of the @code{print} command if you want to
11334 execute a function from your program that does not return anything
11335 (a.k.a.@: @dfn{a void function}), but without cluttering the output
11336 with @code{void} returned values that @value{GDBN} will otherwise
11337 print. If the result is not void, it is printed and saved in the
11341 It is possible for the function you call via the @code{print} or
11342 @code{call} command to generate a signal (e.g., if there's a bug in
11343 the function, or if you passed it incorrect arguments). What happens
11344 in that case is controlled by the @code{set unwindonsignal} command.
11347 @item set unwindonsignal
11348 @kindex set unwindonsignal
11349 @cindex unwind stack in called functions
11350 @cindex call dummy stack unwinding
11351 Set unwinding of the stack if a signal is received while in a function
11352 that @value{GDBN} called in the program being debugged. If set to on,
11353 @value{GDBN} unwinds the stack it created for the call and restores
11354 the context to what it was before the call. If set to off (the
11355 default), @value{GDBN} stops in the frame where the signal was
11358 @item show unwindonsignal
11359 @kindex show unwindonsignal
11360 Show the current setting of stack unwinding in the functions called by
11364 @cindex weak alias functions
11365 Sometimes, a function you wish to call is actually a @dfn{weak alias}
11366 for another function. In such case, @value{GDBN} might not pick up
11367 the type information, including the types of the function arguments,
11368 which causes @value{GDBN} to call the inferior function incorrectly.
11369 As a result, the called function will function erroneously and may
11370 even crash. A solution to that is to use the name of the aliased
11374 @section Patching Programs
11376 @cindex patching binaries
11377 @cindex writing into executables
11378 @cindex writing into corefiles
11380 By default, @value{GDBN} opens the file containing your program's
11381 executable code (or the corefile) read-only. This prevents accidental
11382 alterations to machine code; but it also prevents you from intentionally
11383 patching your program's binary.
11385 If you'd like to be able to patch the binary, you can specify that
11386 explicitly with the @code{set write} command. For example, you might
11387 want to turn on internal debugging flags, or even to make emergency
11393 @itemx set write off
11394 If you specify @samp{set write on}, @value{GDBN} opens executable and
11395 core files for both reading and writing; if you specify @samp{set write
11396 off} (the default), @value{GDBN} opens them read-only.
11398 If you have already loaded a file, you must load it again (using the
11399 @code{exec-file} or @code{core-file} command) after changing @code{set
11400 write}, for your new setting to take effect.
11404 Display whether executable files and core files are opened for writing
11405 as well as reading.
11409 @chapter @value{GDBN} Files
11411 @value{GDBN} needs to know the file name of the program to be debugged,
11412 both in order to read its symbol table and in order to start your
11413 program. To debug a core dump of a previous run, you must also tell
11414 @value{GDBN} the name of the core dump file.
11417 * Files:: Commands to specify files
11418 * Separate Debug Files:: Debugging information in separate files
11419 * Symbol Errors:: Errors reading symbol files
11423 @section Commands to Specify Files
11425 @cindex symbol table
11426 @cindex core dump file
11428 You may want to specify executable and core dump file names. The usual
11429 way to do this is at start-up time, using the arguments to
11430 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
11431 Out of @value{GDBN}}).
11433 Occasionally it is necessary to change to a different file during a
11434 @value{GDBN} session. Or you may run @value{GDBN} and forget to
11435 specify a file you want to use. Or you are debugging a remote target
11436 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
11437 Program}). In these situations the @value{GDBN} commands to specify
11438 new files are useful.
11441 @cindex executable file
11443 @item file @var{filename}
11444 Use @var{filename} as the program to be debugged. It is read for its
11445 symbols and for the contents of pure memory. It is also the program
11446 executed when you use the @code{run} command. If you do not specify a
11447 directory and the file is not found in the @value{GDBN} working directory,
11448 @value{GDBN} uses the environment variable @code{PATH} as a list of
11449 directories to search, just as the shell does when looking for a program
11450 to run. You can change the value of this variable, for both @value{GDBN}
11451 and your program, using the @code{path} command.
11453 @cindex unlinked object files
11454 @cindex patching object files
11455 You can load unlinked object @file{.o} files into @value{GDBN} using
11456 the @code{file} command. You will not be able to ``run'' an object
11457 file, but you can disassemble functions and inspect variables. Also,
11458 if the underlying BFD functionality supports it, you could use
11459 @kbd{gdb -write} to patch object files using this technique. Note
11460 that @value{GDBN} can neither interpret nor modify relocations in this
11461 case, so branches and some initialized variables will appear to go to
11462 the wrong place. But this feature is still handy from time to time.
11465 @code{file} with no argument makes @value{GDBN} discard any information it
11466 has on both executable file and the symbol table.
11469 @item exec-file @r{[} @var{filename} @r{]}
11470 Specify that the program to be run (but not the symbol table) is found
11471 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
11472 if necessary to locate your program. Omitting @var{filename} means to
11473 discard information on the executable file.
11475 @kindex symbol-file
11476 @item symbol-file @r{[} @var{filename} @r{]}
11477 Read symbol table information from file @var{filename}. @code{PATH} is
11478 searched when necessary. Use the @code{file} command to get both symbol
11479 table and program to run from the same file.
11481 @code{symbol-file} with no argument clears out @value{GDBN} information on your
11482 program's symbol table.
11484 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
11485 some breakpoints and auto-display expressions. This is because they may
11486 contain pointers to the internal data recording symbols and data types,
11487 which are part of the old symbol table data being discarded inside
11490 @code{symbol-file} does not repeat if you press @key{RET} again after
11493 When @value{GDBN} is configured for a particular environment, it
11494 understands debugging information in whatever format is the standard
11495 generated for that environment; you may use either a @sc{gnu} compiler, or
11496 other compilers that adhere to the local conventions.
11497 Best results are usually obtained from @sc{gnu} compilers; for example,
11498 using @code{@value{NGCC}} you can generate debugging information for
11501 For most kinds of object files, with the exception of old SVR3 systems
11502 using COFF, the @code{symbol-file} command does not normally read the
11503 symbol table in full right away. Instead, it scans the symbol table
11504 quickly to find which source files and which symbols are present. The
11505 details are read later, one source file at a time, as they are needed.
11507 The purpose of this two-stage reading strategy is to make @value{GDBN}
11508 start up faster. For the most part, it is invisible except for
11509 occasional pauses while the symbol table details for a particular source
11510 file are being read. (The @code{set verbose} command can turn these
11511 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
11512 Warnings and Messages}.)
11514 We have not implemented the two-stage strategy for COFF yet. When the
11515 symbol table is stored in COFF format, @code{symbol-file} reads the
11516 symbol table data in full right away. Note that ``stabs-in-COFF''
11517 still does the two-stage strategy, since the debug info is actually
11521 @cindex reading symbols immediately
11522 @cindex symbols, reading immediately
11523 @item symbol-file @var{filename} @r{[} -readnow @r{]}
11524 @itemx file @var{filename} @r{[} -readnow @r{]}
11525 You can override the @value{GDBN} two-stage strategy for reading symbol
11526 tables by using the @samp{-readnow} option with any of the commands that
11527 load symbol table information, if you want to be sure @value{GDBN} has the
11528 entire symbol table available.
11530 @c FIXME: for now no mention of directories, since this seems to be in
11531 @c flux. 13mar1992 status is that in theory GDB would look either in
11532 @c current dir or in same dir as myprog; but issues like competing
11533 @c GDB's, or clutter in system dirs, mean that in practice right now
11534 @c only current dir is used. FFish says maybe a special GDB hierarchy
11535 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
11539 @item core-file @r{[}@var{filename}@r{]}
11541 Specify the whereabouts of a core dump file to be used as the ``contents
11542 of memory''. Traditionally, core files contain only some parts of the
11543 address space of the process that generated them; @value{GDBN} can access the
11544 executable file itself for other parts.
11546 @code{core-file} with no argument specifies that no core file is
11549 Note that the core file is ignored when your program is actually running
11550 under @value{GDBN}. So, if you have been running your program and you
11551 wish to debug a core file instead, you must kill the subprocess in which
11552 the program is running. To do this, use the @code{kill} command
11553 (@pxref{Kill Process, ,Killing the Child Process}).
11555 @kindex add-symbol-file
11556 @cindex dynamic linking
11557 @item add-symbol-file @var{filename} @var{address}
11558 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
11559 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
11560 The @code{add-symbol-file} command reads additional symbol table
11561 information from the file @var{filename}. You would use this command
11562 when @var{filename} has been dynamically loaded (by some other means)
11563 into the program that is running. @var{address} should be the memory
11564 address at which the file has been loaded; @value{GDBN} cannot figure
11565 this out for itself. You can additionally specify an arbitrary number
11566 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
11567 section name and base address for that section. You can specify any
11568 @var{address} as an expression.
11570 The symbol table of the file @var{filename} is added to the symbol table
11571 originally read with the @code{symbol-file} command. You can use the
11572 @code{add-symbol-file} command any number of times; the new symbol data
11573 thus read keeps adding to the old. To discard all old symbol data
11574 instead, use the @code{symbol-file} command without any arguments.
11576 @cindex relocatable object files, reading symbols from
11577 @cindex object files, relocatable, reading symbols from
11578 @cindex reading symbols from relocatable object files
11579 @cindex symbols, reading from relocatable object files
11580 @cindex @file{.o} files, reading symbols from
11581 Although @var{filename} is typically a shared library file, an
11582 executable file, or some other object file which has been fully
11583 relocated for loading into a process, you can also load symbolic
11584 information from relocatable @file{.o} files, as long as:
11588 the file's symbolic information refers only to linker symbols defined in
11589 that file, not to symbols defined by other object files,
11591 every section the file's symbolic information refers to has actually
11592 been loaded into the inferior, as it appears in the file, and
11594 you can determine the address at which every section was loaded, and
11595 provide these to the @code{add-symbol-file} command.
11599 Some embedded operating systems, like Sun Chorus and VxWorks, can load
11600 relocatable files into an already running program; such systems
11601 typically make the requirements above easy to meet. However, it's
11602 important to recognize that many native systems use complex link
11603 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
11604 assembly, for example) that make the requirements difficult to meet. In
11605 general, one cannot assume that using @code{add-symbol-file} to read a
11606 relocatable object file's symbolic information will have the same effect
11607 as linking the relocatable object file into the program in the normal
11610 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
11612 @kindex add-symbol-file-from-memory
11613 @cindex @code{syscall DSO}
11614 @cindex load symbols from memory
11615 @item add-symbol-file-from-memory @var{address}
11616 Load symbols from the given @var{address} in a dynamically loaded
11617 object file whose image is mapped directly into the inferior's memory.
11618 For example, the Linux kernel maps a @code{syscall DSO} into each
11619 process's address space; this DSO provides kernel-specific code for
11620 some system calls. The argument can be any expression whose
11621 evaluation yields the address of the file's shared object file header.
11622 For this command to work, you must have used @code{symbol-file} or
11623 @code{exec-file} commands in advance.
11625 @kindex add-shared-symbol-files
11627 @item add-shared-symbol-files @var{library-file}
11628 @itemx assf @var{library-file}
11629 The @code{add-shared-symbol-files} command can currently be used only
11630 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
11631 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
11632 @value{GDBN} automatically looks for shared libraries, however if
11633 @value{GDBN} does not find yours, you can invoke
11634 @code{add-shared-symbol-files}. It takes one argument: the shared
11635 library's file name. @code{assf} is a shorthand alias for
11636 @code{add-shared-symbol-files}.
11639 @item section @var{section} @var{addr}
11640 The @code{section} command changes the base address of the named
11641 @var{section} of the exec file to @var{addr}. This can be used if the
11642 exec file does not contain section addresses, (such as in the
11643 @code{a.out} format), or when the addresses specified in the file
11644 itself are wrong. Each section must be changed separately. The
11645 @code{info files} command, described below, lists all the sections and
11649 @kindex info target
11652 @code{info files} and @code{info target} are synonymous; both print the
11653 current target (@pxref{Targets, ,Specifying a Debugging Target}),
11654 including the names of the executable and core dump files currently in
11655 use by @value{GDBN}, and the files from which symbols were loaded. The
11656 command @code{help target} lists all possible targets rather than
11659 @kindex maint info sections
11660 @item maint info sections
11661 Another command that can give you extra information about program sections
11662 is @code{maint info sections}. In addition to the section information
11663 displayed by @code{info files}, this command displays the flags and file
11664 offset of each section in the executable and core dump files. In addition,
11665 @code{maint info sections} provides the following command options (which
11666 may be arbitrarily combined):
11670 Display sections for all loaded object files, including shared libraries.
11671 @item @var{sections}
11672 Display info only for named @var{sections}.
11673 @item @var{section-flags}
11674 Display info only for sections for which @var{section-flags} are true.
11675 The section flags that @value{GDBN} currently knows about are:
11678 Section will have space allocated in the process when loaded.
11679 Set for all sections except those containing debug information.
11681 Section will be loaded from the file into the child process memory.
11682 Set for pre-initialized code and data, clear for @code{.bss} sections.
11684 Section needs to be relocated before loading.
11686 Section cannot be modified by the child process.
11688 Section contains executable code only.
11690 Section contains data only (no executable code).
11692 Section will reside in ROM.
11694 Section contains data for constructor/destructor lists.
11696 Section is not empty.
11698 An instruction to the linker to not output the section.
11699 @item COFF_SHARED_LIBRARY
11700 A notification to the linker that the section contains
11701 COFF shared library information.
11703 Section contains common symbols.
11706 @kindex set trust-readonly-sections
11707 @cindex read-only sections
11708 @item set trust-readonly-sections on
11709 Tell @value{GDBN} that readonly sections in your object file
11710 really are read-only (i.e.@: that their contents will not change).
11711 In that case, @value{GDBN} can fetch values from these sections
11712 out of the object file, rather than from the target program.
11713 For some targets (notably embedded ones), this can be a significant
11714 enhancement to debugging performance.
11716 The default is off.
11718 @item set trust-readonly-sections off
11719 Tell @value{GDBN} not to trust readonly sections. This means that
11720 the contents of the section might change while the program is running,
11721 and must therefore be fetched from the target when needed.
11723 @item show trust-readonly-sections
11724 Show the current setting of trusting readonly sections.
11727 All file-specifying commands allow both absolute and relative file names
11728 as arguments. @value{GDBN} always converts the file name to an absolute file
11729 name and remembers it that way.
11731 @cindex shared libraries
11732 @value{GDBN} supports GNU/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
11733 and IBM RS/6000 AIX shared libraries.
11735 @value{GDBN} automatically loads symbol definitions from shared libraries
11736 when you use the @code{run} command, or when you examine a core file.
11737 (Before you issue the @code{run} command, @value{GDBN} does not understand
11738 references to a function in a shared library, however---unless you are
11739 debugging a core file).
11741 On HP-UX, if the program loads a library explicitly, @value{GDBN}
11742 automatically loads the symbols at the time of the @code{shl_load} call.
11744 @c FIXME: some @value{GDBN} release may permit some refs to undef
11745 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
11746 @c FIXME...lib; check this from time to time when updating manual
11748 There are times, however, when you may wish to not automatically load
11749 symbol definitions from shared libraries, such as when they are
11750 particularly large or there are many of them.
11752 To control the automatic loading of shared library symbols, use the
11756 @kindex set auto-solib-add
11757 @item set auto-solib-add @var{mode}
11758 If @var{mode} is @code{on}, symbols from all shared object libraries
11759 will be loaded automatically when the inferior begins execution, you
11760 attach to an independently started inferior, or when the dynamic linker
11761 informs @value{GDBN} that a new library has been loaded. If @var{mode}
11762 is @code{off}, symbols must be loaded manually, using the
11763 @code{sharedlibrary} command. The default value is @code{on}.
11765 @cindex memory used for symbol tables
11766 If your program uses lots of shared libraries with debug info that
11767 takes large amounts of memory, you can decrease the @value{GDBN}
11768 memory footprint by preventing it from automatically loading the
11769 symbols from shared libraries. To that end, type @kbd{set
11770 auto-solib-add off} before running the inferior, then load each
11771 library whose debug symbols you do need with @kbd{sharedlibrary
11772 @var{regexp}}, where @var{regexp} is a regular expression that matches
11773 the libraries whose symbols you want to be loaded.
11775 @kindex show auto-solib-add
11776 @item show auto-solib-add
11777 Display the current autoloading mode.
11780 @cindex load shared library
11781 To explicitly load shared library symbols, use the @code{sharedlibrary}
11785 @kindex info sharedlibrary
11788 @itemx info sharedlibrary
11789 Print the names of the shared libraries which are currently loaded.
11791 @kindex sharedlibrary
11793 @item sharedlibrary @var{regex}
11794 @itemx share @var{regex}
11795 Load shared object library symbols for files matching a
11796 Unix regular expression.
11797 As with files loaded automatically, it only loads shared libraries
11798 required by your program for a core file or after typing @code{run}. If
11799 @var{regex} is omitted all shared libraries required by your program are
11802 @item nosharedlibrary
11803 @kindex nosharedlibrary
11804 @cindex unload symbols from shared libraries
11805 Unload all shared object library symbols. This discards all symbols
11806 that have been loaded from all shared libraries. Symbols from shared
11807 libraries that were loaded by explicit user requests are not
11811 Sometimes you may wish that @value{GDBN} stops and gives you control
11812 when any of shared library events happen. Use the @code{set
11813 stop-on-solib-events} command for this:
11816 @item set stop-on-solib-events
11817 @kindex set stop-on-solib-events
11818 This command controls whether @value{GDBN} should give you control
11819 when the dynamic linker notifies it about some shared library event.
11820 The most common event of interest is loading or unloading of a new
11823 @item show stop-on-solib-events
11824 @kindex show stop-on-solib-events
11825 Show whether @value{GDBN} stops and gives you control when shared
11826 library events happen.
11829 Shared libraries are also supported in many cross or remote debugging
11830 configurations. A copy of the target's libraries need to be present on the
11831 host system; they need to be the same as the target libraries, although the
11832 copies on the target can be stripped as long as the copies on the host are
11835 @cindex where to look for shared libraries
11836 For remote debugging, you need to tell @value{GDBN} where the target
11837 libraries are, so that it can load the correct copies---otherwise, it
11838 may try to load the host's libraries. @value{GDBN} has two variables
11839 to specify the search directories for target libraries.
11842 @cindex prefix for shared library file names
11843 @cindex system root, alternate
11844 @kindex set solib-absolute-prefix
11845 @kindex set sysroot
11846 @item set sysroot @var{path}
11847 Use @var{path} as the system root for the program being debugged. Any
11848 absolute shared library paths will be prefixed with @var{path}; many
11849 runtime loaders store the absolute paths to the shared library in the
11850 target program's memory. If you use @code{set sysroot} to find shared
11851 libraries, they need to be laid out in the same way that they are on
11852 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
11855 The @code{set solib-absolute-prefix} command is an alias for @code{set
11858 @cindex default system root
11859 @cindex @samp{--with-sysroot}
11860 You can set the default system root by using the configure-time
11861 @samp{--with-sysroot} option. If the system root is inside
11862 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
11863 @samp{--exec-prefix}), then the default system root will be updated
11864 automatically if the installed @value{GDBN} is moved to a new
11867 @kindex show sysroot
11869 Display the current shared library prefix.
11871 @kindex set solib-search-path
11872 @item set solib-search-path @var{path}
11873 If this variable is set, @var{path} is a colon-separated list of
11874 directories to search for shared libraries. @samp{solib-search-path}
11875 is used after @samp{sysroot} fails to locate the library, or if the
11876 path to the library is relative instead of absolute. If you want to
11877 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
11878 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
11879 finding your host's libraries. @samp{sysroot} is preferred; setting
11880 it to a nonexistent directory may interfere with automatic loading
11881 of shared library symbols.
11883 @kindex show solib-search-path
11884 @item show solib-search-path
11885 Display the current shared library search path.
11889 @node Separate Debug Files
11890 @section Debugging Information in Separate Files
11891 @cindex separate debugging information files
11892 @cindex debugging information in separate files
11893 @cindex @file{.debug} subdirectories
11894 @cindex debugging information directory, global
11895 @cindex global debugging information directory
11896 @cindex build ID, and separate debugging files
11897 @cindex @file{.build-id} directory
11899 @value{GDBN} allows you to put a program's debugging information in a
11900 file separate from the executable itself, in a way that allows
11901 @value{GDBN} to find and load the debugging information automatically.
11902 Since debugging information can be very large---sometimes larger
11903 than the executable code itself---some systems distribute debugging
11904 information for their executables in separate files, which users can
11905 install only when they need to debug a problem.
11907 @value{GDBN} supports two ways of specifying the separate debug info
11912 The executable contains a @dfn{debug link} that specifies the name of
11913 the separate debug info file. The separate debug file's name is
11914 usually @file{@var{executable}.debug}, where @var{executable} is the
11915 name of the corresponding executable file without leading directories
11916 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
11917 debug link specifies a CRC32 checksum for the debug file, which
11918 @value{GDBN} uses to validate that the executable and the debug file
11919 came from the same build.
11922 The executable contains a @dfn{build ID}, a unique signature that is
11923 also present in the corresponding debug info file. (This is supported
11924 only on some operating systems, notably on @sc{gnu}/Linux. For more
11925 details about this feature, see
11926 @uref{http://fedoraproject.org/wiki/Releases/FeatureBuildId, the
11927 Fedora Project's description of the buid ID feature}.) The debug info
11928 file's name is not specified explicitly by the debug ID, but can be
11929 computed from the build ID, see below.
11932 Depending on the way the debug info file is specified, @value{GDBN}
11933 uses two different methods of looking for the debug file:
11937 For the ``debug link'' method, @value{GDBN} looks up the named file in
11938 the directory of the executable file, then in a subdirectory of that
11939 directory named @file{.debug}, and finally under the global debug
11940 directory, in a subdirectory whose name is identical to the leading
11941 directories of the executable's absolute file name.
11944 For the ``debug ID'' method, @value{GDBN} looks in the
11945 @file{.build-id} subdirectory of the global debug directory for a file
11946 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
11947 first 2 hex characters of the debug ID signature, and @var{nnnnnnnn}
11948 are the rest of the signature. (Real signatures are 32 or more
11949 characters, not 10.)
11952 So, for example, suppose you ask @value{GDBN} to debug
11953 @file{/usr/bin/ls}, which has a @dfn{debug link} that specifies the
11954 file @file{ls.debug}, and a @dfn{build id} whose value in hex is
11955 @code{abcdef1234}. If the global debug directory is
11956 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
11957 debug information files, in the indicated order:
11961 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
11963 @file{/usr/bin/ls.debug}
11965 @file{/usr/bin/.debug/ls.debug}
11967 @file{/usr/lib/debug/usr/bin/ls.debug}.
11970 You can set the global debugging info directory's name, and view the
11971 name @value{GDBN} is currently using.
11975 @kindex set debug-file-directory
11976 @item set debug-file-directory @var{directory}
11977 Set the directory which @value{GDBN} searches for separate debugging
11978 information files to @var{directory}.
11980 @kindex show debug-file-directory
11981 @item show debug-file-directory
11982 Show the directory @value{GDBN} searches for separate debugging
11987 @cindex @code{.gnu_debuglink} sections
11988 @cindex debug link sections
11989 A debug link is a special section of the executable file named
11990 @code{.gnu_debuglink}. The section must contain:
11994 A filename, with any leading directory components removed, followed by
11997 zero to three bytes of padding, as needed to reach the next four-byte
11998 boundary within the section, and
12000 a four-byte CRC checksum, stored in the same endianness used for the
12001 executable file itself. The checksum is computed on the debugging
12002 information file's full contents by the function given below, passing
12003 zero as the @var{crc} argument.
12006 Any executable file format can carry a debug link, as long as it can
12007 contain a section named @code{.gnu_debuglink} with the contents
12010 @cindex @code{.note.gnu.build-id} sections
12011 @cindex build ID sections
12012 A build ID is a special section of the executable file named
12013 @code{.note.gnu.build-id}. This section contains unique
12014 identification for the built files---it remains the same across
12015 multiple builds of the same build tree. The default algorithm SHA1
12016 produces 160 bits (40 hexadecimal characters) of the content. The
12017 same section with an identical value is present in the original built
12018 binary with symbols, in its stripped variant, and in the separate
12019 debugging information file.
12021 The debugging information file itself should be an ordinary
12022 executable, containing a full set of linker symbols, sections, and
12023 debugging information. The sections of the debugging information file
12024 should have the same names, addresses, and sizes as the original file,
12025 but they need not contain any data---much like a @code{.bss} section
12026 in an ordinary executable.
12028 @sc{gnu} binary utilities (Binutils) package includes the
12029 @samp{objcopy} utility that can produce
12030 the separated executable / debugging information file pairs using the
12031 following commands:
12034 @kbd{objcopy --only-keep-debug foo foo.debug}
12036 @kbd{objcopy --add-gnu-debuglink="foo.debug" "foo"}
12040 These commands remove the debugging
12041 information from the executable file @file{foo}, place it in the file
12042 @file{foo.debug}, and leave behind a debug link in @file{foo}. Ulrich
12043 Drepper's @file{elfutils} package, starting with version 0.53, contains
12044 a version of the @code{strip} command such that the command @kbd{strip foo -f
12045 foo.debug} has the same functionality as the three commands above.
12047 Since there are many different ways to compute CRC's for the debug
12048 link (different polynomials, reversals, byte ordering, etc.), the
12049 simplest way to describe the CRC used in @code{.gnu_debuglink}
12050 sections is to give the complete code for a function that computes it:
12052 @kindex gnu_debuglink_crc32
12055 gnu_debuglink_crc32 (unsigned long crc,
12056 unsigned char *buf, size_t len)
12058 static const unsigned long crc32_table[256] =
12060 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
12061 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
12062 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
12063 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
12064 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
12065 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
12066 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
12067 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
12068 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
12069 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
12070 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
12071 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
12072 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
12073 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
12074 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
12075 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
12076 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
12077 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
12078 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
12079 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
12080 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
12081 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
12082 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
12083 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
12084 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
12085 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
12086 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
12087 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
12088 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
12089 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
12090 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
12091 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
12092 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
12093 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
12094 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
12095 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
12096 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
12097 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
12098 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
12099 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
12100 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
12101 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
12102 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
12103 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
12104 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
12105 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
12106 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
12107 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
12108 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
12109 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
12110 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
12113 unsigned char *end;
12115 crc = ~crc & 0xffffffff;
12116 for (end = buf + len; buf < end; ++buf)
12117 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
12118 return ~crc & 0xffffffff;
12123 This computation does not apply to the ``build ID'' method.
12126 @node Symbol Errors
12127 @section Errors Reading Symbol Files
12129 While reading a symbol file, @value{GDBN} occasionally encounters problems,
12130 such as symbol types it does not recognize, or known bugs in compiler
12131 output. By default, @value{GDBN} does not notify you of such problems, since
12132 they are relatively common and primarily of interest to people
12133 debugging compilers. If you are interested in seeing information
12134 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
12135 only one message about each such type of problem, no matter how many
12136 times the problem occurs; or you can ask @value{GDBN} to print more messages,
12137 to see how many times the problems occur, with the @code{set
12138 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
12141 The messages currently printed, and their meanings, include:
12144 @item inner block not inside outer block in @var{symbol}
12146 The symbol information shows where symbol scopes begin and end
12147 (such as at the start of a function or a block of statements). This
12148 error indicates that an inner scope block is not fully contained
12149 in its outer scope blocks.
12151 @value{GDBN} circumvents the problem by treating the inner block as if it had
12152 the same scope as the outer block. In the error message, @var{symbol}
12153 may be shown as ``@code{(don't know)}'' if the outer block is not a
12156 @item block at @var{address} out of order
12158 The symbol information for symbol scope blocks should occur in
12159 order of increasing addresses. This error indicates that it does not
12162 @value{GDBN} does not circumvent this problem, and has trouble
12163 locating symbols in the source file whose symbols it is reading. (You
12164 can often determine what source file is affected by specifying
12165 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
12168 @item bad block start address patched
12170 The symbol information for a symbol scope block has a start address
12171 smaller than the address of the preceding source line. This is known
12172 to occur in the SunOS 4.1.1 (and earlier) C compiler.
12174 @value{GDBN} circumvents the problem by treating the symbol scope block as
12175 starting on the previous source line.
12177 @item bad string table offset in symbol @var{n}
12180 Symbol number @var{n} contains a pointer into the string table which is
12181 larger than the size of the string table.
12183 @value{GDBN} circumvents the problem by considering the symbol to have the
12184 name @code{foo}, which may cause other problems if many symbols end up
12187 @item unknown symbol type @code{0x@var{nn}}
12189 The symbol information contains new data types that @value{GDBN} does
12190 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
12191 uncomprehended information, in hexadecimal.
12193 @value{GDBN} circumvents the error by ignoring this symbol information.
12194 This usually allows you to debug your program, though certain symbols
12195 are not accessible. If you encounter such a problem and feel like
12196 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
12197 on @code{complain}, then go up to the function @code{read_dbx_symtab}
12198 and examine @code{*bufp} to see the symbol.
12200 @item stub type has NULL name
12202 @value{GDBN} could not find the full definition for a struct or class.
12204 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
12205 The symbol information for a C@t{++} member function is missing some
12206 information that recent versions of the compiler should have output for
12209 @item info mismatch between compiler and debugger
12211 @value{GDBN} could not parse a type specification output by the compiler.
12216 @chapter Specifying a Debugging Target
12218 @cindex debugging target
12219 A @dfn{target} is the execution environment occupied by your program.
12221 Often, @value{GDBN} runs in the same host environment as your program;
12222 in that case, the debugging target is specified as a side effect when
12223 you use the @code{file} or @code{core} commands. When you need more
12224 flexibility---for example, running @value{GDBN} on a physically separate
12225 host, or controlling a standalone system over a serial port or a
12226 realtime system over a TCP/IP connection---you can use the @code{target}
12227 command to specify one of the target types configured for @value{GDBN}
12228 (@pxref{Target Commands, ,Commands for Managing Targets}).
12230 @cindex target architecture
12231 It is possible to build @value{GDBN} for several different @dfn{target
12232 architectures}. When @value{GDBN} is built like that, you can choose
12233 one of the available architectures with the @kbd{set architecture}
12237 @kindex set architecture
12238 @kindex show architecture
12239 @item set architecture @var{arch}
12240 This command sets the current target architecture to @var{arch}. The
12241 value of @var{arch} can be @code{"auto"}, in addition to one of the
12242 supported architectures.
12244 @item show architecture
12245 Show the current target architecture.
12247 @item set processor
12249 @kindex set processor
12250 @kindex show processor
12251 These are alias commands for, respectively, @code{set architecture}
12252 and @code{show architecture}.
12256 * Active Targets:: Active targets
12257 * Target Commands:: Commands for managing targets
12258 * Byte Order:: Choosing target byte order
12261 @node Active Targets
12262 @section Active Targets
12264 @cindex stacking targets
12265 @cindex active targets
12266 @cindex multiple targets
12268 There are three classes of targets: processes, core files, and
12269 executable files. @value{GDBN} can work concurrently on up to three
12270 active targets, one in each class. This allows you to (for example)
12271 start a process and inspect its activity without abandoning your work on
12274 For example, if you execute @samp{gdb a.out}, then the executable file
12275 @code{a.out} is the only active target. If you designate a core file as
12276 well---presumably from a prior run that crashed and coredumped---then
12277 @value{GDBN} has two active targets and uses them in tandem, looking
12278 first in the corefile target, then in the executable file, to satisfy
12279 requests for memory addresses. (Typically, these two classes of target
12280 are complementary, since core files contain only a program's
12281 read-write memory---variables and so on---plus machine status, while
12282 executable files contain only the program text and initialized data.)
12284 When you type @code{run}, your executable file becomes an active process
12285 target as well. When a process target is active, all @value{GDBN}
12286 commands requesting memory addresses refer to that target; addresses in
12287 an active core file or executable file target are obscured while the
12288 process target is active.
12290 Use the @code{core-file} and @code{exec-file} commands to select a new
12291 core file or executable target (@pxref{Files, ,Commands to Specify
12292 Files}). To specify as a target a process that is already running, use
12293 the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
12296 @node Target Commands
12297 @section Commands for Managing Targets
12300 @item target @var{type} @var{parameters}
12301 Connects the @value{GDBN} host environment to a target machine or
12302 process. A target is typically a protocol for talking to debugging
12303 facilities. You use the argument @var{type} to specify the type or
12304 protocol of the target machine.
12306 Further @var{parameters} are interpreted by the target protocol, but
12307 typically include things like device names or host names to connect
12308 with, process numbers, and baud rates.
12310 The @code{target} command does not repeat if you press @key{RET} again
12311 after executing the command.
12313 @kindex help target
12315 Displays the names of all targets available. To display targets
12316 currently selected, use either @code{info target} or @code{info files}
12317 (@pxref{Files, ,Commands to Specify Files}).
12319 @item help target @var{name}
12320 Describe a particular target, including any parameters necessary to
12323 @kindex set gnutarget
12324 @item set gnutarget @var{args}
12325 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
12326 knows whether it is reading an @dfn{executable},
12327 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
12328 with the @code{set gnutarget} command. Unlike most @code{target} commands,
12329 with @code{gnutarget} the @code{target} refers to a program, not a machine.
12332 @emph{Warning:} To specify a file format with @code{set gnutarget},
12333 you must know the actual BFD name.
12337 @xref{Files, , Commands to Specify Files}.
12339 @kindex show gnutarget
12340 @item show gnutarget
12341 Use the @code{show gnutarget} command to display what file format
12342 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
12343 @value{GDBN} will determine the file format for each file automatically,
12344 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
12347 @cindex common targets
12348 Here are some common targets (available, or not, depending on the GDB
12353 @item target exec @var{program}
12354 @cindex executable file target
12355 An executable file. @samp{target exec @var{program}} is the same as
12356 @samp{exec-file @var{program}}.
12358 @item target core @var{filename}
12359 @cindex core dump file target
12360 A core dump file. @samp{target core @var{filename}} is the same as
12361 @samp{core-file @var{filename}}.
12363 @item target remote @var{medium}
12364 @cindex remote target
12365 A remote system connected to @value{GDBN} via a serial line or network
12366 connection. This command tells @value{GDBN} to use its own remote
12367 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
12369 For example, if you have a board connected to @file{/dev/ttya} on the
12370 machine running @value{GDBN}, you could say:
12373 target remote /dev/ttya
12376 @code{target remote} supports the @code{load} command. This is only
12377 useful if you have some other way of getting the stub to the target
12378 system, and you can put it somewhere in memory where it won't get
12379 clobbered by the download.
12382 @cindex built-in simulator target
12383 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
12391 works; however, you cannot assume that a specific memory map, device
12392 drivers, or even basic I/O is available, although some simulators do
12393 provide these. For info about any processor-specific simulator details,
12394 see the appropriate section in @ref{Embedded Processors, ,Embedded
12399 Some configurations may include these targets as well:
12403 @item target nrom @var{dev}
12404 @cindex NetROM ROM emulator target
12405 NetROM ROM emulator. This target only supports downloading.
12409 Different targets are available on different configurations of @value{GDBN};
12410 your configuration may have more or fewer targets.
12412 Many remote targets require you to download the executable's code once
12413 you've successfully established a connection. You may wish to control
12414 various aspects of this process.
12419 @kindex set hash@r{, for remote monitors}
12420 @cindex hash mark while downloading
12421 This command controls whether a hash mark @samp{#} is displayed while
12422 downloading a file to the remote monitor. If on, a hash mark is
12423 displayed after each S-record is successfully downloaded to the
12427 @kindex show hash@r{, for remote monitors}
12428 Show the current status of displaying the hash mark.
12430 @item set debug monitor
12431 @kindex set debug monitor
12432 @cindex display remote monitor communications
12433 Enable or disable display of communications messages between
12434 @value{GDBN} and the remote monitor.
12436 @item show debug monitor
12437 @kindex show debug monitor
12438 Show the current status of displaying communications between
12439 @value{GDBN} and the remote monitor.
12444 @kindex load @var{filename}
12445 @item load @var{filename}
12446 Depending on what remote debugging facilities are configured into
12447 @value{GDBN}, the @code{load} command may be available. Where it exists, it
12448 is meant to make @var{filename} (an executable) available for debugging
12449 on the remote system---by downloading, or dynamic linking, for example.
12450 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
12451 the @code{add-symbol-file} command.
12453 If your @value{GDBN} does not have a @code{load} command, attempting to
12454 execute it gets the error message ``@code{You can't do that when your
12455 target is @dots{}}''
12457 The file is loaded at whatever address is specified in the executable.
12458 For some object file formats, you can specify the load address when you
12459 link the program; for other formats, like a.out, the object file format
12460 specifies a fixed address.
12461 @c FIXME! This would be a good place for an xref to the GNU linker doc.
12463 Depending on the remote side capabilities, @value{GDBN} may be able to
12464 load programs into flash memory.
12466 @code{load} does not repeat if you press @key{RET} again after using it.
12470 @section Choosing Target Byte Order
12472 @cindex choosing target byte order
12473 @cindex target byte order
12475 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
12476 offer the ability to run either big-endian or little-endian byte
12477 orders. Usually the executable or symbol will include a bit to
12478 designate the endian-ness, and you will not need to worry about
12479 which to use. However, you may still find it useful to adjust
12480 @value{GDBN}'s idea of processor endian-ness manually.
12484 @item set endian big
12485 Instruct @value{GDBN} to assume the target is big-endian.
12487 @item set endian little
12488 Instruct @value{GDBN} to assume the target is little-endian.
12490 @item set endian auto
12491 Instruct @value{GDBN} to use the byte order associated with the
12495 Display @value{GDBN}'s current idea of the target byte order.
12499 Note that these commands merely adjust interpretation of symbolic
12500 data on the host, and that they have absolutely no effect on the
12504 @node Remote Debugging
12505 @chapter Debugging Remote Programs
12506 @cindex remote debugging
12508 If you are trying to debug a program running on a machine that cannot run
12509 @value{GDBN} in the usual way, it is often useful to use remote debugging.
12510 For example, you might use remote debugging on an operating system kernel,
12511 or on a small system which does not have a general purpose operating system
12512 powerful enough to run a full-featured debugger.
12514 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
12515 to make this work with particular debugging targets. In addition,
12516 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
12517 but not specific to any particular target system) which you can use if you
12518 write the remote stubs---the code that runs on the remote system to
12519 communicate with @value{GDBN}.
12521 Other remote targets may be available in your
12522 configuration of @value{GDBN}; use @code{help target} to list them.
12525 * Connecting:: Connecting to a remote target
12526 * Server:: Using the gdbserver program
12527 * Remote Configuration:: Remote configuration
12528 * Remote Stub:: Implementing a remote stub
12532 @section Connecting to a Remote Target
12534 On the @value{GDBN} host machine, you will need an unstripped copy of
12535 your program, since @value{GDBN} needs symbol and debugging information.
12536 Start up @value{GDBN} as usual, using the name of the local copy of your
12537 program as the first argument.
12539 @cindex @code{target remote}
12540 @value{GDBN} can communicate with the target over a serial line, or
12541 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
12542 each case, @value{GDBN} uses the same protocol for debugging your
12543 program; only the medium carrying the debugging packets varies. The
12544 @code{target remote} command establishes a connection to the target.
12545 Its arguments indicate which medium to use:
12549 @item target remote @var{serial-device}
12550 @cindex serial line, @code{target remote}
12551 Use @var{serial-device} to communicate with the target. For example,
12552 to use a serial line connected to the device named @file{/dev/ttyb}:
12555 target remote /dev/ttyb
12558 If you're using a serial line, you may want to give @value{GDBN} the
12559 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
12560 (@pxref{Remote Configuration, set remotebaud}) before the
12561 @code{target} command.
12563 @item target remote @code{@var{host}:@var{port}}
12564 @itemx target remote @code{tcp:@var{host}:@var{port}}
12565 @cindex @acronym{TCP} port, @code{target remote}
12566 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
12567 The @var{host} may be either a host name or a numeric @acronym{IP}
12568 address; @var{port} must be a decimal number. The @var{host} could be
12569 the target machine itself, if it is directly connected to the net, or
12570 it might be a terminal server which in turn has a serial line to the
12573 For example, to connect to port 2828 on a terminal server named
12577 target remote manyfarms:2828
12580 If your remote target is actually running on the same machine as your
12581 debugger session (e.g.@: a simulator for your target running on the
12582 same host), you can omit the hostname. For example, to connect to
12583 port 1234 on your local machine:
12586 target remote :1234
12590 Note that the colon is still required here.
12592 @item target remote @code{udp:@var{host}:@var{port}}
12593 @cindex @acronym{UDP} port, @code{target remote}
12594 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
12595 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
12598 target remote udp:manyfarms:2828
12601 When using a @acronym{UDP} connection for remote debugging, you should
12602 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
12603 can silently drop packets on busy or unreliable networks, which will
12604 cause havoc with your debugging session.
12606 @item target remote | @var{command}
12607 @cindex pipe, @code{target remote} to
12608 Run @var{command} in the background and communicate with it using a
12609 pipe. The @var{command} is a shell command, to be parsed and expanded
12610 by the system's command shell, @code{/bin/sh}; it should expect remote
12611 protocol packets on its standard input, and send replies on its
12612 standard output. You could use this to run a stand-alone simulator
12613 that speaks the remote debugging protocol, to make net connections
12614 using programs like @code{ssh}, or for other similar tricks.
12616 If @var{command} closes its standard output (perhaps by exiting),
12617 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
12618 program has already exited, this will have no effect.)
12622 Once the connection has been established, you can use all the usual
12623 commands to examine and change data and to step and continue the
12626 @cindex interrupting remote programs
12627 @cindex remote programs, interrupting
12628 Whenever @value{GDBN} is waiting for the remote program, if you type the
12629 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
12630 program. This may or may not succeed, depending in part on the hardware
12631 and the serial drivers the remote system uses. If you type the
12632 interrupt character once again, @value{GDBN} displays this prompt:
12635 Interrupted while waiting for the program.
12636 Give up (and stop debugging it)? (y or n)
12639 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
12640 (If you decide you want to try again later, you can use @samp{target
12641 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
12642 goes back to waiting.
12645 @kindex detach (remote)
12647 When you have finished debugging the remote program, you can use the
12648 @code{detach} command to release it from @value{GDBN} control.
12649 Detaching from the target normally resumes its execution, but the results
12650 will depend on your particular remote stub. After the @code{detach}
12651 command, @value{GDBN} is free to connect to another target.
12655 The @code{disconnect} command behaves like @code{detach}, except that
12656 the target is generally not resumed. It will wait for @value{GDBN}
12657 (this instance or another one) to connect and continue debugging. After
12658 the @code{disconnect} command, @value{GDBN} is again free to connect to
12661 @cindex send command to remote monitor
12662 @cindex extend @value{GDBN} for remote targets
12663 @cindex add new commands for external monitor
12665 @item monitor @var{cmd}
12666 This command allows you to send arbitrary commands directly to the
12667 remote monitor. Since @value{GDBN} doesn't care about the commands it
12668 sends like this, this command is the way to extend @value{GDBN}---you
12669 can add new commands that only the external monitor will understand
12674 @section Using the @code{gdbserver} Program
12677 @cindex remote connection without stubs
12678 @code{gdbserver} is a control program for Unix-like systems, which
12679 allows you to connect your program with a remote @value{GDBN} via
12680 @code{target remote}---but without linking in the usual debugging stub.
12682 @code{gdbserver} is not a complete replacement for the debugging stubs,
12683 because it requires essentially the same operating-system facilities
12684 that @value{GDBN} itself does. In fact, a system that can run
12685 @code{gdbserver} to connect to a remote @value{GDBN} could also run
12686 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
12687 because it is a much smaller program than @value{GDBN} itself. It is
12688 also easier to port than all of @value{GDBN}, so you may be able to get
12689 started more quickly on a new system by using @code{gdbserver}.
12690 Finally, if you develop code for real-time systems, you may find that
12691 the tradeoffs involved in real-time operation make it more convenient to
12692 do as much development work as possible on another system, for example
12693 by cross-compiling. You can use @code{gdbserver} to make a similar
12694 choice for debugging.
12696 @value{GDBN} and @code{gdbserver} communicate via either a serial line
12697 or a TCP connection, using the standard @value{GDBN} remote serial
12701 @item On the target machine,
12702 you need to have a copy of the program you want to debug.
12703 @code{gdbserver} does not need your program's symbol table, so you can
12704 strip the program if necessary to save space. @value{GDBN} on the host
12705 system does all the symbol handling.
12707 To use the server, you must tell it how to communicate with @value{GDBN};
12708 the name of your program; and the arguments for your program. The usual
12712 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
12715 @var{comm} is either a device name (to use a serial line) or a TCP
12716 hostname and portnumber. For example, to debug Emacs with the argument
12717 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
12721 target> gdbserver /dev/com1 emacs foo.txt
12724 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
12727 To use a TCP connection instead of a serial line:
12730 target> gdbserver host:2345 emacs foo.txt
12733 The only difference from the previous example is the first argument,
12734 specifying that you are communicating with the host @value{GDBN} via
12735 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
12736 expect a TCP connection from machine @samp{host} to local TCP port 2345.
12737 (Currently, the @samp{host} part is ignored.) You can choose any number
12738 you want for the port number as long as it does not conflict with any
12739 TCP ports already in use on the target system (for example, @code{23} is
12740 reserved for @code{telnet}).@footnote{If you choose a port number that
12741 conflicts with another service, @code{gdbserver} prints an error message
12742 and exits.} You must use the same port number with the host @value{GDBN}
12743 @code{target remote} command.
12745 On some targets, @code{gdbserver} can also attach to running programs.
12746 This is accomplished via the @code{--attach} argument. The syntax is:
12749 target> gdbserver @var{comm} --attach @var{pid}
12752 @var{pid} is the process ID of a currently running process. It isn't necessary
12753 to point @code{gdbserver} at a binary for the running process.
12756 @cindex attach to a program by name
12757 You can debug processes by name instead of process ID if your target has the
12758 @code{pidof} utility:
12761 target> gdbserver @var{comm} --attach `pidof @var{program}`
12764 In case more than one copy of @var{program} is running, or @var{program}
12765 has multiple threads, most versions of @code{pidof} support the
12766 @code{-s} option to only return the first process ID.
12768 @item On the host machine,
12769 first make sure you have the necessary symbol files. Load symbols for
12770 your application using the @code{file} command before you connect. Use
12771 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
12772 was compiled with the correct sysroot using @code{--with-system-root}).
12774 The symbol file and target libraries must exactly match the executable
12775 and libraries on the target, with one exception: the files on the host
12776 system should not be stripped, even if the files on the target system
12777 are. Mismatched or missing files will lead to confusing results
12778 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
12779 files may also prevent @code{gdbserver} from debugging multi-threaded
12782 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
12783 For TCP connections, you must start up @code{gdbserver} prior to using
12784 the @code{target remote} command. Otherwise you may get an error whose
12785 text depends on the host system, but which usually looks something like
12786 @samp{Connection refused}. You don't need to use the @code{load}
12787 command in @value{GDBN} when using @code{gdbserver}, since the program is
12788 already on the target.
12792 @subsection Monitor Commands for @code{gdbserver}
12793 @cindex monitor commands, for @code{gdbserver}
12795 During a @value{GDBN} session using @code{gdbserver}, you can use the
12796 @code{monitor} command to send special requests to @code{gdbserver}.
12797 Here are the available commands; they are only of interest when
12798 debugging @value{GDBN} or @code{gdbserver}.
12802 List the available monitor commands.
12804 @item monitor set debug 0
12805 @itemx monitor set debug 1
12806 Disable or enable general debugging messages.
12808 @item monitor set remote-debug 0
12809 @itemx monitor set remote-debug 1
12810 Disable or enable specific debugging messages associated with the remote
12811 protocol (@pxref{Remote Protocol}).
12815 @node Remote Configuration
12816 @section Remote Configuration
12819 @kindex show remote
12820 This section documents the configuration options available when
12821 debugging remote programs. For the options related to the File I/O
12822 extensions of the remote protocol, see @ref{system,
12823 system-call-allowed}.
12826 @item set remoteaddresssize @var{bits}
12827 @cindex address size for remote targets
12828 @cindex bits in remote address
12829 Set the maximum size of address in a memory packet to the specified
12830 number of bits. @value{GDBN} will mask off the address bits above
12831 that number, when it passes addresses to the remote target. The
12832 default value is the number of bits in the target's address.
