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 * Extending GDB:: Extending @value{GDBN}
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 * Inferiors:: Debugging multiple inferiors
1789 * Threads:: Debugging programs with multiple threads
1790 * Processes:: Debugging programs with multiple processes
1791 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1795 @section Compiling for Debugging
1797 In order to debug a program effectively, you need to generate
1798 debugging information when you compile it. This debugging information
1799 is stored in the object file; it describes the data type of each
1800 variable or function and the correspondence between source line numbers
1801 and addresses in the executable code.
1803 To request debugging information, specify the @samp{-g} option when you run
1806 Programs that are to be shipped to your customers are compiled with
1807 optimizations, using the @samp{-O} compiler option. However, many
1808 compilers are unable to handle the @samp{-g} and @samp{-O} options
1809 together. Using those compilers, you cannot generate optimized
1810 executables containing debugging information.
1812 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1813 without @samp{-O}, making it possible to debug optimized code. We
1814 recommend that you @emph{always} use @samp{-g} whenever you compile a
1815 program. You may think your program is correct, but there is no sense
1816 in pushing your luck.
1818 @cindex optimized code, debugging
1819 @cindex debugging optimized code
1820 When you debug a program compiled with @samp{-g -O}, remember that the
1821 optimizer is rearranging your code; the debugger shows you what is
1822 really there. Do not be too surprised when the execution path does not
1823 exactly match your source file! An extreme example: if you define a
1824 variable, but never use it, @value{GDBN} never sees that
1825 variable---because the compiler optimizes it out of existence.
1827 Some things do not work as well with @samp{-g -O} as with just
1828 @samp{-g}, particularly on machines with instruction scheduling. If in
1829 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1830 please report it to us as a bug (including a test case!).
1831 @xref{Variables}, for more information about debugging optimized code.
1833 Older versions of the @sc{gnu} C compiler permitted a variant option
1834 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1835 format; if your @sc{gnu} C compiler has this option, do not use it.
1837 @value{GDBN} knows about preprocessor macros and can show you their
1838 expansion (@pxref{Macros}). Most compilers do not include information
1839 about preprocessor macros in the debugging information if you specify
1840 the @option{-g} flag alone, because this information is rather large.
1841 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1842 provides macro information if you specify the options
1843 @option{-gdwarf-2} and @option{-g3}; the former option requests
1844 debugging information in the Dwarf 2 format, and the latter requests
1845 ``extra information''. In the future, we hope to find more compact
1846 ways to represent macro information, so that it can be included with
1851 @section Starting your Program
1857 @kindex r @r{(@code{run})}
1860 Use the @code{run} command to start your program under @value{GDBN}.
1861 You must first specify the program name (except on VxWorks) with an
1862 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1863 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1864 (@pxref{Files, ,Commands to Specify Files}).
1868 If you are running your program in an execution environment that
1869 supports processes, @code{run} creates an inferior process and makes
1870 that process run your program. In some environments without processes,
1871 @code{run} jumps to the start of your program. Other targets,
1872 like @samp{remote}, are always running. If you get an error
1873 message like this one:
1876 The "remote" target does not support "run".
1877 Try "help target" or "continue".
1881 then use @code{continue} to run your program. You may need @code{load}
1882 first (@pxref{load}).
1884 The execution of a program is affected by certain information it
1885 receives from its superior. @value{GDBN} provides ways to specify this
1886 information, which you must do @emph{before} starting your program. (You
1887 can change it after starting your program, but such changes only affect
1888 your program the next time you start it.) This information may be
1889 divided into four categories:
1892 @item The @emph{arguments.}
1893 Specify the arguments to give your program as the arguments of the
1894 @code{run} command. If a shell is available on your target, the shell
1895 is used to pass the arguments, so that you may use normal conventions
1896 (such as wildcard expansion or variable substitution) in describing
1898 In Unix systems, you can control which shell is used with the
1899 @code{SHELL} environment variable.
1900 @xref{Arguments, ,Your Program's Arguments}.
1902 @item The @emph{environment.}
1903 Your program normally inherits its environment from @value{GDBN}, but you can
1904 use the @value{GDBN} commands @code{set environment} and @code{unset
1905 environment} to change parts of the environment that affect
1906 your program. @xref{Environment, ,Your Program's Environment}.
1908 @item The @emph{working directory.}
1909 Your program inherits its working directory from @value{GDBN}. You can set
1910 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1911 @xref{Working Directory, ,Your Program's Working Directory}.
1913 @item The @emph{standard input and output.}
1914 Your program normally uses the same device for standard input and
1915 standard output as @value{GDBN} is using. You can redirect input and output
1916 in the @code{run} command line, or you can use the @code{tty} command to
1917 set a different device for your program.
1918 @xref{Input/Output, ,Your Program's Input and Output}.
1921 @emph{Warning:} While input and output redirection work, you cannot use
1922 pipes to pass the output of the program you are debugging to another
1923 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1927 When you issue the @code{run} command, your program begins to execute
1928 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1929 of how to arrange for your program to stop. Once your program has
1930 stopped, you may call functions in your program, using the @code{print}
1931 or @code{call} commands. @xref{Data, ,Examining Data}.
1933 If the modification time of your symbol file has changed since the last
1934 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1935 table, and reads it again. When it does this, @value{GDBN} tries to retain
1936 your current breakpoints.
1941 @cindex run to main procedure
1942 The name of the main procedure can vary from language to language.
1943 With C or C@t{++}, the main procedure name is always @code{main}, but
1944 other languages such as Ada do not require a specific name for their
1945 main procedure. The debugger provides a convenient way to start the
1946 execution of the program and to stop at the beginning of the main
1947 procedure, depending on the language used.
1949 The @samp{start} command does the equivalent of setting a temporary
1950 breakpoint at the beginning of the main procedure and then invoking
1951 the @samp{run} command.
1953 @cindex elaboration phase
1954 Some programs contain an @dfn{elaboration} phase where some startup code is
1955 executed before the main procedure is called. This depends on the
1956 languages used to write your program. In C@t{++}, for instance,
1957 constructors for static and global objects are executed before
1958 @code{main} is called. It is therefore possible that the debugger stops
1959 before reaching the main procedure. However, the temporary breakpoint
1960 will remain to halt execution.
1962 Specify the arguments to give to your program as arguments to the
1963 @samp{start} command. These arguments will be given verbatim to the
1964 underlying @samp{run} command. Note that the same arguments will be
1965 reused if no argument is provided during subsequent calls to
1966 @samp{start} or @samp{run}.
1968 It is sometimes necessary to debug the program during elaboration. In
1969 these cases, using the @code{start} command would stop the execution of
1970 your program too late, as the program would have already completed the
1971 elaboration phase. Under these circumstances, insert breakpoints in your
1972 elaboration code before running your program.
1974 @kindex set exec-wrapper
1975 @item set exec-wrapper @var{wrapper}
1976 @itemx show exec-wrapper
1977 @itemx unset exec-wrapper
1978 When @samp{exec-wrapper} is set, the specified wrapper is used to
1979 launch programs for debugging. @value{GDBN} starts your program
1980 with a shell command of the form @kbd{exec @var{wrapper}
1981 @var{program}}. Quoting is added to @var{program} and its
1982 arguments, but not to @var{wrapper}, so you should add quotes if
1983 appropriate for your shell. The wrapper runs until it executes
1984 your program, and then @value{GDBN} takes control.
1986 You can use any program that eventually calls @code{execve} with
1987 its arguments as a wrapper. Several standard Unix utilities do
1988 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
1989 with @code{exec "$@@"} will also work.
1991 For example, you can use @code{env} to pass an environment variable to
1992 the debugged program, without setting the variable in your shell's
1996 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2000 This command is available when debugging locally on most targets, excluding
2001 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2003 @kindex set disable-randomization
2004 @item set disable-randomization
2005 @itemx set disable-randomization on
2006 This option (enabled by default in @value{GDBN}) will turn off the native
2007 randomization of the virtual address space of the started program. This option
2008 is useful for multiple debugging sessions to make the execution better
2009 reproducible and memory addresses reusable across debugging sessions.
2011 This feature is implemented only on @sc{gnu}/Linux. You can get the same
2015 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2018 @item set disable-randomization off
2019 Leave the behavior of the started executable unchanged. Some bugs rear their
2020 ugly heads only when the program is loaded at certain addresses. If your bug
2021 disappears when you run the program under @value{GDBN}, that might be because
2022 @value{GDBN} by default disables the address randomization on platforms, such
2023 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2024 disable-randomization off} to try to reproduce such elusive bugs.
2026 The virtual address space randomization is implemented only on @sc{gnu}/Linux.
2027 It protects the programs against some kinds of security attacks. In these
2028 cases the attacker needs to know the exact location of a concrete executable
2029 code. Randomizing its location makes it impossible to inject jumps misusing
2030 a code at its expected addresses.
2032 Prelinking shared libraries provides a startup performance advantage but it
2033 makes addresses in these libraries predictable for privileged processes by
2034 having just unprivileged access at the target system. Reading the shared
2035 library binary gives enough information for assembling the malicious code
2036 misusing it. Still even a prelinked shared library can get loaded at a new
2037 random address just requiring the regular relocation process during the
2038 startup. Shared libraries not already prelinked are always loaded at
2039 a randomly chosen address.
2041 Position independent executables (PIE) contain position independent code
2042 similar to the shared libraries and therefore such executables get loaded at
2043 a randomly chosen address upon startup. PIE executables always load even
2044 already prelinked shared libraries at a random address. You can build such
2045 executable using @command{gcc -fPIE -pie}.
2047 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2048 (as long as the randomization is enabled).
2050 @item show disable-randomization
2051 Show the current setting of the explicit disable of the native randomization of
2052 the virtual address space of the started program.
2057 @section Your Program's Arguments
2059 @cindex arguments (to your program)
2060 The arguments to your program can be specified by the arguments of the
2062 They are passed to a shell, which expands wildcard characters and
2063 performs redirection of I/O, and thence to your program. Your
2064 @code{SHELL} environment variable (if it exists) specifies what shell
2065 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2066 the default shell (@file{/bin/sh} on Unix).
2068 On non-Unix systems, the program is usually invoked directly by
2069 @value{GDBN}, which emulates I/O redirection via the appropriate system
2070 calls, and the wildcard characters are expanded by the startup code of
2071 the program, not by the shell.
2073 @code{run} with no arguments uses the same arguments used by the previous
2074 @code{run}, or those set by the @code{set args} command.
2079 Specify the arguments to be used the next time your program is run. If
2080 @code{set args} has no arguments, @code{run} executes your program
2081 with no arguments. Once you have run your program with arguments,
2082 using @code{set args} before the next @code{run} is the only way to run
2083 it again without arguments.
2087 Show the arguments to give your program when it is started.
2091 @section Your Program's Environment
2093 @cindex environment (of your program)
2094 The @dfn{environment} consists of a set of environment variables and
2095 their values. Environment variables conventionally record such things as
2096 your user name, your home directory, your terminal type, and your search
2097 path for programs to run. Usually you set up environment variables with
2098 the shell and they are inherited by all the other programs you run. When
2099 debugging, it can be useful to try running your program with a modified
2100 environment without having to start @value{GDBN} over again.
2104 @item path @var{directory}
2105 Add @var{directory} to the front of the @code{PATH} environment variable
2106 (the search path for executables) that will be passed to your program.
2107 The value of @code{PATH} used by @value{GDBN} does not change.
2108 You may specify several directory names, separated by whitespace or by a
2109 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2110 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2111 is moved to the front, so it is searched sooner.
2113 You can use the string @samp{$cwd} to refer to whatever is the current
2114 working directory at the time @value{GDBN} searches the path. If you
2115 use @samp{.} instead, it refers to the directory where you executed the
2116 @code{path} command. @value{GDBN} replaces @samp{.} in the
2117 @var{directory} argument (with the current path) before adding
2118 @var{directory} to the search path.
2119 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2120 @c document that, since repeating it would be a no-op.
2124 Display the list of search paths for executables (the @code{PATH}
2125 environment variable).
2127 @kindex show environment
2128 @item show environment @r{[}@var{varname}@r{]}
2129 Print the value of environment variable @var{varname} to be given to
2130 your program when it starts. If you do not supply @var{varname},
2131 print the names and values of all environment variables to be given to
2132 your program. You can abbreviate @code{environment} as @code{env}.
2134 @kindex set environment
2135 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2136 Set environment variable @var{varname} to @var{value}. The value
2137 changes for your program only, not for @value{GDBN} itself. @var{value} may
2138 be any string; the values of environment variables are just strings, and
2139 any interpretation is supplied by your program itself. The @var{value}
2140 parameter is optional; if it is eliminated, the variable is set to a
2142 @c "any string" here does not include leading, trailing
2143 @c blanks. Gnu asks: does anyone care?
2145 For example, this command:
2152 tells the debugged program, when subsequently run, that its user is named
2153 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2154 are not actually required.)
2156 @kindex unset environment
2157 @item unset environment @var{varname}
2158 Remove variable @var{varname} from the environment to be passed to your
2159 program. This is different from @samp{set env @var{varname} =};
2160 @code{unset environment} removes the variable from the environment,
2161 rather than assigning it an empty value.
2164 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2166 by your @code{SHELL} environment variable if it exists (or
2167 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2168 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2169 @file{.bashrc} for BASH---any variables you set in that file affect
2170 your program. You may wish to move setting of environment variables to
2171 files that are only run when you sign on, such as @file{.login} or
2174 @node Working Directory
2175 @section Your Program's Working Directory
2177 @cindex working directory (of your program)
2178 Each time you start your program with @code{run}, it inherits its
2179 working directory from the current working directory of @value{GDBN}.
2180 The @value{GDBN} working directory is initially whatever it inherited
2181 from its parent process (typically the shell), but you can specify a new
2182 working directory in @value{GDBN} with the @code{cd} command.
2184 The @value{GDBN} working directory also serves as a default for the commands
2185 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2190 @cindex change working directory
2191 @item cd @var{directory}
2192 Set the @value{GDBN} working directory to @var{directory}.
2196 Print the @value{GDBN} working directory.
2199 It is generally impossible to find the current working directory of
2200 the process being debugged (since a program can change its directory
2201 during its run). If you work on a system where @value{GDBN} is
2202 configured with the @file{/proc} support, you can use the @code{info
2203 proc} command (@pxref{SVR4 Process Information}) to find out the
2204 current working directory of the debuggee.
2207 @section Your Program's Input and Output
2212 By default, the program you run under @value{GDBN} does input and output to
2213 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2214 to its own terminal modes to interact with you, but it records the terminal
2215 modes your program was using and switches back to them when you continue
2216 running your program.
2219 @kindex info terminal
2221 Displays information recorded by @value{GDBN} about the terminal modes your
2225 You can redirect your program's input and/or output using shell
2226 redirection with the @code{run} command. For example,
2233 starts your program, diverting its output to the file @file{outfile}.
2236 @cindex controlling terminal
2237 Another way to specify where your program should do input and output is
2238 with the @code{tty} command. This command accepts a file name as
2239 argument, and causes this file to be the default for future @code{run}
2240 commands. It also resets the controlling terminal for the child
2241 process, for future @code{run} commands. For example,
2248 directs that processes started with subsequent @code{run} commands
2249 default to do input and output on the terminal @file{/dev/ttyb} and have
2250 that as their controlling terminal.
2252 An explicit redirection in @code{run} overrides the @code{tty} command's
2253 effect on the input/output device, but not its effect on the controlling
2256 When you use the @code{tty} command or redirect input in the @code{run}
2257 command, only the input @emph{for your program} is affected. The input
2258 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2259 for @code{set inferior-tty}.
2261 @cindex inferior tty
2262 @cindex set inferior controlling terminal
2263 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2264 display the name of the terminal that will be used for future runs of your
2268 @item set inferior-tty /dev/ttyb
2269 @kindex set inferior-tty
2270 Set the tty for the program being debugged to /dev/ttyb.
2272 @item show inferior-tty
2273 @kindex show inferior-tty
2274 Show the current tty for the program being debugged.
2278 @section Debugging an Already-running Process
2283 @item attach @var{process-id}
2284 This command attaches to a running process---one that was started
2285 outside @value{GDBN}. (@code{info files} shows your active
2286 targets.) The command takes as argument a process ID. The usual way to
2287 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2288 or with the @samp{jobs -l} shell command.
2290 @code{attach} does not repeat if you press @key{RET} a second time after
2291 executing the command.
2294 To use @code{attach}, your program must be running in an environment
2295 which supports processes; for example, @code{attach} does not work for
2296 programs on bare-board targets that lack an operating system. You must
2297 also have permission to send the process a signal.
2299 When you use @code{attach}, the debugger finds the program running in
2300 the process first by looking in the current working directory, then (if
2301 the program is not found) by using the source file search path
2302 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2303 the @code{file} command to load the program. @xref{Files, ,Commands to
2306 The first thing @value{GDBN} does after arranging to debug the specified
2307 process is to stop it. You can examine and modify an attached process
2308 with all the @value{GDBN} commands that are ordinarily available when
2309 you start processes with @code{run}. You can insert breakpoints; you
2310 can step and continue; you can modify storage. If you would rather the
2311 process continue running, you may use the @code{continue} command after
2312 attaching @value{GDBN} to the process.
2317 When you have finished debugging the attached process, you can use the
2318 @code{detach} command to release it from @value{GDBN} control. Detaching
2319 the process continues its execution. After the @code{detach} command,
2320 that process and @value{GDBN} become completely independent once more, and you
2321 are ready to @code{attach} another process or start one with @code{run}.
2322 @code{detach} does not repeat if you press @key{RET} again after
2323 executing the command.
2326 If you exit @value{GDBN} while you have an attached process, you detach
2327 that process. If you use the @code{run} command, you kill that process.
2328 By default, @value{GDBN} asks for confirmation if you try to do either of these
2329 things; you can control whether or not you need to confirm by using the
2330 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2334 @section Killing the Child Process
2339 Kill the child process in which your program is running under @value{GDBN}.
2342 This command is useful if you wish to debug a core dump instead of a
2343 running process. @value{GDBN} ignores any core dump file while your program
2346 On some operating systems, a program cannot be executed outside @value{GDBN}
2347 while you have breakpoints set on it inside @value{GDBN}. You can use the
2348 @code{kill} command in this situation to permit running your program
2349 outside the debugger.
2351 The @code{kill} command is also useful if you wish to recompile and
2352 relink your program, since on many systems it is impossible to modify an
2353 executable file while it is running in a process. In this case, when you
2354 next type @code{run}, @value{GDBN} notices that the file has changed, and
2355 reads the symbol table again (while trying to preserve your current
2356 breakpoint settings).
2359 @section Debugging Multiple Inferiors
2361 Some @value{GDBN} targets are able to run multiple processes created
2362 from a single executable. This can happen, for instance, with an
2363 embedded system reporting back several processes via the remote
2367 @value{GDBN} represents the state of each program execution with an
2368 object called an @dfn{inferior}. An inferior typically corresponds to
2369 a process, but is more general and applies also to targets that do not
2370 have processes. Inferiors may be created before a process runs, and
2371 may (in future) be retained after a process exits. Each run of an
2372 executable creates a new inferior, as does each attachment to an
2373 existing process. Inferiors have unique identifiers that are
2374 different from process ids, and may optionally be named as well.
2375 Usually each inferior will also have its own distinct address space,
2376 although some embedded targets may have several inferiors running in
2377 different parts of a single space.
2379 Each inferior may in turn have multiple threads running in it.
2381 To find out what inferiors exist at any moment, use @code{info inferiors}:
2384 @kindex info inferiors
2385 @item info inferiors
2386 Print a list of all inferiors currently being managed by @value{GDBN}.
2388 @kindex set print inferior-events
2389 @cindex print messages on inferior start and exit
2390 @item set print inferior-events
2391 @itemx set print inferior-events on
2392 @itemx set print inferior-events off
2393 The @code{set print inferior-events} command allows you to enable or
2394 disable printing of messages when @value{GDBN} notices that new
2395 inferiors have started or that inferiors have exited or have been
2396 detached. By default, these messages will not be printed.
2398 @kindex show print inferior-events
2399 @item show print inferior-events
2400 Show whether messages will be printed when @value{GDBN} detects that
2401 inferiors have started, exited or have been detached.
2405 @section Debugging Programs with Multiple Threads
2407 @cindex threads of execution
2408 @cindex multiple threads
2409 @cindex switching threads
2410 In some operating systems, such as HP-UX and Solaris, a single program
2411 may have more than one @dfn{thread} of execution. The precise semantics
2412 of threads differ from one operating system to another, but in general
2413 the threads of a single program are akin to multiple processes---except
2414 that they share one address space (that is, they can all examine and
2415 modify the same variables). On the other hand, each thread has its own
2416 registers and execution stack, and perhaps private memory.
2418 @value{GDBN} provides these facilities for debugging multi-thread
2422 @item automatic notification of new threads
2423 @item @samp{thread @var{threadno}}, a command to switch among threads
2424 @item @samp{info threads}, a command to inquire about existing threads
2425 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2426 a command to apply a command to a list of threads
2427 @item thread-specific breakpoints
2428 @item @samp{set print thread-events}, which controls printing of
2429 messages on thread start and exit.
2433 @emph{Warning:} These facilities are not yet available on every
2434 @value{GDBN} configuration where the operating system supports threads.
2435 If your @value{GDBN} does not support threads, these commands have no
2436 effect. For example, a system without thread support shows no output
2437 from @samp{info threads}, and always rejects the @code{thread} command,
2441 (@value{GDBP}) info threads
2442 (@value{GDBP}) thread 1
2443 Thread ID 1 not known. Use the "info threads" command to
2444 see the IDs of currently known threads.
2446 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2447 @c doesn't support threads"?
2450 @cindex focus of debugging
2451 @cindex current thread
2452 The @value{GDBN} thread debugging facility allows you to observe all
2453 threads while your program runs---but whenever @value{GDBN} takes
2454 control, one thread in particular is always the focus of debugging.
2455 This thread is called the @dfn{current thread}. Debugging commands show
2456 program information from the perspective of the current thread.
2458 @cindex @code{New} @var{systag} message
2459 @cindex thread identifier (system)
2460 @c FIXME-implementors!! It would be more helpful if the [New...] message
2461 @c included GDB's numeric thread handle, so you could just go to that
2462 @c thread without first checking `info threads'.
2463 Whenever @value{GDBN} detects a new thread in your program, it displays
2464 the target system's identification for the thread with a message in the
2465 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2466 whose form varies depending on the particular system. For example, on
2467 @sc{gnu}/Linux, you might see
2470 [New Thread 46912507313328 (LWP 25582)]
2474 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2475 the @var{systag} is simply something like @samp{process 368}, with no
2478 @c FIXME!! (1) Does the [New...] message appear even for the very first
2479 @c thread of a program, or does it only appear for the
2480 @c second---i.e.@: when it becomes obvious we have a multithread
2482 @c (2) *Is* there necessarily a first thread always? Or do some
2483 @c multithread systems permit starting a program with multiple
2484 @c threads ab initio?
2486 @cindex thread number
2487 @cindex thread identifier (GDB)
2488 For debugging purposes, @value{GDBN} associates its own thread
2489 number---always a single integer---with each thread in your program.
2492 @kindex info threads
2494 Display a summary of all threads currently in your
2495 program. @value{GDBN} displays for each thread (in this order):
2499 the thread number assigned by @value{GDBN}
2502 the target system's thread identifier (@var{systag})
2505 the current stack frame summary for that thread
2509 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2510 indicates the current thread.
2514 @c end table here to get a little more width for example
2517 (@value{GDBP}) info threads
2518 3 process 35 thread 27 0x34e5 in sigpause ()
2519 2 process 35 thread 23 0x34e5 in sigpause ()
2520 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2526 @cindex debugging multithreaded programs (on HP-UX)
2527 @cindex thread identifier (GDB), on HP-UX
2528 For debugging purposes, @value{GDBN} associates its own thread
2529 number---a small integer assigned in thread-creation order---with each
2530 thread in your program.
2532 @cindex @code{New} @var{systag} message, on HP-UX
2533 @cindex thread identifier (system), on HP-UX
2534 @c FIXME-implementors!! It would be more helpful if the [New...] message
2535 @c included GDB's numeric thread handle, so you could just go to that
2536 @c thread without first checking `info threads'.
2537 Whenever @value{GDBN} detects a new thread in your program, it displays
2538 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2539 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2540 whose form varies depending on the particular system. For example, on
2544 [New thread 2 (system thread 26594)]
2548 when @value{GDBN} notices a new thread.
2551 @kindex info threads (HP-UX)
2553 Display a summary of all threads currently in your
2554 program. @value{GDBN} displays for each thread (in this order):
2557 @item the thread number assigned by @value{GDBN}
2559 @item the target system's thread identifier (@var{systag})
2561 @item the current stack frame summary for that thread
2565 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2566 indicates the current thread.
2570 @c end table here to get a little more width for example
2573 (@value{GDBP}) info threads
2574 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2576 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2577 from /usr/lib/libc.2
2578 1 system thread 27905 0x7b003498 in _brk () \@*
2579 from /usr/lib/libc.2
2582 On Solaris, you can display more information about user threads with a
2583 Solaris-specific command:
2586 @item maint info sol-threads
2587 @kindex maint info sol-threads
2588 @cindex thread info (Solaris)
2589 Display info on Solaris user threads.
2593 @kindex thread @var{threadno}
2594 @item thread @var{threadno}
2595 Make thread number @var{threadno} the current thread. The command
2596 argument @var{threadno} is the internal @value{GDBN} thread number, as
2597 shown in the first field of the @samp{info threads} display.
2598 @value{GDBN} responds by displaying the system identifier of the thread
2599 you selected, and its current stack frame summary:
2602 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2603 (@value{GDBP}) thread 2
2604 [Switching to process 35 thread 23]
2605 0x34e5 in sigpause ()
2609 As with the @samp{[New @dots{}]} message, the form of the text after
2610 @samp{Switching to} depends on your system's conventions for identifying
2613 @kindex thread apply
2614 @cindex apply command to several threads
2615 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2616 The @code{thread apply} command allows you to apply the named
2617 @var{command} to one or more threads. Specify the numbers of the
2618 threads that you want affected with the command argument
2619 @var{threadno}. It can be a single thread number, one of the numbers
2620 shown in the first field of the @samp{info threads} display; or it
2621 could be a range of thread numbers, as in @code{2-4}. To apply a
2622 command to all threads, type @kbd{thread apply all @var{command}}.
2624 @kindex set print thread-events
2625 @cindex print messages on thread start and exit
2626 @item set print thread-events
2627 @itemx set print thread-events on
2628 @itemx set print thread-events off
2629 The @code{set print thread-events} command allows you to enable or
2630 disable printing of messages when @value{GDBN} notices that new threads have
2631 started or that threads have exited. By default, these messages will
2632 be printed if detection of these events is supported by the target.
2633 Note that these messages cannot be disabled on all targets.
2635 @kindex show print thread-events
2636 @item show print thread-events
2637 Show whether messages will be printed when @value{GDBN} detects that threads
2638 have started and exited.
2641 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2642 more information about how @value{GDBN} behaves when you stop and start
2643 programs with multiple threads.
2645 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2646 watchpoints in programs with multiple threads.
2649 @section Debugging Programs with Multiple Processes
2651 @cindex fork, debugging programs which call
2652 @cindex multiple processes
2653 @cindex processes, multiple
2654 On most systems, @value{GDBN} has no special support for debugging
2655 programs which create additional processes using the @code{fork}
2656 function. When a program forks, @value{GDBN} will continue to debug the
2657 parent process and the child process will run unimpeded. If you have
2658 set a breakpoint in any code which the child then executes, the child
2659 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2660 will cause it to terminate.
2662 However, if you want to debug the child process there is a workaround
2663 which isn't too painful. Put a call to @code{sleep} in the code which
2664 the child process executes after the fork. It may be useful to sleep
2665 only if a certain environment variable is set, or a certain file exists,
2666 so that the delay need not occur when you don't want to run @value{GDBN}
2667 on the child. While the child is sleeping, use the @code{ps} program to
2668 get its process ID. Then tell @value{GDBN} (a new invocation of
2669 @value{GDBN} if you are also debugging the parent process) to attach to
2670 the child process (@pxref{Attach}). From that point on you can debug
2671 the child process just like any other process which you attached to.
2673 On some systems, @value{GDBN} provides support for debugging programs that
2674 create additional processes using the @code{fork} or @code{vfork} functions.
2675 Currently, the only platforms with this feature are HP-UX (11.x and later
2676 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2678 By default, when a program forks, @value{GDBN} will continue to debug
2679 the parent process and the child process will run unimpeded.
2681 If you want to follow the child process instead of the parent process,
2682 use the command @w{@code{set follow-fork-mode}}.
2685 @kindex set follow-fork-mode
2686 @item set follow-fork-mode @var{mode}
2687 Set the debugger response to a program call of @code{fork} or
2688 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2689 process. The @var{mode} argument can be:
2693 The original process is debugged after a fork. The child process runs
2694 unimpeded. This is the default.
2697 The new process is debugged after a fork. The parent process runs
2702 @kindex show follow-fork-mode
2703 @item show follow-fork-mode
2704 Display the current debugger response to a @code{fork} or @code{vfork} call.
2707 @cindex debugging multiple processes
2708 On Linux, if you want to debug both the parent and child processes, use the
2709 command @w{@code{set detach-on-fork}}.
2712 @kindex set detach-on-fork
2713 @item set detach-on-fork @var{mode}
2714 Tells gdb whether to detach one of the processes after a fork, or
2715 retain debugger control over them both.
2719 The child process (or parent process, depending on the value of
2720 @code{follow-fork-mode}) will be detached and allowed to run
2721 independently. This is the default.
2724 Both processes will be held under the control of @value{GDBN}.
2725 One process (child or parent, depending on the value of
2726 @code{follow-fork-mode}) is debugged as usual, while the other
2731 @kindex show detach-on-fork
2732 @item show detach-on-fork
2733 Show whether detach-on-fork mode is on/off.
2736 If you choose to set @samp{detach-on-fork} mode off, then
2737 @value{GDBN} will retain control of all forked processes (including
2738 nested forks). You can list the forked processes under the control of
2739 @value{GDBN} by using the @w{@code{info forks}} command, and switch
2740 from one fork to another by using the @w{@code{fork}} command.
2745 Print a list of all forked processes under the control of @value{GDBN}.
2746 The listing will include a fork id, a process id, and the current
2747 position (program counter) of the process.
2749 @kindex fork @var{fork-id}
2750 @item fork @var{fork-id}
2751 Make fork number @var{fork-id} the current process. The argument
2752 @var{fork-id} is the internal fork number assigned by @value{GDBN},
2753 as shown in the first field of the @samp{info forks} display.
2755 @kindex process @var{process-id}
2756 @item process @var{process-id}
2757 Make process number @var{process-id} the current process. The
2758 argument @var{process-id} must be one that is listed in the output of
2763 To quit debugging one of the forked processes, you can either detach
2764 from it by using the @w{@code{detach fork}} command (allowing it to
2765 run independently), or delete (and kill) it using the
2766 @w{@code{delete fork}} command.
2769 @kindex detach fork @var{fork-id}
2770 @item detach fork @var{fork-id}
2771 Detach from the process identified by @value{GDBN} fork number
2772 @var{fork-id}, and remove it from the fork list. The process will be
2773 allowed to run independently.
2775 @kindex delete fork @var{fork-id}
2776 @item delete fork @var{fork-id}
2777 Kill the process identified by @value{GDBN} fork number @var{fork-id},
2778 and remove it from the fork list.
2782 If you ask to debug a child process and a @code{vfork} is followed by an
2783 @code{exec}, @value{GDBN} executes the new target up to the first
2784 breakpoint in the new target. If you have a breakpoint set on
2785 @code{main} in your original program, the breakpoint will also be set on
2786 the child process's @code{main}.
2788 When a child process is spawned by @code{vfork}, you cannot debug the
2789 child or parent until an @code{exec} call completes.
2791 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2792 call executes, the new target restarts. To restart the parent process,
2793 use the @code{file} command with the parent executable name as its
2796 You can use the @code{catch} command to make @value{GDBN} stop whenever
2797 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2798 Catchpoints, ,Setting Catchpoints}.
2800 @node Checkpoint/Restart
2801 @section Setting a @emph{Bookmark} to Return to Later
2806 @cindex snapshot of a process
2807 @cindex rewind program state
2809 On certain operating systems@footnote{Currently, only
2810 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
2811 program's state, called a @dfn{checkpoint}, and come back to it
2814 Returning to a checkpoint effectively undoes everything that has
2815 happened in the program since the @code{checkpoint} was saved. This
2816 includes changes in memory, registers, and even (within some limits)
2817 system state. Effectively, it is like going back in time to the
2818 moment when the checkpoint was saved.
2820 Thus, if you're stepping thru a program and you think you're
2821 getting close to the point where things go wrong, you can save
2822 a checkpoint. Then, if you accidentally go too far and miss
2823 the critical statement, instead of having to restart your program
2824 from the beginning, you can just go back to the checkpoint and
2825 start again from there.
2827 This can be especially useful if it takes a lot of time or
2828 steps to reach the point where you think the bug occurs.
2830 To use the @code{checkpoint}/@code{restart} method of debugging:
2835 Save a snapshot of the debugged program's current execution state.
2836 The @code{checkpoint} command takes no arguments, but each checkpoint
2837 is assigned a small integer id, similar to a breakpoint id.
2839 @kindex info checkpoints
2840 @item info checkpoints
2841 List the checkpoints that have been saved in the current debugging
2842 session. For each checkpoint, the following information will be
2849 @item Source line, or label
2852 @kindex restart @var{checkpoint-id}
2853 @item restart @var{checkpoint-id}
2854 Restore the program state that was saved as checkpoint number
2855 @var{checkpoint-id}. All program variables, registers, stack frames
2856 etc.@: will be returned to the values that they had when the checkpoint
2857 was saved. In essence, gdb will ``wind back the clock'' to the point
2858 in time when the checkpoint was saved.
2860 Note that breakpoints, @value{GDBN} variables, command history etc.
2861 are not affected by restoring a checkpoint. In general, a checkpoint
2862 only restores things that reside in the program being debugged, not in
2865 @kindex delete checkpoint @var{checkpoint-id}
2866 @item delete checkpoint @var{checkpoint-id}
2867 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
2871 Returning to a previously saved checkpoint will restore the user state
2872 of the program being debugged, plus a significant subset of the system
2873 (OS) state, including file pointers. It won't ``un-write'' data from
2874 a file, but it will rewind the file pointer to the previous location,
2875 so that the previously written data can be overwritten. For files
2876 opened in read mode, the pointer will also be restored so that the
2877 previously read data can be read again.
2879 Of course, characters that have been sent to a printer (or other
2880 external device) cannot be ``snatched back'', and characters received
2881 from eg.@: a serial device can be removed from internal program buffers,
2882 but they cannot be ``pushed back'' into the serial pipeline, ready to
2883 be received again. Similarly, the actual contents of files that have
2884 been changed cannot be restored (at this time).
2886 However, within those constraints, you actually can ``rewind'' your
2887 program to a previously saved point in time, and begin debugging it
2888 again --- and you can change the course of events so as to debug a
2889 different execution path this time.
2891 @cindex checkpoints and process id
2892 Finally, there is one bit of internal program state that will be
2893 different when you return to a checkpoint --- the program's process
2894 id. Each checkpoint will have a unique process id (or @var{pid}),
2895 and each will be different from the program's original @var{pid}.
2896 If your program has saved a local copy of its process id, this could
2897 potentially pose a problem.
2899 @subsection A Non-obvious Benefit of Using Checkpoints
2901 On some systems such as @sc{gnu}/Linux, address space randomization
2902 is performed on new processes for security reasons. This makes it
2903 difficult or impossible to set a breakpoint, or watchpoint, on an
2904 absolute address if you have to restart the program, since the
2905 absolute location of a symbol will change from one execution to the
2908 A checkpoint, however, is an @emph{identical} copy of a process.
2909 Therefore if you create a checkpoint at (eg.@:) the start of main,
2910 and simply return to that checkpoint instead of restarting the
2911 process, you can avoid the effects of address randomization and
2912 your symbols will all stay in the same place.
2915 @chapter Stopping and Continuing
2917 The principal purposes of using a debugger are so that you can stop your
2918 program before it terminates; or so that, if your program runs into
2919 trouble, you can investigate and find out why.
2921 Inside @value{GDBN}, your program may stop for any of several reasons,
2922 such as a signal, a breakpoint, or reaching a new line after a
2923 @value{GDBN} command such as @code{step}. You may then examine and
2924 change variables, set new breakpoints or remove old ones, and then
2925 continue execution. Usually, the messages shown by @value{GDBN} provide
2926 ample explanation of the status of your program---but you can also
2927 explicitly request this information at any time.
2930 @kindex info program
2932 Display information about the status of your program: whether it is
2933 running or not, what process it is, and why it stopped.
2937 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2938 * Continuing and Stepping:: Resuming execution
2940 * Thread Stops:: Stopping and starting multi-thread programs
2944 @section Breakpoints, Watchpoints, and Catchpoints
2947 A @dfn{breakpoint} makes your program stop whenever a certain point in
2948 the program is reached. For each breakpoint, you can add conditions to
2949 control in finer detail whether your program stops. You can set
2950 breakpoints with the @code{break} command and its variants (@pxref{Set
2951 Breaks, ,Setting Breakpoints}), to specify the place where your program
2952 should stop by line number, function name or exact address in the
2955 On some systems, you can set breakpoints in shared libraries before
2956 the executable is run. There is a minor limitation on HP-UX systems:
2957 you must wait until the executable is run in order to set breakpoints
2958 in shared library routines that are not called directly by the program
2959 (for example, routines that are arguments in a @code{pthread_create}
2963 @cindex data breakpoints
2964 @cindex memory tracing
2965 @cindex breakpoint on memory address
2966 @cindex breakpoint on variable modification
2967 A @dfn{watchpoint} is a special breakpoint that stops your program
2968 when the value of an expression changes. The expression may be a value
2969 of a variable, or it could involve values of one or more variables
2970 combined by operators, such as @samp{a + b}. This is sometimes called
2971 @dfn{data breakpoints}. You must use a different command to set
2972 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
2973 from that, you can manage a watchpoint like any other breakpoint: you
2974 enable, disable, and delete both breakpoints and watchpoints using the
2977 You can arrange to have values from your program displayed automatically
2978 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2982 @cindex breakpoint on events
2983 A @dfn{catchpoint} is another special breakpoint that stops your program
2984 when a certain kind of event occurs, such as the throwing of a C@t{++}
2985 exception or the loading of a library. As with watchpoints, you use a
2986 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2987 Catchpoints}), but aside from that, you can manage a catchpoint like any
2988 other breakpoint. (To stop when your program receives a signal, use the
2989 @code{handle} command; see @ref{Signals, ,Signals}.)
2991 @cindex breakpoint numbers
2992 @cindex numbers for breakpoints
2993 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2994 catchpoint when you create it; these numbers are successive integers
2995 starting with one. In many of the commands for controlling various
2996 features of breakpoints you use the breakpoint number to say which
2997 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2998 @dfn{disabled}; if disabled, it has no effect on your program until you
3001 @cindex breakpoint ranges
3002 @cindex ranges of breakpoints
3003 Some @value{GDBN} commands accept a range of breakpoints on which to
3004 operate. A breakpoint range is either a single breakpoint number, like
3005 @samp{5}, or two such numbers, in increasing order, separated by a
3006 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3007 all breakpoints in that range are operated on.
3010 * Set Breaks:: Setting breakpoints
3011 * Set Watchpoints:: Setting watchpoints
3012 * Set Catchpoints:: Setting catchpoints
3013 * Delete Breaks:: Deleting breakpoints
3014 * Disabling:: Disabling breakpoints
3015 * Conditions:: Break conditions
3016 * Break Commands:: Breakpoint command lists
3017 * Error in Breakpoints:: ``Cannot insert breakpoints''
3018 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3022 @subsection Setting Breakpoints
3024 @c FIXME LMB what does GDB do if no code on line of breakpt?
3025 @c consider in particular declaration with/without initialization.
3027 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3030 @kindex b @r{(@code{break})}
3031 @vindex $bpnum@r{, convenience variable}
3032 @cindex latest breakpoint
3033 Breakpoints are set with the @code{break} command (abbreviated
3034 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3035 number of the breakpoint you've set most recently; see @ref{Convenience
3036 Vars,, Convenience Variables}, for a discussion of what you can do with
3037 convenience variables.
3040 @item break @var{location}
3041 Set a breakpoint at the given @var{location}, which can specify a
3042 function name, a line number, or an address of an instruction.
3043 (@xref{Specify Location}, for a list of all the possible ways to
3044 specify a @var{location}.) The breakpoint will stop your program just
3045 before it executes any of the code in the specified @var{location}.
3047 When using source languages that permit overloading of symbols, such as
3048 C@t{++}, a function name may refer to more than one possible place to break.
3049 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3053 When called without any arguments, @code{break} sets a breakpoint at
3054 the next instruction to be executed in the selected stack frame
3055 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3056 innermost, this makes your program stop as soon as control
3057 returns to that frame. This is similar to the effect of a
3058 @code{finish} command in the frame inside the selected frame---except
3059 that @code{finish} does not leave an active breakpoint. If you use
3060 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3061 the next time it reaches the current location; this may be useful
3064 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3065 least one instruction has been executed. If it did not do this, you
3066 would be unable to proceed past a breakpoint without first disabling the
3067 breakpoint. This rule applies whether or not the breakpoint already
3068 existed when your program stopped.
3070 @item break @dots{} if @var{cond}
3071 Set a breakpoint with condition @var{cond}; evaluate the expression
3072 @var{cond} each time the breakpoint is reached, and stop only if the
3073 value is nonzero---that is, if @var{cond} evaluates as true.
3074 @samp{@dots{}} stands for one of the possible arguments described
3075 above (or no argument) specifying where to break. @xref{Conditions,
3076 ,Break Conditions}, for more information on breakpoint conditions.
3079 @item tbreak @var{args}
3080 Set a breakpoint enabled only for one stop. @var{args} are the
3081 same as for the @code{break} command, and the breakpoint is set in the same
3082 way, but the breakpoint is automatically deleted after the first time your
3083 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3086 @cindex hardware breakpoints
3087 @item hbreak @var{args}
3088 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3089 @code{break} command and the breakpoint is set in the same way, but the
3090 breakpoint requires hardware support and some target hardware may not
3091 have this support. The main purpose of this is EPROM/ROM code
3092 debugging, so you can set a breakpoint at an instruction without
3093 changing the instruction. This can be used with the new trap-generation
3094 provided by SPARClite DSU and most x86-based targets. These targets
3095 will generate traps when a program accesses some data or instruction
3096 address that is assigned to the debug registers. However the hardware
3097 breakpoint registers can take a limited number of breakpoints. For
3098 example, on the DSU, only two data breakpoints can be set at a time, and
3099 @value{GDBN} will reject this command if more than two are used. Delete
3100 or disable unused hardware breakpoints before setting new ones
3101 (@pxref{Disabling, ,Disabling Breakpoints}).
3102 @xref{Conditions, ,Break Conditions}.
3103 For remote targets, you can restrict the number of hardware
3104 breakpoints @value{GDBN} will use, see @ref{set remote
3105 hardware-breakpoint-limit}.
3108 @item thbreak @var{args}
3109 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3110 are the same as for the @code{hbreak} command and the breakpoint is set in
3111 the same way. However, like the @code{tbreak} command,
3112 the breakpoint is automatically deleted after the
3113 first time your program stops there. Also, like the @code{hbreak}
3114 command, the breakpoint requires hardware support and some target hardware
3115 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3116 See also @ref{Conditions, ,Break Conditions}.
3119 @cindex regular expression
3120 @cindex breakpoints in functions matching a regexp
3121 @cindex set breakpoints in many functions
3122 @item rbreak @var{regex}
3123 Set breakpoints on all functions matching the regular expression
3124 @var{regex}. This command sets an unconditional breakpoint on all
3125 matches, printing a list of all breakpoints it set. Once these
3126 breakpoints are set, they are treated just like the breakpoints set with
3127 the @code{break} command. You can delete them, disable them, or make
3128 them conditional the same way as any other breakpoint.
3130 The syntax of the regular expression is the standard one used with tools
3131 like @file{grep}. Note that this is different from the syntax used by
3132 shells, so for instance @code{foo*} matches all functions that include
3133 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3134 @code{.*} leading and trailing the regular expression you supply, so to
3135 match only functions that begin with @code{foo}, use @code{^foo}.
3137 @cindex non-member C@t{++} functions, set breakpoint in
3138 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3139 breakpoints on overloaded functions that are not members of any special
3142 @cindex set breakpoints on all functions
3143 The @code{rbreak} command can be used to set breakpoints in
3144 @strong{all} the functions in a program, like this:
3147 (@value{GDBP}) rbreak .
3150 @kindex info breakpoints
3151 @cindex @code{$_} and @code{info breakpoints}
3152 @item info breakpoints @r{[}@var{n}@r{]}
3153 @itemx info break @r{[}@var{n}@r{]}
3154 @itemx info watchpoints @r{[}@var{n}@r{]}
3155 Print a table of all breakpoints, watchpoints, and catchpoints set and
3156 not deleted. Optional argument @var{n} means print information only
3157 about the specified breakpoint (or watchpoint or catchpoint). For
3158 each breakpoint, following columns are printed:
3161 @item Breakpoint Numbers
3163 Breakpoint, watchpoint, or catchpoint.
3165 Whether the breakpoint is marked to be disabled or deleted when hit.
3166 @item Enabled or Disabled
3167 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3168 that are not enabled.
3170 Where the breakpoint is in your program, as a memory address. For a
3171 pending breakpoint whose address is not yet known, this field will
3172 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3173 library that has the symbol or line referred by breakpoint is loaded.
3174 See below for details. A breakpoint with several locations will
3175 have @samp{<MULTIPLE>} in this field---see below for details.
3177 Where the breakpoint is in the source for your program, as a file and
3178 line number. For a pending breakpoint, the original string passed to
3179 the breakpoint command will be listed as it cannot be resolved until
3180 the appropriate shared library is loaded in the future.
3184 If a breakpoint is conditional, @code{info break} shows the condition on
3185 the line following the affected breakpoint; breakpoint commands, if any,
3186 are listed after that. A pending breakpoint is allowed to have a condition
3187 specified for it. The condition is not parsed for validity until a shared
3188 library is loaded that allows the pending breakpoint to resolve to a
3192 @code{info break} with a breakpoint
3193 number @var{n} as argument lists only that breakpoint. The
3194 convenience variable @code{$_} and the default examining-address for
3195 the @code{x} command are set to the address of the last breakpoint
3196 listed (@pxref{Memory, ,Examining Memory}).
3199 @code{info break} displays a count of the number of times the breakpoint
3200 has been hit. This is especially useful in conjunction with the
3201 @code{ignore} command. You can ignore a large number of breakpoint
3202 hits, look at the breakpoint info to see how many times the breakpoint
3203 was hit, and then run again, ignoring one less than that number. This
3204 will get you quickly to the last hit of that breakpoint.
3207 @value{GDBN} allows you to set any number of breakpoints at the same place in
3208 your program. There is nothing silly or meaningless about this. When
3209 the breakpoints are conditional, this is even useful
3210 (@pxref{Conditions, ,Break Conditions}).
3212 @cindex multiple locations, breakpoints
3213 @cindex breakpoints, multiple locations
3214 It is possible that a breakpoint corresponds to several locations
3215 in your program. Examples of this situation are:
3219 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3220 instances of the function body, used in different cases.
3223 For a C@t{++} template function, a given line in the function can
3224 correspond to any number of instantiations.
3227 For an inlined function, a given source line can correspond to
3228 several places where that function is inlined.
3231 In all those cases, @value{GDBN} will insert a breakpoint at all
3232 the relevant locations@footnote{
3233 As of this writing, multiple-location breakpoints work only if there's
3234 line number information for all the locations. This means that they
3235 will generally not work in system libraries, unless you have debug
3236 info with line numbers for them.}.
3238 A breakpoint with multiple locations is displayed in the breakpoint
3239 table using several rows---one header row, followed by one row for
3240 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3241 address column. The rows for individual locations contain the actual
3242 addresses for locations, and show the functions to which those
3243 locations belong. The number column for a location is of the form
3244 @var{breakpoint-number}.@var{location-number}.
3249 Num Type Disp Enb Address What
3250 1 breakpoint keep y <MULTIPLE>
3252 breakpoint already hit 1 time
3253 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3254 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3257 Each location can be individually enabled or disabled by passing
3258 @var{breakpoint-number}.@var{location-number} as argument to the
3259 @code{enable} and @code{disable} commands. Note that you cannot
3260 delete the individual locations from the list, you can only delete the
3261 entire list of locations that belong to their parent breakpoint (with
3262 the @kbd{delete @var{num}} command, where @var{num} is the number of
3263 the parent breakpoint, 1 in the above example). Disabling or enabling
3264 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3265 that belong to that breakpoint.
3267 @cindex pending breakpoints
3268 It's quite common to have a breakpoint inside a shared library.
3269 Shared libraries can be loaded and unloaded explicitly,
3270 and possibly repeatedly, as the program is executed. To support
3271 this use case, @value{GDBN} updates breakpoint locations whenever
3272 any shared library is loaded or unloaded. Typically, you would
3273 set a breakpoint in a shared library at the beginning of your
3274 debugging session, when the library is not loaded, and when the
3275 symbols from the library are not available. When you try to set
3276 breakpoint, @value{GDBN} will ask you if you want to set
3277 a so called @dfn{pending breakpoint}---breakpoint whose address
3278 is not yet resolved.
3280 After the program is run, whenever a new shared library is loaded,
3281 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3282 shared library contains the symbol or line referred to by some
3283 pending breakpoint, that breakpoint is resolved and becomes an
3284 ordinary breakpoint. When a library is unloaded, all breakpoints
3285 that refer to its symbols or source lines become pending again.
3287 This logic works for breakpoints with multiple locations, too. For
3288 example, if you have a breakpoint in a C@t{++} template function, and
3289 a newly loaded shared library has an instantiation of that template,
3290 a new location is added to the list of locations for the breakpoint.
3292 Except for having unresolved address, pending breakpoints do not
3293 differ from regular breakpoints. You can set conditions or commands,
3294 enable and disable them and perform other breakpoint operations.
3296 @value{GDBN} provides some additional commands for controlling what
3297 happens when the @samp{break} command cannot resolve breakpoint
3298 address specification to an address:
3300 @kindex set breakpoint pending
3301 @kindex show breakpoint pending
3303 @item set breakpoint pending auto
3304 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3305 location, it queries you whether a pending breakpoint should be created.
3307 @item set breakpoint pending on
3308 This indicates that an unrecognized breakpoint location should automatically
3309 result in a pending breakpoint being created.
3311 @item set breakpoint pending off
3312 This indicates that pending breakpoints are not to be created. Any
3313 unrecognized breakpoint location results in an error. This setting does
3314 not affect any pending breakpoints previously created.
3316 @item show breakpoint pending
3317 Show the current behavior setting for creating pending breakpoints.
3320 The settings above only affect the @code{break} command and its
3321 variants. Once breakpoint is set, it will be automatically updated
3322 as shared libraries are loaded and unloaded.
3324 @cindex automatic hardware breakpoints
3325 For some targets, @value{GDBN} can automatically decide if hardware or
3326 software breakpoints should be used, depending on whether the
3327 breakpoint address is read-only or read-write. This applies to
3328 breakpoints set with the @code{break} command as well as to internal
3329 breakpoints set by commands like @code{next} and @code{finish}. For
3330 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3333 You can control this automatic behaviour with the following commands::
3335 @kindex set breakpoint auto-hw
3336 @kindex show breakpoint auto-hw
3338 @item set breakpoint auto-hw on
3339 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3340 will try to use the target memory map to decide if software or hardware
3341 breakpoint must be used.
3343 @item set breakpoint auto-hw off
3344 This indicates @value{GDBN} should not automatically select breakpoint
3345 type. If the target provides a memory map, @value{GDBN} will warn when
3346 trying to set software breakpoint at a read-only address.
3349 @value{GDBN} normally implements breakpoints by replacing the program code
3350 at the breakpoint address with a special instruction, which, when
3351 executed, given control to the debugger. By default, the program
3352 code is so modified only when the program is resumed. As soon as
3353 the program stops, @value{GDBN} restores the original instructions. This
3354 behaviour guards against leaving breakpoints inserted in the
3355 target should gdb abrubptly disconnect. However, with slow remote
3356 targets, inserting and removing breakpoint can reduce the performance.
3357 This behavior can be controlled with the following commands::
3359 @kindex set breakpoint always-inserted
3360 @kindex show breakpoint always-inserted
3362 @item set breakpoint always-inserted off
3363 All breakpoints, including newly added by the user, are inserted in
3364 the target only when the target is resumed. All breakpoints are
3365 removed from the target when it stops.
3367 @item set breakpoint always-inserted on
3368 Causes all breakpoints to be inserted in the target at all times. If
3369 the user adds a new breakpoint, or changes an existing breakpoint, the
3370 breakpoints in the target are updated immediately. A breakpoint is
3371 removed from the target only when breakpoint itself is removed.
3373 @cindex non-stop mode, and @code{breakpoint always-inserted}
3374 @item set breakpoint always-inserted auto
3375 This is the default mode. If @value{GDBN} is controlling the inferior
3376 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3377 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3378 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3379 @code{breakpoint always-inserted} mode is off.
3382 @cindex negative breakpoint numbers
3383 @cindex internal @value{GDBN} breakpoints
3384 @value{GDBN} itself sometimes sets breakpoints in your program for
3385 special purposes, such as proper handling of @code{longjmp} (in C
3386 programs). These internal breakpoints are assigned negative numbers,
3387 starting with @code{-1}; @samp{info breakpoints} does not display them.
3388 You can see these breakpoints with the @value{GDBN} maintenance command
3389 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3392 @node Set Watchpoints
3393 @subsection Setting Watchpoints
3395 @cindex setting watchpoints
3396 You can use a watchpoint to stop execution whenever the value of an
3397 expression changes, without having to predict a particular place where
3398 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3399 The expression may be as simple as the value of a single variable, or
3400 as complex as many variables combined by operators. Examples include:
3404 A reference to the value of a single variable.
3407 An address cast to an appropriate data type. For example,
3408 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3409 address (assuming an @code{int} occupies 4 bytes).
3412 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3413 expression can use any operators valid in the program's native
3414 language (@pxref{Languages}).
3417 You can set a watchpoint on an expression even if the expression can
3418 not be evaluated yet. For instance, you can set a watchpoint on
3419 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3420 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3421 the expression produces a valid value. If the expression becomes
3422 valid in some other way than changing a variable (e.g.@: if the memory
3423 pointed to by @samp{*global_ptr} becomes readable as the result of a
3424 @code{malloc} call), @value{GDBN} may not stop until the next time
3425 the expression changes.
3427 @cindex software watchpoints
3428 @cindex hardware watchpoints
3429 Depending on your system, watchpoints may be implemented in software or
3430 hardware. @value{GDBN} does software watchpointing by single-stepping your
3431 program and testing the variable's value each time, which is hundreds of
3432 times slower than normal execution. (But this may still be worth it, to
3433 catch errors where you have no clue what part of your program is the
3436 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3437 x86-based targets, @value{GDBN} includes support for hardware
3438 watchpoints, which do not slow down the running of your program.
3442 @item watch @var{expr} @r{[}thread @var{threadnum}@r{]}
3443 Set a watchpoint for an expression. @value{GDBN} will break when the
3444 expression @var{expr} is written into by the program and its value
3445 changes. The simplest (and the most popular) use of this command is
3446 to watch the value of a single variable:
3449 (@value{GDBP}) watch foo
3452 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3453 clause, @value{GDBN} breaks only when the thread identified by
3454 @var{threadnum} changes the value of @var{expr}. If any other threads
3455 change the value of @var{expr}, @value{GDBN} will not break. Note
3456 that watchpoints restricted to a single thread in this way only work
3457 with Hardware Watchpoints.
3460 @item rwatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3461 Set a watchpoint that will break when the value of @var{expr} is read
3465 @item awatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3466 Set a watchpoint that will break when @var{expr} is either read from
3467 or written into by the program.
3469 @kindex info watchpoints @r{[}@var{n}@r{]}
3470 @item info watchpoints
3471 This command prints a list of watchpoints, breakpoints, and catchpoints;
3472 it is the same as @code{info break} (@pxref{Set Breaks}).
3475 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3476 watchpoints execute very quickly, and the debugger reports a change in
3477 value at the exact instruction where the change occurs. If @value{GDBN}
3478 cannot set a hardware watchpoint, it sets a software watchpoint, which
3479 executes more slowly and reports the change in value at the next
3480 @emph{statement}, not the instruction, after the change occurs.
3482 @cindex use only software watchpoints
3483 You can force @value{GDBN} to use only software watchpoints with the
3484 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3485 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3486 the underlying system supports them. (Note that hardware-assisted
3487 watchpoints that were set @emph{before} setting
3488 @code{can-use-hw-watchpoints} to zero will still use the hardware
3489 mechanism of watching expression values.)
3492 @item set can-use-hw-watchpoints
3493 @kindex set can-use-hw-watchpoints
3494 Set whether or not to use hardware watchpoints.
3496 @item show can-use-hw-watchpoints
3497 @kindex show can-use-hw-watchpoints
3498 Show the current mode of using hardware watchpoints.
3501 For remote targets, you can restrict the number of hardware
3502 watchpoints @value{GDBN} will use, see @ref{set remote
3503 hardware-breakpoint-limit}.
3505 When you issue the @code{watch} command, @value{GDBN} reports
3508 Hardware watchpoint @var{num}: @var{expr}
3512 if it was able to set a hardware watchpoint.
3514 Currently, the @code{awatch} and @code{rwatch} commands can only set
3515 hardware watchpoints, because accesses to data that don't change the
3516 value of the watched expression cannot be detected without examining
3517 every instruction as it is being executed, and @value{GDBN} does not do
3518 that currently. If @value{GDBN} finds that it is unable to set a
3519 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3520 will print a message like this:
3523 Expression cannot be implemented with read/access watchpoint.
3526 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3527 data type of the watched expression is wider than what a hardware
3528 watchpoint on the target machine can handle. For example, some systems
3529 can only watch regions that are up to 4 bytes wide; on such systems you
3530 cannot set hardware watchpoints for an expression that yields a
3531 double-precision floating-point number (which is typically 8 bytes
3532 wide). As a work-around, it might be possible to break the large region
3533 into a series of smaller ones and watch them with separate watchpoints.
3535 If you set too many hardware watchpoints, @value{GDBN} might be unable
3536 to insert all of them when you resume the execution of your program.
3537 Since the precise number of active watchpoints is unknown until such
3538 time as the program is about to be resumed, @value{GDBN} might not be
3539 able to warn you about this when you set the watchpoints, and the
3540 warning will be printed only when the program is resumed:
3543 Hardware watchpoint @var{num}: Could not insert watchpoint
3547 If this happens, delete or disable some of the watchpoints.
3549 Watching complex expressions that reference many variables can also
3550 exhaust the resources available for hardware-assisted watchpoints.
3551 That's because @value{GDBN} needs to watch every variable in the
3552 expression with separately allocated resources.
3554 If you call a function interactively using @code{print} or @code{call},
3555 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3556 kind of breakpoint or the call completes.
3558 @value{GDBN} automatically deletes watchpoints that watch local
3559 (automatic) variables, or expressions that involve such variables, when
3560 they go out of scope, that is, when the execution leaves the block in
3561 which these variables were defined. In particular, when the program
3562 being debugged terminates, @emph{all} local variables go out of scope,
3563 and so only watchpoints that watch global variables remain set. If you
3564 rerun the program, you will need to set all such watchpoints again. One
3565 way of doing that would be to set a code breakpoint at the entry to the
3566 @code{main} function and when it breaks, set all the watchpoints.
3568 @cindex watchpoints and threads
3569 @cindex threads and watchpoints
3570 In multi-threaded programs, watchpoints will detect changes to the
3571 watched expression from every thread.
3574 @emph{Warning:} In multi-threaded programs, software watchpoints
3575 have only limited usefulness. If @value{GDBN} creates a software
3576 watchpoint, it can only watch the value of an expression @emph{in a
3577 single thread}. If you are confident that the expression can only
3578 change due to the current thread's activity (and if you are also
3579 confident that no other thread can become current), then you can use
3580 software watchpoints as usual. However, @value{GDBN} may not notice
3581 when a non-current thread's activity changes the expression. (Hardware
3582 watchpoints, in contrast, watch an expression in all threads.)
3585 @xref{set remote hardware-watchpoint-limit}.
3587 @node Set Catchpoints
3588 @subsection Setting Catchpoints
3589 @cindex catchpoints, setting
3590 @cindex exception handlers
3591 @cindex event handling
3593 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3594 kinds of program events, such as C@t{++} exceptions or the loading of a
3595 shared library. Use the @code{catch} command to set a catchpoint.
3599 @item catch @var{event}
3600 Stop when @var{event} occurs. @var{event} can be any of the following:
3603 @cindex stop on C@t{++} exceptions
3604 The throwing of a C@t{++} exception.
3607 The catching of a C@t{++} exception.
3610 @cindex Ada exception catching
3611 @cindex catch Ada exceptions
3612 An Ada exception being raised. If an exception name is specified
3613 at the end of the command (eg @code{catch exception Program_Error}),
3614 the debugger will stop only when this specific exception is raised.
3615 Otherwise, the debugger stops execution when any Ada exception is raised.
3617 When inserting an exception catchpoint on a user-defined exception whose
3618 name is identical to one of the exceptions defined by the language, the
3619 fully qualified name must be used as the exception name. Otherwise,
3620 @value{GDBN} will assume that it should stop on the pre-defined exception
3621 rather than the user-defined one. For instance, assuming an exception
3622 called @code{Constraint_Error} is defined in package @code{Pck}, then
3623 the command to use to catch such exceptions is @kbd{catch exception
3624 Pck.Constraint_Error}.
3626 @item exception unhandled
3627 An exception that was raised but is not handled by the program.
3630 A failed Ada assertion.
3633 @cindex break on fork/exec
3634 A call to @code{exec}. This is currently only available for HP-UX
3638 A call to @code{fork}. This is currently only available for HP-UX
3642 A call to @code{vfork}. This is currently only available for HP-UX
3646 @itemx load @var{libname}
3647 @cindex break on load/unload of shared library
3648 The dynamic loading of any shared library, or the loading of the library
3649 @var{libname}. This is currently only available for HP-UX.
3652 @itemx unload @var{libname}
3653 The unloading of any dynamically loaded shared library, or the unloading
3654 of the library @var{libname}. This is currently only available for HP-UX.
3657 @item tcatch @var{event}
3658 Set a catchpoint that is enabled only for one stop. The catchpoint is
3659 automatically deleted after the first time the event is caught.
3663 Use the @code{info break} command to list the current catchpoints.
3665 There are currently some limitations to C@t{++} exception handling
3666 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
3670 If you call a function interactively, @value{GDBN} normally returns
3671 control to you when the function has finished executing. If the call
3672 raises an exception, however, the call may bypass the mechanism that
3673 returns control to you and cause your program either to abort or to
3674 simply continue running until it hits a breakpoint, catches a signal
3675 that @value{GDBN} is listening for, or exits. This is the case even if
3676 you set a catchpoint for the exception; catchpoints on exceptions are
3677 disabled within interactive calls.
3680 You cannot raise an exception interactively.
3683 You cannot install an exception handler interactively.
3686 @cindex raise exceptions
3687 Sometimes @code{catch} is not the best way to debug exception handling:
3688 if you need to know exactly where an exception is raised, it is better to
3689 stop @emph{before} the exception handler is called, since that way you
3690 can see the stack before any unwinding takes place. If you set a
3691 breakpoint in an exception handler instead, it may not be easy to find
3692 out where the exception was raised.
3694 To stop just before an exception handler is called, you need some
3695 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3696 raised by calling a library function named @code{__raise_exception}
3697 which has the following ANSI C interface:
3700 /* @var{addr} is where the exception identifier is stored.
3701 @var{id} is the exception identifier. */
3702 void __raise_exception (void **addr, void *id);
3706 To make the debugger catch all exceptions before any stack
3707 unwinding takes place, set a breakpoint on @code{__raise_exception}
3708 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
3710 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
3711 that depends on the value of @var{id}, you can stop your program when
3712 a specific exception is raised. You can use multiple conditional
3713 breakpoints to stop your program when any of a number of exceptions are
3718 @subsection Deleting Breakpoints
3720 @cindex clearing breakpoints, watchpoints, catchpoints
3721 @cindex deleting breakpoints, watchpoints, catchpoints
3722 It is often necessary to eliminate a breakpoint, watchpoint, or
3723 catchpoint once it has done its job and you no longer want your program
3724 to stop there. This is called @dfn{deleting} the breakpoint. A
3725 breakpoint that has been deleted no longer exists; it is forgotten.
3727 With the @code{clear} command you can delete breakpoints according to
3728 where they are in your program. With the @code{delete} command you can
3729 delete individual breakpoints, watchpoints, or catchpoints by specifying
3730 their breakpoint numbers.
3732 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3733 automatically ignores breakpoints on the first instruction to be executed
3734 when you continue execution without changing the execution address.
3739 Delete any breakpoints at the next instruction to be executed in the
3740 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
3741 the innermost frame is selected, this is a good way to delete a
3742 breakpoint where your program just stopped.
3744 @item clear @var{location}
3745 Delete any breakpoints set at the specified @var{location}.
3746 @xref{Specify Location}, for the various forms of @var{location}; the
3747 most useful ones are listed below:
3750 @item clear @var{function}
3751 @itemx clear @var{filename}:@var{function}
3752 Delete any breakpoints set at entry to the named @var{function}.
3754 @item clear @var{linenum}
3755 @itemx clear @var{filename}:@var{linenum}
3756 Delete any breakpoints set at or within the code of the specified
3757 @var{linenum} of the specified @var{filename}.
3760 @cindex delete breakpoints
3762 @kindex d @r{(@code{delete})}
3763 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3764 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3765 ranges specified as arguments. If no argument is specified, delete all
3766 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3767 confirm off}). You can abbreviate this command as @code{d}.
3771 @subsection Disabling Breakpoints
3773 @cindex enable/disable a breakpoint
3774 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3775 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3776 it had been deleted, but remembers the information on the breakpoint so
3777 that you can @dfn{enable} it again later.
3779 You disable and enable breakpoints, watchpoints, and catchpoints with
3780 the @code{enable} and @code{disable} commands, optionally specifying one
3781 or more breakpoint numbers as arguments. Use @code{info break} or
3782 @code{info watch} to print a list of breakpoints, watchpoints, and
3783 catchpoints if you do not know which numbers to use.
3785 Disabling and enabling a breakpoint that has multiple locations
3786 affects all of its locations.
3788 A breakpoint, watchpoint, or catchpoint can have any of four different
3789 states of enablement:
3793 Enabled. The breakpoint stops your program. A breakpoint set
3794 with the @code{break} command starts out in this state.
3796 Disabled. The breakpoint has no effect on your program.
3798 Enabled once. The breakpoint stops your program, but then becomes
3801 Enabled for deletion. The breakpoint stops your program, but
3802 immediately after it does so it is deleted permanently. A breakpoint
3803 set with the @code{tbreak} command starts out in this state.
3806 You can use the following commands to enable or disable breakpoints,
3807 watchpoints, and catchpoints:
3811 @kindex dis @r{(@code{disable})}
3812 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3813 Disable the specified breakpoints---or all breakpoints, if none are
3814 listed. A disabled breakpoint has no effect but is not forgotten. All
3815 options such as ignore-counts, conditions and commands are remembered in
3816 case the breakpoint is enabled again later. You may abbreviate
3817 @code{disable} as @code{dis}.
3820 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3821 Enable the specified breakpoints (or all defined breakpoints). They
3822 become effective once again in stopping your program.
3824 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3825 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3826 of these breakpoints immediately after stopping your program.
3828 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3829 Enable the specified breakpoints to work once, then die. @value{GDBN}
3830 deletes any of these breakpoints as soon as your program stops there.
3831 Breakpoints set by the @code{tbreak} command start out in this state.
3834 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3835 @c confusing: tbreak is also initially enabled.
3836 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3837 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
3838 subsequently, they become disabled or enabled only when you use one of
3839 the commands above. (The command @code{until} can set and delete a
3840 breakpoint of its own, but it does not change the state of your other
3841 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3845 @subsection Break Conditions
3846 @cindex conditional breakpoints
3847 @cindex breakpoint conditions
3849 @c FIXME what is scope of break condition expr? Context where wanted?
3850 @c in particular for a watchpoint?
3851 The simplest sort of breakpoint breaks every time your program reaches a
3852 specified place. You can also specify a @dfn{condition} for a
3853 breakpoint. A condition is just a Boolean expression in your
3854 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3855 a condition evaluates the expression each time your program reaches it,
3856 and your program stops only if the condition is @emph{true}.
3858 This is the converse of using assertions for program validation; in that
3859 situation, you want to stop when the assertion is violated---that is,
3860 when the condition is false. In C, if you want to test an assertion expressed
3861 by the condition @var{assert}, you should set the condition
3862 @samp{! @var{assert}} on the appropriate breakpoint.
3864 Conditions are also accepted for watchpoints; you may not need them,
3865 since a watchpoint is inspecting the value of an expression anyhow---but
3866 it might be simpler, say, to just set a watchpoint on a variable name,
3867 and specify a condition that tests whether the new value is an interesting
3870 Break conditions can have side effects, and may even call functions in
3871 your program. This can be useful, for example, to activate functions
3872 that log program progress, or to use your own print functions to
3873 format special data structures. The effects are completely predictable
3874 unless there is another enabled breakpoint at the same address. (In
3875 that case, @value{GDBN} might see the other breakpoint first and stop your
3876 program without checking the condition of this one.) Note that
3877 breakpoint commands are usually more convenient and flexible than break
3879 purpose of performing side effects when a breakpoint is reached
3880 (@pxref{Break Commands, ,Breakpoint Command Lists}).
3882 Break conditions can be specified when a breakpoint is set, by using
3883 @samp{if} in the arguments to the @code{break} command. @xref{Set
3884 Breaks, ,Setting Breakpoints}. They can also be changed at any time
3885 with the @code{condition} command.
3887 You can also use the @code{if} keyword with the @code{watch} command.
3888 The @code{catch} command does not recognize the @code{if} keyword;
3889 @code{condition} is the only way to impose a further condition on a
3894 @item condition @var{bnum} @var{expression}
3895 Specify @var{expression} as the break condition for breakpoint,
3896 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3897 breakpoint @var{bnum} stops your program only if the value of
3898 @var{expression} is true (nonzero, in C). When you use
3899 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3900 syntactic correctness, and to determine whether symbols in it have
3901 referents in the context of your breakpoint. If @var{expression} uses
3902 symbols not referenced in the context of the breakpoint, @value{GDBN}
3903 prints an error message:
3906 No symbol "foo" in current context.
3911 not actually evaluate @var{expression} at the time the @code{condition}
3912 command (or a command that sets a breakpoint with a condition, like
3913 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3915 @item condition @var{bnum}
3916 Remove the condition from breakpoint number @var{bnum}. It becomes
3917 an ordinary unconditional breakpoint.
3920 @cindex ignore count (of breakpoint)
3921 A special case of a breakpoint condition is to stop only when the
3922 breakpoint has been reached a certain number of times. This is so
3923 useful that there is a special way to do it, using the @dfn{ignore
3924 count} of the breakpoint. Every breakpoint has an ignore count, which
3925 is an integer. Most of the time, the ignore count is zero, and
3926 therefore has no effect. But if your program reaches a breakpoint whose
3927 ignore count is positive, then instead of stopping, it just decrements
3928 the ignore count by one and continues. As a result, if the ignore count
3929 value is @var{n}, the breakpoint does not stop the next @var{n} times
3930 your program reaches it.
3934 @item ignore @var{bnum} @var{count}
3935 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3936 The next @var{count} times the breakpoint is reached, your program's
3937 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3940 To make the breakpoint stop the next time it is reached, specify
3943 When you use @code{continue} to resume execution of your program from a
3944 breakpoint, you can specify an ignore count directly as an argument to
3945 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3946 Stepping,,Continuing and Stepping}.
3948 If a breakpoint has a positive ignore count and a condition, the
3949 condition is not checked. Once the ignore count reaches zero,
3950 @value{GDBN} resumes checking the condition.
3952 You could achieve the effect of the ignore count with a condition such
3953 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3954 is decremented each time. @xref{Convenience Vars, ,Convenience
3958 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3961 @node Break Commands
3962 @subsection Breakpoint Command Lists
3964 @cindex breakpoint commands
3965 You can give any breakpoint (or watchpoint or catchpoint) a series of
3966 commands to execute when your program stops due to that breakpoint. For
3967 example, you might want to print the values of certain expressions, or
3968 enable other breakpoints.
3972 @kindex end@r{ (breakpoint commands)}
3973 @item commands @r{[}@var{bnum}@r{]}
3974 @itemx @dots{} @var{command-list} @dots{}
3976 Specify a list of commands for breakpoint number @var{bnum}. The commands
3977 themselves appear on the following lines. Type a line containing just
3978 @code{end} to terminate the commands.
3980 To remove all commands from a breakpoint, type @code{commands} and
3981 follow it immediately with @code{end}; that is, give no commands.
3983 With no @var{bnum} argument, @code{commands} refers to the last
3984 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3985 recently encountered).
3988 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3989 disabled within a @var{command-list}.
3991 You can use breakpoint commands to start your program up again. Simply
3992 use the @code{continue} command, or @code{step}, or any other command
3993 that resumes execution.
3995 Any other commands in the command list, after a command that resumes
3996 execution, are ignored. This is because any time you resume execution
3997 (even with a simple @code{next} or @code{step}), you may encounter
3998 another breakpoint---which could have its own command list, leading to
3999 ambiguities about which list to execute.
4002 If the first command you specify in a command list is @code{silent}, the
4003 usual message about stopping at a breakpoint is not printed. This may
4004 be desirable for breakpoints that are to print a specific message and
4005 then continue. If none of the remaining commands print anything, you
4006 see no sign that the breakpoint was reached. @code{silent} is
4007 meaningful only at the beginning of a breakpoint command list.
4009 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4010 print precisely controlled output, and are often useful in silent
4011 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4013 For example, here is how you could use breakpoint commands to print the
4014 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4020 printf "x is %d\n",x
4025 One application for breakpoint commands is to compensate for one bug so
4026 you can test for another. Put a breakpoint just after the erroneous line
4027 of code, give it a condition to detect the case in which something
4028 erroneous has been done, and give it commands to assign correct values
4029 to any variables that need them. End with the @code{continue} command
4030 so that your program does not stop, and start with the @code{silent}
4031 command so that no output is produced. Here is an example:
4042 @c @ifclear BARETARGET
4043 @node Error in Breakpoints
4044 @subsection ``Cannot insert breakpoints''
4046 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
4048 Under some operating systems, breakpoints cannot be used in a program if
4049 any other process is running that program. In this situation,
4050 attempting to run or continue a program with a breakpoint causes
4051 @value{GDBN} to print an error message:
4054 Cannot insert breakpoints.
4055 The same program may be running in another process.
4058 When this happens, you have three ways to proceed:
4062 Remove or disable the breakpoints, then continue.
4065 Suspend @value{GDBN}, and copy the file containing your program to a new
4066 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
4067 that @value{GDBN} should run your program under that name.
4068 Then start your program again.
4071 Relink your program so that the text segment is nonsharable, using the
4072 linker option @samp{-N}. The operating system limitation may not apply
4073 to nonsharable executables.
4077 A similar message can be printed if you request too many active
4078 hardware-assisted breakpoints and watchpoints:
4080 @c FIXME: the precise wording of this message may change; the relevant
4081 @c source change is not committed yet (Sep 3, 1999).
4083 Stopped; cannot insert breakpoints.
4084 You may have requested too many hardware breakpoints and watchpoints.
4088 This message is printed when you attempt to resume the program, since
4089 only then @value{GDBN} knows exactly how many hardware breakpoints and
4090 watchpoints it needs to insert.
4092 When this message is printed, you need to disable or remove some of the
4093 hardware-assisted breakpoints and watchpoints, and then continue.
4095 @node Breakpoint-related Warnings
4096 @subsection ``Breakpoint address adjusted...''
4097 @cindex breakpoint address adjusted
4099 Some processor architectures place constraints on the addresses at
4100 which breakpoints may be placed. For architectures thus constrained,
4101 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4102 with the constraints dictated by the architecture.
4104 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4105 a VLIW architecture in which a number of RISC-like instructions may be
4106 bundled together for parallel execution. The FR-V architecture
4107 constrains the location of a breakpoint instruction within such a
4108 bundle to the instruction with the lowest address. @value{GDBN}
4109 honors this constraint by adjusting a breakpoint's address to the
4110 first in the bundle.
4112 It is not uncommon for optimized code to have bundles which contain
4113 instructions from different source statements, thus it may happen that
4114 a breakpoint's address will be adjusted from one source statement to
4115 another. Since this adjustment may significantly alter @value{GDBN}'s
4116 breakpoint related behavior from what the user expects, a warning is
4117 printed when the breakpoint is first set and also when the breakpoint
4120 A warning like the one below is printed when setting a breakpoint
4121 that's been subject to address adjustment:
4124 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4127 Such warnings are printed both for user settable and @value{GDBN}'s
4128 internal breakpoints. If you see one of these warnings, you should
4129 verify that a breakpoint set at the adjusted address will have the
4130 desired affect. If not, the breakpoint in question may be removed and
4131 other breakpoints may be set which will have the desired behavior.
4132 E.g., it may be sufficient to place the breakpoint at a later
4133 instruction. A conditional breakpoint may also be useful in some
4134 cases to prevent the breakpoint from triggering too often.
4136 @value{GDBN} will also issue a warning when stopping at one of these
4137 adjusted breakpoints:
4140 warning: Breakpoint 1 address previously adjusted from 0x00010414
4144 When this warning is encountered, it may be too late to take remedial
4145 action except in cases where the breakpoint is hit earlier or more
4146 frequently than expected.
4148 @node Continuing and Stepping
4149 @section Continuing and Stepping
4153 @cindex resuming execution
4154 @dfn{Continuing} means resuming program execution until your program
4155 completes normally. In contrast, @dfn{stepping} means executing just
4156 one more ``step'' of your program, where ``step'' may mean either one
4157 line of source code, or one machine instruction (depending on what
4158 particular command you use). Either when continuing or when stepping,
4159 your program may stop even sooner, due to a breakpoint or a signal. (If
4160 it stops due to a signal, you may want to use @code{handle}, or use
4161 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4165 @kindex c @r{(@code{continue})}
4166 @kindex fg @r{(resume foreground execution)}
4167 @item continue @r{[}@var{ignore-count}@r{]}
4168 @itemx c @r{[}@var{ignore-count}@r{]}
4169 @itemx fg @r{[}@var{ignore-count}@r{]}
4170 Resume program execution, at the address where your program last stopped;
4171 any breakpoints set at that address are bypassed. The optional argument
4172 @var{ignore-count} allows you to specify a further number of times to
4173 ignore a breakpoint at this location; its effect is like that of
4174 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4176 The argument @var{ignore-count} is meaningful only when your program
4177 stopped due to a breakpoint. At other times, the argument to
4178 @code{continue} is ignored.
4180 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4181 debugged program is deemed to be the foreground program) are provided
4182 purely for convenience, and have exactly the same behavior as
4186 To resume execution at a different place, you can use @code{return}
4187 (@pxref{Returning, ,Returning from a Function}) to go back to the
4188 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4189 Different Address}) to go to an arbitrary location in your program.
4191 A typical technique for using stepping is to set a breakpoint
4192 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4193 beginning of the function or the section of your program where a problem
4194 is believed to lie, run your program until it stops at that breakpoint,
4195 and then step through the suspect area, examining the variables that are
4196 interesting, until you see the problem happen.
4200 @kindex s @r{(@code{step})}
4202 Continue running your program until control reaches a different source
4203 line, then stop it and return control to @value{GDBN}. This command is
4204 abbreviated @code{s}.
4207 @c "without debugging information" is imprecise; actually "without line
4208 @c numbers in the debugging information". (gcc -g1 has debugging info but
4209 @c not line numbers). But it seems complex to try to make that
4210 @c distinction here.
4211 @emph{Warning:} If you use the @code{step} command while control is
4212 within a function that was compiled without debugging information,
4213 execution proceeds until control reaches a function that does have
4214 debugging information. Likewise, it will not step into a function which
4215 is compiled without debugging information. To step through functions
4216 without debugging information, use the @code{stepi} command, described
4220 The @code{step} command only stops at the first instruction of a source
4221 line. This prevents the multiple stops that could otherwise occur in
4222 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4223 to stop if a function that has debugging information is called within
4224 the line. In other words, @code{step} @emph{steps inside} any functions
4225 called within the line.
4227 Also, the @code{step} command only enters a function if there is line
4228 number information for the function. Otherwise it acts like the
4229 @code{next} command. This avoids problems when using @code{cc -gl}
4230 on MIPS machines. Previously, @code{step} entered subroutines if there
4231 was any debugging information about the routine.
4233 @item step @var{count}
4234 Continue running as in @code{step}, but do so @var{count} times. If a
4235 breakpoint is reached, or a signal not related to stepping occurs before
4236 @var{count} steps, stepping stops right away.
4239 @kindex n @r{(@code{next})}
4240 @item next @r{[}@var{count}@r{]}
4241 Continue to the next source line in the current (innermost) stack frame.
4242 This is similar to @code{step}, but function calls that appear within
4243 the line of code are executed without stopping. Execution stops when
4244 control reaches a different line of code at the original stack level
4245 that was executing when you gave the @code{next} command. This command
4246 is abbreviated @code{n}.
4248 An argument @var{count} is a repeat count, as for @code{step}.
4251 @c FIX ME!! Do we delete this, or is there a way it fits in with
4252 @c the following paragraph? --- Vctoria
4254 @c @code{next} within a function that lacks debugging information acts like
4255 @c @code{step}, but any function calls appearing within the code of the
4256 @c function are executed without stopping.
4258 The @code{next} command only stops at the first instruction of a
4259 source line. This prevents multiple stops that could otherwise occur in
4260 @code{switch} statements, @code{for} loops, etc.
4262 @kindex set step-mode
4264 @cindex functions without line info, and stepping
4265 @cindex stepping into functions with no line info
4266 @itemx set step-mode on
4267 The @code{set step-mode on} command causes the @code{step} command to
4268 stop at the first instruction of a function which contains no debug line
4269 information rather than stepping over it.
4271 This is useful in cases where you may be interested in inspecting the
4272 machine instructions of a function which has no symbolic info and do not
4273 want @value{GDBN} to automatically skip over this function.
4275 @item set step-mode off
4276 Causes the @code{step} command to step over any functions which contains no
4277 debug information. This is the default.
4279 @item show step-mode
4280 Show whether @value{GDBN} will stop in or step over functions without
4281 source line debug information.
4284 @kindex fin @r{(@code{finish})}
4286 Continue running until just after function in the selected stack frame
4287 returns. Print the returned value (if any). This command can be
4288 abbreviated as @code{fin}.
4290 Contrast this with the @code{return} command (@pxref{Returning,
4291 ,Returning from a Function}).
4294 @kindex u @r{(@code{until})}
4295 @cindex run until specified location
4298 Continue running until a source line past the current line, in the
4299 current stack frame, is reached. This command is used to avoid single
4300 stepping through a loop more than once. It is like the @code{next}
4301 command, except that when @code{until} encounters a jump, it
4302 automatically continues execution until the program counter is greater
4303 than the address of the jump.
4305 This means that when you reach the end of a loop after single stepping
4306 though it, @code{until} makes your program continue execution until it
4307 exits the loop. In contrast, a @code{next} command at the end of a loop
4308 simply steps back to the beginning of the loop, which forces you to step
4309 through the next iteration.
4311 @code{until} always stops your program if it attempts to exit the current
4314 @code{until} may produce somewhat counterintuitive results if the order
4315 of machine code does not match the order of the source lines. For
4316 example, in the following excerpt from a debugging session, the @code{f}
4317 (@code{frame}) command shows that execution is stopped at line
4318 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4322 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4324 (@value{GDBP}) until
4325 195 for ( ; argc > 0; NEXTARG) @{
4328 This happened because, for execution efficiency, the compiler had
4329 generated code for the loop closure test at the end, rather than the
4330 start, of the loop---even though the test in a C @code{for}-loop is
4331 written before the body of the loop. The @code{until} command appeared
4332 to step back to the beginning of the loop when it advanced to this
4333 expression; however, it has not really gone to an earlier
4334 statement---not in terms of the actual machine code.
4336 @code{until} with no argument works by means of single
4337 instruction stepping, and hence is slower than @code{until} with an
4340 @item until @var{location}
4341 @itemx u @var{location}
4342 Continue running your program until either the specified location is
4343 reached, or the current stack frame returns. @var{location} is any of
4344 the forms described in @ref{Specify Location}.
4345 This form of the command uses temporary breakpoints, and
4346 hence is quicker than @code{until} without an argument. The specified
4347 location is actually reached only if it is in the current frame. This
4348 implies that @code{until} can be used to skip over recursive function
4349 invocations. For instance in the code below, if the current location is
4350 line @code{96}, issuing @code{until 99} will execute the program up to
4351 line @code{99} in the same invocation of factorial, i.e., after the inner
4352 invocations have returned.
4355 94 int factorial (int value)
4357 96 if (value > 1) @{
4358 97 value *= factorial (value - 1);
4365 @kindex advance @var{location}
4366 @itemx advance @var{location}
4367 Continue running the program up to the given @var{location}. An argument is
4368 required, which should be of one of the forms described in
4369 @ref{Specify Location}.
4370 Execution will also stop upon exit from the current stack
4371 frame. This command is similar to @code{until}, but @code{advance} will
4372 not skip over recursive function calls, and the target location doesn't
4373 have to be in the same frame as the current one.
4377 @kindex si @r{(@code{stepi})}
4379 @itemx stepi @var{arg}
4381 Execute one machine instruction, then stop and return to the debugger.
4383 It is often useful to do @samp{display/i $pc} when stepping by machine
4384 instructions. This makes @value{GDBN} automatically display the next
4385 instruction to be executed, each time your program stops. @xref{Auto
4386 Display,, Automatic Display}.
4388 An argument is a repeat count, as in @code{step}.
4392 @kindex ni @r{(@code{nexti})}
4394 @itemx nexti @var{arg}
4396 Execute one machine instruction, but if it is a function call,
4397 proceed until the function returns.
4399 An argument is a repeat count, as in @code{next}.
4406 A signal is an asynchronous event that can happen in a program. The
4407 operating system defines the possible kinds of signals, and gives each
4408 kind a name and a number. For example, in Unix @code{SIGINT} is the
4409 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4410 @code{SIGSEGV} is the signal a program gets from referencing a place in
4411 memory far away from all the areas in use; @code{SIGALRM} occurs when
4412 the alarm clock timer goes off (which happens only if your program has
4413 requested an alarm).
4415 @cindex fatal signals
4416 Some signals, including @code{SIGALRM}, are a normal part of the
4417 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4418 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4419 program has not specified in advance some other way to handle the signal.
4420 @code{SIGINT} does not indicate an error in your program, but it is normally
4421 fatal so it can carry out the purpose of the interrupt: to kill the program.
4423 @value{GDBN} has the ability to detect any occurrence of a signal in your
4424 program. You can tell @value{GDBN} in advance what to do for each kind of
4427 @cindex handling signals
4428 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4429 @code{SIGALRM} be silently passed to your program
4430 (so as not to interfere with their role in the program's functioning)
4431 but to stop your program immediately whenever an error signal happens.
4432 You can change these settings with the @code{handle} command.
4435 @kindex info signals
4439 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4440 handle each one. You can use this to see the signal numbers of all
4441 the defined types of signals.
4443 @item info signals @var{sig}
4444 Similar, but print information only about the specified signal number.
4446 @code{info handle} is an alias for @code{info signals}.
4449 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4450 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4451 can be the number of a signal or its name (with or without the
4452 @samp{SIG} at the beginning); a list of signal numbers of the form
4453 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4454 known signals. Optional arguments @var{keywords}, described below,
4455 say what change to make.
4459 The keywords allowed by the @code{handle} command can be abbreviated.
4460 Their full names are:
4464 @value{GDBN} should not stop your program when this signal happens. It may
4465 still print a message telling you that the signal has come in.
4468 @value{GDBN} should stop your program when this signal happens. This implies
4469 the @code{print} keyword as well.
4472 @value{GDBN} should print a message when this signal happens.
4475 @value{GDBN} should not mention the occurrence of the signal at all. This
4476 implies the @code{nostop} keyword as well.
4480 @value{GDBN} should allow your program to see this signal; your program
4481 can handle the signal, or else it may terminate if the signal is fatal
4482 and not handled. @code{pass} and @code{noignore} are synonyms.
4486 @value{GDBN} should not allow your program to see this signal.
4487 @code{nopass} and @code{ignore} are synonyms.
4491 When a signal stops your program, the signal is not visible to the
4493 continue. Your program sees the signal then, if @code{pass} is in
4494 effect for the signal in question @emph{at that time}. In other words,
4495 after @value{GDBN} reports a signal, you can use the @code{handle}
4496 command with @code{pass} or @code{nopass} to control whether your
4497 program sees that signal when you continue.
4499 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4500 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4501 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4504 You can also use the @code{signal} command to prevent your program from
4505 seeing a signal, or cause it to see a signal it normally would not see,
4506 or to give it any signal at any time. For example, if your program stopped
4507 due to some sort of memory reference error, you might store correct
4508 values into the erroneous variables and continue, hoping to see more
4509 execution; but your program would probably terminate immediately as
4510 a result of the fatal signal once it saw the signal. To prevent this,
4511 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4515 @section Stopping and Starting Multi-thread Programs
4517 @cindex stopped threads
4518 @cindex threads, stopped
4520 @cindex continuing threads
4521 @cindex threads, continuing
4523 @value{GDBN} supports debugging programs with multiple threads
4524 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
4525 are two modes of controlling execution of your program within the
4526 debugger. In the default mode, referred to as @dfn{all-stop mode},
4527 when any thread in your program stops (for example, at a breakpoint
4528 or while being stepped), all other threads in the program are also stopped by
4529 @value{GDBN}. On some targets, @value{GDBN} also supports
4530 @dfn{non-stop mode}, in which other threads can continue to run freely while
4531 you examine the stopped thread in the debugger.
4534 * All-Stop Mode:: All threads stop when GDB takes control
4535 * Non-Stop Mode:: Other threads continue to execute
4536 * Background Execution:: Running your program asynchronously
4537 * Thread-Specific Breakpoints:: Controlling breakpoints
4538 * Interrupted System Calls:: GDB may interfere with system calls
4542 @subsection All-Stop Mode
4544 @cindex all-stop mode
4546 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
4547 @emph{all} threads of execution stop, not just the current thread. This
4548 allows you to examine the overall state of the program, including
4549 switching between threads, without worrying that things may change
4552 Conversely, whenever you restart the program, @emph{all} threads start
4553 executing. @emph{This is true even when single-stepping} with commands
4554 like @code{step} or @code{next}.
4556 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4557 Since thread scheduling is up to your debugging target's operating
4558 system (not controlled by @value{GDBN}), other threads may
4559 execute more than one statement while the current thread completes a
4560 single step. Moreover, in general other threads stop in the middle of a
4561 statement, rather than at a clean statement boundary, when the program
4564 You might even find your program stopped in another thread after
4565 continuing or even single-stepping. This happens whenever some other
4566 thread runs into a breakpoint, a signal, or an exception before the
4567 first thread completes whatever you requested.
