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, 2007, 2008
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 @ifset VERSION_PACKAGE
53 @value{VERSION_PACKAGE}
55 Version @value{GDBVN}.
57 Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,@*
58 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006@*
59 Free Software Foundation, Inc.
61 Permission is granted to copy, distribute and/or modify this document
62 under the terms of the GNU Free Documentation License, Version 1.1 or
63 any later version published by the Free Software Foundation; with the
64 Invariant Sections being ``Free Software'' and ``Free Software Needs
65 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
66 and with the Back-Cover Texts as in (a) below.
68 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
69 this GNU Manual. Buying copies from GNU Press supports the FSF in
70 developing GNU and promoting software freedom.''
74 @title Debugging with @value{GDBN}
75 @subtitle The @sc{gnu} Source-Level Debugger
77 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
78 @ifset VERSION_PACKAGE
80 @subtitle @value{VERSION_PACKAGE}
82 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
86 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
87 \hfill {\it Debugging with @value{GDBN}}\par
88 \hfill \TeX{}info \texinfoversion\par
92 @vskip 0pt plus 1filll
93 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995,
94 1996, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2006
95 Free Software Foundation, Inc.
97 Published by the Free Software Foundation @*
98 51 Franklin Street, Fifth Floor,
99 Boston, MA 02110-1301, USA@*
100 ISBN 1-882114-77-9 @*
102 Permission is granted to copy, distribute and/or modify this document
103 under the terms of the GNU Free Documentation License, Version 1.1 or
104 any later version published by the Free Software Foundation; with the
105 Invariant Sections being ``Free Software'' and ``Free Software Needs
106 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
107 and with the Back-Cover Texts as in (a) below.
109 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
110 this GNU Manual. Buying copies from GNU Press supports the FSF in
111 developing GNU and promoting software freedom.''
113 This edition of the GDB manual is dedicated to the memory of Fred
114 Fish. Fred was a long-standing contributor to GDB and to Free
115 software in general. We will miss him.
120 @node Top, Summary, (dir), (dir)
122 @top Debugging with @value{GDBN}
124 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
126 This is the @value{EDITION} Edition, for @value{GDBN}
127 @ifset VERSION_PACKAGE
128 @value{VERSION_PACKAGE}
130 Version @value{GDBVN}.
132 Copyright (C) 1988-2006 Free Software Foundation, Inc.
134 This edition of the GDB manual is dedicated to the memory of Fred
135 Fish. Fred was a long-standing contributor to GDB and to Free
136 software in general. We will miss him.
139 * Summary:: Summary of @value{GDBN}
140 * Sample Session:: A sample @value{GDBN} session
142 * Invocation:: Getting in and out of @value{GDBN}
143 * Commands:: @value{GDBN} commands
144 * Running:: Running programs under @value{GDBN}
145 * Stopping:: Stopping and continuing
146 * Stack:: Examining the stack
147 * Source:: Examining source files
148 * Data:: Examining data
149 * Macros:: Preprocessor Macros
150 * Tracepoints:: Debugging remote targets non-intrusively
151 * Overlays:: Debugging programs that use overlays
153 * Languages:: Using @value{GDBN} with different languages
155 * Symbols:: Examining the symbol table
156 * Altering:: Altering execution
157 * GDB Files:: @value{GDBN} files
158 * Targets:: Specifying a debugging target
159 * Remote Debugging:: Debugging remote programs
160 * Configurations:: Configuration-specific information
161 * Controlling GDB:: Controlling @value{GDBN}
162 * Sequences:: Canned sequences of commands
163 * Interpreters:: Command Interpreters
164 * TUI:: @value{GDBN} Text User Interface
165 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
166 * GDB/MI:: @value{GDBN}'s Machine Interface.
167 * Annotations:: @value{GDBN}'s annotation interface.
169 * GDB Bugs:: Reporting bugs in @value{GDBN}
171 * Command Line Editing:: Command Line Editing
172 * Using History Interactively:: Using History Interactively
173 * Formatting Documentation:: How to format and print @value{GDBN} documentation
174 * Installing GDB:: Installing GDB
175 * Maintenance Commands:: Maintenance Commands
176 * Remote Protocol:: GDB Remote Serial Protocol
177 * Agent Expressions:: The GDB Agent Expression Mechanism
178 * Target Descriptions:: How targets can describe themselves to
180 * Copying:: GNU General Public License says
181 how you can copy and share GDB
182 * GNU Free Documentation License:: The license for this documentation
191 @unnumbered Summary of @value{GDBN}
193 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
194 going on ``inside'' another program while it executes---or what another
195 program was doing at the moment it crashed.
197 @value{GDBN} can do four main kinds of things (plus other things in support of
198 these) to help you catch bugs in the act:
202 Start your program, specifying anything that might affect its behavior.
205 Make your program stop on specified conditions.
208 Examine what has happened, when your program has stopped.
211 Change things in your program, so you can experiment with correcting the
212 effects of one bug and go on to learn about another.
215 You can use @value{GDBN} to debug programs written in C and C@t{++}.
216 For more information, see @ref{Supported Languages,,Supported Languages}.
217 For more information, see @ref{C,,C and C++}.
220 Support for Modula-2 is partial. For information on Modula-2, see
221 @ref{Modula-2,,Modula-2}.
224 Debugging Pascal programs which use sets, subranges, file variables, or
225 nested functions does not currently work. @value{GDBN} does not support
226 entering expressions, printing values, or similar features using Pascal
230 @value{GDBN} can be used to debug programs written in Fortran, although
231 it may be necessary to refer to some variables with a trailing
234 @value{GDBN} can be used to debug programs written in Objective-C,
235 using either the Apple/NeXT or the GNU Objective-C runtime.
238 * Free Software:: Freely redistributable software
239 * Contributors:: Contributors to GDB
243 @unnumberedsec Free Software
245 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
246 General Public License
247 (GPL). The GPL gives you the freedom to copy or adapt a licensed
248 program---but every person getting a copy also gets with it the
249 freedom to modify that copy (which means that they must get access to
250 the source code), and the freedom to distribute further copies.
251 Typical software companies use copyrights to limit your freedoms; the
252 Free Software Foundation uses the GPL to preserve these freedoms.
254 Fundamentally, the General Public License is a license which says that
255 you have these freedoms and that you cannot take these freedoms away
258 @unnumberedsec Free Software Needs Free Documentation
260 The biggest deficiency in the free software community today is not in
261 the software---it is the lack of good free documentation that we can
262 include with the free software. Many of our most important
263 programs do not come with free reference manuals and free introductory
264 texts. Documentation is an essential part of any software package;
265 when an important free software package does not come with a free
266 manual and a free tutorial, that is a major gap. We have many such
269 Consider Perl, for instance. The tutorial manuals that people
270 normally use are non-free. How did this come about? Because the
271 authors of those manuals published them with restrictive terms---no
272 copying, no modification, source files not available---which exclude
273 them from the free software world.
275 That wasn't the first time this sort of thing happened, and it was far
276 from the last. Many times we have heard a GNU user eagerly describe a
277 manual that he is writing, his intended contribution to the community,
278 only to learn that he had ruined everything by signing a publication
279 contract to make it non-free.
281 Free documentation, like free software, is a matter of freedom, not
282 price. The problem with the non-free manual is not that publishers
283 charge a price for printed copies---that in itself is fine. (The Free
284 Software Foundation sells printed copies of manuals, too.) The
285 problem is the restrictions on the use of the manual. Free manuals
286 are available in source code form, and give you permission to copy and
287 modify. Non-free manuals do not allow this.
289 The criteria of freedom for a free manual are roughly the same as for
290 free software. Redistribution (including the normal kinds of
291 commercial redistribution) must be permitted, so that the manual can
292 accompany every copy of the program, both on-line and on paper.
294 Permission for modification of the technical content is crucial too.
295 When people modify the software, adding or changing features, if they
296 are conscientious they will change the manual too---so they can
297 provide accurate and clear documentation for the modified program. A
298 manual that leaves you no choice but to write a new manual to document
299 a changed version of the program is not really available to our
302 Some kinds of limits on the way modification is handled are
303 acceptable. For example, requirements to preserve the original
304 author's copyright notice, the distribution terms, or the list of
305 authors, are ok. It is also no problem to require modified versions
306 to include notice that they were modified. Even entire sections that
307 may not be deleted or changed are acceptable, as long as they deal
308 with nontechnical topics (like this one). These kinds of restrictions
309 are acceptable because they don't obstruct the community's normal use
312 However, it must be possible to modify all the @emph{technical}
313 content of the manual, and then distribute the result in all the usual
314 media, through all the usual channels. Otherwise, the restrictions
315 obstruct the use of the manual, it is not free, and we need another
316 manual to replace it.
318 Please spread the word about this issue. Our community continues to
319 lose manuals to proprietary publishing. If we spread the word that
320 free software needs free reference manuals and free tutorials, perhaps
321 the next person who wants to contribute by writing documentation will
322 realize, before it is too late, that only free manuals contribute to
323 the free software community.
325 If you are writing documentation, please insist on publishing it under
326 the GNU Free Documentation License or another free documentation
327 license. Remember that this decision requires your approval---you
328 don't have to let the publisher decide. Some commercial publishers
329 will use a free license if you insist, but they will not propose the
330 option; it is up to you to raise the issue and say firmly that this is
331 what you want. If the publisher you are dealing with refuses, please
332 try other publishers. If you're not sure whether a proposed license
333 is free, write to @email{licensing@@gnu.org}.
335 You can encourage commercial publishers to sell more free, copylefted
336 manuals and tutorials by buying them, and particularly by buying
337 copies from the publishers that paid for their writing or for major
338 improvements. Meanwhile, try to avoid buying non-free documentation
339 at all. Check the distribution terms of a manual before you buy it,
340 and insist that whoever seeks your business must respect your freedom.
341 Check the history of the book, and try to reward the publishers that
342 have paid or pay the authors to work on it.
344 The Free Software Foundation maintains a list of free documentation
345 published by other publishers, at
346 @url{http://www.fsf.org/doc/other-free-books.html}.
349 @unnumberedsec Contributors to @value{GDBN}
351 Richard Stallman was the original author of @value{GDBN}, and of many
352 other @sc{gnu} programs. Many others have contributed to its
353 development. This section attempts to credit major contributors. One
354 of the virtues of free software is that everyone is free to contribute
355 to it; with regret, we cannot actually acknowledge everyone here. The
356 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
357 blow-by-blow account.
359 Changes much prior to version 2.0 are lost in the mists of time.
362 @emph{Plea:} Additions to this section are particularly welcome. If you
363 or your friends (or enemies, to be evenhanded) have been unfairly
364 omitted from this list, we would like to add your names!
367 So that they may not regard their many labors as thankless, we
368 particularly thank those who shepherded @value{GDBN} through major
370 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
371 Jim Blandy (release 4.18);
372 Jason Molenda (release 4.17);
373 Stan Shebs (release 4.14);
374 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
375 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
376 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
377 Jim Kingdon (releases 3.5, 3.4, and 3.3);
378 and Randy Smith (releases 3.2, 3.1, and 3.0).
380 Richard Stallman, assisted at various times by Peter TerMaat, Chris
381 Hanson, and Richard Mlynarik, handled releases through 2.8.
383 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
384 in @value{GDBN}, with significant additional contributions from Per
385 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
386 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
387 much general update work leading to release 3.0).
389 @value{GDBN} uses the BFD subroutine library to examine multiple
390 object-file formats; BFD was a joint project of David V.
391 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
393 David Johnson wrote the original COFF support; Pace Willison did
394 the original support for encapsulated COFF.
396 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
398 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
399 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
401 Jean-Daniel Fekete contributed Sun 386i support.
402 Chris Hanson improved the HP9000 support.
403 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
404 David Johnson contributed Encore Umax support.
405 Jyrki Kuoppala contributed Altos 3068 support.
406 Jeff Law contributed HP PA and SOM support.
407 Keith Packard contributed NS32K support.
408 Doug Rabson contributed Acorn Risc Machine support.
409 Bob Rusk contributed Harris Nighthawk CX-UX support.
410 Chris Smith contributed Convex support (and Fortran debugging).
411 Jonathan Stone contributed Pyramid support.
412 Michael Tiemann contributed SPARC support.
413 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
414 Pace Willison contributed Intel 386 support.
415 Jay Vosburgh contributed Symmetry support.
416 Marko Mlinar contributed OpenRISC 1000 support.
418 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
420 Rich Schaefer and Peter Schauer helped with support of SunOS shared
423 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
424 about several machine instruction sets.
426 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
427 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
428 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
429 and RDI targets, respectively.
431 Brian Fox is the author of the readline libraries providing
432 command-line editing and command history.
434 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
435 Modula-2 support, and contributed the Languages chapter of this manual.
437 Fred Fish wrote most of the support for Unix System Vr4.
438 He also enhanced the command-completion support to cover C@t{++} overloaded
441 Hitachi America (now Renesas America), Ltd. sponsored the support for
442 H8/300, H8/500, and Super-H processors.
444 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
446 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
449 Toshiba sponsored the support for the TX39 Mips processor.
451 Matsushita sponsored the support for the MN10200 and MN10300 processors.
453 Fujitsu sponsored the support for SPARClite and FR30 processors.
455 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
458 Michael Snyder added support for tracepoints.
460 Stu Grossman wrote gdbserver.
462 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
463 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
465 The following people at the Hewlett-Packard Company contributed
466 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
467 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
468 compiler, and the Text User Interface (nee Terminal User Interface):
469 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
470 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
471 provided HP-specific information in this manual.
473 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
474 Robert Hoehne made significant contributions to the DJGPP port.
476 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
477 development since 1991. Cygnus engineers who have worked on @value{GDBN}
478 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
479 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
480 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
481 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
482 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
483 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
484 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
485 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
486 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
487 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
488 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
489 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
490 Zuhn have made contributions both large and small.
492 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
493 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
495 Jim Blandy added support for preprocessor macros, while working for Red
498 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
499 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
500 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
501 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
502 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
503 with the migration of old architectures to this new framework.
505 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
506 unwinder framework, this consisting of a fresh new design featuring
507 frame IDs, independent frame sniffers, and the sentinel frame. Mark
508 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
509 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
510 trad unwinders. The architecture-specific changes, each involving a
511 complete rewrite of the architecture's frame code, were carried out by
512 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
513 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
514 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
515 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
518 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
519 Tensilica, Inc.@: contributed support for Xtensa processors. Others
520 who have worked on the Xtensa port of @value{GDBN} in the past include
521 Steve Tjiang, John Newlin, and Scott Foehner.
524 @chapter A Sample @value{GDBN} Session
526 You can use this manual at your leisure to read all about @value{GDBN}.
527 However, a handful of commands are enough to get started using the
528 debugger. This chapter illustrates those commands.
531 In this sample session, we emphasize user input like this: @b{input},
532 to make it easier to pick out from the surrounding output.
535 @c FIXME: this example may not be appropriate for some configs, where
536 @c FIXME...primary interest is in remote use.
538 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
539 processor) exhibits the following bug: sometimes, when we change its
540 quote strings from the default, the commands used to capture one macro
541 definition within another stop working. In the following short @code{m4}
542 session, we define a macro @code{foo} which expands to @code{0000}; we
543 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
544 same thing. However, when we change the open quote string to
545 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
546 procedure fails to define a new synonym @code{baz}:
555 @b{define(bar,defn(`foo'))}
559 @b{changequote(<QUOTE>,<UNQUOTE>)}
561 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
564 m4: End of input: 0: fatal error: EOF in string
568 Let us use @value{GDBN} to try to see what is going on.
571 $ @b{@value{GDBP} m4}
572 @c FIXME: this falsifies the exact text played out, to permit smallbook
573 @c FIXME... format to come out better.
574 @value{GDBN} is free software and you are welcome to distribute copies
575 of it under certain conditions; type "show copying" to see
577 There is absolutely no warranty for @value{GDBN}; type "show warranty"
580 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
585 @value{GDBN} reads only enough symbol data to know where to find the
586 rest when needed; as a result, the first prompt comes up very quickly.
587 We now tell @value{GDBN} to use a narrower display width than usual, so
588 that examples fit in this manual.
591 (@value{GDBP}) @b{set width 70}
595 We need to see how the @code{m4} built-in @code{changequote} works.
596 Having looked at the source, we know the relevant subroutine is
597 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
598 @code{break} command.
601 (@value{GDBP}) @b{break m4_changequote}
602 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
606 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
607 control; as long as control does not reach the @code{m4_changequote}
608 subroutine, the program runs as usual:
611 (@value{GDBP}) @b{run}
612 Starting program: /work/Editorial/gdb/gnu/m4/m4
620 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
621 suspends execution of @code{m4}, displaying information about the
622 context where it stops.
625 @b{changequote(<QUOTE>,<UNQUOTE>)}
627 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
629 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
633 Now we use the command @code{n} (@code{next}) to advance execution to
634 the next line of the current function.
638 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
643 @code{set_quotes} looks like a promising subroutine. We can go into it
644 by using the command @code{s} (@code{step}) instead of @code{next}.
645 @code{step} goes to the next line to be executed in @emph{any}
646 subroutine, so it steps into @code{set_quotes}.
650 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
652 530 if (lquote != def_lquote)
656 The display that shows the subroutine where @code{m4} is now
657 suspended (and its arguments) is called a stack frame display. It
658 shows a summary of the stack. We can use the @code{backtrace}
659 command (which can also be spelled @code{bt}), to see where we are
660 in the stack as a whole: the @code{backtrace} command displays a
661 stack frame for each active subroutine.
664 (@value{GDBP}) @b{bt}
665 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
667 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
669 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
670 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
672 #4 0x79dc in expand_input () at macro.c:40
673 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
677 We step through a few more lines to see what happens. The first two
678 times, we can use @samp{s}; the next two times we use @code{n} to avoid
679 falling into the @code{xstrdup} subroutine.
683 0x3b5c 532 if (rquote != def_rquote)
685 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
686 def_lquote : xstrdup(lq);
688 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
691 538 len_lquote = strlen(rquote);
695 The last line displayed looks a little odd; we can examine the variables
696 @code{lquote} and @code{rquote} to see if they are in fact the new left
697 and right quotes we specified. We use the command @code{p}
698 (@code{print}) to see their values.
701 (@value{GDBP}) @b{p lquote}
702 $1 = 0x35d40 "<QUOTE>"
703 (@value{GDBP}) @b{p rquote}
704 $2 = 0x35d50 "<UNQUOTE>"
708 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
709 To look at some context, we can display ten lines of source
710 surrounding the current line with the @code{l} (@code{list}) command.
716 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
718 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
721 538 len_lquote = strlen(rquote);
722 539 len_rquote = strlen(lquote);
729 Let us step past the two lines that set @code{len_lquote} and
730 @code{len_rquote}, and then examine the values of those variables.
734 539 len_rquote = strlen(lquote);
737 (@value{GDBP}) @b{p len_lquote}
739 (@value{GDBP}) @b{p len_rquote}
744 That certainly looks wrong, assuming @code{len_lquote} and
745 @code{len_rquote} are meant to be the lengths of @code{lquote} and
746 @code{rquote} respectively. We can set them to better values using
747 the @code{p} command, since it can print the value of
748 any expression---and that expression can include subroutine calls and
752 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
754 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
759 Is that enough to fix the problem of using the new quotes with the
760 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
761 executing with the @code{c} (@code{continue}) command, and then try the
762 example that caused trouble initially:
768 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
775 Success! The new quotes now work just as well as the default ones. The
776 problem seems to have been just the two typos defining the wrong
777 lengths. We allow @code{m4} exit by giving it an EOF as input:
781 Program exited normally.
785 The message @samp{Program exited normally.} is from @value{GDBN}; it
786 indicates @code{m4} has finished executing. We can end our @value{GDBN}
787 session with the @value{GDBN} @code{quit} command.
790 (@value{GDBP}) @b{quit}
794 @chapter Getting In and Out of @value{GDBN}
796 This chapter discusses how to start @value{GDBN}, and how to get out of it.
800 type @samp{@value{GDBP}} to start @value{GDBN}.
802 type @kbd{quit} or @kbd{Ctrl-d} to exit.
806 * Invoking GDB:: How to start @value{GDBN}
807 * Quitting GDB:: How to quit @value{GDBN}
808 * Shell Commands:: How to use shell commands inside @value{GDBN}
809 * Logging Output:: How to log @value{GDBN}'s output to a file
813 @section Invoking @value{GDBN}
815 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
816 @value{GDBN} reads commands from the terminal until you tell it to exit.
818 You can also run @code{@value{GDBP}} with a variety of arguments and options,
819 to specify more of your debugging environment at the outset.
821 The command-line options described here are designed
822 to cover a variety of situations; in some environments, some of these
823 options may effectively be unavailable.
825 The most usual way to start @value{GDBN} is with one argument,
826 specifying an executable program:
829 @value{GDBP} @var{program}
833 You can also start with both an executable program and a core file
837 @value{GDBP} @var{program} @var{core}
840 You can, instead, specify a process ID as a second argument, if you want
841 to debug a running process:
844 @value{GDBP} @var{program} 1234
848 would attach @value{GDBN} to process @code{1234} (unless you also have a file
849 named @file{1234}; @value{GDBN} does check for a core file first).
851 Taking advantage of the second command-line argument requires a fairly
852 complete operating system; when you use @value{GDBN} as a remote
853 debugger attached to a bare board, there may not be any notion of
854 ``process'', and there is often no way to get a core dump. @value{GDBN}
855 will warn you if it is unable to attach or to read core dumps.
857 You can optionally have @code{@value{GDBP}} pass any arguments after the
858 executable file to the inferior using @code{--args}. This option stops
861 @value{GDBP} --args gcc -O2 -c foo.c
863 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
864 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
866 You can run @code{@value{GDBP}} without printing the front material, which describes
867 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
874 You can further control how @value{GDBN} starts up by using command-line
875 options. @value{GDBN} itself can remind you of the options available.
885 to display all available options and briefly describe their use
886 (@samp{@value{GDBP} -h} is a shorter equivalent).
888 All options and command line arguments you give are processed
889 in sequential order. The order makes a difference when the
890 @samp{-x} option is used.
894 * File Options:: Choosing files
895 * Mode Options:: Choosing modes
896 * Startup:: What @value{GDBN} does during startup
900 @subsection Choosing Files
902 When @value{GDBN} starts, it reads any arguments other than options as
903 specifying an executable file and core file (or process ID). This is
904 the same as if the arguments were specified by the @samp{-se} and
905 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
906 first argument that does not have an associated option flag as
907 equivalent to the @samp{-se} option followed by that argument; and the
908 second argument that does not have an associated option flag, if any, as
909 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
910 If the second argument begins with a decimal digit, @value{GDBN} will
911 first attempt to attach to it as a process, and if that fails, attempt
912 to open it as a corefile. If you have a corefile whose name begins with
913 a digit, you can prevent @value{GDBN} from treating it as a pid by
914 prefixing it with @file{./}, e.g.@: @file{./12345}.
916 If @value{GDBN} has not been configured to included core file support,
917 such as for most embedded targets, then it will complain about a second
918 argument and ignore it.
920 Many options have both long and short forms; both are shown in the
921 following list. @value{GDBN} also recognizes the long forms if you truncate
922 them, so long as enough of the option is present to be unambiguous.
923 (If you prefer, you can flag option arguments with @samp{--} rather
924 than @samp{-}, though we illustrate the more usual convention.)
926 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
927 @c way, both those who look for -foo and --foo in the index, will find
931 @item -symbols @var{file}
933 @cindex @code{--symbols}
935 Read symbol table from file @var{file}.
937 @item -exec @var{file}
939 @cindex @code{--exec}
941 Use file @var{file} as the executable file to execute when appropriate,
942 and for examining pure data in conjunction with a core dump.
946 Read symbol table from file @var{file} and use it as the executable
949 @item -core @var{file}
951 @cindex @code{--core}
953 Use file @var{file} as a core dump to examine.
955 @item -pid @var{number}
956 @itemx -p @var{number}
959 Connect to process ID @var{number}, as with the @code{attach} command.
961 @item -command @var{file}
963 @cindex @code{--command}
965 Execute @value{GDBN} commands from file @var{file}. @xref{Command
966 Files,, Command files}.
968 @item -eval-command @var{command}
969 @itemx -ex @var{command}
970 @cindex @code{--eval-command}
972 Execute a single @value{GDBN} command.
974 This option may be used multiple times to call multiple commands. It may
975 also be interleaved with @samp{-command} as required.
978 @value{GDBP} -ex 'target sim' -ex 'load' \
979 -x setbreakpoints -ex 'run' a.out
982 @item -directory @var{directory}
983 @itemx -d @var{directory}
984 @cindex @code{--directory}
986 Add @var{directory} to the path to search for source and script files.
990 @cindex @code{--readnow}
992 Read each symbol file's entire symbol table immediately, rather than
993 the default, which is to read it incrementally as it is needed.
994 This makes startup slower, but makes future operations faster.
999 @subsection Choosing Modes
1001 You can run @value{GDBN} in various alternative modes---for example, in
1002 batch mode or quiet mode.
1009 Do not execute commands found in any initialization files. Normally,
1010 @value{GDBN} executes the commands in these files after all the command
1011 options and arguments have been processed. @xref{Command Files,,Command
1017 @cindex @code{--quiet}
1018 @cindex @code{--silent}
1020 ``Quiet''. Do not print the introductory and copyright messages. These
1021 messages are also suppressed in batch mode.
1024 @cindex @code{--batch}
1025 Run in batch mode. Exit with status @code{0} after processing all the
1026 command files specified with @samp{-x} (and all commands from
1027 initialization files, if not inhibited with @samp{-n}). Exit with
1028 nonzero status if an error occurs in executing the @value{GDBN} commands
1029 in the command files.
1031 Batch mode may be useful for running @value{GDBN} as a filter, for
1032 example to download and run a program on another computer; in order to
1033 make this more useful, the message
1036 Program exited normally.
1040 (which is ordinarily issued whenever a program running under
1041 @value{GDBN} control terminates) is not issued when running in batch
1045 @cindex @code{--batch-silent}
1046 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1047 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1048 unaffected). This is much quieter than @samp{-silent} and would be useless
1049 for an interactive session.
1051 This is particularly useful when using targets that give @samp{Loading section}
1052 messages, for example.
1054 Note that targets that give their output via @value{GDBN}, as opposed to
1055 writing directly to @code{stdout}, will also be made silent.
1057 @item -return-child-result
1058 @cindex @code{--return-child-result}
1059 The return code from @value{GDBN} will be the return code from the child
1060 process (the process being debugged), with the following exceptions:
1064 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1065 internal error. In this case the exit code is the same as it would have been
1066 without @samp{-return-child-result}.
1068 The user quits with an explicit value. E.g., @samp{quit 1}.
1070 The child process never runs, or is not allowed to terminate, in which case
1071 the exit code will be -1.
1074 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1075 when @value{GDBN} is being used as a remote program loader or simulator
1080 @cindex @code{--nowindows}
1082 ``No windows''. If @value{GDBN} comes with a graphical user interface
1083 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1084 interface. If no GUI is available, this option has no effect.
1088 @cindex @code{--windows}
1090 If @value{GDBN} includes a GUI, then this option requires it to be
1093 @item -cd @var{directory}
1095 Run @value{GDBN} using @var{directory} as its working directory,
1096 instead of the current directory.
1100 @cindex @code{--fullname}
1102 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1103 subprocess. It tells @value{GDBN} to output the full file name and line
1104 number in a standard, recognizable fashion each time a stack frame is
1105 displayed (which includes each time your program stops). This
1106 recognizable format looks like two @samp{\032} characters, followed by
1107 the file name, line number and character position separated by colons,
1108 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1109 @samp{\032} characters as a signal to display the source code for the
1113 @cindex @code{--epoch}
1114 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1115 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1116 routines so as to allow Epoch to display values of expressions in a
1119 @item -annotate @var{level}
1120 @cindex @code{--annotate}
1121 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1122 effect is identical to using @samp{set annotate @var{level}}
1123 (@pxref{Annotations}). The annotation @var{level} controls how much
1124 information @value{GDBN} prints together with its prompt, values of
1125 expressions, source lines, and other types of output. Level 0 is the
1126 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1127 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1128 that control @value{GDBN}, and level 2 has been deprecated.
1130 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1134 @cindex @code{--args}
1135 Change interpretation of command line so that arguments following the
1136 executable file are passed as command line arguments to the inferior.
1137 This option stops option processing.
1139 @item -baud @var{bps}
1141 @cindex @code{--baud}
1143 Set the line speed (baud rate or bits per second) of any serial
1144 interface used by @value{GDBN} for remote debugging.
1146 @item -l @var{timeout}
1148 Set the timeout (in seconds) of any communication used by @value{GDBN}
1149 for remote debugging.
1151 @item -tty @var{device}
1152 @itemx -t @var{device}
1153 @cindex @code{--tty}
1155 Run using @var{device} for your program's standard input and output.
1156 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1158 @c resolve the situation of these eventually
1160 @cindex @code{--tui}
1161 Activate the @dfn{Text User Interface} when starting. The Text User
1162 Interface manages several text windows on the terminal, showing
1163 source, assembly, registers and @value{GDBN} command outputs
1164 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1165 Text User Interface can be enabled by invoking the program
1166 @samp{@value{GDBTUI}}. Do not use this option if you run @value{GDBN} from
1167 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1170 @c @cindex @code{--xdb}
1171 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1172 @c For information, see the file @file{xdb_trans.html}, which is usually
1173 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1176 @item -interpreter @var{interp}
1177 @cindex @code{--interpreter}
1178 Use the interpreter @var{interp} for interface with the controlling
1179 program or device. This option is meant to be set by programs which
1180 communicate with @value{GDBN} using it as a back end.
1181 @xref{Interpreters, , Command Interpreters}.
1183 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1184 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1185 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1186 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1187 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1188 @sc{gdb/mi} interfaces are no longer supported.
1191 @cindex @code{--write}
1192 Open the executable and core files for both reading and writing. This
1193 is equivalent to the @samp{set write on} command inside @value{GDBN}
1197 @cindex @code{--statistics}
1198 This option causes @value{GDBN} to print statistics about time and
1199 memory usage after it completes each command and returns to the prompt.
1202 @cindex @code{--version}
1203 This option causes @value{GDBN} to print its version number and
1204 no-warranty blurb, and exit.
1209 @subsection What @value{GDBN} Does During Startup
1210 @cindex @value{GDBN} startup
1212 Here's the description of what @value{GDBN} does during session startup:
1216 Sets up the command interpreter as specified by the command line
1217 (@pxref{Mode Options, interpreter}).
1221 Reads the @dfn{init file} (if any) in your home directory@footnote{On
1222 DOS/Windows systems, the home directory is the one pointed to by the
1223 @code{HOME} environment variable.} and executes all the commands in
1227 Processes command line options and operands.
1230 Reads and executes the commands from init file (if any) in the current
1231 working directory. This is only done if the current directory is
1232 different from your home directory. Thus, you can have more than one
1233 init file, one generic in your home directory, and another, specific
1234 to the program you are debugging, in the directory where you invoke
1238 Reads command files specified by the @samp{-x} option. @xref{Command
1239 Files}, for more details about @value{GDBN} command files.
1242 Reads the command history recorded in the @dfn{history file}.
1243 @xref{Command History}, for more details about the command history and the
1244 files where @value{GDBN} records it.
1247 Init files use the same syntax as @dfn{command files} (@pxref{Command
1248 Files}) and are processed by @value{GDBN} in the same way. The init
1249 file in your home directory can set options (such as @samp{set
1250 complaints}) that affect subsequent processing of command line options
1251 and operands. Init files are not executed if you use the @samp{-nx}
1252 option (@pxref{Mode Options, ,Choosing Modes}).
1254 @cindex init file name
1255 @cindex @file{.gdbinit}
1256 @cindex @file{gdb.ini}
1257 The @value{GDBN} init files are normally called @file{.gdbinit}.
1258 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1259 the limitations of file names imposed by DOS filesystems. The Windows
1260 ports of @value{GDBN} use the standard name, but if they find a
1261 @file{gdb.ini} file, they warn you about that and suggest to rename
1262 the file to the standard name.
1266 @section Quitting @value{GDBN}
1267 @cindex exiting @value{GDBN}
1268 @cindex leaving @value{GDBN}
1271 @kindex quit @r{[}@var{expression}@r{]}
1272 @kindex q @r{(@code{quit})}
1273 @item quit @r{[}@var{expression}@r{]}
1275 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1276 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1277 do not supply @var{expression}, @value{GDBN} will terminate normally;
1278 otherwise it will terminate using the result of @var{expression} as the
1283 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1284 terminates the action of any @value{GDBN} command that is in progress and
1285 returns to @value{GDBN} command level. It is safe to type the interrupt
1286 character at any time because @value{GDBN} does not allow it to take effect
1287 until a time when it is safe.
1289 If you have been using @value{GDBN} to control an attached process or
1290 device, you can release it with the @code{detach} command
1291 (@pxref{Attach, ,Debugging an Already-running Process}).
1293 @node Shell Commands
1294 @section Shell Commands
1296 If you need to execute occasional shell commands during your
1297 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1298 just use the @code{shell} command.
1302 @cindex shell escape
1303 @item shell @var{command string}
1304 Invoke a standard shell to execute @var{command string}.
1305 If it exists, the environment variable @code{SHELL} determines which
1306 shell to run. Otherwise @value{GDBN} uses the default shell
1307 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1310 The utility @code{make} is often needed in development environments.
1311 You do not have to use the @code{shell} command for this purpose in
1316 @cindex calling make
1317 @item make @var{make-args}
1318 Execute the @code{make} program with the specified
1319 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1322 @node Logging Output
1323 @section Logging Output
1324 @cindex logging @value{GDBN} output
1325 @cindex save @value{GDBN} output to a file
1327 You may want to save the output of @value{GDBN} commands to a file.
1328 There are several commands to control @value{GDBN}'s logging.
1332 @item set logging on
1334 @item set logging off
1336 @cindex logging file name
1337 @item set logging file @var{file}
1338 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1339 @item set logging overwrite [on|off]
1340 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1341 you want @code{set logging on} to overwrite the logfile instead.
1342 @item set logging redirect [on|off]
1343 By default, @value{GDBN} output will go to both the terminal and the logfile.
1344 Set @code{redirect} if you want output to go only to the log file.
1345 @kindex show logging
1347 Show the current values of the logging settings.
1351 @chapter @value{GDBN} Commands
1353 You can abbreviate a @value{GDBN} command to the first few letters of the command
1354 name, if that abbreviation is unambiguous; and you can repeat certain
1355 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1356 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1357 show you the alternatives available, if there is more than one possibility).
1360 * Command Syntax:: How to give commands to @value{GDBN}
1361 * Completion:: Command completion
1362 * Help:: How to ask @value{GDBN} for help
1365 @node Command Syntax
1366 @section Command Syntax
1368 A @value{GDBN} command is a single line of input. There is no limit on
1369 how long it can be. It starts with a command name, which is followed by
1370 arguments whose meaning depends on the command name. For example, the
1371 command @code{step} accepts an argument which is the number of times to
1372 step, as in @samp{step 5}. You can also use the @code{step} command
1373 with no arguments. Some commands do not allow any arguments.
1375 @cindex abbreviation
1376 @value{GDBN} command names may always be truncated if that abbreviation is
1377 unambiguous. Other possible command abbreviations are listed in the
1378 documentation for individual commands. In some cases, even ambiguous
1379 abbreviations are allowed; for example, @code{s} is specially defined as
1380 equivalent to @code{step} even though there are other commands whose
1381 names start with @code{s}. You can test abbreviations by using them as
1382 arguments to the @code{help} command.
1384 @cindex repeating commands
1385 @kindex RET @r{(repeat last command)}
1386 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1387 repeat the previous command. Certain commands (for example, @code{run})
1388 will not repeat this way; these are commands whose unintentional
1389 repetition might cause trouble and which you are unlikely to want to
1390 repeat. User-defined commands can disable this feature; see
1391 @ref{Define, dont-repeat}.
1393 The @code{list} and @code{x} commands, when you repeat them with
1394 @key{RET}, construct new arguments rather than repeating
1395 exactly as typed. This permits easy scanning of source or memory.
1397 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1398 output, in a way similar to the common utility @code{more}
1399 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1400 @key{RET} too many in this situation, @value{GDBN} disables command
1401 repetition after any command that generates this sort of display.
1403 @kindex # @r{(a comment)}
1405 Any text from a @kbd{#} to the end of the line is a comment; it does
1406 nothing. This is useful mainly in command files (@pxref{Command
1407 Files,,Command Files}).
1409 @cindex repeating command sequences
1410 @kindex Ctrl-o @r{(operate-and-get-next)}
1411 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1412 commands. This command accepts the current line, like @key{RET}, and
1413 then fetches the next line relative to the current line from the history
1417 @section Command Completion
1420 @cindex word completion
1421 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1422 only one possibility; it can also show you what the valid possibilities
1423 are for the next word in a command, at any time. This works for @value{GDBN}
1424 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1426 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1427 of a word. If there is only one possibility, @value{GDBN} fills in the
1428 word, and waits for you to finish the command (or press @key{RET} to
1429 enter it). For example, if you type
1431 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1432 @c complete accuracy in these examples; space introduced for clarity.
1433 @c If texinfo enhancements make it unnecessary, it would be nice to
1434 @c replace " @key" by "@key" in the following...
1436 (@value{GDBP}) info bre @key{TAB}
1440 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1441 the only @code{info} subcommand beginning with @samp{bre}:
1444 (@value{GDBP}) info breakpoints
1448 You can either press @key{RET} at this point, to run the @code{info
1449 breakpoints} command, or backspace and enter something else, if
1450 @samp{breakpoints} does not look like the command you expected. (If you
1451 were sure you wanted @code{info breakpoints} in the first place, you
1452 might as well just type @key{RET} immediately after @samp{info bre},
1453 to exploit command abbreviations rather than command completion).
1455 If there is more than one possibility for the next word when you press
1456 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1457 characters and try again, or just press @key{TAB} a second time;
1458 @value{GDBN} displays all the possible completions for that word. For
1459 example, you might want to set a breakpoint on a subroutine whose name
1460 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1461 just sounds the bell. Typing @key{TAB} again displays all the
1462 function names in your program that begin with those characters, for
1466 (@value{GDBP}) b make_ @key{TAB}
1467 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1468 make_a_section_from_file make_environ
1469 make_abs_section make_function_type
1470 make_blockvector make_pointer_type
1471 make_cleanup make_reference_type
1472 make_command make_symbol_completion_list
1473 (@value{GDBP}) b make_
1477 After displaying the available possibilities, @value{GDBN} copies your
1478 partial input (@samp{b make_} in the example) so you can finish the
1481 If you just want to see the list of alternatives in the first place, you
1482 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1483 means @kbd{@key{META} ?}. You can type this either by holding down a
1484 key designated as the @key{META} shift on your keyboard (if there is
1485 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1487 @cindex quotes in commands
1488 @cindex completion of quoted strings
1489 Sometimes the string you need, while logically a ``word'', may contain
1490 parentheses or other characters that @value{GDBN} normally excludes from
1491 its notion of a word. To permit word completion to work in this
1492 situation, you may enclose words in @code{'} (single quote marks) in
1493 @value{GDBN} commands.
1495 The most likely situation where you might need this is in typing the
1496 name of a C@t{++} function. This is because C@t{++} allows function
1497 overloading (multiple definitions of the same function, distinguished
1498 by argument type). For example, when you want to set a breakpoint you
1499 may need to distinguish whether you mean the version of @code{name}
1500 that takes an @code{int} parameter, @code{name(int)}, or the version
1501 that takes a @code{float} parameter, @code{name(float)}. To use the
1502 word-completion facilities in this situation, type a single quote
1503 @code{'} at the beginning of the function name. This alerts
1504 @value{GDBN} that it may need to consider more information than usual
1505 when you press @key{TAB} or @kbd{M-?} to request word completion:
1508 (@value{GDBP}) b 'bubble( @kbd{M-?}
1509 bubble(double,double) bubble(int,int)
1510 (@value{GDBP}) b 'bubble(
1513 In some cases, @value{GDBN} can tell that completing a name requires using
1514 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1515 completing as much as it can) if you do not type the quote in the first
1519 (@value{GDBP}) b bub @key{TAB}
1520 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1521 (@value{GDBP}) b 'bubble(
1525 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1526 you have not yet started typing the argument list when you ask for
1527 completion on an overloaded symbol.
1529 For more information about overloaded functions, see @ref{C Plus Plus
1530 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1531 overload-resolution off} to disable overload resolution;
1532 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1534 @cindex completion of structure field names
1535 @cindex structure field name completion
1536 @cindex completion of union field names
1537 @cindex union field name completion
1538 When completing in an expression which looks up a field in a
1539 structure, @value{GDBN} also tries@footnote{The completer can be
1540 confused by certain kinds of invalid expressions. Also, it only
1541 examines the static type of the expression, not the dynamic type.} to
1542 limit completions to the field names available in the type of the
1546 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1547 magic to_delete to_fputs to_put to_rewind
1548 to_data to_flush to_isatty to_read to_write
1552 This is because the @code{gdb_stdout} is a variable of the type
1553 @code{struct ui_file} that is defined in @value{GDBN} sources as
1560 ui_file_flush_ftype *to_flush;
1561 ui_file_write_ftype *to_write;
1562 ui_file_fputs_ftype *to_fputs;
1563 ui_file_read_ftype *to_read;
1564 ui_file_delete_ftype *to_delete;
1565 ui_file_isatty_ftype *to_isatty;
1566 ui_file_rewind_ftype *to_rewind;
1567 ui_file_put_ftype *to_put;
1574 @section Getting Help
1575 @cindex online documentation
1578 You can always ask @value{GDBN} itself for information on its commands,
1579 using the command @code{help}.
1582 @kindex h @r{(@code{help})}
1585 You can use @code{help} (abbreviated @code{h}) with no arguments to
1586 display a short list of named classes of commands:
1590 List of classes of commands:
1592 aliases -- Aliases of other commands
1593 breakpoints -- Making program stop at certain points
1594 data -- Examining data
1595 files -- Specifying and examining files
1596 internals -- Maintenance commands
1597 obscure -- Obscure features
1598 running -- Running the program
1599 stack -- Examining the stack
1600 status -- Status inquiries
1601 support -- Support facilities
1602 tracepoints -- Tracing of program execution without
1603 stopping the program
1604 user-defined -- User-defined commands
1606 Type "help" followed by a class name for a list of
1607 commands in that class.
1608 Type "help" followed by command name for full
1610 Command name abbreviations are allowed if unambiguous.
1613 @c the above line break eliminates huge line overfull...
1615 @item help @var{class}
1616 Using one of the general help classes as an argument, you can get a
1617 list of the individual commands in that class. For example, here is the
1618 help display for the class @code{status}:
1621 (@value{GDBP}) help status
1626 @c Line break in "show" line falsifies real output, but needed
1627 @c to fit in smallbook page size.
1628 info -- Generic command for showing things
1629 about the program being debugged
1630 show -- Generic command for showing things
1633 Type "help" followed by command name for full
1635 Command name abbreviations are allowed if unambiguous.
1639 @item help @var{command}
1640 With a command name as @code{help} argument, @value{GDBN} displays a
1641 short paragraph on how to use that command.
1644 @item apropos @var{args}
1645 The @code{apropos} command searches through all of the @value{GDBN}
1646 commands, and their documentation, for the regular expression specified in
1647 @var{args}. It prints out all matches found. For example:
1658 set symbol-reloading -- Set dynamic symbol table reloading
1659 multiple times in one run
1660 show symbol-reloading -- Show dynamic symbol table reloading
1661 multiple times in one run
1666 @item complete @var{args}
1667 The @code{complete @var{args}} command lists all the possible completions
1668 for the beginning of a command. Use @var{args} to specify the beginning of the
1669 command you want completed. For example:
1675 @noindent results in:
1686 @noindent This is intended for use by @sc{gnu} Emacs.
1689 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1690 and @code{show} to inquire about the state of your program, or the state
1691 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1692 manual introduces each of them in the appropriate context. The listings
1693 under @code{info} and under @code{show} in the Index point to
1694 all the sub-commands. @xref{Index}.
1699 @kindex i @r{(@code{info})}
1701 This command (abbreviated @code{i}) is for describing the state of your
1702 program. For example, you can show the arguments passed to a function
1703 with @code{info args}, list the registers currently in use with @code{info
1704 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1705 You can get a complete list of the @code{info} sub-commands with
1706 @w{@code{help info}}.
1710 You can assign the result of an expression to an environment variable with
1711 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1712 @code{set prompt $}.
1716 In contrast to @code{info}, @code{show} is for describing the state of
1717 @value{GDBN} itself.
1718 You can change most of the things you can @code{show}, by using the
1719 related command @code{set}; for example, you can control what number
1720 system is used for displays with @code{set radix}, or simply inquire
1721 which is currently in use with @code{show radix}.
1724 To display all the settable parameters and their current
1725 values, you can use @code{show} with no arguments; you may also use
1726 @code{info set}. Both commands produce the same display.
1727 @c FIXME: "info set" violates the rule that "info" is for state of
1728 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1729 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1733 Here are three miscellaneous @code{show} subcommands, all of which are
1734 exceptional in lacking corresponding @code{set} commands:
1737 @kindex show version
1738 @cindex @value{GDBN} version number
1740 Show what version of @value{GDBN} is running. You should include this
1741 information in @value{GDBN} bug-reports. If multiple versions of
1742 @value{GDBN} are in use at your site, you may need to determine which
1743 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1744 commands are introduced, and old ones may wither away. Also, many
1745 system vendors ship variant versions of @value{GDBN}, and there are
1746 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1747 The version number is the same as the one announced when you start
1750 @kindex show copying
1751 @kindex info copying
1752 @cindex display @value{GDBN} copyright
1755 Display information about permission for copying @value{GDBN}.
1757 @kindex show warranty
1758 @kindex info warranty
1760 @itemx info warranty
1761 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1762 if your version of @value{GDBN} comes with one.
1767 @chapter Running Programs Under @value{GDBN}
1769 When you run a program under @value{GDBN}, you must first generate
1770 debugging information when you compile it.
1772 You may start @value{GDBN} with its arguments, if any, in an environment
1773 of your choice. If you are doing native debugging, you may redirect
1774 your program's input and output, debug an already running process, or
1775 kill a child process.
1778 * Compilation:: Compiling for debugging
1779 * Starting:: Starting your program
1780 * Arguments:: Your program's arguments
1781 * Environment:: Your program's environment
1783 * Working Directory:: Your program's working directory
1784 * Input/Output:: Your program's input and output
1785 * Attach:: Debugging an already-running process
1786 * Kill Process:: Killing the child process
1788 * Threads:: Debugging programs with multiple threads
1789 * Processes:: Debugging programs with multiple processes
1790 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1794 @section Compiling for Debugging
1796 In order to debug a program effectively, you need to generate
1797 debugging information when you compile it. This debugging information
1798 is stored in the object file; it describes the data type of each
1799 variable or function and the correspondence between source line numbers
1800 and addresses in the executable code.
1802 To request debugging information, specify the @samp{-g} option when you run
1805 Programs that are to be shipped to your customers are compiled with
1806 optimizations, using the @samp{-O} compiler option. However, many
1807 compilers are unable to handle the @samp{-g} and @samp{-O} options
1808 together. Using those compilers, you cannot generate optimized
1809 executables containing debugging information.
1811 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1812 without @samp{-O}, making it possible to debug optimized code. We
1813 recommend that you @emph{always} use @samp{-g} whenever you compile a
1814 program. You may think your program is correct, but there is no sense
1815 in pushing your luck.
1817 @cindex optimized code, debugging
1818 @cindex debugging optimized code
1819 When you debug a program compiled with @samp{-g -O}, remember that the
1820 optimizer is rearranging your code; the debugger shows you what is
1821 really there. Do not be too surprised when the execution path does not
1822 exactly match your source file! An extreme example: if you define a
1823 variable, but never use it, @value{GDBN} never sees that
1824 variable---because the compiler optimizes it out of existence.
1826 Some things do not work as well with @samp{-g -O} as with just
1827 @samp{-g}, particularly on machines with instruction scheduling. If in
1828 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1829 please report it to us as a bug (including a test case!).
1830 @xref{Variables}, for more information about debugging optimized code.
1832 Older versions of the @sc{gnu} C compiler permitted a variant option
1833 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1834 format; if your @sc{gnu} C compiler has this option, do not use it.
1836 @value{GDBN} knows about preprocessor macros and can show you their
1837 expansion (@pxref{Macros}). Most compilers do not include information
1838 about preprocessor macros in the debugging information if you specify
1839 the @option{-g} flag alone, because this information is rather large.
1840 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1841 provides macro information if you specify the options
1842 @option{-gdwarf-2} and @option{-g3}; the former option requests
1843 debugging information in the Dwarf 2 format, and the latter requests
1844 ``extra information''. In the future, we hope to find more compact
1845 ways to represent macro information, so that it can be included with
1850 @section Starting your Program
1856 @kindex r @r{(@code{run})}
1859 Use the @code{run} command to start your program under @value{GDBN}.
1860 You must first specify the program name (except on VxWorks) with an
1861 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1862 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1863 (@pxref{Files, ,Commands to Specify Files}).
1867 If you are running your program in an execution environment that
1868 supports processes, @code{run} creates an inferior process and makes
1869 that process run your program. In some environments without processes,
1870 @code{run} jumps to the start of your program. Other targets,
1871 like @samp{remote}, are always running. If you get an error
1872 message like this one:
1875 The "remote" target does not support "run".
1876 Try "help target" or "continue".
1880 then use @code{continue} to run your program. You may need @code{load}
1881 first (@pxref{load}).
1883 The execution of a program is affected by certain information it
1884 receives from its superior. @value{GDBN} provides ways to specify this
1885 information, which you must do @emph{before} starting your program. (You
1886 can change it after starting your program, but such changes only affect
1887 your program the next time you start it.) This information may be
1888 divided into four categories:
1891 @item The @emph{arguments.}
1892 Specify the arguments to give your program as the arguments of the
1893 @code{run} command. If a shell is available on your target, the shell
1894 is used to pass the arguments, so that you may use normal conventions
1895 (such as wildcard expansion or variable substitution) in describing
1897 In Unix systems, you can control which shell is used with the
1898 @code{SHELL} environment variable.
1899 @xref{Arguments, ,Your Program's Arguments}.
1901 @item The @emph{environment.}
1902 Your program normally inherits its environment from @value{GDBN}, but you can
1903 use the @value{GDBN} commands @code{set environment} and @code{unset
1904 environment} to change parts of the environment that affect
1905 your program. @xref{Environment, ,Your Program's Environment}.
1907 @item The @emph{working directory.}
1908 Your program inherits its working directory from @value{GDBN}. You can set
1909 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1910 @xref{Working Directory, ,Your Program's Working Directory}.
1912 @item The @emph{standard input and output.}
1913 Your program normally uses the same device for standard input and
1914 standard output as @value{GDBN} is using. You can redirect input and output
1915 in the @code{run} command line, or you can use the @code{tty} command to
1916 set a different device for your program.
1917 @xref{Input/Output, ,Your Program's Input and Output}.
1920 @emph{Warning:} While input and output redirection work, you cannot use
1921 pipes to pass the output of the program you are debugging to another
1922 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1926 When you issue the @code{run} command, your program begins to execute
1927 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1928 of how to arrange for your program to stop. Once your program has
1929 stopped, you may call functions in your program, using the @code{print}
1930 or @code{call} commands. @xref{Data, ,Examining Data}.
1932 If the modification time of your symbol file has changed since the last
1933 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1934 table, and reads it again. When it does this, @value{GDBN} tries to retain
1935 your current breakpoints.
1940 @cindex run to main procedure
1941 The name of the main procedure can vary from language to language.
1942 With C or C@t{++}, the main procedure name is always @code{main}, but
1943 other languages such as Ada do not require a specific name for their
1944 main procedure. The debugger provides a convenient way to start the
1945 execution of the program and to stop at the beginning of the main
1946 procedure, depending on the language used.
1948 The @samp{start} command does the equivalent of setting a temporary
1949 breakpoint at the beginning of the main procedure and then invoking
1950 the @samp{run} command.
1952 @cindex elaboration phase
1953 Some programs contain an @dfn{elaboration} phase where some startup code is
1954 executed before the main procedure is called. This depends on the
1955 languages used to write your program. In C@t{++}, for instance,
1956 constructors for static and global objects are executed before
1957 @code{main} is called. It is therefore possible that the debugger stops
1958 before reaching the main procedure. However, the temporary breakpoint
1959 will remain to halt execution.
1961 Specify the arguments to give to your program as arguments to the
1962 @samp{start} command. These arguments will be given verbatim to the
1963 underlying @samp{run} command. Note that the same arguments will be
1964 reused if no argument is provided during subsequent calls to
1965 @samp{start} or @samp{run}.
1967 It is sometimes necessary to debug the program during elaboration. In
1968 these cases, using the @code{start} command would stop the execution of
1969 your program too late, as the program would have already completed the
1970 elaboration phase. Under these circumstances, insert breakpoints in your
1971 elaboration code before running your program.
1973 @kindex set exec-wrapper
1974 @item set exec-wrapper @var{wrapper}
1975 @itemx show exec-wrapper
1976 @itemx unset exec-wrapper
1977 When @samp{exec-wrapper} is set, the specified wrapper is used to
1978 launch programs for debugging. @value{GDBN} starts your program
1979 with a shell command of the form @kbd{exec @var{wrapper}
1980 @var{program}}. Quoting is added to @var{program} and its
1981 arguments, but not to @var{wrapper}, so you should add quotes if
1982 appropriate for your shell. The wrapper runs until it executes
1983 your program, and then @value{GDBN} takes control.
1985 You can use any program that eventually calls @code{execve} with
1986 its arguments as a wrapper. Several standard Unix utilities do
1987 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
1988 with @code{exec "$@@"} will also work.
1990 For example, you can use @code{env} to pass an environment variable to
1991 the debugged program, without setting the variable in your shell's
1995 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
1999 This command is available when debugging locally on most targets, excluding
2000 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2002 @kindex set disable-randomization
2003 @item set disable-randomization
2004 @itemx set disable-randomization on
2005 This option (enabled by default in @value{GDBN}) will turn off the native
2006 randomization of the virtual address space of the started program. This option
2007 is useful for multiple debugging sessions to make the execution better
2008 reproducible and memory addresses reusable across debugging sessions.
2010 This feature is implemented only on @sc{gnu}/Linux. You can get the same
2014 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2017 @item set disable-randomization off
2018 Leave the behavior of the started executable unchanged. Some bugs rear their
2019 ugly heads only when the program is loaded at certain addresses. If your bug
2020 disappears when you run the program under @value{GDBN}, that might be because
2021 @value{GDBN} by default disables the address randomization on platforms, such
2022 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2023 disable-randomization off} to try to reproduce such elusive bugs.
2025 The virtual address space randomization is implemented only on @sc{gnu}/Linux.
2026 It protects the programs against some kinds of security attacks. In these
2027 cases the attacker needs to know the exact location of a concrete executable
2028 code. Randomizing its location makes it impossible to inject jumps misusing
2029 a code at its expected addresses.
2031 Prelinking shared libraries provides a startup performance advantage but it
2032 makes addresses in these libraries predictable for privileged processes by
2033 having just unprivileged access at the target system. Reading the shared
2034 library binary gives enough information for assembling the malicious code
2035 misusing it. Still even a prelinked shared library can get loaded at a new
2036 random address just requiring the regular relocation process during the
2037 startup. Shared libraries not already prelinked are always loaded at
2038 a randomly chosen address.
2040 Position independent executables (PIE) contain position independent code
2041 similar to the shared libraries and therefore such executables get loaded at
2042 a randomly chosen address upon startup. PIE executables always load even
2043 already prelinked shared libraries at a random address. You can build such
2044 executable using @command{gcc -fPIE -pie}.
2046 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2047 (as long as the randomization is enabled).
2049 @item show disable-randomization
2050 Show the current setting of the explicit disable of the native randomization of
2051 the virtual address space of the started program.
2056 @section Your Program's Arguments
2058 @cindex arguments (to your program)
2059 The arguments to your program can be specified by the arguments of the
2061 They are passed to a shell, which expands wildcard characters and
2062 performs redirection of I/O, and thence to your program. Your
2063 @code{SHELL} environment variable (if it exists) specifies what shell
2064 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2065 the default shell (@file{/bin/sh} on Unix).
2067 On non-Unix systems, the program is usually invoked directly by
2068 @value{GDBN}, which emulates I/O redirection via the appropriate system
2069 calls, and the wildcard characters are expanded by the startup code of
2070 the program, not by the shell.
2072 @code{run} with no arguments uses the same arguments used by the previous
2073 @code{run}, or those set by the @code{set args} command.
2078 Specify the arguments to be used the next time your program is run. If
2079 @code{set args} has no arguments, @code{run} executes your program
2080 with no arguments. Once you have run your program with arguments,
2081 using @code{set args} before the next @code{run} is the only way to run
2082 it again without arguments.
2086 Show the arguments to give your program when it is started.
2090 @section Your Program's Environment
2092 @cindex environment (of your program)
2093 The @dfn{environment} consists of a set of environment variables and
2094 their values. Environment variables conventionally record such things as
2095 your user name, your home directory, your terminal type, and your search
2096 path for programs to run. Usually you set up environment variables with
2097 the shell and they are inherited by all the other programs you run. When
2098 debugging, it can be useful to try running your program with a modified
2099 environment without having to start @value{GDBN} over again.
2103 @item path @var{directory}
2104 Add @var{directory} to the front of the @code{PATH} environment variable
2105 (the search path for executables) that will be passed to your program.
2106 The value of @code{PATH} used by @value{GDBN} does not change.
2107 You may specify several directory names, separated by whitespace or by a
2108 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2109 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2110 is moved to the front, so it is searched sooner.
2112 You can use the string @samp{$cwd} to refer to whatever is the current
2113 working directory at the time @value{GDBN} searches the path. If you
2114 use @samp{.} instead, it refers to the directory where you executed the
2115 @code{path} command. @value{GDBN} replaces @samp{.} in the
2116 @var{directory} argument (with the current path) before adding
2117 @var{directory} to the search path.
2118 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2119 @c document that, since repeating it would be a no-op.
2123 Display the list of search paths for executables (the @code{PATH}
2124 environment variable).
2126 @kindex show environment
2127 @item show environment @r{[}@var{varname}@r{]}
2128 Print the value of environment variable @var{varname} to be given to
2129 your program when it starts. If you do not supply @var{varname},
2130 print the names and values of all environment variables to be given to
2131 your program. You can abbreviate @code{environment} as @code{env}.
2133 @kindex set environment
2134 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2135 Set environment variable @var{varname} to @var{value}. The value
2136 changes for your program only, not for @value{GDBN} itself. @var{value} may
2137 be any string; the values of environment variables are just strings, and
2138 any interpretation is supplied by your program itself. The @var{value}
2139 parameter is optional; if it is eliminated, the variable is set to a
2141 @c "any string" here does not include leading, trailing
2142 @c blanks. Gnu asks: does anyone care?
2144 For example, this command:
2151 tells the debugged program, when subsequently run, that its user is named
2152 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2153 are not actually required.)
2155 @kindex unset environment
2156 @item unset environment @var{varname}
2157 Remove variable @var{varname} from the environment to be passed to your
2158 program. This is different from @samp{set env @var{varname} =};
2159 @code{unset environment} removes the variable from the environment,
2160 rather than assigning it an empty value.
2163 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2165 by your @code{SHELL} environment variable if it exists (or
2166 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2167 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2168 @file{.bashrc} for BASH---any variables you set in that file affect
2169 your program. You may wish to move setting of environment variables to
2170 files that are only run when you sign on, such as @file{.login} or
2173 @node Working Directory
2174 @section Your Program's Working Directory
2176 @cindex working directory (of your program)
2177 Each time you start your program with @code{run}, it inherits its
2178 working directory from the current working directory of @value{GDBN}.
2179 The @value{GDBN} working directory is initially whatever it inherited
2180 from its parent process (typically the shell), but you can specify a new
2181 working directory in @value{GDBN} with the @code{cd} command.
2183 The @value{GDBN} working directory also serves as a default for the commands
2184 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2189 @cindex change working directory
2190 @item cd @var{directory}
2191 Set the @value{GDBN} working directory to @var{directory}.
2195 Print the @value{GDBN} working directory.
2198 It is generally impossible to find the current working directory of
2199 the process being debugged (since a program can change its directory
2200 during its run). If you work on a system where @value{GDBN} is
2201 configured with the @file{/proc} support, you can use the @code{info
2202 proc} command (@pxref{SVR4 Process Information}) to find out the
2203 current working directory of the debuggee.
2206 @section Your Program's Input and Output
2211 By default, the program you run under @value{GDBN} does input and output to
2212 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2213 to its own terminal modes to interact with you, but it records the terminal
2214 modes your program was using and switches back to them when you continue
2215 running your program.
2218 @kindex info terminal
2220 Displays information recorded by @value{GDBN} about the terminal modes your
2224 You can redirect your program's input and/or output using shell
2225 redirection with the @code{run} command. For example,
2232 starts your program, diverting its output to the file @file{outfile}.
2235 @cindex controlling terminal
2236 Another way to specify where your program should do input and output is
2237 with the @code{tty} command. This command accepts a file name as
2238 argument, and causes this file to be the default for future @code{run}
2239 commands. It also resets the controlling terminal for the child
2240 process, for future @code{run} commands. For example,
2247 directs that processes started with subsequent @code{run} commands
2248 default to do input and output on the terminal @file{/dev/ttyb} and have
2249 that as their controlling terminal.
2251 An explicit redirection in @code{run} overrides the @code{tty} command's
2252 effect on the input/output device, but not its effect on the controlling
2255 When you use the @code{tty} command or redirect input in the @code{run}
2256 command, only the input @emph{for your program} is affected. The input
2257 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2258 for @code{set inferior-tty}.
2260 @cindex inferior tty
2261 @cindex set inferior controlling terminal
2262 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2263 display the name of the terminal that will be used for future runs of your
2267 @item set inferior-tty /dev/ttyb
2268 @kindex set inferior-tty
2269 Set the tty for the program being debugged to /dev/ttyb.
2271 @item show inferior-tty
2272 @kindex show inferior-tty
2273 Show the current tty for the program being debugged.
2277 @section Debugging an Already-running Process
2282 @item attach @var{process-id}
2283 This command attaches to a running process---one that was started
2284 outside @value{GDBN}. (@code{info files} shows your active
2285 targets.) The command takes as argument a process ID. The usual way to
2286 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2287 or with the @samp{jobs -l} shell command.
2289 @code{attach} does not repeat if you press @key{RET} a second time after
2290 executing the command.
2293 To use @code{attach}, your program must be running in an environment
2294 which supports processes; for example, @code{attach} does not work for
2295 programs on bare-board targets that lack an operating system. You must
2296 also have permission to send the process a signal.
2298 When you use @code{attach}, the debugger finds the program running in
2299 the process first by looking in the current working directory, then (if
2300 the program is not found) by using the source file search path
2301 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2302 the @code{file} command to load the program. @xref{Files, ,Commands to
2305 The first thing @value{GDBN} does after arranging to debug the specified
2306 process is to stop it. You can examine and modify an attached process
2307 with all the @value{GDBN} commands that are ordinarily available when
2308 you start processes with @code{run}. You can insert breakpoints; you
2309 can step and continue; you can modify storage. If you would rather the
2310 process continue running, you may use the @code{continue} command after
2311 attaching @value{GDBN} to the process.
2316 When you have finished debugging the attached process, you can use the
2317 @code{detach} command to release it from @value{GDBN} control. Detaching
2318 the process continues its execution. After the @code{detach} command,
2319 that process and @value{GDBN} become completely independent once more, and you
2320 are ready to @code{attach} another process or start one with @code{run}.
2321 @code{detach} does not repeat if you press @key{RET} again after
2322 executing the command.
2325 If you exit @value{GDBN} while you have an attached process, you detach
2326 that process. If you use the @code{run} command, you kill that process.
2327 By default, @value{GDBN} asks for confirmation if you try to do either of these
2328 things; you can control whether or not you need to confirm by using the
2329 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2333 @section Killing the Child Process
2338 Kill the child process in which your program is running under @value{GDBN}.
2341 This command is useful if you wish to debug a core dump instead of a
2342 running process. @value{GDBN} ignores any core dump file while your program
2345 On some operating systems, a program cannot be executed outside @value{GDBN}
2346 while you have breakpoints set on it inside @value{GDBN}. You can use the
2347 @code{kill} command in this situation to permit running your program
2348 outside the debugger.
2350 The @code{kill} command is also useful if you wish to recompile and
2351 relink your program, since on many systems it is impossible to modify an
2352 executable file while it is running in a process. In this case, when you
2353 next type @code{run}, @value{GDBN} notices that the file has changed, and
2354 reads the symbol table again (while trying to preserve your current
2355 breakpoint settings).
2358 @section Debugging Programs with Multiple Threads
2360 @cindex threads of execution
2361 @cindex multiple threads
2362 @cindex switching threads
2363 In some operating systems, such as HP-UX and Solaris, a single program
2364 may have more than one @dfn{thread} of execution. The precise semantics
2365 of threads differ from one operating system to another, but in general
2366 the threads of a single program are akin to multiple processes---except
2367 that they share one address space (that is, they can all examine and
2368 modify the same variables). On the other hand, each thread has its own
2369 registers and execution stack, and perhaps private memory.
2371 @value{GDBN} provides these facilities for debugging multi-thread
2375 @item automatic notification of new threads
2376 @item @samp{thread @var{threadno}}, a command to switch among threads
2377 @item @samp{info threads}, a command to inquire about existing threads
2378 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2379 a command to apply a command to a list of threads
2380 @item thread-specific breakpoints
2381 @item @samp{set print thread-events}, which controls printing of
2382 messages on thread start and exit.
2386 @emph{Warning:} These facilities are not yet available on every
2387 @value{GDBN} configuration where the operating system supports threads.
2388 If your @value{GDBN} does not support threads, these commands have no
2389 effect. For example, a system without thread support shows no output
2390 from @samp{info threads}, and always rejects the @code{thread} command,
2394 (@value{GDBP}) info threads
2395 (@value{GDBP}) thread 1
2396 Thread ID 1 not known. Use the "info threads" command to
2397 see the IDs of currently known threads.
2399 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2400 @c doesn't support threads"?
2403 @cindex focus of debugging
2404 @cindex current thread
2405 The @value{GDBN} thread debugging facility allows you to observe all
2406 threads while your program runs---but whenever @value{GDBN} takes
2407 control, one thread in particular is always the focus of debugging.
2408 This thread is called the @dfn{current thread}. Debugging commands show
2409 program information from the perspective of the current thread.
2411 @cindex @code{New} @var{systag} message
2412 @cindex thread identifier (system)
2413 @c FIXME-implementors!! It would be more helpful if the [New...] message
2414 @c included GDB's numeric thread handle, so you could just go to that
2415 @c thread without first checking `info threads'.
2416 Whenever @value{GDBN} detects a new thread in your program, it displays
2417 the target system's identification for the thread with a message in the
2418 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2419 whose form varies depending on the particular system. For example, on
2420 @sc{gnu}/Linux, you might see
2423 [New Thread 46912507313328 (LWP 25582)]
2427 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2428 the @var{systag} is simply something like @samp{process 368}, with no
2431 @c FIXME!! (1) Does the [New...] message appear even for the very first
2432 @c thread of a program, or does it only appear for the
2433 @c second---i.e.@: when it becomes obvious we have a multithread
2435 @c (2) *Is* there necessarily a first thread always? Or do some
2436 @c multithread systems permit starting a program with multiple
2437 @c threads ab initio?
2439 @cindex thread number
2440 @cindex thread identifier (GDB)
2441 For debugging purposes, @value{GDBN} associates its own thread
2442 number---always a single integer---with each thread in your program.
2445 @kindex info threads
2447 Display a summary of all threads currently in your
2448 program. @value{GDBN} displays for each thread (in this order):
2452 the thread number assigned by @value{GDBN}
2455 the target system's thread identifier (@var{systag})
2458 the current stack frame summary for that thread
2462 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2463 indicates the current thread.
2467 @c end table here to get a little more width for example
2470 (@value{GDBP}) info threads
2471 3 process 35 thread 27 0x34e5 in sigpause ()
2472 2 process 35 thread 23 0x34e5 in sigpause ()
2473 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2479 @cindex debugging multithreaded programs (on HP-UX)
2480 @cindex thread identifier (GDB), on HP-UX
2481 For debugging purposes, @value{GDBN} associates its own thread
2482 number---a small integer assigned in thread-creation order---with each
2483 thread in your program.
2485 @cindex @code{New} @var{systag} message, on HP-UX
2486 @cindex thread identifier (system), on HP-UX
2487 @c FIXME-implementors!! It would be more helpful if the [New...] message
2488 @c included GDB's numeric thread handle, so you could just go to that
2489 @c thread without first checking `info threads'.
2490 Whenever @value{GDBN} detects a new thread in your program, it displays
2491 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2492 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2493 whose form varies depending on the particular system. For example, on
2497 [New thread 2 (system thread 26594)]
2501 when @value{GDBN} notices a new thread.
2504 @kindex info threads (HP-UX)
2506 Display a summary of all threads currently in your
2507 program. @value{GDBN} displays for each thread (in this order):
2510 @item the thread number assigned by @value{GDBN}
2512 @item the target system's thread identifier (@var{systag})
2514 @item the current stack frame summary for that thread
2518 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2519 indicates the current thread.
2523 @c end table here to get a little more width for example
2526 (@value{GDBP}) info threads
2527 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2529 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2530 from /usr/lib/libc.2
2531 1 system thread 27905 0x7b003498 in _brk () \@*
2532 from /usr/lib/libc.2
2535 On Solaris, you can display more information about user threads with a
2536 Solaris-specific command:
2539 @item maint info sol-threads
2540 @kindex maint info sol-threads
2541 @cindex thread info (Solaris)
2542 Display info on Solaris user threads.
2546 @kindex thread @var{threadno}
2547 @item thread @var{threadno}
2548 Make thread number @var{threadno} the current thread. The command
2549 argument @var{threadno} is the internal @value{GDBN} thread number, as
2550 shown in the first field of the @samp{info threads} display.
2551 @value{GDBN} responds by displaying the system identifier of the thread
2552 you selected, and its current stack frame summary:
2555 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2556 (@value{GDBP}) thread 2
2557 [Switching to process 35 thread 23]
2558 0x34e5 in sigpause ()
2562 As with the @samp{[New @dots{}]} message, the form of the text after
2563 @samp{Switching to} depends on your system's conventions for identifying
2566 @kindex thread apply
2567 @cindex apply command to several threads
2568 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2569 The @code{thread apply} command allows you to apply the named
2570 @var{command} to one or more threads. Specify the numbers of the
2571 threads that you want affected with the command argument
2572 @var{threadno}. It can be a single thread number, one of the numbers
2573 shown in the first field of the @samp{info threads} display; or it
2574 could be a range of thread numbers, as in @code{2-4}. To apply a
2575 command to all threads, type @kbd{thread apply all @var{command}}.
2577 @kindex set print thread-events
2578 @cindex print messages on thread start and exit
2579 @item set print thread-events
2580 @itemx set print thread-events on
2581 @itemx set print thread-events off
2582 The @code{set print thread-events} command allows you to enable or
2583 disable printing of messages when @value{GDBN} notices that new threads have
2584 started or that threads have exited. By default, these messages will
2585 be printed if detection of these events is supported by the target.
2586 Note that these messages cannot be disabled on all targets.
2588 @kindex show print thread-events
2589 @item show print thread-events
2590 Show whether messages will be printed when @value{GDBN} detects that threads
2591 have started and exited.
2594 @cindex automatic thread selection
2595 @cindex switching threads automatically
2596 @cindex threads, automatic switching
2597 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2598 signal, it automatically selects the thread where that breakpoint or
2599 signal happened. @value{GDBN} alerts you to the context switch with a
2600 message of the form @samp{[Switching to @var{systag}]} to identify the
2603 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2604 more information about how @value{GDBN} behaves when you stop and start
2605 programs with multiple threads.
2607 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2608 watchpoints in programs with multiple threads.
2611 @section Debugging Programs with Multiple Processes
2613 @cindex fork, debugging programs which call
2614 @cindex multiple processes
2615 @cindex processes, multiple
2616 On most systems, @value{GDBN} has no special support for debugging
2617 programs which create additional processes using the @code{fork}
2618 function. When a program forks, @value{GDBN} will continue to debug the
2619 parent process and the child process will run unimpeded. If you have
2620 set a breakpoint in any code which the child then executes, the child
2621 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2622 will cause it to terminate.
2624 However, if you want to debug the child process there is a workaround
2625 which isn't too painful. Put a call to @code{sleep} in the code which
2626 the child process executes after the fork. It may be useful to sleep
2627 only if a certain environment variable is set, or a certain file exists,
2628 so that the delay need not occur when you don't want to run @value{GDBN}
2629 on the child. While the child is sleeping, use the @code{ps} program to
2630 get its process ID. Then tell @value{GDBN} (a new invocation of
2631 @value{GDBN} if you are also debugging the parent process) to attach to
2632 the child process (@pxref{Attach}). From that point on you can debug
2633 the child process just like any other process which you attached to.
2635 On some systems, @value{GDBN} provides support for debugging programs that
2636 create additional processes using the @code{fork} or @code{vfork} functions.
2637 Currently, the only platforms with this feature are HP-UX (11.x and later
2638 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2640 By default, when a program forks, @value{GDBN} will continue to debug
2641 the parent process and the child process will run unimpeded.
2643 If you want to follow the child process instead of the parent process,
2644 use the command @w{@code{set follow-fork-mode}}.
2647 @kindex set follow-fork-mode
2648 @item set follow-fork-mode @var{mode}
2649 Set the debugger response to a program call of @code{fork} or
2650 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2651 process. The @var{mode} argument can be:
2655 The original process is debugged after a fork. The child process runs
2656 unimpeded. This is the default.
2659 The new process is debugged after a fork. The parent process runs
2664 @kindex show follow-fork-mode
2665 @item show follow-fork-mode
2666 Display the current debugger response to a @code{fork} or @code{vfork} call.
2669 @cindex debugging multiple processes
2670 On Linux, if you want to debug both the parent and child processes, use the
2671 command @w{@code{set detach-on-fork}}.
2674 @kindex set detach-on-fork
2675 @item set detach-on-fork @var{mode}
2676 Tells gdb whether to detach one of the processes after a fork, or
2677 retain debugger control over them both.
2681 The child process (or parent process, depending on the value of
2682 @code{follow-fork-mode}) will be detached and allowed to run
2683 independently. This is the default.
2686 Both processes will be held under the control of @value{GDBN}.
2687 One process (child or parent, depending on the value of
2688 @code{follow-fork-mode}) is debugged as usual, while the other
2693 @kindex show detach-on-fork
2694 @item show detach-on-fork
2695 Show whether detach-on-fork mode is on/off.
2698 If you choose to set @samp{detach-on-fork} mode off, then
2699 @value{GDBN} will retain control of all forked processes (including
2700 nested forks). You can list the forked processes under the control of
2701 @value{GDBN} by using the @w{@code{info forks}} command, and switch
2702 from one fork to another by using the @w{@code{fork}} command.
2707 Print a list of all forked processes under the control of @value{GDBN}.
2708 The listing will include a fork id, a process id, and the current
2709 position (program counter) of the process.
2711 @kindex fork @var{fork-id}
2712 @item fork @var{fork-id}
2713 Make fork number @var{fork-id} the current process. The argument
2714 @var{fork-id} is the internal fork number assigned by @value{GDBN},
2715 as shown in the first field of the @samp{info forks} display.
2717 @kindex process @var{process-id}
2718 @item process @var{process-id}
2719 Make process number @var{process-id} the current process. The
2720 argument @var{process-id} must be one that is listed in the output of
2725 To quit debugging one of the forked processes, you can either detach
2726 from it by using the @w{@code{detach fork}} command (allowing it to
2727 run independently), or delete (and kill) it using the
2728 @w{@code{delete fork}} command.
2731 @kindex detach fork @var{fork-id}
2732 @item detach fork @var{fork-id}
2733 Detach from the process identified by @value{GDBN} fork number
2734 @var{fork-id}, and remove it from the fork list. The process will be
2735 allowed to run independently.
2737 @kindex delete fork @var{fork-id}
2738 @item delete fork @var{fork-id}
2739 Kill the process identified by @value{GDBN} fork number @var{fork-id},
2740 and remove it from the fork list.
2744 If you ask to debug a child process and a @code{vfork} is followed by an
2745 @code{exec}, @value{GDBN} executes the new target up to the first
2746 breakpoint in the new target. If you have a breakpoint set on
2747 @code{main} in your original program, the breakpoint will also be set on
2748 the child process's @code{main}.
2750 When a child process is spawned by @code{vfork}, you cannot debug the
2751 child or parent until an @code{exec} call completes.
2753 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2754 call executes, the new target restarts. To restart the parent process,
2755 use the @code{file} command with the parent executable name as its
2758 You can use the @code{catch} command to make @value{GDBN} stop whenever
2759 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2760 Catchpoints, ,Setting Catchpoints}.
2762 @node Checkpoint/Restart
2763 @section Setting a @emph{Bookmark} to Return to Later
2768 @cindex snapshot of a process
2769 @cindex rewind program state
2771 On certain operating systems@footnote{Currently, only
2772 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
2773 program's state, called a @dfn{checkpoint}, and come back to it
2776 Returning to a checkpoint effectively undoes everything that has
2777 happened in the program since the @code{checkpoint} was saved. This
2778 includes changes in memory, registers, and even (within some limits)
2779 system state. Effectively, it is like going back in time to the
2780 moment when the checkpoint was saved.
2782 Thus, if you're stepping thru a program and you think you're
2783 getting close to the point where things go wrong, you can save
2784 a checkpoint. Then, if you accidentally go too far and miss
2785 the critical statement, instead of having to restart your program
2786 from the beginning, you can just go back to the checkpoint and
2787 start again from there.
2789 This can be especially useful if it takes a lot of time or
2790 steps to reach the point where you think the bug occurs.
2792 To use the @code{checkpoint}/@code{restart} method of debugging:
2797 Save a snapshot of the debugged program's current execution state.
2798 The @code{checkpoint} command takes no arguments, but each checkpoint
2799 is assigned a small integer id, similar to a breakpoint id.
2801 @kindex info checkpoints
2802 @item info checkpoints
2803 List the checkpoints that have been saved in the current debugging
2804 session. For each checkpoint, the following information will be
2811 @item Source line, or label
2814 @kindex restart @var{checkpoint-id}
2815 @item restart @var{checkpoint-id}
2816 Restore the program state that was saved as checkpoint number
2817 @var{checkpoint-id}. All program variables, registers, stack frames
2818 etc.@: will be returned to the values that they had when the checkpoint
2819 was saved. In essence, gdb will ``wind back the clock'' to the point
2820 in time when the checkpoint was saved.
2822 Note that breakpoints, @value{GDBN} variables, command history etc.
2823 are not affected by restoring a checkpoint. In general, a checkpoint
2824 only restores things that reside in the program being debugged, not in
2827 @kindex delete checkpoint @var{checkpoint-id}
2828 @item delete checkpoint @var{checkpoint-id}
2829 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
2833 Returning to a previously saved checkpoint will restore the user state
2834 of the program being debugged, plus a significant subset of the system
2835 (OS) state, including file pointers. It won't ``un-write'' data from
2836 a file, but it will rewind the file pointer to the previous location,
2837 so that the previously written data can be overwritten. For files
2838 opened in read mode, the pointer will also be restored so that the
2839 previously read data can be read again.
2841 Of course, characters that have been sent to a printer (or other
2842 external device) cannot be ``snatched back'', and characters received
2843 from eg.@: a serial device can be removed from internal program buffers,
2844 but they cannot be ``pushed back'' into the serial pipeline, ready to
2845 be received again. Similarly, the actual contents of files that have
2846 been changed cannot be restored (at this time).
2848 However, within those constraints, you actually can ``rewind'' your
2849 program to a previously saved point in time, and begin debugging it
2850 again --- and you can change the course of events so as to debug a
2851 different execution path this time.
2853 @cindex checkpoints and process id
2854 Finally, there is one bit of internal program state that will be
2855 different when you return to a checkpoint --- the program's process
2856 id. Each checkpoint will have a unique process id (or @var{pid}),
2857 and each will be different from the program's original @var{pid}.
2858 If your program has saved a local copy of its process id, this could
2859 potentially pose a problem.
2861 @subsection A Non-obvious Benefit of Using Checkpoints
2863 On some systems such as @sc{gnu}/Linux, address space randomization
2864 is performed on new processes for security reasons. This makes it
2865 difficult or impossible to set a breakpoint, or watchpoint, on an
2866 absolute address if you have to restart the program, since the
2867 absolute location of a symbol will change from one execution to the
2870 A checkpoint, however, is an @emph{identical} copy of a process.
2871 Therefore if you create a checkpoint at (eg.@:) the start of main,
2872 and simply return to that checkpoint instead of restarting the
2873 process, you can avoid the effects of address randomization and
2874 your symbols will all stay in the same place.
2877 @chapter Stopping and Continuing
2879 The principal purposes of using a debugger are so that you can stop your
2880 program before it terminates; or so that, if your program runs into
2881 trouble, you can investigate and find out why.
2883 Inside @value{GDBN}, your program may stop for any of several reasons,
2884 such as a signal, a breakpoint, or reaching a new line after a
2885 @value{GDBN} command such as @code{step}. You may then examine and
2886 change variables, set new breakpoints or remove old ones, and then
2887 continue execution. Usually, the messages shown by @value{GDBN} provide
2888 ample explanation of the status of your program---but you can also
2889 explicitly request this information at any time.
2892 @kindex info program
2894 Display information about the status of your program: whether it is
2895 running or not, what process it is, and why it stopped.
2899 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2900 * Continuing and Stepping:: Resuming execution
2902 * Thread Stops:: Stopping and starting multi-thread programs
2906 @section Breakpoints, Watchpoints, and Catchpoints
2909 A @dfn{breakpoint} makes your program stop whenever a certain point in
2910 the program is reached. For each breakpoint, you can add conditions to
2911 control in finer detail whether your program stops. You can set
2912 breakpoints with the @code{break} command and its variants (@pxref{Set
2913 Breaks, ,Setting Breakpoints}), to specify the place where your program
2914 should stop by line number, function name or exact address in the
2917 On some systems, you can set breakpoints in shared libraries before
2918 the executable is run. There is a minor limitation on HP-UX systems:
2919 you must wait until the executable is run in order to set breakpoints
2920 in shared library routines that are not called directly by the program
2921 (for example, routines that are arguments in a @code{pthread_create}
2925 @cindex data breakpoints
2926 @cindex memory tracing
2927 @cindex breakpoint on memory address
2928 @cindex breakpoint on variable modification
2929 A @dfn{watchpoint} is a special breakpoint that stops your program
2930 when the value of an expression changes. The expression may be a value
2931 of a variable, or it could involve values of one or more variables
2932 combined by operators, such as @samp{a + b}. This is sometimes called
2933 @dfn{data breakpoints}. You must use a different command to set
2934 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
2935 from that, you can manage a watchpoint like any other breakpoint: you
2936 enable, disable, and delete both breakpoints and watchpoints using the
2939 You can arrange to have values from your program displayed automatically
2940 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2944 @cindex breakpoint on events
2945 A @dfn{catchpoint} is another special breakpoint that stops your program
2946 when a certain kind of event occurs, such as the throwing of a C@t{++}
2947 exception or the loading of a library. As with watchpoints, you use a
2948 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2949 Catchpoints}), but aside from that, you can manage a catchpoint like any
2950 other breakpoint. (To stop when your program receives a signal, use the
2951 @code{handle} command; see @ref{Signals, ,Signals}.)
2953 @cindex breakpoint numbers
2954 @cindex numbers for breakpoints
2955 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2956 catchpoint when you create it; these numbers are successive integers
2957 starting with one. In many of the commands for controlling various
2958 features of breakpoints you use the breakpoint number to say which
2959 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2960 @dfn{disabled}; if disabled, it has no effect on your program until you
2963 @cindex breakpoint ranges
2964 @cindex ranges of breakpoints
2965 Some @value{GDBN} commands accept a range of breakpoints on which to
2966 operate. A breakpoint range is either a single breakpoint number, like
2967 @samp{5}, or two such numbers, in increasing order, separated by a
2968 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2969 all breakpoints in that range are operated on.
2972 * Set Breaks:: Setting breakpoints
2973 * Set Watchpoints:: Setting watchpoints
2974 * Set Catchpoints:: Setting catchpoints
2975 * Delete Breaks:: Deleting breakpoints
2976 * Disabling:: Disabling breakpoints
2977 * Conditions:: Break conditions
2978 * Break Commands:: Breakpoint command lists
2979 * Error in Breakpoints:: ``Cannot insert breakpoints''
2980 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
2984 @subsection Setting Breakpoints
2986 @c FIXME LMB what does GDB do if no code on line of breakpt?
2987 @c consider in particular declaration with/without initialization.
2989 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2992 @kindex b @r{(@code{break})}
2993 @vindex $bpnum@r{, convenience variable}
2994 @cindex latest breakpoint
2995 Breakpoints are set with the @code{break} command (abbreviated
2996 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2997 number of the breakpoint you've set most recently; see @ref{Convenience
2998 Vars,, Convenience Variables}, for a discussion of what you can do with
2999 convenience variables.
3002 @item break @var{location}
3003 Set a breakpoint at the given @var{location}, which can specify a
3004 function name, a line number, or an address of an instruction.
3005 (@xref{Specify Location}, for a list of all the possible ways to
3006 specify a @var{location}.) The breakpoint will stop your program just
3007 before it executes any of the code in the specified @var{location}.
3009 When using source languages that permit overloading of symbols, such as
3010 C@t{++}, a function name may refer to more than one possible place to break.
3011 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3015 When called without any arguments, @code{break} sets a breakpoint at
3016 the next instruction to be executed in the selected stack frame
3017 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3018 innermost, this makes your program stop as soon as control
3019 returns to that frame. This is similar to the effect of a
3020 @code{finish} command in the frame inside the selected frame---except
3021 that @code{finish} does not leave an active breakpoint. If you use
3022 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3023 the next time it reaches the current location; this may be useful
3026 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3027 least one instruction has been executed. If it did not do this, you
3028 would be unable to proceed past a breakpoint without first disabling the
3029 breakpoint. This rule applies whether or not the breakpoint already
3030 existed when your program stopped.
3032 @item break @dots{} if @var{cond}
3033 Set a breakpoint with condition @var{cond}; evaluate the expression
3034 @var{cond} each time the breakpoint is reached, and stop only if the
3035 value is nonzero---that is, if @var{cond} evaluates as true.
3036 @samp{@dots{}} stands for one of the possible arguments described
3037 above (or no argument) specifying where to break. @xref{Conditions,
3038 ,Break Conditions}, for more information on breakpoint conditions.
3041 @item tbreak @var{args}
3042 Set a breakpoint enabled only for one stop. @var{args} are the
3043 same as for the @code{break} command, and the breakpoint is set in the same
3044 way, but the breakpoint is automatically deleted after the first time your
3045 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3048 @cindex hardware breakpoints
3049 @item hbreak @var{args}
3050 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3051 @code{break} command and the breakpoint is set in the same way, but the
3052 breakpoint requires hardware support and some target hardware may not
3053 have this support. The main purpose of this is EPROM/ROM code
3054 debugging, so you can set a breakpoint at an instruction without
3055 changing the instruction. This can be used with the new trap-generation
3056 provided by SPARClite DSU and most x86-based targets. These targets
3057 will generate traps when a program accesses some data or instruction
3058 address that is assigned to the debug registers. However the hardware
3059 breakpoint registers can take a limited number of breakpoints. For
3060 example, on the DSU, only two data breakpoints can be set at a time, and
3061 @value{GDBN} will reject this command if more than two are used. Delete
3062 or disable unused hardware breakpoints before setting new ones
3063 (@pxref{Disabling, ,Disabling Breakpoints}).
3064 @xref{Conditions, ,Break Conditions}.
3065 For remote targets, you can restrict the number of hardware
3066 breakpoints @value{GDBN} will use, see @ref{set remote
3067 hardware-breakpoint-limit}.
3070 @item thbreak @var{args}
3071 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3072 are the same as for the @code{hbreak} command and the breakpoint is set in
3073 the same way. However, like the @code{tbreak} command,
3074 the breakpoint is automatically deleted after the
3075 first time your program stops there. Also, like the @code{hbreak}
3076 command, the breakpoint requires hardware support and some target hardware
3077 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3078 See also @ref{Conditions, ,Break Conditions}.
3081 @cindex regular expression
3082 @cindex breakpoints in functions matching a regexp
3083 @cindex set breakpoints in many functions
3084 @item rbreak @var{regex}
3085 Set breakpoints on all functions matching the regular expression
3086 @var{regex}. This command sets an unconditional breakpoint on all
3087 matches, printing a list of all breakpoints it set. Once these
3088 breakpoints are set, they are treated just like the breakpoints set with
3089 the @code{break} command. You can delete them, disable them, or make
3090 them conditional the same way as any other breakpoint.
3092 The syntax of the regular expression is the standard one used with tools
3093 like @file{grep}. Note that this is different from the syntax used by
3094 shells, so for instance @code{foo*} matches all functions that include
3095 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3096 @code{.*} leading and trailing the regular expression you supply, so to
3097 match only functions that begin with @code{foo}, use @code{^foo}.
3099 @cindex non-member C@t{++} functions, set breakpoint in
3100 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3101 breakpoints on overloaded functions that are not members of any special
3104 @cindex set breakpoints on all functions
3105 The @code{rbreak} command can be used to set breakpoints in
3106 @strong{all} the functions in a program, like this:
3109 (@value{GDBP}) rbreak .
3112 @kindex info breakpoints
3113 @cindex @code{$_} and @code{info breakpoints}
3114 @item info breakpoints @r{[}@var{n}@r{]}
3115 @itemx info break @r{[}@var{n}@r{]}
3116 @itemx info watchpoints @r{[}@var{n}@r{]}
3117 Print a table of all breakpoints, watchpoints, and catchpoints set and
3118 not deleted. Optional argument @var{n} means print information only
3119 about the specified breakpoint (or watchpoint or catchpoint). For
3120 each breakpoint, following columns are printed:
3123 @item Breakpoint Numbers
3125 Breakpoint, watchpoint, or catchpoint.
3127 Whether the breakpoint is marked to be disabled or deleted when hit.
3128 @item Enabled or Disabled
3129 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3130 that are not enabled.
3132 Where the breakpoint is in your program, as a memory address. For a
3133 pending breakpoint whose address is not yet known, this field will
3134 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3135 library that has the symbol or line referred by breakpoint is loaded.
3136 See below for details. A breakpoint with several locations will
3137 have @samp{<MULTIPLE>} in this field---see below for details.
3139 Where the breakpoint is in the source for your program, as a file and
3140 line number. For a pending breakpoint, the original string passed to
3141 the breakpoint command will be listed as it cannot be resolved until
3142 the appropriate shared library is loaded in the future.
3146 If a breakpoint is conditional, @code{info break} shows the condition on
3147 the line following the affected breakpoint; breakpoint commands, if any,
3148 are listed after that. A pending breakpoint is allowed to have a condition
3149 specified for it. The condition is not parsed for validity until a shared
3150 library is loaded that allows the pending breakpoint to resolve to a
3154 @code{info break} with a breakpoint
3155 number @var{n} as argument lists only that breakpoint. The
3156 convenience variable @code{$_} and the default examining-address for
3157 the @code{x} command are set to the address of the last breakpoint
3158 listed (@pxref{Memory, ,Examining Memory}).
3161 @code{info break} displays a count of the number of times the breakpoint
3162 has been hit. This is especially useful in conjunction with the
3163 @code{ignore} command. You can ignore a large number of breakpoint
3164 hits, look at the breakpoint info to see how many times the breakpoint
3165 was hit, and then run again, ignoring one less than that number. This
3166 will get you quickly to the last hit of that breakpoint.
3169 @value{GDBN} allows you to set any number of breakpoints at the same place in
3170 your program. There is nothing silly or meaningless about this. When
3171 the breakpoints are conditional, this is even useful
3172 (@pxref{Conditions, ,Break Conditions}).
3174 @cindex multiple locations, breakpoints
3175 @cindex breakpoints, multiple locations
3176 It is possible that a breakpoint corresponds to several locations
3177 in your program. Examples of this situation are:
3181 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3182 instances of the function body, used in different cases.
3185 For a C@t{++} template function, a given line in the function can
3186 correspond to any number of instantiations.
3189 For an inlined function, a given source line can correspond to
3190 several places where that function is inlined.
3193 In all those cases, @value{GDBN} will insert a breakpoint at all
3194 the relevant locations@footnote{
3195 As of this writing, multiple-location breakpoints work only if there's
3196 line number information for all the locations. This means that they
3197 will generally not work in system libraries, unless you have debug
3198 info with line numbers for them.}.
3200 A breakpoint with multiple locations is displayed in the breakpoint
3201 table using several rows---one header row, followed by one row for
3202 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3203 address column. The rows for individual locations contain the actual
3204 addresses for locations, and show the functions to which those
3205 locations belong. The number column for a location is of the form
3206 @var{breakpoint-number}.@var{location-number}.
3211 Num Type Disp Enb Address What
3212 1 breakpoint keep y <MULTIPLE>
3214 breakpoint already hit 1 time
3215 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3216 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3219 Each location can be individually enabled or disabled by passing
3220 @var{breakpoint-number}.@var{location-number} as argument to the
3221 @code{enable} and @code{disable} commands. Note that you cannot
3222 delete the individual locations from the list, you can only delete the
3223 entire list of locations that belong to their parent breakpoint (with
3224 the @kbd{delete @var{num}} command, where @var{num} is the number of
3225 the parent breakpoint, 1 in the above example). Disabling or enabling
3226 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3227 that belong to that breakpoint.
3229 @cindex pending breakpoints
3230 It's quite common to have a breakpoint inside a shared library.
3231 Shared libraries can be loaded and unloaded explicitly,
3232 and possibly repeatedly, as the program is executed. To support
3233 this use case, @value{GDBN} updates breakpoint locations whenever
3234 any shared library is loaded or unloaded. Typically, you would
3235 set a breakpoint in a shared library at the beginning of your
3236 debugging session, when the library is not loaded, and when the
3237 symbols from the library are not available. When you try to set
3238 breakpoint, @value{GDBN} will ask you if you want to set
3239 a so called @dfn{pending breakpoint}---breakpoint whose address
3240 is not yet resolved.
3242 After the program is run, whenever a new shared library is loaded,
3243 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3244 shared library contains the symbol or line referred to by some
3245 pending breakpoint, that breakpoint is resolved and becomes an
3246 ordinary breakpoint. When a library is unloaded, all breakpoints
3247 that refer to its symbols or source lines become pending again.