12834 @item show remoteaddresssize
12835 Show the current value of remote address size in bits.
12837 @item set remotebaud @var{n}
12838 @cindex baud rate for remote targets
12839 Set the baud rate for the remote serial I/O to @var{n} baud. The
12840 value is used to set the speed of the serial port used for debugging
12843 @item show remotebaud
12844 Show the current speed of the remote connection.
12846 @item set remotebreak
12847 @cindex interrupt remote programs
12848 @cindex BREAK signal instead of Ctrl-C
12849 @anchor{set remotebreak}
12850 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
12851 when you type @kbd{Ctrl-c} to interrupt the program running
12852 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
12853 character instead. The default is off, since most remote systems
12854 expect to see @samp{Ctrl-C} as the interrupt signal.
12856 @item show remotebreak
12857 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
12858 interrupt the remote program.
12860 @item set remoteflow on
12861 @itemx set remoteflow off
12862 @kindex set remoteflow
12863 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
12864 on the serial port used to communicate to the remote target.
12866 @item show remoteflow
12867 @kindex show remoteflow
12868 Show the current setting of hardware flow control.
12870 @item set remotelogbase @var{base}
12871 Set the base (a.k.a.@: radix) of logging serial protocol
12872 communications to @var{base}. Supported values of @var{base} are:
12873 @code{ascii}, @code{octal}, and @code{hex}. The default is
12876 @item show remotelogbase
12877 Show the current setting of the radix for logging remote serial
12880 @item set remotelogfile @var{file}
12881 @cindex record serial communications on file
12882 Record remote serial communications on the named @var{file}. The
12883 default is not to record at all.
12885 @item show remotelogfile.
12886 Show the current setting of the file name on which to record the
12887 serial communications.
12889 @item set remotetimeout @var{num}
12890 @cindex timeout for serial communications
12891 @cindex remote timeout
12892 Set the timeout limit to wait for the remote target to respond to
12893 @var{num} seconds. The default is 2 seconds.
12895 @item show remotetimeout
12896 Show the current number of seconds to wait for the remote target
12899 @cindex limit hardware breakpoints and watchpoints
12900 @cindex remote target, limit break- and watchpoints
12901 @anchor{set remote hardware-watchpoint-limit}
12902 @anchor{set remote hardware-breakpoint-limit}
12903 @item set remote hardware-watchpoint-limit @var{limit}
12904 @itemx set remote hardware-breakpoint-limit @var{limit}
12905 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
12906 watchpoints. A limit of -1, the default, is treated as unlimited.
12909 @cindex remote packets, enabling and disabling
12910 The @value{GDBN} remote protocol autodetects the packets supported by
12911 your debugging stub. If you need to override the autodetection, you
12912 can use these commands to enable or disable individual packets. Each
12913 packet can be set to @samp{on} (the remote target supports this
12914 packet), @samp{off} (the remote target does not support this packet),
12915 or @samp{auto} (detect remote target support for this packet). They
12916 all default to @samp{auto}. For more information about each packet,
12917 see @ref{Remote Protocol}.
12919 During normal use, you should not have to use any of these commands.
12920 If you do, that may be a bug in your remote debugging stub, or a bug
12921 in @value{GDBN}. You may want to report the problem to the
12922 @value{GDBN} developers.
12924 For each packet @var{name}, the command to enable or disable the
12925 packet is @code{set remote @var{name}-packet}. The available settings
12928 @multitable @columnfractions 0.28 0.32 0.25
12931 @tab Related Features
12933 @item @code{fetch-register}
12935 @tab @code{info registers}
12937 @item @code{set-register}
12941 @item @code{binary-download}
12943 @tab @code{load}, @code{set}
12945 @item @code{read-aux-vector}
12946 @tab @code{qXfer:auxv:read}
12947 @tab @code{info auxv}
12949 @item @code{symbol-lookup}
12950 @tab @code{qSymbol}
12951 @tab Detecting multiple threads
12953 @item @code{verbose-resume}
12955 @tab Stepping or resuming multiple threads
12957 @item @code{software-breakpoint}
12961 @item @code{hardware-breakpoint}
12965 @item @code{write-watchpoint}
12969 @item @code{read-watchpoint}
12973 @item @code{access-watchpoint}
12977 @item @code{target-features}
12978 @tab @code{qXfer:features:read}
12979 @tab @code{set architecture}
12981 @item @code{library-info}
12982 @tab @code{qXfer:libraries:read}
12983 @tab @code{info sharedlibrary}
12985 @item @code{memory-map}
12986 @tab @code{qXfer:memory-map:read}
12987 @tab @code{info mem}
12989 @item @code{read-spu-object}
12990 @tab @code{qXfer:spu:read}
12991 @tab @code{info spu}
12993 @item @code{write-spu-object}
12994 @tab @code{qXfer:spu:write}
12995 @tab @code{info spu}
12997 @item @code{get-thread-local-@*storage-address}
12998 @tab @code{qGetTLSAddr}
12999 @tab Displaying @code{__thread} variables
13001 @item @code{supported-packets}
13002 @tab @code{qSupported}
13003 @tab Remote communications parameters
13005 @item @code{pass-signals}
13006 @tab @code{QPassSignals}
13007 @tab @code{handle @var{signal}}
13012 @section Implementing a Remote Stub
13014 @cindex debugging stub, example
13015 @cindex remote stub, example
13016 @cindex stub example, remote debugging
13017 The stub files provided with @value{GDBN} implement the target side of the
13018 communication protocol, and the @value{GDBN} side is implemented in the
13019 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
13020 these subroutines to communicate, and ignore the details. (If you're
13021 implementing your own stub file, you can still ignore the details: start
13022 with one of the existing stub files. @file{sparc-stub.c} is the best
13023 organized, and therefore the easiest to read.)
13025 @cindex remote serial debugging, overview
13026 To debug a program running on another machine (the debugging
13027 @dfn{target} machine), you must first arrange for all the usual
13028 prerequisites for the program to run by itself. For example, for a C
13033 A startup routine to set up the C runtime environment; these usually
13034 have a name like @file{crt0}. The startup routine may be supplied by
13035 your hardware supplier, or you may have to write your own.
13038 A C subroutine library to support your program's
13039 subroutine calls, notably managing input and output.
13042 A way of getting your program to the other machine---for example, a
13043 download program. These are often supplied by the hardware
13044 manufacturer, but you may have to write your own from hardware
13048 The next step is to arrange for your program to use a serial port to
13049 communicate with the machine where @value{GDBN} is running (the @dfn{host}
13050 machine). In general terms, the scheme looks like this:
13054 @value{GDBN} already understands how to use this protocol; when everything
13055 else is set up, you can simply use the @samp{target remote} command
13056 (@pxref{Targets,,Specifying a Debugging Target}).
13058 @item On the target,
13059 you must link with your program a few special-purpose subroutines that
13060 implement the @value{GDBN} remote serial protocol. The file containing these
13061 subroutines is called a @dfn{debugging stub}.
13063 On certain remote targets, you can use an auxiliary program
13064 @code{gdbserver} instead of linking a stub into your program.
13065 @xref{Server,,Using the @code{gdbserver} Program}, for details.
13068 The debugging stub is specific to the architecture of the remote
13069 machine; for example, use @file{sparc-stub.c} to debug programs on
13072 @cindex remote serial stub list
13073 These working remote stubs are distributed with @value{GDBN}:
13078 @cindex @file{i386-stub.c}
13081 For Intel 386 and compatible architectures.
13084 @cindex @file{m68k-stub.c}
13085 @cindex Motorola 680x0
13087 For Motorola 680x0 architectures.
13090 @cindex @file{sh-stub.c}
13093 For Renesas SH architectures.
13096 @cindex @file{sparc-stub.c}
13098 For @sc{sparc} architectures.
13100 @item sparcl-stub.c
13101 @cindex @file{sparcl-stub.c}
13104 For Fujitsu @sc{sparclite} architectures.
13108 The @file{README} file in the @value{GDBN} distribution may list other
13109 recently added stubs.
13112 * Stub Contents:: What the stub can do for you
13113 * Bootstrapping:: What you must do for the stub
13114 * Debug Session:: Putting it all together
13117 @node Stub Contents
13118 @subsection What the Stub Can Do for You
13120 @cindex remote serial stub
13121 The debugging stub for your architecture supplies these three
13125 @item set_debug_traps
13126 @findex set_debug_traps
13127 @cindex remote serial stub, initialization
13128 This routine arranges for @code{handle_exception} to run when your
13129 program stops. You must call this subroutine explicitly near the
13130 beginning of your program.
13132 @item handle_exception
13133 @findex handle_exception
13134 @cindex remote serial stub, main routine
13135 This is the central workhorse, but your program never calls it
13136 explicitly---the setup code arranges for @code{handle_exception} to
13137 run when a trap is triggered.
13139 @code{handle_exception} takes control when your program stops during
13140 execution (for example, on a breakpoint), and mediates communications
13141 with @value{GDBN} on the host machine. This is where the communications
13142 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
13143 representative on the target machine. It begins by sending summary
13144 information on the state of your program, then continues to execute,
13145 retrieving and transmitting any information @value{GDBN} needs, until you
13146 execute a @value{GDBN} command that makes your program resume; at that point,
13147 @code{handle_exception} returns control to your own code on the target
13151 @cindex @code{breakpoint} subroutine, remote
13152 Use this auxiliary subroutine to make your program contain a
13153 breakpoint. Depending on the particular situation, this may be the only
13154 way for @value{GDBN} to get control. For instance, if your target
13155 machine has some sort of interrupt button, you won't need to call this;
13156 pressing the interrupt button transfers control to
13157 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
13158 simply receiving characters on the serial port may also trigger a trap;
13159 again, in that situation, you don't need to call @code{breakpoint} from
13160 your own program---simply running @samp{target remote} from the host
13161 @value{GDBN} session gets control.
13163 Call @code{breakpoint} if none of these is true, or if you simply want
13164 to make certain your program stops at a predetermined point for the
13165 start of your debugging session.
13168 @node Bootstrapping
13169 @subsection What You Must Do for the Stub
13171 @cindex remote stub, support routines
13172 The debugging stubs that come with @value{GDBN} are set up for a particular
13173 chip architecture, but they have no information about the rest of your
13174 debugging target machine.
13176 First of all you need to tell the stub how to communicate with the
13180 @item int getDebugChar()
13181 @findex getDebugChar
13182 Write this subroutine to read a single character from the serial port.
13183 It may be identical to @code{getchar} for your target system; a
13184 different name is used to allow you to distinguish the two if you wish.
13186 @item void putDebugChar(int)
13187 @findex putDebugChar
13188 Write this subroutine to write a single character to the serial port.
13189 It may be identical to @code{putchar} for your target system; a
13190 different name is used to allow you to distinguish the two if you wish.
13193 @cindex control C, and remote debugging
13194 @cindex interrupting remote targets
13195 If you want @value{GDBN} to be able to stop your program while it is
13196 running, you need to use an interrupt-driven serial driver, and arrange
13197 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
13198 character). That is the character which @value{GDBN} uses to tell the
13199 remote system to stop.
13201 Getting the debugging target to return the proper status to @value{GDBN}
13202 probably requires changes to the standard stub; one quick and dirty way
13203 is to just execute a breakpoint instruction (the ``dirty'' part is that
13204 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
13206 Other routines you need to supply are:
13209 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
13210 @findex exceptionHandler
13211 Write this function to install @var{exception_address} in the exception
13212 handling tables. You need to do this because the stub does not have any
13213 way of knowing what the exception handling tables on your target system
13214 are like (for example, the processor's table might be in @sc{rom},
13215 containing entries which point to a table in @sc{ram}).
13216 @var{exception_number} is the exception number which should be changed;
13217 its meaning is architecture-dependent (for example, different numbers
13218 might represent divide by zero, misaligned access, etc). When this
13219 exception occurs, control should be transferred directly to
13220 @var{exception_address}, and the processor state (stack, registers,
13221 and so on) should be just as it is when a processor exception occurs. So if
13222 you want to use a jump instruction to reach @var{exception_address}, it
13223 should be a simple jump, not a jump to subroutine.
13225 For the 386, @var{exception_address} should be installed as an interrupt
13226 gate so that interrupts are masked while the handler runs. The gate
13227 should be at privilege level 0 (the most privileged level). The
13228 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
13229 help from @code{exceptionHandler}.
13231 @item void flush_i_cache()
13232 @findex flush_i_cache
13233 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
13234 instruction cache, if any, on your target machine. If there is no
13235 instruction cache, this subroutine may be a no-op.
13237 On target machines that have instruction caches, @value{GDBN} requires this
13238 function to make certain that the state of your program is stable.
13242 You must also make sure this library routine is available:
13245 @item void *memset(void *, int, int)
13247 This is the standard library function @code{memset} that sets an area of
13248 memory to a known value. If you have one of the free versions of
13249 @code{libc.a}, @code{memset} can be found there; otherwise, you must
13250 either obtain it from your hardware manufacturer, or write your own.
13253 If you do not use the GNU C compiler, you may need other standard
13254 library subroutines as well; this varies from one stub to another,
13255 but in general the stubs are likely to use any of the common library
13256 subroutines which @code{@value{NGCC}} generates as inline code.
13259 @node Debug Session
13260 @subsection Putting it All Together
13262 @cindex remote serial debugging summary
13263 In summary, when your program is ready to debug, you must follow these
13268 Make sure you have defined the supporting low-level routines
13269 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
13271 @code{getDebugChar}, @code{putDebugChar},
13272 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
13276 Insert these lines near the top of your program:
13284 For the 680x0 stub only, you need to provide a variable called
13285 @code{exceptionHook}. Normally you just use:
13288 void (*exceptionHook)() = 0;
13292 but if before calling @code{set_debug_traps}, you set it to point to a
13293 function in your program, that function is called when
13294 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
13295 error). The function indicated by @code{exceptionHook} is called with
13296 one parameter: an @code{int} which is the exception number.
13299 Compile and link together: your program, the @value{GDBN} debugging stub for
13300 your target architecture, and the supporting subroutines.
13303 Make sure you have a serial connection between your target machine and
13304 the @value{GDBN} host, and identify the serial port on the host.
13307 @c The "remote" target now provides a `load' command, so we should
13308 @c document that. FIXME.
13309 Download your program to your target machine (or get it there by
13310 whatever means the manufacturer provides), and start it.
13313 Start @value{GDBN} on the host, and connect to the target
13314 (@pxref{Connecting,,Connecting to a Remote Target}).
13318 @node Configurations
13319 @chapter Configuration-Specific Information
13321 While nearly all @value{GDBN} commands are available for all native and
13322 cross versions of the debugger, there are some exceptions. This chapter
13323 describes things that are only available in certain configurations.
13325 There are three major categories of configurations: native
13326 configurations, where the host and target are the same, embedded
13327 operating system configurations, which are usually the same for several
13328 different processor architectures, and bare embedded processors, which
13329 are quite different from each other.
13334 * Embedded Processors::
13341 This section describes details specific to particular native
13346 * BSD libkvm Interface:: Debugging BSD kernel memory images
13347 * SVR4 Process Information:: SVR4 process information
13348 * DJGPP Native:: Features specific to the DJGPP port
13349 * Cygwin Native:: Features specific to the Cygwin port
13350 * Hurd Native:: Features specific to @sc{gnu} Hurd
13351 * Neutrino:: Features specific to QNX Neutrino
13357 On HP-UX systems, if you refer to a function or variable name that
13358 begins with a dollar sign, @value{GDBN} searches for a user or system
13359 name first, before it searches for a convenience variable.
13362 @node BSD libkvm Interface
13363 @subsection BSD libkvm Interface
13366 @cindex kernel memory image
13367 @cindex kernel crash dump
13369 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
13370 interface that provides a uniform interface for accessing kernel virtual
13371 memory images, including live systems and crash dumps. @value{GDBN}
13372 uses this interface to allow you to debug live kernels and kernel crash
13373 dumps on many native BSD configurations. This is implemented as a
13374 special @code{kvm} debugging target. For debugging a live system, load
13375 the currently running kernel into @value{GDBN} and connect to the
13379 (@value{GDBP}) @b{target kvm}
13382 For debugging crash dumps, provide the file name of the crash dump as an
13386 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
13389 Once connected to the @code{kvm} target, the following commands are
13395 Set current context from the @dfn{Process Control Block} (PCB) address.
13398 Set current context from proc address. This command isn't available on
13399 modern FreeBSD systems.
13402 @node SVR4 Process Information
13403 @subsection SVR4 Process Information
13405 @cindex examine process image
13406 @cindex process info via @file{/proc}
13408 Many versions of SVR4 and compatible systems provide a facility called
13409 @samp{/proc} that can be used to examine the image of a running
13410 process using file-system subroutines. If @value{GDBN} is configured
13411 for an operating system with this facility, the command @code{info
13412 proc} is available to report information about the process running
13413 your program, or about any process running on your system. @code{info
13414 proc} works only on SVR4 systems that include the @code{procfs} code.
13415 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
13416 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
13422 @itemx info proc @var{process-id}
13423 Summarize available information about any running process. If a
13424 process ID is specified by @var{process-id}, display information about
13425 that process; otherwise display information about the program being
13426 debugged. The summary includes the debugged process ID, the command
13427 line used to invoke it, its current working directory, and its
13428 executable file's absolute file name.
13430 On some systems, @var{process-id} can be of the form
13431 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
13432 within a process. If the optional @var{pid} part is missing, it means
13433 a thread from the process being debugged (the leading @samp{/} still
13434 needs to be present, or else @value{GDBN} will interpret the number as
13435 a process ID rather than a thread ID).
13437 @item info proc mappings
13438 @cindex memory address space mappings
13439 Report the memory address space ranges accessible in the program, with
13440 information on whether the process has read, write, or execute access
13441 rights to each range. On @sc{gnu}/Linux systems, each memory range
13442 includes the object file which is mapped to that range, instead of the
13443 memory access rights to that range.
13445 @item info proc stat
13446 @itemx info proc status
13447 @cindex process detailed status information
13448 These subcommands are specific to @sc{gnu}/Linux systems. They show
13449 the process-related information, including the user ID and group ID;
13450 how many threads are there in the process; its virtual memory usage;
13451 the signals that are pending, blocked, and ignored; its TTY; its
13452 consumption of system and user time; its stack size; its @samp{nice}
13453 value; etc. For more information, see the @samp{proc} man page
13454 (type @kbd{man 5 proc} from your shell prompt).
13456 @item info proc all
13457 Show all the information about the process described under all of the
13458 above @code{info proc} subcommands.
13461 @comment These sub-options of 'info proc' were not included when
13462 @comment procfs.c was re-written. Keep their descriptions around
13463 @comment against the day when someone finds the time to put them back in.
13464 @kindex info proc times
13465 @item info proc times
13466 Starting time, user CPU time, and system CPU time for your program and
13469 @kindex info proc id
13471 Report on the process IDs related to your program: its own process ID,
13472 the ID of its parent, the process group ID, and the session ID.
13475 @item set procfs-trace
13476 @kindex set procfs-trace
13477 @cindex @code{procfs} API calls
13478 This command enables and disables tracing of @code{procfs} API calls.
13480 @item show procfs-trace
13481 @kindex show procfs-trace
13482 Show the current state of @code{procfs} API call tracing.
13484 @item set procfs-file @var{file}
13485 @kindex set procfs-file
13486 Tell @value{GDBN} to write @code{procfs} API trace to the named
13487 @var{file}. @value{GDBN} appends the trace info to the previous
13488 contents of the file. The default is to display the trace on the
13491 @item show procfs-file
13492 @kindex show procfs-file
13493 Show the file to which @code{procfs} API trace is written.
13495 @item proc-trace-entry
13496 @itemx proc-trace-exit
13497 @itemx proc-untrace-entry
13498 @itemx proc-untrace-exit
13499 @kindex proc-trace-entry
13500 @kindex proc-trace-exit
13501 @kindex proc-untrace-entry
13502 @kindex proc-untrace-exit
13503 These commands enable and disable tracing of entries into and exits
13504 from the @code{syscall} interface.
13507 @kindex info pidlist
13508 @cindex process list, QNX Neutrino
13509 For QNX Neutrino only, this command displays the list of all the
13510 processes and all the threads within each process.
13513 @kindex info meminfo
13514 @cindex mapinfo list, QNX Neutrino
13515 For QNX Neutrino only, this command displays the list of all mapinfos.
13519 @subsection Features for Debugging @sc{djgpp} Programs
13520 @cindex @sc{djgpp} debugging
13521 @cindex native @sc{djgpp} debugging
13522 @cindex MS-DOS-specific commands
13525 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
13526 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
13527 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
13528 top of real-mode DOS systems and their emulations.
13530 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
13531 defines a few commands specific to the @sc{djgpp} port. This
13532 subsection describes those commands.
13537 This is a prefix of @sc{djgpp}-specific commands which print
13538 information about the target system and important OS structures.
13541 @cindex MS-DOS system info
13542 @cindex free memory information (MS-DOS)
13543 @item info dos sysinfo
13544 This command displays assorted information about the underlying
13545 platform: the CPU type and features, the OS version and flavor, the
13546 DPMI version, and the available conventional and DPMI memory.
13551 @cindex segment descriptor tables
13552 @cindex descriptor tables display
13554 @itemx info dos ldt
13555 @itemx info dos idt
13556 These 3 commands display entries from, respectively, Global, Local,
13557 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
13558 tables are data structures which store a descriptor for each segment
13559 that is currently in use. The segment's selector is an index into a
13560 descriptor table; the table entry for that index holds the
13561 descriptor's base address and limit, and its attributes and access
13564 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
13565 segment (used for both data and the stack), and a DOS segment (which
13566 allows access to DOS/BIOS data structures and absolute addresses in
13567 conventional memory). However, the DPMI host will usually define
13568 additional segments in order to support the DPMI environment.
13570 @cindex garbled pointers
13571 These commands allow to display entries from the descriptor tables.
13572 Without an argument, all entries from the specified table are
13573 displayed. An argument, which should be an integer expression, means
13574 display a single entry whose index is given by the argument. For
13575 example, here's a convenient way to display information about the
13576 debugged program's data segment:
13579 @exdent @code{(@value{GDBP}) info dos ldt $ds}
13580 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
13584 This comes in handy when you want to see whether a pointer is outside
13585 the data segment's limit (i.e.@: @dfn{garbled}).
13587 @cindex page tables display (MS-DOS)
13589 @itemx info dos pte
13590 These two commands display entries from, respectively, the Page
13591 Directory and the Page Tables. Page Directories and Page Tables are
13592 data structures which control how virtual memory addresses are mapped
13593 into physical addresses. A Page Table includes an entry for every
13594 page of memory that is mapped into the program's address space; there
13595 may be several Page Tables, each one holding up to 4096 entries. A
13596 Page Directory has up to 4096 entries, one each for every Page Table
13597 that is currently in use.
13599 Without an argument, @kbd{info dos pde} displays the entire Page
13600 Directory, and @kbd{info dos pte} displays all the entries in all of
13601 the Page Tables. An argument, an integer expression, given to the
13602 @kbd{info dos pde} command means display only that entry from the Page
13603 Directory table. An argument given to the @kbd{info dos pte} command
13604 means display entries from a single Page Table, the one pointed to by
13605 the specified entry in the Page Directory.
13607 @cindex direct memory access (DMA) on MS-DOS
13608 These commands are useful when your program uses @dfn{DMA} (Direct
13609 Memory Access), which needs physical addresses to program the DMA
13612 These commands are supported only with some DPMI servers.
13614 @cindex physical address from linear address
13615 @item info dos address-pte @var{addr}
13616 This command displays the Page Table entry for a specified linear
13617 address. The argument @var{addr} is a linear address which should
13618 already have the appropriate segment's base address added to it,
13619 because this command accepts addresses which may belong to @emph{any}
13620 segment. For example, here's how to display the Page Table entry for
13621 the page where a variable @code{i} is stored:
13624 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
13625 @exdent @code{Page Table entry for address 0x11a00d30:}
13626 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
13630 This says that @code{i} is stored at offset @code{0xd30} from the page
13631 whose physical base address is @code{0x02698000}, and shows all the
13632 attributes of that page.
13634 Note that you must cast the addresses of variables to a @code{char *},
13635 since otherwise the value of @code{__djgpp_base_address}, the base
13636 address of all variables and functions in a @sc{djgpp} program, will
13637 be added using the rules of C pointer arithmetics: if @code{i} is
13638 declared an @code{int}, @value{GDBN} will add 4 times the value of
13639 @code{__djgpp_base_address} to the address of @code{i}.
13641 Here's another example, it displays the Page Table entry for the
13645 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
13646 @exdent @code{Page Table entry for address 0x29110:}
13647 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
13651 (The @code{+ 3} offset is because the transfer buffer's address is the
13652 3rd member of the @code{_go32_info_block} structure.) The output
13653 clearly shows that this DPMI server maps the addresses in conventional
13654 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
13655 linear (@code{0x29110}) addresses are identical.
13657 This command is supported only with some DPMI servers.
13660 @cindex DOS serial data link, remote debugging
13661 In addition to native debugging, the DJGPP port supports remote
13662 debugging via a serial data link. The following commands are specific
13663 to remote serial debugging in the DJGPP port of @value{GDBN}.
13666 @kindex set com1base
13667 @kindex set com1irq
13668 @kindex set com2base
13669 @kindex set com2irq
13670 @kindex set com3base
13671 @kindex set com3irq
13672 @kindex set com4base
13673 @kindex set com4irq
13674 @item set com1base @var{addr}
13675 This command sets the base I/O port address of the @file{COM1} serial
13678 @item set com1irq @var{irq}
13679 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
13680 for the @file{COM1} serial port.
13682 There are similar commands @samp{set com2base}, @samp{set com3irq},
13683 etc.@: for setting the port address and the @code{IRQ} lines for the
13686 @kindex show com1base
13687 @kindex show com1irq
13688 @kindex show com2base
13689 @kindex show com2irq
13690 @kindex show com3base
13691 @kindex show com3irq
13692 @kindex show com4base
13693 @kindex show com4irq
13694 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
13695 display the current settings of the base address and the @code{IRQ}
13696 lines used by the COM ports.
13699 @kindex info serial
13700 @cindex DOS serial port status
13701 This command prints the status of the 4 DOS serial ports. For each
13702 port, it prints whether it's active or not, its I/O base address and
13703 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
13704 counts of various errors encountered so far.
13708 @node Cygwin Native
13709 @subsection Features for Debugging MS Windows PE Executables
13710 @cindex MS Windows debugging
13711 @cindex native Cygwin debugging
13712 @cindex Cygwin-specific commands
13714 @value{GDBN} supports native debugging of MS Windows programs, including
13715 DLLs with and without symbolic debugging information. There are various
13716 additional Cygwin-specific commands, described in this section.
13717 Working with DLLs that have no debugging symbols is described in
13718 @ref{Non-debug DLL Symbols}.
13723 This is a prefix of MS Windows-specific commands which print
13724 information about the target system and important OS structures.
13726 @item info w32 selector
13727 This command displays information returned by
13728 the Win32 API @code{GetThreadSelectorEntry} function.
13729 It takes an optional argument that is evaluated to
13730 a long value to give the information about this given selector.
13731 Without argument, this command displays information
13732 about the six segment registers.
13736 This is a Cygwin-specific alias of @code{info shared}.
13738 @kindex dll-symbols
13740 This command loads symbols from a dll similarly to
13741 add-sym command but without the need to specify a base address.
13743 @kindex set cygwin-exceptions
13744 @cindex debugging the Cygwin DLL
13745 @cindex Cygwin DLL, debugging
13746 @item set cygwin-exceptions @var{mode}
13747 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
13748 happen inside the Cygwin DLL. If @var{mode} is @code{off},
13749 @value{GDBN} will delay recognition of exceptions, and may ignore some
13750 exceptions which seem to be caused by internal Cygwin DLL
13751 ``bookkeeping''. This option is meant primarily for debugging the
13752 Cygwin DLL itself; the default value is @code{off} to avoid annoying
13753 @value{GDBN} users with false @code{SIGSEGV} signals.
13755 @kindex show cygwin-exceptions
13756 @item show cygwin-exceptions
13757 Displays whether @value{GDBN} will break on exceptions that happen
13758 inside the Cygwin DLL itself.
13760 @kindex set new-console
13761 @item set new-console @var{mode}
13762 If @var{mode} is @code{on} the debuggee will
13763 be started in a new console on next start.
13764 If @var{mode} is @code{off}i, the debuggee will
13765 be started in the same console as the debugger.
13767 @kindex show new-console
13768 @item show new-console
13769 Displays whether a new console is used
13770 when the debuggee is started.
13772 @kindex set new-group
13773 @item set new-group @var{mode}
13774 This boolean value controls whether the debuggee should
13775 start a new group or stay in the same group as the debugger.
13776 This affects the way the Windows OS handles
13779 @kindex show new-group
13780 @item show new-group
13781 Displays current value of new-group boolean.
13783 @kindex set debugevents
13784 @item set debugevents
13785 This boolean value adds debug output concerning kernel events related
13786 to the debuggee seen by the debugger. This includes events that
13787 signal thread and process creation and exit, DLL loading and
13788 unloading, console interrupts, and debugging messages produced by the
13789 Windows @code{OutputDebugString} API call.
13791 @kindex set debugexec
13792 @item set debugexec
13793 This boolean value adds debug output concerning execute events
13794 (such as resume thread) seen by the debugger.
13796 @kindex set debugexceptions
13797 @item set debugexceptions
13798 This boolean value adds debug output concerning exceptions in the
13799 debuggee seen by the debugger.
13801 @kindex set debugmemory
13802 @item set debugmemory
13803 This boolean value adds debug output concerning debuggee memory reads
13804 and writes by the debugger.
13808 This boolean values specifies whether the debuggee is called
13809 via a shell or directly (default value is on).
13813 Displays if the debuggee will be started with a shell.
13818 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
13821 @node Non-debug DLL Symbols
13822 @subsubsection Support for DLLs without Debugging Symbols
13823 @cindex DLLs with no debugging symbols
13824 @cindex Minimal symbols and DLLs
13826 Very often on windows, some of the DLLs that your program relies on do
13827 not include symbolic debugging information (for example,
13828 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
13829 symbols in a DLL, it relies on the minimal amount of symbolic
13830 information contained in the DLL's export table. This section
13831 describes working with such symbols, known internally to @value{GDBN} as
13832 ``minimal symbols''.
13834 Note that before the debugged program has started execution, no DLLs
13835 will have been loaded. The easiest way around this problem is simply to
13836 start the program --- either by setting a breakpoint or letting the
13837 program run once to completion. It is also possible to force
13838 @value{GDBN} to load a particular DLL before starting the executable ---
13839 see the shared library information in @ref{Files}, or the
13840 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
13841 explicitly loading symbols from a DLL with no debugging information will
13842 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
13843 which may adversely affect symbol lookup performance.
13845 @subsubsection DLL Name Prefixes
13847 In keeping with the naming conventions used by the Microsoft debugging
13848 tools, DLL export symbols are made available with a prefix based on the
13849 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
13850 also entered into the symbol table, so @code{CreateFileA} is often
13851 sufficient. In some cases there will be name clashes within a program
13852 (particularly if the executable itself includes full debugging symbols)
13853 necessitating the use of the fully qualified name when referring to the
13854 contents of the DLL. Use single-quotes around the name to avoid the
13855 exclamation mark (``!'') being interpreted as a language operator.
13857 Note that the internal name of the DLL may be all upper-case, even
13858 though the file name of the DLL is lower-case, or vice-versa. Since
13859 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
13860 some confusion. If in doubt, try the @code{info functions} and
13861 @code{info variables} commands or even @code{maint print msymbols}
13862 (@pxref{Symbols}). Here's an example:
13865 (@value{GDBP}) info function CreateFileA
13866 All functions matching regular expression "CreateFileA":
13868 Non-debugging symbols:
13869 0x77e885f4 CreateFileA
13870 0x77e885f4 KERNEL32!CreateFileA
13874 (@value{GDBP}) info function !
13875 All functions matching regular expression "!":
13877 Non-debugging symbols:
13878 0x6100114c cygwin1!__assert
13879 0x61004034 cygwin1!_dll_crt0@@0
13880 0x61004240 cygwin1!dll_crt0(per_process *)
13884 @subsubsection Working with Minimal Symbols
13886 Symbols extracted from a DLL's export table do not contain very much
13887 type information. All that @value{GDBN} can do is guess whether a symbol
13888 refers to a function or variable depending on the linker section that
13889 contains the symbol. Also note that the actual contents of the memory
13890 contained in a DLL are not available unless the program is running. This
13891 means that you cannot examine the contents of a variable or disassemble
13892 a function within a DLL without a running program.
13894 Variables are generally treated as pointers and dereferenced
13895 automatically. For this reason, it is often necessary to prefix a
13896 variable name with the address-of operator (``&'') and provide explicit
13897 type information in the command. Here's an example of the type of
13901 (@value{GDBP}) print 'cygwin1!__argv'
13906 (@value{GDBP}) x 'cygwin1!__argv'
13907 0x10021610: "\230y\""
13910 And two possible solutions:
13913 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
13914 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
13918 (@value{GDBP}) x/2x &'cygwin1!__argv'
13919 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
13920 (@value{GDBP}) x/x 0x10021608
13921 0x10021608: 0x0022fd98
13922 (@value{GDBP}) x/s 0x0022fd98
13923 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
13926 Setting a break point within a DLL is possible even before the program
13927 starts execution. However, under these circumstances, @value{GDBN} can't
13928 examine the initial instructions of the function in order to skip the
13929 function's frame set-up code. You can work around this by using ``*&''
13930 to set the breakpoint at a raw memory address:
13933 (@value{GDBP}) break *&'python22!PyOS_Readline'
13934 Breakpoint 1 at 0x1e04eff0
13937 The author of these extensions is not entirely convinced that setting a
13938 break point within a shared DLL like @file{kernel32.dll} is completely
13942 @subsection Commands Specific to @sc{gnu} Hurd Systems
13943 @cindex @sc{gnu} Hurd debugging
13945 This subsection describes @value{GDBN} commands specific to the
13946 @sc{gnu} Hurd native debugging.
13951 @kindex set signals@r{, Hurd command}
13952 @kindex set sigs@r{, Hurd command}
13953 This command toggles the state of inferior signal interception by
13954 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
13955 affected by this command. @code{sigs} is a shorthand alias for
13960 @kindex show signals@r{, Hurd command}
13961 @kindex show sigs@r{, Hurd command}
13962 Show the current state of intercepting inferior's signals.
13964 @item set signal-thread
13965 @itemx set sigthread
13966 @kindex set signal-thread
13967 @kindex set sigthread
13968 This command tells @value{GDBN} which thread is the @code{libc} signal
13969 thread. That thread is run when a signal is delivered to a running
13970 process. @code{set sigthread} is the shorthand alias of @code{set
13973 @item show signal-thread
13974 @itemx show sigthread
13975 @kindex show signal-thread
13976 @kindex show sigthread
13977 These two commands show which thread will run when the inferior is
13978 delivered a signal.
13981 @kindex set stopped@r{, Hurd command}
13982 This commands tells @value{GDBN} that the inferior process is stopped,
13983 as with the @code{SIGSTOP} signal. The stopped process can be
13984 continued by delivering a signal to it.
13987 @kindex show stopped@r{, Hurd command}
13988 This command shows whether @value{GDBN} thinks the debuggee is
13991 @item set exceptions
13992 @kindex set exceptions@r{, Hurd command}
13993 Use this command to turn off trapping of exceptions in the inferior.
13994 When exception trapping is off, neither breakpoints nor
13995 single-stepping will work. To restore the default, set exception
13998 @item show exceptions
13999 @kindex show exceptions@r{, Hurd command}
14000 Show the current state of trapping exceptions in the inferior.
14002 @item set task pause
14003 @kindex set task@r{, Hurd commands}
14004 @cindex task attributes (@sc{gnu} Hurd)
14005 @cindex pause current task (@sc{gnu} Hurd)
14006 This command toggles task suspension when @value{GDBN} has control.
14007 Setting it to on takes effect immediately, and the task is suspended
14008 whenever @value{GDBN} gets control. Setting it to off will take
14009 effect the next time the inferior is continued. If this option is set
14010 to off, you can use @code{set thread default pause on} or @code{set
14011 thread pause on} (see below) to pause individual threads.
14013 @item show task pause
14014 @kindex show task@r{, Hurd commands}
14015 Show the current state of task suspension.
14017 @item set task detach-suspend-count
14018 @cindex task suspend count
14019 @cindex detach from task, @sc{gnu} Hurd
14020 This command sets the suspend count the task will be left with when
14021 @value{GDBN} detaches from it.
14023 @item show task detach-suspend-count
14024 Show the suspend count the task will be left with when detaching.
14026 @item set task exception-port
14027 @itemx set task excp
14028 @cindex task exception port, @sc{gnu} Hurd
14029 This command sets the task exception port to which @value{GDBN} will
14030 forward exceptions. The argument should be the value of the @dfn{send
14031 rights} of the task. @code{set task excp} is a shorthand alias.
14033 @item set noninvasive
14034 @cindex noninvasive task options
14035 This command switches @value{GDBN} to a mode that is the least
14036 invasive as far as interfering with the inferior is concerned. This
14037 is the same as using @code{set task pause}, @code{set exceptions}, and
14038 @code{set signals} to values opposite to the defaults.
14040 @item info send-rights
14041 @itemx info receive-rights
14042 @itemx info port-rights
14043 @itemx info port-sets
14044 @itemx info dead-names
14047 @cindex send rights, @sc{gnu} Hurd
14048 @cindex receive rights, @sc{gnu} Hurd
14049 @cindex port rights, @sc{gnu} Hurd
14050 @cindex port sets, @sc{gnu} Hurd
14051 @cindex dead names, @sc{gnu} Hurd
14052 These commands display information about, respectively, send rights,
14053 receive rights, port rights, port sets, and dead names of a task.
14054 There are also shorthand aliases: @code{info ports} for @code{info
14055 port-rights} and @code{info psets} for @code{info port-sets}.
14057 @item set thread pause
14058 @kindex set thread@r{, Hurd command}
14059 @cindex thread properties, @sc{gnu} Hurd
14060 @cindex pause current thread (@sc{gnu} Hurd)
14061 This command toggles current thread suspension when @value{GDBN} has
14062 control. Setting it to on takes effect immediately, and the current
14063 thread is suspended whenever @value{GDBN} gets control. Setting it to
14064 off will take effect the next time the inferior is continued.
14065 Normally, this command has no effect, since when @value{GDBN} has
14066 control, the whole task is suspended. However, if you used @code{set
14067 task pause off} (see above), this command comes in handy to suspend
14068 only the current thread.
14070 @item show thread pause
14071 @kindex show thread@r{, Hurd command}
14072 This command shows the state of current thread suspension.
14074 @item set thread run
14075 This command sets whether the current thread is allowed to run.
14077 @item show thread run
14078 Show whether the current thread is allowed to run.
14080 @item set thread detach-suspend-count
14081 @cindex thread suspend count, @sc{gnu} Hurd
14082 @cindex detach from thread, @sc{gnu} Hurd
14083 This command sets the suspend count @value{GDBN} will leave on a
14084 thread when detaching. This number is relative to the suspend count
14085 found by @value{GDBN} when it notices the thread; use @code{set thread
14086 takeover-suspend-count} to force it to an absolute value.
14088 @item show thread detach-suspend-count
14089 Show the suspend count @value{GDBN} will leave on the thread when
14092 @item set thread exception-port
14093 @itemx set thread excp
14094 Set the thread exception port to which to forward exceptions. This
14095 overrides the port set by @code{set task exception-port} (see above).
14096 @code{set thread excp} is the shorthand alias.
14098 @item set thread takeover-suspend-count
14099 Normally, @value{GDBN}'s thread suspend counts are relative to the
14100 value @value{GDBN} finds when it notices each thread. This command
14101 changes the suspend counts to be absolute instead.
14103 @item set thread default
14104 @itemx show thread default
14105 @cindex thread default settings, @sc{gnu} Hurd
14106 Each of the above @code{set thread} commands has a @code{set thread
14107 default} counterpart (e.g., @code{set thread default pause}, @code{set
14108 thread default exception-port}, etc.). The @code{thread default}
14109 variety of commands sets the default thread properties for all
14110 threads; you can then change the properties of individual threads with
14111 the non-default commands.
14116 @subsection QNX Neutrino
14117 @cindex QNX Neutrino
14119 @value{GDBN} provides the following commands specific to the QNX
14123 @item set debug nto-debug
14124 @kindex set debug nto-debug
14125 When set to on, enables debugging messages specific to the QNX
14128 @item show debug nto-debug
14129 @kindex show debug nto-debug
14130 Show the current state of QNX Neutrino messages.
14135 @section Embedded Operating Systems
14137 This section describes configurations involving the debugging of
14138 embedded operating systems that are available for several different
14142 * VxWorks:: Using @value{GDBN} with VxWorks
14145 @value{GDBN} includes the ability to debug programs running on
14146 various real-time operating systems.
14149 @subsection Using @value{GDBN} with VxWorks
14155 @kindex target vxworks
14156 @item target vxworks @var{machinename}
14157 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
14158 is the target system's machine name or IP address.
14162 On VxWorks, @code{load} links @var{filename} dynamically on the
14163 current target system as well as adding its symbols in @value{GDBN}.
14165 @value{GDBN} enables developers to spawn and debug tasks running on networked
14166 VxWorks targets from a Unix host. Already-running tasks spawned from
14167 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
14168 both the Unix host and on the VxWorks target. The program
14169 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
14170 installed with the name @code{vxgdb}, to distinguish it from a
14171 @value{GDBN} for debugging programs on the host itself.)
14174 @item VxWorks-timeout @var{args}
14175 @kindex vxworks-timeout
14176 All VxWorks-based targets now support the option @code{vxworks-timeout}.
14177 This option is set by the user, and @var{args} represents the number of
14178 seconds @value{GDBN} waits for responses to rpc's. You might use this if
14179 your VxWorks target is a slow software simulator or is on the far side
14180 of a thin network line.
14183 The following information on connecting to VxWorks was current when
14184 this manual was produced; newer releases of VxWorks may use revised
14187 @findex INCLUDE_RDB
14188 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
14189 to include the remote debugging interface routines in the VxWorks
14190 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
14191 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
14192 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
14193 source debugging task @code{tRdbTask} when VxWorks is booted. For more
14194 information on configuring and remaking VxWorks, see the manufacturer's
14196 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
14198 Once you have included @file{rdb.a} in your VxWorks system image and set
14199 your Unix execution search path to find @value{GDBN}, you are ready to
14200 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
14201 @code{vxgdb}, depending on your installation).
14203 @value{GDBN} comes up showing the prompt:
14210 * VxWorks Connection:: Connecting to VxWorks
14211 * VxWorks Download:: VxWorks download
14212 * VxWorks Attach:: Running tasks
14215 @node VxWorks Connection
14216 @subsubsection Connecting to VxWorks
14218 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
14219 network. To connect to a target whose host name is ``@code{tt}'', type:
14222 (vxgdb) target vxworks tt
14226 @value{GDBN} displays messages like these:
14229 Attaching remote machine across net...
14234 @value{GDBN} then attempts to read the symbol tables of any object modules
14235 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
14236 these files by searching the directories listed in the command search
14237 path (@pxref{Environment, ,Your Program's Environment}); if it fails
14238 to find an object file, it displays a message such as:
14241 prog.o: No such file or directory.
14244 When this happens, add the appropriate directory to the search path with
14245 the @value{GDBN} command @code{path}, and execute the @code{target}
14248 @node VxWorks Download
14249 @subsubsection VxWorks Download
14251 @cindex download to VxWorks
14252 If you have connected to the VxWorks target and you want to debug an
14253 object that has not yet been loaded, you can use the @value{GDBN}
14254 @code{load} command to download a file from Unix to VxWorks
14255 incrementally. The object file given as an argument to the @code{load}
14256 command is actually opened twice: first by the VxWorks target in order
14257 to download the code, then by @value{GDBN} in order to read the symbol
14258 table. This can lead to problems if the current working directories on
14259 the two systems differ. If both systems have NFS mounted the same
14260 filesystems, you can avoid these problems by using absolute paths.
14261 Otherwise, it is simplest to set the working directory on both systems
14262 to the directory in which the object file resides, and then to reference
14263 the file by its name, without any path. For instance, a program
14264 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
14265 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
14266 program, type this on VxWorks:
14269 -> cd "@var{vxpath}/vw/demo/rdb"
14273 Then, in @value{GDBN}, type:
14276 (vxgdb) cd @var{hostpath}/vw/demo/rdb
14277 (vxgdb) load prog.o
14280 @value{GDBN} displays a response similar to this:
14283 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
14286 You can also use the @code{load} command to reload an object module
14287 after editing and recompiling the corresponding source file. Note that
14288 this makes @value{GDBN} delete all currently-defined breakpoints,
14289 auto-displays, and convenience variables, and to clear the value
14290 history. (This is necessary in order to preserve the integrity of
14291 debugger's data structures that reference the target system's symbol
14294 @node VxWorks Attach
14295 @subsubsection Running Tasks
14297 @cindex running VxWorks tasks
14298 You can also attach to an existing task using the @code{attach} command as
14302 (vxgdb) attach @var{task}
14306 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
14307 or suspended when you attach to it. Running tasks are suspended at
14308 the time of attachment.
14310 @node Embedded Processors
14311 @section Embedded Processors
14313 This section goes into details specific to particular embedded
14316 @cindex send command to simulator
14317 Whenever a specific embedded processor has a simulator, @value{GDBN}
14318 allows to send an arbitrary command to the simulator.
14321 @item sim @var{command}
14322 @kindex sim@r{, a command}
14323 Send an arbitrary @var{command} string to the simulator. Consult the
14324 documentation for the specific simulator in use for information about
14325 acceptable commands.
14331 * M32R/D:: Renesas M32R/D
14332 * M68K:: Motorola M68K
14333 * MIPS Embedded:: MIPS Embedded
14334 * OpenRISC 1000:: OpenRisc 1000
14335 * PA:: HP PA Embedded
14336 * PowerPC:: PowerPC
14337 * Sparclet:: Tsqware Sparclet
14338 * Sparclite:: Fujitsu Sparclite
14339 * Z8000:: Zilog Z8000
14342 * Super-H:: Renesas Super-H
14351 @item target rdi @var{dev}
14352 ARM Angel monitor, via RDI library interface to ADP protocol. You may
14353 use this target to communicate with both boards running the Angel
14354 monitor, or with the EmbeddedICE JTAG debug device.
14357 @item target rdp @var{dev}
14362 @value{GDBN} provides the following ARM-specific commands:
14365 @item set arm disassembler
14367 This commands selects from a list of disassembly styles. The
14368 @code{"std"} style is the standard style.
14370 @item show arm disassembler
14372 Show the current disassembly style.
14374 @item set arm apcs32
14375 @cindex ARM 32-bit mode
14376 This command toggles ARM operation mode between 32-bit and 26-bit.
14378 @item show arm apcs32
14379 Display the current usage of the ARM 32-bit mode.
14381 @item set arm fpu @var{fputype}
14382 This command sets the ARM floating-point unit (FPU) type. The
14383 argument @var{fputype} can be one of these:
14387 Determine the FPU type by querying the OS ABI.
14389 Software FPU, with mixed-endian doubles on little-endian ARM
14392 GCC-compiled FPA co-processor.
14394 Software FPU with pure-endian doubles.
14400 Show the current type of the FPU.
14403 This command forces @value{GDBN} to use the specified ABI.
14406 Show the currently used ABI.
14408 @item set debug arm
14409 Toggle whether to display ARM-specific debugging messages from the ARM
14410 target support subsystem.
14412 @item show debug arm
14413 Show whether ARM-specific debugging messages are enabled.
14416 The following commands are available when an ARM target is debugged
14417 using the RDI interface:
14420 @item rdilogfile @r{[}@var{file}@r{]}
14422 @cindex ADP (Angel Debugger Protocol) logging
14423 Set the filename for the ADP (Angel Debugger Protocol) packet log.
14424 With an argument, sets the log file to the specified @var{file}. With
14425 no argument, show the current log file name. The default log file is
14428 @item rdilogenable @r{[}@var{arg}@r{]}
14429 @kindex rdilogenable
14430 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
14431 enables logging, with an argument 0 or @code{"no"} disables it. With
14432 no arguments displays the current setting. When logging is enabled,
14433 ADP packets exchanged between @value{GDBN} and the RDI target device
14434 are logged to a file.