4569 @cindex automatic thread selection
4570 @cindex switching threads automatically
4571 @cindex threads, automatic switching
4572 Whenever @value{GDBN} stops your program, due to a breakpoint or a
4573 signal, it automatically selects the thread where that breakpoint or
4574 signal happened. @value{GDBN} alerts you to the context switch with a
4575 message such as @samp{[Switching to Thread @var{n}]} to identify the
4578 On some OSes, you can modify @value{GDBN}'s default behavior by
4579 locking the OS scheduler to allow only a single thread to run.
4582 @item set scheduler-locking @var{mode}
4583 @cindex scheduler locking mode
4584 @cindex lock scheduler
4585 Set the scheduler locking mode. If it is @code{off}, then there is no
4586 locking and any thread may run at any time. If @code{on}, then only the
4587 current thread may run when the inferior is resumed. The @code{step}
4588 mode optimizes for single-stepping; it prevents other threads
4589 from preempting the current thread while you are stepping, so that
4590 the focus of debugging does not change unexpectedly.
4591 Other threads only rarely (or never) get a chance to run
4592 when you step. They are more likely to run when you @samp{next} over a
4593 function call, and they are completely free to run when you use commands
4594 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4595 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
4596 the current thread away from the thread that you are debugging.
4598 @item show scheduler-locking
4599 Display the current scheduler locking mode.
4603 @subsection Non-Stop Mode
4605 @cindex non-stop mode
4607 @c This section is really only a place-holder, and needs to be expanded
4608 @c with more details.
4610 For some multi-threaded targets, @value{GDBN} supports an optional
4611 mode of operation in which you can examine stopped program threads in
4612 the debugger while other threads continue to execute freely. This
4613 minimizes intrusion when debugging live systems, such as programs
4614 where some threads have real-time constraints or must continue to
4615 respond to external events. This is referred to as @dfn{non-stop} mode.
4617 In non-stop mode, when a thread stops to report a debugging event,
4618 @emph{only} that thread is stopped; @value{GDBN} does not stop other
4619 threads as well, in contrast to the all-stop mode behavior. Additionally,
4620 execution commands such as @code{continue} and @code{step} apply by default
4621 only to the current thread in non-stop mode, rather than all threads as
4622 in all-stop mode. This allows you to control threads explicitly in
4623 ways that are not possible in all-stop mode --- for example, stepping
4624 one thread while allowing others to run freely, stepping
4625 one thread while holding all others stopped, or stepping several threads
4626 independently and simultaneously.
4628 To enter non-stop mode, use this sequence of commands before you run
4629 or attach to your program:
4632 # Enable the async interface.
4635 # If using the CLI, pagination breaks non-stop.
4638 # Finally, turn it on!
4642 You can use these commands to manipulate the non-stop mode setting:
4645 @kindex set non-stop
4646 @item set non-stop on
4647 Enable selection of non-stop mode.
4648 @item set non-stop off
4649 Disable selection of non-stop mode.
4650 @kindex show non-stop
4652 Show the current non-stop enablement setting.
4655 Note these commands only reflect whether non-stop mode is enabled,
4656 not whether the currently-executing program is being run in non-stop mode.
4657 In particular, the @code{set non-stop} preference is only consulted when
4658 @value{GDBN} starts or connects to the target program, and it is generally
4659 not possible to switch modes once debugging has started. Furthermore,
4660 since not all targets support non-stop mode, even when you have enabled
4661 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
4664 In non-stop mode, all execution commands apply only to the current thread
4665 by default. That is, @code{continue} only continues one thread.
4666 To continue all threads, issue @code{continue -a} or @code{c -a}.
4668 You can use @value{GDBN}'s background execution commands
4669 (@pxref{Background Execution}) to run some threads in the background
4670 while you continue to examine or step others from @value{GDBN}.
4671 The MI execution commands (@pxref{GDB/MI Program Execution}) are
4672 always executed asynchronously in non-stop mode.
4674 Suspending execution is done with the @code{interrupt} command when
4675 running in the background, or @kbd{Ctrl-c} during foreground execution.
4676 In all-stop mode, this stops the whole process;
4677 but in non-stop mode the interrupt applies only to the current thread.
4678 To stop the whole program, use @code{interrupt -a}.
4680 Other execution commands do not currently support the @code{-a} option.
4682 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
4683 that thread current, as it does in all-stop mode. This is because the
4684 thread stop notifications are asynchronous with respect to @value{GDBN}'s
4685 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
4686 changed to a different thread just as you entered a command to operate on the
4687 previously current thread.
4689 @node Background Execution
4690 @subsection Background Execution
4692 @cindex foreground execution
4693 @cindex background execution
4694 @cindex asynchronous execution
4695 @cindex execution, foreground, background and asynchronous
4697 @value{GDBN}'s execution commands have two variants: the normal
4698 foreground (synchronous) behavior, and a background
4699 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
4700 the program to report that some thread has stopped before prompting for
4701 another command. In background execution, @value{GDBN} immediately gives
4702 a command prompt so that you can issue other commands while your program runs.
4704 To specify background execution, add a @code{&} to the command. For example,
4705 the background form of the @code{continue} command is @code{continue&}, or
4706 just @code{c&}. The execution commands that accept background execution
4712 @xref{Starting, , Starting your Program}.
4716 @xref{Attach, , Debugging an Already-running Process}.
4720 @xref{Continuing and Stepping, step}.
4724 @xref{Continuing and Stepping, stepi}.
4728 @xref{Continuing and Stepping, next}.
4732 @xref{Continuing and Stepping, continue}.
4736 @xref{Continuing and Stepping, finish}.
4740 @xref{Continuing and Stepping, until}.
4744 Background execution is especially useful in conjunction with non-stop
4745 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
4746 However, you can also use these commands in the normal all-stop mode with
4747 the restriction that you cannot issue another execution command until the
4748 previous one finishes. Examples of commands that are valid in all-stop
4749 mode while the program is running include @code{help} and @code{info break}.
4751 You can interrupt your program while it is running in the background by
4752 using the @code{interrupt} command.
4759 Suspend execution of the running program. In all-stop mode,
4760 @code{interrupt} stops the whole process, but in non-stop mode, it stops
4761 only the current thread. To stop the whole program in non-stop mode,
4762 use @code{interrupt -a}.
4765 You may need to explicitly enable async mode before you can use background
4766 execution commands, with the @code{set target-async 1} command. If the
4767 target doesn't support async mode, @value{GDBN} issues an error message
4768 if you attempt to use the background execution commands.
4770 @node Thread-Specific Breakpoints
4771 @subsection Thread-Specific Breakpoints
4773 When your program has multiple threads (@pxref{Threads,, Debugging
4774 Programs with Multiple Threads}), you can choose whether to set
4775 breakpoints on all threads, or on a particular thread.
4778 @cindex breakpoints and threads
4779 @cindex thread breakpoints
4780 @kindex break @dots{} thread @var{threadno}
4781 @item break @var{linespec} thread @var{threadno}
4782 @itemx break @var{linespec} thread @var{threadno} if @dots{}
4783 @var{linespec} specifies source lines; there are several ways of
4784 writing them (@pxref{Specify Location}), but the effect is always to
4785 specify some source line.
4787 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
4788 to specify that you only want @value{GDBN} to stop the program when a
4789 particular thread reaches this breakpoint. @var{threadno} is one of the
4790 numeric thread identifiers assigned by @value{GDBN}, shown in the first
4791 column of the @samp{info threads} display.
4793 If you do not specify @samp{thread @var{threadno}} when you set a
4794 breakpoint, the breakpoint applies to @emph{all} threads of your
4797 You can use the @code{thread} qualifier on conditional breakpoints as
4798 well; in this case, place @samp{thread @var{threadno}} before the
4799 breakpoint condition, like this:
4802 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
4807 @node Interrupted System Calls
4808 @subsection Interrupted System Calls
4810 @cindex thread breakpoints and system calls
4811 @cindex system calls and thread breakpoints
4812 @cindex premature return from system calls
4813 There is an unfortunate side effect when using @value{GDBN} to debug
4814 multi-threaded programs. If one thread stops for a
4815 breakpoint, or for some other reason, and another thread is blocked in a
4816 system call, then the system call may return prematurely. This is a
4817 consequence of the interaction between multiple threads and the signals
4818 that @value{GDBN} uses to implement breakpoints and other events that
4821 To handle this problem, your program should check the return value of
4822 each system call and react appropriately. This is good programming
4825 For example, do not write code like this:
4831 The call to @code{sleep} will return early if a different thread stops
4832 at a breakpoint or for some other reason.
4834 Instead, write this:
4839 unslept = sleep (unslept);
4842 A system call is allowed to return early, so the system is still
4843 conforming to its specification. But @value{GDBN} does cause your
4844 multi-threaded program to behave differently than it would without
4847 Also, @value{GDBN} uses internal breakpoints in the thread library to
4848 monitor certain events such as thread creation and thread destruction.
4849 When such an event happens, a system call in another thread may return
4850 prematurely, even though your program does not appear to stop.
4855 @chapter Examining the Stack
4857 When your program has stopped, the first thing you need to know is where it
4858 stopped and how it got there.
4861 Each time your program performs a function call, information about the call
4863 That information includes the location of the call in your program,
4864 the arguments of the call,
4865 and the local variables of the function being called.
4866 The information is saved in a block of data called a @dfn{stack frame}.
4867 The stack frames are allocated in a region of memory called the @dfn{call
4870 When your program stops, the @value{GDBN} commands for examining the
4871 stack allow you to see all of this information.
4873 @cindex selected frame
4874 One of the stack frames is @dfn{selected} by @value{GDBN} and many
4875 @value{GDBN} commands refer implicitly to the selected frame. In
4876 particular, whenever you ask @value{GDBN} for the value of a variable in
4877 your program, the value is found in the selected frame. There are
4878 special @value{GDBN} commands to select whichever frame you are
4879 interested in. @xref{Selection, ,Selecting a Frame}.
4881 When your program stops, @value{GDBN} automatically selects the
4882 currently executing frame and describes it briefly, similar to the
4883 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
4886 * Frames:: Stack frames
4887 * Backtrace:: Backtraces
4888 * Selection:: Selecting a frame
4889 * Frame Info:: Information on a frame
4894 @section Stack Frames
4896 @cindex frame, definition
4898 The call stack is divided up into contiguous pieces called @dfn{stack
4899 frames}, or @dfn{frames} for short; each frame is the data associated
4900 with one call to one function. The frame contains the arguments given
4901 to the function, the function's local variables, and the address at
4902 which the function is executing.
4904 @cindex initial frame
4905 @cindex outermost frame
4906 @cindex innermost frame
4907 When your program is started, the stack has only one frame, that of the
4908 function @code{main}. This is called the @dfn{initial} frame or the
4909 @dfn{outermost} frame. Each time a function is called, a new frame is
4910 made. Each time a function returns, the frame for that function invocation
4911 is eliminated. If a function is recursive, there can be many frames for
4912 the same function. The frame for the function in which execution is
4913 actually occurring is called the @dfn{innermost} frame. This is the most
4914 recently created of all the stack frames that still exist.
4916 @cindex frame pointer
4917 Inside your program, stack frames are identified by their addresses. A
4918 stack frame consists of many bytes, each of which has its own address; each
4919 kind of computer has a convention for choosing one byte whose
4920 address serves as the address of the frame. Usually this address is kept
4921 in a register called the @dfn{frame pointer register}
4922 (@pxref{Registers, $fp}) while execution is going on in that frame.
4924 @cindex frame number
4925 @value{GDBN} assigns numbers to all existing stack frames, starting with
4926 zero for the innermost frame, one for the frame that called it,
4927 and so on upward. These numbers do not really exist in your program;
4928 they are assigned by @value{GDBN} to give you a way of designating stack
4929 frames in @value{GDBN} commands.
4931 @c The -fomit-frame-pointer below perennially causes hbox overflow
4932 @c underflow problems.
4933 @cindex frameless execution
4934 Some compilers provide a way to compile functions so that they operate
4935 without stack frames. (For example, the @value{NGCC} option
4937 @samp{-fomit-frame-pointer}
4939 generates functions without a frame.)
4940 This is occasionally done with heavily used library functions to save
4941 the frame setup time. @value{GDBN} has limited facilities for dealing
4942 with these function invocations. If the innermost function invocation
4943 has no stack frame, @value{GDBN} nevertheless regards it as though
4944 it had a separate frame, which is numbered zero as usual, allowing
4945 correct tracing of the function call chain. However, @value{GDBN} has
4946 no provision for frameless functions elsewhere in the stack.
4949 @kindex frame@r{, command}
4950 @cindex current stack frame
4951 @item frame @var{args}
4952 The @code{frame} command allows you to move from one stack frame to another,
4953 and to print the stack frame you select. @var{args} may be either the
4954 address of the frame or the stack frame number. Without an argument,
4955 @code{frame} prints the current stack frame.
4957 @kindex select-frame
4958 @cindex selecting frame silently
4960 The @code{select-frame} command allows you to move from one stack frame
4961 to another without printing the frame. This is the silent version of
4969 @cindex call stack traces
4970 A backtrace is a summary of how your program got where it is. It shows one
4971 line per frame, for many frames, starting with the currently executing
4972 frame (frame zero), followed by its caller (frame one), and on up the
4977 @kindex bt @r{(@code{backtrace})}
4980 Print a backtrace of the entire stack: one line per frame for all
4981 frames in the stack.
4983 You can stop the backtrace at any time by typing the system interrupt
4984 character, normally @kbd{Ctrl-c}.
4986 @item backtrace @var{n}
4988 Similar, but print only the innermost @var{n} frames.
4990 @item backtrace -@var{n}
4992 Similar, but print only the outermost @var{n} frames.
4994 @item backtrace full
4996 @itemx bt full @var{n}
4997 @itemx bt full -@var{n}
4998 Print the values of the local variables also. @var{n} specifies the
4999 number of frames to print, as described above.
5004 The names @code{where} and @code{info stack} (abbreviated @code{info s})
5005 are additional aliases for @code{backtrace}.
5007 @cindex multiple threads, backtrace
5008 In a multi-threaded program, @value{GDBN} by default shows the
5009 backtrace only for the current thread. To display the backtrace for
5010 several or all of the threads, use the command @code{thread apply}
5011 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
5012 apply all backtrace}, @value{GDBN} will display the backtrace for all
5013 the threads; this is handy when you debug a core dump of a
5014 multi-threaded program.
5016 Each line in the backtrace shows the frame number and the function name.
5017 The program counter value is also shown---unless you use @code{set
5018 print address off}. The backtrace also shows the source file name and
5019 line number, as well as the arguments to the function. The program
5020 counter value is omitted if it is at the beginning of the code for that
5023 Here is an example of a backtrace. It was made with the command
5024 @samp{bt 3}, so it shows the innermost three frames.
5028 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5030 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
5031 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
5033 (More stack frames follow...)
5038 The display for frame zero does not begin with a program counter
5039 value, indicating that your program has stopped at the beginning of the
5040 code for line @code{993} of @code{builtin.c}.
5042 @cindex value optimized out, in backtrace
5043 @cindex function call arguments, optimized out
5044 If your program was compiled with optimizations, some compilers will
5045 optimize away arguments passed to functions if those arguments are
5046 never used after the call. Such optimizations generate code that
5047 passes arguments through registers, but doesn't store those arguments
5048 in the stack frame. @value{GDBN} has no way of displaying such
5049 arguments in stack frames other than the innermost one. Here's what
5050 such a backtrace might look like:
5054 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5056 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
5057 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
5059 (More stack frames follow...)
5064 The values of arguments that were not saved in their stack frames are
5065 shown as @samp{<value optimized out>}.
5067 If you need to display the values of such optimized-out arguments,
5068 either deduce that from other variables whose values depend on the one
5069 you are interested in, or recompile without optimizations.
5071 @cindex backtrace beyond @code{main} function
5072 @cindex program entry point
5073 @cindex startup code, and backtrace
5074 Most programs have a standard user entry point---a place where system
5075 libraries and startup code transition into user code. For C this is
5076 @code{main}@footnote{
5077 Note that embedded programs (the so-called ``free-standing''
5078 environment) are not required to have a @code{main} function as the
5079 entry point. They could even have multiple entry points.}.
5080 When @value{GDBN} finds the entry function in a backtrace
5081 it will terminate the backtrace, to avoid tracing into highly
5082 system-specific (and generally uninteresting) code.
5084 If you need to examine the startup code, or limit the number of levels
5085 in a backtrace, you can change this behavior:
5088 @item set backtrace past-main
5089 @itemx set backtrace past-main on
5090 @kindex set backtrace
5091 Backtraces will continue past the user entry point.
5093 @item set backtrace past-main off
5094 Backtraces will stop when they encounter the user entry point. This is the
5097 @item show backtrace past-main
5098 @kindex show backtrace
5099 Display the current user entry point backtrace policy.
5101 @item set backtrace past-entry
5102 @itemx set backtrace past-entry on
5103 Backtraces will continue past the internal entry point of an application.
5104 This entry point is encoded by the linker when the application is built,
5105 and is likely before the user entry point @code{main} (or equivalent) is called.
5107 @item set backtrace past-entry off
5108 Backtraces will stop when they encounter the internal entry point of an
5109 application. This is the default.
5111 @item show backtrace past-entry
5112 Display the current internal entry point backtrace policy.
5114 @item set backtrace limit @var{n}
5115 @itemx set backtrace limit 0
5116 @cindex backtrace limit
5117 Limit the backtrace to @var{n} levels. A value of zero means
5120 @item show backtrace limit
5121 Display the current limit on backtrace levels.
5125 @section Selecting a Frame
5127 Most commands for examining the stack and other data in your program work on
5128 whichever stack frame is selected at the moment. Here are the commands for
5129 selecting a stack frame; all of them finish by printing a brief description
5130 of the stack frame just selected.
5133 @kindex frame@r{, selecting}
5134 @kindex f @r{(@code{frame})}
5137 Select frame number @var{n}. Recall that frame zero is the innermost
5138 (currently executing) frame, frame one is the frame that called the
5139 innermost one, and so on. The highest-numbered frame is the one for
5142 @item frame @var{addr}
5144 Select the frame at address @var{addr}. This is useful mainly if the
5145 chaining of stack frames has been damaged by a bug, making it
5146 impossible for @value{GDBN} to assign numbers properly to all frames. In
5147 addition, this can be useful when your program has multiple stacks and
5148 switches between them.
5150 On the SPARC architecture, @code{frame} needs two addresses to
5151 select an arbitrary frame: a frame pointer and a stack pointer.
5153 On the MIPS and Alpha architecture, it needs two addresses: a stack
5154 pointer and a program counter.
5156 On the 29k architecture, it needs three addresses: a register stack
5157 pointer, a program counter, and a memory stack pointer.
5161 Move @var{n} frames up the stack. For positive numbers @var{n}, this
5162 advances toward the outermost frame, to higher frame numbers, to frames
5163 that have existed longer. @var{n} defaults to one.
5166 @kindex do @r{(@code{down})}
5168 Move @var{n} frames down the stack. For positive numbers @var{n}, this
5169 advances toward the innermost frame, to lower frame numbers, to frames
5170 that were created more recently. @var{n} defaults to one. You may
5171 abbreviate @code{down} as @code{do}.
5174 All of these commands end by printing two lines of output describing the
5175 frame. The first line shows the frame number, the function name, the
5176 arguments, and the source file and line number of execution in that
5177 frame. The second line shows the text of that source line.
5185 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
5187 10 read_input_file (argv[i]);
5191 After such a printout, the @code{list} command with no arguments
5192 prints ten lines centered on the point of execution in the frame.
5193 You can also edit the program at the point of execution with your favorite
5194 editing program by typing @code{edit}.
5195 @xref{List, ,Printing Source Lines},
5199 @kindex down-silently
5201 @item up-silently @var{n}
5202 @itemx down-silently @var{n}
5203 These two commands are variants of @code{up} and @code{down},
5204 respectively; they differ in that they do their work silently, without
5205 causing display of the new frame. They are intended primarily for use
5206 in @value{GDBN} command scripts, where the output might be unnecessary and
5211 @section Information About a Frame
5213 There are several other commands to print information about the selected
5219 When used without any argument, this command does not change which
5220 frame is selected, but prints a brief description of the currently
5221 selected stack frame. It can be abbreviated @code{f}. With an
5222 argument, this command is used to select a stack frame.
5223 @xref{Selection, ,Selecting a Frame}.
5226 @kindex info f @r{(@code{info frame})}
5229 This command prints a verbose description of the selected stack frame,
5234 the address of the frame
5236 the address of the next frame down (called by this frame)
5238 the address of the next frame up (caller of this frame)
5240 the language in which the source code corresponding to this frame is written
5242 the address of the frame's arguments
5244 the address of the frame's local variables
5246 the program counter saved in it (the address of execution in the caller frame)
5248 which registers were saved in the frame
5251 @noindent The verbose description is useful when
5252 something has gone wrong that has made the stack format fail to fit
5253 the usual conventions.
5255 @item info frame @var{addr}
5256 @itemx info f @var{addr}
5257 Print a verbose description of the frame at address @var{addr}, without
5258 selecting that frame. The selected frame remains unchanged by this
5259 command. This requires the same kind of address (more than one for some
5260 architectures) that you specify in the @code{frame} command.
5261 @xref{Selection, ,Selecting a Frame}.
5265 Print the arguments of the selected frame, each on a separate line.
5269 Print the local variables of the selected frame, each on a separate
5270 line. These are all variables (declared either static or automatic)
5271 accessible at the point of execution of the selected frame.
5274 @cindex catch exceptions, list active handlers
5275 @cindex exception handlers, how to list
5277 Print a list of all the exception handlers that are active in the
5278 current stack frame at the current point of execution. To see other
5279 exception handlers, visit the associated frame (using the @code{up},
5280 @code{down}, or @code{frame} commands); then type @code{info catch}.
5281 @xref{Set Catchpoints, , Setting Catchpoints}.
5287 @chapter Examining Source Files
5289 @value{GDBN} can print parts of your program's source, since the debugging
5290 information recorded in the program tells @value{GDBN} what source files were
5291 used to build it. When your program stops, @value{GDBN} spontaneously prints
5292 the line where it stopped. Likewise, when you select a stack frame
5293 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
5294 execution in that frame has stopped. You can print other portions of
5295 source files by explicit command.
5297 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
5298 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
5299 @value{GDBN} under @sc{gnu} Emacs}.
5302 * List:: Printing source lines
5303 * Specify Location:: How to specify code locations
5304 * Edit:: Editing source files
5305 * Search:: Searching source files
5306 * Source Path:: Specifying source directories
5307 * Machine Code:: Source and machine code
5311 @section Printing Source Lines
5314 @kindex l @r{(@code{list})}
5315 To print lines from a source file, use the @code{list} command
5316 (abbreviated @code{l}). By default, ten lines are printed.
5317 There are several ways to specify what part of the file you want to
5318 print; see @ref{Specify Location}, for the full list.
5320 Here are the forms of the @code{list} command most commonly used:
5323 @item list @var{linenum}
5324 Print lines centered around line number @var{linenum} in the
5325 current source file.
5327 @item list @var{function}
5328 Print lines centered around the beginning of function
5332 Print more lines. If the last lines printed were printed with a
5333 @code{list} command, this prints lines following the last lines
5334 printed; however, if the last line printed was a solitary line printed
5335 as part of displaying a stack frame (@pxref{Stack, ,Examining the
5336 Stack}), this prints lines centered around that line.
5339 Print lines just before the lines last printed.
5342 @cindex @code{list}, how many lines to display
5343 By default, @value{GDBN} prints ten source lines with any of these forms of
5344 the @code{list} command. You can change this using @code{set listsize}:
5347 @kindex set listsize
5348 @item set listsize @var{count}
5349 Make the @code{list} command display @var{count} source lines (unless
5350 the @code{list} argument explicitly specifies some other number).
5352 @kindex show listsize
5354 Display the number of lines that @code{list} prints.
5357 Repeating a @code{list} command with @key{RET} discards the argument,
5358 so it is equivalent to typing just @code{list}. This is more useful
5359 than listing the same lines again. An exception is made for an
5360 argument of @samp{-}; that argument is preserved in repetition so that
5361 each repetition moves up in the source file.
5363 In general, the @code{list} command expects you to supply zero, one or two
5364 @dfn{linespecs}. Linespecs specify source lines; there are several ways
5365 of writing them (@pxref{Specify Location}), but the effect is always
5366 to specify some source line.
5368 Here is a complete description of the possible arguments for @code{list}:
5371 @item list @var{linespec}
5372 Print lines centered around the line specified by @var{linespec}.
5374 @item list @var{first},@var{last}
5375 Print lines from @var{first} to @var{last}. Both arguments are
5376 linespecs. When a @code{list} command has two linespecs, and the
5377 source file of the second linespec is omitted, this refers to
5378 the same source file as the first linespec.
5380 @item list ,@var{last}
5381 Print lines ending with @var{last}.
5383 @item list @var{first},
5384 Print lines starting with @var{first}.
5387 Print lines just after the lines last printed.
5390 Print lines just before the lines last printed.
5393 As described in the preceding table.
5396 @node Specify Location
5397 @section Specifying a Location
5398 @cindex specifying location
5401 Several @value{GDBN} commands accept arguments that specify a location
5402 of your program's code. Since @value{GDBN} is a source-level
5403 debugger, a location usually specifies some line in the source code;
5404 for that reason, locations are also known as @dfn{linespecs}.
5406 Here are all the different ways of specifying a code location that
5407 @value{GDBN} understands:
5411 Specifies the line number @var{linenum} of the current source file.
5414 @itemx +@var{offset}
5415 Specifies the line @var{offset} lines before or after the @dfn{current
5416 line}. For the @code{list} command, the current line is the last one
5417 printed; for the breakpoint commands, this is the line at which
5418 execution stopped in the currently selected @dfn{stack frame}
5419 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
5420 used as the second of the two linespecs in a @code{list} command,
5421 this specifies the line @var{offset} lines up or down from the first
5424 @item @var{filename}:@var{linenum}
5425 Specifies the line @var{linenum} in the source file @var{filename}.
5427 @item @var{function}
5428 Specifies the line that begins the body of the function @var{function}.
5429 For example, in C, this is the line with the open brace.
5431 @item @var{filename}:@var{function}
5432 Specifies the line that begins the body of the function @var{function}
5433 in the file @var{filename}. You only need the file name with a
5434 function name to avoid ambiguity when there are identically named
5435 functions in different source files.
5437 @item *@var{address}
5438 Specifies the program address @var{address}. For line-oriented
5439 commands, such as @code{list} and @code{edit}, this specifies a source
5440 line that contains @var{address}. For @code{break} and other
5441 breakpoint oriented commands, this can be used to set breakpoints in
5442 parts of your program which do not have debugging information or
5445 Here @var{address} may be any expression valid in the current working
5446 language (@pxref{Languages, working language}) that specifies a code
5447 address. In addition, as a convenience, @value{GDBN} extends the
5448 semantics of expressions used in locations to cover the situations
5449 that frequently happen during debugging. Here are the various forms
5453 @item @var{expression}
5454 Any expression valid in the current working language.
5456 @item @var{funcaddr}
5457 An address of a function or procedure derived from its name. In C,
5458 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
5459 simply the function's name @var{function} (and actually a special case
5460 of a valid expression). In Pascal and Modula-2, this is
5461 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
5462 (although the Pascal form also works).
5464 This form specifies the address of the function's first instruction,
5465 before the stack frame and arguments have been set up.
5467 @item '@var{filename}'::@var{funcaddr}
5468 Like @var{funcaddr} above, but also specifies the name of the source
5469 file explicitly. This is useful if the name of the function does not
5470 specify the function unambiguously, e.g., if there are several
5471 functions with identical names in different source files.
5478 @section Editing Source Files
5479 @cindex editing source files
5482 @kindex e @r{(@code{edit})}
5483 To edit the lines in a source file, use the @code{edit} command.
5484 The editing program of your choice
5485 is invoked with the current line set to
5486 the active line in the program.
5487 Alternatively, there are several ways to specify what part of the file you
5488 want to print if you want to see other parts of the program:
5491 @item edit @var{location}
5492 Edit the source file specified by @code{location}. Editing starts at
5493 that @var{location}, e.g., at the specified source line of the
5494 specified file. @xref{Specify Location}, for all the possible forms
5495 of the @var{location} argument; here are the forms of the @code{edit}
5496 command most commonly used:
5499 @item edit @var{number}
5500 Edit the current source file with @var{number} as the active line number.
5502 @item edit @var{function}
5503 Edit the file containing @var{function} at the beginning of its definition.
5508 @subsection Choosing your Editor
5509 You can customize @value{GDBN} to use any editor you want
5511 The only restriction is that your editor (say @code{ex}), recognizes the
5512 following command-line syntax:
5514 ex +@var{number} file
5516 The optional numeric value +@var{number} specifies the number of the line in
5517 the file where to start editing.}.
5518 By default, it is @file{@value{EDITOR}}, but you can change this
5519 by setting the environment variable @code{EDITOR} before using
5520 @value{GDBN}. For example, to configure @value{GDBN} to use the
5521 @code{vi} editor, you could use these commands with the @code{sh} shell:
5527 or in the @code{csh} shell,
5529 setenv EDITOR /usr/bin/vi
5534 @section Searching Source Files
5535 @cindex searching source files
5537 There are two commands for searching through the current source file for a
5542 @kindex forward-search
5543 @item forward-search @var{regexp}
5544 @itemx search @var{regexp}
5545 The command @samp{forward-search @var{regexp}} checks each line,
5546 starting with the one following the last line listed, for a match for
5547 @var{regexp}. It lists the line that is found. You can use the
5548 synonym @samp{search @var{regexp}} or abbreviate the command name as
5551 @kindex reverse-search
5552 @item reverse-search @var{regexp}
5553 The command @samp{reverse-search @var{regexp}} checks each line, starting
5554 with the one before the last line listed and going backward, for a match
5555 for @var{regexp}. It lists the line that is found. You can abbreviate
5556 this command as @code{rev}.
5560 @section Specifying Source Directories
5563 @cindex directories for source files
5564 Executable programs sometimes do not record the directories of the source
5565 files from which they were compiled, just the names. Even when they do,
5566 the directories could be moved between the compilation and your debugging
5567 session. @value{GDBN} has a list of directories to search for source files;
5568 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
5569 it tries all the directories in the list, in the order they are present
5570 in the list, until it finds a file with the desired name.
5572 For example, suppose an executable references the file
5573 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
5574 @file{/mnt/cross}. The file is first looked up literally; if this
5575 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
5576 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
5577 message is printed. @value{GDBN} does not look up the parts of the
5578 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
5579 Likewise, the subdirectories of the source path are not searched: if
5580 the source path is @file{/mnt/cross}, and the binary refers to
5581 @file{foo.c}, @value{GDBN} would not find it under
5582 @file{/mnt/cross/usr/src/foo-1.0/lib}.
5584 Plain file names, relative file names with leading directories, file
5585 names containing dots, etc.@: are all treated as described above; for
5586 instance, if the source path is @file{/mnt/cross}, and the source file
5587 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
5588 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
5589 that---@file{/mnt/cross/foo.c}.
5591 Note that the executable search path is @emph{not} used to locate the
5594 Whenever you reset or rearrange the source path, @value{GDBN} clears out
5595 any information it has cached about where source files are found and where
5596 each line is in the file.
5600 When you start @value{GDBN}, its source path includes only @samp{cdir}
5601 and @samp{cwd}, in that order.
5602 To add other directories, use the @code{directory} command.
5604 The search path is used to find both program source files and @value{GDBN}
5605 script files (read using the @samp{-command} option and @samp{source} command).
5607 In addition to the source path, @value{GDBN} provides a set of commands
5608 that manage a list of source path substitution rules. A @dfn{substitution
5609 rule} specifies how to rewrite source directories stored in the program's
5610 debug information in case the sources were moved to a different
5611 directory between compilation and debugging. A rule is made of
5612 two strings, the first specifying what needs to be rewritten in
5613 the path, and the second specifying how it should be rewritten.
5614 In @ref{set substitute-path}, we name these two parts @var{from} and
5615 @var{to} respectively. @value{GDBN} does a simple string replacement
5616 of @var{from} with @var{to} at the start of the directory part of the
5617 source file name, and uses that result instead of the original file
5618 name to look up the sources.
5620 Using the previous example, suppose the @file{foo-1.0} tree has been
5621 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
5622 @value{GDBN} to replace @file{/usr/src} in all source path names with
5623 @file{/mnt/cross}. The first lookup will then be
5624 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
5625 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
5626 substitution rule, use the @code{set substitute-path} command
5627 (@pxref{set substitute-path}).
5629 To avoid unexpected substitution results, a rule is applied only if the
5630 @var{from} part of the directory name ends at a directory separator.
5631 For instance, a rule substituting @file{/usr/source} into
5632 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
5633 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
5634 is applied only at the beginning of the directory name, this rule will
5635 not be applied to @file{/root/usr/source/baz.c} either.
5637 In many cases, you can achieve the same result using the @code{directory}
5638 command. However, @code{set substitute-path} can be more efficient in
5639 the case where the sources are organized in a complex tree with multiple
5640 subdirectories. With the @code{directory} command, you need to add each
5641 subdirectory of your project. If you moved the entire tree while
5642 preserving its internal organization, then @code{set substitute-path}
5643 allows you to direct the debugger to all the sources with one single
5646 @code{set substitute-path} is also more than just a shortcut command.
5647 The source path is only used if the file at the original location no
5648 longer exists. On the other hand, @code{set substitute-path} modifies
5649 the debugger behavior to look at the rewritten location instead. So, if
5650 for any reason a source file that is not relevant to your executable is
5651 located at the original location, a substitution rule is the only
5652 method available to point @value{GDBN} at the new location.
5655 @item directory @var{dirname} @dots{}
5656 @item dir @var{dirname} @dots{}
5657 Add directory @var{dirname} to the front of the source path. Several
5658 directory names may be given to this command, separated by @samp{:}
5659 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
5660 part of absolute file names) or
5661 whitespace. You may specify a directory that is already in the source
5662 path; this moves it forward, so @value{GDBN} searches it sooner.
5666 @vindex $cdir@r{, convenience variable}
5667 @vindex $cwd@r{, convenience variable}
5668 @cindex compilation directory
5669 @cindex current directory
5670 @cindex working directory
5671 @cindex directory, current
5672 @cindex directory, compilation
5673 You can use the string @samp{$cdir} to refer to the compilation
5674 directory (if one is recorded), and @samp{$cwd} to refer to the current
5675 working directory. @samp{$cwd} is not the same as @samp{.}---the former
5676 tracks the current working directory as it changes during your @value{GDBN}
5677 session, while the latter is immediately expanded to the current
5678 directory at the time you add an entry to the source path.
5681 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
5683 @c RET-repeat for @code{directory} is explicitly disabled, but since
5684 @c repeating it would be a no-op we do not say that. (thanks to RMS)
5686 @item show directories
5687 @kindex show directories
5688 Print the source path: show which directories it contains.
5690 @anchor{set substitute-path}
5691 @item set substitute-path @var{from} @var{to}
5692 @kindex set substitute-path
5693 Define a source path substitution rule, and add it at the end of the
5694 current list of existing substitution rules. If a rule with the same
5695 @var{from} was already defined, then the old rule is also deleted.
5697 For example, if the file @file{/foo/bar/baz.c} was moved to
5698 @file{/mnt/cross/baz.c}, then the command
5701 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
5705 will tell @value{GDBN} to replace @samp{/usr/src} with
5706 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
5707 @file{baz.c} even though it was moved.
5709 In the case when more than one substitution rule have been defined,
5710 the rules are evaluated one by one in the order where they have been
5711 defined. The first one matching, if any, is selected to perform
5714 For instance, if we had entered the following commands:
5717 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
5718 (@value{GDBP}) set substitute-path /usr/src /mnt/src
5722 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
5723 @file{/mnt/include/defs.h} by using the first rule. However, it would
5724 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
5725 @file{/mnt/src/lib/foo.c}.
5728 @item unset substitute-path [path]
5729 @kindex unset substitute-path
5730 If a path is specified, search the current list of substitution rules
5731 for a rule that would rewrite that path. Delete that rule if found.
5732 A warning is emitted by the debugger if no rule could be found.
5734 If no path is specified, then all substitution rules are deleted.
5736 @item show substitute-path [path]
5737 @kindex show substitute-path
5738 If a path is specified, then print the source path substitution rule
5739 which would rewrite that path, if any.
5741 If no path is specified, then print all existing source path substitution
5746 If your source path is cluttered with directories that are no longer of
5747 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
5748 versions of source. You can correct the situation as follows:
5752 Use @code{directory} with no argument to reset the source path to its default value.
5755 Use @code{directory} with suitable arguments to reinstall the
5756 directories you want in the source path. You can add all the
5757 directories in one command.
5761 @section Source and Machine Code
5762 @cindex source line and its code address
5764 You can use the command @code{info line} to map source lines to program
5765 addresses (and vice versa), and the command @code{disassemble} to display
5766 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
5767 mode, the @code{info line} command causes the arrow to point to the
5768 line specified. Also, @code{info line} prints addresses in symbolic form as
5773 @item info line @var{linespec}
5774 Print the starting and ending addresses of the compiled code for
5775 source line @var{linespec}. You can specify source lines in any of
5776 the ways documented in @ref{Specify Location}.
5779 For example, we can use @code{info line} to discover the location of
5780 the object code for the first line of function
5781 @code{m4_changequote}:
5783 @c FIXME: I think this example should also show the addresses in
5784 @c symbolic form, as they usually would be displayed.
5786 (@value{GDBP}) info line m4_changequote
5787 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
5791 @cindex code address and its source line
5792 We can also inquire (using @code{*@var{addr}} as the form for
5793 @var{linespec}) what source line covers a particular address:
5795 (@value{GDBP}) info line *0x63ff
5796 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
5799 @cindex @code{$_} and @code{info line}
5800 @cindex @code{x} command, default address
5801 @kindex x@r{(examine), and} info line
5802 After @code{info line}, the default address for the @code{x} command
5803 is changed to the starting address of the line, so that @samp{x/i} is
5804 sufficient to begin examining the machine code (@pxref{Memory,
5805 ,Examining Memory}). Also, this address is saved as the value of the
5806 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
5811 @cindex assembly instructions
5812 @cindex instructions, assembly
5813 @cindex machine instructions
5814 @cindex listing machine instructions
5816 @itemx disassemble /m
5817 This specialized command dumps a range of memory as machine
5818 instructions. It can also print mixed source+disassembly by specifying
5819 the @code{/m} modifier.
5820 The default memory range is the function surrounding the
5821 program counter of the selected frame. A single argument to this
5822 command is a program counter value; @value{GDBN} dumps the function
5823 surrounding this value. Two arguments specify a range of addresses
5824 (first inclusive, second exclusive) to dump.
5827 The following example shows the disassembly of a range of addresses of
5828 HP PA-RISC 2.0 code:
5831 (@value{GDBP}) disas 0x32c4 0x32e4
5832 Dump of assembler code from 0x32c4 to 0x32e4:
5833 0x32c4 <main+204>: addil 0,dp
5834 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
5835 0x32cc <main+212>: ldil 0x3000,r31
5836 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
5837 0x32d4 <main+220>: ldo 0(r31),rp
5838 0x32d8 <main+224>: addil -0x800,dp
5839 0x32dc <main+228>: ldo 0x588(r1),r26
5840 0x32e0 <main+232>: ldil 0x3000,r31
5841 End of assembler dump.
5844 Here is an example showing mixed source+assembly for Intel x86:
5847 (@value{GDBP}) disas /m main
5848 Dump of assembler code for function main:
5850 0x08048330 <main+0>: push %ebp
5851 0x08048331 <main+1>: mov %esp,%ebp
5852 0x08048333 <main+3>: sub $0x8,%esp
5853 0x08048336 <main+6>: and $0xfffffff0,%esp
5854 0x08048339 <main+9>: sub $0x10,%esp
5856 6 printf ("Hello.\n");
5857 0x0804833c <main+12>: movl $0x8048440,(%esp)
5858 0x08048343 <main+19>: call 0x8048284 <puts@@plt>
5862 0x08048348 <main+24>: mov $0x0,%eax
5863 0x0804834d <main+29>: leave
5864 0x0804834e <main+30>: ret
5866 End of assembler dump.
5869 Some architectures have more than one commonly-used set of instruction
5870 mnemonics or other syntax.
5872 For programs that were dynamically linked and use shared libraries,
5873 instructions that call functions or branch to locations in the shared
5874 libraries might show a seemingly bogus location---it's actually a
5875 location of the relocation table. On some architectures, @value{GDBN}
5876 might be able to resolve these to actual function names.
5879 @kindex set disassembly-flavor
5880 @cindex Intel disassembly flavor
5881 @cindex AT&T disassembly flavor
5882 @item set disassembly-flavor @var{instruction-set}
5883 Select the instruction set to use when disassembling the
5884 program via the @code{disassemble} or @code{x/i} commands.
5886 Currently this command is only defined for the Intel x86 family. You
5887 can set @var{instruction-set} to either @code{intel} or @code{att}.
5888 The default is @code{att}, the AT&T flavor used by default by Unix
5889 assemblers for x86-based targets.
5891 @kindex show disassembly-flavor
5892 @item show disassembly-flavor
5893 Show the current setting of the disassembly flavor.
5898 @chapter Examining Data
5900 @cindex printing data
5901 @cindex examining data
5904 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
5905 @c document because it is nonstandard... Under Epoch it displays in a
5906 @c different window or something like that.
5907 The usual way to examine data in your program is with the @code{print}
5908 command (abbreviated @code{p}), or its synonym @code{inspect}. It
5909 evaluates and prints the value of an expression of the language your
5910 program is written in (@pxref{Languages, ,Using @value{GDBN} with
5911 Different Languages}).
5914 @item print @var{expr}
5915 @itemx print /@var{f} @var{expr}
5916 @var{expr} is an expression (in the source language). By default the
5917 value of @var{expr} is printed in a format appropriate to its data type;
5918 you can choose a different format by specifying @samp{/@var{f}}, where
5919 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
5923 @itemx print /@var{f}
5924 @cindex reprint the last value
5925 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
5926 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
5927 conveniently inspect the same value in an alternative format.
5930 A more low-level way of examining data is with the @code{x} command.
5931 It examines data in memory at a specified address and prints it in a
5932 specified format. @xref{Memory, ,Examining Memory}.
5934 If you are interested in information about types, or about how the
5935 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
5936 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
5940 * Expressions:: Expressions
5941 * Ambiguous Expressions:: Ambiguous Expressions
5942 * Variables:: Program variables
5943 * Arrays:: Artificial arrays
5944 * Output Formats:: Output formats
5945 * Memory:: Examining memory
5946 * Auto Display:: Automatic display
5947 * Print Settings:: Print settings
5948 * Value History:: Value history
5949 * Convenience Vars:: Convenience variables
5950 * Registers:: Registers
5951 * Floating Point Hardware:: Floating point hardware
5952 * Vector Unit:: Vector Unit
5953 * OS Information:: Auxiliary data provided by operating system
5954 * Memory Region Attributes:: Memory region attributes
5955 * Dump/Restore Files:: Copy between memory and a file
5956 * Core File Generation:: Cause a program dump its core
5957 * Character Sets:: Debugging programs that use a different
5958 character set than GDB does
5959 * Caching Remote Data:: Data caching for remote targets
5960 * Searching Memory:: Searching memory for a sequence of bytes
5964 @section Expressions
5967 @code{print} and many other @value{GDBN} commands accept an expression and
5968 compute its value. Any kind of constant, variable or operator defined
5969 by the programming language you are using is valid in an expression in
5970 @value{GDBN}. This includes conditional expressions, function calls,
5971 casts, and string constants. It also includes preprocessor macros, if
5972 you compiled your program to include this information; see
5975 @cindex arrays in expressions
5976 @value{GDBN} supports array constants in expressions input by
5977 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
5978 you can use the command @code{print @{1, 2, 3@}} to create an array
5979 of three integers. If you pass an array to a function or assign it
5980 to a program variable, @value{GDBN} copies the array to memory that
5981 is @code{malloc}ed in the target program.
5983 Because C is so widespread, most of the expressions shown in examples in
5984 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
5985 Languages}, for information on how to use expressions in other
5988 In this section, we discuss operators that you can use in @value{GDBN}
5989 expressions regardless of your programming language.
5991 @cindex casts, in expressions
5992 Casts are supported in all languages, not just in C, because it is so
5993 useful to cast a number into a pointer in order to examine a structure
5994 at that address in memory.
5995 @c FIXME: casts supported---Mod2 true?
5997 @value{GDBN} supports these operators, in addition to those common
5998 to programming languages:
6002 @samp{@@} is a binary operator for treating parts of memory as arrays.
6003 @xref{Arrays, ,Artificial Arrays}, for more information.
6006 @samp{::} allows you to specify a variable in terms of the file or
6007 function where it is defined. @xref{Variables, ,Program Variables}.
6009 @cindex @{@var{type}@}
6010 @cindex type casting memory
6011 @cindex memory, viewing as typed object
6012 @cindex casts, to view memory
6013 @item @{@var{type}@} @var{addr}
6014 Refers to an object of type @var{type} stored at address @var{addr} in
6015 memory. @var{addr} may be any expression whose value is an integer or
6016 pointer (but parentheses are required around binary operators, just as in
6017 a cast). This construct is allowed regardless of what kind of data is
6018 normally supposed to reside at @var{addr}.
6021 @node Ambiguous Expressions
6022 @section Ambiguous Expressions
6023 @cindex ambiguous expressions
6025 Expressions can sometimes contain some ambiguous elements. For instance,
6026 some programming languages (notably Ada, C@t{++} and Objective-C) permit
6027 a single function name to be defined several times, for application in
6028 different contexts. This is called @dfn{overloading}. Another example
6029 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
6030 templates and is typically instantiated several times, resulting in
6031 the same function name being defined in different contexts.
6033 In some cases and depending on the language, it is possible to adjust
6034 the expression to remove the ambiguity. For instance in C@t{++}, you
6035 can specify the signature of the function you want to break on, as in
6036 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
6037 qualified name of your function often makes the expression unambiguous
6040 When an ambiguity that needs to be resolved is detected, the debugger
6041 has the capability to display a menu of numbered choices for each
6042 possibility, and then waits for the selection with the prompt @samp{>}.
6043 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
6044 aborts the current command. If the command in which the expression was
6045 used allows more than one choice to be selected, the next option in the
6046 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
6049 For example, the following session excerpt shows an attempt to set a
6050 breakpoint at the overloaded symbol @code{String::after}.
6051 We choose three particular definitions of that function name:
6053 @c FIXME! This is likely to change to show arg type lists, at least
6056 (@value{GDBP}) b String::after
6059 [2] file:String.cc; line number:867
6060 [3] file:String.cc; line number:860
6061 [4] file:String.cc; line number:875
6062 [5] file:String.cc; line number:853
6063 [6] file:String.cc; line number:846
6064 [7] file:String.cc; line number:735
6066 Breakpoint 1 at 0xb26c: file String.cc, line 867.
6067 Breakpoint 2 at 0xb344: file String.cc, line 875.
6068 Breakpoint 3 at 0xafcc: file String.cc, line 846.
6069 Multiple breakpoints were set.
6070 Use the "delete" command to delete unwanted
6077 @kindex set multiple-symbols
6078 @item set multiple-symbols @var{mode}
6079 @cindex multiple-symbols menu
6081 This option allows you to adjust the debugger behavior when an expression
6084 By default, @var{mode} is set to @code{all}. If the command with which
6085 the expression is used allows more than one choice, then @value{GDBN}
6086 automatically selects all possible choices. For instance, inserting
6087 a breakpoint on a function using an ambiguous name results in a breakpoint
6088 inserted on each possible match. However, if a unique choice must be made,
6089 then @value{GDBN} uses the menu to help you disambiguate the expression.
6090 For instance, printing the address of an overloaded function will result
6091 in the use of the menu.
6093 When @var{mode} is set to @code{ask}, the debugger always uses the menu
6094 when an ambiguity is detected.
6096 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
6097 an error due to the ambiguity and the command is aborted.
6099 @kindex show multiple-symbols
6100 @item show multiple-symbols
6101 Show the current value of the @code{multiple-symbols} setting.
6105 @section Program Variables
6107 The most common kind of expression to use is the name of a variable
6110 Variables in expressions are understood in the selected stack frame
6111 (@pxref{Selection, ,Selecting a Frame}); they must be either:
6115 global (or file-static)
6122 visible according to the scope rules of the
6123 programming language from the point of execution in that frame
6126 @noindent This means that in the function
6141 you can examine and use the variable @code{a} whenever your program is
6142 executing within the function @code{foo}, but you can only use or
6143 examine the variable @code{b} while your program is executing inside
6144 the block where @code{b} is declared.
6146 @cindex variable name conflict
6147 There is an exception: you can refer to a variable or function whose
6148 scope is a single source file even if the current execution point is not
6149 in this file. But it is possible to have more than one such variable or
6150 function with the same name (in different source files). If that
6151 happens, referring to that name has unpredictable effects. If you wish,
6152 you can specify a static variable in a particular function or file,
6153 using the colon-colon (@code{::}) notation:
6155 @cindex colon-colon, context for variables/functions
6157 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
6158 @cindex @code{::}, context for variables/functions
6161 @var{file}::@var{variable}
6162 @var{function}::@var{variable}
6166 Here @var{file} or @var{function} is the name of the context for the
6167 static @var{variable}. In the case of file names, you can use quotes to
6168 make sure @value{GDBN} parses the file name as a single word---for example,
6169 to print a global value of @code{x} defined in @file{f2.c}:
6172 (@value{GDBP}) p 'f2.c'::x
6175 @cindex C@t{++} scope resolution
6176 This use of @samp{::} is very rarely in conflict with the very similar
6177 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
6178 scope resolution operator in @value{GDBN} expressions.
6179 @c FIXME: Um, so what happens in one of those rare cases where it's in
6182 @cindex wrong values
6183 @cindex variable values, wrong
6184 @cindex function entry/exit, wrong values of variables
6185 @cindex optimized code, wrong values of variables
6187 @emph{Warning:} Occasionally, a local variable may appear to have the
6188 wrong value at certain points in a function---just after entry to a new
6189 scope, and just before exit.
6191 You may see this problem when you are stepping by machine instructions.
6192 This is because, on most machines, it takes more than one instruction to
6193 set up a stack frame (including local variable definitions); if you are
6194 stepping by machine instructions, variables may appear to have the wrong
6195 values until the stack frame is completely built. On exit, it usually
6196 also takes more than one machine instruction to destroy a stack frame;
6197 after you begin stepping through that group of instructions, local
6198 variable definitions may be gone.
6200 This may also happen when the compiler does significant optimizations.
6201 To be sure of always seeing accurate values, turn off all optimization
6204 @cindex ``No symbol "foo" in current context''
6205 Another possible effect of compiler optimizations is to optimize
6206 unused variables out of existence, or assign variables to registers (as
6207 opposed to memory addresses). Depending on the support for such cases
6208 offered by the debug info format used by the compiler, @value{GDBN}
6209 might not be able to display values for such local variables. If that
6210 happens, @value{GDBN} will print a message like this:
6213 No symbol "foo" in current context.
6216 To solve such problems, either recompile without optimizations, or use a
6217 different debug info format, if the compiler supports several such
6218 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
6219 usually supports the @option{-gstabs+} option. @option{-gstabs+}
6220 produces debug info in a format that is superior to formats such as
6221 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
6222 an effective form for debug info. @xref{Debugging Options,,Options
6223 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
6224 Compiler Collection (GCC)}.
6225 @xref{C, ,C and C@t{++}}, for more information about debug info formats
6226 that are best suited to C@t{++} programs.
6228 If you ask to print an object whose contents are unknown to
6229 @value{GDBN}, e.g., because its data type is not completely specified
6230 by the debug information, @value{GDBN} will say @samp{<incomplete
6231 type>}. @xref{Symbols, incomplete type}, for more about this.
6233 Strings are identified as arrays of @code{char} values without specified
6234 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
6235 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
6236 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
6237 defines literal string type @code{"char"} as @code{char} without a sign.
6242 signed char var1[] = "A";
6245 You get during debugging
6250 $2 = @{65 'A', 0 '\0'@}
6254 @section Artificial Arrays
6256 @cindex artificial array
6258 @kindex @@@r{, referencing memory as an array}
6259 It is often useful to print out several successive objects of the
6260 same type in memory; a section of an array, or an array of
6261 dynamically determined size for which only a pointer exists in the
6264 You can do this by referring to a contiguous span of memory as an
6265 @dfn{artificial array}, using the binary operator @samp{@@}. The left
6266 operand of @samp{@@} should be the first element of the desired array
6267 and be an individual object. The right operand should be the desired length
6268 of the array. The result is an array value whose elements are all of
6269 the type of the left argument. The first element is actually the left
6270 argument; the second element comes from bytes of memory immediately
6271 following those that hold the first element, and so on. Here is an
6272 example. If a program says
6275 int *array = (int *) malloc (len * sizeof (int));
6279 you can print the contents of @code{array} with
6285 The left operand of @samp{@@} must reside in memory. Array values made
6286 with @samp{@@} in this way behave just like other arrays in terms of
6287 subscripting, and are coerced to pointers when used in expressions.
6288 Artificial arrays most often appear in expressions via the value history
6289 (@pxref{Value History, ,Value History}), after printing one out.
6291 Another way to create an artificial array is to use a cast.
6292 This re-interprets a value as if it were an array.
6293 The value need not be in memory:
6295 (@value{GDBP}) p/x (short[2])0x12345678
6296 $1 = @{0x1234, 0x5678@}
6299 As a convenience, if you leave the array length out (as in
6300 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
6301 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
6303 (@value{GDBP}) p/x (short[])0x12345678
6304 $2 = @{0x1234, 0x5678@}
6307 Sometimes the artificial array mechanism is not quite enough; in
6308 moderately complex data structures, the elements of interest may not
6309 actually be adjacent---for example, if you are interested in the values
6310 of pointers in an array. One useful work-around in this situation is
6311 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
6312 Variables}) as a counter in an expression that prints the first
6313 interesting value, and then repeat that expression via @key{RET}. For
6314 instance, suppose you have an array @code{dtab} of pointers to
6315 structures, and you are interested in the values of a field @code{fv}
6316 in each structure. Here is an example of what you might type:
6326 @node Output Formats
6327 @section Output Formats
6329 @cindex formatted output
6330 @cindex output formats
6331 By default, @value{GDBN} prints a value according to its data type. Sometimes
6332 this is not what you want. For example, you might want to print a number
6333 in hex, or a pointer in decimal. Or you might want to view data in memory
6334 at a certain address as a character string or as an instruction. To do
6335 these things, specify an @dfn{output format} when you print a value.
6337 The simplest use of output formats is to say how to print a value
6338 already computed. This is done by starting the arguments of the
6339 @code{print} command with a slash and a format letter. The format
6340 letters supported are:
6344 Regard the bits of the value as an integer, and print the integer in
6348 Print as integer in signed decimal.
6351 Print as integer in unsigned decimal.
6354 Print as integer in octal.
6357 Print as integer in binary. The letter @samp{t} stands for ``two''.
6358 @footnote{@samp{b} cannot be used because these format letters are also
6359 used with the @code{x} command, where @samp{b} stands for ``byte'';
6360 see @ref{Memory,,Examining Memory}.}
6363 @cindex unknown address, locating
6364 @cindex locate address
6365 Print as an address, both absolute in hexadecimal and as an offset from
6366 the nearest preceding symbol. You can use this format used to discover
6367 where (in what function) an unknown address is located:
6370 (@value{GDBP}) p/a 0x54320
6371 $3 = 0x54320 <_initialize_vx+396>
6375 The command @code{info symbol 0x54320} yields similar results.
6376 @xref{Symbols, info symbol}.
6379 Regard as an integer and print it as a character constant. This
6380 prints both the numerical value and its character representation. The
6381 character representation is replaced with the octal escape @samp{\nnn}
6382 for characters outside the 7-bit @sc{ascii} range.
6384 Without this format, @value{GDBN} displays @code{char},
6385 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
6386 constants. Single-byte members of vectors are displayed as integer
6390 Regard the bits of the value as a floating point number and print
6391 using typical floating point syntax.
6394 @cindex printing strings
6395 @cindex printing byte arrays
6396 Regard as a string, if possible. With this format, pointers to single-byte
6397 data are displayed as null-terminated strings and arrays of single-byte data
6398 are displayed as fixed-length strings. Other values are displayed in their
6401 Without this format, @value{GDBN} displays pointers to and arrays of
6402 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
6403 strings. Single-byte members of a vector are displayed as an integer
6407 For example, to print the program counter in hex (@pxref{Registers}), type
6414 Note that no space is required before the slash; this is because command
6415 names in @value{GDBN} cannot contain a slash.
6417 To reprint the last value in the value history with a different format,
6418 you can use the @code{print} command with just a format and no
6419 expression. For example, @samp{p/x} reprints the last value in hex.
6422 @section Examining Memory
6424 You can use the command @code{x} (for ``examine'') to examine memory in
6425 any of several formats, independently of your program's data types.
6427 @cindex examining memory
6429 @kindex x @r{(examine memory)}
6430 @item x/@var{nfu} @var{addr}
6433 Use the @code{x} command to examine memory.
6436 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
6437 much memory to display and how to format it; @var{addr} is an
6438 expression giving the address where you want to start displaying memory.
6439 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
6440 Several commands set convenient defaults for @var{addr}.
6443 @item @var{n}, the repeat count
6444 The repeat count is a decimal integer; the default is 1. It specifies
6445 how much memory (counting by units @var{u}) to display.
6446 @c This really is **decimal**; unaffected by 'set radix' as of GDB
6449 @item @var{f}, the display format
6450 The display format is one of the formats used by @code{print}
6451 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
6452 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
6453 The default is @samp{x} (hexadecimal) initially. The default changes
6454 each time you use either @code{x} or @code{print}.
6456 @item @var{u}, the unit size
6457 The unit size is any of
6463 Halfwords (two bytes).
6465 Words (four bytes). This is the initial default.
6467 Giant words (eight bytes).
6470 Each time you specify a unit size with @code{x}, that size becomes the
6471 default unit the next time you use @code{x}. (For the @samp{s} and
6472 @samp{i} formats, the unit size is ignored and is normally not written.)
6474 @item @var{addr}, starting display address
6475 @var{addr} is the address where you want @value{GDBN} to begin displaying
6476 memory. The expression need not have a pointer value (though it may);
6477 it is always interpreted as an integer address of a byte of memory.
6478 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
6479 @var{addr} is usually just after the last address examined---but several
6480 other commands also set the default address: @code{info breakpoints} (to
6481 the address of the last breakpoint listed), @code{info line} (to the
6482 starting address of a line), and @code{print} (if you use it to display
6483 a value from memory).
6486 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
6487 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
6488 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
6489 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
6490 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
6492 Since the letters indicating unit sizes are all distinct from the
6493 letters specifying output formats, you do not have to remember whether
6494 unit size or format comes first; either order works. The output
6495 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
6496 (However, the count @var{n} must come first; @samp{wx4} does not work.)
6498 Even though the unit size @var{u} is ignored for the formats @samp{s}
6499 and @samp{i}, you might still want to use a count @var{n}; for example,
6500 @samp{3i} specifies that you want to see three machine instructions,
6501 including any operands. For convenience, especially when used with
6502 the @code{display} command, the @samp{i} format also prints branch delay
6503 slot instructions, if any, beyond the count specified, which immediately
6504 follow the last instruction that is within the count. The command
6505 @code{disassemble} gives an alternative way of inspecting machine
6506 instructions; see @ref{Machine Code,,Source and Machine Code}.
6508 All the defaults for the arguments to @code{x} are designed to make it
6509 easy to continue scanning memory with minimal specifications each time
6510 you use @code{x}. For example, after you have inspected three machine
6511 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
6512 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
6513 the repeat count @var{n} is used again; the other arguments default as
6514 for successive uses of @code{x}.
6516 @cindex @code{$_}, @code{$__}, and value history
6517 The addresses and contents printed by the @code{x} command are not saved
6518 in the value history because there is often too much of them and they
6519 would get in the way. Instead, @value{GDBN} makes these values available for
6520 subsequent use in expressions as values of the convenience variables
6521 @code{$_} and @code{$__}. After an @code{x} command, the last address
6522 examined is available for use in expressions in the convenience variable
6523 @code{$_}. The contents of that address, as examined, are available in
6524 the convenience variable @code{$__}.
6526 If the @code{x} command has a repeat count, the address and contents saved
6527 are from the last memory unit printed; this is not the same as the last
6528 address printed if several units were printed on the last line of output.
6530 @cindex remote memory comparison
6531 @cindex verify remote memory image
6532 When you are debugging a program running on a remote target machine
6533 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
6534 remote machine's memory against the executable file you downloaded to
6535 the target. The @code{compare-sections} command is provided for such
6539 @kindex compare-sections
6540 @item compare-sections @r{[}@var{section-name}@r{]}
6541 Compare the data of a loadable section @var{section-name} in the
6542 executable file of the program being debugged with the same section in
6543 the remote machine's memory, and report any mismatches. With no
6544 arguments, compares all loadable sections. This command's
6545 availability depends on the target's support for the @code{"qCRC"}
6550 @section Automatic Display
6551 @cindex automatic display
6552 @cindex display of expressions
6554 If you find that you want to print the value of an expression frequently
6555 (to see how it changes), you might want to add it to the @dfn{automatic
6556 display list} so that @value{GDBN} prints its value each time your program stops.
6557 Each expression added to the list is given a number to identify it;
6558 to remove an expression from the list, you specify that number.
6559 The automatic display looks like this:
6563 3: bar[5] = (struct hack *) 0x3804
6567 This display shows item numbers, expressions and their current values. As with
6568 displays you request manually using @code{x} or @code{print}, you can
6569 specify the output format you prefer; in fact, @code{display} decides
6570 whether to use @code{print} or @code{x} depending your format
6571 specification---it uses @code{x} if you specify either the @samp{i}
6572 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
6576 @item display @var{expr}
6577 Add the expression @var{expr} to the list of expressions to display
6578 each time your program stops. @xref{Expressions, ,Expressions}.
6580 @code{display} does not repeat if you press @key{RET} again after using it.
6582 @item display/@var{fmt} @var{expr}
6583 For @var{fmt} specifying only a display format and not a size or
6584 count, add the expression @var{expr} to the auto-display list but
6585 arrange to display it each time in the specified format @var{fmt}.
6586 @xref{Output Formats,,Output Formats}.
6588 @item display/@var{fmt} @var{addr}
6589 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
6590 number of units, add the expression @var{addr} as a memory address to
6591 be examined each time your program stops. Examining means in effect
6592 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
6595 For example, @samp{display/i $pc} can be helpful, to see the machine
6596 instruction about to be executed each time execution stops (@samp{$pc}
6597 is a common name for the program counter; @pxref{Registers, ,Registers}).
6600 @kindex delete display
6602 @item undisplay @var{dnums}@dots{}
6603 @itemx delete display @var{dnums}@dots{}
6604 Remove item numbers @var{dnums} from the list of expressions to display.
6606 @code{undisplay} does not repeat if you press @key{RET} after using it.
6607 (Otherwise you would just get the error @samp{No display number @dots{}}.)
6609 @kindex disable display
6610 @item disable display @var{dnums}@dots{}
6611 Disable the display of item numbers @var{dnums}. A disabled display
6612 item is not printed automatically, but is not forgotten. It may be
6613 enabled again later.
6615 @kindex enable display
6616 @item enable display @var{dnums}@dots{}
6617 Enable display of item numbers @var{dnums}. It becomes effective once
6618 again in auto display of its expression, until you specify otherwise.
6621 Display the current values of the expressions on the list, just as is
6622 done when your program stops.
6624 @kindex info display
6626 Print the list of expressions previously set up to display
6627 automatically, each one with its item number, but without showing the
6628 values. This includes disabled expressions, which are marked as such.
6629 It also includes expressions which would not be displayed right now
6630 because they refer to automatic variables not currently available.
6633 @cindex display disabled out of scope
6634 If a display expression refers to local variables, then it does not make
6635 sense outside the lexical context for which it was set up. Such an
6636 expression is disabled when execution enters a context where one of its
6637 variables is not defined. For example, if you give the command
6638 @code{display last_char} while inside a function with an argument
6639 @code{last_char}, @value{GDBN} displays this argument while your program
6640 continues to stop inside that function. When it stops elsewhere---where
6641 there is no variable @code{last_char}---the display is disabled
6642 automatically. The next time your program stops where @code{last_char}
6643 is meaningful, you can enable the display expression once again.
6645 @node Print Settings
6646 @section Print Settings
6648 @cindex format options
6649 @cindex print settings
6650 @value{GDBN} provides the following ways to control how arrays, structures,
6651 and symbols are printed.
6654 These settings are useful for debugging programs in any language:
6658 @item set print address
6659 @itemx set print address on
6660 @cindex print/don't print memory addresses
6661 @value{GDBN} prints memory addresses showing the location of stack
6662 traces, structure values, pointer values, breakpoints, and so forth,
6663 even when it also displays the contents of those addresses. The default
6664 is @code{on}. For example, this is what a stack frame display looks like with
6665 @code{set print address on}:
6670 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
6672 530 if (lquote != def_lquote)
6676 @item set print address off
6677 Do not print addresses when displaying their contents. For example,
6678 this is the same stack frame displayed with @code{set print address off}:
6682 (@value{GDBP}) set print addr off
6684 #0 set_quotes (lq="<<", rq=">>") at input.c:530
6685 530 if (lquote != def_lquote)
6689 You can use @samp{set print address off} to eliminate all machine
6690 dependent displays from the @value{GDBN} interface. For example, with
6691 @code{print address off}, you should get the same text for backtraces on
6692 all machines---whether or not they involve pointer arguments.
6695 @item show print address
6696 Show whether or not addresses are to be printed.
6699 When @value{GDBN} prints a symbolic address, it normally prints the
6700 closest earlier symbol plus an offset. If that symbol does not uniquely
6701 identify the address (for example, it is a name whose scope is a single
6702 source file), you may need to clarify. One way to do this is with
6703 @code{info line}, for example @samp{info line *0x4537}. Alternately,
6704 you can set @value{GDBN} to print the source file and line number when
6705 it prints a symbolic address:
6708 @item set print symbol-filename on
6709 @cindex source file and line of a symbol
6710 @cindex symbol, source file and line
6711 Tell @value{GDBN} to print the source file name and line number of a
6712 symbol in the symbolic form of an address.
6714 @item set print symbol-filename off
6715 Do not print source file name and line number of a symbol. This is the
6718 @item show print symbol-filename
6719 Show whether or not @value{GDBN} will print the source file name and
6720 line number of a symbol in the symbolic form of an address.
6723 Another situation where it is helpful to show symbol filenames and line
6724 numbers is when disassembling code; @value{GDBN} shows you the line
6725 number and source file that corresponds to each instruction.
6727 Also, you may wish to see the symbolic form only if the address being
6728 printed is reasonably close to the closest earlier symbol:
6731 @item set print max-symbolic-offset @var{max-offset}
6732 @cindex maximum value for offset of closest symbol
6733 Tell @value{GDBN} to only display the symbolic form of an address if the
6734 offset between the closest earlier symbol and the address is less than
6735 @var{max-offset}. The default is 0, which tells @value{GDBN}
6736 to always print the symbolic form of an address if any symbol precedes it.
6738 @item show print max-symbolic-offset
6739 Ask how large the maximum offset is that @value{GDBN} prints in a
6743 @cindex wild pointer, interpreting
6744 @cindex pointer, finding referent
6745 If you have a pointer and you are not sure where it points, try
6746 @samp{set print symbol-filename on}. Then you can determine the name
6747 and source file location of the variable where it points, using
6748 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
6749 For example, here @value{GDBN} shows that a variable @code{ptt} points
6750 at another variable @code{t}, defined in @file{hi2.c}:
6753 (@value{GDBP}) set print symbol-filename on
6754 (@value{GDBP}) p/a ptt
6755 $4 = 0xe008 <t in hi2.c>
6759 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
6760 does not show the symbol name and filename of the referent, even with
6761 the appropriate @code{set print} options turned on.
6764 Other settings control how different kinds of objects are printed:
6767 @item set print array
6768 @itemx set print array on
6769 @cindex pretty print arrays
6770 Pretty print arrays. This format is more convenient to read,
6771 but uses more space. The default is off.
6773 @item set print array off
6774 Return to compressed format for arrays.
6776 @item show print array
6777 Show whether compressed or pretty format is selected for displaying
6780 @cindex print array indexes
6781 @item set print array-indexes
6782 @itemx set print array-indexes on
6783 Print the index of each element when displaying arrays. May be more
6784 convenient to locate a given element in the array or quickly find the
6785 index of a given element in that printed array. The default is off.
6787 @item set print array-indexes off
6788 Stop printing element indexes when displaying arrays.
6790 @item show print array-indexes
6791 Show whether the index of each element is printed when displaying
6794 @item set print elements @var{number-of-elements}
6795 @cindex number of array elements to print
6796 @cindex limit on number of printed array elements
6797 Set a limit on how many elements of an array @value{GDBN} will print.
6798 If @value{GDBN} is printing a large array, it stops printing after it has
6799 printed the number of elements set by the @code{set print elements} command.
6800 This limit also applies to the display of strings.
6801 When @value{GDBN} starts, this limit is set to 200.
6802 Setting @var{number-of-elements} to zero means that the printing is unlimited.
6804 @item show print elements
6805 Display the number of elements of a large array that @value{GDBN} will print.
6806 If the number is 0, then the printing is unlimited.
6808 @item set print frame-arguments @var{value}
6809 @cindex printing frame argument values
6810 @cindex print all frame argument values
6811 @cindex print frame argument values for scalars only
6812 @cindex do not print frame argument values
6813 This command allows to control how the values of arguments are printed
6814 when the debugger prints a frame (@pxref{Frames}). The possible
6819 The values of all arguments are printed. This is the default.
6822 Print the value of an argument only if it is a scalar. The value of more
6823 complex arguments such as arrays, structures, unions, etc, is replaced
6824 by @code{@dots{}}. Here is an example where only scalar arguments are shown:
6827 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
6832 None of the argument values are printed. Instead, the value of each argument
6833 is replaced by @code{@dots{}}. In this case, the example above now becomes:
6836 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
6841 By default, all argument values are always printed. But this command
6842 can be useful in several cases. For instance, it can be used to reduce
6843 the amount of information printed in each frame, making the backtrace
6844 more readable. Also, this command can be used to improve performance
6845 when displaying Ada frames, because the computation of large arguments
6846 can sometimes be CPU-intensive, especiallly in large applications.
6847 Setting @code{print frame-arguments} to @code{scalars} or @code{none}
6848 avoids this computation, thus speeding up the display of each Ada frame.
6850 @item show print frame-arguments
6851 Show how the value of arguments should be displayed when printing a frame.
6853 @item set print repeats
6854 @cindex repeated array elements
6855 Set the threshold for suppressing display of repeated array
6856 elements. When the number of consecutive identical elements of an
6857 array exceeds the threshold, @value{GDBN} prints the string
6858 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
6859 identical repetitions, instead of displaying the identical elements
6860 themselves. Setting the threshold to zero will cause all elements to
6861 be individually printed. The default threshold is 10.
6863 @item show print repeats
6864 Display the current threshold for printing repeated identical
6867 @item set print null-stop
6868 @cindex @sc{null} elements in arrays
6869 Cause @value{GDBN} to stop printing the characters of an array when the first
6870 @sc{null} is encountered. This is useful when large arrays actually
6871 contain only short strings.
6874 @item show print null-stop
6875 Show whether @value{GDBN} stops printing an array on the first
6876 @sc{null} character.
6878 @item set print pretty on
6879 @cindex print structures in indented form
6880 @cindex indentation in structure display
6881 Cause @value{GDBN} to print structures in an indented format with one member
6882 per line, like this:
6897 @item set print pretty off
6898 Cause @value{GDBN} to print structures in a compact format, like this:
6902 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
6903 meat = 0x54 "Pork"@}
6908 This is the default format.
6910 @item show print pretty
6911 Show which format @value{GDBN} is using to print structures.
6913 @item set print sevenbit-strings on
6914 @cindex eight-bit characters in strings
6915 @cindex octal escapes in strings
6916 Print using only seven-bit characters; if this option is set,
6917 @value{GDBN} displays any eight-bit characters (in strings or
6918 character values) using the notation @code{\}@var{nnn}. This setting is
6919 best if you are working in English (@sc{ascii}) and you use the
6920 high-order bit of characters as a marker or ``meta'' bit.
6922 @item set print sevenbit-strings off
6923 Print full eight-bit characters. This allows the use of more
6924 international character sets, and is the default.
6926 @item show print sevenbit-strings
6927 Show whether or not @value{GDBN} is printing only seven-bit characters.
6929 @item set print union on
6930 @cindex unions in structures, printing
6931 Tell @value{GDBN} to print unions which are contained in structures
6932 and other unions. This is the default setting.
6934 @item set print union off
6935 Tell @value{GDBN} not to print unions which are contained in
6936 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
6939 @item show print union
6940 Ask @value{GDBN} whether or not it will print unions which are contained in
6941 structures and other unions.
6943 For example, given the declarations
6946 typedef enum @{Tree, Bug@} Species;
6947 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
6948 typedef enum @{Caterpillar, Cocoon, Butterfly@}
6959 struct thing foo = @{Tree, @{Acorn@}@};
6963 with @code{set print union on} in effect @samp{p foo} would print
6966 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
6970 and with @code{set print union off} in effect it would print
6973 $1 = @{it = Tree, form = @{...@}@}
6977 @code{set print union} affects programs written in C-like languages
6983 These settings are of interest when debugging C@t{++} programs:
6986 @cindex demangling C@t{++} names
6987 @item set print demangle
6988 @itemx set print demangle on
6989 Print C@t{++} names in their source form rather than in the encoded
6990 (``mangled'') form passed to the assembler and linker for type-safe
6991 linkage. The default is on.
6993 @item show print demangle
6994 Show whether C@t{++} names are printed in mangled or demangled form.
6996 @item set print asm-demangle
6997 @itemx set print asm-demangle on
6998 Print C@t{++} names in their source form rather than their mangled form, even
6999 in assembler code printouts such as instruction disassemblies.
7002 @item show print asm-demangle
7003 Show whether C@t{++} names in assembly listings are printed in mangled
7006 @cindex C@t{++} symbol decoding style
7007 @cindex symbol decoding style, C@t{++}
7008 @kindex set demangle-style
7009 @item set demangle-style @var{style}
7010 Choose among several encoding schemes used by different compilers to
7011 represent C@t{++} names. The choices for @var{style} are currently:
7015 Allow @value{GDBN} to choose a decoding style by inspecting your program.
7018 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
7019 This is the default.
7022 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
7025 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
7028 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
7029 @strong{Warning:} this setting alone is not sufficient to allow
7030 debugging @code{cfront}-generated executables. @value{GDBN} would
7031 require further enhancement to permit that.
7034 If you omit @var{style}, you will see a list of possible formats.
7036 @item show demangle-style
7037 Display the encoding style currently in use for decoding C@t{++} symbols.
7039 @item set print object
7040 @itemx set print object on
7041 @cindex derived type of an object, printing
7042 @cindex display derived types
7043 When displaying a pointer to an object, identify the @emph{actual}
7044 (derived) type of the object rather than the @emph{declared} type, using
7045 the virtual function table.
7047 @item set print object off
7048 Display only the declared type of objects, without reference to the
7049 virtual function table. This is the default setting.
7051 @item show print object
7052 Show whether actual, or declared, object types are displayed.
7054 @item set print static-members
7055 @itemx set print static-members on
7056 @cindex static members of C@t{++} objects
7057 Print static members when displaying a C@t{++} object. The default is on.
7059 @item set print static-members off
7060 Do not print static members when displaying a C@t{++} object.
7062 @item show print static-members
7063 Show whether C@t{++} static members are printed or not.
7065 @item set print pascal_static-members
7066 @itemx set print pascal_static-members on
7067 @cindex static members of Pascal objects
7068 @cindex Pascal objects, static members display
7069 Print static members when displaying a Pascal object. The default is on.
7071 @item set print pascal_static-members off
7072 Do not print static members when displaying a Pascal object.
7074 @item show print pascal_static-members
7075 Show whether Pascal static members are printed or not.
7077 @c These don't work with HP ANSI C++ yet.
7078 @item set print vtbl
7079 @itemx set print vtbl on
7080 @cindex pretty print C@t{++} virtual function tables
7081 @cindex virtual functions (C@t{++}) display
7082 @cindex VTBL display
7083 Pretty print C@t{++} virtual function tables. The default is off.
7084 (The @code{vtbl} commands do not work on programs compiled with the HP
7085 ANSI C@t{++} compiler (@code{aCC}).)
7087 @item set print vtbl off
7088 Do not pretty print C@t{++} virtual function tables.
7090 @item show print vtbl
7091 Show whether C@t{++} virtual function tables are pretty printed, or not.
7095 @section Value History
7097 @cindex value history
7098 @cindex history of values printed by @value{GDBN}
7099 Values printed by the @code{print} command are saved in the @value{GDBN}
7100 @dfn{value history}. This allows you to refer to them in other expressions.
7101 Values are kept until the symbol table is re-read or discarded
7102 (for example with the @code{file} or @code{symbol-file} commands).
7103 When the symbol table changes, the value history is discarded,
7104 since the values may contain pointers back to the types defined in the
7109 @cindex history number
7110 The values printed are given @dfn{history numbers} by which you can
7111 refer to them. These are successive integers starting with one.
7112 @code{print} shows you the history number assigned to a value by
7113 printing @samp{$@var{num} = } before the value; here @var{num} is the
7116 To refer to any previous value, use @samp{$} followed by the value's
7117 history number. The way @code{print} labels its output is designed to
7118 remind you of this. Just @code{$} refers to the most recent value in
7119 the history, and @code{$$} refers to the value before that.
7120 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
7121 is the value just prior to @code{$$}, @code{$$1} is equivalent to
7122 @code{$$}, and @code{$$0} is equivalent to @code{$}.
7124 For example, suppose you have just printed a pointer to a structure and
7125 want to see the contents of the structure. It suffices to type
7131 If you have a chain of structures where the component @code{next} points
7132 to the next one, you can print the contents of the next one with this:
7139 You can print successive links in the chain by repeating this
7140 command---which you can do by just typing @key{RET}.
7142 Note that the history records values, not expressions. If the value of
7143 @code{x} is 4 and you type these commands:
7151 then the value recorded in the value history by the @code{print} command
7152 remains 4 even though the value of @code{x} has changed.
7157 Print the last ten values in the value history, with their item numbers.
7158 This is like @samp{p@ $$9} repeated ten times, except that @code{show
7159 values} does not change the history.
7161 @item show values @var{n}
7162 Print ten history values centered on history item number @var{n}.
7165 Print ten history values just after the values last printed. If no more
7166 values are available, @code{show values +} produces no display.
7169 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
7170 same effect as @samp{show values +}.
7172 @node Convenience Vars
7173 @section Convenience Variables
7175 @cindex convenience variables
7176 @cindex user-defined variables
7177 @value{GDBN} provides @dfn{convenience variables} that you can use within
7178 @value{GDBN} to hold on to a value and refer to it later. These variables
7179 exist entirely within @value{GDBN}; they are not part of your program, and
7180 setting a convenience variable has no direct effect on further execution
7181 of your program. That is why you can use them freely.
7183 Convenience variables are prefixed with @samp{$}. Any name preceded by
7184 @samp{$} can be used for a convenience variable, unless it is one of
7185 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
7186 (Value history references, in contrast, are @emph{numbers} preceded
7187 by @samp{$}. @xref{Value History, ,Value History}.)
7189 You can save a value in a convenience variable with an assignment
7190 expression, just as you would set a variable in your program.
7194 set $foo = *object_ptr
7198 would save in @code{$foo} the value contained in the object pointed to by
7201 Using a convenience variable for the first time creates it, but its
7202 value is @code{void} until you assign a new value. You can alter the
7203 value with another assignment at any time.
7205 Convenience variables have no fixed types. You can assign a convenience
7206 variable any type of value, including structures and arrays, even if
7207 that variable already has a value of a different type. The convenience
7208 variable, when used as an expression, has the type of its current value.
7211 @kindex show convenience
7212 @cindex show all user variables
7213 @item show convenience
7214 Print a list of convenience variables used so far, and their values.
7215 Abbreviated @code{show conv}.
7217 @kindex init-if-undefined
7218 @cindex convenience variables, initializing
7219 @item init-if-undefined $@var{variable} = @var{expression}
7220 Set a convenience variable if it has not already been set. This is useful
7221 for user-defined commands that keep some state. It is similar, in concept,
7222 to using local static variables with initializers in C (except that
7223 convenience variables are global). It can also be used to allow users to
7224 override default values used in a command script.
7226 If the variable is already defined then the expression is not evaluated so
7227 any side-effects do not occur.
7230 One of the ways to use a convenience variable is as a counter to be
7231 incremented or a pointer to be advanced. For example, to print
7232 a field from successive elements of an array of structures:
7236 print bar[$i++]->contents
7240 Repeat that command by typing @key{RET}.
7242 Some convenience variables are created automatically by @value{GDBN} and given
7243 values likely to be useful.
7246 @vindex $_@r{, convenience variable}
7248 The variable @code{$_} is automatically set by the @code{x} command to
7249 the last address examined (@pxref{Memory, ,Examining Memory}). Other
7250 commands which provide a default address for @code{x} to examine also
7251 set @code{$_} to that address; these commands include @code{info line}
7252 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
7253 except when set by the @code{x} command, in which case it is a pointer
7254 to the type of @code{$__}.
7256 @vindex $__@r{, convenience variable}
7258 The variable @code{$__} is automatically set by the @code{x} command
7259 to the value found in the last address examined. Its type is chosen
7260 to match the format in which the data was printed.
7263 @vindex $_exitcode@r{, convenience variable}
7264 The variable @code{$_exitcode} is automatically set to the exit code when
7265 the program being debugged terminates.
7268 On HP-UX systems, if you refer to a function or variable name that
7269 begins with a dollar sign, @value{GDBN} searches for a user or system
7270 name first, before it searches for a convenience variable.
7276 You can refer to machine register contents, in expressions, as variables
7277 with names starting with @samp{$}. The names of registers are different
7278 for each machine; use @code{info registers} to see the names used on
7282 @kindex info registers
7283 @item info registers
7284 Print the names and values of all registers except floating-point
7285 and vector registers (in the selected stack frame).
7287 @kindex info all-registers
7288 @cindex floating point registers
7289 @item info all-registers
7290 Print the names and values of all registers, including floating-point
7291 and vector registers (in the selected stack frame).
7293 @item info registers @var{regname} @dots{}
7294 Print the @dfn{relativized} value of each specified register @var{regname}.
7295 As discussed in detail below, register values are normally relative to
7296 the selected stack frame. @var{regname} may be any register name valid on
7297 the machine you are using, with or without the initial @samp{$}.
7300 @cindex stack pointer register
7301 @cindex program counter register
7302 @cindex process status register
7303 @cindex frame pointer register
7304 @cindex standard registers
7305 @value{GDBN} has four ``standard'' register names that are available (in
7306 expressions) on most machines---whenever they do not conflict with an
7307 architecture's canonical mnemonics for registers. The register names
7308 @code{$pc} and @code{$sp} are used for the program counter register and
7309 the stack pointer. @code{$fp} is used for a register that contains a
7310 pointer to the current stack frame, and @code{$ps} is used for a
7311 register that contains the processor status. For example,
7312 you could print the program counter in hex with
7319 or print the instruction to be executed next with
7326 or add four to the stack pointer@footnote{This is a way of removing
7327 one word from the stack, on machines where stacks grow downward in
7328 memory (most machines, nowadays). This assumes that the innermost
7329 stack frame is selected; setting @code{$sp} is not allowed when other
7330 stack frames are selected. To pop entire frames off the stack,
7331 regardless of machine architecture, use @code{return};
7332 see @ref{Returning, ,Returning from a Function}.} with
7338 Whenever possible, these four standard register names are available on
7339 your machine even though the machine has different canonical mnemonics,
7340 so long as there is no conflict. The @code{info registers} command
7341 shows the canonical names. For example, on the SPARC, @code{info
7342 registers} displays the processor status register as @code{$psr} but you
7343 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
7344 is an alias for the @sc{eflags} register.
7346 @value{GDBN} always considers the contents of an ordinary register as an
7347 integer when the register is examined in this way. Some machines have
7348 special registers which can hold nothing but floating point; these
7349 registers are considered to have floating point values. There is no way
7350 to refer to the contents of an ordinary register as floating point value
7351 (although you can @emph{print} it as a floating point value with
7352 @samp{print/f $@var{regname}}).
7354 Some registers have distinct ``raw'' and ``virtual'' data formats. This
7355 means that the data format in which the register contents are saved by
7356 the operating system is not the same one that your program normally
7357 sees. For example, the registers of the 68881 floating point
7358 coprocessor are always saved in ``extended'' (raw) format, but all C
7359 programs expect to work with ``double'' (virtual) format. In such
7360 cases, @value{GDBN} normally works with the virtual format only (the format
7361 that makes sense for your program), but the @code{info registers} command
7362 prints the data in both formats.
7364 @cindex SSE registers (x86)
7365 @cindex MMX registers (x86)
7366 Some machines have special registers whose contents can be interpreted
7367 in several different ways. For example, modern x86-based machines
7368 have SSE and MMX registers that can hold several values packed
7369 together in several different formats. @value{GDBN} refers to such
7370 registers in @code{struct} notation:
7373 (@value{GDBP}) print $xmm1
7375 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
7376 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
7377 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
7378 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
7379 v4_int32 = @{0, 20657912, 11, 13@},
7380 v2_int64 = @{88725056443645952, 55834574859@},
7381 uint128 = 0x0000000d0000000b013b36f800000000
7386 To set values of such registers, you need to tell @value{GDBN} which
7387 view of the register you wish to change, as if you were assigning
7388 value to a @code{struct} member:
7391 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
7394 Normally, register values are relative to the selected stack frame
7395 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
7396 value that the register would contain if all stack frames farther in
7397 were exited and their saved registers restored. In order to see the
7398 true contents of hardware registers, you must select the innermost
7399 frame (with @samp{frame 0}).
7401 However, @value{GDBN} must deduce where registers are saved, from the machine
7402 code generated by your compiler. If some registers are not saved, or if
7403 @value{GDBN} is unable to locate the saved registers, the selected stack
7404 frame makes no difference.
7406 @node Floating Point Hardware
7407 @section Floating Point Hardware
7408 @cindex floating point
7410 Depending on the configuration, @value{GDBN} may be able to give
7411 you more information about the status of the floating point hardware.
7416 Display hardware-dependent information about the floating
7417 point unit. The exact contents and layout vary depending on the
7418 floating point chip. Currently, @samp{info float} is supported on
7419 the ARM and x86 machines.
7423 @section Vector Unit
7426 Depending on the configuration, @value{GDBN} may be able to give you
7427 more information about the status of the vector unit.
7432 Display information about the vector unit. The exact contents and
7433 layout vary depending on the hardware.
7436 @node OS Information
7437 @section Operating System Auxiliary Information
7438 @cindex OS information
7440 @value{GDBN} provides interfaces to useful OS facilities that can help
7441 you debug your program.
7443 @cindex @code{ptrace} system call
7444 @cindex @code{struct user} contents
7445 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
7446 machines), it interfaces with the inferior via the @code{ptrace}
7447 system call. The operating system creates a special sata structure,
7448 called @code{struct user}, for this interface. You can use the
7449 command @code{info udot} to display the contents of this data
7455 Display the contents of the @code{struct user} maintained by the OS
7456 kernel for the program being debugged. @value{GDBN} displays the
7457 contents of @code{struct user} as a list of hex numbers, similar to
7458 the @code{examine} command.
7461 @cindex auxiliary vector
7462 @cindex vector, auxiliary
7463 Some operating systems supply an @dfn{auxiliary vector} to programs at
7464 startup. This is akin to the arguments and environment that you
7465 specify for a program, but contains a system-dependent variety of
7466 binary values that tell system libraries important details about the
7467 hardware, operating system, and process. Each value's purpose is
7468 identified by an integer tag; the meanings are well-known but system-specific.
7469 Depending on the configuration and operating system facilities,
7470 @value{GDBN} may be able to show you this information. For remote
7471 targets, this functionality may further depend on the remote stub's
7472 support of the @samp{qXfer:auxv:read} packet, see
7473 @ref{qXfer auxiliary vector read}.
7478 Display the auxiliary vector of the inferior, which can be either a
7479 live process or a core dump file. @value{GDBN} prints each tag value
7480 numerically, and also shows names and text descriptions for recognized
7481 tags. Some values in the vector are numbers, some bit masks, and some
7482 pointers to strings or other data. @value{GDBN} displays each value in the
7483 most appropriate form for a recognized tag, and in hexadecimal for
7484 an unrecognized tag.
7488 @node Memory Region Attributes
7489 @section Memory Region Attributes
7490 @cindex memory region attributes
7492 @dfn{Memory region attributes} allow you to describe special handling
7493 required by regions of your target's memory. @value{GDBN} uses
7494 attributes to determine whether to allow certain types of memory
7495 accesses; whether to use specific width accesses; and whether to cache
7496 target memory. By default the description of memory regions is
7497 fetched from the target (if the current target supports this), but the
7498 user can override the fetched regions.
7500 Defined memory regions can be individually enabled and disabled. When a
7501 memory region is disabled, @value{GDBN} uses the default attributes when
7502 accessing memory in that region. Similarly, if no memory regions have
7503 been defined, @value{GDBN} uses the default attributes when accessing
7506 When a memory region is defined, it is given a number to identify it;
7507 to enable, disable, or remove a memory region, you specify that number.
7511 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
7512 Define a memory region bounded by @var{lower} and @var{upper} with
7513 attributes @var{attributes}@dots{}, and add it to the list of regions
7514 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
7515 case: it is treated as the target's maximum memory address.
7516 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
7519 Discard any user changes to the memory regions and use target-supplied
7520 regions, if available, or no regions if the target does not support.
7523 @item delete mem @var{nums}@dots{}
7524 Remove memory regions @var{nums}@dots{} from the list of regions
7525 monitored by @value{GDBN}.
7528 @item disable mem @var{nums}@dots{}
7529 Disable monitoring of memory regions @var{nums}@dots{}.
7530 A disabled memory region is not forgotten.
7531 It may be enabled again later.
7534 @item enable mem @var{nums}@dots{}
7535 Enable monitoring of memory regions @var{nums}@dots{}.
7539 Print a table of all defined memory regions, with the following columns
7543 @item Memory Region Number
7544 @item Enabled or Disabled.
7545 Enabled memory regions are marked with @samp{y}.
7546 Disabled memory regions are marked with @samp{n}.
7549 The address defining the inclusive lower bound of the memory region.
7552 The address defining the exclusive upper bound of the memory region.
7555 The list of attributes set for this memory region.
7560 @subsection Attributes
7562 @subsubsection Memory Access Mode
7563 The access mode attributes set whether @value{GDBN} may make read or
7564 write accesses to a memory region.
7566 While these attributes prevent @value{GDBN} from performing invalid
7567 memory accesses, they do nothing to prevent the target system, I/O DMA,
7568 etc.@: from accessing memory.
7572 Memory is read only.
7574 Memory is write only.
7576 Memory is read/write. This is the default.
7579 @subsubsection Memory Access Size
7580 The access size attribute tells @value{GDBN} to use specific sized
7581 accesses in the memory region. Often memory mapped device registers
7582 require specific sized accesses. If no access size attribute is
7583 specified, @value{GDBN} may use accesses of any size.