3249 This logic works for breakpoints with multiple locations, too. For
3250 example, if you have a breakpoint in a C@t{++} template function, and
3251 a newly loaded shared library has an instantiation of that template,
3252 a new location is added to the list of locations for the breakpoint.
3254 Except for having unresolved address, pending breakpoints do not
3255 differ from regular breakpoints. You can set conditions or commands,
3256 enable and disable them and perform other breakpoint operations.
3258 @value{GDBN} provides some additional commands for controlling what
3259 happens when the @samp{break} command cannot resolve breakpoint
3260 address specification to an address:
3262 @kindex set breakpoint pending
3263 @kindex show breakpoint pending
3265 @item set breakpoint pending auto
3266 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3267 location, it queries you whether a pending breakpoint should be created.
3269 @item set breakpoint pending on
3270 This indicates that an unrecognized breakpoint location should automatically
3271 result in a pending breakpoint being created.
3273 @item set breakpoint pending off
3274 This indicates that pending breakpoints are not to be created. Any
3275 unrecognized breakpoint location results in an error. This setting does
3276 not affect any pending breakpoints previously created.
3278 @item show breakpoint pending
3279 Show the current behavior setting for creating pending breakpoints.
3282 The settings above only affect the @code{break} command and its
3283 variants. Once breakpoint is set, it will be automatically updated
3284 as shared libraries are loaded and unloaded.
3286 @cindex automatic hardware breakpoints
3287 For some targets, @value{GDBN} can automatically decide if hardware or
3288 software breakpoints should be used, depending on whether the
3289 breakpoint address is read-only or read-write. This applies to
3290 breakpoints set with the @code{break} command as well as to internal
3291 breakpoints set by commands like @code{next} and @code{finish}. For
3292 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3295 You can control this automatic behaviour with the following commands::
3297 @kindex set breakpoint auto-hw
3298 @kindex show breakpoint auto-hw
3300 @item set breakpoint auto-hw on
3301 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3302 will try to use the target memory map to decide if software or hardware
3303 breakpoint must be used.
3305 @item set breakpoint auto-hw off
3306 This indicates @value{GDBN} should not automatically select breakpoint
3307 type. If the target provides a memory map, @value{GDBN} will warn when
3308 trying to set software breakpoint at a read-only address.
3311 @value{GDBN} normally implements breakpoints by replacing the program code
3312 at the breakpoint address with a special instruction, which, when
3313 executed, given control to the debugger. By default, the program
3314 code is so modified only when the program is resumed. As soon as
3315 the program stops, @value{GDBN} restores the original instructions. This
3316 behaviour guards against leaving breakpoints inserted in the
3317 target should gdb abrubptly disconnect. However, with slow remote
3318 targets, inserting and removing breakpoint can reduce the performance.
3319 This behavior can be controlled with the following commands::
3321 @kindex set breakpoint always-inserted
3322 @kindex show breakpoint always-inserted
3324 @item set breakpoint always-inserted off
3325 This is the default behaviour. All breakpoints, including newly added
3326 by the user, are inserted in the target only when the target is
3327 resumed. All breakpoints are removed from the target when it stops.
3329 @item set breakpoint always-inserted on
3330 Causes all breakpoints to be inserted in the target at all times. If
3331 the user adds a new breakpoint, or changes an existing breakpoint, the
3332 breakpoints in the target are updated immediately. A breakpoint is
3333 removed from the target only when breakpoint itself is removed.
3336 @cindex negative breakpoint numbers
3337 @cindex internal @value{GDBN} breakpoints
3338 @value{GDBN} itself sometimes sets breakpoints in your program for
3339 special purposes, such as proper handling of @code{longjmp} (in C
3340 programs). These internal breakpoints are assigned negative numbers,
3341 starting with @code{-1}; @samp{info breakpoints} does not display them.
3342 You can see these breakpoints with the @value{GDBN} maintenance command
3343 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3346 @node Set Watchpoints
3347 @subsection Setting Watchpoints
3349 @cindex setting watchpoints
3350 You can use a watchpoint to stop execution whenever the value of an
3351 expression changes, without having to predict a particular place where
3352 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3353 The expression may be as simple as the value of a single variable, or
3354 as complex as many variables combined by operators. Examples include:
3358 A reference to the value of a single variable.
3361 An address cast to an appropriate data type. For example,
3362 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3363 address (assuming an @code{int} occupies 4 bytes).
3366 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3367 expression can use any operators valid in the program's native
3368 language (@pxref{Languages}).
3371 You can set a watchpoint on an expression even if the expression can
3372 not be evaluated yet. For instance, you can set a watchpoint on
3373 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3374 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3375 the expression produces a valid value. If the expression becomes
3376 valid in some other way than changing a variable (e.g.@: if the memory
3377 pointed to by @samp{*global_ptr} becomes readable as the result of a
3378 @code{malloc} call), @value{GDBN} may not stop until the next time
3379 the expression changes.
3381 @cindex software watchpoints
3382 @cindex hardware watchpoints
3383 Depending on your system, watchpoints may be implemented in software or
3384 hardware. @value{GDBN} does software watchpointing by single-stepping your
3385 program and testing the variable's value each time, which is hundreds of
3386 times slower than normal execution. (But this may still be worth it, to
3387 catch errors where you have no clue what part of your program is the
3390 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3391 x86-based targets, @value{GDBN} includes support for hardware
3392 watchpoints, which do not slow down the running of your program.
3396 @item watch @var{expr} @r{[}thread @var{threadnum}@r{]}
3397 Set a watchpoint for an expression. @value{GDBN} will break when the
3398 expression @var{expr} is written into by the program and its value
3399 changes. The simplest (and the most popular) use of this command is
3400 to watch the value of a single variable:
3403 (@value{GDBP}) watch foo
3406 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3407 clause, @value{GDBN} breaks only when the thread identified by
3408 @var{threadnum} changes the value of @var{expr}. If any other threads
3409 change the value of @var{expr}, @value{GDBN} will not break. Note
3410 that watchpoints restricted to a single thread in this way only work
3411 with Hardware Watchpoints.
3414 @item rwatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3415 Set a watchpoint that will break when the value of @var{expr} is read
3419 @item awatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3420 Set a watchpoint that will break when @var{expr} is either read from
3421 or written into by the program.
3423 @kindex info watchpoints @r{[}@var{n}@r{]}
3424 @item info watchpoints
3425 This command prints a list of watchpoints, breakpoints, and catchpoints;
3426 it is the same as @code{info break} (@pxref{Set Breaks}).
3429 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3430 watchpoints execute very quickly, and the debugger reports a change in
3431 value at the exact instruction where the change occurs. If @value{GDBN}
3432 cannot set a hardware watchpoint, it sets a software watchpoint, which
3433 executes more slowly and reports the change in value at the next
3434 @emph{statement}, not the instruction, after the change occurs.
3436 @cindex use only software watchpoints
3437 You can force @value{GDBN} to use only software watchpoints with the
3438 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3439 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3440 the underlying system supports them. (Note that hardware-assisted
3441 watchpoints that were set @emph{before} setting
3442 @code{can-use-hw-watchpoints} to zero will still use the hardware
3443 mechanism of watching expression values.)
3446 @item set can-use-hw-watchpoints
3447 @kindex set can-use-hw-watchpoints
3448 Set whether or not to use hardware watchpoints.
3450 @item show can-use-hw-watchpoints
3451 @kindex show can-use-hw-watchpoints
3452 Show the current mode of using hardware watchpoints.
3455 For remote targets, you can restrict the number of hardware
3456 watchpoints @value{GDBN} will use, see @ref{set remote
3457 hardware-breakpoint-limit}.
3459 When you issue the @code{watch} command, @value{GDBN} reports
3462 Hardware watchpoint @var{num}: @var{expr}
3466 if it was able to set a hardware watchpoint.
3468 Currently, the @code{awatch} and @code{rwatch} commands can only set
3469 hardware watchpoints, because accesses to data that don't change the
3470 value of the watched expression cannot be detected without examining
3471 every instruction as it is being executed, and @value{GDBN} does not do
3472 that currently. If @value{GDBN} finds that it is unable to set a
3473 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3474 will print a message like this:
3477 Expression cannot be implemented with read/access watchpoint.
3480 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3481 data type of the watched expression is wider than what a hardware
3482 watchpoint on the target machine can handle. For example, some systems
3483 can only watch regions that are up to 4 bytes wide; on such systems you
3484 cannot set hardware watchpoints for an expression that yields a
3485 double-precision floating-point number (which is typically 8 bytes
3486 wide). As a work-around, it might be possible to break the large region
3487 into a series of smaller ones and watch them with separate watchpoints.
3489 If you set too many hardware watchpoints, @value{GDBN} might be unable
3490 to insert all of them when you resume the execution of your program.
3491 Since the precise number of active watchpoints is unknown until such
3492 time as the program is about to be resumed, @value{GDBN} might not be
3493 able to warn you about this when you set the watchpoints, and the
3494 warning will be printed only when the program is resumed:
3497 Hardware watchpoint @var{num}: Could not insert watchpoint
3501 If this happens, delete or disable some of the watchpoints.
3503 Watching complex expressions that reference many variables can also
3504 exhaust the resources available for hardware-assisted watchpoints.
3505 That's because @value{GDBN} needs to watch every variable in the
3506 expression with separately allocated resources.
3508 If you call a function interactively using @code{print} or @code{call},
3509 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3510 kind of breakpoint or the call completes.
3512 @value{GDBN} automatically deletes watchpoints that watch local
3513 (automatic) variables, or expressions that involve such variables, when
3514 they go out of scope, that is, when the execution leaves the block in
3515 which these variables were defined. In particular, when the program
3516 being debugged terminates, @emph{all} local variables go out of scope,
3517 and so only watchpoints that watch global variables remain set. If you
3518 rerun the program, you will need to set all such watchpoints again. One
3519 way of doing that would be to set a code breakpoint at the entry to the
3520 @code{main} function and when it breaks, set all the watchpoints.
3522 @cindex watchpoints and threads
3523 @cindex threads and watchpoints
3524 In multi-threaded programs, watchpoints will detect changes to the
3525 watched expression from every thread.
3528 @emph{Warning:} In multi-threaded programs, software watchpoints
3529 have only limited usefulness. If @value{GDBN} creates a software
3530 watchpoint, it can only watch the value of an expression @emph{in a
3531 single thread}. If you are confident that the expression can only
3532 change due to the current thread's activity (and if you are also
3533 confident that no other thread can become current), then you can use
3534 software watchpoints as usual. However, @value{GDBN} may not notice
3535 when a non-current thread's activity changes the expression. (Hardware
3536 watchpoints, in contrast, watch an expression in all threads.)
3539 @xref{set remote hardware-watchpoint-limit}.
3541 @node Set Catchpoints
3542 @subsection Setting Catchpoints
3543 @cindex catchpoints, setting
3544 @cindex exception handlers
3545 @cindex event handling
3547 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3548 kinds of program events, such as C@t{++} exceptions or the loading of a
3549 shared library. Use the @code{catch} command to set a catchpoint.
3553 @item catch @var{event}
3554 Stop when @var{event} occurs. @var{event} can be any of the following:
3557 @cindex stop on C@t{++} exceptions
3558 The throwing of a C@t{++} exception.
3561 The catching of a C@t{++} exception.
3564 @cindex Ada exception catching
3565 @cindex catch Ada exceptions
3566 An Ada exception being raised. If an exception name is specified
3567 at the end of the command (eg @code{catch exception Program_Error}),
3568 the debugger will stop only when this specific exception is raised.
3569 Otherwise, the debugger stops execution when any Ada exception is raised.
3571 @item exception unhandled
3572 An exception that was raised but is not handled by the program.
3575 A failed Ada assertion.
3578 @cindex break on fork/exec
3579 A call to @code{exec}. This is currently only available for HP-UX
3583 A call to @code{fork}. This is currently only available for HP-UX
3587 A call to @code{vfork}. This is currently only available for HP-UX
3591 @itemx load @var{libname}
3592 @cindex break on load/unload of shared library
3593 The dynamic loading of any shared library, or the loading of the library
3594 @var{libname}. This is currently only available for HP-UX.
3597 @itemx unload @var{libname}
3598 The unloading of any dynamically loaded shared library, or the unloading
3599 of the library @var{libname}. This is currently only available for HP-UX.
3602 @item tcatch @var{event}
3603 Set a catchpoint that is enabled only for one stop. The catchpoint is
3604 automatically deleted after the first time the event is caught.
3608 Use the @code{info break} command to list the current catchpoints.
3610 There are currently some limitations to C@t{++} exception handling
3611 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
3615 If you call a function interactively, @value{GDBN} normally returns
3616 control to you when the function has finished executing. If the call
3617 raises an exception, however, the call may bypass the mechanism that
3618 returns control to you and cause your program either to abort or to
3619 simply continue running until it hits a breakpoint, catches a signal
3620 that @value{GDBN} is listening for, or exits. This is the case even if
3621 you set a catchpoint for the exception; catchpoints on exceptions are
3622 disabled within interactive calls.
3625 You cannot raise an exception interactively.
3628 You cannot install an exception handler interactively.
3631 @cindex raise exceptions
3632 Sometimes @code{catch} is not the best way to debug exception handling:
3633 if you need to know exactly where an exception is raised, it is better to
3634 stop @emph{before} the exception handler is called, since that way you
3635 can see the stack before any unwinding takes place. If you set a
3636 breakpoint in an exception handler instead, it may not be easy to find
3637 out where the exception was raised.
3639 To stop just before an exception handler is called, you need some
3640 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3641 raised by calling a library function named @code{__raise_exception}
3642 which has the following ANSI C interface:
3645 /* @var{addr} is where the exception identifier is stored.
3646 @var{id} is the exception identifier. */
3647 void __raise_exception (void **addr, void *id);
3651 To make the debugger catch all exceptions before any stack
3652 unwinding takes place, set a breakpoint on @code{__raise_exception}
3653 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
3655 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
3656 that depends on the value of @var{id}, you can stop your program when
3657 a specific exception is raised. You can use multiple conditional
3658 breakpoints to stop your program when any of a number of exceptions are
3663 @subsection Deleting Breakpoints
3665 @cindex clearing breakpoints, watchpoints, catchpoints
3666 @cindex deleting breakpoints, watchpoints, catchpoints
3667 It is often necessary to eliminate a breakpoint, watchpoint, or
3668 catchpoint once it has done its job and you no longer want your program
3669 to stop there. This is called @dfn{deleting} the breakpoint. A
3670 breakpoint that has been deleted no longer exists; it is forgotten.
3672 With the @code{clear} command you can delete breakpoints according to
3673 where they are in your program. With the @code{delete} command you can
3674 delete individual breakpoints, watchpoints, or catchpoints by specifying
3675 their breakpoint numbers.
3677 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3678 automatically ignores breakpoints on the first instruction to be executed
3679 when you continue execution without changing the execution address.
3684 Delete any breakpoints at the next instruction to be executed in the
3685 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
3686 the innermost frame is selected, this is a good way to delete a
3687 breakpoint where your program just stopped.
3689 @item clear @var{location}
3690 Delete any breakpoints set at the specified @var{location}.
3691 @xref{Specify Location}, for the various forms of @var{location}; the
3692 most useful ones are listed below:
3695 @item clear @var{function}
3696 @itemx clear @var{filename}:@var{function}
3697 Delete any breakpoints set at entry to the named @var{function}.
3699 @item clear @var{linenum}
3700 @itemx clear @var{filename}:@var{linenum}
3701 Delete any breakpoints set at or within the code of the specified
3702 @var{linenum} of the specified @var{filename}.
3705 @cindex delete breakpoints
3707 @kindex d @r{(@code{delete})}
3708 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3709 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3710 ranges specified as arguments. If no argument is specified, delete all
3711 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3712 confirm off}). You can abbreviate this command as @code{d}.
3716 @subsection Disabling Breakpoints
3718 @cindex enable/disable a breakpoint
3719 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3720 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3721 it had been deleted, but remembers the information on the breakpoint so
3722 that you can @dfn{enable} it again later.
3724 You disable and enable breakpoints, watchpoints, and catchpoints with
3725 the @code{enable} and @code{disable} commands, optionally specifying one
3726 or more breakpoint numbers as arguments. Use @code{info break} or
3727 @code{info watch} to print a list of breakpoints, watchpoints, and
3728 catchpoints if you do not know which numbers to use.
3730 Disabling and enabling a breakpoint that has multiple locations
3731 affects all of its locations.
3733 A breakpoint, watchpoint, or catchpoint can have any of four different
3734 states of enablement:
3738 Enabled. The breakpoint stops your program. A breakpoint set
3739 with the @code{break} command starts out in this state.
3741 Disabled. The breakpoint has no effect on your program.
3743 Enabled once. The breakpoint stops your program, but then becomes
3746 Enabled for deletion. The breakpoint stops your program, but
3747 immediately after it does so it is deleted permanently. A breakpoint
3748 set with the @code{tbreak} command starts out in this state.
3751 You can use the following commands to enable or disable breakpoints,
3752 watchpoints, and catchpoints:
3756 @kindex dis @r{(@code{disable})}
3757 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3758 Disable the specified breakpoints---or all breakpoints, if none are
3759 listed. A disabled breakpoint has no effect but is not forgotten. All
3760 options such as ignore-counts, conditions and commands are remembered in
3761 case the breakpoint is enabled again later. You may abbreviate
3762 @code{disable} as @code{dis}.
3765 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3766 Enable the specified breakpoints (or all defined breakpoints). They
3767 become effective once again in stopping your program.
3769 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3770 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3771 of these breakpoints immediately after stopping your program.
3773 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3774 Enable the specified breakpoints to work once, then die. @value{GDBN}
3775 deletes any of these breakpoints as soon as your program stops there.
3776 Breakpoints set by the @code{tbreak} command start out in this state.
3779 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3780 @c confusing: tbreak is also initially enabled.
3781 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3782 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
3783 subsequently, they become disabled or enabled only when you use one of
3784 the commands above. (The command @code{until} can set and delete a
3785 breakpoint of its own, but it does not change the state of your other
3786 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3790 @subsection Break Conditions
3791 @cindex conditional breakpoints
3792 @cindex breakpoint conditions
3794 @c FIXME what is scope of break condition expr? Context where wanted?
3795 @c in particular for a watchpoint?
3796 The simplest sort of breakpoint breaks every time your program reaches a
3797 specified place. You can also specify a @dfn{condition} for a
3798 breakpoint. A condition is just a Boolean expression in your
3799 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3800 a condition evaluates the expression each time your program reaches it,
3801 and your program stops only if the condition is @emph{true}.
3803 This is the converse of using assertions for program validation; in that
3804 situation, you want to stop when the assertion is violated---that is,
3805 when the condition is false. In C, if you want to test an assertion expressed
3806 by the condition @var{assert}, you should set the condition
3807 @samp{! @var{assert}} on the appropriate breakpoint.
3809 Conditions are also accepted for watchpoints; you may not need them,
3810 since a watchpoint is inspecting the value of an expression anyhow---but
3811 it might be simpler, say, to just set a watchpoint on a variable name,
3812 and specify a condition that tests whether the new value is an interesting
3815 Break conditions can have side effects, and may even call functions in
3816 your program. This can be useful, for example, to activate functions
3817 that log program progress, or to use your own print functions to
3818 format special data structures. The effects are completely predictable
3819 unless there is another enabled breakpoint at the same address. (In
3820 that case, @value{GDBN} might see the other breakpoint first and stop your
3821 program without checking the condition of this one.) Note that
3822 breakpoint commands are usually more convenient and flexible than break
3824 purpose of performing side effects when a breakpoint is reached
3825 (@pxref{Break Commands, ,Breakpoint Command Lists}).
3827 Break conditions can be specified when a breakpoint is set, by using
3828 @samp{if} in the arguments to the @code{break} command. @xref{Set
3829 Breaks, ,Setting Breakpoints}. They can also be changed at any time
3830 with the @code{condition} command.
3832 You can also use the @code{if} keyword with the @code{watch} command.
3833 The @code{catch} command does not recognize the @code{if} keyword;
3834 @code{condition} is the only way to impose a further condition on a
3839 @item condition @var{bnum} @var{expression}
3840 Specify @var{expression} as the break condition for breakpoint,
3841 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3842 breakpoint @var{bnum} stops your program only if the value of
3843 @var{expression} is true (nonzero, in C). When you use
3844 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3845 syntactic correctness, and to determine whether symbols in it have
3846 referents in the context of your breakpoint. If @var{expression} uses
3847 symbols not referenced in the context of the breakpoint, @value{GDBN}
3848 prints an error message:
3851 No symbol "foo" in current context.
3856 not actually evaluate @var{expression} at the time the @code{condition}
3857 command (or a command that sets a breakpoint with a condition, like
3858 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3860 @item condition @var{bnum}
3861 Remove the condition from breakpoint number @var{bnum}. It becomes
3862 an ordinary unconditional breakpoint.
3865 @cindex ignore count (of breakpoint)
3866 A special case of a breakpoint condition is to stop only when the
3867 breakpoint has been reached a certain number of times. This is so
3868 useful that there is a special way to do it, using the @dfn{ignore
3869 count} of the breakpoint. Every breakpoint has an ignore count, which
3870 is an integer. Most of the time, the ignore count is zero, and
3871 therefore has no effect. But if your program reaches a breakpoint whose
3872 ignore count is positive, then instead of stopping, it just decrements
3873 the ignore count by one and continues. As a result, if the ignore count
3874 value is @var{n}, the breakpoint does not stop the next @var{n} times
3875 your program reaches it.
3879 @item ignore @var{bnum} @var{count}
3880 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3881 The next @var{count} times the breakpoint is reached, your program's
3882 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3885 To make the breakpoint stop the next time it is reached, specify
3888 When you use @code{continue} to resume execution of your program from a
3889 breakpoint, you can specify an ignore count directly as an argument to
3890 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3891 Stepping,,Continuing and Stepping}.
3893 If a breakpoint has a positive ignore count and a condition, the
3894 condition is not checked. Once the ignore count reaches zero,
3895 @value{GDBN} resumes checking the condition.
3897 You could achieve the effect of the ignore count with a condition such
3898 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3899 is decremented each time. @xref{Convenience Vars, ,Convenience
3903 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3906 @node Break Commands
3907 @subsection Breakpoint Command Lists
3909 @cindex breakpoint commands
3910 You can give any breakpoint (or watchpoint or catchpoint) a series of
3911 commands to execute when your program stops due to that breakpoint. For
3912 example, you might want to print the values of certain expressions, or
3913 enable other breakpoints.
3917 @kindex end@r{ (breakpoint commands)}
3918 @item commands @r{[}@var{bnum}@r{]}
3919 @itemx @dots{} @var{command-list} @dots{}
3921 Specify a list of commands for breakpoint number @var{bnum}. The commands
3922 themselves appear on the following lines. Type a line containing just
3923 @code{end} to terminate the commands.
3925 To remove all commands from a breakpoint, type @code{commands} and
3926 follow it immediately with @code{end}; that is, give no commands.
3928 With no @var{bnum} argument, @code{commands} refers to the last
3929 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3930 recently encountered).
3933 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3934 disabled within a @var{command-list}.
3936 You can use breakpoint commands to start your program up again. Simply
3937 use the @code{continue} command, or @code{step}, or any other command
3938 that resumes execution.
3940 Any other commands in the command list, after a command that resumes
3941 execution, are ignored. This is because any time you resume execution
3942 (even with a simple @code{next} or @code{step}), you may encounter
3943 another breakpoint---which could have its own command list, leading to
3944 ambiguities about which list to execute.
3947 If the first command you specify in a command list is @code{silent}, the
3948 usual message about stopping at a breakpoint is not printed. This may
3949 be desirable for breakpoints that are to print a specific message and
3950 then continue. If none of the remaining commands print anything, you
3951 see no sign that the breakpoint was reached. @code{silent} is
3952 meaningful only at the beginning of a breakpoint command list.
3954 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3955 print precisely controlled output, and are often useful in silent
3956 breakpoints. @xref{Output, ,Commands for Controlled Output}.
3958 For example, here is how you could use breakpoint commands to print the
3959 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3965 printf "x is %d\n",x
3970 One application for breakpoint commands is to compensate for one bug so
3971 you can test for another. Put a breakpoint just after the erroneous line
3972 of code, give it a condition to detect the case in which something
3973 erroneous has been done, and give it commands to assign correct values
3974 to any variables that need them. End with the @code{continue} command
3975 so that your program does not stop, and start with the @code{silent}
3976 command so that no output is produced. Here is an example:
3987 @c @ifclear BARETARGET
3988 @node Error in Breakpoints
3989 @subsection ``Cannot insert breakpoints''
3991 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3993 Under some operating systems, breakpoints cannot be used in a program if
3994 any other process is running that program. In this situation,
3995 attempting to run or continue a program with a breakpoint causes
3996 @value{GDBN} to print an error message:
3999 Cannot insert breakpoints.
4000 The same program may be running in another process.
4003 When this happens, you have three ways to proceed:
4007 Remove or disable the breakpoints, then continue.
4010 Suspend @value{GDBN}, and copy the file containing your program to a new
4011 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
4012 that @value{GDBN} should run your program under that name.
4013 Then start your program again.
4016 Relink your program so that the text segment is nonsharable, using the
4017 linker option @samp{-N}. The operating system limitation may not apply
4018 to nonsharable executables.
4022 A similar message can be printed if you request too many active
4023 hardware-assisted breakpoints and watchpoints:
4025 @c FIXME: the precise wording of this message may change; the relevant
4026 @c source change is not committed yet (Sep 3, 1999).
4028 Stopped; cannot insert breakpoints.
4029 You may have requested too many hardware breakpoints and watchpoints.
4033 This message is printed when you attempt to resume the program, since
4034 only then @value{GDBN} knows exactly how many hardware breakpoints and
4035 watchpoints it needs to insert.
4037 When this message is printed, you need to disable or remove some of the
4038 hardware-assisted breakpoints and watchpoints, and then continue.
4040 @node Breakpoint-related Warnings
4041 @subsection ``Breakpoint address adjusted...''
4042 @cindex breakpoint address adjusted
4044 Some processor architectures place constraints on the addresses at
4045 which breakpoints may be placed. For architectures thus constrained,
4046 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4047 with the constraints dictated by the architecture.
4049 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4050 a VLIW architecture in which a number of RISC-like instructions may be
4051 bundled together for parallel execution. The FR-V architecture
4052 constrains the location of a breakpoint instruction within such a
4053 bundle to the instruction with the lowest address. @value{GDBN}
4054 honors this constraint by adjusting a breakpoint's address to the
4055 first in the bundle.
4057 It is not uncommon for optimized code to have bundles which contain
4058 instructions from different source statements, thus it may happen that
4059 a breakpoint's address will be adjusted from one source statement to
4060 another. Since this adjustment may significantly alter @value{GDBN}'s
4061 breakpoint related behavior from what the user expects, a warning is
4062 printed when the breakpoint is first set and also when the breakpoint
4065 A warning like the one below is printed when setting a breakpoint
4066 that's been subject to address adjustment:
4069 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4072 Such warnings are printed both for user settable and @value{GDBN}'s
4073 internal breakpoints. If you see one of these warnings, you should
4074 verify that a breakpoint set at the adjusted address will have the
4075 desired affect. If not, the breakpoint in question may be removed and
4076 other breakpoints may be set which will have the desired behavior.
4077 E.g., it may be sufficient to place the breakpoint at a later
4078 instruction. A conditional breakpoint may also be useful in some
4079 cases to prevent the breakpoint from triggering too often.
4081 @value{GDBN} will also issue a warning when stopping at one of these
4082 adjusted breakpoints:
4085 warning: Breakpoint 1 address previously adjusted from 0x00010414
4089 When this warning is encountered, it may be too late to take remedial
4090 action except in cases where the breakpoint is hit earlier or more
4091 frequently than expected.
4093 @node Continuing and Stepping
4094 @section Continuing and Stepping
4098 @cindex resuming execution
4099 @dfn{Continuing} means resuming program execution until your program
4100 completes normally. In contrast, @dfn{stepping} means executing just
4101 one more ``step'' of your program, where ``step'' may mean either one
4102 line of source code, or one machine instruction (depending on what
4103 particular command you use). Either when continuing or when stepping,
4104 your program may stop even sooner, due to a breakpoint or a signal. (If
4105 it stops due to a signal, you may want to use @code{handle}, or use
4106 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4110 @kindex c @r{(@code{continue})}
4111 @kindex fg @r{(resume foreground execution)}
4112 @item continue @r{[}@var{ignore-count}@r{]}
4113 @itemx c @r{[}@var{ignore-count}@r{]}
4114 @itemx fg @r{[}@var{ignore-count}@r{]}
4115 Resume program execution, at the address where your program last stopped;
4116 any breakpoints set at that address are bypassed. The optional argument
4117 @var{ignore-count} allows you to specify a further number of times to
4118 ignore a breakpoint at this location; its effect is like that of
4119 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4121 The argument @var{ignore-count} is meaningful only when your program
4122 stopped due to a breakpoint. At other times, the argument to
4123 @code{continue} is ignored.
4125 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4126 debugged program is deemed to be the foreground program) are provided
4127 purely for convenience, and have exactly the same behavior as
4131 To resume execution at a different place, you can use @code{return}
4132 (@pxref{Returning, ,Returning from a Function}) to go back to the
4133 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4134 Different Address}) to go to an arbitrary location in your program.
4136 A typical technique for using stepping is to set a breakpoint
4137 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4138 beginning of the function or the section of your program where a problem
4139 is believed to lie, run your program until it stops at that breakpoint,
4140 and then step through the suspect area, examining the variables that are
4141 interesting, until you see the problem happen.
4145 @kindex s @r{(@code{step})}
4147 Continue running your program until control reaches a different source
4148 line, then stop it and return control to @value{GDBN}. This command is
4149 abbreviated @code{s}.
4152 @c "without debugging information" is imprecise; actually "without line
4153 @c numbers in the debugging information". (gcc -g1 has debugging info but
4154 @c not line numbers). But it seems complex to try to make that
4155 @c distinction here.
4156 @emph{Warning:} If you use the @code{step} command while control is
4157 within a function that was compiled without debugging information,
4158 execution proceeds until control reaches a function that does have
4159 debugging information. Likewise, it will not step into a function which
4160 is compiled without debugging information. To step through functions
4161 without debugging information, use the @code{stepi} command, described
4165 The @code{step} command only stops at the first instruction of a source
4166 line. This prevents the multiple stops that could otherwise occur in
4167 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4168 to stop if a function that has debugging information is called within
4169 the line. In other words, @code{step} @emph{steps inside} any functions
4170 called within the line.
4172 Also, the @code{step} command only enters a function if there is line
4173 number information for the function. Otherwise it acts like the
4174 @code{next} command. This avoids problems when using @code{cc -gl}
4175 on MIPS machines. Previously, @code{step} entered subroutines if there
4176 was any debugging information about the routine.
4178 @item step @var{count}
4179 Continue running as in @code{step}, but do so @var{count} times. If a
4180 breakpoint is reached, or a signal not related to stepping occurs before
4181 @var{count} steps, stepping stops right away.
4184 @kindex n @r{(@code{next})}
4185 @item next @r{[}@var{count}@r{]}
4186 Continue to the next source line in the current (innermost) stack frame.
4187 This is similar to @code{step}, but function calls that appear within
4188 the line of code are executed without stopping. Execution stops when
4189 control reaches a different line of code at the original stack level
4190 that was executing when you gave the @code{next} command. This command
4191 is abbreviated @code{n}.
4193 An argument @var{count} is a repeat count, as for @code{step}.
4196 @c FIX ME!! Do we delete this, or is there a way it fits in with
4197 @c the following paragraph? --- Vctoria
4199 @c @code{next} within a function that lacks debugging information acts like
4200 @c @code{step}, but any function calls appearing within the code of the
4201 @c function are executed without stopping.
4203 The @code{next} command only stops at the first instruction of a
4204 source line. This prevents multiple stops that could otherwise occur in
4205 @code{switch} statements, @code{for} loops, etc.
4207 @kindex set step-mode
4209 @cindex functions without line info, and stepping
4210 @cindex stepping into functions with no line info
4211 @itemx set step-mode on
4212 The @code{set step-mode on} command causes the @code{step} command to
4213 stop at the first instruction of a function which contains no debug line
4214 information rather than stepping over it.
4216 This is useful in cases where you may be interested in inspecting the
4217 machine instructions of a function which has no symbolic info and do not
4218 want @value{GDBN} to automatically skip over this function.
4220 @item set step-mode off
4221 Causes the @code{step} command to step over any functions which contains no
4222 debug information. This is the default.
4224 @item show step-mode
4225 Show whether @value{GDBN} will stop in or step over functions without
4226 source line debug information.
4229 @kindex fin @r{(@code{finish})}
4231 Continue running until just after function in the selected stack frame
4232 returns. Print the returned value (if any). This command can be
4233 abbreviated as @code{fin}.
4235 Contrast this with the @code{return} command (@pxref{Returning,
4236 ,Returning from a Function}).
4239 @kindex u @r{(@code{until})}
4240 @cindex run until specified location
4243 Continue running until a source line past the current line, in the
4244 current stack frame, is reached. This command is used to avoid single
4245 stepping through a loop more than once. It is like the @code{next}
4246 command, except that when @code{until} encounters a jump, it
4247 automatically continues execution until the program counter is greater
4248 than the address of the jump.
4250 This means that when you reach the end of a loop after single stepping
4251 though it, @code{until} makes your program continue execution until it
4252 exits the loop. In contrast, a @code{next} command at the end of a loop
4253 simply steps back to the beginning of the loop, which forces you to step
4254 through the next iteration.
4256 @code{until} always stops your program if it attempts to exit the current
4259 @code{until} may produce somewhat counterintuitive results if the order
4260 of machine code does not match the order of the source lines. For
4261 example, in the following excerpt from a debugging session, the @code{f}
4262 (@code{frame}) command shows that execution is stopped at line
4263 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4267 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4269 (@value{GDBP}) until
4270 195 for ( ; argc > 0; NEXTARG) @{
4273 This happened because, for execution efficiency, the compiler had
4274 generated code for the loop closure test at the end, rather than the
4275 start, of the loop---even though the test in a C @code{for}-loop is
4276 written before the body of the loop. The @code{until} command appeared
4277 to step back to the beginning of the loop when it advanced to this
4278 expression; however, it has not really gone to an earlier
4279 statement---not in terms of the actual machine code.
4281 @code{until} with no argument works by means of single
4282 instruction stepping, and hence is slower than @code{until} with an
4285 @item until @var{location}
4286 @itemx u @var{location}
4287 Continue running your program until either the specified location is
4288 reached, or the current stack frame returns. @var{location} is any of
4289 the forms described in @ref{Specify Location}.
4290 This form of the command uses temporary breakpoints, and
4291 hence is quicker than @code{until} without an argument. The specified
4292 location is actually reached only if it is in the current frame. This
4293 implies that @code{until} can be used to skip over recursive function
4294 invocations. For instance in the code below, if the current location is
4295 line @code{96}, issuing @code{until 99} will execute the program up to
4296 line @code{99} in the same invocation of factorial, i.e., after the inner
4297 invocations have returned.
4300 94 int factorial (int value)
4302 96 if (value > 1) @{
4303 97 value *= factorial (value - 1);
4310 @kindex advance @var{location}
4311 @itemx advance @var{location}
4312 Continue running the program up to the given @var{location}. An argument is
4313 required, which should be of one of the forms described in
4314 @ref{Specify Location}.
4315 Execution will also stop upon exit from the current stack
4316 frame. This command is similar to @code{until}, but @code{advance} will
4317 not skip over recursive function calls, and the target location doesn't
4318 have to be in the same frame as the current one.
4322 @kindex si @r{(@code{stepi})}
4324 @itemx stepi @var{arg}
4326 Execute one machine instruction, then stop and return to the debugger.
4328 It is often useful to do @samp{display/i $pc} when stepping by machine
4329 instructions. This makes @value{GDBN} automatically display the next
4330 instruction to be executed, each time your program stops. @xref{Auto
4331 Display,, Automatic Display}.
4333 An argument is a repeat count, as in @code{step}.
4337 @kindex ni @r{(@code{nexti})}
4339 @itemx nexti @var{arg}
4341 Execute one machine instruction, but if it is a function call,
4342 proceed until the function returns.
4344 An argument is a repeat count, as in @code{next}.
4351 A signal is an asynchronous event that can happen in a program. The
4352 operating system defines the possible kinds of signals, and gives each
4353 kind a name and a number. For example, in Unix @code{SIGINT} is the
4354 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4355 @code{SIGSEGV} is the signal a program gets from referencing a place in
4356 memory far away from all the areas in use; @code{SIGALRM} occurs when
4357 the alarm clock timer goes off (which happens only if your program has
4358 requested an alarm).
4360 @cindex fatal signals
4361 Some signals, including @code{SIGALRM}, are a normal part of the
4362 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4363 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4364 program has not specified in advance some other way to handle the signal.
4365 @code{SIGINT} does not indicate an error in your program, but it is normally
4366 fatal so it can carry out the purpose of the interrupt: to kill the program.
4368 @value{GDBN} has the ability to detect any occurrence of a signal in your
4369 program. You can tell @value{GDBN} in advance what to do for each kind of
4372 @cindex handling signals
4373 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4374 @code{SIGALRM} be silently passed to your program
4375 (so as not to interfere with their role in the program's functioning)
4376 but to stop your program immediately whenever an error signal happens.
4377 You can change these settings with the @code{handle} command.
4380 @kindex info signals
4384 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4385 handle each one. You can use this to see the signal numbers of all
4386 the defined types of signals.
4388 @item info signals @var{sig}
4389 Similar, but print information only about the specified signal number.
4391 @code{info handle} is an alias for @code{info signals}.
4394 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4395 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4396 can be the number of a signal or its name (with or without the
4397 @samp{SIG} at the beginning); a list of signal numbers of the form
4398 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4399 known signals. Optional arguments @var{keywords}, described below,
4400 say what change to make.
4404 The keywords allowed by the @code{handle} command can be abbreviated.
4405 Their full names are:
4409 @value{GDBN} should not stop your program when this signal happens. It may
4410 still print a message telling you that the signal has come in.
4413 @value{GDBN} should stop your program when this signal happens. This implies
4414 the @code{print} keyword as well.
4417 @value{GDBN} should print a message when this signal happens.
4420 @value{GDBN} should not mention the occurrence of the signal at all. This
4421 implies the @code{nostop} keyword as well.
4425 @value{GDBN} should allow your program to see this signal; your program
4426 can handle the signal, or else it may terminate if the signal is fatal
4427 and not handled. @code{pass} and @code{noignore} are synonyms.
4431 @value{GDBN} should not allow your program to see this signal.
4432 @code{nopass} and @code{ignore} are synonyms.
4436 When a signal stops your program, the signal is not visible to the
4438 continue. Your program sees the signal then, if @code{pass} is in
4439 effect for the signal in question @emph{at that time}. In other words,
4440 after @value{GDBN} reports a signal, you can use the @code{handle}
4441 command with @code{pass} or @code{nopass} to control whether your
4442 program sees that signal when you continue.
4444 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4445 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4446 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4449 You can also use the @code{signal} command to prevent your program from
4450 seeing a signal, or cause it to see a signal it normally would not see,
4451 or to give it any signal at any time. For example, if your program stopped
4452 due to some sort of memory reference error, you might store correct
4453 values into the erroneous variables and continue, hoping to see more
4454 execution; but your program would probably terminate immediately as
4455 a result of the fatal signal once it saw the signal. To prevent this,
4456 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4460 @section Stopping and Starting Multi-thread Programs
4462 When your program has multiple threads (@pxref{Threads,, Debugging
4463 Programs with Multiple Threads}), you can choose whether to set
4464 breakpoints on all threads, or on a particular thread.
4467 @cindex breakpoints and threads
4468 @cindex thread breakpoints
4469 @kindex break @dots{} thread @var{threadno}
4470 @item break @var{linespec} thread @var{threadno}
4471 @itemx break @var{linespec} thread @var{threadno} if @dots{}
4472 @var{linespec} specifies source lines; there are several ways of
4473 writing them (@pxref{Specify Location}), but the effect is always to
4474 specify some source line.
4476 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
4477 to specify that you only want @value{GDBN} to stop the program when a
4478 particular thread reaches this breakpoint. @var{threadno} is one of the
4479 numeric thread identifiers assigned by @value{GDBN}, shown in the first
4480 column of the @samp{info threads} display.
4482 If you do not specify @samp{thread @var{threadno}} when you set a
4483 breakpoint, the breakpoint applies to @emph{all} threads of your
4486 You can use the @code{thread} qualifier on conditional breakpoints as
4487 well; in this case, place @samp{thread @var{threadno}} before the
4488 breakpoint condition, like this:
4491 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
4496 @cindex stopped threads
4497 @cindex threads, stopped
4498 Whenever your program stops under @value{GDBN} for any reason,
4499 @emph{all} threads of execution stop, not just the current thread. This
4500 allows you to examine the overall state of the program, including
4501 switching between threads, without worrying that things may change
4504 @cindex thread breakpoints and system calls
4505 @cindex system calls and thread breakpoints
4506 @cindex premature return from system calls
4507 There is an unfortunate side effect. If one thread stops for a
4508 breakpoint, or for some other reason, and another thread is blocked in a
4509 system call, then the system call may return prematurely. This is a
4510 consequence of the interaction between multiple threads and the signals
4511 that @value{GDBN} uses to implement breakpoints and other events that
4514 To handle this problem, your program should check the return value of
4515 each system call and react appropriately. This is good programming
4518 For example, do not write code like this:
4524 The call to @code{sleep} will return early if a different thread stops
4525 at a breakpoint or for some other reason.
4527 Instead, write this:
4532 unslept = sleep (unslept);
4535 A system call is allowed to return early, so the system is still
4536 conforming to its specification. But @value{GDBN} does cause your
4537 multi-threaded program to behave differently than it would without
4540 Also, @value{GDBN} uses internal breakpoints in the thread library to
4541 monitor certain events such as thread creation and thread destruction.
4542 When such an event happens, a system call in another thread may return
4543 prematurely, even though your program does not appear to stop.
4545 @cindex continuing threads
4546 @cindex threads, continuing
4547 Conversely, whenever you restart the program, @emph{all} threads start
4548 executing. @emph{This is true even when single-stepping} with commands
4549 like @code{step} or @code{next}.
4551 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4552 Since thread scheduling is up to your debugging target's operating
4553 system (not controlled by @value{GDBN}), other threads may
4554 execute more than one statement while the current thread completes a
4555 single step. Moreover, in general other threads stop in the middle of a
4556 statement, rather than at a clean statement boundary, when the program
4559 You might even find your program stopped in another thread after
4560 continuing or even single-stepping. This happens whenever some other
4561 thread runs into a breakpoint, a signal, or an exception before the
4562 first thread completes whatever you requested.
4564 On some OSes, you can lock the OS scheduler and thus allow only a single
4568 @item set scheduler-locking @var{mode}
4569 @cindex scheduler locking mode
4570 @cindex lock scheduler
4571 Set the scheduler locking mode. If it is @code{off}, then there is no
4572 locking and any thread may run at any time. If @code{on}, then only the
4573 current thread may run when the inferior is resumed. The @code{step}
4574 mode optimizes for single-stepping. It stops other threads from
4575 ``seizing the prompt'' by preempting the current thread while you are
4576 stepping. Other threads will only rarely (or never) get a chance to run
4577 when you step. They are more likely to run when you @samp{next} over a
4578 function call, and they are completely free to run when you use commands
4579 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4580 thread hits a breakpoint during its timeslice, they will never steal the
4581 @value{GDBN} prompt away from the thread that you are debugging.
4583 @item show scheduler-locking
4584 Display the current scheduler locking mode.
4589 @chapter Examining the Stack
4591 When your program has stopped, the first thing you need to know is where it
4592 stopped and how it got there.
4595 Each time your program performs a function call, information about the call
4597 That information includes the location of the call in your program,
4598 the arguments of the call,
4599 and the local variables of the function being called.
4600 The information is saved in a block of data called a @dfn{stack frame}.
4601 The stack frames are allocated in a region of memory called the @dfn{call
4604 When your program stops, the @value{GDBN} commands for examining the
4605 stack allow you to see all of this information.
4607 @cindex selected frame
4608 One of the stack frames is @dfn{selected} by @value{GDBN} and many
4609 @value{GDBN} commands refer implicitly to the selected frame. In
4610 particular, whenever you ask @value{GDBN} for the value of a variable in
4611 your program, the value is found in the selected frame. There are
4612 special @value{GDBN} commands to select whichever frame you are
4613 interested in. @xref{Selection, ,Selecting a Frame}.
4615 When your program stops, @value{GDBN} automatically selects the
4616 currently executing frame and describes it briefly, similar to the
4617 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
4620 * Frames:: Stack frames
4621 * Backtrace:: Backtraces
4622 * Selection:: Selecting a frame
4623 * Frame Info:: Information on a frame
4628 @section Stack Frames
4630 @cindex frame, definition
4632 The call stack is divided up into contiguous pieces called @dfn{stack
4633 frames}, or @dfn{frames} for short; each frame is the data associated
4634 with one call to one function. The frame contains the arguments given
4635 to the function, the function's local variables, and the address at
4636 which the function is executing.
4638 @cindex initial frame
4639 @cindex outermost frame
4640 @cindex innermost frame
4641 When your program is started, the stack has only one frame, that of the
4642 function @code{main}. This is called the @dfn{initial} frame or the
4643 @dfn{outermost} frame. Each time a function is called, a new frame is
4644 made. Each time a function returns, the frame for that function invocation
4645 is eliminated. If a function is recursive, there can be many frames for
4646 the same function. The frame for the function in which execution is
4647 actually occurring is called the @dfn{innermost} frame. This is the most
4648 recently created of all the stack frames that still exist.
4650 @cindex frame pointer
4651 Inside your program, stack frames are identified by their addresses. A
4652 stack frame consists of many bytes, each of which has its own address; each
4653 kind of computer has a convention for choosing one byte whose
4654 address serves as the address of the frame. Usually this address is kept
4655 in a register called the @dfn{frame pointer register}
4656 (@pxref{Registers, $fp}) while execution is going on in that frame.
4658 @cindex frame number
4659 @value{GDBN} assigns numbers to all existing stack frames, starting with
4660 zero for the innermost frame, one for the frame that called it,
4661 and so on upward. These numbers do not really exist in your program;
4662 they are assigned by @value{GDBN} to give you a way of designating stack
4663 frames in @value{GDBN} commands.
4665 @c The -fomit-frame-pointer below perennially causes hbox overflow
4666 @c underflow problems.
4667 @cindex frameless execution
4668 Some compilers provide a way to compile functions so that they operate
4669 without stack frames. (For example, the @value{NGCC} option
4671 @samp{-fomit-frame-pointer}
4673 generates functions without a frame.)
4674 This is occasionally done with heavily used library functions to save
4675 the frame setup time. @value{GDBN} has limited facilities for dealing
4676 with these function invocations. If the innermost function invocation
4677 has no stack frame, @value{GDBN} nevertheless regards it as though
4678 it had a separate frame, which is numbered zero as usual, allowing
4679 correct tracing of the function call chain. However, @value{GDBN} has
4680 no provision for frameless functions elsewhere in the stack.
4683 @kindex frame@r{, command}
4684 @cindex current stack frame
4685 @item frame @var{args}
4686 The @code{frame} command allows you to move from one stack frame to another,
4687 and to print the stack frame you select. @var{args} may be either the
4688 address of the frame or the stack frame number. Without an argument,
4689 @code{frame} prints the current stack frame.
4691 @kindex select-frame
4692 @cindex selecting frame silently
4694 The @code{select-frame} command allows you to move from one stack frame
4695 to another without printing the frame. This is the silent version of
4703 @cindex call stack traces
4704 A backtrace is a summary of how your program got where it is. It shows one
4705 line per frame, for many frames, starting with the currently executing
4706 frame (frame zero), followed by its caller (frame one), and on up the
4711 @kindex bt @r{(@code{backtrace})}
4714 Print a backtrace of the entire stack: one line per frame for all
4715 frames in the stack.
4717 You can stop the backtrace at any time by typing the system interrupt
4718 character, normally @kbd{Ctrl-c}.
4720 @item backtrace @var{n}
4722 Similar, but print only the innermost @var{n} frames.
4724 @item backtrace -@var{n}
4726 Similar, but print only the outermost @var{n} frames.
4728 @item backtrace full
4730 @itemx bt full @var{n}
4731 @itemx bt full -@var{n}
4732 Print the values of the local variables also. @var{n} specifies the
4733 number of frames to print, as described above.
4738 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4739 are additional aliases for @code{backtrace}.
4741 @cindex multiple threads, backtrace
4742 In a multi-threaded program, @value{GDBN} by default shows the
4743 backtrace only for the current thread. To display the backtrace for
4744 several or all of the threads, use the command @code{thread apply}
4745 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
4746 apply all backtrace}, @value{GDBN} will display the backtrace for all
4747 the threads; this is handy when you debug a core dump of a
4748 multi-threaded program.
4750 Each line in the backtrace shows the frame number and the function name.
4751 The program counter value is also shown---unless you use @code{set
4752 print address off}. The backtrace also shows the source file name and
4753 line number, as well as the arguments to the function. The program
4754 counter value is omitted if it is at the beginning of the code for that
4757 Here is an example of a backtrace. It was made with the command
4758 @samp{bt 3}, so it shows the innermost three frames.
4762 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4764 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4765 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4767 (More stack frames follow...)
4772 The display for frame zero does not begin with a program counter
4773 value, indicating that your program has stopped at the beginning of the
4774 code for line @code{993} of @code{builtin.c}.
4776 @cindex value optimized out, in backtrace
4777 @cindex function call arguments, optimized out
4778 If your program was compiled with optimizations, some compilers will
4779 optimize away arguments passed to functions if those arguments are
4780 never used after the call. Such optimizations generate code that
4781 passes arguments through registers, but doesn't store those arguments
4782 in the stack frame. @value{GDBN} has no way of displaying such
4783 arguments in stack frames other than the innermost one. Here's what
4784 such a backtrace might look like:
4788 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4790 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
4791 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
4793 (More stack frames follow...)
4798 The values of arguments that were not saved in their stack frames are
4799 shown as @samp{<value optimized out>}.
4801 If you need to display the values of such optimized-out arguments,
4802 either deduce that from other variables whose values depend on the one
4803 you are interested in, or recompile without optimizations.
4805 @cindex backtrace beyond @code{main} function
4806 @cindex program entry point
4807 @cindex startup code, and backtrace
4808 Most programs have a standard user entry point---a place where system
4809 libraries and startup code transition into user code. For C this is
4810 @code{main}@footnote{
4811 Note that embedded programs (the so-called ``free-standing''
4812 environment) are not required to have a @code{main} function as the
4813 entry point. They could even have multiple entry points.}.
4814 When @value{GDBN} finds the entry function in a backtrace
4815 it will terminate the backtrace, to avoid tracing into highly
4816 system-specific (and generally uninteresting) code.
4818 If you need to examine the startup code, or limit the number of levels
4819 in a backtrace, you can change this behavior:
4822 @item set backtrace past-main
4823 @itemx set backtrace past-main on
4824 @kindex set backtrace
4825 Backtraces will continue past the user entry point.
4827 @item set backtrace past-main off
4828 Backtraces will stop when they encounter the user entry point. This is the
4831 @item show backtrace past-main
4832 @kindex show backtrace
4833 Display the current user entry point backtrace policy.
4835 @item set backtrace past-entry
4836 @itemx set backtrace past-entry on
4837 Backtraces will continue past the internal entry point of an application.
4838 This entry point is encoded by the linker when the application is built,
4839 and is likely before the user entry point @code{main} (or equivalent) is called.
4841 @item set backtrace past-entry off
4842 Backtraces will stop when they encounter the internal entry point of an
4843 application. This is the default.
4845 @item show backtrace past-entry
4846 Display the current internal entry point backtrace policy.
4848 @item set backtrace limit @var{n}
4849 @itemx set backtrace limit 0
4850 @cindex backtrace limit
4851 Limit the backtrace to @var{n} levels. A value of zero means
4854 @item show backtrace limit
4855 Display the current limit on backtrace levels.
4859 @section Selecting a Frame
4861 Most commands for examining the stack and other data in your program work on
4862 whichever stack frame is selected at the moment. Here are the commands for
4863 selecting a stack frame; all of them finish by printing a brief description
4864 of the stack frame just selected.
4867 @kindex frame@r{, selecting}
4868 @kindex f @r{(@code{frame})}
4871 Select frame number @var{n}. Recall that frame zero is the innermost
4872 (currently executing) frame, frame one is the frame that called the
4873 innermost one, and so on. The highest-numbered frame is the one for
4876 @item frame @var{addr}
4878 Select the frame at address @var{addr}. This is useful mainly if the
4879 chaining of stack frames has been damaged by a bug, making it
4880 impossible for @value{GDBN} to assign numbers properly to all frames. In
4881 addition, this can be useful when your program has multiple stacks and
4882 switches between them.
4884 On the SPARC architecture, @code{frame} needs two addresses to
4885 select an arbitrary frame: a frame pointer and a stack pointer.
4887 On the MIPS and Alpha architecture, it needs two addresses: a stack
4888 pointer and a program counter.
4890 On the 29k architecture, it needs three addresses: a register stack
4891 pointer, a program counter, and a memory stack pointer.
4895 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4896 advances toward the outermost frame, to higher frame numbers, to frames
4897 that have existed longer. @var{n} defaults to one.
4900 @kindex do @r{(@code{down})}
4902 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4903 advances toward the innermost frame, to lower frame numbers, to frames
4904 that were created more recently. @var{n} defaults to one. You may
4905 abbreviate @code{down} as @code{do}.
4908 All of these commands end by printing two lines of output describing the
4909 frame. The first line shows the frame number, the function name, the
4910 arguments, and the source file and line number of execution in that
4911 frame. The second line shows the text of that source line.
4919 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4921 10 read_input_file (argv[i]);
4925 After such a printout, the @code{list} command with no arguments
4926 prints ten lines centered on the point of execution in the frame.
4927 You can also edit the program at the point of execution with your favorite
4928 editing program by typing @code{edit}.
4929 @xref{List, ,Printing Source Lines},
4933 @kindex down-silently
4935 @item up-silently @var{n}
4936 @itemx down-silently @var{n}
4937 These two commands are variants of @code{up} and @code{down},
4938 respectively; they differ in that they do their work silently, without
4939 causing display of the new frame. They are intended primarily for use
4940 in @value{GDBN} command scripts, where the output might be unnecessary and
4945 @section Information About a Frame
4947 There are several other commands to print information about the selected
4953 When used without any argument, this command does not change which
4954 frame is selected, but prints a brief description of the currently
4955 selected stack frame. It can be abbreviated @code{f}. With an
4956 argument, this command is used to select a stack frame.
4957 @xref{Selection, ,Selecting a Frame}.
4960 @kindex info f @r{(@code{info frame})}
4963 This command prints a verbose description of the selected stack frame,
4968 the address of the frame
4970 the address of the next frame down (called by this frame)
4972 the address of the next frame up (caller of this frame)
4974 the language in which the source code corresponding to this frame is written
4976 the address of the frame's arguments
4978 the address of the frame's local variables
4980 the program counter saved in it (the address of execution in the caller frame)
4982 which registers were saved in the frame
4985 @noindent The verbose description is useful when
4986 something has gone wrong that has made the stack format fail to fit
4987 the usual conventions.
4989 @item info frame @var{addr}
4990 @itemx info f @var{addr}
4991 Print a verbose description of the frame at address @var{addr}, without
4992 selecting that frame. The selected frame remains unchanged by this
4993 command. This requires the same kind of address (more than one for some
4994 architectures) that you specify in the @code{frame} command.
4995 @xref{Selection, ,Selecting a Frame}.
4999 Print the arguments of the selected frame, each on a separate line.
5003 Print the local variables of the selected frame, each on a separate
5004 line. These are all variables (declared either static or automatic)
5005 accessible at the point of execution of the selected frame.
5008 @cindex catch exceptions, list active handlers
5009 @cindex exception handlers, how to list
5011 Print a list of all the exception handlers that are active in the
5012 current stack frame at the current point of execution. To see other
5013 exception handlers, visit the associated frame (using the @code{up},
5014 @code{down}, or @code{frame} commands); then type @code{info catch}.
5015 @xref{Set Catchpoints, , Setting Catchpoints}.
5021 @chapter Examining Source Files
5023 @value{GDBN} can print parts of your program's source, since the debugging
5024 information recorded in the program tells @value{GDBN} what source files were
5025 used to build it. When your program stops, @value{GDBN} spontaneously prints
5026 the line where it stopped. Likewise, when you select a stack frame
5027 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
5028 execution in that frame has stopped. You can print other portions of
5029 source files by explicit command.
5031 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
5032 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
5033 @value{GDBN} under @sc{gnu} Emacs}.
5036 * List:: Printing source lines
5037 * Specify Location:: How to specify code locations
5038 * Edit:: Editing source files
5039 * Search:: Searching source files
5040 * Source Path:: Specifying source directories
5041 * Machine Code:: Source and machine code
5045 @section Printing Source Lines
5048 @kindex l @r{(@code{list})}
5049 To print lines from a source file, use the @code{list} command
5050 (abbreviated @code{l}). By default, ten lines are printed.
5051 There are several ways to specify what part of the file you want to
5052 print; see @ref{Specify Location}, for the full list.
5054 Here are the forms of the @code{list} command most commonly used:
5057 @item list @var{linenum}
5058 Print lines centered around line number @var{linenum} in the
5059 current source file.
5061 @item list @var{function}
5062 Print lines centered around the beginning of function
5066 Print more lines. If the last lines printed were printed with a
5067 @code{list} command, this prints lines following the last lines
5068 printed; however, if the last line printed was a solitary line printed
5069 as part of displaying a stack frame (@pxref{Stack, ,Examining the
5070 Stack}), this prints lines centered around that line.
5073 Print lines just before the lines last printed.
5076 @cindex @code{list}, how many lines to display
5077 By default, @value{GDBN} prints ten source lines with any of these forms of
5078 the @code{list} command. You can change this using @code{set listsize}:
5081 @kindex set listsize
5082 @item set listsize @var{count}
5083 Make the @code{list} command display @var{count} source lines (unless
5084 the @code{list} argument explicitly specifies some other number).
5086 @kindex show listsize
5088 Display the number of lines that @code{list} prints.
5091 Repeating a @code{list} command with @key{RET} discards the argument,
5092 so it is equivalent to typing just @code{list}. This is more useful
5093 than listing the same lines again. An exception is made for an
5094 argument of @samp{-}; that argument is preserved in repetition so that
5095 each repetition moves up in the source file.
5097 In general, the @code{list} command expects you to supply zero, one or two
5098 @dfn{linespecs}. Linespecs specify source lines; there are several ways
5099 of writing them (@pxref{Specify Location}), but the effect is always
5100 to specify some source line.
5102 Here is a complete description of the possible arguments for @code{list}:
5105 @item list @var{linespec}
5106 Print lines centered around the line specified by @var{linespec}.
5108 @item list @var{first},@var{last}
5109 Print lines from @var{first} to @var{last}. Both arguments are
5110 linespecs. When a @code{list} command has two linespecs, and the
5111 source file of the second linespec is omitted, this refers to
5112 the same source file as the first linespec.
5114 @item list ,@var{last}
5115 Print lines ending with @var{last}.
5117 @item list @var{first},
5118 Print lines starting with @var{first}.
5121 Print lines just after the lines last printed.
5124 Print lines just before the lines last printed.
5127 As described in the preceding table.
5130 @node Specify Location
5131 @section Specifying a Location
5132 @cindex specifying location
5135 Several @value{GDBN} commands accept arguments that specify a location
5136 of your program's code. Since @value{GDBN} is a source-level
5137 debugger, a location usually specifies some line in the source code;
5138 for that reason, locations are also known as @dfn{linespecs}.
5140 Here are all the different ways of specifying a code location that
5141 @value{GDBN} understands:
5145 Specifies the line number @var{linenum} of the current source file.
5148 @itemx +@var{offset}
5149 Specifies the line @var{offset} lines before or after the @dfn{current
5150 line}. For the @code{list} command, the current line is the last one
5151 printed; for the breakpoint commands, this is the line at which
5152 execution stopped in the currently selected @dfn{stack frame}
5153 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
5154 used as the second of the two linespecs in a @code{list} command,
5155 this specifies the line @var{offset} lines up or down from the first
5158 @item @var{filename}:@var{linenum}
5159 Specifies the line @var{linenum} in the source file @var{filename}.
5161 @item @var{function}
5162 Specifies the line that begins the body of the function @var{function}.
5163 For example, in C, this is the line with the open brace.
5165 @item @var{filename}:@var{function}
5166 Specifies the line that begins the body of the function @var{function}
5167 in the file @var{filename}. You only need the file name with a
5168 function name to avoid ambiguity when there are identically named
5169 functions in different source files.
5171 @item *@var{address}
5172 Specifies the program address @var{address}. For line-oriented
5173 commands, such as @code{list} and @code{edit}, this specifies a source
5174 line that contains @var{address}. For @code{break} and other
5175 breakpoint oriented commands, this can be used to set breakpoints in
5176 parts of your program which do not have debugging information or
5179 Here @var{address} may be any expression valid in the current working
5180 language (@pxref{Languages, working language}) that specifies a code
5181 address. In addition, as a convenience, @value{GDBN} extends the
5182 semantics of expressions used in locations to cover the situations
5183 that frequently happen during debugging. Here are the various forms
5187 @item @var{expression}
5188 Any expression valid in the current working language.
5190 @item @var{funcaddr}
5191 An address of a function or procedure derived from its name. In C,
5192 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
5193 simply the function's name @var{function} (and actually a special case
5194 of a valid expression). In Pascal and Modula-2, this is
5195 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
5196 (although the Pascal form also works).
5198 This form specifies the address of the function's first instruction,
5199 before the stack frame and arguments have been set up.
5201 @item '@var{filename}'::@var{funcaddr}
5202 Like @var{funcaddr} above, but also specifies the name of the source
5203 file explicitly. This is useful if the name of the function does not
5204 specify the function unambiguously, e.g., if there are several
5205 functions with identical names in different source files.
5212 @section Editing Source Files
5213 @cindex editing source files
5216 @kindex e @r{(@code{edit})}
5217 To edit the lines in a source file, use the @code{edit} command.
5218 The editing program of your choice
5219 is invoked with the current line set to
5220 the active line in the program.
5221 Alternatively, there are several ways to specify what part of the file you
5222 want to print if you want to see other parts of the program:
5225 @item edit @var{location}
5226 Edit the source file specified by @code{location}. Editing starts at
5227 that @var{location}, e.g., at the specified source line of the
5228 specified file. @xref{Specify Location}, for all the possible forms
5229 of the @var{location} argument; here are the forms of the @code{edit}
5230 command most commonly used:
5233 @item edit @var{number}
5234 Edit the current source file with @var{number} as the active line number.
5236 @item edit @var{function}
5237 Edit the file containing @var{function} at the beginning of its definition.
5242 @subsection Choosing your Editor
5243 You can customize @value{GDBN} to use any editor you want
5245 The only restriction is that your editor (say @code{ex}), recognizes the
5246 following command-line syntax:
5248 ex +@var{number} file
5250 The optional numeric value +@var{number} specifies the number of the line in
5251 the file where to start editing.}.
5252 By default, it is @file{@value{EDITOR}}, but you can change this
5253 by setting the environment variable @code{EDITOR} before using
5254 @value{GDBN}. For example, to configure @value{GDBN} to use the
5255 @code{vi} editor, you could use these commands with the @code{sh} shell:
5261 or in the @code{csh} shell,
5263 setenv EDITOR /usr/bin/vi
5268 @section Searching Source Files
5269 @cindex searching source files
5271 There are two commands for searching through the current source file for a
5276 @kindex forward-search
5277 @item forward-search @var{regexp}
5278 @itemx search @var{regexp}
5279 The command @samp{forward-search @var{regexp}} checks each line,
5280 starting with the one following the last line listed, for a match for
5281 @var{regexp}. It lists the line that is found. You can use the
5282 synonym @samp{search @var{regexp}} or abbreviate the command name as
5285 @kindex reverse-search
5286 @item reverse-search @var{regexp}
5287 The command @samp{reverse-search @var{regexp}} checks each line, starting
5288 with the one before the last line listed and going backward, for a match
5289 for @var{regexp}. It lists the line that is found. You can abbreviate
5290 this command as @code{rev}.
5294 @section Specifying Source Directories
5297 @cindex directories for source files
5298 Executable programs sometimes do not record the directories of the source
5299 files from which they were compiled, just the names. Even when they do,
5300 the directories could be moved between the compilation and your debugging
5301 session. @value{GDBN} has a list of directories to search for source files;
5302 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
5303 it tries all the directories in the list, in the order they are present
5304 in the list, until it finds a file with the desired name.
5306 For example, suppose an executable references the file
5307 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
5308 @file{/mnt/cross}. The file is first looked up literally; if this
5309 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
5310 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
5311 message is printed. @value{GDBN} does not look up the parts of the
5312 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
5313 Likewise, the subdirectories of the source path are not searched: if
5314 the source path is @file{/mnt/cross}, and the binary refers to
5315 @file{foo.c}, @value{GDBN} would not find it under
5316 @file{/mnt/cross/usr/src/foo-1.0/lib}.
5318 Plain file names, relative file names with leading directories, file
5319 names containing dots, etc.@: are all treated as described above; for
5320 instance, if the source path is @file{/mnt/cross}, and the source file
5321 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
5322 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
5323 that---@file{/mnt/cross/foo.c}.
5325 Note that the executable search path is @emph{not} used to locate the
5328 Whenever you reset or rearrange the source path, @value{GDBN} clears out
5329 any information it has cached about where source files are found and where
5330 each line is in the file.
5334 When you start @value{GDBN}, its source path includes only @samp{cdir}
5335 and @samp{cwd}, in that order.
5336 To add other directories, use the @code{directory} command.
5338 The search path is used to find both program source files and @value{GDBN}
5339 script files (read using the @samp{-command} option and @samp{source} command).
5341 In addition to the source path, @value{GDBN} provides a set of commands
5342 that manage a list of source path substitution rules. A @dfn{substitution
5343 rule} specifies how to rewrite source directories stored in the program's
5344 debug information in case the sources were moved to a different
5345 directory between compilation and debugging. A rule is made of
5346 two strings, the first specifying what needs to be rewritten in
5347 the path, and the second specifying how it should be rewritten.
5348 In @ref{set substitute-path}, we name these two parts @var{from} and
5349 @var{to} respectively. @value{GDBN} does a simple string replacement
5350 of @var{from} with @var{to} at the start of the directory part of the
5351 source file name, and uses that result instead of the original file
5352 name to look up the sources.
5354 Using the previous example, suppose the @file{foo-1.0} tree has been
5355 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
5356 @value{GDBN} to replace @file{/usr/src} in all source path names with
5357 @file{/mnt/cross}. The first lookup will then be
5358 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
5359 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
5360 substitution rule, use the @code{set substitute-path} command
5361 (@pxref{set substitute-path}).
5363 To avoid unexpected substitution results, a rule is applied only if the
5364 @var{from} part of the directory name ends at a directory separator.
5365 For instance, a rule substituting @file{/usr/source} into
5366 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
5367 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
5368 is applied only at the beginning of the directory name, this rule will
5369 not be applied to @file{/root/usr/source/baz.c} either.
5371 In many cases, you can achieve the same result using the @code{directory}
5372 command. However, @code{set substitute-path} can be more efficient in
5373 the case where the sources are organized in a complex tree with multiple
5374 subdirectories. With the @code{directory} command, you need to add each
5375 subdirectory of your project. If you moved the entire tree while
5376 preserving its internal organization, then @code{set substitute-path}
5377 allows you to direct the debugger to all the sources with one single
5380 @code{set substitute-path} is also more than just a shortcut command.
5381 The source path is only used if the file at the original location no
5382 longer exists. On the other hand, @code{set substitute-path} modifies
5383 the debugger behavior to look at the rewritten location instead. So, if
5384 for any reason a source file that is not relevant to your executable is
5385 located at the original location, a substitution rule is the only
5386 method available to point @value{GDBN} at the new location.
5389 @item directory @var{dirname} @dots{}
5390 @item dir @var{dirname} @dots{}
5391 Add directory @var{dirname} to the front of the source path. Several
5392 directory names may be given to this command, separated by @samp{:}
5393 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
5394 part of absolute file names) or
5395 whitespace. You may specify a directory that is already in the source
5396 path; this moves it forward, so @value{GDBN} searches it sooner.
5400 @vindex $cdir@r{, convenience variable}
5401 @vindex $cwd@r{, convenience variable}
5402 @cindex compilation directory
5403 @cindex current directory
5404 @cindex working directory
5405 @cindex directory, current
5406 @cindex directory, compilation
5407 You can use the string @samp{$cdir} to refer to the compilation
5408 directory (if one is recorded), and @samp{$cwd} to refer to the current
5409 working directory. @samp{$cwd} is not the same as @samp{.}---the former
5410 tracks the current working directory as it changes during your @value{GDBN}
5411 session, while the latter is immediately expanded to the current
5412 directory at the time you add an entry to the source path.
5415 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
5417 @c RET-repeat for @code{directory} is explicitly disabled, but since
5418 @c repeating it would be a no-op we do not say that. (thanks to RMS)
5420 @item show directories
5421 @kindex show directories
5422 Print the source path: show which directories it contains.
5424 @anchor{set substitute-path}
5425 @item set substitute-path @var{from} @var{to}
5426 @kindex set substitute-path
5427 Define a source path substitution rule, and add it at the end of the
5428 current list of existing substitution rules. If a rule with the same
5429 @var{from} was already defined, then the old rule is also deleted.
5431 For example, if the file @file{/foo/bar/baz.c} was moved to
5432 @file{/mnt/cross/baz.c}, then the command
5435 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
5439 will tell @value{GDBN} to replace @samp{/usr/src} with
5440 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
5441 @file{baz.c} even though it was moved.
5443 In the case when more than one substitution rule have been defined,
5444 the rules are evaluated one by one in the order where they have been
5445 defined. The first one matching, if any, is selected to perform
5448 For instance, if we had entered the following commands:
5451 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
5452 (@value{GDBP}) set substitute-path /usr/src /mnt/src
5456 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
5457 @file{/mnt/include/defs.h} by using the first rule. However, it would
5458 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
5459 @file{/mnt/src/lib/foo.c}.
5462 @item unset substitute-path [path]
5463 @kindex unset substitute-path
5464 If a path is specified, search the current list of substitution rules
5465 for a rule that would rewrite that path. Delete that rule if found.
5466 A warning is emitted by the debugger if no rule could be found.
5468 If no path is specified, then all substitution rules are deleted.
5470 @item show substitute-path [path]
5471 @kindex show substitute-path
5472 If a path is specified, then print the source path substitution rule
5473 which would rewrite that path, if any.
5475 If no path is specified, then print all existing source path substitution
5480 If your source path is cluttered with directories that are no longer of
5481 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
5482 versions of source. You can correct the situation as follows:
5486 Use @code{directory} with no argument to reset the source path to its default value.
5489 Use @code{directory} with suitable arguments to reinstall the
5490 directories you want in the source path. You can add all the
5491 directories in one command.
5495 @section Source and Machine Code
5496 @cindex source line and its code address
5498 You can use the command @code{info line} to map source lines to program
5499 addresses (and vice versa), and the command @code{disassemble} to display
5500 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
5501 mode, the @code{info line} command causes the arrow to point to the
5502 line specified. Also, @code{info line} prints addresses in symbolic form as
5507 @item info line @var{linespec}
5508 Print the starting and ending addresses of the compiled code for
5509 source line @var{linespec}. You can specify source lines in any of
5510 the ways documented in @ref{Specify Location}.
5513 For example, we can use @code{info line} to discover the location of
5514 the object code for the first line of function
5515 @code{m4_changequote}:
5517 @c FIXME: I think this example should also show the addresses in
5518 @c symbolic form, as they usually would be displayed.
5520 (@value{GDBP}) info line m4_changequote
5521 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
5525 @cindex code address and its source line
5526 We can also inquire (using @code{*@var{addr}} as the form for
5527 @var{linespec}) what source line covers a particular address:
5529 (@value{GDBP}) info line *0x63ff
5530 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
5533 @cindex @code{$_} and @code{info line}
5534 @cindex @code{x} command, default address
5535 @kindex x@r{(examine), and} info line
5536 After @code{info line}, the default address for the @code{x} command
5537 is changed to the starting address of the line, so that @samp{x/i} is
5538 sufficient to begin examining the machine code (@pxref{Memory,
5539 ,Examining Memory}). Also, this address is saved as the value of the
5540 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
5545 @cindex assembly instructions
5546 @cindex instructions, assembly
5547 @cindex machine instructions
5548 @cindex listing machine instructions
5550 @itemx disassemble /m
5551 This specialized command dumps a range of memory as machine
5552 instructions. It can also print mixed source+disassembly by specifying
5553 the @code{/m} modifier.
5554 The default memory range is the function surrounding the
5555 program counter of the selected frame. A single argument to this
5556 command is a program counter value; @value{GDBN} dumps the function
5557 surrounding this value. Two arguments specify a range of addresses
5558 (first inclusive, second exclusive) to dump.
5561 The following example shows the disassembly of a range of addresses of
5562 HP PA-RISC 2.0 code:
5565 (@value{GDBP}) disas 0x32c4 0x32e4
5566 Dump of assembler code from 0x32c4 to 0x32e4:
5567 0x32c4 <main+204>: addil 0,dp
5568 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
5569 0x32cc <main+212>: ldil 0x3000,r31
5570 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
5571 0x32d4 <main+220>: ldo 0(r31),rp
5572 0x32d8 <main+224>: addil -0x800,dp
5573 0x32dc <main+228>: ldo 0x588(r1),r26
5574 0x32e0 <main+232>: ldil 0x3000,r31
5575 End of assembler dump.
5578 Here is an example showing mixed source+assembly for Intel x86:
5581 (@value{GDBP}) disas /m main
5582 Dump of assembler code for function main:
5584 0x08048330 <main+0>: push %ebp
5585 0x08048331 <main+1>: mov %esp,%ebp
5586 0x08048333 <main+3>: sub $0x8,%esp
5587 0x08048336 <main+6>: and $0xfffffff0,%esp
5588 0x08048339 <main+9>: sub $0x10,%esp
5590 6 printf ("Hello.\n");
5591 0x0804833c <main+12>: movl $0x8048440,(%esp)
5592 0x08048343 <main+19>: call 0x8048284 <puts@@plt>
5596 0x08048348 <main+24>: mov $0x0,%eax
5597 0x0804834d <main+29>: leave
5598 0x0804834e <main+30>: ret
5600 End of assembler dump.
5603 Some architectures have more than one commonly-used set of instruction
5604 mnemonics or other syntax.
5606 For programs that were dynamically linked and use shared libraries,
5607 instructions that call functions or branch to locations in the shared
5608 libraries might show a seemingly bogus location---it's actually a
5609 location of the relocation table. On some architectures, @value{GDBN}
5610 might be able to resolve these to actual function names.
5613 @kindex set disassembly-flavor
5614 @cindex Intel disassembly flavor
5615 @cindex AT&T disassembly flavor
5616 @item set disassembly-flavor @var{instruction-set}
5617 Select the instruction set to use when disassembling the
5618 program via the @code{disassemble} or @code{x/i} commands.
5620 Currently this command is only defined for the Intel x86 family. You
5621 can set @var{instruction-set} to either @code{intel} or @code{att}.
5622 The default is @code{att}, the AT&T flavor used by default by Unix
5623 assemblers for x86-based targets.
5625 @kindex show disassembly-flavor
5626 @item show disassembly-flavor
5627 Show the current setting of the disassembly flavor.
5632 @chapter Examining Data
5634 @cindex printing data
5635 @cindex examining data
5638 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
5639 @c document because it is nonstandard... Under Epoch it displays in a
5640 @c different window or something like that.
5641 The usual way to examine data in your program is with the @code{print}
5642 command (abbreviated @code{p}), or its synonym @code{inspect}. It
5643 evaluates and prints the value of an expression of the language your
5644 program is written in (@pxref{Languages, ,Using @value{GDBN} with
5645 Different Languages}).
5648 @item print @var{expr}
5649 @itemx print /@var{f} @var{expr}
5650 @var{expr} is an expression (in the source language). By default the
5651 value of @var{expr} is printed in a format appropriate to its data type;
5652 you can choose a different format by specifying @samp{/@var{f}}, where
5653 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
5657 @itemx print /@var{f}
5658 @cindex reprint the last value
5659 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
5660 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
5661 conveniently inspect the same value in an alternative format.
5664 A more low-level way of examining data is with the @code{x} command.
5665 It examines data in memory at a specified address and prints it in a
5666 specified format. @xref{Memory, ,Examining Memory}.
5668 If you are interested in information about types, or about how the
5669 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
5670 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
5674 * Expressions:: Expressions
5675 * Ambiguous Expressions:: Ambiguous Expressions
5676 * Variables:: Program variables
5677 * Arrays:: Artificial arrays
5678 * Output Formats:: Output formats
5679 * Memory:: Examining memory
5680 * Auto Display:: Automatic display
5681 * Print Settings:: Print settings
5682 * Value History:: Value history
5683 * Convenience Vars:: Convenience variables
5684 * Registers:: Registers
5685 * Floating Point Hardware:: Floating point hardware
5686 * Vector Unit:: Vector Unit
5687 * OS Information:: Auxiliary data provided by operating system
5688 * Memory Region Attributes:: Memory region attributes
5689 * Dump/Restore Files:: Copy between memory and a file
5690 * Core File Generation:: Cause a program dump its core
5691 * Character Sets:: Debugging programs that use a different
5692 character set than GDB does
5693 * Caching Remote Data:: Data caching for remote targets
5694 * Searching Memory:: Searching memory for a sequence of bytes
5698 @section Expressions
5701 @code{print} and many other @value{GDBN} commands accept an expression and
5702 compute its value. Any kind of constant, variable or operator defined
5703 by the programming language you are using is valid in an expression in
5704 @value{GDBN}. This includes conditional expressions, function calls,
5705 casts, and string constants. It also includes preprocessor macros, if
5706 you compiled your program to include this information; see
5709 @cindex arrays in expressions
5710 @value{GDBN} supports array constants in expressions input by
5711 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
5712 you can use the command @code{print @{1, 2, 3@}} to create an array
5713 of three integers. If you pass an array to a function or assign it
5714 to a program variable, @value{GDBN} copies the array to memory that
5715 is @code{malloc}ed in the target program.
5717 Because C is so widespread, most of the expressions shown in examples in
5718 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
5719 Languages}, for information on how to use expressions in other
5722 In this section, we discuss operators that you can use in @value{GDBN}
5723 expressions regardless of your programming language.
5725 @cindex casts, in expressions
5726 Casts are supported in all languages, not just in C, because it is so
5727 useful to cast a number into a pointer in order to examine a structure
5728 at that address in memory.
5729 @c FIXME: casts supported---Mod2 true?
5731 @value{GDBN} supports these operators, in addition to those common
5732 to programming languages:
5736 @samp{@@} is a binary operator for treating parts of memory as arrays.
5737 @xref{Arrays, ,Artificial Arrays}, for more information.
5740 @samp{::} allows you to specify a variable in terms of the file or
5741 function where it is defined. @xref{Variables, ,Program Variables}.
5743 @cindex @{@var{type}@}
5744 @cindex type casting memory
5745 @cindex memory, viewing as typed object
5746 @cindex casts, to view memory
5747 @item @{@var{type}@} @var{addr}
5748 Refers to an object of type @var{type} stored at address @var{addr} in
5749 memory. @var{addr} may be any expression whose value is an integer or
5750 pointer (but parentheses are required around binary operators, just as in
5751 a cast). This construct is allowed regardless of what kind of data is
5752 normally supposed to reside at @var{addr}.
5755 @node Ambiguous Expressions
5756 @section Ambiguous Expressions
5757 @cindex ambiguous expressions
5759 Expressions can sometimes contain some ambiguous elements. For instance,
5760 some programming languages (notably Ada, C@t{++} and Objective-C) permit
5761 a single function name to be defined several times, for application in
5762 different contexts. This is called @dfn{overloading}. Another example
5763 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
5764 templates and is typically instantiated several times, resulting in
5765 the same function name being defined in different contexts.
5767 In some cases and depending on the language, it is possible to adjust
5768 the expression to remove the ambiguity. For instance in C@t{++}, you
5769 can specify the signature of the function you want to break on, as in
5770 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
5771 qualified name of your function often makes the expression unambiguous
5774 When an ambiguity that needs to be resolved is detected, the debugger
5775 has the capability to display a menu of numbered choices for each
5776 possibility, and then waits for the selection with the prompt @samp{>}.
5777 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
5778 aborts the current command. If the command in which the expression was
5779 used allows more than one choice to be selected, the next option in the
5780 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
5783 For example, the following session excerpt shows an attempt to set a
5784 breakpoint at the overloaded symbol @code{String::after}.
5785 We choose three particular definitions of that function name:
5787 @c FIXME! This is likely to change to show arg type lists, at least
5790 (@value{GDBP}) b String::after
5793 [2] file:String.cc; line number:867
5794 [3] file:String.cc; line number:860
5795 [4] file:String.cc; line number:875
5796 [5] file:String.cc; line number:853
5797 [6] file:String.cc; line number:846
5798 [7] file:String.cc; line number:735
5800 Breakpoint 1 at 0xb26c: file String.cc, line 867.
5801 Breakpoint 2 at 0xb344: file String.cc, line 875.
5802 Breakpoint 3 at 0xafcc: file String.cc, line 846.
5803 Multiple breakpoints were set.
5804 Use the "delete" command to delete unwanted
5811 @kindex set multiple-symbols
5812 @item set multiple-symbols @var{mode}
5813 @cindex multiple-symbols menu
5815 This option allows you to adjust the debugger behavior when an expression
5818 By default, @var{mode} is set to @code{all}. If the command with which
5819 the expression is used allows more than one choice, then @value{GDBN}
5820 automatically selects all possible choices. For instance, inserting
5821 a breakpoint on a function using an ambiguous name results in a breakpoint
5822 inserted on each possible match. However, if a unique choice must be made,
5823 then @value{GDBN} uses the menu to help you disambiguate the expression.
5824 For instance, printing the address of an overloaded function will result
5825 in the use of the menu.
5827 When @var{mode} is set to @code{ask}, the debugger always uses the menu
5828 when an ambiguity is detected.
5830 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
5831 an error due to the ambiguity and the command is aborted.
5833 @kindex show multiple-symbols
5834 @item show multiple-symbols
5835 Show the current value of the @code{multiple-symbols} setting.
5839 @section Program Variables
5841 The most common kind of expression to use is the name of a variable
5844 Variables in expressions are understood in the selected stack frame
5845 (@pxref{Selection, ,Selecting a Frame}); they must be either:
5849 global (or file-static)
5856 visible according to the scope rules of the
5857 programming language from the point of execution in that frame
5860 @noindent This means that in the function
5875 you can examine and use the variable @code{a} whenever your program is
5876 executing within the function @code{foo}, but you can only use or
5877 examine the variable @code{b} while your program is executing inside
5878 the block where @code{b} is declared.
5880 @cindex variable name conflict
5881 There is an exception: you can refer to a variable or function whose
5882 scope is a single source file even if the current execution point is not
5883 in this file. But it is possible to have more than one such variable or
5884 function with the same name (in different source files). If that
5885 happens, referring to that name has unpredictable effects. If you wish,
5886 you can specify a static variable in a particular function or file,
5887 using the colon-colon (@code{::}) notation:
5889 @cindex colon-colon, context for variables/functions
5891 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
5892 @cindex @code{::}, context for variables/functions
5895 @var{file}::@var{variable}
5896 @var{function}::@var{variable}
5900 Here @var{file} or @var{function} is the name of the context for the
5901 static @var{variable}. In the case of file names, you can use quotes to
5902 make sure @value{GDBN} parses the file name as a single word---for example,
5903 to print a global value of @code{x} defined in @file{f2.c}:
5906 (@value{GDBP}) p 'f2.c'::x
5909 @cindex C@t{++} scope resolution
5910 This use of @samp{::} is very rarely in conflict with the very similar
5911 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
5912 scope resolution operator in @value{GDBN} expressions.
5913 @c FIXME: Um, so what happens in one of those rare cases where it's in
5916 @cindex wrong values
5917 @cindex variable values, wrong
5918 @cindex function entry/exit, wrong values of variables
5919 @cindex optimized code, wrong values of variables
5921 @emph{Warning:} Occasionally, a local variable may appear to have the
5922 wrong value at certain points in a function---just after entry to a new
5923 scope, and just before exit.
5925 You may see this problem when you are stepping by machine instructions.
5926 This is because, on most machines, it takes more than one instruction to
5927 set up a stack frame (including local variable definitions); if you are
5928 stepping by machine instructions, variables may appear to have the wrong
5929 values until the stack frame is completely built. On exit, it usually
5930 also takes more than one machine instruction to destroy a stack frame;
5931 after you begin stepping through that group of instructions, local
5932 variable definitions may be gone.
5934 This may also happen when the compiler does significant optimizations.
5935 To be sure of always seeing accurate values, turn off all optimization
5938 @cindex ``No symbol "foo" in current context''
5939 Another possible effect of compiler optimizations is to optimize
5940 unused variables out of existence, or assign variables to registers (as
5941 opposed to memory addresses). Depending on the support for such cases
5942 offered by the debug info format used by the compiler, @value{GDBN}
5943 might not be able to display values for such local variables. If that
5944 happens, @value{GDBN} will print a message like this:
5947 No symbol "foo" in current context.
5950 To solve such problems, either recompile without optimizations, or use a
5951 different debug info format, if the compiler supports several such
5952 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
5953 usually supports the @option{-gstabs+} option. @option{-gstabs+}
5954 produces debug info in a format that is superior to formats such as
5955 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
5956 an effective form for debug info. @xref{Debugging Options,,Options
5957 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
5958 Compiler Collection (GCC)}.
5959 @xref{C, ,C and C@t{++}}, for more information about debug info formats
5960 that are best suited to C@t{++} programs.
5962 If you ask to print an object whose contents are unknown to
5963 @value{GDBN}, e.g., because its data type is not completely specified
5964 by the debug information, @value{GDBN} will say @samp{<incomplete
5965 type>}. @xref{Symbols, incomplete type}, for more about this.
5967 Strings are identified as arrays of @code{char} values without specified
5968 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
5969 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
5970 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
5971 defines literal string type @code{"char"} as @code{char} without a sign.
5976 signed char var1[] = "A";
5979 You get during debugging
5984 $2 = @{65 'A', 0 '\0'@}
5988 @section Artificial Arrays
5990 @cindex artificial array
5992 @kindex @@@r{, referencing memory as an array}
5993 It is often useful to print out several successive objects of the
5994 same type in memory; a section of an array, or an array of
5995 dynamically determined size for which only a pointer exists in the
5998 You can do this by referring to a contiguous span of memory as an
5999 @dfn{artificial array}, using the binary operator @samp{@@}. The left
6000 operand of @samp{@@} should be the first element of the desired array
6001 and be an individual object. The right operand should be the desired length
6002 of the array. The result is an array value whose elements are all of
6003 the type of the left argument. The first element is actually the left
6004 argument; the second element comes from bytes of memory immediately
6005 following those that hold the first element, and so on. Here is an
6006 example. If a program says
6009 int *array = (int *) malloc (len * sizeof (int));
6013 you can print the contents of @code{array} with
6019 The left operand of @samp{@@} must reside in memory. Array values made
6020 with @samp{@@} in this way behave just like other arrays in terms of
6021 subscripting, and are coerced to pointers when used in expressions.
6022 Artificial arrays most often appear in expressions via the value history
6023 (@pxref{Value History, ,Value History}), after printing one out.
6025 Another way to create an artificial array is to use a cast.
6026 This re-interprets a value as if it were an array.
6027 The value need not be in memory:
6029 (@value{GDBP}) p/x (short[2])0x12345678
6030 $1 = @{0x1234, 0x5678@}
6033 As a convenience, if you leave the array length out (as in
6034 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
6035 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
6037 (@value{GDBP}) p/x (short[])0x12345678
6038 $2 = @{0x1234, 0x5678@}
6041 Sometimes the artificial array mechanism is not quite enough; in
6042 moderately complex data structures, the elements of interest may not
6043 actually be adjacent---for example, if you are interested in the values
6044 of pointers in an array. One useful work-around in this situation is
6045 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
6046 Variables}) as a counter in an expression that prints the first
6047 interesting value, and then repeat that expression via @key{RET}. For
6048 instance, suppose you have an array @code{dtab} of pointers to
6049 structures, and you are interested in the values of a field @code{fv}
6050 in each structure. Here is an example of what you might type:
6060 @node Output Formats
6061 @section Output Formats
6063 @cindex formatted output
6064 @cindex output formats
6065 By default, @value{GDBN} prints a value according to its data type. Sometimes
6066 this is not what you want. For example, you might want to print a number
6067 in hex, or a pointer in decimal. Or you might want to view data in memory
6068 at a certain address as a character string or as an instruction. To do
6069 these things, specify an @dfn{output format} when you print a value.
6071 The simplest use of output formats is to say how to print a value
6072 already computed. This is done by starting the arguments of the
6073 @code{print} command with a slash and a format letter. The format
6074 letters supported are:
6078 Regard the bits of the value as an integer, and print the integer in
6082 Print as integer in signed decimal.
6085 Print as integer in unsigned decimal.
6088 Print as integer in octal.
6091 Print as integer in binary. The letter @samp{t} stands for ``two''.
6092 @footnote{@samp{b} cannot be used because these format letters are also
6093 used with the @code{x} command, where @samp{b} stands for ``byte'';
6094 see @ref{Memory,,Examining Memory}.}
6097 @cindex unknown address, locating
6098 @cindex locate address
6099 Print as an address, both absolute in hexadecimal and as an offset from
6100 the nearest preceding symbol. You can use this format used to discover
6101 where (in what function) an unknown address is located:
6104 (@value{GDBP}) p/a 0x54320
6105 $3 = 0x54320 <_initialize_vx+396>
6109 The command @code{info symbol 0x54320} yields similar results.
6110 @xref{Symbols, info symbol}.
6113 Regard as an integer and print it as a character constant. This
6114 prints both the numerical value and its character representation. The
6115 character representation is replaced with the octal escape @samp{\nnn}
6116 for characters outside the 7-bit @sc{ascii} range.
6118 Without this format, @value{GDBN} displays @code{char},
6119 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
6120 constants. Single-byte members of vectors are displayed as integer
6124 Regard the bits of the value as a floating point number and print
6125 using typical floating point syntax.
6128 @cindex printing strings
6129 @cindex printing byte arrays
6130 Regard as a string, if possible. With this format, pointers to single-byte
6131 data are displayed as null-terminated strings and arrays of single-byte data
6132 are displayed as fixed-length strings. Other values are displayed in their
6135 Without this format, @value{GDBN} displays pointers to and arrays of
6136 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
6137 strings. Single-byte members of a vector are displayed as an integer
6141 For example, to print the program counter in hex (@pxref{Registers}), type
6148 Note that no space is required before the slash; this is because command
6149 names in @value{GDBN} cannot contain a slash.
6151 To reprint the last value in the value history with a different format,
6152 you can use the @code{print} command with just a format and no
6153 expression. For example, @samp{p/x} reprints the last value in hex.
6156 @section Examining Memory
6158 You can use the command @code{x} (for ``examine'') to examine memory in
6159 any of several formats, independently of your program's data types.
6161 @cindex examining memory
6163 @kindex x @r{(examine memory)}
6164 @item x/@var{nfu} @var{addr}
6167 Use the @code{x} command to examine memory.
6170 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
6171 much memory to display and how to format it; @var{addr} is an
6172 expression giving the address where you want to start displaying memory.
6173 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
6174 Several commands set convenient defaults for @var{addr}.
6177 @item @var{n}, the repeat count
6178 The repeat count is a decimal integer; the default is 1. It specifies
6179 how much memory (counting by units @var{u}) to display.
6180 @c This really is **decimal**; unaffected by 'set radix' as of GDB
6183 @item @var{f}, the display format
6184 The display format is one of the formats used by @code{print}
6185 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
6186 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
6187 The default is @samp{x} (hexadecimal) initially. The default changes
6188 each time you use either @code{x} or @code{print}.
6190 @item @var{u}, the unit size
6191 The unit size is any of
6197 Halfwords (two bytes).
6199 Words (four bytes). This is the initial default.
6201 Giant words (eight bytes).
6204 Each time you specify a unit size with @code{x}, that size becomes the
6205 default unit the next time you use @code{x}. (For the @samp{s} and
6206 @samp{i} formats, the unit size is ignored and is normally not written.)
6208 @item @var{addr}, starting display address
6209 @var{addr} is the address where you want @value{GDBN} to begin displaying
6210 memory. The expression need not have a pointer value (though it may);
6211 it is always interpreted as an integer address of a byte of memory.
6212 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
6213 @var{addr} is usually just after the last address examined---but several
6214 other commands also set the default address: @code{info breakpoints} (to
6215 the address of the last breakpoint listed), @code{info line} (to the
6216 starting address of a line), and @code{print} (if you use it to display
6217 a value from memory).
6220 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
6221 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
6222 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
6223 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
6224 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
6226 Since the letters indicating unit sizes are all distinct from the
6227 letters specifying output formats, you do not have to remember whether
6228 unit size or format comes first; either order works. The output
6229 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
6230 (However, the count @var{n} must come first; @samp{wx4} does not work.)
6232 Even though the unit size @var{u} is ignored for the formats @samp{s}
6233 and @samp{i}, you might still want to use a count @var{n}; for example,
6234 @samp{3i} specifies that you want to see three machine instructions,
6235 including any operands. For convenience, especially when used with
6236 the @code{display} command, the @samp{i} format also prints branch delay
6237 slot instructions, if any, beyond the count specified, which immediately
6238 follow the last instruction that is within the count. The command
6239 @code{disassemble} gives an alternative way of inspecting machine
6240 instructions; see @ref{Machine Code,,Source and Machine Code}.
6242 All the defaults for the arguments to @code{x} are designed to make it
6243 easy to continue scanning memory with minimal specifications each time
6244 you use @code{x}. For example, after you have inspected three machine
6245 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
6246 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
6247 the repeat count @var{n} is used again; the other arguments default as
6248 for successive uses of @code{x}.
6250 @cindex @code{$_}, @code{$__}, and value history
6251 The addresses and contents printed by the @code{x} command are not saved
6252 in the value history because there is often too much of them and they
6253 would get in the way. Instead, @value{GDBN} makes these values available for
6254 subsequent use in expressions as values of the convenience variables
6255 @code{$_} and @code{$__}. After an @code{x} command, the last address
6256 examined is available for use in expressions in the convenience variable
6257 @code{$_}. The contents of that address, as examined, are available in
6258 the convenience variable @code{$__}.