14436 @item set rdiromatzero
14437 @kindex set rdiromatzero
14438 @cindex ROM at zero address, RDI
14439 Tell @value{GDBN} whether the target has ROM at address 0. If on,
14440 vector catching is disabled, so that zero address can be used. If off
14441 (the default), vector catching is enabled. For this command to take
14442 effect, it needs to be invoked prior to the @code{target rdi} command.
14444 @item show rdiromatzero
14445 @kindex show rdiromatzero
14446 Show the current setting of ROM at zero address.
14448 @item set rdiheartbeat
14449 @kindex set rdiheartbeat
14450 @cindex RDI heartbeat
14451 Enable or disable RDI heartbeat packets. It is not recommended to
14452 turn on this option, since it confuses ARM and EPI JTAG interface, as
14453 well as the Angel monitor.
14455 @item show rdiheartbeat
14456 @kindex show rdiheartbeat
14457 Show the setting of RDI heartbeat packets.
14462 @subsection Renesas M32R/D and M32R/SDI
14465 @kindex target m32r
14466 @item target m32r @var{dev}
14467 Renesas M32R/D ROM monitor.
14469 @kindex target m32rsdi
14470 @item target m32rsdi @var{dev}
14471 Renesas M32R SDI server, connected via parallel port to the board.
14474 The following @value{GDBN} commands are specific to the M32R monitor:
14477 @item set download-path @var{path}
14478 @kindex set download-path
14479 @cindex find downloadable @sc{srec} files (M32R)
14480 Set the default path for finding downloadable @sc{srec} files.
14482 @item show download-path
14483 @kindex show download-path
14484 Show the default path for downloadable @sc{srec} files.
14486 @item set board-address @var{addr}
14487 @kindex set board-address
14488 @cindex M32-EVA target board address
14489 Set the IP address for the M32R-EVA target board.
14491 @item show board-address
14492 @kindex show board-address
14493 Show the current IP address of the target board.
14495 @item set server-address @var{addr}
14496 @kindex set server-address
14497 @cindex download server address (M32R)
14498 Set the IP address for the download server, which is the @value{GDBN}'s
14501 @item show server-address
14502 @kindex show server-address
14503 Display the IP address of the download server.
14505 @item upload @r{[}@var{file}@r{]}
14506 @kindex upload@r{, M32R}
14507 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
14508 upload capability. If no @var{file} argument is given, the current
14509 executable file is uploaded.
14511 @item tload @r{[}@var{file}@r{]}
14512 @kindex tload@r{, M32R}
14513 Test the @code{upload} command.
14516 The following commands are available for M32R/SDI:
14521 @cindex reset SDI connection, M32R
14522 This command resets the SDI connection.
14526 This command shows the SDI connection status.
14529 @kindex debug_chaos
14530 @cindex M32R/Chaos debugging
14531 Instructs the remote that M32R/Chaos debugging is to be used.
14533 @item use_debug_dma
14534 @kindex use_debug_dma
14535 Instructs the remote to use the DEBUG_DMA method of accessing memory.
14538 @kindex use_mon_code
14539 Instructs the remote to use the MON_CODE method of accessing memory.
14542 @kindex use_ib_break
14543 Instructs the remote to set breakpoints by IB break.
14545 @item use_dbt_break
14546 @kindex use_dbt_break
14547 Instructs the remote to set breakpoints by DBT.
14553 The Motorola m68k configuration includes ColdFire support, and a
14554 target command for the following ROM monitor.
14558 @kindex target dbug
14559 @item target dbug @var{dev}
14560 dBUG ROM monitor for Motorola ColdFire.
14564 @node MIPS Embedded
14565 @subsection MIPS Embedded
14567 @cindex MIPS boards
14568 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
14569 MIPS board attached to a serial line. This is available when
14570 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
14573 Use these @value{GDBN} commands to specify the connection to your target board:
14576 @item target mips @var{port}
14577 @kindex target mips @var{port}
14578 To run a program on the board, start up @code{@value{GDBP}} with the
14579 name of your program as the argument. To connect to the board, use the
14580 command @samp{target mips @var{port}}, where @var{port} is the name of
14581 the serial port connected to the board. If the program has not already
14582 been downloaded to the board, you may use the @code{load} command to
14583 download it. You can then use all the usual @value{GDBN} commands.
14585 For example, this sequence connects to the target board through a serial
14586 port, and loads and runs a program called @var{prog} through the
14590 host$ @value{GDBP} @var{prog}
14591 @value{GDBN} is free software and @dots{}
14592 (@value{GDBP}) target mips /dev/ttyb
14593 (@value{GDBP}) load @var{prog}
14597 @item target mips @var{hostname}:@var{portnumber}
14598 On some @value{GDBN} host configurations, you can specify a TCP
14599 connection (for instance, to a serial line managed by a terminal
14600 concentrator) instead of a serial port, using the syntax
14601 @samp{@var{hostname}:@var{portnumber}}.
14603 @item target pmon @var{port}
14604 @kindex target pmon @var{port}
14607 @item target ddb @var{port}
14608 @kindex target ddb @var{port}
14609 NEC's DDB variant of PMON for Vr4300.
14611 @item target lsi @var{port}
14612 @kindex target lsi @var{port}
14613 LSI variant of PMON.
14615 @kindex target r3900
14616 @item target r3900 @var{dev}
14617 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
14619 @kindex target array
14620 @item target array @var{dev}
14621 Array Tech LSI33K RAID controller board.
14627 @value{GDBN} also supports these special commands for MIPS targets:
14630 @item set mipsfpu double
14631 @itemx set mipsfpu single
14632 @itemx set mipsfpu none
14633 @itemx set mipsfpu auto
14634 @itemx show mipsfpu
14635 @kindex set mipsfpu
14636 @kindex show mipsfpu
14637 @cindex MIPS remote floating point
14638 @cindex floating point, MIPS remote
14639 If your target board does not support the MIPS floating point
14640 coprocessor, you should use the command @samp{set mipsfpu none} (if you
14641 need this, you may wish to put the command in your @value{GDBN} init
14642 file). This tells @value{GDBN} how to find the return value of
14643 functions which return floating point values. It also allows
14644 @value{GDBN} to avoid saving the floating point registers when calling
14645 functions on the board. If you are using a floating point coprocessor
14646 with only single precision floating point support, as on the @sc{r4650}
14647 processor, use the command @samp{set mipsfpu single}. The default
14648 double precision floating point coprocessor may be selected using
14649 @samp{set mipsfpu double}.
14651 In previous versions the only choices were double precision or no
14652 floating point, so @samp{set mipsfpu on} will select double precision
14653 and @samp{set mipsfpu off} will select no floating point.
14655 As usual, you can inquire about the @code{mipsfpu} variable with
14656 @samp{show mipsfpu}.
14658 @item set timeout @var{seconds}
14659 @itemx set retransmit-timeout @var{seconds}
14660 @itemx show timeout
14661 @itemx show retransmit-timeout
14662 @cindex @code{timeout}, MIPS protocol
14663 @cindex @code{retransmit-timeout}, MIPS protocol
14664 @kindex set timeout
14665 @kindex show timeout
14666 @kindex set retransmit-timeout
14667 @kindex show retransmit-timeout
14668 You can control the timeout used while waiting for a packet, in the MIPS
14669 remote protocol, with the @code{set timeout @var{seconds}} command. The
14670 default is 5 seconds. Similarly, you can control the timeout used while
14671 waiting for an acknowledgement of a packet with the @code{set
14672 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
14673 You can inspect both values with @code{show timeout} and @code{show
14674 retransmit-timeout}. (These commands are @emph{only} available when
14675 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
14677 The timeout set by @code{set timeout} does not apply when @value{GDBN}
14678 is waiting for your program to stop. In that case, @value{GDBN} waits
14679 forever because it has no way of knowing how long the program is going
14680 to run before stopping.
14682 @item set syn-garbage-limit @var{num}
14683 @kindex set syn-garbage-limit@r{, MIPS remote}
14684 @cindex synchronize with remote MIPS target
14685 Limit the maximum number of characters @value{GDBN} should ignore when
14686 it tries to synchronize with the remote target. The default is 10
14687 characters. Setting the limit to -1 means there's no limit.
14689 @item show syn-garbage-limit
14690 @kindex show syn-garbage-limit@r{, MIPS remote}
14691 Show the current limit on the number of characters to ignore when
14692 trying to synchronize with the remote system.
14694 @item set monitor-prompt @var{prompt}
14695 @kindex set monitor-prompt@r{, MIPS remote}
14696 @cindex remote monitor prompt
14697 Tell @value{GDBN} to expect the specified @var{prompt} string from the
14698 remote monitor. The default depends on the target:
14708 @item show monitor-prompt
14709 @kindex show monitor-prompt@r{, MIPS remote}
14710 Show the current strings @value{GDBN} expects as the prompt from the
14713 @item set monitor-warnings
14714 @kindex set monitor-warnings@r{, MIPS remote}
14715 Enable or disable monitor warnings about hardware breakpoints. This
14716 has effect only for the @code{lsi} target. When on, @value{GDBN} will
14717 display warning messages whose codes are returned by the @code{lsi}
14718 PMON monitor for breakpoint commands.
14720 @item show monitor-warnings
14721 @kindex show monitor-warnings@r{, MIPS remote}
14722 Show the current setting of printing monitor warnings.
14724 @item pmon @var{command}
14725 @kindex pmon@r{, MIPS remote}
14726 @cindex send PMON command
14727 This command allows sending an arbitrary @var{command} string to the
14728 monitor. The monitor must be in debug mode for this to work.
14731 @node OpenRISC 1000
14732 @subsection OpenRISC 1000
14733 @cindex OpenRISC 1000
14735 @cindex or1k boards
14736 See OR1k Architecture document (@uref{www.opencores.org}) for more information
14737 about platform and commands.
14741 @kindex target jtag
14742 @item target jtag jtag://@var{host}:@var{port}
14744 Connects to remote JTAG server.
14745 JTAG remote server can be either an or1ksim or JTAG server,
14746 connected via parallel port to the board.
14748 Example: @code{target jtag jtag://localhost:9999}
14751 @item or1ksim @var{command}
14752 If connected to @code{or1ksim} OpenRISC 1000 Architectural
14753 Simulator, proprietary commands can be executed.
14755 @kindex info or1k spr
14756 @item info or1k spr
14757 Displays spr groups.
14759 @item info or1k spr @var{group}
14760 @itemx info or1k spr @var{groupno}
14761 Displays register names in selected group.
14763 @item info or1k spr @var{group} @var{register}
14764 @itemx info or1k spr @var{register}
14765 @itemx info or1k spr @var{groupno} @var{registerno}
14766 @itemx info or1k spr @var{registerno}
14767 Shows information about specified spr register.
14770 @item spr @var{group} @var{register} @var{value}
14771 @itemx spr @var{register @var{value}}
14772 @itemx spr @var{groupno} @var{registerno @var{value}}
14773 @itemx spr @var{registerno @var{value}}
14774 Writes @var{value} to specified spr register.
14777 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
14778 It is very similar to @value{GDBN} trace, except it does not interfere with normal
14779 program execution and is thus much faster. Hardware breakpoints/watchpoint
14780 triggers can be set using:
14783 Load effective address/data
14785 Store effective address/data
14787 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
14792 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
14793 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
14795 @code{htrace} commands:
14796 @cindex OpenRISC 1000 htrace
14799 @item hwatch @var{conditional}
14800 Set hardware watchpoint on combination of Load/Store Effective Address(es)
14801 or Data. For example:
14803 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
14805 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
14809 Display information about current HW trace configuration.
14811 @item htrace trigger @var{conditional}
14812 Set starting criteria for HW trace.
14814 @item htrace qualifier @var{conditional}
14815 Set acquisition qualifier for HW trace.
14817 @item htrace stop @var{conditional}
14818 Set HW trace stopping criteria.
14820 @item htrace record [@var{data}]*
14821 Selects the data to be recorded, when qualifier is met and HW trace was
14824 @item htrace enable
14825 @itemx htrace disable
14826 Enables/disables the HW trace.
14828 @item htrace rewind [@var{filename}]
14829 Clears currently recorded trace data.
14831 If filename is specified, new trace file is made and any newly collected data
14832 will be written there.
14834 @item htrace print [@var{start} [@var{len}]]
14835 Prints trace buffer, using current record configuration.
14837 @item htrace mode continuous
14838 Set continuous trace mode.
14840 @item htrace mode suspend
14841 Set suspend trace mode.
14846 @subsection PowerPC
14849 @kindex target dink32
14850 @item target dink32 @var{dev}
14851 DINK32 ROM monitor.
14853 @kindex target ppcbug
14854 @item target ppcbug @var{dev}
14855 @kindex target ppcbug1
14856 @item target ppcbug1 @var{dev}
14857 PPCBUG ROM monitor for PowerPC.
14860 @item target sds @var{dev}
14861 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
14864 @cindex SDS protocol
14865 The following commands specific to the SDS protocol are supported
14869 @item set sdstimeout @var{nsec}
14870 @kindex set sdstimeout
14871 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
14872 default is 2 seconds.
14874 @item show sdstimeout
14875 @kindex show sdstimeout
14876 Show the current value of the SDS timeout.
14878 @item sds @var{command}
14879 @kindex sds@r{, a command}
14880 Send the specified @var{command} string to the SDS monitor.
14885 @subsection HP PA Embedded
14889 @kindex target op50n
14890 @item target op50n @var{dev}
14891 OP50N monitor, running on an OKI HPPA board.
14893 @kindex target w89k
14894 @item target w89k @var{dev}
14895 W89K monitor, running on a Winbond HPPA board.
14900 @subsection Tsqware Sparclet
14904 @value{GDBN} enables developers to debug tasks running on
14905 Sparclet targets from a Unix host.
14906 @value{GDBN} uses code that runs on
14907 both the Unix host and on the Sparclet target. The program
14908 @code{@value{GDBP}} is installed and executed on the Unix host.
14911 @item remotetimeout @var{args}
14912 @kindex remotetimeout
14913 @value{GDBN} supports the option @code{remotetimeout}.
14914 This option is set by the user, and @var{args} represents the number of
14915 seconds @value{GDBN} waits for responses.
14918 @cindex compiling, on Sparclet
14919 When compiling for debugging, include the options @samp{-g} to get debug
14920 information and @samp{-Ttext} to relocate the program to where you wish to
14921 load it on the target. You may also want to add the options @samp{-n} or
14922 @samp{-N} in order to reduce the size of the sections. Example:
14925 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
14928 You can use @code{objdump} to verify that the addresses are what you intended:
14931 sparclet-aout-objdump --headers --syms prog
14934 @cindex running, on Sparclet
14936 your Unix execution search path to find @value{GDBN}, you are ready to
14937 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
14938 (or @code{sparclet-aout-gdb}, depending on your installation).
14940 @value{GDBN} comes up showing the prompt:
14947 * Sparclet File:: Setting the file to debug
14948 * Sparclet Connection:: Connecting to Sparclet
14949 * Sparclet Download:: Sparclet download
14950 * Sparclet Execution:: Running and debugging
14953 @node Sparclet File
14954 @subsubsection Setting File to Debug
14956 The @value{GDBN} command @code{file} lets you choose with program to debug.
14959 (gdbslet) file prog
14963 @value{GDBN} then attempts to read the symbol table of @file{prog}.
14964 @value{GDBN} locates
14965 the file by searching the directories listed in the command search
14967 If the file was compiled with debug information (option @samp{-g}), source
14968 files will be searched as well.
14969 @value{GDBN} locates
14970 the source files by searching the directories listed in the directory search
14971 path (@pxref{Environment, ,Your Program's Environment}).
14973 to find a file, it displays a message such as:
14976 prog: No such file or directory.
14979 When this happens, add the appropriate directories to the search paths with
14980 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
14981 @code{target} command again.
14983 @node Sparclet Connection
14984 @subsubsection Connecting to Sparclet
14986 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
14987 To connect to a target on serial port ``@code{ttya}'', type:
14990 (gdbslet) target sparclet /dev/ttya
14991 Remote target sparclet connected to /dev/ttya
14992 main () at ../prog.c:3
14996 @value{GDBN} displays messages like these:
15002 @node Sparclet Download
15003 @subsubsection Sparclet Download
15005 @cindex download to Sparclet
15006 Once connected to the Sparclet target,
15007 you can use the @value{GDBN}
15008 @code{load} command to download the file from the host to the target.
15009 The file name and load offset should be given as arguments to the @code{load}
15011 Since the file format is aout, the program must be loaded to the starting
15012 address. You can use @code{objdump} to find out what this value is. The load
15013 offset is an offset which is added to the VMA (virtual memory address)
15014 of each of the file's sections.
15015 For instance, if the program
15016 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
15017 and bss at 0x12010170, in @value{GDBN}, type:
15020 (gdbslet) load prog 0x12010000
15021 Loading section .text, size 0xdb0 vma 0x12010000
15024 If the code is loaded at a different address then what the program was linked
15025 to, you may need to use the @code{section} and @code{add-symbol-file} commands
15026 to tell @value{GDBN} where to map the symbol table.
15028 @node Sparclet Execution
15029 @subsubsection Running and Debugging
15031 @cindex running and debugging Sparclet programs
15032 You can now begin debugging the task using @value{GDBN}'s execution control
15033 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
15034 manual for the list of commands.
15038 Breakpoint 1 at 0x12010000: file prog.c, line 3.
15040 Starting program: prog
15041 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
15042 3 char *symarg = 0;
15044 4 char *execarg = "hello!";
15049 @subsection Fujitsu Sparclite
15053 @kindex target sparclite
15054 @item target sparclite @var{dev}
15055 Fujitsu sparclite boards, used only for the purpose of loading.
15056 You must use an additional command to debug the program.
15057 For example: target remote @var{dev} using @value{GDBN} standard
15063 @subsection Zilog Z8000
15066 @cindex simulator, Z8000
15067 @cindex Zilog Z8000 simulator
15069 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
15072 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
15073 unsegmented variant of the Z8000 architecture) or the Z8001 (the
15074 segmented variant). The simulator recognizes which architecture is
15075 appropriate by inspecting the object code.
15078 @item target sim @var{args}
15080 @kindex target sim@r{, with Z8000}
15081 Debug programs on a simulated CPU. If the simulator supports setup
15082 options, specify them via @var{args}.
15086 After specifying this target, you can debug programs for the simulated
15087 CPU in the same style as programs for your host computer; use the
15088 @code{file} command to load a new program image, the @code{run} command
15089 to run your program, and so on.
15091 As well as making available all the usual machine registers
15092 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
15093 additional items of information as specially named registers:
15098 Counts clock-ticks in the simulator.
15101 Counts instructions run in the simulator.
15104 Execution time in 60ths of a second.
15108 You can refer to these values in @value{GDBN} expressions with the usual
15109 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
15110 conditional breakpoint that suspends only after at least 5000
15111 simulated clock ticks.
15114 @subsection Atmel AVR
15117 When configured for debugging the Atmel AVR, @value{GDBN} supports the
15118 following AVR-specific commands:
15121 @item info io_registers
15122 @kindex info io_registers@r{, AVR}
15123 @cindex I/O registers (Atmel AVR)
15124 This command displays information about the AVR I/O registers. For
15125 each register, @value{GDBN} prints its number and value.
15132 When configured for debugging CRIS, @value{GDBN} provides the
15133 following CRIS-specific commands:
15136 @item set cris-version @var{ver}
15137 @cindex CRIS version
15138 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
15139 The CRIS version affects register names and sizes. This command is useful in
15140 case autodetection of the CRIS version fails.
15142 @item show cris-version
15143 Show the current CRIS version.
15145 @item set cris-dwarf2-cfi
15146 @cindex DWARF-2 CFI and CRIS
15147 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
15148 Change to @samp{off} when using @code{gcc-cris} whose version is below
15151 @item show cris-dwarf2-cfi
15152 Show the current state of using DWARF-2 CFI.
15154 @item set cris-mode @var{mode}
15156 Set the current CRIS mode to @var{mode}. It should only be changed when
15157 debugging in guru mode, in which case it should be set to
15158 @samp{guru} (the default is @samp{normal}).
15160 @item show cris-mode
15161 Show the current CRIS mode.
15165 @subsection Renesas Super-H
15168 For the Renesas Super-H processor, @value{GDBN} provides these
15173 @kindex regs@r{, Super-H}
15174 Show the values of all Super-H registers.
15178 @node Architectures
15179 @section Architectures
15181 This section describes characteristics of architectures that affect
15182 all uses of @value{GDBN} with the architecture, both native and cross.
15189 * HPPA:: HP PA architecture
15190 * SPU:: Cell Broadband Engine SPU architecture
15194 @subsection x86 Architecture-specific Issues
15197 @item set struct-convention @var{mode}
15198 @kindex set struct-convention
15199 @cindex struct return convention
15200 @cindex struct/union returned in registers
15201 Set the convention used by the inferior to return @code{struct}s and
15202 @code{union}s from functions to @var{mode}. Possible values of
15203 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
15204 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
15205 are returned on the stack, while @code{"reg"} means that a
15206 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
15207 be returned in a register.
15209 @item show struct-convention
15210 @kindex show struct-convention
15211 Show the current setting of the convention to return @code{struct}s
15220 @kindex set rstack_high_address
15221 @cindex AMD 29K register stack
15222 @cindex register stack, AMD29K
15223 @item set rstack_high_address @var{address}
15224 On AMD 29000 family processors, registers are saved in a separate
15225 @dfn{register stack}. There is no way for @value{GDBN} to determine the
15226 extent of this stack. Normally, @value{GDBN} just assumes that the
15227 stack is ``large enough''. This may result in @value{GDBN} referencing
15228 memory locations that do not exist. If necessary, you can get around
15229 this problem by specifying the ending address of the register stack with
15230 the @code{set rstack_high_address} command. The argument should be an
15231 address, which you probably want to precede with @samp{0x} to specify in
15234 @kindex show rstack_high_address
15235 @item show rstack_high_address
15236 Display the current limit of the register stack, on AMD 29000 family
15244 See the following section.
15249 @cindex stack on Alpha
15250 @cindex stack on MIPS
15251 @cindex Alpha stack
15253 Alpha- and MIPS-based computers use an unusual stack frame, which
15254 sometimes requires @value{GDBN} to search backward in the object code to
15255 find the beginning of a function.
15257 @cindex response time, MIPS debugging
15258 To improve response time (especially for embedded applications, where
15259 @value{GDBN} may be restricted to a slow serial line for this search)
15260 you may want to limit the size of this search, using one of these
15264 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
15265 @item set heuristic-fence-post @var{limit}
15266 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
15267 search for the beginning of a function. A value of @var{0} (the
15268 default) means there is no limit. However, except for @var{0}, the
15269 larger the limit the more bytes @code{heuristic-fence-post} must search
15270 and therefore the longer it takes to run. You should only need to use
15271 this command when debugging a stripped executable.
15273 @item show heuristic-fence-post
15274 Display the current limit.
15278 These commands are available @emph{only} when @value{GDBN} is configured
15279 for debugging programs on Alpha or MIPS processors.
15281 Several MIPS-specific commands are available when debugging MIPS
15285 @item set mips abi @var{arg}
15286 @kindex set mips abi
15287 @cindex set ABI for MIPS
15288 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
15289 values of @var{arg} are:
15293 The default ABI associated with the current binary (this is the
15304 @item show mips abi
15305 @kindex show mips abi
15306 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
15309 @itemx show mipsfpu
15310 @xref{MIPS Embedded, set mipsfpu}.
15312 @item set mips mask-address @var{arg}
15313 @kindex set mips mask-address
15314 @cindex MIPS addresses, masking
15315 This command determines whether the most-significant 32 bits of 64-bit
15316 MIPS addresses are masked off. The argument @var{arg} can be
15317 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
15318 setting, which lets @value{GDBN} determine the correct value.
15320 @item show mips mask-address
15321 @kindex show mips mask-address
15322 Show whether the upper 32 bits of MIPS addresses are masked off or
15325 @item set remote-mips64-transfers-32bit-regs
15326 @kindex set remote-mips64-transfers-32bit-regs
15327 This command controls compatibility with 64-bit MIPS targets that
15328 transfer data in 32-bit quantities. If you have an old MIPS 64 target
15329 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
15330 and 64 bits for other registers, set this option to @samp{on}.
15332 @item show remote-mips64-transfers-32bit-regs
15333 @kindex show remote-mips64-transfers-32bit-regs
15334 Show the current setting of compatibility with older MIPS 64 targets.
15336 @item set debug mips
15337 @kindex set debug mips
15338 This command turns on and off debugging messages for the MIPS-specific
15339 target code in @value{GDBN}.
15341 @item show debug mips
15342 @kindex show debug mips
15343 Show the current setting of MIPS debugging messages.
15349 @cindex HPPA support
15351 When @value{GDBN} is debugging the HP PA architecture, it provides the
15352 following special commands:
15355 @item set debug hppa
15356 @kindex set debug hppa
15357 This command determines whether HPPA architecture-specific debugging
15358 messages are to be displayed.
15360 @item show debug hppa
15361 Show whether HPPA debugging messages are displayed.
15363 @item maint print unwind @var{address}
15364 @kindex maint print unwind@r{, HPPA}
15365 This command displays the contents of the unwind table entry at the
15366 given @var{address}.
15372 @subsection Cell Broadband Engine SPU architecture
15373 @cindex Cell Broadband Engine
15376 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
15377 it provides the following special commands:
15380 @item info spu event
15382 Display SPU event facility status. Shows current event mask
15383 and pending event status.
15385 @item info spu signal
15386 Display SPU signal notification facility status. Shows pending
15387 signal-control word and signal notification mode of both signal
15388 notification channels.
15390 @item info spu mailbox
15391 Display SPU mailbox facility status. Shows all pending entries,
15392 in order of processing, in each of the SPU Write Outbound,
15393 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
15396 Display MFC DMA status. Shows all pending commands in the MFC
15397 DMA queue. For each entry, opcode, tag, class IDs, effective
15398 and local store addresses and transfer size are shown.
15400 @item info spu proxydma
15401 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
15402 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
15403 and local store addresses and transfer size are shown.
15408 @node Controlling GDB
15409 @chapter Controlling @value{GDBN}
15411 You can alter the way @value{GDBN} interacts with you by using the
15412 @code{set} command. For commands controlling how @value{GDBN} displays
15413 data, see @ref{Print Settings, ,Print Settings}. Other settings are
15418 * Editing:: Command editing
15419 * Command History:: Command history
15420 * Screen Size:: Screen size
15421 * Numbers:: Numbers
15422 * ABI:: Configuring the current ABI
15423 * Messages/Warnings:: Optional warnings and messages
15424 * Debugging Output:: Optional messages about internal happenings
15432 @value{GDBN} indicates its readiness to read a command by printing a string
15433 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
15434 can change the prompt string with the @code{set prompt} command. For
15435 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
15436 the prompt in one of the @value{GDBN} sessions so that you can always tell
15437 which one you are talking to.
15439 @emph{Note:} @code{set prompt} does not add a space for you after the
15440 prompt you set. This allows you to set a prompt which ends in a space
15441 or a prompt that does not.
15445 @item set prompt @var{newprompt}
15446 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
15448 @kindex show prompt
15450 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
15454 @section Command Editing
15456 @cindex command line editing
15458 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
15459 @sc{gnu} library provides consistent behavior for programs which provide a
15460 command line interface to the user. Advantages are @sc{gnu} Emacs-style
15461 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
15462 substitution, and a storage and recall of command history across
15463 debugging sessions.
15465 You may control the behavior of command line editing in @value{GDBN} with the
15466 command @code{set}.
15469 @kindex set editing
15472 @itemx set editing on
15473 Enable command line editing (enabled by default).
15475 @item set editing off
15476 Disable command line editing.
15478 @kindex show editing
15480 Show whether command line editing is enabled.
15483 @xref{Command Line Editing}, for more details about the Readline
15484 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
15485 encouraged to read that chapter.
15487 @node Command History
15488 @section Command History
15489 @cindex command history
15491 @value{GDBN} can keep track of the commands you type during your
15492 debugging sessions, so that you can be certain of precisely what
15493 happened. Use these commands to manage the @value{GDBN} command
15496 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
15497 package, to provide the history facility. @xref{Using History
15498 Interactively}, for the detailed description of the History library.
15500 To issue a command to @value{GDBN} without affecting certain aspects of
15501 the state which is seen by users, prefix it with @samp{server }
15502 (@pxref{Server Prefix}). This
15503 means that this command will not affect the command history, nor will it
15504 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
15505 pressed on a line by itself.
15507 @cindex @code{server}, command prefix
15508 The server prefix does not affect the recording of values into the value
15509 history; to print a value without recording it into the value history,
15510 use the @code{output} command instead of the @code{print} command.
15512 Here is the description of @value{GDBN} commands related to command
15516 @cindex history substitution
15517 @cindex history file
15518 @kindex set history filename
15519 @cindex @env{GDBHISTFILE}, environment variable
15520 @item set history filename @var{fname}
15521 Set the name of the @value{GDBN} command history file to @var{fname}.
15522 This is the file where @value{GDBN} reads an initial command history
15523 list, and where it writes the command history from this session when it
15524 exits. You can access this list through history expansion or through
15525 the history command editing characters listed below. This file defaults
15526 to the value of the environment variable @code{GDBHISTFILE}, or to
15527 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
15530 @cindex save command history
15531 @kindex set history save
15532 @item set history save
15533 @itemx set history save on
15534 Record command history in a file, whose name may be specified with the
15535 @code{set history filename} command. By default, this option is disabled.
15537 @item set history save off
15538 Stop recording command history in a file.
15540 @cindex history size
15541 @kindex set history size
15542 @cindex @env{HISTSIZE}, environment variable
15543 @item set history size @var{size}
15544 Set the number of commands which @value{GDBN} keeps in its history list.
15545 This defaults to the value of the environment variable
15546 @code{HISTSIZE}, or to 256 if this variable is not set.
15549 History expansion assigns special meaning to the character @kbd{!}.
15550 @xref{Event Designators}, for more details.
15552 @cindex history expansion, turn on/off
15553 Since @kbd{!} is also the logical not operator in C, history expansion
15554 is off by default. If you decide to enable history expansion with the
15555 @code{set history expansion on} command, you may sometimes need to
15556 follow @kbd{!} (when it is used as logical not, in an expression) with
15557 a space or a tab to prevent it from being expanded. The readline
15558 history facilities do not attempt substitution on the strings
15559 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
15561 The commands to control history expansion are:
15564 @item set history expansion on
15565 @itemx set history expansion
15566 @kindex set history expansion
15567 Enable history expansion. History expansion is off by default.
15569 @item set history expansion off
15570 Disable history expansion.
15573 @kindex show history
15575 @itemx show history filename
15576 @itemx show history save
15577 @itemx show history size
15578 @itemx show history expansion
15579 These commands display the state of the @value{GDBN} history parameters.
15580 @code{show history} by itself displays all four states.
15585 @kindex show commands
15586 @cindex show last commands
15587 @cindex display command history
15588 @item show commands
15589 Display the last ten commands in the command history.
15591 @item show commands @var{n}
15592 Print ten commands centered on command number @var{n}.
15594 @item show commands +
15595 Print ten commands just after the commands last printed.
15599 @section Screen Size
15600 @cindex size of screen
15601 @cindex pauses in output
15603 Certain commands to @value{GDBN} may produce large amounts of
15604 information output to the screen. To help you read all of it,
15605 @value{GDBN} pauses and asks you for input at the end of each page of
15606 output. Type @key{RET} when you want to continue the output, or @kbd{q}
15607 to discard the remaining output. Also, the screen width setting
15608 determines when to wrap lines of output. Depending on what is being
15609 printed, @value{GDBN} tries to break the line at a readable place,
15610 rather than simply letting it overflow onto the following line.
15612 Normally @value{GDBN} knows the size of the screen from the terminal
15613 driver software. For example, on Unix @value{GDBN} uses the termcap data base
15614 together with the value of the @code{TERM} environment variable and the
15615 @code{stty rows} and @code{stty cols} settings. If this is not correct,
15616 you can override it with the @code{set height} and @code{set
15623 @kindex show height
15624 @item set height @var{lpp}
15626 @itemx set width @var{cpl}
15628 These @code{set} commands specify a screen height of @var{lpp} lines and
15629 a screen width of @var{cpl} characters. The associated @code{show}
15630 commands display the current settings.
15632 If you specify a height of zero lines, @value{GDBN} does not pause during
15633 output no matter how long the output is. This is useful if output is to a
15634 file or to an editor buffer.
15636 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
15637 from wrapping its output.
15639 @item set pagination on
15640 @itemx set pagination off
15641 @kindex set pagination
15642 Turn the output pagination on or off; the default is on. Turning
15643 pagination off is the alternative to @code{set height 0}.
15645 @item show pagination
15646 @kindex show pagination
15647 Show the current pagination mode.
15652 @cindex number representation
15653 @cindex entering numbers
15655 You can always enter numbers in octal, decimal, or hexadecimal in
15656 @value{GDBN} by the usual conventions: octal numbers begin with
15657 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
15658 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
15659 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
15660 10; likewise, the default display for numbers---when no particular
15661 format is specified---is base 10. You can change the default base for
15662 both input and output with the commands described below.
15665 @kindex set input-radix
15666 @item set input-radix @var{base}
15667 Set the default base for numeric input. Supported choices
15668 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15669 specified either unambiguously or using the current input radix; for
15673 set input-radix 012
15674 set input-radix 10.
15675 set input-radix 0xa
15679 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
15680 leaves the input radix unchanged, no matter what it was, since
15681 @samp{10}, being without any leading or trailing signs of its base, is
15682 interpreted in the current radix. Thus, if the current radix is 16,
15683 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
15686 @kindex set output-radix
15687 @item set output-radix @var{base}
15688 Set the default base for numeric display. Supported choices
15689 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15690 specified either unambiguously or using the current input radix.
15692 @kindex show input-radix
15693 @item show input-radix
15694 Display the current default base for numeric input.
15696 @kindex show output-radix
15697 @item show output-radix
15698 Display the current default base for numeric display.
15700 @item set radix @r{[}@var{base}@r{]}
15704 These commands set and show the default base for both input and output
15705 of numbers. @code{set radix} sets the radix of input and output to
15706 the same base; without an argument, it resets the radix back to its
15707 default value of 10.
15712 @section Configuring the Current ABI
15714 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
15715 application automatically. However, sometimes you need to override its
15716 conclusions. Use these commands to manage @value{GDBN}'s view of the
15723 One @value{GDBN} configuration can debug binaries for multiple operating
15724 system targets, either via remote debugging or native emulation.
15725 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
15726 but you can override its conclusion using the @code{set osabi} command.
15727 One example where this is useful is in debugging of binaries which use
15728 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
15729 not have the same identifying marks that the standard C library for your
15734 Show the OS ABI currently in use.
15737 With no argument, show the list of registered available OS ABI's.
15739 @item set osabi @var{abi}
15740 Set the current OS ABI to @var{abi}.
15743 @cindex float promotion
15745 Generally, the way that an argument of type @code{float} is passed to a
15746 function depends on whether the function is prototyped. For a prototyped
15747 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
15748 according to the architecture's convention for @code{float}. For unprototyped
15749 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
15750 @code{double} and then passed.
15752 Unfortunately, some forms of debug information do not reliably indicate whether
15753 a function is prototyped. If @value{GDBN} calls a function that is not marked
15754 as prototyped, it consults @kbd{set coerce-float-to-double}.
15757 @kindex set coerce-float-to-double
15758 @item set coerce-float-to-double
15759 @itemx set coerce-float-to-double on
15760 Arguments of type @code{float} will be promoted to @code{double} when passed
15761 to an unprototyped function. This is the default setting.
15763 @item set coerce-float-to-double off
15764 Arguments of type @code{float} will be passed directly to unprototyped
15767 @kindex show coerce-float-to-double
15768 @item show coerce-float-to-double
15769 Show the current setting of promoting @code{float} to @code{double}.
15773 @kindex show cp-abi
15774 @value{GDBN} needs to know the ABI used for your program's C@t{++}
15775 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
15776 used to build your application. @value{GDBN} only fully supports
15777 programs with a single C@t{++} ABI; if your program contains code using
15778 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
15779 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
15780 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
15781 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
15782 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
15783 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
15788 Show the C@t{++} ABI currently in use.
15791 With no argument, show the list of supported C@t{++} ABI's.
15793 @item set cp-abi @var{abi}
15794 @itemx set cp-abi auto
15795 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
15798 @node Messages/Warnings
15799 @section Optional Warnings and Messages
15801 @cindex verbose operation
15802 @cindex optional warnings
15803 By default, @value{GDBN} is silent about its inner workings. If you are
15804 running on a slow machine, you may want to use the @code{set verbose}
15805 command. This makes @value{GDBN} tell you when it does a lengthy
15806 internal operation, so you will not think it has crashed.
15808 Currently, the messages controlled by @code{set verbose} are those
15809 which announce that the symbol table for a source file is being read;
15810 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
15813 @kindex set verbose
15814 @item set verbose on
15815 Enables @value{GDBN} output of certain informational messages.
15817 @item set verbose off
15818 Disables @value{GDBN} output of certain informational messages.
15820 @kindex show verbose
15822 Displays whether @code{set verbose} is on or off.
15825 By default, if @value{GDBN} encounters bugs in the symbol table of an
15826 object file, it is silent; but if you are debugging a compiler, you may
15827 find this information useful (@pxref{Symbol Errors, ,Errors Reading
15832 @kindex set complaints
15833 @item set complaints @var{limit}
15834 Permits @value{GDBN} to output @var{limit} complaints about each type of
15835 unusual symbols before becoming silent about the problem. Set
15836 @var{limit} to zero to suppress all complaints; set it to a large number
15837 to prevent complaints from being suppressed.
15839 @kindex show complaints
15840 @item show complaints
15841 Displays how many symbol complaints @value{GDBN} is permitted to produce.
15845 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
15846 lot of stupid questions to confirm certain commands. For example, if
15847 you try to run a program which is already running:
15851 The program being debugged has been started already.
15852 Start it from the beginning? (y or n)
15855 If you are willing to unflinchingly face the consequences of your own
15856 commands, you can disable this ``feature'':
15860 @kindex set confirm
15862 @cindex confirmation
15863 @cindex stupid questions
15864 @item set confirm off
15865 Disables confirmation requests.
15867 @item set confirm on
15868 Enables confirmation requests (the default).
15870 @kindex show confirm
15872 Displays state of confirmation requests.
15876 @cindex command tracing
15877 If you need to debug user-defined commands or sourced files you may find it
15878 useful to enable @dfn{command tracing}. In this mode each command will be
15879 printed as it is executed, prefixed with one or more @samp{+} symbols, the
15880 quantity denoting the call depth of each command.
15883 @kindex set trace-commands
15884 @cindex command scripts, debugging
15885 @item set trace-commands on
15886 Enable command tracing.
15887 @item set trace-commands off
15888 Disable command tracing.
15889 @item show trace-commands
15890 Display the current state of command tracing.
15893 @node Debugging Output
15894 @section Optional Messages about Internal Happenings
15895 @cindex optional debugging messages
15897 @value{GDBN} has commands that enable optional debugging messages from
15898 various @value{GDBN} subsystems; normally these commands are of
15899 interest to @value{GDBN} maintainers, or when reporting a bug. This
15900 section documents those commands.
15903 @kindex set exec-done-display
15904 @item set exec-done-display
15905 Turns on or off the notification of asynchronous commands'
15906 completion. When on, @value{GDBN} will print a message when an
15907 asynchronous command finishes its execution. The default is off.
15908 @kindex show exec-done-display
15909 @item show exec-done-display
15910 Displays the current setting of asynchronous command completion
15913 @cindex gdbarch debugging info
15914 @cindex architecture debugging info
15915 @item set debug arch
15916 Turns on or off display of gdbarch debugging info. The default is off
15918 @item show debug arch
15919 Displays the current state of displaying gdbarch debugging info.
15920 @item set debug aix-thread
15921 @cindex AIX threads
15922 Display debugging messages about inner workings of the AIX thread
15924 @item show debug aix-thread
15925 Show the current state of AIX thread debugging info display.
15926 @item set debug event
15927 @cindex event debugging info
15928 Turns on or off display of @value{GDBN} event debugging info. The
15930 @item show debug event
15931 Displays the current state of displaying @value{GDBN} event debugging
15933 @item set debug expression
15934 @cindex expression debugging info
15935 Turns on or off display of debugging info about @value{GDBN}
15936 expression parsing. The default is off.
15937 @item show debug expression
15938 Displays the current state of displaying debugging info about
15939 @value{GDBN} expression parsing.
15940 @item set debug frame
15941 @cindex frame debugging info
15942 Turns on or off display of @value{GDBN} frame debugging info. The
15944 @item show debug frame
15945 Displays the current state of displaying @value{GDBN} frame debugging
15947 @item set debug infrun
15948 @cindex inferior debugging info
15949 Turns on or off display of @value{GDBN} debugging info for running the inferior.
15950 The default is off. @file{infrun.c} contains GDB's runtime state machine used
15951 for implementing operations such as single-stepping the inferior.
15952 @item show debug infrun
15953 Displays the current state of @value{GDBN} inferior debugging.
15954 @item set debug lin-lwp
15955 @cindex @sc{gnu}/Linux LWP debug messages
15956 @cindex Linux lightweight processes
15957 Turns on or off debugging messages from the Linux LWP debug support.
15958 @item show debug lin-lwp
15959 Show the current state of Linux LWP debugging messages.
15960 @item set debug observer
15961 @cindex observer debugging info
15962 Turns on or off display of @value{GDBN} observer debugging. This
15963 includes info such as the notification of observable events.
15964 @item show debug observer
15965 Displays the current state of observer debugging.
15966 @item set debug overload
15967 @cindex C@t{++} overload debugging info
15968 Turns on or off display of @value{GDBN} C@t{++} overload debugging
15969 info. This includes info such as ranking of functions, etc. The default
15971 @item show debug overload
15972 Displays the current state of displaying @value{GDBN} C@t{++} overload
15974 @cindex packets, reporting on stdout
15975 @cindex serial connections, debugging
15976 @cindex debug remote protocol
15977 @cindex remote protocol debugging
15978 @cindex display remote packets
15979 @item set debug remote
15980 Turns on or off display of reports on all packets sent back and forth across
15981 the serial line to the remote machine. The info is printed on the
15982 @value{GDBN} standard output stream. The default is off.
15983 @item show debug remote
15984 Displays the state of display of remote packets.
15985 @item set debug serial
15986 Turns on or off display of @value{GDBN} serial debugging info. The
15988 @item show debug serial
15989 Displays the current state of displaying @value{GDBN} serial debugging
15991 @item set debug solib-frv
15992 @cindex FR-V shared-library debugging
15993 Turns on or off debugging messages for FR-V shared-library code.
15994 @item show debug solib-frv
15995 Display the current state of FR-V shared-library code debugging
15997 @item set debug target
15998 @cindex target debugging info
15999 Turns on or off display of @value{GDBN} target debugging info. This info
16000 includes what is going on at the target level of GDB, as it happens. The
16001 default is 0. Set it to 1 to track events, and to 2 to also track the
16002 value of large memory transfers. Changes to this flag do not take effect
16003 until the next time you connect to a target or use the @code{run} command.
16004 @item show debug target
16005 Displays the current state of displaying @value{GDBN} target debugging
16007 @item set debugvarobj
16008 @cindex variable object debugging info
16009 Turns on or off display of @value{GDBN} variable object debugging
16010 info. The default is off.
16011 @item show debugvarobj
16012 Displays the current state of displaying @value{GDBN} variable object
16014 @item set debug xml
16015 @cindex XML parser debugging
16016 Turns on or off debugging messages for built-in XML parsers.
16017 @item show debug xml
16018 Displays the current state of XML debugging messages.
16022 @chapter Canned Sequences of Commands
16024 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
16025 Command Lists}), @value{GDBN} provides two ways to store sequences of
16026 commands for execution as a unit: user-defined commands and command
16030 * Define:: How to define your own commands
16031 * Hooks:: Hooks for user-defined commands
16032 * Command Files:: How to write scripts of commands to be stored in a file
16033 * Output:: Commands for controlled output
16037 @section User-defined Commands
16039 @cindex user-defined command
16040 @cindex arguments, to user-defined commands
16041 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
16042 which you assign a new name as a command. This is done with the
16043 @code{define} command. User commands may accept up to 10 arguments
16044 separated by whitespace. Arguments are accessed within the user command
16045 via @code{$arg0@dots{}$arg9}. A trivial example:
16049 print $arg0 + $arg1 + $arg2
16054 To execute the command use:
16061 This defines the command @code{adder}, which prints the sum of
16062 its three arguments. Note the arguments are text substitutions, so they may
16063 reference variables, use complex expressions, or even perform inferior
16066 @cindex argument count in user-defined commands
16067 @cindex how many arguments (user-defined commands)
16068 In addition, @code{$argc} may be used to find out how many arguments have
16069 been passed. This expands to a number in the range 0@dots{}10.
16074 print $arg0 + $arg1
16077 print $arg0 + $arg1 + $arg2
16085 @item define @var{commandname}
16086 Define a command named @var{commandname}. If there is already a command
16087 by that name, you are asked to confirm that you want to redefine it.
16089 The definition of the command is made up of other @value{GDBN} command lines,
16090 which are given following the @code{define} command. The end of these
16091 commands is marked by a line containing @code{end}.
16094 @kindex end@r{ (user-defined commands)}
16095 @item document @var{commandname}
16096 Document the user-defined command @var{commandname}, so that it can be
16097 accessed by @code{help}. The command @var{commandname} must already be
16098 defined. This command reads lines of documentation just as @code{define}
16099 reads the lines of the command definition, ending with @code{end}.
16100 After the @code{document} command is finished, @code{help} on command
16101 @var{commandname} displays the documentation you have written.
16103 You may use the @code{document} command again to change the
16104 documentation of a command. Redefining the command with @code{define}
16105 does not change the documentation.
16107 @kindex dont-repeat
16108 @cindex don't repeat command
16110 Used inside a user-defined command, this tells @value{GDBN} that this
16111 command should not be repeated when the user hits @key{RET}
16112 (@pxref{Command Syntax, repeat last command}).
16114 @kindex help user-defined
16115 @item help user-defined
16116 List all user-defined commands, with the first line of the documentation
16121 @itemx show user @var{commandname}
16122 Display the @value{GDBN} commands used to define @var{commandname} (but
16123 not its documentation). If no @var{commandname} is given, display the
16124 definitions for all user-defined commands.
16126 @cindex infinite recursion in user-defined commands
16127 @kindex show max-user-call-depth
16128 @kindex set max-user-call-depth
16129 @item show max-user-call-depth
16130 @itemx set max-user-call-depth
16131 The value of @code{max-user-call-depth} controls how many recursion
16132 levels are allowed in user-defined commands before @value{GDBN} suspects an
16133 infinite recursion and aborts the command.
16136 In addition to the above commands, user-defined commands frequently
16137 use control flow commands, described in @ref{Command Files}.
16139 When user-defined commands are executed, the
16140 commands of the definition are not printed. An error in any command
16141 stops execution of the user-defined command.
16143 If used interactively, commands that would ask for confirmation proceed
16144 without asking when used inside a user-defined command. Many @value{GDBN}
16145 commands that normally print messages to say what they are doing omit the
16146 messages when used in a user-defined command.
16149 @section User-defined Command Hooks
16150 @cindex command hooks
16151 @cindex hooks, for commands
16152 @cindex hooks, pre-command
16155 You may define @dfn{hooks}, which are a special kind of user-defined
16156 command. Whenever you run the command @samp{foo}, if the user-defined
16157 command @samp{hook-foo} exists, it is executed (with no arguments)
16158 before that command.
16160 @cindex hooks, post-command
16162 A hook may also be defined which is run after the command you executed.
16163 Whenever you run the command @samp{foo}, if the user-defined command
16164 @samp{hookpost-foo} exists, it is executed (with no arguments) after
16165 that command. Post-execution hooks may exist simultaneously with
16166 pre-execution hooks, for the same command.
16168 It is valid for a hook to call the command which it hooks. If this
16169 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
16171 @c It would be nice if hookpost could be passed a parameter indicating
16172 @c if the command it hooks executed properly or not. FIXME!