7587 Use 8 bit memory accesses.
7589 Use 16 bit memory accesses.
7591 Use 32 bit memory accesses.
7593 Use 64 bit memory accesses.
7596 @c @subsubsection Hardware/Software Breakpoints
7597 @c The hardware/software breakpoint attributes set whether @value{GDBN}
7598 @c will use hardware or software breakpoints for the internal breakpoints
7599 @c used by the step, next, finish, until, etc. commands.
7603 @c Always use hardware breakpoints
7604 @c @item swbreak (default)
7607 @subsubsection Data Cache
7608 The data cache attributes set whether @value{GDBN} will cache target
7609 memory. While this generally improves performance by reducing debug
7610 protocol overhead, it can lead to incorrect results because @value{GDBN}
7611 does not know about volatile variables or memory mapped device
7616 Enable @value{GDBN} to cache target memory.
7618 Disable @value{GDBN} from caching target memory. This is the default.
7621 @subsection Memory Access Checking
7622 @value{GDBN} can be instructed to refuse accesses to memory that is
7623 not explicitly described. This can be useful if accessing such
7624 regions has undesired effects for a specific target, or to provide
7625 better error checking. The following commands control this behaviour.
7628 @kindex set mem inaccessible-by-default
7629 @item set mem inaccessible-by-default [on|off]
7630 If @code{on} is specified, make @value{GDBN} treat memory not
7631 explicitly described by the memory ranges as non-existent and refuse accesses
7632 to such memory. The checks are only performed if there's at least one
7633 memory range defined. If @code{off} is specified, make @value{GDBN}
7634 treat the memory not explicitly described by the memory ranges as RAM.
7635 The default value is @code{on}.
7636 @kindex show mem inaccessible-by-default
7637 @item show mem inaccessible-by-default
7638 Show the current handling of accesses to unknown memory.
7642 @c @subsubsection Memory Write Verification
7643 @c The memory write verification attributes set whether @value{GDBN}
7644 @c will re-reads data after each write to verify the write was successful.
7648 @c @item noverify (default)
7651 @node Dump/Restore Files
7652 @section Copy Between Memory and a File
7653 @cindex dump/restore files
7654 @cindex append data to a file
7655 @cindex dump data to a file
7656 @cindex restore data from a file
7658 You can use the commands @code{dump}, @code{append}, and
7659 @code{restore} to copy data between target memory and a file. The
7660 @code{dump} and @code{append} commands write data to a file, and the
7661 @code{restore} command reads data from a file back into the inferior's
7662 memory. Files may be in binary, Motorola S-record, Intel hex, or
7663 Tektronix Hex format; however, @value{GDBN} can only append to binary
7669 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7670 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
7671 Dump the contents of memory from @var{start_addr} to @var{end_addr},
7672 or the value of @var{expr}, to @var{filename} in the given format.
7674 The @var{format} parameter may be any one of:
7681 Motorola S-record format.
7683 Tektronix Hex format.
7686 @value{GDBN} uses the same definitions of these formats as the
7687 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
7688 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
7692 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7693 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
7694 Append the contents of memory from @var{start_addr} to @var{end_addr},
7695 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
7696 (@value{GDBN} can only append data to files in raw binary form.)
7699 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
7700 Restore the contents of file @var{filename} into memory. The
7701 @code{restore} command can automatically recognize any known @sc{bfd}
7702 file format, except for raw binary. To restore a raw binary file you
7703 must specify the optional keyword @code{binary} after the filename.
7705 If @var{bias} is non-zero, its value will be added to the addresses
7706 contained in the file. Binary files always start at address zero, so
7707 they will be restored at address @var{bias}. Other bfd files have
7708 a built-in location; they will be restored at offset @var{bias}
7711 If @var{start} and/or @var{end} are non-zero, then only data between
7712 file offset @var{start} and file offset @var{end} will be restored.
7713 These offsets are relative to the addresses in the file, before
7714 the @var{bias} argument is applied.
7718 @node Core File Generation
7719 @section How to Produce a Core File from Your Program
7720 @cindex dump core from inferior
7722 A @dfn{core file} or @dfn{core dump} is a file that records the memory
7723 image of a running process and its process status (register values
7724 etc.). Its primary use is post-mortem debugging of a program that
7725 crashed while it ran outside a debugger. A program that crashes
7726 automatically produces a core file, unless this feature is disabled by
7727 the user. @xref{Files}, for information on invoking @value{GDBN} in
7728 the post-mortem debugging mode.
7730 Occasionally, you may wish to produce a core file of the program you
7731 are debugging in order to preserve a snapshot of its state.
7732 @value{GDBN} has a special command for that.
7736 @kindex generate-core-file
7737 @item generate-core-file [@var{file}]
7738 @itemx gcore [@var{file}]
7739 Produce a core dump of the inferior process. The optional argument
7740 @var{file} specifies the file name where to put the core dump. If not
7741 specified, the file name defaults to @file{core.@var{pid}}, where
7742 @var{pid} is the inferior process ID.
7744 Note that this command is implemented only for some systems (as of
7745 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
7748 @node Character Sets
7749 @section Character Sets
7750 @cindex character sets
7752 @cindex translating between character sets
7753 @cindex host character set
7754 @cindex target character set
7756 If the program you are debugging uses a different character set to
7757 represent characters and strings than the one @value{GDBN} uses itself,
7758 @value{GDBN} can automatically translate between the character sets for
7759 you. The character set @value{GDBN} uses we call the @dfn{host
7760 character set}; the one the inferior program uses we call the
7761 @dfn{target character set}.
7763 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
7764 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
7765 remote protocol (@pxref{Remote Debugging}) to debug a program
7766 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
7767 then the host character set is Latin-1, and the target character set is
7768 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
7769 target-charset EBCDIC-US}, then @value{GDBN} translates between
7770 @sc{ebcdic} and Latin 1 as you print character or string values, or use
7771 character and string literals in expressions.
7773 @value{GDBN} has no way to automatically recognize which character set
7774 the inferior program uses; you must tell it, using the @code{set
7775 target-charset} command, described below.
7777 Here are the commands for controlling @value{GDBN}'s character set
7781 @item set target-charset @var{charset}
7782 @kindex set target-charset
7783 Set the current target character set to @var{charset}. We list the
7784 character set names @value{GDBN} recognizes below, but if you type
7785 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7786 list the target character sets it supports.
7790 @item set host-charset @var{charset}
7791 @kindex set host-charset
7792 Set the current host character set to @var{charset}.
7794 By default, @value{GDBN} uses a host character set appropriate to the
7795 system it is running on; you can override that default using the
7796 @code{set host-charset} command.
7798 @value{GDBN} can only use certain character sets as its host character
7799 set. We list the character set names @value{GDBN} recognizes below, and
7800 indicate which can be host character sets, but if you type
7801 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7802 list the host character sets it supports.
7804 @item set charset @var{charset}
7806 Set the current host and target character sets to @var{charset}. As
7807 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
7808 @value{GDBN} will list the name of the character sets that can be used
7809 for both host and target.
7813 @kindex show charset
7814 Show the names of the current host and target charsets.
7816 @itemx show host-charset
7817 @kindex show host-charset
7818 Show the name of the current host charset.
7820 @itemx show target-charset
7821 @kindex show target-charset
7822 Show the name of the current target charset.
7826 @value{GDBN} currently includes support for the following character
7832 @cindex ASCII character set
7833 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
7837 @cindex ISO 8859-1 character set
7838 @cindex ISO Latin 1 character set
7839 The ISO Latin 1 character set. This extends @sc{ascii} with accented
7840 characters needed for French, German, and Spanish. @value{GDBN} can use
7841 this as its host character set.
7845 @cindex EBCDIC character set
7846 @cindex IBM1047 character set
7847 Variants of the @sc{ebcdic} character set, used on some of IBM's
7848 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
7849 @value{GDBN} cannot use these as its host character set.
7853 Note that these are all single-byte character sets. More work inside
7854 @value{GDBN} is needed to support multi-byte or variable-width character
7855 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
7857 Here is an example of @value{GDBN}'s character set support in action.
7858 Assume that the following source code has been placed in the file
7859 @file{charset-test.c}:
7865 = @{72, 101, 108, 108, 111, 44, 32, 119,
7866 111, 114, 108, 100, 33, 10, 0@};
7867 char ibm1047_hello[]
7868 = @{200, 133, 147, 147, 150, 107, 64, 166,
7869 150, 153, 147, 132, 90, 37, 0@};
7873 printf ("Hello, world!\n");
7877 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
7878 containing the string @samp{Hello, world!} followed by a newline,
7879 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
7881 We compile the program, and invoke the debugger on it:
7884 $ gcc -g charset-test.c -o charset-test
7885 $ gdb -nw charset-test
7886 GNU gdb 2001-12-19-cvs
7887 Copyright 2001 Free Software Foundation, Inc.
7892 We can use the @code{show charset} command to see what character sets
7893 @value{GDBN} is currently using to interpret and display characters and
7897 (@value{GDBP}) show charset
7898 The current host and target character set is `ISO-8859-1'.
7902 For the sake of printing this manual, let's use @sc{ascii} as our
7903 initial character set:
7905 (@value{GDBP}) set charset ASCII
7906 (@value{GDBP}) show charset
7907 The current host and target character set is `ASCII'.
7911 Let's assume that @sc{ascii} is indeed the correct character set for our
7912 host system --- in other words, let's assume that if @value{GDBN} prints
7913 characters using the @sc{ascii} character set, our terminal will display
7914 them properly. Since our current target character set is also
7915 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
7918 (@value{GDBP}) print ascii_hello
7919 $1 = 0x401698 "Hello, world!\n"
7920 (@value{GDBP}) print ascii_hello[0]
7925 @value{GDBN} uses the target character set for character and string
7926 literals you use in expressions:
7929 (@value{GDBP}) print '+'
7934 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
7937 @value{GDBN} relies on the user to tell it which character set the
7938 target program uses. If we print @code{ibm1047_hello} while our target
7939 character set is still @sc{ascii}, we get jibberish:
7942 (@value{GDBP}) print ibm1047_hello
7943 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
7944 (@value{GDBP}) print ibm1047_hello[0]
7949 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
7950 @value{GDBN} tells us the character sets it supports:
7953 (@value{GDBP}) set target-charset
7954 ASCII EBCDIC-US IBM1047 ISO-8859-1
7955 (@value{GDBP}) set target-charset
7958 We can select @sc{ibm1047} as our target character set, and examine the
7959 program's strings again. Now the @sc{ascii} string is wrong, but
7960 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
7961 target character set, @sc{ibm1047}, to the host character set,
7962 @sc{ascii}, and they display correctly:
7965 (@value{GDBP}) set target-charset IBM1047
7966 (@value{GDBP}) show charset
7967 The current host character set is `ASCII'.
7968 The current target character set is `IBM1047'.
7969 (@value{GDBP}) print ascii_hello
7970 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
7971 (@value{GDBP}) print ascii_hello[0]
7973 (@value{GDBP}) print ibm1047_hello
7974 $8 = 0x4016a8 "Hello, world!\n"
7975 (@value{GDBP}) print ibm1047_hello[0]
7980 As above, @value{GDBN} uses the target character set for character and
7981 string literals you use in expressions:
7984 (@value{GDBP}) print '+'
7989 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
7992 @node Caching Remote Data
7993 @section Caching Data of Remote Targets
7994 @cindex caching data of remote targets
7996 @value{GDBN} can cache data exchanged between the debugger and a
7997 remote target (@pxref{Remote Debugging}). Such caching generally improves
7998 performance, because it reduces the overhead of the remote protocol by
7999 bundling memory reads and writes into large chunks. Unfortunately,
8000 @value{GDBN} does not currently know anything about volatile
8001 registers, and thus data caching will produce incorrect results when
8002 volatile registers are in use.
8005 @kindex set remotecache
8006 @item set remotecache on
8007 @itemx set remotecache off
8008 Set caching state for remote targets. When @code{ON}, use data
8009 caching. By default, this option is @code{OFF}.
8011 @kindex show remotecache
8012 @item show remotecache
8013 Show the current state of data caching for remote targets.
8017 Print the information about the data cache performance. The
8018 information displayed includes: the dcache width and depth; and for
8019 each cache line, how many times it was referenced, and its data and
8020 state (invalid, dirty, valid). This command is useful for debugging
8021 the data cache operation.
8024 @node Searching Memory
8025 @section Search Memory
8026 @cindex searching memory
8028 Memory can be searched for a particular sequence of bytes with the
8029 @code{find} command.
8033 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8034 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8035 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
8036 etc. The search begins at address @var{start_addr} and continues for either
8037 @var{len} bytes or through to @var{end_addr} inclusive.
8040 @var{s} and @var{n} are optional parameters.
8041 They may be specified in either order, apart or together.
8044 @item @var{s}, search query size
8045 The size of each search query value.
8051 halfwords (two bytes)
8055 giant words (eight bytes)
8058 All values are interpreted in the current language.
8059 This means, for example, that if the current source language is C/C@t{++}
8060 then searching for the string ``hello'' includes the trailing '\0'.
8062 If the value size is not specified, it is taken from the
8063 value's type in the current language.
8064 This is useful when one wants to specify the search
8065 pattern as a mixture of types.
8066 Note that this means, for example, that in the case of C-like languages
8067 a search for an untyped 0x42 will search for @samp{(int) 0x42}
8068 which is typically four bytes.
8070 @item @var{n}, maximum number of finds
8071 The maximum number of matches to print. The default is to print all finds.
8074 You can use strings as search values. Quote them with double-quotes
8076 The string value is copied into the search pattern byte by byte,
8077 regardless of the endianness of the target and the size specification.
8079 The address of each match found is printed as well as a count of the
8080 number of matches found.
8082 The address of the last value found is stored in convenience variable
8084 A count of the number of matches is stored in @samp{$numfound}.
8086 For example, if stopped at the @code{printf} in this function:
8092 static char hello[] = "hello-hello";
8093 static struct @{ char c; short s; int i; @}
8094 __attribute__ ((packed)) mixed
8095 = @{ 'c', 0x1234, 0x87654321 @};
8096 printf ("%s\n", hello);
8101 you get during debugging:
8104 (gdb) find &hello[0], +sizeof(hello), "hello"
8105 0x804956d <hello.1620+6>
8107 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
8108 0x8049567 <hello.1620>
8109 0x804956d <hello.1620+6>
8111 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
8112 0x8049567 <hello.1620>
8114 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
8115 0x8049560 <mixed.1625>
8117 (gdb) print $numfound
8120 $2 = (void *) 0x8049560
8124 @chapter C Preprocessor Macros
8126 Some languages, such as C and C@t{++}, provide a way to define and invoke
8127 ``preprocessor macros'' which expand into strings of tokens.
8128 @value{GDBN} can evaluate expressions containing macro invocations, show
8129 the result of macro expansion, and show a macro's definition, including
8130 where it was defined.
8132 You may need to compile your program specially to provide @value{GDBN}
8133 with information about preprocessor macros. Most compilers do not
8134 include macros in their debugging information, even when you compile
8135 with the @option{-g} flag. @xref{Compilation}.
8137 A program may define a macro at one point, remove that definition later,
8138 and then provide a different definition after that. Thus, at different
8139 points in the program, a macro may have different definitions, or have
8140 no definition at all. If there is a current stack frame, @value{GDBN}
8141 uses the macros in scope at that frame's source code line. Otherwise,
8142 @value{GDBN} uses the macros in scope at the current listing location;
8145 Whenever @value{GDBN} evaluates an expression, it always expands any
8146 macro invocations present in the expression. @value{GDBN} also provides
8147 the following commands for working with macros explicitly.
8151 @kindex macro expand
8152 @cindex macro expansion, showing the results of preprocessor
8153 @cindex preprocessor macro expansion, showing the results of
8154 @cindex expanding preprocessor macros
8155 @item macro expand @var{expression}
8156 @itemx macro exp @var{expression}
8157 Show the results of expanding all preprocessor macro invocations in
8158 @var{expression}. Since @value{GDBN} simply expands macros, but does
8159 not parse the result, @var{expression} need not be a valid expression;
8160 it can be any string of tokens.
8163 @item macro expand-once @var{expression}
8164 @itemx macro exp1 @var{expression}
8165 @cindex expand macro once
8166 @i{(This command is not yet implemented.)} Show the results of
8167 expanding those preprocessor macro invocations that appear explicitly in
8168 @var{expression}. Macro invocations appearing in that expansion are
8169 left unchanged. This command allows you to see the effect of a
8170 particular macro more clearly, without being confused by further
8171 expansions. Since @value{GDBN} simply expands macros, but does not
8172 parse the result, @var{expression} need not be a valid expression; it
8173 can be any string of tokens.
8176 @cindex macro definition, showing
8177 @cindex definition, showing a macro's
8178 @item info macro @var{macro}
8179 Show the definition of the macro named @var{macro}, and describe the
8180 source location where that definition was established.
8182 @kindex macro define
8183 @cindex user-defined macros
8184 @cindex defining macros interactively
8185 @cindex macros, user-defined
8186 @item macro define @var{macro} @var{replacement-list}
8187 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
8188 Introduce a definition for a preprocessor macro named @var{macro},
8189 invocations of which are replaced by the tokens given in
8190 @var{replacement-list}. The first form of this command defines an
8191 ``object-like'' macro, which takes no arguments; the second form
8192 defines a ``function-like'' macro, which takes the arguments given in
8195 A definition introduced by this command is in scope in every
8196 expression evaluated in @value{GDBN}, until it is removed with the
8197 @code{macro undef} command, described below. The definition overrides
8198 all definitions for @var{macro} present in the program being debugged,
8199 as well as any previous user-supplied definition.
8202 @item macro undef @var{macro}
8203 Remove any user-supplied definition for the macro named @var{macro}.
8204 This command only affects definitions provided with the @code{macro
8205 define} command, described above; it cannot remove definitions present
8206 in the program being debugged.
8210 List all the macros defined using the @code{macro define} command.
8213 @cindex macros, example of debugging with
8214 Here is a transcript showing the above commands in action. First, we
8215 show our source files:
8223 #define ADD(x) (M + x)
8228 printf ("Hello, world!\n");
8230 printf ("We're so creative.\n");
8232 printf ("Goodbye, world!\n");
8239 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
8240 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
8241 compiler includes information about preprocessor macros in the debugging
8245 $ gcc -gdwarf-2 -g3 sample.c -o sample
8249 Now, we start @value{GDBN} on our sample program:
8253 GNU gdb 2002-05-06-cvs
8254 Copyright 2002 Free Software Foundation, Inc.
8255 GDB is free software, @dots{}
8259 We can expand macros and examine their definitions, even when the
8260 program is not running. @value{GDBN} uses the current listing position
8261 to decide which macro definitions are in scope:
8264 (@value{GDBP}) list main
8267 5 #define ADD(x) (M + x)
8272 10 printf ("Hello, world!\n");
8274 12 printf ("We're so creative.\n");
8275 (@value{GDBP}) info macro ADD
8276 Defined at /home/jimb/gdb/macros/play/sample.c:5
8277 #define ADD(x) (M + x)
8278 (@value{GDBP}) info macro Q
8279 Defined at /home/jimb/gdb/macros/play/sample.h:1
8280 included at /home/jimb/gdb/macros/play/sample.c:2
8282 (@value{GDBP}) macro expand ADD(1)
8283 expands to: (42 + 1)
8284 (@value{GDBP}) macro expand-once ADD(1)
8285 expands to: once (M + 1)
8289 In the example above, note that @code{macro expand-once} expands only
8290 the macro invocation explicit in the original text --- the invocation of
8291 @code{ADD} --- but does not expand the invocation of the macro @code{M},
8292 which was introduced by @code{ADD}.
8294 Once the program is running, @value{GDBN} uses the macro definitions in
8295 force at the source line of the current stack frame:
8298 (@value{GDBP}) break main
8299 Breakpoint 1 at 0x8048370: file sample.c, line 10.
8301 Starting program: /home/jimb/gdb/macros/play/sample
8303 Breakpoint 1, main () at sample.c:10
8304 10 printf ("Hello, world!\n");
8308 At line 10, the definition of the macro @code{N} at line 9 is in force:
8311 (@value{GDBP}) info macro N
8312 Defined at /home/jimb/gdb/macros/play/sample.c:9
8314 (@value{GDBP}) macro expand N Q M
8316 (@value{GDBP}) print N Q M
8321 As we step over directives that remove @code{N}'s definition, and then
8322 give it a new definition, @value{GDBN} finds the definition (or lack
8323 thereof) in force at each point:
8328 12 printf ("We're so creative.\n");
8329 (@value{GDBP}) info macro N
8330 The symbol `N' has no definition as a C/C++ preprocessor macro
8331 at /home/jimb/gdb/macros/play/sample.c:12
8334 14 printf ("Goodbye, world!\n");
8335 (@value{GDBP}) info macro N
8336 Defined at /home/jimb/gdb/macros/play/sample.c:13
8338 (@value{GDBP}) macro expand N Q M
8339 expands to: 1729 < 42
8340 (@value{GDBP}) print N Q M
8347 @chapter Tracepoints
8348 @c This chapter is based on the documentation written by Michael
8349 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
8352 In some applications, it is not feasible for the debugger to interrupt
8353 the program's execution long enough for the developer to learn
8354 anything helpful about its behavior. If the program's correctness
8355 depends on its real-time behavior, delays introduced by a debugger
8356 might cause the program to change its behavior drastically, or perhaps
8357 fail, even when the code itself is correct. It is useful to be able
8358 to observe the program's behavior without interrupting it.
8360 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
8361 specify locations in the program, called @dfn{tracepoints}, and
8362 arbitrary expressions to evaluate when those tracepoints are reached.
8363 Later, using the @code{tfind} command, you can examine the values
8364 those expressions had when the program hit the tracepoints. The
8365 expressions may also denote objects in memory---structures or arrays,
8366 for example---whose values @value{GDBN} should record; while visiting
8367 a particular tracepoint, you may inspect those objects as if they were
8368 in memory at that moment. However, because @value{GDBN} records these
8369 values without interacting with you, it can do so quickly and
8370 unobtrusively, hopefully not disturbing the program's behavior.
8372 The tracepoint facility is currently available only for remote
8373 targets. @xref{Targets}. In addition, your remote target must know
8374 how to collect trace data. This functionality is implemented in the
8375 remote stub; however, none of the stubs distributed with @value{GDBN}
8376 support tracepoints as of this writing. The format of the remote
8377 packets used to implement tracepoints are described in @ref{Tracepoint
8380 This chapter describes the tracepoint commands and features.
8384 * Analyze Collected Data::
8385 * Tracepoint Variables::
8388 @node Set Tracepoints
8389 @section Commands to Set Tracepoints
8391 Before running such a @dfn{trace experiment}, an arbitrary number of
8392 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
8393 tracepoint has a number assigned to it by @value{GDBN}. Like with
8394 breakpoints, tracepoint numbers are successive integers starting from
8395 one. Many of the commands associated with tracepoints take the
8396 tracepoint number as their argument, to identify which tracepoint to
8399 For each tracepoint, you can specify, in advance, some arbitrary set
8400 of data that you want the target to collect in the trace buffer when
8401 it hits that tracepoint. The collected data can include registers,
8402 local variables, or global data. Later, you can use @value{GDBN}
8403 commands to examine the values these data had at the time the
8406 This section describes commands to set tracepoints and associated
8407 conditions and actions.
8410 * Create and Delete Tracepoints::
8411 * Enable and Disable Tracepoints::
8412 * Tracepoint Passcounts::
8413 * Tracepoint Actions::
8414 * Listing Tracepoints::
8415 * Starting and Stopping Trace Experiments::
8418 @node Create and Delete Tracepoints
8419 @subsection Create and Delete Tracepoints
8422 @cindex set tracepoint
8425 The @code{trace} command is very similar to the @code{break} command.
8426 Its argument can be a source line, a function name, or an address in
8427 the target program. @xref{Set Breaks}. The @code{trace} command
8428 defines a tracepoint, which is a point in the target program where the
8429 debugger will briefly stop, collect some data, and then allow the
8430 program to continue. Setting a tracepoint or changing its commands
8431 doesn't take effect until the next @code{tstart} command; thus, you
8432 cannot change the tracepoint attributes once a trace experiment is
8435 Here are some examples of using the @code{trace} command:
8438 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
8440 (@value{GDBP}) @b{trace +2} // 2 lines forward
8442 (@value{GDBP}) @b{trace my_function} // first source line of function
8444 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
8446 (@value{GDBP}) @b{trace *0x2117c4} // an address
8450 You can abbreviate @code{trace} as @code{tr}.
8453 @cindex last tracepoint number
8454 @cindex recent tracepoint number
8455 @cindex tracepoint number
8456 The convenience variable @code{$tpnum} records the tracepoint number
8457 of the most recently set tracepoint.
8459 @kindex delete tracepoint
8460 @cindex tracepoint deletion
8461 @item delete tracepoint @r{[}@var{num}@r{]}
8462 Permanently delete one or more tracepoints. With no argument, the
8463 default is to delete all tracepoints.
8468 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
8470 (@value{GDBP}) @b{delete trace} // remove all tracepoints
8474 You can abbreviate this command as @code{del tr}.
8477 @node Enable and Disable Tracepoints
8478 @subsection Enable and Disable Tracepoints
8481 @kindex disable tracepoint
8482 @item disable tracepoint @r{[}@var{num}@r{]}
8483 Disable tracepoint @var{num}, or all tracepoints if no argument
8484 @var{num} is given. A disabled tracepoint will have no effect during
8485 the next trace experiment, but it is not forgotten. You can re-enable
8486 a disabled tracepoint using the @code{enable tracepoint} command.
8488 @kindex enable tracepoint
8489 @item enable tracepoint @r{[}@var{num}@r{]}
8490 Enable tracepoint @var{num}, or all tracepoints. The enabled
8491 tracepoints will become effective the next time a trace experiment is
8495 @node Tracepoint Passcounts
8496 @subsection Tracepoint Passcounts
8500 @cindex tracepoint pass count
8501 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
8502 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
8503 automatically stop a trace experiment. If a tracepoint's passcount is
8504 @var{n}, then the trace experiment will be automatically stopped on
8505 the @var{n}'th time that tracepoint is hit. If the tracepoint number
8506 @var{num} is not specified, the @code{passcount} command sets the
8507 passcount of the most recently defined tracepoint. If no passcount is
8508 given, the trace experiment will run until stopped explicitly by the
8514 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
8515 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
8517 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
8518 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
8519 (@value{GDBP}) @b{trace foo}
8520 (@value{GDBP}) @b{pass 3}
8521 (@value{GDBP}) @b{trace bar}
8522 (@value{GDBP}) @b{pass 2}
8523 (@value{GDBP}) @b{trace baz}
8524 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
8525 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
8526 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
8527 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
8531 @node Tracepoint Actions
8532 @subsection Tracepoint Action Lists
8536 @cindex tracepoint actions
8537 @item actions @r{[}@var{num}@r{]}
8538 This command will prompt for a list of actions to be taken when the
8539 tracepoint is hit. If the tracepoint number @var{num} is not
8540 specified, this command sets the actions for the one that was most
8541 recently defined (so that you can define a tracepoint and then say
8542 @code{actions} without bothering about its number). You specify the
8543 actions themselves on the following lines, one action at a time, and
8544 terminate the actions list with a line containing just @code{end}. So
8545 far, the only defined actions are @code{collect} and
8546 @code{while-stepping}.
8548 @cindex remove actions from a tracepoint
8549 To remove all actions from a tracepoint, type @samp{actions @var{num}}
8550 and follow it immediately with @samp{end}.
8553 (@value{GDBP}) @b{collect @var{data}} // collect some data
8555 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
8557 (@value{GDBP}) @b{end} // signals the end of actions.
8560 In the following example, the action list begins with @code{collect}
8561 commands indicating the things to be collected when the tracepoint is
8562 hit. Then, in order to single-step and collect additional data
8563 following the tracepoint, a @code{while-stepping} command is used,
8564 followed by the list of things to be collected while stepping. The
8565 @code{while-stepping} command is terminated by its own separate
8566 @code{end} command. Lastly, the action list is terminated by an
8570 (@value{GDBP}) @b{trace foo}
8571 (@value{GDBP}) @b{actions}
8572 Enter actions for tracepoint 1, one per line:
8581 @kindex collect @r{(tracepoints)}
8582 @item collect @var{expr1}, @var{expr2}, @dots{}
8583 Collect values of the given expressions when the tracepoint is hit.
8584 This command accepts a comma-separated list of any valid expressions.
8585 In addition to global, static, or local variables, the following
8586 special arguments are supported:
8590 collect all registers
8593 collect all function arguments
8596 collect all local variables.
8599 You can give several consecutive @code{collect} commands, each one
8600 with a single argument, or one @code{collect} command with several
8601 arguments separated by commas: the effect is the same.
8603 The command @code{info scope} (@pxref{Symbols, info scope}) is
8604 particularly useful for figuring out what data to collect.
8606 @kindex while-stepping @r{(tracepoints)}
8607 @item while-stepping @var{n}
8608 Perform @var{n} single-step traces after the tracepoint, collecting
8609 new data at each step. The @code{while-stepping} command is
8610 followed by the list of what to collect while stepping (followed by
8611 its own @code{end} command):
8615 > collect $regs, myglobal
8621 You may abbreviate @code{while-stepping} as @code{ws} or
8625 @node Listing Tracepoints
8626 @subsection Listing Tracepoints
8629 @kindex info tracepoints
8631 @cindex information about tracepoints
8632 @item info tracepoints @r{[}@var{num}@r{]}
8633 Display information about the tracepoint @var{num}. If you don't specify
8634 a tracepoint number, displays information about all the tracepoints
8635 defined so far. For each tracepoint, the following information is
8642 whether it is enabled or disabled
8646 its passcount as given by the @code{passcount @var{n}} command
8648 its step count as given by the @code{while-stepping @var{n}} command
8650 where in the source files is the tracepoint set
8652 its action list as given by the @code{actions} command
8656 (@value{GDBP}) @b{info trace}
8657 Num Enb Address PassC StepC What
8658 1 y 0x002117c4 0 0 <gdb_asm>
8659 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
8660 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
8665 This command can be abbreviated @code{info tp}.
8668 @node Starting and Stopping Trace Experiments
8669 @subsection Starting and Stopping Trace Experiments
8673 @cindex start a new trace experiment
8674 @cindex collected data discarded
8676 This command takes no arguments. It starts the trace experiment, and
8677 begins collecting data. This has the side effect of discarding all
8678 the data collected in the trace buffer during the previous trace
8682 @cindex stop a running trace experiment
8684 This command takes no arguments. It ends the trace experiment, and
8685 stops collecting data.
8687 @strong{Note}: a trace experiment and data collection may stop
8688 automatically if any tracepoint's passcount is reached
8689 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
8692 @cindex status of trace data collection
8693 @cindex trace experiment, status of
8695 This command displays the status of the current trace data
8699 Here is an example of the commands we described so far:
8702 (@value{GDBP}) @b{trace gdb_c_test}
8703 (@value{GDBP}) @b{actions}
8704 Enter actions for tracepoint #1, one per line.
8705 > collect $regs,$locals,$args
8710 (@value{GDBP}) @b{tstart}
8711 [time passes @dots{}]
8712 (@value{GDBP}) @b{tstop}
8716 @node Analyze Collected Data
8717 @section Using the Collected Data
8719 After the tracepoint experiment ends, you use @value{GDBN} commands
8720 for examining the trace data. The basic idea is that each tracepoint
8721 collects a trace @dfn{snapshot} every time it is hit and another
8722 snapshot every time it single-steps. All these snapshots are
8723 consecutively numbered from zero and go into a buffer, and you can
8724 examine them later. The way you examine them is to @dfn{focus} on a
8725 specific trace snapshot. When the remote stub is focused on a trace
8726 snapshot, it will respond to all @value{GDBN} requests for memory and
8727 registers by reading from the buffer which belongs to that snapshot,
8728 rather than from @emph{real} memory or registers of the program being
8729 debugged. This means that @strong{all} @value{GDBN} commands
8730 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
8731 behave as if we were currently debugging the program state as it was
8732 when the tracepoint occurred. Any requests for data that are not in
8733 the buffer will fail.
8736 * tfind:: How to select a trace snapshot
8737 * tdump:: How to display all data for a snapshot
8738 * save-tracepoints:: How to save tracepoints for a future run
8742 @subsection @code{tfind @var{n}}
8745 @cindex select trace snapshot
8746 @cindex find trace snapshot
8747 The basic command for selecting a trace snapshot from the buffer is
8748 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
8749 counting from zero. If no argument @var{n} is given, the next
8750 snapshot is selected.
8752 Here are the various forms of using the @code{tfind} command.
8756 Find the first snapshot in the buffer. This is a synonym for
8757 @code{tfind 0} (since 0 is the number of the first snapshot).
8760 Stop debugging trace snapshots, resume @emph{live} debugging.
8763 Same as @samp{tfind none}.
8766 No argument means find the next trace snapshot.
8769 Find the previous trace snapshot before the current one. This permits
8770 retracing earlier steps.
8772 @item tfind tracepoint @var{num}
8773 Find the next snapshot associated with tracepoint @var{num}. Search
8774 proceeds forward from the last examined trace snapshot. If no
8775 argument @var{num} is given, it means find the next snapshot collected
8776 for the same tracepoint as the current snapshot.
8778 @item tfind pc @var{addr}
8779 Find the next snapshot associated with the value @var{addr} of the
8780 program counter. Search proceeds forward from the last examined trace
8781 snapshot. If no argument @var{addr} is given, it means find the next
8782 snapshot with the same value of PC as the current snapshot.
8784 @item tfind outside @var{addr1}, @var{addr2}
8785 Find the next snapshot whose PC is outside the given range of
8788 @item tfind range @var{addr1}, @var{addr2}
8789 Find the next snapshot whose PC is between @var{addr1} and
8790 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
8792 @item tfind line @r{[}@var{file}:@r{]}@var{n}
8793 Find the next snapshot associated with the source line @var{n}. If
8794 the optional argument @var{file} is given, refer to line @var{n} in
8795 that source file. Search proceeds forward from the last examined
8796 trace snapshot. If no argument @var{n} is given, it means find the
8797 next line other than the one currently being examined; thus saying
8798 @code{tfind line} repeatedly can appear to have the same effect as
8799 stepping from line to line in a @emph{live} debugging session.
8802 The default arguments for the @code{tfind} commands are specifically
8803 designed to make it easy to scan through the trace buffer. For
8804 instance, @code{tfind} with no argument selects the next trace
8805 snapshot, and @code{tfind -} with no argument selects the previous
8806 trace snapshot. So, by giving one @code{tfind} command, and then
8807 simply hitting @key{RET} repeatedly you can examine all the trace
8808 snapshots in order. Or, by saying @code{tfind -} and then hitting
8809 @key{RET} repeatedly you can examine the snapshots in reverse order.
8810 The @code{tfind line} command with no argument selects the snapshot
8811 for the next source line executed. The @code{tfind pc} command with
8812 no argument selects the next snapshot with the same program counter
8813 (PC) as the current frame. The @code{tfind tracepoint} command with
8814 no argument selects the next trace snapshot collected by the same
8815 tracepoint as the current one.
8817 In addition to letting you scan through the trace buffer manually,
8818 these commands make it easy to construct @value{GDBN} scripts that
8819 scan through the trace buffer and print out whatever collected data
8820 you are interested in. Thus, if we want to examine the PC, FP, and SP
8821 registers from each trace frame in the buffer, we can say this:
8824 (@value{GDBP}) @b{tfind start}
8825 (@value{GDBP}) @b{while ($trace_frame != -1)}
8826 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
8827 $trace_frame, $pc, $sp, $fp
8831 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
8832 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
8833 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
8834 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
8835 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
8836 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
8837 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
8838 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
8839 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
8840 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
8841 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
8844 Or, if we want to examine the variable @code{X} at each source line in
8848 (@value{GDBP}) @b{tfind start}
8849 (@value{GDBP}) @b{while ($trace_frame != -1)}
8850 > printf "Frame %d, X == %d\n", $trace_frame, X
8860 @subsection @code{tdump}
8862 @cindex dump all data collected at tracepoint
8863 @cindex tracepoint data, display
8865 This command takes no arguments. It prints all the data collected at
8866 the current trace snapshot.
8869 (@value{GDBP}) @b{trace 444}
8870 (@value{GDBP}) @b{actions}
8871 Enter actions for tracepoint #2, one per line:
8872 > collect $regs, $locals, $args, gdb_long_test
8875 (@value{GDBP}) @b{tstart}
8877 (@value{GDBP}) @b{tfind line 444}
8878 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
8880 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
8882 (@value{GDBP}) @b{tdump}
8883 Data collected at tracepoint 2, trace frame 1:
8884 d0 0xc4aa0085 -995491707
8888 d4 0x71aea3d 119204413
8893 a1 0x3000668 50333288
8896 a4 0x3000698 50333336
8898 fp 0x30bf3c 0x30bf3c
8899 sp 0x30bf34 0x30bf34
8901 pc 0x20b2c8 0x20b2c8
8905 p = 0x20e5b4 "gdb-test"
8912 gdb_long_test = 17 '\021'
8917 @node save-tracepoints
8918 @subsection @code{save-tracepoints @var{filename}}
8919 @kindex save-tracepoints
8920 @cindex save tracepoints for future sessions
8922 This command saves all current tracepoint definitions together with
8923 their actions and passcounts, into a file @file{@var{filename}}
8924 suitable for use in a later debugging session. To read the saved
8925 tracepoint definitions, use the @code{source} command (@pxref{Command
8928 @node Tracepoint Variables
8929 @section Convenience Variables for Tracepoints
8930 @cindex tracepoint variables
8931 @cindex convenience variables for tracepoints
8934 @vindex $trace_frame
8935 @item (int) $trace_frame
8936 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
8937 snapshot is selected.
8940 @item (int) $tracepoint
8941 The tracepoint for the current trace snapshot.
8944 @item (int) $trace_line
8945 The line number for the current trace snapshot.
8948 @item (char []) $trace_file
8949 The source file for the current trace snapshot.
8952 @item (char []) $trace_func
8953 The name of the function containing @code{$tracepoint}.
8956 Note: @code{$trace_file} is not suitable for use in @code{printf},
8957 use @code{output} instead.
8959 Here's a simple example of using these convenience variables for
8960 stepping through all the trace snapshots and printing some of their
8964 (@value{GDBP}) @b{tfind start}
8966 (@value{GDBP}) @b{while $trace_frame != -1}
8967 > output $trace_file
8968 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
8974 @chapter Debugging Programs That Use Overlays
8977 If your program is too large to fit completely in your target system's
8978 memory, you can sometimes use @dfn{overlays} to work around this
8979 problem. @value{GDBN} provides some support for debugging programs that
8983 * How Overlays Work:: A general explanation of overlays.
8984 * Overlay Commands:: Managing overlays in @value{GDBN}.
8985 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
8986 mapped by asking the inferior.
8987 * Overlay Sample Program:: A sample program using overlays.
8990 @node How Overlays Work
8991 @section How Overlays Work
8992 @cindex mapped overlays
8993 @cindex unmapped overlays
8994 @cindex load address, overlay's
8995 @cindex mapped address
8996 @cindex overlay area
8998 Suppose you have a computer whose instruction address space is only 64
8999 kilobytes long, but which has much more memory which can be accessed by
9000 other means: special instructions, segment registers, or memory
9001 management hardware, for example. Suppose further that you want to
9002 adapt a program which is larger than 64 kilobytes to run on this system.
9004 One solution is to identify modules of your program which are relatively
9005 independent, and need not call each other directly; call these modules
9006 @dfn{overlays}. Separate the overlays from the main program, and place
9007 their machine code in the larger memory. Place your main program in
9008 instruction memory, but leave at least enough space there to hold the
9009 largest overlay as well.
9011 Now, to call a function located in an overlay, you must first copy that
9012 overlay's machine code from the large memory into the space set aside
9013 for it in the instruction memory, and then jump to its entry point
9016 @c NB: In the below the mapped area's size is greater or equal to the
9017 @c size of all overlays. This is intentional to remind the developer
9018 @c that overlays don't necessarily need to be the same size.
9022 Data Instruction Larger
9023 Address Space Address Space Address Space
9024 +-----------+ +-----------+ +-----------+
9026 +-----------+ +-----------+ +-----------+<-- overlay 1
9027 | program | | main | .----| overlay 1 | load address
9028 | variables | | program | | +-----------+
9029 | and heap | | | | | |
9030 +-----------+ | | | +-----------+<-- overlay 2
9031 | | +-----------+ | | | load address
9032 +-----------+ | | | .-| overlay 2 |
9034 mapped --->+-----------+ | | +-----------+
9036 | overlay | <-' | | |
9037 | area | <---' +-----------+<-- overlay 3
9038 | | <---. | | load address
9039 +-----------+ `--| overlay 3 |
9046 @anchor{A code overlay}A code overlay
9050 The diagram (@pxref{A code overlay}) shows a system with separate data
9051 and instruction address spaces. To map an overlay, the program copies
9052 its code from the larger address space to the instruction address space.
9053 Since the overlays shown here all use the same mapped address, only one
9054 may be mapped at a time. For a system with a single address space for
9055 data and instructions, the diagram would be similar, except that the
9056 program variables and heap would share an address space with the main
9057 program and the overlay area.
9059 An overlay loaded into instruction memory and ready for use is called a
9060 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
9061 instruction memory. An overlay not present (or only partially present)
9062 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
9063 is its address in the larger memory. The mapped address is also called
9064 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
9065 called the @dfn{load memory address}, or @dfn{LMA}.
9067 Unfortunately, overlays are not a completely transparent way to adapt a
9068 program to limited instruction memory. They introduce a new set of
9069 global constraints you must keep in mind as you design your program:
9074 Before calling or returning to a function in an overlay, your program
9075 must make sure that overlay is actually mapped. Otherwise, the call or
9076 return will transfer control to the right address, but in the wrong
9077 overlay, and your program will probably crash.
9080 If the process of mapping an overlay is expensive on your system, you
9081 will need to choose your overlays carefully to minimize their effect on
9082 your program's performance.
9085 The executable file you load onto your system must contain each
9086 overlay's instructions, appearing at the overlay's load address, not its
9087 mapped address. However, each overlay's instructions must be relocated
9088 and its symbols defined as if the overlay were at its mapped address.
9089 You can use GNU linker scripts to specify different load and relocation
9090 addresses for pieces of your program; see @ref{Overlay Description,,,
9091 ld.info, Using ld: the GNU linker}.
9094 The procedure for loading executable files onto your system must be able
9095 to load their contents into the larger address space as well as the
9096 instruction and data spaces.
9100 The overlay system described above is rather simple, and could be
9101 improved in many ways:
9106 If your system has suitable bank switch registers or memory management
9107 hardware, you could use those facilities to make an overlay's load area
9108 contents simply appear at their mapped address in instruction space.
9109 This would probably be faster than copying the overlay to its mapped
9110 area in the usual way.
9113 If your overlays are small enough, you could set aside more than one
9114 overlay area, and have more than one overlay mapped at a time.
9117 You can use overlays to manage data, as well as instructions. In
9118 general, data overlays are even less transparent to your design than
9119 code overlays: whereas code overlays only require care when you call or
9120 return to functions, data overlays require care every time you access
9121 the data. Also, if you change the contents of a data overlay, you
9122 must copy its contents back out to its load address before you can copy a
9123 different data overlay into the same mapped area.
9128 @node Overlay Commands
9129 @section Overlay Commands
9131 To use @value{GDBN}'s overlay support, each overlay in your program must
9132 correspond to a separate section of the executable file. The section's
9133 virtual memory address and load memory address must be the overlay's
9134 mapped and load addresses. Identifying overlays with sections allows
9135 @value{GDBN} to determine the appropriate address of a function or
9136 variable, depending on whether the overlay is mapped or not.
9138 @value{GDBN}'s overlay commands all start with the word @code{overlay};
9139 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
9144 Disable @value{GDBN}'s overlay support. When overlay support is
9145 disabled, @value{GDBN} assumes that all functions and variables are
9146 always present at their mapped addresses. By default, @value{GDBN}'s
9147 overlay support is disabled.
9149 @item overlay manual
9150 @cindex manual overlay debugging
9151 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
9152 relies on you to tell it which overlays are mapped, and which are not,
9153 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
9154 commands described below.
9156 @item overlay map-overlay @var{overlay}
9157 @itemx overlay map @var{overlay}
9158 @cindex map an overlay
9159 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
9160 be the name of the object file section containing the overlay. When an
9161 overlay is mapped, @value{GDBN} assumes it can find the overlay's
9162 functions and variables at their mapped addresses. @value{GDBN} assumes
9163 that any other overlays whose mapped ranges overlap that of
9164 @var{overlay} are now unmapped.
9166 @item overlay unmap-overlay @var{overlay}
9167 @itemx overlay unmap @var{overlay}
9168 @cindex unmap an overlay
9169 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
9170 must be the name of the object file section containing the overlay.
9171 When an overlay is unmapped, @value{GDBN} assumes it can find the
9172 overlay's functions and variables at their load addresses.
9175 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
9176 consults a data structure the overlay manager maintains in the inferior
9177 to see which overlays are mapped. For details, see @ref{Automatic
9180 @item overlay load-target
9182 @cindex reloading the overlay table
9183 Re-read the overlay table from the inferior. Normally, @value{GDBN}
9184 re-reads the table @value{GDBN} automatically each time the inferior
9185 stops, so this command should only be necessary if you have changed the
9186 overlay mapping yourself using @value{GDBN}. This command is only
9187 useful when using automatic overlay debugging.
9189 @item overlay list-overlays
9191 @cindex listing mapped overlays
9192 Display a list of the overlays currently mapped, along with their mapped
9193 addresses, load addresses, and sizes.
9197 Normally, when @value{GDBN} prints a code address, it includes the name
9198 of the function the address falls in:
9201 (@value{GDBP}) print main
9202 $3 = @{int ()@} 0x11a0 <main>
9205 When overlay debugging is enabled, @value{GDBN} recognizes code in
9206 unmapped overlays, and prints the names of unmapped functions with
9207 asterisks around them. For example, if @code{foo} is a function in an
9208 unmapped overlay, @value{GDBN} prints it this way:
9211 (@value{GDBP}) overlay list
9212 No sections are mapped.
9213 (@value{GDBP}) print foo
9214 $5 = @{int (int)@} 0x100000 <*foo*>
9217 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
9221 (@value{GDBP}) overlay list
9222 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
9223 mapped at 0x1016 - 0x104a
9224 (@value{GDBP}) print foo
9225 $6 = @{int (int)@} 0x1016 <foo>
9228 When overlay debugging is enabled, @value{GDBN} can find the correct
9229 address for functions and variables in an overlay, whether or not the
9230 overlay is mapped. This allows most @value{GDBN} commands, like
9231 @code{break} and @code{disassemble}, to work normally, even on unmapped
9232 code. However, @value{GDBN}'s breakpoint support has some limitations:
9236 @cindex breakpoints in overlays
9237 @cindex overlays, setting breakpoints in
9238 You can set breakpoints in functions in unmapped overlays, as long as
9239 @value{GDBN} can write to the overlay at its load address.
9241 @value{GDBN} can not set hardware or simulator-based breakpoints in
9242 unmapped overlays. However, if you set a breakpoint at the end of your
9243 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
9244 you are using manual overlay management), @value{GDBN} will re-set its
9245 breakpoints properly.
9249 @node Automatic Overlay Debugging
9250 @section Automatic Overlay Debugging
9251 @cindex automatic overlay debugging
9253 @value{GDBN} can automatically track which overlays are mapped and which
9254 are not, given some simple co-operation from the overlay manager in the
9255 inferior. If you enable automatic overlay debugging with the
9256 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
9257 looks in the inferior's memory for certain variables describing the
9258 current state of the overlays.
9260 Here are the variables your overlay manager must define to support
9261 @value{GDBN}'s automatic overlay debugging:
9265 @item @code{_ovly_table}:
9266 This variable must be an array of the following structures:
9271 /* The overlay's mapped address. */
9274 /* The size of the overlay, in bytes. */
9277 /* The overlay's load address. */
9280 /* Non-zero if the overlay is currently mapped;
9282 unsigned long mapped;
9286 @item @code{_novlys}:
9287 This variable must be a four-byte signed integer, holding the total
9288 number of elements in @code{_ovly_table}.
9292 To decide whether a particular overlay is mapped or not, @value{GDBN}
9293 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
9294 @code{lma} members equal the VMA and LMA of the overlay's section in the
9295 executable file. When @value{GDBN} finds a matching entry, it consults
9296 the entry's @code{mapped} member to determine whether the overlay is
9299 In addition, your overlay manager may define a function called
9300 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
9301 will silently set a breakpoint there. If the overlay manager then
9302 calls this function whenever it has changed the overlay table, this
9303 will enable @value{GDBN} to accurately keep track of which overlays
9304 are in program memory, and update any breakpoints that may be set
9305 in overlays. This will allow breakpoints to work even if the
9306 overlays are kept in ROM or other non-writable memory while they
9307 are not being executed.
9309 @node Overlay Sample Program
9310 @section Overlay Sample Program
9311 @cindex overlay example program
9313 When linking a program which uses overlays, you must place the overlays
9314 at their load addresses, while relocating them to run at their mapped
9315 addresses. To do this, you must write a linker script (@pxref{Overlay
9316 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
9317 since linker scripts are specific to a particular host system, target
9318 architecture, and target memory layout, this manual cannot provide
9319 portable sample code demonstrating @value{GDBN}'s overlay support.
9321 However, the @value{GDBN} source distribution does contain an overlaid
9322 program, with linker scripts for a few systems, as part of its test
9323 suite. The program consists of the following files from
9324 @file{gdb/testsuite/gdb.base}:
9328 The main program file.
9330 A simple overlay manager, used by @file{overlays.c}.
9335 Overlay modules, loaded and used by @file{overlays.c}.
9338 Linker scripts for linking the test program on the @code{d10v-elf}
9339 and @code{m32r-elf} targets.
9342 You can build the test program using the @code{d10v-elf} GCC
9343 cross-compiler like this:
9346 $ d10v-elf-gcc -g -c overlays.c
9347 $ d10v-elf-gcc -g -c ovlymgr.c
9348 $ d10v-elf-gcc -g -c foo.c
9349 $ d10v-elf-gcc -g -c bar.c
9350 $ d10v-elf-gcc -g -c baz.c
9351 $ d10v-elf-gcc -g -c grbx.c
9352 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
9353 baz.o grbx.o -Wl,-Td10v.ld -o overlays
9356 The build process is identical for any other architecture, except that
9357 you must substitute the appropriate compiler and linker script for the
9358 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
9362 @chapter Using @value{GDBN} with Different Languages
9365 Although programming languages generally have common aspects, they are
9366 rarely expressed in the same manner. For instance, in ANSI C,
9367 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
9368 Modula-2, it is accomplished by @code{p^}. Values can also be
9369 represented (and displayed) differently. Hex numbers in C appear as
9370 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
9372 @cindex working language
9373 Language-specific information is built into @value{GDBN} for some languages,
9374 allowing you to express operations like the above in your program's
9375 native language, and allowing @value{GDBN} to output values in a manner
9376 consistent with the syntax of your program's native language. The
9377 language you use to build expressions is called the @dfn{working
9381 * Setting:: Switching between source languages
9382 * Show:: Displaying the language
9383 * Checks:: Type and range checks
9384 * Supported Languages:: Supported languages
9385 * Unsupported Languages:: Unsupported languages
9389 @section Switching Between Source Languages
9391 There are two ways to control the working language---either have @value{GDBN}
9392 set it automatically, or select it manually yourself. You can use the
9393 @code{set language} command for either purpose. On startup, @value{GDBN}
9394 defaults to setting the language automatically. The working language is
9395 used to determine how expressions you type are interpreted, how values
9398 In addition to the working language, every source file that
9399 @value{GDBN} knows about has its own working language. For some object
9400 file formats, the compiler might indicate which language a particular
9401 source file is in. However, most of the time @value{GDBN} infers the
9402 language from the name of the file. The language of a source file
9403 controls whether C@t{++} names are demangled---this way @code{backtrace} can
9404 show each frame appropriately for its own language. There is no way to
9405 set the language of a source file from within @value{GDBN}, but you can
9406 set the language associated with a filename extension. @xref{Show, ,
9407 Displaying the Language}.
9409 This is most commonly a problem when you use a program, such
9410 as @code{cfront} or @code{f2c}, that generates C but is written in
9411 another language. In that case, make the
9412 program use @code{#line} directives in its C output; that way
9413 @value{GDBN} will know the correct language of the source code of the original
9414 program, and will display that source code, not the generated C code.
9417 * Filenames:: Filename extensions and languages.
9418 * Manually:: Setting the working language manually
9419 * Automatically:: Having @value{GDBN} infer the source language
9423 @subsection List of Filename Extensions and Languages
9425 If a source file name ends in one of the following extensions, then
9426 @value{GDBN} infers that its language is the one indicated.
9447 Objective-C source file
9454 Modula-2 source file
9458 Assembler source file. This actually behaves almost like C, but
9459 @value{GDBN} does not skip over function prologues when stepping.
9462 In addition, you may set the language associated with a filename
9463 extension. @xref{Show, , Displaying the Language}.
9466 @subsection Setting the Working Language
9468 If you allow @value{GDBN} to set the language automatically,
9469 expressions are interpreted the same way in your debugging session and
9472 @kindex set language
9473 If you wish, you may set the language manually. To do this, issue the
9474 command @samp{set language @var{lang}}, where @var{lang} is the name of
9476 @code{c} or @code{modula-2}.
9477 For a list of the supported languages, type @samp{set language}.
9479 Setting the language manually prevents @value{GDBN} from updating the working
9480 language automatically. This can lead to confusion if you try
9481 to debug a program when the working language is not the same as the
9482 source language, when an expression is acceptable to both
9483 languages---but means different things. For instance, if the current
9484 source file were written in C, and @value{GDBN} was parsing Modula-2, a
9492 might not have the effect you intended. In C, this means to add
9493 @code{b} and @code{c} and place the result in @code{a}. The result
9494 printed would be the value of @code{a}. In Modula-2, this means to compare
9495 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
9498 @subsection Having @value{GDBN} Infer the Source Language
9500 To have @value{GDBN} set the working language automatically, use
9501 @samp{set language local} or @samp{set language auto}. @value{GDBN}
9502 then infers the working language. That is, when your program stops in a
9503 frame (usually by encountering a breakpoint), @value{GDBN} sets the
9504 working language to the language recorded for the function in that
9505 frame. If the language for a frame is unknown (that is, if the function
9506 or block corresponding to the frame was defined in a source file that
9507 does not have a recognized extension), the current working language is
9508 not changed, and @value{GDBN} issues a warning.
9510 This may not seem necessary for most programs, which are written
9511 entirely in one source language. However, program modules and libraries
9512 written in one source language can be used by a main program written in
9513 a different source language. Using @samp{set language auto} in this
9514 case frees you from having to set the working language manually.
9517 @section Displaying the Language
9519 The following commands help you find out which language is the
9520 working language, and also what language source files were written in.
9524 @kindex show language
9525 Display the current working language. This is the
9526 language you can use with commands such as @code{print} to
9527 build and compute expressions that may involve variables in your program.
9530 @kindex info frame@r{, show the source language}
9531 Display the source language for this frame. This language becomes the
9532 working language if you use an identifier from this frame.
9533 @xref{Frame Info, ,Information about a Frame}, to identify the other
9534 information listed here.
9537 @kindex info source@r{, show the source language}
9538 Display the source language of this source file.
9539 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
9540 information listed here.
9543 In unusual circumstances, you may have source files with extensions
9544 not in the standard list. You can then set the extension associated
9545 with a language explicitly:
9548 @item set extension-language @var{ext} @var{language}
9549 @kindex set extension-language
9550 Tell @value{GDBN} that source files with extension @var{ext} are to be
9551 assumed as written in the source language @var{language}.
9553 @item info extensions
9554 @kindex info extensions
9555 List all the filename extensions and the associated languages.
9559 @section Type and Range Checking
9562 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
9563 checking are included, but they do not yet have any effect. This
9564 section documents the intended facilities.
9566 @c FIXME remove warning when type/range code added
9568 Some languages are designed to guard you against making seemingly common
9569 errors through a series of compile- and run-time checks. These include
9570 checking the type of arguments to functions and operators, and making
9571 sure mathematical overflows are caught at run time. Checks such as
9572 these help to ensure a program's correctness once it has been compiled
9573 by eliminating type mismatches, and providing active checks for range
9574 errors when your program is running.
9576 @value{GDBN} can check for conditions like the above if you wish.
9577 Although @value{GDBN} does not check the statements in your program,
9578 it can check expressions entered directly into @value{GDBN} for
9579 evaluation via the @code{print} command, for example. As with the
9580 working language, @value{GDBN} can also decide whether or not to check
9581 automatically based on your program's source language.
9582 @xref{Supported Languages, ,Supported Languages}, for the default
9583 settings of supported languages.
9586 * Type Checking:: An overview of type checking
9587 * Range Checking:: An overview of range checking
9590 @cindex type checking
9591 @cindex checks, type
9593 @subsection An Overview of Type Checking
9595 Some languages, such as Modula-2, are strongly typed, meaning that the
9596 arguments to operators and functions have to be of the correct type,
9597 otherwise an error occurs. These checks prevent type mismatch
9598 errors from ever causing any run-time problems. For example,
9606 The second example fails because the @code{CARDINAL} 1 is not
9607 type-compatible with the @code{REAL} 2.3.
9609 For the expressions you use in @value{GDBN} commands, you can tell the
9610 @value{GDBN} type checker to skip checking;
9611 to treat any mismatches as errors and abandon the expression;
9612 or to only issue warnings when type mismatches occur,
9613 but evaluate the expression anyway. When you choose the last of
9614 these, @value{GDBN} evaluates expressions like the second example above, but
9615 also issues a warning.
9617 Even if you turn type checking off, there may be other reasons
9618 related to type that prevent @value{GDBN} from evaluating an expression.
9619 For instance, @value{GDBN} does not know how to add an @code{int} and
9620 a @code{struct foo}. These particular type errors have nothing to do
9621 with the language in use, and usually arise from expressions, such as
9622 the one described above, which make little sense to evaluate anyway.
9624 Each language defines to what degree it is strict about type. For
9625 instance, both Modula-2 and C require the arguments to arithmetical
9626 operators to be numbers. In C, enumerated types and pointers can be
9627 represented as numbers, so that they are valid arguments to mathematical
9628 operators. @xref{Supported Languages, ,Supported Languages}, for further
9629 details on specific languages.
9631 @value{GDBN} provides some additional commands for controlling the type checker:
9633 @kindex set check type
9634 @kindex show check type
9636 @item set check type auto
9637 Set type checking on or off based on the current working language.
9638 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9641 @item set check type on
9642 @itemx set check type off
9643 Set type checking on or off, overriding the default setting for the
9644 current working language. Issue a warning if the setting does not
9645 match the language default. If any type mismatches occur in
9646 evaluating an expression while type checking is on, @value{GDBN} prints a
9647 message and aborts evaluation of the expression.
9649 @item set check type warn
9650 Cause the type checker to issue warnings, but to always attempt to
9651 evaluate the expression. Evaluating the expression may still
9652 be impossible for other reasons. For example, @value{GDBN} cannot add
9653 numbers and structures.
9656 Show the current setting of the type checker, and whether or not @value{GDBN}
9657 is setting it automatically.
9660 @cindex range checking
9661 @cindex checks, range
9662 @node Range Checking
9663 @subsection An Overview of Range Checking
9665 In some languages (such as Modula-2), it is an error to exceed the
9666 bounds of a type; this is enforced with run-time checks. Such range
9667 checking is meant to ensure program correctness by making sure
9668 computations do not overflow, or indices on an array element access do
9669 not exceed the bounds of the array.
9671 For expressions you use in @value{GDBN} commands, you can tell
9672 @value{GDBN} to treat range errors in one of three ways: ignore them,
9673 always treat them as errors and abandon the expression, or issue
9674 warnings but evaluate the expression anyway.
9676 A range error can result from numerical overflow, from exceeding an
9677 array index bound, or when you type a constant that is not a member
9678 of any type. Some languages, however, do not treat overflows as an
9679 error. In many implementations of C, mathematical overflow causes the
9680 result to ``wrap around'' to lower values---for example, if @var{m} is
9681 the largest integer value, and @var{s} is the smallest, then
9684 @var{m} + 1 @result{} @var{s}
9687 This, too, is specific to individual languages, and in some cases
9688 specific to individual compilers or machines. @xref{Supported Languages, ,
9689 Supported Languages}, for further details on specific languages.
9691 @value{GDBN} provides some additional commands for controlling the range checker:
9693 @kindex set check range
9694 @kindex show check range
9696 @item set check range auto
9697 Set range checking on or off based on the current working language.
9698 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9701 @item set check range on
9702 @itemx set check range off
9703 Set range checking on or off, overriding the default setting for the
9704 current working language. A warning is issued if the setting does not
9705 match the language default. If a range error occurs and range checking is on,
9706 then a message is printed and evaluation of the expression is aborted.
9708 @item set check range warn
9709 Output messages when the @value{GDBN} range checker detects a range error,
9710 but attempt to evaluate the expression anyway. Evaluating the
9711 expression may still be impossible for other reasons, such as accessing
9712 memory that the process does not own (a typical example from many Unix
9716 Show the current setting of the range checker, and whether or not it is
9717 being set automatically by @value{GDBN}.
9720 @node Supported Languages
9721 @section Supported Languages
9723 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
9724 assembly, Modula-2, and Ada.
9725 @c This is false ...
9726 Some @value{GDBN} features may be used in expressions regardless of the
9727 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
9728 and the @samp{@{type@}addr} construct (@pxref{Expressions,
9729 ,Expressions}) can be used with the constructs of any supported
9732 The following sections detail to what degree each source language is
9733 supported by @value{GDBN}. These sections are not meant to be language
9734 tutorials or references, but serve only as a reference guide to what the
9735 @value{GDBN} expression parser accepts, and what input and output
9736 formats should look like for different languages. There are many good
9737 books written on each of these languages; please look to these for a
9738 language reference or tutorial.
9742 * Objective-C:: Objective-C
9745 * Modula-2:: Modula-2
9750 @subsection C and C@t{++}
9752 @cindex C and C@t{++}
9753 @cindex expressions in C or C@t{++}
9755 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
9756 to both languages. Whenever this is the case, we discuss those languages
9760 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
9761 @cindex @sc{gnu} C@t{++}
9762 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
9763 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
9764 effectively, you must compile your C@t{++} programs with a supported
9765 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
9766 compiler (@code{aCC}).
9768 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
9769 format; if it doesn't work on your system, try the stabs+ debugging
9770 format. You can select those formats explicitly with the @code{g++}
9771 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
9772 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
9773 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
9776 * C Operators:: C and C@t{++} operators
9777 * C Constants:: C and C@t{++} constants
9778 * C Plus Plus Expressions:: C@t{++} expressions
9779 * C Defaults:: Default settings for C and C@t{++}
9780 * C Checks:: C and C@t{++} type and range checks
9781 * Debugging C:: @value{GDBN} and C
9782 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
9783 * Decimal Floating Point:: Numbers in Decimal Floating Point format
9787 @subsubsection C and C@t{++} Operators
9789 @cindex C and C@t{++} operators
9791 Operators must be defined on values of specific types. For instance,
9792 @code{+} is defined on numbers, but not on structures. Operators are
9793 often defined on groups of types.
9795 For the purposes of C and C@t{++}, the following definitions hold:
9800 @emph{Integral types} include @code{int} with any of its storage-class
9801 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
9804 @emph{Floating-point types} include @code{float}, @code{double}, and
9805 @code{long double} (if supported by the target platform).
9808 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
9811 @emph{Scalar types} include all of the above.
9816 The following operators are supported. They are listed here
9817 in order of increasing precedence:
9821 The comma or sequencing operator. Expressions in a comma-separated list
9822 are evaluated from left to right, with the result of the entire
9823 expression being the last expression evaluated.
9826 Assignment. The value of an assignment expression is the value
9827 assigned. Defined on scalar types.
9830 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
9831 and translated to @w{@code{@var{a} = @var{a op b}}}.
9832 @w{@code{@var{op}=}} and @code{=} have the same precedence.
9833 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
9834 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
9837 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
9838 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
9842 Logical @sc{or}. Defined on integral types.
9845 Logical @sc{and}. Defined on integral types.
9848 Bitwise @sc{or}. Defined on integral types.
9851 Bitwise exclusive-@sc{or}. Defined on integral types.
9854 Bitwise @sc{and}. Defined on integral types.
9857 Equality and inequality. Defined on scalar types. The value of these
9858 expressions is 0 for false and non-zero for true.
9860 @item <@r{, }>@r{, }<=@r{, }>=
9861 Less than, greater than, less than or equal, greater than or equal.
9862 Defined on scalar types. The value of these expressions is 0 for false
9863 and non-zero for true.
9866 left shift, and right shift. Defined on integral types.
9869 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9872 Addition and subtraction. Defined on integral types, floating-point types and
9875 @item *@r{, }/@r{, }%
9876 Multiplication, division, and modulus. Multiplication and division are
9877 defined on integral and floating-point types. Modulus is defined on
9881 Increment and decrement. When appearing before a variable, the
9882 operation is performed before the variable is used in an expression;
9883 when appearing after it, the variable's value is used before the
9884 operation takes place.
9887 Pointer dereferencing. Defined on pointer types. Same precedence as
9891 Address operator. Defined on variables. Same precedence as @code{++}.
9893 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
9894 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
9895 to examine the address
9896 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
9900 Negative. Defined on integral and floating-point types. Same
9901 precedence as @code{++}.
9904 Logical negation. Defined on integral types. Same precedence as
9908 Bitwise complement operator. Defined on integral types. Same precedence as
9913 Structure member, and pointer-to-structure member. For convenience,
9914 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
9915 pointer based on the stored type information.
9916 Defined on @code{struct} and @code{union} data.
9919 Dereferences of pointers to members.
9922 Array indexing. @code{@var{a}[@var{i}]} is defined as
9923 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
9926 Function parameter list. Same precedence as @code{->}.
9929 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
9930 and @code{class} types.
9933 Doubled colons also represent the @value{GDBN} scope operator
9934 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
9938 If an operator is redefined in the user code, @value{GDBN} usually
9939 attempts to invoke the redefined version instead of using the operator's
9943 @subsubsection C and C@t{++} Constants
9945 @cindex C and C@t{++} constants
9947 @value{GDBN} allows you to express the constants of C and C@t{++} in the
9952 Integer constants are a sequence of digits. Octal constants are
9953 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
9954 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
9955 @samp{l}, specifying that the constant should be treated as a
9959 Floating point constants are a sequence of digits, followed by a decimal
9960 point, followed by a sequence of digits, and optionally followed by an
9961 exponent. An exponent is of the form:
9962 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
9963 sequence of digits. The @samp{+} is optional for positive exponents.
9964 A floating-point constant may also end with a letter @samp{f} or
9965 @samp{F}, specifying that the constant should be treated as being of
9966 the @code{float} (as opposed to the default @code{double}) type; or with
9967 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
9971 Enumerated constants consist of enumerated identifiers, or their
9972 integral equivalents.
9975 Character constants are a single character surrounded by single quotes
9976 (@code{'}), or a number---the ordinal value of the corresponding character
9977 (usually its @sc{ascii} value). Within quotes, the single character may
9978 be represented by a letter or by @dfn{escape sequences}, which are of
9979 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
9980 of the character's ordinal value; or of the form @samp{\@var{x}}, where
9981 @samp{@var{x}} is a predefined special character---for example,
9982 @samp{\n} for newline.
9985 String constants are a sequence of character constants surrounded by
9986 double quotes (@code{"}). Any valid character constant (as described
9987 above) may appear. Double quotes within the string must be preceded by
9988 a backslash, so for instance @samp{"a\"b'c"} is a string of five
9992 Pointer constants are an integral value. You can also write pointers
9993 to constants using the C operator @samp{&}.
9996 Array constants are comma-separated lists surrounded by braces @samp{@{}
9997 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
9998 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
9999 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
10002 @node C Plus Plus Expressions
10003 @subsubsection C@t{++} Expressions
10005 @cindex expressions in C@t{++}
10006 @value{GDBN} expression handling can interpret most C@t{++} expressions.
10008 @cindex debugging C@t{++} programs
10009 @cindex C@t{++} compilers
10010 @cindex debug formats and C@t{++}
10011 @cindex @value{NGCC} and C@t{++}
10013 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
10014 proper compiler and the proper debug format. Currently, @value{GDBN}
10015 works best when debugging C@t{++} code that is compiled with
10016 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
10017 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
10018 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
10019 stabs+ as their default debug format, so you usually don't need to
10020 specify a debug format explicitly. Other compilers and/or debug formats
10021 are likely to work badly or not at all when using @value{GDBN} to debug
10027 @cindex member functions
10029 Member function calls are allowed; you can use expressions like
10032 count = aml->GetOriginal(x, y)
10035 @vindex this@r{, inside C@t{++} member functions}
10036 @cindex namespace in C@t{++}
10038 While a member function is active (in the selected stack frame), your
10039 expressions have the same namespace available as the member function;
10040 that is, @value{GDBN} allows implicit references to the class instance
10041 pointer @code{this} following the same rules as C@t{++}.
10043 @cindex call overloaded functions
10044 @cindex overloaded functions, calling
10045 @cindex type conversions in C@t{++}
10047 You can call overloaded functions; @value{GDBN} resolves the function
10048 call to the right definition, with some restrictions. @value{GDBN} does not
10049 perform overload resolution involving user-defined type conversions,
10050 calls to constructors, or instantiations of templates that do not exist
10051 in the program. It also cannot handle ellipsis argument lists or
10054 It does perform integral conversions and promotions, floating-point
10055 promotions, arithmetic conversions, pointer conversions, conversions of
10056 class objects to base classes, and standard conversions such as those of
10057 functions or arrays to pointers; it requires an exact match on the
10058 number of function arguments.
10060 Overload resolution is always performed, unless you have specified
10061 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
10062 ,@value{GDBN} Features for C@t{++}}.
10064 You must specify @code{set overload-resolution off} in order to use an
10065 explicit function signature to call an overloaded function, as in
10067 p 'foo(char,int)'('x', 13)
10070 The @value{GDBN} command-completion facility can simplify this;
10071 see @ref{Completion, ,Command Completion}.
10073 @cindex reference declarations
10075 @value{GDBN} understands variables declared as C@t{++} references; you can use
10076 them in expressions just as you do in C@t{++} source---they are automatically
10079 In the parameter list shown when @value{GDBN} displays a frame, the values of
10080 reference variables are not displayed (unlike other variables); this
10081 avoids clutter, since references are often used for large structures.
10082 The @emph{address} of a reference variable is always shown, unless
10083 you have specified @samp{set print address off}.
10086 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
10087 expressions can use it just as expressions in your program do. Since
10088 one scope may be defined in another, you can use @code{::} repeatedly if
10089 necessary, for example in an expression like
10090 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
10091 resolving name scope by reference to source files, in both C and C@t{++}
10092 debugging (@pxref{Variables, ,Program Variables}).
10095 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
10096 calling virtual functions correctly, printing out virtual bases of
10097 objects, calling functions in a base subobject, casting objects, and
10098 invoking user-defined operators.
10101 @subsubsection C and C@t{++} Defaults
10103 @cindex C and C@t{++} defaults
10105 If you allow @value{GDBN} to set type and range checking automatically, they
10106 both default to @code{off} whenever the working language changes to
10107 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
10108 selects the working language.
10110 If you allow @value{GDBN} to set the language automatically, it
10111 recognizes source files whose names end with @file{.c}, @file{.C}, or
10112 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
10113 these files, it sets the working language to C or C@t{++}.
10114 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
10115 for further details.
10117 @c Type checking is (a) primarily motivated by Modula-2, and (b)
10118 @c unimplemented. If (b) changes, it might make sense to let this node
10119 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
10122 @subsubsection C and C@t{++} Type and Range Checks
10124 @cindex C and C@t{++} checks
10126 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
10127 is not used. However, if you turn type checking on, @value{GDBN}
10128 considers two variables type equivalent if:
10132 The two variables are structured and have the same structure, union, or
10136 The two variables have the same type name, or types that have been
10137 declared equivalent through @code{typedef}.
10140 @c leaving this out because neither J Gilmore nor R Pesch understand it.
10143 The two @code{struct}, @code{union}, or @code{enum} variables are
10144 declared in the same declaration. (Note: this may not be true for all C
10149 Range checking, if turned on, is done on mathematical operations. Array
10150 indices are not checked, since they are often used to index a pointer
10151 that is not itself an array.
10154 @subsubsection @value{GDBN} and C
10156 The @code{set print union} and @code{show print union} commands apply to
10157 the @code{union} type. When set to @samp{on}, any @code{union} that is
10158 inside a @code{struct} or @code{class} is also printed. Otherwise, it
10159 appears as @samp{@{...@}}.
10161 The @code{@@} operator aids in the debugging of dynamic arrays, formed
10162 with pointers and a memory allocation function. @xref{Expressions,
10165 @node Debugging C Plus Plus
10166 @subsubsection @value{GDBN} Features for C@t{++}
10168 @cindex commands for C@t{++}
10170 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
10171 designed specifically for use with C@t{++}. Here is a summary:
10174 @cindex break in overloaded functions
10175 @item @r{breakpoint menus}
10176 When you want a breakpoint in a function whose name is overloaded,
10177 @value{GDBN} has the capability to display a menu of possible breakpoint
10178 locations to help you specify which function definition you want.
10179 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
10181 @cindex overloading in C@t{++}
10182 @item rbreak @var{regex}
10183 Setting breakpoints using regular expressions is helpful for setting
10184 breakpoints on overloaded functions that are not members of any special
10186 @xref{Set Breaks, ,Setting Breakpoints}.
10188 @cindex C@t{++} exception handling
10191 Debug C@t{++} exception handling using these commands. @xref{Set
10192 Catchpoints, , Setting Catchpoints}.
10194 @cindex inheritance
10195 @item ptype @var{typename}
10196 Print inheritance relationships as well as other information for type
10198 @xref{Symbols, ,Examining the Symbol Table}.
10200 @cindex C@t{++} symbol display
10201 @item set print demangle
10202 @itemx show print demangle
10203 @itemx set print asm-demangle
10204 @itemx show print asm-demangle
10205 Control whether C@t{++} symbols display in their source form, both when
10206 displaying code as C@t{++} source and when displaying disassemblies.
10207 @xref{Print Settings, ,Print Settings}.
10209 @item set print object
10210 @itemx show print object
10211 Choose whether to print derived (actual) or declared types of objects.
10212 @xref{Print Settings, ,Print Settings}.
10214 @item set print vtbl
10215 @itemx show print vtbl
10216 Control the format for printing virtual function tables.
10217 @xref{Print Settings, ,Print Settings}.
10218 (The @code{vtbl} commands do not work on programs compiled with the HP
10219 ANSI C@t{++} compiler (@code{aCC}).)
10221 @kindex set overload-resolution
10222 @cindex overloaded functions, overload resolution
10223 @item set overload-resolution on
10224 Enable overload resolution for C@t{++} expression evaluation. The default
10225 is on. For overloaded functions, @value{GDBN} evaluates the arguments
10226 and searches for a function whose signature matches the argument types,
10227 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
10228 Expressions, ,C@t{++} Expressions}, for details).
10229 If it cannot find a match, it emits a message.
10231 @item set overload-resolution off
10232 Disable overload resolution for C@t{++} expression evaluation. For
10233 overloaded functions that are not class member functions, @value{GDBN}
10234 chooses the first function of the specified name that it finds in the
10235 symbol table, whether or not its arguments are of the correct type. For
10236 overloaded functions that are class member functions, @value{GDBN}
10237 searches for a function whose signature @emph{exactly} matches the
10240 @kindex show overload-resolution
10241 @item show overload-resolution
10242 Show the current setting of overload resolution.
10244 @item @r{Overloaded symbol names}
10245 You can specify a particular definition of an overloaded symbol, using
10246 the same notation that is used to declare such symbols in C@t{++}: type
10247 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
10248 also use the @value{GDBN} command-line word completion facilities to list the
10249 available choices, or to finish the type list for you.
10250 @xref{Completion,, Command Completion}, for details on how to do this.
10253 @node Decimal Floating Point
10254 @subsubsection Decimal Floating Point format
10255 @cindex decimal floating point format
10257 @value{GDBN} can examine, set and perform computations with numbers in
10258 decimal floating point format, which in the C language correspond to the
10259 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
10260 specified by the extension to support decimal floating-point arithmetic.
10262 There are two encodings in use, depending on the architecture: BID (Binary
10263 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
10264 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
10267 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
10268 to manipulate decimal floating point numbers, it is not possible to convert
10269 (using a cast, for example) integers wider than 32-bit to decimal float.
10271 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
10272 point computations, error checking in decimal float operations ignores
10273 underflow, overflow and divide by zero exceptions.
10275 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
10276 to inspect @code{_Decimal128} values stored in floating point registers. See
10277 @ref{PowerPC,,PowerPC} for more details.
10280 @subsection Objective-C
10282 @cindex Objective-C
10283 This section provides information about some commands and command
10284 options that are useful for debugging Objective-C code. See also
10285 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
10286 few more commands specific to Objective-C support.
10289 * Method Names in Commands::
10290 * The Print Command with Objective-C::
10293 @node Method Names in Commands
10294 @subsubsection Method Names in Commands
10296 The following commands have been extended to accept Objective-C method
10297 names as line specifications:
10299 @kindex clear@r{, and Objective-C}
10300 @kindex break@r{, and Objective-C}
10301 @kindex info line@r{, and Objective-C}
10302 @kindex jump@r{, and Objective-C}
10303 @kindex list@r{, and Objective-C}
10307 @item @code{info line}
10312 A fully qualified Objective-C method name is specified as
10315 -[@var{Class} @var{methodName}]
10318 where the minus sign is used to indicate an instance method and a
10319 plus sign (not shown) is used to indicate a class method. The class
10320 name @var{Class} and method name @var{methodName} are enclosed in
10321 brackets, similar to the way messages are specified in Objective-C
10322 source code. For example, to set a breakpoint at the @code{create}
10323 instance method of class @code{Fruit} in the program currently being
10327 break -[Fruit create]
10330 To list ten program lines around the @code{initialize} class method,
10334 list +[NSText initialize]
10337 In the current version of @value{GDBN}, the plus or minus sign is
10338 required. In future versions of @value{GDBN}, the plus or minus
10339 sign will be optional, but you can use it to narrow the search. It
10340 is also possible to specify just a method name:
10346 You must specify the complete method name, including any colons. If
10347 your program's source files contain more than one @code{create} method,
10348 you'll be presented with a numbered list of classes that implement that
10349 method. Indicate your choice by number, or type @samp{0} to exit if
10352 As another example, to clear a breakpoint established at the
10353 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
10356 clear -[NSWindow makeKeyAndOrderFront:]
10359 @node The Print Command with Objective-C
10360 @subsubsection The Print Command With Objective-C
10361 @cindex Objective-C, print objects
10362 @kindex print-object
10363 @kindex po @r{(@code{print-object})}
10365 The print command has also been extended to accept methods. For example:
10368 print -[@var{object} hash]
10371 @cindex print an Objective-C object description
10372 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
10374 will tell @value{GDBN} to send the @code{hash} message to @var{object}
10375 and print the result. Also, an additional command has been added,
10376 @code{print-object} or @code{po} for short, which is meant to print
10377 the description of an object. However, this command may only work
10378 with certain Objective-C libraries that have a particular hook
10379 function, @code{_NSPrintForDebugger}, defined.
10382 @subsection Fortran
10383 @cindex Fortran-specific support in @value{GDBN}
10385 @value{GDBN} can be used to debug programs written in Fortran, but it
10386 currently supports only the features of Fortran 77 language.
10388 @cindex trailing underscore, in Fortran symbols
10389 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
10390 among them) append an underscore to the names of variables and
10391 functions. When you debug programs compiled by those compilers, you
10392 will need to refer to variables and functions with a trailing
10396 * Fortran Operators:: Fortran operators and expressions
10397 * Fortran Defaults:: Default settings for Fortran
10398 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
10401 @node Fortran Operators
10402 @subsubsection Fortran Operators and Expressions
10404 @cindex Fortran operators and expressions
10406 Operators must be defined on values of specific types. For instance,
10407 @code{+} is defined on numbers, but not on characters or other non-
10408 arithmetic types. Operators are often defined on groups of types.
10412 The exponentiation operator. It raises the first operand to the power
10416 The range operator. Normally used in the form of array(low:high) to
10417 represent a section of array.
10420 The access component operator. Normally used to access elements in derived
10421 types. Also suitable for unions. As unions aren't part of regular Fortran,
10422 this can only happen when accessing a register that uses a gdbarch-defined
10426 @node Fortran Defaults
10427 @subsubsection Fortran Defaults
10429 @cindex Fortran Defaults
10431 Fortran symbols are usually case-insensitive, so @value{GDBN} by
10432 default uses case-insensitive matches for Fortran symbols. You can
10433 change that with the @samp{set case-insensitive} command, see
10434 @ref{Symbols}, for the details.
10436 @node Special Fortran Commands
10437 @subsubsection Special Fortran Commands
10439 @cindex Special Fortran commands
10441 @value{GDBN} has some commands to support Fortran-specific features,
10442 such as displaying common blocks.
10445 @cindex @code{COMMON} blocks, Fortran
10446 @kindex info common
10447 @item info common @r{[}@var{common-name}@r{]}
10448 This command prints the values contained in the Fortran @code{COMMON}
10449 block whose name is @var{common-name}. With no argument, the names of
10450 all @code{COMMON} blocks visible at the current program location are
10457 @cindex Pascal support in @value{GDBN}, limitations
10458 Debugging Pascal programs which use sets, subranges, file variables, or
10459 nested functions does not currently work. @value{GDBN} does not support
10460 entering expressions, printing values, or similar features using Pascal
10463 The Pascal-specific command @code{set print pascal_static-members}
10464 controls whether static members of Pascal objects are displayed.
10465 @xref{Print Settings, pascal_static-members}.
10468 @subsection Modula-2
10470 @cindex Modula-2, @value{GDBN} support
10472 The extensions made to @value{GDBN} to support Modula-2 only support
10473 output from the @sc{gnu} Modula-2 compiler (which is currently being
10474 developed). Other Modula-2 compilers are not currently supported, and
10475 attempting to debug executables produced by them is most likely
10476 to give an error as @value{GDBN} reads in the executable's symbol
10479 @cindex expressions in Modula-2
10481 * M2 Operators:: Built-in operators
10482 * Built-In Func/Proc:: Built-in functions and procedures
10483 * M2 Constants:: Modula-2 constants
10484 * M2 Types:: Modula-2 types
10485 * M2 Defaults:: Default settings for Modula-2
10486 * Deviations:: Deviations from standard Modula-2
10487 * M2 Checks:: Modula-2 type and range checks
10488 * M2 Scope:: The scope operators @code{::} and @code{.}
10489 * GDB/M2:: @value{GDBN} and Modula-2
10493 @subsubsection Operators
10494 @cindex Modula-2 operators
10496 Operators must be defined on values of specific types. For instance,
10497 @code{+} is defined on numbers, but not on structures. Operators are
10498 often defined on groups of types. For the purposes of Modula-2, the
10499 following definitions hold:
10504 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
10508 @emph{Character types} consist of @code{CHAR} and its subranges.
10511 @emph{Floating-point types} consist of @code{REAL}.
10514 @emph{Pointer types} consist of anything declared as @code{POINTER TO
10518 @emph{Scalar types} consist of all of the above.
10521 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
10524 @emph{Boolean types} consist of @code{BOOLEAN}.
10528 The following operators are supported, and appear in order of
10529 increasing precedence:
10533 Function argument or array index separator.
10536 Assignment. The value of @var{var} @code{:=} @var{value} is
10540 Less than, greater than on integral, floating-point, or enumerated
10544 Less than or equal to, greater than or equal to
10545 on integral, floating-point and enumerated types, or set inclusion on
10546 set types. Same precedence as @code{<}.
10548 @item =@r{, }<>@r{, }#
10549 Equality and two ways of expressing inequality, valid on scalar types.
10550 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
10551 available for inequality, since @code{#} conflicts with the script
10555 Set membership. Defined on set types and the types of their members.
10556 Same precedence as @code{<}.
10559 Boolean disjunction. Defined on boolean types.
10562 Boolean conjunction. Defined on boolean types.
10565 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
10568 Addition and subtraction on integral and floating-point types, or union
10569 and difference on set types.
10572 Multiplication on integral and floating-point types, or set intersection
10576 Division on floating-point types, or symmetric set difference on set
10577 types. Same precedence as @code{*}.
10580 Integer division and remainder. Defined on integral types. Same
10581 precedence as @code{*}.
10584 Negative. Defined on @code{INTEGER} and @code{REAL} data.
10587 Pointer dereferencing. Defined on pointer types.
10590 Boolean negation. Defined on boolean types. Same precedence as
10594 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
10595 precedence as @code{^}.
10598 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
10601 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
10605 @value{GDBN} and Modula-2 scope operators.
10609 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
10610 treats the use of the operator @code{IN}, or the use of operators
10611 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
10612 @code{<=}, and @code{>=} on sets as an error.
10616 @node Built-In Func/Proc
10617 @subsubsection Built-in Functions and Procedures
10618 @cindex Modula-2 built-ins
10620 Modula-2 also makes available several built-in procedures and functions.
10621 In describing these, the following metavariables are used:
10626 represents an @code{ARRAY} variable.
10629 represents a @code{CHAR} constant or variable.
10632 represents a variable or constant of integral type.
10635 represents an identifier that belongs to a set. Generally used in the
10636 same function with the metavariable @var{s}. The type of @var{s} should
10637 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
10640 represents a variable or constant of integral or floating-point type.
10643 represents a variable or constant of floating-point type.
10649 represents a variable.
10652 represents a variable or constant of one of many types. See the
10653 explanation of the function for details.
10656 All Modula-2 built-in procedures also return a result, described below.
10660 Returns the absolute value of @var{n}.
10663 If @var{c} is a lower case letter, it returns its upper case
10664 equivalent, otherwise it returns its argument.
10667 Returns the character whose ordinal value is @var{i}.
10670 Decrements the value in the variable @var{v} by one. Returns the new value.
10672 @item DEC(@var{v},@var{i})
10673 Decrements the value in the variable @var{v} by @var{i}. Returns the
10676 @item EXCL(@var{m},@var{s})
10677 Removes the element @var{m} from the set @var{s}. Returns the new
10680 @item FLOAT(@var{i})
10681 Returns the floating point equivalent of the integer @var{i}.
10683 @item HIGH(@var{a})
10684 Returns the index of the last member of @var{a}.
10687 Increments the value in the variable @var{v} by one. Returns the new value.
10689 @item INC(@var{v},@var{i})
10690 Increments the value in the variable @var{v} by @var{i}. Returns the
10693 @item INCL(@var{m},@var{s})
10694 Adds the element @var{m} to the set @var{s} if it is not already
10695 there. Returns the new set.
10698 Returns the maximum value of the type @var{t}.
10701 Returns the minimum value of the type @var{t}.
10704 Returns boolean TRUE if @var{i} is an odd number.
10707 Returns the ordinal value of its argument. For example, the ordinal
10708 value of a character is its @sc{ascii} value (on machines supporting the
10709 @sc{ascii} character set). @var{x} must be of an ordered type, which include
10710 integral, character and enumerated types.
10712 @item SIZE(@var{x})
10713 Returns the size of its argument. @var{x} can be a variable or a type.
10715 @item TRUNC(@var{r})
10716 Returns the integral part of @var{r}.
10718 @item TSIZE(@var{x})
10719 Returns the size of its argument. @var{x} can be a variable or a type.
10721 @item VAL(@var{t},@var{i})
10722 Returns the member of the type @var{t} whose ordinal value is @var{i}.
10726 @emph{Warning:} Sets and their operations are not yet supported, so
10727 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
10731 @cindex Modula-2 constants
10733 @subsubsection Constants
10735 @value{GDBN} allows you to express the constants of Modula-2 in the following
10741 Integer constants are simply a sequence of digits. When used in an
10742 expression, a constant is interpreted to be type-compatible with the
10743 rest of the expression. Hexadecimal integers are specified by a
10744 trailing @samp{H}, and octal integers by a trailing @samp{B}.
10747 Floating point constants appear as a sequence of digits, followed by a
10748 decimal point and another sequence of digits. An optional exponent can
10749 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
10750 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
10751 digits of the floating point constant must be valid decimal (base 10)
10755 Character constants consist of a single character enclosed by a pair of
10756 like quotes, either single (@code{'}) or double (@code{"}). They may
10757 also be expressed by their ordinal value (their @sc{ascii} value, usually)
10758 followed by a @samp{C}.
10761 String constants consist of a sequence of characters enclosed by a
10762 pair of like quotes, either single (@code{'}) or double (@code{"}).
10763 Escape sequences in the style of C are also allowed. @xref{C
10764 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
10768 Enumerated constants consist of an enumerated identifier.
10771 Boolean constants consist of the identifiers @code{TRUE} and
10775 Pointer constants consist of integral values only.
10778 Set constants are not yet supported.
10782 @subsubsection Modula-2 Types
10783 @cindex Modula-2 types
10785 Currently @value{GDBN} can print the following data types in Modula-2
10786 syntax: array types, record types, set types, pointer types, procedure
10787 types, enumerated types, subrange types and base types. You can also
10788 print the contents of variables declared using these type.
10789 This section gives a number of simple source code examples together with
10790 sample @value{GDBN} sessions.
10792 The first example contains the following section of code:
10801 and you can request @value{GDBN} to interrogate the type and value of
10802 @code{r} and @code{s}.
10805 (@value{GDBP}) print s
10807 (@value{GDBP}) ptype s
10809 (@value{GDBP}) print r
10811 (@value{GDBP}) ptype r
10816 Likewise if your source code declares @code{s} as:
10820 s: SET ['A'..'Z'] ;
10824 then you may query the type of @code{s} by:
10827 (@value{GDBP}) ptype s
10828 type = SET ['A'..'Z']
10832 Note that at present you cannot interactively manipulate set
10833 expressions using the debugger.
10835 The following example shows how you might declare an array in Modula-2
10836 and how you can interact with @value{GDBN} to print its type and contents:
10840 s: ARRAY [-10..10] OF CHAR ;
10844 (@value{GDBP}) ptype s
10845 ARRAY [-10..10] OF CHAR
10848 Note that the array handling is not yet complete and although the type
10849 is printed correctly, expression handling still assumes that all
10850 arrays have a lower bound of zero and not @code{-10} as in the example
10853 Here are some more type related Modula-2 examples:
10857 colour = (blue, red, yellow, green) ;
10858 t = [blue..yellow] ;
10866 The @value{GDBN} interaction shows how you can query the data type
10867 and value of a variable.
10870 (@value{GDBP}) print s
10872 (@value{GDBP}) ptype t
10873 type = [blue..yellow]
10877 In this example a Modula-2 array is declared and its contents
10878 displayed. Observe that the contents are written in the same way as
10879 their @code{C} counterparts.
10883 s: ARRAY [1..5] OF CARDINAL ;
10889 (@value{GDBP}) print s
10890 $1 = @{1, 0, 0, 0, 0@}
10891 (@value{GDBP}) ptype s
10892 type = ARRAY [1..5] OF CARDINAL
10895 The Modula-2 language interface to @value{GDBN} also understands
10896 pointer types as shown in this example:
10900 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
10907 and you can request that @value{GDBN} describes the type of @code{s}.
10910 (@value{GDBP}) ptype s
10911 type = POINTER TO ARRAY [1..5] OF CARDINAL
10914 @value{GDBN} handles compound types as we can see in this example.