6260 If the @code{x} command has a repeat count, the address and contents saved
6261 are from the last memory unit printed; this is not the same as the last
6262 address printed if several units were printed on the last line of output.
6264 @cindex remote memory comparison
6265 @cindex verify remote memory image
6266 When you are debugging a program running on a remote target machine
6267 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
6268 remote machine's memory against the executable file you downloaded to
6269 the target. The @code{compare-sections} command is provided for such
6273 @kindex compare-sections
6274 @item compare-sections @r{[}@var{section-name}@r{]}
6275 Compare the data of a loadable section @var{section-name} in the
6276 executable file of the program being debugged with the same section in
6277 the remote machine's memory, and report any mismatches. With no
6278 arguments, compares all loadable sections. This command's
6279 availability depends on the target's support for the @code{"qCRC"}
6284 @section Automatic Display
6285 @cindex automatic display
6286 @cindex display of expressions
6288 If you find that you want to print the value of an expression frequently
6289 (to see how it changes), you might want to add it to the @dfn{automatic
6290 display list} so that @value{GDBN} prints its value each time your program stops.
6291 Each expression added to the list is given a number to identify it;
6292 to remove an expression from the list, you specify that number.
6293 The automatic display looks like this:
6297 3: bar[5] = (struct hack *) 0x3804
6301 This display shows item numbers, expressions and their current values. As with
6302 displays you request manually using @code{x} or @code{print}, you can
6303 specify the output format you prefer; in fact, @code{display} decides
6304 whether to use @code{print} or @code{x} depending your format
6305 specification---it uses @code{x} if you specify either the @samp{i}
6306 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
6310 @item display @var{expr}
6311 Add the expression @var{expr} to the list of expressions to display
6312 each time your program stops. @xref{Expressions, ,Expressions}.
6314 @code{display} does not repeat if you press @key{RET} again after using it.
6316 @item display/@var{fmt} @var{expr}
6317 For @var{fmt} specifying only a display format and not a size or
6318 count, add the expression @var{expr} to the auto-display list but
6319 arrange to display it each time in the specified format @var{fmt}.
6320 @xref{Output Formats,,Output Formats}.
6322 @item display/@var{fmt} @var{addr}
6323 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
6324 number of units, add the expression @var{addr} as a memory address to
6325 be examined each time your program stops. Examining means in effect
6326 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
6329 For example, @samp{display/i $pc} can be helpful, to see the machine
6330 instruction about to be executed each time execution stops (@samp{$pc}
6331 is a common name for the program counter; @pxref{Registers, ,Registers}).
6334 @kindex delete display
6336 @item undisplay @var{dnums}@dots{}
6337 @itemx delete display @var{dnums}@dots{}
6338 Remove item numbers @var{dnums} from the list of expressions to display.
6340 @code{undisplay} does not repeat if you press @key{RET} after using it.
6341 (Otherwise you would just get the error @samp{No display number @dots{}}.)
6343 @kindex disable display
6344 @item disable display @var{dnums}@dots{}
6345 Disable the display of item numbers @var{dnums}. A disabled display
6346 item is not printed automatically, but is not forgotten. It may be
6347 enabled again later.
6349 @kindex enable display
6350 @item enable display @var{dnums}@dots{}
6351 Enable display of item numbers @var{dnums}. It becomes effective once
6352 again in auto display of its expression, until you specify otherwise.
6355 Display the current values of the expressions on the list, just as is
6356 done when your program stops.
6358 @kindex info display
6360 Print the list of expressions previously set up to display
6361 automatically, each one with its item number, but without showing the
6362 values. This includes disabled expressions, which are marked as such.
6363 It also includes expressions which would not be displayed right now
6364 because they refer to automatic variables not currently available.
6367 @cindex display disabled out of scope
6368 If a display expression refers to local variables, then it does not make
6369 sense outside the lexical context for which it was set up. Such an
6370 expression is disabled when execution enters a context where one of its
6371 variables is not defined. For example, if you give the command
6372 @code{display last_char} while inside a function with an argument
6373 @code{last_char}, @value{GDBN} displays this argument while your program
6374 continues to stop inside that function. When it stops elsewhere---where
6375 there is no variable @code{last_char}---the display is disabled
6376 automatically. The next time your program stops where @code{last_char}
6377 is meaningful, you can enable the display expression once again.
6379 @node Print Settings
6380 @section Print Settings
6382 @cindex format options
6383 @cindex print settings
6384 @value{GDBN} provides the following ways to control how arrays, structures,
6385 and symbols are printed.
6388 These settings are useful for debugging programs in any language:
6392 @item set print address
6393 @itemx set print address on
6394 @cindex print/don't print memory addresses
6395 @value{GDBN} prints memory addresses showing the location of stack
6396 traces, structure values, pointer values, breakpoints, and so forth,
6397 even when it also displays the contents of those addresses. The default
6398 is @code{on}. For example, this is what a stack frame display looks like with
6399 @code{set print address on}:
6404 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
6406 530 if (lquote != def_lquote)
6410 @item set print address off
6411 Do not print addresses when displaying their contents. For example,
6412 this is the same stack frame displayed with @code{set print address off}:
6416 (@value{GDBP}) set print addr off
6418 #0 set_quotes (lq="<<", rq=">>") at input.c:530
6419 530 if (lquote != def_lquote)
6423 You can use @samp{set print address off} to eliminate all machine
6424 dependent displays from the @value{GDBN} interface. For example, with
6425 @code{print address off}, you should get the same text for backtraces on
6426 all machines---whether or not they involve pointer arguments.
6429 @item show print address
6430 Show whether or not addresses are to be printed.
6433 When @value{GDBN} prints a symbolic address, it normally prints the
6434 closest earlier symbol plus an offset. If that symbol does not uniquely
6435 identify the address (for example, it is a name whose scope is a single
6436 source file), you may need to clarify. One way to do this is with
6437 @code{info line}, for example @samp{info line *0x4537}. Alternately,
6438 you can set @value{GDBN} to print the source file and line number when
6439 it prints a symbolic address:
6442 @item set print symbol-filename on
6443 @cindex source file and line of a symbol
6444 @cindex symbol, source file and line
6445 Tell @value{GDBN} to print the source file name and line number of a
6446 symbol in the symbolic form of an address.
6448 @item set print symbol-filename off
6449 Do not print source file name and line number of a symbol. This is the
6452 @item show print symbol-filename
6453 Show whether or not @value{GDBN} will print the source file name and
6454 line number of a symbol in the symbolic form of an address.
6457 Another situation where it is helpful to show symbol filenames and line
6458 numbers is when disassembling code; @value{GDBN} shows you the line
6459 number and source file that corresponds to each instruction.
6461 Also, you may wish to see the symbolic form only if the address being
6462 printed is reasonably close to the closest earlier symbol:
6465 @item set print max-symbolic-offset @var{max-offset}
6466 @cindex maximum value for offset of closest symbol
6467 Tell @value{GDBN} to only display the symbolic form of an address if the
6468 offset between the closest earlier symbol and the address is less than
6469 @var{max-offset}. The default is 0, which tells @value{GDBN}
6470 to always print the symbolic form of an address if any symbol precedes it.
6472 @item show print max-symbolic-offset
6473 Ask how large the maximum offset is that @value{GDBN} prints in a
6477 @cindex wild pointer, interpreting
6478 @cindex pointer, finding referent
6479 If you have a pointer and you are not sure where it points, try
6480 @samp{set print symbol-filename on}. Then you can determine the name
6481 and source file location of the variable where it points, using
6482 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
6483 For example, here @value{GDBN} shows that a variable @code{ptt} points
6484 at another variable @code{t}, defined in @file{hi2.c}:
6487 (@value{GDBP}) set print symbol-filename on
6488 (@value{GDBP}) p/a ptt
6489 $4 = 0xe008 <t in hi2.c>
6493 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
6494 does not show the symbol name and filename of the referent, even with
6495 the appropriate @code{set print} options turned on.
6498 Other settings control how different kinds of objects are printed:
6501 @item set print array
6502 @itemx set print array on
6503 @cindex pretty print arrays
6504 Pretty print arrays. This format is more convenient to read,
6505 but uses more space. The default is off.
6507 @item set print array off
6508 Return to compressed format for arrays.
6510 @item show print array
6511 Show whether compressed or pretty format is selected for displaying
6514 @cindex print array indexes
6515 @item set print array-indexes
6516 @itemx set print array-indexes on
6517 Print the index of each element when displaying arrays. May be more
6518 convenient to locate a given element in the array or quickly find the
6519 index of a given element in that printed array. The default is off.
6521 @item set print array-indexes off
6522 Stop printing element indexes when displaying arrays.
6524 @item show print array-indexes
6525 Show whether the index of each element is printed when displaying
6528 @item set print elements @var{number-of-elements}
6529 @cindex number of array elements to print
6530 @cindex limit on number of printed array elements
6531 Set a limit on how many elements of an array @value{GDBN} will print.
6532 If @value{GDBN} is printing a large array, it stops printing after it has
6533 printed the number of elements set by the @code{set print elements} command.
6534 This limit also applies to the display of strings.
6535 When @value{GDBN} starts, this limit is set to 200.
6536 Setting @var{number-of-elements} to zero means that the printing is unlimited.
6538 @item show print elements
6539 Display the number of elements of a large array that @value{GDBN} will print.
6540 If the number is 0, then the printing is unlimited.
6542 @item set print frame-arguments @var{value}
6543 @cindex printing frame argument values
6544 @cindex print all frame argument values
6545 @cindex print frame argument values for scalars only
6546 @cindex do not print frame argument values
6547 This command allows to control how the values of arguments are printed
6548 when the debugger prints a frame (@pxref{Frames}). The possible
6553 The values of all arguments are printed. This is the default.
6556 Print the value of an argument only if it is a scalar. The value of more
6557 complex arguments such as arrays, structures, unions, etc, is replaced
6558 by @code{@dots{}}. Here is an example where only scalar arguments are shown:
6561 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
6566 None of the argument values are printed. Instead, the value of each argument
6567 is replaced by @code{@dots{}}. In this case, the example above now becomes:
6570 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
6575 By default, all argument values are always printed. But this command
6576 can be useful in several cases. For instance, it can be used to reduce
6577 the amount of information printed in each frame, making the backtrace
6578 more readable. Also, this command can be used to improve performance
6579 when displaying Ada frames, because the computation of large arguments
6580 can sometimes be CPU-intensive, especiallly in large applications.
6581 Setting @code{print frame-arguments} to @code{scalars} or @code{none}
6582 avoids this computation, thus speeding up the display of each Ada frame.
6584 @item show print frame-arguments
6585 Show how the value of arguments should be displayed when printing a frame.
6587 @item set print repeats
6588 @cindex repeated array elements
6589 Set the threshold for suppressing display of repeated array
6590 elements. When the number of consecutive identical elements of an
6591 array exceeds the threshold, @value{GDBN} prints the string
6592 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
6593 identical repetitions, instead of displaying the identical elements
6594 themselves. Setting the threshold to zero will cause all elements to
6595 be individually printed. The default threshold is 10.
6597 @item show print repeats
6598 Display the current threshold for printing repeated identical
6601 @item set print null-stop
6602 @cindex @sc{null} elements in arrays
6603 Cause @value{GDBN} to stop printing the characters of an array when the first
6604 @sc{null} is encountered. This is useful when large arrays actually
6605 contain only short strings.
6608 @item show print null-stop
6609 Show whether @value{GDBN} stops printing an array on the first
6610 @sc{null} character.
6612 @item set print pretty on
6613 @cindex print structures in indented form
6614 @cindex indentation in structure display
6615 Cause @value{GDBN} to print structures in an indented format with one member
6616 per line, like this:
6631 @item set print pretty off
6632 Cause @value{GDBN} to print structures in a compact format, like this:
6636 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
6637 meat = 0x54 "Pork"@}
6642 This is the default format.
6644 @item show print pretty
6645 Show which format @value{GDBN} is using to print structures.
6647 @item set print sevenbit-strings on
6648 @cindex eight-bit characters in strings
6649 @cindex octal escapes in strings
6650 Print using only seven-bit characters; if this option is set,
6651 @value{GDBN} displays any eight-bit characters (in strings or
6652 character values) using the notation @code{\}@var{nnn}. This setting is
6653 best if you are working in English (@sc{ascii}) and you use the
6654 high-order bit of characters as a marker or ``meta'' bit.
6656 @item set print sevenbit-strings off
6657 Print full eight-bit characters. This allows the use of more
6658 international character sets, and is the default.
6660 @item show print sevenbit-strings
6661 Show whether or not @value{GDBN} is printing only seven-bit characters.
6663 @item set print union on
6664 @cindex unions in structures, printing
6665 Tell @value{GDBN} to print unions which are contained in structures
6666 and other unions. This is the default setting.
6668 @item set print union off
6669 Tell @value{GDBN} not to print unions which are contained in
6670 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
6673 @item show print union
6674 Ask @value{GDBN} whether or not it will print unions which are contained in
6675 structures and other unions.
6677 For example, given the declarations
6680 typedef enum @{Tree, Bug@} Species;
6681 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
6682 typedef enum @{Caterpillar, Cocoon, Butterfly@}
6693 struct thing foo = @{Tree, @{Acorn@}@};
6697 with @code{set print union on} in effect @samp{p foo} would print
6700 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
6704 and with @code{set print union off} in effect it would print
6707 $1 = @{it = Tree, form = @{...@}@}
6711 @code{set print union} affects programs written in C-like languages
6717 These settings are of interest when debugging C@t{++} programs:
6720 @cindex demangling C@t{++} names
6721 @item set print demangle
6722 @itemx set print demangle on
6723 Print C@t{++} names in their source form rather than in the encoded
6724 (``mangled'') form passed to the assembler and linker for type-safe
6725 linkage. The default is on.
6727 @item show print demangle
6728 Show whether C@t{++} names are printed in mangled or demangled form.
6730 @item set print asm-demangle
6731 @itemx set print asm-demangle on
6732 Print C@t{++} names in their source form rather than their mangled form, even
6733 in assembler code printouts such as instruction disassemblies.
6736 @item show print asm-demangle
6737 Show whether C@t{++} names in assembly listings are printed in mangled
6740 @cindex C@t{++} symbol decoding style
6741 @cindex symbol decoding style, C@t{++}
6742 @kindex set demangle-style
6743 @item set demangle-style @var{style}
6744 Choose among several encoding schemes used by different compilers to
6745 represent C@t{++} names. The choices for @var{style} are currently:
6749 Allow @value{GDBN} to choose a decoding style by inspecting your program.
6752 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
6753 This is the default.
6756 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
6759 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
6762 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
6763 @strong{Warning:} this setting alone is not sufficient to allow
6764 debugging @code{cfront}-generated executables. @value{GDBN} would
6765 require further enhancement to permit that.
6768 If you omit @var{style}, you will see a list of possible formats.
6770 @item show demangle-style
6771 Display the encoding style currently in use for decoding C@t{++} symbols.
6773 @item set print object
6774 @itemx set print object on
6775 @cindex derived type of an object, printing
6776 @cindex display derived types
6777 When displaying a pointer to an object, identify the @emph{actual}
6778 (derived) type of the object rather than the @emph{declared} type, using
6779 the virtual function table.
6781 @item set print object off
6782 Display only the declared type of objects, without reference to the
6783 virtual function table. This is the default setting.
6785 @item show print object
6786 Show whether actual, or declared, object types are displayed.
6788 @item set print static-members
6789 @itemx set print static-members on
6790 @cindex static members of C@t{++} objects
6791 Print static members when displaying a C@t{++} object. The default is on.
6793 @item set print static-members off
6794 Do not print static members when displaying a C@t{++} object.
6796 @item show print static-members
6797 Show whether C@t{++} static members are printed or not.
6799 @item set print pascal_static-members
6800 @itemx set print pascal_static-members on
6801 @cindex static members of Pascal objects
6802 @cindex Pascal objects, static members display
6803 Print static members when displaying a Pascal object. The default is on.
6805 @item set print pascal_static-members off
6806 Do not print static members when displaying a Pascal object.
6808 @item show print pascal_static-members
6809 Show whether Pascal static members are printed or not.
6811 @c These don't work with HP ANSI C++ yet.
6812 @item set print vtbl
6813 @itemx set print vtbl on
6814 @cindex pretty print C@t{++} virtual function tables
6815 @cindex virtual functions (C@t{++}) display
6816 @cindex VTBL display
6817 Pretty print C@t{++} virtual function tables. The default is off.
6818 (The @code{vtbl} commands do not work on programs compiled with the HP
6819 ANSI C@t{++} compiler (@code{aCC}).)
6821 @item set print vtbl off
6822 Do not pretty print C@t{++} virtual function tables.
6824 @item show print vtbl
6825 Show whether C@t{++} virtual function tables are pretty printed, or not.
6829 @section Value History
6831 @cindex value history
6832 @cindex history of values printed by @value{GDBN}
6833 Values printed by the @code{print} command are saved in the @value{GDBN}
6834 @dfn{value history}. This allows you to refer to them in other expressions.
6835 Values are kept until the symbol table is re-read or discarded
6836 (for example with the @code{file} or @code{symbol-file} commands).
6837 When the symbol table changes, the value history is discarded,
6838 since the values may contain pointers back to the types defined in the
6843 @cindex history number
6844 The values printed are given @dfn{history numbers} by which you can
6845 refer to them. These are successive integers starting with one.
6846 @code{print} shows you the history number assigned to a value by
6847 printing @samp{$@var{num} = } before the value; here @var{num} is the
6850 To refer to any previous value, use @samp{$} followed by the value's
6851 history number. The way @code{print} labels its output is designed to
6852 remind you of this. Just @code{$} refers to the most recent value in
6853 the history, and @code{$$} refers to the value before that.
6854 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
6855 is the value just prior to @code{$$}, @code{$$1} is equivalent to
6856 @code{$$}, and @code{$$0} is equivalent to @code{$}.
6858 For example, suppose you have just printed a pointer to a structure and
6859 want to see the contents of the structure. It suffices to type
6865 If you have a chain of structures where the component @code{next} points
6866 to the next one, you can print the contents of the next one with this:
6873 You can print successive links in the chain by repeating this
6874 command---which you can do by just typing @key{RET}.
6876 Note that the history records values, not expressions. If the value of
6877 @code{x} is 4 and you type these commands:
6885 then the value recorded in the value history by the @code{print} command
6886 remains 4 even though the value of @code{x} has changed.
6891 Print the last ten values in the value history, with their item numbers.
6892 This is like @samp{p@ $$9} repeated ten times, except that @code{show
6893 values} does not change the history.
6895 @item show values @var{n}
6896 Print ten history values centered on history item number @var{n}.
6899 Print ten history values just after the values last printed. If no more
6900 values are available, @code{show values +} produces no display.
6903 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
6904 same effect as @samp{show values +}.
6906 @node Convenience Vars
6907 @section Convenience Variables
6909 @cindex convenience variables
6910 @cindex user-defined variables
6911 @value{GDBN} provides @dfn{convenience variables} that you can use within
6912 @value{GDBN} to hold on to a value and refer to it later. These variables
6913 exist entirely within @value{GDBN}; they are not part of your program, and
6914 setting a convenience variable has no direct effect on further execution
6915 of your program. That is why you can use them freely.
6917 Convenience variables are prefixed with @samp{$}. Any name preceded by
6918 @samp{$} can be used for a convenience variable, unless it is one of
6919 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
6920 (Value history references, in contrast, are @emph{numbers} preceded
6921 by @samp{$}. @xref{Value History, ,Value History}.)
6923 You can save a value in a convenience variable with an assignment
6924 expression, just as you would set a variable in your program.
6928 set $foo = *object_ptr
6932 would save in @code{$foo} the value contained in the object pointed to by
6935 Using a convenience variable for the first time creates it, but its
6936 value is @code{void} until you assign a new value. You can alter the
6937 value with another assignment at any time.
6939 Convenience variables have no fixed types. You can assign a convenience
6940 variable any type of value, including structures and arrays, even if
6941 that variable already has a value of a different type. The convenience
6942 variable, when used as an expression, has the type of its current value.
6945 @kindex show convenience
6946 @cindex show all user variables
6947 @item show convenience
6948 Print a list of convenience variables used so far, and their values.
6949 Abbreviated @code{show conv}.
6951 @kindex init-if-undefined
6952 @cindex convenience variables, initializing
6953 @item init-if-undefined $@var{variable} = @var{expression}
6954 Set a convenience variable if it has not already been set. This is useful
6955 for user-defined commands that keep some state. It is similar, in concept,
6956 to using local static variables with initializers in C (except that
6957 convenience variables are global). It can also be used to allow users to
6958 override default values used in a command script.
6960 If the variable is already defined then the expression is not evaluated so
6961 any side-effects do not occur.
6964 One of the ways to use a convenience variable is as a counter to be
6965 incremented or a pointer to be advanced. For example, to print
6966 a field from successive elements of an array of structures:
6970 print bar[$i++]->contents
6974 Repeat that command by typing @key{RET}.
6976 Some convenience variables are created automatically by @value{GDBN} and given
6977 values likely to be useful.
6980 @vindex $_@r{, convenience variable}
6982 The variable @code{$_} is automatically set by the @code{x} command to
6983 the last address examined (@pxref{Memory, ,Examining Memory}). Other
6984 commands which provide a default address for @code{x} to examine also
6985 set @code{$_} to that address; these commands include @code{info line}
6986 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
6987 except when set by the @code{x} command, in which case it is a pointer
6988 to the type of @code{$__}.
6990 @vindex $__@r{, convenience variable}
6992 The variable @code{$__} is automatically set by the @code{x} command
6993 to the value found in the last address examined. Its type is chosen
6994 to match the format in which the data was printed.
6997 @vindex $_exitcode@r{, convenience variable}
6998 The variable @code{$_exitcode} is automatically set to the exit code when
6999 the program being debugged terminates.
7002 On HP-UX systems, if you refer to a function or variable name that
7003 begins with a dollar sign, @value{GDBN} searches for a user or system
7004 name first, before it searches for a convenience variable.
7010 You can refer to machine register contents, in expressions, as variables
7011 with names starting with @samp{$}. The names of registers are different
7012 for each machine; use @code{info registers} to see the names used on
7016 @kindex info registers
7017 @item info registers
7018 Print the names and values of all registers except floating-point
7019 and vector registers (in the selected stack frame).
7021 @kindex info all-registers
7022 @cindex floating point registers
7023 @item info all-registers
7024 Print the names and values of all registers, including floating-point
7025 and vector registers (in the selected stack frame).
7027 @item info registers @var{regname} @dots{}
7028 Print the @dfn{relativized} value of each specified register @var{regname}.
7029 As discussed in detail below, register values are normally relative to
7030 the selected stack frame. @var{regname} may be any register name valid on
7031 the machine you are using, with or without the initial @samp{$}.
7034 @cindex stack pointer register
7035 @cindex program counter register
7036 @cindex process status register
7037 @cindex frame pointer register
7038 @cindex standard registers
7039 @value{GDBN} has four ``standard'' register names that are available (in
7040 expressions) on most machines---whenever they do not conflict with an
7041 architecture's canonical mnemonics for registers. The register names
7042 @code{$pc} and @code{$sp} are used for the program counter register and
7043 the stack pointer. @code{$fp} is used for a register that contains a
7044 pointer to the current stack frame, and @code{$ps} is used for a
7045 register that contains the processor status. For example,
7046 you could print the program counter in hex with
7053 or print the instruction to be executed next with
7060 or add four to the stack pointer@footnote{This is a way of removing
7061 one word from the stack, on machines where stacks grow downward in
7062 memory (most machines, nowadays). This assumes that the innermost
7063 stack frame is selected; setting @code{$sp} is not allowed when other
7064 stack frames are selected. To pop entire frames off the stack,
7065 regardless of machine architecture, use @code{return};
7066 see @ref{Returning, ,Returning from a Function}.} with
7072 Whenever possible, these four standard register names are available on
7073 your machine even though the machine has different canonical mnemonics,
7074 so long as there is no conflict. The @code{info registers} command
7075 shows the canonical names. For example, on the SPARC, @code{info
7076 registers} displays the processor status register as @code{$psr} but you
7077 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
7078 is an alias for the @sc{eflags} register.
7080 @value{GDBN} always considers the contents of an ordinary register as an
7081 integer when the register is examined in this way. Some machines have
7082 special registers which can hold nothing but floating point; these
7083 registers are considered to have floating point values. There is no way
7084 to refer to the contents of an ordinary register as floating point value
7085 (although you can @emph{print} it as a floating point value with
7086 @samp{print/f $@var{regname}}).
7088 Some registers have distinct ``raw'' and ``virtual'' data formats. This
7089 means that the data format in which the register contents are saved by
7090 the operating system is not the same one that your program normally
7091 sees. For example, the registers of the 68881 floating point
7092 coprocessor are always saved in ``extended'' (raw) format, but all C
7093 programs expect to work with ``double'' (virtual) format. In such
7094 cases, @value{GDBN} normally works with the virtual format only (the format
7095 that makes sense for your program), but the @code{info registers} command
7096 prints the data in both formats.
7098 @cindex SSE registers (x86)
7099 @cindex MMX registers (x86)
7100 Some machines have special registers whose contents can be interpreted
7101 in several different ways. For example, modern x86-based machines
7102 have SSE and MMX registers that can hold several values packed
7103 together in several different formats. @value{GDBN} refers to such
7104 registers in @code{struct} notation:
7107 (@value{GDBP}) print $xmm1
7109 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
7110 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
7111 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
7112 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
7113 v4_int32 = @{0, 20657912, 11, 13@},
7114 v2_int64 = @{88725056443645952, 55834574859@},
7115 uint128 = 0x0000000d0000000b013b36f800000000
7120 To set values of such registers, you need to tell @value{GDBN} which
7121 view of the register you wish to change, as if you were assigning
7122 value to a @code{struct} member:
7125 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
7128 Normally, register values are relative to the selected stack frame
7129 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
7130 value that the register would contain if all stack frames farther in
7131 were exited and their saved registers restored. In order to see the
7132 true contents of hardware registers, you must select the innermost
7133 frame (with @samp{frame 0}).
7135 However, @value{GDBN} must deduce where registers are saved, from the machine
7136 code generated by your compiler. If some registers are not saved, or if
7137 @value{GDBN} is unable to locate the saved registers, the selected stack
7138 frame makes no difference.
7140 @node Floating Point Hardware
7141 @section Floating Point Hardware
7142 @cindex floating point
7144 Depending on the configuration, @value{GDBN} may be able to give
7145 you more information about the status of the floating point hardware.
7150 Display hardware-dependent information about the floating
7151 point unit. The exact contents and layout vary depending on the
7152 floating point chip. Currently, @samp{info float} is supported on
7153 the ARM and x86 machines.
7157 @section Vector Unit
7160 Depending on the configuration, @value{GDBN} may be able to give you
7161 more information about the status of the vector unit.
7166 Display information about the vector unit. The exact contents and
7167 layout vary depending on the hardware.
7170 @node OS Information
7171 @section Operating System Auxiliary Information
7172 @cindex OS information
7174 @value{GDBN} provides interfaces to useful OS facilities that can help
7175 you debug your program.
7177 @cindex @code{ptrace} system call
7178 @cindex @code{struct user} contents
7179 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
7180 machines), it interfaces with the inferior via the @code{ptrace}
7181 system call. The operating system creates a special sata structure,
7182 called @code{struct user}, for this interface. You can use the
7183 command @code{info udot} to display the contents of this data
7189 Display the contents of the @code{struct user} maintained by the OS
7190 kernel for the program being debugged. @value{GDBN} displays the
7191 contents of @code{struct user} as a list of hex numbers, similar to
7192 the @code{examine} command.
7195 @cindex auxiliary vector
7196 @cindex vector, auxiliary
7197 Some operating systems supply an @dfn{auxiliary vector} to programs at
7198 startup. This is akin to the arguments and environment that you
7199 specify for a program, but contains a system-dependent variety of
7200 binary values that tell system libraries important details about the
7201 hardware, operating system, and process. Each value's purpose is
7202 identified by an integer tag; the meanings are well-known but system-specific.
7203 Depending on the configuration and operating system facilities,
7204 @value{GDBN} may be able to show you this information. For remote
7205 targets, this functionality may further depend on the remote stub's
7206 support of the @samp{qXfer:auxv:read} packet, see
7207 @ref{qXfer auxiliary vector read}.
7212 Display the auxiliary vector of the inferior, which can be either a
7213 live process or a core dump file. @value{GDBN} prints each tag value
7214 numerically, and also shows names and text descriptions for recognized
7215 tags. Some values in the vector are numbers, some bit masks, and some
7216 pointers to strings or other data. @value{GDBN} displays each value in the
7217 most appropriate form for a recognized tag, and in hexadecimal for
7218 an unrecognized tag.
7222 @node Memory Region Attributes
7223 @section Memory Region Attributes
7224 @cindex memory region attributes
7226 @dfn{Memory region attributes} allow you to describe special handling
7227 required by regions of your target's memory. @value{GDBN} uses
7228 attributes to determine whether to allow certain types of memory
7229 accesses; whether to use specific width accesses; and whether to cache
7230 target memory. By default the description of memory regions is
7231 fetched from the target (if the current target supports this), but the
7232 user can override the fetched regions.
7234 Defined memory regions can be individually enabled and disabled. When a
7235 memory region is disabled, @value{GDBN} uses the default attributes when
7236 accessing memory in that region. Similarly, if no memory regions have
7237 been defined, @value{GDBN} uses the default attributes when accessing
7240 When a memory region is defined, it is given a number to identify it;
7241 to enable, disable, or remove a memory region, you specify that number.
7245 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
7246 Define a memory region bounded by @var{lower} and @var{upper} with
7247 attributes @var{attributes}@dots{}, and add it to the list of regions
7248 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
7249 case: it is treated as the target's maximum memory address.
7250 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
7253 Discard any user changes to the memory regions and use target-supplied
7254 regions, if available, or no regions if the target does not support.
7257 @item delete mem @var{nums}@dots{}
7258 Remove memory regions @var{nums}@dots{} from the list of regions
7259 monitored by @value{GDBN}.
7262 @item disable mem @var{nums}@dots{}
7263 Disable monitoring of memory regions @var{nums}@dots{}.
7264 A disabled memory region is not forgotten.
7265 It may be enabled again later.
7268 @item enable mem @var{nums}@dots{}
7269 Enable monitoring of memory regions @var{nums}@dots{}.
7273 Print a table of all defined memory regions, with the following columns
7277 @item Memory Region Number
7278 @item Enabled or Disabled.
7279 Enabled memory regions are marked with @samp{y}.
7280 Disabled memory regions are marked with @samp{n}.
7283 The address defining the inclusive lower bound of the memory region.
7286 The address defining the exclusive upper bound of the memory region.
7289 The list of attributes set for this memory region.
7294 @subsection Attributes
7296 @subsubsection Memory Access Mode
7297 The access mode attributes set whether @value{GDBN} may make read or
7298 write accesses to a memory region.
7300 While these attributes prevent @value{GDBN} from performing invalid
7301 memory accesses, they do nothing to prevent the target system, I/O DMA,
7302 etc.@: from accessing memory.
7306 Memory is read only.
7308 Memory is write only.
7310 Memory is read/write. This is the default.
7313 @subsubsection Memory Access Size
7314 The access size attribute tells @value{GDBN} to use specific sized
7315 accesses in the memory region. Often memory mapped device registers
7316 require specific sized accesses. If no access size attribute is
7317 specified, @value{GDBN} may use accesses of any size.
7321 Use 8 bit memory accesses.
7323 Use 16 bit memory accesses.
7325 Use 32 bit memory accesses.
7327 Use 64 bit memory accesses.
7330 @c @subsubsection Hardware/Software Breakpoints
7331 @c The hardware/software breakpoint attributes set whether @value{GDBN}
7332 @c will use hardware or software breakpoints for the internal breakpoints
7333 @c used by the step, next, finish, until, etc. commands.
7337 @c Always use hardware breakpoints
7338 @c @item swbreak (default)
7341 @subsubsection Data Cache
7342 The data cache attributes set whether @value{GDBN} will cache target
7343 memory. While this generally improves performance by reducing debug
7344 protocol overhead, it can lead to incorrect results because @value{GDBN}
7345 does not know about volatile variables or memory mapped device
7350 Enable @value{GDBN} to cache target memory.
7352 Disable @value{GDBN} from caching target memory. This is the default.
7355 @subsection Memory Access Checking
7356 @value{GDBN} can be instructed to refuse accesses to memory that is
7357 not explicitly described. This can be useful if accessing such
7358 regions has undesired effects for a specific target, or to provide
7359 better error checking. The following commands control this behaviour.
7362 @kindex set mem inaccessible-by-default
7363 @item set mem inaccessible-by-default [on|off]
7364 If @code{on} is specified, make @value{GDBN} treat memory not
7365 explicitly described by the memory ranges as non-existent and refuse accesses
7366 to such memory. The checks are only performed if there's at least one
7367 memory range defined. If @code{off} is specified, make @value{GDBN}
7368 treat the memory not explicitly described by the memory ranges as RAM.
7369 The default value is @code{on}.
7370 @kindex show mem inaccessible-by-default
7371 @item show mem inaccessible-by-default
7372 Show the current handling of accesses to unknown memory.
7376 @c @subsubsection Memory Write Verification
7377 @c The memory write verification attributes set whether @value{GDBN}
7378 @c will re-reads data after each write to verify the write was successful.
7382 @c @item noverify (default)
7385 @node Dump/Restore Files
7386 @section Copy Between Memory and a File
7387 @cindex dump/restore files
7388 @cindex append data to a file
7389 @cindex dump data to a file
7390 @cindex restore data from a file
7392 You can use the commands @code{dump}, @code{append}, and
7393 @code{restore} to copy data between target memory and a file. The
7394 @code{dump} and @code{append} commands write data to a file, and the
7395 @code{restore} command reads data from a file back into the inferior's
7396 memory. Files may be in binary, Motorola S-record, Intel hex, or
7397 Tektronix Hex format; however, @value{GDBN} can only append to binary
7403 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7404 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
7405 Dump the contents of memory from @var{start_addr} to @var{end_addr},
7406 or the value of @var{expr}, to @var{filename} in the given format.
7408 The @var{format} parameter may be any one of:
7415 Motorola S-record format.
7417 Tektronix Hex format.
7420 @value{GDBN} uses the same definitions of these formats as the
7421 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
7422 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
7426 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7427 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
7428 Append the contents of memory from @var{start_addr} to @var{end_addr},
7429 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
7430 (@value{GDBN} can only append data to files in raw binary form.)
7433 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
7434 Restore the contents of file @var{filename} into memory. The
7435 @code{restore} command can automatically recognize any known @sc{bfd}
7436 file format, except for raw binary. To restore a raw binary file you
7437 must specify the optional keyword @code{binary} after the filename.
7439 If @var{bias} is non-zero, its value will be added to the addresses
7440 contained in the file. Binary files always start at address zero, so
7441 they will be restored at address @var{bias}. Other bfd files have
7442 a built-in location; they will be restored at offset @var{bias}
7445 If @var{start} and/or @var{end} are non-zero, then only data between
7446 file offset @var{start} and file offset @var{end} will be restored.
7447 These offsets are relative to the addresses in the file, before
7448 the @var{bias} argument is applied.
7452 @node Core File Generation
7453 @section How to Produce a Core File from Your Program
7454 @cindex dump core from inferior
7456 A @dfn{core file} or @dfn{core dump} is a file that records the memory
7457 image of a running process and its process status (register values
7458 etc.). Its primary use is post-mortem debugging of a program that
7459 crashed while it ran outside a debugger. A program that crashes
7460 automatically produces a core file, unless this feature is disabled by
7461 the user. @xref{Files}, for information on invoking @value{GDBN} in
7462 the post-mortem debugging mode.
7464 Occasionally, you may wish to produce a core file of the program you
7465 are debugging in order to preserve a snapshot of its state.
7466 @value{GDBN} has a special command for that.
7470 @kindex generate-core-file
7471 @item generate-core-file [@var{file}]
7472 @itemx gcore [@var{file}]
7473 Produce a core dump of the inferior process. The optional argument
7474 @var{file} specifies the file name where to put the core dump. If not
7475 specified, the file name defaults to @file{core.@var{pid}}, where
7476 @var{pid} is the inferior process ID.
7478 Note that this command is implemented only for some systems (as of
7479 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
7482 @node Character Sets
7483 @section Character Sets
7484 @cindex character sets
7486 @cindex translating between character sets
7487 @cindex host character set
7488 @cindex target character set
7490 If the program you are debugging uses a different character set to
7491 represent characters and strings than the one @value{GDBN} uses itself,
7492 @value{GDBN} can automatically translate between the character sets for
7493 you. The character set @value{GDBN} uses we call the @dfn{host
7494 character set}; the one the inferior program uses we call the
7495 @dfn{target character set}.
7497 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
7498 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
7499 remote protocol (@pxref{Remote Debugging}) to debug a program
7500 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
7501 then the host character set is Latin-1, and the target character set is
7502 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
7503 target-charset EBCDIC-US}, then @value{GDBN} translates between
7504 @sc{ebcdic} and Latin 1 as you print character or string values, or use
7505 character and string literals in expressions.
7507 @value{GDBN} has no way to automatically recognize which character set
7508 the inferior program uses; you must tell it, using the @code{set
7509 target-charset} command, described below.
7511 Here are the commands for controlling @value{GDBN}'s character set
7515 @item set target-charset @var{charset}
7516 @kindex set target-charset
7517 Set the current target character set to @var{charset}. We list the
7518 character set names @value{GDBN} recognizes below, but if you type
7519 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7520 list the target character sets it supports.
7524 @item set host-charset @var{charset}
7525 @kindex set host-charset
7526 Set the current host character set to @var{charset}.
7528 By default, @value{GDBN} uses a host character set appropriate to the
7529 system it is running on; you can override that default using the
7530 @code{set host-charset} command.
7532 @value{GDBN} can only use certain character sets as its host character
7533 set. We list the character set names @value{GDBN} recognizes below, and
7534 indicate which can be host character sets, but if you type
7535 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7536 list the host character sets it supports.
7538 @item set charset @var{charset}
7540 Set the current host and target character sets to @var{charset}. As
7541 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
7542 @value{GDBN} will list the name of the character sets that can be used
7543 for both host and target.
7547 @kindex show charset
7548 Show the names of the current host and target charsets.
7550 @itemx show host-charset
7551 @kindex show host-charset
7552 Show the name of the current host charset.
7554 @itemx show target-charset
7555 @kindex show target-charset
7556 Show the name of the current target charset.
7560 @value{GDBN} currently includes support for the following character
7566 @cindex ASCII character set
7567 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
7571 @cindex ISO 8859-1 character set
7572 @cindex ISO Latin 1 character set
7573 The ISO Latin 1 character set. This extends @sc{ascii} with accented
7574 characters needed for French, German, and Spanish. @value{GDBN} can use
7575 this as its host character set.
7579 @cindex EBCDIC character set
7580 @cindex IBM1047 character set
7581 Variants of the @sc{ebcdic} character set, used on some of IBM's
7582 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
7583 @value{GDBN} cannot use these as its host character set.
7587 Note that these are all single-byte character sets. More work inside
7588 @value{GDBN} is needed to support multi-byte or variable-width character
7589 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
7591 Here is an example of @value{GDBN}'s character set support in action.
7592 Assume that the following source code has been placed in the file
7593 @file{charset-test.c}:
7599 = @{72, 101, 108, 108, 111, 44, 32, 119,
7600 111, 114, 108, 100, 33, 10, 0@};
7601 char ibm1047_hello[]
7602 = @{200, 133, 147, 147, 150, 107, 64, 166,
7603 150, 153, 147, 132, 90, 37, 0@};
7607 printf ("Hello, world!\n");
7611 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
7612 containing the string @samp{Hello, world!} followed by a newline,
7613 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
7615 We compile the program, and invoke the debugger on it:
7618 $ gcc -g charset-test.c -o charset-test
7619 $ gdb -nw charset-test
7620 GNU gdb 2001-12-19-cvs
7621 Copyright 2001 Free Software Foundation, Inc.
7626 We can use the @code{show charset} command to see what character sets
7627 @value{GDBN} is currently using to interpret and display characters and
7631 (@value{GDBP}) show charset
7632 The current host and target character set is `ISO-8859-1'.
7636 For the sake of printing this manual, let's use @sc{ascii} as our
7637 initial character set:
7639 (@value{GDBP}) set charset ASCII
7640 (@value{GDBP}) show charset
7641 The current host and target character set is `ASCII'.
7645 Let's assume that @sc{ascii} is indeed the correct character set for our
7646 host system --- in other words, let's assume that if @value{GDBN} prints
7647 characters using the @sc{ascii} character set, our terminal will display
7648 them properly. Since our current target character set is also
7649 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
7652 (@value{GDBP}) print ascii_hello
7653 $1 = 0x401698 "Hello, world!\n"
7654 (@value{GDBP}) print ascii_hello[0]
7659 @value{GDBN} uses the target character set for character and string
7660 literals you use in expressions:
7663 (@value{GDBP}) print '+'
7668 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
7671 @value{GDBN} relies on the user to tell it which character set the
7672 target program uses. If we print @code{ibm1047_hello} while our target
7673 character set is still @sc{ascii}, we get jibberish:
7676 (@value{GDBP}) print ibm1047_hello
7677 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
7678 (@value{GDBP}) print ibm1047_hello[0]
7683 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
7684 @value{GDBN} tells us the character sets it supports:
7687 (@value{GDBP}) set target-charset
7688 ASCII EBCDIC-US IBM1047 ISO-8859-1
7689 (@value{GDBP}) set target-charset
7692 We can select @sc{ibm1047} as our target character set, and examine the
7693 program's strings again. Now the @sc{ascii} string is wrong, but
7694 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
7695 target character set, @sc{ibm1047}, to the host character set,
7696 @sc{ascii}, and they display correctly:
7699 (@value{GDBP}) set target-charset IBM1047
7700 (@value{GDBP}) show charset
7701 The current host character set is `ASCII'.
7702 The current target character set is `IBM1047'.
7703 (@value{GDBP}) print ascii_hello
7704 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
7705 (@value{GDBP}) print ascii_hello[0]
7707 (@value{GDBP}) print ibm1047_hello
7708 $8 = 0x4016a8 "Hello, world!\n"
7709 (@value{GDBP}) print ibm1047_hello[0]
7714 As above, @value{GDBN} uses the target character set for character and
7715 string literals you use in expressions:
7718 (@value{GDBP}) print '+'
7723 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
7726 @node Caching Remote Data
7727 @section Caching Data of Remote Targets
7728 @cindex caching data of remote targets
7730 @value{GDBN} can cache data exchanged between the debugger and a
7731 remote target (@pxref{Remote Debugging}). Such caching generally improves
7732 performance, because it reduces the overhead of the remote protocol by
7733 bundling memory reads and writes into large chunks. Unfortunately,
7734 @value{GDBN} does not currently know anything about volatile
7735 registers, and thus data caching will produce incorrect results when
7736 volatile registers are in use.
7739 @kindex set remotecache
7740 @item set remotecache on
7741 @itemx set remotecache off
7742 Set caching state for remote targets. When @code{ON}, use data
7743 caching. By default, this option is @code{OFF}.
7745 @kindex show remotecache
7746 @item show remotecache
7747 Show the current state of data caching for remote targets.
7751 Print the information about the data cache performance. The
7752 information displayed includes: the dcache width and depth; and for
7753 each cache line, how many times it was referenced, and its data and
7754 state (dirty, bad, ok, etc.). This command is useful for debugging
7755 the data cache operation.
7758 @node Searching Memory
7759 @section Search Memory
7760 @cindex searching memory
7762 Memory can be searched for a particular sequence of bytes with the
7763 @code{find} command.
7767 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
7768 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
7769 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
7770 etc. The search begins at address @var{start_addr} and continues for either
7771 @var{len} bytes or through to @var{end_addr} inclusive.
7774 @var{s} and @var{n} are optional parameters.
7775 They may be specified in either order, apart or together.
7778 @item @var{s}, search query size
7779 The size of each search query value.
7785 halfwords (two bytes)
7789 giant words (eight bytes)
7792 All values are interpreted in the current language.
7793 This means, for example, that if the current source language is C/C@t{++}
7794 then searching for the string ``hello'' includes the trailing '\0'.
7796 If the value size is not specified, it is taken from the
7797 value's type in the current language.
7798 This is useful when one wants to specify the search
7799 pattern as a mixture of types.
7800 Note that this means, for example, that in the case of C-like languages
7801 a search for an untyped 0x42 will search for @samp{(int) 0x42}
7802 which is typically four bytes.
7804 @item @var{n}, maximum number of finds
7805 The maximum number of matches to print. The default is to print all finds.
7808 You can use strings as search values. Quote them with double-quotes
7810 The string value is copied into the search pattern byte by byte,
7811 regardless of the endianness of the target and the size specification.
7813 The address of each match found is printed as well as a count of the
7814 number of matches found.
7816 The address of the last value found is stored in convenience variable
7818 A count of the number of matches is stored in @samp{$numfound}.
7820 For example, if stopped at the @code{printf} in this function:
7826 static char hello[] = "hello-hello";
7827 static struct @{ char c; short s; int i; @}
7828 __attribute__ ((packed)) mixed
7829 = @{ 'c', 0x1234, 0x87654321 @};
7830 printf ("%s\n", hello);
7835 you get during debugging:
7838 (gdb) find &hello[0], +sizeof(hello), "hello"
7839 0x804956d <hello.1620+6>
7841 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
7842 0x8049567 <hello.1620>
7843 0x804956d <hello.1620+6>
7845 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
7846 0x8049567 <hello.1620>
7848 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
7849 0x8049560 <mixed.1625>
7851 (gdb) print $numfound
7854 $2 = (void *) 0x8049560
7858 @chapter C Preprocessor Macros
7860 Some languages, such as C and C@t{++}, provide a way to define and invoke
7861 ``preprocessor macros'' which expand into strings of tokens.
7862 @value{GDBN} can evaluate expressions containing macro invocations, show
7863 the result of macro expansion, and show a macro's definition, including
7864 where it was defined.
7866 You may need to compile your program specially to provide @value{GDBN}
7867 with information about preprocessor macros. Most compilers do not
7868 include macros in their debugging information, even when you compile
7869 with the @option{-g} flag. @xref{Compilation}.
7871 A program may define a macro at one point, remove that definition later,
7872 and then provide a different definition after that. Thus, at different
7873 points in the program, a macro may have different definitions, or have
7874 no definition at all. If there is a current stack frame, @value{GDBN}
7875 uses the macros in scope at that frame's source code line. Otherwise,
7876 @value{GDBN} uses the macros in scope at the current listing location;
7879 At the moment, @value{GDBN} does not support the @code{##}
7880 token-splicing operator, the @code{#} stringification operator, or
7881 variable-arity macros.
7883 Whenever @value{GDBN} evaluates an expression, it always expands any
7884 macro invocations present in the expression. @value{GDBN} also provides
7885 the following commands for working with macros explicitly.
7889 @kindex macro expand
7890 @cindex macro expansion, showing the results of preprocessor
7891 @cindex preprocessor macro expansion, showing the results of
7892 @cindex expanding preprocessor macros
7893 @item macro expand @var{expression}
7894 @itemx macro exp @var{expression}
7895 Show the results of expanding all preprocessor macro invocations in
7896 @var{expression}. Since @value{GDBN} simply expands macros, but does
7897 not parse the result, @var{expression} need not be a valid expression;
7898 it can be any string of tokens.
7901 @item macro expand-once @var{expression}
7902 @itemx macro exp1 @var{expression}
7903 @cindex expand macro once
7904 @i{(This command is not yet implemented.)} Show the results of
7905 expanding those preprocessor macro invocations that appear explicitly in
7906 @var{expression}. Macro invocations appearing in that expansion are
7907 left unchanged. This command allows you to see the effect of a
7908 particular macro more clearly, without being confused by further
7909 expansions. Since @value{GDBN} simply expands macros, but does not
7910 parse the result, @var{expression} need not be a valid expression; it
7911 can be any string of tokens.
7914 @cindex macro definition, showing
7915 @cindex definition, showing a macro's
7916 @item info macro @var{macro}
7917 Show the definition of the macro named @var{macro}, and describe the
7918 source location where that definition was established.
7920 @kindex macro define
7921 @cindex user-defined macros
7922 @cindex defining macros interactively
7923 @cindex macros, user-defined
7924 @item macro define @var{macro} @var{replacement-list}
7925 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
7926 Introduce a definition for a preprocessor macro named @var{macro},
7927 invocations of which are replaced by the tokens given in
7928 @var{replacement-list}. The first form of this command defines an
7929 ``object-like'' macro, which takes no arguments; the second form
7930 defines a ``function-like'' macro, which takes the arguments given in
7933 A definition introduced by this command is in scope in every
7934 expression evaluated in @value{GDBN}, until it is removed with the
7935 @code{macro undef} command, described below. The definition overrides
7936 all definitions for @var{macro} present in the program being debugged,
7937 as well as any previous user-supplied definition.
7940 @item macro undef @var{macro}
7941 Remove any user-supplied definition for the macro named @var{macro}.
7942 This command only affects definitions provided with the @code{macro
7943 define} command, described above; it cannot remove definitions present
7944 in the program being debugged.
7948 List all the macros defined using the @code{macro define} command.
7951 @cindex macros, example of debugging with
7952 Here is a transcript showing the above commands in action. First, we
7953 show our source files:
7961 #define ADD(x) (M + x)
7966 printf ("Hello, world!\n");
7968 printf ("We're so creative.\n");
7970 printf ("Goodbye, world!\n");
7977 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
7978 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
7979 compiler includes information about preprocessor macros in the debugging
7983 $ gcc -gdwarf-2 -g3 sample.c -o sample
7987 Now, we start @value{GDBN} on our sample program:
7991 GNU gdb 2002-05-06-cvs
7992 Copyright 2002 Free Software Foundation, Inc.
7993 GDB is free software, @dots{}
7997 We can expand macros and examine their definitions, even when the
7998 program is not running. @value{GDBN} uses the current listing position
7999 to decide which macro definitions are in scope:
8002 (@value{GDBP}) list main
8005 5 #define ADD(x) (M + x)
8010 10 printf ("Hello, world!\n");
8012 12 printf ("We're so creative.\n");
8013 (@value{GDBP}) info macro ADD
8014 Defined at /home/jimb/gdb/macros/play/sample.c:5
8015 #define ADD(x) (M + x)
8016 (@value{GDBP}) info macro Q
8017 Defined at /home/jimb/gdb/macros/play/sample.h:1
8018 included at /home/jimb/gdb/macros/play/sample.c:2
8020 (@value{GDBP}) macro expand ADD(1)
8021 expands to: (42 + 1)
8022 (@value{GDBP}) macro expand-once ADD(1)
8023 expands to: once (M + 1)
8027 In the example above, note that @code{macro expand-once} expands only
8028 the macro invocation explicit in the original text --- the invocation of
8029 @code{ADD} --- but does not expand the invocation of the macro @code{M},
8030 which was introduced by @code{ADD}.
8032 Once the program is running, @value{GDBN} uses the macro definitions in
8033 force at the source line of the current stack frame:
8036 (@value{GDBP}) break main
8037 Breakpoint 1 at 0x8048370: file sample.c, line 10.
8039 Starting program: /home/jimb/gdb/macros/play/sample
8041 Breakpoint 1, main () at sample.c:10
8042 10 printf ("Hello, world!\n");
8046 At line 10, the definition of the macro @code{N} at line 9 is in force:
8049 (@value{GDBP}) info macro N
8050 Defined at /home/jimb/gdb/macros/play/sample.c:9
8052 (@value{GDBP}) macro expand N Q M
8054 (@value{GDBP}) print N Q M
8059 As we step over directives that remove @code{N}'s definition, and then
8060 give it a new definition, @value{GDBN} finds the definition (or lack
8061 thereof) in force at each point:
8066 12 printf ("We're so creative.\n");
8067 (@value{GDBP}) info macro N
8068 The symbol `N' has no definition as a C/C++ preprocessor macro
8069 at /home/jimb/gdb/macros/play/sample.c:12
8072 14 printf ("Goodbye, world!\n");
8073 (@value{GDBP}) info macro N
8074 Defined at /home/jimb/gdb/macros/play/sample.c:13
8076 (@value{GDBP}) macro expand N Q M
8077 expands to: 1729 < 42
8078 (@value{GDBP}) print N Q M
8085 @chapter Tracepoints
8086 @c This chapter is based on the documentation written by Michael
8087 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
8090 In some applications, it is not feasible for the debugger to interrupt
8091 the program's execution long enough for the developer to learn
8092 anything helpful about its behavior. If the program's correctness
8093 depends on its real-time behavior, delays introduced by a debugger
8094 might cause the program to change its behavior drastically, or perhaps
8095 fail, even when the code itself is correct. It is useful to be able
8096 to observe the program's behavior without interrupting it.
8098 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
8099 specify locations in the program, called @dfn{tracepoints}, and
8100 arbitrary expressions to evaluate when those tracepoints are reached.
8101 Later, using the @code{tfind} command, you can examine the values
8102 those expressions had when the program hit the tracepoints. The
8103 expressions may also denote objects in memory---structures or arrays,
8104 for example---whose values @value{GDBN} should record; while visiting
8105 a particular tracepoint, you may inspect those objects as if they were
8106 in memory at that moment. However, because @value{GDBN} records these
8107 values without interacting with you, it can do so quickly and
8108 unobtrusively, hopefully not disturbing the program's behavior.
8110 The tracepoint facility is currently available only for remote
8111 targets. @xref{Targets}. In addition, your remote target must know
8112 how to collect trace data. This functionality is implemented in the
8113 remote stub; however, none of the stubs distributed with @value{GDBN}
8114 support tracepoints as of this writing. The format of the remote
8115 packets used to implement tracepoints are described in @ref{Tracepoint
8118 This chapter describes the tracepoint commands and features.
8122 * Analyze Collected Data::
8123 * Tracepoint Variables::
8126 @node Set Tracepoints
8127 @section Commands to Set Tracepoints
8129 Before running such a @dfn{trace experiment}, an arbitrary number of
8130 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
8131 tracepoint has a number assigned to it by @value{GDBN}. Like with
8132 breakpoints, tracepoint numbers are successive integers starting from
8133 one. Many of the commands associated with tracepoints take the
8134 tracepoint number as their argument, to identify which tracepoint to
8137 For each tracepoint, you can specify, in advance, some arbitrary set
8138 of data that you want the target to collect in the trace buffer when
8139 it hits that tracepoint. The collected data can include registers,
8140 local variables, or global data. Later, you can use @value{GDBN}
8141 commands to examine the values these data had at the time the
8144 This section describes commands to set tracepoints and associated
8145 conditions and actions.
8148 * Create and Delete Tracepoints::
8149 * Enable and Disable Tracepoints::
8150 * Tracepoint Passcounts::
8151 * Tracepoint Actions::
8152 * Listing Tracepoints::
8153 * Starting and Stopping Trace Experiments::
8156 @node Create and Delete Tracepoints
8157 @subsection Create and Delete Tracepoints
8160 @cindex set tracepoint
8163 The @code{trace} command is very similar to the @code{break} command.
8164 Its argument can be a source line, a function name, or an address in
8165 the target program. @xref{Set Breaks}. The @code{trace} command
8166 defines a tracepoint, which is a point in the target program where the
8167 debugger will briefly stop, collect some data, and then allow the
8168 program to continue. Setting a tracepoint or changing its commands
8169 doesn't take effect until the next @code{tstart} command; thus, you
8170 cannot change the tracepoint attributes once a trace experiment is
8173 Here are some examples of using the @code{trace} command:
8176 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
8178 (@value{GDBP}) @b{trace +2} // 2 lines forward
8180 (@value{GDBP}) @b{trace my_function} // first source line of function
8182 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
8184 (@value{GDBP}) @b{trace *0x2117c4} // an address
8188 You can abbreviate @code{trace} as @code{tr}.
8191 @cindex last tracepoint number
8192 @cindex recent tracepoint number
8193 @cindex tracepoint number
8194 The convenience variable @code{$tpnum} records the tracepoint number
8195 of the most recently set tracepoint.
8197 @kindex delete tracepoint
8198 @cindex tracepoint deletion
8199 @item delete tracepoint @r{[}@var{num}@r{]}
8200 Permanently delete one or more tracepoints. With no argument, the
8201 default is to delete all tracepoints.
8206 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
8208 (@value{GDBP}) @b{delete trace} // remove all tracepoints
8212 You can abbreviate this command as @code{del tr}.
8215 @node Enable and Disable Tracepoints
8216 @subsection Enable and Disable Tracepoints
8219 @kindex disable tracepoint
8220 @item disable tracepoint @r{[}@var{num}@r{]}
8221 Disable tracepoint @var{num}, or all tracepoints if no argument
8222 @var{num} is given. A disabled tracepoint will have no effect during
8223 the next trace experiment, but it is not forgotten. You can re-enable
8224 a disabled tracepoint using the @code{enable tracepoint} command.
8226 @kindex enable tracepoint
8227 @item enable tracepoint @r{[}@var{num}@r{]}
8228 Enable tracepoint @var{num}, or all tracepoints. The enabled
8229 tracepoints will become effective the next time a trace experiment is
8233 @node Tracepoint Passcounts
8234 @subsection Tracepoint Passcounts
8238 @cindex tracepoint pass count
8239 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
8240 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
8241 automatically stop a trace experiment. If a tracepoint's passcount is
8242 @var{n}, then the trace experiment will be automatically stopped on
8243 the @var{n}'th time that tracepoint is hit. If the tracepoint number
8244 @var{num} is not specified, the @code{passcount} command sets the
8245 passcount of the most recently defined tracepoint. If no passcount is
8246 given, the trace experiment will run until stopped explicitly by the
8252 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
8253 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
8255 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
8256 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
8257 (@value{GDBP}) @b{trace foo}
8258 (@value{GDBP}) @b{pass 3}
8259 (@value{GDBP}) @b{trace bar}
8260 (@value{GDBP}) @b{pass 2}
8261 (@value{GDBP}) @b{trace baz}
8262 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
8263 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
8264 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
8265 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
8269 @node Tracepoint Actions
8270 @subsection Tracepoint Action Lists
8274 @cindex tracepoint actions
8275 @item actions @r{[}@var{num}@r{]}
8276 This command will prompt for a list of actions to be taken when the
8277 tracepoint is hit. If the tracepoint number @var{num} is not
8278 specified, this command sets the actions for the one that was most
8279 recently defined (so that you can define a tracepoint and then say
8280 @code{actions} without bothering about its number). You specify the
8281 actions themselves on the following lines, one action at a time, and
8282 terminate the actions list with a line containing just @code{end}. So
8283 far, the only defined actions are @code{collect} and
8284 @code{while-stepping}.
8286 @cindex remove actions from a tracepoint
8287 To remove all actions from a tracepoint, type @samp{actions @var{num}}
8288 and follow it immediately with @samp{end}.
8291 (@value{GDBP}) @b{collect @var{data}} // collect some data
8293 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
8295 (@value{GDBP}) @b{end} // signals the end of actions.
8298 In the following example, the action list begins with @code{collect}
8299 commands indicating the things to be collected when the tracepoint is
8300 hit. Then, in order to single-step and collect additional data
8301 following the tracepoint, a @code{while-stepping} command is used,
8302 followed by the list of things to be collected while stepping. The
8303 @code{while-stepping} command is terminated by its own separate
8304 @code{end} command. Lastly, the action list is terminated by an
8308 (@value{GDBP}) @b{trace foo}
8309 (@value{GDBP}) @b{actions}
8310 Enter actions for tracepoint 1, one per line:
8319 @kindex collect @r{(tracepoints)}
8320 @item collect @var{expr1}, @var{expr2}, @dots{}
8321 Collect values of the given expressions when the tracepoint is hit.
8322 This command accepts a comma-separated list of any valid expressions.
8323 In addition to global, static, or local variables, the following
8324 special arguments are supported:
8328 collect all registers
8331 collect all function arguments
8334 collect all local variables.
8337 You can give several consecutive @code{collect} commands, each one
8338 with a single argument, or one @code{collect} command with several
8339 arguments separated by commas: the effect is the same.
8341 The command @code{info scope} (@pxref{Symbols, info scope}) is
8342 particularly useful for figuring out what data to collect.
8344 @kindex while-stepping @r{(tracepoints)}
8345 @item while-stepping @var{n}
8346 Perform @var{n} single-step traces after the tracepoint, collecting
8347 new data at each step. The @code{while-stepping} command is
8348 followed by the list of what to collect while stepping (followed by
8349 its own @code{end} command):
8353 > collect $regs, myglobal
8359 You may abbreviate @code{while-stepping} as @code{ws} or
8363 @node Listing Tracepoints
8364 @subsection Listing Tracepoints
8367 @kindex info tracepoints
8369 @cindex information about tracepoints
8370 @item info tracepoints @r{[}@var{num}@r{]}
8371 Display information about the tracepoint @var{num}. If you don't specify
8372 a tracepoint number, displays information about all the tracepoints
8373 defined so far. For each tracepoint, the following information is
8380 whether it is enabled or disabled
8384 its passcount as given by the @code{passcount @var{n}} command
8386 its step count as given by the @code{while-stepping @var{n}} command
8388 where in the source files is the tracepoint set
8390 its action list as given by the @code{actions} command
8394 (@value{GDBP}) @b{info trace}
8395 Num Enb Address PassC StepC What
8396 1 y 0x002117c4 0 0 <gdb_asm>
8397 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
8398 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
8403 This command can be abbreviated @code{info tp}.
8406 @node Starting and Stopping Trace Experiments
8407 @subsection Starting and Stopping Trace Experiments
8411 @cindex start a new trace experiment
8412 @cindex collected data discarded
8414 This command takes no arguments. It starts the trace experiment, and
8415 begins collecting data. This has the side effect of discarding all
8416 the data collected in the trace buffer during the previous trace
8420 @cindex stop a running trace experiment
8422 This command takes no arguments. It ends the trace experiment, and
8423 stops collecting data.
8425 @strong{Note}: a trace experiment and data collection may stop
8426 automatically if any tracepoint's passcount is reached
8427 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
8430 @cindex status of trace data collection
8431 @cindex trace experiment, status of
8433 This command displays the status of the current trace data
8437 Here is an example of the commands we described so far:
8440 (@value{GDBP}) @b{trace gdb_c_test}
8441 (@value{GDBP}) @b{actions}
8442 Enter actions for tracepoint #1, one per line.
8443 > collect $regs,$locals,$args
8448 (@value{GDBP}) @b{tstart}
8449 [time passes @dots{}]
8450 (@value{GDBP}) @b{tstop}
8454 @node Analyze Collected Data
8455 @section Using the Collected Data
8457 After the tracepoint experiment ends, you use @value{GDBN} commands
8458 for examining the trace data. The basic idea is that each tracepoint
8459 collects a trace @dfn{snapshot} every time it is hit and another
8460 snapshot every time it single-steps. All these snapshots are
8461 consecutively numbered from zero and go into a buffer, and you can
8462 examine them later. The way you examine them is to @dfn{focus} on a
8463 specific trace snapshot. When the remote stub is focused on a trace
8464 snapshot, it will respond to all @value{GDBN} requests for memory and
8465 registers by reading from the buffer which belongs to that snapshot,
8466 rather than from @emph{real} memory or registers of the program being
8467 debugged. This means that @strong{all} @value{GDBN} commands
8468 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
8469 behave as if we were currently debugging the program state as it was
8470 when the tracepoint occurred. Any requests for data that are not in
8471 the buffer will fail.
8474 * tfind:: How to select a trace snapshot
8475 * tdump:: How to display all data for a snapshot
8476 * save-tracepoints:: How to save tracepoints for a future run
8480 @subsection @code{tfind @var{n}}
8483 @cindex select trace snapshot
8484 @cindex find trace snapshot
8485 The basic command for selecting a trace snapshot from the buffer is
8486 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
8487 counting from zero. If no argument @var{n} is given, the next
8488 snapshot is selected.
8490 Here are the various forms of using the @code{tfind} command.
8494 Find the first snapshot in the buffer. This is a synonym for
8495 @code{tfind 0} (since 0 is the number of the first snapshot).
8498 Stop debugging trace snapshots, resume @emph{live} debugging.
8501 Same as @samp{tfind none}.
8504 No argument means find the next trace snapshot.
8507 Find the previous trace snapshot before the current one. This permits
8508 retracing earlier steps.
8510 @item tfind tracepoint @var{num}
8511 Find the next snapshot associated with tracepoint @var{num}. Search
8512 proceeds forward from the last examined trace snapshot. If no
8513 argument @var{num} is given, it means find the next snapshot collected
8514 for the same tracepoint as the current snapshot.
8516 @item tfind pc @var{addr}
8517 Find the next snapshot associated with the value @var{addr} of the
8518 program counter. Search proceeds forward from the last examined trace
8519 snapshot. If no argument @var{addr} is given, it means find the next
8520 snapshot with the same value of PC as the current snapshot.
8522 @item tfind outside @var{addr1}, @var{addr2}
8523 Find the next snapshot whose PC is outside the given range of
8526 @item tfind range @var{addr1}, @var{addr2}
8527 Find the next snapshot whose PC is between @var{addr1} and
8528 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
8530 @item tfind line @r{[}@var{file}:@r{]}@var{n}
8531 Find the next snapshot associated with the source line @var{n}. If
8532 the optional argument @var{file} is given, refer to line @var{n} in
8533 that source file. Search proceeds forward from the last examined
8534 trace snapshot. If no argument @var{n} is given, it means find the
8535 next line other than the one currently being examined; thus saying
8536 @code{tfind line} repeatedly can appear to have the same effect as
8537 stepping from line to line in a @emph{live} debugging session.
8540 The default arguments for the @code{tfind} commands are specifically
8541 designed to make it easy to scan through the trace buffer. For
8542 instance, @code{tfind} with no argument selects the next trace
8543 snapshot, and @code{tfind -} with no argument selects the previous
8544 trace snapshot. So, by giving one @code{tfind} command, and then
8545 simply hitting @key{RET} repeatedly you can examine all the trace
8546 snapshots in order. Or, by saying @code{tfind -} and then hitting
8547 @key{RET} repeatedly you can examine the snapshots in reverse order.
8548 The @code{tfind line} command with no argument selects the snapshot
8549 for the next source line executed. The @code{tfind pc} command with
8550 no argument selects the next snapshot with the same program counter
8551 (PC) as the current frame. The @code{tfind tracepoint} command with
8552 no argument selects the next trace snapshot collected by the same
8553 tracepoint as the current one.
8555 In addition to letting you scan through the trace buffer manually,
8556 these commands make it easy to construct @value{GDBN} scripts that
8557 scan through the trace buffer and print out whatever collected data
8558 you are interested in. Thus, if we want to examine the PC, FP, and SP
8559 registers from each trace frame in the buffer, we can say this:
8562 (@value{GDBP}) @b{tfind start}
8563 (@value{GDBP}) @b{while ($trace_frame != -1)}
8564 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
8565 $trace_frame, $pc, $sp, $fp
8569 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
8570 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
8571 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
8572 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
8573 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
8574 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
8575 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
8576 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
8577 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
8578 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
8579 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
8582 Or, if we want to examine the variable @code{X} at each source line in
8586 (@value{GDBP}) @b{tfind start}
8587 (@value{GDBP}) @b{while ($trace_frame != -1)}
8588 > printf "Frame %d, X == %d\n", $trace_frame, X
8598 @subsection @code{tdump}
8600 @cindex dump all data collected at tracepoint
8601 @cindex tracepoint data, display
8603 This command takes no arguments. It prints all the data collected at
8604 the current trace snapshot.
8607 (@value{GDBP}) @b{trace 444}
8608 (@value{GDBP}) @b{actions}
8609 Enter actions for tracepoint #2, one per line:
8610 > collect $regs, $locals, $args, gdb_long_test
8613 (@value{GDBP}) @b{tstart}
8615 (@value{GDBP}) @b{tfind line 444}
8616 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
8618 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
8620 (@value{GDBP}) @b{tdump}
8621 Data collected at tracepoint 2, trace frame 1:
8622 d0 0xc4aa0085 -995491707
8626 d4 0x71aea3d 119204413
8631 a1 0x3000668 50333288
8634 a4 0x3000698 50333336
8636 fp 0x30bf3c 0x30bf3c
8637 sp 0x30bf34 0x30bf34
8639 pc 0x20b2c8 0x20b2c8
8643 p = 0x20e5b4 "gdb-test"
8650 gdb_long_test = 17 '\021'
8655 @node save-tracepoints
8656 @subsection @code{save-tracepoints @var{filename}}
8657 @kindex save-tracepoints
8658 @cindex save tracepoints for future sessions
8660 This command saves all current tracepoint definitions together with
8661 their actions and passcounts, into a file @file{@var{filename}}
8662 suitable for use in a later debugging session. To read the saved
8663 tracepoint definitions, use the @code{source} command (@pxref{Command
8666 @node Tracepoint Variables
8667 @section Convenience Variables for Tracepoints
8668 @cindex tracepoint variables
8669 @cindex convenience variables for tracepoints
8672 @vindex $trace_frame
8673 @item (int) $trace_frame
8674 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
8675 snapshot is selected.
8678 @item (int) $tracepoint
8679 The tracepoint for the current trace snapshot.
8682 @item (int) $trace_line
8683 The line number for the current trace snapshot.
8686 @item (char []) $trace_file
8687 The source file for the current trace snapshot.
8690 @item (char []) $trace_func
8691 The name of the function containing @code{$tracepoint}.
8694 Note: @code{$trace_file} is not suitable for use in @code{printf},
8695 use @code{output} instead.
8697 Here's a simple example of using these convenience variables for
8698 stepping through all the trace snapshots and printing some of their
8702 (@value{GDBP}) @b{tfind start}
8704 (@value{GDBP}) @b{while $trace_frame != -1}
8705 > output $trace_file
8706 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
8712 @chapter Debugging Programs That Use Overlays
8715 If your program is too large to fit completely in your target system's
8716 memory, you can sometimes use @dfn{overlays} to work around this
8717 problem. @value{GDBN} provides some support for debugging programs that
8721 * How Overlays Work:: A general explanation of overlays.
8722 * Overlay Commands:: Managing overlays in @value{GDBN}.
8723 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
8724 mapped by asking the inferior.
8725 * Overlay Sample Program:: A sample program using overlays.
8728 @node How Overlays Work
8729 @section How Overlays Work
8730 @cindex mapped overlays
8731 @cindex unmapped overlays
8732 @cindex load address, overlay's
8733 @cindex mapped address
8734 @cindex overlay area
8736 Suppose you have a computer whose instruction address space is only 64
8737 kilobytes long, but which has much more memory which can be accessed by
8738 other means: special instructions, segment registers, or memory
8739 management hardware, for example. Suppose further that you want to
8740 adapt a program which is larger than 64 kilobytes to run on this system.
8742 One solution is to identify modules of your program which are relatively
8743 independent, and need not call each other directly; call these modules
8744 @dfn{overlays}. Separate the overlays from the main program, and place
8745 their machine code in the larger memory. Place your main program in
8746 instruction memory, but leave at least enough space there to hold the
8747 largest overlay as well.
8749 Now, to call a function located in an overlay, you must first copy that
8750 overlay's machine code from the large memory into the space set aside
8751 for it in the instruction memory, and then jump to its entry point
8754 @c NB: In the below the mapped area's size is greater or equal to the
8755 @c size of all overlays. This is intentional to remind the developer
8756 @c that overlays don't necessarily need to be the same size.
8760 Data Instruction Larger
8761 Address Space Address Space Address Space
8762 +-----------+ +-----------+ +-----------+
8764 +-----------+ +-----------+ +-----------+<-- overlay 1
8765 | program | | main | .----| overlay 1 | load address
8766 | variables | | program | | +-----------+
8767 | and heap | | | | | |
8768 +-----------+ | | | +-----------+<-- overlay 2
8769 | | +-----------+ | | | load address
8770 +-----------+ | | | .-| overlay 2 |
8772 mapped --->+-----------+ | | +-----------+
8774 | overlay | <-' | | |
8775 | area | <---' +-----------+<-- overlay 3
8776 | | <---. | | load address
8777 +-----------+ `--| overlay 3 |
8784 @anchor{A code overlay}A code overlay
8788 The diagram (@pxref{A code overlay}) shows a system with separate data
8789 and instruction address spaces. To map an overlay, the program copies
8790 its code from the larger address space to the instruction address space.
8791 Since the overlays shown here all use the same mapped address, only one
8792 may be mapped at a time. For a system with a single address space for
8793 data and instructions, the diagram would be similar, except that the
8794 program variables and heap would share an address space with the main
8795 program and the overlay area.
8797 An overlay loaded into instruction memory and ready for use is called a
8798 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
8799 instruction memory. An overlay not present (or only partially present)
8800 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
8801 is its address in the larger memory. The mapped address is also called
8802 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
8803 called the @dfn{load memory address}, or @dfn{LMA}.
8805 Unfortunately, overlays are not a completely transparent way to adapt a
8806 program to limited instruction memory. They introduce a new set of
8807 global constraints you must keep in mind as you design your program:
8812 Before calling or returning to a function in an overlay, your program
8813 must make sure that overlay is actually mapped. Otherwise, the call or
8814 return will transfer control to the right address, but in the wrong
8815 overlay, and your program will probably crash.
8818 If the process of mapping an overlay is expensive on your system, you
8819 will need to choose your overlays carefully to minimize their effect on
8820 your program's performance.
8823 The executable file you load onto your system must contain each
8824 overlay's instructions, appearing at the overlay's load address, not its
8825 mapped address. However, each overlay's instructions must be relocated
8826 and its symbols defined as if the overlay were at its mapped address.
8827 You can use GNU linker scripts to specify different load and relocation
8828 addresses for pieces of your program; see @ref{Overlay Description,,,
8829 ld.info, Using ld: the GNU linker}.
8832 The procedure for loading executable files onto your system must be able
8833 to load their contents into the larger address space as well as the
8834 instruction and data spaces.
8838 The overlay system described above is rather simple, and could be
8839 improved in many ways:
8844 If your system has suitable bank switch registers or memory management
8845 hardware, you could use those facilities to make an overlay's load area
8846 contents simply appear at their mapped address in instruction space.
8847 This would probably be faster than copying the overlay to its mapped
8848 area in the usual way.
8851 If your overlays are small enough, you could set aside more than one
8852 overlay area, and have more than one overlay mapped at a time.
8855 You can use overlays to manage data, as well as instructions. In
8856 general, data overlays are even less transparent to your design than
8857 code overlays: whereas code overlays only require care when you call or
8858 return to functions, data overlays require care every time you access
8859 the data. Also, if you change the contents of a data overlay, you
8860 must copy its contents back out to its load address before you can copy a
8861 different data overlay into the same mapped area.
8866 @node Overlay Commands
8867 @section Overlay Commands
8869 To use @value{GDBN}'s overlay support, each overlay in your program must
8870 correspond to a separate section of the executable file. The section's
8871 virtual memory address and load memory address must be the overlay's
8872 mapped and load addresses. Identifying overlays with sections allows
8873 @value{GDBN} to determine the appropriate address of a function or
8874 variable, depending on whether the overlay is mapped or not.
8876 @value{GDBN}'s overlay commands all start with the word @code{overlay};
8877 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
8882 Disable @value{GDBN}'s overlay support. When overlay support is
8883 disabled, @value{GDBN} assumes that all functions and variables are
8884 always present at their mapped addresses. By default, @value{GDBN}'s
8885 overlay support is disabled.
8887 @item overlay manual
8888 @cindex manual overlay debugging
8889 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
8890 relies on you to tell it which overlays are mapped, and which are not,
8891 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
8892 commands described below.
8894 @item overlay map-overlay @var{overlay}
8895 @itemx overlay map @var{overlay}
8896 @cindex map an overlay
8897 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
8898 be the name of the object file section containing the overlay. When an
8899 overlay is mapped, @value{GDBN} assumes it can find the overlay's
8900 functions and variables at their mapped addresses. @value{GDBN} assumes
8901 that any other overlays whose mapped ranges overlap that of
8902 @var{overlay} are now unmapped.
8904 @item overlay unmap-overlay @var{overlay}
8905 @itemx overlay unmap @var{overlay}
8906 @cindex unmap an overlay
8907 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
8908 must be the name of the object file section containing the overlay.
8909 When an overlay is unmapped, @value{GDBN} assumes it can find the
8910 overlay's functions and variables at their load addresses.
8913 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
8914 consults a data structure the overlay manager maintains in the inferior
8915 to see which overlays are mapped. For details, see @ref{Automatic
8918 @item overlay load-target
8920 @cindex reloading the overlay table
8921 Re-read the overlay table from the inferior. Normally, @value{GDBN}
8922 re-reads the table @value{GDBN} automatically each time the inferior
8923 stops, so this command should only be necessary if you have changed the
8924 overlay mapping yourself using @value{GDBN}. This command is only
8925 useful when using automatic overlay debugging.
8927 @item overlay list-overlays
8929 @cindex listing mapped overlays
8930 Display a list of the overlays currently mapped, along with their mapped
8931 addresses, load addresses, and sizes.
8935 Normally, when @value{GDBN} prints a code address, it includes the name
8936 of the function the address falls in:
8939 (@value{GDBP}) print main
8940 $3 = @{int ()@} 0x11a0 <main>
8943 When overlay debugging is enabled, @value{GDBN} recognizes code in
8944 unmapped overlays, and prints the names of unmapped functions with
8945 asterisks around them. For example, if @code{foo} is a function in an
8946 unmapped overlay, @value{GDBN} prints it this way:
8949 (@value{GDBP}) overlay list
8950 No sections are mapped.
8951 (@value{GDBP}) print foo
8952 $5 = @{int (int)@} 0x100000 <*foo*>
8955 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
8959 (@value{GDBP}) overlay list
8960 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
8961 mapped at 0x1016 - 0x104a
8962 (@value{GDBP}) print foo
8963 $6 = @{int (int)@} 0x1016 <foo>
8966 When overlay debugging is enabled, @value{GDBN} can find the correct
8967 address for functions and variables in an overlay, whether or not the
8968 overlay is mapped. This allows most @value{GDBN} commands, like
8969 @code{break} and @code{disassemble}, to work normally, even on unmapped
8970 code. However, @value{GDBN}'s breakpoint support has some limitations:
8974 @cindex breakpoints in overlays
8975 @cindex overlays, setting breakpoints in
8976 You can set breakpoints in functions in unmapped overlays, as long as
8977 @value{GDBN} can write to the overlay at its load address.
8979 @value{GDBN} can not set hardware or simulator-based breakpoints in
8980 unmapped overlays. However, if you set a breakpoint at the end of your
8981 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
8982 you are using manual overlay management), @value{GDBN} will re-set its
8983 breakpoints properly.
8987 @node Automatic Overlay Debugging
8988 @section Automatic Overlay Debugging
8989 @cindex automatic overlay debugging
8991 @value{GDBN} can automatically track which overlays are mapped and which
8992 are not, given some simple co-operation from the overlay manager in the
8993 inferior. If you enable automatic overlay debugging with the
8994 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
8995 looks in the inferior's memory for certain variables describing the
8996 current state of the overlays.
8998 Here are the variables your overlay manager must define to support
8999 @value{GDBN}'s automatic overlay debugging:
9003 @item @code{_ovly_table}:
9004 This variable must be an array of the following structures:
9009 /* The overlay's mapped address. */
9012 /* The size of the overlay, in bytes. */
9015 /* The overlay's load address. */
9018 /* Non-zero if the overlay is currently mapped;
9020 unsigned long mapped;
9024 @item @code{_novlys}:
9025 This variable must be a four-byte signed integer, holding the total
9026 number of elements in @code{_ovly_table}.
9030 To decide whether a particular overlay is mapped or not, @value{GDBN}
9031 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
9032 @code{lma} members equal the VMA and LMA of the overlay's section in the
9033 executable file. When @value{GDBN} finds a matching entry, it consults
9034 the entry's @code{mapped} member to determine whether the overlay is
9037 In addition, your overlay manager may define a function called
9038 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
9039 will silently set a breakpoint there. If the overlay manager then
9040 calls this function whenever it has changed the overlay table, this
9041 will enable @value{GDBN} to accurately keep track of which overlays
9042 are in program memory, and update any breakpoints that may be set
9043 in overlays. This will allow breakpoints to work even if the
9044 overlays are kept in ROM or other non-writable memory while they
9045 are not being executed.
9047 @node Overlay Sample Program
9048 @section Overlay Sample Program
9049 @cindex overlay example program
9051 When linking a program which uses overlays, you must place the overlays
9052 at their load addresses, while relocating them to run at their mapped
9053 addresses. To do this, you must write a linker script (@pxref{Overlay
9054 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
9055 since linker scripts are specific to a particular host system, target
9056 architecture, and target memory layout, this manual cannot provide
9057 portable sample code demonstrating @value{GDBN}'s overlay support.
9059 However, the @value{GDBN} source distribution does contain an overlaid
9060 program, with linker scripts for a few systems, as part of its test
9061 suite. The program consists of the following files from
9062 @file{gdb/testsuite/gdb.base}:
9066 The main program file.
9068 A simple overlay manager, used by @file{overlays.c}.
9073 Overlay modules, loaded and used by @file{overlays.c}.
9076 Linker scripts for linking the test program on the @code{d10v-elf}
9077 and @code{m32r-elf} targets.
9080 You can build the test program using the @code{d10v-elf} GCC
9081 cross-compiler like this:
9084 $ d10v-elf-gcc -g -c overlays.c
9085 $ d10v-elf-gcc -g -c ovlymgr.c
9086 $ d10v-elf-gcc -g -c foo.c
9087 $ d10v-elf-gcc -g -c bar.c
9088 $ d10v-elf-gcc -g -c baz.c
9089 $ d10v-elf-gcc -g -c grbx.c
9090 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
9091 baz.o grbx.o -Wl,-Td10v.ld -o overlays
9094 The build process is identical for any other architecture, except that
9095 you must substitute the appropriate compiler and linker script for the
9096 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
9100 @chapter Using @value{GDBN} with Different Languages
9103 Although programming languages generally have common aspects, they are
9104 rarely expressed in the same manner. For instance, in ANSI C,
9105 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
9106 Modula-2, it is accomplished by @code{p^}. Values can also be
9107 represented (and displayed) differently. Hex numbers in C appear as
9108 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
9110 @cindex working language
9111 Language-specific information is built into @value{GDBN} for some languages,
9112 allowing you to express operations like the above in your program's
9113 native language, and allowing @value{GDBN} to output values in a manner
9114 consistent with the syntax of your program's native language. The
9115 language you use to build expressions is called the @dfn{working
9119 * Setting:: Switching between source languages
9120 * Show:: Displaying the language
9121 * Checks:: Type and range checks
9122 * Supported Languages:: Supported languages
9123 * Unsupported Languages:: Unsupported languages
9127 @section Switching Between Source Languages
9129 There are two ways to control the working language---either have @value{GDBN}
9130 set it automatically, or select it manually yourself. You can use the
9131 @code{set language} command for either purpose. On startup, @value{GDBN}
9132 defaults to setting the language automatically. The working language is
9133 used to determine how expressions you type are interpreted, how values
9136 In addition to the working language, every source file that
9137 @value{GDBN} knows about has its own working language. For some object
9138 file formats, the compiler might indicate which language a particular
9139 source file is in. However, most of the time @value{GDBN} infers the
9140 language from the name of the file. The language of a source file
9141 controls whether C@t{++} names are demangled---this way @code{backtrace} can
9142 show each frame appropriately for its own language. There is no way to
9143 set the language of a source file from within @value{GDBN}, but you can
9144 set the language associated with a filename extension. @xref{Show, ,
9145 Displaying the Language}.
9147 This is most commonly a problem when you use a program, such
9148 as @code{cfront} or @code{f2c}, that generates C but is written in
9149 another language. In that case, make the
9150 program use @code{#line} directives in its C output; that way
9151 @value{GDBN} will know the correct language of the source code of the original
9152 program, and will display that source code, not the generated C code.
9155 * Filenames:: Filename extensions and languages.
9156 * Manually:: Setting the working language manually
9157 * Automatically:: Having @value{GDBN} infer the source language
9161 @subsection List of Filename Extensions and Languages
9163 If a source file name ends in one of the following extensions, then
9164 @value{GDBN} infers that its language is the one indicated.
9185 Objective-C source file
9192 Modula-2 source file
9196 Assembler source file. This actually behaves almost like C, but
9197 @value{GDBN} does not skip over function prologues when stepping.
9200 In addition, you may set the language associated with a filename
9201 extension. @xref{Show, , Displaying the Language}.
9204 @subsection Setting the Working Language
9206 If you allow @value{GDBN} to set the language automatically,
9207 expressions are interpreted the same way in your debugging session and
9210 @kindex set language
9211 If you wish, you may set the language manually. To do this, issue the
9212 command @samp{set language @var{lang}}, where @var{lang} is the name of
9214 @code{c} or @code{modula-2}.
9215 For a list of the supported languages, type @samp{set language}.
9217 Setting the language manually prevents @value{GDBN} from updating the working
9218 language automatically. This can lead to confusion if you try
9219 to debug a program when the working language is not the same as the
9220 source language, when an expression is acceptable to both
9221 languages---but means different things. For instance, if the current
9222 source file were written in C, and @value{GDBN} was parsing Modula-2, a
9230 might not have the effect you intended. In C, this means to add
9231 @code{b} and @code{c} and place the result in @code{a}. The result
9232 printed would be the value of @code{a}. In Modula-2, this means to compare
9233 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
9236 @subsection Having @value{GDBN} Infer the Source Language
9238 To have @value{GDBN} set the working language automatically, use
9239 @samp{set language local} or @samp{set language auto}. @value{GDBN}
9240 then infers the working language. That is, when your program stops in a
9241 frame (usually by encountering a breakpoint), @value{GDBN} sets the
9242 working language to the language recorded for the function in that
9243 frame. If the language for a frame is unknown (that is, if the function
9244 or block corresponding to the frame was defined in a source file that
9245 does not have a recognized extension), the current working language is
9246 not changed, and @value{GDBN} issues a warning.
9248 This may not seem necessary for most programs, which are written
9249 entirely in one source language. However, program modules and libraries
9250 written in one source language can be used by a main program written in
9251 a different source language. Using @samp{set language auto} in this
9252 case frees you from having to set the working language manually.
9255 @section Displaying the Language
9257 The following commands help you find out which language is the
9258 working language, and also what language source files were written in.
9262 @kindex show language
9263 Display the current working language. This is the
9264 language you can use with commands such as @code{print} to
9265 build and compute expressions that may involve variables in your program.
9268 @kindex info frame@r{, show the source language}
9269 Display the source language for this frame. This language becomes the
9270 working language if you use an identifier from this frame.
9271 @xref{Frame Info, ,Information about a Frame}, to identify the other
9272 information listed here.
9275 @kindex info source@r{, show the source language}
9276 Display the source language of this source file.
9277 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
9278 information listed here.
9281 In unusual circumstances, you may have source files with extensions
9282 not in the standard list. You can then set the extension associated
9283 with a language explicitly:
9286 @item set extension-language @var{ext} @var{language}
9287 @kindex set extension-language
9288 Tell @value{GDBN} that source files with extension @var{ext} are to be
9289 assumed as written in the source language @var{language}.
9291 @item info extensions
9292 @kindex info extensions
9293 List all the filename extensions and the associated languages.
9297 @section Type and Range Checking
9300 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
9301 checking are included, but they do not yet have any effect. This
9302 section documents the intended facilities.
9304 @c FIXME remove warning when type/range code added
9306 Some languages are designed to guard you against making seemingly common
9307 errors through a series of compile- and run-time checks. These include
9308 checking the type of arguments to functions and operators, and making
9309 sure mathematical overflows are caught at run time. Checks such as
9310 these help to ensure a program's correctness once it has been compiled
9311 by eliminating type mismatches, and providing active checks for range
9312 errors when your program is running.
9314 @value{GDBN} can check for conditions like the above if you wish.
9315 Although @value{GDBN} does not check the statements in your program,
9316 it can check expressions entered directly into @value{GDBN} for
9317 evaluation via the @code{print} command, for example. As with the
9318 working language, @value{GDBN} can also decide whether or not to check
9319 automatically based on your program's source language.
9320 @xref{Supported Languages, ,Supported Languages}, for the default
9321 settings of supported languages.
9324 * Type Checking:: An overview of type checking
9325 * Range Checking:: An overview of range checking
9328 @cindex type checking
9329 @cindex checks, type
9331 @subsection An Overview of Type Checking
9333 Some languages, such as Modula-2, are strongly typed, meaning that the
9334 arguments to operators and functions have to be of the correct type,
9335 otherwise an error occurs. These checks prevent type mismatch
9336 errors from ever causing any run-time problems. For example,
9344 The second example fails because the @code{CARDINAL} 1 is not
9345 type-compatible with the @code{REAL} 2.3.
9347 For the expressions you use in @value{GDBN} commands, you can tell the
9348 @value{GDBN} type checker to skip checking;
9349 to treat any mismatches as errors and abandon the expression;
9350 or to only issue warnings when type mismatches occur,
9351 but evaluate the expression anyway. When you choose the last of
9352 these, @value{GDBN} evaluates expressions like the second example above, but
9353 also issues a warning.
9355 Even if you turn type checking off, there may be other reasons
9356 related to type that prevent @value{GDBN} from evaluating an expression.
9357 For instance, @value{GDBN} does not know how to add an @code{int} and
9358 a @code{struct foo}. These particular type errors have nothing to do
9359 with the language in use, and usually arise from expressions, such as
9360 the one described above, which make little sense to evaluate anyway.
9362 Each language defines to what degree it is strict about type. For
9363 instance, both Modula-2 and C require the arguments to arithmetical
9364 operators to be numbers. In C, enumerated types and pointers can be
9365 represented as numbers, so that they are valid arguments to mathematical
9366 operators. @xref{Supported Languages, ,Supported Languages}, for further
9367 details on specific languages.
9369 @value{GDBN} provides some additional commands for controlling the type checker:
9371 @kindex set check type
9372 @kindex show check type
9374 @item set check type auto
9375 Set type checking on or off based on the current working language.
9376 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9379 @item set check type on
9380 @itemx set check type off
9381 Set type checking on or off, overriding the default setting for the
9382 current working language. Issue a warning if the setting does not
9383 match the language default. If any type mismatches occur in
9384 evaluating an expression while type checking is on, @value{GDBN} prints a
9385 message and aborts evaluation of the expression.
9387 @item set check type warn
9388 Cause the type checker to issue warnings, but to always attempt to
9389 evaluate the expression. Evaluating the expression may still
9390 be impossible for other reasons. For example, @value{GDBN} cannot add
9391 numbers and structures.
9394 Show the current setting of the type checker, and whether or not @value{GDBN}
9395 is setting it automatically.
9398 @cindex range checking
9399 @cindex checks, range
9400 @node Range Checking
9401 @subsection An Overview of Range Checking
9403 In some languages (such as Modula-2), it is an error to exceed the
9404 bounds of a type; this is enforced with run-time checks. Such range
9405 checking is meant to ensure program correctness by making sure
9406 computations do not overflow, or indices on an array element access do
9407 not exceed the bounds of the array.
9409 For expressions you use in @value{GDBN} commands, you can tell
9410 @value{GDBN} to treat range errors in one of three ways: ignore them,
9411 always treat them as errors and abandon the expression, or issue
9412 warnings but evaluate the expression anyway.
9414 A range error can result from numerical overflow, from exceeding an
9415 array index bound, or when you type a constant that is not a member
9416 of any type. Some languages, however, do not treat overflows as an
9417 error. In many implementations of C, mathematical overflow causes the
9418 result to ``wrap around'' to lower values---for example, if @var{m} is
9419 the largest integer value, and @var{s} is the smallest, then
9422 @var{m} + 1 @result{} @var{s}
9425 This, too, is specific to individual languages, and in some cases
9426 specific to individual compilers or machines. @xref{Supported Languages, ,
9427 Supported Languages}, for further details on specific languages.
9429 @value{GDBN} provides some additional commands for controlling the range checker:
9431 @kindex set check range
9432 @kindex show check range
9434 @item set check range auto
9435 Set range checking on or off based on the current working language.
9436 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9439 @item set check range on
9440 @itemx set check range off
9441 Set range checking on or off, overriding the default setting for the
9442 current working language. A warning is issued if the setting does not
9443 match the language default. If a range error occurs and range checking is on,
9444 then a message is printed and evaluation of the expression is aborted.
9446 @item set check range warn
9447 Output messages when the @value{GDBN} range checker detects a range error,
9448 but attempt to evaluate the expression anyway. Evaluating the
9449 expression may still be impossible for other reasons, such as accessing
9450 memory that the process does not own (a typical example from many Unix
9454 Show the current setting of the range checker, and whether or not it is
9455 being set automatically by @value{GDBN}.
9458 @node Supported Languages
9459 @section Supported Languages
9461 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
9462 assembly, Modula-2, and Ada.
9463 @c This is false ...
9464 Some @value{GDBN} features may be used in expressions regardless of the
9465 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
9466 and the @samp{@{type@}addr} construct (@pxref{Expressions,
9467 ,Expressions}) can be used with the constructs of any supported
9470 The following sections detail to what degree each source language is
9471 supported by @value{GDBN}. These sections are not meant to be language
9472 tutorials or references, but serve only as a reference guide to what the
9473 @value{GDBN} expression parser accepts, and what input and output
9474 formats should look like for different languages. There are many good
9475 books written on each of these languages; please look to these for a
9476 language reference or tutorial.
9480 * Objective-C:: Objective-C
9483 * Modula-2:: Modula-2
9488 @subsection C and C@t{++}
9490 @cindex C and C@t{++}
9491 @cindex expressions in C or C@t{++}
9493 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
9494 to both languages. Whenever this is the case, we discuss those languages
9498 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
9499 @cindex @sc{gnu} C@t{++}
9500 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
9501 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
9502 effectively, you must compile your C@t{++} programs with a supported
9503 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
9504 compiler (@code{aCC}).
9506 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
9507 format; if it doesn't work on your system, try the stabs+ debugging
9508 format. You can select those formats explicitly with the @code{g++}
9509 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
9510 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
9511 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
9514 * C Operators:: C and C@t{++} operators
9515 * C Constants:: C and C@t{++} constants
9516 * C Plus Plus Expressions:: C@t{++} expressions
9517 * C Defaults:: Default settings for C and C@t{++}
9518 * C Checks:: C and C@t{++} type and range checks
9519 * Debugging C:: @value{GDBN} and C
9520 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
9521 * Decimal Floating Point:: Numbers in Decimal Floating Point format
9525 @subsubsection C and C@t{++} Operators
9527 @cindex C and C@t{++} operators
9529 Operators must be defined on values of specific types. For instance,
9530 @code{+} is defined on numbers, but not on structures. Operators are
9531 often defined on groups of types.