16174 @kindex stop@r{, a pseudo-command}
16175 In addition, a pseudo-command, @samp{stop} exists. Defining
16176 (@samp{hook-stop}) makes the associated commands execute every time
16177 execution stops in your program: before breakpoint commands are run,
16178 displays are printed, or the stack frame is printed.
16180 For example, to ignore @code{SIGALRM} signals while
16181 single-stepping, but treat them normally during normal execution,
16186 handle SIGALRM nopass
16190 handle SIGALRM pass
16193 define hook-continue
16194 handle SIGALRM pass
16198 As a further example, to hook at the beginning and end of the @code{echo}
16199 command, and to add extra text to the beginning and end of the message,
16207 define hookpost-echo
16211 (@value{GDBP}) echo Hello World
16212 <<<---Hello World--->>>
16217 You can define a hook for any single-word command in @value{GDBN}, but
16218 not for command aliases; you should define a hook for the basic command
16219 name, e.g.@: @code{backtrace} rather than @code{bt}.
16220 @c FIXME! So how does Joe User discover whether a command is an alias
16222 If an error occurs during the execution of your hook, execution of
16223 @value{GDBN} commands stops and @value{GDBN} issues a prompt
16224 (before the command that you actually typed had a chance to run).
16226 If you try to define a hook which does not match any known command, you
16227 get a warning from the @code{define} command.
16229 @node Command Files
16230 @section Command Files
16232 @cindex command files
16233 @cindex scripting commands
16234 A command file for @value{GDBN} is a text file made of lines that are
16235 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
16236 also be included. An empty line in a command file does nothing; it
16237 does not mean to repeat the last command, as it would from the
16240 You can request the execution of a command file with the @code{source}
16245 @cindex execute commands from a file
16246 @item source [@code{-v}] @var{filename}
16247 Execute the command file @var{filename}.
16250 The lines in a command file are generally executed sequentially,
16251 unless the order of execution is changed by one of the
16252 @emph{flow-control commands} described below. The commands are not
16253 printed as they are executed. An error in any command terminates
16254 execution of the command file and control is returned to the console.
16256 @value{GDBN} searches for @var{filename} in the current directory and then
16257 on the search path (specified with the @samp{directory} command).
16259 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
16260 each command as it is executed. The option must be given before
16261 @var{filename}, and is interpreted as part of the filename anywhere else.
16263 Commands that would ask for confirmation if used interactively proceed
16264 without asking when used in a command file. Many @value{GDBN} commands that
16265 normally print messages to say what they are doing omit the messages
16266 when called from command files.
16268 @value{GDBN} also accepts command input from standard input. In this
16269 mode, normal output goes to standard output and error output goes to
16270 standard error. Errors in a command file supplied on standard input do
16271 not terminate execution of the command file---execution continues with
16275 gdb < cmds > log 2>&1
16278 (The syntax above will vary depending on the shell used.) This example
16279 will execute commands from the file @file{cmds}. All output and errors
16280 would be directed to @file{log}.
16282 Since commands stored on command files tend to be more general than
16283 commands typed interactively, they frequently need to deal with
16284 complicated situations, such as different or unexpected values of
16285 variables and symbols, changes in how the program being debugged is
16286 built, etc. @value{GDBN} provides a set of flow-control commands to
16287 deal with these complexities. Using these commands, you can write
16288 complex scripts that loop over data structures, execute commands
16289 conditionally, etc.
16296 This command allows to include in your script conditionally executed
16297 commands. The @code{if} command takes a single argument, which is an
16298 expression to evaluate. It is followed by a series of commands that
16299 are executed only if the expression is true (its value is nonzero).
16300 There can then optionally be an @code{else} line, followed by a series
16301 of commands that are only executed if the expression was false. The
16302 end of the list is marked by a line containing @code{end}.
16306 This command allows to write loops. Its syntax is similar to
16307 @code{if}: the command takes a single argument, which is an expression
16308 to evaluate, and must be followed by the commands to execute, one per
16309 line, terminated by an @code{end}. These commands are called the
16310 @dfn{body} of the loop. The commands in the body of @code{while} are
16311 executed repeatedly as long as the expression evaluates to true.
16315 This command exits the @code{while} loop in whose body it is included.
16316 Execution of the script continues after that @code{while}s @code{end}
16319 @kindex loop_continue
16320 @item loop_continue
16321 This command skips the execution of the rest of the body of commands
16322 in the @code{while} loop in whose body it is included. Execution
16323 branches to the beginning of the @code{while} loop, where it evaluates
16324 the controlling expression.
16326 @kindex end@r{ (if/else/while commands)}
16328 Terminate the block of commands that are the body of @code{if},
16329 @code{else}, or @code{while} flow-control commands.
16334 @section Commands for Controlled Output
16336 During the execution of a command file or a user-defined command, normal
16337 @value{GDBN} output is suppressed; the only output that appears is what is
16338 explicitly printed by the commands in the definition. This section
16339 describes three commands useful for generating exactly the output you
16344 @item echo @var{text}
16345 @c I do not consider backslash-space a standard C escape sequence
16346 @c because it is not in ANSI.
16347 Print @var{text}. Nonprinting characters can be included in
16348 @var{text} using C escape sequences, such as @samp{\n} to print a
16349 newline. @strong{No newline is printed unless you specify one.}
16350 In addition to the standard C escape sequences, a backslash followed
16351 by a space stands for a space. This is useful for displaying a
16352 string with spaces at the beginning or the end, since leading and
16353 trailing spaces are otherwise trimmed from all arguments.
16354 To print @samp{@w{ }and foo =@w{ }}, use the command
16355 @samp{echo \@w{ }and foo = \@w{ }}.
16357 A backslash at the end of @var{text} can be used, as in C, to continue
16358 the command onto subsequent lines. For example,
16361 echo This is some text\n\
16362 which is continued\n\
16363 onto several lines.\n
16366 produces the same output as
16369 echo This is some text\n
16370 echo which is continued\n
16371 echo onto several lines.\n
16375 @item output @var{expression}
16376 Print the value of @var{expression} and nothing but that value: no
16377 newlines, no @samp{$@var{nn} = }. The value is not entered in the
16378 value history either. @xref{Expressions, ,Expressions}, for more information
16381 @item output/@var{fmt} @var{expression}
16382 Print the value of @var{expression} in format @var{fmt}. You can use
16383 the same formats as for @code{print}. @xref{Output Formats,,Output
16384 Formats}, for more information.
16387 @item printf @var{string}, @var{expressions}@dots{}
16388 Print the values of the @var{expressions} under the control of
16389 @var{string}. The @var{expressions} are separated by commas and may be
16390 either numbers or pointers. Their values are printed as specified by
16391 @var{string}, exactly as if your program were to execute the C
16393 @c FIXME: the above implies that at least all ANSI C formats are
16394 @c supported, but it isn't true: %E and %G don't work (or so it seems).
16395 @c Either this is a bug, or the manual should document what formats are
16399 printf (@var{string}, @var{expressions}@dots{});
16402 For example, you can print two values in hex like this:
16405 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
16408 The only backslash-escape sequences that you can use in the format
16409 string are the simple ones that consist of backslash followed by a
16414 @chapter Command Interpreters
16415 @cindex command interpreters
16417 @value{GDBN} supports multiple command interpreters, and some command
16418 infrastructure to allow users or user interface writers to switch
16419 between interpreters or run commands in other interpreters.
16421 @value{GDBN} currently supports two command interpreters, the console
16422 interpreter (sometimes called the command-line interpreter or @sc{cli})
16423 and the machine interface interpreter (or @sc{gdb/mi}). This manual
16424 describes both of these interfaces in great detail.
16426 By default, @value{GDBN} will start with the console interpreter.
16427 However, the user may choose to start @value{GDBN} with another
16428 interpreter by specifying the @option{-i} or @option{--interpreter}
16429 startup options. Defined interpreters include:
16433 @cindex console interpreter
16434 The traditional console or command-line interpreter. This is the most often
16435 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
16436 @value{GDBN} will use this interpreter.
16439 @cindex mi interpreter
16440 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
16441 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
16442 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
16446 @cindex mi2 interpreter
16447 The current @sc{gdb/mi} interface.
16450 @cindex mi1 interpreter
16451 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
16455 @cindex invoke another interpreter
16456 The interpreter being used by @value{GDBN} may not be dynamically
16457 switched at runtime. Although possible, this could lead to a very
16458 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
16459 enters the command "interpreter-set console" in a console view,
16460 @value{GDBN} would switch to using the console interpreter, rendering
16461 the IDE inoperable!
16463 @kindex interpreter-exec
16464 Although you may only choose a single interpreter at startup, you may execute
16465 commands in any interpreter from the current interpreter using the appropriate
16466 command. If you are running the console interpreter, simply use the
16467 @code{interpreter-exec} command:
16470 interpreter-exec mi "-data-list-register-names"
16473 @sc{gdb/mi} has a similar command, although it is only available in versions of
16474 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
16477 @chapter @value{GDBN} Text User Interface
16479 @cindex Text User Interface
16482 * TUI Overview:: TUI overview
16483 * TUI Keys:: TUI key bindings
16484 * TUI Single Key Mode:: TUI single key mode
16485 * TUI Commands:: TUI-specific commands
16486 * TUI Configuration:: TUI configuration variables
16489 The @value{GDBN} Text User Interface (TUI) is a terminal
16490 interface which uses the @code{curses} library to show the source
16491 file, the assembly output, the program registers and @value{GDBN}
16492 commands in separate text windows. The TUI mode is supported only
16493 on platforms where a suitable version of the @code{curses} library
16496 @pindex @value{GDBTUI}
16497 The TUI mode is enabled by default when you invoke @value{GDBN} as
16498 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
16499 You can also switch in and out of TUI mode while @value{GDBN} runs by
16500 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
16501 @xref{TUI Keys, ,TUI Key Bindings}.
16504 @section TUI Overview
16506 In TUI mode, @value{GDBN} can display several text windows:
16510 This window is the @value{GDBN} command window with the @value{GDBN}
16511 prompt and the @value{GDBN} output. The @value{GDBN} input is still
16512 managed using readline.
16515 The source window shows the source file of the program. The current
16516 line and active breakpoints are displayed in this window.
16519 The assembly window shows the disassembly output of the program.
16522 This window shows the processor registers. Registers are highlighted
16523 when their values change.
16526 The source and assembly windows show the current program position
16527 by highlighting the current line and marking it with a @samp{>} marker.
16528 Breakpoints are indicated with two markers. The first marker
16529 indicates the breakpoint type:
16533 Breakpoint which was hit at least once.
16536 Breakpoint which was never hit.
16539 Hardware breakpoint which was hit at least once.
16542 Hardware breakpoint which was never hit.
16545 The second marker indicates whether the breakpoint is enabled or not:
16549 Breakpoint is enabled.
16552 Breakpoint is disabled.
16555 The source, assembly and register windows are updated when the current
16556 thread changes, when the frame changes, or when the program counter
16559 These windows are not all visible at the same time. The command
16560 window is always visible. The others can be arranged in several
16571 source and assembly,
16574 source and registers, or
16577 assembly and registers.
16580 A status line above the command window shows the following information:
16584 Indicates the current @value{GDBN} target.
16585 (@pxref{Targets, ,Specifying a Debugging Target}).
16588 Gives the current process or thread number.
16589 When no process is being debugged, this field is set to @code{No process}.
16592 Gives the current function name for the selected frame.
16593 The name is demangled if demangling is turned on (@pxref{Print Settings}).
16594 When there is no symbol corresponding to the current program counter,
16595 the string @code{??} is displayed.
16598 Indicates the current line number for the selected frame.
16599 When the current line number is not known, the string @code{??} is displayed.
16602 Indicates the current program counter address.
16606 @section TUI Key Bindings
16607 @cindex TUI key bindings
16609 The TUI installs several key bindings in the readline keymaps
16610 (@pxref{Command Line Editing}). The following key bindings
16611 are installed for both TUI mode and the @value{GDBN} standard mode.
16620 Enter or leave the TUI mode. When leaving the TUI mode,
16621 the curses window management stops and @value{GDBN} operates using
16622 its standard mode, writing on the terminal directly. When reentering
16623 the TUI mode, control is given back to the curses windows.
16624 The screen is then refreshed.
16628 Use a TUI layout with only one window. The layout will
16629 either be @samp{source} or @samp{assembly}. When the TUI mode
16630 is not active, it will switch to the TUI mode.
16632 Think of this key binding as the Emacs @kbd{C-x 1} binding.
16636 Use a TUI layout with at least two windows. When the current
16637 layout already has two windows, the next layout with two windows is used.
16638 When a new layout is chosen, one window will always be common to the
16639 previous layout and the new one.
16641 Think of it as the Emacs @kbd{C-x 2} binding.
16645 Change the active window. The TUI associates several key bindings
16646 (like scrolling and arrow keys) with the active window. This command
16647 gives the focus to the next TUI window.
16649 Think of it as the Emacs @kbd{C-x o} binding.
16653 Switch in and out of the TUI SingleKey mode that binds single
16654 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
16657 The following key bindings only work in the TUI mode:
16662 Scroll the active window one page up.
16666 Scroll the active window one page down.
16670 Scroll the active window one line up.
16674 Scroll the active window one line down.
16678 Scroll the active window one column left.
16682 Scroll the active window one column right.
16686 Refresh the screen.
16689 Because the arrow keys scroll the active window in the TUI mode, they
16690 are not available for their normal use by readline unless the command
16691 window has the focus. When another window is active, you must use
16692 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
16693 and @kbd{C-f} to control the command window.
16695 @node TUI Single Key Mode
16696 @section TUI Single Key Mode
16697 @cindex TUI single key mode
16699 The TUI also provides a @dfn{SingleKey} mode, which binds several
16700 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
16701 switch into this mode, where the following key bindings are used:
16704 @kindex c @r{(SingleKey TUI key)}
16708 @kindex d @r{(SingleKey TUI key)}
16712 @kindex f @r{(SingleKey TUI key)}
16716 @kindex n @r{(SingleKey TUI key)}
16720 @kindex q @r{(SingleKey TUI key)}
16722 exit the SingleKey mode.
16724 @kindex r @r{(SingleKey TUI key)}
16728 @kindex s @r{(SingleKey TUI key)}
16732 @kindex u @r{(SingleKey TUI key)}
16736 @kindex v @r{(SingleKey TUI key)}
16740 @kindex w @r{(SingleKey TUI key)}
16745 Other keys temporarily switch to the @value{GDBN} command prompt.
16746 The key that was pressed is inserted in the editing buffer so that
16747 it is possible to type most @value{GDBN} commands without interaction
16748 with the TUI SingleKey mode. Once the command is entered the TUI
16749 SingleKey mode is restored. The only way to permanently leave
16750 this mode is by typing @kbd{q} or @kbd{C-x s}.
16754 @section TUI-specific Commands
16755 @cindex TUI commands
16757 The TUI has specific commands to control the text windows.
16758 These commands are always available, even when @value{GDBN} is not in
16759 the TUI mode. When @value{GDBN} is in the standard mode, most
16760 of these commands will automatically switch to the TUI mode.
16765 List and give the size of all displayed windows.
16769 Display the next layout.
16772 Display the previous layout.
16775 Display the source window only.
16778 Display the assembly window only.
16781 Display the source and assembly window.
16784 Display the register window together with the source or assembly window.
16788 Make the next window active for scrolling.
16791 Make the previous window active for scrolling.
16794 Make the source window active for scrolling.
16797 Make the assembly window active for scrolling.
16800 Make the register window active for scrolling.
16803 Make the command window active for scrolling.
16807 Refresh the screen. This is similar to typing @kbd{C-L}.
16809 @item tui reg float
16811 Show the floating point registers in the register window.
16813 @item tui reg general
16814 Show the general registers in the register window.
16817 Show the next register group. The list of register groups as well as
16818 their order is target specific. The predefined register groups are the
16819 following: @code{general}, @code{float}, @code{system}, @code{vector},
16820 @code{all}, @code{save}, @code{restore}.
16822 @item tui reg system
16823 Show the system registers in the register window.
16827 Update the source window and the current execution point.
16829 @item winheight @var{name} +@var{count}
16830 @itemx winheight @var{name} -@var{count}
16832 Change the height of the window @var{name} by @var{count}
16833 lines. Positive counts increase the height, while negative counts
16836 @item tabset @var{nchars}
16838 Set the width of tab stops to be @var{nchars} characters.
16841 @node TUI Configuration
16842 @section TUI Configuration Variables
16843 @cindex TUI configuration variables
16845 Several configuration variables control the appearance of TUI windows.
16848 @item set tui border-kind @var{kind}
16849 @kindex set tui border-kind
16850 Select the border appearance for the source, assembly and register windows.
16851 The possible values are the following:
16854 Use a space character to draw the border.
16857 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
16860 Use the Alternate Character Set to draw the border. The border is
16861 drawn using character line graphics if the terminal supports them.
16864 @item set tui border-mode @var{mode}
16865 @kindex set tui border-mode
16866 @itemx set tui active-border-mode @var{mode}
16867 @kindex set tui active-border-mode
16868 Select the display attributes for the borders of the inactive windows
16869 or the active window. The @var{mode} can be one of the following:
16872 Use normal attributes to display the border.
16878 Use reverse video mode.
16881 Use half bright mode.
16883 @item half-standout
16884 Use half bright and standout mode.
16887 Use extra bright or bold mode.
16889 @item bold-standout
16890 Use extra bright or bold and standout mode.
16895 @chapter Using @value{GDBN} under @sc{gnu} Emacs
16898 @cindex @sc{gnu} Emacs
16899 A special interface allows you to use @sc{gnu} Emacs to view (and
16900 edit) the source files for the program you are debugging with
16903 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
16904 executable file you want to debug as an argument. This command starts
16905 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
16906 created Emacs buffer.
16907 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
16909 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
16914 All ``terminal'' input and output goes through an Emacs buffer, called
16917 This applies both to @value{GDBN} commands and their output, and to the input
16918 and output done by the program you are debugging.
16920 This is useful because it means that you can copy the text of previous
16921 commands and input them again; you can even use parts of the output
16924 All the facilities of Emacs' Shell mode are available for interacting
16925 with your program. In particular, you can send signals the usual
16926 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
16930 @value{GDBN} displays source code through Emacs.
16932 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
16933 source file for that frame and puts an arrow (@samp{=>}) at the
16934 left margin of the current line. Emacs uses a separate buffer for
16935 source display, and splits the screen to show both your @value{GDBN} session
16938 Explicit @value{GDBN} @code{list} or search commands still produce output as
16939 usual, but you probably have no reason to use them from Emacs.
16942 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
16943 a graphical mode, enabled by default, which provides further buffers
16944 that can control the execution and describe the state of your program.
16945 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
16947 If you specify an absolute file name when prompted for the @kbd{M-x
16948 gdb} argument, then Emacs sets your current working directory to where
16949 your program resides. If you only specify the file name, then Emacs
16950 sets your current working directory to to the directory associated
16951 with the previous buffer. In this case, @value{GDBN} may find your
16952 program by searching your environment's @code{PATH} variable, but on
16953 some operating systems it might not find the source. So, although the
16954 @value{GDBN} input and output session proceeds normally, the auxiliary
16955 buffer does not display the current source and line of execution.
16957 The initial working directory of @value{GDBN} is printed on the top
16958 line of the GUD buffer and this serves as a default for the commands
16959 that specify files for @value{GDBN} to operate on. @xref{Files,
16960 ,Commands to Specify Files}.
16962 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
16963 need to call @value{GDBN} by a different name (for example, if you
16964 keep several configurations around, with different names) you can
16965 customize the Emacs variable @code{gud-gdb-command-name} to run the
16968 In the GUD buffer, you can use these special Emacs commands in
16969 addition to the standard Shell mode commands:
16973 Describe the features of Emacs' GUD Mode.
16976 Execute to another source line, like the @value{GDBN} @code{step} command; also
16977 update the display window to show the current file and location.
16980 Execute to next source line in this function, skipping all function
16981 calls, like the @value{GDBN} @code{next} command. Then update the display window
16982 to show the current file and location.
16985 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
16986 display window accordingly.
16989 Execute until exit from the selected stack frame, like the @value{GDBN}
16990 @code{finish} command.
16993 Continue execution of your program, like the @value{GDBN} @code{continue}
16997 Go up the number of frames indicated by the numeric argument
16998 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
16999 like the @value{GDBN} @code{up} command.
17002 Go down the number of frames indicated by the numeric argument, like the
17003 @value{GDBN} @code{down} command.
17006 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
17007 tells @value{GDBN} to set a breakpoint on the source line point is on.
17009 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
17010 separate frame which shows a backtrace when the GUD buffer is current.
17011 Move point to any frame in the stack and type @key{RET} to make it
17012 become the current frame and display the associated source in the
17013 source buffer. Alternatively, click @kbd{Mouse-2} to make the
17014 selected frame become the current one. In graphical mode, the
17015 speedbar displays watch expressions.
17017 If you accidentally delete the source-display buffer, an easy way to get
17018 it back is to type the command @code{f} in the @value{GDBN} buffer, to
17019 request a frame display; when you run under Emacs, this recreates
17020 the source buffer if necessary to show you the context of the current
17023 The source files displayed in Emacs are in ordinary Emacs buffers
17024 which are visiting the source files in the usual way. You can edit
17025 the files with these buffers if you wish; but keep in mind that @value{GDBN}
17026 communicates with Emacs in terms of line numbers. If you add or
17027 delete lines from the text, the line numbers that @value{GDBN} knows cease
17028 to correspond properly with the code.
17030 A more detailed description of Emacs' interaction with @value{GDBN} is
17031 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
17034 @c The following dropped because Epoch is nonstandard. Reactivate
17035 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
17037 @kindex Emacs Epoch environment
17041 Version 18 of @sc{gnu} Emacs has a built-in window system
17042 called the @code{epoch}
17043 environment. Users of this environment can use a new command,
17044 @code{inspect} which performs identically to @code{print} except that
17045 each value is printed in its own window.
17050 @chapter The @sc{gdb/mi} Interface
17052 @unnumberedsec Function and Purpose
17054 @cindex @sc{gdb/mi}, its purpose
17055 @sc{gdb/mi} is a line based machine oriented text interface to
17056 @value{GDBN} and is activated by specifying using the
17057 @option{--interpreter} command line option (@pxref{Mode Options}). It
17058 is specifically intended to support the development of systems which
17059 use the debugger as just one small component of a larger system.
17061 This chapter is a specification of the @sc{gdb/mi} interface. It is written
17062 in the form of a reference manual.
17064 Note that @sc{gdb/mi} is still under construction, so some of the
17065 features described below are incomplete and subject to change
17066 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
17068 @unnumberedsec Notation and Terminology
17070 @cindex notational conventions, for @sc{gdb/mi}
17071 This chapter uses the following notation:
17075 @code{|} separates two alternatives.
17078 @code{[ @var{something} ]} indicates that @var{something} is optional:
17079 it may or may not be given.
17082 @code{( @var{group} )*} means that @var{group} inside the parentheses
17083 may repeat zero or more times.
17086 @code{( @var{group} )+} means that @var{group} inside the parentheses
17087 may repeat one or more times.
17090 @code{"@var{string}"} means a literal @var{string}.
17094 @heading Dependencies
17098 * GDB/MI Command Syntax::
17099 * GDB/MI Compatibility with CLI::
17100 * GDB/MI Development and Front Ends::
17101 * GDB/MI Output Records::
17102 * GDB/MI Simple Examples::
17103 * GDB/MI Command Description Format::
17104 * GDB/MI Breakpoint Commands::
17105 * GDB/MI Program Context::
17106 * GDB/MI Thread Commands::
17107 * GDB/MI Program Execution::
17108 * GDB/MI Stack Manipulation::
17109 * GDB/MI Variable Objects::
17110 * GDB/MI Data Manipulation::
17111 * GDB/MI Tracepoint Commands::
17112 * GDB/MI Symbol Query::
17113 * GDB/MI File Commands::
17115 * GDB/MI Kod Commands::
17116 * GDB/MI Memory Overlay Commands::
17117 * GDB/MI Signal Handling Commands::
17119 * GDB/MI Target Manipulation::
17120 * GDB/MI Miscellaneous Commands::
17123 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17124 @node GDB/MI Command Syntax
17125 @section @sc{gdb/mi} Command Syntax
17128 * GDB/MI Input Syntax::
17129 * GDB/MI Output Syntax::
17132 @node GDB/MI Input Syntax
17133 @subsection @sc{gdb/mi} Input Syntax
17135 @cindex input syntax for @sc{gdb/mi}
17136 @cindex @sc{gdb/mi}, input syntax
17138 @item @var{command} @expansion{}
17139 @code{@var{cli-command} | @var{mi-command}}
17141 @item @var{cli-command} @expansion{}
17142 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
17143 @var{cli-command} is any existing @value{GDBN} CLI command.
17145 @item @var{mi-command} @expansion{}
17146 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
17147 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
17149 @item @var{token} @expansion{}
17150 "any sequence of digits"
17152 @item @var{option} @expansion{}
17153 @code{"-" @var{parameter} [ " " @var{parameter} ]}
17155 @item @var{parameter} @expansion{}
17156 @code{@var{non-blank-sequence} | @var{c-string}}
17158 @item @var{operation} @expansion{}
17159 @emph{any of the operations described in this chapter}
17161 @item @var{non-blank-sequence} @expansion{}
17162 @emph{anything, provided it doesn't contain special characters such as
17163 "-", @var{nl}, """ and of course " "}
17165 @item @var{c-string} @expansion{}
17166 @code{""" @var{seven-bit-iso-c-string-content} """}
17168 @item @var{nl} @expansion{}
17177 The CLI commands are still handled by the @sc{mi} interpreter; their
17178 output is described below.
17181 The @code{@var{token}}, when present, is passed back when the command
17185 Some @sc{mi} commands accept optional arguments as part of the parameter
17186 list. Each option is identified by a leading @samp{-} (dash) and may be
17187 followed by an optional argument parameter. Options occur first in the
17188 parameter list and can be delimited from normal parameters using
17189 @samp{--} (this is useful when some parameters begin with a dash).
17196 We want easy access to the existing CLI syntax (for debugging).
17199 We want it to be easy to spot a @sc{mi} operation.
17202 @node GDB/MI Output Syntax
17203 @subsection @sc{gdb/mi} Output Syntax
17205 @cindex output syntax of @sc{gdb/mi}
17206 @cindex @sc{gdb/mi}, output syntax
17207 The output from @sc{gdb/mi} consists of zero or more out-of-band records
17208 followed, optionally, by a single result record. This result record
17209 is for the most recent command. The sequence of output records is
17210 terminated by @samp{(gdb)}.
17212 If an input command was prefixed with a @code{@var{token}} then the
17213 corresponding output for that command will also be prefixed by that same
17217 @item @var{output} @expansion{}
17218 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
17220 @item @var{result-record} @expansion{}
17221 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
17223 @item @var{out-of-band-record} @expansion{}
17224 @code{@var{async-record} | @var{stream-record}}
17226 @item @var{async-record} @expansion{}
17227 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
17229 @item @var{exec-async-output} @expansion{}
17230 @code{[ @var{token} ] "*" @var{async-output}}
17232 @item @var{status-async-output} @expansion{}
17233 @code{[ @var{token} ] "+" @var{async-output}}
17235 @item @var{notify-async-output} @expansion{}
17236 @code{[ @var{token} ] "=" @var{async-output}}
17238 @item @var{async-output} @expansion{}
17239 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
17241 @item @var{result-class} @expansion{}
17242 @code{"done" | "running" | "connected" | "error" | "exit"}
17244 @item @var{async-class} @expansion{}
17245 @code{"stopped" | @var{others}} (where @var{others} will be added
17246 depending on the needs---this is still in development).
17248 @item @var{result} @expansion{}
17249 @code{ @var{variable} "=" @var{value}}
17251 @item @var{variable} @expansion{}
17252 @code{ @var{string} }
17254 @item @var{value} @expansion{}
17255 @code{ @var{const} | @var{tuple} | @var{list} }
17257 @item @var{const} @expansion{}
17258 @code{@var{c-string}}
17260 @item @var{tuple} @expansion{}
17261 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
17263 @item @var{list} @expansion{}
17264 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
17265 @var{result} ( "," @var{result} )* "]" }
17267 @item @var{stream-record} @expansion{}
17268 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
17270 @item @var{console-stream-output} @expansion{}
17271 @code{"~" @var{c-string}}
17273 @item @var{target-stream-output} @expansion{}
17274 @code{"@@" @var{c-string}}
17276 @item @var{log-stream-output} @expansion{}
17277 @code{"&" @var{c-string}}
17279 @item @var{nl} @expansion{}
17282 @item @var{token} @expansion{}
17283 @emph{any sequence of digits}.
17291 All output sequences end in a single line containing a period.
17294 The @code{@var{token}} is from the corresponding request. If an execution
17295 command is interrupted by the @samp{-exec-interrupt} command, the
17296 @var{token} associated with the @samp{*stopped} message is the one of the
17297 original execution command, not the one of the interrupt command.
17300 @cindex status output in @sc{gdb/mi}
17301 @var{status-async-output} contains on-going status information about the
17302 progress of a slow operation. It can be discarded. All status output is
17303 prefixed by @samp{+}.
17306 @cindex async output in @sc{gdb/mi}
17307 @var{exec-async-output} contains asynchronous state change on the target
17308 (stopped, started, disappeared). All async output is prefixed by
17312 @cindex notify output in @sc{gdb/mi}
17313 @var{notify-async-output} contains supplementary information that the
17314 client should handle (e.g., a new breakpoint information). All notify
17315 output is prefixed by @samp{=}.
17318 @cindex console output in @sc{gdb/mi}
17319 @var{console-stream-output} is output that should be displayed as is in the
17320 console. It is the textual response to a CLI command. All the console
17321 output is prefixed by @samp{~}.
17324 @cindex target output in @sc{gdb/mi}
17325 @var{target-stream-output} is the output produced by the target program.
17326 All the target output is prefixed by @samp{@@}.
17329 @cindex log output in @sc{gdb/mi}
17330 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
17331 instance messages that should be displayed as part of an error log. All
17332 the log output is prefixed by @samp{&}.
17335 @cindex list output in @sc{gdb/mi}
17336 New @sc{gdb/mi} commands should only output @var{lists} containing
17342 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
17343 details about the various output records.
17345 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17346 @node GDB/MI Compatibility with CLI
17347 @section @sc{gdb/mi} Compatibility with CLI
17349 @cindex compatibility, @sc{gdb/mi} and CLI
17350 @cindex @sc{gdb/mi}, compatibility with CLI
17352 For the developers convenience CLI commands can be entered directly,
17353 but there may be some unexpected behaviour. For example, commands
17354 that query the user will behave as if the user replied yes, breakpoint
17355 command lists are not executed and some CLI commands, such as
17356 @code{if}, @code{when} and @code{define}, prompt for further input with
17357 @samp{>}, which is not valid MI output.
17359 This feature may be removed at some stage in the future and it is
17360 recommended that front ends use the @code{-interpreter-exec} command
17361 (@pxref{-interpreter-exec}).
17363 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17364 @node GDB/MI Development and Front Ends
17365 @section @sc{gdb/mi} Development and Front Ends
17366 @cindex @sc{gdb/mi} development
17368 The application which takes the MI output and presents the state of the
17369 program being debugged to the user is called a @dfn{front end}.
17371 Although @sc{gdb/mi} is still incomplete, it is currently being used
17372 by a variety of front ends to @value{GDBN}. This makes it difficult
17373 to introduce new functionality without breaking existing usage. This
17374 section tries to minimize the problems by describing how the protocol
17377 Some changes in MI need not break a carefully designed front end, and
17378 for these the MI version will remain unchanged. The following is a
17379 list of changes that may occur within one level, so front ends should
17380 parse MI output in a way that can handle them:
17384 New MI commands may be added.
17387 New fields may be added to the output of any MI command.
17390 The range of values for fields with specified values, e.g.,
17391 @code{in_scope} (@pxref{-var-update}) may be extended.
17393 @c The format of field's content e.g type prefix, may change so parse it
17394 @c at your own risk. Yes, in general?
17396 @c The order of fields may change? Shouldn't really matter but it might
17397 @c resolve inconsistencies.
17400 If the changes are likely to break front ends, the MI version level
17401 will be increased by one. This will allow the front end to parse the
17402 output according to the MI version. Apart from mi0, new versions of
17403 @value{GDBN} will not support old versions of MI and it will be the
17404 responsibility of the front end to work with the new one.
17406 @c Starting with mi3, add a new command -mi-version that prints the MI
17409 The best way to avoid unexpected changes in MI that might break your front
17410 end is to make your project known to @value{GDBN} developers and
17411 follow development on @email{gdb@@sourceware.org} and
17412 @email{gdb-patches@@sourceware.org}. There is also the mailing list
17413 @email{dmi-discuss@@lists.freestandards.org}, hosted by the Free Standards
17414 Group, which has the aim of creating a more general MI protocol
17415 called Debugger Machine Interface (DMI) that will become a standard
17416 for all debuggers, not just @value{GDBN}.
17417 @cindex mailing lists
17419 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17420 @node GDB/MI Output Records
17421 @section @sc{gdb/mi} Output Records
17424 * GDB/MI Result Records::
17425 * GDB/MI Stream Records::
17426 * GDB/MI Out-of-band Records::
17429 @node GDB/MI Result Records
17430 @subsection @sc{gdb/mi} Result Records
17432 @cindex result records in @sc{gdb/mi}
17433 @cindex @sc{gdb/mi}, result records
17434 In addition to a number of out-of-band notifications, the response to a
17435 @sc{gdb/mi} command includes one of the following result indications:
17439 @item "^done" [ "," @var{results} ]
17440 The synchronous operation was successful, @code{@var{results}} are the return
17445 @c Is this one correct? Should it be an out-of-band notification?
17446 The asynchronous operation was successfully started. The target is
17451 @value{GDBN} has connected to a remote target.
17453 @item "^error" "," @var{c-string}
17455 The operation failed. The @code{@var{c-string}} contains the corresponding
17460 @value{GDBN} has terminated.
17464 @node GDB/MI Stream Records
17465 @subsection @sc{gdb/mi} Stream Records
17467 @cindex @sc{gdb/mi}, stream records
17468 @cindex stream records in @sc{gdb/mi}
17469 @value{GDBN} internally maintains a number of output streams: the console, the
17470 target, and the log. The output intended for each of these streams is
17471 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
17473 Each stream record begins with a unique @dfn{prefix character} which
17474 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
17475 Syntax}). In addition to the prefix, each stream record contains a
17476 @code{@var{string-output}}. This is either raw text (with an implicit new
17477 line) or a quoted C string (which does not contain an implicit newline).
17480 @item "~" @var{string-output}
17481 The console output stream contains text that should be displayed in the
17482 CLI console window. It contains the textual responses to CLI commands.
17484 @item "@@" @var{string-output}
17485 The target output stream contains any textual output from the running
17486 target. This is only present when GDB's event loop is truly
17487 asynchronous, which is currently only the case for remote targets.
17489 @item "&" @var{string-output}
17490 The log stream contains debugging messages being produced by @value{GDBN}'s
17494 @node GDB/MI Out-of-band Records
17495 @subsection @sc{gdb/mi} Out-of-band Records
17497 @cindex out-of-band records in @sc{gdb/mi}
17498 @cindex @sc{gdb/mi}, out-of-band records
17499 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
17500 additional changes that have occurred. Those changes can either be a
17501 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
17502 target activity (e.g., target stopped).
17504 The following is a preliminary list of possible out-of-band records.
17505 In particular, the @var{exec-async-output} records.
17508 @item *stopped,reason="@var{reason}"
17511 @var{reason} can be one of the following:
17514 @item breakpoint-hit
17515 A breakpoint was reached.
17516 @item watchpoint-trigger
17517 A watchpoint was triggered.
17518 @item read-watchpoint-trigger
17519 A read watchpoint was triggered.
17520 @item access-watchpoint-trigger
17521 An access watchpoint was triggered.
17522 @item function-finished
17523 An -exec-finish or similar CLI command was accomplished.
17524 @item location-reached
17525 An -exec-until or similar CLI command was accomplished.
17526 @item watchpoint-scope
17527 A watchpoint has gone out of scope.
17528 @item end-stepping-range
17529 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
17530 similar CLI command was accomplished.
17531 @item exited-signalled
17532 The inferior exited because of a signal.
17534 The inferior exited.
17535 @item exited-normally
17536 The inferior exited normally.
17537 @item signal-received
17538 A signal was received by the inferior.
17542 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17543 @node GDB/MI Simple Examples
17544 @section Simple Examples of @sc{gdb/mi} Interaction
17545 @cindex @sc{gdb/mi}, simple examples
17547 This subsection presents several simple examples of interaction using
17548 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
17549 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
17550 the output received from @sc{gdb/mi}.
17552 Note the line breaks shown in the examples are here only for
17553 readability, they don't appear in the real output.
17555 @subheading Setting a Breakpoint
17557 Setting a breakpoint generates synchronous output which contains detailed
17558 information of the breakpoint.
17561 -> -break-insert main
17562 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
17563 enabled="y",addr="0x08048564",func="main",file="myprog.c",
17564 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
17568 @subheading Program Execution
17570 Program execution generates asynchronous records and MI gives the
17571 reason that execution stopped.
17577 <- *stopped,reason="breakpoint-hit",bkptno="1",thread-id="0",
17578 frame=@{addr="0x08048564",func="main",
17579 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
17580 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
17585 <- *stopped,reason="exited-normally"
17589 @subheading Quitting @value{GDBN}
17591 Quitting @value{GDBN} just prints the result class @samp{^exit}.
17599 @subheading A Bad Command
17601 Here's what happens if you pass a non-existent command:
17605 <- ^error,msg="Undefined MI command: rubbish"
17610 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17611 @node GDB/MI Command Description Format
17612 @section @sc{gdb/mi} Command Description Format
17614 The remaining sections describe blocks of commands. Each block of
17615 commands is laid out in a fashion similar to this section.
17617 @subheading Motivation
17619 The motivation for this collection of commands.
17621 @subheading Introduction
17623 A brief introduction to this collection of commands as a whole.
17625 @subheading Commands
17627 For each command in the block, the following is described:
17629 @subsubheading Synopsis
17632 -command @var{args}@dots{}
17635 @subsubheading Result
17637 @subsubheading @value{GDBN} Command
17639 The corresponding @value{GDBN} CLI command(s), if any.
17641 @subsubheading Example
17643 Example(s) formatted for readability. Some of the described commands have
17644 not been implemented yet and these are labeled N.A.@: (not available).
17647 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17648 @node GDB/MI Breakpoint Commands
17649 @section @sc{gdb/mi} Breakpoint Commands
17651 @cindex breakpoint commands for @sc{gdb/mi}
17652 @cindex @sc{gdb/mi}, breakpoint commands
17653 This section documents @sc{gdb/mi} commands for manipulating
17656 @subheading The @code{-break-after} Command
17657 @findex -break-after
17659 @subsubheading Synopsis
17662 -break-after @var{number} @var{count}
17665 The breakpoint number @var{number} is not in effect until it has been
17666 hit @var{count} times. To see how this is reflected in the output of
17667 the @samp{-break-list} command, see the description of the
17668 @samp{-break-list} command below.
17670 @subsubheading @value{GDBN} Command
17672 The corresponding @value{GDBN} command is @samp{ignore}.
17674 @subsubheading Example
17679 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",
17680 fullname="/home/foo/hello.c",line="5",times="0"@}
17687 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17688 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17689 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17690 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17691 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17692 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17693 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17694 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17695 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
17696 line="5",times="0",ignore="3"@}]@}
17701 @subheading The @code{-break-catch} Command
17702 @findex -break-catch
17704 @subheading The @code{-break-commands} Command
17705 @findex -break-commands
17709 @subheading The @code{-break-condition} Command
17710 @findex -break-condition
17712 @subsubheading Synopsis
17715 -break-condition @var{number} @var{expr}
17718 Breakpoint @var{number} will stop the program only if the condition in
17719 @var{expr} is true. The condition becomes part of the
17720 @samp{-break-list} output (see the description of the @samp{-break-list}
17723 @subsubheading @value{GDBN} Command
17725 The corresponding @value{GDBN} command is @samp{condition}.
17727 @subsubheading Example
17731 -break-condition 1 1
17735 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17736 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17737 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17738 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17739 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17740 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17741 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17742 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17743 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
17744 line="5",cond="1",times="0",ignore="3"@}]@}
17748 @subheading The @code{-break-delete} Command
17749 @findex -break-delete
17751 @subsubheading Synopsis
17754 -break-delete ( @var{breakpoint} )+
17757 Delete the breakpoint(s) whose number(s) are specified in the argument
17758 list. This is obviously reflected in the breakpoint list.
17760 @subsubheading @value{GDBN} Command
17762 The corresponding @value{GDBN} command is @samp{delete}.
17764 @subsubheading Example
17772 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
17773 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17774 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17775 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17776 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17777 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17778 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17783 @subheading The @code{-break-disable} Command
17784 @findex -break-disable
17786 @subsubheading Synopsis
17789 -break-disable ( @var{breakpoint} )+
17792 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
17793 break list is now set to @samp{n} for the named @var{breakpoint}(s).
17795 @subsubheading @value{GDBN} Command
17797 The corresponding @value{GDBN} command is @samp{disable}.
17799 @subsubheading Example
17807 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17808 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17809 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17810 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17811 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17812 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17813 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17814 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
17815 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
17816 line="5",times="0"@}]@}
17820 @subheading The @code{-break-enable} Command
17821 @findex -break-enable
17823 @subsubheading Synopsis
17826 -break-enable ( @var{breakpoint} )+
17829 Enable (previously disabled) @var{breakpoint}(s).
17831 @subsubheading @value{GDBN} Command
17833 The corresponding @value{GDBN} command is @samp{enable}.
17835 @subsubheading Example
17843 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17844 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17845 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17846 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17847 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17848 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17849 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17850 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
17851 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
17852 line="5",times="0"@}]@}
17856 @subheading The @code{-break-info} Command
17857 @findex -break-info
17859 @subsubheading Synopsis
17862 -break-info @var{breakpoint}
17866 Get information about a single breakpoint.
17868 @subsubheading @value{GDBN} Command
17870 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
17872 @subsubheading Example
17875 @subheading The @code{-break-insert} Command
17876 @findex -break-insert
17878 @subsubheading Synopsis
17881 -break-insert [ -t ] [ -h ] [ -r ]
17882 [ -c @var{condition} ] [ -i @var{ignore-count} ]
17883 [ -p @var{thread} ] [ @var{line} | @var{addr} ]
17887 If specified, @var{line}, can be one of:
17894 @item filename:linenum
17895 @item filename:function
17899 The possible optional parameters of this command are:
17903 Insert a temporary breakpoint.
17905 Insert a hardware breakpoint.
17906 @item -c @var{condition}
17907 Make the breakpoint conditional on @var{condition}.
17908 @item -i @var{ignore-count}
17909 Initialize the @var{ignore-count}.
17911 Insert a regular breakpoint in all the functions whose names match the
17912 given regular expression. Other flags are not applicable to regular
17916 @subsubheading Result
17918 The result is in the form:
17921 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
17922 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
17923 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
17924 times="@var{times}"@}
17928 where @var{number} is the @value{GDBN} number for this breakpoint,
17929 @var{funcname} is the name of the function where the breakpoint was
17930 inserted, @var{filename} is the name of the source file which contains
17931 this function, @var{lineno} is the source line number within that file
17932 and @var{times} the number of times that the breakpoint has been hit
17933 (always 0 for -break-insert but may be greater for -break-info or -break-list
17934 which use the same output).
17936 Note: this format is open to change.
17937 @c An out-of-band breakpoint instead of part of the result?
17939 @subsubheading @value{GDBN} Command
17941 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
17942 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
17944 @subsubheading Example
17949 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
17950 fullname="/home/foo/recursive2.c,line="4",times="0"@}
17952 -break-insert -t foo
17953 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
17954 fullname="/home/foo/recursive2.c,line="11",times="0"@}
17957 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17958 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17959 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17960 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17961 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17962 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17963 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17964 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17965 addr="0x0001072c", func="main",file="recursive2.c",
17966 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
17967 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
17968 addr="0x00010774",func="foo",file="recursive2.c",
17969 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
17971 -break-insert -r foo.*
17972 ~int foo(int, int);
17973 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
17974 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
17978 @subheading The @code{-break-list} Command
17979 @findex -break-list
17981 @subsubheading Synopsis
17987 Displays the list of inserted breakpoints, showing the following fields:
17991 number of the breakpoint
17993 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
17995 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
17998 is the breakpoint enabled or no: @samp{y} or @samp{n}
18000 memory location at which the breakpoint is set
18002 logical location of the breakpoint, expressed by function name, file
18005 number of times the breakpoint has been hit
18008 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
18009 @code{body} field is an empty list.
18011 @subsubheading @value{GDBN} Command
18013 The corresponding @value{GDBN} command is @samp{info break}.
18015 @subsubheading Example
18020 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18021 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18022 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18023 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18024 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18025 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18026 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18027 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18028 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
18029 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
18030 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
18031 line="13",times="0"@}]@}
18035 Here's an example of the result when there are no breakpoints:
18040 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
18041 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18042 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18043 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18044 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18045 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18046 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18051 @subheading The @code{-break-watch} Command
18052 @findex -break-watch
18054 @subsubheading Synopsis
18057 -break-watch [ -a | -r ]
18060 Create a watchpoint. With the @samp{-a} option it will create an
18061 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
18062 read from or on a write to the memory location. With the @samp{-r}
18063 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
18064 trigger only when the memory location is accessed for reading. Without
18065 either of the options, the watchpoint created is a regular watchpoint,
18066 i.e., it will trigger when the memory location is accessed for writing.
18067 @xref{Set Watchpoints, , Setting Watchpoints}.
18069 Note that @samp{-break-list} will report a single list of watchpoints and
18070 breakpoints inserted.
18072 @subsubheading @value{GDBN} Command
18074 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
18077 @subsubheading Example
18079 Setting a watchpoint on a variable in the @code{main} function:
18084 ^done,wpt=@{number="2",exp="x"@}
18089 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
18090 value=@{old="-268439212",new="55"@},
18091 frame=@{func="main",args=[],file="recursive2.c",
18092 fullname="/home/foo/bar/recursive2.c",line="5"@}
18096 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
18097 the program execution twice: first for the variable changing value, then
18098 for the watchpoint going out of scope.
18103 ^done,wpt=@{number="5",exp="C"@}
18108 *stopped,reason="watchpoint-trigger",
18109 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
18110 frame=@{func="callee4",args=[],
18111 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18112 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
18117 *stopped,reason="watchpoint-scope",wpnum="5",
18118 frame=@{func="callee3",args=[@{name="strarg",
18119 value="0x11940 \"A string argument.\""@}],
18120 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18121 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18125 Listing breakpoints and watchpoints, at different points in the program
18126 execution. Note that once the watchpoint goes out of scope, it is
18132 ^done,wpt=@{number="2",exp="C"@}
18135 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18136 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18137 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18138 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18139 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18140 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18141 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18142 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18143 addr="0x00010734",func="callee4",
18144 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18145 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
18146 bkpt=@{number="2",type="watchpoint",disp="keep",
18147 enabled="y",addr="",what="C",times="0"@}]@}
18152 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
18153 value=@{old="-276895068",new="3"@},
18154 frame=@{func="callee4",args=[],
18155 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18156 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
18159 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18160 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18161 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18162 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18163 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18164 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18165 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18166 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18167 addr="0x00010734",func="callee4",
18168 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18169 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
18170 bkpt=@{number="2",type="watchpoint",disp="keep",
18171 enabled="y",addr="",what="C",times="-5"@}]@}
18175 ^done,reason="watchpoint-scope",wpnum="2",
18176 frame=@{func="callee3",args=[@{name="strarg",
18177 value="0x11940 \"A string argument.\""@}],
18178 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18179 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18182 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18183 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18184 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18185 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18186 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18187 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18188 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18189 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18190 addr="0x00010734",func="callee4",
18191 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18192 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
18197 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18198 @node GDB/MI Program Context
18199 @section @sc{gdb/mi} Program Context
18201 @subheading The @code{-exec-arguments} Command
18202 @findex -exec-arguments
18205 @subsubheading Synopsis
18208 -exec-arguments @var{args}
18211 Set the inferior program arguments, to be used in the next
18214 @subsubheading @value{GDBN} Command
18216 The corresponding @value{GDBN} command is @samp{set args}.
18218 @subsubheading Example
18221 Don't have one around.
18224 @subheading The @code{-exec-show-arguments} Command
18225 @findex -exec-show-arguments
18227 @subsubheading Synopsis
18230 -exec-show-arguments
18233 Print the arguments of the program.
18235 @subsubheading @value{GDBN} Command
18237 The corresponding @value{GDBN} command is @samp{show args}.
18239 @subsubheading Example
18243 @subheading The @code{-environment-cd} Command
18244 @findex -environment-cd
18246 @subsubheading Synopsis
18249 -environment-cd @var{pathdir}
18252 Set @value{GDBN}'s working directory.
18254 @subsubheading @value{GDBN} Command
18256 The corresponding @value{GDBN} command is @samp{cd}.
18258 @subsubheading Example
18262 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18268 @subheading The @code{-environment-directory} Command
18269 @findex -environment-directory
18271 @subsubheading Synopsis
18274 -environment-directory [ -r ] [ @var{pathdir} ]+
18277 Add directories @var{pathdir} to beginning of search path for source files.
18278 If the @samp{-r} option is used, the search path is reset to the default
18279 search path. If directories @var{pathdir} are supplied in addition to the
18280 @samp{-r} option, the search path is first reset and then addition
18282 Multiple directories may be specified, separated by blanks. Specifying
18283 multiple directories in a single command
18284 results in the directories added to the beginning of the
18285 search path in the same order they were presented in the command.