10915 Here we combine array types, record types, pointer types and subrange
10926 myarray = ARRAY myrange OF CARDINAL ;
10927 myrange = [-2..2] ;
10929 s: POINTER TO ARRAY myrange OF foo ;
10933 and you can ask @value{GDBN} to describe the type of @code{s} as shown
10937 (@value{GDBP}) ptype s
10938 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
10941 f3 : ARRAY [-2..2] OF CARDINAL;
10946 @subsubsection Modula-2 Defaults
10947 @cindex Modula-2 defaults
10949 If type and range checking are set automatically by @value{GDBN}, they
10950 both default to @code{on} whenever the working language changes to
10951 Modula-2. This happens regardless of whether you or @value{GDBN}
10952 selected the working language.
10954 If you allow @value{GDBN} to set the language automatically, then entering
10955 code compiled from a file whose name ends with @file{.mod} sets the
10956 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
10957 Infer the Source Language}, for further details.
10960 @subsubsection Deviations from Standard Modula-2
10961 @cindex Modula-2, deviations from
10963 A few changes have been made to make Modula-2 programs easier to debug.
10964 This is done primarily via loosening its type strictness:
10968 Unlike in standard Modula-2, pointer constants can be formed by
10969 integers. This allows you to modify pointer variables during
10970 debugging. (In standard Modula-2, the actual address contained in a
10971 pointer variable is hidden from you; it can only be modified
10972 through direct assignment to another pointer variable or expression that
10973 returned a pointer.)
10976 C escape sequences can be used in strings and characters to represent
10977 non-printable characters. @value{GDBN} prints out strings with these
10978 escape sequences embedded. Single non-printable characters are
10979 printed using the @samp{CHR(@var{nnn})} format.
10982 The assignment operator (@code{:=}) returns the value of its right-hand
10986 All built-in procedures both modify @emph{and} return their argument.
10990 @subsubsection Modula-2 Type and Range Checks
10991 @cindex Modula-2 checks
10994 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
10997 @c FIXME remove warning when type/range checks added
10999 @value{GDBN} considers two Modula-2 variables type equivalent if:
11003 They are of types that have been declared equivalent via a @code{TYPE
11004 @var{t1} = @var{t2}} statement
11007 They have been declared on the same line. (Note: This is true of the
11008 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
11011 As long as type checking is enabled, any attempt to combine variables
11012 whose types are not equivalent is an error.
11014 Range checking is done on all mathematical operations, assignment, array
11015 index bounds, and all built-in functions and procedures.
11018 @subsubsection The Scope Operators @code{::} and @code{.}
11020 @cindex @code{.}, Modula-2 scope operator
11021 @cindex colon, doubled as scope operator
11023 @vindex colon-colon@r{, in Modula-2}
11024 @c Info cannot handle :: but TeX can.
11027 @vindex ::@r{, in Modula-2}
11030 There are a few subtle differences between the Modula-2 scope operator
11031 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
11036 @var{module} . @var{id}
11037 @var{scope} :: @var{id}
11041 where @var{scope} is the name of a module or a procedure,
11042 @var{module} the name of a module, and @var{id} is any declared
11043 identifier within your program, except another module.
11045 Using the @code{::} operator makes @value{GDBN} search the scope
11046 specified by @var{scope} for the identifier @var{id}. If it is not
11047 found in the specified scope, then @value{GDBN} searches all scopes
11048 enclosing the one specified by @var{scope}.
11050 Using the @code{.} operator makes @value{GDBN} search the current scope for
11051 the identifier specified by @var{id} that was imported from the
11052 definition module specified by @var{module}. With this operator, it is
11053 an error if the identifier @var{id} was not imported from definition
11054 module @var{module}, or if @var{id} is not an identifier in
11058 @subsubsection @value{GDBN} and Modula-2
11060 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
11061 Five subcommands of @code{set print} and @code{show print} apply
11062 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
11063 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
11064 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
11065 analogue in Modula-2.
11067 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
11068 with any language, is not useful with Modula-2. Its
11069 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
11070 created in Modula-2 as they can in C or C@t{++}. However, because an
11071 address can be specified by an integral constant, the construct
11072 @samp{@{@var{type}@}@var{adrexp}} is still useful.
11074 @cindex @code{#} in Modula-2
11075 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
11076 interpreted as the beginning of a comment. Use @code{<>} instead.
11082 The extensions made to @value{GDBN} for Ada only support
11083 output from the @sc{gnu} Ada (GNAT) compiler.
11084 Other Ada compilers are not currently supported, and
11085 attempting to debug executables produced by them is most likely
11089 @cindex expressions in Ada
11091 * Ada Mode Intro:: General remarks on the Ada syntax
11092 and semantics supported by Ada mode
11094 * Omissions from Ada:: Restrictions on the Ada expression syntax.
11095 * Additions to Ada:: Extensions of the Ada expression syntax.
11096 * Stopping Before Main Program:: Debugging the program during elaboration.
11097 * Ada Glitches:: Known peculiarities of Ada mode.
11100 @node Ada Mode Intro
11101 @subsubsection Introduction
11102 @cindex Ada mode, general
11104 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
11105 syntax, with some extensions.
11106 The philosophy behind the design of this subset is
11110 That @value{GDBN} should provide basic literals and access to operations for
11111 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
11112 leaving more sophisticated computations to subprograms written into the
11113 program (which therefore may be called from @value{GDBN}).
11116 That type safety and strict adherence to Ada language restrictions
11117 are not particularly important to the @value{GDBN} user.
11120 That brevity is important to the @value{GDBN} user.
11123 Thus, for brevity, the debugger acts as if all names declared in
11124 user-written packages are directly visible, even if they are not visible
11125 according to Ada rules, thus making it unnecessary to fully qualify most
11126 names with their packages, regardless of context. Where this causes
11127 ambiguity, @value{GDBN} asks the user's intent.
11129 The debugger will start in Ada mode if it detects an Ada main program.
11130 As for other languages, it will enter Ada mode when stopped in a program that
11131 was translated from an Ada source file.
11133 While in Ada mode, you may use `@t{--}' for comments. This is useful
11134 mostly for documenting command files. The standard @value{GDBN} comment
11135 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
11136 middle (to allow based literals).
11138 The debugger supports limited overloading. Given a subprogram call in which
11139 the function symbol has multiple definitions, it will use the number of
11140 actual parameters and some information about their types to attempt to narrow
11141 the set of definitions. It also makes very limited use of context, preferring
11142 procedures to functions in the context of the @code{call} command, and
11143 functions to procedures elsewhere.
11145 @node Omissions from Ada
11146 @subsubsection Omissions from Ada
11147 @cindex Ada, omissions from
11149 Here are the notable omissions from the subset:
11153 Only a subset of the attributes are supported:
11157 @t{'First}, @t{'Last}, and @t{'Length}
11158 on array objects (not on types and subtypes).
11161 @t{'Min} and @t{'Max}.
11164 @t{'Pos} and @t{'Val}.
11170 @t{'Range} on array objects (not subtypes), but only as the right
11171 operand of the membership (@code{in}) operator.
11174 @t{'Access}, @t{'Unchecked_Access}, and
11175 @t{'Unrestricted_Access} (a GNAT extension).
11183 @code{Characters.Latin_1} are not available and
11184 concatenation is not implemented. Thus, escape characters in strings are
11185 not currently available.
11188 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
11189 equality of representations. They will generally work correctly
11190 for strings and arrays whose elements have integer or enumeration types.
11191 They may not work correctly for arrays whose element
11192 types have user-defined equality, for arrays of real values
11193 (in particular, IEEE-conformant floating point, because of negative
11194 zeroes and NaNs), and for arrays whose elements contain unused bits with
11195 indeterminate values.
11198 The other component-by-component array operations (@code{and}, @code{or},
11199 @code{xor}, @code{not}, and relational tests other than equality)
11200 are not implemented.
11203 @cindex array aggregates (Ada)
11204 @cindex record aggregates (Ada)
11205 @cindex aggregates (Ada)
11206 There is limited support for array and record aggregates. They are
11207 permitted only on the right sides of assignments, as in these examples:
11210 set An_Array := (1, 2, 3, 4, 5, 6)
11211 set An_Array := (1, others => 0)
11212 set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
11213 set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
11214 set A_Record := (1, "Peter", True);
11215 set A_Record := (Name => "Peter", Id => 1, Alive => True)
11219 discriminant's value by assigning an aggregate has an
11220 undefined effect if that discriminant is used within the record.
11221 However, you can first modify discriminants by directly assigning to
11222 them (which normally would not be allowed in Ada), and then performing an
11223 aggregate assignment. For example, given a variable @code{A_Rec}
11224 declared to have a type such as:
11227 type Rec (Len : Small_Integer := 0) is record
11229 Vals : IntArray (1 .. Len);
11233 you can assign a value with a different size of @code{Vals} with two
11238 set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
11241 As this example also illustrates, @value{GDBN} is very loose about the usual
11242 rules concerning aggregates. You may leave out some of the
11243 components of an array or record aggregate (such as the @code{Len}
11244 component in the assignment to @code{A_Rec} above); they will retain their
11245 original values upon assignment. You may freely use dynamic values as
11246 indices in component associations. You may even use overlapping or
11247 redundant component associations, although which component values are
11248 assigned in such cases is not defined.
11251 Calls to dispatching subprograms are not implemented.
11254 The overloading algorithm is much more limited (i.e., less selective)
11255 than that of real Ada. It makes only limited use of the context in
11256 which a subexpression appears to resolve its meaning, and it is much
11257 looser in its rules for allowing type matches. As a result, some
11258 function calls will be ambiguous, and the user will be asked to choose
11259 the proper resolution.
11262 The @code{new} operator is not implemented.
11265 Entry calls are not implemented.
11268 Aside from printing, arithmetic operations on the native VAX floating-point
11269 formats are not supported.
11272 It is not possible to slice a packed array.
11275 The names @code{True} and @code{False}, when not part of a qualified name,
11276 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
11278 Should your program
11279 redefine these names in a package or procedure (at best a dubious practice),
11280 you will have to use fully qualified names to access their new definitions.
11283 @node Additions to Ada
11284 @subsubsection Additions to Ada
11285 @cindex Ada, deviations from
11287 As it does for other languages, @value{GDBN} makes certain generic
11288 extensions to Ada (@pxref{Expressions}):
11292 If the expression @var{E} is a variable residing in memory (typically
11293 a local variable or array element) and @var{N} is a positive integer,
11294 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
11295 @var{N}-1 adjacent variables following it in memory as an array. In
11296 Ada, this operator is generally not necessary, since its prime use is
11297 in displaying parts of an array, and slicing will usually do this in
11298 Ada. However, there are occasional uses when debugging programs in
11299 which certain debugging information has been optimized away.
11302 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
11303 appears in function or file @var{B}.'' When @var{B} is a file name,
11304 you must typically surround it in single quotes.
11307 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
11308 @var{type} that appears at address @var{addr}.''
11311 A name starting with @samp{$} is a convenience variable
11312 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
11315 In addition, @value{GDBN} provides a few other shortcuts and outright
11316 additions specific to Ada:
11320 The assignment statement is allowed as an expression, returning
11321 its right-hand operand as its value. Thus, you may enter
11325 print A(tmp := y + 1)
11329 The semicolon is allowed as an ``operator,'' returning as its value
11330 the value of its right-hand operand.
11331 This allows, for example,
11332 complex conditional breaks:
11336 condition 1 (report(i); k += 1; A(k) > 100)
11340 Rather than use catenation and symbolic character names to introduce special
11341 characters into strings, one may instead use a special bracket notation,
11342 which is also used to print strings. A sequence of characters of the form
11343 @samp{["@var{XX}"]} within a string or character literal denotes the
11344 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
11345 sequence of characters @samp{["""]} also denotes a single quotation mark
11346 in strings. For example,
11348 "One line.["0a"]Next line.["0a"]"
11351 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
11355 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
11356 @t{'Max} is optional (and is ignored in any case). For example, it is valid
11364 When printing arrays, @value{GDBN} uses positional notation when the
11365 array has a lower bound of 1, and uses a modified named notation otherwise.
11366 For example, a one-dimensional array of three integers with a lower bound
11367 of 3 might print as
11374 That is, in contrast to valid Ada, only the first component has a @code{=>}
11378 You may abbreviate attributes in expressions with any unique,
11379 multi-character subsequence of
11380 their names (an exact match gets preference).
11381 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
11382 in place of @t{a'length}.
11385 @cindex quoting Ada internal identifiers
11386 Since Ada is case-insensitive, the debugger normally maps identifiers you type
11387 to lower case. The GNAT compiler uses upper-case characters for
11388 some of its internal identifiers, which are normally of no interest to users.
11389 For the rare occasions when you actually have to look at them,
11390 enclose them in angle brackets to avoid the lower-case mapping.
11393 @value{GDBP} print <JMPBUF_SAVE>[0]
11397 Printing an object of class-wide type or dereferencing an
11398 access-to-class-wide value will display all the components of the object's
11399 specific type (as indicated by its run-time tag). Likewise, component
11400 selection on such a value will operate on the specific type of the
11405 @node Stopping Before Main Program
11406 @subsubsection Stopping at the Very Beginning
11408 @cindex breakpointing Ada elaboration code
11409 It is sometimes necessary to debug the program during elaboration, and
11410 before reaching the main procedure.
11411 As defined in the Ada Reference
11412 Manual, the elaboration code is invoked from a procedure called
11413 @code{adainit}. To run your program up to the beginning of
11414 elaboration, simply use the following two commands:
11415 @code{tbreak adainit} and @code{run}.
11418 @subsubsection Known Peculiarities of Ada Mode
11419 @cindex Ada, problems
11421 Besides the omissions listed previously (@pxref{Omissions from Ada}),
11422 we know of several problems with and limitations of Ada mode in
11424 some of which will be fixed with planned future releases of the debugger
11425 and the GNU Ada compiler.
11429 Currently, the debugger
11430 has insufficient information to determine whether certain pointers represent
11431 pointers to objects or the objects themselves.
11432 Thus, the user may have to tack an extra @code{.all} after an expression
11433 to get it printed properly.
11436 Static constants that the compiler chooses not to materialize as objects in
11437 storage are invisible to the debugger.
11440 Named parameter associations in function argument lists are ignored (the
11441 argument lists are treated as positional).
11444 Many useful library packages are currently invisible to the debugger.
11447 Fixed-point arithmetic, conversions, input, and output is carried out using
11448 floating-point arithmetic, and may give results that only approximate those on
11452 The type of the @t{'Address} attribute may not be @code{System.Address}.
11455 The GNAT compiler never generates the prefix @code{Standard} for any of
11456 the standard symbols defined by the Ada language. @value{GDBN} knows about
11457 this: it will strip the prefix from names when you use it, and will never
11458 look for a name you have so qualified among local symbols, nor match against
11459 symbols in other packages or subprograms. If you have
11460 defined entities anywhere in your program other than parameters and
11461 local variables whose simple names match names in @code{Standard},
11462 GNAT's lack of qualification here can cause confusion. When this happens,
11463 you can usually resolve the confusion
11464 by qualifying the problematic names with package
11465 @code{Standard} explicitly.
11468 @node Unsupported Languages
11469 @section Unsupported Languages
11471 @cindex unsupported languages
11472 @cindex minimal language
11473 In addition to the other fully-supported programming languages,
11474 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
11475 It does not represent a real programming language, but provides a set
11476 of capabilities close to what the C or assembly languages provide.
11477 This should allow most simple operations to be performed while debugging
11478 an application that uses a language currently not supported by @value{GDBN}.
11480 If the language is set to @code{auto}, @value{GDBN} will automatically
11481 select this language if the current frame corresponds to an unsupported
11485 @chapter Examining the Symbol Table
11487 The commands described in this chapter allow you to inquire about the
11488 symbols (names of variables, functions and types) defined in your
11489 program. This information is inherent in the text of your program and
11490 does not change as your program executes. @value{GDBN} finds it in your
11491 program's symbol table, in the file indicated when you started @value{GDBN}
11492 (@pxref{File Options, ,Choosing Files}), or by one of the
11493 file-management commands (@pxref{Files, ,Commands to Specify Files}).
11495 @cindex symbol names
11496 @cindex names of symbols
11497 @cindex quoting names
11498 Occasionally, you may need to refer to symbols that contain unusual
11499 characters, which @value{GDBN} ordinarily treats as word delimiters. The
11500 most frequent case is in referring to static variables in other
11501 source files (@pxref{Variables,,Program Variables}). File names
11502 are recorded in object files as debugging symbols, but @value{GDBN} would
11503 ordinarily parse a typical file name, like @file{foo.c}, as the three words
11504 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
11505 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
11512 looks up the value of @code{x} in the scope of the file @file{foo.c}.
11515 @cindex case-insensitive symbol names
11516 @cindex case sensitivity in symbol names
11517 @kindex set case-sensitive
11518 @item set case-sensitive on
11519 @itemx set case-sensitive off
11520 @itemx set case-sensitive auto
11521 Normally, when @value{GDBN} looks up symbols, it matches their names
11522 with case sensitivity determined by the current source language.
11523 Occasionally, you may wish to control that. The command @code{set
11524 case-sensitive} lets you do that by specifying @code{on} for
11525 case-sensitive matches or @code{off} for case-insensitive ones. If
11526 you specify @code{auto}, case sensitivity is reset to the default
11527 suitable for the source language. The default is case-sensitive
11528 matches for all languages except for Fortran, for which the default is
11529 case-insensitive matches.
11531 @kindex show case-sensitive
11532 @item show case-sensitive
11533 This command shows the current setting of case sensitivity for symbols
11536 @kindex info address
11537 @cindex address of a symbol
11538 @item info address @var{symbol}
11539 Describe where the data for @var{symbol} is stored. For a register
11540 variable, this says which register it is kept in. For a non-register
11541 local variable, this prints the stack-frame offset at which the variable
11544 Note the contrast with @samp{print &@var{symbol}}, which does not work
11545 at all for a register variable, and for a stack local variable prints
11546 the exact address of the current instantiation of the variable.
11548 @kindex info symbol
11549 @cindex symbol from address
11550 @cindex closest symbol and offset for an address
11551 @item info symbol @var{addr}
11552 Print the name of a symbol which is stored at the address @var{addr}.
11553 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
11554 nearest symbol and an offset from it:
11557 (@value{GDBP}) info symbol 0x54320
11558 _initialize_vx + 396 in section .text
11562 This is the opposite of the @code{info address} command. You can use
11563 it to find out the name of a variable or a function given its address.
11566 @item whatis [@var{arg}]
11567 Print the data type of @var{arg}, which can be either an expression or
11568 a data type. With no argument, print the data type of @code{$}, the
11569 last value in the value history. If @var{arg} is an expression, it is
11570 not actually evaluated, and any side-effecting operations (such as
11571 assignments or function calls) inside it do not take place. If
11572 @var{arg} is a type name, it may be the name of a type or typedef, or
11573 for C code it may have the form @samp{class @var{class-name}},
11574 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
11575 @samp{enum @var{enum-tag}}.
11576 @xref{Expressions, ,Expressions}.
11579 @item ptype [@var{arg}]
11580 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
11581 detailed description of the type, instead of just the name of the type.
11582 @xref{Expressions, ,Expressions}.
11584 For example, for this variable declaration:
11587 struct complex @{double real; double imag;@} v;
11591 the two commands give this output:
11595 (@value{GDBP}) whatis v
11596 type = struct complex
11597 (@value{GDBP}) ptype v
11598 type = struct complex @{
11606 As with @code{whatis}, using @code{ptype} without an argument refers to
11607 the type of @code{$}, the last value in the value history.
11609 @cindex incomplete type
11610 Sometimes, programs use opaque data types or incomplete specifications
11611 of complex data structure. If the debug information included in the
11612 program does not allow @value{GDBN} to display a full declaration of
11613 the data type, it will say @samp{<incomplete type>}. For example,
11614 given these declarations:
11618 struct foo *fooptr;
11622 but no definition for @code{struct foo} itself, @value{GDBN} will say:
11625 (@value{GDBP}) ptype foo
11626 $1 = <incomplete type>
11630 ``Incomplete type'' is C terminology for data types that are not
11631 completely specified.
11634 @item info types @var{regexp}
11636 Print a brief description of all types whose names match the regular
11637 expression @var{regexp} (or all types in your program, if you supply
11638 no argument). Each complete typename is matched as though it were a
11639 complete line; thus, @samp{i type value} gives information on all
11640 types in your program whose names include the string @code{value}, but
11641 @samp{i type ^value$} gives information only on types whose complete
11642 name is @code{value}.
11644 This command differs from @code{ptype} in two ways: first, like
11645 @code{whatis}, it does not print a detailed description; second, it
11646 lists all source files where a type is defined.
11649 @cindex local variables
11650 @item info scope @var{location}
11651 List all the variables local to a particular scope. This command
11652 accepts a @var{location} argument---a function name, a source line, or
11653 an address preceded by a @samp{*}, and prints all the variables local
11654 to the scope defined by that location. (@xref{Specify Location}, for
11655 details about supported forms of @var{location}.) For example:
11658 (@value{GDBP}) @b{info scope command_line_handler}
11659 Scope for command_line_handler:
11660 Symbol rl is an argument at stack/frame offset 8, length 4.
11661 Symbol linebuffer is in static storage at address 0x150a18, length 4.
11662 Symbol linelength is in static storage at address 0x150a1c, length 4.
11663 Symbol p is a local variable in register $esi, length 4.
11664 Symbol p1 is a local variable in register $ebx, length 4.
11665 Symbol nline is a local variable in register $edx, length 4.
11666 Symbol repeat is a local variable at frame offset -8, length 4.
11670 This command is especially useful for determining what data to collect
11671 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
11674 @kindex info source
11676 Show information about the current source file---that is, the source file for
11677 the function containing the current point of execution:
11680 the name of the source file, and the directory containing it,
11682 the directory it was compiled in,
11684 its length, in lines,
11686 which programming language it is written in,
11688 whether the executable includes debugging information for that file, and
11689 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
11691 whether the debugging information includes information about
11692 preprocessor macros.
11696 @kindex info sources
11698 Print the names of all source files in your program for which there is
11699 debugging information, organized into two lists: files whose symbols
11700 have already been read, and files whose symbols will be read when needed.
11702 @kindex info functions
11703 @item info functions
11704 Print the names and data types of all defined functions.
11706 @item info functions @var{regexp}
11707 Print the names and data types of all defined functions
11708 whose names contain a match for regular expression @var{regexp}.
11709 Thus, @samp{info fun step} finds all functions whose names
11710 include @code{step}; @samp{info fun ^step} finds those whose names
11711 start with @code{step}. If a function name contains characters
11712 that conflict with the regular expression language (e.g.@:
11713 @samp{operator*()}), they may be quoted with a backslash.
11715 @kindex info variables
11716 @item info variables
11717 Print the names and data types of all variables that are declared
11718 outside of functions (i.e.@: excluding local variables).
11720 @item info variables @var{regexp}
11721 Print the names and data types of all variables (except for local
11722 variables) whose names contain a match for regular expression
11725 @kindex info classes
11726 @cindex Objective-C, classes and selectors
11728 @itemx info classes @var{regexp}
11729 Display all Objective-C classes in your program, or
11730 (with the @var{regexp} argument) all those matching a particular regular
11733 @kindex info selectors
11734 @item info selectors
11735 @itemx info selectors @var{regexp}
11736 Display all Objective-C selectors in your program, or
11737 (with the @var{regexp} argument) all those matching a particular regular
11741 This was never implemented.
11742 @kindex info methods
11744 @itemx info methods @var{regexp}
11745 The @code{info methods} command permits the user to examine all defined
11746 methods within C@t{++} program, or (with the @var{regexp} argument) a
11747 specific set of methods found in the various C@t{++} classes. Many
11748 C@t{++} classes provide a large number of methods. Thus, the output
11749 from the @code{ptype} command can be overwhelming and hard to use. The
11750 @code{info-methods} command filters the methods, printing only those
11751 which match the regular-expression @var{regexp}.
11754 @cindex reloading symbols
11755 Some systems allow individual object files that make up your program to
11756 be replaced without stopping and restarting your program. For example,
11757 in VxWorks you can simply recompile a defective object file and keep on
11758 running. If you are running on one of these systems, you can allow
11759 @value{GDBN} to reload the symbols for automatically relinked modules:
11762 @kindex set symbol-reloading
11763 @item set symbol-reloading on
11764 Replace symbol definitions for the corresponding source file when an
11765 object file with a particular name is seen again.
11767 @item set symbol-reloading off
11768 Do not replace symbol definitions when encountering object files of the
11769 same name more than once. This is the default state; if you are not
11770 running on a system that permits automatic relinking of modules, you
11771 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
11772 may discard symbols when linking large programs, that may contain
11773 several modules (from different directories or libraries) with the same
11776 @kindex show symbol-reloading
11777 @item show symbol-reloading
11778 Show the current @code{on} or @code{off} setting.
11781 @cindex opaque data types
11782 @kindex set opaque-type-resolution
11783 @item set opaque-type-resolution on
11784 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
11785 declared as a pointer to a @code{struct}, @code{class}, or
11786 @code{union}---for example, @code{struct MyType *}---that is used in one
11787 source file although the full declaration of @code{struct MyType} is in
11788 another source file. The default is on.
11790 A change in the setting of this subcommand will not take effect until
11791 the next time symbols for a file are loaded.
11793 @item set opaque-type-resolution off
11794 Tell @value{GDBN} not to resolve opaque types. In this case, the type
11795 is printed as follows:
11797 @{<no data fields>@}
11800 @kindex show opaque-type-resolution
11801 @item show opaque-type-resolution
11802 Show whether opaque types are resolved or not.
11804 @kindex set print symbol-loading
11805 @cindex print messages when symbols are loaded
11806 @item set print symbol-loading
11807 @itemx set print symbol-loading on
11808 @itemx set print symbol-loading off
11809 The @code{set print symbol-loading} command allows you to enable or
11810 disable printing of messages when @value{GDBN} loads symbols.
11811 By default, these messages will be printed, and normally this is what
11812 you want. Disabling these messages is useful when debugging applications
11813 with lots of shared libraries where the quantity of output can be more
11814 annoying than useful.
11816 @kindex show print symbol-loading
11817 @item show print symbol-loading
11818 Show whether messages will be printed when @value{GDBN} loads symbols.
11820 @kindex maint print symbols
11821 @cindex symbol dump
11822 @kindex maint print psymbols
11823 @cindex partial symbol dump
11824 @item maint print symbols @var{filename}
11825 @itemx maint print psymbols @var{filename}
11826 @itemx maint print msymbols @var{filename}
11827 Write a dump of debugging symbol data into the file @var{filename}.
11828 These commands are used to debug the @value{GDBN} symbol-reading code. Only
11829 symbols with debugging data are included. If you use @samp{maint print
11830 symbols}, @value{GDBN} includes all the symbols for which it has already
11831 collected full details: that is, @var{filename} reflects symbols for
11832 only those files whose symbols @value{GDBN} has read. You can use the
11833 command @code{info sources} to find out which files these are. If you
11834 use @samp{maint print psymbols} instead, the dump shows information about
11835 symbols that @value{GDBN} only knows partially---that is, symbols defined in
11836 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
11837 @samp{maint print msymbols} dumps just the minimal symbol information
11838 required for each object file from which @value{GDBN} has read some symbols.
11839 @xref{Files, ,Commands to Specify Files}, for a discussion of how
11840 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
11842 @kindex maint info symtabs
11843 @kindex maint info psymtabs
11844 @cindex listing @value{GDBN}'s internal symbol tables
11845 @cindex symbol tables, listing @value{GDBN}'s internal
11846 @cindex full symbol tables, listing @value{GDBN}'s internal
11847 @cindex partial symbol tables, listing @value{GDBN}'s internal
11848 @item maint info symtabs @r{[} @var{regexp} @r{]}
11849 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
11851 List the @code{struct symtab} or @code{struct partial_symtab}
11852 structures whose names match @var{regexp}. If @var{regexp} is not
11853 given, list them all. The output includes expressions which you can
11854 copy into a @value{GDBN} debugging this one to examine a particular
11855 structure in more detail. For example:
11858 (@value{GDBP}) maint info psymtabs dwarf2read
11859 @{ objfile /home/gnu/build/gdb/gdb
11860 ((struct objfile *) 0x82e69d0)
11861 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
11862 ((struct partial_symtab *) 0x8474b10)
11865 text addresses 0x814d3c8 -- 0x8158074
11866 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
11867 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
11868 dependencies (none)
11871 (@value{GDBP}) maint info symtabs
11875 We see that there is one partial symbol table whose filename contains
11876 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
11877 and we see that @value{GDBN} has not read in any symtabs yet at all.
11878 If we set a breakpoint on a function, that will cause @value{GDBN} to
11879 read the symtab for the compilation unit containing that function:
11882 (@value{GDBP}) break dwarf2_psymtab_to_symtab
11883 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
11885 (@value{GDBP}) maint info symtabs
11886 @{ objfile /home/gnu/build/gdb/gdb
11887 ((struct objfile *) 0x82e69d0)
11888 @{ symtab /home/gnu/src/gdb/dwarf2read.c
11889 ((struct symtab *) 0x86c1f38)
11892 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
11893 linetable ((struct linetable *) 0x8370fa0)
11894 debugformat DWARF 2
11903 @chapter Altering Execution
11905 Once you think you have found an error in your program, you might want to
11906 find out for certain whether correcting the apparent error would lead to
11907 correct results in the rest of the run. You can find the answer by
11908 experiment, using the @value{GDBN} features for altering execution of the
11911 For example, you can store new values into variables or memory
11912 locations, give your program a signal, restart it at a different
11913 address, or even return prematurely from a function.
11916 * Assignment:: Assignment to variables
11917 * Jumping:: Continuing at a different address
11918 * Signaling:: Giving your program a signal
11919 * Returning:: Returning from a function
11920 * Calling:: Calling your program's functions
11921 * Patching:: Patching your program
11925 @section Assignment to Variables
11928 @cindex setting variables
11929 To alter the value of a variable, evaluate an assignment expression.
11930 @xref{Expressions, ,Expressions}. For example,
11937 stores the value 4 into the variable @code{x}, and then prints the
11938 value of the assignment expression (which is 4).
11939 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
11940 information on operators in supported languages.
11942 @kindex set variable
11943 @cindex variables, setting
11944 If you are not interested in seeing the value of the assignment, use the
11945 @code{set} command instead of the @code{print} command. @code{set} is
11946 really the same as @code{print} except that the expression's value is
11947 not printed and is not put in the value history (@pxref{Value History,
11948 ,Value History}). The expression is evaluated only for its effects.
11950 If the beginning of the argument string of the @code{set} command
11951 appears identical to a @code{set} subcommand, use the @code{set
11952 variable} command instead of just @code{set}. This command is identical
11953 to @code{set} except for its lack of subcommands. For example, if your
11954 program has a variable @code{width}, you get an error if you try to set
11955 a new value with just @samp{set width=13}, because @value{GDBN} has the
11956 command @code{set width}:
11959 (@value{GDBP}) whatis width
11961 (@value{GDBP}) p width
11963 (@value{GDBP}) set width=47
11964 Invalid syntax in expression.
11968 The invalid expression, of course, is @samp{=47}. In
11969 order to actually set the program's variable @code{width}, use
11972 (@value{GDBP}) set var width=47
11975 Because the @code{set} command has many subcommands that can conflict
11976 with the names of program variables, it is a good idea to use the
11977 @code{set variable} command instead of just @code{set}. For example, if
11978 your program has a variable @code{g}, you run into problems if you try
11979 to set a new value with just @samp{set g=4}, because @value{GDBN} has
11980 the command @code{set gnutarget}, abbreviated @code{set g}:
11984 (@value{GDBP}) whatis g
11988 (@value{GDBP}) set g=4
11992 The program being debugged has been started already.
11993 Start it from the beginning? (y or n) y
11994 Starting program: /home/smith/cc_progs/a.out
11995 "/home/smith/cc_progs/a.out": can't open to read symbols:
11996 Invalid bfd target.
11997 (@value{GDBP}) show g
11998 The current BFD target is "=4".
12003 The program variable @code{g} did not change, and you silently set the
12004 @code{gnutarget} to an invalid value. In order to set the variable
12008 (@value{GDBP}) set var g=4
12011 @value{GDBN} allows more implicit conversions in assignments than C; you can
12012 freely store an integer value into a pointer variable or vice versa,
12013 and you can convert any structure to any other structure that is the
12014 same length or shorter.
12015 @comment FIXME: how do structs align/pad in these conversions?
12016 @comment /doc@cygnus.com 18dec1990
12018 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
12019 construct to generate a value of specified type at a specified address
12020 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
12021 to memory location @code{0x83040} as an integer (which implies a certain size
12022 and representation in memory), and
12025 set @{int@}0x83040 = 4
12029 stores the value 4 into that memory location.
12032 @section Continuing at a Different Address
12034 Ordinarily, when you continue your program, you do so at the place where
12035 it stopped, with the @code{continue} command. You can instead continue at
12036 an address of your own choosing, with the following commands:
12040 @item jump @var{linespec}
12041 @itemx jump @var{location}
12042 Resume execution at line @var{linespec} or at address given by
12043 @var{location}. Execution stops again immediately if there is a
12044 breakpoint there. @xref{Specify Location}, for a description of the
12045 different forms of @var{linespec} and @var{location}. It is common
12046 practice to use the @code{tbreak} command in conjunction with
12047 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
12049 The @code{jump} command does not change the current stack frame, or
12050 the stack pointer, or the contents of any memory location or any
12051 register other than the program counter. If line @var{linespec} is in
12052 a different function from the one currently executing, the results may
12053 be bizarre if the two functions expect different patterns of arguments or
12054 of local variables. For this reason, the @code{jump} command requests
12055 confirmation if the specified line is not in the function currently
12056 executing. However, even bizarre results are predictable if you are
12057 well acquainted with the machine-language code of your program.
12060 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
12061 On many systems, you can get much the same effect as the @code{jump}
12062 command by storing a new value into the register @code{$pc}. The
12063 difference is that this does not start your program running; it only
12064 changes the address of where it @emph{will} run when you continue. For
12072 makes the next @code{continue} command or stepping command execute at
12073 address @code{0x485}, rather than at the address where your program stopped.
12074 @xref{Continuing and Stepping, ,Continuing and Stepping}.
12076 The most common occasion to use the @code{jump} command is to back
12077 up---perhaps with more breakpoints set---over a portion of a program
12078 that has already executed, in order to examine its execution in more
12083 @section Giving your Program a Signal
12084 @cindex deliver a signal to a program
12088 @item signal @var{signal}
12089 Resume execution where your program stopped, but immediately give it the
12090 signal @var{signal}. @var{signal} can be the name or the number of a
12091 signal. For example, on many systems @code{signal 2} and @code{signal
12092 SIGINT} are both ways of sending an interrupt signal.
12094 Alternatively, if @var{signal} is zero, continue execution without
12095 giving a signal. This is useful when your program stopped on account of
12096 a signal and would ordinary see the signal when resumed with the
12097 @code{continue} command; @samp{signal 0} causes it to resume without a
12100 @code{signal} does not repeat when you press @key{RET} a second time
12101 after executing the command.
12105 Invoking the @code{signal} command is not the same as invoking the
12106 @code{kill} utility from the shell. Sending a signal with @code{kill}
12107 causes @value{GDBN} to decide what to do with the signal depending on
12108 the signal handling tables (@pxref{Signals}). The @code{signal} command
12109 passes the signal directly to your program.
12113 @section Returning from a Function
12116 @cindex returning from a function
12119 @itemx return @var{expression}
12120 You can cancel execution of a function call with the @code{return}
12121 command. If you give an
12122 @var{expression} argument, its value is used as the function's return
12126 When you use @code{return}, @value{GDBN} discards the selected stack frame
12127 (and all frames within it). You can think of this as making the
12128 discarded frame return prematurely. If you wish to specify a value to
12129 be returned, give that value as the argument to @code{return}.
12131 This pops the selected stack frame (@pxref{Selection, ,Selecting a
12132 Frame}), and any other frames inside of it, leaving its caller as the
12133 innermost remaining frame. That frame becomes selected. The
12134 specified value is stored in the registers used for returning values
12137 The @code{return} command does not resume execution; it leaves the
12138 program stopped in the state that would exist if the function had just
12139 returned. In contrast, the @code{finish} command (@pxref{Continuing
12140 and Stepping, ,Continuing and Stepping}) resumes execution until the
12141 selected stack frame returns naturally.
12144 @section Calling Program Functions
12147 @cindex calling functions
12148 @cindex inferior functions, calling
12149 @item print @var{expr}
12150 Evaluate the expression @var{expr} and display the resulting value.
12151 @var{expr} may include calls to functions in the program being
12155 @item call @var{expr}
12156 Evaluate the expression @var{expr} without displaying @code{void}
12159 You can use this variant of the @code{print} command if you want to
12160 execute a function from your program that does not return anything
12161 (a.k.a.@: @dfn{a void function}), but without cluttering the output
12162 with @code{void} returned values that @value{GDBN} will otherwise
12163 print. If the result is not void, it is printed and saved in the
12167 It is possible for the function you call via the @code{print} or
12168 @code{call} command to generate a signal (e.g., if there's a bug in
12169 the function, or if you passed it incorrect arguments). What happens
12170 in that case is controlled by the @code{set unwindonsignal} command.
12173 @item set unwindonsignal
12174 @kindex set unwindonsignal
12175 @cindex unwind stack in called functions
12176 @cindex call dummy stack unwinding
12177 Set unwinding of the stack if a signal is received while in a function
12178 that @value{GDBN} called in the program being debugged. If set to on,
12179 @value{GDBN} unwinds the stack it created for the call and restores
12180 the context to what it was before the call. If set to off (the
12181 default), @value{GDBN} stops in the frame where the signal was
12184 @item show unwindonsignal
12185 @kindex show unwindonsignal
12186 Show the current setting of stack unwinding in the functions called by
12190 @cindex weak alias functions
12191 Sometimes, a function you wish to call is actually a @dfn{weak alias}
12192 for another function. In such case, @value{GDBN} might not pick up
12193 the type information, including the types of the function arguments,
12194 which causes @value{GDBN} to call the inferior function incorrectly.
12195 As a result, the called function will function erroneously and may
12196 even crash. A solution to that is to use the name of the aliased
12200 @section Patching Programs
12202 @cindex patching binaries
12203 @cindex writing into executables
12204 @cindex writing into corefiles
12206 By default, @value{GDBN} opens the file containing your program's
12207 executable code (or the corefile) read-only. This prevents accidental
12208 alterations to machine code; but it also prevents you from intentionally
12209 patching your program's binary.
12211 If you'd like to be able to patch the binary, you can specify that
12212 explicitly with the @code{set write} command. For example, you might
12213 want to turn on internal debugging flags, or even to make emergency
12219 @itemx set write off
12220 If you specify @samp{set write on}, @value{GDBN} opens executable and
12221 core files for both reading and writing; if you specify @samp{set write
12222 off} (the default), @value{GDBN} opens them read-only.
12224 If you have already loaded a file, you must load it again (using the
12225 @code{exec-file} or @code{core-file} command) after changing @code{set
12226 write}, for your new setting to take effect.
12230 Display whether executable files and core files are opened for writing
12231 as well as reading.
12235 @chapter @value{GDBN} Files
12237 @value{GDBN} needs to know the file name of the program to be debugged,
12238 both in order to read its symbol table and in order to start your
12239 program. To debug a core dump of a previous run, you must also tell
12240 @value{GDBN} the name of the core dump file.
12243 * Files:: Commands to specify files
12244 * Separate Debug Files:: Debugging information in separate files
12245 * Symbol Errors:: Errors reading symbol files
12249 @section Commands to Specify Files
12251 @cindex symbol table
12252 @cindex core dump file
12254 You may want to specify executable and core dump file names. The usual
12255 way to do this is at start-up time, using the arguments to
12256 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
12257 Out of @value{GDBN}}).
12259 Occasionally it is necessary to change to a different file during a
12260 @value{GDBN} session. Or you may run @value{GDBN} and forget to
12261 specify a file you want to use. Or you are debugging a remote target
12262 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
12263 Program}). In these situations the @value{GDBN} commands to specify
12264 new files are useful.
12267 @cindex executable file
12269 @item file @var{filename}
12270 Use @var{filename} as the program to be debugged. It is read for its
12271 symbols and for the contents of pure memory. It is also the program
12272 executed when you use the @code{run} command. If you do not specify a
12273 directory and the file is not found in the @value{GDBN} working directory,
12274 @value{GDBN} uses the environment variable @code{PATH} as a list of
12275 directories to search, just as the shell does when looking for a program
12276 to run. You can change the value of this variable, for both @value{GDBN}
12277 and your program, using the @code{path} command.
12279 @cindex unlinked object files
12280 @cindex patching object files
12281 You can load unlinked object @file{.o} files into @value{GDBN} using
12282 the @code{file} command. You will not be able to ``run'' an object
12283 file, but you can disassemble functions and inspect variables. Also,
12284 if the underlying BFD functionality supports it, you could use
12285 @kbd{gdb -write} to patch object files using this technique. Note
12286 that @value{GDBN} can neither interpret nor modify relocations in this
12287 case, so branches and some initialized variables will appear to go to
12288 the wrong place. But this feature is still handy from time to time.
12291 @code{file} with no argument makes @value{GDBN} discard any information it
12292 has on both executable file and the symbol table.
12295 @item exec-file @r{[} @var{filename} @r{]}
12296 Specify that the program to be run (but not the symbol table) is found
12297 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
12298 if necessary to locate your program. Omitting @var{filename} means to
12299 discard information on the executable file.
12301 @kindex symbol-file
12302 @item symbol-file @r{[} @var{filename} @r{]}
12303 Read symbol table information from file @var{filename}. @code{PATH} is
12304 searched when necessary. Use the @code{file} command to get both symbol
12305 table and program to run from the same file.
12307 @code{symbol-file} with no argument clears out @value{GDBN} information on your
12308 program's symbol table.
12310 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
12311 some breakpoints and auto-display expressions. This is because they may
12312 contain pointers to the internal data recording symbols and data types,
12313 which are part of the old symbol table data being discarded inside
12316 @code{symbol-file} does not repeat if you press @key{RET} again after
12319 When @value{GDBN} is configured for a particular environment, it
12320 understands debugging information in whatever format is the standard
12321 generated for that environment; you may use either a @sc{gnu} compiler, or
12322 other compilers that adhere to the local conventions.
12323 Best results are usually obtained from @sc{gnu} compilers; for example,
12324 using @code{@value{NGCC}} you can generate debugging information for
12327 For most kinds of object files, with the exception of old SVR3 systems
12328 using COFF, the @code{symbol-file} command does not normally read the
12329 symbol table in full right away. Instead, it scans the symbol table
12330 quickly to find which source files and which symbols are present. The
12331 details are read later, one source file at a time, as they are needed.
12333 The purpose of this two-stage reading strategy is to make @value{GDBN}
12334 start up faster. For the most part, it is invisible except for
12335 occasional pauses while the symbol table details for a particular source
12336 file are being read. (The @code{set verbose} command can turn these
12337 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
12338 Warnings and Messages}.)
12340 We have not implemented the two-stage strategy for COFF yet. When the
12341 symbol table is stored in COFF format, @code{symbol-file} reads the
12342 symbol table data in full right away. Note that ``stabs-in-COFF''
12343 still does the two-stage strategy, since the debug info is actually
12347 @cindex reading symbols immediately
12348 @cindex symbols, reading immediately
12349 @item symbol-file @var{filename} @r{[} -readnow @r{]}
12350 @itemx file @var{filename} @r{[} -readnow @r{]}
12351 You can override the @value{GDBN} two-stage strategy for reading symbol
12352 tables by using the @samp{-readnow} option with any of the commands that
12353 load symbol table information, if you want to be sure @value{GDBN} has the
12354 entire symbol table available.
12356 @c FIXME: for now no mention of directories, since this seems to be in
12357 @c flux. 13mar1992 status is that in theory GDB would look either in
12358 @c current dir or in same dir as myprog; but issues like competing
12359 @c GDB's, or clutter in system dirs, mean that in practice right now
12360 @c only current dir is used. FFish says maybe a special GDB hierarchy
12361 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
12365 @item core-file @r{[}@var{filename}@r{]}
12367 Specify the whereabouts of a core dump file to be used as the ``contents
12368 of memory''. Traditionally, core files contain only some parts of the
12369 address space of the process that generated them; @value{GDBN} can access the
12370 executable file itself for other parts.
12372 @code{core-file} with no argument specifies that no core file is
12375 Note that the core file is ignored when your program is actually running
12376 under @value{GDBN}. So, if you have been running your program and you
12377 wish to debug a core file instead, you must kill the subprocess in which
12378 the program is running. To do this, use the @code{kill} command
12379 (@pxref{Kill Process, ,Killing the Child Process}).
12381 @kindex add-symbol-file
12382 @cindex dynamic linking
12383 @item add-symbol-file @var{filename} @var{address}
12384 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
12385 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
12386 The @code{add-symbol-file} command reads additional symbol table
12387 information from the file @var{filename}. You would use this command
12388 when @var{filename} has been dynamically loaded (by some other means)
12389 into the program that is running. @var{address} should be the memory
12390 address at which the file has been loaded; @value{GDBN} cannot figure
12391 this out for itself. You can additionally specify an arbitrary number
12392 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
12393 section name and base address for that section. You can specify any
12394 @var{address} as an expression.
12396 The symbol table of the file @var{filename} is added to the symbol table
12397 originally read with the @code{symbol-file} command. You can use the
12398 @code{add-symbol-file} command any number of times; the new symbol data
12399 thus read keeps adding to the old. To discard all old symbol data
12400 instead, use the @code{symbol-file} command without any arguments.
12402 @cindex relocatable object files, reading symbols from
12403 @cindex object files, relocatable, reading symbols from
12404 @cindex reading symbols from relocatable object files
12405 @cindex symbols, reading from relocatable object files
12406 @cindex @file{.o} files, reading symbols from
12407 Although @var{filename} is typically a shared library file, an
12408 executable file, or some other object file which has been fully
12409 relocated for loading into a process, you can also load symbolic
12410 information from relocatable @file{.o} files, as long as:
12414 the file's symbolic information refers only to linker symbols defined in
12415 that file, not to symbols defined by other object files,
12417 every section the file's symbolic information refers to has actually
12418 been loaded into the inferior, as it appears in the file, and
12420 you can determine the address at which every section was loaded, and
12421 provide these to the @code{add-symbol-file} command.
12425 Some embedded operating systems, like Sun Chorus and VxWorks, can load
12426 relocatable files into an already running program; such systems
12427 typically make the requirements above easy to meet. However, it's
12428 important to recognize that many native systems use complex link
12429 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
12430 assembly, for example) that make the requirements difficult to meet. In
12431 general, one cannot assume that using @code{add-symbol-file} to read a
12432 relocatable object file's symbolic information will have the same effect
12433 as linking the relocatable object file into the program in the normal
12436 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
12438 @kindex add-symbol-file-from-memory
12439 @cindex @code{syscall DSO}
12440 @cindex load symbols from memory
12441 @item add-symbol-file-from-memory @var{address}
12442 Load symbols from the given @var{address} in a dynamically loaded
12443 object file whose image is mapped directly into the inferior's memory.
12444 For example, the Linux kernel maps a @code{syscall DSO} into each
12445 process's address space; this DSO provides kernel-specific code for
12446 some system calls. The argument can be any expression whose
12447 evaluation yields the address of the file's shared object file header.
12448 For this command to work, you must have used @code{symbol-file} or
12449 @code{exec-file} commands in advance.
12451 @kindex add-shared-symbol-files
12453 @item add-shared-symbol-files @var{library-file}
12454 @itemx assf @var{library-file}
12455 The @code{add-shared-symbol-files} command can currently be used only
12456 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
12457 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
12458 @value{GDBN} automatically looks for shared libraries, however if
12459 @value{GDBN} does not find yours, you can invoke
12460 @code{add-shared-symbol-files}. It takes one argument: the shared
12461 library's file name. @code{assf} is a shorthand alias for
12462 @code{add-shared-symbol-files}.
12465 @item section @var{section} @var{addr}
12466 The @code{section} command changes the base address of the named
12467 @var{section} of the exec file to @var{addr}. This can be used if the
12468 exec file does not contain section addresses, (such as in the
12469 @code{a.out} format), or when the addresses specified in the file
12470 itself are wrong. Each section must be changed separately. The
12471 @code{info files} command, described below, lists all the sections and
12475 @kindex info target
12478 @code{info files} and @code{info target} are synonymous; both print the
12479 current target (@pxref{Targets, ,Specifying a Debugging Target}),
12480 including the names of the executable and core dump files currently in
12481 use by @value{GDBN}, and the files from which symbols were loaded. The
12482 command @code{help target} lists all possible targets rather than
12485 @kindex maint info sections
12486 @item maint info sections
12487 Another command that can give you extra information about program sections
12488 is @code{maint info sections}. In addition to the section information
12489 displayed by @code{info files}, this command displays the flags and file
12490 offset of each section in the executable and core dump files. In addition,
12491 @code{maint info sections} provides the following command options (which
12492 may be arbitrarily combined):
12496 Display sections for all loaded object files, including shared libraries.
12497 @item @var{sections}
12498 Display info only for named @var{sections}.
12499 @item @var{section-flags}
12500 Display info only for sections for which @var{section-flags} are true.
12501 The section flags that @value{GDBN} currently knows about are:
12504 Section will have space allocated in the process when loaded.
12505 Set for all sections except those containing debug information.
12507 Section will be loaded from the file into the child process memory.
12508 Set for pre-initialized code and data, clear for @code{.bss} sections.
12510 Section needs to be relocated before loading.
12512 Section cannot be modified by the child process.
12514 Section contains executable code only.
12516 Section contains data only (no executable code).
12518 Section will reside in ROM.
12520 Section contains data for constructor/destructor lists.
12522 Section is not empty.
12524 An instruction to the linker to not output the section.
12525 @item COFF_SHARED_LIBRARY
12526 A notification to the linker that the section contains
12527 COFF shared library information.
12529 Section contains common symbols.
12532 @kindex set trust-readonly-sections
12533 @cindex read-only sections
12534 @item set trust-readonly-sections on
12535 Tell @value{GDBN} that readonly sections in your object file
12536 really are read-only (i.e.@: that their contents will not change).
12537 In that case, @value{GDBN} can fetch values from these sections
12538 out of the object file, rather than from the target program.
12539 For some targets (notably embedded ones), this can be a significant
12540 enhancement to debugging performance.
12542 The default is off.
12544 @item set trust-readonly-sections off
12545 Tell @value{GDBN} not to trust readonly sections. This means that
12546 the contents of the section might change while the program is running,
12547 and must therefore be fetched from the target when needed.
12549 @item show trust-readonly-sections
12550 Show the current setting of trusting readonly sections.
12553 All file-specifying commands allow both absolute and relative file names
12554 as arguments. @value{GDBN} always converts the file name to an absolute file
12555 name and remembers it that way.
12557 @cindex shared libraries
12558 @anchor{Shared Libraries}
12559 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
12560 and IBM RS/6000 AIX shared libraries.
12562 On MS-Windows @value{GDBN} must be linked with the Expat library to support
12563 shared libraries. @xref{Expat}.
12565 @value{GDBN} automatically loads symbol definitions from shared libraries
12566 when you use the @code{run} command, or when you examine a core file.
12567 (Before you issue the @code{run} command, @value{GDBN} does not understand
12568 references to a function in a shared library, however---unless you are
12569 debugging a core file).
12571 On HP-UX, if the program loads a library explicitly, @value{GDBN}
12572 automatically loads the symbols at the time of the @code{shl_load} call.
12574 @c FIXME: some @value{GDBN} release may permit some refs to undef
12575 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
12576 @c FIXME...lib; check this from time to time when updating manual
12578 There are times, however, when you may wish to not automatically load
12579 symbol definitions from shared libraries, such as when they are
12580 particularly large or there are many of them.
12582 To control the automatic loading of shared library symbols, use the
12586 @kindex set auto-solib-add
12587 @item set auto-solib-add @var{mode}
12588 If @var{mode} is @code{on}, symbols from all shared object libraries
12589 will be loaded automatically when the inferior begins execution, you
12590 attach to an independently started inferior, or when the dynamic linker
12591 informs @value{GDBN} that a new library has been loaded. If @var{mode}
12592 is @code{off}, symbols must be loaded manually, using the
12593 @code{sharedlibrary} command. The default value is @code{on}.
12595 @cindex memory used for symbol tables
12596 If your program uses lots of shared libraries with debug info that
12597 takes large amounts of memory, you can decrease the @value{GDBN}
12598 memory footprint by preventing it from automatically loading the
12599 symbols from shared libraries. To that end, type @kbd{set
12600 auto-solib-add off} before running the inferior, then load each
12601 library whose debug symbols you do need with @kbd{sharedlibrary
12602 @var{regexp}}, where @var{regexp} is a regular expression that matches
12603 the libraries whose symbols you want to be loaded.
12605 @kindex show auto-solib-add
12606 @item show auto-solib-add
12607 Display the current autoloading mode.
12610 @cindex load shared library
12611 To explicitly load shared library symbols, use the @code{sharedlibrary}
12615 @kindex info sharedlibrary
12618 @itemx info sharedlibrary
12619 Print the names of the shared libraries which are currently loaded.
12621 @kindex sharedlibrary
12623 @item sharedlibrary @var{regex}
12624 @itemx share @var{regex}
12625 Load shared object library symbols for files matching a
12626 Unix regular expression.
12627 As with files loaded automatically, it only loads shared libraries
12628 required by your program for a core file or after typing @code{run}. If
12629 @var{regex} is omitted all shared libraries required by your program are
12632 @item nosharedlibrary
12633 @kindex nosharedlibrary
12634 @cindex unload symbols from shared libraries
12635 Unload all shared object library symbols. This discards all symbols
12636 that have been loaded from all shared libraries. Symbols from shared
12637 libraries that were loaded by explicit user requests are not
12641 Sometimes you may wish that @value{GDBN} stops and gives you control
12642 when any of shared library events happen. Use the @code{set
12643 stop-on-solib-events} command for this:
12646 @item set stop-on-solib-events
12647 @kindex set stop-on-solib-events
12648 This command controls whether @value{GDBN} should give you control
12649 when the dynamic linker notifies it about some shared library event.
12650 The most common event of interest is loading or unloading of a new
12653 @item show stop-on-solib-events
12654 @kindex show stop-on-solib-events
12655 Show whether @value{GDBN} stops and gives you control when shared
12656 library events happen.
12659 Shared libraries are also supported in many cross or remote debugging
12660 configurations. @value{GDBN} needs to have access to the target's libraries;
12661 this can be accomplished either by providing copies of the libraries
12662 on the host system, or by asking @value{GDBN} to automatically retrieve the
12663 libraries from the target. If copies of the target libraries are
12664 provided, they need to be the same as the target libraries, although the
12665 copies on the target can be stripped as long as the copies on the host are
12668 @cindex where to look for shared libraries
12669 For remote debugging, you need to tell @value{GDBN} where the target
12670 libraries are, so that it can load the correct copies---otherwise, it
12671 may try to load the host's libraries. @value{GDBN} has two variables
12672 to specify the search directories for target libraries.
12675 @cindex prefix for shared library file names
12676 @cindex system root, alternate
12677 @kindex set solib-absolute-prefix
12678 @kindex set sysroot
12679 @item set sysroot @var{path}
12680 Use @var{path} as the system root for the program being debugged. Any
12681 absolute shared library paths will be prefixed with @var{path}; many
12682 runtime loaders store the absolute paths to the shared library in the
12683 target program's memory. If you use @code{set sysroot} to find shared
12684 libraries, they need to be laid out in the same way that they are on
12685 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
12688 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
12689 retrieve the target libraries from the remote system. This is only
12690 supported when using a remote target that supports the @code{remote get}
12691 command (@pxref{File Transfer,,Sending files to a remote system}).
12692 The part of @var{path} following the initial @file{remote:}
12693 (if present) is used as system root prefix on the remote file system.
12694 @footnote{If you want to specify a local system root using a directory
12695 that happens to be named @file{remote:}, you need to use some equivalent
12696 variant of the name like @file{./remote:}.}
12698 The @code{set solib-absolute-prefix} command is an alias for @code{set
12701 @cindex default system root
12702 @cindex @samp{--with-sysroot}
12703 You can set the default system root by using the configure-time
12704 @samp{--with-sysroot} option. If the system root is inside
12705 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
12706 @samp{--exec-prefix}), then the default system root will be updated
12707 automatically if the installed @value{GDBN} is moved to a new
12710 @kindex show sysroot
12712 Display the current shared library prefix.
12714 @kindex set solib-search-path
12715 @item set solib-search-path @var{path}
12716 If this variable is set, @var{path} is a colon-separated list of
12717 directories to search for shared libraries. @samp{solib-search-path}
12718 is used after @samp{sysroot} fails to locate the library, or if the
12719 path to the library is relative instead of absolute. If you want to
12720 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
12721 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
12722 finding your host's libraries. @samp{sysroot} is preferred; setting
12723 it to a nonexistent directory may interfere with automatic loading
12724 of shared library symbols.
12726 @kindex show solib-search-path
12727 @item show solib-search-path
12728 Display the current shared library search path.
12732 @node Separate Debug Files
12733 @section Debugging Information in Separate Files
12734 @cindex separate debugging information files
12735 @cindex debugging information in separate files
12736 @cindex @file{.debug} subdirectories
12737 @cindex debugging information directory, global
12738 @cindex global debugging information directory
12739 @cindex build ID, and separate debugging files
12740 @cindex @file{.build-id} directory
12742 @value{GDBN} allows you to put a program's debugging information in a
12743 file separate from the executable itself, in a way that allows
12744 @value{GDBN} to find and load the debugging information automatically.
12745 Since debugging information can be very large---sometimes larger
12746 than the executable code itself---some systems distribute debugging
12747 information for their executables in separate files, which users can
12748 install only when they need to debug a problem.
12750 @value{GDBN} supports two ways of specifying the separate debug info
12755 The executable contains a @dfn{debug link} that specifies the name of
12756 the separate debug info file. The separate debug file's name is
12757 usually @file{@var{executable}.debug}, where @var{executable} is the
12758 name of the corresponding executable file without leading directories
12759 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
12760 debug link specifies a CRC32 checksum for the debug file, which
12761 @value{GDBN} uses to validate that the executable and the debug file
12762 came from the same build.
12765 The executable contains a @dfn{build ID}, a unique bit string that is
12766 also present in the corresponding debug info file. (This is supported
12767 only on some operating systems, notably those which use the ELF format
12768 for binary files and the @sc{gnu} Binutils.) For more details about
12769 this feature, see the description of the @option{--build-id}
12770 command-line option in @ref{Options, , Command Line Options, ld.info,
12771 The GNU Linker}. The debug info file's name is not specified
12772 explicitly by the build ID, but can be computed from the build ID, see
12776 Depending on the way the debug info file is specified, @value{GDBN}
12777 uses two different methods of looking for the debug file:
12781 For the ``debug link'' method, @value{GDBN} looks up the named file in
12782 the directory of the executable file, then in a subdirectory of that
12783 directory named @file{.debug}, and finally under the global debug
12784 directory, in a subdirectory whose name is identical to the leading
12785 directories of the executable's absolute file name.
12788 For the ``build ID'' method, @value{GDBN} looks in the
12789 @file{.build-id} subdirectory of the global debug directory for a file
12790 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
12791 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
12792 are the rest of the bit string. (Real build ID strings are 32 or more
12793 hex characters, not 10.)
12796 So, for example, suppose you ask @value{GDBN} to debug
12797 @file{/usr/bin/ls}, which has a debug link that specifies the
12798 file @file{ls.debug}, and a build ID whose value in hex is
12799 @code{abcdef1234}. If the global debug directory is
12800 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
12801 debug information files, in the indicated order:
12805 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
12807 @file{/usr/bin/ls.debug}
12809 @file{/usr/bin/.debug/ls.debug}
12811 @file{/usr/lib/debug/usr/bin/ls.debug}.
12814 You can set the global debugging info directory's name, and view the
12815 name @value{GDBN} is currently using.
12819 @kindex set debug-file-directory
12820 @item set debug-file-directory @var{directory}
12821 Set the directory which @value{GDBN} searches for separate debugging
12822 information files to @var{directory}.
12824 @kindex show debug-file-directory
12825 @item show debug-file-directory
12826 Show the directory @value{GDBN} searches for separate debugging
12831 @cindex @code{.gnu_debuglink} sections
12832 @cindex debug link sections
12833 A debug link is a special section of the executable file named
12834 @code{.gnu_debuglink}. The section must contain:
12838 A filename, with any leading directory components removed, followed by
12841 zero to three bytes of padding, as needed to reach the next four-byte
12842 boundary within the section, and
12844 a four-byte CRC checksum, stored in the same endianness used for the
12845 executable file itself. The checksum is computed on the debugging
12846 information file's full contents by the function given below, passing
12847 zero as the @var{crc} argument.
12850 Any executable file format can carry a debug link, as long as it can
12851 contain a section named @code{.gnu_debuglink} with the contents
12854 @cindex @code{.note.gnu.build-id} sections
12855 @cindex build ID sections
12856 The build ID is a special section in the executable file (and in other
12857 ELF binary files that @value{GDBN} may consider). This section is
12858 often named @code{.note.gnu.build-id}, but that name is not mandatory.
12859 It contains unique identification for the built files---the ID remains
12860 the same across multiple builds of the same build tree. The default
12861 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
12862 content for the build ID string. The same section with an identical
12863 value is present in the original built binary with symbols, in its
12864 stripped variant, and in the separate debugging information file.
12866 The debugging information file itself should be an ordinary
12867 executable, containing a full set of linker symbols, sections, and
12868 debugging information. The sections of the debugging information file
12869 should have the same names, addresses, and sizes as the original file,
12870 but they need not contain any data---much like a @code{.bss} section
12871 in an ordinary executable.
12873 The @sc{gnu} binary utilities (Binutils) package includes the
12874 @samp{objcopy} utility that can produce
12875 the separated executable / debugging information file pairs using the
12876 following commands:
12879 @kbd{objcopy --only-keep-debug foo foo.debug}
12884 These commands remove the debugging
12885 information from the executable file @file{foo} and place it in the file
12886 @file{foo.debug}. You can use the first, second or both methods to link the
12891 The debug link method needs the following additional command to also leave
12892 behind a debug link in @file{foo}:
12895 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
12898 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
12899 a version of the @code{strip} command such that the command @kbd{strip foo -f
12900 foo.debug} has the same functionality as the two @code{objcopy} commands and
12901 the @code{ln -s} command above, together.
12904 Build ID gets embedded into the main executable using @code{ld --build-id} or
12905 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
12906 compatibility fixes for debug files separation are present in @sc{gnu} binary
12907 utilities (Binutils) package since version 2.18.
12912 Since there are many different ways to compute CRC's for the debug
12913 link (different polynomials, reversals, byte ordering, etc.), the
12914 simplest way to describe the CRC used in @code{.gnu_debuglink}
12915 sections is to give the complete code for a function that computes it:
12917 @kindex gnu_debuglink_crc32
12920 gnu_debuglink_crc32 (unsigned long crc,
12921 unsigned char *buf, size_t len)
12923 static const unsigned long crc32_table[256] =
12925 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
12926 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
12927 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
12928 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
12929 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
12930 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
12931 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
12932 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
12933 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
12934 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
12935 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
12936 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
12937 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
12938 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
12939 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
12940 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
12941 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
12942 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
12943 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
12944 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
12945 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
12946 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
12947 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
12948 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
12949 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
12950 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
12951 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
12952 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
12953 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
12954 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
12955 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
12956 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
12957 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
12958 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
12959 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
12960 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
12961 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
12962 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
12963 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
12964 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
12965 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
12966 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
12967 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
12968 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
12969 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
12970 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
12971 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
12972 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
12973 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
12974 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
12975 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
12978 unsigned char *end;
12980 crc = ~crc & 0xffffffff;
12981 for (end = buf + len; buf < end; ++buf)
12982 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
12983 return ~crc & 0xffffffff;
12988 This computation does not apply to the ``build ID'' method.
12991 @node Symbol Errors
12992 @section Errors Reading Symbol Files
12994 While reading a symbol file, @value{GDBN} occasionally encounters problems,
12995 such as symbol types it does not recognize, or known bugs in compiler
12996 output. By default, @value{GDBN} does not notify you of such problems, since
12997 they are relatively common and primarily of interest to people
12998 debugging compilers. If you are interested in seeing information
12999 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
13000 only one message about each such type of problem, no matter how many
13001 times the problem occurs; or you can ask @value{GDBN} to print more messages,
13002 to see how many times the problems occur, with the @code{set
13003 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
13006 The messages currently printed, and their meanings, include:
13009 @item inner block not inside outer block in @var{symbol}
13011 The symbol information shows where symbol scopes begin and end
13012 (such as at the start of a function or a block of statements). This
13013 error indicates that an inner scope block is not fully contained
13014 in its outer scope blocks.
13016 @value{GDBN} circumvents the problem by treating the inner block as if it had
13017 the same scope as the outer block. In the error message, @var{symbol}
13018 may be shown as ``@code{(don't know)}'' if the outer block is not a
13021 @item block at @var{address} out of order
13023 The symbol information for symbol scope blocks should occur in
13024 order of increasing addresses. This error indicates that it does not
13027 @value{GDBN} does not circumvent this problem, and has trouble
13028 locating symbols in the source file whose symbols it is reading. (You
13029 can often determine what source file is affected by specifying
13030 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
13033 @item bad block start address patched
13035 The symbol information for a symbol scope block has a start address
13036 smaller than the address of the preceding source line. This is known
13037 to occur in the SunOS 4.1.1 (and earlier) C compiler.
13039 @value{GDBN} circumvents the problem by treating the symbol scope block as
13040 starting on the previous source line.
13042 @item bad string table offset in symbol @var{n}
13045 Symbol number @var{n} contains a pointer into the string table which is
13046 larger than the size of the string table.
13048 @value{GDBN} circumvents the problem by considering the symbol to have the
13049 name @code{foo}, which may cause other problems if many symbols end up
13052 @item unknown symbol type @code{0x@var{nn}}
13054 The symbol information contains new data types that @value{GDBN} does
13055 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
13056 uncomprehended information, in hexadecimal.
13058 @value{GDBN} circumvents the error by ignoring this symbol information.
13059 This usually allows you to debug your program, though certain symbols
13060 are not accessible. If you encounter such a problem and feel like
13061 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
13062 on @code{complain}, then go up to the function @code{read_dbx_symtab}
13063 and examine @code{*bufp} to see the symbol.
13065 @item stub type has NULL name
13067 @value{GDBN} could not find the full definition for a struct or class.
13069 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
13070 The symbol information for a C@t{++} member function is missing some
13071 information that recent versions of the compiler should have output for
13074 @item info mismatch between compiler and debugger
13076 @value{GDBN} could not parse a type specification output by the compiler.
13081 @chapter Specifying a Debugging Target
13083 @cindex debugging target
13084 A @dfn{target} is the execution environment occupied by your program.
13086 Often, @value{GDBN} runs in the same host environment as your program;
13087 in that case, the debugging target is specified as a side effect when
13088 you use the @code{file} or @code{core} commands. When you need more
13089 flexibility---for example, running @value{GDBN} on a physically separate
13090 host, or controlling a standalone system over a serial port or a
13091 realtime system over a TCP/IP connection---you can use the @code{target}
13092 command to specify one of the target types configured for @value{GDBN}
13093 (@pxref{Target Commands, ,Commands for Managing Targets}).
13095 @cindex target architecture
13096 It is possible to build @value{GDBN} for several different @dfn{target
13097 architectures}. When @value{GDBN} is built like that, you can choose
13098 one of the available architectures with the @kbd{set architecture}
13102 @kindex set architecture
13103 @kindex show architecture
13104 @item set architecture @var{arch}
13105 This command sets the current target architecture to @var{arch}. The
13106 value of @var{arch} can be @code{"auto"}, in addition to one of the
13107 supported architectures.
13109 @item show architecture
13110 Show the current target architecture.
13112 @item set processor
13114 @kindex set processor
13115 @kindex show processor
13116 These are alias commands for, respectively, @code{set architecture}
13117 and @code{show architecture}.
13121 * Active Targets:: Active targets
13122 * Target Commands:: Commands for managing targets
13123 * Byte Order:: Choosing target byte order
13126 @node Active Targets
13127 @section Active Targets
13129 @cindex stacking targets
13130 @cindex active targets
13131 @cindex multiple targets
13133 There are three classes of targets: processes, core files, and
13134 executable files. @value{GDBN} can work concurrently on up to three
13135 active targets, one in each class. This allows you to (for example)
13136 start a process and inspect its activity without abandoning your work on
13139 For example, if you execute @samp{gdb a.out}, then the executable file
13140 @code{a.out} is the only active target. If you designate a core file as
13141 well---presumably from a prior run that crashed and coredumped---then
13142 @value{GDBN} has two active targets and uses them in tandem, looking
13143 first in the corefile target, then in the executable file, to satisfy
13144 requests for memory addresses. (Typically, these two classes of target
13145 are complementary, since core files contain only a program's
13146 read-write memory---variables and so on---plus machine status, while
13147 executable files contain only the program text and initialized data.)
13149 When you type @code{run}, your executable file becomes an active process
13150 target as well. When a process target is active, all @value{GDBN}
13151 commands requesting memory addresses refer to that target; addresses in
13152 an active core file or executable file target are obscured while the
13153 process target is active.
13155 Use the @code{core-file} and @code{exec-file} commands to select a new
13156 core file or executable target (@pxref{Files, ,Commands to Specify
13157 Files}). To specify as a target a process that is already running, use
13158 the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
13161 @node Target Commands
13162 @section Commands for Managing Targets
13165 @item target @var{type} @var{parameters}
13166 Connects the @value{GDBN} host environment to a target machine or
13167 process. A target is typically a protocol for talking to debugging
13168 facilities. You use the argument @var{type} to specify the type or
13169 protocol of the target machine.
13171 Further @var{parameters} are interpreted by the target protocol, but
13172 typically include things like device names or host names to connect
13173 with, process numbers, and baud rates.
13175 The @code{target} command does not repeat if you press @key{RET} again
13176 after executing the command.
13178 @kindex help target
13180 Displays the names of all targets available. To display targets
13181 currently selected, use either @code{info target} or @code{info files}
13182 (@pxref{Files, ,Commands to Specify Files}).
13184 @item help target @var{name}
13185 Describe a particular target, including any parameters necessary to
13188 @kindex set gnutarget
13189 @item set gnutarget @var{args}
13190 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
13191 knows whether it is reading an @dfn{executable},
13192 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
13193 with the @code{set gnutarget} command. Unlike most @code{target} commands,
13194 with @code{gnutarget} the @code{target} refers to a program, not a machine.
13197 @emph{Warning:} To specify a file format with @code{set gnutarget},
13198 you must know the actual BFD name.
13202 @xref{Files, , Commands to Specify Files}.
13204 @kindex show gnutarget
13205 @item show gnutarget
13206 Use the @code{show gnutarget} command to display what file format
13207 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
13208 @value{GDBN} will determine the file format for each file automatically,
13209 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
13212 @cindex common targets
13213 Here are some common targets (available, or not, depending on the GDB
13218 @item target exec @var{program}
13219 @cindex executable file target
13220 An executable file. @samp{target exec @var{program}} is the same as
13221 @samp{exec-file @var{program}}.
13223 @item target core @var{filename}
13224 @cindex core dump file target
13225 A core dump file. @samp{target core @var{filename}} is the same as
13226 @samp{core-file @var{filename}}.
13228 @item target remote @var{medium}
13229 @cindex remote target
13230 A remote system connected to @value{GDBN} via a serial line or network
13231 connection. This command tells @value{GDBN} to use its own remote
13232 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
13234 For example, if you have a board connected to @file{/dev/ttya} on the
13235 machine running @value{GDBN}, you could say:
13238 target remote /dev/ttya
13241 @code{target remote} supports the @code{load} command. This is only
13242 useful if you have some other way of getting the stub to the target
13243 system, and you can put it somewhere in memory where it won't get
13244 clobbered by the download.
13247 @cindex built-in simulator target
13248 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
13256 works; however, you cannot assume that a specific memory map, device
13257 drivers, or even basic I/O is available, although some simulators do
13258 provide these. For info about any processor-specific simulator details,
13259 see the appropriate section in @ref{Embedded Processors, ,Embedded
13264 Some configurations may include these targets as well:
13268 @item target nrom @var{dev}
13269 @cindex NetROM ROM emulator target
13270 NetROM ROM emulator. This target only supports downloading.
13274 Different targets are available on different configurations of @value{GDBN};
13275 your configuration may have more or fewer targets.
13277 Many remote targets require you to download the executable's code once
13278 you've successfully established a connection. You may wish to control
13279 various aspects of this process.
13284 @kindex set hash@r{, for remote monitors}
13285 @cindex hash mark while downloading
13286 This command controls whether a hash mark @samp{#} is displayed while
13287 downloading a file to the remote monitor. If on, a hash mark is
13288 displayed after each S-record is successfully downloaded to the
13292 @kindex show hash@r{, for remote monitors}
13293 Show the current status of displaying the hash mark.
13295 @item set debug monitor
13296 @kindex set debug monitor
13297 @cindex display remote monitor communications
13298 Enable or disable display of communications messages between
13299 @value{GDBN} and the remote monitor.
13301 @item show debug monitor
13302 @kindex show debug monitor
13303 Show the current status of displaying communications between
13304 @value{GDBN} and the remote monitor.
13309 @kindex load @var{filename}
13310 @item load @var{filename}
13312 Depending on what remote debugging facilities are configured into
13313 @value{GDBN}, the @code{load} command may be available. Where it exists, it
13314 is meant to make @var{filename} (an executable) available for debugging
13315 on the remote system---by downloading, or dynamic linking, for example.
13316 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
13317 the @code{add-symbol-file} command.
13319 If your @value{GDBN} does not have a @code{load} command, attempting to
13320 execute it gets the error message ``@code{You can't do that when your
13321 target is @dots{}}''
13323 The file is loaded at whatever address is specified in the executable.
13324 For some object file formats, you can specify the load address when you
13325 link the program; for other formats, like a.out, the object file format
13326 specifies a fixed address.
13327 @c FIXME! This would be a good place for an xref to the GNU linker doc.
13329 Depending on the remote side capabilities, @value{GDBN} may be able to
13330 load programs into flash memory.
13332 @code{load} does not repeat if you press @key{RET} again after using it.
13336 @section Choosing Target Byte Order
13338 @cindex choosing target byte order
13339 @cindex target byte order
13341 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
13342 offer the ability to run either big-endian or little-endian byte
13343 orders. Usually the executable or symbol will include a bit to
13344 designate the endian-ness, and you will not need to worry about
13345 which to use. However, you may still find it useful to adjust
13346 @value{GDBN}'s idea of processor endian-ness manually.
13350 @item set endian big
13351 Instruct @value{GDBN} to assume the target is big-endian.
13353 @item set endian little
13354 Instruct @value{GDBN} to assume the target is little-endian.
13356 @item set endian auto
13357 Instruct @value{GDBN} to use the byte order associated with the
13361 Display @value{GDBN}'s current idea of the target byte order.
13365 Note that these commands merely adjust interpretation of symbolic
13366 data on the host, and that they have absolutely no effect on the
13370 @node Remote Debugging
13371 @chapter Debugging Remote Programs
13372 @cindex remote debugging
13374 If you are trying to debug a program running on a machine that cannot run
13375 @value{GDBN} in the usual way, it is often useful to use remote debugging.
13376 For example, you might use remote debugging on an operating system kernel,
13377 or on a small system which does not have a general purpose operating system
13378 powerful enough to run a full-featured debugger.
13380 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
13381 to make this work with particular debugging targets. In addition,
13382 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
13383 but not specific to any particular target system) which you can use if you
13384 write the remote stubs---the code that runs on the remote system to
13385 communicate with @value{GDBN}.
13387 Other remote targets may be available in your
13388 configuration of @value{GDBN}; use @code{help target} to list them.
13391 * Connecting:: Connecting to a remote target
13392 * File Transfer:: Sending files to a remote system
13393 * Server:: Using the gdbserver program
13394 * Remote Configuration:: Remote configuration
13395 * Remote Stub:: Implementing a remote stub
13399 @section Connecting to a Remote Target
13401 On the @value{GDBN} host machine, you will need an unstripped copy of
13402 your program, since @value{GDBN} needs symbol and debugging information.
13403 Start up @value{GDBN} as usual, using the name of the local copy of your
13404 program as the first argument.
13406 @cindex @code{target remote}
13407 @value{GDBN} can communicate with the target over a serial line, or
13408 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
13409 each case, @value{GDBN} uses the same protocol for debugging your
13410 program; only the medium carrying the debugging packets varies. The
13411 @code{target remote} command establishes a connection to the target.
13412 Its arguments indicate which medium to use:
13416 @item target remote @var{serial-device}
13417 @cindex serial line, @code{target remote}
13418 Use @var{serial-device} to communicate with the target. For example,
13419 to use a serial line connected to the device named @file{/dev/ttyb}:
13422 target remote /dev/ttyb
13425 If you're using a serial line, you may want to give @value{GDBN} the
13426 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
13427 (@pxref{Remote Configuration, set remotebaud}) before the
13428 @code{target} command.
13430 @item target remote @code{@var{host}:@var{port}}
13431 @itemx target remote @code{tcp:@var{host}:@var{port}}
13432 @cindex @acronym{TCP} port, @code{target remote}
13433 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
13434 The @var{host} may be either a host name or a numeric @acronym{IP}
13435 address; @var{port} must be a decimal number. The @var{host} could be
13436 the target machine itself, if it is directly connected to the net, or
13437 it might be a terminal server which in turn has a serial line to the
13440 For example, to connect to port 2828 on a terminal server named
13444 target remote manyfarms:2828
13447 If your remote target is actually running on the same machine as your
13448 debugger session (e.g.@: a simulator for your target running on the
13449 same host), you can omit the hostname. For example, to connect to
13450 port 1234 on your local machine:
13453 target remote :1234
13457 Note that the colon is still required here.
13459 @item target remote @code{udp:@var{host}:@var{port}}
13460 @cindex @acronym{UDP} port, @code{target remote}
13461 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
13462 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
13465 target remote udp:manyfarms:2828
13468 When using a @acronym{UDP} connection for remote debugging, you should
13469 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
13470 can silently drop packets on busy or unreliable networks, which will
13471 cause havoc with your debugging session.
13473 @item target remote | @var{command}
13474 @cindex pipe, @code{target remote} to
13475 Run @var{command} in the background and communicate with it using a
13476 pipe. The @var{command} is a shell command, to be parsed and expanded
13477 by the system's command shell, @code{/bin/sh}; it should expect remote
13478 protocol packets on its standard input, and send replies on its
13479 standard output. You could use this to run a stand-alone simulator
13480 that speaks the remote debugging protocol, to make net connections
13481 using programs like @code{ssh}, or for other similar tricks.
13483 If @var{command} closes its standard output (perhaps by exiting),
13484 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
13485 program has already exited, this will have no effect.)
13489 Once the connection has been established, you can use all the usual
13490 commands to examine and change data. The remote program is already
13491 running; you can use @kbd{step} and @kbd{continue}, and you do not
13492 need to use @kbd{run}.
13494 @cindex interrupting remote programs
13495 @cindex remote programs, interrupting
13496 Whenever @value{GDBN} is waiting for the remote program, if you type the
13497 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
13498 program. This may or may not succeed, depending in part on the hardware
13499 and the serial drivers the remote system uses. If you type the
13500 interrupt character once again, @value{GDBN} displays this prompt:
13503 Interrupted while waiting for the program.
13504 Give up (and stop debugging it)? (y or n)
13507 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
13508 (If you decide you want to try again later, you can use @samp{target
13509 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
13510 goes back to waiting.
13513 @kindex detach (remote)
13515 When you have finished debugging the remote program, you can use the
13516 @code{detach} command to release it from @value{GDBN} control.
13517 Detaching from the target normally resumes its execution, but the results
13518 will depend on your particular remote stub. After the @code{detach}
13519 command, @value{GDBN} is free to connect to another target.
13523 The @code{disconnect} command behaves like @code{detach}, except that
13524 the target is generally not resumed. It will wait for @value{GDBN}
13525 (this instance or another one) to connect and continue debugging. After
13526 the @code{disconnect} command, @value{GDBN} is again free to connect to
13529 @cindex send command to remote monitor
13530 @cindex extend @value{GDBN} for remote targets
13531 @cindex add new commands for external monitor
13533 @item monitor @var{cmd}
13534 This command allows you to send arbitrary commands directly to the
13535 remote monitor. Since @value{GDBN} doesn't care about the commands it
13536 sends like this, this command is the way to extend @value{GDBN}---you
13537 can add new commands that only the external monitor will understand
13541 @node File Transfer
13542 @section Sending files to a remote system
13543 @cindex remote target, file transfer
13544 @cindex file transfer
13545 @cindex sending files to remote systems
13547 Some remote targets offer the ability to transfer files over the same
13548 connection used to communicate with @value{GDBN}. This is convenient
13549 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
13550 running @code{gdbserver} over a network interface. For other targets,
13551 e.g.@: embedded devices with only a single serial port, this may be
13552 the only way to upload or download files.
13554 Not all remote targets support these commands.
13558 @item remote put @var{hostfile} @var{targetfile}
13559 Copy file @var{hostfile} from the host system (the machine running
13560 @value{GDBN}) to @var{targetfile} on the target system.
13563 @item remote get @var{targetfile} @var{hostfile}
13564 Copy file @var{targetfile} from the target system to @var{hostfile}
13565 on the host system.
13567 @kindex remote delete
13568 @item remote delete @var{targetfile}
13569 Delete @var{targetfile} from the target system.
13574 @section Using the @code{gdbserver} Program
13577 @cindex remote connection without stubs
13578 @code{gdbserver} is a control program for Unix-like systems, which
13579 allows you to connect your program with a remote @value{GDBN} via
13580 @code{target remote}---but without linking in the usual debugging stub.
13582 @code{gdbserver} is not a complete replacement for the debugging stubs,
13583 because it requires essentially the same operating-system facilities
13584 that @value{GDBN} itself does. In fact, a system that can run
13585 @code{gdbserver} to connect to a remote @value{GDBN} could also run
13586 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
13587 because it is a much smaller program than @value{GDBN} itself. It is
13588 also easier to port than all of @value{GDBN}, so you may be able to get
13589 started more quickly on a new system by using @code{gdbserver}.
13590 Finally, if you develop code for real-time systems, you may find that
13591 the tradeoffs involved in real-time operation make it more convenient to
13592 do as much development work as possible on another system, for example
13593 by cross-compiling. You can use @code{gdbserver} to make a similar
13594 choice for debugging.
13596 @value{GDBN} and @code{gdbserver} communicate via either a serial line
13597 or a TCP connection, using the standard @value{GDBN} remote serial
13601 @emph{Warning:} @code{gdbserver} does not have any built-in security.
13602 Do not run @code{gdbserver} connected to any public network; a
13603 @value{GDBN} connection to @code{gdbserver} provides access to the
13604 target system with the same privileges as the user running
13608 @subsection Running @code{gdbserver}
13609 @cindex arguments, to @code{gdbserver}
13611 Run @code{gdbserver} on the target system. You need a copy of the
13612 program you want to debug, including any libraries it requires.
13613 @code{gdbserver} does not need your program's symbol table, so you can
13614 strip the program if necessary to save space. @value{GDBN} on the host
13615 system does all the symbol handling.
13617 To use the server, you must tell it how to communicate with @value{GDBN};
13618 the name of your program; and the arguments for your program. The usual
13622 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
13625 @var{comm} is either a device name (to use a serial line) or a TCP
13626 hostname and portnumber. For example, to debug Emacs with the argument
13627 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
13631 target> gdbserver /dev/com1 emacs foo.txt
13634 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
13637 To use a TCP connection instead of a serial line:
13640 target> gdbserver host:2345 emacs foo.txt
13643 The only difference from the previous example is the first argument,
13644 specifying that you are communicating with the host @value{GDBN} via
13645 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
13646 expect a TCP connection from machine @samp{host} to local TCP port 2345.
13647 (Currently, the @samp{host} part is ignored.) You can choose any number
13648 you want for the port number as long as it does not conflict with any
13649 TCP ports already in use on the target system (for example, @code{23} is
13650 reserved for @code{telnet}).@footnote{If you choose a port number that
13651 conflicts with another service, @code{gdbserver} prints an error message
13652 and exits.} You must use the same port number with the host @value{GDBN}
13653 @code{target remote} command.
13655 @subsubsection Attaching to a Running Program
13657 On some targets, @code{gdbserver} can also attach to running programs.
13658 This is accomplished via the @code{--attach} argument. The syntax is:
13661 target> gdbserver --attach @var{comm} @var{pid}
13664 @var{pid} is the process ID of a currently running process. It isn't necessary
13665 to point @code{gdbserver} at a binary for the running process.
13668 @cindex attach to a program by name
13669 You can debug processes by name instead of process ID if your target has the
13670 @code{pidof} utility:
13673 target> gdbserver --attach @var{comm} `pidof @var{program}`
13676 In case more than one copy of @var{program} is running, or @var{program}
13677 has multiple threads, most versions of @code{pidof} support the
13678 @code{-s} option to only return the first process ID.
13680 @subsubsection Multi-Process Mode for @code{gdbserver}
13681 @cindex gdbserver, multiple processes
13682 @cindex multiple processes with gdbserver
13684 When you connect to @code{gdbserver} using @code{target remote},
13685 @code{gdbserver} debugs the specified program only once. When the
13686 program exits, or you detach from it, @value{GDBN} closes the connection
13687 and @code{gdbserver} exits.
13689 If you connect using @kbd{target extended-remote}, @code{gdbserver}
13690 enters multi-process mode. When the debugged program exits, or you
13691 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
13692 though no program is running. The @code{run} and @code{attach}
13693 commands instruct @code{gdbserver} to run or attach to a new program.
13694 The @code{run} command uses @code{set remote exec-file} (@pxref{set
13695 remote exec-file}) to select the program to run. Command line
13696 arguments are supported, except for wildcard expansion and I/O
13697 redirection (@pxref{Arguments}).
13699 To start @code{gdbserver} without supplying an initial command to run
13700 or process ID to attach, use the @option{--multi} command line option.
13701 Then you can connect using @kbd{target extended-remote} and start
13702 the program you want to debug.
13704 @code{gdbserver} does not automatically exit in multi-process mode.
13705 You can terminate it by using @code{monitor exit}
13706 (@pxref{Monitor Commands for gdbserver}).
13708 @subsubsection Other Command-Line Arguments for @code{gdbserver}
13710 You can include @option{--debug} on the @code{gdbserver} command line.
13711 @code{gdbserver} will display extra status information about the debugging
13712 process. This option is intended for @code{gdbserver} development and
13713 for bug reports to the developers.
13715 The @option{--wrapper} option specifies a wrapper to launch programs
13716 for debugging. The option should be followed by the name of the
13717 wrapper, then any command-line arguments to pass to the wrapper, then
13718 @kbd{--} indicating the end of the wrapper arguments.
13720 @code{gdbserver} runs the specified wrapper program with a combined
13721 command line including the wrapper arguments, then the name of the
13722 program to debug, then any arguments to the program. The wrapper
13723 runs until it executes your program, and then @value{GDBN} gains control.
13725 You can use any program that eventually calls @code{execve} with
13726 its arguments as a wrapper. Several standard Unix utilities do
13727 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
13728 with @code{exec "$@@"} will also work.
13730 For example, you can use @code{env} to pass an environment variable to
13731 the debugged program, without setting the variable in @code{gdbserver}'s
13735 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
13738 @subsection Connecting to @code{gdbserver}
13740 Run @value{GDBN} on the host system.
13742 First make sure you have the necessary symbol files. Load symbols for
13743 your application using the @code{file} command before you connect. Use
13744 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
13745 was compiled with the correct sysroot using @code{--with-sysroot}).
13747 The symbol file and target libraries must exactly match the executable
13748 and libraries on the target, with one exception: the files on the host
13749 system should not be stripped, even if the files on the target system
13750 are. Mismatched or missing files will lead to confusing results
13751 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
13752 files may also prevent @code{gdbserver} from debugging multi-threaded
13755 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
13756 For TCP connections, you must start up @code{gdbserver} prior to using
13757 the @code{target remote} command. Otherwise you may get an error whose
13758 text depends on the host system, but which usually looks something like
13759 @samp{Connection refused}. Don't use the @code{load}
13760 command in @value{GDBN} when using @code{gdbserver}, since the program is
13761 already on the target.
13763 @subsection Monitor Commands for @code{gdbserver}
13764 @cindex monitor commands, for @code{gdbserver}
13765 @anchor{Monitor Commands for gdbserver}
13767 During a @value{GDBN} session using @code{gdbserver}, you can use the
13768 @code{monitor} command to send special requests to @code{gdbserver}.
13769 Here are the available commands.
13773 List the available monitor commands.
13775 @item monitor set debug 0
13776 @itemx monitor set debug 1
13777 Disable or enable general debugging messages.
13779 @item monitor set remote-debug 0
13780 @itemx monitor set remote-debug 1
13781 Disable or enable specific debugging messages associated with the remote
13782 protocol (@pxref{Remote Protocol}).
13785 Tell gdbserver to exit immediately. This command should be followed by
13786 @code{disconnect} to close the debugging session. @code{gdbserver} will
13787 detach from any attached processes and kill any processes it created.
13788 Use @code{monitor exit} to terminate @code{gdbserver} at the end
13789 of a multi-process mode debug session.
13793 @node Remote Configuration
13794 @section Remote Configuration
13797 @kindex show remote
13798 This section documents the configuration options available when
13799 debugging remote programs. For the options related to the File I/O
13800 extensions of the remote protocol, see @ref{system,
13801 system-call-allowed}.
13804 @item set remoteaddresssize @var{bits}
13805 @cindex address size for remote targets
13806 @cindex bits in remote address
13807 Set the maximum size of address in a memory packet to the specified
13808 number of bits. @value{GDBN} will mask off the address bits above
13809 that number, when it passes addresses to the remote target. The
13810 default value is the number of bits in the target's address.
13812 @item show remoteaddresssize
13813 Show the current value of remote address size in bits.
13815 @item set remotebaud @var{n}
13816 @cindex baud rate for remote targets
13817 Set the baud rate for the remote serial I/O to @var{n} baud. The
13818 value is used to set the speed of the serial port used for debugging
13821 @item show remotebaud
13822 Show the current speed of the remote connection.
13824 @item set remotebreak
13825 @cindex interrupt remote programs
13826 @cindex BREAK signal instead of Ctrl-C
13827 @anchor{set remotebreak}
13828 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
13829 when you type @kbd{Ctrl-c} to interrupt the program running
13830 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
13831 character instead. The default is off, since most remote systems
13832 expect to see @samp{Ctrl-C} as the interrupt signal.
13834 @item show remotebreak
13835 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
13836 interrupt the remote program.
13838 @item set remoteflow on
13839 @itemx set remoteflow off
13840 @kindex set remoteflow
13841 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
13842 on the serial port used to communicate to the remote target.
13844 @item show remoteflow
13845 @kindex show remoteflow
13846 Show the current setting of hardware flow control.
13848 @item set remotelogbase @var{base}
13849 Set the base (a.k.a.@: radix) of logging serial protocol
13850 communications to @var{base}. Supported values of @var{base} are:
13851 @code{ascii}, @code{octal}, and @code{hex}. The default is
13854 @item show remotelogbase
13855 Show the current setting of the radix for logging remote serial
13858 @item set remotelogfile @var{file}
13859 @cindex record serial communications on file
13860 Record remote serial communications on the named @var{file}. The
13861 default is not to record at all.
13863 @item show remotelogfile.
13864 Show the current setting of the file name on which to record the
13865 serial communications.
13867 @item set remotetimeout @var{num}
13868 @cindex timeout for serial communications
13869 @cindex remote timeout
13870 Set the timeout limit to wait for the remote target to respond to
13871 @var{num} seconds. The default is 2 seconds.