9533 For the purposes of C and C@t{++}, the following definitions hold:
9538 @emph{Integral types} include @code{int} with any of its storage-class
9539 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
9542 @emph{Floating-point types} include @code{float}, @code{double}, and
9543 @code{long double} (if supported by the target platform).
9546 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
9549 @emph{Scalar types} include all of the above.
9554 The following operators are supported. They are listed here
9555 in order of increasing precedence:
9559 The comma or sequencing operator. Expressions in a comma-separated list
9560 are evaluated from left to right, with the result of the entire
9561 expression being the last expression evaluated.
9564 Assignment. The value of an assignment expression is the value
9565 assigned. Defined on scalar types.
9568 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
9569 and translated to @w{@code{@var{a} = @var{a op b}}}.
9570 @w{@code{@var{op}=}} and @code{=} have the same precedence.
9571 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
9572 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
9575 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
9576 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
9580 Logical @sc{or}. Defined on integral types.
9583 Logical @sc{and}. Defined on integral types.
9586 Bitwise @sc{or}. Defined on integral types.
9589 Bitwise exclusive-@sc{or}. Defined on integral types.
9592 Bitwise @sc{and}. Defined on integral types.
9595 Equality and inequality. Defined on scalar types. The value of these
9596 expressions is 0 for false and non-zero for true.
9598 @item <@r{, }>@r{, }<=@r{, }>=
9599 Less than, greater than, less than or equal, greater than or equal.
9600 Defined on scalar types. The value of these expressions is 0 for false
9601 and non-zero for true.
9604 left shift, and right shift. Defined on integral types.
9607 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9610 Addition and subtraction. Defined on integral types, floating-point types and
9613 @item *@r{, }/@r{, }%
9614 Multiplication, division, and modulus. Multiplication and division are
9615 defined on integral and floating-point types. Modulus is defined on
9619 Increment and decrement. When appearing before a variable, the
9620 operation is performed before the variable is used in an expression;
9621 when appearing after it, the variable's value is used before the
9622 operation takes place.
9625 Pointer dereferencing. Defined on pointer types. Same precedence as
9629 Address operator. Defined on variables. Same precedence as @code{++}.
9631 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
9632 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
9633 to examine the address
9634 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
9638 Negative. Defined on integral and floating-point types. Same
9639 precedence as @code{++}.
9642 Logical negation. Defined on integral types. Same precedence as
9646 Bitwise complement operator. Defined on integral types. Same precedence as
9651 Structure member, and pointer-to-structure member. For convenience,
9652 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
9653 pointer based on the stored type information.
9654 Defined on @code{struct} and @code{union} data.
9657 Dereferences of pointers to members.
9660 Array indexing. @code{@var{a}[@var{i}]} is defined as
9661 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
9664 Function parameter list. Same precedence as @code{->}.
9667 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
9668 and @code{class} types.
9671 Doubled colons also represent the @value{GDBN} scope operator
9672 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
9676 If an operator is redefined in the user code, @value{GDBN} usually
9677 attempts to invoke the redefined version instead of using the operator's
9681 @subsubsection C and C@t{++} Constants
9683 @cindex C and C@t{++} constants
9685 @value{GDBN} allows you to express the constants of C and C@t{++} in the
9690 Integer constants are a sequence of digits. Octal constants are
9691 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
9692 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
9693 @samp{l}, specifying that the constant should be treated as a
9697 Floating point constants are a sequence of digits, followed by a decimal
9698 point, followed by a sequence of digits, and optionally followed by an
9699 exponent. An exponent is of the form:
9700 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
9701 sequence of digits. The @samp{+} is optional for positive exponents.
9702 A floating-point constant may also end with a letter @samp{f} or
9703 @samp{F}, specifying that the constant should be treated as being of
9704 the @code{float} (as opposed to the default @code{double}) type; or with
9705 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
9709 Enumerated constants consist of enumerated identifiers, or their
9710 integral equivalents.
9713 Character constants are a single character surrounded by single quotes
9714 (@code{'}), or a number---the ordinal value of the corresponding character
9715 (usually its @sc{ascii} value). Within quotes, the single character may
9716 be represented by a letter or by @dfn{escape sequences}, which are of
9717 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
9718 of the character's ordinal value; or of the form @samp{\@var{x}}, where
9719 @samp{@var{x}} is a predefined special character---for example,
9720 @samp{\n} for newline.
9723 String constants are a sequence of character constants surrounded by
9724 double quotes (@code{"}). Any valid character constant (as described
9725 above) may appear. Double quotes within the string must be preceded by
9726 a backslash, so for instance @samp{"a\"b'c"} is a string of five
9730 Pointer constants are an integral value. You can also write pointers
9731 to constants using the C operator @samp{&}.
9734 Array constants are comma-separated lists surrounded by braces @samp{@{}
9735 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
9736 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
9737 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
9740 @node C Plus Plus Expressions
9741 @subsubsection C@t{++} Expressions
9743 @cindex expressions in C@t{++}
9744 @value{GDBN} expression handling can interpret most C@t{++} expressions.
9746 @cindex debugging C@t{++} programs
9747 @cindex C@t{++} compilers
9748 @cindex debug formats and C@t{++}
9749 @cindex @value{NGCC} and C@t{++}
9751 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
9752 proper compiler and the proper debug format. Currently, @value{GDBN}
9753 works best when debugging C@t{++} code that is compiled with
9754 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
9755 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
9756 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
9757 stabs+ as their default debug format, so you usually don't need to
9758 specify a debug format explicitly. Other compilers and/or debug formats
9759 are likely to work badly or not at all when using @value{GDBN} to debug
9765 @cindex member functions
9767 Member function calls are allowed; you can use expressions like
9770 count = aml->GetOriginal(x, y)
9773 @vindex this@r{, inside C@t{++} member functions}
9774 @cindex namespace in C@t{++}
9776 While a member function is active (in the selected stack frame), your
9777 expressions have the same namespace available as the member function;
9778 that is, @value{GDBN} allows implicit references to the class instance
9779 pointer @code{this} following the same rules as C@t{++}.
9781 @cindex call overloaded functions
9782 @cindex overloaded functions, calling
9783 @cindex type conversions in C@t{++}
9785 You can call overloaded functions; @value{GDBN} resolves the function
9786 call to the right definition, with some restrictions. @value{GDBN} does not
9787 perform overload resolution involving user-defined type conversions,
9788 calls to constructors, or instantiations of templates that do not exist
9789 in the program. It also cannot handle ellipsis argument lists or
9792 It does perform integral conversions and promotions, floating-point
9793 promotions, arithmetic conversions, pointer conversions, conversions of
9794 class objects to base classes, and standard conversions such as those of
9795 functions or arrays to pointers; it requires an exact match on the
9796 number of function arguments.
9798 Overload resolution is always performed, unless you have specified
9799 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
9800 ,@value{GDBN} Features for C@t{++}}.
9802 You must specify @code{set overload-resolution off} in order to use an
9803 explicit function signature to call an overloaded function, as in
9805 p 'foo(char,int)'('x', 13)
9808 The @value{GDBN} command-completion facility can simplify this;
9809 see @ref{Completion, ,Command Completion}.
9811 @cindex reference declarations
9813 @value{GDBN} understands variables declared as C@t{++} references; you can use
9814 them in expressions just as you do in C@t{++} source---they are automatically
9817 In the parameter list shown when @value{GDBN} displays a frame, the values of
9818 reference variables are not displayed (unlike other variables); this
9819 avoids clutter, since references are often used for large structures.
9820 The @emph{address} of a reference variable is always shown, unless
9821 you have specified @samp{set print address off}.
9824 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
9825 expressions can use it just as expressions in your program do. Since
9826 one scope may be defined in another, you can use @code{::} repeatedly if
9827 necessary, for example in an expression like
9828 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
9829 resolving name scope by reference to source files, in both C and C@t{++}
9830 debugging (@pxref{Variables, ,Program Variables}).
9833 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
9834 calling virtual functions correctly, printing out virtual bases of
9835 objects, calling functions in a base subobject, casting objects, and
9836 invoking user-defined operators.
9839 @subsubsection C and C@t{++} Defaults
9841 @cindex C and C@t{++} defaults
9843 If you allow @value{GDBN} to set type and range checking automatically, they
9844 both default to @code{off} whenever the working language changes to
9845 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
9846 selects the working language.
9848 If you allow @value{GDBN} to set the language automatically, it
9849 recognizes source files whose names end with @file{.c}, @file{.C}, or
9850 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
9851 these files, it sets the working language to C or C@t{++}.
9852 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
9853 for further details.
9855 @c Type checking is (a) primarily motivated by Modula-2, and (b)
9856 @c unimplemented. If (b) changes, it might make sense to let this node
9857 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
9860 @subsubsection C and C@t{++} Type and Range Checks
9862 @cindex C and C@t{++} checks
9864 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
9865 is not used. However, if you turn type checking on, @value{GDBN}
9866 considers two variables type equivalent if:
9870 The two variables are structured and have the same structure, union, or
9874 The two variables have the same type name, or types that have been
9875 declared equivalent through @code{typedef}.
9878 @c leaving this out because neither J Gilmore nor R Pesch understand it.
9881 The two @code{struct}, @code{union}, or @code{enum} variables are
9882 declared in the same declaration. (Note: this may not be true for all C
9887 Range checking, if turned on, is done on mathematical operations. Array
9888 indices are not checked, since they are often used to index a pointer
9889 that is not itself an array.
9892 @subsubsection @value{GDBN} and C
9894 The @code{set print union} and @code{show print union} commands apply to
9895 the @code{union} type. When set to @samp{on}, any @code{union} that is
9896 inside a @code{struct} or @code{class} is also printed. Otherwise, it
9897 appears as @samp{@{...@}}.
9899 The @code{@@} operator aids in the debugging of dynamic arrays, formed
9900 with pointers and a memory allocation function. @xref{Expressions,
9903 @node Debugging C Plus Plus
9904 @subsubsection @value{GDBN} Features for C@t{++}
9906 @cindex commands for C@t{++}
9908 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
9909 designed specifically for use with C@t{++}. Here is a summary:
9912 @cindex break in overloaded functions
9913 @item @r{breakpoint menus}
9914 When you want a breakpoint in a function whose name is overloaded,
9915 @value{GDBN} has the capability to display a menu of possible breakpoint
9916 locations to help you specify which function definition you want.
9917 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
9919 @cindex overloading in C@t{++}
9920 @item rbreak @var{regex}
9921 Setting breakpoints using regular expressions is helpful for setting
9922 breakpoints on overloaded functions that are not members of any special
9924 @xref{Set Breaks, ,Setting Breakpoints}.
9926 @cindex C@t{++} exception handling
9929 Debug C@t{++} exception handling using these commands. @xref{Set
9930 Catchpoints, , Setting Catchpoints}.
9933 @item ptype @var{typename}
9934 Print inheritance relationships as well as other information for type
9936 @xref{Symbols, ,Examining the Symbol Table}.
9938 @cindex C@t{++} symbol display
9939 @item set print demangle
9940 @itemx show print demangle
9941 @itemx set print asm-demangle
9942 @itemx show print asm-demangle
9943 Control whether C@t{++} symbols display in their source form, both when
9944 displaying code as C@t{++} source and when displaying disassemblies.
9945 @xref{Print Settings, ,Print Settings}.
9947 @item set print object
9948 @itemx show print object
9949 Choose whether to print derived (actual) or declared types of objects.
9950 @xref{Print Settings, ,Print Settings}.
9952 @item set print vtbl
9953 @itemx show print vtbl
9954 Control the format for printing virtual function tables.
9955 @xref{Print Settings, ,Print Settings}.
9956 (The @code{vtbl} commands do not work on programs compiled with the HP
9957 ANSI C@t{++} compiler (@code{aCC}).)
9959 @kindex set overload-resolution
9960 @cindex overloaded functions, overload resolution
9961 @item set overload-resolution on
9962 Enable overload resolution for C@t{++} expression evaluation. The default
9963 is on. For overloaded functions, @value{GDBN} evaluates the arguments
9964 and searches for a function whose signature matches the argument types,
9965 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
9966 Expressions, ,C@t{++} Expressions}, for details).
9967 If it cannot find a match, it emits a message.
9969 @item set overload-resolution off
9970 Disable overload resolution for C@t{++} expression evaluation. For
9971 overloaded functions that are not class member functions, @value{GDBN}
9972 chooses the first function of the specified name that it finds in the
9973 symbol table, whether or not its arguments are of the correct type. For
9974 overloaded functions that are class member functions, @value{GDBN}
9975 searches for a function whose signature @emph{exactly} matches the
9978 @kindex show overload-resolution
9979 @item show overload-resolution
9980 Show the current setting of overload resolution.
9982 @item @r{Overloaded symbol names}
9983 You can specify a particular definition of an overloaded symbol, using
9984 the same notation that is used to declare such symbols in C@t{++}: type
9985 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
9986 also use the @value{GDBN} command-line word completion facilities to list the
9987 available choices, or to finish the type list for you.
9988 @xref{Completion,, Command Completion}, for details on how to do this.
9991 @node Decimal Floating Point
9992 @subsubsection Decimal Floating Point format
9993 @cindex decimal floating point format
9995 @value{GDBN} can examine, set and perform computations with numbers in
9996 decimal floating point format, which in the C language correspond to the
9997 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
9998 specified by the extension to support decimal floating-point arithmetic.
10000 There are two encodings in use, depending on the architecture: BID (Binary
10001 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
10002 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
10005 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
10006 to manipulate decimal floating point numbers, it is not possible to convert
10007 (using a cast, for example) integers wider than 32-bit to decimal float.
10009 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
10010 point computations, error checking in decimal float operations ignores
10011 underflow, overflow and divide by zero exceptions.
10013 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
10014 to inspect @code{_Decimal128} values stored in floating point registers. See
10015 @ref{PowerPC,,PowerPC} for more details.
10018 @subsection Objective-C
10020 @cindex Objective-C
10021 This section provides information about some commands and command
10022 options that are useful for debugging Objective-C code. See also
10023 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
10024 few more commands specific to Objective-C support.
10027 * Method Names in Commands::
10028 * The Print Command with Objective-C::
10031 @node Method Names in Commands
10032 @subsubsection Method Names in Commands
10034 The following commands have been extended to accept Objective-C method
10035 names as line specifications:
10037 @kindex clear@r{, and Objective-C}
10038 @kindex break@r{, and Objective-C}
10039 @kindex info line@r{, and Objective-C}
10040 @kindex jump@r{, and Objective-C}
10041 @kindex list@r{, and Objective-C}
10045 @item @code{info line}
10050 A fully qualified Objective-C method name is specified as
10053 -[@var{Class} @var{methodName}]
10056 where the minus sign is used to indicate an instance method and a
10057 plus sign (not shown) is used to indicate a class method. The class
10058 name @var{Class} and method name @var{methodName} are enclosed in
10059 brackets, similar to the way messages are specified in Objective-C
10060 source code. For example, to set a breakpoint at the @code{create}
10061 instance method of class @code{Fruit} in the program currently being
10065 break -[Fruit create]
10068 To list ten program lines around the @code{initialize} class method,
10072 list +[NSText initialize]
10075 In the current version of @value{GDBN}, the plus or minus sign is
10076 required. In future versions of @value{GDBN}, the plus or minus
10077 sign will be optional, but you can use it to narrow the search. It
10078 is also possible to specify just a method name:
10084 You must specify the complete method name, including any colons. If
10085 your program's source files contain more than one @code{create} method,
10086 you'll be presented with a numbered list of classes that implement that
10087 method. Indicate your choice by number, or type @samp{0} to exit if
10090 As another example, to clear a breakpoint established at the
10091 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
10094 clear -[NSWindow makeKeyAndOrderFront:]
10097 @node The Print Command with Objective-C
10098 @subsubsection The Print Command With Objective-C
10099 @cindex Objective-C, print objects
10100 @kindex print-object
10101 @kindex po @r{(@code{print-object})}
10103 The print command has also been extended to accept methods. For example:
10106 print -[@var{object} hash]
10109 @cindex print an Objective-C object description
10110 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
10112 will tell @value{GDBN} to send the @code{hash} message to @var{object}
10113 and print the result. Also, an additional command has been added,
10114 @code{print-object} or @code{po} for short, which is meant to print
10115 the description of an object. However, this command may only work
10116 with certain Objective-C libraries that have a particular hook
10117 function, @code{_NSPrintForDebugger}, defined.
10120 @subsection Fortran
10121 @cindex Fortran-specific support in @value{GDBN}
10123 @value{GDBN} can be used to debug programs written in Fortran, but it
10124 currently supports only the features of Fortran 77 language.
10126 @cindex trailing underscore, in Fortran symbols
10127 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
10128 among them) append an underscore to the names of variables and
10129 functions. When you debug programs compiled by those compilers, you
10130 will need to refer to variables and functions with a trailing
10134 * Fortran Operators:: Fortran operators and expressions
10135 * Fortran Defaults:: Default settings for Fortran
10136 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
10139 @node Fortran Operators
10140 @subsubsection Fortran Operators and Expressions
10142 @cindex Fortran operators and expressions
10144 Operators must be defined on values of specific types. For instance,
10145 @code{+} is defined on numbers, but not on characters or other non-
10146 arithmetic types. Operators are often defined on groups of types.
10150 The exponentiation operator. It raises the first operand to the power
10154 The range operator. Normally used in the form of array(low:high) to
10155 represent a section of array.
10158 The access component operator. Normally used to access elements in derived
10159 types. Also suitable for unions. As unions aren't part of regular Fortran,
10160 this can only happen when accessing a register that uses a gdbarch-defined
10164 @node Fortran Defaults
10165 @subsubsection Fortran Defaults
10167 @cindex Fortran Defaults
10169 Fortran symbols are usually case-insensitive, so @value{GDBN} by
10170 default uses case-insensitive matches for Fortran symbols. You can
10171 change that with the @samp{set case-insensitive} command, see
10172 @ref{Symbols}, for the details.
10174 @node Special Fortran Commands
10175 @subsubsection Special Fortran Commands
10177 @cindex Special Fortran commands
10179 @value{GDBN} has some commands to support Fortran-specific features,
10180 such as displaying common blocks.
10183 @cindex @code{COMMON} blocks, Fortran
10184 @kindex info common
10185 @item info common @r{[}@var{common-name}@r{]}
10186 This command prints the values contained in the Fortran @code{COMMON}
10187 block whose name is @var{common-name}. With no argument, the names of
10188 all @code{COMMON} blocks visible at the current program location are
10195 @cindex Pascal support in @value{GDBN}, limitations
10196 Debugging Pascal programs which use sets, subranges, file variables, or
10197 nested functions does not currently work. @value{GDBN} does not support
10198 entering expressions, printing values, or similar features using Pascal
10201 The Pascal-specific command @code{set print pascal_static-members}
10202 controls whether static members of Pascal objects are displayed.
10203 @xref{Print Settings, pascal_static-members}.
10206 @subsection Modula-2
10208 @cindex Modula-2, @value{GDBN} support
10210 The extensions made to @value{GDBN} to support Modula-2 only support
10211 output from the @sc{gnu} Modula-2 compiler (which is currently being
10212 developed). Other Modula-2 compilers are not currently supported, and
10213 attempting to debug executables produced by them is most likely
10214 to give an error as @value{GDBN} reads in the executable's symbol
10217 @cindex expressions in Modula-2
10219 * M2 Operators:: Built-in operators
10220 * Built-In Func/Proc:: Built-in functions and procedures
10221 * M2 Constants:: Modula-2 constants
10222 * M2 Types:: Modula-2 types
10223 * M2 Defaults:: Default settings for Modula-2
10224 * Deviations:: Deviations from standard Modula-2
10225 * M2 Checks:: Modula-2 type and range checks
10226 * M2 Scope:: The scope operators @code{::} and @code{.}
10227 * GDB/M2:: @value{GDBN} and Modula-2
10231 @subsubsection Operators
10232 @cindex Modula-2 operators
10234 Operators must be defined on values of specific types. For instance,
10235 @code{+} is defined on numbers, but not on structures. Operators are
10236 often defined on groups of types. For the purposes of Modula-2, the
10237 following definitions hold:
10242 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
10246 @emph{Character types} consist of @code{CHAR} and its subranges.
10249 @emph{Floating-point types} consist of @code{REAL}.
10252 @emph{Pointer types} consist of anything declared as @code{POINTER TO
10256 @emph{Scalar types} consist of all of the above.
10259 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
10262 @emph{Boolean types} consist of @code{BOOLEAN}.
10266 The following operators are supported, and appear in order of
10267 increasing precedence:
10271 Function argument or array index separator.
10274 Assignment. The value of @var{var} @code{:=} @var{value} is
10278 Less than, greater than on integral, floating-point, or enumerated
10282 Less than or equal to, greater than or equal to
10283 on integral, floating-point and enumerated types, or set inclusion on
10284 set types. Same precedence as @code{<}.
10286 @item =@r{, }<>@r{, }#
10287 Equality and two ways of expressing inequality, valid on scalar types.
10288 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
10289 available for inequality, since @code{#} conflicts with the script
10293 Set membership. Defined on set types and the types of their members.
10294 Same precedence as @code{<}.
10297 Boolean disjunction. Defined on boolean types.
10300 Boolean conjunction. Defined on boolean types.
10303 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
10306 Addition and subtraction on integral and floating-point types, or union
10307 and difference on set types.
10310 Multiplication on integral and floating-point types, or set intersection
10314 Division on floating-point types, or symmetric set difference on set
10315 types. Same precedence as @code{*}.
10318 Integer division and remainder. Defined on integral types. Same
10319 precedence as @code{*}.
10322 Negative. Defined on @code{INTEGER} and @code{REAL} data.
10325 Pointer dereferencing. Defined on pointer types.
10328 Boolean negation. Defined on boolean types. Same precedence as
10332 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
10333 precedence as @code{^}.
10336 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
10339 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
10343 @value{GDBN} and Modula-2 scope operators.
10347 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
10348 treats the use of the operator @code{IN}, or the use of operators
10349 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
10350 @code{<=}, and @code{>=} on sets as an error.
10354 @node Built-In Func/Proc
10355 @subsubsection Built-in Functions and Procedures
10356 @cindex Modula-2 built-ins
10358 Modula-2 also makes available several built-in procedures and functions.
10359 In describing these, the following metavariables are used:
10364 represents an @code{ARRAY} variable.
10367 represents a @code{CHAR} constant or variable.
10370 represents a variable or constant of integral type.
10373 represents an identifier that belongs to a set. Generally used in the
10374 same function with the metavariable @var{s}. The type of @var{s} should
10375 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
10378 represents a variable or constant of integral or floating-point type.
10381 represents a variable or constant of floating-point type.
10387 represents a variable.
10390 represents a variable or constant of one of many types. See the
10391 explanation of the function for details.
10394 All Modula-2 built-in procedures also return a result, described below.
10398 Returns the absolute value of @var{n}.
10401 If @var{c} is a lower case letter, it returns its upper case
10402 equivalent, otherwise it returns its argument.
10405 Returns the character whose ordinal value is @var{i}.
10408 Decrements the value in the variable @var{v} by one. Returns the new value.
10410 @item DEC(@var{v},@var{i})
10411 Decrements the value in the variable @var{v} by @var{i}. Returns the
10414 @item EXCL(@var{m},@var{s})
10415 Removes the element @var{m} from the set @var{s}. Returns the new
10418 @item FLOAT(@var{i})
10419 Returns the floating point equivalent of the integer @var{i}.
10421 @item HIGH(@var{a})
10422 Returns the index of the last member of @var{a}.
10425 Increments the value in the variable @var{v} by one. Returns the new value.
10427 @item INC(@var{v},@var{i})
10428 Increments the value in the variable @var{v} by @var{i}. Returns the
10431 @item INCL(@var{m},@var{s})
10432 Adds the element @var{m} to the set @var{s} if it is not already
10433 there. Returns the new set.
10436 Returns the maximum value of the type @var{t}.
10439 Returns the minimum value of the type @var{t}.
10442 Returns boolean TRUE if @var{i} is an odd number.
10445 Returns the ordinal value of its argument. For example, the ordinal
10446 value of a character is its @sc{ascii} value (on machines supporting the
10447 @sc{ascii} character set). @var{x} must be of an ordered type, which include
10448 integral, character and enumerated types.
10450 @item SIZE(@var{x})
10451 Returns the size of its argument. @var{x} can be a variable or a type.
10453 @item TRUNC(@var{r})
10454 Returns the integral part of @var{r}.
10456 @item TSIZE(@var{x})
10457 Returns the size of its argument. @var{x} can be a variable or a type.
10459 @item VAL(@var{t},@var{i})
10460 Returns the member of the type @var{t} whose ordinal value is @var{i}.
10464 @emph{Warning:} Sets and their operations are not yet supported, so
10465 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
10469 @cindex Modula-2 constants
10471 @subsubsection Constants
10473 @value{GDBN} allows you to express the constants of Modula-2 in the following
10479 Integer constants are simply a sequence of digits. When used in an
10480 expression, a constant is interpreted to be type-compatible with the
10481 rest of the expression. Hexadecimal integers are specified by a
10482 trailing @samp{H}, and octal integers by a trailing @samp{B}.
10485 Floating point constants appear as a sequence of digits, followed by a
10486 decimal point and another sequence of digits. An optional exponent can
10487 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
10488 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
10489 digits of the floating point constant must be valid decimal (base 10)
10493 Character constants consist of a single character enclosed by a pair of
10494 like quotes, either single (@code{'}) or double (@code{"}). They may
10495 also be expressed by their ordinal value (their @sc{ascii} value, usually)
10496 followed by a @samp{C}.
10499 String constants consist of a sequence of characters enclosed by a
10500 pair of like quotes, either single (@code{'}) or double (@code{"}).
10501 Escape sequences in the style of C are also allowed. @xref{C
10502 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
10506 Enumerated constants consist of an enumerated identifier.
10509 Boolean constants consist of the identifiers @code{TRUE} and
10513 Pointer constants consist of integral values only.
10516 Set constants are not yet supported.
10520 @subsubsection Modula-2 Types
10521 @cindex Modula-2 types
10523 Currently @value{GDBN} can print the following data types in Modula-2
10524 syntax: array types, record types, set types, pointer types, procedure
10525 types, enumerated types, subrange types and base types. You can also
10526 print the contents of variables declared using these type.
10527 This section gives a number of simple source code examples together with
10528 sample @value{GDBN} sessions.
10530 The first example contains the following section of code:
10539 and you can request @value{GDBN} to interrogate the type and value of
10540 @code{r} and @code{s}.
10543 (@value{GDBP}) print s
10545 (@value{GDBP}) ptype s
10547 (@value{GDBP}) print r
10549 (@value{GDBP}) ptype r
10554 Likewise if your source code declares @code{s} as:
10558 s: SET ['A'..'Z'] ;
10562 then you may query the type of @code{s} by:
10565 (@value{GDBP}) ptype s
10566 type = SET ['A'..'Z']
10570 Note that at present you cannot interactively manipulate set
10571 expressions using the debugger.
10573 The following example shows how you might declare an array in Modula-2
10574 and how you can interact with @value{GDBN} to print its type and contents:
10578 s: ARRAY [-10..10] OF CHAR ;
10582 (@value{GDBP}) ptype s
10583 ARRAY [-10..10] OF CHAR
10586 Note that the array handling is not yet complete and although the type
10587 is printed correctly, expression handling still assumes that all
10588 arrays have a lower bound of zero and not @code{-10} as in the example
10591 Here are some more type related Modula-2 examples:
10595 colour = (blue, red, yellow, green) ;
10596 t = [blue..yellow] ;
10604 The @value{GDBN} interaction shows how you can query the data type
10605 and value of a variable.
10608 (@value{GDBP}) print s
10610 (@value{GDBP}) ptype t
10611 type = [blue..yellow]
10615 In this example a Modula-2 array is declared and its contents
10616 displayed. Observe that the contents are written in the same way as
10617 their @code{C} counterparts.
10621 s: ARRAY [1..5] OF CARDINAL ;
10627 (@value{GDBP}) print s
10628 $1 = @{1, 0, 0, 0, 0@}
10629 (@value{GDBP}) ptype s
10630 type = ARRAY [1..5] OF CARDINAL
10633 The Modula-2 language interface to @value{GDBN} also understands
10634 pointer types as shown in this example:
10638 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
10645 and you can request that @value{GDBN} describes the type of @code{s}.
10648 (@value{GDBP}) ptype s
10649 type = POINTER TO ARRAY [1..5] OF CARDINAL
10652 @value{GDBN} handles compound types as we can see in this example.
10653 Here we combine array types, record types, pointer types and subrange
10664 myarray = ARRAY myrange OF CARDINAL ;
10665 myrange = [-2..2] ;
10667 s: POINTER TO ARRAY myrange OF foo ;
10671 and you can ask @value{GDBN} to describe the type of @code{s} as shown
10675 (@value{GDBP}) ptype s
10676 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
10679 f3 : ARRAY [-2..2] OF CARDINAL;
10684 @subsubsection Modula-2 Defaults
10685 @cindex Modula-2 defaults
10687 If type and range checking are set automatically by @value{GDBN}, they
10688 both default to @code{on} whenever the working language changes to
10689 Modula-2. This happens regardless of whether you or @value{GDBN}
10690 selected the working language.
10692 If you allow @value{GDBN} to set the language automatically, then entering
10693 code compiled from a file whose name ends with @file{.mod} sets the
10694 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
10695 Infer the Source Language}, for further details.
10698 @subsubsection Deviations from Standard Modula-2
10699 @cindex Modula-2, deviations from
10701 A few changes have been made to make Modula-2 programs easier to debug.
10702 This is done primarily via loosening its type strictness:
10706 Unlike in standard Modula-2, pointer constants can be formed by
10707 integers. This allows you to modify pointer variables during
10708 debugging. (In standard Modula-2, the actual address contained in a
10709 pointer variable is hidden from you; it can only be modified
10710 through direct assignment to another pointer variable or expression that
10711 returned a pointer.)
10714 C escape sequences can be used in strings and characters to represent
10715 non-printable characters. @value{GDBN} prints out strings with these
10716 escape sequences embedded. Single non-printable characters are
10717 printed using the @samp{CHR(@var{nnn})} format.
10720 The assignment operator (@code{:=}) returns the value of its right-hand
10724 All built-in procedures both modify @emph{and} return their argument.
10728 @subsubsection Modula-2 Type and Range Checks
10729 @cindex Modula-2 checks
10732 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
10735 @c FIXME remove warning when type/range checks added
10737 @value{GDBN} considers two Modula-2 variables type equivalent if:
10741 They are of types that have been declared equivalent via a @code{TYPE
10742 @var{t1} = @var{t2}} statement
10745 They have been declared on the same line. (Note: This is true of the
10746 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
10749 As long as type checking is enabled, any attempt to combine variables
10750 whose types are not equivalent is an error.
10752 Range checking is done on all mathematical operations, assignment, array
10753 index bounds, and all built-in functions and procedures.
10756 @subsubsection The Scope Operators @code{::} and @code{.}
10758 @cindex @code{.}, Modula-2 scope operator
10759 @cindex colon, doubled as scope operator
10761 @vindex colon-colon@r{, in Modula-2}
10762 @c Info cannot handle :: but TeX can.
10765 @vindex ::@r{, in Modula-2}
10768 There are a few subtle differences between the Modula-2 scope operator
10769 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
10774 @var{module} . @var{id}
10775 @var{scope} :: @var{id}
10779 where @var{scope} is the name of a module or a procedure,
10780 @var{module} the name of a module, and @var{id} is any declared
10781 identifier within your program, except another module.
10783 Using the @code{::} operator makes @value{GDBN} search the scope
10784 specified by @var{scope} for the identifier @var{id}. If it is not
10785 found in the specified scope, then @value{GDBN} searches all scopes
10786 enclosing the one specified by @var{scope}.
10788 Using the @code{.} operator makes @value{GDBN} search the current scope for
10789 the identifier specified by @var{id} that was imported from the
10790 definition module specified by @var{module}. With this operator, it is
10791 an error if the identifier @var{id} was not imported from definition
10792 module @var{module}, or if @var{id} is not an identifier in
10796 @subsubsection @value{GDBN} and Modula-2
10798 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
10799 Five subcommands of @code{set print} and @code{show print} apply
10800 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
10801 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
10802 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
10803 analogue in Modula-2.
10805 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
10806 with any language, is not useful with Modula-2. Its
10807 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
10808 created in Modula-2 as they can in C or C@t{++}. However, because an
10809 address can be specified by an integral constant, the construct
10810 @samp{@{@var{type}@}@var{adrexp}} is still useful.
10812 @cindex @code{#} in Modula-2
10813 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
10814 interpreted as the beginning of a comment. Use @code{<>} instead.
10820 The extensions made to @value{GDBN} for Ada only support
10821 output from the @sc{gnu} Ada (GNAT) compiler.
10822 Other Ada compilers are not currently supported, and
10823 attempting to debug executables produced by them is most likely
10827 @cindex expressions in Ada
10829 * Ada Mode Intro:: General remarks on the Ada syntax
10830 and semantics supported by Ada mode
10832 * Omissions from Ada:: Restrictions on the Ada expression syntax.
10833 * Additions to Ada:: Extensions of the Ada expression syntax.
10834 * Stopping Before Main Program:: Debugging the program during elaboration.
10835 * Ada Glitches:: Known peculiarities of Ada mode.
10838 @node Ada Mode Intro
10839 @subsubsection Introduction
10840 @cindex Ada mode, general
10842 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
10843 syntax, with some extensions.
10844 The philosophy behind the design of this subset is
10848 That @value{GDBN} should provide basic literals and access to operations for
10849 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
10850 leaving more sophisticated computations to subprograms written into the
10851 program (which therefore may be called from @value{GDBN}).
10854 That type safety and strict adherence to Ada language restrictions
10855 are not particularly important to the @value{GDBN} user.
10858 That brevity is important to the @value{GDBN} user.
10861 Thus, for brevity, the debugger acts as if there were
10862 implicit @code{with} and @code{use} clauses in effect for all user-written
10863 packages, making it unnecessary to fully qualify most names with
10864 their packages, regardless of context. Where this causes ambiguity,
10865 @value{GDBN} asks the user's intent.
10867 The debugger will start in Ada mode if it detects an Ada main program.
10868 As for other languages, it will enter Ada mode when stopped in a program that
10869 was translated from an Ada source file.
10871 While in Ada mode, you may use `@t{--}' for comments. This is useful
10872 mostly for documenting command files. The standard @value{GDBN} comment
10873 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
10874 middle (to allow based literals).
10876 The debugger supports limited overloading. Given a subprogram call in which
10877 the function symbol has multiple definitions, it will use the number of
10878 actual parameters and some information about their types to attempt to narrow
10879 the set of definitions. It also makes very limited use of context, preferring
10880 procedures to functions in the context of the @code{call} command, and
10881 functions to procedures elsewhere.
10883 @node Omissions from Ada
10884 @subsubsection Omissions from Ada
10885 @cindex Ada, omissions from
10887 Here are the notable omissions from the subset:
10891 Only a subset of the attributes are supported:
10895 @t{'First}, @t{'Last}, and @t{'Length}
10896 on array objects (not on types and subtypes).
10899 @t{'Min} and @t{'Max}.
10902 @t{'Pos} and @t{'Val}.
10908 @t{'Range} on array objects (not subtypes), but only as the right
10909 operand of the membership (@code{in}) operator.
10912 @t{'Access}, @t{'Unchecked_Access}, and
10913 @t{'Unrestricted_Access} (a GNAT extension).
10921 @code{Characters.Latin_1} are not available and
10922 concatenation is not implemented. Thus, escape characters in strings are
10923 not currently available.
10926 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
10927 equality of representations. They will generally work correctly
10928 for strings and arrays whose elements have integer or enumeration types.
10929 They may not work correctly for arrays whose element
10930 types have user-defined equality, for arrays of real values
10931 (in particular, IEEE-conformant floating point, because of negative
10932 zeroes and NaNs), and for arrays whose elements contain unused bits with
10933 indeterminate values.
10936 The other component-by-component array operations (@code{and}, @code{or},
10937 @code{xor}, @code{not}, and relational tests other than equality)
10938 are not implemented.
10941 @cindex array aggregates (Ada)
10942 @cindex record aggregates (Ada)
10943 @cindex aggregates (Ada)
10944 There is limited support for array and record aggregates. They are
10945 permitted only on the right sides of assignments, as in these examples:
10948 set An_Array := (1, 2, 3, 4, 5, 6)
10949 set An_Array := (1, others => 0)
10950 set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
10951 set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
10952 set A_Record := (1, "Peter", True);
10953 set A_Record := (Name => "Peter", Id => 1, Alive => True)
10957 discriminant's value by assigning an aggregate has an
10958 undefined effect if that discriminant is used within the record.
10959 However, you can first modify discriminants by directly assigning to
10960 them (which normally would not be allowed in Ada), and then performing an
10961 aggregate assignment. For example, given a variable @code{A_Rec}
10962 declared to have a type such as:
10965 type Rec (Len : Small_Integer := 0) is record
10967 Vals : IntArray (1 .. Len);
10971 you can assign a value with a different size of @code{Vals} with two
10976 set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
10979 As this example also illustrates, @value{GDBN} is very loose about the usual
10980 rules concerning aggregates. You may leave out some of the
10981 components of an array or record aggregate (such as the @code{Len}
10982 component in the assignment to @code{A_Rec} above); they will retain their
10983 original values upon assignment. You may freely use dynamic values as
10984 indices in component associations. You may even use overlapping or
10985 redundant component associations, although which component values are
10986 assigned in such cases is not defined.
10989 Calls to dispatching subprograms are not implemented.
10992 The overloading algorithm is much more limited (i.e., less selective)
10993 than that of real Ada. It makes only limited use of the context in
10994 which a subexpression appears to resolve its meaning, and it is much
10995 looser in its rules for allowing type matches. As a result, some
10996 function calls will be ambiguous, and the user will be asked to choose
10997 the proper resolution.
11000 The @code{new} operator is not implemented.
11003 Entry calls are not implemented.
11006 Aside from printing, arithmetic operations on the native VAX floating-point
11007 formats are not supported.
11010 It is not possible to slice a packed array.
11013 @node Additions to Ada
11014 @subsubsection Additions to Ada
11015 @cindex Ada, deviations from
11017 As it does for other languages, @value{GDBN} makes certain generic
11018 extensions to Ada (@pxref{Expressions}):
11022 If the expression @var{E} is a variable residing in memory (typically
11023 a local variable or array element) and @var{N} is a positive integer,
11024 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
11025 @var{N}-1 adjacent variables following it in memory as an array. In
11026 Ada, this operator is generally not necessary, since its prime use is
11027 in displaying parts of an array, and slicing will usually do this in
11028 Ada. However, there are occasional uses when debugging programs in
11029 which certain debugging information has been optimized away.
11032 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
11033 appears in function or file @var{B}.'' When @var{B} is a file name,
11034 you must typically surround it in single quotes.
11037 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
11038 @var{type} that appears at address @var{addr}.''
11041 A name starting with @samp{$} is a convenience variable
11042 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
11045 In addition, @value{GDBN} provides a few other shortcuts and outright
11046 additions specific to Ada:
11050 The assignment statement is allowed as an expression, returning
11051 its right-hand operand as its value. Thus, you may enter
11055 print A(tmp := y + 1)
11059 The semicolon is allowed as an ``operator,'' returning as its value
11060 the value of its right-hand operand.
11061 This allows, for example,
11062 complex conditional breaks:
11066 condition 1 (report(i); k += 1; A(k) > 100)
11070 Rather than use catenation and symbolic character names to introduce special
11071 characters into strings, one may instead use a special bracket notation,
11072 which is also used to print strings. A sequence of characters of the form
11073 @samp{["@var{XX}"]} within a string or character literal denotes the
11074 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
11075 sequence of characters @samp{["""]} also denotes a single quotation mark
11076 in strings. For example,
11078 "One line.["0a"]Next line.["0a"]"
11081 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
11085 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
11086 @t{'Max} is optional (and is ignored in any case). For example, it is valid
11094 When printing arrays, @value{GDBN} uses positional notation when the
11095 array has a lower bound of 1, and uses a modified named notation otherwise.
11096 For example, a one-dimensional array of three integers with a lower bound
11097 of 3 might print as
11104 That is, in contrast to valid Ada, only the first component has a @code{=>}
11108 You may abbreviate attributes in expressions with any unique,
11109 multi-character subsequence of
11110 their names (an exact match gets preference).
11111 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
11112 in place of @t{a'length}.
11115 @cindex quoting Ada internal identifiers
11116 Since Ada is case-insensitive, the debugger normally maps identifiers you type
11117 to lower case. The GNAT compiler uses upper-case characters for
11118 some of its internal identifiers, which are normally of no interest to users.
11119 For the rare occasions when you actually have to look at them,
11120 enclose them in angle brackets to avoid the lower-case mapping.
11123 @value{GDBP} print <JMPBUF_SAVE>[0]
11127 Printing an object of class-wide type or dereferencing an
11128 access-to-class-wide value will display all the components of the object's
11129 specific type (as indicated by its run-time tag). Likewise, component
11130 selection on such a value will operate on the specific type of the
11135 @node Stopping Before Main Program
11136 @subsubsection Stopping at the Very Beginning
11138 @cindex breakpointing Ada elaboration code
11139 It is sometimes necessary to debug the program during elaboration, and
11140 before reaching the main procedure.
11141 As defined in the Ada Reference
11142 Manual, the elaboration code is invoked from a procedure called
11143 @code{adainit}. To run your program up to the beginning of
11144 elaboration, simply use the following two commands:
11145 @code{tbreak adainit} and @code{run}.
11148 @subsubsection Known Peculiarities of Ada Mode
11149 @cindex Ada, problems
11151 Besides the omissions listed previously (@pxref{Omissions from Ada}),
11152 we know of several problems with and limitations of Ada mode in
11154 some of which will be fixed with planned future releases of the debugger
11155 and the GNU Ada compiler.
11159 Currently, the debugger
11160 has insufficient information to determine whether certain pointers represent
11161 pointers to objects or the objects themselves.
11162 Thus, the user may have to tack an extra @code{.all} after an expression
11163 to get it printed properly.
11166 Static constants that the compiler chooses not to materialize as objects in
11167 storage are invisible to the debugger.
11170 Named parameter associations in function argument lists are ignored (the
11171 argument lists are treated as positional).
11174 Many useful library packages are currently invisible to the debugger.
11177 Fixed-point arithmetic, conversions, input, and output is carried out using
11178 floating-point arithmetic, and may give results that only approximate those on
11182 The type of the @t{'Address} attribute may not be @code{System.Address}.
11185 The GNAT compiler never generates the prefix @code{Standard} for any of
11186 the standard symbols defined by the Ada language. @value{GDBN} knows about
11187 this: it will strip the prefix from names when you use it, and will never
11188 look for a name you have so qualified among local symbols, nor match against
11189 symbols in other packages or subprograms. If you have
11190 defined entities anywhere in your program other than parameters and
11191 local variables whose simple names match names in @code{Standard},
11192 GNAT's lack of qualification here can cause confusion. When this happens,
11193 you can usually resolve the confusion
11194 by qualifying the problematic names with package
11195 @code{Standard} explicitly.
11198 @node Unsupported Languages
11199 @section Unsupported Languages
11201 @cindex unsupported languages
11202 @cindex minimal language
11203 In addition to the other fully-supported programming languages,
11204 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
11205 It does not represent a real programming language, but provides a set
11206 of capabilities close to what the C or assembly languages provide.
11207 This should allow most simple operations to be performed while debugging
11208 an application that uses a language currently not supported by @value{GDBN}.
11210 If the language is set to @code{auto}, @value{GDBN} will automatically
11211 select this language if the current frame corresponds to an unsupported
11215 @chapter Examining the Symbol Table
11217 The commands described in this chapter allow you to inquire about the
11218 symbols (names of variables, functions and types) defined in your
11219 program. This information is inherent in the text of your program and
11220 does not change as your program executes. @value{GDBN} finds it in your
11221 program's symbol table, in the file indicated when you started @value{GDBN}
11222 (@pxref{File Options, ,Choosing Files}), or by one of the
11223 file-management commands (@pxref{Files, ,Commands to Specify Files}).
11225 @cindex symbol names
11226 @cindex names of symbols
11227 @cindex quoting names
11228 Occasionally, you may need to refer to symbols that contain unusual
11229 characters, which @value{GDBN} ordinarily treats as word delimiters. The
11230 most frequent case is in referring to static variables in other
11231 source files (@pxref{Variables,,Program Variables}). File names
11232 are recorded in object files as debugging symbols, but @value{GDBN} would
11233 ordinarily parse a typical file name, like @file{foo.c}, as the three words
11234 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
11235 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
11242 looks up the value of @code{x} in the scope of the file @file{foo.c}.
11245 @cindex case-insensitive symbol names
11246 @cindex case sensitivity in symbol names
11247 @kindex set case-sensitive
11248 @item set case-sensitive on
11249 @itemx set case-sensitive off
11250 @itemx set case-sensitive auto
11251 Normally, when @value{GDBN} looks up symbols, it matches their names
11252 with case sensitivity determined by the current source language.
11253 Occasionally, you may wish to control that. The command @code{set
11254 case-sensitive} lets you do that by specifying @code{on} for
11255 case-sensitive matches or @code{off} for case-insensitive ones. If
11256 you specify @code{auto}, case sensitivity is reset to the default
11257 suitable for the source language. The default is case-sensitive
11258 matches for all languages except for Fortran, for which the default is
11259 case-insensitive matches.
11261 @kindex show case-sensitive
11262 @item show case-sensitive
11263 This command shows the current setting of case sensitivity for symbols
11266 @kindex info address
11267 @cindex address of a symbol
11268 @item info address @var{symbol}
11269 Describe where the data for @var{symbol} is stored. For a register
11270 variable, this says which register it is kept in. For a non-register
11271 local variable, this prints the stack-frame offset at which the variable
11274 Note the contrast with @samp{print &@var{symbol}}, which does not work
11275 at all for a register variable, and for a stack local variable prints
11276 the exact address of the current instantiation of the variable.
11278 @kindex info symbol
11279 @cindex symbol from address
11280 @cindex closest symbol and offset for an address
11281 @item info symbol @var{addr}
11282 Print the name of a symbol which is stored at the address @var{addr}.
11283 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
11284 nearest symbol and an offset from it:
11287 (@value{GDBP}) info symbol 0x54320
11288 _initialize_vx + 396 in section .text
11292 This is the opposite of the @code{info address} command. You can use
11293 it to find out the name of a variable or a function given its address.
11296 @item whatis [@var{arg}]
11297 Print the data type of @var{arg}, which can be either an expression or
11298 a data type. With no argument, print the data type of @code{$}, the
11299 last value in the value history. If @var{arg} is an expression, it is
11300 not actually evaluated, and any side-effecting operations (such as
11301 assignments or function calls) inside it do not take place. If
11302 @var{arg} is a type name, it may be the name of a type or typedef, or
11303 for C code it may have the form @samp{class @var{class-name}},
11304 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
11305 @samp{enum @var{enum-tag}}.
11306 @xref{Expressions, ,Expressions}.
11309 @item ptype [@var{arg}]
11310 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
11311 detailed description of the type, instead of just the name of the type.
11312 @xref{Expressions, ,Expressions}.
11314 For example, for this variable declaration:
11317 struct complex @{double real; double imag;@} v;
11321 the two commands give this output:
11325 (@value{GDBP}) whatis v
11326 type = struct complex
11327 (@value{GDBP}) ptype v
11328 type = struct complex @{
11336 As with @code{whatis}, using @code{ptype} without an argument refers to
11337 the type of @code{$}, the last value in the value history.
11339 @cindex incomplete type
11340 Sometimes, programs use opaque data types or incomplete specifications
11341 of complex data structure. If the debug information included in the
11342 program does not allow @value{GDBN} to display a full declaration of
11343 the data type, it will say @samp{<incomplete type>}. For example,
11344 given these declarations:
11348 struct foo *fooptr;
11352 but no definition for @code{struct foo} itself, @value{GDBN} will say:
11355 (@value{GDBP}) ptype foo
11356 $1 = <incomplete type>
11360 ``Incomplete type'' is C terminology for data types that are not
11361 completely specified.
11364 @item info types @var{regexp}
11366 Print a brief description of all types whose names match the regular
11367 expression @var{regexp} (or all types in your program, if you supply
11368 no argument). Each complete typename is matched as though it were a
11369 complete line; thus, @samp{i type value} gives information on all
11370 types in your program whose names include the string @code{value}, but
11371 @samp{i type ^value$} gives information only on types whose complete
11372 name is @code{value}.
11374 This command differs from @code{ptype} in two ways: first, like
11375 @code{whatis}, it does not print a detailed description; second, it
11376 lists all source files where a type is defined.
11379 @cindex local variables
11380 @item info scope @var{location}
11381 List all the variables local to a particular scope. This command
11382 accepts a @var{location} argument---a function name, a source line, or
11383 an address preceded by a @samp{*}, and prints all the variables local
11384 to the scope defined by that location. (@xref{Specify Location}, for
11385 details about supported forms of @var{location}.) For example:
11388 (@value{GDBP}) @b{info scope command_line_handler}
11389 Scope for command_line_handler:
11390 Symbol rl is an argument at stack/frame offset 8, length 4.
11391 Symbol linebuffer is in static storage at address 0x150a18, length 4.
11392 Symbol linelength is in static storage at address 0x150a1c, length 4.
11393 Symbol p is a local variable in register $esi, length 4.
11394 Symbol p1 is a local variable in register $ebx, length 4.
11395 Symbol nline is a local variable in register $edx, length 4.
11396 Symbol repeat is a local variable at frame offset -8, length 4.
11400 This command is especially useful for determining what data to collect
11401 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
11404 @kindex info source
11406 Show information about the current source file---that is, the source file for
11407 the function containing the current point of execution:
11410 the name of the source file, and the directory containing it,
11412 the directory it was compiled in,
11414 its length, in lines,
11416 which programming language it is written in,
11418 whether the executable includes debugging information for that file, and
11419 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
11421 whether the debugging information includes information about
11422 preprocessor macros.
11426 @kindex info sources
11428 Print the names of all source files in your program for which there is
11429 debugging information, organized into two lists: files whose symbols
11430 have already been read, and files whose symbols will be read when needed.
11432 @kindex info functions
11433 @item info functions
11434 Print the names and data types of all defined functions.
11436 @item info functions @var{regexp}
11437 Print the names and data types of all defined functions
11438 whose names contain a match for regular expression @var{regexp}.
11439 Thus, @samp{info fun step} finds all functions whose names
11440 include @code{step}; @samp{info fun ^step} finds those whose names
11441 start with @code{step}. If a function name contains characters
11442 that conflict with the regular expression language (e.g.@:
11443 @samp{operator*()}), they may be quoted with a backslash.
11445 @kindex info variables
11446 @item info variables
11447 Print the names and data types of all variables that are declared
11448 outside of functions (i.e.@: excluding local variables).
11450 @item info variables @var{regexp}
11451 Print the names and data types of all variables (except for local
11452 variables) whose names contain a match for regular expression
11455 @kindex info classes
11456 @cindex Objective-C, classes and selectors
11458 @itemx info classes @var{regexp}
11459 Display all Objective-C classes in your program, or
11460 (with the @var{regexp} argument) all those matching a particular regular
11463 @kindex info selectors
11464 @item info selectors
11465 @itemx info selectors @var{regexp}
11466 Display all Objective-C selectors in your program, or
11467 (with the @var{regexp} argument) all those matching a particular regular
11471 This was never implemented.
11472 @kindex info methods
11474 @itemx info methods @var{regexp}
11475 The @code{info methods} command permits the user to examine all defined
11476 methods within C@t{++} program, or (with the @var{regexp} argument) a
11477 specific set of methods found in the various C@t{++} classes. Many
11478 C@t{++} classes provide a large number of methods. Thus, the output
11479 from the @code{ptype} command can be overwhelming and hard to use. The
11480 @code{info-methods} command filters the methods, printing only those
11481 which match the regular-expression @var{regexp}.
11484 @cindex reloading symbols
11485 Some systems allow individual object files that make up your program to
11486 be replaced without stopping and restarting your program. For example,
11487 in VxWorks you can simply recompile a defective object file and keep on
11488 running. If you are running on one of these systems, you can allow
11489 @value{GDBN} to reload the symbols for automatically relinked modules:
11492 @kindex set symbol-reloading
11493 @item set symbol-reloading on
11494 Replace symbol definitions for the corresponding source file when an
11495 object file with a particular name is seen again.
11497 @item set symbol-reloading off
11498 Do not replace symbol definitions when encountering object files of the
11499 same name more than once. This is the default state; if you are not
11500 running on a system that permits automatic relinking of modules, you
11501 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
11502 may discard symbols when linking large programs, that may contain
11503 several modules (from different directories or libraries) with the same
11506 @kindex show symbol-reloading
11507 @item show symbol-reloading
11508 Show the current @code{on} or @code{off} setting.
11511 @cindex opaque data types
11512 @kindex set opaque-type-resolution
11513 @item set opaque-type-resolution on
11514 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
11515 declared as a pointer to a @code{struct}, @code{class}, or
11516 @code{union}---for example, @code{struct MyType *}---that is used in one
11517 source file although the full declaration of @code{struct MyType} is in
11518 another source file. The default is on.
11520 A change in the setting of this subcommand will not take effect until
11521 the next time symbols for a file are loaded.
11523 @item set opaque-type-resolution off
11524 Tell @value{GDBN} not to resolve opaque types. In this case, the type
11525 is printed as follows:
11527 @{<no data fields>@}
11530 @kindex show opaque-type-resolution
11531 @item show opaque-type-resolution
11532 Show whether opaque types are resolved or not.
11534 @kindex set print symbol-loading
11535 @cindex print messages when symbols are loaded
11536 @item set print symbol-loading
11537 @itemx set print symbol-loading on
11538 @itemx set print symbol-loading off
11539 The @code{set print symbol-loading} command allows you to enable or
11540 disable printing of messages when @value{GDBN} loads symbols.
11541 By default, these messages will be printed, and normally this is what
11542 you want. Disabling these messages is useful when debugging applications
11543 with lots of shared libraries where the quantity of output can be more
11544 annoying than useful.
11546 @kindex show print symbol-loading
11547 @item show print symbol-loading
11548 Show whether messages will be printed when @value{GDBN} loads symbols.
11550 @kindex maint print symbols
11551 @cindex symbol dump
11552 @kindex maint print psymbols
11553 @cindex partial symbol dump
11554 @item maint print symbols @var{filename}
11555 @itemx maint print psymbols @var{filename}
11556 @itemx maint print msymbols @var{filename}
11557 Write a dump of debugging symbol data into the file @var{filename}.
11558 These commands are used to debug the @value{GDBN} symbol-reading code. Only
11559 symbols with debugging data are included. If you use @samp{maint print
11560 symbols}, @value{GDBN} includes all the symbols for which it has already
11561 collected full details: that is, @var{filename} reflects symbols for
11562 only those files whose symbols @value{GDBN} has read. You can use the
11563 command @code{info sources} to find out which files these are. If you
11564 use @samp{maint print psymbols} instead, the dump shows information about
11565 symbols that @value{GDBN} only knows partially---that is, symbols defined in
11566 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
11567 @samp{maint print msymbols} dumps just the minimal symbol information
11568 required for each object file from which @value{GDBN} has read some symbols.
11569 @xref{Files, ,Commands to Specify Files}, for a discussion of how
11570 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
11572 @kindex maint info symtabs
11573 @kindex maint info psymtabs
11574 @cindex listing @value{GDBN}'s internal symbol tables
11575 @cindex symbol tables, listing @value{GDBN}'s internal
11576 @cindex full symbol tables, listing @value{GDBN}'s internal
11577 @cindex partial symbol tables, listing @value{GDBN}'s internal
11578 @item maint info symtabs @r{[} @var{regexp} @r{]}
11579 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
11581 List the @code{struct symtab} or @code{struct partial_symtab}
11582 structures whose names match @var{regexp}. If @var{regexp} is not
11583 given, list them all. The output includes expressions which you can
11584 copy into a @value{GDBN} debugging this one to examine a particular
11585 structure in more detail. For example:
11588 (@value{GDBP}) maint info psymtabs dwarf2read
11589 @{ objfile /home/gnu/build/gdb/gdb
11590 ((struct objfile *) 0x82e69d0)
11591 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
11592 ((struct partial_symtab *) 0x8474b10)
11595 text addresses 0x814d3c8 -- 0x8158074
11596 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
11597 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
11598 dependencies (none)
11601 (@value{GDBP}) maint info symtabs
11605 We see that there is one partial symbol table whose filename contains
11606 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
11607 and we see that @value{GDBN} has not read in any symtabs yet at all.
11608 If we set a breakpoint on a function, that will cause @value{GDBN} to
11609 read the symtab for the compilation unit containing that function:
11612 (@value{GDBP}) break dwarf2_psymtab_to_symtab
11613 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
11615 (@value{GDBP}) maint info symtabs
11616 @{ objfile /home/gnu/build/gdb/gdb
11617 ((struct objfile *) 0x82e69d0)
11618 @{ symtab /home/gnu/src/gdb/dwarf2read.c
11619 ((struct symtab *) 0x86c1f38)
11622 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
11623 linetable ((struct linetable *) 0x8370fa0)
11624 debugformat DWARF 2
11633 @chapter Altering Execution
11635 Once you think you have found an error in your program, you might want to
11636 find out for certain whether correcting the apparent error would lead to
11637 correct results in the rest of the run. You can find the answer by
11638 experiment, using the @value{GDBN} features for altering execution of the
11641 For example, you can store new values into variables or memory
11642 locations, give your program a signal, restart it at a different
11643 address, or even return prematurely from a function.
11646 * Assignment:: Assignment to variables
11647 * Jumping:: Continuing at a different address
11648 * Signaling:: Giving your program a signal
11649 * Returning:: Returning from a function
11650 * Calling:: Calling your program's functions
11651 * Patching:: Patching your program
11655 @section Assignment to Variables
11658 @cindex setting variables
11659 To alter the value of a variable, evaluate an assignment expression.
11660 @xref{Expressions, ,Expressions}. For example,
11667 stores the value 4 into the variable @code{x}, and then prints the
11668 value of the assignment expression (which is 4).
11669 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
11670 information on operators in supported languages.
11672 @kindex set variable
11673 @cindex variables, setting
11674 If you are not interested in seeing the value of the assignment, use the
11675 @code{set} command instead of the @code{print} command. @code{set} is
11676 really the same as @code{print} except that the expression's value is
11677 not printed and is not put in the value history (@pxref{Value History,
11678 ,Value History}). The expression is evaluated only for its effects.
11680 If the beginning of the argument string of the @code{set} command
11681 appears identical to a @code{set} subcommand, use the @code{set
11682 variable} command instead of just @code{set}. This command is identical
11683 to @code{set} except for its lack of subcommands. For example, if your
11684 program has a variable @code{width}, you get an error if you try to set
11685 a new value with just @samp{set width=13}, because @value{GDBN} has the
11686 command @code{set width}:
11689 (@value{GDBP}) whatis width
11691 (@value{GDBP}) p width
11693 (@value{GDBP}) set width=47
11694 Invalid syntax in expression.
11698 The invalid expression, of course, is @samp{=47}. In
11699 order to actually set the program's variable @code{width}, use
11702 (@value{GDBP}) set var width=47
11705 Because the @code{set} command has many subcommands that can conflict
11706 with the names of program variables, it is a good idea to use the
11707 @code{set variable} command instead of just @code{set}. For example, if
11708 your program has a variable @code{g}, you run into problems if you try
11709 to set a new value with just @samp{set g=4}, because @value{GDBN} has
11710 the command @code{set gnutarget}, abbreviated @code{set g}:
11714 (@value{GDBP}) whatis g
11718 (@value{GDBP}) set g=4
11722 The program being debugged has been started already.
11723 Start it from the beginning? (y or n) y
11724 Starting program: /home/smith/cc_progs/a.out
11725 "/home/smith/cc_progs/a.out": can't open to read symbols:
11726 Invalid bfd target.
11727 (@value{GDBP}) show g
11728 The current BFD target is "=4".
11733 The program variable @code{g} did not change, and you silently set the
11734 @code{gnutarget} to an invalid value. In order to set the variable
11738 (@value{GDBP}) set var g=4
11741 @value{GDBN} allows more implicit conversions in assignments than C; you can
11742 freely store an integer value into a pointer variable or vice versa,
11743 and you can convert any structure to any other structure that is the
11744 same length or shorter.
11745 @comment FIXME: how do structs align/pad in these conversions?
11746 @comment /doc@cygnus.com 18dec1990
11748 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
11749 construct to generate a value of specified type at a specified address
11750 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
11751 to memory location @code{0x83040} as an integer (which implies a certain size
11752 and representation in memory), and
11755 set @{int@}0x83040 = 4
11759 stores the value 4 into that memory location.
11762 @section Continuing at a Different Address
11764 Ordinarily, when you continue your program, you do so at the place where
11765 it stopped, with the @code{continue} command. You can instead continue at
11766 an address of your own choosing, with the following commands:
11770 @item jump @var{linespec}
11771 @itemx jump @var{location}
11772 Resume execution at line @var{linespec} or at address given by
11773 @var{location}. Execution stops again immediately if there is a
11774 breakpoint there. @xref{Specify Location}, for a description of the
11775 different forms of @var{linespec} and @var{location}. It is common
11776 practice to use the @code{tbreak} command in conjunction with
11777 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
11779 The @code{jump} command does not change the current stack frame, or
11780 the stack pointer, or the contents of any memory location or any
11781 register other than the program counter. If line @var{linespec} is in
11782 a different function from the one currently executing, the results may
11783 be bizarre if the two functions expect different patterns of arguments or
11784 of local variables. For this reason, the @code{jump} command requests
11785 confirmation if the specified line is not in the function currently
11786 executing. However, even bizarre results are predictable if you are
11787 well acquainted with the machine-language code of your program.
11790 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
11791 On many systems, you can get much the same effect as the @code{jump}
11792 command by storing a new value into the register @code{$pc}. The
11793 difference is that this does not start your program running; it only
11794 changes the address of where it @emph{will} run when you continue. For
11802 makes the next @code{continue} command or stepping command execute at
11803 address @code{0x485}, rather than at the address where your program stopped.
11804 @xref{Continuing and Stepping, ,Continuing and Stepping}.
11806 The most common occasion to use the @code{jump} command is to back
11807 up---perhaps with more breakpoints set---over a portion of a program
11808 that has already executed, in order to examine its execution in more
11813 @section Giving your Program a Signal
11814 @cindex deliver a signal to a program
11818 @item signal @var{signal}
11819 Resume execution where your program stopped, but immediately give it the
11820 signal @var{signal}. @var{signal} can be the name or the number of a
11821 signal. For example, on many systems @code{signal 2} and @code{signal
11822 SIGINT} are both ways of sending an interrupt signal.
11824 Alternatively, if @var{signal} is zero, continue execution without
11825 giving a signal. This is useful when your program stopped on account of
11826 a signal and would ordinary see the signal when resumed with the
11827 @code{continue} command; @samp{signal 0} causes it to resume without a
11830 @code{signal} does not repeat when you press @key{RET} a second time
11831 after executing the command.
11835 Invoking the @code{signal} command is not the same as invoking the
11836 @code{kill} utility from the shell. Sending a signal with @code{kill}
11837 causes @value{GDBN} to decide what to do with the signal depending on
11838 the signal handling tables (@pxref{Signals}). The @code{signal} command
11839 passes the signal directly to your program.
11843 @section Returning from a Function
11846 @cindex returning from a function
11849 @itemx return @var{expression}
11850 You can cancel execution of a function call with the @code{return}
11851 command. If you give an
11852 @var{expression} argument, its value is used as the function's return
11856 When you use @code{return}, @value{GDBN} discards the selected stack frame
11857 (and all frames within it). You can think of this as making the
11858 discarded frame return prematurely. If you wish to specify a value to
11859 be returned, give that value as the argument to @code{return}.
11861 This pops the selected stack frame (@pxref{Selection, ,Selecting a
11862 Frame}), and any other frames inside of it, leaving its caller as the
11863 innermost remaining frame. That frame becomes selected. The
11864 specified value is stored in the registers used for returning values
11867 The @code{return} command does not resume execution; it leaves the
11868 program stopped in the state that would exist if the function had just
11869 returned. In contrast, the @code{finish} command (@pxref{Continuing
11870 and Stepping, ,Continuing and Stepping}) resumes execution until the
11871 selected stack frame returns naturally.
11874 @section Calling Program Functions
11877 @cindex calling functions
11878 @cindex inferior functions, calling
11879 @item print @var{expr}
11880 Evaluate the expression @var{expr} and display the resulting value.
11881 @var{expr} may include calls to functions in the program being
11885 @item call @var{expr}
11886 Evaluate the expression @var{expr} without displaying @code{void}
11889 You can use this variant of the @code{print} command if you want to
11890 execute a function from your program that does not return anything
11891 (a.k.a.@: @dfn{a void function}), but without cluttering the output
11892 with @code{void} returned values that @value{GDBN} will otherwise
11893 print. If the result is not void, it is printed and saved in the
11897 It is possible for the function you call via the @code{print} or
11898 @code{call} command to generate a signal (e.g., if there's a bug in
11899 the function, or if you passed it incorrect arguments). What happens
11900 in that case is controlled by the @code{set unwindonsignal} command.
11903 @item set unwindonsignal
11904 @kindex set unwindonsignal
11905 @cindex unwind stack in called functions
11906 @cindex call dummy stack unwinding
11907 Set unwinding of the stack if a signal is received while in a function
11908 that @value{GDBN} called in the program being debugged. If set to on,
11909 @value{GDBN} unwinds the stack it created for the call and restores
11910 the context to what it was before the call. If set to off (the
11911 default), @value{GDBN} stops in the frame where the signal was
11914 @item show unwindonsignal
11915 @kindex show unwindonsignal
11916 Show the current setting of stack unwinding in the functions called by
11920 @cindex weak alias functions
11921 Sometimes, a function you wish to call is actually a @dfn{weak alias}
11922 for another function. In such case, @value{GDBN} might not pick up
11923 the type information, including the types of the function arguments,
11924 which causes @value{GDBN} to call the inferior function incorrectly.
11925 As a result, the called function will function erroneously and may
11926 even crash. A solution to that is to use the name of the aliased
11930 @section Patching Programs
11932 @cindex patching binaries
11933 @cindex writing into executables
11934 @cindex writing into corefiles
11936 By default, @value{GDBN} opens the file containing your program's
11937 executable code (or the corefile) read-only. This prevents accidental
11938 alterations to machine code; but it also prevents you from intentionally
11939 patching your program's binary.
11941 If you'd like to be able to patch the binary, you can specify that
11942 explicitly with the @code{set write} command. For example, you might
11943 want to turn on internal debugging flags, or even to make emergency
11949 @itemx set write off
11950 If you specify @samp{set write on}, @value{GDBN} opens executable and
11951 core files for both reading and writing; if you specify @samp{set write
11952 off} (the default), @value{GDBN} opens them read-only.
11954 If you have already loaded a file, you must load it again (using the
11955 @code{exec-file} or @code{core-file} command) after changing @code{set
11956 write}, for your new setting to take effect.
11960 Display whether executable files and core files are opened for writing
11961 as well as reading.
11965 @chapter @value{GDBN} Files
11967 @value{GDBN} needs to know the file name of the program to be debugged,
11968 both in order to read its symbol table and in order to start your
11969 program. To debug a core dump of a previous run, you must also tell
11970 @value{GDBN} the name of the core dump file.
11973 * Files:: Commands to specify files
11974 * Separate Debug Files:: Debugging information in separate files
11975 * Symbol Errors:: Errors reading symbol files
11979 @section Commands to Specify Files
11981 @cindex symbol table
11982 @cindex core dump file
11984 You may want to specify executable and core dump file names. The usual
11985 way to do this is at start-up time, using the arguments to
11986 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
11987 Out of @value{GDBN}}).
11989 Occasionally it is necessary to change to a different file during a
11990 @value{GDBN} session. Or you may run @value{GDBN} and forget to
11991 specify a file you want to use. Or you are debugging a remote target
11992 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
11993 Program}). In these situations the @value{GDBN} commands to specify
11994 new files are useful.
11997 @cindex executable file
11999 @item file @var{filename}
12000 Use @var{filename} as the program to be debugged. It is read for its
12001 symbols and for the contents of pure memory. It is also the program
12002 executed when you use the @code{run} command. If you do not specify a
12003 directory and the file is not found in the @value{GDBN} working directory,
12004 @value{GDBN} uses the environment variable @code{PATH} as a list of
12005 directories to search, just as the shell does when looking for a program
12006 to run. You can change the value of this variable, for both @value{GDBN}
12007 and your program, using the @code{path} command.
12009 @cindex unlinked object files
12010 @cindex patching object files
12011 You can load unlinked object @file{.o} files into @value{GDBN} using
12012 the @code{file} command. You will not be able to ``run'' an object
12013 file, but you can disassemble functions and inspect variables. Also,
12014 if the underlying BFD functionality supports it, you could use
12015 @kbd{gdb -write} to patch object files using this technique. Note
12016 that @value{GDBN} can neither interpret nor modify relocations in this
12017 case, so branches and some initialized variables will appear to go to
12018 the wrong place. But this feature is still handy from time to time.
12021 @code{file} with no argument makes @value{GDBN} discard any information it
12022 has on both executable file and the symbol table.
12025 @item exec-file @r{[} @var{filename} @r{]}
12026 Specify that the program to be run (but not the symbol table) is found
12027 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
12028 if necessary to locate your program. Omitting @var{filename} means to
12029 discard information on the executable file.
12031 @kindex symbol-file
12032 @item symbol-file @r{[} @var{filename} @r{]}
12033 Read symbol table information from file @var{filename}. @code{PATH} is
12034 searched when necessary. Use the @code{file} command to get both symbol
12035 table and program to run from the same file.
12037 @code{symbol-file} with no argument clears out @value{GDBN} information on your
12038 program's symbol table.
12040 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
12041 some breakpoints and auto-display expressions. This is because they may
12042 contain pointers to the internal data recording symbols and data types,
12043 which are part of the old symbol table data being discarded inside
12046 @code{symbol-file} does not repeat if you press @key{RET} again after
12049 When @value{GDBN} is configured for a particular environment, it
12050 understands debugging information in whatever format is the standard
12051 generated for that environment; you may use either a @sc{gnu} compiler, or
12052 other compilers that adhere to the local conventions.
12053 Best results are usually obtained from @sc{gnu} compilers; for example,
12054 using @code{@value{NGCC}} you can generate debugging information for
12057 For most kinds of object files, with the exception of old SVR3 systems
12058 using COFF, the @code{symbol-file} command does not normally read the
12059 symbol table in full right away. Instead, it scans the symbol table
12060 quickly to find which source files and which symbols are present. The
12061 details are read later, one source file at a time, as they are needed.
12063 The purpose of this two-stage reading strategy is to make @value{GDBN}
12064 start up faster. For the most part, it is invisible except for
12065 occasional pauses while the symbol table details for a particular source
12066 file are being read. (The @code{set verbose} command can turn these
12067 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
12068 Warnings and Messages}.)
12070 We have not implemented the two-stage strategy for COFF yet. When the
12071 symbol table is stored in COFF format, @code{symbol-file} reads the
12072 symbol table data in full right away. Note that ``stabs-in-COFF''
12073 still does the two-stage strategy, since the debug info is actually
12077 @cindex reading symbols immediately
12078 @cindex symbols, reading immediately
12079 @item symbol-file @var{filename} @r{[} -readnow @r{]}
12080 @itemx file @var{filename} @r{[} -readnow @r{]}
12081 You can override the @value{GDBN} two-stage strategy for reading symbol
12082 tables by using the @samp{-readnow} option with any of the commands that
12083 load symbol table information, if you want to be sure @value{GDBN} has the
12084 entire symbol table available.
12086 @c FIXME: for now no mention of directories, since this seems to be in
12087 @c flux. 13mar1992 status is that in theory GDB would look either in
12088 @c current dir or in same dir as myprog; but issues like competing
12089 @c GDB's, or clutter in system dirs, mean that in practice right now
12090 @c only current dir is used. FFish says maybe a special GDB hierarchy
12091 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
12095 @item core-file @r{[}@var{filename}@r{]}
12097 Specify the whereabouts of a core dump file to be used as the ``contents
12098 of memory''. Traditionally, core files contain only some parts of the
12099 address space of the process that generated them; @value{GDBN} can access the
12100 executable file itself for other parts.
12102 @code{core-file} with no argument specifies that no core file is
12105 Note that the core file is ignored when your program is actually running
12106 under @value{GDBN}. So, if you have been running your program and you
12107 wish to debug a core file instead, you must kill the subprocess in which
12108 the program is running. To do this, use the @code{kill} command
12109 (@pxref{Kill Process, ,Killing the Child Process}).
12111 @kindex add-symbol-file
12112 @cindex dynamic linking
12113 @item add-symbol-file @var{filename} @var{address}
12114 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
12115 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
12116 The @code{add-symbol-file} command reads additional symbol table
12117 information from the file @var{filename}. You would use this command
12118 when @var{filename} has been dynamically loaded (by some other means)
12119 into the program that is running. @var{address} should be the memory
12120 address at which the file has been loaded; @value{GDBN} cannot figure
12121 this out for itself. You can additionally specify an arbitrary number
12122 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
12123 section name and base address for that section. You can specify any
12124 @var{address} as an expression.
12126 The symbol table of the file @var{filename} is added to the symbol table
12127 originally read with the @code{symbol-file} command. You can use the
12128 @code{add-symbol-file} command any number of times; the new symbol data
12129 thus read keeps adding to the old. To discard all old symbol data
12130 instead, use the @code{symbol-file} command without any arguments.
12132 @cindex relocatable object files, reading symbols from
12133 @cindex object files, relocatable, reading symbols from
12134 @cindex reading symbols from relocatable object files
12135 @cindex symbols, reading from relocatable object files
12136 @cindex @file{.o} files, reading symbols from
12137 Although @var{filename} is typically a shared library file, an
12138 executable file, or some other object file which has been fully
12139 relocated for loading into a process, you can also load symbolic
12140 information from relocatable @file{.o} files, as long as:
12144 the file's symbolic information refers only to linker symbols defined in
12145 that file, not to symbols defined by other object files,
12147 every section the file's symbolic information refers to has actually
12148 been loaded into the inferior, as it appears in the file, and
12150 you can determine the address at which every section was loaded, and
12151 provide these to the @code{add-symbol-file} command.
12155 Some embedded operating systems, like Sun Chorus and VxWorks, can load
12156 relocatable files into an already running program; such systems
12157 typically make the requirements above easy to meet. However, it's
12158 important to recognize that many native systems use complex link
12159 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
12160 assembly, for example) that make the requirements difficult to meet. In
12161 general, one cannot assume that using @code{add-symbol-file} to read a
12162 relocatable object file's symbolic information will have the same effect
12163 as linking the relocatable object file into the program in the normal
12166 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
12168 @kindex add-symbol-file-from-memory
12169 @cindex @code{syscall DSO}
12170 @cindex load symbols from memory
12171 @item add-symbol-file-from-memory @var{address}
12172 Load symbols from the given @var{address} in a dynamically loaded
12173 object file whose image is mapped directly into the inferior's memory.
12174 For example, the Linux kernel maps a @code{syscall DSO} into each
12175 process's address space; this DSO provides kernel-specific code for
12176 some system calls. The argument can be any expression whose
12177 evaluation yields the address of the file's shared object file header.
12178 For this command to work, you must have used @code{symbol-file} or
12179 @code{exec-file} commands in advance.
12181 @kindex add-shared-symbol-files
12183 @item add-shared-symbol-files @var{library-file}
12184 @itemx assf @var{library-file}
12185 The @code{add-shared-symbol-files} command can currently be used only
12186 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
12187 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
12188 @value{GDBN} automatically looks for shared libraries, however if
12189 @value{GDBN} does not find yours, you can invoke
12190 @code{add-shared-symbol-files}. It takes one argument: the shared
12191 library's file name. @code{assf} is a shorthand alias for
12192 @code{add-shared-symbol-files}.
12195 @item section @var{section} @var{addr}
12196 The @code{section} command changes the base address of the named
12197 @var{section} of the exec file to @var{addr}. This can be used if the
12198 exec file does not contain section addresses, (such as in the
12199 @code{a.out} format), or when the addresses specified in the file
12200 itself are wrong. Each section must be changed separately. The
12201 @code{info files} command, described below, lists all the sections and
12205 @kindex info target
12208 @code{info files} and @code{info target} are synonymous; both print the
12209 current target (@pxref{Targets, ,Specifying a Debugging Target}),
12210 including the names of the executable and core dump files currently in
12211 use by @value{GDBN}, and the files from which symbols were loaded. The
12212 command @code{help target} lists all possible targets rather than
12215 @kindex maint info sections
12216 @item maint info sections
12217 Another command that can give you extra information about program sections
12218 is @code{maint info sections}. In addition to the section information
12219 displayed by @code{info files}, this command displays the flags and file
12220 offset of each section in the executable and core dump files. In addition,
12221 @code{maint info sections} provides the following command options (which
12222 may be arbitrarily combined):
12226 Display sections for all loaded object files, including shared libraries.
12227 @item @var{sections}
12228 Display info only for named @var{sections}.
12229 @item @var{section-flags}
12230 Display info only for sections for which @var{section-flags} are true.
12231 The section flags that @value{GDBN} currently knows about are:
12234 Section will have space allocated in the process when loaded.
12235 Set for all sections except those containing debug information.
12237 Section will be loaded from the file into the child process memory.
12238 Set for pre-initialized code and data, clear for @code{.bss} sections.
12240 Section needs to be relocated before loading.
12242 Section cannot be modified by the child process.
12244 Section contains executable code only.
12246 Section contains data only (no executable code).
12248 Section will reside in ROM.
12250 Section contains data for constructor/destructor lists.
12252 Section is not empty.
12254 An instruction to the linker to not output the section.
12255 @item COFF_SHARED_LIBRARY
12256 A notification to the linker that the section contains
12257 COFF shared library information.
12259 Section contains common symbols.
12262 @kindex set trust-readonly-sections
12263 @cindex read-only sections
12264 @item set trust-readonly-sections on
12265 Tell @value{GDBN} that readonly sections in your object file
12266 really are read-only (i.e.@: that their contents will not change).
12267 In that case, @value{GDBN} can fetch values from these sections
12268 out of the object file, rather than from the target program.
12269 For some targets (notably embedded ones), this can be a significant
12270 enhancement to debugging performance.
12272 The default is off.
12274 @item set trust-readonly-sections off
12275 Tell @value{GDBN} not to trust readonly sections. This means that
12276 the contents of the section might change while the program is running,
12277 and must therefore be fetched from the target when needed.
12279 @item show trust-readonly-sections
12280 Show the current setting of trusting readonly sections.
12283 All file-specifying commands allow both absolute and relative file names
12284 as arguments. @value{GDBN} always converts the file name to an absolute file
12285 name and remembers it that way.
12287 @cindex shared libraries
12288 @anchor{Shared Libraries}
12289 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
12290 and IBM RS/6000 AIX shared libraries.
12292 On MS-Windows @value{GDBN} must be linked with the Expat library to support
12293 shared libraries. @xref{Expat}.
12295 @value{GDBN} automatically loads symbol definitions from shared libraries
12296 when you use the @code{run} command, or when you examine a core file.
12297 (Before you issue the @code{run} command, @value{GDBN} does not understand
12298 references to a function in a shared library, however---unless you are
12299 debugging a core file).
12301 On HP-UX, if the program loads a library explicitly, @value{GDBN}
12302 automatically loads the symbols at the time of the @code{shl_load} call.
12304 @c FIXME: some @value{GDBN} release may permit some refs to undef
12305 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
12306 @c FIXME...lib; check this from time to time when updating manual
12308 There are times, however, when you may wish to not automatically load
12309 symbol definitions from shared libraries, such as when they are
12310 particularly large or there are many of them.
12312 To control the automatic loading of shared library symbols, use the
12316 @kindex set auto-solib-add
12317 @item set auto-solib-add @var{mode}
12318 If @var{mode} is @code{on}, symbols from all shared object libraries
12319 will be loaded automatically when the inferior begins execution, you
12320 attach to an independently started inferior, or when the dynamic linker
12321 informs @value{GDBN} that a new library has been loaded. If @var{mode}
12322 is @code{off}, symbols must be loaded manually, using the
12323 @code{sharedlibrary} command. The default value is @code{on}.
12325 @cindex memory used for symbol tables
12326 If your program uses lots of shared libraries with debug info that
12327 takes large amounts of memory, you can decrease the @value{GDBN}
12328 memory footprint by preventing it from automatically loading the
12329 symbols from shared libraries. To that end, type @kbd{set
12330 auto-solib-add off} before running the inferior, then load each
12331 library whose debug symbols you do need with @kbd{sharedlibrary
12332 @var{regexp}}, where @var{regexp} is a regular expression that matches
12333 the libraries whose symbols you want to be loaded.
12335 @kindex show auto-solib-add
12336 @item show auto-solib-add
12337 Display the current autoloading mode.
12340 @cindex load shared library
12341 To explicitly load shared library symbols, use the @code{sharedlibrary}
12345 @kindex info sharedlibrary
12348 @itemx info sharedlibrary
12349 Print the names of the shared libraries which are currently loaded.
12351 @kindex sharedlibrary
12353 @item sharedlibrary @var{regex}
12354 @itemx share @var{regex}
12355 Load shared object library symbols for files matching a
12356 Unix regular expression.
12357 As with files loaded automatically, it only loads shared libraries
12358 required by your program for a core file or after typing @code{run}. If
12359 @var{regex} is omitted all shared libraries required by your program are
12362 @item nosharedlibrary
12363 @kindex nosharedlibrary
12364 @cindex unload symbols from shared libraries
12365 Unload all shared object library symbols. This discards all symbols
12366 that have been loaded from all shared libraries. Symbols from shared
12367 libraries that were loaded by explicit user requests are not
12371 Sometimes you may wish that @value{GDBN} stops and gives you control
12372 when any of shared library events happen. Use the @code{set
12373 stop-on-solib-events} command for this:
12376 @item set stop-on-solib-events
12377 @kindex set stop-on-solib-events
12378 This command controls whether @value{GDBN} should give you control
12379 when the dynamic linker notifies it about some shared library event.
12380 The most common event of interest is loading or unloading of a new
12383 @item show stop-on-solib-events
12384 @kindex show stop-on-solib-events
12385 Show whether @value{GDBN} stops and gives you control when shared
12386 library events happen.
12389 Shared libraries are also supported in many cross or remote debugging
12390 configurations. A copy of the target's libraries need to be present on the
12391 host system; they need to be the same as the target libraries, although the
12392 copies on the target can be stripped as long as the copies on the host are
12395 @cindex where to look for shared libraries
12396 For remote debugging, you need to tell @value{GDBN} where the target
12397 libraries are, so that it can load the correct copies---otherwise, it
12398 may try to load the host's libraries. @value{GDBN} has two variables
12399 to specify the search directories for target libraries.
12402 @cindex prefix for shared library file names
12403 @cindex system root, alternate
12404 @kindex set solib-absolute-prefix
12405 @kindex set sysroot
12406 @item set sysroot @var{path}
12407 Use @var{path} as the system root for the program being debugged. Any
12408 absolute shared library paths will be prefixed with @var{path}; many
12409 runtime loaders store the absolute paths to the shared library in the
12410 target program's memory. If you use @code{set sysroot} to find shared
12411 libraries, they need to be laid out in the same way that they are on
12412 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
12415 The @code{set solib-absolute-prefix} command is an alias for @code{set
12418 @cindex default system root
12419 @cindex @samp{--with-sysroot}
12420 You can set the default system root by using the configure-time
12421 @samp{--with-sysroot} option. If the system root is inside
12422 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
12423 @samp{--exec-prefix}), then the default system root will be updated
12424 automatically if the installed @value{GDBN} is moved to a new
12427 @kindex show sysroot
12429 Display the current shared library prefix.
12431 @kindex set solib-search-path
12432 @item set solib-search-path @var{path}
12433 If this variable is set, @var{path} is a colon-separated list of
12434 directories to search for shared libraries. @samp{solib-search-path}
12435 is used after @samp{sysroot} fails to locate the library, or if the
12436 path to the library is relative instead of absolute. If you want to
12437 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
12438 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
12439 finding your host's libraries. @samp{sysroot} is preferred; setting
12440 it to a nonexistent directory may interfere with automatic loading
12441 of shared library symbols.
12443 @kindex show solib-search-path
12444 @item show solib-search-path
12445 Display the current shared library search path.
12449 @node Separate Debug Files
12450 @section Debugging Information in Separate Files
12451 @cindex separate debugging information files
12452 @cindex debugging information in separate files
12453 @cindex @file{.debug} subdirectories
12454 @cindex debugging information directory, global
12455 @cindex global debugging information directory
12456 @cindex build ID, and separate debugging files
12457 @cindex @file{.build-id} directory
12459 @value{GDBN} allows you to put a program's debugging information in a
12460 file separate from the executable itself, in a way that allows
12461 @value{GDBN} to find and load the debugging information automatically.
12462 Since debugging information can be very large---sometimes larger
12463 than the executable code itself---some systems distribute debugging
12464 information for their executables in separate files, which users can
12465 install only when they need to debug a problem.
12467 @value{GDBN} supports two ways of specifying the separate debug info
12472 The executable contains a @dfn{debug link} that specifies the name of
12473 the separate debug info file. The separate debug file's name is
12474 usually @file{@var{executable}.debug}, where @var{executable} is the
12475 name of the corresponding executable file without leading directories
12476 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
12477 debug link specifies a CRC32 checksum for the debug file, which
12478 @value{GDBN} uses to validate that the executable and the debug file
12479 came from the same build.
12482 The executable contains a @dfn{build ID}, a unique bit string that is
12483 also present in the corresponding debug info file. (This is supported
12484 only on some operating systems, notably those which use the ELF format
12485 for binary files and the @sc{gnu} Binutils.) For more details about
12486 this feature, see the description of the @option{--build-id}
12487 command-line option in @ref{Options, , Command Line Options, ld.info,
12488 The GNU Linker}. The debug info file's name is not specified
12489 explicitly by the build ID, but can be computed from the build ID, see
12493 Depending on the way the debug info file is specified, @value{GDBN}
12494 uses two different methods of looking for the debug file:
12498 For the ``debug link'' method, @value{GDBN} looks up the named file in
12499 the directory of the executable file, then in a subdirectory of that
12500 directory named @file{.debug}, and finally under the global debug
12501 directory, in a subdirectory whose name is identical to the leading
12502 directories of the executable's absolute file name.
12505 For the ``build ID'' method, @value{GDBN} looks in the
12506 @file{.build-id} subdirectory of the global debug directory for a file
12507 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
12508 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
12509 are the rest of the bit string. (Real build ID strings are 32 or more
12510 hex characters, not 10.)
12513 So, for example, suppose you ask @value{GDBN} to debug
12514 @file{/usr/bin/ls}, which has a debug link that specifies the
12515 file @file{ls.debug}, and a build ID whose value in hex is
12516 @code{abcdef1234}. If the global debug directory is
12517 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
12518 debug information files, in the indicated order:
12522 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
12524 @file{/usr/bin/ls.debug}
12526 @file{/usr/bin/.debug/ls.debug}
12528 @file{/usr/lib/debug/usr/bin/ls.debug}.
12531 You can set the global debugging info directory's name, and view the
12532 name @value{GDBN} is currently using.
12536 @kindex set debug-file-directory
12537 @item set debug-file-directory @var{directory}
12538 Set the directory which @value{GDBN} searches for separate debugging
12539 information files to @var{directory}.
12541 @kindex show debug-file-directory
12542 @item show debug-file-directory
12543 Show the directory @value{GDBN} searches for separate debugging
12548 @cindex @code{.gnu_debuglink} sections
12549 @cindex debug link sections
12550 A debug link is a special section of the executable file named
12551 @code{.gnu_debuglink}. The section must contain:
12555 A filename, with any leading directory components removed, followed by
12558 zero to three bytes of padding, as needed to reach the next four-byte
12559 boundary within the section, and
12561 a four-byte CRC checksum, stored in the same endianness used for the
12562 executable file itself. The checksum is computed on the debugging
12563 information file's full contents by the function given below, passing
12564 zero as the @var{crc} argument.
12567 Any executable file format can carry a debug link, as long as it can
12568 contain a section named @code{.gnu_debuglink} with the contents
12571 @cindex @code{.note.gnu.build-id} sections
12572 @cindex build ID sections
12573 The build ID is a special section in the executable file (and in other
12574 ELF binary files that @value{GDBN} may consider). This section is
12575 often named @code{.note.gnu.build-id}, but that name is not mandatory.
12576 It contains unique identification for the built files---the ID remains
12577 the same across multiple builds of the same build tree. The default
12578 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
12579 content for the build ID string. The same section with an identical
12580 value is present in the original built binary with symbols, in its
12581 stripped variant, and in the separate debugging information file.
12583 The debugging information file itself should be an ordinary
12584 executable, containing a full set of linker symbols, sections, and
12585 debugging information. The sections of the debugging information file
12586 should have the same names, addresses, and sizes as the original file,
12587 but they need not contain any data---much like a @code{.bss} section
12588 in an ordinary executable.
12590 The @sc{gnu} binary utilities (Binutils) package includes the
12591 @samp{objcopy} utility that can produce
12592 the separated executable / debugging information file pairs using the
12593 following commands:
12596 @kbd{objcopy --only-keep-debug foo foo.debug}
12601 These commands remove the debugging
12602 information from the executable file @file{foo} and place it in the file
12603 @file{foo.debug}. You can use the first, second or both methods to link the
12608 The debug link method needs the following additional command to also leave
12609 behind a debug link in @file{foo}:
12612 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
12615 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
12616 a version of the @code{strip} command such that the command @kbd{strip foo -f
12617 foo.debug} has the same functionality as the two @code{objcopy} commands and
12618 the @code{ln -s} command above, together.
12621 Build ID gets embedded into the main executable using @code{ld --build-id} or
12622 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
12623 compatibility fixes for debug files separation are present in @sc{gnu} binary
12624 utilities (Binutils) package since version 2.18.
12629 Since there are many different ways to compute CRC's for the debug
12630 link (different polynomials, reversals, byte ordering, etc.), the
12631 simplest way to describe the CRC used in @code{.gnu_debuglink}
12632 sections is to give the complete code for a function that computes it:
12634 @kindex gnu_debuglink_crc32
12637 gnu_debuglink_crc32 (unsigned long crc,
12638 unsigned char *buf, size_t len)
12640 static const unsigned long crc32_table[256] =
12642 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
12643 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
12644 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
12645 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
12646 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
12647 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
12648 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
12649 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
12650 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
12651 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
12652 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
12653 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
12654 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
12655 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
12656 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
12657 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
12658 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
12659 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
12660 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
12661 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
12662 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
12663 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
12664 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
12665 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
12666 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
12667 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
12668 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
12669 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
12670 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
12671 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
12672 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
12673 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
12674 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
12675 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
12676 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
12677 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
12678 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
12679 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
12680 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
12681 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
12682 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
12683 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
12684 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
12685 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
12686 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
12687 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
12688 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
12689 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
12690 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
12691 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
12692 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
12695 unsigned char *end;
12697 crc = ~crc & 0xffffffff;
12698 for (end = buf + len; buf < end; ++buf)
12699 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
12700 return ~crc & 0xffffffff;
12705 This computation does not apply to the ``build ID'' method.
12708 @node Symbol Errors
12709 @section Errors Reading Symbol Files
12711 While reading a symbol file, @value{GDBN} occasionally encounters problems,
12712 such as symbol types it does not recognize, or known bugs in compiler
12713 output. By default, @value{GDBN} does not notify you of such problems, since
12714 they are relatively common and primarily of interest to people
12715 debugging compilers. If you are interested in seeing information
12716 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
12717 only one message about each such type of problem, no matter how many
12718 times the problem occurs; or you can ask @value{GDBN} to print more messages,
12719 to see how many times the problems occur, with the @code{set
12720 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
12723 The messages currently printed, and their meanings, include:
12726 @item inner block not inside outer block in @var{symbol}
12728 The symbol information shows where symbol scopes begin and end
12729 (such as at the start of a function or a block of statements). This
12730 error indicates that an inner scope block is not fully contained
12731 in its outer scope blocks.
12733 @value{GDBN} circumvents the problem by treating the inner block as if it had
12734 the same scope as the outer block. In the error message, @var{symbol}
12735 may be shown as ``@code{(don't know)}'' if the outer block is not a
12738 @item block at @var{address} out of order
12740 The symbol information for symbol scope blocks should occur in
12741 order of increasing addresses. This error indicates that it does not
12744 @value{GDBN} does not circumvent this problem, and has trouble
12745 locating symbols in the source file whose symbols it is reading. (You
12746 can often determine what source file is affected by specifying
12747 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
12750 @item bad block start address patched
12752 The symbol information for a symbol scope block has a start address
12753 smaller than the address of the preceding source line. This is known
12754 to occur in the SunOS 4.1.1 (and earlier) C compiler.
12756 @value{GDBN} circumvents the problem by treating the symbol scope block as
12757 starting on the previous source line.
12759 @item bad string table offset in symbol @var{n}
12762 Symbol number @var{n} contains a pointer into the string table which is
12763 larger than the size of the string table.
12765 @value{GDBN} circumvents the problem by considering the symbol to have the
12766 name @code{foo}, which may cause other problems if many symbols end up
12769 @item unknown symbol type @code{0x@var{nn}}
12771 The symbol information contains new data types that @value{GDBN} does
12772 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
12773 uncomprehended information, in hexadecimal.
12775 @value{GDBN} circumvents the error by ignoring this symbol information.
12776 This usually allows you to debug your program, though certain symbols
12777 are not accessible. If you encounter such a problem and feel like
12778 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
12779 on @code{complain}, then go up to the function @code{read_dbx_symtab}
12780 and examine @code{*bufp} to see the symbol.
12782 @item stub type has NULL name
12784 @value{GDBN} could not find the full definition for a struct or class.
12786 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
12787 The symbol information for a C@t{++} member function is missing some
12788 information that recent versions of the compiler should have output for
12791 @item info mismatch between compiler and debugger
12793 @value{GDBN} could not parse a type specification output by the compiler.
12798 @chapter Specifying a Debugging Target
12800 @cindex debugging target
12801 A @dfn{target} is the execution environment occupied by your program.
12803 Often, @value{GDBN} runs in the same host environment as your program;
12804 in that case, the debugging target is specified as a side effect when
12805 you use the @code{file} or @code{core} commands. When you need more
12806 flexibility---for example, running @value{GDBN} on a physically separate
12807 host, or controlling a standalone system over a serial port or a
12808 realtime system over a TCP/IP connection---you can use the @code{target}
12809 command to specify one of the target types configured for @value{GDBN}
12810 (@pxref{Target Commands, ,Commands for Managing Targets}).