18286 If blanks are needed as
18287 part of a directory name, double-quotes should be used around
18288 the name. In the command output, the path will show up separated
18289 by the system directory-separator character. The directory-separator
18290 character must not be used
18291 in any directory name.
18292 If no directories are specified, the current search path is displayed.
18294 @subsubheading @value{GDBN} Command
18296 The corresponding @value{GDBN} command is @samp{dir}.
18298 @subsubheading Example
18302 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18303 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18305 -environment-directory ""
18306 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18308 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
18309 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
18311 -environment-directory -r
18312 ^done,source-path="$cdir:$cwd"
18317 @subheading The @code{-environment-path} Command
18318 @findex -environment-path
18320 @subsubheading Synopsis
18323 -environment-path [ -r ] [ @var{pathdir} ]+
18326 Add directories @var{pathdir} to beginning of search path for object files.
18327 If the @samp{-r} option is used, the search path is reset to the original
18328 search path that existed at gdb start-up. If directories @var{pathdir} are
18329 supplied in addition to the
18330 @samp{-r} option, the search path is first reset and then addition
18332 Multiple directories may be specified, separated by blanks. Specifying
18333 multiple directories in a single command
18334 results in the directories added to the beginning of the
18335 search path in the same order they were presented in the command.
18336 If blanks are needed as
18337 part of a directory name, double-quotes should be used around
18338 the name. In the command output, the path will show up separated
18339 by the system directory-separator character. The directory-separator
18340 character must not be used
18341 in any directory name.
18342 If no directories are specified, the current path is displayed.
18345 @subsubheading @value{GDBN} Command
18347 The corresponding @value{GDBN} command is @samp{path}.
18349 @subsubheading Example
18354 ^done,path="/usr/bin"
18356 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
18357 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
18359 -environment-path -r /usr/local/bin
18360 ^done,path="/usr/local/bin:/usr/bin"
18365 @subheading The @code{-environment-pwd} Command
18366 @findex -environment-pwd
18368 @subsubheading Synopsis
18374 Show the current working directory.
18376 @subsubheading @value{GDBN} Command
18378 The corresponding @value{GDBN} command is @samp{pwd}.
18380 @subsubheading Example
18385 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
18389 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18390 @node GDB/MI Thread Commands
18391 @section @sc{gdb/mi} Thread Commands
18394 @subheading The @code{-thread-info} Command
18395 @findex -thread-info
18397 @subsubheading Synopsis
18403 @subsubheading @value{GDBN} Command
18407 @subsubheading Example
18411 @subheading The @code{-thread-list-all-threads} Command
18412 @findex -thread-list-all-threads
18414 @subsubheading Synopsis
18417 -thread-list-all-threads
18420 @subsubheading @value{GDBN} Command
18422 The equivalent @value{GDBN} command is @samp{info threads}.
18424 @subsubheading Example
18428 @subheading The @code{-thread-list-ids} Command
18429 @findex -thread-list-ids
18431 @subsubheading Synopsis
18437 Produces a list of the currently known @value{GDBN} thread ids. At the
18438 end of the list it also prints the total number of such threads.
18440 @subsubheading @value{GDBN} Command
18442 Part of @samp{info threads} supplies the same information.
18444 @subsubheading Example
18446 No threads present, besides the main process:
18451 ^done,thread-ids=@{@},number-of-threads="0"
18461 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
18462 number-of-threads="3"
18467 @subheading The @code{-thread-select} Command
18468 @findex -thread-select
18470 @subsubheading Synopsis
18473 -thread-select @var{threadnum}
18476 Make @var{threadnum} the current thread. It prints the number of the new
18477 current thread, and the topmost frame for that thread.
18479 @subsubheading @value{GDBN} Command
18481 The corresponding @value{GDBN} command is @samp{thread}.
18483 @subsubheading Example
18490 *stopped,reason="end-stepping-range",thread-id="2",line="187",
18491 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
18495 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
18496 number-of-threads="3"
18499 ^done,new-thread-id="3",
18500 frame=@{level="0",func="vprintf",
18501 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
18502 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
18506 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18507 @node GDB/MI Program Execution
18508 @section @sc{gdb/mi} Program Execution
18510 These are the asynchronous commands which generate the out-of-band
18511 record @samp{*stopped}. Currently @value{GDBN} only really executes
18512 asynchronously with remote targets and this interaction is mimicked in
18515 @subheading The @code{-exec-continue} Command
18516 @findex -exec-continue
18518 @subsubheading Synopsis
18524 Resumes the execution of the inferior program until a breakpoint is
18525 encountered, or until the inferior exits.
18527 @subsubheading @value{GDBN} Command
18529 The corresponding @value{GDBN} corresponding is @samp{continue}.
18531 @subsubheading Example
18538 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
18539 file="hello.c",fullname="/home/foo/bar/hello.c",line="13"@}
18544 @subheading The @code{-exec-finish} Command
18545 @findex -exec-finish
18547 @subsubheading Synopsis
18553 Resumes the execution of the inferior program until the current
18554 function is exited. Displays the results returned by the function.
18556 @subsubheading @value{GDBN} Command
18558 The corresponding @value{GDBN} command is @samp{finish}.
18560 @subsubheading Example
18562 Function returning @code{void}.
18569 *stopped,reason="function-finished",frame=@{func="main",args=[],
18570 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
18574 Function returning other than @code{void}. The name of the internal
18575 @value{GDBN} variable storing the result is printed, together with the
18582 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
18583 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
18584 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
18585 gdb-result-var="$1",return-value="0"
18590 @subheading The @code{-exec-interrupt} Command
18591 @findex -exec-interrupt
18593 @subsubheading Synopsis
18599 Interrupts the background execution of the target. Note how the token
18600 associated with the stop message is the one for the execution command
18601 that has been interrupted. The token for the interrupt itself only
18602 appears in the @samp{^done} output. If the user is trying to
18603 interrupt a non-running program, an error message will be printed.
18605 @subsubheading @value{GDBN} Command
18607 The corresponding @value{GDBN} command is @samp{interrupt}.
18609 @subsubheading Example
18620 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
18621 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
18622 fullname="/home/foo/bar/try.c",line="13"@}
18627 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
18632 @subheading The @code{-exec-next} Command
18635 @subsubheading Synopsis
18641 Resumes execution of the inferior program, stopping when the beginning
18642 of the next source line is reached.
18644 @subsubheading @value{GDBN} Command
18646 The corresponding @value{GDBN} command is @samp{next}.
18648 @subsubheading Example
18654 *stopped,reason="end-stepping-range",line="8",file="hello.c"
18659 @subheading The @code{-exec-next-instruction} Command
18660 @findex -exec-next-instruction
18662 @subsubheading Synopsis
18665 -exec-next-instruction
18668 Executes one machine instruction. If the instruction is a function
18669 call, continues until the function returns. If the program stops at an
18670 instruction in the middle of a source line, the address will be
18673 @subsubheading @value{GDBN} Command
18675 The corresponding @value{GDBN} command is @samp{nexti}.
18677 @subsubheading Example
18681 -exec-next-instruction
18685 *stopped,reason="end-stepping-range",
18686 addr="0x000100d4",line="5",file="hello.c"
18691 @subheading The @code{-exec-return} Command
18692 @findex -exec-return
18694 @subsubheading Synopsis
18700 Makes current function return immediately. Doesn't execute the inferior.
18701 Displays the new current frame.
18703 @subsubheading @value{GDBN} Command
18705 The corresponding @value{GDBN} command is @samp{return}.
18707 @subsubheading Example
18711 200-break-insert callee4
18712 200^done,bkpt=@{number="1",addr="0x00010734",
18713 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
18718 000*stopped,reason="breakpoint-hit",bkptno="1",
18719 frame=@{func="callee4",args=[],
18720 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18721 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
18727 111^done,frame=@{level="0",func="callee3",
18728 args=[@{name="strarg",
18729 value="0x11940 \"A string argument.\""@}],
18730 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18731 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18736 @subheading The @code{-exec-run} Command
18739 @subsubheading Synopsis
18745 Starts execution of the inferior from the beginning. The inferior
18746 executes until either a breakpoint is encountered or the program
18747 exits. In the latter case the output will include an exit code, if
18748 the program has exited exceptionally.
18750 @subsubheading @value{GDBN} Command
18752 The corresponding @value{GDBN} command is @samp{run}.
18754 @subsubheading Examples
18759 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
18764 *stopped,reason="breakpoint-hit",bkptno="1",
18765 frame=@{func="main",args=[],file="recursive2.c",
18766 fullname="/home/foo/bar/recursive2.c",line="4"@}
18771 Program exited normally:
18779 *stopped,reason="exited-normally"
18784 Program exited exceptionally:
18792 *stopped,reason="exited",exit-code="01"
18796 Another way the program can terminate is if it receives a signal such as
18797 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
18801 *stopped,reason="exited-signalled",signal-name="SIGINT",
18802 signal-meaning="Interrupt"
18806 @c @subheading -exec-signal
18809 @subheading The @code{-exec-step} Command
18812 @subsubheading Synopsis
18818 Resumes execution of the inferior program, stopping when the beginning
18819 of the next source line is reached, if the next source line is not a
18820 function call. If it is, stop at the first instruction of the called
18823 @subsubheading @value{GDBN} Command
18825 The corresponding @value{GDBN} command is @samp{step}.
18827 @subsubheading Example
18829 Stepping into a function:
18835 *stopped,reason="end-stepping-range",
18836 frame=@{func="foo",args=[@{name="a",value="10"@},
18837 @{name="b",value="0"@}],file="recursive2.c",
18838 fullname="/home/foo/bar/recursive2.c",line="11"@}
18848 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
18853 @subheading The @code{-exec-step-instruction} Command
18854 @findex -exec-step-instruction
18856 @subsubheading Synopsis
18859 -exec-step-instruction
18862 Resumes the inferior which executes one machine instruction. The
18863 output, once @value{GDBN} has stopped, will vary depending on whether
18864 we have stopped in the middle of a source line or not. In the former
18865 case, the address at which the program stopped will be printed as
18868 @subsubheading @value{GDBN} Command
18870 The corresponding @value{GDBN} command is @samp{stepi}.
18872 @subsubheading Example
18876 -exec-step-instruction
18880 *stopped,reason="end-stepping-range",
18881 frame=@{func="foo",args=[],file="try.c",
18882 fullname="/home/foo/bar/try.c",line="10"@}
18884 -exec-step-instruction
18888 *stopped,reason="end-stepping-range",
18889 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
18890 fullname="/home/foo/bar/try.c",line="10"@}
18895 @subheading The @code{-exec-until} Command
18896 @findex -exec-until
18898 @subsubheading Synopsis
18901 -exec-until [ @var{location} ]
18904 Executes the inferior until the @var{location} specified in the
18905 argument is reached. If there is no argument, the inferior executes
18906 until a source line greater than the current one is reached. The
18907 reason for stopping in this case will be @samp{location-reached}.
18909 @subsubheading @value{GDBN} Command
18911 The corresponding @value{GDBN} command is @samp{until}.
18913 @subsubheading Example
18917 -exec-until recursive2.c:6
18921 *stopped,reason="location-reached",frame=@{func="main",args=[],
18922 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
18927 @subheading -file-clear
18928 Is this going away????
18931 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18932 @node GDB/MI Stack Manipulation
18933 @section @sc{gdb/mi} Stack Manipulation Commands
18936 @subheading The @code{-stack-info-frame} Command
18937 @findex -stack-info-frame
18939 @subsubheading Synopsis
18945 Get info on the selected frame.
18947 @subsubheading @value{GDBN} Command
18949 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
18950 (without arguments).
18952 @subsubheading Example
18957 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
18958 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18959 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
18963 @subheading The @code{-stack-info-depth} Command
18964 @findex -stack-info-depth
18966 @subsubheading Synopsis
18969 -stack-info-depth [ @var{max-depth} ]
18972 Return the depth of the stack. If the integer argument @var{max-depth}
18973 is specified, do not count beyond @var{max-depth} frames.
18975 @subsubheading @value{GDBN} Command
18977 There's no equivalent @value{GDBN} command.
18979 @subsubheading Example
18981 For a stack with frame levels 0 through 11:
18988 -stack-info-depth 4
18991 -stack-info-depth 12
18994 -stack-info-depth 11
18997 -stack-info-depth 13
19002 @subheading The @code{-stack-list-arguments} Command
19003 @findex -stack-list-arguments
19005 @subsubheading Synopsis
19008 -stack-list-arguments @var{show-values}
19009 [ @var{low-frame} @var{high-frame} ]
19012 Display a list of the arguments for the frames between @var{low-frame}
19013 and @var{high-frame} (inclusive). If @var{low-frame} and
19014 @var{high-frame} are not provided, list the arguments for the whole
19015 call stack. If the two arguments are equal, show the single frame
19016 at the corresponding level. It is an error if @var{low-frame} is
19017 larger than the actual number of frames. On the other hand,
19018 @var{high-frame} may be larger than the actual number of frames, in
19019 which case only existing frames will be returned.
19021 The @var{show-values} argument must have a value of 0 or 1. A value of
19022 0 means that only the names of the arguments are listed, a value of 1
19023 means that both names and values of the arguments are printed.
19025 @subsubheading @value{GDBN} Command
19027 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
19028 @samp{gdb_get_args} command which partially overlaps with the
19029 functionality of @samp{-stack-list-arguments}.
19031 @subsubheading Example
19038 frame=@{level="0",addr="0x00010734",func="callee4",
19039 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19040 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
19041 frame=@{level="1",addr="0x0001076c",func="callee3",
19042 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19043 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
19044 frame=@{level="2",addr="0x0001078c",func="callee2",
19045 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19046 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
19047 frame=@{level="3",addr="0x000107b4",func="callee1",
19048 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19049 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
19050 frame=@{level="4",addr="0x000107e0",func="main",
19051 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19052 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
19054 -stack-list-arguments 0
19057 frame=@{level="0",args=[]@},
19058 frame=@{level="1",args=[name="strarg"]@},
19059 frame=@{level="2",args=[name="intarg",name="strarg"]@},
19060 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
19061 frame=@{level="4",args=[]@}]
19063 -stack-list-arguments 1
19066 frame=@{level="0",args=[]@},
19068 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19069 frame=@{level="2",args=[
19070 @{name="intarg",value="2"@},
19071 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19072 @{frame=@{level="3",args=[
19073 @{name="intarg",value="2"@},
19074 @{name="strarg",value="0x11940 \"A string argument.\""@},
19075 @{name="fltarg",value="3.5"@}]@},
19076 frame=@{level="4",args=[]@}]
19078 -stack-list-arguments 0 2 2
19079 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
19081 -stack-list-arguments 1 2 2
19082 ^done,stack-args=[frame=@{level="2",
19083 args=[@{name="intarg",value="2"@},
19084 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
19088 @c @subheading -stack-list-exception-handlers
19091 @subheading The @code{-stack-list-frames} Command
19092 @findex -stack-list-frames
19094 @subsubheading Synopsis
19097 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
19100 List the frames currently on the stack. For each frame it displays the
19105 The frame number, 0 being the topmost frame, i.e., the innermost function.
19107 The @code{$pc} value for that frame.
19111 File name of the source file where the function lives.
19113 Line number corresponding to the @code{$pc}.
19116 If invoked without arguments, this command prints a backtrace for the
19117 whole stack. If given two integer arguments, it shows the frames whose
19118 levels are between the two arguments (inclusive). If the two arguments
19119 are equal, it shows the single frame at the corresponding level. It is
19120 an error if @var{low-frame} is larger than the actual number of
19121 frames. On the other hand, @var{high-frame} may be larger than the
19122 actual number of frames, in which case only existing frames will be returned.
19124 @subsubheading @value{GDBN} Command
19126 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
19128 @subsubheading Example
19130 Full stack backtrace:
19136 [frame=@{level="0",addr="0x0001076c",func="foo",
19137 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
19138 frame=@{level="1",addr="0x000107a4",func="foo",
19139 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19140 frame=@{level="2",addr="0x000107a4",func="foo",
19141 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19142 frame=@{level="3",addr="0x000107a4",func="foo",
19143 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19144 frame=@{level="4",addr="0x000107a4",func="foo",
19145 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19146 frame=@{level="5",addr="0x000107a4",func="foo",
19147 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19148 frame=@{level="6",addr="0x000107a4",func="foo",
19149 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19150 frame=@{level="7",addr="0x000107a4",func="foo",
19151 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19152 frame=@{level="8",addr="0x000107a4",func="foo",
19153 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19154 frame=@{level="9",addr="0x000107a4",func="foo",
19155 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19156 frame=@{level="10",addr="0x000107a4",func="foo",
19157 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19158 frame=@{level="11",addr="0x00010738",func="main",
19159 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
19163 Show frames between @var{low_frame} and @var{high_frame}:
19167 -stack-list-frames 3 5
19169 [frame=@{level="3",addr="0x000107a4",func="foo",
19170 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19171 frame=@{level="4",addr="0x000107a4",func="foo",
19172 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19173 frame=@{level="5",addr="0x000107a4",func="foo",
19174 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
19178 Show a single frame:
19182 -stack-list-frames 3 3
19184 [frame=@{level="3",addr="0x000107a4",func="foo",
19185 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
19190 @subheading The @code{-stack-list-locals} Command
19191 @findex -stack-list-locals
19193 @subsubheading Synopsis
19196 -stack-list-locals @var{print-values}
19199 Display the local variable names for the selected frame. If
19200 @var{print-values} is 0 or @code{--no-values}, print only the names of
19201 the variables; if it is 1 or @code{--all-values}, print also their
19202 values; and if it is 2 or @code{--simple-values}, print the name,
19203 type and value for simple data types and the name and type for arrays,
19204 structures and unions. In this last case, a frontend can immediately
19205 display the value of simple data types and create variable objects for
19206 other data types when the user wishes to explore their values in
19209 @subsubheading @value{GDBN} Command
19211 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
19213 @subsubheading Example
19217 -stack-list-locals 0
19218 ^done,locals=[name="A",name="B",name="C"]
19220 -stack-list-locals --all-values
19221 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
19222 @{name="C",value="@{1, 2, 3@}"@}]
19223 -stack-list-locals --simple-values
19224 ^done,locals=[@{name="A",type="int",value="1"@},
19225 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
19230 @subheading The @code{-stack-select-frame} Command
19231 @findex -stack-select-frame
19233 @subsubheading Synopsis
19236 -stack-select-frame @var{framenum}
19239 Change the selected frame. Select a different frame @var{framenum} on
19242 @subsubheading @value{GDBN} Command
19244 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
19245 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
19247 @subsubheading Example
19251 -stack-select-frame 2
19256 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19257 @node GDB/MI Variable Objects
19258 @section @sc{gdb/mi} Variable Objects
19262 @subheading Motivation for Variable Objects in @sc{gdb/mi}
19264 For the implementation of a variable debugger window (locals, watched
19265 expressions, etc.), we are proposing the adaptation of the existing code
19266 used by @code{Insight}.
19268 The two main reasons for that are:
19272 It has been proven in practice (it is already on its second generation).
19275 It will shorten development time (needless to say how important it is
19279 The original interface was designed to be used by Tcl code, so it was
19280 slightly changed so it could be used through @sc{gdb/mi}. This section
19281 describes the @sc{gdb/mi} operations that will be available and gives some
19282 hints about their use.
19284 @emph{Note}: In addition to the set of operations described here, we
19285 expect the @sc{gui} implementation of a variable window to require, at
19286 least, the following operations:
19289 @item @code{-gdb-show} @code{output-radix}
19290 @item @code{-stack-list-arguments}
19291 @item @code{-stack-list-locals}
19292 @item @code{-stack-select-frame}
19297 @subheading Introduction to Variable Objects
19299 @cindex variable objects in @sc{gdb/mi}
19301 Variable objects are "object-oriented" MI interface for examining and
19302 changing values of expressions. Unlike some other MI interfaces that
19303 work with expressions, variable objects are specifically designed for
19304 simple and efficient presentation in the frontend. A variable object
19305 is identified by string name. When a variable object is created, the
19306 frontend specifies the expression for that variable object. The
19307 expression can be a simple variable, or it can be an arbitrary complex
19308 expression, and can even involve CPU registers. After creating a
19309 variable object, the frontend can invoke other variable object
19310 operations---for example to obtain or change the value of a variable
19311 object, or to change display format.
19313 Variable objects have hierarchical tree structure. Any variable object
19314 that corresponds to a composite type, such as structure in C, has
19315 a number of child variable objects, for example corresponding to each
19316 element of a structure. A child variable object can itself have
19317 children, recursively. Recursion ends when we reach
19318 leaf variable objects, which always have built-in types. Child variable
19319 objects are created only by explicit request, so if a frontend
19320 is not interested in the children of a particular variable object, no
19321 child will be created.
19323 For a leaf variable object it is possible to obtain its value as a
19324 string, or set the value from a string. String value can be also
19325 obtained for a non-leaf variable object, but it's generally a string
19326 that only indicates the type of the object, and does not list its
19327 contents. Assignment to a non-leaf variable object is not allowed.
19329 A frontend does not need to read the values of all variable objects each time
19330 the program stops. Instead, MI provides an update command that lists all
19331 variable objects whose values has changed since the last update
19332 operation. This considerably reduces the amount of data that must
19333 be transferred to the frontend. As noted above, children variable
19334 objects are created on demand, and only leaf variable objects have a
19335 real value. As result, gdb will read target memory only for leaf
19336 variables that frontend has created.
19338 The automatic update is not always desirable. For example, a frontend
19339 might want to keep a value of some expression for future reference,
19340 and never update it. For another example, fetching memory is
19341 relatively slow for embedded targets, so a frontend might want
19342 to disable automatic update for the variables that are either not
19343 visible on the screen, or ``closed''. This is possible using so
19344 called ``frozen variable objects''. Such variable objects are never
19345 implicitly updated.
19347 The following is the complete set of @sc{gdb/mi} operations defined to
19348 access this functionality:
19350 @multitable @columnfractions .4 .6
19351 @item @strong{Operation}
19352 @tab @strong{Description}
19354 @item @code{-var-create}
19355 @tab create a variable object
19356 @item @code{-var-delete}
19357 @tab delete the variable object and/or its children
19358 @item @code{-var-set-format}
19359 @tab set the display format of this variable
19360 @item @code{-var-show-format}
19361 @tab show the display format of this variable
19362 @item @code{-var-info-num-children}
19363 @tab tells how many children this object has
19364 @item @code{-var-list-children}
19365 @tab return a list of the object's children
19366 @item @code{-var-info-type}
19367 @tab show the type of this variable object
19368 @item @code{-var-info-expression}
19369 @tab print parent-relative expression that this variable object represents
19370 @item @code{-var-info-path-expression}
19371 @tab print full expression that this variable object represents
19372 @item @code{-var-show-attributes}
19373 @tab is this variable editable? does it exist here?
19374 @item @code{-var-evaluate-expression}
19375 @tab get the value of this variable
19376 @item @code{-var-assign}
19377 @tab set the value of this variable
19378 @item @code{-var-update}
19379 @tab update the variable and its children
19380 @item @code{-var-set-frozen}
19381 @tab set frozeness attribute
19384 In the next subsection we describe each operation in detail and suggest
19385 how it can be used.
19387 @subheading Description And Use of Operations on Variable Objects
19389 @subheading The @code{-var-create} Command
19390 @findex -var-create
19392 @subsubheading Synopsis
19395 -var-create @{@var{name} | "-"@}
19396 @{@var{frame-addr} | "*"@} @var{expression}
19399 This operation creates a variable object, which allows the monitoring of
19400 a variable, the result of an expression, a memory cell or a CPU
19403 The @var{name} parameter is the string by which the object can be
19404 referenced. It must be unique. If @samp{-} is specified, the varobj
19405 system will generate a string ``varNNNNNN'' automatically. It will be
19406 unique provided that one does not specify @var{name} on that format.
19407 The command fails if a duplicate name is found.
19409 The frame under which the expression should be evaluated can be
19410 specified by @var{frame-addr}. A @samp{*} indicates that the current
19411 frame should be used.
19413 @var{expression} is any expression valid on the current language set (must not
19414 begin with a @samp{*}), or one of the following:
19418 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
19421 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
19424 @samp{$@var{regname}} --- a CPU register name
19427 @subsubheading Result
19429 This operation returns the name, number of children and the type of the
19430 object created. Type is returned as a string as the ones generated by
19431 the @value{GDBN} CLI:
19434 name="@var{name}",numchild="N",type="@var{type}"
19438 @subheading The @code{-var-delete} Command
19439 @findex -var-delete
19441 @subsubheading Synopsis
19444 -var-delete [ -c ] @var{name}
19447 Deletes a previously created variable object and all of its children.
19448 With the @samp{-c} option, just deletes the children.
19450 Returns an error if the object @var{name} is not found.
19453 @subheading The @code{-var-set-format} Command
19454 @findex -var-set-format
19456 @subsubheading Synopsis
19459 -var-set-format @var{name} @var{format-spec}
19462 Sets the output format for the value of the object @var{name} to be
19465 The syntax for the @var{format-spec} is as follows:
19468 @var{format-spec} @expansion{}
19469 @{binary | decimal | hexadecimal | octal | natural@}
19472 The natural format is the default format choosen automatically
19473 based on the variable type (like decimal for an @code{int}, hex
19474 for pointers, etc.).
19476 For a variable with children, the format is set only on the
19477 variable itself, and the children are not affected.
19479 @subheading The @code{-var-show-format} Command
19480 @findex -var-show-format
19482 @subsubheading Synopsis
19485 -var-show-format @var{name}
19488 Returns the format used to display the value of the object @var{name}.
19491 @var{format} @expansion{}
19496 @subheading The @code{-var-info-num-children} Command
19497 @findex -var-info-num-children
19499 @subsubheading Synopsis
19502 -var-info-num-children @var{name}
19505 Returns the number of children of a variable object @var{name}:
19512 @subheading The @code{-var-list-children} Command
19513 @findex -var-list-children
19515 @subsubheading Synopsis
19518 -var-list-children [@var{print-values}] @var{name}
19520 @anchor{-var-list-children}
19522 Return a list of the children of the specified variable object and
19523 create variable objects for them, if they do not already exist. With
19524 a single argument or if @var{print-values} has a value for of 0 or
19525 @code{--no-values}, print only the names of the variables; if
19526 @var{print-values} is 1 or @code{--all-values}, also print their
19527 values; and if it is 2 or @code{--simple-values} print the name and
19528 value for simple data types and just the name for arrays, structures
19531 @subsubheading Example
19535 -var-list-children n
19536 ^done,numchild=@var{n},children=[@{name=@var{name},
19537 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
19539 -var-list-children --all-values n
19540 ^done,numchild=@var{n},children=[@{name=@var{name},
19541 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
19545 @subheading The @code{-var-info-type} Command
19546 @findex -var-info-type
19548 @subsubheading Synopsis
19551 -var-info-type @var{name}
19554 Returns the type of the specified variable @var{name}. The type is
19555 returned as a string in the same format as it is output by the
19559 type=@var{typename}
19563 @subheading The @code{-var-info-expression} Command
19564 @findex -var-info-expression
19566 @subsubheading Synopsis
19569 -var-info-expression @var{name}
19572 Returns a string that is suitable for presenting this
19573 variable object in user interface. The string is generally
19574 not valid expression in the current language, and cannot be evaluated.
19576 For example, if @code{a} is an array, and variable object
19577 @code{A} was created for @code{a}, then we'll get this output:
19580 (gdb) -var-info-expression A.1
19581 ^done,lang="C",exp="1"
19585 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
19587 Note that the output of the @code{-var-list-children} command also
19588 includes those expressions, so the @code{-var-info-expression} command
19591 @subheading The @code{-var-info-path-expression} Command
19592 @findex -var-info-path-expression
19594 @subsubheading Synopsis
19597 -var-info-path-expression @var{name}
19600 Returns an expression that can be evaluated in the current
19601 context and will yield the same value that a variable object has.
19602 Compare this with the @code{-var-info-expression} command, which
19603 result can be used only for UI presentation. Typical use of
19604 the @code{-var-info-path-expression} command is creating a
19605 watchpoint from a variable object.
19607 For example, suppose @code{C} is a C@t{++} class, derived from class
19608 @code{Base}, and that the @code{Base} class has a member called
19609 @code{m_size}. Assume a variable @code{c} is has the type of
19610 @code{C} and a variable object @code{C} was created for variable
19611 @code{c}. Then, we'll get this output:
19613 (gdb) -var-info-path-expression C.Base.public.m_size
19614 ^done,path_expr=((Base)c).m_size)
19617 @subheading The @code{-var-show-attributes} Command
19618 @findex -var-show-attributes
19620 @subsubheading Synopsis
19623 -var-show-attributes @var{name}
19626 List attributes of the specified variable object @var{name}:
19629 status=@var{attr} [ ( ,@var{attr} )* ]
19633 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
19635 @subheading The @code{-var-evaluate-expression} Command
19636 @findex -var-evaluate-expression
19638 @subsubheading Synopsis
19641 -var-evaluate-expression @var{name}
19644 Evaluates the expression that is represented by the specified variable
19645 object and returns its value as a string. The format of the
19646 string can be changed using the @code{-var-set-format} command.
19652 Note that one must invoke @code{-var-list-children} for a variable
19653 before the value of a child variable can be evaluated.
19655 @subheading The @code{-var-assign} Command
19656 @findex -var-assign
19658 @subsubheading Synopsis
19661 -var-assign @var{name} @var{expression}
19664 Assigns the value of @var{expression} to the variable object specified
19665 by @var{name}. The object must be @samp{editable}. If the variable's
19666 value is altered by the assign, the variable will show up in any
19667 subsequent @code{-var-update} list.
19669 @subsubheading Example
19677 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
19681 @subheading The @code{-var-update} Command
19682 @findex -var-update
19684 @subsubheading Synopsis
19687 -var-update [@var{print-values}] @{@var{name} | "*"@}
19690 Reevaluate the expressions corresponding to the variable object
19691 @var{name} and all its direct and indirect children, and return the
19692 list of variable objects whose values have changed; @var{name} must
19693 be a root variable object. Here, ``changed'' means that the result of
19694 @code{-var-evaluate-expression} before and after the
19695 @code{-var-update} is different. If @samp{*} is used as the variable
19696 object names, all existing variable objects are updated, except
19697 for frozen ones (@pxref{-var-set-frozen}). The option
19698 @var{print-values} determines whether both names and values, or just
19699 names are printed. The possible values of this options are the same
19700 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
19701 recommended to use the @samp{--all-values} option, to reduce the
19702 number of MI commands needed on each program stop.
19705 @subsubheading Example
19712 -var-update --all-values var1
19713 ^done,changelist=[@{name="var1",value="3",in_scope="true",
19714 type_changed="false"@}]
19718 @anchor{-var-update}
19719 The field in_scope may take three values:
19723 The variable object's current value is valid.
19726 The variable object does not currently hold a valid value but it may
19727 hold one in the future if its associated expression comes back into
19731 The variable object no longer holds a valid value.
19732 This can occur when the executable file being debugged has changed,
19733 either through recompilation or by using the @value{GDBN} @code{file}
19734 command. The front end should normally choose to delete these variable
19738 In the future new values may be added to this list so the front should
19739 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
19741 @subheading The @code{-var-set-frozen} Command
19742 @findex -var-set-frozen
19743 @anchor{-var-set-frozen}
19745 @subsubheading Synopsis
19748 -var-set-frozen @var{name} @var{flag}
19751 Set the frozenness flag on the variable object @var{name}. The
19752 @var{flag} parameter should be either @samp{1} to make the variable
19753 frozen or @samp{0} to make it unfrozen. If a variable object is
19754 frozen, then neither itself, nor any of its children, are
19755 implicitly updated by @code{-var-update} of
19756 a parent variable or by @code{-var-update *}. Only
19757 @code{-var-update} of the variable itself will update its value and
19758 values of its children. After a variable object is unfrozen, it is
19759 implicitly updated by all subsequent @code{-var-update} operations.
19760 Unfreezing a variable does not update it, only subsequent
19761 @code{-var-update} does.
19763 @subsubheading Example
19767 -var-set-frozen V 1
19773 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19774 @node GDB/MI Data Manipulation
19775 @section @sc{gdb/mi} Data Manipulation
19777 @cindex data manipulation, in @sc{gdb/mi}
19778 @cindex @sc{gdb/mi}, data manipulation
19779 This section describes the @sc{gdb/mi} commands that manipulate data:
19780 examine memory and registers, evaluate expressions, etc.
19782 @c REMOVED FROM THE INTERFACE.
19783 @c @subheading -data-assign
19784 @c Change the value of a program variable. Plenty of side effects.
19785 @c @subsubheading GDB Command
19787 @c @subsubheading Example
19790 @subheading The @code{-data-disassemble} Command
19791 @findex -data-disassemble
19793 @subsubheading Synopsis
19797 [ -s @var{start-addr} -e @var{end-addr} ]
19798 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
19806 @item @var{start-addr}
19807 is the beginning address (or @code{$pc})
19808 @item @var{end-addr}
19810 @item @var{filename}
19811 is the name of the file to disassemble
19812 @item @var{linenum}
19813 is the line number to disassemble around
19815 is the number of disassembly lines to be produced. If it is -1,
19816 the whole function will be disassembled, in case no @var{end-addr} is
19817 specified. If @var{end-addr} is specified as a non-zero value, and
19818 @var{lines} is lower than the number of disassembly lines between
19819 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
19820 displayed; if @var{lines} is higher than the number of lines between
19821 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
19824 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
19828 @subsubheading Result
19830 The output for each instruction is composed of four fields:
19839 Note that whatever included in the instruction field, is not manipulated
19840 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
19842 @subsubheading @value{GDBN} Command
19844 There's no direct mapping from this command to the CLI.
19846 @subsubheading Example
19848 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
19852 -data-disassemble -s $pc -e "$pc + 20" -- 0
19855 @{address="0x000107c0",func-name="main",offset="4",
19856 inst="mov 2, %o0"@},
19857 @{address="0x000107c4",func-name="main",offset="8",
19858 inst="sethi %hi(0x11800), %o2"@},
19859 @{address="0x000107c8",func-name="main",offset="12",
19860 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
19861 @{address="0x000107cc",func-name="main",offset="16",
19862 inst="sethi %hi(0x11800), %o2"@},
19863 @{address="0x000107d0",func-name="main",offset="20",
19864 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
19868 Disassemble the whole @code{main} function. Line 32 is part of
19872 -data-disassemble -f basics.c -l 32 -- 0
19874 @{address="0x000107bc",func-name="main",offset="0",
19875 inst="save %sp, -112, %sp"@},
19876 @{address="0x000107c0",func-name="main",offset="4",
19877 inst="mov 2, %o0"@},
19878 @{address="0x000107c4",func-name="main",offset="8",
19879 inst="sethi %hi(0x11800), %o2"@},
19881 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
19882 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
19886 Disassemble 3 instructions from the start of @code{main}:
19890 -data-disassemble -f basics.c -l 32 -n 3 -- 0
19892 @{address="0x000107bc",func-name="main",offset="0",
19893 inst="save %sp, -112, %sp"@},
19894 @{address="0x000107c0",func-name="main",offset="4",
19895 inst="mov 2, %o0"@},
19896 @{address="0x000107c4",func-name="main",offset="8",
19897 inst="sethi %hi(0x11800), %o2"@}]
19901 Disassemble 3 instructions from the start of @code{main} in mixed mode:
19905 -data-disassemble -f basics.c -l 32 -n 3 -- 1
19907 src_and_asm_line=@{line="31",
19908 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
19909 testsuite/gdb.mi/basics.c",line_asm_insn=[
19910 @{address="0x000107bc",func-name="main",offset="0",
19911 inst="save %sp, -112, %sp"@}]@},
19912 src_and_asm_line=@{line="32",
19913 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
19914 testsuite/gdb.mi/basics.c",line_asm_insn=[
19915 @{address="0x000107c0",func-name="main",offset="4",
19916 inst="mov 2, %o0"@},
19917 @{address="0x000107c4",func-name="main",offset="8",
19918 inst="sethi %hi(0x11800), %o2"@}]@}]
19923 @subheading The @code{-data-evaluate-expression} Command
19924 @findex -data-evaluate-expression
19926 @subsubheading Synopsis
19929 -data-evaluate-expression @var{expr}
19932 Evaluate @var{expr} as an expression. The expression could contain an
19933 inferior function call. The function call will execute synchronously.
19934 If the expression contains spaces, it must be enclosed in double quotes.
19936 @subsubheading @value{GDBN} Command
19938 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
19939 @samp{call}. In @code{gdbtk} only, there's a corresponding
19940 @samp{gdb_eval} command.
19942 @subsubheading Example
19944 In the following example, the numbers that precede the commands are the
19945 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
19946 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
19950 211-data-evaluate-expression A
19953 311-data-evaluate-expression &A
19954 311^done,value="0xefffeb7c"
19956 411-data-evaluate-expression A+3
19959 511-data-evaluate-expression "A + 3"
19965 @subheading The @code{-data-list-changed-registers} Command
19966 @findex -data-list-changed-registers
19968 @subsubheading Synopsis
19971 -data-list-changed-registers
19974 Display a list of the registers that have changed.
19976 @subsubheading @value{GDBN} Command
19978 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
19979 has the corresponding command @samp{gdb_changed_register_list}.
19981 @subsubheading Example
19983 On a PPC MBX board:
19991 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
19992 args=[],file="try.c",fullname="/home/foo/bar/try.c",line="5"@}
19994 -data-list-changed-registers
19995 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
19996 "10","11","13","14","15","16","17","18","19","20","21","22","23",
19997 "24","25","26","27","28","30","31","64","65","66","67","69"]
20002 @subheading The @code{-data-list-register-names} Command
20003 @findex -data-list-register-names
20005 @subsubheading Synopsis
20008 -data-list-register-names [ ( @var{regno} )+ ]
20011 Show a list of register names for the current target. If no arguments
20012 are given, it shows a list of the names of all the registers. If
20013 integer numbers are given as arguments, it will print a list of the
20014 names of the registers corresponding to the arguments. To ensure
20015 consistency between a register name and its number, the output list may
20016 include empty register names.
20018 @subsubheading @value{GDBN} Command
20020 @value{GDBN} does not have a command which corresponds to
20021 @samp{-data-list-register-names}. In @code{gdbtk} there is a
20022 corresponding command @samp{gdb_regnames}.
20024 @subsubheading Example
20026 For the PPC MBX board:
20029 -data-list-register-names
20030 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
20031 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
20032 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
20033 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
20034 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
20035 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
20036 "", "pc","ps","cr","lr","ctr","xer"]
20038 -data-list-register-names 1 2 3
20039 ^done,register-names=["r1","r2","r3"]
20043 @subheading The @code{-data-list-register-values} Command
20044 @findex -data-list-register-values
20046 @subsubheading Synopsis
20049 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
20052 Display the registers' contents. @var{fmt} is the format according to
20053 which the registers' contents are to be returned, followed by an optional
20054 list of numbers specifying the registers to display. A missing list of
20055 numbers indicates that the contents of all the registers must be returned.
20057 Allowed formats for @var{fmt} are:
20074 @subsubheading @value{GDBN} Command
20076 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
20077 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
20079 @subsubheading Example
20081 For a PPC MBX board (note: line breaks are for readability only, they
20082 don't appear in the actual output):
20086 -data-list-register-values r 64 65
20087 ^done,register-values=[@{number="64",value="0xfe00a300"@},
20088 @{number="65",value="0x00029002"@}]
20090 -data-list-register-values x
20091 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
20092 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
20093 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
20094 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
20095 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
20096 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
20097 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
20098 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
20099 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
20100 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
20101 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
20102 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
20103 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
20104 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
20105 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
20106 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
20107 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
20108 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
20109 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
20110 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
20111 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
20112 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
20113 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
20114 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
20115 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
20116 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
20117 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
20118 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
20119 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
20120 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
20121 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
20122 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
20123 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
20124 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
20125 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
20126 @{number="69",value="0x20002b03"@}]
20131 @subheading The @code{-data-read-memory} Command
20132 @findex -data-read-memory
20134 @subsubheading Synopsis
20137 -data-read-memory [ -o @var{byte-offset} ]
20138 @var{address} @var{word-format} @var{word-size}
20139 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
20146 @item @var{address}
20147 An expression specifying the address of the first memory word to be
20148 read. Complex expressions containing embedded white space should be
20149 quoted using the C convention.
20151 @item @var{word-format}
20152 The format to be used to print the memory words. The notation is the
20153 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
20156 @item @var{word-size}
20157 The size of each memory word in bytes.
20159 @item @var{nr-rows}
20160 The number of rows in the output table.
20162 @item @var{nr-cols}
20163 The number of columns in the output table.
20166 If present, indicates that each row should include an @sc{ascii} dump. The
20167 value of @var{aschar} is used as a padding character when a byte is not a
20168 member of the printable @sc{ascii} character set (printable @sc{ascii}
20169 characters are those whose code is between 32 and 126, inclusively).
20171 @item @var{byte-offset}
20172 An offset to add to the @var{address} before fetching memory.
20175 This command displays memory contents as a table of @var{nr-rows} by
20176 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
20177 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
20178 (returned as @samp{total-bytes}). Should less than the requested number
20179 of bytes be returned by the target, the missing words are identified
20180 using @samp{N/A}. The number of bytes read from the target is returned
20181 in @samp{nr-bytes} and the starting address used to read memory in
20184 The address of the next/previous row or page is available in
20185 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
20188 @subsubheading @value{GDBN} Command
20190 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
20191 @samp{gdb_get_mem} memory read command.
20193 @subsubheading Example
20195 Read six bytes of memory starting at @code{bytes+6} but then offset by
20196 @code{-6} bytes. Format as three rows of two columns. One byte per
20197 word. Display each word in hex.
20201 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
20202 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
20203 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
20204 prev-page="0x0000138a",memory=[
20205 @{addr="0x00001390",data=["0x00","0x01"]@},
20206 @{addr="0x00001392",data=["0x02","0x03"]@},
20207 @{addr="0x00001394",data=["0x04","0x05"]@}]
20211 Read two bytes of memory starting at address @code{shorts + 64} and
20212 display as a single word formatted in decimal.
20216 5-data-read-memory shorts+64 d 2 1 1
20217 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
20218 next-row="0x00001512",prev-row="0x0000150e",
20219 next-page="0x00001512",prev-page="0x0000150e",memory=[
20220 @{addr="0x00001510",data=["128"]@}]
20224 Read thirty two bytes of memory starting at @code{bytes+16} and format
20225 as eight rows of four columns. Include a string encoding with @samp{x}
20226 used as the non-printable character.
20230 4-data-read-memory bytes+16 x 1 8 4 x
20231 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
20232 next-row="0x000013c0",prev-row="0x0000139c",
20233 next-page="0x000013c0",prev-page="0x00001380",memory=[
20234 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
20235 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
20236 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
20237 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
20238 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
20239 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
20240 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
20241 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
20245 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20246 @node GDB/MI Tracepoint Commands
20247 @section @sc{gdb/mi} Tracepoint Commands
20249 The tracepoint commands are not yet implemented.
20251 @c @subheading -trace-actions
20253 @c @subheading -trace-delete
20255 @c @subheading -trace-disable
20257 @c @subheading -trace-dump
20259 @c @subheading -trace-enable
20261 @c @subheading -trace-exists
20263 @c @subheading -trace-find
20265 @c @subheading -trace-frame-number
20267 @c @subheading -trace-info
20269 @c @subheading -trace-insert
20271 @c @subheading -trace-list
20273 @c @subheading -trace-pass-count
20275 @c @subheading -trace-save
20277 @c @subheading -trace-start
20279 @c @subheading -trace-stop
20282 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20283 @node GDB/MI Symbol Query
20284 @section @sc{gdb/mi} Symbol Query Commands
20287 @subheading The @code{-symbol-info-address} Command
20288 @findex -symbol-info-address
20290 @subsubheading Synopsis
20293 -symbol-info-address @var{symbol}
20296 Describe where @var{symbol} is stored.
20298 @subsubheading @value{GDBN} Command
20300 The corresponding @value{GDBN} command is @samp{info address}.
20302 @subsubheading Example
20306 @subheading The @code{-symbol-info-file} Command
20307 @findex -symbol-info-file
20309 @subsubheading Synopsis
20315 Show the file for the symbol.
20317 @subsubheading @value{GDBN} Command
20319 There's no equivalent @value{GDBN} command. @code{gdbtk} has
20320 @samp{gdb_find_file}.
20322 @subsubheading Example
20326 @subheading The @code{-symbol-info-function} Command
20327 @findex -symbol-info-function
20329 @subsubheading Synopsis
20332 -symbol-info-function
20335 Show which function the symbol lives in.
20337 @subsubheading @value{GDBN} Command
20339 @samp{gdb_get_function} in @code{gdbtk}.
20341 @subsubheading Example
20345 @subheading The @code{-symbol-info-line} Command
20346 @findex -symbol-info-line
20348 @subsubheading Synopsis
20354 Show the core addresses of the code for a source line.
20356 @subsubheading @value{GDBN} Command
20358 The corresponding @value{GDBN} command is @samp{info line}.
20359 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
20361 @subsubheading Example
20365 @subheading The @code{-symbol-info-symbol} Command
20366 @findex -symbol-info-symbol
20368 @subsubheading Synopsis
20371 -symbol-info-symbol @var{addr}
20374 Describe what symbol is at location @var{addr}.
20376 @subsubheading @value{GDBN} Command
20378 The corresponding @value{GDBN} command is @samp{info symbol}.
20380 @subsubheading Example
20384 @subheading The @code{-symbol-list-functions} Command
20385 @findex -symbol-list-functions
20387 @subsubheading Synopsis
20390 -symbol-list-functions
20393 List the functions in the executable.
20395 @subsubheading @value{GDBN} Command
20397 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
20398 @samp{gdb_search} in @code{gdbtk}.
20400 @subsubheading Example
20404 @subheading The @code{-symbol-list-lines} Command
20405 @findex -symbol-list-lines
20407 @subsubheading Synopsis
20410 -symbol-list-lines @var{filename}
20413 Print the list of lines that contain code and their associated program
20414 addresses for the given source filename. The entries are sorted in
20415 ascending PC order.
20417 @subsubheading @value{GDBN} Command
20419 There is no corresponding @value{GDBN} command.
20421 @subsubheading Example
20424 -symbol-list-lines basics.c
20425 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
20430 @subheading The @code{-symbol-list-types} Command
20431 @findex -symbol-list-types
20433 @subsubheading Synopsis
20439 List all the type names.
20441 @subsubheading @value{GDBN} Command
20443 The corresponding commands are @samp{info types} in @value{GDBN},
20444 @samp{gdb_search} in @code{gdbtk}.
20446 @subsubheading Example
20450 @subheading The @code{-symbol-list-variables} Command
20451 @findex -symbol-list-variables
20453 @subsubheading Synopsis
20456 -symbol-list-variables
20459 List all the global and static variable names.
20461 @subsubheading @value{GDBN} Command
20463 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
20465 @subsubheading Example
20469 @subheading The @code{-symbol-locate} Command
20470 @findex -symbol-locate
20472 @subsubheading Synopsis
20478 @subsubheading @value{GDBN} Command
20480 @samp{gdb_loc} in @code{gdbtk}.