13873 @item show remotetimeout
13874 Show the current number of seconds to wait for the remote target
13877 @cindex limit hardware breakpoints and watchpoints
13878 @cindex remote target, limit break- and watchpoints
13879 @anchor{set remote hardware-watchpoint-limit}
13880 @anchor{set remote hardware-breakpoint-limit}
13881 @item set remote hardware-watchpoint-limit @var{limit}
13882 @itemx set remote hardware-breakpoint-limit @var{limit}
13883 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
13884 watchpoints. A limit of -1, the default, is treated as unlimited.
13886 @item set remote exec-file @var{filename}
13887 @itemx show remote exec-file
13888 @anchor{set remote exec-file}
13889 @cindex executable file, for remote target
13890 Select the file used for @code{run} with @code{target
13891 extended-remote}. This should be set to a filename valid on the
13892 target system. If it is not set, the target will use a default
13893 filename (e.g.@: the last program run).
13896 @cindex remote packets, enabling and disabling
13897 The @value{GDBN} remote protocol autodetects the packets supported by
13898 your debugging stub. If you need to override the autodetection, you
13899 can use these commands to enable or disable individual packets. Each
13900 packet can be set to @samp{on} (the remote target supports this
13901 packet), @samp{off} (the remote target does not support this packet),
13902 or @samp{auto} (detect remote target support for this packet). They
13903 all default to @samp{auto}. For more information about each packet,
13904 see @ref{Remote Protocol}.
13906 During normal use, you should not have to use any of these commands.
13907 If you do, that may be a bug in your remote debugging stub, or a bug
13908 in @value{GDBN}. You may want to report the problem to the
13909 @value{GDBN} developers.
13911 For each packet @var{name}, the command to enable or disable the
13912 packet is @code{set remote @var{name}-packet}. The available settings
13915 @multitable @columnfractions 0.28 0.32 0.25
13918 @tab Related Features
13920 @item @code{fetch-register}
13922 @tab @code{info registers}
13924 @item @code{set-register}
13928 @item @code{binary-download}
13930 @tab @code{load}, @code{set}
13932 @item @code{read-aux-vector}
13933 @tab @code{qXfer:auxv:read}
13934 @tab @code{info auxv}
13936 @item @code{symbol-lookup}
13937 @tab @code{qSymbol}
13938 @tab Detecting multiple threads
13940 @item @code{attach}
13941 @tab @code{vAttach}
13944 @item @code{verbose-resume}
13946 @tab Stepping or resuming multiple threads
13952 @item @code{software-breakpoint}
13956 @item @code{hardware-breakpoint}
13960 @item @code{write-watchpoint}
13964 @item @code{read-watchpoint}
13968 @item @code{access-watchpoint}
13972 @item @code{target-features}
13973 @tab @code{qXfer:features:read}
13974 @tab @code{set architecture}
13976 @item @code{library-info}
13977 @tab @code{qXfer:libraries:read}
13978 @tab @code{info sharedlibrary}
13980 @item @code{memory-map}
13981 @tab @code{qXfer:memory-map:read}
13982 @tab @code{info mem}
13984 @item @code{read-spu-object}
13985 @tab @code{qXfer:spu:read}
13986 @tab @code{info spu}
13988 @item @code{write-spu-object}
13989 @tab @code{qXfer:spu:write}
13990 @tab @code{info spu}
13992 @item @code{get-thread-local-@*storage-address}
13993 @tab @code{qGetTLSAddr}
13994 @tab Displaying @code{__thread} variables
13996 @item @code{search-memory}
13997 @tab @code{qSearch:memory}
14000 @item @code{supported-packets}
14001 @tab @code{qSupported}
14002 @tab Remote communications parameters
14004 @item @code{pass-signals}
14005 @tab @code{QPassSignals}
14006 @tab @code{handle @var{signal}}
14008 @item @code{hostio-close-packet}
14009 @tab @code{vFile:close}
14010 @tab @code{remote get}, @code{remote put}
14012 @item @code{hostio-open-packet}
14013 @tab @code{vFile:open}
14014 @tab @code{remote get}, @code{remote put}
14016 @item @code{hostio-pread-packet}
14017 @tab @code{vFile:pread}
14018 @tab @code{remote get}, @code{remote put}
14020 @item @code{hostio-pwrite-packet}
14021 @tab @code{vFile:pwrite}
14022 @tab @code{remote get}, @code{remote put}
14024 @item @code{hostio-unlink-packet}
14025 @tab @code{vFile:unlink}
14026 @tab @code{remote delete}
14028 @item @code{noack-packet}
14029 @tab @code{QStartNoAckMode}
14030 @tab Packet acknowledgment
14034 @section Implementing a Remote Stub
14036 @cindex debugging stub, example
14037 @cindex remote stub, example
14038 @cindex stub example, remote debugging
14039 The stub files provided with @value{GDBN} implement the target side of the
14040 communication protocol, and the @value{GDBN} side is implemented in the
14041 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
14042 these subroutines to communicate, and ignore the details. (If you're
14043 implementing your own stub file, you can still ignore the details: start
14044 with one of the existing stub files. @file{sparc-stub.c} is the best
14045 organized, and therefore the easiest to read.)
14047 @cindex remote serial debugging, overview
14048 To debug a program running on another machine (the debugging
14049 @dfn{target} machine), you must first arrange for all the usual
14050 prerequisites for the program to run by itself. For example, for a C
14055 A startup routine to set up the C runtime environment; these usually
14056 have a name like @file{crt0}. The startup routine may be supplied by
14057 your hardware supplier, or you may have to write your own.
14060 A C subroutine library to support your program's
14061 subroutine calls, notably managing input and output.
14064 A way of getting your program to the other machine---for example, a
14065 download program. These are often supplied by the hardware
14066 manufacturer, but you may have to write your own from hardware
14070 The next step is to arrange for your program to use a serial port to
14071 communicate with the machine where @value{GDBN} is running (the @dfn{host}
14072 machine). In general terms, the scheme looks like this:
14076 @value{GDBN} already understands how to use this protocol; when everything
14077 else is set up, you can simply use the @samp{target remote} command
14078 (@pxref{Targets,,Specifying a Debugging Target}).
14080 @item On the target,
14081 you must link with your program a few special-purpose subroutines that
14082 implement the @value{GDBN} remote serial protocol. The file containing these
14083 subroutines is called a @dfn{debugging stub}.
14085 On certain remote targets, you can use an auxiliary program
14086 @code{gdbserver} instead of linking a stub into your program.
14087 @xref{Server,,Using the @code{gdbserver} Program}, for details.
14090 The debugging stub is specific to the architecture of the remote
14091 machine; for example, use @file{sparc-stub.c} to debug programs on
14094 @cindex remote serial stub list
14095 These working remote stubs are distributed with @value{GDBN}:
14100 @cindex @file{i386-stub.c}
14103 For Intel 386 and compatible architectures.
14106 @cindex @file{m68k-stub.c}
14107 @cindex Motorola 680x0
14109 For Motorola 680x0 architectures.
14112 @cindex @file{sh-stub.c}
14115 For Renesas SH architectures.
14118 @cindex @file{sparc-stub.c}
14120 For @sc{sparc} architectures.
14122 @item sparcl-stub.c
14123 @cindex @file{sparcl-stub.c}
14126 For Fujitsu @sc{sparclite} architectures.
14130 The @file{README} file in the @value{GDBN} distribution may list other
14131 recently added stubs.
14134 * Stub Contents:: What the stub can do for you
14135 * Bootstrapping:: What you must do for the stub
14136 * Debug Session:: Putting it all together
14139 @node Stub Contents
14140 @subsection What the Stub Can Do for You
14142 @cindex remote serial stub
14143 The debugging stub for your architecture supplies these three
14147 @item set_debug_traps
14148 @findex set_debug_traps
14149 @cindex remote serial stub, initialization
14150 This routine arranges for @code{handle_exception} to run when your
14151 program stops. You must call this subroutine explicitly near the
14152 beginning of your program.
14154 @item handle_exception
14155 @findex handle_exception
14156 @cindex remote serial stub, main routine
14157 This is the central workhorse, but your program never calls it
14158 explicitly---the setup code arranges for @code{handle_exception} to
14159 run when a trap is triggered.
14161 @code{handle_exception} takes control when your program stops during
14162 execution (for example, on a breakpoint), and mediates communications
14163 with @value{GDBN} on the host machine. This is where the communications
14164 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
14165 representative on the target machine. It begins by sending summary
14166 information on the state of your program, then continues to execute,
14167 retrieving and transmitting any information @value{GDBN} needs, until you
14168 execute a @value{GDBN} command that makes your program resume; at that point,
14169 @code{handle_exception} returns control to your own code on the target
14173 @cindex @code{breakpoint} subroutine, remote
14174 Use this auxiliary subroutine to make your program contain a
14175 breakpoint. Depending on the particular situation, this may be the only
14176 way for @value{GDBN} to get control. For instance, if your target
14177 machine has some sort of interrupt button, you won't need to call this;
14178 pressing the interrupt button transfers control to
14179 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
14180 simply receiving characters on the serial port may also trigger a trap;
14181 again, in that situation, you don't need to call @code{breakpoint} from
14182 your own program---simply running @samp{target remote} from the host
14183 @value{GDBN} session gets control.
14185 Call @code{breakpoint} if none of these is true, or if you simply want
14186 to make certain your program stops at a predetermined point for the
14187 start of your debugging session.
14190 @node Bootstrapping
14191 @subsection What You Must Do for the Stub
14193 @cindex remote stub, support routines
14194 The debugging stubs that come with @value{GDBN} are set up for a particular
14195 chip architecture, but they have no information about the rest of your
14196 debugging target machine.
14198 First of all you need to tell the stub how to communicate with the
14202 @item int getDebugChar()
14203 @findex getDebugChar
14204 Write this subroutine to read a single character from the serial port.
14205 It may be identical to @code{getchar} for your target system; a
14206 different name is used to allow you to distinguish the two if you wish.
14208 @item void putDebugChar(int)
14209 @findex putDebugChar
14210 Write this subroutine to write a single character to the serial port.
14211 It may be identical to @code{putchar} for your target system; a
14212 different name is used to allow you to distinguish the two if you wish.
14215 @cindex control C, and remote debugging
14216 @cindex interrupting remote targets
14217 If you want @value{GDBN} to be able to stop your program while it is
14218 running, you need to use an interrupt-driven serial driver, and arrange
14219 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
14220 character). That is the character which @value{GDBN} uses to tell the
14221 remote system to stop.
14223 Getting the debugging target to return the proper status to @value{GDBN}
14224 probably requires changes to the standard stub; one quick and dirty way
14225 is to just execute a breakpoint instruction (the ``dirty'' part is that
14226 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
14228 Other routines you need to supply are:
14231 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
14232 @findex exceptionHandler
14233 Write this function to install @var{exception_address} in the exception
14234 handling tables. You need to do this because the stub does not have any
14235 way of knowing what the exception handling tables on your target system
14236 are like (for example, the processor's table might be in @sc{rom},
14237 containing entries which point to a table in @sc{ram}).
14238 @var{exception_number} is the exception number which should be changed;
14239 its meaning is architecture-dependent (for example, different numbers
14240 might represent divide by zero, misaligned access, etc). When this
14241 exception occurs, control should be transferred directly to
14242 @var{exception_address}, and the processor state (stack, registers,
14243 and so on) should be just as it is when a processor exception occurs. So if
14244 you want to use a jump instruction to reach @var{exception_address}, it
14245 should be a simple jump, not a jump to subroutine.
14247 For the 386, @var{exception_address} should be installed as an interrupt
14248 gate so that interrupts are masked while the handler runs. The gate
14249 should be at privilege level 0 (the most privileged level). The
14250 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
14251 help from @code{exceptionHandler}.
14253 @item void flush_i_cache()
14254 @findex flush_i_cache
14255 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
14256 instruction cache, if any, on your target machine. If there is no
14257 instruction cache, this subroutine may be a no-op.
14259 On target machines that have instruction caches, @value{GDBN} requires this
14260 function to make certain that the state of your program is stable.
14264 You must also make sure this library routine is available:
14267 @item void *memset(void *, int, int)
14269 This is the standard library function @code{memset} that sets an area of
14270 memory to a known value. If you have one of the free versions of
14271 @code{libc.a}, @code{memset} can be found there; otherwise, you must
14272 either obtain it from your hardware manufacturer, or write your own.
14275 If you do not use the GNU C compiler, you may need other standard
14276 library subroutines as well; this varies from one stub to another,
14277 but in general the stubs are likely to use any of the common library
14278 subroutines which @code{@value{NGCC}} generates as inline code.
14281 @node Debug Session
14282 @subsection Putting it All Together
14284 @cindex remote serial debugging summary
14285 In summary, when your program is ready to debug, you must follow these
14290 Make sure you have defined the supporting low-level routines
14291 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
14293 @code{getDebugChar}, @code{putDebugChar},
14294 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
14298 Insert these lines near the top of your program:
14306 For the 680x0 stub only, you need to provide a variable called
14307 @code{exceptionHook}. Normally you just use:
14310 void (*exceptionHook)() = 0;
14314 but if before calling @code{set_debug_traps}, you set it to point to a
14315 function in your program, that function is called when
14316 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
14317 error). The function indicated by @code{exceptionHook} is called with
14318 one parameter: an @code{int} which is the exception number.
14321 Compile and link together: your program, the @value{GDBN} debugging stub for
14322 your target architecture, and the supporting subroutines.
14325 Make sure you have a serial connection between your target machine and
14326 the @value{GDBN} host, and identify the serial port on the host.
14329 @c The "remote" target now provides a `load' command, so we should
14330 @c document that. FIXME.
14331 Download your program to your target machine (or get it there by
14332 whatever means the manufacturer provides), and start it.
14335 Start @value{GDBN} on the host, and connect to the target
14336 (@pxref{Connecting,,Connecting to a Remote Target}).
14340 @node Configurations
14341 @chapter Configuration-Specific Information
14343 While nearly all @value{GDBN} commands are available for all native and
14344 cross versions of the debugger, there are some exceptions. This chapter
14345 describes things that are only available in certain configurations.
14347 There are three major categories of configurations: native
14348 configurations, where the host and target are the same, embedded
14349 operating system configurations, which are usually the same for several
14350 different processor architectures, and bare embedded processors, which
14351 are quite different from each other.
14356 * Embedded Processors::
14363 This section describes details specific to particular native
14368 * BSD libkvm Interface:: Debugging BSD kernel memory images
14369 * SVR4 Process Information:: SVR4 process information
14370 * DJGPP Native:: Features specific to the DJGPP port
14371 * Cygwin Native:: Features specific to the Cygwin port
14372 * Hurd Native:: Features specific to @sc{gnu} Hurd
14373 * Neutrino:: Features specific to QNX Neutrino
14379 On HP-UX systems, if you refer to a function or variable name that
14380 begins with a dollar sign, @value{GDBN} searches for a user or system
14381 name first, before it searches for a convenience variable.
14384 @node BSD libkvm Interface
14385 @subsection BSD libkvm Interface
14388 @cindex kernel memory image
14389 @cindex kernel crash dump
14391 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
14392 interface that provides a uniform interface for accessing kernel virtual
14393 memory images, including live systems and crash dumps. @value{GDBN}
14394 uses this interface to allow you to debug live kernels and kernel crash
14395 dumps on many native BSD configurations. This is implemented as a
14396 special @code{kvm} debugging target. For debugging a live system, load
14397 the currently running kernel into @value{GDBN} and connect to the
14401 (@value{GDBP}) @b{target kvm}
14404 For debugging crash dumps, provide the file name of the crash dump as an
14408 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
14411 Once connected to the @code{kvm} target, the following commands are
14417 Set current context from the @dfn{Process Control Block} (PCB) address.
14420 Set current context from proc address. This command isn't available on
14421 modern FreeBSD systems.
14424 @node SVR4 Process Information
14425 @subsection SVR4 Process Information
14427 @cindex examine process image
14428 @cindex process info via @file{/proc}
14430 Many versions of SVR4 and compatible systems provide a facility called
14431 @samp{/proc} that can be used to examine the image of a running
14432 process using file-system subroutines. If @value{GDBN} is configured
14433 for an operating system with this facility, the command @code{info
14434 proc} is available to report information about the process running
14435 your program, or about any process running on your system. @code{info
14436 proc} works only on SVR4 systems that include the @code{procfs} code.
14437 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
14438 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
14444 @itemx info proc @var{process-id}
14445 Summarize available information about any running process. If a
14446 process ID is specified by @var{process-id}, display information about
14447 that process; otherwise display information about the program being
14448 debugged. The summary includes the debugged process ID, the command
14449 line used to invoke it, its current working directory, and its
14450 executable file's absolute file name.
14452 On some systems, @var{process-id} can be of the form
14453 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
14454 within a process. If the optional @var{pid} part is missing, it means
14455 a thread from the process being debugged (the leading @samp{/} still
14456 needs to be present, or else @value{GDBN} will interpret the number as
14457 a process ID rather than a thread ID).
14459 @item info proc mappings
14460 @cindex memory address space mappings
14461 Report the memory address space ranges accessible in the program, with
14462 information on whether the process has read, write, or execute access
14463 rights to each range. On @sc{gnu}/Linux systems, each memory range
14464 includes the object file which is mapped to that range, instead of the
14465 memory access rights to that range.
14467 @item info proc stat
14468 @itemx info proc status
14469 @cindex process detailed status information
14470 These subcommands are specific to @sc{gnu}/Linux systems. They show
14471 the process-related information, including the user ID and group ID;
14472 how many threads are there in the process; its virtual memory usage;
14473 the signals that are pending, blocked, and ignored; its TTY; its
14474 consumption of system and user time; its stack size; its @samp{nice}
14475 value; etc. For more information, see the @samp{proc} man page
14476 (type @kbd{man 5 proc} from your shell prompt).
14478 @item info proc all
14479 Show all the information about the process described under all of the
14480 above @code{info proc} subcommands.
14483 @comment These sub-options of 'info proc' were not included when
14484 @comment procfs.c was re-written. Keep their descriptions around
14485 @comment against the day when someone finds the time to put them back in.
14486 @kindex info proc times
14487 @item info proc times
14488 Starting time, user CPU time, and system CPU time for your program and
14491 @kindex info proc id
14493 Report on the process IDs related to your program: its own process ID,
14494 the ID of its parent, the process group ID, and the session ID.
14497 @item set procfs-trace
14498 @kindex set procfs-trace
14499 @cindex @code{procfs} API calls
14500 This command enables and disables tracing of @code{procfs} API calls.
14502 @item show procfs-trace
14503 @kindex show procfs-trace
14504 Show the current state of @code{procfs} API call tracing.
14506 @item set procfs-file @var{file}
14507 @kindex set procfs-file
14508 Tell @value{GDBN} to write @code{procfs} API trace to the named
14509 @var{file}. @value{GDBN} appends the trace info to the previous
14510 contents of the file. The default is to display the trace on the
14513 @item show procfs-file
14514 @kindex show procfs-file
14515 Show the file to which @code{procfs} API trace is written.
14517 @item proc-trace-entry
14518 @itemx proc-trace-exit
14519 @itemx proc-untrace-entry
14520 @itemx proc-untrace-exit
14521 @kindex proc-trace-entry
14522 @kindex proc-trace-exit
14523 @kindex proc-untrace-entry
14524 @kindex proc-untrace-exit
14525 These commands enable and disable tracing of entries into and exits
14526 from the @code{syscall} interface.
14529 @kindex info pidlist
14530 @cindex process list, QNX Neutrino
14531 For QNX Neutrino only, this command displays the list of all the
14532 processes and all the threads within each process.
14535 @kindex info meminfo
14536 @cindex mapinfo list, QNX Neutrino
14537 For QNX Neutrino only, this command displays the list of all mapinfos.
14541 @subsection Features for Debugging @sc{djgpp} Programs
14542 @cindex @sc{djgpp} debugging
14543 @cindex native @sc{djgpp} debugging
14544 @cindex MS-DOS-specific commands
14547 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
14548 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
14549 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
14550 top of real-mode DOS systems and their emulations.
14552 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
14553 defines a few commands specific to the @sc{djgpp} port. This
14554 subsection describes those commands.
14559 This is a prefix of @sc{djgpp}-specific commands which print
14560 information about the target system and important OS structures.
14563 @cindex MS-DOS system info
14564 @cindex free memory information (MS-DOS)
14565 @item info dos sysinfo
14566 This command displays assorted information about the underlying
14567 platform: the CPU type and features, the OS version and flavor, the
14568 DPMI version, and the available conventional and DPMI memory.
14573 @cindex segment descriptor tables
14574 @cindex descriptor tables display
14576 @itemx info dos ldt
14577 @itemx info dos idt
14578 These 3 commands display entries from, respectively, Global, Local,
14579 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
14580 tables are data structures which store a descriptor for each segment
14581 that is currently in use. The segment's selector is an index into a
14582 descriptor table; the table entry for that index holds the
14583 descriptor's base address and limit, and its attributes and access
14586 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
14587 segment (used for both data and the stack), and a DOS segment (which
14588 allows access to DOS/BIOS data structures and absolute addresses in
14589 conventional memory). However, the DPMI host will usually define
14590 additional segments in order to support the DPMI environment.
14592 @cindex garbled pointers
14593 These commands allow to display entries from the descriptor tables.
14594 Without an argument, all entries from the specified table are
14595 displayed. An argument, which should be an integer expression, means
14596 display a single entry whose index is given by the argument. For
14597 example, here's a convenient way to display information about the
14598 debugged program's data segment:
14601 @exdent @code{(@value{GDBP}) info dos ldt $ds}
14602 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
14606 This comes in handy when you want to see whether a pointer is outside
14607 the data segment's limit (i.e.@: @dfn{garbled}).
14609 @cindex page tables display (MS-DOS)
14611 @itemx info dos pte
14612 These two commands display entries from, respectively, the Page
14613 Directory and the Page Tables. Page Directories and Page Tables are
14614 data structures which control how virtual memory addresses are mapped
14615 into physical addresses. A Page Table includes an entry for every
14616 page of memory that is mapped into the program's address space; there
14617 may be several Page Tables, each one holding up to 4096 entries. A
14618 Page Directory has up to 4096 entries, one each for every Page Table
14619 that is currently in use.
14621 Without an argument, @kbd{info dos pde} displays the entire Page
14622 Directory, and @kbd{info dos pte} displays all the entries in all of
14623 the Page Tables. An argument, an integer expression, given to the
14624 @kbd{info dos pde} command means display only that entry from the Page
14625 Directory table. An argument given to the @kbd{info dos pte} command
14626 means display entries from a single Page Table, the one pointed to by
14627 the specified entry in the Page Directory.
14629 @cindex direct memory access (DMA) on MS-DOS
14630 These commands are useful when your program uses @dfn{DMA} (Direct
14631 Memory Access), which needs physical addresses to program the DMA
14634 These commands are supported only with some DPMI servers.
14636 @cindex physical address from linear address
14637 @item info dos address-pte @var{addr}
14638 This command displays the Page Table entry for a specified linear
14639 address. The argument @var{addr} is a linear address which should
14640 already have the appropriate segment's base address added to it,
14641 because this command accepts addresses which may belong to @emph{any}
14642 segment. For example, here's how to display the Page Table entry for
14643 the page where a variable @code{i} is stored:
14646 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
14647 @exdent @code{Page Table entry for address 0x11a00d30:}
14648 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
14652 This says that @code{i} is stored at offset @code{0xd30} from the page
14653 whose physical base address is @code{0x02698000}, and shows all the
14654 attributes of that page.
14656 Note that you must cast the addresses of variables to a @code{char *},
14657 since otherwise the value of @code{__djgpp_base_address}, the base
14658 address of all variables and functions in a @sc{djgpp} program, will
14659 be added using the rules of C pointer arithmetics: if @code{i} is
14660 declared an @code{int}, @value{GDBN} will add 4 times the value of
14661 @code{__djgpp_base_address} to the address of @code{i}.
14663 Here's another example, it displays the Page Table entry for the
14667 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
14668 @exdent @code{Page Table entry for address 0x29110:}
14669 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
14673 (The @code{+ 3} offset is because the transfer buffer's address is the
14674 3rd member of the @code{_go32_info_block} structure.) The output
14675 clearly shows that this DPMI server maps the addresses in conventional
14676 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
14677 linear (@code{0x29110}) addresses are identical.
14679 This command is supported only with some DPMI servers.
14682 @cindex DOS serial data link, remote debugging
14683 In addition to native debugging, the DJGPP port supports remote
14684 debugging via a serial data link. The following commands are specific
14685 to remote serial debugging in the DJGPP port of @value{GDBN}.
14688 @kindex set com1base
14689 @kindex set com1irq
14690 @kindex set com2base
14691 @kindex set com2irq
14692 @kindex set com3base
14693 @kindex set com3irq
14694 @kindex set com4base
14695 @kindex set com4irq
14696 @item set com1base @var{addr}
14697 This command sets the base I/O port address of the @file{COM1} serial
14700 @item set com1irq @var{irq}
14701 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
14702 for the @file{COM1} serial port.
14704 There are similar commands @samp{set com2base}, @samp{set com3irq},
14705 etc.@: for setting the port address and the @code{IRQ} lines for the
14708 @kindex show com1base
14709 @kindex show com1irq
14710 @kindex show com2base
14711 @kindex show com2irq
14712 @kindex show com3base
14713 @kindex show com3irq
14714 @kindex show com4base
14715 @kindex show com4irq
14716 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
14717 display the current settings of the base address and the @code{IRQ}
14718 lines used by the COM ports.
14721 @kindex info serial
14722 @cindex DOS serial port status
14723 This command prints the status of the 4 DOS serial ports. For each
14724 port, it prints whether it's active or not, its I/O base address and
14725 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
14726 counts of various errors encountered so far.
14730 @node Cygwin Native
14731 @subsection Features for Debugging MS Windows PE Executables
14732 @cindex MS Windows debugging
14733 @cindex native Cygwin debugging
14734 @cindex Cygwin-specific commands
14736 @value{GDBN} supports native debugging of MS Windows programs, including
14737 DLLs with and without symbolic debugging information. There are various
14738 additional Cygwin-specific commands, described in this section.
14739 Working with DLLs that have no debugging symbols is described in
14740 @ref{Non-debug DLL Symbols}.
14745 This is a prefix of MS Windows-specific commands which print
14746 information about the target system and important OS structures.
14748 @item info w32 selector
14749 This command displays information returned by
14750 the Win32 API @code{GetThreadSelectorEntry} function.
14751 It takes an optional argument that is evaluated to
14752 a long value to give the information about this given selector.
14753 Without argument, this command displays information
14754 about the six segment registers.
14758 This is a Cygwin-specific alias of @code{info shared}.
14760 @kindex dll-symbols
14762 This command loads symbols from a dll similarly to
14763 add-sym command but without the need to specify a base address.
14765 @kindex set cygwin-exceptions
14766 @cindex debugging the Cygwin DLL
14767 @cindex Cygwin DLL, debugging
14768 @item set cygwin-exceptions @var{mode}
14769 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
14770 happen inside the Cygwin DLL. If @var{mode} is @code{off},
14771 @value{GDBN} will delay recognition of exceptions, and may ignore some
14772 exceptions which seem to be caused by internal Cygwin DLL
14773 ``bookkeeping''. This option is meant primarily for debugging the
14774 Cygwin DLL itself; the default value is @code{off} to avoid annoying
14775 @value{GDBN} users with false @code{SIGSEGV} signals.
14777 @kindex show cygwin-exceptions
14778 @item show cygwin-exceptions
14779 Displays whether @value{GDBN} will break on exceptions that happen
14780 inside the Cygwin DLL itself.
14782 @kindex set new-console
14783 @item set new-console @var{mode}
14784 If @var{mode} is @code{on} the debuggee will
14785 be started in a new console on next start.
14786 If @var{mode} is @code{off}i, the debuggee will
14787 be started in the same console as the debugger.
14789 @kindex show new-console
14790 @item show new-console
14791 Displays whether a new console is used
14792 when the debuggee is started.
14794 @kindex set new-group
14795 @item set new-group @var{mode}
14796 This boolean value controls whether the debuggee should
14797 start a new group or stay in the same group as the debugger.
14798 This affects the way the Windows OS handles
14801 @kindex show new-group
14802 @item show new-group
14803 Displays current value of new-group boolean.
14805 @kindex set debugevents
14806 @item set debugevents
14807 This boolean value adds debug output concerning kernel events related
14808 to the debuggee seen by the debugger. This includes events that
14809 signal thread and process creation and exit, DLL loading and
14810 unloading, console interrupts, and debugging messages produced by the
14811 Windows @code{OutputDebugString} API call.
14813 @kindex set debugexec
14814 @item set debugexec
14815 This boolean value adds debug output concerning execute events
14816 (such as resume thread) seen by the debugger.
14818 @kindex set debugexceptions
14819 @item set debugexceptions
14820 This boolean value adds debug output concerning exceptions in the
14821 debuggee seen by the debugger.
14823 @kindex set debugmemory
14824 @item set debugmemory
14825 This boolean value adds debug output concerning debuggee memory reads
14826 and writes by the debugger.
14830 This boolean values specifies whether the debuggee is called
14831 via a shell or directly (default value is on).
14835 Displays if the debuggee will be started with a shell.
14840 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
14843 @node Non-debug DLL Symbols
14844 @subsubsection Support for DLLs without Debugging Symbols
14845 @cindex DLLs with no debugging symbols
14846 @cindex Minimal symbols and DLLs
14848 Very often on windows, some of the DLLs that your program relies on do
14849 not include symbolic debugging information (for example,
14850 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
14851 symbols in a DLL, it relies on the minimal amount of symbolic
14852 information contained in the DLL's export table. This section
14853 describes working with such symbols, known internally to @value{GDBN} as
14854 ``minimal symbols''.
14856 Note that before the debugged program has started execution, no DLLs
14857 will have been loaded. The easiest way around this problem is simply to
14858 start the program --- either by setting a breakpoint or letting the
14859 program run once to completion. It is also possible to force
14860 @value{GDBN} to load a particular DLL before starting the executable ---
14861 see the shared library information in @ref{Files}, or the
14862 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
14863 explicitly loading symbols from a DLL with no debugging information will
14864 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
14865 which may adversely affect symbol lookup performance.
14867 @subsubsection DLL Name Prefixes
14869 In keeping with the naming conventions used by the Microsoft debugging
14870 tools, DLL export symbols are made available with a prefix based on the
14871 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
14872 also entered into the symbol table, so @code{CreateFileA} is often
14873 sufficient. In some cases there will be name clashes within a program
14874 (particularly if the executable itself includes full debugging symbols)
14875 necessitating the use of the fully qualified name when referring to the
14876 contents of the DLL. Use single-quotes around the name to avoid the
14877 exclamation mark (``!'') being interpreted as a language operator.
14879 Note that the internal name of the DLL may be all upper-case, even
14880 though the file name of the DLL is lower-case, or vice-versa. Since
14881 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
14882 some confusion. If in doubt, try the @code{info functions} and
14883 @code{info variables} commands or even @code{maint print msymbols}
14884 (@pxref{Symbols}). Here's an example:
14887 (@value{GDBP}) info function CreateFileA
14888 All functions matching regular expression "CreateFileA":
14890 Non-debugging symbols:
14891 0x77e885f4 CreateFileA
14892 0x77e885f4 KERNEL32!CreateFileA
14896 (@value{GDBP}) info function !
14897 All functions matching regular expression "!":
14899 Non-debugging symbols:
14900 0x6100114c cygwin1!__assert
14901 0x61004034 cygwin1!_dll_crt0@@0
14902 0x61004240 cygwin1!dll_crt0(per_process *)
14906 @subsubsection Working with Minimal Symbols
14908 Symbols extracted from a DLL's export table do not contain very much
14909 type information. All that @value{GDBN} can do is guess whether a symbol
14910 refers to a function or variable depending on the linker section that
14911 contains the symbol. Also note that the actual contents of the memory
14912 contained in a DLL are not available unless the program is running. This
14913 means that you cannot examine the contents of a variable or disassemble
14914 a function within a DLL without a running program.
14916 Variables are generally treated as pointers and dereferenced
14917 automatically. For this reason, it is often necessary to prefix a
14918 variable name with the address-of operator (``&'') and provide explicit
14919 type information in the command. Here's an example of the type of
14923 (@value{GDBP}) print 'cygwin1!__argv'
14928 (@value{GDBP}) x 'cygwin1!__argv'
14929 0x10021610: "\230y\""
14932 And two possible solutions:
14935 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
14936 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
14940 (@value{GDBP}) x/2x &'cygwin1!__argv'
14941 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
14942 (@value{GDBP}) x/x 0x10021608
14943 0x10021608: 0x0022fd98
14944 (@value{GDBP}) x/s 0x0022fd98
14945 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
14948 Setting a break point within a DLL is possible even before the program
14949 starts execution. However, under these circumstances, @value{GDBN} can't
14950 examine the initial instructions of the function in order to skip the
14951 function's frame set-up code. You can work around this by using ``*&''
14952 to set the breakpoint at a raw memory address:
14955 (@value{GDBP}) break *&'python22!PyOS_Readline'
14956 Breakpoint 1 at 0x1e04eff0
14959 The author of these extensions is not entirely convinced that setting a
14960 break point within a shared DLL like @file{kernel32.dll} is completely
14964 @subsection Commands Specific to @sc{gnu} Hurd Systems
14965 @cindex @sc{gnu} Hurd debugging
14967 This subsection describes @value{GDBN} commands specific to the
14968 @sc{gnu} Hurd native debugging.
14973 @kindex set signals@r{, Hurd command}
14974 @kindex set sigs@r{, Hurd command}
14975 This command toggles the state of inferior signal interception by
14976 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
14977 affected by this command. @code{sigs} is a shorthand alias for
14982 @kindex show signals@r{, Hurd command}
14983 @kindex show sigs@r{, Hurd command}
14984 Show the current state of intercepting inferior's signals.
14986 @item set signal-thread
14987 @itemx set sigthread
14988 @kindex set signal-thread
14989 @kindex set sigthread
14990 This command tells @value{GDBN} which thread is the @code{libc} signal
14991 thread. That thread is run when a signal is delivered to a running
14992 process. @code{set sigthread} is the shorthand alias of @code{set
14995 @item show signal-thread
14996 @itemx show sigthread
14997 @kindex show signal-thread
14998 @kindex show sigthread
14999 These two commands show which thread will run when the inferior is
15000 delivered a signal.
15003 @kindex set stopped@r{, Hurd command}
15004 This commands tells @value{GDBN} that the inferior process is stopped,
15005 as with the @code{SIGSTOP} signal. The stopped process can be
15006 continued by delivering a signal to it.
15009 @kindex show stopped@r{, Hurd command}
15010 This command shows whether @value{GDBN} thinks the debuggee is
15013 @item set exceptions
15014 @kindex set exceptions@r{, Hurd command}
15015 Use this command to turn off trapping of exceptions in the inferior.
15016 When exception trapping is off, neither breakpoints nor
15017 single-stepping will work. To restore the default, set exception
15020 @item show exceptions
15021 @kindex show exceptions@r{, Hurd command}
15022 Show the current state of trapping exceptions in the inferior.
15024 @item set task pause
15025 @kindex set task@r{, Hurd commands}
15026 @cindex task attributes (@sc{gnu} Hurd)
15027 @cindex pause current task (@sc{gnu} Hurd)
15028 This command toggles task suspension when @value{GDBN} has control.
15029 Setting it to on takes effect immediately, and the task is suspended
15030 whenever @value{GDBN} gets control. Setting it to off will take
15031 effect the next time the inferior is continued. If this option is set
15032 to off, you can use @code{set thread default pause on} or @code{set
15033 thread pause on} (see below) to pause individual threads.
15035 @item show task pause
15036 @kindex show task@r{, Hurd commands}
15037 Show the current state of task suspension.
15039 @item set task detach-suspend-count
15040 @cindex task suspend count
15041 @cindex detach from task, @sc{gnu} Hurd
15042 This command sets the suspend count the task will be left with when
15043 @value{GDBN} detaches from it.
15045 @item show task detach-suspend-count
15046 Show the suspend count the task will be left with when detaching.
15048 @item set task exception-port
15049 @itemx set task excp
15050 @cindex task exception port, @sc{gnu} Hurd
15051 This command sets the task exception port to which @value{GDBN} will
15052 forward exceptions. The argument should be the value of the @dfn{send
15053 rights} of the task. @code{set task excp} is a shorthand alias.
15055 @item set noninvasive
15056 @cindex noninvasive task options
15057 This command switches @value{GDBN} to a mode that is the least
15058 invasive as far as interfering with the inferior is concerned. This
15059 is the same as using @code{set task pause}, @code{set exceptions}, and
15060 @code{set signals} to values opposite to the defaults.
15062 @item info send-rights
15063 @itemx info receive-rights
15064 @itemx info port-rights
15065 @itemx info port-sets
15066 @itemx info dead-names
15069 @cindex send rights, @sc{gnu} Hurd
15070 @cindex receive rights, @sc{gnu} Hurd
15071 @cindex port rights, @sc{gnu} Hurd
15072 @cindex port sets, @sc{gnu} Hurd
15073 @cindex dead names, @sc{gnu} Hurd
15074 These commands display information about, respectively, send rights,
15075 receive rights, port rights, port sets, and dead names of a task.
15076 There are also shorthand aliases: @code{info ports} for @code{info
15077 port-rights} and @code{info psets} for @code{info port-sets}.
15079 @item set thread pause
15080 @kindex set thread@r{, Hurd command}
15081 @cindex thread properties, @sc{gnu} Hurd
15082 @cindex pause current thread (@sc{gnu} Hurd)
15083 This command toggles current thread suspension when @value{GDBN} has
15084 control. Setting it to on takes effect immediately, and the current
15085 thread is suspended whenever @value{GDBN} gets control. Setting it to
15086 off will take effect the next time the inferior is continued.
15087 Normally, this command has no effect, since when @value{GDBN} has
15088 control, the whole task is suspended. However, if you used @code{set
15089 task pause off} (see above), this command comes in handy to suspend
15090 only the current thread.
15092 @item show thread pause
15093 @kindex show thread@r{, Hurd command}
15094 This command shows the state of current thread suspension.
15096 @item set thread run
15097 This command sets whether the current thread is allowed to run.
15099 @item show thread run
15100 Show whether the current thread is allowed to run.
15102 @item set thread detach-suspend-count
15103 @cindex thread suspend count, @sc{gnu} Hurd
15104 @cindex detach from thread, @sc{gnu} Hurd
15105 This command sets the suspend count @value{GDBN} will leave on a
15106 thread when detaching. This number is relative to the suspend count
15107 found by @value{GDBN} when it notices the thread; use @code{set thread
15108 takeover-suspend-count} to force it to an absolute value.
15110 @item show thread detach-suspend-count
15111 Show the suspend count @value{GDBN} will leave on the thread when
15114 @item set thread exception-port
15115 @itemx set thread excp
15116 Set the thread exception port to which to forward exceptions. This
15117 overrides the port set by @code{set task exception-port} (see above).
15118 @code{set thread excp} is the shorthand alias.
15120 @item set thread takeover-suspend-count
15121 Normally, @value{GDBN}'s thread suspend counts are relative to the
15122 value @value{GDBN} finds when it notices each thread. This command
15123 changes the suspend counts to be absolute instead.
15125 @item set thread default
15126 @itemx show thread default
15127 @cindex thread default settings, @sc{gnu} Hurd
15128 Each of the above @code{set thread} commands has a @code{set thread
15129 default} counterpart (e.g., @code{set thread default pause}, @code{set
15130 thread default exception-port}, etc.). The @code{thread default}
15131 variety of commands sets the default thread properties for all
15132 threads; you can then change the properties of individual threads with
15133 the non-default commands.
15138 @subsection QNX Neutrino
15139 @cindex QNX Neutrino
15141 @value{GDBN} provides the following commands specific to the QNX
15145 @item set debug nto-debug
15146 @kindex set debug nto-debug
15147 When set to on, enables debugging messages specific to the QNX
15150 @item show debug nto-debug
15151 @kindex show debug nto-debug
15152 Show the current state of QNX Neutrino messages.
15157 @section Embedded Operating Systems
15159 This section describes configurations involving the debugging of
15160 embedded operating systems that are available for several different
15164 * VxWorks:: Using @value{GDBN} with VxWorks
15167 @value{GDBN} includes the ability to debug programs running on
15168 various real-time operating systems.
15171 @subsection Using @value{GDBN} with VxWorks
15177 @kindex target vxworks
15178 @item target vxworks @var{machinename}
15179 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
15180 is the target system's machine name or IP address.
15184 On VxWorks, @code{load} links @var{filename} dynamically on the
15185 current target system as well as adding its symbols in @value{GDBN}.
15187 @value{GDBN} enables developers to spawn and debug tasks running on networked
15188 VxWorks targets from a Unix host. Already-running tasks spawned from
15189 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
15190 both the Unix host and on the VxWorks target. The program
15191 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
15192 installed with the name @code{vxgdb}, to distinguish it from a
15193 @value{GDBN} for debugging programs on the host itself.)
15196 @item VxWorks-timeout @var{args}
15197 @kindex vxworks-timeout
15198 All VxWorks-based targets now support the option @code{vxworks-timeout}.
15199 This option is set by the user, and @var{args} represents the number of
15200 seconds @value{GDBN} waits for responses to rpc's. You might use this if
15201 your VxWorks target is a slow software simulator or is on the far side
15202 of a thin network line.
15205 The following information on connecting to VxWorks was current when
15206 this manual was produced; newer releases of VxWorks may use revised
15209 @findex INCLUDE_RDB
15210 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
15211 to include the remote debugging interface routines in the VxWorks
15212 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
15213 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
15214 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
15215 source debugging task @code{tRdbTask} when VxWorks is booted. For more
15216 information on configuring and remaking VxWorks, see the manufacturer's
15218 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
15220 Once you have included @file{rdb.a} in your VxWorks system image and set
15221 your Unix execution search path to find @value{GDBN}, you are ready to
15222 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
15223 @code{vxgdb}, depending on your installation).
15225 @value{GDBN} comes up showing the prompt:
15232 * VxWorks Connection:: Connecting to VxWorks
15233 * VxWorks Download:: VxWorks download
15234 * VxWorks Attach:: Running tasks
15237 @node VxWorks Connection
15238 @subsubsection Connecting to VxWorks
15240 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
15241 network. To connect to a target whose host name is ``@code{tt}'', type:
15244 (vxgdb) target vxworks tt
15248 @value{GDBN} displays messages like these:
15251 Attaching remote machine across net...
15256 @value{GDBN} then attempts to read the symbol tables of any object modules
15257 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
15258 these files by searching the directories listed in the command search
15259 path (@pxref{Environment, ,Your Program's Environment}); if it fails
15260 to find an object file, it displays a message such as:
15263 prog.o: No such file or directory.
15266 When this happens, add the appropriate directory to the search path with
15267 the @value{GDBN} command @code{path}, and execute the @code{target}
15270 @node VxWorks Download
15271 @subsubsection VxWorks Download
15273 @cindex download to VxWorks
15274 If you have connected to the VxWorks target and you want to debug an
15275 object that has not yet been loaded, you can use the @value{GDBN}
15276 @code{load} command to download a file from Unix to VxWorks
15277 incrementally. The object file given as an argument to the @code{load}
15278 command is actually opened twice: first by the VxWorks target in order
15279 to download the code, then by @value{GDBN} in order to read the symbol
15280 table. This can lead to problems if the current working directories on
15281 the two systems differ. If both systems have NFS mounted the same
15282 filesystems, you can avoid these problems by using absolute paths.
15283 Otherwise, it is simplest to set the working directory on both systems
15284 to the directory in which the object file resides, and then to reference
15285 the file by its name, without any path. For instance, a program
15286 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
15287 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
15288 program, type this on VxWorks:
15291 -> cd "@var{vxpath}/vw/demo/rdb"
15295 Then, in @value{GDBN}, type:
15298 (vxgdb) cd @var{hostpath}/vw/demo/rdb
15299 (vxgdb) load prog.o
15302 @value{GDBN} displays a response similar to this:
15305 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
15308 You can also use the @code{load} command to reload an object module
15309 after editing and recompiling the corresponding source file. Note that
15310 this makes @value{GDBN} delete all currently-defined breakpoints,
15311 auto-displays, and convenience variables, and to clear the value
15312 history. (This is necessary in order to preserve the integrity of
15313 debugger's data structures that reference the target system's symbol
15316 @node VxWorks Attach
15317 @subsubsection Running Tasks
15319 @cindex running VxWorks tasks
15320 You can also attach to an existing task using the @code{attach} command as
15324 (vxgdb) attach @var{task}
15328 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
15329 or suspended when you attach to it. Running tasks are suspended at
15330 the time of attachment.
15332 @node Embedded Processors
15333 @section Embedded Processors
15335 This section goes into details specific to particular embedded
15338 @cindex send command to simulator
15339 Whenever a specific embedded processor has a simulator, @value{GDBN}
15340 allows to send an arbitrary command to the simulator.
15343 @item sim @var{command}
15344 @kindex sim@r{, a command}
15345 Send an arbitrary @var{command} string to the simulator. Consult the
15346 documentation for the specific simulator in use for information about
15347 acceptable commands.
15353 * M32R/D:: Renesas M32R/D
15354 * M68K:: Motorola M68K
15355 * MIPS Embedded:: MIPS Embedded
15356 * OpenRISC 1000:: OpenRisc 1000
15357 * PA:: HP PA Embedded
15358 * PowerPC Embedded:: PowerPC Embedded
15359 * Sparclet:: Tsqware Sparclet
15360 * Sparclite:: Fujitsu Sparclite
15361 * Z8000:: Zilog Z8000
15364 * Super-H:: Renesas Super-H
15373 @item target rdi @var{dev}
15374 ARM Angel monitor, via RDI library interface to ADP protocol. You may
15375 use this target to communicate with both boards running the Angel
15376 monitor, or with the EmbeddedICE JTAG debug device.
15379 @item target rdp @var{dev}
15384 @value{GDBN} provides the following ARM-specific commands:
15387 @item set arm disassembler
15389 This commands selects from a list of disassembly styles. The
15390 @code{"std"} style is the standard style.
15392 @item show arm disassembler
15394 Show the current disassembly style.
15396 @item set arm apcs32
15397 @cindex ARM 32-bit mode
15398 This command toggles ARM operation mode between 32-bit and 26-bit.
15400 @item show arm apcs32
15401 Display the current usage of the ARM 32-bit mode.
15403 @item set arm fpu @var{fputype}
15404 This command sets the ARM floating-point unit (FPU) type. The
15405 argument @var{fputype} can be one of these:
15409 Determine the FPU type by querying the OS ABI.
15411 Software FPU, with mixed-endian doubles on little-endian ARM
15414 GCC-compiled FPA co-processor.
15416 Software FPU with pure-endian doubles.
15422 Show the current type of the FPU.
15425 This command forces @value{GDBN} to use the specified ABI.
15428 Show the currently used ABI.
15430 @item set arm fallback-mode (arm|thumb|auto)
15431 @value{GDBN} uses the symbol table, when available, to determine
15432 whether instructions are ARM or Thumb. This command controls
15433 @value{GDBN}'s default behavior when the symbol table is not
15434 available. The default is @samp{auto}, which causes @value{GDBN} to
15435 use the current execution mode (from the @code{T} bit in the @code{CPSR}
15438 @item show arm fallback-mode
15439 Show the current fallback instruction mode.
15441 @item set arm force-mode (arm|thumb|auto)
15442 This command overrides use of the symbol table to determine whether
15443 instructions are ARM or Thumb. The default is @samp{auto}, which
15444 causes @value{GDBN} to use the symbol table and then the setting
15445 of @samp{set arm fallback-mode}.
15447 @item show arm force-mode
15448 Show the current forced instruction mode.
15450 @item set debug arm
15451 Toggle whether to display ARM-specific debugging messages from the ARM
15452 target support subsystem.
15454 @item show debug arm
15455 Show whether ARM-specific debugging messages are enabled.
15458 The following commands are available when an ARM target is debugged
15459 using the RDI interface:
15462 @item rdilogfile @r{[}@var{file}@r{]}
15464 @cindex ADP (Angel Debugger Protocol) logging
15465 Set the filename for the ADP (Angel Debugger Protocol) packet log.
15466 With an argument, sets the log file to the specified @var{file}. With
15467 no argument, show the current log file name. The default log file is
15470 @item rdilogenable @r{[}@var{arg}@r{]}
15471 @kindex rdilogenable
15472 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
15473 enables logging, with an argument 0 or @code{"no"} disables it. With
15474 no arguments displays the current setting. When logging is enabled,
15475 ADP packets exchanged between @value{GDBN} and the RDI target device
15476 are logged to a file.
15478 @item set rdiromatzero
15479 @kindex set rdiromatzero
15480 @cindex ROM at zero address, RDI
15481 Tell @value{GDBN} whether the target has ROM at address 0. If on,
15482 vector catching is disabled, so that zero address can be used. If off
15483 (the default), vector catching is enabled. For this command to take
15484 effect, it needs to be invoked prior to the @code{target rdi} command.
15486 @item show rdiromatzero
15487 @kindex show rdiromatzero
15488 Show the current setting of ROM at zero address.
15490 @item set rdiheartbeat
15491 @kindex set rdiheartbeat
15492 @cindex RDI heartbeat
15493 Enable or disable RDI heartbeat packets. It is not recommended to
15494 turn on this option, since it confuses ARM and EPI JTAG interface, as
15495 well as the Angel monitor.
15497 @item show rdiheartbeat
15498 @kindex show rdiheartbeat
15499 Show the setting of RDI heartbeat packets.
15504 @subsection Renesas M32R/D and M32R/SDI
15507 @kindex target m32r
15508 @item target m32r @var{dev}
15509 Renesas M32R/D ROM monitor.
15511 @kindex target m32rsdi
15512 @item target m32rsdi @var{dev}
15513 Renesas M32R SDI server, connected via parallel port to the board.
15516 The following @value{GDBN} commands are specific to the M32R monitor:
15519 @item set download-path @var{path}
15520 @kindex set download-path
15521 @cindex find downloadable @sc{srec} files (M32R)
15522 Set the default path for finding downloadable @sc{srec} files.
15524 @item show download-path
15525 @kindex show download-path
15526 Show the default path for downloadable @sc{srec} files.
15528 @item set board-address @var{addr}
15529 @kindex set board-address
15530 @cindex M32-EVA target board address
15531 Set the IP address for the M32R-EVA target board.
15533 @item show board-address
15534 @kindex show board-address
15535 Show the current IP address of the target board.
15537 @item set server-address @var{addr}
15538 @kindex set server-address
15539 @cindex download server address (M32R)
15540 Set the IP address for the download server, which is the @value{GDBN}'s
15543 @item show server-address
15544 @kindex show server-address
15545 Display the IP address of the download server.
15547 @item upload @r{[}@var{file}@r{]}
15548 @kindex upload@r{, M32R}
15549 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
15550 upload capability. If no @var{file} argument is given, the current
15551 executable file is uploaded.
15553 @item tload @r{[}@var{file}@r{]}
15554 @kindex tload@r{, M32R}
15555 Test the @code{upload} command.
15558 The following commands are available for M32R/SDI:
15563 @cindex reset SDI connection, M32R
15564 This command resets the SDI connection.
15568 This command shows the SDI connection status.
15571 @kindex debug_chaos
15572 @cindex M32R/Chaos debugging
15573 Instructs the remote that M32R/Chaos debugging is to be used.
15575 @item use_debug_dma
15576 @kindex use_debug_dma
15577 Instructs the remote to use the DEBUG_DMA method of accessing memory.
15580 @kindex use_mon_code
15581 Instructs the remote to use the MON_CODE method of accessing memory.
15584 @kindex use_ib_break
15585 Instructs the remote to set breakpoints by IB break.
15587 @item use_dbt_break
15588 @kindex use_dbt_break
15589 Instructs the remote to set breakpoints by DBT.
15595 The Motorola m68k configuration includes ColdFire support, and a
15596 target command for the following ROM monitor.
15600 @kindex target dbug
15601 @item target dbug @var{dev}
15602 dBUG ROM monitor for Motorola ColdFire.
15606 @node MIPS Embedded
15607 @subsection MIPS Embedded
15609 @cindex MIPS boards
15610 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
15611 MIPS board attached to a serial line. This is available when
15612 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
15615 Use these @value{GDBN} commands to specify the connection to your target board:
15618 @item target mips @var{port}
15619 @kindex target mips @var{port}
15620 To run a program on the board, start up @code{@value{GDBP}} with the
15621 name of your program as the argument. To connect to the board, use the
15622 command @samp{target mips @var{port}}, where @var{port} is the name of
15623 the serial port connected to the board. If the program has not already
15624 been downloaded to the board, you may use the @code{load} command to
15625 download it. You can then use all the usual @value{GDBN} commands.
15627 For example, this sequence connects to the target board through a serial
15628 port, and loads and runs a program called @var{prog} through the
15632 host$ @value{GDBP} @var{prog}
15633 @value{GDBN} is free software and @dots{}
15634 (@value{GDBP}) target mips /dev/ttyb
15635 (@value{GDBP}) load @var{prog}
15639 @item target mips @var{hostname}:@var{portnumber}
15640 On some @value{GDBN} host configurations, you can specify a TCP
15641 connection (for instance, to a serial line managed by a terminal
15642 concentrator) instead of a serial port, using the syntax
15643 @samp{@var{hostname}:@var{portnumber}}.
15645 @item target pmon @var{port}
15646 @kindex target pmon @var{port}
15649 @item target ddb @var{port}
15650 @kindex target ddb @var{port}
15651 NEC's DDB variant of PMON for Vr4300.
15653 @item target lsi @var{port}
15654 @kindex target lsi @var{port}
15655 LSI variant of PMON.
15657 @kindex target r3900
15658 @item target r3900 @var{dev}
15659 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
15661 @kindex target array
15662 @item target array @var{dev}
15663 Array Tech LSI33K RAID controller board.
15669 @value{GDBN} also supports these special commands for MIPS targets:
15672 @item set mipsfpu double
15673 @itemx set mipsfpu single
15674 @itemx set mipsfpu none
15675 @itemx set mipsfpu auto
15676 @itemx show mipsfpu
15677 @kindex set mipsfpu
15678 @kindex show mipsfpu
15679 @cindex MIPS remote floating point
15680 @cindex floating point, MIPS remote
15681 If your target board does not support the MIPS floating point
15682 coprocessor, you should use the command @samp{set mipsfpu none} (if you
15683 need this, you may wish to put the command in your @value{GDBN} init
15684 file). This tells @value{GDBN} how to find the return value of
15685 functions which return floating point values. It also allows
15686 @value{GDBN} to avoid saving the floating point registers when calling
15687 functions on the board. If you are using a floating point coprocessor
15688 with only single precision floating point support, as on the @sc{r4650}
15689 processor, use the command @samp{set mipsfpu single}. The default
15690 double precision floating point coprocessor may be selected using
15691 @samp{set mipsfpu double}.
15693 In previous versions the only choices were double precision or no
15694 floating point, so @samp{set mipsfpu on} will select double precision
15695 and @samp{set mipsfpu off} will select no floating point.
15697 As usual, you can inquire about the @code{mipsfpu} variable with
15698 @samp{show mipsfpu}.
15700 @item set timeout @var{seconds}
15701 @itemx set retransmit-timeout @var{seconds}
15702 @itemx show timeout
15703 @itemx show retransmit-timeout
15704 @cindex @code{timeout}, MIPS protocol
15705 @cindex @code{retransmit-timeout}, MIPS protocol
15706 @kindex set timeout
15707 @kindex show timeout
15708 @kindex set retransmit-timeout
15709 @kindex show retransmit-timeout
15710 You can control the timeout used while waiting for a packet, in the MIPS
15711 remote protocol, with the @code{set timeout @var{seconds}} command. The
15712 default is 5 seconds. Similarly, you can control the timeout used while
15713 waiting for an acknowledgment of a packet with the @code{set
15714 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
15715 You can inspect both values with @code{show timeout} and @code{show
15716 retransmit-timeout}. (These commands are @emph{only} available when
15717 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
15719 The timeout set by @code{set timeout} does not apply when @value{GDBN}
15720 is waiting for your program to stop. In that case, @value{GDBN} waits
15721 forever because it has no way of knowing how long the program is going
15722 to run before stopping.
15724 @item set syn-garbage-limit @var{num}
15725 @kindex set syn-garbage-limit@r{, MIPS remote}
15726 @cindex synchronize with remote MIPS target
15727 Limit the maximum number of characters @value{GDBN} should ignore when
15728 it tries to synchronize with the remote target. The default is 10
15729 characters. Setting the limit to -1 means there's no limit.
15731 @item show syn-garbage-limit
15732 @kindex show syn-garbage-limit@r{, MIPS remote}
15733 Show the current limit on the number of characters to ignore when
15734 trying to synchronize with the remote system.
15736 @item set monitor-prompt @var{prompt}
15737 @kindex set monitor-prompt@r{, MIPS remote}
15738 @cindex remote monitor prompt
15739 Tell @value{GDBN} to expect the specified @var{prompt} string from the
15740 remote monitor. The default depends on the target:
15750 @item show monitor-prompt
15751 @kindex show monitor-prompt@r{, MIPS remote}
15752 Show the current strings @value{GDBN} expects as the prompt from the
15755 @item set monitor-warnings
15756 @kindex set monitor-warnings@r{, MIPS remote}
15757 Enable or disable monitor warnings about hardware breakpoints. This
15758 has effect only for the @code{lsi} target. When on, @value{GDBN} will
15759 display warning messages whose codes are returned by the @code{lsi}
15760 PMON monitor for breakpoint commands.
15762 @item show monitor-warnings
15763 @kindex show monitor-warnings@r{, MIPS remote}
15764 Show the current setting of printing monitor warnings.
15766 @item pmon @var{command}
15767 @kindex pmon@r{, MIPS remote}
15768 @cindex send PMON command
15769 This command allows sending an arbitrary @var{command} string to the
15770 monitor. The monitor must be in debug mode for this to work.
15773 @node OpenRISC 1000
15774 @subsection OpenRISC 1000
15775 @cindex OpenRISC 1000
15777 @cindex or1k boards
15778 See OR1k Architecture document (@uref{www.opencores.org}) for more information
15779 about platform and commands.
15783 @kindex target jtag
15784 @item target jtag jtag://@var{host}:@var{port}
15786 Connects to remote JTAG server.
15787 JTAG remote server can be either an or1ksim or JTAG server,
15788 connected via parallel port to the board.
15790 Example: @code{target jtag jtag://localhost:9999}
15793 @item or1ksim @var{command}
15794 If connected to @code{or1ksim} OpenRISC 1000 Architectural
15795 Simulator, proprietary commands can be executed.
15797 @kindex info or1k spr
15798 @item info or1k spr
15799 Displays spr groups.
15801 @item info or1k spr @var{group}
15802 @itemx info or1k spr @var{groupno}
15803 Displays register names in selected group.
15805 @item info or1k spr @var{group} @var{register}
15806 @itemx info or1k spr @var{register}
15807 @itemx info or1k spr @var{groupno} @var{registerno}
15808 @itemx info or1k spr @var{registerno}
15809 Shows information about specified spr register.
15812 @item spr @var{group} @var{register} @var{value}
15813 @itemx spr @var{register @var{value}}
15814 @itemx spr @var{groupno} @var{registerno @var{value}}
15815 @itemx spr @var{registerno @var{value}}
15816 Writes @var{value} to specified spr register.
15819 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
15820 It is very similar to @value{GDBN} trace, except it does not interfere with normal
15821 program execution and is thus much faster. Hardware breakpoints/watchpoint
15822 triggers can be set using:
15825 Load effective address/data
15827 Store effective address/data
15829 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
15834 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
15835 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
15837 @code{htrace} commands:
15838 @cindex OpenRISC 1000 htrace
15841 @item hwatch @var{conditional}
15842 Set hardware watchpoint on combination of Load/Store Effective Address(es)
15843 or Data. For example:
15845 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
15847 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
15851 Display information about current HW trace configuration.
15853 @item htrace trigger @var{conditional}
15854 Set starting criteria for HW trace.
15856 @item htrace qualifier @var{conditional}
15857 Set acquisition qualifier for HW trace.
15859 @item htrace stop @var{conditional}
15860 Set HW trace stopping criteria.
15862 @item htrace record [@var{data}]*
15863 Selects the data to be recorded, when qualifier is met and HW trace was
15866 @item htrace enable
15867 @itemx htrace disable
15868 Enables/disables the HW trace.
15870 @item htrace rewind [@var{filename}]
15871 Clears currently recorded trace data.
15873 If filename is specified, new trace file is made and any newly collected data
15874 will be written there.
15876 @item htrace print [@var{start} [@var{len}]]
15877 Prints trace buffer, using current record configuration.
15879 @item htrace mode continuous
15880 Set continuous trace mode.
15882 @item htrace mode suspend
15883 Set suspend trace mode.
15887 @node PowerPC Embedded
15888 @subsection PowerPC Embedded
15890 @value{GDBN} provides the following PowerPC-specific commands:
15893 @kindex set powerpc
15894 @item set powerpc soft-float
15895 @itemx show powerpc soft-float
15896 Force @value{GDBN} to use (or not use) a software floating point calling
15897 convention. By default, @value{GDBN} selects the calling convention based
15898 on the selected architecture and the provided executable file.
15900 @item set powerpc vector-abi
15901 @itemx show powerpc vector-abi
15902 Force @value{GDBN} to use the specified calling convention for vector
15903 arguments and return values. The valid options are @samp{auto};
15904 @samp{generic}, to avoid vector registers even if they are present;
15905 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
15906 registers. By default, @value{GDBN} selects the calling convention
15907 based on the selected architecture and the provided executable file.
15909 @kindex target dink32
15910 @item target dink32 @var{dev}
15911 DINK32 ROM monitor.
15913 @kindex target ppcbug
15914 @item target ppcbug @var{dev}
15915 @kindex target ppcbug1
15916 @item target ppcbug1 @var{dev}
15917 PPCBUG ROM monitor for PowerPC.
15920 @item target sds @var{dev}
15921 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
15924 @cindex SDS protocol
15925 The following commands specific to the SDS protocol are supported
15929 @item set sdstimeout @var{nsec}
15930 @kindex set sdstimeout
15931 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
15932 default is 2 seconds.
15934 @item show sdstimeout
15935 @kindex show sdstimeout
15936 Show the current value of the SDS timeout.
15938 @item sds @var{command}
15939 @kindex sds@r{, a command}
15940 Send the specified @var{command} string to the SDS monitor.
15945 @subsection HP PA Embedded
15949 @kindex target op50n
15950 @item target op50n @var{dev}
15951 OP50N monitor, running on an OKI HPPA board.
15953 @kindex target w89k
15954 @item target w89k @var{dev}
15955 W89K monitor, running on a Winbond HPPA board.
15960 @subsection Tsqware Sparclet
15964 @value{GDBN} enables developers to debug tasks running on
15965 Sparclet targets from a Unix host.
15966 @value{GDBN} uses code that runs on
15967 both the Unix host and on the Sparclet target. The program
15968 @code{@value{GDBP}} is installed and executed on the Unix host.
15971 @item remotetimeout @var{args}
15972 @kindex remotetimeout
15973 @value{GDBN} supports the option @code{remotetimeout}.
15974 This option is set by the user, and @var{args} represents the number of
15975 seconds @value{GDBN} waits for responses.
15978 @cindex compiling, on Sparclet
15979 When compiling for debugging, include the options @samp{-g} to get debug
15980 information and @samp{-Ttext} to relocate the program to where you wish to
15981 load it on the target. You may also want to add the options @samp{-n} or
15982 @samp{-N} in order to reduce the size of the sections. Example:
15985 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
15988 You can use @code{objdump} to verify that the addresses are what you intended:
15991 sparclet-aout-objdump --headers --syms prog
15994 @cindex running, on Sparclet
15996 your Unix execution search path to find @value{GDBN}, you are ready to
15997 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
15998 (or @code{sparclet-aout-gdb}, depending on your installation).
16000 @value{GDBN} comes up showing the prompt:
16007 * Sparclet File:: Setting the file to debug
16008 * Sparclet Connection:: Connecting to Sparclet
16009 * Sparclet Download:: Sparclet download
16010 * Sparclet Execution:: Running and debugging
16013 @node Sparclet File
16014 @subsubsection Setting File to Debug
16016 The @value{GDBN} command @code{file} lets you choose with program to debug.
16019 (gdbslet) file prog
16023 @value{GDBN} then attempts to read the symbol table of @file{prog}.
16024 @value{GDBN} locates
16025 the file by searching the directories listed in the command search
16027 If the file was compiled with debug information (option @samp{-g}), source
16028 files will be searched as well.
16029 @value{GDBN} locates
16030 the source files by searching the directories listed in the directory search
16031 path (@pxref{Environment, ,Your Program's Environment}).
16033 to find a file, it displays a message such as:
16036 prog: No such file or directory.
16039 When this happens, add the appropriate directories to the search paths with
16040 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
16041 @code{target} command again.
16043 @node Sparclet Connection
16044 @subsubsection Connecting to Sparclet
16046 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
16047 To connect to a target on serial port ``@code{ttya}'', type:
16050 (gdbslet) target sparclet /dev/ttya
16051 Remote target sparclet connected to /dev/ttya
16052 main () at ../prog.c:3
16056 @value{GDBN} displays messages like these:
16062 @node Sparclet Download
16063 @subsubsection Sparclet Download
16065 @cindex download to Sparclet
16066 Once connected to the Sparclet target,
16067 you can use the @value{GDBN}
16068 @code{load} command to download the file from the host to the target.
16069 The file name and load offset should be given as arguments to the @code{load}
16071 Since the file format is aout, the program must be loaded to the starting
16072 address. You can use @code{objdump} to find out what this value is. The load
16073 offset is an offset which is added to the VMA (virtual memory address)
16074 of each of the file's sections.
16075 For instance, if the program
16076 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
16077 and bss at 0x12010170, in @value{GDBN}, type:
16080 (gdbslet) load prog 0x12010000
16081 Loading section .text, size 0xdb0 vma 0x12010000
16084 If the code is loaded at a different address then what the program was linked
16085 to, you may need to use the @code{section} and @code{add-symbol-file} commands
16086 to tell @value{GDBN} where to map the symbol table.
16088 @node Sparclet Execution
16089 @subsubsection Running and Debugging
16091 @cindex running and debugging Sparclet programs
16092 You can now begin debugging the task using @value{GDBN}'s execution control
16093 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
16094 manual for the list of commands.
16098 Breakpoint 1 at 0x12010000: file prog.c, line 3.
16100 Starting program: prog
16101 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
16102 3 char *symarg = 0;
16104 4 char *execarg = "hello!";
16109 @subsection Fujitsu Sparclite
16113 @kindex target sparclite
16114 @item target sparclite @var{dev}
16115 Fujitsu sparclite boards, used only for the purpose of loading.
16116 You must use an additional command to debug the program.
16117 For example: target remote @var{dev} using @value{GDBN} standard
16123 @subsection Zilog Z8000
16126 @cindex simulator, Z8000
16127 @cindex Zilog Z8000 simulator
16129 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
16132 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
16133 unsegmented variant of the Z8000 architecture) or the Z8001 (the
16134 segmented variant). The simulator recognizes which architecture is
16135 appropriate by inspecting the object code.
16138 @item target sim @var{args}
16140 @kindex target sim@r{, with Z8000}
16141 Debug programs on a simulated CPU. If the simulator supports setup
16142 options, specify them via @var{args}.
16146 After specifying this target, you can debug programs for the simulated
16147 CPU in the same style as programs for your host computer; use the
16148 @code{file} command to load a new program image, the @code{run} command
16149 to run your program, and so on.
16151 As well as making available all the usual machine registers
16152 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
16153 additional items of information as specially named registers:
16158 Counts clock-ticks in the simulator.
16161 Counts instructions run in the simulator.
16164 Execution time in 60ths of a second.
16168 You can refer to these values in @value{GDBN} expressions with the usual
16169 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
16170 conditional breakpoint that suspends only after at least 5000
16171 simulated clock ticks.
16174 @subsection Atmel AVR
16177 When configured for debugging the Atmel AVR, @value{GDBN} supports the
16178 following AVR-specific commands:
16181 @item info io_registers
16182 @kindex info io_registers@r{, AVR}
16183 @cindex I/O registers (Atmel AVR)
16184 This command displays information about the AVR I/O registers. For
16185 each register, @value{GDBN} prints its number and value.
16192 When configured for debugging CRIS, @value{GDBN} provides the
16193 following CRIS-specific commands:
16196 @item set cris-version @var{ver}
16197 @cindex CRIS version
16198 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
16199 The CRIS version affects register names and sizes. This command is useful in
16200 case autodetection of the CRIS version fails.
16202 @item show cris-version
16203 Show the current CRIS version.
16205 @item set cris-dwarf2-cfi
16206 @cindex DWARF-2 CFI and CRIS
16207 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
16208 Change to @samp{off} when using @code{gcc-cris} whose version is below
16211 @item show cris-dwarf2-cfi
16212 Show the current state of using DWARF-2 CFI.
16214 @item set cris-mode @var{mode}
16216 Set the current CRIS mode to @var{mode}. It should only be changed when
16217 debugging in guru mode, in which case it should be set to
16218 @samp{guru} (the default is @samp{normal}).
16220 @item show cris-mode
16221 Show the current CRIS mode.
16225 @subsection Renesas Super-H
16228 For the Renesas Super-H processor, @value{GDBN} provides these
16233 @kindex regs@r{, Super-H}
16234 Show the values of all Super-H registers.
16236 @item set sh calling-convention @var{convention}
16237 @kindex set sh calling-convention
16238 Set the calling-convention used when calling functions from @value{GDBN}.
16239 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
16240 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
16241 convention. If the DWARF-2 information of the called function specifies
16242 that the function follows the Renesas calling convention, the function
16243 is called using the Renesas calling convention. If the calling convention
16244 is set to @samp{renesas}, the Renesas calling convention is always used,
16245 regardless of the DWARF-2 information. This can be used to override the
16246 default of @samp{gcc} if debug information is missing, or the compiler
16247 does not emit the DWARF-2 calling convention entry for a function.
16249 @item show sh calling-convention
16250 @kindex show sh calling-convention
16251 Show the current calling convention setting.
16256 @node Architectures
16257 @section Architectures
16259 This section describes characteristics of architectures that affect
16260 all uses of @value{GDBN} with the architecture, both native and cross.
16267 * HPPA:: HP PA architecture
16268 * SPU:: Cell Broadband Engine SPU architecture
16273 @subsection x86 Architecture-specific Issues
16276 @item set struct-convention @var{mode}
16277 @kindex set struct-convention
16278 @cindex struct return convention
16279 @cindex struct/union returned in registers
16280 Set the convention used by the inferior to return @code{struct}s and
16281 @code{union}s from functions to @var{mode}. Possible values of
16282 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
16283 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
16284 are returned on the stack, while @code{"reg"} means that a
16285 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
16286 be returned in a register.
16288 @item show struct-convention
16289 @kindex show struct-convention
16290 Show the current setting of the convention to return @code{struct}s
16299 @kindex set rstack_high_address
16300 @cindex AMD 29K register stack
16301 @cindex register stack, AMD29K
16302 @item set rstack_high_address @var{address}
16303 On AMD 29000 family processors, registers are saved in a separate
16304 @dfn{register stack}. There is no way for @value{GDBN} to determine the
16305 extent of this stack. Normally, @value{GDBN} just assumes that the
16306 stack is ``large enough''. This may result in @value{GDBN} referencing
16307 memory locations that do not exist. If necessary, you can get around
16308 this problem by specifying the ending address of the register stack with
16309 the @code{set rstack_high_address} command. The argument should be an
16310 address, which you probably want to precede with @samp{0x} to specify in
16313 @kindex show rstack_high_address
16314 @item show rstack_high_address
16315 Display the current limit of the register stack, on AMD 29000 family
16323 See the following section.
16328 @cindex stack on Alpha
16329 @cindex stack on MIPS
16330 @cindex Alpha stack
16332 Alpha- and MIPS-based computers use an unusual stack frame, which
16333 sometimes requires @value{GDBN} to search backward in the object code to
16334 find the beginning of a function.
16336 @cindex response time, MIPS debugging
16337 To improve response time (especially for embedded applications, where
16338 @value{GDBN} may be restricted to a slow serial line for this search)
16339 you may want to limit the size of this search, using one of these
16343 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
16344 @item set heuristic-fence-post @var{limit}
16345 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
16346 search for the beginning of a function. A value of @var{0} (the
16347 default) means there is no limit. However, except for @var{0}, the
16348 larger the limit the more bytes @code{heuristic-fence-post} must search
16349 and therefore the longer it takes to run. You should only need to use
16350 this command when debugging a stripped executable.
16352 @item show heuristic-fence-post
16353 Display the current limit.
16357 These commands are available @emph{only} when @value{GDBN} is configured
16358 for debugging programs on Alpha or MIPS processors.
16360 Several MIPS-specific commands are available when debugging MIPS
16364 @item set mips abi @var{arg}
16365 @kindex set mips abi
16366 @cindex set ABI for MIPS
16367 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
16368 values of @var{arg} are:
16372 The default ABI associated with the current binary (this is the
16383 @item show mips abi
16384 @kindex show mips abi
16385 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
16388 @itemx show mipsfpu
16389 @xref{MIPS Embedded, set mipsfpu}.
16391 @item set mips mask-address @var{arg}
16392 @kindex set mips mask-address
16393 @cindex MIPS addresses, masking
16394 This command determines whether the most-significant 32 bits of 64-bit
16395 MIPS addresses are masked off. The argument @var{arg} can be
16396 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
16397 setting, which lets @value{GDBN} determine the correct value.
16399 @item show mips mask-address
16400 @kindex show mips mask-address
16401 Show whether the upper 32 bits of MIPS addresses are masked off or
16404 @item set remote-mips64-transfers-32bit-regs
16405 @kindex set remote-mips64-transfers-32bit-regs
16406 This command controls compatibility with 64-bit MIPS targets that
16407 transfer data in 32-bit quantities. If you have an old MIPS 64 target
16408 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
16409 and 64 bits for other registers, set this option to @samp{on}.
16411 @item show remote-mips64-transfers-32bit-regs
16412 @kindex show remote-mips64-transfers-32bit-regs
16413 Show the current setting of compatibility with older MIPS 64 targets.
16415 @item set debug mips
16416 @kindex set debug mips
16417 This command turns on and off debugging messages for the MIPS-specific
16418 target code in @value{GDBN}.
16420 @item show debug mips
16421 @kindex show debug mips
16422 Show the current setting of MIPS debugging messages.
16428 @cindex HPPA support
16430 When @value{GDBN} is debugging the HP PA architecture, it provides the
16431 following special commands:
16434 @item set debug hppa
16435 @kindex set debug hppa
16436 This command determines whether HPPA architecture-specific debugging
16437 messages are to be displayed.
16439 @item show debug hppa
16440 Show whether HPPA debugging messages are displayed.
16442 @item maint print unwind @var{address}
16443 @kindex maint print unwind@r{, HPPA}
16444 This command displays the contents of the unwind table entry at the
16445 given @var{address}.
16451 @subsection Cell Broadband Engine SPU architecture
16452 @cindex Cell Broadband Engine
16455 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
16456 it provides the following special commands:
16459 @item info spu event
16461 Display SPU event facility status. Shows current event mask
16462 and pending event status.
16464 @item info spu signal
16465 Display SPU signal notification facility status. Shows pending
16466 signal-control word and signal notification mode of both signal
16467 notification channels.
16469 @item info spu mailbox
16470 Display SPU mailbox facility status. Shows all pending entries,
16471 in order of processing, in each of the SPU Write Outbound,
16472 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
16475 Display MFC DMA status. Shows all pending commands in the MFC
16476 DMA queue. For each entry, opcode, tag, class IDs, effective
16477 and local store addresses and transfer size are shown.
16479 @item info spu proxydma
16480 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
16481 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
16482 and local store addresses and transfer size are shown.
16487 @subsection PowerPC
16488 @cindex PowerPC architecture
16490 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
16491 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
16492 numbers stored in the floating point registers. These values must be stored
16493 in two consecutive registers, always starting at an even register like
16494 @code{f0} or @code{f2}.
16496 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
16497 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
16498 @code{f2} and @code{f3} for @code{$dl1} and so on.
16500 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
16501 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
16504 @node Controlling GDB
16505 @chapter Controlling @value{GDBN}
16507 You can alter the way @value{GDBN} interacts with you by using the
16508 @code{set} command. For commands controlling how @value{GDBN} displays
16509 data, see @ref{Print Settings, ,Print Settings}. Other settings are
16514 * Editing:: Command editing
16515 * Command History:: Command history
16516 * Screen Size:: Screen size
16517 * Numbers:: Numbers
16518 * ABI:: Configuring the current ABI
16519 * Messages/Warnings:: Optional warnings and messages
16520 * Debugging Output:: Optional messages about internal happenings
16528 @value{GDBN} indicates its readiness to read a command by printing a string
16529 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
16530 can change the prompt string with the @code{set prompt} command. For
16531 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
16532 the prompt in one of the @value{GDBN} sessions so that you can always tell
16533 which one you are talking to.
16535 @emph{Note:} @code{set prompt} does not add a space for you after the
16536 prompt you set. This allows you to set a prompt which ends in a space
16537 or a prompt that does not.
16541 @item set prompt @var{newprompt}
16542 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
16544 @kindex show prompt
16546 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
16550 @section Command Editing
16552 @cindex command line editing
16554 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
16555 @sc{gnu} library provides consistent behavior for programs which provide a
16556 command line interface to the user. Advantages are @sc{gnu} Emacs-style
16557 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
16558 substitution, and a storage and recall of command history across
16559 debugging sessions.
16561 You may control the behavior of command line editing in @value{GDBN} with the
16562 command @code{set}.
16565 @kindex set editing
16568 @itemx set editing on
16569 Enable command line editing (enabled by default).
16571 @item set editing off
16572 Disable command line editing.
16574 @kindex show editing
16576 Show whether command line editing is enabled.
16579 @xref{Command Line Editing}, for more details about the Readline
16580 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
16581 encouraged to read that chapter.
16583 @node Command History
16584 @section Command History
16585 @cindex command history
16587 @value{GDBN} can keep track of the commands you type during your
16588 debugging sessions, so that you can be certain of precisely what
16589 happened. Use these commands to manage the @value{GDBN} command
16592 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
16593 package, to provide the history facility. @xref{Using History
16594 Interactively}, for the detailed description of the History library.
16596 To issue a command to @value{GDBN} without affecting certain aspects of
16597 the state which is seen by users, prefix it with @samp{server }
16598 (@pxref{Server Prefix}). This
16599 means that this command will not affect the command history, nor will it
16600 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
16601 pressed on a line by itself.
16603 @cindex @code{server}, command prefix
16604 The server prefix does not affect the recording of values into the value
16605 history; to print a value without recording it into the value history,
16606 use the @code{output} command instead of the @code{print} command.
16608 Here is the description of @value{GDBN} commands related to command
16612 @cindex history substitution
16613 @cindex history file
16614 @kindex set history filename
16615 @cindex @env{GDBHISTFILE}, environment variable
16616 @item set history filename @var{fname}
16617 Set the name of the @value{GDBN} command history file to @var{fname}.
16618 This is the file where @value{GDBN} reads an initial command history
16619 list, and where it writes the command history from this session when it
16620 exits. You can access this list through history expansion or through
16621 the history command editing characters listed below. This file defaults
16622 to the value of the environment variable @code{GDBHISTFILE}, or to
16623 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
16626 @cindex save command history
16627 @kindex set history save
16628 @item set history save
16629 @itemx set history save on
16630 Record command history in a file, whose name may be specified with the
16631 @code{set history filename} command. By default, this option is disabled.
16633 @item set history save off
16634 Stop recording command history in a file.
16636 @cindex history size
16637 @kindex set history size
16638 @cindex @env{HISTSIZE}, environment variable
16639 @item set history size @var{size}
16640 Set the number of commands which @value{GDBN} keeps in its history list.
16641 This defaults to the value of the environment variable
16642 @code{HISTSIZE}, or to 256 if this variable is not set.
16645 History expansion assigns special meaning to the character @kbd{!}.
16646 @xref{Event Designators}, for more details.
16648 @cindex history expansion, turn on/off
16649 Since @kbd{!} is also the logical not operator in C, history expansion
16650 is off by default. If you decide to enable history expansion with the
16651 @code{set history expansion on} command, you may sometimes need to
16652 follow @kbd{!} (when it is used as logical not, in an expression) with
16653 a space or a tab to prevent it from being expanded. The readline
16654 history facilities do not attempt substitution on the strings
16655 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
16657 The commands to control history expansion are:
16660 @item set history expansion on
16661 @itemx set history expansion
16662 @kindex set history expansion
16663 Enable history expansion. History expansion is off by default.
16665 @item set history expansion off
16666 Disable history expansion.
16669 @kindex show history
16671 @itemx show history filename
16672 @itemx show history save
16673 @itemx show history size
16674 @itemx show history expansion
16675 These commands display the state of the @value{GDBN} history parameters.
16676 @code{show history} by itself displays all four states.
16681 @kindex show commands
16682 @cindex show last commands
16683 @cindex display command history
16684 @item show commands
16685 Display the last ten commands in the command history.
16687 @item show commands @var{n}
16688 Print ten commands centered on command number @var{n}.
16690 @item show commands +
16691 Print ten commands just after the commands last printed.
16695 @section Screen Size
16696 @cindex size of screen
16697 @cindex pauses in output
16699 Certain commands to @value{GDBN} may produce large amounts of
16700 information output to the screen. To help you read all of it,
16701 @value{GDBN} pauses and asks you for input at the end of each page of
16702 output. Type @key{RET} when you want to continue the output, or @kbd{q}
16703 to discard the remaining output. Also, the screen width setting
16704 determines when to wrap lines of output. Depending on what is being
16705 printed, @value{GDBN} tries to break the line at a readable place,
16706 rather than simply letting it overflow onto the following line.
16708 Normally @value{GDBN} knows the size of the screen from the terminal
16709 driver software. For example, on Unix @value{GDBN} uses the termcap data base
16710 together with the value of the @code{TERM} environment variable and the
16711 @code{stty rows} and @code{stty cols} settings. If this is not correct,
16712 you can override it with the @code{set height} and @code{set
16719 @kindex show height
16720 @item set height @var{lpp}
16722 @itemx set width @var{cpl}
16724 These @code{set} commands specify a screen height of @var{lpp} lines and
16725 a screen width of @var{cpl} characters. The associated @code{show}
16726 commands display the current settings.
16728 If you specify a height of zero lines, @value{GDBN} does not pause during
16729 output no matter how long the output is. This is useful if output is to a
16730 file or to an editor buffer.
16732 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
16733 from wrapping its output.
16735 @item set pagination on
16736 @itemx set pagination off
16737 @kindex set pagination
16738 Turn the output pagination on or off; the default is on. Turning
16739 pagination off is the alternative to @code{set height 0}.
16741 @item show pagination
16742 @kindex show pagination
16743 Show the current pagination mode.
16748 @cindex number representation
16749 @cindex entering numbers
16751 You can always enter numbers in octal, decimal, or hexadecimal in
16752 @value{GDBN} by the usual conventions: octal numbers begin with
16753 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
16754 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
16755 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
16756 10; likewise, the default display for numbers---when no particular
16757 format is specified---is base 10. You can change the default base for
16758 both input and output with the commands described below.
16761 @kindex set input-radix
16762 @item set input-radix @var{base}
16763 Set the default base for numeric input. Supported choices
16764 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
16765 specified either unambiguously or using the current input radix; for
16769 set input-radix 012
16770 set input-radix 10.
16771 set input-radix 0xa
16775 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
16776 leaves the input radix unchanged, no matter what it was, since
16777 @samp{10}, being without any leading or trailing signs of its base, is
16778 interpreted in the current radix. Thus, if the current radix is 16,
16779 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
16782 @kindex set output-radix
16783 @item set output-radix @var{base}
16784 Set the default base for numeric display. Supported choices
16785 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
16786 specified either unambiguously or using the current input radix.
16788 @kindex show input-radix
16789 @item show input-radix
16790 Display the current default base for numeric input.
16792 @kindex show output-radix
16793 @item show output-radix
16794 Display the current default base for numeric display.
16796 @item set radix @r{[}@var{base}@r{]}
16800 These commands set and show the default base for both input and output
16801 of numbers. @code{set radix} sets the radix of input and output to
16802 the same base; without an argument, it resets the radix back to its
16803 default value of 10.
16808 @section Configuring the Current ABI
16810 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
16811 application automatically. However, sometimes you need to override its
16812 conclusions. Use these commands to manage @value{GDBN}'s view of the
16819 One @value{GDBN} configuration can debug binaries for multiple operating
16820 system targets, either via remote debugging or native emulation.
16821 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
16822 but you can override its conclusion using the @code{set osabi} command.
16823 One example where this is useful is in debugging of binaries which use
16824 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
16825 not have the same identifying marks that the standard C library for your
16830 Show the OS ABI currently in use.
16833 With no argument, show the list of registered available OS ABI's.
16835 @item set osabi @var{abi}
16836 Set the current OS ABI to @var{abi}.
16839 @cindex float promotion
16841 Generally, the way that an argument of type @code{float} is passed to a
16842 function depends on whether the function is prototyped. For a prototyped
16843 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
16844 according to the architecture's convention for @code{float}. For unprototyped
16845 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
16846 @code{double} and then passed.
16848 Unfortunately, some forms of debug information do not reliably indicate whether
16849 a function is prototyped. If @value{GDBN} calls a function that is not marked
16850 as prototyped, it consults @kbd{set coerce-float-to-double}.
16853 @kindex set coerce-float-to-double
16854 @item set coerce-float-to-double
16855 @itemx set coerce-float-to-double on
16856 Arguments of type @code{float} will be promoted to @code{double} when passed
16857 to an unprototyped function. This is the default setting.
16859 @item set coerce-float-to-double off
16860 Arguments of type @code{float} will be passed directly to unprototyped
16863 @kindex show coerce-float-to-double
16864 @item show coerce-float-to-double
16865 Show the current setting of promoting @code{float} to @code{double}.
16869 @kindex show cp-abi
16870 @value{GDBN} needs to know the ABI used for your program's C@t{++}
16871 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
16872 used to build your application. @value{GDBN} only fully supports
16873 programs with a single C@t{++} ABI; if your program contains code using
16874 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
16875 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
16876 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
16877 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
16878 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
16879 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
16884 Show the C@t{++} ABI currently in use.
16887 With no argument, show the list of supported C@t{++} ABI's.
16889 @item set cp-abi @var{abi}
16890 @itemx set cp-abi auto
16891 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
16894 @node Messages/Warnings
16895 @section Optional Warnings and Messages
16897 @cindex verbose operation
16898 @cindex optional warnings
16899 By default, @value{GDBN} is silent about its inner workings. If you are
16900 running on a slow machine, you may want to use the @code{set verbose}
16901 command. This makes @value{GDBN} tell you when it does a lengthy
16902 internal operation, so you will not think it has crashed.
16904 Currently, the messages controlled by @code{set verbose} are those
16905 which announce that the symbol table for a source file is being read;
16906 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
16909 @kindex set verbose
16910 @item set verbose on
16911 Enables @value{GDBN} output of certain informational messages.
16913 @item set verbose off
16914 Disables @value{GDBN} output of certain informational messages.
16916 @kindex show verbose
16918 Displays whether @code{set verbose} is on or off.
16921 By default, if @value{GDBN} encounters bugs in the symbol table of an
16922 object file, it is silent; but if you are debugging a compiler, you may
16923 find this information useful (@pxref{Symbol Errors, ,Errors Reading
16928 @kindex set complaints
16929 @item set complaints @var{limit}
16930 Permits @value{GDBN} to output @var{limit} complaints about each type of
16931 unusual symbols before becoming silent about the problem. Set
16932 @var{limit} to zero to suppress all complaints; set it to a large number
16933 to prevent complaints from being suppressed.
16935 @kindex show complaints
16936 @item show complaints
16937 Displays how many symbol complaints @value{GDBN} is permitted to produce.
16941 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
16942 lot of stupid questions to confirm certain commands. For example, if
16943 you try to run a program which is already running:
16947 The program being debugged has been started already.
16948 Start it from the beginning? (y or n)
16951 If you are willing to unflinchingly face the consequences of your own
16952 commands, you can disable this ``feature'':
16956 @kindex set confirm
16958 @cindex confirmation
16959 @cindex stupid questions
16960 @item set confirm off
16961 Disables confirmation requests.
16963 @item set confirm on
16964 Enables confirmation requests (the default).
16966 @kindex show confirm
16968 Displays state of confirmation requests.
16972 @cindex command tracing
16973 If you need to debug user-defined commands or sourced files you may find it
16974 useful to enable @dfn{command tracing}. In this mode each command will be
16975 printed as it is executed, prefixed with one or more @samp{+} symbols, the
16976 quantity denoting the call depth of each command.
16979 @kindex set trace-commands
16980 @cindex command scripts, debugging
16981 @item set trace-commands on
16982 Enable command tracing.
16983 @item set trace-commands off
16984 Disable command tracing.
16985 @item show trace-commands
16986 Display the current state of command tracing.
16989 @node Debugging Output
16990 @section Optional Messages about Internal Happenings
16991 @cindex optional debugging messages
16993 @value{GDBN} has commands that enable optional debugging messages from
16994 various @value{GDBN} subsystems; normally these commands are of
16995 interest to @value{GDBN} maintainers, or when reporting a bug. This
16996 section documents those commands.
16999 @kindex set exec-done-display
17000 @item set exec-done-display
17001 Turns on or off the notification of asynchronous commands'
17002 completion. When on, @value{GDBN} will print a message when an
17003 asynchronous command finishes its execution. The default is off.
17004 @kindex show exec-done-display
17005 @item show exec-done-display
17006 Displays the current setting of asynchronous command completion
17009 @cindex gdbarch debugging info
17010 @cindex architecture debugging info
17011 @item set debug arch
17012 Turns on or off display of gdbarch debugging info. The default is off
17014 @item show debug arch
17015 Displays the current state of displaying gdbarch debugging info.
17016 @item set debug aix-thread
17017 @cindex AIX threads
17018 Display debugging messages about inner workings of the AIX thread
17020 @item show debug aix-thread
17021 Show the current state of AIX thread debugging info display.
17022 @item set debug displaced
17023 @cindex displaced stepping debugging info
17024 Turns on or off display of @value{GDBN} debugging info for the
17025 displaced stepping support. The default is off.
17026 @item show debug displaced
17027 Displays the current state of displaying @value{GDBN} debugging info
17028 related to displaced stepping.
17029 @item set debug event
17030 @cindex event debugging info
17031 Turns on or off display of @value{GDBN} event debugging info. The
17033 @item show debug event
17034 Displays the current state of displaying @value{GDBN} event debugging
17036 @item set debug expression
17037 @cindex expression debugging info
17038 Turns on or off display of debugging info about @value{GDBN}
17039 expression parsing. The default is off.
17040 @item show debug expression
17041 Displays the current state of displaying debugging info about
17042 @value{GDBN} expression parsing.
17043 @item set debug frame
17044 @cindex frame debugging info
17045 Turns on or off display of @value{GDBN} frame debugging info. The
17047 @item show debug frame
17048 Displays the current state of displaying @value{GDBN} frame debugging
17050 @item set debug infrun
17051 @cindex inferior debugging info
17052 Turns on or off display of @value{GDBN} debugging info for running the inferior.
17053 The default is off. @file{infrun.c} contains GDB's runtime state machine used
17054 for implementing operations such as single-stepping the inferior.