12812 @cindex target architecture
12813 It is possible to build @value{GDBN} for several different @dfn{target
12814 architectures}. When @value{GDBN} is built like that, you can choose
12815 one of the available architectures with the @kbd{set architecture}
12819 @kindex set architecture
12820 @kindex show architecture
12821 @item set architecture @var{arch}
12822 This command sets the current target architecture to @var{arch}. The
12823 value of @var{arch} can be @code{"auto"}, in addition to one of the
12824 supported architectures.
12826 @item show architecture
12827 Show the current target architecture.
12829 @item set processor
12831 @kindex set processor
12832 @kindex show processor
12833 These are alias commands for, respectively, @code{set architecture}
12834 and @code{show architecture}.
12838 * Active Targets:: Active targets
12839 * Target Commands:: Commands for managing targets
12840 * Byte Order:: Choosing target byte order
12843 @node Active Targets
12844 @section Active Targets
12846 @cindex stacking targets
12847 @cindex active targets
12848 @cindex multiple targets
12850 There are three classes of targets: processes, core files, and
12851 executable files. @value{GDBN} can work concurrently on up to three
12852 active targets, one in each class. This allows you to (for example)
12853 start a process and inspect its activity without abandoning your work on
12856 For example, if you execute @samp{gdb a.out}, then the executable file
12857 @code{a.out} is the only active target. If you designate a core file as
12858 well---presumably from a prior run that crashed and coredumped---then
12859 @value{GDBN} has two active targets and uses them in tandem, looking
12860 first in the corefile target, then in the executable file, to satisfy
12861 requests for memory addresses. (Typically, these two classes of target
12862 are complementary, since core files contain only a program's
12863 read-write memory---variables and so on---plus machine status, while
12864 executable files contain only the program text and initialized data.)
12866 When you type @code{run}, your executable file becomes an active process
12867 target as well. When a process target is active, all @value{GDBN}
12868 commands requesting memory addresses refer to that target; addresses in
12869 an active core file or executable file target are obscured while the
12870 process target is active.
12872 Use the @code{core-file} and @code{exec-file} commands to select a new
12873 core file or executable target (@pxref{Files, ,Commands to Specify
12874 Files}). To specify as a target a process that is already running, use
12875 the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
12878 @node Target Commands
12879 @section Commands for Managing Targets
12882 @item target @var{type} @var{parameters}
12883 Connects the @value{GDBN} host environment to a target machine or
12884 process. A target is typically a protocol for talking to debugging
12885 facilities. You use the argument @var{type} to specify the type or
12886 protocol of the target machine.
12888 Further @var{parameters} are interpreted by the target protocol, but
12889 typically include things like device names or host names to connect
12890 with, process numbers, and baud rates.
12892 The @code{target} command does not repeat if you press @key{RET} again
12893 after executing the command.
12895 @kindex help target
12897 Displays the names of all targets available. To display targets
12898 currently selected, use either @code{info target} or @code{info files}
12899 (@pxref{Files, ,Commands to Specify Files}).
12901 @item help target @var{name}
12902 Describe a particular target, including any parameters necessary to
12905 @kindex set gnutarget
12906 @item set gnutarget @var{args}
12907 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
12908 knows whether it is reading an @dfn{executable},
12909 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
12910 with the @code{set gnutarget} command. Unlike most @code{target} commands,
12911 with @code{gnutarget} the @code{target} refers to a program, not a machine.
12914 @emph{Warning:} To specify a file format with @code{set gnutarget},
12915 you must know the actual BFD name.
12919 @xref{Files, , Commands to Specify Files}.
12921 @kindex show gnutarget
12922 @item show gnutarget
12923 Use the @code{show gnutarget} command to display what file format
12924 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
12925 @value{GDBN} will determine the file format for each file automatically,
12926 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
12929 @cindex common targets
12930 Here are some common targets (available, or not, depending on the GDB
12935 @item target exec @var{program}
12936 @cindex executable file target
12937 An executable file. @samp{target exec @var{program}} is the same as
12938 @samp{exec-file @var{program}}.
12940 @item target core @var{filename}
12941 @cindex core dump file target
12942 A core dump file. @samp{target core @var{filename}} is the same as
12943 @samp{core-file @var{filename}}.
12945 @item target remote @var{medium}
12946 @cindex remote target
12947 A remote system connected to @value{GDBN} via a serial line or network
12948 connection. This command tells @value{GDBN} to use its own remote
12949 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
12951 For example, if you have a board connected to @file{/dev/ttya} on the
12952 machine running @value{GDBN}, you could say:
12955 target remote /dev/ttya
12958 @code{target remote} supports the @code{load} command. This is only
12959 useful if you have some other way of getting the stub to the target
12960 system, and you can put it somewhere in memory where it won't get
12961 clobbered by the download.
12964 @cindex built-in simulator target
12965 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
12973 works; however, you cannot assume that a specific memory map, device
12974 drivers, or even basic I/O is available, although some simulators do
12975 provide these. For info about any processor-specific simulator details,
12976 see the appropriate section in @ref{Embedded Processors, ,Embedded
12981 Some configurations may include these targets as well:
12985 @item target nrom @var{dev}
12986 @cindex NetROM ROM emulator target
12987 NetROM ROM emulator. This target only supports downloading.
12991 Different targets are available on different configurations of @value{GDBN};
12992 your configuration may have more or fewer targets.
12994 Many remote targets require you to download the executable's code once
12995 you've successfully established a connection. You may wish to control
12996 various aspects of this process.
13001 @kindex set hash@r{, for remote monitors}
13002 @cindex hash mark while downloading
13003 This command controls whether a hash mark @samp{#} is displayed while
13004 downloading a file to the remote monitor. If on, a hash mark is
13005 displayed after each S-record is successfully downloaded to the
13009 @kindex show hash@r{, for remote monitors}
13010 Show the current status of displaying the hash mark.
13012 @item set debug monitor
13013 @kindex set debug monitor
13014 @cindex display remote monitor communications
13015 Enable or disable display of communications messages between
13016 @value{GDBN} and the remote monitor.
13018 @item show debug monitor
13019 @kindex show debug monitor
13020 Show the current status of displaying communications between
13021 @value{GDBN} and the remote monitor.
13026 @kindex load @var{filename}
13027 @item load @var{filename}
13029 Depending on what remote debugging facilities are configured into
13030 @value{GDBN}, the @code{load} command may be available. Where it exists, it
13031 is meant to make @var{filename} (an executable) available for debugging
13032 on the remote system---by downloading, or dynamic linking, for example.
13033 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
13034 the @code{add-symbol-file} command.
13036 If your @value{GDBN} does not have a @code{load} command, attempting to
13037 execute it gets the error message ``@code{You can't do that when your
13038 target is @dots{}}''
13040 The file is loaded at whatever address is specified in the executable.
13041 For some object file formats, you can specify the load address when you
13042 link the program; for other formats, like a.out, the object file format
13043 specifies a fixed address.
13044 @c FIXME! This would be a good place for an xref to the GNU linker doc.
13046 Depending on the remote side capabilities, @value{GDBN} may be able to
13047 load programs into flash memory.
13049 @code{load} does not repeat if you press @key{RET} again after using it.
13053 @section Choosing Target Byte Order
13055 @cindex choosing target byte order
13056 @cindex target byte order
13058 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
13059 offer the ability to run either big-endian or little-endian byte
13060 orders. Usually the executable or symbol will include a bit to
13061 designate the endian-ness, and you will not need to worry about
13062 which to use. However, you may still find it useful to adjust
13063 @value{GDBN}'s idea of processor endian-ness manually.
13067 @item set endian big
13068 Instruct @value{GDBN} to assume the target is big-endian.
13070 @item set endian little
13071 Instruct @value{GDBN} to assume the target is little-endian.
13073 @item set endian auto
13074 Instruct @value{GDBN} to use the byte order associated with the
13078 Display @value{GDBN}'s current idea of the target byte order.
13082 Note that these commands merely adjust interpretation of symbolic
13083 data on the host, and that they have absolutely no effect on the
13087 @node Remote Debugging
13088 @chapter Debugging Remote Programs
13089 @cindex remote debugging
13091 If you are trying to debug a program running on a machine that cannot run
13092 @value{GDBN} in the usual way, it is often useful to use remote debugging.
13093 For example, you might use remote debugging on an operating system kernel,
13094 or on a small system which does not have a general purpose operating system
13095 powerful enough to run a full-featured debugger.
13097 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
13098 to make this work with particular debugging targets. In addition,
13099 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
13100 but not specific to any particular target system) which you can use if you
13101 write the remote stubs---the code that runs on the remote system to
13102 communicate with @value{GDBN}.
13104 Other remote targets may be available in your
13105 configuration of @value{GDBN}; use @code{help target} to list them.
13108 * Connecting:: Connecting to a remote target
13109 * File Transfer:: Sending files to a remote system
13110 * Server:: Using the gdbserver program
13111 * Remote Configuration:: Remote configuration
13112 * Remote Stub:: Implementing a remote stub
13116 @section Connecting to a Remote Target
13118 On the @value{GDBN} host machine, you will need an unstripped copy of
13119 your program, since @value{GDBN} needs symbol and debugging information.
13120 Start up @value{GDBN} as usual, using the name of the local copy of your
13121 program as the first argument.
13123 @cindex @code{target remote}
13124 @value{GDBN} can communicate with the target over a serial line, or
13125 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
13126 each case, @value{GDBN} uses the same protocol for debugging your
13127 program; only the medium carrying the debugging packets varies. The
13128 @code{target remote} command establishes a connection to the target.
13129 Its arguments indicate which medium to use:
13133 @item target remote @var{serial-device}
13134 @cindex serial line, @code{target remote}
13135 Use @var{serial-device} to communicate with the target. For example,
13136 to use a serial line connected to the device named @file{/dev/ttyb}:
13139 target remote /dev/ttyb
13142 If you're using a serial line, you may want to give @value{GDBN} the
13143 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
13144 (@pxref{Remote Configuration, set remotebaud}) before the
13145 @code{target} command.
13147 @item target remote @code{@var{host}:@var{port}}
13148 @itemx target remote @code{tcp:@var{host}:@var{port}}
13149 @cindex @acronym{TCP} port, @code{target remote}
13150 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
13151 The @var{host} may be either a host name or a numeric @acronym{IP}
13152 address; @var{port} must be a decimal number. The @var{host} could be
13153 the target machine itself, if it is directly connected to the net, or
13154 it might be a terminal server which in turn has a serial line to the
13157 For example, to connect to port 2828 on a terminal server named
13161 target remote manyfarms:2828
13164 If your remote target is actually running on the same machine as your
13165 debugger session (e.g.@: a simulator for your target running on the
13166 same host), you can omit the hostname. For example, to connect to
13167 port 1234 on your local machine:
13170 target remote :1234
13174 Note that the colon is still required here.
13176 @item target remote @code{udp:@var{host}:@var{port}}
13177 @cindex @acronym{UDP} port, @code{target remote}
13178 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
13179 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
13182 target remote udp:manyfarms:2828
13185 When using a @acronym{UDP} connection for remote debugging, you should
13186 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
13187 can silently drop packets on busy or unreliable networks, which will
13188 cause havoc with your debugging session.
13190 @item target remote | @var{command}
13191 @cindex pipe, @code{target remote} to
13192 Run @var{command} in the background and communicate with it using a
13193 pipe. The @var{command} is a shell command, to be parsed and expanded
13194 by the system's command shell, @code{/bin/sh}; it should expect remote
13195 protocol packets on its standard input, and send replies on its
13196 standard output. You could use this to run a stand-alone simulator
13197 that speaks the remote debugging protocol, to make net connections
13198 using programs like @code{ssh}, or for other similar tricks.
13200 If @var{command} closes its standard output (perhaps by exiting),
13201 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
13202 program has already exited, this will have no effect.)
13206 Once the connection has been established, you can use all the usual
13207 commands to examine and change data. The remote program is already
13208 running; you can use @kbd{step} and @kbd{continue}, and you do not
13209 need to use @kbd{run}.
13211 @cindex interrupting remote programs
13212 @cindex remote programs, interrupting
13213 Whenever @value{GDBN} is waiting for the remote program, if you type the
13214 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
13215 program. This may or may not succeed, depending in part on the hardware
13216 and the serial drivers the remote system uses. If you type the
13217 interrupt character once again, @value{GDBN} displays this prompt:
13220 Interrupted while waiting for the program.
13221 Give up (and stop debugging it)? (y or n)
13224 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
13225 (If you decide you want to try again later, you can use @samp{target
13226 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
13227 goes back to waiting.
13230 @kindex detach (remote)
13232 When you have finished debugging the remote program, you can use the
13233 @code{detach} command to release it from @value{GDBN} control.
13234 Detaching from the target normally resumes its execution, but the results
13235 will depend on your particular remote stub. After the @code{detach}
13236 command, @value{GDBN} is free to connect to another target.
13240 The @code{disconnect} command behaves like @code{detach}, except that
13241 the target is generally not resumed. It will wait for @value{GDBN}
13242 (this instance or another one) to connect and continue debugging. After
13243 the @code{disconnect} command, @value{GDBN} is again free to connect to
13246 @cindex send command to remote monitor
13247 @cindex extend @value{GDBN} for remote targets
13248 @cindex add new commands for external monitor
13250 @item monitor @var{cmd}
13251 This command allows you to send arbitrary commands directly to the
13252 remote monitor. Since @value{GDBN} doesn't care about the commands it
13253 sends like this, this command is the way to extend @value{GDBN}---you
13254 can add new commands that only the external monitor will understand
13258 @node File Transfer
13259 @section Sending files to a remote system
13260 @cindex remote target, file transfer
13261 @cindex file transfer
13262 @cindex sending files to remote systems
13264 Some remote targets offer the ability to transfer files over the same
13265 connection used to communicate with @value{GDBN}. This is convenient
13266 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
13267 running @code{gdbserver} over a network interface. For other targets,
13268 e.g.@: embedded devices with only a single serial port, this may be
13269 the only way to upload or download files.
13271 Not all remote targets support these commands.
13275 @item remote put @var{hostfile} @var{targetfile}
13276 Copy file @var{hostfile} from the host system (the machine running
13277 @value{GDBN}) to @var{targetfile} on the target system.
13280 @item remote get @var{targetfile} @var{hostfile}
13281 Copy file @var{targetfile} from the target system to @var{hostfile}
13282 on the host system.
13284 @kindex remote delete
13285 @item remote delete @var{targetfile}
13286 Delete @var{targetfile} from the target system.
13291 @section Using the @code{gdbserver} Program
13294 @cindex remote connection without stubs
13295 @code{gdbserver} is a control program for Unix-like systems, which
13296 allows you to connect your program with a remote @value{GDBN} via
13297 @code{target remote}---but without linking in the usual debugging stub.
13299 @code{gdbserver} is not a complete replacement for the debugging stubs,
13300 because it requires essentially the same operating-system facilities
13301 that @value{GDBN} itself does. In fact, a system that can run
13302 @code{gdbserver} to connect to a remote @value{GDBN} could also run
13303 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
13304 because it is a much smaller program than @value{GDBN} itself. It is
13305 also easier to port than all of @value{GDBN}, so you may be able to get
13306 started more quickly on a new system by using @code{gdbserver}.
13307 Finally, if you develop code for real-time systems, you may find that
13308 the tradeoffs involved in real-time operation make it more convenient to
13309 do as much development work as possible on another system, for example
13310 by cross-compiling. You can use @code{gdbserver} to make a similar
13311 choice for debugging.
13313 @value{GDBN} and @code{gdbserver} communicate via either a serial line
13314 or a TCP connection, using the standard @value{GDBN} remote serial
13318 @emph{Warning:} @code{gdbserver} does not have any built-in security.
13319 Do not run @code{gdbserver} connected to any public network; a
13320 @value{GDBN} connection to @code{gdbserver} provides access to the
13321 target system with the same privileges as the user running
13325 @subsection Running @code{gdbserver}
13326 @cindex arguments, to @code{gdbserver}
13328 Run @code{gdbserver} on the target system. You need a copy of the
13329 program you want to debug, including any libraries it requires.
13330 @code{gdbserver} does not need your program's symbol table, so you can
13331 strip the program if necessary to save space. @value{GDBN} on the host
13332 system does all the symbol handling.
13334 To use the server, you must tell it how to communicate with @value{GDBN};
13335 the name of your program; and the arguments for your program. The usual
13339 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
13342 @var{comm} is either a device name (to use a serial line) or a TCP
13343 hostname and portnumber. For example, to debug Emacs with the argument
13344 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
13348 target> gdbserver /dev/com1 emacs foo.txt
13351 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
13354 To use a TCP connection instead of a serial line:
13357 target> gdbserver host:2345 emacs foo.txt
13360 The only difference from the previous example is the first argument,
13361 specifying that you are communicating with the host @value{GDBN} via
13362 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
13363 expect a TCP connection from machine @samp{host} to local TCP port 2345.
13364 (Currently, the @samp{host} part is ignored.) You can choose any number
13365 you want for the port number as long as it does not conflict with any
13366 TCP ports already in use on the target system (for example, @code{23} is
13367 reserved for @code{telnet}).@footnote{If you choose a port number that
13368 conflicts with another service, @code{gdbserver} prints an error message
13369 and exits.} You must use the same port number with the host @value{GDBN}
13370 @code{target remote} command.
13372 @subsubsection Attaching to a Running Program
13374 On some targets, @code{gdbserver} can also attach to running programs.
13375 This is accomplished via the @code{--attach} argument. The syntax is:
13378 target> gdbserver --attach @var{comm} @var{pid}
13381 @var{pid} is the process ID of a currently running process. It isn't necessary
13382 to point @code{gdbserver} at a binary for the running process.
13385 @cindex attach to a program by name
13386 You can debug processes by name instead of process ID if your target has the
13387 @code{pidof} utility:
13390 target> gdbserver --attach @var{comm} `pidof @var{program}`
13393 In case more than one copy of @var{program} is running, or @var{program}
13394 has multiple threads, most versions of @code{pidof} support the
13395 @code{-s} option to only return the first process ID.
13397 @subsubsection Multi-Process Mode for @code{gdbserver}
13398 @cindex gdbserver, multiple processes
13399 @cindex multiple processes with gdbserver
13401 When you connect to @code{gdbserver} using @code{target remote},
13402 @code{gdbserver} debugs the specified program only once. When the
13403 program exits, or you detach from it, @value{GDBN} closes the connection
13404 and @code{gdbserver} exits.
13406 If you connect using @kbd{target extended-remote}, @code{gdbserver}
13407 enters multi-process mode. When the debugged program exits, or you
13408 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
13409 though no program is running. The @code{run} and @code{attach}
13410 commands instruct @code{gdbserver} to run or attach to a new program.
13411 The @code{run} command uses @code{set remote exec-file} (@pxref{set
13412 remote exec-file}) to select the program to run. Command line
13413 arguments are supported, except for wildcard expansion and I/O
13414 redirection (@pxref{Arguments}).
13416 To start @code{gdbserver} without supplying an initial command to run
13417 or process ID to attach, use the @option{--multi} command line option.
13418 Then you can connect using @kbd{target extended-remote} and start
13419 the program you want to debug.
13421 @code{gdbserver} does not automatically exit in multi-process mode.
13422 You can terminate it by using @code{monitor exit}
13423 (@pxref{Monitor Commands for gdbserver}).
13425 @subsubsection Other Command-Line Arguments for @code{gdbserver}
13427 You can include @option{--debug} on the @code{gdbserver} command line.
13428 @code{gdbserver} will display extra status information about the debugging
13429 process. This option is intended for @code{gdbserver} development and
13430 for bug reports to the developers.
13432 The @option{--wrapper} option specifies a wrapper to launch programs
13433 for debugging. The option should be followed by the name of the
13434 wrapper, then any command-line arguments to pass to the wrapper, then
13435 @kbd{--} indicating the end of the wrapper arguments.
13437 @code{gdbserver} runs the specified wrapper program with a combined
13438 command line including the wrapper arguments, then the name of the
13439 program to debug, then any arguments to the program. The wrapper
13440 runs until it executes your program, and then @value{GDBN} gains control.
13442 You can use any program that eventually calls @code{execve} with
13443 its arguments as a wrapper. Several standard Unix utilities do
13444 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
13445 with @code{exec "$@@"} will also work.
13447 For example, you can use @code{env} to pass an environment variable to
13448 the debugged program, without setting the variable in @code{gdbserver}'s
13452 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
13455 @subsection Connecting to @code{gdbserver}
13457 Run @value{GDBN} on the host system.
13459 First make sure you have the necessary symbol files. Load symbols for
13460 your application using the @code{file} command before you connect. Use
13461 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
13462 was compiled with the correct sysroot using @code{--with-sysroot}).
13464 The symbol file and target libraries must exactly match the executable
13465 and libraries on the target, with one exception: the files on the host
13466 system should not be stripped, even if the files on the target system
13467 are. Mismatched or missing files will lead to confusing results
13468 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
13469 files may also prevent @code{gdbserver} from debugging multi-threaded
13472 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
13473 For TCP connections, you must start up @code{gdbserver} prior to using
13474 the @code{target remote} command. Otherwise you may get an error whose
13475 text depends on the host system, but which usually looks something like
13476 @samp{Connection refused}. Don't use the @code{load}
13477 command in @value{GDBN} when using @code{gdbserver}, since the program is
13478 already on the target.
13480 @subsection Monitor Commands for @code{gdbserver}
13481 @cindex monitor commands, for @code{gdbserver}
13482 @anchor{Monitor Commands for gdbserver}
13484 During a @value{GDBN} session using @code{gdbserver}, you can use the
13485 @code{monitor} command to send special requests to @code{gdbserver}.
13486 Here are the available commands.
13490 List the available monitor commands.
13492 @item monitor set debug 0
13493 @itemx monitor set debug 1
13494 Disable or enable general debugging messages.
13496 @item monitor set remote-debug 0
13497 @itemx monitor set remote-debug 1
13498 Disable or enable specific debugging messages associated with the remote
13499 protocol (@pxref{Remote Protocol}).
13502 Tell gdbserver to exit immediately. This command should be followed by
13503 @code{disconnect} to close the debugging session. @code{gdbserver} will
13504 detach from any attached processes and kill any processes it created.
13505 Use @code{monitor exit} to terminate @code{gdbserver} at the end
13506 of a multi-process mode debug session.
13510 @node Remote Configuration
13511 @section Remote Configuration
13514 @kindex show remote
13515 This section documents the configuration options available when
13516 debugging remote programs. For the options related to the File I/O
13517 extensions of the remote protocol, see @ref{system,
13518 system-call-allowed}.
13521 @item set remoteaddresssize @var{bits}
13522 @cindex address size for remote targets
13523 @cindex bits in remote address
13524 Set the maximum size of address in a memory packet to the specified
13525 number of bits. @value{GDBN} will mask off the address bits above
13526 that number, when it passes addresses to the remote target. The
13527 default value is the number of bits in the target's address.
13529 @item show remoteaddresssize
13530 Show the current value of remote address size in bits.
13532 @item set remotebaud @var{n}
13533 @cindex baud rate for remote targets
13534 Set the baud rate for the remote serial I/O to @var{n} baud. The
13535 value is used to set the speed of the serial port used for debugging
13538 @item show remotebaud
13539 Show the current speed of the remote connection.
13541 @item set remotebreak
13542 @cindex interrupt remote programs
13543 @cindex BREAK signal instead of Ctrl-C
13544 @anchor{set remotebreak}
13545 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
13546 when you type @kbd{Ctrl-c} to interrupt the program running
13547 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
13548 character instead. The default is off, since most remote systems
13549 expect to see @samp{Ctrl-C} as the interrupt signal.
13551 @item show remotebreak
13552 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
13553 interrupt the remote program.
13555 @item set remoteflow on
13556 @itemx set remoteflow off
13557 @kindex set remoteflow
13558 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
13559 on the serial port used to communicate to the remote target.
13561 @item show remoteflow
13562 @kindex show remoteflow
13563 Show the current setting of hardware flow control.
13565 @item set remotelogbase @var{base}
13566 Set the base (a.k.a.@: radix) of logging serial protocol
13567 communications to @var{base}. Supported values of @var{base} are:
13568 @code{ascii}, @code{octal}, and @code{hex}. The default is
13571 @item show remotelogbase
13572 Show the current setting of the radix for logging remote serial
13575 @item set remotelogfile @var{file}
13576 @cindex record serial communications on file
13577 Record remote serial communications on the named @var{file}. The
13578 default is not to record at all.
13580 @item show remotelogfile.
13581 Show the current setting of the file name on which to record the
13582 serial communications.
13584 @item set remotetimeout @var{num}
13585 @cindex timeout for serial communications
13586 @cindex remote timeout
13587 Set the timeout limit to wait for the remote target to respond to
13588 @var{num} seconds. The default is 2 seconds.
13590 @item show remotetimeout
13591 Show the current number of seconds to wait for the remote target
13594 @cindex limit hardware breakpoints and watchpoints
13595 @cindex remote target, limit break- and watchpoints
13596 @anchor{set remote hardware-watchpoint-limit}
13597 @anchor{set remote hardware-breakpoint-limit}
13598 @item set remote hardware-watchpoint-limit @var{limit}
13599 @itemx set remote hardware-breakpoint-limit @var{limit}
13600 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
13601 watchpoints. A limit of -1, the default, is treated as unlimited.
13603 @item set remote exec-file @var{filename}
13604 @itemx show remote exec-file
13605 @anchor{set remote exec-file}
13606 @cindex executable file, for remote target
13607 Select the file used for @code{run} with @code{target
13608 extended-remote}. This should be set to a filename valid on the
13609 target system. If it is not set, the target will use a default
13610 filename (e.g.@: the last program run).
13613 @cindex remote packets, enabling and disabling
13614 The @value{GDBN} remote protocol autodetects the packets supported by
13615 your debugging stub. If you need to override the autodetection, you
13616 can use these commands to enable or disable individual packets. Each
13617 packet can be set to @samp{on} (the remote target supports this
13618 packet), @samp{off} (the remote target does not support this packet),
13619 or @samp{auto} (detect remote target support for this packet). They
13620 all default to @samp{auto}. For more information about each packet,
13621 see @ref{Remote Protocol}.
13623 During normal use, you should not have to use any of these commands.
13624 If you do, that may be a bug in your remote debugging stub, or a bug
13625 in @value{GDBN}. You may want to report the problem to the
13626 @value{GDBN} developers.
13628 For each packet @var{name}, the command to enable or disable the
13629 packet is @code{set remote @var{name}-packet}. The available settings
13632 @multitable @columnfractions 0.28 0.32 0.25
13635 @tab Related Features
13637 @item @code{fetch-register}
13639 @tab @code{info registers}
13641 @item @code{set-register}
13645 @item @code{binary-download}
13647 @tab @code{load}, @code{set}
13649 @item @code{read-aux-vector}
13650 @tab @code{qXfer:auxv:read}
13651 @tab @code{info auxv}
13653 @item @code{symbol-lookup}
13654 @tab @code{qSymbol}
13655 @tab Detecting multiple threads
13657 @item @code{attach}
13658 @tab @code{vAttach}
13661 @item @code{verbose-resume}
13663 @tab Stepping or resuming multiple threads
13669 @item @code{software-breakpoint}
13673 @item @code{hardware-breakpoint}
13677 @item @code{write-watchpoint}
13681 @item @code{read-watchpoint}
13685 @item @code{access-watchpoint}
13689 @item @code{target-features}
13690 @tab @code{qXfer:features:read}
13691 @tab @code{set architecture}
13693 @item @code{library-info}
13694 @tab @code{qXfer:libraries:read}
13695 @tab @code{info sharedlibrary}
13697 @item @code{memory-map}
13698 @tab @code{qXfer:memory-map:read}
13699 @tab @code{info mem}
13701 @item @code{read-spu-object}
13702 @tab @code{qXfer:spu:read}
13703 @tab @code{info spu}
13705 @item @code{write-spu-object}
13706 @tab @code{qXfer:spu:write}
13707 @tab @code{info spu}
13709 @item @code{get-thread-local-@*storage-address}
13710 @tab @code{qGetTLSAddr}
13711 @tab Displaying @code{__thread} variables
13713 @item @code{search-memory}
13714 @tab @code{qSearch:memory}
13717 @item @code{supported-packets}
13718 @tab @code{qSupported}
13719 @tab Remote communications parameters
13721 @item @code{pass-signals}
13722 @tab @code{QPassSignals}
13723 @tab @code{handle @var{signal}}
13725 @item @code{hostio-close-packet}
13726 @tab @code{vFile:close}
13727 @tab @code{remote get}, @code{remote put}
13729 @item @code{hostio-open-packet}
13730 @tab @code{vFile:open}
13731 @tab @code{remote get}, @code{remote put}
13733 @item @code{hostio-pread-packet}
13734 @tab @code{vFile:pread}
13735 @tab @code{remote get}, @code{remote put}
13737 @item @code{hostio-pwrite-packet}
13738 @tab @code{vFile:pwrite}
13739 @tab @code{remote get}, @code{remote put}
13741 @item @code{hostio-unlink-packet}
13742 @tab @code{vFile:unlink}
13743 @tab @code{remote delete}
13747 @section Implementing a Remote Stub
13749 @cindex debugging stub, example
13750 @cindex remote stub, example
13751 @cindex stub example, remote debugging
13752 The stub files provided with @value{GDBN} implement the target side of the
13753 communication protocol, and the @value{GDBN} side is implemented in the
13754 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
13755 these subroutines to communicate, and ignore the details. (If you're
13756 implementing your own stub file, you can still ignore the details: start
13757 with one of the existing stub files. @file{sparc-stub.c} is the best
13758 organized, and therefore the easiest to read.)
13760 @cindex remote serial debugging, overview
13761 To debug a program running on another machine (the debugging
13762 @dfn{target} machine), you must first arrange for all the usual
13763 prerequisites for the program to run by itself. For example, for a C
13768 A startup routine to set up the C runtime environment; these usually
13769 have a name like @file{crt0}. The startup routine may be supplied by
13770 your hardware supplier, or you may have to write your own.
13773 A C subroutine library to support your program's
13774 subroutine calls, notably managing input and output.
13777 A way of getting your program to the other machine---for example, a
13778 download program. These are often supplied by the hardware
13779 manufacturer, but you may have to write your own from hardware
13783 The next step is to arrange for your program to use a serial port to
13784 communicate with the machine where @value{GDBN} is running (the @dfn{host}
13785 machine). In general terms, the scheme looks like this:
13789 @value{GDBN} already understands how to use this protocol; when everything
13790 else is set up, you can simply use the @samp{target remote} command
13791 (@pxref{Targets,,Specifying a Debugging Target}).
13793 @item On the target,
13794 you must link with your program a few special-purpose subroutines that
13795 implement the @value{GDBN} remote serial protocol. The file containing these
13796 subroutines is called a @dfn{debugging stub}.
13798 On certain remote targets, you can use an auxiliary program
13799 @code{gdbserver} instead of linking a stub into your program.
13800 @xref{Server,,Using the @code{gdbserver} Program}, for details.
13803 The debugging stub is specific to the architecture of the remote
13804 machine; for example, use @file{sparc-stub.c} to debug programs on
13807 @cindex remote serial stub list
13808 These working remote stubs are distributed with @value{GDBN}:
13813 @cindex @file{i386-stub.c}
13816 For Intel 386 and compatible architectures.
13819 @cindex @file{m68k-stub.c}
13820 @cindex Motorola 680x0
13822 For Motorola 680x0 architectures.
13825 @cindex @file{sh-stub.c}
13828 For Renesas SH architectures.
13831 @cindex @file{sparc-stub.c}
13833 For @sc{sparc} architectures.
13835 @item sparcl-stub.c
13836 @cindex @file{sparcl-stub.c}
13839 For Fujitsu @sc{sparclite} architectures.
13843 The @file{README} file in the @value{GDBN} distribution may list other
13844 recently added stubs.
13847 * Stub Contents:: What the stub can do for you
13848 * Bootstrapping:: What you must do for the stub
13849 * Debug Session:: Putting it all together
13852 @node Stub Contents
13853 @subsection What the Stub Can Do for You
13855 @cindex remote serial stub
13856 The debugging stub for your architecture supplies these three
13860 @item set_debug_traps
13861 @findex set_debug_traps
13862 @cindex remote serial stub, initialization
13863 This routine arranges for @code{handle_exception} to run when your
13864 program stops. You must call this subroutine explicitly near the
13865 beginning of your program.
13867 @item handle_exception
13868 @findex handle_exception
13869 @cindex remote serial stub, main routine
13870 This is the central workhorse, but your program never calls it
13871 explicitly---the setup code arranges for @code{handle_exception} to
13872 run when a trap is triggered.
13874 @code{handle_exception} takes control when your program stops during
13875 execution (for example, on a breakpoint), and mediates communications
13876 with @value{GDBN} on the host machine. This is where the communications
13877 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
13878 representative on the target machine. It begins by sending summary
13879 information on the state of your program, then continues to execute,
13880 retrieving and transmitting any information @value{GDBN} needs, until you
13881 execute a @value{GDBN} command that makes your program resume; at that point,
13882 @code{handle_exception} returns control to your own code on the target
13886 @cindex @code{breakpoint} subroutine, remote
13887 Use this auxiliary subroutine to make your program contain a
13888 breakpoint. Depending on the particular situation, this may be the only
13889 way for @value{GDBN} to get control. For instance, if your target
13890 machine has some sort of interrupt button, you won't need to call this;
13891 pressing the interrupt button transfers control to
13892 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
13893 simply receiving characters on the serial port may also trigger a trap;
13894 again, in that situation, you don't need to call @code{breakpoint} from
13895 your own program---simply running @samp{target remote} from the host
13896 @value{GDBN} session gets control.
13898 Call @code{breakpoint} if none of these is true, or if you simply want
13899 to make certain your program stops at a predetermined point for the
13900 start of your debugging session.
13903 @node Bootstrapping
13904 @subsection What You Must Do for the Stub
13906 @cindex remote stub, support routines
13907 The debugging stubs that come with @value{GDBN} are set up for a particular
13908 chip architecture, but they have no information about the rest of your
13909 debugging target machine.
13911 First of all you need to tell the stub how to communicate with the
13915 @item int getDebugChar()
13916 @findex getDebugChar
13917 Write this subroutine to read a single character from the serial port.
13918 It may be identical to @code{getchar} for your target system; a
13919 different name is used to allow you to distinguish the two if you wish.
13921 @item void putDebugChar(int)
13922 @findex putDebugChar
13923 Write this subroutine to write a single character to the serial port.
13924 It may be identical to @code{putchar} for your target system; a
13925 different name is used to allow you to distinguish the two if you wish.
13928 @cindex control C, and remote debugging
13929 @cindex interrupting remote targets
13930 If you want @value{GDBN} to be able to stop your program while it is
13931 running, you need to use an interrupt-driven serial driver, and arrange
13932 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
13933 character). That is the character which @value{GDBN} uses to tell the
13934 remote system to stop.
13936 Getting the debugging target to return the proper status to @value{GDBN}
13937 probably requires changes to the standard stub; one quick and dirty way
13938 is to just execute a breakpoint instruction (the ``dirty'' part is that
13939 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
13941 Other routines you need to supply are:
13944 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
13945 @findex exceptionHandler
13946 Write this function to install @var{exception_address} in the exception
13947 handling tables. You need to do this because the stub does not have any
13948 way of knowing what the exception handling tables on your target system
13949 are like (for example, the processor's table might be in @sc{rom},
13950 containing entries which point to a table in @sc{ram}).
13951 @var{exception_number} is the exception number which should be changed;
13952 its meaning is architecture-dependent (for example, different numbers
13953 might represent divide by zero, misaligned access, etc). When this
13954 exception occurs, control should be transferred directly to
13955 @var{exception_address}, and the processor state (stack, registers,
13956 and so on) should be just as it is when a processor exception occurs. So if
13957 you want to use a jump instruction to reach @var{exception_address}, it
13958 should be a simple jump, not a jump to subroutine.
13960 For the 386, @var{exception_address} should be installed as an interrupt
13961 gate so that interrupts are masked while the handler runs. The gate
13962 should be at privilege level 0 (the most privileged level). The
13963 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
13964 help from @code{exceptionHandler}.
13966 @item void flush_i_cache()
13967 @findex flush_i_cache
13968 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
13969 instruction cache, if any, on your target machine. If there is no
13970 instruction cache, this subroutine may be a no-op.
13972 On target machines that have instruction caches, @value{GDBN} requires this
13973 function to make certain that the state of your program is stable.
13977 You must also make sure this library routine is available:
13980 @item void *memset(void *, int, int)
13982 This is the standard library function @code{memset} that sets an area of
13983 memory to a known value. If you have one of the free versions of
13984 @code{libc.a}, @code{memset} can be found there; otherwise, you must
13985 either obtain it from your hardware manufacturer, or write your own.
13988 If you do not use the GNU C compiler, you may need other standard
13989 library subroutines as well; this varies from one stub to another,
13990 but in general the stubs are likely to use any of the common library
13991 subroutines which @code{@value{NGCC}} generates as inline code.
13994 @node Debug Session
13995 @subsection Putting it All Together
13997 @cindex remote serial debugging summary
13998 In summary, when your program is ready to debug, you must follow these
14003 Make sure you have defined the supporting low-level routines
14004 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
14006 @code{getDebugChar}, @code{putDebugChar},
14007 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
14011 Insert these lines near the top of your program:
14019 For the 680x0 stub only, you need to provide a variable called
14020 @code{exceptionHook}. Normally you just use:
14023 void (*exceptionHook)() = 0;
14027 but if before calling @code{set_debug_traps}, you set it to point to a
14028 function in your program, that function is called when
14029 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
14030 error). The function indicated by @code{exceptionHook} is called with
14031 one parameter: an @code{int} which is the exception number.
14034 Compile and link together: your program, the @value{GDBN} debugging stub for
14035 your target architecture, and the supporting subroutines.
14038 Make sure you have a serial connection between your target machine and
14039 the @value{GDBN} host, and identify the serial port on the host.
14042 @c The "remote" target now provides a `load' command, so we should
14043 @c document that. FIXME.
14044 Download your program to your target machine (or get it there by
14045 whatever means the manufacturer provides), and start it.
14048 Start @value{GDBN} on the host, and connect to the target
14049 (@pxref{Connecting,,Connecting to a Remote Target}).
14053 @node Configurations
14054 @chapter Configuration-Specific Information
14056 While nearly all @value{GDBN} commands are available for all native and
14057 cross versions of the debugger, there are some exceptions. This chapter
14058 describes things that are only available in certain configurations.
14060 There are three major categories of configurations: native
14061 configurations, where the host and target are the same, embedded
14062 operating system configurations, which are usually the same for several
14063 different processor architectures, and bare embedded processors, which
14064 are quite different from each other.
14069 * Embedded Processors::
14076 This section describes details specific to particular native
14081 * BSD libkvm Interface:: Debugging BSD kernel memory images
14082 * SVR4 Process Information:: SVR4 process information
14083 * DJGPP Native:: Features specific to the DJGPP port
14084 * Cygwin Native:: Features specific to the Cygwin port
14085 * Hurd Native:: Features specific to @sc{gnu} Hurd
14086 * Neutrino:: Features specific to QNX Neutrino
14092 On HP-UX systems, if you refer to a function or variable name that
14093 begins with a dollar sign, @value{GDBN} searches for a user or system
14094 name first, before it searches for a convenience variable.
14097 @node BSD libkvm Interface
14098 @subsection BSD libkvm Interface
14101 @cindex kernel memory image
14102 @cindex kernel crash dump
14104 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
14105 interface that provides a uniform interface for accessing kernel virtual
14106 memory images, including live systems and crash dumps. @value{GDBN}
14107 uses this interface to allow you to debug live kernels and kernel crash
14108 dumps on many native BSD configurations. This is implemented as a
14109 special @code{kvm} debugging target. For debugging a live system, load
14110 the currently running kernel into @value{GDBN} and connect to the
14114 (@value{GDBP}) @b{target kvm}
14117 For debugging crash dumps, provide the file name of the crash dump as an
14121 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
14124 Once connected to the @code{kvm} target, the following commands are
14130 Set current context from the @dfn{Process Control Block} (PCB) address.
14133 Set current context from proc address. This command isn't available on
14134 modern FreeBSD systems.
14137 @node SVR4 Process Information
14138 @subsection SVR4 Process Information
14140 @cindex examine process image
14141 @cindex process info via @file{/proc}
14143 Many versions of SVR4 and compatible systems provide a facility called
14144 @samp{/proc} that can be used to examine the image of a running
14145 process using file-system subroutines. If @value{GDBN} is configured
14146 for an operating system with this facility, the command @code{info
14147 proc} is available to report information about the process running
14148 your program, or about any process running on your system. @code{info
14149 proc} works only on SVR4 systems that include the @code{procfs} code.
14150 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
14151 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
14157 @itemx info proc @var{process-id}
14158 Summarize available information about any running process. If a
14159 process ID is specified by @var{process-id}, display information about
14160 that process; otherwise display information about the program being
14161 debugged. The summary includes the debugged process ID, the command
14162 line used to invoke it, its current working directory, and its
14163 executable file's absolute file name.
14165 On some systems, @var{process-id} can be of the form
14166 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
14167 within a process. If the optional @var{pid} part is missing, it means
14168 a thread from the process being debugged (the leading @samp{/} still
14169 needs to be present, or else @value{GDBN} will interpret the number as
14170 a process ID rather than a thread ID).
14172 @item info proc mappings
14173 @cindex memory address space mappings
14174 Report the memory address space ranges accessible in the program, with
14175 information on whether the process has read, write, or execute access
14176 rights to each range. On @sc{gnu}/Linux systems, each memory range
14177 includes the object file which is mapped to that range, instead of the
14178 memory access rights to that range.
14180 @item info proc stat
14181 @itemx info proc status
14182 @cindex process detailed status information
14183 These subcommands are specific to @sc{gnu}/Linux systems. They show
14184 the process-related information, including the user ID and group ID;
14185 how many threads are there in the process; its virtual memory usage;
14186 the signals that are pending, blocked, and ignored; its TTY; its
14187 consumption of system and user time; its stack size; its @samp{nice}
14188 value; etc. For more information, see the @samp{proc} man page
14189 (type @kbd{man 5 proc} from your shell prompt).
14191 @item info proc all
14192 Show all the information about the process described under all of the
14193 above @code{info proc} subcommands.
14196 @comment These sub-options of 'info proc' were not included when
14197 @comment procfs.c was re-written. Keep their descriptions around
14198 @comment against the day when someone finds the time to put them back in.
14199 @kindex info proc times
14200 @item info proc times
14201 Starting time, user CPU time, and system CPU time for your program and
14204 @kindex info proc id
14206 Report on the process IDs related to your program: its own process ID,
14207 the ID of its parent, the process group ID, and the session ID.
14210 @item set procfs-trace
14211 @kindex set procfs-trace
14212 @cindex @code{procfs} API calls
14213 This command enables and disables tracing of @code{procfs} API calls.
14215 @item show procfs-trace
14216 @kindex show procfs-trace
14217 Show the current state of @code{procfs} API call tracing.
14219 @item set procfs-file @var{file}
14220 @kindex set procfs-file
14221 Tell @value{GDBN} to write @code{procfs} API trace to the named
14222 @var{file}. @value{GDBN} appends the trace info to the previous
14223 contents of the file. The default is to display the trace on the
14226 @item show procfs-file
14227 @kindex show procfs-file
14228 Show the file to which @code{procfs} API trace is written.
14230 @item proc-trace-entry
14231 @itemx proc-trace-exit
14232 @itemx proc-untrace-entry
14233 @itemx proc-untrace-exit
14234 @kindex proc-trace-entry
14235 @kindex proc-trace-exit
14236 @kindex proc-untrace-entry
14237 @kindex proc-untrace-exit
14238 These commands enable and disable tracing of entries into and exits
14239 from the @code{syscall} interface.
14242 @kindex info pidlist
14243 @cindex process list, QNX Neutrino
14244 For QNX Neutrino only, this command displays the list of all the
14245 processes and all the threads within each process.
14248 @kindex info meminfo
14249 @cindex mapinfo list, QNX Neutrino
14250 For QNX Neutrino only, this command displays the list of all mapinfos.
14254 @subsection Features for Debugging @sc{djgpp} Programs
14255 @cindex @sc{djgpp} debugging
14256 @cindex native @sc{djgpp} debugging
14257 @cindex MS-DOS-specific commands
14260 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
14261 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
14262 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
14263 top of real-mode DOS systems and their emulations.
14265 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
14266 defines a few commands specific to the @sc{djgpp} port. This
14267 subsection describes those commands.
14272 This is a prefix of @sc{djgpp}-specific commands which print
14273 information about the target system and important OS structures.
14276 @cindex MS-DOS system info
14277 @cindex free memory information (MS-DOS)
14278 @item info dos sysinfo
14279 This command displays assorted information about the underlying
14280 platform: the CPU type and features, the OS version and flavor, the
14281 DPMI version, and the available conventional and DPMI memory.
14286 @cindex segment descriptor tables
14287 @cindex descriptor tables display
14289 @itemx info dos ldt
14290 @itemx info dos idt
14291 These 3 commands display entries from, respectively, Global, Local,
14292 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
14293 tables are data structures which store a descriptor for each segment
14294 that is currently in use. The segment's selector is an index into a
14295 descriptor table; the table entry for that index holds the
14296 descriptor's base address and limit, and its attributes and access
14299 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
14300 segment (used for both data and the stack), and a DOS segment (which
14301 allows access to DOS/BIOS data structures and absolute addresses in
14302 conventional memory). However, the DPMI host will usually define
14303 additional segments in order to support the DPMI environment.
14305 @cindex garbled pointers
14306 These commands allow to display entries from the descriptor tables.
14307 Without an argument, all entries from the specified table are
14308 displayed. An argument, which should be an integer expression, means
14309 display a single entry whose index is given by the argument. For
14310 example, here's a convenient way to display information about the
14311 debugged program's data segment:
14314 @exdent @code{(@value{GDBP}) info dos ldt $ds}
14315 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
14319 This comes in handy when you want to see whether a pointer is outside
14320 the data segment's limit (i.e.@: @dfn{garbled}).
14322 @cindex page tables display (MS-DOS)
14324 @itemx info dos pte
14325 These two commands display entries from, respectively, the Page
14326 Directory and the Page Tables. Page Directories and Page Tables are
14327 data structures which control how virtual memory addresses are mapped
14328 into physical addresses. A Page Table includes an entry for every
14329 page of memory that is mapped into the program's address space; there
14330 may be several Page Tables, each one holding up to 4096 entries. A
14331 Page Directory has up to 4096 entries, one each for every Page Table
14332 that is currently in use.
14334 Without an argument, @kbd{info dos pde} displays the entire Page
14335 Directory, and @kbd{info dos pte} displays all the entries in all of
14336 the Page Tables. An argument, an integer expression, given to the
14337 @kbd{info dos pde} command means display only that entry from the Page
14338 Directory table. An argument given to the @kbd{info dos pte} command
14339 means display entries from a single Page Table, the one pointed to by
14340 the specified entry in the Page Directory.
14342 @cindex direct memory access (DMA) on MS-DOS
14343 These commands are useful when your program uses @dfn{DMA} (Direct
14344 Memory Access), which needs physical addresses to program the DMA
14347 These commands are supported only with some DPMI servers.
14349 @cindex physical address from linear address
14350 @item info dos address-pte @var{addr}
14351 This command displays the Page Table entry for a specified linear
14352 address. The argument @var{addr} is a linear address which should
14353 already have the appropriate segment's base address added to it,
14354 because this command accepts addresses which may belong to @emph{any}
14355 segment. For example, here's how to display the Page Table entry for
14356 the page where a variable @code{i} is stored:
14359 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
14360 @exdent @code{Page Table entry for address 0x11a00d30:}
14361 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
14365 This says that @code{i} is stored at offset @code{0xd30} from the page
14366 whose physical base address is @code{0x02698000}, and shows all the
14367 attributes of that page.
14369 Note that you must cast the addresses of variables to a @code{char *},
14370 since otherwise the value of @code{__djgpp_base_address}, the base
14371 address of all variables and functions in a @sc{djgpp} program, will
14372 be added using the rules of C pointer arithmetics: if @code{i} is
14373 declared an @code{int}, @value{GDBN} will add 4 times the value of
14374 @code{__djgpp_base_address} to the address of @code{i}.
14376 Here's another example, it displays the Page Table entry for the
14380 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
14381 @exdent @code{Page Table entry for address 0x29110:}
14382 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
14386 (The @code{+ 3} offset is because the transfer buffer's address is the
14387 3rd member of the @code{_go32_info_block} structure.) The output
14388 clearly shows that this DPMI server maps the addresses in conventional
14389 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
14390 linear (@code{0x29110}) addresses are identical.
14392 This command is supported only with some DPMI servers.
14395 @cindex DOS serial data link, remote debugging
14396 In addition to native debugging, the DJGPP port supports remote
14397 debugging via a serial data link. The following commands are specific
14398 to remote serial debugging in the DJGPP port of @value{GDBN}.
14401 @kindex set com1base
14402 @kindex set com1irq
14403 @kindex set com2base
14404 @kindex set com2irq
14405 @kindex set com3base
14406 @kindex set com3irq
14407 @kindex set com4base
14408 @kindex set com4irq
14409 @item set com1base @var{addr}
14410 This command sets the base I/O port address of the @file{COM1} serial
14413 @item set com1irq @var{irq}
14414 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
14415 for the @file{COM1} serial port.
14417 There are similar commands @samp{set com2base}, @samp{set com3irq},
14418 etc.@: for setting the port address and the @code{IRQ} lines for the
14421 @kindex show com1base
14422 @kindex show com1irq
14423 @kindex show com2base
14424 @kindex show com2irq
14425 @kindex show com3base
14426 @kindex show com3irq
14427 @kindex show com4base
14428 @kindex show com4irq
14429 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
14430 display the current settings of the base address and the @code{IRQ}
14431 lines used by the COM ports.
14434 @kindex info serial
14435 @cindex DOS serial port status
14436 This command prints the status of the 4 DOS serial ports. For each
14437 port, it prints whether it's active or not, its I/O base address and
14438 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
14439 counts of various errors encountered so far.
14443 @node Cygwin Native
14444 @subsection Features for Debugging MS Windows PE Executables
14445 @cindex MS Windows debugging
14446 @cindex native Cygwin debugging
14447 @cindex Cygwin-specific commands
14449 @value{GDBN} supports native debugging of MS Windows programs, including
14450 DLLs with and without symbolic debugging information. There are various
14451 additional Cygwin-specific commands, described in this section.
14452 Working with DLLs that have no debugging symbols is described in
14453 @ref{Non-debug DLL Symbols}.
14458 This is a prefix of MS Windows-specific commands which print
14459 information about the target system and important OS structures.
14461 @item info w32 selector
14462 This command displays information returned by
14463 the Win32 API @code{GetThreadSelectorEntry} function.
14464 It takes an optional argument that is evaluated to
14465 a long value to give the information about this given selector.
14466 Without argument, this command displays information
14467 about the six segment registers.
14471 This is a Cygwin-specific alias of @code{info shared}.
14473 @kindex dll-symbols
14475 This command loads symbols from a dll similarly to
14476 add-sym command but without the need to specify a base address.
14478 @kindex set cygwin-exceptions
14479 @cindex debugging the Cygwin DLL
14480 @cindex Cygwin DLL, debugging
14481 @item set cygwin-exceptions @var{mode}
14482 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
14483 happen inside the Cygwin DLL. If @var{mode} is @code{off},
14484 @value{GDBN} will delay recognition of exceptions, and may ignore some
14485 exceptions which seem to be caused by internal Cygwin DLL
14486 ``bookkeeping''. This option is meant primarily for debugging the
14487 Cygwin DLL itself; the default value is @code{off} to avoid annoying
14488 @value{GDBN} users with false @code{SIGSEGV} signals.
14490 @kindex show cygwin-exceptions
14491 @item show cygwin-exceptions
14492 Displays whether @value{GDBN} will break on exceptions that happen
14493 inside the Cygwin DLL itself.
14495 @kindex set new-console
14496 @item set new-console @var{mode}
14497 If @var{mode} is @code{on} the debuggee will
14498 be started in a new console on next start.
14499 If @var{mode} is @code{off}i, the debuggee will
14500 be started in the same console as the debugger.
14502 @kindex show new-console
14503 @item show new-console
14504 Displays whether a new console is used
14505 when the debuggee is started.
14507 @kindex set new-group
14508 @item set new-group @var{mode}
14509 This boolean value controls whether the debuggee should
14510 start a new group or stay in the same group as the debugger.
14511 This affects the way the Windows OS handles
14514 @kindex show new-group
14515 @item show new-group
14516 Displays current value of new-group boolean.
14518 @kindex set debugevents
14519 @item set debugevents
14520 This boolean value adds debug output concerning kernel events related
14521 to the debuggee seen by the debugger. This includes events that
14522 signal thread and process creation and exit, DLL loading and
14523 unloading, console interrupts, and debugging messages produced by the
14524 Windows @code{OutputDebugString} API call.
14526 @kindex set debugexec
14527 @item set debugexec
14528 This boolean value adds debug output concerning execute events
14529 (such as resume thread) seen by the debugger.
14531 @kindex set debugexceptions
14532 @item set debugexceptions
14533 This boolean value adds debug output concerning exceptions in the
14534 debuggee seen by the debugger.
14536 @kindex set debugmemory
14537 @item set debugmemory
14538 This boolean value adds debug output concerning debuggee memory reads
14539 and writes by the debugger.
14543 This boolean values specifies whether the debuggee is called
14544 via a shell or directly (default value is on).
14548 Displays if the debuggee will be started with a shell.
14553 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
14556 @node Non-debug DLL Symbols
14557 @subsubsection Support for DLLs without Debugging Symbols
14558 @cindex DLLs with no debugging symbols
14559 @cindex Minimal symbols and DLLs
14561 Very often on windows, some of the DLLs that your program relies on do
14562 not include symbolic debugging information (for example,
14563 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
14564 symbols in a DLL, it relies on the minimal amount of symbolic
14565 information contained in the DLL's export table. This section
14566 describes working with such symbols, known internally to @value{GDBN} as
14567 ``minimal symbols''.
14569 Note that before the debugged program has started execution, no DLLs
14570 will have been loaded. The easiest way around this problem is simply to
14571 start the program --- either by setting a breakpoint or letting the
14572 program run once to completion. It is also possible to force
14573 @value{GDBN} to load a particular DLL before starting the executable ---
14574 see the shared library information in @ref{Files}, or the
14575 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
14576 explicitly loading symbols from a DLL with no debugging information will
14577 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
14578 which may adversely affect symbol lookup performance.
14580 @subsubsection DLL Name Prefixes
14582 In keeping with the naming conventions used by the Microsoft debugging
14583 tools, DLL export symbols are made available with a prefix based on the
14584 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
14585 also entered into the symbol table, so @code{CreateFileA} is often
14586 sufficient. In some cases there will be name clashes within a program
14587 (particularly if the executable itself includes full debugging symbols)
14588 necessitating the use of the fully qualified name when referring to the
14589 contents of the DLL. Use single-quotes around the name to avoid the
14590 exclamation mark (``!'') being interpreted as a language operator.
14592 Note that the internal name of the DLL may be all upper-case, even
14593 though the file name of the DLL is lower-case, or vice-versa. Since
14594 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
14595 some confusion. If in doubt, try the @code{info functions} and
14596 @code{info variables} commands or even @code{maint print msymbols}
14597 (@pxref{Symbols}). Here's an example:
14600 (@value{GDBP}) info function CreateFileA
14601 All functions matching regular expression "CreateFileA":
14603 Non-debugging symbols:
14604 0x77e885f4 CreateFileA
14605 0x77e885f4 KERNEL32!CreateFileA
14609 (@value{GDBP}) info function !
14610 All functions matching regular expression "!":
14612 Non-debugging symbols:
14613 0x6100114c cygwin1!__assert
14614 0x61004034 cygwin1!_dll_crt0@@0
14615 0x61004240 cygwin1!dll_crt0(per_process *)
14619 @subsubsection Working with Minimal Symbols
14621 Symbols extracted from a DLL's export table do not contain very much
14622 type information. All that @value{GDBN} can do is guess whether a symbol
14623 refers to a function or variable depending on the linker section that
14624 contains the symbol. Also note that the actual contents of the memory
14625 contained in a DLL are not available unless the program is running. This
14626 means that you cannot examine the contents of a variable or disassemble
14627 a function within a DLL without a running program.
14629 Variables are generally treated as pointers and dereferenced
14630 automatically. For this reason, it is often necessary to prefix a
14631 variable name with the address-of operator (``&'') and provide explicit
14632 type information in the command. Here's an example of the type of
14636 (@value{GDBP}) print 'cygwin1!__argv'
14641 (@value{GDBP}) x 'cygwin1!__argv'
14642 0x10021610: "\230y\""
14645 And two possible solutions:
14648 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
14649 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
14653 (@value{GDBP}) x/2x &'cygwin1!__argv'
14654 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
14655 (@value{GDBP}) x/x 0x10021608
14656 0x10021608: 0x0022fd98
14657 (@value{GDBP}) x/s 0x0022fd98
14658 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
14661 Setting a break point within a DLL is possible even before the program
14662 starts execution. However, under these circumstances, @value{GDBN} can't
14663 examine the initial instructions of the function in order to skip the
14664 function's frame set-up code. You can work around this by using ``*&''
14665 to set the breakpoint at a raw memory address:
14668 (@value{GDBP}) break *&'python22!PyOS_Readline'
14669 Breakpoint 1 at 0x1e04eff0
14672 The author of these extensions is not entirely convinced that setting a
14673 break point within a shared DLL like @file{kernel32.dll} is completely
14677 @subsection Commands Specific to @sc{gnu} Hurd Systems
14678 @cindex @sc{gnu} Hurd debugging
14680 This subsection describes @value{GDBN} commands specific to the
14681 @sc{gnu} Hurd native debugging.
14686 @kindex set signals@r{, Hurd command}
14687 @kindex set sigs@r{, Hurd command}
14688 This command toggles the state of inferior signal interception by
14689 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
14690 affected by this command. @code{sigs} is a shorthand alias for
14695 @kindex show signals@r{, Hurd command}
14696 @kindex show sigs@r{, Hurd command}
14697 Show the current state of intercepting inferior's signals.
14699 @item set signal-thread
14700 @itemx set sigthread
14701 @kindex set signal-thread
14702 @kindex set sigthread
14703 This command tells @value{GDBN} which thread is the @code{libc} signal
14704 thread. That thread is run when a signal is delivered to a running
14705 process. @code{set sigthread} is the shorthand alias of @code{set
14708 @item show signal-thread
14709 @itemx show sigthread
14710 @kindex show signal-thread
14711 @kindex show sigthread
14712 These two commands show which thread will run when the inferior is
14713 delivered a signal.
14716 @kindex set stopped@r{, Hurd command}
14717 This commands tells @value{GDBN} that the inferior process is stopped,
14718 as with the @code{SIGSTOP} signal. The stopped process can be
14719 continued by delivering a signal to it.
14722 @kindex show stopped@r{, Hurd command}
14723 This command shows whether @value{GDBN} thinks the debuggee is
14726 @item set exceptions
14727 @kindex set exceptions@r{, Hurd command}
14728 Use this command to turn off trapping of exceptions in the inferior.
14729 When exception trapping is off, neither breakpoints nor
14730 single-stepping will work. To restore the default, set exception
14733 @item show exceptions
14734 @kindex show exceptions@r{, Hurd command}
14735 Show the current state of trapping exceptions in the inferior.
14737 @item set task pause
14738 @kindex set task@r{, Hurd commands}
14739 @cindex task attributes (@sc{gnu} Hurd)
14740 @cindex pause current task (@sc{gnu} Hurd)
14741 This command toggles task suspension when @value{GDBN} has control.
14742 Setting it to on takes effect immediately, and the task is suspended
14743 whenever @value{GDBN} gets control. Setting it to off will take
14744 effect the next time the inferior is continued. If this option is set
14745 to off, you can use @code{set thread default pause on} or @code{set
14746 thread pause on} (see below) to pause individual threads.
14748 @item show task pause
14749 @kindex show task@r{, Hurd commands}
14750 Show the current state of task suspension.
14752 @item set task detach-suspend-count
14753 @cindex task suspend count
14754 @cindex detach from task, @sc{gnu} Hurd
14755 This command sets the suspend count the task will be left with when
14756 @value{GDBN} detaches from it.
14758 @item show task detach-suspend-count
14759 Show the suspend count the task will be left with when detaching.
14761 @item set task exception-port
14762 @itemx set task excp
14763 @cindex task exception port, @sc{gnu} Hurd
14764 This command sets the task exception port to which @value{GDBN} will
14765 forward exceptions. The argument should be the value of the @dfn{send
14766 rights} of the task. @code{set task excp} is a shorthand alias.
14768 @item set noninvasive
14769 @cindex noninvasive task options
14770 This command switches @value{GDBN} to a mode that is the least
14771 invasive as far as interfering with the inferior is concerned. This
14772 is the same as using @code{set task pause}, @code{set exceptions}, and
14773 @code{set signals} to values opposite to the defaults.
14775 @item info send-rights
14776 @itemx info receive-rights
14777 @itemx info port-rights
14778 @itemx info port-sets
14779 @itemx info dead-names
14782 @cindex send rights, @sc{gnu} Hurd
14783 @cindex receive rights, @sc{gnu} Hurd
14784 @cindex port rights, @sc{gnu} Hurd
14785 @cindex port sets, @sc{gnu} Hurd
14786 @cindex dead names, @sc{gnu} Hurd
14787 These commands display information about, respectively, send rights,
14788 receive rights, port rights, port sets, and dead names of a task.
14789 There are also shorthand aliases: @code{info ports} for @code{info
14790 port-rights} and @code{info psets} for @code{info port-sets}.
14792 @item set thread pause
14793 @kindex set thread@r{, Hurd command}
14794 @cindex thread properties, @sc{gnu} Hurd
14795 @cindex pause current thread (@sc{gnu} Hurd)
14796 This command toggles current thread suspension when @value{GDBN} has
14797 control. Setting it to on takes effect immediately, and the current
14798 thread is suspended whenever @value{GDBN} gets control. Setting it to
14799 off will take effect the next time the inferior is continued.
14800 Normally, this command has no effect, since when @value{GDBN} has
14801 control, the whole task is suspended. However, if you used @code{set
14802 task pause off} (see above), this command comes in handy to suspend
14803 only the current thread.
14805 @item show thread pause
14806 @kindex show thread@r{, Hurd command}
14807 This command shows the state of current thread suspension.
14809 @item set thread run
14810 This command sets whether the current thread is allowed to run.
14812 @item show thread run
14813 Show whether the current thread is allowed to run.
14815 @item set thread detach-suspend-count
14816 @cindex thread suspend count, @sc{gnu} Hurd
14817 @cindex detach from thread, @sc{gnu} Hurd
14818 This command sets the suspend count @value{GDBN} will leave on a
14819 thread when detaching. This number is relative to the suspend count
14820 found by @value{GDBN} when it notices the thread; use @code{set thread
14821 takeover-suspend-count} to force it to an absolute value.
14823 @item show thread detach-suspend-count
14824 Show the suspend count @value{GDBN} will leave on the thread when
14827 @item set thread exception-port
14828 @itemx set thread excp
14829 Set the thread exception port to which to forward exceptions. This
14830 overrides the port set by @code{set task exception-port} (see above).
14831 @code{set thread excp} is the shorthand alias.
14833 @item set thread takeover-suspend-count
14834 Normally, @value{GDBN}'s thread suspend counts are relative to the
14835 value @value{GDBN} finds when it notices each thread. This command
14836 changes the suspend counts to be absolute instead.
14838 @item set thread default
14839 @itemx show thread default
14840 @cindex thread default settings, @sc{gnu} Hurd
14841 Each of the above @code{set thread} commands has a @code{set thread
14842 default} counterpart (e.g., @code{set thread default pause}, @code{set
14843 thread default exception-port}, etc.). The @code{thread default}
14844 variety of commands sets the default thread properties for all
14845 threads; you can then change the properties of individual threads with
14846 the non-default commands.
14851 @subsection QNX Neutrino
14852 @cindex QNX Neutrino
14854 @value{GDBN} provides the following commands specific to the QNX
14858 @item set debug nto-debug
14859 @kindex set debug nto-debug
14860 When set to on, enables debugging messages specific to the QNX
14863 @item show debug nto-debug
14864 @kindex show debug nto-debug
14865 Show the current state of QNX Neutrino messages.
14870 @section Embedded Operating Systems
14872 This section describes configurations involving the debugging of
14873 embedded operating systems that are available for several different
14877 * VxWorks:: Using @value{GDBN} with VxWorks
14880 @value{GDBN} includes the ability to debug programs running on
14881 various real-time operating systems.
14884 @subsection Using @value{GDBN} with VxWorks
14890 @kindex target vxworks
14891 @item target vxworks @var{machinename}
14892 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
14893 is the target system's machine name or IP address.
14897 On VxWorks, @code{load} links @var{filename} dynamically on the
14898 current target system as well as adding its symbols in @value{GDBN}.
14900 @value{GDBN} enables developers to spawn and debug tasks running on networked
14901 VxWorks targets from a Unix host. Already-running tasks spawned from
14902 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
14903 both the Unix host and on the VxWorks target. The program
14904 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
14905 installed with the name @code{vxgdb}, to distinguish it from a
14906 @value{GDBN} for debugging programs on the host itself.)
14909 @item VxWorks-timeout @var{args}
14910 @kindex vxworks-timeout
14911 All VxWorks-based targets now support the option @code{vxworks-timeout}.
14912 This option is set by the user, and @var{args} represents the number of
14913 seconds @value{GDBN} waits for responses to rpc's. You might use this if
14914 your VxWorks target is a slow software simulator or is on the far side
14915 of a thin network line.
14918 The following information on connecting to VxWorks was current when
14919 this manual was produced; newer releases of VxWorks may use revised
14922 @findex INCLUDE_RDB
14923 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
14924 to include the remote debugging interface routines in the VxWorks
14925 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
14926 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
14927 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
14928 source debugging task @code{tRdbTask} when VxWorks is booted. For more
14929 information on configuring and remaking VxWorks, see the manufacturer's
14931 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
14933 Once you have included @file{rdb.a} in your VxWorks system image and set
14934 your Unix execution search path to find @value{GDBN}, you are ready to
14935 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
14936 @code{vxgdb}, depending on your installation).
14938 @value{GDBN} comes up showing the prompt:
14945 * VxWorks Connection:: Connecting to VxWorks
14946 * VxWorks Download:: VxWorks download
14947 * VxWorks Attach:: Running tasks
14950 @node VxWorks Connection
14951 @subsubsection Connecting to VxWorks
14953 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
14954 network. To connect to a target whose host name is ``@code{tt}'', type:
14957 (vxgdb) target vxworks tt
14961 @value{GDBN} displays messages like these:
14964 Attaching remote machine across net...
14969 @value{GDBN} then attempts to read the symbol tables of any object modules
14970 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
14971 these files by searching the directories listed in the command search
14972 path (@pxref{Environment, ,Your Program's Environment}); if it fails
14973 to find an object file, it displays a message such as:
14976 prog.o: No such file or directory.
14979 When this happens, add the appropriate directory to the search path with
14980 the @value{GDBN} command @code{path}, and execute the @code{target}
14983 @node VxWorks Download
14984 @subsubsection VxWorks Download
14986 @cindex download to VxWorks
14987 If you have connected to the VxWorks target and you want to debug an
14988 object that has not yet been loaded, you can use the @value{GDBN}
14989 @code{load} command to download a file from Unix to VxWorks
14990 incrementally. The object file given as an argument to the @code{load}
14991 command is actually opened twice: first by the VxWorks target in order
14992 to download the code, then by @value{GDBN} in order to read the symbol
14993 table. This can lead to problems if the current working directories on
14994 the two systems differ. If both systems have NFS mounted the same
14995 filesystems, you can avoid these problems by using absolute paths.
14996 Otherwise, it is simplest to set the working directory on both systems
14997 to the directory in which the object file resides, and then to reference
14998 the file by its name, without any path. For instance, a program
14999 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
15000 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
15001 program, type this on VxWorks:
15004 -> cd "@var{vxpath}/vw/demo/rdb"
15008 Then, in @value{GDBN}, type:
15011 (vxgdb) cd @var{hostpath}/vw/demo/rdb
15012 (vxgdb) load prog.o
15015 @value{GDBN} displays a response similar to this:
15018 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
15021 You can also use the @code{load} command to reload an object module
15022 after editing and recompiling the corresponding source file. Note that
15023 this makes @value{GDBN} delete all currently-defined breakpoints,
15024 auto-displays, and convenience variables, and to clear the value
15025 history. (This is necessary in order to preserve the integrity of
15026 debugger's data structures that reference the target system's symbol
15029 @node VxWorks Attach
15030 @subsubsection Running Tasks
15032 @cindex running VxWorks tasks
15033 You can also attach to an existing task using the @code{attach} command as
15037 (vxgdb) attach @var{task}
15041 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
15042 or suspended when you attach to it. Running tasks are suspended at
15043 the time of attachment.
15045 @node Embedded Processors
15046 @section Embedded Processors
15048 This section goes into details specific to particular embedded
15051 @cindex send command to simulator
15052 Whenever a specific embedded processor has a simulator, @value{GDBN}
15053 allows to send an arbitrary command to the simulator.
15056 @item sim @var{command}
15057 @kindex sim@r{, a command}
15058 Send an arbitrary @var{command} string to the simulator. Consult the
15059 documentation for the specific simulator in use for information about
15060 acceptable commands.
15066 * M32R/D:: Renesas M32R/D
15067 * M68K:: Motorola M68K
15068 * MIPS Embedded:: MIPS Embedded
15069 * OpenRISC 1000:: OpenRisc 1000
15070 * PA:: HP PA Embedded
15071 * PowerPC Embedded:: PowerPC Embedded
15072 * Sparclet:: Tsqware Sparclet
15073 * Sparclite:: Fujitsu Sparclite
15074 * Z8000:: Zilog Z8000
15077 * Super-H:: Renesas Super-H
15086 @item target rdi @var{dev}
15087 ARM Angel monitor, via RDI library interface to ADP protocol. You may
15088 use this target to communicate with both boards running the Angel
15089 monitor, or with the EmbeddedICE JTAG debug device.
15092 @item target rdp @var{dev}
15097 @value{GDBN} provides the following ARM-specific commands:
15100 @item set arm disassembler
15102 This commands selects from a list of disassembly styles. The
15103 @code{"std"} style is the standard style.
15105 @item show arm disassembler
15107 Show the current disassembly style.
15109 @item set arm apcs32
15110 @cindex ARM 32-bit mode
15111 This command toggles ARM operation mode between 32-bit and 26-bit.
15113 @item show arm apcs32
15114 Display the current usage of the ARM 32-bit mode.
15116 @item set arm fpu @var{fputype}
15117 This command sets the ARM floating-point unit (FPU) type. The
15118 argument @var{fputype} can be one of these:
15122 Determine the FPU type by querying the OS ABI.
15124 Software FPU, with mixed-endian doubles on little-endian ARM
15127 GCC-compiled FPA co-processor.
15129 Software FPU with pure-endian doubles.
15135 Show the current type of the FPU.
15138 This command forces @value{GDBN} to use the specified ABI.
15141 Show the currently used ABI.
15143 @item set arm fallback-mode (arm|thumb|auto)
15144 @value{GDBN} uses the symbol table, when available, to determine
15145 whether instructions are ARM or Thumb. This command controls
15146 @value{GDBN}'s default behavior when the symbol table is not
15147 available. The default is @samp{auto}, which causes @value{GDBN} to
15148 use the current execution mode (from the @code{T} bit in the @code{CPSR}
15151 @item show arm fallback-mode
15152 Show the current fallback instruction mode.
15154 @item set arm force-mode (arm|thumb|auto)
15155 This command overrides use of the symbol table to determine whether
15156 instructions are ARM or Thumb. The default is @samp{auto}, which
15157 causes @value{GDBN} to use the symbol table and then the setting
15158 of @samp{set arm fallback-mode}.
15160 @item show arm force-mode
15161 Show the current forced instruction mode.
15163 @item set debug arm
15164 Toggle whether to display ARM-specific debugging messages from the ARM
15165 target support subsystem.
15167 @item show debug arm
15168 Show whether ARM-specific debugging messages are enabled.
15171 The following commands are available when an ARM target is debugged
15172 using the RDI interface:
15175 @item rdilogfile @r{[}@var{file}@r{]}
15177 @cindex ADP (Angel Debugger Protocol) logging
15178 Set the filename for the ADP (Angel Debugger Protocol) packet log.
15179 With an argument, sets the log file to the specified @var{file}. With
15180 no argument, show the current log file name. The default log file is
15183 @item rdilogenable @r{[}@var{arg}@r{]}
15184 @kindex rdilogenable
15185 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
15186 enables logging, with an argument 0 or @code{"no"} disables it. With
15187 no arguments displays the current setting. When logging is enabled,
15188 ADP packets exchanged between @value{GDBN} and the RDI target device
15189 are logged to a file.
15191 @item set rdiromatzero
15192 @kindex set rdiromatzero
15193 @cindex ROM at zero address, RDI
15194 Tell @value{GDBN} whether the target has ROM at address 0. If on,
15195 vector catching is disabled, so that zero address can be used. If off
15196 (the default), vector catching is enabled. For this command to take
15197 effect, it needs to be invoked prior to the @code{target rdi} command.
15199 @item show rdiromatzero
15200 @kindex show rdiromatzero
15201 Show the current setting of ROM at zero address.
15203 @item set rdiheartbeat
15204 @kindex set rdiheartbeat
15205 @cindex RDI heartbeat
15206 Enable or disable RDI heartbeat packets. It is not recommended to
15207 turn on this option, since it confuses ARM and EPI JTAG interface, as
15208 well as the Angel monitor.
15210 @item show rdiheartbeat
15211 @kindex show rdiheartbeat
15212 Show the setting of RDI heartbeat packets.
15217 @subsection Renesas M32R/D and M32R/SDI
15220 @kindex target m32r
15221 @item target m32r @var{dev}
15222 Renesas M32R/D ROM monitor.
15224 @kindex target m32rsdi
15225 @item target m32rsdi @var{dev}
15226 Renesas M32R SDI server, connected via parallel port to the board.
15229 The following @value{GDBN} commands are specific to the M32R monitor:
15232 @item set download-path @var{path}
15233 @kindex set download-path
15234 @cindex find downloadable @sc{srec} files (M32R)
15235 Set the default path for finding downloadable @sc{srec} files.
15237 @item show download-path
15238 @kindex show download-path
15239 Show the default path for downloadable @sc{srec} files.
15241 @item set board-address @var{addr}
15242 @kindex set board-address
15243 @cindex M32-EVA target board address
15244 Set the IP address for the M32R-EVA target board.
15246 @item show board-address
15247 @kindex show board-address
15248 Show the current IP address of the target board.
15250 @item set server-address @var{addr}
15251 @kindex set server-address
15252 @cindex download server address (M32R)
15253 Set the IP address for the download server, which is the @value{GDBN}'s
15256 @item show server-address
15257 @kindex show server-address
15258 Display the IP address of the download server.
15260 @item upload @r{[}@var{file}@r{]}
15261 @kindex upload@r{, M32R}
15262 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
15263 upload capability. If no @var{file} argument is given, the current
15264 executable file is uploaded.
15266 @item tload @r{[}@var{file}@r{]}
15267 @kindex tload@r{, M32R}
15268 Test the @code{upload} command.
15271 The following commands are available for M32R/SDI:
15276 @cindex reset SDI connection, M32R
15277 This command resets the SDI connection.
15281 This command shows the SDI connection status.
15284 @kindex debug_chaos
15285 @cindex M32R/Chaos debugging
15286 Instructs the remote that M32R/Chaos debugging is to be used.
15288 @item use_debug_dma
15289 @kindex use_debug_dma
15290 Instructs the remote to use the DEBUG_DMA method of accessing memory.
15293 @kindex use_mon_code
15294 Instructs the remote to use the MON_CODE method of accessing memory.
15297 @kindex use_ib_break
15298 Instructs the remote to set breakpoints by IB break.
15300 @item use_dbt_break
15301 @kindex use_dbt_break
15302 Instructs the remote to set breakpoints by DBT.
15308 The Motorola m68k configuration includes ColdFire support, and a
15309 target command for the following ROM monitor.
15313 @kindex target dbug
15314 @item target dbug @var{dev}
15315 dBUG ROM monitor for Motorola ColdFire.
15319 @node MIPS Embedded
15320 @subsection MIPS Embedded
15322 @cindex MIPS boards
15323 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
15324 MIPS board attached to a serial line. This is available when
15325 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
15328 Use these @value{GDBN} commands to specify the connection to your target board:
15331 @item target mips @var{port}
15332 @kindex target mips @var{port}
15333 To run a program on the board, start up @code{@value{GDBP}} with the
15334 name of your program as the argument. To connect to the board, use the
15335 command @samp{target mips @var{port}}, where @var{port} is the name of
15336 the serial port connected to the board. If the program has not already
15337 been downloaded to the board, you may use the @code{load} command to
15338 download it. You can then use all the usual @value{GDBN} commands.
15340 For example, this sequence connects to the target board through a serial
15341 port, and loads and runs a program called @var{prog} through the
15345 host$ @value{GDBP} @var{prog}
15346 @value{GDBN} is free software and @dots{}
15347 (@value{GDBP}) target mips /dev/ttyb
15348 (@value{GDBP}) load @var{prog}
15352 @item target mips @var{hostname}:@var{portnumber}
15353 On some @value{GDBN} host configurations, you can specify a TCP
15354 connection (for instance, to a serial line managed by a terminal
15355 concentrator) instead of a serial port, using the syntax
15356 @samp{@var{hostname}:@var{portnumber}}.
15358 @item target pmon @var{port}
15359 @kindex target pmon @var{port}
15362 @item target ddb @var{port}
15363 @kindex target ddb @var{port}
15364 NEC's DDB variant of PMON for Vr4300.
15366 @item target lsi @var{port}
15367 @kindex target lsi @var{port}
15368 LSI variant of PMON.
15370 @kindex target r3900
15371 @item target r3900 @var{dev}
15372 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
15374 @kindex target array
15375 @item target array @var{dev}
15376 Array Tech LSI33K RAID controller board.
15382 @value{GDBN} also supports these special commands for MIPS targets:
15385 @item set mipsfpu double
15386 @itemx set mipsfpu single
15387 @itemx set mipsfpu none
15388 @itemx set mipsfpu auto
15389 @itemx show mipsfpu
15390 @kindex set mipsfpu
15391 @kindex show mipsfpu
15392 @cindex MIPS remote floating point
15393 @cindex floating point, MIPS remote
15394 If your target board does not support the MIPS floating point
15395 coprocessor, you should use the command @samp{set mipsfpu none} (if you
15396 need this, you may wish to put the command in your @value{GDBN} init
15397 file). This tells @value{GDBN} how to find the return value of
15398 functions which return floating point values. It also allows
15399 @value{GDBN} to avoid saving the floating point registers when calling
15400 functions on the board. If you are using a floating point coprocessor
15401 with only single precision floating point support, as on the @sc{r4650}
15402 processor, use the command @samp{set mipsfpu single}. The default
15403 double precision floating point coprocessor may be selected using
15404 @samp{set mipsfpu double}.
15406 In previous versions the only choices were double precision or no
15407 floating point, so @samp{set mipsfpu on} will select double precision
15408 and @samp{set mipsfpu off} will select no floating point.
15410 As usual, you can inquire about the @code{mipsfpu} variable with
15411 @samp{show mipsfpu}.
15413 @item set timeout @var{seconds}
15414 @itemx set retransmit-timeout @var{seconds}
15415 @itemx show timeout
15416 @itemx show retransmit-timeout
15417 @cindex @code{timeout}, MIPS protocol
15418 @cindex @code{retransmit-timeout}, MIPS protocol
15419 @kindex set timeout
15420 @kindex show timeout
15421 @kindex set retransmit-timeout
15422 @kindex show retransmit-timeout
15423 You can control the timeout used while waiting for a packet, in the MIPS
15424 remote protocol, with the @code{set timeout @var{seconds}} command. The
15425 default is 5 seconds. Similarly, you can control the timeout used while
15426 waiting for an acknowledgement of a packet with the @code{set
15427 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
15428 You can inspect both values with @code{show timeout} and @code{show
15429 retransmit-timeout}. (These commands are @emph{only} available when
15430 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
15432 The timeout set by @code{set timeout} does not apply when @value{GDBN}
15433 is waiting for your program to stop. In that case, @value{GDBN} waits
15434 forever because it has no way of knowing how long the program is going
15435 to run before stopping.
15437 @item set syn-garbage-limit @var{num}
15438 @kindex set syn-garbage-limit@r{, MIPS remote}
15439 @cindex synchronize with remote MIPS target
15440 Limit the maximum number of characters @value{GDBN} should ignore when
15441 it tries to synchronize with the remote target. The default is 10
15442 characters. Setting the limit to -1 means there's no limit.
15444 @item show syn-garbage-limit
15445 @kindex show syn-garbage-limit@r{, MIPS remote}
15446 Show the current limit on the number of characters to ignore when
15447 trying to synchronize with the remote system.
15449 @item set monitor-prompt @var{prompt}
15450 @kindex set monitor-prompt@r{, MIPS remote}
15451 @cindex remote monitor prompt
15452 Tell @value{GDBN} to expect the specified @var{prompt} string from the
15453 remote monitor. The default depends on the target:
15463 @item show monitor-prompt
15464 @kindex show monitor-prompt@r{, MIPS remote}
15465 Show the current strings @value{GDBN} expects as the prompt from the
15468 @item set monitor-warnings
15469 @kindex set monitor-warnings@r{, MIPS remote}
15470 Enable or disable monitor warnings about hardware breakpoints. This
15471 has effect only for the @code{lsi} target. When on, @value{GDBN} will
15472 display warning messages whose codes are returned by the @code{lsi}
15473 PMON monitor for breakpoint commands.
15475 @item show monitor-warnings
15476 @kindex show monitor-warnings@r{, MIPS remote}
15477 Show the current setting of printing monitor warnings.
15479 @item pmon @var{command}
15480 @kindex pmon@r{, MIPS remote}
15481 @cindex send PMON command
15482 This command allows sending an arbitrary @var{command} string to the
15483 monitor. The monitor must be in debug mode for this to work.
15486 @node OpenRISC 1000
15487 @subsection OpenRISC 1000
15488 @cindex OpenRISC 1000
15490 @cindex or1k boards
15491 See OR1k Architecture document (@uref{www.opencores.org}) for more information
15492 about platform and commands.
15496 @kindex target jtag
15497 @item target jtag jtag://@var{host}:@var{port}
15499 Connects to remote JTAG server.
15500 JTAG remote server can be either an or1ksim or JTAG server,
15501 connected via parallel port to the board.
15503 Example: @code{target jtag jtag://localhost:9999}
15506 @item or1ksim @var{command}
15507 If connected to @code{or1ksim} OpenRISC 1000 Architectural
15508 Simulator, proprietary commands can be executed.
15510 @kindex info or1k spr
15511 @item info or1k spr
15512 Displays spr groups.
15514 @item info or1k spr @var{group}
15515 @itemx info or1k spr @var{groupno}
15516 Displays register names in selected group.
15518 @item info or1k spr @var{group} @var{register}
15519 @itemx info or1k spr @var{register}
15520 @itemx info or1k spr @var{groupno} @var{registerno}
15521 @itemx info or1k spr @var{registerno}
15522 Shows information about specified spr register.
15525 @item spr @var{group} @var{register} @var{value}
15526 @itemx spr @var{register @var{value}}
15527 @itemx spr @var{groupno} @var{registerno @var{value}}
15528 @itemx spr @var{registerno @var{value}}
15529 Writes @var{value} to specified spr register.
15532 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
15533 It is very similar to @value{GDBN} trace, except it does not interfere with normal
15534 program execution and is thus much faster. Hardware breakpoints/watchpoint
15535 triggers can be set using:
15538 Load effective address/data
15540 Store effective address/data
15542 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
15547 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
15548 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
15550 @code{htrace} commands:
15551 @cindex OpenRISC 1000 htrace
15554 @item hwatch @var{conditional}
15555 Set hardware watchpoint on combination of Load/Store Effective Address(es)
15556 or Data. For example:
15558 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
15560 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
15564 Display information about current HW trace configuration.
15566 @item htrace trigger @var{conditional}
15567 Set starting criteria for HW trace.
15569 @item htrace qualifier @var{conditional}
15570 Set acquisition qualifier for HW trace.
15572 @item htrace stop @var{conditional}
15573 Set HW trace stopping criteria.
15575 @item htrace record [@var{data}]*
15576 Selects the data to be recorded, when qualifier is met and HW trace was
15579 @item htrace enable
15580 @itemx htrace disable
15581 Enables/disables the HW trace.
15583 @item htrace rewind [@var{filename}]
15584 Clears currently recorded trace data.
15586 If filename is specified, new trace file is made and any newly collected data
15587 will be written there.
15589 @item htrace print [@var{start} [@var{len}]]
15590 Prints trace buffer, using current record configuration.
15592 @item htrace mode continuous
15593 Set continuous trace mode.
15595 @item htrace mode suspend
15596 Set suspend trace mode.
15600 @node PowerPC Embedded
15601 @subsection PowerPC Embedded
15603 @value{GDBN} provides the following PowerPC-specific commands:
15606 @kindex set powerpc
15607 @item set powerpc soft-float
15608 @itemx show powerpc soft-float
15609 Force @value{GDBN} to use (or not use) a software floating point calling
15610 convention. By default, @value{GDBN} selects the calling convention based
15611 on the selected architecture and the provided executable file.
15613 @item set powerpc vector-abi
15614 @itemx show powerpc vector-abi
15615 Force @value{GDBN} to use the specified calling convention for vector
15616 arguments and return values. The valid options are @samp{auto};
15617 @samp{generic}, to avoid vector registers even if they are present;
15618 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
15619 registers. By default, @value{GDBN} selects the calling convention
15620 based on the selected architecture and the provided executable file.
15622 @kindex target dink32
15623 @item target dink32 @var{dev}
15624 DINK32 ROM monitor.
15626 @kindex target ppcbug
15627 @item target ppcbug @var{dev}
15628 @kindex target ppcbug1
15629 @item target ppcbug1 @var{dev}
15630 PPCBUG ROM monitor for PowerPC.
15633 @item target sds @var{dev}
15634 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
15637 @cindex SDS protocol
15638 The following commands specific to the SDS protocol are supported
15642 @item set sdstimeout @var{nsec}
15643 @kindex set sdstimeout
15644 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
15645 default is 2 seconds.
15647 @item show sdstimeout
15648 @kindex show sdstimeout
15649 Show the current value of the SDS timeout.
15651 @item sds @var{command}
15652 @kindex sds@r{, a command}
15653 Send the specified @var{command} string to the SDS monitor.
15658 @subsection HP PA Embedded
15662 @kindex target op50n
15663 @item target op50n @var{dev}
15664 OP50N monitor, running on an OKI HPPA board.
15666 @kindex target w89k
15667 @item target w89k @var{dev}
15668 W89K monitor, running on a Winbond HPPA board.
15673 @subsection Tsqware Sparclet
15677 @value{GDBN} enables developers to debug tasks running on
15678 Sparclet targets from a Unix host.
15679 @value{GDBN} uses code that runs on
15680 both the Unix host and on the Sparclet target. The program
15681 @code{@value{GDBP}} is installed and executed on the Unix host.
15684 @item remotetimeout @var{args}
15685 @kindex remotetimeout
15686 @value{GDBN} supports the option @code{remotetimeout}.
15687 This option is set by the user, and @var{args} represents the number of
15688 seconds @value{GDBN} waits for responses.
15691 @cindex compiling, on Sparclet
15692 When compiling for debugging, include the options @samp{-g} to get debug
15693 information and @samp{-Ttext} to relocate the program to where you wish to
15694 load it on the target. You may also want to add the options @samp{-n} or
15695 @samp{-N} in order to reduce the size of the sections. Example:
15698 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
15701 You can use @code{objdump} to verify that the addresses are what you intended:
15704 sparclet-aout-objdump --headers --syms prog
15707 @cindex running, on Sparclet
15709 your Unix execution search path to find @value{GDBN}, you are ready to
15710 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
15711 (or @code{sparclet-aout-gdb}, depending on your installation).
15713 @value{GDBN} comes up showing the prompt:
15720 * Sparclet File:: Setting the file to debug
15721 * Sparclet Connection:: Connecting to Sparclet
15722 * Sparclet Download:: Sparclet download
15723 * Sparclet Execution:: Running and debugging
15726 @node Sparclet File
15727 @subsubsection Setting File to Debug
15729 The @value{GDBN} command @code{file} lets you choose with program to debug.
15732 (gdbslet) file prog
15736 @value{GDBN} then attempts to read the symbol table of @file{prog}.
15737 @value{GDBN} locates
15738 the file by searching the directories listed in the command search
15740 If the file was compiled with debug information (option @samp{-g}), source
15741 files will be searched as well.
15742 @value{GDBN} locates
15743 the source files by searching the directories listed in the directory search
15744 path (@pxref{Environment, ,Your Program's Environment}).
15746 to find a file, it displays a message such as:
15749 prog: No such file or directory.
15752 When this happens, add the appropriate directories to the search paths with
15753 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
15754 @code{target} command again.
15756 @node Sparclet Connection
15757 @subsubsection Connecting to Sparclet
15759 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
15760 To connect to a target on serial port ``@code{ttya}'', type:
15763 (gdbslet) target sparclet /dev/ttya
15764 Remote target sparclet connected to /dev/ttya
15765 main () at ../prog.c:3
15769 @value{GDBN} displays messages like these:
15775 @node Sparclet Download
15776 @subsubsection Sparclet Download
15778 @cindex download to Sparclet
15779 Once connected to the Sparclet target,
15780 you can use the @value{GDBN}
15781 @code{load} command to download the file from the host to the target.
15782 The file name and load offset should be given as arguments to the @code{load}
15784 Since the file format is aout, the program must be loaded to the starting
15785 address. You can use @code{objdump} to find out what this value is. The load
15786 offset is an offset which is added to the VMA (virtual memory address)
15787 of each of the file's sections.
15788 For instance, if the program
15789 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
15790 and bss at 0x12010170, in @value{GDBN}, type:
15793 (gdbslet) load prog 0x12010000
15794 Loading section .text, size 0xdb0 vma 0x12010000
15797 If the code is loaded at a different address then what the program was linked
15798 to, you may need to use the @code{section} and @code{add-symbol-file} commands
15799 to tell @value{GDBN} where to map the symbol table.
15801 @node Sparclet Execution
15802 @subsubsection Running and Debugging
15804 @cindex running and debugging Sparclet programs
15805 You can now begin debugging the task using @value{GDBN}'s execution control
15806 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
15807 manual for the list of commands.
15811 Breakpoint 1 at 0x12010000: file prog.c, line 3.
15813 Starting program: prog
15814 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
15815 3 char *symarg = 0;
15817 4 char *execarg = "hello!";
15822 @subsection Fujitsu Sparclite
15826 @kindex target sparclite
15827 @item target sparclite @var{dev}
15828 Fujitsu sparclite boards, used only for the purpose of loading.
15829 You must use an additional command to debug the program.
15830 For example: target remote @var{dev} using @value{GDBN} standard
15836 @subsection Zilog Z8000
15839 @cindex simulator, Z8000
15840 @cindex Zilog Z8000 simulator
15842 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
15845 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
15846 unsegmented variant of the Z8000 architecture) or the Z8001 (the
15847 segmented variant). The simulator recognizes which architecture is
15848 appropriate by inspecting the object code.
15851 @item target sim @var{args}
15853 @kindex target sim@r{, with Z8000}
15854 Debug programs on a simulated CPU. If the simulator supports setup
15855 options, specify them via @var{args}.
15859 After specifying this target, you can debug programs for the simulated
15860 CPU in the same style as programs for your host computer; use the
15861 @code{file} command to load a new program image, the @code{run} command
15862 to run your program, and so on.
15864 As well as making available all the usual machine registers
15865 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
15866 additional items of information as specially named registers:
15871 Counts clock-ticks in the simulator.
15874 Counts instructions run in the simulator.
15877 Execution time in 60ths of a second.
15881 You can refer to these values in @value{GDBN} expressions with the usual
15882 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
15883 conditional breakpoint that suspends only after at least 5000
15884 simulated clock ticks.
15887 @subsection Atmel AVR
15890 When configured for debugging the Atmel AVR, @value{GDBN} supports the
15891 following AVR-specific commands:
15894 @item info io_registers
15895 @kindex info io_registers@r{, AVR}
15896 @cindex I/O registers (Atmel AVR)
15897 This command displays information about the AVR I/O registers. For
15898 each register, @value{GDBN} prints its number and value.
15905 When configured for debugging CRIS, @value{GDBN} provides the
15906 following CRIS-specific commands:
15909 @item set cris-version @var{ver}
15910 @cindex CRIS version
15911 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
15912 The CRIS version affects register names and sizes. This command is useful in
15913 case autodetection of the CRIS version fails.
15915 @item show cris-version
15916 Show the current CRIS version.
15918 @item set cris-dwarf2-cfi
15919 @cindex DWARF-2 CFI and CRIS
15920 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
15921 Change to @samp{off} when using @code{gcc-cris} whose version is below
15924 @item show cris-dwarf2-cfi
15925 Show the current state of using DWARF-2 CFI.
15927 @item set cris-mode @var{mode}
15929 Set the current CRIS mode to @var{mode}. It should only be changed when
15930 debugging in guru mode, in which case it should be set to
15931 @samp{guru} (the default is @samp{normal}).
15933 @item show cris-mode
15934 Show the current CRIS mode.
15938 @subsection Renesas Super-H
15941 For the Renesas Super-H processor, @value{GDBN} provides these
15946 @kindex regs@r{, Super-H}
15947 Show the values of all Super-H registers.
15949 @item set sh calling-convention @var{convention}
15950 @kindex set sh calling-convention
15951 Set the calling-convention used when calling functions from @value{GDBN}.
15952 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
15953 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
15954 convention. If the DWARF-2 information of the called function specifies
15955 that the function follows the Renesas calling convention, the function
15956 is called using the Renesas calling convention. If the calling convention
15957 is set to @samp{renesas}, the Renesas calling convention is always used,
15958 regardless of the DWARF-2 information. This can be used to override the
15959 default of @samp{gcc} if debug information is missing, or the compiler
15960 does not emit the DWARF-2 calling convention entry for a function.
15962 @item show sh calling-convention
15963 @kindex show sh calling-convention
15964 Show the current calling convention setting.
15969 @node Architectures
15970 @section Architectures
15972 This section describes characteristics of architectures that affect
15973 all uses of @value{GDBN} with the architecture, both native and cross.