20482 @subsubheading Example
20486 @subheading The @code{-symbol-type} Command
20487 @findex -symbol-type
20489 @subsubheading Synopsis
20492 -symbol-type @var{variable}
20495 Show type of @var{variable}.
20497 @subsubheading @value{GDBN} Command
20499 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
20500 @samp{gdb_obj_variable}.
20502 @subsubheading Example
20506 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20507 @node GDB/MI File Commands
20508 @section @sc{gdb/mi} File Commands
20510 This section describes the GDB/MI commands to specify executable file names
20511 and to read in and obtain symbol table information.
20513 @subheading The @code{-file-exec-and-symbols} Command
20514 @findex -file-exec-and-symbols
20516 @subsubheading Synopsis
20519 -file-exec-and-symbols @var{file}
20522 Specify the executable file to be debugged. This file is the one from
20523 which the symbol table is also read. If no file is specified, the
20524 command clears the executable and symbol information. If breakpoints
20525 are set when using this command with no arguments, @value{GDBN} will produce
20526 error messages. Otherwise, no output is produced, except a completion
20529 @subsubheading @value{GDBN} Command
20531 The corresponding @value{GDBN} command is @samp{file}.
20533 @subsubheading Example
20537 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
20543 @subheading The @code{-file-exec-file} Command
20544 @findex -file-exec-file
20546 @subsubheading Synopsis
20549 -file-exec-file @var{file}
20552 Specify the executable file to be debugged. Unlike
20553 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
20554 from this file. If used without argument, @value{GDBN} clears the information
20555 about the executable file. No output is produced, except a completion
20558 @subsubheading @value{GDBN} Command
20560 The corresponding @value{GDBN} command is @samp{exec-file}.
20562 @subsubheading Example
20566 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
20572 @subheading The @code{-file-list-exec-sections} Command
20573 @findex -file-list-exec-sections
20575 @subsubheading Synopsis
20578 -file-list-exec-sections
20581 List the sections of the current executable file.
20583 @subsubheading @value{GDBN} Command
20585 The @value{GDBN} command @samp{info file} shows, among the rest, the same
20586 information as this command. @code{gdbtk} has a corresponding command
20587 @samp{gdb_load_info}.
20589 @subsubheading Example
20593 @subheading The @code{-file-list-exec-source-file} Command
20594 @findex -file-list-exec-source-file
20596 @subsubheading Synopsis
20599 -file-list-exec-source-file
20602 List the line number, the current source file, and the absolute path
20603 to the current source file for the current executable.
20605 @subsubheading @value{GDBN} Command
20607 The @value{GDBN} equivalent is @samp{info source}
20609 @subsubheading Example
20613 123-file-list-exec-source-file
20614 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c"
20619 @subheading The @code{-file-list-exec-source-files} Command
20620 @findex -file-list-exec-source-files
20622 @subsubheading Synopsis
20625 -file-list-exec-source-files
20628 List the source files for the current executable.
20630 It will always output the filename, but only when @value{GDBN} can find
20631 the absolute file name of a source file, will it output the fullname.
20633 @subsubheading @value{GDBN} Command
20635 The @value{GDBN} equivalent is @samp{info sources}.
20636 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
20638 @subsubheading Example
20641 -file-list-exec-source-files
20643 @{file=foo.c,fullname=/home/foo.c@},
20644 @{file=/home/bar.c,fullname=/home/bar.c@},
20645 @{file=gdb_could_not_find_fullpath.c@}]
20649 @subheading The @code{-file-list-shared-libraries} Command
20650 @findex -file-list-shared-libraries
20652 @subsubheading Synopsis
20655 -file-list-shared-libraries
20658 List the shared libraries in the program.
20660 @subsubheading @value{GDBN} Command
20662 The corresponding @value{GDBN} command is @samp{info shared}.
20664 @subsubheading Example
20668 @subheading The @code{-file-list-symbol-files} Command
20669 @findex -file-list-symbol-files
20671 @subsubheading Synopsis
20674 -file-list-symbol-files
20679 @subsubheading @value{GDBN} Command
20681 The corresponding @value{GDBN} command is @samp{info file} (part of it).
20683 @subsubheading Example
20687 @subheading The @code{-file-symbol-file} Command
20688 @findex -file-symbol-file
20690 @subsubheading Synopsis
20693 -file-symbol-file @var{file}
20696 Read symbol table info from the specified @var{file} argument. When
20697 used without arguments, clears @value{GDBN}'s symbol table info. No output is
20698 produced, except for a completion notification.
20700 @subsubheading @value{GDBN} Command
20702 The corresponding @value{GDBN} command is @samp{symbol-file}.
20704 @subsubheading Example
20708 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
20714 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20715 @node GDB/MI Memory Overlay Commands
20716 @section @sc{gdb/mi} Memory Overlay Commands
20718 The memory overlay commands are not implemented.
20720 @c @subheading -overlay-auto
20722 @c @subheading -overlay-list-mapping-state
20724 @c @subheading -overlay-list-overlays
20726 @c @subheading -overlay-map
20728 @c @subheading -overlay-off
20730 @c @subheading -overlay-on
20732 @c @subheading -overlay-unmap
20734 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20735 @node GDB/MI Signal Handling Commands
20736 @section @sc{gdb/mi} Signal Handling Commands
20738 Signal handling commands are not implemented.
20740 @c @subheading -signal-handle
20742 @c @subheading -signal-list-handle-actions
20744 @c @subheading -signal-list-signal-types
20748 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20749 @node GDB/MI Target Manipulation
20750 @section @sc{gdb/mi} Target Manipulation Commands
20753 @subheading The @code{-target-attach} Command
20754 @findex -target-attach
20756 @subsubheading Synopsis
20759 -target-attach @var{pid} | @var{file}
20762 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
20764 @subsubheading @value{GDBN} Command
20766 The corresponding @value{GDBN} command is @samp{attach}.
20768 @subsubheading Example
20772 @subheading The @code{-target-compare-sections} Command
20773 @findex -target-compare-sections
20775 @subsubheading Synopsis
20778 -target-compare-sections [ @var{section} ]
20781 Compare data of section @var{section} on target to the exec file.
20782 Without the argument, all sections are compared.
20784 @subsubheading @value{GDBN} Command
20786 The @value{GDBN} equivalent is @samp{compare-sections}.
20788 @subsubheading Example
20792 @subheading The @code{-target-detach} Command
20793 @findex -target-detach
20795 @subsubheading Synopsis
20801 Detach from the remote target which normally resumes its execution.
20804 @subsubheading @value{GDBN} Command
20806 The corresponding @value{GDBN} command is @samp{detach}.
20808 @subsubheading Example
20818 @subheading The @code{-target-disconnect} Command
20819 @findex -target-disconnect
20821 @subsubheading Synopsis
20827 Disconnect from the remote target. There's no output and the target is
20828 generally not resumed.
20830 @subsubheading @value{GDBN} Command
20832 The corresponding @value{GDBN} command is @samp{disconnect}.
20834 @subsubheading Example
20844 @subheading The @code{-target-download} Command
20845 @findex -target-download
20847 @subsubheading Synopsis
20853 Loads the executable onto the remote target.
20854 It prints out an update message every half second, which includes the fields:
20858 The name of the section.
20860 The size of what has been sent so far for that section.
20862 The size of the section.
20864 The total size of what was sent so far (the current and the previous sections).
20866 The size of the overall executable to download.
20870 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
20871 @sc{gdb/mi} Output Syntax}).
20873 In addition, it prints the name and size of the sections, as they are
20874 downloaded. These messages include the following fields:
20878 The name of the section.
20880 The size of the section.
20882 The size of the overall executable to download.
20886 At the end, a summary is printed.
20888 @subsubheading @value{GDBN} Command
20890 The corresponding @value{GDBN} command is @samp{load}.
20892 @subsubheading Example
20894 Note: each status message appears on a single line. Here the messages
20895 have been broken down so that they can fit onto a page.
20900 +download,@{section=".text",section-size="6668",total-size="9880"@}
20901 +download,@{section=".text",section-sent="512",section-size="6668",
20902 total-sent="512",total-size="9880"@}
20903 +download,@{section=".text",section-sent="1024",section-size="6668",
20904 total-sent="1024",total-size="9880"@}
20905 +download,@{section=".text",section-sent="1536",section-size="6668",
20906 total-sent="1536",total-size="9880"@}
20907 +download,@{section=".text",section-sent="2048",section-size="6668",
20908 total-sent="2048",total-size="9880"@}
20909 +download,@{section=".text",section-sent="2560",section-size="6668",
20910 total-sent="2560",total-size="9880"@}
20911 +download,@{section=".text",section-sent="3072",section-size="6668",
20912 total-sent="3072",total-size="9880"@}
20913 +download,@{section=".text",section-sent="3584",section-size="6668",
20914 total-sent="3584",total-size="9880"@}
20915 +download,@{section=".text",section-sent="4096",section-size="6668",
20916 total-sent="4096",total-size="9880"@}
20917 +download,@{section=".text",section-sent="4608",section-size="6668",
20918 total-sent="4608",total-size="9880"@}
20919 +download,@{section=".text",section-sent="5120",section-size="6668",
20920 total-sent="5120",total-size="9880"@}
20921 +download,@{section=".text",section-sent="5632",section-size="6668",
20922 total-sent="5632",total-size="9880"@}
20923 +download,@{section=".text",section-sent="6144",section-size="6668",
20924 total-sent="6144",total-size="9880"@}
20925 +download,@{section=".text",section-sent="6656",section-size="6668",
20926 total-sent="6656",total-size="9880"@}
20927 +download,@{section=".init",section-size="28",total-size="9880"@}
20928 +download,@{section=".fini",section-size="28",total-size="9880"@}
20929 +download,@{section=".data",section-size="3156",total-size="9880"@}
20930 +download,@{section=".data",section-sent="512",section-size="3156",
20931 total-sent="7236",total-size="9880"@}
20932 +download,@{section=".data",section-sent="1024",section-size="3156",
20933 total-sent="7748",total-size="9880"@}
20934 +download,@{section=".data",section-sent="1536",section-size="3156",
20935 total-sent="8260",total-size="9880"@}
20936 +download,@{section=".data",section-sent="2048",section-size="3156",
20937 total-sent="8772",total-size="9880"@}
20938 +download,@{section=".data",section-sent="2560",section-size="3156",
20939 total-sent="9284",total-size="9880"@}
20940 +download,@{section=".data",section-sent="3072",section-size="3156",
20941 total-sent="9796",total-size="9880"@}
20942 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
20948 @subheading The @code{-target-exec-status} Command
20949 @findex -target-exec-status
20951 @subsubheading Synopsis
20954 -target-exec-status
20957 Provide information on the state of the target (whether it is running or
20958 not, for instance).
20960 @subsubheading @value{GDBN} Command
20962 There's no equivalent @value{GDBN} command.
20964 @subsubheading Example
20968 @subheading The @code{-target-list-available-targets} Command
20969 @findex -target-list-available-targets
20971 @subsubheading Synopsis
20974 -target-list-available-targets
20977 List the possible targets to connect to.
20979 @subsubheading @value{GDBN} Command
20981 The corresponding @value{GDBN} command is @samp{help target}.
20983 @subsubheading Example
20987 @subheading The @code{-target-list-current-targets} Command
20988 @findex -target-list-current-targets
20990 @subsubheading Synopsis
20993 -target-list-current-targets
20996 Describe the current target.
20998 @subsubheading @value{GDBN} Command
21000 The corresponding information is printed by @samp{info file} (among
21003 @subsubheading Example
21007 @subheading The @code{-target-list-parameters} Command
21008 @findex -target-list-parameters
21010 @subsubheading Synopsis
21013 -target-list-parameters
21018 @subsubheading @value{GDBN} Command
21022 @subsubheading Example
21026 @subheading The @code{-target-select} Command
21027 @findex -target-select
21029 @subsubheading Synopsis
21032 -target-select @var{type} @var{parameters @dots{}}
21035 Connect @value{GDBN} to the remote target. This command takes two args:
21039 The type of target, for instance @samp{async}, @samp{remote}, etc.
21040 @item @var{parameters}
21041 Device names, host names and the like. @xref{Target Commands, ,
21042 Commands for Managing Targets}, for more details.
21045 The output is a connection notification, followed by the address at
21046 which the target program is, in the following form:
21049 ^connected,addr="@var{address}",func="@var{function name}",
21050 args=[@var{arg list}]
21053 @subsubheading @value{GDBN} Command
21055 The corresponding @value{GDBN} command is @samp{target}.
21057 @subsubheading Example
21061 -target-select async /dev/ttya
21062 ^connected,addr="0xfe00a300",func="??",args=[]
21066 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21067 @node GDB/MI Miscellaneous Commands
21068 @section Miscellaneous @sc{gdb/mi} Commands
21070 @c @subheading -gdb-complete
21072 @subheading The @code{-gdb-exit} Command
21075 @subsubheading Synopsis
21081 Exit @value{GDBN} immediately.
21083 @subsubheading @value{GDBN} Command
21085 Approximately corresponds to @samp{quit}.
21087 @subsubheading Example
21096 @subheading The @code{-exec-abort} Command
21097 @findex -exec-abort
21099 @subsubheading Synopsis
21105 Kill the inferior running program.
21107 @subsubheading @value{GDBN} Command
21109 The corresponding @value{GDBN} command is @samp{kill}.
21111 @subsubheading Example
21115 @subheading The @code{-gdb-set} Command
21118 @subsubheading Synopsis
21124 Set an internal @value{GDBN} variable.
21125 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
21127 @subsubheading @value{GDBN} Command
21129 The corresponding @value{GDBN} command is @samp{set}.
21131 @subsubheading Example
21141 @subheading The @code{-gdb-show} Command
21144 @subsubheading Synopsis
21150 Show the current value of a @value{GDBN} variable.
21152 @subsubheading @value{GDBN} Command
21154 The corresponding @value{GDBN} command is @samp{show}.
21156 @subsubheading Example
21165 @c @subheading -gdb-source
21168 @subheading The @code{-gdb-version} Command
21169 @findex -gdb-version
21171 @subsubheading Synopsis
21177 Show version information for @value{GDBN}. Used mostly in testing.
21179 @subsubheading @value{GDBN} Command
21181 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
21182 default shows this information when you start an interactive session.
21184 @subsubheading Example
21186 @c This example modifies the actual output from GDB to avoid overfull
21192 ~Copyright 2000 Free Software Foundation, Inc.
21193 ~GDB is free software, covered by the GNU General Public License, and
21194 ~you are welcome to change it and/or distribute copies of it under
21195 ~ certain conditions.
21196 ~Type "show copying" to see the conditions.
21197 ~There is absolutely no warranty for GDB. Type "show warranty" for
21199 ~This GDB was configured as
21200 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
21205 @subheading The @code{-interpreter-exec} Command
21206 @findex -interpreter-exec
21208 @subheading Synopsis
21211 -interpreter-exec @var{interpreter} @var{command}
21213 @anchor{-interpreter-exec}
21215 Execute the specified @var{command} in the given @var{interpreter}.
21217 @subheading @value{GDBN} Command
21219 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
21221 @subheading Example
21225 -interpreter-exec console "break main"
21226 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
21227 &"During symbol reading, bad structure-type format.\n"
21228 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
21233 @subheading The @code{-inferior-tty-set} Command
21234 @findex -inferior-tty-set
21236 @subheading Synopsis
21239 -inferior-tty-set /dev/pts/1
21242 Set terminal for future runs of the program being debugged.
21244 @subheading @value{GDBN} Command
21246 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
21248 @subheading Example
21252 -inferior-tty-set /dev/pts/1
21257 @subheading The @code{-inferior-tty-show} Command
21258 @findex -inferior-tty-show
21260 @subheading Synopsis
21266 Show terminal for future runs of program being debugged.
21268 @subheading @value{GDBN} Command
21270 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
21272 @subheading Example
21276 -inferior-tty-set /dev/pts/1
21280 ^done,inferior_tty_terminal="/dev/pts/1"
21284 @subheading The @code{-enable-timings} Command
21285 @findex -enable-timings
21287 @subheading Synopsis
21290 -enable-timings [yes | no]
21293 Toggle the printing of the wallclock, user and system times for an MI
21294 command as a field in its output. This command is to help frontend
21295 developers optimize the performance of their code. No argument is
21296 equivalent to @samp{yes}.
21298 @subheading @value{GDBN} Command
21302 @subheading Example
21310 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
21311 addr="0x080484ed",func="main",file="myprog.c",
21312 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
21313 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
21321 *stopped,reason="breakpoint-hit",bkptno="1",thread-id="0",
21322 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
21323 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
21324 fullname="/home/nickrob/myprog.c",line="73"@}
21329 @chapter @value{GDBN} Annotations
21331 This chapter describes annotations in @value{GDBN}. Annotations were
21332 designed to interface @value{GDBN} to graphical user interfaces or other
21333 similar programs which want to interact with @value{GDBN} at a
21334 relatively high level.
21336 The annotation mechanism has largely been superseded by @sc{gdb/mi}
21340 This is Edition @value{EDITION}, @value{DATE}.
21344 * Annotations Overview:: What annotations are; the general syntax.
21345 * Server Prefix:: Issuing a command without affecting user state.
21346 * Prompting:: Annotations marking @value{GDBN}'s need for input.
21347 * Errors:: Annotations for error messages.
21348 * Invalidation:: Some annotations describe things now invalid.
21349 * Annotations for Running::
21350 Whether the program is running, how it stopped, etc.
21351 * Source Annotations:: Annotations describing source code.
21354 @node Annotations Overview
21355 @section What is an Annotation?
21356 @cindex annotations
21358 Annotations start with a newline character, two @samp{control-z}
21359 characters, and the name of the annotation. If there is no additional
21360 information associated with this annotation, the name of the annotation
21361 is followed immediately by a newline. If there is additional
21362 information, the name of the annotation is followed by a space, the
21363 additional information, and a newline. The additional information
21364 cannot contain newline characters.
21366 Any output not beginning with a newline and two @samp{control-z}
21367 characters denotes literal output from @value{GDBN}. Currently there is
21368 no need for @value{GDBN} to output a newline followed by two
21369 @samp{control-z} characters, but if there was such a need, the
21370 annotations could be extended with an @samp{escape} annotation which
21371 means those three characters as output.
21373 The annotation @var{level}, which is specified using the
21374 @option{--annotate} command line option (@pxref{Mode Options}), controls
21375 how much information @value{GDBN} prints together with its prompt,
21376 values of expressions, source lines, and other types of output. Level 0
21377 is for no annotations, level 1 is for use when @value{GDBN} is run as a
21378 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
21379 for programs that control @value{GDBN}, and level 2 annotations have
21380 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
21381 Interface, annotate, GDB's Obsolete Annotations}).
21384 @kindex set annotate
21385 @item set annotate @var{level}
21386 The @value{GDBN} command @code{set annotate} sets the level of
21387 annotations to the specified @var{level}.
21389 @item show annotate
21390 @kindex show annotate
21391 Show the current annotation level.
21394 This chapter describes level 3 annotations.
21396 A simple example of starting up @value{GDBN} with annotations is:
21399 $ @kbd{gdb --annotate=3}
21401 Copyright 2003 Free Software Foundation, Inc.
21402 GDB is free software, covered by the GNU General Public License,
21403 and you are welcome to change it and/or distribute copies of it
21404 under certain conditions.
21405 Type "show copying" to see the conditions.
21406 There is absolutely no warranty for GDB. Type "show warranty"
21408 This GDB was configured as "i386-pc-linux-gnu"
21419 Here @samp{quit} is input to @value{GDBN}; the rest is output from
21420 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
21421 denotes a @samp{control-z} character) are annotations; the rest is
21422 output from @value{GDBN}.
21424 @node Server Prefix
21425 @section The Server Prefix
21426 @cindex server prefix
21428 If you prefix a command with @samp{server } then it will not affect
21429 the command history, nor will it affect @value{GDBN}'s notion of which
21430 command to repeat if @key{RET} is pressed on a line by itself. This
21431 means that commands can be run behind a user's back by a front-end in
21432 a transparent manner.
21434 The server prefix does not affect the recording of values into the value
21435 history; to print a value without recording it into the value history,
21436 use the @code{output} command instead of the @code{print} command.
21439 @section Annotation for @value{GDBN} Input
21441 @cindex annotations for prompts
21442 When @value{GDBN} prompts for input, it annotates this fact so it is possible
21443 to know when to send output, when the output from a given command is
21446 Different kinds of input each have a different @dfn{input type}. Each
21447 input type has three annotations: a @code{pre-} annotation, which
21448 denotes the beginning of any prompt which is being output, a plain
21449 annotation, which denotes the end of the prompt, and then a @code{post-}
21450 annotation which denotes the end of any echo which may (or may not) be
21451 associated with the input. For example, the @code{prompt} input type
21452 features the following annotations:
21460 The input types are
21463 @findex pre-prompt annotation
21464 @findex prompt annotation
21465 @findex post-prompt annotation
21467 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
21469 @findex pre-commands annotation
21470 @findex commands annotation
21471 @findex post-commands annotation
21473 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
21474 command. The annotations are repeated for each command which is input.
21476 @findex pre-overload-choice annotation
21477 @findex overload-choice annotation
21478 @findex post-overload-choice annotation
21479 @item overload-choice
21480 When @value{GDBN} wants the user to select between various overloaded functions.
21482 @findex pre-query annotation
21483 @findex query annotation
21484 @findex post-query annotation
21486 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
21488 @findex pre-prompt-for-continue annotation
21489 @findex prompt-for-continue annotation
21490 @findex post-prompt-for-continue annotation
21491 @item prompt-for-continue
21492 When @value{GDBN} is asking the user to press return to continue. Note: Don't
21493 expect this to work well; instead use @code{set height 0} to disable
21494 prompting. This is because the counting of lines is buggy in the
21495 presence of annotations.
21500 @cindex annotations for errors, warnings and interrupts
21502 @findex quit annotation
21507 This annotation occurs right before @value{GDBN} responds to an interrupt.
21509 @findex error annotation
21514 This annotation occurs right before @value{GDBN} responds to an error.
21516 Quit and error annotations indicate that any annotations which @value{GDBN} was
21517 in the middle of may end abruptly. For example, if a
21518 @code{value-history-begin} annotation is followed by a @code{error}, one
21519 cannot expect to receive the matching @code{value-history-end}. One
21520 cannot expect not to receive it either, however; an error annotation
21521 does not necessarily mean that @value{GDBN} is immediately returning all the way
21524 @findex error-begin annotation
21525 A quit or error annotation may be preceded by
21531 Any output between that and the quit or error annotation is the error
21534 Warning messages are not yet annotated.
21535 @c If we want to change that, need to fix warning(), type_error(),
21536 @c range_error(), and possibly other places.
21539 @section Invalidation Notices
21541 @cindex annotations for invalidation messages
21542 The following annotations say that certain pieces of state may have
21546 @findex frames-invalid annotation
21547 @item ^Z^Zframes-invalid
21549 The frames (for example, output from the @code{backtrace} command) may
21552 @findex breakpoints-invalid annotation
21553 @item ^Z^Zbreakpoints-invalid
21555 The breakpoints may have changed. For example, the user just added or
21556 deleted a breakpoint.
21559 @node Annotations for Running
21560 @section Running the Program
21561 @cindex annotations for running programs
21563 @findex starting annotation
21564 @findex stopping annotation
21565 When the program starts executing due to a @value{GDBN} command such as
21566 @code{step} or @code{continue},
21572 is output. When the program stops,
21578 is output. Before the @code{stopped} annotation, a variety of
21579 annotations describe how the program stopped.
21582 @findex exited annotation
21583 @item ^Z^Zexited @var{exit-status}
21584 The program exited, and @var{exit-status} is the exit status (zero for
21585 successful exit, otherwise nonzero).
21587 @findex signalled annotation
21588 @findex signal-name annotation
21589 @findex signal-name-end annotation
21590 @findex signal-string annotation
21591 @findex signal-string-end annotation
21592 @item ^Z^Zsignalled
21593 The program exited with a signal. After the @code{^Z^Zsignalled}, the
21594 annotation continues:
21600 ^Z^Zsignal-name-end
21604 ^Z^Zsignal-string-end
21609 where @var{name} is the name of the signal, such as @code{SIGILL} or
21610 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
21611 as @code{Illegal Instruction} or @code{Segmentation fault}.
21612 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
21613 user's benefit and have no particular format.
21615 @findex signal annotation
21617 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
21618 just saying that the program received the signal, not that it was
21619 terminated with it.
21621 @findex breakpoint annotation
21622 @item ^Z^Zbreakpoint @var{number}
21623 The program hit breakpoint number @var{number}.
21625 @findex watchpoint annotation
21626 @item ^Z^Zwatchpoint @var{number}
21627 The program hit watchpoint number @var{number}.
21630 @node Source Annotations
21631 @section Displaying Source
21632 @cindex annotations for source display
21634 @findex source annotation
21635 The following annotation is used instead of displaying source code:
21638 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
21641 where @var{filename} is an absolute file name indicating which source
21642 file, @var{line} is the line number within that file (where 1 is the
21643 first line in the file), @var{character} is the character position
21644 within the file (where 0 is the first character in the file) (for most
21645 debug formats this will necessarily point to the beginning of a line),
21646 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
21647 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
21648 @var{addr} is the address in the target program associated with the
21649 source which is being displayed. @var{addr} is in the form @samp{0x}
21650 followed by one or more lowercase hex digits (note that this does not
21651 depend on the language).
21654 @chapter Reporting Bugs in @value{GDBN}
21655 @cindex bugs in @value{GDBN}
21656 @cindex reporting bugs in @value{GDBN}
21658 Your bug reports play an essential role in making @value{GDBN} reliable.
21660 Reporting a bug may help you by bringing a solution to your problem, or it
21661 may not. But in any case the principal function of a bug report is to help
21662 the entire community by making the next version of @value{GDBN} work better. Bug
21663 reports are your contribution to the maintenance of @value{GDBN}.
21665 In order for a bug report to serve its purpose, you must include the
21666 information that enables us to fix the bug.
21669 * Bug Criteria:: Have you found a bug?
21670 * Bug Reporting:: How to report bugs
21674 @section Have You Found a Bug?
21675 @cindex bug criteria
21677 If you are not sure whether you have found a bug, here are some guidelines:
21680 @cindex fatal signal
21681 @cindex debugger crash
21682 @cindex crash of debugger
21684 If the debugger gets a fatal signal, for any input whatever, that is a
21685 @value{GDBN} bug. Reliable debuggers never crash.
21687 @cindex error on valid input
21689 If @value{GDBN} produces an error message for valid input, that is a
21690 bug. (Note that if you're cross debugging, the problem may also be
21691 somewhere in the connection to the target.)
21693 @cindex invalid input
21695 If @value{GDBN} does not produce an error message for invalid input,
21696 that is a bug. However, you should note that your idea of
21697 ``invalid input'' might be our idea of ``an extension'' or ``support
21698 for traditional practice''.
21701 If you are an experienced user of debugging tools, your suggestions
21702 for improvement of @value{GDBN} are welcome in any case.
21705 @node Bug Reporting
21706 @section How to Report Bugs
21707 @cindex bug reports
21708 @cindex @value{GDBN} bugs, reporting
21710 A number of companies and individuals offer support for @sc{gnu} products.
21711 If you obtained @value{GDBN} from a support organization, we recommend you
21712 contact that organization first.
21714 You can find contact information for many support companies and
21715 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
21717 @c should add a web page ref...
21719 In any event, we also recommend that you submit bug reports for
21720 @value{GDBN}. The preferred method is to submit them directly using
21721 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
21722 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
21725 @strong{Do not send bug reports to @samp{info-gdb}, or to
21726 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
21727 not want to receive bug reports. Those that do have arranged to receive
21730 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
21731 serves as a repeater. The mailing list and the newsgroup carry exactly
21732 the same messages. Often people think of posting bug reports to the
21733 newsgroup instead of mailing them. This appears to work, but it has one
21734 problem which can be crucial: a newsgroup posting often lacks a mail
21735 path back to the sender. Thus, if we need to ask for more information,
21736 we may be unable to reach you. For this reason, it is better to send
21737 bug reports to the mailing list.
21739 The fundamental principle of reporting bugs usefully is this:
21740 @strong{report all the facts}. If you are not sure whether to state a
21741 fact or leave it out, state it!
21743 Often people omit facts because they think they know what causes the
21744 problem and assume that some details do not matter. Thus, you might
21745 assume that the name of the variable you use in an example does not matter.
21746 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
21747 stray memory reference which happens to fetch from the location where that
21748 name is stored in memory; perhaps, if the name were different, the contents
21749 of that location would fool the debugger into doing the right thing despite
21750 the bug. Play it safe and give a specific, complete example. That is the
21751 easiest thing for you to do, and the most helpful.
21753 Keep in mind that the purpose of a bug report is to enable us to fix the
21754 bug. It may be that the bug has been reported previously, but neither
21755 you nor we can know that unless your bug report is complete and
21758 Sometimes people give a few sketchy facts and ask, ``Does this ring a
21759 bell?'' Those bug reports are useless, and we urge everyone to
21760 @emph{refuse to respond to them} except to chide the sender to report
21763 To enable us to fix the bug, you should include all these things:
21767 The version of @value{GDBN}. @value{GDBN} announces it if you start
21768 with no arguments; you can also print it at any time using @code{show
21771 Without this, we will not know whether there is any point in looking for
21772 the bug in the current version of @value{GDBN}.
21775 The type of machine you are using, and the operating system name and
21779 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
21780 ``@value{GCC}--2.8.1''.
21783 What compiler (and its version) was used to compile the program you are
21784 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
21785 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
21786 to get this information; for other compilers, see the documentation for
21790 The command arguments you gave the compiler to compile your example and
21791 observe the bug. For example, did you use @samp{-O}? To guarantee
21792 you will not omit something important, list them all. A copy of the
21793 Makefile (or the output from make) is sufficient.
21795 If we were to try to guess the arguments, we would probably guess wrong
21796 and then we might not encounter the bug.
21799 A complete input script, and all necessary source files, that will
21803 A description of what behavior you observe that you believe is
21804 incorrect. For example, ``It gets a fatal signal.''
21806 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
21807 will certainly notice it. But if the bug is incorrect output, we might
21808 not notice unless it is glaringly wrong. You might as well not give us
21809 a chance to make a mistake.
21811 Even if the problem you experience is a fatal signal, you should still
21812 say so explicitly. Suppose something strange is going on, such as, your
21813 copy of @value{GDBN} is out of synch, or you have encountered a bug in
21814 the C library on your system. (This has happened!) Your copy might
21815 crash and ours would not. If you told us to expect a crash, then when
21816 ours fails to crash, we would know that the bug was not happening for
21817 us. If you had not told us to expect a crash, then we would not be able
21818 to draw any conclusion from our observations.
21821 @cindex recording a session script
21822 To collect all this information, you can use a session recording program
21823 such as @command{script}, which is available on many Unix systems.
21824 Just run your @value{GDBN} session inside @command{script} and then
21825 include the @file{typescript} file with your bug report.
21827 Another way to record a @value{GDBN} session is to run @value{GDBN}
21828 inside Emacs and then save the entire buffer to a file.
21831 If you wish to suggest changes to the @value{GDBN} source, send us context
21832 diffs. If you even discuss something in the @value{GDBN} source, refer to
21833 it by context, not by line number.
21835 The line numbers in our development sources will not match those in your
21836 sources. Your line numbers would convey no useful information to us.
21840 Here are some things that are not necessary:
21844 A description of the envelope of the bug.
21846 Often people who encounter a bug spend a lot of time investigating
21847 which changes to the input file will make the bug go away and which
21848 changes will not affect it.
21850 This is often time consuming and not very useful, because the way we
21851 will find the bug is by running a single example under the debugger
21852 with breakpoints, not by pure deduction from a series of examples.
21853 We recommend that you save your time for something else.
21855 Of course, if you can find a simpler example to report @emph{instead}
21856 of the original one, that is a convenience for us. Errors in the
21857 output will be easier to spot, running under the debugger will take
21858 less time, and so on.
21860 However, simplification is not vital; if you do not want to do this,
21861 report the bug anyway and send us the entire test case you used.
21864 A patch for the bug.
21866 A patch for the bug does help us if it is a good one. But do not omit
21867 the necessary information, such as the test case, on the assumption that
21868 a patch is all we need. We might see problems with your patch and decide
21869 to fix the problem another way, or we might not understand it at all.
21871 Sometimes with a program as complicated as @value{GDBN} it is very hard to
21872 construct an example that will make the program follow a certain path
21873 through the code. If you do not send us the example, we will not be able
21874 to construct one, so we will not be able to verify that the bug is fixed.
21876 And if we cannot understand what bug you are trying to fix, or why your
21877 patch should be an improvement, we will not install it. A test case will
21878 help us to understand.
21881 A guess about what the bug is or what it depends on.
21883 Such guesses are usually wrong. Even we cannot guess right about such
21884 things without first using the debugger to find the facts.
21887 @c The readline documentation is distributed with the readline code
21888 @c and consists of the two following files:
21890 @c inc-hist.texinfo
21891 @c Use -I with makeinfo to point to the appropriate directory,
21892 @c environment var TEXINPUTS with TeX.
21893 @include rluser.texi
21894 @include inc-hist.texinfo
21897 @node Formatting Documentation
21898 @appendix Formatting Documentation
21900 @cindex @value{GDBN} reference card
21901 @cindex reference card
21902 The @value{GDBN} 4 release includes an already-formatted reference card, ready
21903 for printing with PostScript or Ghostscript, in the @file{gdb}
21904 subdirectory of the main source directory@footnote{In
21905 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
21906 release.}. If you can use PostScript or Ghostscript with your printer,
21907 you can print the reference card immediately with @file{refcard.ps}.
21909 The release also includes the source for the reference card. You
21910 can format it, using @TeX{}, by typing:
21916 The @value{GDBN} reference card is designed to print in @dfn{landscape}
21917 mode on US ``letter'' size paper;
21918 that is, on a sheet 11 inches wide by 8.5 inches
21919 high. You will need to specify this form of printing as an option to
21920 your @sc{dvi} output program.
21922 @cindex documentation
21924 All the documentation for @value{GDBN} comes as part of the machine-readable
21925 distribution. The documentation is written in Texinfo format, which is
21926 a documentation system that uses a single source file to produce both
21927 on-line information and a printed manual. You can use one of the Info
21928 formatting commands to create the on-line version of the documentation
21929 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
21931 @value{GDBN} includes an already formatted copy of the on-line Info
21932 version of this manual in the @file{gdb} subdirectory. The main Info
21933 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
21934 subordinate files matching @samp{gdb.info*} in the same directory. If
21935 necessary, you can print out these files, or read them with any editor;
21936 but they are easier to read using the @code{info} subsystem in @sc{gnu}
21937 Emacs or the standalone @code{info} program, available as part of the
21938 @sc{gnu} Texinfo distribution.
21940 If you want to format these Info files yourself, you need one of the
21941 Info formatting programs, such as @code{texinfo-format-buffer} or
21944 If you have @code{makeinfo} installed, and are in the top level
21945 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
21946 version @value{GDBVN}), you can make the Info file by typing:
21953 If you want to typeset and print copies of this manual, you need @TeX{},
21954 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
21955 Texinfo definitions file.
21957 @TeX{} is a typesetting program; it does not print files directly, but
21958 produces output files called @sc{dvi} files. To print a typeset
21959 document, you need a program to print @sc{dvi} files. If your system
21960 has @TeX{} installed, chances are it has such a program. The precise
21961 command to use depends on your system; @kbd{lpr -d} is common; another
21962 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
21963 require a file name without any extension or a @samp{.dvi} extension.
21965 @TeX{} also requires a macro definitions file called
21966 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
21967 written in Texinfo format. On its own, @TeX{} cannot either read or
21968 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
21969 and is located in the @file{gdb-@var{version-number}/texinfo}
21972 If you have @TeX{} and a @sc{dvi} printer program installed, you can
21973 typeset and print this manual. First switch to the @file{gdb}
21974 subdirectory of the main source directory (for example, to
21975 @file{gdb-@value{GDBVN}/gdb}) and type:
21981 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
21983 @node Installing GDB
21984 @appendix Installing @value{GDBN}
21985 @cindex installation
21988 * Requirements:: Requirements for building @value{GDBN}
21989 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
21990 * Separate Objdir:: Compiling @value{GDBN} in another directory
21991 * Config Names:: Specifying names for hosts and targets
21992 * Configure Options:: Summary of options for configure
21996 @section Requirements for Building @value{GDBN}
21997 @cindex building @value{GDBN}, requirements for
21999 Building @value{GDBN} requires various tools and packages to be available.
22000 Other packages will be used only if they are found.
22002 @heading Tools/Packages Necessary for Building @value{GDBN}
22004 @item ISO C90 compiler
22005 @value{GDBN} is written in ISO C90. It should be buildable with any
22006 working C90 compiler, e.g.@: GCC.
22010 @heading Tools/Packages Optional for Building @value{GDBN}
22014 @value{GDBN} can use the Expat XML parsing library. This library may be
22015 included with your operating system distribution; if it is not, you
22016 can get the latest version from @url{http://expat.sourceforge.net}.
22017 The @file{configure} script will search for this library in several
22018 standard locations; if it is installed in an unusual path, you can
22019 use the @option{--with-libexpat-prefix} option to specify its location.
22021 Expat is used for remote protocol memory maps (@pxref{Memory Map Format})
22022 and for target descriptions (@pxref{Target Descriptions}).
22026 @node Running Configure
22027 @section Invoking the @value{GDBN} @file{configure} Script
22028 @cindex configuring @value{GDBN}
22029 @value{GDBN} comes with a @file{configure} script that automates the process
22030 of preparing @value{GDBN} for installation; you can then use @code{make} to
22031 build the @code{gdb} program.
22033 @c irrelevant in info file; it's as current as the code it lives with.
22034 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
22035 look at the @file{README} file in the sources; we may have improved the
22036 installation procedures since publishing this manual.}
22039 The @value{GDBN} distribution includes all the source code you need for
22040 @value{GDBN} in a single directory, whose name is usually composed by
22041 appending the version number to @samp{gdb}.
22043 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
22044 @file{gdb-@value{GDBVN}} directory. That directory contains:
22047 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
22048 script for configuring @value{GDBN} and all its supporting libraries
22050 @item gdb-@value{GDBVN}/gdb
22051 the source specific to @value{GDBN} itself
22053 @item gdb-@value{GDBVN}/bfd
22054 source for the Binary File Descriptor library
22056 @item gdb-@value{GDBVN}/include
22057 @sc{gnu} include files
22059 @item gdb-@value{GDBVN}/libiberty
22060 source for the @samp{-liberty} free software library
22062 @item gdb-@value{GDBVN}/opcodes
22063 source for the library of opcode tables and disassemblers
22065 @item gdb-@value{GDBVN}/readline
22066 source for the @sc{gnu} command-line interface
22068 @item gdb-@value{GDBVN}/glob
22069 source for the @sc{gnu} filename pattern-matching subroutine
22071 @item gdb-@value{GDBVN}/mmalloc
22072 source for the @sc{gnu} memory-mapped malloc package
22075 The simplest way to configure and build @value{GDBN} is to run @file{configure}
22076 from the @file{gdb-@var{version-number}} source directory, which in
22077 this example is the @file{gdb-@value{GDBVN}} directory.
22079 First switch to the @file{gdb-@var{version-number}} source directory
22080 if you are not already in it; then run @file{configure}. Pass the
22081 identifier for the platform on which @value{GDBN} will run as an
22087 cd gdb-@value{GDBVN}
22088 ./configure @var{host}
22093 where @var{host} is an identifier such as @samp{sun4} or
22094 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
22095 (You can often leave off @var{host}; @file{configure} tries to guess the
22096 correct value by examining your system.)
22098 Running @samp{configure @var{host}} and then running @code{make} builds the
22099 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
22100 libraries, then @code{gdb} itself. The configured source files, and the
22101 binaries, are left in the corresponding source directories.
22104 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
22105 system does not recognize this automatically when you run a different
22106 shell, you may need to run @code{sh} on it explicitly:
22109 sh configure @var{host}
22112 If you run @file{configure} from a directory that contains source
22113 directories for multiple libraries or programs, such as the
22114 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
22116 creates configuration files for every directory level underneath (unless
22117 you tell it not to, with the @samp{--norecursion} option).
22119 You should run the @file{configure} script from the top directory in the
22120 source tree, the @file{gdb-@var{version-number}} directory. If you run
22121 @file{configure} from one of the subdirectories, you will configure only
22122 that subdirectory. That is usually not what you want. In particular,
22123 if you run the first @file{configure} from the @file{gdb} subdirectory
22124 of the @file{gdb-@var{version-number}} directory, you will omit the
22125 configuration of @file{bfd}, @file{readline}, and other sibling
22126 directories of the @file{gdb} subdirectory. This leads to build errors
22127 about missing include files such as @file{bfd/bfd.h}.
22129 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
22130 However, you should make sure that the shell on your path (named by
22131 the @samp{SHELL} environment variable) is publicly readable. Remember
22132 that @value{GDBN} uses the shell to start your program---some systems refuse to
22133 let @value{GDBN} debug child processes whose programs are not readable.
22135 @node Separate Objdir
22136 @section Compiling @value{GDBN} in Another Directory
22138 If you want to run @value{GDBN} versions for several host or target machines,
22139 you need a different @code{gdb} compiled for each combination of
22140 host and target. @file{configure} is designed to make this easy by
22141 allowing you to generate each configuration in a separate subdirectory,
22142 rather than in the source directory. If your @code{make} program
22143 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
22144 @code{make} in each of these directories builds the @code{gdb}
22145 program specified there.
22147 To build @code{gdb} in a separate directory, run @file{configure}
22148 with the @samp{--srcdir} option to specify where to find the source.
22149 (You also need to specify a path to find @file{configure}
22150 itself from your working directory. If the path to @file{configure}
22151 would be the same as the argument to @samp{--srcdir}, you can leave out
22152 the @samp{--srcdir} option; it is assumed.)
22154 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
22155 separate directory for a Sun 4 like this:
22159 cd gdb-@value{GDBVN}
22162 ../gdb-@value{GDBVN}/configure sun4
22167 When @file{configure} builds a configuration using a remote source
22168 directory, it creates a tree for the binaries with the same structure
22169 (and using the same names) as the tree under the source directory. In
22170 the example, you'd find the Sun 4 library @file{libiberty.a} in the
22171 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
22172 @file{gdb-sun4/gdb}.
22174 Make sure that your path to the @file{configure} script has just one
22175 instance of @file{gdb} in it. If your path to @file{configure} looks
22176 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
22177 one subdirectory of @value{GDBN}, not the whole package. This leads to
22178 build errors about missing include files such as @file{bfd/bfd.h}.
22180 One popular reason to build several @value{GDBN} configurations in separate
22181 directories is to configure @value{GDBN} for cross-compiling (where
22182 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
22183 programs that run on another machine---the @dfn{target}).
22184 You specify a cross-debugging target by
22185 giving the @samp{--target=@var{target}} option to @file{configure}.
22187 When you run @code{make} to build a program or library, you must run
22188 it in a configured directory---whatever directory you were in when you
22189 called @file{configure} (or one of its subdirectories).
22191 The @code{Makefile} that @file{configure} generates in each source
22192 directory also runs recursively. If you type @code{make} in a source
22193 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
22194 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
22195 will build all the required libraries, and then build GDB.
22197 When you have multiple hosts or targets configured in separate
22198 directories, you can run @code{make} on them in parallel (for example,
22199 if they are NFS-mounted on each of the hosts); they will not interfere
22203 @section Specifying Names for Hosts and Targets
22205 The specifications used for hosts and targets in the @file{configure}
22206 script are based on a three-part naming scheme, but some short predefined
22207 aliases are also supported. The full naming scheme encodes three pieces
22208 of information in the following pattern:
22211 @var{architecture}-@var{vendor}-@var{os}
22214 For example, you can use the alias @code{sun4} as a @var{host} argument,
22215 or as the value for @var{target} in a @code{--target=@var{target}}
22216 option. The equivalent full name is @samp{sparc-sun-sunos4}.
22218 The @file{configure} script accompanying @value{GDBN} does not provide
22219 any query facility to list all supported host and target names or
22220 aliases. @file{configure} calls the Bourne shell script
22221 @code{config.sub} to map abbreviations to full names; you can read the
22222 script, if you wish, or you can use it to test your guesses on
22223 abbreviations---for example:
22226 % sh config.sub i386-linux
22228 % sh config.sub alpha-linux
22229 alpha-unknown-linux-gnu
22230 % sh config.sub hp9k700
22232 % sh config.sub sun4
22233 sparc-sun-sunos4.1.1
22234 % sh config.sub sun3
22235 m68k-sun-sunos4.1.1
22236 % sh config.sub i986v
22237 Invalid configuration `i986v': machine `i986v' not recognized
22241 @code{config.sub} is also distributed in the @value{GDBN} source
22242 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
22244 @node Configure Options
22245 @section @file{configure} Options
22247 Here is a summary of the @file{configure} options and arguments that
22248 are most often useful for building @value{GDBN}. @file{configure} also has
22249 several other options not listed here. @inforef{What Configure
22250 Does,,configure.info}, for a full explanation of @file{configure}.
22253 configure @r{[}--help@r{]}
22254 @r{[}--prefix=@var{dir}@r{]}
22255 @r{[}--exec-prefix=@var{dir}@r{]}
22256 @r{[}--srcdir=@var{dirname}@r{]}
22257 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
22258 @r{[}--target=@var{target}@r{]}
22263 You may introduce options with a single @samp{-} rather than
22264 @samp{--} if you prefer; but you may abbreviate option names if you use
22269 Display a quick summary of how to invoke @file{configure}.
22271 @item --prefix=@var{dir}
22272 Configure the source to install programs and files under directory
22275 @item --exec-prefix=@var{dir}
22276 Configure the source to install programs under directory
22279 @c avoid splitting the warning from the explanation:
22281 @item --srcdir=@var{dirname}
22282 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
22283 @code{make} that implements the @code{VPATH} feature.}@*
22284 Use this option to make configurations in directories separate from the
22285 @value{GDBN} source directories. Among other things, you can use this to
22286 build (or maintain) several configurations simultaneously, in separate
22287 directories. @file{configure} writes configuration-specific files in
22288 the current directory, but arranges for them to use the source in the
22289 directory @var{dirname}. @file{configure} creates directories under
22290 the working directory in parallel to the source directories below
22293 @item --norecursion
22294 Configure only the directory level where @file{configure} is executed; do not
22295 propagate configuration to subdirectories.
22297 @item --target=@var{target}
22298 Configure @value{GDBN} for cross-debugging programs running on the specified
22299 @var{target}. Without this option, @value{GDBN} is configured to debug
22300 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
22302 There is no convenient way to generate a list of all available targets.
22304 @item @var{host} @dots{}
22305 Configure @value{GDBN} to run on the specified @var{host}.
22307 There is no convenient way to generate a list of all available hosts.
22310 There are many other options available as well, but they are generally
22311 needed for special purposes only.
22313 @node Maintenance Commands
22314 @appendix Maintenance Commands
22315 @cindex maintenance commands
22316 @cindex internal commands
22318 In addition to commands intended for @value{GDBN} users, @value{GDBN}
22319 includes a number of commands intended for @value{GDBN} developers,
22320 that are not documented elsewhere in this manual. These commands are
22321 provided here for reference. (For commands that turn on debugging
22322 messages, see @ref{Debugging Output}.)
22325 @kindex maint agent
22326 @item maint agent @var{expression}
22327 Translate the given @var{expression} into remote agent bytecodes.
22328 This command is useful for debugging the Agent Expression mechanism
22329 (@pxref{Agent Expressions}).
22331 @kindex maint info breakpoints
22332 @item @anchor{maint info breakpoints}maint info breakpoints
22333 Using the same format as @samp{info breakpoints}, display both the
22334 breakpoints you've set explicitly, and those @value{GDBN} is using for
22335 internal purposes. Internal breakpoints are shown with negative
22336 breakpoint numbers. The type column identifies what kind of breakpoint
22341 Normal, explicitly set breakpoint.
22344 Normal, explicitly set watchpoint.
22347 Internal breakpoint, used to handle correctly stepping through
22348 @code{longjmp} calls.