17055 @item show debug infrun
17056 Displays the current state of @value{GDBN} inferior debugging.
17057 @item set debug lin-lwp
17058 @cindex @sc{gnu}/Linux LWP debug messages
17059 @cindex Linux lightweight processes
17060 Turns on or off debugging messages from the Linux LWP debug support.
17061 @item show debug lin-lwp
17062 Show the current state of Linux LWP debugging messages.
17063 @item set debug lin-lwp-async
17064 @cindex @sc{gnu}/Linux LWP async debug messages
17065 @cindex Linux lightweight processes
17066 Turns on or off debugging messages from the Linux LWP async debug support.
17067 @item show debug lin-lwp-async
17068 Show the current state of Linux LWP async debugging messages.
17069 @item set debug observer
17070 @cindex observer debugging info
17071 Turns on or off display of @value{GDBN} observer debugging. This
17072 includes info such as the notification of observable events.
17073 @item show debug observer
17074 Displays the current state of observer debugging.
17075 @item set debug overload
17076 @cindex C@t{++} overload debugging info
17077 Turns on or off display of @value{GDBN} C@t{++} overload debugging
17078 info. This includes info such as ranking of functions, etc. The default
17080 @item show debug overload
17081 Displays the current state of displaying @value{GDBN} C@t{++} overload
17083 @cindex packets, reporting on stdout
17084 @cindex serial connections, debugging
17085 @cindex debug remote protocol
17086 @cindex remote protocol debugging
17087 @cindex display remote packets
17088 @item set debug remote
17089 Turns on or off display of reports on all packets sent back and forth across
17090 the serial line to the remote machine. The info is printed on the
17091 @value{GDBN} standard output stream. The default is off.
17092 @item show debug remote
17093 Displays the state of display of remote packets.
17094 @item set debug serial
17095 Turns on or off display of @value{GDBN} serial debugging info. The
17097 @item show debug serial
17098 Displays the current state of displaying @value{GDBN} serial debugging
17100 @item set debug solib-frv
17101 @cindex FR-V shared-library debugging
17102 Turns on or off debugging messages for FR-V shared-library code.
17103 @item show debug solib-frv
17104 Display the current state of FR-V shared-library code debugging
17106 @item set debug target
17107 @cindex target debugging info
17108 Turns on or off display of @value{GDBN} target debugging info. This info
17109 includes what is going on at the target level of GDB, as it happens. The
17110 default is 0. Set it to 1 to track events, and to 2 to also track the
17111 value of large memory transfers. Changes to this flag do not take effect
17112 until the next time you connect to a target or use the @code{run} command.
17113 @item show debug target
17114 Displays the current state of displaying @value{GDBN} target debugging
17116 @item set debug timestamp
17117 @cindex timestampping debugging info
17118 Turns on or off display of timestamps with @value{GDBN} debugging info.
17119 When enabled, seconds and microseconds are displayed before each debugging
17121 @item show debug timestamp
17122 Displays the current state of displaying timestamps with @value{GDBN}
17124 @item set debugvarobj
17125 @cindex variable object debugging info
17126 Turns on or off display of @value{GDBN} variable object debugging
17127 info. The default is off.
17128 @item show debugvarobj
17129 Displays the current state of displaying @value{GDBN} variable object
17131 @item set debug xml
17132 @cindex XML parser debugging
17133 Turns on or off debugging messages for built-in XML parsers.
17134 @item show debug xml
17135 Displays the current state of XML debugging messages.
17138 @node Extending GDB
17139 @chapter Extending @value{GDBN}
17140 @cindex extending GDB
17142 @value{GDBN} provides two mechanisms for extension. The first is based
17143 on composition of @value{GDBN} commands, and the second is based on the
17144 Python scripting language.
17147 * Sequences:: Canned Sequences of Commands
17148 * Python:: Scripting @value{GDBN} using Python
17152 @section Canned Sequences of Commands
17154 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
17155 Command Lists}), @value{GDBN} provides two ways to store sequences of
17156 commands for execution as a unit: user-defined commands and command
17160 * Define:: How to define your own commands
17161 * Hooks:: Hooks for user-defined commands
17162 * Command Files:: How to write scripts of commands to be stored in a file
17163 * Output:: Commands for controlled output
17167 @subsection User-defined Commands
17169 @cindex user-defined command
17170 @cindex arguments, to user-defined commands
17171 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
17172 which you assign a new name as a command. This is done with the
17173 @code{define} command. User commands may accept up to 10 arguments
17174 separated by whitespace. Arguments are accessed within the user command
17175 via @code{$arg0@dots{}$arg9}. A trivial example:
17179 print $arg0 + $arg1 + $arg2
17184 To execute the command use:
17191 This defines the command @code{adder}, which prints the sum of
17192 its three arguments. Note the arguments are text substitutions, so they may
17193 reference variables, use complex expressions, or even perform inferior
17196 @cindex argument count in user-defined commands
17197 @cindex how many arguments (user-defined commands)
17198 In addition, @code{$argc} may be used to find out how many arguments have
17199 been passed. This expands to a number in the range 0@dots{}10.
17204 print $arg0 + $arg1
17207 print $arg0 + $arg1 + $arg2
17215 @item define @var{commandname}
17216 Define a command named @var{commandname}. If there is already a command
17217 by that name, you are asked to confirm that you want to redefine it.
17219 The definition of the command is made up of other @value{GDBN} command lines,
17220 which are given following the @code{define} command. The end of these
17221 commands is marked by a line containing @code{end}.
17224 @kindex end@r{ (user-defined commands)}
17225 @item document @var{commandname}
17226 Document the user-defined command @var{commandname}, so that it can be
17227 accessed by @code{help}. The command @var{commandname} must already be
17228 defined. This command reads lines of documentation just as @code{define}
17229 reads the lines of the command definition, ending with @code{end}.
17230 After the @code{document} command is finished, @code{help} on command
17231 @var{commandname} displays the documentation you have written.
17233 You may use the @code{document} command again to change the
17234 documentation of a command. Redefining the command with @code{define}
17235 does not change the documentation.
17237 @kindex dont-repeat
17238 @cindex don't repeat command
17240 Used inside a user-defined command, this tells @value{GDBN} that this
17241 command should not be repeated when the user hits @key{RET}
17242 (@pxref{Command Syntax, repeat last command}).
17244 @kindex help user-defined
17245 @item help user-defined
17246 List all user-defined commands, with the first line of the documentation
17251 @itemx show user @var{commandname}
17252 Display the @value{GDBN} commands used to define @var{commandname} (but
17253 not its documentation). If no @var{commandname} is given, display the
17254 definitions for all user-defined commands.
17256 @cindex infinite recursion in user-defined commands
17257 @kindex show max-user-call-depth
17258 @kindex set max-user-call-depth
17259 @item show max-user-call-depth
17260 @itemx set max-user-call-depth
17261 The value of @code{max-user-call-depth} controls how many recursion
17262 levels are allowed in user-defined commands before @value{GDBN} suspects an
17263 infinite recursion and aborts the command.
17266 In addition to the above commands, user-defined commands frequently
17267 use control flow commands, described in @ref{Command Files}.
17269 When user-defined commands are executed, the
17270 commands of the definition are not printed. An error in any command
17271 stops execution of the user-defined command.
17273 If used interactively, commands that would ask for confirmation proceed
17274 without asking when used inside a user-defined command. Many @value{GDBN}
17275 commands that normally print messages to say what they are doing omit the
17276 messages when used in a user-defined command.
17279 @subsection User-defined Command Hooks
17280 @cindex command hooks
17281 @cindex hooks, for commands
17282 @cindex hooks, pre-command
17285 You may define @dfn{hooks}, which are a special kind of user-defined
17286 command. Whenever you run the command @samp{foo}, if the user-defined
17287 command @samp{hook-foo} exists, it is executed (with no arguments)
17288 before that command.
17290 @cindex hooks, post-command
17292 A hook may also be defined which is run after the command you executed.
17293 Whenever you run the command @samp{foo}, if the user-defined command
17294 @samp{hookpost-foo} exists, it is executed (with no arguments) after
17295 that command. Post-execution hooks may exist simultaneously with
17296 pre-execution hooks, for the same command.
17298 It is valid for a hook to call the command which it hooks. If this
17299 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
17301 @c It would be nice if hookpost could be passed a parameter indicating
17302 @c if the command it hooks executed properly or not. FIXME!
17304 @kindex stop@r{, a pseudo-command}
17305 In addition, a pseudo-command, @samp{stop} exists. Defining
17306 (@samp{hook-stop}) makes the associated commands execute every time
17307 execution stops in your program: before breakpoint commands are run,
17308 displays are printed, or the stack frame is printed.
17310 For example, to ignore @code{SIGALRM} signals while
17311 single-stepping, but treat them normally during normal execution,
17316 handle SIGALRM nopass
17320 handle SIGALRM pass
17323 define hook-continue
17324 handle SIGALRM pass
17328 As a further example, to hook at the beginning and end of the @code{echo}
17329 command, and to add extra text to the beginning and end of the message,
17337 define hookpost-echo
17341 (@value{GDBP}) echo Hello World
17342 <<<---Hello World--->>>
17347 You can define a hook for any single-word command in @value{GDBN}, but
17348 not for command aliases; you should define a hook for the basic command
17349 name, e.g.@: @code{backtrace} rather than @code{bt}.
17350 @c FIXME! So how does Joe User discover whether a command is an alias
17352 If an error occurs during the execution of your hook, execution of
17353 @value{GDBN} commands stops and @value{GDBN} issues a prompt
17354 (before the command that you actually typed had a chance to run).
17356 If you try to define a hook which does not match any known command, you
17357 get a warning from the @code{define} command.
17359 @node Command Files
17360 @subsection Command Files
17362 @cindex command files
17363 @cindex scripting commands
17364 A command file for @value{GDBN} is a text file made of lines that are
17365 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
17366 also be included. An empty line in a command file does nothing; it
17367 does not mean to repeat the last command, as it would from the
17370 You can request the execution of a command file with the @code{source}
17375 @cindex execute commands from a file
17376 @item source [@code{-v}] @var{filename}
17377 Execute the command file @var{filename}.
17380 The lines in a command file are generally executed sequentially,
17381 unless the order of execution is changed by one of the
17382 @emph{flow-control commands} described below. The commands are not
17383 printed as they are executed. An error in any command terminates
17384 execution of the command file and control is returned to the console.
17386 @value{GDBN} searches for @var{filename} in the current directory and then
17387 on the search path (specified with the @samp{directory} command).
17389 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
17390 each command as it is executed. The option must be given before
17391 @var{filename}, and is interpreted as part of the filename anywhere else.
17393 Commands that would ask for confirmation if used interactively proceed
17394 without asking when used in a command file. Many @value{GDBN} commands that
17395 normally print messages to say what they are doing omit the messages
17396 when called from command files.
17398 @value{GDBN} also accepts command input from standard input. In this
17399 mode, normal output goes to standard output and error output goes to
17400 standard error. Errors in a command file supplied on standard input do
17401 not terminate execution of the command file---execution continues with
17405 gdb < cmds > log 2>&1
17408 (The syntax above will vary depending on the shell used.) This example
17409 will execute commands from the file @file{cmds}. All output and errors
17410 would be directed to @file{log}.
17412 Since commands stored on command files tend to be more general than
17413 commands typed interactively, they frequently need to deal with
17414 complicated situations, such as different or unexpected values of
17415 variables and symbols, changes in how the program being debugged is
17416 built, etc. @value{GDBN} provides a set of flow-control commands to
17417 deal with these complexities. Using these commands, you can write
17418 complex scripts that loop over data structures, execute commands
17419 conditionally, etc.
17426 This command allows to include in your script conditionally executed
17427 commands. The @code{if} command takes a single argument, which is an
17428 expression to evaluate. It is followed by a series of commands that
17429 are executed only if the expression is true (its value is nonzero).
17430 There can then optionally be an @code{else} line, followed by a series
17431 of commands that are only executed if the expression was false. The
17432 end of the list is marked by a line containing @code{end}.
17436 This command allows to write loops. Its syntax is similar to
17437 @code{if}: the command takes a single argument, which is an expression
17438 to evaluate, and must be followed by the commands to execute, one per
17439 line, terminated by an @code{end}. These commands are called the
17440 @dfn{body} of the loop. The commands in the body of @code{while} are
17441 executed repeatedly as long as the expression evaluates to true.
17445 This command exits the @code{while} loop in whose body it is included.
17446 Execution of the script continues after that @code{while}s @code{end}
17449 @kindex loop_continue
17450 @item loop_continue
17451 This command skips the execution of the rest of the body of commands
17452 in the @code{while} loop in whose body it is included. Execution
17453 branches to the beginning of the @code{while} loop, where it evaluates
17454 the controlling expression.
17456 @kindex end@r{ (if/else/while commands)}
17458 Terminate the block of commands that are the body of @code{if},
17459 @code{else}, or @code{while} flow-control commands.
17464 @subsection Commands for Controlled Output
17466 During the execution of a command file or a user-defined command, normal
17467 @value{GDBN} output is suppressed; the only output that appears is what is
17468 explicitly printed by the commands in the definition. This section
17469 describes three commands useful for generating exactly the output you
17474 @item echo @var{text}
17475 @c I do not consider backslash-space a standard C escape sequence
17476 @c because it is not in ANSI.
17477 Print @var{text}. Nonprinting characters can be included in
17478 @var{text} using C escape sequences, such as @samp{\n} to print a
17479 newline. @strong{No newline is printed unless you specify one.}
17480 In addition to the standard C escape sequences, a backslash followed
17481 by a space stands for a space. This is useful for displaying a
17482 string with spaces at the beginning or the end, since leading and
17483 trailing spaces are otherwise trimmed from all arguments.
17484 To print @samp{@w{ }and foo =@w{ }}, use the command
17485 @samp{echo \@w{ }and foo = \@w{ }}.
17487 A backslash at the end of @var{text} can be used, as in C, to continue
17488 the command onto subsequent lines. For example,
17491 echo This is some text\n\
17492 which is continued\n\
17493 onto several lines.\n
17496 produces the same output as
17499 echo This is some text\n
17500 echo which is continued\n
17501 echo onto several lines.\n
17505 @item output @var{expression}
17506 Print the value of @var{expression} and nothing but that value: no
17507 newlines, no @samp{$@var{nn} = }. The value is not entered in the
17508 value history either. @xref{Expressions, ,Expressions}, for more information
17511 @item output/@var{fmt} @var{expression}
17512 Print the value of @var{expression} in format @var{fmt}. You can use
17513 the same formats as for @code{print}. @xref{Output Formats,,Output
17514 Formats}, for more information.
17517 @item printf @var{template}, @var{expressions}@dots{}
17518 Print the values of one or more @var{expressions} under the control of
17519 the string @var{template}. To print several values, make
17520 @var{expressions} be a comma-separated list of individual expressions,
17521 which may be either numbers or pointers. Their values are printed as
17522 specified by @var{template}, exactly as a C program would do by
17523 executing the code below:
17526 printf (@var{template}, @var{expressions}@dots{});
17529 As in @code{C} @code{printf}, ordinary characters in @var{template}
17530 are printed verbatim, while @dfn{conversion specification} introduced
17531 by the @samp{%} character cause subsequent @var{expressions} to be
17532 evaluated, their values converted and formatted according to type and
17533 style information encoded in the conversion specifications, and then
17536 For example, you can print two values in hex like this:
17539 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
17542 @code{printf} supports all the standard @code{C} conversion
17543 specifications, including the flags and modifiers between the @samp{%}
17544 character and the conversion letter, with the following exceptions:
17548 The argument-ordering modifiers, such as @samp{2$}, are not supported.
17551 The modifier @samp{*} is not supported for specifying precision or
17555 The @samp{'} flag (for separation of digits into groups according to
17556 @code{LC_NUMERIC'}) is not supported.
17559 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
17563 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
17566 The conversion letters @samp{a} and @samp{A} are not supported.
17570 Note that the @samp{ll} type modifier is supported only if the
17571 underlying @code{C} implementation used to build @value{GDBN} supports
17572 the @code{long long int} type, and the @samp{L} type modifier is
17573 supported only if @code{long double} type is available.
17575 As in @code{C}, @code{printf} supports simple backslash-escape
17576 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
17577 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
17578 single character. Octal and hexadecimal escape sequences are not
17581 Additionally, @code{printf} supports conversion specifications for DFP
17582 (@dfn{Decimal Floating Point}) types using the following length modifiers
17583 together with a floating point specifier.
17588 @samp{H} for printing @code{Decimal32} types.
17591 @samp{D} for printing @code{Decimal64} types.
17594 @samp{DD} for printing @code{Decimal128} types.
17597 If the underlying @code{C} implementation used to build @value{GDBN} has
17598 support for the three length modifiers for DFP types, other modifiers
17599 such as width and precision will also be available for @value{GDBN} to use.
17601 In case there is no such @code{C} support, no additional modifiers will be
17602 available and the value will be printed in the standard way.
17604 Here's an example of printing DFP types using the above conversion letters:
17606 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
17612 @section Scripting @value{GDBN} using Python
17613 @cindex python scripting
17614 @cindex scripting with python
17616 You can script @value{GDBN} using the @uref{http://www.python.org/,
17617 Python programming language}. This feature is available only if
17618 @value{GDBN} was configured using @option{--with-python}.
17621 * Python Commands:: Accessing Python from @value{GDBN}.
17622 * Python API:: Accessing @value{GDBN} from Python.
17625 @node Python Commands
17626 @subsection Python Commands
17627 @cindex python commands
17628 @cindex commands to access python
17630 @value{GDBN} provides one command for accessing the Python interpreter,
17631 and one related setting:
17635 @item python @r{[}@var{code}@r{]}
17636 The @code{python} command can be used to evaluate Python code.
17638 If given an argument, the @code{python} command will evaluate the
17639 argument as a Python command. For example:
17642 (@value{GDBP}) python print 23
17646 If you do not provide an argument to @code{python}, it will act as a
17647 multi-line command, like @code{define}. In this case, the Python
17648 script is made up of subsequent command lines, given after the
17649 @code{python} command. This command list is terminated using a line
17650 containing @code{end}. For example:
17653 (@value{GDBP}) python
17655 End with a line saying just "end".
17661 @kindex maint set python print-stack
17662 @item maint set python print-stack
17663 By default, @value{GDBN} will print a stack trace when an error occurs
17664 in a Python script. This can be controlled using @code{maint set
17665 python print-stack}: if @code{on}, the default, then Python stack
17666 printing is enabled; if @code{off}, then Python stack printing is
17671 @subsection Python API
17673 @cindex programming in python
17675 @cindex python stdout
17676 @cindex python pagination
17677 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
17678 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
17679 A Python program which outputs to one of these streams may have its
17680 output interrupted by the user (@pxref{Screen Size}). In this
17681 situation, a Python @code{KeyboardInterrupt} exception is thrown.
17684 * Basic Python:: Basic Python Functions.
17685 * Exception Handling::
17689 @subsubsection Basic Python
17691 @cindex python functions
17692 @cindex python module
17694 @value{GDBN} introduces a new Python module, named @code{gdb}. All
17695 methods and classes added by @value{GDBN} are placed in this module.
17696 @value{GDBN} automatically @code{import}s the @code{gdb} module for
17697 use in all scripts evaluated by the @code{python} command.
17699 @findex gdb.execute
17700 @defun execute command
17701 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
17702 If a GDB exception happens while @var{command} runs, it is
17703 translated as described in @ref{Exception Handling,,Exception Handling}.
17704 If no exceptions occur, this function returns @code{None}.
17707 @findex gdb.get_parameter
17708 @defun get_parameter parameter
17709 Return the value of a @value{GDBN} parameter. @var{parameter} is a
17710 string naming the parameter to look up; @var{parameter} may contain
17711 spaces if the parameter has a multi-part name. For example,
17712 @samp{print object} is a valid parameter name.
17714 If the named parameter does not exist, this function throws a
17715 @code{RuntimeError}. Otherwise, the parameter's value is converted to
17716 a Python value of the appropriate type, and returned.
17720 @defun write string
17721 Print a string to @value{GDBN}'s paginated standard output stream.
17722 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
17723 call this function.
17728 Flush @value{GDBN}'s paginated standard output stream. Flushing
17729 @code{sys.stdout} or @code{sys.stderr} will automatically call this
17733 @node Exception Handling
17734 @subsubsection Exception Handling
17735 @cindex python exceptions
17736 @cindex exceptions, python
17738 When executing the @code{python} command, Python exceptions
17739 uncaught within the Python code are translated to calls to
17740 @value{GDBN} error-reporting mechanism. If the command that called
17741 @code{python} does not handle the error, @value{GDBN} will
17742 terminate it and print an error message containing the Python
17743 exception name, the associated value, and the Python call stack
17744 backtrace at the point where the exception was raised. Example:
17747 (@value{GDBP}) python print foo
17748 Traceback (most recent call last):
17749 File "<string>", line 1, in <module>
17750 NameError: name 'foo' is not defined
17753 @value{GDBN} errors that happen in @value{GDBN} commands invoked by Python
17754 code are converted to Python @code{RuntimeError} exceptions. User
17755 interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
17756 prompt) is translated to a Python @code{KeyboardInterrupt}
17757 exception. If you catch these exceptions in your Python code, your
17758 exception handler will see @code{RuntimeError} or
17759 @code{KeyboardInterrupt} as the exception type, the @value{GDBN} error
17760 message as its value, and the Python call stack backtrace at the
17761 Python statement closest to where the @value{GDBN} error occured as the
17765 @chapter Command Interpreters
17766 @cindex command interpreters
17768 @value{GDBN} supports multiple command interpreters, and some command
17769 infrastructure to allow users or user interface writers to switch
17770 between interpreters or run commands in other interpreters.
17772 @value{GDBN} currently supports two command interpreters, the console
17773 interpreter (sometimes called the command-line interpreter or @sc{cli})
17774 and the machine interface interpreter (or @sc{gdb/mi}). This manual
17775 describes both of these interfaces in great detail.
17777 By default, @value{GDBN} will start with the console interpreter.
17778 However, the user may choose to start @value{GDBN} with another
17779 interpreter by specifying the @option{-i} or @option{--interpreter}
17780 startup options. Defined interpreters include:
17784 @cindex console interpreter
17785 The traditional console or command-line interpreter. This is the most often
17786 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
17787 @value{GDBN} will use this interpreter.
17790 @cindex mi interpreter
17791 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
17792 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
17793 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
17797 @cindex mi2 interpreter
17798 The current @sc{gdb/mi} interface.
17801 @cindex mi1 interpreter
17802 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
17806 @cindex invoke another interpreter
17807 The interpreter being used by @value{GDBN} may not be dynamically
17808 switched at runtime. Although possible, this could lead to a very
17809 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
17810 enters the command "interpreter-set console" in a console view,
17811 @value{GDBN} would switch to using the console interpreter, rendering
17812 the IDE inoperable!
17814 @kindex interpreter-exec
17815 Although you may only choose a single interpreter at startup, you may execute
17816 commands in any interpreter from the current interpreter using the appropriate
17817 command. If you are running the console interpreter, simply use the
17818 @code{interpreter-exec} command:
17821 interpreter-exec mi "-data-list-register-names"
17824 @sc{gdb/mi} has a similar command, although it is only available in versions of
17825 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
17828 @chapter @value{GDBN} Text User Interface
17830 @cindex Text User Interface
17833 * TUI Overview:: TUI overview
17834 * TUI Keys:: TUI key bindings
17835 * TUI Single Key Mode:: TUI single key mode
17836 * TUI Commands:: TUI-specific commands
17837 * TUI Configuration:: TUI configuration variables
17840 The @value{GDBN} Text User Interface (TUI) is a terminal
17841 interface which uses the @code{curses} library to show the source
17842 file, the assembly output, the program registers and @value{GDBN}
17843 commands in separate text windows. The TUI mode is supported only
17844 on platforms where a suitable version of the @code{curses} library
17847 @pindex @value{GDBTUI}
17848 The TUI mode is enabled by default when you invoke @value{GDBN} as
17849 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
17850 You can also switch in and out of TUI mode while @value{GDBN} runs by
17851 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
17852 @xref{TUI Keys, ,TUI Key Bindings}.
17855 @section TUI Overview
17857 In TUI mode, @value{GDBN} can display several text windows:
17861 This window is the @value{GDBN} command window with the @value{GDBN}
17862 prompt and the @value{GDBN} output. The @value{GDBN} input is still
17863 managed using readline.
17866 The source window shows the source file of the program. The current
17867 line and active breakpoints are displayed in this window.
17870 The assembly window shows the disassembly output of the program.
17873 This window shows the processor registers. Registers are highlighted
17874 when their values change.
17877 The source and assembly windows show the current program position
17878 by highlighting the current line and marking it with a @samp{>} marker.
17879 Breakpoints are indicated with two markers. The first marker
17880 indicates the breakpoint type:
17884 Breakpoint which was hit at least once.
17887 Breakpoint which was never hit.
17890 Hardware breakpoint which was hit at least once.
17893 Hardware breakpoint which was never hit.
17896 The second marker indicates whether the breakpoint is enabled or not:
17900 Breakpoint is enabled.
17903 Breakpoint is disabled.
17906 The source, assembly and register windows are updated when the current
17907 thread changes, when the frame changes, or when the program counter
17910 These windows are not all visible at the same time. The command
17911 window is always visible. The others can be arranged in several
17922 source and assembly,
17925 source and registers, or
17928 assembly and registers.
17931 A status line above the command window shows the following information:
17935 Indicates the current @value{GDBN} target.
17936 (@pxref{Targets, ,Specifying a Debugging Target}).
17939 Gives the current process or thread number.
17940 When no process is being debugged, this field is set to @code{No process}.
17943 Gives the current function name for the selected frame.
17944 The name is demangled if demangling is turned on (@pxref{Print Settings}).
17945 When there is no symbol corresponding to the current program counter,
17946 the string @code{??} is displayed.
17949 Indicates the current line number for the selected frame.
17950 When the current line number is not known, the string @code{??} is displayed.
17953 Indicates the current program counter address.
17957 @section TUI Key Bindings
17958 @cindex TUI key bindings
17960 The TUI installs several key bindings in the readline keymaps
17961 (@pxref{Command Line Editing}). The following key bindings
17962 are installed for both TUI mode and the @value{GDBN} standard mode.
17971 Enter or leave the TUI mode. When leaving the TUI mode,
17972 the curses window management stops and @value{GDBN} operates using
17973 its standard mode, writing on the terminal directly. When reentering
17974 the TUI mode, control is given back to the curses windows.
17975 The screen is then refreshed.
17979 Use a TUI layout with only one window. The layout will
17980 either be @samp{source} or @samp{assembly}. When the TUI mode
17981 is not active, it will switch to the TUI mode.
17983 Think of this key binding as the Emacs @kbd{C-x 1} binding.
17987 Use a TUI layout with at least two windows. When the current
17988 layout already has two windows, the next layout with two windows is used.
17989 When a new layout is chosen, one window will always be common to the
17990 previous layout and the new one.
17992 Think of it as the Emacs @kbd{C-x 2} binding.
17996 Change the active window. The TUI associates several key bindings
17997 (like scrolling and arrow keys) with the active window. This command
17998 gives the focus to the next TUI window.
18000 Think of it as the Emacs @kbd{C-x o} binding.
18004 Switch in and out of the TUI SingleKey mode that binds single
18005 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
18008 The following key bindings only work in the TUI mode:
18013 Scroll the active window one page up.
18017 Scroll the active window one page down.
18021 Scroll the active window one line up.
18025 Scroll the active window one line down.
18029 Scroll the active window one column left.
18033 Scroll the active window one column right.
18037 Refresh the screen.
18040 Because the arrow keys scroll the active window in the TUI mode, they
18041 are not available for their normal use by readline unless the command
18042 window has the focus. When another window is active, you must use
18043 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
18044 and @kbd{C-f} to control the command window.
18046 @node TUI Single Key Mode
18047 @section TUI Single Key Mode
18048 @cindex TUI single key mode
18050 The TUI also provides a @dfn{SingleKey} mode, which binds several
18051 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
18052 switch into this mode, where the following key bindings are used:
18055 @kindex c @r{(SingleKey TUI key)}
18059 @kindex d @r{(SingleKey TUI key)}
18063 @kindex f @r{(SingleKey TUI key)}
18067 @kindex n @r{(SingleKey TUI key)}
18071 @kindex q @r{(SingleKey TUI key)}
18073 exit the SingleKey mode.
18075 @kindex r @r{(SingleKey TUI key)}
18079 @kindex s @r{(SingleKey TUI key)}
18083 @kindex u @r{(SingleKey TUI key)}
18087 @kindex v @r{(SingleKey TUI key)}
18091 @kindex w @r{(SingleKey TUI key)}
18096 Other keys temporarily switch to the @value{GDBN} command prompt.
18097 The key that was pressed is inserted in the editing buffer so that
18098 it is possible to type most @value{GDBN} commands without interaction
18099 with the TUI SingleKey mode. Once the command is entered the TUI
18100 SingleKey mode is restored. The only way to permanently leave
18101 this mode is by typing @kbd{q} or @kbd{C-x s}.
18105 @section TUI-specific Commands
18106 @cindex TUI commands
18108 The TUI has specific commands to control the text windows.
18109 These commands are always available, even when @value{GDBN} is not in
18110 the TUI mode. When @value{GDBN} is in the standard mode, most
18111 of these commands will automatically switch to the TUI mode.
18116 List and give the size of all displayed windows.
18120 Display the next layout.
18123 Display the previous layout.
18126 Display the source window only.
18129 Display the assembly window only.
18132 Display the source and assembly window.
18135 Display the register window together with the source or assembly window.
18139 Make the next window active for scrolling.
18142 Make the previous window active for scrolling.
18145 Make the source window active for scrolling.
18148 Make the assembly window active for scrolling.
18151 Make the register window active for scrolling.
18154 Make the command window active for scrolling.
18158 Refresh the screen. This is similar to typing @kbd{C-L}.
18160 @item tui reg float
18162 Show the floating point registers in the register window.
18164 @item tui reg general
18165 Show the general registers in the register window.
18168 Show the next register group. The list of register groups as well as
18169 their order is target specific. The predefined register groups are the
18170 following: @code{general}, @code{float}, @code{system}, @code{vector},
18171 @code{all}, @code{save}, @code{restore}.
18173 @item tui reg system
18174 Show the system registers in the register window.
18178 Update the source window and the current execution point.
18180 @item winheight @var{name} +@var{count}
18181 @itemx winheight @var{name} -@var{count}
18183 Change the height of the window @var{name} by @var{count}
18184 lines. Positive counts increase the height, while negative counts
18187 @item tabset @var{nchars}
18189 Set the width of tab stops to be @var{nchars} characters.
18192 @node TUI Configuration
18193 @section TUI Configuration Variables
18194 @cindex TUI configuration variables
18196 Several configuration variables control the appearance of TUI windows.
18199 @item set tui border-kind @var{kind}
18200 @kindex set tui border-kind
18201 Select the border appearance for the source, assembly and register windows.
18202 The possible values are the following:
18205 Use a space character to draw the border.
18208 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
18211 Use the Alternate Character Set to draw the border. The border is
18212 drawn using character line graphics if the terminal supports them.
18215 @item set tui border-mode @var{mode}
18216 @kindex set tui border-mode
18217 @itemx set tui active-border-mode @var{mode}
18218 @kindex set tui active-border-mode
18219 Select the display attributes for the borders of the inactive windows
18220 or the active window. The @var{mode} can be one of the following:
18223 Use normal attributes to display the border.
18229 Use reverse video mode.
18232 Use half bright mode.
18234 @item half-standout
18235 Use half bright and standout mode.
18238 Use extra bright or bold mode.
18240 @item bold-standout
18241 Use extra bright or bold and standout mode.
18246 @chapter Using @value{GDBN} under @sc{gnu} Emacs
18249 @cindex @sc{gnu} Emacs
18250 A special interface allows you to use @sc{gnu} Emacs to view (and
18251 edit) the source files for the program you are debugging with
18254 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
18255 executable file you want to debug as an argument. This command starts
18256 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
18257 created Emacs buffer.
18258 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
18260 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
18265 All ``terminal'' input and output goes through an Emacs buffer, called
18268 This applies both to @value{GDBN} commands and their output, and to the input
18269 and output done by the program you are debugging.
18271 This is useful because it means that you can copy the text of previous
18272 commands and input them again; you can even use parts of the output
18275 All the facilities of Emacs' Shell mode are available for interacting
18276 with your program. In particular, you can send signals the usual
18277 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
18281 @value{GDBN} displays source code through Emacs.
18283 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
18284 source file for that frame and puts an arrow (@samp{=>}) at the
18285 left margin of the current line. Emacs uses a separate buffer for
18286 source display, and splits the screen to show both your @value{GDBN} session
18289 Explicit @value{GDBN} @code{list} or search commands still produce output as
18290 usual, but you probably have no reason to use them from Emacs.
18293 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
18294 a graphical mode, enabled by default, which provides further buffers
18295 that can control the execution and describe the state of your program.
18296 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
18298 If you specify an absolute file name when prompted for the @kbd{M-x
18299 gdb} argument, then Emacs sets your current working directory to where
18300 your program resides. If you only specify the file name, then Emacs
18301 sets your current working directory to to the directory associated
18302 with the previous buffer. In this case, @value{GDBN} may find your
18303 program by searching your environment's @code{PATH} variable, but on
18304 some operating systems it might not find the source. So, although the
18305 @value{GDBN} input and output session proceeds normally, the auxiliary
18306 buffer does not display the current source and line of execution.
18308 The initial working directory of @value{GDBN} is printed on the top
18309 line of the GUD buffer and this serves as a default for the commands
18310 that specify files for @value{GDBN} to operate on. @xref{Files,
18311 ,Commands to Specify Files}.
18313 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
18314 need to call @value{GDBN} by a different name (for example, if you
18315 keep several configurations around, with different names) you can
18316 customize the Emacs variable @code{gud-gdb-command-name} to run the
18319 In the GUD buffer, you can use these special Emacs commands in
18320 addition to the standard Shell mode commands:
18324 Describe the features of Emacs' GUD Mode.
18327 Execute to another source line, like the @value{GDBN} @code{step} command; also
18328 update the display window to show the current file and location.
18331 Execute to next source line in this function, skipping all function
18332 calls, like the @value{GDBN} @code{next} command. Then update the display window
18333 to show the current file and location.
18336 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
18337 display window accordingly.
18340 Execute until exit from the selected stack frame, like the @value{GDBN}
18341 @code{finish} command.
18344 Continue execution of your program, like the @value{GDBN} @code{continue}
18348 Go up the number of frames indicated by the numeric argument
18349 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
18350 like the @value{GDBN} @code{up} command.
18353 Go down the number of frames indicated by the numeric argument, like the
18354 @value{GDBN} @code{down} command.
18357 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
18358 tells @value{GDBN} to set a breakpoint on the source line point is on.
18360 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
18361 separate frame which shows a backtrace when the GUD buffer is current.
18362 Move point to any frame in the stack and type @key{RET} to make it
18363 become the current frame and display the associated source in the
18364 source buffer. Alternatively, click @kbd{Mouse-2} to make the
18365 selected frame become the current one. In graphical mode, the
18366 speedbar displays watch expressions.
18368 If you accidentally delete the source-display buffer, an easy way to get
18369 it back is to type the command @code{f} in the @value{GDBN} buffer, to
18370 request a frame display; when you run under Emacs, this recreates
18371 the source buffer if necessary to show you the context of the current
18374 The source files displayed in Emacs are in ordinary Emacs buffers
18375 which are visiting the source files in the usual way. You can edit
18376 the files with these buffers if you wish; but keep in mind that @value{GDBN}
18377 communicates with Emacs in terms of line numbers. If you add or
18378 delete lines from the text, the line numbers that @value{GDBN} knows cease
18379 to correspond properly with the code.
18381 A more detailed description of Emacs' interaction with @value{GDBN} is
18382 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
18385 @c The following dropped because Epoch is nonstandard. Reactivate
18386 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
18388 @kindex Emacs Epoch environment
18392 Version 18 of @sc{gnu} Emacs has a built-in window system
18393 called the @code{epoch}
18394 environment. Users of this environment can use a new command,
18395 @code{inspect} which performs identically to @code{print} except that
18396 each value is printed in its own window.
18401 @chapter The @sc{gdb/mi} Interface
18403 @unnumberedsec Function and Purpose
18405 @cindex @sc{gdb/mi}, its purpose
18406 @sc{gdb/mi} is a line based machine oriented text interface to
18407 @value{GDBN} and is activated by specifying using the
18408 @option{--interpreter} command line option (@pxref{Mode Options}). It
18409 is specifically intended to support the development of systems which
18410 use the debugger as just one small component of a larger system.
18412 This chapter is a specification of the @sc{gdb/mi} interface. It is written
18413 in the form of a reference manual.
18415 Note that @sc{gdb/mi} is still under construction, so some of the
18416 features described below are incomplete and subject to change
18417 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
18419 @unnumberedsec Notation and Terminology
18421 @cindex notational conventions, for @sc{gdb/mi}
18422 This chapter uses the following notation:
18426 @code{|} separates two alternatives.
18429 @code{[ @var{something} ]} indicates that @var{something} is optional:
18430 it may or may not be given.
18433 @code{( @var{group} )*} means that @var{group} inside the parentheses
18434 may repeat zero or more times.
18437 @code{( @var{group} )+} means that @var{group} inside the parentheses
18438 may repeat one or more times.
18441 @code{"@var{string}"} means a literal @var{string}.
18445 @heading Dependencies
18449 * GDB/MI Command Syntax::
18450 * GDB/MI Compatibility with CLI::
18451 * GDB/MI Development and Front Ends::
18452 * GDB/MI Output Records::
18453 * GDB/MI Simple Examples::
18454 * GDB/MI Command Description Format::
18455 * GDB/MI Breakpoint Commands::
18456 * GDB/MI Program Context::
18457 * GDB/MI Thread Commands::
18458 * GDB/MI Program Execution::
18459 * GDB/MI Stack Manipulation::
18460 * GDB/MI Variable Objects::
18461 * GDB/MI Data Manipulation::
18462 * GDB/MI Tracepoint Commands::
18463 * GDB/MI Symbol Query::
18464 * GDB/MI File Commands::
18466 * GDB/MI Kod Commands::
18467 * GDB/MI Memory Overlay Commands::
18468 * GDB/MI Signal Handling Commands::
18470 * GDB/MI Target Manipulation::
18471 * GDB/MI File Transfer Commands::
18472 * GDB/MI Miscellaneous Commands::
18475 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18476 @node GDB/MI Command Syntax
18477 @section @sc{gdb/mi} Command Syntax
18480 * GDB/MI Input Syntax::
18481 * GDB/MI Output Syntax::
18484 @node GDB/MI Input Syntax
18485 @subsection @sc{gdb/mi} Input Syntax
18487 @cindex input syntax for @sc{gdb/mi}
18488 @cindex @sc{gdb/mi}, input syntax
18490 @item @var{command} @expansion{}
18491 @code{@var{cli-command} | @var{mi-command}}
18493 @item @var{cli-command} @expansion{}
18494 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
18495 @var{cli-command} is any existing @value{GDBN} CLI command.
18497 @item @var{mi-command} @expansion{}
18498 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
18499 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
18501 @item @var{token} @expansion{}
18502 "any sequence of digits"
18504 @item @var{option} @expansion{}
18505 @code{"-" @var{parameter} [ " " @var{parameter} ]}
18507 @item @var{parameter} @expansion{}
18508 @code{@var{non-blank-sequence} | @var{c-string}}
18510 @item @var{operation} @expansion{}
18511 @emph{any of the operations described in this chapter}
18513 @item @var{non-blank-sequence} @expansion{}
18514 @emph{anything, provided it doesn't contain special characters such as
18515 "-", @var{nl}, """ and of course " "}
18517 @item @var{c-string} @expansion{}
18518 @code{""" @var{seven-bit-iso-c-string-content} """}
18520 @item @var{nl} @expansion{}
18529 The CLI commands are still handled by the @sc{mi} interpreter; their
18530 output is described below.
18533 The @code{@var{token}}, when present, is passed back when the command
18537 Some @sc{mi} commands accept optional arguments as part of the parameter
18538 list. Each option is identified by a leading @samp{-} (dash) and may be
18539 followed by an optional argument parameter. Options occur first in the
18540 parameter list and can be delimited from normal parameters using
18541 @samp{--} (this is useful when some parameters begin with a dash).
18548 We want easy access to the existing CLI syntax (for debugging).
18551 We want it to be easy to spot a @sc{mi} operation.
18554 @node GDB/MI Output Syntax
18555 @subsection @sc{gdb/mi} Output Syntax
18557 @cindex output syntax of @sc{gdb/mi}
18558 @cindex @sc{gdb/mi}, output syntax
18559 The output from @sc{gdb/mi} consists of zero or more out-of-band records
18560 followed, optionally, by a single result record. This result record
18561 is for the most recent command. The sequence of output records is
18562 terminated by @samp{(gdb)}.
18564 If an input command was prefixed with a @code{@var{token}} then the
18565 corresponding output for that command will also be prefixed by that same
18569 @item @var{output} @expansion{}
18570 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
18572 @item @var{result-record} @expansion{}
18573 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
18575 @item @var{out-of-band-record} @expansion{}
18576 @code{@var{async-record} | @var{stream-record}}
18578 @item @var{async-record} @expansion{}
18579 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
18581 @item @var{exec-async-output} @expansion{}
18582 @code{[ @var{token} ] "*" @var{async-output}}
18584 @item @var{status-async-output} @expansion{}
18585 @code{[ @var{token} ] "+" @var{async-output}}
18587 @item @var{notify-async-output} @expansion{}
18588 @code{[ @var{token} ] "=" @var{async-output}}
18590 @item @var{async-output} @expansion{}
18591 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
18593 @item @var{result-class} @expansion{}
18594 @code{"done" | "running" | "connected" | "error" | "exit"}
18596 @item @var{async-class} @expansion{}
18597 @code{"stopped" | @var{others}} (where @var{others} will be added
18598 depending on the needs---this is still in development).
18600 @item @var{result} @expansion{}
18601 @code{ @var{variable} "=" @var{value}}
18603 @item @var{variable} @expansion{}
18604 @code{ @var{string} }
18606 @item @var{value} @expansion{}
18607 @code{ @var{const} | @var{tuple} | @var{list} }
18609 @item @var{const} @expansion{}
18610 @code{@var{c-string}}
18612 @item @var{tuple} @expansion{}
18613 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
18615 @item @var{list} @expansion{}
18616 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
18617 @var{result} ( "," @var{result} )* "]" }
18619 @item @var{stream-record} @expansion{}
18620 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
18622 @item @var{console-stream-output} @expansion{}
18623 @code{"~" @var{c-string}}
18625 @item @var{target-stream-output} @expansion{}
18626 @code{"@@" @var{c-string}}
18628 @item @var{log-stream-output} @expansion{}
18629 @code{"&" @var{c-string}}
18631 @item @var{nl} @expansion{}
18634 @item @var{token} @expansion{}
18635 @emph{any sequence of digits}.
18643 All output sequences end in a single line containing a period.
18646 The @code{@var{token}} is from the corresponding request. Note that
18647 for all async output, while the token is allowed by the grammar and
18648 may be output by future versions of @value{GDBN} for select async
18649 output messages, it is generally omitted. Frontends should treat
18650 all async output as reporting general changes in the state of the
18651 target and there should be no need to associate async output to any
18655 @cindex status output in @sc{gdb/mi}
18656 @var{status-async-output} contains on-going status information about the
18657 progress of a slow operation. It can be discarded. All status output is
18658 prefixed by @samp{+}.
18661 @cindex async output in @sc{gdb/mi}
18662 @var{exec-async-output} contains asynchronous state change on the target
18663 (stopped, started, disappeared). All async output is prefixed by
18667 @cindex notify output in @sc{gdb/mi}
18668 @var{notify-async-output} contains supplementary information that the
18669 client should handle (e.g., a new breakpoint information). All notify
18670 output is prefixed by @samp{=}.
18673 @cindex console output in @sc{gdb/mi}
18674 @var{console-stream-output} is output that should be displayed as is in the
18675 console. It is the textual response to a CLI command. All the console
18676 output is prefixed by @samp{~}.
18679 @cindex target output in @sc{gdb/mi}
18680 @var{target-stream-output} is the output produced by the target program.
18681 All the target output is prefixed by @samp{@@}.
18684 @cindex log output in @sc{gdb/mi}
18685 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
18686 instance messages that should be displayed as part of an error log. All
18687 the log output is prefixed by @samp{&}.
18690 @cindex list output in @sc{gdb/mi}
18691 New @sc{gdb/mi} commands should only output @var{lists} containing
18697 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
18698 details about the various output records.
18700 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18701 @node GDB/MI Compatibility with CLI
18702 @section @sc{gdb/mi} Compatibility with CLI
18704 @cindex compatibility, @sc{gdb/mi} and CLI
18705 @cindex @sc{gdb/mi}, compatibility with CLI
18707 For the developers convenience CLI commands can be entered directly,
18708 but there may be some unexpected behaviour. For example, commands
18709 that query the user will behave as if the user replied yes, breakpoint
18710 command lists are not executed and some CLI commands, such as
18711 @code{if}, @code{when} and @code{define}, prompt for further input with
18712 @samp{>}, which is not valid MI output.
18714 This feature may be removed at some stage in the future and it is
18715 recommended that front ends use the @code{-interpreter-exec} command
18716 (@pxref{-interpreter-exec}).
18718 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18719 @node GDB/MI Development and Front Ends
18720 @section @sc{gdb/mi} Development and Front Ends
18721 @cindex @sc{gdb/mi} development
18723 The application which takes the MI output and presents the state of the
18724 program being debugged to the user is called a @dfn{front end}.
18726 Although @sc{gdb/mi} is still incomplete, it is currently being used
18727 by a variety of front ends to @value{GDBN}. This makes it difficult
18728 to introduce new functionality without breaking existing usage. This
18729 section tries to minimize the problems by describing how the protocol
18732 Some changes in MI need not break a carefully designed front end, and
18733 for these the MI version will remain unchanged. The following is a
18734 list of changes that may occur within one level, so front ends should
18735 parse MI output in a way that can handle them:
18739 New MI commands may be added.
18742 New fields may be added to the output of any MI command.
18745 The range of values for fields with specified values, e.g.,
18746 @code{in_scope} (@pxref{-var-update}) may be extended.
18748 @c The format of field's content e.g type prefix, may change so parse it
18749 @c at your own risk. Yes, in general?
18751 @c The order of fields may change? Shouldn't really matter but it might
18752 @c resolve inconsistencies.
18755 If the changes are likely to break front ends, the MI version level
18756 will be increased by one. This will allow the front end to parse the
18757 output according to the MI version. Apart from mi0, new versions of
18758 @value{GDBN} will not support old versions of MI and it will be the
18759 responsibility of the front end to work with the new one.
18761 @c Starting with mi3, add a new command -mi-version that prints the MI
18764 The best way to avoid unexpected changes in MI that might break your front
18765 end is to make your project known to @value{GDBN} developers and
18766 follow development on @email{gdb@@sourceware.org} and
18767 @email{gdb-patches@@sourceware.org}.
18768 @cindex mailing lists
18770 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18771 @node GDB/MI Output Records
18772 @section @sc{gdb/mi} Output Records
18775 * GDB/MI Result Records::
18776 * GDB/MI Stream Records::
18777 * GDB/MI Async Records::
18780 @node GDB/MI Result Records
18781 @subsection @sc{gdb/mi} Result Records
18783 @cindex result records in @sc{gdb/mi}
18784 @cindex @sc{gdb/mi}, result records
18785 In addition to a number of out-of-band notifications, the response to a
18786 @sc{gdb/mi} command includes one of the following result indications:
18790 @item "^done" [ "," @var{results} ]
18791 The synchronous operation was successful, @code{@var{results}} are the return
18796 @c Is this one correct? Should it be an out-of-band notification?
18797 The asynchronous operation was successfully started. The target is
18802 @value{GDBN} has connected to a remote target.
18804 @item "^error" "," @var{c-string}
18806 The operation failed. The @code{@var{c-string}} contains the corresponding
18811 @value{GDBN} has terminated.
18815 @node GDB/MI Stream Records
18816 @subsection @sc{gdb/mi} Stream Records
18818 @cindex @sc{gdb/mi}, stream records
18819 @cindex stream records in @sc{gdb/mi}
18820 @value{GDBN} internally maintains a number of output streams: the console, the
18821 target, and the log. The output intended for each of these streams is
18822 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
18824 Each stream record begins with a unique @dfn{prefix character} which
18825 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
18826 Syntax}). In addition to the prefix, each stream record contains a
18827 @code{@var{string-output}}. This is either raw text (with an implicit new
18828 line) or a quoted C string (which does not contain an implicit newline).
18831 @item "~" @var{string-output}
18832 The console output stream contains text that should be displayed in the
18833 CLI console window. It contains the textual responses to CLI commands.
18835 @item "@@" @var{string-output}
18836 The target output stream contains any textual output from the running
18837 target. This is only present when GDB's event loop is truly
18838 asynchronous, which is currently only the case for remote targets.
18840 @item "&" @var{string-output}
18841 The log stream contains debugging messages being produced by @value{GDBN}'s
18845 @node GDB/MI Async Records
18846 @subsection @sc{gdb/mi} Async Records
18848 @cindex async records in @sc{gdb/mi}
18849 @cindex @sc{gdb/mi}, async records
18850 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
18851 additional changes that have occurred. Those changes can either be a
18852 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
18853 target activity (e.g., target stopped).
18855 The following is the list of possible async records:
18859 @item *running,thread-id="@var{thread}"
18860 The target is now running. The @var{thread} field tells which
18861 specific thread is now running, and can be @samp{all} if all threads
18862 are running. The frontend should assume that no interaction with a
18863 running thread is possible after this notification is produced.
18864 The frontend should not assume that this notification is output
18865 only once for any command. @value{GDBN} may emit this notification
18866 several times, either for different threads, because it cannot resume
18867 all threads together, or even for a single thread, if the thread must
18868 be stepped though some code before letting it run freely.
18870 @item *stopped,reason="@var{reason}"
18871 The target has stopped. The @var{reason} field can have one of the
18875 @item breakpoint-hit
18876 A breakpoint was reached.
18877 @item watchpoint-trigger
18878 A watchpoint was triggered.
18879 @item read-watchpoint-trigger
18880 A read watchpoint was triggered.
18881 @item access-watchpoint-trigger
18882 An access watchpoint was triggered.
18883 @item function-finished
18884 An -exec-finish or similar CLI command was accomplished.
18885 @item location-reached
18886 An -exec-until or similar CLI command was accomplished.
18887 @item watchpoint-scope
18888 A watchpoint has gone out of scope.
18889 @item end-stepping-range
18890 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
18891 similar CLI command was accomplished.
18892 @item exited-signalled
18893 The inferior exited because of a signal.
18895 The inferior exited.
18896 @item exited-normally
18897 The inferior exited normally.
18898 @item signal-received
18899 A signal was received by the inferior.
18902 @item =thread-created,id="@var{id}"
18903 @itemx =thread-exited,id="@var{id}"
18904 A thread either was created, or has exited. The @var{id} field
18905 contains the @value{GDBN} identifier of the thread.
18910 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18911 @node GDB/MI Simple Examples
18912 @section Simple Examples of @sc{gdb/mi} Interaction
18913 @cindex @sc{gdb/mi}, simple examples
18915 This subsection presents several simple examples of interaction using
18916 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
18917 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
18918 the output received from @sc{gdb/mi}.
18920 Note the line breaks shown in the examples are here only for
18921 readability, they don't appear in the real output.
18923 @subheading Setting a Breakpoint
18925 Setting a breakpoint generates synchronous output which contains detailed
18926 information of the breakpoint.
18929 -> -break-insert main
18930 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
18931 enabled="y",addr="0x08048564",func="main",file="myprog.c",
18932 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
18936 @subheading Program Execution
18938 Program execution generates asynchronous records and MI gives the
18939 reason that execution stopped.
18945 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
18946 frame=@{addr="0x08048564",func="main",
18947 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
18948 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
18953 <- *stopped,reason="exited-normally"
18957 @subheading Quitting @value{GDBN}
18959 Quitting @value{GDBN} just prints the result class @samp{^exit}.
18967 @subheading A Bad Command
18969 Here's what happens if you pass a non-existent command:
18973 <- ^error,msg="Undefined MI command: rubbish"
18978 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18979 @node GDB/MI Command Description Format
18980 @section @sc{gdb/mi} Command Description Format
18982 The remaining sections describe blocks of commands. Each block of
18983 commands is laid out in a fashion similar to this section.
18985 @subheading Motivation
18987 The motivation for this collection of commands.
18989 @subheading Introduction
18991 A brief introduction to this collection of commands as a whole.
18993 @subheading Commands
18995 For each command in the block, the following is described:
18997 @subsubheading Synopsis
19000 -command @var{args}@dots{}
19003 @subsubheading Result
19005 @subsubheading @value{GDBN} Command
19007 The corresponding @value{GDBN} CLI command(s), if any.
19009 @subsubheading Example
19011 Example(s) formatted for readability. Some of the described commands have
19012 not been implemented yet and these are labeled N.A.@: (not available).
19015 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19016 @node GDB/MI Breakpoint Commands
19017 @section @sc{gdb/mi} Breakpoint Commands
19019 @cindex breakpoint commands for @sc{gdb/mi}
19020 @cindex @sc{gdb/mi}, breakpoint commands
19021 This section documents @sc{gdb/mi} commands for manipulating
19024 @subheading The @code{-break-after} Command
19025 @findex -break-after
19027 @subsubheading Synopsis
19030 -break-after @var{number} @var{count}
19033 The breakpoint number @var{number} is not in effect until it has been
19034 hit @var{count} times. To see how this is reflected in the output of
19035 the @samp{-break-list} command, see the description of the
19036 @samp{-break-list} command below.
19038 @subsubheading @value{GDBN} Command
19040 The corresponding @value{GDBN} command is @samp{ignore}.
19042 @subsubheading Example
19047 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
19048 enabled="y",addr="0x000100d0",func="main",file="hello.c",
19049 fullname="/home/foo/hello.c",line="5",times="0"@}
19056 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
19057 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19058 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19059 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19060 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19061 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19062 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19063 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
19064 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
19065 line="5",times="0",ignore="3"@}]@}
19070 @subheading The @code{-break-catch} Command
19071 @findex -break-catch
19073 @subheading The @code{-break-commands} Command
19074 @findex -break-commands
19078 @subheading The @code{-break-condition} Command
19079 @findex -break-condition
19081 @subsubheading Synopsis
19084 -break-condition @var{number} @var{expr}
19087 Breakpoint @var{number} will stop the program only if the condition in
19088 @var{expr} is true. The condition becomes part of the
19089 @samp{-break-list} output (see the description of the @samp{-break-list}
19092 @subsubheading @value{GDBN} Command
19094 The corresponding @value{GDBN} command is @samp{condition}.
19096 @subsubheading Example
19100 -break-condition 1 1
19104 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
19105 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19106 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19107 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19108 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19109 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19110 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19111 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
19112 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
19113 line="5",cond="1",times="0",ignore="3"@}]@}
19117 @subheading The @code{-break-delete} Command
19118 @findex -break-delete
19120 @subsubheading Synopsis
19123 -break-delete ( @var{breakpoint} )+
19126 Delete the breakpoint(s) whose number(s) are specified in the argument
19127 list. This is obviously reflected in the breakpoint list.
19129 @subsubheading @value{GDBN} Command
19131 The corresponding @value{GDBN} command is @samp{delete}.
19133 @subsubheading Example
19141 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
19142 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19143 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19144 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19145 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19146 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19147 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19152 @subheading The @code{-break-disable} Command
19153 @findex -break-disable
19155 @subsubheading Synopsis
19158 -break-disable ( @var{breakpoint} )+
19161 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
19162 break list is now set to @samp{n} for the named @var{breakpoint}(s).
19164 @subsubheading @value{GDBN} Command
19166 The corresponding @value{GDBN} command is @samp{disable}.
19168 @subsubheading Example
19176 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
19177 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19178 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19179 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19180 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19181 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19182 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19183 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
19184 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
19185 line="5",times="0"@}]@}
19189 @subheading The @code{-break-enable} Command
19190 @findex -break-enable
19192 @subsubheading Synopsis
19195 -break-enable ( @var{breakpoint} )+
19198 Enable (previously disabled) @var{breakpoint}(s).
19200 @subsubheading @value{GDBN} Command
19202 The corresponding @value{GDBN} command is @samp{enable}.
19204 @subsubheading Example
19212 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
19213 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19214 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19215 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19216 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19217 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19218 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19219 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
19220 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
19221 line="5",times="0"@}]@}
19225 @subheading The @code{-break-info} Command
19226 @findex -break-info
19228 @subsubheading Synopsis
19231 -break-info @var{breakpoint}
19235 Get information about a single breakpoint.
19237 @subsubheading @value{GDBN} Command
19239 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
19241 @subsubheading Example
19244 @subheading The @code{-break-insert} Command
19245 @findex -break-insert
19247 @subsubheading Synopsis
19250 -break-insert [ -t ] [ -h ] [ -f ]
19251 [ -c @var{condition} ] [ -i @var{ignore-count} ]
19252 [ -p @var{thread} ] [ @var{location} ]
19256 If specified, @var{location}, can be one of:
19263 @item filename:linenum
19264 @item filename:function
19268 The possible optional parameters of this command are:
19272 Insert a temporary breakpoint.
19274 Insert a hardware breakpoint.
19275 @item -c @var{condition}
19276 Make the breakpoint conditional on @var{condition}.
19277 @item -i @var{ignore-count}
19278 Initialize the @var{ignore-count}.
19280 If @var{location} cannot be parsed (for example if it
19281 refers to unknown files or functions), create a pending
19282 breakpoint. Without this flag, @value{GDBN} will report
19283 an error, and won't create a breakpoint, if @var{location}
19287 @subsubheading Result
19289 The result is in the form:
19292 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
19293 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
19294 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
19295 times="@var{times}"@}
19299 where @var{number} is the @value{GDBN} number for this breakpoint,
19300 @var{funcname} is the name of the function where the breakpoint was
19301 inserted, @var{filename} is the name of the source file which contains
19302 this function, @var{lineno} is the source line number within that file
19303 and @var{times} the number of times that the breakpoint has been hit
19304 (always 0 for -break-insert but may be greater for -break-info or -break-list
19305 which use the same output).
19307 Note: this format is open to change.
19308 @c An out-of-band breakpoint instead of part of the result?
19310 @subsubheading @value{GDBN} Command
19312 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
19313 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
19315 @subsubheading Example
19320 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
19321 fullname="/home/foo/recursive2.c,line="4",times="0"@}
19323 -break-insert -t foo
19324 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
19325 fullname="/home/foo/recursive2.c,line="11",times="0"@}
19328 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
19329 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19330 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19331 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19332 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19333 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19334 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19335 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
19336 addr="0x0001072c", func="main",file="recursive2.c",
19337 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
19338 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
19339 addr="0x00010774",func="foo",file="recursive2.c",
19340 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
19342 -break-insert -r foo.*
19343 ~int foo(int, int);
19344 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
19345 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
19349 @subheading The @code{-break-list} Command
19350 @findex -break-list
19352 @subsubheading Synopsis
19358 Displays the list of inserted breakpoints, showing the following fields:
19362 number of the breakpoint
19364 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
19366 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
19369 is the breakpoint enabled or no: @samp{y} or @samp{n}
19371 memory location at which the breakpoint is set
19373 logical location of the breakpoint, expressed by function name, file
19376 number of times the breakpoint has been hit
19379 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
19380 @code{body} field is an empty list.
19382 @subsubheading @value{GDBN} Command
19384 The corresponding @value{GDBN} command is @samp{info break}.
19386 @subsubheading Example
19391 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
19392 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19393 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19394 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19395 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19396 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19397 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19398 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
19399 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
19400 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
19401 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
19402 line="13",times="0"@}]@}
19406 Here's an example of the result when there are no breakpoints:
19411 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
19412 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19413 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19414 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19415 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19416 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19417 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19422 @subheading The @code{-break-watch} Command
19423 @findex -break-watch
19425 @subsubheading Synopsis
19428 -break-watch [ -a | -r ]
19431 Create a watchpoint. With the @samp{-a} option it will create an
19432 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
19433 read from or on a write to the memory location. With the @samp{-r}
19434 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
19435 trigger only when the memory location is accessed for reading. Without
19436 either of the options, the watchpoint created is a regular watchpoint,
19437 i.e., it will trigger when the memory location is accessed for writing.
19438 @xref{Set Watchpoints, , Setting Watchpoints}.
19440 Note that @samp{-break-list} will report a single list of watchpoints and
19441 breakpoints inserted.
19443 @subsubheading @value{GDBN} Command
19445 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
19448 @subsubheading Example
19450 Setting a watchpoint on a variable in the @code{main} function:
19455 ^done,wpt=@{number="2",exp="x"@}
19460 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
19461 value=@{old="-268439212",new="55"@},
19462 frame=@{func="main",args=[],file="recursive2.c",
19463 fullname="/home/foo/bar/recursive2.c",line="5"@}
19467 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
19468 the program execution twice: first for the variable changing value, then
19469 for the watchpoint going out of scope.
19474 ^done,wpt=@{number="5",exp="C"@}
19479 *stopped,reason="watchpoint-trigger",
19480 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
19481 frame=@{func="callee4",args=[],
19482 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19483 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
19488 *stopped,reason="watchpoint-scope",wpnum="5",
19489 frame=@{func="callee3",args=[@{name="strarg",
19490 value="0x11940 \"A string argument.\""@}],
19491 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19492 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
19496 Listing breakpoints and watchpoints, at different points in the program
19497 execution. Note that once the watchpoint goes out of scope, it is
19503 ^done,wpt=@{number="2",exp="C"@}
19506 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
19507 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19508 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19509 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19510 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19511 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19512 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19513 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
19514 addr="0x00010734",func="callee4",
19515 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19516 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
19517 bkpt=@{number="2",type="watchpoint",disp="keep",
19518 enabled="y",addr="",what="C",times="0"@}]@}
19523 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
19524 value=@{old="-276895068",new="3"@},
19525 frame=@{func="callee4",args=[],
19526 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19527 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
19530 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
19531 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19532 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19533 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19534 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19535 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19536 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19537 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
19538 addr="0x00010734",func="callee4",
19539 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19540 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
19541 bkpt=@{number="2",type="watchpoint",disp="keep",
19542 enabled="y",addr="",what="C",times="-5"@}]@}
19546 ^done,reason="watchpoint-scope",wpnum="2",
19547 frame=@{func="callee3",args=[@{name="strarg",
19548 value="0x11940 \"A string argument.\""@}],
19549 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19550 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
19553 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
19554 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19555 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19556 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19557 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19558 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19559 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19560 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
19561 addr="0x00010734",func="callee4",
19562 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19563 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
19568 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19569 @node GDB/MI Program Context
19570 @section @sc{gdb/mi} Program Context
19572 @subheading The @code{-exec-arguments} Command
19573 @findex -exec-arguments
19576 @subsubheading Synopsis
19579 -exec-arguments @var{args}
19582 Set the inferior program arguments, to be used in the next
19585 @subsubheading @value{GDBN} Command
19587 The corresponding @value{GDBN} command is @samp{set args}.
19589 @subsubheading Example
19593 -exec-arguments -v word
19599 @subheading The @code{-exec-show-arguments} Command
19600 @findex -exec-show-arguments
19602 @subsubheading Synopsis
19605 -exec-show-arguments
19608 Print the arguments of the program.
19610 @subsubheading @value{GDBN} Command
19612 The corresponding @value{GDBN} command is @samp{show args}.
19614 @subsubheading Example
19618 @subheading The @code{-environment-cd} Command
19619 @findex -environment-cd
19621 @subsubheading Synopsis
19624 -environment-cd @var{pathdir}
19627 Set @value{GDBN}'s working directory.
19629 @subsubheading @value{GDBN} Command
19631 The corresponding @value{GDBN} command is @samp{cd}.
19633 @subsubheading Example
19637 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
19643 @subheading The @code{-environment-directory} Command
19644 @findex -environment-directory
19646 @subsubheading Synopsis
19649 -environment-directory [ -r ] [ @var{pathdir} ]+
19652 Add directories @var{pathdir} to beginning of search path for source files.
19653 If the @samp{-r} option is used, the search path is reset to the default
19654 search path. If directories @var{pathdir} are supplied in addition to the
19655 @samp{-r} option, the search path is first reset and then addition
19657 Multiple directories may be specified, separated by blanks. Specifying
19658 multiple directories in a single command
19659 results in the directories added to the beginning of the
19660 search path in the same order they were presented in the command.
19661 If blanks are needed as
19662 part of a directory name, double-quotes should be used around
19663 the name. In the command output, the path will show up separated
19664 by the system directory-separator character. The directory-separator
19665 character must not be used
19666 in any directory name.
19667 If no directories are specified, the current search path is displayed.
19669 @subsubheading @value{GDBN} Command
19671 The corresponding @value{GDBN} command is @samp{dir}.
19673 @subsubheading Example
19677 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
19678 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
19680 -environment-directory ""
19681 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
19683 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
19684 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
19686 -environment-directory -r
19687 ^done,source-path="$cdir:$cwd"
19692 @subheading The @code{-environment-path} Command
19693 @findex -environment-path
19695 @subsubheading Synopsis
19698 -environment-path [ -r ] [ @var{pathdir} ]+
19701 Add directories @var{pathdir} to beginning of search path for object files.
19702 If the @samp{-r} option is used, the search path is reset to the original
19703 search path that existed at gdb start-up. If directories @var{pathdir} are
19704 supplied in addition to the
19705 @samp{-r} option, the search path is first reset and then addition
19707 Multiple directories may be specified, separated by blanks. Specifying
19708 multiple directories in a single command
19709 results in the directories added to the beginning of the
19710 search path in the same order they were presented in the command.
19711 If blanks are needed as
19712 part of a directory name, double-quotes should be used around
19713 the name. In the command output, the path will show up separated
19714 by the system directory-separator character. The directory-separator
19715 character must not be used
19716 in any directory name.
19717 If no directories are specified, the current path is displayed.
19720 @subsubheading @value{GDBN} Command
19722 The corresponding @value{GDBN} command is @samp{path}.
19724 @subsubheading Example
19729 ^done,path="/usr/bin"
19731 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
19732 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
19734 -environment-path -r /usr/local/bin
19735 ^done,path="/usr/local/bin:/usr/bin"
19740 @subheading The @code{-environment-pwd} Command
19741 @findex -environment-pwd
19743 @subsubheading Synopsis
19749 Show the current working directory.
19751 @subsubheading @value{GDBN} Command
19753 The corresponding @value{GDBN} command is @samp{pwd}.
19755 @subsubheading Example
19760 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
19764 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19765 @node GDB/MI Thread Commands
19766 @section @sc{gdb/mi} Thread Commands
19769 @subheading The @code{-thread-info} Command
19770 @findex -thread-info
19772 @subsubheading Synopsis
19775 -thread-info [ @var{thread-id} ]
19778 Reports information about either a specific thread, if
19779 the @var{thread-id} parameter is present, or about all
19780 threads. When printing information about all threads,
19781 also reports the current thread.
19783 @subsubheading @value{GDBN} Command
19785 The @samp{info thread} command prints the same information
19788 @subsubheading Example
19793 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
19794 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},
19795 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
19796 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
19797 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@}@}],
19798 current-thread-id="1"
19802 @subheading The @code{-thread-list-ids} Command
19803 @findex -thread-list-ids
19805 @subsubheading Synopsis
19811 Produces a list of the currently known @value{GDBN} thread ids. At the
19812 end of the list it also prints the total number of such threads.
19814 @subsubheading @value{GDBN} Command
19816 Part of @samp{info threads} supplies the same information.
19818 @subsubheading Example
19820 No threads present, besides the main process:
19825 ^done,thread-ids=@{@},number-of-threads="0"
19835 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
19836 number-of-threads="3"
19841 @subheading The @code{-thread-select} Command
19842 @findex -thread-select
19844 @subsubheading Synopsis
19847 -thread-select @var{threadnum}
19850 Make @var{threadnum} the current thread. It prints the number of the new
19851 current thread, and the topmost frame for that thread.
19853 @subsubheading @value{GDBN} Command
19855 The corresponding @value{GDBN} command is @samp{thread}.
19857 @subsubheading Example
19864 *stopped,reason="end-stepping-range",thread-id="2",line="187",
19865 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
19869 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
19870 number-of-threads="3"
19873 ^done,new-thread-id="3",
19874 frame=@{level="0",func="vprintf",
19875 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
19876 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
19880 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19881 @node GDB/MI Program Execution
19882 @section @sc{gdb/mi} Program Execution
19884 These are the asynchronous commands which generate the out-of-band
19885 record @samp{*stopped}. Currently @value{GDBN} only really executes
19886 asynchronously with remote targets and this interaction is mimicked in
19889 @subheading The @code{-exec-continue} Command
19890 @findex -exec-continue
19892 @subsubheading Synopsis
19898 Resumes the execution of the inferior program until a breakpoint is
19899 encountered, or until the inferior exits.
19901 @subsubheading @value{GDBN} Command
19903 The corresponding @value{GDBN} corresponding is @samp{continue}.
19905 @subsubheading Example
19912 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
19913 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
19919 @subheading The @code{-exec-finish} Command
19920 @findex -exec-finish
19922 @subsubheading Synopsis
19928 Resumes the execution of the inferior program until the current
19929 function is exited. Displays the results returned by the function.
19931 @subsubheading @value{GDBN} Command
19933 The corresponding @value{GDBN} command is @samp{finish}.
19935 @subsubheading Example
19937 Function returning @code{void}.
19944 *stopped,reason="function-finished",frame=@{func="main",args=[],
19945 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
19949 Function returning other than @code{void}. The name of the internal
19950 @value{GDBN} variable storing the result is printed, together with the
19957 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
19958 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
19959 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19960 gdb-result-var="$1",return-value="0"
19965 @subheading The @code{-exec-interrupt} Command
19966 @findex -exec-interrupt
19968 @subsubheading Synopsis
19974 Interrupts the background execution of the target. Note how the token
19975 associated with the stop message is the one for the execution command
19976 that has been interrupted. The token for the interrupt itself only
19977 appears in the @samp{^done} output. If the user is trying to
19978 interrupt a non-running program, an error message will be printed.
19980 @subsubheading @value{GDBN} Command
19982 The corresponding @value{GDBN} command is @samp{interrupt}.
19984 @subsubheading Example
19995 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
19996 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
19997 fullname="/home/foo/bar/try.c",line="13"@}
20002 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
20007 @subheading The @code{-exec-next} Command
20010 @subsubheading Synopsis
20016 Resumes execution of the inferior program, stopping when the beginning
20017 of the next source line is reached.
20019 @subsubheading @value{GDBN} Command
20021 The corresponding @value{GDBN} command is @samp{next}.
20023 @subsubheading Example
20029 *stopped,reason="end-stepping-range",line="8",file="hello.c"
20034 @subheading The @code{-exec-next-instruction} Command
20035 @findex -exec-next-instruction
20037 @subsubheading Synopsis
20040 -exec-next-instruction
20043 Executes one machine instruction. If the instruction is a function
20044 call, continues until the function returns. If the program stops at an
20045 instruction in the middle of a source line, the address will be
20048 @subsubheading @value{GDBN} Command
20050 The corresponding @value{GDBN} command is @samp{nexti}.
20052 @subsubheading Example
20056 -exec-next-instruction
20060 *stopped,reason="end-stepping-range",
20061 addr="0x000100d4",line="5",file="hello.c"
20066 @subheading The @code{-exec-return} Command
20067 @findex -exec-return
20069 @subsubheading Synopsis
20075 Makes current function return immediately. Doesn't execute the inferior.
20076 Displays the new current frame.
20078 @subsubheading @value{GDBN} Command
20080 The corresponding @value{GDBN} command is @samp{return}.
20082 @subsubheading Example
20086 200-break-insert callee4
20087 200^done,bkpt=@{number="1",addr="0x00010734",
20088 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
20093 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
20094 frame=@{func="callee4",args=[],
20095 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20096 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
20102 111^done,frame=@{level="0",func="callee3",
20103 args=[@{name="strarg",
20104 value="0x11940 \"A string argument.\""@}],
20105 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20106 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
20111 @subheading The @code{-exec-run} Command
20114 @subsubheading Synopsis
20120 Starts execution of the inferior from the beginning. The inferior
20121 executes until either a breakpoint is encountered or the program
20122 exits. In the latter case the output will include an exit code, if
20123 the program has exited exceptionally.
20125 @subsubheading @value{GDBN} Command
20127 The corresponding @value{GDBN} command is @samp{run}.
20129 @subsubheading Examples
20134 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
20139 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
20140 frame=@{func="main",args=[],file="recursive2.c",
20141 fullname="/home/foo/bar/recursive2.c",line="4"@}
20146 Program exited normally:
20154 *stopped,reason="exited-normally"
20159 Program exited exceptionally:
20167 *stopped,reason="exited",exit-code="01"
20171 Another way the program can terminate is if it receives a signal such as
20172 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
20176 *stopped,reason="exited-signalled",signal-name="SIGINT",
20177 signal-meaning="Interrupt"
20181 @c @subheading -exec-signal
20184 @subheading The @code{-exec-step} Command
20187 @subsubheading Synopsis
20193 Resumes execution of the inferior program, stopping when the beginning
20194 of the next source line is reached, if the next source line is not a
20195 function call. If it is, stop at the first instruction of the called
20198 @subsubheading @value{GDBN} Command
20200 The corresponding @value{GDBN} command is @samp{step}.
20202 @subsubheading Example
20204 Stepping into a function:
20210 *stopped,reason="end-stepping-range",
20211 frame=@{func="foo",args=[@{name="a",value="10"@},
20212 @{name="b",value="0"@}],file="recursive2.c",
20213 fullname="/home/foo/bar/recursive2.c",line="11"@}
20223 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
20228 @subheading The @code{-exec-step-instruction} Command
20229 @findex -exec-step-instruction
20231 @subsubheading Synopsis
20234 -exec-step-instruction
20237 Resumes the inferior which executes one machine instruction. The
20238 output, once @value{GDBN} has stopped, will vary depending on whether
20239 we have stopped in the middle of a source line or not. In the former
20240 case, the address at which the program stopped will be printed as
20243 @subsubheading @value{GDBN} Command
20245 The corresponding @value{GDBN} command is @samp{stepi}.
20247 @subsubheading Example
20251 -exec-step-instruction
20255 *stopped,reason="end-stepping-range",
20256 frame=@{func="foo",args=[],file="try.c",
20257 fullname="/home/foo/bar/try.c",line="10"@}
20259 -exec-step-instruction
20263 *stopped,reason="end-stepping-range",
20264 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
20265 fullname="/home/foo/bar/try.c",line="10"@}
20270 @subheading The @code{-exec-until} Command
20271 @findex -exec-until
20273 @subsubheading Synopsis
20276 -exec-until [ @var{location} ]
20279 Executes the inferior until the @var{location} specified in the
20280 argument is reached. If there is no argument, the inferior executes
20281 until a source line greater than the current one is reached. The
20282 reason for stopping in this case will be @samp{location-reached}.
20284 @subsubheading @value{GDBN} Command
20286 The corresponding @value{GDBN} command is @samp{until}.
20288 @subsubheading Example
20292 -exec-until recursive2.c:6
20296 *stopped,reason="location-reached",frame=@{func="main",args=[],
20297 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
20302 @subheading -file-clear
20303 Is this going away????
20306 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20307 @node GDB/MI Stack Manipulation
20308 @section @sc{gdb/mi} Stack Manipulation Commands
20311 @subheading The @code{-stack-info-frame} Command
20312 @findex -stack-info-frame
20314 @subsubheading Synopsis
20320 Get info on the selected frame.
20322 @subsubheading @value{GDBN} Command
20324 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
20325 (without arguments).
20327 @subsubheading Example
20332 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
20333 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20334 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
20338 @subheading The @code{-stack-info-depth} Command
20339 @findex -stack-info-depth
20341 @subsubheading Synopsis
20344 -stack-info-depth [ @var{max-depth} ]
20347 Return the depth of the stack. If the integer argument @var{max-depth}
20348 is specified, do not count beyond @var{max-depth} frames.
20350 @subsubheading @value{GDBN} Command
20352 There's no equivalent @value{GDBN} command.
20354 @subsubheading Example
20356 For a stack with frame levels 0 through 11:
20363 -stack-info-depth 4
20366 -stack-info-depth 12
20369 -stack-info-depth 11
20372 -stack-info-depth 13
20377 @subheading The @code{-stack-list-arguments} Command
20378 @findex -stack-list-arguments
20380 @subsubheading Synopsis
20383 -stack-list-arguments @var{show-values}
20384 [ @var{low-frame} @var{high-frame} ]
20387 Display a list of the arguments for the frames between @var{low-frame}
20388 and @var{high-frame} (inclusive). If @var{low-frame} and
20389 @var{high-frame} are not provided, list the arguments for the whole
20390 call stack. If the two arguments are equal, show the single frame
20391 at the corresponding level. It is an error if @var{low-frame} is
20392 larger than the actual number of frames. On the other hand,
20393 @var{high-frame} may be larger than the actual number of frames, in
20394 which case only existing frames will be returned.
20396 The @var{show-values} argument must have a value of 0 or 1. A value of
20397 0 means that only the names of the arguments are listed, a value of 1
20398 means that both names and values of the arguments are printed.
20400 @subsubheading @value{GDBN} Command
20402 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
20403 @samp{gdb_get_args} command which partially overlaps with the
20404 functionality of @samp{-stack-list-arguments}.
20406 @subsubheading Example
20413 frame=@{level="0",addr="0x00010734",func="callee4",
20414 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20415 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
20416 frame=@{level="1",addr="0x0001076c",func="callee3",
20417 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20418 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
20419 frame=@{level="2",addr="0x0001078c",func="callee2",
20420 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20421 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
20422 frame=@{level="3",addr="0x000107b4",func="callee1",
20423 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20424 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
20425 frame=@{level="4",addr="0x000107e0",func="main",
20426 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20427 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
20429 -stack-list-arguments 0
20432 frame=@{level="0",args=[]@},
20433 frame=@{level="1",args=[name="strarg"]@},
20434 frame=@{level="2",args=[name="intarg",name="strarg"]@},
20435 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
20436 frame=@{level="4",args=[]@}]
20438 -stack-list-arguments 1
20441 frame=@{level="0",args=[]@},
20443 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
20444 frame=@{level="2",args=[
20445 @{name="intarg",value="2"@},
20446 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
20447 @{frame=@{level="3",args=[
20448 @{name="intarg",value="2"@},
20449 @{name="strarg",value="0x11940 \"A string argument.\""@},
20450 @{name="fltarg",value="3.5"@}]@},
20451 frame=@{level="4",args=[]@}]
20453 -stack-list-arguments 0 2 2
20454 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
20456 -stack-list-arguments 1 2 2
20457 ^done,stack-args=[frame=@{level="2",
20458 args=[@{name="intarg",value="2"@},
20459 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
20463 @c @subheading -stack-list-exception-handlers
20466 @subheading The @code{-stack-list-frames} Command
20467 @findex -stack-list-frames
20469 @subsubheading Synopsis
20472 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
20475 List the frames currently on the stack. For each frame it displays the
20480 The frame number, 0 being the topmost frame, i.e., the innermost function.
20482 The @code{$pc} value for that frame.
20486 File name of the source file where the function lives.
20488 Line number corresponding to the @code{$pc}.
20491 If invoked without arguments, this command prints a backtrace for the
20492 whole stack. If given two integer arguments, it shows the frames whose
20493 levels are between the two arguments (inclusive). If the two arguments
20494 are equal, it shows the single frame at the corresponding level. It is
20495 an error if @var{low-frame} is larger than the actual number of
20496 frames. On the other hand, @var{high-frame} may be larger than the
20497 actual number of frames, in which case only existing frames will be returned.
20499 @subsubheading @value{GDBN} Command
20501 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
20503 @subsubheading Example
20505 Full stack backtrace:
20511 [frame=@{level="0",addr="0x0001076c",func="foo",
20512 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
20513 frame=@{level="1",addr="0x000107a4",func="foo",
20514 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20515 frame=@{level="2",addr="0x000107a4",func="foo",
20516 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20517 frame=@{level="3",addr="0x000107a4",func="foo",
20518 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20519 frame=@{level="4",addr="0x000107a4",func="foo",
20520 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20521 frame=@{level="5",addr="0x000107a4",func="foo",
20522 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20523 frame=@{level="6",addr="0x000107a4",func="foo",
20524 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20525 frame=@{level="7",addr="0x000107a4",func="foo",
20526 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20527 frame=@{level="8",addr="0x000107a4",func="foo",
20528 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20529 frame=@{level="9",addr="0x000107a4",func="foo",
20530 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20531 frame=@{level="10",addr="0x000107a4",func="foo",
20532 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20533 frame=@{level="11",addr="0x00010738",func="main",
20534 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
20538 Show frames between @var{low_frame} and @var{high_frame}:
20542 -stack-list-frames 3 5
20544 [frame=@{level="3",addr="0x000107a4",func="foo",
20545 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20546 frame=@{level="4",addr="0x000107a4",func="foo",
20547 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20548 frame=@{level="5",addr="0x000107a4",func="foo",
20549 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
20553 Show a single frame:
20557 -stack-list-frames 3 3
20559 [frame=@{level="3",addr="0x000107a4",func="foo",
20560 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
20565 @subheading The @code{-stack-list-locals} Command
20566 @findex -stack-list-locals
20568 @subsubheading Synopsis
20571 -stack-list-locals @var{print-values}
20574 Display the local variable names for the selected frame. If
20575 @var{print-values} is 0 or @code{--no-values}, print only the names of
20576 the variables; if it is 1 or @code{--all-values}, print also their
20577 values; and if it is 2 or @code{--simple-values}, print the name,
20578 type and value for simple data types and the name and type for arrays,
20579 structures and unions. In this last case, a frontend can immediately
20580 display the value of simple data types and create variable objects for
20581 other data types when the user wishes to explore their values in
20584 @subsubheading @value{GDBN} Command
20586 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
20588 @subsubheading Example
20592 -stack-list-locals 0
20593 ^done,locals=[name="A",name="B",name="C"]
20595 -stack-list-locals --all-values
20596 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
20597 @{name="C",value="@{1, 2, 3@}"@}]
20598 -stack-list-locals --simple-values
20599 ^done,locals=[@{name="A",type="int",value="1"@},
20600 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
20605 @subheading The @code{-stack-select-frame} Command
20606 @findex -stack-select-frame
20608 @subsubheading Synopsis
20611 -stack-select-frame @var{framenum}
20614 Change the selected frame. Select a different frame @var{framenum} on
20617 @subsubheading @value{GDBN} Command
20619 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
20620 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
20622 @subsubheading Example
20626 -stack-select-frame 2
20631 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20632 @node GDB/MI Variable Objects
20633 @section @sc{gdb/mi} Variable Objects
20637 @subheading Motivation for Variable Objects in @sc{gdb/mi}
20639 For the implementation of a variable debugger window (locals, watched
20640 expressions, etc.), we are proposing the adaptation of the existing code
20641 used by @code{Insight}.
20643 The two main reasons for that are:
20647 It has been proven in practice (it is already on its second generation).
20650 It will shorten development time (needless to say how important it is
20654 The original interface was designed to be used by Tcl code, so it was
20655 slightly changed so it could be used through @sc{gdb/mi}. This section
20656 describes the @sc{gdb/mi} operations that will be available and gives some
20657 hints about their use.
20659 @emph{Note}: In addition to the set of operations described here, we
20660 expect the @sc{gui} implementation of a variable window to require, at
20661 least, the following operations:
20664 @item @code{-gdb-show} @code{output-radix}
20665 @item @code{-stack-list-arguments}
20666 @item @code{-stack-list-locals}
20667 @item @code{-stack-select-frame}
20672 @subheading Introduction to Variable Objects
20674 @cindex variable objects in @sc{gdb/mi}
20676 Variable objects are "object-oriented" MI interface for examining and
20677 changing values of expressions. Unlike some other MI interfaces that
20678 work with expressions, variable objects are specifically designed for
20679 simple and efficient presentation in the frontend. A variable object
20680 is identified by string name. When a variable object is created, the
20681 frontend specifies the expression for that variable object. The
20682 expression can be a simple variable, or it can be an arbitrary complex
20683 expression, and can even involve CPU registers. After creating a
20684 variable object, the frontend can invoke other variable object
20685 operations---for example to obtain or change the value of a variable
20686 object, or to change display format.
20688 Variable objects have hierarchical tree structure. Any variable object
20689 that corresponds to a composite type, such as structure in C, has
20690 a number of child variable objects, for example corresponding to each
20691 element of a structure. A child variable object can itself have
20692 children, recursively. Recursion ends when we reach
20693 leaf variable objects, which always have built-in types. Child variable
20694 objects are created only by explicit request, so if a frontend
20695 is not interested in the children of a particular variable object, no
20696 child will be created.
20698 For a leaf variable object it is possible to obtain its value as a
20699 string, or set the value from a string. String value can be also
20700 obtained for a non-leaf variable object, but it's generally a string
20701 that only indicates the type of the object, and does not list its
20702 contents. Assignment to a non-leaf variable object is not allowed.
20704 A frontend does not need to read the values of all variable objects each time
20705 the program stops. Instead, MI provides an update command that lists all
20706 variable objects whose values has changed since the last update
20707 operation. This considerably reduces the amount of data that must
20708 be transferred to the frontend. As noted above, children variable
20709 objects are created on demand, and only leaf variable objects have a
20710 real value. As result, gdb will read target memory only for leaf
20711 variables that frontend has created.
20713 The automatic update is not always desirable. For example, a frontend
20714 might want to keep a value of some expression for future reference,
20715 and never update it. For another example, fetching memory is
20716 relatively slow for embedded targets, so a frontend might want
20717 to disable automatic update for the variables that are either not
20718 visible on the screen, or ``closed''. This is possible using so
20719 called ``frozen variable objects''. Such variable objects are never
20720 implicitly updated.
20722 The following is the complete set of @sc{gdb/mi} operations defined to
20723 access this functionality:
20725 @multitable @columnfractions .4 .6
20726 @item @strong{Operation}
20727 @tab @strong{Description}
20729 @item @code{-var-create}
20730 @tab create a variable object
20731 @item @code{-var-delete}
20732 @tab delete the variable object and/or its children
20733 @item @code{-var-set-format}
20734 @tab set the display format of this variable
20735 @item @code{-var-show-format}
20736 @tab show the display format of this variable
20737 @item @code{-var-info-num-children}
20738 @tab tells how many children this object has
20739 @item @code{-var-list-children}
20740 @tab return a list of the object's children
20741 @item @code{-var-info-type}
20742 @tab show the type of this variable object
20743 @item @code{-var-info-expression}
20744 @tab print parent-relative expression that this variable object represents
20745 @item @code{-var-info-path-expression}
20746 @tab print full expression that this variable object represents
20747 @item @code{-var-show-attributes}
20748 @tab is this variable editable? does it exist here?
20749 @item @code{-var-evaluate-expression}
20750 @tab get the value of this variable
20751 @item @code{-var-assign}
20752 @tab set the value of this variable
20753 @item @code{-var-update}
20754 @tab update the variable and its children
20755 @item @code{-var-set-frozen}
20756 @tab set frozeness attribute
20759 In the next subsection we describe each operation in detail and suggest
20760 how it can be used.
20762 @subheading Description And Use of Operations on Variable Objects
20764 @subheading The @code{-var-create} Command
20765 @findex -var-create
20767 @subsubheading Synopsis
20770 -var-create @{@var{name} | "-"@}
20771 @{@var{frame-addr} | "*"@} @var{expression}
20774 This operation creates a variable object, which allows the monitoring of
20775 a variable, the result of an expression, a memory cell or a CPU
20778 The @var{name} parameter is the string by which the object can be
20779 referenced. It must be unique. If @samp{-} is specified, the varobj
20780 system will generate a string ``varNNNNNN'' automatically. It will be
20781 unique provided that one does not specify @var{name} on that format.
20782 The command fails if a duplicate name is found.
20784 The frame under which the expression should be evaluated can be
20785 specified by @var{frame-addr}. A @samp{*} indicates that the current
20786 frame should be used.
20788 @var{expression} is any expression valid on the current language set (must not
20789 begin with a @samp{*}), or one of the following:
20793 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
20796 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
20799 @samp{$@var{regname}} --- a CPU register name
20802 @subsubheading Result
20804 This operation returns the name, number of children and the type of the
20805 object created. Type is returned as a string as the ones generated by
20806 the @value{GDBN} CLI:
20809 name="@var{name}",numchild="N",type="@var{type}"
20813 @subheading The @code{-var-delete} Command
20814 @findex -var-delete
20816 @subsubheading Synopsis
20819 -var-delete [ -c ] @var{name}
20822 Deletes a previously created variable object and all of its children.
20823 With the @samp{-c} option, just deletes the children.
20825 Returns an error if the object @var{name} is not found.
20828 @subheading The @code{-var-set-format} Command
20829 @findex -var-set-format
20831 @subsubheading Synopsis
20834 -var-set-format @var{name} @var{format-spec}
20837 Sets the output format for the value of the object @var{name} to be
20840 @anchor{-var-set-format}
20841 The syntax for the @var{format-spec} is as follows:
20844 @var{format-spec} @expansion{}
20845 @{binary | decimal | hexadecimal | octal | natural@}
20848 The natural format is the default format choosen automatically
20849 based on the variable type (like decimal for an @code{int}, hex
20850 for pointers, etc.).
20852 For a variable with children, the format is set only on the
20853 variable itself, and the children are not affected.
20855 @subheading The @code{-var-show-format} Command
20856 @findex -var-show-format
20858 @subsubheading Synopsis
20861 -var-show-format @var{name}
20864 Returns the format used to display the value of the object @var{name}.
20867 @var{format} @expansion{}
20872 @subheading The @code{-var-info-num-children} Command
20873 @findex -var-info-num-children
20875 @subsubheading Synopsis
20878 -var-info-num-children @var{name}
20881 Returns the number of children of a variable object @var{name}:
20888 @subheading The @code{-var-list-children} Command
20889 @findex -var-list-children
20891 @subsubheading Synopsis
20894 -var-list-children [@var{print-values}] @var{name}
20896 @anchor{-var-list-children}
20898 Return a list of the children of the specified variable object and
20899 create variable objects for them, if they do not already exist. With
20900 a single argument or if @var{print-values} has a value for of 0 or
20901 @code{--no-values}, print only the names of the variables; if
20902 @var{print-values} is 1 or @code{--all-values}, also print their
20903 values; and if it is 2 or @code{--simple-values} print the name and
20904 value for simple data types and just the name for arrays, structures
20907 @subsubheading Example
20911 -var-list-children n
20912 ^done,numchild=@var{n},children=[@{name=@var{name},
20913 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
20915 -var-list-children --all-values n
20916 ^done,numchild=@var{n},children=[@{name=@var{name},
20917 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
20921 @subheading The @code{-var-info-type} Command
20922 @findex -var-info-type
20924 @subsubheading Synopsis
20927 -var-info-type @var{name}
20930 Returns the type of the specified variable @var{name}. The type is
20931 returned as a string in the same format as it is output by the
20935 type=@var{typename}
20939 @subheading The @code{-var-info-expression} Command
20940 @findex -var-info-expression
20942 @subsubheading Synopsis
20945 -var-info-expression @var{name}
20948 Returns a string that is suitable for presenting this
20949 variable object in user interface. The string is generally
20950 not valid expression in the current language, and cannot be evaluated.