15980 * HPPA:: HP PA architecture
15981 * SPU:: Cell Broadband Engine SPU architecture
15986 @subsection x86 Architecture-specific Issues
15989 @item set struct-convention @var{mode}
15990 @kindex set struct-convention
15991 @cindex struct return convention
15992 @cindex struct/union returned in registers
15993 Set the convention used by the inferior to return @code{struct}s and
15994 @code{union}s from functions to @var{mode}. Possible values of
15995 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
15996 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
15997 are returned on the stack, while @code{"reg"} means that a
15998 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
15999 be returned in a register.
16001 @item show struct-convention
16002 @kindex show struct-convention
16003 Show the current setting of the convention to return @code{struct}s
16012 @kindex set rstack_high_address
16013 @cindex AMD 29K register stack
16014 @cindex register stack, AMD29K
16015 @item set rstack_high_address @var{address}
16016 On AMD 29000 family processors, registers are saved in a separate
16017 @dfn{register stack}. There is no way for @value{GDBN} to determine the
16018 extent of this stack. Normally, @value{GDBN} just assumes that the
16019 stack is ``large enough''. This may result in @value{GDBN} referencing
16020 memory locations that do not exist. If necessary, you can get around
16021 this problem by specifying the ending address of the register stack with
16022 the @code{set rstack_high_address} command. The argument should be an
16023 address, which you probably want to precede with @samp{0x} to specify in
16026 @kindex show rstack_high_address
16027 @item show rstack_high_address
16028 Display the current limit of the register stack, on AMD 29000 family
16036 See the following section.
16041 @cindex stack on Alpha
16042 @cindex stack on MIPS
16043 @cindex Alpha stack
16045 Alpha- and MIPS-based computers use an unusual stack frame, which
16046 sometimes requires @value{GDBN} to search backward in the object code to
16047 find the beginning of a function.
16049 @cindex response time, MIPS debugging
16050 To improve response time (especially for embedded applications, where
16051 @value{GDBN} may be restricted to a slow serial line for this search)
16052 you may want to limit the size of this search, using one of these
16056 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
16057 @item set heuristic-fence-post @var{limit}
16058 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
16059 search for the beginning of a function. A value of @var{0} (the
16060 default) means there is no limit. However, except for @var{0}, the
16061 larger the limit the more bytes @code{heuristic-fence-post} must search
16062 and therefore the longer it takes to run. You should only need to use
16063 this command when debugging a stripped executable.
16065 @item show heuristic-fence-post
16066 Display the current limit.
16070 These commands are available @emph{only} when @value{GDBN} is configured
16071 for debugging programs on Alpha or MIPS processors.
16073 Several MIPS-specific commands are available when debugging MIPS
16077 @item set mips abi @var{arg}
16078 @kindex set mips abi
16079 @cindex set ABI for MIPS
16080 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
16081 values of @var{arg} are:
16085 The default ABI associated with the current binary (this is the
16096 @item show mips abi
16097 @kindex show mips abi
16098 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
16101 @itemx show mipsfpu
16102 @xref{MIPS Embedded, set mipsfpu}.
16104 @item set mips mask-address @var{arg}
16105 @kindex set mips mask-address
16106 @cindex MIPS addresses, masking
16107 This command determines whether the most-significant 32 bits of 64-bit
16108 MIPS addresses are masked off. The argument @var{arg} can be
16109 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
16110 setting, which lets @value{GDBN} determine the correct value.
16112 @item show mips mask-address
16113 @kindex show mips mask-address
16114 Show whether the upper 32 bits of MIPS addresses are masked off or
16117 @item set remote-mips64-transfers-32bit-regs
16118 @kindex set remote-mips64-transfers-32bit-regs
16119 This command controls compatibility with 64-bit MIPS targets that
16120 transfer data in 32-bit quantities. If you have an old MIPS 64 target
16121 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
16122 and 64 bits for other registers, set this option to @samp{on}.
16124 @item show remote-mips64-transfers-32bit-regs
16125 @kindex show remote-mips64-transfers-32bit-regs
16126 Show the current setting of compatibility with older MIPS 64 targets.
16128 @item set debug mips
16129 @kindex set debug mips
16130 This command turns on and off debugging messages for the MIPS-specific
16131 target code in @value{GDBN}.
16133 @item show debug mips
16134 @kindex show debug mips
16135 Show the current setting of MIPS debugging messages.
16141 @cindex HPPA support
16143 When @value{GDBN} is debugging the HP PA architecture, it provides the
16144 following special commands:
16147 @item set debug hppa
16148 @kindex set debug hppa
16149 This command determines whether HPPA architecture-specific debugging
16150 messages are to be displayed.
16152 @item show debug hppa
16153 Show whether HPPA debugging messages are displayed.
16155 @item maint print unwind @var{address}
16156 @kindex maint print unwind@r{, HPPA}
16157 This command displays the contents of the unwind table entry at the
16158 given @var{address}.
16164 @subsection Cell Broadband Engine SPU architecture
16165 @cindex Cell Broadband Engine
16168 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
16169 it provides the following special commands:
16172 @item info spu event
16174 Display SPU event facility status. Shows current event mask
16175 and pending event status.
16177 @item info spu signal
16178 Display SPU signal notification facility status. Shows pending
16179 signal-control word and signal notification mode of both signal
16180 notification channels.
16182 @item info spu mailbox
16183 Display SPU mailbox facility status. Shows all pending entries,
16184 in order of processing, in each of the SPU Write Outbound,
16185 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
16188 Display MFC DMA status. Shows all pending commands in the MFC
16189 DMA queue. For each entry, opcode, tag, class IDs, effective
16190 and local store addresses and transfer size are shown.
16192 @item info spu proxydma
16193 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
16194 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
16195 and local store addresses and transfer size are shown.
16200 @subsection PowerPC
16201 @cindex PowerPC architecture
16203 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
16204 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
16205 numbers stored in the floating point registers. These values must be stored
16206 in two consecutive registers, always starting at an even register like
16207 @code{f0} or @code{f2}.
16209 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
16210 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
16211 @code{f2} and @code{f3} for @code{$dl1} and so on.
16214 @node Controlling GDB
16215 @chapter Controlling @value{GDBN}
16217 You can alter the way @value{GDBN} interacts with you by using the
16218 @code{set} command. For commands controlling how @value{GDBN} displays
16219 data, see @ref{Print Settings, ,Print Settings}. Other settings are
16224 * Editing:: Command editing
16225 * Command History:: Command history
16226 * Screen Size:: Screen size
16227 * Numbers:: Numbers
16228 * ABI:: Configuring the current ABI
16229 * Messages/Warnings:: Optional warnings and messages
16230 * Debugging Output:: Optional messages about internal happenings
16238 @value{GDBN} indicates its readiness to read a command by printing a string
16239 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
16240 can change the prompt string with the @code{set prompt} command. For
16241 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
16242 the prompt in one of the @value{GDBN} sessions so that you can always tell
16243 which one you are talking to.
16245 @emph{Note:} @code{set prompt} does not add a space for you after the
16246 prompt you set. This allows you to set a prompt which ends in a space
16247 or a prompt that does not.
16251 @item set prompt @var{newprompt}
16252 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
16254 @kindex show prompt
16256 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
16260 @section Command Editing
16262 @cindex command line editing
16264 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
16265 @sc{gnu} library provides consistent behavior for programs which provide a
16266 command line interface to the user. Advantages are @sc{gnu} Emacs-style
16267 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
16268 substitution, and a storage and recall of command history across
16269 debugging sessions.
16271 You may control the behavior of command line editing in @value{GDBN} with the
16272 command @code{set}.
16275 @kindex set editing
16278 @itemx set editing on
16279 Enable command line editing (enabled by default).
16281 @item set editing off
16282 Disable command line editing.
16284 @kindex show editing
16286 Show whether command line editing is enabled.
16289 @xref{Command Line Editing}, for more details about the Readline
16290 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
16291 encouraged to read that chapter.
16293 @node Command History
16294 @section Command History
16295 @cindex command history
16297 @value{GDBN} can keep track of the commands you type during your
16298 debugging sessions, so that you can be certain of precisely what
16299 happened. Use these commands to manage the @value{GDBN} command
16302 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
16303 package, to provide the history facility. @xref{Using History
16304 Interactively}, for the detailed description of the History library.
16306 To issue a command to @value{GDBN} without affecting certain aspects of
16307 the state which is seen by users, prefix it with @samp{server }
16308 (@pxref{Server Prefix}). This
16309 means that this command will not affect the command history, nor will it
16310 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
16311 pressed on a line by itself.
16313 @cindex @code{server}, command prefix
16314 The server prefix does not affect the recording of values into the value
16315 history; to print a value without recording it into the value history,
16316 use the @code{output} command instead of the @code{print} command.
16318 Here is the description of @value{GDBN} commands related to command
16322 @cindex history substitution
16323 @cindex history file
16324 @kindex set history filename
16325 @cindex @env{GDBHISTFILE}, environment variable
16326 @item set history filename @var{fname}
16327 Set the name of the @value{GDBN} command history file to @var{fname}.
16328 This is the file where @value{GDBN} reads an initial command history
16329 list, and where it writes the command history from this session when it
16330 exits. You can access this list through history expansion or through
16331 the history command editing characters listed below. This file defaults
16332 to the value of the environment variable @code{GDBHISTFILE}, or to
16333 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
16336 @cindex save command history
16337 @kindex set history save
16338 @item set history save
16339 @itemx set history save on
16340 Record command history in a file, whose name may be specified with the
16341 @code{set history filename} command. By default, this option is disabled.
16343 @item set history save off
16344 Stop recording command history in a file.
16346 @cindex history size
16347 @kindex set history size
16348 @cindex @env{HISTSIZE}, environment variable
16349 @item set history size @var{size}
16350 Set the number of commands which @value{GDBN} keeps in its history list.
16351 This defaults to the value of the environment variable
16352 @code{HISTSIZE}, or to 256 if this variable is not set.
16355 History expansion assigns special meaning to the character @kbd{!}.
16356 @xref{Event Designators}, for more details.
16358 @cindex history expansion, turn on/off
16359 Since @kbd{!} is also the logical not operator in C, history expansion
16360 is off by default. If you decide to enable history expansion with the
16361 @code{set history expansion on} command, you may sometimes need to
16362 follow @kbd{!} (when it is used as logical not, in an expression) with
16363 a space or a tab to prevent it from being expanded. The readline
16364 history facilities do not attempt substitution on the strings
16365 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
16367 The commands to control history expansion are:
16370 @item set history expansion on
16371 @itemx set history expansion
16372 @kindex set history expansion
16373 Enable history expansion. History expansion is off by default.
16375 @item set history expansion off
16376 Disable history expansion.
16379 @kindex show history
16381 @itemx show history filename
16382 @itemx show history save
16383 @itemx show history size
16384 @itemx show history expansion
16385 These commands display the state of the @value{GDBN} history parameters.
16386 @code{show history} by itself displays all four states.
16391 @kindex show commands
16392 @cindex show last commands
16393 @cindex display command history
16394 @item show commands
16395 Display the last ten commands in the command history.
16397 @item show commands @var{n}
16398 Print ten commands centered on command number @var{n}.
16400 @item show commands +
16401 Print ten commands just after the commands last printed.
16405 @section Screen Size
16406 @cindex size of screen
16407 @cindex pauses in output
16409 Certain commands to @value{GDBN} may produce large amounts of
16410 information output to the screen. To help you read all of it,
16411 @value{GDBN} pauses and asks you for input at the end of each page of
16412 output. Type @key{RET} when you want to continue the output, or @kbd{q}
16413 to discard the remaining output. Also, the screen width setting
16414 determines when to wrap lines of output. Depending on what is being
16415 printed, @value{GDBN} tries to break the line at a readable place,
16416 rather than simply letting it overflow onto the following line.
16418 Normally @value{GDBN} knows the size of the screen from the terminal
16419 driver software. For example, on Unix @value{GDBN} uses the termcap data base
16420 together with the value of the @code{TERM} environment variable and the
16421 @code{stty rows} and @code{stty cols} settings. If this is not correct,
16422 you can override it with the @code{set height} and @code{set
16429 @kindex show height
16430 @item set height @var{lpp}
16432 @itemx set width @var{cpl}
16434 These @code{set} commands specify a screen height of @var{lpp} lines and
16435 a screen width of @var{cpl} characters. The associated @code{show}
16436 commands display the current settings.
16438 If you specify a height of zero lines, @value{GDBN} does not pause during
16439 output no matter how long the output is. This is useful if output is to a
16440 file or to an editor buffer.
16442 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
16443 from wrapping its output.
16445 @item set pagination on
16446 @itemx set pagination off
16447 @kindex set pagination
16448 Turn the output pagination on or off; the default is on. Turning
16449 pagination off is the alternative to @code{set height 0}.
16451 @item show pagination
16452 @kindex show pagination
16453 Show the current pagination mode.
16458 @cindex number representation
16459 @cindex entering numbers
16461 You can always enter numbers in octal, decimal, or hexadecimal in
16462 @value{GDBN} by the usual conventions: octal numbers begin with
16463 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
16464 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
16465 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
16466 10; likewise, the default display for numbers---when no particular
16467 format is specified---is base 10. You can change the default base for
16468 both input and output with the commands described below.
16471 @kindex set input-radix
16472 @item set input-radix @var{base}
16473 Set the default base for numeric input. Supported choices
16474 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
16475 specified either unambiguously or using the current input radix; for
16479 set input-radix 012
16480 set input-radix 10.
16481 set input-radix 0xa
16485 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
16486 leaves the input radix unchanged, no matter what it was, since
16487 @samp{10}, being without any leading or trailing signs of its base, is
16488 interpreted in the current radix. Thus, if the current radix is 16,
16489 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
16492 @kindex set output-radix
16493 @item set output-radix @var{base}
16494 Set the default base for numeric display. Supported choices
16495 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
16496 specified either unambiguously or using the current input radix.
16498 @kindex show input-radix
16499 @item show input-radix
16500 Display the current default base for numeric input.
16502 @kindex show output-radix
16503 @item show output-radix
16504 Display the current default base for numeric display.
16506 @item set radix @r{[}@var{base}@r{]}
16510 These commands set and show the default base for both input and output
16511 of numbers. @code{set radix} sets the radix of input and output to
16512 the same base; without an argument, it resets the radix back to its
16513 default value of 10.
16518 @section Configuring the Current ABI
16520 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
16521 application automatically. However, sometimes you need to override its
16522 conclusions. Use these commands to manage @value{GDBN}'s view of the
16529 One @value{GDBN} configuration can debug binaries for multiple operating
16530 system targets, either via remote debugging or native emulation.
16531 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
16532 but you can override its conclusion using the @code{set osabi} command.
16533 One example where this is useful is in debugging of binaries which use
16534 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
16535 not have the same identifying marks that the standard C library for your
16540 Show the OS ABI currently in use.
16543 With no argument, show the list of registered available OS ABI's.
16545 @item set osabi @var{abi}
16546 Set the current OS ABI to @var{abi}.
16549 @cindex float promotion
16551 Generally, the way that an argument of type @code{float} is passed to a
16552 function depends on whether the function is prototyped. For a prototyped
16553 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
16554 according to the architecture's convention for @code{float}. For unprototyped
16555 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
16556 @code{double} and then passed.
16558 Unfortunately, some forms of debug information do not reliably indicate whether
16559 a function is prototyped. If @value{GDBN} calls a function that is not marked
16560 as prototyped, it consults @kbd{set coerce-float-to-double}.
16563 @kindex set coerce-float-to-double
16564 @item set coerce-float-to-double
16565 @itemx set coerce-float-to-double on
16566 Arguments of type @code{float} will be promoted to @code{double} when passed
16567 to an unprototyped function. This is the default setting.
16569 @item set coerce-float-to-double off
16570 Arguments of type @code{float} will be passed directly to unprototyped
16573 @kindex show coerce-float-to-double
16574 @item show coerce-float-to-double
16575 Show the current setting of promoting @code{float} to @code{double}.
16579 @kindex show cp-abi
16580 @value{GDBN} needs to know the ABI used for your program's C@t{++}
16581 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
16582 used to build your application. @value{GDBN} only fully supports
16583 programs with a single C@t{++} ABI; if your program contains code using
16584 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
16585 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
16586 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
16587 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
16588 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
16589 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
16594 Show the C@t{++} ABI currently in use.
16597 With no argument, show the list of supported C@t{++} ABI's.
16599 @item set cp-abi @var{abi}
16600 @itemx set cp-abi auto
16601 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
16604 @node Messages/Warnings
16605 @section Optional Warnings and Messages
16607 @cindex verbose operation
16608 @cindex optional warnings
16609 By default, @value{GDBN} is silent about its inner workings. If you are
16610 running on a slow machine, you may want to use the @code{set verbose}
16611 command. This makes @value{GDBN} tell you when it does a lengthy
16612 internal operation, so you will not think it has crashed.
16614 Currently, the messages controlled by @code{set verbose} are those
16615 which announce that the symbol table for a source file is being read;
16616 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
16619 @kindex set verbose
16620 @item set verbose on
16621 Enables @value{GDBN} output of certain informational messages.
16623 @item set verbose off
16624 Disables @value{GDBN} output of certain informational messages.
16626 @kindex show verbose
16628 Displays whether @code{set verbose} is on or off.
16631 By default, if @value{GDBN} encounters bugs in the symbol table of an
16632 object file, it is silent; but if you are debugging a compiler, you may
16633 find this information useful (@pxref{Symbol Errors, ,Errors Reading
16638 @kindex set complaints
16639 @item set complaints @var{limit}
16640 Permits @value{GDBN} to output @var{limit} complaints about each type of
16641 unusual symbols before becoming silent about the problem. Set
16642 @var{limit} to zero to suppress all complaints; set it to a large number
16643 to prevent complaints from being suppressed.
16645 @kindex show complaints
16646 @item show complaints
16647 Displays how many symbol complaints @value{GDBN} is permitted to produce.
16651 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
16652 lot of stupid questions to confirm certain commands. For example, if
16653 you try to run a program which is already running:
16657 The program being debugged has been started already.
16658 Start it from the beginning? (y or n)
16661 If you are willing to unflinchingly face the consequences of your own
16662 commands, you can disable this ``feature'':
16666 @kindex set confirm
16668 @cindex confirmation
16669 @cindex stupid questions
16670 @item set confirm off
16671 Disables confirmation requests.
16673 @item set confirm on
16674 Enables confirmation requests (the default).
16676 @kindex show confirm
16678 Displays state of confirmation requests.
16682 @cindex command tracing
16683 If you need to debug user-defined commands or sourced files you may find it
16684 useful to enable @dfn{command tracing}. In this mode each command will be
16685 printed as it is executed, prefixed with one or more @samp{+} symbols, the
16686 quantity denoting the call depth of each command.
16689 @kindex set trace-commands
16690 @cindex command scripts, debugging
16691 @item set trace-commands on
16692 Enable command tracing.
16693 @item set trace-commands off
16694 Disable command tracing.
16695 @item show trace-commands
16696 Display the current state of command tracing.
16699 @node Debugging Output
16700 @section Optional Messages about Internal Happenings
16701 @cindex optional debugging messages
16703 @value{GDBN} has commands that enable optional debugging messages from
16704 various @value{GDBN} subsystems; normally these commands are of
16705 interest to @value{GDBN} maintainers, or when reporting a bug. This
16706 section documents those commands.
16709 @kindex set exec-done-display
16710 @item set exec-done-display
16711 Turns on or off the notification of asynchronous commands'
16712 completion. When on, @value{GDBN} will print a message when an
16713 asynchronous command finishes its execution. The default is off.
16714 @kindex show exec-done-display
16715 @item show exec-done-display
16716 Displays the current setting of asynchronous command completion
16719 @cindex gdbarch debugging info
16720 @cindex architecture debugging info
16721 @item set debug arch
16722 Turns on or off display of gdbarch debugging info. The default is off
16724 @item show debug arch
16725 Displays the current state of displaying gdbarch debugging info.
16726 @item set debug aix-thread
16727 @cindex AIX threads
16728 Display debugging messages about inner workings of the AIX thread
16730 @item show debug aix-thread
16731 Show the current state of AIX thread debugging info display.
16732 @item set debug displaced
16733 @cindex displaced stepping debugging info
16734 Turns on or off display of @value{GDBN} debugging info for the
16735 displaced stepping support. The default is off.
16736 @item show debug displaced
16737 Displays the current state of displaying @value{GDBN} debugging info
16738 related to displaced stepping.
16739 @item set debug event
16740 @cindex event debugging info
16741 Turns on or off display of @value{GDBN} event debugging info. The
16743 @item show debug event
16744 Displays the current state of displaying @value{GDBN} event debugging
16746 @item set debug expression
16747 @cindex expression debugging info
16748 Turns on or off display of debugging info about @value{GDBN}
16749 expression parsing. The default is off.
16750 @item show debug expression
16751 Displays the current state of displaying debugging info about
16752 @value{GDBN} expression parsing.
16753 @item set debug frame
16754 @cindex frame debugging info
16755 Turns on or off display of @value{GDBN} frame debugging info. The
16757 @item show debug frame
16758 Displays the current state of displaying @value{GDBN} frame debugging
16760 @item set debug infrun
16761 @cindex inferior debugging info
16762 Turns on or off display of @value{GDBN} debugging info for running the inferior.
16763 The default is off. @file{infrun.c} contains GDB's runtime state machine used
16764 for implementing operations such as single-stepping the inferior.
16765 @item show debug infrun
16766 Displays the current state of @value{GDBN} inferior debugging.
16767 @item set debug lin-lwp
16768 @cindex @sc{gnu}/Linux LWP debug messages
16769 @cindex Linux lightweight processes
16770 Turns on or off debugging messages from the Linux LWP debug support.
16771 @item show debug lin-lwp
16772 Show the current state of Linux LWP debugging messages.
16773 @item set debug lin-lwp-async
16774 @cindex @sc{gnu}/Linux LWP async debug messages
16775 @cindex Linux lightweight processes
16776 Turns on or off debugging messages from the Linux LWP async debug support.
16777 @item show debug lin-lwp-async
16778 Show the current state of Linux LWP async debugging messages.
16779 @item set debug observer
16780 @cindex observer debugging info
16781 Turns on or off display of @value{GDBN} observer debugging. This
16782 includes info such as the notification of observable events.
16783 @item show debug observer
16784 Displays the current state of observer debugging.
16785 @item set debug overload
16786 @cindex C@t{++} overload debugging info
16787 Turns on or off display of @value{GDBN} C@t{++} overload debugging
16788 info. This includes info such as ranking of functions, etc. The default
16790 @item show debug overload
16791 Displays the current state of displaying @value{GDBN} C@t{++} overload
16793 @cindex packets, reporting on stdout
16794 @cindex serial connections, debugging
16795 @cindex debug remote protocol
16796 @cindex remote protocol debugging
16797 @cindex display remote packets
16798 @item set debug remote
16799 Turns on or off display of reports on all packets sent back and forth across
16800 the serial line to the remote machine. The info is printed on the
16801 @value{GDBN} standard output stream. The default is off.
16802 @item show debug remote
16803 Displays the state of display of remote packets.
16804 @item set debug serial
16805 Turns on or off display of @value{GDBN} serial debugging info. The
16807 @item show debug serial
16808 Displays the current state of displaying @value{GDBN} serial debugging
16810 @item set debug solib-frv
16811 @cindex FR-V shared-library debugging
16812 Turns on or off debugging messages for FR-V shared-library code.
16813 @item show debug solib-frv
16814 Display the current state of FR-V shared-library code debugging
16816 @item set debug target
16817 @cindex target debugging info
16818 Turns on or off display of @value{GDBN} target debugging info. This info
16819 includes what is going on at the target level of GDB, as it happens. The
16820 default is 0. Set it to 1 to track events, and to 2 to also track the
16821 value of large memory transfers. Changes to this flag do not take effect
16822 until the next time you connect to a target or use the @code{run} command.
16823 @item show debug target
16824 Displays the current state of displaying @value{GDBN} target debugging
16826 @item set debug timestamp
16827 @cindex timestampping debugging info
16828 Turns on or off display of timestamps with @value{GDBN} debugging info.
16829 When enabled, seconds and microseconds are displayed before each debugging
16831 @item show debug timestamp
16832 Displays the current state of displaying timestamps with @value{GDBN}
16834 @item set debugvarobj
16835 @cindex variable object debugging info
16836 Turns on or off display of @value{GDBN} variable object debugging
16837 info. The default is off.
16838 @item show debugvarobj
16839 Displays the current state of displaying @value{GDBN} variable object
16841 @item set debug xml
16842 @cindex XML parser debugging
16843 Turns on or off debugging messages for built-in XML parsers.
16844 @item show debug xml
16845 Displays the current state of XML debugging messages.
16849 @chapter Canned Sequences of Commands
16851 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
16852 Command Lists}), @value{GDBN} provides two ways to store sequences of
16853 commands for execution as a unit: user-defined commands and command
16857 * Define:: How to define your own commands
16858 * Hooks:: Hooks for user-defined commands
16859 * Command Files:: How to write scripts of commands to be stored in a file
16860 * Output:: Commands for controlled output
16864 @section User-defined Commands
16866 @cindex user-defined command
16867 @cindex arguments, to user-defined commands
16868 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
16869 which you assign a new name as a command. This is done with the
16870 @code{define} command. User commands may accept up to 10 arguments
16871 separated by whitespace. Arguments are accessed within the user command
16872 via @code{$arg0@dots{}$arg9}. A trivial example:
16876 print $arg0 + $arg1 + $arg2
16881 To execute the command use:
16888 This defines the command @code{adder}, which prints the sum of
16889 its three arguments. Note the arguments are text substitutions, so they may
16890 reference variables, use complex expressions, or even perform inferior
16893 @cindex argument count in user-defined commands
16894 @cindex how many arguments (user-defined commands)
16895 In addition, @code{$argc} may be used to find out how many arguments have
16896 been passed. This expands to a number in the range 0@dots{}10.
16901 print $arg0 + $arg1
16904 print $arg0 + $arg1 + $arg2
16912 @item define @var{commandname}
16913 Define a command named @var{commandname}. If there is already a command
16914 by that name, you are asked to confirm that you want to redefine it.
16916 The definition of the command is made up of other @value{GDBN} command lines,
16917 which are given following the @code{define} command. The end of these
16918 commands is marked by a line containing @code{end}.
16921 @kindex end@r{ (user-defined commands)}
16922 @item document @var{commandname}
16923 Document the user-defined command @var{commandname}, so that it can be
16924 accessed by @code{help}. The command @var{commandname} must already be
16925 defined. This command reads lines of documentation just as @code{define}
16926 reads the lines of the command definition, ending with @code{end}.
16927 After the @code{document} command is finished, @code{help} on command
16928 @var{commandname} displays the documentation you have written.
16930 You may use the @code{document} command again to change the
16931 documentation of a command. Redefining the command with @code{define}
16932 does not change the documentation.
16934 @kindex dont-repeat
16935 @cindex don't repeat command
16937 Used inside a user-defined command, this tells @value{GDBN} that this
16938 command should not be repeated when the user hits @key{RET}
16939 (@pxref{Command Syntax, repeat last command}).
16941 @kindex help user-defined
16942 @item help user-defined
16943 List all user-defined commands, with the first line of the documentation
16948 @itemx show user @var{commandname}
16949 Display the @value{GDBN} commands used to define @var{commandname} (but
16950 not its documentation). If no @var{commandname} is given, display the
16951 definitions for all user-defined commands.
16953 @cindex infinite recursion in user-defined commands
16954 @kindex show max-user-call-depth
16955 @kindex set max-user-call-depth
16956 @item show max-user-call-depth
16957 @itemx set max-user-call-depth
16958 The value of @code{max-user-call-depth} controls how many recursion
16959 levels are allowed in user-defined commands before @value{GDBN} suspects an
16960 infinite recursion and aborts the command.
16963 In addition to the above commands, user-defined commands frequently
16964 use control flow commands, described in @ref{Command Files}.
16966 When user-defined commands are executed, the
16967 commands of the definition are not printed. An error in any command
16968 stops execution of the user-defined command.
16970 If used interactively, commands that would ask for confirmation proceed
16971 without asking when used inside a user-defined command. Many @value{GDBN}
16972 commands that normally print messages to say what they are doing omit the
16973 messages when used in a user-defined command.
16976 @section User-defined Command Hooks
16977 @cindex command hooks
16978 @cindex hooks, for commands
16979 @cindex hooks, pre-command
16982 You may define @dfn{hooks}, which are a special kind of user-defined
16983 command. Whenever you run the command @samp{foo}, if the user-defined
16984 command @samp{hook-foo} exists, it is executed (with no arguments)
16985 before that command.
16987 @cindex hooks, post-command
16989 A hook may also be defined which is run after the command you executed.
16990 Whenever you run the command @samp{foo}, if the user-defined command
16991 @samp{hookpost-foo} exists, it is executed (with no arguments) after
16992 that command. Post-execution hooks may exist simultaneously with
16993 pre-execution hooks, for the same command.
16995 It is valid for a hook to call the command which it hooks. If this
16996 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
16998 @c It would be nice if hookpost could be passed a parameter indicating
16999 @c if the command it hooks executed properly or not. FIXME!
17001 @kindex stop@r{, a pseudo-command}
17002 In addition, a pseudo-command, @samp{stop} exists. Defining
17003 (@samp{hook-stop}) makes the associated commands execute every time
17004 execution stops in your program: before breakpoint commands are run,
17005 displays are printed, or the stack frame is printed.
17007 For example, to ignore @code{SIGALRM} signals while
17008 single-stepping, but treat them normally during normal execution,
17013 handle SIGALRM nopass
17017 handle SIGALRM pass
17020 define hook-continue
17021 handle SIGALRM pass
17025 As a further example, to hook at the beginning and end of the @code{echo}
17026 command, and to add extra text to the beginning and end of the message,
17034 define hookpost-echo
17038 (@value{GDBP}) echo Hello World
17039 <<<---Hello World--->>>
17044 You can define a hook for any single-word command in @value{GDBN}, but
17045 not for command aliases; you should define a hook for the basic command
17046 name, e.g.@: @code{backtrace} rather than @code{bt}.
17047 @c FIXME! So how does Joe User discover whether a command is an alias
17049 If an error occurs during the execution of your hook, execution of
17050 @value{GDBN} commands stops and @value{GDBN} issues a prompt
17051 (before the command that you actually typed had a chance to run).
17053 If you try to define a hook which does not match any known command, you
17054 get a warning from the @code{define} command.
17056 @node Command Files
17057 @section Command Files
17059 @cindex command files
17060 @cindex scripting commands
17061 A command file for @value{GDBN} is a text file made of lines that are
17062 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
17063 also be included. An empty line in a command file does nothing; it
17064 does not mean to repeat the last command, as it would from the
17067 You can request the execution of a command file with the @code{source}
17072 @cindex execute commands from a file
17073 @item source [@code{-v}] @var{filename}
17074 Execute the command file @var{filename}.
17077 The lines in a command file are generally executed sequentially,
17078 unless the order of execution is changed by one of the
17079 @emph{flow-control commands} described below. The commands are not
17080 printed as they are executed. An error in any command terminates
17081 execution of the command file and control is returned to the console.
17083 @value{GDBN} searches for @var{filename} in the current directory and then
17084 on the search path (specified with the @samp{directory} command).
17086 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
17087 each command as it is executed. The option must be given before
17088 @var{filename}, and is interpreted as part of the filename anywhere else.
17090 Commands that would ask for confirmation if used interactively proceed
17091 without asking when used in a command file. Many @value{GDBN} commands that
17092 normally print messages to say what they are doing omit the messages
17093 when called from command files.
17095 @value{GDBN} also accepts command input from standard input. In this
17096 mode, normal output goes to standard output and error output goes to
17097 standard error. Errors in a command file supplied on standard input do
17098 not terminate execution of the command file---execution continues with
17102 gdb < cmds > log 2>&1
17105 (The syntax above will vary depending on the shell used.) This example
17106 will execute commands from the file @file{cmds}. All output and errors
17107 would be directed to @file{log}.
17109 Since commands stored on command files tend to be more general than
17110 commands typed interactively, they frequently need to deal with
17111 complicated situations, such as different or unexpected values of
17112 variables and symbols, changes in how the program being debugged is
17113 built, etc. @value{GDBN} provides a set of flow-control commands to
17114 deal with these complexities. Using these commands, you can write
17115 complex scripts that loop over data structures, execute commands
17116 conditionally, etc.
17123 This command allows to include in your script conditionally executed
17124 commands. The @code{if} command takes a single argument, which is an
17125 expression to evaluate. It is followed by a series of commands that
17126 are executed only if the expression is true (its value is nonzero).
17127 There can then optionally be an @code{else} line, followed by a series
17128 of commands that are only executed if the expression was false. The
17129 end of the list is marked by a line containing @code{end}.
17133 This command allows to write loops. Its syntax is similar to
17134 @code{if}: the command takes a single argument, which is an expression
17135 to evaluate, and must be followed by the commands to execute, one per
17136 line, terminated by an @code{end}. These commands are called the
17137 @dfn{body} of the loop. The commands in the body of @code{while} are
17138 executed repeatedly as long as the expression evaluates to true.
17142 This command exits the @code{while} loop in whose body it is included.
17143 Execution of the script continues after that @code{while}s @code{end}
17146 @kindex loop_continue
17147 @item loop_continue
17148 This command skips the execution of the rest of the body of commands
17149 in the @code{while} loop in whose body it is included. Execution
17150 branches to the beginning of the @code{while} loop, where it evaluates
17151 the controlling expression.
17153 @kindex end@r{ (if/else/while commands)}
17155 Terminate the block of commands that are the body of @code{if},
17156 @code{else}, or @code{while} flow-control commands.
17161 @section Commands for Controlled Output
17163 During the execution of a command file or a user-defined command, normal
17164 @value{GDBN} output is suppressed; the only output that appears is what is
17165 explicitly printed by the commands in the definition. This section
17166 describes three commands useful for generating exactly the output you
17171 @item echo @var{text}
17172 @c I do not consider backslash-space a standard C escape sequence
17173 @c because it is not in ANSI.
17174 Print @var{text}. Nonprinting characters can be included in
17175 @var{text} using C escape sequences, such as @samp{\n} to print a
17176 newline. @strong{No newline is printed unless you specify one.}
17177 In addition to the standard C escape sequences, a backslash followed
17178 by a space stands for a space. This is useful for displaying a
17179 string with spaces at the beginning or the end, since leading and
17180 trailing spaces are otherwise trimmed from all arguments.
17181 To print @samp{@w{ }and foo =@w{ }}, use the command
17182 @samp{echo \@w{ }and foo = \@w{ }}.
17184 A backslash at the end of @var{text} can be used, as in C, to continue
17185 the command onto subsequent lines. For example,
17188 echo This is some text\n\
17189 which is continued\n\
17190 onto several lines.\n
17193 produces the same output as
17196 echo This is some text\n
17197 echo which is continued\n
17198 echo onto several lines.\n
17202 @item output @var{expression}
17203 Print the value of @var{expression} and nothing but that value: no
17204 newlines, no @samp{$@var{nn} = }. The value is not entered in the
17205 value history either. @xref{Expressions, ,Expressions}, for more information
17208 @item output/@var{fmt} @var{expression}
17209 Print the value of @var{expression} in format @var{fmt}. You can use
17210 the same formats as for @code{print}. @xref{Output Formats,,Output
17211 Formats}, for more information.
17214 @item printf @var{template}, @var{expressions}@dots{}
17215 Print the values of one or more @var{expressions} under the control of
17216 the string @var{template}. To print several values, make
17217 @var{expressions} be a comma-separated list of individual expressions,
17218 which may be either numbers or pointers. Their values are printed as
17219 specified by @var{template}, exactly as a C program would do by
17220 executing the code below:
17223 printf (@var{template}, @var{expressions}@dots{});
17226 As in @code{C} @code{printf}, ordinary characters in @var{template}
17227 are printed verbatim, while @dfn{conversion specification} introduced
17228 by the @samp{%} character cause subsequent @var{expressions} to be
17229 evaluated, their values converted and formatted according to type and
17230 style information encoded in the conversion specifications, and then
17233 For example, you can print two values in hex like this:
17236 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
17239 @code{printf} supports all the standard @code{C} conversion
17240 specifications, including the flags and modifiers between the @samp{%}
17241 character and the conversion letter, with the following exceptions:
17245 The argument-ordering modifiers, such as @samp{2$}, are not supported.
17248 The modifier @samp{*} is not supported for specifying precision or
17252 The @samp{'} flag (for separation of digits into groups according to
17253 @code{LC_NUMERIC'}) is not supported.
17256 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
17260 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
17263 The conversion letters @samp{a} and @samp{A} are not supported.
17267 Note that the @samp{ll} type modifier is supported only if the
17268 underlying @code{C} implementation used to build @value{GDBN} supports
17269 the @code{long long int} type, and the @samp{L} type modifier is
17270 supported only if @code{long double} type is available.
17272 As in @code{C}, @code{printf} supports simple backslash-escape
17273 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
17274 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
17275 single character. Octal and hexadecimal escape sequences are not
17278 Additionally, @code{printf} supports conversion specifications for DFP
17279 (@dfn{Decimal Floating Point}) types using the following length modifiers
17280 together with a floating point specifier.
17285 @samp{H} for printing @code{Decimal32} types.
17288 @samp{D} for printing @code{Decimal64} types.
17291 @samp{DD} for printing @code{Decimal128} types.
17294 If the underlying @code{C} implementation used to build @value{GDBN} has
17295 support for the three length modifiers for DFP types, other modifiers
17296 such as width and precision will also be available for @value{GDBN} to use.
17298 In case there is no such @code{C} support, no additional modifiers will be
17299 available and the value will be printed in the standard way.
17301 Here's an example of printing DFP types using the above conversion letters:
17303 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
17309 @chapter Command Interpreters
17310 @cindex command interpreters
17312 @value{GDBN} supports multiple command interpreters, and some command
17313 infrastructure to allow users or user interface writers to switch
17314 between interpreters or run commands in other interpreters.
17316 @value{GDBN} currently supports two command interpreters, the console
17317 interpreter (sometimes called the command-line interpreter or @sc{cli})
17318 and the machine interface interpreter (or @sc{gdb/mi}). This manual
17319 describes both of these interfaces in great detail.
17321 By default, @value{GDBN} will start with the console interpreter.
17322 However, the user may choose to start @value{GDBN} with another
17323 interpreter by specifying the @option{-i} or @option{--interpreter}
17324 startup options. Defined interpreters include:
17328 @cindex console interpreter
17329 The traditional console or command-line interpreter. This is the most often
17330 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
17331 @value{GDBN} will use this interpreter.
17334 @cindex mi interpreter
17335 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
17336 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
17337 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
17341 @cindex mi2 interpreter
17342 The current @sc{gdb/mi} interface.
17345 @cindex mi1 interpreter
17346 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
17350 @cindex invoke another interpreter
17351 The interpreter being used by @value{GDBN} may not be dynamically
17352 switched at runtime. Although possible, this could lead to a very
17353 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
17354 enters the command "interpreter-set console" in a console view,
17355 @value{GDBN} would switch to using the console interpreter, rendering
17356 the IDE inoperable!
17358 @kindex interpreter-exec
17359 Although you may only choose a single interpreter at startup, you may execute
17360 commands in any interpreter from the current interpreter using the appropriate
17361 command. If you are running the console interpreter, simply use the
17362 @code{interpreter-exec} command:
17365 interpreter-exec mi "-data-list-register-names"
17368 @sc{gdb/mi} has a similar command, although it is only available in versions of
17369 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
17372 @chapter @value{GDBN} Text User Interface
17374 @cindex Text User Interface
17377 * TUI Overview:: TUI overview
17378 * TUI Keys:: TUI key bindings
17379 * TUI Single Key Mode:: TUI single key mode
17380 * TUI Commands:: TUI-specific commands
17381 * TUI Configuration:: TUI configuration variables
17384 The @value{GDBN} Text User Interface (TUI) is a terminal
17385 interface which uses the @code{curses} library to show the source
17386 file, the assembly output, the program registers and @value{GDBN}
17387 commands in separate text windows. The TUI mode is supported only
17388 on platforms where a suitable version of the @code{curses} library
17391 @pindex @value{GDBTUI}
17392 The TUI mode is enabled by default when you invoke @value{GDBN} as
17393 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
17394 You can also switch in and out of TUI mode while @value{GDBN} runs by
17395 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
17396 @xref{TUI Keys, ,TUI Key Bindings}.
17399 @section TUI Overview
17401 In TUI mode, @value{GDBN} can display several text windows:
17405 This window is the @value{GDBN} command window with the @value{GDBN}
17406 prompt and the @value{GDBN} output. The @value{GDBN} input is still
17407 managed using readline.
17410 The source window shows the source file of the program. The current
17411 line and active breakpoints are displayed in this window.
17414 The assembly window shows the disassembly output of the program.
17417 This window shows the processor registers. Registers are highlighted
17418 when their values change.
17421 The source and assembly windows show the current program position
17422 by highlighting the current line and marking it with a @samp{>} marker.
17423 Breakpoints are indicated with two markers. The first marker
17424 indicates the breakpoint type:
17428 Breakpoint which was hit at least once.
17431 Breakpoint which was never hit.
17434 Hardware breakpoint which was hit at least once.
17437 Hardware breakpoint which was never hit.
17440 The second marker indicates whether the breakpoint is enabled or not:
17444 Breakpoint is enabled.
17447 Breakpoint is disabled.
17450 The source, assembly and register windows are updated when the current
17451 thread changes, when the frame changes, or when the program counter
17454 These windows are not all visible at the same time. The command
17455 window is always visible. The others can be arranged in several
17466 source and assembly,
17469 source and registers, or
17472 assembly and registers.
17475 A status line above the command window shows the following information:
17479 Indicates the current @value{GDBN} target.
17480 (@pxref{Targets, ,Specifying a Debugging Target}).
17483 Gives the current process or thread number.
17484 When no process is being debugged, this field is set to @code{No process}.
17487 Gives the current function name for the selected frame.
17488 The name is demangled if demangling is turned on (@pxref{Print Settings}).
17489 When there is no symbol corresponding to the current program counter,
17490 the string @code{??} is displayed.
17493 Indicates the current line number for the selected frame.
17494 When the current line number is not known, the string @code{??} is displayed.
17497 Indicates the current program counter address.
17501 @section TUI Key Bindings
17502 @cindex TUI key bindings
17504 The TUI installs several key bindings in the readline keymaps
17505 (@pxref{Command Line Editing}). The following key bindings
17506 are installed for both TUI mode and the @value{GDBN} standard mode.
17515 Enter or leave the TUI mode. When leaving the TUI mode,
17516 the curses window management stops and @value{GDBN} operates using
17517 its standard mode, writing on the terminal directly. When reentering
17518 the TUI mode, control is given back to the curses windows.
17519 The screen is then refreshed.
17523 Use a TUI layout with only one window. The layout will
17524 either be @samp{source} or @samp{assembly}. When the TUI mode
17525 is not active, it will switch to the TUI mode.
17527 Think of this key binding as the Emacs @kbd{C-x 1} binding.
17531 Use a TUI layout with at least two windows. When the current
17532 layout already has two windows, the next layout with two windows is used.
17533 When a new layout is chosen, one window will always be common to the
17534 previous layout and the new one.
17536 Think of it as the Emacs @kbd{C-x 2} binding.
17540 Change the active window. The TUI associates several key bindings
17541 (like scrolling and arrow keys) with the active window. This command
17542 gives the focus to the next TUI window.
17544 Think of it as the Emacs @kbd{C-x o} binding.
17548 Switch in and out of the TUI SingleKey mode that binds single
17549 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
17552 The following key bindings only work in the TUI mode:
17557 Scroll the active window one page up.
17561 Scroll the active window one page down.
17565 Scroll the active window one line up.
17569 Scroll the active window one line down.
17573 Scroll the active window one column left.
17577 Scroll the active window one column right.
17581 Refresh the screen.
17584 Because the arrow keys scroll the active window in the TUI mode, they
17585 are not available for their normal use by readline unless the command
17586 window has the focus. When another window is active, you must use
17587 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
17588 and @kbd{C-f} to control the command window.
17590 @node TUI Single Key Mode
17591 @section TUI Single Key Mode
17592 @cindex TUI single key mode
17594 The TUI also provides a @dfn{SingleKey} mode, which binds several
17595 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
17596 switch into this mode, where the following key bindings are used:
17599 @kindex c @r{(SingleKey TUI key)}
17603 @kindex d @r{(SingleKey TUI key)}
17607 @kindex f @r{(SingleKey TUI key)}
17611 @kindex n @r{(SingleKey TUI key)}
17615 @kindex q @r{(SingleKey TUI key)}
17617 exit the SingleKey mode.
17619 @kindex r @r{(SingleKey TUI key)}
17623 @kindex s @r{(SingleKey TUI key)}
17627 @kindex u @r{(SingleKey TUI key)}
17631 @kindex v @r{(SingleKey TUI key)}
17635 @kindex w @r{(SingleKey TUI key)}
17640 Other keys temporarily switch to the @value{GDBN} command prompt.
17641 The key that was pressed is inserted in the editing buffer so that
17642 it is possible to type most @value{GDBN} commands without interaction
17643 with the TUI SingleKey mode. Once the command is entered the TUI
17644 SingleKey mode is restored. The only way to permanently leave
17645 this mode is by typing @kbd{q} or @kbd{C-x s}.
17649 @section TUI-specific Commands
17650 @cindex TUI commands
17652 The TUI has specific commands to control the text windows.
17653 These commands are always available, even when @value{GDBN} is not in
17654 the TUI mode. When @value{GDBN} is in the standard mode, most
17655 of these commands will automatically switch to the TUI mode.
17660 List and give the size of all displayed windows.
17664 Display the next layout.
17667 Display the previous layout.
17670 Display the source window only.
17673 Display the assembly window only.
17676 Display the source and assembly window.
17679 Display the register window together with the source or assembly window.
17683 Make the next window active for scrolling.
17686 Make the previous window active for scrolling.
17689 Make the source window active for scrolling.
17692 Make the assembly window active for scrolling.
17695 Make the register window active for scrolling.
17698 Make the command window active for scrolling.
17702 Refresh the screen. This is similar to typing @kbd{C-L}.
17704 @item tui reg float
17706 Show the floating point registers in the register window.
17708 @item tui reg general
17709 Show the general registers in the register window.
17712 Show the next register group. The list of register groups as well as
17713 their order is target specific. The predefined register groups are the
17714 following: @code{general}, @code{float}, @code{system}, @code{vector},
17715 @code{all}, @code{save}, @code{restore}.
17717 @item tui reg system
17718 Show the system registers in the register window.
17722 Update the source window and the current execution point.
17724 @item winheight @var{name} +@var{count}
17725 @itemx winheight @var{name} -@var{count}
17727 Change the height of the window @var{name} by @var{count}
17728 lines. Positive counts increase the height, while negative counts
17731 @item tabset @var{nchars}
17733 Set the width of tab stops to be @var{nchars} characters.
17736 @node TUI Configuration
17737 @section TUI Configuration Variables
17738 @cindex TUI configuration variables
17740 Several configuration variables control the appearance of TUI windows.
17743 @item set tui border-kind @var{kind}
17744 @kindex set tui border-kind
17745 Select the border appearance for the source, assembly and register windows.
17746 The possible values are the following:
17749 Use a space character to draw the border.
17752 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
17755 Use the Alternate Character Set to draw the border. The border is
17756 drawn using character line graphics if the terminal supports them.
17759 @item set tui border-mode @var{mode}
17760 @kindex set tui border-mode
17761 @itemx set tui active-border-mode @var{mode}
17762 @kindex set tui active-border-mode
17763 Select the display attributes for the borders of the inactive windows
17764 or the active window. The @var{mode} can be one of the following:
17767 Use normal attributes to display the border.
17773 Use reverse video mode.
17776 Use half bright mode.
17778 @item half-standout
17779 Use half bright and standout mode.
17782 Use extra bright or bold mode.
17784 @item bold-standout
17785 Use extra bright or bold and standout mode.
17790 @chapter Using @value{GDBN} under @sc{gnu} Emacs
17793 @cindex @sc{gnu} Emacs
17794 A special interface allows you to use @sc{gnu} Emacs to view (and
17795 edit) the source files for the program you are debugging with
17798 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
17799 executable file you want to debug as an argument. This command starts
17800 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
17801 created Emacs buffer.
17802 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
17804 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
17809 All ``terminal'' input and output goes through an Emacs buffer, called
17812 This applies both to @value{GDBN} commands and their output, and to the input
17813 and output done by the program you are debugging.
17815 This is useful because it means that you can copy the text of previous
17816 commands and input them again; you can even use parts of the output
17819 All the facilities of Emacs' Shell mode are available for interacting
17820 with your program. In particular, you can send signals the usual
17821 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
17825 @value{GDBN} displays source code through Emacs.
17827 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
17828 source file for that frame and puts an arrow (@samp{=>}) at the
17829 left margin of the current line. Emacs uses a separate buffer for
17830 source display, and splits the screen to show both your @value{GDBN} session
17833 Explicit @value{GDBN} @code{list} or search commands still produce output as
17834 usual, but you probably have no reason to use them from Emacs.
17837 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
17838 a graphical mode, enabled by default, which provides further buffers
17839 that can control the execution and describe the state of your program.
17840 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
17842 If you specify an absolute file name when prompted for the @kbd{M-x
17843 gdb} argument, then Emacs sets your current working directory to where
17844 your program resides. If you only specify the file name, then Emacs
17845 sets your current working directory to to the directory associated
17846 with the previous buffer. In this case, @value{GDBN} may find your
17847 program by searching your environment's @code{PATH} variable, but on
17848 some operating systems it might not find the source. So, although the
17849 @value{GDBN} input and output session proceeds normally, the auxiliary
17850 buffer does not display the current source and line of execution.
17852 The initial working directory of @value{GDBN} is printed on the top
17853 line of the GUD buffer and this serves as a default for the commands
17854 that specify files for @value{GDBN} to operate on. @xref{Files,
17855 ,Commands to Specify Files}.
17857 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
17858 need to call @value{GDBN} by a different name (for example, if you
17859 keep several configurations around, with different names) you can
17860 customize the Emacs variable @code{gud-gdb-command-name} to run the
17863 In the GUD buffer, you can use these special Emacs commands in
17864 addition to the standard Shell mode commands:
17868 Describe the features of Emacs' GUD Mode.
17871 Execute to another source line, like the @value{GDBN} @code{step} command; also
17872 update the display window to show the current file and location.
17875 Execute to next source line in this function, skipping all function
17876 calls, like the @value{GDBN} @code{next} command. Then update the display window
17877 to show the current file and location.
17880 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
17881 display window accordingly.
17884 Execute until exit from the selected stack frame, like the @value{GDBN}
17885 @code{finish} command.
17888 Continue execution of your program, like the @value{GDBN} @code{continue}
17892 Go up the number of frames indicated by the numeric argument
17893 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
17894 like the @value{GDBN} @code{up} command.
17897 Go down the number of frames indicated by the numeric argument, like the
17898 @value{GDBN} @code{down} command.
17901 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
17902 tells @value{GDBN} to set a breakpoint on the source line point is on.
17904 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
17905 separate frame which shows a backtrace when the GUD buffer is current.
17906 Move point to any frame in the stack and type @key{RET} to make it
17907 become the current frame and display the associated source in the
17908 source buffer. Alternatively, click @kbd{Mouse-2} to make the
17909 selected frame become the current one. In graphical mode, the
17910 speedbar displays watch expressions.
17912 If you accidentally delete the source-display buffer, an easy way to get
17913 it back is to type the command @code{f} in the @value{GDBN} buffer, to
17914 request a frame display; when you run under Emacs, this recreates
17915 the source buffer if necessary to show you the context of the current
17918 The source files displayed in Emacs are in ordinary Emacs buffers
17919 which are visiting the source files in the usual way. You can edit
17920 the files with these buffers if you wish; but keep in mind that @value{GDBN}
17921 communicates with Emacs in terms of line numbers. If you add or
17922 delete lines from the text, the line numbers that @value{GDBN} knows cease
17923 to correspond properly with the code.
17925 A more detailed description of Emacs' interaction with @value{GDBN} is
17926 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
17929 @c The following dropped because Epoch is nonstandard. Reactivate
17930 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
17932 @kindex Emacs Epoch environment
17936 Version 18 of @sc{gnu} Emacs has a built-in window system
17937 called the @code{epoch}
17938 environment. Users of this environment can use a new command,
17939 @code{inspect} which performs identically to @code{print} except that
17940 each value is printed in its own window.
17945 @chapter The @sc{gdb/mi} Interface
17947 @unnumberedsec Function and Purpose
17949 @cindex @sc{gdb/mi}, its purpose
17950 @sc{gdb/mi} is a line based machine oriented text interface to
17951 @value{GDBN} and is activated by specifying using the
17952 @option{--interpreter} command line option (@pxref{Mode Options}). It
17953 is specifically intended to support the development of systems which
17954 use the debugger as just one small component of a larger system.
17956 This chapter is a specification of the @sc{gdb/mi} interface. It is written
17957 in the form of a reference manual.
17959 Note that @sc{gdb/mi} is still under construction, so some of the
17960 features described below are incomplete and subject to change
17961 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
17963 @unnumberedsec Notation and Terminology
17965 @cindex notational conventions, for @sc{gdb/mi}
17966 This chapter uses the following notation:
17970 @code{|} separates two alternatives.
17973 @code{[ @var{something} ]} indicates that @var{something} is optional:
17974 it may or may not be given.
17977 @code{( @var{group} )*} means that @var{group} inside the parentheses
17978 may repeat zero or more times.
17981 @code{( @var{group} )+} means that @var{group} inside the parentheses
17982 may repeat one or more times.
17985 @code{"@var{string}"} means a literal @var{string}.
17989 @heading Dependencies
17993 * GDB/MI Command Syntax::
17994 * GDB/MI Compatibility with CLI::
17995 * GDB/MI Development and Front Ends::
17996 * GDB/MI Output Records::
17997 * GDB/MI Simple Examples::
17998 * GDB/MI Command Description Format::
17999 * GDB/MI Breakpoint Commands::
18000 * GDB/MI Program Context::
18001 * GDB/MI Thread Commands::
18002 * GDB/MI Program Execution::
18003 * GDB/MI Stack Manipulation::
18004 * GDB/MI Variable Objects::
18005 * GDB/MI Data Manipulation::
18006 * GDB/MI Tracepoint Commands::
18007 * GDB/MI Symbol Query::
18008 * GDB/MI File Commands::
18010 * GDB/MI Kod Commands::
18011 * GDB/MI Memory Overlay Commands::
18012 * GDB/MI Signal Handling Commands::
18014 * GDB/MI Target Manipulation::
18015 * GDB/MI File Transfer Commands::
18016 * GDB/MI Miscellaneous Commands::
18019 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18020 @node GDB/MI Command Syntax
18021 @section @sc{gdb/mi} Command Syntax
18024 * GDB/MI Input Syntax::
18025 * GDB/MI Output Syntax::
18028 @node GDB/MI Input Syntax
18029 @subsection @sc{gdb/mi} Input Syntax
18031 @cindex input syntax for @sc{gdb/mi}
18032 @cindex @sc{gdb/mi}, input syntax
18034 @item @var{command} @expansion{}
18035 @code{@var{cli-command} | @var{mi-command}}
18037 @item @var{cli-command} @expansion{}
18038 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
18039 @var{cli-command} is any existing @value{GDBN} CLI command.
18041 @item @var{mi-command} @expansion{}
18042 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
18043 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
18045 @item @var{token} @expansion{}
18046 "any sequence of digits"
18048 @item @var{option} @expansion{}
18049 @code{"-" @var{parameter} [ " " @var{parameter} ]}
18051 @item @var{parameter} @expansion{}
18052 @code{@var{non-blank-sequence} | @var{c-string}}
18054 @item @var{operation} @expansion{}
18055 @emph{any of the operations described in this chapter}
18057 @item @var{non-blank-sequence} @expansion{}
18058 @emph{anything, provided it doesn't contain special characters such as
18059 "-", @var{nl}, """ and of course " "}
18061 @item @var{c-string} @expansion{}
18062 @code{""" @var{seven-bit-iso-c-string-content} """}
18064 @item @var{nl} @expansion{}
18073 The CLI commands are still handled by the @sc{mi} interpreter; their
18074 output is described below.
18077 The @code{@var{token}}, when present, is passed back when the command
18081 Some @sc{mi} commands accept optional arguments as part of the parameter
18082 list. Each option is identified by a leading @samp{-} (dash) and may be
18083 followed by an optional argument parameter. Options occur first in the
18084 parameter list and can be delimited from normal parameters using
18085 @samp{--} (this is useful when some parameters begin with a dash).
18092 We want easy access to the existing CLI syntax (for debugging).
18095 We want it to be easy to spot a @sc{mi} operation.
18098 @node GDB/MI Output Syntax
18099 @subsection @sc{gdb/mi} Output Syntax
18101 @cindex output syntax of @sc{gdb/mi}
18102 @cindex @sc{gdb/mi}, output syntax
18103 The output from @sc{gdb/mi} consists of zero or more out-of-band records
18104 followed, optionally, by a single result record. This result record
18105 is for the most recent command. The sequence of output records is
18106 terminated by @samp{(gdb)}.
18108 If an input command was prefixed with a @code{@var{token}} then the
18109 corresponding output for that command will also be prefixed by that same
18113 @item @var{output} @expansion{}
18114 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
18116 @item @var{result-record} @expansion{}
18117 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
18119 @item @var{out-of-band-record} @expansion{}
18120 @code{@var{async-record} | @var{stream-record}}
18122 @item @var{async-record} @expansion{}
18123 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
18125 @item @var{exec-async-output} @expansion{}
18126 @code{[ @var{token} ] "*" @var{async-output}}
18128 @item @var{status-async-output} @expansion{}
18129 @code{[ @var{token} ] "+" @var{async-output}}
18131 @item @var{notify-async-output} @expansion{}
18132 @code{[ @var{token} ] "=" @var{async-output}}
18134 @item @var{async-output} @expansion{}
18135 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
18137 @item @var{result-class} @expansion{}
18138 @code{"done" | "running" | "connected" | "error" | "exit"}
18140 @item @var{async-class} @expansion{}
18141 @code{"stopped" | @var{others}} (where @var{others} will be added
18142 depending on the needs---this is still in development).
18144 @item @var{result} @expansion{}
18145 @code{ @var{variable} "=" @var{value}}
18147 @item @var{variable} @expansion{}
18148 @code{ @var{string} }
18150 @item @var{value} @expansion{}
18151 @code{ @var{const} | @var{tuple} | @var{list} }
18153 @item @var{const} @expansion{}
18154 @code{@var{c-string}}
18156 @item @var{tuple} @expansion{}
18157 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
18159 @item @var{list} @expansion{}
18160 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
18161 @var{result} ( "," @var{result} )* "]" }
18163 @item @var{stream-record} @expansion{}
18164 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
18166 @item @var{console-stream-output} @expansion{}
18167 @code{"~" @var{c-string}}
18169 @item @var{target-stream-output} @expansion{}
18170 @code{"@@" @var{c-string}}
18172 @item @var{log-stream-output} @expansion{}
18173 @code{"&" @var{c-string}}
18175 @item @var{nl} @expansion{}
18178 @item @var{token} @expansion{}
18179 @emph{any sequence of digits}.
18187 All output sequences end in a single line containing a period.
18190 The @code{@var{token}} is from the corresponding request. Note that
18191 for all async output, while the token is allowed by the grammar and
18192 may be output by future versions of @value{GDBN} for select async
18193 output messages, it is generally omitted. Frontends should treat
18194 all async output as reporting general changes in the state of the
18195 target and there should be no need to associate async output to any
18199 @cindex status output in @sc{gdb/mi}
18200 @var{status-async-output} contains on-going status information about the
18201 progress of a slow operation. It can be discarded. All status output is
18202 prefixed by @samp{+}.
18205 @cindex async output in @sc{gdb/mi}
18206 @var{exec-async-output} contains asynchronous state change on the target
18207 (stopped, started, disappeared). All async output is prefixed by
18211 @cindex notify output in @sc{gdb/mi}
18212 @var{notify-async-output} contains supplementary information that the
18213 client should handle (e.g., a new breakpoint information). All notify
18214 output is prefixed by @samp{=}.
18217 @cindex console output in @sc{gdb/mi}
18218 @var{console-stream-output} is output that should be displayed as is in the
18219 console. It is the textual response to a CLI command. All the console
18220 output is prefixed by @samp{~}.
18223 @cindex target output in @sc{gdb/mi}
18224 @var{target-stream-output} is the output produced by the target program.
18225 All the target output is prefixed by @samp{@@}.
18228 @cindex log output in @sc{gdb/mi}
18229 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
18230 instance messages that should be displayed as part of an error log. All
18231 the log output is prefixed by @samp{&}.
18234 @cindex list output in @sc{gdb/mi}
18235 New @sc{gdb/mi} commands should only output @var{lists} containing
18241 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
18242 details about the various output records.
18244 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18245 @node GDB/MI Compatibility with CLI
18246 @section @sc{gdb/mi} Compatibility with CLI
18248 @cindex compatibility, @sc{gdb/mi} and CLI
18249 @cindex @sc{gdb/mi}, compatibility with CLI
18251 For the developers convenience CLI commands can be entered directly,
18252 but there may be some unexpected behaviour. For example, commands
18253 that query the user will behave as if the user replied yes, breakpoint
18254 command lists are not executed and some CLI commands, such as
18255 @code{if}, @code{when} and @code{define}, prompt for further input with
18256 @samp{>}, which is not valid MI output.
18258 This feature may be removed at some stage in the future and it is
18259 recommended that front ends use the @code{-interpreter-exec} command
18260 (@pxref{-interpreter-exec}).
18262 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18263 @node GDB/MI Development and Front Ends
18264 @section @sc{gdb/mi} Development and Front Ends
18265 @cindex @sc{gdb/mi} development
18267 The application which takes the MI output and presents the state of the
18268 program being debugged to the user is called a @dfn{front end}.
18270 Although @sc{gdb/mi} is still incomplete, it is currently being used
18271 by a variety of front ends to @value{GDBN}. This makes it difficult
18272 to introduce new functionality without breaking existing usage. This
18273 section tries to minimize the problems by describing how the protocol
18276 Some changes in MI need not break a carefully designed front end, and
18277 for these the MI version will remain unchanged. The following is a
18278 list of changes that may occur within one level, so front ends should
18279 parse MI output in a way that can handle them:
18283 New MI commands may be added.
18286 New fields may be added to the output of any MI command.
18289 The range of values for fields with specified values, e.g.,
18290 @code{in_scope} (@pxref{-var-update}) may be extended.
18292 @c The format of field's content e.g type prefix, may change so parse it
18293 @c at your own risk. Yes, in general?
18295 @c The order of fields may change? Shouldn't really matter but it might
18296 @c resolve inconsistencies.
18299 If the changes are likely to break front ends, the MI version level
18300 will be increased by one. This will allow the front end to parse the
18301 output according to the MI version. Apart from mi0, new versions of
18302 @value{GDBN} will not support old versions of MI and it will be the
18303 responsibility of the front end to work with the new one.
18305 @c Starting with mi3, add a new command -mi-version that prints the MI
18308 The best way to avoid unexpected changes in MI that might break your front
18309 end is to make your project known to @value{GDBN} developers and
18310 follow development on @email{gdb@@sourceware.org} and
18311 @email{gdb-patches@@sourceware.org}.
18312 @cindex mailing lists
18314 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18315 @node GDB/MI Output Records
18316 @section @sc{gdb/mi} Output Records
18319 * GDB/MI Result Records::
18320 * GDB/MI Stream Records::
18321 * GDB/MI Async Records::
18324 @node GDB/MI Result Records
18325 @subsection @sc{gdb/mi} Result Records
18327 @cindex result records in @sc{gdb/mi}
18328 @cindex @sc{gdb/mi}, result records
18329 In addition to a number of out-of-band notifications, the response to a
18330 @sc{gdb/mi} command includes one of the following result indications:
18334 @item "^done" [ "," @var{results} ]
18335 The synchronous operation was successful, @code{@var{results}} are the return
18340 @c Is this one correct? Should it be an out-of-band notification?
18341 The asynchronous operation was successfully started. The target is
18346 @value{GDBN} has connected to a remote target.
18348 @item "^error" "," @var{c-string}
18350 The operation failed. The @code{@var{c-string}} contains the corresponding
18355 @value{GDBN} has terminated.
18359 @node GDB/MI Stream Records
18360 @subsection @sc{gdb/mi} Stream Records
18362 @cindex @sc{gdb/mi}, stream records
18363 @cindex stream records in @sc{gdb/mi}
18364 @value{GDBN} internally maintains a number of output streams: the console, the
18365 target, and the log. The output intended for each of these streams is
18366 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
18368 Each stream record begins with a unique @dfn{prefix character} which
18369 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
18370 Syntax}). In addition to the prefix, each stream record contains a
18371 @code{@var{string-output}}. This is either raw text (with an implicit new
18372 line) or a quoted C string (which does not contain an implicit newline).
18375 @item "~" @var{string-output}
18376 The console output stream contains text that should be displayed in the
18377 CLI console window. It contains the textual responses to CLI commands.
18379 @item "@@" @var{string-output}
18380 The target output stream contains any textual output from the running
18381 target. This is only present when GDB's event loop is truly
18382 asynchronous, which is currently only the case for remote targets.
18384 @item "&" @var{string-output}
18385 The log stream contains debugging messages being produced by @value{GDBN}'s
18389 @node GDB/MI Async Records
18390 @subsection @sc{gdb/mi} Async Records
18392 @cindex async records in @sc{gdb/mi}
18393 @cindex @sc{gdb/mi}, async records
18394 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
18395 additional changes that have occurred. Those changes can either be a
18396 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
18397 target activity (e.g., target stopped).
18399 The following is the list of possible async records:
18403 @item *running,thread-id="@var{thread}"
18404 The target is now running. The @var{thread} field tells which
18405 specific thread is now running, and can be @samp{all} if all threads
18406 are running. The frontend should assume that no interaction with a
18407 running thread is possible after this notification is produced.
18408 The frontend should not assume that this notification is output
18409 only once for any command. @value{GDBN} may emit this notification
18410 several times, either for different threads, because it cannot resume
18411 all threads together, or even for a single thread, if the thread must
18412 be stepped though some code before letting it run freely.
18414 @item *stopped,reason="@var{reason}"
18415 The target has stopped. The @var{reason} field can have one of the
18419 @item breakpoint-hit
18420 A breakpoint was reached.
18421 @item watchpoint-trigger
18422 A watchpoint was triggered.
18423 @item read-watchpoint-trigger
18424 A read watchpoint was triggered.
18425 @item access-watchpoint-trigger
18426 An access watchpoint was triggered.
18427 @item function-finished
18428 An -exec-finish or similar CLI command was accomplished.
18429 @item location-reached
18430 An -exec-until or similar CLI command was accomplished.
18431 @item watchpoint-scope
18432 A watchpoint has gone out of scope.
18433 @item end-stepping-range
18434 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
18435 similar CLI command was accomplished.
18436 @item exited-signalled
18437 The inferior exited because of a signal.
18439 The inferior exited.
18440 @item exited-normally
18441 The inferior exited normally.
18442 @item signal-received
18443 A signal was received by the inferior.
18446 @item =thread-created,id="@var{id}"
18447 @itemx =thread-exited,id="@var{id}"
18448 A thread either was created, or has exited. The @var{id} field
18449 contains the @value{GDBN} identifier of the thread.
18454 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18455 @node GDB/MI Simple Examples
18456 @section Simple Examples of @sc{gdb/mi} Interaction
18457 @cindex @sc{gdb/mi}, simple examples
18459 This subsection presents several simple examples of interaction using
18460 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
18461 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
18462 the output received from @sc{gdb/mi}.
18464 Note the line breaks shown in the examples are here only for
18465 readability, they don't appear in the real output.
18467 @subheading Setting a Breakpoint
18469 Setting a breakpoint generates synchronous output which contains detailed
18470 information of the breakpoint.
18473 -> -break-insert main
18474 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
18475 enabled="y",addr="0x08048564",func="main",file="myprog.c",
18476 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
18480 @subheading Program Execution
18482 Program execution generates asynchronous records and MI gives the
18483 reason that execution stopped.
18489 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
18490 frame=@{addr="0x08048564",func="main",
18491 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
18492 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
18497 <- *stopped,reason="exited-normally"
18501 @subheading Quitting @value{GDBN}
18503 Quitting @value{GDBN} just prints the result class @samp{^exit}.
18511 @subheading A Bad Command
18513 Here's what happens if you pass a non-existent command:
18517 <- ^error,msg="Undefined MI command: rubbish"
18522 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18523 @node GDB/MI Command Description Format
18524 @section @sc{gdb/mi} Command Description Format
18526 The remaining sections describe blocks of commands. Each block of
18527 commands is laid out in a fashion similar to this section.
18529 @subheading Motivation
18531 The motivation for this collection of commands.
18533 @subheading Introduction
18535 A brief introduction to this collection of commands as a whole.
18537 @subheading Commands
18539 For each command in the block, the following is described:
18541 @subsubheading Synopsis
18544 -command @var{args}@dots{}
18547 @subsubheading Result
18549 @subsubheading @value{GDBN} Command
18551 The corresponding @value{GDBN} CLI command(s), if any.
18553 @subsubheading Example
18555 Example(s) formatted for readability. Some of the described commands have
18556 not been implemented yet and these are labeled N.A.@: (not available).
18559 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18560 @node GDB/MI Breakpoint Commands
18561 @section @sc{gdb/mi} Breakpoint Commands
18563 @cindex breakpoint commands for @sc{gdb/mi}
18564 @cindex @sc{gdb/mi}, breakpoint commands
18565 This section documents @sc{gdb/mi} commands for manipulating
18568 @subheading The @code{-break-after} Command
18569 @findex -break-after
18571 @subsubheading Synopsis
18574 -break-after @var{number} @var{count}
18577 The breakpoint number @var{number} is not in effect until it has been
18578 hit @var{count} times. To see how this is reflected in the output of
18579 the @samp{-break-list} command, see the description of the
18580 @samp{-break-list} command below.
18582 @subsubheading @value{GDBN} Command
18584 The corresponding @value{GDBN} command is @samp{ignore}.
18586 @subsubheading Example
18591 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
18592 enabled="y",addr="0x000100d0",func="main",file="hello.c",
18593 fullname="/home/foo/hello.c",line="5",times="0"@}
18600 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18601 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18602 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18603 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18604 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18605 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18606 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18607 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18608 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18609 line="5",times="0",ignore="3"@}]@}
18614 @subheading The @code{-break-catch} Command
18615 @findex -break-catch
18617 @subheading The @code{-break-commands} Command
18618 @findex -break-commands
18622 @subheading The @code{-break-condition} Command
18623 @findex -break-condition
18625 @subsubheading Synopsis
18628 -break-condition @var{number} @var{expr}
18631 Breakpoint @var{number} will stop the program only if the condition in
18632 @var{expr} is true. The condition becomes part of the
18633 @samp{-break-list} output (see the description of the @samp{-break-list}
18636 @subsubheading @value{GDBN} Command
18638 The corresponding @value{GDBN} command is @samp{condition}.
18640 @subsubheading Example
18644 -break-condition 1 1
18648 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18649 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18650 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18651 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18652 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18653 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18654 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18655 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18656 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18657 line="5",cond="1",times="0",ignore="3"@}]@}
18661 @subheading The @code{-break-delete} Command
18662 @findex -break-delete
18664 @subsubheading Synopsis
18667 -break-delete ( @var{breakpoint} )+
18670 Delete the breakpoint(s) whose number(s) are specified in the argument
18671 list. This is obviously reflected in the breakpoint list.
18673 @subsubheading @value{GDBN} Command
18675 The corresponding @value{GDBN} command is @samp{delete}.
18677 @subsubheading Example
18685 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
18686 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18687 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18688 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18689 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18690 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18691 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18696 @subheading The @code{-break-disable} Command
18697 @findex -break-disable
18699 @subsubheading Synopsis
18702 -break-disable ( @var{breakpoint} )+
18705 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
18706 break list is now set to @samp{n} for the named @var{breakpoint}(s).
18708 @subsubheading @value{GDBN} Command
18710 The corresponding @value{GDBN} command is @samp{disable}.
18712 @subsubheading Example
18720 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18721 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18722 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18723 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18724 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18725 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18726 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18727 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
18728 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18729 line="5",times="0"@}]@}
18733 @subheading The @code{-break-enable} Command
18734 @findex -break-enable
18736 @subsubheading Synopsis
18739 -break-enable ( @var{breakpoint} )+
18742 Enable (previously disabled) @var{breakpoint}(s).
18744 @subsubheading @value{GDBN} Command
18746 The corresponding @value{GDBN} command is @samp{enable}.
18748 @subsubheading Example
18756 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18757 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18758 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18759 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18760 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18761 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18762 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18763 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
18764 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18765 line="5",times="0"@}]@}
18769 @subheading The @code{-break-info} Command
18770 @findex -break-info
18772 @subsubheading Synopsis
18775 -break-info @var{breakpoint}
18779 Get information about a single breakpoint.
18781 @subsubheading @value{GDBN} Command
18783 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
18785 @subsubheading Example
18788 @subheading The @code{-break-insert} Command
18789 @findex -break-insert
18791 @subsubheading Synopsis
18794 -break-insert [ -t ] [ -h ] [ -f ]
18795 [ -c @var{condition} ] [ -i @var{ignore-count} ]
18796 [ -p @var{thread} ] [ @var{location} ]
18800 If specified, @var{location}, can be one of:
18807 @item filename:linenum
18808 @item filename:function
18812 The possible optional parameters of this command are:
18816 Insert a temporary breakpoint.
18818 Insert a hardware breakpoint.
18819 @item -c @var{condition}
18820 Make the breakpoint conditional on @var{condition}.
18821 @item -i @var{ignore-count}
18822 Initialize the @var{ignore-count}.
18824 If @var{location} cannot be parsed (for example if it
18825 refers to unknown files or functions), create a pending
18826 breakpoint. Without this flag, @value{GDBN} will report
18827 an error, and won't create a breakpoint, if @var{location}
18831 @subsubheading Result
18833 The result is in the form:
18836 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
18837 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
18838 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
18839 times="@var{times}"@}
18843 where @var{number} is the @value{GDBN} number for this breakpoint,
18844 @var{funcname} is the name of the function where the breakpoint was
18845 inserted, @var{filename} is the name of the source file which contains
18846 this function, @var{lineno} is the source line number within that file
18847 and @var{times} the number of times that the breakpoint has been hit
18848 (always 0 for -break-insert but may be greater for -break-info or -break-list
18849 which use the same output).
18851 Note: this format is open to change.
18852 @c An out-of-band breakpoint instead of part of the result?
18854 @subsubheading @value{GDBN} Command
18856 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
18857 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
18859 @subsubheading Example
18864 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
18865 fullname="/home/foo/recursive2.c,line="4",times="0"@}
18867 -break-insert -t foo
18868 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
18869 fullname="/home/foo/recursive2.c,line="11",times="0"@}
18872 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18873 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18874 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18875 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18876 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18877 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18878 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18879 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18880 addr="0x0001072c", func="main",file="recursive2.c",
18881 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
18882 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
18883 addr="0x00010774",func="foo",file="recursive2.c",
18884 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
18886 -break-insert -r foo.*
18887 ~int foo(int, int);
18888 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
18889 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
18893 @subheading The @code{-break-list} Command
18894 @findex -break-list
18896 @subsubheading Synopsis
18902 Displays the list of inserted breakpoints, showing the following fields:
18906 number of the breakpoint
18908 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
18910 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
18913 is the breakpoint enabled or no: @samp{y} or @samp{n}
18915 memory location at which the breakpoint is set
18917 logical location of the breakpoint, expressed by function name, file
18920 number of times the breakpoint has been hit
18923 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
18924 @code{body} field is an empty list.
18926 @subsubheading @value{GDBN} Command
18928 The corresponding @value{GDBN} command is @samp{info break}.
18930 @subsubheading Example
18935 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18936 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18937 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18938 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18939 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18940 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18941 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18942 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18943 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
18944 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
18945 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
18946 line="13",times="0"@}]@}
18950 Here's an example of the result when there are no breakpoints:
18955 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
18956 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18957 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18958 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18959 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18960 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18961 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18966 @subheading The @code{-break-watch} Command
18967 @findex -break-watch
18969 @subsubheading Synopsis
18972 -break-watch [ -a | -r ]
18975 Create a watchpoint. With the @samp{-a} option it will create an
18976 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
18977 read from or on a write to the memory location. With the @samp{-r}
18978 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
18979 trigger only when the memory location is accessed for reading. Without
18980 either of the options, the watchpoint created is a regular watchpoint,
18981 i.e., it will trigger when the memory location is accessed for writing.
18982 @xref{Set Watchpoints, , Setting Watchpoints}.
18984 Note that @samp{-break-list} will report a single list of watchpoints and
18985 breakpoints inserted.
18987 @subsubheading @value{GDBN} Command
18989 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
18992 @subsubheading Example
18994 Setting a watchpoint on a variable in the @code{main} function:
18999 ^done,wpt=@{number="2",exp="x"@}
19004 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
19005 value=@{old="-268439212",new="55"@},
19006 frame=@{func="main",args=[],file="recursive2.c",
19007 fullname="/home/foo/bar/recursive2.c",line="5"@}
19011 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
19012 the program execution twice: first for the variable changing value, then
19013 for the watchpoint going out of scope.
19018 ^done,wpt=@{number="5",exp="C"@}
19023 *stopped,reason="watchpoint-trigger",
19024 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
19025 frame=@{func="callee4",args=[],
19026 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19027 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
19032 *stopped,reason="watchpoint-scope",wpnum="5",
19033 frame=@{func="callee3",args=[@{name="strarg",
19034 value="0x11940 \"A string argument.\""@}],
19035 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19036 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
19040 Listing breakpoints and watchpoints, at different points in the program
19041 execution. Note that once the watchpoint goes out of scope, it is
19047 ^done,wpt=@{number="2",exp="C"@}
19050 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
19051 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19052 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19053 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19054 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19055 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19056 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19057 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
19058 addr="0x00010734",func="callee4",
19059 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19060 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
19061 bkpt=@{number="2",type="watchpoint",disp="keep",
19062 enabled="y",addr="",what="C",times="0"@}]@}
19067 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
19068 value=@{old="-276895068",new="3"@},
19069 frame=@{func="callee4",args=[],
19070 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19071 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
19074 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
19075 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19076 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19077 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19078 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19079 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19080 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19081 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
19082 addr="0x00010734",func="callee4",
19083 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19084 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
19085 bkpt=@{number="2",type="watchpoint",disp="keep",
19086 enabled="y",addr="",what="C",times="-5"@}]@}
19090 ^done,reason="watchpoint-scope",wpnum="2",
19091 frame=@{func="callee3",args=[@{name="strarg",
19092 value="0x11940 \"A string argument.\""@}],
19093 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19094 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
19097 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
19098 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19099 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19100 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19101 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19102 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19103 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19104 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
19105 addr="0x00010734",func="callee4",
19106 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19107 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
19112 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19113 @node GDB/MI Program Context
19114 @section @sc{gdb/mi} Program Context
19116 @subheading The @code{-exec-arguments} Command
19117 @findex -exec-arguments
19120 @subsubheading Synopsis
19123 -exec-arguments @var{args}
19126 Set the inferior program arguments, to be used in the next
19129 @subsubheading @value{GDBN} Command
19131 The corresponding @value{GDBN} command is @samp{set args}.
19133 @subsubheading Example
19137 -exec-arguments -v word
19143 @subheading The @code{-exec-show-arguments} Command
19144 @findex -exec-show-arguments
19146 @subsubheading Synopsis
19149 -exec-show-arguments
19152 Print the arguments of the program.
19154 @subsubheading @value{GDBN} Command
19156 The corresponding @value{GDBN} command is @samp{show args}.
19158 @subsubheading Example
19162 @subheading The @code{-environment-cd} Command
19163 @findex -environment-cd
19165 @subsubheading Synopsis
19168 -environment-cd @var{pathdir}
19171 Set @value{GDBN}'s working directory.
19173 @subsubheading @value{GDBN} Command
19175 The corresponding @value{GDBN} command is @samp{cd}.
19177 @subsubheading Example
19181 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
19187 @subheading The @code{-environment-directory} Command
19188 @findex -environment-directory
19190 @subsubheading Synopsis
19193 -environment-directory [ -r ] [ @var{pathdir} ]+
19196 Add directories @var{pathdir} to beginning of search path for source files.
19197 If the @samp{-r} option is used, the search path is reset to the default
19198 search path. If directories @var{pathdir} are supplied in addition to the
19199 @samp{-r} option, the search path is first reset and then addition
19201 Multiple directories may be specified, separated by blanks. Specifying
19202 multiple directories in a single command
19203 results in the directories added to the beginning of the
19204 search path in the same order they were presented in the command.
19205 If blanks are needed as
19206 part of a directory name, double-quotes should be used around
19207 the name. In the command output, the path will show up separated
19208 by the system directory-separator character. The directory-separator
19209 character must not be used
19210 in any directory name.
19211 If no directories are specified, the current search path is displayed.
19213 @subsubheading @value{GDBN} Command
19215 The corresponding @value{GDBN} command is @samp{dir}.
19217 @subsubheading Example
19221 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
19222 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
19224 -environment-directory ""
19225 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
19227 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
19228 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
19230 -environment-directory -r
19231 ^done,source-path="$cdir:$cwd"
19236 @subheading The @code{-environment-path} Command
19237 @findex -environment-path
19239 @subsubheading Synopsis
19242 -environment-path [ -r ] [ @var{pathdir} ]+
19245 Add directories @var{pathdir} to beginning of search path for object files.
19246 If the @samp{-r} option is used, the search path is reset to the original
19247 search path that existed at gdb start-up. If directories @var{pathdir} are
19248 supplied in addition to the
19249 @samp{-r} option, the search path is first reset and then addition
19251 Multiple directories may be specified, separated by blanks. Specifying
19252 multiple directories in a single command
19253 results in the directories added to the beginning of the
19254 search path in the same order they were presented in the command.
19255 If blanks are needed as
19256 part of a directory name, double-quotes should be used around
19257 the name. In the command output, the path will show up separated
19258 by the system directory-separator character. The directory-separator
19259 character must not be used
19260 in any directory name.
19261 If no directories are specified, the current path is displayed.
19264 @subsubheading @value{GDBN} Command
19266 The corresponding @value{GDBN} command is @samp{path}.
19268 @subsubheading Example
19273 ^done,path="/usr/bin"
19275 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
19276 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
19278 -environment-path -r /usr/local/bin
19279 ^done,path="/usr/local/bin:/usr/bin"
19284 @subheading The @code{-environment-pwd} Command
19285 @findex -environment-pwd
19287 @subsubheading Synopsis
19293 Show the current working directory.
19295 @subsubheading @value{GDBN} Command
19297 The corresponding @value{GDBN} command is @samp{pwd}.
19299 @subsubheading Example
19304 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
19308 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19309 @node GDB/MI Thread Commands
19310 @section @sc{gdb/mi} Thread Commands
19313 @subheading The @code{-thread-info} Command
19314 @findex -thread-info
19316 @subsubheading Synopsis
19319 -thread-info [ @var{thread-id} ]
19322 Reports information about either a specific thread, if
19323 the @var{thread-id} parameter is present, or about all
19324 threads. When printing information about all threads,
19325 also reports the current thread.
19327 @subsubheading @value{GDBN} Command
19329 The @samp{info thread} command prints the same information
19332 @subsubheading Example
19337 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
19338 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},
19339 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
19340 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
19341 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@}@}],
19342 current-thread-id="1"
19346 @subheading The @code{-thread-list-ids} Command
19347 @findex -thread-list-ids
19349 @subsubheading Synopsis
19355 Produces a list of the currently known @value{GDBN} thread ids. At the
19356 end of the list it also prints the total number of such threads.
19358 @subsubheading @value{GDBN} Command
19360 Part of @samp{info threads} supplies the same information.
19362 @subsubheading Example
19364 No threads present, besides the main process:
19369 ^done,thread-ids=@{@},number-of-threads="0"
19379 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
19380 number-of-threads="3"
19385 @subheading The @code{-thread-select} Command
19386 @findex -thread-select
19388 @subsubheading Synopsis
19391 -thread-select @var{threadnum}
19394 Make @var{threadnum} the current thread. It prints the number of the new
19395 current thread, and the topmost frame for that thread.
19397 @subsubheading @value{GDBN} Command
19399 The corresponding @value{GDBN} command is @samp{thread}.
19401 @subsubheading Example
19408 *stopped,reason="end-stepping-range",thread-id="2",line="187",
19409 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
19413 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
19414 number-of-threads="3"
19417 ^done,new-thread-id="3",
19418 frame=@{level="0",func="vprintf",
19419 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
19420 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
19424 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19425 @node GDB/MI Program Execution
19426 @section @sc{gdb/mi} Program Execution
19428 These are the asynchronous commands which generate the out-of-band
19429 record @samp{*stopped}. Currently @value{GDBN} only really executes
19430 asynchronously with remote targets and this interaction is mimicked in
19433 @subheading The @code{-exec-continue} Command
19434 @findex -exec-continue
19436 @subsubheading Synopsis
19442 Resumes the execution of the inferior program until a breakpoint is
19443 encountered, or until the inferior exits.
19445 @subsubheading @value{GDBN} Command
19447 The corresponding @value{GDBN} corresponding is @samp{continue}.
19449 @subsubheading Example
19456 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
19457 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
19463 @subheading The @code{-exec-finish} Command
19464 @findex -exec-finish
19466 @subsubheading Synopsis
19472 Resumes the execution of the inferior program until the current
19473 function is exited. Displays the results returned by the function.
19475 @subsubheading @value{GDBN} Command
19477 The corresponding @value{GDBN} command is @samp{finish}.
19479 @subsubheading Example
19481 Function returning @code{void}.
19488 *stopped,reason="function-finished",frame=@{func="main",args=[],
19489 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
19493 Function returning other than @code{void}. The name of the internal
19494 @value{GDBN} variable storing the result is printed, together with the
19501 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
19502 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
19503 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19504 gdb-result-var="$1",return-value="0"
19509 @subheading The @code{-exec-interrupt} Command
19510 @findex -exec-interrupt
19512 @subsubheading Synopsis
19518 Interrupts the background execution of the target. Note how the token
19519 associated with the stop message is the one for the execution command
19520 that has been interrupted. The token for the interrupt itself only
19521 appears in the @samp{^done} output. If the user is trying to
19522 interrupt a non-running program, an error message will be printed.
19524 @subsubheading @value{GDBN} Command
19526 The corresponding @value{GDBN} command is @samp{interrupt}.
19528 @subsubheading Example
19539 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
19540 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
19541 fullname="/home/foo/bar/try.c",line="13"@}
19546 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
19551 @subheading The @code{-exec-next} Command
19554 @subsubheading Synopsis
19560 Resumes execution of the inferior program, stopping when the beginning
19561 of the next source line is reached.
19563 @subsubheading @value{GDBN} Command
19565 The corresponding @value{GDBN} command is @samp{next}.
19567 @subsubheading Example
19573 *stopped,reason="end-stepping-range",line="8",file="hello.c"
19578 @subheading The @code{-exec-next-instruction} Command
19579 @findex -exec-next-instruction
19581 @subsubheading Synopsis
19584 -exec-next-instruction
19587 Executes one machine instruction. If the instruction is a function
19588 call, continues until the function returns. If the program stops at an
19589 instruction in the middle of a source line, the address will be
19592 @subsubheading @value{GDBN} Command
19594 The corresponding @value{GDBN} command is @samp{nexti}.
19596 @subsubheading Example
19600 -exec-next-instruction
19604 *stopped,reason="end-stepping-range",
19605 addr="0x000100d4",line="5",file="hello.c"
19610 @subheading The @code{-exec-return} Command
19611 @findex -exec-return
19613 @subsubheading Synopsis
19619 Makes current function return immediately. Doesn't execute the inferior.
19620 Displays the new current frame.
19622 @subsubheading @value{GDBN} Command
19624 The corresponding @value{GDBN} command is @samp{return}.
19626 @subsubheading Example
19630 200-break-insert callee4
19631 200^done,bkpt=@{number="1",addr="0x00010734",
19632 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
19637 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
19638 frame=@{func="callee4",args=[],
19639 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19640 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
19646 111^done,frame=@{level="0",func="callee3",
19647 args=[@{name="strarg",
19648 value="0x11940 \"A string argument.\""@}],
19649 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19650 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
19655 @subheading The @code{-exec-run} Command
19658 @subsubheading Synopsis
19664 Starts execution of the inferior from the beginning. The inferior
19665 executes until either a breakpoint is encountered or the program
19666 exits. In the latter case the output will include an exit code, if
19667 the program has exited exceptionally.
19669 @subsubheading @value{GDBN} Command
19671 The corresponding @value{GDBN} command is @samp{run}.
19673 @subsubheading Examples
19678 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
19683 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
19684 frame=@{func="main",args=[],file="recursive2.c",
19685 fullname="/home/foo/bar/recursive2.c",line="4"@}
19690 Program exited normally:
19698 *stopped,reason="exited-normally"
19703 Program exited exceptionally:
19711 *stopped,reason="exited",exit-code="01"
19715 Another way the program can terminate is if it receives a signal such as
19716 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
19720 *stopped,reason="exited-signalled",signal-name="SIGINT",
19721 signal-meaning="Interrupt"
19725 @c @subheading -exec-signal
19728 @subheading The @code{-exec-step} Command
19731 @subsubheading Synopsis
19737 Resumes execution of the inferior program, stopping when the beginning
19738 of the next source line is reached, if the next source line is not a
19739 function call. If it is, stop at the first instruction of the called
19742 @subsubheading @value{GDBN} Command
19744 The corresponding @value{GDBN} command is @samp{step}.
19746 @subsubheading Example
19748 Stepping into a function:
19754 *stopped,reason="end-stepping-range",
19755 frame=@{func="foo",args=[@{name="a",value="10"@},
19756 @{name="b",value="0"@}],file="recursive2.c",
19757 fullname="/home/foo/bar/recursive2.c",line="11"@}
19767 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
19772 @subheading The @code{-exec-step-instruction} Command
19773 @findex -exec-step-instruction
19775 @subsubheading Synopsis
19778 -exec-step-instruction
19781 Resumes the inferior which executes one machine instruction. The
19782 output, once @value{GDBN} has stopped, will vary depending on whether
19783 we have stopped in the middle of a source line or not. In the former
19784 case, the address at which the program stopped will be printed as
19787 @subsubheading @value{GDBN} Command
19789 The corresponding @value{GDBN} command is @samp{stepi}.
19791 @subsubheading Example
19795 -exec-step-instruction
19799 *stopped,reason="end-stepping-range",
19800 frame=@{func="foo",args=[],file="try.c",
19801 fullname="/home/foo/bar/try.c",line="10"@}
19803 -exec-step-instruction
19807 *stopped,reason="end-stepping-range",
19808 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
19809 fullname="/home/foo/bar/try.c",line="10"@}
19814 @subheading The @code{-exec-until} Command
19815 @findex -exec-until
19817 @subsubheading Synopsis
19820 -exec-until [ @var{location} ]
19823 Executes the inferior until the @var{location} specified in the
19824 argument is reached. If there is no argument, the inferior executes
19825 until a source line greater than the current one is reached. The
19826 reason for stopping in this case will be @samp{location-reached}.
19828 @subsubheading @value{GDBN} Command
19830 The corresponding @value{GDBN} command is @samp{until}.
19832 @subsubheading Example
19836 -exec-until recursive2.c:6
19840 *stopped,reason="location-reached",frame=@{func="main",args=[],
19841 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
19846 @subheading -file-clear
19847 Is this going away????
19850 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19851 @node GDB/MI Stack Manipulation
19852 @section @sc{gdb/mi} Stack Manipulation Commands
19855 @subheading The @code{-stack-info-frame} Command
19856 @findex -stack-info-frame
19858 @subsubheading Synopsis
19864 Get info on the selected frame.
19866 @subsubheading @value{GDBN} Command
19868 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
19869 (without arguments).
19871 @subsubheading Example
19876 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
19877 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19878 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
19882 @subheading The @code{-stack-info-depth} Command
19883 @findex -stack-info-depth
19885 @subsubheading Synopsis
19888 -stack-info-depth [ @var{max-depth} ]
19891 Return the depth of the stack. If the integer argument @var{max-depth}
19892 is specified, do not count beyond @var{max-depth} frames.
19894 @subsubheading @value{GDBN} Command
19896 There's no equivalent @value{GDBN} command.
19898 @subsubheading Example
19900 For a stack with frame levels 0 through 11:
19907 -stack-info-depth 4
19910 -stack-info-depth 12
19913 -stack-info-depth 11
19916 -stack-info-depth 13
19921 @subheading The @code{-stack-list-arguments} Command
19922 @findex -stack-list-arguments
19924 @subsubheading Synopsis
19927 -stack-list-arguments @var{show-values}
19928 [ @var{low-frame} @var{high-frame} ]
19931 Display a list of the arguments for the frames between @var{low-frame}
19932 and @var{high-frame} (inclusive). If @var{low-frame} and
19933 @var{high-frame} are not provided, list the arguments for the whole
19934 call stack. If the two arguments are equal, show the single frame
19935 at the corresponding level. It is an error if @var{low-frame} is
19936 larger than the actual number of frames. On the other hand,
19937 @var{high-frame} may be larger than the actual number of frames, in
19938 which case only existing frames will be returned.
19940 The @var{show-values} argument must have a value of 0 or 1. A value of
19941 0 means that only the names of the arguments are listed, a value of 1
19942 means that both names and values of the arguments are printed.
19944 @subsubheading @value{GDBN} Command
19946 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
19947 @samp{gdb_get_args} command which partially overlaps with the
19948 functionality of @samp{-stack-list-arguments}.