22350 @item longjmp resume
22351 Internal breakpoint at the target of a @code{longjmp}.
22354 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
22357 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
22360 Shared library events.
22364 @kindex maint check-symtabs
22365 @item maint check-symtabs
22366 Check the consistency of psymtabs and symtabs.
22368 @kindex maint cplus first_component
22369 @item maint cplus first_component @var{name}
22370 Print the first C@t{++} class/namespace component of @var{name}.
22372 @kindex maint cplus namespace
22373 @item maint cplus namespace
22374 Print the list of possible C@t{++} namespaces.
22376 @kindex maint demangle
22377 @item maint demangle @var{name}
22378 Demangle a C@t{++} or Objective-C mangled @var{name}.
22380 @kindex maint deprecate
22381 @kindex maint undeprecate
22382 @cindex deprecated commands
22383 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
22384 @itemx maint undeprecate @var{command}
22385 Deprecate or undeprecate the named @var{command}. Deprecated commands
22386 cause @value{GDBN} to issue a warning when you use them. The optional
22387 argument @var{replacement} says which newer command should be used in
22388 favor of the deprecated one; if it is given, @value{GDBN} will mention
22389 the replacement as part of the warning.
22391 @kindex maint dump-me
22392 @item maint dump-me
22393 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
22394 Cause a fatal signal in the debugger and force it to dump its core.
22395 This is supported only on systems which support aborting a program
22396 with the @code{SIGQUIT} signal.
22398 @kindex maint internal-error
22399 @kindex maint internal-warning
22400 @item maint internal-error @r{[}@var{message-text}@r{]}
22401 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
22402 Cause @value{GDBN} to call the internal function @code{internal_error}
22403 or @code{internal_warning} and hence behave as though an internal error
22404 or internal warning has been detected. In addition to reporting the
22405 internal problem, these functions give the user the opportunity to
22406 either quit @value{GDBN} or create a core file of the current
22407 @value{GDBN} session.
22409 These commands take an optional parameter @var{message-text} that is
22410 used as the text of the error or warning message.
22412 Here's an example of using @code{internal-error}:
22415 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
22416 @dots{}/maint.c:121: internal-error: testing, 1, 2
22417 A problem internal to GDB has been detected. Further
22418 debugging may prove unreliable.
22419 Quit this debugging session? (y or n) @kbd{n}
22420 Create a core file? (y or n) @kbd{n}
22424 @kindex maint packet
22425 @item maint packet @var{text}
22426 If @value{GDBN} is talking to an inferior via the serial protocol,
22427 then this command sends the string @var{text} to the inferior, and
22428 displays the response packet. @value{GDBN} supplies the initial
22429 @samp{$} character, the terminating @samp{#} character, and the
22432 @kindex maint print architecture
22433 @item maint print architecture @r{[}@var{file}@r{]}
22434 Print the entire architecture configuration. The optional argument
22435 @var{file} names the file where the output goes.
22437 @kindex maint print dummy-frames
22438 @item maint print dummy-frames
22439 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
22442 (@value{GDBP}) @kbd{b add}
22444 (@value{GDBP}) @kbd{print add(2,3)}
22445 Breakpoint 2, add (a=2, b=3) at @dots{}
22447 The program being debugged stopped while in a function called from GDB.
22449 (@value{GDBP}) @kbd{maint print dummy-frames}
22450 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
22451 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
22452 call_lo=0x01014000 call_hi=0x01014001
22456 Takes an optional file parameter.
22458 @kindex maint print registers
22459 @kindex maint print raw-registers
22460 @kindex maint print cooked-registers
22461 @kindex maint print register-groups
22462 @item maint print registers @r{[}@var{file}@r{]}
22463 @itemx maint print raw-registers @r{[}@var{file}@r{]}
22464 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
22465 @itemx maint print register-groups @r{[}@var{file}@r{]}
22466 Print @value{GDBN}'s internal register data structures.
22468 The command @code{maint print raw-registers} includes the contents of
22469 the raw register cache; the command @code{maint print cooked-registers}
22470 includes the (cooked) value of all registers; and the command
22471 @code{maint print register-groups} includes the groups that each
22472 register is a member of. @xref{Registers,, Registers, gdbint,
22473 @value{GDBN} Internals}.
22475 These commands take an optional parameter, a file name to which to
22476 write the information.
22478 @kindex maint print reggroups
22479 @item maint print reggroups @r{[}@var{file}@r{]}
22480 Print @value{GDBN}'s internal register group data structures. The
22481 optional argument @var{file} tells to what file to write the
22484 The register groups info looks like this:
22487 (@value{GDBP}) @kbd{maint print reggroups}
22500 This command forces @value{GDBN} to flush its internal register cache.
22502 @kindex maint print objfiles
22503 @cindex info for known object files
22504 @item maint print objfiles
22505 Print a dump of all known object files. For each object file, this
22506 command prints its name, address in memory, and all of its psymtabs
22509 @kindex maint print statistics
22510 @cindex bcache statistics
22511 @item maint print statistics
22512 This command prints, for each object file in the program, various data
22513 about that object file followed by the byte cache (@dfn{bcache})
22514 statistics for the object file. The objfile data includes the number
22515 of minimal, partial, full, and stabs symbols, the number of types
22516 defined by the objfile, the number of as yet unexpanded psym tables,
22517 the number of line tables and string tables, and the amount of memory
22518 used by the various tables. The bcache statistics include the counts,
22519 sizes, and counts of duplicates of all and unique objects, max,
22520 average, and median entry size, total memory used and its overhead and
22521 savings, and various measures of the hash table size and chain
22524 @kindex maint print target-stack
22525 @cindex target stack description
22526 @item maint print target-stack
22527 A @dfn{target} is an interface between the debugger and a particular
22528 kind of file or process. Targets can be stacked in @dfn{strata},
22529 so that more than one target can potentially respond to a request.
22530 In particular, memory accesses will walk down the stack of targets
22531 until they find a target that is interested in handling that particular
22534 This command prints a short description of each layer that was pushed on
22535 the @dfn{target stack}, starting from the top layer down to the bottom one.
22537 @kindex maint print type
22538 @cindex type chain of a data type
22539 @item maint print type @var{expr}
22540 Print the type chain for a type specified by @var{expr}. The argument
22541 can be either a type name or a symbol. If it is a symbol, the type of
22542 that symbol is described. The type chain produced by this command is
22543 a recursive definition of the data type as stored in @value{GDBN}'s
22544 data structures, including its flags and contained types.
22546 @kindex maint set dwarf2 max-cache-age
22547 @kindex maint show dwarf2 max-cache-age
22548 @item maint set dwarf2 max-cache-age
22549 @itemx maint show dwarf2 max-cache-age
22550 Control the DWARF 2 compilation unit cache.
22552 @cindex DWARF 2 compilation units cache
22553 In object files with inter-compilation-unit references, such as those
22554 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
22555 reader needs to frequently refer to previously read compilation units.
22556 This setting controls how long a compilation unit will remain in the
22557 cache if it is not referenced. A higher limit means that cached
22558 compilation units will be stored in memory longer, and more total
22559 memory will be used. Setting it to zero disables caching, which will
22560 slow down @value{GDBN} startup, but reduce memory consumption.
22562 @kindex maint set profile
22563 @kindex maint show profile
22564 @cindex profiling GDB
22565 @item maint set profile
22566 @itemx maint show profile
22567 Control profiling of @value{GDBN}.
22569 Profiling will be disabled until you use the @samp{maint set profile}
22570 command to enable it. When you enable profiling, the system will begin
22571 collecting timing and execution count data; when you disable profiling or
22572 exit @value{GDBN}, the results will be written to a log file. Remember that
22573 if you use profiling, @value{GDBN} will overwrite the profiling log file
22574 (often called @file{gmon.out}). If you have a record of important profiling
22575 data in a @file{gmon.out} file, be sure to move it to a safe location.
22577 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
22578 compiled with the @samp{-pg} compiler option.
22580 @kindex maint show-debug-regs
22581 @cindex x86 hardware debug registers
22582 @item maint show-debug-regs
22583 Control whether to show variables that mirror the x86 hardware debug
22584 registers. Use @code{ON} to enable, @code{OFF} to disable. If
22585 enabled, the debug registers values are shown when @value{GDBN} inserts or
22586 removes a hardware breakpoint or watchpoint, and when the inferior
22587 triggers a hardware-assisted breakpoint or watchpoint.
22589 @kindex maint space
22590 @cindex memory used by commands
22592 Control whether to display memory usage for each command. If set to a
22593 nonzero value, @value{GDBN} will display how much memory each command
22594 took, following the command's own output. This can also be requested
22595 by invoking @value{GDBN} with the @option{--statistics} command-line
22596 switch (@pxref{Mode Options}).
22599 @cindex time of command execution
22601 Control whether to display the execution time for each command. If
22602 set to a nonzero value, @value{GDBN} will display how much time it
22603 took to execute each command, following the command's own output.
22604 This can also be requested by invoking @value{GDBN} with the
22605 @option{--statistics} command-line switch (@pxref{Mode Options}).
22607 @kindex maint translate-address
22608 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
22609 Find the symbol stored at the location specified by the address
22610 @var{addr} and an optional section name @var{section}. If found,
22611 @value{GDBN} prints the name of the closest symbol and an offset from
22612 the symbol's location to the specified address. This is similar to
22613 the @code{info address} command (@pxref{Symbols}), except that this
22614 command also allows to find symbols in other sections.
22618 The following command is useful for non-interactive invocations of
22619 @value{GDBN}, such as in the test suite.
22622 @item set watchdog @var{nsec}
22623 @kindex set watchdog
22624 @cindex watchdog timer
22625 @cindex timeout for commands
22626 Set the maximum number of seconds @value{GDBN} will wait for the
22627 target operation to finish. If this time expires, @value{GDBN}
22628 reports and error and the command is aborted.
22630 @item show watchdog
22631 Show the current setting of the target wait timeout.
22634 @node Remote Protocol
22635 @appendix @value{GDBN} Remote Serial Protocol
22640 * Stop Reply Packets::
22641 * General Query Packets::
22642 * Register Packet Format::
22643 * Tracepoint Packets::
22646 * File-I/O Remote Protocol Extension::
22647 * Library List Format::
22648 * Memory Map Format::
22654 There may be occasions when you need to know something about the
22655 protocol---for example, if there is only one serial port to your target
22656 machine, you might want your program to do something special if it
22657 recognizes a packet meant for @value{GDBN}.
22659 In the examples below, @samp{->} and @samp{<-} are used to indicate
22660 transmitted and received data, respectively.
22662 @cindex protocol, @value{GDBN} remote serial
22663 @cindex serial protocol, @value{GDBN} remote
22664 @cindex remote serial protocol
22665 All @value{GDBN} commands and responses (other than acknowledgments) are
22666 sent as a @var{packet}. A @var{packet} is introduced with the character
22667 @samp{$}, the actual @var{packet-data}, and the terminating character
22668 @samp{#} followed by a two-digit @var{checksum}:
22671 @code{$}@var{packet-data}@code{#}@var{checksum}
22675 @cindex checksum, for @value{GDBN} remote
22677 The two-digit @var{checksum} is computed as the modulo 256 sum of all
22678 characters between the leading @samp{$} and the trailing @samp{#} (an
22679 eight bit unsigned checksum).
22681 Implementors should note that prior to @value{GDBN} 5.0 the protocol
22682 specification also included an optional two-digit @var{sequence-id}:
22685 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
22688 @cindex sequence-id, for @value{GDBN} remote
22690 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
22691 has never output @var{sequence-id}s. Stubs that handle packets added
22692 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
22694 @cindex acknowledgment, for @value{GDBN} remote
22695 When either the host or the target machine receives a packet, the first
22696 response expected is an acknowledgment: either @samp{+} (to indicate
22697 the package was received correctly) or @samp{-} (to request
22701 -> @code{$}@var{packet-data}@code{#}@var{checksum}
22706 The host (@value{GDBN}) sends @var{command}s, and the target (the
22707 debugging stub incorporated in your program) sends a @var{response}. In
22708 the case of step and continue @var{command}s, the response is only sent
22709 when the operation has completed (the target has again stopped).
22711 @var{packet-data} consists of a sequence of characters with the
22712 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
22715 @cindex remote protocol, field separator
22716 Fields within the packet should be separated using @samp{,} @samp{;} or
22717 @samp{:}. Except where otherwise noted all numbers are represented in
22718 @sc{hex} with leading zeros suppressed.
22720 Implementors should note that prior to @value{GDBN} 5.0, the character
22721 @samp{:} could not appear as the third character in a packet (as it
22722 would potentially conflict with the @var{sequence-id}).
22724 @cindex remote protocol, binary data
22725 @anchor{Binary Data}
22726 Binary data in most packets is encoded either as two hexadecimal
22727 digits per byte of binary data. This allowed the traditional remote
22728 protocol to work over connections which were only seven-bit clean.
22729 Some packets designed more recently assume an eight-bit clean
22730 connection, and use a more efficient encoding to send and receive
22733 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
22734 as an escape character. Any escaped byte is transmitted as the escape
22735 character followed by the original character XORed with @code{0x20}.
22736 For example, the byte @code{0x7d} would be transmitted as the two
22737 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
22738 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
22739 @samp{@}}) must always be escaped. Responses sent by the stub
22740 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
22741 is not interpreted as the start of a run-length encoded sequence
22744 Response @var{data} can be run-length encoded to save space. A @samp{*}
22745 means that the next character is an @sc{ascii} encoding giving a repeat count
22746 which stands for that many repetitions of the character preceding the
22747 @samp{*}. The encoding is @code{n+29}, yielding a printable character
22748 where @code{n >=3} (which is where rle starts to win). The printable
22749 characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric
22750 value greater than 126 should not be used.
22757 means the same as "0000".
22759 The error response returned for some packets includes a two character
22760 error number. That number is not well defined.
22762 @cindex empty response, for unsupported packets
22763 For any @var{command} not supported by the stub, an empty response
22764 (@samp{$#00}) should be returned. That way it is possible to extend the
22765 protocol. A newer @value{GDBN} can tell if a packet is supported based
22768 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
22769 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
22775 The following table provides a complete list of all currently defined
22776 @var{command}s and their corresponding response @var{data}.
22777 @xref{File-I/O Remote Protocol Extension}, for details about the File
22778 I/O extension of the remote protocol.
22780 Each packet's description has a template showing the packet's overall
22781 syntax, followed by an explanation of the packet's meaning. We
22782 include spaces in some of the templates for clarity; these are not
22783 part of the packet's syntax. No @value{GDBN} packet uses spaces to
22784 separate its components. For example, a template like @samp{foo
22785 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
22786 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
22787 @var{baz}. @value{GDBN} does not transmit a space character between the
22788 @samp{foo} and the @var{bar}, or between the @var{bar} and the
22791 Note that all packet forms beginning with an upper- or lower-case
22792 letter, other than those described here, are reserved for future use.
22794 Here are the packet descriptions.
22799 @cindex @samp{!} packet
22800 Enable extended mode. In extended mode, the remote server is made
22801 persistent. The @samp{R} packet is used to restart the program being
22807 The remote target both supports and has enabled extended mode.
22811 @cindex @samp{?} packet
22812 Indicate the reason the target halted. The reply is the same as for
22816 @xref{Stop Reply Packets}, for the reply specifications.
22818 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
22819 @cindex @samp{A} packet
22820 Initialized @code{argv[]} array passed into program. @var{arglen}
22821 specifies the number of bytes in the hex encoded byte stream
22822 @var{arg}. See @code{gdbserver} for more details.
22827 The arguments were set.
22833 @cindex @samp{b} packet
22834 (Don't use this packet; its behavior is not well-defined.)
22835 Change the serial line speed to @var{baud}.
22837 JTC: @emph{When does the transport layer state change? When it's
22838 received, or after the ACK is transmitted. In either case, there are
22839 problems if the command or the acknowledgment packet is dropped.}
22841 Stan: @emph{If people really wanted to add something like this, and get
22842 it working for the first time, they ought to modify ser-unix.c to send
22843 some kind of out-of-band message to a specially-setup stub and have the
22844 switch happen "in between" packets, so that from remote protocol's point
22845 of view, nothing actually happened.}
22847 @item B @var{addr},@var{mode}
22848 @cindex @samp{B} packet
22849 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
22850 breakpoint at @var{addr}.
22852 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
22853 (@pxref{insert breakpoint or watchpoint packet}).
22855 @item c @r{[}@var{addr}@r{]}
22856 @cindex @samp{c} packet
22857 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
22858 resume at current address.
22861 @xref{Stop Reply Packets}, for the reply specifications.
22863 @item C @var{sig}@r{[};@var{addr}@r{]}
22864 @cindex @samp{C} packet
22865 Continue with signal @var{sig} (hex signal number). If
22866 @samp{;@var{addr}} is omitted, resume at same address.
22869 @xref{Stop Reply Packets}, for the reply specifications.
22872 @cindex @samp{d} packet
22875 Don't use this packet; instead, define a general set packet
22876 (@pxref{General Query Packets}).
22879 @cindex @samp{D} packet
22880 Detach @value{GDBN} from the remote system. Sent to the remote target
22881 before @value{GDBN} disconnects via the @code{detach} command.
22891 @item F @var{RC},@var{EE},@var{CF};@var{XX}
22892 @cindex @samp{F} packet
22893 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
22894 This is part of the File-I/O protocol extension. @xref{File-I/O
22895 Remote Protocol Extension}, for the specification.
22898 @anchor{read registers packet}
22899 @cindex @samp{g} packet
22900 Read general registers.
22904 @item @var{XX@dots{}}
22905 Each byte of register data is described by two hex digits. The bytes
22906 with the register are transmitted in target byte order. The size of
22907 each register and their position within the @samp{g} packet are
22908 determined by the @value{GDBN} internal gdbarch functions
22909 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
22910 specification of several standard @samp{g} packets is specified below.
22915 @item G @var{XX@dots{}}
22916 @cindex @samp{G} packet
22917 Write general registers. @xref{read registers packet}, for a
22918 description of the @var{XX@dots{}} data.
22928 @item H @var{c} @var{t}
22929 @cindex @samp{H} packet
22930 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
22931 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
22932 should be @samp{c} for step and continue operations, @samp{g} for other
22933 operations. The thread designator @var{t} may be @samp{-1}, meaning all
22934 the threads, a thread number, or @samp{0} which means pick any thread.
22945 @c 'H': How restrictive (or permissive) is the thread model. If a
22946 @c thread is selected and stopped, are other threads allowed
22947 @c to continue to execute? As I mentioned above, I think the
22948 @c semantics of each command when a thread is selected must be
22949 @c described. For example:
22951 @c 'g': If the stub supports threads and a specific thread is
22952 @c selected, returns the register block from that thread;
22953 @c otherwise returns current registers.
22955 @c 'G' If the stub supports threads and a specific thread is
22956 @c selected, sets the registers of the register block of
22957 @c that thread; otherwise sets current registers.
22959 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
22960 @anchor{cycle step packet}
22961 @cindex @samp{i} packet
22962 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
22963 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
22964 step starting at that address.
22967 @cindex @samp{I} packet
22968 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
22972 @cindex @samp{k} packet
22975 FIXME: @emph{There is no description of how to operate when a specific
22976 thread context has been selected (i.e.@: does 'k' kill only that
22979 @item m @var{addr},@var{length}
22980 @cindex @samp{m} packet
22981 Read @var{length} bytes of memory starting at address @var{addr}.
22982 Note that @var{addr} may not be aligned to any particular boundary.
22984 The stub need not use any particular size or alignment when gathering
22985 data from memory for the response; even if @var{addr} is word-aligned
22986 and @var{length} is a multiple of the word size, the stub is free to
22987 use byte accesses, or not. For this reason, this packet may not be
22988 suitable for accessing memory-mapped I/O devices.
22989 @cindex alignment of remote memory accesses
22990 @cindex size of remote memory accesses
22991 @cindex memory, alignment and size of remote accesses
22995 @item @var{XX@dots{}}
22996 Memory contents; each byte is transmitted as a two-digit hexadecimal
22997 number. The reply may contain fewer bytes than requested if the
22998 server was able to read only part of the region of memory.
23003 @item M @var{addr},@var{length}:@var{XX@dots{}}
23004 @cindex @samp{M} packet
23005 Write @var{length} bytes of memory starting at address @var{addr}.
23006 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
23007 hexadecimal number.
23014 for an error (this includes the case where only part of the data was
23019 @cindex @samp{p} packet
23020 Read the value of register @var{n}; @var{n} is in hex.
23021 @xref{read registers packet}, for a description of how the returned
23022 register value is encoded.
23026 @item @var{XX@dots{}}
23027 the register's value
23031 Indicating an unrecognized @var{query}.
23034 @item P @var{n@dots{}}=@var{r@dots{}}
23035 @anchor{write register packet}
23036 @cindex @samp{P} packet
23037 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
23038 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
23039 digits for each byte in the register (target byte order).
23049 @item q @var{name} @var{params}@dots{}
23050 @itemx Q @var{name} @var{params}@dots{}
23051 @cindex @samp{q} packet
23052 @cindex @samp{Q} packet
23053 General query (@samp{q}) and set (@samp{Q}). These packets are
23054 described fully in @ref{General Query Packets}.
23057 @cindex @samp{r} packet
23058 Reset the entire system.
23060 Don't use this packet; use the @samp{R} packet instead.
23063 @cindex @samp{R} packet
23064 Restart the program being debugged. @var{XX}, while needed, is ignored.
23065 This packet is only available in extended mode.
23067 The @samp{R} packet has no reply.
23069 @item s @r{[}@var{addr}@r{]}
23070 @cindex @samp{s} packet
23071 Single step. @var{addr} is the address at which to resume. If
23072 @var{addr} is omitted, resume at same address.
23075 @xref{Stop Reply Packets}, for the reply specifications.
23077 @item S @var{sig}@r{[};@var{addr}@r{]}
23078 @anchor{step with signal packet}
23079 @cindex @samp{S} packet
23080 Step with signal. This is analogous to the @samp{C} packet, but
23081 requests a single-step, rather than a normal resumption of execution.
23084 @xref{Stop Reply Packets}, for the reply specifications.
23086 @item t @var{addr}:@var{PP},@var{MM}
23087 @cindex @samp{t} packet
23088 Search backwards starting at address @var{addr} for a match with pattern
23089 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
23090 @var{addr} must be at least 3 digits.
23093 @cindex @samp{T} packet
23094 Find out if the thread XX is alive.
23099 thread is still alive
23105 Packets starting with @samp{v} are identified by a multi-letter name,
23106 up to the first @samp{;} or @samp{?} (or the end of the packet).
23108 @item vCont@r{[};@var{action}@r{[}:@var{tid}@r{]]}@dots{}
23109 @cindex @samp{vCont} packet
23110 Resume the inferior, specifying different actions for each thread.
23111 If an action is specified with no @var{tid}, then it is applied to any
23112 threads that don't have a specific action specified; if no default action is
23113 specified then other threads should remain stopped. Specifying multiple
23114 default actions is an error; specifying no actions is also an error.
23115 Thread IDs are specified in hexadecimal. Currently supported actions are:
23121 Continue with signal @var{sig}. @var{sig} should be two hex digits.
23125 Step with signal @var{sig}. @var{sig} should be two hex digits.
23128 The optional @var{addr} argument normally associated with these packets is
23129 not supported in @samp{vCont}.
23132 @xref{Stop Reply Packets}, for the reply specifications.
23135 @cindex @samp{vCont?} packet
23136 Request a list of actions supported by the @samp{vCont} packet.
23140 @item vCont@r{[};@var{action}@dots{}@r{]}
23141 The @samp{vCont} packet is supported. Each @var{action} is a supported
23142 command in the @samp{vCont} packet.
23144 The @samp{vCont} packet is not supported.
23147 @item vFlashErase:@var{addr},@var{length}
23148 @cindex @samp{vFlashErase} packet
23149 Direct the stub to erase @var{length} bytes of flash starting at
23150 @var{addr}. The region may enclose any number of flash blocks, but
23151 its start and end must fall on block boundaries, as indicated by the
23152 flash block size appearing in the memory map (@pxref{Memory Map
23153 Format}). @value{GDBN} groups flash memory programming operations
23154 together, and sends a @samp{vFlashDone} request after each group; the
23155 stub is allowed to delay erase operation until the @samp{vFlashDone}
23156 packet is received.
23166 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
23167 @cindex @samp{vFlashWrite} packet
23168 Direct the stub to write data to flash address @var{addr}. The data
23169 is passed in binary form using the same encoding as for the @samp{X}
23170 packet (@pxref{Binary Data}). The memory ranges specified by
23171 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
23172 not overlap, and must appear in order of increasing addresses
23173 (although @samp{vFlashErase} packets for higher addresses may already
23174 have been received; the ordering is guaranteed only between
23175 @samp{vFlashWrite} packets). If a packet writes to an address that was
23176 neither erased by a preceding @samp{vFlashErase} packet nor by some other
23177 target-specific method, the results are unpredictable.
23185 for vFlashWrite addressing non-flash memory
23191 @cindex @samp{vFlashDone} packet
23192 Indicate to the stub that flash programming operation is finished.
23193 The stub is permitted to delay or batch the effects of a group of
23194 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
23195 @samp{vFlashDone} packet is received. The contents of the affected
23196 regions of flash memory are unpredictable until the @samp{vFlashDone}
23197 request is completed.
23199 @item X @var{addr},@var{length}:@var{XX@dots{}}
23201 @cindex @samp{X} packet
23202 Write data to memory, where the data is transmitted in binary.
23203 @var{addr} is address, @var{length} is number of bytes,
23204 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
23214 @item z @var{type},@var{addr},@var{length}
23215 @itemx Z @var{type},@var{addr},@var{length}
23216 @anchor{insert breakpoint or watchpoint packet}
23217 @cindex @samp{z} packet
23218 @cindex @samp{Z} packets
23219 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
23220 watchpoint starting at address @var{address} and covering the next
23221 @var{length} bytes.
23223 Each breakpoint and watchpoint packet @var{type} is documented
23226 @emph{Implementation notes: A remote target shall return an empty string
23227 for an unrecognized breakpoint or watchpoint packet @var{type}. A
23228 remote target shall support either both or neither of a given
23229 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
23230 avoid potential problems with duplicate packets, the operations should
23231 be implemented in an idempotent way.}
23233 @item z0,@var{addr},@var{length}
23234 @itemx Z0,@var{addr},@var{length}
23235 @cindex @samp{z0} packet
23236 @cindex @samp{Z0} packet
23237 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
23238 @var{addr} of size @var{length}.
23240 A memory breakpoint is implemented by replacing the instruction at
23241 @var{addr} with a software breakpoint or trap instruction. The
23242 @var{length} is used by targets that indicates the size of the
23243 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
23244 @sc{mips} can insert either a 2 or 4 byte breakpoint).
23246 @emph{Implementation note: It is possible for a target to copy or move
23247 code that contains memory breakpoints (e.g., when implementing
23248 overlays). The behavior of this packet, in the presence of such a
23249 target, is not defined.}
23261 @item z1,@var{addr},@var{length}
23262 @itemx Z1,@var{addr},@var{length}
23263 @cindex @samp{z1} packet
23264 @cindex @samp{Z1} packet
23265 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
23266 address @var{addr} of size @var{length}.
23268 A hardware breakpoint is implemented using a mechanism that is not
23269 dependant on being able to modify the target's memory.
23271 @emph{Implementation note: A hardware breakpoint is not affected by code
23284 @item z2,@var{addr},@var{length}
23285 @itemx Z2,@var{addr},@var{length}
23286 @cindex @samp{z2} packet
23287 @cindex @samp{Z2} packet
23288 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint.
23300 @item z3,@var{addr},@var{length}
23301 @itemx Z3,@var{addr},@var{length}
23302 @cindex @samp{z3} packet
23303 @cindex @samp{Z3} packet
23304 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint.
23316 @item z4,@var{addr},@var{length}
23317 @itemx Z4,@var{addr},@var{length}
23318 @cindex @samp{z4} packet
23319 @cindex @samp{Z4} packet
23320 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint.
23334 @node Stop Reply Packets
23335 @section Stop Reply Packets
23336 @cindex stop reply packets
23338 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
23339 receive any of the below as a reply. In the case of the @samp{C},
23340 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
23341 when the target halts. In the below the exact meaning of @dfn{signal
23342 number} is defined by the header @file{include/gdb/signals.h} in the
23343 @value{GDBN} source code.
23345 As in the description of request packets, we include spaces in the
23346 reply templates for clarity; these are not part of the reply packet's
23347 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
23353 The program received signal number @var{AA} (a two-digit hexadecimal
23354 number). This is equivalent to a @samp{T} response with no
23355 @var{n}:@var{r} pairs.
23357 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
23358 @cindex @samp{T} packet reply
23359 The program received signal number @var{AA} (a two-digit hexadecimal
23360 number). This is equivalent to an @samp{S} response, except that the
23361 @samp{@var{n}:@var{r}} pairs can carry values of important registers
23362 and other information directly in the stop reply packet, reducing
23363 round-trip latency. Single-step and breakpoint traps are reported
23364 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
23368 If @var{n} is a hexadecimal number, it is a register number, and the
23369 corresponding @var{r} gives that register's value. @var{r} is a
23370 series of bytes in target byte order, with each byte given by a
23371 two-digit hex number.
23374 If @var{n} is @samp{thread}, then @var{r} is the thread process ID, in
23378 If @var{n} is a recognized @dfn{stop reason}, it describes a more
23379 specific event that stopped the target. The currently defined stop
23380 reasons are listed below. @var{aa} should be @samp{05}, the trap
23381 signal. At most one stop reason should be present.
23384 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
23385 and go on to the next; this allows us to extend the protocol in the
23389 The currently defined stop reasons are:
23395 The packet indicates a watchpoint hit, and @var{r} is the data address, in
23398 @cindex shared library events, remote reply
23400 The packet indicates that the loaded libraries have changed.
23401 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
23402 list of loaded libraries. @var{r} is ignored.
23406 The process exited, and @var{AA} is the exit status. This is only
23407 applicable to certain targets.
23410 The process terminated with signal @var{AA}.
23412 @item O @var{XX}@dots{}
23413 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
23414 written as the program's console output. This can happen at any time
23415 while the program is running and the debugger should continue to wait
23416 for @samp{W}, @samp{T}, etc.
23418 @item F @var{call-id},@var{parameter}@dots{}
23419 @var{call-id} is the identifier which says which host system call should
23420 be called. This is just the name of the function. Translation into the
23421 correct system call is only applicable as it's defined in @value{GDBN}.
23422 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
23425 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
23426 this very system call.
23428 The target replies with this packet when it expects @value{GDBN} to
23429 call a host system call on behalf of the target. @value{GDBN} replies
23430 with an appropriate @samp{F} packet and keeps up waiting for the next
23431 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
23432 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
23433 Protocol Extension}, for more details.
23437 @node General Query Packets
23438 @section General Query Packets
23439 @cindex remote query requests
23441 Packets starting with @samp{q} are @dfn{general query packets};
23442 packets starting with @samp{Q} are @dfn{general set packets}. General
23443 query and set packets are a semi-unified form for retrieving and
23444 sending information to and from the stub.
23446 The initial letter of a query or set packet is followed by a name
23447 indicating what sort of thing the packet applies to. For example,
23448 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
23449 definitions with the stub. These packet names follow some
23454 The name must not contain commas, colons or semicolons.
23456 Most @value{GDBN} query and set packets have a leading upper case
23459 The names of custom vendor packets should use a company prefix, in
23460 lower case, followed by a period. For example, packets designed at
23461 the Acme Corporation might begin with @samp{qacme.foo} (for querying
23462 foos) or @samp{Qacme.bar} (for setting bars).
23465 The name of a query or set packet should be separated from any
23466 parameters by a @samp{:}; the parameters themselves should be
23467 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
23468 full packet name, and check for a separator or the end of the packet,
23469 in case two packet names share a common prefix. New packets should not begin
23470 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
23471 packets predate these conventions, and have arguments without any terminator
23472 for the packet name; we suspect they are in widespread use in places that
23473 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
23474 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
23477 Like the descriptions of the other packets, each description here
23478 has a template showing the packet's overall syntax, followed by an
23479 explanation of the packet's meaning. We include spaces in some of the
23480 templates for clarity; these are not part of the packet's syntax. No
23481 @value{GDBN} packet uses spaces to separate its components.
23483 Here are the currently defined query and set packets:
23488 @cindex current thread, remote request
23489 @cindex @samp{qC} packet
23490 Return the current thread id.
23495 Where @var{pid} is an unsigned hexadecimal process id.
23496 @item @r{(anything else)}
23497 Any other reply implies the old pid.
23500 @item qCRC:@var{addr},@var{length}
23501 @cindex CRC of memory block, remote request
23502 @cindex @samp{qCRC} packet
23503 Compute the CRC checksum of a block of memory.
23507 An error (such as memory fault)
23508 @item C @var{crc32}
23509 The specified memory region's checksum is @var{crc32}.
23513 @itemx qsThreadInfo
23514 @cindex list active threads, remote request
23515 @cindex @samp{qfThreadInfo} packet
23516 @cindex @samp{qsThreadInfo} packet
23517 Obtain a list of all active thread ids from the target (OS). Since there
23518 may be too many active threads to fit into one reply packet, this query
23519 works iteratively: it may require more than one query/reply sequence to
23520 obtain the entire list of threads. The first query of the sequence will
23521 be the @samp{qfThreadInfo} query; subsequent queries in the
23522 sequence will be the @samp{qsThreadInfo} query.
23524 NOTE: This packet replaces the @samp{qL} query (see below).
23530 @item m @var{id},@var{id}@dots{}
23531 a comma-separated list of thread ids
23533 (lower case letter @samp{L}) denotes end of list.
23536 In response to each query, the target will reply with a list of one or
23537 more thread ids, in big-endian unsigned hex, separated by commas.
23538 @value{GDBN} will respond to each reply with a request for more thread
23539 ids (using the @samp{qs} form of the query), until the target responds
23540 with @samp{l} (lower-case el, for @dfn{last}).
23542 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
23543 @cindex get thread-local storage address, remote request
23544 @cindex @samp{qGetTLSAddr} packet
23545 Fetch the address associated with thread local storage specified
23546 by @var{thread-id}, @var{offset}, and @var{lm}.
23548 @var{thread-id} is the (big endian, hex encoded) thread id associated with the
23549 thread for which to fetch the TLS address.
23551 @var{offset} is the (big endian, hex encoded) offset associated with the
23552 thread local variable. (This offset is obtained from the debug
23553 information associated with the variable.)
23555 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
23556 the load module associated with the thread local storage. For example,
23557 a @sc{gnu}/Linux system will pass the link map address of the shared
23558 object associated with the thread local storage under consideration.
23559 Other operating environments may choose to represent the load module
23560 differently, so the precise meaning of this parameter will vary.
23564 @item @var{XX}@dots{}
23565 Hex encoded (big endian) bytes representing the address of the thread
23566 local storage requested.
23569 An error occurred. @var{nn} are hex digits.
23572 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
23575 @item qL @var{startflag} @var{threadcount} @var{nextthread}
23576 Obtain thread information from RTOS. Where: @var{startflag} (one hex
23577 digit) is one to indicate the first query and zero to indicate a
23578 subsequent query; @var{threadcount} (two hex digits) is the maximum
23579 number of threads the response packet can contain; and @var{nextthread}
23580 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
23581 returned in the response as @var{argthread}.
23583 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
23587 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
23588 Where: @var{count} (two hex digits) is the number of threads being
23589 returned; @var{done} (one hex digit) is zero to indicate more threads
23590 and one indicates no further threads; @var{argthreadid} (eight hex
23591 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
23592 is a sequence of thread IDs from the target. @var{threadid} (eight hex
23593 digits). See @code{remote.c:parse_threadlist_response()}.
23597 @cindex section offsets, remote request
23598 @cindex @samp{qOffsets} packet
23599 Get section offsets that the target used when relocating the downloaded
23604 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
23605 Relocate the @code{Text} section by @var{xxx} from its original address.
23606 Relocate the @code{Data} section by @var{yyy} from its original address.
23607 If the object file format provides segment information (e.g.@: @sc{elf}
23608 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
23609 segments by the supplied offsets.
23611 @emph{Note: while a @code{Bss} offset may be included in the response,
23612 @value{GDBN} ignores this and instead applies the @code{Data} offset
23613 to the @code{Bss} section.}
23615 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
23616 Relocate the first segment of the object file, which conventionally
23617 contains program code, to a starting address of @var{xxx}. If
23618 @samp{DataSeg} is specified, relocate the second segment, which
23619 conventionally contains modifiable data, to a starting address of
23620 @var{yyy}. @value{GDBN} will report an error if the object file
23621 does not contain segment information, or does not contain at least
23622 as many segments as mentioned in the reply. Extra segments are
23623 kept at fixed offsets relative to the last relocated segment.
23626 @item qP @var{mode} @var{threadid}
23627 @cindex thread information, remote request
23628 @cindex @samp{qP} packet
23629 Returns information on @var{threadid}. Where: @var{mode} is a hex
23630 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
23632 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
23635 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
23637 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
23638 @cindex pass signals to inferior, remote request
23639 @cindex @samp{QPassSignals} packet
23640 @anchor{QPassSignals}
23641 Each listed @var{signal} should be passed directly to the inferior process.
23642 Signals are numbered identically to continue packets and stop replies
23643 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
23644 strictly greater than the previous item. These signals do not need to stop
23645 the inferior, or be reported to @value{GDBN}. All other signals should be
23646 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
23647 combine; any earlier @samp{QPassSignals} list is completely replaced by the
23648 new list. This packet improves performance when using @samp{handle
23649 @var{signal} nostop noprint pass}.
23654 The request succeeded.
23657 An error occurred. @var{nn} are hex digits.
23660 An empty reply indicates that @samp{QPassSignals} is not supported by
23664 Use of this packet is controlled by the @code{set remote pass-signals}
23665 command (@pxref{Remote Configuration, set remote pass-signals}).
23666 This packet is not probed by default; the remote stub must request it,
23667 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
23669 @item qRcmd,@var{command}
23670 @cindex execute remote command, remote request
23671 @cindex @samp{qRcmd} packet
23672 @var{command} (hex encoded) is passed to the local interpreter for
23673 execution. Invalid commands should be reported using the output
23674 string. Before the final result packet, the target may also respond
23675 with a number of intermediate @samp{O@var{output}} console output
23676 packets. @emph{Implementors should note that providing access to a
23677 stubs's interpreter may have security implications}.
23682 A command response with no output.
23684 A command response with the hex encoded output string @var{OUTPUT}.
23686 Indicate a badly formed request.
23688 An empty reply indicates that @samp{qRcmd} is not recognized.
23691 (Note that the @code{qRcmd} packet's name is separated from the
23692 command by a @samp{,}, not a @samp{:}, contrary to the naming
23693 conventions above. Please don't use this packet as a model for new
23696 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
23697 @cindex supported packets, remote query
23698 @cindex features of the remote protocol
23699 @cindex @samp{qSupported} packet
23700 @anchor{qSupported}
23701 Tell the remote stub about features supported by @value{GDBN}, and
23702 query the stub for features it supports. This packet allows
23703 @value{GDBN} and the remote stub to take advantage of each others'
23704 features. @samp{qSupported} also consolidates multiple feature probes
23705 at startup, to improve @value{GDBN} performance---a single larger
23706 packet performs better than multiple smaller probe packets on
23707 high-latency links. Some features may enable behavior which must not
23708 be on by default, e.g.@: because it would confuse older clients or
23709 stubs. Other features may describe packets which could be
23710 automatically probed for, but are not. These features must be
23711 reported before @value{GDBN} will use them. This ``default
23712 unsupported'' behavior is not appropriate for all packets, but it
23713 helps to keep the initial connection time under control with new
23714 versions of @value{GDBN} which support increasing numbers of packets.
23718 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
23719 The stub supports or does not support each returned @var{stubfeature},
23720 depending on the form of each @var{stubfeature} (see below for the
23723 An empty reply indicates that @samp{qSupported} is not recognized,
23724 or that no features needed to be reported to @value{GDBN}.
23727 The allowed forms for each feature (either a @var{gdbfeature} in the
23728 @samp{qSupported} packet, or a @var{stubfeature} in the response)
23732 @item @var{name}=@var{value}
23733 The remote protocol feature @var{name} is supported, and associated
23734 with the specified @var{value}. The format of @var{value} depends
23735 on the feature, but it must not include a semicolon.
23737 The remote protocol feature @var{name} is supported, and does not
23738 need an associated value.
23740 The remote protocol feature @var{name} is not supported.
23742 The remote protocol feature @var{name} may be supported, and
23743 @value{GDBN} should auto-detect support in some other way when it is
23744 needed. This form will not be used for @var{gdbfeature} notifications,
23745 but may be used for @var{stubfeature} responses.
23748 Whenever the stub receives a @samp{qSupported} request, the
23749 supplied set of @value{GDBN} features should override any previous
23750 request. This allows @value{GDBN} to put the stub in a known
23751 state, even if the stub had previously been communicating with
23752 a different version of @value{GDBN}.
23754 No values of @var{gdbfeature} (for the packet sent by @value{GDBN})
23755 are defined yet. Stubs should ignore any unknown values for
23756 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
23757 packet supports receiving packets of unlimited length (earlier
23758 versions of @value{GDBN} may reject overly long responses). Values
23759 for @var{gdbfeature} may be defined in the future to let the stub take
23760 advantage of new features in @value{GDBN}, e.g.@: incompatible
23761 improvements in the remote protocol---support for unlimited length
23762 responses would be a @var{gdbfeature} example, if it were not implied by
23763 the @samp{qSupported} query. The stub's reply should be independent
23764 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
23765 describes all the features it supports, and then the stub replies with
23766 all the features it supports.
23768 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
23769 responses, as long as each response uses one of the standard forms.
23771 Some features are flags. A stub which supports a flag feature
23772 should respond with a @samp{+} form response. Other features
23773 require values, and the stub should respond with an @samp{=}
23776 Each feature has a default value, which @value{GDBN} will use if
23777 @samp{qSupported} is not available or if the feature is not mentioned
23778 in the @samp{qSupported} response. The default values are fixed; a
23779 stub is free to omit any feature responses that match the defaults.
23781 Not all features can be probed, but for those which can, the probing
23782 mechanism is useful: in some cases, a stub's internal
23783 architecture may not allow the protocol layer to know some information
23784 about the underlying target in advance. This is especially common in
23785 stubs which may be configured for multiple targets.
23787 These are the currently defined stub features and their properties:
23789 @multitable @columnfractions 0.35 0.2 0.12 0.2
23790 @c NOTE: The first row should be @headitem, but we do not yet require
23791 @c a new enough version of Texinfo (4.7) to use @headitem.
23793 @tab Value Required
23797 @item @samp{PacketSize}
23802 @item @samp{qXfer:auxv:read}
23807 @item @samp{qXfer:features:read}
23812 @item @samp{qXfer:libraries:read}
23817 @item @samp{qXfer:memory-map:read}
23822 @item @samp{qXfer:spu:read}
23827 @item @samp{qXfer:spu:write}
23832 @item @samp{QPassSignals}
23839 These are the currently defined stub features, in more detail:
23842 @cindex packet size, remote protocol
23843 @item PacketSize=@var{bytes}
23844 The remote stub can accept packets up to at least @var{bytes} in
23845 length. @value{GDBN} will send packets up to this size for bulk
23846 transfers, and will never send larger packets. This is a limit on the
23847 data characters in the packet, including the frame and checksum.
23848 There is no trailing NUL byte in a remote protocol packet; if the stub
23849 stores packets in a NUL-terminated format, it should allow an extra
23850 byte in its buffer for the NUL. If this stub feature is not supported,
23851 @value{GDBN} guesses based on the size of the @samp{g} packet response.
23853 @item qXfer:auxv:read
23854 The remote stub understands the @samp{qXfer:auxv:read} packet
23855 (@pxref{qXfer auxiliary vector read}).
23857 @item qXfer:features:read
23858 The remote stub understands the @samp{qXfer:features:read} packet
23859 (@pxref{qXfer target description read}).
23861 @item qXfer:libraries:read
23862 The remote stub understands the @samp{qXfer:libraries:read} packet
23863 (@pxref{qXfer library list read}).
23865 @item qXfer:memory-map:read
23866 The remote stub understands the @samp{qXfer:memory-map:read} packet
23867 (@pxref{qXfer memory map read}).
23869 @item qXfer:spu:read
23870 The remote stub understands the @samp{qXfer:spu:read} packet
23871 (@pxref{qXfer spu read}).
23873 @item qXfer:spu:write
23874 The remote stub understands the @samp{qXfer:spu:write} packet
23875 (@pxref{qXfer spu write}).
23878 The remote stub understands the @samp{QPassSignals} packet
23879 (@pxref{QPassSignals}).
23884 @cindex symbol lookup, remote request
23885 @cindex @samp{qSymbol} packet
23886 Notify the target that @value{GDBN} is prepared to serve symbol lookup
23887 requests. Accept requests from the target for the values of symbols.
23892 The target does not need to look up any (more) symbols.
23893 @item qSymbol:@var{sym_name}
23894 The target requests the value of symbol @var{sym_name} (hex encoded).
23895 @value{GDBN} may provide the value by using the
23896 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
23900 @item qSymbol:@var{sym_value}:@var{sym_name}
23901 Set the value of @var{sym_name} to @var{sym_value}.
23903 @var{sym_name} (hex encoded) is the name of a symbol whose value the
23904 target has previously requested.
23906 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
23907 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
23913 The target does not need to look up any (more) symbols.
23914 @item qSymbol:@var{sym_name}
23915 The target requests the value of a new symbol @var{sym_name} (hex
23916 encoded). @value{GDBN} will continue to supply the values of symbols
23917 (if available), until the target ceases to request them.
23922 @xref{Tracepoint Packets}.
23924 @item qThreadExtraInfo,@var{id}
23925 @cindex thread attributes info, remote request
23926 @cindex @samp{qThreadExtraInfo} packet
23927 Obtain a printable string description of a thread's attributes from
23928 the target OS. @var{id} is a thread-id in big-endian hex. This
23929 string may contain anything that the target OS thinks is interesting
23930 for @value{GDBN} to tell the user about the thread. The string is
23931 displayed in @value{GDBN}'s @code{info threads} display. Some
23932 examples of possible thread extra info strings are @samp{Runnable}, or
23933 @samp{Blocked on Mutex}.
23937 @item @var{XX}@dots{}
23938 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
23939 comprising the printable string containing the extra information about
23940 the thread's attributes.
23943 (Note that the @code{qThreadExtraInfo} packet's name is separated from
23944 the command by a @samp{,}, not a @samp{:}, contrary to the naming
23945 conventions above. Please don't use this packet as a model for new
23953 @xref{Tracepoint Packets}.
23955 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
23956 @cindex read special object, remote request
23957 @cindex @samp{qXfer} packet
23958 @anchor{qXfer read}
23959 Read uninterpreted bytes from the target's special data area
23960 identified by the keyword @var{object}. Request @var{length} bytes
23961 starting at @var{offset} bytes into the data. The content and
23962 encoding of @var{annex} is specific to @var{object}; it can supply
23963 additional details about what data to access.
23965 Here are the specific requests of this form defined so far. All
23966 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
23967 formats, listed below.
23970 @item qXfer:auxv:read::@var{offset},@var{length}
23971 @anchor{qXfer auxiliary vector read}
23972 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
23973 auxiliary vector}. Note @var{annex} must be empty.
23975 This packet is not probed by default; the remote stub must request it,
23976 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
23978 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
23979 @anchor{qXfer target description read}
23980 Access the @dfn{target description}. @xref{Target Descriptions}. The
23981 annex specifies which XML document to access. The main description is
23982 always loaded from the @samp{target.xml} annex.
23984 This packet is not probed by default; the remote stub must request it,
23985 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
23987 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
23988 @anchor{qXfer library list read}
23989 Access the target's list of loaded libraries. @xref{Library List Format}.
23990 The annex part of the generic @samp{qXfer} packet must be empty
23991 (@pxref{qXfer read}).
23993 Targets which maintain a list of libraries in the program's memory do
23994 not need to implement this packet; it is designed for platforms where
23995 the operating system manages the list of loaded libraries.
23997 This packet is not probed by default; the remote stub must request it,
23998 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24000 @item qXfer:memory-map:read::@var{offset},@var{length}
24001 @anchor{qXfer memory map read}
24002 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
24003 annex part of the generic @samp{qXfer} packet must be empty
24004 (@pxref{qXfer read}).