20952 For example, if @code{a} is an array, and variable object
20953 @code{A} was created for @code{a}, then we'll get this output:
20956 (gdb) -var-info-expression A.1
20957 ^done,lang="C",exp="1"
20961 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
20963 Note that the output of the @code{-var-list-children} command also
20964 includes those expressions, so the @code{-var-info-expression} command
20967 @subheading The @code{-var-info-path-expression} Command
20968 @findex -var-info-path-expression
20970 @subsubheading Synopsis
20973 -var-info-path-expression @var{name}
20976 Returns an expression that can be evaluated in the current
20977 context and will yield the same value that a variable object has.
20978 Compare this with the @code{-var-info-expression} command, which
20979 result can be used only for UI presentation. Typical use of
20980 the @code{-var-info-path-expression} command is creating a
20981 watchpoint from a variable object.
20983 For example, suppose @code{C} is a C@t{++} class, derived from class
20984 @code{Base}, and that the @code{Base} class has a member called
20985 @code{m_size}. Assume a variable @code{c} is has the type of
20986 @code{C} and a variable object @code{C} was created for variable
20987 @code{c}. Then, we'll get this output:
20989 (gdb) -var-info-path-expression C.Base.public.m_size
20990 ^done,path_expr=((Base)c).m_size)
20993 @subheading The @code{-var-show-attributes} Command
20994 @findex -var-show-attributes
20996 @subsubheading Synopsis
20999 -var-show-attributes @var{name}
21002 List attributes of the specified variable object @var{name}:
21005 status=@var{attr} [ ( ,@var{attr} )* ]
21009 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
21011 @subheading The @code{-var-evaluate-expression} Command
21012 @findex -var-evaluate-expression
21014 @subsubheading Synopsis
21017 -var-evaluate-expression [-f @var{format-spec}] @var{name}
21020 Evaluates the expression that is represented by the specified variable
21021 object and returns its value as a string. The format of the string
21022 can be specified with the @samp{-f} option. The possible values of
21023 this option are the same as for @code{-var-set-format}
21024 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
21025 the current display format will be used. The current display format
21026 can be changed using the @code{-var-set-format} command.
21032 Note that one must invoke @code{-var-list-children} for a variable
21033 before the value of a child variable can be evaluated.
21035 @subheading The @code{-var-assign} Command
21036 @findex -var-assign
21038 @subsubheading Synopsis
21041 -var-assign @var{name} @var{expression}
21044 Assigns the value of @var{expression} to the variable object specified
21045 by @var{name}. The object must be @samp{editable}. If the variable's
21046 value is altered by the assign, the variable will show up in any
21047 subsequent @code{-var-update} list.
21049 @subsubheading Example
21057 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
21061 @subheading The @code{-var-update} Command
21062 @findex -var-update
21064 @subsubheading Synopsis
21067 -var-update [@var{print-values}] @{@var{name} | "*"@}
21070 Reevaluate the expressions corresponding to the variable object
21071 @var{name} and all its direct and indirect children, and return the
21072 list of variable objects whose values have changed; @var{name} must
21073 be a root variable object. Here, ``changed'' means that the result of
21074 @code{-var-evaluate-expression} before and after the
21075 @code{-var-update} is different. If @samp{*} is used as the variable
21076 object names, all existing variable objects are updated, except
21077 for frozen ones (@pxref{-var-set-frozen}). The option
21078 @var{print-values} determines whether both names and values, or just
21079 names are printed. The possible values of this option are the same
21080 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
21081 recommended to use the @samp{--all-values} option, to reduce the
21082 number of MI commands needed on each program stop.
21085 @subsubheading Example
21092 -var-update --all-values var1
21093 ^done,changelist=[@{name="var1",value="3",in_scope="true",
21094 type_changed="false"@}]
21098 @anchor{-var-update}
21099 The field in_scope may take three values:
21103 The variable object's current value is valid.
21106 The variable object does not currently hold a valid value but it may
21107 hold one in the future if its associated expression comes back into
21111 The variable object no longer holds a valid value.
21112 This can occur when the executable file being debugged has changed,
21113 either through recompilation or by using the @value{GDBN} @code{file}
21114 command. The front end should normally choose to delete these variable
21118 In the future new values may be added to this list so the front should
21119 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
21121 @subheading The @code{-var-set-frozen} Command
21122 @findex -var-set-frozen
21123 @anchor{-var-set-frozen}
21125 @subsubheading Synopsis
21128 -var-set-frozen @var{name} @var{flag}
21131 Set the frozenness flag on the variable object @var{name}. The
21132 @var{flag} parameter should be either @samp{1} to make the variable
21133 frozen or @samp{0} to make it unfrozen. If a variable object is
21134 frozen, then neither itself, nor any of its children, are
21135 implicitly updated by @code{-var-update} of
21136 a parent variable or by @code{-var-update *}. Only
21137 @code{-var-update} of the variable itself will update its value and
21138 values of its children. After a variable object is unfrozen, it is
21139 implicitly updated by all subsequent @code{-var-update} operations.
21140 Unfreezing a variable does not update it, only subsequent
21141 @code{-var-update} does.
21143 @subsubheading Example
21147 -var-set-frozen V 1
21153 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21154 @node GDB/MI Data Manipulation
21155 @section @sc{gdb/mi} Data Manipulation
21157 @cindex data manipulation, in @sc{gdb/mi}
21158 @cindex @sc{gdb/mi}, data manipulation
21159 This section describes the @sc{gdb/mi} commands that manipulate data:
21160 examine memory and registers, evaluate expressions, etc.
21162 @c REMOVED FROM THE INTERFACE.
21163 @c @subheading -data-assign
21164 @c Change the value of a program variable. Plenty of side effects.
21165 @c @subsubheading GDB Command
21167 @c @subsubheading Example
21170 @subheading The @code{-data-disassemble} Command
21171 @findex -data-disassemble
21173 @subsubheading Synopsis
21177 [ -s @var{start-addr} -e @var{end-addr} ]
21178 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
21186 @item @var{start-addr}
21187 is the beginning address (or @code{$pc})
21188 @item @var{end-addr}
21190 @item @var{filename}
21191 is the name of the file to disassemble
21192 @item @var{linenum}
21193 is the line number to disassemble around
21195 is the number of disassembly lines to be produced. If it is -1,
21196 the whole function will be disassembled, in case no @var{end-addr} is
21197 specified. If @var{end-addr} is specified as a non-zero value, and
21198 @var{lines} is lower than the number of disassembly lines between
21199 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
21200 displayed; if @var{lines} is higher than the number of lines between
21201 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
21204 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
21208 @subsubheading Result
21210 The output for each instruction is composed of four fields:
21219 Note that whatever included in the instruction field, is not manipulated
21220 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
21222 @subsubheading @value{GDBN} Command
21224 There's no direct mapping from this command to the CLI.
21226 @subsubheading Example
21228 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
21232 -data-disassemble -s $pc -e "$pc + 20" -- 0
21235 @{address="0x000107c0",func-name="main",offset="4",
21236 inst="mov 2, %o0"@},
21237 @{address="0x000107c4",func-name="main",offset="8",
21238 inst="sethi %hi(0x11800), %o2"@},
21239 @{address="0x000107c8",func-name="main",offset="12",
21240 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
21241 @{address="0x000107cc",func-name="main",offset="16",
21242 inst="sethi %hi(0x11800), %o2"@},
21243 @{address="0x000107d0",func-name="main",offset="20",
21244 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
21248 Disassemble the whole @code{main} function. Line 32 is part of
21252 -data-disassemble -f basics.c -l 32 -- 0
21254 @{address="0x000107bc",func-name="main",offset="0",
21255 inst="save %sp, -112, %sp"@},
21256 @{address="0x000107c0",func-name="main",offset="4",
21257 inst="mov 2, %o0"@},
21258 @{address="0x000107c4",func-name="main",offset="8",
21259 inst="sethi %hi(0x11800), %o2"@},
21261 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
21262 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
21266 Disassemble 3 instructions from the start of @code{main}:
21270 -data-disassemble -f basics.c -l 32 -n 3 -- 0
21272 @{address="0x000107bc",func-name="main",offset="0",
21273 inst="save %sp, -112, %sp"@},
21274 @{address="0x000107c0",func-name="main",offset="4",
21275 inst="mov 2, %o0"@},
21276 @{address="0x000107c4",func-name="main",offset="8",
21277 inst="sethi %hi(0x11800), %o2"@}]
21281 Disassemble 3 instructions from the start of @code{main} in mixed mode:
21285 -data-disassemble -f basics.c -l 32 -n 3 -- 1
21287 src_and_asm_line=@{line="31",
21288 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
21289 testsuite/gdb.mi/basics.c",line_asm_insn=[
21290 @{address="0x000107bc",func-name="main",offset="0",
21291 inst="save %sp, -112, %sp"@}]@},
21292 src_and_asm_line=@{line="32",
21293 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
21294 testsuite/gdb.mi/basics.c",line_asm_insn=[
21295 @{address="0x000107c0",func-name="main",offset="4",
21296 inst="mov 2, %o0"@},
21297 @{address="0x000107c4",func-name="main",offset="8",
21298 inst="sethi %hi(0x11800), %o2"@}]@}]
21303 @subheading The @code{-data-evaluate-expression} Command
21304 @findex -data-evaluate-expression
21306 @subsubheading Synopsis
21309 -data-evaluate-expression @var{expr}
21312 Evaluate @var{expr} as an expression. The expression could contain an
21313 inferior function call. The function call will execute synchronously.
21314 If the expression contains spaces, it must be enclosed in double quotes.
21316 @subsubheading @value{GDBN} Command
21318 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
21319 @samp{call}. In @code{gdbtk} only, there's a corresponding
21320 @samp{gdb_eval} command.
21322 @subsubheading Example
21324 In the following example, the numbers that precede the commands are the
21325 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
21326 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
21330 211-data-evaluate-expression A
21333 311-data-evaluate-expression &A
21334 311^done,value="0xefffeb7c"
21336 411-data-evaluate-expression A+3
21339 511-data-evaluate-expression "A + 3"
21345 @subheading The @code{-data-list-changed-registers} Command
21346 @findex -data-list-changed-registers
21348 @subsubheading Synopsis
21351 -data-list-changed-registers
21354 Display a list of the registers that have changed.
21356 @subsubheading @value{GDBN} Command
21358 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
21359 has the corresponding command @samp{gdb_changed_register_list}.
21361 @subsubheading Example
21363 On a PPC MBX board:
21371 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
21372 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
21375 -data-list-changed-registers
21376 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
21377 "10","11","13","14","15","16","17","18","19","20","21","22","23",
21378 "24","25","26","27","28","30","31","64","65","66","67","69"]
21383 @subheading The @code{-data-list-register-names} Command
21384 @findex -data-list-register-names
21386 @subsubheading Synopsis
21389 -data-list-register-names [ ( @var{regno} )+ ]
21392 Show a list of register names for the current target. If no arguments
21393 are given, it shows a list of the names of all the registers. If
21394 integer numbers are given as arguments, it will print a list of the
21395 names of the registers corresponding to the arguments. To ensure
21396 consistency between a register name and its number, the output list may
21397 include empty register names.
21399 @subsubheading @value{GDBN} Command
21401 @value{GDBN} does not have a command which corresponds to
21402 @samp{-data-list-register-names}. In @code{gdbtk} there is a
21403 corresponding command @samp{gdb_regnames}.
21405 @subsubheading Example
21407 For the PPC MBX board:
21410 -data-list-register-names
21411 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
21412 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
21413 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
21414 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
21415 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
21416 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
21417 "", "pc","ps","cr","lr","ctr","xer"]
21419 -data-list-register-names 1 2 3
21420 ^done,register-names=["r1","r2","r3"]
21424 @subheading The @code{-data-list-register-values} Command
21425 @findex -data-list-register-values
21427 @subsubheading Synopsis
21430 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
21433 Display the registers' contents. @var{fmt} is the format according to
21434 which the registers' contents are to be returned, followed by an optional
21435 list of numbers specifying the registers to display. A missing list of
21436 numbers indicates that the contents of all the registers must be returned.
21438 Allowed formats for @var{fmt} are:
21455 @subsubheading @value{GDBN} Command
21457 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
21458 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
21460 @subsubheading Example
21462 For a PPC MBX board (note: line breaks are for readability only, they
21463 don't appear in the actual output):
21467 -data-list-register-values r 64 65
21468 ^done,register-values=[@{number="64",value="0xfe00a300"@},
21469 @{number="65",value="0x00029002"@}]
21471 -data-list-register-values x
21472 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
21473 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
21474 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
21475 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
21476 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
21477 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
21478 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
21479 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
21480 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
21481 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
21482 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
21483 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
21484 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
21485 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
21486 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
21487 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
21488 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
21489 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
21490 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
21491 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
21492 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
21493 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
21494 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
21495 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
21496 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
21497 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
21498 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
21499 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
21500 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
21501 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
21502 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
21503 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
21504 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
21505 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
21506 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
21507 @{number="69",value="0x20002b03"@}]
21512 @subheading The @code{-data-read-memory} Command
21513 @findex -data-read-memory
21515 @subsubheading Synopsis
21518 -data-read-memory [ -o @var{byte-offset} ]
21519 @var{address} @var{word-format} @var{word-size}
21520 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
21527 @item @var{address}
21528 An expression specifying the address of the first memory word to be
21529 read. Complex expressions containing embedded white space should be
21530 quoted using the C convention.
21532 @item @var{word-format}
21533 The format to be used to print the memory words. The notation is the
21534 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
21537 @item @var{word-size}
21538 The size of each memory word in bytes.
21540 @item @var{nr-rows}
21541 The number of rows in the output table.
21543 @item @var{nr-cols}
21544 The number of columns in the output table.
21547 If present, indicates that each row should include an @sc{ascii} dump. The
21548 value of @var{aschar} is used as a padding character when a byte is not a
21549 member of the printable @sc{ascii} character set (printable @sc{ascii}
21550 characters are those whose code is between 32 and 126, inclusively).
21552 @item @var{byte-offset}
21553 An offset to add to the @var{address} before fetching memory.
21556 This command displays memory contents as a table of @var{nr-rows} by
21557 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
21558 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
21559 (returned as @samp{total-bytes}). Should less than the requested number
21560 of bytes be returned by the target, the missing words are identified
21561 using @samp{N/A}. The number of bytes read from the target is returned
21562 in @samp{nr-bytes} and the starting address used to read memory in
21565 The address of the next/previous row or page is available in
21566 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
21569 @subsubheading @value{GDBN} Command
21571 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
21572 @samp{gdb_get_mem} memory read command.
21574 @subsubheading Example
21576 Read six bytes of memory starting at @code{bytes+6} but then offset by
21577 @code{-6} bytes. Format as three rows of two columns. One byte per
21578 word. Display each word in hex.
21582 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
21583 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
21584 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
21585 prev-page="0x0000138a",memory=[
21586 @{addr="0x00001390",data=["0x00","0x01"]@},
21587 @{addr="0x00001392",data=["0x02","0x03"]@},
21588 @{addr="0x00001394",data=["0x04","0x05"]@}]
21592 Read two bytes of memory starting at address @code{shorts + 64} and
21593 display as a single word formatted in decimal.
21597 5-data-read-memory shorts+64 d 2 1 1
21598 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
21599 next-row="0x00001512",prev-row="0x0000150e",
21600 next-page="0x00001512",prev-page="0x0000150e",memory=[
21601 @{addr="0x00001510",data=["128"]@}]
21605 Read thirty two bytes of memory starting at @code{bytes+16} and format
21606 as eight rows of four columns. Include a string encoding with @samp{x}
21607 used as the non-printable character.
21611 4-data-read-memory bytes+16 x 1 8 4 x
21612 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
21613 next-row="0x000013c0",prev-row="0x0000139c",
21614 next-page="0x000013c0",prev-page="0x00001380",memory=[
21615 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
21616 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
21617 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
21618 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
21619 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
21620 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
21621 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
21622 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
21626 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21627 @node GDB/MI Tracepoint Commands
21628 @section @sc{gdb/mi} Tracepoint Commands
21630 The tracepoint commands are not yet implemented.
21632 @c @subheading -trace-actions
21634 @c @subheading -trace-delete
21636 @c @subheading -trace-disable
21638 @c @subheading -trace-dump
21640 @c @subheading -trace-enable
21642 @c @subheading -trace-exists
21644 @c @subheading -trace-find
21646 @c @subheading -trace-frame-number
21648 @c @subheading -trace-info
21650 @c @subheading -trace-insert
21652 @c @subheading -trace-list
21654 @c @subheading -trace-pass-count
21656 @c @subheading -trace-save
21658 @c @subheading -trace-start
21660 @c @subheading -trace-stop
21663 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21664 @node GDB/MI Symbol Query
21665 @section @sc{gdb/mi} Symbol Query Commands
21668 @subheading The @code{-symbol-info-address} Command
21669 @findex -symbol-info-address
21671 @subsubheading Synopsis
21674 -symbol-info-address @var{symbol}
21677 Describe where @var{symbol} is stored.
21679 @subsubheading @value{GDBN} Command
21681 The corresponding @value{GDBN} command is @samp{info address}.
21683 @subsubheading Example
21687 @subheading The @code{-symbol-info-file} Command
21688 @findex -symbol-info-file
21690 @subsubheading Synopsis
21696 Show the file for the symbol.
21698 @subsubheading @value{GDBN} Command
21700 There's no equivalent @value{GDBN} command. @code{gdbtk} has
21701 @samp{gdb_find_file}.
21703 @subsubheading Example
21707 @subheading The @code{-symbol-info-function} Command
21708 @findex -symbol-info-function
21710 @subsubheading Synopsis
21713 -symbol-info-function
21716 Show which function the symbol lives in.
21718 @subsubheading @value{GDBN} Command
21720 @samp{gdb_get_function} in @code{gdbtk}.
21722 @subsubheading Example
21726 @subheading The @code{-symbol-info-line} Command
21727 @findex -symbol-info-line
21729 @subsubheading Synopsis
21735 Show the core addresses of the code for a source line.
21737 @subsubheading @value{GDBN} Command
21739 The corresponding @value{GDBN} command is @samp{info line}.
21740 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
21742 @subsubheading Example
21746 @subheading The @code{-symbol-info-symbol} Command
21747 @findex -symbol-info-symbol
21749 @subsubheading Synopsis
21752 -symbol-info-symbol @var{addr}
21755 Describe what symbol is at location @var{addr}.
21757 @subsubheading @value{GDBN} Command
21759 The corresponding @value{GDBN} command is @samp{info symbol}.
21761 @subsubheading Example
21765 @subheading The @code{-symbol-list-functions} Command
21766 @findex -symbol-list-functions
21768 @subsubheading Synopsis
21771 -symbol-list-functions
21774 List the functions in the executable.
21776 @subsubheading @value{GDBN} Command
21778 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
21779 @samp{gdb_search} in @code{gdbtk}.
21781 @subsubheading Example
21785 @subheading The @code{-symbol-list-lines} Command
21786 @findex -symbol-list-lines
21788 @subsubheading Synopsis
21791 -symbol-list-lines @var{filename}
21794 Print the list of lines that contain code and their associated program
21795 addresses for the given source filename. The entries are sorted in
21796 ascending PC order.
21798 @subsubheading @value{GDBN} Command
21800 There is no corresponding @value{GDBN} command.
21802 @subsubheading Example
21805 -symbol-list-lines basics.c
21806 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
21811 @subheading The @code{-symbol-list-types} Command
21812 @findex -symbol-list-types
21814 @subsubheading Synopsis
21820 List all the type names.
21822 @subsubheading @value{GDBN} Command
21824 The corresponding commands are @samp{info types} in @value{GDBN},
21825 @samp{gdb_search} in @code{gdbtk}.
21827 @subsubheading Example
21831 @subheading The @code{-symbol-list-variables} Command
21832 @findex -symbol-list-variables
21834 @subsubheading Synopsis
21837 -symbol-list-variables
21840 List all the global and static variable names.
21842 @subsubheading @value{GDBN} Command
21844 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
21846 @subsubheading Example
21850 @subheading The @code{-symbol-locate} Command
21851 @findex -symbol-locate
21853 @subsubheading Synopsis
21859 @subsubheading @value{GDBN} Command
21861 @samp{gdb_loc} in @code{gdbtk}.
21863 @subsubheading Example
21867 @subheading The @code{-symbol-type} Command
21868 @findex -symbol-type
21870 @subsubheading Synopsis
21873 -symbol-type @var{variable}
21876 Show type of @var{variable}.
21878 @subsubheading @value{GDBN} Command
21880 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
21881 @samp{gdb_obj_variable}.
21883 @subsubheading Example
21887 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21888 @node GDB/MI File Commands
21889 @section @sc{gdb/mi} File Commands
21891 This section describes the GDB/MI commands to specify executable file names
21892 and to read in and obtain symbol table information.
21894 @subheading The @code{-file-exec-and-symbols} Command
21895 @findex -file-exec-and-symbols
21897 @subsubheading Synopsis
21900 -file-exec-and-symbols @var{file}
21903 Specify the executable file to be debugged. This file is the one from
21904 which the symbol table is also read. If no file is specified, the
21905 command clears the executable and symbol information. If breakpoints
21906 are set when using this command with no arguments, @value{GDBN} will produce
21907 error messages. Otherwise, no output is produced, except a completion
21910 @subsubheading @value{GDBN} Command
21912 The corresponding @value{GDBN} command is @samp{file}.
21914 @subsubheading Example
21918 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
21924 @subheading The @code{-file-exec-file} Command
21925 @findex -file-exec-file
21927 @subsubheading Synopsis
21930 -file-exec-file @var{file}
21933 Specify the executable file to be debugged. Unlike
21934 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
21935 from this file. If used without argument, @value{GDBN} clears the information
21936 about the executable file. No output is produced, except a completion
21939 @subsubheading @value{GDBN} Command
21941 The corresponding @value{GDBN} command is @samp{exec-file}.
21943 @subsubheading Example
21947 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
21953 @subheading The @code{-file-list-exec-sections} Command
21954 @findex -file-list-exec-sections
21956 @subsubheading Synopsis
21959 -file-list-exec-sections
21962 List the sections of the current executable file.
21964 @subsubheading @value{GDBN} Command
21966 The @value{GDBN} command @samp{info file} shows, among the rest, the same
21967 information as this command. @code{gdbtk} has a corresponding command
21968 @samp{gdb_load_info}.
21970 @subsubheading Example
21974 @subheading The @code{-file-list-exec-source-file} Command
21975 @findex -file-list-exec-source-file
21977 @subsubheading Synopsis
21980 -file-list-exec-source-file
21983 List the line number, the current source file, and the absolute path
21984 to the current source file for the current executable. The macro
21985 information field has a value of @samp{1} or @samp{0} depending on
21986 whether or not the file includes preprocessor macro information.
21988 @subsubheading @value{GDBN} Command
21990 The @value{GDBN} equivalent is @samp{info source}
21992 @subsubheading Example
21996 123-file-list-exec-source-file
21997 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
22002 @subheading The @code{-file-list-exec-source-files} Command
22003 @findex -file-list-exec-source-files
22005 @subsubheading Synopsis
22008 -file-list-exec-source-files
22011 List the source files for the current executable.
22013 It will always output the filename, but only when @value{GDBN} can find
22014 the absolute file name of a source file, will it output the fullname.
22016 @subsubheading @value{GDBN} Command
22018 The @value{GDBN} equivalent is @samp{info sources}.
22019 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
22021 @subsubheading Example
22024 -file-list-exec-source-files
22026 @{file=foo.c,fullname=/home/foo.c@},
22027 @{file=/home/bar.c,fullname=/home/bar.c@},
22028 @{file=gdb_could_not_find_fullpath.c@}]
22032 @subheading The @code{-file-list-shared-libraries} Command
22033 @findex -file-list-shared-libraries
22035 @subsubheading Synopsis
22038 -file-list-shared-libraries
22041 List the shared libraries in the program.
22043 @subsubheading @value{GDBN} Command
22045 The corresponding @value{GDBN} command is @samp{info shared}.
22047 @subsubheading Example
22051 @subheading The @code{-file-list-symbol-files} Command
22052 @findex -file-list-symbol-files
22054 @subsubheading Synopsis
22057 -file-list-symbol-files
22062 @subsubheading @value{GDBN} Command
22064 The corresponding @value{GDBN} command is @samp{info file} (part of it).
22066 @subsubheading Example
22070 @subheading The @code{-file-symbol-file} Command
22071 @findex -file-symbol-file
22073 @subsubheading Synopsis
22076 -file-symbol-file @var{file}
22079 Read symbol table info from the specified @var{file} argument. When
22080 used without arguments, clears @value{GDBN}'s symbol table info. No output is
22081 produced, except for a completion notification.
22083 @subsubheading @value{GDBN} Command
22085 The corresponding @value{GDBN} command is @samp{symbol-file}.
22087 @subsubheading Example
22091 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
22097 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22098 @node GDB/MI Memory Overlay Commands
22099 @section @sc{gdb/mi} Memory Overlay Commands
22101 The memory overlay commands are not implemented.
22103 @c @subheading -overlay-auto
22105 @c @subheading -overlay-list-mapping-state
22107 @c @subheading -overlay-list-overlays
22109 @c @subheading -overlay-map
22111 @c @subheading -overlay-off
22113 @c @subheading -overlay-on
22115 @c @subheading -overlay-unmap
22117 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22118 @node GDB/MI Signal Handling Commands
22119 @section @sc{gdb/mi} Signal Handling Commands
22121 Signal handling commands are not implemented.
22123 @c @subheading -signal-handle
22125 @c @subheading -signal-list-handle-actions
22127 @c @subheading -signal-list-signal-types
22131 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22132 @node GDB/MI Target Manipulation
22133 @section @sc{gdb/mi} Target Manipulation Commands
22136 @subheading The @code{-target-attach} Command
22137 @findex -target-attach
22139 @subsubheading Synopsis
22142 -target-attach @var{pid} | @var{file}
22145 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
22147 @subsubheading @value{GDBN} Command
22149 The corresponding @value{GDBN} command is @samp{attach}.
22151 @subsubheading Example
22155 =thread-created,id="1"
22156 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
22161 @subheading The @code{-target-compare-sections} Command
22162 @findex -target-compare-sections
22164 @subsubheading Synopsis
22167 -target-compare-sections [ @var{section} ]
22170 Compare data of section @var{section} on target to the exec file.
22171 Without the argument, all sections are compared.
22173 @subsubheading @value{GDBN} Command
22175 The @value{GDBN} equivalent is @samp{compare-sections}.
22177 @subsubheading Example
22181 @subheading The @code{-target-detach} Command
22182 @findex -target-detach
22184 @subsubheading Synopsis
22190 Detach from the remote target which normally resumes its execution.
22193 @subsubheading @value{GDBN} Command
22195 The corresponding @value{GDBN} command is @samp{detach}.
22197 @subsubheading Example
22207 @subheading The @code{-target-disconnect} Command
22208 @findex -target-disconnect
22210 @subsubheading Synopsis
22216 Disconnect from the remote target. There's no output and the target is
22217 generally not resumed.
22219 @subsubheading @value{GDBN} Command
22221 The corresponding @value{GDBN} command is @samp{disconnect}.
22223 @subsubheading Example
22233 @subheading The @code{-target-download} Command
22234 @findex -target-download
22236 @subsubheading Synopsis
22242 Loads the executable onto the remote target.
22243 It prints out an update message every half second, which includes the fields:
22247 The name of the section.
22249 The size of what has been sent so far for that section.
22251 The size of the section.
22253 The total size of what was sent so far (the current and the previous sections).
22255 The size of the overall executable to download.
22259 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
22260 @sc{gdb/mi} Output Syntax}).
22262 In addition, it prints the name and size of the sections, as they are
22263 downloaded. These messages include the following fields:
22267 The name of the section.
22269 The size of the section.
22271 The size of the overall executable to download.
22275 At the end, a summary is printed.
22277 @subsubheading @value{GDBN} Command
22279 The corresponding @value{GDBN} command is @samp{load}.
22281 @subsubheading Example
22283 Note: each status message appears on a single line. Here the messages
22284 have been broken down so that they can fit onto a page.
22289 +download,@{section=".text",section-size="6668",total-size="9880"@}
22290 +download,@{section=".text",section-sent="512",section-size="6668",
22291 total-sent="512",total-size="9880"@}
22292 +download,@{section=".text",section-sent="1024",section-size="6668",
22293 total-sent="1024",total-size="9880"@}
22294 +download,@{section=".text",section-sent="1536",section-size="6668",
22295 total-sent="1536",total-size="9880"@}
22296 +download,@{section=".text",section-sent="2048",section-size="6668",
22297 total-sent="2048",total-size="9880"@}
22298 +download,@{section=".text",section-sent="2560",section-size="6668",
22299 total-sent="2560",total-size="9880"@}
22300 +download,@{section=".text",section-sent="3072",section-size="6668",
22301 total-sent="3072",total-size="9880"@}
22302 +download,@{section=".text",section-sent="3584",section-size="6668",
22303 total-sent="3584",total-size="9880"@}
22304 +download,@{section=".text",section-sent="4096",section-size="6668",
22305 total-sent="4096",total-size="9880"@}
22306 +download,@{section=".text",section-sent="4608",section-size="6668",
22307 total-sent="4608",total-size="9880"@}
22308 +download,@{section=".text",section-sent="5120",section-size="6668",
22309 total-sent="5120",total-size="9880"@}
22310 +download,@{section=".text",section-sent="5632",section-size="6668",
22311 total-sent="5632",total-size="9880"@}
22312 +download,@{section=".text",section-sent="6144",section-size="6668",
22313 total-sent="6144",total-size="9880"@}
22314 +download,@{section=".text",section-sent="6656",section-size="6668",
22315 total-sent="6656",total-size="9880"@}
22316 +download,@{section=".init",section-size="28",total-size="9880"@}
22317 +download,@{section=".fini",section-size="28",total-size="9880"@}
22318 +download,@{section=".data",section-size="3156",total-size="9880"@}
22319 +download,@{section=".data",section-sent="512",section-size="3156",
22320 total-sent="7236",total-size="9880"@}
22321 +download,@{section=".data",section-sent="1024",section-size="3156",
22322 total-sent="7748",total-size="9880"@}
22323 +download,@{section=".data",section-sent="1536",section-size="3156",
22324 total-sent="8260",total-size="9880"@}
22325 +download,@{section=".data",section-sent="2048",section-size="3156",
22326 total-sent="8772",total-size="9880"@}
22327 +download,@{section=".data",section-sent="2560",section-size="3156",
22328 total-sent="9284",total-size="9880"@}
22329 +download,@{section=".data",section-sent="3072",section-size="3156",
22330 total-sent="9796",total-size="9880"@}
22331 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
22337 @subheading The @code{-target-exec-status} Command
22338 @findex -target-exec-status
22340 @subsubheading Synopsis
22343 -target-exec-status
22346 Provide information on the state of the target (whether it is running or
22347 not, for instance).
22349 @subsubheading @value{GDBN} Command
22351 There's no equivalent @value{GDBN} command.
22353 @subsubheading Example
22357 @subheading The @code{-target-list-available-targets} Command
22358 @findex -target-list-available-targets
22360 @subsubheading Synopsis
22363 -target-list-available-targets
22366 List the possible targets to connect to.
22368 @subsubheading @value{GDBN} Command
22370 The corresponding @value{GDBN} command is @samp{help target}.
22372 @subsubheading Example
22376 @subheading The @code{-target-list-current-targets} Command
22377 @findex -target-list-current-targets
22379 @subsubheading Synopsis
22382 -target-list-current-targets
22385 Describe the current target.
22387 @subsubheading @value{GDBN} Command
22389 The corresponding information is printed by @samp{info file} (among
22392 @subsubheading Example
22396 @subheading The @code{-target-list-parameters} Command
22397 @findex -target-list-parameters
22399 @subsubheading Synopsis
22402 -target-list-parameters
22407 @subsubheading @value{GDBN} Command
22411 @subsubheading Example
22415 @subheading The @code{-target-select} Command
22416 @findex -target-select
22418 @subsubheading Synopsis
22421 -target-select @var{type} @var{parameters @dots{}}
22424 Connect @value{GDBN} to the remote target. This command takes two args:
22428 The type of target, for instance @samp{remote}, etc.
22429 @item @var{parameters}
22430 Device names, host names and the like. @xref{Target Commands, ,
22431 Commands for Managing Targets}, for more details.
22434 The output is a connection notification, followed by the address at
22435 which the target program is, in the following form:
22438 ^connected,addr="@var{address}",func="@var{function name}",
22439 args=[@var{arg list}]
22442 @subsubheading @value{GDBN} Command
22444 The corresponding @value{GDBN} command is @samp{target}.
22446 @subsubheading Example
22450 -target-select remote /dev/ttya
22451 ^connected,addr="0xfe00a300",func="??",args=[]
22455 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22456 @node GDB/MI File Transfer Commands
22457 @section @sc{gdb/mi} File Transfer Commands
22460 @subheading The @code{-target-file-put} Command
22461 @findex -target-file-put
22463 @subsubheading Synopsis
22466 -target-file-put @var{hostfile} @var{targetfile}
22469 Copy file @var{hostfile} from the host system (the machine running
22470 @value{GDBN}) to @var{targetfile} on the target system.
22472 @subsubheading @value{GDBN} Command
22474 The corresponding @value{GDBN} command is @samp{remote put}.
22476 @subsubheading Example
22480 -target-file-put localfile remotefile
22486 @subheading The @code{-target-file-get} Command
22487 @findex -target-file-get
22489 @subsubheading Synopsis
22492 -target-file-get @var{targetfile} @var{hostfile}
22495 Copy file @var{targetfile} from the target system to @var{hostfile}
22496 on the host system.
22498 @subsubheading @value{GDBN} Command
22500 The corresponding @value{GDBN} command is @samp{remote get}.
22502 @subsubheading Example
22506 -target-file-get remotefile localfile
22512 @subheading The @code{-target-file-delete} Command
22513 @findex -target-file-delete
22515 @subsubheading Synopsis
22518 -target-file-delete @var{targetfile}
22521 Delete @var{targetfile} from the target system.
22523 @subsubheading @value{GDBN} Command
22525 The corresponding @value{GDBN} command is @samp{remote delete}.
22527 @subsubheading Example
22531 -target-file-delete remotefile
22537 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22538 @node GDB/MI Miscellaneous Commands
22539 @section Miscellaneous @sc{gdb/mi} Commands
22541 @c @subheading -gdb-complete
22543 @subheading The @code{-gdb-exit} Command
22546 @subsubheading Synopsis
22552 Exit @value{GDBN} immediately.
22554 @subsubheading @value{GDBN} Command
22556 Approximately corresponds to @samp{quit}.
22558 @subsubheading Example
22567 @subheading The @code{-exec-abort} Command
22568 @findex -exec-abort
22570 @subsubheading Synopsis
22576 Kill the inferior running program.
22578 @subsubheading @value{GDBN} Command
22580 The corresponding @value{GDBN} command is @samp{kill}.
22582 @subsubheading Example
22586 @subheading The @code{-gdb-set} Command
22589 @subsubheading Synopsis
22595 Set an internal @value{GDBN} variable.
22596 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
22598 @subsubheading @value{GDBN} Command
22600 The corresponding @value{GDBN} command is @samp{set}.
22602 @subsubheading Example
22612 @subheading The @code{-gdb-show} Command
22615 @subsubheading Synopsis
22621 Show the current value of a @value{GDBN} variable.
22623 @subsubheading @value{GDBN} Command
22625 The corresponding @value{GDBN} command is @samp{show}.
22627 @subsubheading Example
22636 @c @subheading -gdb-source
22639 @subheading The @code{-gdb-version} Command
22640 @findex -gdb-version
22642 @subsubheading Synopsis
22648 Show version information for @value{GDBN}. Used mostly in testing.
22650 @subsubheading @value{GDBN} Command
22652 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
22653 default shows this information when you start an interactive session.
22655 @subsubheading Example
22657 @c This example modifies the actual output from GDB to avoid overfull
22663 ~Copyright 2000 Free Software Foundation, Inc.
22664 ~GDB is free software, covered by the GNU General Public License, and
22665 ~you are welcome to change it and/or distribute copies of it under
22666 ~ certain conditions.
22667 ~Type "show copying" to see the conditions.
22668 ~There is absolutely no warranty for GDB. Type "show warranty" for
22670 ~This GDB was configured as
22671 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
22676 @subheading The @code{-list-features} Command
22677 @findex -list-features
22679 Returns a list of particular features of the MI protocol that
22680 this version of gdb implements. A feature can be a command,
22681 or a new field in an output of some command, or even an
22682 important bugfix. While a frontend can sometimes detect presence
22683 of a feature at runtime, it is easier to perform detection at debugger
22686 The command returns a list of strings, with each string naming an
22687 available feature. Each returned string is just a name, it does not
22688 have any internal structure. The list of possible feature names
22694 (gdb) -list-features
22695 ^done,result=["feature1","feature2"]
22698 The current list of features is:
22701 @item frozen-varobjs
22702 Indicates presence of the @code{-var-set-frozen} command, as well
22703 as possible presense of the @code{frozen} field in the output
22704 of @code{-varobj-create}.
22705 @item pending-breakpoints
22706 Indicates presence of the @option{-f} option to the @code{-break-insert} command.
22708 Indicates presence of the @code{-thread-info} command.
22712 @subheading The @code{-list-target-features} Command
22713 @findex -list-target-features
22715 Returns a list of particular features that are supported by the
22716 target. Those features affect the permitted MI commands, but
22717 unlike the features reported by the @code{-list-features} command, the
22718 features depend on which target GDB is using at the moment. Whenever
22719 a target can change, due to commands such as @code{-target-select},
22720 @code{-target-attach} or @code{-exec-run}, the list of target features
22721 may change, and the frontend should obtain it again.
22725 (gdb) -list-features
22726 ^done,result=["async"]
22729 The current list of features is:
22733 Indicates that the target is capable of asynchronous command
22734 execution, which means that @value{GDBN} will accept further commands
22735 while the target is running.
22740 @subheading The @code{-interpreter-exec} Command
22741 @findex -interpreter-exec
22743 @subheading Synopsis
22746 -interpreter-exec @var{interpreter} @var{command}
22748 @anchor{-interpreter-exec}
22750 Execute the specified @var{command} in the given @var{interpreter}.
22752 @subheading @value{GDBN} Command
22754 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
22756 @subheading Example
22760 -interpreter-exec console "break main"
22761 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
22762 &"During symbol reading, bad structure-type format.\n"
22763 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
22768 @subheading The @code{-inferior-tty-set} Command
22769 @findex -inferior-tty-set
22771 @subheading Synopsis
22774 -inferior-tty-set /dev/pts/1
22777 Set terminal for future runs of the program being debugged.
22779 @subheading @value{GDBN} Command
22781 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
22783 @subheading Example
22787 -inferior-tty-set /dev/pts/1
22792 @subheading The @code{-inferior-tty-show} Command
22793 @findex -inferior-tty-show
22795 @subheading Synopsis
22801 Show terminal for future runs of program being debugged.
22803 @subheading @value{GDBN} Command
22805 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
22807 @subheading Example
22811 -inferior-tty-set /dev/pts/1
22815 ^done,inferior_tty_terminal="/dev/pts/1"
22819 @subheading The @code{-enable-timings} Command
22820 @findex -enable-timings
22822 @subheading Synopsis
22825 -enable-timings [yes | no]
22828 Toggle the printing of the wallclock, user and system times for an MI
22829 command as a field in its output. This command is to help frontend
22830 developers optimize the performance of their code. No argument is
22831 equivalent to @samp{yes}.
22833 @subheading @value{GDBN} Command
22837 @subheading Example
22845 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
22846 addr="0x080484ed",func="main",file="myprog.c",
22847 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
22848 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
22856 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
22857 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
22858 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
22859 fullname="/home/nickrob/myprog.c",line="73"@}
22864 @chapter @value{GDBN} Annotations
22866 This chapter describes annotations in @value{GDBN}. Annotations were
22867 designed to interface @value{GDBN} to graphical user interfaces or other
22868 similar programs which want to interact with @value{GDBN} at a
22869 relatively high level.
22871 The annotation mechanism has largely been superseded by @sc{gdb/mi}
22875 This is Edition @value{EDITION}, @value{DATE}.
22879 * Annotations Overview:: What annotations are; the general syntax.
22880 * Server Prefix:: Issuing a command without affecting user state.
22881 * Prompting:: Annotations marking @value{GDBN}'s need for input.
22882 * Errors:: Annotations for error messages.
22883 * Invalidation:: Some annotations describe things now invalid.
22884 * Annotations for Running::
22885 Whether the program is running, how it stopped, etc.
22886 * Source Annotations:: Annotations describing source code.
22889 @node Annotations Overview
22890 @section What is an Annotation?
22891 @cindex annotations
22893 Annotations start with a newline character, two @samp{control-z}
22894 characters, and the name of the annotation. If there is no additional
22895 information associated with this annotation, the name of the annotation
22896 is followed immediately by a newline. If there is additional
22897 information, the name of the annotation is followed by a space, the
22898 additional information, and a newline. The additional information
22899 cannot contain newline characters.
22901 Any output not beginning with a newline and two @samp{control-z}
22902 characters denotes literal output from @value{GDBN}. Currently there is
22903 no need for @value{GDBN} to output a newline followed by two
22904 @samp{control-z} characters, but if there was such a need, the
22905 annotations could be extended with an @samp{escape} annotation which
22906 means those three characters as output.
22908 The annotation @var{level}, which is specified using the
22909 @option{--annotate} command line option (@pxref{Mode Options}), controls
22910 how much information @value{GDBN} prints together with its prompt,
22911 values of expressions, source lines, and other types of output. Level 0
22912 is for no annotations, level 1 is for use when @value{GDBN} is run as a
22913 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
22914 for programs that control @value{GDBN}, and level 2 annotations have
22915 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
22916 Interface, annotate, GDB's Obsolete Annotations}).
22919 @kindex set annotate
22920 @item set annotate @var{level}
22921 The @value{GDBN} command @code{set annotate} sets the level of
22922 annotations to the specified @var{level}.
22924 @item show annotate
22925 @kindex show annotate
22926 Show the current annotation level.
22929 This chapter describes level 3 annotations.
22931 A simple example of starting up @value{GDBN} with annotations is:
22934 $ @kbd{gdb --annotate=3}
22936 Copyright 2003 Free Software Foundation, Inc.
22937 GDB is free software, covered by the GNU General Public License,
22938 and you are welcome to change it and/or distribute copies of it
22939 under certain conditions.
22940 Type "show copying" to see the conditions.
22941 There is absolutely no warranty for GDB. Type "show warranty"
22943 This GDB was configured as "i386-pc-linux-gnu"
22954 Here @samp{quit} is input to @value{GDBN}; the rest is output from
22955 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
22956 denotes a @samp{control-z} character) are annotations; the rest is
22957 output from @value{GDBN}.
22959 @node Server Prefix
22960 @section The Server Prefix
22961 @cindex server prefix
22963 If you prefix a command with @samp{server } then it will not affect
22964 the command history, nor will it affect @value{GDBN}'s notion of which
22965 command to repeat if @key{RET} is pressed on a line by itself. This
22966 means that commands can be run behind a user's back by a front-end in
22967 a transparent manner.
22969 The server prefix does not affect the recording of values into the value
22970 history; to print a value without recording it into the value history,
22971 use the @code{output} command instead of the @code{print} command.
22974 @section Annotation for @value{GDBN} Input
22976 @cindex annotations for prompts
22977 When @value{GDBN} prompts for input, it annotates this fact so it is possible
22978 to know when to send output, when the output from a given command is
22981 Different kinds of input each have a different @dfn{input type}. Each
22982 input type has three annotations: a @code{pre-} annotation, which
22983 denotes the beginning of any prompt which is being output, a plain
22984 annotation, which denotes the end of the prompt, and then a @code{post-}
22985 annotation which denotes the end of any echo which may (or may not) be
22986 associated with the input. For example, the @code{prompt} input type
22987 features the following annotations:
22995 The input types are
22998 @findex pre-prompt annotation
22999 @findex prompt annotation
23000 @findex post-prompt annotation
23002 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
23004 @findex pre-commands annotation
23005 @findex commands annotation
23006 @findex post-commands annotation
23008 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
23009 command. The annotations are repeated for each command which is input.
23011 @findex pre-overload-choice annotation
23012 @findex overload-choice annotation
23013 @findex post-overload-choice annotation
23014 @item overload-choice
23015 When @value{GDBN} wants the user to select between various overloaded functions.
23017 @findex pre-query annotation
23018 @findex query annotation
23019 @findex post-query annotation
23021 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
23023 @findex pre-prompt-for-continue annotation
23024 @findex prompt-for-continue annotation
23025 @findex post-prompt-for-continue annotation
23026 @item prompt-for-continue
23027 When @value{GDBN} is asking the user to press return to continue. Note: Don't
23028 expect this to work well; instead use @code{set height 0} to disable
23029 prompting. This is because the counting of lines is buggy in the
23030 presence of annotations.
23035 @cindex annotations for errors, warnings and interrupts
23037 @findex quit annotation
23042 This annotation occurs right before @value{GDBN} responds to an interrupt.
23044 @findex error annotation
23049 This annotation occurs right before @value{GDBN} responds to an error.
23051 Quit and error annotations indicate that any annotations which @value{GDBN} was
23052 in the middle of may end abruptly. For example, if a
23053 @code{value-history-begin} annotation is followed by a @code{error}, one
23054 cannot expect to receive the matching @code{value-history-end}. One
23055 cannot expect not to receive it either, however; an error annotation
23056 does not necessarily mean that @value{GDBN} is immediately returning all the way
23059 @findex error-begin annotation
23060 A quit or error annotation may be preceded by
23066 Any output between that and the quit or error annotation is the error
23069 Warning messages are not yet annotated.
23070 @c If we want to change that, need to fix warning(), type_error(),
23071 @c range_error(), and possibly other places.
23074 @section Invalidation Notices
23076 @cindex annotations for invalidation messages
23077 The following annotations say that certain pieces of state may have
23081 @findex frames-invalid annotation
23082 @item ^Z^Zframes-invalid
23084 The frames (for example, output from the @code{backtrace} command) may
23087 @findex breakpoints-invalid annotation
23088 @item ^Z^Zbreakpoints-invalid
23090 The breakpoints may have changed. For example, the user just added or
23091 deleted a breakpoint.
23094 @node Annotations for Running
23095 @section Running the Program
23096 @cindex annotations for running programs
23098 @findex starting annotation
23099 @findex stopping annotation
23100 When the program starts executing due to a @value{GDBN} command such as
23101 @code{step} or @code{continue},
23107 is output. When the program stops,
23113 is output. Before the @code{stopped} annotation, a variety of
23114 annotations describe how the program stopped.
23117 @findex exited annotation
23118 @item ^Z^Zexited @var{exit-status}
23119 The program exited, and @var{exit-status} is the exit status (zero for
23120 successful exit, otherwise nonzero).
23122 @findex signalled annotation
23123 @findex signal-name annotation
23124 @findex signal-name-end annotation
23125 @findex signal-string annotation
23126 @findex signal-string-end annotation
23127 @item ^Z^Zsignalled
23128 The program exited with a signal. After the @code{^Z^Zsignalled}, the
23129 annotation continues:
23135 ^Z^Zsignal-name-end
23139 ^Z^Zsignal-string-end
23144 where @var{name} is the name of the signal, such as @code{SIGILL} or
23145 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
23146 as @code{Illegal Instruction} or @code{Segmentation fault}.
23147 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
23148 user's benefit and have no particular format.
23150 @findex signal annotation
23152 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
23153 just saying that the program received the signal, not that it was
23154 terminated with it.
23156 @findex breakpoint annotation
23157 @item ^Z^Zbreakpoint @var{number}
23158 The program hit breakpoint number @var{number}.
23160 @findex watchpoint annotation
23161 @item ^Z^Zwatchpoint @var{number}
23162 The program hit watchpoint number @var{number}.
23165 @node Source Annotations
23166 @section Displaying Source
23167 @cindex annotations for source display
23169 @findex source annotation
23170 The following annotation is used instead of displaying source code:
23173 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
23176 where @var{filename} is an absolute file name indicating which source
23177 file, @var{line} is the line number within that file (where 1 is the
23178 first line in the file), @var{character} is the character position
23179 within the file (where 0 is the first character in the file) (for most
23180 debug formats this will necessarily point to the beginning of a line),
23181 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
23182 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
23183 @var{addr} is the address in the target program associated with the
23184 source which is being displayed. @var{addr} is in the form @samp{0x}
23185 followed by one or more lowercase hex digits (note that this does not
23186 depend on the language).
23189 @chapter Reporting Bugs in @value{GDBN}
23190 @cindex bugs in @value{GDBN}
23191 @cindex reporting bugs in @value{GDBN}
23193 Your bug reports play an essential role in making @value{GDBN} reliable.
23195 Reporting a bug may help you by bringing a solution to your problem, or it
23196 may not. But in any case the principal function of a bug report is to help
23197 the entire community by making the next version of @value{GDBN} work better. Bug
23198 reports are your contribution to the maintenance of @value{GDBN}.
23200 In order for a bug report to serve its purpose, you must include the
23201 information that enables us to fix the bug.
23204 * Bug Criteria:: Have you found a bug?
23205 * Bug Reporting:: How to report bugs
23209 @section Have You Found a Bug?
23210 @cindex bug criteria
23212 If you are not sure whether you have found a bug, here are some guidelines:
23215 @cindex fatal signal
23216 @cindex debugger crash
23217 @cindex crash of debugger
23219 If the debugger gets a fatal signal, for any input whatever, that is a
23220 @value{GDBN} bug. Reliable debuggers never crash.
23222 @cindex error on valid input
23224 If @value{GDBN} produces an error message for valid input, that is a
23225 bug. (Note that if you're cross debugging, the problem may also be
23226 somewhere in the connection to the target.)
23228 @cindex invalid input
23230 If @value{GDBN} does not produce an error message for invalid input,
23231 that is a bug. However, you should note that your idea of
23232 ``invalid input'' might be our idea of ``an extension'' or ``support
23233 for traditional practice''.
23236 If you are an experienced user of debugging tools, your suggestions
23237 for improvement of @value{GDBN} are welcome in any case.
23240 @node Bug Reporting
23241 @section How to Report Bugs
23242 @cindex bug reports
23243 @cindex @value{GDBN} bugs, reporting
23245 A number of companies and individuals offer support for @sc{gnu} products.
23246 If you obtained @value{GDBN} from a support organization, we recommend you
23247 contact that organization first.
23249 You can find contact information for many support companies and
23250 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
23252 @c should add a web page ref...
23255 @ifset BUGURL_DEFAULT
23256 In any event, we also recommend that you submit bug reports for
23257 @value{GDBN}. The preferred method is to submit them directly using
23258 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
23259 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
23262 @strong{Do not send bug reports to @samp{info-gdb}, or to
23263 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
23264 not want to receive bug reports. Those that do have arranged to receive
23267 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
23268 serves as a repeater. The mailing list and the newsgroup carry exactly
23269 the same messages. Often people think of posting bug reports to the
23270 newsgroup instead of mailing them. This appears to work, but it has one
23271 problem which can be crucial: a newsgroup posting often lacks a mail
23272 path back to the sender. Thus, if we need to ask for more information,
23273 we may be unable to reach you. For this reason, it is better to send
23274 bug reports to the mailing list.
23276 @ifclear BUGURL_DEFAULT
23277 In any event, we also recommend that you submit bug reports for
23278 @value{GDBN} to @value{BUGURL}.
23282 The fundamental principle of reporting bugs usefully is this:
23283 @strong{report all the facts}. If you are not sure whether to state a
23284 fact or leave it out, state it!
23286 Often people omit facts because they think they know what causes the
23287 problem and assume that some details do not matter. Thus, you might
23288 assume that the name of the variable you use in an example does not matter.
23289 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
23290 stray memory reference which happens to fetch from the location where that
23291 name is stored in memory; perhaps, if the name were different, the contents
23292 of that location would fool the debugger into doing the right thing despite
23293 the bug. Play it safe and give a specific, complete example. That is the
23294 easiest thing for you to do, and the most helpful.
23296 Keep in mind that the purpose of a bug report is to enable us to fix the
23297 bug. It may be that the bug has been reported previously, but neither
23298 you nor we can know that unless your bug report is complete and
23301 Sometimes people give a few sketchy facts and ask, ``Does this ring a
23302 bell?'' Those bug reports are useless, and we urge everyone to
23303 @emph{refuse to respond to them} except to chide the sender to report
23306 To enable us to fix the bug, you should include all these things:
23310 The version of @value{GDBN}. @value{GDBN} announces it if you start
23311 with no arguments; you can also print it at any time using @code{show
23314 Without this, we will not know whether there is any point in looking for
23315 the bug in the current version of @value{GDBN}.
23318 The type of machine you are using, and the operating system name and
23322 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
23323 ``@value{GCC}--2.8.1''.
23326 What compiler (and its version) was used to compile the program you are
23327 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
23328 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
23329 to get this information; for other compilers, see the documentation for
23333 The command arguments you gave the compiler to compile your example and
23334 observe the bug. For example, did you use @samp{-O}? To guarantee
23335 you will not omit something important, list them all. A copy of the
23336 Makefile (or the output from make) is sufficient.
23338 If we were to try to guess the arguments, we would probably guess wrong
23339 and then we might not encounter the bug.
23342 A complete input script, and all necessary source files, that will
23346 A description of what behavior you observe that you believe is
23347 incorrect. For example, ``It gets a fatal signal.''
23349 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
23350 will certainly notice it. But if the bug is incorrect output, we might
23351 not notice unless it is glaringly wrong. You might as well not give us
23352 a chance to make a mistake.
23354 Even if the problem you experience is a fatal signal, you should still
23355 say so explicitly. Suppose something strange is going on, such as, your
23356 copy of @value{GDBN} is out of synch, or you have encountered a bug in
23357 the C library on your system. (This has happened!) Your copy might
23358 crash and ours would not. If you told us to expect a crash, then when
23359 ours fails to crash, we would know that the bug was not happening for
23360 us. If you had not told us to expect a crash, then we would not be able
23361 to draw any conclusion from our observations.
23364 @cindex recording a session script
23365 To collect all this information, you can use a session recording program
23366 such as @command{script}, which is available on many Unix systems.
23367 Just run your @value{GDBN} session inside @command{script} and then
23368 include the @file{typescript} file with your bug report.
23370 Another way to record a @value{GDBN} session is to run @value{GDBN}
23371 inside Emacs and then save the entire buffer to a file.
23374 If you wish to suggest changes to the @value{GDBN} source, send us context
23375 diffs. If you even discuss something in the @value{GDBN} source, refer to
23376 it by context, not by line number.
23378 The line numbers in our development sources will not match those in your
23379 sources. Your line numbers would convey no useful information to us.
23383 Here are some things that are not necessary:
23387 A description of the envelope of the bug.
23389 Often people who encounter a bug spend a lot of time investigating
23390 which changes to the input file will make the bug go away and which
23391 changes will not affect it.
23393 This is often time consuming and not very useful, because the way we
23394 will find the bug is by running a single example under the debugger
23395 with breakpoints, not by pure deduction from a series of examples.
23396 We recommend that you save your time for something else.
23398 Of course, if you can find a simpler example to report @emph{instead}
23399 of the original one, that is a convenience for us. Errors in the
23400 output will be easier to spot, running under the debugger will take
23401 less time, and so on.
23403 However, simplification is not vital; if you do not want to do this,
23404 report the bug anyway and send us the entire test case you used.
23407 A patch for the bug.
23409 A patch for the bug does help us if it is a good one. But do not omit
23410 the necessary information, such as the test case, on the assumption that
23411 a patch is all we need. We might see problems with your patch and decide
23412 to fix the problem another way, or we might not understand it at all.
23414 Sometimes with a program as complicated as @value{GDBN} it is very hard to
23415 construct an example that will make the program follow a certain path
23416 through the code. If you do not send us the example, we will not be able
23417 to construct one, so we will not be able to verify that the bug is fixed.
23419 And if we cannot understand what bug you are trying to fix, or why your
23420 patch should be an improvement, we will not install it. A test case will
23421 help us to understand.
23424 A guess about what the bug is or what it depends on.
23426 Such guesses are usually wrong. Even we cannot guess right about such
23427 things without first using the debugger to find the facts.
23430 @c The readline documentation is distributed with the readline code
23431 @c and consists of the two following files:
23433 @c inc-hist.texinfo
23434 @c Use -I with makeinfo to point to the appropriate directory,
23435 @c environment var TEXINPUTS with TeX.
23436 @include rluser.texi
23437 @include inc-hist.texinfo
23440 @node Formatting Documentation
23441 @appendix Formatting Documentation
23443 @cindex @value{GDBN} reference card
23444 @cindex reference card
23445 The @value{GDBN} 4 release includes an already-formatted reference card, ready
23446 for printing with PostScript or Ghostscript, in the @file{gdb}
23447 subdirectory of the main source directory@footnote{In
23448 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
23449 release.}. If you can use PostScript or Ghostscript with your printer,
23450 you can print the reference card immediately with @file{refcard.ps}.
23452 The release also includes the source for the reference card. You
23453 can format it, using @TeX{}, by typing:
23459 The @value{GDBN} reference card is designed to print in @dfn{landscape}
23460 mode on US ``letter'' size paper;
23461 that is, on a sheet 11 inches wide by 8.5 inches
23462 high. You will need to specify this form of printing as an option to
23463 your @sc{dvi} output program.
23465 @cindex documentation
23467 All the documentation for @value{GDBN} comes as part of the machine-readable
23468 distribution. The documentation is written in Texinfo format, which is
23469 a documentation system that uses a single source file to produce both
23470 on-line information and a printed manual. You can use one of the Info
23471 formatting commands to create the on-line version of the documentation
23472 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
23474 @value{GDBN} includes an already formatted copy of the on-line Info
23475 version of this manual in the @file{gdb} subdirectory. The main Info
23476 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
23477 subordinate files matching @samp{gdb.info*} in the same directory. If
23478 necessary, you can print out these files, or read them with any editor;
23479 but they are easier to read using the @code{info} subsystem in @sc{gnu}
23480 Emacs or the standalone @code{info} program, available as part of the
23481 @sc{gnu} Texinfo distribution.
23483 If you want to format these Info files yourself, you need one of the
23484 Info formatting programs, such as @code{texinfo-format-buffer} or
23487 If you have @code{makeinfo} installed, and are in the top level
23488 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
23489 version @value{GDBVN}), you can make the Info file by typing:
23496 If you want to typeset and print copies of this manual, you need @TeX{},
23497 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
23498 Texinfo definitions file.
23500 @TeX{} is a typesetting program; it does not print files directly, but
23501 produces output files called @sc{dvi} files. To print a typeset
23502 document, you need a program to print @sc{dvi} files. If your system
23503 has @TeX{} installed, chances are it has such a program. The precise
23504 command to use depends on your system; @kbd{lpr -d} is common; another
23505 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
23506 require a file name without any extension or a @samp{.dvi} extension.
23508 @TeX{} also requires a macro definitions file called
23509 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
23510 written in Texinfo format. On its own, @TeX{} cannot either read or
23511 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
23512 and is located in the @file{gdb-@var{version-number}/texinfo}
23515 If you have @TeX{} and a @sc{dvi} printer program installed, you can
23516 typeset and print this manual. First switch to the @file{gdb}
23517 subdirectory of the main source directory (for example, to
23518 @file{gdb-@value{GDBVN}/gdb}) and type:
23524 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
23526 @node Installing GDB
23527 @appendix Installing @value{GDBN}
23528 @cindex installation
23531 * Requirements:: Requirements for building @value{GDBN}
23532 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
23533 * Separate Objdir:: Compiling @value{GDBN} in another directory
23534 * Config Names:: Specifying names for hosts and targets
23535 * Configure Options:: Summary of options for configure
23539 @section Requirements for Building @value{GDBN}
23540 @cindex building @value{GDBN}, requirements for
23542 Building @value{GDBN} requires various tools and packages to be available.
23543 Other packages will be used only if they are found.
23545 @heading Tools/Packages Necessary for Building @value{GDBN}
23547 @item ISO C90 compiler
23548 @value{GDBN} is written in ISO C90. It should be buildable with any
23549 working C90 compiler, e.g.@: GCC.
23553 @heading Tools/Packages Optional for Building @value{GDBN}
23557 @value{GDBN} can use the Expat XML parsing library. This library may be
23558 included with your operating system distribution; if it is not, you
23559 can get the latest version from @url{http://expat.sourceforge.net}.
23560 The @file{configure} script will search for this library in several
23561 standard locations; if it is installed in an unusual path, you can
23562 use the @option{--with-libexpat-prefix} option to specify its location.
23568 Remote protocol memory maps (@pxref{Memory Map Format})
23570 Target descriptions (@pxref{Target Descriptions})
23572 Remote shared library lists (@pxref{Library List Format})
23574 MS-Windows shared libraries (@pxref{Shared Libraries})
23578 @cindex compressed debug sections
23579 @value{GDBN} will use the @samp{zlib} library, if available, to read
23580 compressed debug sections. Some linkers, such as GNU gold, are capable
23581 of producing binaries with compressed debug sections. If @value{GDBN}
23582 is compiled with @samp{zlib}, it will be able to read the debug
23583 information in such binaries.
23585 The @samp{zlib} library is likely included with your operating system
23586 distribution; if it is not, you can get the latest version from
23587 @url{http://zlib.net}.
23591 @node Running Configure
23592 @section Invoking the @value{GDBN} @file{configure} Script
23593 @cindex configuring @value{GDBN}
23594 @value{GDBN} comes with a @file{configure} script that automates the process
23595 of preparing @value{GDBN} for installation; you can then use @code{make} to
23596 build the @code{gdb} program.
23598 @c irrelevant in info file; it's as current as the code it lives with.
23599 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
23600 look at the @file{README} file in the sources; we may have improved the
23601 installation procedures since publishing this manual.}
23604 The @value{GDBN} distribution includes all the source code you need for
23605 @value{GDBN} in a single directory, whose name is usually composed by
23606 appending the version number to @samp{gdb}.
23608 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
23609 @file{gdb-@value{GDBVN}} directory. That directory contains:
23612 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
23613 script for configuring @value{GDBN} and all its supporting libraries
23615 @item gdb-@value{GDBVN}/gdb
23616 the source specific to @value{GDBN} itself
23618 @item gdb-@value{GDBVN}/bfd
23619 source for the Binary File Descriptor library
23621 @item gdb-@value{GDBVN}/include
23622 @sc{gnu} include files
23624 @item gdb-@value{GDBVN}/libiberty
23625 source for the @samp{-liberty} free software library
23627 @item gdb-@value{GDBVN}/opcodes
23628 source for the library of opcode tables and disassemblers
23630 @item gdb-@value{GDBVN}/readline
23631 source for the @sc{gnu} command-line interface
23633 @item gdb-@value{GDBVN}/glob
23634 source for the @sc{gnu} filename pattern-matching subroutine
23636 @item gdb-@value{GDBVN}/mmalloc
23637 source for the @sc{gnu} memory-mapped malloc package
23640 The simplest way to configure and build @value{GDBN} is to run @file{configure}
23641 from the @file{gdb-@var{version-number}} source directory, which in
23642 this example is the @file{gdb-@value{GDBVN}} directory.
23644 First switch to the @file{gdb-@var{version-number}} source directory
23645 if you are not already in it; then run @file{configure}. Pass the
23646 identifier for the platform on which @value{GDBN} will run as an
23652 cd gdb-@value{GDBVN}
23653 ./configure @var{host}
23658 where @var{host} is an identifier such as @samp{sun4} or
23659 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
23660 (You can often leave off @var{host}; @file{configure} tries to guess the
23661 correct value by examining your system.)
23663 Running @samp{configure @var{host}} and then running @code{make} builds the
23664 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
23665 libraries, then @code{gdb} itself. The configured source files, and the
23666 binaries, are left in the corresponding source directories.
23669 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
23670 system does not recognize this automatically when you run a different
23671 shell, you may need to run @code{sh} on it explicitly:
23674 sh configure @var{host}
23677 If you run @file{configure} from a directory that contains source
23678 directories for multiple libraries or programs, such as the
23679 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
23681 creates configuration files for every directory level underneath (unless
23682 you tell it not to, with the @samp{--norecursion} option).
23684 You should run the @file{configure} script from the top directory in the
23685 source tree, the @file{gdb-@var{version-number}} directory. If you run
23686 @file{configure} from one of the subdirectories, you will configure only
23687 that subdirectory. That is usually not what you want. In particular,
23688 if you run the first @file{configure} from the @file{gdb} subdirectory
23689 of the @file{gdb-@var{version-number}} directory, you will omit the
23690 configuration of @file{bfd}, @file{readline}, and other sibling
23691 directories of the @file{gdb} subdirectory. This leads to build errors
23692 about missing include files such as @file{bfd/bfd.h}.
23694 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
23695 However, you should make sure that the shell on your path (named by
23696 the @samp{SHELL} environment variable) is publicly readable. Remember
23697 that @value{GDBN} uses the shell to start your program---some systems refuse to
23698 let @value{GDBN} debug child processes whose programs are not readable.
23700 @node Separate Objdir
23701 @section Compiling @value{GDBN} in Another Directory
23703 If you want to run @value{GDBN} versions for several host or target machines,
23704 you need a different @code{gdb} compiled for each combination of
23705 host and target. @file{configure} is designed to make this easy by
23706 allowing you to generate each configuration in a separate subdirectory,
23707 rather than in the source directory. If your @code{make} program
23708 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
23709 @code{make} in each of these directories builds the @code{gdb}
23710 program specified there.
23712 To build @code{gdb} in a separate directory, run @file{configure}
23713 with the @samp{--srcdir} option to specify where to find the source.
23714 (You also need to specify a path to find @file{configure}
23715 itself from your working directory. If the path to @file{configure}
23716 would be the same as the argument to @samp{--srcdir}, you can leave out
23717 the @samp{--srcdir} option; it is assumed.)
23719 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
23720 separate directory for a Sun 4 like this:
23724 cd gdb-@value{GDBVN}
23727 ../gdb-@value{GDBVN}/configure sun4
23732 When @file{configure} builds a configuration using a remote source
23733 directory, it creates a tree for the binaries with the same structure
23734 (and using the same names) as the tree under the source directory. In
23735 the example, you'd find the Sun 4 library @file{libiberty.a} in the
23736 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
23737 @file{gdb-sun4/gdb}.
23739 Make sure that your path to the @file{configure} script has just one
23740 instance of @file{gdb} in it. If your path to @file{configure} looks
23741 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
23742 one subdirectory of @value{GDBN}, not the whole package. This leads to
23743 build errors about missing include files such as @file{bfd/bfd.h}.
23745 One popular reason to build several @value{GDBN} configurations in separate
23746 directories is to configure @value{GDBN} for cross-compiling (where
23747 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
23748 programs that run on another machine---the @dfn{target}).
23749 You specify a cross-debugging target by
23750 giving the @samp{--target=@var{target}} option to @file{configure}.
23752 When you run @code{make} to build a program or library, you must run
23753 it in a configured directory---whatever directory you were in when you
23754 called @file{configure} (or one of its subdirectories).
23756 The @code{Makefile} that @file{configure} generates in each source
23757 directory also runs recursively. If you type @code{make} in a source
23758 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
23759 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
23760 will build all the required libraries, and then build GDB.
23762 When you have multiple hosts or targets configured in separate
23763 directories, you can run @code{make} on them in parallel (for example,
23764 if they are NFS-mounted on each of the hosts); they will not interfere
23768 @section Specifying Names for Hosts and Targets
23770 The specifications used for hosts and targets in the @file{configure}
23771 script are based on a three-part naming scheme, but some short predefined
23772 aliases are also supported. The full naming scheme encodes three pieces
23773 of information in the following pattern:
23776 @var{architecture}-@var{vendor}-@var{os}
23779 For example, you can use the alias @code{sun4} as a @var{host} argument,
23780 or as the value for @var{target} in a @code{--target=@var{target}}
23781 option. The equivalent full name is @samp{sparc-sun-sunos4}.
23783 The @file{configure} script accompanying @value{GDBN} does not provide
23784 any query facility to list all supported host and target names or
23785 aliases. @file{configure} calls the Bourne shell script
23786 @code{config.sub} to map abbreviations to full names; you can read the
23787 script, if you wish, or you can use it to test your guesses on
23788 abbreviations---for example:
23791 % sh config.sub i386-linux
23793 % sh config.sub alpha-linux
23794 alpha-unknown-linux-gnu
23795 % sh config.sub hp9k700
23797 % sh config.sub sun4
23798 sparc-sun-sunos4.1.1
23799 % sh config.sub sun3
23800 m68k-sun-sunos4.1.1
23801 % sh config.sub i986v
23802 Invalid configuration `i986v': machine `i986v' not recognized
23806 @code{config.sub} is also distributed in the @value{GDBN} source
23807 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
23809 @node Configure Options
23810 @section @file{configure} Options
23812 Here is a summary of the @file{configure} options and arguments that
23813 are most often useful for building @value{GDBN}. @file{configure} also has
23814 several other options not listed here. @inforef{What Configure
23815 Does,,configure.info}, for a full explanation of @file{configure}.
23818 configure @r{[}--help@r{]}
23819 @r{[}--prefix=@var{dir}@r{]}
23820 @r{[}--exec-prefix=@var{dir}@r{]}
23821 @r{[}--srcdir=@var{dirname}@r{]}
23822 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
23823 @r{[}--target=@var{target}@r{]}
23828 You may introduce options with a single @samp{-} rather than
23829 @samp{--} if you prefer; but you may abbreviate option names if you use
23834 Display a quick summary of how to invoke @file{configure}.
23836 @item --prefix=@var{dir}
23837 Configure the source to install programs and files under directory
23840 @item --exec-prefix=@var{dir}
23841 Configure the source to install programs under directory
23844 @c avoid splitting the warning from the explanation:
23846 @item --srcdir=@var{dirname}
23847 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
23848 @code{make} that implements the @code{VPATH} feature.}@*
23849 Use this option to make configurations in directories separate from the
23850 @value{GDBN} source directories. Among other things, you can use this to
23851 build (or maintain) several configurations simultaneously, in separate
23852 directories. @file{configure} writes configuration-specific files in
23853 the current directory, but arranges for them to use the source in the
23854 directory @var{dirname}. @file{configure} creates directories under
23855 the working directory in parallel to the source directories below
23858 @item --norecursion
23859 Configure only the directory level where @file{configure} is executed; do not
23860 propagate configuration to subdirectories.
23862 @item --target=@var{target}
23863 Configure @value{GDBN} for cross-debugging programs running on the specified
23864 @var{target}. Without this option, @value{GDBN} is configured to debug
23865 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
23867 There is no convenient way to generate a list of all available targets.
23869 @item @var{host} @dots{}
23870 Configure @value{GDBN} to run on the specified @var{host}.
23872 There is no convenient way to generate a list of all available hosts.
23875 There are many other options available as well, but they are generally
23876 needed for special purposes only.
23878 @node Maintenance Commands
23879 @appendix Maintenance Commands
23880 @cindex maintenance commands
23881 @cindex internal commands
23883 In addition to commands intended for @value{GDBN} users, @value{GDBN}
23884 includes a number of commands intended for @value{GDBN} developers,
23885 that are not documented elsewhere in this manual. These commands are
23886 provided here for reference. (For commands that turn on debugging
23887 messages, see @ref{Debugging Output}.)
23890 @kindex maint agent
23891 @item maint agent @var{expression}
23892 Translate the given @var{expression} into remote agent bytecodes.
23893 This command is useful for debugging the Agent Expression mechanism
23894 (@pxref{Agent Expressions}).
23896 @kindex maint info breakpoints
23897 @item @anchor{maint info breakpoints}maint info breakpoints
23898 Using the same format as @samp{info breakpoints}, display both the
23899 breakpoints you've set explicitly, and those @value{GDBN} is using for
23900 internal purposes. Internal breakpoints are shown with negative
23901 breakpoint numbers. The type column identifies what kind of breakpoint
23906 Normal, explicitly set breakpoint.
23909 Normal, explicitly set watchpoint.
23912 Internal breakpoint, used to handle correctly stepping through
23913 @code{longjmp} calls.
23915 @item longjmp resume
23916 Internal breakpoint at the target of a @code{longjmp}.
23919 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
23922 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
23925 Shared library events.
23929 @kindex maint set can-use-displaced-stepping
23930 @kindex maint show can-use-displaced-stepping
23931 @cindex displaced stepping support
23932 @cindex out-of-line single-stepping
23933 @item maint set can-use-displaced-stepping
23934 @itemx maint show can-use-displaced-stepping
23935 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
23936 if the target supports it. The default is on. Displaced stepping is
23937 a way to single-step over breakpoints without removing them from the
23938 inferior, by executing an out-of-line copy of the instruction that was
23939 originally at the breakpoint location. It is also known as
23940 out-of-line single-stepping.
23942 @kindex maint check-symtabs
23943 @item maint check-symtabs
23944 Check the consistency of psymtabs and symtabs.
23946 @kindex maint cplus first_component
23947 @item maint cplus first_component @var{name}
23948 Print the first C@t{++} class/namespace component of @var{name}.
23950 @kindex maint cplus namespace
23951 @item maint cplus namespace
23952 Print the list of possible C@t{++} namespaces.
23954 @kindex maint demangle
23955 @item maint demangle @var{name}
23956 Demangle a C@t{++} or Objective-C mangled @var{name}.
23958 @kindex maint deprecate
23959 @kindex maint undeprecate
23960 @cindex deprecated commands
23961 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
23962 @itemx maint undeprecate @var{command}
23963 Deprecate or undeprecate the named @var{command}. Deprecated commands
23964 cause @value{GDBN} to issue a warning when you use them. The optional
23965 argument @var{replacement} says which newer command should be used in
23966 favor of the deprecated one; if it is given, @value{GDBN} will mention
23967 the replacement as part of the warning.
23969 @kindex maint dump-me
23970 @item maint dump-me
23971 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
23972 Cause a fatal signal in the debugger and force it to dump its core.
23973 This is supported only on systems which support aborting a program
23974 with the @code{SIGQUIT} signal.
23976 @kindex maint internal-error
23977 @kindex maint internal-warning
23978 @item maint internal-error @r{[}@var{message-text}@r{]}
23979 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
23980 Cause @value{GDBN} to call the internal function @code{internal_error}
23981 or @code{internal_warning} and hence behave as though an internal error
23982 or internal warning has been detected. In addition to reporting the
23983 internal problem, these functions give the user the opportunity to
23984 either quit @value{GDBN} or create a core file of the current
23985 @value{GDBN} session.
23987 These commands take an optional parameter @var{message-text} that is
23988 used as the text of the error or warning message.
23990 Here's an example of using @code{internal-error}:
23993 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
23994 @dots{}/maint.c:121: internal-error: testing, 1, 2
23995 A problem internal to GDB has been detected. Further
23996 debugging may prove unreliable.
23997 Quit this debugging session? (y or n) @kbd{n}
23998 Create a core file? (y or n) @kbd{n}
24002 @kindex maint packet
24003 @item maint packet @var{text}
24004 If @value{GDBN} is talking to an inferior via the serial protocol,
24005 then this command sends the string @var{text} to the inferior, and
24006 displays the response packet. @value{GDBN} supplies the initial
24007 @samp{$} character, the terminating @samp{#} character, and the
24010 @kindex maint print architecture
24011 @item maint print architecture @r{[}@var{file}@r{]}
24012 Print the entire architecture configuration. The optional argument
24013 @var{file} names the file where the output goes.
24015 @kindex maint print c-tdesc
24016 @item maint print c-tdesc
24017 Print the current target description (@pxref{Target Descriptions}) as
24018 a C source file. The created source file can be used in @value{GDBN}
24019 when an XML parser is not available to parse the description.
24021 @kindex maint print dummy-frames
24022 @item maint print dummy-frames
24023 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
24026 (@value{GDBP}) @kbd{b add}
24028 (@value{GDBP}) @kbd{print add(2,3)}
24029 Breakpoint 2, add (a=2, b=3) at @dots{}
24031 The program being debugged stopped while in a function called from GDB.
24033 (@value{GDBP}) @kbd{maint print dummy-frames}
24034 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
24035 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
24036 call_lo=0x01014000 call_hi=0x01014001
24040 Takes an optional file parameter.
24042 @kindex maint print registers
24043 @kindex maint print raw-registers
24044 @kindex maint print cooked-registers
24045 @kindex maint print register-groups
24046 @item maint print registers @r{[}@var{file}@r{]}
24047 @itemx maint print raw-registers @r{[}@var{file}@r{]}
24048 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
24049 @itemx maint print register-groups @r{[}@var{file}@r{]}
24050 Print @value{GDBN}'s internal register data structures.
24052 The command @code{maint print raw-registers} includes the contents of
24053 the raw register cache; the command @code{maint print cooked-registers}
24054 includes the (cooked) value of all registers; and the command
24055 @code{maint print register-groups} includes the groups that each
24056 register is a member of. @xref{Registers,, Registers, gdbint,
24057 @value{GDBN} Internals}.
24059 These commands take an optional parameter, a file name to which to
24060 write the information.
24062 @kindex maint print reggroups
24063 @item maint print reggroups @r{[}@var{file}@r{]}
24064 Print @value{GDBN}'s internal register group data structures. The
24065 optional argument @var{file} tells to what file to write the
24068 The register groups info looks like this:
24071 (@value{GDBP}) @kbd{maint print reggroups}
24084 This command forces @value{GDBN} to flush its internal register cache.
24086 @kindex maint print objfiles
24087 @cindex info for known object files
24088 @item maint print objfiles
24089 Print a dump of all known object files. For each object file, this
24090 command prints its name, address in memory, and all of its psymtabs
24093 @kindex maint print statistics
24094 @cindex bcache statistics
24095 @item maint print statistics
24096 This command prints, for each object file in the program, various data
24097 about that object file followed by the byte cache (@dfn{bcache})
24098 statistics for the object file. The objfile data includes the number
24099 of minimal, partial, full, and stabs symbols, the number of types
24100 defined by the objfile, the number of as yet unexpanded psym tables,
24101 the number of line tables and string tables, and the amount of memory
24102 used by the various tables. The bcache statistics include the counts,
24103 sizes, and counts of duplicates of all and unique objects, max,
24104 average, and median entry size, total memory used and its overhead and
24105 savings, and various measures of the hash table size and chain
24108 @kindex maint print target-stack
24109 @cindex target stack description
24110 @item maint print target-stack
24111 A @dfn{target} is an interface between the debugger and a particular
24112 kind of file or process. Targets can be stacked in @dfn{strata},
24113 so that more than one target can potentially respond to a request.
24114 In particular, memory accesses will walk down the stack of targets
24115 until they find a target that is interested in handling that particular
24118 This command prints a short description of each layer that was pushed on
24119 the @dfn{target stack}, starting from the top layer down to the bottom one.
24121 @kindex maint print type
24122 @cindex type chain of a data type
24123 @item maint print type @var{expr}
24124 Print the type chain for a type specified by @var{expr}. The argument
24125 can be either a type name or a symbol. If it is a symbol, the type of
24126 that symbol is described. The type chain produced by this command is
24127 a recursive definition of the data type as stored in @value{GDBN}'s
24128 data structures, including its flags and contained types.
24130 @kindex maint set dwarf2 max-cache-age
24131 @kindex maint show dwarf2 max-cache-age
24132 @item maint set dwarf2 max-cache-age
24133 @itemx maint show dwarf2 max-cache-age
24134 Control the DWARF 2 compilation unit cache.
24136 @cindex DWARF 2 compilation units cache
24137 In object files with inter-compilation-unit references, such as those
24138 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
24139 reader needs to frequently refer to previously read compilation units.
24140 This setting controls how long a compilation unit will remain in the
24141 cache if it is not referenced. A higher limit means that cached
24142 compilation units will be stored in memory longer, and more total
24143 memory will be used. Setting it to zero disables caching, which will
24144 slow down @value{GDBN} startup, but reduce memory consumption.
24146 @kindex maint set profile
24147 @kindex maint show profile
24148 @cindex profiling GDB
24149 @item maint set profile
24150 @itemx maint show profile
24151 Control profiling of @value{GDBN}.
24153 Profiling will be disabled until you use the @samp{maint set profile}
24154 command to enable it. When you enable profiling, the system will begin
24155 collecting timing and execution count data; when you disable profiling or
24156 exit @value{GDBN}, the results will be written to a log file. Remember that
24157 if you use profiling, @value{GDBN} will overwrite the profiling log file
24158 (often called @file{gmon.out}). If you have a record of important profiling
24159 data in a @file{gmon.out} file, be sure to move it to a safe location.
24161 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
24162 compiled with the @samp{-pg} compiler option.
24164 @kindex maint set linux-async
24165 @kindex maint show linux-async
24166 @cindex asynchronous support
24167 @item maint set linux-async
24168 @itemx maint show linux-async
24169 Control the GNU/Linux native asynchronous support
24170 (@pxref{Background Execution}) of @value{GDBN}.
24172 GNU/Linux native asynchronous support will be disabled until you use
24173 the @samp{maint set linux-async} command to enable it.
24175 @kindex maint set remote-async
24176 @kindex maint show remote-async
24177 @cindex asynchronous support
24178 @item maint set remote-async
24179 @itemx maint show remote-async
24180 Control the remote asynchronous support
24181 (@pxref{Background Execution}) of @value{GDBN}.
24183 Remote asynchronous support will be disabled until you use
24184 the @samp{maint set remote-async} command to enable it.
24186 @kindex maint show-debug-regs
24187 @cindex x86 hardware debug registers
24188 @item maint show-debug-regs
24189 Control whether to show variables that mirror the x86 hardware debug
24190 registers. Use @code{ON} to enable, @code{OFF} to disable. If
24191 enabled, the debug registers values are shown when @value{GDBN} inserts or
24192 removes a hardware breakpoint or watchpoint, and when the inferior
24193 triggers a hardware-assisted breakpoint or watchpoint.
24195 @kindex maint space
24196 @cindex memory used by commands
24198 Control whether to display memory usage for each command. If set to a
24199 nonzero value, @value{GDBN} will display how much memory each command
24200 took, following the command's own output. This can also be requested
24201 by invoking @value{GDBN} with the @option{--statistics} command-line
24202 switch (@pxref{Mode Options}).
24205 @cindex time of command execution
24207 Control whether to display the execution time for each command. If
24208 set to a nonzero value, @value{GDBN} will display how much time it
24209 took to execute each command, following the command's own output.
24210 The time is not printed for the commands that run the target, since
24211 there's no mechanism currently to compute how much time was spend
24212 by @value{GDBN} and how much time was spend by the program been debugged.
24213 it's not possibly currently
24214 This can also be requested by invoking @value{GDBN} with the
24215 @option{--statistics} command-line switch (@pxref{Mode Options}).
24217 @kindex maint translate-address
24218 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
24219 Find the symbol stored at the location specified by the address
24220 @var{addr} and an optional section name @var{section}. If found,
24221 @value{GDBN} prints the name of the closest symbol and an offset from
24222 the symbol's location to the specified address. This is similar to
24223 the @code{info address} command (@pxref{Symbols}), except that this
24224 command also allows to find symbols in other sections.
24228 The following command is useful for non-interactive invocations of
24229 @value{GDBN}, such as in the test suite.
24232 @item set watchdog @var{nsec}
24233 @kindex set watchdog
24234 @cindex watchdog timer
24235 @cindex timeout for commands
24236 Set the maximum number of seconds @value{GDBN} will wait for the
24237 target operation to finish. If this time expires, @value{GDBN}
24238 reports and error and the command is aborted.
24240 @item show watchdog
24241 Show the current setting of the target wait timeout.
24244 @node Remote Protocol
24245 @appendix @value{GDBN} Remote Serial Protocol
24250 * Stop Reply Packets::
24251 * General Query Packets::
24252 * Register Packet Format::
24253 * Tracepoint Packets::
24254 * Host I/O Packets::
24256 * Packet Acknowledgment::
24258 * File-I/O Remote Protocol Extension::
24259 * Library List Format::
24260 * Memory Map Format::
24266 There may be occasions when you need to know something about the
24267 protocol---for example, if there is only one serial port to your target
24268 machine, you might want your program to do something special if it
24269 recognizes a packet meant for @value{GDBN}.
24271 In the examples below, @samp{->} and @samp{<-} are used to indicate
24272 transmitted and received data, respectively.
24274 @cindex protocol, @value{GDBN} remote serial
24275 @cindex serial protocol, @value{GDBN} remote
24276 @cindex remote serial protocol
24277 All @value{GDBN} commands and responses (other than acknowledgments) are
24278 sent as a @var{packet}. A @var{packet} is introduced with the character
24279 @samp{$}, the actual @var{packet-data}, and the terminating character
24280 @samp{#} followed by a two-digit @var{checksum}:
24283 @code{$}@var{packet-data}@code{#}@var{checksum}
24287 @cindex checksum, for @value{GDBN} remote
24289 The two-digit @var{checksum} is computed as the modulo 256 sum of all
24290 characters between the leading @samp{$} and the trailing @samp{#} (an
24291 eight bit unsigned checksum).
24293 Implementors should note that prior to @value{GDBN} 5.0 the protocol
24294 specification also included an optional two-digit @var{sequence-id}:
24297 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
24300 @cindex sequence-id, for @value{GDBN} remote
24302 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
24303 has never output @var{sequence-id}s. Stubs that handle packets added
24304 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
24306 When either the host or the target machine receives a packet, the first
24307 response expected is an acknowledgment: either @samp{+} (to indicate
24308 the package was received correctly) or @samp{-} (to request
24312 -> @code{$}@var{packet-data}@code{#}@var{checksum}
24317 The @samp{+}/@samp{-} acknowledgments can be disabled
24318 once a connection is established.
24319 @xref{Packet Acknowledgment}, for details.
24321 The host (@value{GDBN}) sends @var{command}s, and the target (the
24322 debugging stub incorporated in your program) sends a @var{response}. In
24323 the case of step and continue @var{command}s, the response is only sent
24324 when the operation has completed (the target has again stopped).
24326 @var{packet-data} consists of a sequence of characters with the
24327 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
24330 @cindex remote protocol, field separator
24331 Fields within the packet should be separated using @samp{,} @samp{;} or
24332 @samp{:}. Except where otherwise noted all numbers are represented in
24333 @sc{hex} with leading zeros suppressed.
24335 Implementors should note that prior to @value{GDBN} 5.0, the character
24336 @samp{:} could not appear as the third character in a packet (as it
24337 would potentially conflict with the @var{sequence-id}).
24339 @cindex remote protocol, binary data
24340 @anchor{Binary Data}
24341 Binary data in most packets is encoded either as two hexadecimal
24342 digits per byte of binary data. This allowed the traditional remote
24343 protocol to work over connections which were only seven-bit clean.
24344 Some packets designed more recently assume an eight-bit clean
24345 connection, and use a more efficient encoding to send and receive
24348 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
24349 as an escape character. Any escaped byte is transmitted as the escape
24350 character followed by the original character XORed with @code{0x20}.
24351 For example, the byte @code{0x7d} would be transmitted as the two
24352 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
24353 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
24354 @samp{@}}) must always be escaped. Responses sent by the stub
24355 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
24356 is not interpreted as the start of a run-length encoded sequence
24359 Response @var{data} can be run-length encoded to save space.
24360 Run-length encoding replaces runs of identical characters with one
24361 instance of the repeated character, followed by a @samp{*} and a
24362 repeat count. The repeat count is itself sent encoded, to avoid
24363 binary characters in @var{data}: a value of @var{n} is sent as
24364 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
24365 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
24366 code 32) for a repeat count of 3. (This is because run-length
24367 encoding starts to win for counts 3 or more.) Thus, for example,
24368 @samp{0* } is a run-length encoding of ``0000'': the space character
24369 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
24372 The printable characters @samp{#} and @samp{$} or with a numeric value
24373 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
24374 seven repeats (@samp{$}) can be expanded using a repeat count of only
24375 five (@samp{"}). For example, @samp{00000000} can be encoded as
24378 The error response returned for some packets includes a two character
24379 error number. That number is not well defined.
24381 @cindex empty response, for unsupported packets
24382 For any @var{command} not supported by the stub, an empty response
24383 (@samp{$#00}) should be returned. That way it is possible to extend the
24384 protocol. A newer @value{GDBN} can tell if a packet is supported based
24387 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
24388 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
24394 The following table provides a complete list of all currently defined
24395 @var{command}s and their corresponding response @var{data}.
24396 @xref{File-I/O Remote Protocol Extension}, for details about the File
24397 I/O extension of the remote protocol.
24399 Each packet's description has a template showing the packet's overall
24400 syntax, followed by an explanation of the packet's meaning. We
24401 include spaces in some of the templates for clarity; these are not
24402 part of the packet's syntax. No @value{GDBN} packet uses spaces to
24403 separate its components. For example, a template like @samp{foo
24404 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
24405 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
24406 @var{baz}. @value{GDBN} does not transmit a space character between the
24407 @samp{foo} and the @var{bar}, or between the @var{bar} and the
24410 @cindex @var{thread-id}, in remote protocol
24411 @anchor{thread-id syntax}
24412 Several packets and replies include a @var{thread-id} field to identify
24413 a thread. Normally these are positive numbers with a target-specific
24414 interpretation, formatted as big-endian hex strings. A @var{thread-id}
24415 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
24418 In addition, the remote protocol supports a multiprocess feature in
24419 which the @var{thread-id} syntax is extended to optionally include both
24420 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
24421 The @var{pid} (process) and @var{tid} (thread) components each have the
24422 format described above: a positive number with target-specific
24423 interpretation formatted as a big-endian hex string, literal @samp{-1}
24424 to indicate all processes or threads (respectively), or @samp{0} to
24425 indicate an arbitrary process or thread. Specifying just a process, as
24426 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
24427 error to specify all processes but a specific thread, such as
24428 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
24429 for those packets and replies explicitly documented to include a process
24430 ID, rather than a @var{thread-id}.
24432 The multiprocess @var{thread-id} syntax extensions are only used if both
24433 @value{GDBN} and the stub report support for the @samp{multiprocess}
24434 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
24437 Note that all packet forms beginning with an upper- or lower-case
24438 letter, other than those described here, are reserved for future use.
24440 Here are the packet descriptions.
24445 @cindex @samp{!} packet
24446 @anchor{extended mode}
24447 Enable extended mode. In extended mode, the remote server is made
24448 persistent. The @samp{R} packet is used to restart the program being
24454 The remote target both supports and has enabled extended mode.
24458 @cindex @samp{?} packet
24459 Indicate the reason the target halted. The reply is the same as for
24463 @xref{Stop Reply Packets}, for the reply specifications.
24465 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
24466 @cindex @samp{A} packet
24467 Initialized @code{argv[]} array passed into program. @var{arglen}
24468 specifies the number of bytes in the hex encoded byte stream
24469 @var{arg}. See @code{gdbserver} for more details.
24474 The arguments were set.
24480 @cindex @samp{b} packet
24481 (Don't use this packet; its behavior is not well-defined.)
24482 Change the serial line speed to @var{baud}.
24484 JTC: @emph{When does the transport layer state change? When it's
24485 received, or after the ACK is transmitted. In either case, there are
24486 problems if the command or the acknowledgment packet is dropped.}
24488 Stan: @emph{If people really wanted to add something like this, and get
24489 it working for the first time, they ought to modify ser-unix.c to send
24490 some kind of out-of-band message to a specially-setup stub and have the
24491 switch happen "in between" packets, so that from remote protocol's point
24492 of view, nothing actually happened.}
24494 @item B @var{addr},@var{mode}
24495 @cindex @samp{B} packet
24496 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
24497 breakpoint at @var{addr}.
24499 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
24500 (@pxref{insert breakpoint or watchpoint packet}).
24502 @item c @r{[}@var{addr}@r{]}
24503 @cindex @samp{c} packet
24504 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
24505 resume at current address.
24508 @xref{Stop Reply Packets}, for the reply specifications.