19950 @subsubheading Example
19957 frame=@{level="0",addr="0x00010734",func="callee4",
19958 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19959 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
19960 frame=@{level="1",addr="0x0001076c",func="callee3",
19961 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19962 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
19963 frame=@{level="2",addr="0x0001078c",func="callee2",
19964 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19965 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
19966 frame=@{level="3",addr="0x000107b4",func="callee1",
19967 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19968 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
19969 frame=@{level="4",addr="0x000107e0",func="main",
19970 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19971 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
19973 -stack-list-arguments 0
19976 frame=@{level="0",args=[]@},
19977 frame=@{level="1",args=[name="strarg"]@},
19978 frame=@{level="2",args=[name="intarg",name="strarg"]@},
19979 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
19980 frame=@{level="4",args=[]@}]
19982 -stack-list-arguments 1
19985 frame=@{level="0",args=[]@},
19987 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19988 frame=@{level="2",args=[
19989 @{name="intarg",value="2"@},
19990 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19991 @{frame=@{level="3",args=[
19992 @{name="intarg",value="2"@},
19993 @{name="strarg",value="0x11940 \"A string argument.\""@},
19994 @{name="fltarg",value="3.5"@}]@},
19995 frame=@{level="4",args=[]@}]
19997 -stack-list-arguments 0 2 2
19998 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
20000 -stack-list-arguments 1 2 2
20001 ^done,stack-args=[frame=@{level="2",
20002 args=[@{name="intarg",value="2"@},
20003 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
20007 @c @subheading -stack-list-exception-handlers
20010 @subheading The @code{-stack-list-frames} Command
20011 @findex -stack-list-frames
20013 @subsubheading Synopsis
20016 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
20019 List the frames currently on the stack. For each frame it displays the
20024 The frame number, 0 being the topmost frame, i.e., the innermost function.
20026 The @code{$pc} value for that frame.
20030 File name of the source file where the function lives.
20032 Line number corresponding to the @code{$pc}.
20035 If invoked without arguments, this command prints a backtrace for the
20036 whole stack. If given two integer arguments, it shows the frames whose
20037 levels are between the two arguments (inclusive). If the two arguments
20038 are equal, it shows the single frame at the corresponding level. It is
20039 an error if @var{low-frame} is larger than the actual number of
20040 frames. On the other hand, @var{high-frame} may be larger than the
20041 actual number of frames, in which case only existing frames will be returned.
20043 @subsubheading @value{GDBN} Command
20045 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
20047 @subsubheading Example
20049 Full stack backtrace:
20055 [frame=@{level="0",addr="0x0001076c",func="foo",
20056 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
20057 frame=@{level="1",addr="0x000107a4",func="foo",
20058 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20059 frame=@{level="2",addr="0x000107a4",func="foo",
20060 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20061 frame=@{level="3",addr="0x000107a4",func="foo",
20062 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20063 frame=@{level="4",addr="0x000107a4",func="foo",
20064 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20065 frame=@{level="5",addr="0x000107a4",func="foo",
20066 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20067 frame=@{level="6",addr="0x000107a4",func="foo",
20068 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20069 frame=@{level="7",addr="0x000107a4",func="foo",
20070 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20071 frame=@{level="8",addr="0x000107a4",func="foo",
20072 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20073 frame=@{level="9",addr="0x000107a4",func="foo",
20074 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20075 frame=@{level="10",addr="0x000107a4",func="foo",
20076 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20077 frame=@{level="11",addr="0x00010738",func="main",
20078 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
20082 Show frames between @var{low_frame} and @var{high_frame}:
20086 -stack-list-frames 3 5
20088 [frame=@{level="3",addr="0x000107a4",func="foo",
20089 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20090 frame=@{level="4",addr="0x000107a4",func="foo",
20091 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20092 frame=@{level="5",addr="0x000107a4",func="foo",
20093 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
20097 Show a single frame:
20101 -stack-list-frames 3 3
20103 [frame=@{level="3",addr="0x000107a4",func="foo",
20104 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
20109 @subheading The @code{-stack-list-locals} Command
20110 @findex -stack-list-locals
20112 @subsubheading Synopsis
20115 -stack-list-locals @var{print-values}
20118 Display the local variable names for the selected frame. If
20119 @var{print-values} is 0 or @code{--no-values}, print only the names of
20120 the variables; if it is 1 or @code{--all-values}, print also their
20121 values; and if it is 2 or @code{--simple-values}, print the name,
20122 type and value for simple data types and the name and type for arrays,
20123 structures and unions. In this last case, a frontend can immediately
20124 display the value of simple data types and create variable objects for
20125 other data types when the user wishes to explore their values in
20128 @subsubheading @value{GDBN} Command
20130 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
20132 @subsubheading Example
20136 -stack-list-locals 0
20137 ^done,locals=[name="A",name="B",name="C"]
20139 -stack-list-locals --all-values
20140 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
20141 @{name="C",value="@{1, 2, 3@}"@}]
20142 -stack-list-locals --simple-values
20143 ^done,locals=[@{name="A",type="int",value="1"@},
20144 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
20149 @subheading The @code{-stack-select-frame} Command
20150 @findex -stack-select-frame
20152 @subsubheading Synopsis
20155 -stack-select-frame @var{framenum}
20158 Change the selected frame. Select a different frame @var{framenum} on
20161 @subsubheading @value{GDBN} Command
20163 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
20164 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
20166 @subsubheading Example
20170 -stack-select-frame 2
20175 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20176 @node GDB/MI Variable Objects
20177 @section @sc{gdb/mi} Variable Objects
20181 @subheading Motivation for Variable Objects in @sc{gdb/mi}
20183 For the implementation of a variable debugger window (locals, watched
20184 expressions, etc.), we are proposing the adaptation of the existing code
20185 used by @code{Insight}.
20187 The two main reasons for that are:
20191 It has been proven in practice (it is already on its second generation).
20194 It will shorten development time (needless to say how important it is
20198 The original interface was designed to be used by Tcl code, so it was
20199 slightly changed so it could be used through @sc{gdb/mi}. This section
20200 describes the @sc{gdb/mi} operations that will be available and gives some
20201 hints about their use.
20203 @emph{Note}: In addition to the set of operations described here, we
20204 expect the @sc{gui} implementation of a variable window to require, at
20205 least, the following operations:
20208 @item @code{-gdb-show} @code{output-radix}
20209 @item @code{-stack-list-arguments}
20210 @item @code{-stack-list-locals}
20211 @item @code{-stack-select-frame}
20216 @subheading Introduction to Variable Objects
20218 @cindex variable objects in @sc{gdb/mi}
20220 Variable objects are "object-oriented" MI interface for examining and
20221 changing values of expressions. Unlike some other MI interfaces that
20222 work with expressions, variable objects are specifically designed for
20223 simple and efficient presentation in the frontend. A variable object
20224 is identified by string name. When a variable object is created, the
20225 frontend specifies the expression for that variable object. The
20226 expression can be a simple variable, or it can be an arbitrary complex
20227 expression, and can even involve CPU registers. After creating a
20228 variable object, the frontend can invoke other variable object
20229 operations---for example to obtain or change the value of a variable
20230 object, or to change display format.
20232 Variable objects have hierarchical tree structure. Any variable object
20233 that corresponds to a composite type, such as structure in C, has
20234 a number of child variable objects, for example corresponding to each
20235 element of a structure. A child variable object can itself have
20236 children, recursively. Recursion ends when we reach
20237 leaf variable objects, which always have built-in types. Child variable
20238 objects are created only by explicit request, so if a frontend
20239 is not interested in the children of a particular variable object, no
20240 child will be created.
20242 For a leaf variable object it is possible to obtain its value as a
20243 string, or set the value from a string. String value can be also
20244 obtained for a non-leaf variable object, but it's generally a string
20245 that only indicates the type of the object, and does not list its
20246 contents. Assignment to a non-leaf variable object is not allowed.
20248 A frontend does not need to read the values of all variable objects each time
20249 the program stops. Instead, MI provides an update command that lists all
20250 variable objects whose values has changed since the last update
20251 operation. This considerably reduces the amount of data that must
20252 be transferred to the frontend. As noted above, children variable
20253 objects are created on demand, and only leaf variable objects have a
20254 real value. As result, gdb will read target memory only for leaf
20255 variables that frontend has created.
20257 The automatic update is not always desirable. For example, a frontend
20258 might want to keep a value of some expression for future reference,
20259 and never update it. For another example, fetching memory is
20260 relatively slow for embedded targets, so a frontend might want
20261 to disable automatic update for the variables that are either not
20262 visible on the screen, or ``closed''. This is possible using so
20263 called ``frozen variable objects''. Such variable objects are never
20264 implicitly updated.
20266 The following is the complete set of @sc{gdb/mi} operations defined to
20267 access this functionality:
20269 @multitable @columnfractions .4 .6
20270 @item @strong{Operation}
20271 @tab @strong{Description}
20273 @item @code{-var-create}
20274 @tab create a variable object
20275 @item @code{-var-delete}
20276 @tab delete the variable object and/or its children
20277 @item @code{-var-set-format}
20278 @tab set the display format of this variable
20279 @item @code{-var-show-format}
20280 @tab show the display format of this variable
20281 @item @code{-var-info-num-children}
20282 @tab tells how many children this object has
20283 @item @code{-var-list-children}
20284 @tab return a list of the object's children
20285 @item @code{-var-info-type}
20286 @tab show the type of this variable object
20287 @item @code{-var-info-expression}
20288 @tab print parent-relative expression that this variable object represents
20289 @item @code{-var-info-path-expression}
20290 @tab print full expression that this variable object represents
20291 @item @code{-var-show-attributes}
20292 @tab is this variable editable? does it exist here?
20293 @item @code{-var-evaluate-expression}
20294 @tab get the value of this variable
20295 @item @code{-var-assign}
20296 @tab set the value of this variable
20297 @item @code{-var-update}
20298 @tab update the variable and its children
20299 @item @code{-var-set-frozen}
20300 @tab set frozeness attribute
20303 In the next subsection we describe each operation in detail and suggest
20304 how it can be used.
20306 @subheading Description And Use of Operations on Variable Objects
20308 @subheading The @code{-var-create} Command
20309 @findex -var-create
20311 @subsubheading Synopsis
20314 -var-create @{@var{name} | "-"@}
20315 @{@var{frame-addr} | "*"@} @var{expression}
20318 This operation creates a variable object, which allows the monitoring of
20319 a variable, the result of an expression, a memory cell or a CPU
20322 The @var{name} parameter is the string by which the object can be
20323 referenced. It must be unique. If @samp{-} is specified, the varobj
20324 system will generate a string ``varNNNNNN'' automatically. It will be
20325 unique provided that one does not specify @var{name} on that format.
20326 The command fails if a duplicate name is found.
20328 The frame under which the expression should be evaluated can be
20329 specified by @var{frame-addr}. A @samp{*} indicates that the current
20330 frame should be used.
20332 @var{expression} is any expression valid on the current language set (must not
20333 begin with a @samp{*}), or one of the following:
20337 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
20340 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
20343 @samp{$@var{regname}} --- a CPU register name
20346 @subsubheading Result
20348 This operation returns the name, number of children and the type of the
20349 object created. Type is returned as a string as the ones generated by
20350 the @value{GDBN} CLI:
20353 name="@var{name}",numchild="N",type="@var{type}"
20357 @subheading The @code{-var-delete} Command
20358 @findex -var-delete
20360 @subsubheading Synopsis
20363 -var-delete [ -c ] @var{name}
20366 Deletes a previously created variable object and all of its children.
20367 With the @samp{-c} option, just deletes the children.
20369 Returns an error if the object @var{name} is not found.
20372 @subheading The @code{-var-set-format} Command
20373 @findex -var-set-format
20375 @subsubheading Synopsis
20378 -var-set-format @var{name} @var{format-spec}
20381 Sets the output format for the value of the object @var{name} to be
20384 @anchor{-var-set-format}
20385 The syntax for the @var{format-spec} is as follows:
20388 @var{format-spec} @expansion{}
20389 @{binary | decimal | hexadecimal | octal | natural@}
20392 The natural format is the default format choosen automatically
20393 based on the variable type (like decimal for an @code{int}, hex
20394 for pointers, etc.).
20396 For a variable with children, the format is set only on the
20397 variable itself, and the children are not affected.
20399 @subheading The @code{-var-show-format} Command
20400 @findex -var-show-format
20402 @subsubheading Synopsis
20405 -var-show-format @var{name}
20408 Returns the format used to display the value of the object @var{name}.
20411 @var{format} @expansion{}
20416 @subheading The @code{-var-info-num-children} Command
20417 @findex -var-info-num-children
20419 @subsubheading Synopsis
20422 -var-info-num-children @var{name}
20425 Returns the number of children of a variable object @var{name}:
20432 @subheading The @code{-var-list-children} Command
20433 @findex -var-list-children
20435 @subsubheading Synopsis
20438 -var-list-children [@var{print-values}] @var{name}
20440 @anchor{-var-list-children}
20442 Return a list of the children of the specified variable object and
20443 create variable objects for them, if they do not already exist. With
20444 a single argument or if @var{print-values} has a value for of 0 or
20445 @code{--no-values}, print only the names of the variables; if
20446 @var{print-values} is 1 or @code{--all-values}, also print their
20447 values; and if it is 2 or @code{--simple-values} print the name and
20448 value for simple data types and just the name for arrays, structures
20451 @subsubheading Example
20455 -var-list-children n
20456 ^done,numchild=@var{n},children=[@{name=@var{name},
20457 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
20459 -var-list-children --all-values n
20460 ^done,numchild=@var{n},children=[@{name=@var{name},
20461 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
20465 @subheading The @code{-var-info-type} Command
20466 @findex -var-info-type
20468 @subsubheading Synopsis
20471 -var-info-type @var{name}
20474 Returns the type of the specified variable @var{name}. The type is
20475 returned as a string in the same format as it is output by the
20479 type=@var{typename}
20483 @subheading The @code{-var-info-expression} Command
20484 @findex -var-info-expression
20486 @subsubheading Synopsis
20489 -var-info-expression @var{name}
20492 Returns a string that is suitable for presenting this
20493 variable object in user interface. The string is generally
20494 not valid expression in the current language, and cannot be evaluated.
20496 For example, if @code{a} is an array, and variable object
20497 @code{A} was created for @code{a}, then we'll get this output:
20500 (gdb) -var-info-expression A.1
20501 ^done,lang="C",exp="1"
20505 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
20507 Note that the output of the @code{-var-list-children} command also
20508 includes those expressions, so the @code{-var-info-expression} command
20511 @subheading The @code{-var-info-path-expression} Command
20512 @findex -var-info-path-expression
20514 @subsubheading Synopsis
20517 -var-info-path-expression @var{name}
20520 Returns an expression that can be evaluated in the current
20521 context and will yield the same value that a variable object has.
20522 Compare this with the @code{-var-info-expression} command, which
20523 result can be used only for UI presentation. Typical use of
20524 the @code{-var-info-path-expression} command is creating a
20525 watchpoint from a variable object.
20527 For example, suppose @code{C} is a C@t{++} class, derived from class
20528 @code{Base}, and that the @code{Base} class has a member called
20529 @code{m_size}. Assume a variable @code{c} is has the type of
20530 @code{C} and a variable object @code{C} was created for variable
20531 @code{c}. Then, we'll get this output:
20533 (gdb) -var-info-path-expression C.Base.public.m_size
20534 ^done,path_expr=((Base)c).m_size)
20537 @subheading The @code{-var-show-attributes} Command
20538 @findex -var-show-attributes
20540 @subsubheading Synopsis
20543 -var-show-attributes @var{name}
20546 List attributes of the specified variable object @var{name}:
20549 status=@var{attr} [ ( ,@var{attr} )* ]
20553 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
20555 @subheading The @code{-var-evaluate-expression} Command
20556 @findex -var-evaluate-expression
20558 @subsubheading Synopsis
20561 -var-evaluate-expression [-f @var{format-spec}] @var{name}
20564 Evaluates the expression that is represented by the specified variable
20565 object and returns its value as a string. The format of the string
20566 can be specified with the @samp{-f} option. The possible values of
20567 this option are the same as for @code{-var-set-format}
20568 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
20569 the current display format will be used. The current display format
20570 can be changed using the @code{-var-set-format} command.
20576 Note that one must invoke @code{-var-list-children} for a variable
20577 before the value of a child variable can be evaluated.
20579 @subheading The @code{-var-assign} Command
20580 @findex -var-assign
20582 @subsubheading Synopsis
20585 -var-assign @var{name} @var{expression}
20588 Assigns the value of @var{expression} to the variable object specified
20589 by @var{name}. The object must be @samp{editable}. If the variable's
20590 value is altered by the assign, the variable will show up in any
20591 subsequent @code{-var-update} list.
20593 @subsubheading Example
20601 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
20605 @subheading The @code{-var-update} Command
20606 @findex -var-update
20608 @subsubheading Synopsis
20611 -var-update [@var{print-values}] @{@var{name} | "*"@}
20614 Reevaluate the expressions corresponding to the variable object
20615 @var{name} and all its direct and indirect children, and return the
20616 list of variable objects whose values have changed; @var{name} must
20617 be a root variable object. Here, ``changed'' means that the result of
20618 @code{-var-evaluate-expression} before and after the
20619 @code{-var-update} is different. If @samp{*} is used as the variable
20620 object names, all existing variable objects are updated, except
20621 for frozen ones (@pxref{-var-set-frozen}). The option
20622 @var{print-values} determines whether both names and values, or just
20623 names are printed. The possible values of this option are the same
20624 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
20625 recommended to use the @samp{--all-values} option, to reduce the
20626 number of MI commands needed on each program stop.
20629 @subsubheading Example
20636 -var-update --all-values var1
20637 ^done,changelist=[@{name="var1",value="3",in_scope="true",
20638 type_changed="false"@}]
20642 @anchor{-var-update}
20643 The field in_scope may take three values:
20647 The variable object's current value is valid.
20650 The variable object does not currently hold a valid value but it may
20651 hold one in the future if its associated expression comes back into
20655 The variable object no longer holds a valid value.
20656 This can occur when the executable file being debugged has changed,
20657 either through recompilation or by using the @value{GDBN} @code{file}
20658 command. The front end should normally choose to delete these variable
20662 In the future new values may be added to this list so the front should
20663 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
20665 @subheading The @code{-var-set-frozen} Command
20666 @findex -var-set-frozen
20667 @anchor{-var-set-frozen}
20669 @subsubheading Synopsis
20672 -var-set-frozen @var{name} @var{flag}
20675 Set the frozenness flag on the variable object @var{name}. The
20676 @var{flag} parameter should be either @samp{1} to make the variable
20677 frozen or @samp{0} to make it unfrozen. If a variable object is
20678 frozen, then neither itself, nor any of its children, are
20679 implicitly updated by @code{-var-update} of
20680 a parent variable or by @code{-var-update *}. Only
20681 @code{-var-update} of the variable itself will update its value and
20682 values of its children. After a variable object is unfrozen, it is
20683 implicitly updated by all subsequent @code{-var-update} operations.
20684 Unfreezing a variable does not update it, only subsequent
20685 @code{-var-update} does.
20687 @subsubheading Example
20691 -var-set-frozen V 1
20697 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20698 @node GDB/MI Data Manipulation
20699 @section @sc{gdb/mi} Data Manipulation
20701 @cindex data manipulation, in @sc{gdb/mi}
20702 @cindex @sc{gdb/mi}, data manipulation
20703 This section describes the @sc{gdb/mi} commands that manipulate data:
20704 examine memory and registers, evaluate expressions, etc.
20706 @c REMOVED FROM THE INTERFACE.
20707 @c @subheading -data-assign
20708 @c Change the value of a program variable. Plenty of side effects.
20709 @c @subsubheading GDB Command
20711 @c @subsubheading Example
20714 @subheading The @code{-data-disassemble} Command
20715 @findex -data-disassemble
20717 @subsubheading Synopsis
20721 [ -s @var{start-addr} -e @var{end-addr} ]
20722 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
20730 @item @var{start-addr}
20731 is the beginning address (or @code{$pc})
20732 @item @var{end-addr}
20734 @item @var{filename}
20735 is the name of the file to disassemble
20736 @item @var{linenum}
20737 is the line number to disassemble around
20739 is the number of disassembly lines to be produced. If it is -1,
20740 the whole function will be disassembled, in case no @var{end-addr} is
20741 specified. If @var{end-addr} is specified as a non-zero value, and
20742 @var{lines} is lower than the number of disassembly lines between
20743 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
20744 displayed; if @var{lines} is higher than the number of lines between
20745 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
20748 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
20752 @subsubheading Result
20754 The output for each instruction is composed of four fields:
20763 Note that whatever included in the instruction field, is not manipulated
20764 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
20766 @subsubheading @value{GDBN} Command
20768 There's no direct mapping from this command to the CLI.
20770 @subsubheading Example
20772 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
20776 -data-disassemble -s $pc -e "$pc + 20" -- 0
20779 @{address="0x000107c0",func-name="main",offset="4",
20780 inst="mov 2, %o0"@},
20781 @{address="0x000107c4",func-name="main",offset="8",
20782 inst="sethi %hi(0x11800), %o2"@},
20783 @{address="0x000107c8",func-name="main",offset="12",
20784 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
20785 @{address="0x000107cc",func-name="main",offset="16",
20786 inst="sethi %hi(0x11800), %o2"@},
20787 @{address="0x000107d0",func-name="main",offset="20",
20788 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
20792 Disassemble the whole @code{main} function. Line 32 is part of
20796 -data-disassemble -f basics.c -l 32 -- 0
20798 @{address="0x000107bc",func-name="main",offset="0",
20799 inst="save %sp, -112, %sp"@},
20800 @{address="0x000107c0",func-name="main",offset="4",
20801 inst="mov 2, %o0"@},
20802 @{address="0x000107c4",func-name="main",offset="8",
20803 inst="sethi %hi(0x11800), %o2"@},
20805 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
20806 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
20810 Disassemble 3 instructions from the start of @code{main}:
20814 -data-disassemble -f basics.c -l 32 -n 3 -- 0
20816 @{address="0x000107bc",func-name="main",offset="0",
20817 inst="save %sp, -112, %sp"@},
20818 @{address="0x000107c0",func-name="main",offset="4",
20819 inst="mov 2, %o0"@},
20820 @{address="0x000107c4",func-name="main",offset="8",
20821 inst="sethi %hi(0x11800), %o2"@}]
20825 Disassemble 3 instructions from the start of @code{main} in mixed mode:
20829 -data-disassemble -f basics.c -l 32 -n 3 -- 1
20831 src_and_asm_line=@{line="31",
20832 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
20833 testsuite/gdb.mi/basics.c",line_asm_insn=[
20834 @{address="0x000107bc",func-name="main",offset="0",
20835 inst="save %sp, -112, %sp"@}]@},
20836 src_and_asm_line=@{line="32",
20837 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
20838 testsuite/gdb.mi/basics.c",line_asm_insn=[
20839 @{address="0x000107c0",func-name="main",offset="4",
20840 inst="mov 2, %o0"@},
20841 @{address="0x000107c4",func-name="main",offset="8",
20842 inst="sethi %hi(0x11800), %o2"@}]@}]
20847 @subheading The @code{-data-evaluate-expression} Command
20848 @findex -data-evaluate-expression
20850 @subsubheading Synopsis
20853 -data-evaluate-expression @var{expr}
20856 Evaluate @var{expr} as an expression. The expression could contain an
20857 inferior function call. The function call will execute synchronously.
20858 If the expression contains spaces, it must be enclosed in double quotes.
20860 @subsubheading @value{GDBN} Command
20862 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
20863 @samp{call}. In @code{gdbtk} only, there's a corresponding
20864 @samp{gdb_eval} command.
20866 @subsubheading Example
20868 In the following example, the numbers that precede the commands are the
20869 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
20870 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
20874 211-data-evaluate-expression A
20877 311-data-evaluate-expression &A
20878 311^done,value="0xefffeb7c"
20880 411-data-evaluate-expression A+3
20883 511-data-evaluate-expression "A + 3"
20889 @subheading The @code{-data-list-changed-registers} Command
20890 @findex -data-list-changed-registers
20892 @subsubheading Synopsis
20895 -data-list-changed-registers
20898 Display a list of the registers that have changed.
20900 @subsubheading @value{GDBN} Command
20902 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
20903 has the corresponding command @samp{gdb_changed_register_list}.
20905 @subsubheading Example
20907 On a PPC MBX board:
20915 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
20916 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
20919 -data-list-changed-registers
20920 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
20921 "10","11","13","14","15","16","17","18","19","20","21","22","23",
20922 "24","25","26","27","28","30","31","64","65","66","67","69"]
20927 @subheading The @code{-data-list-register-names} Command
20928 @findex -data-list-register-names
20930 @subsubheading Synopsis
20933 -data-list-register-names [ ( @var{regno} )+ ]
20936 Show a list of register names for the current target. If no arguments
20937 are given, it shows a list of the names of all the registers. If
20938 integer numbers are given as arguments, it will print a list of the
20939 names of the registers corresponding to the arguments. To ensure
20940 consistency between a register name and its number, the output list may
20941 include empty register names.
20943 @subsubheading @value{GDBN} Command
20945 @value{GDBN} does not have a command which corresponds to
20946 @samp{-data-list-register-names}. In @code{gdbtk} there is a
20947 corresponding command @samp{gdb_regnames}.
20949 @subsubheading Example
20951 For the PPC MBX board:
20954 -data-list-register-names
20955 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
20956 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
20957 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
20958 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
20959 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
20960 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
20961 "", "pc","ps","cr","lr","ctr","xer"]
20963 -data-list-register-names 1 2 3
20964 ^done,register-names=["r1","r2","r3"]
20968 @subheading The @code{-data-list-register-values} Command
20969 @findex -data-list-register-values
20971 @subsubheading Synopsis
20974 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
20977 Display the registers' contents. @var{fmt} is the format according to
20978 which the registers' contents are to be returned, followed by an optional
20979 list of numbers specifying the registers to display. A missing list of
20980 numbers indicates that the contents of all the registers must be returned.
20982 Allowed formats for @var{fmt} are:
20999 @subsubheading @value{GDBN} Command
21001 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
21002 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
21004 @subsubheading Example
21006 For a PPC MBX board (note: line breaks are for readability only, they
21007 don't appear in the actual output):
21011 -data-list-register-values r 64 65
21012 ^done,register-values=[@{number="64",value="0xfe00a300"@},
21013 @{number="65",value="0x00029002"@}]
21015 -data-list-register-values x
21016 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
21017 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
21018 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
21019 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
21020 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
21021 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
21022 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
21023 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
21024 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
21025 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
21026 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
21027 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
21028 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
21029 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
21030 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
21031 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
21032 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
21033 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
21034 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
21035 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
21036 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
21037 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
21038 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
21039 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
21040 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
21041 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
21042 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
21043 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
21044 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
21045 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
21046 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
21047 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
21048 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
21049 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
21050 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
21051 @{number="69",value="0x20002b03"@}]
21056 @subheading The @code{-data-read-memory} Command
21057 @findex -data-read-memory
21059 @subsubheading Synopsis
21062 -data-read-memory [ -o @var{byte-offset} ]
21063 @var{address} @var{word-format} @var{word-size}
21064 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
21071 @item @var{address}
21072 An expression specifying the address of the first memory word to be
21073 read. Complex expressions containing embedded white space should be
21074 quoted using the C convention.
21076 @item @var{word-format}
21077 The format to be used to print the memory words. The notation is the
21078 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
21081 @item @var{word-size}
21082 The size of each memory word in bytes.
21084 @item @var{nr-rows}
21085 The number of rows in the output table.
21087 @item @var{nr-cols}
21088 The number of columns in the output table.
21091 If present, indicates that each row should include an @sc{ascii} dump. The
21092 value of @var{aschar} is used as a padding character when a byte is not a
21093 member of the printable @sc{ascii} character set (printable @sc{ascii}
21094 characters are those whose code is between 32 and 126, inclusively).
21096 @item @var{byte-offset}
21097 An offset to add to the @var{address} before fetching memory.
21100 This command displays memory contents as a table of @var{nr-rows} by
21101 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
21102 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
21103 (returned as @samp{total-bytes}). Should less than the requested number
21104 of bytes be returned by the target, the missing words are identified
21105 using @samp{N/A}. The number of bytes read from the target is returned
21106 in @samp{nr-bytes} and the starting address used to read memory in
21109 The address of the next/previous row or page is available in
21110 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
21113 @subsubheading @value{GDBN} Command
21115 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
21116 @samp{gdb_get_mem} memory read command.
21118 @subsubheading Example
21120 Read six bytes of memory starting at @code{bytes+6} but then offset by
21121 @code{-6} bytes. Format as three rows of two columns. One byte per
21122 word. Display each word in hex.
21126 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
21127 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
21128 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
21129 prev-page="0x0000138a",memory=[
21130 @{addr="0x00001390",data=["0x00","0x01"]@},
21131 @{addr="0x00001392",data=["0x02","0x03"]@},
21132 @{addr="0x00001394",data=["0x04","0x05"]@}]
21136 Read two bytes of memory starting at address @code{shorts + 64} and
21137 display as a single word formatted in decimal.
21141 5-data-read-memory shorts+64 d 2 1 1
21142 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
21143 next-row="0x00001512",prev-row="0x0000150e",
21144 next-page="0x00001512",prev-page="0x0000150e",memory=[
21145 @{addr="0x00001510",data=["128"]@}]
21149 Read thirty two bytes of memory starting at @code{bytes+16} and format
21150 as eight rows of four columns. Include a string encoding with @samp{x}
21151 used as the non-printable character.
21155 4-data-read-memory bytes+16 x 1 8 4 x
21156 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
21157 next-row="0x000013c0",prev-row="0x0000139c",
21158 next-page="0x000013c0",prev-page="0x00001380",memory=[
21159 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
21160 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
21161 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
21162 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
21163 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
21164 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
21165 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
21166 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
21170 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21171 @node GDB/MI Tracepoint Commands
21172 @section @sc{gdb/mi} Tracepoint Commands
21174 The tracepoint commands are not yet implemented.
21176 @c @subheading -trace-actions
21178 @c @subheading -trace-delete
21180 @c @subheading -trace-disable
21182 @c @subheading -trace-dump
21184 @c @subheading -trace-enable
21186 @c @subheading -trace-exists
21188 @c @subheading -trace-find
21190 @c @subheading -trace-frame-number
21192 @c @subheading -trace-info
21194 @c @subheading -trace-insert
21196 @c @subheading -trace-list
21198 @c @subheading -trace-pass-count
21200 @c @subheading -trace-save
21202 @c @subheading -trace-start
21204 @c @subheading -trace-stop
21207 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21208 @node GDB/MI Symbol Query
21209 @section @sc{gdb/mi} Symbol Query Commands
21212 @subheading The @code{-symbol-info-address} Command
21213 @findex -symbol-info-address
21215 @subsubheading Synopsis
21218 -symbol-info-address @var{symbol}
21221 Describe where @var{symbol} is stored.
21223 @subsubheading @value{GDBN} Command
21225 The corresponding @value{GDBN} command is @samp{info address}.
21227 @subsubheading Example
21231 @subheading The @code{-symbol-info-file} Command
21232 @findex -symbol-info-file
21234 @subsubheading Synopsis
21240 Show the file for the symbol.
21242 @subsubheading @value{GDBN} Command
21244 There's no equivalent @value{GDBN} command. @code{gdbtk} has
21245 @samp{gdb_find_file}.
21247 @subsubheading Example
21251 @subheading The @code{-symbol-info-function} Command
21252 @findex -symbol-info-function
21254 @subsubheading Synopsis
21257 -symbol-info-function
21260 Show which function the symbol lives in.
21262 @subsubheading @value{GDBN} Command
21264 @samp{gdb_get_function} in @code{gdbtk}.
21266 @subsubheading Example
21270 @subheading The @code{-symbol-info-line} Command
21271 @findex -symbol-info-line
21273 @subsubheading Synopsis
21279 Show the core addresses of the code for a source line.
21281 @subsubheading @value{GDBN} Command
21283 The corresponding @value{GDBN} command is @samp{info line}.
21284 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
21286 @subsubheading Example
21290 @subheading The @code{-symbol-info-symbol} Command
21291 @findex -symbol-info-symbol
21293 @subsubheading Synopsis
21296 -symbol-info-symbol @var{addr}
21299 Describe what symbol is at location @var{addr}.
21301 @subsubheading @value{GDBN} Command
21303 The corresponding @value{GDBN} command is @samp{info symbol}.
21305 @subsubheading Example
21309 @subheading The @code{-symbol-list-functions} Command
21310 @findex -symbol-list-functions
21312 @subsubheading Synopsis
21315 -symbol-list-functions
21318 List the functions in the executable.
21320 @subsubheading @value{GDBN} Command
21322 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
21323 @samp{gdb_search} in @code{gdbtk}.
21325 @subsubheading Example
21329 @subheading The @code{-symbol-list-lines} Command
21330 @findex -symbol-list-lines
21332 @subsubheading Synopsis
21335 -symbol-list-lines @var{filename}
21338 Print the list of lines that contain code and their associated program
21339 addresses for the given source filename. The entries are sorted in
21340 ascending PC order.
21342 @subsubheading @value{GDBN} Command
21344 There is no corresponding @value{GDBN} command.
21346 @subsubheading Example
21349 -symbol-list-lines basics.c
21350 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
21355 @subheading The @code{-symbol-list-types} Command
21356 @findex -symbol-list-types
21358 @subsubheading Synopsis
21364 List all the type names.
21366 @subsubheading @value{GDBN} Command
21368 The corresponding commands are @samp{info types} in @value{GDBN},
21369 @samp{gdb_search} in @code{gdbtk}.
21371 @subsubheading Example
21375 @subheading The @code{-symbol-list-variables} Command
21376 @findex -symbol-list-variables
21378 @subsubheading Synopsis
21381 -symbol-list-variables
21384 List all the global and static variable names.
21386 @subsubheading @value{GDBN} Command
21388 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
21390 @subsubheading Example
21394 @subheading The @code{-symbol-locate} Command
21395 @findex -symbol-locate
21397 @subsubheading Synopsis
21403 @subsubheading @value{GDBN} Command
21405 @samp{gdb_loc} in @code{gdbtk}.
21407 @subsubheading Example
21411 @subheading The @code{-symbol-type} Command
21412 @findex -symbol-type
21414 @subsubheading Synopsis
21417 -symbol-type @var{variable}
21420 Show type of @var{variable}.
21422 @subsubheading @value{GDBN} Command
21424 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
21425 @samp{gdb_obj_variable}.
21427 @subsubheading Example
21431 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21432 @node GDB/MI File Commands
21433 @section @sc{gdb/mi} File Commands
21435 This section describes the GDB/MI commands to specify executable file names
21436 and to read in and obtain symbol table information.
21438 @subheading The @code{-file-exec-and-symbols} Command
21439 @findex -file-exec-and-symbols
21441 @subsubheading Synopsis
21444 -file-exec-and-symbols @var{file}
21447 Specify the executable file to be debugged. This file is the one from
21448 which the symbol table is also read. If no file is specified, the
21449 command clears the executable and symbol information. If breakpoints
21450 are set when using this command with no arguments, @value{GDBN} will produce
21451 error messages. Otherwise, no output is produced, except a completion
21454 @subsubheading @value{GDBN} Command
21456 The corresponding @value{GDBN} command is @samp{file}.
21458 @subsubheading Example
21462 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
21468 @subheading The @code{-file-exec-file} Command
21469 @findex -file-exec-file
21471 @subsubheading Synopsis
21474 -file-exec-file @var{file}
21477 Specify the executable file to be debugged. Unlike
21478 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
21479 from this file. If used without argument, @value{GDBN} clears the information
21480 about the executable file. No output is produced, except a completion
21483 @subsubheading @value{GDBN} Command
21485 The corresponding @value{GDBN} command is @samp{exec-file}.
21487 @subsubheading Example
21491 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
21497 @subheading The @code{-file-list-exec-sections} Command
21498 @findex -file-list-exec-sections
21500 @subsubheading Synopsis
21503 -file-list-exec-sections
21506 List the sections of the current executable file.
21508 @subsubheading @value{GDBN} Command
21510 The @value{GDBN} command @samp{info file} shows, among the rest, the same
21511 information as this command. @code{gdbtk} has a corresponding command
21512 @samp{gdb_load_info}.
21514 @subsubheading Example
21518 @subheading The @code{-file-list-exec-source-file} Command
21519 @findex -file-list-exec-source-file
21521 @subsubheading Synopsis
21524 -file-list-exec-source-file
21527 List the line number, the current source file, and the absolute path
21528 to the current source file for the current executable. The macro
21529 information field has a value of @samp{1} or @samp{0} depending on
21530 whether or not the file includes preprocessor macro information.
21532 @subsubheading @value{GDBN} Command
21534 The @value{GDBN} equivalent is @samp{info source}
21536 @subsubheading Example
21540 123-file-list-exec-source-file
21541 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
21546 @subheading The @code{-file-list-exec-source-files} Command
21547 @findex -file-list-exec-source-files
21549 @subsubheading Synopsis
21552 -file-list-exec-source-files
21555 List the source files for the current executable.
21557 It will always output the filename, but only when @value{GDBN} can find
21558 the absolute file name of a source file, will it output the fullname.
21560 @subsubheading @value{GDBN} Command
21562 The @value{GDBN} equivalent is @samp{info sources}.
21563 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
21565 @subsubheading Example
21568 -file-list-exec-source-files
21570 @{file=foo.c,fullname=/home/foo.c@},
21571 @{file=/home/bar.c,fullname=/home/bar.c@},
21572 @{file=gdb_could_not_find_fullpath.c@}]
21576 @subheading The @code{-file-list-shared-libraries} Command
21577 @findex -file-list-shared-libraries
21579 @subsubheading Synopsis
21582 -file-list-shared-libraries
21585 List the shared libraries in the program.
21587 @subsubheading @value{GDBN} Command
21589 The corresponding @value{GDBN} command is @samp{info shared}.
21591 @subsubheading Example
21595 @subheading The @code{-file-list-symbol-files} Command
21596 @findex -file-list-symbol-files
21598 @subsubheading Synopsis
21601 -file-list-symbol-files
21606 @subsubheading @value{GDBN} Command
21608 The corresponding @value{GDBN} command is @samp{info file} (part of it).
21610 @subsubheading Example
21614 @subheading The @code{-file-symbol-file} Command
21615 @findex -file-symbol-file
21617 @subsubheading Synopsis
21620 -file-symbol-file @var{file}
21623 Read symbol table info from the specified @var{file} argument. When
21624 used without arguments, clears @value{GDBN}'s symbol table info. No output is
21625 produced, except for a completion notification.
21627 @subsubheading @value{GDBN} Command
21629 The corresponding @value{GDBN} command is @samp{symbol-file}.
21631 @subsubheading Example
21635 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
21641 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21642 @node GDB/MI Memory Overlay Commands
21643 @section @sc{gdb/mi} Memory Overlay Commands
21645 The memory overlay commands are not implemented.
21647 @c @subheading -overlay-auto
21649 @c @subheading -overlay-list-mapping-state
21651 @c @subheading -overlay-list-overlays
21653 @c @subheading -overlay-map
21655 @c @subheading -overlay-off
21657 @c @subheading -overlay-on
21659 @c @subheading -overlay-unmap
21661 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21662 @node GDB/MI Signal Handling Commands
21663 @section @sc{gdb/mi} Signal Handling Commands
21665 Signal handling commands are not implemented.
21667 @c @subheading -signal-handle
21669 @c @subheading -signal-list-handle-actions
21671 @c @subheading -signal-list-signal-types
21675 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21676 @node GDB/MI Target Manipulation
21677 @section @sc{gdb/mi} Target Manipulation Commands
21680 @subheading The @code{-target-attach} Command
21681 @findex -target-attach
21683 @subsubheading Synopsis
21686 -target-attach @var{pid} | @var{file}
21689 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
21691 @subsubheading @value{GDBN} Command
21693 The corresponding @value{GDBN} command is @samp{attach}.
21695 @subsubheading Example
21699 =thread-created,id="1"
21700 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
21705 @subheading The @code{-target-compare-sections} Command
21706 @findex -target-compare-sections
21708 @subsubheading Synopsis
21711 -target-compare-sections [ @var{section} ]
21714 Compare data of section @var{section} on target to the exec file.
21715 Without the argument, all sections are compared.
21717 @subsubheading @value{GDBN} Command
21719 The @value{GDBN} equivalent is @samp{compare-sections}.
21721 @subsubheading Example
21725 @subheading The @code{-target-detach} Command
21726 @findex -target-detach
21728 @subsubheading Synopsis
21734 Detach from the remote target which normally resumes its execution.
21737 @subsubheading @value{GDBN} Command
21739 The corresponding @value{GDBN} command is @samp{detach}.
21741 @subsubheading Example
21751 @subheading The @code{-target-disconnect} Command
21752 @findex -target-disconnect
21754 @subsubheading Synopsis
21760 Disconnect from the remote target. There's no output and the target is
21761 generally not resumed.
21763 @subsubheading @value{GDBN} Command
21765 The corresponding @value{GDBN} command is @samp{disconnect}.
21767 @subsubheading Example
21777 @subheading The @code{-target-download} Command
21778 @findex -target-download
21780 @subsubheading Synopsis
21786 Loads the executable onto the remote target.
21787 It prints out an update message every half second, which includes the fields:
21791 The name of the section.
21793 The size of what has been sent so far for that section.
21795 The size of the section.
21797 The total size of what was sent so far (the current and the previous sections).
21799 The size of the overall executable to download.
21803 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
21804 @sc{gdb/mi} Output Syntax}).
21806 In addition, it prints the name and size of the sections, as they are
21807 downloaded. These messages include the following fields:
21811 The name of the section.
21813 The size of the section.
21815 The size of the overall executable to download.
21819 At the end, a summary is printed.
21821 @subsubheading @value{GDBN} Command
21823 The corresponding @value{GDBN} command is @samp{load}.
21825 @subsubheading Example
21827 Note: each status message appears on a single line. Here the messages
21828 have been broken down so that they can fit onto a page.
21833 +download,@{section=".text",section-size="6668",total-size="9880"@}
21834 +download,@{section=".text",section-sent="512",section-size="6668",
21835 total-sent="512",total-size="9880"@}
21836 +download,@{section=".text",section-sent="1024",section-size="6668",
21837 total-sent="1024",total-size="9880"@}
21838 +download,@{section=".text",section-sent="1536",section-size="6668",
21839 total-sent="1536",total-size="9880"@}
21840 +download,@{section=".text",section-sent="2048",section-size="6668",
21841 total-sent="2048",total-size="9880"@}
21842 +download,@{section=".text",section-sent="2560",section-size="6668",
21843 total-sent="2560",total-size="9880"@}
21844 +download,@{section=".text",section-sent="3072",section-size="6668",
21845 total-sent="3072",total-size="9880"@}
21846 +download,@{section=".text",section-sent="3584",section-size="6668",
21847 total-sent="3584",total-size="9880"@}
21848 +download,@{section=".text",section-sent="4096",section-size="6668",
21849 total-sent="4096",total-size="9880"@}
21850 +download,@{section=".text",section-sent="4608",section-size="6668",
21851 total-sent="4608",total-size="9880"@}
21852 +download,@{section=".text",section-sent="5120",section-size="6668",
21853 total-sent="5120",total-size="9880"@}
21854 +download,@{section=".text",section-sent="5632",section-size="6668",
21855 total-sent="5632",total-size="9880"@}
21856 +download,@{section=".text",section-sent="6144",section-size="6668",
21857 total-sent="6144",total-size="9880"@}
21858 +download,@{section=".text",section-sent="6656",section-size="6668",
21859 total-sent="6656",total-size="9880"@}
21860 +download,@{section=".init",section-size="28",total-size="9880"@}
21861 +download,@{section=".fini",section-size="28",total-size="9880"@}
21862 +download,@{section=".data",section-size="3156",total-size="9880"@}
21863 +download,@{section=".data",section-sent="512",section-size="3156",
21864 total-sent="7236",total-size="9880"@}
21865 +download,@{section=".data",section-sent="1024",section-size="3156",
21866 total-sent="7748",total-size="9880"@}
21867 +download,@{section=".data",section-sent="1536",section-size="3156",
21868 total-sent="8260",total-size="9880"@}
21869 +download,@{section=".data",section-sent="2048",section-size="3156",
21870 total-sent="8772",total-size="9880"@}
21871 +download,@{section=".data",section-sent="2560",section-size="3156",
21872 total-sent="9284",total-size="9880"@}
21873 +download,@{section=".data",section-sent="3072",section-size="3156",
21874 total-sent="9796",total-size="9880"@}
21875 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
21881 @subheading The @code{-target-exec-status} Command
21882 @findex -target-exec-status
21884 @subsubheading Synopsis
21887 -target-exec-status
21890 Provide information on the state of the target (whether it is running or
21891 not, for instance).
21893 @subsubheading @value{GDBN} Command
21895 There's no equivalent @value{GDBN} command.
21897 @subsubheading Example
21901 @subheading The @code{-target-list-available-targets} Command
21902 @findex -target-list-available-targets
21904 @subsubheading Synopsis
21907 -target-list-available-targets
21910 List the possible targets to connect to.
21912 @subsubheading @value{GDBN} Command
21914 The corresponding @value{GDBN} command is @samp{help target}.
21916 @subsubheading Example
21920 @subheading The @code{-target-list-current-targets} Command
21921 @findex -target-list-current-targets
21923 @subsubheading Synopsis
21926 -target-list-current-targets
21929 Describe the current target.
21931 @subsubheading @value{GDBN} Command
21933 The corresponding information is printed by @samp{info file} (among
21936 @subsubheading Example
21940 @subheading The @code{-target-list-parameters} Command
21941 @findex -target-list-parameters
21943 @subsubheading Synopsis
21946 -target-list-parameters
21951 @subsubheading @value{GDBN} Command
21955 @subsubheading Example
21959 @subheading The @code{-target-select} Command
21960 @findex -target-select
21962 @subsubheading Synopsis
21965 -target-select @var{type} @var{parameters @dots{}}
21968 Connect @value{GDBN} to the remote target. This command takes two args:
21972 The type of target, for instance @samp{remote}, etc.
21973 @item @var{parameters}
21974 Device names, host names and the like. @xref{Target Commands, ,
21975 Commands for Managing Targets}, for more details.
21978 The output is a connection notification, followed by the address at
21979 which the target program is, in the following form:
21982 ^connected,addr="@var{address}",func="@var{function name}",
21983 args=[@var{arg list}]
21986 @subsubheading @value{GDBN} Command
21988 The corresponding @value{GDBN} command is @samp{target}.
21990 @subsubheading Example
21994 -target-select remote /dev/ttya
21995 ^connected,addr="0xfe00a300",func="??",args=[]
21999 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22000 @node GDB/MI File Transfer Commands
22001 @section @sc{gdb/mi} File Transfer Commands
22004 @subheading The @code{-target-file-put} Command
22005 @findex -target-file-put
22007 @subsubheading Synopsis
22010 -target-file-put @var{hostfile} @var{targetfile}
22013 Copy file @var{hostfile} from the host system (the machine running
22014 @value{GDBN}) to @var{targetfile} on the target system.
22016 @subsubheading @value{GDBN} Command
22018 The corresponding @value{GDBN} command is @samp{remote put}.
22020 @subsubheading Example
22024 -target-file-put localfile remotefile
22030 @subheading The @code{-target-file-get} Command
22031 @findex -target-file-get
22033 @subsubheading Synopsis
22036 -target-file-get @var{targetfile} @var{hostfile}
22039 Copy file @var{targetfile} from the target system to @var{hostfile}
22040 on the host system.
22042 @subsubheading @value{GDBN} Command
22044 The corresponding @value{GDBN} command is @samp{remote get}.
22046 @subsubheading Example
22050 -target-file-get remotefile localfile
22056 @subheading The @code{-target-file-delete} Command
22057 @findex -target-file-delete
22059 @subsubheading Synopsis
22062 -target-file-delete @var{targetfile}
22065 Delete @var{targetfile} from the target system.
22067 @subsubheading @value{GDBN} Command
22069 The corresponding @value{GDBN} command is @samp{remote delete}.
22071 @subsubheading Example
22075 -target-file-delete remotefile
22081 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22082 @node GDB/MI Miscellaneous Commands
22083 @section Miscellaneous @sc{gdb/mi} Commands
22085 @c @subheading -gdb-complete
22087 @subheading The @code{-gdb-exit} Command
22090 @subsubheading Synopsis
22096 Exit @value{GDBN} immediately.
22098 @subsubheading @value{GDBN} Command
22100 Approximately corresponds to @samp{quit}.
22102 @subsubheading Example
22111 @subheading The @code{-exec-abort} Command
22112 @findex -exec-abort
22114 @subsubheading Synopsis
22120 Kill the inferior running program.
22122 @subsubheading @value{GDBN} Command
22124 The corresponding @value{GDBN} command is @samp{kill}.
22126 @subsubheading Example
22130 @subheading The @code{-gdb-set} Command
22133 @subsubheading Synopsis
22139 Set an internal @value{GDBN} variable.
22140 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
22142 @subsubheading @value{GDBN} Command
22144 The corresponding @value{GDBN} command is @samp{set}.
22146 @subsubheading Example
22156 @subheading The @code{-gdb-show} Command
22159 @subsubheading Synopsis
22165 Show the current value of a @value{GDBN} variable.
22167 @subsubheading @value{GDBN} Command
22169 The corresponding @value{GDBN} command is @samp{show}.
22171 @subsubheading Example
22180 @c @subheading -gdb-source
22183 @subheading The @code{-gdb-version} Command
22184 @findex -gdb-version
22186 @subsubheading Synopsis
22192 Show version information for @value{GDBN}. Used mostly in testing.
22194 @subsubheading @value{GDBN} Command
22196 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
22197 default shows this information when you start an interactive session.
22199 @subsubheading Example
22201 @c This example modifies the actual output from GDB to avoid overfull
22207 ~Copyright 2000 Free Software Foundation, Inc.
22208 ~GDB is free software, covered by the GNU General Public License, and
22209 ~you are welcome to change it and/or distribute copies of it under
22210 ~ certain conditions.
22211 ~Type "show copying" to see the conditions.
22212 ~There is absolutely no warranty for GDB. Type "show warranty" for
22214 ~This GDB was configured as
22215 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
22220 @subheading The @code{-list-features} Command
22221 @findex -list-features
22223 Returns a list of particular features of the MI protocol that
22224 this version of gdb implements. A feature can be a command,
22225 or a new field in an output of some command, or even an
22226 important bugfix. While a frontend can sometimes detect presence
22227 of a feature at runtime, it is easier to perform detection at debugger
22230 The command returns a list of strings, with each string naming an
22231 available feature. Each returned string is just a name, it does not
22232 have any internal structure. The list of possible feature names
22238 (gdb) -list-features
22239 ^done,result=["feature1","feature2"]
22242 The current list of features is:
22246 @samp{frozen-varobjs}---indicates presence of the
22247 @code{-var-set-frozen} command, as well as possible presense of the
22248 @code{frozen} field in the output of @code{-varobj-create}.
22250 @samp{pending-breakpoints}---indicates presence of the @code{-f}
22251 option to the @code{-break-insert} command.
22253 @samp{thread-info}---indicates presence of the @code{-thread-info} command.
22257 @subheading The @code{-interpreter-exec} Command
22258 @findex -interpreter-exec
22260 @subheading Synopsis
22263 -interpreter-exec @var{interpreter} @var{command}
22265 @anchor{-interpreter-exec}
22267 Execute the specified @var{command} in the given @var{interpreter}.
22269 @subheading @value{GDBN} Command
22271 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
22273 @subheading Example
22277 -interpreter-exec console "break main"
22278 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
22279 &"During symbol reading, bad structure-type format.\n"
22280 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
22285 @subheading The @code{-inferior-tty-set} Command
22286 @findex -inferior-tty-set
22288 @subheading Synopsis
22291 -inferior-tty-set /dev/pts/1
22294 Set terminal for future runs of the program being debugged.
22296 @subheading @value{GDBN} Command
22298 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
22300 @subheading Example
22304 -inferior-tty-set /dev/pts/1
22309 @subheading The @code{-inferior-tty-show} Command
22310 @findex -inferior-tty-show
22312 @subheading Synopsis
22318 Show terminal for future runs of program being debugged.
22320 @subheading @value{GDBN} Command
22322 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
22324 @subheading Example
22328 -inferior-tty-set /dev/pts/1
22332 ^done,inferior_tty_terminal="/dev/pts/1"
22336 @subheading The @code{-enable-timings} Command
22337 @findex -enable-timings
22339 @subheading Synopsis
22342 -enable-timings [yes | no]
22345 Toggle the printing of the wallclock, user and system times for an MI
22346 command as a field in its output. This command is to help frontend
22347 developers optimize the performance of their code. No argument is
22348 equivalent to @samp{yes}.
22350 @subheading @value{GDBN} Command
22354 @subheading Example
22362 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
22363 addr="0x080484ed",func="main",file="myprog.c",
22364 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
22365 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
22373 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
22374 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
22375 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
22376 fullname="/home/nickrob/myprog.c",line="73"@}
22381 @chapter @value{GDBN} Annotations
22383 This chapter describes annotations in @value{GDBN}. Annotations were
22384 designed to interface @value{GDBN} to graphical user interfaces or other
22385 similar programs which want to interact with @value{GDBN} at a
22386 relatively high level.
22388 The annotation mechanism has largely been superseded by @sc{gdb/mi}
22392 This is Edition @value{EDITION}, @value{DATE}.
22396 * Annotations Overview:: What annotations are; the general syntax.
22397 * Server Prefix:: Issuing a command without affecting user state.
22398 * Prompting:: Annotations marking @value{GDBN}'s need for input.
22399 * Errors:: Annotations for error messages.
22400 * Invalidation:: Some annotations describe things now invalid.
22401 * Annotations for Running::
22402 Whether the program is running, how it stopped, etc.
22403 * Source Annotations:: Annotations describing source code.
22406 @node Annotations Overview
22407 @section What is an Annotation?
22408 @cindex annotations
22410 Annotations start with a newline character, two @samp{control-z}
22411 characters, and the name of the annotation. If there is no additional
22412 information associated with this annotation, the name of the annotation
22413 is followed immediately by a newline. If there is additional
22414 information, the name of the annotation is followed by a space, the
22415 additional information, and a newline. The additional information
22416 cannot contain newline characters.
22418 Any output not beginning with a newline and two @samp{control-z}
22419 characters denotes literal output from @value{GDBN}. Currently there is
22420 no need for @value{GDBN} to output a newline followed by two
22421 @samp{control-z} characters, but if there was such a need, the
22422 annotations could be extended with an @samp{escape} annotation which
22423 means those three characters as output.
22425 The annotation @var{level}, which is specified using the
22426 @option{--annotate} command line option (@pxref{Mode Options}), controls
22427 how much information @value{GDBN} prints together with its prompt,
22428 values of expressions, source lines, and other types of output. Level 0
22429 is for no annotations, level 1 is for use when @value{GDBN} is run as a
22430 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
22431 for programs that control @value{GDBN}, and level 2 annotations have
22432 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
22433 Interface, annotate, GDB's Obsolete Annotations}).
22436 @kindex set annotate
22437 @item set annotate @var{level}
22438 The @value{GDBN} command @code{set annotate} sets the level of
22439 annotations to the specified @var{level}.
22441 @item show annotate
22442 @kindex show annotate
22443 Show the current annotation level.
22446 This chapter describes level 3 annotations.
22448 A simple example of starting up @value{GDBN} with annotations is:
22451 $ @kbd{gdb --annotate=3}
22453 Copyright 2003 Free Software Foundation, Inc.
22454 GDB is free software, covered by the GNU General Public License,
22455 and you are welcome to change it and/or distribute copies of it
22456 under certain conditions.
22457 Type "show copying" to see the conditions.
22458 There is absolutely no warranty for GDB. Type "show warranty"
22460 This GDB was configured as "i386-pc-linux-gnu"
22471 Here @samp{quit} is input to @value{GDBN}; the rest is output from
22472 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
22473 denotes a @samp{control-z} character) are annotations; the rest is
22474 output from @value{GDBN}.
22476 @node Server Prefix
22477 @section The Server Prefix
22478 @cindex server prefix
22480 If you prefix a command with @samp{server } then it will not affect
22481 the command history, nor will it affect @value{GDBN}'s notion of which
22482 command to repeat if @key{RET} is pressed on a line by itself. This
22483 means that commands can be run behind a user's back by a front-end in
22484 a transparent manner.
22486 The server prefix does not affect the recording of values into the value
22487 history; to print a value without recording it into the value history,
22488 use the @code{output} command instead of the @code{print} command.
22491 @section Annotation for @value{GDBN} Input
22493 @cindex annotations for prompts
22494 When @value{GDBN} prompts for input, it annotates this fact so it is possible
22495 to know when to send output, when the output from a given command is
22498 Different kinds of input each have a different @dfn{input type}. Each
22499 input type has three annotations: a @code{pre-} annotation, which
22500 denotes the beginning of any prompt which is being output, a plain
22501 annotation, which denotes the end of the prompt, and then a @code{post-}
22502 annotation which denotes the end of any echo which may (or may not) be
22503 associated with the input. For example, the @code{prompt} input type
22504 features the following annotations:
22512 The input types are
22515 @findex pre-prompt annotation
22516 @findex prompt annotation
22517 @findex post-prompt annotation
22519 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
22521 @findex pre-commands annotation
22522 @findex commands annotation
22523 @findex post-commands annotation
22525 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
22526 command. The annotations are repeated for each command which is input.
22528 @findex pre-overload-choice annotation
22529 @findex overload-choice annotation
22530 @findex post-overload-choice annotation
22531 @item overload-choice
22532 When @value{GDBN} wants the user to select between various overloaded functions.
22534 @findex pre-query annotation
22535 @findex query annotation
22536 @findex post-query annotation
22538 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
22540 @findex pre-prompt-for-continue annotation
22541 @findex prompt-for-continue annotation
22542 @findex post-prompt-for-continue annotation
22543 @item prompt-for-continue
22544 When @value{GDBN} is asking the user to press return to continue. Note: Don't
22545 expect this to work well; instead use @code{set height 0} to disable
22546 prompting. This is because the counting of lines is buggy in the
22547 presence of annotations.
22552 @cindex annotations for errors, warnings and interrupts
22554 @findex quit annotation
22559 This annotation occurs right before @value{GDBN} responds to an interrupt.
22561 @findex error annotation
22566 This annotation occurs right before @value{GDBN} responds to an error.
22568 Quit and error annotations indicate that any annotations which @value{GDBN} was
22569 in the middle of may end abruptly. For example, if a
22570 @code{value-history-begin} annotation is followed by a @code{error}, one
22571 cannot expect to receive the matching @code{value-history-end}. One
22572 cannot expect not to receive it either, however; an error annotation
22573 does not necessarily mean that @value{GDBN} is immediately returning all the way
22576 @findex error-begin annotation
22577 A quit or error annotation may be preceded by
22583 Any output between that and the quit or error annotation is the error
22586 Warning messages are not yet annotated.
22587 @c If we want to change that, need to fix warning(), type_error(),
22588 @c range_error(), and possibly other places.
22591 @section Invalidation Notices
22593 @cindex annotations for invalidation messages
22594 The following annotations say that certain pieces of state may have
22598 @findex frames-invalid annotation
22599 @item ^Z^Zframes-invalid
22601 The frames (for example, output from the @code{backtrace} command) may
22604 @findex breakpoints-invalid annotation
22605 @item ^Z^Zbreakpoints-invalid
22607 The breakpoints may have changed. For example, the user just added or
22608 deleted a breakpoint.
22611 @node Annotations for Running
22612 @section Running the Program
22613 @cindex annotations for running programs
22615 @findex starting annotation
22616 @findex stopping annotation
22617 When the program starts executing due to a @value{GDBN} command such as
22618 @code{step} or @code{continue},
22624 is output. When the program stops,
22630 is output. Before the @code{stopped} annotation, a variety of
22631 annotations describe how the program stopped.
22634 @findex exited annotation
22635 @item ^Z^Zexited @var{exit-status}
22636 The program exited, and @var{exit-status} is the exit status (zero for
22637 successful exit, otherwise nonzero).
22639 @findex signalled annotation
22640 @findex signal-name annotation
22641 @findex signal-name-end annotation
22642 @findex signal-string annotation
22643 @findex signal-string-end annotation
22644 @item ^Z^Zsignalled
22645 The program exited with a signal. After the @code{^Z^Zsignalled}, the
22646 annotation continues:
22652 ^Z^Zsignal-name-end
22656 ^Z^Zsignal-string-end
22661 where @var{name} is the name of the signal, such as @code{SIGILL} or
22662 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
22663 as @code{Illegal Instruction} or @code{Segmentation fault}.
22664 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
22665 user's benefit and have no particular format.
22667 @findex signal annotation
22669 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
22670 just saying that the program received the signal, not that it was
22671 terminated with it.
22673 @findex breakpoint annotation
22674 @item ^Z^Zbreakpoint @var{number}
22675 The program hit breakpoint number @var{number}.
22677 @findex watchpoint annotation
22678 @item ^Z^Zwatchpoint @var{number}
22679 The program hit watchpoint number @var{number}.
22682 @node Source Annotations
22683 @section Displaying Source
22684 @cindex annotations for source display
22686 @findex source annotation
22687 The following annotation is used instead of displaying source code:
22690 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
22693 where @var{filename} is an absolute file name indicating which source
22694 file, @var{line} is the line number within that file (where 1 is the
22695 first line in the file), @var{character} is the character position
22696 within the file (where 0 is the first character in the file) (for most
22697 debug formats this will necessarily point to the beginning of a line),
22698 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
22699 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
22700 @var{addr} is the address in the target program associated with the
22701 source which is being displayed. @var{addr} is in the form @samp{0x}
22702 followed by one or more lowercase hex digits (note that this does not
22703 depend on the language).
22706 @chapter Reporting Bugs in @value{GDBN}
22707 @cindex bugs in @value{GDBN}
22708 @cindex reporting bugs in @value{GDBN}
22710 Your bug reports play an essential role in making @value{GDBN} reliable.
22712 Reporting a bug may help you by bringing a solution to your problem, or it
22713 may not. But in any case the principal function of a bug report is to help
22714 the entire community by making the next version of @value{GDBN} work better. Bug
22715 reports are your contribution to the maintenance of @value{GDBN}.
22717 In order for a bug report to serve its purpose, you must include the
22718 information that enables us to fix the bug.
22721 * Bug Criteria:: Have you found a bug?
22722 * Bug Reporting:: How to report bugs
22726 @section Have You Found a Bug?
22727 @cindex bug criteria
22729 If you are not sure whether you have found a bug, here are some guidelines:
22732 @cindex fatal signal
22733 @cindex debugger crash
22734 @cindex crash of debugger
22736 If the debugger gets a fatal signal, for any input whatever, that is a
22737 @value{GDBN} bug. Reliable debuggers never crash.
22739 @cindex error on valid input
22741 If @value{GDBN} produces an error message for valid input, that is a
22742 bug. (Note that if you're cross debugging, the problem may also be
22743 somewhere in the connection to the target.)
22745 @cindex invalid input
22747 If @value{GDBN} does not produce an error message for invalid input,
22748 that is a bug. However, you should note that your idea of
22749 ``invalid input'' might be our idea of ``an extension'' or ``support
22750 for traditional practice''.
22753 If you are an experienced user of debugging tools, your suggestions
22754 for improvement of @value{GDBN} are welcome in any case.
22757 @node Bug Reporting
22758 @section How to Report Bugs
22759 @cindex bug reports
22760 @cindex @value{GDBN} bugs, reporting
22762 A number of companies and individuals offer support for @sc{gnu} products.
22763 If you obtained @value{GDBN} from a support organization, we recommend you
22764 contact that organization first.
22766 You can find contact information for many support companies and
22767 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
22769 @c should add a web page ref...
22772 @ifset BUGURL_DEFAULT
22773 In any event, we also recommend that you submit bug reports for
22774 @value{GDBN}. The preferred method is to submit them directly using
22775 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
22776 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
22779 @strong{Do not send bug reports to @samp{info-gdb}, or to
22780 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
22781 not want to receive bug reports. Those that do have arranged to receive
22784 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
22785 serves as a repeater. The mailing list and the newsgroup carry exactly
22786 the same messages. Often people think of posting bug reports to the
22787 newsgroup instead of mailing them. This appears to work, but it has one
22788 problem which can be crucial: a newsgroup posting often lacks a mail
22789 path back to the sender. Thus, if we need to ask for more information,
22790 we may be unable to reach you. For this reason, it is better to send
22791 bug reports to the mailing list.
22793 @ifclear BUGURL_DEFAULT
22794 In any event, we also recommend that you submit bug reports for
22795 @value{GDBN} to @value{BUGURL}.
22799 The fundamental principle of reporting bugs usefully is this:
22800 @strong{report all the facts}. If you are not sure whether to state a
22801 fact or leave it out, state it!
22803 Often people omit facts because they think they know what causes the
22804 problem and assume that some details do not matter. Thus, you might
22805 assume that the name of the variable you use in an example does not matter.
22806 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
22807 stray memory reference which happens to fetch from the location where that
22808 name is stored in memory; perhaps, if the name were different, the contents
22809 of that location would fool the debugger into doing the right thing despite
22810 the bug. Play it safe and give a specific, complete example. That is the
22811 easiest thing for you to do, and the most helpful.
22813 Keep in mind that the purpose of a bug report is to enable us to fix the
22814 bug. It may be that the bug has been reported previously, but neither
22815 you nor we can know that unless your bug report is complete and
22818 Sometimes people give a few sketchy facts and ask, ``Does this ring a
22819 bell?'' Those bug reports are useless, and we urge everyone to
22820 @emph{refuse to respond to them} except to chide the sender to report
22823 To enable us to fix the bug, you should include all these things:
22827 The version of @value{GDBN}. @value{GDBN} announces it if you start
22828 with no arguments; you can also print it at any time using @code{show
22831 Without this, we will not know whether there is any point in looking for
22832 the bug in the current version of @value{GDBN}.
22835 The type of machine you are using, and the operating system name and
22839 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
22840 ``@value{GCC}--2.8.1''.
22843 What compiler (and its version) was used to compile the program you are
22844 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
22845 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
22846 to get this information; for other compilers, see the documentation for
22850 The command arguments you gave the compiler to compile your example and
22851 observe the bug. For example, did you use @samp{-O}? To guarantee
22852 you will not omit something important, list them all. A copy of the
22853 Makefile (or the output from make) is sufficient.
22855 If we were to try to guess the arguments, we would probably guess wrong
22856 and then we might not encounter the bug.
22859 A complete input script, and all necessary source files, that will
22863 A description of what behavior you observe that you believe is
22864 incorrect. For example, ``It gets a fatal signal.''
22866 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
22867 will certainly notice it. But if the bug is incorrect output, we might
22868 not notice unless it is glaringly wrong. You might as well not give us
22869 a chance to make a mistake.
22871 Even if the problem you experience is a fatal signal, you should still
22872 say so explicitly. Suppose something strange is going on, such as, your
22873 copy of @value{GDBN} is out of synch, or you have encountered a bug in
22874 the C library on your system. (This has happened!) Your copy might
22875 crash and ours would not. If you told us to expect a crash, then when
22876 ours fails to crash, we would know that the bug was not happening for
22877 us. If you had not told us to expect a crash, then we would not be able
22878 to draw any conclusion from our observations.
22881 @cindex recording a session script
22882 To collect all this information, you can use a session recording program
22883 such as @command{script}, which is available on many Unix systems.
22884 Just run your @value{GDBN} session inside @command{script} and then
22885 include the @file{typescript} file with your bug report.
22887 Another way to record a @value{GDBN} session is to run @value{GDBN}
22888 inside Emacs and then save the entire buffer to a file.
22891 If you wish to suggest changes to the @value{GDBN} source, send us context
22892 diffs. If you even discuss something in the @value{GDBN} source, refer to
22893 it by context, not by line number.
22895 The line numbers in our development sources will not match those in your
22896 sources. Your line numbers would convey no useful information to us.
22900 Here are some things that are not necessary:
22904 A description of the envelope of the bug.
22906 Often people who encounter a bug spend a lot of time investigating
22907 which changes to the input file will make the bug go away and which
22908 changes will not affect it.
22910 This is often time consuming and not very useful, because the way we
22911 will find the bug is by running a single example under the debugger
22912 with breakpoints, not by pure deduction from a series of examples.
22913 We recommend that you save your time for something else.
22915 Of course, if you can find a simpler example to report @emph{instead}
22916 of the original one, that is a convenience for us. Errors in the
22917 output will be easier to spot, running under the debugger will take
22918 less time, and so on.
22920 However, simplification is not vital; if you do not want to do this,
22921 report the bug anyway and send us the entire test case you used.
22924 A patch for the bug.
22926 A patch for the bug does help us if it is a good one. But do not omit
22927 the necessary information, such as the test case, on the assumption that
22928 a patch is all we need. We might see problems with your patch and decide
22929 to fix the problem another way, or we might not understand it at all.
22931 Sometimes with a program as complicated as @value{GDBN} it is very hard to
22932 construct an example that will make the program follow a certain path
22933 through the code. If you do not send us the example, we will not be able
22934 to construct one, so we will not be able to verify that the bug is fixed.
22936 And if we cannot understand what bug you are trying to fix, or why your
22937 patch should be an improvement, we will not install it. A test case will
22938 help us to understand.
22941 A guess about what the bug is or what it depends on.
22943 Such guesses are usually wrong. Even we cannot guess right about such
22944 things without first using the debugger to find the facts.
22947 @c The readline documentation is distributed with the readline code
22948 @c and consists of the two following files:
22950 @c inc-hist.texinfo
22951 @c Use -I with makeinfo to point to the appropriate directory,
22952 @c environment var TEXINPUTS with TeX.
22953 @include rluser.texi
22954 @include inc-hist.texinfo
22957 @node Formatting Documentation
22958 @appendix Formatting Documentation
22960 @cindex @value{GDBN} reference card
22961 @cindex reference card
22962 The @value{GDBN} 4 release includes an already-formatted reference card, ready
22963 for printing with PostScript or Ghostscript, in the @file{gdb}
22964 subdirectory of the main source directory@footnote{In
22965 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
22966 release.}. If you can use PostScript or Ghostscript with your printer,
22967 you can print the reference card immediately with @file{refcard.ps}.
22969 The release also includes the source for the reference card. You
22970 can format it, using @TeX{}, by typing:
22976 The @value{GDBN} reference card is designed to print in @dfn{landscape}
22977 mode on US ``letter'' size paper;
22978 that is, on a sheet 11 inches wide by 8.5 inches
22979 high. You will need to specify this form of printing as an option to
22980 your @sc{dvi} output program.
22982 @cindex documentation
22984 All the documentation for @value{GDBN} comes as part of the machine-readable
22985 distribution. The documentation is written in Texinfo format, which is
22986 a documentation system that uses a single source file to produce both
22987 on-line information and a printed manual. You can use one of the Info
22988 formatting commands to create the on-line version of the documentation
22989 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
22991 @value{GDBN} includes an already formatted copy of the on-line Info
22992 version of this manual in the @file{gdb} subdirectory. The main Info
22993 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
22994 subordinate files matching @samp{gdb.info*} in the same directory. If
22995 necessary, you can print out these files, or read them with any editor;
22996 but they are easier to read using the @code{info} subsystem in @sc{gnu}
22997 Emacs or the standalone @code{info} program, available as part of the
22998 @sc{gnu} Texinfo distribution.
23000 If you want to format these Info files yourself, you need one of the
23001 Info formatting programs, such as @code{texinfo-format-buffer} or
23004 If you have @code{makeinfo} installed, and are in the top level
23005 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
23006 version @value{GDBVN}), you can make the Info file by typing:
23013 If you want to typeset and print copies of this manual, you need @TeX{},
23014 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
23015 Texinfo definitions file.
23017 @TeX{} is a typesetting program; it does not print files directly, but
23018 produces output files called @sc{dvi} files. To print a typeset
23019 document, you need a program to print @sc{dvi} files. If your system
23020 has @TeX{} installed, chances are it has such a program. The precise
23021 command to use depends on your system; @kbd{lpr -d} is common; another
23022 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
23023 require a file name without any extension or a @samp{.dvi} extension.
23025 @TeX{} also requires a macro definitions file called
23026 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
23027 written in Texinfo format. On its own, @TeX{} cannot either read or
23028 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
23029 and is located in the @file{gdb-@var{version-number}/texinfo}
23032 If you have @TeX{} and a @sc{dvi} printer program installed, you can
23033 typeset and print this manual. First switch to the @file{gdb}
23034 subdirectory of the main source directory (for example, to
23035 @file{gdb-@value{GDBVN}/gdb}) and type:
23041 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
23043 @node Installing GDB
23044 @appendix Installing @value{GDBN}
23045 @cindex installation
23048 * Requirements:: Requirements for building @value{GDBN}
23049 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
23050 * Separate Objdir:: Compiling @value{GDBN} in another directory
23051 * Config Names:: Specifying names for hosts and targets
23052 * Configure Options:: Summary of options for configure
23056 @section Requirements for Building @value{GDBN}
23057 @cindex building @value{GDBN}, requirements for
23059 Building @value{GDBN} requires various tools and packages to be available.
23060 Other packages will be used only if they are found.
23062 @heading Tools/Packages Necessary for Building @value{GDBN}
23064 @item ISO C90 compiler
23065 @value{GDBN} is written in ISO C90. It should be buildable with any
23066 working C90 compiler, e.g.@: GCC.
23070 @heading Tools/Packages Optional for Building @value{GDBN}
23074 @value{GDBN} can use the Expat XML parsing library. This library may be
23075 included with your operating system distribution; if it is not, you
23076 can get the latest version from @url{http://expat.sourceforge.net}.
23077 The @file{configure} script will search for this library in several
23078 standard locations; if it is installed in an unusual path, you can
23079 use the @option{--with-libexpat-prefix} option to specify its location.
23085 Remote protocol memory maps (@pxref{Memory Map Format})
23087 Target descriptions (@pxref{Target Descriptions})
23089 Remote shared library lists (@pxref{Library List Format})
23091 MS-Windows shared libraries (@pxref{Shared Libraries})
23095 @cindex compressed debug sections
23096 @value{GDBN} will use the @samp{zlib} library, if available, to read
23097 compressed debug sections. Some linkers, such as GNU gold, are capable
23098 of producing binaries with compressed debug sections. If @value{GDBN}
23099 is compiled with @samp{zlib}, it will be able to read the debug
23100 information in such binaries.
23102 The @samp{zlib} library is likely included with your operating system
23103 distribution; if it is not, you can get the latest version from
23104 @url{http://zlib.net}.
23108 @node Running Configure
23109 @section Invoking the @value{GDBN} @file{configure} Script
23110 @cindex configuring @value{GDBN}
23111 @value{GDBN} comes with a @file{configure} script that automates the process
23112 of preparing @value{GDBN} for installation; you can then use @code{make} to
23113 build the @code{gdb} program.
23115 @c irrelevant in info file; it's as current as the code it lives with.
23116 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
23117 look at the @file{README} file in the sources; we may have improved the
23118 installation procedures since publishing this manual.}
23121 The @value{GDBN} distribution includes all the source code you need for
23122 @value{GDBN} in a single directory, whose name is usually composed by
23123 appending the version number to @samp{gdb}.
23125 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
23126 @file{gdb-@value{GDBVN}} directory. That directory contains:
23129 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
23130 script for configuring @value{GDBN} and all its supporting libraries
23132 @item gdb-@value{GDBVN}/gdb
23133 the source specific to @value{GDBN} itself
23135 @item gdb-@value{GDBVN}/bfd
23136 source for the Binary File Descriptor library
23138 @item gdb-@value{GDBVN}/include
23139 @sc{gnu} include files
23141 @item gdb-@value{GDBVN}/libiberty
23142 source for the @samp{-liberty} free software library
23144 @item gdb-@value{GDBVN}/opcodes
23145 source for the library of opcode tables and disassemblers
23147 @item gdb-@value{GDBVN}/readline
23148 source for the @sc{gnu} command-line interface
23150 @item gdb-@value{GDBVN}/glob
23151 source for the @sc{gnu} filename pattern-matching subroutine
23153 @item gdb-@value{GDBVN}/mmalloc
23154 source for the @sc{gnu} memory-mapped malloc package
23157 The simplest way to configure and build @value{GDBN} is to run @file{configure}
23158 from the @file{gdb-@var{version-number}} source directory, which in
23159 this example is the @file{gdb-@value{GDBVN}} directory.
23161 First switch to the @file{gdb-@var{version-number}} source directory
23162 if you are not already in it; then run @file{configure}. Pass the
23163 identifier for the platform on which @value{GDBN} will run as an
23169 cd gdb-@value{GDBVN}
23170 ./configure @var{host}
23175 where @var{host} is an identifier such as @samp{sun4} or
23176 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
23177 (You can often leave off @var{host}; @file{configure} tries to guess the
23178 correct value by examining your system.)
23180 Running @samp{configure @var{host}} and then running @code{make} builds the
23181 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
23182 libraries, then @code{gdb} itself. The configured source files, and the
23183 binaries, are left in the corresponding source directories.
23186 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
23187 system does not recognize this automatically when you run a different
23188 shell, you may need to run @code{sh} on it explicitly:
23191 sh configure @var{host}
23194 If you run @file{configure} from a directory that contains source
23195 directories for multiple libraries or programs, such as the
23196 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
23198 creates configuration files for every directory level underneath (unless
23199 you tell it not to, with the @samp{--norecursion} option).
23201 You should run the @file{configure} script from the top directory in the
23202 source tree, the @file{gdb-@var{version-number}} directory. If you run
23203 @file{configure} from one of the subdirectories, you will configure only
23204 that subdirectory. That is usually not what you want. In particular,
23205 if you run the first @file{configure} from the @file{gdb} subdirectory
23206 of the @file{gdb-@var{version-number}} directory, you will omit the
23207 configuration of @file{bfd}, @file{readline}, and other sibling
23208 directories of the @file{gdb} subdirectory. This leads to build errors
23209 about missing include files such as @file{bfd/bfd.h}.
23211 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
23212 However, you should make sure that the shell on your path (named by
23213 the @samp{SHELL} environment variable) is publicly readable. Remember
23214 that @value{GDBN} uses the shell to start your program---some systems refuse to
23215 let @value{GDBN} debug child processes whose programs are not readable.
23217 @node Separate Objdir
23218 @section Compiling @value{GDBN} in Another Directory
23220 If you want to run @value{GDBN} versions for several host or target machines,
23221 you need a different @code{gdb} compiled for each combination of
23222 host and target. @file{configure} is designed to make this easy by
23223 allowing you to generate each configuration in a separate subdirectory,
23224 rather than in the source directory. If your @code{make} program
23225 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
23226 @code{make} in each of these directories builds the @code{gdb}
23227 program specified there.
23229 To build @code{gdb} in a separate directory, run @file{configure}
23230 with the @samp{--srcdir} option to specify where to find the source.
23231 (You also need to specify a path to find @file{configure}
23232 itself from your working directory. If the path to @file{configure}
23233 would be the same as the argument to @samp{--srcdir}, you can leave out
23234 the @samp{--srcdir} option; it is assumed.)
23236 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
23237 separate directory for a Sun 4 like this:
23241 cd gdb-@value{GDBVN}
23244 ../gdb-@value{GDBVN}/configure sun4
23249 When @file{configure} builds a configuration using a remote source
23250 directory, it creates a tree for the binaries with the same structure
23251 (and using the same names) as the tree under the source directory. In
23252 the example, you'd find the Sun 4 library @file{libiberty.a} in the
23253 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
23254 @file{gdb-sun4/gdb}.
23256 Make sure that your path to the @file{configure} script has just one
23257 instance of @file{gdb} in it. If your path to @file{configure} looks
23258 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
23259 one subdirectory of @value{GDBN}, not the whole package. This leads to
23260 build errors about missing include files such as @file{bfd/bfd.h}.
23262 One popular reason to build several @value{GDBN} configurations in separate
23263 directories is to configure @value{GDBN} for cross-compiling (where
23264 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
23265 programs that run on another machine---the @dfn{target}).
23266 You specify a cross-debugging target by
23267 giving the @samp{--target=@var{target}} option to @file{configure}.
23269 When you run @code{make} to build a program or library, you must run
23270 it in a configured directory---whatever directory you were in when you
23271 called @file{configure} (or one of its subdirectories).
23273 The @code{Makefile} that @file{configure} generates in each source
23274 directory also runs recursively. If you type @code{make} in a source
23275 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
23276 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
23277 will build all the required libraries, and then build GDB.
23279 When you have multiple hosts or targets configured in separate
23280 directories, you can run @code{make} on them in parallel (for example,
23281 if they are NFS-mounted on each of the hosts); they will not interfere
23285 @section Specifying Names for Hosts and Targets
23287 The specifications used for hosts and targets in the @file{configure}
23288 script are based on a three-part naming scheme, but some short predefined
23289 aliases are also supported. The full naming scheme encodes three pieces
23290 of information in the following pattern:
23293 @var{architecture}-@var{vendor}-@var{os}
23296 For example, you can use the alias @code{sun4} as a @var{host} argument,
23297 or as the value for @var{target} in a @code{--target=@var{target}}
23298 option. The equivalent full name is @samp{sparc-sun-sunos4}.
23300 The @file{configure} script accompanying @value{GDBN} does not provide
23301 any query facility to list all supported host and target names or
23302 aliases. @file{configure} calls the Bourne shell script
23303 @code{config.sub} to map abbreviations to full names; you can read the
23304 script, if you wish, or you can use it to test your guesses on
23305 abbreviations---for example:
23308 % sh config.sub i386-linux
23310 % sh config.sub alpha-linux
23311 alpha-unknown-linux-gnu
23312 % sh config.sub hp9k700
23314 % sh config.sub sun4
23315 sparc-sun-sunos4.1.1
23316 % sh config.sub sun3
23317 m68k-sun-sunos4.1.1
23318 % sh config.sub i986v
23319 Invalid configuration `i986v': machine `i986v' not recognized
23323 @code{config.sub} is also distributed in the @value{GDBN} source
23324 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
23326 @node Configure Options
23327 @section @file{configure} Options
23329 Here is a summary of the @file{configure} options and arguments that
23330 are most often useful for building @value{GDBN}. @file{configure} also has
23331 several other options not listed here. @inforef{What Configure
23332 Does,,configure.info}, for a full explanation of @file{configure}.
23335 configure @r{[}--help@r{]}
23336 @r{[}--prefix=@var{dir}@r{]}
23337 @r{[}--exec-prefix=@var{dir}@r{]}
23338 @r{[}--srcdir=@var{dirname}@r{]}
23339 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
23340 @r{[}--target=@var{target}@r{]}
23345 You may introduce options with a single @samp{-} rather than
23346 @samp{--} if you prefer; but you may abbreviate option names if you use
23351 Display a quick summary of how to invoke @file{configure}.
23353 @item --prefix=@var{dir}
23354 Configure the source to install programs and files under directory
23357 @item --exec-prefix=@var{dir}
23358 Configure the source to install programs under directory
23361 @c avoid splitting the warning from the explanation:
23363 @item --srcdir=@var{dirname}
23364 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
23365 @code{make} that implements the @code{VPATH} feature.}@*
23366 Use this option to make configurations in directories separate from the
23367 @value{GDBN} source directories. Among other things, you can use this to
23368 build (or maintain) several configurations simultaneously, in separate
23369 directories. @file{configure} writes configuration-specific files in
23370 the current directory, but arranges for them to use the source in the
23371 directory @var{dirname}. @file{configure} creates directories under
23372 the working directory in parallel to the source directories below
23375 @item --norecursion
23376 Configure only the directory level where @file{configure} is executed; do not
23377 propagate configuration to subdirectories.
23379 @item --target=@var{target}
23380 Configure @value{GDBN} for cross-debugging programs running on the specified
23381 @var{target}. Without this option, @value{GDBN} is configured to debug
23382 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
23384 There is no convenient way to generate a list of all available targets.
23386 @item @var{host} @dots{}
23387 Configure @value{GDBN} to run on the specified @var{host}.
23389 There is no convenient way to generate a list of all available hosts.
23392 There are many other options available as well, but they are generally
23393 needed for special purposes only.
23395 @node Maintenance Commands
23396 @appendix Maintenance Commands
23397 @cindex maintenance commands
23398 @cindex internal commands
23400 In addition to commands intended for @value{GDBN} users, @value{GDBN}
23401 includes a number of commands intended for @value{GDBN} developers,
23402 that are not documented elsewhere in this manual. These commands are
23403 provided here for reference. (For commands that turn on debugging
23404 messages, see @ref{Debugging Output}.)
23407 @kindex maint agent
23408 @item maint agent @var{expression}
23409 Translate the given @var{expression} into remote agent bytecodes.
23410 This command is useful for debugging the Agent Expression mechanism
23411 (@pxref{Agent Expressions}).
23413 @kindex maint info breakpoints
23414 @item @anchor{maint info breakpoints}maint info breakpoints
23415 Using the same format as @samp{info breakpoints}, display both the
23416 breakpoints you've set explicitly, and those @value{GDBN} is using for
23417 internal purposes. Internal breakpoints are shown with negative
23418 breakpoint numbers. The type column identifies what kind of breakpoint
23423 Normal, explicitly set breakpoint.
23426 Normal, explicitly set watchpoint.
23429 Internal breakpoint, used to handle correctly stepping through
23430 @code{longjmp} calls.
23432 @item longjmp resume
23433 Internal breakpoint at the target of a @code{longjmp}.
23436 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
23439 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
23442 Shared library events.
23446 @kindex maint set can-use-displaced-stepping
23447 @kindex maint show can-use-displaced-stepping
23448 @cindex displaced stepping support
23449 @cindex out-of-line single-stepping
23450 @item maint set can-use-displaced-stepping
23451 @itemx maint show can-use-displaced-stepping
23452 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
23453 if the target supports it. The default is on. Displaced stepping is
23454 a way to single-step over breakpoints without removing them from the
23455 inferior, by executing an out-of-line copy of the instruction that was
23456 originally at the breakpoint location. It is also known as
23457 out-of-line single-stepping.
23459 @kindex maint check-symtabs
23460 @item maint check-symtabs
23461 Check the consistency of psymtabs and symtabs.
23463 @kindex maint cplus first_component
23464 @item maint cplus first_component @var{name}
23465 Print the first C@t{++} class/namespace component of @var{name}.
23467 @kindex maint cplus namespace
23468 @item maint cplus namespace
23469 Print the list of possible C@t{++} namespaces.
23471 @kindex maint demangle
23472 @item maint demangle @var{name}
23473 Demangle a C@t{++} or Objective-C mangled @var{name}.
23475 @kindex maint deprecate
23476 @kindex maint undeprecate
23477 @cindex deprecated commands
23478 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
23479 @itemx maint undeprecate @var{command}
23480 Deprecate or undeprecate the named @var{command}. Deprecated commands
23481 cause @value{GDBN} to issue a warning when you use them. The optional
23482 argument @var{replacement} says which newer command should be used in
23483 favor of the deprecated one; if it is given, @value{GDBN} will mention
23484 the replacement as part of the warning.
23486 @kindex maint dump-me
23487 @item maint dump-me
23488 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
23489 Cause a fatal signal in the debugger and force it to dump its core.
23490 This is supported only on systems which support aborting a program
23491 with the @code{SIGQUIT} signal.
23493 @kindex maint internal-error
23494 @kindex maint internal-warning
23495 @item maint internal-error @r{[}@var{message-text}@r{]}
23496 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
23497 Cause @value{GDBN} to call the internal function @code{internal_error}
23498 or @code{internal_warning} and hence behave as though an internal error
23499 or internal warning has been detected. In addition to reporting the
23500 internal problem, these functions give the user the opportunity to
23501 either quit @value{GDBN} or create a core file of the current
23502 @value{GDBN} session.
23504 These commands take an optional parameter @var{message-text} that is
23505 used as the text of the error or warning message.
23507 Here's an example of using @code{internal-error}:
23510 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
23511 @dots{}/maint.c:121: internal-error: testing, 1, 2
23512 A problem internal to GDB has been detected. Further
23513 debugging may prove unreliable.
23514 Quit this debugging session? (y or n) @kbd{n}
23515 Create a core file? (y or n) @kbd{n}
23519 @kindex maint packet
23520 @item maint packet @var{text}
23521 If @value{GDBN} is talking to an inferior via the serial protocol,
23522 then this command sends the string @var{text} to the inferior, and
23523 displays the response packet. @value{GDBN} supplies the initial
23524 @samp{$} character, the terminating @samp{#} character, and the
23527 @kindex maint print architecture
23528 @item maint print architecture @r{[}@var{file}@r{]}
23529 Print the entire architecture configuration. The optional argument
23530 @var{file} names the file where the output goes.
23532 @kindex maint print c-tdesc
23533 @item maint print c-tdesc
23534 Print the current target description (@pxref{Target Descriptions}) as
23535 a C source file. The created source file can be used in @value{GDBN}
23536 when an XML parser is not available to parse the description.
23538 @kindex maint print dummy-frames
23539 @item maint print dummy-frames
23540 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
23543 (@value{GDBP}) @kbd{b add}
23545 (@value{GDBP}) @kbd{print add(2,3)}
23546 Breakpoint 2, add (a=2, b=3) at @dots{}
23548 The program being debugged stopped while in a function called from GDB.
23550 (@value{GDBP}) @kbd{maint print dummy-frames}
23551 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
23552 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
23553 call_lo=0x01014000 call_hi=0x01014001
23557 Takes an optional file parameter.
23559 @kindex maint print registers
23560 @kindex maint print raw-registers
23561 @kindex maint print cooked-registers
23562 @kindex maint print register-groups
23563 @item maint print registers @r{[}@var{file}@r{]}
23564 @itemx maint print raw-registers @r{[}@var{file}@r{]}
23565 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
23566 @itemx maint print register-groups @r{[}@var{file}@r{]}
23567 Print @value{GDBN}'s internal register data structures.
23569 The command @code{maint print raw-registers} includes the contents of
23570 the raw register cache; the command @code{maint print cooked-registers}
23571 includes the (cooked) value of all registers; and the command
23572 @code{maint print register-groups} includes the groups that each
23573 register is a member of. @xref{Registers,, Registers, gdbint,
23574 @value{GDBN} Internals}.
23576 These commands take an optional parameter, a file name to which to
23577 write the information.
23579 @kindex maint print reggroups
23580 @item maint print reggroups @r{[}@var{file}@r{]}
23581 Print @value{GDBN}'s internal register group data structures. The
23582 optional argument @var{file} tells to what file to write the
23585 The register groups info looks like this:
23588 (@value{GDBP}) @kbd{maint print reggroups}
23601 This command forces @value{GDBN} to flush its internal register cache.
23603 @kindex maint print objfiles
23604 @cindex info for known object files
23605 @item maint print objfiles
23606 Print a dump of all known object files. For each object file, this
23607 command prints its name, address in memory, and all of its psymtabs
23610 @kindex maint print statistics
23611 @cindex bcache statistics
23612 @item maint print statistics
23613 This command prints, for each object file in the program, various data
23614 about that object file followed by the byte cache (@dfn{bcache})
23615 statistics for the object file. The objfile data includes the number
23616 of minimal, partial, full, and stabs symbols, the number of types
23617 defined by the objfile, the number of as yet unexpanded psym tables,
23618 the number of line tables and string tables, and the amount of memory
23619 used by the various tables. The bcache statistics include the counts,
23620 sizes, and counts of duplicates of all and unique objects, max,
23621 average, and median entry size, total memory used and its overhead and
23622 savings, and various measures of the hash table size and chain
23625 @kindex maint print target-stack
23626 @cindex target stack description
23627 @item maint print target-stack
23628 A @dfn{target} is an interface between the debugger and a particular
23629 kind of file or process. Targets can be stacked in @dfn{strata},
23630 so that more than one target can potentially respond to a request.
23631 In particular, memory accesses will walk down the stack of targets
23632 until they find a target that is interested in handling that particular
23635 This command prints a short description of each layer that was pushed on
23636 the @dfn{target stack}, starting from the top layer down to the bottom one.
23638 @kindex maint print type
23639 @cindex type chain of a data type
23640 @item maint print type @var{expr}
23641 Print the type chain for a type specified by @var{expr}. The argument
23642 can be either a type name or a symbol. If it is a symbol, the type of
23643 that symbol is described. The type chain produced by this command is
23644 a recursive definition of the data type as stored in @value{GDBN}'s
23645 data structures, including its flags and contained types.
23647 @kindex maint set dwarf2 max-cache-age
23648 @kindex maint show dwarf2 max-cache-age
23649 @item maint set dwarf2 max-cache-age
23650 @itemx maint show dwarf2 max-cache-age
23651 Control the DWARF 2 compilation unit cache.
23653 @cindex DWARF 2 compilation units cache
23654 In object files with inter-compilation-unit references, such as those
23655 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
23656 reader needs to frequently refer to previously read compilation units.
23657 This setting controls how long a compilation unit will remain in the
23658 cache if it is not referenced. A higher limit means that cached
23659 compilation units will be stored in memory longer, and more total
23660 memory will be used. Setting it to zero disables caching, which will
23661 slow down @value{GDBN} startup, but reduce memory consumption.
23663 @kindex maint set profile
23664 @kindex maint show profile
23665 @cindex profiling GDB
23666 @item maint set profile
23667 @itemx maint show profile
23668 Control profiling of @value{GDBN}.
23670 Profiling will be disabled until you use the @samp{maint set profile}
23671 command to enable it. When you enable profiling, the system will begin
23672 collecting timing and execution count data; when you disable profiling or
23673 exit @value{GDBN}, the results will be written to a log file. Remember that
23674 if you use profiling, @value{GDBN} will overwrite the profiling log file
23675 (often called @file{gmon.out}). If you have a record of important profiling
23676 data in a @file{gmon.out} file, be sure to move it to a safe location.
23678 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
23679 compiled with the @samp{-pg} compiler option.
23681 @kindex maint set linux-async
23682 @kindex maint show linux-async
23683 @cindex asynchronous support
23684 @item maint set linux-async
23685 @itemx maint show linux-async
23686 Control the GNU/Linux native asynchronous support of @value{GDBN}.
23688 GNU/Linux native asynchronous support will be disabled until you use
23689 the @samp{maint set linux-async} command to enable it.
23691 @kindex maint set remote-async
23692 @kindex maint show remote-async
23693 @cindex asynchronous support
23694 @item maint set remote-async
23695 @itemx maint show remote-async
23696 Control the remote asynchronous support of @value{GDBN}.
23698 Remote asynchronous support will be disabled until you use
23699 the @samp{maint set remote-async} command to enable it.
23701 @kindex maint show-debug-regs
23702 @cindex x86 hardware debug registers
23703 @item maint show-debug-regs
23704 Control whether to show variables that mirror the x86 hardware debug
23705 registers. Use @code{ON} to enable, @code{OFF} to disable. If
23706 enabled, the debug registers values are shown when @value{GDBN} inserts or
23707 removes a hardware breakpoint or watchpoint, and when the inferior
23708 triggers a hardware-assisted breakpoint or watchpoint.
23710 @kindex maint space
23711 @cindex memory used by commands
23713 Control whether to display memory usage for each command. If set to a
23714 nonzero value, @value{GDBN} will display how much memory each command
23715 took, following the command's own output. This can also be requested
23716 by invoking @value{GDBN} with the @option{--statistics} command-line
23717 switch (@pxref{Mode Options}).
23720 @cindex time of command execution
23722 Control whether to display the execution time for each command. If
23723 set to a nonzero value, @value{GDBN} will display how much time it
23724 took to execute each command, following the command's own output.
23725 The time is not printed for the commands that run the target, since
23726 there's no mechanism currently to compute how much time was spend
23727 by @value{GDBN} and how much time was spend by the program been debugged.
23728 it's not possibly currently
23729 This can also be requested by invoking @value{GDBN} with the
23730 @option{--statistics} command-line switch (@pxref{Mode Options}).