24006 This packet is not probed by default; the remote stub must request it,
24007 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24009 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
24010 @anchor{qXfer spu read}
24011 Read contents of an @code{spufs} file on the target system. The
24012 annex specifies which file to read; it must be of the form
24013 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
24014 in the target process, and @var{name} identifes the @code{spufs} file
24015 in that context to be accessed.
24017 This packet is not probed by default; the remote stub must request it,
24018 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24024 Data @var{data} (@pxref{Binary Data}) has been read from the
24025 target. There may be more data at a higher address (although
24026 it is permitted to return @samp{m} even for the last valid
24027 block of data, as long as at least one byte of data was read).
24028 @var{data} may have fewer bytes than the @var{length} in the
24032 Data @var{data} (@pxref{Binary Data}) has been read from the target.
24033 There is no more data to be read. @var{data} may have fewer bytes
24034 than the @var{length} in the request.
24037 The @var{offset} in the request is at the end of the data.
24038 There is no more data to be read.
24041 The request was malformed, or @var{annex} was invalid.
24044 The offset was invalid, or there was an error encountered reading the data.
24045 @var{nn} is a hex-encoded @code{errno} value.
24048 An empty reply indicates the @var{object} string was not recognized by
24049 the stub, or that the object does not support reading.
24052 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
24053 @cindex write data into object, remote request
24054 Write uninterpreted bytes into the target's special data area
24055 identified by the keyword @var{object}, starting at @var{offset} bytes
24056 into the data. @var{data}@dots{} is the binary-encoded data
24057 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
24058 is specific to @var{object}; it can supply additional details about what data
24061 Here are the specific requests of this form defined so far. All
24062 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
24063 formats, listed below.
24066 @item qXfer:@var{spu}:write:@var{annex}:@var{offset}:@var{data}@dots{}
24067 @anchor{qXfer spu write}
24068 Write @var{data} to an @code{spufs} file on the target system. The
24069 annex specifies which file to write; it must be of the form
24070 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
24071 in the target process, and @var{name} identifes the @code{spufs} file
24072 in that context to be accessed.
24074 This packet is not probed by default; the remote stub must request it,
24075 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24081 @var{nn} (hex encoded) is the number of bytes written.
24082 This may be fewer bytes than supplied in the request.
24085 The request was malformed, or @var{annex} was invalid.
24088 The offset was invalid, or there was an error encountered writing the data.
24089 @var{nn} is a hex-encoded @code{errno} value.
24092 An empty reply indicates the @var{object} string was not
24093 recognized by the stub, or that the object does not support writing.
24096 @item qXfer:@var{object}:@var{operation}:@dots{}
24097 Requests of this form may be added in the future. When a stub does
24098 not recognize the @var{object} keyword, or its support for
24099 @var{object} does not recognize the @var{operation} keyword, the stub
24100 must respond with an empty packet.
24104 @node Register Packet Format
24105 @section Register Packet Format
24107 The following @code{g}/@code{G} packets have previously been defined.
24108 In the below, some thirty-two bit registers are transferred as
24109 sixty-four bits. Those registers should be zero/sign extended (which?)
24110 to fill the space allocated. Register bytes are transferred in target
24111 byte order. The two nibbles within a register byte are transferred
24112 most-significant - least-significant.
24118 All registers are transferred as thirty-two bit quantities in the order:
24119 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
24120 registers; fsr; fir; fp.
24124 All registers are transferred as sixty-four bit quantities (including
24125 thirty-two bit registers such as @code{sr}). The ordering is the same
24130 @node Tracepoint Packets
24131 @section Tracepoint Packets
24132 @cindex tracepoint packets
24133 @cindex packets, tracepoint
24135 Here we describe the packets @value{GDBN} uses to implement
24136 tracepoints (@pxref{Tracepoints}).
24140 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}@r{[}-@r{]}
24141 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
24142 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
24143 the tracepoint is disabled. @var{step} is the tracepoint's step
24144 count, and @var{pass} is its pass count. If the trailing @samp{-} is
24145 present, further @samp{QTDP} packets will follow to specify this
24146 tracepoint's actions.
24151 The packet was understood and carried out.
24153 The packet was not recognized.
24156 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
24157 Define actions to be taken when a tracepoint is hit. @var{n} and
24158 @var{addr} must be the same as in the initial @samp{QTDP} packet for
24159 this tracepoint. This packet may only be sent immediately after
24160 another @samp{QTDP} packet that ended with a @samp{-}. If the
24161 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
24162 specifying more actions for this tracepoint.
24164 In the series of action packets for a given tracepoint, at most one
24165 can have an @samp{S} before its first @var{action}. If such a packet
24166 is sent, it and the following packets define ``while-stepping''
24167 actions. Any prior packets define ordinary actions --- that is, those
24168 taken when the tracepoint is first hit. If no action packet has an
24169 @samp{S}, then all the packets in the series specify ordinary
24170 tracepoint actions.
24172 The @samp{@var{action}@dots{}} portion of the packet is a series of
24173 actions, concatenated without separators. Each action has one of the
24179 Collect the registers whose bits are set in @var{mask}. @var{mask} is
24180 a hexadecimal number whose @var{i}'th bit is set if register number
24181 @var{i} should be collected. (The least significant bit is numbered
24182 zero.) Note that @var{mask} may be any number of digits long; it may
24183 not fit in a 32-bit word.
24185 @item M @var{basereg},@var{offset},@var{len}
24186 Collect @var{len} bytes of memory starting at the address in register
24187 number @var{basereg}, plus @var{offset}. If @var{basereg} is
24188 @samp{-1}, then the range has a fixed address: @var{offset} is the
24189 address of the lowest byte to collect. The @var{basereg},
24190 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
24191 values (the @samp{-1} value for @var{basereg} is a special case).
24193 @item X @var{len},@var{expr}
24194 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
24195 it directs. @var{expr} is an agent expression, as described in
24196 @ref{Agent Expressions}. Each byte of the expression is encoded as a
24197 two-digit hex number in the packet; @var{len} is the number of bytes
24198 in the expression (and thus one-half the number of hex digits in the
24203 Any number of actions may be packed together in a single @samp{QTDP}
24204 packet, as long as the packet does not exceed the maximum packet
24205 length (400 bytes, for many stubs). There may be only one @samp{R}
24206 action per tracepoint, and it must precede any @samp{M} or @samp{X}
24207 actions. Any registers referred to by @samp{M} and @samp{X} actions
24208 must be collected by a preceding @samp{R} action. (The
24209 ``while-stepping'' actions are treated as if they were attached to a
24210 separate tracepoint, as far as these restrictions are concerned.)
24215 The packet was understood and carried out.
24217 The packet was not recognized.
24220 @item QTFrame:@var{n}
24221 Select the @var{n}'th tracepoint frame from the buffer, and use the
24222 register and memory contents recorded there to answer subsequent
24223 request packets from @value{GDBN}.
24225 A successful reply from the stub indicates that the stub has found the
24226 requested frame. The response is a series of parts, concatenated
24227 without separators, describing the frame we selected. Each part has
24228 one of the following forms:
24232 The selected frame is number @var{n} in the trace frame buffer;
24233 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
24234 was no frame matching the criteria in the request packet.
24237 The selected trace frame records a hit of tracepoint number @var{t};
24238 @var{t} is a hexadecimal number.
24242 @item QTFrame:pc:@var{addr}
24243 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
24244 currently selected frame whose PC is @var{addr};
24245 @var{addr} is a hexadecimal number.
24247 @item QTFrame:tdp:@var{t}
24248 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
24249 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
24250 is a hexadecimal number.
24252 @item QTFrame:range:@var{start}:@var{end}
24253 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
24254 currently selected frame whose PC is between @var{start} (inclusive)
24255 and @var{end} (exclusive); @var{start} and @var{end} are hexadecimal
24258 @item QTFrame:outside:@var{start}:@var{end}
24259 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
24260 frame @emph{outside} the given range of addresses.
24263 Begin the tracepoint experiment. Begin collecting data from tracepoint
24264 hits in the trace frame buffer.
24267 End the tracepoint experiment. Stop collecting trace frames.
24270 Clear the table of tracepoints, and empty the trace frame buffer.
24272 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
24273 Establish the given ranges of memory as ``transparent''. The stub
24274 will answer requests for these ranges from memory's current contents,
24275 if they were not collected as part of the tracepoint hit.
24277 @value{GDBN} uses this to mark read-only regions of memory, like those
24278 containing program code. Since these areas never change, they should
24279 still have the same contents they did when the tracepoint was hit, so
24280 there's no reason for the stub to refuse to provide their contents.
24283 Ask the stub if there is a trace experiment running right now.
24288 There is no trace experiment running.
24290 There is a trace experiment running.
24297 @section Interrupts
24298 @cindex interrupts (remote protocol)
24300 When a program on the remote target is running, @value{GDBN} may
24301 attempt to interrupt it by sending a @samp{Ctrl-C} or a @code{BREAK},
24302 control of which is specified via @value{GDBN}'s @samp{remotebreak}
24303 setting (@pxref{set remotebreak}).
24305 The precise meaning of @code{BREAK} is defined by the transport
24306 mechanism and may, in fact, be undefined. @value{GDBN} does
24307 not currently define a @code{BREAK} mechanism for any of the network
24310 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
24311 transport mechanisms. It is represented by sending the single byte
24312 @code{0x03} without any of the usual packet overhead described in
24313 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
24314 transmitted as part of a packet, it is considered to be packet data
24315 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
24316 (@pxref{X packet}), used for binary downloads, may include an unescaped
24317 @code{0x03} as part of its packet.
24319 Stubs are not required to recognize these interrupt mechanisms and the
24320 precise meaning associated with receipt of the interrupt is
24321 implementation defined. If the stub is successful at interrupting the
24322 running program, it is expected that it will send one of the Stop
24323 Reply Packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
24324 of successfully stopping the program. Interrupts received while the
24325 program is stopped will be discarded.
24330 Example sequence of a target being re-started. Notice how the restart
24331 does not get any direct output:
24336 @emph{target restarts}
24339 <- @code{T001:1234123412341234}
24343 Example sequence of a target being stepped by a single instruction:
24346 -> @code{G1445@dots{}}
24351 <- @code{T001:1234123412341234}
24355 <- @code{1455@dots{}}
24359 @node File-I/O Remote Protocol Extension
24360 @section File-I/O Remote Protocol Extension
24361 @cindex File-I/O remote protocol extension
24364 * File-I/O Overview::
24365 * Protocol Basics::
24366 * The F Request Packet::
24367 * The F Reply Packet::
24368 * The Ctrl-C Message::
24370 * List of Supported Calls::
24371 * Protocol-specific Representation of Datatypes::
24373 * File-I/O Examples::
24376 @node File-I/O Overview
24377 @subsection File-I/O Overview
24378 @cindex file-i/o overview
24380 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
24381 target to use the host's file system and console I/O to perform various
24382 system calls. System calls on the target system are translated into a
24383 remote protocol packet to the host system, which then performs the needed
24384 actions and returns a response packet to the target system.
24385 This simulates file system operations even on targets that lack file systems.
24387 The protocol is defined to be independent of both the host and target systems.
24388 It uses its own internal representation of datatypes and values. Both
24389 @value{GDBN} and the target's @value{GDBN} stub are responsible for
24390 translating the system-dependent value representations into the internal
24391 protocol representations when data is transmitted.
24393 The communication is synchronous. A system call is possible only when
24394 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
24395 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
24396 the target is stopped to allow deterministic access to the target's
24397 memory. Therefore File-I/O is not interruptible by target signals. On
24398 the other hand, it is possible to interrupt File-I/O by a user interrupt
24399 (@samp{Ctrl-C}) within @value{GDBN}.
24401 The target's request to perform a host system call does not finish
24402 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
24403 after finishing the system call, the target returns to continuing the
24404 previous activity (continue, step). No additional continue or step
24405 request from @value{GDBN} is required.
24408 (@value{GDBP}) continue
24409 <- target requests 'system call X'
24410 target is stopped, @value{GDBN} executes system call
24411 -> @value{GDBN} returns result
24412 ... target continues, @value{GDBN} returns to wait for the target
24413 <- target hits breakpoint and sends a Txx packet
24416 The protocol only supports I/O on the console and to regular files on
24417 the host file system. Character or block special devices, pipes,
24418 named pipes, sockets or any other communication method on the host
24419 system are not supported by this protocol.
24421 @node Protocol Basics
24422 @subsection Protocol Basics
24423 @cindex protocol basics, file-i/o
24425 The File-I/O protocol uses the @code{F} packet as the request as well
24426 as reply packet. Since a File-I/O system call can only occur when
24427 @value{GDBN} is waiting for a response from the continuing or stepping target,
24428 the File-I/O request is a reply that @value{GDBN} has to expect as a result
24429 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
24430 This @code{F} packet contains all information needed to allow @value{GDBN}
24431 to call the appropriate host system call:
24435 A unique identifier for the requested system call.
24438 All parameters to the system call. Pointers are given as addresses
24439 in the target memory address space. Pointers to strings are given as
24440 pointer/length pair. Numerical values are given as they are.
24441 Numerical control flags are given in a protocol-specific representation.
24445 At this point, @value{GDBN} has to perform the following actions.
24449 If the parameters include pointer values to data needed as input to a
24450 system call, @value{GDBN} requests this data from the target with a
24451 standard @code{m} packet request. This additional communication has to be
24452 expected by the target implementation and is handled as any other @code{m}
24456 @value{GDBN} translates all value from protocol representation to host
24457 representation as needed. Datatypes are coerced into the host types.
24460 @value{GDBN} calls the system call.
24463 It then coerces datatypes back to protocol representation.
24466 If the system call is expected to return data in buffer space specified
24467 by pointer parameters to the call, the data is transmitted to the
24468 target using a @code{M} or @code{X} packet. This packet has to be expected
24469 by the target implementation and is handled as any other @code{M} or @code{X}
24474 Eventually @value{GDBN} replies with another @code{F} packet which contains all
24475 necessary information for the target to continue. This at least contains
24482 @code{errno}, if has been changed by the system call.
24489 After having done the needed type and value coercion, the target continues
24490 the latest continue or step action.
24492 @node The F Request Packet
24493 @subsection The @code{F} Request Packet
24494 @cindex file-i/o request packet
24495 @cindex @code{F} request packet
24497 The @code{F} request packet has the following format:
24500 @item F@var{call-id},@var{parameter@dots{}}
24502 @var{call-id} is the identifier to indicate the host system call to be called.
24503 This is just the name of the function.
24505 @var{parameter@dots{}} are the parameters to the system call.
24506 Parameters are hexadecimal integer values, either the actual values in case
24507 of scalar datatypes, pointers to target buffer space in case of compound
24508 datatypes and unspecified memory areas, or pointer/length pairs in case
24509 of string parameters. These are appended to the @var{call-id} as a
24510 comma-delimited list. All values are transmitted in ASCII
24511 string representation, pointer/length pairs separated by a slash.
24517 @node The F Reply Packet
24518 @subsection The @code{F} Reply Packet
24519 @cindex file-i/o reply packet
24520 @cindex @code{F} reply packet
24522 The @code{F} reply packet has the following format:
24526 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
24528 @var{retcode} is the return code of the system call as hexadecimal value.
24530 @var{errno} is the @code{errno} set by the call, in protocol-specific
24532 This parameter can be omitted if the call was successful.
24534 @var{Ctrl-C flag} is only sent if the user requested a break. In this
24535 case, @var{errno} must be sent as well, even if the call was successful.
24536 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
24543 or, if the call was interrupted before the host call has been performed:
24550 assuming 4 is the protocol-specific representation of @code{EINTR}.
24555 @node The Ctrl-C Message
24556 @subsection The @samp{Ctrl-C} Message
24557 @cindex ctrl-c message, in file-i/o protocol
24559 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
24560 reply packet (@pxref{The F Reply Packet}),
24561 the target should behave as if it had
24562 gotten a break message. The meaning for the target is ``system call
24563 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
24564 (as with a break message) and return to @value{GDBN} with a @code{T02}
24567 It's important for the target to know in which
24568 state the system call was interrupted. There are two possible cases:
24572 The system call hasn't been performed on the host yet.
24575 The system call on the host has been finished.
24579 These two states can be distinguished by the target by the value of the
24580 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
24581 call hasn't been performed. This is equivalent to the @code{EINTR} handling
24582 on POSIX systems. In any other case, the target may presume that the
24583 system call has been finished --- successfully or not --- and should behave
24584 as if the break message arrived right after the system call.
24586 @value{GDBN} must behave reliably. If the system call has not been called
24587 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
24588 @code{errno} in the packet. If the system call on the host has been finished
24589 before the user requests a break, the full action must be finished by
24590 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
24591 The @code{F} packet may only be sent when either nothing has happened
24592 or the full action has been completed.
24595 @subsection Console I/O
24596 @cindex console i/o as part of file-i/o
24598 By default and if not explicitly closed by the target system, the file
24599 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
24600 on the @value{GDBN} console is handled as any other file output operation
24601 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
24602 by @value{GDBN} so that after the target read request from file descriptor
24603 0 all following typing is buffered until either one of the following
24608 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
24610 system call is treated as finished.
24613 The user presses @key{RET}. This is treated as end of input with a trailing
24617 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
24618 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
24622 If the user has typed more characters than fit in the buffer given to
24623 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
24624 either another @code{read(0, @dots{})} is requested by the target, or debugging
24625 is stopped at the user's request.
24628 @node List of Supported Calls
24629 @subsection List of Supported Calls
24630 @cindex list of supported file-i/o calls
24647 @unnumberedsubsubsec open
24648 @cindex open, file-i/o system call
24653 int open(const char *pathname, int flags);
24654 int open(const char *pathname, int flags, mode_t mode);
24658 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
24661 @var{flags} is the bitwise @code{OR} of the following values:
24665 If the file does not exist it will be created. The host
24666 rules apply as far as file ownership and time stamps
24670 When used with @code{O_CREAT}, if the file already exists it is
24671 an error and open() fails.
24674 If the file already exists and the open mode allows
24675 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
24676 truncated to zero length.
24679 The file is opened in append mode.
24682 The file is opened for reading only.
24685 The file is opened for writing only.
24688 The file is opened for reading and writing.
24692 Other bits are silently ignored.
24696 @var{mode} is the bitwise @code{OR} of the following values:
24700 User has read permission.
24703 User has write permission.
24706 Group has read permission.
24709 Group has write permission.
24712 Others have read permission.
24715 Others have write permission.
24719 Other bits are silently ignored.
24722 @item Return value:
24723 @code{open} returns the new file descriptor or -1 if an error
24730 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
24733 @var{pathname} refers to a directory.
24736 The requested access is not allowed.
24739 @var{pathname} was too long.
24742 A directory component in @var{pathname} does not exist.
24745 @var{pathname} refers to a device, pipe, named pipe or socket.
24748 @var{pathname} refers to a file on a read-only filesystem and
24749 write access was requested.
24752 @var{pathname} is an invalid pointer value.
24755 No space on device to create the file.
24758 The process already has the maximum number of files open.
24761 The limit on the total number of files open on the system
24765 The call was interrupted by the user.
24771 @unnumberedsubsubsec close
24772 @cindex close, file-i/o system call
24781 @samp{Fclose,@var{fd}}
24783 @item Return value:
24784 @code{close} returns zero on success, or -1 if an error occurred.
24790 @var{fd} isn't a valid open file descriptor.
24793 The call was interrupted by the user.
24799 @unnumberedsubsubsec read
24800 @cindex read, file-i/o system call
24805 int read(int fd, void *buf, unsigned int count);
24809 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
24811 @item Return value:
24812 On success, the number of bytes read is returned.
24813 Zero indicates end of file. If count is zero, read
24814 returns zero as well. On error, -1 is returned.
24820 @var{fd} is not a valid file descriptor or is not open for
24824 @var{bufptr} is an invalid pointer value.
24827 The call was interrupted by the user.
24833 @unnumberedsubsubsec write
24834 @cindex write, file-i/o system call
24839 int write(int fd, const void *buf, unsigned int count);
24843 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
24845 @item Return value:
24846 On success, the number of bytes written are returned.
24847 Zero indicates nothing was written. On error, -1
24854 @var{fd} is not a valid file descriptor or is not open for
24858 @var{bufptr} is an invalid pointer value.
24861 An attempt was made to write a file that exceeds the
24862 host-specific maximum file size allowed.
24865 No space on device to write the data.
24868 The call was interrupted by the user.
24874 @unnumberedsubsubsec lseek
24875 @cindex lseek, file-i/o system call
24880 long lseek (int fd, long offset, int flag);
24884 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
24886 @var{flag} is one of:
24890 The offset is set to @var{offset} bytes.
24893 The offset is set to its current location plus @var{offset}
24897 The offset is set to the size of the file plus @var{offset}
24901 @item Return value:
24902 On success, the resulting unsigned offset in bytes from
24903 the beginning of the file is returned. Otherwise, a
24904 value of -1 is returned.
24910 @var{fd} is not a valid open file descriptor.
24913 @var{fd} is associated with the @value{GDBN} console.
24916 @var{flag} is not a proper value.
24919 The call was interrupted by the user.
24925 @unnumberedsubsubsec rename
24926 @cindex rename, file-i/o system call
24931 int rename(const char *oldpath, const char *newpath);
24935 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
24937 @item Return value:
24938 On success, zero is returned. On error, -1 is returned.
24944 @var{newpath} is an existing directory, but @var{oldpath} is not a
24948 @var{newpath} is a non-empty directory.
24951 @var{oldpath} or @var{newpath} is a directory that is in use by some
24955 An attempt was made to make a directory a subdirectory
24959 A component used as a directory in @var{oldpath} or new
24960 path is not a directory. Or @var{oldpath} is a directory
24961 and @var{newpath} exists but is not a directory.
24964 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
24967 No access to the file or the path of the file.
24971 @var{oldpath} or @var{newpath} was too long.
24974 A directory component in @var{oldpath} or @var{newpath} does not exist.
24977 The file is on a read-only filesystem.
24980 The device containing the file has no room for the new
24984 The call was interrupted by the user.
24990 @unnumberedsubsubsec unlink
24991 @cindex unlink, file-i/o system call
24996 int unlink(const char *pathname);
25000 @samp{Funlink,@var{pathnameptr}/@var{len}}
25002 @item Return value:
25003 On success, zero is returned. On error, -1 is returned.
25009 No access to the file or the path of the file.
25012 The system does not allow unlinking of directories.
25015 The file @var{pathname} cannot be unlinked because it's
25016 being used by another process.
25019 @var{pathnameptr} is an invalid pointer value.
25022 @var{pathname} was too long.
25025 A directory component in @var{pathname} does not exist.
25028 A component of the path is not a directory.
25031 The file is on a read-only filesystem.
25034 The call was interrupted by the user.
25040 @unnumberedsubsubsec stat/fstat
25041 @cindex fstat, file-i/o system call
25042 @cindex stat, file-i/o system call
25047 int stat(const char *pathname, struct stat *buf);
25048 int fstat(int fd, struct stat *buf);
25052 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
25053 @samp{Ffstat,@var{fd},@var{bufptr}}
25055 @item Return value:
25056 On success, zero is returned. On error, -1 is returned.
25062 @var{fd} is not a valid open file.
25065 A directory component in @var{pathname} does not exist or the
25066 path is an empty string.
25069 A component of the path is not a directory.
25072 @var{pathnameptr} is an invalid pointer value.
25075 No access to the file or the path of the file.
25078 @var{pathname} was too long.
25081 The call was interrupted by the user.
25087 @unnumberedsubsubsec gettimeofday
25088 @cindex gettimeofday, file-i/o system call
25093 int gettimeofday(struct timeval *tv, void *tz);
25097 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
25099 @item Return value:
25100 On success, 0 is returned, -1 otherwise.
25106 @var{tz} is a non-NULL pointer.
25109 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
25115 @unnumberedsubsubsec isatty
25116 @cindex isatty, file-i/o system call
25121 int isatty(int fd);
25125 @samp{Fisatty,@var{fd}}
25127 @item Return value:
25128 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
25134 The call was interrupted by the user.
25139 Note that the @code{isatty} call is treated as a special case: it returns
25140 1 to the target if the file descriptor is attached
25141 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
25142 would require implementing @code{ioctl} and would be more complex than
25147 @unnumberedsubsubsec system
25148 @cindex system, file-i/o system call
25153 int system(const char *command);
25157 @samp{Fsystem,@var{commandptr}/@var{len}}
25159 @item Return value:
25160 If @var{len} is zero, the return value indicates whether a shell is
25161 available. A zero return value indicates a shell is not available.
25162 For non-zero @var{len}, the value returned is -1 on error and the
25163 return status of the command otherwise. Only the exit status of the
25164 command is returned, which is extracted from the host's @code{system}
25165 return value by calling @code{WEXITSTATUS(retval)}. In case
25166 @file{/bin/sh} could not be executed, 127 is returned.
25172 The call was interrupted by the user.
25177 @value{GDBN} takes over the full task of calling the necessary host calls
25178 to perform the @code{system} call. The return value of @code{system} on
25179 the host is simplified before it's returned
25180 to the target. Any termination signal information from the child process
25181 is discarded, and the return value consists
25182 entirely of the exit status of the called command.
25184 Due to security concerns, the @code{system} call is by default refused
25185 by @value{GDBN}. The user has to allow this call explicitly with the
25186 @code{set remote system-call-allowed 1} command.
25189 @item set remote system-call-allowed
25190 @kindex set remote system-call-allowed
25191 Control whether to allow the @code{system} calls in the File I/O
25192 protocol for the remote target. The default is zero (disabled).
25194 @item show remote system-call-allowed
25195 @kindex show remote system-call-allowed
25196 Show whether the @code{system} calls are allowed in the File I/O
25200 @node Protocol-specific Representation of Datatypes
25201 @subsection Protocol-specific Representation of Datatypes
25202 @cindex protocol-specific representation of datatypes, in file-i/o protocol
25205 * Integral Datatypes::
25207 * Memory Transfer::
25212 @node Integral Datatypes
25213 @unnumberedsubsubsec Integral Datatypes
25214 @cindex integral datatypes, in file-i/o protocol
25216 The integral datatypes used in the system calls are @code{int},
25217 @code{unsigned int}, @code{long}, @code{unsigned long},
25218 @code{mode_t}, and @code{time_t}.
25220 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
25221 implemented as 32 bit values in this protocol.
25223 @code{long} and @code{unsigned long} are implemented as 64 bit types.
25225 @xref{Limits}, for corresponding MIN and MAX values (similar to those
25226 in @file{limits.h}) to allow range checking on host and target.
25228 @code{time_t} datatypes are defined as seconds since the Epoch.
25230 All integral datatypes transferred as part of a memory read or write of a
25231 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
25234 @node Pointer Values
25235 @unnumberedsubsubsec Pointer Values
25236 @cindex pointer values, in file-i/o protocol
25238 Pointers to target data are transmitted as they are. An exception
25239 is made for pointers to buffers for which the length isn't
25240 transmitted as part of the function call, namely strings. Strings
25241 are transmitted as a pointer/length pair, both as hex values, e.g.@:
25248 which is a pointer to data of length 18 bytes at position 0x1aaf.
25249 The length is defined as the full string length in bytes, including
25250 the trailing null byte. For example, the string @code{"hello world"}
25251 at address 0x123456 is transmitted as
25257 @node Memory Transfer
25258 @unnumberedsubsubsec Memory Transfer
25259 @cindex memory transfer, in file-i/o protocol
25261 Structured data which is transferred using a memory read or write (for
25262 example, a @code{struct stat}) is expected to be in a protocol-specific format
25263 with all scalar multibyte datatypes being big endian. Translation to
25264 this representation needs to be done both by the target before the @code{F}
25265 packet is sent, and by @value{GDBN} before
25266 it transfers memory to the target. Transferred pointers to structured
25267 data should point to the already-coerced data at any time.
25271 @unnumberedsubsubsec struct stat
25272 @cindex struct stat, in file-i/o protocol
25274 The buffer of type @code{struct stat} used by the target and @value{GDBN}
25275 is defined as follows:
25279 unsigned int st_dev; /* device */
25280 unsigned int st_ino; /* inode */
25281 mode_t st_mode; /* protection */
25282 unsigned int st_nlink; /* number of hard links */
25283 unsigned int st_uid; /* user ID of owner */
25284 unsigned int st_gid; /* group ID of owner */
25285 unsigned int st_rdev; /* device type (if inode device) */
25286 unsigned long st_size; /* total size, in bytes */
25287 unsigned long st_blksize; /* blocksize for filesystem I/O */
25288 unsigned long st_blocks; /* number of blocks allocated */
25289 time_t st_atime; /* time of last access */
25290 time_t st_mtime; /* time of last modification */
25291 time_t st_ctime; /* time of last change */
25295 The integral datatypes conform to the definitions given in the
25296 appropriate section (see @ref{Integral Datatypes}, for details) so this
25297 structure is of size 64 bytes.
25299 The values of several fields have a restricted meaning and/or
25305 A value of 0 represents a file, 1 the console.
25308 No valid meaning for the target. Transmitted unchanged.
25311 Valid mode bits are described in @ref{Constants}. Any other
25312 bits have currently no meaning for the target.
25317 No valid meaning for the target. Transmitted unchanged.
25322 These values have a host and file system dependent
25323 accuracy. Especially on Windows hosts, the file system may not
25324 support exact timing values.
25327 The target gets a @code{struct stat} of the above representation and is
25328 responsible for coercing it to the target representation before
25331 Note that due to size differences between the host, target, and protocol
25332 representations of @code{struct stat} members, these members could eventually
25333 get truncated on the target.
25335 @node struct timeval
25336 @unnumberedsubsubsec struct timeval
25337 @cindex struct timeval, in file-i/o protocol
25339 The buffer of type @code{struct timeval} used by the File-I/O protocol
25340 is defined as follows:
25344 time_t tv_sec; /* second */
25345 long tv_usec; /* microsecond */
25349 The integral datatypes conform to the definitions given in the
25350 appropriate section (see @ref{Integral Datatypes}, for details) so this
25351 structure is of size 8 bytes.
25354 @subsection Constants
25355 @cindex constants, in file-i/o protocol
25357 The following values are used for the constants inside of the
25358 protocol. @value{GDBN} and target are responsible for translating these
25359 values before and after the call as needed.
25370 @unnumberedsubsubsec Open Flags
25371 @cindex open flags, in file-i/o protocol
25373 All values are given in hexadecimal representation.
25385 @node mode_t Values
25386 @unnumberedsubsubsec mode_t Values
25387 @cindex mode_t values, in file-i/o protocol
25389 All values are given in octal representation.
25406 @unnumberedsubsubsec Errno Values
25407 @cindex errno values, in file-i/o protocol
25409 All values are given in decimal representation.
25434 @code{EUNKNOWN} is used as a fallback error value if a host system returns
25435 any error value not in the list of supported error numbers.
25438 @unnumberedsubsubsec Lseek Flags
25439 @cindex lseek flags, in file-i/o protocol
25448 @unnumberedsubsubsec Limits
25449 @cindex limits, in file-i/o protocol
25451 All values are given in decimal representation.
25454 INT_MIN -2147483648
25456 UINT_MAX 4294967295
25457 LONG_MIN -9223372036854775808
25458 LONG_MAX 9223372036854775807
25459 ULONG_MAX 18446744073709551615
25462 @node File-I/O Examples
25463 @subsection File-I/O Examples
25464 @cindex file-i/o examples
25466 Example sequence of a write call, file descriptor 3, buffer is at target
25467 address 0x1234, 6 bytes should be written:
25470 <- @code{Fwrite,3,1234,6}
25471 @emph{request memory read from target}
25474 @emph{return "6 bytes written"}
25478 Example sequence of a read call, file descriptor 3, buffer is at target
25479 address 0x1234, 6 bytes should be read:
25482 <- @code{Fread,3,1234,6}
25483 @emph{request memory write to target}
25484 -> @code{X1234,6:XXXXXX}
25485 @emph{return "6 bytes read"}
25489 Example sequence of a read call, call fails on the host due to invalid
25490 file descriptor (@code{EBADF}):
25493 <- @code{Fread,3,1234,6}
25497 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
25501 <- @code{Fread,3,1234,6}
25506 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
25510 <- @code{Fread,3,1234,6}
25511 -> @code{X1234,6:XXXXXX}
25515 @node Library List Format
25516 @section Library List Format
25517 @cindex library list format, remote protocol
25519 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
25520 same process as your application to manage libraries. In this case,
25521 @value{GDBN} can use the loader's symbol table and normal memory
25522 operations to maintain a list of shared libraries. On other
25523 platforms, the operating system manages loaded libraries.
25524 @value{GDBN} can not retrieve the list of currently loaded libraries
25525 through memory operations, so it uses the @samp{qXfer:libraries:read}
25526 packet (@pxref{qXfer library list read}) instead. The remote stub
25527 queries the target's operating system and reports which libraries
25530 The @samp{qXfer:libraries:read} packet returns an XML document which
25531 lists loaded libraries and their offsets. Each library has an
25532 associated name and one or more segment base addresses, which report
25533 where the library was loaded in memory. The segment bases are start
25534 addresses, not relocation offsets; they do not depend on the library's
25535 link-time base addresses.
25537 A simple memory map, with one loaded library relocated by a single
25538 offset, looks like this:
25542 <library name="/lib/libc.so.6">
25543 <segment address="0x10000000"/>
25548 The format of a library list is described by this DTD:
25551 <!-- library-list: Root element with versioning -->
25552 <!ELEMENT library-list (library)*>
25553 <!ATTLIST library-list version CDATA #FIXED "1.0">
25554 <!ELEMENT library (segment)*>
25555 <!ATTLIST library name CDATA #REQUIRED>
25556 <!ELEMENT segment EMPTY>
25557 <!ATTLIST segment address CDATA #REQUIRED>
25560 @node Memory Map Format
25561 @section Memory Map Format
25562 @cindex memory map format
25564 To be able to write into flash memory, @value{GDBN} needs to obtain a
25565 memory map from the target. This section describes the format of the
25568 The memory map is obtained using the @samp{qXfer:memory-map:read}
25569 (@pxref{qXfer memory map read}) packet and is an XML document that
25570 lists memory regions. The top-level structure of the document is shown below:
25573 <?xml version="1.0"?>
25574 <!DOCTYPE memory-map
25575 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
25576 "http://sourceware.org/gdb/gdb-memory-map.dtd">
25582 Each region can be either:
25587 A region of RAM starting at @var{addr} and extending for @var{length}
25591 <memory type="ram" start="@var{addr}" length="@var{length}"/>
25596 A region of read-only memory:
25599 <memory type="rom" start="@var{addr}" length="@var{length}"/>
25604 A region of flash memory, with erasure blocks @var{blocksize}
25608 <memory type="flash" start="@var{addr}" length="@var{length}">
25609 <property name="blocksize">@var{blocksize}</property>
25615 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
25616 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
25617 packets to write to addresses in such ranges.
25619 The formal DTD for memory map format is given below:
25622 <!-- ................................................... -->
25623 <!-- Memory Map XML DTD ................................ -->
25624 <!-- File: memory-map.dtd .............................. -->
25625 <!-- .................................... .............. -->
25626 <!-- memory-map.dtd -->
25627 <!-- memory-map: Root element with versioning -->
25628 <!ELEMENT memory-map (memory | property)>
25629 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
25630 <!ELEMENT memory (property)>
25631 <!-- memory: Specifies a memory region,
25632 and its type, or device. -->
25633 <!ATTLIST memory type CDATA #REQUIRED
25634 start CDATA #REQUIRED
25635 length CDATA #REQUIRED
25636 device CDATA #IMPLIED>
25637 <!-- property: Generic attribute tag -->
25638 <!ELEMENT property (#PCDATA | property)*>
25639 <!ATTLIST property name CDATA #REQUIRED>
25642 @include agentexpr.texi
25644 @node Target Descriptions
25645 @appendix Target Descriptions
25646 @cindex target descriptions
25648 @strong{Warning:} target descriptions are still under active development,
25649 and the contents and format may change between @value{GDBN} releases.
25650 The format is expected to stabilize in the future.
25652 One of the challenges of using @value{GDBN} to debug embedded systems
25653 is that there are so many minor variants of each processor
25654 architecture in use. It is common practice for vendors to start with
25655 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
25656 and then make changes to adapt it to a particular market niche. Some
25657 architectures have hundreds of variants, available from dozens of
25658 vendors. This leads to a number of problems:
25662 With so many different customized processors, it is difficult for
25663 the @value{GDBN} maintainers to keep up with the changes.
25665 Since individual variants may have short lifetimes or limited
25666 audiences, it may not be worthwhile to carry information about every
25667 variant in the @value{GDBN} source tree.
25669 When @value{GDBN} does support the architecture of the embedded system
25670 at hand, the task of finding the correct architecture name to give the
25671 @command{set architecture} command can be error-prone.
25674 To address these problems, the @value{GDBN} remote protocol allows a
25675 target system to not only identify itself to @value{GDBN}, but to
25676 actually describe its own features. This lets @value{GDBN} support
25677 processor variants it has never seen before --- to the extent that the
25678 descriptions are accurate, and that @value{GDBN} understands them.
25680 @value{GDBN} must be compiled with Expat support to support XML target
25681 descriptions. @xref{Expat}.
25684 * Retrieving Descriptions:: How descriptions are fetched from a target.
25685 * Target Description Format:: The contents of a target description.
25686 * Predefined Target Types:: Standard types available for target
25688 * Standard Target Features:: Features @value{GDBN} knows about.
25691 @node Retrieving Descriptions
25692 @section Retrieving Descriptions
25694 Target descriptions can be read from the target automatically, or
25695 specified by the user manually. The default behavior is to read the
25696 description from the target. @value{GDBN} retrieves it via the remote
25697 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
25698 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
25699 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
25700 XML document, of the form described in @ref{Target Description
25703 Alternatively, you can specify a file to read for the target description.
25704 If a file is set, the target will not be queried. The commands to
25705 specify a file are:
25708 @cindex set tdesc filename
25709 @item set tdesc filename @var{path}
25710 Read the target description from @var{path}.
25712 @cindex unset tdesc filename
25713 @item unset tdesc filename
25714 Do not read the XML target description from a file. @value{GDBN}
25715 will use the description supplied by the current target.
25717 @cindex show tdesc filename
25718 @item show tdesc filename
25719 Show the filename to read for a target description, if any.
25723 @node Target Description Format
25724 @section Target Description Format
25725 @cindex target descriptions, XML format
25727 A target description annex is an @uref{http://www.w3.org/XML/, XML}
25728 document which complies with the Document Type Definition provided in
25729 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
25730 means you can use generally available tools like @command{xmllint} to
25731 check that your feature descriptions are well-formed and valid.
25732 However, to help people unfamiliar with XML write descriptions for
25733 their targets, we also describe the grammar here.
25735 Target descriptions can identify the architecture of the remote target
25736 and (for some architectures) provide information about custom register
25737 sets. @value{GDBN} can use this information to autoconfigure for your
25738 target, or to warn you if you connect to an unsupported target.
25740 Here is a simple target description:
25743 <target version="1.0">
25744 <architecture>i386:x86-64</architecture>
25749 This minimal description only says that the target uses
25750 the x86-64 architecture.
25752 A target description has the following overall form, with [ ] marking
25753 optional elements and @dots{} marking repeatable elements. The elements
25754 are explained further below.
25757 <?xml version="1.0"?>
25758 <!DOCTYPE target SYSTEM "gdb-target.dtd">
25759 <target version="1.0">
25760 @r{[}@var{architecture}@r{]}
25761 @r{[}@var{feature}@dots{}@r{]}
25766 The description is generally insensitive to whitespace and line
25767 breaks, under the usual common-sense rules. The XML version
25768 declaration and document type declaration can generally be omitted
25769 (@value{GDBN} does not require them), but specifying them may be
25770 useful for XML validation tools. The @samp{version} attribute for
25771 @samp{<target>} may also be omitted, but we recommend
25772 including it; if future versions of @value{GDBN} use an incompatible
25773 revision of @file{gdb-target.dtd}, they will detect and report
25774 the version mismatch.
25776 @subsection Inclusion
25777 @cindex target descriptions, inclusion
25780 @cindex <xi:include>
25783 It can sometimes be valuable to split a target description up into
25784 several different annexes, either for organizational purposes, or to
25785 share files between different possible target descriptions. You can
25786 divide a description into multiple files by replacing any element of
25787 the target description with an inclusion directive of the form:
25790 <xi:include href="@var{document}"/>
25794 When @value{GDBN} encounters an element of this form, it will retrieve
25795 the named XML @var{document}, and replace the inclusion directive with
25796 the contents of that document. If the current description was read
25797 using @samp{qXfer}, then so will be the included document;
25798 @var{document} will be interpreted as the name of an annex. If the
25799 current description was read from a file, @value{GDBN} will look for
25800 @var{document} as a file in the same directory where it found the
25801 original description.
25803 @subsection Architecture
25804 @cindex <architecture>
25806 An @samp{<architecture>} element has this form:
25809 <architecture>@var{arch}</architecture>
25812 @var{arch} is an architecture name from the same selection
25813 accepted by @code{set architecture} (@pxref{Targets, ,Specifying a
25814 Debugging Target}).
25816 @subsection Features
25819 Each @samp{<feature>} describes some logical portion of the target
25820 system. Features are currently used to describe available CPU
25821 registers and the types of their contents. A @samp{<feature>} element
25825 <feature name="@var{name}">
25826 @r{[}@var{type}@dots{}@r{]}
25832 Each feature's name should be unique within the description. The name
25833 of a feature does not matter unless @value{GDBN} has some special
25834 knowledge of the contents of that feature; if it does, the feature
25835 should have its standard name. @xref{Standard Target Features}.
25839 Any register's value is a collection of bits which @value{GDBN} must
25840 interpret. The default interpretation is a two's complement integer,
25841 but other types can be requested by name in the register description.
25842 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
25843 Target Types}), and the description can define additional composite types.
25845 Each type element must have an @samp{id} attribute, which gives
25846 a unique (within the containing @samp{<feature>}) name to the type.
25847 Types must be defined before they are used.
25850 Some targets offer vector registers, which can be treated as arrays
25851 of scalar elements. These types are written as @samp{<vector>} elements,
25852 specifying the array element type, @var{type}, and the number of elements,
25856 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
25860 If a register's value is usefully viewed in multiple ways, define it
25861 with a union type containing the useful representations. The
25862 @samp{<union>} element contains one or more @samp{<field>} elements,
25863 each of which has a @var{name} and a @var{type}:
25866 <union id="@var{id}">
25867 <field name="@var{name}" type="@var{type}"/>
25872 @subsection Registers
25875 Each register is represented as an element with this form:
25878 <reg name="@var{name}"
25879 bitsize="@var{size}"
25880 @r{[}regnum="@var{num}"@r{]}
25881 @r{[}save-restore="@var{save-restore}"@r{]}
25882 @r{[}type="@var{type}"@r{]}
25883 @r{[}group="@var{group}"@r{]}/>
25887 The components are as follows:
25892 The register's name; it must be unique within the target description.
25895 The register's size, in bits.
25898 The register's number. If omitted, a register's number is one greater
25899 than that of the previous register (either in the current feature or in
25900 a preceeding feature); the first register in the target description
25901 defaults to zero. This register number is used to read or write
25902 the register; e.g.@: it is used in the remote @code{p} and @code{P}
25903 packets, and registers appear in the @code{g} and @code{G} packets
25904 in order of increasing register number.
25907 Whether the register should be preserved across inferior function
25908 calls; this must be either @code{yes} or @code{no}. The default is
25909 @code{yes}, which is appropriate for most registers except for
25910 some system control registers; this is not related to the target's
25914 The type of the register. @var{type} may be a predefined type, a type
25915 defined in the current feature, or one of the special types @code{int}
25916 and @code{float}. @code{int} is an integer type of the correct size
25917 for @var{bitsize}, and @code{float} is a floating point type (in the
25918 architecture's normal floating point format) of the correct size for
25919 @var{bitsize}. The default is @code{int}.
25922 The register group to which this register belongs. @var{group} must
25923 be either @code{general}, @code{float}, or @code{vector}. If no
25924 @var{group} is specified, @value{GDBN} will not display the register
25925 in @code{info registers}.
25929 @node Predefined Target Types
25930 @section Predefined Target Types
25931 @cindex target descriptions, predefined types
25933 Type definitions in the self-description can build up composite types
25934 from basic building blocks, but can not define fundamental types. Instead,
25935 standard identifiers are provided by @value{GDBN} for the fundamental
25936 types. The currently supported types are:
25944 Signed integer types holding the specified number of bits.
25950 Unsigned integer types holding the specified number of bits.
25954 Pointers to unspecified code and data. The program counter and
25955 any dedicated return address register may be marked as code
25956 pointers; printing a code pointer converts it into a symbolic
25957 address. The stack pointer and any dedicated address registers
25958 may be marked as data pointers.
25961 Single precision IEEE floating point.
25964 Double precision IEEE floating point.
25967 The 12-byte extended precision format used by ARM FPA registers.
25971 @node Standard Target Features
25972 @section Standard Target Features
25973 @cindex target descriptions, standard features
25975 A target description must contain either no registers or all the
25976 target's registers. If the description contains no registers, then
25977 @value{GDBN} will assume a default register layout, selected based on
25978 the architecture. If the description contains any registers, the
25979 default layout will not be used; the standard registers must be
25980 described in the target description, in such a way that @value{GDBN}
25981 can recognize them.
25983 This is accomplished by giving specific names to feature elements
25984 which contain standard registers. @value{GDBN} will look for features
25985 with those names and verify that they contain the expected registers;
25986 if any known feature is missing required registers, or if any required
25987 feature is missing, @value{GDBN} will reject the target
25988 description. You can add additional registers to any of the
25989 standard features --- @value{GDBN} will display them just as if
25990 they were added to an unrecognized feature.
25992 This section lists the known features and their expected contents.
25993 Sample XML documents for these features are included in the
25994 @value{GDBN} source tree, in the directory @file{gdb/features}.
25996 Names recognized by @value{GDBN} should include the name of the
25997 company or organization which selected the name, and the overall
25998 architecture to which the feature applies; so e.g.@: the feature
25999 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
26001 The names of registers are not case sensitive for the purpose
26002 of recognizing standard features, but @value{GDBN} will only display
26003 registers using the capitalization used in the description.
26012 @subsection ARM Features
26013 @cindex target descriptions, ARM features
26015 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
26016 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
26017 @samp{lr}, @samp{pc}, and @samp{cpsr}.
26019 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
26020 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
26022 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
26023 it should contain at least registers @samp{wR0} through @samp{wR15} and
26024 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
26025 @samp{wCSSF}, and @samp{wCASF} registers are optional.
26027 @subsection MIPS Features
26028 @cindex target descriptions, MIPS features
26030 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
26031 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
26032 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
26035 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
26036 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
26037 registers. They may be 32-bit or 64-bit depending on the target.
26039 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
26040 it may be optional in a future version of @value{GDBN}. It should
26041 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
26042 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
26044 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
26045 contain a single register, @samp{restart}, which is used by the
26046 Linux kernel to control restartable syscalls.
26048 @node M68K Features
26049 @subsection M68K Features
26050 @cindex target descriptions, M68K features
26053 @item @samp{org.gnu.gdb.m68k.core}
26054 @itemx @samp{org.gnu.gdb.coldfire.core}
26055 @itemx @samp{org.gnu.gdb.fido.core}
26056 One of those features must be always present.
26057 The feature that is present determines which flavor of m86k is
26058 used. The feature that is present should contain registers
26059 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
26060 @samp{sp}, @samp{ps} and @samp{pc}.
26062 @item @samp{org.gnu.gdb.coldfire.fp}
26063 This feature is optional. If present, it should contain registers
26064 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
26080 % I think something like @colophon should be in texinfo. In the
26082 \long\def\colophon{\hbox to0pt{}\vfill
26083 \centerline{The body of this manual is set in}
26084 \centerline{\fontname\tenrm,}
26085 \centerline{with headings in {\bf\fontname\tenbf}}
26086 \centerline{and examples in {\tt\fontname\tentt}.}
26087 \centerline{{\it\fontname\tenit\/},}
26088 \centerline{{\bf\fontname\tenbf}, and}
26089 \centerline{{\sl\fontname\tensl\/}}
26090 \centerline{are used for emphasis.}\vfill}
26092 % Blame: doc@cygnus.com, 1991.