24510 @item C @var{sig}@r{[};@var{addr}@r{]}
24511 @cindex @samp{C} packet
24512 Continue with signal @var{sig} (hex signal number). If
24513 @samp{;@var{addr}} is omitted, resume at same address.
24516 @xref{Stop Reply Packets}, for the reply specifications.
24519 @cindex @samp{d} packet
24522 Don't use this packet; instead, define a general set packet
24523 (@pxref{General Query Packets}).
24527 @cindex @samp{D} packet
24528 The first form of the packet is used to detach @value{GDBN} from the
24529 remote system. It is sent to the remote target
24530 before @value{GDBN} disconnects via the @code{detach} command.
24532 The second form, including a process ID, is used when multiprocess
24533 protocol extensions are enabled (@pxref{multiprocess extensions}), to
24534 detach only a specific process. The @var{pid} is specified as a
24535 big-endian hex string.
24545 @item F @var{RC},@var{EE},@var{CF};@var{XX}
24546 @cindex @samp{F} packet
24547 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
24548 This is part of the File-I/O protocol extension. @xref{File-I/O
24549 Remote Protocol Extension}, for the specification.
24552 @anchor{read registers packet}
24553 @cindex @samp{g} packet
24554 Read general registers.
24558 @item @var{XX@dots{}}
24559 Each byte of register data is described by two hex digits. The bytes
24560 with the register are transmitted in target byte order. The size of
24561 each register and their position within the @samp{g} packet are
24562 determined by the @value{GDBN} internal gdbarch functions
24563 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
24564 specification of several standard @samp{g} packets is specified below.
24569 @item G @var{XX@dots{}}
24570 @cindex @samp{G} packet
24571 Write general registers. @xref{read registers packet}, for a
24572 description of the @var{XX@dots{}} data.
24582 @item H @var{c} @var{thread-id}
24583 @cindex @samp{H} packet
24584 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
24585 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
24586 should be @samp{c} for step and continue operations, @samp{g} for other
24587 operations. The thread designator @var{thread-id} has the format and
24588 interpretation described in @ref{thread-id syntax}.
24599 @c 'H': How restrictive (or permissive) is the thread model. If a
24600 @c thread is selected and stopped, are other threads allowed
24601 @c to continue to execute? As I mentioned above, I think the
24602 @c semantics of each command when a thread is selected must be
24603 @c described. For example:
24605 @c 'g': If the stub supports threads and a specific thread is
24606 @c selected, returns the register block from that thread;
24607 @c otherwise returns current registers.
24609 @c 'G' If the stub supports threads and a specific thread is
24610 @c selected, sets the registers of the register block of
24611 @c that thread; otherwise sets current registers.
24613 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
24614 @anchor{cycle step packet}
24615 @cindex @samp{i} packet
24616 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
24617 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
24618 step starting at that address.
24621 @cindex @samp{I} packet
24622 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
24626 @cindex @samp{k} packet
24629 FIXME: @emph{There is no description of how to operate when a specific
24630 thread context has been selected (i.e.@: does 'k' kill only that
24633 @item m @var{addr},@var{length}
24634 @cindex @samp{m} packet
24635 Read @var{length} bytes of memory starting at address @var{addr}.
24636 Note that @var{addr} may not be aligned to any particular boundary.
24638 The stub need not use any particular size or alignment when gathering
24639 data from memory for the response; even if @var{addr} is word-aligned
24640 and @var{length} is a multiple of the word size, the stub is free to
24641 use byte accesses, or not. For this reason, this packet may not be
24642 suitable for accessing memory-mapped I/O devices.
24643 @cindex alignment of remote memory accesses
24644 @cindex size of remote memory accesses
24645 @cindex memory, alignment and size of remote accesses
24649 @item @var{XX@dots{}}
24650 Memory contents; each byte is transmitted as a two-digit hexadecimal
24651 number. The reply may contain fewer bytes than requested if the
24652 server was able to read only part of the region of memory.
24657 @item M @var{addr},@var{length}:@var{XX@dots{}}
24658 @cindex @samp{M} packet
24659 Write @var{length} bytes of memory starting at address @var{addr}.
24660 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
24661 hexadecimal number.
24668 for an error (this includes the case where only part of the data was
24673 @cindex @samp{p} packet
24674 Read the value of register @var{n}; @var{n} is in hex.
24675 @xref{read registers packet}, for a description of how the returned
24676 register value is encoded.
24680 @item @var{XX@dots{}}
24681 the register's value
24685 Indicating an unrecognized @var{query}.
24688 @item P @var{n@dots{}}=@var{r@dots{}}
24689 @anchor{write register packet}
24690 @cindex @samp{P} packet
24691 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
24692 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
24693 digits for each byte in the register (target byte order).
24703 @item q @var{name} @var{params}@dots{}
24704 @itemx Q @var{name} @var{params}@dots{}
24705 @cindex @samp{q} packet
24706 @cindex @samp{Q} packet
24707 General query (@samp{q}) and set (@samp{Q}). These packets are
24708 described fully in @ref{General Query Packets}.
24711 @cindex @samp{r} packet
24712 Reset the entire system.
24714 Don't use this packet; use the @samp{R} packet instead.
24717 @cindex @samp{R} packet
24718 Restart the program being debugged. @var{XX}, while needed, is ignored.
24719 This packet is only available in extended mode (@pxref{extended mode}).
24721 The @samp{R} packet has no reply.
24723 @item s @r{[}@var{addr}@r{]}
24724 @cindex @samp{s} packet
24725 Single step. @var{addr} is the address at which to resume. If
24726 @var{addr} is omitted, resume at same address.
24729 @xref{Stop Reply Packets}, for the reply specifications.
24731 @item S @var{sig}@r{[};@var{addr}@r{]}
24732 @anchor{step with signal packet}
24733 @cindex @samp{S} packet
24734 Step with signal. This is analogous to the @samp{C} packet, but
24735 requests a single-step, rather than a normal resumption of execution.
24738 @xref{Stop Reply Packets}, for the reply specifications.
24740 @item t @var{addr}:@var{PP},@var{MM}
24741 @cindex @samp{t} packet
24742 Search backwards starting at address @var{addr} for a match with pattern
24743 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
24744 @var{addr} must be at least 3 digits.
24746 @item T @var{thread-id}
24747 @cindex @samp{T} packet
24748 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
24753 thread is still alive
24759 Packets starting with @samp{v} are identified by a multi-letter name,
24760 up to the first @samp{;} or @samp{?} (or the end of the packet).
24762 @item vAttach;@var{pid}
24763 @cindex @samp{vAttach} packet
24764 Attach to a new process with the specified process ID. @var{pid} is a
24765 hexadecimal integer identifying the process. The attached process is
24768 This packet is only available in extended mode (@pxref{extended mode}).
24774 @item @r{Any stop packet}
24775 for success (@pxref{Stop Reply Packets})
24778 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
24779 @cindex @samp{vCont} packet
24780 Resume the inferior, specifying different actions for each thread.
24781 If an action is specified with no @var{thread-id}, then it is applied to any
24782 threads that don't have a specific action specified; if no default action is
24783 specified then other threads should remain stopped. Specifying multiple
24784 default actions is an error; specifying no actions is also an error.
24785 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
24787 Currently supported actions are:
24793 Continue with signal @var{sig}. @var{sig} should be two hex digits.
24797 Step with signal @var{sig}. @var{sig} should be two hex digits.
24800 The optional @var{addr} argument normally associated with these packets is
24801 not supported in @samp{vCont}.
24804 @xref{Stop Reply Packets}, for the reply specifications.
24807 @cindex @samp{vCont?} packet
24808 Request a list of actions supported by the @samp{vCont} packet.
24812 @item vCont@r{[};@var{action}@dots{}@r{]}
24813 The @samp{vCont} packet is supported. Each @var{action} is a supported
24814 command in the @samp{vCont} packet.
24816 The @samp{vCont} packet is not supported.
24819 @item vFile:@var{operation}:@var{parameter}@dots{}
24820 @cindex @samp{vFile} packet
24821 Perform a file operation on the target system. For details,
24822 see @ref{Host I/O Packets}.
24824 @item vFlashErase:@var{addr},@var{length}
24825 @cindex @samp{vFlashErase} packet
24826 Direct the stub to erase @var{length} bytes of flash starting at
24827 @var{addr}. The region may enclose any number of flash blocks, but
24828 its start and end must fall on block boundaries, as indicated by the
24829 flash block size appearing in the memory map (@pxref{Memory Map
24830 Format}). @value{GDBN} groups flash memory programming operations
24831 together, and sends a @samp{vFlashDone} request after each group; the
24832 stub is allowed to delay erase operation until the @samp{vFlashDone}
24833 packet is received.
24835 The stub must support @samp{vCont} if it reports support for
24836 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
24837 this case @samp{vCont} actions can be specified to apply to all threads
24838 in a process by using the @samp{p@var{pid}.-1} form of the
24849 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
24850 @cindex @samp{vFlashWrite} packet
24851 Direct the stub to write data to flash address @var{addr}. The data
24852 is passed in binary form using the same encoding as for the @samp{X}
24853 packet (@pxref{Binary Data}). The memory ranges specified by
24854 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
24855 not overlap, and must appear in order of increasing addresses
24856 (although @samp{vFlashErase} packets for higher addresses may already
24857 have been received; the ordering is guaranteed only between
24858 @samp{vFlashWrite} packets). If a packet writes to an address that was
24859 neither erased by a preceding @samp{vFlashErase} packet nor by some other
24860 target-specific method, the results are unpredictable.
24868 for vFlashWrite addressing non-flash memory
24874 @cindex @samp{vFlashDone} packet
24875 Indicate to the stub that flash programming operation is finished.
24876 The stub is permitted to delay or batch the effects of a group of
24877 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
24878 @samp{vFlashDone} packet is received. The contents of the affected
24879 regions of flash memory are unpredictable until the @samp{vFlashDone}
24880 request is completed.
24882 @item vKill;@var{pid}
24883 @cindex @samp{vKill} packet
24884 Kill the process with the specified process ID. @var{pid} is a
24885 hexadecimal integer identifying the process. This packet is used in
24886 preference to @samp{k} when multiprocess protocol extensions are
24887 supported; see @ref{multiprocess extensions}.
24897 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
24898 @cindex @samp{vRun} packet
24899 Run the program @var{filename}, passing it each @var{argument} on its
24900 command line. The file and arguments are hex-encoded strings. If
24901 @var{filename} is an empty string, the stub may use a default program
24902 (e.g.@: the last program run). The program is created in the stopped
24905 This packet is only available in extended mode (@pxref{extended mode}).
24911 @item @r{Any stop packet}
24912 for success (@pxref{Stop Reply Packets})
24915 @item X @var{addr},@var{length}:@var{XX@dots{}}
24917 @cindex @samp{X} packet
24918 Write data to memory, where the data is transmitted in binary.
24919 @var{addr} is address, @var{length} is number of bytes,
24920 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
24930 @item z @var{type},@var{addr},@var{length}
24931 @itemx Z @var{type},@var{addr},@var{length}
24932 @anchor{insert breakpoint or watchpoint packet}
24933 @cindex @samp{z} packet
24934 @cindex @samp{Z} packets
24935 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
24936 watchpoint starting at address @var{address} and covering the next
24937 @var{length} bytes.
24939 Each breakpoint and watchpoint packet @var{type} is documented
24942 @emph{Implementation notes: A remote target shall return an empty string
24943 for an unrecognized breakpoint or watchpoint packet @var{type}. A
24944 remote target shall support either both or neither of a given
24945 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
24946 avoid potential problems with duplicate packets, the operations should
24947 be implemented in an idempotent way.}
24949 @item z0,@var{addr},@var{length}
24950 @itemx Z0,@var{addr},@var{length}
24951 @cindex @samp{z0} packet
24952 @cindex @samp{Z0} packet
24953 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
24954 @var{addr} of size @var{length}.
24956 A memory breakpoint is implemented by replacing the instruction at
24957 @var{addr} with a software breakpoint or trap instruction. The
24958 @var{length} is used by targets that indicates the size of the
24959 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
24960 @sc{mips} can insert either a 2 or 4 byte breakpoint).
24962 @emph{Implementation note: It is possible for a target to copy or move
24963 code that contains memory breakpoints (e.g., when implementing
24964 overlays). The behavior of this packet, in the presence of such a
24965 target, is not defined.}
24977 @item z1,@var{addr},@var{length}
24978 @itemx Z1,@var{addr},@var{length}
24979 @cindex @samp{z1} packet
24980 @cindex @samp{Z1} packet
24981 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
24982 address @var{addr} of size @var{length}.
24984 A hardware breakpoint is implemented using a mechanism that is not
24985 dependant on being able to modify the target's memory.
24987 @emph{Implementation note: A hardware breakpoint is not affected by code
25000 @item z2,@var{addr},@var{length}
25001 @itemx Z2,@var{addr},@var{length}
25002 @cindex @samp{z2} packet
25003 @cindex @samp{Z2} packet
25004 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint.
25016 @item z3,@var{addr},@var{length}
25017 @itemx Z3,@var{addr},@var{length}
25018 @cindex @samp{z3} packet
25019 @cindex @samp{Z3} packet
25020 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint.
25032 @item z4,@var{addr},@var{length}
25033 @itemx Z4,@var{addr},@var{length}
25034 @cindex @samp{z4} packet
25035 @cindex @samp{Z4} packet
25036 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint.
25050 @node Stop Reply Packets
25051 @section Stop Reply Packets
25052 @cindex stop reply packets
25054 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
25055 receive any of the below as a reply. In the case of the @samp{C},
25056 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
25057 when the target halts. In the below the exact meaning of @dfn{signal
25058 number} is defined by the header @file{include/gdb/signals.h} in the
25059 @value{GDBN} source code.
25061 As in the description of request packets, we include spaces in the
25062 reply templates for clarity; these are not part of the reply packet's
25063 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
25069 The program received signal number @var{AA} (a two-digit hexadecimal
25070 number). This is equivalent to a @samp{T} response with no
25071 @var{n}:@var{r} pairs.
25073 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
25074 @cindex @samp{T} packet reply
25075 The program received signal number @var{AA} (a two-digit hexadecimal
25076 number). This is equivalent to an @samp{S} response, except that the
25077 @samp{@var{n}:@var{r}} pairs can carry values of important registers
25078 and other information directly in the stop reply packet, reducing
25079 round-trip latency. Single-step and breakpoint traps are reported
25080 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
25084 If @var{n} is a hexadecimal number, it is a register number, and the
25085 corresponding @var{r} gives that register's value. @var{r} is a
25086 series of bytes in target byte order, with each byte given by a
25087 two-digit hex number.
25090 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
25091 the stopped thread, as specified in @ref{thread-id syntax}.
25094 If @var{n} is a recognized @dfn{stop reason}, it describes a more
25095 specific event that stopped the target. The currently defined stop
25096 reasons are listed below. @var{aa} should be @samp{05}, the trap
25097 signal. At most one stop reason should be present.
25100 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
25101 and go on to the next; this allows us to extend the protocol in the
25105 The currently defined stop reasons are:
25111 The packet indicates a watchpoint hit, and @var{r} is the data address, in
25114 @cindex shared library events, remote reply
25116 The packet indicates that the loaded libraries have changed.
25117 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
25118 list of loaded libraries. @var{r} is ignored.
25122 @itemx W @var{AA} ; process:@var{pid}
25123 The process exited, and @var{AA} is the exit status. This is only
25124 applicable to certain targets.
25126 The second form of the response, including the process ID of the exited
25127 process, can be used only when @value{GDBN} has reported support for
25128 multiprocess protocol extensions; see @ref{multiprocess extensions}.
25129 The @var{pid} is formatted as a big-endian hex string.
25132 @itemx X @var{AA} ; process:@var{pid}
25133 The process terminated with signal @var{AA}.
25135 The second form of the response, including the process ID of the
25136 terminated process, can be used only when @value{GDBN} has reported
25137 support for multiprocess protocol extensions; see @ref{multiprocess
25138 extensions}. The @var{pid} is formatted as a big-endian hex string.
25140 @item O @var{XX}@dots{}
25141 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
25142 written as the program's console output. This can happen at any time
25143 while the program is running and the debugger should continue to wait
25144 for @samp{W}, @samp{T}, etc.
25146 @item F @var{call-id},@var{parameter}@dots{}
25147 @var{call-id} is the identifier which says which host system call should
25148 be called. This is just the name of the function. Translation into the
25149 correct system call is only applicable as it's defined in @value{GDBN}.
25150 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
25153 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
25154 this very system call.
25156 The target replies with this packet when it expects @value{GDBN} to
25157 call a host system call on behalf of the target. @value{GDBN} replies
25158 with an appropriate @samp{F} packet and keeps up waiting for the next
25159 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
25160 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
25161 Protocol Extension}, for more details.
25165 @node General Query Packets
25166 @section General Query Packets
25167 @cindex remote query requests
25169 Packets starting with @samp{q} are @dfn{general query packets};
25170 packets starting with @samp{Q} are @dfn{general set packets}. General
25171 query and set packets are a semi-unified form for retrieving and
25172 sending information to and from the stub.
25174 The initial letter of a query or set packet is followed by a name
25175 indicating what sort of thing the packet applies to. For example,
25176 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
25177 definitions with the stub. These packet names follow some
25182 The name must not contain commas, colons or semicolons.
25184 Most @value{GDBN} query and set packets have a leading upper case
25187 The names of custom vendor packets should use a company prefix, in
25188 lower case, followed by a period. For example, packets designed at
25189 the Acme Corporation might begin with @samp{qacme.foo} (for querying
25190 foos) or @samp{Qacme.bar} (for setting bars).
25193 The name of a query or set packet should be separated from any
25194 parameters by a @samp{:}; the parameters themselves should be
25195 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
25196 full packet name, and check for a separator or the end of the packet,
25197 in case two packet names share a common prefix. New packets should not begin
25198 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
25199 packets predate these conventions, and have arguments without any terminator
25200 for the packet name; we suspect they are in widespread use in places that
25201 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
25202 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
25205 Like the descriptions of the other packets, each description here
25206 has a template showing the packet's overall syntax, followed by an
25207 explanation of the packet's meaning. We include spaces in some of the
25208 templates for clarity; these are not part of the packet's syntax. No
25209 @value{GDBN} packet uses spaces to separate its components.
25211 Here are the currently defined query and set packets:
25216 @cindex current thread, remote request
25217 @cindex @samp{qC} packet
25218 Return the current thread ID.
25222 @item QC @var{thread-id}
25223 Where @var{thread-id} is a thread ID as documented in
25224 @ref{thread-id syntax}.
25225 @item @r{(anything else)}
25226 Any other reply implies the old thread ID.
25229 @item qCRC:@var{addr},@var{length}
25230 @cindex CRC of memory block, remote request
25231 @cindex @samp{qCRC} packet
25232 Compute the CRC checksum of a block of memory.
25236 An error (such as memory fault)
25237 @item C @var{crc32}
25238 The specified memory region's checksum is @var{crc32}.
25242 @itemx qsThreadInfo
25243 @cindex list active threads, remote request
25244 @cindex @samp{qfThreadInfo} packet
25245 @cindex @samp{qsThreadInfo} packet
25246 Obtain a list of all active thread IDs from the target (OS). Since there
25247 may be too many active threads to fit into one reply packet, this query
25248 works iteratively: it may require more than one query/reply sequence to
25249 obtain the entire list of threads. The first query of the sequence will
25250 be the @samp{qfThreadInfo} query; subsequent queries in the
25251 sequence will be the @samp{qsThreadInfo} query.
25253 NOTE: This packet replaces the @samp{qL} query (see below).
25257 @item m @var{thread-id}
25259 @item m @var{thread-id},@var{thread-id}@dots{}
25260 a comma-separated list of thread IDs
25262 (lower case letter @samp{L}) denotes end of list.
25265 In response to each query, the target will reply with a list of one or
25266 more thread IDs, separated by commas.
25267 @value{GDBN} will respond to each reply with a request for more thread
25268 ids (using the @samp{qs} form of the query), until the target responds
25269 with @samp{l} (lower-case el, for @dfn{last}).
25270 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
25273 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
25274 @cindex get thread-local storage address, remote request
25275 @cindex @samp{qGetTLSAddr} packet
25276 Fetch the address associated with thread local storage specified
25277 by @var{thread-id}, @var{offset}, and @var{lm}.
25279 @var{thread-id} is the thread ID associated with the
25280 thread for which to fetch the TLS address. @xref{thread-id syntax}.
25282 @var{offset} is the (big endian, hex encoded) offset associated with the
25283 thread local variable. (This offset is obtained from the debug
25284 information associated with the variable.)
25286 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
25287 the load module associated with the thread local storage. For example,
25288 a @sc{gnu}/Linux system will pass the link map address of the shared
25289 object associated with the thread local storage under consideration.
25290 Other operating environments may choose to represent the load module
25291 differently, so the precise meaning of this parameter will vary.
25295 @item @var{XX}@dots{}
25296 Hex encoded (big endian) bytes representing the address of the thread
25297 local storage requested.
25300 An error occurred. @var{nn} are hex digits.
25303 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
25306 @item qL @var{startflag} @var{threadcount} @var{nextthread}
25307 Obtain thread information from RTOS. Where: @var{startflag} (one hex
25308 digit) is one to indicate the first query and zero to indicate a
25309 subsequent query; @var{threadcount} (two hex digits) is the maximum
25310 number of threads the response packet can contain; and @var{nextthread}
25311 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
25312 returned in the response as @var{argthread}.
25314 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
25318 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
25319 Where: @var{count} (two hex digits) is the number of threads being
25320 returned; @var{done} (one hex digit) is zero to indicate more threads
25321 and one indicates no further threads; @var{argthreadid} (eight hex
25322 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
25323 is a sequence of thread IDs from the target. @var{threadid} (eight hex
25324 digits). See @code{remote.c:parse_threadlist_response()}.
25328 @cindex section offsets, remote request
25329 @cindex @samp{qOffsets} packet
25330 Get section offsets that the target used when relocating the downloaded
25335 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
25336 Relocate the @code{Text} section by @var{xxx} from its original address.
25337 Relocate the @code{Data} section by @var{yyy} from its original address.
25338 If the object file format provides segment information (e.g.@: @sc{elf}
25339 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
25340 segments by the supplied offsets.
25342 @emph{Note: while a @code{Bss} offset may be included in the response,
25343 @value{GDBN} ignores this and instead applies the @code{Data} offset
25344 to the @code{Bss} section.}
25346 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
25347 Relocate the first segment of the object file, which conventionally
25348 contains program code, to a starting address of @var{xxx}. If
25349 @samp{DataSeg} is specified, relocate the second segment, which
25350 conventionally contains modifiable data, to a starting address of
25351 @var{yyy}. @value{GDBN} will report an error if the object file
25352 does not contain segment information, or does not contain at least
25353 as many segments as mentioned in the reply. Extra segments are
25354 kept at fixed offsets relative to the last relocated segment.
25357 @item qP @var{mode} @var{thread-id}
25358 @cindex thread information, remote request
25359 @cindex @samp{qP} packet
25360 Returns information on @var{thread-id}. Where: @var{mode} is a hex
25361 encoded 32 bit mode; @var{thread-id} is a thread ID
25362 (@pxref{thread-id syntax}).
25364 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
25367 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
25369 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
25370 @cindex pass signals to inferior, remote request
25371 @cindex @samp{QPassSignals} packet
25372 @anchor{QPassSignals}
25373 Each listed @var{signal} should be passed directly to the inferior process.
25374 Signals are numbered identically to continue packets and stop replies
25375 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
25376 strictly greater than the previous item. These signals do not need to stop
25377 the inferior, or be reported to @value{GDBN}. All other signals should be
25378 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
25379 combine; any earlier @samp{QPassSignals} list is completely replaced by the
25380 new list. This packet improves performance when using @samp{handle
25381 @var{signal} nostop noprint pass}.
25386 The request succeeded.
25389 An error occurred. @var{nn} are hex digits.
25392 An empty reply indicates that @samp{QPassSignals} is not supported by
25396 Use of this packet is controlled by the @code{set remote pass-signals}
25397 command (@pxref{Remote Configuration, set remote pass-signals}).
25398 This packet is not probed by default; the remote stub must request it,
25399 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25401 @item qRcmd,@var{command}
25402 @cindex execute remote command, remote request
25403 @cindex @samp{qRcmd} packet
25404 @var{command} (hex encoded) is passed to the local interpreter for
25405 execution. Invalid commands should be reported using the output
25406 string. Before the final result packet, the target may also respond
25407 with a number of intermediate @samp{O@var{output}} console output
25408 packets. @emph{Implementors should note that providing access to a
25409 stubs's interpreter may have security implications}.
25414 A command response with no output.
25416 A command response with the hex encoded output string @var{OUTPUT}.
25418 Indicate a badly formed request.
25420 An empty reply indicates that @samp{qRcmd} is not recognized.
25423 (Note that the @code{qRcmd} packet's name is separated from the
25424 command by a @samp{,}, not a @samp{:}, contrary to the naming
25425 conventions above. Please don't use this packet as a model for new
25428 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
25429 @cindex searching memory, in remote debugging
25430 @cindex @samp{qSearch:memory} packet
25431 @anchor{qSearch memory}
25432 Search @var{length} bytes at @var{address} for @var{search-pattern}.
25433 @var{address} and @var{length} are encoded in hex.
25434 @var{search-pattern} is a sequence of bytes, hex encoded.
25439 The pattern was not found.
25441 The pattern was found at @var{address}.
25443 A badly formed request or an error was encountered while searching memory.
25445 An empty reply indicates that @samp{qSearch:memory} is not recognized.
25448 @item QStartNoAckMode
25449 @cindex @samp{QStartNoAckMode} packet
25450 @anchor{QStartNoAckMode}
25451 Request that the remote stub disable the normal @samp{+}/@samp{-}
25452 protocol acknowledgments (@pxref{Packet Acknowledgment}).
25457 The stub has switched to no-acknowledgment mode.
25458 @value{GDBN} acknowledges this reponse,
25459 but neither the stub nor @value{GDBN} shall send or expect further
25460 @samp{+}/@samp{-} acknowledgments in the current connection.
25462 An empty reply indicates that the stub does not support no-acknowledgment mode.
25465 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
25466 @cindex supported packets, remote query
25467 @cindex features of the remote protocol
25468 @cindex @samp{qSupported} packet
25469 @anchor{qSupported}
25470 Tell the remote stub about features supported by @value{GDBN}, and
25471 query the stub for features it supports. This packet allows
25472 @value{GDBN} and the remote stub to take advantage of each others'
25473 features. @samp{qSupported} also consolidates multiple feature probes
25474 at startup, to improve @value{GDBN} performance---a single larger
25475 packet performs better than multiple smaller probe packets on
25476 high-latency links. Some features may enable behavior which must not
25477 be on by default, e.g.@: because it would confuse older clients or
25478 stubs. Other features may describe packets which could be
25479 automatically probed for, but are not. These features must be
25480 reported before @value{GDBN} will use them. This ``default
25481 unsupported'' behavior is not appropriate for all packets, but it
25482 helps to keep the initial connection time under control with new
25483 versions of @value{GDBN} which support increasing numbers of packets.
25487 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
25488 The stub supports or does not support each returned @var{stubfeature},
25489 depending on the form of each @var{stubfeature} (see below for the
25492 An empty reply indicates that @samp{qSupported} is not recognized,
25493 or that no features needed to be reported to @value{GDBN}.
25496 The allowed forms for each feature (either a @var{gdbfeature} in the
25497 @samp{qSupported} packet, or a @var{stubfeature} in the response)
25501 @item @var{name}=@var{value}
25502 The remote protocol feature @var{name} is supported, and associated
25503 with the specified @var{value}. The format of @var{value} depends
25504 on the feature, but it must not include a semicolon.
25506 The remote protocol feature @var{name} is supported, and does not
25507 need an associated value.
25509 The remote protocol feature @var{name} is not supported.
25511 The remote protocol feature @var{name} may be supported, and
25512 @value{GDBN} should auto-detect support in some other way when it is
25513 needed. This form will not be used for @var{gdbfeature} notifications,
25514 but may be used for @var{stubfeature} responses.
25517 Whenever the stub receives a @samp{qSupported} request, the
25518 supplied set of @value{GDBN} features should override any previous
25519 request. This allows @value{GDBN} to put the stub in a known
25520 state, even if the stub had previously been communicating with
25521 a different version of @value{GDBN}.
25523 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
25528 This feature indicates whether @value{GDBN} supports multiprocess
25529 extensions to the remote protocol. @value{GDBN} does not use such
25530 extensions unless the stub also reports that it supports them by
25531 including @samp{multiprocess+} in its @samp{qSupported} reply.
25532 @xref{multiprocess extensions}, for details.
25535 Stubs should ignore any unknown values for
25536 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
25537 packet supports receiving packets of unlimited length (earlier
25538 versions of @value{GDBN} may reject overly long responses). Additional values
25539 for @var{gdbfeature} may be defined in the future to let the stub take
25540 advantage of new features in @value{GDBN}, e.g.@: incompatible
25541 improvements in the remote protocol---the @samp{multiprocess} feature is
25542 an example of such a feature. The stub's reply should be independent
25543 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
25544 describes all the features it supports, and then the stub replies with
25545 all the features it supports.
25547 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
25548 responses, as long as each response uses one of the standard forms.
25550 Some features are flags. A stub which supports a flag feature
25551 should respond with a @samp{+} form response. Other features
25552 require values, and the stub should respond with an @samp{=}
25555 Each feature has a default value, which @value{GDBN} will use if
25556 @samp{qSupported} is not available or if the feature is not mentioned
25557 in the @samp{qSupported} response. The default values are fixed; a
25558 stub is free to omit any feature responses that match the defaults.
25560 Not all features can be probed, but for those which can, the probing
25561 mechanism is useful: in some cases, a stub's internal
25562 architecture may not allow the protocol layer to know some information
25563 about the underlying target in advance. This is especially common in
25564 stubs which may be configured for multiple targets.
25566 These are the currently defined stub features and their properties:
25568 @multitable @columnfractions 0.35 0.2 0.12 0.2
25569 @c NOTE: The first row should be @headitem, but we do not yet require
25570 @c a new enough version of Texinfo (4.7) to use @headitem.
25572 @tab Value Required
25576 @item @samp{PacketSize}
25581 @item @samp{qXfer:auxv:read}
25586 @item @samp{qXfer:features:read}
25591 @item @samp{qXfer:libraries:read}
25596 @item @samp{qXfer:memory-map:read}
25601 @item @samp{qXfer:spu:read}
25606 @item @samp{qXfer:spu:write}
25611 @item @samp{QPassSignals}
25616 @item @samp{QStartNoAckMode}
25621 @item @samp{multiprocess}
25628 These are the currently defined stub features, in more detail:
25631 @cindex packet size, remote protocol
25632 @item PacketSize=@var{bytes}
25633 The remote stub can accept packets up to at least @var{bytes} in
25634 length. @value{GDBN} will send packets up to this size for bulk
25635 transfers, and will never send larger packets. This is a limit on the
25636 data characters in the packet, including the frame and checksum.
25637 There is no trailing NUL byte in a remote protocol packet; if the stub
25638 stores packets in a NUL-terminated format, it should allow an extra
25639 byte in its buffer for the NUL. If this stub feature is not supported,
25640 @value{GDBN} guesses based on the size of the @samp{g} packet response.
25642 @item qXfer:auxv:read
25643 The remote stub understands the @samp{qXfer:auxv:read} packet
25644 (@pxref{qXfer auxiliary vector read}).
25646 @item qXfer:features:read
25647 The remote stub understands the @samp{qXfer:features:read} packet
25648 (@pxref{qXfer target description read}).
25650 @item qXfer:libraries:read
25651 The remote stub understands the @samp{qXfer:libraries:read} packet
25652 (@pxref{qXfer library list read}).
25654 @item qXfer:memory-map:read
25655 The remote stub understands the @samp{qXfer:memory-map:read} packet
25656 (@pxref{qXfer memory map read}).
25658 @item qXfer:spu:read
25659 The remote stub understands the @samp{qXfer:spu:read} packet
25660 (@pxref{qXfer spu read}).
25662 @item qXfer:spu:write
25663 The remote stub understands the @samp{qXfer:spu:write} packet
25664 (@pxref{qXfer spu write}).
25667 The remote stub understands the @samp{QPassSignals} packet
25668 (@pxref{QPassSignals}).
25670 @item QStartNoAckMode
25671 The remote stub understands the @samp{QStartNoAckMode} packet and
25672 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
25675 @anchor{multiprocess extensions}
25676 @cindex multiprocess extensions, in remote protocol
25677 The remote stub understands the multiprocess extensions to the remote
25678 protocol syntax. The multiprocess extensions affect the syntax of
25679 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
25680 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
25681 replies. Note that reporting this feature indicates support for the
25682 syntactic extensions only, not that the stub necessarily supports
25683 debugging of more than one process at a time. The stub must not use
25684 multiprocess extensions in packet replies unless @value{GDBN} has also
25685 indicated it supports them in its @samp{qSupported} request.
25690 @cindex symbol lookup, remote request
25691 @cindex @samp{qSymbol} packet
25692 Notify the target that @value{GDBN} is prepared to serve symbol lookup
25693 requests. Accept requests from the target for the values of symbols.
25698 The target does not need to look up any (more) symbols.
25699 @item qSymbol:@var{sym_name}
25700 The target requests the value of symbol @var{sym_name} (hex encoded).
25701 @value{GDBN} may provide the value by using the
25702 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
25706 @item qSymbol:@var{sym_value}:@var{sym_name}
25707 Set the value of @var{sym_name} to @var{sym_value}.
25709 @var{sym_name} (hex encoded) is the name of a symbol whose value the
25710 target has previously requested.
25712 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
25713 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
25719 The target does not need to look up any (more) symbols.
25720 @item qSymbol:@var{sym_name}
25721 The target requests the value of a new symbol @var{sym_name} (hex
25722 encoded). @value{GDBN} will continue to supply the values of symbols
25723 (if available), until the target ceases to request them.
25728 @xref{Tracepoint Packets}.
25730 @item qThreadExtraInfo,@var{thread-id}
25731 @cindex thread attributes info, remote request
25732 @cindex @samp{qThreadExtraInfo} packet
25733 Obtain a printable string description of a thread's attributes from
25734 the target OS. @var{thread-id} is a thread ID;
25735 see @ref{thread-id syntax}. This
25736 string may contain anything that the target OS thinks is interesting
25737 for @value{GDBN} to tell the user about the thread. The string is
25738 displayed in @value{GDBN}'s @code{info threads} display. Some
25739 examples of possible thread extra info strings are @samp{Runnable}, or
25740 @samp{Blocked on Mutex}.
25744 @item @var{XX}@dots{}
25745 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
25746 comprising the printable string containing the extra information about
25747 the thread's attributes.
25750 (Note that the @code{qThreadExtraInfo} packet's name is separated from
25751 the command by a @samp{,}, not a @samp{:}, contrary to the naming
25752 conventions above. Please don't use this packet as a model for new
25760 @xref{Tracepoint Packets}.
25762 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
25763 @cindex read special object, remote request
25764 @cindex @samp{qXfer} packet
25765 @anchor{qXfer read}
25766 Read uninterpreted bytes from the target's special data area
25767 identified by the keyword @var{object}. Request @var{length} bytes
25768 starting at @var{offset} bytes into the data. The content and
25769 encoding of @var{annex} is specific to @var{object}; it can supply
25770 additional details about what data to access.
25772 Here are the specific requests of this form defined so far. All
25773 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
25774 formats, listed below.
25777 @item qXfer:auxv:read::@var{offset},@var{length}
25778 @anchor{qXfer auxiliary vector read}
25779 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
25780 auxiliary vector}. Note @var{annex} must be empty.
25782 This packet is not probed by default; the remote stub must request it,
25783 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25785 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
25786 @anchor{qXfer target description read}
25787 Access the @dfn{target description}. @xref{Target Descriptions}. The
25788 annex specifies which XML document to access. The main description is
25789 always loaded from the @samp{target.xml} annex.
25791 This packet is not probed by default; the remote stub must request it,
25792 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25794 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
25795 @anchor{qXfer library list read}
25796 Access the target's list of loaded libraries. @xref{Library List Format}.
25797 The annex part of the generic @samp{qXfer} packet must be empty
25798 (@pxref{qXfer read}).
25800 Targets which maintain a list of libraries in the program's memory do
25801 not need to implement this packet; it is designed for platforms where
25802 the operating system manages the list of loaded libraries.
25804 This packet is not probed by default; the remote stub must request it,
25805 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25807 @item qXfer:memory-map:read::@var{offset},@var{length}
25808 @anchor{qXfer memory map read}
25809 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
25810 annex part of the generic @samp{qXfer} packet must be empty
25811 (@pxref{qXfer read}).
25813 This packet is not probed by default; the remote stub must request it,
25814 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25816 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
25817 @anchor{qXfer spu read}
25818 Read contents of an @code{spufs} file on the target system. The
25819 annex specifies which file to read; it must be of the form
25820 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
25821 in the target process, and @var{name} identifes the @code{spufs} file
25822 in that context to be accessed.
25824 This packet is not probed by default; the remote stub must request it,
25825 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25831 Data @var{data} (@pxref{Binary Data}) has been read from the
25832 target. There may be more data at a higher address (although
25833 it is permitted to return @samp{m} even for the last valid
25834 block of data, as long as at least one byte of data was read).
25835 @var{data} may have fewer bytes than the @var{length} in the
25839 Data @var{data} (@pxref{Binary Data}) has been read from the target.
25840 There is no more data to be read. @var{data} may have fewer bytes
25841 than the @var{length} in the request.
25844 The @var{offset} in the request is at the end of the data.
25845 There is no more data to be read.
25848 The request was malformed, or @var{annex} was invalid.
25851 The offset was invalid, or there was an error encountered reading the data.
25852 @var{nn} is a hex-encoded @code{errno} value.
25855 An empty reply indicates the @var{object} string was not recognized by
25856 the stub, or that the object does not support reading.
25859 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
25860 @cindex write data into object, remote request
25861 Write uninterpreted bytes into the target's special data area
25862 identified by the keyword @var{object}, starting at @var{offset} bytes
25863 into the data. @var{data}@dots{} is the binary-encoded data
25864 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
25865 is specific to @var{object}; it can supply additional details about what data
25868 Here are the specific requests of this form defined so far. All
25869 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
25870 formats, listed below.
25873 @item qXfer:@var{spu}:write:@var{annex}:@var{offset}:@var{data}@dots{}
25874 @anchor{qXfer spu write}
25875 Write @var{data} to an @code{spufs} file on the target system. The
25876 annex specifies which file to write; it must be of the form
25877 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
25878 in the target process, and @var{name} identifes the @code{spufs} file
25879 in that context to be accessed.
25881 This packet is not probed by default; the remote stub must request it,
25882 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25888 @var{nn} (hex encoded) is the number of bytes written.
25889 This may be fewer bytes than supplied in the request.
25892 The request was malformed, or @var{annex} was invalid.
25895 The offset was invalid, or there was an error encountered writing the data.
25896 @var{nn} is a hex-encoded @code{errno} value.
25899 An empty reply indicates the @var{object} string was not
25900 recognized by the stub, or that the object does not support writing.
25903 @item qXfer:@var{object}:@var{operation}:@dots{}
25904 Requests of this form may be added in the future. When a stub does
25905 not recognize the @var{object} keyword, or its support for
25906 @var{object} does not recognize the @var{operation} keyword, the stub
25907 must respond with an empty packet.
25911 @node Register Packet Format
25912 @section Register Packet Format
25914 The following @code{g}/@code{G} packets have previously been defined.
25915 In the below, some thirty-two bit registers are transferred as
25916 sixty-four bits. Those registers should be zero/sign extended (which?)
25917 to fill the space allocated. Register bytes are transferred in target
25918 byte order. The two nibbles within a register byte are transferred
25919 most-significant - least-significant.
25925 All registers are transferred as thirty-two bit quantities in the order:
25926 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
25927 registers; fsr; fir; fp.
25931 All registers are transferred as sixty-four bit quantities (including
25932 thirty-two bit registers such as @code{sr}). The ordering is the same
25937 @node Tracepoint Packets
25938 @section Tracepoint Packets
25939 @cindex tracepoint packets
25940 @cindex packets, tracepoint
25942 Here we describe the packets @value{GDBN} uses to implement
25943 tracepoints (@pxref{Tracepoints}).
25947 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}@r{[}-@r{]}
25948 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
25949 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
25950 the tracepoint is disabled. @var{step} is the tracepoint's step
25951 count, and @var{pass} is its pass count. If the trailing @samp{-} is
25952 present, further @samp{QTDP} packets will follow to specify this
25953 tracepoint's actions.
25958 The packet was understood and carried out.
25960 The packet was not recognized.
25963 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
25964 Define actions to be taken when a tracepoint is hit. @var{n} and
25965 @var{addr} must be the same as in the initial @samp{QTDP} packet for
25966 this tracepoint. This packet may only be sent immediately after
25967 another @samp{QTDP} packet that ended with a @samp{-}. If the
25968 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
25969 specifying more actions for this tracepoint.
25971 In the series of action packets for a given tracepoint, at most one
25972 can have an @samp{S} before its first @var{action}. If such a packet
25973 is sent, it and the following packets define ``while-stepping''
25974 actions. Any prior packets define ordinary actions --- that is, those
25975 taken when the tracepoint is first hit. If no action packet has an
25976 @samp{S}, then all the packets in the series specify ordinary
25977 tracepoint actions.
25979 The @samp{@var{action}@dots{}} portion of the packet is a series of
25980 actions, concatenated without separators. Each action has one of the
25986 Collect the registers whose bits are set in @var{mask}. @var{mask} is
25987 a hexadecimal number whose @var{i}'th bit is set if register number
25988 @var{i} should be collected. (The least significant bit is numbered
25989 zero.) Note that @var{mask} may be any number of digits long; it may
25990 not fit in a 32-bit word.
25992 @item M @var{basereg},@var{offset},@var{len}
25993 Collect @var{len} bytes of memory starting at the address in register
25994 number @var{basereg}, plus @var{offset}. If @var{basereg} is
25995 @samp{-1}, then the range has a fixed address: @var{offset} is the
25996 address of the lowest byte to collect. The @var{basereg},
25997 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
25998 values (the @samp{-1} value for @var{basereg} is a special case).
26000 @item X @var{len},@var{expr}
26001 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
26002 it directs. @var{expr} is an agent expression, as described in
26003 @ref{Agent Expressions}. Each byte of the expression is encoded as a
26004 two-digit hex number in the packet; @var{len} is the number of bytes
26005 in the expression (and thus one-half the number of hex digits in the
26010 Any number of actions may be packed together in a single @samp{QTDP}
26011 packet, as long as the packet does not exceed the maximum packet
26012 length (400 bytes, for many stubs). There may be only one @samp{R}
26013 action per tracepoint, and it must precede any @samp{M} or @samp{X}
26014 actions. Any registers referred to by @samp{M} and @samp{X} actions
26015 must be collected by a preceding @samp{R} action. (The
26016 ``while-stepping'' actions are treated as if they were attached to a
26017 separate tracepoint, as far as these restrictions are concerned.)
26022 The packet was understood and carried out.
26024 The packet was not recognized.
26027 @item QTFrame:@var{n}
26028 Select the @var{n}'th tracepoint frame from the buffer, and use the
26029 register and memory contents recorded there to answer subsequent
26030 request packets from @value{GDBN}.
26032 A successful reply from the stub indicates that the stub has found the
26033 requested frame. The response is a series of parts, concatenated
26034 without separators, describing the frame we selected. Each part has
26035 one of the following forms:
26039 The selected frame is number @var{n} in the trace frame buffer;
26040 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
26041 was no frame matching the criteria in the request packet.
26044 The selected trace frame records a hit of tracepoint number @var{t};
26045 @var{t} is a hexadecimal number.
26049 @item QTFrame:pc:@var{addr}
26050 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
26051 currently selected frame whose PC is @var{addr};
26052 @var{addr} is a hexadecimal number.
26054 @item QTFrame:tdp:@var{t}
26055 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
26056 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
26057 is a hexadecimal number.
26059 @item QTFrame:range:@var{start}:@var{end}
26060 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
26061 currently selected frame whose PC is between @var{start} (inclusive)
26062 and @var{end} (exclusive); @var{start} and @var{end} are hexadecimal
26065 @item QTFrame:outside:@var{start}:@var{end}
26066 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
26067 frame @emph{outside} the given range of addresses.
26070 Begin the tracepoint experiment. Begin collecting data from tracepoint
26071 hits in the trace frame buffer.
26074 End the tracepoint experiment. Stop collecting trace frames.
26077 Clear the table of tracepoints, and empty the trace frame buffer.
26079 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
26080 Establish the given ranges of memory as ``transparent''. The stub
26081 will answer requests for these ranges from memory's current contents,
26082 if they were not collected as part of the tracepoint hit.
26084 @value{GDBN} uses this to mark read-only regions of memory, like those
26085 containing program code. Since these areas never change, they should
26086 still have the same contents they did when the tracepoint was hit, so
26087 there's no reason for the stub to refuse to provide their contents.
26090 Ask the stub if there is a trace experiment running right now.
26095 There is no trace experiment running.
26097 There is a trace experiment running.
26103 @node Host I/O Packets
26104 @section Host I/O Packets
26105 @cindex Host I/O, remote protocol
26106 @cindex file transfer, remote protocol
26108 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
26109 operations on the far side of a remote link. For example, Host I/O is
26110 used to upload and download files to a remote target with its own
26111 filesystem. Host I/O uses the same constant values and data structure
26112 layout as the target-initiated File-I/O protocol. However, the
26113 Host I/O packets are structured differently. The target-initiated
26114 protocol relies on target memory to store parameters and buffers.
26115 Host I/O requests are initiated by @value{GDBN}, and the
26116 target's memory is not involved. @xref{File-I/O Remote Protocol
26117 Extension}, for more details on the target-initiated protocol.
26119 The Host I/O request packets all encode a single operation along with
26120 its arguments. They have this format:
26124 @item vFile:@var{operation}: @var{parameter}@dots{}
26125 @var{operation} is the name of the particular request; the target
26126 should compare the entire packet name up to the second colon when checking
26127 for a supported operation. The format of @var{parameter} depends on
26128 the operation. Numbers are always passed in hexadecimal. Negative
26129 numbers have an explicit minus sign (i.e.@: two's complement is not
26130 used). Strings (e.g.@: filenames) are encoded as a series of
26131 hexadecimal bytes. The last argument to a system call may be a
26132 buffer of escaped binary data (@pxref{Binary Data}).
26136 The valid responses to Host I/O packets are:
26140 @item F @var{result} [, @var{errno}] [; @var{attachment}]
26141 @var{result} is the integer value returned by this operation, usually
26142 non-negative for success and -1 for errors. If an error has occured,
26143 @var{errno} will be included in the result. @var{errno} will have a
26144 value defined by the File-I/O protocol (@pxref{Errno Values}). For
26145 operations which return data, @var{attachment} supplies the data as a
26146 binary buffer. Binary buffers in response packets are escaped in the
26147 normal way (@pxref{Binary Data}). See the individual packet
26148 documentation for the interpretation of @var{result} and
26152 An empty response indicates that this operation is not recognized.
26156 These are the supported Host I/O operations:
26159 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
26160 Open a file at @var{pathname} and return a file descriptor for it, or
26161 return -1 if an error occurs. @var{pathname} is a string,
26162 @var{flags} is an integer indicating a mask of open flags
26163 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
26164 of mode bits to use if the file is created (@pxref{mode_t Values}).
26165 @xref{open}, for details of the open flags and mode values.
26167 @item vFile:close: @var{fd}
26168 Close the open file corresponding to @var{fd} and return 0, or
26169 -1 if an error occurs.
26171 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
26172 Read data from the open file corresponding to @var{fd}. Up to
26173 @var{count} bytes will be read from the file, starting at @var{offset}
26174 relative to the start of the file. The target may read fewer bytes;
26175 common reasons include packet size limits and an end-of-file
26176 condition. The number of bytes read is returned. Zero should only be
26177 returned for a successful read at the end of the file, or if
26178 @var{count} was zero.
26180 The data read should be returned as a binary attachment on success.
26181 If zero bytes were read, the response should include an empty binary
26182 attachment (i.e.@: a trailing semicolon). The return value is the
26183 number of target bytes read; the binary attachment may be longer if
26184 some characters were escaped.
26186 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
26187 Write @var{data} (a binary buffer) to the open file corresponding
26188 to @var{fd}. Start the write at @var{offset} from the start of the
26189 file. Unlike many @code{write} system calls, there is no
26190 separate @var{count} argument; the length of @var{data} in the
26191 packet is used. @samp{vFile:write} returns the number of bytes written,
26192 which may be shorter than the length of @var{data}, or -1 if an
26195 @item vFile:unlink: @var{pathname}
26196 Delete the file at @var{pathname} on the target. Return 0,
26197 or -1 if an error occurs. @var{pathname} is a string.
26202 @section Interrupts
26203 @cindex interrupts (remote protocol)
26205 When a program on the remote target is running, @value{GDBN} may
26206 attempt to interrupt it by sending a @samp{Ctrl-C} or a @code{BREAK},
26207 control of which is specified via @value{GDBN}'s @samp{remotebreak}
26208 setting (@pxref{set remotebreak}).
26210 The precise meaning of @code{BREAK} is defined by the transport
26211 mechanism and may, in fact, be undefined. @value{GDBN} does not
26212 currently define a @code{BREAK} mechanism for any of the network
26213 interfaces except for TCP, in which case @value{GDBN} sends the
26214 @code{telnet} BREAK sequence.
26216 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
26217 transport mechanisms. It is represented by sending the single byte
26218 @code{0x03} without any of the usual packet overhead described in
26219 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
26220 transmitted as part of a packet, it is considered to be packet data
26221 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
26222 (@pxref{X packet}), used for binary downloads, may include an unescaped
26223 @code{0x03} as part of its packet.
26225 Stubs are not required to recognize these interrupt mechanisms and the
26226 precise meaning associated with receipt of the interrupt is
26227 implementation defined. If the stub is successful at interrupting the
26228 running program, it is expected that it will send one of the Stop
26229 Reply Packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
26230 of successfully stopping the program. Interrupts received while the
26231 program is stopped will be discarded.
26233 @node Packet Acknowledgment
26234 @section Packet Acknowledgment
26236 @cindex acknowledgment, for @value{GDBN} remote
26237 @cindex packet acknowledgment, for @value{GDBN} remote
26238 By default, when either the host or the target machine receives a packet,
26239 the first response expected is an acknowledgment: either @samp{+} (to indicate
26240 the package was received correctly) or @samp{-} (to request retransmission).
26241 This mechanism allows the @value{GDBN} remote protocol to operate over
26242 unreliable transport mechanisms, such as a serial line.
26244 In cases where the transport mechanism is itself reliable (such as a pipe or
26245 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
26246 It may be desirable to disable them in that case to reduce communication
26247 overhead, or for other reasons. This can be accomplished by means of the
26248 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
26250 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
26251 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
26252 and response format still includes the normal checksum, as described in
26253 @ref{Overview}, but the checksum may be ignored by the receiver.
26255 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
26256 no-acknowledgment mode, it should report that to @value{GDBN}
26257 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
26258 @pxref{qSupported}.
26259 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
26260 disabled via the @code{set remote noack-packet off} command
26261 (@pxref{Remote Configuration}),
26262 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
26263 Only then may the stub actually turn off packet acknowledgments.
26264 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
26265 response, which can be safely ignored by the stub.
26267 Note that @code{set remote noack-packet} command only affects negotiation
26268 between @value{GDBN} and the stub when subsequent connections are made;
26269 it does not affect the protocol acknowledgment state for any current
26271 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
26272 new connection is established,
26273 there is also no protocol request to re-enable the acknowledgments
26274 for the current connection, once disabled.
26280 Example sequence of a target being re-started. Notice how the restart
26281 does not get any direct output:
26286 @emph{target restarts}
26289 <- @code{T001:1234123412341234}
26293 Example sequence of a target being stepped by a single instruction:
26296 -> @code{G1445@dots{}}
26301 <- @code{T001:1234123412341234}
26305 <- @code{1455@dots{}}
26309 @node File-I/O Remote Protocol Extension
26310 @section File-I/O Remote Protocol Extension
26311 @cindex File-I/O remote protocol extension
26314 * File-I/O Overview::
26315 * Protocol Basics::
26316 * The F Request Packet::
26317 * The F Reply Packet::
26318 * The Ctrl-C Message::
26320 * List of Supported Calls::
26321 * Protocol-specific Representation of Datatypes::
26323 * File-I/O Examples::
26326 @node File-I/O Overview
26327 @subsection File-I/O Overview
26328 @cindex file-i/o overview
26330 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
26331 target to use the host's file system and console I/O to perform various
26332 system calls. System calls on the target system are translated into a
26333 remote protocol packet to the host system, which then performs the needed
26334 actions and returns a response packet to the target system.
26335 This simulates file system operations even on targets that lack file systems.
26337 The protocol is defined to be independent of both the host and target systems.
26338 It uses its own internal representation of datatypes and values. Both
26339 @value{GDBN} and the target's @value{GDBN} stub are responsible for
26340 translating the system-dependent value representations into the internal
26341 protocol representations when data is transmitted.
26343 The communication is synchronous. A system call is possible only when
26344 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
26345 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
26346 the target is stopped to allow deterministic access to the target's
26347 memory. Therefore File-I/O is not interruptible by target signals. On
26348 the other hand, it is possible to interrupt File-I/O by a user interrupt
26349 (@samp{Ctrl-C}) within @value{GDBN}.
26351 The target's request to perform a host system call does not finish
26352 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
26353 after finishing the system call, the target returns to continuing the
26354 previous activity (continue, step). No additional continue or step
26355 request from @value{GDBN} is required.
26358 (@value{GDBP}) continue
26359 <- target requests 'system call X'
26360 target is stopped, @value{GDBN} executes system call
26361 -> @value{GDBN} returns result
26362 ... target continues, @value{GDBN} returns to wait for the target
26363 <- target hits breakpoint and sends a Txx packet
26366 The protocol only supports I/O on the console and to regular files on
26367 the host file system. Character or block special devices, pipes,
26368 named pipes, sockets or any other communication method on the host
26369 system are not supported by this protocol.
26371 @node Protocol Basics
26372 @subsection Protocol Basics
26373 @cindex protocol basics, file-i/o
26375 The File-I/O protocol uses the @code{F} packet as the request as well
26376 as reply packet. Since a File-I/O system call can only occur when
26377 @value{GDBN} is waiting for a response from the continuing or stepping target,
26378 the File-I/O request is a reply that @value{GDBN} has to expect as a result
26379 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
26380 This @code{F} packet contains all information needed to allow @value{GDBN}
26381 to call the appropriate host system call:
26385 A unique identifier for the requested system call.
26388 All parameters to the system call. Pointers are given as addresses
26389 in the target memory address space. Pointers to strings are given as
26390 pointer/length pair. Numerical values are given as they are.
26391 Numerical control flags are given in a protocol-specific representation.
26395 At this point, @value{GDBN} has to perform the following actions.
26399 If the parameters include pointer values to data needed as input to a
26400 system call, @value{GDBN} requests this data from the target with a
26401 standard @code{m} packet request. This additional communication has to be
26402 expected by the target implementation and is handled as any other @code{m}
26406 @value{GDBN} translates all value from protocol representation to host
26407 representation as needed. Datatypes are coerced into the host types.
26410 @value{GDBN} calls the system call.
26413 It then coerces datatypes back to protocol representation.
26416 If the system call is expected to return data in buffer space specified
26417 by pointer parameters to the call, the data is transmitted to the
26418 target using a @code{M} or @code{X} packet. This packet has to be expected
26419 by the target implementation and is handled as any other @code{M} or @code{X}
26424 Eventually @value{GDBN} replies with another @code{F} packet which contains all
26425 necessary information for the target to continue. This at least contains
26432 @code{errno}, if has been changed by the system call.
26439 After having done the needed type and value coercion, the target continues
26440 the latest continue or step action.
26442 @node The F Request Packet
26443 @subsection The @code{F} Request Packet
26444 @cindex file-i/o request packet
26445 @cindex @code{F} request packet
26447 The @code{F} request packet has the following format:
26450 @item F@var{call-id},@var{parameter@dots{}}
26452 @var{call-id} is the identifier to indicate the host system call to be called.
26453 This is just the name of the function.
26455 @var{parameter@dots{}} are the parameters to the system call.
26456 Parameters are hexadecimal integer values, either the actual values in case
26457 of scalar datatypes, pointers to target buffer space in case of compound
26458 datatypes and unspecified memory areas, or pointer/length pairs in case
26459 of string parameters. These are appended to the @var{call-id} as a
26460 comma-delimited list. All values are transmitted in ASCII
26461 string representation, pointer/length pairs separated by a slash.
26467 @node The F Reply Packet
26468 @subsection The @code{F} Reply Packet
26469 @cindex file-i/o reply packet
26470 @cindex @code{F} reply packet
26472 The @code{F} reply packet has the following format:
26476 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
26478 @var{retcode} is the return code of the system call as hexadecimal value.
26480 @var{errno} is the @code{errno} set by the call, in protocol-specific
26482 This parameter can be omitted if the call was successful.
26484 @var{Ctrl-C flag} is only sent if the user requested a break. In this
26485 case, @var{errno} must be sent as well, even if the call was successful.
26486 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
26493 or, if the call was interrupted before the host call has been performed:
26500 assuming 4 is the protocol-specific representation of @code{EINTR}.
26505 @node The Ctrl-C Message
26506 @subsection The @samp{Ctrl-C} Message
26507 @cindex ctrl-c message, in file-i/o protocol
26509 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
26510 reply packet (@pxref{The F Reply Packet}),
26511 the target should behave as if it had
26512 gotten a break message. The meaning for the target is ``system call
26513 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
26514 (as with a break message) and return to @value{GDBN} with a @code{T02}
26517 It's important for the target to know in which
26518 state the system call was interrupted. There are two possible cases:
26522 The system call hasn't been performed on the host yet.
26525 The system call on the host has been finished.
26529 These two states can be distinguished by the target by the value of the
26530 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
26531 call hasn't been performed. This is equivalent to the @code{EINTR} handling
26532 on POSIX systems. In any other case, the target may presume that the
26533 system call has been finished --- successfully or not --- and should behave
26534 as if the break message arrived right after the system call.
26536 @value{GDBN} must behave reliably. If the system call has not been called
26537 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
26538 @code{errno} in the packet. If the system call on the host has been finished
26539 before the user requests a break, the full action must be finished by
26540 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
26541 The @code{F} packet may only be sent when either nothing has happened
26542 or the full action has been completed.
26545 @subsection Console I/O
26546 @cindex console i/o as part of file-i/o
26548 By default and if not explicitly closed by the target system, the file
26549 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
26550 on the @value{GDBN} console is handled as any other file output operation
26551 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
26552 by @value{GDBN} so that after the target read request from file descriptor
26553 0 all following typing is buffered until either one of the following
26558 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
26560 system call is treated as finished.
26563 The user presses @key{RET}. This is treated as end of input with a trailing
26567 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
26568 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
26572 If the user has typed more characters than fit in the buffer given to
26573 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
26574 either another @code{read(0, @dots{})} is requested by the target, or debugging
26575 is stopped at the user's request.
26578 @node List of Supported Calls
26579 @subsection List of Supported Calls
26580 @cindex list of supported file-i/o calls
26597 @unnumberedsubsubsec open
26598 @cindex open, file-i/o system call
26603 int open(const char *pathname, int flags);
26604 int open(const char *pathname, int flags, mode_t mode);
26608 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
26611 @var{flags} is the bitwise @code{OR} of the following values:
26615 If the file does not exist it will be created. The host
26616 rules apply as far as file ownership and time stamps
26620 When used with @code{O_CREAT}, if the file already exists it is
26621 an error and open() fails.
26624 If the file already exists and the open mode allows
26625 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
26626 truncated to zero length.
26629 The file is opened in append mode.
26632 The file is opened for reading only.
26635 The file is opened for writing only.
26638 The file is opened for reading and writing.
26642 Other bits are silently ignored.
26646 @var{mode} is the bitwise @code{OR} of the following values:
26650 User has read permission.
26653 User has write permission.
26656 Group has read permission.
26659 Group has write permission.
26662 Others have read permission.
26665 Others have write permission.
26669 Other bits are silently ignored.
26672 @item Return value:
26673 @code{open} returns the new file descriptor or -1 if an error
26680 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
26683 @var{pathname} refers to a directory.
26686 The requested access is not allowed.
26689 @var{pathname} was too long.
26692 A directory component in @var{pathname} does not exist.
26695 @var{pathname} refers to a device, pipe, named pipe or socket.
26698 @var{pathname} refers to a file on a read-only filesystem and
26699 write access was requested.
26702 @var{pathname} is an invalid pointer value.
26705 No space on device to create the file.
26708 The process already has the maximum number of files open.
26711 The limit on the total number of files open on the system
26715 The call was interrupted by the user.
26721 @unnumberedsubsubsec close
26722 @cindex close, file-i/o system call
26731 @samp{Fclose,@var{fd}}
26733 @item Return value:
26734 @code{close} returns zero on success, or -1 if an error occurred.
26740 @var{fd} isn't a valid open file descriptor.
26743 The call was interrupted by the user.
26749 @unnumberedsubsubsec read
26750 @cindex read, file-i/o system call
26755 int read(int fd, void *buf, unsigned int count);
26759 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
26761 @item Return value:
26762 On success, the number of bytes read is returned.
26763 Zero indicates end of file. If count is zero, read
26764 returns zero as well. On error, -1 is returned.
26770 @var{fd} is not a valid file descriptor or is not open for
26774 @var{bufptr} is an invalid pointer value.
26777 The call was interrupted by the user.
26783 @unnumberedsubsubsec write
26784 @cindex write, file-i/o system call
26789 int write(int fd, const void *buf, unsigned int count);
26793 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
26795 @item Return value:
26796 On success, the number of bytes written are returned.
26797 Zero indicates nothing was written. On error, -1
26804 @var{fd} is not a valid file descriptor or is not open for
26808 @var{bufptr} is an invalid pointer value.
26811 An attempt was made to write a file that exceeds the
26812 host-specific maximum file size allowed.
26815 No space on device to write the data.
26818 The call was interrupted by the user.
26824 @unnumberedsubsubsec lseek
26825 @cindex lseek, file-i/o system call
26830 long lseek (int fd, long offset, int flag);
26834 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
26836 @var{flag} is one of:
26840 The offset is set to @var{offset} bytes.
26843 The offset is set to its current location plus @var{offset}
26847 The offset is set to the size of the file plus @var{offset}
26851 @item Return value:
26852 On success, the resulting unsigned offset in bytes from
26853 the beginning of the file is returned. Otherwise, a
26854 value of -1 is returned.
26860 @var{fd} is not a valid open file descriptor.
26863 @var{fd} is associated with the @value{GDBN} console.
26866 @var{flag} is not a proper value.
26869 The call was interrupted by the user.
26875 @unnumberedsubsubsec rename
26876 @cindex rename, file-i/o system call
26881 int rename(const char *oldpath, const char *newpath);
26885 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
26887 @item Return value:
26888 On success, zero is returned. On error, -1 is returned.
26894 @var{newpath} is an existing directory, but @var{oldpath} is not a
26898 @var{newpath} is a non-empty directory.
26901 @var{oldpath} or @var{newpath} is a directory that is in use by some
26905 An attempt was made to make a directory a subdirectory
26909 A component used as a directory in @var{oldpath} or new
26910 path is not a directory. Or @var{oldpath} is a directory
26911 and @var{newpath} exists but is not a directory.
26914 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
26917 No access to the file or the path of the file.
26921 @var{oldpath} or @var{newpath} was too long.
26924 A directory component in @var{oldpath} or @var{newpath} does not exist.
26927 The file is on a read-only filesystem.
26930 The device containing the file has no room for the new
26934 The call was interrupted by the user.
26940 @unnumberedsubsubsec unlink
26941 @cindex unlink, file-i/o system call
26946 int unlink(const char *pathname);
26950 @samp{Funlink,@var{pathnameptr}/@var{len}}
26952 @item Return value:
26953 On success, zero is returned. On error, -1 is returned.
26959 No access to the file or the path of the file.
26962 The system does not allow unlinking of directories.
26965 The file @var{pathname} cannot be unlinked because it's
26966 being used by another process.
26969 @var{pathnameptr} is an invalid pointer value.
26972 @var{pathname} was too long.
26975 A directory component in @var{pathname} does not exist.
26978 A component of the path is not a directory.
26981 The file is on a read-only filesystem.
26984 The call was interrupted by the user.
26990 @unnumberedsubsubsec stat/fstat
26991 @cindex fstat, file-i/o system call
26992 @cindex stat, file-i/o system call
26997 int stat(const char *pathname, struct stat *buf);
26998 int fstat(int fd, struct stat *buf);
27002 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
27003 @samp{Ffstat,@var{fd},@var{bufptr}}
27005 @item Return value:
27006 On success, zero is returned. On error, -1 is returned.
27012 @var{fd} is not a valid open file.
27015 A directory component in @var{pathname} does not exist or the
27016 path is an empty string.
27019 A component of the path is not a directory.
27022 @var{pathnameptr} is an invalid pointer value.
27025 No access to the file or the path of the file.
27028 @var{pathname} was too long.
27031 The call was interrupted by the user.
27037 @unnumberedsubsubsec gettimeofday
27038 @cindex gettimeofday, file-i/o system call
27043 int gettimeofday(struct timeval *tv, void *tz);
27047 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
27049 @item Return value:
27050 On success, 0 is returned, -1 otherwise.
27056 @var{tz} is a non-NULL pointer.
27059 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
27065 @unnumberedsubsubsec isatty
27066 @cindex isatty, file-i/o system call
27071 int isatty(int fd);
27075 @samp{Fisatty,@var{fd}}
27077 @item Return value:
27078 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
27084 The call was interrupted by the user.
27089 Note that the @code{isatty} call is treated as a special case: it returns
27090 1 to the target if the file descriptor is attached
27091 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
27092 would require implementing @code{ioctl} and would be more complex than
27097 @unnumberedsubsubsec system
27098 @cindex system, file-i/o system call
27103 int system(const char *command);
27107 @samp{Fsystem,@var{commandptr}/@var{len}}
27109 @item Return value:
27110 If @var{len} is zero, the return value indicates whether a shell is
27111 available. A zero return value indicates a shell is not available.
27112 For non-zero @var{len}, the value returned is -1 on error and the
27113 return status of the command otherwise. Only the exit status of the
27114 command is returned, which is extracted from the host's @code{system}
27115 return value by calling @code{WEXITSTATUS(retval)}. In case
27116 @file{/bin/sh} could not be executed, 127 is returned.
27122 The call was interrupted by the user.
27127 @value{GDBN} takes over the full task of calling the necessary host calls
27128 to perform the @code{system} call. The return value of @code{system} on
27129 the host is simplified before it's returned
27130 to the target. Any termination signal information from the child process
27131 is discarded, and the return value consists
27132 entirely of the exit status of the called command.
27134 Due to security concerns, the @code{system} call is by default refused
27135 by @value{GDBN}. The user has to allow this call explicitly with the
27136 @code{set remote system-call-allowed 1} command.
27139 @item set remote system-call-allowed
27140 @kindex set remote system-call-allowed
27141 Control whether to allow the @code{system} calls in the File I/O
27142 protocol for the remote target. The default is zero (disabled).
27144 @item show remote system-call-allowed
27145 @kindex show remote system-call-allowed
27146 Show whether the @code{system} calls are allowed in the File I/O
27150 @node Protocol-specific Representation of Datatypes
27151 @subsection Protocol-specific Representation of Datatypes
27152 @cindex protocol-specific representation of datatypes, in file-i/o protocol
27155 * Integral Datatypes::
27157 * Memory Transfer::
27162 @node Integral Datatypes
27163 @unnumberedsubsubsec Integral Datatypes
27164 @cindex integral datatypes, in file-i/o protocol
27166 The integral datatypes used in the system calls are @code{int},
27167 @code{unsigned int}, @code{long}, @code{unsigned long},
27168 @code{mode_t}, and @code{time_t}.
27170 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
27171 implemented as 32 bit values in this protocol.
27173 @code{long} and @code{unsigned long} are implemented as 64 bit types.
27175 @xref{Limits}, for corresponding MIN and MAX values (similar to those
27176 in @file{limits.h}) to allow range checking on host and target.
27178 @code{time_t} datatypes are defined as seconds since the Epoch.
27180 All integral datatypes transferred as part of a memory read or write of a
27181 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
27184 @node Pointer Values
27185 @unnumberedsubsubsec Pointer Values
27186 @cindex pointer values, in file-i/o protocol
27188 Pointers to target data are transmitted as they are. An exception
27189 is made for pointers to buffers for which the length isn't
27190 transmitted as part of the function call, namely strings. Strings
27191 are transmitted as a pointer/length pair, both as hex values, e.g.@:
27198 which is a pointer to data of length 18 bytes at position 0x1aaf.
27199 The length is defined as the full string length in bytes, including
27200 the trailing null byte. For example, the string @code{"hello world"}
27201 at address 0x123456 is transmitted as
27207 @node Memory Transfer
27208 @unnumberedsubsubsec Memory Transfer
27209 @cindex memory transfer, in file-i/o protocol
27211 Structured data which is transferred using a memory read or write (for
27212 example, a @code{struct stat}) is expected to be in a protocol-specific format
27213 with all scalar multibyte datatypes being big endian. Translation to
27214 this representation needs to be done both by the target before the @code{F}
27215 packet is sent, and by @value{GDBN} before
27216 it transfers memory to the target. Transferred pointers to structured
27217 data should point to the already-coerced data at any time.
27221 @unnumberedsubsubsec struct stat
27222 @cindex struct stat, in file-i/o protocol
27224 The buffer of type @code{struct stat} used by the target and @value{GDBN}
27225 is defined as follows:
27229 unsigned int st_dev; /* device */
27230 unsigned int st_ino; /* inode */
27231 mode_t st_mode; /* protection */
27232 unsigned int st_nlink; /* number of hard links */
27233 unsigned int st_uid; /* user ID of owner */
27234 unsigned int st_gid; /* group ID of owner */
27235 unsigned int st_rdev; /* device type (if inode device) */
27236 unsigned long st_size; /* total size, in bytes */
27237 unsigned long st_blksize; /* blocksize for filesystem I/O */
27238 unsigned long st_blocks; /* number of blocks allocated */
27239 time_t st_atime; /* time of last access */
27240 time_t st_mtime; /* time of last modification */
27241 time_t st_ctime; /* time of last change */
27245 The integral datatypes conform to the definitions given in the
27246 appropriate section (see @ref{Integral Datatypes}, for details) so this
27247 structure is of size 64 bytes.
27249 The values of several fields have a restricted meaning and/or
27255 A value of 0 represents a file, 1 the console.
27258 No valid meaning for the target. Transmitted unchanged.
27261 Valid mode bits are described in @ref{Constants}. Any other
27262 bits have currently no meaning for the target.
27267 No valid meaning for the target. Transmitted unchanged.
27272 These values have a host and file system dependent
27273 accuracy. Especially on Windows hosts, the file system may not
27274 support exact timing values.
27277 The target gets a @code{struct stat} of the above representation and is
27278 responsible for coercing it to the target representation before
27281 Note that due to size differences between the host, target, and protocol
27282 representations of @code{struct stat} members, these members could eventually
27283 get truncated on the target.
27285 @node struct timeval
27286 @unnumberedsubsubsec struct timeval
27287 @cindex struct timeval, in file-i/o protocol
27289 The buffer of type @code{struct timeval} used by the File-I/O protocol
27290 is defined as follows:
27294 time_t tv_sec; /* second */
27295 long tv_usec; /* microsecond */
27299 The integral datatypes conform to the definitions given in the
27300 appropriate section (see @ref{Integral Datatypes}, for details) so this
27301 structure is of size 8 bytes.
27304 @subsection Constants
27305 @cindex constants, in file-i/o protocol
27307 The following values are used for the constants inside of the
27308 protocol. @value{GDBN} and target are responsible for translating these
27309 values before and after the call as needed.
27320 @unnumberedsubsubsec Open Flags
27321 @cindex open flags, in file-i/o protocol
27323 All values are given in hexadecimal representation.
27335 @node mode_t Values
27336 @unnumberedsubsubsec mode_t Values
27337 @cindex mode_t values, in file-i/o protocol
27339 All values are given in octal representation.
27356 @unnumberedsubsubsec Errno Values
27357 @cindex errno values, in file-i/o protocol
27359 All values are given in decimal representation.
27384 @code{EUNKNOWN} is used as a fallback error value if a host system returns
27385 any error value not in the list of supported error numbers.
27388 @unnumberedsubsubsec Lseek Flags
27389 @cindex lseek flags, in file-i/o protocol
27398 @unnumberedsubsubsec Limits
27399 @cindex limits, in file-i/o protocol
27401 All values are given in decimal representation.
27404 INT_MIN -2147483648
27406 UINT_MAX 4294967295
27407 LONG_MIN -9223372036854775808
27408 LONG_MAX 9223372036854775807
27409 ULONG_MAX 18446744073709551615
27412 @node File-I/O Examples
27413 @subsection File-I/O Examples
27414 @cindex file-i/o examples
27416 Example sequence of a write call, file descriptor 3, buffer is at target
27417 address 0x1234, 6 bytes should be written:
27420 <- @code{Fwrite,3,1234,6}
27421 @emph{request memory read from target}
27424 @emph{return "6 bytes written"}
27428 Example sequence of a read call, file descriptor 3, buffer is at target
27429 address 0x1234, 6 bytes should be read:
27432 <- @code{Fread,3,1234,6}
27433 @emph{request memory write to target}
27434 -> @code{X1234,6:XXXXXX}
27435 @emph{return "6 bytes read"}
27439 Example sequence of a read call, call fails on the host due to invalid
27440 file descriptor (@code{EBADF}):
27443 <- @code{Fread,3,1234,6}
27447 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
27451 <- @code{Fread,3,1234,6}
27456 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
27460 <- @code{Fread,3,1234,6}
27461 -> @code{X1234,6:XXXXXX}
27465 @node Library List Format
27466 @section Library List Format
27467 @cindex library list format, remote protocol
27469 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
27470 same process as your application to manage libraries. In this case,
27471 @value{GDBN} can use the loader's symbol table and normal memory
27472 operations to maintain a list of shared libraries. On other
27473 platforms, the operating system manages loaded libraries.
27474 @value{GDBN} can not retrieve the list of currently loaded libraries
27475 through memory operations, so it uses the @samp{qXfer:libraries:read}
27476 packet (@pxref{qXfer library list read}) instead. The remote stub
27477 queries the target's operating system and reports which libraries
27480 The @samp{qXfer:libraries:read} packet returns an XML document which
27481 lists loaded libraries and their offsets. Each library has an
27482 associated name and one or more segment or section base addresses,
27483 which report where the library was loaded in memory.
27485 For the common case of libraries that are fully linked binaries, the
27486 library should have a list of segments. If the target supports
27487 dynamic linking of a relocatable object file, its library XML element
27488 should instead include a list of allocated sections. The segment or
27489 section bases are start addresses, not relocation offsets; they do not
27490 depend on the library's link-time base addresses.
27492 @value{GDBN} must be linked with the Expat library to support XML
27493 library lists. @xref{Expat}.
27495 A simple memory map, with one loaded library relocated by a single
27496 offset, looks like this:
27500 <library name="/lib/libc.so.6">
27501 <segment address="0x10000000"/>
27506 Another simple memory map, with one loaded library with three
27507 allocated sections (.text, .data, .bss), looks like this:
27511 <library name="sharedlib.o">
27512 <section address="0x10000000"/>
27513 <section address="0x20000000"/>
27514 <section address="0x30000000"/>
27519 The format of a library list is described by this DTD:
27522 <!-- library-list: Root element with versioning -->
27523 <!ELEMENT library-list (library)*>
27524 <!ATTLIST library-list version CDATA #FIXED "1.0">
27525 <!ELEMENT library (segment*, section*)>
27526 <!ATTLIST library name CDATA #REQUIRED>
27527 <!ELEMENT segment EMPTY>
27528 <!ATTLIST segment address CDATA #REQUIRED>
27529 <!ELEMENT section EMPTY>
27530 <!ATTLIST section address CDATA #REQUIRED>
27533 In addition, segments and section descriptors cannot be mixed within a
27534 single library element, and you must supply at least one segment or
27535 section for each library.
27537 @node Memory Map Format
27538 @section Memory Map Format
27539 @cindex memory map format
27541 To be able to write into flash memory, @value{GDBN} needs to obtain a
27542 memory map from the target. This section describes the format of the
27545 The memory map is obtained using the @samp{qXfer:memory-map:read}
27546 (@pxref{qXfer memory map read}) packet and is an XML document that
27547 lists memory regions.
27549 @value{GDBN} must be linked with the Expat library to support XML
27550 memory maps. @xref{Expat}.
27552 The top-level structure of the document is shown below:
27555 <?xml version="1.0"?>
27556 <!DOCTYPE memory-map
27557 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
27558 "http://sourceware.org/gdb/gdb-memory-map.dtd">
27564 Each region can be either:
27569 A region of RAM starting at @var{addr} and extending for @var{length}
27573 <memory type="ram" start="@var{addr}" length="@var{length}"/>
27578 A region of read-only memory:
27581 <memory type="rom" start="@var{addr}" length="@var{length}"/>
27586 A region of flash memory, with erasure blocks @var{blocksize}
27590 <memory type="flash" start="@var{addr}" length="@var{length}">
27591 <property name="blocksize">@var{blocksize}</property>
27597 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
27598 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
27599 packets to write to addresses in such ranges.
27601 The formal DTD for memory map format is given below:
27604 <!-- ................................................... -->
27605 <!-- Memory Map XML DTD ................................ -->
27606 <!-- File: memory-map.dtd .............................. -->
27607 <!-- .................................... .............. -->
27608 <!-- memory-map.dtd -->
27609 <!-- memory-map: Root element with versioning -->
27610 <!ELEMENT memory-map (memory | property)>
27611 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
27612 <!ELEMENT memory (property)>
27613 <!-- memory: Specifies a memory region,
27614 and its type, or device. -->
27615 <!ATTLIST memory type CDATA #REQUIRED
27616 start CDATA #REQUIRED
27617 length CDATA #REQUIRED
27618 device CDATA #IMPLIED>
27619 <!-- property: Generic attribute tag -->
27620 <!ELEMENT property (#PCDATA | property)*>
27621 <!ATTLIST property name CDATA #REQUIRED>
27624 @include agentexpr.texi
27626 @node Target Descriptions
27627 @appendix Target Descriptions
27628 @cindex target descriptions
27630 @strong{Warning:} target descriptions are still under active development,
27631 and the contents and format may change between @value{GDBN} releases.
27632 The format is expected to stabilize in the future.
27634 One of the challenges of using @value{GDBN} to debug embedded systems
27635 is that there are so many minor variants of each processor
27636 architecture in use. It is common practice for vendors to start with
27637 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
27638 and then make changes to adapt it to a particular market niche. Some
27639 architectures have hundreds of variants, available from dozens of
27640 vendors. This leads to a number of problems:
27644 With so many different customized processors, it is difficult for
27645 the @value{GDBN} maintainers to keep up with the changes.
27647 Since individual variants may have short lifetimes or limited
27648 audiences, it may not be worthwhile to carry information about every
27649 variant in the @value{GDBN} source tree.
27651 When @value{GDBN} does support the architecture of the embedded system
27652 at hand, the task of finding the correct architecture name to give the
27653 @command{set architecture} command can be error-prone.
27656 To address these problems, the @value{GDBN} remote protocol allows a
27657 target system to not only identify itself to @value{GDBN}, but to
27658 actually describe its own features. This lets @value{GDBN} support
27659 processor variants it has never seen before --- to the extent that the
27660 descriptions are accurate, and that @value{GDBN} understands them.
27662 @value{GDBN} must be linked with the Expat library to support XML
27663 target descriptions. @xref{Expat}.
27666 * Retrieving Descriptions:: How descriptions are fetched from a target.
27667 * Target Description Format:: The contents of a target description.
27668 * Predefined Target Types:: Standard types available for target
27670 * Standard Target Features:: Features @value{GDBN} knows about.
27673 @node Retrieving Descriptions
27674 @section Retrieving Descriptions
27676 Target descriptions can be read from the target automatically, or
27677 specified by the user manually. The default behavior is to read the
27678 description from the target. @value{GDBN} retrieves it via the remote
27679 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
27680 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
27681 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
27682 XML document, of the form described in @ref{Target Description
27685 Alternatively, you can specify a file to read for the target description.
27686 If a file is set, the target will not be queried. The commands to
27687 specify a file are:
27690 @cindex set tdesc filename
27691 @item set tdesc filename @var{path}
27692 Read the target description from @var{path}.
27694 @cindex unset tdesc filename
27695 @item unset tdesc filename
27696 Do not read the XML target description from a file. @value{GDBN}
27697 will use the description supplied by the current target.
27699 @cindex show tdesc filename
27700 @item show tdesc filename
27701 Show the filename to read for a target description, if any.
27705 @node Target Description Format
27706 @section Target Description Format
27707 @cindex target descriptions, XML format
27709 A target description annex is an @uref{http://www.w3.org/XML/, XML}
27710 document which complies with the Document Type Definition provided in
27711 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
27712 means you can use generally available tools like @command{xmllint} to
27713 check that your feature descriptions are well-formed and valid.
27714 However, to help people unfamiliar with XML write descriptions for
27715 their targets, we also describe the grammar here.
27717 Target descriptions can identify the architecture of the remote target
27718 and (for some architectures) provide information about custom register
27719 sets. @value{GDBN} can use this information to autoconfigure for your
27720 target, or to warn you if you connect to an unsupported target.
27722 Here is a simple target description:
27725 <target version="1.0">
27726 <architecture>i386:x86-64</architecture>
27731 This minimal description only says that the target uses
27732 the x86-64 architecture.
27734 A target description has the following overall form, with [ ] marking
27735 optional elements and @dots{} marking repeatable elements. The elements
27736 are explained further below.
27739 <?xml version="1.0"?>
27740 <!DOCTYPE target SYSTEM "gdb-target.dtd">
27741 <target version="1.0">
27742 @r{[}@var{architecture}@r{]}
27743 @r{[}@var{feature}@dots{}@r{]}
27748 The description is generally insensitive to whitespace and line
27749 breaks, under the usual common-sense rules. The XML version
27750 declaration and document type declaration can generally be omitted
27751 (@value{GDBN} does not require them), but specifying them may be
27752 useful for XML validation tools. The @samp{version} attribute for
27753 @samp{<target>} may also be omitted, but we recommend
27754 including it; if future versions of @value{GDBN} use an incompatible
27755 revision of @file{gdb-target.dtd}, they will detect and report
27756 the version mismatch.
27758 @subsection Inclusion
27759 @cindex target descriptions, inclusion
27762 @cindex <xi:include>
27765 It can sometimes be valuable to split a target description up into
27766 several different annexes, either for organizational purposes, or to
27767 share files between different possible target descriptions. You can
27768 divide a description into multiple files by replacing any element of
27769 the target description with an inclusion directive of the form:
27772 <xi:include href="@var{document}"/>
27776 When @value{GDBN} encounters an element of this form, it will retrieve
27777 the named XML @var{document}, and replace the inclusion directive with
27778 the contents of that document. If the current description was read
27779 using @samp{qXfer}, then so will be the included document;
27780 @var{document} will be interpreted as the name of an annex. If the
27781 current description was read from a file, @value{GDBN} will look for
27782 @var{document} as a file in the same directory where it found the
27783 original description.
27785 @subsection Architecture
27786 @cindex <architecture>
27788 An @samp{<architecture>} element has this form:
27791 <architecture>@var{arch}</architecture>
27794 @var{arch} is an architecture name from the same selection
27795 accepted by @code{set architecture} (@pxref{Targets, ,Specifying a
27796 Debugging Target}).
27798 @subsection Features
27801 Each @samp{<feature>} describes some logical portion of the target
27802 system. Features are currently used to describe available CPU
27803 registers and the types of their contents. A @samp{<feature>} element
27807 <feature name="@var{name}">
27808 @r{[}@var{type}@dots{}@r{]}
27814 Each feature's name should be unique within the description. The name
27815 of a feature does not matter unless @value{GDBN} has some special
27816 knowledge of the contents of that feature; if it does, the feature
27817 should have its standard name. @xref{Standard Target Features}.
27821 Any register's value is a collection of bits which @value{GDBN} must
27822 interpret. The default interpretation is a two's complement integer,
27823 but other types can be requested by name in the register description.
27824 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
27825 Target Types}), and the description can define additional composite types.
27827 Each type element must have an @samp{id} attribute, which gives
27828 a unique (within the containing @samp{<feature>}) name to the type.
27829 Types must be defined before they are used.
27832 Some targets offer vector registers, which can be treated as arrays
27833 of scalar elements. These types are written as @samp{<vector>} elements,
27834 specifying the array element type, @var{type}, and the number of elements,
27838 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
27842 If a register's value is usefully viewed in multiple ways, define it
27843 with a union type containing the useful representations. The
27844 @samp{<union>} element contains one or more @samp{<field>} elements,
27845 each of which has a @var{name} and a @var{type}:
27848 <union id="@var{id}">
27849 <field name="@var{name}" type="@var{type}"/>
27854 @subsection Registers
27857 Each register is represented as an element with this form:
27860 <reg name="@var{name}"
27861 bitsize="@var{size}"
27862 @r{[}regnum="@var{num}"@r{]}
27863 @r{[}save-restore="@var{save-restore}"@r{]}
27864 @r{[}type="@var{type}"@r{]}
27865 @r{[}group="@var{group}"@r{]}/>
27869 The components are as follows:
27874 The register's name; it must be unique within the target description.
27877 The register's size, in bits.
27880 The register's number. If omitted, a register's number is one greater
27881 than that of the previous register (either in the current feature or in
27882 a preceeding feature); the first register in the target description
27883 defaults to zero. This register number is used to read or write
27884 the register; e.g.@: it is used in the remote @code{p} and @code{P}
27885 packets, and registers appear in the @code{g} and @code{G} packets
27886 in order of increasing register number.
27889 Whether the register should be preserved across inferior function
27890 calls; this must be either @code{yes} or @code{no}. The default is
27891 @code{yes}, which is appropriate for most registers except for
27892 some system control registers; this is not related to the target's
27896 The type of the register. @var{type} may be a predefined type, a type
27897 defined in the current feature, or one of the special types @code{int}
27898 and @code{float}. @code{int} is an integer type of the correct size
27899 for @var{bitsize}, and @code{float} is a floating point type (in the
27900 architecture's normal floating point format) of the correct size for
27901 @var{bitsize}. The default is @code{int}.
27904 The register group to which this register belongs. @var{group} must
27905 be either @code{general}, @code{float}, or @code{vector}. If no
27906 @var{group} is specified, @value{GDBN} will not display the register
27907 in @code{info registers}.
27911 @node Predefined Target Types
27912 @section Predefined Target Types
27913 @cindex target descriptions, predefined types
27915 Type definitions in the self-description can build up composite types
27916 from basic building blocks, but can not define fundamental types. Instead,
27917 standard identifiers are provided by @value{GDBN} for the fundamental
27918 types. The currently supported types are:
27927 Signed integer types holding the specified number of bits.
27934 Unsigned integer types holding the specified number of bits.
27938 Pointers to unspecified code and data. The program counter and
27939 any dedicated return address register may be marked as code
27940 pointers; printing a code pointer converts it into a symbolic
27941 address. The stack pointer and any dedicated address registers
27942 may be marked as data pointers.
27945 Single precision IEEE floating point.
27948 Double precision IEEE floating point.
27951 The 12-byte extended precision format used by ARM FPA registers.
27955 @node Standard Target Features
27956 @section Standard Target Features
27957 @cindex target descriptions, standard features
27959 A target description must contain either no registers or all the
27960 target's registers. If the description contains no registers, then
27961 @value{GDBN} will assume a default register layout, selected based on
27962 the architecture. If the description contains any registers, the
27963 default layout will not be used; the standard registers must be
27964 described in the target description, in such a way that @value{GDBN}
27965 can recognize them.
27967 This is accomplished by giving specific names to feature elements
27968 which contain standard registers. @value{GDBN} will look for features
27969 with those names and verify that they contain the expected registers;
27970 if any known feature is missing required registers, or if any required
27971 feature is missing, @value{GDBN} will reject the target
27972 description. You can add additional registers to any of the
27973 standard features --- @value{GDBN} will display them just as if
27974 they were added to an unrecognized feature.
27976 This section lists the known features and their expected contents.
27977 Sample XML documents for these features are included in the
27978 @value{GDBN} source tree, in the directory @file{gdb/features}.
27980 Names recognized by @value{GDBN} should include the name of the
27981 company or organization which selected the name, and the overall
27982 architecture to which the feature applies; so e.g.@: the feature
27983 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
27985 The names of registers are not case sensitive for the purpose
27986 of recognizing standard features, but @value{GDBN} will only display
27987 registers using the capitalization used in the description.
27993 * PowerPC Features::
27998 @subsection ARM Features
27999 @cindex target descriptions, ARM features
28001 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
28002 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
28003 @samp{lr}, @samp{pc}, and @samp{cpsr}.
28005 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
28006 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
28008 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
28009 it should contain at least registers @samp{wR0} through @samp{wR15} and
28010 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
28011 @samp{wCSSF}, and @samp{wCASF} registers are optional.
28013 @node MIPS Features
28014 @subsection MIPS Features
28015 @cindex target descriptions, MIPS features
28017 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
28018 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
28019 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
28022 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
28023 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
28024 registers. They may be 32-bit or 64-bit depending on the target.
28026 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
28027 it may be optional in a future version of @value{GDBN}. It should
28028 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
28029 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
28031 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
28032 contain a single register, @samp{restart}, which is used by the
28033 Linux kernel to control restartable syscalls.
28035 @node M68K Features
28036 @subsection M68K Features
28037 @cindex target descriptions, M68K features
28040 @item @samp{org.gnu.gdb.m68k.core}
28041 @itemx @samp{org.gnu.gdb.coldfire.core}
28042 @itemx @samp{org.gnu.gdb.fido.core}
28043 One of those features must be always present.
28044 The feature that is present determines which flavor of m86k is
28045 used. The feature that is present should contain registers
28046 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
28047 @samp{sp}, @samp{ps} and @samp{pc}.
28049 @item @samp{org.gnu.gdb.coldfire.fp}
28050 This feature is optional. If present, it should contain registers
28051 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
28055 @node PowerPC Features
28056 @subsection PowerPC Features
28057 @cindex target descriptions, PowerPC features
28059 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
28060 targets. It should contain registers @samp{r0} through @samp{r31},
28061 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
28062 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
28064 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
28065 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
28067 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
28068 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
28071 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
28072 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
28073 will combine these registers with the floating point registers
28074 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
28075 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
28076 through @samp{vs63}, the set of vector registers for POWER7.
28078 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
28079 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
28080 @samp{spefscr}. SPE targets should provide 32-bit registers in
28081 @samp{org.gnu.gdb.power.core} and provide the upper halves in
28082 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
28083 these to present registers @samp{ev0} through @samp{ev31} to the
28098 % I think something like @colophon should be in texinfo. In the
28100 \long\def\colophon{\hbox to0pt{}\vfill
28101 \centerline{The body of this manual is set in}
28102 \centerline{\fontname\tenrm,}
28103 \centerline{with headings in {\bf\fontname\tenbf}}
28104 \centerline{and examples in {\tt\fontname\tentt}.}
28105 \centerline{{\it\fontname\tenit\/},}
28106 \centerline{{\bf\fontname\tenbf}, and}
28107 \centerline{{\sl\fontname\tensl\/}}
28108 \centerline{are used for emphasis.}\vfill}
28110 % Blame: doc@cygnus.com, 1991.