23732 @kindex maint translate-address
23733 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
23734 Find the symbol stored at the location specified by the address
23735 @var{addr} and an optional section name @var{section}. If found,
23736 @value{GDBN} prints the name of the closest symbol and an offset from
23737 the symbol's location to the specified address. This is similar to
23738 the @code{info address} command (@pxref{Symbols}), except that this
23739 command also allows to find symbols in other sections.
23743 The following command is useful for non-interactive invocations of
23744 @value{GDBN}, such as in the test suite.
23747 @item set watchdog @var{nsec}
23748 @kindex set watchdog
23749 @cindex watchdog timer
23750 @cindex timeout for commands
23751 Set the maximum number of seconds @value{GDBN} will wait for the
23752 target operation to finish. If this time expires, @value{GDBN}
23753 reports and error and the command is aborted.
23755 @item show watchdog
23756 Show the current setting of the target wait timeout.
23759 @node Remote Protocol
23760 @appendix @value{GDBN} Remote Serial Protocol
23765 * Stop Reply Packets::
23766 * General Query Packets::
23767 * Register Packet Format::
23768 * Tracepoint Packets::
23769 * Host I/O Packets::
23772 * File-I/O Remote Protocol Extension::
23773 * Library List Format::
23774 * Memory Map Format::
23780 There may be occasions when you need to know something about the
23781 protocol---for example, if there is only one serial port to your target
23782 machine, you might want your program to do something special if it
23783 recognizes a packet meant for @value{GDBN}.
23785 In the examples below, @samp{->} and @samp{<-} are used to indicate
23786 transmitted and received data, respectively.
23788 @cindex protocol, @value{GDBN} remote serial
23789 @cindex serial protocol, @value{GDBN} remote
23790 @cindex remote serial protocol
23791 All @value{GDBN} commands and responses (other than acknowledgments) are
23792 sent as a @var{packet}. A @var{packet} is introduced with the character
23793 @samp{$}, the actual @var{packet-data}, and the terminating character
23794 @samp{#} followed by a two-digit @var{checksum}:
23797 @code{$}@var{packet-data}@code{#}@var{checksum}
23801 @cindex checksum, for @value{GDBN} remote
23803 The two-digit @var{checksum} is computed as the modulo 256 sum of all
23804 characters between the leading @samp{$} and the trailing @samp{#} (an
23805 eight bit unsigned checksum).
23807 Implementors should note that prior to @value{GDBN} 5.0 the protocol
23808 specification also included an optional two-digit @var{sequence-id}:
23811 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
23814 @cindex sequence-id, for @value{GDBN} remote
23816 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
23817 has never output @var{sequence-id}s. Stubs that handle packets added
23818 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
23820 @cindex acknowledgment, for @value{GDBN} remote
23821 When either the host or the target machine receives a packet, the first
23822 response expected is an acknowledgment: either @samp{+} (to indicate
23823 the package was received correctly) or @samp{-} (to request
23827 -> @code{$}@var{packet-data}@code{#}@var{checksum}
23832 The host (@value{GDBN}) sends @var{command}s, and the target (the
23833 debugging stub incorporated in your program) sends a @var{response}. In
23834 the case of step and continue @var{command}s, the response is only sent
23835 when the operation has completed (the target has again stopped).
23837 @var{packet-data} consists of a sequence of characters with the
23838 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
23841 @cindex remote protocol, field separator
23842 Fields within the packet should be separated using @samp{,} @samp{;} or
23843 @samp{:}. Except where otherwise noted all numbers are represented in
23844 @sc{hex} with leading zeros suppressed.
23846 Implementors should note that prior to @value{GDBN} 5.0, the character
23847 @samp{:} could not appear as the third character in a packet (as it
23848 would potentially conflict with the @var{sequence-id}).
23850 @cindex remote protocol, binary data
23851 @anchor{Binary Data}
23852 Binary data in most packets is encoded either as two hexadecimal
23853 digits per byte of binary data. This allowed the traditional remote
23854 protocol to work over connections which were only seven-bit clean.
23855 Some packets designed more recently assume an eight-bit clean
23856 connection, and use a more efficient encoding to send and receive
23859 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
23860 as an escape character. Any escaped byte is transmitted as the escape
23861 character followed by the original character XORed with @code{0x20}.
23862 For example, the byte @code{0x7d} would be transmitted as the two
23863 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
23864 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
23865 @samp{@}}) must always be escaped. Responses sent by the stub
23866 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
23867 is not interpreted as the start of a run-length encoded sequence
23870 Response @var{data} can be run-length encoded to save space.
23871 Run-length encoding replaces runs of identical characters with one
23872 instance of the repeated character, followed by a @samp{*} and a
23873 repeat count. The repeat count is itself sent encoded, to avoid
23874 binary characters in @var{data}: a value of @var{n} is sent as
23875 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
23876 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
23877 code 32) for a repeat count of 3. (This is because run-length
23878 encoding starts to win for counts 3 or more.) Thus, for example,
23879 @samp{0* } is a run-length encoding of ``0000'': the space character
23880 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
23883 The printable characters @samp{#} and @samp{$} or with a numeric value
23884 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
23885 seven repeats (@samp{$}) can be expanded using a repeat count of only
23886 five (@samp{"}). For example, @samp{00000000} can be encoded as
23889 The error response returned for some packets includes a two character
23890 error number. That number is not well defined.
23892 @cindex empty response, for unsupported packets
23893 For any @var{command} not supported by the stub, an empty response
23894 (@samp{$#00}) should be returned. That way it is possible to extend the
23895 protocol. A newer @value{GDBN} can tell if a packet is supported based
23898 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
23899 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
23905 The following table provides a complete list of all currently defined
23906 @var{command}s and their corresponding response @var{data}.
23907 @xref{File-I/O Remote Protocol Extension}, for details about the File
23908 I/O extension of the remote protocol.
23910 Each packet's description has a template showing the packet's overall
23911 syntax, followed by an explanation of the packet's meaning. We
23912 include spaces in some of the templates for clarity; these are not
23913 part of the packet's syntax. No @value{GDBN} packet uses spaces to
23914 separate its components. For example, a template like @samp{foo
23915 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
23916 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
23917 @var{baz}. @value{GDBN} does not transmit a space character between the
23918 @samp{foo} and the @var{bar}, or between the @var{bar} and the
23921 Note that all packet forms beginning with an upper- or lower-case
23922 letter, other than those described here, are reserved for future use.
23924 Here are the packet descriptions.
23929 @cindex @samp{!} packet
23930 @anchor{extended mode}
23931 Enable extended mode. In extended mode, the remote server is made
23932 persistent. The @samp{R} packet is used to restart the program being
23938 The remote target both supports and has enabled extended mode.
23942 @cindex @samp{?} packet
23943 Indicate the reason the target halted. The reply is the same as for
23947 @xref{Stop Reply Packets}, for the reply specifications.
23949 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
23950 @cindex @samp{A} packet
23951 Initialized @code{argv[]} array passed into program. @var{arglen}
23952 specifies the number of bytes in the hex encoded byte stream
23953 @var{arg}. See @code{gdbserver} for more details.
23958 The arguments were set.
23964 @cindex @samp{b} packet
23965 (Don't use this packet; its behavior is not well-defined.)
23966 Change the serial line speed to @var{baud}.
23968 JTC: @emph{When does the transport layer state change? When it's
23969 received, or after the ACK is transmitted. In either case, there are
23970 problems if the command or the acknowledgment packet is dropped.}
23972 Stan: @emph{If people really wanted to add something like this, and get
23973 it working for the first time, they ought to modify ser-unix.c to send
23974 some kind of out-of-band message to a specially-setup stub and have the
23975 switch happen "in between" packets, so that from remote protocol's point
23976 of view, nothing actually happened.}
23978 @item B @var{addr},@var{mode}
23979 @cindex @samp{B} packet
23980 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
23981 breakpoint at @var{addr}.
23983 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
23984 (@pxref{insert breakpoint or watchpoint packet}).
23986 @item c @r{[}@var{addr}@r{]}
23987 @cindex @samp{c} packet
23988 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
23989 resume at current address.
23992 @xref{Stop Reply Packets}, for the reply specifications.
23994 @item C @var{sig}@r{[};@var{addr}@r{]}
23995 @cindex @samp{C} packet
23996 Continue with signal @var{sig} (hex signal number). If
23997 @samp{;@var{addr}} is omitted, resume at same address.
24000 @xref{Stop Reply Packets}, for the reply specifications.
24003 @cindex @samp{d} packet
24006 Don't use this packet; instead, define a general set packet
24007 (@pxref{General Query Packets}).
24010 @cindex @samp{D} packet
24011 Detach @value{GDBN} from the remote system. Sent to the remote target
24012 before @value{GDBN} disconnects via the @code{detach} command.
24022 @item F @var{RC},@var{EE},@var{CF};@var{XX}
24023 @cindex @samp{F} packet
24024 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
24025 This is part of the File-I/O protocol extension. @xref{File-I/O
24026 Remote Protocol Extension}, for the specification.
24029 @anchor{read registers packet}
24030 @cindex @samp{g} packet
24031 Read general registers.
24035 @item @var{XX@dots{}}
24036 Each byte of register data is described by two hex digits. The bytes
24037 with the register are transmitted in target byte order. The size of
24038 each register and their position within the @samp{g} packet are
24039 determined by the @value{GDBN} internal gdbarch functions
24040 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
24041 specification of several standard @samp{g} packets is specified below.
24046 @item G @var{XX@dots{}}
24047 @cindex @samp{G} packet
24048 Write general registers. @xref{read registers packet}, for a
24049 description of the @var{XX@dots{}} data.
24059 @item H @var{c} @var{t}
24060 @cindex @samp{H} packet
24061 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
24062 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
24063 should be @samp{c} for step and continue operations, @samp{g} for other
24064 operations. The thread designator @var{t} may be @samp{-1}, meaning all
24065 the threads, a thread number, or @samp{0} which means pick any thread.
24076 @c 'H': How restrictive (or permissive) is the thread model. If a
24077 @c thread is selected and stopped, are other threads allowed
24078 @c to continue to execute? As I mentioned above, I think the
24079 @c semantics of each command when a thread is selected must be
24080 @c described. For example:
24082 @c 'g': If the stub supports threads and a specific thread is
24083 @c selected, returns the register block from that thread;
24084 @c otherwise returns current registers.
24086 @c 'G' If the stub supports threads and a specific thread is
24087 @c selected, sets the registers of the register block of
24088 @c that thread; otherwise sets current registers.
24090 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
24091 @anchor{cycle step packet}
24092 @cindex @samp{i} packet
24093 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
24094 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
24095 step starting at that address.
24098 @cindex @samp{I} packet
24099 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
24103 @cindex @samp{k} packet
24106 FIXME: @emph{There is no description of how to operate when a specific
24107 thread context has been selected (i.e.@: does 'k' kill only that
24110 @item m @var{addr},@var{length}
24111 @cindex @samp{m} packet
24112 Read @var{length} bytes of memory starting at address @var{addr}.
24113 Note that @var{addr} may not be aligned to any particular boundary.
24115 The stub need not use any particular size or alignment when gathering
24116 data from memory for the response; even if @var{addr} is word-aligned
24117 and @var{length} is a multiple of the word size, the stub is free to
24118 use byte accesses, or not. For this reason, this packet may not be
24119 suitable for accessing memory-mapped I/O devices.
24120 @cindex alignment of remote memory accesses
24121 @cindex size of remote memory accesses
24122 @cindex memory, alignment and size of remote accesses
24126 @item @var{XX@dots{}}
24127 Memory contents; each byte is transmitted as a two-digit hexadecimal
24128 number. The reply may contain fewer bytes than requested if the
24129 server was able to read only part of the region of memory.
24134 @item M @var{addr},@var{length}:@var{XX@dots{}}
24135 @cindex @samp{M} packet
24136 Write @var{length} bytes of memory starting at address @var{addr}.
24137 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
24138 hexadecimal number.
24145 for an error (this includes the case where only part of the data was
24150 @cindex @samp{p} packet
24151 Read the value of register @var{n}; @var{n} is in hex.
24152 @xref{read registers packet}, for a description of how the returned
24153 register value is encoded.
24157 @item @var{XX@dots{}}
24158 the register's value
24162 Indicating an unrecognized @var{query}.
24165 @item P @var{n@dots{}}=@var{r@dots{}}
24166 @anchor{write register packet}
24167 @cindex @samp{P} packet
24168 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
24169 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
24170 digits for each byte in the register (target byte order).
24180 @item q @var{name} @var{params}@dots{}
24181 @itemx Q @var{name} @var{params}@dots{}
24182 @cindex @samp{q} packet
24183 @cindex @samp{Q} packet
24184 General query (@samp{q}) and set (@samp{Q}). These packets are
24185 described fully in @ref{General Query Packets}.
24188 @cindex @samp{r} packet
24189 Reset the entire system.
24191 Don't use this packet; use the @samp{R} packet instead.
24194 @cindex @samp{R} packet
24195 Restart the program being debugged. @var{XX}, while needed, is ignored.
24196 This packet is only available in extended mode (@pxref{extended mode}).
24198 The @samp{R} packet has no reply.
24200 @item s @r{[}@var{addr}@r{]}
24201 @cindex @samp{s} packet
24202 Single step. @var{addr} is the address at which to resume. If
24203 @var{addr} is omitted, resume at same address.
24206 @xref{Stop Reply Packets}, for the reply specifications.
24208 @item S @var{sig}@r{[};@var{addr}@r{]}
24209 @anchor{step with signal packet}
24210 @cindex @samp{S} packet
24211 Step with signal. This is analogous to the @samp{C} packet, but
24212 requests a single-step, rather than a normal resumption of execution.
24215 @xref{Stop Reply Packets}, for the reply specifications.
24217 @item t @var{addr}:@var{PP},@var{MM}
24218 @cindex @samp{t} packet
24219 Search backwards starting at address @var{addr} for a match with pattern
24220 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
24221 @var{addr} must be at least 3 digits.
24224 @cindex @samp{T} packet
24225 Find out if the thread XX is alive.
24230 thread is still alive
24236 Packets starting with @samp{v} are identified by a multi-letter name,
24237 up to the first @samp{;} or @samp{?} (or the end of the packet).
24239 @item vAttach;@var{pid}
24240 @cindex @samp{vAttach} packet
24241 Attach to a new process with the specified process ID. @var{pid} is a
24242 hexadecimal integer identifying the process. The attached process is
24245 This packet is only available in extended mode (@pxref{extended mode}).
24251 @item @r{Any stop packet}
24252 for success (@pxref{Stop Reply Packets})
24255 @item vCont@r{[};@var{action}@r{[}:@var{tid}@r{]]}@dots{}
24256 @cindex @samp{vCont} packet
24257 Resume the inferior, specifying different actions for each thread.
24258 If an action is specified with no @var{tid}, then it is applied to any
24259 threads that don't have a specific action specified; if no default action is
24260 specified then other threads should remain stopped. Specifying multiple
24261 default actions is an error; specifying no actions is also an error.
24262 Thread IDs are specified in hexadecimal. Currently supported actions are:
24268 Continue with signal @var{sig}. @var{sig} should be two hex digits.
24272 Step with signal @var{sig}. @var{sig} should be two hex digits.
24275 The optional @var{addr} argument normally associated with these packets is
24276 not supported in @samp{vCont}.
24279 @xref{Stop Reply Packets}, for the reply specifications.
24282 @cindex @samp{vCont?} packet
24283 Request a list of actions supported by the @samp{vCont} packet.
24287 @item vCont@r{[};@var{action}@dots{}@r{]}
24288 The @samp{vCont} packet is supported. Each @var{action} is a supported
24289 command in the @samp{vCont} packet.
24291 The @samp{vCont} packet is not supported.
24294 @item vFile:@var{operation}:@var{parameter}@dots{}
24295 @cindex @samp{vFile} packet
24296 Perform a file operation on the target system. For details,
24297 see @ref{Host I/O Packets}.
24299 @item vFlashErase:@var{addr},@var{length}
24300 @cindex @samp{vFlashErase} packet
24301 Direct the stub to erase @var{length} bytes of flash starting at
24302 @var{addr}. The region may enclose any number of flash blocks, but
24303 its start and end must fall on block boundaries, as indicated by the
24304 flash block size appearing in the memory map (@pxref{Memory Map
24305 Format}). @value{GDBN} groups flash memory programming operations
24306 together, and sends a @samp{vFlashDone} request after each group; the
24307 stub is allowed to delay erase operation until the @samp{vFlashDone}
24308 packet is received.
24318 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
24319 @cindex @samp{vFlashWrite} packet
24320 Direct the stub to write data to flash address @var{addr}. The data
24321 is passed in binary form using the same encoding as for the @samp{X}
24322 packet (@pxref{Binary Data}). The memory ranges specified by
24323 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
24324 not overlap, and must appear in order of increasing addresses
24325 (although @samp{vFlashErase} packets for higher addresses may already
24326 have been received; the ordering is guaranteed only between
24327 @samp{vFlashWrite} packets). If a packet writes to an address that was
24328 neither erased by a preceding @samp{vFlashErase} packet nor by some other
24329 target-specific method, the results are unpredictable.
24337 for vFlashWrite addressing non-flash memory
24343 @cindex @samp{vFlashDone} packet
24344 Indicate to the stub that flash programming operation is finished.
24345 The stub is permitted to delay or batch the effects of a group of
24346 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
24347 @samp{vFlashDone} packet is received. The contents of the affected
24348 regions of flash memory are unpredictable until the @samp{vFlashDone}
24349 request is completed.
24351 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
24352 @cindex @samp{vRun} packet
24353 Run the program @var{filename}, passing it each @var{argument} on its
24354 command line. The file and arguments are hex-encoded strings. If
24355 @var{filename} is an empty string, the stub may use a default program
24356 (e.g.@: the last program run). The program is created in the stopped
24359 This packet is only available in extended mode (@pxref{extended mode}).
24365 @item @r{Any stop packet}
24366 for success (@pxref{Stop Reply Packets})
24369 @item X @var{addr},@var{length}:@var{XX@dots{}}
24371 @cindex @samp{X} packet
24372 Write data to memory, where the data is transmitted in binary.
24373 @var{addr} is address, @var{length} is number of bytes,
24374 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
24384 @item z @var{type},@var{addr},@var{length}
24385 @itemx Z @var{type},@var{addr},@var{length}
24386 @anchor{insert breakpoint or watchpoint packet}
24387 @cindex @samp{z} packet
24388 @cindex @samp{Z} packets
24389 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
24390 watchpoint starting at address @var{address} and covering the next
24391 @var{length} bytes.
24393 Each breakpoint and watchpoint packet @var{type} is documented
24396 @emph{Implementation notes: A remote target shall return an empty string
24397 for an unrecognized breakpoint or watchpoint packet @var{type}. A
24398 remote target shall support either both or neither of a given
24399 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
24400 avoid potential problems with duplicate packets, the operations should
24401 be implemented in an idempotent way.}
24403 @item z0,@var{addr},@var{length}
24404 @itemx Z0,@var{addr},@var{length}
24405 @cindex @samp{z0} packet
24406 @cindex @samp{Z0} packet
24407 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
24408 @var{addr} of size @var{length}.
24410 A memory breakpoint is implemented by replacing the instruction at
24411 @var{addr} with a software breakpoint or trap instruction. The
24412 @var{length} is used by targets that indicates the size of the
24413 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
24414 @sc{mips} can insert either a 2 or 4 byte breakpoint).
24416 @emph{Implementation note: It is possible for a target to copy or move
24417 code that contains memory breakpoints (e.g., when implementing
24418 overlays). The behavior of this packet, in the presence of such a
24419 target, is not defined.}
24431 @item z1,@var{addr},@var{length}
24432 @itemx Z1,@var{addr},@var{length}
24433 @cindex @samp{z1} packet
24434 @cindex @samp{Z1} packet
24435 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
24436 address @var{addr} of size @var{length}.
24438 A hardware breakpoint is implemented using a mechanism that is not
24439 dependant on being able to modify the target's memory.
24441 @emph{Implementation note: A hardware breakpoint is not affected by code
24454 @item z2,@var{addr},@var{length}
24455 @itemx Z2,@var{addr},@var{length}
24456 @cindex @samp{z2} packet
24457 @cindex @samp{Z2} packet
24458 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint.
24470 @item z3,@var{addr},@var{length}
24471 @itemx Z3,@var{addr},@var{length}
24472 @cindex @samp{z3} packet
24473 @cindex @samp{Z3} packet
24474 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint.
24486 @item z4,@var{addr},@var{length}
24487 @itemx Z4,@var{addr},@var{length}
24488 @cindex @samp{z4} packet
24489 @cindex @samp{Z4} packet
24490 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint.
24504 @node Stop Reply Packets
24505 @section Stop Reply Packets
24506 @cindex stop reply packets
24508 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
24509 receive any of the below as a reply. In the case of the @samp{C},
24510 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
24511 when the target halts. In the below the exact meaning of @dfn{signal
24512 number} is defined by the header @file{include/gdb/signals.h} in the
24513 @value{GDBN} source code.
24515 As in the description of request packets, we include spaces in the
24516 reply templates for clarity; these are not part of the reply packet's
24517 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
24523 The program received signal number @var{AA} (a two-digit hexadecimal
24524 number). This is equivalent to a @samp{T} response with no
24525 @var{n}:@var{r} pairs.
24527 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
24528 @cindex @samp{T} packet reply
24529 The program received signal number @var{AA} (a two-digit hexadecimal
24530 number). This is equivalent to an @samp{S} response, except that the
24531 @samp{@var{n}:@var{r}} pairs can carry values of important registers
24532 and other information directly in the stop reply packet, reducing
24533 round-trip latency. Single-step and breakpoint traps are reported
24534 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
24538 If @var{n} is a hexadecimal number, it is a register number, and the
24539 corresponding @var{r} gives that register's value. @var{r} is a
24540 series of bytes in target byte order, with each byte given by a
24541 two-digit hex number.
24544 If @var{n} is @samp{thread}, then @var{r} is the thread process ID, in
24548 If @var{n} is a recognized @dfn{stop reason}, it describes a more
24549 specific event that stopped the target. The currently defined stop
24550 reasons are listed below. @var{aa} should be @samp{05}, the trap
24551 signal. At most one stop reason should be present.
24554 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
24555 and go on to the next; this allows us to extend the protocol in the
24559 The currently defined stop reasons are:
24565 The packet indicates a watchpoint hit, and @var{r} is the data address, in
24568 @cindex shared library events, remote reply
24570 The packet indicates that the loaded libraries have changed.
24571 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
24572 list of loaded libraries. @var{r} is ignored.
24576 The process exited, and @var{AA} is the exit status. This is only
24577 applicable to certain targets.
24580 The process terminated with signal @var{AA}.
24582 @item O @var{XX}@dots{}
24583 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
24584 written as the program's console output. This can happen at any time
24585 while the program is running and the debugger should continue to wait
24586 for @samp{W}, @samp{T}, etc.
24588 @item F @var{call-id},@var{parameter}@dots{}
24589 @var{call-id} is the identifier which says which host system call should
24590 be called. This is just the name of the function. Translation into the
24591 correct system call is only applicable as it's defined in @value{GDBN}.
24592 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
24595 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
24596 this very system call.
24598 The target replies with this packet when it expects @value{GDBN} to
24599 call a host system call on behalf of the target. @value{GDBN} replies
24600 with an appropriate @samp{F} packet and keeps up waiting for the next
24601 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
24602 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
24603 Protocol Extension}, for more details.
24607 @node General Query Packets
24608 @section General Query Packets
24609 @cindex remote query requests
24611 Packets starting with @samp{q} are @dfn{general query packets};
24612 packets starting with @samp{Q} are @dfn{general set packets}. General
24613 query and set packets are a semi-unified form for retrieving and
24614 sending information to and from the stub.
24616 The initial letter of a query or set packet is followed by a name
24617 indicating what sort of thing the packet applies to. For example,
24618 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
24619 definitions with the stub. These packet names follow some
24624 The name must not contain commas, colons or semicolons.
24626 Most @value{GDBN} query and set packets have a leading upper case
24629 The names of custom vendor packets should use a company prefix, in
24630 lower case, followed by a period. For example, packets designed at
24631 the Acme Corporation might begin with @samp{qacme.foo} (for querying
24632 foos) or @samp{Qacme.bar} (for setting bars).
24635 The name of a query or set packet should be separated from any
24636 parameters by a @samp{:}; the parameters themselves should be
24637 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
24638 full packet name, and check for a separator or the end of the packet,
24639 in case two packet names share a common prefix. New packets should not begin
24640 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
24641 packets predate these conventions, and have arguments without any terminator
24642 for the packet name; we suspect they are in widespread use in places that
24643 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
24644 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
24647 Like the descriptions of the other packets, each description here
24648 has a template showing the packet's overall syntax, followed by an
24649 explanation of the packet's meaning. We include spaces in some of the
24650 templates for clarity; these are not part of the packet's syntax. No
24651 @value{GDBN} packet uses spaces to separate its components.
24653 Here are the currently defined query and set packets:
24658 @cindex current thread, remote request
24659 @cindex @samp{qC} packet
24660 Return the current thread id.
24665 Where @var{pid} is an unsigned hexadecimal process id.
24666 @item @r{(anything else)}
24667 Any other reply implies the old pid.
24670 @item qCRC:@var{addr},@var{length}
24671 @cindex CRC of memory block, remote request
24672 @cindex @samp{qCRC} packet
24673 Compute the CRC checksum of a block of memory.
24677 An error (such as memory fault)
24678 @item C @var{crc32}
24679 The specified memory region's checksum is @var{crc32}.
24683 @itemx qsThreadInfo
24684 @cindex list active threads, remote request
24685 @cindex @samp{qfThreadInfo} packet
24686 @cindex @samp{qsThreadInfo} packet
24687 Obtain a list of all active thread ids from the target (OS). Since there
24688 may be too many active threads to fit into one reply packet, this query
24689 works iteratively: it may require more than one query/reply sequence to
24690 obtain the entire list of threads. The first query of the sequence will
24691 be the @samp{qfThreadInfo} query; subsequent queries in the
24692 sequence will be the @samp{qsThreadInfo} query.
24694 NOTE: This packet replaces the @samp{qL} query (see below).
24700 @item m @var{id},@var{id}@dots{}
24701 a comma-separated list of thread ids
24703 (lower case letter @samp{L}) denotes end of list.
24706 In response to each query, the target will reply with a list of one or
24707 more thread ids, in big-endian unsigned hex, separated by commas.
24708 @value{GDBN} will respond to each reply with a request for more thread
24709 ids (using the @samp{qs} form of the query), until the target responds
24710 with @samp{l} (lower-case el, for @dfn{last}).
24712 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
24713 @cindex get thread-local storage address, remote request
24714 @cindex @samp{qGetTLSAddr} packet
24715 Fetch the address associated with thread local storage specified
24716 by @var{thread-id}, @var{offset}, and @var{lm}.
24718 @var{thread-id} is the (big endian, hex encoded) thread id associated with the
24719 thread for which to fetch the TLS address.
24721 @var{offset} is the (big endian, hex encoded) offset associated with the
24722 thread local variable. (This offset is obtained from the debug
24723 information associated with the variable.)
24725 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
24726 the load module associated with the thread local storage. For example,
24727 a @sc{gnu}/Linux system will pass the link map address of the shared
24728 object associated with the thread local storage under consideration.
24729 Other operating environments may choose to represent the load module
24730 differently, so the precise meaning of this parameter will vary.
24734 @item @var{XX}@dots{}
24735 Hex encoded (big endian) bytes representing the address of the thread
24736 local storage requested.
24739 An error occurred. @var{nn} are hex digits.
24742 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
24745 @item qL @var{startflag} @var{threadcount} @var{nextthread}
24746 Obtain thread information from RTOS. Where: @var{startflag} (one hex
24747 digit) is one to indicate the first query and zero to indicate a
24748 subsequent query; @var{threadcount} (two hex digits) is the maximum
24749 number of threads the response packet can contain; and @var{nextthread}
24750 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
24751 returned in the response as @var{argthread}.
24753 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
24757 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
24758 Where: @var{count} (two hex digits) is the number of threads being
24759 returned; @var{done} (one hex digit) is zero to indicate more threads
24760 and one indicates no further threads; @var{argthreadid} (eight hex
24761 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
24762 is a sequence of thread IDs from the target. @var{threadid} (eight hex
24763 digits). See @code{remote.c:parse_threadlist_response()}.
24767 @cindex section offsets, remote request
24768 @cindex @samp{qOffsets} packet
24769 Get section offsets that the target used when relocating the downloaded
24774 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
24775 Relocate the @code{Text} section by @var{xxx} from its original address.
24776 Relocate the @code{Data} section by @var{yyy} from its original address.
24777 If the object file format provides segment information (e.g.@: @sc{elf}
24778 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
24779 segments by the supplied offsets.
24781 @emph{Note: while a @code{Bss} offset may be included in the response,
24782 @value{GDBN} ignores this and instead applies the @code{Data} offset
24783 to the @code{Bss} section.}
24785 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
24786 Relocate the first segment of the object file, which conventionally
24787 contains program code, to a starting address of @var{xxx}. If
24788 @samp{DataSeg} is specified, relocate the second segment, which
24789 conventionally contains modifiable data, to a starting address of
24790 @var{yyy}. @value{GDBN} will report an error if the object file
24791 does not contain segment information, or does not contain at least
24792 as many segments as mentioned in the reply. Extra segments are
24793 kept at fixed offsets relative to the last relocated segment.
24796 @item qP @var{mode} @var{threadid}
24797 @cindex thread information, remote request
24798 @cindex @samp{qP} packet
24799 Returns information on @var{threadid}. Where: @var{mode} is a hex
24800 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
24802 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
24805 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
24807 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
24808 @cindex pass signals to inferior, remote request
24809 @cindex @samp{QPassSignals} packet
24810 @anchor{QPassSignals}
24811 Each listed @var{signal} should be passed directly to the inferior process.
24812 Signals are numbered identically to continue packets and stop replies
24813 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
24814 strictly greater than the previous item. These signals do not need to stop
24815 the inferior, or be reported to @value{GDBN}. All other signals should be
24816 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
24817 combine; any earlier @samp{QPassSignals} list is completely replaced by the
24818 new list. This packet improves performance when using @samp{handle
24819 @var{signal} nostop noprint pass}.
24824 The request succeeded.
24827 An error occurred. @var{nn} are hex digits.
24830 An empty reply indicates that @samp{QPassSignals} is not supported by
24834 Use of this packet is controlled by the @code{set remote pass-signals}
24835 command (@pxref{Remote Configuration, set remote pass-signals}).
24836 This packet is not probed by default; the remote stub must request it,
24837 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24839 @item qRcmd,@var{command}
24840 @cindex execute remote command, remote request
24841 @cindex @samp{qRcmd} packet
24842 @var{command} (hex encoded) is passed to the local interpreter for
24843 execution. Invalid commands should be reported using the output
24844 string. Before the final result packet, the target may also respond
24845 with a number of intermediate @samp{O@var{output}} console output
24846 packets. @emph{Implementors should note that providing access to a
24847 stubs's interpreter may have security implications}.
24852 A command response with no output.
24854 A command response with the hex encoded output string @var{OUTPUT}.
24856 Indicate a badly formed request.
24858 An empty reply indicates that @samp{qRcmd} is not recognized.
24861 (Note that the @code{qRcmd} packet's name is separated from the
24862 command by a @samp{,}, not a @samp{:}, contrary to the naming
24863 conventions above. Please don't use this packet as a model for new
24866 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
24867 @cindex searching memory, in remote debugging
24868 @cindex @samp{qSearch:memory} packet
24869 @anchor{qSearch memory}
24870 Search @var{length} bytes at @var{address} for @var{search-pattern}.
24871 @var{address} and @var{length} are encoded in hex.
24872 @var{search-pattern} is a sequence of bytes, hex encoded.
24877 The pattern was not found.
24879 The pattern was found at @var{address}.
24881 A badly formed request or an error was encountered while searching memory.
24883 An empty reply indicates that @samp{qSearch:memory} is not recognized.
24886 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
24887 @cindex supported packets, remote query
24888 @cindex features of the remote protocol
24889 @cindex @samp{qSupported} packet
24890 @anchor{qSupported}
24891 Tell the remote stub about features supported by @value{GDBN}, and
24892 query the stub for features it supports. This packet allows
24893 @value{GDBN} and the remote stub to take advantage of each others'
24894 features. @samp{qSupported} also consolidates multiple feature probes
24895 at startup, to improve @value{GDBN} performance---a single larger
24896 packet performs better than multiple smaller probe packets on
24897 high-latency links. Some features may enable behavior which must not
24898 be on by default, e.g.@: because it would confuse older clients or
24899 stubs. Other features may describe packets which could be
24900 automatically probed for, but are not. These features must be
24901 reported before @value{GDBN} will use them. This ``default
24902 unsupported'' behavior is not appropriate for all packets, but it
24903 helps to keep the initial connection time under control with new
24904 versions of @value{GDBN} which support increasing numbers of packets.
24908 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
24909 The stub supports or does not support each returned @var{stubfeature},
24910 depending on the form of each @var{stubfeature} (see below for the
24913 An empty reply indicates that @samp{qSupported} is not recognized,
24914 or that no features needed to be reported to @value{GDBN}.
24917 The allowed forms for each feature (either a @var{gdbfeature} in the
24918 @samp{qSupported} packet, or a @var{stubfeature} in the response)
24922 @item @var{name}=@var{value}
24923 The remote protocol feature @var{name} is supported, and associated
24924 with the specified @var{value}. The format of @var{value} depends
24925 on the feature, but it must not include a semicolon.
24927 The remote protocol feature @var{name} is supported, and does not
24928 need an associated value.
24930 The remote protocol feature @var{name} is not supported.
24932 The remote protocol feature @var{name} may be supported, and
24933 @value{GDBN} should auto-detect support in some other way when it is
24934 needed. This form will not be used for @var{gdbfeature} notifications,
24935 but may be used for @var{stubfeature} responses.
24938 Whenever the stub receives a @samp{qSupported} request, the
24939 supplied set of @value{GDBN} features should override any previous
24940 request. This allows @value{GDBN} to put the stub in a known
24941 state, even if the stub had previously been communicating with
24942 a different version of @value{GDBN}.
24944 No values of @var{gdbfeature} (for the packet sent by @value{GDBN})
24945 are defined yet. Stubs should ignore any unknown values for
24946 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
24947 packet supports receiving packets of unlimited length (earlier
24948 versions of @value{GDBN} may reject overly long responses). Values
24949 for @var{gdbfeature} may be defined in the future to let the stub take
24950 advantage of new features in @value{GDBN}, e.g.@: incompatible
24951 improvements in the remote protocol---support for unlimited length
24952 responses would be a @var{gdbfeature} example, if it were not implied by
24953 the @samp{qSupported} query. The stub's reply should be independent
24954 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
24955 describes all the features it supports, and then the stub replies with
24956 all the features it supports.
24958 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
24959 responses, as long as each response uses one of the standard forms.
24961 Some features are flags. A stub which supports a flag feature
24962 should respond with a @samp{+} form response. Other features
24963 require values, and the stub should respond with an @samp{=}
24966 Each feature has a default value, which @value{GDBN} will use if
24967 @samp{qSupported} is not available or if the feature is not mentioned
24968 in the @samp{qSupported} response. The default values are fixed; a
24969 stub is free to omit any feature responses that match the defaults.
24971 Not all features can be probed, but for those which can, the probing
24972 mechanism is useful: in some cases, a stub's internal
24973 architecture may not allow the protocol layer to know some information
24974 about the underlying target in advance. This is especially common in
24975 stubs which may be configured for multiple targets.
24977 These are the currently defined stub features and their properties:
24979 @multitable @columnfractions 0.35 0.2 0.12 0.2
24980 @c NOTE: The first row should be @headitem, but we do not yet require
24981 @c a new enough version of Texinfo (4.7) to use @headitem.
24983 @tab Value Required
24987 @item @samp{PacketSize}
24992 @item @samp{qXfer:auxv:read}
24997 @item @samp{qXfer:features:read}
25002 @item @samp{qXfer:libraries:read}
25007 @item @samp{qXfer:memory-map:read}
25012 @item @samp{qXfer:spu:read}
25017 @item @samp{qXfer:spu:write}
25022 @item @samp{QPassSignals}
25029 These are the currently defined stub features, in more detail:
25032 @cindex packet size, remote protocol
25033 @item PacketSize=@var{bytes}
25034 The remote stub can accept packets up to at least @var{bytes} in
25035 length. @value{GDBN} will send packets up to this size for bulk
25036 transfers, and will never send larger packets. This is a limit on the
25037 data characters in the packet, including the frame and checksum.
25038 There is no trailing NUL byte in a remote protocol packet; if the stub
25039 stores packets in a NUL-terminated format, it should allow an extra
25040 byte in its buffer for the NUL. If this stub feature is not supported,
25041 @value{GDBN} guesses based on the size of the @samp{g} packet response.
25043 @item qXfer:auxv:read
25044 The remote stub understands the @samp{qXfer:auxv:read} packet
25045 (@pxref{qXfer auxiliary vector read}).
25047 @item qXfer:features:read
25048 The remote stub understands the @samp{qXfer:features:read} packet
25049 (@pxref{qXfer target description read}).
25051 @item qXfer:libraries:read
25052 The remote stub understands the @samp{qXfer:libraries:read} packet
25053 (@pxref{qXfer library list read}).
25055 @item qXfer:memory-map:read
25056 The remote stub understands the @samp{qXfer:memory-map:read} packet
25057 (@pxref{qXfer memory map read}).
25059 @item qXfer:spu:read
25060 The remote stub understands the @samp{qXfer:spu:read} packet
25061 (@pxref{qXfer spu read}).
25063 @item qXfer:spu:write
25064 The remote stub understands the @samp{qXfer:spu:write} packet
25065 (@pxref{qXfer spu write}).
25068 The remote stub understands the @samp{QPassSignals} packet
25069 (@pxref{QPassSignals}).
25074 @cindex symbol lookup, remote request
25075 @cindex @samp{qSymbol} packet
25076 Notify the target that @value{GDBN} is prepared to serve symbol lookup
25077 requests. Accept requests from the target for the values of symbols.
25082 The target does not need to look up any (more) symbols.
25083 @item qSymbol:@var{sym_name}
25084 The target requests the value of symbol @var{sym_name} (hex encoded).
25085 @value{GDBN} may provide the value by using the
25086 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
25090 @item qSymbol:@var{sym_value}:@var{sym_name}
25091 Set the value of @var{sym_name} to @var{sym_value}.
25093 @var{sym_name} (hex encoded) is the name of a symbol whose value the
25094 target has previously requested.
25096 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
25097 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
25103 The target does not need to look up any (more) symbols.
25104 @item qSymbol:@var{sym_name}
25105 The target requests the value of a new symbol @var{sym_name} (hex
25106 encoded). @value{GDBN} will continue to supply the values of symbols
25107 (if available), until the target ceases to request them.
25112 @xref{Tracepoint Packets}.
25114 @item qThreadExtraInfo,@var{id}
25115 @cindex thread attributes info, remote request
25116 @cindex @samp{qThreadExtraInfo} packet
25117 Obtain a printable string description of a thread's attributes from
25118 the target OS. @var{id} is a thread-id in big-endian hex. This
25119 string may contain anything that the target OS thinks is interesting
25120 for @value{GDBN} to tell the user about the thread. The string is
25121 displayed in @value{GDBN}'s @code{info threads} display. Some
25122 examples of possible thread extra info strings are @samp{Runnable}, or
25123 @samp{Blocked on Mutex}.
25127 @item @var{XX}@dots{}
25128 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
25129 comprising the printable string containing the extra information about
25130 the thread's attributes.
25133 (Note that the @code{qThreadExtraInfo} packet's name is separated from
25134 the command by a @samp{,}, not a @samp{:}, contrary to the naming
25135 conventions above. Please don't use this packet as a model for new
25143 @xref{Tracepoint Packets}.
25145 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
25146 @cindex read special object, remote request
25147 @cindex @samp{qXfer} packet
25148 @anchor{qXfer read}
25149 Read uninterpreted bytes from the target's special data area
25150 identified by the keyword @var{object}. Request @var{length} bytes
25151 starting at @var{offset} bytes into the data. The content and
25152 encoding of @var{annex} is specific to @var{object}; it can supply
25153 additional details about what data to access.
25155 Here are the specific requests of this form defined so far. All
25156 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
25157 formats, listed below.
25160 @item qXfer:auxv:read::@var{offset},@var{length}
25161 @anchor{qXfer auxiliary vector read}
25162 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
25163 auxiliary vector}. Note @var{annex} must be empty.
25165 This packet is not probed by default; the remote stub must request it,
25166 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25168 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
25169 @anchor{qXfer target description read}
25170 Access the @dfn{target description}. @xref{Target Descriptions}. The
25171 annex specifies which XML document to access. The main description is
25172 always loaded from the @samp{target.xml} annex.
25174 This packet is not probed by default; the remote stub must request it,
25175 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25177 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
25178 @anchor{qXfer library list read}
25179 Access the target's list of loaded libraries. @xref{Library List Format}.
25180 The annex part of the generic @samp{qXfer} packet must be empty
25181 (@pxref{qXfer read}).
25183 Targets which maintain a list of libraries in the program's memory do
25184 not need to implement this packet; it is designed for platforms where
25185 the operating system manages the list of loaded libraries.
25187 This packet is not probed by default; the remote stub must request it,
25188 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25190 @item qXfer:memory-map:read::@var{offset},@var{length}
25191 @anchor{qXfer memory map read}
25192 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
25193 annex part of the generic @samp{qXfer} packet must be empty
25194 (@pxref{qXfer read}).
25196 This packet is not probed by default; the remote stub must request it,
25197 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25199 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
25200 @anchor{qXfer spu read}
25201 Read contents of an @code{spufs} file on the target system. The
25202 annex specifies which file to read; it must be of the form
25203 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
25204 in the target process, and @var{name} identifes the @code{spufs} file
25205 in that context to be accessed.
25207 This packet is not probed by default; the remote stub must request it,
25208 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25214 Data @var{data} (@pxref{Binary Data}) has been read from the
25215 target. There may be more data at a higher address (although
25216 it is permitted to return @samp{m} even for the last valid
25217 block of data, as long as at least one byte of data was read).
25218 @var{data} may have fewer bytes than the @var{length} in the
25222 Data @var{data} (@pxref{Binary Data}) has been read from the target.
25223 There is no more data to be read. @var{data} may have fewer bytes
25224 than the @var{length} in the request.
25227 The @var{offset} in the request is at the end of the data.
25228 There is no more data to be read.
25231 The request was malformed, or @var{annex} was invalid.
25234 The offset was invalid, or there was an error encountered reading the data.
25235 @var{nn} is a hex-encoded @code{errno} value.
25238 An empty reply indicates the @var{object} string was not recognized by
25239 the stub, or that the object does not support reading.
25242 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
25243 @cindex write data into object, remote request
25244 Write uninterpreted bytes into the target's special data area
25245 identified by the keyword @var{object}, starting at @var{offset} bytes
25246 into the data. @var{data}@dots{} is the binary-encoded data
25247 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
25248 is specific to @var{object}; it can supply additional details about what data
25251 Here are the specific requests of this form defined so far. All
25252 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
25253 formats, listed below.
25256 @item qXfer:@var{spu}:write:@var{annex}:@var{offset}:@var{data}@dots{}
25257 @anchor{qXfer spu write}
25258 Write @var{data} to an @code{spufs} file on the target system. The
25259 annex specifies which file to write; it must be of the form
25260 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
25261 in the target process, and @var{name} identifes the @code{spufs} file
25262 in that context to be accessed.
25264 This packet is not probed by default; the remote stub must request it,
25265 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25271 @var{nn} (hex encoded) is the number of bytes written.
25272 This may be fewer bytes than supplied in the request.
25275 The request was malformed, or @var{annex} was invalid.
25278 The offset was invalid, or there was an error encountered writing the data.
25279 @var{nn} is a hex-encoded @code{errno} value.
25282 An empty reply indicates the @var{object} string was not
25283 recognized by the stub, or that the object does not support writing.
25286 @item qXfer:@var{object}:@var{operation}:@dots{}
25287 Requests of this form may be added in the future. When a stub does
25288 not recognize the @var{object} keyword, or its support for
25289 @var{object} does not recognize the @var{operation} keyword, the stub
25290 must respond with an empty packet.
25294 @node Register Packet Format
25295 @section Register Packet Format
25297 The following @code{g}/@code{G} packets have previously been defined.
25298 In the below, some thirty-two bit registers are transferred as
25299 sixty-four bits. Those registers should be zero/sign extended (which?)
25300 to fill the space allocated. Register bytes are transferred in target
25301 byte order. The two nibbles within a register byte are transferred
25302 most-significant - least-significant.
25308 All registers are transferred as thirty-two bit quantities in the order:
25309 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
25310 registers; fsr; fir; fp.
25314 All registers are transferred as sixty-four bit quantities (including
25315 thirty-two bit registers such as @code{sr}). The ordering is the same
25320 @node Tracepoint Packets
25321 @section Tracepoint Packets
25322 @cindex tracepoint packets
25323 @cindex packets, tracepoint
25325 Here we describe the packets @value{GDBN} uses to implement
25326 tracepoints (@pxref{Tracepoints}).
25330 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}@r{[}-@r{]}
25331 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
25332 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
25333 the tracepoint is disabled. @var{step} is the tracepoint's step
25334 count, and @var{pass} is its pass count. If the trailing @samp{-} is
25335 present, further @samp{QTDP} packets will follow to specify this
25336 tracepoint's actions.
25341 The packet was understood and carried out.
25343 The packet was not recognized.
25346 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
25347 Define actions to be taken when a tracepoint is hit. @var{n} and
25348 @var{addr} must be the same as in the initial @samp{QTDP} packet for
25349 this tracepoint. This packet may only be sent immediately after
25350 another @samp{QTDP} packet that ended with a @samp{-}. If the
25351 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
25352 specifying more actions for this tracepoint.
25354 In the series of action packets for a given tracepoint, at most one
25355 can have an @samp{S} before its first @var{action}. If such a packet
25356 is sent, it and the following packets define ``while-stepping''
25357 actions. Any prior packets define ordinary actions --- that is, those
25358 taken when the tracepoint is first hit. If no action packet has an
25359 @samp{S}, then all the packets in the series specify ordinary
25360 tracepoint actions.
25362 The @samp{@var{action}@dots{}} portion of the packet is a series of
25363 actions, concatenated without separators. Each action has one of the
25369 Collect the registers whose bits are set in @var{mask}. @var{mask} is
25370 a hexadecimal number whose @var{i}'th bit is set if register number
25371 @var{i} should be collected. (The least significant bit is numbered
25372 zero.) Note that @var{mask} may be any number of digits long; it may
25373 not fit in a 32-bit word.
25375 @item M @var{basereg},@var{offset},@var{len}
25376 Collect @var{len} bytes of memory starting at the address in register
25377 number @var{basereg}, plus @var{offset}. If @var{basereg} is
25378 @samp{-1}, then the range has a fixed address: @var{offset} is the
25379 address of the lowest byte to collect. The @var{basereg},
25380 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
25381 values (the @samp{-1} value for @var{basereg} is a special case).
25383 @item X @var{len},@var{expr}
25384 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
25385 it directs. @var{expr} is an agent expression, as described in
25386 @ref{Agent Expressions}. Each byte of the expression is encoded as a
25387 two-digit hex number in the packet; @var{len} is the number of bytes
25388 in the expression (and thus one-half the number of hex digits in the
25393 Any number of actions may be packed together in a single @samp{QTDP}
25394 packet, as long as the packet does not exceed the maximum packet
25395 length (400 bytes, for many stubs). There may be only one @samp{R}
25396 action per tracepoint, and it must precede any @samp{M} or @samp{X}
25397 actions. Any registers referred to by @samp{M} and @samp{X} actions
25398 must be collected by a preceding @samp{R} action. (The
25399 ``while-stepping'' actions are treated as if they were attached to a
25400 separate tracepoint, as far as these restrictions are concerned.)
25405 The packet was understood and carried out.
25407 The packet was not recognized.
25410 @item QTFrame:@var{n}
25411 Select the @var{n}'th tracepoint frame from the buffer, and use the
25412 register and memory contents recorded there to answer subsequent
25413 request packets from @value{GDBN}.
25415 A successful reply from the stub indicates that the stub has found the
25416 requested frame. The response is a series of parts, concatenated
25417 without separators, describing the frame we selected. Each part has
25418 one of the following forms:
25422 The selected frame is number @var{n} in the trace frame buffer;
25423 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
25424 was no frame matching the criteria in the request packet.
25427 The selected trace frame records a hit of tracepoint number @var{t};
25428 @var{t} is a hexadecimal number.
25432 @item QTFrame:pc:@var{addr}
25433 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
25434 currently selected frame whose PC is @var{addr};
25435 @var{addr} is a hexadecimal number.
25437 @item QTFrame:tdp:@var{t}
25438 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
25439 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
25440 is a hexadecimal number.
25442 @item QTFrame:range:@var{start}:@var{end}
25443 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
25444 currently selected frame whose PC is between @var{start} (inclusive)
25445 and @var{end} (exclusive); @var{start} and @var{end} are hexadecimal
25448 @item QTFrame:outside:@var{start}:@var{end}
25449 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
25450 frame @emph{outside} the given range of addresses.
25453 Begin the tracepoint experiment. Begin collecting data from tracepoint
25454 hits in the trace frame buffer.
25457 End the tracepoint experiment. Stop collecting trace frames.
25460 Clear the table of tracepoints, and empty the trace frame buffer.
25462 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
25463 Establish the given ranges of memory as ``transparent''. The stub
25464 will answer requests for these ranges from memory's current contents,
25465 if they were not collected as part of the tracepoint hit.
25467 @value{GDBN} uses this to mark read-only regions of memory, like those
25468 containing program code. Since these areas never change, they should
25469 still have the same contents they did when the tracepoint was hit, so
25470 there's no reason for the stub to refuse to provide their contents.
25473 Ask the stub if there is a trace experiment running right now.
25478 There is no trace experiment running.
25480 There is a trace experiment running.
25486 @node Host I/O Packets
25487 @section Host I/O Packets
25488 @cindex Host I/O, remote protocol
25489 @cindex file transfer, remote protocol
25491 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
25492 operations on the far side of a remote link. For example, Host I/O is
25493 used to upload and download files to a remote target with its own
25494 filesystem. Host I/O uses the same constant values and data structure
25495 layout as the target-initiated File-I/O protocol. However, the
25496 Host I/O packets are structured differently. The target-initiated
25497 protocol relies on target memory to store parameters and buffers.
25498 Host I/O requests are initiated by @value{GDBN}, and the
25499 target's memory is not involved. @xref{File-I/O Remote Protocol
25500 Extension}, for more details on the target-initiated protocol.
25502 The Host I/O request packets all encode a single operation along with
25503 its arguments. They have this format:
25507 @item vFile:@var{operation}: @var{parameter}@dots{}
25508 @var{operation} is the name of the particular request; the target
25509 should compare the entire packet name up to the second colon when checking
25510 for a supported operation. The format of @var{parameter} depends on
25511 the operation. Numbers are always passed in hexadecimal. Negative
25512 numbers have an explicit minus sign (i.e.@: two's complement is not
25513 used). Strings (e.g.@: filenames) are encoded as a series of
25514 hexadecimal bytes. The last argument to a system call may be a
25515 buffer of escaped binary data (@pxref{Binary Data}).
25519 The valid responses to Host I/O packets are:
25523 @item F @var{result} [, @var{errno}] [; @var{attachment}]
25524 @var{result} is the integer value returned by this operation, usually
25525 non-negative for success and -1 for errors. If an error has occured,
25526 @var{errno} will be included in the result. @var{errno} will have a
25527 value defined by the File-I/O protocol (@pxref{Errno Values}). For
25528 operations which return data, @var{attachment} supplies the data as a
25529 binary buffer. Binary buffers in response packets are escaped in the
25530 normal way (@pxref{Binary Data}). See the individual packet
25531 documentation for the interpretation of @var{result} and
25535 An empty response indicates that this operation is not recognized.
25539 These are the supported Host I/O operations:
25542 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
25543 Open a file at @var{pathname} and return a file descriptor for it, or
25544 return -1 if an error occurs. @var{pathname} is a string,
25545 @var{flags} is an integer indicating a mask of open flags
25546 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
25547 of mode bits to use if the file is created (@pxref{mode_t Values}).
25548 @xref{open}, for details of the open flags and mode values.
25550 @item vFile:close: @var{fd}
25551 Close the open file corresponding to @var{fd} and return 0, or
25552 -1 if an error occurs.
25554 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
25555 Read data from the open file corresponding to @var{fd}. Up to
25556 @var{count} bytes will be read from the file, starting at @var{offset}
25557 relative to the start of the file. The target may read fewer bytes;
25558 common reasons include packet size limits and an end-of-file
25559 condition. The number of bytes read is returned. Zero should only be
25560 returned for a successful read at the end of the file, or if
25561 @var{count} was zero.
25563 The data read should be returned as a binary attachment on success.
25564 If zero bytes were read, the response should include an empty binary
25565 attachment (i.e.@: a trailing semicolon). The return value is the
25566 number of target bytes read; the binary attachment may be longer if
25567 some characters were escaped.
25569 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
25570 Write @var{data} (a binary buffer) to the open file corresponding
25571 to @var{fd}. Start the write at @var{offset} from the start of the
25572 file. Unlike many @code{write} system calls, there is no
25573 separate @var{count} argument; the length of @var{data} in the
25574 packet is used. @samp{vFile:write} returns the number of bytes written,
25575 which may be shorter than the length of @var{data}, or -1 if an
25578 @item vFile:unlink: @var{pathname}
25579 Delete the file at @var{pathname} on the target. Return 0,
25580 or -1 if an error occurs. @var{pathname} is a string.
25585 @section Interrupts
25586 @cindex interrupts (remote protocol)
25588 When a program on the remote target is running, @value{GDBN} may
25589 attempt to interrupt it by sending a @samp{Ctrl-C} or a @code{BREAK},
25590 control of which is specified via @value{GDBN}'s @samp{remotebreak}
25591 setting (@pxref{set remotebreak}).
25593 The precise meaning of @code{BREAK} is defined by the transport
25594 mechanism and may, in fact, be undefined. @value{GDBN} does
25595 not currently define a @code{BREAK} mechanism for any of the network
25598 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
25599 transport mechanisms. It is represented by sending the single byte
25600 @code{0x03} without any of the usual packet overhead described in
25601 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
25602 transmitted as part of a packet, it is considered to be packet data
25603 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
25604 (@pxref{X packet}), used for binary downloads, may include an unescaped
25605 @code{0x03} as part of its packet.
25607 Stubs are not required to recognize these interrupt mechanisms and the
25608 precise meaning associated with receipt of the interrupt is
25609 implementation defined. If the stub is successful at interrupting the
25610 running program, it is expected that it will send one of the Stop
25611 Reply Packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
25612 of successfully stopping the program. Interrupts received while the
25613 program is stopped will be discarded.
25618 Example sequence of a target being re-started. Notice how the restart
25619 does not get any direct output:
25624 @emph{target restarts}
25627 <- @code{T001:1234123412341234}
25631 Example sequence of a target being stepped by a single instruction:
25634 -> @code{G1445@dots{}}
25639 <- @code{T001:1234123412341234}
25643 <- @code{1455@dots{}}
25647 @node File-I/O Remote Protocol Extension
25648 @section File-I/O Remote Protocol Extension
25649 @cindex File-I/O remote protocol extension
25652 * File-I/O Overview::
25653 * Protocol Basics::
25654 * The F Request Packet::
25655 * The F Reply Packet::
25656 * The Ctrl-C Message::
25658 * List of Supported Calls::
25659 * Protocol-specific Representation of Datatypes::
25661 * File-I/O Examples::
25664 @node File-I/O Overview
25665 @subsection File-I/O Overview
25666 @cindex file-i/o overview
25668 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
25669 target to use the host's file system and console I/O to perform various
25670 system calls. System calls on the target system are translated into a
25671 remote protocol packet to the host system, which then performs the needed
25672 actions and returns a response packet to the target system.
25673 This simulates file system operations even on targets that lack file systems.
25675 The protocol is defined to be independent of both the host and target systems.
25676 It uses its own internal representation of datatypes and values. Both
25677 @value{GDBN} and the target's @value{GDBN} stub are responsible for
25678 translating the system-dependent value representations into the internal
25679 protocol representations when data is transmitted.
25681 The communication is synchronous. A system call is possible only when
25682 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
25683 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
25684 the target is stopped to allow deterministic access to the target's
25685 memory. Therefore File-I/O is not interruptible by target signals. On
25686 the other hand, it is possible to interrupt File-I/O by a user interrupt
25687 (@samp{Ctrl-C}) within @value{GDBN}.
25689 The target's request to perform a host system call does not finish
25690 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
25691 after finishing the system call, the target returns to continuing the
25692 previous activity (continue, step). No additional continue or step
25693 request from @value{GDBN} is required.
25696 (@value{GDBP}) continue
25697 <- target requests 'system call X'
25698 target is stopped, @value{GDBN} executes system call
25699 -> @value{GDBN} returns result
25700 ... target continues, @value{GDBN} returns to wait for the target
25701 <- target hits breakpoint and sends a Txx packet
25704 The protocol only supports I/O on the console and to regular files on
25705 the host file system. Character or block special devices, pipes,
25706 named pipes, sockets or any other communication method on the host
25707 system are not supported by this protocol.
25709 @node Protocol Basics
25710 @subsection Protocol Basics
25711 @cindex protocol basics, file-i/o
25713 The File-I/O protocol uses the @code{F} packet as the request as well
25714 as reply packet. Since a File-I/O system call can only occur when
25715 @value{GDBN} is waiting for a response from the continuing or stepping target,
25716 the File-I/O request is a reply that @value{GDBN} has to expect as a result
25717 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
25718 This @code{F} packet contains all information needed to allow @value{GDBN}
25719 to call the appropriate host system call:
25723 A unique identifier for the requested system call.
25726 All parameters to the system call. Pointers are given as addresses
25727 in the target memory address space. Pointers to strings are given as
25728 pointer/length pair. Numerical values are given as they are.
25729 Numerical control flags are given in a protocol-specific representation.
25733 At this point, @value{GDBN} has to perform the following actions.
25737 If the parameters include pointer values to data needed as input to a
25738 system call, @value{GDBN} requests this data from the target with a
25739 standard @code{m} packet request. This additional communication has to be
25740 expected by the target implementation and is handled as any other @code{m}
25744 @value{GDBN} translates all value from protocol representation to host
25745 representation as needed. Datatypes are coerced into the host types.
25748 @value{GDBN} calls the system call.
25751 It then coerces datatypes back to protocol representation.
25754 If the system call is expected to return data in buffer space specified
25755 by pointer parameters to the call, the data is transmitted to the
25756 target using a @code{M} or @code{X} packet. This packet has to be expected
25757 by the target implementation and is handled as any other @code{M} or @code{X}
25762 Eventually @value{GDBN} replies with another @code{F} packet which contains all
25763 necessary information for the target to continue. This at least contains
25770 @code{errno}, if has been changed by the system call.
25777 After having done the needed type and value coercion, the target continues
25778 the latest continue or step action.
25780 @node The F Request Packet
25781 @subsection The @code{F} Request Packet
25782 @cindex file-i/o request packet
25783 @cindex @code{F} request packet
25785 The @code{F} request packet has the following format:
25788 @item F@var{call-id},@var{parameter@dots{}}
25790 @var{call-id} is the identifier to indicate the host system call to be called.
25791 This is just the name of the function.
25793 @var{parameter@dots{}} are the parameters to the system call.
25794 Parameters are hexadecimal integer values, either the actual values in case
25795 of scalar datatypes, pointers to target buffer space in case of compound
25796 datatypes and unspecified memory areas, or pointer/length pairs in case
25797 of string parameters. These are appended to the @var{call-id} as a
25798 comma-delimited list. All values are transmitted in ASCII
25799 string representation, pointer/length pairs separated by a slash.
25805 @node The F Reply Packet
25806 @subsection The @code{F} Reply Packet
25807 @cindex file-i/o reply packet
25808 @cindex @code{F} reply packet
25810 The @code{F} reply packet has the following format:
25814 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
25816 @var{retcode} is the return code of the system call as hexadecimal value.
25818 @var{errno} is the @code{errno} set by the call, in protocol-specific
25820 This parameter can be omitted if the call was successful.
25822 @var{Ctrl-C flag} is only sent if the user requested a break. In this
25823 case, @var{errno} must be sent as well, even if the call was successful.
25824 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
25831 or, if the call was interrupted before the host call has been performed:
25838 assuming 4 is the protocol-specific representation of @code{EINTR}.
25843 @node The Ctrl-C Message
25844 @subsection The @samp{Ctrl-C} Message
25845 @cindex ctrl-c message, in file-i/o protocol
25847 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
25848 reply packet (@pxref{The F Reply Packet}),
25849 the target should behave as if it had
25850 gotten a break message. The meaning for the target is ``system call
25851 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
25852 (as with a break message) and return to @value{GDBN} with a @code{T02}
25855 It's important for the target to know in which
25856 state the system call was interrupted. There are two possible cases:
25860 The system call hasn't been performed on the host yet.
25863 The system call on the host has been finished.
25867 These two states can be distinguished by the target by the value of the
25868 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
25869 call hasn't been performed. This is equivalent to the @code{EINTR} handling
25870 on POSIX systems. In any other case, the target may presume that the
25871 system call has been finished --- successfully or not --- and should behave
25872 as if the break message arrived right after the system call.
25874 @value{GDBN} must behave reliably. If the system call has not been called
25875 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
25876 @code{errno} in the packet. If the system call on the host has been finished
25877 before the user requests a break, the full action must be finished by
25878 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
25879 The @code{F} packet may only be sent when either nothing has happened
25880 or the full action has been completed.
25883 @subsection Console I/O
25884 @cindex console i/o as part of file-i/o
25886 By default and if not explicitly closed by the target system, the file
25887 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
25888 on the @value{GDBN} console is handled as any other file output operation
25889 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
25890 by @value{GDBN} so that after the target read request from file descriptor
25891 0 all following typing is buffered until either one of the following
25896 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
25898 system call is treated as finished.
25901 The user presses @key{RET}. This is treated as end of input with a trailing
25905 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
25906 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
25910 If the user has typed more characters than fit in the buffer given to
25911 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
25912 either another @code{read(0, @dots{})} is requested by the target, or debugging
25913 is stopped at the user's request.
25916 @node List of Supported Calls
25917 @subsection List of Supported Calls
25918 @cindex list of supported file-i/o calls
25935 @unnumberedsubsubsec open
25936 @cindex open, file-i/o system call
25941 int open(const char *pathname, int flags);
25942 int open(const char *pathname, int flags, mode_t mode);
25946 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
25949 @var{flags} is the bitwise @code{OR} of the following values:
25953 If the file does not exist it will be created. The host
25954 rules apply as far as file ownership and time stamps
25958 When used with @code{O_CREAT}, if the file already exists it is
25959 an error and open() fails.
25962 If the file already exists and the open mode allows
25963 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
25964 truncated to zero length.
25967 The file is opened in append mode.
25970 The file is opened for reading only.
25973 The file is opened for writing only.
25976 The file is opened for reading and writing.
25980 Other bits are silently ignored.
25984 @var{mode} is the bitwise @code{OR} of the following values:
25988 User has read permission.
25991 User has write permission.
25994 Group has read permission.
25997 Group has write permission.
26000 Others have read permission.
26003 Others have write permission.
26007 Other bits are silently ignored.
26010 @item Return value:
26011 @code{open} returns the new file descriptor or -1 if an error
26018 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
26021 @var{pathname} refers to a directory.
26024 The requested access is not allowed.
26027 @var{pathname} was too long.
26030 A directory component in @var{pathname} does not exist.
26033 @var{pathname} refers to a device, pipe, named pipe or socket.
26036 @var{pathname} refers to a file on a read-only filesystem and
26037 write access was requested.
26040 @var{pathname} is an invalid pointer value.
26043 No space on device to create the file.
26046 The process already has the maximum number of files open.
26049 The limit on the total number of files open on the system
26053 The call was interrupted by the user.
26059 @unnumberedsubsubsec close
26060 @cindex close, file-i/o system call
26069 @samp{Fclose,@var{fd}}
26071 @item Return value:
26072 @code{close} returns zero on success, or -1 if an error occurred.
26078 @var{fd} isn't a valid open file descriptor.
26081 The call was interrupted by the user.
26087 @unnumberedsubsubsec read
26088 @cindex read, file-i/o system call
26093 int read(int fd, void *buf, unsigned int count);
26097 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
26099 @item Return value:
26100 On success, the number of bytes read is returned.
26101 Zero indicates end of file. If count is zero, read
26102 returns zero as well. On error, -1 is returned.
26108 @var{fd} is not a valid file descriptor or is not open for
26112 @var{bufptr} is an invalid pointer value.
26115 The call was interrupted by the user.
26121 @unnumberedsubsubsec write
26122 @cindex write, file-i/o system call
26127 int write(int fd, const void *buf, unsigned int count);
26131 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
26133 @item Return value:
26134 On success, the number of bytes written are returned.
26135 Zero indicates nothing was written. On error, -1
26142 @var{fd} is not a valid file descriptor or is not open for
26146 @var{bufptr} is an invalid pointer value.
26149 An attempt was made to write a file that exceeds the
26150 host-specific maximum file size allowed.
26153 No space on device to write the data.
26156 The call was interrupted by the user.
26162 @unnumberedsubsubsec lseek
26163 @cindex lseek, file-i/o system call
26168 long lseek (int fd, long offset, int flag);
26172 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
26174 @var{flag} is one of:
26178 The offset is set to @var{offset} bytes.
26181 The offset is set to its current location plus @var{offset}
26185 The offset is set to the size of the file plus @var{offset}
26189 @item Return value:
26190 On success, the resulting unsigned offset in bytes from
26191 the beginning of the file is returned. Otherwise, a
26192 value of -1 is returned.
26198 @var{fd} is not a valid open file descriptor.
26201 @var{fd} is associated with the @value{GDBN} console.
26204 @var{flag} is not a proper value.
26207 The call was interrupted by the user.
26213 @unnumberedsubsubsec rename
26214 @cindex rename, file-i/o system call
26219 int rename(const char *oldpath, const char *newpath);
26223 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
26225 @item Return value:
26226 On success, zero is returned. On error, -1 is returned.
26232 @var{newpath} is an existing directory, but @var{oldpath} is not a
26236 @var{newpath} is a non-empty directory.
26239 @var{oldpath} or @var{newpath} is a directory that is in use by some
26243 An attempt was made to make a directory a subdirectory
26247 A component used as a directory in @var{oldpath} or new
26248 path is not a directory. Or @var{oldpath} is a directory
26249 and @var{newpath} exists but is not a directory.
26252 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
26255 No access to the file or the path of the file.
26259 @var{oldpath} or @var{newpath} was too long.
26262 A directory component in @var{oldpath} or @var{newpath} does not exist.
26265 The file is on a read-only filesystem.
26268 The device containing the file has no room for the new
26272 The call was interrupted by the user.
26278 @unnumberedsubsubsec unlink
26279 @cindex unlink, file-i/o system call
26284 int unlink(const char *pathname);
26288 @samp{Funlink,@var{pathnameptr}/@var{len}}
26290 @item Return value:
26291 On success, zero is returned. On error, -1 is returned.
26297 No access to the file or the path of the file.
26300 The system does not allow unlinking of directories.
26303 The file @var{pathname} cannot be unlinked because it's
26304 being used by another process.
26307 @var{pathnameptr} is an invalid pointer value.
26310 @var{pathname} was too long.
26313 A directory component in @var{pathname} does not exist.
26316 A component of the path is not a directory.
26319 The file is on a read-only filesystem.
26322 The call was interrupted by the user.
26328 @unnumberedsubsubsec stat/fstat
26329 @cindex fstat, file-i/o system call
26330 @cindex stat, file-i/o system call
26335 int stat(const char *pathname, struct stat *buf);
26336 int fstat(int fd, struct stat *buf);
26340 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
26341 @samp{Ffstat,@var{fd},@var{bufptr}}
26343 @item Return value:
26344 On success, zero is returned. On error, -1 is returned.
26350 @var{fd} is not a valid open file.
26353 A directory component in @var{pathname} does not exist or the
26354 path is an empty string.
26357 A component of the path is not a directory.
26360 @var{pathnameptr} is an invalid pointer value.
26363 No access to the file or the path of the file.
26366 @var{pathname} was too long.
26369 The call was interrupted by the user.
26375 @unnumberedsubsubsec gettimeofday
26376 @cindex gettimeofday, file-i/o system call
26381 int gettimeofday(struct timeval *tv, void *tz);
26385 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
26387 @item Return value:
26388 On success, 0 is returned, -1 otherwise.
26394 @var{tz} is a non-NULL pointer.
26397 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
26403 @unnumberedsubsubsec isatty
26404 @cindex isatty, file-i/o system call
26409 int isatty(int fd);
26413 @samp{Fisatty,@var{fd}}
26415 @item Return value:
26416 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
26422 The call was interrupted by the user.
26427 Note that the @code{isatty} call is treated as a special case: it returns
26428 1 to the target if the file descriptor is attached
26429 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
26430 would require implementing @code{ioctl} and would be more complex than
26435 @unnumberedsubsubsec system
26436 @cindex system, file-i/o system call
26441 int system(const char *command);
26445 @samp{Fsystem,@var{commandptr}/@var{len}}
26447 @item Return value:
26448 If @var{len} is zero, the return value indicates whether a shell is
26449 available. A zero return value indicates a shell is not available.
26450 For non-zero @var{len}, the value returned is -1 on error and the
26451 return status of the command otherwise. Only the exit status of the
26452 command is returned, which is extracted from the host's @code{system}
26453 return value by calling @code{WEXITSTATUS(retval)}. In case
26454 @file{/bin/sh} could not be executed, 127 is returned.
26460 The call was interrupted by the user.
26465 @value{GDBN} takes over the full task of calling the necessary host calls
26466 to perform the @code{system} call. The return value of @code{system} on
26467 the host is simplified before it's returned
26468 to the target. Any termination signal information from the child process
26469 is discarded, and the return value consists
26470 entirely of the exit status of the called command.
26472 Due to security concerns, the @code{system} call is by default refused
26473 by @value{GDBN}. The user has to allow this call explicitly with the
26474 @code{set remote system-call-allowed 1} command.
26477 @item set remote system-call-allowed
26478 @kindex set remote system-call-allowed
26479 Control whether to allow the @code{system} calls in the File I/O
26480 protocol for the remote target. The default is zero (disabled).
26482 @item show remote system-call-allowed
26483 @kindex show remote system-call-allowed
26484 Show whether the @code{system} calls are allowed in the File I/O
26488 @node Protocol-specific Representation of Datatypes
26489 @subsection Protocol-specific Representation of Datatypes
26490 @cindex protocol-specific representation of datatypes, in file-i/o protocol
26493 * Integral Datatypes::
26495 * Memory Transfer::
26500 @node Integral Datatypes
26501 @unnumberedsubsubsec Integral Datatypes
26502 @cindex integral datatypes, in file-i/o protocol
26504 The integral datatypes used in the system calls are @code{int},
26505 @code{unsigned int}, @code{long}, @code{unsigned long},
26506 @code{mode_t}, and @code{time_t}.
26508 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
26509 implemented as 32 bit values in this protocol.
26511 @code{long} and @code{unsigned long} are implemented as 64 bit types.
26513 @xref{Limits}, for corresponding MIN and MAX values (similar to those
26514 in @file{limits.h}) to allow range checking on host and target.
26516 @code{time_t} datatypes are defined as seconds since the Epoch.
26518 All integral datatypes transferred as part of a memory read or write of a
26519 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
26522 @node Pointer Values
26523 @unnumberedsubsubsec Pointer Values
26524 @cindex pointer values, in file-i/o protocol
26526 Pointers to target data are transmitted as they are. An exception
26527 is made for pointers to buffers for which the length isn't
26528 transmitted as part of the function call, namely strings. Strings
26529 are transmitted as a pointer/length pair, both as hex values, e.g.@:
26536 which is a pointer to data of length 18 bytes at position 0x1aaf.
26537 The length is defined as the full string length in bytes, including
26538 the trailing null byte. For example, the string @code{"hello world"}
26539 at address 0x123456 is transmitted as
26545 @node Memory Transfer
26546 @unnumberedsubsubsec Memory Transfer
26547 @cindex memory transfer, in file-i/o protocol
26549 Structured data which is transferred using a memory read or write (for
26550 example, a @code{struct stat}) is expected to be in a protocol-specific format
26551 with all scalar multibyte datatypes being big endian. Translation to
26552 this representation needs to be done both by the target before the @code{F}
26553 packet is sent, and by @value{GDBN} before
26554 it transfers memory to the target. Transferred pointers to structured
26555 data should point to the already-coerced data at any time.
26559 @unnumberedsubsubsec struct stat
26560 @cindex struct stat, in file-i/o protocol
26562 The buffer of type @code{struct stat} used by the target and @value{GDBN}
26563 is defined as follows:
26567 unsigned int st_dev; /* device */
26568 unsigned int st_ino; /* inode */
26569 mode_t st_mode; /* protection */
26570 unsigned int st_nlink; /* number of hard links */
26571 unsigned int st_uid; /* user ID of owner */
26572 unsigned int st_gid; /* group ID of owner */
26573 unsigned int st_rdev; /* device type (if inode device) */
26574 unsigned long st_size; /* total size, in bytes */
26575 unsigned long st_blksize; /* blocksize for filesystem I/O */
26576 unsigned long st_blocks; /* number of blocks allocated */
26577 time_t st_atime; /* time of last access */
26578 time_t st_mtime; /* time of last modification */
26579 time_t st_ctime; /* time of last change */
26583 The integral datatypes conform to the definitions given in the
26584 appropriate section (see @ref{Integral Datatypes}, for details) so this
26585 structure is of size 64 bytes.
26587 The values of several fields have a restricted meaning and/or
26593 A value of 0 represents a file, 1 the console.
26596 No valid meaning for the target. Transmitted unchanged.
26599 Valid mode bits are described in @ref{Constants}. Any other
26600 bits have currently no meaning for the target.
26605 No valid meaning for the target. Transmitted unchanged.
26610 These values have a host and file system dependent
26611 accuracy. Especially on Windows hosts, the file system may not
26612 support exact timing values.
26615 The target gets a @code{struct stat} of the above representation and is
26616 responsible for coercing it to the target representation before
26619 Note that due to size differences between the host, target, and protocol
26620 representations of @code{struct stat} members, these members could eventually
26621 get truncated on the target.
26623 @node struct timeval
26624 @unnumberedsubsubsec struct timeval
26625 @cindex struct timeval, in file-i/o protocol
26627 The buffer of type @code{struct timeval} used by the File-I/O protocol
26628 is defined as follows:
26632 time_t tv_sec; /* second */
26633 long tv_usec; /* microsecond */
26637 The integral datatypes conform to the definitions given in the
26638 appropriate section (see @ref{Integral Datatypes}, for details) so this
26639 structure is of size 8 bytes.
26642 @subsection Constants
26643 @cindex constants, in file-i/o protocol
26645 The following values are used for the constants inside of the
26646 protocol. @value{GDBN} and target are responsible for translating these
26647 values before and after the call as needed.
26658 @unnumberedsubsubsec Open Flags
26659 @cindex open flags, in file-i/o protocol
26661 All values are given in hexadecimal representation.
26673 @node mode_t Values
26674 @unnumberedsubsubsec mode_t Values
26675 @cindex mode_t values, in file-i/o protocol
26677 All values are given in octal representation.
26694 @unnumberedsubsubsec Errno Values
26695 @cindex errno values, in file-i/o protocol
26697 All values are given in decimal representation.
26722 @code{EUNKNOWN} is used as a fallback error value if a host system returns
26723 any error value not in the list of supported error numbers.
26726 @unnumberedsubsubsec Lseek Flags
26727 @cindex lseek flags, in file-i/o protocol
26736 @unnumberedsubsubsec Limits
26737 @cindex limits, in file-i/o protocol
26739 All values are given in decimal representation.
26742 INT_MIN -2147483648
26744 UINT_MAX 4294967295
26745 LONG_MIN -9223372036854775808
26746 LONG_MAX 9223372036854775807
26747 ULONG_MAX 18446744073709551615
26750 @node File-I/O Examples
26751 @subsection File-I/O Examples
26752 @cindex file-i/o examples
26754 Example sequence of a write call, file descriptor 3, buffer is at target
26755 address 0x1234, 6 bytes should be written:
26758 <- @code{Fwrite,3,1234,6}
26759 @emph{request memory read from target}
26762 @emph{return "6 bytes written"}
26766 Example sequence of a read call, file descriptor 3, buffer is at target
26767 address 0x1234, 6 bytes should be read:
26770 <- @code{Fread,3,1234,6}
26771 @emph{request memory write to target}
26772 -> @code{X1234,6:XXXXXX}
26773 @emph{return "6 bytes read"}
26777 Example sequence of a read call, call fails on the host due to invalid
26778 file descriptor (@code{EBADF}):
26781 <- @code{Fread,3,1234,6}
26785 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
26789 <- @code{Fread,3,1234,6}
26794 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
26798 <- @code{Fread,3,1234,6}
26799 -> @code{X1234,6:XXXXXX}
26803 @node Library List Format
26804 @section Library List Format
26805 @cindex library list format, remote protocol
26807 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
26808 same process as your application to manage libraries. In this case,
26809 @value{GDBN} can use the loader's symbol table and normal memory
26810 operations to maintain a list of shared libraries. On other
26811 platforms, the operating system manages loaded libraries.
26812 @value{GDBN} can not retrieve the list of currently loaded libraries
26813 through memory operations, so it uses the @samp{qXfer:libraries:read}
26814 packet (@pxref{qXfer library list read}) instead. The remote stub
26815 queries the target's operating system and reports which libraries
26818 The @samp{qXfer:libraries:read} packet returns an XML document which
26819 lists loaded libraries and their offsets. Each library has an
26820 associated name and one or more segment or section base addresses,
26821 which report where the library was loaded in memory.
26823 For the common case of libraries that are fully linked binaries, the
26824 library should have a list of segments. If the target supports
26825 dynamic linking of a relocatable object file, its library XML element
26826 should instead include a list of allocated sections. The segment or
26827 section bases are start addresses, not relocation offsets; they do not
26828 depend on the library's link-time base addresses.
26830 @value{GDBN} must be linked with the Expat library to support XML
26831 library lists. @xref{Expat}.
26833 A simple memory map, with one loaded library relocated by a single
26834 offset, looks like this:
26838 <library name="/lib/libc.so.6">
26839 <segment address="0x10000000"/>
26844 Another simple memory map, with one loaded library with three
26845 allocated sections (.text, .data, .bss), looks like this:
26849 <library name="sharedlib.o">
26850 <section address="0x10000000"/>
26851 <section address="0x20000000"/>
26852 <section address="0x30000000"/>
26857 The format of a library list is described by this DTD:
26860 <!-- library-list: Root element with versioning -->
26861 <!ELEMENT library-list (library)*>
26862 <!ATTLIST library-list version CDATA #FIXED "1.0">
26863 <!ELEMENT library (segment*, section*)>
26864 <!ATTLIST library name CDATA #REQUIRED>
26865 <!ELEMENT segment EMPTY>
26866 <!ATTLIST segment address CDATA #REQUIRED>
26867 <!ELEMENT section EMPTY>
26868 <!ATTLIST section address CDATA #REQUIRED>
26871 In addition, segments and section descriptors cannot be mixed within a
26872 single library element, and you must supply at least one segment or
26873 section for each library.
26875 @node Memory Map Format
26876 @section Memory Map Format
26877 @cindex memory map format
26879 To be able to write into flash memory, @value{GDBN} needs to obtain a
26880 memory map from the target. This section describes the format of the
26883 The memory map is obtained using the @samp{qXfer:memory-map:read}
26884 (@pxref{qXfer memory map read}) packet and is an XML document that
26885 lists memory regions.
26887 @value{GDBN} must be linked with the Expat library to support XML
26888 memory maps. @xref{Expat}.
26890 The top-level structure of the document is shown below:
26893 <?xml version="1.0"?>
26894 <!DOCTYPE memory-map
26895 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
26896 "http://sourceware.org/gdb/gdb-memory-map.dtd">
26902 Each region can be either:
26907 A region of RAM starting at @var{addr} and extending for @var{length}
26911 <memory type="ram" start="@var{addr}" length="@var{length}"/>
26916 A region of read-only memory:
26919 <memory type="rom" start="@var{addr}" length="@var{length}"/>
26924 A region of flash memory, with erasure blocks @var{blocksize}
26928 <memory type="flash" start="@var{addr}" length="@var{length}">
26929 <property name="blocksize">@var{blocksize}</property>
26935 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
26936 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
26937 packets to write to addresses in such ranges.
26939 The formal DTD for memory map format is given below:
26942 <!-- ................................................... -->
26943 <!-- Memory Map XML DTD ................................ -->
26944 <!-- File: memory-map.dtd .............................. -->
26945 <!-- .................................... .............. -->
26946 <!-- memory-map.dtd -->
26947 <!-- memory-map: Root element with versioning -->
26948 <!ELEMENT memory-map (memory | property)>
26949 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
26950 <!ELEMENT memory (property)>
26951 <!-- memory: Specifies a memory region,
26952 and its type, or device. -->
26953 <!ATTLIST memory type CDATA #REQUIRED
26954 start CDATA #REQUIRED
26955 length CDATA #REQUIRED
26956 device CDATA #IMPLIED>
26957 <!-- property: Generic attribute tag -->
26958 <!ELEMENT property (#PCDATA | property)*>
26959 <!ATTLIST property name CDATA #REQUIRED>
26962 @include agentexpr.texi
26964 @node Target Descriptions
26965 @appendix Target Descriptions
26966 @cindex target descriptions
26968 @strong{Warning:} target descriptions are still under active development,
26969 and the contents and format may change between @value{GDBN} releases.
26970 The format is expected to stabilize in the future.
26972 One of the challenges of using @value{GDBN} to debug embedded systems
26973 is that there are so many minor variants of each processor
26974 architecture in use. It is common practice for vendors to start with
26975 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
26976 and then make changes to adapt it to a particular market niche. Some
26977 architectures have hundreds of variants, available from dozens of
26978 vendors. This leads to a number of problems:
26982 With so many different customized processors, it is difficult for
26983 the @value{GDBN} maintainers to keep up with the changes.
26985 Since individual variants may have short lifetimes or limited
26986 audiences, it may not be worthwhile to carry information about every
26987 variant in the @value{GDBN} source tree.
26989 When @value{GDBN} does support the architecture of the embedded system
26990 at hand, the task of finding the correct architecture name to give the
26991 @command{set architecture} command can be error-prone.
26994 To address these problems, the @value{GDBN} remote protocol allows a
26995 target system to not only identify itself to @value{GDBN}, but to
26996 actually describe its own features. This lets @value{GDBN} support
26997 processor variants it has never seen before --- to the extent that the
26998 descriptions are accurate, and that @value{GDBN} understands them.
27000 @value{GDBN} must be linked with the Expat library to support XML
27001 target descriptions. @xref{Expat}.
27004 * Retrieving Descriptions:: How descriptions are fetched from a target.
27005 * Target Description Format:: The contents of a target description.
27006 * Predefined Target Types:: Standard types available for target
27008 * Standard Target Features:: Features @value{GDBN} knows about.
27011 @node Retrieving Descriptions
27012 @section Retrieving Descriptions
27014 Target descriptions can be read from the target automatically, or
27015 specified by the user manually. The default behavior is to read the
27016 description from the target. @value{GDBN} retrieves it via the remote
27017 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
27018 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
27019 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
27020 XML document, of the form described in @ref{Target Description
27023 Alternatively, you can specify a file to read for the target description.
27024 If a file is set, the target will not be queried. The commands to
27025 specify a file are:
27028 @cindex set tdesc filename
27029 @item set tdesc filename @var{path}
27030 Read the target description from @var{path}.
27032 @cindex unset tdesc filename
27033 @item unset tdesc filename
27034 Do not read the XML target description from a file. @value{GDBN}
27035 will use the description supplied by the current target.
27037 @cindex show tdesc filename
27038 @item show tdesc filename
27039 Show the filename to read for a target description, if any.
27043 @node Target Description Format
27044 @section Target Description Format
27045 @cindex target descriptions, XML format
27047 A target description annex is an @uref{http://www.w3.org/XML/, XML}
27048 document which complies with the Document Type Definition provided in
27049 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
27050 means you can use generally available tools like @command{xmllint} to
27051 check that your feature descriptions are well-formed and valid.
27052 However, to help people unfamiliar with XML write descriptions for
27053 their targets, we also describe the grammar here.
27055 Target descriptions can identify the architecture of the remote target
27056 and (for some architectures) provide information about custom register
27057 sets. @value{GDBN} can use this information to autoconfigure for your
27058 target, or to warn you if you connect to an unsupported target.
27060 Here is a simple target description:
27063 <target version="1.0">
27064 <architecture>i386:x86-64</architecture>
27069 This minimal description only says that the target uses
27070 the x86-64 architecture.
27072 A target description has the following overall form, with [ ] marking
27073 optional elements and @dots{} marking repeatable elements. The elements
27074 are explained further below.
27077 <?xml version="1.0"?>
27078 <!DOCTYPE target SYSTEM "gdb-target.dtd">
27079 <target version="1.0">
27080 @r{[}@var{architecture}@r{]}
27081 @r{[}@var{feature}@dots{}@r{]}
27086 The description is generally insensitive to whitespace and line
27087 breaks, under the usual common-sense rules. The XML version
27088 declaration and document type declaration can generally be omitted
27089 (@value{GDBN} does not require them), but specifying them may be
27090 useful for XML validation tools. The @samp{version} attribute for
27091 @samp{<target>} may also be omitted, but we recommend
27092 including it; if future versions of @value{GDBN} use an incompatible
27093 revision of @file{gdb-target.dtd}, they will detect and report
27094 the version mismatch.
27096 @subsection Inclusion
27097 @cindex target descriptions, inclusion
27100 @cindex <xi:include>
27103 It can sometimes be valuable to split a target description up into
27104 several different annexes, either for organizational purposes, or to
27105 share files between different possible target descriptions. You can
27106 divide a description into multiple files by replacing any element of
27107 the target description with an inclusion directive of the form:
27110 <xi:include href="@var{document}"/>
27114 When @value{GDBN} encounters an element of this form, it will retrieve
27115 the named XML @var{document}, and replace the inclusion directive with
27116 the contents of that document. If the current description was read
27117 using @samp{qXfer}, then so will be the included document;
27118 @var{document} will be interpreted as the name of an annex. If the
27119 current description was read from a file, @value{GDBN} will look for
27120 @var{document} as a file in the same directory where it found the
27121 original description.
27123 @subsection Architecture
27124 @cindex <architecture>
27126 An @samp{<architecture>} element has this form:
27129 <architecture>@var{arch}</architecture>
27132 @var{arch} is an architecture name from the same selection
27133 accepted by @code{set architecture} (@pxref{Targets, ,Specifying a
27134 Debugging Target}).
27136 @subsection Features
27139 Each @samp{<feature>} describes some logical portion of the target
27140 system. Features are currently used to describe available CPU
27141 registers and the types of their contents. A @samp{<feature>} element
27145 <feature name="@var{name}">
27146 @r{[}@var{type}@dots{}@r{]}
27152 Each feature's name should be unique within the description. The name
27153 of a feature does not matter unless @value{GDBN} has some special
27154 knowledge of the contents of that feature; if it does, the feature
27155 should have its standard name. @xref{Standard Target Features}.
27159 Any register's value is a collection of bits which @value{GDBN} must
27160 interpret. The default interpretation is a two's complement integer,
27161 but other types can be requested by name in the register description.
27162 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
27163 Target Types}), and the description can define additional composite types.
27165 Each type element must have an @samp{id} attribute, which gives
27166 a unique (within the containing @samp{<feature>}) name to the type.
27167 Types must be defined before they are used.
27170 Some targets offer vector registers, which can be treated as arrays
27171 of scalar elements. These types are written as @samp{<vector>} elements,
27172 specifying the array element type, @var{type}, and the number of elements,
27176 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
27180 If a register's value is usefully viewed in multiple ways, define it
27181 with a union type containing the useful representations. The
27182 @samp{<union>} element contains one or more @samp{<field>} elements,
27183 each of which has a @var{name} and a @var{type}:
27186 <union id="@var{id}">
27187 <field name="@var{name}" type="@var{type}"/>
27192 @subsection Registers
27195 Each register is represented as an element with this form:
27198 <reg name="@var{name}"
27199 bitsize="@var{size}"
27200 @r{[}regnum="@var{num}"@r{]}
27201 @r{[}save-restore="@var{save-restore}"@r{]}
27202 @r{[}type="@var{type}"@r{]}
27203 @r{[}group="@var{group}"@r{]}/>
27207 The components are as follows:
27212 The register's name; it must be unique within the target description.
27215 The register's size, in bits.
27218 The register's number. If omitted, a register's number is one greater
27219 than that of the previous register (either in the current feature or in
27220 a preceeding feature); the first register in the target description
27221 defaults to zero. This register number is used to read or write
27222 the register; e.g.@: it is used in the remote @code{p} and @code{P}
27223 packets, and registers appear in the @code{g} and @code{G} packets
27224 in order of increasing register number.
27227 Whether the register should be preserved across inferior function
27228 calls; this must be either @code{yes} or @code{no}. The default is
27229 @code{yes}, which is appropriate for most registers except for
27230 some system control registers; this is not related to the target's
27234 The type of the register. @var{type} may be a predefined type, a type
27235 defined in the current feature, or one of the special types @code{int}
27236 and @code{float}. @code{int} is an integer type of the correct size
27237 for @var{bitsize}, and @code{float} is a floating point type (in the
27238 architecture's normal floating point format) of the correct size for
27239 @var{bitsize}. The default is @code{int}.
27242 The register group to which this register belongs. @var{group} must
27243 be either @code{general}, @code{float}, or @code{vector}. If no
27244 @var{group} is specified, @value{GDBN} will not display the register
27245 in @code{info registers}.
27249 @node Predefined Target Types
27250 @section Predefined Target Types
27251 @cindex target descriptions, predefined types
27253 Type definitions in the self-description can build up composite types
27254 from basic building blocks, but can not define fundamental types. Instead,
27255 standard identifiers are provided by @value{GDBN} for the fundamental
27256 types. The currently supported types are:
27265 Signed integer types holding the specified number of bits.
27272 Unsigned integer types holding the specified number of bits.
27276 Pointers to unspecified code and data. The program counter and
27277 any dedicated return address register may be marked as code
27278 pointers; printing a code pointer converts it into a symbolic
27279 address. The stack pointer and any dedicated address registers
27280 may be marked as data pointers.
27283 Single precision IEEE floating point.
27286 Double precision IEEE floating point.
27289 The 12-byte extended precision format used by ARM FPA registers.
27293 @node Standard Target Features
27294 @section Standard Target Features
27295 @cindex target descriptions, standard features
27297 A target description must contain either no registers or all the
27298 target's registers. If the description contains no registers, then
27299 @value{GDBN} will assume a default register layout, selected based on
27300 the architecture. If the description contains any registers, the
27301 default layout will not be used; the standard registers must be
27302 described in the target description, in such a way that @value{GDBN}
27303 can recognize them.
27305 This is accomplished by giving specific names to feature elements
27306 which contain standard registers. @value{GDBN} will look for features
27307 with those names and verify that they contain the expected registers;
27308 if any known feature is missing required registers, or if any required
27309 feature is missing, @value{GDBN} will reject the target
27310 description. You can add additional registers to any of the
27311 standard features --- @value{GDBN} will display them just as if
27312 they were added to an unrecognized feature.
27314 This section lists the known features and their expected contents.
27315 Sample XML documents for these features are included in the
27316 @value{GDBN} source tree, in the directory @file{gdb/features}.
27318 Names recognized by @value{GDBN} should include the name of the
27319 company or organization which selected the name, and the overall
27320 architecture to which the feature applies; so e.g.@: the feature
27321 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
27323 The names of registers are not case sensitive for the purpose
27324 of recognizing standard features, but @value{GDBN} will only display
27325 registers using the capitalization used in the description.
27331 * PowerPC Features::
27336 @subsection ARM Features
27337 @cindex target descriptions, ARM features
27339 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
27340 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
27341 @samp{lr}, @samp{pc}, and @samp{cpsr}.
27343 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
27344 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
27346 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
27347 it should contain at least registers @samp{wR0} through @samp{wR15} and
27348 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
27349 @samp{wCSSF}, and @samp{wCASF} registers are optional.
27351 @node MIPS Features
27352 @subsection MIPS Features
27353 @cindex target descriptions, MIPS features
27355 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
27356 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
27357 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
27360 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
27361 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
27362 registers. They may be 32-bit or 64-bit depending on the target.
27364 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
27365 it may be optional in a future version of @value{GDBN}. It should
27366 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
27367 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
27369 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
27370 contain a single register, @samp{restart}, which is used by the
27371 Linux kernel to control restartable syscalls.
27373 @node M68K Features
27374 @subsection M68K Features
27375 @cindex target descriptions, M68K features
27378 @item @samp{org.gnu.gdb.m68k.core}
27379 @itemx @samp{org.gnu.gdb.coldfire.core}
27380 @itemx @samp{org.gnu.gdb.fido.core}
27381 One of those features must be always present.
27382 The feature that is present determines which flavor of m86k is
27383 used. The feature that is present should contain registers
27384 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
27385 @samp{sp}, @samp{ps} and @samp{pc}.
27387 @item @samp{org.gnu.gdb.coldfire.fp}
27388 This feature is optional. If present, it should contain registers
27389 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
27393 @node PowerPC Features
27394 @subsection PowerPC Features
27395 @cindex target descriptions, PowerPC features
27397 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
27398 targets. It should contain registers @samp{r0} through @samp{r31},
27399 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
27400 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
27402 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
27403 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
27405 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
27406 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
27409 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
27410 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
27411 @samp{spefscr}. SPE targets should provide 32-bit registers in
27412 @samp{org.gnu.gdb.power.core} and provide the upper halves in
27413 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
27414 these to present registers @samp{ev0} through @samp{ev31} to the
27429 % I think something like @colophon should be in texinfo. In the
27431 \long\def\colophon{\hbox to0pt{}\vfill
27432 \centerline{The body of this manual is set in}
27433 \centerline{\fontname\tenrm,}
27434 \centerline{with headings in {\bf\fontname\tenbf}}
27435 \centerline{and examples in {\tt\fontname\tentt}.}
27436 \centerline{{\it\fontname\tenit\/},}
27437 \centerline{{\bf\fontname\tenbf}, and}
27438 \centerline{{\sl\fontname\tensl\/}}
27439 \centerline{are used for emphasis.}\vfill}
27441 % Blame: doc@cygnus.com, 1991.